WO2024205169A1 - Lithium metal battery and preparation method therefor - Google Patents

Abstract

Provided are a lithium metal battery and a preparation method therefor, the lithium metal battery comprising an anode, a cathode, and an electrolyte arranged between the anode and the cathode, wherein, in an X-ray photoelectron spectroscopy (XPS) analysis spectrum obtained for the surface of the anode, the ratio of an area (A1) for an Li1s peak to the total area (B1+B2) of an area (B1) for an F1s peak and an area (B2) for a B1s peak is 1:0.7 to 1:1.2, and the electrolyte comprises a nitrile-based compound, a lithium salt, and a carbonate-based compound, wherein the lithium salt comprises lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF₄), and the amount of the nitrile-based compound is 3 wt% to 45 wt%, based on 100 wt% of the total weight of the electrolyte.

Description

Lithium metal battery and its manufacturing method

It relates to a lithium metal battery and a method for manufacturing the same.

Lithium metal batteries mainly use carbon-based negative electrode active materials such as graphite. Carbon-based negative electrode active materials have no volume change during charging and discharging, so the stability of lithium metal batteries is high, but their capacity is small, so a negative electrode active material with a higher capacity is required.

Lithium metal, which has a much larger theoretical electric capacity than carbon-based negative electrode materials, can be used as a negative electrode material.

When lithium metal is charged and discharged, dendrites are formed on the surface of the lithium metal due to a side reaction with the electrolyte, and the growth of the dendrites can cause a short circuit between the positive and negative electrodes, which can reduce the life characteristics of a lithium metal battery containing lithium metal.

In addition, in the case of lithium metal batteries, despite the high energy density, the battery capacity decreases rapidly because it is difficult to control the dendritic lithium growth when Li ions are electroplated on the anode surface. To solve this problem, it has been proposed to form a coating layer that suppresses Li growth. However, according to this method, the effect of improving the battery capacity and lifespan is not satisfactory, and the battery manufacturing cost increases, so there is room for improvement.

One aspect is to provide a lithium metal battery with a new structure.

Another aspect is to provide a method for manufacturing the lithium metal battery described above.

In a lithium metal battery comprising a cathode, an anode, and an electrolyte layer disposed between the cathode and the anode according to one aspect,

In the X-ray photoelectron spectroscopy (XPS) analysis obtained for the above cathode surface, the ratio of the total area (B1+B2) of the area of the Li1s peak (A1), the area of the F1s peak (B1), and the area of the B1s peak (B2) is 1:0.7 to 1:1.2.

The above electrolyte layer comprises a nitrile compound, a lithium salt, and a carbonate compound,

The above lithium salts include lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF ₄ ).

A lithium metal battery is provided in which the content of the nitrile compound is 3 wt% to 45 wt% based on 100 wt% of the total weight of the electrolyte layer.

The above nitrile compound is butyronitrile, valeronitrile, propionitrile, acetonitrile, or a combination thereof.

The concentration of the above lithium salt is 1 to 5 M. And the mixing weight ratio of the LiDFOB and LiBF ₄ is 1:2 to 1:0.5.

The above carbonate compound is fluoroethylene carbonate (FEC), dimethyl carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, or a combination thereof.

In the Raman analysis spectrum obtained for the above cathode surface, the area (Ac) of the peak at wave numbers 695 to 725 eV is 25 to 40%, or 27 to 40%, based on the total Raman analysis area of the electrolyte layer.

The peak at wavelengths 695–725 eV is the Li coordinated DFOB related peak.

Here, the total concentration of lithium salt is 1.0 to 2.4 M, 1.0 to 1.6 M, for example, 1.2 M. The concentration of LiDFOB salt in the lithium salt is, for example, 0.6 M. And as the concentration of lithium salt increases, the above area can increase proportionally.

In the Raman analysis spectrum obtained for the above cathode surface, a ratio (Ac/A _d ) of the area of the peak at wave numbers 695 to 725 eV (Ac) to the area of the peak at wave numbers 715 to 745 eV (Ad) is 0.4 to 1. The peak at wave numbers 715 to 745 eV is a free FEC related peak. Here, the total concentration of the lithium salt is 1.0 to 2.4 M, 1.0 to 1.6 M, for example, 1.2 M. The concentration of LiDFOB salt in the lithium salt is, for example, 0.6 M. The concentration of LiDFOB salt in the lithium salt is, for example, 0.6 M. And as the concentration of the lithium salt increases, the area can increase proportionally.

The above carbonate compound contains FEC and DEC, and the mixing weight ratio of FEC and DEC is 1:10 to 1:1.

The above negative electrode may include a negative electrode collector.

The above negative electrode further includes a lithium metal layer disposed on the negative electrode collector,

The above lithium metal layer may include a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof.

The above negative electrode may further include a protective layer disposed on the lithium metal layer.

The above electrolyte layer is a liquid electrolyte, a gel electrolyte, a solid electrolyte or a combination thereof. The solid electrolyte may further include an oxide-based solid electrolyte, a sulfide-based solid electrolyte or a combination thereof.

The above lithium alloy contains lithium and a first metal, and the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum or a combination thereof.

The above negative electrode may include a negative electrode active material layer between a lithium metal layer and an electrolyte layer.

The above positive electrode includes a positive electrode current collector and a positive electrode active material layer, and at least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, and the base film includes a polymer, and the polymer includes polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof.

The above metal layer includes indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li) or an alloy thereof.

The above lithium metal battery may further include a separator.

Step for preparing the cathode according to other aspects;

Steps to prepare the anode;

A step of preparing an assembly using the above positive and negative electrodes; and

Comprising a step of providing an electrolyte layer to the above assembly,

The above electrolyte layer comprises a nitrile compound, a lithium salt, and a carbonate compound,

The above lithium salts include lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF ₄ ).

A method for manufacturing a lithium metal battery is provided, which manufactures the above-described lithium metal battery in which the content of the nitrile compound is 3 wt% to 45 wt% based on 100 wt% of the total weight of the electrolyte layer.

In the step of preparing the above assembly, a separator can be placed between the positive and negative electrodes.

According to one aspect , a lithium metal battery with improved initial capacity and cycle performance is provided by using an electrolyte layer containing a nitrile compound and a carbonate compound having strong interactions between cations and anions.

Figure 1a schematically illustrates a laminated structure of a lithium metal battery according to one embodiment.

Figure 1b schematically illustrates a laminated structure of a lithium metal battery according to another embodiment.

Figures 2a to 2f show XPS analysis spectra of the lithium metal surface of the lithium metal batteries of Example 1 and Comparative Example 1.

Figure 3a is a Raman analysis spectrum of F1s on the lithium metal surface in the lithium metal battery of Example 1.

Figure 3b is a Raman analysis spectrum of F1s on the lithium metal surface in the lithium metal battery of Comparative Example 1.

Figure 4 is a graph showing charge/discharge characteristics of the lithium metal battery of Example 9 and the lithium ion battery of Comparative Example 4.

Figure 5 is a schematic diagram of a lithium metal battery according to one embodiment.

Figure 6 is a schematic diagram of a lithium metal battery according to another embodiment.

Figure 7 is a schematic diagram of a lithium metal battery according to another embodiment.

<Explanation of the main symbols in the drawing>

1: Lithium metal battery 2, 20: Cathode

3, 10: Anode 4: Separator

5: Battery case 6: Cap assembly

7: Battery structure 8: Electrode tab

The present inventive concept described below can undergo various transformations and have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present inventive concept to specific embodiments, but should be understood to include all transformations, equivalents, or substitutes included in the technical scope of the present inventive concept.

The terminology used below is only used to describe specific embodiments and is not intended to limit the present creative idea. The singular expression includes the plural expression unless the context clearly indicates otherwise. Hereinafter, the terms "comprises" or "has" and the like are intended to indicate the presence of a feature, number, step, operation, component, part, ingredient, material or a combination thereof described in the specification, but should be understood to not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, ingredients, materials or combinations thereof. The "/" used below may be interpreted as "and" or "or" depending on the context.

In order to clearly express various layers and regions in the drawings, the thickness is shown enlarged or reduced. Similar parts are designated by the same drawing reference numerals throughout the specification. When a part such as a layer, film, region, or plate is referred to as being “on” or “over” another part throughout the specification, this includes not only the case where it is directly above the other part, but also the case where there is another part in between. The terms first, second, etc. may be used throughout the specification to describe various components, but the components should not be limited by the terms. The terms are used only to distinguish one component from another. In the present specification and the drawings, components having substantially the same functional configuration are referred to by the same reference numerals, and redundant descriptions are omitted.

In the present disclosure, the "particle diameter" of a particle refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter of a particle can be measured using a particle size analyzer (PSA). The "particle diameter" of a particle is, for example, an average particle diameter. The average particle diameter is, for example, a median particle diameter (D50). The median particle diameter (D50) is, for example, the size of a particle corresponding to 50% of the cumulative volume calculated from the side of a particle having a small particle size in a size distribution of particles measured by a laser diffraction method. The average particle diameter and average major axis length of a particle can be measured using a scanning electron microscope. When the size of a particle is measured using a scanning electron microscope, it is determined as an average value of 30 or more randomly extracted particles of 1 μm or more excluding fine particles.

As used herein, “metal” includes both metals and metalloids such as silicon and germanium, in either an elemental or ionic state.

As used herein, “alloy” means a mixture of two or more metals.

In the present disclosure, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation.

In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to a positive electrode active material or a negative electrode active material.

In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from a positive electrode active material or a negative electrode active material.

In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

In the present disclosure, “cathode” and “anode” mean electrodes at which electrochemical oxidation and delithiation occur during a discharge process.

In the present disclosure, thickness means average thickness.

Hereinafter, lithium metal batteries and their manufacturing methods according to embodiments will be described in more detail.

A non-cathode lithium metal battery is a battery that uses only an anode current collector without an anode active material layer. When charging, lithium ions transferred from the cathode are deposited/electrodeposited on the surface of the anode current collector, and when discharging, the lithium deposited/electrodeposited on the anode current collector is eluted again and inserted into the cathode, thereby operating the battery.

In the case of a non-cathode lithium metal battery, lithium metal is not added during battery assembly, but in the process of lithium ions generated from the anode changing to the cathode, lithium ions are converted to lithium and attached to the cathode through electroplating, thereby minimizing unused space, which can greatly improve the energy density of the battery. However, if the growth method of lithium metal is not controlled, precipitation or dendrites may grow toward the cathode, causing an irreversible reaction or an increase in current within the battery.

The present inventors have solved the above-described problems and provided a lithium metal battery using an electrolyte layer containing a solvent designed to form clusters having a coordination structure with a solvent that is a component of an SEI (Solid Electrolyte Interphase) film existing on the surface of an anode, which has the same components constituting the film but can move more to the surface of the anode or form a film earlier than when formed as a single substance during film formation, so as to suppress dendrite growth on a lithium metal. As a result, a more solid SEI film is formed on the surface of the lithium anode.

A lithium metal battery according to an embodiment of the present invention includes an anode, an anode, and an electrolyte layer disposed between the anode and the cathode, wherein a ratio of a total area (B1+B2) of an area (A1) of a Li1s peak, an area (B1) of a F1s peak, and an area (B2) of a B1s peak is 1:0.7 to 1:1.2 in X-ray photoelectron spectroscopy (XPS) analysis obtained for a surface of the anode, and the electrolyte layer includes a nitrile compound, a lithium salt, and a carbonate compound, wherein the lithium salt includes lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF ₄ ), and the content of the nitrile compound is 3 to 45 wt% based on 100 wt% of the total weight of the electrolyte layer.

In the XPS analysis spectrum obtained for the above cathode surface, the ratio of the total area (B1+B2) of the area of the F1s peak (B1) and the area of the B1s peak (B2) and the area of the O1s peak (C1) is in the range of 1:0.6 to 1:1.3.

In the above XPS analysis spectrum, the ratio of the area of the Li1s peak (A1) originating from the cation to the area of the F1s peak (B1) originating from the anion and the total area (B1+B2) of the B1s peak (B2) has, for example, a range of 1:0.75 to 1:2, 1:0.8 to 1:2, 1:0.85 to 1:2, 1:0.9 to 1:2, or 1:0.95 to 1:2.

In the XPS analysis spectrum obtained for the above cathode surface, the ratio of the total area (B1+B2) of the area of the F1s peak (B1) and the area of the B1s peak (B2) originating from the anion to the area of the O1s peak (C1) originating from the anion is, for example, in the range of 1:0.6 to 1:1.25, 1:0.6 to 1:1.2, 1:0.6 to 1:1.1, 1:0.7 to 1:1.1, 1:0.75 to 1:1.1, 1:0.8 to 1:1.1, 1:0.85 to 1:1.1, or 1:0.9 to 1:1.1.

The XPS analysis spectrum obtained for the above negative electrode is an XPS analysis spectrum obtained for a lithium metal surface. In the XPS spectrum, the Li1s peak is related to cations, the F1s peak and B1s peak are related to anions, and the O1s peak is related to solvent and anions.

The above electrolyte layer includes a nitrile compound, a lithium salt, and a carbonate compound, and the lithium salt includes lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF ₄ ). In addition, a lithium metal battery is provided in which the content of the nitrile compound is 3 wt% to 45 wt% based on 100 wt% of the total weight of the electrolyte layer.

The above negative electrode may include a negative electrode collector and lithium metal.

The concentration of the lithium salt is 1 to 5 M, 1 to 3 M, 1.0 to 2.4 M, 1.0 to 1.6 M. The mixing weight ratio of the LiDFOB and LiBF ₄ is 1:2 to 1:0.3, or 1:1.5 to 1:0.5. When the concentration of the lithium salt and the mixing weight ratio of LiDFOB and LiBF ₄ are within the above ranges, a lithium metal battery having improved performance can be manufactured. If the content of LiBF ₄ is more than the above range, better interaction of the nitrile-based compound with LiDFOB is confirmed, but the probability of encountering LiDFOB is greatly reduced, which may be disadvantageous for film formation, and if the content of LiDFOB is more than the above range, the viscosity of the electrolyte layer increases, which may lower the mobility, and thus the initial capacity of the lithium metal battery may decrease.

In lithium metal batteries, the control of lithium ion deposition and desorption directly affects the lifespan. Therefore, it is common to use a large amount of salt that reduces lithium dissociation characteristics to improve the characteristics of lithium metal batteries.

However, in a lithium metal battery according to one embodiment, the inorganic component of the cathode film is strengthened through the use of a nitrile compound, which acts as a medium to enable the movement of anions to the cathode together with lithium.

In a lithium metal battery, two salts are used as an electrolyte layer to endure the charge/discharge life called lithium deposition. One of the two salts is a film-forming salt to form a solid film, and the other salt is a lithium salt to help lithium ion transfer during continuous charge/discharge. In this case, since the affinity of the two salts for lithium cations is different, the lithium salt dissociation does not occur, and thus, a solvent that can help dissociation is required in addition to the solvent used in existing lithium ion batteries. Accordingly, in a lithium metal battery according to one embodiment, a nitrile compound such as butyronitrile with improved anion interaction can be applied to improve the long life and resistance characteristics.

Nitrile compounds utilize neutral molecules with improved anion interactions in addition to lithium cation interactions. Using an electrolyte layer containing such nitrile compounds can provide a lithium metal battery with improved longevity and reduced resistance.

The composition of the SEI layer existing on the lithium metal surface can be analyzed through the XPS analysis spectrum obtained for the lithium metal surface. The XPS analysis spectrum obtained for the lithium metal surface is for the lithium metal surface charged at a current corresponding to 0.05 to 0.2 compared to the capacity when the lithium metal battery has been in the second cycle or lower after formation, and the charge rate involved in the film formation is involved in the capacity.

In a lithium metal battery according to an embodiment, when a nitrile compound such as butyronitrile (BN) having excellent affinity for both cations and anions is used on the negative electrode surface, the cation and anion (difluorooxalateborate anion or tetrafluoroborate anion) are bonded to BN, so that when the Li cation moves from the positive electrode to the anion, the content of the anion on the negative electrode surface increases, and the effect of forming a film including the performing anion on the surface when the lithium cation is electrodeposited is obtained. In the existing electrolyte layer, it has a lithium metal surface/cation/solvent structure, and the solvent is decomposed to form an SEI, and the performance of the lithium metal battery may be deteriorated due to the formation of an organic SEI.

However, in a lithium metal battery according to an embodiment of the present invention, SEI with increased inorganic (anion) content can be formed on the lithium metal surface by using a nitrile compound such as BN. As a result, the performance of the lithium metal battery is improved.

If a nitrile compound is not added to the electrolyte layer, electrons are supplied to lithium ions on the negative electrode current collector, forming a lithium electrodeposition layer. The solvent component existing around the lithium ions is decomposed, forming an SEI layer containing organic substances on the lithium metal surface. However, if the SEI layer contains organic substances, the life characteristics of the lithium metal battery may deteriorate.

Nitrile compounds are neutral molecules with very strong lithium cation and anion interactions, and by using them, anions can be induced to move together with the initial charge lithium ions moving from the positive electrode to the negative electrode. As a result, more anions can be induced to exist in the negative electrode, and as a result, a robust film rich in boron and fluorine, which are anions, can be formed by abundant clustered solvation structures.

When the content of the nitrile compound is within the above range, the cluster in which ions are not completely dissociated and three or more ions exist simultaneously increases, and although the constituent materials of such clusters are the same, their configurations are different, so that they form a film earlier than other structures. Such a nitrile compound has excellent cation and anion interactions, so that it has excellent affinity for cations and anions. Therefore, when this is used, anions increase in addition to cations around lithium, so that an SEI layer with increased inorganic content can be formed on the lithium metal surface. At this time, the thickness of the SEI layer is 50 nm or less, 30 nm or less, or 1 to 25 nm. When an SEI layer with increased inorganic content exists on the lithium metal surface in this way, a lithium metal battery with improved life characteristics can be manufactured.

Nitrile compounds have the property of bringing in anions, and thus the performance of lithium metal batteries is improved due to the film in which the anions increase. If the content of the nitrile compounds is less than 3 wt% based on 100 wt% of the total weight of the electrolyte layer, the effect of the existence of anions other than the solvent around the lithium is minimal, and if it exceeds 45 wt%, solvents such as VC, VEC, and FEC are not contained in the cluster containing the lithium salt and solvent, and thus hardly participate in the formation of the SEI film. As a result, since the SEI film is formed only with salts and nitrile compounds such as BN, the performance of the lithium metal battery may deteriorate.

Nitrile compounds are, for example, butyronitrile, valeronitrile, propionitrile, acetonitrile, or a combination thereof. The dipole moments, lithium cation interaction energies, and dipole moments of butyronitrile, valeronitrile, fluoroethylene, and dimethyl carbonate are as shown in Table 1 below. And Table 2 below shows the dipole moments, lithium cation interaction energies, and dipole moments for solvents.

division Li+ interaction energy (eV) Anion interaction energy (eV) Dipole moment (eV) Valeronitrile -1.71 -0.15 4.09 Butyronitrile -1.69 -0.16 4.12 Propionitrile -1.65 -0.09 4.14 Acetonitrile -1.61 -0.11 4.03

division Li+ interaction energy (eV) Anion interaction energy (eV) Dipole moment (eV) EC -1.86 -0.36 5.63 FEC -1.65 -0.43 5.05 DMC -1.7 0.16 0.19 DEC -1.92 0.12 0.35

As shown in Table 1, in the case of nitrile compounds, the Li ⁺ interaction energy that the solvent must have is relatively weak compared to low-viscosity commercial solvents such as DMC or DEC, but it was confirmed that the anion interaction energy and dipole moment were greatly improved while securing the FEC level, so it was found that it was greatly improved compared to other commercial solvents as a low-viscosity solvent. However, since solvents also interact with each other, the presence or absence of aggregate structure formation and resistance characteristics in a mixture state must be considered.

When the formation of the aggregate structure and the dissociation equilibrium constant were confirmed, it was found that the characteristics were the best when BN was maintained at 3 wt% to 45 wt%.

The content of the above carbonate compound is 30 to 95 wt%, or 40 to 90 wt%, based on 100 wt% of the total weight of the nitrile compound and the carbonate compound.

If the content of the carbonate compound is within the above range, the properties of the salt and organic matter in the lithium salt coordination cluster are appropriately controlled, thereby improving lithium mobility and manufacturing a lithium metal battery with improved initial capacity and life characteristics. If the content of the carbonate compound exceeds 90 wt%, the proportion of clusters of an appropriate size decreases, thereby changing the composition of the SEI film, which can be confirmed by complex system calculations utilizing equilibrium energy.

The above carbonate compound includes FEC and DEC, and the mixing weight ratio of FEC and DEC is 1:10 to 1:1, 1:8 to 1:1, 1:5 to 1:1, or 1:3 to 1:1.

In the above Raman analysis spectrum, the area (Ac) of the peak at wave numbers 695 to 725 cm ^-1 is 25 to 40%, or 27 to 40%, based on the total Raman analysis area of the electrolyte layer. When the Raman analysis spectrum is investigated, the total concentration of the lithium salt is 1.0 to 2.4 M, 1.0 to 1.6 M, for example, 1.2 M. The concentration of LiDFOB salt in the lithium salt is, for example, 0.6 M. The area increases proportionally as the lithium salt concentration of the electrolyte layer increases.

In the above Raman analysis spectrum, the ratio (Ac/A _d ) of the area of the peak at wave numbers 695 to 725 cm ^-1 to the area of the peak at wave numbers 715 to 745 eV (Ad) is 0.4 to 1. When examining this Raman analysis spectrum, the total concentration of the lithium salt here is 1.0 to 2.4 M, 1.0 to 1.6 M, for example, 1.2 M. The concentration of LiDFOB salt in the lithium salt is, for example, 0.6 M.

The ratio (Ac/A _d ) of the above areas (Ad) increases proportionally as the lithium salt concentration in the electrolyte layer increases.

Here, the peak (peak c) at wavenumbers 695 to 725 eV is the Li coordinated DFOB-peak, the peak (peak d) at wavenumbers 715 to 745 eV is for free FEC, and the peak (peak e) at wavenumbers 735 to 750 eV is for Li+ coordinated FEC peak.

The electrolyte layer according to one embodiment may further contain a non-aqueous organic solvent in addition to the above-described carbonate compound.

Non-aqueous organic solvents that can be used include carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvents.

Examples of the carbonate solvent that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate, and the like. Examples of the ester solvent that can be used include methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, caprolactone, and the like. Examples of the ether solvent that can be used include diethyl ether, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In addition, cyclohexanone, etc. can be used as the ketone solvent. In addition, ethyl alcohol, isopropyl alcohol, etc. can be used as the alcohol solvent, and examples of the aprotic solvent that can be used include amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, 1,4-dioxolane, sulfolanes, sulfoxides, etc.

In terms of cell performance, a lithium metal battery according to an embodiment of the present invention can improve the initial capacity by increasing the total amount of lithium salt that can be dissolved or increasing the number of available Li ions in an electrolyte layer with the same salt concentration if the cation affinity of the solvent is strong, and the cycle performance of the lithium metal battery can be improved if the anion affinity of the molecule is strong.

In a lithium metal battery according to one embodiment, the negative electrode includes a negative electrode collector.

The above negative electrode further includes a lithium metal layer disposed on the negative electrode collector,

The above lithium metal layer includes a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof.

The above lithium alloy contains lithium and a first metal, and the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum or a combination thereof.

The above negative electrode contains a negative electrode active material layer between a lithium metal layer and an electrolyte layer, and the negative electrode active material layer contains a carbon-based material; a mixture of a carbon-based material and at least one selected from a metal and a metalloid; a composite of a carbon-based material and at least one selected from a metal and a metalloid; or a combination thereof.

The above carbon-based material includes amorphous carbon, and the average particle diameter of the amorphous carbon is 10 nm to 100 nm, and the carbon-based material includes carbon black, carbon nanotubes, carbon nanofibers, fullerene, activated carbon, carbon fibers, or a combination thereof.

The above negative electrode further includes a protective layer disposed on the lithium metal layer.

The electrolyte of the above electrolyte layer includes a liquid electrolyte, a gel electrolyte, a solid electrolyte or a combination thereof, and the solid electrolyte includes an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte or a combination thereof.

By using a lithium metal battery according to one embodiment, a method of increasing the participation of a lithium salt, which is expensive compared to a solvent, in the SEI film can reduce the battery manufacturing cost. In addition, it is known that forming a solvation structure that is not completely dissociated significantly inhibits ionic conductivity and reduces the lifespan in a lithium ion battery, but in a lithium metal battery according to one embodiment, by using an electrolyte layer having an incompletely dissociated solvation structure, side reactions occurring in the process of lithium electrodeposition on a negative electrode current collector can be effectively suppressed, thereby improving the lifespan.

According to one embodiment, when a lithium metal battery uses an electrolyte layer containing a nitrile compound such as butyronitrile, when forming a solvation structure of Li ions, neutral molecules are coordinated around Li and in the process of solvation, more electrolyte layers are located inside the first shell, and since the lithium metal battery electrolyte layer is friendly to cations and anions, anions are also located. In the case of a lithium ion battery solvent used for complete dissociation of lithium ions, it is advantageous to induce complete solvent, so a substance that is friendly to lithium cations but relatively less friendly to anions is used. When such a solvent is used, the lithium transfer characteristics are rather poor in general lithium ion batteries, so it is not used. However, when applied to a lithium metal battery according to one embodiment, a strong film is unexpectedly formed on the surface of the negative electrode, which can effectively improve the growth of lithium metal.

When a cation, anion, and electrolyte layer by a single embodiment exist inside the first solvation shell, one or more ions already exist, and this enables the formation of a structure in which three or more cations and anions can exist due to reasons such as the balance of attractive forces between them.

During the first charge, anions move to the lithium surface along with the movement of lithium ions. At this time, in the process of lithium ions being deposited and changing into lithium metal, an SEI film is formed on the surface. The film usually contains an organic substance containing cations and some anions, but according to one embodiment, since more anions move along with lithium, the amount of anion components increases, and this film improves the performance of the lithium metal battery.

Referring to Fig. 1a, an electrolyte layer (30) is laminated on a negative electrode current collector (21). The negative electrode (20) contains a negative electrode current collector (21), and a negative electrode active material layer is absent. The electrolyte layer (30) may contain a separator.

The membrane contains a porous substrate, wherein the porous substrate contains polypropylene, polyethylene, or a combination thereof.

The electrolyte layer may contain an electrolyte, and the electrolyte may be a solid electrolyte, a gel electrolyte, a liquid electrolyte, or a combination thereof.

A positive electrode (10) is placed on top of the above electrolyte layer (30). The positive electrode (10) contains a positive electrode active material layer (12) and a positive electrode current collector (11).

An electrolyte may be further included between the separator (30) and the anode (10). The electrolyte may be a gel electrolyte, a solid electrolyte, a liquid electrolyte, or a combination thereof.

A protective layer may be further disposed on the negative electrode collector (21).

The electrolyte layer (30) is, for example, a separator containing a porous substrate. The pores of the separator may contain a liquid electrolyte or a gel-type polymer electrolyte containing a liquid electrolyte and a cross-linked polymer.

The pore diameter of the membrane is generally 0.01 to 10 ㎛, and the thickness can be generally 5 to 20 ㎛. As such a membrane, for example, an olefin-based polymer such as polypropylene; a sheet or nonwoven fabric made of glass fiber or polyethylene, etc. are used. When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte can also serve as the membrane.

Among the above membranes, specific examples of olefin-based polymers include polyethylene, polypropylene, or multilayer membranes of two or more layers thereof, and mixed multilayer membranes such as a polyethylene/polypropylene two-layer membrane, a polyethylene/polypropylene/polyethylene three-layer membrane, and a polypropylene/polyethylene/polypropylene three-layer membrane may be used.

According to another embodiment, a ceramic coating layer can be formed on both sides of a porous substrate constituting the separator.

By forming a ceramic coating layer, the cell performance of a lithium battery can be improved by suppressing the formation of lithium dendrites through the rigidity of the ceramic coating layer without significantly increasing the resistance of the cell. In addition, by employing a separator having the above-described ceramic coating layer, heat resistance is secured, thereby improving the heat shrinkage characteristics and reducing the material cost of the lithium battery through a reduction in the separator margin for ensuring safety during cell design. In addition, the growth of dendrites on the negative electrode is physically suppressed, thereby improving the long-term life at room temperature and high temperature.

The ceramic coating layer contains inorganic particles and a binder.

Any inorganic particle that can be used when forming a coating layer of a separation membrane can be used, for example, any one of the inorganic oxides of SiO ₂ , Al ₂ O ₃ , Al(OH) ₃ , AlO(OH), TiO ₂ , BaTiO ₃ , ZnO ₂ , Mg(OH) ₂ , AIN(Aluminum Nitride), SiC(Silicon Carbide), BoN(Boron Nitride) or a combination thereof can be used.

As the inorganic particles, BaTiO ₃ , BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-a La _a Zr _1-b Ti _b O ₃ (PLZT, where 0<a<1 and 0<b<1), Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiC or a combination thereof can be used, all of which have a dielectric constant of 5 or higher.

In addition to the ceramic coating layer, inorganic particles having lithium ion transfer capability, such as lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _c Ti _d (PO ₄ ) ₃ , 0<d<2, 0<d<3), lithium aluminum titanium phosphate (Li _a1 Al _b1 Ti _c1 (PO ₄ ) ₃ , 0<a1<2, 0<b1<1, 0<c1<3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ , etc. (LiAlTiP) _a2 O _b2 series glass (0<a2<4, 0<b2<13), lithium lanthanum titanate (Li _a3 La _b3 TiO ₃ , 0<a3<2, 0<b3<3), Li _3.25 Ge _0.25 P _0.75 S ₄ , etc. The same lithium germanium thiophosphate (Li _a4 Ge _b4 P _c2 S _d , 0<a4<4, 0<b4<1, 0<c2<1, 0<d<5), lithium nitride such as Li ₃ N (Li _a5 N _b5 , 0<a5<4, 0<b5<2), SiS ₂ series glass such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ (Li _a6 Si _b6 S _c3 , 0<a6<3, 0<b6<2, 0<c4<4), P ₂ S ₅ series glass such as LiI-Li ₂ SP ₂ S ₅ (Li _a7 P _b7 S _c5 , 0<a7<3, 0<b7<3, 0<c5<7), or mixtures thereof may be further contained.

The above liquid electrolyte contains a lithium salt and an organic solvent.

As the organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphoric acid, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, and ethyl propionate can be used. Carbonate solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, and diethyl carbonate can be used.

Any lithium salt commonly used in lithium secondary batteries can be used as the lithium salt, and as a material that is easily dissolved in the non-aqueous solvent, for example, one or more of the following materials can be used: LiSCN, LiN(CN) ₂ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiC(FSO ₂ ) ₃ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ CF ₃ ) 2 , LiN(SO ₂ F) ₂ , LiSbF ₆ , LiPF ₃ ( _{CF 2} CF ₃ ) ₃ , LiPF ₃ (CF ₃ ) _{3 ,} and LiB(C ₂ O ₄ ) ₂ .

The concentration of the lithium salt may be, for example, 1 to 5 M, 1 to 3 M, 1 to 2.5 M, 1.0 to 2.4 M, or 1.0 to 1.6 M in the liquid electrolyte. In the above range, a sufficient amount of lithium ions required for charging and discharging a lithium metal battery can be generated.

As shown in Fig. 1b, a negative electrode active material layer (22) can be placed between the negative electrode current collector (21) and the separator (30).

According to one embodiment, the negative electrode active material layer (22) can be arranged at the time of assembling the lithium metal battery. According to another embodiment, the negative electrode active material layer can include the negative electrode active material layer by plating lithium metal after charging. The negative electrode active material layer can be a lithium plating layer (plated lithium layer).

The above negative electrode active material layer (22) contains lithium metal or a lithium alloy.

The thickness of the negative electrode active material layer is 1 to 500 um or 10 to 500 um. When the thickness of the negative electrode active material layer is within the above range, the cycle characteristics are improved without decreasing the energy density of the lithium metal battery.

When the negative electrode active material layer is arranged at the time of assembly, it may include only a carbon-based material, a carbon-based material, and at least one selected from metals and metalloids.

The above carbon-based material includes amorphous carbon, and the average particle size of the amorphous carbon is 10 nm to 100 nm, and the carbon-based material includes carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, or a combination thereof.

The above negative active material layer includes a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof, wherein the lithium alloy contains lithium and a first metal.

The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum or a combination thereof.

The negative electrode active material layer (22) may include, for example, lithium foil, lithium powder, or a combination thereof. The lithium foil may include, for example, lithium metal foil, lithium alloy foil, or a combination thereof. The lithium powder may include lithium metal powder, lithium alloy powder, or a combination thereof. A lithium alloy is an alloy of lithium and another metal that can be alloyed with lithium, such as a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, a lithium-tin alloy, etc. The negative electrode active material layer including the lithium metal foil may be, for example, a lithium metal layer. The negative electrode active material layer including the lithium alloy foil may be, for example, a lithium alloy layer. The negative electrode active material layer including the lithium metal powder and/or the lithium alloy powder may be introduced by coating a slurry including the lithium powder and a binder, etc. on the negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer can be made of a metal-based negative electrode active material.

The negative current collector is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative current collector is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited thereto, and any material that is used as an electrode current collector in the relevant technical field may be used. The negative current collector may be composed of one of the above-described metals, or may be composed of an alloy or a coating material of two or more metals. The negative current collector is, for example, in the form of a plate or a foil.

In a lithium metal battery according to an embodiment of the present invention, a protective layer may be further introduced between the negative electrode current collector and the separator. It is also possible to further introduce a protective layer between the negative electrode active material layer and the separator.

The protective layer contains a polymer such as, for example, polyvinyl alcohol, polyimide, vinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, carboxymethyl cellulose, styrene butyrene rubber, or a polymer and an inorganic filler. Examples of the inorganic filler include SiO ₂ , Al ₂ O ₃ , Al(OH) ₃ , AlO(OH), TiO ₂ , BaTiO ₃ , ZnO ₂ , Mg(OH) ₂ , AIN(Aluminum Nitride), SiC(Silicon Carbide), BoN(Boron Nitride) or a combination thereof. Introducing a further protective layer in this way can minimize contact between lithium and the electrolyte, thereby reducing side reactions, and can suppress lithium dendrite growth by creating a uniform flow of lithium ions throughout the electrode.

The thickness of the protective layer is, for example, 1 to 20 um.

In one embodiment of the present invention, the positive electrode current collector (11) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. Since the base film includes a thermoplastic polymer, the base film may be liquefied when a short circuit occurs, thereby suppressing a rapid increase in current. The base film may be, for example, an insulator. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The metal layer may act as an electrochemical fuse and may be cut off when an overcurrent occurs, thereby performing a short circuit prevention function. The limit current and the maximum current may be controlled by controlling the thickness of the metal layer. The metal layer may be plated or deposited on the base film. When the thickness of the metal layer is reduced, the limit current and/or the maximum current of the negative electrode current collector (521b, 522b) decrease, so that the stability of the lithium battery during a short circuit may be improved. A lead tab may be added on the metal layer for connection to the outside. The lead tab may be welded to the metal layer or the metal layer/base film laminate by ultrasonic welding, laser welding, spot welding, or the like. When the base film and/or the metal layer are melted during welding, the metal layer may be electrically connected to the lead tab. In order to make the welding of the metal layer and the lead tab more solid, a metal piece (metal ship) may be added between the metal layer and the lead tab. The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, or the like. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, or the like. After arranging a metal piece on a metal layer, the lead tab can be welded to a metal piece/metal layer laminate or a metal piece/metal layer/base film laminate by welding the metal piece with the lead tab. During welding, the base film, the metal layer, and/or the metal piece melts, so that the metal layer or the metal layer/metal piece laminate can be electrically connected to the lead tab. A metal chip and/or a lead tab can be added to a portion on the metal layer. The base film can have a thickness of, for example, 1 to 50 ㎛, 1.5 to 50 ㎛, 1.5 to 40 ㎛, or 1 to 30 ㎛. When the base film has a thickness in this range, the weight of the electrode assembly can be reduced more effectively. The melting point of the base film can be, for example, 100 to 300°C, 100 to 250°C, or 100 to 200°C. Since the base film has a melting point in this range, the base film can be easily combined with the lead tab during the process of welding the lead tab by melting. Surface treatment such as corona treatment can be performed on the base film to improve the adhesion between the base film and the metal layer. The thickness of the metal layer can be, for example, 0.01 to 3 ㎛, 0.1 to 3 ㎛, 0.1 to 2 ㎛, or 0.1 to ㎛. Since the metal layer has a thickness in this range, the stability of the electrode assembly can be secured while maintaining conductivity. The thickness of the metal piece can be, for example, 2 to 10 ㎛, 2 to 7 ㎛, or 4 to 6 ㎛. Since the metal piece has a thickness in this range, the connection between the metal layer and the lead tab can be performed more easily. Since the negative electrode current collector has this structure, the weight of the electrode can be reduced, and as a result, the energy density can be improved.

In one embodiment of the present invention, the positive electrode current collector may include, for example, a base film and a metal layer disposed on one or both surfaces of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. Since the base film includes a thermoplastic polymer, the base film may be liquefied when a short circuit occurs, thereby suppressing a rapid increase in current. The base film may be, for example, an insulator. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode current collector may additionally include a metal piece and/or a lead tab. For more specific details on the base film, metal layer, metal piece and lead tab of the positive electrode collector, refer to the negative electrode collector described above. Since the positive electrode collector has this structure, the weight of the electrode can be reduced, and as a result, the energy density can be improved.

The negative active material layer may contain a negative active material and a binder.

The negative active material has, for example, a particle form. The negative active material having a particle form has an average particle diameter of, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 100 nm, or 20 nm to 80 nm. When the negative active material has an average particle diameter in this range, reversible plating and/or dissolution of lithium can be facilitated during charge and discharge. The average particle diameter of the negative active material is, for example, a median diameter (D50) measured using a laser particle size distribution analyzer.

The negative electrode active material may include, for example, at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material. The carbon-based negative electrode active material may be, for example, amorphous carbon. The carbon-based negative electrode active material is, but is not necessarily limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., and any material classified as amorphous carbon in the relevant technical field may be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. The metal or metalloid negative electrode active material includes, but is not necessarily limited to, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), and any metal or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used. For example, nickel (Ni) does not form an alloy with lithium, and therefore is not a metal negative electrode active material in the present specification. The negative electrode active material layer includes a type of negative electrode active material among these negative electrode active materials, or includes a mixture of a plurality of different negative electrode active materials. For example, the negative electrode active material layer may include a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture may be, for example, a weight ratio of 10:1 to 1:2, 10:1 to 1:1, 7:1 to 1:1, 5:1 to 1:1, or 4:1 to 2:1. The negative active material included in the negative active material layer may include a mixture of first particles made of, for example, amorphous carbon and second particles made of a metal or a metalloid. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The content of the second particles is 8 to 60 wt%, 10 to 50 wt%, 15 to 40 wt%, or 20 to 30 wt% based on the total weight of the mixture. When the second particles have a content in this range, the cycle characteristics of, for example, a lithium metal battery are further improved.

The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride/hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, or the like, but is not necessarily limited thereto and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders. When the negative electrode active material layer does not include a binder, the negative electrode active material layer can be easily separated from the ceramic coating layer (21) or the negative electrode current collector (21). The content of the binder included in the negative electrode active material layer may be, for example, 1 to 20 wt% with respect to the total weight of the negative electrode active material layer.

When the negative electrode active material layer is present, the thickness of the negative electrode active material layer may be, for example, 1% to 50%, 1% to 30%, 1% to 10%, or 1% to 5% of the thickness of the positive electrode active material layer. If the thickness of the negative electrode active material layer is too thin, lithium dendrites formed between the negative electrode active material layer and the negative electrode current collector may collapse the negative electrode active material layer, making it difficult to improve the cycle characteristics of the lithium metal battery. If the thickness of the negative electrode active material layer increases excessively, the energy density of the lithium metal battery employing the negative electrode (20) may decrease and it may be difficult to improve the cycle characteristics.

When the thickness of the negative electrode active material layer decreases, for example, the charge capacity of the negative electrode active material layer also decreases. The charge capacity of the negative electrode active material layer may be, for example, 0.1% to 50%, 1% to 30%, 1% to 10%, 1% to 5%, or 1% to 2% of the charge capacity. If the charge capacity of the negative electrode active material layer is too small, lithium dendrites formed between the negative electrode active material layer and the negative electrode current collector may collapse the negative electrode active material layer, making it difficult to improve the cycle characteristics of the lithium metal battery. If the charge capacity of the negative electrode active material layer increases too much, the energy density of the lithium metal battery employing the negative electrode (20) may decrease, and it may be difficult to improve the cycle characteristics. The charge capacity of the positive electrode active material layer is obtained by multiplying the charge capacity density (mAh/g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer. When several types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values is the charge capacity of the positive electrode active material layer. The charge capacity of the negative electrode active material layer is also calculated in the same way. That is, the charge capacity of the negative electrode active material layer is obtained by multiplying the charge capacity density (mAh/g) of the negative electrode active material by the mass of the negative electrode active material in the negative electrode active material layer. When several types of negative electrode active materials are used, the charge capacity density × mass value is calculated for each negative electrode active material, and the sum of these values is the capacity of the negative electrode active material layer. Here, the charge capacity densities of the positive electrode active material and the negative electrode active material are capacities estimated using an all-solid-state half-cell using lithium metal as a counter electrode. The charge capacities of the positive electrode active material layer and the negative electrode active material layer are directly measured by the charge capacity measurement using the all-solid-state half-cell. The charge capacity density is obtained by dividing the measured charge capacity by the mass of each active material. Alternatively, the charge capacity of the positive electrode active material layer and the negative electrode active material layer may be the initial charge capacity measured at the first charge cycle.

[Lithium metal battery]

According to one embodiment, a lithium metal battery includes a cathode; an anode; and a separator disposed between the cathode and the anode. Such a lithium metal battery can simultaneously provide excellent life characteristics. The lithium metal battery may be, for example, a lithium primary battery, a lithium secondary battery, a lithium-sulfur battery, a lithium-air battery, etc., but is not limited thereto, and any lithium metal battery used in the relevant technical field may be used.

Lithium metal batteries are manufactured by, for example, the following exemplary methods, but are not necessarily limited to these methods and are adjusted according to required conditions.

(Bipolar)

First, a cathode active material composition is prepared by mixing a cathode active material, a conductive agent, a binder, and a solvent. The prepared cathode active material composition is directly coated on an aluminum current collector and dried to produce a cathode plate having a cathode active material layer formed thereon. Alternatively, the cathode active material composition is cast on a separate support, and then the film obtained by peeling off the support is laminated on the aluminum current collector to produce a cathode plate having a cathode active material layer formed thereon.

The cathode active material is a lithium-containing metal oxide, and any one commonly used in the art can be used without limitation. For example, at least one compound oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used, and specific examples thereof include Li _a A _1-b B _b D ₂ (wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li _a E _1-b B _b O _2-c D _c (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05); LiE _2-b B _b O _4-c D _c (wherein 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li _a Ni _1-bc Co _b B _c D _α (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c D _α (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); A compound represented by any one of the chemical formulas of LiFePO ₄ can be used.

In the chemical formula representing the compound described above, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of the compound described above, or it is also possible to use a mixture of the compound described above and the compound having a coating layer added. The coating layer added to the surface of the above-described compound includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The method for forming the coating layer is selected within a range that does not adversely affect the properties of the positive electrode active material. The coating method is, for example, spray coating, dipping, etc. Since the specific coating method is well understood by those engaged in the relevant field, a detailed description thereof will be omitted.

The cathode active material is, for example, Li _a Ni _x Co _y M _z O _2-b A _b (1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0<y≤0.3, 0<z≤0.3, and x+y+z=1, where M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, and A is F, S, Cl, Br or a combination thereof), LiNi _x Co _y Mn _z O ₂ (0.8≤x≤0.95, 0≤y≤0.2, 0<z≤0.2, and x+y+z=1), LiNi _x Co _y Al _z O ₂ (0.8≤x≤0.95, 0≤y≤0.2, 0<z≤0.2, and x+y+z=1), LiNi _x Co _y Mn _z Al _w O ₂ (0.8≤x≤0.95, 0≤y≤0.2, 0<z≤0.2, 0<w≤0.2, and x+y+z+w=1), Li _a Co _x M _y O _2-b A _b (1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1, and M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), Boron (B) or a combination thereof, and A is F, S, Cl, Br or a combination thereof), Li _a Ni _x Mn _y M' _z O _2-b A _b (1.0≤a≤1.2, 0≤b≤0.2, 0<x≤0.3, 0.5≤y<1, 0<z≤0.3, and x+y+z=1, and M' is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, and A is F, S, Cl, Br or a combination thereof), Li _a M1 _x M2 _y PO _4-b X _b (wherein, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9<x+y<1.1, 0≤b≤2, and M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof, M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof), Li _a M3 _z PO ₄ (0.90≤a≤1.1, 0.9≤z≤1.1, and M3 is chromium (Cr), Manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination of these.

The conductive material may include, but is not limited to, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. Any conductive material used in the relevant technical field may be used. Alternatively, the anode may not include a separate conductive material, for example.

Examples of binders used include vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the aforementioned polymers, styrene butadiene rubber-based polymers, and examples of solvents used include, but are not limited to, N-methylpyrrolidone (NMP), acetone, water, etc., and any solvent used in the relevant technical field may be used.

It is also possible to form pores inside the electrode plate by further adding a plasticizer or a pore forming agent to the positive electrode active material composition.

The contents of the cathode active material, conductive agent, binder, and solvent used in the cathode are at levels typically used in lithium batteries. Depending on the purpose and configuration of the lithium metal battery, one or more of the conductive agent, binder, and solvent may be omitted.

The binder content included in the positive electrode may be 0.1 wt% to 10 wt% or 0.1 wt% to 5 wt% of the total weight of the positive electrode active material layer. The positive electrode active material content included in the positive electrode may be 80 wt% to 99 wt%, 90 wt% to 99 wt% or 95 wt% to 99 wt% of the total weight of the positive electrode active material layer.

The positive electrode collector uses, for example, a plate or foil made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode collector may be omitted. The positive electrode collector (11) may further include a carbon layer disposed on one or both surfaces of the metal substrate. By additionally disposing the carbon layer on the metal substrate, the metal of the metal substrate can be prevented from being corroded by the solid electrolyte included in the positive electrode layer, and the interfacial resistance between the positive electrode active material layer (12) and the positive electrode collector (11) can be reduced. The carbon layer may have a thickness of, for example, 1 ㎛ to 5 ㎛, 1 ㎛ to 4 ㎛, or 1 ㎛ to 3 ㎛. If the carbon layer is too thin, it may be difficult to completely block contact between the metal substrate and the solid electrolyte. If the carbon layer is too thick, the energy density of the all-solid-state secondary battery may decrease. The carbon layer may include amorphous carbon, crystalline carbon, etc.

The thickness of the positive electrode collector is, for example, 1 ㎛ to 100 ㎛, 1 ㎛ to 50 ㎛, 5 ㎛ to 25 ㎛, or 10 ㎛ to 20 ㎛. The thickness of the positive electrode collector is not necessarily limited to the thickness range described above and may be selected depending on the required characteristics of the lithium metal battery.

The cathode current collector may include, for example, a base film and a metal layer disposed on one or both surfaces of the base film. The base film may include, for example, a polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. Since the cathode current collector has such a structure, the weight of the electrode can be reduced, and as a result, the energy density of the lithium metal battery can be improved.

(Separator)

Next, a separator to be inserted between the anode and cathode is prepared.

Any separator that is commonly used in lithium batteries can be used. For example, a separator having low resistance to ion movement of the electrolyte and excellent electrolyte absorption capability is used. The separator is selected from, for example, glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and is in the form of a nonwoven fabric or a woven fabric. For lithium ion batteries, a rollable separator such as polyethylene or polypropylene is used, and for lithium ion polymer batteries, a separator having excellent organic electrolyte absorption capability is used.

The membrane is manufactured by the following exemplary methods, but is not limited to these methods and may be adjusted according to required conditions.

First, a membrane composition is prepared by mixing a polymer resin, a filler, and a solvent. The membrane composition is directly coated on the top of an electrode and dried to form a membrane. Alternatively, the membrane composition is cast on a support and dried, and then a membrane film peeled from the support is laminated on the top of an electrode to form a membrane.

The polymer used in the manufacture of the membrane is not particularly limited, and any polymer used as a binder for the electrode plates may be used. For example, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof may be used.

(cathode)

The cathode contains a cathode current collector.

In one embodiment of the present invention, the negative electrode current collector may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. Since the base film includes a thermoplastic polymer, the base film may be liquefied when a short circuit occurs, thereby suppressing a rapid increase in current. The base film may be, for example, an insulator. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The metal layer may act as an electrochemical fuse and may be cut off when an overcurrent occurs, thereby performing a short circuit prevention function. The limit current and the maximum current may be controlled by controlling the thickness of the metal layer. The metal layer may be plated or deposited on the base film. When the thickness of the metal layer is reduced, the limit current and/or the maximum current of the negative electrode current collector (521b, 522b) decrease, so that the stability of the lithium battery during a short circuit may be improved. A lead tab may be added on the metal layer for connection to the outside. The lead tab may be welded to the metal layer or the metal layer/base film laminate by ultrasonic welding, laser welding, spot welding, or the like. When the base film and/or the metal layer are melted during welding, the metal layer may be electrically connected to the lead tab. In order to make the welding of the metal layer and the lead tab more solid, a metal piece (metal ship) may be added between the metal layer and the lead tab. The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, or the like. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, or the like. After arranging a metal piece on a metal layer, the lead tab can be welded to a metal piece/metal layer laminate or a metal piece/metal layer/base film laminate by welding the metal piece with the lead tab. During welding, the base film, the metal layer, and/or the metal piece melts, so that the metal layer or the metal layer/metal piece laminate can be electrically connected to the lead tab. A metal chip and/or a lead tab can be added to a portion on the metal layer. The base film can have a thickness of, for example, 1 to 50 ㎛, 1.5 to 50 ㎛, 1.5 to 40 ㎛, or 1 to 30 ㎛. When the base film has a thickness in this range, the weight of the electrode assembly can be reduced more effectively. The melting point of the base film can be, for example, 100 to 300°C, 100 to 250°C, or 100 to 200°C. Since the base film has a melting point in this range, the base film can be easily combined with the lead tab during the process of welding the lead tab by melting. Surface treatment such as corona treatment can be performed on the base film to improve the adhesion between the base film and the metal layer. The thickness of the metal layer can be, for example, 0.01 ㎛ to 3 ㎛, 0.1 ㎛ to 3 ㎛, 0.1 ㎛ to 2 ㎛, or 0.1 to 1 ㎛. Since the metal layer has a thickness in this range, the stability of the electrode assembly can be secured while maintaining conductivity. The thickness of the metal piece can be, for example, 2 ㎛ to 10 ㎛, 2 ㎛ to 7 ㎛, or 4 ㎛ to 6 ㎛. Since the metal layer has a thickness in this range, the connection between the metal layer and the lead tab can be performed more easily. Since the negative electrode current collector has this structure, the weight of the electrode can be reduced, and as a result, the energy density can be improved.

A negative electrode active material layer may be formed on the negative electrode current collector. The negative electrode active material layer may be formed as a lithium deposition layer after charging. Alternatively, the negative electrode active material layer may be formed using a negative electrode active material during battery assembly.

The method of forming a negative electrode active material layer using a negative electrode active material can be manufactured in the same manner as described above, except that the negative electrode active material is used instead of the positive electrode active material when forming the positive electrode active material layer.

The lithium metal battery may further include, for example, a thin film including an element capable of forming an alloy with lithium on one surface of the negative electrode current collector. The thin film is disposed between the negative electrode current collector and the negative electrode active material layer. The thin film includes, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but is not necessarily limited thereto, and any element capable of forming an alloy with lithium in the relevant technical field may be used. The thin film may be composed of one of these metals, or may be composed of an alloy of several types of metals. By disposing the thin film on one surface of the negative electrode current collector, for example, the deposition form of the first negative electrode active material layer deposited between the thin film and the negative electrode active material layer becomes flatter, and the cycle characteristics of the lithium metal battery may be further improved.

(Separator)

A separation membrane according to an embodiment of the present invention is used.

Organic electrolytes are manufactured, for example, by dissolving lithium salts in organic solvents.

Any organic solvent used in the art may be used. Examples of the organic solvent include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

Any lithium salt used in the art may be used. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiSbF 6 , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO _{2 ) 2} N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ )(1≤x≤20, 1≤y≤20), LiCl, LiI or mixtures thereof. The concentration of the lithium salt is 0.1 M to 5.0 M, 0.1 M to 3.0 M, 1.0 to 2.4 M, 1.0 to 1.6 M, for example, 1.2 M.

The lithium metal battery according to one embodiment may further include a solid electrolyte, a gel electrolyte, a liquid electrolyte, or a combination thereof. The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

A gel electrolyte is an electrolyte that contains a cross-linked polymer and a liquid electrolyte and has a gel form.

The solid electrolyte is, for example, an oxide-based solid electrolyte. _The oxide-based solid electrolyte is Li _{1+x+y Al x Ti 2 -x} Si _y P _{3 -y} O ₁₂ (0<x<2, _0≤y <3), Li _{3 PO 4} , _Li (Al, _Ga ) _{x ( Ti} , _{Ge ) 2-x Si y P 3 - y O 12 ( 0≤x≤1 0≤y≤1 ) , Li 2} , Li _3+x La ₃ M ₂ O ₁₂ (M = Te, Nb, or Zr, x is an integer from 1 to 10). The solid electrolyte is manufactured by a sintering method, etc. For example, the oxide-based solid electrolyte is a garnet-type solid electrolyte selected from Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) and Li _3+x La ₃ Zr _2-a M _a O ₁₂ (M doped LLZO, M = Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10, 0<a<2).

The sulfide-based solid electrolyte may include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof. The sulfide-based solid electrolyte particles may include Li ₂ S, P ₂ S ₅ , SiS ₂ , GeS ₂ , B ₂ S _{3 ,} or a combination thereof. The sulfide-based solid electrolyte particles may be Li ₂ S or P ₂ S ₅ . Sulfide-based solid electrolyte particles are known to have high lithium ion conductivity compared to other inorganic compounds. For example, the sulfide-based solid electrolyte includes Li ₂ S and P ₂ S ₅ . When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte includes Li ₂ SP ₂ S ₅ , the mixing molar ratio of Li ₂ S to P ₂ S ₅ may be, for example, in a range of about 50:50 to about 90:10. Additionally, an inorganic solid electrolyte prepared by adding Li ₃ PO ₄ , a halogen, a halogen compound, Li _2+2x Zn _1-x GeO ₄ ("LISICON", 0≤x<1), Li _3+y PO _4-x N _x ("LIPON", 0<x<4, 0<y<3), Li _3.25 Ge _0.25 P _0.75 S ₄ ("ThioLISICON"), Li ₂ O-Al ₂ O ₃ -TiO ₂ -P ₂ O ₅ ("LATP"), or the like to Li ₂ SP ₂ S ₅ , SiS ₂ , GeS ₂ , B ₂ S ₃ , or a combination thereof can be used as the sulfide solid electrolyte. Non-limiting examples of the sulfide solid electrolyte material include Li ₂ SP ₂ S ₅ ; Li ₂ SP ₂ S ₅ -LiX (X = halogen element); Li ₂ SP ₂ S ₅ -Li ₂ O; Li ₂ SP ₂ S ₅ -Li ₂ O-LiI; Li ₂ S-SiS ₂ ; Li ₂ S-SiS ₂ -LiI; Li ₂ S-SiS ₂ -LiBr; Li ₂ S-SiS ₂ -LiCl; Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI; Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI; Li ₂ SB ₂ S ₃ ; Li ₂ SP ₂ S ₅ -Z _m S _n (0<m<10, 0<n<10, Z=Ge, Zn or Ga); Li ₂ S-GeS ₂ ; Li ₂ S-SiS ₂ -Li ₃ PO ₄ ; and Li ₂ S-SiS ₂ -Li _p MO _q (0<p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga or In). In this regard, the sulfide-based solid electrolyte material can be manufactured by treating the raw material starting material of the sulfide-based solid electrolyte material (e.g., Li ₂ S, P ₂ S ₅ , etc.) by a melt quenching method, a mechanical milling method, or the like. In addition, a calcinations process can be performed after the treatment. The sulfide-based solid electrolyte can be amorphous, crystalline, or a mixed state thereof.

The above sulfide-based solid electrolyte is, for example, Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiX, where X is a halogen element, Li ₂ SP ₂ S ₅ -Li ₂ O, Li ₂ SP ₂ S ₅ -Li ₂ O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -Z _m S _n , where m, n is a positive number, and Z is one of Ge, Zn, or Ga, Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _p MO _q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, and at least one selected from Li _7-x PS _6-x Cl _x (0<x<2), Li _7-x PS _6-x Br _x (0<x<2), and Li _7-x PS _6-x I _x (0<x<2).

. The sulfide-based solid electrolyte is manufactured by processing starting materials such as Li ₂ S, P ₂ S ₅ by a melting rapid cooling method or a mechanical milling method. In addition, a heat treatment may be performed after the processing. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, a material containing sulfur (S), phosphorus (P), and lithium (Li) as constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material containing Li ₂ SP ₂ S ₅ . When using a sulfide-based solid electrolyte material containing Li ₂ SP ₂ S ₅ to form the solid electrolyte, the mixing molar ratio of Li ₂ S and P ₂ S ₅ is, for example, in a range of Li ₂ S : P ₂ S ₅ = 50 : 50 to 90 : 10.

The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 1:

<Chemical formula 1>

_Li ⁺ _{12- nx} ^{A n +}

In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N ₃ , and 1(n(5, 0(x(2). The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li _{7 -x} PS _{6-x Cl x} , 0≤x≤2, Li _7-x PS _{6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x} , 0≤x≤2. The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li ₆ PS ₅ Cl, Li ₆ PS ₅ Br and Li ₆ PS ₅ I.

The density of the argyrodite-type solid electrolyte can be 1.5 to 2.0 g/cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g/cc or more, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

The elastic modulus, i.e., Young's modulus, of the sulfide-based solid electrolyte can be, for example, 35 GPa or less, 30 GPa or less, 27 GPa or less, 25 GPa or less, or 23 GPa or less. The elastic modulus, i.e., Young's modulus, of the sulfide-based solid electrolyte can be, for example, 10 to 35 GPa, 10 to 30 GPa, 10 to 27 GPa, 10 to 25 GPa, or 10 to 23 GPa. Since the sulfide-based solid electrolyte has an elastic modulus in this range, the temperature and/or pressure required for sintering, etc. is reduced, and therefore, sintering of the solid electrolyte can be performed more easily.

A polymer solid electrolyte is an electrolyte that includes, for example, a mixture of a lithium salt and a polymer, or a polymer having an ion-conducting functional group. A polymer solid electrolyte is, for example, a polymer electrolyte that does not include a liquid electrolyte. Polymers included in the polymer solid electrolyte include, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA), poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), Polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone), SPEEK, sulfonated poly(arylene ether ketone ketone sulfone), SPAEKKS, sulfonated poly(aryl ether ketone), SPAEK, poly[bis(benzimidazobenzisoquinolinones)], SPBIBI, poly(styrene sulfonate), PSS, lithium 9,10-diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi ⁺ ) or a combination thereof, but is not limited thereto, and any that can be used as a polymer electrolyte in the relevant art may be used. The lithium salt may be any that can be used as a lithium salt in the relevant art. The lithium salt is, for example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof.

A gel electrolyte is, for example, a gel polymer electrolyte. A gel polymer electrolyte is, for example, an electrolyte comprising a liquid electrolyte and a polymer, or comprising an organic solvent and a polymer having an ion-conducting functional group. The liquid electrolyte can be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer can be selected from polymers used in solid polymer electrolytes. The organic solvent can be selected from organic solvents used in liquid electrolytes. The lithium salt can be selected from lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature and is liquid at room temperature or a room temperature molten salt that consists only of ions. The ionic liquid may include at least one selected from compounds comprising, for example, a) at least one cation selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) at least one anion selected from BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, SO4-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-. A gel polymer electrolyte can be formed by impregnating a polymer solid electrolyte into an electrolyte solution within a lithium battery. The gel electrolyte may further contain inorganic particles.

(lithium metal battery)

Referring to Fig. 5, a lithium metal battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2), and an electrolyte layer (4). The electrolyte layer may contain a separator.

According to one embodiment, a separator can be used as an electrolyte layer (4).

An electrolyte (not shown) may be placed between the separator and the cathode. The cathode (3), the anode (2), and the electrolyte layer (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). An organic electrolyte is injected into the battery case (5) and sealed with a cap assembly (6), thereby completing the lithium metal battery (1). The battery case (5) is cylindrical, but is not necessarily limited to this shape, and may be, for example, square, thin-film, etc.

Referring to FIG. 6, a lithium metal battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2), and an electrolyte layer (4). The electrolyte layer may contain a separator. According to one embodiment, a separator may be used as the electrolyte layer (4).

An electrolyte layer (4) is arranged between the positive electrode (3) and the negative electrode (2), and the positive electrode (3), the negative electrode (2), and the electrolyte layer (4) are wound or folded to form a battery structure (7). According to one embodiment, a separator may be used as the electrolyte layer (4). The battery structure (7) formed in this manner is accommodated in a battery case (5). An electrode tab (8) that acts as an electrical path for inducing current formed in the battery structure (7) to the outside may be included. An organic electrolyte is injected into the battery case (5) and sealed to complete the lithium metal battery (1). The battery case (5) is square, but is not necessarily limited to this shape, and may be, for example, cylindrical, thin-film, etc.

An electrolyte (not shown) may be placed between the separator and the anode.

Referring to FIG. 7, a lithium metal battery (1) according to one embodiment includes a cathode (3), an anode (2), and an electrolyte layer (4). An electrolyte layer (4) is arranged between the cathode (3) and the anode (2), thereby forming a battery structure. The electrolyte layer may include a separator containing a porous substrate.

A gel-type polymer electrolyte can be placed between the separator and the anode.

The battery structure (7) is stacked in a bi-cell structure and then accommodated in a battery case (5). It may include an electrode tab (8) that acts as an electrical path for guiding the current formed in the battery structure (7) to the outside. An organic electrolyte is injected into the battery case (5) and sealed, thereby completing the lithium metal battery (1). The battery case (5) is square, but is not necessarily limited to this shape, and may have, for example, a cylindrical shape, a thin film shape, etc.

In Fig. 7, an electrolyte can be placed instead of the separator (4), and an electrolyte (not shown) can be placed between the separator and the anode.

The pouch-type lithium metal battery corresponds to the lithium metal batteries of FIGS. 6 and 7, each of which uses a pouch as a battery case. The pouch-type lithium metal battery includes one or more battery structures. A separator is disposed between a cathode and an anode to form a battery structure. The battery structures are laminated in a bi-cell structure, then impregnated with an organic electrolyte, and accommodated and sealed in a pouch, thereby completing a pouch-type lithium metal battery. For example, although not shown in the drawings, the above-described cathode, anode, and separator may be simply laminated and accommodated in a pouch in the form of an electrode assembly, or may be wound or folded into a jellyroll-type electrode assembly and then accommodated in a pouch. Subsequently, an organic electrolyte is injected into the pouch and sealed, thereby completing a lithium metal battery.

The lithium metal battery of the present disclosure has excellent discharge capacity and life characteristics and high energy density, and is therefore used in, for example, electric vehicles (EVs). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it is used in fields that require a large amount of power storage. For example, it is used in electric bicycles, power tools, etc.

A plurality of lithium metal batteries are stacked to form a battery module, and the plurality of battery modules form a battery pack. This battery pack can be used in all devices requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc. The battery module includes, for example, a plurality of batteries and a frame that holds them. The battery pack includes, for example, a plurality of battery modules and a bus bar that connects them. The battery module and/or the battery pack may further include a cooling device. The plurality of battery packs are controlled by a battery management system. The battery management system includes a battery pack and a battery control device connected to the battery pack.

[Method for manufacturing lithium metal batteries]

According to one embodiment, a lithium metal battery includes a step of preparing an anode; a step of preparing an anode; a step of preparing an assembly using the anode and the cathode; and a step of providing an electrolyte to the assembly, wherein the electrolyte includes a nitrile compound, a lithium salt, and a carbonate compound, and the lithium salt includes lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF ₄ ), and a content of the nitrile compound is 3 wt% to 45 wt% based on 100 wt% of the total weight of the electrolyte. A lithium metal battery can be manufactured.

An assembly can be prepared by interposing a separator between the positive and negative electrodes.

The above electrolyte may further include a solid electrolyte, a liquid electrolyte, a gel electrolyte, or a combination thereof. And the solid electrolyte includes an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

The above gel electrolyte can be formed by injecting and crosslinking a gel-type electrolyte composition including a polymerizable monomer, a liquid electrolyte, and an initiator into an assembly. The step of injecting the composition for forming a gel-type polymer electrolyte into the assembly can be an impregnation step performed under vacuum so that the composition can sufficiently penetrate into the pores of the porous substrate.

A method for forming a gel-type polymer electrolyte may include a method of curing using heat, UV, or high-energy radiation (electron beam, γ-ray). The curing reaction using heat may be performed at a temperature of 40 to 120°C, for example, 50 to 90°C, for 30 to 120 minutes.

The above heat treatment varies depending on the type of polymerizable monomer, but is performed at, for example, 40 to 120°C.

The composition for forming the above gel-type polymer electrolyte may further include a crosslinking agent, a temperature-responsive initiator, etc. to assist in crosslinking of the crosslinkable monomer. The crosslinking agent, initiator, etc. are not particularly limited as long as they are generally used in the relevant technical field.

Trimethylolpropane triacrylate, etc. can be used as a crosslinking monomer.

The initiator can be, for example, benzoin ethyl ether.

The content of the crosslinking agent, initiator, etc. may be within a conventional range. The content of the initiator may be, for example, 0.1 to 5 parts by weight, or 0.2 to 3 parts by weight, based on 100 parts by weight of the total content of the monomer for forming the crosslinking polymer. Using the gel-type polymer electrolyte formed in this way, the ionic conductivity can be maintained at a value close to that of the liquid electrolyte, and the gel-type polymer electrolyte inside the positive and negative electrodes can play a role in preventing leakage of the liquid electrolyte. The electrolyte can be trapped in the polymer matrix of the gel-type polymer electrolyte and maintained within the polymer matrix, thereby helping the smooth movement of lithium ions. In addition, the excellent electrochemical properties of the polymer can suppress the electrolyte decomposition reaction within a range of -1 V to 5 V.

The ionic conductivity of the gel polymer electrolyte is 0.26 mS/cm or more, for example, 0.26 to 1.0 mS/cm, or 0.3 to 1.0 mS/cm.

The present creative idea is explained more specifically through the following examples and comparative examples. However, the examples are provided to illustrate the present creative idea and the scope of the present creative idea is not limited to these examples.

Example 1: BN 10%, FEC and DEC in 42:48 weight ratio, 0.6 M LiDFOB and 0.6 M LiBF ₄

A polyethylene single film with a thickness of 20 μm was laminated as a separator on a copper foil with a thickness of 10 μm as a negative current collector, and a cathode was laminated on the other side of the separator to manufacture a laminate. A liquid electrolyte was injected into the prepared laminate to manufacture a lithium metal battery.

Lithium metal batteries have a cathode/separator/negative electrode collector structure.

A liquid electrolyte was prepared by adding 0.6 M lithium difluoro(oxalate)borate (LiDFOB) and 0.6 M LiBF 4 to a mixed solvent of fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and butyronitrile (BN) in a weight ratio of _42:48:10 . Here, the content of BN is 10 wt% based on 100 wt% of the total weight of the liquid electrolyte.

The above anode was manufactured according to the following method.

Li _1.04 Ni _0.88 Co _0.1 Al _0.02 O ₂ powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then PVDF (polyvinylidene fluoride) binder solution was added to prepare a cathode active material slurry having a weight ratio of active material:carbon conductive material:binder = 95.5:2:2.5.

The manufactured slurry was coated on a 15 ㎛ thick aluminum substrate using a coater, dried under reduced pressure at 120°C, and then rolled into a sheet using a roll press to manufacture a positive electrode.

Example 2: BN 25%, FEC and DEC with 33:42 weight ratio, 0.6 M LiDFOB and 0.6 M LiBF ₄

A lithium metal battery was manufactured in the same manner as in Example 1, except that the content of BN, FEC, and DEC in the manufacture of the liquid electrolyte was changed to the conditions shown in Table 3 below.

Example 3: BN 43%, FEC and DEC at 19:38 wt. ratio, 0.6 M LiDFOB and 0.6 M LiBF ₄

A lithium metal battery was manufactured in the same manner as in Example 1, except that the content of BN, FEC, and DEC in the manufacture of the liquid electrolyte was changed to the conditions shown in Table 3 below.

Example 4: BN 25%, FEC and DEC in 33:41 weight ratio, 0.8 M LiDFOB and 0.8 M LiBF ₄

A lithium metal battery was manufactured in the same manner as in Example 1, except that the content of BN, FEC, and DEC in the manufacture of the liquid electrolyte was changed to the conditions shown in Table 3 below.

Example 5: BN 43%, FEC and DEC at 19:38 wt. ratio, 0.8 M LiDFOB and 0.8 M LiBF ₄

A lithium metal battery was manufactured in the same manner as in Example 1, except that the content of BN, FEC, and DEC in the manufacture of the liquid electrolyte was changed to the conditions shown in Table 3 below.

Example 6

A lithium metal battery was manufactured in the same manner as in Example 1, except that the mixing weight ratio of 0.4 M LiDFOB and 0.6 M LiBF ₄ was changed to 2:3 (1:1.5).

Example 7

A lithium metal battery was manufactured in the same manner as in Example 1, except that the mixing weight ratio of 0.9 M LiDFOB and 0.6 M LiBF ₄ was changed to 3:2 (1:0.67).

Example 8

A lithium metal battery was manufactured in the same manner as in Example 1, except that the mixing weight ratio of 1.1 M LiDFOB and 0.6 M LiBF ₄ was changed to 1:0.55.

Example 9: Lithium metal battery

A positive electrode was manufactured in the same manner as in Example 1, except that LiCoO ₂ was used instead of Li _1.04 Ni _0.88 Co _0.1 Al _0.02 O ₂ powder as the positive electrode active material during the manufacture of the positive electrode.

Comparative Example 1: BN-free, 45:55 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄

A lithium metal battery was manufactured by following the same method as Example 1, except that the liquid electrolyte was obtained by the following process without adding butyronitrile as a liquid electrolyte.

A liquid electrolyte was prepared by adding 0.6 M LiDFOB (lithium difluoro(oxalate)borate) and 0.6 M LiBF ₄ to a mixed solvent of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) in a weight ratio of 45:55.

Comparative Example 2: BN 52%, FEC and DEC with 11:37 weight ratio, 0.6M LiDFOB and 0.6M LiBF ₄

A lithium metal battery was manufactured in the same manner as in Example 1, except that the liquid electrolyte was manufactured by adding 0.6 M LiDFOB (lithium difluoro(oxalate)borate) and 0.6 M LiBF ₄ to a 2:1 volume ratio mixed solvent of fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and butyronitrile (BN) in a weight ratio of 11:37:52.

Comparative Example 3: BN 52%, FEC and DEC with 11:37 weight ratio, 0.8M LiDFOB and 0.8M LiBF ₄

When manufacturing a liquid electrolyte, 0.8 M LiDFOB (lithium difluoro(oxalate)borate) and 0.8 M LiBF ₄ were added to a mixed solvent of fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and BN in a weight ratio of 11:37:52 to prepare a mixture.

Comparative Example 4: Graphite Anode Lithium Secondary Battery

On a 10 μm thick copper foil as a negative current collector, 9.51 g of graphite, 0.003 g of CNT as a conductive material, 0.05 g of carbon black, 0.20 g of aqueous styrene-butadiene rubber (SBR) as a binder, and 0.08 g of CMC as a thickener were mixed. These were added to water as a solvent and mixed to prepare a negative electrode slurry. The prepared negative electrode slurry was applied to one surface of a copper current collector and dried at about 60°C for 24 hours to form a negative electrode active material layer. A 20 μm thick polyethylene single film was laminated as a separator thereon, and a positive electrode was laminated on the other surface of the separator to prepare a laminate. A liquid electrolyte was injected into the prepared laminate to prepare a lithium metal battery.

A positive electrode was manufactured in the same manner as in Example 1, except that LiCoO ₂ was used instead of Li _1.04 Ni _0.88 Co _0.1 Al _0.02 O ₂ powder as the positive electrode active material during the manufacture of the positive electrode.

Lithium metal batteries have a cathode/separator/negative electrode active material layer/negative electrode current collector structure.

Table 3 below summarizes the composition of the electrolyte used in some of the above examples and comparative examples.

division Content of LiDFOB (M) Content of LiBF4 (M) Weight ratio FEC DEC BN Example 1 0.6 0.6 42 48 10 Example 2 0.6 0.6 33 42 25 Example 3 0.6 0.6 19 38 43 Example 4 0.8 0.8 33 41 25 Example 5 0.8 0.8 19 38 43 Comparative Example 13 0.6 0.6 45 55 - Comparative Example 2 0.6 0.6 11 37 52 Comparative Example 3 0.8 0.8 11 37 52

Evaluation Example 1: XPS Analysis

The XPS analysis spectra of the lithium metal surfaces of the lithium metal batteries of Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated. The XPS analysis was performed using ESCALAB250 (Thermofischer), X-ray source: Al Kα (1486.6 eV) mono 500 μm, pass energy: 30 eV, CAE mode, calibrated by C 248.8 eV.

The evaluation results are shown in Table 4 and FIGS. 2a to 2f below. FIG. 2 shows the evaluation results for Example 1 and Comparative Example 1. In addition, Table 4 below shows the ratio of the elemental area of B1s and F1s originating from anions to the elemental area of Li 1s originating from lithium ions, which are cations, in the lithium metal batteries of Examples 1 to 5 and Comparative Examples 1 to 3.

In Table 4 below, the area for each element was calculated by adding the spectrum areas of each element and setting them as 100, and then adding up the areas corresponding to each element. In addition, Table 5 below shows the atomic percentages of Example 1 and Comparative Example 1.

The area of the Li1s peak refers to the total area of Li-F, LiOH, Li2Co2, and LiBO2 peaks appearing at binding energies of 280 to 294 eV, the area of the B1s peak refers to the total area of BF, B=O, BO, BN, and LixBFy peaks appearing at binding energies of 186 to 200 eV, and the F1s peak refers to the total area of BF, and Li-F peaks appearing at binding energies of 682 to 692 eV. And the O1s peak refers to the total area of CO, _B2O3 , _CO3 , N-( _C =O), _LiB02 , and Li-O peaks appearing at binding energies of 527 to 537 eV.

division Electrolyte Area of Li1s peak (A1): Area of F1s peak (B1) and total area of B1s peak (B1+B2) Total area of the area of the F1s peak (B1) and the area of the B1s peak (B2) (B1+B2): Area of the O1s peak (C1) Example 1 BN 10%, 42:48 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 1:0.75
1:1.3 Example 2 BN 25%, 33:41 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 1:0.86
1:1.17 Example 3 BN 43%, 19:38 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 1:0.99

1:0.97 Example 4 BN 25%, 33:41 weight ratio FEC and DEC, 0.8M LiDFOB and 0.8M LiBF ₄ 1:1.03
1:0.79 Example 5 BN 43%, 19:38 weight ratio FEC and DEC, 0.8M LiDFOB and 0.8M LiBF ₄ 1:1.19
1:0.65 Comparative Example 1 BN free, 45:55 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 1:0.68 1:1.51 Comparative Example 2 BN 52%, 11:37 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 1:1.27 1:0.88 Comparative Example 3 BN 52% , 11:37 weight ratio FEC and DEC, 0.8M LiDFOB and 0.8M LiBF ₄ 1:1.33 1:0.59

Referring to Table 4, when the component formed from anions in the film increases to form a film, and in the case of organic molecules participating in the film-forming reaction, when the film is formed through organic molecules induced by CO ₃ , the lithium metal battery employing this has improved high-temperature charge/discharge characteristics and capacity retention rate, as can be seen from Evaluation Examples 3 and 4 below. In particular, as the BN content increased, the intensity and area of the BF peak of F1s and the Li-F peak and the BF peak of B1s continuously increased. However, in cases where the CO ₃ peak of O1s significantly decreased as in Comparative Examples 2 and 3, it was confirmed that the high-temperature charge/discharge characteristics and the capacity retention rate deteriorated due to the deterioration of the film characteristics in the part formed by the organic substance, as can be seen from Evaluation Examples 3 and 4 below.

In addition, referring to FIGS. 2a to 2f, it was found that the lithium metal battery of Example 1 had stronger intensities of BF peak, CN, BO, and Li-F peaks and increased peak areas compared to the lithium metal battery of Comparative Example 1. These results were obtained by using BN, a neutral molecule having strong anion interaction in addition to Li ⁺ interaction according to Example 1, to induce anions to move together when lithium ions move from the positive electrode to the negative electrode during the initial charge, thereby forming a strong film on the negative electrode rich in B and F, which are rich in anions.

division Li1s C1s O1s F1s B1s N1s Cop3 Example 1 25.9 28.6 25.2 11.3 8.1 0.6 0.2 Comparative Example 1 26.3 27.5 27.3 10.4 7.7 0.5 0.2

From Table 5, we could know the ratio of elements that contributed to the components of the organic and inorganic complex film formed on the lithium metal surface. Since the film component is mainly observed on the surface, each element originates from the liquid electrolyte, and from this, we can know the components of the substances that participated in the cluster participating in the film formation. By confirming the degree to which the sum of the 1s peak area of B originating from the anion and the F1s peak area originating from the anion and FEC increases compared to the cation, we could know whether the anion included in the solvation cluster increased.

Evaluation Example 2: Raman Analysis

In the lithium metal batteries of Example 1 and Comparative Example 1, Raman analysis of F1s on the lithium metal surface was performed.

Raman analysis was performed using LabRAM HR Evolution (HORIBA) (laser system: 325, 532, 633, 785, 1064 nm, lowest Raman shift: approximately 50 cm-1, spatial resolution: approximately 200 nm).

The Raman analysis results are shown in Figs. 3a and 3b, and through these, the area (Ac) of the peak (peak c) at wavenumbers 695 to 725 eV and the area (Ad) of the peak (peak d) at wavenumbers 715 to 745 eV and their area ratio (Ac/A _d ) were investigated, and some of them are shown in Table 6 below. The peak (peak c) at wavenumbers 695 to 725 cm ^-1 is a Li coordinated DFOB-peak, and the peak (peak d) at wavenumbers 715 to 745 cm ^-1 is a Free It is for FEC, and the peak (peak e) at wavenumber 735 to 750 cm ^-1 is Li coordinated FEC. It's about peak.

division LiDFOB:LiBF4 1:1 Area of each peak (%) Area ratio (Ac/A _d ) Li coordinated
DFOB-
peak c
(695-725 cm ^-1 ) Free FEC
peak d
(715-745 cm ^-1 ) Li coordinated
FEC
735-750 cm ^-1) Example 1 0.6M 0.6M 37.75% 57.5% 4.75% 0.7 Comparative Example 1 0.6M 0.6M 23.6% 69.8% 6.6% 0.3

Referring to Table 6, it was found that the area ratio (Ac/A _d ) of peak c, which is a Li coordinated DFOB- peak, and the area ratio of peak d related to free FEC in the lithium metal battery of Example 1 increased compared to the area ratio (Ac/A _d ) of the lithium metal battery of Comparative Example 1.

From this, it was found that the lithium metal battery using the electrolyte with 10 wt% BN added according to Example 1 had a higher concentration of anions around lithium compared to the lithium metal battery of Comparative Example 1 using the electrolyte not containing butyronitrile (BN), and thus an SEI film with a relatively high inorganic content was formed on the lithium metal surface.

Evaluation Example 3: High Temperature (45℃) Lifespan

The charge/discharge characteristics of the lithium metal batteries of Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated under the following conditions.

The cell was charged under constant current at 0.1 C rate at 45°C until the voltage reached 4.3 V (vs. Li), then cut-off at 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the cell was discharged under constant current at 0.1 C rate until the voltage reached 3.0 V (vs. Li) (formation cycle).

A lithium metal battery that had undergone a Mars cycle was charged under constant current at 0.2 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged under constant current at 0.5 C rate until the voltage reached 3.0 V (vs. Li) (1 ^st cycle). These cycles were repeated under the same conditions up to the ^200th cycle.

In all charge/discharge cycles, a pause of 10 minutes was allowed after one charge/discharge cycle. Some of the results of the room temperature charge/discharge experiments are shown in Figs. 2a to 2c. The capacity retention rate is defined by Equation 1 below and the results are shown in Table 7 below.

<Formula 1>

Capacity retention rate [%] = [Discharge capacity at ^200th cycle / Discharge capacity at ^2nd cycle] × 100

division Electrolyte Capacity retention rate
(%) Example 1 BN 10%, 42:48 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 84.8 Example 2 BN 25%, 33:41 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 83.0 Example 3 BN 43%, 19:38 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 84.2 Example 4 BN 25%, 33:41 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 84.1 Example 5 BN 43%, 19:38 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 85.6 Comparative Example 1 BN free, 45:55 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 79.3 Comparative Example 2 BN 52%, 11:37 weight ratio FEC and DEC, 0.6M LiDFOB and 0.6M LiBF ₄ 78.2 Comparative Example 3 BN 52%, 11:37 weight ratio FEC and DEC, 0.8M LiDFOB and 0.8M LiBF ₄ 81.6

As shown in Table 7, the lithium metal batteries of Comparative Examples 1 to 3 had a reduced capacity retention rate due to lithium and electrolyte side reactions resulting from dendrite growth.

In comparison, the lithium metal batteries of Examples 1 to 5 showed improved capacity retention rates, unlike the lithium metal batteries of Comparative Examples 1 to 3. This improved capacity retention rate is because the liquid electrolyte physically suppressed dendrite growth compared to the case where BN was not used at the same molar concentration due to the effect of a film on the lithium metal formed robustly by changing the composition of the material arriving at the initial negative electrode by changing the component within the Li solvation shell, thereby improving the high-temperature long-term life characteristics. In addition, the lithium metal batteries of Examples 1 to 5 showed improved capacity retention rates because the anion interaction was improved, thereby improving the initial completeness of the film.

Evaluation Example 4: Viscosity, initial capacity and capacity retention rate

The conductivity, viscosity, initial capacity and capacity retention rate of the electrolytes of lithium metal batteries manufactured according to Examples 1, 6 and 7 were investigated and are shown in Table 7 below.

In Table 7 below, the initial capacity and capacity retention rate were analyzed according to the following conditions.

The cell was charged under constant current at 0.1 C rate at 25°C until the voltage reached 4.3 V (vs. Li), then cut-off at 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the cell was discharged under constant current at 0.1 C rate until the voltage reached 3.0 V (vs. Li) (formation cycle).

A lithium metal battery that had undergone a Mars cycle was charged under constant current at 0.2 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged under constant current at 0.5 C rate until the voltage reached 3.0 V (vs. Li) (1 ^st cycle). These cycles were repeated under the same conditions up to the ^60th cycle.

In all charge/discharge cycles, a pause of 10 minutes was allowed after one charge/discharge cycle. The initial capacity is defined by Equation 2 below, and the capacity retention rate is defined by Equation 3 below, and the results are shown in Table 8 below.

<Formula 2>

Initial capacity (%) = (discharge capacity in 1st cycle / charge capacity in 1st cycle) × 100

<Formula 3>

Capacity retention rate [%] = [Discharge capacity at ^60th cycle / Discharge capacity at ^2nd cycle] × 100

division Salt rain
(LiDFOB:LiBF ₄ ) Viscosity Initial capacity (%) Capacity retention rate (%)
@ 60cycle Example 1 1:1 4.84 100% 91 Example 6 2:3(1:1.5) 3.83 100% 82 Example 7 3:2(1:0.67) 5.32 97% 85

Referring to Table 8, it was found that the lithium metal batteries of Examples 1, 6, and 7 had excellent capacities due to reduced resistance because the movement of Li ions was improved. In addition, when the mixing weight ratio of LiDFOB and LiBF ₄ was between 2:3 or 3:2 (Examples 6 and 7), it was confirmed that BN had better interaction with LiDFOB, but when the content of LiBF ₄ was more than the above range (Example 6), the probability of encountering _LiDFOB was reduced, so that the capacity retention rate decreased compared to the lithium metal battery of Example 1, and when the content of LiDFOB was more than the above range (Example 7), the ratio of salt to the total weight increased, so that the mobility decreased due to the increase in viscosity, so that the initial capacity decreased compared to Example 1.

Evaluation Example 5: Charge/Discharge Characteristics

The charge/discharge characteristics of the lithium metal battery of Example 9 and the lithium ion battery of Comparative Example 5 were evaluated as follows.

The battery was charged under constant current at 0.1 C rate at 25°C until the voltage reached 4.48 V (vs. Li), then cut-off at 0.05 C rate while maintaining 4.48 V in constant voltage mode. Subsequently, the battery was discharged under constant current at 0.1 C rate until the voltage reached 3.0 V (vs. Li) (formation cycle).

A lithium metal battery that had undergone a Mars cycle was charged at a constant current of 0.2 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C rate until the voltage reached 3.0 V (vs. Li) (1 ^st cycle).

The lithium metal battery that had undergone the first cycle was charged under constant current at 0.33 C rate at 25°C until the voltage reached 4.48 V (vs. Li), and then cut-off at 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged under constant current at 1.0 C rate until the voltage reached 3.0 V (vs. Li) (2 ^nd cycle). These cycles were repeated under the same conditions up to the ^120th cycle.

In all charge/discharge cycles, a pause of 10 minutes was allowed after each charge/discharge cycle. The results of the charge/discharge characteristic evaluation are shown in Fig. 4.

As shown in Fig. 4, it was found that the lithium metal battery of Example 9 had significantly improved life characteristics compared to Comparative Example 5. These results show that the lithium metal battery of Example 9 had improved life because the anion interaction was improved in the case of Comparative Example 1, thereby improving the initial completeness of the film.

Evaluation Example 6: High-rate characteristics

The high-rate characteristics of the lithium metal batteries of Example 1 and Comparative Example 1 were evaluated according to the following methods.

The lithium metal batteries manufactured in Example 1 and Comparative Example 1 were charged under constant current at a current of 0.1 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off was performed at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the batteries were discharged under constant current at a current of 0.1 C rate until the voltage reached 2.8 V (vs. Li) (1 ^st cycle, formation cycle).

A lithium battery that had undergone ^{the 1st} cycle was charged under constant current at a current of 0.2C rate at 45℃ until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged under constant current at a 0.2C rate until the voltage reached 2.8 V (vs. Li) (2 ^nd cycle).

The ^2nd cycle was repeated under the same conditions until the ^11th cycle.

The lithium battery that had undergone ^{the 11th} cycle was charged under constant current at a current of 0.2 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged under constant current at a current of 0.5 C rate until the voltage reached 2.8 V (vs. Li) ( ^12th cycle).

The 12th cycle was repeated under the same conditions until the ^21st cycle.

The lithium battery that had undergone ^{the 21st} cycle was charged under constant current at a current of 0.2C rate at 45℃ until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05C rate while maintaining 4.3 V in constant voltage mode. Subsequently, it was discharged under constant current at a 1C rate until the voltage reached 2.8 V (vs. Li) ( ^22nd cycle).

The ^22nd cycle was repeated under the same conditions until the ^31st cycle.

A lithium battery that had undergone 31 ^cycles was charged under constant current at 0.2 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged under constant current at 2 C rate until the voltage reached 2.8 V (vs. Li) (32 ^nd cycle).

The 32nd cycle was repeated under the same conditions until the ^41st cycle.

These cycles were repeated under the same conditions until the ^50th cycle (50 repetitions).

In all the above charge/discharge cycles, a pause of 10 minutes was allowed after each charge/discharge cycle.

Some of the results of the above charge-discharge experiment are shown in Table 9 below. The high-rate characteristics are defined by Equation 5 below.

<Formula 5>

High rate characteristics [%] = [Discharge capacity at ^32nd cycle (2C rate) / Discharge capacity at ^2nd cycle (0.2C rate)] × 100

division High rate characteristics (%) Example 1 91.6 Comparative Example 1 90.4

Referring to Table 9, it was found that the lithium metal battery of Example 1 had improved high-rate characteristics because the movement of lithium (Li) ions was improved in the case of Comparative Example 1.

Although exemplary embodiments have been described in detail with reference to the attached drawings, the present creative idea is not limited to these examples. It is self-evident that a person having ordinary knowledge in the technical field to which the present creative idea belongs can derive various modified or altered examples within the scope of the technical idea described in the patent claims, and these also naturally fall within the technical scope of the present creative idea.

Claims (20)

In a lithium metal battery including a cathode, an anode, and an electrolyte layer disposed between the cathode and the anode, In the X-ray photoelectron spectroscopy (XPS) analysis spectrum obtained for the above cathode surface, The ratio of the total area (B1+B2) of the area of the Li1s peak (A1), the area of the F1s peak (B1), and the area of the B1s peak (B2) is 1:0.7 to 1:1.2, The above electrolyte layer comprises a nitrile compound, a lithium salt, and a carbonate compound, The above lithium salts include lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF ₄ ). A lithium metal battery wherein the content of the nitrile compound is 3 wt% to 45 wt% based on 100 wt% of the total weight of the electrolyte layer. In the first paragraph, A lithium metal battery, wherein the ratio of the total area (B1+B2) of the area of the F1s peak (B1) and the area of the B1s peak (B2) and the area of the O1s peak (C1) in the XPS analysis spectrum obtained for the above-mentioned cathode surface is in the range of 1:0.6 to 1:1.3. In the first paragraph, A lithium metal battery, wherein the nitrile compound is butyronitrile, valeronitrile, propionitrile, acetonitrile, or a combination thereof. In the first paragraph, A lithium metal battery wherein the concentration of the lithium salt is 1 to 5 M. In the first paragraph, A lithium metal battery, wherein the mixing weight ratio of lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF ₄ ) is 1:2 to 1:0.3. In the first paragraph, A lithium metal battery, wherein the carbonate compound is fluoroethylene carbonate, dimethyl carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, or a combination thereof. In the first paragraph, A lithium metal battery, wherein the area (Ac) of the peak at wave numbers 695 cm ^-1 to 725 cm ^-1 in the Raman analysis spectrum obtained for the cathode surface is 25% to 40% based on the total Raman analysis area of the electrolyte layer. In the first paragraph, A lithium metal battery, wherein a ratio (Ac/ _Ad ) of the area of the peak at wave numbers 695 cm ^-1 to 725 cm ^-1 and the area of the peak at wave numbers 715 to 745 eV in a Raman analysis spectrum obtained for the cathode surface is 0.4 to 1. In the first paragraph, The above carbonate compounds include fluoroethylene carbonate (FEC) and diethyl carbonate (DEC). A lithium metal battery wherein the mixing weight ratio of the above FEC and DEC is 1:10 to 1:1. In the first paragraph, A lithium metal battery, wherein the negative electrode comprises a negative electrode collector. In Article 10, The above negative electrode further includes a lithium metal layer disposed on the negative electrode collector, A lithium metal battery, wherein the lithium metal layer comprises a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof. In Article 11, A lithium metal battery, wherein the negative electrode further comprises a protective layer disposed on a lithium metal layer. In the first paragraph, The above electrolyte layer comprises a liquid electrolyte, a gel electrolyte, a solid electrolyte or a combination thereof, A lithium metal battery, wherein the solid electrolyte comprises an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof. In Article 13, A lithium metal battery wherein the solid electrolyte further comprises an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a combination thereof. In Article 11, The above lithium alloy contains lithium and a first metal, A lithium metal battery wherein the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum or a combination thereof. In Article 11, The above negative electrode is a lithium metal battery including a negative electrode active material layer between a lithium metal layer and an electrolyte layer. In the first paragraph, The above positive electrode includes a positive electrode current collector and a positive electrode active material layer, At least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, The above base film contains a polymer, The above polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof. A lithium metal battery, wherein the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. In the first paragraph, The above lithium metal battery is a lithium metal battery further comprising a separator. In Article 18, The above separator comprises a porous substrate, The above porous substrate is a lithium metal battery including polypropylene, polyethylene, or a combination thereof. Step of preparing the cathode; Steps to prepare the anode; A step of preparing an assembly using the above positive and negative electrodes; and Comprising a step of providing an electrolyte layer to the above assembly, The above electrolyte layer comprises a nitrile compound, a lithium salt, and a carbonate compound, The above lithium salts include lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF ₄ ). A method for manufacturing a lithium metal battery, wherein the content of the nitrile compound is 3 wt% to 45 wt% based on 100 wt% of the total weight of the electrolyte.

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