WO2024144309A1 - Silicon-polymer composite, preparation method therefor, and anode active material comprising same - Google Patents

Abstract

The present invention relates to a silicon-polymer composite, a preparation method therefor, and an anode active material comprising same. In the silicon-polymer composite according to an embodiment of the present invention, the original shape of silicon particles is preserved because a polymer thin film has excellent thickness uniformity, and the polymer thin film has little impact on electrical conductivity and lithium-ion conductivity, and thus, when the silicon-polymer composite is used as an anode active material, the silicon-polymer composite acts as a stable solid electrolyte interphase layer between silicon and an electrolyte, while still maintaining the high specific power and high Coulombic efficiency of silicon which is the main anode active material. Accordingly, degradation in battery performance and battery lifespan may be suppressed.

Description

Silicone-polymer composite, manufacturing method thereof, and negative electrode active material containing the same

The present invention relates to a method for manufacturing a silicon-polymer composite, and more specifically, to a silicon-polymer composite, a method for manufacturing the same, and a negative electrode active material containing the same.

With the recent development of the information and communication industry, demand for electronic devices is rapidly increasing, and as the electric vehicle market becomes more active, demand for batteries used in these electronic devices and electric vehicles is also increasing significantly.

Secondary batteries, such as lithium secondary batteries and all-solid-state batteries containing a liquid electrolyte, have high energy density and have a small degree of self-discharge when not in use, so they are most widely used for this purpose. Secondary batteries generally consist of a positive electrode, a negative electrode, and an electrolyte (liquid or solid), and carbon-based materials such as graphite are widely used as negative active materials for secondary batteries.

Recently, attempts have been made to use silicon-based anode active materials to improve the capacity of secondary batteries. Silicon, in theory, has a very high energy density, so it is attracting attention as a next-generation battery anode active material to replace graphite. However, during charging and discharging, it reacts with lithium and increases in volume by up to 300%, so as charging and discharging progresses, silicon, the anode active material, is shredded. It has problems with very poor mechanical stability.

To solve this problem, Japanese Patent No. 4393610 discloses a negative electrode active material in which silicon is complexed with carbon in a mechanical processing process and the surface of the silicon particles is covered with a carbon layer using a chemical vapor deposition (CVD) method. , there are limits to suppressing volume expansion and contraction during charging and discharging.

In addition, the silicon-based negative electrode active material has a problem in that the solid electrolyte interphase (SEI) layer, which is excessively generated during the process of crushing and micronizing the silicon raw material, is unstable, causing a decrease in the stability and electrical performance of the battery.

The purpose of the present invention is to provide a silicon-polymer composite that has excellent thickness uniformity of the polymer thin film, preserves the existing shape of the silicon particles, and can suppress degradation of battery performance and lifespan when used as a negative electrode active material.

Another object of the present invention is to provide a method for producing the above silicone-polymer composite.

Another object of the present invention is to provide a negative electrode active material containing the above silicon-polymer composite.

The present invention provides a method for producing a silicon-polymer composite including forming a polymer thin film on the surface of a silicon particle through initiator-based chemical vapor deposition (iCVD).

According to one embodiment of the present invention, forming the polymer thin film includes (1) supplying silicon particles into a reactor, (2) supplying monomers and initiators to the reactor supplied with silicon particles, and (3) activating the initiator to polymerize the monomer, thereby forming a polymer thin film on the surface of the silicon particle.

Additionally, the silicon particles may be non-porous silicon particles.

Additionally, the silicon particles may have an average particle diameter of 10 nm to 50 ㎛.

Additionally, the polymer thin film may have a thickness of 1 nm to 10 ㎛.

Additionally, in step (2), the monomer may be supplied at a flow rate of 0.1 sccm to 10 sccm, and the initiator may be supplied at a flow rate of 0.1 sccm to 5 sccm.

Additionally, the initiator may be activated through a predetermined heat treatment, and the heat treatment may be performed at a temperature of 135 to 350°C.

Additionally, step (3) may be performed for 10 minutes to 6 hours under vacuum at a pressure of 50 to 1,000 mTorr.

In addition, after forming the polymer thin film, the step of forming a carbon thin film on the surface of the polymer thin film may be further included.

Additionally, the carbon thin film may have a thickness of 1 nm to 1 ㎛.

Additionally, the present invention provides a silicone-polymer composite prepared by the above-described method for producing a silicone-polymer composite.

Additionally, the present invention provides a negative electrode active material including the above-described silicon-polymer composite and a carbon-based negative electrode material.

In addition, the present invention provides an all-solid-state battery comprising a SEI (Solid Electrolyte Interphase) film containing the above-described silicon-polymer composite.

The silicon-polymer composite according to an embodiment of the present invention has excellent thickness uniformity of the polymer thin film, so the existing shape of the silicon particles is preserved, and the polymer thin film has little effect on electrical conductivity and lithium ion conductivity, so it can be used as a negative electrode active material. In this case, the high specific power and coulombic efficiency of silicon, the main cathode active material, can be maintained, while acting as a stable solid electrolyte interface layer between silicon and electrolyte to suppress degradation of battery performance and lifespan.

Figure 1 schematically shows the process of forming a polymer thin film on the surface of a silicon particle by initiator-based chemical vapor deposition (iCVD) according to an embodiment of the present invention.

Figure 2 is a TEM image of bare silicon particles before forming a polymer thin film on the surface of the silicon particles according to an embodiment of the present invention.

Figure 3 is a photograph showing the degree to which particles are dispersed in water before and after forming a polymer thin film on the surface of silicon particles according to an embodiment of the present invention (Example 1).

Figure 4 is a TEM image of a silicon-polymer composite (Example 1) according to an embodiment of the present invention.

Figure 5 is a photograph of energy dispersive optical analysis of a silicon-polymer composite according to an embodiment of the present invention.

Figure 6 is a TEM image of a silicon-polymer composite (Example 2) according to an embodiment of the present invention.

Figure 7 is a graph comparing the nitrogen atom content of bare silicon particles and a silicon-polymer composite (Example 2) according to an embodiment of the present invention.

Figure 8 is a TEM image of a silicon-polymer composite (Example 3) according to an embodiment of the present invention.

Figure 9 is a TEM image of a silicon-polymer composite (Example 4) according to an embodiment of the present invention.

Figure 10 is a TEM image of bare silicon particles, a silicon-polymer composite according to an embodiment of the present invention (Example 4), and a silicon-polymer composite on which polymer coating was performed in a liquid phase (Comparative Example 1).

Figure 11 is a graph measuring the initial charge/discharge efficiency and capacity maintenance ratio of a battery using bare silicon particles and a battery using a silicon-polymer composite (Example 1) according to an embodiment of the present invention (Preparation Example 1).

The present invention is not limited to the content disclosed below, but may be modified into various forms as long as the gist of the invention is not changed.

In this specification, “includes” means that other components may be further included unless otherwise specified.

All numbers and expressions indicating amounts of components, reaction conditions, etc. described in this specification should be understood as being modified by the term “about” in all cases unless otherwise stated.

In this specification, the description that one component is formed above/below another component, or is connected or combined with each other, includes all those formed, connected, or combined directly between these components or indirectly through other components. do.

Hereinafter, the present invention will be described in more detail.

Silicone-polymer composite

The present invention provides a silicone-polymer composite manufactured by a silicone-polymer composite manufacturing method described later. The silicon-polymer composite is implemented by including silicon particles and a polymer thin film formed on the surface of the silicon particles.

silicon particles

The silicone-polymer composite according to one embodiment of the present invention includes silicon particles.

Since the silicon particles play a role in charging lithium, when the silicon-polymer composite according to an embodiment of the present invention is used as a negative electrode active material, the silicon particles can function as a main negative electrode active material.

The silicon particles may be any one or more of porous silicon particles and non-porous silicon particles, but are preferably non-porous silicon particles. Accordingly, the thickness uniformity of the polymer thin film is excellent, and the existing shape of the silicon particles is preserved. , when used as a negative electrode active material, it can be more advantageous in terms of suppressing the decline in battery performance and lifespan.

Additionally, the silicon particles may be crystalline or amorphous, and may preferably be amorphous or a similar phase in terms of expansion/contraction and battery performance during charging and discharging of the secondary battery. When the silicon particles are crystalline, the smaller the size of the crystallites, the more dense a composite can be obtained, thereby strengthening the strength of the matrix and preventing cracking. Accordingly, the initial efficiency or cycle life characteristics of the secondary battery can be improved. On the other hand, when the silicon particles are amorphous or similar, expansion or contraction during charging and discharging of the secondary battery is small, and battery performance such as capacity characteristics can be improved.

The size of the silicon particles may be selected so that the silicon-polymer composite according to an embodiment of the present invention is suitable for use as a negative electrode active material. Specifically, the average particle diameter of the silicon particles may be 10 nm to 50 ㎛, preferably 10 nm to 25 ㎛. As the silicon particles satisfy the average particle diameter range, it can be more advantageous to achieve the purpose of the present invention.

The silicon particles may further include a silicon oxide compound. The silicon oxide compound may be represented by the general formula SiO _x (0.5≤x≤2). Here, if the value of there is.

The content of the silicon oxide compound in the silicon particles may be 50% by weight or less based on the total weight of the silicon particles. If the content of the silicon oxide compound in the silicon particles exceeds 50% by weight, the initial efficiency of the secondary battery may decrease.

The silicon particles may further contain elements such as carbon and magnesium in addition to silicon and oxygen, but the content of silicon in the silicon particles is 1 to 80% by weight of the total silicon content in the silicon-polymer composite, preferably 5 to 5% by weight. It may be selected to be 50% by weight. If the total silicon content in the silicon-polymer composite is less than 1% by weight, the amount of active material that stores and releases lithium is insufficient, and the charge and discharge capacity of the secondary battery may decrease. If the total silicon content in the silicon-polymer composite exceeds 80% by weight, the charge and discharge capacity of the secondary battery can be increased, but the expansion and contraction of the electrode during charge and discharge become excessively large, and the negative electrode active material powder becomes more finely divided, The cycle characteristics of the secondary battery may deteriorate.

polymer thin film

The silicon-polymer composite according to one embodiment of the present invention includes a polymer thin film formed on the surface of the silicon particle.

In the silicon-polymer composite according to an embodiment of the present invention, the polymer thin film on the surface of the silicon particle is formed by initiator-based chemical vapor deposition (iCVD), which will be described later.

The polymer thin film is formed by iCVD, and the type of material is not particularly limited as long as it has little effect on the electrical conductivity and lithium ion conductivity of the negative electrode active material. Specifically, the polymer thin film is any one of vinyl or acrylate monomers containing one or more of a siloxane group, an amine group, a fluorine group, a glycidyl group, and an aromatic hydrocarbon group. One or more may be polymerized or copolymerized.

In an embodiment of the present invention, the polymer thin film is 4-vinyl pyridine (4VP), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (2 ,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane), 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10, 10,10-heptadecafluorodecyl methacrylate (3,3, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate, PFDMA), 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, V4D4) , 1,3,5-trivinyl-1,3,5-trivinylcyclotrisiloxane (1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, V3D3), hexavinyldisiloxane (HVDS), Glycidyl methacrylate, divinylbenzene, diethylene glycol divinyl ether, diethylene glycol diacrylate (DEGDA), ethylene glycol dimethacrylate, dimethylaminoethyl methacrylate, methacrylic acid and 1, 3-diethenyl-1,1,3,3-tetramethyl-disiloxane, 1H,1H,2H,2H-perfluorodecyl acrylate, perfluorodecyl methacrylate, dodecafluoroheptyl acrylate, Pentafluorophenyl methacrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-pentadecafluorononyl acrylate, 2-methyl- 3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-pentadecafluorononyl acrylate, 3,3,4,4,5,5, 6,6,7,7,8,8,8-tridecafluorooctyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,7,7,8,8, 8-tridecafluorooctyl acrylate, 3,3,4,4,5,5,6,6,7,7,7-undecafluoroheptyl acrylate, 2-methyl-3,3,4, 4,5,5,6,6,7,7,7-undecafluoroheptyl acrylate, 3,3,4,4,5,5,6,6,6-nonafluorohexyl acrylate, 2 -Methyl-3,3,4,4,5,5,6,6,6-nonafluorohexyl acrylate, 3,3,4,4,5,5,6,6,7,7,8, 8,9,9,10,10,11,11,11-nonadecafluoroundecyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,7,7,8 ,8,9,9,10,10,11,11,11-nonadecafluoroundecyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8, 9,9,10,10,11,11,12,12,12-heneicosafluorododecyl acrylate, 2-methyl-3,3,4,4,5,5,6,6,7, 7,8,8,9,9,10,10,11,11,12,12,12-Heneicosafluorododecyl acrylate, 3,3,4,4,5,5,6,6, 7,7,8,8,9,9,10,10,11,11,12,12,13,13,13-tricosafluorotridecyl acrylate, 2-methyl-3,3,4,4, 5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,13-tricosafluorotridecyl acrylate, 3,3, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14-Pentacosafluoro tetradecyl acrylate, and 2-methyl-3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12, Consisting of 13,13,14,14,14-pentacosafluorotetradecyl acrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, and diethylaminoethyl acrylate. It may be polymerized from one or more monomers selected from the group.

In a preferred embodiment of the present invention, the polymer thin film is 1H,1H,2H,2H-perfluorodecyl acrylate, dimethylaminomethyl styrene, divinylbenzene, glycidyl methacrylate, 1,3,5,7 -1 selected from the group consisting of tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane and hexavinyldisiloxane It may be polymerized from more than one type of monomer, but is not particularly limited to these.

In an embodiment of the present invention, the thickness of the polymer thin film may be 1 nm to 10 ㎛, preferably 1 nm to 1 ㎛, more preferably 10 to 100 nm. When the thickness of the polymer thin film is within this range, it has little effect on the electrical conductivity and lithium ion conductivity of the negative electrode active material, and acts as a stable solid electrolyte interface layer between silicon and electrolyte to prevent battery life from being reduced. .

carbon thin film

The silicon-polymer composite according to one embodiment of the present invention may further include a carbon thin film formed on the surface of the polymer thin film, thereby producing a silicon-polymer-carbon composite.

When the silicon-polymer composite according to an embodiment of the present invention further includes a carbon thin film to produce a silicon-polymer-carbon composite, the silicon-polymer-carbon composite can secure appropriate electrical conductivity and its specific surface area can be increased. Since it can be adjusted appropriately, when used as a negative active material for a secondary battery, the lifespan characteristics and capacity of the secondary battery can be further improved.

The electrical conductivity of the negative electrode active material is an important factor that facilitates electron movement during electrochemical reactions. If the carbon content contained in the silicon-polymer composite used as the negative electrode active material is insufficient, the electrical conductivity of the negative electrode active material may not be sufficient. In this case, by additionally forming a carbon thin film on the surface of the silicon-polymer composite to manufacture silicon-polymer-carbon, the charge/discharge capacity, initial charge efficiency, and capacity maintenance rate of the secondary battery are improved, and excellent electrical conductivity is provided. Side reactions of the electrolyte can be suppressed and the performance of secondary batteries can be further improved.

In the silicon-polymer-carbon composite according to an embodiment of the present invention, the thickness of the carbon thin film may be 1 nm to 1 ㎛, preferably 3 to 150 nm, and more preferably 5 to 100 nm. When the thickness of the carbon thin film is within this range, a decrease in capacity of the secondary battery can be suppressed while improving conductivity.

The carbon thin film may include one or more types selected from graphene, carbon nanotubes, carbon nanofibers, and graphite. Specifically, the carbon thin film may include graphene and may further include graphite, but is not particularly limited thereto.

Manufacturing method of silicone-polymer composite

A silicon-polymer composite according to an embodiment of the present invention is a manufacturing method comprising forming a polymer thin film on the surface of a silicon particle through initiator-based chemical vapor deposition (iCVD). It is manufactured.

Initiator-based chemical vapor deposition (iCVD) refers to a process of polymerizing monomers by decomposing a vapor phase initiator into radicals. In the initiator-based chemical vapor deposition method, deposition of a polymer thin film occurs by supplying energy from a heat source such as a heated filament or UV, so it does not seem to be much different from the existing CVD process for inorganic thin film deposition, but the iCVD process has a temperature of 135~350℃. The initiator is activated at a low temperature in the range, preferably in the range of 140 to 340°C. In addition, the surface temperature of the silicon particles on which the polymer thin film is deposited is maintained low in the range of 10 to 50°C, preferably in the range of 13 to 45°C. Due to this low surface temperature, iCVD can be useful for depositing polymer thin films on various substrates that are vulnerable to mechanical or chemical shock. In addition, the iCVD process is carried out in a vacuum condition in the range of 50 to 1,000 mTorr, preferably in the range of 60 to 900 mTorr, so high vacuum equipment is not required.

Meanwhile, according to one embodiment of the present invention, the step of forming the polymer thin film includes (1) supplying silicon particles into a reactor, (2) supplying monomers and initiators to the reactor supplied with silicon particles. , and (3) activating the initiator to polymerize the monomer, thereby forming a polymer thin film on the surface of the silicon particle.

Figure 1 schematically shows the process of forming a polymer thin film on the surface of a silicon particle by initiator-based chemical vapor deposition (iCVD) according to an embodiment of the present invention. A method for manufacturing a silicone-polymer composite according to an embodiment of the present invention will be described with reference to FIG. 1.

Step (1)

In step (1) above, silicon particles are supplied into the reactor.

The reactor used in the method for producing a silicon-polymer composite according to an embodiment of the present invention is capable of forming a polymer thin film on the surface of a silicon particle using an initiator-based chemical vapor deposition (iCVD) method described later, and its structure is There are no particular restrictions.

In an embodiment of the present invention, the reactor 10 may include a chamber 100, a mounting portion 200, an inlet 300, an outlet 400, and a heating portion 500.

The silicon particles may be placed on the mounting part 200 provided at the bottom of the chamber 100 of the reactor 10. The shape, size, and material of the mounting part are not particularly limited as long as it can accommodate the silicon particles. Specifically, the mounting portion may be of a flat shape in which the silicon particles can be spread out and arranged so as not to overlap each other as much as possible. More specifically, a silicon substrate (wafer) may be used as a mounting part to accommodate the silicon particles, but is not particularly limited thereto.

The mounting portion may be connected to a position changing means (not shown) that can change the position of the silicon particles. The position change means changes or rotates the position of the silicon particles placed on the silicon substrate by, for example, vibrating or moving the mounting part, which is a silicon substrate, so that a polymer thin film is evenly formed on the surface of the silicon particles in step (3), which will be described later. It can be done, but is not particularly limited to this.

Step (2)

In step (2) above, monomers and initiators are fed into the reactor.

At this time, the monomer (M) and the initiator (I) may be vaporized and supplied to the chamber 100 through the inlet 300 of the reactor 10.

The monomer (M) is a volatile material that can be activated by an initiator (I) to form a polymer. Details of the monomer are as described in the silicon-polymer complex section above.

The initiator (I) is a substance that is decomposed by heat or light to form free radicals, and its type is not particularly limited as long as it is a substance that can form a polymer by activating the monomer. Preferably, the initiator may be peroxide. Specifically, the initiator includes at least one selected from the group consisting of di-t-butyl peroxide, t-butyl peroxybenzoate, benzoyl peroxide, methyl ethyl ketone peroxide, lauryl peroxide, and benzophenone. It can be done, but is not particularly limited to these. Most preferably, the initiator may be di-t-butyl peroxide.

At this time, the monomer flow rate in the reactor may be 0.1 sccm to 10 sccm. Specifically, the monomer flow rate is 0.1 sccm or more, or 0.2 sccm or more and 10 sccm or less. It may be 5 sccm or less, or 4 sccm or less.

Additionally, the initiator flow rate in the reactor may be 0.1 sccm to 5 sccm. Specifically, the initiator flow rate may be 0.1 sccm or more, 5 sccm or less, 3 sccm or less, or 2 sccm or less.

Step (3)

In step (3) above, the initiator is activated to polymerize the monomer, thereby forming a polymer thin film on the surface of the silicon particle.

First, the initiator (I) supplied into the chamber 100 of the reactor 10 in a vaporized state is activated in contact with the heating unit 500 to form free radicals (I ^* ). The heating unit may be, for example, a plurality of filaments heated by electricity, but is not particularly limited thereto. The temperature of the heating unit is not limited as long as it can decompose and activate the initiator, but is preferably in the range of 135 to 350 ℃, more preferably 140 to 340 ℃ in terms of preventing changes in the characteristics of the reactants, etc. can be advantageous.

Free radicals (I ^* ) and monomers (M) generated from the initiator move to the bottom of the chamber and are adsorbed on the surface of the silicon particles accommodated in the mounting unit 200. The monomer adsorbed on the surface of the silicon particle is activated (M ^* ) by free radicals (I ^* ) and polymerization proceeds to form a polymer thin film on the surface of the silicon particle.

The gaseous initiator and monomer remaining after being used in the reaction in step (3) above may be discharged out of the reactor through the outlet 400.

In step (3) above, in order to increase the adsorption rate of the monomers and free radicals, it is desirable to keep the temperature of the silicon particle surface low. Specifically, the temperature of the surface of the silicon particle is preferably in the range of 10 to 50°C, preferably in the range of 13 to 45°C, but is not particularly limited to this range. In order to maintain the temperature of the surface of the silicon particle in the above range, the reactor 10 may additionally include a cooling unit (not shown) disposed below the mounting unit 200. The cooling method and structure of the cooling unit (not shown) are not particularly limited as long as the temperature of the silicon particle surface can be controlled within the above range.

Step (3) above can be performed in a vacuum condition in the range of 50 to 1,000 mTorr, preferably 60 to 900 mTorr. This vacuum range can be provided with a simple rotary pump rather than a high vacuum pump. Additionally, step (3) may be performed for 10 minutes to 6 hours, preferably 30 minutes to 2 hours, but is not limited thereto. However, as the reaction time satisfies the above time range, a polymer thin film of the desired thickness can be uniformly formed.

The physical properties of the polymer thin film formed in step (3) above can be easily adjusted by controlling the process variables of iCVD. That is, the molecular weight, thickness, composition, deposition rate, etc. of the polymer thin film can be easily adjusted by controlling the pressure and temperature within the chamber, reaction time, flow rate of the initiator and monomer, surface temperature of the heating part and silicon particles, etc.

Additional steps

The method for manufacturing a silicon-polymer composite according to an embodiment of the present invention may further include forming a carbon thin film on the surface of the polymer thin film after forming the polymer thin film.

The step of forming a carbon thin film on the surface of the polymer thin film of the silicon-polymer composite may be performed using devices and methods known in the technical field to which the present invention pertains, such as chemical pyrolysis deposition, but is not particularly limited thereto.

In an embodiment of the present invention, the step of forming a carbon thin film on the surface of the polymer thin film of the silicon-polymer composite may be performed by heat treating the silicon-polymer composite at a temperature of 400 to 1,200° C. in the presence of a gaseous carbon source. there is.

In a preferred embodiment of the invention, the carbon source is methane, ethane, propane, butane, methanol, ethanol, propanol, propanediol, butanediol, ethylene, propylene, butylene, butadiene, cyclopentene, acetylene, benzene, toluene, xyl. It may include at least one member selected from the group consisting of ene, ethylbenzene, naphthalene, anthracene, and dibutylhydroxy toluene, but is not particularly limited thereto.

The step of forming a carbon thin film on the surface of the polymer thin film of the silicon-polymer composite may be performed in the presence of at least one inert gas selected from the group consisting of hydrogen, nitrogen, helium, and argon in addition to the carbon source.

The reaction time (heat treatment time) for forming the carbon thin film can be appropriately adjusted depending on the heat treatment temperature, pressure during heat treatment, composition of the gas mixture, and desired carbon coating amount. For example, the above reaction time may be 10 minutes to 100 hours, specifically 30 minutes to 90 hours, and more specifically 50 minutes to 40 hours, but is not particularly limited to this range.

In an embodiment of the present invention, the step of forming a carbon thin film on the surface of the polymer thin film of the silicon-polymer composite includes mixing the silicon-polymer composite with a solution in which the carbon source is dispersed in a solvent as needed, drying the mixture, and It can be performed by heat treatment at a temperature of ~1,400°C.

In a preferred embodiment of the present invention, the carbon source may be selected from the group consisting of pitch, hydrocarbon-based materials and petroleum-based materials. More specifically, the pitch may be petroleum-based pitch, coal-based pitch, or a mixture thereof, the hydrocarbon-based material may be furfuryl alcohol or phenol-based resin, and the petroleum-based material may be pyrolysis fuel oil. fuel oil (PFO), naphtha cracking bottom oil (NCB), ethylene cracker bottom oil (EBO), vacuum residue (VR), de-asphalted oil; DAO), atmospheric residue (AR), fluid catalytic cracking decant oil (FCC-DO), residue fluid catalytic cracking decant oil (RFCC-DO), or heavy aromatic oil. You can. The solvent may be tetrahydrofuran (THF) or alcohol.

Through the carbon thin film forming step, a silicon-polymer-carbon composite in which a carbon thin film is formed uniformly over the entire surface of the polymer thin film of the silicon-polymer composite can be obtained. When forming the carbon thin film on the surface of the polymer thin film of the silicon-polymer composite, the type of monomer, the process conditions for forming the polymer thin film, the type of carbon source, and the process conditions for forming the carbon thin film are appropriately adjusted to ensure that the polymer thin film is substantially formed. A carbon thin film can be formed on the surface without being damaged. That is, when forming the carbon thin film on the surface of the polymer thin film of the silicon-polymer composite, 10 to 100% by weight, preferably 50 to 100% by weight, more preferably 80 to 100% by weight of the polymer thin film. Silicon particles may remain on the surface. When the silicon-polymer-carbon composite obtained in this way is used as a negative electrode active material, the electrical conductivity of the negative electrode active material can be improved without structural change.

In the method for producing a silicone-polymer composite or a silicone-polymer-carbon composite according to an embodiment of the present invention, the obtained silicone-polymer composite or silicone-polymer-carbon composite may be disintegrated or pulverized and classified. Through classification, the particle size distribution of the composite can be made uniform. Here, dry classification, wet classification, or classification using a sieve may be used for classification.

negative active material

According to another embodiment of the present invention, a negative electrode active material including the silicon-polymer composite is provided.

The anode active material according to an embodiment of the present invention may further include a carbon-based anode material, specifically a graphite-based anode material, in addition to the silicon-polymer composite or the silicon-polymer-carbon composite. For example, the negative electrode active material may be obtained by mixing a silicon-polymer composite or a silicon-polymer-carbon composite according to an embodiment of the present invention with a carbon-based negative electrode material, for example, a graphite-based negative electrode material.

Here, the carbon-based negative electrode material includes, for example, natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon, carbon fiber, carbon nanotube, pyrolytic carbon, coke, organic polymer compound sintered body, and carbon black. It may include at least one member selected from the group consisting of, but is not particularly limited to, these.

The content of the carbon-based negative electrode material in the negative electrode active material according to an embodiment of the present invention may be 2 to 80% by weight, preferably 5 to 70% by weight, and more preferably 30 to 70% by weight, based on the total weight of the negative electrode active material. .

The anode active material according to embodiments of the present invention can be effectively used to manufacture secondary batteries, specifically, the anode of a lithium secondary battery and the anode of an all-solid-state battery.

solid-state battery

According to another embodiment of the present invention, an all-solid-state battery including a solid electrolyte interphase (SEI) film including the silicon-polymer composite is provided.

The all-solid-state battery may be an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte between the positive electrode and the negative electrode, and the negative electrode may include a negative electrode active material layer, and at least a portion of the negative electrode active material particles of the negative electrode active material layer. It may include a solid electrolyte interphase (SEI) film containing the silicon-polymer complex described above.

Meanwhile, the negative electrode active material particles may be a carbon-based negative electrode material, and in this case, since the content may be the same as that described in the above-mentioned content regarding the negative electrode active material, the related description will be omitted.

In addition, in addition to the negative electrode active material particles and the SEI film of the all-solid-state battery, the negative electrode composition, positive electrode composition, and solid electrolyte composition can be applied to known all-solid-state batteries, and are not particularly limited in the present invention.

Example

The present invention will be described in more detail through examples below. The following examples are merely illustrative of the present invention, and the scope of the present invention is not limited thereto.

<Example 1>

Preparation of silicone-polymer composites

A silicone-polymer composite was prepared using the reactor schematically shown in Figure 1. 5 g of silicon powder with average particle diameters of 20 ㎛ and 2 ㎛ were spread evenly on a circular silicon wafer. Vaporized monomers and initiators were supplied into the reactor chamber through the inlet to form a polymer thin film (pPFDA) on the surface of the silicon particles. The specific conditions of the materials and processes used in Example 1 are as follows.

- Non-porous silicon particles: average particle diameter of 20 ㎛ and 2 ㎛ (REC Silicon)

- Monomer: 1H,1H,2H,2H-perfluorodecyl acrylate (Aldrich, 97%)

- Initiator: di-t-butyl peroxide (Aldrich, 98%)

- Initiator average feed flow rate: 0.26 sccm

- Monomer average feed flow rate: 0.425 sccm

- Filament temperature: 140℃

- Pressure in reactor chamber: 80 mTorr

- Surface temperature of reactor mounting part (silicon wafer): 38℃

<Experimental Example 1>

(1) X-ray photoelectron spectroscopy

Silicon particles before and after the polymer thin film was formed were analyzed for elements on the particle surface using X-ray photoelectron spectroscopy (Multilab 2000, Thermo). The results are shown in Table 1.

Silicon particle size carbon fluoride Oxygen silicon 20㎛ Before forming polymer thin film 42.46 0 24.18 33.36 After forming a polymer thin film 20.34 21.79 18.2 39.67 2㎛ Before forming polymer thin film 24.82 0.3 25.01 49.87 After forming a polymer thin film 25.36 21.8 17.18 35.66

As can be seen from Table 1, almost no fluorine was measured on the surface of the silicon particles before the polymer thin film was formed, but a significant amount of fluorine was measured after forming the polymer thin film on the silicon particles by the manufacturing method of the present invention. . Therefore, it can be seen that a silicon-polymer composite in which a fluorine-containing polymer thin film was formed on the surface of the silicon particle was manufactured by the manufacturing method of the present invention. (2) Water dispersibility

0.3 g each of the silicon particles before the polymer thin film was formed and the silicon-polymer composite obtained in Example 1 were dispersed for 10 minutes by impregnating them in 10 ml of water. The results are shown in Figure 3.

It can be seen that the silicon particles before the polymer thin film is formed are sufficiently dispersed in water (Figure 3a), showing hydrophilicity. On the other hand, the silicon-polymer composite on which the polymer thin film was formed was not dispersed in water but formed a layer on the water surface (Figure 3b), indicating that the surface was modified to be hydrophobic. This indicates that a silicon-polymer composite in which a fluorine-containing polymer thin film was formed on the surface of the silicon particle was manufactured by the manufacturing method of the present invention.

(3) Transmission electron microscopy-energy dispersive optical analysis

Observation of silicon particles with an average particle diameter of 20 ㎛ on which a polymer thin film was formed using a transmission electron microscope (TEM)-energy dispersive spectrometer (EDS) (Tecnai G2 F30 S-Twin, FEI company) did. The TEM analysis results are shown in Figure 4, and the EDS analysis results are shown in Figure 5 and Tables 2 and 3.

atomic % average A B C Si 87.87 92.26 2.33 68.30 C 6.79 3.47 92.82 23.66 F 1.29 0.59 0 1.16 Al 0.46 0 0 0.33 O 6.03 3.68 4.85 6.56

atomic % D E F 0.26 1.07 C 1.91 13.67 Si 97.83 85.26

As a result, from the bare silicon particles in FIG. 2 and the TEM photo in FIG. 4, the silicon-polymer composite obtained in Example 1 formed a uniform thin film with a thickness of about 5 nm without problems such as particle breakage, substantially retaining its original state. It can be seen that the shape is maintained. Figure 5 and Tables 2 and 3 show the area where the silicone-polymer complex exists (portions marked A and B in Fig. 5a and portions marked D and E in Fig. 5b) and the silicon-polymer composite. This shows the EDS analysis results of the area where does not exist (the part marked C in Figure 5a). All fluorine, a component of the monomer, was observed in areas where the silicone-polymer complex was present, whereas fluorine, a component of the monomer, was not observed in areas where the silicone-polymer complex was not present. Therefore, it can be seen qualitatively that a silicon-polymer composite with a polymer thin film formed on the surface of the silicon particle was manufactured by the manufacturing method of the present invention.

<Example 2>

A silicon-polymer composite was prepared in the same manner as in Example 1, except that the following details were changed to form a polymer thin film (pDMAMS) on the surface of the silicon particles.

- Non-porous silicon particles: average particle diameter 20 ㎛ (REC Silicon)

- Monomer: Dimethylaminomethyl styrene (Acros, 90%)

- Pressure in reactor chamber: 160 mTorr

- Surface temperature of reactor mounting part (silicon wafer): 35℃

<Experimental Example 2>

(1) Transmission electron microscopy-energy dispersive optical analysis

Transmission electron microscope (TEM) - energy dispersive spectrometer (EDS) (Tecnai G2 F30 S-Twin, FEI) on silicon particles with an average particle diameter of 20 ㎛ (Example 2) on which a polymer thin film was formed. company) was observed. The TEM analysis results are shown in Figure 6, and the EDS analysis results are shown in Figure 7.

As a result, from the bare silicon particles in FIG. 2 and the TEM photo in FIG. 6, it was found that the silicon-polymer composite obtained in Example 2 formed a uniform thin film with a thickness of about 5 nm and substantially maintained its original shape. .

In addition, as shown in Figure 7, the silicon-polymer composite obtained in Example 2 was confirmed to have a predetermined nitrogen atom, indicating that a silicon-polymer composite in which a polymer thin film was formed on the surface of the silicon particle was manufactured by the manufacturing method of the present invention. I could tell from the sex as well.

<Example 3>

A silicone-polymer composite was prepared in the same manner as in Example 1, except that the following details were changed to form a polymer thin film (pDVB) on the surface of the silicon particle.

- Non-porous silicon particles: average particle diameter 20 ㎛ (REC Silicon)

- Monomer: Divinylbenzene (Aldrich, 80%)

- Pressure in reactor chamber: 450 mTorr

- Surface temperature of reactor mounting part (silicon wafer): 23℃

<Experimental Example 3>

(1) Transmission electron microscopy analysis

Silicon particles with an average particle diameter of 20 ㎛ (Example 3) on which a polymer thin film was formed were observed using a transmission electron microscope (TEM). The TEM analysis results are shown in Figure 8.

As a result, from the bare silicon particles in FIG. 2 and the TEM photo in FIG. 8, it was found that the silicon-polymer composite obtained in Example 3 formed a uniform thin film with a thickness of about 10 nm and substantially maintained its original shape. .

<Example 4>

A silicone-polymer composite was prepared in the same manner as in Example 1, except that the following details were changed to form a polymer thin film (pGMA) on the surface of the silicon particle.

- Non-porous silicon particles: average particle diameter 20 ㎛ (REC Silicon)

- Monomer: Glycidyl methacrylate (Alcrich, 97%)

- Pressure in reactor chamber: 300 mTorr

- Surface temperature of reactor mounting part (silicon wafer): 30℃

<Experimental Example 4>

(1) Transmission electron microscopy analysis

Silicon particles with an average particle diameter of 20 ㎛ (Example 4) on which a polymer thin film was formed were observed using a transmission electron microscope (TEM). The TEM analysis results are shown in Figure 9.

As a result, from the bare silicon particles in FIG. 2 and the TEM photo in FIG. 9, it was found that the silicon-polymer composite obtained in Example 4 formed a uniform thin film with a thickness of about 10 nm and substantially maintained its original shape. .

<Comparative Example 1>

Preparation of silicone-polymer composites

0.5 g of silicon powder with an average particle diameter of 20 ㎛ was added to 10 ml of a solution of 3% by weight polydivinylbenzene (pDVB) dissolved in toluene solvent, and incubated at 40 rpm for 120 minutes at room temperature (25°C). ), the liquid-coated silicon powder was taken out and dried at room temperature (25°C) for 12 hours to prepare a liquid-coated silicone-polymer composite.

<Experimental Example 5>

(1) Transmission electron microscope comparative analysis

Transmitted electrons for the bare silicon particles (FIGS. 10a to 10d), the silicone-polymer composite obtained in Example 4 (FIGS. 10e to 10h), and the liquid coated silicone-polymer composite obtained in Comparative Example 1 (FIGS. 10i to 10l). It was observed using a transmission electron microscope (TEM). The TEM analysis results are shown in Figure 10.

As a result, it was confirmed that in the case of the silicone-polymer composite according to Example 4 (FIGS. 10e to 10h), the shape of the bare silicon particles (FIGS. 10a to 10d) was maintained and a polymer coating of uniform thickness was achieved.

On the other hand, in the case of the liquid coated silicone-polymer composite obtained in Comparative Example 1 (FIGS. 10i to 10l), the shape of the bare silicon particle (FIGS. 10a to 10d) is not maintained, and an atypical shape unrelated to the shape of the bare silicon particle is formed. It was confirmed that the polymer was coated in this shape.

In summary, it can be seen that the iCVD method must be used to coat polymers of uniform thickness on silicon particles.

<Manufacturing Example 1>

A half coin cell was manufactured using the silicone-polymer composite prepared according to Example 1. Half coin cell manufacturing conditions are shown below.

- Composition (AM:CM:BM) = 8:1:1 (where AM, CM, and BM are active material (porous carbon support on which silane is deposited), conductor (Super P carbon black), and binder (styrene-butadiene), respectively. Rubber/carboxymethyl cellulose 5:5).

- Area capacity (mAh/㎠): 4.5

- Electrolyte: 1.3 M LiPF ₆ EC/EMC/DMC 3:5:2, FEC 10%, LiBF4 0.2%, VC 0.5%, PS 1% (here, EC, EMC, DMC, FEC, VC, PS are ethylene carbonate) , ethyl methyl carbonate, dimethyl carbonate, fluoroethylene carbonate, vinylene carbonate, and propane sultone, respectively.)

<Experimental Example 6>

(1) Electrochemical evaluation

For the lithium secondary battery manufactured according to Preparation Example 1, the initial charge/discharge efficiency, ^initial coulombic efficiency (ICE), and capacity retention (%) were measured under the following conditions, and are shown in Table 4 and Figure 11 below. shown in

- Cut-off voltage (V): forming 0.005-1.5, cycle test 0.005-1.5

- C-Rate (C): forming 0.1-0.1, 0.01C cut-off (CV) at 0.005V

Charge capacity(mAh/g) Discharge capacity(mAh/g) ICE (%) 14 ^th cycle capacity retention (%) Bare Si application 3935.9 3123.0 79.3 5.7 Example 1 Application 3784.9 2909.5 76.9 6.3

As a result, as can be seen in Table 4 and Figure 11, it can be seen that the initial discharge efficiency and ICE are at similar levels, while the capacity maintenance rate is increased. Specifically, in the case of Preparation Example 1, compared to the Bare Si application example, Bare While minimizing the decrease in charge/discharge capacity that occurs when coating a predetermined material on the Si surface, a significant increase of more than 10% in terms of the relative rate of capacity maintenance was achieved.

Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in the present specification, and those skilled in the art who understand the spirit of the present invention can add components within the scope of the same spirit. , other embodiments can be easily proposed by change, deletion, addition, etc., but this will also be said to be within the scope of the present invention.

Claims (13)

A method for producing a silicon-polymer composite comprising: forming a polymer thin film on the surface of a silicon particle through initiator-based chemical vapor deposition (iCVD). According to paragraph 1, The step of forming the polymer thin film is, (1) supplying silicon particles into the reactor; (2) supplying monomers and initiators to the reactor supplied with silicon particles; and (3) activating the initiator to polymerize the monomer, thereby forming a polymer thin film on the surface of the silicon particle. According to paragraph 1, The silicon particles are non-porous silicon particles. A method of producing a silicon-polymer composite. According to paragraph 1, The silicon particles are a method of producing a silicon-polymer composite having an average particle diameter of 10 nm to 50 ㎛. According to paragraph 1, The polymer thin film is a method of producing a silicon-polymer composite having a thickness of 1 nm to 10 ㎛. The method of claim 2, wherein in step (2), The monomer is supplied at a flow rate of 0.1 sccm to 10 sccm, The initiator is supplied at a flow rate of 0.1 sccm to 5 sccm. According to paragraph 2, The initiator is activated through a predetermined heat treatment, A method of manufacturing a silicone-polymer composite in which the heat treatment is performed at a temperature of 135 to 350°C. According to paragraph 2, The step (3) is a method of manufacturing a silicone-polymer composite performed for 10 minutes to 6 hours under vacuum at a pressure of 50 to 1,000 mTorr. The method of claim 1, wherein after forming the polymer thin film, A method for producing a silicon-polymer composite further comprising forming a carbon thin film on the surface of the polymer thin film. According to clause 9, The carbon thin film is a method of producing a silicon-polymer composite having a thickness of 1 nm to 1 ㎛. A silicone-polymer composite manufactured by the method for producing a silicone-polymer composite according to any one of claims 1 to 10. Silicone-polymer composite according to claim 11; and A negative electrode active material containing a carbon-based negative electrode material. An all-solid-state battery comprising a SEI (Solid Electrolyte Interphase) film comprising the silicon-polymer composite according to claim 11.

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