WO2025107907A1 - Battery cell, battery and electric apparatus - Google Patents

Abstract

A battery cell, a battery and an electric apparatus. The battery cell comprises a positive electrode sheet and a negative electrode sheet. The negative electrode sheet comprises a negative current collector, two insulating coatings arranged on the surface of the negative current collector that is close to the positive electrode sheet, and an interface modification layer located between the two insulating coatings, wherein the thickness of each insulating coating is denoted as H₁μm, and the width thereof is denoted as W₁mm, the thickness of the interface modification layer is denoted as H₀μm, and the negative electrode sheet meets: |H₁-H₀|≤W₁ and W₁<0. Thus, the problem of dendrite growth at a negative electrode end portion can be ameliorated, so that batteries have good cycle performance, and negative electrode sheets can also have good processing performance, such that continuous winding can be performed.

Description

Battery cells, batteries and electrical devices

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese patent application 202323160569.8, filed on November 22, 2023, entitled “Battery Cell, Battery and Electrical Device,” the entire contents of which are incorporated herein by reference.

Technical Field

The present application relates to a battery cell, a battery and an electrical device.

Background Art

As energy and environmental issues become increasingly prominent, the new energy industry has received more and more attention. In order to further improve the energy density of batteries, negative electrode-free batteries have been developed. The dendrite growth problem of negative electrode-free batteries has become one of the key issues restricting the commercialization of negative electrode-free batteries. At present, an insulating coating is usually set on the negative electrode to limit dendrite growth. However, in order to effectively reduce the dendrite growth problem, the insulating coating usually needs to be made thicker, and the current equipment and production lines make it difficult to achieve continuous winding of thicker insulating coatings. Abnormal points are prone to occur during the winding process, which affects the preparation and practical application of the battery.

Summary of the invention

The present application provides a battery cell, a battery and an electrical device, which can reduce the problem of dendrite growth at the negative terminal, so that the battery has good cycle performance, and can also make the negative electrode sheet have good processing performance and can be continuously wound.

In a first aspect, the present application provides a negative electrode sheet, comprising a positive electrode sheet and a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector, two insulating coatings arranged on the surface of the negative electrode current collector close to the positive electrode sheet, and an interface modification layer located between the two insulating coatings; the thickness of the insulating coating is denoted as H ₁ μm and the width is denoted as W ₁ mm, the thickness of the interface modification layer is denoted as H ₀ μm, and the negative electrode sheet satisfies: |H ₁ -H ₀ |≤W ₁ and W ₁ >0.

The width of the insulating coating is greater than or equal to the absolute value of the difference between the thickness of the insulating coating and the thickness of the interface modification layer, which is beneficial to improving the processing performance of the negative electrode sheet and the battery. When the width of the insulating coating is less than the absolute value of the difference between the thickness of the insulating coating and the thickness of the interface modification layer, there will be an obvious convex line when the negative electrode sheet is rolled up. When the convex line is too high and too narrow, it will cause the surface flatness of the film roll to decrease and the difficulty of aligning the concave and convex positions will increase, which will easily lead to abnormal problems such as bulging, wavy edges, tearing, and coating shedding on the film roll, affecting the processing performance of the negative electrode sheet and the battery.

Therefore, the battery cell provided by the embodiment of the present application can not only reduce the problem of internal short circuit of the battery caused by the growth of dendrites at the negative terminal, so that the battery has high reliability and good cycle performance, but also make the negative electrode sheet have good processing performance and can be continuously rolled up, which is also conducive to the commercial production of battery cells. At the same time, the preparation of battery cells is compatible with current equipment and production lines, which can also reduce the production cost of battery cells.

In some embodiments, 0.5≤W ₁ ≤20, optionally, 1≤W ₁ ≤10. The width of the insulating coating within the above range can be better compatible with the production line of current equipment, realize continuous winding of the negative electrode sheet, and is also beneficial to the commercial production of the battery. In addition, it is also beneficial for the battery to have a high energy density.

In some embodiments, 0≤|H ₁ -H ₀ |/W ₁ ≤0.6, and optionally, 0≤|H ₁ -H ₀ |/W ₁ ≤0.4. This is beneficial to improving the processing performance of the negative electrode sheet and facilitating continuous winding of the negative electrode sheet.

In some embodiments, H ₁ >H ₀ . This can further reduce the problem of short circuit in the battery caused by dendrite growth at the negative terminal during the battery charge and discharge process, and make the battery have high reliability and good cycle performance.

In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, and the width of the interface modification layer is greater than the width of the positive electrode active material layer. This is beneficial for the alkali metal to be preferentially deposited on the interface modification layer when the battery is charged, and to avoid the alkali metal from being deposited on the insulating coating as much as possible, thereby reducing the capacity loss of the battery.

In some embodiments, the width of the interface modification layer is W ₀ mm, 0.01≤W ₁ /W ₀ ≤0.1, and optionally, 0.01≤W ₁ /W ₀ ≤0.05. This is beneficial to improving the processing performance of the negative electrode sheet and can also make the battery have a high energy density.

In some embodiments, the width of the interface modification layer is denoted as W ₀ mm, 50≤W ₀ ≤200, optionally, 70≤W ₀ ≤150.

In some embodiments, 0<H ₀ ≤100, optionally, 0.5≤H ₀ ≤50.

In some embodiments, 0.5≤H ₁ ≤100, optionally, 1≤H ₁ ≤50. When the thickness of the insulating coating is within the above range, the short circuit problem in the battery caused by dendrite growth at the negative terminal during battery charge and discharge can be reduced, and the battery can have a higher energy density.

In some embodiments, the density of the insulating coating is greater than or equal to 20%, and can be 50%-80%. This can reduce the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, inorganic insulating fillers are dispersed in the insulating coating. The inorganic insulating fillers are electronic insulating materials, which are conducive to the alkali metal being preferentially deposited on the interface modification layer and avoiding the alkali metal from being deposited on the insulating coating as much as possible, thereby reducing the capacity loss of the battery.

In some embodiments, the volume distribution particle size Dv50 of the inorganic insulating filler is less than or equal to 2 μm, and can be selected as 0.001 μm-0.5 μm. When the volume distribution particle size Dv50 of the inorganic insulating filler is within the above range, it is conducive to the close stacking of the inorganic insulating filler, and can also improve the density of the insulating coating, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, the volume distribution particle size Dv50 of the inorganic insulating filler is recorded as D ₁ μm, and H ₁ /D ₁ ≥ 5. This can improve the density and uniformity of the insulating coating, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

In some embodiments, the tap density of the inorganic insulating filler is 0.8 g/cm ³ -2.0 g/cm ³ , and can be optionally 0.95 g/cm ³ -1.40 g/cm ³ . When the tap density of the inorganic insulating filler is within the above range, the density of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

In some embodiments, the specific surface area of the inorganic insulating filler is ^3m2 /g- ^25m2 /g, and can be ^7m2 /g- ^20m2 /g. When the specific surface area of the inorganic insulating filler is within the above range, the density of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

In some embodiments, the surface density of the insulating coating is 0.06 mg/cm ² -13.0 mg/cm ² , and can be optionally 0.10 mg/cm ² -3.50 mg/cm ² . When the surface density of the insulating coating is within the above range, the density and uniformity of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

In some embodiments, the interface modification layer is dispersed with an alkali metal affinity material, and the alkali metal affinity material is a sodium affinity material or a lithium affinity material. Thus, the interface modification layer can provide some active points to induce uniform deposition of alkali metals, and can also reduce the volume expansion of the negative electrode sheet, thereby improving the cycle performance of the battery, and can further reduce the problem of internal short circuit of the battery caused by dendrite growth at the negative terminal during the battery charging and discharging process, so that the battery has high reliability.

In some embodiments, the battery cell further includes a separator, the separator is located between the positive electrode sheet and the negative electrode sheet, and the bonding force between the insulating coating and the separator is greater than the bonding force between the interface modification layer and the separator. This can make the insulating coating and the separator bond better, and can further reduce the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, the bonding force between the insulating coating and the isolation film is 3N/m-50N/m, and can be 4N/m-25N/m. This can make the insulating coating and the isolation film bond better, and can further reduce the negative end dendrites growing along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, the insulating coating includes a first sublayer and a second sublayer located between the first sublayer and the negative electrode current collector, the first sublayer is not dispersed with inorganic insulating fillers, and the second sublayer is dispersed with inorganic insulating fillers. This can make the insulating coating better bonded to the separator, and can further reduce the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, the insulating coating includes a first sublayer and a second sublayer located between the first sublayer and the negative electrode current collector, the first sublayer is dispersed with an inorganic insulating filler, the second sublayer is dispersed with an inorganic insulating filler, and the weight content of the inorganic insulating filler in the first sublayer is less than the weight content of the inorganic insulating filler in the second sublayer. This can make the insulating coating better bonded to the separator, and can further reduce the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, the ratio of the thickness of the first sublayer to the second sublayer is (0.1-0.9): 1, and can be optionally (0.2-0.5): 1. When the ratio of the thickness of the first sublayer to the second sublayer is within the above range, the insulating coating can be better bonded to the isolation film, and the insulating coating can have high density, high uniformity and good resistance to dendrite puncture, thereby further reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

In some embodiments, the battery cell is a negative electrode-free sodium battery cell or a negative electrode-free lithium battery cell.

In a second aspect, the present application provides a battery, comprising the negative electrode plate of the first aspect of the present application.

In a third aspect, the present application provides an electrical device, comprising the battery of the second aspect of the present application, wherein the battery is used to provide electrical energy.

The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some implementation methods of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

FIG1 is a schematic diagram showing the structure of an electrode assembly provided in some embodiments of the present application.

FIG. 2 is a schematic diagram showing the structure of an electrode assembly provided in some other embodiments of the present application.

FIG3 is a schematic diagram showing an electrical device including a battery provided in an embodiment of the present application as a power source.

In the drawings, the drawings are not necessarily drawn to scale.

The reference numerals are as follows: 101, negative electrode current collector; 102, insulating coating; 1021, first sublayer; 1022, second sublayer; 103, interface modification layer; 201, positive electrode current collector; 202, positive electrode active material layer; 300, isolation film; T, thickness direction; W, width direction.

DETAILED DESCRIPTION

Hereinafter, the battery cells, batteries and electrical devices of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

"Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values or not including end values, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

If there is no special explanation, all embodiments and optional embodiments of the present application may be combined with each other to form a new technical solution without conflict, and such a technical solution shall be deemed to be included in the disclosure of the present application.

If there is no special explanation, all technical features and optional technical features of this application shall apply to the The features can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

Unless otherwise specified, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

Unless otherwise specified, the values of the parameters mentioned in this application can be measured by various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise specified, the test temperature of each parameter is 25°C.

The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

In the description of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of the various components in the embodiments of the present application shown in the drawings are only exemplary and should not constitute any limitation to the present application.

In the present application, the terms "plurality" and "multiple" refer to two or more.

The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack.

A battery cell is the smallest unit of a battery, which can independently realize the functions of charging and discharging. The battery cell can be cylindrical, rectangular or in other shapes, etc., which is not limited in the embodiments of the present application.

When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed connection through a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a case and battery cells, and the battery cells or battery modules are accommodated in the case. In some embodiments, the case may serve as part of the chassis structure of the vehicle. For example, part of the case may become at least a part of the floor of the vehicle, or part of the case may become at least a part of the crossbeam and longitudinal beam of the vehicle.

In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

In some embodiments, battery cells may be assembled into a battery module. The battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module.

In some embodiments, the battery modules may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

In some embodiments, the battery cells can also be directly assembled into a battery pack. The battery pack can contain multiple battery cells, and the specific number can be adjusted according to the application and capacity of the battery pack.

The embodiment of the present application provides a battery cell. The battery cell is a battery cell without a negative electrode, for example, a sodium battery cell without a negative electrode or a lithium battery cell without a negative electrode.

A battery without a negative electrode generally refers to a battery that does not actively set a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery. For example, during the manufacturing process of the battery, a negative electrode active material layer is not formed by coating or deposition of carbonaceous active materials (such as graphite, hard carbon, etc.) at the negative electrode. When the battery is charged for the first time, ions gain electrons on the negative electrode side and are deposited at the negative electrode to form metals. When discharged, the metals can be converted into ions and return to the positive electrode, realizing cyclic charge and discharge. Compared with other batteries, batteries without negative electrodes can achieve higher energy density because they do not have a conventional negative electrode active material layer.

The battery cell includes an electrode assembly and an outer package. The electrode assembly can be a wound structure or a laminated structure, which is not limited in the embodiments of the present application. The outer package can be used to encapsulate the electrode assembly. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS). The number of electrode assemblies contained in the battery cell can be one or more, which can be adjusted according to demand.

FIG1 is a schematic diagram showing the structure of an electrode assembly provided in some embodiments of the present application.

As shown in FIG. 1 , the electrode assembly of the battery cell includes a separator 300 , a positive electrode sheet and a negative electrode sheet, and the separator 300 is located between the positive electrode sheet and the negative electrode sheet.

The negative electrode plate includes a negative electrode current collector 101 , two insulating coatings 102 arranged on the surface of the negative electrode current collector 101 close to the positive electrode plate, and an interface modification layer 103 located between the two insulating coatings 102 .

The thickness of the insulating coating 102 is recorded as H ₁ μm, the width is recorded as W ₁ mm, the thickness of the interface modification layer 103 is recorded as H ₀ μm, and the negative electrode sheet satisfies: |H ₁ -H ₀ |≤W ₁ and W ₁ > 0. |H ₁ -H ₀ | represents the absolute value of the difference between H ₁ and H ₀ .

An interface modification layer is usually set on the negative electrode surface of the negative electrode-free battery, which can induce uniform metal deposition and alleviate the volume expansion of the negative electrode plate during the charging and discharging process. For safety reasons, the negative electrode plate usually includes an overhang area (i.e., the area where the negative electrode plate and the positive electrode plate do not overlap) and a non-overhang area (i.e., the area where the negative electrode plate and the positive electrode plate overlap). During the battery charging and discharging process, the overhang area will have serious dendrite problems. The continuous growth of dendrites will pierce the isolation membrane, causing an internal short circuit, which poses a safety hazard to the battery. The two ends of the interface modification layer in the width direction are empty foil areas. This area usually has serious dendrite problems. The continuous growth of dendrites toward the isolation membrane will pierce the isolation membrane, causing an internal short circuit, which poses a serious safety hazard to the battery.

The negative electrode plate provided in the embodiment of the present application is provided with two insulating coatings at both ends of the interface modification layer in the width direction. The electronic conductivity of the insulating coating is poor, thereby avoiding the deposition of alkali metals on the insulating coating as much as possible, and reducing the problem of internal short circuit in the battery caused by dendrite growth at the end position of the interface modification layer.

However, in order to effectively reduce the short circuit problem in the battery caused by dendrite growth at the negative terminal, the insulating coating usually needs to be made thicker. However, current equipment and production lines make it difficult to achieve continuous winding of thicker insulating coatings, which affects the processing performance of the negative electrode sheets and batteries and limits their practical application.

The insulating coating and the interface modification layer of the negative electrode plate provided in the embodiment of the present application satisfy |H ₁ −H ₀ |≤W ₁ and W ₁ >0.

The width of the insulating coating is greater than or equal to the absolute value of the difference between the thickness of the insulating coating and the thickness of the interface modification layer, which is beneficial to improving the processing performance of the negative electrode and the battery. When the width of the insulating coating is less than the absolute value of the difference between the thickness of the insulating coating and the thickness of the interface modification layer, there will be an obvious convex line when the negative electrode is rolled up, and the convex line is too high and too narrow. This will cause the surface flatness of the film roll to decrease and the difficulty of aligning the concave and convex positions to increase, which will easily lead to abnormal problems such as bulging, wavy edges, tearing, coating shedding, etc. on the film roll, affecting the processing performance of the negative electrode and battery.

Therefore, the battery cell provided by the embodiment of the present application can not only reduce the problem of internal short circuit of the battery caused by the growth of dendrites at the negative terminal, so that the battery has high reliability and good cycle performance, but also make the negative electrode sheet have good processing performance and can be continuously rolled up, which is also conducive to the commercial production of battery cells. At the same time, the preparation of battery cells is compatible with current equipment and production lines, which can also reduce the production cost of battery cells.

In some embodiments, the width W ₁ mm of the insulating coating 102 satisfies 0.5≤W ₁ ≤20, and optionally, 1≤W ₁ ≤10. The width of the insulating coating within the above range can be better compatible with the production line of current equipment, realize continuous winding of the negative electrode sheet, and is also beneficial to the commercial production of the battery. In addition, it is also beneficial for the battery to have a high energy density.

In some embodiments, 0≤|H ₁ -H ₀ |/W ₁ ≤0.8, optionally, 0≤|H ₁ -H ₀ |/W ₁ ≤0.6, 0≤|H ₁ -H ₀ |/W ₁ ≤0.5, 0≤|H ₁ -H ₀ |/W ₁ ≤0.4. This is beneficial to improving the processing performance of the negative electrode sheet and facilitating continuous winding of the negative electrode sheet.

In some embodiments, the thickness _H1 μm of the insulating coating 102 and the thickness _H0 μm of the interface modification layer 103 satisfy _H1 > _H0 . This can further reduce the problem of internal short circuit in the battery caused by dendrite growth at the negative terminal during battery charge and discharge, and make the battery have high reliability and good cycle performance.

In some embodiments, the positive electrode sheet includes a positive current collector 201 and a positive active material layer 202 located on at least one side of the positive current collector 201, and the width of the interface modification layer 103 can be greater than the width of the positive active material layer 202. This is conducive to the alkali metal being preferentially deposited on the interface modification layer when the battery is charged, and the alkali metal is prevented from being deposited on the insulating coating as much as possible, thereby reducing the capacity loss of the battery.

In some embodiments, the width of the insulating coating 102 is W ₁ mm, the width of the interface modification layer 103 is W ₀ mm, 0.01≤W ₁ /W ₀ ≤0.1, optionally, 0.01≤W ₁ /W ₀ ≤0.05. This is beneficial to improving the processing performance of the negative electrode sheet and can also make the battery have a high energy density.

In some embodiments, the width of the interface modification layer 103 is denoted as W ₀ mm, 50≤W ₀ ≤200, optionally, 70≤W ₀ ≤150.

In some embodiments, the thickness of the interface modification layer 103 is denoted as H ₀ μm, 0＜H ₀ ≤100, optionally, 0.5≤H ₀ ≤50.

In some embodiments, the thickness of the insulating coating 102 is recorded as H ₁ μm, 0.5≤H ₁ ≤100, optionally, 1≤H ₁ ≤50. When the thickness of the insulating coating is within the above range, the short circuit problem in the battery caused by dendrite growth at the negative terminal during battery charging and discharging can be reduced, and the battery can also have a higher energy density.

The thickness of the insulating coating 102 and the thickness of the interface modification layer 103 can be measured using a micrometer. For accuracy, multiple positions (eg, 5-10) can be measured and then an average value can be taken.

The width of the insulating coating 102 and the width of the interface modification layer 103 can be measured using a soft ruler with a minimum quantile of 0.5 mm. For accuracy, multiple positions (eg, 5-10) can be measured and then the average value can be taken.

In some embodiments, the density of the insulating coating 102 may be greater than or equal to 20%, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

Optionally, the density of the insulating coating 102 may be 30%-85%, 50%-80%, thereby further reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby further reducing the internal short circuit problem of the battery.

The density of the insulating coating is well known in the art and can be measured using instruments and methods known in the art. Density of insulating coating = ( _P1 / _P2 ) × 100%. _P1 represents the apparent density of the sample, which can be calculated based on the weight and volume of the sample; _P2 represents the true density of the sample, which can be measured using a true density tester using an inert gas (such as nitrogen) as a medium and a gas displacement method in accordance with GB/T 24586-2009. During the test, a sample of a suitable size can be cut out from the area of the negative electrode sheet that contains the insulating coating but does not contain the interface modification layer for testing. When the insulating coating is located on both surfaces of the negative electrode current collector, the insulating coating on one side can be scraped off for testing.

In some embodiments, inorganic insulating fillers are dispersed in the insulating coating 102. The inorganic insulating fillers are electronic insulating materials, which are conducive to the alkali metal being preferentially deposited on the interface modification layer and avoiding the alkali metal from being deposited on the insulating coating as much as possible, thereby reducing the capacity loss of the battery.

The density of the insulating coating is related to the parameters of the insulating coating (such as thickness, surface density, etc.), the parameters of the inorganic insulating filler in the insulating coating (such as particle size, particle morphology, particle stacking morphology), and the content of the inorganic insulating filler and the binder. The density of the insulating coating can be adjusted by adjusting one or more of the above parameters.

In some embodiments, the volume distribution particle size Dv50 of the inorganic insulating filler may be less than or equal to 2 μm, and may be optionally 0.001 μm-0.5 μm. When the volume distribution particle size Dv50 of the inorganic insulating filler is within the above range, it is conducive to the close stacking of the inorganic insulating filler, and can also improve the density of the insulating coating, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

The volume distribution particle size Dv50 of the material is well known in the art, which indicates the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured using instruments and methods well known in the art. For example, it can be conveniently measured using a laser particle size analyzer with reference to GB/T19077-2016. The test instrument can be the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.

In some embodiments, the thickness of the insulating coating 102 is recorded as H ₁ μm, the volume distribution particle size Dv50 of the inorganic insulating filler is recorded as D ₁ μm, and H ₁ /D ₁ ≥ 5. H ₁ /D ₁ can reflect the number of stacking layers of the inorganic insulating filler. When the number of stacking layers of the inorganic insulating filler is large, the density and uniformity of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, the tap density of the inorganic insulating filler may be 0.8 g/cm ³ -2.0 g/cm ³ , and may be 0.95 g/cm ³ -1.40 g/cm ³ . When the tap density of the inorganic insulating filler is within the above range, the density of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

The tap density of a material is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester in accordance with GB/T 5162-2006. The test instrument can be Dandong Better BT-301, and the test parameters are as follows: vibration frequency 250±15 times/minute, amplitude 3±0.2mm, vibration number 5000 times, and measuring cylinder 25mL.

In some embodiments, the specific surface area of the inorganic insulating filler may be ^3m2 /g- ^25m2 /g, and may be ^7m2 /g- ^20m2 /g. When the specific surface area of the inorganic insulating filler is within the above range, the density of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

The specific surface area of a material is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured by referring to GB/T 19587-2017, using the nitrogen adsorption specific surface area analysis test method, and calculated using the BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be measured by the ASAP 3020 surface area and pore size analyzer of Micromeritics, USA.

The inorganic insulating filler in the insulating coating is a known material and can also be directly commercially available. In some embodiments, the inorganic insulating filler in the insulating coating includes one or more of ceramics, silicates, minerals, and glasses. Optionally, the inorganic insulating filler includes one or more of aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, aluminum magnesium silicate, lithium magnesium silicate, sodium magnesium silicate, boehmite, mica, bentonite, hectorite, kaolin, and talc.

The insulating coating layer also contains a binder, which is used to bind the inorganic insulating filler to the negative electrode current collector. The binder in the insulating coating layer is a known material and can also be directly commercially available. In some embodiments, the binder in the insulating coating includes styrene-butadiene copolymer, acrylate-styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic rubber, butyl rubber, styrene-butadiene rubber, fluororubber, polyethylene, polypropylene, ethylene propylene diene rubber (EPM), ethylene propylene diene rubber (EPDM), polyethylene oxide, polyepichlorohydrin, polyvinyl pyrrolidone, polyphosphazene, polyacrylonitrile, polystyrene, polyvinyl pyridine, chlorosulfonated polyethylene, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyacrylic acid (PAA), polyimide, polyamideimide, polyimide-polyamideimide copolymer, and one or more of the polymers in which the foregoing polymers are partially or fully substituted with alkali metals.

In some embodiments, the weight content of the inorganic insulating filler in the insulating coating may be 10%-90%, optionally 10%-80%, and more optionally 20%-70%, based on the total weight of the insulating coating.

In some embodiments, the weight content of the binder in the insulating coating may be greater than or equal to 10%, optionally 20%-90%, and more optionally 30%-80%, based on the total weight of the insulating coating.

By adjusting the weight content of the inorganic insulating filler and/or binder in the insulating coating within the above range, the density and uniformity of the insulating coating can be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

In some embodiments, the surface density of the insulating coating may be 0.06 mg/cm ² -13.0 mg/cm ² , and may be 0.10 mg/cm ² -3.50 mg/cm ² . When the surface density of the insulating coating is within the above range, the density and uniformity of the insulating coating may be improved, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

In some embodiments, an alkali metal affinity material is dispersed in the interface modification layer 103, and the alkali metal affinity material is a sodium affinity material or a lithium affinity material. The interface modification layer 103 is a sodium affinity layer or a lithium affinity layer. Thus, the interface modification layer can provide some active points to induce uniform deposition of alkali metals, and can also reduce the volume expansion of the negative electrode sheet, thereby improving the cycle performance of the battery, and can further reduce the problem of internal short circuit of the battery caused by dendrite growth at the negative terminal during the battery charging and discharging process, so that the battery has high reliability.

In some embodiments, the alkali metal affinity material in the interface modification layer 103 is a known material and can also be directly commercially available, for example, it can include one or more of carbon materials, metals, metal alloys, and metal oxides. The metal elements in the metals, metal alloys, and metal oxides are all known elements, for example, they can include one or more of Zn, Ag, Al, Mg, Sn, and Au.

In some embodiments, the carbon material may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, soft carbon, and hard carbon.

In order to improve the battery performance, the negative electrode of the negative electrode-free battery can also be provided with some conventional substances that can be used as negative electrode active materials, such as carbon materials. Although these substances have a certain capacity, due to their low content and the fact that they are not used as the main negative electrode active materials in the battery, the battery thus constructed can still be regarded as a negative electrode-free battery. The CB (Cell Balance) value of a negative electrode-free battery is usually very small. For example, in some embodiments, the CB value of a negative electrode-free battery can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery divided by the unit area capacity of the positive electrode. Since the negative electrode-free battery does not contain or only contains a small amount of negative electrode active materials, the unit area capacity of the negative electrode is small, and thus the CB value is very small, for example, usually less than or equal to 0.1.

The interface modification layer may also include a binder. The binder is a known material and may also be directly commercially available. In some embodiments, the binder in the interface modification layer 103 may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), sodium carboxymethyl cellulose (CMC), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

In some embodiments, the weight content of the alkali metal affinity material in the interface modification layer 103 may be 2%-98%, optionally 5%-80%, based on the total weight of the interface modification layer 103 .

In some embodiments, the weight content of the binder in the interface modification layer 103 may be 2%-98%, optionally 20%-95%, based on the total weight of the interface modification layer 103 .

In some embodiments, the bonding force between the insulating coating 102 and the isolation film 300 may be greater than the bonding force between the interface modification layer 103 and the isolation film 300. This can make the insulating coating and the isolation film bonded better, and can further reduce the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, the bonding force between the insulating coating 102 and the isolation film 300 is 3N/m-50N/m, and can be 4N/m-25N/m. This can make the insulating coating and the isolation film bonded better, and can further reduce the negative end dendrites growing along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

FIG. 2 is a schematic diagram showing the structure of an electrode assembly provided in some other embodiments of the present application.

As shown in FIG. 2 , in some embodiments, the insulating coating 102 may include a first sublayer 1021 and a second sublayer 1022 located between the first sublayer 1021 and the negative electrode current collector 101 .

In some embodiments, the first sublayer 1021 is not dispersed with inorganic insulating fillers, and the second sublayer 1022 is dispersed with inorganic insulating fillers. This can make the insulating coating and the isolation film bonded better, and can further reduce the negative terminal dendrites growing along the pores of the insulating coating during the battery charging and discharging process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance. At this time, the weight content of the binder in the first sublayer 1021 is 100%.

In some embodiments, inorganic insulating fillers are dispersed in the first sublayer 1021, and inorganic insulating fillers are dispersed in the second sublayer 1022, and the weight content of the inorganic insulating fillers in the first sublayer 1021 is less than the weight content of the inorganic insulating fillers in the second sublayer 1022. This can make the insulating coating and the isolation film bond better, and can further reduce the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and can also make the battery have high reliability and good cycle performance.

In some embodiments, the weight content of the first binder in the first sub-layer 1021 is greater than or equal to 15%, and the weight content of the inorganic insulating filler is less than or equal to 85%, based on the total weight of the first sub-layer.

This can make the insulating coating and the isolation membrane bond better, and can further reduce the continuous growth of dendrites at the negative end along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

In some embodiments, the weight content of the binder in the second sub-layer 1022 may be 1%-30%, and the weight content of the inorganic insulating filler may be 70%-99%, based on the total weight of the second sub-layer.

Optionally, the weight content of the binder in the second sub-layer 1022 may be 5%-30%, and the weight content of the inorganic insulating filler may be 70%-95%, based on the total weight of the second sub-layer.

This can make the insulating coating have high density, high uniformity and good resistance to dendrite puncture, thereby reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during battery charging and discharging, thereby reducing the internal short circuit problem of the battery and making the battery have high reliability and good cycle performance.

The types of inorganic insulating fillers in the first sublayer and the second sublayer can be the same or different, and the types of binders in the first sublayer and the second sublayer can be the same or different. The types of inorganic insulating fillers and binders can be as described above and will not be repeated here.

In some embodiments, the thickness ratio of the first sublayer 1021 to the second sublayer 1022 may be (0.1-0.9): 1, and may be (0.2-0.5): 1. When the thickness ratio of the first sublayer to the second sublayer is within the above range, the insulating coating and the isolation film can be better bonded, and the insulating coating can have high density, high uniformity, and good resistance to dendrite puncture, thereby further reducing the continuous growth of dendrites at the negative terminal along the pores of the insulating coating during the battery charge and discharge process, thereby reducing the internal short circuit problem of the battery, and also making the battery have high reliability and good cycle performance.

In some embodiments, the negative electrode current collector 101 may include one or more of a metal foil, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, a carbon paper current collector, and a composite current collector.

In some embodiments, the negative electrode current collector 101 may have a porous structure. For example, the negative electrode current collector 101 may include one or more of a porous aluminum foil, a porous copper foil, and a porous stainless steel foil.

In some embodiments, the negative electrode current collector 101 may include a polymer material base layer and a metal layer formed on at least one side of the polymer material base layer.

Optionally, the metal material in the metal layer may include one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

Optionally, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

The preparation method of the negative electrode sheet is well known. In some embodiments, the interface modification layer slurry and the insulating coating slurry can be coated on the negative electrode current collector and dried. The coating method can include gravure coating, micro gravure coating, extrusion coating, transfer coating or spraying.

The positive electrode sheet includes a positive electrode current collector 201 and a positive electrode active material layer located on at least one side of the positive electrode current collector 201. 202. The positive electrode current collector 201 has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer 202 is located on any one or both of the two opposite surfaces of the positive electrode current collector 201. As shown in FIG. 1 and FIG. 2, the positive electrode active material layer 202 is located on one side of the positive electrode current collector 201, but the present application is not limited thereto.

The positive electrode active material layer 202 includes a positive electrode active material.

When the battery cell is a negative electrode-free lithium battery cell, the positive electrode active material includes a material capable of extracting and inserting lithium. As an example, the positive electrode active material may include one or more of a lithium transition metal oxide, a lithium-containing phosphate, and their respective modified compounds. Examples of lithium transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of lithium-containing phosphates may include one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.

When the battery cell is a sodium battery cell without a negative electrode, the positive electrode active material includes a material capable of extracting and embedding sodium. As an example, the positive electrode active material may include one or more of a layered transition metal oxide (including P2 type, O3 type, etc.), a polyanion material (such as phosphate, fluorophosphate, pyrophosphate, sulfate, etc.), and a Prussian material.

In some embodiments, as examples, the positive electrode active material may include _{one or more of} NaFeO2, NaCoO2, _NaCrO2 , _NaMnO2 , _NaNiO2 , _Na0.67MO2 (M may include at least two of Fe, Co, Cr, Mn, Ni, V, Ti, and Mo), _NaMO2 (M may include at least two of Fe, Co _, Ni, _V , Ti, and Mo), _NaFePO4 , _NaMnPO4 , _NaCoPO4 , _Na4Fe3 ( _PO4 ) _2O7 , _Na3V2 ( _PO4 ) _2F3 , _Na3V2 ( _PO4 ) _{3 ,} sodium iron pyrophosphate, Prussian blue, _Prussian white, and _their respective modified compounds.

The modified compounds of the above-mentioned positive electrode active materials may be the ones that undergo doping modification and/or surface coating modification on the positive electrode active materials.

In some embodiments, the positive active material layer 202 may further include a positive conductive agent, which may include, for example, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode active material layer 202 may further include a positive electrode binder. As an example, the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylic resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) One or more.

In some embodiments, the positive electrode current collector 201 may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one side of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

The positive electrode active material layer 202 is usually formed by coating the positive electrode slurry on the positive electrode current collector 201, drying and cold pressing. The positive electrode slurry is usually a mixture of the positive electrode active material, an optional positive electrode conductive agent, an optional positive electrode binder and any The other components are dispersed in a solvent and stirred uniformly. The solvent may be N-methylpyrrolidone (NMP).

The separator 300 is disposed between the positive electrode sheet and the negative electrode sheet, and mainly plays the role of preventing internal short circuit. The present application has no particular limitation on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

In some embodiments, the material of the isolation film 300 may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation film 300 may be a single-layer film or a multi-layer composite film. When the isolation film 300 is a multi-layer composite film, the materials of each layer are the same or different.

The battery cell also includes an electrolyte. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can include one or more selected from solid electrolytes and liquid electrolytes (ie, electrolytes).

In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

When the battery cell is a negative electrode-free lithium battery cell, as an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO ₂ F ₂ ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

When the battery cell is a negative electrode-free sodium battery cell, as an example, the electrolyte salt may include one or more of sodium hexafluorophosphate (NaPF ₆ ), sodium tetrafluoroborate (NaBF ₄ ), sodium perchlorate (NaClO ₄ ), sodium hexafluoroarsenate (NaAsF ₆ ), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO ₂ F ₂ ), sodium difluorobis(oxalatophosphate) (NaDFOP), and sodium tetrafluorooxalatophosphate (NaTFOP).

In some embodiments, the solvent may include one or more of an ester solvent, a sulfone solvent, and an ether solvent. As an example, the solvent may include but is not limited to one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), diethyl sulfone (ESE), dimethoxymethane (DMM), diethylene glycol dimethyl ether (DG), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), and tetraethylene glycol dimethyl ether.

In some embodiments, the electrolyte may also optionally include additives, for example, additives that can improve certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high temperature performance of the battery, additives that improve the low temperature power performance of the battery, etc.

The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and/or a lamination process, and the electrode assembly is placed in an outer package, and the above-mentioned electrolyte is injected after drying. After packaging, standing, formation and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

The embodiment of the present application also provides an electrical device, which includes a battery provided in the embodiment of the present application, and the battery is used to provide electrical energy. The battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

The electrical device can select a specific type of battery, such as a battery cell, a battery module or a battery pack, according to its usage requirements.

Fig. 3 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module may be used.

As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

Example

The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present application are apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

Example 1

(1) Preparation of negative electrode sheet

Carbon nanotubes (CNT) and sodium carboxymethyl cellulose (CMC) were fully stirred and mixed in a proper amount of solvent deionized water at a weight ratio of 80:20 to form an interface modification layer slurry.

The inorganic insulating filler alumina and the binder polyacrylic acid (PAA) were fully stirred and mixed in a proper amount of solvent deionized water at a weight ratio of 70:30 to form an insulating coating slurry. The volume distribution particle size Dv50 of the alumina was 0.25 μm, the tap density was 1.38 g/cm ³ , and the specific surface area was 13.4 m ² /g.

The interface modification layer slurry is coated on the surface of the negative electrode current collector copper foil, and the insulating coating slurry is coated on both ends of the interface modification layer slurry in the width direction. After drying and welding the negative electrode tabs, the negative electrode sheet is obtained.

The width _W1 of the two insulating coating layers is 5 mm, the thickness _H1 is 5 μm, the surface density is 0.5 mg/ ^cm2 , and the compactness is 50%.

The width _W0 of the interface modification layer was 85 mm, and the thickness _H0 was 5 μm.

(2) Preparation of positive electrode sheet

The positive electrode active material sodium iron pyrophosphate, the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a proper amount of solvent NMP at a weight ratio of 90:5:5 to form a uniform positive electrode slurry; the positive electrode slurry is coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

(3) Preparation of electrolyte

The fully dried NaPF ₆ was dissolved in diethylene glycol dimethyl ether (DEGDME) to prepare an electrolyte with a concentration of 1 mol/L.

(4) Preparation of isolation membrane

A porous polyethylene membrane was used as the separator.

(5) Preparation of batteries

The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a negative electrode-free sodium battery is obtained.

Example 2 to Example 5

The preparation method of the battery is similar to that of Example 1, except that in the preparation of the negative electrode sheet, the width of the insulating coating, the thickness of the insulating coating and/or the thickness of the interface modification layer are different. The specific parameters are detailed in Table 1.

Comparative Example 1

The preparation method of the battery is similar to that of Example 1-1, except that the preparation process of the negative electrode plate is different.

Carbon nanotubes (CNT) and sodium carboxymethyl cellulose (CMC) were fully stirred and mixed in a proper amount of solvent deionized water at a weight ratio of 80:20 to form an interface modification layer slurry.

The interface modification layer slurry is coated on the surface of the negative electrode current collector copper foil, and after drying and welding the negative electrode tab, a negative electrode sheet is obtained.

Comparative Example 2

The preparation method of the battery is similar to that of Example 1, except that in the preparation of the negative electrode plate, the thickness of the insulating coating is different. The specific parameters are shown in Table 1.

Performance Testing

(1) Cyclic performance test

At 25°C, the prepared battery was charged at 1C constant current to a voltage of 3.65V, then charged at 3.65V constant voltage to a current of 0.05C, and after standing for 5 minutes, the battery was discharged at 1C constant current to a voltage of 2.0V. This is a charge and discharge cycle process, and the discharge capacity this time is the discharge capacity of the battery after the first cycle. The battery was cycled 500 times in the above manner.

The capacity retention rate of the battery after 500 cycles = the discharge capacity after 500 cycles / the discharge capacity after the first cycle.

(2) Sodium analysis test

At 25°C, the prepared battery was charged at a constant current of 5C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After standing for 5 minutes, the battery was discharged at a constant current of 1C to a voltage of 2.0V. This was a charge and discharge cycle. The battery was cycled 10 times in the above manner, then charged at a constant current of 5C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, and the battery was disassembled to observe the sodium precipitation at the junction of the interface modification layer at the negative terminal and the insulating coating.

The degree of sodium precipitation can be determined according to the following situations. Failure: The width of the area where sodium dendrites precipitate is greater than or equal to 80% of the width of the insulating coating. Severe precipitation: The width of the area where sodium dendrites precipitate is greater than or equal to 50% but less than 80% of the width of the insulating coating. Moderate precipitation: The width of the area where sodium dendrites precipitate is greater than or equal to 20% but less than 50% of the width of the insulating coating. Slight precipitation: The width of the area where sodium dendrites precipitate is greater than or equal to 5% but less than 20% of the width of the insulating coating. No precipitation: The width of the area where sodium dendrites precipitate is less than 5% of the width of the insulating coating.

(3) Negative electrode processing performance test

The negative electrode sheet prepared above was rolled up separately, with the core diameter between 30mm and 60mm. The length position when any of the following abnormalities occurred during the rolling of the negative electrode sheet was recorded as the abnormal point: the length of the wave edge of the sheet was greater than 20mm, the length of the tear of the sheet was greater than 20mm, the length of the area where the insulation coating fell off was greater than 20mm, and the length of the area where the interface modification layer fell off was greater than 20mm. The total length of the negative electrode sheet from the start of rolling up to the occurrence of three abnormal points was collected as the processing performance of the negative electrode sheet. Judgment criteria: If the winding length exceeds 3000m, no further testing will be conducted, and it is considered that the negative electrode sheet can basically meet the requirements of mass production processing.

The test results are shown in Table 1. Since no insulating coating is provided on the negative electrode current collector of Comparative Example 1, "failure" means that the width of the region where sodium dendrites are precipitated is greater than 5 mm.

Table 1

It can be seen from the test results in Table 1 that by adjusting the thickness H ₁ μm of the insulating coating of the negative electrode plate, the width W ₁ mm of the insulating coating, and the thickness H ₀ μm of the interface modification layer to satisfy |H ₁ -H ₀ |≤W ₁ and W ₁ >0, the negative electrode plate can have good processing performance, reduce the degree of sodium precipitation, reduce the internal short circuit problem caused by dendrite growth at the negative end during battery charging and discharging, and also make the battery have good cycle performance.

It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims (18)

A battery cell comprises a positive electrode sheet and a negative electrode sheet, wherein: The negative electrode plate comprises a negative electrode current collector, two insulating coatings arranged on the surface of the negative electrode current collector close to the positive electrode plate, and an interface modification layer located between the two insulating coatings; The thickness of the insulating coating is denoted as H ₁ μm, and the width is denoted as W ₁ mm. The thickness of the interface modification layer is denoted as H ₀ μm. The negative electrode sheet satisfies: |H ₁ −H ₀ |≤W ₁ and W ₁ >0. The battery cell according to claim 1, wherein: 0.5≤W ₁ ≤20, optionally, 1≤W ₁ ≤10; and/or, 0≤|H ₁ −H ₀ |/W ₁ ≤0.6. Optionally, 0≤|H ₁ −H ₀ |/W ₁ ≤0.4. The battery cell according to any one of claims 1 to 2, wherein H ₁ >H ₀ . The battery cell according to any one of claims 1 to 3, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, and the width of the interface modification layer is greater than the width of the positive electrode active material layer. The battery cell according to any one of claims 1 to 4, wherein the width of the interface modification layer is W ₀ mm, 0.01≤W ₁ /W ₀ ≤0.1, optionally, 0.01≤W ₁ /W ₀ ≤0.05; and/or, 50≤W ₀ ≤200, optionally, 70≤W ₀ ≤150. The battery cell according to any one of claims 1 to 5, wherein: 0＜H ₀ ≤100, optionally, 0.5≤H ₀ ≤50; and/or, 0.5≤H ₁ ≤100, optionally, 1≤H ₁ ≤50. The battery cell according to any one of claims 1 to 6, wherein the density of the insulating coating is greater than or equal to 20%, and can be optionally 50%-80%. The battery cell according to any one of claims 1 to 7, wherein an inorganic insulating filler is dispersed in the insulating coating. The battery cell according to claim 8, wherein the insulating coating satisfies at least one of the following conditions (1) to (4): (1) The volume distribution particle size Dv50 of the inorganic insulating filler is less than or equal to 2 μm, and can be selected to be 0.001 μm-0.5 μm; (2) The volume distribution particle size Dv50 of the inorganic insulating filler is denoted as D ₁ μm, H ₁ /D ₁ ≥5; (3) The tap density of the inorganic insulating filler is 0.8 g/cm ³ -2.0 g/cm ³ , and can be 0.95 g/cm ³ -1.40 g/cm ³ ; (4) The specific surface area of the inorganic insulating filler is 3 m ² /g-25 ^{m 2} /g, and can be 7 m ² /g-20 m ² /g. The battery cell according to any one of claims 1 to 9, wherein the surface density of the insulating coating is 0.06 mg/cm ² -13.0 mg/cm ² , and optionally 0.10 mg/cm ² -3.50 mg/cm ² . The battery cell according to any one of claims 1 to 10, wherein an alkali metal affinity material is dispersed in the interface modification layer, and the alkali metal affinity material is a sodium affinity material or a lithium affinity material. The battery cell according to any one of claims 1 to 11, wherein the battery cell further comprises a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet. The bonding force between the insulating coating and the isolation film is greater than the bonding force between the interface modification layer and the isolation film; and/or, The bonding force between the insulating coating and the isolation film is 3N/m-50N/m, and can be optionally 4N/m-25N/m. The battery cell according to any one of claims 1 to 12, wherein the insulating coating comprises a first sublayer and a second sublayer located between the first sublayer and the negative electrode current collector, the first sublayer is not dispersed with an inorganic insulating filler, and the second sublayer is dispersed with an inorganic insulating filler. A battery cell according to any one of claims 1 to 12, wherein the insulating coating comprises a first sublayer and a second sublayer located between the first sublayer and the negative electrode current collector, an inorganic insulating filler is dispersed in the first sublayer, an inorganic insulating filler is dispersed in the second sublayer, and the weight content of the inorganic insulating filler in the first sublayer is less than the weight content of the inorganic insulating filler in the second sublayer. The battery cell according to any one of claims 13-14, wherein the ratio of the thickness of the first sublayer to the second sublayer is (0.1-0.9):1, and can be optionally (0.2-0.5):1. The battery cell according to any one of claims 1 to 15, wherein the battery cell is a negative electrode-free sodium battery cell or a negative electrode-free lithium battery cell. A battery comprising the battery monomer according to any one of claims 1 to 16. An electrical device comprising the battery according to claim 17, wherein the battery is used to provide electrical energy.