Negative electrode sheet, battery cell, battery, and power using device

Abstract

The application relates to a negative electrode sheet, a battery monomer, a battery and a power utilization device. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material and a metal salt, and the negative electrode sheet satisfies: 0.40 <= a / m <= 5.20; wherein a nm represents a volume average particle size D v50 of the metal salt; and m g / L represents a solubility of the metal salt in an electrolyte.

Description

TECHNICAL FIELD

[0001] The present application relates to a negative electrode sheet, a battery monomer, a battery and a power utilization device. BACKGROUND

[0002] Battery monomers have reliable working performance, and advantages such as no pollution and no memory effect, and are widely used. For example, as environmental protection issues are increasingly valued, new energy vehicles are increasingly popular, and the demand for power type battery monomers will show explosive growth.

[0003] As the application range of batteries is more and more extensive, the requirements for the performance of batteries are gradually strict. However, the cycle performance and storage performance of battery monomers are still relatively poor, and need to be further improved. SUMMARY

[0004] The present application provides a negative electrode sheet, a battery monomer, a battery and a power utilization device, and the cycle performance and storage performance of the battery monomer described in the present application can be improved.

[0005] In a first aspect, the embodiments of the present application provide a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material and a metal salt, the negative electrode sheet satisfying: 0.40≤a / m≤5.20; wherein a nm represents the volume average particle size Dv50 of the metal salt; m g / L represents the solubility of the metal salt in the electrolyte. v50

[0006] According to the negative electrode sheet of the embodiments of the present application, when the volume average particle size of the metal salt and the solubility of the metal salt satisfy the above relationship, the metal salt can gradually dissolve in the electrolyte during the cycle charging and discharging process of the battery monomer, and even dissolve in the whole life cycle of the battery monomer. The metal salt can continuously act on the surface of the active material, and can form a uniform and dense interface film on the surface of the active material. The structural stability of the interface film is high, which can play a good protective role on the active material and improve the cycle life of the battery monomer. For example, the metal salt acts on the surface of the positive electrode active material to participate in the formation of the positive electrode electrolyte interface (CEI) film, which plays a good protective role on the positive electrode active material, or the metal salt acts on the surface of the negative electrode active material to participate in the formation of the solid electrolyte interface (SEI) film, which plays a good protective role on the negative electrode active material.

[0007] ​In some embodiments, 1.25≤a / m≤5.00. When the negative electrode sheet satisfies the above range, the metal salt can continuously release during the cycle charging and discharging of the battery cell, thereby being able to play a good protective role on the active material and prolong the cycle performance of the battery cell.

[0008] In some embodiments, 3≤a≤300. The volume average particle size D v50 When the above range is satisfied, the volume average particle size of the metal salt is relatively small, which is more conducive to the uniform dispersion of the metal salt in the negative electrode active material layer, the metal salt dissolved in the electrolyte is uniformly distributed, so that the metal salt can be uniformly dispersed on the surface of the active material layer to form an interface film with uniform performance, thereby further improving the cycle performance of the battery cell using the negative electrode sheet.

[0009] In some embodiments, 1≤m≤100. When the solubility of the metal salt in the electrolyte is in the above range, the metal salt can be dissolved in the electrolyte to some extent, and the metal salt can be gradually released into the electrolyte, so that the electrolyte can continuously act on the system to improve the cycle performance of the battery cell.

[0010] In some embodiments, the negative electrode sheet satisfies: 0.167≤a / b≤100; optionally, 2.5≤a / b≤12.5; further optionally, 2.8≤a / b≤8.5; wherein a nm represents the volume average particle size D v50 of the metal salt; and b μm represents the volume average particle size D v50 of the negative electrode active material.

[0011] According to the negative electrode sheet of the embodiments of the present application, when the volume average particle size of the metal salt and the volume average particle size of the negative electrode active material are in the above range, the metal salt is uniformly distributed in the negative electrode active material layer, which is conducive to the uniform release and dissolution of the metal salt in the electrolyte, the metal salt dissolved in the electrolyte is uniformly formed on the surface of the active material to form a uniform and dense interface film, thereby further improving the cycle performance of the battery cell using the negative electrode sheet; in addition, the metal salt basically does not interfere with the adhesion between the negative electrode active material particles, thereby being able to improve the adhesion between the negative electrode active material particles, and also being able to improve the compaction density of the negative electrode active material layer after compaction, thereby improving the energy density of the battery cell.

[0012] In some embodiments, 1≤b≤30, b μm represents the volume average particle size D v50 of the negative electrode active material. When the volume average particle size of the negative electrode active material is in the above range, it is conducive to further improving the cycle performance of the battery cell, etc.

[0013] In some embodiments, the negative electrode tab satisfies: 0.4≤c / d≤1500; optionally, 0.4≤c / d≤100; wherein c% represents the mass content of the metal salt relative to the total mass of the negative electrode active material layer; d mg / cm 2 represents the area density of the negative electrode active material layer.

[0014] According to the negative electrode tab of the embodiments of the present application, when the negative electrode tab satisfies the above range, the metal salt dissolved in the electrolyte participates in the film formation reaction and is consumed, and then the metal salt in the negative electrode active material layer is dissolved in the electrolyte, which can enable the metal salt to be continuously released into the electrolyte during the cycle charging and discharging of the battery cell, the release time of the metal salt is longer, and even the metal salt is dissolved in the whole life cycle of the battery cell, and the metal salt can continuously participate in the film formation reaction on the surface of the active material, thereby continuously protecting the surface of the active material and prolonging the cycle life of the battery cell.

[0015] In some embodiments, 0.1≤c≤15; optionally, 1≤c≤10; c% represents the mass content of the metal salt relative to the total mass of the negative electrode active material layer. When the mass content of the metal salt is in the above range, the surface of the active material can be more continuously protected, and the cycle life of the battery cell is prolonged.

[0016] In some embodiments, 0.01≤d≤0.25; optionally, 0.10≤d≤0.25; d mg / cm 2 represents the area density of the negative electrode active material layer. When the area density of the negative electrode active material layer is in the above range, the energy density of the battery cell can be further improved.

[0017] In some embodiments, the metal salt comprises at least one of a nitrate salt, a nitrite salt, a phosphate salt, a sulfate salt, and a halide salt.

[0018] In some embodiments, the nitrate salt comprises at least one of an alkali metal nitrate, silver nitrate, and copper nitrate.

[0019] In some embodiments, the nitrite salt comprises at least one of an alkali metal nitrite, silver nitrite, and copper nitrite.

[0020] In some embodiments, the phosphate salt comprises at least one of an alkali metal phosphite, silver phosphite, and copper phosphite.

[0021] In some embodiments, the sulfate salt comprises at least one of an alkali metal sulfate, silver sulfate, and copper sulfate.

[0022] In some embodiments, the halide salt comprises at least one of an alkali metal halide, silver halide, and copper halide.

[0023] In a second aspect, the application also provides a battery monomer, which comprises the negative electrode plate according to any one of the embodiments of the first aspect of the application.

[0024] In a third aspect, the application also provides a battery, which comprises the battery monomer according to any one of the embodiments of the second aspect of the application.

[0025] In a fourth aspect, the application also provides an electric device, which comprises the battery according to any one of the embodiments of the third aspect of the application. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed to be used in the embodiments of the application will be briefly introduced as follows. Obviously, the drawings described below are only some of the embodiments of the application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of the drawings.

[0027] Figure 1 is a schematic diagram of an embodiment of the battery monomer of the application.

[0028] Figure 2 is a schematic diagram of an embodiment of the battery monomer of Figure 1 .

[0029] Figure 3 is a schematic diagram of an embodiment of the battery module of the application.

[0030] Figure 4 is a schematic diagram of an embodiment of the battery pack of the application.

[0031] Figure 5 is a schematic diagram of an embodiment of the battery pack of Figure 4 .

[0032] Figure 6 is a schematic diagram of an embodiment of the electric device comprising the battery monomer of the application as a power supply.

[0033] The drawings are not necessarily drawn according to the actual scale.

[0034] The reference signs are explained as follows:

[0035] 1, battery pack; 2, upper box body; 3, lower box body; 4, battery module;

[0036] 5, battery monomer; 51, shell; 52, electrode assembly;

[0037] 53, cover plate;

[0038] 6, electric device. DETAILED DESCRIPTION

[0039] Hereinafter, specific embodiments of the negative electrode sheet, the battery cell, the battery, and the power using device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known to those skilled in the art, repeated description of substantially identical configurations, is omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0040] The ranges disclosed herein are defined by their lower and upper limits. Ranges that include both endpoints are inclusive of the endpoints. Ranges that exclude both endpoints are not inclusive of the endpoints. Ranges that include one or both endpoints are inclusive of the endpoint(s) and ranges that exclude one or both endpoints are not inclusive of the endpoint(s). Ranges are defined by their lower and upper limits. Unless specifically stated otherwise, the use of a range of values for a parameter includes each and every value and sub-range within the range. Exemplary values for physical parameters, such as temperature and pressure, are included in ranges unless otherwise stated herein. All ranges and parameters, including those for quantities, are inclusive of the recited endpoint and endpoints, unless expressly stated otherwise. For example, a range of "about 1% to 20%" is inclusive of from 1% to 20% and is also inclusive of from 20% to 1%. All individual values and sub-ranges from the stated ranges for parameters are included and disclosed. When no range or specific value is given, the range of values, for example, useful in the application is contemplated, for example, from 1 to 100. It is specifically intended that at least some minimum and maximum values for parameters be included in the disclosure as potential

[0041] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0042] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0043] If not specified otherwise, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0044] If not specified otherwise, the terms "comprising" and "including" mentioned in the present application mean open-ended, and can also mean closed-ended. For example, the terms "comprising" and "including" can mean that other components not listed can also be included, or can mean that only the listed components are included.

[0045] If not specified otherwise, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0046] The battery cell comprises an electrode assembly and an electrolyte, the electrode assembly comprises a positive electrode sheet and a negative electrode sheet and a separator, the positive electrode sheet comprises a positive active material capable of providing active ions, the negative electrode sheet comprises a negative active material, and the separator is located between the positive electrode sheet and the negative electrode sheet to insulate the positive electrode sheet and the negative electrode sheet, and the active ions such as sodium ions and lithium ions migrate between the positive electrode sheet and the negative electrode sheet through the electrolyte, thereby realizing the charging and discharging of the battery cell.

[0047] The contact interface between the active material and the electrolyte is a solid-liquid contact interface, and side reactions are prone to occur at the interface, causing the active material to be consumed or even destroyed, which may shorten the cycle life of the battery cell. In order to improve the cycle life of the battery cell, in the related art, it is hoped that by adding a film-forming additive to the electrolyte, the film-forming additive participates in the film-forming reaction on the surface of the active material, thereby playing a protective role on the active material; however, part of the film-forming additive has low solubility in the electrolyte, and it is difficult to realize the use by adding it to the electrolyte, so it cannot effectively improve the cycle life of the battery cell.

[0048] In view of the above problems, the metal salt is added in the negative active material layer of the negative electrode sheet, and during the cycle charging and discharging of the battery cell, the metal salt can be dissolved in the electrolyte to a certain extent and participate in the film forming reaction on the surface of the active material to form an interface film on the surface of the active material, thereby playing a good protective role on the active material and improving the cycle life of the battery cell.

[0049] Negative electrode sheet

[0050] In a first aspect, the embodiments of the present application provide a negative electrode sheet, which comprises a negative current collector and a negative active material layer arranged on at least one side of the negative current collector, the negative active material layer comprising a negative active material and a metal salt, and the negative electrode sheet satisfies 0.40≤a / m≤5.20; a nm represents the volume average particle size D v50 of the metal salt; and m g / L represents the solubility of the metal salt in the electrolyte.

[0051] The metal salt is configured to participate in the film forming reaction on the surface of the active material, that is, the metal salt can participate in the film forming reaction on the surface of the positive active material or the surface of the negative active material, which can be understood as that the metal salt is a film forming additive.

[0052] Dissolution refers to the process of mixing two or more substances to form a uniform phase, and solubility refers to the mass of the metal salt dissolved when the metal salt in the electrolyte reaches a saturated state. The solubility of the metal salt in the electrolyte is relatively low, and it is not easy to release and dissolve into the electrolyte; with the increase of the solubility, the amount of the metal salt dissolved in the electrolyte increases, and the more metal salt on the surface of the active material can participate in the film forming reaction.

[0053] The volume average particle size of the metal salt is related to the contact area of the electrolyte, the smaller the volume average particle size of the metal salt, the larger the specific surface area of the metal salt, and the larger the contact area of the metal salt and the electrolyte, which is more conducive to the dissolution of the metal salt.

[0054] When the volume average particle size of the metal salt and the solubility of the metal salt satisfy the above relationship, the metal salt can gradually dissolve in the electrolyte during the cycle charging and discharging of the battery cell, and even dissolve in the whole life cycle of the battery cell. The metal salt can continuously act on the surface of the active material, and can form a uniform and dense interface film on the surface of the active material. The interface film has high structural stability and can provide good protection for the active material, thereby improving the cycle life of the battery cell. For example, the metal salt acts on the surface of the positive active material to participate in the formation of the cathode electrolyte interface (CEI) film, thereby providing good protection for the positive active material. Or the metal salt acts on the surface of the negative active material to participate in the formation of the solid electrolyte interface (SEI) film, thereby providing good protection for the negative active material.

[0055] In the embodiments of the present application, the electrolyte can be a standard electrolyte, for example, the electrolyte includes an electrolyte salt and an organic solvent, the electrolyte salt includes 1 mol / L lithium hexafluorophosphate, and the organic solvent includes ethylene carbonate EC and dimethyl carbonate DEC in a volume ratio of 3:7. The solubility of the metal salt can be detected by the following method:

[0056] 100 mL of electrolyte (as a solvent) is measured;

[0057] A metal salt with a mass M0 (as a solute) is weighed;

[0058] The metal salt is gradually added to 100 mL of electrolyte, and the metal salt is continuously stirred to make the metal salt fully dissolved, until the system is saturated (saturation is manifested as having solid precipitate). The solid precipitate is separated from the system by filtration and dried as part of the undissolved metal salt;

[0059] The mass M1 of the undissolved metal salt is weighed, the mass of the metal salt dissolved in the electrolyte (M0-M1) is calculated, and the solubility of the metal salt (M0-M1) / 0.1L is calculated.

[0060] In the embodiments of the present application, D v50 represents the particle size corresponding to 50% of the volume distribution of the particles, which can be tested by using devices and methods known in the art, for example, according to the test standard GB / T 19077-2016. Specifically, a certain amount of the above negative active material is taken as a sample, and the volume average particle size D v50 .

[0061] In some embodiments, 1.25≤a / m≤5.00, when the negative electrode tab satisfies the above range, the metal salt can continuously release during the cyclic charging and discharging process of the battery cell, thereby being able to play a good protective role on the active material and prolong the cycle performance of the battery cell.

[0062] Exemplarily, a / m can be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.25, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.5, 3.6, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, or a range composed of any two of the above values.

[0063] In some embodiments, 3≤a≤300. The volume average particle size D v50 When the above range is satisfied, the volume average particle size of the metal salt is relatively small, which is more conducive to the uniform dispersion of the metal salt in the negative electrode active material layer, the metal salt dissolved in the electrolyte is more uniformly distributed, so that the metal salt can be uniformly dispersed on the surface of the active material layer to form an interface film with uniform performance, thereby further improving the cycle performance of the battery cell using the negative electrode tab.

[0064] Exemplarily, the volume average particle size D v50 may be 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 12nm, 15nm, 18nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 28nm, 30nm, 32nm, 35nm, 38nm, 40nm, 42nm, 45nm, 48nm, 50nm, 55nm, 60nm, 62.5nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 98nm, 100nm, 110nm, 111nm, 120nm, 150nm, 180nm, 200nm, 220nm, 240nm, 250nm, 280nm, 300nm, or a range composed of any two of the above values.

[0065] In order to further improve the cycle performance of the battery cell, the volume average particle size of the metal salt can be further selected according to its own solubility, for example, when the solubility of the metal salt is relatively high, the volume average particle size of the metal salt can be relatively large, for example, when the solubility of the metal salt is 40g / L to 100g / L, the volume average particle size thereof can be 62.5nm to 250nm.

[0066] In some embodiments, 1≤m≤100. When the solubility of the metal salt in the electrolyte is in the above range, the metal salt can be dissolved in the electrolyte to some extent, and the metal salt can be gradually released into the electrolyte, so that the electrolyte can continuously act on the system, thereby improving the cycle performance of the battery cell.

[0067] For example, the solubility of the metal salt in the electrolyte can be 1 g / L, 2 g / L, 4 g / L, 5 g / L, 8 g / L, 10 g / L, 12 g / L, 13 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, 22 g / L, 25 g / L, 26 g / L, 28 g / L, 30 g / L, 32 g / L, 34 g / L, 35 g / L, 36 g / L, 38 g / L, 40 g / L, 42 g / L, 45 g / L, 46 g / L, 48 g / L, 50 g / L, 52 g / L, 55 g / L, 58 g / L, 60 g / L, 62 g / L, 65 g / L, 68 g / L, 70 g / L, 72 g / L, 75 g / L, 78 g / L, 80 g / L, 82 g / L, 85 g / L, 88 g / L, 90 g / L, 92 g / L, 95 g / L, 98 g / L, 100 g / L, or a range formed by any two of the above values.

[0068] In some embodiments, the negative electrode sheet also satisfies: 0.167≤a / b≤100; a nm represents the volume average particle size D v50 of the metal salt; and b μm represents the volume average particle size D v50 of the negative electrode active material.

[0069] When the volume average particle size of the metal salt and the volume average particle size of the negative electrode active material are in the above range, the metal salt is uniformly distributed in the negative electrode active material layer, which is conducive to the uniform release and dissolution of the metal salt in the electrolyte. The metal salt dissolved in the electrolyte uniformly forms a film on the surface of the active material, thereby forming a uniform and high-density interface film, further improving the cycle performance of the battery cell using the negative electrode sheet. In addition, the metal salt does not interfere with the adhesion between the negative electrode active material particles, thereby improving the adhesion between the negative electrode active material particles, and also improving the compaction density of the negative electrode active material layer after compaction, thereby improving the energy density of the battery cell. In order to further improve the cycle performance of the battery cell, etc., 2.5≤a / b≤12.5 can be optionally selected; and 2.8≤a / b≤8.5 can be further optionally selected.

[0070] Exemplarily, a / b can be 0.167, 0.170, 0.175, 0.180, 0.185, 0.190, 0.195, 0.200, 0.210, 0.220, 0.230, 0.240, 0.250, 0.500, 1.0, 2.0, 2.5, 2.8, 3.0, 5.0, 8.0, 8.5, 10.0, 12.0, 12.5, 14.0, 15.0, 18.0, 20.0, 25.0, 30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0, 100.0, or a range between any two of the above values.

[0071] In some embodiments, 1≤b≤30. When the volume average particle size of the negative active material is in the above range, the cycle performance of the battery cell can be further improved.

[0072] Exemplarily, b can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 22 μm, 23 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, or a range between any two of the above values.

[0073] In some embodiments, the negative electrode sheet also satisfies: 0.4≤c / d≤1500; wherein c% represents the mass content of the metal salt relative to the total mass of the negative active material layer; d mg / cm 2 represents the area density of the negative active material layer.

[0074] When the negative electrode sheet satisfies the above range, the metal salt dissolved in the electrolyte is consumed in the film formation reaction, and then the metal salt in the negative active material layer is dissolved in the electrolyte, which can enable the metal salt to be continuously released into the electrolyte during the cycle charging and discharging of the battery cell, the release time of the metal salt is longer, and even the metal salt is dissolved in the whole life cycle of the battery cell. The metal salt can continuously participate in the film formation reaction on the surface of the active material, thereby continuously protecting the surface of the active material and prolonging the cycle life of the battery cell. Optionally, 0.4≤c / d≤100.

[0075] Exemplarily, c / d can be 0.4, 0.45, 0.5, 0.6, 1, 1.5, 2, 3, 5, 6, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 40, 45, 48, 50, 52, 55, 58, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, or a range between any two of the above values.

[0076] In some embodiments, 0.1≤c≤15. When the mass content of the metal salt is in the above range, the active material surface can be more continuously protected, and the cycle life of the battery cell can be prolonged. Alternatively, 1≤c≤10.

[0077] Exemplarily, the mass content of the metal salt can be 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range between any two of the above values.

[0078] In the embodiments of the present application, the mass content of the metal salt is the meaning known in the art, and can be detected by using the devices and methods known in the art. For example, the negative electrode sheet can be tested by using a scanning electron microscope-energy spectrometer (SEM-EDS) according to the standard GB / T 17359-2012 “Quantitative analysis by micro-beam analysis energy spectrum method”, and the element distribution of the negative electrode sheet is observed to calculate the mass content of the metal salt.

[0079] In some embodiments, 0.01≤d≤0.25. When the area density of the negative electrode active material layer is in the above range, the energy density of the battery cell can be further improved. Alternatively, 0.10≤d≤0.25.

[0080] Exemplarily, the area density of the negative electrode active material layer can be 0.01 mg / cm 2 , 0.02 mg / cm 2 , 0.03 mg / cm 2 , 0.05 mg / cm 2 , 0.08 mg / cm 2 , 0.10 mg / cm 2 , 0.12 mg / cm 2 , 0.15 mg / cm 2 , 0.16 mg / cm 2 , 0.18 mg / cm 2 , 0.20 mg / cm2 0.22 mg / cm 2 0.23 mg / cm 2 0.24 mg / cm 2 0.25 mg / cm 2 or a range between any two of the above values.

[0081] In the embodiments of the present application, the area density of the negative active material layer is the meaning known in the art, which can be tested by the methods known in the art. For example, a single-side coated and cold-pressed negative electrode sheet (if it is a double-side coated negative electrode sheet, the negative active material layer on one side can be wiped off first) is punched into a small round piece with an area of S1, weighed, and recorded as M1. Then the negative active material layer of the above weighed negative electrode sheet is wiped off, the weight of the negative current collector is weighed and recorded as M0, and the area density of the negative active material layer = (the weight of the negative electrode sheet M1 - the weight of the negative current collector M0) / S1.

[0082] In some embodiments, the metal salt comprises at least one of a nitrate salt, a nitrite salt, a phosphate salt, a sulfate salt, and a halide salt.

[0083] As some examples, the nitrate salt comprises at least one of an alkali metal nitrate, silver nitrate, and copper nitrate.

[0084] As some examples, the nitrite salt comprises at least one of an alkali metal nitrite, silver nitrite, and copper nitrite.

[0085] As some examples, the phosphate salt comprises at least one of an alkali metal phosphite, silver phosphite, and copper phosphite.

[0086] As some examples, the sulfate salt comprises at least one of an alkali metal sulfate, silver sulfate, and copper sulfate.

[0087] As some examples, the halide salt comprises at least one of an alkali metal halide, silver halide, and copper halide.

[0088] As some examples, the alkali metal nitrate comprises at least one of lithium nitrate, rubidium nitrate, sodium nitrate, potassium nitrate, and cesium nitrate.

[0089] As some examples, the alkali metal nitrite comprises at least one of lithium nitrite, rubidium nitrite, sodium nitrite, potassium nitrite, and cesium nitrite.

[0090] As some examples, the alkali metal phosphate comprises at least one of lithium phosphate, rubidium phosphate, sodium phosphate, potassium phosphate, and cesium phosphate.

[0091] As some examples, the alkali metal sulfate comprises at least one of lithium sulfate, rubidium sulfate, sodium sulfate, potassium sulfate, and cesium sulfate.

[0092] Exemplarily, the halogenated salt can be at least one of a fluorinated salt, a brominated salt, and a chlorinated salt. For example, the fluorinated salt includes at least one of lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, silver fluoride, and copper fluoride. The brominated salt includes at least one of lithium bromide, sodium bromide, potassium bromide, cesium bromide, silver bromide, and copper bromide. The chlorinated salt includes at least one of lithium chloride, sodium chloride, potassium chloride, cesium chloride, silver chloride, and copper chloride.

[0093] In some embodiments, the negative active material can employ a negative active material for a battery cell known in the art. As an example, the negative active material can include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate. The silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0094] Optionally, the negative active material includes artificial graphite and / or natural graphite. Graphite material has the advantages of high capacity and high compacted density; and since graphite undergoes volume expansion during charging and discharging, the SEI film on the surface thereof can be damaged, exposing the surface of the graphite particles, which have many surface defects, to the electrolyte, causing side reactions, affecting the stability of the properties of the graphite material, and deteriorating the cycle performance. The embodiments of the present application, however, add metal salt to the negative active material layer, which forms a continuous and stable SEI film on the surface of the graphite particles, thereby improving the cycle performance of the battery cell.

[0095] In some embodiments, the negative active material layer can also optionally include a negative conductive agent. The embodiments of the present application do not have a particular limitation on the type of the negative conductive agent, and as an example, the negative conductive agent can include at least one of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage content of the negative conductive agent is ≤ 5% based on the total mass of the negative active material layer.

[0096] In some embodiments, the negative active material layer can further optionally include a negative binder. The present embodiments do not have a particular limitation on the type of the negative binder, and as an example, the negative binder can include at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage content of the negative binder is ≤ 5% based on the total mass of the negative active material layer.

[0097] In some embodiments, the negative active material layer can further optionally include other auxiliary agents. As an example, the other auxiliary agents can include a thickening agent, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor material, etc. In some embodiments, the mass percentage content of the other auxiliary agents is ≤ 2% based on the total mass of the negative active material layer.

[0098] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0099] The negative current collector has two surfaces opposite in the thickness direction thereof, and the negative active material layer is disposed on either one or both of the two opposite surfaces of the negative current collector. The relevant parameters mentioned in the present embodiments, such as the mass content of the metal salt in the negative active material layer, refer to the mass content of the metal salt in the negative active material layer on one side of the negative current collector.

[0100] The negative active material layer is generally formed by coating a negative slurry on a negative current collector, drying, and cold pressing. The negative slurry is generally formed by dispersing and uniformly stirring a negative active material, a metal salt, an optional conductive agent, an optional binder, and other optional auxiliary agents in a negative solvent. The negative solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0101] The negative electrode sheet does not exclude other additional functional layers other than the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet described in the present application further includes a conductive primer layer (for example, composed of a conductive agent and a binder) interposed between the negative electrode current collector and the negative electrode active material layer, provided on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet described in the present application further includes a protective layer covering the surface of the negative electrode active material layer.

[0102] Battery cell

[0103] In a second aspect, the present application provides a battery cell including a negative electrode sheet. The negative electrode sheet can be the negative electrode sheet of any one of the embodiments of the second aspect of the present application. Due to the use of the negative electrode sheet, the cycle life of the battery cell can be prolonged.

[0104] [Positive electrode sheet]

[0105] In some embodiments, the battery cell further includes a positive electrode sheet.

[0106] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material.

[0107] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode active material layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0108] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0109] In some embodiments, the positive electrode active material can be a positive electrode active material known in the art for use in a battery cell. As an example, the positive electrode active material can include at least one of the following materials: a layered structure positive electrode active material (such as a material of ternary, lithium / sodium nickelate, lithium / sodium cobaltate, lithium / sodium manganate, lithium / sodium-rich layered, and rock salt phase layered, etc.), an olivine-type phosphate active material, a spinel structure positive electrode active material (such as spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spinel lithium manganate, and lithium nickel manganate, etc.).

[0110] Exemplarily, the general formula of the layered structure positive electrode active material is Li x A y Ni a Co b Mn c M (1-a-b-c) Y z , wherein 0≤x≤2.1, 0≤y≤2.1, and 0.9≤x+y≤2.1; 0≤a≤1, 0≤b≤1, 0≤c≤1, and 0.1≤a+b+c≤1; 1.8≤z≤3.5; A includes one or more of Na, K, Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y includes one or more of O, F. Specifically, the layered structure positive electrode active material can include lithium cobaltate LCO, lithium nickelate LNO, lithium manganate LMO, etc.

[0111] Optionally, the layered structure positive electrode active material is a ternary material, for example, 0 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), and LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523).

[0112] Exemplarily, the general formula of the olivine-type phosphate active material is Li x A y Me a M b P 1-c X c Y zwherein 0≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, Mg; Me includes one or more of Mn, Fe, Co, Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X includes one or more of S, Si, Cl, B, C, N; Y includes one or more of O, F. Specifically, the olivine-type phosphate active material includes one or more of LiFeP04, LiMnP04, LiNiP04, and LiCoP04.

[0113] Exemplarily, the general formula of the spinel-structured positive electrode active material is Li x A y Mn a M 2-a Y z wherein 0≤x≤2, 0≤y≤1, and 0.9≤x+y≤2; 0.5≤a≤2; 3≤z≤5; A includes one or more of Na, K, Mg; M includes one or more of Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y includes one or more of O, F. Specifically, the spinel-structured positive electrode active material includes one or more of LiMn204, LiNi 0.5 Mn 1.5 O4, LiCr 0.3 Mn 1.7 O4, Li 1.1 Al 0.1 Mn 1.9 O4, Li2Mn204, and Li 1.5 Mn2O4.

[0114] In some embodiments, the positive electrode active material layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0115] In some embodiments, the positive electrode active material layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0116] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and then drying, cold-pressing, and the like to obtain the positive electrode tab.

[0117] [Electrolyte]

[0118] In some embodiments, the battery cell further includes an electrolyte.

[0119] During the charging and discharging of the battery cell, active ions are inserted and extracted between the positive electrode tab and the negative electrode tab, and the electrolyte plays a role in conducting the active ions between the positive electrode tab and the negative electrode tab. The type of electrolyte is not particularly limited in the present application and can be selected according to actual needs.

[0120] The electrolyte includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0121] As an example, the electrolyte salt can include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (LiDFOB), lithium bisoxalato borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP).

[0122] As an example, the solvent can include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0123] In some embodiments, the electrolyte solution can further include an additive. For example, the additive can include a film-forming additive such as a cathode film-forming additive, etc., and can also include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature performance of the battery, an additive for improving low-temperature power performance of the battery, etc.

[0124] [Separator]

[0125] In some embodiments, the battery cell further includes a separator.

[0126] The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0127] In some embodiments, the material of the separator can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0128] In some embodiments, the cathode electrode sheet, the separator, and the anode electrode sheet can be made into an electrode assembly through a rolling process and / or a stacking process.

[0129] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte solution described above.

[0130] In some embodiments, the outer package of the battery cell can be a hard shell such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package such as a pouch-type soft package. The material of the soft package can be plastic such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0131] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, Figure 1 is a square battery cell 5 as an example.

[0132] In some embodiments, as shown in Figure 2 The outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator film can be wound and / or stacked to form an electrode assembly 52. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to the needs.

[0133] The preparation method of the battery cell of the present application is known. In some embodiments, the positive electrode sheet, the separator film, the negative electrode sheet, and the electrolyte can be assembled to form a battery cell. For example, the positive electrode sheet, the separator film, the negative electrode sheet can be wound and / or stacked to form an electrode assembly, the electrode assembly is placed in the outer package, and after drying, the electrolyte is injected, and then the vacuum packaging, standing, formation, shaping and other processes are carried out to obtain the battery cell.

[0134] In some embodiments of the present application, the battery cell according to the present application can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0135] Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in Figure 3 In the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0136] Optionally, the battery module 4 can further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0137] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0138] Figure 4 and Figure 5 is a schematic diagram of a battery pack 1 as an example. As shown in Figure 4 and Figure 5As shown, the battery pack 1 can include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery case includes an upper case 2 and a lower case 3, the upper case 2 being configured to cover the lower case 3 and form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0139] The battery according to the embodiments of the present application can include one battery cell or a plurality of battery cells, and in the case of including a plurality of battery cells, the battery can include a battery module or a battery pack.

[0140] Electric device

[0141] The third aspect of the embodiments of the present application provides a power consuming device including at least one of the battery cell, the battery module, or the battery pack according to the embodiments of the present application. The battery cell, the battery module, or the battery pack can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can be, but is not limited to, a mobile device (e.g., a mobile phone, a notebook computer, etc.), an electric vehicle (e.g., 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.

[0142] The power consuming device can select the battery cell, the battery module, or the battery pack according to its use requirements.

[0143] Figure 6 FIG. 6 is a schematic diagram of a power consuming device 6 as an example. The power consuming device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the power consuming device 6, a battery pack or a battery module can be used.

[0144] The power consuming device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power consuming device usually requires thinness, and a battery cell can be used as a power source.

[0145] Embodiment

[0146] The embodiments described below more specifically describe the disclosure of the present application, which are merely illustrative and various modifications and changes within the scope of the disclosure of the present application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the embodiments are commercially available.

[0147] Example 1

[0148] 1、 Preparation of positive electrode sheet

[0149] An aluminum foil with a thickness of 12 μm was used as the positive current collector.

[0150] The positive active material lithium iron phosphate, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2 in an appropriate amount of solvent N-methyl pyrrolidone (NMP) to obtain a positive electrode slurry; the positive electrode slurry was coated on the positive current collector aluminum foil, and through processes such as drying, cold pressing, slitting, and cutting, a positive electrode sheet was obtained.

[0151] 2. Preparation of negative electrode sheet

[0152] A copper foil with a thickness of 8 μm was used as the negative current collector.

[0153] A mixture of natural graphite as the negative active material, a metal salt, a conductive agent conductive carbon black, a binder styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (mass ratio of 1:1) was mixed uniformly in deionized water to prepare a negative electrode slurry. The mass ratio of natural graphite, metal salt, conductive agent, and binder in the solid components of the negative electrode slurry was 95:1:2:2. The negative electrode slurry was coated on the current collector copper foil and dried at 85°C, and then cold pressed to obtain a negative electrode sheet containing a negative active material layer.

[0154] 3. Preparation of electrolyte

[0155] In an environment with a water content of less than 10 ppm, organic solvents ethylene carbonate EC and diethyl carbonate DEC were mixed in a volume ratio of 3:7 to obtain an electrolyte solvent, and then lithium salt lithium hexafluorophosphate was mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0156] 4. Preparation of lithium ion battery

[0157] The positive electrode sheet, a polyethylene PE separator, and the negative electrode sheet were stacked in order and wound to obtain an electrode assembly; the electrode assembly was placed in an outer package, dried, and then injected with an electrolyte, and then subjected to processes such as vacuum packaging, standing, formation, and shaping to obtain a lithium ion battery.

[0158] Examples 2-1 to 2-8

[0159] A lithium ion battery was prepared by a method similar to that of Example 1, except that the volume average particle diameter D v50 of the metal salt was adjusted in Examples 2-1 to 2-8.

[0160] Examples 3-1 to 3-4

[0161] The lithium ion battery was prepared by a similar method to Example 1, except that the addition amount of the metal salt was adjusted in Example 3-1 to Example 3-4.

[0162] Example 4-1 to Example 4-5

[0163] The lithium ion battery was prepared by a similar method to Example 1, except that the type of metal salt was adjusted in Example 4-1 to Example 4-5.

[0164] Comparative Example 1

[0165] The lithium ion battery was prepared by a similar method to Example 1, except that no metal salt was added to the negative electrode sheet in Comparative Example 1, and the negative electrode sheet was prepared as follows:

[0166] A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0167] A mixture of natural graphite as the negative electrode active material, conductive agent conductive carbon black, binder styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (mass ratio 1:1) was mixed uniformly in deionized water to prepare a negative electrode slurry. The mass ratio of natural graphite, conductive agent, and binder in the solid content of the negative electrode slurry was 96:2:2. The negative electrode slurry was coated on the current collector copper foil and dried at 85°C, and then cold-pressed to obtain a negative electrode sheet containing a negative electrode active material layer.

[0168] Comparative Example 2 and Comparative Example 3

[0169] The lithium ion battery was prepared by a similar method to Example 1, except that a metal salt was added to the negative electrode slurry in Comparative Example 2 and Comparative Example 3, and the volume average particle size D v50 .

[0170] The relevant parameters of the examples and comparative examples are shown in Table 1.

[0171] Test section

[0172] 1. Cycle performance test of lithium ion battery

[0173] At 25°C, the lithium ion battery was charged at a charge rate of 0.33C to 4.0V, and discharged at a rate of 0.33C to 2.0V. The capacity of the lithium ion battery was attenuated to 80% of the initial capacity, and the cycle number was recorded.

[0174] Test result

[0175] The test results are shown in Table 1

[0176] Table 1

[0177]

[0178]

[0179] As can be seen from Table 1, the comparative example 1 does not add metal salt in the negative electrode sheet, and during the charging and discharging process of the lithium ion battery monomer, the SEI film cannot be formed on the surface of the negative electrode active material to protect the negative electrode active material, which may cause side reactions at the interface of the negative electrode active material, resulting in consumption or even destruction of the negative electrode active material, and deterioration of the cycle performance of the lithium ion battery.

[0180] Compared with the comparative example 1, the comparative examples 2 and 3 add metal salt in the negative electrode sheet, and the metal salt can be dissolved in the electrolyte to a certain extent to participate in the film forming reaction and protect the negative electrode active material, but the protection effect is relatively small, and the improvement of the cycle performance of the lithium ion battery is limited.

[0181] However, the application embodiment can continuously act on the surface of the active material and continuously participate in the film forming reaction to continuously protect the active material when a / m is in the range of 0.40 to 5.20, especially in the range of 1.25 to 5.00, thereby significantly improving the cycle performance of the lithium ion battery.

[0182] It is found through the comparative examples 3-1 to 3-4 that the protective effect on the surface of the active material is enhanced with the increase of the amount of metal salt added, and the cycle performance of the lithium ion battery is further improved; however, with the further increase of the amount of metal salt added, the amount of negative electrode active material may be reduced, which is not conducive to the improvement of the capacity of the lithium ion battery.

[0183] The application embodiment selects different types of metal salts, which can all improve the lithium ion battery. By controlling the type of metal salt, the cycle performance of the lithium ion battery can be affected to a certain extent.

[0184] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as a limitation of the application, and the embodiments can be changed, replaced and modified without departing from the spirit, principles and scope of the application.

Claims

1. A negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material and a metal salt. The negative electrode sheet satisfies the following conditions: 0.40 ≤ a / m ≤ 5.20, 3 ≤ a ≤ 300, 1 ≤ m ≤ 100, 2.5 ≤ a / b ≤ 12.5, where... a nm represents the volume average particle size D of the metal salt. v50 ; mg / L represents the solubility of the metal salt in the electrolyte; b μm represents the volume average particle size D of the negative electrode active material. v50 .

2. The negative electrode sheet according to claim 1, wherein, 1.25≤a / m≤5.

00.

3. The negative electrode sheet according to claim 1, wherein, The negative electrode sheet satisfies: 2.8≤a / b≤8.

5.

4. The negative electrode sheet according to claim 1, wherein, 1≤b≤30， b μm represents the volume average particle size D of the negative electrode active material. v50 .

5. The negative electrode sheet according to claim 1, wherein, The negative electrode sheet satisfies: 0.4 ≤ c / d ≤ 1500; where, c% represents the mass content of the metal salt relative to the total mass of the negative electrode active material layer; d mg / cm 2 This represents the areal density of the negative electrode active material layer.

6. The negative electrode sheet according to claim 5, wherein, The negative electrode sheet satisfies: 0.4≤c / d≤100.

7. The negative electrode sheet according to claim 1, wherein, 0.1≤c≤15； c% represents the mass content of the metal salt relative to the total mass of the negative electrode active material layer.

8. The negative electrode sheet according to claim 7, wherein, 1≤c≤10。 9. The negative electrode sheet according to claim 1, wherein, 0.01≤d≤0.25； d mg / cm 2 This represents the areal density of the negative electrode active material layer.

10. The negative electrode sheet according to claim 9, wherein, 0.10≤d≤0.25。 11. The negative electrode sheet according to claim 1, wherein, The metal salt includes at least one of nitrates, nitrites, phosphates, sulfates, and halides.

12. The negative electrode sheet according to claim 11, wherein, The nitrate includes at least one of alkali metal nitrates, silver nitrate, and copper nitrate.

13. The negative electrode sheet according to claim 11, wherein, The nitrite includes at least one of alkali metal nitrite, silver nitrite, and copper nitrite.

14. The negative electrode sheet according to claim 11, wherein, The phosphate includes at least one of alkali metal phosphites, silver phosphites, and copper phosphites.

15. The negative electrode sheet according to claim 11, wherein, The sulfate includes at least one of alkali metal sulfate, silver sulfate, and copper sulfate.

16. The negative electrode sheet according to claim 11, wherein, The halide salts include at least one of alkali metal halides, silver halides, and copper halides.

17. A battery cell comprising a negative electrode sheet as claimed in any one of claims 1 to 16.

18. A battery comprising a battery cell as described in claim 17.

19. An electrical device comprising the battery as claimed in claim 18.

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