A battery cell, a battery, and an electric device

Abstract

The application provides a battery monomer, a battery and a power utilization device. The battery monomer comprises a negative electrode sheet, and the negative electrode sheet comprises: a negative electrode current collector; a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer being arranged between the negative electrode current collector and the second negative electrode active material layer; wherein the first negative electrode active material layer comprises first graphite and a composite coating material, the composite coating material coating at least part of the surface of the first graphite; and the composite coating material comprises a lithiated inorganic salt compound and an organic compound. The battery monomer provided by the application can further improve the charging and discharging performance in a low-temperature environment on the premise of balancing other performances of the battery monomer.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0002] When a battery cell is in a low-temperature environment, the migration rate of lithium ions in the battery cell may be affected, which may affect the charge and discharge performance of the battery cell in a low-temperature environment.

[0003] While existing solutions can alleviate the degradation of battery cell charge-discharge performance at low temperatures, they may still affect other performance characteristics of the battery cells. Therefore, developing a battery cell that further improves charge-discharge performance at low temperatures while balancing other performance aspects is a pressing technical challenge. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, battery and electrical device that can further improve the charge and discharge performance in low temperature environment while balancing other performance of the battery cell.

[0005] To achieve the above objectives, this application provides a battery cell, a battery, and an electrical device.

[0006] A first aspect of this application provides a battery cell including a negative electrode sheet, the negative electrode sheet comprising: a negative current collector; a first negative active material layer and a second negative active material layer, the first negative active material layer being disposed between the negative current collector and the second negative active material layer; wherein the first negative active material layer comprises a first graphite and a composite coating material, the composite coating material coating at least a portion of the surface of the first graphite; the composite coating material comprises a lithium-ionized inorganic salt compound and an organic compound.

[0007] In this embodiment, the first graphite in the first negative electrode active material layer located near the negative electrode current collector contains a composite coating material. The dense lithium-ion inorganic salt compound component in the composite coating material can improve the high Young's modulus of the composite coating material and reduce the desolvation energy barrier and lithium-ion diffusion energy barrier, allowing lithium ions to migrate rapidly within the composite coating material. This enables the composite coating material to form a lithium-conducting interface, improving the desolvation capability and lithium-ion migration rate on the side of the negative electrode near the negative electrode current collector under low-temperature conditions, thereby improving the charge-discharge performance of the battery cell under low-temperature conditions. Furthermore, using the first graphite containing the composite coating material only in the first negative electrode active material layer near the negative electrode current collector can improve the charge-discharge performance of the battery cell under low-temperature conditions while also reducing the additional electrode load on the negative electrode, thus balancing the different performance characteristics of the battery cell.

[0008] In any embodiment, the lithium-ionized inorganic salt compound includes at least one of the following: lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxarateborate, lithium dihydrogen phosphate, and lithium hexafluoroarsenate.

[0009] In any embodiment, the organic compound has the following structural formula:

[0010]

[0011] Wherein, R1 includes at least one of the following: —Me, —Et, —Pr, —Bu, —Ph, —EtOH, —CH2COOH, —CH2CH2NH2, —(CH2CH2O) n H;R2 includes at least one of the following: —OH, —COOH, —NH2, —SO3H.

[0012] In the embodiments of this application, the organic compound component in the composite coating material has a flexible polymer backbone, which can provide sufficient elasticity and a low glass transition temperature for the composite coating material. In addition, the nonpolar side group R1 is beneficial for the affinity coating of graphite, while the polar side group R2 can form intermolecular hydrogen bonds, which is beneficial for improving intermolecular cohesion and enhancing the structural stability of the coating material.

[0013] In any embodiment, the mass ratio I of the inorganic element in the lithium-ion inorganic salt compound in the first negative electrode active material layer and the second negative electrode active material layer satisfies: 0.005≤I≤0.02.

[0014] In the embodiments of this application, the mass ratio range of the lithium-ion inorganic salt compound in the composite coating material in the first negative electrode active material layer and the second negative electrode active material layer can achieve the technical effect of improving the desolvation capability and lithium ion migration rate on the side of the negative electrode sheet near the negative electrode current collector under low temperature conditions, while also avoiding the problem that the composite coating material cannot meet the interface requirements due to excessive lithium-ion inorganic salt compound content.

[0015] In any embodiment, the second negative electrode active material layer 63 includes a second graphite, and the first graphite and the second graphite satisfy at least one of the following: the graphitization degree G1 of the first graphite and the graphitization degree G2 of the second graphite satisfy: G1>G2; the Dv501 of the first graphite and the Dv502 of the second graphite satisfy: Dv501>Dv502; the powder 2T compaction density D1 of the first graphite and the powder 2T compaction density D2 of the second graphite satisfy: D1>D2.

[0016] In this embodiment, the second negative electrode active material layer on the side away from the negative electrode current collector has higher kinetic performance, thereby improving the conductivity of the negative electrode active material layer on the side away from the negative electrode current collector in the negative electrode sheet. Furthermore, by not using graphite material containing composite coating materials in the second negative electrode active material layer, the charge-discharge performance of the battery cell under low-temperature conditions can be improved, while also reducing the impact of additional material load on the technical effect of the second negative electrode active material layer in improving conductivity. This simultaneously balances the different performance characteristics of battery cells with thicker negative electrode sheets (for example, high volumetric energy density battery cells have thicker negative electrode active material layers, which increases the distance between the surface of the negative electrode sheet and the negative electrode current collector, further weakening the conductivity of the negative electrode active material layer on the side away from the negative electrode current collector).

[0017] In any embodiment, the mass ratio W of the first graphite to the second graphite satisfies: 0.25 ≤ W ≤ 4.

[0018] In the embodiments of this application, the mass ratio range of the first graphite and the second graphite can enable both the first graphite and the second graphite to fully exert their corresponding technical effects.

[0019] In any embodiment, the specific capacity C1 of the first graphite satisfies 360mAh / g≤C1≤365Ah / g, the specific capacity C2 of the second graphite satisfies 350mAh / g≤C2≤355Ah / g.

[0020] In this embodiment, the first graphite containing the composite coating material is applied to the first negative electrode active material layer near the negative electrode current collector of the battery cell with high volumetric energy density. This improves the desolvation capability and lithium-ion migration rate of the negative electrode near the negative electrode current collector under low temperature conditions, while also reducing the impact of additional material load on the technical effect of improving the conductivity of the second negative electrode active material layer. Thus, it balances the different performances of the battery cell with high volumetric energy density and a thicker negative electrode.

[0021] In any embodiment, the first negative electrode active material layer includes a lithium-ionized binder.

[0022] In this embodiment, a lithiated binder can also be used in the first negative electrode active material layer located near the negative electrode current collector. The lithium-ion exchange effect in the lithiated binder can provide a lithium-conducting bridge, thereby improving the lithium-ion diffusion capability between the binder and the negative electrode active material. This further improves the lithium-ion migration rate within the negative electrode sheet near the negative electrode current collector under low-temperature conditions, ultimately further improving the charge-discharge performance of the battery cell under low-temperature conditions. Furthermore, the hydrogen bonds and ionic dipole interactions between the lithiated binder and the negative electrode active material can simultaneously establish better interfacial adhesion.

[0023] In any embodiment, the mass percentage A of the lithium binder in the first negative electrode active material layer 62 satisfies: 0.005 ≤ A ≤ 0.015.

[0024] In this embodiment, the range of the mass percentage of the lithium-ion binder in the first negative electrode active material layer allows the lithium-ion binder added to the first negative electrode active material layer to have better lithium-ion conduction performance and lithium-ion diffusion coefficient, thereby better improving the charge-discharge performance of the battery cell under low-temperature conditions. Furthermore, when the mass percentage of the lithium-ion binder in the first negative electrode active material layer meets the above-mentioned range, the adhesion force between the hydrogen bonds of the lithium-ion binder and the negative electrode active material will also meet production requirements. Simultaneously, the above-mentioned range of the mass percentage of the lithium-ion binder in the first negative electrode active material layer also accommodates the requirements for graphite processability and high volumetric energy density.

[0025] In any embodiment, the lithium-ionized binder includes at least one of the following: lithium-ionized carboxymethyl cellulose, lithium-ionized styrene-butadiene rubber, lithium-ionized polyacrylic acid, lithium-ionized polyethylene glycol, and lithium-ionized sodium alginate.

[0026] In any embodiment, the negative electrode sheet satisfies at least one of the following: the specific capacity of the negative electrode sheet is 356mAh / g-362mAh / g, and the 2T compaction density of the negative electrode sheet is 1.7g / cm³. 3 -1.75g / cm 3 .

[0027] A second aspect of this application provides a battery, including the battery cell of the first aspect of this application.

[0028] A third aspect of this application provides an electrical device comprising a battery cell of the first aspect of this application and / or a battery of the second aspect of this application. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the negative electrode sheet according to one embodiment of this application.

[0030] Figure 2 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0031] Figure 3 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0032] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0033] Figure 5 This is a schematic diagram of a battery according to one embodiment of this application.

[0034] Figure 6 yes Figure 5 An exploded view of a battery according to one embodiment of this application is shown.

[0035] Figure 7 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1 Battery; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery cell; 6 Negative electrode sheet; 61 Negative current collector; 62 First negative electrode active material layer; 63 Second negative electrode active material layer. Detailed Implementation

[0038] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the electrode plates, battery cells, battery modules, batteries, and power-consuming devices of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0039] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0041] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0042] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] During the research on the performance of battery cells, the applicant discovered that when the battery cell is in a low-temperature environment, lithium ions may generate a concentration gradient in the thickness direction of the negative electrode sheet. The diffusion rate of lithium ions on the side closer to the negative electrode current collector may be much lower than that on the side farther away from the current collector, thereby deteriorating the capacity utilization of graphite in the negative electrode active material layer on the side closer to the current collector. Consequently, the low-temperature charge and discharge performance of the battery cell cannot meet the usage requirements, and the battery cell may even experience lithium plating.

[0044] Among the related solutions, there are technical approaches that improve the low-temperature charge-discharge performance of individual battery cells by modifying the electrolyte composition. However, the electrolytes used in these solutions may have issues such as poor compatibility with high-capacity graphite, unstable film formation, and corrosion of aluminum foil, thus failing to achieve a balanced performance of individual battery cells.

[0045] In view of this, embodiments of this application provide a battery cell including a negative electrode sheet, wherein the negative electrode sheet includes: a negative current collector; a first negative active material layer and a second negative active material layer, the first negative active material layer being disposed on at least one side of the surface of the negative current collector, and the first negative active material layer being disposed between the negative current collector and the second negative active material layer; wherein the first negative active material layer includes a first graphite and a composite coating material, the composite coating material covering at least a portion of the surface of the first graphite; the composite coating material includes a lithium-ion inorganic salt compound and an organic compound. In this way, the charge-discharge performance of the battery cell in low-temperature environments can be further improved while balancing other performance characteristics of the battery cell.

[0046] [Battery cell]

[0047] In one embodiment of this application, a battery cell 5 is provided. The battery cell 5 includes a negative electrode 6. For example... Figures 1 to 2 As shown, the negative electrode sheet 6 includes a negative electrode current collector 61, a first negative electrode active material layer 62, and a second negative electrode active material layer 63. The first negative electrode active material layer 62 is disposed between the negative electrode current collector 61 and the second negative electrode active material layer 63. The first negative electrode active material layer 62 includes a first graphite and a composite coating material, the composite coating material covering at least a portion of the surface of the first graphite. The composite coating material includes a lithium-ionized inorganic salt compound and an organic compound.

[0048] Specifically, the first negative electrode active material layer 62 is disposed between the negative electrode current collector 61 and the second negative electrode active material layer 63. The first negative electrode active material layer 62 may be disposed on at least one side of the surface of the negative electrode current collector 61, the second negative electrode active material layer 63 may be disposed on the surface of the first negative electrode active material layer 62, or the second negative electrode active material layer 63 may be disposed on both the surface of the negative electrode current collector 61 and the surface of the first negative electrode active material layer 62. As an example, the negative electrode current collector 61 may have two surfaces opposite each other in its thickness direction. The first negative electrode active material layer 62 is disposed on either or both of the opposite surfaces of the negative electrode current collector 61. The second negative electrode active material layer 63 may be disposed on the surface of the first negative electrode active material layer 62 located on either or both of the opposite surfaces of the negative electrode current collector 61, or it may be disposed on either or both of the opposite surfaces of the negative electrode current collector 61.

[0049] Specifically, the composite coating material coats at least a portion of the surface of the first graphite. This can be either a portion of the surface of the first graphite surrounded by the composite coating material, or all surfaces of the first graphite completely encapsulated by the composite coating material. As an example, in the first negative electrode active material layer 62, there can be both a first graphite partially surrounded by the composite coating material and a first graphite completely encapsulated by the composite coating material, or only a first graphite partially surrounded by the composite coating material, or only a first graphite completely encapsulated by the composite coating material.

[0050] In this embodiment, the first graphite in the first negative electrode active material layer 62 located near the negative electrode current collector 61 contains a composite coating material. The dense lithium-ion inorganic salt compound component in the composite coating material can improve the high Young's modulus of the composite coating material and reduce the desolvation energy barrier and lithium-ion diffusion energy barrier, allowing lithium ions to migrate rapidly in the composite coating material. This enables the composite coating material to form a lithium-conducting interface, improving the desolvation capability and lithium-ion migration rate of the negative electrode sheet 6 near the negative electrode current collector 61 under low-temperature conditions, thereby improving the charge-discharge performance of the battery cell 5 under low-temperature conditions. Furthermore, using the first graphite containing the composite coating material only in the first negative electrode active material layer 62 near the negative electrode current collector 61 can improve the charge-discharge performance of the battery cell 5 under low-temperature conditions while also reducing the additional electrode load on the negative electrode sheet 6, thereby balancing the different performance characteristics of the battery cell 5.

[0051] In some embodiments, the lithium-ionized inorganic salt compound includes at least one of the following: lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxarate borate, lithium dihydrogen phosphate, and lithium hexafluoroarsenate.

[0052] In some embodiments, the organic compound has the following structural formula:

[0053]

[0054] Wherein, R1 includes at least one of the following: —Me, —Et, —Pr, —Bu, —Ph, —EtOH, —CH2COOH, —CH2CH2NH2, —(CH2CH2O) n H;R2 includes at least one of the following: —OH, —COOH, —NH2, —SO3H.

[0055] Optionally, a:b:c satisfies: 5:0:5 to 5:5:0.

[0056] a:b:c can be 5:0:5, 5:1:4, 5:2:3, 5:3:2, 5:4:1, 5:5:0, or any value within the above range.

[0057] In the embodiments of this application, the organic compound component in the composite coating material has a flexible polymer backbone, which can provide sufficient elasticity and a low glass transition temperature for the composite coating material. In addition, the nonpolar side group R1 is beneficial for the affinity coating of graphite, while the polar side group R2 can form intermolecular hydrogen bonds, which is beneficial for improving intermolecular cohesion and enhancing the structural stability of the coating material.

[0058] In some embodiments, the mass ratio I of the inorganic element in the lithium-ion inorganic salt compound in the first negative electrode active material layer 62 and the second negative electrode active material layer 63 satisfies: 0.005≤I≤0.02.

[0059] I can be 0.005, 0.01, 0.015, 0.02, or any value within the above range.

[0060] It should be noted that the mass ratio of inorganic elements in the lithium-ion inorganic salt compound in the first negative electrode active material layer 62 and the second negative electrode active material layer 63 can also be referred to as: the mass ratio of inorganic elements in the lithium-ion inorganic salt compound in the total mass of the first negative electrode active material layer 62 and the second negative electrode active material layer 63.

[0061] In the embodiments of this application, the mass ratio range of the lithium-ion inorganic salt compound in the composite coating material in the first negative electrode active material layer 62 and the second negative electrode active material layer 63 can achieve the technical effect of improving the desolvation capability and lithium-ion migration rate of the negative electrode sheet 6 near the negative electrode current collector 61 under low temperature conditions, while also avoiding the problem that the composite coating material cannot meet the interface requirements due to excessive lithium-ion inorganic salt compound content.

[0062] In some embodiments, the second negative electrode active material layer 63 includes a second graphite, and the first graphite and the second graphite satisfy at least one of the following: the degree of graphitization G1 of the first graphite and the degree of graphitization G2 of the second graphite satisfy: G1>G2; the Dv501 of the first graphite and the Dv502 of the second graphite satisfy: Dv501>Dv502; the 2T compaction density D1 of the first graphite and the 2T compaction density D2 of the second graphite satisfy: D1>D2.

[0063] It is understandable that when at least one of the parameters—the degree of graphitization, Dv50, and powder compaction density—is higher than that of the second graphite, it can be considered that the kinetic properties of the second graphite are higher than those of the first graphite. For example, the specific capacity of the first graphite is 360 mAh / g-365 mAh / g, the degree of graphitization is 94%-95%, the Dv50 is 15 μm-20 μm, and the 2T powder compaction density is 1.8 g / cm³. 3 -2.1g / cm 3Furthermore, the specific capacity of the second graphite is 350mAh / g-355mAh / g, the degree of graphitization is 92%-94%, the Dv50 is 10μm-12μm, and the compacted density of the 2T powder is 1.5g / cm³. 3 -1.8g / cm 3 At that time, the second graphite had higher kinetic performance and lower specific capacity compared to the first graphite.

[0064] In this embodiment, the second negative electrode active material layer 63 on the side away from the negative electrode current collector 61 has higher kinetic performance, thereby improving the conductivity of the negative electrode active material layer on the side away from the negative electrode current collector 61 in the negative electrode sheet 6. Furthermore, by not using graphite material containing composite coating materials in the second negative electrode active material layer 63, the charge-discharge performance of the battery cell 5 under low-temperature conditions can be improved, while also reducing the impact of additional material load on the technical effect of improving the conductivity of the second negative electrode active material layer 63. This simultaneously balances the different performance characteristics of battery cells with thicker negative electrode sheets (for example, high volumetric energy density battery cells have thicker negative electrode active material layers, which increases the distance between the surface of the negative electrode sheet and the negative electrode current collector, further weakening the conductivity of the negative electrode active material layer on the side away from the negative electrode current collector).

[0065] In some implementations, the mass ratio W of the first graphite to the second graphite satisfies: 0.25 ≤ W ≤ 4.

[0066] W can be 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4 or any value within the above range.

[0067] In the embodiments of this application, the mass ratio range of the first graphite and the second graphite can enable both the first graphite and the second graphite to fully exert their corresponding technical effects.

[0068] In some embodiments, the specific capacity C1 of the first graphite satisfies 360mAh / g≤C1≤365Ah / g, the specific capacity C2 of the second graphite satisfies 350mAh / g≤C2≤355Ah / g.

[0069] C1 can be 360mAh / g, 361mAh / g, 362mAh / g, 363mAh / g, 364mAh / g, 365mAh / g or any value within the above range; C2 can be 350mAh / g, 351mAh / g, 352mAh / g, 353mAh / g, 354mAh / g, 355mAh / g or any value within the above range.

[0070] For example, the battery cell 5 may include a high nickel ratio positive electrode active material (e.g., LiNi). 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2 or NCM9) and a high volumetric energy density ternary graphite system battery cell with a graphite system capacity of 360mAh / g.

[0071] In this embodiment, the first graphite containing the composite coating material is applied to the first negative electrode active material layer 62 on the side of the high volumetric energy density battery cell 5 near the negative electrode current collector 61. This improves the desolvation capability and lithium-ion migration rate on the side of the negative electrode sheet 6 near the negative electrode current collector 61 under low temperature conditions, while also reducing the impact of additional material load on the technical effect of improving the conductivity of the second negative electrode active material layer 63. This balances the different performances of the high volumetric energy density battery cell with a thicker negative electrode sheet.

[0072] In some embodiments, the first negative electrode active material layer 62 includes a lithium binder.

[0073] In this embodiment, a lithiated binder can also be used in the first negative electrode active material layer 62 located near the negative electrode current collector 61. The lithium-ion exchange effect in the lithiated binder can provide a lithium-conducting bridge, thereby improving the lithium-ion diffusion capability between the binder and the negative electrode active material. This further improves the lithium-ion migration rate within the negative electrode sheet 6 near the negative electrode current collector 61 under low-temperature conditions, ultimately further improving the charge-discharge performance of the battery cell 5 under low-temperature conditions. Furthermore, the hydrogen bonds and ionic dipole interactions between the lithiated binder and the negative electrode active material can simultaneously establish better interfacial adhesion.

[0074] Optionally, the mass percentage A of the lithium binder in the first negative electrode active material layer 62 satisfies: 0.005 ≤ A ≤ 0.015.

[0075] A can be 0.005, 0.01, 0.015, or any value within the above range.

[0076] In this embodiment, the mass percentage range of the lithium-ion binder in the first negative electrode active material layer 62 allows the lithium-ion binder added to the first negative electrode active material layer 62 to have better lithium-ion conduction performance and lithium-ion diffusion coefficient, thereby better improving the charge-discharge performance of the battery cell 5 under low-temperature conditions. Furthermore, when the mass percentage of the lithium-ion binder in the first negative electrode active material layer 62 meets the above-mentioned range, the adhesion force between the hydrogen bonds of the lithium-ion binder and the negative electrode active material will also meet production requirements. Simultaneously, the above-mentioned mass percentage range of the lithium-ion binder in the first negative electrode active material layer 62 also accommodates the requirements for graphite processability and high volumetric energy density.

[0077] Optionally, the lithium-ionized binder includes at least one of the following: lithium-ionized carboxymethyl cellulose, lithium-ionized styrene-butadiene rubber, lithium-ionized polyacrylic acid, lithium-ionized polyethylene glycol, and lithium-ionized sodium alginate.

[0078] In some embodiments, the negative electrode 6 satisfies at least one of the following: the specific capacity of the negative electrode 6 is 356mAh / g-362mAh / g, and the 2T compaction density of the negative electrode 6 is 1.7g / cm³. 3 -1.75g / cm 3 .

[0079] The capacity of the negative electrode plate 6 can be 356mAh / g, 356.5mAh / g, 356.8mAh / g, 357mAh / g, 357.5mAh / g, 357.5mAh / g, 358mAh / g, 358.5mAh / g, 359mAh / g, 359.5mAh / g, 359.8mAh / g, 360mAh / g, 360.2mAh / g, 360.5mAh / g, 360.7mAh / g, 361mAh / g, 361.2mAh / g, 361.5 mAh / g, 362 mAh / g, or any value within the above range. The 2T compaction density of the negative electrode sheet 6 can be 1.7 g / cm³. 3 1.71g / cm 3 1.72g / cm 3 1.73g / cm 3 1.74 g / cm 3 1.75g / cm 3 Or any value within the above range.

[0080] In addition, the battery cell, battery module, battery and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0081] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0082] [Positive electrode plate]

[0083] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0084] In some embodiments, the positive electrode active material layer may employ positive electrode active materials known in the art for use in batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0085] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0086] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0087] In some embodiments, the positive electrode sheet can be prepared by dispersing the positive active material, conductive agent, binder and any other components in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0088] [Negative electrode plate]

[0089] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector. The negative electrode can be the negative electrode 6 described above.

[0090] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. The negative electrode current collector may be copper foil. The composite negative electrode current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from one or more of elemental silicon, silicon-oxygen compounds, silicon-carbon compounds, silicon-nitrogen compounds, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0092] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0093] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0094] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0095] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode film, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0096] [Electrolytes]

[0097] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0098] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0099] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0100] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0101] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0102] [Isolation membrane]

[0103] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0104] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0105] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0106] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0107] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 The battery cell 5 is used as an example. Battery cell 5 may include a housing. A positive electrode, a negative electrode, and a separator may be formed into an electrode assembly via a winding or stacking process. The electrode assembly is encapsulated within the housing. An electrolyte is immersed in the electrode assembly. The battery cell 5 may contain one or more electrode assemblies, which can be selected by those skilled in the art according to specific practical needs.

[0109] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0110] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0111] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0112] In some embodiments, the battery modules described above can also be assembled into a battery. The number of battery modules contained in the battery can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery.

[0113] Figure 5 and Figure 6 This is battery 1 as an example. (See reference...) Figure 5 and Figure 6 The battery 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0114] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery provided in this application. The battery cell, battery module, or battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0115] As the electrical device, a single battery cell, a battery module, or a battery can be selected according to its usage requirements.

[0116] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, batteries or battery modules can be used.

[0117] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0118] [Example]

[0119] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0120] Example 1

[0121] (1) Preparation of negative electrode sheet

[0122] I. Preparation of negative electrode active materials

[0123] The selected graphite is commercially available first graphite (also known as "Graphite 1"), with a specific capacity of 362.2 mAh / g, a graphitization degree of 94.2%, a Dv50 of 16 μm, and a 2T powder compaction density of 1.8 g / cm³. 3 Graphite material is used as the first negative electrode active material layer. Organic compounds are selected. As a precursor, R1 is —(CH2CH2O). nH, R2 are -OH and -SO3H, and a:b:c satisfies 5:0:5 to 5:5:0. The above precursors are dissolved in appropriate pure water to obtain a precursor dispersion. Solutions of different precursor materials are mixed with the first graphite to ensure uniform dispersion. Lithium-based inorganic salt LiFSI, at a mass ratio of 5%, is added to the mixture. The mixture is then uniformly dispersed using high-speed dispersion and other methods, stirred at 100-2000 rpm for 1-24 hours. The prepared slurry is then spray-dried with an inlet air temperature of 160-220℃ and an airflow rate of 30 L / min. The powder obtained from the spray drying is further dried to completely evaporate any residual solvent. It is then sieved through a 300-600 mesh screen to remove large particles or impurities, yielding the first graphite coated with the composite coating material.

[0124] II. Preparation of Lithium-Ionized Binder

[0125] Solution A is obtained by dissolving LiOH·H2O in deionized water. Solution B is obtained by dissolving sodium carboxymethyl cellulose (CMC) in deionized water. The required amounts of solution A and solution B are stirred and mixed at 25°C to adjust the degree of lithiation. Then, the mixture is neutralized to pH 7 with oxalic acid, acetic acid, or dilute hydrochloric acid to obtain the lithiation binder lithium carboxymethyl cellulose (CMC-Li).

[0126] III. Preparation of the negative electrode sheet

[0127] The first graphite coated with the composite coating material prepared above, the conductive agent carbon black, the binder styrene-butadiene rubber, and the prepared lithium-ion binder CMC-Li were mixed and homogenized at a weight ratio of 96:1.2:1.8:1 to obtain the first negative electrode active material layer slurry; the second graphite (also known as "graphite 2"), which can be obtained commercially, has a specific capacity of 354 mAh / g, a graphitization degree of 93%, a Dv50 of 11.6 μm, and a 2T powder compaction density of 1.65 g / cm³. 3 The conductive agent carbon black, the binder styrene-butadiene rubber, and the binder CMC are mixed and homogenized in a ratio of 95:1:2:2 to obtain the second negative electrode active material layer slurry. The first and second negative electrode active material layer slurries are coated onto the negative electrode current collector using a dual-die coating machine, and then dried in an oven at a temperature of 80-110℃, controlling the water content to be less than 150ppm, to obtain the negative electrode sheet.

[0128] (2) Preparation of positive electrode sheet

[0129] I. Preparation of positive electrode slurry

[0130] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1O2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 93:5:1. The mixture is stirred and mixed at a speed of 400 r / s-1000 r / s, and then wetted, kneaded and dispersed to obtain the positive electrode slurry.

[0131] II. Preparation of Positive Electrode Sheet

[0132] The prepared positive electrode slurry was uniformly coated onto an aluminum foil current collector and dried at 80℃-150℃, with the water content controlled to be less than 150ppm. After cold pressing and slitting, the positive electrode sheet was obtained.

[0133] (3) Separating membrane

[0134] A polyethylene film with a thickness of 13μm was selected as the separator.

[0135] (4) Electrolyte

[0136] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution at a concentration of 1 mol / L to obtain the electrolyte.

[0137] (5) Preparation of battery cells

[0138] The positive electrode, separator, and negative electrode are arranged in the order of "separator—negative electrode—separator—positive electrode," so that the separator acts as a barrier between the positive and negative electrodes. One end of the positive electrode, negative electrode, and two separators is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. A motor is used to rotate the winding shaft to wind the positive electrode, negative electrode, and two separators. After baking, electrolyte injection, and formation, a single battery cell is obtained.

[0139] Example 2-3

[0140] The difference between Examples 2-3 and Example 1 is that the mass ratio of binder 1 in the first negative electrode active material coating is different, and the mass ratio of inorganic component elements in the composite coating material in the first negative electrode active material coating and the second negative electrode active material coating is different.

[0141] Examples 4-5

[0142] The difference between Examples 4-5 and Example 1 is that the mass ratio of graphite 1 to graphite 2 is different.

[0143] Example 6

[0144] The difference between Example 6 and Example 1 is that the components of adhesive 1 are different.

[0145] Comparative Examples 1-2

[0146] The difference between Comparative Examples 1-2 and Example 1 is that no composite coating material is present in graphite 1.

[0147] The specific parameters of the battery cells in Examples 1-6 and Comparative Examples 1-2 are shown in Table 1 below.

[0148] Table 1: Specific parameters of Examples 1-6 and Comparative Examples 1-2

[0149] In addition, the battery cells in Examples 1-6 and Comparative Examples 1-2 were subjected to performance tests. The test results are shown in Table 2 below.

[0150] Table 2: Performance test results of Examples 1-6 and Comparative Examples 1-2

[0151] Referring to Examples 1-5 and Comparative Example 1, in Examples 1-5, when the first negative electrode active material layer near the current collector of the battery cell contains graphite material including a composite coating material, compared to Comparative Example 1-2 without graphite material including the composite coating material, it exhibits a higher lithium plating window voltage at -10°C, higher capacity retention after constant current charge-discharge at a charge rate of 3C in the charge-discharge rate test, and higher capacity retention under low temperature conditions of 10°C and -10°C. This demonstrates that when the first negative electrode active material layer near the current collector of the battery cell contains graphite material including a composite coating material, the charge-discharge performance of the battery cell in low-temperature environments can be improved.

[0152] Referring to Examples 1-6, in Examples 1-5, when the battery cell contains a lithium-bound binder CMC-Li in the first negative electrode active material layer near the current collector, compared to Example 6 which does not contain a lithium-bound binder CMC-Li, it exhibits a higher -10°C lithium plating window voltage, higher capacity retention after constant current charge-discharge at a charge rate of 3C in the charge-discharge rate test, and higher capacity retention under low-temperature conditions of 10°C and -10°C. This demonstrates that when the battery cell contains a lithium-bound binder in the first negative electrode active material layer near the current collector, the charge-discharge performance of the battery cell in low-temperature environments can be further improved.

[0153] [Testing methods for individual battery cell parameters]

[0154] The battery cells being tested can be either freshly assembled and unformed, or they can be battery cells removed from electrical devices (such as vehicles).

[0155] (1) Mass percentage test of inorganic component elements in the first and second negative electrode active material layers

[0156] The negative electrode sheet was fully discharged to its designed minimum cutoff voltage. After cleaning the negative electrode sheet with dimethyl carbonate solution, the negative electrode sheet was scraped off to obtain negative electrode sheet powder. The negative electrode sheet powder was then subjected to inductively coupled plasma (ICP) testing to analyze the content of inorganic elements F, S, N, and P in the negative electrode sheet powder.

[0157] (2) Lithium plating window test at -10℃

[0158] The battery cells and testing equipment were placed in an ambient temperature chamber, the temperature was adjusted to -10℃ and kept stable, and the battery cells to be tested were allowed to stand for more than 4 hours. The battery cells were charged with a constant current of 0.5C to the cutoff voltage, and then discharged with a constant current of 0.05C to the lower limit voltage, ensuring that the battery cells were in the same initial state. The batteries were charged with constant current at different charging rates (0.1C, 0.3C, 0.5C, 0.7C, 0.8C), and the voltage, current, temperature, and other data were recorded during the charging process. During charging, impedance analysis was used; when the impedance-voltage or impedance-state-of-charge curve showed a downward inflection point at the end of charging, lithium plating was considered to have begun. The tests at different charging rates were repeated to ensure the accuracy and reliability of the data. Results were recorded and analyzed, including the voltage value, state of charge (SOC), and corresponding charging rate at the time of lithium plating. The maximum charging voltage and corresponding charging rate at -10℃ without lithium plating were determined, thus defining the lithium plating window.

[0159] (3) Charge / discharge rate test

[0160] Under a test environment of 25℃, the battery cell to be tested was left to stand for more than 4 hours, then charged with a constant current of 0.5C, with a cutoff voltage of 4.2V, followed by constant voltage charging at 4.2V, with a cutoff current of 0.05C. After standing for 10 minutes, it was discharged with a constant current of 0.33C, with a cutoff voltage of 2.5V, and the discharge capacity at this time was recorded as Y1. After standing for 10 minutes, it was charged with a constant current of 1C, with a cutoff voltage of 4.2V, followed by constant voltage charging at 4.2V, with a cutoff current of 0.05C. After standing for 10 minutes, it was discharged with a constant current of 0.33C, with a cutoff voltage of 2.5V, and the discharge capacity at this time was recorded as Y2. At this point, the capacity retention rate of the lithium-ion battery after the 1C rate test can be obtained as Y2 / Y1×100%. After resting for 10 minutes, it is charged at a constant current of 2C, with a cutoff voltage of 4.2V. Then, it is charged at a constant voltage of 4.2V, with a cutoff current of 0.05C. After resting for another 10 minutes, it is discharged at a constant current of 0.33C, with a cutoff voltage of 2.5V. The discharge capacity at this point is recorded as Y3. The capacity retention rate of the lithium-ion battery after the 2C rate test can then be obtained as: Y3 / Y1 × 100%. After resting for 10 minutes, charge at a constant current of 3C, with a cutoff voltage of 4.2V. Then charge at a constant voltage of 4.2V, with a cutoff current of 0.05C. After resting for 10 minutes, discharge at a constant current of 0.33C, with a cutoff voltage of 2.5V. Record the discharge capacity at this point as Y4. The capacity retention rate of the lithium-ion battery after the 3C rate test can be obtained as Y4 / Y1 × 100%.

[0161] (4) Temperature capacity retention test

[0162] The prepared battery cells were charged with a constant current of 0.33C to a cutoff voltage of 4.2V, then charged with a constant voltage at 4.2V to a cutoff current of 0.05C, and then discharged at 0.33C to 2.5V. This process was repeated twice, and the second discharge capacity D0 was recorded. The battery cells were then charged with a constant current of 0.33C to a cutoff voltage of 4.2V, then charged with a constant voltage at 4.2V to a cutoff current of 0.05C, and then stored in a constant temperature environment of 25℃ / 10℃ / -10℃ for 4 hours. The cells were then charged with a constant current of 0.33C to a cutoff voltage of 4.2V, then charged with a constant voltage at 4.2V to a cutoff current of 0.05C, and then discharged at 0.33C to 2.5V. The capacity was recorded as Dn. The value of Dn divided by D0 was used as the capacity retention rate of the battery cells at different temperatures.

[0163] (5) Negative electrode specific capacity test

[0164] The prepared battery cells were charged to 2.0V (to lithium potential) at a current density of 0.05C, allowed to stand for 10 minutes, and then discharged to 0.005V (to lithium potential) at a current density of 0.1C. The charge-discharge cycle was repeated 3 times, and the specific capacity of the 3rd cycle was taken.

[0165] (6) Powder compaction density test A certain amount of powder is placed in a compaction mold. The mold is then placed on a compaction density instrument. Different pressures are set, and the thickness of the powder (thickness after depressurization) under different pressures can be read on the instrument. The compaction density of the powder under the corresponding pressure is calculated using pC = m / V. Pressure setting range: Anode: 0.1T-5T, with standard powder compaction density output at 2T pressure. Where pC = m / V = m / In (S*H): pC is the compacted density of the powder (g / cm³). 3 m is the sample mass in g, and S is the mold bottom area: 1.327 cm². 2 H represents the compaction thickness in cm.

[0166] (7) Test of compaction density of negative electrode sheet

[0167] The prepared negative electrode sheet was cold-pressed on a roller press at a pressure of 2T and a speed of 5m / min to obtain a negative electrode sheet of the target thickness. The thickness of the negative electrode sheet was measured using a thickness gauge. The mass of the negative electrode sheet was weighed using a high-precision balance. According to the formula: compaction density (g / cm³) 3 = Electrode surface density (g / cm³) 2 ) / Target thickness of negative electrode sheet, calculate the compaction density of negative electrode sheet.

[0168] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, Includes a negative electrode sheet, wherein the negative electrode sheet comprises: Negative electrode current collector; A first negative electrode active material layer and a second negative electrode active material layer, wherein the first negative electrode active material layer is disposed between the negative electrode current collector and the second negative electrode active material layer; wherein... The first negative electrode active material layer includes a first graphite and a composite coating material, wherein the composite coating material coats at least a portion of the surface of the first graphite; The composite coating material includes lithium-ion inorganic salt compounds and organic compounds.

2. The battery cell according to claim 1, characterized in that, The lithium-ionized inorganic salt compound includes at least one of the following: lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxarateborate, lithium dihydrogen phosphate, and lithium hexafluoroarsenate.

3. The battery cell according to claim 1 or 2, characterized in that, The organic compound has the following structural formula: Wherein, R1 includes at least one of the following: —Me, —Et, —Pr, —Bu, —Ph, —EtOH, —CH2COOH, —CH2CH2NH2, —(CH2CH2O) n H; R2 includes at least one of the following: —OH, —COOH, —NH2, —SO3H.

4. The battery cell according to any one of claims 1-3, characterized in that, The mass ratio I of the inorganic elements in the lithium-ion inorganic salt compound in the first negative electrode active material layer and the second negative electrode active material layer satisfies: 0.005≤I≤0.

02.

5. The battery cell according to any one of claims 1-4, characterized in that, The second negative electrode active material layer includes a second graphite, and the first graphite and the second graphite satisfy at least one of the following: the graphitization degree G1 of the first graphite and the graphitization degree G2 of the second graphite satisfy: G1>G2; the Dv501 of the first graphite and the Dv502 of the second graphite satisfy: Dv501>Dv502, the compaction density D1 of the first graphite powder 2T and the compaction density D2 of the second graphite powder 2T satisfy: D1>D2.

6. The battery cell according to claim 5, characterized in that, The mass ratio W of the first graphite to the second graphite satisfies: 0.25≤W≤4.

7. The battery cell according to claim 5 or 6, characterized in that, The specific capacity C1 of the first graphite satisfies 360mAh / g≤C1≤365Ah / g, and the specific capacity C2 of the second graphite satisfies 350mAh / g≤C2≤355Ah / g.

8. The battery cell according to any one of claims 1-7, characterized in that, The first negative electrode active material layer includes a lithium binder.

9. The battery cell according to claim 8, characterized in that, The mass percentage A of the lithium binder in the first negative electrode active material layer satisfies: 0.005 ≤ A ≤ 0.

015.

10. The battery cell according to claim 8 or 9, characterized in that, The lithium-based binder includes at least one of the following: lithium-based carboxymethyl cellulose, lithium-based styrene-butadiene rubber, lithium-based polyacrylic acid, lithium-based polyethylene glycol, and lithium-based sodium alginate.

11. The battery cell according to any one of claims 1-10, characterized in that, The negative electrode sheet satisfies at least one of the following: the specific capacity of the negative electrode sheet is 356mAh / g-362mAh / g, and the 2T compaction density of the negative electrode sheet is 1.7g / cm³. 3 -1.75g / cm 3 .

12. A battery, characterized in that, Includes the battery cell according to any one of claims 1-11.

13. An electrical appliance, characterized in that, It includes at least one of the following: the battery cell according to any one of claims 1-11, and the battery according to claim 12.

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