Battery cells, battery devices, and power-consuming devices

Abstract

This application discloses a battery cell, a battery device, and an electrical device. The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. The positive electrode film layer of the positive electrode sheet includes a positive electrode active material, which includes a lithium-containing phosphate, and the porosity of the positive electrode sheet is 20-30%. The thickness of the positive electrode current collector is 5-8% of the thickness of the positive electrode sheet. The negative electrode film layer of the negative electrode sheet includes a negative electrode active material, which includes graphite, and the porosity of the negative electrode sheet is 24-33%. The thickness of the negative electrode current collector is 2.5-5% of the thickness of the negative electrode sheet. The technical solution of this application takes into account the battery's good fast charging performance, power performance, and high energy density.

Description

[0001] This application claims priority to PCT international application PCT / CN2025 / 077650, entitled “Battery Cell, Battery Device, and Electrical Device,” filed on February 17, 2025, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a battery cell, a battery device, and an electrical device. Background Art

[0003] In recent years, as the application scope of batteries has become wider and wider, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0004] With the application and promotion of batteries, the requirements for battery fast charging performance and energy density are becoming higher and higher. Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery device, and an electrical device, aiming to take into account the battery's good fast charging performance, good power performance and high energy density.

[0006] In a first aspect, the present application provides a battery cell comprising an electrode assembly and an electrolyte; wherein the electrode assembly comprises a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprises a positive electrode collector and a positive electrode film layer located on at least one side of the positive electrode collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing phosphate, and the porosity of the positive electrode sheet is 20-30%; the thickness of the positive electrode collector is 5%-8% of the thickness of the positive electrode sheet; the negative electrode sheet comprises a negative electrode collector and a negative electrode film layer located on at least one side of the negative electrode collector, the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprises graphite, and the porosity of the negative electrode sheet is 24-33%; the thickness of the negative electrode collector is 2.5%-5% of the thickness of the negative electrode sheet.

[0007] In the battery cell provided in the present application, by combining the positive electrode sheet with the above porosity, the negative electrode sheet with the above porosity with the positive electrode current collector with the above thickness, and the negative electrode current collector with the above thickness, the transmission distance of ions in the electrode material can be shortened, thereby improving the fast charging performance and power performance of the battery cell, and reducing the space occupied by inactive materials, thereby improving the energy density of the battery cell.

[0008] In any embodiment, the porosity of the positive electrode sheet is 25-30%, which is beneficial for the battery cell to have good fast charging performance and power performance while also achieving high energy density.

[0009] In any embodiment, the porosity of the negative electrode sheet is 25-30%, thereby facilitating the battery cell to have good fast charging performance and power performance while also achieving high energy density.

[0010] In any embodiment, the thickness of the positive electrode current collector is 5% to 7.5% of the thickness of the positive electrode sheet, thereby further reducing the space occupied by inactive materials and improving the energy density of the battery cell.

[0011] In any embodiment, the thickness of the negative electrode current collector is 3.5% to 5% of the thickness of the negative electrode plate, thereby further reducing the space occupied by inactive materials and improving the energy density of the battery cell.

[0012] In any embodiment, when the state of charge (SOC) of the battery cell is 0%, the compaction density of the negative electrode film layer on a single side of the negative electrode sheet is 1.3-1.52 g / cc. Therefore, a suitable compaction density is conducive to further adjusting the porosity of the negative electrode sheet to an appropriate range.

[0013] In any embodiment, the surface density of the negative electrode film layer on a single side of the negative electrode sheet is 0.12-0.18 g / 1540.25 mm 2 Therefore, a suitable surface density is conducive to further adjusting the porosity of the negative electrode sheet to a suitable range.

[0014] In any embodiment, when the state of charge (SOC) of the battery cell is 0%, the compaction density of the positive electrode film layer on a single side of the positive electrode sheet is 2.3-2.6 g / cc. Therefore, a suitable compaction density is conducive to further adjusting the porosity of the positive electrode sheet to an appropriate range.

[0015] In any embodiment, the surface density of the positive electrode film layer on a single side of the positive electrode sheet is 0.25-0.33 g / 1540.25 mm 2 Therefore, a suitable surface density is conducive to further adjusting the porosity of the positive electrode sheet to a suitable range.

[0016] In any embodiment, the negative electrode film layer includes a first film layer and a second film layer, the first film layer is disposed on at least one surface of the negative electrode current collector, and the second film layer is disposed on a surface of the first film layer facing away from the current collector;

[0017] The first membrane layer contains a first negative electrode active material; the second membrane layer contains a second negative electrode active material; the average particle size of the longest diameter of the graphite in the second negative electrode active material is smaller than the average particle size of the longest diameter of the graphite in the first negative electrode active material. As a result, the average particle size of the longest diameter of the graphite used in the second membrane layer is relatively smaller, and the ion transmission distance in the second membrane layer is relatively shorter, which is beneficial for further improving the fast charging performance of the battery cell. The average particle size of the longest diameter of the graphite used in the first membrane layer is relatively larger, and the compaction density of the first membrane layer is relatively higher, which is beneficial for achieving good energy density.

[0018] In any embodiment, the longest average particle size of the graphite in the first negative electrode active material is 7 to 18 μm, thereby facilitating the first film layer to have a relatively higher compaction density.

[0019] In any embodiment, the graphite in the first negative electrode active material includes at least one of artificial graphite and natural graphite.

[0020] In any embodiment, the graphite in the first negative active material includes graphite in a secondary particle morphology.

[0021] In any embodiment, the volume distribution particle size Dv50 of the graphite in the first negative electrode active material is 7 to 15 μm.

[0022] In any embodiment, the graphite in the first negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100-500 nm. The carbon coating layer is beneficial to improving the conductivity of the negative electrode active material.

[0023] In any embodiment, the graphite in the first negative electrode active material has a degree of graphitization of 90-94%.

[0024] In any embodiment, the first negative electrode active material further comprises a silicon material, wherein the silicon element in the silicon material accounts for 0.5-10% by weight of the first negative electrode active material. The addition of the silicon material is conducive to further improving the energy density of the battery cell.

[0025] In any embodiment, the longest average particle size of the graphite in the second negative electrode active material is 6 to 10 μm, thereby facilitating the ion transport distance in the second membrane layer to be relatively shorter.

[0026] In any embodiment, the graphite in the second negative electrode active material includes at least one of artificial graphite and natural graphite.

[0027] In any embodiment, the graphite in the second negative electrode active material includes a negative electrode active material having a secondary particle morphology.

[0028] In any embodiment, the volume distribution particle size Dv50 of the graphite in the second negative electrode active material is 7 to 15 μm.

[0029] In any embodiment, the graphite in the second negative electrode active material includes a carbon coating layer, wherein the thickness of the carbon coating layer is 100-500 nm. The carbon coating layer is beneficial for improving the conductivity of the graphite.

[0030] In any embodiment, the graphite in the second negative electrode active material has a degree of graphitization of 90-94%.

[0031] In any embodiment, the second negative electrode active material further comprises a silicon material, wherein the silicon element in the silicon material accounts for 0.5-10% by weight of the second negative electrode active material. The addition of the silicon material is conducive to further improving the energy density of the battery cell.

[0032] In any embodiment, the thickness of the first film layer is 30% to 70% of the total thickness of the negative electrode film layer, thereby facilitating the first film layer to play a role in taking into account the energy density of the battery cell.

[0033] In any embodiment, the thickness of the second film layer is 30% to 70% of the total thickness of the negative electrode film layer, thereby further improving the fast charging performance of the battery cell.

[0034] In any embodiment, the lithium-containing phosphate includes lithium iron phosphate, which includes a metal element, including at least one of aluminum, titanium, and vanadium. Adding the metal element to the lithium iron phosphate is beneficial for increasing the compaction density of the positive electrode active material.

[0035] In any embodiment, the metal element includes aluminum, and the weight percentage of aluminum in the lithium-containing phosphate is 0.02% to 0.25%. This is beneficial for aluminum doping to increase the compaction density of the positive electrode active material and further improve the cycle performance of the battery cell.

[0036] In any embodiment, the metal element includes titanium, and the mass proportion of titanium in the lithium-containing phosphate is 0.15% to 0.35%. This is beneficial for titanium doping to increase the compaction density of the positive electrode active material and further increase the battery capacity.

[0037] In any embodiment, the metal element includes vanadium, and the mass proportion of vanadium in the lithium-containing phosphate is 0.03% to 0.2%. This is beneficial for enhancing the compaction density of the positive electrode active material and further improving the charge and discharge performance of the battery cell.

[0038] In any embodiment, the lithium-containing phosphate includes lithium-containing phosphate in the form of primary particles and lithium-containing phosphate in the form of secondary particles. The mixed use of primary particles and secondary particles is beneficial to further adjust the compaction density of the positive electrode active material.

[0039] In any embodiment, the longest average particle size of the primary lithium phosphate particles is 300-800 nm, thereby shortening the ion transmission distance and improving the fast charging performance.

[0040] In any embodiment, the longest average particle size of the secondary lithium-containing phosphate particles is 8 μm to 15 μm. The secondary particles are usually composed of lithium-containing phosphate particles with smaller primary particles, which is beneficial for shortening the ion transmission distance.

[0041] In any embodiment, the secondary particle morphology of the lithium-containing phosphate is spherical or quasi-spherical.

[0042] In any embodiment, the volume distribution particle size Dv50 of the lithium-containing phosphate is 5 to 15 μm.

[0043] In any embodiment, the electrolyte includes an electrolyte salt and a solvent, wherein the solvent includes a chain carboxylate and a chain carbonate, wherein the chain carboxylate accounts for 8.5% to 40% by weight of the electrolyte, and the chain carbonate accounts for 8.5% to 50% by weight of the electrolyte. Adding a certain amount of chain carbonate to the chain carboxylate solvent can reduce the amount of the chain carboxylate solvent in the electrolyte, reduce the degree of side reactions of the chain carboxylate solvent, and improve the battery cycle performance while ensuring fast charging performance.

[0044] In any embodiment, the mass proportion of the chain carboxylate in the electrolyte is 10% to 25.5%, thereby further optimizing the fast charging performance and cycle performance of the battery cell.

[0045] In any embodiment, the linear carbonate accounts for 10% to 42.5% by weight of the electrolyte, thereby further optimizing the fast charging performance and cycle performance of the battery cell.

[0046] In any embodiment, the chain carboxylate comprises the chain carboxylate described in Formula I,

[0047]

[0048] Formula I

[0049] Wherein, R1 includes any one of an alkyl group having 1 to 3 carbon atoms and an alkenyl group having 2 to 4 carbon atoms; R2 includes an alkyl group having 1 to 3 carbon atoms. The chain carboxylate of the above structure has a suitable viscosity, which helps reduce the transport resistance of ions in the electrolyte.

[0050] In any embodiment, the chain carboxylic acid ester includes at least one of ethyl acrylate, propyl acetate, and ethyl propionate, thereby further reducing the ion transport resistance in the electrolyte.

[0051] In any embodiment, the linear carbonate comprises the linear carbonate described in Formula II,

[0052]

[0053] Formula II

[0054] Wherein, R3 and R4 independently include an alkyl group having 1 to 3 carbon atoms. The addition of the chain carbonate is beneficial to reduce gas generation during the cycle of the battery cell, thereby improving the cycle performance.

[0055] In any embodiment, the linear carbonate comprises at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The linear carbonate has a suitable viscosity, which is beneficial for reducing the ion transport resistance in the electrolyte and reducing the gas generated by the battery cell during the cycle, thereby improving the cycle performance.

[0056] In any embodiment, the solvent further comprises a cyclic carbonate. The addition of the cyclic carbonate is beneficial for reducing the solvation effect of the electrolyte, reducing the binding ability of the solvent and ions, making it easier for the ions to dissociate from the solvent, thereby further improving the fast charging performance.

[0057] In any embodiment, the cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate. The above suitable cyclic carbonate is beneficial to play its role in reducing the solvation effect of the electrolyte.

[0058] In any embodiment, the mass proportion of the cyclic carbonate in the electrolyte is 10% to 51.5%, thereby further optimizing the fast charging performance of the battery cell.

[0059] In any embodiment, the electrolyte further includes a first additive comprising at least one of lithium difluorophosphate and lithium fluorosulfonate. The addition of the first additive improves the SEI film, increases the ionic conductivity of the electrolyte, and further improves the fast-charging performance and cycling performance of the battery cell.

[0060] In any embodiment, the first additive accounts for 0.02% to 2% by weight in the electrolyte, thereby facilitating the first additive's role in improving the SEI film and enhancing the ionic conductivity of the electrolyte.

[0061] In any embodiment, the electrolyte further includes a second additive, which includes at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone. The addition of the second additive is beneficial for improving the SEI film and further improving the cycle performance of the battery cell.

[0062] In any embodiment, the second additive accounts for 3% to 7% by weight of the electrolyte, thereby facilitating the second additive's role in improving the SEI film.

[0063] In any embodiment, the ionic conductivity of the electrolyte is 11-13 ms / cm at 25° C. Therefore, suitable ionic conductivity is conducive to rapid migration of ions between electrodes.

[0064] In a second aspect, the present application provides a battery device comprising the battery cell according to the first aspect of the present application.

[0065] In a third aspect, the present application provides an electrical device comprising the battery device of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 is a schematic diagram of a battery cell according to one embodiment of the present application;

[0067] Figure 2 yes Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0068] Figure 3 is a schematic diagram of a battery module according to one embodiment of the present application;

[0069] Figure 4 is a schematic diagram of a battery pack according to one embodiment of the present application;

[0070] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0071] Figure 6 FIG2 is a schematic diagram of an electrical device using a battery cell according to an embodiment of the present application as a power source.

[0072] Description of reference numerals:

[0073] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0074] Below, the embodiments of the battery cells, battery devices, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0075] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0076] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0077] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0078] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0079] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0080] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module, or a battery pack.

[0081] A battery cell is the smallest unit that makes up a battery and can independently realize the function of charging and discharging. When there are multiple battery cells, multiple battery cells are connected in series, in parallel or in mixed connection through a busbar. This application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 1 The battery cell 5 is a square structure as an example.

[0082] In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed within the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbars or longitudinal beams.

[0083] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0084] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0085] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0086] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0087] In some embodiments, the above-mentioned battery cells and battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack 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 pack.

[0088] Figure 4 and Figure 5 The battery pack 1 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0089] The battery provided in the embodiments of the present application may include a lithium-ion battery.

[0090] A battery cell includes an electrode assembly and an electrolyte.

[0091] The electrode assembly includes a positive electrode sheet and a negative electrode sheet. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode sheets.

[0092] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0093] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0094] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0095] An embodiment of the present application provides a battery cell, comprising an electrode assembly and an electrolyte; wherein the electrode assembly comprises a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprises a positive electrode collector and a positive electrode film layer located on at least one side of the positive electrode collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing phosphate, and the porosity of the positive electrode sheet is 20-30%; the thickness of the positive electrode collector is 5%-8% of the thickness of the positive electrode sheet; the negative electrode sheet comprises a negative electrode collector and a negative electrode film layer located on at least one side of the negative electrode collector, the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprises graphite, and the porosity of the negative electrode sheet is 24-33%; the thickness of the negative electrode collector is 2.5%-5% of the thickness of the negative electrode sheet.

[0096] Herein, the porosity of the positive electrode sheet and the porosity of the negative electrode sheet can be tested using methods known in the art. For example, the test is based on the national standard GB / T24586-2009, and the electrode sheet is immersed in ethyl methyl carbonate (EMC) for cleaning; and the test instrument true density meter (American Micron AccuPycII1340) is used to measure based on the gas displacement method. Among them, the percentage of the pore volume in the electrode sheet to the total volume of the electrode sheet is the electrode sheet porosity, and the calculation formula is: Porosity = (V-V0) / V×100%, where V0 is the true volume of the electrode sheet and V is the apparent volume of the electrode sheet.

[0097] The positive electrode current collector has two surfaces that are opposite to each other in the thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector. Similarly, the negative electrode current collector has two surfaces that are opposite to each other in the thickness direction, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0098] Herein, when the positive electrode film is disposed on both sides of the positive electrode current collector, the positive electrode sheet thickness refers to the sum of the thickness of the positive electrode current collector and the thickness of the two positive electrode film layers disposed on its two sides. Similarly, when the negative electrode film is disposed on both sides of the negative electrode current collector, the negative electrode sheet thickness refers to the sum of the thickness of the negative electrode current collector and the thickness of the two negative electrode film layers disposed on its two sides.

[0099] In the battery cell provided in the present application, by combining the positive electrode sheet with the above porosity, the negative electrode sheet with the above porosity with the positive electrode current collector with the above thickness, and the negative electrode current collector with the above thickness, the transmission distance of ions in the electrode material can be shortened, thereby improving the fast charging performance and power performance of the battery cell, and reducing the space occupied by inactive materials, thereby improving the energy density of the battery cell.

[0100] Optionally, the porosity of the positive electrode sheet may be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or a range consisting of any two of the above values. The porosity of the negative electrode sheet may be 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or a range consisting of any two of the above values.

[0101] Alternatively, the thickness of the positive electrode current collector may be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8% of the thickness of the positive electrode sheet, or a range consisting of any two of the above values. The thickness of the negative electrode current collector may be 2.5%, 3%, 3.5%, 4%, 4.5%, 5% of the thickness of the negative electrode sheet, or a range consisting of any two of the above values.

[0102] In any embodiment, the porosity of the positive electrode sheet is 25-30%, which is beneficial for the battery cell to have good fast charging performance and power performance while also achieving high energy density.

[0103] In any embodiment, the porosity of the negative electrode sheet is 25-30%, thereby facilitating the battery cell to have good fast charging performance and power performance while also achieving high energy density.

[0104] In any embodiment, the thickness of the positive electrode current collector is 5% to 7.5% of the thickness of the positive electrode sheet, thereby further reducing the space occupied by inactive materials and improving the energy density of the battery cell.

[0105] In any embodiment, the thickness of the negative electrode current collector is 3.5% to 5% of the thickness of the negative electrode plate, thereby further reducing the space occupied by inactive materials and improving the energy density of the battery cell.

[0106] In some embodiments, when the state of charge (SOC) of the battery cell is 0%, the compaction density of the negative electrode film layer on a single side of the negative electrode sheet is 1.3-1.52 g / cc. Therefore, a suitable compaction density is conducive to further adjusting the porosity of the negative electrode sheet to an appropriate range. Under the condition that the state of charge (SOC) of the battery cell is 0%, the compaction density of the negative electrode film layer on a single side of the negative electrode sheet may be 1.3g / cc, 1.31g / cc, 1.32g / cc, 1.33g / cc, 1.34g / cc, 1.35g / cc, 1.36g / cc, 1.37g / cc, 1.38g / cc, 1.39g / cc, 1.4g / cc, 1.41g / cc, 1.42g / cc, 1.43g / cc, 1.44g / cc, 1.45g / cc, 1.46g / cc, 1.47g / cc, 1.48g / cc, 1.49g / cc, 1.5g / cc, 1.51g / cc, 1.52g / cc or a numerical range consisting of any two of the above values.

[0107] In this application, the compaction density of the pole piece has a meaning well known in the art and can be tested using methods known in the art. When the state of charge (SOC) of the battery cell is 0%, the pole piece is removed from the lithium-ion battery, and a certain area of ​​the pole piece is taken. The mass and thickness of the pole piece and the current collector after the film layer is removed are measured respectively. The compaction density of the pole piece is calculated according to the following formula: Pole piece compaction density = (pole piece mass - current collector mass) / [(pole piece thickness - current collector thickness) × pole piece area].

[0108] In some embodiments, the surface density of the negative electrode film layer on a single side of the negative electrode sheet is 0.12-0.18 g / 1540.25 mm 2 Therefore, the appropriate surface density is conducive to further adjusting the porosity of the negative electrode sheet to an appropriate range. The surface density of the negative electrode film layer on a single side of the negative electrode sheet can be 0.12g / 1540.25mm 2 、0.13g / 1540.25mm 2 、0.14g / 1540.25mm 2 、0.15g / 1540.25mm 2 、0.16g / 1540.25mm 2 、0.17g / 1540.25mm 2 、0.18g / 1540.25mm 2 Or a numerical range consisting of any two of the above values.

[0109] In this application, the surface density of the film layer has a meaning well known in the art and can be tested using methods known in the art. For example, take a pole piece that is coated on one side and cold pressed (if it is a pole piece coated on both sides, the film layer on one side can be wiped off), punch it into small discs with an area of ​​S1, weigh it, and record it as M1. Then wipe off the film layer of the pole piece after the above weighing, weigh the weight of the current collector, and record it as M0. The single-side density of the film layer = (M1 - M0) / S1. In order to ensure the accuracy of the test results, multiple groups (for example, 10 groups) of test samples can be tested, and the average value can be calculated as the test result.

[0110] In some embodiments, under the condition that the state of charge SOC of the battery cell is 0%, the compaction density of the single-sided positive electrode film layer of the positive electrode sheet is 2.3~2.6g / cc. Thus, the appropriate compaction density is conducive to further adjusting the porosity of the positive electrode sheet within a suitable range. Under the condition that the state of charge SOC of the battery cell is 0%, the compaction density of the single-sided positive electrode film layer of the positive electrode sheet can be 2.3g / cc, 2.31g / cc, 2.32g / cc, 2.33g / cc, 2.34g / cc, 2.35g / cc, 2.36g / cc, 2.37g / cc, 2.38g / cc, 2.39g / cc, 2.4g / cc, 2.41g / cc, 2.42g / cc, 2.43g / cc, 2.44g / cc, 2.45g / cc, 2.46g / cc, 2.47g / cc, 2.48g / cc, 2.49g / cc, 2.5g / cc, 2.51g / cc, 2.52g / cc, 2.53g / cc, 2.54g / cc, 2.55g / cc, 2.56g / cc, 2.57g / cc, 2.58g / cc, 2.59g / cc, 2.6g / cc or a numerical range consisting of any two of the above values.

[0111] In some embodiments, the surface density of the single-sided positive electrode film layer of the positive electrode sheet is 0.25~0.33g / 1540.25mm 2 Therefore, the appropriate surface density is conducive to further adjusting the porosity of the positive electrode sheet to an appropriate range. The surface density of the single-sided positive electrode film layer of the positive electrode sheet can be 0.25g / 1540.25mm 2 、0.26g / 1540.25mm 2 , 0.27g / 1540.25mm 2 、0.28g / 1540.25mm 2 , 0.29g / 1540.25mm 2 、0.3g / 1540.25mm 2 、0.31g / 1540.25mm 2、0.32g / 1540.25mm 2 、0.33g / 1540.25mm 2 Or a numerical range consisting of any two of the above values.

[0112] In some embodiments, the positive electrode 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) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0113] In some embodiments, the positive electrode film layer may further optionally include a binder. For example, the binder may 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 acrylate resin.

[0114] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0115] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0116] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper 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 (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0117] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0118] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0119] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0120] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0121] In some embodiments, the negative electrode film layer includes a first film layer and a second film layer, the first film layer is disposed on at least one surface of the negative electrode current collector, and the second film layer is disposed on a surface of the first film layer that faces away from the current collector;

[0122] The first film layer contains a first negative electrode active material; the second film layer contains a second negative electrode active material; and the longest average particle size of graphite in the second negative electrode active material is smaller than the longest average particle size of graphite in the first negative electrode active material.

[0123] In this article, "the longest diameter average particle size" refers to the process of ion polishing and cutting the electrode along the thickness direction to expose the cross-section of the film layer. The cross-section of the film layer can be tested by scanning electron microscopy (SEM). At a magnification of 1000 times in the SEM scene, more than 50 particles are randomly selected and the length of the longest straight line passing through the center point of a single particle and extending to the periphery of the particle is measured. The average length of the longest straight lines of these particles is then taken.

[0124] The graphite used in the second film layer has a relatively smaller average particle size in its longest diameter, shortening the ion transport distance in the second film layer, which helps further improve the fast-charging performance of the battery cells. The graphite used in the first film layer has a relatively larger average particle size in its longest diameter, resulting in a relatively higher compaction density, which helps achieve a good energy density.

[0125] In some embodiments, the longest average particle size of the graphite in the first negative electrode active material is 7 to 18 μm. This facilitates the first film layer to have a relatively higher compaction density. The longest average particle size of the graphite in the first negative electrode active material can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, or a range consisting of any two of these values.

[0126] In some embodiments, the graphite in the first negative electrode active material includes at least one of artificial graphite and natural graphite.

[0127] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flake structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0128] In some embodiments, the graphite in the first negative active material includes graphite having a secondary particle morphology.

[0129] In this application, particles with primary particle morphology refer to primary particles. Primary particles are the smallest unit of particles within a certain observation range. Primary particles may contain any form of defects, but it is impossible to define smaller particles within a primary particle. Primary particles may aggregate under physical forces such as van der Waals forces, but this aggregation is easily disaggregated by external forces such as ultrasound, stirring, and roller compaction, ensuring that the main component form of the active material in the membrane layer remains primary particles.

[0130] In this application, particles with secondary particle morphology refer to secondary particles. Secondary particles are formed by the agglomeration of primary particles and are not easily dispersed under external forces such as ultrasound. However, after cutting the cross section of the secondary particles, it can be seen that the secondary particles are formed by the agglomeration of many primary particles.

[0131] In some embodiments, the volume distribution particle size Dv50 of the graphite in the first negative electrode active material is 7 to 15 μm. The volume distribution particle size Dv50 of the graphite in the first negative electrode active material can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a numerical range consisting of any two of the above values.

[0132] In this application, the volume distribution particle size Dv50 of a material represents the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%, and can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0133] In some embodiments, the graphite in the first negative electrode active material includes a carbon coating layer having a thickness of 100 to 500 nm. The carbon coating layer helps improve the conductivity of the negative electrode active material. The thickness of the carbon coating layer can be 100 nm, 150 nm, 200 nm, 350 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a range consisting of any two of the above values.

[0134] The thickness of the coating can be characterized using transmission electron microscopy (TEM). By observing the negative electrode active material using TEM, the coating layer covering the surface of the negative electrode active material can be clearly observed based on the differences in the lattice fringes. Five locations within the coating layer are randomly selected for testing, and the average value is calculated as the average thickness of the coating layer.

[0135] In some embodiments, the graphite in the first negative electrode active material has a degree of graphitization of 90-94%. A high degree of graphitization indicates smaller interlayer spacing, smaller lattice rotation, less scattered stacking of layers, and more orderly arrangement. This results in a higher specific capacity and facilitates the production of high-energy-density battery cells. The degree of graphitization of the first negative electrode active material can be 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, or a range consisting of any two of these values.

[0136] In this article, the term "degree of graphitization" macroscopically characterizes the proportion of the material that reaches a complete graphite crystal structure; microscopically, it refers to the degree to which the carbon structure in different transition states approaches the ideal graphite crystal.

[0137] In this application, the degree of graphitization of graphite can be tested using instruments and methods known in the art. For example, an X-ray diffractometer (such as a Bruker D8 Discover) can be used for testing. The test can refer to JISK 0131-1996 and JB / T 4220-2011. The average interlayer spacing d002 of the C(002) plane in the material's crystal structure is obtained. The degree of graphitization is then calculated using the formula g = (0.344 - d002) / (0.344 - 0.3354) × 100%. In the above formula, d002 is the average interlayer spacing of the C(002) plane in the material's crystal structure, expressed in nanometers (nm).

[0138] In some embodiments, the first negative electrode active material further comprises a silicon material, wherein the mass proportion of silicon in the silicon material in the first negative electrode active material is 0.5-10%. The addition of silicon material helps to further improve the energy density of the battery cell. The mass proportion of silicon in the silicon material in the first negative electrode active material can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a numerical range consisting of any two of the above values.

[0139] In the present application, the silicon content can be measured using instruments and methods known in the art. For example, the negative electrode active material can be placed in an appropriate amount of concentrated nitric acid as a digestion solvent and digested using a plate digestion method. Finally, the solvent can be dissolved and extracted using hydrochloric acid. The resulting solution can then be diluted to an appropriate volume and quantitatively measured using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0140] In some embodiments, the average particle size of the longest diameter of the graphite in the second negative electrode active material is 6 to 10 μm. This facilitates the effect of a relatively shorter ion transport distance in the second membrane layer. The average particle size of the longest diameter of the graphite in the second negative electrode active material can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range consisting of any two of these values.

[0141] In some embodiments, the graphite in the second negative electrode active material includes at least one of artificial graphite and natural graphite.

[0142] In some embodiments, the graphite in the second negative active material includes graphite having a secondary particle morphology.

[0143] In some embodiments, the volume distribution particle size Dv50 of the graphite in the second negative electrode active material is 7 to 15 μm. The volume distribution particle size Dv50 of the graphite in the second negative electrode active material can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a numerical range consisting of any two of the above values.

[0144] In some embodiments, the graphite in the second negative electrode active material includes a carbon coating layer having a thickness of 100 to 500 nm. The carbon coating layer helps improve the electrical conductivity of the graphite. The thickness of the carbon coating layer can be 100 nm, 150 nm, 200 nm, 350 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a range consisting of any two of the above values.

[0145] In some embodiments, the graphite in the second negative electrode active material has a degree of graphitization of 90-94%. A high degree of graphitization indicates smaller interlayer spacing, smaller lattice rotation, less scattered stacking of layers, and more orderly arrangement. This leads to a higher specific capacity and facilitates the production of high-energy-density battery cells. The graphite in the second negative electrode active material can have a degree of graphitization of 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, or a range consisting of any two of these values.

[0146] In some embodiments, the second negative electrode active material further comprises a silicon material, wherein the mass proportion of silicon in the silicon material is 0.5-10%. The addition of the silicon material helps further improve the energy density of the battery cell. The mass proportion of silicon in the silicon material in the second negative electrode active material can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a numerical range consisting of any two of the above values.

[0147] In some embodiments, the thickness of the first film layer is 30% to 70% of the total thickness of the negative electrode film layer. This facilitates the first film layer's role in balancing the energy density of the battery cell. The thickness of the first film layer can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% of the total thickness of the negative electrode film layer, or a range consisting of any two of these values.

[0148] In some embodiments, the thickness of the second film layer is 30% to 70% of the total thickness of the negative electrode film layer. This helps further improve the fast charging performance of the battery cell. The thickness of the second film layer can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% of the total thickness of the negative electrode film layer, or a range consisting of any two of these values.

[0149] The thickness of the first and second film layers can be characterized using transmission electron microscopy (SEM). A cross-section of the negative electrode sheet is observed using a SEM. Based on the difference in the longest average particle size of the active material in the first and second film layers, the thickness of the first and second film layers is determined. For example, the observations are repeated five times and the average value is calculated.

[0150] In some embodiments, the lithium-containing phosphate includes lithium iron phosphate, which includes a metal element, including at least one of aluminum, titanium, and vanadium. Adding the metal element to the lithium iron phosphate helps increase the compaction density of the positive electrode active material.

[0151] In the present application, the aluminum, titanium, and vanadium contents in lithium-containing phosphates can be tested using instruments and methods known in the art. For example, the lithium-containing phosphate can be placed in an appropriate amount of concentrated nitric acid as a digestion solvent and digested using a plate digestion method. Finally, the extraction solvent can be dissolved with hydrochloric acid. The resulting solution can then be diluted to an appropriate volume and quantitatively tested using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0152] In some embodiments, the metal element includes aluminum, and the weight percentage of aluminum in the lithium-containing phosphate is 0.02% to 0.25%. This is beneficial for aluminum doping to increase the compaction density of the positive electrode active material and further improve the cycle performance of the battery cell. The weight percentage of aluminum in the lithium-containing phosphate can be 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, or a numerical range consisting of any two of the above values.

[0153] In some embodiments, the metal element includes titanium, and the mass proportion of the titanium in the lithium-containing phosphate is 0.15% to 0.35%. As a result, it is beneficial to play the role of titanium doping in increasing the compaction density of the positive electrode active material and further increasing the battery capacity. The mass proportion of titanium in the lithium-containing phosphate can be 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, or a numerical range consisting of any two of the above values.

[0154] In some embodiments, the metal element includes vanadium, and the mass proportion of the vanadium in the lithium-containing phosphate is 0.03% to 0.2%. This is beneficial for vanadium doping to increase the compaction density of the positive electrode active material and further improve the charge and discharge performance of the battery cell. The mass proportion of vanadium in the lithium-containing phosphate can be 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, or a numerical range consisting of any two of the above values.

[0155] In some embodiments, the lithium-containing phosphate includes a primary particle-shaped lithium-containing phosphate and a secondary particle-shaped lithium-containing phosphate. The mixed use of the primary and secondary particles is beneficial for further adjusting the compaction density of the positive electrode active material.

[0156] In some embodiments, the longest average particle size of the primary particle morphology of the lithium-containing phosphate is 300-800 nm. This helps shorten the ion transmission distance and thus improve the fast charging performance. The longest average particle size of the primary particle morphology of the lithium-containing phosphate can be 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or a numerical range consisting of any two of the above values.

[0157] In some embodiments, the longest average particle size of the lithium-containing phosphate in the secondary particle morphology is 8μm to 15μm. Secondary particles are generally composed of lithium-containing phosphates with smaller primary particles, which helps to shorten the ion transmission distance. The longest average particle size of the lithium-containing phosphate in the secondary particle morphology can be 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, or a numerical range consisting of any two of the above values.

[0158] In some embodiments, the secondary particles of the lithium-containing phosphate are spherical or quasi-spherical. Spherical refers to a material with a sphericity of 1, and quasi-spherical refers to a material with a sphericity close to 1 but not 1.

[0159] In some embodiments, the volume distribution particle size Dv50 of the lithium-containing phosphate is 5 to 15 μm. The volume distribution particle size Dv50 of the lithium-containing phosphate can be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, or a numerical range consisting of any two of the above values.

[0160] In any embodiment, the electrolyte includes an electrolyte salt and a solvent, wherein the solvent includes a chain carboxylate and a chain carbonate, wherein the chain carboxylate accounts for 8.5% to 40% by weight of the electrolyte, and the chain carbonate accounts for 8.5% to 50% by weight of the electrolyte. Adding a certain amount of chain carbonate to the chain carboxylate solvent can reduce the amount of the chain carboxylate solvent in the electrolyte, reduce the degree of side reactions of the chain carboxylate solvent, and improve the battery cycle performance while ensuring fast charging performance.

[0161] Herein, the types and mass contents of each component in the electrolyte can be obtained by detecting the electrolyte by any method known to those skilled in the art. As an example, the composition and content of the electrolyte can be characterized by one or more of gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS). For example, referring to GB / T-9722-2006 / GB / T6041-2002, gas chromatography and mass spectrometry are used. After the gas chromatography separates the components in the sample, each component is broken into ion fragments in the mass spectrometer and separated according to the mass-to-charge ratio (m / z) to form a specific mass spectrum, thereby obtaining a qualitative analysis of each organic component in the electrolyte. Then, the organic components in the electrolyte are separated in a chromatographic column and a detection signal spectrum of each component is generated. The retention time is used for component qualitative analysis, and the peak area is corrected by standardization to achieve quantitative analysis of the organic components in the electrolyte. Referring to JY / T0578-2020, nuclear magnetic resonance spectroscopy (NMR) was used to obtain qualitative and quantitative analysis of the components in the electrolyte.

[0162] The electrolyte referred to herein can be fresh electrolyte or electrolyte obtained by disassembling a battery cell. The electrolyte obtained by disassembling a battery cell can be free electrolyte in the battery casing or electrolyte obtained by centrifugation from a pole piece.

[0163] Optionally, the mass proportion of the chain carboxylic acid ester in the electrolyte can be 8.5%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40% or a numerical range consisting of any two of the above values. Optionally, the mass proportion of the linear carbonate in the electrolyte can be 8.5%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or a numerical range consisting of any two of the above values.

[0164] The addition of chain carboxylate solvents to the electrolyte is not only beneficial to improving the lithium ion conductivity of the electrolyte, but also can reduce the viscosity of the electrolyte, increase the transfer rate of lithium ions at the solid-liquid interface of the battery monomer, and improve the fast charging performance of the battery. However, chain carboxylate solvents have high reactivity and are easily decomposed during the battery cycle, resulting in battery gas production. Adding a certain amount of chain carbonate to the chain carboxylate solvent can reduce the amount of chain carboxylate solvent in the electrolyte, reduce the degree of side reactions of the chain carboxylate solvent, and improve battery cycle performance. In some embodiments, the electrolyte salt in the electrolyte can be selected from the sodium salt electrolyte selected from sodium hexafluorophosphate (NaPF6), sodium difluorooxalatoborate (NaDFOB), sodium tetrafluoroborate (NaBF4), sodium bis(oxalatoborate) (NaBOB), sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide (NaFSI), sodium trifluoromethylsulfonate, sodium bis(trifluoromethylsulfonyl)imide (NaTFSI). At least one of them.

[0165] In some embodiments, the battery cell further includes a separator. The separator base film may be made of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator base film may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator base film is a multi-layer composite film, the materials of the individual layers may be the same or different, without particular limitation.

[0166] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0167] In some embodiments, the mass proportion of the linear carboxylate in the electrolyte is 10% to 25.5%, thereby further optimizing the fast charging performance and cycle performance of the battery cell.

[0168] In some embodiments, the linear carbonate accounts for 10% to 42.5% by weight of the electrolyte, thereby further optimizing the fast charging performance and cycle performance of the battery cell.

[0169] In some embodiments, the linear carboxylate comprises the linear carboxylate described in Formula I,

[0170]

[0171] Formula I

[0172] Wherein, R1 includes any one of an alkyl group having 1 to 3 carbon atoms and an alkenyl group having 2 to 4 carbon atoms; R2 includes an alkyl group having 1 to 3 carbon atoms. The chain carboxylate of the above structure has a suitable viscosity, which helps reduce the transport resistance of ions in the electrolyte.

[0173] As used herein, "alkyl having 1 to 3 carbon atoms" refers to a straight or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, with no unsaturation, having from 1 to 3 carbon atoms, and attached to the rest of the molecule by a single bond. Examples include, but are not limited to, methyl (-CH3), ethyl (-CH2CH3), 1-propyl (-CH2CH2CH3), and 2-propyl (-CH(CH3)2).

[0174] As used herein, an "alkenyl group having 2 to 4 carbon atoms" refers to a straight or branched hydrocarbon group having 2 to 4 carbon atoms and at least one carbon-carbon double bond. Examples include, but are not limited to, ethenyl, 1-propenyl, 1-propenyl, 2-propenyl, 1-butenyl, and 2-butenyl.

[0175] In some embodiments, the chain carboxylic acid ester includes at least one of ethyl acrylate, propyl acetate, and ethyl propionate, thereby further reducing the ion transport resistance in the electrolyte.

[0176] In some embodiments, the linear carbonate comprises the linear carbonate described in Formula II,

[0177]

[0178] Formula II

[0179] Wherein, R3 and R4 independently include an alkyl group having 1 to 3 carbon atoms. The addition of the chain carbonate is beneficial to reduce gas generation during the cycle of the battery cell, thereby improving the cycle performance.

[0180] In some embodiments, the linear carbonate comprises at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The linear carbonate has a suitable viscosity, which helps reduce the ion transport resistance in the electrolyte and reduces gas generation in the battery cell during cycling, thereby improving cycling performance.

[0181] In some embodiments, the solvent further comprises a cyclic carbonate. The addition of the cyclic carbonate helps reduce the solvation effect of the electrolyte, reduces the binding capacity of the solvent to ions, and makes it easier for ions to dissociate from the solvent, thereby further improving the fast charging performance.

[0182] In some embodiments, the cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate. The above suitable cyclic carbonate is beneficial to play its role in reducing the solvation effect of the electrolyte.

[0183] In some embodiments, the mass proportion of cyclic carbonate in the electrolyte is 10% to 51.5%. This is conducive to further optimization of the fast charging performance of the battery cell. The mass proportion of cyclic carbonate in the electrolyte can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 51.5% or a numerical range consisting of any two of the above values.

[0184] In some embodiments, the electrolyte further includes a first additive comprising at least one of lithium difluorophosphate and lithium fluorosulfonate. The addition of the first additive improves the SEI film, increases the ionic conductivity of the electrolyte, and further improves the fast-charging and cycling performance of the battery cell.

[0185] In some embodiments, the mass proportion of the first additive in the electrolyte is 0.02% to 2%. Thus, it is beneficial to play the role of the first additive in improving the SEI film and improving the ionic conductivity of the electrolyte. The mass proportion of the first additive in the electrolyte can be 0.02%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2% or a numerical range consisting of any two of the above values.

[0186] In some embodiments, the electrolyte further includes a second additive comprising at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone. The addition of the second additive helps improve the SEI film and further improves the cycling performance of the battery cell.

[0187] In some embodiments, the second additive comprises 3% to 7% by weight of the electrolyte. This facilitates the second additive's role in improving the SEI film. The second additive may comprise 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7% by weight of the electrolyte, or any two of these values.

[0188] In some embodiments, the ionic conductivity of the electrolyte at 25°C is 11-13 ms / cm. Thus, suitable ionic conductivity facilitates rapid ion migration between the electrodes. The ionic conductivity of the electrolyte at 25°C can be 11 ms / cm, 11.5 ms / cm, 12 ms / cm, 12.5 ms / cm, 13 ms / cm, or a range consisting of any two of these values.

[0189] In this application, the ionic conductivity of the electrolyte is the ability to describe the conductive process formed by the directional movement of dissociated ions in the electrolyte in an electric field, and can be tested by any known method in the art. As an example, disassemble the battery cell, take about 100mL of electrolyte sample with a dry, clean, corrosion-resistant sample bottle, seal it in a constant temperature water bath, shake the sample from time to time, and keep the temperature at 25°C (deviation ±0.5°C). After the sample temperature is constant, use a commercially available conductivity meter to test its conductivity. After the conductivity meter is wiped clean with calibration fluid, place it vertically in the liquid to be tested, click to start the test, and record the test results after the data is stable for more than 10 seconds.

[0190] An embodiment of the present application also provides a battery device, including the battery cell provided by the present application.

[0191] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0192] Figure 6 This is an example of an electric device. This device is 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 the battery cells in this device, a battery pack or battery module can be used.

[0193] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0194] An embodiment of the present application also provides an electrical device, including the battery device provided in the present application.

[0195] Example

[0196] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0197] Example 1

[0198] 1. Preparation of positive electrode sheet

[0199] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer. The positive electrode film layer is arranged on both sides of the positive electrode current collector, and the positive electrode current collector is aluminum foil.

[0200] The positive electrode film layer includes a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) uniformly coated on the surface of the positive electrode current collector, and then dried and cold pressed to form a film layer. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black in a weight ratio of 90:5:5.

[0201] The positive electrode active material includes lithium iron phosphate particles and metal elements located in the lithium iron phosphate particles. The metal elements include Al, V, and Ti. Among them, the mass proportion of Al, V, and Ti in the lithium iron phosphate particles is 0.15%.

[0202] The lithium iron phosphate particles consist of primary particles and secondary particles formed by agglomeration of the primary particles. The secondary particles are spherical or quasi-spherical in shape. The primary particles have an average maximum diameter of 600 nm, while the secondary particles have an average maximum diameter of 10 μm. The volume-distributed particle size (Dv50) of the lithium iron phosphate particles is 7 μm.

[0203] The surface density of the single-sided positive electrode film layer is 0.28g / 1540.25mm 2 .

[0204] When the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided positive electrode film layer of the positive electrode sheet is 2.4 g / cc.

[0205] The porosity of the positive electrode sheet is 25%, and the thickness of the positive electrode current collector is 6% of the thickness of the positive electrode sheet.

[0206] 2. Preparation of negative electrode sheet

[0207] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer. The negative electrode film layer is arranged on both sides of the negative electrode current collector, and the negative electrode current collector is copper foil.

[0208] The negative electrode film layer includes a first film layer and a second film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector, drying and cold pressing.

[0209] The first film layer, disposed on the surface of the negative electrode current collector, comprises a first negative electrode active material, a conductive agent, acetylene black, a negative electrode binder, and a thickener, sodium carboxymethyl cellulose, in a mass ratio of 96.5:0.5:2:1. The negative electrode active material comprises graphite and silicon oxide, with silicon comprising 5% by mass. The graphite comprises artificial graphite and a carbon coating layer, which is coated on the surface of the artificial graphite. The carbon coating layer is 200 nm thick and has a graphitization degree of 92%. The graphite has an average maximum particle size of 12 μm.

[0210] The second film layer, applied to the surface of the negative electrode current collector, comprises a negative electrode active material, a conductive agent, acetylene black, a negative electrode binder, and a thickener, sodium carboxymethyl cellulose, in a mass ratio of 96.5:0.5:2:1. The negative electrode active material comprises graphite and silicon oxide, with silicon accounting for 5% by mass of the first negative electrode active material. The graphite comprises artificial graphite and a carbon coating layer, which is coated on the surface of the artificial graphite. The carbon coating layer is 200 nm thick and has a graphitization degree of 92%. The graphite has an average maximum particle size of 9 μm.

[0211] The thickness of the first film layer is 50% of the total thickness of the negative electrode film layer, and the thickness of the second film layer is 50% of the total thickness of the negative electrode film layer.

[0212] The surface density of the single-sided negative electrode film is 0.13g / 1540.25mm 2 .

[0213] When the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided negative electrode film layer of the negative electrode sheet is 1.4 g / cc.

[0214] The porosity of the negative electrode sheet is 28%, and the thickness of the negative electrode current collector is 4% of the thickness of the negative electrode sheet.

[0215] 3. Isolation film

[0216] The separator is a 7 μm polyethylene film layer.

[0217] 4. Preparation of electrolyte

[0218] The electrolyte includes an organic solvent, a lithium salt and an additive. After mixing the components of each organic solvent, the lithium salt and the additive are added to prepare an electrolyte. The organic solvent includes ethyl acrylate, dimethyl carbonate and propylene carbonate. Based on the total mass of the electrolyte, the mass proportion of ethyl acrylate is 20%, the mass proportion of dimethyl carbonate is 20%, and the mass proportion of propylene carbonate is 40%. The lithium salt is lithium hexafluorophosphate. Based on the total mass of the electrolyte, the mass proportion of lithium hexafluorophosphate is 15%. The additives include lithium difluorophosphate and vinylene carbonate. Based on the total mass of the electrolyte, the mass proportion of lithium difluorophosphate is 1%, and the mass proportion of vinylene carbonate is 4%.

[0219] 5. Preparation of battery cells

[0220] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, to obtain a laminated electrode assembly. The electrode assembly is placed in an outer packaging shell, on which a positive terminal and a negative terminal are provided. After baking, the electrolyte is injected, and after vacuum packaging, standing, formation, shaping and other processes, a battery cell is obtained.

[0221] Examples 2-9 and Comparative Examples 1-9 were prepared using a method similar to that of Example 1 to prepare battery cells. The differences from Example 1 are shown in Table 1.

[0222] Performance testing:

[0223] (1) Battery fast charging performance test:

[0224] The batteries of the above embodiments and comparative examples were charged and discharged for the first time at a current of 1C, specifically including: at 25°C, charging the battery at a constant current rate of 1C to a voltage of 3.65V, then charging at a constant voltage to a current of ≤0.05C, standing for 5 minutes, and then discharging at a constant current rate of 0.33C to a voltage of 2.5V, and recording its actual capacity as C0. The battery was then charged at a constant current of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, and 5C0 in sequence to a full battery charge cut-off voltage of 3.65V, and the corresponding SOC state when the battery was charged to 3.65V at each rate was recorded. After each charging was completed, it was discharged at 1C0 to a full battery discharge cut-off voltage of 2.1V, and different SOC states were plotted. From the OC-charge rate curve, read the charge rates corresponding to 10% SOC, 20% SOC, ... 80% SOC, respectively, and record them as C(10% SOC), C(20% SOC), C(30% SOC), C(40% SOC), C(50% SOC), C(60% SOC), C(70% SOC), C(80% SOC), to obtain the maximum charge rate at the corresponding state of charge, i.e., the fast charge window. The 10-80% charging time is 6 / C(10% SOC) + 6 / C(20% SOC) + 6 / C(30% SOC) + 6 / C(40% SOC) + 6 / C(50% SOC) + 6 / C(60% SOC) + 6 / C(70% SOC) + 6 / C(80% SOC), in minutes.

[0225] (2) Internal resistance performance test:

[0226] The batteries of the above embodiments and comparative examples were charged and discharged for the first time at a current of 1C (i.e., the current value at which the theoretical capacity is completely discharged within 1 hour). Specifically, the battery was charged and discharged at a constant current rate of 1C to a voltage of 3.65V at 25°C, then charged at a constant voltage to a current of ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.5C for 1 hour to 50% of the capacity. The battery was then discharged at a constant current of 4C0 (the current size is denoted as I) for 10 seconds, and the voltage U1 before discharge and the voltage U2 after discharge were recorded. The internal resistance R=(U1-U2) / I.

[0227] (3) Energy density test:

[0228] At 25°C, fully charge the assembled battery at a 0.5C rate and fully discharge it at a 0.5C rate, and record the actual discharge energy at this time; weigh the battery using an electronic balance at 25°C; the ratio of the battery's actual 0.5C discharge energy to the battery weight is the battery's energy density.

[0229]

[0230] The porosity of the electrodes in Comparative Examples 1 and 3 is relatively low, which can improve the energy density of the battery. However, the low porosity and large internal resistance are not conducive to fast charging, and the charging time is too long. In addition, the low porosity and large DC internal resistance can easily lead to poor power performance.

[0231] The porosity of the electrodes in Comparative Examples 2 and 4 is relatively high, which is beneficial to the movement of ions and the improvement of fast charging and power performance, but the battery energy density decreases too much.

[0232] In Comparative Examples 5 and 7, the thickness of the current collector is relatively small, and the space occupied in the battery is small, the battery energy density is improved, but the DC internal resistance is increased, and the power performance is too poor.

[0233] In Comparative Examples 6 and 8, the thickness of the current collector accounts for a relatively large proportion. Although the DC internal resistance of the current collector is reduced, the current collector occupies battery space and the battery energy density decreases too much.

[0234] In the embodiments of the present application, by adjusting the porosity of the positive electrode sheet to 20-30%, the thickness of the positive electrode current collector to 5-8% of the thickness of the positive electrode sheet; the porosity of the negative electrode sheet to 24-33%, and the thickness of the negative electrode current collector to 2.5-5% of the thickness of the negative electrode sheet, this can shorten the ion transmission distance in the electrode material, improve the fast charging performance and power performance of the battery cell, and reduce the space occupied by inactive materials, thereby increasing the energy density of the battery cell.

[0235] Examples 10-13 use a method similar to that of Example 1 to prepare battery cells. The differences from Example 1 are shown in Table 2.

[0236] Table 2

[0237]

[0238] It can be seen from Examples 1 and 10 that when the average particle size of the longest diameter of graphite in the two film layers used in the negative electrode is the same, the number of cycles and energy density are improved to a certain extent, but the fast charging performance deteriorates. In Example 1, the average particle size of the longest diameter of graphite in the two film layers is different. After particle grading, the fast charging performance is better while taking into account both good number of cycles and energy density. The average particle size of the longest diameter of graphite used in the second film layer of Example 1 is relatively smaller, and the ion transmission distance of ions in the second film layer is relatively shorter, which is conducive to further improving the fast charging performance of the battery cell. The average particle size of the longest diameter of graphite used in the first film layer is relatively larger, and the compaction density of the first film layer is relatively higher, which is conducive to taking into account good energy density.

[0239] As can be seen from Examples 1, 10-13, the maximum average particle size of the graphite in the first film layer of the negative electrode sheet is reduced, which is beneficial for reducing DC internal resistance and improving power performance. The maximum average particle size of the primary particles and the maximum average particle size of the secondary particles of the active material in the positive electrode sheet are reduced, which is beneficial for reducing DC internal resistance and improving power performance.

[0240] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: It includes an electrode assembly and an electrolyte; wherein the electrode assembly includes a positive electrode sheet and a negative electrode sheet, The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a lithium-containing phosphate. The lithium-containing phosphate includes a metal element. The metal element includes Ti. The porosity of the positive electrode sheet is greater than 20% and less than 30%. The thickness of the positive electrode current collector is 5% to 8% of the thickness of the positive electrode sheet. The negative electrode plate includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, and the porosity of the negative electrode plate is greater than 24% and less than 33%; the thickness of the negative electrode current collector is 2.5% to 5% of the thickness of the negative electrode plate.

2. The battery cell according to claim 1, wherein: The porosity of the positive electrode sheet is not less than 25% and less than 30%.

3. The battery cell according to claim 1, wherein: The porosity of the negative electrode plate is 25-30%.

4. The battery cell according to claim 1, wherein: The thickness of the positive electrode current collector is 5% to 7.5% of the thickness of the positive electrode sheet.

5. The battery cell according to claim 1, characterized in that The thickness of the negative electrode current collector is 3.5% to 5% of the thickness of the negative electrode plate.

6. The battery cell according to claim 1, characterized in that When the state of charge (SOC) of the battery cell is 0%, the compaction density of the negative electrode film layer on a single side of the negative electrode plate is 1.3-1.52 g / cc.

7. The battery cell according to claim 1, characterized in that The surface density of the negative electrode film layer on a single side of the negative electrode plate is 0.12-0.18 g / 1540.25 mm 2 .

8. The battery cell according to claim 1, wherein: When the state of charge (SOC) of the battery cell is 0%, the compaction density of the positive electrode film layer on a single side of the positive electrode sheet is 2.3-2.6 g / cc.

9. The battery cell according to claim 1, characterized in that The surface density of the single-sided positive electrode film layer of the positive electrode sheet is 0.25~0.33g / 1540.25mm 2 .

10. The battery cell according to claim 1, characterized in that The negative electrode film layer includes a first film layer and a second film layer, wherein the first film layer is disposed on at least one surface of the negative electrode current collector, and the second film layer is disposed on a surface of the first film layer facing away from the current collector; The first film layer contains a first negative electrode active material; the second film layer contains a second negative electrode active material; the longest average particle size of graphite in the second negative electrode active material is smaller than the longest average particle size of graphite in the first negative electrode active material.

11. The battery cell according to claim 10, characterized in that The longest average particle size of the graphite in the first negative electrode active material is 7 to 18 μm.

12. The battery cell according to claim 10 or 11, characterized in that: The graphite in the first negative electrode active material includes at least one of artificial graphite and natural graphite.

13. The battery cell according to claim 10, characterized in that The graphite in the first negative electrode active material includes graphite in a secondary particle morphology.

14. The battery cell according to claim 10, characterized in that The volume distribution particle size Dv50 of the graphite in the first negative electrode active material is 7-15 μm.

15. The battery cell according to claim 10, characterized in that The graphite in the first negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100-500 nm.

16. The battery cell according to claim 10, characterized in that The graphite in the first negative electrode active material has a graphitization degree of 90-94%.

17. The battery cell according to claim 10, characterized in that The first negative electrode active material further includes a silicon material, and the mass proportion of silicon element in the silicon material in the first negative electrode active material is 0.5-10%.

18. The battery cell according to claim 10, characterized in that The longest average particle size of the graphite in the second negative electrode active material is 6 to 10 μm.

19. The battery cell according to claim 10, characterized in that The graphite in the second negative electrode active material includes at least one of artificial graphite and natural graphite.

20. The battery cell according to claim 10, characterized in that The graphite in the second negative electrode active material includes graphite in a secondary particle morphology.

21. The battery cell according to claim 10, characterized in that The volume distribution particle size Dv50 of the graphite in the second negative electrode active material is 7-15 μm.

22. The battery cell according to claim 10, characterized in that The graphite in the second negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100-500 nm.

23. The battery cell according to claim 10, characterized in that The graphite in the second negative electrode active material has a graphitization degree of 90-94%.

24. The battery cell according to claim 10, characterized in that The second negative electrode active material further includes a silicon material, and the mass proportion of silicon element in the silicon material in the second negative electrode active material is 0.5-10%.

25. The battery cell according to claim 10, characterized in that The thickness of the first film layer is 30% to 70% of the total thickness of the negative electrode film layer.

26. The battery cell according to claim 10, characterized in that The thickness of the second film layer is 30% to 70% of the total thickness of the negative electrode film layer.

27. The battery cell according to claim 1, characterized in that The metal element further includes at least one of aluminum and vanadium.

28. The battery cell according to claim 27, characterized in that The metal element includes aluminum, and the mass proportion of the aluminum in the lithium-containing phosphate is 0.02% to 0.25%.

29. The battery cell according to claim 27 or 28, characterized in that: The metal element includes titanium, and the mass proportion of the titanium in the lithium-containing phosphate is 0.15% to 0.35%.

30. The battery cell according to claim 27, wherein: The metal element includes vanadium, and the mass proportion of the vanadium in the lithium-containing phosphate is 0.03% to 0.2%.

31. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes lithium-containing phosphate in the form of primary particles and lithium-containing phosphate in the form of secondary particles.

32. The battery cell according to claim 31, characterized in that The longest average particle size of the lithium-containing phosphate in the primary particle morphology is 300-800 nm.

33. The battery cell according to claim 31 or 32, characterized in that: The longest average particle size of the lithium-containing phosphate in the secondary particle morphology is 8 μm to 15 μm.

34. The battery cell according to claim 31, characterized in that The secondary particles of the lithium-containing phosphate are spherical or quasi-spherical.

35. The battery cell according to claim 1, characterized in that The volume distribution particle size Dv50 of the lithium-containing phosphate is 5-15 μm.

36. The battery cell according to claim 1, characterized in that The electrolyte includes an electrolyte salt and a solvent, the solvent includes a chain carboxylate and a chain carbonate, the chain carboxylate accounts for 8.5% to 40% by mass in the electrolyte, and the chain carbonate accounts for 8.5% to 50% by mass in the electrolyte.

37. The battery cell according to claim 36, characterized in that The mass proportion of the chain carboxylic acid ester in the electrolyte is 10% to 25.5%.

38. The battery cell according to claim 36, characterized in that The mass proportion of the chain carbonate in the electrolyte is 10% to 42.5%.

39. The battery cell according to any one of claims 36 to 38, characterized in that: The chain carboxylic acid ester includes the chain carboxylic acid ester described in Formula I, Formula I Wherein, R1 includes any one of an alkyl group having 1 to 3 carbon atoms and an alkenyl group having 1 to 3 carbon atoms; R2 includes an alkyl group having 1 to 3 carbon atoms.

40. The battery cell according to claim 36, wherein: The chain carboxylic acid ester includes at least one of ethyl acrylate, propyl acetate, and ethyl propionate.

41. The battery cell according to claim 36, characterized in that The chain carbonate includes the chain carbonate described in formula II, Formula II Wherein, R3 and R4 independently include an alkyl group having 1 to 3 carbon atoms.

42. The battery cell according to claim 36, characterized in that The chain carbonate includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

43. The battery cell according to claim 36, characterized in that The solvent also includes cyclic carbonates.

44. The battery cell according to claim 43, characterized in that The cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate.

45. The battery cell according to claim 43 or 44, characterized in that: The mass proportion of the cyclic carbonate in the electrolyte is 10% to 51.5%.

46. ​​The battery cell according to claim 36, characterized in that The electrolyte further includes a first additive, which includes at least one of lithium difluorophosphate and lithium fluorosulfonate.

47. The battery cell according to claim 46, characterized in that The mass proportion of the first additive in the electrolyte is 0.02% to 2%.

48. The battery cell according to claim 36, characterized in that The electrolyte further includes a second additive, which includes at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone.

49. The battery cell according to claim 48, characterized in that The mass proportion of the second additive in the electrolyte is 3% to 7%.

50. The battery cell according to claim 36, wherein: The ionic conductivity of the electrolyte at 25° C. is 11-13 ms / cm.

51. A battery device, characterized in that: Comprising the battery cell according to any one of claims 1 to 50.

52. An electrical device, characterized in that: Comprising a battery device as claimed in claim 51.

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