Battery cell, battery device, and electric device

Abstract

The invention discloses a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly and an electrolyte; wherein the electrode assembly comprises a positive electrode plate and a negative electrode plate, a positive electrode film layer of the positive electrode plate comprises a positive electrode active material, the positive electrode active material comprises lithium-containing phosphate, and the porosity of the positive electrode plate is 20-30%; the thickness of the positive current collector is 5-8% of the thickness of the positive pole piece; a negative electrode film layer of the negative electrode plate comprises a negative electrode active material, the negative electrode active material comprises graphite, and the porosity of the negative electrode plate is 24-33%; and the thickness of the negative current collector is 2.5%-5% of the thickness of the negative pole piece. According to the technical scheme, good fast charging performance, power performance and high energy density of the battery are considered.

Description

[0001] This application claims the priority of the PCT international application "Battery Cell, Battery Device, and Electrical Device" with the application number PCT / CN2025 / 077650, filed on February 17, 2025. The entire content of this application is incorporated into this application by reference. Technical Field

[0002] This application relates to the technical field of batteries, and particularly relates to a battery cell, a battery device, and an electrical device. Background Art

[0003] In recent years, with the increasingly wide application range of batteries, batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

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

[0005] This application is made in view of the above problems, and its purpose is to provide a battery cell, a battery device, and an electrical device, aiming to balance good fast charging performance, good power performance, and high energy density of the battery.

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

[0007] In the battery cell provided by this application, through the cooperation of the positive electrode tab with the above porosity, the negative electrode tab with the above porosity, the positive current collector with the above thickness, and the negative current collector with the above thickness, it can not only shorten the ion transport distance in the electrode material, improve the fast charging performance and power performance of the battery cell, but also reduce the space occupied by non-active materials and improve the energy density of the battery cell.

[0008] In any implementation manner, the porosity of the positive electrode tab is 25% - 30%. Thus, it is beneficial for the battery cell to balance high energy density while having good fast charging performance and power performance.

[0009] In any embodiment, the porosity of the negative electrode plate is 25% to 30%. Thus, it is beneficial for the battery cell to have good fast charging performance and power performance while taking into account a high energy density.

[0010] In any embodiment, the thickness of the positive current collector is 5% to 7.5% of the thickness of the positive electrode plate. Thus, it is beneficial to further reduce the space occupied by the non-active material and improve the energy density of the battery cell.

[0011] In any embodiment, the thickness of the negative current collector is 3.5% to 5% of the thickness of the negative electrode plate. Thus, it is beneficial to further reduce the space occupied by the non-active material and improve the energy density of the battery cell.

[0012] In any embodiment, under the condition that 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 plate is 1.3 to 1.52 g / cc. Thus, a suitable compaction density is beneficial to further adjust the porosity of the negative electrode plate within a suitable range.

[0013] In any embodiment, the areal density of the single-sided negative electrode film layer of the negative electrode plate is 0.12 to 0.18 g / 1540.25 mm 2 . Thus, a suitable areal density is beneficial to further adjust the porosity of the negative electrode plate within a suitable range.

[0014] In any embodiment, 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 plate is 2.3 to 2.6 g / cc. Thus, a suitable compaction density is beneficial to further adjust the porosity of the positive electrode plate within a suitable range.

[0015] In any embodiment, the areal density of the single-sided positive electrode film layer of the positive electrode plate is 0.25 to 0.33 g / 1540.25 mm 2 . Thus, a suitable areal density is beneficial to further adjust the porosity of the positive electrode plate within 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 current collector, and the second film layer is disposed on the surface of the first film layer facing away from the current collector; Among them, the first film layer contains a first negative electrode active material; the second film layer contains a second negative electrode active material; the average longest diameter particle size of graphite in the second negative electrode active material is smaller than that of graphite in the first negative electrode active material. Thus, the average longest diameter particle size of graphite used in the second film layer is relatively smaller, and the ion transport distance of ions in the second film layer is relatively shorter, which is beneficial to further improving the fast charging performance of the battery cell. The average longest diameter particle size of graphite used in the first film layer is relatively larger, and the tap density of the first film layer is relatively higher, which is beneficial to taking into account good energy density.

[0017] In any embodiment, the average longest diameter particle size of graphite in the first negative electrode active material is 7 - 18 μm. Thus, it is beneficial to play the role of the relatively higher tap density of the first film layer.

[0018] In any embodiment, the graphite in the first negative electrode active material includes at least one of artificial graphite and natural graphite.

[0019] In any embodiment, the graphite in the first negative electrode active material includes graphite with a secondary particle morphology.

[0020] In any embodiment, the volume distribution particle size Dv50 of graphite in the first negative electrode active material is 7 - 15 μm.

[0021] 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.

[0022] In any embodiment, the graphitization degree of graphite in the first negative electrode active material is 90 - 94%.

[0023] In any embodiment, the first negative electrode active material further includes a silicon material, and the mass ratio of silicon element in the silicon material in the first negative electrode active material is 0.5 - 10%. The addition of the silicon material is beneficial to further improving the energy density of the battery cell.

[0024] In any embodiment, the average longest diameter particle size of graphite in the second negative electrode active material is 6 - 10 μm. Thus, it is beneficial to play the role of the relatively shorter ion transport distance of ions in the second film layer.

[0025] In any embodiment, the graphite in the second negative electrode active material includes at least one of artificial graphite and natural graphite.

[0026] In any embodiment, the graphite in the second negative electrode active material includes a negative electrode active material with a secondary particle morphology.

[0027] In any embodiment, the volume distribution particle size Dv50 of graphite in the second negative electrode active material is 7 to 15 μm.

[0028] In any embodiment, the graphite in the second negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100 to 500 nm. The carbon coating layer is beneficial to improving the conductivity of graphite.

[0029] In any embodiment, the graphitization degree of graphite in the second negative electrode active material is 90 to 94%.

[0030] In any embodiment, the second negative electrode active material further includes a silicon material, and the mass ratio of silicon element in the silicon material in the second negative electrode active material is 0.5 to 10%. The addition of the silicon material is beneficial to further improving the energy density of the battery cell. In any embodiment, the thickness of the first film layer is 30% to 70% of the total thickness of the negative electrode film layer. Thus, it is beneficial to play the role of the first film layer in taking into account the energy density of the battery cell.

[0031] In any embodiment, the thickness of the second film layer is 30% to 70% of the total thickness of the negative electrode film layer. Thus, it is beneficial to further improve the fast charging performance of the battery cell.

[0032] In any embodiment, the lithium-containing phosphate includes lithium iron phosphate, and the lithium iron phosphate includes metal elements, and the metal elements include at least one of aluminum, titanium, and vanadium. Adding the above metal elements to lithium iron phosphate is beneficial to improving the tap density of the positive electrode active material.

[0033] In any embodiment, the metal element includes aluminum, and the mass ratio of aluminum in the lithium-containing phosphate is 0.02% to 0.25%. Thus, it is beneficial to play the role of aluminum doping in improving the tap density of the positive electrode active material and further improving the cycle performance of the battery cell.

[0034] In any embodiment, the metal element includes titanium, and the mass ratio of titanium in the lithium-containing phosphate is 0.15% to 0.35%. Thus, it is beneficial to play the role of titanium doping in improving the tap density of the positive electrode active material and further increasing the battery capacity.

[0035] In any embodiment, the metal element includes vanadium, and the mass ratio of vanadium in the lithium-containing phosphate is 0.03% to 0.2%. Thus, it is beneficial to play the role of vanadium doping in improving the tap density of the positive electrode active material and further improving the charge and discharge performance of the battery cell.

[0036] In any embodiment, the lithium-containing phosphate includes a lithium-containing phosphate with a primary particle morphology and a lithium-containing phosphate with a secondary particle morphology. The mixed use of primary particles and secondary particles is beneficial to further adjust the tap density of the cathode active material.

[0037] In any embodiment, the average longest diameter of the lithium-containing phosphate with a primary particle morphology is 300 - 800 nm. Thereby, it is beneficial to shorten the ion transport distance and further improve the fast charging performance.

[0038] In any embodiment, the average longest diameter of the lithium-containing phosphate with a secondary particle morphology is 8 μm - 15 μm. The secondary particles are usually composed of a combination of lithium-containing phosphates with smaller primary particles, which is beneficial to shorten the ion transport distance.

[0039] In any embodiment, the lithium-containing phosphate with a secondary particle morphology is spherical or quasi-spherical.

[0040] In any embodiment, the volume distribution particle size Dv50 of the lithium-containing phosphate is 5 - 15 μm.

[0041] In any embodiment, the electrolyte includes an electrolyte salt and a solvent. The solvent includes a chain carboxylic ester and a chain carbonate. The mass ratio of the chain carboxylic ester in the electrolyte is 8.5% - 40%, and the mass ratio of the chain carbonate in the electrolyte is 8.5% - 50%. Adding a certain amount of chain carbonate to the chain carboxylic ester solvent can reduce the amount of the chain carboxylic ester solvent in the electrolyte, reduce the side reaction degree of the chain carboxylic ester solvent, and improve the battery cycle performance while ensuring the fast charging performance.

[0042] In any embodiment, the mass ratio of the chain carboxylic ester in the electrolyte is 10% - 25.5%. Thereby, it is beneficial to further optimize the fast charging performance and cycle performance of the battery cell.

[0043] In any embodiment, the mass ratio of the chain carbonate in the electrolyte is 10% - 42.5%. Thereby, it is beneficial to further optimize the fast charging performance and cycle performance of the battery cell.

[0044] In any embodiment, the chain carboxylic ester includes the chain carboxylic ester represented by Formula I,

[0045] Formula I wherein, R 1 includes any one of an alkyl group with 1 - 3 carbon atoms and an alkenyl group with 2 - 4 carbon atoms; R 1 includes an alkyl group with 1 - 3 carbon atoms. The chain carboxylic ester with the above structure has a suitable viscosity, which is beneficial to reduce the ion transport resistance in the electrolyte.

[0046] In any embodiment, the chain carboxylic acid ester includes at least one of ethyl acrylate, propyl acetate, and ethyl propionate. Thus, it is beneficial to further reduce the ion transport resistance in the electrolyte.

[0047] In any embodiment, the chain carbonate includes the chain carbonate represented by Formula II,

[0048] Formula II wherein R 3 and R 4 independently include an alkyl group having 1 to 3 carbon atoms. The addition of the chain carbonate is beneficial to reduce the generation of gas during the cycling of the battery monomer, thereby improving the cycling performance.

[0049] In any embodiment, the chain carbonate includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The above-mentioned chain carbonate has a suitable viscosity, which is beneficial to reducing the ion transport resistance in the electrolyte and reducing the generation of gas during the cycling of the battery monomer, thereby improving the cycling performance.

[0050] In any embodiment, the solvent further includes a cyclic carbonate. The addition of the cyclic carbonate is beneficial to reducing the solvation effect of the electrolyte, reducing the binding ability between the solvent and the ions, and making it easier for the ions to dissociate from the solvent, thereby further improving the fast charging performance.

[0051] In any embodiment, the cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate. The above-mentioned suitable cyclic carbonate is beneficial to exert its function of reducing the solvation effect of the electrolyte.

[0052] In any embodiment, the mass percentage of the cyclic carbonate in the electrolyte is 10% - 51.5%. Thus, it is beneficial to further optimize the fast charging performance of the battery monomer.

[0053] In any embodiment, the electrolyte further includes a first additive, and the first additive includes at least one of lithium difluorophosphate and lithium fluorosulfonate. The addition of the first additive is beneficial to improving the SEI film, enhancing the ionic conductivity of the electrolyte, and further improving the fast charging performance and cycling performance of the battery monomer.

[0054] In any embodiment, the mass percentage of the first additive in the electrolyte is 0.02% - 2%. Thus, it is beneficial to exert the function of the first additive to improve the SEI film and enhance the ionic conductivity of the electrolyte.

[0055] In any embodiment, the electrolyte further includes a second additive, which includes at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3 - propanesultone. The addition of the second additive is beneficial to improving the SEI film and further improving the cycling performance of the battery cell.

[0056] In any embodiment, the mass ratio of the second additive in the electrolyte is 3% - 7%. Thus, it is beneficial to exert the role of the second additive in improving the SEI film.

[0057] In any embodiment, the ionic conductivity of the electrolyte at 25 °C is 11 - 13 mS / cm. Thus, the appropriate ionic conductivity is beneficial to the rapid migration of ions between the electrodes.

[0058] In a second aspect, the present application provides a battery device, including the battery cell of the first aspect of the present application.

[0059] In a third aspect, the present application provides an electrical device, including the battery device of the second aspect of the present application. Description of the Drawings

[0060] Figure 1 is a schematic diagram of a battery cell according to an embodiment of the present application; Figure 2 is Figure 1 the exploded view of the battery cell according to an embodiment of the present application shown in; Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application; Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application; Figure 5 is Figure 4 the exploded view of the battery pack according to an embodiment of the present application shown in; Figure 6 is a schematic diagram of an electrical device using the battery cell according to an embodiment of the present application as a power source.

[0061] Description of the Reference Numerals: 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Embodiments

[0062] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0063] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0064] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0065] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0066] If there is no special instruction, all steps of the present application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0067] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application are open-ended, and can also be closed-ended. For example, the terms "comprising" and "including" can mean that other components not listed may also be included or comprised, or only the listed components may be included or comprised.

[0068] The battery mentioned in the embodiments of this application can be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, battery packs, etc.

[0069] A battery cell is the smallest unit that makes up a battery and can independently perform the functions of charging and discharging. When there are multiple battery cells, the multiple battery cells are connected in series, parallel or in a hybrid connection through a busbar component. This application places no particular limitation on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 1 is a battery cell 5 with a square structure as an example.

[0070] In some embodiments, the battery can 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 can be a battery pack, which includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body. In some embodiments, the box body can be part of the chassis structure of a vehicle. For example, part of the box body can become at least part of the vehicle floor, or part of the box body can become at least part of the cross beams and longitudinal beams of the vehicle. In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc. In some embodiments, battery cells can be assembled into a battery module, and the number of battery cells included in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.

[0071] Figure 3 is a battery module 4 as an example. Refer to Figure 3 , in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the multiple battery cells 5 can be fixed by fasteners.

[0072] Optionally, the battery module 4 can further include a housing with an accommodation space, and the multiple battery cells 5 are accommodated in the accommodation space.

[0073] In some embodiments, the above battery cells and battery modules can also be assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0074] Figure 4 and Figure 5 is Battery Pack 1 as an example. Refer to Figure 4 and Figure 5 , in Battery Pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box can be included. 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 a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0075] The battery provided by the embodiments of the present application can include a lithium-ion battery.

[0076] The battery cell includes an electrode assembly and an electrolyte.

[0077] The electrode assembly includes a positive electrode tab and a negative electrode tab. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode tab and the negative electrode tab.

[0078] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0079] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be enumerated.

[0080] In some embodiments, refer to Figure 2 , the outer package can include a housing 51 and a cover plate 53. Among them, the housing 51 can include a bottom plate and side plates connected to the bottom plate. The bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can cover the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator can be formed into an electrode assembly 52 through a winding process or a stacking 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 included in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0081] An embodiment of the present application provides a battery cell, which includes an electrode assembly and an electrolyte; wherein, the electrode assembly includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive active material, and the positive active material includes a lithium-containing phosphate. The porosity of the positive electrode plate is 20% to 30%; the thickness of the positive current collector is 5% to 8% of the thickness of the positive electrode plate; the negative electrode plate includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a negative active material, and the negative active material includes graphite. The porosity of the negative electrode plate is 24% to 33%; the thickness of the negative current collector is 2.5% to 5% of the thickness of the negative electrode plate.

[0082] In this article, the porosity of the positive electrode plate and the porosity of the negative electrode plate can be tested by methods known in the art. For example, it is tested based on the national standard GB / T24586-2009. The electrode plate is immersed in ethylene methyl carbonate (EMC) for cleaning; the true density meter (AccuPycII1340 of Micromeritics, USA) is used as a test instrument to measure based on the gas displacement method. Among them, the percentage of the pore volume in the electrode plate accounting for the total volume of the electrode plate is the porosity of the electrode plate. The calculation formula is: porosity = (V - V0) / V × 100%, where V0 is the true volume of the electrode plate and V is the apparent volume of the electrode plate.

[0083] The positive current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive current collector. Similarly, the negative current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative current collector.

[0084] In this article, when the positive electrode film layer is disposed on both side surfaces of the positive current collector at the same time, the thickness of the positive electrode plate refers to the sum of the thickness of the positive current collector and the thicknesses of the two positive electrode film layers disposed on its two side surfaces. Similarly, when the negative electrode film layer is disposed on both side surfaces of the negative current collector at the same time, the thickness of the negative electrode plate refers to the sum of the thickness of the negative current collector and the thicknesses of the two negative electrode film layers disposed on its two side surfaces.

[0085] In the battery cell provided by the present application, through the cooperation of the positive electrode plate with the above porosity, the negative electrode plate with the above porosity, the positive current collector with the above thickness, and the negative current collector with the above thickness, the transmission distance of ions in the electrode material can be shortened, the fast charging performance and power performance of the battery cell can be improved, and the space occupied by the non-active material can be reduced, thereby improving the energy density of the battery cell.

[0086] Optionally, the porosity of the positive electrode sheet can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or any numerical range composed of any two of these values. The porosity of the negative electrode sheet can be 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or any numerical range composed of any two of these values.

[0087] Optionally, the thickness of the positive current collector can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8% of the thickness of the positive electrode sheet or any numerical range composed of any two of these values. The thickness of the negative current collector can be 2.5%, 3%, 3.5%, 4%, 4.5%, 5% of the thickness of the negative electrode sheet or any numerical range composed of any two of these values.

[0088] In any embodiment, the porosity of the positive electrode sheet is 25% - 30%. Thus, it is beneficial for the battery cell to have good fast charging performance and power performance while taking into account high energy density.

[0089] In any embodiment, the porosity of the negative electrode sheet is 25% - 30%. Thus, it is beneficial for the battery cell to have good fast charging performance and power performance while taking into account high energy density.

[0090] In any embodiment, the thickness of the positive current collector is 5% - 7.5% of the thickness of the positive electrode sheet. Thus, it is beneficial to further reduce the space occupied by the inactive material and improve the energy density of the battery cell.

[0091] In any embodiment, the thickness of the negative current collector is 3.5% - 5% of the thickness of the negative electrode sheet. Thus, it is beneficial to further reduce the space occupied by the inactive material and improve the energy density of the battery cell.

[0092] In some embodiments, under the condition that the state of charge (SOC) of the battery cell is 0%, the tap density of the single-sided negative electrode film layer of the negative electrode sheet is 1.3 to 1.52 g / cc. Thus, a suitable tap density is beneficial to further adjust the porosity of the negative electrode sheet within a suitable range. Under the condition that the state of charge (SOC) of the battery cell is 0%, the tap density of the single-sided negative electrode film layer of the negative electrode sheet can be 1.3 g / cc, 1.31 g / cc, 1.32 g / cc, 1.33 g / cc, 1.34 g / cc, 1.35 g / cc, 1.36 g / cc, 1.37 g / cc, 1.38 g / cc, 1.39 g / cc, 1.4 g / cc, 1.41 g / cc, 1.42 g / cc, 1.43 g / cc, 1.44 g / cc, 1.45 g / cc, 1.46 g / cc, 1.47 g / cc, 1.48 g / cc, 1.49 g / cc, 1.5 g / cc, 1.51 g / cc, 1.52 g / cc or any numerical range composed of any two of the above values.

[0093] In the present application, the tap density of the electrode sheet has the meaning well-known in the art and can be measured by methods known in the art. Under the condition that the state of charge (SOC) of the battery cell is 0%, the electrode sheet is removed from the lithium-ion battery, and a certain area of the electrode sheet is taken. The mass and thickness of the electrode sheet and the current collector after removing the film layer are measured respectively. According to the following formula, the tap density of the electrode sheet is calculated. Tap density of the electrode sheet = (mass of the electrode sheet - mass of the current collector) / [(thickness of the electrode sheet - thickness of the current collector) × area of the electrode sheet].

[0094] In some embodiments, the areal density of the single-sided negative electrode film layer of the negative electrode sheet is 0.12 to 0.18 g / 1540.25 mm 2 . Thus, a suitable areal density is beneficial to further adjust the porosity of the negative electrode sheet within a suitable range. The areal density of the single-sided negative electrode film layer of the negative electrode sheet can be 0.12 g / 1540.25 mm 2 , 0.13 g / 1540.25 mm 2 , 0.14 g / 1540.25 mm 2 , 0.15 g / 1540.25 mm 2 , 0.16 g / 1540.25 mm 2 , 0.17 g / 1540.25 mm 2 , 0.18 g / 1540.25 mm 2 or any numerical range composed of any two of the above values.

[0095] In this application, the areal density of the film layer has the meaning well-known in the art and can be measured by methods known in the art. For example, take a single-sided coated and cold-pressed electrode sheet (if it is a double-sided coated electrode sheet, the film layer on one side can be wiped off), punch it into small round pieces with an area of S1, weigh it, and record it as M1. Then wipe off the film layer of the above-mentioned weighed electrode sheet and weigh the weight of the current collector, and record it as M0. The areal density of the single-sided film layer = (M1 - M0) / S1. To ensure the accuracy of the test results, multiple groups (for example, 10 groups) of samples to be tested can be tested, and the average value can be calculated as the test result.

[0096] In some embodiments, under the condition that the state of charge (SOC) of the battery cell is 0%, the tap density of the single-sided positive electrode film layer of the positive electrode sheet is 2.3 - 2.6 g / cc. Thus, a suitable tap density is beneficial to further adjust 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 tap density of the single-sided positive electrode film layer of the positive electrode sheet can be 2.3 g / cc, 2.31 g / cc, 2.32 g / cc, 2.33 g / cc, 2.34 g / cc, 2.35 g / cc, 2.36 g / cc, 2.37 g / cc, 2.38 g / cc, 2.39 g / cc, 2.4 g / cc, 2.41 g / cc, 2.42 g / cc, 2.43 g / cc, 2.44 g / cc, 2.45 g / cc, 2.46 g / cc, 2.47 g / cc, 2.48 g / cc, 2.49 g / cc, 2.5 g / cc, 2.51 g / cc, 2.52 g / cc, 2.53 g / cc, 2.54 g / cc, 2.55 g / cc, 2.56 g / cc, 2.57 g / cc, 2.58 g / cc, 2.59 g / cc, 2.6 g / cc or any numerical range composed of any two of the above values.

[0097] In some embodiments, the areal density of the single-sided positive electrode film layer of the positive electrode sheet is 0.25 - 0.33 g / 1540.25 mm 2 . Thus, a suitable areal density is beneficial to further adjust the porosity of the positive electrode sheet within a suitable range. The areal density of the single-sided positive electrode film layer of the positive electrode sheet can be 0.25 g / 1540.25 mm 2 , 0.26 g / 1540.25 mm 2 , 0.27 g / 1540.25 mm 2 , 0.28 g / 1540.25 mm 2 , 0.29 g / 1540.25 mm 2 , 0.3 g / 1540.25 mm 2 , 0.31 g / 1540.25 mm 2, 0.32 g / 1540.25 mm 2 , 0.33 g / 1540.25 mm 2 Or a numerical range composed of any two of the above values.

[0098] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0099] In some embodiments, the positive electrode film layer may optionally further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride - tetrafluoroethylene - propylene terpolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene terpolymer, tetrafluoroethylene - hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0100] In some embodiments, the positive electrode film layer may optionally further include a conductive agent. As an 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.

[0101] In some embodiments, the positive electrode plate can be prepared in the following manner: Disperse the components for preparing the positive electrode plate described above, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (such as N - methylpyrrolidone) to form a positive electrode slurry; coat the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0102] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0103] In some embodiments, the negative electrode film layer may further optionally 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).

[0104] In some embodiments, the negative electrode film layer may further optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0105] In some embodiments, the negative electrode film layer may further optionally include other additives, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0106] In some embodiments, the negative electrode plate can be prepared in the following manner: dispersing the components for preparing the negative electrode plate described above, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0107] 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 the surface of the first film layer facing away from the current collector; wherein, the first film layer contains a first negative electrode active material; the second film layer contains a second negative electrode active material; the average longest diameter of graphite in the second negative electrode active material is smaller than the average longest diameter of graphite in the first negative electrode active material.

[0108] As used herein, the "average longest diameter" means that the electrode plate is ion-polished and cut along the thickness direction of the electrode plate 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 scenario, more than 50 particles are randomly selected, and the length of the longest straight line passing through the center point of each particle and extending to the outer periphery of the particle is measured. Then, the average value of the longest straight line lengths of these particles is taken.

[0109] The average longest diameter of graphite used in the second film layer is relatively smaller, and the ion transport distance in the second film layer is relatively shorter, which is beneficial to further improving the fast charging performance of the battery cell. While the average 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 beneficial to taking into account good energy density.

[0110] In some embodiments, the average longest diameter particle size of graphite in the first negative electrode active material is 7 to 18 μm. Thus, it is beneficial to exert the effect that the compaction density of the first film layer is relatively higher. The average longest diameter particle size of 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 numerical range composed of any two of the above values.

[0111] In some embodiments, the graphite in the first negative electrode active material includes at least one of artificial graphite and natural graphite.

[0112] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by a scanning electron microscope (SEM). There are voids between flake structures in the SEM cross-sectional view of natural graphite, and the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or can be distinguished by the XRD spectrum obtained by the X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and only the 2H phase exists in the XRD spectrum of artificial graphite.

[0113] In some embodiments, the graphite in the first negative electrode active material includes graphite with a secondary particle morphology.

[0114] In this application, a particle with a primary particle morphology refers to a primary particle. A primary particle is the smallest unit of a particle within a certain observation range. There may be any form of defects inside the primary particle, but it is impossible to define smaller particles within the primary particle. Primary particles may aggregate under physical actions such as van der Waals forces, but this aggregation is easily depolymerized under external forces such as ultrasonic waves, stirring, and rolling, so that the main composition form of the active material in the film layer is still primary particles.

[0115] In this application, a particle with a secondary particle morphology refers to a secondary particle. A secondary particle is formed by the aggregation of primary particles and is not easily dispersed under external forces such as ultrasonic waves. However, after cutting the cross-section of the secondary particle, it can be seen that the secondary particle is formed by the aggregation of numerous primary particles.

[0116] In some embodiments, the volume distribution particle size Dv50 of graphite in the first negative electrode active material is 7 to 15 μm. The volume distribution particle size Dv50 of 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 composed of any two of the above values.

[0117] In this application, the volume-based particle size Dv50 of the material represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and it can be measured by instruments and methods known in the art. For example, it can be conveniently measured with reference to GB / T 19077-2016 Laser Diffraction Method for Particle Size Distribution using a laser particle size analyzer. The test instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Limited, UK.

[0118] In some embodiments, 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 electrical 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 any numerical range composed of any two of the above values.

[0119] The thickness of the coating layer can be characterized by transmission electron microscopy (TEM) testing. Observe the negative electrode active material through transmission electron microscopy. According to the difference in lattice fringes, the coating layer coated on the surface of the negative electrode active material can be clearly observed. Randomly select 5 positions in the coating layer for testing, and calculate the average value as the average thickness of the coating layer.

[0120] In some embodiments, the graphitization degree of the graphite in the first negative electrode active material is 90 - 94%. A high graphitization degree of the material indicates a small graphite layer spacing, less lattice rotation, less disordered stacking of the layers, more ordered arrangement, a high specific capacity of the material, and is beneficial to obtaining a battery cell with a high energy density. The graphitization degree of the first negative electrode active material can be 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94% or any numerical range composed of any two of the above values.

[0121] In this article, the term "graphitization degree" macroscopically characterizes what proportion of the material reaches a complete graphite crystal structure; microscopically, it refers to the degree to which different transitional carbon structures approach an ideal graphite crystal.

[0122] In the present application, the graphitization degree of graphite can be tested by instruments and methods known in the art. For example, it can be tested using an X-ray diffractometer (such as Bruker D8 Discover), and the test can refer to JISK 0131-1996 and JB / T4220-2011 to obtain the average layer spacing d002 of the C(002) crystal plane in the crystal structure of the material, and then the graphitization degree can be calculated according to the formula g = (0.344 - d002) / (0.344 - 0.3354)×100%. In the above formula, d002 is the average layer spacing of the C(002) crystal plane in the crystal structure of the material expressed in nanometers (nm).

[0123] In some embodiments, the first negative electrode active material further includes a silicon material, and the mass ratio of silicon element in the silicon material in the first negative electrode active material is 0.5 to 10%. The addition of the silicon material is beneficial to further improve the energy density of the battery cell. The mass ratio of silicon element 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 any numerical range composed of any two of the above values.

[0124] In the present application, the content of silicon element can be tested by instruments and methods known in the art. For example, the negative electrode active material can be placed in an appropriate digestion solvent, concentrated nitric acid solvent, and digested by the flat plate digestion method. Finally, the extraction solvent is dissolved with hydrochloric acid, and then the obtained solution is fixed to an appropriate volume and quantitatively tested using an inductively coupled plasma optical emission spectrometer ICP-OES.

[0125] In some embodiments, the average longest diameter particle size of graphite in the second negative electrode active material is 6 to 10 μm. Thus, it is beneficial to play the role that the ion transport distance in the second film layer is relatively shorter. The average longest diameter particle size of graphite in the second negative electrode active material can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any numerical range composed of any two of the above values.

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

[0127] In some embodiments, the graphite in the second negative electrode active material includes graphite with a secondary particle morphology.

[0128] In some embodiments, the volume-based particle size Dv50 of graphite in the second negative electrode active material is 7 to 15 μm. The volume-based particle size Dv50 of 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 composed of any two of the above values.

[0129] In some embodiments, the graphite in the second negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100 to 500 nm. The carbon coating layer is beneficial to improving the electrical conductivity of 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 numerical range composed of any two of the above values.

[0130] In some embodiments, the graphitization degree of graphite in the second negative electrode active material is 90 to 94%. A high graphitization degree of the material indicates a small graphite layer spacing, less lattice rotation, less disordered stacking of the layers, orderly arrangement, a high specific capacity of the material, and is beneficial to obtaining a battery cell with a high energy density. The graphitization degree of graphite in the second negative electrode active material can be 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, or a numerical range composed of any two of the above values.

[0131] In some embodiments, the second negative electrode active material further includes a silicon material, and the mass ratio of silicon element in the silicon material in the second negative electrode active material is 0.5 to 10%. The addition of the silicon material is beneficial to further improving the energy density of the battery cell. The mass ratio of silicon element 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 composed of any two of the above values.

[0132] In some embodiments, the thickness of the first film layer is 30% to 70% of the total thickness of the negative electrode film layer. Thus, it is beneficial to play the role of the first film layer in taking into account 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 numerical range composed of any two of the above values.

[0133] In some embodiments, the thickness of the second film layer is 30% to 70% of the total thickness of the negative electrode film layer. Thus, it is beneficial to 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% or any numerical range composed of any two of the above values of the total thickness of the negative electrode film layer.

[0134] The thicknesses of the first film layer and the second film layer can be characterized by transmission electron microscopy (SEM) tests. The cross-section of the negative electrode sheet is observed by scanning electron microscopy, and the thicknesses of the first film layer and the second film layer are observed based on the difference in the average maximum particle diameter of the active materials in the first film layer and the second film layer. For example, after observing 5 times, the average value is taken.

[0135] In some embodiments, the lithium-containing phosphate includes lithium iron phosphate, and the lithium iron phosphate includes metal elements, and the metal elements include at least one of aluminum, titanium, and vanadium. Adding the above metal elements to lithium iron phosphate is beneficial to improving the tap density of the positive electrode active material.

[0136] In this application, the contents of aluminum, titanium, and vanadium in the lithium-containing phosphate can be tested by instruments and methods known in the art. For example, the lithium-containing phosphate can be placed in a proper digestion solvent, concentrated nitric acid solvent, and digested by the plate digestion method. Finally, it is dissolved with hydrochloric acid to extract the solvent, and then the obtained solution is fixed to an appropriate volume and quantitatively tested by an inductively coupled plasma optical emission spectrometer ICP-OES.

[0137] In some embodiments, the metal element includes aluminum, and the mass ratio of aluminum in the lithium-containing phosphate is 0.02% to 0.25%. Thus, it is beneficial to play the role of aluminum doping in improving the tap density of the positive electrode active material and further improving the cycle performance of the battery cell. The mass ratio 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 any numerical range composed of any two of the above values.

[0138] In some embodiments, the metal element includes titanium, and the mass percentage of titanium in the lithium-containing phosphate is 0.15% to 0.35%. Thus, it is beneficial to play the role of titanium doping in improving the tap density of the cathode active material and further improving the battery capacity. The mass percentage 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 composed of any two of the above values.

[0139] In some embodiments, the metal element includes vanadium, and the mass percentage of vanadium in the lithium-containing phosphate is 0.03% to 0.2%. Thus, it is beneficial to play the role of vanadium doping in improving the tap density of the cathode active material and further improving the charge and discharge performance of the battery cell. The mass percentage 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 composed of any two of the above values.

[0140] In some embodiments, the lithium-containing phosphate includes lithium-containing phosphate with a primary particle morphology and lithium-containing phosphate with a secondary particle morphology. The mixed use of primary particles and secondary particles is beneficial to further adjust the tap density of the cathode active material.

[0141] In some embodiments, the average longest diameter of the lithium-containing phosphate with a primary particle morphology is 300 to 800 nm. Thus, it is beneficial to shorten the ion transport distance and further improve the fast charging performance. The average longest diameter of the lithium-containing phosphate with a primary particle morphology 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 composed of any two of the above values.

[0142] In some embodiments, the average longest diameter of the lithium-containing phosphate in the secondary particle morphology is 8 μm to 15 μm. The secondary particles are usually composed of lithium-containing phosphates of primary particles with smaller particle sizes, which is beneficial to shortening the ion transport distance. The average longest diameter of the lithium-containing phosphate in the secondary particle morphology can be 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, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm or any numerical range composed of any two of the above values.

[0143] In some embodiments, the lithium-containing phosphate in the secondary particle morphology is 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.

[0144] 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 any numerical range composed of any two of the above values.

[0145] In any embodiment, the electrolyte includes an electrolyte salt and a solvent. The solvent includes a chain carboxylic ester and a chain carbonate. The mass percentage of the chain carboxylic ester in the electrolyte is 8.5% to 40%, and the mass percentage of the chain carbonate in the electrolyte is 8.5% to 50%. Adding a certain amount of chain carbonate to the chain carboxylic ester solvent can reduce the amount of the chain carboxylic ester solvent used in the electrolyte, reduce the side reaction degree of the chain carboxylic ester solvent, and improve the battery cycle performance while ensuring the fast charging performance.

[0146] In this text, the types and mass contents of each component in the electrolyte can be obtained by detecting the electrolyte through any method known to those skilled in the art. As an example, 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) can be used to characterize the components and contents of the electrolyte. Exemplarily, referring to GB / T-9722-2006 / GB / T6041-2002, gas chromatography and mass spectrometry are used in combination. After the gas chromatography separates the components in the sample, each component is broken into ion fragments in the mass spectrometry and separated according to the mass-to-charge ratio (m / z) to form a specific mass spectrum, obtaining the qualitative analysis of each organic component in the electrolyte. Then, each organic component in the electrolyte is separated in the chromatographic column to generate a detection signal spectrum of each component, and the components are qualitatively analyzed using the retention time, and the peak area is calibrated with a standard to achieve quantification, obtaining the quantitative test analysis of the organic components in the electrolyte. Referring to JY / T0578-2020, nuclear magnetic resonance spectroscopy (NMR) is used to obtain the qualitative and quantitative analysis of the components in the electrolyte.

[0147] The electrolyte referred to in this text can be either a fresh electrolyte or an electrolyte obtained by disassembling a battery cell. The electrolyte obtained by disassembling a battery cell can be either the electrolyte free in the battery case or the electrolyte centrifuged from the electrode sheets.

[0148] Optionally, the mass percentage 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 any numerical range composed of any two of the above values. Optionally, the mass percentage of the chain 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 any numerical range composed of any two of the above values.

[0149] The addition of chain carboxylic acid esters as solvents in the electrolyte not only helps to improve the lithium-ion conductivity of the electrolyte, but also can reduce the viscosity of the electrolyte, increase the transport rate of lithium ions at the solid-liquid interface of the battery monomer, and improve the fast charging performance of the battery. However, chain carboxylic acid esters as solvents have high reactivity and are prone to decomposition during the battery cycling process, resulting in gas generation in the battery. Adding a certain amount of chain carbonates to the chain carboxylic acid esters as solvents can reduce the amount of chain carboxylic acid esters as solvents in the electrolyte, reduce the degree of side reactions of the chain carboxylic acid esters as solvents, and improve the battery cycling performance. In some embodiments, the electrolyte salt can be selected from the group consisting of sodium salts including sodium hexafluorophosphate (NaPF6), sodium difluorooxalate borate (NaDFOB), sodium tetrafluoroborate (NaBF4), sodium bis(oxalato)borate (NaBOB), sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide (NaFSI), sodium trifluoromethanesulfonate, and sodium bis(trifluoromethylsulfonyl)imide (NaTFSI).

[0150] In some embodiments, the battery monomer further includes a separator, and the material of the separator base film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator base film can 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 each layer can be the same or different, without particular limitation.

[0151] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0152] In some embodiments, the mass percentage of the chain carboxylic acid ester in the electrolyte is 10% - 25.5%. Thus, it is beneficial to further optimize the fast charging performance and cycling performance of the battery monomer.

[0153] In some embodiments, the mass percentage of the chain carbonate in the electrolyte is 10% - 42.5%. Thus, it is beneficial to further optimize the fast charging performance and cycling performance of the battery monomer.

[0154] In some embodiments, the chain carboxylic acid ester includes the chain carboxylic acid ester represented by Formula I

[0155] Formula I wherein, R 1 includes any one of an alkyl group having 1 - 3 carbon atoms and an alkenyl group having 2 - 4 carbon atoms; R 1 includes an alkyl group having 1 - 3 carbon atoms. The chain carboxylic acid ester having the above structure has a suitable viscosity, which is beneficial to reducing the transport resistance of ions in the electrolyte.

[0156] As used herein, "alkyl group having 1 to 3 carbon atoms" refers to a straight-chain or branched-chain hydrocarbon group consisting only of carbon and hydrogen atoms, without unsaturation in the group, having 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), 2-propyl (-CH(CH3)2).

[0157] As used herein, "alkenyl group having 2 to 4 carbon atoms" is a straight-chain or branched-chain hydrocarbon group having 2 to 4 carbon atoms and at least one carbon-carbon double bond. Examples include, but are not limited to: vinyl, 1-propenyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl.

[0158] In some embodiments, the chain carboxylic acid ester includes at least one of ethyl acrylate, propyl acetate, and ethyl propionate. Thus, it is beneficial to further reduce the ion transport resistance in the electrolyte.

[0159] In some embodiments, the chain carbonate includes the chain carbonate represented by Formula II,

[0160] Formula II wherein R 3 and R 4 independently include alkyl groups having 1 to 3 carbon atoms. The addition of the chain carbonate is beneficial to reducing the generation of gas in the battery monomer during cycling, thereby improving the cycling performance.

[0161] In some embodiments, the chain carbonate includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The above chain carbonates have appropriate viscosities, which are beneficial to reducing the ion transport resistance in the electrolyte and reducing the generation of gas in the battery monomer during cycling, thereby improving the cycling performance.

[0162] In some embodiments, the solvent further includes a cyclic carbonate. The addition of the cyclic carbonate is beneficial to reducing the solvation effect of the electrolyte, reducing the binding ability between the solvent and the ions, and making it easier for the ions to dissociate from the solvent, thereby further improving the fast charging performance.

[0163] In some embodiments, the cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate. The above appropriate cyclic carbonates are beneficial to exerting their function of reducing the solvation effect of the electrolyte.

[0164] In some embodiments, the mass percentage of the cyclic carbonate in the electrolyte is 10% to 51.5%. Thus, it is beneficial to further optimize the fast charging performance of the battery cell. The mass percentage of the 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 any numerical range composed of any two of the above values.

[0165] In some embodiments, the electrolyte further includes a first additive, and the first additive includes at least one of lithium difluorophosphate and lithium fluorosulfonate. The addition of the first additive is beneficial to improving the SEI film, enhancing the ionic conductivity of the electrolyte, and further improving the fast charging performance and cycle performance of the battery cell.

[0166] In some embodiments, the mass percentage of the first additive in the electrolyte is 0.02% to 2%. Thus, it is beneficial to exert the function of the first additive in improving the SEI film and enhancing the ionic conductivity of the electrolyte. The mass percentage 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 any numerical range composed of any two of the above values.

[0167] In some embodiments, the electrolyte further includes a second additive, and the second additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3 - propanesultone. The addition of the second additive is beneficial to improving the SEI film and further improving the cycle performance of the battery cell.

[0168] In some embodiments, the mass percentage of the second additive in the electrolyte is 3% to 7%. Thus, it is beneficial to exert the effect of the second additive in improving the SEI film. The mass percentage of the second additive in the electrolyte can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7% or any numerical range composed of any two of the above values.

[0169] In some embodiments, the ionic conductivity of the electrolyte at 25 °C is 11 to 13 mS / cm. Thus, the appropriate ionic conductivity is beneficial for the rapid migration of ions 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 any numerical range composed of any two of the above values.

[0170] In the present application, the ionic conductivity of the electrolyte describes the ability of the ions dissociated from the electrolyte to move directionally in an electric field to form a conductive process, and can be tested by any well-known method in the art. As an example, disassemble the battery cell, take about 100 mL of electrolyte sample with a dry, clean and corrosion-resistant sample bottle, seal it and place it in a constant temperature water bath, shake the sample from time to time, and keep the temperature constant at 25 °C (deviation ±0.5 °C). After the temperature of the sample is constant, use a commercially available conductivity meter to test its conductivity. After wiping the conductivity meter clean with the calibration solution, vertically place it into the liquid to be tested, click to start the test, and record the test result after the data is stable for more than 10 s.

[0171] The embodiment of the present application further provides a battery device, including the battery cell provided by the present application.

[0172] As the electrical device, the battery cell, battery module or battery pack can be selected according to its usage requirements.

[0173] Figure 6 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery cell, a battery pack or a battery module can be used.

[0174] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinning, and a battery cell can be used as the power source.

[0175] The embodiment of the present application further provides an electrical device, including the battery device provided by the present application.

[0176] Embodiment The embodiments of the present application will be described below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those specific technologies or conditions not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchases.

[0177] Example 1 1. Preparation of the positive electrode sheet The positive electrode sheet includes a positive current collector and a positive electrode film layer. The positive electrode film layer is disposed on both sides of the positive current collector, and the positive current collector is aluminum foil.

[0178] The positive electrode film layer is formed by uniformly coating a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on the surface of the positive current collector, followed by drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black with a weight ratio of 90:5:5.

[0179] 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 ratio of Al, V, and Ti in the lithium iron phosphate particles is 0.15% each.

[0180] The lithium iron phosphate particles include primary particles and secondary particles formed by the aggregation of primary particles. The secondary particles are spherical and quasi-spherical. The average longest diameter of the primary particles is 600 nm, and the average longest diameter of the secondary particles is 10 μm. The volume distribution particle size Dv50 of the lithium iron phosphate particles is 7 μm.

[0181] The areal density of the single-sided positive electrode film layer is 0.28 g / 1540.25 mm 2 .

[0182] Under the condition that the state of charge SOC of the battery cell is 0%, the tap density of the single-sided positive electrode film layer of the positive electrode sheet is 2.4 g / cc.

[0183] The porosity of the positive electrode sheet is 25%. The thickness of the positive current collector is 6% of the thickness of the positive electrode sheet.

[0184] 2. Preparation of the negative electrode sheet The negative electrode sheet includes a negative current collector and a negative electrode film layer. The negative electrode film layer is disposed on both sides of the negative current collector, and the negative current collector is copper foil.

[0185] The negative electrode film layer includes a first film layer and a second film layer formed by uniformly coating a negative electrode slurry (the solvent is deionized water) on the surface of the negative current collector, followed by drying and cold pressing.

[0186] The first film layer is disposed on the surface of the negative electrode current collector, and it includes a first negative electrode active material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickening agent with a mass ratio of 96.5:0.5:2:1. The negative electrode active material includes graphite and silicon oxide. The mass proportion of silicon element in the first negative electrode active material is 5%. The graphite includes artificial graphite and a carbon coating layer. The carbon coating layer covers the surface of the artificial graphite. The thickness of the carbon coating layer is 200 nm, and the graphitization degree of the graphite is 92%. The average longest diameter particle size of the graphite is 12 μm.

[0187] The second film layer is disposed on the surface of the negative electrode current collector, and it includes a negative electrode active material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickening agent with a mass ratio of 96.5:0.5:2:1. The negative electrode active material includes graphite and silicon oxide. The mass proportion of silicon element in the first negative electrode active material is 5%. The graphite includes artificial graphite and a carbon coating layer. The carbon coating layer covers the surface of the artificial graphite. The thickness of the carbon coating layer is 200 nm, and the graphitization degree of the graphite is 92%. The average longest diameter particle size of the graphite is 9 μm.

[0188] 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.

[0189] The areal density of the single-sided negative electrode film layer is 0.13 g / 1540.25 mm 2 。

[0190] Under the condition that 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 plate is 1.4 g / cc.

[0191] The porosity of the negative electrode plate is 28%. The thickness of the negative electrode current collector is 4% of the thickness of the negative electrode plate.

[0192] 3. Separator The separator is a 7-μm polyethylene film layer.

[0193] 4. Preparation of electrolyte The electrolyte includes organic solvents, lithium salts, and additives. After mixing the components of the organic solvents, lithium salts and additives are added to prepare the electrolyte. The organic solvents include 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%.

[0194] 5. Preparation of Battery Cell Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining a stacked electrode assembly. Place the electrode assembly in an outer packaging case, and set positive and negative terminals on the outer packaging case. After baking, inject the electrolyte, and through processes such as vacuum packaging, standing, formation, and shaping, obtain the battery cell.

[0195] Battery cells in Examples 2 - 9 and Comparative Examples 1 - 9 were prepared by a method similar to that of Example 1. The differences from Example 1 are shown in Table 1.

[0196] Performance Test: (1) Fast Charging Performance Test of Battery: Charge and discharge the batteries of the above-mentioned examples and comparative examples for the first time at a current of 1C. Specifically, at 25°C, charge the battery at a constant current of 1C rate until the voltage reaches 3.65V, then charge at a constant voltage until the current ≤ 0.05C, stand for 5 minutes, and then discharge at a constant current of 0.33C rate until the voltage reaches 2.5V. Record its actual capacity as C0. Then charge the battery at constant current of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, 5C0 respectively until the full battery charging cut-off voltage of 3.65V, and record the SOC state corresponding to the battery when it is charged to 3.65V at each rate. After each charge is completed, discharge at 1C0 until the full battery discharge cut-off voltage of 2.1V. Plot a curve of different SOC - charging rates, and read the charging rates corresponding to 10% SOC, 20% SOC... 80% SOC from this curve, which are respectively denoted 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 charging rate under the corresponding state of charge, that is, the fast charging window. The charging time from 10 - 80% 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), with the unit of minutes.

[0197] (2) Internal Resistance Performance Test: The batteries of the above embodiments and comparative examples were first charged and discharged at a current of 1C (i.e., the current value for completely discharging the theoretical capacity within 1 h), specifically including: at 25 °C, the battery was charged at a constant current of 1C rate until the voltage reached 3.65V, then charged at a constant voltage until the current ≤ 0.05C, left standing for 5 min, and then discharged at a constant current of 0.5C rate for 1 h until 50% of the battery power. Then the battery was discharged at a constant current of 4C0 (the current magnitude is denoted as I) for 10 s, and the voltage U1 before discharge and the voltage U2 after discharge were recorded. The internal resistance R = (U1 - U2) / I.

[0198] (3)Energy density test: At 25 °C, the assembled battery was fully charged at a rate of 0.5C and fully discharged at a rate of 0.5C, and the actual discharge energy at this time was recorded; at 25 °C, the battery was weighed using an electronic balance; the ratio of the actual discharge energy of the battery at 0.5C to the battery weight was the energy density of the battery.

[0199]

[0200] In Comparative Example 1 and Comparative Example 3, the porosity of the electrode sheets was relatively low, which could improve the energy density of the battery. However, due to the low porosity, the internal resistance was large, which was not conducive to fast charging, resulting in too long charging time. Moreover, due to the low porosity, the DC internal resistance was large, which was likely to cause poor power performance.

[0201] In Comparative Example 2 and Comparative Example 4, the porosity of the electrode sheets was relatively high, which was beneficial to the movement of ions, beneficial to the improvement of fast charging and power performance, but the energy density of the battery decreased too much.

[0202] In Comparative Example 5 and Comparative Example 7, the proportion of the current collector thickness was relatively small, occupying less space in the battery, and the energy density of the battery was improved. However, the DC internal resistance increased and the power performance was too poor.

[0203] In Comparative Example 6 and Comparative Example 8, the proportion of the current collector thickness was relatively large. Although the DC internal resistance of the current collector decreased, the current collector occupied the space of the battery, and the energy density of the battery decreased too much.

[0204] 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 was 5% - 8% of the thickness of the positive electrode sheet; the porosity of the negative electrode sheet was 24% - 33%; the thickness of the negative electrode current collector was 2.5% - 5% of the thickness of the negative electrode sheet. That is, it could shorten the transmission distance of ions in the electrode material, improve the fast charging performance and power performance of the battery cell, and reduce the space occupied by non-active materials, thereby improving the energy density of the battery cell.

[0205] In Examples 10 - 13, battery cells were prepared using a method similar to that of Example 1. The differences from Example 1 are shown in Table 2.

[0206] Table 2

[0207] As can be seen from Examples 1 and 10, when the average longest diameter particle size of the graphite in the two film layers of the negative electrode sheet is the same, although the number of charge-discharge cycles and the energy density are improved to a certain extent, the fast charging performance deteriorates. In Example 1, the average longest diameter particle sizes of the graphite in the two film layers are different. After particle grading, while the fast charging performance is better, good charge-discharge cycle numbers and energy density are also taken into account. The average longest diameter particle size of the graphite used in the second film layer of Example 1 is relatively smaller, and the ion transport distance of the ions in the second film layer is relatively shorter, which is beneficial to further improving the fast charging performance of the battery cell. The average longest diameter particle size of the graphite used in the first film layer is relatively larger, and the compaction density of the first film layer is relatively higher, which is beneficial to taking into account good energy density.

[0208] As can be seen from Examples 1 and 10-13, reducing the average longest diameter particle size of the graphite in the first film layer of the negative electrode sheet is beneficial to reducing the DC internal resistance and improving the power performance. Reducing the average longest diameter particle size of the primary particles and the average longest diameter particle size of the secondary particles of the active material in the positive electrode sheet is beneficial to reducing the DC internal resistance and improving the power performance.

[0209] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure in essence as the technical idea and achieving the same effect within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that those skilled in the art can think of applied to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A battery cell, characterized in that: The invention comprises an electrode assembly and an electrolyte; wherein the electrode assembly comprises 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, 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 sheet 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 sheet is 24~33%; the thickness of the negative electrode current collector is 2.5%~5% of the thickness of the negative electrode sheet.

2. The battery cell according to claim 1, characterized in that: The porosity of the positive electrode sheet is 25-30%.

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

4. The battery cell according to claim 1, characterized in that: The thickness of the positive electrode current collector is 5% to 7.5% of the thickness of the positive electrode plate.

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, characterized in that: 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 2.3-2.6 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 plate is 0.25-0.33 g / 1540.25 mm 2 .

10. The battery cell according to claim 1, characterized in that: The negative electrode film layer comprises a first film layer and a second film layer, wherein the first film layer is arranged on at least one surface of the negative electrode current collector, and the second film layer is arranged on a surface of the first film layer that is opposite to 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 graphite in the first negative electrode active material is 7-18 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 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 graphitization degree of the graphite in the first negative electrode active material is 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 graphite in the second negative electrode active material is 6-10 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 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 graphitization degree of the graphite in the second negative electrode active material is 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 lithium-containing phosphate includes lithium iron phosphate, the lithium iron phosphate includes a metal element, and the metal element includes at least one of aluminum, titanium, 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, characterized in that: 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 lithium-containing phosphate in the secondary particle morphology is 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 linear 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; R1 includes an alkyl group having 1 to 3 carbon atoms.

40. The battery cell according to claim 36, characterized in that 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 also 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 also 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, characterized in that The ionic conductivity of the electrolyte at 25° C. is 11-13 ms / cm.

51. A battery device, characterized in that: Comprising a battery cell as claimed in 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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