Battery cell, battery device, and electrical equipment

Abstract

The present application provides a battery cell, a battery device, and an electrical device. The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab includes a positive current collector and a positive active material layer provided on at least one side of the positive current collector. The positive active material layer includes a positive active material, and the positive active material includes a lithium-containing phosphate. The compaction density of the positive electrode tab is 2.46 g / cm 3 -2.8 g / cm 3 ; The negative electrode tab includes a negative current collector and a negative active material layer provided on at least one side of the negative current collector. The compaction density of the negative electrode tab is 1.25 g / cm 3 -1.5 g / cm 3 ; The electrolyte includes lithium fluorosulfonylimide and lithium hexafluorophosphate. Based on the total mass of the electrolyte, the ratio of the mass percentage of lithium fluorosulfonylimide to the mass percentage of lithium hexafluorophosphate is 0.4-0.8; The mass of the electrolyte corresponding to each Ah of the battery cell is 2.2 g-3 g.

Description

[0001] This application claims the priority of the international patent application PCT / CN2025 / 082755 titled "Battery Cell, Battery Device and Electrical Equipment" filed on March 14, 2025, and the entire content of this application is incorporated herein by reference. Technical Field

[0002] This application relates to the field of batteries, and specifically, to battery cells, battery devices and electrical equipment. Background Art

[0003] Batteries are not only applied to energy storage power systems such as hydroelectric, thermal, wind and solar power stations, but also widely used in electric transportation such as electric bicycles, electric motorcycles, electric vehicles, as well as in multiple fields such as military equipment and aerospace. During the assembly process of a battery cell, by increasing the volume occupied by the electrode assembly and reducing the volume occupied by the electrolyte, the energy density of the battery cell can be improved. However, after the electrolyte content is reduced, it is difficult to remove the crystal water in the lithium-containing phosphate of the positive active material. During the battery cycling process, the electrolyte salt is prone to hydrolysis to generate HF, which corrodes the solid electrolyte interface (SEI) film on the surface of the negative electrode, resulting in the consumption of the electrolyte and reducing the cycling performance of the battery cell. Summary of the Invention

[0004] In a first aspect of this application, a battery cell is provided. The battery cell includes an electrode assembly and an electrolyte. 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 active material layer disposed on at least one side of the positive current collector. The positive active material layer includes a positive active material. The positive active material includes a lithium-containing phosphate. The tap density of the positive electrode tab is 2.46 g / cm 3 - 2.8 g / cm 3 ;

[0005] The negative electrode tab includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The tap density of the negative electrode tab is 1.25 g / cm 3 - 1.5 g / cm 3 ;

[0006] The electrolyte includes lithium fluorosulfonylimide and lithium hexafluorophosphate. Based on the total mass of the electrolyte, the ratio of the mass fraction of lithium fluorosulfonylimide to the mass fraction of lithium hexafluorophosphate is 0.4 - 0.8;

[0007] The mass of the electrolyte corresponding to each Ah of the battery cell is 2.2 g - 3 g.

[0008] Thus, while increasing the energy density of the battery cell, by controlling the contents of lithium hexafluorophosphate and lithium fluorosulfonylimide, the generation of HF is reduced, the consumption rate of the electrolyte and the additive is decreased, and the lifespan, cycle performance, and fast charging performance of the battery cell are improved.

[0009] According to some embodiments of the present application, the compaction density of the positive electrode sheet is 2.65 g / cm 3 -2.8 g / cm 3 . Thus, the battery cell has a relatively high volumetric energy density.

[0010] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of lithium fluorosulfonylimide is 4% - 8%. Lithium fluorosulfonylimide is not easily hydrolyzed, which can reduce the generation of HF and the corrosion of the SEI film.

[0011] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of lithium hexafluorophosphate is 8% - 12%. Thus, the viscosity of the electrolyte is reduced, and the transmission rate of lithium ions is increased.

[0012] According to some embodiments of the present application, the lithium fluorosulfonylimide includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium perfluorobutanesulfonylimide. Thus, the generation of HF is reduced, and the corrosion of the SEI film is decreased.

[0013] According to some embodiments of the present application, the electrolyte further includes a solvent, and the solvent includes one or two of carbonate solvents and carboxylate solvents. Thus, the conductivity of the electrolyte is increased, and the fast charging performance of the battery cell is improved.

[0014] According to some embodiments of the present application, the carbonate solvents include one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Thus, the dielectric constant of the electrolyte is increased.

[0015] According to some embodiments of the present application, the carboxylate solvent includes a compound represented by Formula I:

[0016]

[0017] Formula I,

[0018] wherein, R5 includes any one of a hydrogen atom, a halogen atom, a C1 - C5 alkyl group, and a C1 - C5 haloalkyl group, and R6 includes any one of a C1 - C5 alkyl group and a C1 - C5 haloalkyl group. Thus, the carboxylate solvents of the above types have a relatively small molecular weight, which can increase the ionic conductivity of the electrolyte and improve the rate performance of the battery cell.

[0019] According to some embodiments of the present application, the carboxylic ester solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate. Thus, the carboxylic ester solvents of the above types have a relatively small molecular weight, which can improve the ionic conductivity of the electrolyte and the rate performance of the battery cell.

[0020] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent is 20%-70%. Thus, the ionic conductivity of the electrolyte is improved.

[0021] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the carboxylic ester solvent is 10%-60%. Thus, while improving the ionic conductivity of the electrolyte, the high-temperature cycle life of the battery cell is improved.

[0022] According to some embodiments of the present application, the electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. Thus, the cycle performance and fast charging performance of the battery cell are improved.

[0023] According to some embodiments of the present application, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Thus, the cycle life of the battery cell is improved.

[0024] According to some embodiments of the present application, the ethylene carbonate derivative includes the compound shown in Formula II,

[0025]

[0026] Formula II,

[0027] wherein R1, R2, R3, and R4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R1, R2, R3, and R4 are not simultaneously hydrogen atoms. Thus, the cycle life of the battery cell is improved.

[0028] According to some embodiments of the present application, the ethylene carbonate derivative includes at least one of the compounds shown in Formula II-1, Formula II-2, and Formula II-3:

[0029]

[0030] Formula II-1, Formula II-2, and Formula II-3.

[0031] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 3% - 8%. Thereby, while improving the cycle life of the battery cell, the impedance of the battery cell is reduced.

[0032] According to some embodiments of the present application, the mass proportion of vinylene carbonate is 2% - 5%. Thereby, a stable SEI film is formed to improve the transport of lithium ions.

[0033] According to some embodiments of the present application, the mass proportion of the ethylene carbonate derivative is 0% - 4%. Thereby, the uniformity and compactness of the SEI film are improved, and the side reaction between the electrolyte and the negative electrode surface is reduced.

[0034] According to some embodiments of the present application, the mass proportion of the ethylene carbonate derivative is 1.5% - 3.5%. Thereby, the uniformity and compactness of the SEI film are improved, and the side reaction between the electrolyte and the negative electrode surface is reduced.

[0035] According to some embodiments of the present application, the sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), 1,3 - propane sultone, butene sulfite, ethylene sulfite, and methylene methyl disulfonate. Thereby, the impedance of the battery cell is reduced, and the fast charging performance of the battery cell is improved.

[0036] According to some embodiments of the present application, the mass proportion of the sulfur-containing additive is 0 - 2%. Thereby, while reducing the impedance of the battery cell, the gas generation of the battery cell is reduced.

[0037] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0.5% - 2%. Thereby, while reducing the impedance of the battery cell, the gas generation of the battery cell is reduced.

[0038] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate. Thereby, the gas generation of the battery cell under high-temperature conditions is reduced.

[0039] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0 - 1%. Thereby, while reducing the gas generation of the battery cell, the film-forming impedance is reduced.

[0040] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% - 1%. Thereby, while reducing the gas generation of the battery cell, the film-forming impedance is reduced.

[0041] According to some embodiments of the present application, the lithium-containing phosphate includes: a matrix; a first coating material located on at least a part of the surface of the matrix, and the first coating material contains carbon elements. Thereby, the conductivity of the lithium-containing phosphate is improved.

[0042] According to some embodiments of the present application, based on the total mass of the lithium-containing phosphate, the mass percentage of the carbon element is 0.8% - 2.3%. Thereby, while improving the conductivity of the lithium-containing phosphate, the loading of the lithium-containing phosphate on the positive electrode sheet is increased, and the energy density of the battery cell is increased.

[0043] According to some embodiments of the present application, the first coating material includes a compound represented by Formula III:

[0044] Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula III,

[0045] where 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn. Thereby, the ionic conductivity and specific capacity of the positive electrode active material are improved, and the fast charging performance and energy density of the battery cell are improved.

[0046] According to some embodiments of the present application, the matrix includes a compound represented by Formula IV:

[0047] Li x1 A y1 Me a1 M2 b1 P 1-c1 X c1 Y z1 Formula IV,

[0048] where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5;

[0049] where A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M2 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or two of O and F. Thereby, the cycle performance and safety of the battery cell are improved.

[0050] According to some embodiments of the present application, the matrix includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. Thereby, the cycle performance and safety of the battery cell are improved.

[0051] According to some embodiments of the present application, the powder compaction density of the positive electrode active material under 30000N is 2.43 g / cm 3 -2.85 g / cm 3 . Thereby, the energy density of the battery cell is improved.

[0052] According to some embodiments of the present application, the single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 -350 mg / 1540.25 mm 2 . Thereby, the energy density of the battery cell is improved.

[0053] According to some embodiments of the present application, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one or two of a carbon-based material and a silicon-based material. Thereby, the energy density and cycle performance of the battery cell are improved.

[0054] According to some embodiments of the present application, the carbon-based material includes graphite. Thereby, the cycle performance of the battery cell is improved.

[0055] According to some embodiments of the present application, the graphite is secondary particles formed by aggregation of primary particles, and at least part of the surface of the secondary particles has a second coating material, and the second coating material includes amorphous carbon. Thereby, the side reaction between the negative electrode surface and the electrolyte is reduced, and the cycle performance of the battery cell is improved.

[0056] According to some embodiments of the present application, based on the total mass of the graphite, the mass ratio of the second coating material is 2%-5%. Thereby, while improving the cycle performance of the battery cell, the energy density of the battery cell is improved.

[0057] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 8.5 μm - 13.8 μm. Thereby, the migration path of lithium ions in the solid phase is shortened, and the fast charging ability of the battery cell is improved; at the same time, the side reaction between graphite and the electrolyte is reduced.

[0058] According to some embodiments of the present application, the negative electrode active material includes a silicon-based material, and based on the total mass of the negative electrode active material layer, the mass ratio of silicon element is 0.3%-5%. Thereby, the energy density of the battery cell is improved.

[0059] According to some embodiments of the present application, the single-sided coating weight of the negative electrode active material layer is 90 mg / 1540.25 mm 2 -140 mg / 1540.25 mm 2 . Thereby, the energy density of the battery cell is increased.

[0060] According to some embodiments of the present application, along the length direction of the battery cell, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1;

[0061] Along the width direction of the battery cell, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH2,

[0062] wherein, OH1 is greater than or equal to OH2. Thereby, while increasing the energy density of the battery cell, the lithium deposition on the negative electrode is reduced.

[0063] According to some embodiments of the present application, 1 mm ≤ OH1 ≤ 4 mm, 1 mm ≤ OH2 ≤ 3 mm. Thereby, while increasing the energy density of the battery cell, the lithium deposition on the negative electrode is reduced.

[0064] According to some embodiments of the present application, a positive electrode tab is provided on the positive electrode plate, and a negative electrode tab is provided on the negative electrode plate. The positive electrode tab extends along the length direction or the width direction of the positive electrode plate, and the negative electrode tab extends along the length direction or the width direction of the negative electrode plate. Thereby, the current transmission efficiency is improved, the resistance of the battery cell is reduced, and the rate performance of the battery cell is improved.

[0065] According to some embodiments of the present application, the electrode assembly includes a separator, and the porosity of the separator is 20% - 70%. Thereby, the transmission efficiency of lithium ions is improved, and the rate performance of the battery cell is improved.

[0066] According to some embodiments of the present application, the porosity of the separator is 35% - 60%. Thereby, the transmission efficiency of lithium ions is improved, and the rate performance of the battery cell is improved.

[0067] According to some embodiments of the present application, the separator includes: a base film; a first functional layer located on at least one side of the base film, the first functional layer including a first inorganic substance; a second functional layer located on the side of the first functional layer away from the base film, the second functional layer including a second inorganic substance and a non-fluoropolymer. Thereby, the heat resistance of the separator is improved, and the safety of the battery cell is improved.

[0068] According to some embodiments of the present application, the non-fluoropolymer includes an acrylate copolymer. Thereby, the adhesion of the non-fluoropolymer is improved, and the risk of peeling off of the second functional layer is reduced.

[0069] According to some embodiments of the present application, the first inorganic substance and the second inorganic substance each independently include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Thereby, the heat resistance of the separator is improved, and the safety of the battery cell is improved.

[0070] According to some embodiments of the present application, the thickness of the base film is 4 μm - 12 μm. Thereby, while reducing the short circuit between the positive and negative electrodes, the volume occupied by the separator in the battery cell is reduced, and the energy density of the battery cell is improved.

[0071] According to some embodiments of the present application, the battery cell includes a housing and a cover assembly. The cover assembly is disposed at at least one end of the housing. The housing and the cover assembly define a receiving cavity. The electrode assembly is disposed in the receiving cavity. The thickness of the housing on the large surface of the battery cell is 0.1 mm - 0.5 mm. Thereby, the energy density of the battery cell is improved.

[0072] According to some embodiments of the present application, the thickness of the housing on the large surface of the battery cell is 0.2 mm - 0.35 mm. Thereby, the energy density of the battery cell is improved.

[0073] According to some embodiments of the present application, the cover assembly includes a first cover assembly and a second cover assembly. The first cover assembly and the second cover assembly are disposed at both ends in the length direction or the width direction of the housing. The first cover assembly includes a first cover and a first electrode terminal. The second cover assembly includes a second cover and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite. Thereby, during charging, the temperature rise of the battery cell is reduced, and further the impedance of the battery cell is reduced.

[0074] According to some embodiments of the present application, the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S, and satisfies 150 mm 2 ≤S≤1000 mm 2 . Thereby, the overcurrent capacity of the battery cell is improved.

[0075] According to some embodiments of the present application, the volumetric energy density of the battery cell is 400 Wh / L - 530 Wh / L.

[0076] The second aspect of the present application provides a battery device, including the battery cell provided in the first aspect of the present application. The battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0077] In a third aspect of the present application, an electrical device is provided, including the battery cell provided in the first aspect of the present application or the battery device provided in the second aspect of the present application, and the battery cell or the battery device provides electrical energy for the electrical device.

[0078] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present application. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0080] Figure 1 is a schematic structural view of a housing according to an embodiment of the present application.

[0081] Figure 2 is a schematic view of the sizes of a positive electrode active material layer and a negative electrode active material layer according to an embodiment of the present application.

[0082] Figure 3 is a schematic structural view of a positive electrode tab according to an embodiment of the present application.

[0083] Figure 4 is a schematic structural view of a positive electrode tab according to another embodiment of the present application.

[0084] Figure 5 is a schematic structural view of a positive electrode tab according to another embodiment of the present application.

[0085] Figure 6 is a schematic structural view of a positive electrode tab according to another embodiment of the present application.

[0086] Figure 7 is a schematic structural view of a negative electrode tab according to an embodiment of the present application.

[0087] Figure 8 is a schematic structural view of a negative electrode tab according to another embodiment of the present application.

[0088] Figure 9 is a schematic structural view of a negative electrode tab according to another embodiment of the present application.

[0089] Figure 10 is a schematic structural view of a negative electrode tab according to another embodiment of the present application.

[0090] Figure 11It is a schematic structural diagram of a separator membrane according to an embodiment of the present application.

[0091] Figure 12 It is a schematic structural diagram of a battery cell according to an embodiment of the present application.

[0092] Figure 13 It is a schematic structural diagram of an electrical device according to an embodiment of the present application.

[0093] Description of reference numerals:

[0094] 1 Battery cell; 11 Housing; 111 Large-surface housing; 121 Positive electrode plate; 1210 Positive electrode tab; 1212 Positive electrode active material layer; 122 Negative electrode plate; 1220 Negative electrode tab; 1222 Negative electrode active material layer; 123 Separator membrane; 1231 Base film; 1232 First functional layer; 1233 Second functional layer. Detailed embodiments

[0095] Hereinafter, embodiments of the technical solution of the present application will be described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application, so they are only examples and cannot be used to limit the protection scope of the present application.

[0096] Referring to "embodiments" herein means that specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0097] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0098] 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 a new technical solution.

[0099] If there is no special instruction, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), indicating that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), indicating 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.

[0100] At present, from the perspective of the development of the market situation, the application of batteries is becoming more and more extensive. Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, but also widely used in electric transportation such as electric bicycles, electric motorcycles, electric vehicles, as well as in many fields such as military equipment and aerospace. With the continuous expansion of the application fields of batteries, the market demand is also continuously increasing. The battery cells in the related technologies cannot meet the requirements of long cycle life and high energy density.

[0101] This application proposes a battery cell. By increasing the compaction density of the positive and negative electrode plates, the occupied space of the electrode assembly is increased, and by reducing the electrolyte injection volume, the weight of the battery cell is reduced, thereby improving the battery energy density. However, because the particles inside the electrode plates are more tightly packed after increasing the compaction density of the positive and negative electrodes, it is difficult to completely bake out the moisture in the electrode plates through the process to control it within a reasonable range during the battery production process. This part of the moisture will slowly be released from the electrode plates during the battery cycle or storage process, causing the lithium salt lithium hexafluorophosphate in the electrolyte to hydrolyze to produce HF. The generation of HF will erode the SEI film, causing the SEI film to continuously repair and regenerate, accelerating the consumption rate of the electrolyte and additives. Since the electrolyte injection volume in this application is controlled within a relatively low range, in order to ensure the battery life, it is necessary to improve the erosion of HF on the SEI during the cycle and storage processes and reduce the consumption rate of the electrolyte and additives. Therefore, by compounding lithium hexafluorophosphate and lithium fluorosulfonylimide salt in the electrolyte and controlling the relative content of the two within a suitable range, the generation of HF during the cycle and storage processes can be reduced, the consumption rate of the electrolyte and additives can be reduced, and the battery cell life can be improved. And the ionization energy of lithium fluorosulfonylimide salt is higher than that of lithium hexafluorophosphate, which can accelerate the transmission rate of lithium ions in the electrolyte, better enable the lithium ions to diffuse in the high-compaction positive and negative electrode plates, and improve the fast charging and cycle performance of the single battery.

[0102] The battery cell proposed in this application can be used in electrical equipment that uses the battery cell as a power source or various energy storage systems that use the battery cell as an energy storage element. The electrical equipment can include, but is not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, etc. Among them, the electric toys can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, electric aircraft toys, etc., and the spacecraft can include airplanes, rockets, space shuttles, spaceships, etc.

[0103] The first aspect of the present application provides a battery cell, which includes an electrode assembly and an electrolyte. 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 active material layer provided on at least one side of the positive current collector. The positive active material layer includes a positive active material, and the positive active material includes a lithium-containing phosphate. The tap density of the positive electrode tab is 2.46 g / cm 3 - 2.8 g / cm 3 ;

[0104] The negative electrode tab includes a negative current collector and a negative active material layer provided on at least one side of the negative current collector. The tap density of the negative electrode tab is 1.3 g / cm 3 - 1.5 g / cm 3 ;

[0105] The electrolyte includes lithium fluorosulfonimide and lithium hexafluorophosphate. Based on the total mass of the electrolyte, the ratio of the mass percentage of lithium fluorosulfonimide to the mass percentage of lithium hexafluorophosphate is 0.4 - 0.8;

[0106] The mass of the electrolyte corresponding to each Ah of the battery cell is 2.2 g - 3 g.

[0107] Thus, while improving the energy density of the battery cell, by controlling the contents of lithium hexafluorophosphate and lithium fluorosulfonimide, the generation of HF is reduced, the consumption rate of the electrolyte and additives is decreased, and the lifespan, cycle performance, and fast charging performance of the battery cell are improved.

[0108] In the present application, the test method for the mass of the electrolyte at a battery cell rated capacity of 1 Ah is as follows: ① Take a battery cell and weigh its mass M0; ② Disassemble the battery cell, pour out the free electrolyte, and take out solid components such as electrode tabs, separator membranes, mechanical parts, and adhesive tapes; ③ Soak and clean the solid components such as electrode tabs, separator membranes, mechanical parts, and adhesive tapes with dimethyl carbonate (DMC) respectively for 24 h, and wash repeatedly more than 3 times; ④ After cleaning, place the solid components such as electrode tabs, separator membranes, mechanical parts, and adhesive tapes in an oven until completely dried; ⑤ Weigh the total mass of the dried solid components such as electrode tabs, separator membranes, mechanical parts, and adhesive tapes, and record the mass as M1; ⑥ The mass of the electrolyte per unit battery rated capacity of 1 Ah of the battery cell = (M0 - M1) / a. a = the rated capacity of the battery cell, in units of Ah. As an example, the mass of the electrolyte corresponding to each Ah of the battery cell can be 2.2 g, 2.3 g, 2.4 g, 2.5 g, 2.6 g, 2.7 g, 2.8 g, 3 g, etc., or can be a range composed of any of the above values. Thus, the space occupied by the electrolyte in the battery cell is reduced, the content of the lithium-containing phosphate is increased, and the energy density of the battery cell is improved.

[0109] The present application provides a method for testing the tap density of a positive electrode plate: Place the battery cell at 25 °C, let it stand for 2 h, charge it at a constant current of 1 / 3C to 3.65 V, charge it at a constant voltage of 3.65 V to 0.05C, let it stand for 2 h, and then discharge it at a rate of 0.33C to 2.0 V. Disassemble the positive electrode plate from the battery cell. For example, take a single-sided coated positive electrode plate (if it is a double-sided coated electrode plate, the positive electrode active material layer on one side can be wiped off first), punch it into small circular pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive electrode active material layer of the above-mentioned weighed positive electrode plate, weigh the weight of the positive electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode active material layer = (M1 - M0) / S1, the thickness of the positive electrode active material layer = H1 - H0, and the tap density of the positive electrode active material layer = the single-sided coating weight of the positive electrode active material layer / the thickness of the positive electrode active material layer.

[0110] As an example, the tap density of the positive electrode plate can be 2.46 g / cm 3 、2.5 g / cm 3 、2.55 g / cm 3 、2.6 g / cm 3 、2.65 g / cm 3 、2.7 g / cm 3 、2.8 g / cm 3 etc., or can be in the range composed of any of the above values. Thereby, the occupied space of the electrode assembly is increased, and the energy density of the battery cell is increased.

[0111] According to some embodiments of the present application, the tap density of the positive electrode plate can be 2.65 g / cm 3 -2.8 g / cm 3 。

[0112] The present application provides a method for testing the tap density of a negative electrode plate: Charge it at a constant current of 1 / 3C to 3.65 V, charge it at a constant voltage of 3.65 V to 0.05C, place the battery cell at 25 °C, let it stand for 2 h, and then discharge it at a rate of 0.33C to 2.0 V. Disassemble the negative electrode plate from the battery cell. For example, take a single-sided coated negative electrode plate (if it is a double-sided coated electrode plate, the negative electrode active material layer on one side can be wiped off first), punch it into small circular pieces with an area of S2, weigh it, record it as M3, and measure its thickness H3. Then wipe off the negative electrode active material layer of the above-mentioned weighed negative electrode plate, weigh the weight of the negative electrode current collector, record it as M2, and measure its thickness H2. The single-sided coating weight of the negative electrode active material layer = (M3 - M2) / S2, the thickness of the negative electrode active material layer = H3 - H2, and the tap density of the negative electrode active material layer = the single-sided coating weight of the negative electrode active material layer / the thickness of the negative electrode active material layer.

[0113] As an example, the compaction density of the negative electrode sheet can be 1.25 g / cm 3 ³, 1.3 g / cm 3 ³, 1.35 g / cm 3 ³, 1.4 g / cm 3 ³, 1.45 g / cm 3 ³, 1.5 g / cm 3 etc., or can be a range composed of any of the above values. Thus, on the one hand, the occupied space of the electrode assembly is increased, and the energy density of the battery cell is increased; on the other hand, after the compaction density of the negative electrode sheet is increased, the porosity of the negative electrode sheet is reduced, and the content of the electrolyte required to be absorbed intrinsically inside the sheet is reduced. When the mass of the electrolyte corresponding to each Ah of the battery cell is small, the requirements for cycling can also be met.

[0114] In this application, the test of the content of lithium fluorosulfonylimide salt and lithium hexafluorophosphate can refer to the standard JY / T 020-2002 General Rules for Ion Chromatography Analysis Method. For example, a newly prepared electrolyte can be taken as a sample, a free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell is taken as a sample, and the ion chromatography analysis method is used for detection. The inorganic ion chromatogram is tested, the corresponding inorganic substances are compared according to the chromatographic peak position, and the percentage of the content of the corresponding inorganic ions is calculated according to the peak area, and then the ratio of the mass fraction of lithium fluorosulfonylimide to the mass fraction of lithium hexafluorophosphate is calculated.

[0115] As an example, the ratio of the mass fraction of lithium fluorosulfonylimide to the mass fraction of lithium hexafluorophosphate can be 0.4, 0.45, 0.5, 0.55, 0.6, 0.8, etc., or can be a range composed of any of the above values. By making the mass fraction of lithium fluorosulfonylimide and the mass fraction of lithium hexafluorophosphate within the above range, on the one hand, the generation of HF is reduced, the corrosion of the SEI film is reduced, the consumption of the electrolyte is reduced, and the cycling performance of the battery cell is improved; on the other hand, the viscosity of the electrolyte is reduced, the lithium ion transport rate is increased, and the fast charging performance of the battery cell is improved.

[0116] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of lithium fluorosulfonylimide can be 4% - 8%. For example, it can be 4%, 4.5%, 5%, 5.5%, 6%, 8%, etc., or can be a range composed of any of the above values. Thus, the generation of HF is reduced, the corrosion of the SEI film is reduced, during the cycling of the battery cell, the consumption of the electrolyte is reduced, and the cycling performance of the battery cell is improved.

[0117] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of lithium hexafluorophosphate can be 8% - 12%. For example, it can be 8%, 9%, 10%, 11%, 12%, etc., or it can be a range composed of any of the above values. Thereby, the viscosity of the electrolyte is reduced, the transmission rate of lithium ions is increased, and the fast charging performance of the battery cell is improved.

[0118] According to some embodiments of the present application, the lithium fluorosulfonylimide includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium perfluorobutanesulfonylimide. Thereby, the generation of HF is reduced, and the corrosion of the SEI film is decreased.

[0119] According to some embodiments of the present application, the electrolyte further includes a solvent, and the solvent includes one or two of carbonate solvents and carboxylate solvents. Thereby, the conductivity of the electrolyte is increased, and the fast charging performance of the battery cell is improved.

[0120] In the present application, after disassembling the battery cell to obtain the electrolyte, reference can be made to GB / T 9722-2023 General Rules for Gas Chromatography of Chemical Reagents, and the solvent of the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography.

[0121] According to some embodiments of the present application, the carbonate solvents may include one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Thereby, the dielectric constant of the electrolyte is increased.

[0122] According to some embodiments of the present application, the carboxylate solvent includes a compound represented by Formula I:

[0123]

[0124] Formula I,

[0125] wherein, R5 includes any one of a hydrogen atom, a halogen atom, an alkyl group with 1 - 5 carbon atoms, and a halogenated alkyl group with 1 - 5 carbon atoms, and R6 includes any one of an alkyl group with 1 - 5 carbon atoms and a halogenated alkyl group with 1 - 5 carbon atoms. Thereby, the carboxylate solvents of the above types have a relatively small molecular weight, which can increase the ionic conductivity of the electrolyte and improve the rate performance of the battery cell.

[0126] According to some embodiments of the present application, the carboxylate solvents include one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate. Thereby, the carboxylate solvents of the above types have a relatively small molecular weight, which can increase the ionic conductivity of the electrolyte and improve the rate performance of the battery cell.

[0127] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent may be 20% - 70%, for example, it may be 20%, 30%, 40%, 50%, 60%, 70%, etc., or it may be a range composed of any of the above values. Thereby, the ionic conductivity of the electrolyte is improved.

[0128] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the carboxylate solvent is 10% - 60%, for example, it may be 10%, 20%, 30%, 40%, 50%, 60%, etc., or it may be a range composed of any of the above values. By making the content of the carboxylate solvent within the above range, on the one hand, the viscosity of the electrolyte can be reduced, the internal resistance of the battery cell can be lowered, the migration rate of lithium ions can be increased, and the fast charging performance of the battery cell can be improved; on the other hand, the risk of gas generation of the electrolyte under high temperature conditions can be reduced, and the high temperature cycle life of the battery cell can be improved, thereby obtaining a battery cell with both excellent fast charging performance and high temperature cycle life.

[0129] According to some embodiments of the present application, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. Thereby, the above types of additives can preferentially decompose on the surfaces of the positive electrode and the negative electrode to form a stable interface film with low impedance, reduce the contact between the electrolyte and the surfaces of the positive electrode and the negative electrode, reduce the risk of electrolyte decomposition, and improve the cycle performance and fast charging performance of the battery cell.

[0130] According to some embodiments of the present application, the carbonate additives include one or more of vinylene carbonate (VC) and ethylene carbonate derivatives. Thereby, the above types of carbonate additives can form a stable interface film on the electrode surface, reduce the side reaction between the electrolyte and the electrode surface, and improve the cycle life of the battery cell.

[0131] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the carbonate additives is 3% - 8%. For example, it may be 3%, 4%, 5%, 6%, 7%, 8%, etc., or it may be a range composed of any of the above values. Thereby, while improving the cycle life of the battery cell, the viscosity of the electrolyte is reduced, and the internal resistance of the battery cell is lowered.

[0132] According to some embodiments of the present application, the mass percentage of vinylene carbonate is 2% - 5%. For example, it can be 2%, 3%, 4%, 5%, etc., or it can be a range composed of any of the above values. Thus, vinylene carbonate has relatively high reactivity, and a uniform and dense SEI film can be formed on the surface of the negative electrode during the first charge and discharge process of the battery, improving the stability of the SEI film. Moreover, the SEI film formed by VC has good ionic conductivity, which can enable lithium ions to be rapidly transported between the electrode and the electrolyte, improving the charge and discharge efficiency of the battery.

[0133] According to some embodiments of the present application, the mass percentage of the ethylene carbonate derivative is 0% - 4%. For example, it can be 0.5%, 1%, 2%, 3%, 4%, etc., or it can be a range composed of any of the above values. According to some specific embodiments of the present application, the mass percentage of the ethylene carbonate derivative is 1.5% - 3.5%. Thus, the interfacial resistance of the SEI film is reduced, the charge and discharge efficiency of the battery is improved, and when used in combination with VC, the stability and integrity of the SEI film can also be enhanced.

[0134] According to some embodiments of the present application, the ethylene carbonate derivative includes the compound shown in Formula II,

[0135]

[0136] Formula II,

[0137] wherein, R1, R2, R3, and R4 each independently include any one of a hydrogen atom, a halogen atom, an alkyl group with 1 - 5 carbon atoms, and a halogenated alkyl group with 1 - 5 carbon atoms, and R1, R2, R3, and R4 are not simultaneously hydrogen atoms. Thus, the cycle life of the battery monomer is improved.

[0138] According to some embodiments of the present application, the ethylene carbonate derivative includes at least one of the compounds shown in Formula II - 1, Formula II - 2, and Formula II - 3:

[0139]

[0140] Formula II - 1, Formula II - 2, Formula II - 3.

[0141] According to some embodiments of the present application, the sulfur - containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), 1,3 - propane sultone, butene sulfite, ethylene sulfite, and methylene methyl disulfonate. Thus, additives of the above types can form an SEI film with high ionic conductivity on the surface of the negative electrode, reduce the resistance of lithium ion transmission at the electrode - electrolyte interface, reduce the impedance of the battery monomer, and improve the fast - charging performance of the battery monomer.

[0142] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate. Thus, the lithium salt additives of the above types can form a stable SEI film on the surface of the negative electrode, reduce the side reactions between the electrolyte and the electrode surface, reduce the decomposition of the electrolyte, and reduce the gas generation of the battery cell under high-temperature conditions.

[0143] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the sulfur-containing additive can be 0% - 2%. For example, it can be 0.5%, 1%, 1.5%, 2%, etc., or it can be a range composed of any of the above values. Thus, while reducing the impedance of the battery cell, the risk of the battery cell being oxidized at a high potential to generate sulfur-containing free radicals is reduced, thereby reducing the decomposition of the solvent caused by the sulfur-containing free radicals and reducing the gas generation of the battery cell. According to some embodiments of the present application, the mass percentage of the sulfur-containing additive can be 0.5% - 2%.

[0144] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive can be 0% - 1%. For example, it can be 0.2%, 0.4%, 0.6%, 0.8%, 1%, etc., or it can be a range composed of any of the above values. Thus, while reducing the gas generation of the battery cell, the content of inorganic components in the SEI film is reduced, and the film-forming impedance is reduced. According to some embodiments of the present application, the mass percentage of the lithium salt additive can be 0.2% - 1%.

[0145] In the present application, after disassembling the battery cell to obtain the electrolyte, reference can be made to GB / T 9722-2023 General Rules for Chemical Reagents - Gas Chromatography to qualitatively and quantitatively analyze the additives in the electrolyte by gas chromatography.

[0146] It should be noted that as the battery cell is charged and discharged, when the addition amounts of the ethylene carbonate derivative, the sulfur-containing additive, and the lithium salt additive are small, and the additives in the electrolyte will be consumed to some extent during formation and charge-discharge cycles to generate the relevant components in the SEI film and / or CEI film, when the content of the ethylene carbonate derivative, the sulfur-containing additive, and the lithium salt additive is measured by gas chromatography after disassembling the battery cell to obtain the electrolyte, the content may be 0.

[0147] Specifically, taking the case where the mass content of the ethylene carbonate derivative is 0 as an example, it may be that the freshly prepared electrolyte does not contain the ethylene carbonate derivative, or the electrolyte obtained after disassembling the battery cell does not contain the ethylene carbonate derivative. This situation may be that the freshly prepared electrolyte does not contain the ethylene carbonate derivative, or a small amount of the ethylene carbonate derivative is added, but it participates in the film-forming reaction of the SEI film during the formation process of the battery cell, resulting in a mass content of 0 for the ethylene carbonate derivative during the detection process. Optionally, the freshly prepared electrolyte includes the ethylene carbonate derivative.

[0148] Furthermore, for adding certain substances, such as additives, to the electrolyte, due to the characteristic that the additives play a role by participating in the film formation on the surface of the active material, the content of the additives in the electrolyte of the battery cell is related to the formation, different battery life cycles, or different battery storage states. Therefore, there may be a difference in the content of the additives between the freshly prepared electrolyte and the electrolyte obtained by reverse disassembling the battery cell. However, those skilled in the art can know the approximate range of the content of the relevant substances in the corresponding freshly prepared electrolyte according to the performance expression level (such as the number of cycle times), residual content, etc. of the battery cell. Similarly, those skilled in the art can also know the approximate range of the content of the non-freshly prepared (i.e., reverse) corresponding to the freshly prepared additive content according to the performance requirements of the battery cell, storage environment, etc.

[0149] Therefore, the additive content mentioned in the technical solution of this application can be the content of the additives actively added to the freshly prepared electrolyte, or the content of the residual additives detected by reverse according to the actual battery state.

[0150] According to some embodiments of the present application, the lithium-containing phosphate includes: a matrix; a first coating material, the first coating material is located on at least part of the surface of the matrix, and the first coating material contains carbon elements. Thereby, a good conductive network is formed between the lithium-containing phosphate particles, improving the electronic conductivity of the lithium-containing phosphate.

[0151] According to some embodiments of the present application, based on the total mass of the lithium-containing phosphate, the mass proportion of the carbon element can be 0.8% - 2.3%. For example, it can be 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.3%, etc., or can be the range composed of any of the above values. Thereby, while improving the electronic conductivity of the lithium-containing phosphate, the influence on lithium ion transmission is reduced, the loading of the lithium-containing phosphate on the positive electrode sheet is increased, and the energy density of the battery cell is improved.

[0152] According to some embodiments of the present application, the first coating material includes the compound shown in Formula III:

[0153] Li3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula III

[0154] where 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn.

[0155] The compound represented by Formula III has excellent ionic conductivity, and together with the carbon element having excellent electrical conductivity in the first coating material, it improves the electrical conductivity and ionic conductivity of the lithium-containing phosphate, which is beneficial to improving the fast charging performance of the battery.

[0156] According to some embodiments of the present application, the matrix includes a compound represented by Formula IV:

[0157] Li x1 A y1 Me a1 M2 b1 P 1-c1 X c1 Y z1 Formula IV

[0158] where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5;

[0159] where A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M2 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F. Thereby, the cycle performance and safety of the battery cell are improved.

[0160] As an example, x1 can be 0.5, 0.7, 0.9, 1.1, 1.3, etc., or can be a range composed of any of the above values.

[0161] It should be noted that due to processes such as formation and cycling of the battery cell, lithium ions will be consumed, so there will be a situation where the measured lithium element content x1 in the positive electrode active material is less than 1. At the same time, if a lithium supplement agent is used for the positive electrode plate and the negative electrode plate, after the battery undergoes processes such as formation and cycling, there will be a situation where the measured lithium element content x1 in the positive electrode active material is greater than 1.

[0162] As an example, y1 can be 0, 0.3, 0.6, 0.9, 1.3, etc., or can be a range composed of any of the above numerical values.

[0163] As an example, a1 can be 0.9, 1.1, 1.3, 1.5, etc., or can be a range composed of any of the above numerical values.

[0164] As an example, b1 can be 0, 0.2, 0.4, 0.5, etc., or can be a range composed of any of the above numerical values.

[0165] As an example, c1 can be 0, 0.2, 0.4, 0.5, etc., or can be a range composed of any of the above numerical values.

[0166] As an example, z1 can be 3, 4, 5, etc., or can be a range composed of any of the above numerical values.

[0167] According to some embodiments of the present application, the matrix may include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. Thereby, the cycle performance and safety of the battery cell are improved.

[0168] According to some embodiments of the present application, the powder compaction density of the positive electrode active material under 30000N is 2.43 g / cm 3 -2.85 g / cm 3 . For example, it can be 2.43 g / cm 3 , 2.5 g / cm 3 , 2.6 g / cm 3 , 2.7 g / cm 3 , 2.8 g / cm 3 etc., or can be a range composed of any of the above numerical values. Thereby, the energy density of the battery cell is improved.

[0169] In the present application, the powder compaction density of the material has the meaning well-known in the art and can be detected by methods and equipment well-known in the art. For example, it can be detected according to the test standard GB / T24533-2019. Specifically, a certain amount of positive electrode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in the UTM7305 type electronic pressure testing machine, pressurized to 3000 kg (equivalent to 30000N), kept under pressure for 30 s, then depressurized, kept for 10 s, and then the powder compaction density of the positive electrode active material under the action of 30000N is recorded and calculated.

[0170] According to some embodiments of the present application, the powder compaction density of the positive electrode active material under 30000N is 2.48 g / cm 3 -2.8 g / cm 3Thus, the energy density and rate performance of the battery cell are improved.

[0171] According to some embodiments of the present application, the single-sided coating weight of the positive electrode active material layer can be 200 mg / 1540.25 mm 2 - 350 mg / 1540.25 mm 2 For example, it can be 200 mg / 1540.25 mm 2 、250 mg / 1540.25 mm 2 、300 mg / 1540.25 mm 2 、350 mg / 1540.25 mm 2 etc., or can be a range composed of any of the above values. Thus, the energy density of the battery cell is improved.

[0172] The present application provides a method for testing the coating weight of the positive electrode active material layer: disassemble the positive electrode plate from the battery cell. For example, take the single-sided coated positive electrode plate (if it is a double-sided coated plate, the positive electrode active material layer on one side can be wiped off first), punch it into small round pieces with an area of S1, weigh it, and record it as M1. Then wipe off the positive electrode active material layer of the above-mentioned weighed positive electrode plate, weigh the weight of the positive electrode current collector, and record it as M0. The single-sided coating weight of the positive electrode active material layer = (M1 - M0) / S1.

[0173] According to some embodiments of the present application, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one or two of a carbon-based material and a silicon-based material. Thus, the energy density and cycle performance of the battery cell are improved.

[0174] According to some embodiments of the present application, the carbon-based material includes graphite. Thus, the cycle performance of the battery cell is improved.

[0175] According to some embodiments of the present application, the graphite is secondary particles formed by aggregation of primary particles, and at least part of the surface of the secondary particles has a second coating material, and the second coating material includes amorphous carbon. Secondary particles refer to particles formed by aggregation of two or more primary particles.

[0176] In this article, amorphous carbon refers to a transitional carbon material with a very low degree of graphitization crystallization, approximately an amorphous form (or a structure without a fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source, which has more end faces and defects and more lithium ion sites.

[0177] Secondary particles can enhance the migration rate of lithium ions, improve the lithium ion transport performance, facilitate the insertion and extraction of lithium ions, and contribute to enhancing the ionic conductivity of the material. The second coating material includes amorphous carbon, which can improve the conductivity of the composite graphite particles. The secondary particles in the core and the coating layer of amorphous carbon jointly improve the electron conduction and ion conduction properties of the material, helping to enhance the fast charging performance of the battery cell.

[0178] According to some embodiments of the present application, based on the total mass of the graphite, the mass proportion of the second coating material can be 2% - 5%. For example, it can be 2%, 3%, 4%, 5%, etc., or it can be a range composed of any of the above values. Thus, while improving the cycle performance of the battery cell, the energy density of the battery cell is increased.

[0179] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite can be 8.5μm - 13.8μm. For example, it can be 8.5μm, 9.5μm, 10.5μm, 11.5μm, 12.5μm, 13.5μm, 13.8μm, etc., or it can be a range composed of any of the above values. Thus, the volume average particle size of the graphite is relatively small, which can shorten the solid-phase migration path of lithium ions and improve the fast charging ability of the battery cell. At the same time, by making the volume average particle size within the above range, the side reaction between the graphite negative electrode and the electrolyte can also be reduced.

[0180] In the present application, Dv50 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%. For example, referring to the standard GB / T 19077 - 2016 / ISO 13320:2009, it is measured using a laser particle size analyzer (Malvern MasterSize 2000). The specific test process is as follows: Discharge the battery cell to 0% SOC, then disassemble it to take the negative electrode sheet, scrape a certain amount of the powder on the electrode sheet with a blade, and then use deionized water to wash it repeatedly by shaking for 5 - 10 times. After drying, sinter it in a tubular furnace at 400°C for 2h. After sintering, take an appropriate amount of the sample to be measured (the sample concentration should ensure a light transmittance of 8% - 12%), add deionized water, and disperse it ultrasonically to ensure that the sample is completely dispersed. Then, measure the sample according to the standard GB / T19077 - 2016 / ISO 13320:2009.

[0181] According to some embodiments of the present application, the negative electrode active material includes a silicon-based material. Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element can be 0.3% - 5%. For example, it can be 0.3%, 1%, 2%, 3%, 4%, 5%, etc., or it can be a range composed of any of the above values. Thus, the energy density of the battery cell is increased.

[0182] The mass content of silicon element in the negative electrode active material layer has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, the negative electrode sheet is immersed in a solvent such as water, the negative electrode active material is separated from the negative electrode current collector, and each substance in the negative electrode film layer is obtained by suction filtration and used as a test sample. The test sample is analyzed by using an inductively coupled plasma - emission spectrometer of model ICAP7400 produced by Thermo Fisher Scientific Company in the United States, and referring to the standard of GB / T30902 - 2014, the content of silicon element can be obtained.

[0183] According to some embodiments of the present application, the single-sided coating weight of the negative electrode active material layer can be 90mg / 1540.25mm 2 -140mg / 1540.25mm 2 . For example, it can be 90mg / 1540.25mm 2 、110mg / 1540.25mm 2 、125mg / 1540.25mm 2 、140mg / 1540.25mm 2 etc., thereby improving the energy density of the battery cell.

[0184] The present application provides a method for testing the coating weight of the negative electrode active material layer: disassemble the battery cell to obtain the negative electrode sheet. For example, take the single-sided coated negative electrode sheet (if it is a double-sided coated sheet, the negative electrode active material layer on one side can be wiped off first), punch it into small round pieces with an area of S2, weigh it, and record it as M3. Then wipe off the negative electrode active material layer of the weighed negative electrode sheet above, weigh the weight of the negative electrode current collector, and record it as M2. The single-sided coating weight of the negative electrode active material layer = (M3 - M2) / S2.

[0185] According to some embodiments of the present application, along the length direction of the battery cell, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1;

[0186] Along the width direction of the battery cell, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH2,

[0187] wherein, OH1 is greater than or equal to OH2.

[0188] Specifically, refer to Figure 1 and Figure 2, the battery cell includes a housing 11 and an electrode assembly. The length direction of the housing 11 is the length direction of the battery cell, and the width direction of the housing 11 is the width direction of the battery cell. The positive electrode plate includes a positive current collector and a positive active material layer 1212 provided on at least one side of the positive current collector; the negative electrode plate includes a negative current collector and a negative active material layer 1222 provided on at least one side of the negative current collector.

[0189] Reference Figure 2 , along the length direction of the battery cell, the size of the positive active material layer 1212 is OH 11 , the size of the negative active material layer 1222 is OH 21 , the difference between the size of the negative active material layer 1222 and the size of the positive active material layer 1212 is OH1 = OH 21 -OH 11 .

[0190] Reference Figure 2 , along the width direction of the battery cell, the size of the positive active material layer 1212 is OH 12 , the size of the negative active material layer 1222 is OH 22 , the difference between the size of the negative active material layer 1222 and the size of the positive active material layer 1212 is OH2 = OH 22 -OH 12 .

[0191] During fast charging, the current flowing through the electrode plate near the tab is large, the temperature is higher, the lithium ion migration rate is faster than other parts, and lithium deposition is likely to occur. By making the size of the negative active material layer larger than that of the positive active material layer, more negative active material layers can receive lithium ions, improving lithium deposition. And since the lithium ion diffusion path is longer in the length direction of the battery cell, by making OH1 greater than or equal to OH2, more negative active material layers can receive lithium ions in the length direction, reducing the risk of lithium ion precipitation at the edge.

[0192] According to some embodiments of the present application, 1 mm ≤ OH1 ≤ 4 mm. For example, it can be 1 mm, 2 mm, 3 mm, 4 mm, etc., or it can be a range composed of any of the above values.

[0193] According to some embodiments of the present application, 1 mm ≤ OH2 ≤ 3 mm. For example, it can be 1 mm, 2 mm, 3 mm, etc., or it can be a range composed of any of the above values.

[0194] Thus, while increasing the energy density of the battery cell, lithium deposition at the negative electrode is reduced.

[0195] In the present application, the sizes of the positive active material layer and the negative active material layer can be measured by a caliper.

[0196] According to some embodiments of the present application, the positive electrode sheet is provided with a positive electrode tab, and the negative electrode sheet is provided with a negative electrode tab, the positive electrode tab extends along the length direction of the positive electrode sheet or along its width direction, and the negative electrode tab extends along the length direction of the negative electrode sheet or along its width direction. Thus, the current transmission efficiency is improved, the resistance of the battery cell is reduced, and the rate performance of the battery cell is improved.

[0197] refer to Figure 3 , along the length direction of the positive electrode sheet 121, only one positive electrode ear 1210 extends out, referring to Figure 4 A positive electrode tab 1210 extends from each end of the positive electrode sheet 121 along the length direction.

[0198] refer to Figure 5 , only one positive electrode tab 1210 extends along the width direction of the positive electrode sheet 121, referring to Figure 6 A positive electrode ear 1210 extends from each end of the positive electrode sheet 121 along the width direction.

[0199] refer to Figure 7 , along the length direction of the negative electrode plate 122, only one negative electrode tab 1220 extends out, referring to Figure 8 A negative electrode tab 1220 extends from each of the two ends of the negative electrode sheet 122 along the length direction.

[0200] refer to Figure 9 , only one negative electrode tab 1220 extends along the width direction of the negative electrode plate 122, referring to Figure 10 A negative electrode tab 1220 extends from each of the two ends of the negative electrode sheet 122 in the width direction.

[0201] According to some embodiments of the present application, the electrode assembly further comprises a separator, and the porosity of the separator is 20%-70%. For example, it can be 20%, 30%, 40%, 50%, 60%, 70%, etc., or can be a range composed of any of the above values. Thus, the transmission efficiency of lithium ions is improved and the rate performance of the battery cell is improved. According to some embodiments of the present application, the porosity of the separator is 35%-60%.

[0202] In this application, porosity refers to the percentage of the pore volume in the separator to the total volume of the separator. The porosity can be tested in accordance with the standard GB / T 36363-2018 "Polyolefin separator for battery monomers". It should be noted that the actual test process can be slightly different from the standard test process to obtain a more accurate test value based on the differences in test instruments, test errors, and in order to eliminate the test effects on porosity as much as possible.

[0203] According to some embodiments of the present application, with reference to Figure 11 , the separator membrane 123 includes: a base film 1231; a first functional layer 1232 located on at least one side of the base film 1231, the first functional layer 1232 including a first inorganic substance; and a second functional layer 1233 located on a side of the first functional layer 1232 away from the base film 1231, the second functional layer 1233 including a second inorganic substance and a non-fluoropolymer. Thereby, the heat resistance of the separator membrane is improved, and the safety of the battery cell is improved.

[0204] According to some embodiments of the present application, the non-fluoropolymer includes an acrylate copolymer. Thereby, the adhesiveness of the non-fluoropolymer is improved, and the risk of peeling off of the second functional layer is reduced.

[0205] According to some embodiments of the present application, the first inorganic substance and the second inorganic substance each independently include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Thereby, the heat resistance of the separator membrane is improved, and the safety of the battery cell is improved.

[0206] According to some embodiments of the present application, the electrode assembly further includes a separator membrane, and the thickness of the separator membrane is 4 μm - 12 μm. For example, it can be 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, etc., or it can be a range composed of any of the above values. Thereby, while reducing the short circuit between the positive and negative electrodes, the volume occupied by the separator membrane in the battery cell is reduced, and the energy density of the battery cell is improved. According to some embodiments of the present application, the thickness of the separator membrane is 5 μm - 12 μm.

[0207] In the present application, the thickness of the base film can be tested by a micrometer.

[0208] According to some embodiments of the present application, the battery cell includes a housing and a cover assembly, the cover assembly is disposed at at least one end of the housing, the housing and the cover assembly define a receiving cavity, and the electrode assembly is disposed in the receiving cavity, with reference to Figure 1 , the battery cell includes a housing 11, and the thickness of the housing 111 on the large surface of the battery cell is 0.1 mm - 0.5 mm. Thereby, the energy density of the battery cell is improved.

[0209] As an example, the thickness of the housing 111 on the large surface can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, etc., or it can be a range composed of any of the above values. According to some embodiments of the present application, the thickness of the housing can be 0.2 mm - 0.35 mm. Thereby, the energy density of the battery cell is improved.

[0210] According to some embodiments of the present application, the cover plate assembly includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly and the second cover plate assembly are disposed at two ends of the housing in the length direction or the width direction. The first cover plate assembly includes a first cover plate and a first electrode terminal, and the second cover plate assembly includes a second cover plate and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite. Thereby, during charging, the temperature rise of the battery cell is reduced, and further the impedance of the battery cell is reduced.

[0211] According to some embodiments of the present application, referring to Figure 12 , the battery cell 1 includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly includes a first cover plate, a first electrode terminal 131, and a third electrode terminal 133. The polarities of the first electrode terminal 131 and the third electrode terminal 133 are opposite. The second cover plate assembly includes a second cover plate, a second electrode terminal 132, and a fourth electrode terminal 134. The polarities of the second electrode terminal 132 and the fourth electrode terminal 134 are opposite.

[0212] According to some embodiments of the present application, the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S, and it satisfies 150 mm 2 ≤ S ≤ 1000 mm 2 . Thereby, the overcurrent capacity of the battery cell is improved, the heat generation of the electrode terminal is reduced, the internal resistance of the battery cell is reduced, and the cycle performance of the battery cell is improved.

[0213] In the present application, the minimum cross-sectional area of the first electrode terminal refers to the minimum cross-sectional area of the first electrode terminal along the direction perpendicular to the current flow direction, and the minimum cross-sectional area of the second electrode terminal refers to the minimum cross-sectional area of the second electrode terminal along the direction perpendicular to the current flow direction.

[0214] In the present application, when testing the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal, it can be calculated according to the shape of the minimum cross-section and its area calculation formula. For example, if the minimum cross-section of the electrode terminal is circular, the minimum cross-sectional area can be obtained by measuring the radius of the circle. If the minimum cross-section is square, the minimum cross-sectional area can be obtained by measuring the length and width of the square.

[0215] As an example, the minimum cross-sectional area S of the first electrode terminal and / or the second electrode terminal can be 150 mm 2 , 300 mm 2 , 450 mm 2 , 600 mm 2 , 750 mm 2 , 900 mm 2 , 1000 mm 2etc., or can be a range composed of any of the above numerical values.

[0216] According to some embodiments of the present application, the volumetric energy density of the battery cell is 400 Wh / L - 530 Wh / L.

[0217] In the present application, when testing the volumetric energy density of the battery cell, the battery cell is placed at 25°C, charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V to 0.05C, and left standing for 30 min; discharged at a constant current of 0.33C to 2.0V, and the discharge capacity A0 at this time is recorded, unit: Ah; the length, width, and height of the battery cell are measured using a caliper, and the volume V0 of the single cell battery is calculated, unit: L; the volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0218] The second aspect of the present application provides a battery device, including the battery cell provided in the first aspect of the present application, and the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0219] The third aspect of the present application provides an electrical device, including the battery cell provided in the first aspect of the present application or the battery device provided in the second aspect of the present application, and the battery cell or the battery device provides electrical energy for the electrical device.

[0220] The electrical device may include mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0221] As the electrical device, the battery device can be selected according to its usage requirements.

[0222] Figure 13 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, a battery pack or a battery module can be adopted.

[0223] As another example of the device, it can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thin and light, and a battery cell can be used as the power source.

[0224] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will further elaborate in detail in combination with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of them. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes any limitation to this application and its application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

[0225] Embodiment 1

[0226] 1. Preparation of the positive electrode plate

[0227] The positive electrode plate includes a positive current collector, a positive active material layer, and a positive conductive layer. The positive active material layer is disposed on both sides of the positive current collector, and the positive conductive layer is located between the positive current collector and the positive active material layer. The positive current collector is aluminum foil.

[0228] The positive conductive layer on the positive current collector is a film layer formed by uniformly mixing a positive conductive agent, superconducting carbon, a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), and then coating and drying on the surface of the positive current collector. The thickness is 1 μm. The mass content of the positive conductive agent in the positive conductive layer is 40%, and the mass content of the positive binder is 60%.

[0229] The positive active material layer includes a film layer formed by uniformly coating a positive electrode paste (with NMP as the solvent) on the surface of the positive conductive layer, followed by drying and cold pressing. The positive active material layer includes a positive active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black with a mass ratio of 97:2:1.

[0230] The positive active material includes lithium iron phosphate particles and a first coating material. The first coating material coats the surface of the lithium iron phosphate particles. The first coating material includes lithium iron titanium phosphate Li2FeTi(PO4)3 and carbon, and the mass content of carbon element is 1.12%.

[0231] The single-sided coating weight of the positive active material layer is 263 mg / 1540.25 mm 2 .

[0232] The compaction density of the positive active material layer is 2.46 g / cm 3 .

[0233] 2. Preparation of the negative electrode plate

[0234] The negative electrode plate includes a negative current collector, a negative active material layer, and a negative conductive layer. The negative active material layer is disposed on both sides of the negative current collector, and the negative conductive layer is located between the negative current collector and the negative active material layer. The negative current collector is a copper foil.

[0235] The negative conductive layer on the negative current collector is a film layer formed by uniformly mixing a negative conductive agent superconducting carbon, a negative binder styrene-butadiene rubber (SBR), a thickener sodium carboxymethyl cellulose (CMC-Na), and a solvent water, and then coating and drying on the surface of the negative current collector. The thickness is 1 μm. The mass content of the negative conductive agent in the negative conductive layer is 35%, the mass content of the negative binder in the negative conductive layer is 60%, and the mass content of the thickener in the negative conductive layer is 5%.

[0236] The negative active material layer includes a film layer formed by uniformly coating a negative electrode paste (with deionized water as the solvent) on the surface of the negative conductive layer, followed by drying and cold pressing.

[0237] The negative active material layer includes a negative active material, a conductive agent acetylene black, a negative binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose with a mass ratio of 96.5:0.5:2:1. The graphite particles include artificial graphite and a second coating material. The second coating material coats the surface of the artificial graphite, and the mass content of carbon element in the second coating material is 3.5%. The Dv50 of the graphite particles is 11.3 μm.

[0238] The single-sided coating weight of the negative active material layer is 120 mg / 1540.25 mm 2 。

[0239] The compaction density of the negative active material layer is 1.35 g / cm 3 。

[0240] The length of the negative active material layer is 4 mm larger than that of the positive active material layer, and the width of the negative active material layer is 3 mm larger than that of the positive active material layer.

[0241] 3. Separator

[0242] The separator includes a base film and functional layers disposed on both sides of the base film. The base film includes a 7-μm polyethylene film layer with a porosity of 42%;

[0243] The functional layer includes a first functional layer and a second functional layer. The first functional layer includes polyacrylate and alumina particles dispersed on the polyacrylate. The first functional layer is a film layer formed by coating a first slurry on one side of the base film, with a thickness of 1 μm and an average particle size of 10 nm for the alumina particles; among them, the first slurry includes alumina particles and a binder polyacrylate;

[0244] The second functional layer is composed of composite particles formed by polyacrylate and polyvinylidene fluoride (PVDF) particles dispersed on the polyacrylate. The second functional layer is a film layer formed by coating the second slurry on the other side of the base film, with a thickness of 5 μm and the average particle size of the PVDF particles being 10 nm. The second slurry includes polyacrylate and PVDF particles.

[0245] 4. Preparation of the electrolyte

[0246] The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0247] After mixing the components of each organic solvent, the lithium salt and the additive are added to prepare the electrolyte.

[0248] The organic solvent includes a chain carboxylic ester solvent (ethyl acetate) with a mass content of 39%, ethylene carbonate EC with a mass content of 27.3%, and dimethyl carbonate with a mass content of 11.7%. The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0249] The additive includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluorooxalate borate LiDFOB with a mass ratio of 4:2:0.5:0.5.

[0250] The lithium salt includes lithium bis(fluorosulfonyl)imide LiFSI with a mass content of 5% and lithium hexafluorophosphate LiPF6 with a mass content of 10%. The mass content of the lithium salt is calculated based on the mass of the electrolyte.

[0251] 5. Preparation of the battery cell

[0252] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked 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. The electrode assembly is placed in a housing, and positive and negative terminals are provided on the housing. After baking, the electrolyte is injected, and through processes such as vacuum packaging, standing, forming, and shaping, the battery cell is obtained.

[0253] The mass of the electrolyte corresponding to each Ah of the battery cell is 2.45 g.

[0254] The housing is an aluminum shell with a cuboid structure, and the thickness of the shell corresponding to the face with the largest area of the cuboid structure is 0.5 mm.

[0255] Performance testing

[0256] 1. Volume energy density

[0257] The battery cells in the examples and comparative examples were placed at 25 °C, charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V to 0.05C, and left standing for 30 min; discharged at a constant current of 0.33C to 2.0V, and the discharge capacity A0 at this time was recorded, unit: Ah; the length, width, and height of the battery cell were measured using a caliper, and the volume V0 of the single battery was calculated, unit: L; the volume energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0258] 2. Fast charging performance

[0259] At 30 °C, after the battery cells in the examples and comparative examples were cycled 200 times according to their respective charge and discharge strategies, they were then charged to 100% SOC according to the corresponding charging strategy. The negative electrode plate was disassembled, the negative electrode plate was unfolded, the lithium deposition area (grayish-white area) was observed, and the lithium deposition area was measured. The degree of lithium deposition was as follows:

[0260] No lithium deposition: Lithium deposition area < 0.05%.

[0261] Slight lithium deposition: Lithium deposition area < 2%.

[0262] Severe lithium deposition: Lithium deposition area ≥ 2%.

[0263] The battery cell was charged, and the charging steps included the following steps:

[0264] Charge at a constant current of 5.0C from 0% SOC to 40% SOC; charge at a constant current of 4.6C from 40% SOC to 45% SOC; charge at a constant current of 4.3C from 45% SOC to 50% SOC; charge at a constant current of 4.0C from 50% SOC to 55% SOC; charge at a constant current of 3.7C from 55% SOC to 60% SOC; charge at a constant current of 3.4C from 60% SOC to 65% SOC; charge at a constant current of 3.1C from 65% SOC to 70% SOC; charge at a constant current of 2.9C from 70% SOC to 75% SOC; charge at a constant current of 2.7C from 75% SOC to 80% SOC; charge at a constant current of 1.8C from 80% SOC to 85% SOC; charge at a constant current of 1.3C from 85% SOC to 90% SOC; charge at a constant current of 0.7C from 90% SOC to 95% SOC; charge at a constant current of 0.33C from 95% SOC to 98% SOC; charge at a constant current of 0.1C from 98% SOC to 100% SOC.

[0265] The cut-off voltage of the last charging step in the above charging steps was 3.65V.

[0266] The discharge strategy was as follows: Discharge at a constant current of 0.33C to the cut-off voltage, such as 2.0V.

[0267] When performing charge and discharge tests on battery cells, the battery cells can be assembled into a battery device, and the required charge and discharge strategies can be regulated through a battery management system for testing.

[0268] 3. Cycle performance

[0269] At 60 °C, the battery cell is charged at a constant current of 0.8C to a charge cut-off voltage of 3.6V, then charged at a constant current of 0.1C to a charge cut-off voltage of 3.65V, and left standing for 30 min; discharged at a constant current of 1C to 3.1V, and left standing for 30 min. This is one charge and discharge cycle. Repeat the above charge and discharge cycle steps until the cycle capacity retention rate (i.e., C n / C0×100%) is 70%, and record the number of cycles. The more cycles, the better the cycle performance of the battery cell.

[0270] 4. Compaction density of the positive electrode

[0271] Place the battery cell at 25 °C and leave it standing for 2 h. Charge it at a constant current of 1 / 3C to 3.65V, charge it at a constant voltage of 3.65V to 0.05C, leave it standing for 2 h, and then discharge it at a rate of 0.33C to 2.0V. Disassemble the positive electrode from the battery cell. For example, take a single-sided coated positive electrode (if it is a double-sided coated electrode, the positive active material layer on one side can be wiped off first), cut it into small round pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive active material layer of the weighed positive electrode, weigh the weight of the positive current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive active material layer = (M1 - M0) / S1, the thickness of the positive active material layer = H1 - H0, and the compaction density of the positive active material layer = the single-sided coating weight of the positive active material layer / the thickness of the positive active material layer.

[0272] 5. Compaction density of the negative electrode

[0273] The battery cell is placed at 25°C and left standing for 2 h. It is charged at a constant current of 1 / 3C to 3.65 V, and then charged at a constant voltage of 3.65 V to 0.05C. The battery cell is placed at 25°C and left standing for 2 h, and then discharged at a rate of 0.33C to 2.0 V. The negative electrode plate of the battery cell is disassembled. For example, a single-sided coated negative electrode plate is taken (if it is a double-sided coated electrode plate, the negative electrode active material layer on one side can be wiped off first), and it is punched into small round pieces with an area of S2, weighed, and recorded as M3. Its thickness H3 is measured. Then, the negative electrode active material layer of the above-mentioned weighed negative electrode plate is wiped off, and the weight of the negative electrode current collector is weighed and recorded as M2. Its thickness H2 is measured. The single-sided coating weight of the negative electrode active material layer = (M3 - M2) / S2, the thickness of the negative electrode active material layer = H3 - H2, and the tap density of the negative electrode active material layer = the single-sided coating weight of the negative electrode active material layer / the thickness of the negative electrode active material layer.

[0274] 5. Mass of electrolyte corresponding to each Ah of the battery cell

[0275] ① Take the battery cell and weigh its mass M0; ② Disassemble the battery cell, pour out the free electrolyte, and take out solid components such as electrode plates, separator membranes, mechanical parts, and adhesive tapes; ③ Soak and clean the solid components such as electrode plates, separator membranes, mechanical parts, and adhesive tapes with dimethyl carbonate (DMC) respectively for 24 h, and wash repeatedly more than 3 times; ④ After cleaning, place the solid components such as electrode plates, separator membranes, mechanical parts, and adhesive tapes in an oven until completely dried; ⑤ Weigh the total mass of the solid components such as electrode plates, separator membranes, mechanical parts, and adhesive tapes, and record the mass as M1; ⑥ The mass of electrolyte under the rated capacity of 1 Ah per unit cell of the battery cell = (M0 - M1) / a. a = the rated capacity of the battery cell, in units of Ah.

[0276] 6. Mass fraction of lithium fluorosulfonylimide and lithium hexafluorophosphate

[0277] The test of the content of lithium fluorosulfonylimide salt and lithium hexafluorophosphate can refer to the standard JY / T 020-2002 General Rules for Ion Chromatographic Analysis Methods. For example, freshly prepared electrolyte can be taken as a sample, or free electrolyte from a fresh battery can be taken as a sample, or a battery cell that has been discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell can be taken as a sample, and the ion chromatographic analysis method is used for detection. The inorganic ion chromatogram is tested, the corresponding inorganic species are compared according to the position of the chromatographic peak, and the percentage of the content of the corresponding inorganic ions is calculated according to the peak area, and then the ratio of the mass fraction of lithium fluorosulfonylimide to the mass fraction of lithium hexafluorophosphate is calculated.

[0278] Comparative Example 1

[0279] The preparation method of the battery cell is the same as that of Example 1, except that the tap density of the positive electrode plate is 2.4 g / cm 3 .

[0280] Example 2

[0281] The preparation method of the battery cell is the same as that of Example 1, except that the tap density of the positive electrode plate is 2.7 g / cm 3 .

[0282] Example 3

[0283] The preparation method of the battery cell is the same as that of Example 1, except that the tap density of the positive electrode plate is 2.8 g / cm 3 .

[0284] Comparative Example 2

[0285] The preparation method of the battery cell is the same as that of Example 1, except that the tap density of the positive electrode plate is 2.85 g / cm 3 .

[0286] Comparative Example 3

[0287] The preparation method of the battery cell is the same as that of Example 1, except that the tap density of the negative electrode plate is 1.1 g / cm 3 .

[0288] Example 4

[0289] The preparation method of the battery cell is the same as that of Example 1, except that the tap density of the negative electrode plate is 1.25 g / cm 3 .

[0290] Example 5

[0291] The preparation method of the battery cell is the same as that of Example 1, except that the tap density of the negative electrode plate is 1.5 g / cm 3 .

[0292] Comparative Example 4

[0293] The preparation method of the battery cell is the same as that of Example 1, except that the tap density of the negative electrode plate is 1.6 g / cm 3 .

[0294] The detailed differences and test results of the battery cells in Examples 1 - 5 and Comparative Examples 1 - 4 are shown in Table 1.

[0295] Table 1

[0296]

[0297] As can be seen from Table 1, when the mass of the electrolyte corresponding to each Ah of the battery cell is within the range to be protected in the present application, the volumetric energy density of the battery cell can be improved by controlling the tap density of the positive electrode plate and the negative electrode plate. And when the tap density of the positive electrode plate is 2.46 g / cm 3 - 2.8 g / cm 3 and the tap density of the negative electrode plate is 1.3 g / cm 3 - 1.5 g / cm 3 , since the electrolyte contains both lithium fluorosulfonylimide and lithium hexafluorophosphate and the ratio of their mass ratios is within a suitable range, a battery cell with good cycling performance can be obtained with less electrolyte. It shows that when the tap densities of the positive electrode plate and the negative electrode plate are within a suitable range, by controlling the contents of lithium fluorosulfonylimide and lithium hexafluorophosphate, the generation of HF can be reduced, the consumption of the electrolyte and additives can be decreased, and a battery cell with both high energy density and good cycling and fast charging performance can be obtained.

[0298] Comparative Example 5

[0299] The preparation method of the battery cell is the same as that of Example 2, except that the tap density of the positive electrode plate is 2.8 g / cm 3 , and the mass of the electrolyte corresponding to each Ah of the battery cell is 2.1 g.

[0300] Example 6

[0301] The preparation method of the battery cell is the same as that of Example 2, except that the tap density of the positive electrode plate is 2.8 g / cm 3 , and the mass of the electrolyte corresponding to each Ah of the battery cell is 2.2 g.

[0302] Example 7

[0303] The preparation method of the battery cell is the same as that of Example 2, except that the mass of the electrolyte corresponding to each Ah of the battery cell is 2.8 g.

[0304] The test results of the battery cells in Comparative Example 5, Example 6 and Example 7 are shown in Table 2.

[0305] Table 2

[0306]

[0307] As can be seen from Table 2, when the compaction density of the positive electrode sheet and the negative electrode sheet is within the range to be protected in this application, and the electrolyte contains both lithium fluorosulfonylimide and lithium hexafluorophosphate, as the mass of the electrolyte corresponding to each Ah of the battery cell increases, the cycling performance of the battery cell gradually improves. However, the volumetric energy density of the battery cell gradually decreases. When the mass of the electrolyte corresponding to each Ah of the battery cell is greater than 3 g, the energy density will continue to decrease. When the mass of the electrolyte corresponding to each Ah of the battery cell is 2.2 g - 3 g, the battery cell has both a relatively high volumetric energy density and good cycling performance.

[0308] Comparative Example 6

[0309] The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of LiFSI is 1%, the mass fraction of LiPF6 is 14%, and the ratio of the mass fractions of LiFSI and LiPF6 is 0.1.

[0310] Example 9

[0311] The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of LiFSI is 4%, the mass fraction of LiPF6 is 11%, and the ratio of the mass fractions of LiFSI and LiPF6 is 0.4.

[0312] Example 10

[0313] The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of LiFSI is 6%, the mass fraction of LiPF6 is 9%, and the ratio of the mass fractions of LiFSI and LiPF6 is 0.7.

[0314] Comparative Example 7

[0315] The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of LiFSI is 9%, the mass fraction of LiPF6 is 6%, and the ratio of the mass fractions of LiFSI and LiPF6 is 1.5.

[0316] The test results of the battery cells in Comparative Example 6, Example 9, Example 10, and Comparative Example 7 are shown in Table 3.

[0317] Table 3

[0318]

[0319] As can be seen from Table 3, by adjusting the contents of LiFSI and LiPF6 in the electrolyte, the ratio of the content of LiFSI to the content of LiPF6 can be adjusted. When the content of LiFSI is low and the content of LiPF6 is high, LiPF6 is prone to hydrolysis to form HF, which corrodes the SEI film and reduces the cycle performance of the battery cell. When the content of LiFSI is high and the content of LiPF6 is low, although the cycle performance of the battery cell can be improved, excessive LiFSI will deteriorate the safety of the battery cell.

[0320] Example 11

[0321] The preparation method of the battery cell is the same as that of Example 2, except that the lithium fluorosulfonylimide is lithium bis(trifluoromethanesulfonyl)imide.

[0322] Example 12

[0323] The preparation method of the battery cell is the same as that of Example 2, except that the lithium fluorosulfonylimide is lithium perfluorobutanesulfonylimide.

[0324] The test results of the battery cells in Example 2, Example 11, and Example 12 are shown in Table 4.

[0325] Table 4

[0326]

[0327] As can be seen from Table 4, adding different types of lithium fluorosulfonylimide to the electrolyte and controlling the ratio of the mass fraction of lithium fluorosulfonylimide to LiPF6 can improve the cycle performance of the battery cell.

[0328] Example 13

[0329] The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of dimethyl carbonate is 14.2%, the mass fraction of VC is 2%, and the mass fraction of FEC is 1.5%.

[0330] Example 14

[0331] The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of dimethyl carbonate is 9.7%, the mass fraction of VC is 5%, and the mass fraction of FEC is 3%.

[0332] Example 15

[0333] The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of VC is 2.5% and the mass fraction of FEC is 3.5%.

[0334] The test results of the battery cells in Example 2, Example 13 - Example 15 are shown in Table 5.

[0335] Table 5

[0336]

[0337] As can be seen from Table 5, by adjusting the content of carbonate additives in the electrolyte, the cycle performance of the battery cell can be improved, indicating that adjusting the content of carbonate additives forms a more stable SEI film, thereby reducing the side reactions between the electrolyte and the electrode surface.

[0338] Example 16

[0339] The preparation method of the battery cell is the same as that of Example 2, except that the mass ratio of EC is 18%, dimethyl carbonate is not contained, and the mass ratio of ethyl acetate is 60%.

[0340] Example 17

[0341] The preparation method of the battery cell is the same as that of Example 2, except that the carboxylic ester solvent is methyl formate, the mass ratio of VC is 5%, and the mass ratio of FEC is 1%.

[0342] Example 18

[0343] The preparation method of the battery cell is the same as that of Example 2, except that the mass ratio of ethyl acetate is 10.2% and the mass ratio of ES is 2%.

[0344] Example 19

[0345] The preparation method of the battery cell is the same as that of Example 2, except that the sulfur-containing additive is vinylene sulfate.

[0346] The test results of the battery cells in Examples 16 - 19 are shown in Table 6.

[0347] Table 6

[0348]

[0349] As can be seen from Table 6, when the compaction density of the positive electrode and the negative electrode, the ratio of the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate, and the content of the electrolyte are all within the ranges proposed in this application, the cycle performance of the battery cell can be further optimized by adjusting the types and contents of carbonate solvents and carboxylic ester solvents in the electrolyte. The carbonate solvent can increase the dielectric constant of the electrolyte, and the carboxylic ester solvent has a small molecular weight and can reduce the viscosity of the electrolyte, thereby further improving the cycle performance and fast charging performance of the battery cell.

[0350] Example 20

[0351] The preparation method of the battery cell is the same as that of Example 2, except that the mass ratio of dimethyl carbonate is 11.2% and the mass ratio of lithium salt additive is 1%.

[0352] Example 21

[0353] The preparation method of the battery cell is the same as that of Example 2, except that the mass ratio of VC is 5%, the mass ratio of FEC is 1%, and the lithium salt additive is lithium difluorophosphate.

[0354] The test results of the battery cells in Example 2, Example 20, and Example 21 are shown in Table 7.

[0355] Table 7

[0356]

[0357] It can be seen from Table 7 that when the compaction density of the positive electrode plate and the negative electrode plate, the ratio of the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate, and the content of the electrolyte are all within the ranges proposed in this application, the cycle performance of the battery cell can be further improved by adjusting the content and type of the lithium salt additive, that is, the lithium salt additive can form a stable SEI film on the surface of the negative electrode, thereby reducing the side reaction between the electrolyte and the electrode surface.

Claims

1. A battery cell, characterized in that, It includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. Among them, The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate. The tap density of the positive electrode sheet is 2.46 g / cm 3 -2.8 g / cm 3 ; The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector, and the tap density of the negative electrode sheet is 1.25 g / cm 3 -1.5 g / cm 3 ; the electrolyte includes lithium fluorosulfonylimide and lithium hexafluorophosphate. Based on the total mass of the electrolyte, the ratio of the mass percentage of lithium fluorosulfonylimide to the mass percentage of lithium hexafluorophosphate is 0.4 - 0.8; the mass of the electrolyte corresponding to each Ah of the battery cell is 2.2 g - 3 g.

2. The battery cell according to claim 1, characterized in that, The tap density of the positive electrode sheet is 2.65 g / cm 3 - 2.8 g / cm 3 .

3. The battery cell according to claim 1 or 2, characterized in that, Based on the total mass of the electrolyte, the mass percentage of lithium fluorosulfonylimide is 4% - 8%.

4. The battery cell according to claim 1 or 2, characterized in that, Based on the total mass of the electrolyte, the mass percentage of lithium hexafluorophosphate is 8% - 12%.

5. The battery cell according to claim 1 or 2, characterized in that, The lithium fluorosulfonylimide includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium perfluorobutanesulfonylimide.

6. The battery cell according to claim 1 or 2, characterized in that, The electrolyte further includes a solvent. The solvent includes one or two of carbonate solvents and carboxylate solvents.

7. The battery cell according to claim 6, wherein The carbonate solvents include one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

8. The battery cell according to claim 6, characterized in that, The carboxylate solvents include the compound shown in Formula I: Formula I, where R5 includes any one of a hydrogen atom, a halogen atom, an alkyl group with 1 - 5 carbon atoms, and a halogenated alkyl group with 1 - 5 carbon atoms, and R6 includes any one of an alkyl group with 1 - 5 carbon atoms and a halogenated alkyl group with 1 - 5 carbon atoms.

9. The battery cell according to claim 6, characterized in that, The carboxylate solvents include one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

10. The battery cell according to claim 6, wherein, Based on the total mass of the electrolyte, the mass percentage of the carbonate solvents is 20% - 70%.

11. The battery cell according to claim 6, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the carboxylate solvents is 10% - 60%.

12. The battery cell according to claim 1 or 2, characterized in that, The electrolyte further includes an additive. The additive includes one or more of carbonate additives, sulfur - containing additives, and lithium salt additives.

13. The battery cell according to claim 12, wherein The carbonate additives include one or more of vinylene carbonate and ethylene carbonate derivatives.

14. The battery cell according to claim 13, characterized in that The ethylene carbonate derivatives include the compound shown in Formula II, Formula II, where R1, R2, R3, and R4 each independently include any one of a hydrogen atom, a halogen atom, an alkyl group with 1 - 5 carbon atoms, and a halogenated alkyl group with 1 - 5 carbon atoms, and R1, R2, R3, and R4 are not simultaneously hydrogen atoms.

15. The battery cell according to claim 13 or 14, characterized in that, The ethylene carbonate derivatives include at least one of the compounds shown in Formula II - 1, Formula II - 2, and Formula II - 3: Formula II - 1, Formula II - 2, Formula II - 3.

16. The battery cell according to claim 13 or 14, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the carbonate additives is 3% - 8%.

17. The battery cell according to claim 13 or 14, characterized in that, The mass percentage of vinylene carbonate is 2% - 5%.

18. The battery cell according to claim 13 or 14, characterized in that, The mass percentage of the ethylene carbonate derivatives is 0% - 4%.

19. The battery cell according to claim 13 or 14, characterized in that, The mass percentage of the ethylene carbonate derivatives is 1.5% - 3.5%.

20. The battery cell according to claim 12, wherein The sulfur - containing additives include one or more of ethylene sulfate, bis(ethylene sulfate), 1,3 - propane sultone, butylene sulfite, ethylene sulfite, and methylene methyl disulfonate.

21. The battery cell according to claim 20, wherein, Based on the total mass of the electrolyte, the mass percentage of the sulfur - containing additives is 0 - 2%.

22. The battery cell according to claim 20 or 21, characterized in that, Based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0.5% - 2%.

23. The battery cell according to claim 12, characterized in that, The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

24. The battery cell according to claim 12, characterized in that, Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0 - 1%.

25. The battery cell according to claim 12, characterized in that, Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% - 1%.

26. The battery cell according to claim 1 or 2, characterized in that, The lithium-containing phosphate includes: a matrix; a first coating material located on at least part of the surface of the matrix, and the first coating material contains carbon.

27. The battery cell according to claim 26, characterized in that, Based on the total mass of the lithium-containing phosphate, the mass proportion of the carbon element is 0.8% - 2.3%.

28. The battery cell according to claim 26, wherein The first coating material includes the compound shown in Formula III: Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula III where 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn.

29. The battery cell according to claim 26, wherein The matrix includes the compound shown in Formula IV: Li x1 A y1 Me a1 M2 b1 P 1-c1 X c1 Y z1 Formula IV where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; where A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M2 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, and La; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

30. The battery cell according to claim 26, wherein The matrix includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

31. The battery cell according to claim 1 or 2, characterized in that, The powder tap density of the positive electrode active material under 30,000 N is 2.43 g / cm 3 -2.85 g / cm 3 .

32. The battery cell according to claim 1 or 2, characterized in that, The single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 - 350 mg / 1540.25 mm 2 .

33. The battery cell according to claim 1 or 2, characterized in that, The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one or two of a carbon-based material and a silicon-based material.

34. The battery cell according to claim 33, characterized in that, The carbon-based material includes graphite.

35. The battery cell according to claim 34, wherein The graphite is secondary particles formed by aggregation of primary particles, and at least part of the surface of the secondary particles has a second coating material, and the second coating material includes amorphous carbon.

36. The battery cell according to claim 35, wherein Based on the total mass of the graphite, the mass proportion of the second coating material is 2% - 5%.

37. The battery cell according to any one of claims 34-36, characterized in that, The volume average particle size Dv50 of the graphite is 8.5 μm - 13.8 μm.

38. The battery cell according to claim 33, wherein, The negative electrode active material includes a silicon-based material. Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 0.3% - 5%.

39. The battery cell according to claim 33, wherein The single-sided coating weight of the negative electrode active material layer is 90 mg / 1540.25 mm 2 -140 mg / 1540.25 mm 2 .

40. The battery cell according to claim 1 or 2, characterized in that, Along the length direction of the battery cell, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1; Along the width direction of the battery cell, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH2, where OH1 is greater than or equal to OH2.

41. The battery cell according to claim 40, characterized in that, 1 mm ≤ OH1 ≤ 4 mm, 1 mm ≤ OH2 ≤ 3 mm.

42. The battery cell according to claim 1 or 2, characterized in that, A positive electrode tab is provided on the positive electrode plate, and a negative electrode tab is provided on the negative electrode plate. The positive electrode tab extends along the length direction or the width direction of the positive electrode plate, and the negative electrode tab extends along the length direction or the width direction of the negative electrode plate.

43. The battery cell according to claim 1 or 2, characterized in that, The electrode assembly further includes a separator, and the porosity of the separator is 20% - 70%.

44. The battery cell according to claim 43, wherein, The porosity of the separator is 35% - 60%.

45. The battery cell according to claim 43, characterized in that, The separator includes: A base film; A first functional layer located on at least one side of the base film, and the first functional layer includes a first inorganic substance; A second functional layer located on the side of the first functional layer away from the base film, and the second functional layer includes a second inorganic substance and a non-fluoropolymer.

46. The battery cell according to claim 45, wherein, The non-fluoropolymer includes an acrylate copolymer.

47. The battery cell according to claim 45 or 46, characterized in that, The first inorganic substance and the second inorganic substance each independently include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

48. The battery cell according to claim 45 or 46, characterized in that, The thickness of the base film is 4 μm - 12 μm.

49. The battery cell according to claim 1 or 2, characterized in that, The battery cell includes a housing and a cover assembly. The cover assembly is provided at at least one end of the housing. The housing and the cover assembly define a receiving cavity. The electrode assembly is disposed in the receiving cavity. The thickness of the housing on the large surface of the battery cell is 0.1 mm - 0.5 mm.

50. The battery cell according to claim 49, wherein, The thickness of the housing on the large surface of the battery cell is 0.2 mm - 0.35 mm.

51. The battery cell according to claim 49, characterized in that, The cover assembly includes a first cover assembly and a second cover assembly. The first cover assembly and the second cover assembly are provided at both ends of the housing in the length direction or the width direction. The first cover assembly includes a first cover and a first electrode terminal. The second cover assembly includes a second cover and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite.

52. The battery cell according to claim 51, wherein The minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S, and they independently satisfy 150 mm 2 ≤ S ≤ 1000 mm 2 .

53. The battery cell according to claim 1 or 2, characterized in that, The volume energy density of the battery cell is 400 Wh / L - 530 Wh / L.

54. A battery device, characterized in that, Including the battery cell according to any one of claims 1 - 53, the battery device is at least one of a battery module, a battery pack, and an energy storage device.

55. An electrical device, characterized in that Including the battery cell according to any one of claims 1 - 53 or the battery device according to claim 54, the battery cell or the battery device provides electrical energy for the electrical equipment.

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