Battery monomer, battery device and electric equipment

Abstract

The invention provides a battery monomer, a battery device and electric equipment, the battery monomer comprises an electrode assembly and an electrolyte, the electrode assembly comprises a positive pole piece and a negative pole piece, the positive pole piece comprises a positive current collector and a positive active material layer arranged on at least one side of the positive current collector, and the positive active material layer comprises a positive active material; the positive electrode active material comprises lithium-containing phosphate, and the compaction density of the positive electrode plate is 2.46 g / cm < 3 >-2.8 g / cm < 3 >; the negative pole piece comprises a negative current collector and a negative active material layer arranged on at least one side of the negative current collector, and the compaction density of the negative pole piece is 1.25 g / cm < 3 >-1.5 g / cm < 3 >; the electrolyte comprises fluorine-containing lithium sulfimide and lithium hexafluorophosphate, and based on the total mass of the electrolyte, the ratio of the mass ratio of the fluorine-containing lithium sulfimide to the mass ratio of the lithium hexafluorophosphate is 0.4-0.8; and the mass of the electrolyte corresponding to each Ah of the battery monomer is 2.2-3g.

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 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 multiple fields such as military equipment and aerospace. During the assembly process of battery cells, the energy density of battery cells can be increased by increasing the volume occupied by the electrode assembly and reducing the volume occupied by the electrolyte. 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 sheet and a negative electrode sheet. The positive electrode sheet 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 sheet is 2.46 g / cm 3 - 2.8 g / cm 3 ; The negative electrode sheet 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 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 fraction of lithium fluorosulfonylimide to the mass fraction 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.

[0005] 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 rates of the electrolyte and the additive are decreased, and the lifespan, cycle performance, and fast charging performance of the battery cell are improved.

[0006] 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.

[0007] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage 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.

[0008] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of lithium hexafluorophosphate is 8% - 12%. Thus, the viscosity of the electrolyte is reduced, and the transport rate of lithium ions is increased.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] According to some embodiments of the present application, the carboxylate solvent includes a compound represented by Formula I:

[0013] Formula I, wherein, R 5 includes any one of a hydrogen atom, a halogen atom, a C1 - C5 alkyl group, and a C1 - C5 haloalkyl group, and R 6 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.

[0014] 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.

[0015] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass ratio of the carbonate solvent is 20% - 70%. Thus, the ionic conductivity of the electrolyte is improved.

[0016] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass ratio 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.

[0017] 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. Thus, the cycle performance and fast charging performance of the battery cell are improved.

[0018] 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.

[0019] According to some embodiments of the present application, the ethylene carbonate derivative includes the compound shown in Formula II,

[0020] Formula II, wherein, R 1 , R 2 , R 3 , R 4 each independently includes any one of a hydrogen atom, a halogen atom, an alkyl group having 1 - 5 carbon atoms, and a halogenated alkyl group having 1 - 5 carbon atoms, and R 1 , R 2 , R 3 , R 4 are not simultaneously hydrogen atoms. Thus, the cycle life of the battery cell is improved.

[0021] 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:

[0022] Formula II-1, Formula II-2, Formula II-3. 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.

[0023] According to some embodiments of the present application, the mass proportion of vinylene carbonate is 2% - 5%. Thereby, a stable SEI film is formed and the lithium ion transport is improved.

[0024] 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.

[0025] 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.

[0026] 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 methanedisulfonate. Thereby, the impedance of the battery cell is reduced and the fast charging performance of the battery cell is improved.

[0027] 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.

[0028] 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.

[0029] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. Thereby, the gas generation of the battery cell under high temperature conditions is reduced.

[0030] 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.

[0031] 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.

[0032] 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 element. Thereby, the conductivity of the lithium-containing phosphate is improved.

[0033] 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 improved.

[0034] According to some embodiments of the present application, the first coating material includes a compound represented by 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. 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.

[0035] According to some embodiments of the present application, the matrix includes a compound represented by 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, 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.

[0036] 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.

[0037] According to some embodiments of the present application, the powder compaction density of the positive electrode active material under 30000N is 2.43g / cm 3 -2.85g / cm 3 . Thereby, the energy density of the battery cell is improved.

[0038] According to some embodiments of the present application, the single-sided coating weight of the positive electrode active material layer is 200mg / 1540.25mm 2 -350mg / 1540.25mm 2 . Thereby, the energy density of the battery cell is improved.

[0039] 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.

[0040] According to some embodiments of the present application, the carbon-based material includes graphite. Thereby, the cycle performance of the battery cell is improved.

[0041] 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.

[0042] 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.

[0043] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 8.5μm-13.8μm. 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.

[0044] 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.

[0045] According to some embodiments of the present application, the single-sided coating weight of the negative electrode active material layer is 90mg / 1540.25mm2 -140 mg / 1540.25 mm 2 Thus, the energy density of the battery cell is increased.

[0046] 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 OH 1 ; 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 OH 2 , wherein, OH 1 is greater than or equal to OH 2 . Thus, while increasing the energy density of the battery cell, the lithium deposition on the negative electrode is reduced.

[0047] According to some embodiments of the present application, 1 mm ≤ OH 1 ≤ 4 mm, 1 mm ≤ OH 2 ≤ 3 mm. Thus, while increasing the energy density of the battery cell, the lithium deposition on the negative electrode is reduced.

[0048] According to some embodiments of the present application, a positive electrode tab is provided on the positive electrode plate, 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. 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.

[0049] According to some embodiments of the present application, the electrode assembly includes a separator, and the porosity of the separator is 20% - 70%. Thus, the transmission efficiency of lithium ions is improved, and the rate performance of the battery cell is improved.

[0050] According to some embodiments of the present application, the porosity of the separator is 35% - 60%. Thus, the transmission efficiency of lithium ions is improved, and the rate performance of the battery cell is improved.

[0051] 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. Thus, the heat resistance of the separator is improved, and the safety of the battery cell is improved.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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 of the large surface of the battery cell is 0.1 mm - 0.5 mm. Thereby, the energy density of the battery cell is improved.

[0056] According to some embodiments of the present application, the thickness of the housing of the large surface of the battery cell is 0.2 mm - 0.35 mm. Thereby, the energy density of the battery cell is improved.

[0057] 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, the temperature rise of the battery cell during charging is reduced, and further the impedance of the battery cell is reduced.

[0058] 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.

[0059] According to some embodiments of the present application, the volume energy density of the battery cell is 400 Wh / L - 530 Wh / L.

[0060] 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.

[0061] The third aspect of the present application provides an electrical device, including the battery cell provided by the first aspect of the present application or the battery device provided by the second aspect of the present application, and the battery cell or the battery device provides electrical energy for the electrical device.

[0062] 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. Description of the Drawings

[0063] 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: Figure 1 is a schematic structural view of a housing according to an embodiment of the present application.

[0064] Figure 2 is a schematic view of the dimensions of a positive electrode active material layer and a negative electrode active material layer according to an embodiment of the present application.

[0065] Figure 3 is a schematic structural view of a positive electrode plate according to an embodiment of the present application.

[0066] Figure 4 is a schematic structural view of a positive electrode plate according to another embodiment of the present application.

[0067] Figure 5 is a schematic structural view of a positive electrode plate according to another embodiment of the present application.

[0068] Figure 6 is a schematic structural view of a positive electrode plate according to another embodiment of the present application.

[0069] Figure 7 is a schematic structural view of a negative electrode plate according to an embodiment of the present application.

[0070] Figure 8 is a schematic structural view of a negative electrode plate according to another embodiment of the present application.

[0071] Figure 9 is a schematic structural view of a negative electrode plate according to another embodiment of the present application.

[0072] Figure 10 is a schematic structural view of a negative electrode plate according to another embodiment of the present application.

[0073] Figure 11 is a schematic structural view of a separator according to an embodiment of the present application.

[0074] Figure 12 It is a schematic structural diagram of a battery cell according to an embodiment of the present application.

[0075] Figure 13 It is a schematic structural diagram of an electrical device according to an embodiment of the present application.

[0076] Description of reference numerals: 1 Battery cell; 11 Housing; 111 Large-surface housing; 121 Positive electrode tab; 1210 Positive electrode ear; 1212 Positive electrode active material layer; 122 Negative electrode tab; 1220 Negative electrode ear; 1222 Negative electrode active material layer; 123 Separator; 1231 Base film; 1232 First functional layer; 1233 Second functional layer. Detailed implementation manners

[0077] 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, and therefore are only examples and cannot be used to limit the protection scope of the present application.

[0078] Referring to "embodiment" herein means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of the present application. The phrase appears in various positions 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 may be combined with other embodiments.

[0079] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0080] If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0081] If there is no special description, all steps of the present application can be carried out in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0082] 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, and 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 monomers in the related technologies cannot meet the requirements of long cycle life and high energy density.

[0083] This application proposes a battery monomer. By increasing the compaction density of the positive and negative electrode sheets, the occupied space of the electrode assembly is increased, and by reducing the electrolyte injection volume, the weight of the battery monomer is reduced, thereby increasing the battery energy density. However, because the particles inside the electrode sheets are more closely packed after increasing the compaction density of the positive and negative electrodes, it is difficult to completely bake out the moisture in the electrode sheets through the process during battery production to control it within a reasonable range. This part of the moisture will slowly be released from the electrode sheets during battery cycling or storage, causing the hydrolysis of lithium hexafluorophosphate in the electrolyte 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 cycling and storage 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 cycling and storage can be reduced, the consumption rate of the electrolyte and additives can be reduced, and the battery monomer 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 lithium ions to diffuse in the high-compaction positive and negative electrode sheets, and improve the fast charging and cycling performance of the monomer battery.

[0084] The battery monomer proposed in this application can be used in electrical equipment that uses the battery monomer as a power source or various energy storage systems that use the battery monomer 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, and electric aircraft toys, etc., and the spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc.

[0085] In the first aspect of the present 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 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 ; 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 ; The electrolyte includes lithium fluorosulfonimide and lithium hexafluorophosphate. Based on the total mass of the electrolyte, the ratio of the mass fraction of lithium fluorosulfonimide to the mass fraction 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.

[0086] 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.

[0087] In the present application, the test method for the mass of the electrolyte at a rated capacity of 1 Ah of the battery cell is as follows: ① Take a battery cell and weigh its mass M 0 ; 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 Immerse and clean the solid components such as electrode tabs, separator membranes, mechanical parts, and adhesive tapes in dimethyl carbonate (DMC) 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 M 1 ; ⑥ The mass of the electrolyte per unit battery rated capacity of 1 Ah of the battery cell = (M 0 - M 1 ) / 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.

[0088] The present application provides a method for testing the tap density of a positive electrode tab: 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 tab from the battery cell. For example, take a single-sided coated positive electrode tab (if it is a double-sided coated tab, the positive electrode active material layer on one side can be wiped off first), and punch it into small round pieces with an area of S 1 and weigh it, record it as M 1 , and measure its thickness H 1 . Then wipe off the positive electrode active material layer of the above-mentioned weighed positive electrode tab, weigh the positive electrode current collector, record it as M 0 , and measure its thickness H 0 . The single-sided coating weight of the positive electrode active material layer = (M 1 - M 0 ) / S 1 , the thickness of the positive electrode active material layer = H 1 - H 0 , 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.

[0089] As an example, the tap density of the positive electrode tab 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 a range composed of any of the above values. Thus, the occupied space of the electrode assembly is increased, and the energy density of the battery cell is increased.

[0090] According to some embodiments of the present application, the tap density of the positive electrode tab can be 2.65 g / cm 3 - 2.8 g / cm 3 .

[0091] The present application provides a method for testing the tap density of a negative electrode tab: 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 tab from the battery cell. For example, take a single-sided coated negative electrode tab (if it is a double-sided coated tab, the negative electrode active material layer on one side can be wiped off first), and punch it into small round pieces with an area of S 2 and weigh it, record it as M 3, measure its thickness H 3 . Then wipe off the negative active material layer of the above-mentioned weighed negative electrode sheet, weigh the weight of the negative current collector, and record it as M 2 , measure its thickness H 2 . The single-sided coating weight of the negative active material layer = (M 3 - M 2 ) / S 2 , the thickness of the negative active material layer = H 3 - H 2 , the tap density of the negative active material layer = the single-sided coating weight of the negative active material layer / the thickness of the negative active material layer.

[0092] As an example, the tap density of the negative electrode sheet can be 1.25 g / cm 3 , 1.3 g / cm 3 , 1.35 g / cm 3 , 1.4 g / cm 3 , 1.45 g / cm 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 tap 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 electrode sheet is reduced. When the mass of the electrolyte corresponding to each Ah of the battery cell is small, the requirements of cycling can also be met.

[0093] 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 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.

[0094] As an example, the ratio of the mass percentage of lithium fluorosulfonimide to the mass percentage 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 percentage of lithium fluorosulfonimide and the mass percentage of lithium hexafluorophosphate within the above range, on the one hand, the generation of HF is reduced, the corrosion of the SEI film is decreased, the consumption of the electrolyte is reduced, and the cycle performance of the battery cell is improved; on the other hand, the viscosity of the electrolyte is decreased, the transmission rate of lithium ions is increased, and the fast charging performance of the battery cell is improved.

[0095] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of lithium fluorosulfonimide 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. Thereby, the generation of HF is reduced, the corrosion of the SEI film is decreased, during the cycle of the battery cell, the consumption of the electrolyte is reduced, and the cycle performance of the battery cell is improved.

[0096] 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 can be a range composed of any of the above values. Thereby, the viscosity of the electrolyte is decreased, the transmission rate of lithium ions is increased, and the fast charging performance of the battery cell is improved.

[0097] According to some embodiments of the present application, the lithium fluorosulfonimide includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium perfluorobutanesulfonimide. Thereby, the generation of HF is reduced, and the corrosion of the SEI film is decreased.

[0098] 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.

[0099] 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 solvent of the electrolyte by gas chromatography.

[0100] According to some embodiments of the present application, the carbonate solvents can 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.

[0101] According to some embodiments of the present application, the carboxylate solvent includes the compound shown in Formula I:

[0102] Formula I, wherein R 5 is any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R 6 is any one of an alkyl group having 1 to 5 carbon atoms and a halogenated alkyl group having 1 to 5 carbon atoms. Thus, the carboxylic acid 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.

[0103] According to some embodiments of the present application, the carboxylic acid ester 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. Thus, the carboxylic acid 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.

[0104] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent can be 20% - 70%, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, etc., or it can be a range composed of any of the above values. Thus, the ionic conductivity of the electrolyte is improved.

[0105] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the carboxylic acid ester solvent is 10% - 60%, for example, it can be 10%, 20%, 30%, 40%, 50%, 60%, etc., or it can be a range composed of any of the above values. By making the content of the carboxylic acid ester 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 reduced, 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.

[0106] 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. Thus, the above types of additives can preferentially decompose on the surfaces of the positive electrode and the negative electrode to form a stable and low-impedance interfacial film, 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.

[0107] According to some embodiments of the present application, the carbonate additive includes one or more of vinylene carbonate (VC) and ethylene carbonate derivatives. Thus, the carbonate additives of the above types can form a stable interfacial film on the electrode surface, reduce the side reactions between the electrolyte and the electrode surface, and improve the cycle life of the battery cell.

[0108] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass ratio of the carbonate additive is 3% - 8%. For example, it can be 3%, 4%, 5%, 6%, 7%, 8%, etc., or it can be a range composed of any of the above values. Thus, 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 reduced.

[0109] According to some embodiments of the present application, the mass ratio of the 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, the reaction activity of vinylene carbonate is relatively high, and a uniform and dense SEI film can be formed on the negative electrode surface during the first charge and discharge process of the battery, improving the stability of the SEI film. Moreover, the SEI film formed by the participation of VC has good ionic conductivity, which can enable lithium ions to be quickly transported between the electrode and the electrolyte, improving the charge and discharge efficiency of the battery.

[0110] According to some embodiments of the present application, the mass ratio 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 ratio 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.

[0111] According to some embodiments of the present application, the ethylene carbonate derivative includes the compound shown in Formula II,

[0112] Formula II, wherein, R 1 、R 2 、R 3 、R 4 each independently 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 R 1 、R 2 、R 3 、R 4 are not simultaneously hydrogen atoms. Thus, the cycle life of the battery cell is improved.

[0113] According to some embodiments of the present application, the ethylene carbonate derivative includes at least one of the compounds represented by Formula II-1, Formula II-2, and Formula II-3:

[0114] Formula II-1, Formula II-2, and Formula II-3.

[0115] 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 methanedisulfonate. Thus, additives of the above types can form a 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 cell, and improve the fast charging performance of the battery cell.

[0116] 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, 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.

[0117] 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 oxidation of the battery cell at high potential to generate sulfur-containing free radicals is reduced, thereby reducing the decomposition of the solvent caused by 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%.

[0118] 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%.

[0119] 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.

[0120] It should be noted that during the charge and discharge of battery cells, when the addition amounts of ethylene carbonate derivatives, sulfur-containing additives, and lithium salt additives are relatively small, and the additives in the electrolyte will be consumed to some extent during formation and charge-discharge cycles, generating relevant components in the SEI film and / or CEI film. When the content of ethylene carbonate derivatives, sulfur-containing additives, and lithium salt additives is tested by gas chromatography after disassembling the battery cell to obtain the electrolyte, the content may be 0.

[0121] Specifically, taking the case where the mass content of ethylene carbonate derivatives is 0 as an example, it may be that no ethylene carbonate derivatives are added to the freshly prepared electrolyte, or the electrolyte obtained after disassembling the battery cell does not contain ethylene carbonate derivatives. This situation may be that no ethylene carbonate derivatives are added to the freshly prepared electrolyte, or a small amount of ethylene carbonate derivatives are added, but they participate in the film-forming reaction of the SEI film during the formation of the battery cell, resulting in a mass content of 0 for ethylene carbonate derivatives during the detection process. Optionally, the freshly prepared electrolyte includes ethylene carbonate derivatives.

[0122] 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 additives in the electrolyte of the battery cell is related to formation, different battery life cycles, or different battery storage states. Therefore, there may be a difference in the content of 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 relevant substances in the corresponding freshly prepared electrolyte based on the performance expression level (such as the number of cycles) and residual content 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) based on the content of the freshly prepared additives, according to the performance requirements of the battery cell, storage environment, etc.

[0123] Therefore, the additive content mentioned in the technical solution of this application can be the content of additives actively added to the freshly prepared electrolyte, or the content of residual additives detected by reverse according to the actual battery state.

[0124] 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.

[0125] 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 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 a range composed of any of the above values. Thus, while improving the electronic conductivity of the lithium-containing phosphate, the influence on lithium ion transport 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.

[0126] According to some embodiments of the present application, 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.

[0127] The compound shown in Formula III has excellent ionic conductivity, and together with the carbon element having excellent conductivity in the first coating material, it improves the conductivity and ionic conductivity of the lithium-containing phosphate, which is beneficial to improving the fast charging performance of the battery.

[0128] According to some embodiments of the present application, 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. Thus, the cycle performance and safety of the battery cell are improved.

[0129] 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 numerical values.

[0130] 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 lithium element content x1 in the positive electrode active material measured is less than 1. At the same time, if a lithium supplement agent is used in 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 lithium element content x 1 is greater than 1.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] As an example, z1 can be 3, 4, 5, etc., or can be a range composed of any of the above numerical values.

[0136] 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.

[0137] 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.

[0138] In this 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 / T 24533-2019. Specifically, a certain amount of cathode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in a UTM7305 type electronic pressure testing machine, pressurized to 3000 kg (equivalent to 30000 N), kept under pressure for 30 s, then the pressure is released, kept for 10 s, and then the powder compaction density of the cathode active material under the action of 30000 N is recorded and calculated.

[0139] According to some embodiments of the present application, the powder compaction density of the cathode active material under 30000 N is 2.48 g / cm 3 -2.8 g / cm 3 . Thus, the energy density and rate performance of the battery cell are improved.

[0140] According to some embodiments of the present application, the single-sided coating weight of the cathode 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.

[0141] The present application provides a method for testing the coating weight of the cathode active material layer: disassemble the cathode electrode sheet from the battery cell. For example, take the single-sided coated cathode electrode sheet (if it is a double-sided coated electrode sheet, the cathode active material layer on one side can be wiped off first), punch it into small round pieces with an area of S 1 , weigh it, and record it as M 1 . Then wipe off the cathode active material layer of the above-mentioned weighed cathode electrode sheet, weigh the weight of the cathode current collector, and record it as M 0 . The single-sided coating weight of the cathode active material layer = (M 1 - M 0 ) / S 1 .

[0142] According to some embodiments of the present application, the negative active material layer includes a negative active material, and the negative 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.

[0143] According to some embodiments of the present application, the carbon-based material includes graphite. Thereby, the cycling performance of the battery cell is improved.

[0144] 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.

[0145] In this article, amorphous carbon refers to a transitional carbon material with a very low degree of graphitization crystallization, similar to 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.

[0146] The secondary particles can improve the migration rate of lithium ions, enhance the transport performance of lithium ions, facilitate the insertion and extraction of lithium ions, and contribute to improving 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 performance and ion conduction performance of the material, contributing to improving the fast charging performance of the battery cell.

[0147] According to some embodiments of the present application, based on the total mass of the graphite, the mass ratio 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. Thereby, while improving the cycling performance of the battery cell, the energy density of the battery cell is also improved.

[0148] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite can be 8.5 μm - 13.8 μm. For example, it can be 8.5 μm, 9.5 μm, 10.5 μm, 11.5 μm, 12.5 μm, 13.5 μm, 13.8 μm, etc., or it can be a range composed of any of the above values. Thereby, 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.

[0149] In this application, Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 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 powder on the electrode sheet with a blade, then use deionized water to wash it repeatedly by shaking 5 - 10 times. After drying, sinter it in a tube 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 at the same time to ensure that the sample is completely dispersed. Then, measure the sample with reference to the standard GB / T19077-2016 / ISO 13320:2009.

[0150] 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 percentage 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. Thereby, the energy density of the battery cell is improved.

[0151] 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, place the negative electrode sheet in a solvent such as water and soak it to separate the negative electrode active material from the negative electrode current collector. Filter the substances in the negative electrode film layer by suction and use it as a test sample. Use an inductively coupled plasma - emission spectrometer of model ICAP7400 from Thermo Fisher Scientific Company in the United States for the test sample, and refer to the standard GB / T30902-2014 to obtain the silicon element content.

[0152] 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, the energy density of the battery cell is improved.

[0153] The present application provides a method for testing the coating weight of a negative electrode active material layer: disassemble the negative electrode plate from a battery cell. For example, take a negative electrode plate with single-sided coating (if it is a double-sided coated plate, the negative electrode active material layer on one side can be wiped off first), and punch it into small circular pieces with an area of S 2 and weigh them, record the weight as M 3 . Then wipe off the negative electrode active material layer of the weighed negative electrode plate above, weigh the weight of the negative electrode current collector, and record it as M 2 . The single-sided coating weight of the negative electrode active material layer = (M 3 - M 2 ) / S 2 .

[0154] 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 OH 1 ; 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 OH 2 , wherein, OH 1 is greater than or equal to OH 2 .

[0155] Specifically, referring 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 electrode current collector and a positive electrode active material layer 1212 provided on at least one side of the positive electrode current collector; the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer 1222 provided on at least one side of the negative electrode current collector.

[0156] Referring to Figure 2 , along the length direction of the battery cell, the size of the positive electrode active material layer 1212 is OH 11 , the size of the negative electrode active material layer 1222 is OH 21 , and the difference between the size of the negative electrode active material layer 1222 and the size of the positive electrode active material layer 1212 is OH 1 = OH 21 - OH 11 .

[0157] Referring to Figure 2 , along the width direction of the battery cell, the size of the positive electrode active material layer 1212 is OH12 The size 1222 of the negative electrode active material layer is OH 22 The difference between the size of the negative electrode active material layer 1222 and the size of the positive electrode active material layer 1212 is OH 2 =OH 22 -OH 12 .

[0158] During fast charging, the current flowing through the electrode tab side of the electrode 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 electrode active material layer larger than the size of the positive electrode active material layer, more negative electrode active material layers can receive lithium ions, improving lithium deposition. And because in the length direction of the battery cell, the lithium ion diffusion path is longer, by making OH 1 greater than or equal to OH 2 , more negative electrode active material layers can receive lithium ions in the length direction, reducing the risk of lithium deposition at the edge.

[0159] According to some embodiments of the present application, 1 mm ≤ OH 1 ≤ 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.

[0160] According to some embodiments of the present application, 1 mm ≤ OH 2 ≤ 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.

[0161] Thus, while increasing the energy density of the battery cell, lithium deposition on the negative electrode is reduced.

[0162] In the present application, the sizes of the positive electrode active material layer and the negative electrode active material layer can be measured by a caliper.

[0163] According to some embodiments of the present application, a positive electrode tab is provided on the positive electrode plate, 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.

[0164] Referring to Figure 3 , only one positive electrode tab 1210 extends along the length direction of the positive electrode plate 121. Referring to Figure 4 , positive electrode tabs 1210 extend from both ends along the length direction of the positive electrode plate 121.

[0165] Referring 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.

[0166] 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.

[0167] 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.

[0168] 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%.

[0169] 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.

[0170] According to some embodiments of the present application, reference Figure 11 The isolation film 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-fluorinated polymer. Thus, the heat resistance of the isolation film is improved, and the safety of the battery cell is improved.

[0171] According to some embodiments of the present application, the non-fluorine polymer includes an acrylic copolymer, thereby improving the adhesion of the non-fluorine polymer and reducing the risk of the second functional layer falling off.

[0172] 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 enhanced.

[0173] According to some embodiments of the present application, the electrode assembly further includes a separator, and the thickness of the separator 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 in the battery cell is reduced, and the energy density of the battery cell is increased. According to some embodiments of the present application, the thickness of the separator is 5 μm - 12 μm.

[0174] In the present application, the thickness of the base film can be tested by a micrometer.

[0175] 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. Refer 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 increased.

[0176] 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 increased.

[0177] 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 of the housing in the length direction or the width direction. The first cover assembly includes a first cover and a first electrode terminal, and 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.

[0178] According to some embodiments of the present application, refer 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.

[0179] 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 150mm 2 ≤S≤1000mm 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.

[0180] 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.

[0181] 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.

[0182] As an example, the minimum cross-sectional area S of the first electrode terminal and / or the second electrode terminal can be 150mm 2 、300mm 2 、450mm 2 、600mm 2 、750mm 2 、900mm 2 、1000mm 2 etc., or can be a range composed of any of the above values.

[0183] According to some embodiments of the present application, the volumetric energy density of the battery cell is 400Wh / L - 530Wh / L.

[0184] 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 minutes; discharged at a constant current of 0.33C to 2.0V, and record the discharge capacity A at this time 0, unit: Ah; Use a caliper to measure the length, width, and height of the battery cell, and calculate the volume V of the single battery cell 0 , unit L; The volume energy density VED of the battery cell = (A 0 × discharge platform voltage) / V 0 , unit Wh / L.

[0185] The second aspect of the present application provides a battery device, including the battery cell provided by 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.

[0186] The third aspect of the present application provides an electrical device, including the battery cell provided by the first aspect of the present application or the battery device provided by the second aspect of the present application. The battery cell or the battery device provides electrical energy for the electrical device.

[0187] The electrical device may include mobile devices (such as mobile phones, laptops, 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.

[0188] As the electrical device, the battery device can be selected according to its usage requirements.

[0189] 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 used.

[0190] Another example of the device 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.

[0191] In order to make the technical problems, technical solutions, and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in combination with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0192] Embodiment 1 1. Preparation of the positive electrode plate 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.

[0193] The positive conductive layer on the positive current collector is a film layer formed by uniformly coating a mixture of a positive conductive agent, superconducting carbon, a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), on the surface of the positive current collector and drying it. 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%.

[0194] 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 and then drying and cold pressing it. 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.

[0195] 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 2 FeTi(PO 4 ) 3 and carbon, and the mass content of carbon element is 1.12%.

[0196] The single-sided coating weight of the positive active material layer is 263 mg / 1540.25 mm 2 .

[0197] The compaction density of the positive active material layer is 2.46 g / cm 3 .

[0198] 2. Preparation of the negative electrode plate 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 copper foil.

[0199] The negative conductive layer on the negative current collector is a film layer formed by uniformly coating a mixture of a negative conductive agent, superconducting carbon, a negative binder, styrene-butadiene rubber (SBR), a thickening agent, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, on the surface of the negative current collector and drying it. 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 thickening agent in the negative conductive layer is 5%.

[0200] The negative electrode active material layer comprises a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer, followed by drying and cold pressing.

[0201] The negative electrode active material layer comprises a negative electrode active material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickening agent, with a mass ratio of 96.5:0.5:2:1. The graphite particles include artificial graphite and a second coating material, which is coated on the surface of the artificial graphite. The mass content of carbon element in the second coating material is 3.5%, and the Dv50 of the graphite particles is 11.3 μm.

[0202] The single-sided coating weight of the negative electrode active material layer is 120 mg / 1540.25 mm 2 。

[0203] The tap density of the negative electrode active material layer is 1.35 g / cm 3 。

[0204] The length of the negative electrode active material layer is 4 mm greater than that of the positive electrode active material layer, and the width of the negative electrode active material layer is 3 mm greater than that of the positive electrode active material layer.

[0205] 3. Separator The separator comprises a base film and functional layers provided on both sides of the base film. The base film comprises a 7-μm polyethylene film layer with a porosity of 42%; The functional layer comprises a first functional layer and a second functional layer. The first functional layer comprises 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 comprises alumina particles and polyacrylate as a binder; The second functional layer is a composite particle formed by polyacrylate and polyvinylidene fluoride (PVDF) particles dispersed on the polyacrylate. The second functional layer is a film layer formed by coating a second slurry on the other side of the base film, with a thickness of 5 μm and an average particle size of 10 nm for the PVDF particles; the second slurry comprises polyacrylate and PVDF particles.

[0206] 4. Preparation of electrolyte The electrolyte comprises an organic solvent, a lithium salt, and an additive.

[0207] After mixing the components of each organic solvent, a lithium salt and an additive are added to prepare the electrolyte.

[0208] The organic solvent comprises 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 contents of the components in the organic solvent are calculated based on the mass of the electrolyte.

[0209] The additives include vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (ES) and lithium difluoro(oxalato)borate (LiDFOB) with a mass ratio of 4:2:0.5:0.5.

[0210] The lithium salts include lithium bis(fluorosulfonyl)imide (LiFSI) with a mass content of 5% and lithium hexafluorophosphate (LiPF₆) with a mass content of 10%. 6 The mass content of the lithium salts is calculated based on the mass of the electrolyte.

[0211] 5. Preparation of the battery cell Stack the above-mentioned positive electrode sheet, separator and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an insulating role, obtaining a stacked electrode assembly. Place the electrode assembly in a casing, and positive and negative terminals are provided on the casing. After baking, inject the electrolyte, and through processes such as vacuum packaging, standing, formation, and shaping, the battery cell is obtained.

[0212] The mass of the electrolyte corresponding to each Ah of the battery cell is 2.45 g.

[0213] The casing is an aluminum casing with a cuboid structure, and the thickness of the casing corresponding to the face with the largest area of the cuboid structure is 0.5 mm.

[0214] Performance test 1. Volumetric energy density Place the battery cells in the examples and comparative examples at 25 °C, charge them at a constant current of 0.33C to 3.65V, then charge them at a constant voltage of 3.65V to 0.05C, and let them stand for 30 min; discharge them at a constant current of 0.33C to 2.0V, and record the discharge capacity A at this time. 0 , unit: Ah; use a caliper to measure the length, width, and height of the battery cell, and calculate the volume V of the single battery cell. 0 , unit: L; the volumetric energy density VED of the battery cell = (A 0 × discharge platform voltage) / V 0 , unit: Wh / L.

[0215] 2. Fast charging performance At 30 °C, after cycling the battery cells in the examples and comparative examples 200 times respectively according to their respective charge-discharge strategies, then charge them to 100% SOC according to the corresponding charging strategy, disassemble the negative electrode sheet, unfold the negative electrode sheet, observe the lithium plating area (grayish-white area), and measure the lithium plating area. The degree of lithium plating is as follows: No lithium plating: lithium plating area < 0.05%.

[0216] Slight lithium plating: lithium plating area < 2%.

[0217] Severe lithium plating: lithium plating area ≥ 2%.

[0218] Charge the battery cell, and the charging steps include the following steps: 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.

[0219] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0220] The discharging strategy is as follows: discharge at a constant current of 0.33C to the cut-off voltage, for example, 2.0V.

[0221] When performing charge and discharge tests on the battery cell above, the battery cell can be assembled in a battery device, and the required charge and discharge strategies can be regulated through a battery management system for testing.

[0222] 3. Cycle performance At 60°C, charge the battery cell at a constant current of 0.8C to the charging cut-off voltage of 3.6V, then charge at a constant current of 0.1C to the charging cut-off voltage of 3.65V, and let it stand for 30 min; discharge at a constant current of 1C to 3.1V, and let it stand 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 / C 0 ×100%) is 70%, and record the number of cycles. The more the number of cycles, the better the cycle performance of the battery cell.

[0223] 4. Compaction density of the positive electrode Place the battery cell at 25°C, let it stand for 2 h, charge at a constant current of 1 / 3C to 3.65V, charge at a constant voltage of 3.65V to 0.05C, let it stand for 2 h, and then discharge 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 electrode active material layer on one side can be wiped off first), and punch it into an area of S 1Small round pieces are taken, weighed, and recorded as M 1 , and its thickness H is measured 1 . Then wipe off the positive active material layer of the above-mentioned weighed positive electrode plate, weigh the weight of the positive current collector, and record it as M 0 , and its thickness H is measured 0 . The single-sided coating weight of the positive active material layer = (M 1 - M 0 ) / S 1 , the thickness of the positive active material layer = H 1 - H 0 , and the tap 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.

[0224] 5. Tap density of the negative 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, 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 battery cell to obtain the negative electrode plate. For example, take a single-sided coated negative electrode plate (if it is a double-sided coated electrode plate, the negative active material layer on one side can be wiped off first), punch it into small round pieces with an area of S 2 , weigh them, and record as M 3 , and measure its thickness H 3 . Then wipe off the negative active material layer of the above-mentioned weighed negative electrode plate, weigh the weight of the negative current collector, and record it as M 2 , and measure its thickness H 2 . The single-sided coating weight of the negative active material layer = (M 3 - M 2 ) / S 2 , the thickness of the negative active material layer = H 3 - H 2 , and the tap density of the negative active material layer = the single-sided coating weight of the negative active material layer / the thickness of the negative active material layer.

[0225] 5. Mass of electrolyte per Ah of the battery cell ① Take a battery cell and weigh its mass M 0 ; 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 them 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 the electrolyte under the rated capacity of 1 Ah per unit cell of the battery cell = (M 0 -M 1 ) / a. a = the rated capacity of the battery cell, unit Ah.

[0226] 6. Mass ratio of lithium fluorosulfonylimide and lithium hexafluorophosphate 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, the newly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or the 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 ratio of lithium fluorosulfonylimide to the mass ratio of lithium hexafluorophosphate is calculated.

[0227] Comparative Example 1 The preparation method of the battery cell is the same as that of Example 1, except that the compaction density of the positive electrode plate is 2.4 g / cm 3 .

[0228] Example 2 The preparation method of the battery cell is the same as that of Example 1, except that the compaction density of the positive electrode plate is 2.7 g / cm 3 .

[0229] Example 3 The preparation method of the battery cell is the same as that of Example 1, except that the compaction density of the positive electrode plate is 2.8 g / cm 3 .

[0230] Comparative Example 2 The preparation method of the battery cell is the same as that of Example 1, except that the compaction density of the positive electrode plate is 2.85 g / cm 3 .

[0231] Comparative Example 3 The preparation method of the battery cell is the same as that of Example 1, except that the compaction density of the negative electrode plate is 1.1 g / cm 3 .

[0232] Example 4 The preparation method of the battery cell is the same as that of Example 1, except that the compaction density of the negative electrode plate is 1.25 g / cm 3 .

[0233] Example 5 The preparation method of the battery cell is the same as that of Example 1, except that the compaction density of the negative electrode plate is 1.5 g / cm 3 .

[0234] Comparative Example 4 The preparation method of the battery cell is the same as that of Example 1, except that the compaction density of the negative electrode plate is 1.6 g / cm 3 .

[0235] The detailed differences and test results of the battery cells in Examples 1-5 and Comparative Examples 1-4 are shown in Table 1.

[0236] Table 1

[0237] As can be seen from Table 1, when the mass of the electrolyte corresponding to each Ah of the battery cell is within the scope protected by this application, by controlling the compaction densities of the positive electrode plate and the negative electrode plate, the volumetric energy density of the battery cell can be improved. And when the compaction density of the positive electrode plate is 2.46 g / cm 3 -2.8 g / cm 3 , and the compaction 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 cycle performance can be obtained with less electrolyte. It shows that when the compaction 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 cycle and fast charging performance can be obtained.

[0238] Comparative Example 5 The preparation method of the battery cell is the same as that of Example 2, except that the compaction 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.

[0239] Example 6 The preparation method of the battery cell is the same as that of Example 2, except that the compaction 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.

[0240] Example 7 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.

[0241] The test results of the battery cells in Comparative Example 5, Example 6, and Example 7 are shown in Table 2.

[0242] Table 2

[0243] As can be seen from Table 2, when the compaction density of the positive electrode sheet and the negative electrode sheet is within the scope protected by 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 cycle 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 cycle performance.

[0244] Comparative Example 6 The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of LiFSI is 1%, and the mass fraction of LiPF 6 is 14%, and the ratio of the mass fractions of LiFSI and LiPF 6 is 0.1.

[0245] Example 9 The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of LiFSI is 4%, and the mass fraction of LiPF 6 is 11%, and the ratio of the mass fractions of LiFSI and LiPF 6 is 0.4.

[0246] Example 10 The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of LiFSI is 6%, and the mass fraction of LiPF 6 is 9%, and the ratio of the mass fractions of LiFSI and LiPF 6 is 0.7.

[0247] Comparative Example 7 The preparation method of the battery cell is the same as that of Example 2, except that the mass fraction of LiFSI is 9%, and the mass fraction of LiPF 6 is 6%, and the ratio of the mass fractions of LiFSI and LiPF 6 is 1.5.

[0248] The test results of the battery cells in Comparative Example 6, Example 9, Example 10, and Comparative Example 7 are shown in Table 3.

[0249] Table 3

[0250] As can be seen from Table 3, by adjusting the contents of LiFSI and LiPF in the electrolyte, the ratio of the content of LiFSI to the content of LiPF can be adjusted. 6 When the content of LiFSI is small and the content of LiPF is large, LiPF is prone to hydrolysis to form HF, which corrodes the SEI film and reduces the cycling performance of the battery cell. When the content of LiFSI is large and the content of LiPF is small, although the cycling performance of the battery cell can be improved, too much LiFSI will deteriorate the safety of the battery cell. 6 When the content of LiFSI is small and the content of LiPF is large, LiPF is prone to hydrolysis to form HF, which corrodes the SEI film and reduces the cycling performance of the battery cell. 6 When the content of LiFSI is small and the content of LiPF is large, LiPF is prone to hydrolysis to form HF, which corrodes the SEI film and reduces the cycling performance of the battery cell. 6 When the content of LiFSI is small and the content of LiPF is large, LiPF is prone to hydrolysis to form HF, which corrodes the SEI film and reduces the cycling performance of the battery cell. When the content of LiFSI is large and the content of LiPF is small, although the cycling performance of the battery cell can be improved, too much LiFSI will deteriorate the safety of the battery cell. 6 When the content of LiFSI is small and the content of LiPF is large, LiPF is prone to hydrolysis to form HF, which corrodes the SEI film and reduces the cycling performance of the battery cell. When the content of LiFSI is large and the content of LiPF is small, although the cycling performance of the battery cell can be improved, too much LiFSI will deteriorate the safety of the battery cell.

[0251] Example 11 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.

[0252] Example 12 The preparation method of the battery cell is the same as that of Example 2, except that the lithium fluorosulfonylimide is lithium perfluorobutanesulfonylimide.

[0253] The test results of the battery cells in Example 2, Example 11, and Example 12 are shown in Table 4.

[0254] Table 4

[0255] 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 LiPF can all play a role in improving the cycling performance of the battery cell. 6 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 LiPF can all play a role in improving the cycling performance of the battery cell.

[0256] Example 13 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%.

[0257] Example 14 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%.

[0258] Example 15 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%.

[0259] The test results of the battery cells in Example 2, Example 13 - Example 15 are shown in Table 5.

[0260] Table 5

[0261] As can be seen from Table 5, by adjusting the content of carbonate additives in the electrolyte, the cycling 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.

[0262] Example 16 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%. Example 17 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%.

[0263] Example 18 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%.

[0264] Example 19 The preparation method of the battery cell is the same as that of Example 2, except that the sulfur-containing additive is vinylene sulfate.

[0265] The test results of the battery cells in Examples 16 - 19 are shown in Table 6.

[0266] Table 6

[0267] As can be seen from Table 6, when the compaction density of the positive electrode plate and the negative electrode plate, 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 cycling 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. Carbonate solvents can increase the dielectric constant of the electrolyte, and carboxylic ester solvents have a small molecular weight and can reduce the viscosity of the electrolyte, thereby further improving the cycling performance and fast charging performance of the battery cell.

[0268] Example 20 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 additives is 1%.

[0269] Example 21 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.

[0270] The test results of the battery cells in Example 2, Example 20, and Example 21 are shown in Table 7.

[0271] Table 7

[0272] As can be seen from Table 7, when the compaction density of the positive electrode and the negative electrode, the ratio of the mass ratio of lithium fluorosulfonimide 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, wherein the electrode assembly includes a positive electrode sheet and a negative electrode sheet, wherein: The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material, wherein the positive electrode active material includes a lithium-containing phosphate, and the compaction density of the positive electrode sheet is 2.46 g / cm 3 -2.8g / cm 3 ; The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The compaction density of the negative electrode sheet is 1.25 g / cm 3 -1.5g / cm 3 ; The electrolyte comprises fluorinated lithium sulfonyl imide and lithium hexafluorophosphate, and based on the total mass of the electrolyte, the ratio of the mass proportion of the fluorinated lithium sulfonyl imide to the mass proportion of the lithium hexafluorophosphate is 0.4-0.8; The mass of the electrolyte corresponding to each Ah of the battery cell is 2.2g-3g.

2. The battery cell according to claim 1, characterized in that: The compaction density of the positive electrode sheet is 2.65 g / cm 3 -2.8g / 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 proportion of the fluorinated sulfonyl imide lithium 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 proportion of the lithium hexafluorophosphate is 8%-12%.

5. The battery cell according to claim 1 or 2, characterized in that: The fluorine-containing lithium sulfonyl imide includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium perfluorobutylsulfonyl imide.

6. The battery cell according to claim 1 or 2, characterized in that: The electrolyte also includes a solvent, and the solvent includes one or both of a carbonate solvent and a carboxylate solvent.

7. The battery cell according to claim 6, characterized in that: The carbonate solvent includes 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 solvent includes a compound shown in Formula I: Formula I, 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.

9. The battery cell according to claim 6, characterized in that: The carboxylate 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.

10. The battery cell according to claim 6, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the carbonate solvent is 20%-70%.

11. The battery cell according to claim 6, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the carboxylic acid ester solvent is 10%-60%.

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

13. The battery cell according to claim 12, characterized in that: The carbonate additive includes one or more of vinylene carbonate and vinyl carbonate derivatives.

14. The battery cell according to claim 13, characterized in that: The ethylene carbonate derivatives include compounds shown in formula II, Formula II, 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 halogenated alkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time.

15. The battery cell according to claim 13 or 14, characterized in that: The ethylene carbonate derivative includes 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 proportion of the carbonate additive is 3%-8%.

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

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

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

20. The battery cell according to claim 12, characterized in that: The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, 1,3-propane sultone, butylene sulfite, vinyl sulfite, and methylene disulfonate.

21. The battery cell according to claim 20, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive 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 difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

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 comprises: matrix; A first coating material is disposed on at least a portion of the surface of the substrate, 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, characterized in that: The first coating material includes a compound shown in formula III: Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula III Among them, 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, characterized in that: The matrix includes a compound shown in formula IV: Li x1 A y1 Me a1 M2 b1 P 1-c1 X c1 Y z1 Formula IV Among them, 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; Among them, 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; and Y includes one or more of O and F.

30. The battery cell according to claim 26, characterized in that 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 compaction density of the positive electrode active material at 30000N is 2.43g / cm 3 -2.85g / 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 -350mg / 1540.25mm 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 both 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, characterized in that: The graphite is a secondary particle formed by aggregation of primary particles, at least a portion of the surface of the secondary particle has a second coating material, and the second coating material includes amorphous carbon.

36. The battery cell according to claim 35, characterized in that 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 to 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, characterized in that: 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 proportion of silicon element is 0.3%-5%.

39. The battery cell according to claim 33, characterized in that The single-sided coating weight of the negative electrode active material layer is 90 mg / 1540.25 mm 2 -140mg / 1540.25mm 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 greater 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; 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, Among them, OH1 is greater than or equal to OH2.

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

42. The battery cell according to claim 1 or 2, characterized in that: 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.

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

44. The battery cell according to claim 43, characterized in that The porosity of the isolation membrane is 35%-60%.

45. The battery cell according to claim 43, characterized in that The isolation film comprises: Basement membrane; A first functional layer, located on at least one side of the base film, wherein the first functional layer comprises a first inorganic substance; The second functional layer is located on a side of the first functional layer away from the base film, and the second functional layer includes a second inorganic substance and a non-fluorine polymer.

46. ​​The battery cell according to claim 45, characterized in that The non-fluorine polymer includes an acrylic copolymer.

47. The battery cell according to claim 45 or 46, characterized in that: The first inorganic substance and the second inorganic substance 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 base film has a thickness of 4 μm-12 μm.

49. The battery cell according to claim 1 or 2, characterized in that: The battery cell comprises a shell and a cover assembly, wherein the cover assembly is arranged at at least one end of the shell, the shell and the cover assembly define a receiving cavity, the electrode assembly is arranged in the receiving cavity, and the shell thickness of the large surface of the battery cell is 0.1mm-0.5mm.

50. The battery cell according to claim 49, characterized in that The shell thickness of the large surface of the battery cell is 0.2mm-0.35mm.

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

52. The battery cell according to claim 51, characterized in that The minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal is S, and each independently satisfies 150mm 2 ≤S≤1000mm 2 .

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

54. A battery device, characterized in that: Comprising the battery monomer described in 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 It comprises the battery cell described in any one of claims 1 to 53 or the battery device described in claim 54, wherein the battery cell or the battery device provides electrical energy for the electrical equipment.

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