Battery cell, battery apparatus, and electric device

Abstract

A battery cell (1), a battery apparatus, and an electric device. The battery cell (1) comprises an electrode assembly and an electrolyte. The electrode assembly comprises a positive electrode sheet (121) and a negative electrode sheet (122). The positive electrode sheet (121) comprises 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 positive electrode active material layer (1212) comprises a positive electrode active material; the positive electrode active material comprises a lithium-containing phosphate; and the compacted density of the positive electrode sheet (121) ranges from 2.46 g / cm3 to 2.8 g / cm3. The negative electrode sheet (122) comprises 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, and the compacted density of the negative electrode sheet (122) ranges from 1.25 g / cm3 to 1.5 g / cm3. The electrolyte comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate; based on the total mass of the electrolyte, the ratio of the mass fraction of the lithium bis(fluorosulfonyl)imide to the mass fraction of the lithium hexafluorophosphate is 0.4-0.8; and the corresponding mass of the electrolyte per Ah of the battery cell ranges from 2.2 g to 3 g.

Description

Battery cells, battery devices and electrical equipment Technical Field

[0001] This application relates to the field of batteries, specifically to battery cells, battery devices, and electrical equipment. Background Technology

[0002] Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. During the assembly of a battery cell, increasing the volume occupied by the electrode assembly and reducing the volume occupied by the electrolyte can improve the energy density of the battery cell. However, with a reduced electrolyte content, the water of crystallization in the lithium phosphate of the positive electrode active material is difficult to remove. During battery cycling, the electrolyte salt is easily hydrolyzed, producing HF that corrodes the electrolyte interphase (SEI) film on the negative electrode surface, causing electrolyte consumption and reducing the cycle performance of the battery cell. Summary of the Invention

[0003] The first aspect of this application provides a battery cell, the battery cell comprising an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode and a negative electrode, the positive electrode comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer comprising a positive active material comprising lithium phosphate, and the compaction density of the positive electrode having a density of 2.46 g / cm³. 3 -2.8g / cm 3 ;

[0004] 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, and the compaction density of the negative electrode sheet is 1.25 g / cm³. 3 -1.5g / cm 3 ;

[0005] The electrolyte comprises lithium fluorosulfonyl imide and lithium hexafluorophosphate, and the mass ratio of the lithium fluorosulfonyl imide to the lithium hexafluorophosphate is 0.4-0.8 based on the total mass of the electrolyte.

[0006] The mass of electrolyte per Ah of the battery cell is 2.2g-3g.

[0007] Therefore, while increasing the energy density of individual battery cells, controlling the content of lithium hexafluorophosphate and lithium fluorosulfonyl imide reduces HF generation, lowers the consumption rate of electrolyte and additives, and improves the lifespan, cycle performance, and fast-charging performance of individual battery cells.

[0008] According to some embodiments of this application, the compaction density of the positive electrode sheet is 2.65 g / cm³. 3 -2.8g / cm 3 Therefore, the volumetric energy density of a single battery cell is relatively high.

[0009] According to some embodiments of this application, the mass percentage of the lithium fluorosulfonylimide is 4%-8% based on the total mass of the electrolyte. Lithium fluorosulfonylimide is not easily hydrolyzed, which reduces HF generation and decreases corrosion of the SEI film.

[0010] According to some embodiments of this application, the lithium hexafluorophosphate accounts for 8%-12% of the total mass of the electrolyte. This reduces the viscosity of the electrolyte and increases the lithium-ion transport rate.

[0011] According to some embodiments of this application, the fluorinated sulfonylimide lithium includes one or more of lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, and lithium perfluorobutylsulfonylimide. This reduces HF generation and decreases corrosion of the SEI film.

[0012] According to some embodiments of this application, the electrolyte further includes a solvent, which includes one or both of carbonate solvents and carboxylic acid ester solvents. This improves the conductivity of the electrolyte and enhances the fast-charging performance of the battery cell.

[0013] According to some embodiments of this application, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. This increases the dielectric constant of the electrolyte.

[0014] According to some embodiments of this application, the carboxylic acid ester solvent includes compounds represented by Formula I:

[0015] R5 includes any one of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, while R6 includes any one of C1-C5 alkyl groups and C1-C5 haloalkyl groups. Therefore, the aforementioned types of carboxylic acid ester solvents have relatively small molecular weights, which can improve the ionic conductivity of the electrolyte and enhance the rate performance of the battery cells.

[0016] According to some embodiments of this application, the carboxylic acid 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. Therefore, the above-mentioned types of carboxylic acid ester solvents have relatively small molecular weights, which can improve the ionic conductivity of the electrolyte and enhance the rate performance of the battery cell.

[0017] According to some embodiments of this application, the carbonate solvent accounts for 20%-70% of the total mass of the electrolyte. This improves the ionic conductivity of the electrolyte.

[0018] According to some embodiments of this application, the mass percentage of the carboxylic acid ester solvent is 10%-60% based on the total mass of the electrolyte. This improves both the ionic conductivity of the electrolyte and the high-temperature cycle life of the battery cell.

[0019] According to some embodiments of this application, the electrolyte further includes additives, which include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. This improves the cycle performance and fast-charging performance of the battery cells.

[0020] According to some embodiments of this application, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. This improves the cycle life of the battery cell.

[0021] According to some embodiments of this application, the ethylene carbonate derivative includes compounds represented by formula Π.

[0022] R1, R2, R3, and R4 each independently include any one of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, and R1, R2, R3, and R4 are not all hydrogen atoms simultaneously. This improves the cycle life of the battery cell.

[0023] [Correction based on Rule 91, 06.08.2025] According to some embodiments of this application, the ethylene carbonate derivative includes at least one of the compounds shown in Formula Π-1, Formula Π-2, and Formula Π-3:

[0024] According to some embodiments of this application, the carbonate additive accounts for 3%-8% of the total mass of the electrolyte. This improves the cycle life of the battery cell while reducing its impedance.

[0025] According to some embodiments of this application, the mass percentage of the vinylene carbonate is 2%-5%. This forms a stable SEI film, improving lithium-ion transport.

[0026] According to some embodiments of this application, the ethylene carbonate derivative accounts for 0%-4% of the mass. This improves the uniformity and density of the SEI film and reduces side reactions between the electrolyte and the negative electrode surface.

[0027] According to some embodiments of this application, the ethylene carbonate derivative accounts for 1.5%-3.5% of the total mass. This improves the uniformity and density of the SEI film and reduces side reactions between the electrolyte and the negative electrode surface.

[0028] According to some embodiments of this application, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, 1,3-propanesulfonate lactone, butene sulfite, vinyl sulfite, and methylene disulfonate. This reduces the impedance of the battery cell and improves its fast-charging performance.

[0029] According to some embodiments of this application, the sulfur-containing additive accounts for 0-2% of the total mass. This reduces the impedance of the battery cell while simultaneously decreasing gas production within the battery cell.

[0030] According to some embodiments of this application, the sulfur-containing additive accounts for 0.5%-2% of the total mass of the electrolyte. This reduces the impedance of the battery cell while simultaneously decreasing gas production within the battery cell.

[0031] According to some embodiments of this application, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate borate). This reduces gas production in battery cells under high-temperature conditions.

[0032] According to some embodiments of this application, the lithium salt additive accounts for 0-1% of the total mass of the electrolyte. This reduces gas generation in individual battery cells while lowering film resistance.

[0033] According to some embodiments of this application, the lithium salt additive accounts for 0.2%-1% of the total mass of the electrolyte. This reduces gas generation in individual battery cells while lowering film resistance.

[0034] According to some embodiments of this application, the lithium-containing phosphate includes: a matrix; and a first coating material located on at least a portion of the surface of the matrix, the first coating material containing carbon. This improves the conductivity of the lithium-containing phosphate.

[0035] According to some embodiments of this application, the carbon element accounts for 0.8%-2.3% of the total mass of the lithium phosphate. This improves the conductivity of the lithium phosphate while increasing the lithium phosphate loading on the positive electrode, thereby increasing the energy density of the battery cell.

[0036] According to some embodiments of this application, the first coating material comprises a compound represented by Formula III: Li 3-d1 Fe 2-d1 M1 d1(PO m1 ) n1 Formula III,

[0037] Wherein, 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn. This improves the ionic conductivity and specific capacity of the positive electrode active material, thereby enhancing the fast-charging performance and energy density of the battery cell.

[0038] According to some embodiments of this application, the matrix comprises a compound represented by Formula IV: Li x1 A y1 Me a1 M2 b1 P 1-c1 X c1 Y z1 Formula IV,

[0039] Wherein, 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;

[0040] Wherein, 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 two of O and F. This improves the cycle performance and safety of the battery cell.

[0041] According to some embodiments of this 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. This improves the cycle performance and safety of the battery cell.

[0042] According to some embodiments of this application, the powder compaction density of the positive electrode active material at 30000N is 2.43 g / cm³. 3 -2.85g / cm 3 This increases the energy density of individual battery cells.

[0043] According to some embodiments of this application, the single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm. 2 -350mg / 1540.25mm 2 This increases the energy density of individual battery cells.

[0044] According to some embodiments of this application, the negative electrode active material layer includes a negative electrode active material, which includes one or both of carbon-based and silicon-based materials. This improves the energy density and cycle performance of the battery cell.

[0045] According to some embodiments of this application, the carbon-based material includes graphite. This improves the cycle performance of the battery cell.

[0046] According to some embodiments of this application, the graphite is secondary particles formed by the aggregation of primary particles, and at least a portion of the surface of the secondary particles has a second coating material, the second coating material comprising amorphous carbon. This reduces side reactions between the negative electrode surface and the electrolyte, improving the cycle performance of the battery cell.

[0047] According to some embodiments of this application, the second coating material accounts for 2%-5% of the total mass of the graphite. This improves both the cycle performance and energy density of the battery cell.

[0048] According to some embodiments of this application, the volume average particle size Dv50 of the graphite is 8.5 μm-13.8 μm. This shortens the migration path of lithium ions in the solid phase, improving the fast-charging capability of the battery cell; simultaneously, it reduces side reactions between the graphite and the electrolyte.

[0049] According to some embodiments of this application, the negative electrode active material includes a silicon-based material, and the mass percentage of silicon element is 0.3%-5% based on the total mass of the negative electrode active material layer. This improves the energy density of the battery cell.

[0050] According to some embodiments of this application, the single-sided coating weight of the negative electrode active material layer is 90 mg / 1540.25 mm. 2 -140mg / 1540.25mm 2 This increases the energy density of individual battery cells.

[0051] According to some embodiments of this application, along the length direction of the battery cell, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1;

[0052] 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.

[0053] Among them, OH1 is greater than or equal to OH2. Therefore, while increasing the energy density of individual battery cells, lithium plating on the negative electrode is reduced.

[0054] According to some embodiments of this application, 1mm ≤ OH1 ≤ 4mm, and 1mm ≤ OH2 ≤ 3mm. This increases the energy density of individual battery cells while reducing lithium plating on the negative electrode.

[0055] According to some embodiments of this application, a positive electrode tab is provided on the positive electrode sheet, and a negative electrode tab is provided on the negative electrode sheet. The positive electrode tab extends along the length direction or the width direction of the positive electrode sheet, and the negative electrode tab extends along the length direction or the width direction of the negative electrode sheet. This improves current transmission efficiency, reduces the resistance of the battery cell, and enhances the rate performance of the battery cell.

[0056] According to some embodiments of this application, the electrode assembly includes a separator with a porosity of 20%-70%. This improves lithium-ion transport efficiency and enhances the rate performance of the battery cell.

[0057] According to some embodiments of this application, the porosity of the separator is 35%-60%. This improves the lithium-ion transport efficiency and enhances the rate performance of the battery cell.

[0058] According to some embodiments of this 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 comprising a first inorganic material; and a second functional layer located on the side of the first functional layer away from the base film, the second functional layer comprising a second inorganic material and a non-fluoropolymer. This improves the heat resistance of the separator and enhances the safety of the battery cell.

[0059] According to some embodiments of this application, the non-fluoropolymer includes acrylate copolymers. This improves the adhesion of the non-fluoropolymer and reduces the risk of the second functional layer detaching.

[0060] According to some embodiments of this application, the first inorganic material and the second inorganic material each independently comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. This improves the heat resistance of the separator and enhances the safety of the battery cell.

[0061] According to some embodiments of this application, the thickness of the base film is 4μm-12μm. This reduces the short circuit between the positive and negative electrodes, decreases the volume occupied by the separator within the battery cell, and increases the energy density of the battery cell.

[0062] According to some embodiments of this application, the battery cell includes a housing and a cover assembly, the cover assembly being disposed at at least one end of the housing, the housing and the cover assembly defining a receiving cavity, and the electrode assembly being disposed within the receiving cavity. The housing thickness of the large surface area of ​​the battery cell is 0.1 mm to 0.5 mm. This improves the energy density of the battery cell.

[0063] According to some embodiments of this application, the thickness of the casing on the large surface of the battery cell is 0.2mm-0.35mm. This increases the energy density of the battery cell.

[0064] According to some embodiments of this application, the cover assembly includes a first cover assembly and a second cover assembly, which are disposed at both ends of the housing in the length or width direction. The first cover assembly includes a first cover plate and a first electrode terminal, and the second cover assembly includes a second cover plate and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite. This reduces the temperature rise of the battery cell during charging, thereby reducing the impedance of the battery cell.

[0065] According to some embodiments of this application, the minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal is S, and satisfies 150 mm. 2 ≤S≤1000mm 2 This improves the overcurrent capacity of individual battery cells.

[0066] According to some embodiments of this application, the volumetric energy density of the battery cell is 400Wh / L-530Wh / L.

[0067] The second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0068] A third aspect of this application provides an electrical device, including a battery cell provided in the first aspect of this application or a battery device provided in the second aspect of this application, wherein the battery cell or the battery device provides electrical energy to the electrical device.

[0069] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0070] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0071] Figure 1 is a schematic diagram of the structure of the housing according to an embodiment of this application.

[0072] Figure 2 is a schematic diagram showing the dimensions of the positive electrode active material layer and the negative electrode active material layer according to an embodiment of this application.

[0073] Figure 3 is a schematic diagram of the structure of the positive electrode sheet according to an embodiment of this application.

[0074] Figure 4 is a schematic diagram of the structure of the positive electrode sheet according to another embodiment of this application.

[0075] Figure 5 is a schematic diagram of the structure of the positive electrode sheet according to another embodiment of this application.

[0076] Figure 6 is a schematic diagram of the structure of the positive electrode sheet according to another embodiment of this application.

[0077] Figure 7 is a schematic diagram of the negative electrode sheet according to an embodiment of this application.

[0078] Figure 8 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0079] Figure 9 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0080] Figure 10 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0081] Figure 11 is a schematic diagram of the structure of the isolation membrane according to an embodiment of this application.

[0082] Figure 12 is a schematic diagram of the structure of a battery cell according to an embodiment of this application.

[0083] Figure 13 is a schematic diagram of the structure of an electrical device according to an embodiment of this application.

[0084] Explanation of reference numerals in the attached drawings: 1 Battery cell; 11 Casing; 111 Large surface of the casing; 121 Positive electrode sheet; 1210 Positive electrode tab; 1212 Positive active material layer; 122 Negative electrode sheet; 1220 Negative electrode tab; 1222 Negative active material layer; 123 Separator; 1231 Base film; 1232 First functional layer; 1233 Second functional layer; 13 Cover plate assembly. Detailed Implementation

[0085] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0086] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0087] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0088] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0089] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0090] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing. However, existing battery cells cannot meet the demands for long-cycle operation and high energy density.

[0091] This application proposes a battery cell that increases the space occupied by the electrode assembly by increasing the compaction density of the positive and negative electrode sheets, and reduces the weight of the battery cell by reducing the electrolyte injection volume, thereby improving the battery energy density. However, because the increased compaction of the positive and negative electrodes results in a more densely packed particle packing within the electrode sheets, it is difficult to completely bake out the moisture from the electrode sheets during battery production to control it within a reasonable range. This moisture will slowly release from the electrode sheets during battery cycling or storage, causing the lithium hexafluorophosphate in the electrolyte to hydrolyze and 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 electrolyte and additives. Because this application controls the electrolyte injection volume within a low range, in order to ensure battery life, it is necessary to improve the erosion of the SEI by HF during cycling and storage, and reduce the consumption rate of electrolyte and additives. Therefore, by compounding lithium hexafluorophosphate and fluorosulfonylimide lithium salt in the electrolyte and controlling their relative content within a suitable range, HF generation during cycling and storage can be reduced, electrolyte and additive consumption rates can be decreased, and battery cell life can be improved. Furthermore, fluorosulfonylimide lithium salt has a higher ionization energy than lithium hexafluorophosphate, which can accelerate the lithium-ion transport rate in the electrolyte, better facilitate lithium-ion diffusion in the high-pressure, high-density positive and negative electrode plates, and improve the fast-charging and cycle performance of individual batteries.

[0092] The battery cells proposed in this application can be used in electrical devices that use the battery cells as a power source or in various energy storage systems that use the battery cells as energy storage elements. Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0093] The first aspect of this application provides a battery cell, the battery cell comprising an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode and a negative electrode, the positive electrode comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer comprising a positive active material comprising lithium phosphate, and the compaction density of the positive electrode having a density of 2.46 g / cm³. 3 -2.8g / cm 3 ;

[0094] 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, and the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 -1.5g / cm 3 ;

[0095] The electrolyte comprises lithium fluorosulfonyl imide and lithium hexafluorophosphate, and the mass ratio of the lithium fluorosulfonyl imide to the lithium hexafluorophosphate is 0.4-0.8 based on the total mass of the electrolyte.

[0096] The mass of electrolyte per Ah of the battery cell is 2.2g-3g.

[0097] Therefore, while increasing the energy density of individual battery cells, controlling the content of lithium hexafluorophosphate and lithium fluorosulfonyl imide reduces HF generation, lowers the consumption rate of electrolyte and additives, and improves the lifespan, cycle performance, and fast-charging performance of individual battery cells.

[0098] In this application, the test method for the electrolyte mass at a rated capacity of 1 Ah for a single battery cell is as follows: ① Take a single battery cell and weigh its mass M0; ② Disassemble the single battery cell, pour out the free electrolyte, and remove the electrode plates, separator, mechanical parts, and adhesive tape, etc.; ③ Soak and clean the electrode plates, separator, mechanical parts, and adhesive tape, etc., with dimethyl carbonate (DMC) for 24 hours, repeating the cleaning process at least 3 times; ④ After cleaning, place the electrode plates, separator, mechanical parts, and adhesive tape, etc., in an oven until completely dry; ⑤ Weigh the total mass of the dried electrode plates, separator, mechanical parts, and adhesive tape, etc., and record the mass as M1; ⑥ The electrolyte mass at a rated capacity of 1 Ah for a single battery cell = (M0 - M1) / a. a = rated capacity of the single battery cell, in Ah. As an example, the mass of electrolyte per Ah of the battery cell can be 2.2g, 2.3g, 2.4g, 2.5g, 2.6g, 2.7g, 2.8g, 3g, etc., or a range of any of the above values. This reduces the space occupied by the electrolyte within the battery cell, increases the lithium phosphate content, and improves the energy density of the battery cell.

[0099] This application provides a method for testing the compaction density of the positive electrode sheet: The battery cell is placed at 25°C and left to stand for 2 hours. It is then charged at a constant current of 1 / 3C to 3.65V, charged at a constant voltage of 3.65V to 0.05C, left to stand for 2 hours, and then discharged at a rate of 0.33C to 2.0V. The positive electrode sheet is disassembled from the battery cell. For example, a single-sided coated positive electrode sheet is taken (if it is a double-sided coated sheet, the positive active material layer on one side can be wiped off first), and it is cut into small circular pieces with an area of ​​S1. The weight of these pieces is recorded as M1, and their thickness H1 is measured. Then, the positive active material layer of the weighed positive electrode sheet is wiped off, the weight of the positive current collector is recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode active material layer = (M1-M0) / S1, the thickness of the positive electrode active material layer = H1-H0, and the compaction 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.

[0100] As an example, the compaction density of the positive electrode sheet can be 2.46 g / cm³. 3 2.5g / cm 3 2.55g / cm 3 2.6g / cm 3 2.65g / cm 3 2.7g / cm 3 2.8g / cm 3 The values ​​can be any range of the aforementioned values. This increases the space occupied by the electrode assembly and improves the energy density of the individual battery cells.

[0101] According to some embodiments of this application, the compaction density of the positive electrode sheet can be 2.65 g / cm³. 3 -2.8g / cm 3 .

[0102] This application provides a method for testing the compaction density of a negative electrode sheet: The battery cell is charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to 0.05C. The cell is placed at 25°C and left to stand for 2 hours, followed by discharge at a rate of 0.33C to 2.0V. The negative electrode sheet is disassembled from the battery cell. For example, a single-sided coated negative electrode sheet (if it is a double-sided coated sheet, the negative active material layer on one side can be wiped off first) is cut into small circular pieces with an area of ​​S2, weighed, and recorded as M3, and its thickness H3 is measured. Then, the negative active material layer of the weighed negative electrode sheet is wiped off, the weight of the negative current collector is weighed and recorded as M2, and its thickness H2 is measured. The single-sided coating weight of the negative electrode active material layer = (M3-M2) / S2, the thickness of the negative electrode active material layer = H3-H2, and the compaction density of the negative electrode active material layer = single-sided coating weight of the negative electrode active material layer / thickness of the negative electrode active material layer.

[0103] As an example, the compaction density of the negative electrode sheet can be 1.25 g / cm³. 3 1.3g / cm 3 1.35g / cm 3 1.4g / cm 3 1.45g / cm 3 1.5g / cm 3 The values ​​can be any range of the aforementioned values. Thus, on the one hand, the space occupied by the electrode assembly is increased, thereby increasing the energy density of the battery cell; on the other hand, after the compaction density of the negative electrode sheet is increased, the porosity of the negative electrode sheet decreases, and the intrinsic electrolyte content required to be absorbed inside the electrode sheet decreases. Even when the mass of electrolyte per Ah of battery cell is relatively small, the cycle requirements can still be met.

[0104] In this application, the testing of the content of lithium fluorosulfonylimide salt and lithium hexafluorophosphate can refer to the standard JY / T020-2002 "General Rules for Ion Chromatographic Analysis". For example, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a fully discharged battery cell can be disassembled in reverse (discharged to the discharge cutoff voltage so that the charge state of the battery cell is about 0% SOC), and the free electrolyte obtained from the battery cell can be used as a sample. Ion chromatography analysis is used to detect the inorganic ion chromatogram, and the corresponding inorganic species are compared according to the chromatographic peak position. The percentage of the corresponding inorganic ion content is calculated according to the peak area, and then the ratio of the mass percentage of lithium fluorosulfonylimide to the mass percentage of lithium hexafluorophosphate is calculated.

[0105] As an example, the mass ratio of the lithium fluorosulfonylimide to the lithium hexafluorophosphate can be 0.4, 0.45, 0.5, 0.55, 0.6, 0.8, or any range of the above values. By keeping the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate within the above range, on the one hand, HF generation is reduced, corrosion of the SEI film is decreased, electrolyte consumption is reduced, and the cycle performance of the battery cell is improved; on the other hand, the viscosity of the electrolyte is reduced, the lithium-ion transport rate is increased, and the fast-charging performance of the battery cell is improved.

[0106] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the lithium fluorosulfonylimide can be 4%-8%, for example, 4%, 4.5%, 5%, 5.5%, 6%, 8%, etc., or any range of the above values. This reduces HF generation, decreases corrosion of the SEI film, reduces electrolyte consumption during battery cell cycling, and improves the cycle performance of the battery cell.

[0107] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of lithium hexafluorophosphate can be 8%-12%, for example, 8%, 9%, 10%, 11%, 12%, etc., or any range of the above values. This reduces the viscosity of the electrolyte, increases the lithium-ion transport rate, and improves the fast-charging performance of the battery cell.

[0108] According to some embodiments of this application, the fluorinated sulfonylimide lithium includes one or more of lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, and lithium perfluorobutylsulfonylimide. This reduces HF generation and decreases corrosion of the SEI film.

[0109] According to some embodiments of this application, the electrolyte further includes a solvent, which includes one or both of carbonate solvents and carboxylic acid ester solvents. This improves the conductivity of the electrolyte and enhances the fast-charging performance of the battery cell.

[0110] In this application, after disassembling the battery cells to obtain the electrolyte, the solvent of the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography, referring to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents".

[0111] According to some embodiments of this application, the carbonate solvent may include one or more of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. This increases the dielectric constant of the electrolyte.

[0112] According to some embodiments of this application, the carboxylic acid ester solvent includes compounds represented by Formula I:

[0113] R5 includes any one of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, while R6 includes any one of C1-C5 alkyl groups and C1-C5 haloalkyl groups. Therefore, the aforementioned types of carboxylic acid ester solvents have relatively small molecular weights, which can improve the ionic conductivity of the electrolyte and enhance the rate performance of the battery cells.

[0114] According to some embodiments of this application, the carboxylic acid 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. Therefore, the above-mentioned types of carboxylic acid ester solvents have relatively small molecular weights, which can improve the ionic conductivity of the electrolyte and enhance the rate performance of the battery cell.

[0115] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent can be 20%-70%, for example, 20%, 30%, 40%, 50%, 60%, 70%, etc., or any range of the above values. This improves the ionic conductivity of the electrolyte.

[0116] According to some embodiments of this 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 any range of the above values. By keeping 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.

[0117] According to some embodiments of this application, the electrolyte further includes additives, which include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. Therefore, the above-mentioned additives can preferentially decompose on the positive and negative electrode surfaces to form stable, low-impedance interface films, reducing the contact between the electrolyte and the positive and negative electrode surfaces, lowering the risk of electrolyte decomposition, and improving the cycle performance and fast-charging performance of the battery cells.

[0118] According to some embodiments of this application, the carbonate additives include one or more of vinylene carbonate (VC) and ethylene carbonate derivatives. Therefore, the above-mentioned carbonate additives can form a stable interfacial film on the electrode surface, reducing side reactions between the electrolyte and the electrode surface, and improving the cycle life of the battery cell.

[0119] According to some embodiments of this application, the mass percentage of the carbonate additive is 3%-8% based on the total mass of the electrolyte. For example, it can be 3%, 4%, 5%, 6%, 7%, 8%, etc., or any range of the above values. This improves the cycle life of the battery cell while reducing the viscosity of the electrolyte and lowering the internal resistance of the battery cell.

[0120] According to some embodiments of this application, the mass percentage of vinylene carbonate is 2%-5%. For example, it can be 2%, 3%, 4%, 5%, or any range of the above values. Therefore, vinylene carbonate has high reactivity, 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. Furthermore, the SEI film formed with the participation of VC has good ionic conductivity, enabling rapid transport of lithium ions between the electrode and the electrolyte, thus improving the charge and discharge efficiency of the battery.

[0121] According to some embodiments of this application, the mass percentage of the ethylene carbonate derivative is 0%-4%. For example, it can be 0.5%, 1%, 2%, 3%, 4%, etc., or any range of the above values. According to some specific embodiments of this application, the mass percentage of the ethylene carbonate derivative is 1.5%-3.5%. This reduces the interfacial resistance of the SEI film, improves the charge and discharge efficiency of the battery, and, when used in conjunction with VC, enhances the stability and integrity of the SEI film.

[0122] According to some embodiments of this application, the ethylene carbonate derivative includes compounds represented by formula Π.

[0123] R1, R2, R3, and R4 each independently include any one of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, and R1, R2, R3, and R4 are not all hydrogen atoms simultaneously. This improves the cycle life of the battery cell.

[0124] [Correction based on Rule 91, 06.08.2025] According to some embodiments of this application, the ethylene carbonate derivative includes at least one of the compounds shown in Formula Π-1, Formula Π-2, and Formula Π-3:

[0125] According to some embodiments of this application, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, 1,3-propanesulfonate lactone, butene sulfite, vinyl sulfite, and methylene disulfonate. Thus, the above-mentioned additives can form a highly ionicly conductive SEI film on the negative electrode surface, reducing the resistance to lithium ion transport at the electrode-electrolyte interface, reducing the impedance of the battery cell, and improving the fast-charging performance of the battery cell.

[0126] According to some embodiments of this application, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate borate). Therefore, the above-mentioned lithium salt additives can form a stable SEI film on the negative electrode surface, reducing side reactions between the electrolyte and the electrode surface, reducing electrolyte decomposition, and reducing gas generation in the battery cell under high-temperature conditions.

[0127] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the sulfur-containing additive can be 0%-2%, for example, 0.5%, 1%, 1.5%, 2%, etc., or any range of the above values. This reduces the impedance of the battery cell while also reducing the risk of the battery cell being oxidized at high potentials to generate sulfur-containing free radicals, thereby reducing solvent decomposition initiated by sulfur-containing free radicals and reducing gas production by the battery cell. According to some embodiments of this application, the mass percentage of the sulfur-containing additive can be 0.5%-2%.

[0128] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive can be 0%-1%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1%, etc., or a range of any of the above values. This reduces gas production in individual battery cells while lowering the content of inorganic components in the SEI film, thus reducing film resistance. According to some embodiments of this application, the mass percentage of the lithium salt additive can be 0.2%-1%.

[0129] In this application, after disassembling the battery cells to obtain the electrolyte, the additives in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography, referring to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents".

[0130] It should be noted that as the battery cell is charged and discharged, when the amount of ethylene carbonate derivatives, sulfur-containing additives and lithium salt additives added is small, and the additives in the electrolyte will be consumed during the formation and charge-discharge cycle, generating the relevant components in the SEI film and / or CEI film, when the electrolyte is obtained after disassembling the battery cell and the content of ethylene carbonate derivatives, sulfur-containing additives and lithium salt additives is tested by gas chromatography, the content may be 0.

[0131] Specifically, taking the case where the mass content of ethylene carbonate derivative is 0 as an example, this could mean that the freshly prepared electrolyte does not contain ethylene carbonate derivative, or that the electrolyte obtained after disassembling the battery cell does not contain ethylene carbonate derivative. This situation could be due to the freshly prepared electrolyte not containing ethylene carbonate derivative, or it could be due to the addition of a small amount of ethylene carbonate derivative, but this derivative participated in the SEI film formation reaction during the battery cell formation process, resulting in a mass content of ethylene carbonate derivative of 0 during the detection process. Optionally, the freshly prepared electrolyte may include ethylene carbonate derivative.

[0132] Furthermore, regarding the addition of certain substances, such as additives, to the electrolyte, the content of additives in the battery cell electrolyte is related to formation, different battery life cycles, or different battery storage states, due to the additives' role in film formation on the surface of active materials. Therefore, the additive content in freshly prepared electrolyte may differ from that in electrolyte obtained from reverse-engineered battery cells. However, those skilled in the art can determine the approximate range of the relevant substance content in the corresponding fresh electrolyte based on the battery cell's performance level (e.g., cycle count) and residual content. Similarly, those skilled in the art can also determine the approximate range of the content in non-freshly prepared (i.e., reverse-engineered) electrolytes based on the additive content in freshly prepared electrolytes, considering the battery cell's performance requirements and storage environment.

[0133] Therefore, the additive content mentioned in the technical solution of this application can be the content of additives actively added to fresh electrolyte, or the content of residual additives detected by reverse detection based on the actual battery state.

[0134] According to some embodiments of this application, the lithium-containing phosphate includes: a matrix; and a first coating material located on at least a portion of the surface of the matrix, the first coating material containing carbon. This forms a good conductive network between the lithium-containing phosphate particles, improving the electronic conductivity of the lithium-containing phosphate.

[0135] According to some embodiments of this application, based on the total mass of the lithium-containing phosphate, the mass percentage of carbon 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 it can be any range of the above values. Therefore, while improving the electronic conductivity of the lithium-containing phosphate, the impact on lithium-ion transport is reduced, the lithium-containing phosphate loading on the positive electrode is increased, and the energy density of the battery cell is improved.

[0136] According to some embodiments of this application, the first coating material comprises a compound represented by Formula III: Li 3-d1 Fe 2-d1 M1d1 (PO m1 ) n1 Formula III,

[0137] Wherein, 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn.

[0138] The compound shown in Formula III has excellent ion-conducting properties. Together with the carbon element in the first coating material, which has excellent electrical conductivity, it improves the conductivity and ion-conducting properties of lithium phosphate, which is beneficial to improving the fast-charging performance of the battery.

[0139] According to some embodiments of this application, the matrix comprises a compound represented by Formula IV: Li x1 A y1 Me a1 M2 b1 P 1-c1 X c1 Y z1 Formula IV,

[0140] Wherein, 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;

[0141] Wherein, 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. This improves the cycle performance and safety of the battery cell.

[0142] As an example, x1 can be 0.5, 0.7, 0.9, 1.1, 1.3, etc., or a range of any of the above values.

[0143] It should be noted that lithium ions are consumed during the formation and cycling processes of battery cells, which may result in the measured lithium content (x1) in the positive electrode active material being less than 1. Conversely, if lithium replenishment agents are used on both the positive and negative electrode plates, the measured lithium content (x1) in the positive electrode active material may be greater than 1 after the battery undergoes formation and cycling.

[0144] As an example, y1 can be 0, 0.3, 0.6, 0.9, 1.3, etc., or it can be a range of any of the above values.

[0145] As an example, a1 can be 0.9, 1.1, 1.3, 1.5, etc., or a range of any of the above values.

[0146] As an example, b1 can be 0, 0.2, 0.4, 0.5, etc., or a range of any of the above values.

[0147] As an example, c1 can be 0, 0.2, 0.4, 0.5, etc., or a range of any of the above values.

[0148] As an example, z1 can be 3, 4, 5, etc., or it can be a range of any of the above values.

[0149] According to some embodiments of this application, the substrate may include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. This improves the cycle performance and safety of the battery cell.

[0150] According to some embodiments of this application, the powder compaction density of the positive electrode active material at 30000N is 2.43 g / cm³. 3 -2.85g / cm 3 For example, it could be 2.43 g / cm³. 3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 The range can be any of the values ​​mentioned above. This increases the energy density of individual battery cells.

[0151] In this application, the powder compaction density of the material has a meaning known in the art and can be tested using methods and equipment known in the art, for example, it can be tested according to the testing standard GB / T24533-2019. Specifically, a certain amount of positive electrode active material is taken as a sample and added to a UTM7305 electronic pressure testing machine with a bottom area of ​​1.327 cm². 2 In the mold, the pressure is increased to 3000 kg (equivalent to 30000 N), held for 30 s, then depressurized and held for 10 s. The compaction density of the positive electrode active material under a force of 30000 N is then recorded and calculated.

[0152] According to some embodiments of this application, the powder compaction density of the positive electrode active material at 30000N is 2.48 g / cm³. 3 -2.8g / cm 3 This improves the energy density and rate performance of individual battery cells.

[0153] According to some embodiments of this application, the single-sided coating weight of the positive electrode active material layer can be 200 mg / 1540.25 mm. 2 -350mg / 1540.25mm 2 For example, it could be 200mg / 1540.25mm. 2 250mg / 1540.25mm 2 300mg / 1540.25mm 2 350mg / 1540.25mm 2 The range can be any of the values ​​mentioned above. This increases the energy density of individual battery cells.

[0154] This application provides a method for testing the coating weight of the positive electrode active material layer: The positive electrode sheet is disassembled from the battery cell, for example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode active material layer on one side can be wiped off first), and cut into small circular pieces with an area of ​​S1. The weight of these pieces is recorded as M1. Then, the positive electrode active material layer of the weighed positive electrode sheet is wiped off, and the weight of the positive electrode current collector is measured and recorded as M0. The single-sided coating weight of the positive electrode active material layer = (M1 - M0) / S1.

[0155] According to some embodiments of this application, the negative electrode active material layer includes a negative electrode active material, which includes one or both of carbon-based and silicon-based materials. This improves the energy density and cycle performance of the battery cell.

[0156] According to some embodiments of this application, the carbon-based material includes graphite. This improves the cycle performance of the battery cell.

[0157] According to some embodiments of this application, the graphite is a secondary particle formed by the aggregation of primary particles, and at least a portion of the surface of the secondary particle has a second coating material, the second coating material comprising amorphous carbon. A secondary particle refers to a particle formed by the aggregation of two or more primary particles.

[0158] In this paper, amorphous carbon refers to transitional carbon materials with very low graphitization and crystallization, exhibiting an approximately amorphous morphology (or lacking a fixed shape and periodic structural regularity). In this application, amorphous carbon refers to the product of carbonization treatment of organic carbon sources, which has numerous end faces and defects, and a large number of lithium ion sites.

[0159] Secondary particles can enhance the migration rate of lithium ions and improve the transport performance of lithium ions, which is beneficial for the insertion and extraction of lithium ions and improves the ionic conductivity of the material. The second coating material includes amorphous carbon, which can improve the conductivity of composite graphite particles. The secondary particles in the core and the amorphous carbon coating layer together improve the conductivity of the material's electron and ion conduction properties, which helps to improve the fast charging performance of the battery cell.

[0160] According to some embodiments of this application, the mass percentage of the second coating material can be 2%-5% based on the total mass of the graphite. For example, it can be 2%, 3%, 4%, 5%, etc., or any range of the above values. This improves both the cycle performance and energy density of the battery cell.

[0161] According to some embodiments of this 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 can be any range of the above values. Therefore, a smaller volume average particle size of graphite can shorten the solid-phase migration path of lithium ions, improve the fast-charging capability of the battery cell, and at the same time, by keeping the volume average particle size within the above range, side reactions between the graphite anode and the electrolyte can also be reduced.

[0162] In this application, Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%, for example, measured using a laser particle size analyzer (Malvern Master Size 2000) according to standard GB / T 19077-2016 / ISO 13320:2009. The specific testing procedure is as follows: the battery cell is discharged to 0% SOC, then the negative electrode is disassembled and a certain amount of powder is scraped off with a blade. The sample is then thoroughly cleaned with deionized water by repeated shaking 5-10 times. After drying, it is sintered in a tube furnace at 400℃ for 2 hours. After sintering, an appropriate amount of the sample to be tested is taken (the sample concentration should be 8%-12% opacity), deionized water is added, and the sample is ultrasonically dispersed to ensure complete dispersion. The sample is then measured according to the standard GB / T19077-2016 / ISO 13320:2009.

[0163] According to some embodiments of this application, the negative electrode active material includes a silicon-based material, and the mass percentage of silicon element can be 0.3%-5% based on the total mass of the negative electrode active material layer. For example, it can be 0.3%, 1%, 2%, 3%, 4%, 5%, etc., or any range of the above values. This improves the energy density of the battery cell.

[0164] The mass content of silicon in the negative electrode active material layer is a well-known concept in the art and can be detected using well-known equipment and methods. For example, the negative electrode sheet can be immersed in a solvent such as water to separate the negative electrode active material from the negative electrode current collector. The substances in the negative electrode film layer can be obtained by filtration and used as a test sample. The silicon content can be obtained by using an ICAP7400 inductively coupled plasma atomic emission spectrometer from Thermo Fisher Scientific, USA, in accordance with the GB / T30902-2014 standard.

[0165] According to some embodiments of this application, the single-sided coating weight of the negative electrode active material layer can be 90 mg / 1540.25 mm. 2 -140mg / 1540.25mm 2 For example, it could be 90mg / 1540.25mm. 2 110mg / 1540.25mm 2 125mg / 1540.25mm 2 140mg / 1540.25mm 2 This increases the energy density of individual battery cells.

[0166] This application provides a method for testing the coating weight of the negative electrode active material layer: The negative electrode sheet is disassembled from the battery cell, for example, a single-sided coated negative electrode sheet (if it is a double-sided coated sheet, the negative electrode active material layer on one side can be wiped off first), and cut into small circular pieces with an area of ​​S2. The weight of these pieces is recorded as M3. Then, the negative electrode active material layer of the weighed negative electrode sheet is wiped off, and the weight of the negative electrode current collector is measured and recorded as M2. The single-sided coating weight of the negative electrode active material layer = (M3 - M2) / S2.

[0167] According to some embodiments of this application, along the length direction of the battery cell, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1;

[0168] 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.

[0169] Among them, OH1 is greater than or equal to OH2.

[0170] Specifically, referring to Figures 1 and 2, the battery cell includes a housing 11 and an electrode assembly. The length direction of the housing 11 is the same as the length direction of the battery cell, and the width direction of the housing 11 is the same as the width direction of the battery cell. The positive electrode includes a positive current collector and a positive active material layer 1212 disposed on at least one side of the positive current collector; the negative electrode includes a negative current collector and a negative active material layer 1222 disposed on at least one side of the negative current collector.

[0171] Referring to Figure 2, along the length 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 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 OH1 = OH. 21 -OH 11 .

[0172] Referring to Figure 2, along the width direction of the battery cell, the size of the positive electrode active material layer 1212 is OH. 12 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 OH2=OH 22 -OH 12 .

[0173] During fast charging, the electrode near the tab experiences higher overcurrent and temperature, leading to faster lithium ion migration and increased susceptibility to lithium deposition. By making the negative electrode active material layer larger than the positive electrode active material layer, more of the negative electrode active material layer can accept lithium ions, improving lithium deposition. Furthermore, since the lithium ion diffusion path is longer along the length of the battery cell, making OH1 greater than or equal to OH2 allows for more negative electrode active material layers to accept lithium ions along the length, reducing the risk of lithium ion deposition at the edges.

[0174] According to some embodiments of this application, 1mm ≤ OH1 ≤ 4mm. For example, it can be 1mm, 2mm, 3mm, 4mm, etc., or it can be any range of the above values.

[0175] According to some embodiments of this application, 1mm ≤ OH2 ≤ 3mm. For example, it can be 1mm, 2mm, 3mm, etc., or it can be any range of the above values.

[0176] Therefore, while increasing the energy density of individual battery cells, lithium plating on the negative electrode is reduced.

[0177] In this application, the dimensions of the positive electrode active material layer and the negative electrode active material layer can be measured using calipers.

[0178] According to some embodiments of this application, a positive electrode tab is provided on the positive electrode sheet, and a negative electrode tab is provided on the negative electrode sheet. The positive electrode tab extends along the length direction or the width direction of the positive electrode sheet, and the negative electrode tab extends along the length direction or the width direction of the negative electrode sheet. This improves current transmission efficiency, reduces the resistance of the battery cell, and enhances the rate performance of the battery cell.

[0179] Referring to Figure 3, there is only one positive electrode tab 1210 extending along the length of the positive electrode plate 121. Referring to Figure 4, there are positive electrode tabs 1210 extending from each end along the length of the positive electrode plate 121.

[0180] Referring to Figure 5, there is only one positive electrode tab 1210 extending along the width direction of the positive electrode plate 121. Referring to Figure 6, there are positive electrode tabs 1210 extending from each end along the width direction of the positive electrode plate 121.

[0181] Referring to Figure 7, there is only one negative electrode tab 1220 extending along the length of the negative electrode plate 122. Referring to Figure 8, there are negative electrode tabs 1220 extending from each end along the length of the negative electrode plate 122.

[0182] Referring to Figure 9, there is only one negative electrode tab 1220 extending along the width direction of the negative electrode plate 122. Referring to Figure 10, there are negative electrode tabs 1220 extending from both ends along the width direction of the negative electrode plate 122.

[0183] According to some embodiments of this application, the electrode assembly further includes a separator membrane with a porosity of 20%-70%. For example, it can be 20%, 30%, 40%, 50%, 60%, 70%, etc., or a range of any of the above values. This improves the lithium-ion transport efficiency and enhances the rate performance of the battery cell. According to some embodiments of this application, the porosity of the separator membrane is 35%-60%.

[0184] In this application, porosity refers to the percentage of the volume of the pores in the separator to the total volume of the separator. Porosity can be tested according to the standard GB / T 36363-2018 "Polyolefin Separators for Battery Cells". It should be noted that the actual testing process may differ slightly from the standard due to differences in testing instruments, testing errors, and to minimize the impact on porosity testing, in order to obtain more accurate test values.

[0185] According to some embodiments of this application, referring to FIG11, the separator 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 comprising a first inorganic material; and a second functional layer 1233 located on the side of the first functional layer 1232 away from the base film 1231, the second functional layer 1233 comprising a second inorganic material and a non-fluoropolymer. This improves the heat resistance of the separator and enhances the safety of the battery cell.

[0186] According to some embodiments of this application, the non-fluoropolymer includes acrylate copolymers. This improves the adhesion of the non-fluoropolymer and reduces the risk of the second functional layer detaching.

[0187] According to some embodiments of this application, the first inorganic material and the second inorganic material each independently comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. This improves the heat resistance of the separator and enhances the safety of the battery cell.

[0188] According to some embodiments of this application, the electrode assembly further includes a separator with a thickness of 4μm-12μm. For example, it can be 4μm, 6μm, 8μm, 10μm, 12μm, or any range of the above values. This reduces the short circuit between the positive and negative electrodes while also reducing the volume occupied by the separator within the battery cell, thereby increasing the energy density of the battery cell. According to some embodiments of this application, the separator has a thickness of 5μm-12μm.

[0189] In this application, the thickness of the base film can be tested using a micrometer.

[0190] According to some embodiments of this application, the battery cell includes a housing and a cover assembly, the cover assembly being disposed at at least one end of the housing, the housing and the cover assembly defining a receiving cavity, and the electrode assembly being disposed within the receiving cavity. Referring to FIG1, the battery cell includes a housing 11, the thickness of the housing 111 on the large surface of the battery cell being 0.1 mm-0.5 mm. This improves the energy density of the battery cell.

[0191] As an example, the thickness of the large-area shell 111 can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, etc., or can be any range of the above values. According to some embodiments of this application, the thickness of the shell can be 0.2mm-0.35mm. This increases the energy density of the battery cell.

[0192] According to some embodiments of this application, the cover assembly includes a first cover assembly and a second cover assembly, which are disposed at both ends of the housing in the length or width direction. The first cover assembly includes a first cover plate and a first electrode terminal, and the second cover assembly includes a second cover plate and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite. This reduces the temperature rise of the battery cell during charging, thereby reducing the impedance of the battery cell.

[0193] According to some embodiments of this application, referring to FIG12, 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, wherein 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, wherein the polarities of the second electrode terminal 132 and the fourth electrode terminal 134 are opposite.

[0194] According to some embodiments of this application, the minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal is S, and satisfies 150 mm. 2 ≤S≤1000mm 2 This improves the overcurrent capacity of individual battery cells, reduces heat generation at the electrode terminals, lowers the internal resistance of individual battery cells, and enhances the cycle performance of individual battery cells.

[0195] In this 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.

[0196] In this application, when testing the minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal, the calculation can be performed based on 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.

[0197] As an example, the minimum cross-sectional area S of the first electrode terminal and / or the second electrode terminal can be 150 mm. 2 300mm 2 450mm 2 600mm 2 750mm 2 900mm 2 1000mm 2 etc., or a range consisting of any of the above values.

[0198] According to some embodiments of this application, the volumetric energy density of the battery cell is 400Wh / L-530Wh / L.

[0199] In this application, when testing the volumetric energy density of a single battery cell, the battery cell is placed at 25°C and charged to 3.65V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 3.65V, and left to stand for 30 minutes; it is then discharged to 2.0V with a constant current of 0.33C, and the discharge capacity A0 at this point is recorded in Ah; the length, width, and height of the battery cell are measured using calipers, and the volume of the single battery cell V0 is calculated in L; the volumetric energy density of the battery cell VED = (A0 × discharge plateau voltage) / V0, in Wh / L.

[0200] The second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0201] A third aspect of this application provides an electrical device, including a battery cell provided in the first aspect of this application or a battery device provided in the second aspect of this application, wherein the battery cell or the battery device provides electrical energy to the electrical device.

[0202] The electrical equipment may include, but is not limited to, 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 and satellites, energy storage systems, etc.

[0203] As for the electrical equipment, the battery device can be selected according to its usage requirements.

[0204] Figure 13 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0205] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0206] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0207] Example 1

[0208] 1. Preparation of positive electrode sheet

[0209] The positive electrode sheet 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.

[0210] The positive electrode conductive layer on the positive electrode current collector is a film formed by uniformly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride PVDF, and the solvent N-methylpyrrolidone (NMP), coating it on the surface of the positive electrode current collector, and drying it. The thickness is 1μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0211] The positive electrode active material layer comprises a film layer formed by uniformly coating the surface of the positive electrode conductive layer with a positive electrode slurry (solvent is NMP) and then drying and cold pressing. The positive electrode active material layer comprises positive electrode active material, binder polyvinylidene fluoride (PVDF) and conductive agent acetylene black in a mass ratio of 97:2:1.

[0212] The positive electrode active material includes lithium iron phosphate particles and a first coating material. The first coating material is coated on the surface of the lithium iron phosphate particles. The first coating material includes lithium titanium iron phosphate (Li2FeTi(PO4)3) and carbon, with a carbon content of 1.12% by mass.

[0213] The single-sided coating weight of the positive electrode active material layer is 263 mg / 1540.25 mm. 2 .

[0214] The compaction density of the positive electrode active material is 2.46 g / cm³. 3 .

[0215] 2. Preparation of negative electrode sheet

[0216] The negative electrode sheet 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.

[0217] The negative electrode conductive layer on the negative electrode current collector is a film formed by uniformly mixing the negative electrode conductive agent superconducting carbon, the negative electrode binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na), and the solvent water, coating it on the surface of the negative electrode current collector, and drying it. The thickness is 1 μm. The mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0218] The negative electrode active material layer comprises a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) onto the surface of the negative electrode conductive layer, followed by drying and cold pressing.

[0219] The negative electrode active material layer includes a negative electrode active material in a mass ratio of 96.5:0.5:2:1, a conductive agent acetylene black, a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose. The graphite particles include artificial graphite and a second coating material, which coats the surface of the artificial graphite. The carbon content in the second coating material is 3.5% by mass, and the Dv50 of the graphite particles is 11.3 μm.

[0220] The single-sided coating weight of the negative electrode active material layer is 120 mg / 1540.25 mm. 2 .

[0221] The compaction density of the negative electrode active material layer is 1.35 g / cm³. 3 .

[0222] The length of the negative electrode active material layer is 4 mm longer than that of the positive electrode active material layer, and the width of the negative electrode active material layer is 3 mm wider than that of the positive electrode active material layer.

[0223] 3. Separating membrane

[0224] The separator includes a base membrane and functional layers disposed on both sides of the base membrane. The base membrane includes a 7μm polyethylene membrane layer with a porosity of 42%.

[0225] The functional layer includes a first functional layer and a second functional layer. The first functional layer includes polyacrylate and alumina particles dispersed on the polyacrylate. The first functional layer is a film layer formed by coating a first slurry onto one side of the base film, with a thickness of 1 μm and an average particle size of 10 nm for the alumina particles. The first slurry includes alumina particles and a binder, polyacrylate.

[0226] 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 the 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 includes polyacrylate and PVDF particles.

[0227] 4. Preparation of electrolyte

[0228] The electrolyte consists of organic solvents, lithium salts, and additives.

[0229] The components of each organic solvent are mixed, and lithium salt and additives are added to prepare an electrolyte.

[0230] The organic solvents include 39% by mass of chain carboxylic acid ester solvents (ethyl acetate), 27.3% by mass of ethylene carbonate EC, and 11.7% by mass of dimethyl carbonate. The mass content of each component in the organic solvents is calculated based on the mass of the electrolyte.

[0231] The additives include vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfite (ES), and lithium difluorooxalate borate (LiDFOB) in a mass ratio of 4:2:0.5:0.5.

[0232] The lithium salt comprises 5% lithium bis(fluorosulfonyl)imide (LiFSI) and 10% lithium hexafluorophosphate (LiPF6) by mass, with the mass content of the lithium salt calculated based on the mass of the electrolyte.

[0233] 5. Preparation of battery cells

[0234] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes, to obtain a stacked electrode assembly. The electrode assembly is placed in a housing, with the positive and negative terminals set on the housing. After baking, electrolyte is injected. After vacuum sealing, settling, formation, and shaping, a battery cell is obtained.

[0235] The mass of electrolyte per Ah of battery cell is 2.45g.

[0236] The outer shell is a rectangular aluminum shell, and the thickness of the shell corresponding to the largest surface area of ​​the rectangular structure is 0.5mm.

[0237] Performance testing

[0238] 1. Volumetric energy density

[0239] The battery cells in the examples and comparative examples were placed at 25°C and charged to 3.65V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 3.65V, and left to stand for 30 minutes; they were then discharged to 2.0V with a constant current of 0.33C, and the discharge capacity A0 was recorded at this time, in Ah; the length, width, and height of the battery cells were measured with calipers, and the volume of the battery cell V0 was calculated, in L; the volumetric energy density of the battery cell VED = (A0 × discharge plateau voltage) / V0, in Wh / L.

[0240] 2. Fast charging performance

[0241] At 30°C, the battery cells in the examples and comparative examples were cycled 200 times according to their respective charge-discharge strategies, and then charged to 100% SOC according to their corresponding charging strategies. The negative electrode was then disassembled, unfolded, and the cleavage region (grayish-white area) was observed and the cleavage area was measured. The degree of cleavage is as follows:

[0242] No lithium plating: Lithium plating area < 0.05%.

[0243] Slight lithium plating: lithium plating area <2%.

[0244] Severe lithium plating: lithium plating area ≥2%.

[0245] The charging process for individual battery cells includes the following steps:

[0246] Charge from 0% SOC to 40% SOC at a constant current of 5.0C; charge from 40% SOC to 45% SOC at a constant current of 4.6C; charge from 45% SOC to 50% SOC at a constant current of 4.3C; charge from 50% SOC to 55% SOC at a constant current of 4.0C; charge from 55% SOC to 60% SOC at a constant current of 3.7C; charge from 60% SOC to 65% SOC at a constant current of 3.4C; charge from 65% SOC to 70% SOC at a constant current of 3.1C; and so on. Charge from 70% SOC to 75% SOC at a constant current of 2.9C; from 75% SOC to 80% SOC at a constant current of 2.7C; from 80% SOC to 85% SOC at a constant current of 1.8C; from 85% SOC to 90% SOC at a constant current of 1.3C; from 90% SOC to 95% SOC at a constant current of 0.7C; from 95% SOC to 98% SOC at a constant current of 0.33C; and from 98% SOC to 100% SOC at a constant current of 0.1C.

[0247] The cutoff voltage for the final charging step in the above charging process is 3.65V.

[0248] The discharge strategy is as follows: discharge at a constant current of 0.33C until the cutoff voltage, for example, 2.0V.

[0249] In the above-mentioned charge and discharge tests of individual battery cells, the individual battery cells can be assembled in a battery device, and the required charge and discharge strategies can be controlled by the battery management system for testing.

[0250] 3. Cyclic performance

[0251] At 60°C, the battery cells are charged at a constant current of 0.8C to the charging cutoff voltage of 3.6V, then charged at a constant current of 0.1C to the charging cutoff voltage of 3.65V, and allowed to stand for 30 minutes; then discharged at a constant current of 1C to 3.1V, and allowed to stand for 30 minutes. This constitutes one charge-discharge cycle. The above charge-discharge cycle steps are repeated until the cycle capacity retention rate (i.e., C) is achieved. n The percentage of (C0×100%) is 70%, and the number of cycles is recorded. The more cycles, the better the cycle performance of the battery cell.

[0252] 4. Compacted density of the positive electrode sheet

[0253] Place the battery cell at 25°C and let it stand for 2 hours. Charge it at a constant current of 1 / 3C to 3.65V, then charge it at a constant voltage of 3.65V to 0.05C. Let it stand for 2 hours, then discharge it at a rate of 0.33C to 2.0V. Disassemble the battery cell to remove the positive electrode sheet. For example, take a single-sided coated positive electrode sheet (if it is a double-sided coated electrode sheet, wipe off the positive active material layer on one side first), cut it into a small circular piece with an area of ​​S1, weigh it, record its weight as M1, and measure its thickness H1. Then wipe off the positive active material layer of the weighed positive electrode sheet, weigh the positive current collector, record its weight as M0, and measure its thickness H0. The single-sided coating weight of the positive active material layer = (M1-M0) / S1, the thickness of the positive active material layer = H1-H0, and the compaction density of the positive active material layer = single-sided coating weight of the positive active material layer / thickness of the positive active material layer.

[0254] 5. Compacted density of the negative electrode sheet

[0255] Place the battery cell at 25°C and let it stand for 2 hours. Charge it at a constant current of 1 / 3C to 3.65V, then charge it at a constant voltage of 3.65V to 0.05C. Place the battery cell at 25°C and let it stand for 2 hours. Then discharge it at a rate of 0.33C to 2.0V. Disassemble the battery cell to remove the negative electrode sheet. For example, take a single-sided coated negative electrode sheet (if it is a double-sided coated electrode sheet, wipe off the negative active material layer on one side first), cut it into a small circular piece with an area of ​​S2, weigh it, record its weight as M3, and measure its thickness H3. Then wipe off the negative active material layer of the weighed negative electrode sheet, weigh the negative current collector, record its weight as M2, and measure its thickness H2. The single-sided coating weight of the negative electrode active material layer = (M3-M2) / S2, the thickness of the negative electrode active material layer = H3-H2, and the compaction density of the negative electrode active material layer = single-sided coating weight of the negative electrode active material layer / thickness of the negative electrode active material layer.

[0256] 5. Mass of electrolyte per Ah of battery cell

[0257] ① Take a single battery cell and weigh it (M0). ② Disassemble the battery cell, pour out the free electrolyte, and remove the electrodes, separator, mechanical parts, and adhesive tape. ③ Soak the electrodes, separator, mechanical parts, and adhesive tape in dimethyl carbonate (DMC) for 24 hours, repeating the cleaning process at least three times. ④ After cleaning, place the electrodes, separator, mechanical parts, and adhesive tape in an oven until completely dry. ⑤ Weigh the total mass of the electrodes, separator, mechanical parts, and adhesive tape, and record the mass as M1. ⑥ The electrolyte mass per unit rated capacity (1 Ah) of the battery cell = (M0 - M1) / a. a = rated capacity of the battery cell, in Ah.

[0258] 6. Mass ratio of lithium fluorosulfonylimide and lithium hexafluorophosphate

[0259] The testing of lithium fluorosulfonylimide salt and lithium hexafluorophosphate content can be referenced in standard JY / T020-2002 "General Rules for Ion Chromatographic Analysis". For example, freshly prepared electrolyte can be used as a sample, the free electrolyte from a fresh battery can be used as a sample, or a fully discharged battery cell can be disassembled in reverse (discharged to the discharge cutoff voltage so that the state of charge of the battery cell is about 0% SOC), and the free electrolyte obtained from the battery cell can be used as a sample. Ion chromatography analysis is used to detect the inorganic ion chromatograms, and the corresponding inorganic ion types are compared according to the chromatographic peak positions. The percentage of the corresponding inorganic ion content is calculated based on the peak area, and then the ratio of the mass percentage of lithium fluorosulfonylimide to the mass percentage of lithium hexafluorophosphate is calculated.

[0260] Comparative Example 1

[0261] The preparation method of the battery cell is the same as in Example 1, except that the compaction density of the positive electrode sheet is 2.4 g / cm³. 3 .

[0262] Example 2

[0263] The preparation method of the battery cell is the same as in Example 1, except that the compaction density of the positive electrode sheet is 2.7 g / cm³. 3 .

[0264] Example 3

[0265] The preparation method of the battery cell is the same as in Example 1, except that the compaction density of the positive electrode sheet is 2.8 g / cm³. 3 .

[0266] Comparative Example 2

[0267] The preparation method of the battery cell is the same as in Example 1, except that the compaction density of the positive electrode sheet is 2.85 g / cm³. 3 .

[0268] Comparative Example 3

[0269] The preparation method of the battery cell is the same as in Example 1, except that the compaction density of the negative electrode sheet is 1.1 g / cm³. 3 .

[0270] Example 4

[0271] The preparation method of the battery cell is the same as in Example 1, except that the compaction density of the negative electrode sheet is 1.25 g / cm³. 3 .

[0272] Example 5

[0273] The preparation method of the battery cell is the same as in Example 1, except that the compaction density of the negative electrode sheet is 1.5 g / cm³. 3 .

[0274] Comparative Example 4

[0275] The preparation method of the battery cell is the same as in Example 1, except that the compaction density of the negative electrode sheet is 1.6 g / cm³. 3 .

[0276] Table 1 shows the detailed differences between the individual battery cells in Examples 1-5 and Comparative Examples 1-4, as well as the test results.

[0277] Table 1

[0278] As shown in Table 1, when the mass of electrolyte per Ah of the battery cell is within the range to be protected in this application, the volumetric energy density of the battery cell can be increased by controlling the compaction density of the positive and negative electrode sheets. Furthermore, when the compaction density of the positive electrode sheet is 2.46 g / cm³... 3 -2.8g / cm 3 The compaction density of the negative electrode sheet is 1.3 g / cm³. 3 -1.5g / cm 3 When the electrolyte contains both lithium fluorosulfonylimide and lithium hexafluorophosphate in a suitable mass ratio, a battery cell with good cycle performance can be obtained with a smaller amount of electrolyte. This indicates that when the compaction density of the positive and negative electrode plates is within a suitable range, controlling the content of lithium fluorosulfonylimide and lithium hexafluorophosphate can reduce HF generation, decrease electrolyte and additive consumption, and obtain a battery cell with both high energy density and good cycle and fast-charging performance.

[0279] Comparative Example 5

[0280] The preparation method of the battery cell is the same as in Example 2, except that the compaction density of the positive electrode sheet is 2.8 g / cm³. 3 The mass of electrolyte per Ah of battery cell is 2.1g.

[0281] Example 6

[0282] The preparation method of the battery cell is the same as in Example 2, except that the compaction density of the positive electrode sheet is 2.8 g / cm³. 3 The mass of electrolyte per Ah of battery cell is 2.2g.

[0283] Example 7

[0284] The preparation method of the battery cell is the same as in Example 2, except that the mass of electrolyte corresponding to each Ah of battery cell is 2.8g.

[0285] The test results of the individual cells in Comparative Example 5, Example 6, and Example 7 are shown in Table 2.

[0286] Table 2

[0287] As shown in Table 2, when the compaction density of the positive and negative electrode sheets is within the range protected by this application, and the electrolyte contains both lithium fluorosulfonylimide and lithium hexafluorophosphate, the cycle performance of the battery cell gradually improves with the increase of the electrolyte mass per Ah. However, the volumetric energy density of the battery cell gradually decreases. When the electrolyte mass per Ah of the battery cell exceeds 3g, the energy density continues to decrease. When the electrolyte mass per Ah of the battery cell is 2.2g-3g, the battery cell exhibits both high volumetric energy density and good cycle performance.

[0288] Comparative Example 6

[0289] The preparation method of the battery cell is the same as in Example 2, except that the mass ratio of LiFSI is 1%, the mass ratio of LiPF6 is 14%, and the mass ratio of LiFSI to LiPF6 is 0.1.

[0290] Example 9

[0291] The preparation method of the battery cell is the same as in Example 2, except that the mass ratio of LiFSI is 4%, the mass ratio of LiPF6 is 11%, and the mass ratio of LiFSI to LiPF6 is 0.4.

[0292] Example 10

[0293] The preparation method of the battery cell is the same as in Example 2, except that the mass ratio of LiFSI is 6%, the mass ratio of LiPF6 is 9%, and the mass ratio of LiFSI to LiPF6 is 0.7.

[0294] Comparative Example 7

[0295] The preparation method of the battery cell is the same as in Example 2, except that the mass ratio of LiFSI is 9%, the mass ratio of LiPF6 is 6%, and the mass ratio of LiFSI to LiPF6 is 1.5.

[0296] The test results of the individual cells in Comparative Example 6, Example 9, Example 10, and Comparative Example 7 are shown in Table 3.

[0297] Table 3

[0298] Table 3 shows that the ratio of LiFSI to LiPF6 can be adjusted by changing the content of LiFSI and LiPF6 in the electrolyte. When the content of LiFSI is low and the content of LiPF6 is high, LiPF6 is prone to hydrolysis to form HF, which corrodes the SEI film and reduces the cycle performance of the battery cell. When the content of LiFSI is high and the content of LiPF6 is low, although the cycle performance of the battery cell can be improved, excessive LiFSI will deteriorate the safety of the battery cell.

[0299] Example 11

[0300] The preparation method of the battery cell is the same as in Example 2, except that the lithium fluorinated sulfonyl imide is lithium bis(trifluoromethanesulfonyl imide).

[0301] Example 12

[0302] The preparation method of the battery cell is the same as in Example 2, except that the lithium fluorinated sulfonyl imide is lithium perfluorobutyl sulfonyl imide.

[0303] The test results of the battery cells in Examples 2, 11, and 12 are shown in Table 4.

[0304] Table 4

[0305] As shown in Table 4, adding different types of lithium fluorosulfonyl imide to the electrolyte and controlling the mass ratio of lithium fluorosulfonyl imide to LiPF6 can improve the cycle performance of the battery cell.

[0306] Example 13

[0307] The preparation method of the battery cell is the same as in Example 2, except that the mass percentage of dimethyl carbonate is 14.2%, the mass percentage of VC is 2%, and the mass percentage of FEC is 1.5%.

[0308] Example 14

[0309] The preparation method of the battery cell is the same as in Example 2, except that the mass percentage of dimethyl carbonate is 9.7%, the mass percentage of VC is 5%, and the mass percentage of FEC is 3%.

[0310] Example 15

[0311] The preparation method of the battery cell is the same as in Example 2, except that the mass ratio of VC is 2.5% and the mass ratio of FEC is 3.5%.

[0312] The test results of the battery cells in Examples 2, 13-15 are shown in Table 5.

[0313] Table 5

[0314] As shown in Table 5, adjusting the content of carbonate additives in the electrolyte can improve the cycle performance of the battery cell, indicating that adjusting the content of carbonate additives forms a more stable SEI film, thereby reducing side reactions between the electrolyte and the electrode surface.

[0315] Example 16

[0316] The preparation method of the battery cells is the same as in Example 2, except that EC accounts for 18% by mass, does not contain dimethyl carbonate, and ethyl acetate accounts for 60% by mass.

[0317] Example 17

[0318] The preparation method of the battery cell is the same as in Example 2, except that the carboxylic acid ester solvent is methyl formate, the mass percentage of VC is 5%, and the mass percentage of FEC is 1%.

[0319] Example 18

[0320] The preparation method of the battery cell is the same as in Example 2, except that the mass percentage of ethyl acetate is 10.2% and the mass percentage of ES is 2%.

[0321] Example 19

[0322] The preparation method of the battery cell is the same as in Example 2, except that the sulfur-containing additive is ethylene sulfate.

[0323] The test results of the battery cells in Examples 16-19 are shown in Table 6.

[0324] Table 6

[0325] As shown in Table 6, when the compaction density of the positive and negative electrode sheets, the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate, and the electrolyte content are all within the ranges proposed in this application, the cycle performance of the battery cell can be further optimized by adjusting the types and contents of carbonate and carboxylic acid ester solvents in the electrolyte. Carbonate solvents can increase the dielectric constant of the electrolyte, while carboxylic acid ester solvents, with their small molecular weight, can reduce the viscosity of the electrolyte, thereby further improving the cycle performance and fast-charging performance of the battery cell.

[0326] Example 20

[0327] The preparation method of the battery cell is the same as in Example 2, except that the mass ratio of dimethyl carbonate is 11.2% and the mass ratio of lithium salt additives is 1%.

[0328] Example 21

[0329] The preparation method of the battery cell is the same as in 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.

[0330] The test results of the individual battery cells in Examples 2, 20, and 21 are shown in Table 7.

[0331] Table 7

[0332] As can be seen from Table 7, when the compaction density of the positive and negative electrode sheets, the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate, and the electrolyte content are all within the range proposed in this application, the cycle performance of the battery cell can be further improved by adjusting the content and type of lithium salt additives. That is, lithium salt additives can form a stable SEI film on the negative electrode surface, thereby reducing the side reactions between the electrolyte and the electrode surface.

Claims

1. A battery cell, comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode and a negative electrode, wherein, The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The positive active material layer includes a positive active material, which includes lithium phosphate. The compacted density of the positive electrode sheet is 2.46 g / cm³. 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, and the compaction density of the negative electrode sheet is 1.25 g / cm³. 3 -1.5g / cm 3 ; The electrolyte comprises lithium fluorosulfonylimide and lithium hexafluorophosphate, and the mass ratio of the lithium fluorosulfonylimide to the lithium hexafluorophosphate is 0.4-0.8 based on the total mass of the electrolyte. The mass of electrolyte per Ah of the battery cell is 2.2g-3g.

2. The battery cell according to claim 1, wherein, The compaction density of the positive electrode sheet is 2.65 g / cm³. 3 -2.8g / cm 3 .

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

4. The battery cell according to any one of claims 1-3, wherein, Based on the total mass of the electrolyte, the mass percentage of lithium hexafluorophosphate is 8%-12%.

5. The battery cell according to any one of claims 1-4, wherein, The fluorinated sulfonyl imide lithium includes one or more of lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, and lithium perfluorobutylsulfonyl imide.

6. The battery cell according to any one of claims 1-5, wherein, The electrolyte also includes a solvent, which includes one or both of carbonate solvents and carboxylic acid ester solvents.

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

8. The battery cell according to claim 6 or 7, wherein, The carboxylic acid ester solvents include compounds represented by Formula I: R5 includes any one of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, and R6 includes any one of C1-C5 alkyl groups and C1-C5 haloalkyl groups.

9. The battery cell according to any one of claims 6-8, wherein, The carboxylic acid ester solvents include one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

10. The battery cell according to any one of claims 6-9, wherein, Based on the total mass of the electrolyte, the mass percentage of the carbonate solvent is 20%-70%.

11. The battery cell according to any one of claims 6-10, wherein, Based on the total mass of the electrolyte, the mass percentage of the carboxylic acid ester solvent is 10%-60%.

12. The battery cell according to any one of claims 1-11, wherein, The electrolyte also includes additives, which include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives.

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

14. The battery cell according to claim 13, wherein, The ethylene carbonate derivatives include compounds represented by formula Π. R1, R2, R3, and R4 each independently include any one of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, and R1, R2, R3, and R4 are not all hydrogen atoms at the same time.

15. [Correction 06.08.2025 according to Rule 91] The battery cell according to claim 13 or 14, wherein, The ethylene carbonate derivatives include at least one of the compounds shown in Formula Π-1, Formula Π-2, and Formula Π-3:

16. The battery cell according to any one of claims 12-15, wherein, Based on the total mass of the electrolyte, the carbonate additive accounts for 3%-8% of the total mass.

17. The battery cell according to any one of claims 13-16, wherein, The mass percentage of the vinylene carbonate is 2%-5%.

18. The battery cell according to any one of claims 13-17, wherein, The ethylene carbonate derivative accounts for 0%-4% of the total mass.

19. The battery cell according to any one of claims 13-18, wherein, The ethylene carbonate derivative comprises 1.5%-3.5% by mass.

20. The battery cell according to claim 12, wherein, The sulfur-containing additives include one or more of vinyl sulfate, vinyl disulfate, 1,3-propanesulfonate lactone, butene sulfite, vinyl sulfite, and methylene disulfonate.

21. The battery cell according to claim 20, wherein, The sulfur-containing additive accounts for 0-2% of the total mass of the electrolyte.

22. The battery cell according to claim 20 or 21, wherein, Based on the total mass of the electrolyte, the sulfur-containing additive accounts for 0.5%-2% of the total mass.

23. The battery cell according to claim 12, wherein, The lithium salt additives include one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium dioxalate borate.

24. The battery cell according to any one of claims 12-22, wherein, The lithium salt additive accounts for 0-1% of the total mass of the electrolyte.

25. The battery cell according to any one of claims 12-24, wherein, Based on the total mass of the electrolyte, the lithium salt additive accounts for 0.2%-1% of the total mass.

26. The battery cell according to any one of claims 1-25, wherein, The lithium-containing phosphate includes: Matrix; A first coating material is located 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, wherein, Based on the total mass of the lithium phosphate, the carbon element accounts for 0.8%-2.3% of the total mass.

28. The battery cell according to claim 26 or 27, wherein, The first coating material comprises the compound represented by Formula III: Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula III, Wherein, 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 any one of claims 26-28, wherein, The matrix comprises a compound of formula IV: Li x1 A y1 Me a1 M2 b1 P 1-c1 X c1 Y z1 Formula IV, Wherein, 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; Wherein, 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 any one of claims 26-29, wherein, The matrix includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

31. The battery cell according to any one of claims 1-30, wherein, The compacted density of the positive electrode active material at 30000N is 2.43 g / cm³. 3 -2.85g / cm 3 .

32. The battery cell according to any one of claims 1-31, wherein, 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 any one of claims 1-32, wherein, The negative electrode active material layer includes a negative electrode active material, which includes one or both of carbon-based materials and silicon-based materials.

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

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

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

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

38. The battery cell according to any one of claims 33-37, wherein, The negative electrode active material includes silicon-based materials, and the mass percentage of silicon element is 0.3%-5% based on the total mass of the negative electrode active material layer.

39. The battery cell according to any one of claims 33-38, wherein, 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 any one of claims 1-39, wherein along the length direction of the battery cell, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1; 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. in, OH1 is greater than or equal to OH2.

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

42. The battery cell according to any one of claims 1-41, wherein, The positive electrode plate is provided with a positive electrode tab, and the negative electrode plate is provided with a negative electrode tab. The positive electrode tab extends along the length direction or the width direction of the positive electrode plate, and the negative electrode tab extends along the length direction or the width direction of the negative electrode plate.

43. The battery cell according to any one of claims 1-42, wherein, The electrode assembly also includes a separator membrane with a porosity of 20%-70%.

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

45. The battery cell according to claim 43 or 44, wherein, The isolation membrane comprises: Base film; A first functional layer is located on at least one side of the base film, and the first functional layer includes a first inorganic material; The second functional layer is located on the side of the first functional layer away from the base film, and the second functional layer includes a second inorganic material and a non-fluoropolymer.

46. ​​The battery cell according to claim 45, wherein, The non-fluoropolymers include acrylate copolymers.

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

48. The battery cell according to any one of claims 45-47, wherein, The thickness of the base film is 4μm-12μm.

49. The battery cell according to any one of claims 1-48, wherein, 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 within the receiving cavity. The thickness of the housing on the large surface of the battery cell is 0.1mm-0.5mm.

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

51. The battery cell according to claim 49 or 50, wherein, The cover plate assembly includes a first cover plate assembly and a second cover plate assembly, which are disposed at both ends of the housing in the length or width direction. The first cover plate assembly includes a first cover plate and a first electrode terminal, and the second cover plate assembly includes a second cover plate and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite.

52. The battery cell according to claim 51, wherein, The minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal is S, and each independently satisfies 150 mm². 2 ≤S≤1000mm 2 .

53. The battery cell according to any one of claims 1-52, wherein, The volumetric energy density of the battery cell is 400Wh / L-530Wh / L.

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

55. An electrical device comprising a battery cell according to any one of claims 1-53 or a battery device according to claim 54, wherein the battery cell or the battery device provides electrical energy to the electrical device.

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