Battery device and power-consuming device

Abstract

The present application relates to a battery device and an electrical device. The battery device includes a thermal insulator and at least two battery cells arranged along a first direction. The battery cells include an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer including a lithium-containing phosphate. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer including graphite particles. The electrolyte includes a fluorine-containing sulfonyl imide salt, and the mass content of the fluorine-containing sulfonyl imide salt in the electrolyte is 2% to 12%. The battery cell includes two first surfaces facing each other along the first direction. The thermal insulator covers at least one of the two first surfaces. The dimension of the thermal insulator along the first direction is 0.3 mm to 5 mm. The present application can improve the cycle performance and reliability of the battery device.

Description

[0001] This application claims priority to PCT international application PCT / CN2025 / 082580, entitled “Battery Device and Electrical Device,” filed on March 14, 2025, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to a battery device and an electrical device. Background Art

[0003] Battery devices have the characteristics of high capacity and long life, so they are widely used in electronic devices such as mobile phones, laptops, electric vehicles,

[0004] Electric vehicles, electric airplanes, electric ships, electric tools, etc. With the development of lithium-ion battery applications, higher requirements are placed on the performance of battery devices, such as the cycle performance and reliability of battery devices. Summary of the Invention

[0005] The present application provides a battery device and an electrical device, which can improve the cycle performance and reliability of the battery device.

[0006] In a first aspect, the present application provides a battery device, comprising a heat insulating member and at least two battery cells arranged along a first direction.

[0007] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector. The positive electrode film layer includes a lithium-containing phosphate. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. The negative electrode film layer includes graphite particles.

[0008] in,

[0009] The electrolyte includes a fluorinated sulfonyl imide salt, wherein the mass content of the fluorinated sulfonyl imide salt in the electrolyte is 2% to 12%;

[0010] The battery cell includes two first surfaces opposite to each other along a first direction, the heat insulator covers at least one of the two first surfaces, and a dimension of the heat insulator along the first direction is 0.3 mm to 5 mm.

[0011] Therefore, in the embodiments of the present application, on the one hand, a material system is selected in which the positive electrode active material includes a lithium-containing phosphate and the negative electrode active material includes graphite particles. The above material system has excellent cycle stability; when the above material system is used, the risk of thermal runaway of the battery cell is low;

[0012] On the other hand, the electrolyte includes a fluorinated sulfonyl imide salt. The introduction of a fluorinated sulfonyl imide salt with a mass content greater than or equal to 2% can reduce the amount of hexafluorophosphate added, thereby reducing the content of hydrofluoric acid produced by the decomposition of hexafluorophosphate, and can alleviate the damage of hydrofluoric acid to the solid electrolyte membrane SEI membrane on the negative electrode side, improve the protection effect of the SEI membrane on the negative electrode active material, and enhance the cycle performance of the battery cell; a thermal insulation member with a preset size is provided to cover the first surface of the thermal insulation member, which can effectively block the rapid conduction of heat to other battery cells, reduce the risk of heat spread, and enhance the reliability of the battery device.

[0013] In some embodiments, the size of the thermal insulation member along the first direction is 0.5 mm to 2.5 mm. When the size of the thermal insulation member is within the above range, heat conduction can be effectively alleviated, and the battery device occupies less space, thereby increasing the energy density of the battery device.

[0014] In some embodiments, the fluorinated sulfonyl imide salt comprises 2% to 6% by weight of the electrolyte, and the thermal insulation member has a dimension along the first direction of 0.5 mm or greater and 1.0 mm or less. The combination of the fluorinated sulfonyl imide salt and the appropriately sized thermal insulation member can effectively improve the thermal insulation member's ability to mitigate heat, while also improving the energy density and reliability of the battery device.

[0015] In some embodiments, the mass content of the fluorinated sulfonyl imide salt in the electrolyte is greater than 6% and less than or equal to 8%, and the dimension of the thermal insulator along the first direction is greater than 1.0 mm and less than or equal to 1.5 mm. The combination of the fluorinated sulfonyl imide salt and the appropriately sized thermal insulator can effectively improve the thermal insulator's ability to mitigate heat, while also improving the energy density and reliability of the battery device.

[0016] In some embodiments, the mass content of the fluorinated sulfonyl imide salt in the electrolyte is greater than 8% and less than or equal to 12%, and the dimension of the thermal insulator along the first direction is greater than 1.5 mm and less than or equal to 2.5 mm. The combination of the fluorinated sulfonyl imide salt and the appropriately sized thermal insulator can effectively improve the thermal insulator's ability to mitigate heat, while also improving the energy density and reliability of the battery device.

[0017] In some embodiments, the volumetric energy density of the battery cell is 400 Wh / L to 530 Wh / L, making the energy density of the battery cell relatively high.

[0018] In some embodiments, the volumetric energy density of the battery cell is between 400Wh / L and 440Wh / L, and the dimension of the thermal insulator along the first direction is greater than or equal to 0.5 mm and less than or equal to 1.0 mm. The energy density of the battery cell and the appropriately sized thermal insulator can effectively improve the thermal insulator's ability to mitigate heat, thereby enhancing the reliability of the battery device.

[0019] In some embodiments, the volumetric energy density of the battery cells is greater than 440 Wh / L and less than or equal to 490 Wh / L, and the dimension of the thermal insulation along the first direction is greater than 1.0 mm and less than or equal to 1.5 mm. The energy density of the battery cells, combined with the appropriately sized thermal insulation, can effectively improve the thermal insulation's ability to mitigate heat, thereby enhancing the reliability of the battery device.

[0020] In some embodiments, the volumetric energy density of the battery cells is greater than 490 Wh / L and less than or equal to 530 Wh / L, and the dimension of the thermal insulation along the first direction is greater than 1.5 mm and less than or equal to 2.5 mm. The energy density of the battery cells, combined with the appropriately sized thermal insulation, can effectively improve the thermal insulation's ability to mitigate heat, thereby enhancing the reliability of the battery device.

[0021] In some embodiments, the battery device satisfies: 0.9≤S2 / S1≤1, where S1 represents the area of the first surface, and its unit is mm 2 ; S2 represents the area of the projection surface of the thermal insulation member perpendicular to the first direction, and its unit is mm 2 When the battery device meets the above conditions, the area covered by the thermal insulation member on the first surface is relatively large, which can more effectively alleviate heat conduction.

[0022] In some embodiments, a battery cell includes an electrode terminal connected to at least one side of the electrode assembly along a second direction perpendicular to the first direction; the battery cell includes two first surfaces opposing each other along the first direction, and a thermal insulator covers the first surfaces; the battery assembly satisfies the following conditions: 0.8 ≤ L2 / L1 ≤ 1, where L1 represents the dimension of the first surface along the second direction, in mm; and L2 represents the dimension of the thermal insulator along the second direction, in mm. When the battery assembly meets these conditions, the thermal insulator covers a relatively large area of the first surface, thereby more effectively mitigating heat conduction.

[0023] In some embodiments, the battery device further satisfies: 2 mm ≤ L1 - L2 ≤ 10 mm. When the battery device satisfies the above conditions, the area covered by the thermal insulation member on the first surface is relatively large, which can more effectively alleviate heat conduction.

[0024] In some embodiments, the battery cell includes an electrode terminal, which is connected to at least one side of the electrode assembly along the second direction; the battery cell includes two first surfaces opposite to each other along the first direction, and the thermal insulation member covers the first surface; wherein the battery device satisfies: 0.9≤H2 / H1≤1, H1 represents the dimension of the first surface along the third direction, and its unit is mm, and the third direction and the second direction are perpendicular to the first direction; H2 represents the dimension of the thermal insulation member along the third direction, and its unit is mm.

[0025] In some embodiments, the battery device further satisfies: 1 mm ≤ H1 - H2 ≤ 10 mm. When the battery device satisfies the above conditions, the area covered by the thermal insulation member on the first surface is relatively large, which can more effectively alleviate heat conduction.

[0026] In some embodiments, the thermal insulation element includes a thermal insulation body and a support member. The support member is disposed around the thermal insulation body, and both the thermal insulation body and the support member cover the surface of the battery cell along the first direction. The support member can support and fix the thermal insulation body, allowing the thermal insulation body to effectively perform its thermal insulation function.

[0027] In some embodiments, the battery cell further includes two second surfaces opposite to each other along a third direction, the two second surfaces being connected by the first surface, the third direction being perpendicular to the first direction, wherein an area of the first surface is greater than an area of the second surface.

[0028] The first surface has a larger area, and the thermal insulation component covers the first surface, which can more effectively alleviate heat diffusion.

[0029] In some embodiments, the thermal insulation member covers both first surfaces of the battery cell, so that the thermal insulation member can more effectively alleviate heat diffusion.

[0030] In some embodiments, the thermal insulation member is bonded to the first surface, and the bonding force between the thermal insulation member and the first surface is strong, so that the thermal insulation member can effectively perform a thermal insulation function.

[0031] In some embodiments, the support member is an annular member that satisfies the following conditions: 10 mm ≤ W1-W2 ≤ 60 mm, where W1 represents the outer dimension of the annular member along the second direction; the battery cell includes an electrode terminal connected to at least one side of the electrode assembly along the second direction, the second direction being perpendicular to the first direction; W2 represents the inner dimension of the annular member along the second direction; and / or the support member satisfies the following conditions: 10 mm ≤ W3-W4 ≤ 60 mm, where W3 represents the outer dimension of the annular member along the third direction; the battery cell includes an electrode terminal connected to at least one side of the electrode assembly along the second direction, the third direction being perpendicular to the first direction; and W4 represents the inner dimension of the annular member along the third direction. When the support member meets the above conditions, it can effectively support and secure the thermal insulation body.

[0032] In some embodiments, the heat-insulating body comprises a heat-insulating material, and the heat-insulating material comprises one or more of aerogel, foam, polyurethane, and silicone rubber. These materials have excellent heat-insulating effects and can effectively alleviate heat diffusion.

[0033] In some embodiments, the support member includes one or more of polysaccharide, polyethylene terephthalate, polyurethane, polyacrylonitrile, polypropylene, polyamide, and aromatic polyamide. These materials have excellent supporting effects and can effectively support the thermal insulation material.

[0034] In some embodiments, the fluorine-containing sulfonyl imide salt includes one or more of bis(fluorosulfonyl)imide salt, bis(trifluoromethanesulfonyl)imide salt, and perfluorobutylsulfonyl imide salt. These materials can improve both the cycle performance and the reliability of the battery device.

[0035] In some embodiments, the mass content of the fluorinated sulfonyl imide salt in the electrolyte is 4% to 8%. When the mass content of the fluorinated sulfonyl imide salt is within the above range, both the cycle performance and the reliability of the battery device can be improved.

[0036] In some embodiments, the electrolyte further comprises hexafluorophosphate, with the mass content of the hexafluorophosphate in the electrolyte being 3% to 13%. The combined use of the fluorinated sulfonyl imide salt and the hexafluorophosphate is beneficial for improving the cycle performance and reliability of the battery device.

[0037] In some embodiments, the electrolyte further includes a carboxylate solvent, including one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate. These carboxylate solvents are beneficial for improving the cycling performance and fast charging performance of the battery cells.

[0038] In some embodiments, the mass content of the carboxylate solvent in the electrolyte is 8% to 60%. The above mass content of the carboxylate solvent is beneficial to improving the cycle performance and fast charging performance of the battery cell.

[0039] In some embodiments, the electrolyte further includes a carbonate solvent, wherein the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Such an electrolyte system is beneficial for further improving the cycle performance of the battery cell.

[0040] In some embodiments, the mass content of the carbonate solvent in the electrolyte is 18% to 70%. The above electrolyte system is conducive to further improving the cycle performance of the battery cell.

[0041] In some embodiments, the electrolyte further comprises an additive; the additive comprises a carbonate additive, the carbonate additive comprises one or more of vinylene carbonate and ethylene carbonate derivatives, the ethylene carbonate derivatives comprise a compound represented by formula A,

[0042] Formula A,

[0043] In formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time; the carbonate additive can participate in the formation of the solid electrolyte interface SEI film at the negative electrode, which is beneficial to improving the cycle performance of the battery cell.

[0044] In some embodiments, the electrolyte further includes a sulfur-containing additive, which includes one or more of vinyl sulfate, vinyl disulfate, 1,3-propane sultone, butylene sulfite, vinyl sulfite, and methylene disulfonate; the sulfur-containing additive can optimize the membrane components of the SEI film and improve the cycle performance of the battery cell.

[0045] In some embodiments, the electrolyte further includes a lithium salt additive, including one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate). Lithium salt additives can optimize the composition of the SEI film and enhance the cycling performance of the battery cell at high energy density.

[0046] In some embodiments, the mass content of the carbonate additive in the electrolyte is 2.5% to 10.0%; the carbonate additive in the above mass content can participate in the formation of the solid electrolyte interface SEI film at the negative electrode, which is beneficial to improving the cycle performance of the battery cell.

[0047] In some embodiments, the mass content of the sulfur-containing additive in the electrolyte is 0% to 2%; the above mass content of the sulfur-containing additive can optimize the film layer components of the SEI film and improve the cycle performance of the battery cell.

[0048] In some embodiments, the lithium salt additive is present in the electrolyte at a mass content of 0% to 1%. This mass content of lithium salt additive can optimize the SEI film composition and improve the cycling performance of the battery cell at high energy density.

[0049] In some embodiments, the single-sided coating weight of the positive electrode film layer is 220 mg / 1540.25 mm 2 Up to 450mg / 1540.25mm 2 When the coating weight of the positive electrode film on one side is within the above range, the heat generated per unit area of the positive electrode sheet will not be too large, thereby improving the cycle performance of the battery cell at high energy density.

[0050] In some embodiments, the single-side coating weight of the negative electrode film layer is 100 mg / 1540.25 mm 2 Up to 200mg / 1540.25mm 2When the single-side coating weight of the negative electrode film layer is within the above range, it is beneficial to improve the energy density and cycle performance of the battery cell.

[0051] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% SOC is 2.6 g / cm 3 Up to 2.8g / cm 3 When the compaction density of the positive electrode film layer is within the above range, the energy density and cycle performance of the battery cell can be improved.

[0052] In some embodiments, the negative electrode layer has a compaction density of 1.2 g / cm2 at 100% state of charge. 3 Up to 1.4g / cm 3 When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density and cycle performance of the battery cell.

[0053] In some embodiments, the lithium-containing phosphate includes phosphate particles and a positive electrode coating layer. The positive electrode coating layer is located on at least a portion of the surface of the phosphate particles and contains carbon. The positive electrode coating layer on the surface of the phosphate particles can enhance the conductivity of the lithium-containing phosphate, facilitate the migration rate of lithium ions, improve the fast charging capability of the battery, reduce the heat generation of the battery cells, and improve the cycling performance of the battery cells.

[0054] In some embodiments, the mass content of carbon is 0.8% to 2.3% based on the mass of the lithium-containing phosphate. When the mass content of carbon is within this range, the conductivity of the lithium-containing phosphate can be significantly improved, which is beneficial for enhancing the ionic and electronic conductivities of the lithium-containing phosphate, and can improve the rapid charging capability of the battery cell at high energy density.

[0055] In some embodiments, the positive electrode coating layer further comprises one or more elements selected from the group consisting of Fe, Ti, Zr, Hf, Ge, and Sn. Such a positive electrode coating layer can enhance the ionic conductivity of the positive electrode active material, improve the rapid charging capability of the battery cell, and increase the specific capacity and energy density of the corresponding battery cell.

[0056] In some embodiments, the phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. These materials have excellent cycle stability and can improve the cycle performance of battery cells.

[0057] In some embodiments, the lithium-containing phosphate comprises a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1Materials, wherein 0.5≤x1≤1.3, 0≤y1≤1.3, 0.5≤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, A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M 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, Hf, Ge, and Ce; X includes one or more of Cl, C, and N; and Y includes one or more of O and F. The above materials have excellent cycle stability and can improve the cycle performance of battery cells.

[0058] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm. When the thickness of the positive electrode current collector is within the above range, the thickness of the positive electrode current collector is relatively thin, which is beneficial to improving the volume energy density of the battery cell.

[0059] In some embodiments, the positive electrode plate further includes a positive conductive layer, which is positioned between the positive current collector and the positive electrode film layer. The positive conductive layer includes a positive conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive conductive layer can further enhance the conductivity of the positive electrode plate, reduce heat generation of the positive electrode plate, and thereby reduce heat generation of the battery cell.

[0060] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode plate can be further improved, and the heat generation of the positive electrode plate can be reduced, thereby reducing the heat generation of the battery cell, and improving the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0061] In some embodiments, the graphite particles include primary graphite particles and a negative electrode coating layer coated on the surface of the primary graphite particles. The primary graphite particles include secondary particles, and the negative electrode coating layer includes carbon. The negative electrode coating layer has excellent electrical conductivity, which can reduce the internal resistance of the negative electrode sheet, reduce heat generation in the battery cell, and improve the cycling performance of the battery cell at high energy density.

[0062] In some embodiments, the graphite bulk particles include one or more of artificial graphite and natural graphite.

[0063] In some embodiments, the carbon content of the negative electrode coating is 2% to 5% by mass, based on the mass of the graphite particles. When the carbon content of the negative electrode coating is within this range, the internal resistance of the negative electrode sheet can be further reduced, the heat generation of the battery cell can be reduced, and the cycling performance of the battery cell at high energy density can be improved.

[0064] In some embodiments, the powder resistivity of the graphite particles is 0.005 Ω·cm to 0.04 Ω·cm. When the graphite particles meet the above conditions, it is beneficial to improve the fast charging capability of the battery cell.

[0065] In some embodiments, the volume average particle size Dv50 of the graphite particles is 9.5 μm to 16.5 μm. When the graphite particles meet the above conditions, it is beneficial to improve the energy density and cycle performance of the battery cell.

[0066] In some embodiments, the negative electrode film layer further comprises a silicon-based material, wherein the mass content of silicon in the negative electrode film layer is 1% to 5%. When the mass content of silicon is within the above range, the energy density and cycle performance of the battery cell can be improved.

[0067] In some embodiments, the silicon-based material includes one or more of elemental silicon, silicon-carbon materials, silicon-oxygen materials, and silicon-nitrogen materials. Alternatively, the silicon-based material includes one or more of silicon-carbon materials, silicon-oxygen materials, and silicon-nitrogen materials. Alternatively, the silicon-based material includes silicon-carbon materials. These materials have high specific capacities, which helps improve the energy density of battery cells.

[0068] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. When the thickness of the negative electrode current collector is within the above range, the thickness of the negative electrode current collector is relatively thin, which is beneficial to improving the volume energy density of the battery cell.

[0069] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, which is positioned between the negative electrode current collector and the negative electrode film layer. The negative electrode conductive layer includes a negative electrode conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The negative electrode conductive layer can further enhance the conductivity of the negative electrode plate, reduce heat generation in the negative electrode plate, and thus reduce heat generation in the battery cell, thereby improving the fast charging performance and high-temperature cycling performance of the battery cell.

[0070] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. When the thickness of the negative electrode conductive layer is within the above range, the conductivity of the negative electrode plate can be further improved, the heat generation of the negative electrode plate can be reduced, and thus the heat generation of the battery cell can be reduced, while also improving the energy density of the battery cell.

[0071] In some embodiments, the electrode assembly further includes a separator, which is positioned between the positive and negative electrode sheets and has a thickness of 4 to 12 μm. When the separator thickness is within this range, the lithium ion migration path through the separator is shortened, further reducing the internal resistance of the battery cell, thereby lowering heat generation and improving the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0072] In some embodiments, the porosity of the separator is 20% to 70%. When the porosity of the separator is within the above range, the migration ability of lithium ions in the separator can be improved, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0073] In some embodiments, the isolation membrane further includes a base membrane and a functional layer disposed on the base membrane, the functional layer including a first functional layer and a second functional layer, the first functional layer being located on one side of the base membrane and including first inorganic particles, the second functional layer being located on the other side of the base membrane, the second functional layer including composite particles, the composite particles including second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles being attached to the surface of the non-fluoropolymer particles and / or dispersed within the non-fluoropolymer particles. The first and second functional layers have good heat resistance, thereby improving the heat resistance of the isolation membrane.

[0074] In some embodiments, the non-fluorinated polymer particles include acrylic copolymers, which have excellent bonding properties and high bonding stability with the base film.

[0075] In some embodiments, the first inorganic particles 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; the first inorganic particles are beneficial to improving the heat resistance and compression modulus of the isolation membrane.

[0076] In some embodiments, the average particle size of the first inorganic particles is 5 nm to 100 nm. When the average particle size of the first inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the isolation film.

[0077] In some embodiments, the second inorganic particles 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. The second inorganic particles can enhance the heat resistance of the second functional layer and can be combined with non-fluoropolymers to form composite particles, thereby further improving the cycle stability and kinetic properties of the isolation membrane, and improving the cycle performance and fast charging performance of the battery cell.

[0078] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0079] In some embodiments, the positive and negative electrode sheets are stacked along the thickness of the battery cell. The electrode assembly further includes a positive electrode tab and a negative electrode tab, with the positive electrode tab connected to at least one side of the positive current collector along the length of the battery cell, and the negative electrode tab connected to at least one side of the negative current collector along the length of the battery cell. Along the length of the battery cell, the negative electrode film layer is larger than the positive electrode film layer, and the difference between the negative and positive electrode film layers is OH1. Along the width of the battery cell, the negative electrode film layer is larger than the positive electrode film layer, and the difference between the negative and positive electrode film layers is OH2, where OH1 is greater than OH2. When the battery cell meets the above conditions, the risk of lithium plating can be reduced and the reliability of the battery cell can be improved.

[0080] In some embodiments, OH1 is 1 mm to 4 mm; and / or OH2 is 1 mm to 3 mm. When the battery cell meets the above conditions, the risk of lithium plating can be reduced and the reliability of the battery cell can be improved.

[0081] In a second aspect, the present application proposes an electrical device, which includes a battery device according to any embodiment of the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0083] Figure 1 A schematic structural diagram of a vehicle provided for some embodiments of the present application.

[0084] Figure 2 Schematic diagram of an explosion of a battery pack provided in some embodiments of the present application.

[0085] Figure 3 for Figure 2 The schematic diagram of the battery module is shown.

[0086] Figure 4 A schematic structural diagram of a battery cell provided in some embodiments of the present application.

[0087] Figure 5 A schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0088] Figure 6 A schematic top view of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0089] Figure 7 Schematic diagram of the structure of battery cells provided in other embodiments of the present application.

[0090] Figure 8 A schematic structural diagram of a battery device provided in some embodiments of the present application.

[0091] Figure 9 Schematic diagram of the structure of the battery device provided in some other embodiments of the present application.

[0092] Figure 10 Schematic diagram of the structure of the battery device provided in some other embodiments of the present application.

[0093] Figure 11 Schematic diagram of the structure of the battery device provided in some other embodiments of the present application.

[0094] Figure 12 Schematic diagram of the structure of the battery device provided in some other embodiments of the present application.

[0095] Figure 13 Schematic diagram of the structure of the battery device provided in some other embodiments of the present application.

[0096] Figure 14 A schematic structural diagram of a thermal insulation component of a battery device provided in some embodiments of the present application.

[0097] Figure 15 This is a schematic diagram of the assembly of the battery cell, thermal insulation and clamp of this application.

[0098] Figure 16 Schematic diagram of the structure of some battery cells for this application.

[0099] The drawings are not necessarily drawn to scale.

[0100] The following are the descriptions of the reference numerals:

[0101] X, thickness direction; Y, width direction; Z, length direction;

[0102] 1. Vehicle; 2. Battery pack; 3. Controller; 4. Motor; 5. Housing; 5a. First housing portion; 5b. Second housing portion; 5c. Accommodation space; 6. Battery module;

[0103] 7. Battery cell; 71. First test battery; 72. Trigger battery;

[0104] 10. Electrode assembly;

[0105] 11. Positive electrode sheet; 111. Positive electrode tab; 112. Positive electrode current collector; 113. Positive electrode film layer;

[0106] 12. Negative electrode sheet; 121. Negative electrode tab; 122. Negative electrode current collector; 123. Negative electrode film layer;

[0107] 13. Isolation film;

[0108] 20. Housing; 21. Shell; 211. First surface; 212. Second surface;

[0109] 22. End cap;

[0110] 31. Positive terminal; 32. Negative terminal;

[0111] 40. Thermal insulation element; 41. Thermal insulation body; 42. Support member;

[0112] 50. Battery device;

[0113] F1, first direction; F2, second direction; F3, third direction;

[0114] 60. Clamp. DETAILED DESCRIPTION

[0115] Below, the embodiments of the battery device and the power device of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary length in the following description and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0116] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0117] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0118] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0119] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which 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 may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0120] In this application, the battery cell can be cylindrical, flat, rectangular or other shapes, and the embodiments of this application do not limit this. Battery cells are generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells and soft-pack battery cells, and the embodiments of this application do not limit this.

[0121] The battery device mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.

[0122] In the related art, when heat accumulates inside a battery cell, thermal runaway may occur. In the case where a battery device includes multiple battery cells, an overheated battery cell may trigger thermal runaway of other battery cells, thereby deteriorating the reliability of the battery device.

[0123] In view of the above problems, the present application selects a material system, wherein the positive electrode active material includes a lithium-containing phosphate, and the negative electrode active material includes graphite. The above material system has relatively excellent cycle stability and a low risk of thermal runaway of the battery cell. However, under the above material system, when the lithium salt in the electrolyte is lithium hexafluorophosphate, the decomposition product (hydrofluoric acid) of the lithium hexafluorophosphate further reacts with the solid electrolyte interface SEI film on the graphite surface, resulting in increased gas production of the battery cell during high-temperature storage, which is not conducive to the long-term cycle performance of the battery cell. The present application adds fluorinated lithium sulfonyl imide to the electrolyte to significantly reduce the hydrofluoric acid content in the electrolyte and improve the cycle performance of the battery cell. Since the fluorinated lithium sulfonyl imide has a temperature contact with the thermal runaway temperature of the battery cell, Due to the characteristics of close decomposition temperature, fast thermal decomposition rate, and intense heat release, for battery cells containing lithium fluorosulfonyl imide, when the battery cells reach the thermal runaway temperature, the electrolyte will quickly release a large amount of heat and high-temperature gas, which will cause the internal heat to increase sharply in a short period of time. A large amount of heat is difficult to release quickly, which aggravates the severity of thermal runaway of the battery cells and significantly increases the safety risk. The present application provides a thermal insulation member, which covers the surface of the battery cell containing a specific content of lithium fluorosulfonyl imide, and makes the size of the thermal insulation member adapt to the content of lithium fluorosulfonyl imide, which can effectively block the rapid conduction of heat to other battery cells, reduce the speed of heat spread when thermal runaway occurs in the battery cell, and improve the reliability of the battery device.

[0124] Therefore, the embodiments of the present application can improve both the cycle performance and the reliability of the battery device.

[0125] The battery cells described in the embodiments of the present application are applicable to battery devices and electrical devices using the battery devices.

[0126] Electrical devices may include vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools, etc. Vehicles may include fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles may include pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0127] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device.

[0128] Figure 1 A schematic structural diagram of a vehicle provided in some embodiments of the present application.

[0129] like Figure 1 As shown, a battery device is provided inside the vehicle 1, and the battery device can be provided at the bottom, head, or tail of the vehicle 1. The battery device can be used to power the vehicle 1, for example, the battery device can serve as an operating power source for the vehicle 1.

[0130] The vehicle 1 may further include a controller 3 and a motor 4 . The controller 3 is used to control the battery device to supply power to the motor 4 , for example, to meet the power requirements of the vehicle 1 during startup, navigation, and driving.

[0131] In some embodiments of the present application, the battery device can serve not only as an operating power source for the vehicle 1 , but also as a driving power source for the vehicle 1 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1 .

[0132] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or hybrid via a busbar.

[0133] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0134] As an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing multiple battery cells to form an independent module. As an example, the battery module may be formed by bundling multiple battery cells with a cable tie.

[0135] In some embodiments, the battery device may be a battery pack 2 (battery pack), which includes a box and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the box.

[0136] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box by fixing the battery module in the box.

[0137] As an example, the battery cell assembly may also be housed in the box by directly fixing the plurality of battery cells to the box.

[0138] Figure 2 Schematic diagram of an explosion of a battery pack provided in some embodiments of the present application. Figure 2 As shown, the battery pack 2 includes a box 5 and a battery cell ( Figure 2 (not shown) the battery cells are housed in the box body 5.

[0139] The housing 5 is used to house battery cells and can have various structures. In some embodiments, the housing 5 can include a first housing portion 5a and a second housing portion 5b, which overlap each other and together define a storage space 5c for accommodating the battery cells. The second housing portion 5b can be a hollow structure with one end open. The first housing portion 5a is a plate-like structure, and the first housing portion 5a overlaps the open side of the second housing portion 5b to form the housing 5 with the storage space 5c. The first housing portion 5a and the second housing portion 5b can also each be a hollow structure with one end open, and the open side of the first housing portion 5a overlaps the open side of the second housing portion 5b to form the housing 5 with the storage space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0140] In order to improve the sealing performance after the first box body 5a and the second box body 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body 5a and the second box body 5b.

[0141] Assuming that the first box body portion 5a covers the top of the second box body portion 5b, the first box body portion 5a can also be called an upper box cover, and the second box body portion 5b can also be called a lower box body.

[0142] Figure 3 for Figure 2The schematic diagram of the battery module is shown.

[0143] In some embodiments, as Figure 3 As shown, there are multiple battery cells 7, which are first connected in series, in parallel, or in mixed series to form a battery module 6. The multiple battery modules 6 are then connected in series, in parallel, or in mixed series to form a whole, which is accommodated in a box.

[0144] The multiple battery cells 7 in the battery module 6 can be electrically connected via a busbar to achieve parallel, series, or mixed connection of the multiple battery cells 7 in the battery module 6. There can be one or more busbars, each of which is used to electrically connect at least two battery cells 7.

[0145] Figure 4 This is a schematic structural diagram of a battery cell 7 provided in some embodiments of the present application. Figure 5 This is a schematic diagram of an explosion of a battery cell 7 provided in some embodiments of the present application.

[0146] like Figure 4 and Figure 5 As shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing 20 , and the electrode assembly 10 is accommodated in the housing 20 .

[0147] The housing 20 can have a variety of shapes, such as a cylinder, a rectangular parallelepiped, etc. The shape of the housing 20 can be determined based on the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, the housing 20 can be a cylindrical structure. If the electrode assembly 10 has a rectangular parallelepiped structure, the housing 20 can be a rectangular parallelepiped structure. Alternatively, the electrode assembly 10 has a rectangular parallelepiped structure.

[0148] The housing 20 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the present embodiment does not impose any particular restrictions on this. Optionally, the inner wall of the housing 20 may further include an insulating layer, which can separate the housing 20 from the electrode assembly 10. The material of the insulating layer can be selected from materials commonly used in the art and is not particularly limited here.

[0149] There may be one or more electrode assemblies 10 housed in the housing 20 .

[0150] In some embodiments, the housing 20 includes a shell 21 and an end cap 22 . The shell 21 has an opening, and the end cap 22 covers the opening. The shell 21 accommodates the electrode assembly.

[0151] In some embodiments, the housing 21 is made of steel, which has high mechanical strength and is less prone to deformation, thereby improving the reliability and cycle performance of the battery cells. Optionally, steel accounts for the largest percentage by mass of the housing 21. Of course, the housing 21 may also be made of aluminum, for example.

[0152] Optionally, the shell 21 is a rectangular parallelepiped structure, for example, the shell 21 includes two first surfaces 211 opposite to each other and two second surfaces 212 opposite to each other, the two second surfaces 212 are connected by two first surfaces 211, and the area of the first surface 211 is larger than the area of the second surface 212.

[0153] Optionally, the thickness of the shell 21 is 0.1mm to 0.5mm, and optionally 0.2mm to 0.35mm. For example, the thickness of the shell 21 is 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, or a range consisting of any two of the above values. When the thickness of the shell 21 is within the above range, the mechanical strength of the shell 21 is high, which can improve the reliability and cycle performance of the battery cell 7. In addition, the shell 21 occupies less space, and the internal space of the shell 21 is more, which is conducive to improving the energy density of the battery cell 7.

[0154] The electrode assembly 10 may be a laminated structure or a wound structure.

[0155] Next, the electrode assembly 10 is described as a laminated structure.

[0156] like Figure 5 As shown, when the electrode assembly 10 has a laminated structure, there are multiple positive electrode sheets 11 and multiple negative electrode sheets 12, and the multiple positive electrode sheets 11 and the multiple negative electrode sheets 12 are stacked along the thickness direction X of the battery cell 7. Optionally, the electrode assembly 10 further includes a separator 13, which is located between the positive electrode sheet 11 and the negative electrode sheet 12.

[0157] In some embodiments, as Figure 5 and Figure 6 As shown, the positive electrode sheet 11 includes at least one positive electrode tab 111, which is connected to a positive electrode current collector 112 and extends out of the positive electrode current collector 112 along the length direction Z of the battery cell 7. Of course, the at least one positive electrode tab 111 can also be connected to the positive electrode current collector 112 and extend out of the positive electrode current collector 112 along the width direction Y of the battery cell 7.

[0158] In some embodiments, the negative electrode sheet 12 includes at least one negative electrode tab 121, which is connected to a negative electrode current collector 122 and extends out of the negative electrode current collector 122 along the length direction Z of the battery cell 7. Of course, the at least one negative electrode tab 121 can also be connected to the negative electrode current collector 122 and extend out of the negative electrode current collector 122 along the width direction Y of the battery cell 7.

[0159] In some embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collector 112 along the length direction Z, and the negative electrode tab 121 is connected to at least one side of the negative electrode current collector 122 along the length direction Z. Along the length direction Z of the battery cell 7, the size of the negative electrode film layer 123 is larger than the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH1; along the width direction Y of the battery cell 7, the size of the negative electrode film layer 123 is larger than the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH2, and OH1 is larger than OH2.

[0160] The negative electrode tab 121 is located on at least one side of the negative electrode current collector 122 along the length direction Z. The current density in the connection area between the negative electrode tab 121 and the negative electrode current collector 122 increases sharply, and lithium deposition and other problems are more likely to occur in this area. In the embodiment of the present application, OH1 is set to be greater than OH2, so that the ability of the area near the negative electrode film layer 123 to receive lithium ions in the length direction Z is stronger, especially the ability of the area near the negative electrode tab 121 of the negative electrode film layer 123 to receive lithium ions, thereby reducing the risk of lithium deposition and improving the reliability of the battery cell 7.

[0161] Exemplarily, OH1 is 0.5 mm to 3.0 mm, such as 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm, or a range consisting of any two of the above values. Along the length direction Z, both sides of the negative electrode film layer 123 extend beyond the positive electrode film layer 113, each side extending beyond OH1 / 2, that is, half the size of OH1. Figure 6 OH1 / 2 is shown in FIG.

[0162] Exemplarily, OH2 is 0.5 mm to 3.0 mm, such as 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm, or a range consisting of any two of the above values. In the width direction Y, both sides of the negative electrode film layer 123 extend beyond the positive electrode film layer 113, each side extending beyond OH2 / 2, i.e., half the size of OH2. Figure 6 OH2 / 2 is shown in FIG.

[0163] In some embodiments, as Figure 7 As shown, the battery cell 7 further includes a positive terminal 31 , which is disposed on the outer shell 20 , and may be disposed on the housing 21 or the end cover 22 .

[0164] The positive terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 are welded. The positive terminal 31 and the positive electrode tab 111 may be connected via an adapter or may not be connected via an adapter. Optionally, the positive terminal 31 and the positive electrode tab 111 are connected without an adapter, that is, the positive terminal 31 and the positive electrode tab 111 are directly welded, which can reduce the resistance at the connection point and help reduce the overall internal resistance of the battery cell 7.

[0165] In some embodiments, the battery cell 7 further includes a negative terminal 32 , which is disposed on the outer shell 20 , and may be disposed on the housing 21 or the end cover 22 .

[0166] The negative terminal 32 is electrically connected to the negative electrode tab 121. Optionally, the negative terminal 32 and the negative electrode tab 121 are welded. The negative terminal 32 and the negative electrode tab 121 may be connected via an adapter or may not be connected via an adapter. Optionally, the negative terminal 32 and the negative electrode tab 121 are connected without an adapter, that is, the negative terminal 32 and the negative electrode tab 121 are directly welded, which can reduce the resistance at the connection and help reduce the overall internal resistance of the battery cell 7.

[0167] Optionally, the number of positive terminals 31 located on the same side of the electrode assembly 10 is at least one, and optionally at least two. At least two positive terminals 31 can increase the current capacity of the positive terminal 31.

[0168] Optionally, the number of negative terminals 32 located on the same side of the electrode assembly 10 is at least one, and optionally at least two. At least two negative terminals 32 can increase the current capacity of the negative terminal 32 .

[0169] In some embodiments, the positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0170] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0171] In some embodiments, as Figure 8 As shown, the battery device 50 includes a heat insulator 40 and at least two battery cells 7 arranged along a first direction F1. The battery cells 7 include an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector. The positive electrode film layer includes a lithium-containing phosphate. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. The negative electrode film layer includes graphite particles.

[0172] in,

[0173] The electrolyte includes a fluorinated sulfonyl imide salt, and the mass content of the fluorinated sulfonyl imide salt in the electrolyte is 2% to 12%; the battery cell 7 includes two first surfaces 211 opposite to each other along a first direction F1, and the thermal insulation member 40 covers at least one of the two first surfaces 211, and the size of the thermal insulation member 40 along the first direction F1 is 0.3 mm to 5 mm.

[0174] On the one hand, the embodiment of the present application selects a material system in which the positive electrode active material includes a lithium-containing phosphate and the negative electrode active material includes graphite particles. The above material system has excellent cycle stability. When the above material system is used, the risk of thermal runaway of the battery cell 7 is low.

[0175] On the other hand, lithium hexafluorophosphate may decompose to produce hydrofluoric acid HF, and the side reaction between hydrofluoric acid and the negative electrode active material, such as the SEI film on the surface of graphite, may lead to increased gas production during high-temperature storage; the electrolyte of the present application also includes a fluorine-containing sulfonyl imide salt, but the effect of the fluorine-containing sulfonyl imide salt with a mass content of less than 2% on improving the thermal stability of the electrolyte is not obvious. The introduction of a fluorine-containing sulfonyl imide salt with a mass content of greater than or equal to 2% can reduce the amount of hexafluorophosphate added, thereby reducing the content of hydrofluoric acid generated by the decomposition of hexafluorophosphate, and can alleviate the damage of hydrofluoric acid to the SEI film, improve the protection effect of the SEI film on the negative electrode active material, and enhance the cycle performance of the battery cell 7;

[0176] However, as the amount of fluorinated sulfonyl imide salt added increases, the risk of thermal diffusion increases. Specifically, the thermal decomposition temperature of the fluorinated sulfonyl imide salt is close to the thermal runaway temperature of the battery cell 7. In addition, the fluorinated sulfonyl imide salt has a fast thermal decomposition rate and a strong heat release, which can quickly release a large amount of heat and high-temperature gas. This causes a sharp increase in the internal heat of the battery cell 7, which is difficult to release quickly, leading to thermal runaway.

[0177] The added amount of the fluorinated sulfonyl imide salt in the embodiment of the present application will not be too high and is less than or equal to 12%, and a heat insulating member 40 with a preset size is provided on the first surface 211 of the battery cell 7. For example, the size of the heat insulating member 40 along the first direction F1 is greater than or equal to 0.3 mm, so that the heat insulating member 40 has a relatively excellent heat insulating effect, can effectively block the rapid conduction of heat to other battery cells 7, reduce the risk of heat spread, and improve the reliability of the battery device 50; as the size of the heat insulating member 40 increases, the heat insulating effect increases, but due to the increase in the space occupied by the heat insulating member 40, the energy density of the battery device 50 is reduced. Therefore, the size of the heat insulating member 40 along the first direction F1 is limited to less than or equal to 5 mm, which can take into account the improvement of the reliability and energy density of the battery device 50.

[0178] Therefore, the embodiment of the present application can improve both the cycle performance and the reliability of the battery device 50 and increase the energy density of the battery device 50 .

[0179] In some embodiments, the volumetric energy density of the battery cell 7 is 400Wh / L to 530Wh / L. For example, the volumetric energy density of the battery cell 7 is 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, 450Wh / L, 460Wh / L, 470Wh / L, 480Wh / L, 490Wh / L, 500Wh / L, 510Wh / L, 520Wh / L, 530Wh / L, or a range consisting of any two of the foregoing values. The volumetric energy density of the battery cell 7 is relatively high.

[0180] In the embodiment of the present application, the volume energy density of the battery cell 7 has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the battery charging upper limit voltage is 3.65V and the battery discharge cut-off voltage is 2.0V.

[0181] Place battery cell 7 at 25°C, charge at a constant current of 0.33C to 3.65V, then charge at a constant voltage of 0.05C, and discharge at a constant current of 0.33C to 2.0V. Record the discharge capacity A0 at this time in Ah. Use calipers to measure the length, width, and height of battery cell 7 (generally calculated based on the dimensions of the battery casing, excluding the height of the electrode terminals and the insulating film outside the casing). Calculate the volume of the single cell V0 in L. The volume energy density of battery cell 7 is VED = (A0 × discharge platform voltage) / V0 in Wh / L.

[0182] In some embodiments, the volume energy density of the battery cell 7 can be increased by the following optional methods:

[0183] From the perspective of active materials, high specific capacity positive and negative active materials can be used. For example, for positive electrode active materials, lithium phosphate materials with higher gram capacity can be used, for example, physically mixing positive electrode active materials with higher gram capacity, such as ternary materials, to improve energy density; for negative electrode active materials, graphite with higher gram capacity can be used, for example, physically mixing negative electrode active materials with higher gram capacity, such as silicon-based materials;

[0184] From the perspective of electrolyte, the energy density of the battery cell 7 can be improved by reducing the amount of electrolyte injected or using an electrolyte that supports higher energy density.

[0185] From the perspective of electrode design, the energy density of the battery cell 7 can be increased by adjusting the compaction density and coating weight of the positive electrode or negative electrode, for example, by increasing the compaction density or coating weight; or by reducing the thickness of the positive electrode collector or negative electrode collector.

[0186] In terms of the separator, the thickness of the separator can be adjusted, for example, the thickness of the separator can be reduced to increase the energy density of the battery cell 7;

[0187] In terms of structural design, the first step is to reduce the proportion of inactive materials such as battery components. For example, by making the battery casing thinner while ensuring its safety and mechanical properties, more active materials can be accommodated in the same space, thereby increasing energy density. For example, the proportion of space occupied by the electrode assembly within the casing cavity can be adjusted.

[0188] At least two battery cells 7 are disposed along the first direction F1 , in other words, at least two battery cells 7 are arranged along the first direction F1 . The first surfaces 211 of the battery cells 7 are perpendicular to the first direction F1 .

[0189] In the embodiment of the present application, the housing of the battery cell 7 may be a rectangular parallelepiped structure, and the first direction F1 may be parallel to the thickness direction of the battery cell 7 .

[0190] The second direction F2 can be parallel to the length direction of the battery cell 7 or the width direction of the battery cell 7. When the second direction F2 is parallel to the length direction of the battery cell 7, the third direction F3 is parallel to the width direction of the battery cell 7; when the second direction F2 is parallel to the width direction of the battery cell 7, the third direction F3 is parallel to the length direction of the battery cell 7.

[0191] The battery cell 7 includes two first surfaces 211 opposite to each other along the first direction F1 .

[0192] When first surface 211 is larger than second surface 212, first surface 211 is the largest surface of the rectangular parallelepiped structure. Thermal insulation 40 at least partially covers first surface 211, effectively mitigating heat transfer. Thermal insulation 40 may cover at least a portion of first surface 211, for example, the entire first surface 211, or a portion of first surface 211.

[0193] [Thermal insulation]

[0194] like Figure 8 As shown, the thermal insulation member 40 covers at least one of the two first surfaces 211 of the battery cell 7 , which can alleviate heat diffusion and improve the reliability of the battery device 50 .

[0195] like Figure 8 and Figure 9As shown, the heat insulating member 40 covers at least one of the two first surfaces 211 of the battery cell 7 , which can alleviate heat conduction.

[0196] In some embodiments, the thermal insulation member 40 covers both first surfaces 211 of some battery cells 7 and covers one first surface 211 of another portion of battery cells 7. For example, the thermal insulation member 40 is disposed between two adjacent battery cells 7, and no thermal insulation member is disposed on the outermost sides of the plurality of battery cells 7 along the first direction F1.

[0197] like Figure 10 As shown, in other embodiments, the heat insulating member 40 covers the two first surfaces 211 of the battery cells 7. Exemplarily, the heat insulating member 40 is disposed between two adjacent battery cells 7, and the heat insulating member 40 is disposed on the outermost sides of the plurality of battery cells 7 along the first direction F1.

[0198] As shown in FIG11 , in some embodiments, the thermal insulation member 40 covers one of the two first surfaces 211 of the battery cell 7 .

[0199] For example, there are 6 battery cells 7, and the 6 battery cells 7 are arranged along the first direction F1. A heat insulating member 40 is set between the 1st battery cell 7 and the 2nd battery cell 7, a heat insulating member 40 is set between the 3rd battery cell 7 and the 4th battery cell 7, and a heat insulating member 40 is set between the 5th battery cell 7 and the 6th battery cell 7.

[0200] The heat insulating member 40 may be a plate structure or other structural forms.

[0201] In the embodiment of the present application, the dimension of the thermal insulation member 40 along the first direction F1 is 0.3 mm to 5 mm, for example, 0.3 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, or a range consisting of any two of the foregoing values. Optionally, the dimension of the thermal insulation member 40 along the first direction F1 is 0.5 mm to 2.5 mm. Figure 8 T1 shown in FIG. 4 represents a dimension of the thermal insulation member 40 along the first direction F1 .

[0202] The dimension of the thermal insulation member 40 along the first direction F1 can be understood as the thickness of the thermal insulation member 40 . Within the above range, heat conduction can be effectively alleviated, and the space occupied by the battery device 50 is small, which can improve the energy density of the battery device 50 .

[0203] As the mass content of the fluorinated sulfonyl imide salt increases, the heat released when the battery cell 7 experiences thermal runaway is higher and the severity of the thermal runaway is greater; in combination with the fluorinated sulfonyl imide salt, the thermal insulation member 40 can be of appropriate thickness to improve the ability of the thermal insulation member 40 to alleviate heat diffusion.

[0204] In some embodiments, the mass content of the fluorine-containing sulfonyl imide salt in the electrolyte is 2% to 6%; and the dimension of the thermal insulation member 40 along the first direction F1 is 0.5 mm to 1.0 mm.

[0205] In some embodiments, the mass content of the fluorine-containing sulfonyl imide salt in the electrolyte is greater than 6% and less than or equal to 8%; and the dimension of the thermal insulation member 40 along the first direction F1 is greater than 1.0 mm and less than or equal to 1.5 mm.

[0206] In some embodiments, the mass content of the fluorine-containing sulfonyl imide salt in the electrolyte is greater than 8% and less than or equal to 12%; and the thermal insulation member 40 is greater than 1.5 mm and less than or equal to 2.5 mm along the first direction F1.

[0207] As the volume energy density of the battery cell 7 increases, more heat is released in the event of thermal runaway; in conjunction with the volume energy density of the battery cell 7, the thermal insulation member 40 can be of an appropriate thickness to improve the ability of the thermal insulation member 40 to alleviate heat diffusion.

[0208] In some embodiments, the volume energy density of the battery cell 7 is 400Wh / L to 440Wh / L; and the dimension of the thermal insulation member 40 along the first direction F1 is 0.5 mm to 1.0 mm.

[0209] In some embodiments, the volume energy density of the battery cell 7 is greater than 440Wh / L and less than or equal to 490Wh / L; and the dimension of the thermal insulation member 40 along the first direction F1 is greater than 1.0 mm and less than or equal to 1.5 mm.

[0210] In some embodiments, the volume energy density of the battery cell 7 is greater than 490Wh / L and less than or equal to 530Wh / L; and the dimension of the thermal insulation member 40 along the first direction F1 is greater than 1.5 mm and less than or equal to 2.5 mm.

[0211] In some embodiments, as Figure 12 As shown, the battery cell 7 includes two first surfaces 211 that oppose each other along a first direction F1, and the thermal insulation member 40 covers the first surfaces 211. When the housing of the battery cell 7 is a rectangular parallelepiped structure, the first surface 211 can be the largest surface of the rectangular parallelepiped structure. The thermal insulation member 40 covers the first surface 211, effectively mitigating heat transfer.

[0212] In some embodiments, the battery device 50 satisfies: 0.9≤S2 / S1≤1,

[0213] S1 represents the area of the first surface 211, and its unit is mm 2 ;

[0214] S2 represents the area of the projection surface of the thermal insulation member 40 perpendicular to the first direction F1, and its unit is mm2 .

[0215] Illustratively, S2 / S1 is 0.9, 0.92, 0.94, 0.95, 0.98, 1.0, or a range consisting of any two of the above values. Figure 12 The area of the surface of the heat insulating member shown in FIG. 5 is S2 , and the first surface 211 of the battery cell 7 is S1 .

[0216] When the battery device 50 meets the above conditions, the area covered by the thermal insulation member 40 on the first surface is relatively large, which can more effectively alleviate heat conduction.

[0217] In some embodiments, the battery cell 7 includes electrode terminals, such as a positive terminal 31 and a negative terminal 32 , which are connected to at least one side of the electrode assembly along a second direction F2 , which is perpendicular to the first direction F1 .

[0218] The battery device 50 satisfies: 0.8≤L2 / L1≤1,

[0219] L1 represents the dimension of the first surface 211 along the second direction F2, and its unit is mm;

[0220] L2 represents the dimension of the thermal insulation member 40 along the second direction F2 , and its unit is mm.

[0221] Illustratively, L2 / L1 is 0.8, 0.82, 0.84, 0.85, 0.88, 0.9, 0.92, 0.94, 0.95, 0.98, 1.0, or a range consisting of any two of the above values. Figure 12 L1 and L2 are shown in FIG.

[0222] When the battery device 50 meets the above conditions, the size of the thermal insulation member 40 covering the first surface 211 is relatively large, which can more effectively alleviate heat conduction.

[0223] In some embodiments, the battery device 50 further satisfies: 2 mm ≤ L1 - L2 ≤ 10 mm.

[0224] Illustratively, L1-L2 may be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or a range consisting of any two of the above values. Figure 12 In the embodiment, both sides of the first surface 211 exceed the thermal insulation member 40, each side exceeds (L1-L2) / 2, and both exceed 1mm to 5mm. Of course, the first surface 211 can exceed the thermal insulation member 40 on only one side.

[0225] When the battery device 50 meets the above conditions, the size of the thermal insulation member 40 covering the first surface is relatively large, which can more effectively alleviate heat conduction.

[0226] In some embodiments, the battery device 50 satisfies: 0.9≤H2 / H1≤1,

[0227] H1 represents the dimension of the first surface 211 along the third direction F3, in mm. The third direction F3 and the second direction F2 are perpendicular to the first direction F1.

[0228] H2 represents the dimension of the heat insulating member 40 along the third direction F3 , and its unit is mm.

[0229] Illustratively, H2 / H1 is 0.9, 0.92, 0.94, 0.95, 0.98, 1.0, or a range consisting of any two of the above values. Figure 12 H1 and H2 are shown in FIG.

[0230] When the battery device 50 meets the above conditions, the size of the thermal insulation member 40 covering the first surface 211 is relatively large, which can more effectively alleviate heat conduction.

[0231] In some embodiments, the battery device 50 further satisfies: 1 mm ≤ H1 - H2 ≤ 10 mm.

[0232] Illustratively, H1-H2 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or a range consisting of any two of the above values. Figure 12 In the embodiment, both sides of the first surface 211 exceed the thermal insulation member 40, and each side exceeds (H1-H2) / 2, and both exceed 0.5mm to 5mm. Of course, the first surface 211 can exceed the thermal insulation member 40 on only one side.

[0233] When the battery device 50 meets the above conditions, the size of the thermal insulation member 40 covering the first surface 211 is relatively large, which can more effectively alleviate heat conduction.

[0234] In some embodiments, the thermal insulation member 40 may be bonded to the first surface 211. This configuration allows the thermal insulation member 40 to fit tightly against the first surface 211, thereby mitigating heat diffusion. Of course, the thermal insulation member 40 may also be in close contact with the first surface 211 without being bonded.

[0235] In some embodiments, the thermal insulation member 40 includes a thermal insulation body 41 and a support member 42 , wherein the support member 42 is disposed around the thermal insulation body 41 , and both the thermal insulation body 41 and the support member 42 cover the surface of the battery cell 7 along the first direction F1 , i.e., the first surface 211 .

[0236] The support member 42 can support and fix the heat insulating body 41 so that the heat insulating body 41 can effectively perform a heat insulating function.

[0237] In some embodiments, as Figure 13 As shown, the support member 42 is an annular member that surrounds the insulation body 41 and effectively supports the insulation body 41. The annular member can be square, rectangular, circular, or other shapes and can be adjusted according to the shape of the first surface 211. For example, if the first surface 211 is rectangular, the annular member is configured as a rectangular structure.

[0238] In some embodiments, the support member 42 satisfies: 10 mm ≤ W1 - W2 ≤ 60 mm,

[0239] W1 represents the size of the outer contour of the annular member along the second direction F2, the second direction F2 being perpendicular to the first direction F1;

[0240] W2 represents the dimension of the inner contour of the annular member along the second direction F2.

[0241] Illustratively, W1-W2 may be 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, or a range consisting of any two of the above values. Figure 13 W1 and W2 are shown, and the dimensions of the annular member are substantially the same everywhere. (W1-W2) / 2 can be considered as the dimension of the annular member along the second direction F2.

[0242] When the supporting member 42 satisfies the above conditions, it can effectively support and fix the heat insulating body 41 .

[0243] In some embodiments, the support member 42 satisfies: 10 mm ≤ W3 - W4 ≤ 60 mm,

[0244] W3 represents the dimension of the outer contour of the annular member along the third direction F3, and the third direction F3, the second direction F2 and the first direction F1 are perpendicular to each other;

[0245] W4 represents the dimension of the inner contour of the annular member along the third direction F3.

[0246] Illustratively, W3-W4 may be 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, or a range consisting of any two of the above values. Figure 13 W3 and W4 are shown, and the dimensions of the annular member are substantially the same everywhere. (W3-W4) / 2 can be considered as the dimension of the annular member along the third direction F3.

[0247] When the supporting member 42 satisfies the above conditions, it can effectively support and fix the heat insulating body 41 .

[0248] In some embodiments, as Figure 14 As shown, the heat insulating body 41 comprises a heat insulating material. Figure 11 The G in the letter indicates thermal insulation material.

[0249] In some embodiments, the thermal insulation material includes one or more of aerogel, foam, polyurethane, and silicone rubber. These materials have excellent thermal insulation effects and can effectively alleviate heat diffusion.

[0250] In some embodiments, the support member 42 may be made of a fiber material. Optionally, the fiber material may include one or more of polysaccharide, polyethylene terephthalate, polyurethane, polyacrylonitrile, polypropylene, polyamide, and aromatic polyamide. These materials have excellent supporting effects and can effectively support the thermal insulation material.

[0251] [Electrolyte]

[0252] Battery cells contain electrolytes. During the charge and discharge process of the battery cells, active ions such as lithium ions are inserted and removed back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting the active ions between the positive and negative electrodes.

[0253] In an embodiment of the present application, the electrolyte salt contains a fluorinated sulfonyl imide salt, and the mass content of the fluorinated sulfonyl imide salt in the electrolyte is 2% to 12%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or a range consisting of any two of the foregoing values. Optionally, the mass content of the fluorinated sulfonyl imide salt in the electrolyte is 4% to 8%.

[0254] When the mass content of the fluorinated sulfonyl imide salt is less than 2%, the amount of hexafluorophosphate added to the electrolyte may be too high. Excessive HF content will damage the SEI film and worsen the cycle life. Moreover, if the amount of the fluorinated sulfonyl imide salt added is too low, the improvement of the thermal stability of the electrolyte will be limited.

[0255] If the mass content of the fluorinated sulfonyl imide salt exceeds 12%, the severity of thermal runaway may be too high, resulting in excessive heat release and heat diffusion to other battery cells, causing thermal runaway in other battery cells and causing reliability issues for the battery device. However, when the mass content of the fluorinated sulfonyl imide salt in the embodiments of the present application is within the above range, it can achieve both improved cycle performance and reliability of the battery device.

[0256] For example, the fluorine-containing sulfonyl imide salt includes one or more of bis(fluorosulfonyl) imide salt, bis(trifluoromethanesulfonyl) imide salt, and perfluorobutylsulfonyl imide salt. These materials can improve both the cycle performance and the reliability of the battery device.

[0257] In some embodiments, the electrolyte further includes hexafluorophosphate, and the mass content of hexafluorophosphate in the electrolyte is 3% to 13%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13% or a range consisting of any two of the above values.

[0258] The combined use of fluorinated sulfonyl imide salt and hexafluorophosphate is beneficial to improving the cycle performance and reliability of battery devices.

[0259] When the electrolyte salt includes a lithium salt, the fluorine-containing sulfonyl imide salt may include a fluorine-containing lithium sulfonyl imide, for example, one or more of lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), and lithium perfluorobutylsulfonyl imide. The hexafluorophosphate salt may include lithium hexafluorophosphate.

[0260] In some embodiments, the electrolyte includes an organic solvent, the organic solvent includes a carboxylate solvent, and the mass content of the carboxylate solvent in the electrolyte is 8% to 60%. Exemplarily, the mass content of the carboxylate solvent is 8%, 10%, 15%, 20%, 25%, 30%, 40%, 45%, 50%, 55%, 60%, or a range consisting of any two of the above values. When the mass content of the carboxylate solvent is greater than or equal to 8%, the viscosity of the electrolyte system is relatively low, which is conducive to the migration of lithium ions; when the mass content of the carboxylate solvent is less than or equal to 60%, the side reaction between the carboxylate solvent and the negative electrode active material is relatively small, which is conducive to improving the cycle performance.

[0261] In some embodiments, the carboxylate solvent may include one or more of a linear carboxylate solvent and a cyclic carboxylate solvent, with the linear carboxylate solvent being preferred. Carboxylate solvents have lower viscosity and better fluidity, which facilitates rapid wetting of the electrode sheet, reduces the risk of localized lithium deposition on the surface of the negative electrode sheet, and improves the reliability of the battery cell.

[0262] Illustratively, the carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0263] The above materials have low viscosity, which can further improve the reliability of battery cells.

[0264] In an embodiment of the present application, the organic solvent further comprises a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 18% to 70%. Exemplarily, the mass content of the carbonate solvent in the electrolyte is 18%, 20%, 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0265] The carbonate solvent in the above mass content can further improve the viscosity of the electrolyte, enhance the wetting performance of the electrode, and make it less likely for local lithium deposition to occur on the surface of the negative electrode, thereby improving the reliability of the battery cell.

[0266] Illustratively, the carbonate-based solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0267] The viscosity of the above materials is relatively low, which is conducive to the rapid infiltration of the electrode. Local lithium deposition is not easy to occur on the surface of the negative electrode, thereby improving the reliability of the battery cell.

[0268] In an embodiment of the present application, the electrolyte further includes additives, including one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. The additives can participate in the formation of an SEI film on the negative electrode side, improve the protection of the negative electrode active material, reduce gas production on the negative electrode side, mitigate the risk of thermal runaway due to gas accumulation, and effectively improve the cycling performance of the battery cell.

[0269] In some embodiments, the mass content of the carbonate additive in the electrolyte is 2.5% to 10.0%, for example, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, or a range consisting of any two of the foregoing values. When the mass content of the carbonate additive is within the above range, the cycling performance of the battery cell can be effectively improved.

[0270] In some embodiments, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives, and the ethylene carbonate derivatives include compounds represented by formula A,

[0271] Formula A,

[0272] In formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time.

[0273] Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time. In other words, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group.

[0274] Illustratively, one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and the rest are hydrogen atoms.

[0275] Illustratively, at least two of Q1, Q2, Q3, and Q4 include a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0276] Illustratively, at least three of Q1, Q2, Q3, and Q4 include a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0277] Illustratively, Q1, Q2, Q3, and Q4 each independently include a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0278] Alternatively, at least one of Q1, Q2, Q3 and Q4 includes a halogen atom or a C1 to C5 haloalkyl group. The halogen atom includes a fluorine atom, a bromine atom or a chlorine atom, and may be a fluorine atom. The C1 to C5 haloalkyl group includes a C1 to C5 fluoroalkyl group, a C1 to C5 bromoalkyl group or a C1 to C5 chloroalkyl group, and may be a fluorine atom. For example, the C1 to C5 fluoroalkyl group includes a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a fluorobutyl group or a fluoropentyl group.

[0279] When the ethylene carbonate derivative includes fluorine atoms, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side, which can reduce the impedance of the film layer while protecting the negative electrode active material, and can more effectively improve the high-temperature cycle performance and fast charging performance of the battery cell.

[0280] For example, the ethylene carbonate derivative includes one or more compounds represented by formula A-1 to formula A-6.

[0281]

[0282] The above materials can further improve the high-temperature cycle performance and fast charging performance of battery cells.

[0283] Optionally, the ethylene carbonate derivative includes one or more of the compounds represented by formula A-1 to the compounds represented by formula A-3. Further optionally, the ethylene carbonate derivative includes the compound represented by formula A-1.

[0284] In some embodiments, the mass content of the sulfur-containing additive in the electrolyte is 0% to 2%, for example, 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, or a range consisting of any two of the foregoing values. The sulfur-containing additive can form a dense SEI film on the negative electrode side, effectively reducing the risk of carboxylic acid ester solvents penetrating the SEI film and reacting with the negative electrode active material, reducing gas generation, and improving the cycling performance of the battery cell.

[0285] Taking the case where the mass content of sulfur-containing additives is 0 as an example,

[0286] It can be that the freshly prepared electrolyte does not contain sulfur additives.

[0287] Alternatively, the electrolyte obtained after disassembling the battery cell does not contain sulfur-containing additives. This may be because the freshly prepared electrolyte does not contain sulfur-containing additives, or a small amount of sulfur-containing additives may be added, but the sulfur-containing additives participate in the SEI film formation reaction during the battery cell formation process, resulting in the sulfur-containing additives having a mass content of 0 during the test.

[0288] Optionally, the freshly prepared electrolyte includes a sulfur-containing additive.

[0289] Furthermore, regarding the addition of certain substances, such as additives, to the electrolyte, the content of additives in the electrolyte of a battery cell is related to the post-formation period, different battery life cycles, or different battery storage states due to the additives' role in film formation on the surface of the active material. Therefore, the additive content in a freshly prepared electrolyte may differ from that in an electrolyte obtained by reverse disassembling a battery. However, those skilled in the art can determine the approximate content range of the relevant substances in the fresh electrolyte corresponding to the battery cell based on the performance level (such as the number of cycles) and residual content. Similarly, those skilled in the art can also determine the approximate content range of the corresponding non-freshly prepared (i.e., after reverse disassembly) electrolyte based on the additive content in the freshly prepared electrolyte, the performance requirements for the battery cell, the storage environment, and so on.

[0290] Therefore, the additive content mentioned in the technical solution of the present application can be the content of the additive actively added to the fresh electrolyte, or it can be the content of the residual additive detected by reverse detection based on the actual battery status.

[0291] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl bissulfate, 1,3 propane sultone, butylene sulfite, vinyl sulfite, and methylene disulfonate.

[0292] In some embodiments, the mass content of the lithium salt additive in the electrolyte is 0% to 1%, for example, 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, or a range consisting of any two of the foregoing values. The lithium salt additive participates in film formation and can optimize the composition of the SEI film. The lithium salt additive can contribute to the formation of an inorganic-rich SEI film. The inorganic substances can enhance the high-temperature and high-voltage stability of the SEI film, thereby improving the cycling performance of the battery cell.

[0293] When the mass content of the lithium salt additive is 0, it means that the lithium salt additive may not be added to the freshly prepared electrolyte, or the electrolyte obtained after disassembling the battery cell does not contain the lithium salt additive.

[0294] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bisoxalatoborate.

[0295] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte are well known in the art and can be detected by equipment and methods well known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to the standard JY / T 0575-2020 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is approximately 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery cell is used as a sample for detection by ion chromatography analysis method.

[0296] In the embodiment of the present application, the types and contents of the organic components in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the organic components of the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography with reference to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0297] [Positive electrode]

[0298] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and comprising a positive electrode active material. For example, the positive electrode current collector may have two opposing surfaces in its thickness direction, and the positive electrode film layer may be disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0299] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge is 2.6 g / cm 3 Up to 2.8g / cm 3For example, the compaction density of the positive electrode film layer of the battery cell at 100% charge state is 2.6g / cm 3 , 2.65g / cm 3 , 2.7g / cm 3 , 2.75g / cm 3 , 2.8g / cm 3 Or a range consisting of any two of the above values.

[0300] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the positive electrode active material of the positive electrode film layer is stacked relatively densely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation and improving the cycle performance of the battery cell.

[0301] In some embodiments, the single-sided coating weight of the positive electrode film layer is 220 mg / 1540.25 mm 2 Up to 450mg / 1540.25mm 2 , for example 220mg / 1540.25mm 2 、230mg / 1540.25mm 2 、240mg / 1540.25mm 2 , 250mg / 1540.25mm², 260mg / 1540.25mm², 270mg / 1540.25mm², 280mg / 1540.25mm², 290mg / 1540.25mm², 300mg / 1540.25mm², 310mg / 1540.25mm², 320mg / 1540.25mm², 330mg / 1540.25mm², 350mg / 1540.25mm², 380mg / 1540.25mm², 400mg / 1540.25mm², 420mg / 1540.25mm², 450mg / 1540.25mm² or a range consisting of any two of the above values.

[0302] When the single-sided coating weight of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell, and the heat generation per unit area of the positive electrode sheet will not be too large, thereby improving the cycle performance of the battery cell.

[0303] The upper limit of charge voltage and the cut-off voltage of discharge of the battery cell vary depending on the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper limit of charge voltage can be 3.65V and the cut-off voltage of discharge can be 2.0V. For another example, when the phosphate material includes lithium manganese iron phosphate, the upper limit of charge voltage can be 4.2V and the cut-off voltage of discharge can be 2.0V. Next, taking the upper limit of charge voltage of 3.65V and the cut-off voltage of discharge of 2.0V as an example, the state of the battery cell is explained: In the embodiment of the present application, the 100% state of charge SOC and 0% state of charge SOC of the battery cell are defined as follows:

[0304] The battery cell is charged at a constant current charge rate of 0.33C to the upper limit of the charge voltage, and then charged at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell. The battery cell is discharged at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0305] In the embodiment of the present application, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) can be tested using the following method: the positive electrode sheet is disassembled from the battery cell, and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet is taken (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), punched into small discs with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. The positive electrode film layer of the weighed positive electrode sheet is then wiped off, and the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (weight of the positive electrode sheet M1 - weight of the positive electrode current collector M0) / S1, the thickness of the positive electrode film layer = thickness of the positive electrode sheet H1 - thickness of the positive electrode current collector H0, and the compaction density of the positive electrode film layer = single-sided coating weight of the positive electrode film layer / thickness of the positive electrode film layer.

[0306] In the case where the battery cell is a lithium-ion battery,

[0307] The lithium-containing phosphate may have an olivine structure, and the modified compound may be a material obtained by doping or coating the phosphate. For example, the lithium-containing phosphate includes phosphate particles and a positive electrode coating layer, the positive electrode coating layer is coated on at least part of the surface of the phosphate particles, and the positive electrode coating layer contains carbon elements.

[0308] Phosphate particles can enhance the conductivity of lithium-containing phosphates by coating the surface with a positive electrode coating layer, which is beneficial to the migration rate of lithium ions, improves the fast charging capability of the battery, reduces the heat generation of the battery cells, and improves the high-temperature cycle performance of the battery cells.

[0309] Examples of phosphate particles include, but are not limited to, one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. These materials have excellent cycle stability and can improve the cycle performance of battery cells.

[0310] In some embodiments, the lithium-containing phosphate comprises a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 A material, wherein 0.5≤x1≤1.3, 0≤y1≤1.3, 0.5≤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, A includes one or more of Na, K and Mg; Me includes one or more of Mn, Fe, Co and Ni; M 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, Hf, Ge and Ce; X includes one or more of Cl, C, N and P; and Y includes one or more of O and F.

[0311] The cycle stability of lithium-containing phosphates is relatively excellent, which is beneficial to improving the cycle performance of battery cells.

[0312] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The battery cells are accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cells is different when discharged to different states. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiment of the present application, the molar content of oxygen O is only a theoretical state value. Lattice oxygen release will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate. The above situations are all within the scope of protection of the present application.

[0313] In some embodiments, the mass content of carbon element is 0.8% to 2.3% based on the mass of the lithium-containing phosphate, for example, 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.3%, or a range consisting of any two of the above values.

[0314] The carbon element is mainly present in the positive electrode coating in the form of a carbon coating layer. The carbon coating layer is loose and porous, which is beneficial to increasing the specific surface area of the material, more conducive to effective contact between the electrolyte and phosphate particles, and conducive to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, it can significantly improve the conductivity of the olivine-structured lithium-containing phosphate, which is beneficial to improving the ionic conductivity and electronic conductivity of the olivine-structured lithium-containing phosphate, and can improve the rapid charging capability of the battery cell at high energy density.

[0315] In some embodiments, the positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

[0316] In some embodiments, the positive electrode coating layer includes a general formula of Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 A compound, wherein 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M3 includes one or more of Ti, Zr, Hf, Ge, and Sn.

[0317] Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 The compound is a fast ion conductor having a NASICON structure, for example, one or more of lithium iron titanium phosphate Li2FeTi(PO4)3, lithium iron zirconium phosphate Li2FeZr(PO4)3, and lithium iron tin phosphate Li2FeSn(PO4)3.

[0318] Fast ion conductors with a NASICON structure are materials with ultrafast ion conduction capabilities. They possess abundant three-dimensional lithium ion diffusion and transport channels, and exhibit advantages such as high ion conduction efficiency and strong structural stability during multiple lithium de- and intercalation processes. Coating phosphate particles with a fast ion conductor containing a NASICON structure can significantly increase the lithium ion transport rate at the positive electrode during multiple lithium de- and intercalation processes, improving the ionic conductivity of the positive electrode active material and the rapid charging capability of the battery cell. Furthermore, it can increase the specific capacity and the energy density of the corresponding battery cell.

[0319] The carbon element and the fast ion conductor can be arranged in layers. For example, the carbon element serves as an independent carbon coating layer, and the fast ion conductor serves as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer facing away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer facing away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0320] Optionally, a carbon coating can be formed by carbonizing an organic carbon source (e.g., glucose, polyethylene glycol, etc.) and coating the surface of the fast ion conductor layer. The carbon coating can partially or completely cover the fast ion conductor layer. The carbon coating can significantly improve the electronic conductivity of the phosphate particles, compensating for their poor electronic conductivity and increasing the energy density of the battery cell.

[0321] The positive electrode active material of this application, based on phosphate particles, fully leverages the advantages of phosphate particles: low cost, high reliability, and good cycling stability. At the same time, the positive electrode coating (fast ion conductor layer and carbon coating) addresses the drawbacks of poor electronic and ionic conductivity. Battery cells prepared with this positive electrode active material can improve the energy density of the battery cell while maintaining excellent cycling performance.

[0322] In the embodiments of this application, the element content in the positive electrode active material has a meaning well known in the art and can be measured using equipment and methods well known in the art. For example, in accordance with EPA 6010D-2014, it can be measured by inductively coupled plasma atomic emission spectrometry (ICP-OES, Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned with DMC, dried, and calcined at high temperature to remove impurities. Then, 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. The sample is then placed on a plate at 180°C for 30 minutes. After digestion on the plate, the volume is adjusted to 100ml, and quantitative analysis is performed using a standard curve method.

[0323] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application embodiment does not particularly limit the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode film layer.

[0324] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and one or more fluorine-containing acrylic resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0325] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include one or more foils made of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. By way of example, the metal material of the metal layer may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. By way of example, the polymer base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0326] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm. When the thickness of the positive electrode current collector is within the above range, it is beneficial to improve the current flow capacity and the fast charging capability of the battery cell.

[0327] The positive electrode film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0328] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0329] In some embodiments, the positive electrode plate further includes a positive electrode conductive layer, which is located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode plate, reduce the heat generated by the positive electrode plate, and thus reduce the heat generated by the battery cell.

[0330] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. For example, the thickness of the positive electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range consisting of any two of the above values.

[0331] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode sheet can be further improved, the heat generation of the positive electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0332] In the embodiment of the present application, the thickness of the positive electrode conductive layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, for example, performing a tomographic scan on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0333] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0334] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Exemplarily, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or a range consisting of any two of the above values.

[0335] Illustratively, the positive electrode conductive agent of the positive electrode conductive layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent of the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet and reducing heat generation in the battery cell.

[0336] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%, illustratively, 50%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0337] Illustratively, the positive electrode binder of the positive conductive layer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorine-containing acrylate resin. The positive electrode binder of the positive conductive layer can improve the bonding performance between the positive electrode current collector and the positive electrode film layer, thereby improving the structural stability of the positive electrode sheet.

[0338] [Negative electrode]

[0339] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0340] In some embodiments, the negative electrode layer has a compaction density of 1.2 g / cm2 at 100% state of charge. 3 Up to 1.4g / cm 3 For example, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge is 1.20 g / cm 3 , 1.22g / cm 3 , 1.25g / cm 3 , 1.28g / cm 3 , 1.3g / cm 3 , 1.32g / cm 3 , 1.35g / cm 3 , 1.40g / cm 3 Or a range consisting of any two of the above values.

[0341] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative electrode active material of the negative electrode film layer is stacked relatively densely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation, and can reduce the amount of gas generated by the decomposition of carboxylic acid ester solvents due to heat accumulation, thereby improving the cycle performance of the battery cell.

[0342] In the embodiment of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% charge state has a meaning well known in the art and can be detected using equipment and methods well known in the art, such as the compaction density test method of the positive electrode film layer.

[0343] In some embodiments, the single-side coating weight of the negative electrode film layer is 100 mg / 1540.25 mm 2 Up to 200mg / 1540.25mm 2 For example, the coating weight of the negative electrode film on one side is 100 mg / 1540.25 mm 2 、110mg / 1540.25mm 2 、120mg / 1540.25mm 2 、122mg / 1540.25mm 2 、125mg / 1540.25mm 2 、128mg / 1540.25mm 2 、130mg / 1540.25mm 2、132mg / 1540.25mm 2 、135mg / 1540.25mm 2 、137mg / 1540.25mm 2 、140mg / 1540.25mm 2 、145mg / 1540.25mm 2 、150mg / 1540.25mm 2 、155mg / 1540.25mm 2 、160mg / 1540.25mm 2 、165mg / 1540.25mm 2 、170mg / 1540.25mm 2 、175mg / 1540.25mm 2 , 200mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0344] When the single-sided coating weight of the negative electrode film layer is within the above range, the energy density of the battery cell can be improved; the heat generation per unit area of the negative electrode sheet will not be too large, and the high-temperature cycle performance of the battery cell can be improved.

[0345] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer has a meaning well known in the art and can be tested using equipment and methods well known in the art. The negative electrode sheet is disassembled from the battery cell and the compaction density of the negative electrode film layer is measured. For example, a single-sided coated negative electrode sheet is taken (if it is a double-sided coated sheet, the negative electrode film layer on one side can be wiped off first), punched into small discs with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. The negative electrode film layer of the weighed negative electrode sheet is then wiped off, the weight of the negative electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the negative electrode film layer = (weight of the negative electrode sheet M1 - weight of the negative electrode current collector M0) / S1.

[0346] In the embodiment of the present application, the negative electrode film layer includes at least one film layer, which can be a single film layer or at least two film layers. The negative electrode film layer can include two film layers, three film layers, four film layers, or even more film layers.

[0347] In the embodiments of this application, the negative electrode active material comprises a carbon-based material, which includes graphite particles. Graphite particles have high cycling stability and can improve the cycling performance of the battery cell. The positive electrode active material of this application is primarily a phosphate system, while the negative electrode active material is primarily a carbon-based material system. The combination of the two results in excellent cycling performance for the battery cell.

[0348] In some embodiments, the volume average particle size Dv50 of the graphite particles is 9.5 μm to 16.5 μm, such as 8.5 μm, 9 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, or a range consisting of any two of the foregoing values.

[0349] The volume average particle size of the graphite particles is relatively small, which makes the solid-phase migration path of lithium ions shorter, and can improve the fast charging capability of the battery cell; however, under fast charging conditions, the side reaction between the small-sized graphite particles and the carboxylic acid ester solvent in the electrolyte is more intense. The electrolyte is further added with a first additive, which can preferentially form a film on the negative electrode side, play an excellent protective role on the negative electrode active material, reduce the risk of side reactions on the negative electrode side, and improve the cycle performance of the battery cell.

[0350] In the embodiment of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, which can be detected using equipment and methods known in the art. For example, the positive electrode active material is used as a sample and the Dv50 of the particles is tested using a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0351] In some embodiments, the powder resistivity of the graphite particles is 0.005 Ω·cm to 0.04 Ω·cm. For example, the powder resistivity of the graphite particles may be 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm, or a range consisting of any two of the foregoing values.

[0352] The powder resistivity of graphite particles is relatively low, which makes the resistance of the negative electrode plate relatively low and the heat generation of the battery cell less. It can reduce the amount of gas generated by the decomposition of carboxylic acid ester solvents due to heat accumulation and improve the cycle performance of the battery cell.

[0353] In the embodiments of the present application, the powder resistivity of the negative electrode active material is well known in the art and can be tested using equipment and methods well known in the art, for example, using a PRCD1100 powder resistivity meter according to the test standard GB / T30835-2014.

[0354] In some embodiments, the graphite particles include primary graphite particles and a negative electrode coating layer, wherein the primary graphite particles include secondary particles, each of which includes a plurality of primary particles. The negative electrode coating layer is coated on the surface of the primary graphite particles, and the negative electrode coating layer includes carbon. The carbon in the negative electrode coating layer is primarily amorphous carbon, which refers to a transitional carbon material with a very low degree of graphitization and crystallization, resulting in a nearly amorphous morphology (or lacking a fixed shape and periodic structural regularity). In this application, amorphous carbon refers to the product of carbonization of an organic carbon source.

[0355] The graphite body particles include secondary particles. There are more migration paths for lithium ions in the graphite body particles, and the migration paths in the primary particles are shorter, which can improve the migration rate of lithium ions. The negative electrode coating layer has more end faces and defects, which increases the number of sites that can be used to deintercalate and deintercalate lithium ions, making the conductivity of the negative electrode coating layer better, which can reduce the internal resistance of the negative electrode plate, reduce the heat generation of the battery cell, and improve the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0356] Illustratively, the graphite body particles include one or more of artificial graphite and natural graphite, and artificial graphite can be selected.

[0357] Optionally, the carbon content of the negative electrode coating layer is 2% to 5% by mass based on the mass of the graphite particles. Exemplarily, the carbon content of the negative electrode coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the foregoing values.

[0358] When the mass content of carbon elements in the negative electrode coating layer is within the above range, the internal resistance of the negative electrode plate can be further reduced, the heat generation of the battery cell can be reduced, and the high-temperature cycle performance of the battery cell under high energy density can be improved.

[0359] In an embodiment of the present application, the graphite particles can be prepared by methods known in the art. Taking the graphite body particles as artificial graphite as an example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and forming a negative electrode coating layer on at least a portion of the surface of the artificial graphite particles after carbonization treatment.

[0360] Optionally, the organic carbon source includes one or more of coal tar, petroleum tar, phenolic resin, and coconut shell. Further, optionally, the organic carbon source includes petroleum tar. Optionally, the softening point of the coal tar or petroleum tar is below 250°C.

[0361] Optionally, the carbonization treatment temperature is 700° C. to 1800° C. Optionally, the carbonization treatment temperature is 1000° C. to 1300° C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized and a negative electrode coating layer containing amorphous carbon can be formed on at least a portion of the surface of the artificial graphite.

[0362] Optionally, the carbonization treatment time is 1 hour to 6 hours.

[0363] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include graphite particles, or the carbon-based material may include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0364] In some embodiments, the negative electrode active material may include not only graphite particles but also silicon-based materials. The introduction of silicon-based materials can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0365] Optionally, based on the mass of the negative electrode film layer, the mass content of silicon in the silicon-based material is 1% to 5%, optionally 1% to 6%. Exemplarily, the mass content of silicon in the silicon-based material is 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, or a range consisting of any two of the above values.

[0366] When the mass content of silicon in the silicon-based material is within the above range, the capacity of the negative electrode active material can be increased, thereby improving the energy density of the battery cell.

[0367] Alternatively, the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0368] In some embodiments, the negative electrode active material may include, in addition to the aforementioned carbon-based materials and optionally silicon-based materials, one or more of tin-based materials and lithium titanate. The tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.

[0369] The qualitative and quantitative properties of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0370] For example, the negative electrode plate is immersed in a solvent such as water to separate the negative electrode active material from the negative electrode current collector, and the substances in the negative electrode film layer are filtered out and used as test samples. The test samples are analyzed by an ICAP7400 inductively coupled plasma-emission spectrometer from Thermo Fisher Scientific, USA, and in accordance with the GB / T30902-2014 standard, the mass content of silicon element can be obtained.

[0371] For example, the present application may also combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis Methods to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0372] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flake structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0373] In some embodiments, the negative electrode film layer further includes a negative electrode binder. The negative electrode binder includes one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the weight content of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0374] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of negative electrode conductive agent. For example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0375] In some embodiments, the negative electrode film layer may also optionally include other additives. Examples of these additives include thickeners, dispersants, and the like, such as sodium carboxymethylcellulose (CMC-Na) and PTC thermistor materials. In some embodiments, the weight content of these additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0376] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include one or more foils of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal material in the metal layer may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0377] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm, for example, 4 μm, 5 μm, 6 μm, or a range consisting of any two of the foregoing values. When the thickness of the negative electrode current collector is within the foregoing range, it is beneficial to improve the current flow capacity and the fast charging capability of the battery cell.

[0378] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0379] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a negative conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0380] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further enhance the conductivity of the negative electrode plate, reduce heat generation of the negative electrode plate, and thus reduce heat generation of the battery cell, thereby improving the fast charging performance and high-temperature cycling performance of the battery cell.

[0381] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. For example, the thickness of the negative electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range consisting of any two of the above values.

[0382] When the thickness of the negative electrode conductive layer is within the above range, the conductivity of the negative electrode sheet can be further improved, the heat generation of the negative electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved.

[0383] In the embodiment of the present application, the thickness of the negative electrode conductive layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, for example, by performing a tomographic scan on the negative electrode sheet to directly measure the thickness of the negative electrode conductive layer.

[0384] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode pole piece and reducing the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector and the negative electrode film layer, thereby improving the structural stability of the negative electrode pole piece.

[0385] In some embodiments, the negative electrode conductive layer may further include other additives, such as thickeners, sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0386] Optionally, the negative electrode conductive agent of the negative electrode conductive layer has a mass content of 20% to 40% in the negative electrode conductive layer. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or a range consisting of any two of the above values.

[0387] Illustratively, the negative electrode conductive agent of the negative electrode conductive layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0388] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%, illustratively 60%, 65%, 70%, 75%, 80%, or a range consisting of any two of the above values.

[0389] Illustratively, the negative electrode binder of the negative electrode conductive layer includes one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0390] [Isolation film]

[0391] In the embodiment of the present application, the isolation film is arranged between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet from the negative electrode sheet.

[0392] In the embodiment of the present application, the isolation membrane includes a base membrane with a porous structure.

[0393] In some embodiments, the base film comprises one or more of glass fiber, nonwoven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0394] Optionally, the polyolefin includes one or more of polyethylene, polypropylene and polyvinylidene fluoride.

[0395] In some embodiments, the porosity of the isolation membrane is 20% to 70%, optionally 35% to 60%. For example, the porosity of the isolation membrane is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0396] When the porosity of the isolation membrane in the embodiment of the present application is within the above range, the migration ability of lithium ions in the isolation membrane can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation and improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0397] Optionally, the porosity of the base film is 20% to 70%, optionally 35% to 60%.

[0398] In the embodiments of this application, porosity refers to the percentage of the pore volume of the separator to the total volume of the separator. Porosity can be tested in accordance with the standard GB / T36363-2018, "Polyolefin Separators for Battery Cells." It should be noted that the actual testing process may vary slightly from the standard to obtain a more accurate test value, depending on instrument differences, test errors, and to minimize the impact of porosity testing.

[0399] In some embodiments, the thickness of the isolation film is 4 μm to 12 μm. For example, the thickness of the isolation film is 4 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range consisting of any two of the above values.

[0400] When the thickness of the isolation membrane is within the above range, the migration path of lithium ions in the isolation membrane is shorter, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0401] In the embodiment of the present application, the isolation membrane may be a base membrane. Optionally, the isolation membrane further includes a functional layer disposed on at least one side of the base membrane. The functional layer may include inorganic particles to enhance the heat resistance of the isolation membrane. Optionally, the functional layer is disposed on both sides of the base membrane.

[0402] In some embodiments, the functional layer includes a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer includes first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer includes composite particles, the composite particles include second inorganic particles and multiple non-fluoropolymer particles, the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0403] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the isolation film.

[0404] Optionally, the first functional layer may include a binder, optionally including one or more of a fluorine-containing binder or a polyacrylic binder, such as polyvinylidene fluoride.

[0405] Optionally, the first inorganic particles 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. The first inorganic particles can improve the heat resistance of the first functional layer.

[0406] Optionally, the average particle size of the first inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, or optionally 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range consisting of any two of the above values. When the average particle size of the first inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0407] In the embodiments of the present application, the thickness of the film layer has a meaning well known in the art, and can be detected using the meanings and equipment well known in the art. For example, a newly prepared isolation membrane can be taken as a sample, or a battery cell that has been fully discharged (discharged to the lower cut-off voltage so that the battery's charged state is approximately 0% SOC) can be reversely disassembled, and the isolation membrane can be obtained from the battery cell. The isolation membrane is dried and used as a sample, and the isolation membrane is cut with an ion beam cutter to form a cross section. Subsequently, a scanning electron microscope is used to measure the thickness of the cross section of the isolation membrane and its various layers.

[0408] The non-fluorinated polymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluorinated polymer particles include an acrylic copolymer. Optionally, the acrylic copolymer includes an acrylate-acrylonitrile-acrylamide-propylene copolymer. Acrylic copolymers have excellent bonding properties and high bonding stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0409] The second inorganic particles in the composite particles make it difficult for the non-fluoropolymer particles to adhere to each other due to the high temperature treatment during the granulation process, so that the composite particles have pores, which is conducive to the transmission of lithium ions and improves the ion conductivity of the separator. The second inorganic particles can also increase the compression modulus of the composite particles. During the charge and discharge process, the composite particles are not easily deformed, making the structure of the separator more stable, which can improve the dynamic performance of the battery cell and improve the fast charging performance. Optionally, compared to the first functional layer, the second functional layer is arranged close to the negative electrode sheet. Since the composite particles are not easily deformed, the separator basically does not cause side effects such as extrusion on the negative electrode sheet, which stabilizes the dynamic performance of the negative electrode sheet. Accordingly, the first functional layer is arranged close to the positive electrode sheet.

[0410] Optionally, the second inorganic particles 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. Optionally, the second inorganic particles include silicon oxide. These second inorganic particles can enhance the heat resistance of the second functional layer and can form composite particles with non-fluoropolymers to further improve the cycle stability and dynamic performance of the separator, thereby improving the cycle performance and fast charging performance of the battery cell.

[0411] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, optionally 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range consisting of any two of the above values. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0412] In the embodiment of the present application, the average particle size of the second inorganic particles has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, after obtaining the isolation film and drying the isolation film as a sample, the isolation film is cut with an ion beam cutter to form a cross section. Subsequently, a scanning electron microscope is used to measure the particle size of the second inorganic particles in the isolation film. The particle sizes of multiple, for example, 50, second inorganic particles are measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0413] Example

[0414] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0415] Example 1

[0416] 1. Preparation of positive electrode sheet

[0417] The positive electrode sheet includes a positive electrode collector, a positive electrode film layer and a positive electrode conductive layer. The positive electrode film layer is arranged on both sides of the positive electrode collector, and the positive electrode conductive layer is located between the positive electrode collector and the positive electrode film layer. The positive electrode collector is aluminum foil.

[0418] The positive conductive layer on the positive electrode current collector is a film layer formed by evenly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride (PVDF) and the solvent N-methylpyrrolidone NMP, and then 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%.

[0419] The positive electrode film layer includes a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) uniformly coated on the surface of the positive electrode conductive layer, and a film layer formed after drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF) and a conductive agent acetylene black in a weight ratio of 97:2:1.

[0420] The positive electrode active material includes lithium iron phosphate particles and a positive electrode coating layer. The positive electrode coating layer is coated on the surface of the lithium iron phosphate particles. The positive electrode coating layer includes lithium iron titanium phosphate Li2FeTi(PO4)3 and carbon element. The mass content of the carbon element is 1.12%.

[0421] The single-sided coating weight of the positive electrode film is 263mg / 1540.25mm 2 .

[0422] 2. Preparation of negative electrode sheet

[0423] The negative electrode plate includes a negative electrode current collector, a negative electrode film layer and a negative electrode conductive layer. The negative electrode film layer is arranged on both sides of the negative electrode current collector. The negative electrode conductive layer is located between the negative electrode current collector and the negative electrode film layer. The negative electrode current collector is copper foil.

[0424] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by evenly 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, and then 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%.

[0425] The negative electrode film layer includes a film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, drying, and cold pressing.

[0426] The negative electrode film layer comprises a negative electrode active material, a conductive agent, acetylene black, a negative electrode binder, and a thickener, sodium carboxymethyl cellulose, in a mass ratio of 96.5:0.5:2:1. The graphite particles comprise artificial graphite and a negative electrode coating layer, which is coated on the surface of the artificial graphite. The carbon content of the negative electrode coating layer is 3.5% by mass. The Dv50 of the graphite particles is 11.3μm.

[0427] The single-sided coating weight of the negative electrode film is 120mg / 1540.25mm 2 .

[0428] The length of the negative electrode film layer is 3 mm greater than that of the positive electrode film layer, and the width of the negative electrode film layer is 3 mm greater than that of the positive electrode film layer.

[0429] 3. Isolation film

[0430] The separator includes a base film and functional layers disposed on both sides of the base film, wherein the base film includes 7 μm polyethylene and has a porosity of 42%;

[0431] The functional layer includes a first functional layer and a second functional layer. The first functional layer is a film layer formed by coating aluminum oxide particles and a binder, polyvinylidene fluoride, on one side of the base film. The thickness is 1 μm, and the average particle size of the aluminum oxide particles is 10 nm.

[0432] The second functional layer is a film layer formed by coating composite particles formed by polyacrylate and silicon oxide particles dispersed on the polyacrylate on the other side of the base film, with a thickness of 1 μm and an average particle size of the silicon oxide particles of 10 nm.

[0433] 4. Preparation of electrolyte

[0434] The electrolyte includes an organic solvent, lithium salt and additives.

[0435] After mixing the components of the organic solvents, lithium salt and additives are added to prepare an electrolyte solution.

[0436] The organic solvent includes a chain carboxylic acid ester solvent (ethyl acetate) with a mass content of 39%, ethylene carbonate EC of 27.3% and dimethyl carbonate of 11.7%. The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0437] The mass content of the additive is 7%, and the additive includes vinylene carbonate VC, fluoroethylene carbonate FEC, vinyl sulfite ES and lithium difluorooxalatoborate LiDFOB in a mass ratio of 3.5:2.5:0.5:0.5.

[0438] The lithium salt includes 5% by mass of lithium bis(fluorosulfonyl)imide LiFSI and 10% by mass of lithium hexafluorophosphate LiPF6, and the mass content of the lithium salt is calculated based on the mass of the electrolyte.

[0439] 5. Preparation of battery cells

[0440] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, to obtain a laminated electrode assembly. The electrode assembly is placed in a shell, on which a positive terminal and a negative terminal are provided. After baking, the electrolyte is injected, and after vacuum packaging, standing, formation, shaping and other processes, a battery cell is obtained.

[0441] The outer shell includes an aluminum shell with a rectangular parallelepiped structure, and the thickness of the largest surface of the rectangular parallelepiped structure (ie, the large surface of the shell) is 0.5 mm.

[0442] The energy density of the battery cell is 423Wh / L.

[0443] The compaction density of the positive electrode film layer of the battery cell at 100% SOC is 2.67g / cm 3 The compaction density of the negative electrode film layer at 100% SOC is 1.33g / cm 3 .

[0444] 6. Preparation of battery device

[0445] The plurality of battery cells are sequentially arranged along their own thickness direction (parallel to the first direction), a heat insulating member is arranged between two adjacent battery cells, and a heat insulating member is arranged on both sides of the plurality of battery cells along the first direction (such as Figure 10The above components are assembled into a box to form a battery device.

[0446] The battery cell is placed vertically, and the dimension along the second direction can be understood as the height dimension of the battery cell, and the dimension along the third direction can be understood as the width dimension of the battery cell.

[0447] Correspondingly, the dimension of the thermal insulation element along the second direction can be understood as the height dimension of the thermal insulation element, and the dimension along the third direction can be understood as the width dimension of the thermal insulation element.

[0448] The thickness of the thermal insulation is 0.8mm, the height L2 is 106mm, the width H2 is 304mm, and the cross-sectional area S2 perpendicular to its own thickness direction is 32224mm 2 .

[0449] The height L1 of the battery cell is 112 mm, the width H1 is 312 mm, and the cross-sectional area perpendicular to its thickness direction is 34944 mm2.

[0450] L2 / L1 is 0.95, L1-L2 is 6mm, H2 / H1 is 0.97, H2-H1 is 8mm, and S2 / S1 is 0.92.

[0451] Comparative Example 1

[0452] A battery device was prepared using a method similar to that of Example 1. Unlike Example 1, no thermal insulation member was provided in the battery device.

[0453] Performance Testing

[0454] 1. Thermal runaway test of battery devices

[0455] like Figure 15 and Figure 16 ,

[0456] Step 1: Take 5 battery cells of the same specifications as test samples, charge the battery cells at a constant current of 0.33C to a charge cut-off voltage of 3.6V, then charge them at a constant current of 0.1C to a charge cut-off voltage of 3.65V, and adjust the SOC state of the battery cells to 100%.

[0457] Step 2: Arrange the five battery cells along their own thickness direction, connect the five battery cells in series, and align the battery cells in length, thickness and width directions. Figure 15 The heat insulating member 40 is arranged in the form of a 1P5S module, and then the five battery cells placed side by side are clamped with a clamping force of 3000N using a clamp 60 to assemble them into a 1P5S module; the height of the clamp 60, the height of the heat insulating member 40 and the height of the battery cells are the same;

[0458] Step 3: Mark the middle battery cell of the five battery cells as the trigger battery 72 , and define the remaining battery cells as the first test battery 71 . Use a needle to trigger the trigger battery 72 in the middle.

[0459] like Figure 16 As shown, the trigger position C is marked, and the position C is located at the geometric center of the bottom wall of the trigger battery 72. The bottom wall and the end cover are arranged opposite to each other along the length direction of the trigger battery 72.

[0460] Place the 1P5S module in a sealed box (leaving only position C of the trigger battery 72 exposed).

[0461] Step 4: Use a bottom needle to puncture the trigger C position (the needle of the flat needle is perpendicular to the length direction of the battery cell), and puncture the trigger battery 72 at a speed of 1mm / s until it runs out of control. Observe for 2 hours after the test, then disassemble the box to observe whether the first test battery 71 has any pressure relief components such as explosion-proof valve opening and thermal runaway, and measure the weight of the first test battery 71 to evaluate the thermal runaway phenomenon of the battery cell.

[0462] 2. Number of cycles of battery cells until SOH reaches 70%

[0463] At 60°C, charge the battery cell at a constant current of 0.8C to a charge cutoff voltage of 3.6V. Then, charge it at a constant current of 0.1C to a charge cutoff voltage of 3.65V and let it rest for 30 minutes. Discharge it at a constant current of 1C to 2.83V and let it rest for 30 minutes. This constitutes one charge-discharge cycle. Repeat these charge-discharge cycles until the cycle capacity retention (i.e., Cn / C0 × 100%) reaches 70%. Record the number of cycles. A higher number of cycles indicates better cycling performance of the battery cell.

[0464] When performing charge and discharge tests on battery cells, the 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.

[0465] The test results are shown in Table 1.

[0466] Table 1

[0467]

[0468] The adjacent battery cell refers to a battery cell adjacent to the trigger battery.

[0469] Comparative Example 1 has relatively excellent cycle performance during normal cycle operation; however, since no thermal insulation is provided, when thermal runaway of the battery is triggered, the heat will quickly diffuse to the adjacent battery cells, causing thermal runaway of other battery cells, resulting in poor reliability of the battery cells.

[0470] Compared with Comparative Example 1, Example 1 sets a thermal insulation member in the battery device, and the battery device still has relatively excellent cycle performance; and the thermal insulation member can effectively alleviate the heat diffusion problem, reduce the risk of thermal runaway, and improve the reliability of the battery cell.

[0471] Example 2-1 to Example 2-6

[0472] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass contents of the fluorine-containing sulfonyl imide salt and lithium hexafluorophosphate were adjusted, and the thickness of the thermal insulation member was adjusted.

[0473] Examples 2-7

[0474] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the type of fluorine-containing sulfonyl imide salt was adjusted.

[0475] Comparative Example 2-1 and Comparative Example 2-2

[0476] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass contents of lithium fluorinated sulfonyl imide and lithium hexafluorophosphate were adjusted, and the thickness of the thermal insulation member was adjusted.

[0477] The test results are shown in Table 2.

[0478] Table 2

[0479]

[0480] In Comparative Example 2-1, a thermal insulation member is provided in the battery device, which can effectively isolate the heat diffusion between other battery cells and reduce the risk of thermal runaway. However, the mass content of lithium bis(fluorosulfonyl)imide is low. Although it can reduce the amount of lithium hexafluorophosphate used in the electrolyte, the electrolyte still contains a large amount of hydrofluoric acid, which causes hydrofluoric acid to damage the SEI film and deteriorate the cycle performance of the battery cell.

[0481] The electrolyte of Comparative Example 2-2 includes a large amount of lithium bis(fluorosulfonyl)imide, which can effectively improve the cycle life of the battery device. Although thermal insulation is provided in the battery device of Comparative Example 2-2, the excessively high content of lithium bis(fluorosulfonyl)imide in the electrolyte results in poor thermal stability. In the event of thermal runaway, a large amount of heat is released, which could potentially trigger thermal runaway in adjacent battery cells.

[0482] In the embodiments of the present application, by synchronously regulating the thickness of lithium bis(fluorosulfonyl)imide and the thermal insulation, when the mass content of lithium bis(fluorosulfonyl)imide is high, the thickness of the thermal insulation is increased to reduce the risk of thermal runaway. For example, the mass content of lithium bis(fluorosulfonyl)imide in Example 2-1 is relatively low, and a thinner thermal insulation is used. When thermal runaway occurs, the heat released by the battery cell is relatively small, and the thinner thermal insulation can effectively isolate the heat diffusion. As the mass content of lithium bis(fluorosulfonyl)imide increases, the acid production in the electrolyte decreases, and the cycle performance is significantly improved; however, when thermal runaway occurs, the instantaneous heat release increases, and the thickness of the thermal insulation is increased synchronously. By increasing the thickness of the thermal insulation, such as in Examples 2-2 to 2-6, the risk of heat diffusion to adjacent battery cells is reduced, thereby improving the reliability of the battery device.

[0483] Various fluorine-containing sulfonyl imide salts are applicable to the present application, such as the lithium bis(fluorosulfonyl imide) of Example 1 and the lithium trifluorosulfonyl imide of Examples 2-6, which can effectively improve the reliability and cycle performance of the battery device.

[0484] Example 3-1 and Example 3-2

[0485] A battery device was prepared using a method similar to that of Example 1. The difference from Example 1 was that the compaction density of the positive electrode film layer and the negative electrode film layer was adjusted, and the thickness of the thermal insulation component was adjusted.

[0486] Example 3-3 and Example 3-4

[0487] A battery device was prepared using a method similar to that of Example 1. The difference from Example 1 was that the coating weight and compaction density of the positive electrode film layer and the negative electrode film layer were adjusted, and the thickness of the thermal insulation member was adjusted.

[0488] In Example 3-3, the negative electrode film layer includes 6% silicon carbide, and the mass content of the graphite particles is simultaneously reduced, so that the mass content of the negative electrode active material in the negative electrode film layer remains substantially unchanged;

[0489] In Example 3-4, the negative electrode film layer includes 10% silicon carbide, and the mass content of graphite particles is simultaneously reduced, so that the mass content of the negative electrode active material in the negative electrode film layer remains substantially unchanged.

[0490] The test results are shown in Table 3.

[0491] Table 3

[0492]

[0493] In Table 3, Example 3-1 and Example 3-2 reduce or increase the volume energy density of the battery cell by the compaction density of the positive and negative electrode film layers. When the volume energy density of the battery cell is relatively low, a relatively thin thermal insulation component can be used to improve both the reliability and cycle performance of the battery cell.

[0494] Examples 3-3 and 3-4 can effectively improve the energy density of the battery cell by increasing the adjustment of the silicon element in the negative electrode film layer, and coordinating the compaction density and coating weight of the positive and negative electrode film layers, while simultaneously increasing the thickness of the thermal insulation component, and can improve the reliability and cycle performance of the battery cell.

[0495] Example 4-1 and Example 4-2

[0496] A battery device was prepared using a method similar to that of Example 1. The difference from Example 1 was that the height of the thermal insulation member was adjusted.

[0497] Example 4-3 and Example 4-4

[0498] A battery device was prepared using a method similar to that of Example 1. The difference from Example 1 was that the width of the thermal insulation member was adjusted.

[0499] The test results are shown in Table 4.

[0500] Table 4

[0501]

[0502] The greater the area of battery cells covered by the thermal insulation, the better it mitigates heat diffusion, reducing the risk of thermal runaway between adjacent battery cells. This effectively improves the reliability of the battery cells and minimizes differences in cycling performance between battery cells. For example, compared to Example 4-2, the thermal insulation of Example 4-1 is taller, covers a larger area of the battery cells, and improves the reliability of the battery cells.

[0503] Compared with Example 4-3, the thermal insulation member of Example 4-4 has a larger width, covers a larger area of the battery cell, and has higher reliability in use of the battery cell.

[0504] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A battery device, characterized in that: comprising a heat insulating member and at least two battery cells arranged along a first direction, The battery cell includes an electrode assembly and an electrolyte, wherein the electrode assembly includes a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode film layer includes a lithium-containing phosphate; the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode film layer includes graphite particles; in, The electrolyte includes a fluorine-containing sulfonyl imide salt, and the mass content of the fluorine-containing sulfonyl imide salt in the electrolyte is 2% to 12%; The battery cell includes two first surfaces facing each other along the first direction, the heat insulating member covers at least one of the two first surfaces, and a dimension of the heat insulating member along the first direction is 0.3 mm to 5 mm. The volume energy density of the battery cell is 400Wh / L to 530Wh / L.

2. The battery device according to claim 1, wherein: A dimension of the heat insulating member along the first direction is 0.5 mm to 2.5 mm.

3. The battery device according to claim 1 or 2, characterized in that The mass content of the fluorinated sulfonyl imide salt in the electrolyte is 2% to 6%; A dimension of the heat insulating member along the first direction is greater than or equal to 0.5 mm and less than or equal to 1.0 mm.

4. The battery device according to claim 1 or 2, characterized in that: The mass content of the fluorinated sulfonyl imide salt in the electrolyte is greater than 6% and less than or equal to 8%; A dimension of the thermal insulation member along the first direction is greater than 1.0 mm and less than or equal to 1.5 mm.

5. The battery device according to claim 1 or 2, characterized in that: The mass content of the fluorinated sulfonyl imide salt in the electrolyte is greater than 8% and less than or equal to 12%; The dimension of the thermal insulation member along the first direction is greater than 1.5 mm and less than or equal to 2.5 mm.

6. The battery device according to claim 1, wherein: The volume energy density of the battery cell is 400Wh / L to 440Wh / L; A dimension of the heat insulating member along the first direction is greater than or equal to 0.5 mm and less than or equal to 1.0 mm.

7. The battery device according to claim 1, wherein: The volume energy density of the battery cell is greater than 440Wh / L and less than or equal to 490Wh / L; A dimension of the thermal insulation member along the first direction is greater than 1.0 mm and less than or equal to 1.5 mm.

8. The battery device according to claim 1, wherein: The volume energy density of the battery cell is greater than 490Wh / L and less than or equal to 530Wh / L; The dimension of the thermal insulation member along the first direction is greater than 1.5 mm and less than or equal to 2.5 mm.

9. The battery device according to claim 1, wherein: The battery device satisfies: 0.9≤S2 / S1≤1, S1 represents the area of the first surface, and its unit is mm 2 ; S2 represents the area of the projection surface of the thermal insulation member perpendicular to the first direction, and its unit is mm 2 .

10. The battery device according to claim 1, wherein: The battery cell includes an electrode terminal connected to at least one side of the electrode assembly along a second direction, the second direction being perpendicular to the first direction; Wherein, the battery device satisfies: 0.8≤L2 / L1≤1, L1 represents the dimension of the first surface along the second direction, in mm; L2 represents the dimension of the thermal insulation component along the second direction, and its unit is mm.

11. The battery device according to claim 10, characterized in that The battery device also satisfies: 2mm≤L1-L2≤10mm.

12. The battery device according to claim 1, wherein: The battery cell includes an electrode terminal connected to at least one side of the electrode assembly along the second direction; Wherein, the battery device satisfies: 0.9≤H2 / H1≤1, H1 represents the dimension of the first surface along the third direction, in mm, and the third direction and the second direction are perpendicular to the first direction. H2 represents the dimension of the thermal insulation member along the third direction, and its unit is mm.

13. The battery device according to claim 12, characterized in that The battery device also satisfies: 1 mm ≤ H1 - H2 ≤ 10 mm.

14. The battery device according to claim 1, wherein: The battery cell further includes two second surfaces opposite to each other along a third direction, the two second surfaces being connected by the first surface, the third direction being perpendicular to the first direction, wherein an area of the first surface is greater than an area of the second surface.

15. The battery device according to claim 1, wherein: The heat insulating member covers the two first surfaces of the battery cell.

16. The battery device according to claim 1, wherein: The thermal insulation member is bonded to the first surface.

17. The battery device according to claim 1, wherein: The heat insulating member includes a heat insulating body and a support member. The support member is disposed around the heat insulating body. Both the heat insulating body and the support member cover the surface of the battery cell along the first direction.

18. The battery device according to claim 17, characterized in that The supporting member is an annular member, The supporting member satisfies: 10mm≤W1-W2≤60mm, W1 represents the size of the outer contour of the annular member along the second direction; the battery cell includes an electrode terminal, and the electrode terminal is connected to at least one side of the electrode assembly along the second direction, and the second direction is perpendicular to the first direction; W2 represents the size of the inner contour of the annular member along the second direction; and / or The supporting member satisfies: 10mm≤W3-W4≤60mm, W3 represents the dimension of the outer contour of the annular member along the third direction; the battery cell includes an electrode terminal, the electrode terminal is connected to at least one side of the electrode assembly along the second direction, and the third direction, the second direction and the first direction are perpendicular to each other; W4 represents the dimension of the inner contour of the annular member along the third direction.

19. The battery device according to claim 17 or 18, characterized in that: The heat-insulating body comprises a heat-insulating material, and the heat-insulating material comprises one or more of aerogel, foam, polyurethane, and silicone rubber; and / or The support member includes one or more of polysaccharide, polyethylene terephthalate, polyurethane, polyacrylonitrile, polypropylene, polyamide, and aromatic polyamide.

20. The battery device according to claim 1, wherein: The fluorine-containing sulfonyl imide salt includes one or more of bisfluorosulfonyl imide salt, bistrifluoromethanesulfonyl imide salt, and perfluorobutylsulfonyl imide salt.

21. The battery device according to claim 1, wherein: The mass content of the fluorine-containing sulfonyl imide salt in the electrolyte is 4% to 8%.

22. The battery device according to claim 1, wherein: The electrolyte further includes hexafluorophosphate, and the mass content of the hexafluorophosphate in the electrolyte is 3% to 13%.

23. The battery device according to claim 1, wherein: The electrolyte further includes a carboxylate solvent, and the carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

24. The battery device according to claim 23, characterized in that The mass content of the carboxylic acid ester solvent in the electrolyte is 8% to 60%.

25. The battery device according to claim 1, wherein: The electrolyte further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

26. The battery device according to claim 25, characterized in that The mass content of the carbonate solvent in the electrolyte is 18% to 70%.

27. The battery device according to claim 1, wherein: The electrolyte further includes an additive; The additive includes a carbonate additive, and the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives, and the ethylene carbonate derivative includes a compound shown in formula A, Formula A, In formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time; and / or The additives include sulfur-containing additives, and the sulfur-containing additives include one or more of vinyl sulfate, vinyl disulfate, 1,3 propane sultone, butylene sulfite, vinyl sulfite, and methylene disulfonate; and / or The additive includes a lithium salt additive, and the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium bis(oxalatoborate).

28. The battery device according to claim 27, characterized in that The mass content of the carbonate additive in the electrolyte is 2.5% to 10.0%; and / or The mass content of the sulfur-containing additive in the electrolyte is 0% to 2%; and / or The mass content of the lithium salt additive in the electrolyte is 0% to 1%.

29. The battery device according to claim 1, wherein: The single-sided coating weight of the positive electrode film layer is 220 mg / 1540.25 mm 2 Up to 450mg / 1540.25mm 2 and / or The single-sided coating weight of the negative electrode film layer is 100 mg / 1540.25 mm 2 Up to 200mg / 1540.25mm 2 .

30. The battery device according to claim 1, wherein: The battery cell is at 100% charge state, and the compaction density of the positive electrode film layer is 2.6 g / cm 3 Up to 2.8g / cm 3 and / or The battery cell is at 100% charge state, and the compaction density of the negative electrode film layer is 1.2 g / cm 3 Up to 1.4g / cm 3 .

31. The battery device according to claim 1, wherein: The lithium-containing phosphate comprises: Phosphate particles, and A positive electrode coating layer is located on at least a portion of the surface of the phosphate particles, and the positive electrode coating layer contains carbon elements.

32. The battery device according to claim 31, wherein: Based on the mass of the lithium-containing phosphate, the mass content of the carbon element is 0.8% to 2.3%.

33. The battery device according to claim 31 or 32, characterized in that: The positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

34. The battery device according to claim 31, wherein: The phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

35. The battery device according to claim 1, wherein: The lithium-containing phosphate includes a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Materials, Among them, 0.5≤x1≤1.3, 0≤y1≤1.3, 0.5≤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, A includes one or more of Na, K and Mg; Me includes one or more of Mn, Fe, Co and Ni; M 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, Hf, Ge and Ce; X includes one or more of Cl, C, N; Y includes one or more of O and F.

36. The battery device according to claim 1, wherein: The thickness of the positive electrode current collector is 10 μm to 15 μm.

37. The battery device according to claim 1, wherein: The positive electrode plate further includes a positive electrode conductive layer, which is located between the positive electrode current collector and the positive electrode film layer. The positive electrode conductive layer includes a positive electrode conductive agent, and the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers; and / or The positive electrode conductive layer includes a positive electrode binder, which includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

38. The battery device according to claim 37, characterized in that The thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

39. The battery device according to claim 1, wherein: The graphite particles include graphite main particles and a negative electrode coating layer coated on the surface of the graphite main particles. The graphite main particles include secondary particles, and the negative electrode coating layer includes carbon elements.

40. The battery device according to claim 39, wherein: The graphite bulk particles include one or more of artificial graphite and natural graphite.

41. The battery device according to claim 39 or 40, characterized in that The mass content of carbon element in the negative electrode coating layer is 2% to 5% based on the mass of the graphite particles.

42. The battery device according to claim 1, wherein: The powder resistivity of the graphite particles is 0.005Ω·cm to 0.04Ω·cm; and / or The volume average particle size Dv50 of the graphite particles is 9.5 μm to 16.5 μm.

43. The battery device according to claim 1, wherein: The negative electrode film layer further comprises a silicon-based material, and the mass content of silicon element of the silicon-based material in the negative electrode film layer is 1% to 5%.

44. The battery device according to claim 43, characterized in that The silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

45. The battery device according to claim 1, wherein: The thickness of the negative electrode current collector is 4 μm to 6 μm.

46. The battery device according to claim 1, characterized in that The negative electrode plate further includes a negative electrode conductive layer, which is located between the negative electrode current collector and the negative electrode film layer. The negative electrode conductive layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers; and / or The negative electrode conductive layer includes a negative electrode binder, which includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

47. The battery device according to claim 46, characterized in that The thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

48. The battery device according to claim 1, wherein: The electrode assembly further includes a separator, which is located between the positive electrode sheet and the negative electrode sheet. The thickness of the isolation film is 4 μm to 12 μm; and / or The isolation film has a porosity of 20% to 70%.

49. The battery device according to claim 48, characterized in that The isolation film includes a base film and a functional layer provided on the base film, wherein the functional layer includes: A first functional layer is located on one side of the base film, and the first functional layer includes first inorganic particles. The second functional layer is located on the other side of the base film, and the second functional layer includes composite particles. The composite particles include second inorganic particles and multiple non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

50. The battery device according to claim 49, wherein: The non-fluoropolymer particles include acrylic copolymers.

51. The battery device according to claim 49 or 50, characterized in that The first inorganic particles 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; and / or The average particle size of the first inorganic particles is 5 nm to 100 nm.

52. The battery device according to claim 49, wherein: The second inorganic particles 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, and / or The average particle size of the second inorganic particles is 5 nm to 100 nm.

53. The battery device according to claim 1, wherein: The electrode assembly further includes a positive electrode tab and a negative electrode tab, wherein the positive electrode tab is connected to at least one side of the positive electrode collector along the length direction of the positive electrode sheet, and the negative electrode tab is connected to at least one side of the negative electrode collector along the length direction; Along the length direction, the size of the negative electrode film layer is larger than that of the positive electrode film layer, and the size difference between the negative electrode film layer and the positive electrode film layer is OH1; Along the width direction of the positive electrode sheet, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the size difference between the negative electrode film layer and the positive electrode film layer is OH2. Among them, OH1 is greater than OH2.

54. The battery device according to claim 53, characterized in that OH1 is 0.5 mm to 3.0 mm; and / or OH2 is 0.5 mm to 3.0 mm.

55. The battery device according to claim 1, wherein The battery cell includes a case that accommodates the electrode assembly and the electrolyte, and the case has a thickness of 0.1 mm to 0.5 mm.

56. An electrical device, characterized in that: A battery device comprising the battery device according to any one of claims 1 to 55.

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