Battery cell, battery device and electrical device

Abstract

The present application relates to a battery cell, a battery device and an electrical device. The battery cell comprises a casing, an electrolyte and an electrode assembly, wherein the casing comprises a casing body and an end cover; the electrolyte and the electrode assembly are accommodated in the casing body, the casing body has an opening, and the end cover covers the opening; the electrode assembly comprises a positive electrode sheet and a negative electrode sheet; the positive electrode sheet comprises a positive electrode current collector, and a positive electrode film layer which is disposed on at least one side of the positive electrode current collector in the direction of thickness of the positive electrode sheet and which includes a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate having an olivine structure; the negative electrode sheet comprises a negative electrode current collector, and a negative electrode film layer which is disposed on at least one side of the negative electrode current collector in the direction of thickness of the negative electrode sheet and which includes a negative electrode active material, wherein the discharge capacity per unit area of the positive electrode film layer ranges from 2.0 mAh / cm2 to 3.7 mAh / cm2; and the dimension of the positive electrode film layer in a first direction ranges from 75 mm to 105 mm, the first direction being parallel to a direction in which the casing body points to the end cover. The present application can further improve the energy density of the battery cell.

Description

Battery cell, battery device and power utilization device TECHNICAL FIELD

[0001] The present application relates to a battery cell, a battery device and a power utilization device. BACKGROUND

[0002] Lithium ion batteries have characteristics of high capacity and long life, and are widely used in electronic devices such as mobile phones, notebook computers, electric vehicles, electric cars, electric planes, electric ships and electric tools, etc. With the development of the application field of lithium ion batteries, higher requirements are put forward for the performance of lithium ion batteries, such as volume energy density and rapid charging performance.

[0003] SUMMARY

[0004] The present application provides a battery cell, a battery device and a power utilization device, which can further improve the energy density of the battery cell.

[0005] In a first aspect, the present application provides a battery cell, the battery cell comprising a shell, an electrolyte and an electrode assembly, the shell comprising a shell body and an end cover, the shell body containing the electrolyte and the electrode assembly, the shell body having an opening, the end cover covering the opening, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet and a separator, the separator being located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer containing a positive electrode active material and being arranged on at least one side of the positive electrode current collector along the thickness direction of the positive electrode sheet, the positive electrode active material comprising lithium-containing olivine structure phosphate; the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer containing a negative electrode active material and being arranged on at least one side of the negative electrode current collector along the thickness direction of the negative electrode sheet, wherein the discharge capacity per unit area of the positive electrode film layer is 2.0 mAh / cm 2 to 3.7 mAh / cm 2 ; the size of the positive electrode film layer along the first direction is 75 mm to 105 mm, and the first direction is parallel to the direction from the shell body to the end cover.

[0006] Therefore, in the embodiments of the present application, when the size of the positive electrode film layer along the first direction is less than 75 mm, the coating size of the positive electrode active material is relatively small, which is not conducive to the improvement of the energy density of the battery cell; with the increase of the size of the positive electrode film layer along the first direction, the coating size of the positive electrode active material can be increased, and the discharge capacity per unit area of the positive electrode film layer is greater than or equal to 2.0 mAh / cm 2 , which can improve the energy density of the battery cell; however, when the discharge capacity per unit area of the positive electrode film layer is greater than 3.7 mAh / cm 2At this time, the coating amount of the positive electrode film layer can be too large, resulting in a large migration resistance of lithium ions, which is not conducive to the improvement of the rapid charging performance of the battery monomer. Further limiting the size of the positive electrode film layer along the first direction to be less than or equal to 105 mm is conducive to improving the energy density and rapid charging performance of the battery monomer to a certain extent. Therefore, when the size of the positive electrode film layer along the first direction in the embodiments of the present application is 75 mm to 105 mm, the discharge capacity per unit area of the positive electrode film layer is 2.0 mAh / cm 2 to 3.7 mAh / cm 2 , which can effectively improve the energy density of the battery monomer and is suitable for the battery monomer of the rapid charging system.

[0007] In some embodiments, the discharge capacity per unit area of the positive electrode film layer is 2.4 mAh / cm 2 to 3.4 mAh / cm 2 . When the discharge capacity per unit area of the positive electrode film layer is in the above range, the energy density of the battery monomer can be further improved.

[0008] In some embodiments, the ratio of the discharge capacity per unit area of the negative electrode film layer to the discharge capacity per unit area of the positive electrode film layer is 1.05 to 1.15, which can be 1.07 to 1.13.

[0009] Therefore, when the ratio of the discharge capacity per unit area of the negative electrode film layer to the discharge capacity per unit area of the positive electrode film layer is in the above range, the lithium ions extracted from the positive electrode film layer can basically be embedded in the negative electrode film layer, reducing the risk of lithium precipitation in the negative electrode film layer and improving the use reliability of the battery monomer. Since the risk of lithium precipitation is low, the loss of lithium is small, which can reduce the capacity loss of the battery monomer and improve its cycle performance and rapid charging performance.

[0010] In some embodiments, the discharge capacity per unit area of the negative electrode film layer is 2.0 mAh / cm 2 to 4.1 mAh / cm 2 , which can be 2.4 mAh / cm 2 to 3.7 mAh / cm 2 . When the discharge capacity per unit area of the negative electrode film layer is in the above range, there are sufficient sites in the negative electrode film layer for lithium to be embedded, which can reduce the risk of lithium precipitation; and is conducive to rapid charging.

[0011] In some embodiments, the conductivity of the electrolyte is 13 mS / cm to 20 mS / cm, which can be 15 mS / cm to 20 mS / cm. The migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery monomer, thereby reducing the heat generation, and can improve the rapid charging performance of the battery monomer.

[0012] In some embodiments, the battery cell has a size along the first direction of 90mm to 130mm. When the battery cell has a size along the first direction within the above range, the size of the positive electrode film layer along the first direction is matched, so that the positive electrode active material coated on the positive electrode film layer is increased, which is conducive to improving the energy density of the battery cell.

[0013] In some embodiments, the battery cell has a size along the first direction of 90mm to 130mm. When the battery cell has a size along the first direction within the above range, the size of the positive electrode film layer along the first direction is matched, so that the positive electrode active material coated on the positive electrode film layer is increased, which is conducive to improving the energy density of the battery cell. 3 to 2.80g / cm 3 , and optionally 2.55g / cm 3 to 2.70g / cm 3 The compaction density of the positive electrode film layer within the above range is conducive to improving the energy density of the battery cell, and because the positive electrode active material in the positive electrode film layer is more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0014] In some embodiments, the positive electrode film layer has a single-side coating weight of 200mg / 1540.25mm 2 to 370mg / 1540.25mm 2 , and optionally 240mg / 1540.25mm 2 to 330mg / 1540.25mm 2 The single-side coating weight of the positive electrode film layer within the above range does not cause excessive heat generation per unit area of the positive electrode sheet, and can also improve the energy density of the battery cell.

[0015] In some embodiments, the positive electrode active material has a powder resistivity of 1Ω·cm to 27.5Ω·cm. The relatively low powder resistivity of the positive electrode active material causes the resistance of the positive electrode sheet to be relatively low, and the battery cell generates less heat.

[0016] In some embodiments, the positive electrode active material has a powder compaction density under 30000N of 2.46g / cm 3 to 2.8g / cm 3 The powder compaction density of the positive electrode active material under 30000N within the above range can improve the energy density of the battery cell, and because the positive electrode active material in the positive electrode film layer is more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0017] In some embodiments, the positive electrode active material has a charge gram capacity at 0.1C rate of 150mAh / g to 170mAh / g. When the charge gram capacity of the positive electrode active material at 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0018] In some embodiments, the olivine-structured lithium phosphate comprises phosphate particles and a coating layer. The coating layer coats the phosphate particles and contains one or more elements selected from C, Fe, Ti, Zr, Hf, Ge, and Sn. The surface coating of the phosphate particles enhances the conductivity of the olivine-structured lithium phosphate, reduces the powder resistivity of the material, and facilitates the migration rate of lithium ions, thereby reducing the heat generation of the battery cell.

[0019] In some embodiments, the phosphate particles comprise the general formula Li x1 A y1 Me a M b P 1-c X c Y z The compound contains 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, where 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, and Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F. Phosphate particles exhibit excellent cycle stability, which is beneficial for improving the cycle performance of battery cells.

[0020] In some embodiments, the coating layer includes a general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor, M2, includes one or more elements selected from Ti, Zr, Hf, Ge, and Sn, where 0 ≤ d ≤ 1, 0 < x2 < 5, and 0 < y2 < 4. Coating the phosphate particles with the fast ion conductor can significantly improve the lithium-ion transport rate during multiple lithium intercalation / deintercalation at the positive electrode, enhance the ionic conductivity of the positive electrode active material, thereby increasing the specific capacity and, further, improving the energy density of the corresponding battery cell.

[0021] In some embodiments, the degree of graphitization of the positive electrode active material is 0.15 to 0.32, optionally 0.19 to 0.26. When the degree of graphitization of the positive electrode active material is within the above range, it is beneficial to improve the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell.

[0022] In some embodiments, the mass content of carbon element in the lithium-containing olivine-structured phosphate is 1% to 2%, and the specific surface area of the lithium-containing olivine-structured phosphate is 5 m 2 / g to 18 m 2 / g, and optionally 7.5 m 2 / g to 14 m 2 / g.

[0023] Therefore, the material with the above mass content of carbon element and the above specific surface area in the embodiments of the present application is more conducive to the effective contact between the electrolyte and the lithium-containing olivine-structured phosphate and the transmission of lithium ions at the phase interface.

[0024] In some embodiments, the lithium-containing olivine-structured phosphate is in a particulate form, and the volume distribution particle size satisfies 1 μm≤Dv50≤2 μm and 0.4 μm≤Dv10≤0.7 μm. The particle size of the lithium-containing olivine-structured phosphate is relatively small, the path of lithium ion deintercalation in the positive electrode active material is relatively short, and the heat generation is relatively small. In addition, the particle size of the positive electrode active material is not too small, and agglomeration basically does not occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0025] In some embodiments, the lithium-containing olivine-structured phosphate is in a particulate form, and the lithium-containing olivine-structured phosphate includes secondary particles, the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. The average particle size of the primary particles is relatively small, the path of lithium ion deintercalation in the positive electrode active material is relatively short, and the heat generation is relatively small.

[0026] In some embodiments, the positive electrode film layer further includes one or more of ternary materials, lithium phosphate, lithium dihydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganite, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. The above materials can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and thus improve the energy density of the battery cell.

[0027] 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 in the above range, the flow capacity of the positive electrode current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0028] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer, and the positive electrode conductive layer 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 sheet and reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery cell.

[0029] In some embodiments, the thickness of the positive electrode conductive layer is 0.5-2 μm. When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode tab can be further improved, the heat generation of the positive electrode tab can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved.

[0030] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode tab, reducing the heat generation of the battery cell, and the positive electrode binder in the positive electrode conductive layer can improve the adhesion between the positive electrode current collector and the positive electrode film layer, thereby improving the structural stability of the positive electrode tab.

[0031] In some embodiments, the positive electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0032] In some embodiments, the positive electrode binder comprises 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 acrylic ester resin.

[0033] In some embodiments, the compaction density of the negative electrode film layer is 1.15-1.36 g / cm 3 at 100% state of charge. 3 In some embodiments, the compaction density of the negative electrode film layer is 1.25-1.36 g / cm 3 at 100% state of charge. 3 When the compaction density of the negative electrode film layer is within the above range, the energy density of the battery cell can be improved, and the resistance of the tab can be further reduced due to the close packing of the negative electrode active material in the negative electrode film layer and the small contact resistance between particles, thereby reducing the heat generation.

[0034] In some embodiments, the single-side coating weight of the negative electrode film layer is 90-170 mg / 1540.25 mm 2 . 2 In some embodiments, the single-side coating weight of the negative electrode film layer is 110-150 mg / 1540.25 mm 2 . 2 When the single-side coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode tab can not be too large, and the energy density of the battery cell can be improved.

[0035] In some embodiments, the powder resistivity of the negative active material is 0.005 Ω·cm to 0.043 Ω·cm. The powder resistivity of the negative active material is relatively low, so that the resistance of the negative electrode sheet is relatively low, and the battery cell generates less heat.

[0036] In some embodiments, the powder compaction density of the negative active material under 20000 N is 1.5 g / cm 3 to 1.85 g / cm 3 When the powder compaction density of the negative active material under 20000 N is in the above range, the energy density of the battery cell can be improved, and the negative active material in the negative electrode film layer can be more tightly packed, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0037] In some embodiments, the charge gram capacity of the negative active material at 0.1C rate is greater than or equal to 350 mAh / g. When the charge gram capacity of the negative active material at 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0038] In some embodiments, the negative active material comprises a carbon-based material, the carbon-based material comprises graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. When the graphitization degree of the graphite particles is in the above range, the conductive performance of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the rapid charging performance of the battery cell.

[0039] In some embodiments, the graphite particles comprise artificial graphite and a carbon coating layer, the artificial graphite comprises secondary particles, and the carbon coating layer is coated on the surface of the artificial graphite. The carbon coating layer has more end faces and defects, so that the number of sites capable of deintercalating lithium ions is more, so that the conductivity of the carbon coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0040] In some embodiments, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. When the mass content of the carbon coating layer is in the above range, the internal resistance of the negative electrode sheet and the heat generation of the battery cell can be further reduced.

[0041] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is arranged on the surface of the negative electrode current collector, the first negative electrode film layer includes a carbon-based material, the second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, the second negative electrode film layer includes a carbon-based material, the carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently includes graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0042] Thus, in the embodiments of the present application, there is a difference in particle size between the first negative electrode film layer and the second negative electrode film layer, which can improve the rapid charging performance of the battery cell. Specifically, during rapid charging, the overpotential of the second negative electrode film layer is generally high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and improve the problem of lithium stripping on the surface of the negative electrode sheet.

[0043] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0044] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is more densely packed, which improves the energy density of the battery cell, and the first negative electrode film layer is relatively sparse in packing, with more pores, which can improve the rapid charging performance of the battery cell.

[0045] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 . When the tap density of the carbon-based material in the first negative electrode film layer is within the appropriate range, the rapid charging performance of the battery cell can be improved.

[0046] In some embodiments, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 . When the tap density of the carbon-based material in the second negative electrode film layer is within the appropriate range, the energy density of the battery cell can be improved.

[0047] In some embodiments, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm. When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the above range, the rapid charging performance can be improved.

[0048] In some embodiments, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm. When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is in the above range, the tortuosity of lithium ion transmission can be reduced, and the rapid charging performance of the battery cell can be improved.

[0049] In some embodiments, the first negative electrode film layer further comprises a first lithium-containing binder, and the second negative electrode film layer further comprises a second lithium-containing binder, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0050] Thus, in the embodiments of the present application, the mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides a relatively large number of freely movable lithium ions for the second negative electrode film layer, which can further improve the rapid charging performance of the battery cell.

[0051] In some embodiments, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. When the mass content of the first lithium-containing binder is in the above range, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0052] In some embodiments, the mass content of lithium in the first lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium is in the above range, the number of freely movable lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0053] In some embodiments, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. When the mass content of lithium in the second lithium-containing binder is in the above range, the deintercalation rate of lithium ions is improved, and the rapid charging performance of the battery cell is improved.

[0054] In some embodiments, the mass content of lithium in the second lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium is in the above range, the number of freely movable lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0055] In some embodiments, the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0056] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery monomer, and is not prone to swelling during the charging and discharging process, and has a stable structure, so that the cycle performance of the negative electrode film layer is improved during the rapid charging and discharging process.

[0057] In some embodiments, the second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0058] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery monomer, and is not prone to swelling during the charging and discharging process, and has a stable structure, so that the cycle performance of the negative electrode film layer is improved during the rapid charging and discharging process.

[0059] In some embodiments, the negative active material further comprises a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10.0%, based on the mass of the negative active material. The introduction of the silicon-based material can improve the capacity of the negative active material and increase the energy density of the battery monomer.

[0060] In some embodiments, the thickness of the negative current collector is 4 μm to 6 μm. When the thickness of the negative current collector is in the above range, the flow capacity of the negative current collector is excellent, and the battery monomer has a high energy density.

[0061] In some embodiments, the negative electrode sheet further comprises a negative conductive layer, and the negative conductive layer is located between the negative electrode film layer and the negative current collector.

[0062] In some embodiments, the thickness of the negative conductive layer is 0.5 μm to 2 μm. The negative conductive layer can further improve the conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery monomer.

[0063] In some embodiments, the negative electrode conductive layer comprises 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 sheet, reducing the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the adhesion between the negative electrode current collector and the negative electrode film layer, improve the structural stability of the negative electrode sheet.

[0064] In some embodiments, the negative electrode conductive agent comprises one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0065] In some embodiments, the negative electrode binder comprises one or more of styrene butadiene rubber, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0066] In some embodiments, the separator film comprises a base film with a porous structure, and the porosity of the base film is 20% to 70%. When the porosity of the separator film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0067] In some embodiments, the carboxylic acid ester-based solvent comprises a chain carboxylic acid ester-based solvent, and the mass content of the chain carboxylic acid ester-based solvent in the organic solvent is greater than or equal to 5% and less than or equal to 75%, optionally greater than or equal to 10% and less than or equal to 75%, optionally 30% to 70%, and optionally 50% to 70%. When the mass content of the chain carboxylic acid ester-based solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is conducive to the migration of lithium ions.

[0068] In some embodiments, the chain carboxylic acid ester-based solvent comprises a compound represented by Formula I,

[0069] In Formula I,

[0070] R1 comprises a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group,

[0071] R2 comprises a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

[0072] Therefore, the chain carboxylic acid ester-based solvent described above in the embodiments of the present application has a relatively high conductivity, which is conducive to improving the rapid charging capability of the battery cell.

[0073] In some embodiments, R1 comprises a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 halogenated alkyl group.

[0074] In some embodiments, R2comprises C1-C3 alkyl or C1-C3 haloalkyl.

[0075] In some embodiments, the chain carboxylate solvent comprises one or more of compounds shown in formula I-1 to formula I-8,

[0076] In some embodiments, the organic solvent further comprises a carbonate solvent, and the carbonate solvent comprises one or more of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. The combination of the carbonate solvent and the chain carboxylate solvent improves the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0077] In some embodiments, the carbonate solvent comprises one or more of vinyl carbonate, dimethyl carbonate and ethyl methyl carbonate.

[0078] In some embodiments, the mass content of the carbonate solvent in the organic solvent is 30% to 70%, or 30% to 50%. The carbonate solvent in the above mass content further improves the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0079] In some embodiments, the electrolyte further comprises an additive, and the additive comprises one or more of a carbonate additive, a sulfur-containing additive and a lithium salt additive. The additive improves the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to the fast charging performance and the cycle performance of the battery cell.

[0080] In some embodiments, the carbonate additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0081] In some embodiments, the sulfur-containing additive comprises one or more of vinyl sulfate DTD, bis vinyl sulfate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES and methyl methylene disulfonate MMDS.

[0082] In some embodiments, the lithium salt additive comprises one or more of lithium difluorophosphate LiPO2F2, lithium difluoro oxalate borate LiDFOB, lithium tetrafluoroborate LiBF4 and lithium bisoxalate borate LiBOB.

[0083] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, or 2% to 8%. The additive in the above mass content effectively improves the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to the fast charging performance and the cycle performance of the battery cell.

[0084] In some embodiments, the electrolyte further comprises a lithium salt, the lithium salt comprises one or more of a fluorine-containing sulfimide salt and lithium hexafluorophosphate LiPF6. The above lithium salt is easy to dissociate, is conducive to the rapid migration of lithium ions, and the electrolyte system is relatively stable and is not easy to decompose, which can improve the cycle performance of the battery cell.

[0085] In some embodiments, the fluorine-containing sulfimide salt comprises one or more of lithium bisfluorosulfimide LiFSI and lithium bis-trifluoromethanesulfonimide LiTFSI.

[0086] In some embodiments, the lithium salt comprises lithium bisfluorosulfimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of lithium bisfluorosulfimide LiFSI is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.5 mol / L to 1.0 mol / L.

[0087] In some embodiments, the ratio of the molar concentration of lithium bisfluorosulfimide and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2 to 1.0.

[0088] In some embodiments, the separator film comprises a base film with a porous structure, and the porosity of the base film is 35% to 60%. When the porosity of the separator film in the embodiments of the present application is in the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0089] In some embodiments, the thickness of the base film is 6 μm to 12 μm. When the thickness of the base film is in the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0090] In some embodiments, the thickness of the base film is 6 μm to 9 μm. When the thickness of the base film is in the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0091] In some embodiments, the separator film comprises a base film and a functional layer arranged on at least one side of the base film, the functional layer comprises 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 comprises first inorganic particles, the second functional layer is located on the other side of the base film, and the second functional layer comprises composite particles, the composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

[0092] In some embodiments, the non-fluoropolymer particles include an acrylate copolymer. The acrylate copolymer has excellent adhesion properties, and has high adhesion stability with the base film.

[0093] 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 above first inorganic particles can improve the heat resistance of the first functional layer.

[0094] 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 above second inorganic particles can improve the heat resistance of the first functional layer.

[0095] 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 in the above range, the heat resistance and the compression modulus of the composite particles can be improved.

[0096] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. When the viscosity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the rapid charging performance of the battery cell.

[0097] In some embodiments, the density of the electrolyte at room temperature is 1.05 g / mL to 1.35 g / mL. When the density of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the rapid charging performance of the battery cell.

[0098] In some embodiments, the base material of the shell includes steel, and the thickness of the shell is 0.1 mm to 0.5 mm, which can be 0.2 mm to 0.35 mm. When the thickness of the shell is in the above range, the mechanical strength of the shell is high, which can improve the use reliability and cycle performance of the battery cell, and the shell occupies less space, and the internal space of the shell is larger, which is beneficial to improve the energy density of the battery cell.

[0099] In some embodiments, the group margin of the battery cell is greater than or equal to 96% and less than 100%, which can be 96.5% to 99.5%. When the group margin is in the above range, the energy density of the battery cell can be improved.

[0100] In some embodiments, the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 min to 12.5 min, and the charging speed of the battery cell is faster, which is more beneficial to improve the rapid charging capability.

[0101] In a second aspect, the present application provides a battery device, the battery device comprising the plurality of battery cells according to any one of the embodiments of the first aspect of the present application.

[0102] In some embodiments, the battery device has a charging time from 10% state of charge to 80% state of charge of 5 min to 12.5 min. The battery device has a faster charging speed, which is more conducive to improving the rapid charging capability.

[0103] In some embodiments, the battery device comprises a box body accommodating the battery cells, wherein the box body has a size of 110 mm to 170 mm along a first direction.

[0104] In a third aspect, the present application provides a power consumption device, the power consumption device comprising the battery device according to any one of the embodiments of the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0105] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0106] FIG. 1 is a structural schematic diagram of a battery cell according to some embodiments of the present application;

[0107] FIG. 2 is an exploded schematic diagram of the battery cell according to some embodiments of the present application;

[0108] FIG. 3 is a structural schematic diagram of a battery module according to some embodiments of the present application;

[0109] FIG. 4 is a structural schematic diagram of a battery pack according to some embodiments of the present application;

[0110] FIG. 5 is an exploded schematic diagram of the battery pack shown in FIG. 4;

[0111] FIG. 6 is a structural schematic diagram of a power consumption device according to some embodiments of the present application.

[0112] The drawings are not necessarily drawn according to the actual proportions.

[0113] The drawings are not necessarily drawn according to the actual proportions.

[0114] The reference signs are explained as follows:

[0115] X, first direction;

[0116] 1: electric device; 2: battery pack; 3: controller; 4: motor; 5: case; 5a: first case portion; 5b: second case portion; 5c: accommodation space; 6: battery module;

[0117] 7: battery cell;

[0118] 10: electrode assembly; 111: first tab; 112: second tab; 12: main body portion;

[0119] 20: housing; 21: case; 22: end cap;

[0120] 31: positive electrode terminal; 32: negative electrode terminal. DETAILED DESCRIPTION

[0121] Hereinafter, embodiments of the battery cell, the battery device, and the electric device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters that are already well known, and repeated description of actually identical structures, are omitted. This is to avoid the following description from becoming unnecessarily lengthy, and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0122] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise stated, a numerical range "a to b" represents a shorthand manner of describing each and every numerical value that is contained in the range between "a" and "b," wherein "a" and "b" are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0" and "5" have been listed herein, and "0 to 5" is merely a shorthand manner of describing each and every numerical value that is contained in the range between "0" and "5." In addition, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0123] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0124] If there is no special description, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0125] If there is no special description, all the steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0126] With the development of the battery field, the energy density requirement of the battery monomer is gradually improved, especially in the case of relatively small battery monomer, it is more difficult to improve the energy density of the battery monomer.

[0127] In view of the above problems, the embodiments of the present application reasonably design the system of the battery monomer, improve the energy density of the battery monomer by improving the discharge capacity of the positive electrode film layer in the battery monomer and the coating size of the positive electrode film layer.

[0128] Battery monomer

[0129] In a first aspect, the embodiments of the present application provide a battery monomer.

[0130] As shown in FIG. 1 and FIG. 2, the battery monomer 7 comprises an electrolyte, an electrode assembly 10 and a shell 20, the electrode assembly 10 comprises a positive electrode sheet, a negative electrode sheet and a separator film, the separator film is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector along the thickness direction of the positive electrode sheet and containing a positive electrode active material, the positive electrode active material comprises lithium-containing phosphate with olivine structure; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector along the thickness direction of the negative electrode sheet and containing a negative electrode active material, the shell 20 comprises a shell body 21 and an end cover 22, the shell body 21 has an opening and contains the electrolyte and the electrode assembly 10, and the end cover 22 covers the opening; wherein the discharge capacity per unit area of the positive electrode film layer is 2.0 mAh / cm 2 to 3.7 mAh / cm 2 , the size of the positive electrode film layer along the first direction X is 75 mm to 105 mm, and the first direction X is parallel to the direction from the shell body 21 to the end cover 22.

[0131] Generally, when the battery cell 7 is assembled to the box body, the battery cell 7 is vertically placed, the height direction of the battery cell 7 is parallel to the direction in which the shell 21 points to the end cover 22, that is, the height direction of the battery cell 7 is parallel to the first direction X.

[0132] When the size of the positive electrode film layer along the first direction X is less than 75 mm, for example, the coating size of the positive electrode active material is relatively small, which is not conducive to the improvement of the energy density of the battery cell 7; with the increase of the size of the positive electrode film layer along the first direction X, the coating size of the positive electrode active material can be increased, so that the discharge capacity per unit area of the positive electrode film layer is greater than or equal to 2.0 mAh / cm 2 , which can improve the energy density of the battery cell 7; however, when the discharge capacity per unit area of the positive electrode film layer is greater than 3.7 mAh / cm 2 , the coating amount of the positive electrode film layer may be too large, resulting in large migration resistance of lithium ions, which is not conducive to the improvement of the rapid charging performance of the battery cell 7, and further limits the size of the positive electrode film layer along the first direction X to be less than or equal to 105 mm, which is conducive to the comprehensive improvement of the energy density and rapid charging performance of the battery cell 7 to a certain extent.

[0133] Therefore, when the size of the positive electrode film layer along the first direction X in the embodiment of the application is 75 mm to 105 mm, the discharge capacity per unit area of the positive electrode film layer is 2.0 mAh / cm 2 to 3.7 mAh / cm 2 , which can effectively improve the energy density of the battery cell 7 and is suitable for the battery cell 7 of the rapid charging system.

[0134] In the embodiment of the application, the discharge capacity per unit area of the positive electrode film layer is 2.0 mAh / cm 2 to 3.7 mAh / cm 2 , which can be 2.4 mAh / cm 2 to 3.4 mAh / cm 2 . For example, the discharge capacity per unit area of the positive electrode film layer is 2.0 mAh / cm 2 , 2.1 mAh / cm 2 , 2.2 mAh / cm 2 , 2.3 mAh / cm 2 , 2.4 mAh / cm 2 , 2.5 mAh / cm 2 , 2.6 mAh / cm 2 , 2.7 mAh / cm 2 , 2.8 mAh / cm 2 , 2.9 mAh / cm 2 , 3.0 mAh / cm 2 , 3.1 mAh / cm2 3.2 mAh / cm2 2 3.3 mAh / cm2 2 3.4 mAh / cm2 2 3.5 mAh / cm2 2 3.6 mAh / cm2 2 3.7 mAh / cm2 2 or a range between any two of the above values.

[0135] In some embodiments, the ratio CB of the discharge capacity per unit area of the negative electrode film layer to the discharge capacity per unit area of the positive electrode film layer is 1.05 to 1.15, which can be optionally 1.07 to 1.13. Illustratively, the ratio CB of the discharge capacity per unit area of the negative electrode film layer to the discharge capacity per unit area of the positive electrode film layer in the battery cell 7 is 1.05, 1.07, 1.1, 1.12, 1.13, 1.14, 1.15, or a range between any two of the above values.

[0136] When the ratio CB of the discharge capacity per unit area of the negative electrode film layer to the discharge capacity per unit area of the positive electrode film layer is within the above range, the lithium ions extracted from the positive electrode film layer can be substantially inserted into the negative electrode film layer, reducing the risk of lithium precipitation in the negative electrode film layer and improving the use reliability of the battery cell 7. Since the risk of lithium precipitation is low, the loss of lithium is less, which can reduce the capacity loss of the battery cell 7 and improve its cycle performance and fast charging performance.

[0137] In some embodiments, the discharge capacity per unit area of the negative electrode film layer is 2.0 mAh / cm2 2 to 4.1 mAh / cm2 2 , which can be optionally 2.4 mAh / cm2 2 to 3.7 mAh / cm2 2 . Illustratively, the discharge capacity per unit area of the negative electrode film layer is 2.0 mAh / cm2 2 , 2.1 mAh / cm2 2 , 2.2 mAh / cm2 2 , 2.3 mAh / cm2 2 , 2.4 mAh / cm2 2 , 2.5 mAh / cm2 2 , 2.6 mAh / cm2 2 , 2.7 mAh / cm2 2 , 2.8 mAh / cm2 2 , 2.9 mAh / cm2 2 , 3.0 mAh / cm2 2 , 3.1 mAh / cm2 2 , 3.2 mAh / cm2 2 , 3.3 mAh / cm2 23.4 mAh / cm 2 3.5 mAh / cm 2 3.6 mAh / cm 2 3.7 mAh / cm 2 3.8 mAh / cm 2 3.9 mAh / cm 2 4.0 mAh / cm 2 4.1 mAh / cm 2 or a range between any two of the above values.

[0138] When the discharge capacity per unit area of the negative electrode film layer is in the above range, there are sufficient sites in the negative electrode film layer for lithium intercalation, which can reduce the risk of lithium precipitation; and is conducive to fast charging.

[0139] In the embodiments of the present application, the CB value can be detected by using devices and methods known in the art, for example, the discharge capacity per unit area of the negative electrode film layer and the discharge capacity per unit area of the positive electrode film layer are calculated respectively, and the ratio of the two is calculated to obtain the CB value;

[0140] The upper limit voltage of charging and the discharge cut-off voltage of the battery monomer 7 are different according to different positive electrode active materials, for example, when the phosphate material includes lithium iron phosphate, the upper limit voltage of charging can be 3.65V, and the discharge cut-off voltage can be 2.0V, for example, when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage of charging can be 4.3V, and the discharge cut-off voltage can be 2.0V, and the following is described taking the upper limit voltage of charging as 3.65V and the discharge cut-off voltage as 2.0V as an example:

[0141] The discharge capacity per unit area of the positive electrode film layer refers to the actual delithiation capacity of the positive electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the positive electrode sheet is taken out, and a CR2430 type half buckle battery of positive electrode-lithium sheet is assembled, the area of the positive electrode sheet used is a*mm 2 wherein the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio); then the assembled half buckle battery is left for 3h, the test is carried out at 25℃, 0.1C is used to charge (Charge) delithiation in the voltage range of 2.0V to 3.65V, then 0.05C is used to discharge (Discharge) lithium intercalation to 2.0V, and the discharge capacity of the second cycle is taken as Y mAh, the actual battery design positive electrode sheet length is bmm, the width is cmm, the number of positive electrode active material coated on the positive electrode current collector is d, then the discharge capacity per unit area of the positive electrode film layer = Y / a*b*c*d.

[0142] Specifically, the discharge capacity of the negative electrode film layer per unit area refers to the actual lithium intercalation capacity of the negative electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode sheet is taken out, and a CR2430 type half-buckle battery of negative electrode-lithium sheet is assembled. The area of the negative electrode sheet used is f mm x i mm 2 wherein the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio); then the assembled half-buckle battery is left to stand for 3 h, the test is carried out at 25°C, and the lithium intercalation is carried out at a voltage interval of 2V-0V at 0.1C, and then the lithium deintercalation is carried out at 0.05C to 2V, and the discharge capacity of the second cycle is taken as Z mAh. The actual battery design negative electrode sheet length is h mm, the width is i mm, the number of negative electrode active material coated on the negative electrode current collector is d, and then the negative electrode lithium intercalation capacity = Z / f*h*i*d.

[0143] In some embodiments, the size of the negative electrode film layer along the length direction of the negative electrode sheet is greater than the size of the positive electrode film layer along the length direction of the positive electrode sheet, and the difference between the two is 0.5mm to 3.0mm, for example, 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, or a range composed of any two of the above values. Since the size of the negative electrode film layer is relatively large, it can provide sufficient lithium intercalation sites for lithium ions, reduce the risk of lithium precipitation, and improve the use reliability of the battery monomer 7.

[0144] In some embodiments, the size of the negative electrode film layer along the width direction of the negative electrode sheet is greater than the size of the positive electrode film layer along the width direction of the positive electrode sheet, and the difference between the two is 0.5mm to 3.0mm, for example, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, or a range composed of any two of the above values. Since the size of the negative electrode film layer is relatively large, it can provide sufficient lithium intercalation sites for lithium ions, reduce the risk of lithium precipitation, and improve the use reliability of the battery monomer 7.

[0145] In some embodiments, the conductivity of the electrolyte at room temperature is 13mS / cm to 20mS / cm, which can be selected to be 15mS / cm to 20mS / cm. For example, the conductivity of the electrolyte at room temperature is 13mS / cm, 13.5mS / cm, 14mS / cm, 14.5mS / cm, 15mS / cm, 15.5mS / cm, 16mS / cm, 16.5mS / cm, 17mS / cm, 17.5mS / cm, 18mS / cm, 18.5mS / cm, 19mS / cm, 19.5mS / cm, 20mS / cm, or a range composed of any two of the above values.

[0146] When the conductivity of the electrolyte at room temperature, for example, 25°C, is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery monomer, thereby reducing heat generation and improving the rapid charging performance of the battery monomer.

[0147] In embodiments of the present application, the conductivity of the electrolyte at room temperature, for example, 25°C, is ionic conductivity, which can be detected by using devices and methods known in the art, for example, by testing according to the industry standard HG-T 4067-2015.

[0148] The conductivity of the electrolyte can be adjusted by adjusting the type and content of the organic solvent in the electrolyte; or by adjusting the type and content of lithium salt and the like in the electrolyte.

[0149] [Electrolyte]

[0150] During the charging and discharging process of the battery monomer, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0151] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. Illustratively, the viscosity of the electrolyte is 2.3 mPa·s, 2.4 mPa·s, 2.5 mPa·s, 2.6 mPa·s, 2.7 mPa·s, 2.8 mPa·s, 2.9 mPa·s, 3.0 mPa·s, 3.1 mPa·s, 3.2 mPa·s, 3.3 mPa·s, 3.4 mPa·s, 3.5 mPa·s, or a range formed by any two of the above values.

[0152] When the viscosity of the electrolyte at room temperature, for example, 25°C, is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery monomer, thereby reducing heat generation and improving the rapid charging performance of the battery monomer.

[0153] In embodiments of the present application, the viscosity of the electrolyte is the meaning known in the art, which can be detected by using devices and methods known in the art, for example, by testing according to GB / T 10247-2008.

[0154] In some embodiments, the density of the electrolyte at room temperature, for example, 25°C, is 1.05 g / mL to 1.35 g / mL. Illustratively, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, or a range formed by any two of the above values.

[0155] When the density of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing the heat generation and improving the rapid charging performance of the battery cell.

[0156] In the embodiments of the present application, the density of the electrolyte is in the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, tested according to GB / T 2013-2010.

[0157] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not particularly limited and can be selected according to actual needs.

[0158] In some embodiments, the organic solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent relative to the mass of the organic solvent is greater than or equal to 5% and less than or equal to 75%, which can be greater than or equal to 10% and less than or equal to 90%, which can be 30% to 70%, or which can be 50% to 70%. Exemplarily, the mass content of the chain carboxylate solvent is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or a range formed by any two of the above values.

[0159] When the mass content of the chain carboxylate solvent is in the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0160] In some embodiments, the chain carboxylate solvent includes a compound shown in Formula I,

[0161] In Formula I, R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group,

[0162] R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

[0163] The chain carboxylate solvent described above has a high conductivity, which is beneficial to improving the rapid charging capacity of the battery cell.

[0164] Optionally, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 halogenated alkyl group. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 halogenated alkyl group.

[0165] Optionally, R2 includes a C1 to C3 alkyl group or a C1 to C3 halogenated alkyl group. Further optionally, R2 includes a C1 to C2 alkyl group or a C1 to C2 halogenated alkyl group.

[0166] In each of the above embodiments, the halogen atom includes one or more of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and optionally, the halogen atom includes a fluorine atom.

[0167] In each of the above embodiments, the halogen atom includes one or more of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and optionally, the halogen atom includes a fluorine atom.

[0168] Exemplarily, the chain carboxylic acid ester solvent includes one or more of a compound shown in Formula I-1 to a compound shown in Formula I-8.

[0169] In some embodiments, the organic solvent further includes a carbonate solvent.

[0170] Optionally, the carbonate solvent includes one or more of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Further optionally, the carbonate solvent includes one or more of vinyl carbonate, dimethyl carbonate, and methyl ethyl carbonate. The combination of the carbonate solvent and the chain carboxylic acid ester solvent improves the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0171] Further optionally, the mass content of the carbonate solvent in the organic solvent is 30% to 70%, and optionally, 30% to 50%. Exemplarily, the mass content of the carbonate solvent in the organic solvent is 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, or a range between any two of the above values. The carbonate solvent with the above mass content further improves the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0172] Exemplarily, the carbonate solvent includes one or more of vinyl carbonate, dimethyl carbonate, and methyl ethyl carbonate, and the mass content of the carbonate solvent is 30% to 50%.

[0173] In some embodiments, the electrolyte further includes an additive. The additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, and the like.

[0174] In some embodiments, the additive includes one or more, and optionally, at least two, of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The additive improves the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0175] In some embodiments, the additive has a mass content of 1% to 10% in the electrolyte, optionally 2% to 8%, further optionally 3.5% to 8%. Illustratively, the additive has a mass content of 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the above values.

[0176] The additive with the above mass content can effectively improve the interface film performance on the positive electrode side and / or the negative electrode side, which is conducive to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0177] Illustratively, the carbonate-based additive includes one or more of vinylene carbonate VC, fluoroethylene carbonate FEC.

[0178] Illustratively, the sulfur-containing additive includes one or more of vinyl sulfonate DTD, bis vinyl sulfonate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methyl methylene disulfite MMDS.

[0179] Optionally, the lithium salt-based additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluoro oxalate borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bisoxalate borate LiBOB.

[0180] Optionally, the vinylene carbonate VC has a mass content of 0.5% to 9% in the electrolyte, optionally 2% to 6%.

[0181] Optionally, the fluoroethylene carbonate FEC has a mass content of 0.1% to 4% in the electrolyte, optionally 0.5% to 3%.

[0182] Optionally, the vinylene carbonate VC has a mass content of 0.5% to 9% in the electrolyte, and the fluoroethylene carbonate FEC has a mass content of 0.1% to 4% in the electrolyte.

[0183] Further optionally, the vinylene carbonate VC has a mass content of 2% to 6% in the electrolyte, and the fluoroethylene carbonate FEC has a mass content of 0.5% to 3% in the electrolyte.

[0184] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfonimide salt and lithium hexafluorophosphate LiPF6. The above lithium salt is easy to dissociate, which is conducive to the rapid migration of lithium ions, and the electrolyte system is relatively stable and is not easy to decompose, which can improve the cycle performance of the battery cell.

[0185] Optionally, the fluorine-containing sulfimide salt includes one or more of lithium bisfluorosulfimide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0186] Optionally, the lithium salt includes lithium bisfluorosulfimide (LiFSI) and lithium hexafluorophosphate (LiPF6), the molar concentration of lithium bisfluorosulfimide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0187] Optionally, the lithium salt includes lithium bisfluorosulfimide (LiFSI) and lithium hexafluorophosphate (LiPF6), the molar concentration of lithium bisfluorosulfimide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0188] Optionally, the lithium salt includes lithium bisfluorosulfimide (LiFSI) and lithium hexafluorophosphate (LiPF6), the molar concentration of lithium bisfluorosulfimide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0189] Optionally, the lithium salt includes lithium bisfluorosulfimide (LiFSI) and lithium hexafluorophosphate (LiPF6), the molar concentration of lithium bisfluorosulfimide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0190] Optionally, the ratio of the molar concentration of lithium bisfluorosulfimide (LiFSI) to the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.2 to 1.0, and optionally 0.2 to 0.5. Optionally, the ratio of the molar concentration of lithium bisfluorosulfimide (LiFSI) to the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range between any two of the above values.

[0191] In the embodiments of the present application, the type and content of the inorganic component / lithium salt concentration in the electrolyte are the meanings known in the art, which can be detected by using the devices and methods known in the art. For example, the inorganic component / lithium salt concentration in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography according to the standard JY / T020-1996 “General Ion Chromatography Analysis Method”. In the embodiments of the present application, the newly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or the free electrolyte of a battery that has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) can be taken as a sample, and the sample is detected by ion chromatography.

[0192] In the embodiments of the present application, the types and contents of the organic components in the electrolyte are in the meanings known in the art, which can be detected by using the devices and methods known in the art, for example, the qualitative and quantitative analysis of the organic components in the electrolyte can be performed by gas chromatography according to GB / T 9722-2006 "General rule for chemical reagent gas chromatography". In the embodiments of the present application, the freshly prepared electrolyte can be taken as the sample, the free electrolyte of the fresh battery can be taken as the sample, or the free electrolyte obtained from the battery which has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0193] In the embodiments of the present application, after the quantitative and qualitative detection of each component in the electrolyte, each component is classified, the chain carboxylic acid ester solvent and the carbonate solvent (for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate) are taken as the constituent components of the organic solvent, and the mass content of each component is calculated based on 100% of the mass of the organic solvent.

[0194] The carbonate additive (for example, vinylene carbonate, fluoroethylene carbonate), the sulfur-containing additive and the lithium salt additive are taken as the additives of the electrolyte, and the mass content of each component is calculated based on 100% of the mass of the electrolyte.

[0195] In some embodiments, the battery cell satisfies 2.45 g / Ah≤d / A≤3.5 g / Ah, which can be optionally 2.45 g / Ah≤d / A≤3.3 g / Ah, wherein d represents the mass of the electrolyte in the battery cell, in units of g, and A represents the rated capacity of the battery cell, in units of Ah. Exemplarily, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah or a range composed of any two of the above values.

[0196] d / A can reflect the liquid retention capacity of the electrolyte, when d / A is in the above range, the electrolyte can have a good infiltration effect on the positive and negative electrode sheets, and can also improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the rapid charging capacity of the battery cell.

[0197] In the embodiments of the present application, d / A of the battery cell can be understood as the liquid retention coefficient, which can be detected by using the devices and methods known in the art, for example, the description is made by taking the battery charging upper limit voltage as 3.65 V and the battery discharging cutoff voltage as 2.0 V according to GB / T 31486-2015 "Electric performance requirements and test methods for power storage batteries for electric vehicles".

[0198] The battery cell is charged at 0.33C to 3.65V at 25°C, then charged at 0.05C, and then discharged at 0.33C to 2.0V, to obtain the capacity A discharged as the denominator, the battery cell is weighed as M0, then the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte are disassembled, the free electrolyte is in a bag, all the solid components are placed in a 60°C oven for more than 4 hours (including but not only the positive electrode sheet, the negative electrode sheet, the separator, and other mechanical parts contributing to M0), then all the components of the battery cell are weighed as M1, and the weight difference between M0 and M1 is taken as the numerator. The liquid retention coefficient is equal to the value obtained by dividing the weight difference between M0 and M1 by the capacity A.

[0199] [Positive electrode sheet]

[0200] 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 including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0201] In some embodiments, the positive electrode film layer has a compaction density of 2.50 g / cm 3 to 2.80 g / cm 3 , optionally 2.55 g / cm 3 to 2.70 g / cm 3 at 100% state of charge (SOC) of the battery cell. 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 , or a range defined by any two of the above values.

[0202] When the compaction density of the positive electrode film layer is in the above range, the energy density of the battery cell can be improved, and the positive electrode active material in the positive electrode film layer is packed more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation under fast charging. Therefore, by adjusting the compaction density of the positive electrode film layer to a reasonable range, the battery cell has high energy density and high charging rate performance.

[0203] In the embodiments of the present application, the 100% state of charge SOC and the 0% state of charge SOC of the battery cell are defined as follows,

[0204] The battery cell is charged to the upper limit voltage at a constant current charging rate of 0.33C, and then charged to 0.05C at a constant voltage, corresponding to the state of 100% SOC of the battery cell; the battery cell is discharged to the cut-off voltage at a constant current discharge rate of 0.33C, corresponding to the state of 0% SOC of the battery cell.

[0205] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 , and optionally 240 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 . For example, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 240 mg / 1540.25 mm 2 , 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 360 mg / 1540.25 mm2 370 mg / 15 40.25 mm 2 or a range between any two of the above values.

[0206] When the single-side coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode tab will not be too large, and the energy density and the charge rate performance of the battery cell can be improved.

[0207] In the embodiments 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 detected by the following method. The positive electrode tab of the battery cell at 100% SOC is disassembled, the compaction density of the positive electrode film layer is measured, for example, the single-side coated positive electrode tab (if it is a double-side coated tab, the positive electrode film layer on one side can be wiped off first), a small disc with an area of S1 is punched out, weighed, recorded as M1, and its thickness H1 is measured. Then the positive electrode film layer of the above weighed positive electrode tab is wiped off, the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-side coating weight of the positive electrode film layer = (the weight of the positive electrode tab M1 - the weight of the positive electrode current collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode tab H1 - the thickness of the positive electrode current collector H0, and the compaction density of the positive electrode film layer = the single-side coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0208] In some embodiments, the powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm, optionally, less than or equal to 20 Ω·cm, optionally, less than or equal to 11 Ω·cm. For example, the powder resistivity of the positive electrode active material can be 27.5 Ω·cm, 20 Ω·cm, 19 Ω·cm, 18 Ω·cm, 17 Ω·cm, 16 Ω·cm, 15 Ω·cm, 14 Ω·cm, 13 Ω·cm, 12 Ω·cm, 11 Ω·cm, 10 Ω·cm, 9 Ω·cm, 8 Ω·cm, 7 Ω·cm, 6 Ω·cm, 5 Ω·cm, 4 Ω·cm, 3 Ω·cm, 2 Ω·cm, 1 Ω·cm, or a range between any two of the above values.

[0209] The relatively low powder resistivity of the positive electrode active material makes the resistance of the positive electrode tab relatively low, and the battery cell generates less heat.

[0210] In the embodiments of the present application, the powder resistivity of the material is the meaning known in the art, which can be detected by the methods and devices known in the art, for example, according to the test standard GB / T30835-2014, using PRCD1100 powder resistivity meter for testing.

[0211] In some embodiments, the powder compaction density of the positive electrode active material at 30000 N is 2.46 g / cm 32.8 g / cm 3 Exemplarily, the powder compaction density of the positive electrode active material under 30000N is 2.46 g / cm 3 , 2.47 g / cm 3 , 2.48 g / cm 3 , 2.49 g / cm 3 , 2.5 g / cm 3 , 2.51 g / cm 3 , 2.55 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 , or a range formed by any two of the above values.

[0212] When the powder compaction density of the positive electrode active material under 30000N is in the above range, the energy density of the battery cell can be improved, and the positive electrode active material in the positive electrode film layer can be more closely stacked, the contact resistance between particles is smaller, which can further reduce the resistance of the pole piece, thereby reducing the heat generation.

[0213] In the embodiments of the present application, the powder compaction density of the material is the meaning known in the art, which can be detected by the method and equipment known in the art according to the test standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample, added into a mold with a bottom area of 1.327 cm 2 of the UTM7305 electronic pressure testing machine, pressurized to 3000 kg (equivalent to 30000N), keep pressure for 30 s, then release pressure, keep for 10 s, then record and calculate the powder compaction density of the positive electrode active material under the action of 30000N.

[0214] In some embodiments, the charging gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g to 170 mAh / g, which can be 157 mAh / g to 170 mAh / g. Illustratively, the charging gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g, 151 mAh / g, 152 mAh / g, 153 mAh / g, 154 mAh / g, 155 mAh / g, 156 mAh / g, 157 mAh / g, 158 mAh / g, 159 mAh / g, 160 mAh / g, 161 mAh / g, 162 mAh / g, 163 mAh / g, 164 mAh / g, 165 mAh / g, 166 mAh / g, 167 mAh / g, 168 mAh / g, 169 mAh / g, 170 mAh / g, or a range between any two of the above values.

[0215] When the charging gram capacity of the positive electrode active material at 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0216] In the embodiments of the present application, the gram capacity of the active material is the meaning known in the art, which can be tested by using the devices and methods known in the art, and the test method of the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used. The half-button battery is assembled by taking lithium metal as the negative electrode and the sample electrode tab containing the above material as the positive electrode. The half-button battery is placed in a battery tester or other testing equipment with the same performance at 23℃±2℃, and the button capacity is obtained by 0.1C rate charging and discharging. Then the capacity is divided by the mass of the active material of the electrode tab to obtain the charging gram capacity parameter.

[0217] In some embodiments, the mass fraction of the olivine-structured lithium-containing phosphate in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%, and the positive electrode active material of the present application can be considered to be an olivine-structured lithium-containing phosphate system. When the mass fraction of the olivine-structured lithium-containing phosphate is less than 100%, the positive electrode active material can also include commonly used positive electrode active materials, for example, can include but is not limited to at least one of lithium-containing transition metal oxides. Examples of lithium-containing transition metal oxides can include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0218] Optionally, the mass fraction of the olivine-structured lithium-containing phosphate in the positive electrode active material is 100%.

[0219] In the embodiments of the present application, the lithium-containing phosphate with olivine structure can be phosphate particles or a material obtained after coating modification of the phosphate particles, for example, the lithium-containing phosphate with olivine structure includes phosphate particles and a coating layer, the coating layer is coated on the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge and Sn.

[0220] The phosphate particles are coated with the coating layer, which can improve the conductivity of the lithium-containing phosphate with olivine structure, reduce the powder resistivity of the material, and be beneficial to the migration rate of lithium ions, improve the rapid charging capability of the battery, and reduce the heat generation of the battery monomer.

[0221] In some embodiments, the phosphate particles include a compound with a general formula of Li x1 A y1 Me a M b P 1-c X c Y z , wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, 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, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The cycle stability of the phosphate particles is relatively excellent, which is beneficial to improving the cycle performance of the battery monomer.

[0222] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4. During the charging and discharging process, the battery cell is accompanied by the deintercalation and consumption of active ions such as Li, and the battery cell has different molar contents of Li when discharged to different states. In the enumeration of the 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, and the positive electrode active material is applied to the battery system. After charging and discharging cycles, the molar content of Li may change. In the enumeration of the positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiments of the application, the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will fluctuate, and the above-mentioned situations are all within the protection scope of the application.

[0223] In some embodiments, the coating layer includes a fast ion conductor with a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 , M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0

[0224] Exemplarily, the fast ion conductor is a material with a NASICON structure, for example, including one or more of lithium titanium iron phosphate Li2FeTi(PO4)3, lithium zirconium iron phosphate Li2FeZr(PO4)3, lithium tin iron phosphate Li2FeSn(PO4)3.

[0225] The fast ion conductor with a NASICON structure is a material with super-fast ion conduction ability, has abundant three-dimensional lithium ion diffusion and transmission channels, and has the advantages of high ion conduction efficiency and strong structural stability in multiple delithiation and lithium intercalation processes. Coating the surface of the phosphate particles with the fast ion conductor containing the NASICON structure can significantly improve the transmission rate of lithium ions in the positive electrode end during multiple delithiation and lithium intercalation, improve the ion conductivity of the positive electrode active material, and improve the rapid charging capacity of the battery cell. In addition, it can also improve the specific capacity and the energy density of the corresponding battery cell.

[0226] In some embodiments, the coating layer further includes elemental carbon.

[0227] The carbon element and the fast ion conductor can be arranged in layers, for example, the carbon element as an independent carbon coating layer and the fast ion conductor 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 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 away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0228] Optionally, the carbon coating layer can be coated on the surface of the fast ion conductor layer by a carbonization process using an organic carbon source (for example, glucose, polyethylene glycol, etc.). The carbon coating layer can partially coat the fast ion conductor layer or completely coat the fast ion conductor layer. The arrangement of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, compensate for the poor electronic conductivity of the phosphate particles, and improve the energy density of the battery cell.

[0229] Specifically, the arrangement of the carbon coating layer provides the following advantages for the positive electrode active material of the application:

[0230] The carbon coating layer in the positive electrode active material of the application provides a suitable channel for the transmission of electrons, which can significantly improve the conduction rate of electrons during multiple delithiation and lithiation processes, improve the electronic conductivity of the lithium-containing phosphate, and improve the charging capacity and energy density of the corresponding battery cell.

[0231] The carbon coating layer of the positive electrode active material of the application is porous, which enables the electrolyte to fully and effectively contact the lithium-containing phosphate, thereby improving the transmission rate of lithium ions at the phase interface and improving the charging capacity of the battery cell.

[0232] Coating a carbon coating layer on the surface of the lithium-containing phosphate not only improves the electronic conductivity of the lithium-containing phosphate, but also improves the structural stability of the positive electrode active material, effectively alleviates the iron dissolution phenomenon of the positive electrode active material during long-term storage and cyclic use of the battery cell, and thus improves the cycle life of the battery cell.

[0233] The positive electrode active material of the application uses lithium-containing phosphate as the base material, fully utilizes the advantages of low cost, high reliability, and good cycle stability of lithium-containing phosphate, and solves the problems of poor electronic conductivity and ionic conductivity by using the coating layer (fast ion conductor layer and carbon coating layer). The battery cell prepared from the positive electrode active material of the application can improve the energy density of the battery cell while having excellent cycle performance.

[0234] In the embodiments of the present application, the content of elements in the positive electrode active material is in the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, referring to EPA 6010D-2014, tested by inductively coupled plasma atomic emission spectrometry, and determined by plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After disassembling the positive electrode sheet from the battery monomer discharged to 0% state of charge SOC, washing and drying with DMC, and removing impurities by high temperature calcination, 0.4g of the positive electrode active material is weighed, 10ml (50% concentration) aqua regia is added thereto. Then it is placed on a 180℃ flat plate for 30min. After digestion on the flat plate, it is diluted to a volume of 100ml, and the quantitative test is carried out by the standard curve method.

[0235] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, which can be 0.19 to 0.26. Illustratively, the graphitization degree of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, or a range composed of any two of the above values.

[0236] When the graphitization degree of the positive electrode active material is in the above range, it is beneficial to improve the conductivity of the positive electrode active material and reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery monomer.

[0237] In the embodiments of the present application, the higher the graphitization degree of the material, the lower the degree of disorder, which can be tested according to the test standard JIS / K 0131-1996 X-ray diffraction analysis method general rules.

[0238] In some embodiments, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine structure lithium-containing phosphate is 5m 2 / g to 18m 2 / g.

[0239] Alternatively, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine structure lithium-containing phosphate is 7.5m 2 / g to 14m 2 / g.

[0240] Illustratively, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or a range composed of any two of the above values.

[0241] For example, the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14m 2 / g, 15m 2 / g, 16m 2 / g, 17m 2 / g, 18m 2 / g or a range formed by any two of the above values.

[0242] The carbon element mainly exists in the form of carbon coating layer in the coating layer, the carbon coating layer is loose and porous, which is beneficial to improve the specific surface area of the material, and is more beneficial to the effective contact between the electrolyte and the phosphate particles, and is beneficial to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is in the above range, the conductivity of the lithium-containing phosphate with olivine structure can be significantly improved, which is beneficial to improve the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the rapid charging capacity and energy density of the battery cell.

[0243] In the embodiments of the present application, the specific surface area of the material has the meaning known in the art, and can be detected by using the devices and methods known in the art, for example, according to the test standard GB / T 19587-2017, taking the positive electrode active material as the sample, and using the Tri-Star 3020 type specific surface area and pore size analyzer of the Micromeritics company of the United States to test the specific surface area.

[0244] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1μm≤Dv50≤2μm, 0.4μm≤Dv10≤0.7μm.

[0245] For example, the Dv50 of the positive electrode active material can be 1μm, 1.1μm, 1.15μm, 1.2μm, 1.25μm, 1.3μm, 1.35μm, 1.4μm, 1.45μm, 1.5μm, 1.55μm, 1.6μm, 1.65μm, 1.7μm, 1.75μm, 1.8μm, 1.85μm, 1.9μm, 1.95μm, 2μm or a range formed by any two of the above values.

[0246] Exemplarily, the Dv10 of the positive electrode active material can be 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, or a range formed by any two of the above values.

[0247] The particle size of the positive electrode active material is relatively small, the path of lithium ion deintercalation in the positive electrode active material is short, and the heat production is less. Moreover, the particle size of the positive electrode active material is not too small, and agglomeration basically does not occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0248] In the embodiments 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, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% in the volume distribution. The detection can be performed by using devices and methods known in the art. For example, the positive electrode active material is taken as a sample, the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0249] When the positive electrode active material includes not only the lithium-containing phosphate with olivine structure but also other materials, the volume distribution particle size of the positive electrode active material refers to the volume distribution particle size of all the positive electrode active materials.

[0250] In some embodiments, the lithium-containing phosphate with olivine structure is in a particulate form, the lithium-containing phosphate with olivine structure includes secondary particles, the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. Exemplarily, the average particle size of the primary particles is 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, or a range formed by any two of the above values.

[0251] The average particle size of the primary particles is relatively small, the path of lithium ion deintercalation in the positive electrode active material is short, and the heat production is less.

[0252] In the embodiments of the present application, the secondary particle refers to an agglomerated particle formed by aggregation of two or more primary particles. The primary particles and the secondary particles can be easily distinguished by experimental means (such as using a scanning electron microscope to take SEM images), and the average particle size of the primary particles can be obtained by SEM testing. The SEM testing parameters can be set as follows: working voltage (EHT) is 10.00 kV, InLens detector is used, working distance is 4.6 mm, and magnification is 1000X.

[0253] In some embodiments, the positive electrode film layer further comprises one or more of a ternary material, lithium phosphate, lithium dihydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metavanadate, lithium tartrate, lithium citrate, lithium nickelate, and lithium ferrite. The above-mentioned materials can act as a lithium supplement, which can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and thus improve the energy density of the battery cell.

[0254] Optionally, the ternary material comprises Li x3 A y3 Ni a3 Co b3 Mn c M3(1-a3-b3-c3)Y3 z3 wherein 0

[0255] Exemplarily, the ternary material comprises LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2.

[0256] In some embodiments, the lithium supplement agent has a mass content of 0.5% to 5% in the positive electrode film layer, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two of the foregoing values. When the mass content of the lithium supplement agent is within the foregoing range, the lithium supplement agent can supplement lithium ions to the positive electrode film layer, compensate for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0257] The lithium supplement agent can be in the same layer as the positive electrode active material, or in different layers. When the lithium supplement agent and the positive electrode active material are in different layers, the lithium supplement agent can be in a lithium supplement layer, and the positive electrode active material can be in a positive electrode active material layer, in other words, the positive electrode film layer includes the lithium supplement layer and the positive electrode active material layer. The positive electrode active material layer can be disposed on at least one side of the positive electrode current collector, and the lithium supplement layer can be between the positive electrode active material layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer can be between the lithium supplement layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be between the positive electrode active material layer and the positive electrode current collector, and the lithium supplement agent in the lithium supplement layer can be gradually released into the system during the cyclic charging and discharging of the battery cell, thereby compensating for the loss of lithium in the battery system.

[0258] In some embodiments, the positive electrode film layer optionally further includes a positive electrode conductive agent. The type of positive electrode conductive agent is not particularly limited in the embodiments of the present application, and as an example, the positive electrode conductive agent includes at least one of super conductive 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.

[0259] In some embodiments, the positive electrode film layer optionally further includes a positive electrode binder. The type of positive electrode binder is not particularly limited in the embodiments of the present application, and as an example, the positive electrode binder can include at least one 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 acrylic ester resin. In some embodiments, the mass content of the positive electrode binder is ≤5% based on the mass of the positive electrode film layer.

[0260] In some embodiments, the positive current collector can employ a metal foil or a composite current collector. As an example of the metal foil, at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy foils can be employed. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer can include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0261] In some embodiments, the ratio of the thickness of the positive current collector to the thickness of the single-sided positive film layer is 0.05 to 0.3. As an example, the ratio of the thickness of the positive current collector to the thickness of the single-sided positive film layer is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, or a range between any two of the aforementioned values.

[0262] When the ratio of the thickness of the positive current collector to the thickness of the single-sided positive film layer is within the aforementioned range, the rapid charging capability and the energy density of the battery cell can be improved.

[0263] In some embodiments, the thickness of the positive current collector is 10 μm to 15 μm, and can be optionally 12 μm to 15 μm. As an example, the thickness of the positive current collector is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, or a range between any two of the aforementioned values.

[0264] When the thickness of the positive current collector is within the aforementioned range, the overcurrent capability of the positive current collector is excellent, and the battery cell can have a high energy density.

[0265] In the embodiments of the present application, the thicknesses of the positive film layer and the positive current collector have the meanings known in the art, and can be detected by using the devices and methods known in the art. For example, the thickness of the positive electrode sheet can be measured by using a micrometer, the thickness of the positive current collector can be measured by using a micrometer after removing the film layer on the surface of the positive current collector, and the thickness of the positive film layer can be measured by subtracting the thickness of the positive current collector from the thickness of the positive electrode sheet when the positive film layer is single-sided coated, or by dividing the thickness of the positive electrode sheet by 2 when the positive film layer is double-sided coated.

[0266] The positive electrode film layer is usually formed by coating a positive electrode slurry on a positive electrode current collector, and then drying and cold-pressing. The positive electrode slurry is usually formed by dispersing and uniformly stirring a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0267] The positive electrode tab does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode tab of the embodiments of the present application further comprises a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer, and arranged on the surface of the positive electrode current collector. In some other embodiments, the positive electrode tab of the embodiments of the present application further comprises a protective layer covering the surface of the positive electrode film layer.

[0268] In some embodiments, the positive electrode tab further comprises a positive electrode conductive layer 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 tab, reduce the heat generation of the positive electrode tab, and thus reduce the heat generation of the battery cell.

[0269] 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 defined by any two of the above values.

[0270] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode tab can be further improved, the heat generation of the positive electrode tab can be reduced, and thus the heat generation of the battery cell can be reduced, while the energy density of the battery cell can be improved.

[0271] In the embodiments of the present application, the thickness of the positive electrode conductive layer has the meaning known in the art, and can be detected by using the devices and methods known in the art, for example, by performing tomography on the positive electrode tab to directly measure the thickness of the positive electrode conductive layer.

[0272] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder.

[0273] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. For example, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or a range defined by any two of the above values.

[0274] For example, the positive electrode conductive agent comprises one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, and thus improve the conductivity of the positive electrode tab and reduce the heat generation of the battery cell.

[0275] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. Illustratively, the mass content of the positive electrode binder in the positive electrode conductive layer is 50%, 60%, 65%, 70%, or a range between any two of the above values.

[0276] Illustratively, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a polyacrylic acid, and a fluorine-containing acrylic ester resin. The positive electrode binder in the positive electrode conductive layer can improve the adhesion between the positive electrode current collector and the positive electrode film layer, and improve the structural stability of the positive electrode tab.

[0277] [Negative electrode tab]

[0278] The negative electrode tab 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 including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0279] In some embodiments, the compaction density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 , optionally 1.25 g / cm 3 to 1.36 g / cm 3 at 100% state of charge of the battery cell. Illustratively, the compaction density of the negative electrode film layer is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 , 1.28 g / cm 3 , 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.36 g / cm 3 or a range between any two of the above values at 100% state of charge of the battery cell.

[0280] When the compaction density of the negative electrode film layer is within the above range, the energy density of the battery cell can be improved, and since the negative electrode active material in the negative electrode film layer is packed more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the tab and thus reduce heat generation.

[0281] In the embodiments of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge is the meaning known in the art, which can be detected by using the equipment and method known in the art, and the detection method is as follows:

[0282] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 , and optionally 110 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2 . For example, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 , 92 mg / 1540.25 mm 2 , 95 mg / 1540.25 mm 2 , 96 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 112 mg / 1540.25 mm 2 , 114 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 116 mg / 1540.25 mm 2 , 118 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 142 mg / 1540.25 mm 2, 145 mg / 1540.25 mm 2 , 148 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 152 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 165 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 or a range formed by any two of the above values.

[0283] When the single-side coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode tab will not be too large, and the energy density of the battery monomer can be improved.

[0284] In the embodiments of the present application, the single-side coating weight of the negative electrode film layer has the meaning known in the art, and can be detected by using the devices and methods known in the art, and the detection method is as described in the foregoing single-side coating weight test method of the film layer.

[0285] In some embodiments, the powder resistivity of the negative electrode active material is 0.005 Ω·cm to 0.043 Ω·cm, and can be 0.04 Ω·cm. For example, the powder resistivity of the negative electrode active material can be 0.043 Ω·cm, 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 formed by any two of the above values.

[0286] The relatively low powder resistivity of the negative electrode active material makes the resistance of the negative electrode tab relatively low, and the battery monomer generates less heat.

[0287] In the embodiments of the present application, the powder resistivity of the negative electrode active material has the meaning known in the art, and can be detected by using the devices and methods known in the art, and the detection method is as described in the foregoing powder resistivity test method of the positive electrode active material.

[0288] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.5 g / cm 3 to 1.85 g / cm 3 , and can be 1.55 g / cm 3 to 1.65 g / cm 3 . For example, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.5 g / cm 31.55 g / cm3 3 1.6 g / cm3 3 1.65 g / cm3 3 1.7 g / cm3 3 1.75 g / cm3 3 1.8 g / cm3 3 1.85 g / cm3 3 or a range between any two of the above values.

[0289] When the powder compaction density of the negative active material at 20000 N is within the above range, the energy density of the battery cell can be improved, and the negative active material in the negative electrode film layer can be more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0290] In the embodiments of the present application, the powder compaction density of the material is the meaning known in the art, which can be detected by the methods and devices known in the art according to the test standard GB / T24533-2009. As an example, a certain amount of negative active material is taken as a sample, which is added into a mold with a bottom area of 1.327 cm 2 of the UTM7305 electronic pressure testing machine, and is pressed to 2000 kg (equivalent to 20000 N), and is kept for 30 s, then is unloaded, and is kept for 10 s, then the powder compaction density of the negative active material under the action of 20000 N is recorded and calculated.

[0291] In some embodiments, the charge gram capacity of the negative active material at 0.1C rate is 350 mAh / g to 480 mAh / g. Illustratively, the charge gram capacity of the negative active material at 0.1C rate is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, or a range between any two of the above values.

[0292] When the charge gram capacity of the negative active material at 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0293] In the embodiments of the present application, the charge gram capacity of the negative active material at 0.1C rate is a meaning known in the art, which can be detected by using the devices and methods known in the art, and the detection method is as follows: the charge gram capacity of the positive active material at 0.1C rate is tested.

[0294] In some embodiments, the negative active material comprises a carbon-based material, and the carbon-based material has high cycle stability, which can improve the cycle performance of the battery cell. Optionally, the mass content of the carbon-based material in the negative active material is greater than or equal to 80% and less than or equal to 100%.

[0295] The positive active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative active material is mainly a carbon-based material system. The two are used together, and the cycle performance of the battery cell is excellent.

[0296] Optionally, the carbon-based material comprises graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. For example, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, or a range formed by any two of the above values.

[0297] When the graphitization degree of the graphite particles is in the above range, the conductive performance of the graphite particles is excellent, which can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the rapid charging performance of the battery cell.

[0298] In some embodiments, the graphite particles comprise artificial graphite and a carbon coating layer, the artificial graphite comprises secondary particles, the secondary particles comprise a plurality of primary particles, and the carbon coating layer is coated on the surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon, which refers to a transition state carbon material with a very low degree of graphitization and crystallization, and an approximate amorphous state (or a structure with no fixed shape and periodicity). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0299] The artificial graphite comprises secondary particles, the migration path of lithium ions in the artificial graphite is more, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions, the carbon coating layer has more end faces and defects, so that the number of sites capable of deintercalating lithium ions is more, and the conductivity of the carbon coating layer is excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0300] Optionally, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. For example, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range formed by any two of the above values.

[0301] When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode sheet can be further reduced, and the heat generation of the battery cell can be reduced.

[0302] In the embodiments of the present application, the graphite particles can be prepared by methods known in the art, for example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and then forming a carbon coating layer on at least part of the surface of the artificial graphite particles after carbonization treatment.

[0303] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of the coal tar pitch and petroleum pitch is below 250°C.

[0304] 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 the appropriate range, the organic carbon source can be carbonized, and a coating layer containing amorphous carbon can be formed on at least part of the surface of the artificial graphite.

[0305] Optionally, the carbonization treatment time is 1h to 6h.

[0306] In some embodiments, the carbon-based material can further include natural graphite. Specifically, the carbon-based material can include graphite particles, or the carbon-based material can include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0307] In some embodiments, the negative electrode active material can further include a silicon-based material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0308] Optionally, the mass content of silicon in the silicon-based material is 0.3% to 10.0%, and optionally 1% to 6%, based on the mass of the negative electrode active material. Illustratively, the mass content of silicon in the silicon-based material is 0.3%, 0.5%, 0.8%, 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%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10%, or a range formed by any two of the above values.

[0309] 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 improved, and the energy density of the battery cell can be improved.

[0310] Optionally, the silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0311] In some embodiments, the negative active material can include at least one of tin-based material and lithium titanate in addition to the carbon-based material and the optional silicon-based material. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0312] The qualitative and quantitative detection of each substance or element in the present application can be performed by using suitable devices and methods known to those skilled in the art, and the relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc., and those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used for qualitative or quantitative determination.

[0313] For example, the negative electrode sheet or the negative active material can be subjected to X-ray powder diffraction test and qualitative analysis by JIS / K0131-1996 X-ray Diffraction Analysis General Method.

[0314] The artificial graphite and the natural graphite can be distinguished by the SEM cross-sectional diagram taken by the scanning electron microscope SEM, the SEM cross-sectional diagram of the natural graphite has gaps between the flaky structures, the SEM cross-sectional diagram of the artificial graphite is dense and has no obvious gaps, or the XRD spectrum obtained by the X-ray diffraction method is used for distinguishing, the XRD spectrum of the natural graphite has obvious 2H phase and 3R phase, and the XRD spectrum of the artificial graphite only has 2H phase.

[0315] The negative electrode film layer in the embodiments of the present application includes at least one film layer, which can be a single layer film layer or at least two layer film layers. Optionally, the negative electrode film layer includes at least two film layers.

[0316] In the case of using a single layer film layer for the negative electrode film layer, the negative active material in the negative electrode film layer includes the carbon-based material and optionally the silicon-based material. In the case of using a single layer film layer, the volume average particle size Dv50 of the negative active material is 8.2 μm to 13.5 μm. Illustratively, the volume average particle size Dv50 of the negative active material is 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 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, 13.2 μm, 13.5 μm, or a range formed by any two of the above values.

[0317] In the case of adopting at least two layers of film layers in the negative electrode film layer, the negative electrode active material in the negative electrode film layer comprises a carbon-based material, and optionally further comprises a silicon-based material, which can be located in one of the at least two layers of film layers or at least two of the at least two layers of film layers. The negative electrode film layer can comprise two layers of film layers, three layers of film layers, four layers of film layers, or even more layers of film layers.

[0318] In some embodiments, the negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is arranged on the surface of the negative electrode current collector, the carbon-based material in the first negative electrode film layer comprises graphite particles, the second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, the carbon-based material in the second negative electrode film layer comprises graphite particles, and the graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer can be the same or different.

[0319] The interface of the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0320] Optionally, the carbon-based material in the first negative electrode film layer further comprises natural graphite.

[0321] The negative electrode film layer comprises at least two layers of film layers, and the layered coating is conducive to improving the rapid charging performance of the battery monomer. Especially when there is a difference between the first negative electrode film layer and the second negative electrode film layer, the difference in the pore of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission can be reduced, and the rapid charging performance of the battery monomer can be improved.

[0322] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which is conducive to improving the compaction density of the negative electrode film layer. When the negative electrode active material comprises graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0323] The difference in particle size in the first negative electrode film layer and the second negative electrode film layer can improve the rapid charging performance of the battery monomer. Specifically, in the rapid charging process, the overpotential of the second negative electrode film layer is usually high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and improve the problem of lithium extraction on the surface of the negative electrode sheet.

[0324] Optionally, the negative active material in the first negative electrode film layer is in a granular form, and the volume average particle size Dv50 of the negative active material is 9.5-18.5 μm, or 9.5-14.6 μm. For example, the volume average particle size of the negative active material is 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 14.6 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, or a range defined by any two of the above values. When the first negative electrode film layer comprises graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5-18.5 μm, or 9.5-14.6 μm.

[0325] When the volume average particle size Dv50 of the negative active material in the first negative electrode film layer is within the above range, on the one hand, the solid-phase transmission path of lithium ions can be shortened, and the fast charging performance can be improved; on the other hand, the material is less likely to agglomerate during preparation, and the stability of the material can be improved.

[0326] Optionally, the negative active material in the second negative electrode film layer is in a granular form, and the volume average particle size Dv50 of the negative active material is 7.8-14.3 μm, or 7.8-11.3 μm. For example, the volume average particle size Dv50 of the negative active material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm, or a range defined by any two of the above values. When the second negative electrode film layer comprises graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8-14.3 μm, or 7.8-11.3 μm.

[0327] When the volume average particle size Dv50 of the negative active material in the second negative electrode film layer is within the above range, on the one hand, the solid-phase transmission path of lithium ions can be shortened, and the fast charging performance can be improved; on the other hand, the material is less likely to agglomerate during preparation, and the stability of the material can be improved; and on the further hand, the negative active material in the second negative electrode film layer with the above volume average particle size range and the negative active material in the first negative electrode film layer cooperate to facilitate the construction of a gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reduce the tortuosity of lithium ion transmission, and improve the fast charging performance of the battery cell.

[0328] In the embodiments of the present application, the volume average particle size Dv50 of the negative active material has the meaning known in the art and can be detected using devices and methods known in the art, such as the volume average particle size Dv50 test method of the positive active material described above.

[0329] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. The tap density can reflect the filling density of the active material in the film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, so that the energy density of the battery cell is improved, and the first negative electrode film layer is relatively sparse in filling, and has more pores, which can improve the rapid charging performance of the battery cell. When the negative active material includes graphite particles, the tap density of the graphite particles in the first negative electrode film layer is less than or equal to the tap density of the graphite particles in the second negative electrode film layer.

[0330] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 , for example, 0.82 g / cm 3 , 0.85 g / cm 3 , 0.88 g / cm 3 , 0.90 g / cm 3 , 0.92 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 , or a range composed of any two of the above values. When the tap density of the carbon-based material in the first negative electrode film layer is within a suitable range, the rapid charging performance of the battery cell can be improved.

[0331] Optionally, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 , for example, 0.90 g / cm 3 , 0.92 g / cm 3 , 0.95 g / cm , 0.98 g / cm , 1.00 g / cm , 1.05 g / cm , 1.08 g / cm , 1.10 g / cm , 1.12 g / cm , 1.15 g / cm , 1.18 g / cm , 1.20 g / cm , 1.21 g / cm , or a range composed of any two of the above values. When the tap density of the carbon-based material in the second negative electrode film layer is within a suitable range, the rapid charging performance of the battery cell can be improved.0.95 g / cm3 3 0.98 g / cm3 3 1.00 g / cm3 3 1.05 g / cm3 3 1.08 g / cm3 3 1.10 g / cm3 3 1.12 g / cm3 3 1.15 g / cm3 3 1.18 g / cm3 3 1.20 g / cm3 3 1.21 g / cm3 3 1.22 g / cm3 3 1.23 g / cm3 3 1.24 g / cm3 3 1.25 g / cm3 3 or a range defined by any two of the above values. When the tap density of the carbon-based material in the second negative electrode film layer is within the appropriate range, the energy density of the battery cell can be improved.

[0332] In embodiments of the present application, the tap density of the material is the meaning known in the art, which can be measured by instruments and methods known in the art. For example, GB / T 5162-2006 can be referred to, and a powder tap density tester can be used for measurement. The testing instrument can use Dandong Bit BT-301.

[0333] Alternatively, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7 to 7:3, which can be 4:6 to 6:4. For example, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7, 4:6, 5:5, 6:4, 7:3, or a range defined by any two of the above values. By adjusting the thickness ratio of the first negative electrode film layer and the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0334] In some embodiments, after the battery cell is subjected to a full charge test cycle of 10 cycles at the beginning of life (BOL), the thickness of the first negative electrode film layer is 15 μm to 65 μm, for example, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range defined by any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0335] In some embodiments, the thickness of the second negative electrode film layer is 15 μm to 65 μm, for example, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range between any two of the above values, after the battery cell is tested for 10 cycles of full charge at the beginning of life (BOL).

[0336] In the embodiments of the present application, for example, the battery charging upper limit voltage is 3.65 V, and the battery discharging cut-off voltage is 2.0 V.

[0337] The BOL full charge test procedure is as follows: at 25°C, charge to 3.65 V at a charging rate of 0.33C of the nominal capacity of the battery, then charge to 0.05C at 3.65 V, stand for 10 min, then discharge to 2.0 V at a discharging rate of 0.33C, stand for 10 min, the above one-time charging and discharging is one cycle, and the cycle is repeated for 10 times, then charge to 3.65 V at a charging rate of 0.33C of the nominal capacity, and charge to 0.05C at 3.65 V, which is the BOL full charge state. In the BOL full charge state, the negative electrode sheet is disassembled, the thickness direction section of the middle region of the negative electrode sheet is observed using a scanning electron microscope, the first negative electrode film layer and the second negative electrode film layer are distinguished according to the interface region, and the thicknesses of the two regions are measured, for example, the thicknesses of 10 positions of the first negative electrode film layer are measured, the average value is calculated as the average value of the first negative electrode film layer, the thicknesses of 10 positions of the second negative electrode film layer are measured, and the average value is calculated as the average value of the second negative electrode film layer.

[0338] In some embodiments, after the battery cell is subjected to the End Of Life (EOL) full charge test, the thickness of the first negative electrode film layer is 15-70 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, or a range defined by any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the first negative electrode film layer and the second negative electrode film layer can regulate the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the rapid charging capability of the battery cell.

[0339] In some embodiments, after the battery cell is subjected to the End Of Life (EOL) full charge test, the thickness of the second negative electrode film layer is 15-70 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, or a range defined by any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the first negative electrode film layer and the second negative electrode film layer can regulate the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the rapid charging capability of the battery cell.

[0340] In the embodiments of the present application, for example, the upper limit voltage of battery charging is 3.65 V, and the discharge cut-off voltage of the battery is 2.0 V.

[0341] The EOL full charge test procedure is as follows: at 60°C, charge at 0.33C of the nominal capacity of the battery to 3.65V, then charge at 3.65V constant voltage to 0.05C, stand for 10min, then discharge at 0.33C discharge rate to 2.0V, stand for 10min, the above one charge-discharge is a cycle, until the battery capacity decays to 80% of the nominal capacity to stop testing. Then at 25°C, charge to 3.65V at a constant current of 0.33C, and charge to 3.65V at a constant voltage of 0.05C, which is the EOL full charge state. In the EOL full charge state, the negative electrode sheet is disassembled, and the thickness direction cross section of the middle region of the negative electrode sheet is observed using a scanning electron microscope. The interface between the first negative electrode film layer and the second negative electrode film layer is distinguished, and the thicknesses of the two regions are measured, respectively. For example, the thicknesses of 10 positions of the first negative electrode film layer are measured, and the average value is calculated as the average value of the first negative electrode film layer. The thicknesses of 10 positions of the second negative electrode film layer are measured, and the average value is calculated as the average value of the second negative electrode film layer.

[0342] In some embodiments, in the case of a single-layer film layer (different from the above-mentioned double-layer film layer) for the negative electrode film layer, the negative electrode film layer further comprises a lithium-containing binder. Optionally, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1% to 1%. Illustratively, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range composed of any two of the above-mentioned values. The lithium element in the lithium-containing binder can exist in ionic form, which can increase the number of free-moving lithium ions in the negative electrode film layer, shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, increase the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery monomer. Optionally, the negative electrode film layer can further comprise a negative electrode binder, for example, the negative electrode binder comprises at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0343] Optionally, the mass content of lithium element in the lithium-containing binder is 3% to 10%. Illustratively, the mass content of lithium element in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range composed of any two of the above-mentioned values. The mass content of lithium element is calculated based on the mass of the lithium-containing binder. When the mass content of lithium element is in the above-mentioned range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, increase the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery monomer.

[0344] Exemplarily, the lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0345] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery monomer, and is not prone to swelling during charging and discharging, and has stable structure, so that the cycle performance of the negative electrode film layer is improved during rapid charging and discharging.

[0346] In some other embodiments, when the negative electrode film layer adopts at least two film layers, the negative electrode film layer further includes a lithium-containing binder.

[0347] Optionally, the first negative electrode film layer further includes a first lithium-containing binder, the second negative electrode film layer further includes a second lithium-containing binder, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. Further optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0348] The mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides relatively more free-moving lithium ions for the second negative electrode film layer, which can further improve the rapid charging performance of the battery monomer.

[0349] Optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range composed of any two of the above values. The lithium element in the first lithium-containing binder can exist in the form of ions, which can increase the number of free-moving lithium ions in the negative electrode film layer, shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery monomer.

[0350] Optionally, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, or 3% to 8%. For example, the mass content of lithium element in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range defined by any two of the above values. When the mass content of lithium element is within the above range, the number of lithium ions that can freely move in the negative electrode film layer is relatively large, the distance of lithium ion diffusion to the surface of the negative electrode film layer is shortened, the deintercalation rate of lithium ions is improved, and the rapid charging performance of the battery cell is improved.

[0351] For example, the first lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, and the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0352] The lithium-containing binder described above can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0353] Optionally, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. For example, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range defined by any two of the above values. The lithium element in the second lithium-containing binder can exist in the form of ions, which can increase the number of lithium ions that can freely move in the negative electrode film layer, shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0354] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0355] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, optionally 3% to 8%. Illustratively, the mass content of lithium element in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range formed by any two of the above values. When the mass content of lithium element is in the above range, the number of lithium ions that can freely move in the negative electrode film layer is relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0356] Illustratively, the second lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, and the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0357] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0358] In some embodiments, the first negative electrode film layer further includes a negative electrode binder, and the second negative electrode film layer further includes a negative electrode binder. The negative electrode binder in the first negative electrode film layer and the negative electrode binder in the second negative electrode film layer each independently includes at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0359] In some embodiments, the total content of the first lithium-containing binder and the negative electrode binder in the first negative electrode film layer is greater than the total content of the second lithium-containing binder and the negative electrode binder in the second negative electrode film layer, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0360] In some embodiments, the negative electrode film layer further optionally comprises a negative electrode conductive agent. The type of the negative electrode conductive agent is not particularly limited in the embodiments of the present application, and the negative electrode conductive agent may, for example, comprise at least one of super P, 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.

[0361] In some embodiments, the negative electrode film layer further optionally comprises a negative electrode binder. In some embodiments, the mass content of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0362] In some embodiments, the negative electrode film layer further optionally comprises other auxiliary agents. The other auxiliary agents may, for example, comprise thickening agents, dispersants, and the like, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, the mass content of the other auxiliary agents is ≤2% based on the total weight of the negative electrode film layer.

[0363] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As examples of the metal foil, at least one of a copper foil, a copper alloy foil, a nickel foil, a nickel alloy foil, a titanium foil, a titanium alloy foil, a silver foil, and a silver alloy foil may be used. The composite current collector may comprise a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As examples of the metal material in the metal material layer, at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. As examples of the polymer material base layer, at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE) may be used.

[0364] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. For example, the thickness of the negative electrode current collector is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or a range defined by any two of the above values.

[0365] When the thickness of the negative electrode current collector is in the above range, the overcurrent capacity of the negative electrode current collector is excellent, and the battery cell can have a high energy density.

[0366] In the embodiments of the present application, the thickness of the negative electrode current collector has the meaning known in the art, and may be measured by using a device and a method known in the art, for example, by washing the film layer on the surface of the negative electrode current collector with a solvent and measuring the thickness of the negative electrode current collector with a micrometer.

[0367] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0368] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a negative electrode 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 this application further includes a protective layer covering the surface of the negative electrode film layer.

[0369] In some embodiments, the negative electrode sheet 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 improve the conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery cell.

[0370] In some embodiments, the thickness of the negative electrode conductive layer is from 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 any combination of two of the above values.

[0371] 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 also be improved.

[0372] In the embodiments of this application, the thickness of the negative electrode conductive layer has a meaning known in the art and can be detected using equipment and methods known in the art, such as the test method for the negative electrode conductive layer described above.

[0373] 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 sheet and reducing the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the adhesion between the negative electrode current collector and the negative electrode film layer, thereby improving the structural stability of the negative electrode sheet.

[0374] In some embodiments, the negative electrode conductive layer may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0375] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 20% to 40%. Illustratively, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or a range consisting of any two of the aforementioned values.

[0376] Illustratively, the negative electrode conductive agent includes one or more of super-p carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0377] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%. Illustratively, the mass content of the negative electrode binder is 60%, 65%, 70%, 75%, 80%, or a range consisting of any two of the aforementioned values.

[0378] Illustratively, the negative electrode binder includes one or more of styrene butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0379] In some embodiments, the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is 1.05 to 1.30, and optionally 1.07 to 1.15. Illustratively, the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3, or a range consisting of any two of the aforementioned values.

[0380] When the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is in the aforementioned range, there are sufficient sites in the negative electrode film layer for lithium intercalation, which can reduce the risk of lithium precipitation and is conducive to fast charging.

[0381] In the embodiments of the present application, the CB value has the meaning known in the art and can be detected using devices and methods known in the art, for example, the capacity of the unit area negative electrode film layer and the capacity of the unit area positive electrode film layer are calculated respectively, and the ratio of the two is calculated to obtain the CB value.

[0382] Specifically, taking the upper limit voltage of battery charging as 3.65V and the discharge cut-off voltage of the battery as 2.0V as an example,

[0383] The capacity of the unit area positive electrode film layer refers to the actual delithiation capacity of the positive electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the positive electrode sheet is taken out, and a CR2430 type half buckle battery of positive electrode-lithium sheet is assembled. The area of the positive electrode sheet used is amm 2The electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then the assembled half-buckle battery is left to stand for 3 h. The test is carried out at 25°C, and the capacity of the discharge buckle in the second cycle is recorded as Y mAh. The length of the positive electrode sheet in the actual battery design is b mm, the width is c mm, the number of surfaces on which the positive electrode active material is coated on the positive electrode current collector is d, and then the capacity of the unit area of the positive electrode film layer is Y / a*b*c*d.

[0384] Specifically, the capacity of the unit area of the negative electrode film layer refers to the actual lithium intercalation capacity of the negative electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode sheet is taken out, and a CR2430 type half-buckle battery of negative electrode-lithium sheet is assembled. The area of the negative electrode sheet is f mm 2 The electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then the assembled half-buckle battery is left to stand for 3 h. The test is carried out at 25°C, and the capacity of the discharge buckle in the second cycle is recorded as Y mAh. The length of the positive electrode sheet in the actual battery design is b mm, the width is c mm, the number of surfaces on which the positive electrode active material is coated on the positive electrode current collector is d, and then the capacity of the unit area of the positive electrode film layer is Y / a*b*c*d.

[0385] [Separation film]

[0386] In the embodiments of the present application, the separation film includes a base film with a porous structure.

[0387] In some embodiments, the base film includes at least one of glass fiber, non-woven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the base film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0388] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0389] In some embodiments, the porosity of the base film is 20% to 70%, and is optionally 35% to 60%. For example, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range between any two of the above values.

[0390] When the porosity of the base film in the embodiments of the present application is in the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0391] In the embodiments of the present application, the porosity refers to the percentage of the volume of the pores in the separator film to the total volume of the separator film. The porosity can be tested according to the standard GB / T 36363-2018 “Polyolefin Separator for Battery Cell”. It should be noted that the actual testing process can be slightly different from the standard in order to eliminate the influence on the testing of the porosity as much as possible, and to obtain more accurate test values according to the differences in testing instruments, testing errors, and testing processes.

[0392] In some embodiments, the thickness of the base film is 6 μm to 12 μm, which can be optionally 6 μm to 9 μm. For example, the thickness of the base film is 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 formed by any two of the above values.

[0393] When the thickness of the base film is in the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0394] In the embodiments of the present application, the separator film can be the base film. Optionally, the separator film further comprises a functional layer disposed on at least one side of the base film, and the functional layer can comprise inorganic particles to improve the heat resistance of the separator film. Optionally, the functional layer is disposed on both sides of the base film.

[0395] In some embodiments, the functional layer comprises 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 comprises first inorganic particles, the second functional layer is located on the other side of the base film, and the second functional layer comprises composite particles, the composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles.

[0396] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

[0397] Optionally, the first functional layer can comprise a binder, which can optionally comprise at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0398] Optionally, the first inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0399] In the embodiments of the present application, the thickness of the base film has the meaning known in the art, which can be detected using the meaning and equipment known in the art. For example, a newly prepared separator film can be taken as a sample, or a battery cell that has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery cell is about 0% SOC) is disassembled in reverse, a separator film is obtained from the battery cell, and the separator film is dried and taken as a sample. The separator film is cut by an ion beam cutter to form a cross section, and then the thickness of the cross section of the separator film and each layer thereof is measured using a scanning electron microscope.

[0400] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers, which optionally include acrylate-acrylonitrile-acrylamide-acryl copolymers. The acrylate copolymers have excellent bonding properties, and have high bonding stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as a molar ratio of 35%:30%:15%:20%, or 40%:20%:10%:30%, or 45%:15%:20%:20%, etc.

[0401] The second inorganic particles in the composite particles prevent the non-fluoropolymer particles from being easily bonded due to high-temperature treatment in the granulation process, so that the composite particles have pores, which are beneficial to the transmission of lithium ions, improve the ion conductivity of the separator film, and the second inorganic particles also improve the compression modulus of the composite particles, so that the composite particles are not easily deformed during charging and discharging, so that the structure of the separator film is more stable, which can improve the kinetic performance of the battery cell and improve the rapid charging performance. Optionally, the second functional layer is arranged close to the negative electrode tab, and since the composite particles are not easily deformed, the separator film basically does not cause side effects such as extrusion to the negative electrode tab, so that the kinetic performance of the negative electrode tab is stable. Correspondingly, the first functional layer is arranged close to the positive electrode tab.

[0402] 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. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer, and can cooperate with the non-fluoropolymer to form composite particles, further improving the cycle stability and kinetic performance of the separator film, and improving the cycle performance and rapid charging performance of the battery cell.

[0403] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, and optionally 5 nm to 20 nm. Illustratively, 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 defined by any two of the above values. When the average particle size of the second inorganic particles is within the above range, the heat resistance and compression modulus of the composite particles can be improved.

[0404] In the embodiments of the present application, the average particle size of the second inorganic particles has the meaning known in the art and can be detected by using the devices and methods known in the art. For example, after the isolation film is obtained, the isolation film is dried as a sample, the isolation film is cut by an ion beam cutter to form a cross section, and then the particle size of the second inorganic particles in the isolation film is measured by using a scanning electron microscope. The particle size of a plurality of, for example, 50, second inorganic particles is measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0405] In some embodiments, the ion conductivity of the isolation film is 0.3 mS / cm to 0.6 mS / cm. Illustratively, the ion conductivity of the isolation film is 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.45 mS / cm, 0.5 mS / cm, 0.55 mS / cm, 0.6 mS / cm, or a range defined by any two of the above values.

[0406] When the ion conductivity of the isolation film is within the above range, the migration ability of lithium ions of the isolation film can be further improved, and the rapid charging performance of the battery cell can be improved.

[0407] In the embodiments of the present application, the ion conductivity of the isolation film has the meaning known in the art and can be detected by using the devices and methods known in the art. For example,

[0408] Preparation of a 2025 type button cell for testing: In a vacuum glove box, lithium pieces were placed into a negative electrode shell, 150 μL of an electrolyte was added, the electrolyte was a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then an isolation film (area of 3.14 cm 2 , thickness of 12 μm) was placed to tightly adhere to the lithium pieces, 25 μL of an electrolyte was added, and finally a positive electrode piece (the positive electrode piece can be the positive electrode piece in Example 1) was placed thereon, and then the button cell was packaged. The assembled button cell was taken out of the vacuum glove box and placed for 24 h for the next step of testing.

[0409] Test: In an electrochemical workstation, tests are carried out in a frequency range of 10 -1 ~10 6 Hz, to obtain the resistance Rb of the separator film, and to calculate the ionic conductivity σ (unit: mS / cm) by the following formula,

[0410] σ = L / (R b x S)

[0411] wherein R b is the resistance of the separator film, and L and S are the thickness and area of the separator film to be tested, respectively.

[0412] In some embodiments, the positive electrode sheet, the separator film and the negative electrode sheet can be made into an electrode assembly through a winding process and / or a stacking process.

[0413] Please continue to refer to FIG. 1 and FIG. 2, the battery cell 7 can include a shell 20.

[0414] In some embodiments, the shell 20 of the battery cell 7 can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The shell 20 of the battery cell 7 can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0415] The shell 20 is a hollow structure, which can be used to package the electrode assembly 10 and the electrolyte described above.

[0416] The preparation method of the battery cell 7 of the embodiments of the present application is known. In some embodiments, the positive electrode sheet, the separator film, the negative electrode sheet and the electrolyte can be assembled to form the battery cell 7. As an example, the positive electrode sheet, the separator film, the negative electrode sheet can be formed into an electrode assembly 10 through a winding process and / or a stacking process, the electrode assembly 10 is placed in the shell 20, the electrolyte is injected after drying, and the battery cell 7 is obtained after processes such as vacuum packaging, standing, formation, shaping, etc.

[0417] In the embodiments of the present application, the shell 20 includes a shell body 21 and an end cover 22, the shell body 21 has an opening, and the end cover 22 covers the opening. The shape of the shell body 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical shell body can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid shell body can be selected. Alternatively, the electrode assembly 10 and the shell body 21 are both cuboid structures.

[0418] In some embodiments, the material of the shell body 21 includes steel, which has high mechanical strength and is not easy to deform, and can improve the use reliability and cycle performance of the battery cell 7. Alternatively, the mass ratio of steel is the highest in the material ratio of the shell body 21.

[0419] Optionally, the thickness of the shell 21 is 0.1mm to 0.5mm, optionally 0.2mm to 0.35mm. Exemplarily, the thickness of the shell is 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm or a range between 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 use reliability and cycle performance of the battery monomer 7; and the shell 21 occupies less space, and the internal space of the shell 21 is larger, which is beneficial to improve the energy density of the battery monomer 7.

[0420] From the appearance of the electrode assembly 10, the electrode assembly 10 includes the main body part 12, the positive electrode tab 111 and the negative electrode tab 112, and the positive electrode tab 111 and the negative electrode tab 112 protrude from the main body part 12. The positive electrode tab 111 is a part of the positive electrode tab without the active material layer, and the negative electrode tab 112 is a part of the negative electrode tab without the active material layer. The positive electrode tab 111 and the negative electrode tab 112 are used to lead out the current in the main body part 12.

[0421] The positive electrode tab 111 and the negative electrode tab 112 can protrude from the same side of the main body part 12, or can respectively extend from opposite sides.

[0422] Optionally, the number of the positive electrode tab 111 on the same side of the main body part 12 is at least one, optionally at least two, and the at least two positive electrode tabs 111 can increase the overcurrent capacity of the positive electrode tab 111.

[0423] Optionally, the positive electrode tab 111 can be arranged on at least one side of the main body part 12, optionally at least two sides.

[0424] Optionally, the number of the negative electrode tab 112 on the same side of the main body part 12 is at least one, optionally at least two, and the at least two negative electrode tabs 112 can increase the overcurrent capacity of the negative electrode tab 112.

[0425] Optionally, the negative electrode tab 112 can be arranged on at least one side of the main body part 12, optionally at least two sides.

[0426] In some embodiments, the battery monomer 7 further includes a positive electrode terminal 31 electrically connected with the positive electrode tab 111. Optionally, the positive electrode terminal 31 and the positive electrode tab 111 are welded, and the positive electrode terminal 31 and the positive electrode tab 111 can be connected through an adapter or without using an adapter; optionally, the positive electrode terminal 31 and the positive electrode tab 111 are not connected through an adapter, i.e. the positive electrode terminal 31 and the positive electrode tab 111 are directly welded, which can reduce the resistance at the connection, and is beneficial to reduce the overall internal resistance of the battery monomer 7.

[0427] In some embodiments, the battery cell 7 further comprises a negative terminal 32 electrically connected with the negative tab 112. Optionally, the negative terminal 32 and the negative tab 112 are welded, and the negative terminal 32 and the negative tab 112 can be connected through an adapter or without an adapter; optionally, the negative terminal 32 and the negative tab 112 are connected without an adapter, i.e., the negative terminal 32 and the negative tab 112 are directly welded, which can reduce the resistance at the connection and is conducive to reducing the overall internal resistance of the battery cell 7.

[0428] Optionally, the number of positive terminals 31 located on the same side of the main body part 12 is at least one, and can be at least two, and the at least two positive terminals 31 can increase the overcurrent capacity of the positive terminal 31.

[0429] Further optionally, the overcurrent area of the single-side positive terminal 31 is 150mm 2 to 1000mm 2 , and can be 200mm 2 to 1000mm 2 The overcurrent area of the single-side positive terminal 31 refers to the sum of the overcurrent areas of all positive terminals 31 located on the same side of the main body part 12. The overcurrent area of the positive terminal 31 can be understood as the cross-sectional area of the positive terminal 31, and the cross section of the positive terminal 31 is perpendicular to the thickness direction of the end cover 22.

[0430] Exemplarily, the overcurrent area of the single-side positive terminal 31 can be 150mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 , 650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , 850mm 2 , 900mm 2 , 950mm 2 , 1000mm 2 , or a range composed of any two of the above values.

[0431] Optionally, the number of negative terminals 32 located on the same side of the main body 12 is at least one, and optionally at least two. The at least two negative terminals 32 can increase the overcurrent capacity of the negative terminals 32.

[0432] Further optionally, the overcurrent area of the single-side negative terminals 32 is 150mm 2 to 1000mm 2 , and optionally 200mm 2 to 1000mm 2 The overcurrent area of the single-side negative terminals 32 refers to the sum of the overcurrent areas of all the negative terminals 32 located on the same side of the main body 12. The overcurrent area of the negative terminals 32 can be understood as the cross-sectional area of the negative terminals 32, and the cross-section of the negative terminals 32 is perpendicular to the thickness direction of the end cover 22.

[0433] Exemplarily, the overcurrent area of the single-side negative terminals 32 can be 150mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 , 650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , 850mm 2 , 900mm 2 , 950mm 2 , 1000mm 2 , or a range formed by any two of the above values.

[0434] In some embodiments, the size of the battery cell 7 along the first direction X is 90mm to 130mm, for example, 90mm, 95mm, 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, or a range formed by any two of the above values. L1 shown in FIG. 1 represents the size of the battery cell 7 along the first direction X, which can be understood as the size from the bottom of the shell 21 to the top of the end cover 22 when the battery cell 7 is vertically placed.

[0435] When the size of the battery cell 7 along the first direction X is in the above range, the size of the positive electrode film layer along the first direction X is matched, so that the positive electrode active material coated on the positive electrode film layer is increased, which is beneficial to improve the energy density of the battery cell 7.

[0436] As shown in FIG. 3, in some embodiments of the present application, the battery cell 7 according to the embodiments of the present application can be assembled into a battery module 6, and the number of battery cells 7 contained in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0437] If the battery cell 7 is multiple, the multiple battery cells 7 can be connected in series or in parallel or in a mixed connection, and the mixed connection means that there are both series connection and parallel connection among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series or in parallel or in a mixed connection, and then the whole of the multiple battery cells 7 is accommodated in the accommodation portion of the battery module 6; of course, the multiple battery cells 7 can be first connected in series or in parallel or in a mixed connection to form the battery module 6, and then the multiple battery modules 6 are connected in series or in parallel or in a mixed connection to form a whole, which is accommodated in the accommodation portion. Alternatively, the battery module 6 can further include an accommodation portion having an accommodation space, and the multiple battery cells 7 are accommodated in the accommodation space.

[0438] As shown in FIG. 4 and FIG. 5, in some embodiments, the above-mentioned battery module 6 can also be assembled into a battery pack 2, and the number of battery modules 6 contained in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device described herein can be a battery module 6 or a battery pack 2.

[0439] The battery pack 2 can include a box 5 and multiple battery modules 6 arranged in the box 5. The box 5 includes a first box portion 5a and a second box portion 5b, and the box 5 has an accommodation space 5c. The first box portion 5a is used to cover the second box portion 5b and form a closed space for accommodating the battery module 6. The multiple battery modules 6 can be arranged in the box 5 in any manner.

[0440] In some embodiments, the size of the box 5 along the first direction X is 110 mm to 170 mm, for example, 110 mm, 115 mm, 120 mm, 125 mm, 130 mm, 135 mm, 140 mm, 145 mm, 150 mm, 155 mm, 160 mm, 165 mm, 168 mm, 170 mm, or a range formed by any two of the above values. L2 shown in FIG. 4 represents the size of the box 5 along the first direction X, which can also be understood as the height dimension of the box 5.

[0441] The first box part 5a and the second box part 5b are mutually covered, and the first box part 5a and the second box part 5b jointly define a containing space 5c for containing the battery monomer. The second box part 5b can be a hollow structure with one end open, and the first box part 5a is a plate structure, which is covered on the open side of the second box part 5b to form a box 5 with the containing space 5c; both the first box part 5a and the second box part 5b can also be a hollow structure with one side open, and the open side of the first box part 5a is covered on the open side of the second box part 5b to form a box 5 with the containing space 5c. Of course, the first box part 5a and the second box 5b can be various shapes, such as a cylinder, a cuboid, etc.

[0442] In order to improve the sealing performance of the first box part 5a and the second box part 5b after being connected, a sealing member such as sealing glue, sealing ring, etc. can also be arranged between the first box part 5a and the second box part 5b.

[0443] Suppose that the first box part 5a is covered on the top of the second box part 5b, the first box part 5a can also be called an upper box cover, and the second box part 5b can also be called a lower box.

[0444] In some embodiments, during the charging process of the battery pack 2 or any battery monomer constituting the battery pack 2 from 0% state of charge SOC to 100% state of charge SOC, the temperature of the external environment where the battery pack 2 is located is room temperature, for example, 30°C.

[0445] In some embodiments, during the process of the battery pack 2 or any battery monomer constituting the battery pack 2 from 10% state of charge SOC to 80% state of charge SOC, the temperature of the external environment where the battery pack 2 is located is room temperature, for example, 30°C.

[0446] In some embodiments, during the charging process of the battery pack 2 or any battery monomer constituting the battery pack 2 from 10% state of charge to 80% state of charge, a plurality of charging steps are included, and the difference between the maximum state of charge of any charging step in the plurality of charging steps and the maximum state of charge of its adjacent charging step is less than or equal to 5% state of charge, for example, 1% state of charge, 1.5% state of charge, 2% state of charge, 2.5% state of charge, 3% state of charge, 3.5% state of charge, 4% state of charge, 4.5% state of charge, 5% state of charge, or a range composed of any two of the above values.

[0447] The battery pack 2 or any battery cell constituting the battery pack 2 includes multiple charging steps from 10% state of charge to 40% state of charge, for any charging step, the battery pack 2 or any battery cell constituting the battery pack 2 can be charged at any rate between 5C and 10C, the charging rate for each charging step can be any value of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value in the range between any two of the above values.

[0448] The battery pack 2 or any battery cell constituting the battery pack 2 also includes multiple charging steps from 40% state of charge to 80% state of charge, for any charging step, the charging rate is less than the charging rate for any charging step from 10% state of charge to 40% state of charge, and the charging rate for the step of charging to 80% state of charge is any value of 2.5C to 5C, for example, it can be 2.7C.

[0449] Exemplarily, the charging steps from 10% to 80% for the battery pack 2 or any battery cell constituting the battery pack 2 can be performed as follows:

[0450] charging from 10% SOC to 15% SOC at 5.0C constant current;

[0451] charging from 15% SOC to 20% SOC at 5.0C constant current;

[0452] charging from 20% SOC to 25% SOC at 5.0C constant current;

[0453] charging from 25% SOC to 30% SOC at 5.0C constant current;

[0454] charging from 30% SOC to 35% SOC at 5.0C constant current;

[0455] charging from 35% SOC to 40% SOC at 5.0C constant current;

[0456] charging from 40% SOC to 45% SOC at 4.6C constant current;

[0457] charging from 45% SOC to 50% SOC at 4.3C constant current;

[0458] charging from 50% SOC to 55% SOC at 4.0C constant current;

[0459] charging from 55% SOC to 60% SOC at 3.7C constant current;

[0460] charging from 60% SOC to 65% SOC at 3.4C constant current;

[0461] charging from 65% SOC to 70% SOC at 3.1C constant current;

[0462] Charge from 70% SOC to 75% SOC at 2.9C constant current;

[0463] Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0464] In some embodiments, the charging time of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge is less than or equal to 12.5 min, optionally 5 min to 12.5 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, for example, 30°C. For example, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min, or a range consisting of any two of the above values.

[0465] In some embodiments, the volumetric energy density of the battery cell is 380 Wh / L to 470 Wh / L, optionally 390 Wh / L to 450 Wh / L. For example, the volumetric energy density of the battery cell is 380 Wh / L, 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, or a range consisting of any two of the above values. The volumetric energy density of the battery cell is high.

[0466] In the embodiments of the present application, the volumetric energy density of the battery cell is the meaning known in the art, which can be detected by using the devices and methods known in the art. For example, taking the battery charging upper limit voltage of 3.65V and the battery discharging cut-off voltage of 2.0V as an example for illustration,

[0467] The battery cell is placed at 25°C, charged to 3.65V at 0.33C constant current, and then charged at constant voltage to 0.05C; discharged to 2.0V at 0.33C constant current, and record the discharge capacity A0, unit: Ah; measure the length, width and height of the battery cell (generally calculated by the size of the battery shell, excluding the height of the electrode terminal, and excluding the insulation film outside the shell) using a caliper, calculate the volume V0 of the battery cell, unit L; the volumetric energy density VED of the battery cell is (A0x discharge platform voltage) / V0, unit Wh / L.

[0468] In some embodiments, the group margin of a single battery cell at 100% state of charge is greater than or equal to 96% and less than 100%, optionally ranging from 96.5% to 99.5%. For example, the group margin of a single battery cell can be 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, or any combination of two of the above values. When the group margin of a single battery cell is within the above range, the volumetric proportion of the electrode assembly is higher, and the energy density of the single battery cell is higher.

[0469] In this embodiment, the group margin refers to the ratio of the actual internal cross-sectional area of ​​a single battery cell to its maximum internal cross-sectional area, which is also known as the fill rate. The group margin is calculated as follows: Group Margin = Electrode Component Thickness / Battery Casing Internal Thickness.

[0470] Electrical appliances

[0471] The second aspect of this application provides an electrical device, which includes a battery device as described in this application, such as a battery cell, battery module, or battery pack. The battery cell, battery module, or battery pack can be the power source of the electrical device or the energy storage unit of the electrical device. The electrical device can be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool, etc. Vehicles can be gasoline-powered vehicles, natural gas-powered vehicles, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.; spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-described electrical device.

[0472] Electrical devices can be equipped with individual battery cells, battery modules, or battery packs depending on their usage requirements.

[0473] Figure 5 is a schematic diagram of an example electrical device 1. This electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 1, a battery pack or battery module can be used.

[0474] The inside of the electric device 1 is provided with a battery pack 2, which can be arranged at the bottom or head or tail of the electric device 1. The battery pack 2 can be used for power supply of the electric device 1, for example, the battery pack 2 can be used as the operating power supply of the electric device 1, and also can be used as the driving power supply of the electric device 1, instead of or partially instead of fuel or natural gas to provide driving power for the electric device 1.

[0475] The electric device 1 can also include a controller 3 and a motor 4, the controller 3 is used to control the battery pack 2 to supply power for the motor 4, for example, for the working power demand of the electric device 1 during starting, navigation and driving.

[0476] As another example of the electric device can be a mobile phone, a tablet computer, a notebook computer, etc. The electric device generally requires thinning, and can use a battery monomer as a power supply.

[0477] The charging process of the electric device can select the following charging mode:

[0478] Charging from 10% SOC to 15% SOC at 5.0C constant current;

[0479] Charging from 15% SOC to 20% SOC at 5.0C constant current;

[0480] Charging from 20% SOC to 25% SOC at 5.0C constant current;

[0481] Charging from 25% SOC to 30% SOC at 5.0C constant current;

[0482] Charging from 30% SOC to 35% SOC at 5.0C constant current;

[0483] Charging from 35% SOC to 40% SOC at 5.0C constant current;

[0484] Charging from 40% SOC to 45% SOC at 4.6C constant current;

[0485] Charging from 45% SOC to 50% SOC at 4.3C constant current;

[0486] Charging from 50% SOC to 55% SOC at 4.0C constant current;

[0487] Charging from 55% SOC to 60% SOC at 3.7C constant current;

[0488] Charging from 60% SOC to 65% SOC at 3.4C constant current;

[0489] Charging from 65% SOC to 70% SOC at 3.1C constant current;

[0490] Charging from 70% SOC to 75% SOC at 2.9C constant current;

[0491] Charged from 75% SOC to 80% SOC at 2.7C constant current.

[0492] In some embodiments, the charging time of the power device from 10% state of charge to 80% state of charge is less than or equal to 12.5 min, optionally 5 min to 12.5 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is 30°C. Illustratively, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min, or a range defined by any two of the above values.

[0493] Embodiments

[0494] The following examples further describe the embodiments disclosed herein and are merely illustrative, as various modifications and changes can be suggested by those skilled in the art. Unless otherwise stated, all proportions, 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 used as received without further purification, and the instruments used in the examples are commercially available.

[0495] Example 1

[0496] 1. Preparation of the positive electrode tab

[0497] The positive electrode tab includes a positive electrode current collector, a positive electrode conductive layer on the positive electrode current collector, and a positive electrode film layer.

[0498] The positive electrode conductive layer on the positive electrode current collector is a film layer formed by uniformly mixing a positive electrode conductive agent, super carbon, and a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and coating the mixture on the surface of the current collector and drying, the thickness of the film layer is 1 pm, 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%.

[0499] The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode slurry (the solvent is N-methyl pyrrolidone (NMP)) on the surface of the positive electrode conductive layer, and 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.

[0500] The positive active material includes lithium iron phosphate and a coating layer, the coating layer is coated on the surface of the lithium iron phosphate, the coating layer includes lithium iron titanium phosphate Li2FeTi(P04)3 and amorphous carbon. The Dv50 of the positive active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0501] The single-side coating weight of the positive film layer is 300 mg / 1540.25 mm 2 .

[0502] 2. Preparation of the negative electrode sheet

[0503] The negative electrode sheet includes a negative current collector, a negative conductive layer on the negative current collector, and a negative film layer. The negative current collector is a copper foil.

[0504] The negative conductive layer on the negative current collector is a film layer formed by uniformly mixing a negative conductive agent, a negative binder, a thickening agent, and a solvent, and then coating the mixture on the surface of the negative current collector and drying. The thickness of the negative conductive layer is 1 μm. The mass content of the negative conductive agent in the negative conductive layer is 35%. The mass content of the negative binder in the negative conductive layer is 60%. The mass content of the thickening agent in the negative conductive layer is 5%.

[0505] The negative film layer includes a film layer formed by uniformly coating a negative slurry (with deionized water as the solvent) on the surface of the negative conductive layer, and then drying and cold pressing.

[0506] The single-side coating weight of the negative film layer is 138 mg / 1540.25 mm 2 .

[0507] The negative film layer includes a first negative film layer and a second negative film layer. The first negative film layer is located on the surface of the negative conductive layer, and the second negative film layer is located on the surface of the first negative film layer.

[0508] The first negative film layer includes graphite particles, a conductive agent, a first lithium-containing binder, a negative binder, and a thickening agent, with a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer is coated on the surface of the artificial graphite. The mass content of the carbon coating layer is 3.5%.

[0509] The second negative electrode film layer comprises graphite particles, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene-butadiene rubber, thickening agent sodium carboxymethyl cellulose, the mass content of lithium element in the second lithium-containing binder is 4.8%, the Dv50 of the graphite particles is 11.3 μm, and the graphite particles comprise artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0510] 3. Isolation film

[0511] The isolation film comprises a base film, and the base film is a 7 μm polyethylene film layer with a porosity of 42%.

[0512] 4. Preparation of electrolyte

[0513] The organic solvent comprises 60% chain carboxylate solvents (ethyl acetate) and 40% carbonate solvents (30% ethylene carbonate EC, 10% dimethyl carbonate), and the mass content of each component in the organic solvent is calculated based on the mass of the organic solvent.

[0514] The mass content of the additive is 6.5% based on the mass of the electrolyte, and the additive comprises vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES and lithium difluoro(oxalato)borate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0515] The lithium salt comprises 1 mol / L lithium hexafluorophosphate LiPF6.

[0516] The conductivity of the electrolyte at room temperature is 16.4 mS / cm.

[0517] 5. Preparation of battery monomer

[0518] The above positive electrode sheet, isolation film and negative electrode sheet are stacked in order, the isolation film is between the positive electrode sheet and the negative electrode sheet to play a separation role, and an electrode assembly is obtained; the electrode assembly is placed in an outer packaging shell, electrolyte is injected after drying, and the battery monomer is obtained through processes such as vacuum packaging, standing, formation and shaping; the battery monomer is vertically placed, the end cover is located on the upper side of the shell, the height direction of the battery monomer is parallel to the first direction, the battery height is 97 mm, and the battery width is 71 mm. The compaction density of the positive electrode film layer of the battery monomer at 100% SOC is 2.72 g / cm 3 , and the compaction density of the negative electrode film layer at 100% SOC is 1.26 g / cm 3 .

[0519] Comparative Example 1 and Comparative Example 2

[0520] A battery cell was prepared in a similar manner to Example 1, except that the coating weight of the positive electrode film layer and the coating weight of the negative electrode film layer were adjusted.

[0521] Example 2-1 to Example 2-3

[0522] A battery cell was prepared in a similar manner to Example 1, except that the coating weight of the positive electrode film layer and the coating weight of the negative electrode film layer were adjusted.

[0523] Example 3-1 to Example 3-3

[0524] A battery cell was prepared in a similar manner to Example 1, except that the coating weight of the negative electrode film layer was adjusted.

[0525] Performance Test

[0526] 1. The charging time of the battery cell from 10% SOC to 80% SOC, specifically using the following charging steps,

[0527] Charging from 10% SOC of the battery at 30°C,

[0528] Charging from 10% SOC to 15% SOC at 5.0C constant current,

[0529] Charging from 15% SOC to 20% SOC at 5.0C constant current,

[0530] Charging from 20% SOC to 25% SOC at 5.0C constant current,

[0531] Charging from 25% SOC to 30% SOC at 5.0C constant current,

[0532] Charging from 30% SOC to 35% SOC at 5.0C constant current,

[0533] Charging from 35% SOC to 40% SOC at 5.0C constant current,

[0534] Charging from 40% SOC to 45% SOC at 4.6C constant current,

[0535] Charging from 45% SOC to 50% SOC at 4.3C constant current,

[0536] Charging from 50% SOC to 55% SOC at 4.0C constant current,

[0537] Charging from 55% SOC to 60% SOC at 3.7C constant current,

[0538] charged from 60% SOC to 65% SOC at 3.4C constant current,

[0539] charged from 65% SOC to 70% SOC at 3.1C constant current,

[0540] charged from 70% SOC to 75% SOC at 2.9C constant current,

[0541] charged from 75% SOC to 80% SOC at 2.7C constant current,

[0542] Record the total charging time.

[0543] Test results

[0544] The test results are shown in Table 1.

[0545] Table 1

[0546] In Table 1,

[0547] The height (dimension along the first direction) of the battery monomer is 97 mm, and the thickness of the battery monomer is 71 mm. The height (dimension along the first direction) of the positive electrode film layer is 80 mm, and the height (dimension along the first direction) of the negative electrode film layer is 83 mm, that is, the height of the negative electrode film layer is greater than that of the positive electrode film layer, and the difference is 3 mm.

[0548] The discharge gram capacity of the positive electrode active material in the positive electrode film layer at 0.1C rate is 157 mAh / g, and the discharge gram capacity of the negative electrode active material in the negative electrode film layer at 0.1C rate is 355 mAh / g.

[0549] The coating weight of the positive electrode film layer in Comparative Example 1 is small, resulting in too small discharge capacity and too small volumetric energy density of the battery monomer, which cannot meet the demand; while the coating weight of the positive electrode film layer in Comparative Example 2 is too large, although it can significantly improve the discharge capacity of the positive electrode film layer and improve the volumetric energy density of the battery monomer, but the impedance of the positive electrode film layer increases, which makes the rapid charging performance of the battery monomer decrease.

[0550] And in the embodiment of the present application, the discharge capacity of the positive electrode film layer per unit area is 2.0 mAh / cm 2 to 3.7 mAh / cm 2 , which can effectively balance the improvement of the volumetric energy density and the rapid charging performance of the battery monomer; the discharge capacity can be effectively controlled by the coating weight, for example, when the coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 , the discharge capacity of the positive electrode film layer is within an appropriate range.

[0551] The discharge capacity of the negative electrode film layer can be further regulated to 2.0 mAh / cm 2 to 4.1 mAh / cm 2 , and the positive electrode film layer is used in combination, which can improve the volume energy density and fast charging performance of the battery monomer, and also can make the CB value in the range of 1.05 to 1.15, reduce the risk of lithium precipitation, and improve the use reliability of the battery monomer. The discharge capacity of the negative electrode film layer can also be effectively regulated by the coating weight, for example, when the coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 , the discharge capacity of the negative electrode film layer is in an appropriate range.

[0552] Example 4

[0553] The battery monomer is prepared by a method similar to that of Example 1, and the difference from Example 1 is that the content of each component of the organic solvent is adjusted.

[0554] The test results are shown in Table 2.

[0555] Table 2

[0556] When the conductivity of the electrolyte is 13 mS / cm to 20 mS / cm, and optionally 15 mS / cm to 20 mS / cm, the migration rate of lithium ions in the battery monomer increases with the increase of the conductivity, which is beneficial to improve the fast charging performance of the battery monomer.

[0557] Comparative Example 3

[0558] The battery monomer is prepared by a method similar to that of Example 1, and the difference from Example 1 is that the size of the battery monomer is adjusted, and the size of the positive electrode film layer and the negative electrode film layer is also adjusted.

[0559] Comparative Example 5

[0560] The battery monomer is prepared by a method similar to that of Example 1, and the difference from Example 1 is that the size of the battery monomer is adjusted, and the size of the positive electrode film layer and the negative electrode film layer is also adjusted.

[0561] The test results are shown in Table 3.

[0562] Table 3

[0563] In Comparative Example 3, the height of the battery monomer is too low to effectively improve the volume energy density of the battery monomer. In the present application, the height of the positive electrode film layer is adjusted to 75 mm to 105 mm, which is beneficial to improve the volume energy density of the battery monomer.

[0564] While the illustrative embodiments have been demonstrated and described, it should be understood that the foregoing embodiments are not to be construed as limiting and that the embodiments can be otherwise altered, modified, and varied, without departing from the spirit, principles, and scope of the application.

Claims

A battery cell includes a casing, an electrolyte, and an electrode assembly. The casing includes a housing and an end cap. The housing contains the electrolyte and the electrode assembly. The housing has an opening, and the end cap closes the opening. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector along the thickness direction of the positive electrode and containing a positive active material, wherein the positive active material includes a lithium phosphate with an olivine structure. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector along the thickness direction of the negative electrode and containing a negative active material. The discharge capacity per unit area of ​​the positive electrode film is 2.0 mAh / cm². 2 Up to 3.7mAh / cm 2 ; The positive electrode film layer has a dimension of 75 mm to 105 mm along a first direction, which is parallel to the direction from the housing to the end cap. According to claim 1, the battery cell, wherein, The discharge capacity of the positive electrode film per unit area is 2.4 mAh / cm². 2 Up to 3.4mAh / cm 2 . The battery cell according to claim 1 or 2, wherein, The ratio of the discharge capacity per unit area of ​​the negative electrode film to the discharge capacity per unit area of ​​the positive electrode film is 1.05 to 1.

15. According to claim 3, the battery cell, wherein, The ratio of the discharge capacity per unit area of ​​the negative electrode film to the discharge capacity per unit area of ​​the positive electrode film is 1.07 to 1.

13. The battery cell according to any one of claims 1 to 4, wherein, The discharge capacity of the negative electrode film per unit area is 2.0 mAh / cm². 2 Up to 4.1mAh / cm 2 . According to claim 5, the battery cell, wherein, The discharge capacity of the negative electrode film per unit area is 2.4 mAh / cm². 2 Up to 3.7mAh / cm 2 . The battery cell according to any one of claims 1 to 6, wherein, The conductivity of the electrolyte is from 13 mS / cm to 20 mS / cm. According to claim 7, the battery cell, wherein, The conductivity of the electrolyte is from 15 mS / cm to 20 mS / cm. The battery cell according to any one of claims 1 to 8, wherein, The dimensions of the battery cell along the first direction are 90 mm to 130 mm. The battery cell according to any one of claims 1 to 9, wherein, When the battery cell is 100% charged, the compaction density of the positive electrode film is 2.50 g / cm³. 3 Up to 2.80 g / cm 3 ; and / or The single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2 Up to 370mg / 1540.25mm 2 . The battery cell according to any one of claims 1 to 10, wherein, The resistivity of the positive electrode active material powder is from 1 Ω·cm to 27.5 Ω·cm. The battery cell according to any one of claims 1 to 11, wherein, The compacted density of the positive electrode active material at 30000N is 2.46 g / cm³. 3 Up to 2.8 g / cm 3 . The battery cell according to any one of claims 1 to 12, wherein, The positive electrode active material has a charging capacity of 150 mAh / g to 170 mAh / g at a 0.1C rate. The battery cell according to any one of claims 1 to 13, wherein, The lithium phosphate with the olivine structure includes: Phosphate particles, and A coating layer that coats the phosphate particles, the coating layer containing one or more elements selected from C, Fe, Ti, Zr, Hf, Ge and Sn. According to claim 14, the battery cell, wherein, The phosphate particles include those with the general formula Li x1 A y1 Me a M b P 1-c X c Y z The compound, wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤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, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F. The battery cell according to claim 14 or 15, wherein, The coating layer includes a general formula Li 3-d Fe 2- d M2 d (PO x2 ) y2 A fast ion conductor, M2 includes one or more elements from Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x2<5, 0<y2<4. The battery cell according to any one of claims 14 to 16, wherein, The degree of graphitization of the lithium phosphate with the olivine structure is 0.15 to 0.

32. The battery cell according to any one of claims 14 to 17, wherein, The lithium phosphate with the olivine structure has a carbon content of 1% to 2% by mass. The specific surface area of ​​the lithium phosphate with the olivine structure is 5 m². 2 / g to 18m 2 / g. The battery cell according to any one of claims 1 to 18, wherein, The volume distribution particle size of the positive electrode active material satisfies: 1μm≤Dv50≤2μm, 0.4μm≤Dv10≤0.7μm. The battery cell according to any one of claims 1 to 19, wherein, The lithium phosphate with olivine structure is granular, and includes secondary particles, which in turn include multiple primary particles. The average particle size of the primary particles is 200 nm to 500 nm. The battery cell according to any one of claims 1 to 20, wherein, The positive electrode film layer also includes one or more of the following: ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, lithium trilithium citrate, lithium nickelate, and lithium ferrite. The battery cell according to any one of claims 1 to 21, wherein, The thickness of the positive current collector is 10 μm to 15 μm. The battery cell according to any one of claims 1 to 22, wherein, The positive electrode sheet further includes a positive conductive layer, which is located between the positive electrode film and the positive electrode current collector. According to claim 23, the battery cell, wherein, The thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. The battery cell according to claim 23 or 24, wherein, The positive electrode conductive layer includes a positive 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, 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 fluorinated acrylate resins. The battery cell according to any one of claims 1 to 25, wherein, When the battery cell is 100% charged, the compaction density of the negative electrode film is 1.15 g / cm³. 3 Up to 1.36 g / cm 3 ; and / or The single-sided coating weight of the negative electrode film is 90 mg / 1540.25 mm. 2 Up to 170mg / 1540.25mm 2 . The battery cell according to any one of claims 1 to 26, wherein, The resistivity of the negative electrode active material powder is from 0.005 Ω·cm to 0.043 Ω·cm. The battery cell according to any one of claims 1 to 27, wherein, The compacted density of the negative electrode active material at 20000N is 1.5 g / cm³. 3 Up to 1.85 g / cm 3 . The battery cell according to any one of claims 1 to 28, wherein, The specific capacity of the negative electrode active material at a 0.1C rate is 350mAh / g to 480mAh / g. The battery cell according to any one of claims 1 to 29, wherein, The negative electrode active material includes a carbon-based material, which includes graphite particles with a graphitization degree of 92.0% to 94.5%. According to claim 30, the battery cell, wherein, The graphite particles include: Artificial graphite, including secondary particles; and A carbon coating layer is applied to the surface of the artificial graphite. According to claim 31, the battery cell, wherein, Based on the total mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%. The battery cell according to any one of claims 30 to 32, wherein, The negative electrode film layer includes: A first negative electrode film layer is disposed on the surface of the negative electrode current collector, and the first negative electrode film layer comprises a carbon-based material, and The second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, and the second negative electrode film layer comprises a carbon-based material. The carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently include graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer. The battery cell according to any one of claims 30 to 33, wherein, The carbon-based material in the first negative electrode film layer also includes natural graphite. The battery cell according to claim 33 or 34, wherein, The tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. The battery cell according to any one of claims 33 to 35, wherein, The tap density of the carbon-based material in the first negative electrode film is 0.82 g / cm³. 3 Up to 1.21 g / cm 3 , and / or The tap density of the carbon-based material in the second negative electrode film is 0.90 g / cm³. 3 Up to 1.25 g / cm 3 . The battery cell according to any one of claims 33 to 36, wherein, The volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm, and / or The volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm. The battery cell according to any one of claims 33 to 37, wherein, The first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the total mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the total mass of the second negative electrode film layer. According to claim 38, the battery cell, wherein, The first lithium-containing binder has a mass content of 0.1% to 1% relative to the total mass of the first negative electrode film layer, and / or The second lithium-containing binder has a mass content of 0.1% to 1% relative to the total mass of the second negative electrode film. The battery cell according to claim 38 or 39, wherein, The lithium content in the first lithium-containing binder is 3% to 10% by mass, and / or The lithium content in the second lithium-containing binder is 3% to 10% by mass. The battery cell according to any one of claims 38 to 40, wherein, The first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%; and / or The second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. The battery cell according to any one of claims 1 to 41, wherein, The negative electrode active material also includes a silicon-based material, wherein the silicon content in the silicon-based material is 0.3% to 10.0% by mass, based on the total mass of the negative electrode active material. The battery cell according to any one of claims 1 to 42, wherein, The thickness of the negative electrode current collector is 4 μm to 6 μm. The battery cell according to any one of claims 1 to 43, wherein, The negative electrode sheet further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector. According to claim 44, the battery cell, wherein, The thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. The battery cell according to claim 44 or 45, wherein, 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, and / or The negative electrode conductive layer includes a negative electrode binder, which includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The battery cell according to any one of claims 1 to 46, wherein, The electrolyte has a viscosity of 2.3 mPa·s to 3.5 mPa·s at room temperature. The battery cell according to any one of claims 1 to 47, wherein, The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature. The battery cell according to any one of claims 1 to 48, wherein, The electrolyte includes an organic solvent, which includes a chain carboxylic acid ester solvent, wherein the chain carboxylic acid ester solvent has a mass content of 5% to 75% in the organic solvent. According to claim 49, the battery cell, wherein, The chain-like carboxylic acid ester solvent has a mass content of 30% to 70% in the organic solvent. The battery cell according to claim 49 or 50, wherein, The chain-like carboxylic acid ester solvents include compounds represented by Formula I. In formula I, R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group. R2 includes C1 to C5 alkyl or C1 to C5 haloalkyl. According to claim 51, the battery cell, wherein, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group or a C1 to C3 haloalkyl group, and / or R2 includes C1 to C3 alkyl or C1 to C3 haloalkyl. The battery cell according to claim 51 or 52, wherein, The chain-like carboxylic acid ester solvents include one or more compounds from Formula I-1 to Formula I-8. The battery cell according to any one of claims 49 to 53, wherein, The organic solvent also includes carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The battery cell according to claim 53 or 54, wherein, The carbonate solvent has a mass content of 30% to 70% in the organic solvent. The battery cell according to any one of claims 1 to 55, wherein, The electrolyte also includes additives, which include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. According to claim 56, the battery cell, wherein, The carbonate additives include one or more of vinylene carbonate and fluoroethylene carbonate, and / or The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, vinyl sulfite, and methylene disulfonate, and / or The lithium salt additives include one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium dioxalate borate. The battery cell according to claim 56 or 57, wherein, The additive is present in the electrolyte at a mass content of 1% to 10%. According to claim 58, the battery cell, wherein, The additive is present in the electrolyte at a mass content of 2% to 8%. The battery cell according to any one of claims 1 to 59, wherein, The electrolyte also includes lithium salts, which include one or more of fluorosulfonyl imide salts and lithium hexafluorophosphate. According to claim 60, the battery cell, wherein, The fluorinated sulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide and lithium bistrifluoromethylsulfonate imide. The battery cell according to claim 60 or 61, wherein, The lithium salt comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, wherein the molar concentration of lithium bis(fluorosulfonyl)imide is from 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate is from 0.5 mol / L to 1.0 mol / L. According to claim 62, the battery cell, wherein, The ratio of the molar concentration of the lithium bis(fluorosulfonyl)imide to the molar concentration of the lithium hexafluorophosphate (LiPF6) is 0.2 to 1.

0. The battery cell according to any one of claims 1 to 63, wherein, The isolation membrane comprises a porous base membrane with a porosity of 20% to 70%. According to claim 64, the battery cell, wherein, The thickness of the base film is 6 μm to 12 μm. The battery cell according to any one of claims 1 to 65, wherein, The isolation membrane includes a base membrane and a functional layer disposed on at least one side of the base membrane, the functional layer including: 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. The second functional layer includes composite particles, which include second inorganic particles and a plurality of 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. According to claim 66, the battery cell, wherein, The non-fluoropolymer particles include acrylate copolymers. The battery cell according to claim 66 or 67, wherein, The first inorganic particles comprise one or more of the following: silicon dioxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium dioxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide; and / or The second inorganic particle includes 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 battery cell according to any one of claims 66 to 68, wherein, The average particle size of the second inorganic particle is 5 nm to 100 nm. The battery cell according to any one of claims 1 to 69, wherein, The base material of the shell includes steel, and the thickness of the shell is 0.1 mm to 0.5 mm. According to claim 70, the battery cell, wherein, The thickness of the shell is 0.2 mm to 0.35 mm. The battery cell according to any one of claims 1 to 71, wherein the group margin of the battery cell is greater than or equal to 96% and less than 100%. According to claim 72, the battery cell has a group margin of 96.5% to 99.5%. The battery cell according to any one of claims 1 to 73, wherein, The charging time for a single battery cell from 10% to 80% state of charge is 5 minutes to 12.5 minutes. A battery device comprising a battery cell as described in any one of claims 1 to 74. The battery device according to claim 75, wherein, The charging time for the battery from 10% state of charge to 80% state of charge is 5 minutes to 12.5 minutes. The battery device according to claim 75 or 76, wherein, The battery device includes a housing that accommodates the individual battery cells, wherein the dimensions of the housing along a first direction are 110 mm to 170 mm. An electrical device comprising the battery device as described in claim 76 or 77.

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