Battery cell, battery apparatus, and electrical apparatus

Abstract

A battery cell, a battery apparatus, and an electrical apparatus. The battery cell comprises an electrode assembly, an electrolyte, and a casing. The electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheet comprises a positive electrode current collector, and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material capable of providing lithium, the positive electrode active material comprising a lithium-containing phosphate having an olivine structure, and the resistance of the positive electrode sheet being 0.1 Ω to 30 Ω. The negative electrode sheet comprises a negative electrode current collector, and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material capable of receiving lithium, and the resistance of the negative electrode sheet being 0.001 Ω to 0.01 Ω. The separator is located between the positive electrode sheet and the negative electrode sheet. The electrolyte comprises an organic solvent. The organic solvent comprises a chain ester solvent, and the electrical conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm. According to the present invention, the amount of heat generated by the battery cell can be reduced, thereby improving the use reliability and cycle performance 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 the characteristics of high capacity and long service life, and are widely used in electronic devices such as mobile phones, notebook computers, electric vehicles, electric vehicles, electric aircraft, electric ships and electric tools. 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 fast charging performance, cycle performance, etc.

[0003] SUMMARY

[0004] The present application provides a battery cell, a battery device and a power utilization device, which can reduce the heat generation of the battery cell and improve the fast charging performance and cycle performance of the battery cell.

[0005] In a first aspect, the present application provides a battery cell, the battery cell comprising an electrode assembly, an electrolyte and a shell, the electrode assembly and the electrolyte being accommodated in the shell, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet and a separator film, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material capable of providing lithium, the positive electrode active material comprising a lithium-containing phosphate with an olivine structure, the positive electrode sheet having a resistance of 0.1 Ω to 30 Ω, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material capable of receiving lithium, the negative electrode sheet having a resistance of 0.001 Ω to 0.01 Ω, the separator film being located between the positive electrode sheet and the negative electrode sheet, the electrolyte comprising an organic solvent, the organic solvent comprising a chain ester solvent, the electrolyte having an electrical conductivity of 13 mS / cm to 20 mS / cm at room temperature.

[0006] Thus, in the embodiments of the present application, the positive electrode active material comprises a lithium-containing phosphate with an olivine structure, which has high cycle stability. By synergistically controlling the positive electrode sheet resistance, the negative electrode sheet resistance and the electrolyte conductivity within a reasonable range, on the one hand, the lithium ion transmission resistance in the battery cell can be reduced, the fast charging capacity of the battery cell can be improved, and the internal resistance DCR of the battery cell can be reduced; on the other hand, the cycle decay caused by excessive temperature rise during fast charging of the battery cell can be improved; and on the other hand, the problem of uneven temperature rise during fast charging of the battery cell can be improved, and the cycle decay problem caused by lithium precipitation can be reduced. In addition, by controlling the positive and negative electrode sheet resistance within a reasonable range, the temperature in the battery cell can be controlled within a reasonable range that the high-conductivity electrolyte can tolerate, thereby reducing the risk of weakening the fast charging performance of the battery due to the volatilization of the solvent components of the electrolyte.

[0007] In some embodiments, the electrolyte has an electrical conductivity of 15 mS / cm to 20 mS / cm at room temperature. When the electrolyte has an electrical conductivity in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0008] In some embodiments, the positive electrode sheet has an electrical resistance of 0.1 Ω to 5 Ω. When the positive electrode sheet has an electrical resistance in the above range, the electrical resistance of the positive electrode sheet is relatively small, which is conducive to reducing the internal resistance of the battery cell.

[0009] In some embodiments, the positive electrode sheet has an electrical resistance of 0.1 Ω to 1 Ω. When the positive electrode sheet has an electrical resistance in the above range, the electrical resistance of the positive electrode sheet is relatively small, which is conducive to reducing the internal resistance of the battery cell.

[0010] In some embodiments, the negative electrode sheet has an electrical resistance of 0.001 Ω to 0.005 Ω. When the negative electrode sheet has an electrical resistance in the above range, the electrical resistance of the negative electrode sheet is relatively small, which is conducive to reducing the internal resistance of the battery cell.

[0011] In some embodiments, the electrolyte has a viscosity of 2.3 mPa·s to 3.5 mPa·s at room temperature. When the electrolyte has a viscosity in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0012] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature. When the electrolyte has a density in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0013] In some embodiments, the battery cell has a positive electrode film layer with a compacted density of 2.50 g / cm 3 to 2.80 g / cm 3 , which can be 2.55 g / cm 3 to 2.70 g / cm 3 at 100% state of charge. When the positive electrode film layer has a compacted density in the above range, it 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 packed relatively tightly, the contact resistance between particles is small, 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-sided coating weight of 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm2 Optionally 240 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 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 of the battery cell can be improved.

[0015] 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 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 more densely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the tab and thus reduce heat generation.

[0016] In some embodiments, the single-side coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 Optionally 110 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 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 will not be too large, and the energy density of the battery cell can be improved.

[0017] In some embodiments, the powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm. 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.

[0018] In some embodiments, the powder compaction density of the positive electrode active material under 30000 N is 2.46 g / cm 3 to 2.8 g / cm 3 When the powder compaction density of the positive electrode active material under 30000 N is within the above range, the energy density of the battery cell can be improved, and since the positive electrode active material in the positive electrode film layer is more densely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the tab and thus reduce heat generation.

[0019] In some embodiments, the charge gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g to 170 mAh / 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.

[0020] 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.

[0021] In some embodiments, the powder compaction density of the negative active material under 20000N is 1.5 g / cm 3 to 1.85 g / cm 3 . When the powder compaction density of the negative active material under 20000N 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.

[0022] 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.

[0023] In some embodiments, the lithium-containing phosphate of olivine structure includes phosphate particles and a coating layer, the coating layer coats the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge and Sn. The phosphate particles are coated with the coating layer on the surface, which can improve the conductivity of the lithium-containing phosphate of olivine structure, reduce the powder resistivity of the material, and facilitate the migration rate of lithium ions, thereby reducing the heat generation of the battery cell.

[0024] In some embodiments, the phosphate particles include 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 comprises one or more of Na, K, Mg, Me comprises one or more of Mn, Fe, Co, Ni, M comprises 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 comprises one or more of S, Si, Cl, B, C, N, and Y comprises one or more of O, F. The cycle stability of the phosphate particles is relatively excellent, which is conducive to improving the cycle performance of the battery cell.

[0025] In some embodiments, the coating layer comprises a compound with a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 ) fast ion conductor, M2 comprises one or more of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0

[0026] In some embodiments, the graphitization degree of the positive active material is 0.15 to 0.32, and can be 0.19 to 0.26. When the graphitization degree of the positive active material is in the above range, the conductivity of the positive active material is improved, and the heat generation of the positive plate is reduced, thereby reducing the heat generation of the battery cell.

[0027] In some embodiments, the mass content of carbon elements 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, and can be 7.5m 2 / g to 14m 2 / g.

[0028] Therefore, the material with the above mass content of carbon elements 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 olivine structure lithium-containing phosphate, and is conducive to the transmission of lithium ions at the phase interface.

[0029] 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, 0.4 μm≤Dv10≤0.7 μm. The particle size of the lithium-containing olivine-structured phosphate is relatively small, the lithium ion has a shorter deintercalation path in the positive electrode active material, and the heat generation is less. Moreover, the particle size of the positive electrode active material is not too small, and the agglomeration is unlikely to occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0030] In some embodiments, the lithium-containing olivine-structured phosphate is in a particulate form, and the lithium-containing olivine-structured phosphate includes secondary particles, and 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 lithium ion has a shorter deintercalation path in the positive electrode active material, and the heat generation is less.

[0031] In some embodiments, the positive electrode film layer further includes one or more of a ternary material, lithium phosphate, lithium hydrogen 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-mentioned materials can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0032] 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-mentioned range, the current-carrying capacity of the positive electrode current collector is relatively excellent, and the battery cell can have a higher energy density.

[0033] In some embodiments, the positive electrode current collector 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 electrode sheet, and reduce the heat generation of the positive electrode electrode sheet, thereby reducing the heat generation of the battery cell.

[0034] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. When the thickness of the positive electrode conductive layer is in the above-mentioned range, the conductivity of the positive electrode electrode sheet can be further improved, the heat generation of the positive electrode electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved.

[0035] In some embodiments, the positive electrode conductive layer includes 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 electrode sheet, 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, and improve the structural stability of the positive electrode electrode sheet.

[0036] In some embodiments, the positive 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.

[0037] In some embodiments, 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 resin.

[0038] In some embodiments, the negative electrode active material includes a carbon-based material, the carbon-based material includes graphite particles, and the graphite particles have a graphitization degree of 92.0% to 94.5%. When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, 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 include artificial graphite and a carbon coating layer, the artificial graphite includes secondary particles, and the carbon coating layer is coated on the surface of the artificial graphite. The carbon coating layer has a large number of end faces and defects, which can increase the number of sites for lithium ion deintercalation, and the carbon coating layer has excellent electrical conductivity, 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 within 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, and 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.

[0042] Therefore, in the embodiments of the present application, the particle sizes in the first negative electrode film layer and the second negative electrode film layer are different, 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 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.

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

[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 within 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] Therefore, 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 within 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 3% to 8%. When the mass content of lithium is within the above range, the number of lithium ions that can freely move in the negative electrode film layer can be relatively large, the distance that lithium ions diffuse to the surface of the negative electrode film layer can be further shortened, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[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 within the above range, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0054] In some embodiments, the mass content of lithium in the second lithium-containing binder is 3% to 10%, or 3% to 8%. When the mass content of lithium is within the above range, the number of lithium ions that can freely move in the negative electrode film layer can be relatively large, the distance that lithium ions diffuse to the surface of the negative electrode film layer can be further shortened, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0055] In some embodiments, the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer 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 number 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 the charging and discharging process, has a stable structure, and the cycle performance of the negative electrode film layer during rapid charging and discharging is improved.

[0057] In some embodiments, the second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer 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 charging and discharging, has stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[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 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 conductive layer comprises one or more of a negative conductive agent and a negative binder. The negative conductive agent in the negative conductive layer can improve the conductivity of the negative conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the heat generation of the battery monomer, and the negative binder in the negative conductive layer can improve the adhesion between the negative current collector and the negative electrode film layer and improve the structural stability of the negative electrode sheet.

[0064] In some embodiments, the negative 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.

[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 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 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.

[0068] In some embodiments, the thickness of the base film is 6 μm to 12 μm. When the thickness of the base film is within 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.

[0069] In some embodiments, the thickness of the base film is 6 μm to 9 μm. When the thickness of the base film is within 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.

[0070] 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 arranged on one side of the base film, the first functional layer comprises first inorganic particles, the second functional layer is arranged 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.

[0071] In some embodiments, the non-fluoropolymer particles comprise an acrylate copolymer. The acrylate copolymer has excellent adhesion, and has high adhesion stability with the base film.

[0072] In some embodiments, 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.

[0073] 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-mentioned second inorganic particles can improve the heat resistance of the first functional layer.

[0074] 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-mentioned range, the heat resistance and the compression modulus of the composite particles can be improved.

[0075] In some embodiments, the carboxylic acid ester-based solvent includes 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 in the above-mentioned range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0076] In some embodiments, the chain carboxylic acid ester-based solvent includes a compound represented by Formula I,

[0077] In Formula I,

[0078] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group,

[0079] R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

[0080] Therefore, the above-mentioned chain carboxylic acid ester-based solvent in the embodiments of the present application has a relatively high conductivity, which is beneficial to improving the rapid charging capability of the battery cell.

[0081] In some embodiments, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 halogenated alkyl group.

[0082] In some embodiments, R2 includes a C1 to C3 alkyl group or a C1 to C3 halogenated alkyl group.

[0083] In some embodiments, the chain carboxylic acid ester-based solvent includes one or more of a compound represented by Formula I-1 to a compound represented by Formula I-8,

[0084] In some embodiments, the organic solvent further includes a carbonate-based solvent, and the carbonate-based solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The above-mentioned carbonate-based solvent and the chain carboxylic acid ester-based solvent are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0085] In some embodiments, the carbonate-based solvent includes one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate.

[0086] In some embodiments, the mass content of the carbonate-based solvent in the organic solvent is 30% to 70%, or optionally 30% to 50%. The carbonate-based solvent in the above mass content can further improve the conductivity of the electrolyte and facilitate the migration of lithium ions.

[0087] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of a carbonate-based additive, a sulfur-containing additive, and a lithium salt-based additive. The additive can improve the performance of the interface film on the positive electrode side and / or the negative electrode side, improve the rapid charging performance of the battery cell, and improve the cycle performance.

[0088] In some embodiments, the carbonate-based additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0089] In some embodiments, 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 disulfonate MMDS.

[0090] In some embodiments, 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.

[0091] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, or optionally 2% to 8%. The additive in the above mass content can effectively improve the performance of the interface film on the positive electrode side and / or the negative electrode side, improve the rapid charging performance of the battery cell, and improve the cycle performance.

[0092] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfonimide salt and lithium hexafluorophosphate LiPF6. The lithium salt is easy to dissociate, facilitates 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.

[0093] In some embodiments, the fluorine-containing sulfonimide salt includes one or more of lithium bisfluorosulfonimide LiFSI and lithium bis-trifluoromethylsulfonimide LiTFSI.

[0094] In some embodiments, the lithium salt comprises lithium bisfluorosulfonylimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of lithium bisfluorosulfonylimide LiFSI is 0.2-0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.5-1.0 mol / L.

[0095] In some embodiments, the ratio of the molar concentration of lithium bisfluorosulfonylimide to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2-1.0.

[0096] In some embodiments, the base material of the shell comprises steel, and the thickness of the shell is 0.1-0.5 mm, optionally 0.2-0.35 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 monomer, and the shell occupies less space, the internal space of the shell is larger, which is conducive to improving the energy density of the battery monomer.

[0097] In some embodiments, the battery monomer further comprises an electrode terminal, and the electrode assembly comprises a tab portion, and the tab portion is directly welded to the electrode terminal. Direct welding can reduce the resistance at the connection, which is conducive to reducing the internal resistance of the battery monomer as a whole.

[0098] In some embodiments, the charging time of the battery monomer from 10% state of charge to 80% state of charge is 5-10.5 min. The charging speed of the battery monomer is faster, which is more conducive to improving the rapid charging capability.

[0099] In the second aspect, the application provides a battery device, which comprises a plurality of battery monomers according to any one of the embodiments of the first aspect of the application.

[0100] In some embodiments, the charging time of the battery device from 10% state of charge to 80% state of charge is 5-10.5 min. The charging speed of the battery device is faster, which is more conducive to improving the rapid charging capability.

[0101] In the third aspect, the application provides a power consumption device, which comprises a battery device according to any one of the embodiments of the second aspect of the application. BRIEF DESCRIPTION OF DRAWINGS

[0102] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments of the application. Obviously, the drawings described below are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0103] FIG. 1 is a structural schematic diagram of a battery monomer provided by some embodiments of the application,

[0104] FIG. 2 is an exploded schematic view of a battery cell according to some embodiments of the present application,

[0105] FIG. 3 is a schematic view of a battery module according to some embodiments of the present application,

[0106] FIG. 4 is a schematic view of a battery pack according to some embodiments of the present application,

[0107] FIG. 5 is a schematic view of an electric device according to some embodiments of the present application.

[0108] The accompanying drawings are merely schematic and are not intended to be actual views of the relative sizes of region described.

[0109] The reference signs in the drawings are explained as follows.

[0110] 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,

[0111] 7: battery cell,

[0112] 10: electrode assembly, 111: first tab, 112: second tab, 12: main body portion,

[0113] 20: housing, 21: case, 22: end cap,

[0114] 31: first electrode terminal, 32: second electrode terminal. DETAILED DESCRIPTION

[0115] Hereinafter, embodiments of the battery cell, the battery device, and the electric device according to the present application are specifically disclosed while appropriately referring to the accompanying drawings. However, there are cases where unnecessary detailed explanations are omitted. For example, there are cases where detailed explanations of matters that are already well known, repeated explanations 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 explanations 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.

[0116] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the same, i.e., every number between the upper and lower limits of a cited range. For example, if a range is stated as 1 to 60, then it is intended that every number between 1 and 60, i.e., 1, 2, 3, etc., through 60, is specifically enumerated in the range. If a range such as 40 to 60 is stated, then it is intended that every number between 40 and 60, i.e., 40, 41, 42, etc., through 60, is specifically enumerated in the range. The same applies to ranges having endpoints of whole numbers. For example, a range of 1 to 5 would include 1, 2, 3, 4, and 5, unless the context clearly indicates otherwise. The use of "between" in the context of a range should be interpreted as specifying open ranges and not inclusive ranges. For example, a range of 1 to 5 inclusive would be interpreted to be from 1 to 5, while a range of 1 to 5, between 1 and 5, or 1 to 5 inclusive would be interpreted from 1 to 5, not including 1 and 5. Additionally, the use of a "to" in a range should be interpreted as specifying an open range. For example, a range of 1 to 5 would be interpreted as 1 to 5, not including 1 and 5. Additionally, when a parameter is stated to be an integer ≥ 2, it is equivalent to stating that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0117] If not specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0118] If not specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0119] If not specified, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, a method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed 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.

[0120] During the charging and discharging process of the battery cell, a thermal effect is generated. Specifically, during the charging process, the external power supply provides electrical energy to the battery cell, and a series of chemical reactions are triggered inside the battery, generating heat energy, so that the temperature of the battery cell increases during the charging process. During the discharging process, the battery cell converts chemical energy into electrical energy, while generating heat energy, so that the temperature of the battery cell increases during the discharging process. The increase in the temperature of the battery cell reduces the reliability of the battery cell, and even causes thermal runaway, and deteriorates the cycle performance, and the above problems are particularly significant in the battery of the fast charging system.

[0121] In view of the above problems, the embodiments of the present application reasonably design the system of the battery monomer, reduce the internal resistance of the battery monomer, and reduce the heat generation of the battery monomer. Specifically, by reasonably configuring the characteristics of the positive electrode sheet, the negative electrode sheet and the electrolyte affecting the internal resistance of the battery, the internal resistance of the battery monomer can be further reduced, thereby reducing the heat generation, and the use reliability and cycle performance of the battery monomer can be improved.

[0122] Battery monomer

[0123] In a first aspect, the embodiments of the present application provide a battery monomer.

[0124] The battery monomer comprises an electrode assembly, an electrolyte and a shell, the electrode assembly and the electrolyte are contained in the shell, the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing phosphate with an olivine structure, the resistance of the positive electrode sheet is 0.1 Ω to 30 Ω, the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer comprises a negative electrode active material, the resistance of the negative electrode sheet is 0.001 Ω to 0.01 Ω, the separator is located between the positive electrode sheet and the negative electrode sheet, the electrolyte comprises an organic solvent, the organic solvent comprises a chain carboxylic acid ester solvent, and the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm.

[0125] In the embodiments of the present application, the positive electrode active material comprises a lithium-containing phosphate with an olivine structure, which has high cycle stability. By synergistically controlling the resistance of the positive electrode sheet, the resistance of the negative electrode sheet and the conductivity of the electrolyte within a reasonable range, on the one hand, the transmission resistance of lithium ions in the battery monomer can be reduced, the rapid charging capacity of the battery can be improved, and the internal resistance DCR of the battery can be reduced; on the other hand, the cycle decay caused by excessive temperature rise during rapid charging of the battery monomer can be improved; on the other hand, the problem of uneven temperature rise during rapid charging of the battery can be improved, and the cycle decay problem caused by lithium precipitation of the battery monomer can be reduced; in addition, by controlling the resistance of the positive and negative electrode sheets within a reasonable range, the temperature in the battery monomer can be controlled within a reasonable range that the high-conductivity electrolyte can withstand, and the risk of weakening the fast charging performance of the battery due to the volatilization of the solvent components of the electrolyte can be reduced.

[0126] In summary, the battery monomer of the embodiments of the present application has the advantages of rapid charging, low DCR, good cycle performance and the like.

[0127] In the embodiments of the present application, the resistance of the positive electrode sheet can be adjusted by adjusting the material quality of the positive electrode active material, such as adjusting the graphitization degree and powder resistivity of the positive electrode active material.

[0128] In the embodiments of the present application, the resistance of the negative electrode sheet can be adjusted by adjusting the material of the negative electrode active material, for example, adjusting the graphitization degree, powder resistivity, etc. of the negative electrode active material.

[0129] In the embodiments of the present application, the conductivity of the electrolyte can be adjusted by adjusting the mass content of the chain carboxylate ester solvent in the organic solvent in the electrolyte.

[0130] The charging upper limit voltage and the discharging cut-off voltage of the battery cell are different according to the positive electrode active material, for example, when the phosphate material includes lithium iron phosphate, the charging upper limit voltage can be 3.65V, and the discharging cut-off voltage can be 2.0V, for example, when the phosphate material includes lithium manganese iron phosphate, the charging upper limit voltage can be 4.3V, and the discharging cut-off voltage can be 2.0V, and then taking the charging upper limit voltage of 3.65V and the discharging cut-off voltage of 2.0V as an example, the state of the battery cell is described as follows: 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,

[0131] The battery cell is charged to the charging 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, and the battery cell is discharged to the cut-off voltage at a constant current discharging rate of 0.33C, corresponding to the state of 0% SOC of the battery cell.

[0132] In the embodiments of the present application, the sheet resistance refers to the ability of current to flow through the sheet (the cross section of the current flow area along the thickness direction of the current collector and the film layer containing the electrode material located on both sides of the current collector), which can be detected by the following equipment and method:

[0133] As an example, after disassembling the sheet from the battery discharged to 0% SOC, the sheet is cleaned more than three times with a solvent such as dimethyl carbonate DMC, 20 parallel samples can be taken along the central axis of the sheet, each sample is symmetrical along the central axis, and the size of each sample is 4cmx25cm, wherein the central axis can be parallel to the length direction of the sheet. The above 20 parallel samples are tested by using a film resistance tester (Yuan Neng Technology, BER2500 model), and the average value is calculated as the sheet resistance.

[0134] [Positive electrode sheet]

[0135] 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 opposite surfaces in the thickness direction thereof, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0136] In the embodiments of the present application, the positive electrode tab has a resistance of 0.1 Ω to 30 Ω, which can be 0.1 Ω to 5 Ω, and further can be 0.1 Ω to 1 Ω. For example, the positive electrode tab has a resistance of 0.1 Ω, 0.5 Ω, 1 Ω, 1.5 Ω, 2 Ω, 2.5 Ω, 3 Ω, 3.5 Ω, 4 Ω, 4.5 Ω, 5 Ω, 5.5 Ω, 6 Ω, 6.5 Ω, 7 Ω, 7.5 Ω, 8 Ω, 8.5 Ω, 9 Ω, 9.5 Ω, 10 Ω, 10.5 Ω, 11 Ω, 11.5 Ω, 12 Ω, 12.5 Ω, 13 Ω, 13.5 Ω, 14 Ω, 14.5 Ω, 15 Ω, 15.5 Ω, 16 Ω, 16.5 Ω, 17 Ω, 17.5 Ω, 18 Ω, 18.5 Ω, 19 Ω, 20 Ω, 21 Ω, 22 Ω, 23 Ω, 24 Ω, 25 Ω, 26 Ω, 27 Ω, 28 Ω, 29 Ω, 30 Ω, or a range formed by any two of the above values.

[0137] When the positive electrode tab has a resistance in the above range, the resistance of the positive electrode tab is more suitable for the resistance of the negative electrode tab and the electrolyte system of the battery monomer, which is beneficial to reduce the internal resistance of the battery monomer and optimize the electrical performance of the battery monomer.

[0138] In some embodiments, the positive electrode film layer has a compacted density of 2.50 g / cm 3 to 2.80 g / cm 3 at 100% state of charge (SOC) of the battery monomer, which can be 2.55 g / cm 3 to 2.70 g / cm 3 . For example, the positive electrode film layer has a compacted density of 2.50 g / cm 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 formed by any two of the above values.

[0139] When the compaction density of the positive electrode film layer is in the above range, the energy density of the battery monomer 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 monomer has high energy density and high charging rate performance.

[0140] 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 , 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 mm 2 , 370 mg / 1540.25 mm 2 or a range composed of any two of the above values.

[0141] When the single-sided coating weight of the positive electrode film layer is in the above range, the heat generation per unit area of the positive electrode sheet will not be too large, and the energy density and charging rate performance of the battery monomer can be improved.

[0142] 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 sheet of the battery cell at 100% state of charge (SOC) is disassembled, the compaction density of the positive electrode film layer is measured, for example, the single-sided coated positive electrode sheet (if it is a double-sided coated sheet, 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 sheet is wiped off, the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight of the positive electrode sheet 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 sheet H1 - the thickness of the positive electrode current collector H0, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0143] 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 defined by any two of the above values.

[0144] The relatively low powder resistivity of the positive electrode active material makes the resistance of the positive electrode sheet relatively low, and the battery cell generates less heat.

[0145] 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.

[0146] In some embodiments, the powder compaction density of the positive electrode active material under 30000N is 2.46g / cm 3 to 2.8g / cm 3 . For example, the powder compaction density of the positive electrode active material under 30000N is 2.46g / cm 3 , 2.47g / cm 3 , 2.48g / cm 3 , 2.49g / cm 3 , 2.5g / cm 3 , 2.51g / cm3 2.55 g / cm3 3 2.58 g / cm3 3 2.60 g / cm3 3 2.65 g / cm3 3 2.68 g / cm3 3 2.70 g / cm3 3 2.72 g / cm3 3 2.75 g / cm3 3 2.78 g / cm3 3 2.80 g / cm3 3 or a range between any two of the above values.

[0147] When the powder compaction density of the positive electrode active material at 30000 N is in the above range, the energy density of the battery monomer can be improved, and the positive electrode active material in the positive electrode film layer can be more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the pole piece, thereby reducing the heat generation.

[0148] 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 cm2 of UTM7305 electronic pressure testing machine, and pressed to 3000 kg (equivalent to 30000 N), and kept for 30 s, then released, kept for 10 s, and then recorded and calculated to obtain the powder compaction density of the positive electrode active material under the action of 30000 N. 2

[0149] In some embodiments, the charge gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g to 170 mAh / g, which can be selected as 157 mAh / g to 170 mAh / g. Exemplarily, the charge 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.

[0150] When the charge gram capacity of the positive electrode active material at 0.1C rate is in the above range, the energy density of the battery monomer is relatively high.​

[0151] 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 coulomb efficiency and the first discharge specific capacity in the national standard GB / T 24533-2019 Appendix G can be used. The half-button type battery is assembled with lithium metal as the negative electrode and the sample electrode piece containing the above-mentioned material as the positive electrode. The half-button type battery is placed in the battery tester or other testing equipment with the same performance under the condition of 23℃±2℃. The button capacity is obtained by 0.1C rate charging and discharging, and then the capacity is divided by the mass of the active material of the electrode piece to obtain the charging gram capacity parameter.

[0152] In some embodiments, the mass percentage 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%. It can be considered that the positive electrode active material of the present application is an olivine-structured lithium-containing phosphate system. When the mass percentage 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.

[0153] Optionally, the mass percentage of the olivine-structured lithium-containing phosphate in the positive electrode active material is 100%.

[0154] In the embodiments of the present application, the olivine-structured lithium-containing phosphate can be a phosphate particle or a material obtained after coating modification, for example, the olivine-structured lithium-containing phosphate includes a phosphate particle and a coating layer, the coating layer is coated on the surface of the phosphate particle, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

[0155] The phosphate particle is coated with a coating layer on the surface, which can improve the electrical conductivity of the olivine-structured lithium-containing phosphate, reduce the powder resistivity of the material, and be beneficial to the migration rate of lithium ions, improve the rapid charging capacity of the battery, and reduce the heat generation of the battery monomer.

[0156] In some embodiments, the phosphate particle includes a general formula of Li x1 A y1 Me a M b P 1-c X c Y zLi1-x1-y1-a-b-c-d-x2-y2-z Me A x1 Me y1 A a Me b A c M2 d X x2 Y y2 A 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 comprises one or more of Na, K, Mg, Me comprises one or more of Mn, Fe, Co, Ni, M comprises 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 comprises one or more of S, Si, Cl, B, C, N, and Y comprises one or more of O, F. The phosphate particles have excellent cycle stability, which is conducive to improving the cycle performance of the battery monomer.

[0157] Exemplarily, the phosphate particles comprise one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charging and discharging process of the battery monomer, active ions such as Li are deintercalated and consumed, and the molar content of Li is different when the battery monomer is discharged to different states. In the enumeration of the positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, 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, and LiCoPO4 in the embodiments of the present 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 practice, the molar content of oxygen O will fluctuate, and the above-mentioned situations are all within the protection scope of the present application.

[0158] In some embodiments, the coating layer comprises a fast ion conductor of the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , M2 comprises one or more of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0

[0159] Exemplarily, the fast ion conductor is a material having a NASICON structure, for example, comprising one or more of lithium titanium iron phosphate Li2FeTi(PO4)3, lithium zirconium iron phosphate Li2FeZr(PO4)3, and lithium tin iron phosphate Li2FeSn(PO4)3.

[0160] The fast ion conductor with 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, strong structural stability, etc. in the process of multiple delithiation and lithium intercalation. Coating the fast ion conductor containing the NASICON structure on the surface of the phosphate particles 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 monomer. In addition, it can also improve the specific capacity and the energy density of the corresponding battery monomer.

[0161] In some embodiments, the coating layer further comprises elemental carbon.

[0162] The elemental carbon and the fast ion conductor can be arranged in layers, for example, the elemental carbon 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, i.e., 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, i.e., the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the elemental carbon and the fast ion conductor can also be arranged in the same layer.

[0163] Optionally, the carbon coating layer can be coated on the surface of the fast ion conductor layer by a carbonization process of an organic carbon source (e.g., 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 conduction performance of the phosphate particles, and improve the energy density of the battery monomer.

[0164] Specifically, the arrangement of the carbon coating layer enables the positive electrode active material of the present application to have the following advantages:

[0165] The carbon coating layer in the positive electrode active material of the present application provides a suitable channel for the transmission of electrons, which can significantly improve the conduction rate of electrons during multiple delithiation and lithium intercalation, improve the electronic conductivity of the lithium-containing phosphate, improve the charging capacity of the corresponding battery monomer, and also improve the energy density.

[0166] The carbon coating layer of the positive electrode active material of the present 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 monomer.

[0167] Coating the lithium-containing phosphate with a carbon coating layer can not only improve the conductivity of the lithium-containing phosphate, but also improve the structural stability of the positive electrode active material, effectively alleviate the iron dissolution phenomenon of the positive electrode active material during long-term storage and cycle use of the battery cell, and thus improve the cycle life of the battery cell.

[0168] The positive electrode active material of the present application uses a lithium-containing phosphate as a substrate, fully utilizes the advantages of low cost, high reliability and good cycle stability of the lithium-containing phosphate, and solves the disadvantages 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 present application can improve the energy density of the battery cell under the premise of excellent cycle performance.

[0169] In the embodiments of the present application, the content of elements in the positive electrode active material is 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, testing by inductively coupled plasma atomic emission spectrometry, and measuring by plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After disassembling the positive electrode sheet from the battery cell 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 standard curve method is used for quantitative testing.

[0170] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, which can be optionally 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.

[0171] 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 cell.

[0172] 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.

[0173] In some embodiments, the mass content of carbon element in the olivine-structured lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine-structured lithium-containing phosphate is 5m 2 / g to 18m 2 / g.

[0174] Optionally, the mass content of carbon element in the olivine-structured lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine-structured lithium-containing phosphate is 7.5m 2 / g to 14m 2 / g.

[0175] Illustratively, the mass content of carbon element in the olivine-structured 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.

[0176] Illustratively, the specific surface area of the olivine-structured lithium-containing phosphate 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 composed of any two of the above values.

[0177] The carbon element mainly exists in the form of a carbon coating layer in the coating layer, and the carbon coating layer is loose and porous, which is conducive to improving the specific surface area of the material, and is more conducive to effective contact between the electrolyte and the phosphate particles, and is conducive 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 olivine-structured lithium-containing phosphate can be significantly improved, which is conducive to improving the ionic conductivity and electronic conductivity of the olivine-structured lithium-containing phosphate, and can improve the rapid charging capacity and energy density of the battery cell.

[0178] In the embodiments of the present application, the specific surface area of the material is in 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 testing the specific surface area by using a Tri-Star 3020 type specific surface area pore size analyzer of the Micromeritics company in the United States.

[0179] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1 μm≤Dv50≤2 μm, 0.4 μm≤Dv10≤0.7 μm.

[0180] Exemplarily, the Dv50 of the positive electrode active material can be 1 μm, 1.1 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.5 μm, 1.55 μm, 1.6 μm, 1.65 μm, 1.7 μm, 1.75 μm, 1.8 μm, 1.85 μm, 1.9 μm, 1.95 μm, 2 μm, or a range formed by any two of the above values.

[0181] 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.

[0182] The particle size of the positive electrode active material is relatively small, the lithium ion has a shorter lithium extraction path in the positive electrode active material, the heat production is less, and 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.

[0183] 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, which can be detected by using the devices and methods known in the art, for example, taking the positive electrode active material as the sample, according to the test standard GB / T 19077-2016, and testing the Dv50 and Dv10 of the particles by using a Mastersizer 2000E type laser particle size analyzer.

[0184] 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.

[0185] In some embodiments, the lithium-containing olivine phosphate is in a particulate form, the lithium-containing olivine phosphate comprises secondary particles, the secondary particles comprise a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. For example, 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 defined by any two of the above values.

[0186] The average particle size of the primary particles is relatively small, the lithium ion deintercalation path in the positive electrode active material is short, and the heat generation is less.

[0187] In the embodiments of the present application, the secondary particle refers to an agglomerated particle formed by two or more primary particles. The primary particles and the secondary particles can be easily distinguished by experimental means (e.g., 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.

[0188] 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, trilithium 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.

[0189] Optionally, the ternary material comprises Li x3 A y3 Ni a3 Co b3 Mn c M3(1-a3-b3-c3)Y3 z3 wherein 0

[0190] Exemplarily, the ternary material includes at least one of 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.

[0191] In some embodiments, the mass content of the lithium supplement agent in the positive electrode film layer is 0.5% to 5%, 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 in the above range, the lithium supplement agent can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0192] The lithium supplement agent can be located in the same layer as the positive electrode active material, or can be located in different layers. When the lithium supplement agent and the positive electrode active material are located in different layers, the lithium supplement agent can be located in a lithium supplement layer, and the positive electrode active material can be located 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 arranged on at least one side of the positive electrode current collector, and the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be arranged on at least one side of the positive electrode current collector, and the positive electrode active material layer can be located between the lithium supplement layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be located 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 to make up for the loss of lithium in the battery system during the cyclic charging and discharging of the battery cell.

[0193] In some embodiments, the positive electrode film layer can further optionally include 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.

[0194] In some embodiments, the positive electrode film layer can further optionally include a positive electrode binder. The embodiments of the present application do not have particular limitations on the type of positive electrode binder, 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, a polyacrylic acid, and a fluorine-containing acrylic ester-based resin. In some embodiments, the mass content of the positive electrode binder is ≤ 5% based on the mass of the positive electrode film layer.

[0195] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. As an example of the metal foil, at least one foil of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy 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, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a 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).

[0196] In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05 to 0.3. As an example, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode 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 defined by any two of the aforementioned values.

[0197] When the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is within the aforementioned range, the rapid charging capability and the energy density of the battery cell can be improved.

[0198] In some embodiments, the thickness of the positive electrode 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 electrode 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 defined by any two of the aforementioned values.

[0199] When the thickness of the positive electrode current collector is within the aforementioned range, the overcurrent capability of the positive electrode current collector is excellent, and the battery cell can have a high energy density.

[0200] In the embodiments of the present application, the thickness of the positive electrode film layer and the positive electrode current collector has the meaning 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 tab can be measured by using a micrometer, the thickness of the positive electrode current collector can be measured by removing the film layer on the surface of the positive electrode current collector, when the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode tab minus the thickness of the positive electrode current collector, and when the positive electrode film layer is coated on both sides, the thickness of the positive electrode film layer is (the thickness of the positive electrode tab minus the thickness of the positive electrode current collector) / 2.

[0201] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, the optional conductive agent, the optional binder and any other components in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0202] 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 arranged 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 arranged on the surface of the positive electrode film layer.

[0203] In some embodiments, the positive electrode tab further comprises a positive electrode conductive layer arranged 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 and reduce the heat generation of the positive electrode tab, thereby reducing the heat generation of the battery cell.

[0204] 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 formed by any two of the above values.

[0205] When the thickness of the positive electrode conductive layer is in 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.

[0206] 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, the thickness of the positive electrode conductive layer can be directly measured by performing tomography on the positive electrode tab.

[0207] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder.

[0208] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Illustratively, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or a range formed by any two of the above values.

[0209] Illustratively, the positive electrode conductive agent includes one or more of super-p, 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, thereby improving the conductivity of the positive electrode sheet and reducing the heat generation of the battery cell.

[0210] 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 is 50%, 60%, 65%, 70%, or a range formed by any two of the above values.

[0211] 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, thereby improving the structural stability of the positive electrode sheet.

[0212] [Negative electrode sheet]

[0213] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and 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.

[0214] In the embodiments of the present application, the resistance of the negative electrode sheet is 0.001 Ω to 0.01 Ω, and optionally 0.001 Ω to 0.005 Ω. Illustratively, the resistance of the negative electrode sheet is 0.001 Ω, 0.002 Ω, 0.003 Ω, 0.004 Ω, 0.005 Ω, 0.006 Ω, 0.007 Ω, 0.008 Ω, 0.009 Ω, 0.01 Ω, or a range formed by any two of the above values.

[0215] When the resistance of the negative electrode sheet is within the above range, the resistance of the negative electrode sheet is relatively small, which is conducive to reducing the internal resistance of the battery cell.

[0216] In the embodiments of the present application, the resistance of the negative electrode sheet is the 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 described above for the resistance test method of the positive electrode sheet.

[0217] In some embodiments, the compaction density of the negative electrode film layer is 1.15 g / cm3to 1.36 g / cm3at 100% state of charge. 3 to 1.36 g / cm3. 3 , optionally 1.25 g / cm3. 3 to 1.36 g / cm3. 3 Exemplarily, the compaction density of the negative electrode film layer is 1.15 g / cm3to 1.36 g / cm3at 100% state of charge. 3 , 1.18 g / cm3. 3 , 1.20 g / cm3. 3 , 1.22 g / cm3. 3 , 1.25 g / cm3. 3 , 1.28 g / cm3. 3 , 1.3 g / cm3. 3 , 1.32 g / cm3. 3 , 1.35 g / cm3. 3 , 1.36 g / cm3. 3 or a range between any two of the above values.

[0218] 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 contact resistance between particles in the negative electrode film layer is small, which can further reduce the resistance of the electrode sheet and thus reduce the heat generation.

[0219] In the embodiments of the present application, the compaction density of the negative electrode film layer at 100% state of charge is the meaning known in the art, which can be detected by using the devices and methods known in the art, and the detection method is the same as the compaction density test method of the positive electrode film layer described above.

[0220] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm2to 170 mg / 1540.25 mm2. 2 to 150 mg / 1540.25 mm2. 2 , optionally 110 mg / 1540.25 mm2. 2 to 150 mg / 1540.25 mm2. 2 Exemplarily, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm2to 170 mg / 1540.25 mm2. 2 , 92 mg / 1540.25 mm2. 2 , 95 mg / 1540.25 mm2. 2 , 96 mg / 1540.25 mm2. 2 , 100 mg / 1540.25 mm2. 2 , 102 mg / 1540.25 mm2. 2 , 104 mg / 1540.25 mm2. 2105 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 between any two of the above values.

[0221] 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.

[0222] 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 test method for the single-side coating weight of the film layer.

[0223] In some embodiments, the powder resistivity of the negative active material is 0.005 Ω·cm to 0.043 Ω·cm, optionally 0.04 Ω·cm. Illustratively, the powder resistivity of the negative 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 defined by any two of the above values.

[0224] The relatively low powder resistivity of the negative active material results in a relatively low resistance of the negative electrode sheet, and less heat generation of the battery cell.

[0225] In the embodiments of the present application, the powder resistivity of the negative active material is in the meaning known in the art, and can be detected by using the devices and methods known in the art, such as the powder resistivity test method of the positive active material described above.

[0226] In some embodiments, the powder compaction density of the negative active material under a pressure of 20000 N is 1.5 g / cm 3 to 1.85 g / cm 3 , optionally 1.55 g / cm 3 to 1.65 g / cm 3 . Illustratively, the powder compaction density of the negative active material under a pressure of 20000 N is 1.5 g / cm 3 , 1.55 g / cm 3 , 1.6 g / cm 3 , 1.65 g / cm 3 , 1.7 g / cm 3 , 1.75 g / cm 3 , 1.8 g / cm 3 , 1.85 g / cm 3 , or a range defined by any two of the above values.

[0227] When the powder compaction density of the negative active material under a pressure of 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 smaller, and the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0228] In the embodiments of the present application, the powder compaction density of the material is in the meaning known in the art, and can be detected by using 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, and a UTM7305 electronic pressure testing machine with a bottom area of 1.327 cm 2The negative active material is put into a mold, and is pressed to 2000kg (equivalent to 20000N), and is kept for 30s, then is unloaded, and is kept for 10s, then the powder compaction density of the negative active material under the action of 20000N is recorded and calculated.

[0229] In some embodiments, the charging gram capacity of the negative active material at 0.1C rate is 350mAh / g to 480mAh / g. Illustratively, the charging gram capacity of the negative active material at 0.1C rate is 350mAh / g, 355mAh / g, 360mAh / g, 365mAh / g, 370mAh / g, 375mAh / g, 380mAh / g, 385mAh / g, 390mAh / g, 395mAh / g, 400mAh / g, 410mAh / g, 420mAh / g, 430mAh / g, 440mAh / g, 450mAh / g, 460mAh / g, 470mAh / g, 480mAh / g or a range consisting of any two of the above.

[0230] When the charging 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.

[0231] In the embodiments of the present application, the charging gram capacity of the negative active material at 0.1C rate is the 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 described above in the charging gram capacity test method of the positive active material at 0.1C rate.

[0232] In some embodiments, the negative active material comprises a carbon-based material, and the cycle stability of the carbon-based material is relatively high, which can improve the cycle performance of the battery cell. Optionally, the mass percentage of the carbon-based material in the negative active material can be greater than or equal to 80% and less than or equal to 100%.

[0233] 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, and the two are used together, and the cycle performance of the battery cell is relatively excellent.

[0234] Optionally, the carbon-based material comprises graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. Illustratively, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5% or a range consisting of any two of the above.

[0235] When the graphitization degree of the graphite particles is in the above range, the conductivity 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.

[0236] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer, the artificial graphite includes secondary particles, the secondary particles include a plurality of primary particles, and the carbon coating layer is coated on a 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 crystallization and an approximate amorphous state (or a structure with no fixed shape and periodicity). In this application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0237] The artificial graphite includes 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 more excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0238] Optionally, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. Illustratively, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range composed of any two of the above values.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] 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 in a suitable 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.

[0243] Optionally, the carbonization treatment time is 1h to 6h.

[0244] In some embodiments, the carbon-based material can also 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.

[0245] In some embodiments, the negative electrode active material may also include a silicon-based material. The introduction of silicon-based materials can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0246] Optionally, based on the mass of the negative electrode active material, the mass content of silicon element in the silicon-based material is 0.3% to 10.0%, optionally 1% to 6%. Exemplarily, the mass content of silicon element 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 consisting of any two of the above values.

[0247] When the mass content of silicon in silicon-based materials is within the above range, it can increase the capacity of the negative electrode active material, thereby improving the energy density of the battery cell.

[0248] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy.

[0249] In some embodiments, the negative electrode active material may include, in addition to the carbon-based materials and optionally silicon-based materials described above, at least one of tin-based materials and lithium titanate. Tin-based materials may include at least one of elemental tin, tin oxides, and tin alloys.

[0250] The qualitative and quantitative analysis of each substance or element in this application can be performed using suitable equipment and methods known to those skilled in the art. Relevant testing methods can be referenced from domestic and international testing standards and enterprise standards. Furthermore, those skilled in the art can adaptively modify certain testing steps / instrument parameters from the perspective of testing accuracy to obtain more accurate results. One testing method can be used for qualitative or quantitative analysis, or several testing methods can be used in combination for qualitative or quantitative determination.

[0251] For example, this application can combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis to perform X-ray powder diffraction tests and qualitative analysis on negative electrode sheets or negative electrode active materials.

[0252] The artificial graphite and the natural graphite can be distinguished by a scanning electron microscope (SEM) cross-section image taken by the SEM, wherein the SEM cross-section image of the natural graphite has gaps between flaky structures, and the SEM cross-section image of the artificial graphite is dense and has no obvious gaps, or distinguished by an X-ray diffraction (XRD) spectrum obtained by the XRD method, wherein 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.

[0253] 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 film layers. Optionally, the negative electrode film layer includes at least two film layers.

[0254] In the case of using a single-layer film layer for the negative electrode film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally, a silicon-based material. In the case of using a single-layer film layer, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm to 13.5 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode 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.

[0255] In the case of using at least two film layers for the negative electrode film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally, a silicon-based material, which can be located in one of the at least two film layers or at least two of the at least two film layers. The negative electrode film layer can include two film layers, three film layers, four film layers, or even more film layers.

[0256] 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 carbon-based material in the first negative electrode film layer includes 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 includes 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.

[0257] The interface of the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and optionally, irregular.

[0258] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0259] The negative electrode film layer includes at least two film layers, and the layered coating is beneficial to improve the rapid charging performance of the battery cell. In particular, when the first negative electrode film layer and the second negative electrode film layer are different, the pore difference of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission is reduced, and the rapid charging performance of the battery cell is improved.

[0260] 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 beneficial to improve the compaction density of the negative electrode film layer. When the negative electrode active material includes 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.

[0261] The particle size difference in the first negative electrode film layer and the second negative electrode film layer can improve the rapid charging performance of the battery cell. Specifically, during 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.

[0262] Optionally, the negative electrode active material in the first negative electrode film layer is in a particle form, and the volume average particle size Dv50 thereof is 9.5 μm to 18.5 μm, which can be 9.5 μm to 14.6 μm. Exemplarily, the volume average particle size of the negative electrode active material in the first negative electrode film layer 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 formed by any two of the above values. When the first negative electrode film layer includes graphite particles, 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, which can be 9.5 μm to 14.6 μm.

[0263] When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is in the above range, on the one hand, the solid-phase transmission path of lithium ions can be shortened, and the rapid charging performance can be improved. On the other hand, the material is not easy to agglomerate during the preparation process, and the stability of the material can be improved.

[0264] Optionally, the volume average particle size Dv50 of the negative active material in the second negative film layer is 7.8 μm to 14.3 μm, or 7.8 μm to 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 film layer comprises graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative film layer is 7.8 μm to 14.3 μm, or 7.8 μm to 11.3 μm.

[0265] When the volume average particle size Dv50 of the negative active material in the second negative film layer is within the above range, on the one hand, the solid-phase transmission path of lithium ions can be shortened, and the rapid 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. On the other hand, the negative active material in the second negative film layer and the negative active material in the first negative film layer cooperate to facilitate the construction of a gradient pore difference between the second negative film layer and the first negative film layer, reduce the tortuosity of lithium ion transmission, and improve the rapid charging performance of the battery cell.

[0266] 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 by using the devices and methods known in the art. The detection method is as described above in the volume average particle size Dv50 test method of the positive active material.

[0267] Optionally, the tap density of the carbon-based material in the first negative film layer is less than or equal to the tap density of the carbon-based material in the second negative 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 film layer is greater than the tap density of the carbon-based material in the first negative film layer, the second negative film layer is more densely filled, so that the energy density of the battery cell is improved, and the first negative film layer is relatively less densely filled, and the pores are more abundant, so that the rapid charging performance of the battery cell can be improved. When the negative active material comprises graphite particles, the tap density of the graphite particles in the first negative film layer is less than or equal to the tap density of the graphite particles in the second negative film layer.

[0268] Optionally, the tap density of the carbon-based material in the first negative film layer is 0.82 g / cm 3Up to 1.21 g / cm 3 For example, 0.82 g / cm³ 3 0.85g / cm 3 0.88g / cm 3 0.90g / cm 3 0.92g / cm 3 0.95g / cm 3 0.98g / cm 3 1.00g / cm 3 1.05g / cm 3 1.08g / cm 3 1.10 g / cm 3 1.12 g / cm 3 1.15g / cm 3 1.18 g / cm 3 1.20g / cm 3 1.21 g / cm 3 Or it can be a range consisting of any two of the above values. When the tap density of the carbon-based material in the first negative electrode film is within a suitable range, it can improve the fast charging performance of the battery cell.

[0269] Optionally, 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 For example, 0.90 g / cm³ 3 0.92g / cm 3 0.95g / cm 3 0.98g / cm 3 1.00g / cm 3 1.05g / cm 3 1.08g / cm 3 1.10 g / cm 3 1.12 g / cm 3 1.15g / cm 3 1.18 g / cm 3 1.20g / cm 3 1.21 g / cm 3 1.22g / cm 3 1.23g / cm 3 1.24 g / cm 3 1.25g / cm 3 Or it can be a range consisting of any two of the above values. When the tap density of the carbon-based material in the second negative electrode film is within a suitable range, it can improve the energy density of the battery cell.

[0270] In the 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 be Dandong Bitai BT-301.

[0271] Optionally, 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, and optionally 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 composed of 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.

[0272] In some embodiments, after the battery cell is subjected to a full charge test cycle for 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 composed of any two of the above values. When the thickness of the first negative electrode film layer is in 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.

[0273] In some embodiments, after the battery cell is subjected to a full charge test cycle for 10 cycles at the beginning of life (BOL), 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 composed of any two of the above values. When the thickness of the second negative electrode film layer is in the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be adjusted and increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0274] 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.

[0275] The BOL full charge test procedure is as follows: at 25°C, charge at a rate of 0.33C of the nominal capacity of the battery to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, stand for 10 min, then discharge at a rate of 0.33C to 2.0V, stand for 10 min, the above one charge-discharge is one cycle, cycle 10 times, then charge at a rate of 0.33C of the nominal capacity of the battery to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, which is the BOL full charge state, in the BOL full charge state, disassemble the negative electrode sheet, use a scanning electron microscope to observe the cross section in the thickness direction of the middle region of the negative electrode sheet, distinguish the two regions according to the interface between the first negative electrode film layer and the second negative electrode film layer, and measure the thicknesses of the two regions respectively, for example, measure the thicknesses of 10 positions of the first negative electrode film layer respectively, calculate the average value as the average value of the first negative electrode film layer, and measure the thicknesses of 10 positions of the second negative electrode film layer, calculate the average value as the average value of the second negative electrode film layer.

[0276] 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 consisting of any two of the above values. When the thickness of the first negative electrode film layer is in the above range, the first negative electrode film layer and the second negative electrode film layer can regulate the increase of 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.

[0277] 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 consisting of any two of the above values. When the thickness of the second negative electrode film layer is in the above range, the first negative electrode film layer and the second negative electrode film layer can regulate the increase of 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.

[0278] In the embodiments of the present application, for example, the battery charging upper limit voltage is 3.65V, and the battery discharging cut-off voltage is 2.0V.

[0279] The EOL full charge test procedure is as follows: at 60°C, charge to 3.65V at a charging rate of 0.33C of the nominal capacity of the battery, then charge to 0.05C at 3.65V constant voltage, stand for 10min, then discharge to 2.0V at a discharging rate of 0.33C, stand for 10min, the above one charge-discharge is one cycle, until the battery capacity decays to 80% of the nominal capacity to stop the test. Then charge to 3.65V at 25°C with 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 first negative electrode film layer and the second negative electrode film layer are distinguished according to the interface, 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, 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.

[0280] In some embodiments, in the case of using 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 lithium ions that can move freely 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).

[0281] 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 formed by any two of the above 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 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.

[0282] Illustratively, the lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, which 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.

[0283] The lithium-containing binder of the above material can provide a certain number 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.

[0284] 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.

[0285] Optionally, 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 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.

[0286] 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 lithium ions that can freely move in the second negative electrode film layer, which can further improve the rapid charging performance of the battery cell.

[0287] 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%. Illustratively, 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 defined by any two of the foregoing. The lithium element in the first lithium-containing binder can exist in the form of ions, can increase the number of lithium ions that move freely in the negative electrode film layer, can shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, can increase the deintercalation rate of lithium ions, and can improve the rapid charging performance of the battery cell.

[0288] Optionally, the mass content of the lithium element in the first lithium-containing binder is 3% to 10%, or 3% to 8%. Illustratively, the mass content of the 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 foregoing. When the mass content of the lithium element is in the foregoing range, the number of lithium ions that move freely in the negative electrode film layer can be relatively large, the distance of lithium ion diffusion to the surface of the negative electrode film layer can be further shortened, the deintercalation rate of lithium ions can be increased, and the rapid charging performance of the battery cell can be improved.

[0289] Illustratively, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer 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%. For example, the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0290] The lithium-containing binder of the foregoing material can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and not easily swell during the charging and discharging process, thereby improving the structural stability and the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0291] 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%. Illustratively, 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 foregoing. The lithium element in the second lithium-containing binder can exist in ionic form, which can increase the number of lithium ions that move freely 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 cell.

[0292] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0293] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, or 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 defined by any two of the foregoing. When the mass content of lithium element is within the foregoing range, the number of lithium ions that move freely 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 cell.

[0294] Illustratively, the second lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, which 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.

[0295] The lithium-containing binder described above can provide a certain number 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 thus improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0296] 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 include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0297] 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.

[0298] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0299] In some embodiments, the negative electrode film layer may optionally include 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.

[0300] In some embodiments, the negative electrode film layer may optionally include other additives. As examples, other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of other additives is ≤2% based on the total weight of the negative electrode film layer.

[0301] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one foil selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material layer may include at least one selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0302] In some embodiments, the thickness of the negative current collector is 4 μm to 6 μm. Illustratively, the thickness of the negative 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.

[0303] When the thickness of the negative current collector is within the above range, the overcurrent capacity of the negative current collector is excellent, and the battery cell has a high energy density.

[0304] In the embodiments of the present application, the thickness of the negative current collector has the meaning known in the art and can be detected by using the devices and methods known in the art, for example, using a solvent to wash off the film layer on the surface of the negative current collector, and measuring the thickness of the negative current collector with a micrometer.

[0305] The negative film layer is usually formed by coating a negative slurry on the negative current collector, drying, and cold pressing. The negative slurry is usually formed by dispersing the negative active material, the optional conductive agent, the optional binder, and other optional additives in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0306] The negative electrode sheet does not exclude other additional functional layers in addition to the negative film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further comprises a negative conductive layer disposed between the negative current collector and the negative film layer and arranged on the surface of the negative current collector. In some other embodiments, the negative electrode sheet of the embodiments of the present application further comprises a protective layer covering the surface of the negative film layer.

[0307] In some embodiments, the negative electrode sheet further comprises a negative conductive layer between the negative film layer and the negative current collector. 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 cell.

[0308] In some embodiments, the thickness of the negative conductive layer is 0.5 μm to 2 μm. Illustratively, the thickness of the negative 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.

[0309] When the thickness of the negative conductive layer is within the above range, the conductivity of the negative electrode sheet can be further improved, the heat generation of the negative electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved.

[0310] In the embodiments of the present application, the thickness of the negative conductive layer has the meaning known in the art and can be detected by using the devices and methods known in the art, and the test method of the negative conductive layer described above can be used.

[0311] 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, and 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.

[0312] In some embodiments, the negative electrode conductive layer can further optionally comprise other auxiliary agents. As an example, the other auxiliary agents can include thickening agents, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0313] 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 above values.

[0314] Illustratively, 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.

[0315] 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 above values.

[0316] Illustratively, the negative electrode binder comprises 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.

[0317] In some embodiments, the ratio CB of the capacity per unit area of the negative electrode film layer to the capacity per unit area of the positive electrode film layer in the battery cell is 1.05 to 1.30, which can be optionally 1.07 to 1.15. Illustratively, the ratio CB of the capacity per unit area of the negative electrode film layer to the capacity per unit area of the 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 above values.

[0318] When the ratio CB of the capacity per unit area of the negative electrode film layer to the capacity per unit area of the positive electrode film layer in the battery cell is within 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.

[0319] In the embodiments of the present application, the CB value is of the meaning known in the art and can be detected by using the devices and methods known in the art, for example, the capacity of the unit area of the negative electrode film layer and the capacity of the unit area of the positive electrode film layer are calculated respectively, and then the ratio of the two is calculated to obtain the CB value.

[0320] Specifically, taking the battery charging upper limit voltage of 3.65V and the battery discharging cut-off voltage of 2.0V as examples,

[0321] The capacity of the unit area of the positive electrode film layer refers to the actual de-lithiation 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-button 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-button battery is placed for 3h, the test is carried out at 25℃, and the capacity of the second cycle is taken as Y mAh. The actual battery design positive electrode sheet length is b mm, the width is c mm, and the number of positive electrode active material coated on the positive electrode current collector is d. Then the capacity of the unit area of the positive electrode film layer = Y / a*b*c*d.

[0322] 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-button battery of negative electrode-lithium sheet is assembled. The area of the negative electrode sheet used is f 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-button battery is placed for 3h, the test is carried out at 25℃, and the 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, and the number of negative electrode active material coated on the negative electrode current collector is d. Then the lithium intercalation capacity of the negative electrode = Z / f*h*i*d.

[0323] [Separation film]

[0324] In the embodiments of the present application, the separation film includes a base film with a porous structure.

[0325] In some embodiments, the base film comprises 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.

[0326] Optionally, the polyolefin comprises at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0327] In some embodiments, the porosity of the base film is 20% to 70%, and is optionally 35% to 60%. Illustratively, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range defined by any two of the foregoing.

[0328] When the porosity of the base 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.

[0329] 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 obtain more accurate test values, according to the differences in testing instruments, testing errors, and in order to eliminate the influence on the test of the porosity as much as possible.

[0330] In some embodiments, the thickness of the base film is 6 μm to 12 μm, and is optionally 6 μm to 9 μm. Illustratively, 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 defined by any two of the foregoing.

[0331] When the thickness of the base film is within 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.

[0332] 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.

[0333] In some embodiments, the functional layer includes a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer includes the first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer includes the composite particles, the composite particles include the second inorganic particles and the 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.

[0334] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separation film.

[0335] Optionally, the first functional layer can include a binder, optionally including at least one of a fluorine-containing binder or a polyacrylic acid binder, for example, polyvinylidene fluoride.

[0336] Optionally, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above-mentioned first inorganic particles can improve the heat resistance of the first functional layer.

[0337] In the embodiments of the present application, the thickness of the base film has the meaning known in the art, which can be detected by using the meaning and equipment known in the art, for example, a newly prepared separation 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 is about 0% SOC) is disassembled in reverse, the separation film is obtained from the battery cell, and the separation film is dried and taken as a sample, the separation film is cut off by using an ion beam cutting instrument to form a cross section, and then the thickness of the cross section of the separation film and each layer thereof is measured by using a scanning electron microscope.

[0338] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers, for example, the non-fluoropolymer particles include an acrylate copolymer, optionally, the acrylate copolymer includes an acrylate-acrylonitrile-acrylamide-propylene copolymer, the acrylate copolymer has excellent bonding performance, and has high bonding stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, for example, the molar ratio is 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0339] The second inorganic particles in the composite particles make it difficult for the non-fluoropolymer particles to adhere to each other due to high-temperature treatment in the granulation process, so that the composite particles have pores, which is beneficial to the transmission of lithium ions, improves the ion conductivity of the isolation film, and the second inorganic particles can also improve the compression modulus of the composite particles. In the charging and discharging process, the composite particles are less likely to deform, making the structure of the isolation film more stable, which can improve the kinetic performance of the battery monomer and improve the rapid charging performance. Optionally, compared with the first functional layer, the second functional layer is arranged close to the negative electrode plate. Due to the fact that the composite particles are less likely to deform, the isolation film is less likely to cause side effects such as extrusion to the negative electrode plate, so that the kinetic performance of the negative electrode plate is stable. Correspondingly, the first functional layer is arranged close to the positive electrode plate.

[0340] 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 form composite particles with non-fluoropolymers, further improving the cycle stability and kinetic performance of the isolation film, and improving the cycle performance and rapid charging performance of the battery monomer.

[0341] 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 composed of any two of the above values. When the average particle size of the second inorganic particles is in the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0342] 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 devices and methods known in the art. For example, after obtaining the isolation film, the isolation film is dried as a sample, the isolation film is cut off using 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 using a scanning electron microscope. The particle sizes of a plurality of, for example, 50, second inorganic particles are measured, and the average value thereof is calculated as the average particle size of the second inorganic particles.

[0343] In some embodiments, the ion conductivity of the separator film is 0.3 mS / cm to 0.6 mS / cm. Exemplarily, the ion conductivity of the separator 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 between any two of the above values.

[0344] When the ion conductivity of the separator film is in the above range, the migration ability of lithium ions of the separator film can be further improved, and the rapid charging performance of the battery cell can be improved.

[0345] In the embodiments of the present application, the ion conductivity of the separator film is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example,

[0346] Preparation of 2025 type button cell for testing: in a vacuum glove box, lithium sheet was put into the negative electrode shell, 150 μL of electrolyte was added, the electrolyte was a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then the separator film (area of 3.14 cm 2 , thickness of 12 μm) was put to make it close to the lithium sheet, 25 μL of electrolyte was added, and finally the positive electrode sheet (the positive electrode sheet can be the positive electrode sheet in Example 1) was placed thereon, and then it 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.

[0347] Test: in an electrochemical workstation, the resistance of the separator film Rb was tested at a frequency range of 10 -1 ~ 10 6 Hz, and the ion conductivity σ (unit: mS / cm) was calculated by the following formula,

[0348] σ = L / (R b × S)

[0349] 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.

[0350] [Electrolyte]

[0351] In some embodiments, the battery cell further comprises an electrolyte.

[0352] During the charging and discharging process of the battery cell, active ions such as lithium 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.

[0353] In the embodiments of the present application, the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, which can be 15 mS / cm to 20 mS / cm. For example, the conductivity of the electrolyte at room temperature is 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm or a range formed by any two of the above values.

[0354] 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 cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0355] In the 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 referring to industry standard HG-T 4067-2015.

[0356] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. For example, 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.

[0357] 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 cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0358] In the 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 referring to GB / T 10247-2008.

[0359] 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. For example, 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.

[0360] 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.

[0361] 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.

[0362] 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.

[0363] 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 75%, 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.

[0364] 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.

[0365] In some embodiments, the chain carboxylate solvent includes a compound shown in Formula I,

[0366] In Formula I,

[0367] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group,

[0368] R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

[0369] The chain carboxylate solvent described above has a high conductivity, which is beneficial to improving the rapid charging capacity of the battery cell.

[0370] 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.

[0371] 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.

[0372] 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.

[0373] In each of the above embodiments, the halogenated alkyl group includes one or more of a fluorinated alkyl group, a chlorinated alkyl group, a brominated alkyl group, and an iodinated alkyl group, and optionally, the halogenated alkyl group includes a fluorinated alkyl group.

[0374] 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,

[0375] In some embodiments, the organic solvent further includes a carbonate solvent.

[0376] 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 above carbonate solvent and chain carboxylic acid ester solvent are used in combination, so that the conductivity of the electrolyte at room temperature is improved, which is beneficial to the migration of lithium ions.

[0377] 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 composed of any two of the above values. The above mass content of the carbonate solvent can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0378] 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%.

[0379] 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 for improving overcharge performance of the battery, an additive for improving high-temperature performance of the battery, an additive for improving low-temperature power performance of the battery, and the like.

[0380] In some embodiments, the additive comprises one or more, optionally at least two, of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The additive can improve the performance of the interface film on the positive electrode side and / or the negative electrode side, improve the rapid charging performance of the battery cell, and improve the cycle performance.

[0381] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. For example, the mass content of the additive in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range defined by any two of the above values.

[0382] The additive with the above mass content can effectively improve the performance of the interface film on the positive electrode side and / or the negative electrode side, improve the rapid charging performance of the battery cell, and improve the cycle performance.

[0383] For example, the carbonate additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0384] For example, the sulfur-containing additive comprises one or more of vinyl sulfite DTD, bis vinyl sulfite 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methyl methylene disulfite MMDS.

[0385] Optionally, 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.

[0386] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, and optionally 2% to 6%.

[0387] Optionally, the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%, and optionally 0.5% to 3%.

[0388] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, and the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%.

[0389] Further optionally, the mass content of the vinylene carbonate VC in the electrolyte is 2% to 6%, and the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.5% to 3%.

[0390] In some embodiments, the electrolyte salt includes a lithium salt, which includes one or more of fluorosulfonylimide salts and lithium hexafluorophosphate (LiPF6). These lithium salts are readily dissociated, facilitating rapid lithium-ion migration, and the electrolyte system is relatively stable and not easily decomposed, thus improving the cycle performance of the battery cells.

[0391] Optionally, the fluorosulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide (LiFSI) and lithium bistrifluoromethanesulfonate (LiTFSI).

[0392] Optionally, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6), wherein the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is from 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is from 0.5 mol / L to 1.0 mol / L.

[0393] For example, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.4 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.7 mol / L.

[0394] For example, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L.

[0395] For example, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.8 mol / L.

[0396] Optionally, the molar ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate (LiPF6) is from 0.2 to 1.0, and optionally from 0.2 to 0.5. Exemplarily, the molar ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate (LiPF6) is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range of any two of the above values.

[0397] In the embodiments of this application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte are well-known in the art and can be detected using well-known equipment and methods. For example, the concentrations of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography using the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography analysis.

[0398] 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.

[0399] 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.

[0400] 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.

[0401] 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.

[0402] 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.

[0403] 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, GB / T 31486-2015 "Performance requirements and test methods for power storage batteries for electric vehicles" can be used for illustration, taking the battery charging upper limit voltage as 3.65 V and the battery discharging cutoff voltage as 2.0 V.

[0404] At 25°C, the battery cell is charged to 3.65V at 0.33C, then charged to 0.05C at constant voltage, and discharged to 2.0V at 0.33C, 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, and the free electrolyte is placed 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 that contribute to M0), then all the components of the battery cell are weighed again 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.

[0405] In some embodiments, the positive electrode sheet, the separator and the negative electrode sheet can be made into an electrode assembly by a winding process and / or a stacking process.

[0406] FIGS. 1 and 2 show a structural schematic diagram of a battery cell.

[0407] In some embodiments, the battery cell 7 can include a shell 20.

[0408] 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).

[0409] The shell 20 is a hollow structure, which can be used to package the electrode assembly 10 and the electrolyte described above.

[0410] 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, 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, the negative electrode sheet can be formed into an electrode assembly 10 by 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.

[0411] In some embodiments, 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.

[0412] 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, and 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.

[0413] In some embodiments, the material of the shell 21 includes steel, which has high mechanical strength and is not easy to deform, thereby improving the use reliability and cycle performance of the battery monomer.

[0414] Optionally, the thickness of the shell 21 is 0.1 mm to 0.5 mm, and can be 0.2 mm to 0.35 mm. For example, the thickness of the shell 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or a range formed by any two of the above values. When the thickness of the shell 21 is in the above range, the shell 21 has high mechanical strength, 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.

[0415] From the appearance of the electrode assembly 10, the electrode assembly 10 includes a main body part 12, a first tab 111 and a second tab 112, and the first tab 111 and the second tab 112 protrude from the main body part 12. The first tab 111 is a part of the first tab that is not coated with an active material layer, and the second tab 112 is a part of the second tab that is not coated with an active material layer. The first tab 111 and the second tab 112 are used to lead out the current in the main body part 12. The polarities of the first tab and the second tab are opposite, that is, one of the first tab and the second tab is a positive electrode tab, and the other of the first tab and the second tab is a negative electrode tab. Of course, the first tab 111 can be a positive electrode tab, and the second tab 112 can be a negative electrode tab.

[0416] Taking the first tab 111 as a negative electrode tab and the second tab 112 as a positive electrode tab as an example, the part of the negative electrode current collector in the negative electrode tab that is not coated with an active material layer is the negative electrode tab, and the active material coated on the negative electrode current collector in the negative electrode tab forms a negative electrode film layer, and the negative electrode film layer and the negative electrode current collector coated with the active material are part of the main body part 12. The part of the positive electrode current collector in the positive electrode tab that is not coated with an active material layer is the positive electrode tab, and the active material coated on the positive electrode current collector in the positive electrode tab forms a positive electrode film layer, and the positive electrode film layer and the positive electrode current collector coated with the active material are part of the main body part 12.

[0417] The first tab 111 and the second tab 112 can protrude from the same side of the main body part 12, or can respectively extend from opposite sides.

[0418] Optionally, the number of the first tabs 111 located on the same side of the main body part 12 is at least one, and can be at least two. The at least two first tabs 111 can increase the flow capacity of the first tab 111.

[0419] Optionally, the number of the second tabs 112 located on the same side of the main body 12 is at least one, and optionally at least two. The at least two second tabs 112 can increase the current carrying capacity of the second tabs 112.

[0420] In some embodiments, the battery cell 7 further comprises a first electrode terminal 31 electrically connected with the first tab 111. Optionally, the first electrode terminal 31 and the first tab 111 are welded, and the first electrode terminal 31 and the first tab 111 can be connected through a connector or without a connector. Optionally, the first electrode terminal 31 and the first tab 111 are directly welded without a connector, which can reduce the resistance at the connection and is conducive to reducing the overall internal resistance of the battery cell 7.

[0421] When the first tab 111 is a negative tab, the first electrode terminal 31 is a negative terminal. When the first tab 111 is a positive tab, the first electrode terminal 31 is a positive terminal.

[0422] In some embodiments, the battery cell 7 further comprises a second electrode terminal 32 electrically connected with the second tab 112. Optionally, the second electrode terminal 32 and the second tab 112 are welded, and the second electrode terminal 32 and the second tab 112 can be connected through a connector or without a connector. Optionally, the second electrode terminal 32 and the second tab 112 are directly welded without a connector, which can reduce the resistance at the connection and is conducive to reducing the overall internal resistance of the battery cell 7.

[0423] When the second tab 112 is a negative tab, the second electrode terminal 32 is a negative terminal. When the second tab 112 is a positive tab, the second electrode terminal 32 is a positive terminal.

[0424] Optionally, the number of the first electrode terminals 31 located on the same side of the main body 12 is at least one, and optionally at least two. The at least two first electrode terminals 31 can increase the current carrying capacity of the first electrode terminals 31.

[0425] Further optionally, the current carrying area of the single-side first electrode terminal 31 is 150mm 2 to 1000mm 2 , and optionally 200mm 2 to 1000mm 2 The current carrying area of the single-side first electrode terminal 31 refers to the sum of the current carrying areas of all the first electrode terminals 31 located on the same side of the main body 12. The current carrying area of the first electrode terminal 31 can be understood as the cross-sectional area of the first electrode terminal 31, which is perpendicular to the thickness direction of the end cover 22.

[0426] Exemplarily, the overcurrent area of the single-side first electrode 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.

[0427] Optionally, the number of the second electrode terminals 32 located at the same side of the main body part 12 is at least one, and can be at least two. The at least two second electrode terminals 32 can increase the overcurrent capacity of the second electrode terminals 32.

[0428] Further optionally, the overcurrent area of the single-side second electrode terminal 32 is 150mm 2 to 1000mm 2 , and can be 200mm 2 to 1000mm 2 . The overcurrent area of the single-side second electrode terminal 32 refers to the sum of the overcurrent areas of all the second electrode terminals 32 located at the same side of the main body part 12. The overcurrent area of the second electrode terminal 32 can be understood as the cross-sectional area of the second electrode terminal 32, which is perpendicular to the thickness direction of the end cover 22.

[0429] Exemplarily, the overcurrent area of the single-side second electrode terminal 32 can be 150mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2, 380 mm 2 , 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 , 850 mm 2 , 900 mm 2 , 950 mm 2 , 1000 mm 2 or a range between any two of the above values.

[0430] 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.

[0431] 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, and are 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.

[0432] As shown in FIG. 4, 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.

[0433] 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 forms a closed space for accommodating the battery module 6. The multiple battery modules 6 can be arranged in the box 5 in any manner.

[0434] 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-shaped 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 part 5b can be various shapes, such as a cylinder, a cuboid, etc.

[0435] 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 be arranged between the first box part 5a and the second box part 5b.

[0436] 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.

[0437] 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 30°C.

[0438] 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 SOC to 80% state of charge SOC, the temperature of the external environment where the battery pack 2 is located is 30°C.

[0439] 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, such as 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.

[0440] 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 charging rate can be any value between 5C to 10C, each charging step corresponding charging rate 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.

[0441] 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 of any charging step from 10% state of charge to 40% state of charge, and the charging rate of the step charging to 80% state of charge is any value between 2.5C to 5C, for example, it can be 2.7C.

[0442] Exemplarily, the charging steps from 10% to 80% of the battery pack 2 or any battery cell constituting the battery pack 2 can be performed as follows:

[0443] charging from 10% SOC to 15% SOC at 5.0C constant current,

[0444] charging from 15% SOC to 20% SOC at 5.0C constant current,

[0445] charging from 20% SOC to 25% SOC at 5.0C constant current,

[0446] charging from 25% SOC to 30% SOC at 5.0C constant current,

[0447] charging from 30% SOC to 35% SOC at 5.0C constant current,

[0448] charging from 35% SOC to 40% SOC at 5.0C constant current,

[0449] charging from 40% SOC to 45% SOC at 4.6C constant current,

[0450] charging from 45% SOC to 50% SOC at 4.3C constant current,

[0451] charging from 50% SOC to 55% SOC at 4.0C constant current,

[0452] charging from 55% SOC to 60% SOC at 3.7C constant current,

[0453] charging from 60% SOC to 65% SOC at 3.4C constant current,

[0454] charging from 65% SOC to 70% SOC at 3.1C constant current,

[0455] Charge from 70% SOC to 75% SOC at 2.9C constant current,

[0456] Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0457] 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 10.5 min, optionally 5 min to 10.5 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. Illustratively, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 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.

[0458] In some embodiments, the volumetric energy density of the battery cell is 390 Wh / L to 500 Wh / L, optionally 410 Wh / L to 470 Wh / L. Illustratively, the volumetric energy density of the battery cell is 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, 480 Wh / L, 490 Wh / L, 500 Wh / L, or a range consisting of any two of the above values. The volumetric energy density of the battery cell is higher.

[0459] 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,

[0460] The battery cell is placed at 25°C, charged to 3.65V at 0.33C constant current, then charged at constant voltage to 0.05C, discharged to 2.0V at 0.33C constant current, and the discharge capacity A0 at this time is recorded, unit: Ah. The length, width and height of the battery cell are measured by using a caliper (generally calculated by the size of the shell of the battery, excluding the height of the electrode terminal, and excluding the insulating film outside the shell), and the volume V0 of the battery cell is calculated, unit: L. The volumetric energy density VED of the battery cell is (A0 x discharge platform voltage) / V0, unit: Wh / L.

[0461] Electric device

[0462] The second aspect of the embodiments of the present application provides a power consuming device comprising the battery device of the embodiments of the present application, such as a battery cell, a battery module or a battery pack. The battery cell, the battery module or the battery pack can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel car, a gas car or a new energy car, the new energy car can be a pure electric car, a hybrid electric car or a range extended electric car, etc., the spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc., the electric toy includes a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy and an electric airplane toy, etc., the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer, etc. The embodiments of the present application do not specially limit the above power consuming device.

[0463] The power consuming device can select a battery cell, a battery module or a battery pack according to its use requirement.

[0464] FIG. 5 is a schematic diagram of a power consuming device 1 as an example. The power consuming device 1 is a pure electric car, a hybrid electric car or a plug-in hybrid electric car, etc. In order to meet the requirement of high power and high energy density of the power consuming device 1, a battery pack or a battery module can be used.

[0465] The power consuming device 1 is internally provided with a battery pack 2, which can be arranged at the bottom, the head or the tail of the power consuming device 1. The battery pack 2 can be used for power supply of the power consuming device 1, for example, the battery pack 2 can be used as an operating power source of the power consuming device 1, and can also be used as a driving power source of the power consuming device 1, instead of or partially instead of fuel or natural gas to provide driving power for the power consuming device 1.

[0466] The power consuming device 1 can further include a controller 3 and a motor 4, the controller 3 is used to control the battery pack 2 to supply power to the motor 4, for example, for the working power requirement of the power consuming device 1 during starting, navigation and running.

[0467] The power consuming device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power consuming device usually requires thinning, and a battery cell can be used as a power source.

[0468] The charging process of the power consuming device can select the following charging mode:

[0469] charging from 10% SOC to 15% SOC at 5.0C constant current,

[0470] Charge from 20% SOC to 25% SOC at 5.0 C constant current,

[0471] Charge from 20% SOC to 25% SOC at 5.0 C constant current,

[0472] Charge from 25% SOC to 30% SOC at 5.0 C constant current,

[0473] Charge from 30% SOC to 35% SOC at 5.0 C constant current,

[0474] Charge from 35% SOC to 40% SOC at 5.0 C constant current,

[0475] Charge from 40% SOC to 45% SOC at 4.6 C constant current,

[0476] Charge from 45% SOC to 50% SOC at 4.3 C constant current,

[0477] Charge from 50% SOC to 55% SOC at 4.0 C constant current,

[0478] Charge from 55% SOC to 60% SOC at 3.7 C constant current,

[0479] Charge from 60% SOC to 65% SOC at 3.4 C constant current,

[0480] Charge from 65% SOC to 70% SOC at 3.1 C constant current,

[0481] Charge from 70% SOC to 75% SOC at 2.9 C constant current,

[0482] Charge from 75% SOC to 80% SOC at 2.7 C constant current.

[0483] In some embodiments, the charging time of the electrical device from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, optionally 5 min to 10.5 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. Illustratively, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 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.

[0484] Embodiments

[0485] The present application will be described in more detail by the following examples which are intended to be illustrative only and should not be considered limiting in any way. Unless otherwise indicated, all parts, percentages and ratios reported herein are on a mass basis and all reagents used in the examples are commercially available or synthesized according to conventional methods and used without further purification, and the instruments used in the examples are commercially available.

[0486] Example 1

[0487] 1. Preparation of positive electrode sheet

[0488] The positive electrode sheet comprises a positive current collector, a positive conductive layer on the positive current collector, and a positive film layer. The positive current collector is an aluminum foil with a thickness of 10 μm.

[0489] The positive conductive layer on the positive current collector is a film layer formed by uniformly mixing a positive conductive agent, super carbon, and a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and then coating the mixture on the surface of the current collector and drying. The thickness of the positive conductive layer is 1 μm, the mass content of the positive conductive agent in the positive conductive layer is 40%, and the mass content of the positive binder is 60%.

[0490] The positive film layer comprises a film layer formed by uniformly coating a positive slurry (with N-methyl pyrrolidone (NMP) as the solvent) on the surface of the positive conductive layer, and then drying and cold pressing. The positive film layer comprises a positive active material, a binder, polyvinylidene fluoride (PVDF), and a conductive agent, acetylene black, in a weight ratio of 97:2:1.

[0491] The positive active material comprises lithium iron phosphate and a coating layer. The coating layer is coated on the surface of the lithium iron phosphate and comprises lithium titanium iron phosphate, Li2FeTi(PO4)3, and amorphous carbon. The Dv50 of the positive active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0492] The single-sided coating weight of the positive film layer is 300 mg / 1540.25 mm 2 .

[0493] 2. Preparation of negative electrode sheet

[0494] The negative electrode sheet comprises 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 with a thickness of 5 μm.

[0495] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing the negative electrode conductive agent super-conductive carbon, the negative electrode binder styrene butadiene rubber SBR, the thickening agent sodium carboxymethyl cellulose (CMC-Na) and the solvent water, and then coating on the surface of the negative electrode current collector and drying, the thickness of the film layer is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickening agent in the negative electrode conductive layer is 5%.

[0496] The negative electrode film layer includes a film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, and then drying and cold pressing.

[0497] The single-side coating weight of the negative electrode film layer is 138 mg / 1540.25 mm 2 .

[0498] 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 located on the surface of the negative electrode conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0499] The first negative electrode film layer includes graphite particles, a conductive agent acetylene black, a first 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%), a negative electrode binder styrene butadiene rubber and a thickening agent sodium carboxymethyl cellulose, the mass content of lithium element 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, and the mass content of the carbon coating layer is 3.5%.

[0500] The second negative electrode film layer includes graphite particles, a 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%), a negative electrode binder styrene butadiene rubber and a 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, the graphite particles include 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%.

[0501] 3, separator film

[0502] The separator film includes a base film, and the base film is a polyethylene film layer with a thickness of 7 μm and a porosity of 42%.

[0503] 4. Preparation of electrolyte

[0504] The electrolyte comprises an organic solvent, a lithium salt and an additive.

[0505] The organic solvent comprises 60% of a chain carboxylate solvent (ethyl acetate) and 40% of a carbonate solvent (30% of ethylene carbonate EC, 10% of dimethyl carbonate).

[0506] The additive has a mass content of 6.5% based on the mass of the electrolyte, and 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.

[0507] The lithium salt comprises 1 mol / L of lithium hexafluorophosphate LiPF6.

[0508] The electrolyte has an electrical conductivity of 16.4 mS / cm at room temperature.

[0509] 5. Preparation of battery cell

[0510] The above positive electrode sheet, separator and negative electrode sheet are stacked in order with the separator between the positive electrode sheet and the negative electrode sheet to play a separating role, to obtain an electrode assembly, the electrode assembly is placed in an outer packaging shell, electrolyte is injected after drying, and the battery cell is obtained after vacuum packaging, standing, formation, shaping and other processes, the compaction density of the positive electrode film layer of the battery cell is 2.72 g / cm3 at 100% SOC, and the compaction density of the negative electrode film layer is 1.26 g / cm3 at 100% SOC. 3 3 .

[0511] Comparative Example 1

[0512] A battery cell is prepared by a method similar to that of Example 1, except that the mass content of carbon element in the positive electrode active material is adjusted to adjust the resistance of the positive electrode sheet.

[0513] Comparative Example 2

[0514] A battery cell is prepared by a method similar to that of Example 1, except that the mass content of the carbon coating layer in the negative electrode active material is adjusted to adjust the resistance of the negative electrode sheet.

[0515] Examples 2-1 to 2-4

[0516] A battery cell is prepared by a method similar to that of Example 1, except that the mass content of carbon element in the positive electrode active material is adjusted to adjust the resistance of the positive electrode sheet.

[0517] ​Example 2-5 and Example 2-6

[0518] The battery cell was prepared by a similar method to Example 1, except that the mass content of the carbon-coated layer in the negative active material was adjusted to adjust the resistance of the negative electrode sheet.

[0519] Example 3-1 and Example 3-2

[0520] The battery cell was prepared by a similar method to Example 1, except that the thickness of the separator film was adjusted.

[0521] Example 3-3 to Example 3-4

[0522] The battery cell was prepared by a similar method to Example 1, except that the porosity of the separator film was adjusted.

[0523] Performance test

[0524] 1. The charging time of the battery cell from 10% SOC to 80% SOC, specifically using the following charging steps,

[0525] Charging from 10% SOC of the battery at 30°C,

[0526] Charging from 10% SOC to 15% SOC at 5.0C constant current,

[0527] Charging from 15% SOC to 20% SOC at 5.0C constant current,

[0528] Charging from 20% SOC to 25% SOC at 5.0C constant current,

[0529] Charging from 25% SOC to 30% SOC at 5.0C constant current,

[0530] Charging from 30% SOC to 35% SOC at 5.0C constant current,

[0531] Charging from 35% SOC to 40% SOC at 5.0C constant current,

[0532] Charging from 40% SOC to 45% SOC at 4.6C constant current,

[0533] Charging from 45% SOC to 50% SOC at 4.3C constant current,

[0534] Charging from 50% SOC to 55% SOC at 4.0C constant current,

[0535] Charging from 55% SOC to 60% SOC at 3.7C constant current,

[0536] Charge from 60% SOC to 65% SOC at 3.4C constant current,

[0537] Charge from 65% SOC to 70% SOC at 3.1C constant current,

[0538] Charge from 70% SOC to 75% SOC at 2.9C constant current,

[0539] Charge from 75% SOC to 80% SOC at 2.7C constant current,

[0540] Record the total charging time.

[0541] 2. DC internal resistance (DCR) test of the battery cell

[0542] The method in GB / T 31467 Performance test specification for high power lithium-ion traction battery for HEV can be referred to.

[0543] For example, at room temperature, charge the battery cell to 3.65V at a constant current of 0.33C, stand for 1 min, then charge to 3.65V at a constant current of 0.1C, stand for 30 min, discharge to 2.0V at a constant current of 0.33C, record the discharge capacity A0 at this time, in Ah, then charge 0.5A0 Ah at a constant current of 0.33C, and adjust the SOC to 50%.

[0544] After the battery cell is placed at -20℃ for 2h, discharge at a constant current of 4C for 10s, and record ΔU 放电 , ΔI 放 电 The discharge DCR data of the lithium ion battery is calculated by the following formula, R 放电 = ΔU 放电 / ΔI 放电 ,

[0545] Wherein, ΔU 放电 represents the voltage change within 10s at the beginning of discharge, and ΔI 放电 represents the current value within 10s at the beginning of discharge.

[0546] 3. Cycle number of the battery cell to 80% SOH

[0547] At room temperature, charge the battery cell to the charge cut-off voltage 3.65V at a constant current of 1C, then discharge to 2.0V at a constant current of 1C, which is one charge-discharge cycle, repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e. Cn / C0x100%) is 80%, and record the cycle number. The more the cycle number is, the better the cycle performance of the battery cell is.

[0548] The test results are shown in Table 1.

[0549] Table 1

[0550] In Table 1,

[0551] The mass content of carbon elements on the surface of the positive active material in Comparative Example 1 is relatively low, so that the conductivity of the positive active material is relatively poor, and the internal resistance of the positive electrode sheet is large.

[0552] The mass content of amorphous carbon on the surface of the graphite particles in Comparative Example 2 is relatively low, so that the conductivity of the graphite particles is relatively poor, and the internal resistance of the negative electrode sheet is large.

[0553] In the case of large internal resistance of Comparative Example 1 and Comparative Example 2, it is not conducive to the rapid charging of the battery cell, and the DCR of the battery cell is high, the battery cell is more prone to heat, so that the electrolyte system is unstable, the organic solvent is easy to volatilize, leading to the internal pressure of the battery cell rising, which is not conducive to the cycle.

[0554] The resistance of the positive electrode sheet in the embodiment of the application is 0.1 Ω to 30 Ω, which can be selected as 0.1 Ω to 25 Ω, and can be selected as 0.1 Ω to 5 Ω. The resistance of the negative electrode sheet is 0.001 Ω to 0.01 Ω, which can be selected as 0.001 Ω to 0.005 Ω, and can be selected as 0.001 Ω to 0.004 Ω. The resistance of the positive electrode sheet and the resistance of the negative electrode sheet are controlled within a reasonable range, so that the DCR of the battery cell is relatively low, the battery cell produces less heat, so that the electrolyte system is relatively stable, the organic solvent is not easy to volatilize, and it is beneficial to improve the cycle performance.

[0555] In Examples 3-1 to 3-4, by adjusting the porosity or thickness of the base film in the separator film, the porosity of the base film is 20% to 70%, which can be selected as 35% to 60%, and the thickness of the base film is 6 μm to 12 μm, which can be selected as 6 μm to 9 μm. In this case, the migration ability of lithium ions in the separator film is strong, which is conducive to rapid charging, and can reduce the internal resistance of the battery cell, thereby reducing heat generation, and is beneficial to improve the cycle performance.

[0556] Comparative Examples 3 and 4

[0557] The battery cell is prepared by a method similar to that of Example 1, and the composition of the organic solvent in the electrolyte is adjusted.

[0558] Examples 4-1 to 4-3

[0559] The battery cell is prepared by a method similar to that of Example 1, and the composition of the organic solvent in the electrolyte is adjusted.

[0560] In Example 4-1,

[0561] The single-side coating weight of the positive film layer is 231 mg / 1540.25 mm 22.72 g / cm3 at 100% SOC 3 ,

[0562] The single-side coating weight of the negative film layer was 110 mg / 1540.25 mm 2 2.72 g / cm3 at 100% SOC 3 ,

[0563] The composition of the organic solvent in the electrolyte was adjusted.

[0564] In Example 4-2,

[0565] The single-side coating weight of the positive film layer was 258 mg / 1540.25 mm 2 2.72 g / cm3 at 100% SOC 3 ,

[0566] The single-side coating weight of the negative film layer was 123 mg / 1540.25 mm 2 1.21 g / cm3 at 100% SOC 3 ,

[0567] The composition of the organic solvent in the electrolyte was adjusted.

[0568] In Example 4-3,

[0569] The single-side coating weight of the positive film layer was 300 mg / 1540.25 mm 2 2.72 g / cm3 at 100% SOC 3 ,

[0570] The single-side coating weight of the negative film layer was 138 mg / 1540.25 mm 2 1.26 g / cm3 at 100% SOC 3 ,

[0571] The composition of the organic solvent in the electrolyte was adjusted.

[0572] The performance test procedure was the same as before, and is not repeated here. The test results are shown in Table 2.

[0573] Table 2

[0574] In Table 2,

[0575] The mass content of ethylene carbonate in the carbonate solvent in Comparative Example 3, Example 4-1 and Example 4-2 was 30%, and the remainder was dimethyl carbonate.

[0576] The conductivity of the electrolyte in Comparative Example 3 is too small, and even if the positive and negative electrode sheet resistances are set within a reasonable range, it is difficult for lithium ions to migrate, the charging capacity of the electrolyte is insufficient, and cycle diving is likely to occur.

[0577] The conductivity of the electrolyte in Comparative Example 4 is too high, and the proportion of low-boiling-point organic solvents is high, which is prone to volatilize during the cycle process, causing the internal pressure of the battery cell to increase and the cycle to deteriorate.

[0578] In Examples 4-1 to 4-3, by setting the positive and negative electrode sheet resistances within a reasonable range, and setting the conductivity of the electrolyte to 13 mS / cm to 20 mS / cm, which can be selected as 15 mS / cm to 20 mS / cm, the migration rate of lithium ions is relatively fast, which is conducive to fast charging, and the electrolyte system is stable, which can improve the cycle performance of the battery cell. Through Examples 4-1 to 4-3, in the case of relatively low conductivity of the electrolyte, further cooperating with the smaller compaction density and / or coating weight of the positive electrode film layer, and / or the smaller compaction density and / or coating weight of the negative electrode film layer, is conducive to fast charging.

[0579] Example 5

[0580] The battery cell is prepared by a method similar to that of Example 1, except that

[0581] The preparation of the positive electrode sheet includes:

[0582] The positive electrode sheet includes a positive electrode current collector, a positive electrode conductive layer on the positive electrode current collector, a positive electrode lithium supplement layer, and a positive electrode film layer. The positive electrode current collector is an aluminum foil with a thickness of 10 μm. The positive electrode conductive layer on the positive electrode current collector is a film layer formed by uniformly mixing a positive electrode conductive agent, superconducting carbon, and a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and coating on the surface of the current collector. The thickness of the positive electrode conductive layer is 1 μm. 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%.

[0583] The positive electrode lithium supplement layer is a film layer formed by uniformly mixing lithium phosphate, a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and coating on the surface of the positive electrode conductive layer. The thickness of the positive electrode lithium supplement layer is 0.5 μm. The mass content of lithium phosphate in the positive electrode lithium supplement layer is 80%.

[0584] 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 lithium supplement 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.

[0585] 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.

[0586] Example 6

[0587] The battery cell is prepared by using a method similar to that of Example 1, and different from Example 1,

[0588] The preparation of the negative electrode tab includes:

[0589] The negative electrode tab includes a negative electrode current collector, a negative electrode conductive layer on the negative electrode current collector, and a negative electrode film layer, the negative electrode current collector is a copper foil with a thickness of 5 μm, the negative electrode conductive layer on the negative electrode current collector is formed by uniformly mixing a negative electrode conductive agent, a negative electrode binder, a thickening agent, and a solvent, and then coating the mixture on the surface of the negative electrode current collector, the thickness of the negative electrode conductive layer is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickening agent in the negative electrode conductive layer is 5%.

[0590] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, and then drying and cold pressing.

[0591] 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 located on the surface of the negative electrode conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0592] The first negative electrode film layer includes a negative electrode active material, a conductive agent, a first lithium-containing binder, a negative electrode binder, and a thickening agent, the mass ratio of the negative electrode active material, the conductive agent, the first lithium-containing binder, the negative electrode binder, and the thickening agent is 96.5:0.5:0.5:1.5:1, the mass content of lithium in the first lithium-containing binder is 4.8%, the negative electrode active material includes graphite particles and a silicon oxide compound, the mass content of silicon in the negative electrode active material is 1.5%, the Dv50 of the graphite particles is 11.6 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, and the mass content of amorphous carbon is 3.5%.

[0593] The second negative electrode film layer comprises a negative electrode active material, a conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer), a negative electrode binder styrene butadiene rubber, and a thickening agent sodium carboxymethyl cellulose, the mass content of lithium in the second lithium-containing binder is 4.8%, the negative electrode active material comprises graphite particles and silicon oxide compounds, the mass content of silicon in the silicon oxide compounds in the negative electrode active material is 1.5%, the Dv50 of the graphite particles is 11.6 μm, 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 amorphous carbon is 3.5%.

[0594] The performance test steps are the same as described above, and will not be repeated here, and the test results are shown in Table 3.

[0595] Table 3

[0596] In Example 5, the lithium supplement is added to the positive electrode tab, which can compensate for the loss of lithium in the battery system and increase the cycle life.

[0597] In Example 6, the silicon-based material is added to the negative electrode tab, which is beneficial to improve the energy density of the battery monomer and can maintain excellent fast charging performance and cycle performance.

[0598] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as a limitation of the present application, and changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell, comprising an electrode assembly, an electrolyte, and a housing, wherein the electrode assembly and the electrolyte are housed within the housing, the electrode assembly comprising a positive electrode, a negative electrode, and a separator, the separator being located between the positive electrode and the 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. The positive electrode film layer includes a positive electrode active material, which includes a lithium phosphate with an olivine structure. The resistance of the positive electrode is from 0.1Ω to 30Ω. The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, and the resistance of the negative electrode sheet is 0.001Ω to 0.01Ω. The electrolyte includes an organic solvent, which includes chain carboxylic acid ester solvents, and the electrolyte has a conductivity of 13 mS / cm to 20 mS / cm at room temperature.

2. The battery cell according to claim 1, wherein, The electrolyte has a conductivity of 15 mS / cm to 20 mS / cm at room temperature.

3. The battery cell according to claim 1 or 2, wherein, The resistance of the positive electrode is 0.1Ω to 5Ω.

4. The battery cell according to claim 3, wherein, The resistance of the positive electrode is 0.1Ω to 1Ω.

5. The battery cell according to any one of claims 1 to 4, wherein, The resistance of the negative electrode is 0.001Ω to 0.005Ω.

6. The battery cell according to any one of claims 1 to 5, wherein, The electrolyte has a viscosity of 2.3 mPa·s to 3.5 mPa·s at room temperature.

7. The battery cell according to any one of claims 1 to 6, wherein, The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature.

8. The battery cell according to any one of claims 1 to 7, 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 .

9. The battery cell according to any one of claims 1 to 8, wherein, When the battery cell is 100% charged, the compaction density of the positive electrode film is 2.55 g / cm³. 3 Up to 2.70 g / cm 3 , and / or The single-sided coating weight of the positive electrode film is 240 mg / 1540.25 mm. 2 Up to 330mg / 1540.25mm 2 .

10. 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 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 .

11. The battery cell according to any one of claims 1 to 10, wherein, When the battery cell is 100% charged, the compaction density of the negative electrode film is 1.25 g / cm³. 3 Up to 1.36 g / cm 3 , and / or The single-sided coating weight of the negative electrode film is 110 mg / 1540.25 mm. 2 Up to 150mg / 1540.25mm 2 .

12. The battery cell according to any one of claims 1 to 11, wherein, The resistivity of the positive electrode active material powder is from 1 Ω·cm to 27.5 Ω·cm.

13. The battery cell according to any one of claims 1 to 12, 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 .

14. The battery cell according to any one of claims 1 to 13, wherein, The positive electrode active material has a charging capacity of 150 mAh / g to 170 mAh / g at a 0.1C rate.

15. The battery cell according to any one of claims 1 to 14, wherein, The resistivity of the negative electrode active material powder is from 0.005 Ω·cm to 0.043 Ω·cm.

16. The battery cell according to any one of claims 1 to 15, 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 .

17. The battery cell according to any one of claims 1 to 16, wherein, The specific capacity of the negative electrode active material at a 0.1C rate is 350mAh / g to 480mAh / g.

18. The battery cell according to any one of claims 1 to 17, 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.

19. The battery cell according to claim 18, 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.

20. The battery cell according to claim 18 or 19, 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.

21. The battery cell according to any one of claims 18 to 20, wherein, The degree of graphitization of the lithium phosphate with the olivine structure is 0.15 to 0.

32.

22. The battery cell according to claim 21, wherein, The degree of graphitization of the lithium phosphate with the olivine structure is 0.19 to 0.

26.

23. The battery cell according to any one of claims 18 to 22, 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.

24. The battery cell according to claim 23, wherein, The specific surface area of ​​the lithium phosphate with the olivine structure is 7.5 m². 2 / g to 14m 2 / g.

25. The battery cell according to any one of claims 1 to 24, wherein, The lithium phosphate with the olivine structure is granular, and its volume distribution particle size satisfies: 1μm≤Dv50≤2μm, 0.4μm≤Dv10≤0.7μm.

26. The battery cell according to any one of claims 1 to 25, 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.

27. The battery cell according to any one of claims 1 to 26, 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.

28. The battery cell according to any one of claims 1 to 27, wherein, The thickness of the positive current collector is 10 μm to 15 μm.

29. The battery cell according to any one of claims 1 to 28, 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.

30. The battery cell according to claim 29, wherein, The thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

31. The battery cell according to claim 29 or 30, 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.

32. The battery cell according to any one of claims 1 to 31, 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%.

33. The battery cell according to claim 32, wherein, The graphite particles include: Artificial graphite, including secondary particles, and A carbon coating layer is applied to the surface of the artificial graphite.

34. The battery cell according to claim 33, wherein, Based on the mass of the graphite particles, the carbon coating layer has a mass content of 2% to 5%.

35. The battery cell according to any one of claims 1 to 34, 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.

36. The battery cell according to claim 35, wherein, The carbon-based material in the first negative electrode film layer also includes natural graphite.

37. The battery cell according to claim 35 or 36, 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.

38. The battery cell according to claim 37, 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 .

39. The battery cell according to any one of claims 35 to 38, 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.

40. The battery cell according to any one of claims 35 to 39, 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, wherein 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.

41. The battery cell according to claim 40, wherein, The first lithium-containing binder has a mass content of 0.1% to 1% relative to 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 second negative electrode film layer.

42. The battery cell according to claim 40 or 41, 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.

43. The battery cell according to any one of claims 40 to 42, 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%.

44. The battery cell according to any one of claims 1 to 43, 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 mass of the negative electrode active material.

45. The battery cell according to any one of claims 1 to 44, wherein, The thickness of the negative electrode current collector is 4 μm to 6 μm.

46. ​​The battery cell according to any one of claims 1 to 45, 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.

47. The battery cell according to claim 46, wherein, The thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

48. The battery cell according to claim 46 or 47, 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.

49. The battery cell according to any one of claims 1 to 48, wherein, The isolation membrane comprises a porous base membrane with a porosity of 20% to 70%.

50. The battery cell according to claim 49, wherein, The porosity of the base membrane is 35% to 60%.

51. The battery cell according to claim 49 or 50, wherein, The thickness of the base film is 6 μm to 12 μm.

52. The battery cell according to claim 51, wherein, The thickness of the base film is 6 μm to 9 μm.

53. The battery cell according to any one of claims 1 to 52, 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.

54. The battery cell according to claim 53, wherein, The non-fluoropolymer particles include acrylate copolymers.

55. The battery cell according to claim 53 or 54, wherein, 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.

56. The battery cell according to any one of claims 53 to 55, wherein, The second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide, and / or The average particle size of the second inorganic particle is 5 nm to 100 nm.

57. The battery cell according to any one of claims 1 to 56, wherein, The chain-like carboxylic acid ester solvent has a mass content of 5% to 75% in the organic solvent.

58. The battery cell according to claim 57, wherein, The chain-like carboxylic acid ester solvent has a mass content of 30% to 70% in the organic solvent.

59. The battery cell according to claim 57 or 58, 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.

60. The battery cell according to claim 59, 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.

61. The battery cell according to claim 59 or 60, wherein, The chain-like carboxylic acid ester solvents include one or more compounds from Formula I-1 to Formula I-8.

62. The battery cell according to any one of claims 1 to 61, wherein, The organic solvent also includes carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

63. The battery cell according to claim 62, wherein, The carbonate solvent has a mass content of 30% to 70% in the organic solvent.

64. The battery cell according to any one of claims 1 to 63, wherein, The electrolyte also includes additives, which include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives.

65. The battery cell according to claim 64, 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.

66. The battery cell according to claim 64 or 65, wherein, The additive is present in the electrolyte at a mass content of 1% to 10%.

67. The battery cell according to claim 66, wherein, The additive is present in the electrolyte at a mass content of 2% to 8%.

68. The battery cell according to any one of claims 1 to 67, wherein, The electrolyte also includes lithium salts, which include one or more of fluorosulfonyl imide salts and lithium hexafluorophosphate.

69. The battery cell according to claim 68, wherein, The fluorinated sulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide and lithium bistrifluoromethylsulfonate imide.

70. The battery cell according to claim 68 or 69, 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.

71. The battery cell according to claim 70, wherein, The molar concentration ratio of the lithium bis(fluorosulfonyl)imide to the molar concentration of the lithium hexafluorophosphate is 0.2 to 1.

0.

72. The battery cell according to any one of claims 1 to 71, wherein, The shell is made of steel and has a thickness of 0.1 mm to 0.5 mm.

73. The battery cell according to claim 72, wherein, The thickness of the shell is 0.2 mm to 0.35 mm.

74. The battery cell according to any one of claims 1 to 73, wherein the battery cell further comprises an electrode terminal, the electrode assembly comprises a tab portion, and the tab portion is directly welded to the electrode terminal.

75. The battery cell according to any one of claims 1 to 74, wherein, The charging time for a single battery cell from 10% to 80% state of charge is 5 to 10.5 minutes.

76. A battery device comprising a plurality of battery cells as claimed in any one of claims 1 to 75.

77. The battery device according to claim 76, wherein, The charging time for the battery device from 10% state of charge to 80% state of charge is 5 min to 10.5 min.

78. An electrical device comprising a battery device as described in claim 76 or 77.

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