Battery cell, battery device, and electric device

Abstract

The present application relates to a battery cell, a battery device, and an electric device. The battery cell comprises an electrode assembly, the electrode assembly comprises a first electrode sheet, a second electrode sheet, and a separator, the separator is disposed between the first electrode sheet and the second electrode sheet, and the polarity of the first electrode sheet is opposite to that of the second electrode sheet; the first electrode sheet comprises a first current collecting portion and a first film layer disposed on at least one side of the first current collecting portion and comprising a first active material; the second electrode sheet comprises a second current collecting portion and a second film layer disposed on at least one side of the second current collecting portion and comprising a second active material; one of the first active material and the second active material comprises a lithium-containing phosphate having an olivine structure, and the other comprises a carbon-based material; and the first current collecting portion comprises a first support layer and a first metal layer disposed on at least one side of the first support layer, the first film layer is disposed on the first metal layer, and the first support layer comprises an organic material. According to the present application, the energy density of a battery cell can be improved.

Description

Battery cells, battery packs and electrical devices Technical Field

[0001] This application relates to a battery cell, a battery device, and an electrical device. Background Technology

[0002] Lithium-ion batteries are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, and power tools due to their high capacity and long lifespan. With the development of lithium-ion battery applications, higher demands are being placed on their performance, such as energy density.

[0003] Summary of the Invention

[0004] This application provides a battery cell, a battery device, and an electrical device that can improve the energy density of the battery cell.

[0005] In a first aspect, this application proposes a battery cell, which includes an electrode assembly, and the electrode assembly package...

[0006] The device includes a first electrode, a second electrode, and a separator, with the separator disposed between the first and second electrodes, and the first and second electrodes having opposite polarities. The first electrode includes a first current collector and a first film layer disposed on at least one side of the first current collector and including a first active material. The second electrode includes a second current collector and a second film layer disposed on at least one side of the second current collector and including a second active material. One of the first and second active materials comprises a lithium phosphate with an olivine structure, and the other comprises a carbon-based material. The first current collector includes a first support layer and a first metal layer disposed on at least one side of the first support layer, with the first film layer disposed on the first metal layer. The first support layer comprises an organic material.

[0007] Therefore, in this embodiment, the positive electrode active material of the battery cell includes a lithium phosphate with an olivine structure, and the negative electrode active material includes a carbon-based material, resulting in excellent structural stability and cycle performance of the battery cell. Based on the above materials, the first current collector of the first electrode adopts a composite structure of a first support layer and a first metal layer. This structure is beneficial for reducing the thickness of the first current collector, thereby increasing the volume ratio of the first film layer. Moreover, the composite structure is more conducive to the capacity utilization of the active material, improving the volumetric energy density of the battery cell. The first metal layer includes a metallic material, which has excellent conductivity. Even with a small thickness of the first metal layer, rapid electron migration can be achieved, which is beneficial for improving the energy density of the battery cell during fast charging. The first support layer includes an organic material, which is lightweight and can further improve the gravimetric energy density of the battery cell. The strong bonding force between the first support layer and the first metal layer results in high structural stability of the first current collector.

[0008] In some embodiments, the second current collecting part comprises a second support layer and a second metal layer arranged on at least one side of the second support layer, and a second film layer is arranged on the second metal layer, and the second support layer comprises an organic material.

[0009] Therefore, in the embodiments of the present application, the second current collecting part of the second pole piece adopts a composite structure of a second support layer and a second metal layer, which is beneficial to thinning the thickness of the second current collecting part, thereby increasing the thickness proportion of the second film layer and further improving the volume energy density of the battery monomer; the second metal layer comprises a metal material, and the conductivity of the metal material is excellent, and the second metal layer can also realize fast electron migration when the thickness of the second metal layer is small, which is beneficial to improving the weight energy density of the battery monomer under the condition of fast charging. The second support layer comprises an organic material, which is relatively light in mass, and the bonding force between the second support layer and the second metal layer is relatively strong, so that the structural stability of the second current collecting part is relatively high.

[0010] In some embodiments, the first pole piece is a positive pole piece, and the first metal layer is a positive metal layer, and the first metal layer is arranged on both sides of the first support layer.

[0011] In some embodiments, the first pole piece is a positive pole piece, and the first current collecting part is a positive current collecting part, and the thickness of the first current collecting part is 5-15 μm, which can be selected as 5-10 μm. When the thickness of the positive current collecting part is in the above range, the thickness of the positive current collecting part is relatively thin, which is beneficial to increasing the thickness of the positive film layer and improving the energy density of the battery monomer.

[0012] In some embodiments, the first pole piece is a positive pole piece, and the thickness of the first metal layer is 0.3-3 μm, which can be selected as 0.5-1.5 μm. When the thickness of the positive metal layer is in the above range, the thickness of the positive metal layer is relatively thin, and its conductivity is relatively excellent, which is beneficial to improving the fast charging performance of the battery monomer.

[0013] In some embodiments, the first pole piece is a positive pole piece, and the first support layer is a positive support layer, and the thickness of the first support layer is 1-10 μm, which can be selected as 3-8 μm. When the thickness of the positive support layer is in the above range, the mechanical strength of the positive current collecting part can be effectively improved; and the bonding force between the positive support layer and the positive metal layer is relatively strong, so that the structural stability of the positive current collecting part is relatively high.

[0014] In some embodiments, the first pole piece is a positive pole piece, and the metal material in the first metal layer comprises at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy, which can be selected as aluminum; the conductivity of the above materials is relatively excellent, so that the internal resistance of the battery monomer is relatively small, and the polarization is small, which is beneficial to improving the fast charging performance of the battery monomer.

[0015] In some embodiments, the first electrode tab is a positive electrode tab, and the organic material in the first support layer comprises at least one of an insulating polymer material and a conductive polymer material, and optionally the insulating polymer material. When the positive electrode support layer is made of insulating material, it is not conductive, which can increase the short-circuit resistance of the battery cell in the event of an abnormal short circuit, greatly reducing the short-circuit current and greatly reducing the short-circuit heat generation, thereby improving the use reliability of the battery cell.

[0016] In some embodiments, the first electrode tab is a positive electrode tab, and the first support layer further comprises an inorganic insulating material.

[0017] In some embodiments, the insulating polymer material comprises at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyoxadiazole, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyphenylene terephthalamide, polypropylene, polyformaldehyde, epoxy resin, phenolic resin, polytetrafluoroethylene, polyphenylene sulfide, polyvinylidene fluoride, silicone rubber, polycarbonate, cellulose and its derivatives, starch and its derivatives, protein and its derivatives, polyvinyl alcohol and its cross-linked products, and polyethylene glycol and its cross-linked products.

[0018] In some embodiments, the positive electrode tab further comprises a positive electrode conductive layer between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode tab and reduce the heat generation of the positive electrode tab, thereby reducing the heat generation of the battery cell.

[0019] In some embodiments, the thickness of the positive electrode conductive layer is 0.1 μm to 2 μm. When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode tab can be further improved, the heat generation of the positive electrode tab can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved.

[0020] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode tab and reducing the heat generation of the battery cell; and the positive electrode binder in the positive electrode conductive layer can improve the adhesion between the positive electrode current collector and the positive electrode film layer, thereby improving the structural stability of the positive electrode tab.

[0021] In some embodiments, the positive electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0022] In some embodiments, the positive electrode binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a polyacrylic acid, and a fluorine-containing acrylic ester resin.

[0023] In some embodiments, the first electrode tab is a negative electrode tab, and the first metal layer is a negative electrode metal layer, and the first metal layer is arranged on both sides of the first support layer.

[0024] In some embodiments, the first electrode tab is a negative electrode tab, and the first current collecting part is a negative electrode current collecting part, and the thickness of the first current collecting part is 2-8.5 μm, or 2-6.5 μm. When the thickness of the negative electrode current collecting part is within the above range, the thickness of the negative electrode current collecting part is relatively thin, which is conducive to increasing the thickness of the negative electrode film layer and improving the energy density of the battery cell.

[0025] In some embodiments, the first electrode tab is a negative electrode tab, and the first metal layer is a negative electrode metal layer, and the thickness of the first metal layer is 0.3-2 μm, or 0.5-1.5 μm. When the thickness of the negative electrode metal layer is within the above range, the thickness of the negative electrode metal layer is relatively thin, and its conductivity is relatively excellent, which is conducive to improving the rapid charging performance of the battery cell.

[0026] In some embodiments, the first electrode tab is a negative electrode tab, and the first support layer is a negative electrode support layer, and the thickness of the first support layer is 1-4.5 μm, or 3-4 μm. When the thickness of the negative electrode support layer is within the above range, the mechanical strength of the negative electrode current collecting part can be effectively improved; and the bonding force between the negative electrode support layer and the negative electrode metal layer is relatively strong, so that the structural stability of the negative electrode current collecting part is relatively high.

[0027] In some embodiments, the first electrode tab is a negative electrode tab, and the metal material in the first metal layer comprises at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy, or copper.

[0028] In some embodiments, the first electrode tab is a negative electrode tab, and the organic material of the first support layer comprises at least one of an insulating high molecular material and a conductive high molecular material, or an insulating high molecular material.

[0029] In some embodiments, the first electrode tab is a negative electrode tab, and the first support layer further comprises an inorganic insulating material.

[0030] In some embodiments, the insulating polymer material includes at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyoxadiazole, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyphenylene terephthalamide, polyacrylonitrile, polyoxymethylene, epoxy resin, phenol formaldehyde resin, polytetrafluoroethylene, polyphenylene sulfide, polyvinylidene fluoride, silicone rubber, polycarbonate, cellulose and its derivatives, starch and its derivatives, protein and its derivatives, polyvinyl alcohol and its crosslinking products, polyethylene glycol and its crosslinking products.

[0031] In some embodiments, the negative electrode tab further includes a negative electrode conductive layer, and the negative electrode conductive layer is located between the first film layer and the first current collector.

[0032] In some embodiments, the negative electrode tab further includes a negative electrode conductive layer, and the negative electrode conductive layer is located between the negative electrode film layer and the negative electrode current collector.

[0033] In some embodiments, the thickness of the negative electrode conductive layer is 0.1 μm to 2 μm. The negative electrode conductive layer can further improve the conductivity of the negative electrode tab, reduce the heat generation of the negative electrode tab, and thus reduce the heat generation of the battery cell.

[0034] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode tab and 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 tab.

[0035] In some embodiments, the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0036] In some embodiments, the negative electrode binder includes one or more of styrene butadiene rubber, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0037] In some embodiments, the olivine-structured lithium-containing phosphate has a powder resistivity of 1 Ω·cm to 27.5 Ω·cm. The relatively low powder resistivity of the positive electrode active material results in a relatively low resistance of the positive electrode tab and a relatively low heat generation of the battery cell.

[0038] In some embodiments, the olivine-structured lithium-containing phosphate has a powder compaction density of 2.46 g / cm 3 to 2.8 g / cm 3The powder compaction density of the positive electrode active material at 30000N in the above range can improve the energy density of the battery monomer, 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.

[0039] In some embodiments, the lithium-containing phosphate with olivine structure has a charge gram capacity of 150mAh / g to 170mAh / g at 0.1C rate. 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.

[0040] In some embodiments, the lithium-containing phosphate with olivine structure has a charge gram capacity of 150mAh / g to 170mAh / g. When the charge gram capacity of the positive electrode active material is in the above range, the energy density of the battery monomer is relatively high.

[0041] In some embodiments, the compaction density of the positive electrode film layer of the battery monomer at 100% state of charge is 2.50g / cm 3 to 2.80g / cm 3 , and optionally 2.55g / cm 3 to 2.70g / cm 3 . When the compaction density of the positive electrode film layer is in the above range, it is beneficial to improve the energy density of the battery monomer; and because the positive electrode active material in the positive electrode film layer is more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the pole piece, thereby reducing the heat generation.

[0042] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200mg / 1540.25mm 2 to 370mg / 1540.25mm 2 , and optionally 240mg / 1540.25mm 2 to 330mg / 1540.25mm 2 . 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 pole piece will not be too large, and the energy density of the battery monomer can be improved.

[0043] In some embodiments, the lithium-containing phosphate with 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 with olivine structure, reduce the powder resistivity of the material, and is beneficial to the migration rate of lithium ions, thereby reducing the heat generation of the battery monomer.

[0044] In some embodiments, the phosphate particles include a compound of the general formula Li x1 A y1 Me a M b P 1-c X c Y z , wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The phosphate particles have excellent cycle stability, which is conducive to improving the cycle performance of the battery cell.

[0045] In some embodiments, the coating layer includes a fast ion conductor of the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , M2 includes one or more of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0 2 x2<5, and 0 2 y2<4. Coating the phosphate particles with the fast ion conductor can significantly improve the transmission rate of lithium ions in the positive electrode end multiple times of lithium extraction / insertion, improve the ion conductivity of the positive electrode active material, and further improve the specific capacity and the energy density of the corresponding battery cell.

[0046] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, and can be 0.19 to 0.26. When the graphitization degree of the positive electrode active material is in the above range, the conductivity of the positive electrode active material is improved, and the heat generation of the positive electrode plate is reduced, thereby reducing the heat generation of the battery cell.

[0047] 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.

[0048] Therefore, the material with the above-mentioned content of carbon element and the above-mentioned specific surface area in the embodiments of the present application is more conducive to the effective contact between the electrolyte and the lithium-containing olivine structure phosphate and the transmission of lithium ions at the phase interface.

[0049] In some embodiments, the lithium-containing olivine structure phosphate is in a particulate form, and the volume distribution particle size satisfies 1 μm≤Dv50≤2 μm and 0.4 μm≤Dv10≤0.7 μm. The lithium-containing olivine structure phosphate has a relatively small particle size, the path of lithium ion deintercalation in the positive electrode active material is relatively short, and the heat generation is relatively small. In addition, the particle size of the positive electrode active material is not too small, and the agglomeration of the positive electrode active material is unlikely to occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0050] In some embodiments, the lithium-containing olivine structure phosphate is in a particulate form, and the lithium-containing olivine structure 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 path of lithium ion deintercalation in the positive electrode active material is relatively short, and the heat generation is relatively small.

[0051] 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, improve the capacity, and thus improve the energy density of the battery cell.

[0052] In some embodiments, the compaction density of the negative electrode film layer of the battery cell is 1.15 g / cm 3 to 1.36 g / cm 3 at 100% state of charge. Optionally, the compaction density of the negative electrode film layer is 1.25 g / cm 3 to 1.36 g / cm 3 . When the compaction density of the negative electrode film layer is in the above-mentioned range, the energy density of the battery cell is improved. In addition, the negative electrode active material in the negative electrode film layer is densely packed, the contact resistance between the particles is small, the resistance of the electrode sheet is further reduced, and the heat generation is reduced.

[0053] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 . Optionally, the single-sided coating weight of the negative electrode film layer is 110 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2The single-side coating weight of the negative electrode film layer is in the above range, the heat generation per unit area of the negative electrode tab is not too large, and the energy density of the battery cell can be improved.

[0054] In some embodiments, the powder resistivity of the negative electrode active material is 0.005 Ω·cm to 0.043 Ω·cm. The powder resistivity of the negative electrode active material is relatively low, so that the resistance of the negative electrode tab is relatively low, and the battery cell generates less heat.

[0055] In some embodiments, the powder compaction density of the negative electrode active material under 20000N is 1.5 g / cm 3 to 1.85 g / cm 3 The powder compaction density of the negative electrode active material under 20000N is in the above range, which can improve the energy density of the battery cell, and the negative electrode active material in the negative electrode film layer can be more closely packed, the contact resistance between particles is small, which can further reduce the resistance of the tab, thereby reducing the heat generation.

[0056] In some embodiments, the charge gram capacity of the negative electrode active material is greater than or equal to 350 mAh / g. When the charge gram capacity of the negative electrode active material is in the above range, the energy density of the battery cell is relatively high.

[0057] In some embodiments, the charge gram capacity of the negative electrode active material at 0.1C rate is greater than or equal to 350 mAh / g. When the charge gram capacity of the negative electrode active material at 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0058] In some embodiments, the negative electrode active material includes a carbon-based material, the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. When the graphitization degree of the graphite particles is in the above range, the conductive performance of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode tab and the heat generation of the battery cell; and can improve the rapid charging performance of the battery cell.

[0059] 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 more end faces and defects, so that the number of sites capable of deintercalating lithium ions is more, so that the conductivity of the carbon coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode tab and the heat generation of the battery cell.

[0060] In some embodiments, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. When the mass content of the carbon coating layer is in the above range, the internal resistance of the negative electrode tab and the heat generation of the battery cell can be further reduced.

[0061] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is arranged on the surface of the negative electrode current collector, the first negative electrode film layer includes a carbon-based material, the second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, the second negative electrode film layer includes a carbon-based material, the carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently includes graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0062] Thus, in the embodiments of the present application, there is a difference in particle size between the first negative electrode film layer and the second negative electrode film layer, which can improve the rapid charging performance of the battery cell. Specifically, during rapid charging, the overpotential of the second negative electrode film layer is 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 stripping on the surface of the negative electrode sheet.

[0063] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0064] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is more densely packed, so that the energy density of the battery cell is improved; the first negative electrode film layer is relatively sparse in packing, and the pores are more abundant, which can improve the rapid charging performance of the battery cell.

[0065] 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 a suitable range, the rapid charging performance of the battery cell can be improved.

[0066] 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 a suitable range, the energy density of the battery cell can be improved.

[0067] 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.

[0068] In some embodiments, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 pm to 14.3 pm. When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is in the above range, the tortuosity of lithium ion transmission can be reduced, and the rapid charging performance of the battery cell can be improved.

[0069] 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.

[0070] Thus, in the embodiments of the present application, the mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides a relatively large number of freely movable lithium ions for the second negative electrode film layer, which can further improve the rapid charging performance of the battery cell.

[0071] In some embodiments, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. When the mass content of the first lithium-containing binder is in the above range, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0072] In some embodiments, the mass content of lithium in the first lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium is in the above range, the number of freely movable lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0073] In some embodiments, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. When the mass content of lithium in the second lithium-containing binder is in the above range, the deintercalation rate of lithium ions is improved, and the rapid charging performance of the battery cell is improved.

[0074] In some embodiments, the mass content of lithium in the second lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium is in the above range, the number of freely movable lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0075] 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, the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers being 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0076] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery monomer, and is not prone to swelling during the charging and discharging process, and has a stable structure, so that the cycle performance of the negative electrode film layer is improved during the rapid charging and discharging process.

[0077] 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, the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers being 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0078] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery monomer, and is not prone to swelling during the charging and discharging process, and has a stable structure, so that the cycle performance of the negative electrode film layer is improved during the rapid charging and discharging process.

[0079] In some embodiments, the negative electrode active material further comprises a silicon-based material, the mass content of silicon in the silicon-based material being 0.3% to 10.0%, based on the mass of the negative electrode active material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery monomer.

[0080] 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 in the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery monomer can be further reduced, thereby reducing heat generation.

[0081] In some embodiments, the thickness of the base film is 6 μm to 12 μm. When the thickness of the base film is in the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery monomer can be further reduced, thereby reducing heat generation.

[0082] In some embodiments, the isolation film comprises a base film and a functional layer disposed on at least one side of the base film, the functional layer comprises a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer comprises first inorganic particles, the second functional layer is located on the other side of the base film, and the second functional layer comprises composite particles, the composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the isolation film.

[0083] 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.

[0084] 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.

[0085] In some embodiments, the second 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 second inorganic particles can improve the heat resistance of the first functional layer.

[0086] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is in the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0087] In some embodiments, the battery cell further comprises an electrolyte, and the electrolyte has an electrical conductivity of 13 mS / cm to 20 mS / cm at room temperature. When the electrical conductivity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the rapid charging performance of the battery cell.

[0088] In some embodiments, the electrolyte has a viscosity of 2.3 mPa·s to 3.5 mPa·s at room temperature. When the viscosity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the rapid charging performance of the battery cell.

[0089] In some embodiments, the electrolyte density at room temperature is between 1.05 g / mL and 1.35 g / mL. When the electrolyte density is within this range, the migration rate of lithium ions in the electrolyte is higher, which can further reduce the internal resistance of the battery cells, thereby reducing heat generation and improving the fast charging performance of the battery cells.

[0090] In some embodiments, the carboxylic acid ester solvent includes a chain-like carboxylic acid ester solvent, which constitutes 4% to 65% of the electrolyte by mass. When the mass content of the chain-like carboxylic acid ester solvent is within this range, the viscosity of the electrolyte system is relatively low, which is beneficial for lithium ion migration.

[0091] In some embodiments, the chain carboxylic acid ester solvent includes compounds represented by Formula I.

[0092] In formula I,

[0093] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0094] R2 includes C1 to C5 alkyl or C1 to C5 haloalkyl.

[0095] Therefore, the above-mentioned chain carboxylic acid ester solvents in the embodiments of this application have high conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0096] In some embodiments, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group.

[0097] In some embodiments, R2 includes C1 to C3 alkyl or C1 to C3 haloalkyl.

[0098] In some embodiments, the chain carboxylic acid ester solvent includes one or more compounds of formulas I-1 to I-8.

[0099] In some embodiments, the organic solvent further includes carbonate solvents, including one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The combined use of these carbonate solvents and chain carboxylic acid ester solvents improves the conductivity of the electrolyte, which is beneficial for lithium ion migration.

[0100] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0101] In some embodiments, the mass content of the carbonate-based solvent in the electrolyte is 25% to 60%. The carbonate-based solvent in the above mass content can further improve the conductivity of the electrolyte and facilitate the migration of lithium ions.

[0102] In some embodiments, the electrolyte further comprises an additive, and the additive comprises 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.

[0103] In some embodiments, the carbonate-based additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0104] In some embodiments, the sulfur-containing additive comprises 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.

[0105] In some embodiments, the lithium salt-based additive comprises one or more of lithium difluorophosphate LiPO2F2, lithium difluoro oxalate borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bisoxalate borate LiBOB.

[0106] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, and 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.

[0107] In some embodiments, the electrolyte further comprises a lithium salt, and the lithium salt comprises 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.

[0108] In some embodiments, the fluorine-containing sulfonimide salt comprises one or more of lithium bisfluorosulfonimide LiFSI and lithium bis-trifluoromethylsulfonimide LiTFSI.

[0109] In some embodiments, the lithium salt comprises lithium bisfluorosulfonimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of lithium bisfluorosulfonimide LiFSI is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.5 mol / L to 1.0 mol / L.

[0110] In some embodiments, the ratio of the molar concentration of lithium bisfluorosulfonylimide to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2 to 1.0.

[0111] In some embodiments, the base material of the shell comprises steel, and the thickness of the shell is 0.1 mm to 0.5 mm, or 0.2 mm to 0.35 mm. When the thickness of the shell is in the above range, the mechanical strength of the shell is high, which can improve the use reliability and cycle performance of the battery monomer; and the shell occupies less space, and the internal space of the shell is larger, which is beneficial to improve the energy density of the battery monomer.

[0112] In some embodiments, the first metal layer comprises a first part and a second part extending from the first part, the first part is provided with the first film layer, and the second part is not provided with the first film layer; the first tab further comprises a first tab, and the first tab is connected with the second part.

[0113] In some embodiments, the battery monomer further comprises a first electrode terminal, and the first tab is directly welded with the first electrode terminal. Direct welding can reduce the resistance of the connection, which is beneficial to reduce the internal resistance of the battery monomer as a whole.

[0114] In some embodiments, at room temperature, the charging time of the battery monomer from 10% state of charge to 80% state of charge is 5 min to 10.5 min, and the charging speed of the battery monomer is faster, which is more conducive to improving the rapid charging capability.

[0115] In some embodiments, the volumetric energy density of the battery monomer is 380 Wh / L to 500 Wh / L, or 410 Wh / L to 470 Wh / L.

[0116] In some embodiments, the gravimetric energy density of the battery monomer is 180 Wh / Kg to 210 Wh / Kg.

[0117] 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.

[0118] In some embodiments, at room temperature, the charging time of the battery from 10% state of charge to 80% state of charge is 5 min to 10.5 min. The charging speed of the battery is faster, which is more conducive to improving the rapid charging capability.

[0119] In the third aspect, the application provides a power consumption device, which comprises the battery device according to any one of the embodiments of the second aspect of the application. BRIEF DESCRIPTION OF DRAWINGS

[0120] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of the drawings.

[0121] FIG. 1 is a structural schematic diagram of a battery cell according to some embodiments of the present application;

[0122] FIG. 2 is an exploded schematic diagram of a battery cell according to some embodiments of the present application;

[0123] FIG. 3 is a structural schematic diagram of an electrode assembly of a battery cell according to some embodiments of the present application;

[0124] FIG. 4 is a structural schematic diagram of a first electrode tab of a battery cell according to some embodiments of the present application;

[0125] FIG. 5 is a sectional schematic diagram of the first electrode tab shown in FIG. 4 along line A-A;

[0126] FIG. 6 is a structural schematic diagram of a second electrode tab of a battery cell according to some embodiments of the present application;

[0127] FIG. 7 is a sectional schematic diagram of the second electrode tab shown in FIG. 4 along line B-B;

[0128] FIG. 8 is a structural schematic diagram of a battery module according to some embodiments of the present application;

[0129] FIG. 9 is a structural schematic diagram of a battery pack according to some embodiments of the present application;

[0130] FIG. 10 is a structural schematic diagram of an electric device according to some embodiments of the present application.

[0131] The drawings are not necessarily drawn according to the actual proportions.

[0132] The reference numerals are explained as follows: 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; 7, battery cell; 10, electrode assembly; 111, first tab; 1111, first tab main portion; 1112, first tab connecting portion; 112, second tab; 12, main portion; 13, first pole piece; 131, first current collecting portion; 1311, first support layer; 1312, first metal layer; 1312a, first portion; 1312b, second portion; 132, first film layer; 14, second pole piece; 141, second current collecting portion; 1411, second support layer; 1412, second metal layer; 142, second film layer; 15, separator; 20, housing; 21, case; 22, end cover; 31, first electrode terminal; 32, second electrode terminal. DETAILED DESCRIPTION

[0133] Hereinafter, embodiments of the battery cell, the battery device, and the electric device of 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.

[0134] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise stated, a numerical range "a to b" indicates a shorthand way of describing each and every intervening real number between the upper and lower limits of that range, in which a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 and 5" have been listed herein, and "0 to 5" is merely a shorthand way of describing those numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0135] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions if no special instructions are given.

[0136] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions if no special instructions are given.

[0137] All steps of the present application can be performed in sequence or randomly if no special instructions are given, and the sequence is preferred. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any order. For example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0138] With the development of the field of battery monomers, the energy density requirement of battery monomers is gradually improved. Compared with nickel-cobalt-manganese oxide batteries, lithium-containing phosphates with olivine structure have low energy density due to low specific capacity and low voltage platform. From the perspective of optimizing lithium iron phosphate battery pole piece, this application introduces a current collecting part that is more conducive to improving the capacity of the pole piece in lithium iron phosphate battery. By increasing the proportion of the volume of the film layer containing active material in the pole piece, the energy density of the lithium iron phosphate battery is improved. In particular, in the lithium iron phosphate battery with high fast charging performance requirements, the film layer of active material on the pole piece is usually thin (more conducive to fast charging), so by introducing a current collecting part that can increase the proportion of the volume of the film layer containing active material in the pole piece, it is more conducive to improving the energy density of the fast charging battery monomer.

[0139] Therefore, the embodiments of the present application reasonably design the system of the battery monomer, introduce a suitable current collecting part to adapt to the pole piece design of the lithium iron phosphate battery, reduce the volume proportion of the current collecting part in the battery monomer, increase the volume proportion of the film layer containing active material, and improve the energy density of the battery monomer.

[0140] Battery monomer

[0141] In a first aspect, the embodiments of the present application propose a battery monomer.

[0142] As shown in FIGS. 1-7, the battery cell 7 comprises an electrode assembly 10 and an electrolyte, the electrode assembly 10 comprises a first electrode tab 13, a second electrode tab 14 and a separator 15 arranged between the first electrode tab 13 and the second electrode tab 14, and the first electrode tab 13 and the second electrode tab 14 have opposite polarities; the first electrode tab 13 comprises a first current collecting part 131 and a first film layer 132 comprising a first active material arranged on at least one side of the first current collecting part 131; the second electrode tab 14 comprises a second current collecting part 141 and a second film layer 142 comprising a second active material arranged on at least one side of the second current collecting part 141; wherein one of the first active material and the second active material comprises a lithium-containing phosphate with an olivine structure, and the other comprises a carbon-based material; the first current collecting part 131 comprises a first support layer 1311 and a first metal layer 1312 arranged on at least one side of the first support layer 1311, the first metal layer 1312 is arranged with the first film layer 132 thereon, the first metal layer 1312 is located between the first support layer 1311 and the first film layer 132, and the first support layer 1311 comprises an organic material. FIG. 3 shows a structural schematic diagram of a wound electrode assembly. It should be noted that the electrode assembly 10 can also have a stacked structure. FIG. 5 shows a structural schematic diagram of the first electrode tab 13, wherein the X direction is parallel to the thickness direction of the first electrode tab 13, and the Y direction is perpendicular to the X direction.

[0143] The positive active material in the battery cell 7 comprises a lithium-containing phosphate with an olivine structure, and the negative active material comprises a carbon-based material, so that the structural stability of the battery cell 7 is excellent, and the cycle performance is excellent.

[0144] On the basis of the above-mentioned materials, the first current collecting part 131 of the first electrode tab 13 adopts a composite structure form of the first support layer 1311 and the first metal layer 1312, which is conducive to reducing the thickness of the first current collecting part 131, thereby facilitating an increase in the volume ratio of the first film layer 132, and the above-mentioned composite structure form is more conducive to the capacity of the active material, thereby improving the volume energy density of the battery cell 7; the first metal layer 1312 comprises a metal material, and the conductivity of the metal material is excellent, so that fast electron migration can be achieved when the thickness of the first metal layer 1312 is small, thereby facilitating an improvement in the energy density of the battery cell 7 under fast charging conditions. The first support layer 1311 comprises an organic material, and the mass is lighter, thereby further improving the weight energy density of the battery cell 7; the bonding force between the first support layer 1311 and the first metal layer 1312 is strong, so that the structural stability of the first current collecting part 131 is high.

[0145] In some embodiments, the second current collecting part 141 comprises a second support layer 1411 and a second metal layer 1412 arranged on at least one side of the second support layer 1411, the second metal layer 1412 is located between the second support layer 1411 and the second film layer 142, and the second support layer 1411 comprises an organic material. FIG. 7 shows a structural schematic diagram of the second pole piece 14, the X direction is parallel to the thickness direction of the second pole piece 14, and the Y direction is perpendicular to the X direction.

[0146] The second current collecting part 141 of the second pole piece 14 adopts a composite structure of the second support layer 1411 and the second metal layer 1412, which is beneficial to reduce the thickness of the second current collecting part 141, thereby increasing the thickness proportion of the second film layer 142, and is beneficial to further improve the volume energy density of the battery monomer 7; the second metal layer 1412 comprises a metal material, and the conductivity of the metal material is excellent. When the thickness of the second metal layer 1412 is small, fast electron migration can also be realized, which is beneficial to improve the weight energy density of the battery monomer 7 in the case of fast charging. The second support layer 1411 comprises an organic material, and the mass of the organic material is lighter. The bonding force between the second support layer 1411 and the second metal layer 1412 is strong, so that the structural stability of the second current collecting part 141 is higher.

[0147] The polarities of the first pole piece 13 and the second pole piece 14 are opposite, for example, the first pole piece 13 is a positive pole piece, and the second pole piece 14 is a negative pole piece, or the first pole piece 13 is a negative pole piece, and the second pole piece 14 is a positive pole piece. When the first pole piece 13 is a positive pole piece, the first current collecting part 131 and the first film layer 132 correspond to a positive current collecting part and a positive film layer respectively; when the second pole piece 14 is a negative pole piece, the second current collecting part 141 and the second film layer 142 correspond to a negative current collecting part and a negative film layer respectively.

[0148] [Positive pole piece]

[0149] The first pole piece is a positive pole piece, the first current collecting part corresponds to a positive current collecting part, the first support layer corresponds to a positive support layer, the first metal layer corresponds to a positive metal layer, the first film layer corresponds to a positive film layer, and the first active material is a positive active material; in this case, the second pole piece is a negative pole piece, the second current collecting part corresponds to a negative current collecting part, the second support layer corresponds to a negative support layer, the second metal layer corresponds to a negative metal layer, the second film layer corresponds to a negative film layer, and the second active material is a negative active material.

[0150] In the case of adopting a composite structure for the positive current collecting part, the negative current collecting part can adopt a conventional negative current collecting part, such as a copper foil structure. Alternatively, in the case of adopting a composite structure for the positive current collecting part, the negative current collecting part can also adopt a composite structure.

[0151] The positive electrode current collector has two opposite surfaces in the thickness direction of the positive electrode tab, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0152] The positive electrode support layer has two opposite surfaces in the thickness direction of the positive electrode tab, and the positive electrode metal layer is disposed on either one or both of the two opposite surfaces of the positive electrode support layer. Optionally, the positive electrode metal layer is disposed on both surfaces of the positive electrode support layer, and the positive electrode metal layer is located between the positive electrode support layer and the positive electrode film layer. The positive electrode support layer plays a supporting and protecting role for the positive electrode conductive layer. Since the positive electrode support layer is generally made of organic polymer material, the density of the positive electrode support layer is generally less than that of the positive electrode metal layer, thereby significantly improving the weight energy density of the battery cell compared with the traditional metal current collector.

[0153] In addition, the positive electrode metal layer adopts a metal layer with small thickness, which can further improve the volume energy density of the battery. In addition, since the positive electrode support layer can play a good bearing and protecting role for the positive electrode metal layer located on its surface, the tab fracture phenomenon commonly seen in traditional current collectors is less likely to occur.

[0154] In some embodiments, the thickness of the positive electrode current collector is 5-15 μm, and optionally 5-10 μm. For example, the thickness of the positive electrode current collector is 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 12 μm, 15 μm, or a range formed by any two of the above values.

[0155] When the thickness of the positive electrode current collector is in the above range, the thickness of the positive electrode current collector is thin, which is beneficial to increase the thickness of the positive electrode film layer and improve the energy density of the battery cell.

[0156] In some embodiments, the thickness of the positive electrode metal layer is 0.3-3 μm, optionally 0.5-1.5 μm. For example, the thickness of the positive electrode metal layer is 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.05 μm, 1.10 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, 2.05 μm, 2.15 μm, 2.2 μm, 2.25 μm, 2.3 μm, 2.35 μm, 2.4 μm, 2.45 μm, 2.5 μm, 2.55 μm, 2.6 μm, 2.65 μm, 2.7 μm, 2.75 μm, 2.8 μm, 2.85 μm, 2.9 μm, 2.95 μm, 3 μm, or a range defined by any two of the above values.

[0157] When the thickness of the positive electrode metal layer is within the above range, the thickness of the positive electrode metal layer is relatively thin, and the conductivity of the positive electrode metal layer is excellent, which is beneficial to the improvement of the rapid charging performance of the battery cell.

[0158] In some embodiments, the metal material in the positive electrode metal layer comprises at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, aluminum-zirconium alloy; optionally, the metal material in the positive electrode metal layer comprises aluminum. The above materials have excellent conductivity, so that the internal resistance of the battery cell is relatively small, and the polarization is small, which is beneficial to the improvement of the rapid charging performance of the battery cell.

[0159] Optionally, the positive electrode metal layer can further comprise at least one of conductive carbon materials, such as graphite, acetylene black, graphene, carbon nanotubes.

[0160] The positive electrode metal layer can be formed on the positive electrode support layer by at least one of mechanical rolling, bonding, vapor deposition, and electroless plating, the vapor deposition being preferably physical vapor deposition (PVD), the physical vapor deposition being preferably at least one of evaporation and sputtering, the evaporation being preferably at least one of vacuum evaporation, thermal evaporation deposition, and electron beam evaporation method (EBEM), the sputtering being preferably magnetron sputtering, and at least one of vapor deposition and electroless plating being preferably used to make the bonding between the positive electrode support layer and the positive electrode metal layer stronger.

[0161] In some embodiments, the thickness of the positive electrode support layer is 1 μm to 10 μm, and can be 3 μm to 8 μm. For example, the thickness of the positive electrode support layer is 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range defined by any two of the above values.

[0162] When the thickness of the positive electrode support layer is in the above range, the mechanical strength of the positive electrode current collecting part can be effectively improved, and the bonding between the positive electrode support layer and the positive electrode metal layer is stronger, so that the structural stability of the positive electrode current collecting part is higher.

[0163] In some embodiments, the positive electrode support layer comprises an organic material, and the organic material comprises at least one of an insulating polymer material and a conductive polymer material. Alternatively, the organic material comprises an insulating polymer material, and when the positive electrode support layer is made of an insulating material, the positive electrode support layer is not conductive, so that the short-circuit resistance of the battery cell under abnormal conditions can be improved, the short-circuit current can be greatly reduced, the short-circuit heat generation can be greatly reduced, and the use reliability of the battery cell can be improved.

[0164] For example, the insulating polymer material comprises at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyoxadiazole, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyphenylene sulfide, polyvinylidene fluoride, silicone rubber, polycarbonate, cellulose and its derivatives, starch and its derivatives, protein and its derivatives, polyvinyl alcohol and its crosslinked product, and polyethylene glycol and its crosslinked product.

[0165] Exemplarily, the conductive polymer material includes a polyazolide polymer material or a doped conjugated polymer material, and more preferably, the conductive polymer material includes at least one of polypyrrole, polyacetylene, polyaniline, and polythiophene.

[0166] Optionally, the positive electrode support layer can further include an inorganic material, which can be an insulating inorganic material, for example, an insulating polymer composite formed by compounding an insulating inorganic material and an insulating polymer material.

[0167] Exemplarily, the inorganic material is preferably at least one of a ceramic material, a glass material, and a ceramic composite material.

[0168] Optionally, the positive electrode support layer can further include an inorganic material, which can be a conductive inorganic material, for example, a conductive polymer composite formed by compounding a conductive inorganic material and a conductive polymer material.

[0169] Exemplarily, the conductive inorganic material includes at least one of a conductive carbon material, a metal material, and a composite conductive material; the conductive carbon material includes at least one of carbon black, carbon nanotube, graphite, acetylene black, and graphene; the metal material includes at least one of nickel, iron, copper, aluminum, or an alloy of the above-mentioned metals; and the composite conductive material includes at least one of nickel-coated graphite powder and nickel-coated carbon fiber.

[0170] In some embodiments, the positive electrode tab 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 tab, reduce the heat generation of the positive electrode tab, and thus reduce the heat generation of the battery cell. Moreover, the positive electrode conductive layer can improve the bonding force between the positive electrode current collector and the positive electrode film layer, improve the connection strength therebetween, and reduce the contact resistance.

[0171] In some embodiments, the thickness of the positive electrode conductive layer is 0.1 μm to 2 μm. Exemplarily, the thickness of the positive electrode conductive layer can be 0.1 μm, 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-mentioned values.

[0172] When the thickness of the positive electrode conductive layer is within the above-mentioned range, the conductivity of the positive electrode tab can be further improved, the heat generation of the positive electrode tab can be reduced, and thus the heat generation of the battery cell can be reduced; and the energy density of the battery cell can be improved.

[0173] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0174] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. For example, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or any combination of two of the above values.

[0175] For example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. 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.

[0176] Optionally, the positive electrode binder has a mass content of 50% to 70% in the positive electrode conductive layer. For example, 50%, 60%, 65%, 70%, or any combination of two of the above values.

[0177] For example, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. 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 enhancing the structural stability of the positive electrode sheet.

[0178] In the embodiments of this application, the thickness of the positive current collector, the positive support layer, the positive metal layer, and the positive conductive layer can be detected using equipment and methods known in the art, such as performing a tomographic scan on the positive electrode sheet to directly measure the thickness of each layer.

[0179] In some embodiments, the compaction density of the positive electrode film layer is 2.50 g / cm³ when the battery cell is at 100% state of charge (SOC). 3 Up to 2.80 g / cm 3 ; 2.55g / cm³ is optional 3 Up to 2.70 g / cm 3 For example, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film is 2.50 g / cm³. 3 2.52g / cm 3 2.55g / cm 3 2.56 g / cm 3 2.57g / cm 3 2.58g / cm 3 2.60g / cm 3 2.62 g / cm 3 2.65g / cm 3 2.68g / cm 3 2.70 g / cm3 2.70 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.

[0180] When the compaction density of the positive electrode film layer is within the above range, the energy density of the battery cell can be improved, and the particles in the positive electrode active material in the positive electrode film layer are closely packed, and the contact resistance between the particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation under fast charging. Therefore, by adjusting the compaction density of the positive electrode film layer to a reasonable range, the battery cell has high energy density and high charging rate performance.

[0181] 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 is 3.65 V, and the discharging cut-off voltage is 2.0 V, or the charging upper limit voltage is 3.7 V, or the charging upper limit voltage is 3.8 V; for example, when the phosphate material includes lithium manganese iron phosphate, the charging upper limit voltage is 4.2 V, and the discharging cut-off voltage is 2.5 V, or the charging upper limit voltage is 4.25 V, or the charging upper limit voltage is 4.35 V.

[0182] 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,

[0183] The battery cell is charged to the charging upper limit voltage at a constant current charging rate of 0.33 C, and then charged to 0.05 C at a constant voltage, corresponding to the state of 100% SOC of the battery cell; the battery cell is discharged to the cut-off voltage at a constant current discharging rate of 0.33 C, corresponding to the state of 0% SOC of the battery cell.

[0184] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; and optionally 240 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 . For example, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 240 mg / 1540.25 mm 2, 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 360 mg / 1540.25 mm 2 , 370 mg / 1540.25 mm 2 , or a range formed by any two of the above values.

[0185] When the single-side coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode tab will not be too large, and the energy density and the charge rate performance of the battery monomer can be improved.

[0186] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery monomer at 100% state of charge SOC can be detected by the following method. The positive electrode tab of the battery monomer at 100% state of charge SOC is disassembled, the compaction density of the positive electrode film layer is measured, for example, the single-side coated positive electrode tab (if it is a double-side coated tab, the positive electrode film layer on one side can be wiped off first), a small disc with an area of S1 is punched, its weight is weighed and recorded as M1, and its thickness H1 is measured. Then the positive electrode film layer of the above weighed positive electrode tab is wiped off, the weight of the positive electrode current collecting part is weighed and recorded as M0, and its thickness H0 is measured. The single-side coating weight of the positive electrode film layer = (the weight of the positive electrode tab M1 - the weight of the positive electrode current collecting part M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode tab H1 - the thickness of the positive electrode current collecting part H0, and the compaction density of the positive electrode film layer = the single-side coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0187] 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. Illustratively, 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 foregoing.

[0188] The relatively low powder resistivity of the positive electrode active material results in a relatively low resistance of the positive electrode tab, and less heat generation of the battery cell.

[0189] In the embodiments of the present application, the powder resistivity of the material is the meaning known in the art, and 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.

[0190] 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 . Illustratively, 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 / cm 3 , 2.55g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.72g / cm 3 , 2.75g / cm 3 , 2.78g / cm 3 , 2.80g / cm 3 or a range defined by any two of the foregoing.

[0191] When the powder compaction density of the positive electrode active material at 30000N is in the above range, the energy density of the battery cell can be improved, and the positive electrode active material in the positive electrode film layer can be more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0192] In the embodiments of the present application, the powder compaction density of the material is the meaning known in the art, which can be detected by the methods and devices known in the art according to the test standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample, added into a mold with a bottom area of 1.327cm 2 of a UTM7305 electronic pressure testing machine, pressurized to 3000kg (equivalent to 30000N), pressure maintained for 30s, then pressure released, maintained for 10s, then the powder compaction density of the positive electrode active material under the action of 30000N is recorded and calculated.

[0193] In some embodiments, the charge gram capacity of the positive electrode active material is 150mAh / g to 170mAh / g, which can be selected as 157mAh / g to 170mAh / g.

[0194] In some embodiments, the charge gram capacity of the positive electrode active material at 0.1C rate is 150mAh / g to 170mAh / g, which can be selected as 157mAh / g to 170mAh / g. For example, the charge gram capacity of the positive electrode active material at 0.1C rate is 150mAh / g, 151mAh / g, 152mAh / g, 153mAh / g, 154mAh / g, 155mAh / g, 156mAh / g, 157mAh / g, 158mAh / g, 159mAh / g, 160mAh / g, 161mAh / g, 162mAh / g, 163mAh / g, 164mAh / g, 165mAh / g, 166mAh / g, 167mAh / g, 168mAh / g, 169mAh / g, 170mAh / g or a range consisting of any two of the above values.

[0195] 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 cell is relatively high.

[0196] In the embodiments of the present application, the gram capacity of the active material has the meaning known in the art, can be tested by using the devices and methods known in the art, and can be tested by using the test method of the first coulomb efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019, using lithium metal as the negative electrode, the sample electrode piece containing the above material as the positive electrode, assembling to form a half-buckle type battery, and then obtaining the buckle capacity by 0.1C rate charging and discharging of the half-buckle type battery at 23°C±2°C on a battery tester or other test equipment with the same performance, and then dividing the capacity by the mass of the active material of the electrode piece to obtain the charging gram capacity parameter.

[0197] 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%, and the positive electrode active material of the present application can be considered to be an olivine-structured lithium-containing phosphate system. When the mass percentage of the olivine-structured lithium-containing phosphate is less than 100%, the positive electrode active material can further 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.

[0198] Optionally, the mass percentage of the olivine-structured lithium-containing phosphate in the positive electrode active material is 100%.

[0199] 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.

[0200] 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 capability of the battery, and reduce the heat generation of the battery monomer.

[0201] 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 (PO4) x1 (SiO4) y1 (SO4) a (BPO4) b (ClO4) c (SbO4) d (XO4) x2 (Y) z, wherein, 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The cycle stability of the phosphate particles is relatively excellent, which is conducive to improving the cycle performance of the battery monomer.

[0202] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The battery monomer will be accompanied by the deintercalation and consumption of active ions such as Li during the charging and discharging process. 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. The positive electrode active material is applied to the battery system. After the charging and discharging cycle, 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. The release of oxygen O from the crystal lattice will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will fluctuate. The above-mentioned situations are all within the protection scope of the present application.

[0203] In some embodiments, the coating layer includes a fast ion conductor with a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 , M2 includes one or more of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0

[0204] Exemplarily, the fast ion conductor is a material with a NASICON structure, for example, including one or more of lithium titanium iron phosphate Li2FeTi(PO4)3, lithium zirconium iron phosphate Li2FeZr(PO4)3, and lithium tin iron phosphate Li2FeSn(PO4)3.

[0205] 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.

[0206] In some embodiments, the coating layer further comprises elemental carbon.

[0207] 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.

[0208] 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.

[0209] Specifically, the arrangement of the carbon coating layer enables the positive electrode active material of the present application to have the following advantages:

[0210] 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.

[0211] 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.

[0212] Coating a carbon coating layer on the surface of the lithium-containing phosphate 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 monomer, thereby improving the cycle life of the battery monomer.

[0213] The positive electrode active material of the present application takes the lithium-containing phosphate as the base material, 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 monomer prepared from the positive electrode active material of the present application can improve the energy density of the battery monomer under the premise of excellent cycle performance.

[0214] 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 EPA6010D-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 monomer discharged to 0% state of charge SOC, washing and drying with DMC, and removing impurities by high temperature calcination, 0.4g of the positive electrode active material is weighed, 10ml (50% concentration) aqua regia is added thereto. Then it is placed on a 180℃ flat plate for 30min. After digestion on the flat plate, it is diluted to a volume of 100mL, and the standard curve method is used for quantitative testing.

[0215] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, which can be selected as 0.19 to 0.26. Exemplarily, 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.

[0216] When the graphitization degree of the positive electrode active material is in the above range, it is beneficial to improve the conductivity of the positive electrode active material and reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery monomer.

[0217] 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.

[0218] In some embodiments, the mass content of carbon element in the lithium-containing olivine-structured phosphate is 1% to 2%, and the specific surface area of the lithium-containing olivine-structured phosphate is 5m 2 / g to 18m 2 / g.

[0219] Optionally, the mass content of carbon element in the lithium-containing olivine-structured phosphate is 1% to 2%, and the specific surface area of the lithium-containing olivine-structured phosphate is 7.5m 2 / g to 14m 2 / g.

[0220] Illustratively, the mass content of carbon element in the lithium-containing olivine-structured 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.

[0221] Illustratively, the specific surface area of the lithium-containing olivine-structured 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.

[0222] 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 the 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 lithium-containing olivine-structured phosphate can be significantly improved, which is conducive to improving the ionic conductivity and electronic conductivity of the lithium-containing olivine-structured phosphate, and can improve the rapid charging capacity and energy density of the battery cell.

[0223] In the embodiments of the present application, the specific surface area of the material has the meaning known in the art, and can be detected by using the devices and methods known in the art, for example, the specific surface area is detected according to the test standard GB / T19587-2017, the positive electrode active material is used as a sample, and the specific surface area is tested by using a Tri-Star3020 type specific surface area pore size analyzer of the United States Micromeritics company.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] The particle size of the positive electrode active material is relatively small, the lithium ion has a shorter deintercalation lithium 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, so that agglomeration basically does not occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0228] 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 devices and methods known in the art. For example, the positive electrode active material is taken as a sample, the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E type laser particle size analyzer according to the test standard GB / T 19077-2016.

[0229] 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.

[0230] In some embodiments, the lithium-containing phosphate with olivine structure is in a particulate form, the lithium-containing phosphate with olivine structure includes secondary particles, the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. Exemplarily, the average particle size of the primary particles is 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, or a range formed by any two of the above values.

[0231] 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 production is less.

[0232] In the embodiments of the present application, the secondary particles refer to agglomerated particles formed by aggregation of 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) of 10.00 kV, InLens detector, working distance of 4.6 mm, and magnification of 1000X.

[0233] In some embodiments, the positive electrode film layer further comprises 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 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.

[0234] Optionally, the ternary material comprises Li x3 A y3 Ni a3 Co b3 Mn c M3(1-a3-b3-c3)Y3 z3 wherein 0

[0235] Exemplarily, the ternary material comprises LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 at least one of O2.

[0236] 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 within the foregoing range, the lithium supplement agent can supplement lithium ions for the positive electrode film layer, compensate for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0237] The lithium supplement agent can be located in the same layer as the positive electrode active material, or in different layers. When the lithium supplement agent and the positive electrode active material are 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 disposed 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 disposed 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 gradually release into the system during the cyclic charging and discharging of the battery cell, thereby compensating for the loss of lithium in the battery system.

[0238] In some embodiments, the positive electrode film layer can further optionally include a positive electrode conductive agent. The embodiments of the present application do not have special limitations on the type of positive electrode conductive agent. 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.

[0239] 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 special limitations on the type of positive electrode binder. 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 resin. In some embodiments, the mass content of the positive electrode binder is ≤5% based on the mass of the positive electrode film layer.

[0240] The positive electrode film layer is usually formed by coating a positive electrode slurry on a positive electrode current collector, and then drying and cold-pressing. The positive electrode slurry is usually formed by dispersing and uniformly stirring a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0241] 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 includes a positive electrode conductive layer arranged on the surface of the positive electrode current collector and sandwiched between the positive electrode current collector and the positive electrode film layer. In some other embodiments, the positive electrode tab of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0242] [Negative electrode tab]

[0243] The first electrode tab can be a negative electrode tab, the first current collector corresponds to a negative electrode current collector, the first support layer corresponds to a negative electrode support layer, the first metal layer corresponds to a negative electrode metal layer, the first film layer corresponds to a negative electrode film layer, and the first active material corresponds to a negative electrode active material. In this case, the second electrode tab can be a positive electrode tab, the second current collector corresponds to a positive electrode current collector, the second support layer corresponds to a positive electrode support layer, the second metal layer corresponds to a positive electrode metal layer, the second film layer corresponds to a positive electrode film layer, and the second active material corresponds to a positive electrode active material.

[0244] In the case of using a composite structure for the negative electrode current collector, the positive electrode current collector can use a conventional positive electrode current collector, such as an aluminum foil or the like. Alternatively, in the case of using a composite structure for the negative electrode current collector, the positive electrode current collector can also use a composite structure.

[0245] The negative electrode current collector has two opposite surfaces in the thickness direction of the negative electrode tab, and the negative electrode film layer is arranged on any one or both of the two opposite surfaces of the negative electrode current collector.

[0246] The negative electrode support layer has two opposite surfaces in the thickness direction of the negative electrode tab, and the negative electrode metal layer is arranged on any one or both of the two opposite surfaces of the negative electrode support layer. Optionally, the negative electrode metal layer is arranged on the two surfaces of the negative electrode support layer, and the negative electrode metal layer is located between the negative electrode support layer and the negative electrode film layer. The negative electrode support layer plays a supporting and protecting role for the negative electrode conductive layer. Since the negative electrode support layer is generally made of an organic polymer material, the density of the negative electrode support layer is generally less than the density of the negative electrode metal layer, thereby significantly improving the weight energy density of the battery cell compared with the conventional metal current collector.

[0247] Further, the negative electrode metal layer adopts a metal layer with a small thickness, which can further improve the volumetric energy density of the battery. Further, the negative electrode support layer can provide good bearing and protection for the negative electrode metal layer on its surface, so that the fracture of the electrode sheet, which is common in the traditional current collector, is less likely to occur.

[0248] In some embodiments, the thickness of the negative electrode current collector is 2-8.5 μm, and optionally 2-6.5 μm. For example, the thickness of the negative electrode current collector is 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 8 μm, 8.5 μm, or a range defined by any two of the above values.

[0249] When the thickness of the negative electrode current collector is in the above range, the thickness of the negative electrode current collector is relatively thin, which is beneficial to increase the thickness of the negative electrode film layer and improve the energy density of the battery cell.

[0250] In some embodiments, the thickness of the negative electrode metal layer is 0.3-2 μm, and optionally 0.5-1.5 μm. For example, the thickness of the negative electrode metal layer is 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.05 μm, 1.10 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 defined by any two of the above values.

[0251] When the thickness of the negative electrode metal layer is in the above range, the thickness of the negative electrode metal layer is relatively thin, and its conductivity is relatively excellent, which is beneficial to improve the rapid charging performance of the battery cell.

[0252] In some embodiments, the metal material in the negative electrode metal layer includes at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy. Optionally, the metal material in the negative electrode metal layer includes copper. The above materials have excellent conductivity, so that the internal resistance of the battery cell is relatively small, and the polarization is small, which is beneficial to improve the rapid charging performance of the battery cell.

[0253] Optionally, the negative electrode metal layer can further include at least one of conductive carbon materials, such as graphite, acetylene black, graphene, and carbon nanotubes.

[0254] The negative electrode metal layer can be formed on the negative electrode support layer by at least one of mechanical rolling, bonding, vapor deposition, and electroless plating, the vapor deposition being preferably physical vapor deposition (PVD), the physical vapor deposition being preferably at least one of evaporation and sputtering, the evaporation being preferably at least one of vacuum evaporation, thermal evaporation deposition, and electron beam evaporation method (EBEM), the sputtering being preferably magnetron sputtering, and at least one of vapor deposition and electroless plating being preferably used to make the bonding between the negative electrode support layer and the negative electrode metal layer stronger.

[0255] In some embodiments, the thickness of the negative electrode support layer is 1 μm to 4.5 μm, and can be 3 μm to 4 μm. For example, the thickness of the negative electrode support layer is 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or a range defined by any two of the above values.

[0256] When the thickness of the negative electrode support layer is in the above range, the mechanical strength of the negative electrode current collector can be effectively improved, and the bonding between the negative electrode support layer and the negative electrode metal layer is stronger, so that the structural stability of the negative electrode current collector is higher.

[0257] In some embodiments, the negative electrode support layer comprises an organic material, and the organic material comprises at least one of an insulating polymer material and a conductive polymer material. Alternatively, the organic material comprises an insulating polymer material, which is not conductive when the negative electrode support layer is made of an insulating material, so that the short-circuit resistance of the battery cell under abnormal conditions can be improved, the short-circuit current can be greatly reduced, the short-circuit heat generation can be greatly reduced, and the use reliability of the battery cell can be improved.

[0258] For example, the insulating polymer material comprises at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene diamine, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyphenylene terephthalamide, polypropylene, polyformaldehyde, epoxy resin, phenolic resin, polytetrafluoroethylene, polyphenylene sulfide, polyvinylidene fluoride, silicone rubber, polycarbonate, cellulose and its derivatives, starch and its derivatives, protein and its derivatives, polyvinyl alcohol and its crosslinked products, and polyethylene glycol and its crosslinked products.

[0259] Exemplarily, the conductive polymer material includes at least one of a polyazolide polymer material or a doped conjugated polymer material, and more preferably, the conductive polymer material includes at least one of a polypyrrole, a polyacetylene, a polyaniline, or a polythiophene.

[0260] Optionally, the negative electrode support layer can further include an inorganic material, which can be an insulating inorganic material, for example, an insulating polymer composite formed by compounding an insulating inorganic material and an insulating polymer material.

[0261] Exemplarily, the inorganic material is preferably at least one of a ceramic material, a glass material, or a ceramic composite material.

[0262] Optionally, the negative electrode support layer can further include an inorganic material, which can be a conductive inorganic material, for example, a conductive polymer composite formed by compounding a conductive inorganic material and a conductive polymer material.

[0263] Exemplarily, the conductive inorganic material includes at least one of a conductive carbon material, a metal material, or a composite conductive material; the conductive carbon material includes at least one of carbon black, a carbon nanotube, graphite, acetylene black, or graphene; the metal material includes at least one of nickel, iron, copper, aluminum, or an alloy of the above-mentioned metals; and the composite conductive material includes at least one of nickel-coated graphite powder or nickel-coated carbon fiber.

[0264] In some embodiments, the negative electrode tab further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode tab, reduce the heat generation of the negative electrode tab, and thus reduce the heat generation of the battery cell. Moreover, the negative electrode conductive layer can improve the bonding force between the negative electrode current collector and the negative electrode film layer, improve the connection strength therebetween, and reduce the contact resistance.

[0265] In some embodiments, the thickness of the negative electrode conductive layer is 0.1 μm to 2 μm. Exemplarily, the thickness of the negative electrode conductive layer can be 0.1 μm, 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-mentioned values.

[0266] When the thickness of the negative electrode conductive layer is within the above-mentioned range, the conductivity of the negative electrode tab can be further improved, the heat generation of the negative electrode tab can be reduced, and thus the heat generation of the battery cell can be reduced; and the energy density of the battery cell can be improved.

[0267] In the embodiments of the present application, the thickness of the negative electrode conductive layer has the meaning known in the art, can be detected by using the devices and methods known in the art, and can be detected by using the test method of the negative electrode conductive layer described above.

[0268] 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 electrical conductivity of the negative electrode conductive layer, thereby improving the electrical conductivity of the negative electrode sheet and reducing the heat generation of the battery cell; the negative electrode binder in the negative electrode conductive layer can improve the adhesion between the negative electrode current collector and the negative electrode film layer, thereby improving the structural stability of the negative electrode sheet.

[0269] In some embodiments, the negative electrode conductive layer can also 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, and the like.

[0270] 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 foregoing.

[0271] Illustratively, the negative electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0272] 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 foregoing.

[0273] 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.

[0274] In the embodiments of the present application, the thickness of the negative electrode current collector, the negative electrode support layer, the negative electrode metal layer, and the negative electrode conductive layer can be detected using devices and methods known in the art, such as tomography of the negative electrode sheet to directly measure the thickness of each layer.

[0275] In some embodiments, the compaction density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 at 100% state of charge of the battery cell. 3 3 Illustratively, the compaction density of the negative electrode film layer is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 ​1.28 g / 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.

[0276] 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 particles in the negative electrode film layer are closely packed, and the contact resistance between the particles is small, so that the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation.

[0277] In the embodiments of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge is a meaning known in the art, which can be detected by using the devices and methods known in the art, and the detection method is as follows:

[0278] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm2 2 to 170 mg / 1540.25 mm2 2 , and optionally 110 mg / 1540.25 mm2 2 to 150 mg / 1540.25 mm2 2 For example, the single-sided coating weight of the negative electrode film layer is 90 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 2 , 105 mg / 1540.25 mm2 2 , 108 mg / 1540.25 mm2 2 , 110 mg / 1540.25 mm2 2 , 112 mg / 1540.25 mm2 2 , 114 mg / 1540.25 mm2 2 , 115 mg / 1540.25 mm2 2 , 116 mg / 1540.25 mm2 2 , 118 mg / 1540.25 mm2 2 , 120 mg / 1540.25 mm2 2, 122 mg / 15 40.25 mm 2 , 125 mg / 15 40.25 mm 2 , 128 mg / 15 40.25 mm 2 , 130 mg / 15 40.25 mm 2 , 132 mg / 15 40.25 mm 2 , 135 mg / 15 40.25 mm 2 , 137 mg / 15 40.25 mm 2 , 140 mg / 15 40.25 mm 2 , 142 mg / 15 40.25 mm 2 , 145 mg / 15 40.25 mm 2 , 148 mg / 15 40.25 mm 2 , 150 mg / 15 40.25 mm 2 , 152 mg / 15 40.25 mm 2 , 155 mg / 15 40.25 mm 2 , 160 mg / 15 40.25 mm 2 , 165 mg / 15 40.25 mm 2 , 170 mg / 15 40.25 mm 2 or a range between any two of the above values.

[0279] 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.

[0280] 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.

[0281] In some embodiments, the powder resistivity of the negative active material is 0.005 Ω·cm to 0.043 Ω·cm, and can be 0.04 Ω·cm. For example, the powder resistivity of the negative 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 between any two of the above values.

[0282] The relatively low powder resistivity of the negative active material makes the resistance of the negative electrode tab relatively low, and the battery monomer generates less heat.

[0283] In the embodiments of the present application, the powder resistivity of the negative active material is in 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 follows: the powder resistivity of the positive active material is detected according to the method described above.

[0284] 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 , and optionally 1.55 g / cm 3 to 1.65 g / cm 3 . For example, 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 composed of any two of the above values.

[0285] 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 film layer can be more closely stacked, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0286] In the embodiments of the present application, the powder compaction density of the material is in the meaning known in the art, which can be detected by using the methods and devices known in the art, and is detected according to the test standard GB / T24533-2009. For example, a certain amount of negative active material is taken as a sample, added into a mold with a bottom area of 1.327 cm 2 of the UTM7305 electronic pressure testing machine, pressurized to 2000 kg (equivalent to 20000 N), keep pressure for 30 s, then release pressure, keep for 10 s, then record and calculate the powder compaction density of the negative active material under the action of 20000 N force.

[0287] In some embodiments, the charge specific capacity of the negative active material is 350 mAh / g to 480 mAh / g.

[0288] In some embodiments, the charge gram capacity of the negative active material at 0.1C rate is 350mAh / g to 480mAh / g. Illustratively, the charge 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 between any two of the above values.

[0289] When the charge gram capacity of the negative active material at 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0290] In the embodiments of the present application, the charge 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 test method of the charge gram capacity of the positive active material at 0.1C rate.

[0291] In some embodiments, the negative active material comprises a carbon-based material, which has high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass fraction 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%.

[0292] 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. When the two are used together, the cycle performance of the battery cell is excellent.

[0293] 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 between any two of the above values.

[0294] When the graphitization degree of the graphite particles is within the above range, the conductive performance of the graphite particles is excellent, which can reduce the heat generation of the negative electrode sheet and the heat generation of the battery cell, and can improve the fast charging performance of the battery cell.

[0295] 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.

[0296] 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.

[0297] 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.

[0298] 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.

[0299] 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 forming a carbon coating layer on at least part of the surface of the artificial graphite particles after carbonization treatment.

[0300] 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 the petroleum pitch is 250°C or lower.

[0301] 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.

[0302] Optionally, the carbonization treatment time is 1h to 6h.

[0303] 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.

[0304] In some embodiments, the negative active material can further include a silicon-based 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 cell.

[0305] Optionally, the silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0306] The silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0307] In some embodiments, the negative active material can further include at least one of a tin-based material and lithium titanate in addition to the carbon-based material and the optional silicon-based material. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0308] In some embodiments, the negative active material can further include at least one of a tin-based material and lithium titanate in addition to the carbon-based material and the optional silicon-based material. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0309] The qualitative and quantitative detection of each substance or element in the present application can be performed by using suitable devices and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. Those skilled in the art can also adaptively change certain detection steps / instrument parameters from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0310] For example, the negative electrode sheet or the negative active material can be subjected to X-ray powder diffraction test and qualitative analysis by using the JIS / K0131-1996 X-ray Diffraction Analysis General Method.

[0311] 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.

[0312] 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.

[0313] In the case of a single-layer film layer of 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 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.

[0314] In the case of at least two film layers of 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.

[0315] 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.

[0316] The interface of the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and optionally, irregular.

[0317] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0318] The negative electrode film layer includes at least two film layers, and the layered coating is conducive to improving 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.

[0319] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which is conducive to improving the compaction density of the negative electrode film layer. When the negative electrode active material 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.

[0320] 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 generally high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and improve the problem of lithium extraction on the surface of the negative electrode sheet.

[0321] 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.

[0322] 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 prone to agglomeration during preparation, and the stability of the material can be improved.

[0323] 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.

[0324] 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.

[0325] 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.

[0326] 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 packed, so that the energy density of the battery cell is improved, and the first negative film layer is relatively sparse in filling, and the pores are more abundant, which can improve the rapid charging performance of the battery cell. 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.

[0327] Optionally, the tap density of the carbon-based material in the first negative film layer is 0.82 g / cm 3 to 1.21 g / cm3 0.82 g / cm3, for example 3 0.85 g / cm3, for example 3 0.88 g / cm3, for example 3 0.90 g / cm3, for example 3 0.92 g / cm3, for example 3 0.95 g / cm3, for example 3 0.98 g / cm3, for example 3 1.00 g / cm3, for example 3 1.05 g / cm3, for example 3 1.08 g / cm3, for example 3 1.10 g / cm3, for example 3 1.12 g / cm3, for example 3 1.15 g / cm3, for example 3 1.18 g / cm3, for example 3 1.20 g / cm3, for example 3 1.21 g / cm3, for example 3 1.22 g / cm3, for example 3 1.23 g / cm3, for example 3 1.24 g / cm3, for example 3 1.25 g / cm3, for example The tap density of the carbon-based material in the first negative electrode film layer is within a suitable range, which can improve the rapid charging performance of the battery monomer.

[0328] Optionally, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm3 3 to 1.25 g / cm3 3 , for example 0.90 g / cm3 3 , 0.92 g / cm3 3 , 0.95 g / cm3 3 , 0.98 g / cm3 3 , 1.00 g / cm3 3 , 1.05 g / cm3 3 , 1.08 g / cm3 3 , 1.10 g / cm3 3 , 1.12 g / cm3 3 , 1.15 g / cm3 3 , 1.18 g / cm3 3 , 1.20 g / cm3 3 , 1.21 g / cm3 3 , 1.22 g / cm3 3 , 1.23 g / cm3 3 , 1.24 g / cm3 3 , 1.25 g / cm3 3 The tap density of the carbon-based material in the second negative electrode film layer is within a suitable range, which can improve the energy density of the battery monomer.

[0329] 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.

[0330] 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.

[0331] 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.

[0332] 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.

[0333] 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.

[0334] The BOL full charge test procedure is as follows: at 25°C, charge at a charge 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 discharge rate of 0.33C to 2.0V, stand for 10 min, the above one charge-discharge is one cycle, cycle for 10 cycles, then charge at a charge 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.

[0335] 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 capacity of the battery cell.

[0336] 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 capacity of the battery cell.

[0337] 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.

[0338] 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 a constant voltage of 3.65V, 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 a constant current of 0.33C at 25°C, 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.

[0339] 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).

[0340] 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.

[0341] 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.

[0342] 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.

[0343] 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.

[0344] 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.

[0345] 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.

[0346] 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.

[0347] 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.

[0348] 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.

[0349] 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.

[0350] 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.

[0351] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0352] 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.

[0353] 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.

[0354] 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.

[0355] In some embodiments, the first negative electrode film layer further comprises a negative electrode binder, and the second negative electrode film layer further comprises 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 comprises at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0356] 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.

[0357] In some embodiments, the negative electrode film layer further optionally comprises a negative electrode conductive agent. The type of the negative electrode conductive agent is not particularly limited in the embodiments of the present application, and as an example, the negative electrode conductive agent can comprise 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 negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0358] In some embodiments, the negative electrode film layer further optionally comprises a negative electrode binder. In some embodiments, the mass content of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0359] In some embodiments, the negative electrode film layer further optionally comprises other auxiliary agents. As an example, the other auxiliary agents can comprise thickening agents, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of the other auxiliary agents is ≤2% based on the total weight of the negative electrode film layer.

[0360] The negative electrode film layer is usually formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually formed by dispersing and uniformly stirring a negative electrode active material, an optional conductive agent, an optional binder, and other optional auxiliary agents in a solvent. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0361] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further comprises a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer, which is arranged on the surface of the negative electrode 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 electrode film layer.

[0362] In some embodiments, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05 to 1.30, which can be optionally 1.07 to 1.15. Exemplarily, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area 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 formed by any two of the above values.

[0363] When the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is in the above range, there are sufficient sites in the negative electrode film layer for lithium intercalation, which can reduce the risk of lithium precipitation; and it is also conducive to fast charging.

[0364] In the embodiments of the present application, the CB value has 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 negative electrode film layer per unit area and the capacity of the positive electrode film layer per unit area are calculated respectively, and the ratio of the two is calculated to obtain the CB value.

[0365] Specifically, taking the upper limit voltage of battery charging as 3.65V and the lower limit voltage of battery discharging as 2.0V as examples,

[0366] The capacity of the positive electrode film layer per unit area refers to the actual delithiation capacity of the positive electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the positive electrode sheet is taken out, and a CR2430 half buckle type battery of positive electrode-lithium sheet is assembled, and the area of the positive electrode sheet used is a*b*c mm 2 wherein the electrolyte is a solution of 1M LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio); then the assembled half buckle type battery is left to stand for 3h, the test is carried out at 25℃, 0.1C is used to charge (Charge) delithiation in the voltage range of 2.0V to 3.65V, then 0.05C is used to discharge (Discharge) lithium intercalation to 2.0V, and the cycle is repeated for 2 times, the discharge capacity of the second cycle is taken as Y mAh, the length of the positive electrode sheet of the actual battery design is b mm, the width is c mm, the number of surfaces of the positive electrode active material coated on the positive electrode current collector is d, and then the capacity of the positive electrode film layer per unit area = Y / a*b*c*d.

[0367] Specifically, the capacity of the negative electrode film layer per unit area refers to the actual lithium intercalation capacity of the negative electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode sheet is taken out, and a CR2430 type half-buckle battery of negative electrode-lithium sheet is assembled. The area of the negative electrode sheet used is fmm 2 wherein the electrolyte is a 1M LiPF6 solution in EC / EMC / DEC = 3 / 5 / 2 (mass ratio); then the assembled half-buckle battery is left to stand for 3h, the test is carried out at 25℃, and the lithium intercalation is carried out by discharging at a voltage interval of 2V-0V at a rate of 0.1C, and then the lithium deintercalation is carried out by charging at a rate of 0.05C to 2V, and the discharge capacity of the second cycle is taken as Z mAh, the actual battery design negative electrode sheet length is hmm, the width is imm, and the number of surfaces of the negative electrode active material coated on the negative electrode current collector is d, then the negative electrode lithium intercalation capacity = Z / f*h*i*d.

[0368] [Separation film]

[0369] In the embodiments of the present application, the separation film comprises a base film with a porous structure.

[0370] 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.

[0371] Optionally, the polyolefin comprises at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0372] In some embodiments, the porosity of the base film is 20% to 70%, and optionally 35% to 60%. For example, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range between any two of the above values.

[0373] 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 separation film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing the heat generation.

[0374] In the embodiments of the present application, the porosity refers to the percentage of the pore volume in the separation film to the total volume of the separation film. The porosity can be tested according to the standard GB / T 36363-2018 "Polyolefin Separation Film for Battery Cell". It should be noted that the actual test process can be slightly different from the standard in order to obtain more accurate test values, according to the differences in test instruments, test errors, and in order to eliminate the influence on the test of the porosity as much as possible.

[0375] In some embodiments, the thickness of the base film is 6-12 μm, optionally 6-9 μm. For example, the thickness of the base film is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range defined by any two of the above values.

[0376] When the thickness of the base film is in the above range, the migration path of lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell, thereby reducing the heat generation.

[0377] 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. 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.

[0378] In some embodiments, the functional layer comprises a first functional layer and a second functional layer. The first functional layer is disposed on one side of the base film and comprises first inorganic particles. The second functional layer is disposed on the other side of the base film and 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.

[0379] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

[0380] Optionally, the first functional layer can comprise a binder, optionally at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0381] Optionally, the first inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0382] In the embodiments of the present application, the thickness of the base film has the meaning known in the art, which can be detected using the meaning and equipment known in the art. For example, a newly prepared separator film can be taken as a sample, or a battery cell that has been fully discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the separator film is obtained from the battery cell and dried as a sample. The separator film is cut off using an ion beam cutting instrument to form a cross section, and then the thickness of the cross section of the separator film and each layer thereof is measured using a scanning electron microscope.

[0383] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers, which optionally include acrylate-acrylonitrile-acrylamide-acryl copolymers. The acrylate copolymers have excellent bonding properties and high bonding stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as 35%:30%:15%:20%, or 40%:20%:10%:30%, or 45%:15%:20%:20%, and the like.

[0384] The second inorganic particles in the composite particles prevent the non-fluoropolymer particles from being easily bonded due to high-temperature treatment during the granulation process, so that the composite particles have pores, which are beneficial to the transmission of lithium ions and improve the ion conductivity of the separator film. In addition, the second inorganic particles can also improve the compression modulus of the composite particles, so that the composite particles are less likely to deform during charging and discharging, making the structure of the separator film more stable and improving the kinetic performance of the battery cell and the rapid charging performance. Optionally, the second functional layer is arranged close to the negative electrode tab, and the separator film is less likely to cause side effects such as extrusion to the negative electrode tab due to the less deformation of the composite particles, so that the kinetic performance of the negative electrode tab is stable. Correspondingly, the first functional layer is arranged close to the positive electrode tab.

[0385] 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 cooperate with the non-fluoropolymer to form composite particles, further improving the cycle stability and kinetic performance of the separator film and the cycle performance and rapid charging performance of the battery cell.

[0386] 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. For example, 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 formed by 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.

[0387] In the embodiments of the present application, the average particle size of the second inorganic particles is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, after the separator film is obtained and dried as a sample, the separator film is cut by an ion beam cutter to form a cross section, and then the particle size of the second inorganic particles in the separator film is measured by using a scanning electron microscope, the particle sizes of a plurality of, for example, 50, second inorganic particles are measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0388] In some embodiments, the ionic conductivity of the separator film is 0.3 mS / cm to 0.6 mS / cm. Illustratively, the ionic 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 consisting of any two of the above values.

[0389] When the ionic 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.

[0390] In the embodiments of the present application, the ionic 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,

[0391] Preparation of a 2025 type button cell for testing: in a vacuum glove box, lithium pieces are placed into a negative electrode shell, 150 μL of an electrolyte is added, the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), a separator film (area of 3.14 cm 2 , thickness of 12 μm) is placed to tightly adhere to the lithium pieces, 25 μL of an electrolyte is added, and finally a positive electrode piece (the positive electrode piece can be the positive electrode piece in Example 1) is placed thereon, and then the button cell is packaged. The assembled button cell is taken out of the vacuum glove box and placed for 24 h for the next step of testing.

[0392] Test: in an electrochemical workstation, a test is performed in a frequency range of 10 -1 ~ 10 6 Hz, the resistance Rb of the separator film is obtained, and the ionic conductivity σ (unit: mS / cm) is calculated by the following formula, σ = L / (R b × S)

[0393] 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.

[0394] [Electrolyte]

[0395] In some embodiments, the battery cell further comprises an electrolyte.

[0396] During the charging and discharging of the battery cell, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in conducting the active ions between the positive electrode sheet and the negative electrode sheet.

[0397] 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.

[0398] When the conductivity of the electrolyte at room temperature, for example 25℃, 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.

[0399] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, for example 25℃, is ionic conductivity, which can be detected by using devices and methods known in the art, for example, referring to industry standard HG-T4067-2015 for testing.

[0400] 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.

[0401] When the viscosity of the electrolyte at room temperature, for example 25℃, 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.

[0402] 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, according to GB / T10247-2008 for testing.

[0403] In some embodiments, the density of the electrolyte at room temperature, for example 25℃, is 1.05 g / mL to 1.35 g / mL. Illustratively, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, or a range between any two of the above values.

[0404] 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 can improve the rapid charging performance of the battery cell.

[0405] In the embodiments of the present application, the density of the electrolyte 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 GB / T 2013-2010 for testing.

[0406] 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.

[0407] 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 electrolyte is greater than or equal to 4% and less than or equal to 65%, which can be selected to be greater than or equal to 8.5% and less than or equal to 65%, or 25% to 60%. Illustratively, the mass content of the chain carboxylate solvent is 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 65%, or a range between any two of the above values.

[0408] 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.

[0409] In some embodiments, the chain carboxylate solvent includes a compound shown in Formula I,

[0410] In Formula I,

[0411] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group,

[0412] R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

[0413] The chain carboxylate solvent described above has a high conductivity, which is beneficial to improving the rapid charging capacity of the battery cell.

[0414] Optionally, R1comprises a hydrogen atom, a halogen atom, a C1to C3alkyl group, or a C1to C3haloalkyl group. Further optionally, R1comprises a hydrogen atom, a halogen atom, a C1to C2alkyl group, or a C1to C2haloalkyl group.

[0415] Optionally, R2comprises a C1to C3alkyl group or a C1to C3haloalkyl group. Further optionally, R2comprises a C1to C2alkyl group or a C1to C2haloalkyl group.

[0416] In each of the above embodiments, the halogen atom comprises one or more of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Optionally, the halogen atom comprises a fluorine atom.

[0417] In each of the above embodiments, the haloalkyl group comprises one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group, and an iodoalkyl group. Optionally, the haloalkyl group comprises a fluoroalkyl group.

[0418] Exemplarily, the chain carboxylate-based solvent comprises one or more of a compound represented by Formula I-1 to a compound represented by Formula I-8,

[0419] In some embodiments, the organic solvent further comprises a carbonate-based solvent.

[0420] Optionally, the carbonate-based solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Further optionally, the carbonate-based solvent comprises one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate. The above carbonate-based solvent and chain carboxylate-based solvent are used in combination, so that the conductivity of the electrolyte is improved, which is conducive to the migration of lithium ions.

[0421] Further optionally, the mass content of the carbonate-based solvent in the electrolyte is 25% to 60%, which can be 25% to 42.5%. Exemplarily, the mass content of the carbonate-based solvent in the electrolyte is 25%, 28%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, or a range composed of any two of the above values. The above mass content of the carbonate-based solvent can further improve the conductivity of the electrolyte at room temperature, which is conducive to the migration of lithium ions.

[0422] Exemplarily, the carbonate-based solvent comprises one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate, and the mass content of the carbonate-based solvent is 25% to 42.5%.

[0423] In some embodiments, the electrolyte further comprises an additive, which can include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, and the like.

[0424] 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 is capable of improving the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0425] 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%. Illustratively, 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 between any two of the foregoing values.

[0426] The additive in the above mass content is capable of effectively improving the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0427] Illustratively, the carbonate additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0428] Illustratively, the sulfur-containing additive comprises one or more of vinyl sulfate DTD, bis vinyl sulfate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methyl methylene disulfite MMDS.

[0429] 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.

[0430] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, and optionally 2% to 6%.

[0431] Optionally, the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%, and optionally 0.5% to 3%.

[0432] 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%.

[0433] 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%.

[0434] In some embodiments, the electrolyte salt comprises a lithium salt, the electrolyte comprises the lithium salt, and the lithium salt comprises one or more of a fluorine-containing sulfimide salt and lithium hexafluorophosphate LiPF6. The above lithium salt is prone to dissociation, which is conducive to the rapid migration of lithium ions; and the electrolyte system is relatively stable and is not prone to decomposition, which can improve the cycle performance of the battery cell.

[0435] Optionally, the fluorine-containing sulfimide salt comprises one or more of lithium bisfluorosulfimide LiFSI and lithium bis-trifluoromethanesulfonimide LiTFSI.

[0436] Optionally, the lithium salt comprises lithium bisfluorosulfimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of the lithium bisfluorosulfimide LiFSI is 0.2 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.5 mol / L to 1.0 mol / L. Illustratively, the molar concentration of the lithium bisfluorosulfimide LiFSI is 0.4 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.7 mol / L. Illustratively, the molar concentration of the lithium bisfluorosulfimide LiFSI is 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.5 mol / L. Illustratively, the molar concentration of the lithium bisfluorosulfimide LiFSI is 0.2 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.8 mol / L.

[0437] Optionally, the ratio of the molar concentration of the lithium bisfluorosulfimide LiFSI to the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.2 to 1.0, and optionally 0.2 to 0.5. Illustratively, the ratio of the molar concentration of the lithium bisfluorosulfimide LiFSI to the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range formed by any two of the above values.

[0438] The qualitative and quantitative detection of the substances or elements in the present application can be carried out by using suitable devices and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. Those skilled in the art can also adaptively change certain detection steps / instrument parameters from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used for qualitative or quantitative determination.

[0439] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt in the electrolyte are in the meanings known in the art, and can be detected by using the devices and methods known in the art, for example, the qualitative or quantitative analysis of the inorganic components / lithium salt in the electrolyte can be performed by ion chromatography according to the standard JY / T020-1996 "General Ion Chromatography Analysis Method". In the embodiments of the present application, the newly prepared electrolyte can be taken as 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) by reverse disassembly can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0440] 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, and 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 the standard GB / T9722-2006 "General Gas Chromatography Method for Chemical Reagents". In the embodiments of the present application, the newly 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) by reverse disassembly can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0441] 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, the carbonate solvent (for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate) is taken as the constituent component of the organic solvent, and the mass content of each component is calculated based on 100% of the mass of the electrolyte.

[0442] The carbonate additive (for example, vinylene carbonate, fluoroethylene carbonate), the sulfur-containing additive and the lithium salt additive are taken as the additive of the electrolyte, and the mass content of each component is calculated based on 100% of the mass of the electrolyte.

[0443] 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.

[0444] The d / A can reflect the liquid retention capability of the electrolyte. When the d / A is within the above range, the electrolyte can have a good infiltration effect on the positive electrode plate and the negative electrode plate, and can improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the rapid charging capability of the battery cell.

[0445] In the embodiments of the present application, the d / A of the battery cell can be understood as a liquid retention coefficient, which can be detected by using devices and methods known in the art. For example, according to GB / T31486-2015 “Power Battery for Electric Vehicles: Electrical Performance Requirements and Test Methods”, the battery charging upper limit voltage is 3.65V, and the battery discharging cut-off voltage is 2.0V.

[0446] At 25°C, the battery cell is charged to 3.65V at 0.33C, and then is charged to 0.05C at constant voltage, and then is discharged to 2.0V at 0.33C constant current, and the discharged capacity A is obtained as the denominator; the battery cell is weighed as M0, and then the positive electrode plate, the negative electrode plate, the separator and the electrolyte are disassembled, and the free electrolyte is in the shell / bag, and all the solid components are placed in a 60°C oven for baking for more than 4 hours (including but not limited to the positive electrode plate, the negative electrode plate, the separator, and other mechanical parts of the disassembled battery cell contributing to M0), and then all the components of the battery cell are weighed as M1, and the weight difference between M0 and M1 is taken as the numerator. The liquid retention coefficient is equal to the value obtained by dividing the weight difference between M0 and M1 by the capacity A.

[0447] In some embodiments, the positive electrode plate, the separator and the negative electrode plate can be made into an electrode assembly by a winding process and / or a stacking process.

[0448] Please continue to refer to FIGS. 1 to 7. In some embodiments, the battery cell 7 can include a shell 20.

[0449] 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 bag-type 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).

[0450] The shell 20 is a hollow structure, which can be used to package the above-mentioned electrode assembly 10 and electrolyte.

[0451] 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 and the negative electrode sheet can be wound and / or laminated to form the electrode assembly 10, the electrode assembly 10 is placed in the shell 20, the electrolyte is injected after drying, and the battery cell 7 is obtained after the processes of vacuum packaging, standing, formation, shaping and the like.

[0452] In some embodiments, the shell 20 includes a shell body 21 having an opening and an end cover 22 covering the opening.

[0453] The shape of the shell body 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical shell body can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid shell body can be selected. Alternatively, the electrode assembly 10 and the shell body 21 are both cuboid structures.

[0454] In some embodiments, the material of the shell body 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 cell. Alternatively, the steel has the highest mass ratio among the materials in the shell body 21.

[0455] Alternatively, the thickness of the shell body 21 is 0.1 mm to 0.5 mm, which can be 0.2 mm to 0.35 mm. For example, the thickness of the shell body 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 composed of any two of the above values. When the thickness of the shell body 21 is in the above range, the mechanical strength of the shell body 21 is high, which can improve the use reliability and cycle performance of the battery cell; and the shell body 21 occupies less space, and the internal space of the shell body 21 is larger, which is beneficial to improve the energy density of the battery cell.

[0456] In some embodiments, the first metal layer includes a first portion and a second portion extending from the first portion, the first portion is provided with the first film layer, and the second portion is not provided with the first film layer.

[0457] The first electrode sheet further includes a first tab connected with the second portion.

[0458] From the appearance of the electrode assembly 10, the electrode assembly 10 includes a main body portion 12, a first tab 111 and a second tab 112, which protrude from the main body portion 12. The first tab 111 and the second tab 112 are used to lead out the current in the main body portion 12. The polarities of the first tab and the second tab are opposite, in other words, 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.

[0459] In some embodiments, the first metal layer 1312 includes a first portion 1312a and a second portion 1312b extending from the first portion 1312a, the first portion 1312a is provided with the first film layer 132, and the second portion 1312b is not provided with the first film layer 132; the first electrode tab 13 further includes a first tab 111 connected with the second portion 1312b. The first electrode tab 13 shown in FIG. 5 shows a connection diagram of the first metal layer 1312 and the first tab 111.

[0460] Optionally, the first tab 111 includes a first tab main body portion 1111 and a first tab connecting portion 1112, the first tab main body portion 1111 is arranged on two surfaces of the second portion 1312b opposite to each other along the thickness direction X, the first tab connecting portion 1112 is connected with the first tab main body portion 1111, and the first tab connecting portion 1112 is located on the side of the second portion 1312b away from the first portion 1312a; this arrangement is conducive to the first tab 111 leading out the current.

[0461] The second tab 112 can adopt a similar structure form as the first tab 111.

[0462] The first tab 111 and the second tab 112 can protrude from the same side of the main body portion 12, or can respectively protrude from opposite sides.

[0463] Optionally, the number of the first tabs 111 located on the same side of the main body portion 12 is at least one, and can be at least two, and the at least two first tabs 111 can increase the current carrying capacity of the first tab 111.

[0464] Optionally, the number of the second tabs 112 located on the same side of the main body portion 12 is at least one, and can be at least two, and the at least two second tabs 112 can increase the current carrying capacity of the second tab 112.

[0465] 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 an adapter or without an adapter. Optionally, the first electrode terminal 31 and the first tab 111 are directly welded without an adapter, which can reduce the resistance at the connection and is conducive to reducing the overall internal resistance of the battery cell 7. 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.

[0466] 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 an adapter or without an adapter. Optionally, the second electrode terminal 32 and the second tab 112 are directly welded without an adapter, which can reduce the resistance at the connection and is conducive to reducing the overall internal resistance of the battery cell 7. 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.

[0467] Optionally, the number of first electrode terminals 31 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 electrode terminals 31 can increase the overcurrent capacity of the first electrode terminal 31.

[0468] Further optionally, the overcurrent area of the single-side first electrode terminal 31 is 150mm 2 to 1000mm 2 , and can be 200mm 2 to 1000mm 2 . The overcurrent area of the single-side first electrode terminal 31 refers to the sum of the overcurrent areas of all first electrode terminals 31 on the same side of the main body part 12. The overcurrent 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 first electrode terminal 31.

[0469] Illustratively, 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 between any two of the above values.

[0470] Optionally, the number of second electrode terminals 32 located on the same side of the main body portion 12 is at least one, and optionally at least two. The at least two second electrode terminals 32 can increase the overcurrent capacity of the second electrode terminals 32.

[0471] Further optionally, the overcurrent area of the single-side second electrode terminals 32 is 150mm 2 to 1000mm 2 , and optionally 200mm 2 to 1000mm 2 . The overcurrent area of the single-side second electrode terminals 32 refers to the sum of the overcurrent areas of all the second electrode terminals 32 located on the same side of the main body portion 12. The overcurrent area of the second electrode terminals 32 can be understood as the cross-sectional area of the second electrode terminals 32, which is perpendicular to the thickness direction of the second electrode terminals 32.

[0472] Illustratively, the overcurrent area of the single-side second electrode terminals 32 can be 150mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 , 650mm 2 , 700mm 2 , 750mm2 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.

[0473] As shown in FIG. 8, 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.

[0474] 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.

[0475] As shown in FIG. 9, 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 herein can be the battery module 6 or the battery pack 2.

[0476] 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.

[0477] The first box portion 5a and the second box portion 5b are mutually covered, and the first box portion 5a and the second box portion 5b together define the accommodation space 5c for accommodating the battery cell. The second box portion 5b can be a hollow structure with one end open, and the first box portion 5a is a plate-shaped structure, which is covered on the open side of the second box portion 5b to form the box 5 with the accommodation space 5c; the first box portion 5a and the second box portion 5b can also be hollow structures with one side open, and the open side of the first box portion 5a is covered on the open side of the second box portion 5b to form the box 5 with the accommodation space 5c. Of course, the first box portion 5a and the second box 5b can be various shapes, such as a cylinder, a cuboid, etc.

[0478] To improve the sealing performance of the first box body part 5a and the second box body part 5b after being connected, a sealing member such as sealing glue, sealing ring, etc. can be arranged between the first box body part 5a and the second box body part 5b.

[0479] Suppose the first box body part 5a is covered on the top of the second box body part 5b, the first box body part 5a can also be called an upper box cover, and the second box body part 5b can also be called a lower box body.

[0480] In some embodiments, the temperature of the external environment in which the battery pack 2 or any battery cell constituting the battery pack 2 is located is room temperature, for example 30°C, during the charging process from 0% state of charge SOC to 100% state of charge SOC.

[0481] In some embodiments, the temperature of the external environment in which the battery pack 2 or any battery cell constituting the battery pack 2 is located is 30°C during the process from 10% state of charge SOC to 80% state of charge SOC.

[0482] In some embodiments, the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge includes a plurality of charging steps, and the difference between the maximum state of charge of any charging step and the maximum state of charge of its adjacent charging step is less than or equal to 5% state of charge, for example 1% state of charge, 1.5% state of charge, 2% state of charge, 2.5% state of charge, 3% state of charge, 3.5% state of charge, 4% state of charge, 4.5% state of charge, 5% state of charge, or a range composed of any two of the above values.

[0483] The charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 40% state of charge includes a plurality of charging steps, and for any charging step, it can be charged at any rate between 5C and 10C, and the corresponding charging rate of each charging step can be any value in the range composed of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a range composed of any two of the above values.

[0484] For example, the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be carried out as follows:

[0485] Charged from 10% SOC to 15% SOC at a constant current of 5.0C;

[0486] Charged from 15% SOC to 20% SOC at a constant current of 5.0C;

[0487] Charged from 20% SOC to 25% SOC at a constant current of 5.0C;

[0488] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0489] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0490] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0491] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0492] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0493] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0494] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0495] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0496] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0497] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0498] Charge from 30% SOC to 35% SOC at 5.0 C constant current.

[0499] In some embodiments, the battery pack 2 or any battery cell constituting the battery pack 2 has a charging time from 10% state of charge to 80% state of charge less than or equal to 10.5 min, optionally 5 min to 10.5 min, and the battery pack 2 is at room temperature, for example 30 °C, at 10% state of charge. Illustratively, the battery pack 2 has a charging time from 10% state of charge to 80% state of charge of 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 between any two of the foregoing values.

[0500] In some embodiments, the volumetric energy density of the battery cell is 380-500 Wh / L, optionally 380-470 Wh / L. Illustratively, the volumetric energy density of the battery cell is 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500 Wh / L or a range defined by any two of the above values. The battery cell has a high volumetric energy density.

[0501] 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 3.65 V and the battery discharge cut-off voltage of 2.0 V as an example for illustration,

[0502] The battery cell is placed at 25°C, charged to 3.65 V at a constant current of 0.33 C, and then charged to 0.05 C at a constant voltage. It is discharged at a constant current of 0.33 C to 2.0 V, and the discharge capacity A0 at this time is recorded, with the unit being Ah. The length, width and height of the battery cell are measured using a caliper (generally calculated based on 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, with the unit being L. The volumetric energy density VED of the battery cell is (A0 x discharge platform voltage) / V0, with the unit being Wh / L.

[0503] In some embodiments, the gravimetric energy density of the battery cell is 180-210 Wh / Kg. Illustratively, the gravimetric energy density of the battery cell is 180, 190, 200, 210 Wh / Kg or a range defined by any two of the above values. The battery cell has a high volumetric energy density.

[0504] 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 3.65 V and the battery discharge cut-off voltage of 2.0 V as an example for illustration,

[0505] The battery cell is placed at 25°C, charged to 3.65 V at a constant current of 0.33 C, and then charged to 0.05 C at a constant voltage. It is discharged at a constant current of 0.33 C to 2.0 V, and the discharge capacity A0 at this time is recorded, with the unit being Ah. The length, width and height of the battery cell are measured using a caliper (generally calculated based on 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, with the unit being L. The volumetric energy density VED of the battery cell is (A0 x discharge platform voltage) / V0, with the unit being Wh / L.

[0506] Electric device

[0507] The second aspect of the embodiments of the present application provides a power utilization 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 utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization 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 automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended electric automobile, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric automobile 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 utilization device.

[0508] The power utilization device can select a battery cell, a battery module or a battery pack according to its use requirement.

[0509] FIG. 10 is a schematic diagram of a power utilization device 1 as an example. The power utilization device 1 is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the power utilization device 1, a battery pack or a battery module can be used.

[0510] The power utilization 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 utilization device 1. The battery pack 2 can be used for power supply of the power utilization device 1, for example, the battery pack 2 can be used as an operating power source of the power utilization device 1, and can also be used as a driving power source of the power utilization device 1, instead of or partially instead of fuel or natural gas to provide driving power for the power utilization device 1.

[0511] The power utilization device 1 can further include a controller 3 and a motor 4, and the controller 3 is used to control the battery pack 2 to supply power to the motor 4, for example, to meet the working power requirement of the power utilization device 1 during starting, navigation and driving.

[0512] The power utilization device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power utilization device usually requires thinning, and a battery cell can be used as a power source.

[0513] The charging process of the power utilization device can select the following charging mode:

[0514] Charging from 10% SOC to 15% SOC at 5.0C constant current;

[0515] Charge from 20% SOC to 25% SOC at 5.0 C constant current;

[0516] Charge from 20% SOC to 25% SOC at 5.0 C constant current;

[0517] Charge from 25% SOC to 30% SOC at 5.0 C constant current;

[0518] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0519] Charge from 35% SOC to 40% SOC at 5.0 C constant current;

[0520] Charge from 40% SOC to 45% SOC at 4.6 C constant current;

[0521] Charge from 45% SOC to 50% SOC at 4.3 C constant current;

[0522] Charge from 50% SOC to 55% SOC at 4.0 C constant current;

[0523] Charge from 55% SOC to 60% SOC at 3.7 C constant current;

[0524] Charge from 60% SOC to 65% SOC at 3.4 C constant current;

[0525] Charge from 65% SOC to 70% SOC at 3.1 C constant current;

[0526] Charge from 70% SOC to 75% SOC at 2.9 C constant current;

[0527] Charge from 75% SOC to 80% SOC at 2.7 C constant current.

[0528] 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.

[0529] Embodiments

[0530] The following examples describe the present application in more detail, which are only used for illustrative purposes, because various modifications and changes within the scope of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further purification, and the instruments used in the examples are commercially available.

[0531] Example 1

[0532] 1. Preparation of positive electrode sheet

[0533] The positive electrode sheet comprises a positive electrode current collector, a positive electrode conductive layer on the positive electrode current collector, and a positive electrode film layer. The positive electrode current collector comprises a positive electrode support layer and a positive electrode metal layer arranged on both sides of the positive electrode support layer.

[0534] The positive electrode conductive layer on the positive electrode current collector is a film layer formed by uniformly mixing a positive electrode conductive agent, super carbon, and a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and then coating on the surface of the current collector and drying. The thickness 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%.

[0535] The positive electrode film layer comprises a film layer formed by uniformly coating a positive electrode slurry (solvent is N-methyl pyrrolidone (NMP)) on the surface of the positive electrode conductive layer, and then drying and cold pressing. The positive electrode film layer comprises a positive electrode active material, a binder, polyvinylidene fluoride (PVDF), and a conductive agent, acetylene black, in a weight ratio of 97:2:1.

[0536] The positive electrode 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 iron titanium phosphate Li2FeTi(PO4)3 and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0537] The single-sided coating weight of the positive electrode film layer is 285 mg / 1540.25 mm 2 .

[0538] 2. Preparation of negative electrode sheet

[0539] The negative electrode sheet comprises 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 comprises a negative electrode support layer and a negative electrode metal layer arranged on both sides of the negative electrode support layer.

[0540] The negative electrode conductive layer on the negative electrode current collector is a film layer 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 and drying it. 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%. The mass content of the thickening agent in the negative electrode conductive layer is 5%.

[0541] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer, and then drying and cold pressing it.

[0542] The single-side coating weight of the negative electrode film layer is 130 mg / 1540.25 mm 2 .

[0543] 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.

[0544] The first negative electrode film layer includes graphite particles, a conductive agent, a first lithium-containing binder, a negative electrode binder, and a thickening agent, with a mass ratio of 96.5:0.5:0.5:1:1.5. The mass content of lithium in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer is coated on the surface of the artificial graphite. The mass content of the carbon coating layer is 3.5%.

[0545] The second negative electrode film layer includes graphite particles, a conductive agent, a second lithium-containing binder, a negative electrode binder, and a thickening agent, with a mass ratio of 97.5:0.5:0.5:0.5:1. The mass content of lithium 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. The mass content of the carbon coating layer is 3.5%.

[0546] 3. Separation film

[0547] The separation film includes a base film, which is a 7 μm polyethylene film layer with a porosity of 42%.

[0548] 4. Preparation of electrolyte

[0549] The electrolyte comprises an organic solvent, a lithium salt and an additive.

[0550] The organic solvent comprises 48.5% of a chain carboxylate solvent (ethyl acetate) and 32.5% of a carbonate solvent (24.5% of ethylene carbonate EC, 8% of dimethyl carbonate).

[0551] 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.

[0552] The lithium salt comprises 1 mol / L of lithium hexafluorophosphate LiPF6.

[0553] The electrolyte has an electrical conductivity of 16.4 mS / cm at room temperature.

[0554] 5. Preparation of battery cell

[0555] 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 2.60 g / cm 3 at 100% SOC, and the compaction density of the negative electrode film layer is 1.26 g / cm 3 at 100% SOC.

[0556] Comparative Example 1

[0557] A battery cell is prepared by a method similar to that of Example 1, except that the positive current collector is an aluminum foil with a thickness of 15 μm and the negative current collector is a copper foil with a thickness of 6 μm.

[0558] Examples 2-1 to 2-7

[0559] A battery cell is prepared by a method similar to that of Example 1, except that the material and thickness of the positive current collector are adjusted.

[0560] Examples 3-1 to 3-7

[0561] A battery cell is prepared by a method similar to that of Example 1, except that the material and thickness of the negative current collector are adjusted.

[0562] The test results are shown in Table 1.

[0563] Table 1

[0564] In Table 1, PET represents polyethylene terephthalate.

[0565] As can be seen from Table 1, compared with the metal foil as the current collector in Comparative Example 1, the composite structure of the current collector in the embodiments of the present application can improve the volume energy density and the weight energy density of the battery monomer.

[0566] In the embodiments of the present application, the battery monomer has excellent rapid charging performance. Under this condition, the coating weight of the positive electrode film layer and the negative electrode film layer is usually thin, and the composite current collector structure can significantly improve the volume ratio of the positive electrode film layer and the negative electrode film layer, thereby improving the volume energy density of the battery monomer. In addition, due to the light weight of the composite current collector, the weight energy density of the battery monomer can also be improved.

[0567] Moreover, when the positive electrode current collector comprises aluminum material, the volume energy density of the battery monomer can be more obviously improved; when the negative electrode current collector comprises copper material, the weight energy density of the battery monomer can be more obviously improved.

[0568] The positive electrode metal layer can improve the conductivity and improve the rapid charging performance.

[0569] Examples 4-1 to 4-4

[0570] The battery monomer was prepared by using a method similar to that of Example 1, and the coating weight of the positive electrode film layer and the negative electrode film layer was adjusted, which was different from that of Example 1.

[0571] Performance test

[0572] 1. Lithium precipitation area test of the battery monomer

[0573] After the battery monomer of each example and the comparative example was cycled for 50 cycles according to the following charging and discharging strategy, the negative electrode sheet in the battery pack was disassembled, the negative electrode sheet was unfolded, the lithium precipitation area (gray-white area) was observed, and the lithium precipitation area was measured. The degree of lithium precipitation is as follows:

[0574] No lithium precipitation: lithium precipitation area <0.05%.

[0575] Mild lithium precipitation: lithium precipitation area <2%.

[0576] Severe lithium precipitation: lithium precipitation area ≥2%.

[0577] The battery monomer was charged at an external environment temperature of 30°C, and the charging steps included the following steps:

[0578] Charged from 0% SOC to 5% SOC at a constant current of 5.0C;

[0579] Charge from 5% SOC to 10% SOC at 5.0C constant current;

[0580] Charge from 10% SOC to 15% SOC at 5.0C constant current;

[0581] Charge from 15% SOC to 20% SOC at 5.0C constant current;

[0582] Charge from 20% SOC to 25% SOC at 5.0C constant current;

[0583] Charge from 25% SOC to 30% SOC at 5.0C constant current;

[0584] Charge from 30% SOC to 35% SOC at 5.0C constant current;

[0585] Charge from 35% SOC to 40% SOC at 5.0C constant current;

[0586] Charge from 40% SOC to 45% SOC at 4.6C constant current;

[0587] Charge from 45% SOC to 50% SOC at 4.3C constant current;

[0588] Charge from 50% SOC to 55% SOC at 4.0C constant current;

[0589] Charge from 55% SOC to 60% SOC at 3.7C constant current;

[0590] Charge from 60% SOC to 65% SOC at 3.4C constant current;

[0591] Charge from 65% SOC to 70% SOC at 3.1C constant current;

[0592] Charge from 70% SOC to 75% SOC at 2.9C constant current;

[0593] Charge from 75% SOC to 80% SOC at 2.7C constant current;

[0594] Charge from 80% SOC to 85% SOC at 1.8C constant current;

[0595] Charge from 85% SOC to 90% SOC at 1.3C constant current;

[0596] Charge from 90% SOC to 95% SOC at 0.7C constant current;

[0597] Charge from 95% SOC to 98% SOC at 0.33C constant current;

[0598] Charge from 98% SOC to 100% SOC at 0.1C constant current.

[0599] The cut-off voltage of the last charging step in the above charging steps is 3.65 V.

[0600] The discharging strategy is as follows: constant current discharge at 0.33 C to a cut-off voltage of, for example, 2.0 V.

[0601] The test results are shown in Table 2.

[0602] Table 2

[0603] By controlling the coating weight of the positive electrode film layer and the negative electrode film layer, the volumetric energy density of the battery monomer can be improved. However, when the coating weight is too high, although the energy density is significantly improved, the risk of lithium precipitation is greater.

[0604] 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

A battery cell includes an electrode assembly including a first electrode tab, a second electrode tab, and a separator disposed between the first electrode tab and the second electrode tab, and the first electrode tab and the second electrode tab have opposite polarities; The first electrode tab includes a first current collector and a first film layer disposed on at least one side of the first current collector and including a first active material; The second electrode tab includes a second current collector and a second film layer disposed on at least one side of the second current collector and including a second active material; wherein One of the first active material and the second active material includes a lithium-containing phosphate with an olivine structure, and the other includes a carbon-based material; The first current collector includes a first support layer and a first metal layer disposed on at least one side of the first support layer, and the first metal layer has the first film layer disposed thereon, and the first support layer includes an organic material. The battery cell of claim 1, wherein, The second current collector includes a second support layer and a second metal layer disposed on at least one side of the second support layer, and the second metal layer has the second film layer disposed thereon, and the second support layer includes an organic material. The battery cell according to claim 1 or 2, wherein, The first electrode tab is a positive electrode tab, and the first metal layer is disposed on both sides of the first support layer. The battery cell of claim 3, wherein, The thickness of the first current collector is 5 μm to 15 μm. The battery cell of claim 4, wherein, The thickness of the first current collector is 5 μm to 10 μm. The battery cell of any one of claims 3 to 5, wherein, The thickness of the first metal layer is 0.3 μm to 3 μm. The battery cell of claim 6, wherein, The thickness of the first metal layer is 0.5 μm to 1.5 μm. The battery cell of any one of claims 3 to 7, wherein, The thickness of the first support layer is 1 μm to 10 μm. The battery cell of claim 8, wherein, The thickness of the first support layer is 3 μm to 8 μm. The battery cell according to any one of claims 3 to 9, wherein The metal material in the first metal layer includes at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy; and / or The organic material in the first support layer includes at least one of an insulating high molecular material and a conductive high molecular material. The battery cell of claim 10, wherein, The first metal conductive layer includes aluminum. The battery cell according to claim 10 or 11, wherein The organic material in the first support layer includes an insulating high molecular material. The battery cell of claim 12, wherein, The first support layer further includes an inorganic insulating material. The battery cell of any one of claims 10 to 13, wherein, The insulating high molecular material includes at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyoxadiazole, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyphenylene sulfide, polyvinylidene fluoride, silicone rubber, polycarbonate, cellulose and its derivatives, starch and its derivatives, protein and its derivatives, polyvinyl alcohol and its crosslinking product, and polyethylene glycol and its crosslinking product. The battery cell of any one of claims 3-14, wherein, The positive electrode tab further includes a positive electrode conductive layer between the first film layer and the first current collector. The battery cell of claim 15, wherein, The thickness of the positive electrode conductive layer is 0.1 μm to 2 μm. The battery cell according to claim 15 or 16, wherein The positive electrode conductive layer includes a positive electrode conductive agent including 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 comprises a positive electrode binder, and the positive electrode binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a polyacrylic acid, and a fluorine-containing acrylic ester resin. The battery cell according to claim 1 or 2, wherein The first metal layer is disposed on both sides of the first support layer. The battery cell of claim 18, wherein, The thickness of the first current collecting part is 2 μm to 8.5 μm. The battery cell of claim 4, wherein, The thickness of the first current collecting part is 2 μm to 6.5 μm. The battery cell of any one of claims 18-20, wherein, The thickness of the first metal layer is 0.3 μm to 2 μm. The battery cell of claim 21, wherein, The thickness of the first metal layer is 0.5 μm to 1.5 μm. The battery cell of any one of claims 18-22, wherein, The thickness of the first support layer is 1 μm to 4.5 μm. The battery cell of claim 23, wherein, The thickness of the first support layer is 3 μm to 4 μm. The battery cell of any one of claims 18 to 24, wherein The metal material in the first metal layer comprises at least one of aluminum, copper, nickel, titanium, silver, a nickel-copper alloy, and an aluminum-zirconium alloy; and / or The organic material of the first support layer comprises at least one of an insulating high molecular material and a conductive high molecular material. The battery cell of claim 25, wherein, The first metal conductive layer comprises copper. The battery cell according to claim 25 or 26, wherein The material of the first support layer comprises an insulating high molecular material. The battery cell of claim 27, wherein, The first support layer further comprises an inorganic insulating material. The battery cell of any one of claims 25-28, wherein, The insulating high molecular material comprises at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyoxymethylene, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyphthaloyl diamine, polyacetal, epoxy resin, phenolic resin, polytetrafluoroethylene, polyphenylene sulfide, polyvinylidene fluoride, silicone rubber, polycarbonate, cellulose and its derivatives, starch and its derivatives, protein and its derivatives, polyvinyl alcohol and its crosslinked product, polyethylene glycol and its crosslinked product. The battery cell of any one of claims 18-29, wherein, The negative electrode sheet further comprises a negative electrode conductive layer, and the negative electrode conductive layer is located between the first film layer and the first current collecting part. The battery cell of claim 30, wherein, The thickness of the negative electrode conductive layer is 0.1 μm to 2 μm. The battery cell of claim 30 or 31, wherein The negative electrode conductive layer comprises a negative electrode conductive agent, and the negative electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and / or The negative electrode conductive layer comprises a negative electrode binder, and the negative electrode binder comprises one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The battery cell of any one of claims 1 to 32, wherein, The powder resistivity of the lithium-containing phosphate with an olivine structure is 1 Ω·cm to 27.5 Ω·cm. The battery cell of any one of claims 1 to 33, wherein, The powder compaction density of the lithium-containing phosphate of olivine structure is 2.46 g / cm 3 to 2.8 g / cm 3 . The battery cell of any one of claims 1 to 34, wherein, The charge gram capacity of the lithium-containing phosphate with an olivine structure is 150 mAh / g to 170 mAh / g. The battery cell of claim 35, wherein, The charge gram capacity of the lithium-containing phosphate with an olivine structure at a 0.1C rate is 150 mAh / g to 170 mAh / g. The battery cell of any one of claims 1 to 36, wherein, The lithium-containing phosphate with an olivine structure comprises: phosphate particles, and a coating layer that coats the phosphate particles, the coating layer containing one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn. The battery cell of claim 37, wherein, The phosphate particles include a compound of a general formula of Li x1 A y1 Me a M b P 1-c X c Y z , wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The battery cell of claim 37 or 38, wherein, The coating layer includes a fast ion conductor of the general formula Li 3-d Fe 2- d M2 d (PO x2 ) y2 , M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0 The battery cell of any one of claims 37-39, wherein, The graphitization degree of the olivine-structure lithium-containing phosphate is 0.15 to 0.

32. The battery cell of any one of claims 37-40, wherein, The mass content of carbon element in the olivine-structure lithium-containing phosphate is 1% to 2%; The lithium-containing phosphate of olivine structure has a specific surface area of 5 m 2 / g to 18 m 2 / g. The battery cell of any one of claims 1-41, wherein, The volume distribution particle size of the olivine-structure lithium-containing phosphate satisfies: 1 μm≤Dv50≤2 μm, 0.4 μm≤Dv10≤0.7 μm. The battery cell of any one of claims 1-42, wherein, The olivine-structure lithium-containing phosphate is in a particulate form, and the olivine-structure lithium-containing phosphate includes secondary particles, the secondary particles including a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. The battery cell of any one of claims 1 to 43, wherein, The powder resistivity of the carbon-based material is 0.005 Ω·cm to 0.043 Ω·cm. The battery cell of any one of claims 1 to 44, wherein, The powder compaction density of the carbon-based material at 20000N is 1.5g / cm 3 to 1.85g / cm 3 . The battery cell of any one of claims 1 to 45, wherein, The charge gram capacity of the carbon-based material is 350 mAh / g to 480 mAh / g. The battery cell of claim 46, wherein, The charge gram capacity of the carbon-based material at a 0.1C rate is 350 mAh / g to 480 mAh / g. The battery cell of any one of claims 1 to 47, wherein, The carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. The battery cell of claim 48, wherein, The graphite particles include: artificial graphite including secondary particles; and a carbon coating layer coated on the surface of the artificial graphite. The battery cell of claim 49, wherein, The mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. The battery cell according to any one of claims 1 to 50, wherein the first active material in the first film layer includes an olivine-structure lithium-containing phosphate; The compacted density of the first film layer is 2.50 g / cm 3 to 2.80 g / cm 3 ; and / or The single-side coating weight of the first film layer is 200 mg / 1540.25 mm 2 up to 370 mg / 1540.25 mm 2 . The battery cell according to any one of claims 1 to 50, wherein the first active material in the first film layer includes a carbon-based material; The compacted density of the first film layer is 1.15 g / cm 3 to 1.36 g / cm 3 ; and / or The single-side coating weight of the first film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 . The battery cell of any one of claims 1 to 52, wherein, The separator film includes a base film of a porous structure, and the porosity of the base film is 20% to 70%. The battery cell of claim 53, wherein, The thickness of the base film is 6 μm to 12 μm. The battery cell of any one of claims 1 to 54, wherein, The separator film includes a base film and a functional layer provided on at least one side of the base film, and the functional layer includes: a first functional layer on one side of the base film, the first functional layer including first inorganic particles, a second functional layer on the other side of the base film, the second functional layer including composite particles, the composite particles including second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles being attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles. The battery cell of claim 55, wherein, The non-fluoropolymer particles include an acrylate-based copolymer. The battery cell of claim 55 or 56, 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. The battery cell of any one of claims 55-57, wherein, The second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide, and / or The average particle size of the second inorganic particles is 5 nm to 100 nm. The battery cell according to any one of claims 1 to 58, further including an electrolyte, the electrolyte having an electrical conductivity of 13 mS / cm to 20 mS / cm at room temperature; and / or The viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s; and / or The density of the electrolyte at room temperature is 1.05 g / mL to 1.35 g / mL. The battery cell of claim 59, wherein, The electrolyte comprises an organic solvent, the organic solvent comprises a chain carboxylate solvent, and the mass content of the mass of the chain carboxylate solvent in the electrolyte is 4% to 65%. The battery cell of claim 60, wherein, The chain carboxylate-based solvent includes a compound represented by Formula I, In formula I, R1 comprises a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group, R2 comprises a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group. The battery cell of claim 60 or 61, wherein, The organic solvent further comprises a carbonate solvent, the carbonate solvent comprises one or more of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The battery cell of claim 62, wherein, The mass content of the carbonate solvent in the electrolyte is 25% to 60%. The battery cell of any one of claims 59-63, wherein, The electrolyte further comprises an additive, the additive comprises one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The battery cell of claim 64, wherein, The carbonate additive comprises one or more of vinylene carbonate, fluoro-vinylene carbonate; and / or The sulfur-containing additive comprises one or more of vinyl sulfate, bis-vinyl sulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methyl methylene disulfonate; and / or The lithium salt additive comprises one or more of lithium difluorophosphate, lithium difluoro oxalate borate, lithium tetrafluoroborate, and lithium bis-oxalate borate. The battery cell of claim 64 or 65, wherein, The mass content of the additive in the electrolyte is 1% to 10%. The battery cell of any one of claims 59-66, wherein, The electrolyte further comprises a lithium salt, the lithium salt comprises one or more of a fluorine-containing sulfonimide salt and lithium hexafluorophosphate. The battery cell of any one of claims 1-67, wherein, The battery cell comprises a shell, the shell contains the electrode assembly and the electrolyte, the material of the shell comprises steel, and the thickness of the shell is 0.1 mm to 0.5 mm. The battery cell of any one of claims 1-68, wherein, The first metal layer comprises a first part and a second part extending from the first part, the first part is provided with a first film layer, and the second part is not provided with the first film layer. The first tab further comprises a first tab, and the first tab is connected with the second part. The battery cell according to claim 69 further comprises a first electrode terminal, and the first electrode terminal is directly welded with the first tab. The battery cell of any one of claims 1-70, wherein, The charging time of the battery cell from 10% state of charge to 80% state of charge at room temperature is 5 min to 10.5 min. The battery cell of any one of claims 1-71, wherein, The volumetric energy density of the battery cell is 380 Wh / L to 500 Wh / L; and / or The gravimetric energy density of the battery cell is 180 Wh / Kg to 210 Wh / Kg. The battery cell of claim 72, wherein, The volumetric energy density of the battery cell is 380 Wh / L to 470 Wh / L. A battery device comprises a plurality of battery cells according to any one of claims 1 to 73. The battery device of claim 74, wherein The charging time of the battery device from 10% state of charge to 80% state of charge at room temperature is 5 min to 10.5 min. An electric device comprises the battery device according to claim 74 or 75.

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