Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device, the battery monomer comprises an electrode assembly, the electrode assembly comprises a first pole piece, a second pole piece and an isolating membrane, the isolating membrane is arranged between the first pole piece and the second pole piece, and the polarity of the first pole piece is opposite to that of the second pole piece; the first pole piece comprises a first current collecting part and a first film layer which is arranged on at least one side of the first current collecting part and comprises a first active material; the second pole piece comprises a second current collecting part and a second film layer which is arranged on at least one side of the second current collecting part and comprises a second active material; wherein one of the first active material and the second active material includes a lithium-containing phosphate of an olivine structure, and the other includes a carbon-based material; the first current collecting part comprises a first supporting layer and a first metal layer arranged on at least one side of the first supporting layer, a first film layer is arranged on the first metal layer, and the first supporting layer comprises an organic material. According to the invention, the energy density of the battery monomer can be improved.

Description

[0001] This application claims the priority of patent application PCT / CN2024 / 109008 entitled “Battery Cell, Battery Device and Electrical Device” filed on July 31, 2024, the entire contents of which are incorporated into the text by reference. Technical Field

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

[0003] Lithium-ion batteries have the characteristics of high capacity and long life, so they are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric aircraft, electric ships and electric tools, etc. With the development of lithium-ion battery application fields, higher requirements are put forward for the performance of lithium-ion batteries, such as energy density. Summary of the invention The present application provides a battery cell, a battery device and an electrical device, which can improve the energy density of the battery cell.

[0004] In a first aspect, the present application proposes a battery cell, the battery cell comprises an electrode assembly, the electrode assembly comprises a first pole piece, a second pole piece and a separator, the separator is arranged between the first pole piece and the second pole piece, and the polarities of the first pole piece and the second pole piece are opposite; the first pole piece comprises a first current collecting portion and a first film layer arranged on at least one side of the first current collecting portion and comprising a first active material; the second pole piece comprises a second current collecting portion and a second film layer arranged on at least one side of the second current collecting portion and comprising a second active material; wherein 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; the first current collecting portion comprises a first supporting layer and a first metal layer arranged on at least one side of the first supporting layer, a first film layer is arranged on the first metal layer, and the first supporting layer comprises an organic material; The first pole piece is a positive pole piece, and the first metal layer is arranged on both sides of the first supporting layer; The thickness of the first current collecting portion is 5 μm to 15 μm; When the battery cell is 100% charged, the compaction density of the first film layer is 2.50 g / cm 3 Up to 2.80g / cm 3 .

[0005] Therefore, in the embodiment of the present application, the positive electrode active material of the battery cell includes an olivine-structured lithium-containing phosphate, and the negative electrode active material includes a carbon-based material, so that the structural stability of the battery cell is relatively excellent and the cycle performance is excellent; on the basis of the above materials, the first current collector of the first pole piece adopts a composite structure of a first support layer and a first metal layer, which is conducive to thinning the thickness of the first current collector, thereby increasing the volume proportion of the first film layer, and the above composite structure is more conducive to the capacity of the active material and improving the volume energy density of the battery cell; the first metal layer includes a metal material, which has excellent conductivity. When the thickness of the first metal layer is small, rapid electron migration can also be achieved, which is conducive to improving the energy density of the battery cell under fast charging. The first support layer includes an organic material, which is light in weight and can further improve the weight energy density of the battery cell. The first pole piece is a positive pole piece, and the first film layer is a positive film layer. When the compaction density of the positive film layer is within the above range, it is conducive to improving the energy density of the battery cell; and because the positive active material in the positive film layer is densely stacked, the contact resistance between particles is small, which can further reduce the resistance of the pole piece, thereby reducing heat generation.

[0006] In some embodiments, the second current collecting portion includes a second supporting layer and a second metal layer disposed on at least one side of the second supporting layer, a second film layer is disposed on the second metal layer, and the second supporting layer includes an organic material.

[0007] Therefore, the second current collector of the second pole piece in the embodiment of the present application adopts a composite structure of a second support layer and a second metal layer, which is conducive to reducing the thickness of the second current collector, thereby increasing the thickness ratio of the second film layer, which is conducive to further improving the volume energy density of the battery cell; the second metal layer includes a metal material, and the metal material has excellent conductivity. When the thickness of the second metal layer is small, rapid electron migration can also be achieved, which is conducive to improving the weight energy density of the battery cell under fast charging. The second support layer includes an organic material, which is light in weight, and the bonding force between the second support layer and the second metal layer is strong, so that the structural stability of the second current collector is relatively high.

[0008] In some embodiments, the first electrode sheet is a positive electrode sheet, the first metal layer is a positive metal layer, and the first metal layer is disposed on both sides of the first supporting layer.

[0009] In some embodiments, the first pole piece is a positive pole piece, the first current collector is a positive current collector, and the thickness of the first current collector is 5 μm to 10 μm. When the thickness of the positive current collector is within the above range, the thickness of the positive current collector is relatively thin, which is conducive to increasing the thickness of the positive electrode film layer and improving the energy density of the battery cell.

[0010] In some embodiments, the first electrode sheet is a positive electrode sheet, and the thickness of the first metal layer is 0.3 μm to 3 μm, and can be 0.5 μm to 1.5 μm. 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 its conductivity is relatively excellent, which is conducive to improving the fast charging performance of the battery cell.

[0011] In some embodiments, the first pole piece is a positive pole piece, the first support layer is a positive support layer, and the thickness of the first support layer is 1 μm to 10 μm, and can be 3 μm to 8 μm. When the thickness of the positive support layer is within the above range, the mechanical strength of the positive current collector can be effectively improved; and the bonding force between the positive support layer and the positive metal layer is strong, so that the structural stability of the positive current collector is relatively high.

[0012] In some embodiments, the first pole piece is a positive pole piece, and 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 aluminum can be selected; 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 improving the fast charging performance of the battery cell.

[0013] In some embodiments, the first electrode is a positive electrode, and the organic material in the first support layer includes at least one of an insulating polymer material and a conductive polymer material, and the insulating polymer material can be selected. When the positive support layer is made of an insulating material, it is non-conductive, which can increase the short-circuit resistance of the battery cell when a short circuit occurs under abnormal circumstances, greatly reduce the short-circuit current, greatly reduce the short-circuit heat generation, and improve the reliability of the battery cell.

[0014] In some embodiments, the first pole piece is a positive pole piece, and the first supporting layer further includes an inorganic insulating material.

[0015] In some embodiments, the insulating polymer material includes at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene dicarboxamide, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylene, 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 products, and polyethylene glycol and its crosslinked products.

[0016] In some embodiments, the positive electrode plate further includes a positive electrode conductive layer, which is located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode plate, reduce the heat generation of the positive electrode plate, and thus reduce the heat generation of the battery cell.

[0017] 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 plate can be further improved, the heat generation of the positive electrode plate can be reduced, and thus the heat generation of the battery cell can be reduced; and the energy density of the battery cell can also be improved.

[0018] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode pole piece and reducing the heat generation of the battery cell; the positive electrode binder in the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector and the positive electrode film layer, and improve the structural stability of the positive electrode pole piece.

[0019] In some embodiments, 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.

[0020] In some embodiments, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorine-containing acrylic resin.

[0021] In some embodiments, the second electrode sheet is a negative electrode sheet, the second metal layer is a negative metal layer, and the second metal layer is disposed on both sides of the second supporting layer.

[0022] In some embodiments, the second pole piece is a negative pole piece, the second current collector is a negative current collector, and the thickness of the second current collector is 2 μm to 8.5 μm, and can be 2 μm to 6.5 μm. When the thickness of the negative current collector is within the above range, the thickness of the negative current collector 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.

[0023] In some embodiments, the second pole piece is a negative pole piece, the second metal layer is a negative metal layer, and the thickness of the second metal layer is 0.3 μm to 2 μm, and can be 0.5 μm to 1.5 μm. When the thickness of the negative metal layer is within the above range, the thickness of the negative metal layer is relatively thin, and its conductivity is relatively excellent, which is conducive to improving the fast charging performance of the battery cell.

[0024] In some embodiments, the second electrode sheet is a negative electrode sheet, the second support layer is a negative electrode support layer, and the thickness of the second support layer is 1 μm to 4.5 μm, and can be 3 μm to 4 μm. When the thickness of the negative electrode support layer is within the above range, the mechanical strength of the negative electrode current collector can be effectively improved; and the bonding force between the negative electrode support layer and the negative electrode metal layer is strong, so that the structural stability of the negative electrode current collector is relatively high.

[0025] In some embodiments, the second electrode plate is a negative electrode plate, and the metal material in the second metal layer includes at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy, and copper can be selected.

[0026] In some embodiments, the second electrode piece is a negative electrode piece, and the organic material of the second supporting layer includes at least one of an insulating polymer material and a conductive polymer material, and can be an insulating polymer material.

[0027] In some embodiments, the second electrode sheet is a negative electrode sheet, and the second supporting layer further includes an inorganic insulating material.

[0028] In some embodiments, the insulating polymer material includes at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene dicarboxamide, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylene, 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 products, and polyethylene glycol and its crosslinked products.

[0029] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, and the negative electrode conductive layer is located between the second film layer and the second current collecting portion.

[0030] In some embodiments, the negative electrode plate 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 collecting portion.

[0031] 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 plate, reduce the heat generation of the negative electrode plate, and thus reduce the heat generation of the battery cell.

[0032] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode pole piece and reducing the heat generation of the battery cell; the negative electrode binder in the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector and the negative electrode film layer and improve the structural stability of the negative electrode pole piece.

[0033] 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.

[0034] In some embodiments, the negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin SR-1B, aqueous acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0035] In some embodiments, the powder resistivity of the olivine-structured lithium-containing phosphate is 1 Ω·cm to 27.5 Ω·cm. The powder resistivity of the positive electrode active material is relatively low, so that the resistance of the positive electrode sheet is relatively low and the heat generation of the battery cell is less.

[0036] In some embodiments, the powder compaction density of the olivine-structured lithium-containing phosphate at 30,000 N is 2.46 g / cm 3 Up to 2.8g / cm 3 When the powder compaction density of the positive electrode active material at 30000N is within the above range, the energy density of the battery cell can be improved, and because the positive electrode active material in the positive electrode film layer can be more densely packed, the contact resistance between particles is small, which can further reduce the resistance of the pole piece, thereby reducing heat generation.

[0037] In some embodiments, the olivine-structured lithium-containing phosphate has a charge capacity of 150 mAh / g to 170 mAh / g at a rate of 0.1 C. When the charge capacity of the positive electrode active material at a rate of 0.1 C is within the above range, the energy density of the battery cell is relatively high.

[0038] In some embodiments, the olivine-structured lithium-containing phosphate has a charge capacity of 150 mAh / g to 170 mAh / g. When the charge capacity of the positive electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0039] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% charge state is 2.55 g / cm 3 Up to 2.70g / cm 3 When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the positive electrode active material in the positive electrode film layer is densely packed, the contact resistance between particles is small, which can further reduce the resistance of the pole piece, thereby reducing heat generation.

[0040] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 , optional: 240mg / 1540.25mm 2 Up to 330mg / 1540.25mm 2When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, and the energy density of the battery cell can be improved.

[0041] In some embodiments, the lithium-containing phosphate with an olivine structure includes phosphate particles and a coating layer, wherein the coating layer coats the phosphate particles, and the coating layer contains one or more elements selected from 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 an olivine structure, reduce the powder resistivity of the material, and facilitate the migration rate of lithium ions, thereby reducing the heat generation of the battery cell.

[0042] In some embodiments, the phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y z Compounds, where 0.5≤x 1 ≤1.3,0≤y 1 ≤1.3, and 0.9≤x 1 +y 1 ≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F. The phosphate particles have excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0043] In some embodiments, the coating layer includes a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor M2 includes one or more elements selected from Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x 2 <5,0<y 2 <4. Coating the fast ion conductor on the surface of phosphate particles can significantly increase the transmission rate of lithium ions in the positive terminal for multiple lithium extraction / insertion, improve the ionic conductivity of the positive electrode active material, and then increase the gram capacity, and further increase the energy density of the corresponding battery cell.

[0044] 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 within the above range, it is beneficial to improve the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell.

[0045] In some embodiments, the mass content of carbon in the lithium-containing phosphate with an olivine structure is 1% to 2%, and the specific surface area of ​​the lithium-containing phosphate with an olivine structure is 5 m 2 / g to 18m 2 / g, optional 7.5m 2 / g to 14m 2 / g.

[0046] Therefore, in the embodiment of the present application, the above-mentioned mass content of carbon elements combined with the above-mentioned specific surface area material is more conducive to the effective contact between the electrolyte and the lithium-containing phosphate with olivine structure, and is conducive to the transmission of lithium ions at the phase interface.

[0047] In some embodiments, the lithium-containing phosphate with an olivine structure is granular, and its volume distribution particle size satisfies: 1µm≤Dv50≤2µm, 0.4µm≤Dv10≤0.7µm. The particle size of the lithium-containing phosphate with an olivine structure is relatively small, the lithium ion deintercalation path in the positive electrode active material is short, the heat generation is small, and the particle size of the positive electrode active material is not too small, and basically no agglomeration occurs during the processing and preparation process, so that the performance of the positive electrode active material is stable.

[0048] In some embodiments, the lithium-containing phosphate with an olivine structure is in a granular form, and the lithium-containing phosphate with an olivine structure 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, and the lithium ion deintercalation path in the positive electrode active material is short, and the heat generation is less.

[0049] In some embodiments, the positive electrode film layer further includes one or more of ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, lithium citrate, lithium nickelate and lithium ferrite. The above materials can supplement lithium ions for the positive electrode film layer, make up for the irreversible lithium ion loss in the system, increase the capacity, and thus increase the energy density of the battery cell.

[0050] In some embodiments, the compaction density of the negative electrode film layer of the battery cell at 100% charge state is 1.15 g / cm 3 Up to 1.36g / cm 3 ; Optional: 1.25g / cm3 Up to 1.36g / cm 3 When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the negative electrode active materials in the negative electrode film layer are densely packed, the contact resistance between particles is small, which can further reduce the resistance of the pole piece, thereby reducing heat generation.

[0051] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 Up to 170mg / 1540.25mm 2 ; Optional: 110mg / 1540.25mm 2 Up to 150mg / 1540.25mm 2 When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generated per unit area of ​​the negative electrode sheet will not be too large, and the energy density of the battery cell can be improved.

[0052] 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 sheet is relatively low and the heat generation of the battery cell is less.

[0053] In some embodiments, the powder compaction density of the negative electrode active material at 20000N is 1.5 g / cm 3 Up to 1.85g / cm 3 When the powder compaction density of the negative electrode active material at 20000N is within the above range, the energy density of the battery cell can be improved, and because the negative electrode active material in the negative electrode film layer can be more densely packed, the contact resistance between particles is small, which can further reduce the resistance of the pole piece, thereby reducing heat generation.

[0054] In some embodiments, the charge capacity of the negative electrode active material is greater than or equal to 350 mAh / g. When the charge capacity of the negative electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0055] In some embodiments, the charge capacity of the negative electrode active material at a rate of 0.1C is greater than or equal to 350 mAh / g. When the charge capacity of the negative electrode active material at a rate of 0.1C is within the above range, the energy density of the battery cell is relatively high.

[0056] 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 within the above range, the graphite particles have excellent electrical conductivity, which can reduce the heat generation of the negative electrode plate and the heat generation of the battery cell; and can improve the fast charging performance of the battery cell.

[0057] 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 that can be used to insert and remove lithium ions is greater, so that the conductivity of the carbon coating layer is relatively excellent, and the internal resistance of the negative electrode plate can be reduced, and the heat generation of the battery cell can be reduced.

[0058] In some embodiments, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode plate can be further reduced and the heat generation of the battery cell can be reduced.

[0059] 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 collecting portion, 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 collecting portion, 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 include graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0060] Therefore, there is a difference in the particle size between the first negative electrode film layer and the second negative electrode film layer in the embodiment of the present application, which can improve the fast charging performance of the battery cell; specifically, during the fast charging process, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer, while the particle size of the second negative electrode film layer in the embodiment of the present application is relatively small, which can shorten the solid phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium plating on the surface of the negative electrode plate.

[0061] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0062] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, so that the energy density of the battery cell is improved; the first negative electrode film layer is filled relatively sparsely, and the pores are more abundant, which can improve the fast charging performance of the battery cell.

[0063] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 Up to 1.21g / cm 3When the tap density of the carbon-based material in the first negative electrode film layer is within an appropriate range, the fast charging performance of the battery cell can be improved.

[0064] In some embodiments, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 Up to 1.25g / cm 3 When the tap density of the carbon-based material in the second negative electrode film layer is within an appropriate range, the energy density of the battery cell can be improved. 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 fast charging performance can be improved.

[0065] In some embodiments, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm. When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is within the above range, the tortuosity of lithium ion transmission can be reduced and the fast charging performance of the battery cell can be improved.

[0066] In some embodiments, the first negative electrode film layer also includes a first lithium-containing binder, and the second negative electrode film layer also includes a second lithium-containing binder, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0067] Therefore, in the embodiment 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 the second negative electrode film layer with a relatively larger number of freely movable lithium ions, which can further improve the fast charging performance of the battery cell.

[0068] In some embodiments, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. When the mass content of the first lithium-containing binder is within the above range, the lithium ion insertion and extraction rate can be increased, and the fast charging performance of the battery cell can be improved.

[0069] In some embodiments, the mass content of lithium in the first lithium-containing binder is 3% to 10%, and can be 3% to 8%. When the mass content of lithium is within the above range, the number of lithium ions that can move freely in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion insertion and extraction, and improve the fast charging performance of the battery cell.

[0070] In some embodiments, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. When the mass content of lithium in the second lithium-containing binder is within the above range, the rate of lithium ion insertion and extraction is increased, and the fast charging performance of the battery cell is improved.

[0071] In some embodiments, the mass content of lithium in the second lithium-containing binder is 3% to 10%, and can be 3% to 8%. When the mass content of lithium is within the above range, the number of lithium ions that can move freely in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion insertion and extraction, and improve the fast charging performance of the battery cell.

[0072] In some embodiments, the first 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%.

[0073] Therefore, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the rapid charging performance of the battery cell; and it is not easy to swell during the charging and discharging process, and has a stable structure, thereby improving the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0074] In some embodiments, 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 lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0075] Therefore, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the rapid charging performance of the battery cell; and it is not easy to swell during the charging and discharging process, and has a stable structure, thereby improving the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0076] In some embodiments, the negative electrode active material further comprises a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10.0%, based on the mass of the negative electrode active material. The introduction of silicon-based materials can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0077] In some embodiments, the separator includes a porous base film, and the porosity of the base film is 20% to 70%. When the porosity of the separator in the embodiment of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0078] In some embodiments, the thickness of the base film is 6 μm to 12 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation.

[0079] In some embodiments, the isolation film includes a base film and a functional layer disposed on at least one side of the base film, the functional layer includes a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer includes first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer includes composite particles, the composite particles include second inorganic particles and 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.

[0080] In some embodiments, the non-fluorine polymer particles include acrylate copolymers. Acrylate copolymers have excellent bonding properties and have high bonding stability with the base film.

[0081] In some embodiments, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The first inorganic particles can improve the heat resistance of the first functional layer.

[0082] In some embodiments, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The second inorganic particles can improve the heat resistance of the first functional layer.

[0083] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0084] In some embodiments, the battery cell further includes an electrolyte, and the conductivity of the electrolyte at room temperature is 13mS / cm to 20mS / cm. When the conductivity of the electrolyte is within 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 fast charging performance of the battery cell.

[0085] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. When the viscosity of the electrolyte is within 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 fast charging performance of the battery cell.

[0086] In some embodiments, the density of the electrolyte at room temperature is 1.05 g / mL to 1.35 g / mL. When the density of the electrolyte is within 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 fast charging performance of the battery cell.

[0087] In some embodiments, the carboxylate solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent in the electrolyte is 4% to 65%. When the mass content of the chain carboxylate solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is conducive to the migration of lithium ions.

[0088] In some embodiments, the linear carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R 1 including a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R 2 Includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0089] Therefore, in the embodiment of the present application, the above-mentioned chain carboxylic acid ester solvent has a high conductivity, which is beneficial to improving the fast charging capability of the battery monomer.

[0090] In some embodiments, R 1 Includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group or a C1 to C3 halogenated alkyl group.

[0091] In some embodiments, in some embodiments, R 2 Includes C1 to C3 alkyl or C1 to C3 halogenated alkyl.

[0092] In some embodiments, the linear carboxylate solvent includes one or more of the compounds represented by formula I-1 to the compounds represented by formula I-8.

[0093] In some embodiments, the organic solvent further comprises a carbonate solvent, and the carbonate solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. The above carbonate solvent and the chain carboxylate solvent are used in combination to improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0094] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0095] In some embodiments, the mass content of carbonate solvent in the electrolyte is 25% to 60%. The above mass content of carbonate solvent can further improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0096] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The above-mentioned additive can improve the interface film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0097] In some embodiments, the carbonate additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0098] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, vinyl sulfite ES, and methylene disulfonate MMDS.

[0099] In some embodiments, the lithium salt additive includes lithium difluorophosphate LiPO 2 F 2 , Lithium difluorooxalate borate LiDFOB, Lithium tetrafluoroborate LiBF 4 , lithium bis(oxalatoborate) LiBOB or more.

[0100] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, and can be 2% to 8%. The above mass content of the additive can effectively improve the interface film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0101] In some embodiments, the electrolyte further comprises a lithium salt, wherein the lithium salt comprises a fluorinated sulfonyl imide salt and lithium hexafluorophosphate LiPF 6 The above lithium salt is easy to dissociate, which is conducive to the rapid migration of lithium ions; and the electrolyte system is relatively stable and not easy to decompose, which can improve the cycle performance of the battery monomer.

[0102] In some embodiments, the fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0103] In some embodiments, the lithium salt includes lithium bis(fluorosulfonyl)imide LiFSI and lithium hexafluorophosphate LiPF. 6 The molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 The molar concentration is 0.5 mol / L to 1.0 mol / L.

[0104] In some embodiments, the molar concentration of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate LiPF 6 The molar concentration ratio is between 0.2 and 1.0.

[0105] In some embodiments, the base material of the shell includes steel, and the thickness of the shell is 0.1 mm to 0.5 mm, and can be 0.2 mm to 0.35 mm. When the thickness of the shell is within the above range, the mechanical strength of the shell is high, which can improve the reliability and cycle performance of the battery cell; and the shell occupies less space, and the internal space of the shell is more, which is conducive to improving the energy density of the battery cell.

[0106] In some embodiments, the first metal layer includes 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 pole piece also includes a first pole ear, and the first pole ear is connected to the second part.

[0107] In some embodiments, the battery cell further includes a first electrode terminal, and the first electrode tab is directly welded to the first electrode terminal. Direct welding can reduce the resistance at the connection, which is beneficial to reducing the internal resistance of the battery cell as a whole.

[0108] In some embodiments, the second metal layer includes a first part and a second part extending from the first part, the first part is provided with a second film layer, and the second part is not provided with the second film layer; the second pole piece also includes a second pole ear, and the second pole ear is connected to the second part.

[0109] In some embodiments, the battery cell further includes a second electrode terminal, and the second electrode terminal is directly welded to the second electrode tab.

[0110] In some embodiments, at room temperature, the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 min to 10.5 min, and the charging speed of the battery cell is faster, which is more conducive to improving the fast charging capability.

[0111] In some embodiments, the volume energy density of the battery cell is 380 Wh / L to 500 Wh / L, and optionally 410 Wh / L to 470 Wh / L.

[0112] In some embodiments, the battery cell has a gravimetric energy density of 180 Wh / Kg to 210 Wh / Kg.

[0113] In a second aspect, the present application proposes a battery device, which includes a plurality of battery cells according to any embodiment of the first aspect of the present application.

[0114] 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 faster the charging speed of the battery, the better the improvement of the fast charging capability.

[0115] In a third aspect, the present application proposes an electrical device, which includes a battery device according to any embodiment of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0117] Figure 1 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application; Figure 2 An exploded schematic diagram of a battery cell provided in some embodiments of the present application; Figure 3 A schematic diagram of the structure of an electrode assembly of a battery cell provided in some embodiments of the present application; Figure 4 A schematic diagram of the structure of a first pole piece of a battery cell provided in some embodiments of the present application; Figure 5 for Figure 4 The schematic cross-sectional view of the first pole piece shown is taken along line AA; Figure 6 A schematic diagram of the structure of a second pole piece of a battery cell provided in some embodiments of the present application; Figure 7 for Figure 6 The cross-sectional schematic diagram of the second pole piece shown is made along the BB line; Figure 8 A schematic diagram of the structure of a battery module provided in some embodiments of the present application; Fig. 9A schematic diagram of the structure of a battery pack provided in some embodiments of the present application; Fig.10 It is a schematic diagram of the structure of an electrical device provided in some embodiments of the present application.

[0118] The drawings are not necessarily drawn to scale.

[0119] The following are the descriptions of the reference numerals: 1. Electric device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box; 5a. First box part; 5b. Second box part; 5c. Accommodation space; 6. Battery module; 7. Battery cells; 10. electrode assembly; 111. first pole lug; 1111. first pole lug main body; 1112. first pole lug connecting portion; 112, second pole ear; 12. Main body; 13. The first pole piece; 131, first current collecting portion; 1311, first supporting layer; 1312, first metal layer; 1312a, first part; 1312b, second part; 132, first film layer; 14. The second pole piece; 141. second current collecting portion; 1411. second supporting layer; 1412. second metal layer; 142, second film layer; 15. Isolation film; 20. housing; 21. shell; 22. end cover; 31. First electrode terminal; 32. Second electrode terminal. DETAILED DESCRIPTION

[0120] Hereinafter, the battery cells, battery devices and power devices of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0121] "Scope" disclosed in the present application is defined in the form of lower limit and upper limit, 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 boundary of a particular range. The scope defined in this way can be inclusive or exclusive of 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 a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following range can all be expected: 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 specified, the numerical range "a to b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed in this document, and "0 to 5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0122] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0123] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0124] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0125] With the development of the field of battery cells, the requirements for the energy density of battery cells are gradually increasing. Compared with nickel-cobalt-manganese oxide batteries, lithium-containing phosphates with olivine structures have low gram capacity and low voltage platform, resulting in lower energy density of battery cells. From the perspective of optimizing the pole piece of a lithium iron phosphate battery, this application introduces a current collector that is more conducive to improving the capacity of the pole piece into the lithium iron phosphate battery, and increases the proportion of the volume of the film layer containing active materials in the pole piece to improve the energy density of the lithium iron phosphate battery. In particular, in lithium iron phosphate batteries with higher requirements for fast charging performance, since the film layer of active materials on the pole piece is usually thinner (more conducive to fast charging), it is more beneficial to improve the energy density of fast-charging battery cells by introducing a current collector that can increase the proportion of the volume of the film layer containing active materials in the pole piece.

[0126] In view of this, the embodiment of the present application rationally designs the system of the battery cell, introduces a suitable current collecting part to adapt to the pole piece design of the lithium iron phosphate battery, reduces the volume proportion of the current collecting part in the battery cell, increases the volume proportion of the membrane layer containing active materials, and improves the energy density of the battery cell.

[0127] Battery Cell In a first aspect, an embodiment of the present application provides a battery cell.

[0128] like Figures 1 to 7 As shown, the battery cell 7 includes an electrode assembly 10 and an electrolyte, the electrode assembly 10 includes a first pole piece 13, a second pole piece 14 and a separator 15, the separator 15 is arranged between the first pole piece 13 and the second pole piece 14, and the polarities of the first pole piece 13 and the second pole piece 14 are opposite; the first pole piece 13 includes a first current collecting portion 131 and a first film layer 132 arranged on at least one side of the first current collecting portion 131 and including a first active material; the second pole piece 14 includes a second current collecting portion 141 and a first film layer 132 arranged on at least one side of the second current collecting portion 141 and including a first active material; A second film layer 142 comprising a second active material; 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 portion 131 comprises a first supporting layer 1311 and a first metal layer 1312 arranged on at least one side of the first supporting layer 1311, the first film layer 132 is arranged on the first metal layer 1312, the first metal layer 1312 is located between the first supporting layer 1311 and the first film layer 132, and the first supporting layer 1311 comprises an organic material. Figure 3 A schematic structural diagram of a wound electrode assembly is shown. It should be noted that the electrode assembly 10 may also be a laminated structure. Figure 5 The schematic diagram of the structure of the first pole piece 13 is shown, the X direction is parallel to the thickness direction of the first pole piece 13, and the Y direction is perpendicular to the X direction.

[0129] The positive electrode active material in the battery cell 7 includes a lithium-containing phosphate with an olivine structure, and the negative electrode active material includes a carbon-based material, so that the battery cell 7 has relatively excellent structural stability and excellent cycle performance.

[0130] On the basis of the above materials, the first current collecting portion 131 of the first pole piece 13 adopts a composite structure of a first supporting layer 1311 and a first metal layer 1312, which is conducive to reducing the thickness of the first current collecting portion 131, thereby increasing the volume proportion of the first film layer 132, and the above composite structure is more conducive to the capacity of the active material, and improving the volume energy density of the battery cell 7; the first metal layer 1312 includes a metal material, which has excellent conductivity. When the thickness of the first metal layer 1312 is small, it can also achieve rapid electron migration, which is conducive to improving the energy density of the battery cell 7 under fast charging. The first supporting layer 1311 includes an organic material, which is light in weight and can further improve the weight energy density of the battery cell 7; the bonding force between the first supporting layer 1311 and the first metal layer 1312 is strong, so that the structural stability of the first current collecting portion 131 is relatively high.

[0131] In some embodiments, the second current collecting portion 141 includes a second supporting layer 1411 and a second metal layer 1412 disposed on at least one side of the second supporting layer 1411 , the second metal layer 1412 is located between the second supporting layer 1411 and the second film layer 142 , and the second supporting layer 1411 includes an organic material. Figure 7 The schematic diagram of the structure of the second pole piece 14 is shown, 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.

[0132] The second current collecting portion 141 of the second pole piece 14 adopts a composite structure of a second supporting layer 1411 and a second metal layer 1412, which is conducive to reducing the thickness of the second current collecting portion 141, thereby increasing the thickness ratio of the second film layer 142, which is conducive to further improving the volume energy density of the battery cell 7; the second metal layer 1412 includes a metal material, which has excellent conductivity. When the thickness of the second metal layer 1412 is small, rapid electron migration can also be achieved, which is conducive to improving the weight energy density of the battery cell 7 under fast charging. The second supporting layer 1411 includes an organic material, which is light in weight, and the bonding force between the second supporting layer 1411 and the second metal layer 1412 is strong, so that the structural stability of the second current collecting portion 141 is relatively high.

[0133] The polarities of the first electrode sheet 13 and the second electrode sheet 14 are opposite, for example, the first electrode sheet 13 is a positive electrode sheet and the second electrode sheet 14 is a negative electrode sheet, or the first electrode sheet 13 is a negative electrode sheet and the second electrode sheet 14 is a positive electrode sheet. When the first electrode sheet 13 is a positive electrode sheet, the first current collector 131 and the first film layer 132 correspond to the positive current collector and the positive film layer respectively; when the second electrode sheet 14 is a negative electrode sheet, the second current collector 141 and the second film layer 142 correspond to the negative current collector and the negative film layer respectively.

[0134] [Positive electrode] The first electrode sheet is a positive electrode sheet, the first current collecting portion corresponds to the positive current collecting portion, the first supporting layer corresponds to the positive supporting layer, the first metal layer corresponds to the positive metal layer, the first film layer corresponds to the positive film layer, and the first active material is the positive active material; in this case, the second electrode sheet is a negative electrode sheet, the second current collecting portion corresponds to the negative current collecting portion, the second supporting layer corresponds to the negative supporting layer, the second metal layer corresponds to the negative metal layer, the second film layer corresponds to the negative film layer, and the second active material is the negative active material.

[0135] When the positive electrode current collector adopts a composite structure, the negative electrode current collector may adopt a conventional negative electrode current collector, such as a copper foil structure. Alternatively, when the positive electrode current collector adopts a composite structure, the negative electrode current collector may also adopt a composite structure.

[0136] The positive electrode current collecting portion has two surfaces opposite to each other in the thickness direction of the positive electrode sheet, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collecting portion.

[0137] The positive electrode support layer has two surfaces opposite to each other in the thickness direction of the positive electrode sheet, and the positive electrode metal layer is arranged on any one or both of the two opposite surfaces of the positive electrode support layer. Optionally, the positive electrode metal layer is arranged 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 supports and protects the positive electrode conductive layer. Since the positive electrode support layer generally adopts organic polymer materials, the density of the positive electrode support layer is usually less than the density of the positive electrode metal layer, so that the weight energy density of the battery cell can be significantly improved compared with the traditional metal current collector.

[0138] In addition, the positive electrode metal layer uses a metal layer with a 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 role in bearing and protecting the positive electrode metal layer located on its surface, it is not easy to cause the pole piece fracture phenomenon commonly seen in traditional current collectors.

[0139] In some embodiments, the thickness of the positive electrode current collector is 5 μm to 15 μm, and can be 5 μm to 10 μm. Exemplarily, 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 consisting of any two of the above values.

[0140] When the thickness of the positive electrode current collector is within the above range, the thickness of the positive electrode current collector is relatively thin, which is beneficial to increase the thickness of the positive electrode film layer and improve the energy density of the battery cell.

[0141] In some embodiments, the thickness of the positive electrode metal layer is 0.3 μm to 3 μm, and can be 0.5 μm to 1.5 μm. Exemplarily, 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 , 1.65μm, 1.7μm, 1.75μm, 1.8μm, 1.85μm, 1.9μm, 1.95μm, 2μm, 2.05μm, 2.15μm, 2.2μm, 2.25μm, 2.3μm, 2.35μm, 2.4μm, 2.45μm, 2.5μm, 2.55μm, 2.6μm, 2.65μm, 2.7μm, 2.75μm, 2.8μm, 2.85μm, 2.9μm, 2.95μm, 3μm or a range consisting of any two of the above values.

[0142] 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 its conductivity is relatively excellent, which is beneficial to the improvement of the fast charging performance of the battery cell.

[0143] In some embodiments, the metal material in the positive 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 positive electrode metal layer includes aluminum. The above materials have excellent electrical conductivity, which makes the internal resistance of the battery cell relatively small and the polarization small, which is conducive to improving the fast charging performance of the battery cell.

[0144] Optionally, the positive electrode metal layer may further include a conductive carbon material, such as at least one of graphite, acetylene black, graphene, and carbon nanotubes.

[0145] 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 method is preferably physical vapor deposition (PVD); the physical vapor deposition method is preferably at least one of evaporation and sputtering; the evaporation method is preferably at least one of vacuum evaporating, thermal evaporation, and electron beam evaporation method (EBEM); the sputtering method is preferably magnetron sputtering; preferably at least one of vapor deposition or electroless plating, so that the bond between the positive electrode support layer and the positive electrode metal layer is more firmly formed.

[0146] 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. Exemplarily, 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 consisting of any two of the above values.

[0147] When the thickness of the positive electrode support layer is within the above range, the mechanical strength of the positive electrode current collector can be effectively improved; and the bonding force between the positive electrode support layer and the positive electrode metal layer is strong, so that the structural stability of the positive electrode current collector is relatively high.

[0148] In some embodiments, the positive electrode support layer includes an organic material, and the organic material includes at least one of an insulating polymer material and a conductive polymer material. Optionally, the organic material includes an insulating polymer material. When the positive electrode support layer is made of an insulating material, it is non-conductive, which can increase the short-circuit resistance of the battery cell when a short circuit occurs under abnormal circumstances, greatly reduce the short-circuit current, greatly reduce the short-circuit heat generation, and improve the reliability of the battery cell.

[0149] Exemplarily, the insulating polymer material includes at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene dicarboxamide, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylene, 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 crosslinks, and polyethylene glycol and its crosslinks.

[0150] Exemplarily, the conductive polymer material includes a polysulfur nitride polymer material or a doped conjugated polymer material. More preferably, the conductive polymer material includes at least one of polypyrrole, polyacetylene, polyaniline, and polythiophene.

[0151] Optionally, the positive electrode support layer may further include an inorganic material, which may be an insulating inorganic material, such as an insulating polymer composite material formed by a composite of an insulating inorganic material and an insulating polymer material.

[0152] Exemplarily, the inorganic material is preferably at least one of a ceramic material, a glass material, and a ceramic composite material.

[0153] Optionally, the positive electrode support layer may further include an inorganic material, which may be a conductive inorganic material, such as a conductive polymer composite material formed by a composite of a conductive inorganic material and a conductive polymer material.

[0154] 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 nanotubes, graphite, acetylene black, and graphene; the metal material includes at least one of nickel, iron, copper, aluminum, or alloys of the above metals; the composite conductive material includes at least one of nickel-coated graphite powder and nickel-coated carbon fiber.

[0155] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer, which is located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode sheet, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell. In addition, 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 between the two, and reduce the contact resistance.

[0156] In some embodiments, the thickness of the positive electrode conductive layer is 0.1 μm to 2 μm. For example, 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 consisting of any two of the above values.

[0157] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode sheet can be further improved, the heat generation of the positive electrode sheet can be reduced, thereby reducing the heat generation of the battery cell; and the energy density of the battery cell can be improved at the same time.

[0158] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0159] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Exemplarily, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or a range consisting of any two of the above values.

[0160] Exemplarily, 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 plate and reducing the heat generation of the battery cell.

[0161] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%, illustratively, 50%, 60%, 65%, 70% or a range consisting of any two of the above values.

[0162] Exemplarily, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin. The positive electrode binder in the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector and the positive electrode film layer, and improve the structural stability of the positive electrode sheet.

[0163] In the embodiment of the present application, the thickness of the positive electrode current collecting portion, the positive electrode supporting layer, the positive electrode metal layer, and the positive electrode conductive layer can be detected using equipment and methods known in the art, for example, by performing a tomographic scan on the positive electrode sheet to directly measure the thickness of each layer.

[0164] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge SOC is 2.50 g / cm 3 Up to 2.80g / cm 3 ; Optional: 2.55g / cm 3 Up to 2.70g / cm 3 For example, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film layer is 2.50 g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.56g / cm 3 , 2.57g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm3 , 2.72g / cm 3 , 2.75g / cm 3 , 2.78g / cm 3 , 2.80g / cm 3 Or a range consisting of any two of the above values.

[0165] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the positive electrode active materials in the positive electrode film layer are densely packed, the contact resistance between particles is small, which can further reduce the resistance of the pole piece, 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 both high energy density and high charge rate performance.

[0166] The upper limit voltage for charging and the lower limit voltage for discharging of the battery cell vary according to the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper limit voltage for charging is 3.65V and the lower limit voltage for discharging is 2.0V, or the upper limit voltage for charging is 3.7V, or the upper limit voltage for charging is 3.8V; for another example, when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage for charging is 4.2V and the lower limit voltage for discharging is 2.5V, or the upper limit voltage for charging is 4.25V, or the upper limit voltage for charging is 4.35V.

[0167] In the embodiment of the present application, the 100% state of charge SOC and 0% state of charge SOC of the battery cell are defined as follows: The battery cell is charged at a constant current charging rate of 0.33C to the upper limit of the charging voltage, and then charged at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell; the battery cell is discharged at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0168] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 ; Optional: 240mg / 1540.25mm 2 Up to 330mg / 1540.25mm 2 For example, the coating weight of the positive electrode film on one side is 200 mg / 1540.25 mm 2 , 210mg / 1540.25mm 2 , 220mg / 1540.25mm 2 、230mg / 1540.25mm 2 , 240mg / 1540.25mm 2, 250mg / 1540.25mm 2 、260mg / 1540.25mm 2 、270mg / 1540.25mm 2 、280mg / 1540.25mm 2 、290mg / 1540.25mm 2 、300mg / 1540.25mm 2 、310mg / 1540.25mm 2 、320mg / 1540.25mm 2 、330mg / 1540.25mm 2 、340mg / 1540.25mm 2 、350mg / 1540.25mm 2 、360mg / 1540.25mm 2 、370mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0169] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, and both the energy density and the charging rate performance of the battery cell can be improved.

[0170] In the embodiment of the present application, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge SOC can be detected by the following method: the positive electrode sheet is disassembled from the battery cell at 100% state of charge SOC, and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), punched into a small disc with an area of ​​S1, weighed, recorded as M1, and its thickness H1 is measured. Then the positive electrode film layer of the weighed positive electrode sheet is wiped off, the weight of the positive current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight of the positive electrode sheet M1-the weight of the positive current collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode sheet H1-the thickness of the positive current collector H0, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0171] 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. Exemplarily, the powder resistivity of the positive electrode active material may 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 consisting of any two of the above values.

[0172] The powder resistivity of the positive electrode active material is relatively low, so that the resistance of the positive electrode sheet is relatively low and the heat generation of the battery cell is less.

[0173] In the embodiments of the present application, the powder resistivity of the material is well known in the art and can be tested using methods and equipment well known in the art, for example, using a PRCD1100 powder resistivity meter for testing according to the test standard GB / T30835-2014.

[0174] In some embodiments, the powder compaction density of the positive electrode active material at 30000N is 2.46 g / cm 3 Up to 2.8 g / cm 3 For example, the powder compaction density of the positive electrode active material at 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 consisting of any two of the above values.

[0175] When the powder compaction density of the positive electrode active material at 30000N is within the above range, the energy density of the battery cell can be improved. Moreover, since the positive electrode active material in the positive electrode film layer can be stacked more densely and the contact resistance between particles is smaller, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0176] In the embodiment of the present application, the powder compaction density of the material has a meaning known in the art, and can be tested by methods and equipment known in the art, and tested according to the test standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample and added to the bottom area of ​​1.327 cm of the UTM7305 electronic pressure testing machine. 2 The mold was pressurized to 3000 kg (equivalent to 30000 N), maintained for 30 seconds, then released and maintained for 10 seconds, and then the powder compaction density of the positive electrode active material under a force of 30000 N was recorded and calculated.

[0177] In some embodiments, the charge capacity of the positive electrode active material is 150 mAh / g to 170 mAh / g, optionally 157 mAh / g to 170 mAh / g.

[0178] In some embodiments, the charge gram capacity of the positive electrode active material at a 0.1C rate is 150 mAh / g to 170 mAh / g, optionally 157 mAh / g to 170 mAh / g. Exemplarily, the charge gram capacity of the positive electrode active material at a 0.1C rate is 150 mAh / g, 151 mAh / g, 152 mAh / g, 153 mAh / g, 154 mAh / g, 155 mAh / g, 156 mAh / g, 157 mAh / g, 158 mAh / g, 159 mAh / g, 160 mAh / g, 161 mAh / g, 162 mAh / g, 163 mAh / g, 164 mAh / g, 165 mAh / g, 166 mAh / g, 167 mAh / g, 168 mAh / g, 169 mAh / g, 170 mAh / g or a range consisting of any two of the above values.

[0179] When the charge gram capacity of the positive electrode active material at a 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0180] In the embodiments of the present application, the gram capacity of the active material has a meaning well known in the art and can be tested using equipment and methods well known in the art. The test method for the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used. Metal lithium is used as the negative electrode and a sample electrode comprising the above material is used as the positive electrode to assemble a half-button battery. Under the conditions of 23°C±2°C, the half-button battery is charged and discharged at a rate of 0.1C on a battery tester or other test equipment with equivalent performance to obtain the charge capacity, and then the capacity is divided by the mass of the active material of the electrode to obtain the charge gram capacity parameter.

[0181] In some embodiments, the mass proportion of the lithium-containing phosphate with an olivine structure in the positive electrode active material may be greater than or equal to 80% and less than or equal to 100%, and the positive electrode active material of the present application may be considered to be a lithium-containing phosphate system with an olivine structure. When the mass proportion of the lithium-containing phosphate with an olivine structure is less than 100%, the positive electrode active material may also include a commonly used positive electrode active material, for example, may include but is not limited to at least one of lithium-containing transition metal oxides. Examples of lithium-containing transition metal oxides may 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.

[0182] Optionally, the mass proportion of the lithium-containing phosphate with an olivine structure in the positive electrode active material is 100%.

[0183] In an embodiment of the present application, the lithium-containing phosphate with an olivine structure may be phosphate particles, or a material obtained by coating and modifying the phosphate particles. For example, the lithium-containing phosphate with an olivine structure includes phosphate particles and a coating layer, wherein the coating layer is coated on the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge and Sn.

[0184] The phosphate particles are coated with a coating layer on the surface, which can improve the conductivity of the lithium-containing phosphate with an olivine structure, reduce the powder resistivity of the material, and is beneficial to the migration rate of lithium ions, thereby improving the fast charging capability of the battery and reducing the heat generation of the battery cell.

[0185] In some embodiments, the phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y z Compounds, where 0.5≤x 1 ≤1.3,0≤y 1 ≤1.3, and 0.9≤x1 +y 1 ≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F. The phosphate particles have excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0186] Exemplarily, the phosphate particles include LiFePO 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4 One or more of the following. During the charging and discharging process, the battery cells are accompanied by the deintercalation and consumption of active ions such as Li. The molar content of Li in the battery cells is different when they are discharged to different states. 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4 In the examples of the present invention, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is used in the battery system, the molar content of Li may change after charge and discharge cycles. 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4 In the enumeration of etc., the molar content of oxygen O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In reality, the molar content of oxygen O will fluctuate. The above situations are all within the protection scope of the present application.

[0187] In some embodiments, the coating layer includes a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor M2 includes one or more elements selected from Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x 2 <5,0<y 2 <4.

[0188] Exemplarily, the fast ion conductor is a material having a NASICON structure, for example, one or more of lithium iron titanium phosphate Li2FeTi(PO4)3, lithium iron zirconium phosphate Li2FeZr(PO4)3, and lithium iron tin phosphate Li2FeSn(PO4)3.

[0189] Fast ion conductors with NASICON structures are materials with ultrafast ion conduction capabilities, rich three-dimensional lithium ion diffusion and transmission channels, and have the advantages of high ion conduction efficiency and strong structural stability during multiple lithium removal and insertion processes. Coating fast ion conductors with NASICON structures on the surface of phosphate particles can significantly increase the transmission rate of lithium ions during multiple lithium removal / insertion at the positive terminal, improve the ionic conductivity of the positive electrode active material, and improve the fast charging capability of the battery cell. In addition, it can also increase the gram capacity and the energy density of the corresponding battery cell.

[0190] In some embodiments, the coating layer further includes carbon.

[0191] The carbon element and the fast ion conductor can be arranged in layers, for example, the carbon element is used as an independent carbon coating layer, and the fast ion conductor is used as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0192] 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 it can completely coat the fast ion conductor layer. The provision of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, make up for the defect of poor electronic conductivity of the phosphate particles, and improve the energy density of the battery cell. Specifically, the provision of the carbon coating layer enables the positive electrode active material of the present application to have the following advantages: 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 in multiple lithium de- and lithium insertion processes, improve the electronic conductivity of lithium-containing phosphates, improve the charging capacity of the corresponding battery cells, and also improve the energy density.

[0193] The carbon coating layer of the positive electrode active material of the present application is loose and porous, which enables the electrolyte to be in full and effective contact with the lithium-containing phosphate, thereby increasing the transmission rate of lithium ions at the interface and improving the charging capacity of the battery cell.

[0194] Coating a carbon coating 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 of the positive electrode active material during long-term storage and cyclic use of the battery cell, thereby improving the cycle life of the battery cell. The positive electrode active material of the present application uses lithium-containing phosphate as a base material, giving full play to the advantages of low cost, high reliability and good cycle stability of lithium-containing phosphate, while using the coating layer (fast ion conductor layer and carbon coating layer) to solve the disadvantages of poor electronic conductivity and ion conductivity. The battery cell prepared by the positive electrode active material of the present application can improve the energy density of the battery cell while having excellent cycle performance. In the embodiment of the present application, the content of elements in the positive electrode active material has a well-known meaning in the art, and can be detected by equipment and methods well-known in the art, for example, with reference to EPA 6010D-2014, tested by inductively coupled plasma atomic emission spectrometry, and measured by plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After the battery cell is discharged to 0% state of charge SOC, the positive electrode sheet is disassembled, washed and dried with DMC, and calcined at high temperature to remove impurities, 0.4g of positive electrode active material is weighed, and 10ml (50% concentration) of aqua regia is added thereto. Then place it on a plate at 180°C for 30min. After digestion on the plate, the volume is fixed to 100mL, and the standard curve method is used for quantitative testing.

[0195] In some embodiments, the degree of graphitization of the positive electrode active material is 0.15 to 0.32, and can be 0.19 to 0.26. Exemplarily, the degree of graphitization 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 consisting of any two of the above values.

[0196] When the graphitization degree of the positive electrode active material is within the above range, it is beneficial to improve the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell.

[0197] In the embodiment 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.

[0198] In some embodiments, the mass content of carbon in the lithium-containing phosphate with an olivine structure is 1% to 2%, and the specific surface area of ​​the lithium-containing phosphate with an olivine structure is 5 m2 / g to 18m 2 / g.

[0199] Optionally, the mass content of carbon in the lithium-containing phosphate with an olivine structure is 1% to 2%, and the specific surface area of ​​the lithium-containing phosphate with an olivine structure is 7.5 m 2 / g to 14m 2 / g.

[0200] Illustratively, the mass content of carbon in the olivine-structured lithium-containing phosphate is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or a range consisting of any two of the above values.

[0201] For example, the specific surface area of ​​the lithium-containing phosphate with olivine structure is 5 m 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 consisting of any two of the above values.

[0202] The carbon element mainly exists in the coating layer in the form of a carbon coating layer. The carbon coating layer is loose and porous, which is beneficial to increasing the specific surface area of ​​the material, more beneficial to the effective contact between the electrolyte and the phosphate particles, and beneficial to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, it can significantly improve the conductivity of the lithium-containing phosphate with an olivine structure, which is beneficial to improving the ionic conductivity and electronic conductivity of the lithium-containing phosphate with an olivine structure, and can improve the rapid charging capability and energy density of the battery cell.

[0203] In the embodiments of the present application, the specific surface area of ​​the material has a well-known meaning in the art and can be detected by using equipment and methods well-known in the art. For example, the positive electrode active material is used as a sample and the specific surface area is tested by a Tri-Star 3020 specific surface area pore size analyzer produced by Micromeritics, USA.

[0204] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1µm≤Dv50≤2µm, 0.4µm≤Dv10≤0.7µm.

[0205] Illustratively, the Dv50 of the positive electrode active material can be 1µm, 1.1µm, 1.15µm, 1.2µm, 1.25µm, 1.3µm, 1.35µm, 1.4µm, 1.45µm, 1.5µm, 1.55µm, 1.6µm, 1.65µm, 1.7µm, 1.75µm, 1.8µm, 1.85µm, 1.9µm, 1.95µm, 2µm, or a range consisting of any two of the above values.

[0206] Illustratively, the Dv10 of the positive electrode active material may be 0.4µm, 0.45µm, 0.5µm, 0.55µm, 0.6µm, 0.65µm, 0.7µm, or a range consisting of any two of the foregoing values.

[0207] The particle size of the positive electrode active material is relatively small, the lithium ion deintercalation path in the positive electrode active material is short, and the heat generated is less. Moreover, the particle size of the above-mentioned positive electrode active material is not too small, and basically no agglomeration will occur during the processing and preparation process, so that the performance of the positive electrode active material is stable.

[0208] In the embodiment of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% of the volume distribution, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% of the volume distribution. It can be detected by equipment and methods known in the art. For example, the positive electrode active material is used as a sample, and the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0209] When the positive electrode active material includes other materials in addition to the lithium-containing phosphate having an olivine structure, 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.

[0210] In some embodiments, the lithium-containing phosphate with an olivine structure is in a granular form, the lithium-containing phosphate with an 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 consisting of any two of the above values.

[0211] The average particle size of the primary particles is relatively small, the lithium ion deintercalation path in the positive electrode active material is shorter, and the heat generated is less.

[0212] In the embodiment of the present application, secondary particles refer to particles in a state of aggregation formed by the aggregation of more than two primary particles. Primary particles and secondary particles can be easily distinguished by experimental means (such as using a scanning electron microscope to take a SEM image), and the average particle size of the primary particles can be obtained by testing in the scanning electron microscope SEM image. The SEM test parameters can be set to: the operating voltage (EHT) is 10.00kV, the InLens detector is used, the working distance is 4.6mm, and the magnification is 1000X.

[0213] In some embodiments, the positive electrode film layer further includes one or more of ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, lithium citrate, lithium nickelate and lithium ferrite. The above materials can be used as lithium supplements, which can supplement lithium ions for the positive electrode film layer, compensate for the irreversible lithium ion loss in the system, increase the capacity, and thus increase the energy density of the battery cell.

[0214] Optionally, the ternary material includes Li x3 A y3 Ni a3 Co b3 Mn c M3 (1-a3-b3-c3) Y3 z3 , where 0<x 3 ≤2.1,0<y 3 ≤2.1, and 0.9≤x 3 +y 3 ≤2.1,0≤a 3 ≤1,0≤b 3 ≤1,0≤c 3 ≤1, and 0.1≤a 3 +b 3 +c 3 ≤1,1.8≤z 3 ≤3.5, A includes one or more of Na, K, and Mg, M3 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, and Y3 includes one or more of O and F.

[0215] Exemplarily, the ternary material includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.80 Co 0.15 Al 0.05 O 2 At least one of .

[0216] In some embodiments, the mass content of the lithium supplement in the positive electrode film layer is 0.5% to 5%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the above values. When the mass content of the lithium supplement is within the above range, it can supplement lithium ions for the positive electrode film layer, compensate for the irreversible lithium ion loss in the system, increase the capacity, and thus increase the energy density of the battery cell.

[0217] The lithium replenisher can be located in the same layer as the positive electrode active material, or in different layers. When the lithium replenisher and the positive electrode active material are located in different layers, the lithium replenisher can be located in the lithium replenisher layer, and the positive electrode active material can be located in the positive electrode active material layer. In other words, the positive electrode film layer includes a lithium replenisher layer and a positive electrode active material layer. The positive electrode active material layer can be arranged on at least one side of the positive electrode current collecting part, and the lithium replenisher layer can be located between the positive electrode active material layer and the positive electrode current collecting part. Alternatively, the lithium replenisher layer can be arranged on at least one side of the positive electrode current collecting part, and the positive electrode active material layer can be located between the lithium replenisher layer and the positive electrode current collecting part. Optionally, the lithium replenisher layer can be located between the positive electrode active material layer and the positive electrode current collecting part. During the cyclic charge and discharge process of the battery cell, the lithium replenisher in the lithium replenisher layer can be gradually released into the system to make up for the lithium loss of the battery system.

[0218] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application embodiment has no particular restrictions on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0219] In some embodiments, the positive electrode film layer may also optionally include a positive electrode binder. The present application embodiment has no particular restrictions on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0220] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0221] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiment of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiment of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0222] [Negative electrode] The first electrode sheet may be a negative electrode sheet, the first current collecting portion corresponds to the negative electrode current collecting portion, the first supporting layer corresponds to the negative electrode supporting layer, the first metal layer corresponds to the negative electrode metal layer, the first film layer corresponds to the negative electrode film layer, and the first active material corresponds to the negative electrode active material; in this case, the second electrode sheet may be a positive electrode sheet, the second current collecting portion corresponds to the positive electrode current collecting portion, the second supporting layer corresponds to the positive electrode supporting layer, the second metal layer corresponds to the positive electrode metal layer, the second film layer corresponds to the positive electrode film layer, and the second active material is the positive electrode active material.

[0223] When the negative electrode current collector adopts a composite structure, the positive electrode current collector may adopt a conventional positive electrode current collector, such as an aluminum foil, etc. Alternatively, when the negative electrode current collector adopts a composite structure, the positive electrode current collector may also adopt a composite structure.

[0224] The negative electrode current collector has two surfaces opposite to each other in the thickness direction of the negative electrode sheet, and the negative electrode film layer is arranged on any one or both of the two opposite surfaces of the negative electrode current collector.

[0225] The negative electrode support layer has two surfaces opposite to each other in the thickness direction of the negative electrode sheet, 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 both 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 supports and protects the negative electrode conductive layer. Since the negative electrode support layer generally adopts organic polymer materials, the density of the negative electrode support layer is usually less than the density of the negative electrode metal layer, so that the weight energy density of the battery cell can be significantly improved compared with the traditional metal current collector.

[0226] In addition, the negative electrode metal layer uses a metal layer with a small thickness, which can further improve the volume energy density of the battery. In addition, since the negative electrode support layer can play a good role in bearing and protecting the negative electrode metal layer located on its surface, it is not easy to cause the pole piece fracture phenomenon commonly seen in traditional current collectors.

[0227] In some embodiments, the thickness of the negative electrode current collector is 2 μm to 8.5 μm, and can be 2 μm to 6.5 μm. Exemplarily, 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 consisting of any two of the above values.

[0228] When the thickness of the negative electrode current collector is within the above range, the thickness of the negative electrode current collector is relatively thin, which is beneficial to increase the thickness of the negative electrode film layer and improve the energy density of the battery cell.

[0229] In some embodiments, the thickness of the negative electrode metal layer is 0.3 μm to 2 μm, and optionally 0.5 μm to 1.5 μm. Exemplarily, the thickness of the negative electrode metal layer is 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, 0.95μm, 1μm, 1.05μm, 1.10μm, 1.15μm, 1.2μm, 1.25μm, 1.3μm, 1.35μm, 1.4μm, 1.45μm, 1.5μm, 1.55μm, 1.6μm, 1.65μm, 1.7μm, 1.75μm, 1.8μm, 1.85μm, 1.9μm, 1.95μm, 2μm, or a range consisting of any two of the above values.

[0230] 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 beneficial to the improvement of the fast charging performance of the battery cell.

[0231] 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 electrical conductivity, which makes the internal resistance of the battery cell relatively small and the polarization small, which is conducive to improving the fast charging performance of the battery cell.

[0232] Optionally, the negative electrode metal layer may further include a conductive carbon material, such as at least one of graphite, acetylene black, graphene, and carbon nanotubes.

[0233] 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 method is preferably physical vapor deposition (PVD); the physical vapor deposition method is preferably at least one of evaporation and sputtering; the evaporation method is preferably at least one of vacuum evaporating, thermal evaporation, and electron beam evaporation method (EBEM); the sputtering method is preferably magnetron sputtering; preferably at least one of vapor deposition or electroless plating, so that the bond between the negative electrode support layer and the negative electrode metal layer is more firmly formed.

[0234] 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. Exemplarily, 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 consisting of any two of the above values.

[0235] When the thickness of the negative electrode support layer is within the above range, the mechanical strength of the negative electrode current collector can be effectively improved; and the bonding force between the negative electrode support layer and the negative electrode metal layer is strong, so that the structural stability of the negative electrode current collector is high.

[0236] In some embodiments, the negative electrode support layer includes an organic material, and the organic material includes at least one of an insulating polymer material and a conductive polymer material. Optionally, the organic material includes an insulating polymer material. When the negative electrode support layer is made of an insulating material, it is non-conductive, which can increase the short-circuit resistance of the battery cell when a short circuit occurs under abnormal circumstances, greatly reduce the short-circuit current, greatly reduce the short-circuit heat generation, and improve the reliability of the battery cell.

[0237] Exemplarily, the insulating polymer material includes at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene dicarboxamide, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylene, 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 crosslinks, and polyethylene glycol and its crosslinks.

[0238] Exemplarily, the conductive polymer material includes a polysulfur nitride polymer material or a doped conjugated polymer material. More preferably, the conductive polymer material includes at least one of polypyrrole, polyacetylene, polyaniline, and polythiophene.

[0239] Optionally, the negative electrode support layer may further include an inorganic material, which may be an insulating inorganic material, such as an insulating polymer composite material formed by a composite of an insulating inorganic material and an insulating polymer material.

[0240] Exemplarily, the inorganic material is preferably at least one of a ceramic material, a glass material, and a ceramic composite material.

[0241] Optionally, the negative electrode support layer may further include an inorganic material, which may be a conductive inorganic material, such as a conductive polymer composite material formed by a composite of a conductive inorganic material and a conductive polymer material.

[0242] 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 nanotubes, graphite, acetylene black, and graphene; the metal material includes at least one of nickel, iron, copper, aluminum, or alloys of the above metals; the composite conductive material includes at least one of nickel-coated graphite powder and nickel-coated carbon fiber.

[0243] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, and thus reduce the heat generation of the battery cell. In addition, 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 between the two, and reduce the contact resistance.

[0244] In some embodiments, the thickness of the negative electrode conductive layer is 0.1 μm to 2 μm. For example, 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 consisting of any two of the above values.

[0245] When the thickness of the negative electrode conductive layer is within the above range, the conductivity of the negative electrode plate can be further improved, the heat generation of the negative electrode plate can be reduced, thereby reducing the heat generation of the battery cell; and the energy density of the battery cell can be improved.

[0246] In the embodiment of the present application, the thickness of the negative electrode conductive layer has a well-known meaning in the art and can be detected by using equipment and methods well-known in the art, and the test method for the negative electrode conductive layer mentioned above can be used.

[0247] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode pole piece and reducing the heat generation of the battery cell; the negative electrode binder in the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector and the negative electrode film layer and improve the structural stability of the negative electrode pole piece.

[0248] In some embodiments, the negative electrode conductive layer may further include other additives, such as, for example, thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0249] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 20% to 40%. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or a range consisting of any two of the above values.

[0250] Illustratively, 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.

[0251] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%, illustratively, 60%, 65%, 70%, 75%, 80% or a range consisting of any two of the above values.

[0252] Illustratively, the negative electrode binder includes one or more of styrene-butadiene rubber SBR, water-soluble unsaturated resin SR-1B, aqueous acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0253] In the embodiment of the present application, the thickness of the negative electrode current collecting part, the negative electrode supporting layer, the negative electrode metal layer, and the negative electrode conductive layer can be detected by using equipment and methods known in the art, for example, performing a tomographic scan on the negative electrode sheet to directly measure the thickness of each layer.

[0254] In some embodiments, the compaction density of the negative electrode film layer of the battery cell at 100% charge state is 1.15 g / cm 3Up to 1.36g / cm 3 ; Optional: 1.25g / cm 3 Up to 1.36g / cm 3 For example, the compaction density of the negative electrode film layer of the battery cell at 100% charge state is 1.15 g / cm 3 , 1.18g / cm 3 , 1.20g / cm 3 , 1.22g / cm 3 , 1.25g / cm 3 , 1.28g / cm 3 , 1.3g / cm 3 , 1.32g / cm 3 , 1.35g / cm 3 , 1.36g / cm 3 Or a range consisting of any two of the above values.

[0255] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the negative electrode active material in the negative electrode film layer is stacked more densely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0256] In the embodiment of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% charge state has a meaning well known in the art and can be detected using equipment and methods well known in the art, and its detection method is such as the compaction density test method of the positive electrode film layer mentioned above.

[0257] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 Up to 170mg / 1540.25mm 2 , optional 110mg / 1540.25mm 2 Up to 150mg / 1540.25mm 2 For example, the coating weight of the negative electrode film on one side is 90 mg / 1540.25 mm 2 、92mg / 1540.25mm 2 、95mg / 1540.25mm 2 、96mg / 1540.25mm 2 、100mg / 1540.25mm 2 、102mg / 1540.25mm 2 、104mg / 1540.25mm 2 、105mg / 1540.25mm 2 、108mg / 1540.25mm 2、110mg / 1540.25mm 2 、112mg / 1540.25mm 2 、114mg / 1540.25mm 2 、115mg / 1540.25mm 2 、116mg / 1540.25mm 2 、118mg / 1540.25mm 2 、120mg / 1540.25mm 2 、122mg / 1540.25mm 2 、125mg / 1540.25mm 2 、128mg / 1540.25mm 2 、130mg / 1540.25mm 2 、132mg / 1540.25mm 2 、135mg / 1540.25mm 2 、137mg / 1540.25mm 2 、140mg / 1540.25mm 2 、142mg / 1540.25mm 2 、145mg / 1540.25mm 2 、148mg / 1540.25mm 2 、150mg / 1540.25mm 2 、152mg / 1540.25mm 2 、155mg / 1540.25mm 2 、160mg / 1540.25mm 2 、165mg / 1540.25mm 2 、170mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0258] When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generated per unit area of ​​the negative electrode sheet will not be too large, and the energy density of the battery cell can be improved.

[0259] In the embodiment of the present application, the single-sided coating weight of the negative electrode film layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, such as the single-sided coating weight test method of the film layer described above.

[0260] In some embodiments, the powder resistivity of the negative electrode active material is 0.005 Ω•cm to 0.043 Ω•cm, and may be 0.04 Ω•cm. For example, the powder resistivity of the negative electrode active material may 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 consisting of any two of the above values.

[0261] The powder resistivity of the negative electrode active material is relatively low, so that the resistance of the negative electrode sheet is relatively low and the heat generation of the battery cell is less.

[0262] In the embodiment of the present application, the powder resistivity of the negative electrode active material is well known in the art and can be detected using equipment and methods well known in the art, such as the powder resistivity test method of the positive electrode active material mentioned above.

[0263] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20000N is 1.5 g / cm 3 Up to 1.85g / cm 3 , optional 1.55g / cm 3 Up to 1.65g / cm 3 For example, the compaction density of the negative electrode active material under a pressure of 20000N is 1.5g / cm 3 , 1.55g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 , 1.75g / cm 3 , 1.8g / cm 3 , 1.85g / cm 3 Or a range consisting of any two of the above values.

[0264] When the powder compaction density of the negative electrode active material at 20000N is within the above range, the energy density of the battery cell can be improved. Moreover, since the negative electrode active material in the negative electrode film layer can be more densely stacked and the contact resistance between particles is smaller, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0265] In the embodiments of the present application, the powder compaction density of the material has a meaning known in the art and can be tested by methods and equipment known in the art in accordance with the test standard GB / T24533-2009. As an example, a certain amount of negative electrode active material is taken as a sample and added to the bottom area of ​​the UTM7305 electronic pressure testing machine with a surface area of ​​1.327 cm 2The mold was pressurized to 2000 kg (equivalent to 20000 N), maintained for 30 seconds, then released and maintained for 10 seconds, and then the powder compaction density of the negative electrode active material under a force of 20000 N was recorded and calculated.

[0266] In some embodiments, the negative electrode active material has a charge capacity of 350 mAh / g to 480 mAh / g.

[0267] In some embodiments, the charge gram capacity of the negative electrode active material at 0.1C rate is 350mAh / g to 480mAh / g. Exemplarily, the charge gram capacity of the negative electrode active material at 0.1C rate is 350mAh / g, 355mAh / g, 360mAh / g, 365mAh / g, 370mAh / g, 375mAh / g, 380mAh / g, 385mAh / g, 390mAh / g, 395mAh / g, 400mAh / g, 410mAh / g, 420mAh / g, 430mAh / g, 440mAh / g, 450mAh / g, 460mAh / g, 470mAh / g, 480mAh / g, or a range consisting of any two of the above values.

[0268] When the charge gram capacity of the negative electrode active material at a 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0269] In the embodiment of the present application, the charge gram capacity of the negative electrode active material at a rate of 0.1C has a meaning well known in the art and can be detected using equipment and methods well known in the art, and the detection method is the same as the charge gram capacity test method of the positive electrode active material at a rate of 0.1C mentioned above.

[0270] In some embodiments, the negative electrode active material includes a carbon-based material, which has high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass proportion of the carbon-based material in the negative electrode active material can be greater than or equal to 80% and less than or equal to 100%.

[0271] The positive electrode active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. The two are used in combination, and the cycle performance of the battery cell is relatively excellent.

[0272] Optionally, the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. Exemplarily, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, or a range consisting of any two of the above values.

[0273] When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, which can reduce the heat generation of the negative electrode plate and the heat generation of the battery cell; and can improve the fast charging performance of the battery cell.

[0274] 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 the surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon, and amorphous carbon refers to a transitional carbon material with a very low degree of graphitization crystallization and a nearly amorphous form (or a structure without a fixed shape and periodicity). In the present application, amorphous carbon refers to the product of carbonization treatment of an organic carbon source.

[0275] Artificial graphite includes secondary particles. There are more migration paths for lithium ions in artificial graphite, and the migration paths in primary particles are shorter, which can improve the migration rate of lithium ions. The carbon coating has more end faces and defects, so that there are more sites for lithium ion insertion and extraction, which makes the conductivity of the carbon coating better, which can reduce the internal resistance of the negative electrode plate and reduce the heat generation of the battery cell.

[0276] Optionally, based on the mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%. Exemplarily, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the above values.

[0277] When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode plate can be further reduced, and the heat generation of the battery cell can be reduced.

[0278] In the embodiment 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 a portion of the surface of the artificial graphite particles after carbonization.

[0279] Optionally, the organic carbon source includes one or more of coal tar, petroleum tar, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum tar. Optionally, the softening point of coal tar and petroleum tar is below 250°C.

[0280] Optionally, the carbonization temperature is 700° C. to 1800° C. Optionally, the carbonization temperature is 1000° C. to 1300° C. When the carbonization temperature is within a suitable range, the organic carbon source can be carbonized and a coating layer containing amorphous carbon can be formed on at least a portion of the surface of the artificial graphite.

[0281] Optionally, the carbonization treatment time is 1 h to 6 h.

[0282] In some embodiments, the carbon-based material may also include natural graphite. Specifically, the carbon-based material may include graphite particles, or the carbon-based material may include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0283] In some embodiments, the negative electrode active material may further include a silicon-based material. The introduction of the silicon-based material can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0284] Optionally, based on the mass of the negative electrode active material, the mass content of silicon in the silicon-based material is 0.3% to 10.0%, optionally 1% to 6%. Exemplarily, the mass content of silicon in the silicon-based material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10% or a range consisting of any two of the above values.

[0285] When the mass content of silicon in the silicon-based material is within the above range, the capacity of the negative electrode active material can be increased, thereby improving the energy density of the battery cell.

[0286] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy material.

[0287] In some embodiments, the negative electrode active material may include at least one of a tin-based material and lithium titanate in addition to the above-mentioned carbon-based material and optional silicon-based material. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0288] The qualitative and quantitative properties of each substance or element in this application can be detected by appropriate equipment 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., and those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0289] For example, the present application may combine JIS / K0131-1996 X-ray diffraction analysis method general rules to perform X-ray powder diffraction test and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0290] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flaky structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0291] In the embodiment of the present application, the negative electrode film layer includes at least one film layer, which may be a single film layer or at least two film layers. Optionally, the negative electrode film layer includes at least two film layers.

[0292] In the case where the negative electrode film layer adopts a single-layer film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes 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 8.2μm to 13.5μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 8.2μm, 8.5μm, 8.8μm, 9μm, 9.2μm, 9.5μm, 9.8μm, 10μm, 10.2μm, 10.5μm, 10.8μm, 11μm, 11.2μm, 11.5μm, 11.8μm, 12μm, 12.2μm, 12.5μm, 12.8μm, 13μm, 13.2μm, 13.5μm or a range consisting of any two of the above values.

[0293] In the case where the negative electrode film layer adopts at least two film layers, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes a silicon-based material, and the silicon-based material can be located in one of the at least two film layers, or in 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.

[0294] 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 collecting portion, 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 collecting portion, 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 may be the same or different.

[0295] The interface between the first negative electrode film layer and the second negative electrode film layer may be regular or irregular, and may optionally be irregular.

[0296] Optionally, the carbon-based material in the first negative electrode film layer also includes natural graphite.

[0297] The negative electrode film layer includes at least two film layers, and layered coating is beneficial to improving the rapid charging performance of the battery cell. In particular, when there is a difference between the first negative electrode film layer and the second negative electrode film layer, the pore difference of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission can be reduced, and the rapid charging performance of the battery cell can be improved.

[0298] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which is beneficial to improve the compaction density of the negative electrode film layer. When the negative electrode active material includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0299] There is a difference in the particle size between the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the implementation manner of the present application, the particle size of the second negative electrode film layer is relatively small, which can shorten the solid phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium plating on the surface of the negative electrode plate.

[0300] Optionally, the negative electrode active material in the first negative electrode film layer is granular, and its volume average particle size Dv50 is 9.5 μm to 18.5 μm, and 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 consisting of 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, and can be 9.5 μm to 14.6 μm.

[0301] 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, on the one hand, the solid phase transmission path of lithium ions can be shortened and the fast charging performance can be improved; on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material.

[0302] Optionally, the negative electrode active material in the second negative electrode film layer is in a granular form, and a volume average particle size Dv50 thereof is 7.8 μm to 14.3 μm, and optionally 7.8 μm to 11.3 μm. Illustratively, the volume average particle size Dv50 of the negative electrode active material is 7.8μm, 8.0μm, 8.2μm, 8.5μm, 8.8μm, 9μm, 9.2μm, 9.5μm, 9.8μm, 10μm, 10.2μm, 10.5μm, 10.8μm, 11μm, 11.3μm, 11.2μm, 11.5μm, 11.8μm, 12μm, 12.2μm, 12.5μm, 12.8μm, 13μm, 13.2μm, 13.5μm, 13.8μm, 14μm, 14.1μm, 14.3μm or a range consisting of any two of the above values. When the second negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm, and can be 7.8 μm to 11.3 μm.

[0303] When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is within the above range, on the one hand, the solid phase transmission path of lithium ions can be shortened and the fast charging performance can be improved; on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material; on still another hand, the combination of the negative electrode active material in the second negative electrode film layer within the above volume average particle size range and the negative electrode active material in the first negative electrode film layer is beneficial to construct a gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reduce the tortuosity of lithium ion transmission, and improve the fast charging performance of the battery cell.

[0304] In the embodiment of the present application, the volume average particle size Dv50 of the negative electrode active material has a meaning well known in the art and can be detected using equipment and methods well known in the art, and the detection method is the same as the volume average particle size Dv50 test method of the positive electrode active material mentioned above.

[0305] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. The tap density can reflect the filling density of the active material in the film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, so that the energy density of the battery cell is improved. The filling of the first negative electrode film layer is relatively sparse, and the pores are more abundant, which can improve the fast charging performance of the battery cell. When the negative electrode active material includes graphite particles, the tap density of the graphite particles in the first negative electrode film layer is less than or equal to the tap density of the graphite particles in the second negative electrode film layer.

[0306] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 Up to 1.21g / cm3 , for example 0.82 g / cm 3 , 0.85g / cm 3 , 0.88g / cm 3 , 0.90g / cm 3 、0.92g / cm 3 , 0.95g / cm 3 、0.98g / cm 3 , 1.00g / cm 3 , 1.05g / cm 3 , 1.08g / cm 3 , 1.10g / cm 3 , 1.12g / cm 3 , 1.15g / cm 3 , 1.18g / cm 3 , 1.20g / cm 3 , 1.21g / cm 3 Or a range consisting of any two of the above values. When the tap density of the carbon-based material in the first negative electrode film layer is within a suitable range, the fast charging performance of the battery cell can be improved.

[0307] Optionally, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 Up to 1.25g / cm 3 , for example 0.90g / cm 3 、0.92g / cm 3 , 0.95g / cm 3 、0.98g / cm 3 , 1.00g / cm 3 , 1.05g / cm 3 , 1.08g / cm 3 , 1.10g / cm 3 , 1.12g / cm 3 , 1.15g / cm 3 , 1.18g / cm 3 , 1.20g / cm 3 , 1.21g / cm 3 , 1.22g / cm 3 , 1.23g / cm 3 , 1.24g / cm 3 , 1.25g / cm 3 Or a range consisting of any two of the above values. When the tap density of the carbon-based material in the second negative electrode film layer is within a suitable range, the energy density of the battery cell can be improved.

[0308] In the embodiments of the present application, the tap density of a material is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester with reference to GB / T5162-2006. The test instrument can be Dandong Better BT-301.

[0309] Optionally, the thickness ratio of the second negative electrode film layer to the thickness ratio of the first negative electrode film layer is 3:7 to 7:3, and can be 4:6 to 6:4. Exemplarily, the thickness ratio of the second negative electrode film layer to the thickness ratio of the first negative electrode film layer is 3:7, 4:6, 5:5, 6:4, 7:3, or a range consisting 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 fast charging capability of the battery cell can be improved.

[0310] In some embodiments, after the battery cell has been fully charged for 10 cycles at the beginning of life (BOL), the thickness of the first negative electrode film layer is 15 μm to 65 μm, such as 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 consisting of any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging capability of the battery cell can be improved.

[0311] In some embodiments, after the battery cell has been fully charged for 10 cycles at the beginning of life (BOL), the thickness of the second negative electrode film layer is 15 μm to 65 μm, such as 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 consisting of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased to reduce the tortuosity of lithium ion transmission and improve the fast charging capability of the battery cell.

[0312] In the implementation manner 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. The BOL full charge test steps are as follows: at 25°C, charge the battery to 3.65V at a charge rate of 0.33C of the nominal capacity, then charge to 0.05C at a constant voltage of 3.65V, let stand for 10 minutes, then discharge to 2.0V at a discharge rate of 0.33C, let stand for 10 minutes, the above charge and discharge is one cycle, cycle 10 times, then charge to 3.65V at a charge rate of 0.33C of the nominal capacity, then charge to 0.05C at a constant voltage of 3.65V. The BOL is in a fully charged state. In the BOL fully charged state, the negative electrode sheet is disassembled, and a tomographic scanning electron microscope is used to observe the cross-section in the thickness direction of the middle area of ​​the negative electrode sheet. The first negative electrode film layer and the second negative electrode film layer are distinguished according to the interface between the two areas, and the thickness of the two areas are measured respectively. For example, the thickness of 10 positions of the first negative electrode film layer is measured respectively, and the average value thereof is calculated as the average value of the first negative electrode film layer, and the thickness of 10 positions of the second negative electrode film layer is measured, and the average value thereof is calculated as the average value of the second negative electrode film layer.

[0313] In some embodiments, after the battery cell is fully charged at the end of life (EOL) test, the thickness of the first negative electrode film layer is 15μm to 70μm, such as 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 35μm, 40μm, 43μm, 45μm, 50μm, 55μm, 60μm, 65μm, 66μm, 67μm, 68μm, 69μm, 70μm or a range consisting of any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the first negative electrode film layer and the second negative electrode film layer can be regulated to increase the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the fast charging capability of the battery cell.

[0314] In some embodiments, after the battery cell is fully charged at the end of life (EOL) test, the thickness of the second negative electrode film layer is 15μm to 70μm, such as 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 35μm, 40μm, 43μm, 45μm, 50μm, 55μm, 60μm, 65μm, 66μm, 67μm, 68μm, 69μm, 70μm or a range consisting of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the first negative electrode film layer and the second negative electrode film layer can be regulated to increase the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the fast charging capability of the battery cell.

[0315] In the implementation manner 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. The specific steps of the EOL full charge test are as follows: at 60°C, charge the battery to 3.65V at a charging rate of 0.33C of the nominal capacity, then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 10 minutes, then discharge it to 2.0V at a discharge rate of 0.33C, let it stand for 10 minutes. The above charge and discharge is one cycle, and the test is stopped until the battery capacity decays to 80% of the nominal capacity. 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 fully charged state. In the EOL fully charged state, disassemble the negative electrode plate, use a tomographic scanning electron microscope to observe the cross-section in the thickness direction of the middle area of ​​the negative electrode plate, distinguish the first negative electrode film layer and the second negative electrode film layer according to the interface of the two areas, and measure the thickness of the two respectively. For example, measure the thickness of 10 positions of the first negative electrode film layer respectively, calculate the average value thereof as the average value of the first negative electrode film layer, measure the thickness of 10 positions of the second negative electrode film layer, and calculate the average value thereof as the average value of the second negative electrode film layer.

[0316] In some embodiments, when the negative electrode film layer adopts a single-layer film layer (as distinguished from the above-mentioned double-layer film layer), the negative electrode film layer also includes 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%. Exemplarily, 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 consisting of any two of the above values. The lithium element in the lithium-containing binder can exist in the form of ions, which can increase the number of lithium ions that can move freely in the negative electrode film layer, shorten the distance that lithium ions diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion insertion and extraction, and improve the fast charging performance of the battery cell. Optionally, the negative electrode film layer may further include a negative electrode binder, for example, the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).

[0317] Optionally, the mass content of lithium in the lithium-containing binder is 3% to 10%. Exemplarily, the mass content of lithium in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two of the above values. The mass content of lithium is calculated based on the mass of the lithium-containing binder. When the mass content of lithium is within the above range, the number of lithium ions that can move freely in the negative electrode film layer is relatively large, which can further shorten the distance that lithium ions diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion deintercalation, and improve the fast charging performance of the battery cell.

[0318] Exemplarily, the lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 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.

[0319] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the rapid charging performance of the battery cell. It is not easy to swell during the charging and discharging process and has a stable structure, thereby improving the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0320] In 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.

[0321] 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, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. Further optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0322] 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 the second negative electrode film layer with a relatively larger number of freely movable lithium ions, which can further improve the fast charging performance of the battery cell.

[0323] Optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range consisting of any two of the above values. The lithium element in the first lithium-containing binder can exist in the form of ions, which can increase the number of lithium ions that can move freely in the negative electrode film layer, shorten the distance that lithium ions diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion deintercalation, and improve the fast charging performance of the battery cell.

[0324] Optionally, the mass content of lithium in the first lithium-containing binder is 3% to 10%, optionally 3% to 8%. Exemplarily, the mass content of lithium in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two of the above values. When the mass content of lithium is within the above range, the number of lithium ions that can move freely in the negative electrode film layer can be relatively large, which can further shorten the distance that lithium ions diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion deintercalation, and improve the fast charging performance of the battery cell.

[0325] Exemplarily, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 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.

[0326] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the rapid charging performance of the battery cell. It is not easy to swell during the charging and discharging process and has a stable structure, thereby improving the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0327] 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%. Exemplarily, 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 consisting of any two of the above values. The lithium element in the second lithium-containing binder can exist in the form of ions, which can increase the number of lithium ions that can move freely in the negative electrode film layer, shorten the distance that lithium ions diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion deintercalation, and improve the fast charging performance of the battery cell.

[0328] The first lithium-containing binder and the second lithium-containing binder may be made of the same material or different materials.

[0329] Optionally, the mass content of lithium in the second lithium-containing binder is 3% to 10%, optionally 3% to 8%. Exemplarily, the mass content of lithium in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two of the above values. When the mass content of lithium is within the above range, the number of lithium ions that can move freely in the negative electrode film layer can be relatively large, which can further shorten the distance that lithium ions diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion deintercalation, and improve the fast charging performance of the battery cell.

[0330] Exemplarily, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 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.

[0331] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the rapid charging performance of the battery cell. It is not easy to swell during the charging and discharging process and has a stable structure, thereby improving the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0332] In some embodiments, the first negative electrode film layer further includes a negative electrode binder, and the second negative electrode film layer further includes a negative electrode binder. The negative electrode binder in the first negative electrode film layer and the negative electrode binder in the second negative electrode film layer each independently include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).

[0333] 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.

[0334] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application embodiment has no particular restrictions on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0335] In some embodiments, the negative electrode film layer may further include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0336] In some embodiments, the negative electrode film layer may further include other additives. As an example, the other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0337] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0338] 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 embodiment of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiment of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0339] In some embodiments, the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer in the battery cell is 1.05 to 1.30, and can be 1.07 to 1.15. Exemplarily, the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3, or a range consisting of any two of the above values.

[0340] When the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer in the battery cell is within the above range, there are sufficient sites in the negative electrode film layer for lithium embedding, which can reduce the risk of lithium plating and is conducive to fast charging.

[0341] In the embodiments of the present application, the CB value has a well-known meaning in the art and can be detected using equipment and methods well-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 separately, and the ratio of the two is calculated to obtain the CB value.

[0342] Specifically, take the battery charging upper limit voltage as 3.65V and the battery discharging cut-off voltage as 2.0V as an example for explanation. The capacity of the positive electrode film layer per unit area refers to the actual lithium-removable capacity of the positive electrode active material. The test method is as follows: disassemble the battery in the PRS340 / 11-119-11 Braun glove box, take the positive electrode plate, and assemble it into a CR2430 model semi-button battery with a positive electrode-lithium plate. The area of ​​the positive electrode plate used is amm 2 , where the electrolyte is 1M LiPF 6 In a solution with EC / EMC / DEC=3 / 5 / 2 (mass ratio); then the assembled half-button battery is left to stand for 3h, and the test is carried out at 25℃, and 0.1C is used to charge (Charge) in the voltage range of 2.0V to 3.65V to delithium, and then 0.05C is used to discharge (Discharge) lithium to 2.0V, and the cycle is repeated twice. The discharge capacity of the second cycle is recorded as YmAh. The positive electrode sheet of the actual battery design is bmm long and cmm wide. The number of surfaces of the positive electrode active material coated on the positive electrode collector is d, then the capacity of the positive electrode film layer per unit area = Y / a*b*c*d.

[0343] Specifically, the capacity of the negative electrode film layer per unit area refers to the actual lithium-insertable capacity of the negative electrode active material. The test method is: disassemble the battery in a PRS340 / 11-119-11 Braun glove box, take the negative electrode plate, and assemble it into a CR2430 model semi-button battery with a negative electrode-lithium plate. The area of ​​the negative electrode plate used is fmm 2 , where the electrolyte is 1M LiPF 6 In a solution with EC / EMC / DEC=3 / 5 / 2 (mass ratio); then the assembled half-button battery is left to stand for 3h, and the test is carried out at 25℃, and 0.1C is used to discharge (Discharge) in the voltage range of 2V-0V to insert lithium, and then 0.05C is used to charge (Discharge) to 2V, and the cycle is repeated twice. The discharge button capacity of the second cycle is recorded as ZmAh. The actual battery design has a negative electrode sheet length of hmm and a width of imm. The number of surfaces of the negative electrode active material coated on the negative electrode collector is d, then the negative electrode lithium insertion capacity = Z / f*h*i*d.

[0344] [Isolation film] In the embodiment of the present application, the isolation membrane includes a base membrane with a porous structure.

[0345] In some embodiments, the base film includes at least one of glass fiber, non-woven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0346] Optionally, the polyolefin includes at least one of polyethylene, polypropylene and polyvinylidene fluoride.

[0347] In some embodiments, the porosity of the base film is 20% to 70%, optionally 35% to 60%. Exemplarily, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range consisting of any two of the above values.

[0348] When the porosity of the base film in the embodiment of the present application is within the above range, the migration ability of lithium ions in the isolation film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0349] In the embodiments of the present application, porosity refers to the percentage of the pore volume in the separator to the total volume of the separator. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin separator for battery monomers". It should be noted that the actual test process can be slightly different from the standard test process according to the difference in test instruments, test errors, and in order to eliminate the test influence on porosity as much as possible, so as to obtain a more accurate test value.

[0350] In some embodiments, the thickness of the base film is 6 μm to 12 μm, and optionally 6 μm to 9 μm. Exemplarily, 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 consisting of any two of the above values.

[0351] When the thickness of the base film is within 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 and thus reduce heat generation.

[0352] In the embodiment of the present application, the isolation film may be a base film, and optionally, the isolation film further comprises a functional layer disposed on at least one side of the base film, and the functional layer may comprise inorganic particles to improve the heat resistance of the isolation film. Optionally, the functional layer is disposed on both sides of the base film.

[0353] In some embodiments, the functional layer includes a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer includes first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer includes composite particles, the composite particles include second inorganic particles and multiple non-fluoropolymer particles, the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles.

[0354] The first functional layer and the second functional layer have good heat resistance and can improve the heat resistance of the isolation film.

[0355] Optionally, the first functional layer may include a binder, optionally including at least one of a fluorine-containing binder or a polyacrylic binder, such as polyvinylidene fluoride.

[0356] Optionally, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide. The first inorganic particles can improve the heat resistance of the first functional layer.

[0357] In the embodiments of the present application, the thickness of the base film has a meaning well known in the art, and can be detected using meanings and equipment well known in the art. For example, a newly prepared isolation membrane can be taken as a sample, or a battery cell that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery's charged state is approximately 0% SOC) can be reversely disassembled, and the isolation membrane can be obtained from the battery cell. The isolation membrane is dried and used as a sample, and the isolation membrane is cut with an ion beam cutter to form a cross section. Subsequently, a scanning electron microscope is used to measure the thickness of the cross section of the isolation membrane and its various layers.

[0358] The non-fluorinated polymer particles in the second functional layer refer to polymers that are non-fluorinated polymers, for example, the non-fluorinated polymer particles include acrylate copolymers, and optionally, the acrylate copolymers include acrylate-acrylonitrile-acrylamide-propylene copolymers, and 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, for example, the molar ratio is 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0359] The second inorganic particles in the composite particles make it difficult for the non-fluorinated polymer particles to adhere to each other due to the high temperature treatment during the granulation process, so that the composite particles have pores, which is conducive to the transmission of lithium ions and improves the ion conductivity of the separator. The second inorganic particles can also increase the compression modulus of the composite particles. During the charge and discharge process, the composite particles are not easy to deform, making the structure of the separator more stable, which can improve the dynamic performance of the battery cell and improve the fast charging performance. Optionally, compared with the first functional layer, the second functional layer is arranged close to the negative electrode sheet. Since the composite particles are not easy to deform, the separator basically does not cause side effects such as extrusion to the negative electrode sheet, making the dynamic performance of the negative electrode sheet stable. Accordingly, the first functional layer is arranged close to the positive electrode sheet.

[0360] 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, and optionally, the second inorganic particles include silicon oxide. The second inorganic particles can improve the heat resistance of the second functional layer, and can form composite particles with non-fluorine polymers to further improve the cycle stability and dynamic performance of the isolation membrane, and improve the cycle performance and fast charging performance of the battery cell.

[0361] The average particle size of the second inorganic particles is 5nm to 100nm, optionally 10nm to 100nm, optionally 5nm to 20nm. Exemplarily, the average particle size of the second inorganic particles is 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm or a range consisting of any two of the above values. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0362] In the embodiment of the present application, the average particle size of the second inorganic particles has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, after obtaining the isolation film, the isolation film is dried as a sample, and the isolation film is cut with an ion beam cutter to form a cross section. Subsequently, a scanning electron microscope is used to measure the particle size of the second inorganic particles in the isolation film. The particle sizes of multiple, for example, 50, second inorganic particles are measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0363] In some embodiments, the ionic conductivity of the isolation membrane is 0.3 mS / cm to 0.6 mS / cm. For example, the ionic conductivity of the isolation membrane 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.

[0364] When the ionic conductivity of the separator is within the above range, the migration ability of lithium ions of the separator can be further improved, thereby improving the fast charging performance of the battery cell.

[0365] In the embodiments of the present application, the ionic conductivity of the isolation membrane has a meaning known in the art and can be detected using equipment and methods known in the art, for example, Prepare the 2025 button battery for testing: In a vacuum glove box, put a lithium sheet into the negative electrode shell of the battery, add 150 μL of electrolyte, and the electrolyte is 1 mol / L LiPF 6 In the solution of EC / EMC / DEC=3 / 5 / 2 (mass ratio), an isolation film (area 3.14cm 2 , with a thickness of 12 μm) to make it close to the lithium sheet, then add 25 μL of electrolyte, and finally place a positive electrode sheet (the positive electrode sheet can be the positive electrode sheet in Example 1) on it and package it. The assembled button battery is taken out of the vacuum glove box and placed for 24 hours for the next test.

[0366] Test: On an electrochemical workstation, at 10 -1 ~10 6 The test was carried out in the frequency range of Hz to obtain the isolation membrane resistance Rb, and the ionic conductivity σ (unit: mS / cm) was calculated by the following formula: σ = L / (R b ×S) Where: R b is the isolation film resistance, L and S are the thickness and area of ​​the isolation film to be measured respectively.

[0367] [Electrolyte] In some embodiments, the battery cell further includes an electrolyte.

[0368] During the charge and discharge process of the battery cell, the active ions are embedded and released back and forth between the positive electrode and the negative electrode, and the electrolyte plays the role of conducting the active ions between the positive electrode and the negative electrode.

[0369] In the embodiment of the present application, the conductivity of the electrolyte at room temperature is 13mS / cm to 20mS / cm, and can be 15mS / cm to 20mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 13mS / cm, 13.5mS / cm, 14mS / cm, 14.5mS / cm, 15mS / cm, 15.5mS / cm, 16mS / cm, 16.5mS / cm, 17mS / cm, 17.5mS / cm, 18mS / cm, 18.5mS / cm, 19mS / cm, 19.5mS / cm, 20mS / cm or a range consisting of any two of the above values.

[0370] When the conductivity of the electrolyte at room temperature, such as 25° C., is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0371] In the embodiment of the present application, the conductivity of the electrolyte at room temperature, such as 25° C., is ionic conductivity, which can be detected using equipment and methods known in the art, such as testing with reference to industry standard HG-T 4067-2015.

[0372] 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 consisting of any two of the above values.

[0373] When the viscosity of the electrolyte at room temperature, such as 25° C., is within 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 fast charging performance of the battery cell.

[0374] In the embodiments of the present application, the viscosity of the electrolyte has a well-known meaning in the art and can be detected using equipment and methods well-known in the art, for example, it can be detected according to GB / T10247-2008.

[0375] In some embodiments, the density of the electrolyte at room temperature, such as 25° C., is 1.05 g / mL to 1.35 g / mL. Exemplarily, 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 consisting of any two of the above values.

[0376] When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0377] In the embodiments of the present application, the density of the electrolyte has a well-known meaning in the art and can be tested using equipment and methods well-known in the art, for example, by referring to GB / T 2013-2010 for testing.

[0378] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not specifically limited and can be selected according to actual needs.

[0379] 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%, and can be greater than or equal to 8.5% and less than or equal to 65%, and can be 25% to 60%. Exemplarily, 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 consisting of any two of the above values.

[0380] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0381] In some embodiments, the linear carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R 1 including a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R 2 Includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0382] The above-mentioned chain carboxylic acid ester solvents have high electrical conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0383] Optionally, R 1Including hydrogen atoms, halogen atoms, C1 to C3 alkyl groups or C1 to C3 haloalkyl groups. 1 Includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group or a C1 to C2 halogenated alkyl group.

[0384] Optionally, R 2 Including C1 to C3 alkyl or C1 to C3 haloalkyl. Further optionally, R 2 Includes C1 to C2 alkyl or C1 to C2 halogenated alkyl.

[0385] In the above-mentioned embodiments, the halogen atom includes one or more of a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Optionally, the halogen atom includes a fluorine atom.

[0386] In the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0387] Illustratively, the chain carboxylate solvent includes one or more of the compounds represented by Formula I-1 to the compounds represented by Formula I-8,

[0388] In some embodiments, the organic solvent further includes a carbonate solvent.

[0389] Optionally, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. Further optionally, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate. The above carbonate solvent and chain carboxylate solvent are used in combination to improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0390] Further optionally, the mass content of the carbonate solvent in the electrolyte is 25% to 60%, optionally 25% to 42.5%. Exemplarily, the mass content of the carbonate 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 consisting of any two of the above values. The above mass content of carbonate solvent can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0391] Illustratively, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, and the mass content of the carbonate solvent is 25% to 42.5%.

[0392] In some embodiments, the electrolyte further includes additives, which may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high temperature performance of the battery, and additives that improve the low temperature power performance of the battery.

[0393] In some embodiments, the additive includes one or more of carbonate additives, sulfur-containing additives and lithium salt additives, and at least two of them can be selected. The above additives can improve the interface film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0394] 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%. Exemplarily, 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 consisting of any two of the above values.

[0395] The additives in the above mass content can effectively improve the interface film performance on the positive electrode side and / or the negative electrode side, which is beneficial to enhance the fast charging performance of the battery cell and improve the cycle performance.

[0396] Illustratively, the carbonate additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0397] Exemplarily, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, vinyl sulfite ES, and methylene disulfonate MMDS.

[0398] Optionally, the lithium salt additive includes lithium difluorophosphate LiPO 2 F 2 , Lithium difluorooxalate borate LiDFOB, Lithium tetrafluoroborate LiBF 4 , lithium bis(oxalatoborate) LiBOB or more.

[0399] Optionally, the mass content of vinylene carbonate VC in the electrolyte is 0.5% to 9%, and optionally 2% to 6%.

[0400] Optionally, the mass content of fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%, and optionally 0.5% to 3%.

[0401] Optionally, the mass content of vinylene carbonate VC in the electrolyte is 0.5% to 9%, and the mass content of fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%.

[0402] Further optionally, the mass content of vinylene carbonate VC in the electrolyte is 2% to 6%, and the mass content of fluoroethylene carbonate FEC in the electrolyte is 0.5% to 3%.

[0403] In some embodiments, the electrolyte salt includes a lithium salt, the electrolyte solution includes a lithium salt, and the lithium salt includes a fluorinated sulfonyl imide salt and lithium hexafluorophosphate LiPF 6 The above lithium salt is easy to dissociate, which is conducive to the rapid migration of lithium ions; and the electrolyte system is relatively stable and not easy to decompose, which can improve the cycle performance of the battery monomer.

[0404] Optionally, the fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0405] Optionally, the lithium salt includes lithium bis(fluorosulfonyl)imide LiFSI and lithium hexafluorophosphate LiPF 6 The molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 The molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.4 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF is 0.5 mol / L to 1.0 mol / L. 6 The molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF is 0.7 mol / L. 6 The molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF is 0.5 mol / L. 6 The molar concentration is 0.8 mol / L.

[0406] Alternatively, the molar concentration of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate LiPF 6 The molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate LiPF is 0.2 to 1.0, and can be 0.2 to 0.5. 6 The molar concentration ratio is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range consisting of any two of the above values.

[0407] The qualitative and quantitative properties of each substance or element in this application can be detected by appropriate equipment 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., and those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0408] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentrations in the electrolyte are well-known in the art, and can be detected by equipment and methods well-known in the art. For example, the inorganic components / lithium salt concentrations in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis methods with reference to the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, a free electrolyte from a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery is charged at about 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery is used as a sample, and the ion chromatography analysis method is used for detection.

[0409] In the embodiments of the present application, the type and content of the organic components in the electrolyte are well-known in the art, and can be detected by using equipment and methods well-known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to perform qualitative and quantitative analysis of the organic components in the electrolyte by gas chromatography. In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, a free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery is charged at about 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery is used as a sample, and the ion chromatography analysis method is used for detection.

[0410] In the embodiment of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified, and the chain carboxylic acid ester solvent and carbonate solvent (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate) are used as the components of the organic solvent, and the mass content of each component is calculated based on the mass of the electrolyte as 100%; Carbonate additives (such as vinylene carbonate, fluoroethylene carbonate), sulfur-containing additives and lithium salt additives are used as additives for the electrolyte, and the mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0411] In some embodiments, the battery cell satisfies: 2.45g / Ah≤d / A≤3.5g / Ah, which may be 2.45g / Ah≤d / A≤3.3g / Ah, wherein d represents the mass of the electrolyte in the battery cell, in g; and A represents the rated capacity of the battery cell, in Ah. For example, d / A may be 3.5g / Ah, 3.3g / Ah, 3.2g / Ah, 3.0g / Ah, 2.8g / Ah, 2.5g / Ah, 2.45g / Ah, or a range consisting of any two of the above values.

[0412] d / A can reflect the electrolyte's ability to retain liquid. When d / A is within the above range, the electrolyte can better wet the positive and negative electrode plates, and can increase the migration rate of lithium ions in the liquid phase, which is beneficial to improving the fast charging capability of the battery cell.

[0413] In the implementation manner of the present application, the d / A of the battery cell can be understood as the liquid retention coefficient, which can be detected by using equipment and methods known in the art. For example, it can be described in accordance with GB / T31486-2015 "Electrical Performance Requirements and Test Methods for Power Batteries for Electric Vehicles", taking the battery charging upper limit voltage as 3.65V and the battery discharge cut-off voltage as 2.0V as an example. At 25°C, charge the battery cell to 3.65V at 0.33C, then charge to 0.05C at constant voltage, and then discharge to 2.0V at 0.33C constant current, and obtain the discharged capacity A as the denominator; weigh the battery cell as M0, and then disassemble the positive electrode sheet, negative electrode sheet, separator and electrolyte, where the free electrolyte is in the shell / bag, and bake all the above solid components in a 60°C oven for more than 4 hours (including but not limited to the positive electrode sheet, negative electrode sheet, separator, and other mechanical parts of the disassembled battery cell that contribute to M0), and then weigh all the components of the battery cell as M1, where the weight difference between M0 and M1 is used as the numerator. The liquid retention coefficient is equal to the value obtained by dividing the weight difference d between M0 and M1 by the capacity A.

[0414] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly by a winding process and / or a lamination process.

[0415] Please continue reading Figures 1 to 7 In some embodiments, the battery cell 7 may include a housing 20 .

[0416] In some embodiments, the housing 20 of the battery cell 7 may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The housing 20 of the battery cell 7 may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0417] The outer shell 20 is a hollow structure, and the outer shell 20 can be used to encapsulate the electrode assembly 10 and the electrolyte.

[0418] The preparation method of the battery cell 7 of the embodiment of the present application is well 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 formed into an electrode assembly 10 through a winding process and / or a lamination process, and the electrode assembly 10 is placed in a housing 20, and the electrolyte is injected after drying, and the battery cell 7 is obtained through vacuum packaging, standing, forming, shaping and other processes.

[0419] In some embodiments, the housing 20 includes a shell 21 and an end cover 22 , wherein the shell 21 has an opening and the end cover 22 covers the opening.

[0420] The shape of the shell 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 can be selected; if the electrode assembly 10 is a rectangular parallelepiped structure, a rectangular parallelepiped shell can be selected. Optionally, both the electrode assembly 10 and the shell 21 are rectangular parallelepiped structures.

[0421] In some embodiments, the material of the housing 21 includes steel, which has high mechanical strength and is not easily deformed, and can improve the reliability and cycle performance of the battery cell. Optionally, the mass percentage of steel is the highest among the materials in the housing 21.

[0422] Optionally, the thickness of the shell 21 is 0.1mm to 0.5mm, and optionally 0.2mm to 0.35mm. Exemplarily, the thickness of the shell is 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, or a range consisting of any two of the above values. When the thickness of the shell 21 is within the above range, the mechanical strength of the shell 21 is high, which can improve the reliability and cycle performance of the battery cell; and the shell 21 occupies less space, and the shell 21 has more internal space, which is conducive to improving the energy density of the battery cell.

[0423] 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; The first pole piece also includes a first pole ear connected to the second portion.

[0424] From the appearance of the electrode assembly 10, the electrode assembly 10 includes a main body 12, a first pole ear 111 and a second pole ear 112, and the first pole ear 111 and the second pole ear 112 protrude from the main body 12. The first pole ear 111 and the second pole ear 112 are used to lead the current in the main body 12. The polarity of the first pole piece and the second pole piece is opposite. In other words, one of the first pole piece and the second pole piece is a positive pole piece, and the other of the first pole piece and the second pole piece is a negative pole piece. Of course, the first pole ear 111 can be a positive pole ear, and the second pole ear 112 can be a negative pole ear.

[0425] 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 a first film layer 132, and the second portion 1312b is not provided with the first film layer 132; the first pole piece 13 also includes a first pole ear 111, and the first pole ear 111 is connected to the second portion 1312b. Figure 5 The first pole piece 13 shown shows a schematic diagram of the connection between the first metal layer 1312 and the first pole ear 111 .

[0426] Optionally, the first pole ear 111 includes a first pole ear main body 1111 and a first pole ear connecting portion 1112, the first pole ear main body 1111 is arranged on two surfaces of the second part 1312b opposite to each other along the thickness direction X, the first pole ear connecting portion 1112 connects the first pole ear main body 1111, and the first pole ear connecting portion 1112 is located on the side of the second part 1312b away from the first part 1312a; this arrangement is conducive to the first pole ear 111 to draw out the current.

[0427] The second electrode tab 112 may have a similar structure to that of the first electrode tab 111 .

[0428] The first electrode tab 111 and the second electrode tab 112 may extend from the same side of the main body 12 , or may extend from opposite sides respectively.

[0429] Optionally, the number of the first pole lugs 111 located on the same side of the main body 12 is at least one, and optionally at least two. The at least two first pole lugs 111 can increase the current carrying capacity of the first pole lugs 111 .

[0430] Optionally, the number of the second pole tabs 112 located on the same side of the main body 12 is at least one, and optionally at least two. The at least two second pole tabs 112 can increase the current carrying capacity of the second pole tabs 112 .

[0431] In some embodiments, the battery cell 7 further includes a first electrode terminal 31, and the first electrode terminal 31 is electrically connected to the first pole tab 111. Optionally, the first electrode terminal 31 and the first pole tab 111 are welded, and the first electrode terminal 31 and the first pole tab 111 may be connected by an adapter or may not be connected by an adapter; optionally, the first electrode terminal 31 and the first pole tab 111 are not connected by an adapter, that is, the first electrode terminal 31 and the first pole tab 111 are directly welded, which can reduce the resistance at the connection point and is conducive to reducing the internal resistance of the battery cell 7 as a whole. When the first pole tab 111 is a negative pole tab, the first electrode terminal 31 is a negative terminal. When the first pole tab 111 is a positive pole tab, the first electrode terminal 31 is a positive terminal.

[0432] In some embodiments, the battery cell 7 further includes a second electrode terminal 32, and the second electrode terminal 32 is electrically connected to the second pole tab 112. Optionally, the second electrode terminal 32 and the second pole tab 112 are welded, and the second electrode terminal 32 and the second pole tab 112 may be connected through an adapter or may not be connected by an adapter; optionally, the second electrode terminal 32 and the second pole tab 112 are not connected by an adapter, that is, the second electrode terminal 32 and the second pole tab 112 are directly welded, which can reduce the resistance at the connection point and is conducive to reducing the internal resistance of the battery cell 7 as a whole. When the second pole tab 112 is a negative pole tab, the second electrode terminal 32 is a negative terminal. When the second pole tab 112 is a positive pole tab, the second electrode terminal 32 is a positive terminal.

[0433] Optionally, the number of the first electrode terminals 31 located on the same side of the main body 12 is at least one, and optionally at least two. At least two first electrode terminals 31 can increase the current capacity of the first electrode terminal 31 .

[0434] Further optionally, the flow area of ​​the first electrode terminal 31 on one side is 150 mm 2 Up to 1000mm 2 , optional 200mm 2 Up to 1000mm 2 The flow area of ​​the first electrode terminal 31 on one side refers to the sum of the flow areas of all the first electrode terminals 31 on the same side of the main body 12. The flow 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.

[0435] For example, the flow area of ​​the first electrode terminal 31 on one side may be 150 mm 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 consisting of any two of the above values.

[0436] Optionally, the number of the second electrode terminals 32 located on the same side of the main body 12 is at least one, and optionally at least two. The at least two second electrode terminals 32 can increase the current capacity of the second electrode terminals 32 .

[0437] Optionally, the flow area of ​​the second electrode terminal 32 on one side is 150 mm 2 Up to 1000mm 2 , optional 200mm 2 Up to 1000mm 2 The flow area of ​​the second electrode terminal 32 on one side refers to the sum of the flow areas of all the second electrode terminals 32 on the same side of the main body 12. The flow area of ​​the second electrode terminal 32 can be understood as the cross-sectional area of ​​the second electrode terminal 32, which is perpendicular to the thickness direction of the second electrode terminal 32.

[0438] For example, the flow area of ​​the second electrode terminal 32 on one side may be 150 mm 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 , 800mm 2 、850mm 2 , 900mm 2 、950mm 2 , 1000mm 2 Or a range consisting of any two of the above values.

[0439] like Figure 8 As shown, in some embodiments of the present application, the battery cells 7 according to the implementation mode of the present application can be assembled into a battery module 6. 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.

[0440] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, in parallel or in mixed connection. Mixed connection means that the multiple battery cells 7 are both connected in series and in parallel. Multiple battery cells 7 can be directly connected in series, in parallel or in mixed connection, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodation part of the battery module 6; of course, multiple battery cells 7 can also be connected in series, in parallel or in mixed connection to form a battery module 6, and then the multiple battery modules 6 are connected in series, in parallel or in mixed connection to form a whole and accommodated in the accommodation part. Optionally, the battery module 6 can also include an accommodation part with an accommodation space, and multiple battery cells 7 are accommodated in the accommodation space.

[0441] like Fig. 9 As shown, in some embodiments, the battery modules 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 a battery module 6 or a battery pack 2.

[0442] The battery pack 2 may include a box body 5 and a plurality of battery modules 6 disposed in the box body 5. The box body 5 includes a first box body portion 5a and a second box body portion 5b. The box body 5 has a receiving space 5c. The first box body portion 5a is used to cover the second box body portion 5b and form a closed space for receiving the battery modules 6. The plurality of battery modules 6 may be arranged in the box body 5 in any manner.

[0443] The first box body part 5a and the second box body part 5b cover each other, and the first box body part 5a and the second box body part 5b together define a storage space 5c for accommodating a battery cell. The second box body part 5b can be a hollow structure with one end open, and the first box body part 5a is a plate-shaped structure. The first box body part 5a covers the open side of the second box body part 5b to form a box body 5 with a storage space 5c; the first box body part 5a and the second box body part 5b can also be a hollow structure with one side open, and the open side of the first box body part 5a covers the open side of the second box body part 5b to form a box body 5 with a storage space 5c. Of course, the first box body part 5a and the second box body part 5b can be in various shapes, such as a cylinder, a cuboid, etc.

[0444] In order to improve the sealing performance after the first box body part 5a and the second box body part 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body part 5a and the second box body part 5b.

[0445] Assuming that the first box body portion 5a covers the top of the second box body portion 5b, the first box body portion 5a can also be called an upper box cover, and the second box body portion 5b can also be called a lower box. In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 0% state of charge SOC to 100% state of charge SOC, the temperature of the external environment of the battery pack 2 is room temperature, for example, 30° C.

[0446] In some embodiments, during the process of the battery pack 2 or any battery cell constituting the battery pack 2 changing from a state of charge SOC of 10% to a state of charge SOC of 80%, the temperature of the external environment of the battery pack 2 is 30°C.

[0447] 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 multiple charging steps, and the difference between the maximum state of charge of any charging step in the multiple charging steps and the maximum state of charge in the 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 consisting of any two of the above values.

[0448] The battery pack 2 or any battery cell constituting the battery pack 2 includes multiple charging steps from a 10% state of charge to a 40% state of charge. For any charging step, it can be charged at any rate between 5C and 10C. The charging rate corresponding to each charging step can be any value of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value in the range consisting of any two of the above values.

[0449] Exemplarily, the charging step of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be performed as follows: Charge from 10% SOC to 15% SOC at 5.0C constant current; Charge from 15% SOC to 20% SOC at 5.0C constant current; Charge from 20% SOC to 25% SOC at 5.0C constant current; Charge from 25% SOC to 30% SOC at 5.0C constant current; Charge from 30% SOC to 35% SOC at 5.0C constant current; Charge from 35% SOC to 40% SOC at 5.0C constant current; Charge from 40% SOC to 45% SOC at 4.6C constant current; Charge from 45% SOC to 50% SOC at 4.3C constant current; Charge from 50% SOC to 55% SOC at 4.0C constant current; Charge from 55% SOC to 60% SOC at 3.7C constant current; Charge from 60% SOC to 65% SOC at 3.4C constant current; Charge from 65% SOC to 70% SOC at 3.1C constant current; Charge from 70% SOC to 75% SOC at 2.9C constant current; Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0450] In some embodiments, the charging time of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, and can be selected from 5 min to 10.5 min. The temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, for example, 30° C. Exemplarily, 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. In some embodiments, the volume energy density of the battery cell is 380Wh / L to 500Wh / L, and can be 380Wh / L to 470 Wh / L. Exemplarily, the volume energy density of the battery cell is 380Wh / L, 390Wh / L, 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, 440Wh / L, 450Wh / L, 460Wh / L, 470Wh / L, 480Wh / L, 490Wh / L, 500Wh / L, or a range consisting of any two of the above values. The volume energy density of the battery cell is relatively high.

[0451] In the embodiments of the present application, the volume energy density of a battery cell has a well-known meaning in the art and can be detected by using well-known equipment and methods in the art. For example, the battery charging upper limit voltage is 3.65V and the battery discharge cut-off voltage is 2.0V. Place the battery cell at 25°C, charge it to 3.65V at a constant current of 0.33C, and then charge it to 0.05C at a constant voltage; discharge it to 2.0V at a constant current of 0.33C, and record the discharge capacity A0 at this time, in Ah; use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the battery shell size, excluding the electrode terminal height and the insulating film outside the shell), and calculate the volume of the single battery V0, in L; the volume energy density of the battery cell VED=(A0×discharge platform voltage) / V0, in Wh / L.

[0452] In some embodiments, the weight energy density of the battery cell is 180Wh / Kg to 210Wh / Kg. Exemplarily, the weight energy density of the battery cell is 180Wh / Kg, 190Wh / Kg, 200Wh / Kg, 210Wh / Kg, or a range consisting of any two of the above values. The volume energy density of the battery cell is relatively high.

[0453] In the embodiments of the present application, the volume energy density of a battery cell has a well-known meaning in the art and can be detected by using well-known equipment and methods in the art. For example, the battery charging upper limit voltage is 3.65V and the battery discharge cut-off voltage is 2.0V. Place the battery cell at 25°C, charge it to 3.65V at a constant current of 0.33C, and then charge it to 0.05C at a constant voltage; discharge it to 2.0V at a constant current of 0.33C, and record the discharge capacity A0 at this time, in Ah; use a card to measure the mass of the electrode assembly in the battery cell, and calculate the weight energy density of the battery cell, in Wh / Kg.

[0454] Electrical devices The second aspect of the embodiment of the present application provides an electric device, which includes a battery device of the embodiment of the present application, such as a battery cell, a battery module or a battery pack. The battery cell, battery module or battery pack can be used as a power source for the electric device, or as an energy storage unit for the electric device. The electric device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, 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 car toy, an electric ship toy and an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly 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 drill, a concrete vibrator and an electric planer, etc. The embodiment of the present application does not impose any special restrictions on the above-mentioned electric device. The electrical device can select a battery cell, a battery module or a battery pack according to its usage requirements.

[0455] Fig.10 1 is a schematic diagram of an exemplary electric device 1. The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device 1 for high power and high energy density, a battery pack or a battery module may be used.

[0456] The electric device 1 is provided with a battery pack 2 inside, and the battery pack 2 can be provided at the bottom, head, or tail of the electric device 1. The battery pack 2 can be used to power the electric device 1. For example, the battery pack 2 can be used as an operating power source for the electric device 1, and can also be used as a driving power source for the electric device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electric device 1.

[0457] The electric device 1 may further include a controller 3 and a motor 4 , wherein the controller 3 is used to control the battery pack 2 to supply power to the motor 4 , for example, to meet the power requirements of the electric device 1 during startup, navigation, and driving.

[0458] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0459] The following charging methods can be selected for the charging process of the electrical device: Charge from 10% SOC to 15% SOC at 5.0C constant current; Charge from 15% SOC to 20% SOC at 5.0C constant current; Charge from 20% SOC to 25% SOC at 5.0C constant current; Charge from 25% SOC to 30% SOC at 5.0C constant current; Charge from 30% SOC to 35% SOC at 5.0C constant current; Charge from 35% SOC to 40% SOC at 5.0C constant current; Charge from 40% SOC to 45% SOC at 4.6C constant current; Charge from 45% SOC to 50% SOC at 4.3C constant current; Charge from 50% SOC to 55% SOC at 4.0C constant current; Charge from 55% SOC to 60% SOC at 3.7C constant current; Charge from 60% SOC to 65% SOC at 3.4C constant current; Charge from 65% SOC to 70% SOC at 3.1C constant current; Charge from 70% SOC to 75% SOC at 2.9C constant current; Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0460] In some embodiments, the charging time of the electric device from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, and can be 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. Exemplarily, 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.

[0461] Example The following examples more specifically describe the contents disclosed in the embodiments of the present application, and these examples are only for illustrative purposes, because it is obvious to those skilled in the art that various modifications and changes are made within the scope of the disclosure of the embodiments of the present application. 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 can be used directly without further processing, and the instruments used in the examples are commercially available.

[0462] Example 1 1. Preparation of positive electrode sheet The positive electrode sheet includes a positive current collecting portion, a positive conductive layer on the positive current collecting portion and a positive film layer. The positive current collecting portion includes a positive support layer and positive metal layers arranged on both sides of the positive support layer.

[0463] The positive electrode conductive layer on the positive electrode current collecting part is a film layer formed by evenly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride (PVDF) and the solvent N-methylpyrrolidone NMP, and then coating it on the surface of the current collecting part and drying it. The thickness is 1 μm, and 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%.

[0464] The positive electrode film layer includes a film layer formed by uniformly coating the positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on the surface of the positive electrode conductive layer, drying, and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black in a weight ratio of 97:2:1.

[0465] The positive electrode active material includes lithium iron phosphate and a coating layer, the coating layer is coated on the surface of the lithium iron phosphate, and the coating layer includes lithium iron titanium phosphate Li2FeTi(PO4)3 and amorphous carbon. The Dv50 of the positive electrode active material is 1.6μm, and the Dv10 is 0.64μm.

[0466] The single-sided coating weight of the positive electrode film is 285mg / 1540.25mm 2 .

[0467] 2. Preparation of negative electrode sheet The negative electrode sheet includes a negative current collecting portion, a negative conductive layer on the negative current collecting portion and a negative film layer. The negative current collecting portion includes a negative support layer and negative metal layers arranged on both sides of the negative support layer.

[0468] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by evenly mixing a negative electrode conductive agent superconducting carbon, a negative electrode binder styrene-butadiene rubber SBR, a thickener sodium carboxymethyl cellulose (CMC-Na) and a solvent water, and then coating it on the surface of the negative electrode current collector and drying it. The thickness is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0469] The negative electrode film layer includes a film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, and then drying and cold pressing.

[0470] The single-sided coating weight of the negative electrode film is 130mg / 1540.25mm 2 .

[0471] The negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer, wherein 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.

[0472] The first negative electrode film layer includes graphite particles with a mass ratio of 96.5:0.5:0.5:1.5:1, a conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose. The mass content of lithium element in the first lithium-containing binder is 4.8%, the Dv50 of the graphite particles is 11.3μm, and the graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0473] The second negative electrode film layer includes graphite particles with a mass ratio of 97.5:0.5:0.5:0.5:1, a conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose. The mass content of lithium element in the second lithium-containing binder is 4.8%, the Dv50 of the graphite particles is 11.3μm, and the graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0474] 3. Isolation film The isolation film comprises a base film, which is a 7 μm polyethylene film layer with a porosity of 42%.

[0475] 4. Preparation of electrolyte The electrolyte includes an organic solvent, a lithium salt and additives.

[0476] The organic solvent includes 48.5% of chain carboxylic acid ester solvent (ethyl acetate) and 32.5% of carbonate solvent (24.5% of ethylene carbonate EC, 8% of dimethyl carbonate), and the mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0477] Based on the mass of the electrolyte, the mass content of the additive is 6.5%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, vinyl sulfite ES and lithium difluorooxalatoborate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0478] Lithium salts include 1 mol / L lithium hexafluorophosphate LiPF 6 .

[0479] The conductivity of the electrolyte at room temperature is 16.4 mS / cm.

[0480] 5. Preparation of battery cells The positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the electrode assembly is placed in an outer packaging shell, and the electrolyte is injected after drying. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained. The compaction density of the positive electrode film layer of the battery cell at 100% SOC is 2.60g / cm 3 The compaction density of the negative electrode film layer at 100% SOC is 1.26g / cm 3 .

[0481] Comparative Example 1 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that a 15 μm aluminum foil was used as the positive electrode current collector, and a 6 μm copper foil was used as the negative electrode current collector.

[0482] Example 2-1 to Example 2-7 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the material and thickness of the positive electrode current collector were adjusted.

[0483] Example 3-1 to Example 3-7 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the material and thickness of the negative electrode current collector were adjusted.

[0484] The test results are shown in Table 1.

[0485] Table 1

[0486] In Table 1, PET stands for polyethylene terephthalate.

[0487] It can be seen from Table 1 that, compared with the comparative example 1 which uses a metal foil as the current collecting part, the current collecting part of the composite structure used in the embodiment of the present application can improve the volume energy density and weight energy density of the battery cell.

[0488] In the embodiment of the present application, the fast charging performance of the battery cell is relatively excellent. Under this condition, the coating weight of the positive electrode film layer and the negative electrode film layer is usually thin, and the use of a composite collecting part structure can significantly increase the volume ratio of the positive electrode film layer and the negative electrode film layer, thereby increasing the volume energy density of the battery cell; and since the composite collecting part is light in weight, the weight energy density of the battery cell can also be increased.

[0489] Moreover, when the positive electrode current collecting part comprises aluminum material, the volume energy density of the battery cell can be more significantly improved; when the negative electrode current collecting part comprises copper material, the weight energy density of the battery cell can be more significantly improved.

[0490] The positive electrode metal layer can improve conductivity and improve fast charging performance.

[0491] Example 4-1 to Example 4-4 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the coating weights of the positive electrode film layer and the negative electrode film layer were adjusted.

[0492] Performance Testing 1. Lithium deposition area test of battery cells After each battery cell of each embodiment and comparative example was cycled 50 times according to the following charge and discharge strategy, it was fully charged to 100% SOC according to the corresponding charging strategy, the negative electrode sheet in the battery pack was disassembled, the negative electrode sheet was unfolded, the decomposition area (gray-white area) was observed, and the decomposition area was measured. The decomposition degree is as follows: No lithium deposition: lithium deposition area <0.05%.

[0493] Slight lithium deposition: lithium deposition area <2%.

[0494] Severe lithium deposition: lithium deposition area ≥ 2%.

[0495] At an ambient temperature of 30°C, the battery cells are charged. The charging process includes the following steps: Charge from 0% SOC to 5% SOC at 5.0C constant current; Charge from 5% SOC to 10% SOC at 5.0C constant current; Charge from 10% SOC to 15% SOC at 5.0C constant current; Charge from 15% SOC to 20% SOC at 5.0C constant current; Charge from 20% SOC to 25% SOC at 5.0C constant current; Charge from 25% SOC to 30% SOC at 5.0C constant current; Charge from 30% SOC to 35% SOC at 5.0C constant current; Charge from 35% SOC to 40% SOC at 5.0C constant current; Charge from 40% SOC to 45% SOC at 4.6C constant current; Charge from 45% SOC to 50% SOC at 4.3C constant current; Charge from 50% SOC to 55% SOC at 4.0C constant current; Charge from 55% SOC to 60% SOC at 3.7C constant current; Charge from 60% SOC to 65% SOC at 3.4C constant current; Charge from 65% SOC to 70% SOC at 3.1C constant current; Charge from 70% SOC to 75% SOC at 2.9C constant current; Charge from 75% SOC to 80% SOC at 2.7C constant current; Charge from 80% SOC to 85% SOC at 1.8C constant current; Charge from 85% SOC to 90% SOC at 1.3C constant current; Charge from 90% SOC to 95% SOC at 0.7C constant current; Charge from 95% SOC to 98% SOC at 0.33C constant current; Charge from 98% SOC to 100% SOC at 0.1C constant current.

[0496] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0497] The discharge strategy is as follows: discharge at a constant current of 0.33C to a cut-off voltage, for example, 2.0V.

[0498] The test results are shown in Table 2.

[0499] Table 2

[0500] By adjusting the coating weight of the positive electrode film layer and the negative electrode film layer, the volume energy density of the battery cell can be improved. However, when the coating weight is too high, although the energy density is significantly improved, the risk of lithium plating is relatively high.

[0501] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions and modifications may be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises an electrode assembly, wherein the electrode assembly comprises a first pole piece, a second pole piece and a separator, wherein the separator is disposed between the first pole piece and the second pole piece, and the first pole piece and the second pole piece have opposite polarities; The first pole piece includes a first current collecting portion and a first film layer disposed on at least one side of the first current collecting portion and including a first active material; The second pole piece includes a second current collecting portion and a second film layer disposed on at least one side of the second current collecting portion and including a second active material; in, One of the first active material and the second active material comprises an olivine-structured lithium-containing phosphate, and the other comprises a carbon-based material; The first current collecting portion includes a first supporting layer and a first metal layer disposed on at least one side of the first supporting layer, the first film layer is disposed on the first metal layer, and the first supporting layer includes an organic material; The first pole piece is a positive pole piece, and the first metal layer is arranged on both sides of the first supporting layer; The thickness of the first current collecting portion is 5 μm to 15 μm; When the battery cell is 100% charged, the compaction density of the first film layer is 2.50 g / cm 3 Up to 2.80g / cm 3 .

2. The battery cell according to claim 1, characterized in that: The second current collecting portion includes a second supporting layer and a second metal layer disposed on at least one side of the second supporting layer, the second film layer is disposed on the second metal layer, and the second supporting layer includes an organic material.

3. The battery cell according to claim 1, characterized in that: The first current collecting portion has a thickness of 5 μm to 10 μm.

4. The battery cell according to claim 1, characterized in that: The thickness of the first metal layer is 0.3 μm to 3 μm.

5. The battery cell according to claim 4, characterized in that: The thickness of the first metal layer is 0.5 μm to 1.5 μm.

6. The battery cell according to claim 1, characterized in that: The first supporting layer has a thickness of 1 μm to 10 μm.

7. The battery cell according to claim 6, characterized in that: The thickness of the first supporting layer is 3 μm to 8 μm.

8. The battery cell according to claim 1, characterized in that: 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 supporting layer includes at least one of an insulating polymer material and a conductive polymer material.

9. The battery cell according to claim 8, characterized in that: The first metal layer includes aluminum.

10. The battery cell according to claim 8 or 9, characterized in that: The organic material in the first supporting layer includes insulating polymer material.

11. The battery cell according to claim 10, characterized in that: The first supporting layer also includes an inorganic insulating material.

12. The battery cell according to claim 8, characterized in that: The insulating polymer material includes at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene dicarboxamide, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylene, 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 products, polyethylene glycol and its crosslinked products.

13. The battery cell according to claim 1, characterized in that: The positive electrode plate further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the first film layer and the first current collecting portion.

14. The battery cell according to claim 13, characterized in that: The thickness of the positive electrode conductive layer is 0.1 μm to 2 μm.

15. The battery cell according to claim 13 or 14, characterized in that: The positive electrode conductive layer includes a positive electrode conductive agent, and the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and / or The positive electrode conductive layer includes a positive electrode binder, and the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

16. The battery cell according to claim 2, characterized in that: The second pole piece is a negative pole piece, and the second metal layer is arranged on both sides of the second supporting layer.

17. The battery cell according to claim 16, characterized in that: The second current collecting portion has a thickness of 2 μm to 8.5 μm.

18. The battery cell according to claim 17, characterized in that: The second current collecting portion has a thickness of 2 μm to 6.5 μm.

19. The battery cell according to claim 16, characterized in that: The second metal layer has a thickness of 0.3 μm to 2 μm.

20. The battery cell according to claim 19, characterized in that: The second metal layer has a thickness of 0.5 μm to 1.5 μm.

21. The battery cell according to claim 16, characterized in that: The second supporting layer has a thickness of 1 μm to 4.5 μm.

22. The battery cell according to claim 21, characterized in that: The second supporting layer has a thickness of 3 μm to 4 μm.

23. The battery cell according to claim 16, characterized in that: The metal material in the second metal layer includes at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy; and / or, The organic material of the second supporting layer includes at least one of an insulating polymer material and a conductive polymer material.

24. The battery cell according to claim 23, characterized in that: The second metal layer includes copper.

25. The battery cell according to claim 23 or 24, characterized in that: The material of the second supporting layer includes insulating polymer material.

26. The battery cell according to claim 25, characterized in that: The second supporting layer also includes an inorganic insulating material.

27. The battery cell according to claim 23, characterized in that: The insulating polymer material includes at least one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene dicarboxamide, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylene, 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 products, polyethylene glycol and its crosslinked products.

28. The battery cell according to claim 16, characterized in that: The negative electrode plate further includes a negative electrode conductive layer, and the negative electrode conductive layer is located between the second film layer and the second current collecting portion.

29. The battery cell according to claim 28, characterized in that: The thickness of the negative electrode conductive layer is 0.1 μm to 2 μm.

30. The battery cell according to claim 28 or 29, characterized in that: The negative electrode conductive layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and / or The negative electrode conductive layer includes a negative electrode binder, and the negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate and carboxymethyl chitosan.

31. The battery cell according to claim 1, characterized in that The powder resistivity of the olivine-structured lithium-containing phosphate is 1 Ω·cm to 27.5 Ω·cm.

32. The battery cell according to claim 1, characterized in that The powder compaction density of the olivine-structured lithium-containing phosphate at 30,000 N is 2.46 g / cm 3 Up to 2.8g / cm 3 .

33. The battery cell according to claim 1, characterized in that: The charge capacity of the olivine-structured lithium-containing phosphate is 150 mAh / g to 170 mAh / g.

34. The battery cell according to claim 33, characterized in that: The olivine-structured lithium-containing phosphate has a charge capacity of 150 mAh / g to 170 mAh / g at a charge rate of 0.1C.

35. The battery cell according to claim 1, characterized in that The lithium-containing phosphate of the olivine structure comprises: Phosphate particles, and A coating layer, wherein the coating layer covers the phosphate particles, and the coating layer contains one or more elements selected from the group consisting of C, Fe, Ti, Zr, Hf, Ge and Sn.

36. The battery cell according to claim 35, characterized in that The phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y z A compound wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F.

37. The battery cell according to claim 35 or 36, characterized in that: The coating layer includes a general formula of Li 3- d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor M2 includes one or more elements of Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x2<5, 0<y2<4.

38. The battery cell according to claim 35, characterized in that: The graphitization degree of the lithium-containing phosphate with an olivine structure is 0.15 to 0.

32.

39. The battery cell according to claim 35, characterized in that The mass content of carbon in the lithium-containing phosphate with olivine structure is 1% to 2%; The specific surface area of ​​the lithium-containing phosphate with olivine structure is 5m 2 / g to 18m 2 / g.

40. The battery cell according to claim 1, characterized in that The volume distribution particle size of the lithium-containing phosphate with an olivine structure satisfies: 1µm≤Dv50≤2µm, 0.4µm≤Dv10≤0.7µm.

41. The battery cell according to claim 1, characterized in that The lithium-containing phosphate with an olivine structure is in a granular form, and 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.

42. The battery cell according to claim 1, characterized in that The powder resistivity of the carbon-based material is 0.005 Ω•cm to 0.043 Ω•cm.

43. The battery cell according to claim 1, characterized in that The powder compaction density of the carbon-based material at 20000N is 1.5g / cm 3 Up to 1.85g / cm 3 .

44. The battery cell according to claim 1, characterized in that The charge capacity of the carbon-based material is 350 mAh / g to 480 mAh / g.

45. The battery cell according to claim 44, characterized in that The carbon-based material has a charge capacity of 350 mAh / g to 480 mAh / g at a charge rate of 0.1C.

46. ​​The battery cell according to claim 1, characterized in that The carbon-based material includes graphite particles, and the graphite particles have a degree of graphitization of 92.0% to 94.5%.

47. The battery cell according to claim 46, characterized in that The graphite particles include: Artificial graphite, including secondary particles; and The carbon coating layer is coated on the surface of the artificial graphite.

48. The battery cell according to claim 47, characterized in that The mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles.

49. The battery cell according to claim 1, characterized in that The single-sided coating weight of the first film layer is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 .

50. The battery cell according to claim 1, characterized in that The second electrode is the negative electrode. The second active material in the second film layer includes a carbon-based material; The compaction density of the second film layer of the battery cell is 1.15 g / cm 3 Up to 1.36g / cm 3 ; and / or The single-sided coating weight of the second film layer is 90 mg / 1540.25 mm 2 Up to 170mg / 1540.25mm 2 .

51. The battery cell according to claim 1, characterized in that The isolation membrane includes a base membrane with a porous structure, and the porosity of the base membrane is 20% to 70%.

52. The battery cell according to claim 51, characterized in that The base film has a thickness of 6 μm to 12 μm.

53. The battery cell according to claim 1, characterized in that The isolation film includes a base film and a functional layer disposed on at least one side of the base film, wherein the functional layer includes: a first functional layer, located on one side of the base film, wherein 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 includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

54. The battery cell according to claim 53, characterized in that The non-fluorine polymer particles include acrylic copolymers.

55. The battery cell according to claim 53 or 54, characterized in that: The first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

56. The battery cell according to claim 54, characterized in that 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.

57. The battery cell according to claim 1, characterized in that The battery cell further comprises an electrolyte, wherein the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm; and / or The viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s; and / or The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature.

58. The battery cell according to claim 57, characterized in that The electrolyte includes an organic solvent, the organic solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent in the electrolyte is 4% to 65%.

59. The battery cell according to claim 58, characterized in that The chain carboxylic acid ester solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

60. The battery cell according to claim 58 or 59, characterized in that: The organic solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

61. The battery cell according to claim 60, characterized in that The mass content of the carbonate solvent in the electrolyte is 25% to 60%.

62. The battery cell according to claim 57, characterized in that The electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives and lithium salt additives.

63. The battery cell according to claim 62, characterized in that: The carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate; and / or The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylene disulfonate; and / or The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

64. The battery cell according to claim 62 or 63, characterized in that: The mass content of the additive in the electrolyte is 1% to 10%.

65. The battery cell according to claim 57, characterized in that The electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfonyl imide salt and lithium hexafluorophosphate.

66. The battery cell according to claim 1, characterized in that The battery cell includes an electrolyte, and the battery cell includes a shell. The shell contains the electrode assembly and the electrolyte. The material of the shell includes steel, and the thickness of the shell is 0.1 mm to 0.5 mm.

67. The battery cell according to claim 1, characterized in that The first metal layer includes a first portion and a second portion extending from the first portion, the first portion is provided with a first film layer, and the second portion is not provided with the first film layer; The first pole piece further includes a first pole lug, and the first pole lug is connected to the second portion.

68. The battery cell according to claim 67, characterized in that The battery cell further includes a first electrode terminal, and the first electrode terminal is directly welded to the first electrode tab.

69. The battery cell according to claim 2, characterized in that: The second metal layer includes a first portion and a second portion extending from the first portion, the first portion is provided with a second film layer, and the second portion is not provided with the second film layer; The second pole piece further includes a second pole lug, and the second pole lug is connected to the second portion.

70. The battery cell according to claim 69, characterized in that The battery cell further includes a second electrode terminal, and the second electrode terminal is directly welded to the second electrode tab.

71. The battery cell according to claim 1, characterized in that At room temperature, the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 min to 10.5 min.

72. The battery cell according to claim 1, characterized in that The volume energy density of the battery cell is 380Wh / L to 500Wh / L; and / or The weight energy density of the battery cell is 180Wh / Kg to 210Wh / Kg.

73. The battery cell according to claim 72, characterized in that The volume energy density of the battery cell is 380 Wh / L to 470 Wh / L.

74. A battery device, characterized in that: The battery device comprises a plurality of battery cells as claimed in any one of claims 1 to 73.

75. The battery device according to claim 74, characterized in that At room temperature, the battery device has a charging time of 5 min to 10.5 min from a 10% state of charge to an 80% state of charge.

76. An electrical device, characterized in that: The electrical device includes a battery device as described in claim 74 or 75.

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