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 positive pole piece, the positive pole piece comprises a positive pole film layer, a positive pole current collecting part and a positive pole lug, the positive pole film layer is arranged on at least one side of the positive pole current collecting part along the thickness direction of the positive pole piece, and the positive pole lug is arranged on the positive pole piece. The positive pole lug is arranged on at least one side of the positive pole current collecting part along the first direction, the positive pole film layer comprises a positive pole active material, the positive pole active material comprises a lithium-containing material with an olivine structure, the single-side coating weight of the positive pole film layer is 200 mg / 1540.25 mm < 2 > to 400 mg / 1540.25 mm < 2 >, and the single-side coating weight of the positive pole film layer is 100 mg / 1540.25 mm < 2 > along the second direction. The distance between a first point of the positive pole current collecting part and the positive pole lug closest to the first point is smaller than or equal to 300mm, the first point is any point of the positive pole current collecting part, and the first direction, the second direction and the thickness direction of the positive pole piece are vertical in pairs. The risk of lithium precipitation of the battery cell can be reduced, and the use reliability of the battery cell is improved.

Description

[0001] This application claims the priority of the PCT international application PCT / CN2024 / 102661, titled "Battery Cell, Battery Device and Electrical Device", filed on June 28, 2024, the entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to a battery cell, a battery device and an electrical device. Background Art

[0003] Battery cells have characteristics such as high capacity and long life, and are therefore widely used in electronic devices, such as mobile phones, laptop computers, battery-powered vehicles, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and power tools, etc. With the development of the application fields of battery cells, higher requirements are put forward for the performance and the use reliability of battery cells. Summary of the Invention

[0004] This application provides a battery cell, a battery device and an electrical device, which can reduce the risk of lithium plating in the battery cell and improve the use reliability of the battery cell.

[0005] In a first aspect, this application proposes a battery cell. The battery cell includes an electrode assembly. The electrode assembly includes a positive electrode tab. The positive electrode tab includes a positive electrode film layer, a positive electrode current collector and at least one positive electrode tab. The positive electrode film layer is disposed on at least one side of the positive electrode current collector along the thickness direction of the positive electrode tab. The positive electrode tab is disposed on at least one side of the positive electrode current collector along a first direction. Wherein, the positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a lithium-containing material with an olivine structure. The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 , along a second direction, the distance between a first point of the positive electrode current collector and the positive electrode tab closest to the first point is less than or equal to 300 mm. The first point is any point of the positive electrode current collector. The first direction, the second direction and the thickness direction of the positive electrode tab are perpendicular to each other in pairs.

[0006] Thus, when the single-sided coating weight of the positive electrode film layer in the embodiment of this application is within the above range, the energy density of the battery cell is relatively high; in the case of the above high energy density, by controlling the distance between any point in the positive electrode current collector and the positive electrode tab closest to the point along the second direction to be less than or equal to 300 mm, the electron transmission path is shorter, each tab bears less current, the current distribution is more uniform, the lithium ions are more uniformly deintercalated or intercalated, and the risk of lithium plating can be reduced; thereby enabling the energy density and use reliability of the battery cell to be improved simultaneously.

[0007] In some embodiments, the positive electrode tab is provided as one or more, and all the positive electrode tabs are disposed on the same side of the positive electrode current collector along the first direction. The dimension of the positive electrode current collector along the first direction is 100 mm to 300 mm. Each positive electrode tab bears a relatively small current, the current distribution is more uniform, the lithium ion deintercalation or intercalation is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and the use reliability of the battery cell to be improved simultaneously.

[0008] In some embodiments, the positive electrode tabs are provided as multiple, and the multiple positive electrode tabs are disposed on both sides of the positive electrode current collector along the first direction. The dimension of the positive electrode current collector along the first direction is 100 mm to 600 mm. Each positive electrode tab bears a relatively small current, the current distribution is more uniform, the lithium ion deintercalation or intercalation is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and the use reliability of the battery cell to be improved simultaneously.

[0009] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 . When the single-sided coating weight of the positive electrode film layer is within the above range, the energy density of the battery cell can be improved while taking other factors into account.

[0010] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm. When the thickness of the positive electrode current collector is within the above range, the current-carrying capacity of the positive electrode current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0011] In some embodiments, the electrode assembly further includes a negative electrode plate, and the negative electrode plate includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode tab. The negative electrode film layer is disposed on at least one side of the negative electrode current collector in the thickness direction, and the negative electrode tab is disposed on at least one side of the negative electrode current collector along the first direction. Wherein, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material. Along the second direction, the distance between the second point of the negative electrode current collector and the negative electrode tab closest to the second point is less than or equal to 300 mm, and the second point is any point of the negative electrode current collector.

[0012] Thus, each negative electrode tab bears a relatively small current, the current distribution is more uniform, the lithium ion deintercalation or intercalation is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and the use reliability of the battery cell to be improved simultaneously.

[0013] In some embodiments, the negative electrode tab is provided as one or more, and all the negative electrode tabs are disposed on the same side of the negative current collector along the first direction. The size of the negative current collector along the first direction is 100 mm to 300 mm. Each negative electrode tab bears a relatively small current, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and service reliability of the battery cell to be improved simultaneously.

[0014] In some embodiments, the negative electrode tab is provided as a plurality, and the plurality of negative electrode tabs are disposed on both sides of the negative current collector along the first direction. The size of the negative current collector along the first direction is 100 mm to 600 mm. Each negative electrode tab bears a relatively small current, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and service reliability of the battery cell to be improved simultaneously.

[0015] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 . When the single-sided coating weight of the negative electrode film layer is within the above range, the energy density of the battery cell can be improved while taking other factors into account.

[0016] In some embodiments, the thickness of the negative current collector is 4 μm to 6 μm. When the thickness of the negative current collector is within the above range, the current-carrying capacity of the negative current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0017] In some embodiments, the electrode assembly is of a wound structure, and the positive electrode tab is provided as a plurality, and the plurality of positive electrode tabs are oppositely disposed along the thickness direction of the electrode assembly. The plurality of positive electrode tabs being oppositely disposed along the thickness direction of the electrode assembly is conducive to connecting the positive electrode tab and the positive electrode adapter.

[0018] In some embodiments, along the second direction, the distance between the first point of the positive current collector and the positive electrode tab closest to the first point is less than or equal to 200 mm. The distance between the tabs is relatively small. By adjusting the setting position of the positive electrode tab, the electron transmission path is shorter, the current borne between the tabs is relatively small, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and service reliability of the battery cell to be improved simultaneously.

[0019] In some embodiments, when the battery cell is in a 100% charged state, the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive current collector is 4.8 to 8.6. When the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive current collector is within the above range, the energy density of the battery cell can be improved.

[0020] In some embodiments, the single-sided coating weight of the positive electrode film layer is 280 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 . When the single-sided coating weight of the positive electrode film layer is within the above range, it is possible to balance and improve the energy density of the battery cell.

[0021] In some embodiments, when the battery cell is in a 100% charged state, the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector is 12.5 to 19.5. When the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector is within the above range, it is possible to improve the energy density of the battery cell.

[0022] In some embodiments, the single-sided coating weight of the negative electrode film layer is 125 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 . When the single-sided coating weight of the negative electrode film layer is within the above range, it is possible to balance and improve the energy density of the battery cell.

[0023] In some embodiments, the electrode assembly is of a stacked structure, and the positive electrode tab is disposed on at least one side of the positive electrode current collector.

[0024] In some embodiments, multiple positive electrode tabs are provided, and the multiple positive electrode tabs are disposed on both sides of the positive electrode current collector along the first direction, and the size of the positive electrode current collector along the first direction is 400 mm to 600 mm. The positive electrode tabs can share the current with each other, the current borne between the tabs is small, and the current distribution is more uniform.

[0025] In some embodiments, two positive electrode tabs are provided, and the two positive electrode tabs are respectively disposed on both sides of the positive electrode current collector along the first direction. The two positive electrode tabs can share the current with each other, the current borne between the tabs is small, and the current distribution is more uniform.

[0026] In some embodiments, multiple negative electrode tabs are provided, and the multiple negative electrode tabs are disposed on both sides of the negative electrode current collector along the first direction, and the size of the negative electrode current collector along the first direction is 400 mm to 600 mm. The negative electrode tabs can share the current with each other, the current borne between the tabs is small, and the current distribution is more uniform.

[0027] In some embodiments, when the battery cell is in a 100% charged state, the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector is 3.5 to 7.0. When the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector is within the above range, it is possible to improve the energy density of the battery cell.

[0028] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2From 360 mg / 1540.25 mm 2 When the single-sided coating weight of the positive electrode film layer is within the above range, it is possible to balance and improve the energy density of the battery cell.

[0029] In some embodiments, when the battery cell is in a 100% charged state, the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector is 10.5 to 17.5. When the single-sided coating weight of the negative electrode film layer is within the above range, it is possible to balance and improve the energy density of the battery cell.

[0030] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 To 164 mg / 1540.25 mm 2 When the single-sided coating weight of the negative electrode film layer is within the above range, it is possible to balance and improve the energy density of the battery cell.

[0031] In some embodiments, the lithium-containing phosphate with an olivine structure includes phosphate particles and a coating layer. The coating layer coats the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn. By surface coating the phosphate particles with the coating layer, the conductivity of the lithium-containing phosphate with an olivine structure can be improved, the powder resistivity of the material can be reduced, and it is beneficial to the migration rate of lithium ions and reduces the heat generation of the battery cell.

[0032] In some embodiments, the phosphate particles include a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z 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, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The phosphate particles have relatively excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0033] In some embodiments, the coating layer comprises a fast ion conductor with the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , where M2 comprises 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 surface of the phosphate particles with the fast ion conductor can significantly improve the transport rate of lithium ions during multiple deintercalation / insertion at the positive electrode, enhance the ionic conductivity of the positive electrode active material, thereby increasing the specific capacity, and further improving the energy density of the corresponding battery cell.

[0034] In some embodiments, the graphitization degree of the positive electrode active material is from 0.15 to 0.32, optionally from 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.

[0035] In some embodiments, the mass content of carbon element in the lithium-containing phosphate with olivine structure is from 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 5 m 2 / g to 18 m 2 / g, optionally 7.5 m 2 / g to 14 m 2 / g.

[0036] Thus, in the embodiments of the present application, the carbon element with the above mass content combined with the material with the above specific surface area is more conducive to the effective contact between the electrolyte and the lithium-containing phosphate with olivine structure, and is beneficial to the transport of lithium ions at the phase interface.

[0037] In some embodiments, the lithium-containing phosphate with olivine structure is granular, and its volume distribution particle size satisfies: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm. The particle size of the lithium-containing phosphate with olivine structure is relatively small, the deintercalation / insertion path of lithium ions in the positive electrode active material is short, the heat generation is less, and the particle size of the above positive electrode active material is not too small, and basically no agglomeration occurs during the processing and preparation, so that the performance of the positive electrode active material is stable.

[0038] In some embodiments, the lithium-containing phosphate with olivine structure is granular, and the lithium-containing phosphate with olivine structure comprises secondary particles, and the secondary particles comprise a plurality of primary particles, and the average particle size of the primary particles is from 200 nm to 500 nm. The average particle size of the primary particles is relatively small, the deintercalation / insertion path of lithium ions in the positive electrode active material is short, and the heat generation is less.

[0039] In some embodiments, the positive electrode tab 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 tab, reduce the heat generation of the positive electrode tab, and thus reduce the heat generation of the battery cell.

[0040] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. When the thickness of the positive electrode conductive layer is within the above range, it can further improve the conductivity of the positive electrode tab, reduce the heat generation of the positive electrode tab, and thus reduce the heat generation of the battery cell, and can also take into account the improvement of the energy density of the battery cell.

[0041] 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 tab 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 tab.

[0042] 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.

[0043] 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 fluorinated acrylate resins.

[0044] 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 conductivity of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode tab and the battery cell, and can also improve the fast charging performance of the battery cell.

[0045] 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 covers the surface of the artificial graphite. The carbon coating layer has more end faces and defects, so that the number of sites capable of intercalating and deintercalating lithium ions is more, and the conductivity of the carbon coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode tab and the heat generation of the battery cell.

[0046] In some embodiments, based on the mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%. When the mass content of the carbon coating layer is within the above range, it can further reduce the internal resistance of the negative electrode tab and the heat generation of the battery cell.

[0047] 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 disposed on the surface of the negative electrode current collector 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 facing away from the negative electrode current collector 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.

[0048] Thus, in the embodiments of the present application, there is a difference in the particle sizes of 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 relatively high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments 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 deposition on the surface layer of the negative electrode sheet.

[0049] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0050] In some embodiments, the tapped density of the carbon-based material in the first negative electrode film layer is less than or equal to the tapped density of the carbon-based material in the second negative electrode film layer. When the tapped density of the carbon-based material in the second negative electrode film layer is greater than the tapped density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, improving the energy density of the battery cell. The first negative electrode film layer is filled relatively sparsely with richer pores, which can improve the fast charging performance of the battery cell.

[0051] In some embodiments, the tapped density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 . When the tapped density of the carbon-based material in the first negative electrode film layer is within a suitable range, it can improve the fast charging performance of the battery cell.

[0052] In some embodiments, the tapped density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 . When the tapped density of the carbon-based material in the second negative electrode film layer is within a suitable range, it can improve the energy density of the battery cell. 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, it can improve the fast charging performance.

[0053] 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 transport can be reduced, and the fast charging performance of the battery cell can be improved.

[0054] In some embodiments, the first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0055] Thus, in the embodiments of the present application, the mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the number of free-moving lithium ions provided by the second lithium-containing binder for the second negative electrode film layer is relatively more, which can further improve the fast charging performance of the battery cell.

[0056] 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 insertion / extraction rate of lithium ions can be improved, and the fast charging performance of the battery cell can be improved.

[0057] In some embodiments, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. When the mass content of lithium element is within the above range, the number of free-moving lithium ions 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, improve the insertion / extraction rate of lithium ions, and improve the fast charging performance of the battery cell.

[0058] 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 element in the second lithium-containing binder is within the above range, the insertion / extraction rate of lithium ions is improved, and the fast charging performance of the battery cell is improved.

[0059] In some embodiments, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. When the mass content of lithium element is within the above range, the number of free-moving lithium ions 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, improve the insertion / extraction rate of lithium ions, and improve the fast charging performance of the battery cell.

[0060] In some embodiments, the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0061] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0062] In some embodiments, the second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0063] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0064] In some embodiments, the negative electrode active material further comprises a silicon-based material, and the mass content of silicon element in the silicon-based material is 0.3% to 10.0% based on the mass of the negative electrode active material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0065] In some embodiments, the negative electrode plate further comprises a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector.

[0066] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. The negative electrode conductive layer can further improve the conductivity of the negative electrode plate and reduce the heat generation of the negative electrode plate, thereby reducing the heat generation of the battery cell.

[0067] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector part and the negative electrode film layer, and improve the structural stability of the negative electrode sheet.

[0068] 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.

[0069] In some embodiments, the negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0070] In some embodiments, the separator includes a base film with a porous structure, and the porosity of the base film is 20% to 70%. When the porosity of the separator in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0071] In some embodiments, the separator includes a base film with a porous structure, and the porosity of the base film is 35% to 60%. When the porosity of the separator in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0072] 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, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0073] In some embodiments, the thickness of the base film is 6 μm to 9 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0074] In some embodiments, the separator includes a base film and a functional layer provided 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, and the first functional layer includes first inorganic particles. The second functional layer is located on the other side of the base film, and the second functional layer includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, and can improve the heat resistance of the separator.

[0075] In some embodiments, the non-fluoropolymer particles comprise an acrylate copolymer. The acrylate copolymer has excellent adhesion properties and a relatively high adhesion stability to the base film.

[0076] In some embodiments, the first inorganic particles comprise one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0077] In some embodiments, the second inorganic particles comprise one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above second inorganic particles can improve the heat resistance of the first functional layer.

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

[0079] In some embodiments, the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm. When the conductivity 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.

[0080] 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 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.

[0081] 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 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.

[0082] In some embodiments, the carboxylic acid ester solvent comprises a chain carboxylic acid ester solvent, and the mass content of the chain carboxylic acid ester solvent in the organic solvent is greater than or equal to 5% and less than or equal to 75%, optionally greater than or equal to 10% and less than or equal to 75%, optionally 30% to 70%, optionally 50% to 70%. 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.

[0083] In some embodiments, the chain carboxylic acid ester solvent comprises a compound represented by Formula I Formula I, In Formula I, R 1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0084] Thus, in the embodiments of the present application, the chain carboxylic ester solvent has a relatively high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0085] In some embodiments, R 1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0086] In some embodiments, in some embodiments, R 2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0087] In some embodiments, the chain carboxylic ester solvent includes one or more of the compounds shown in Formula I-1 to Formula I-8,

[0088] In some embodiments, 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 methyl ethyl carbonate. The above carbonate solvent and the chain carboxylic ester solvent are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0089] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate.

[0090] In some embodiments, the mass content of the carbonate solvent in the organic solvent is 30% to 70%, and can be selected from 30% to 50%. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0091] 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 additives can improve the interfacial 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.

[0092] In some embodiments, the carbonate additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0093] In some embodiments, the sulfur-containing additive includes one or more of vinylene sulfate DTD, bis(vinylene sulfate) 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methylene methylene disulfonate MMDS.

[0094] In some embodiments, the lithium salt additive includes lithium difluorophosphate LiPO 2 F 2 , lithium difluorooxalate borate LiDFOB, lithium tetrafluoroborate LiBF 4 , and one or more of lithium bis(oxalato)borate LiBOB.

[0095] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, and can be optionally 2% to 8%. The additive with the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, is beneficial to improving the fast charging performance of the battery cell, and improves the cycle performance.

[0096] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of fluorosulfonylimide salts and lithium hexafluorophosphate LiPF 6 . The above lithium salts are easy to dissociate, which is beneficial 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 cell.

[0097] In some embodiments, the fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0098] 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 is 0.5 mol / L to 1.0 mol / L.

[0099] In some embodiments, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.2 to 1.0.

[0100] In some embodiments, the base material of the housing includes steel, and the thickness of the housing is 0.1 mm to 0.5 mm, and can be optionally 0.2 mm to 0.35 mm. When the thickness of the housing is within the above range, the mechanical strength of the housing is relatively high, which can improve the use reliability and cycle performance of the battery cell, and the housing occupies less space and there is more internal space in the housing, which is beneficial to improving the energy density of the battery cell.

[0101] In some embodiments, the battery cell further includes a positive terminal, and the positive current collector tab is directly welded to the positive terminal. Direct welding can reduce the resistance at the connection, which is beneficial to reducing the overall internal resistance of the battery cell.

[0102] In some embodiments, the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 min to 10.5 min. The battery cell has a relatively fast charging speed, which is more conducive to improving the fast charging ability.

[0103] In a second aspect, the present application provides a battery device, which includes a plurality of battery cells according to any one of the embodiments in the first aspect of the present application.

[0104] In some embodiments, the charging time of the battery from 10% state of charge to 80% state of charge is 5 min to 10.5 min. The battery has a relatively fast charging speed, which is more conducive to improving the fast charging ability.

[0105] In a third aspect, the present application provides an electrical device, which includes the battery device according to any one of the embodiments in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the drawings.

[0107] Figure 1 It is a schematic structural diagram of a battery cell provided by some embodiments of the present application; Figure 2 It is an exploded schematic diagram of a battery cell provided by some embodiments of the present application; Figure 3 It is a schematic structural diagram of an electrode assembly in a battery cell provided by some embodiments of the present application; Figure 4 It is a schematic cross-sectional structure diagram of a first electrode plate in a battery cell provided by some embodiments of the present application; Figure 5 It is an unfolded schematic structure diagram of a first electrode plate in a battery cell provided by some embodiments of the present application; Figure 6 It is a schematic cross-sectional structure diagram of a second electrode plate in a battery cell provided by some embodiments of the present application; Figure 7 It is an unfolded schematic structure diagram of a second electrode plate in a battery cell provided by some embodiments of the present application; Figure 8Schematic diagram of the unfolded structure of the first electrode sheet in the battery cell provided by some other embodiments of the present application; Figure 9 Schematic diagram of the unfolded structure of the second electrode sheet in the battery cell provided by some other embodiments of the present application; Figure 10 Schematic diagram of the structure of the electrode assembly in the battery cell provided by some other embodiments of the present application; Figure 11 Schematic diagram of the structure of the first electrode sheet in the battery cell provided by some other embodiments of the present application; Figure 12 Schematic diagram of the structure of the first electrode sheet in the battery cell provided by some other embodiments of the present application; Figure 13 Schematic diagram of the structure of the second electrode sheet in the battery cell provided by some other embodiments of the present application; Figure 14 Schematic diagram of the structure of the second electrode sheet in the battery cell provided by some other embodiments of the present application; Figure 15 Schematic diagram of the structure of the battery module provided by some embodiments of the present application; Figure 16 Schematic diagram of the structure of the battery provided by some embodiments of the present application; Figure 17 Schematic diagram of the electrical device provided by some embodiments of the present application.

[0108] The drawings are not necessarily drawn to actual scale.

[0109] Explanation of reference numerals is as follows: Y, the first direction; Z, the second direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, box body; 5a, first box body part; 5b, second box body part; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, tab; 111, positive tab; 112, negative tab; 12, main body part; 13, positive electrode sheet; 131, positive current collector part; 132, positive electrode film layer; 14, negative electrode sheet; 141, negative current collector part; 142, negative electrode film layer; 15, separator; 20, outer shell; 21, housing; 22, end cap; 31, positive terminal; 32, negative terminal; 41, positive adapter; 42, negative adapter. Detailed implementation manners

[0110] Hereinafter, embodiments of the battery cell, battery device, and power consumption device of the present application will be specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there may be cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0111] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. 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 specific range. The range defined in this way can include or not include the end values and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. 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 ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0112] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0113] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0114] Unless otherwise specified, all steps of the present application can be carried out sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0115] The battery cell includes an electrode assembly, and the electrode assembly includes a positive electrode tab and a negative electrode tab. During the charging process, lithium ions are removed from the positive electrode tab and embedded in the negative electrode tab. The removed lithium ions may not be embedded in the negative electrode tab in time, resulting in lithium plating; especially when the distance between the tabs is too large, each tab bears a large current, leading to an increased risk of lithium plating.

[0116] In view of the above problems, the embodiments of the present application design the system of the battery cell. By improving the distance between the tabs, the current borne between the tabs is not too large, the risk of lithium plating of the battery cell is reduced, and the reliability of use of the battery cell is improved.

[0117] battery cell In a first aspect, an embodiment of the present application provides a battery cell.

[0118] The battery cell includes an electrode assembly, and the electrode assembly includes a first electrode tab. The first electrode tab includes a first film layer, a first current collector, and at least one first tab. The first film layer is disposed on at least one side of the first current collector along the thickness direction of the first electrode tab. The first tab is disposed on at least one side of the first current collector along a first direction. Wherein, along a second direction, the distance between any point in the first current collector and the first tab closest to the point is less than or equal to 300 mm, and the first direction, the second direction, and the thickness direction of the first electrode tab are perpendicular to each other in pairs.

[0119] Any point in the first current collector is defined as point P, and point P is randomly selected in the first current collector.

[0120] The first tab may be provided as one or more. When there are multiple first tabs, the first tab closest to point P along the second direction refers to the first tab with the smallest distance from point P along the second direction.

[0121] The first tab closest to point P is defined as the closest tab. The closest tab includes a first edge and a second edge that are opposite to each other along the second direction. The first edge is disposed close to point P, and the second edge is disposed away from point P.

[0122] In the second direction, the distance between point P and the first tab closest to point P refers to the distance between point P and the first edge in the second direction.

[0123] The projection of the tab closest to the current collector in the first direction overlaps with the projection of the first current collector in the first direction. In other words, the projection of the tab closest to the current collector in the first direction is located within the projection of the first current collector in the first direction, where the first direction is parallel to the normal of the projection plane.

[0124] Point P is any point in the first current collector. When the projection of point P in the first direction is located within the projection of the tab closest to the current collector in the first direction, it can be considered that the distance between point P and the tab closest to the current collector in the second direction is 0.

[0125] When the projection of point P in the first direction is located outside the projection of the tab closest to the current collector in the first direction, it can be considered that the distance between the first point and the tab closest to the current collector in the second direction is greater than 0, and this distance is the distance between point P and the first edge in the second direction.

[0126] In the embodiments of the present application, the first electrode tab can be a positive electrode tab or a negative electrode tab.

[0127] As Figures 1 to 5 shown, the battery cell 7 includes an electrode assembly 10, and the electrode assembly 10 includes a positive electrode tab 13, a negative electrode tab 14, and a separator 15. The electrode assembly 10 can be a wound structure or a stacked structure.

[0128] Regardless of whether the electrode assembly 10 is a wound structure or a stacked structure, in some embodiments, the positive electrode tab 13 includes a positive electrode film layer 132, a positive electrode current collector 131, and at least one positive electrode tab 111. The positive electrode film layer 132 is disposed on at least one side of the positive electrode current collector 131 in the thickness direction of the positive electrode tab 13. The positive electrode film layer 132 includes a positive electrode active material, and the positive electrode active material includes a lithium-containing material with an olivine structure. The single-sided coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 , the positive electrode tab 111 is connected to at least one side of the positive electrode current collector 131 in the first direction Y. For the portion of the positive electrode tab 111 where no active material layer is coated, in the second direction Z, the distance between the first point in the positive electrode current collector 131 and the positive electrode tab 111 closest to the first point is less than or equal to 300 mm. Figure 4 The M direction shown in Figure 5 is the thickness direction of the positive electrode tab 13. The Y direction shown in

[0129] is the first direction, and the Z direction is the second direction. The M direction, the Y direction, and the Z direction are perpendicular to each other in pairs. 2 Any point in the positive electrode current collector 131 can be a point with an area. For example, the area of the point is 0.01 mm 2, the area of the point is much smaller than that of the tab, and the size of the point basically does not interfere with the measurement of the spacing.

[0130] The positive tab 111 can be one or more. When there is one positive tab 111, the spacing between the first point (e.g., point A) in the positive current collector 131 and the closest positive tab 111 along the second direction Z refers to the spacing between point A in the positive current collector 131 and this positive tab 111 along the second direction Z.

[0131] When there are multiple positive tabs 111, the positive tab 111 closest to point A among the multiple positive tabs 111 refers to the positive tab 111 closest to point A along the second direction Z, and thus the spacing between this positive tab 111 and point A along the second direction Z is measured.

[0132] As Figure 5 shown, A 1 is any point in the positive current collector 131. A 1 is located at the edge of the positive current collector 131, and its spacing from the closest positive tab 111 along the second direction Z is a 1 , a 1 is less than or equal to 300 mm.

[0133] A 2 is any point in the positive current collector 131. A 2 is located at a position between the two edges of the positive current collector 131, and its spacing from the closest positive tab 111 along the second direction Z is a 2 , and its spacing from other positive tabs 111 is a 3 , a 4 etc. a 3 is greater than a 2 , a 4 is greater than a 2 , a 2 is less than or equal to 300 mm.

[0134] Electrons are introduced or led out to the positive electrode film layer 132 through the positive tab 111, and the coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2, the energy density of the battery cell 7 is relatively high, but at the same time, it may also increase the risk of lithium plating; while in the implementation mode of the present application, by regulating the distance between any point in the positive current collector part 131 and the positive electrode tab 111 closest to this point along the second direction Z to be less than or equal to 300 mm, the electron transmission path is shorter, the current borne by each electrode tab is smaller, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium plating can be reduced; moreover, since the current borne by each electrode tab is smaller, the heat generation of the system can be reduced, and the cycle performance of the battery cell 7 can be improved; further, the positive electrode active material includes a lithium-containing material with an olivine structure, and the lithium-containing material with an olivine structure has a stable structure and excellent cycle stability, which is beneficial to further improving the cycle performance of the battery cell 7.

[0135] In the implementation mode of the present application, the single-sided coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 , and can be optionally 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 . When the single-sided coating weight of the positive electrode film layer 132 is within the above range, the heat generation per unit area of the positive electrode plate 13 will not be too large, and the energy density of the battery cell 7 can be improved while taking it into account.

[0136] Such as Figure 6 and Figure 7 shown, in some implementation modes, the negative electrode plate 14 includes a negative electrode film layer 142, a negative current collector part 141 and at least one negative electrode tab 112. The negative electrode film layer 142 is arranged on at least one side of the negative current collector part 141 along the thickness direction of the negative electrode plate 14. The negative electrode film layer 142 includes a negative electrode active material, and the negative electrode active material includes a carbon-based material. The single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 . The negative electrode tab 112 is connected to at least one side of the negative current collector part 141 along the first direction Y. No negative electrode active material is provided on the negative electrode tab 112. Along the second direction Z, the distance between the second point in the negative current collector part 141 and the negative electrode tab 112 closest to the second point is less than or equal to 300 mm. The thickness direction of the negative electrode plate 14 is parallel to the thickness direction M of the positive electrode plate 13.

[0137] The negative electrode tab 112 can be one or more. The second point in the negative current collector part 141 is any point in the negative current collector part 141, such as point B.

[0138] When there is one negative electrode tab 112, the distance between point B and the negative electrode tab 112 closest to point B in the second direction Z refers to the distance between point B in the negative electrode current collector part 141 and this negative electrode tab 112 in the second direction Z.

[0139] When there are multiple negative electrode tabs 112, the negative electrode tab 112 closest to point B among the multiple negative electrode tabs 112 refers to the negative electrode tab among the multiple negative electrode tabs 112 that is closest to point B in the second direction Z. Thus, measure the distance between this negative electrode tab 112 and point B in the second direction Y.

[0140] As Figure 7 shown, B 1 is any point in the negative electrode current collector part 141. B 1 is located at the edge of the negative electrode current collector part 141, and the distance between it and the closest negative electrode tab 112 in the second direction Z is b 1 , b 1 is less than or equal to 300 mm.

[0141] B 2 is any point in the negative electrode current collector part 141. B 2 is located at a position between two edges of the negative electrode current collector part 141. The distance between it and the closest negative electrode tab 112 in the second direction Z is b 2 , and the distances from it to other negative electrode tabs 112 are b 3 , b 4 , etc. b 3 is greater than b 2 , b 4 is greater than b 2 , b 2 is less than or equal to 300 mm.

[0142] When the single-sided coating weight of the negative electrode film layer 142 is within the above range, the energy density of the battery cell 7 is relatively high. In the case of the above high energy density, electrons are introduced or led out through the negative electrode tab 112. By controlling the distance between any point in the negative electrode current collector part 141 and the negative electrode tab 112 closest to this point in the second direction Z to be less than or equal to 300 mm, the transmission path of electrons is shorter, the current borne between the tabs is smaller, the current distribution is more uniform, the lithium ions are more uniformly deintercalated or intercalated, and the risk of lithium plating can be reduced.

[0143] In the embodiment of the present application, the single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 . When the single-sided coating weight of the negative electrode film layer 142 is within the above range, the heat generation per unit area of the negative electrode plate 14 will not be too large, and the energy density of the battery cell 7 can be improved while taking it into account.

[0144] [Wound Electrode Assembly] Please continue to refer to Figures 1 to 7 , when the electrode assembly 10 has a wound structure, the positive electrode tab 13, the separator 15, and the negative electrode tab 14 are wound in the same direction. After winding, the positive electrode tab 13 includes a plurality of positive electrode ears 111, and the negative electrode tab 14 includes a plurality of negative electrode ears 112.

[0145] When at least two positive electrode ears 111 are provided, the at least two positive electrode ears 111 are oppositely arranged in the thickness direction of the electrode assembly 10. The closer to the winding starting end, the smaller the distance between two adjacent positive electrode ears 111, which is beneficial to connecting the positive electrode ears 111 and the positive electrode adapter 41. Figure 3 In [diagram], X represents the thickness direction of the electrode assembly 10.

[0146] Optionally, at least two positive electrode ears 111 are provided on the same side of the positive current collector 131 along the first direction Y.

[0147] As Figure 8 shown, optionally, at least two positive electrode ears 111 can also be provided on both sides of the positive current collector 131 along the first direction Y.

[0148] Along the second direction Z, the distance between any point in the positive current collector 131 and the positive electrode ear 111 closest to this point is less than or equal to 300 mm, and can be optionally less than or equal to 200 mm. Exemplarily, along the second direction Z, the distance between any point in the positive current collector 131 and the positive electrode ear 111 closest to this point is 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm or the range composed of any two of the above values.

[0149] Optionally, the single-sided coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 ; it can be optionally 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; it can be optionally 280 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm2 , 230 mg / 1540.25 mm 2 , 240 mg / 1540.25 mm 2 , 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 360 mg / 1540.25 mm 2 , 370 mg / 1540.25 mm 2 , 400 mg / 1540.25 mm 2 or a range composed of any two of the above values.

[0150] When the single-sided coating weight of the positive electrode film layer 132 is within the above range, the heat generation amount per unit area of the positive electrode plate 13 will not be too large, and the energy density of the battery cell 7 can be improved while taking it into account.

[0151] In some embodiments, along the first direction Y, the distance between the third point in the positive electrode current collector 131 and the positive electrode tab 111 closest to the third point is less than or equal to 300 mm, and the third point is any point of the positive electrode current collector 131, such as 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm or a range composed of any two of the above values.

[0152] When all the positive electrode tabs 111 are located on the same side of the positive electrode current collector 131, along the first direction Y, the distance between any point (such as point C) in the positive electrode current collector 131 and the positive electrode tab 111 closest to point C refers to the distance between point C in the positive electrode current collector 131 and the positive electrode tab 111 along the first direction Y. Figure 5 c shown in 1 represents the distance between point C and the positive electrode tab 111 along the first direction Y.

[0153] In some embodiments, when all the positive electrode tabs 111 are located on the same side of the positive electrode current collector 131, the dimension of the positive electrode current collector 131 along the first direction Y is less than or equal to 300 mm, and can be selected from 100 mm to 300 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm or the range composed of any two of the above values. Figure 5 In 1 the figure, R

[0154] When the positive electrode tabs 111 are located on both sides of the positive electrode current collector 131, along the first direction Y, the distance between any point in the positive electrode current collector 131, such as point C, and the positive electrode tab 111 closest to point C refers to the distance between the positive electrode tab 111 closest to point C along the first direction Y among the positive electrode tabs 111 on both sides and point C.

[0155] In some embodiments, when the positive electrode tabs 111 are located on both sides of the positive electrode current collector 131, the dimension of the positive electrode current collector 131 along the first direction Y is less than or equal to 600 mm, and can be selected from 100 mm to 600 mm, and can be selected from 400 mm to 600 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm or the range composed of any two of the above values.

[0156] As Figure 8 shown, C is any point in the positive electrode current collector 131, C is located at a position between the two edges of the positive electrode current collector 131, and the distance between it and the positive electrode tab 111 on the closest side along the first direction Y is c 1 , and the distance from the positive electrode tab 111 on the other side is c 2 , c 2 is greater than c 1 , c 1 is less than or equal to 300 mm.

[0157] In the embodiments of the present application, by regulating the distance between any point in the positive electrode current collector 131 and the positive electrode tab 111 closest to this point along the first direction Y to be less than or equal to 300 mm, the transmission path of electrons is shorter, the current borne by each tab is smaller, the current distribution is more uniform, the lithium ion deintercalation or intercalation is more uniform, and the risk of lithium deposition can be further reduced.

[0158] Optionally, when the battery cell 7 is at 100% state of charge, the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive current collector 131 is 4.8 to 8.6, such as 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6 or the range composed of any two of the above values.

[0159] When the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive current collector 131 is within the above range, the energy density of the battery cell 7 can be improved.

[0160] When at least two negative electrode tabs 112 are provided, the at least two negative electrode tabs 112 are oppositely arranged along the thickness direction of the electrode assembly 10, and the distance between adjacent two negative electrode tabs 112 is smaller closer to the winding start end, which is beneficial to connecting the negative electrode tab 112 and the negative adapter 42.

[0161] When at least two negative electrode tabs 112 are provided, the at least two negative electrode tabs 112 are oppositely arranged along the thickness direction of the electrode assembly 10, which is beneficial to connecting the negative electrode tab 112 and the negative adapter 42.

[0162] Optionally, the at least two negative electrode tabs 112 are provided on the same side of the negative current collector 141.

[0163] As Figure 9 shown, optionally, the at least two negative electrode tabs 112 can also be provided on both sides of the negative current collector 141.

[0164] Along the second direction Z, the distance between any point on the negative current collector 141 and the negative electrode tab 112 closest to this point along the second direction Z is less than or equal to 300 mm, and can be optionally less than or equal to 200 mm. Exemplarily, the distance between any point on the negative current collector 141 and the negative electrode tab 112 closest to this point along the second direction Z is 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm or the range composed of any two of the above values.

[0165] Optionally, the single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm 2To 170 mg / 1540.25 mm 2 , optionally 125 mg / 1540.25 mm 2 To 170 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm 2 , 96 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 112 mg / 1540.25 mm 2 , 114 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 116 mg / 1540.25 mm 2 , 118 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 142 mg / 1540.25 mm 2 , 145 mg / 1540.25 mm 2 , 148 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 152 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 165 mg / 1540.25 mm 2 , 167 mg / 1540.25 mm2 、 170 mg / 1540.25 mm 2 Or a range formed by any two of the above values.

[0166] When the single-sided coating weight of the negative electrode film layer 142 is within the above range, the heat generation amount per unit area of the negative electrode sheet 14 will not be too large, and the energy density of the battery cell 7 can be improved while taking it into account.

[0167] In some embodiments, along the first direction Y, the distance between the fourth point in the negative electrode current collector 141 and the negative electrode tab 112 closest to the fourth point is less than or equal to 300 mm. The fourth point is any point in the negative electrode current collector 141, such as 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm or a range formed by any two of the above values.

[0168] When the negative electrode tabs 112 are located on the same side of the negative electrode current collector 141, the distance along the first direction Y between any point (such as point D) in the negative electrode current collector 141 and the negative electrode tab 112 closest to point D refers to the distance along the first direction Y between point D in the negative electrode current collector 141 and the negative electrode tab 112. Figure 7 d shown in 1 is the distance along the first direction Y between point D and the negative electrode tab 112.

[0169] In some embodiments, when all the negative electrode tabs 112 are located on the same side of the negative electrode current collector 141, the size of the negative electrode current collector 141 along the first direction Y is less than or equal to 300 mm, and can be selected from 100 mm to 300 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm or a range formed by any two of the above values. Figure 7 R shown in 2 represents the size of the negative electrode current collector 141 along the first direction Y.

[0170] When the negative electrode tabs 112 are located on both sides of the negative electrode current collector 141, the distance along the first direction Y between any point (such as point D) in the negative electrode current collector 141 and the negative electrode tab 112 closest to point D refers to the distance between the negative electrode tab 112 closest to point D along the first direction Y among the negative electrode tabs 112 on both sides and point D.

[0171] In some embodiments, when all the negative electrode tabs 112 are located on both sides of the negative electrode current collector portion 141, the dimension of the negative electrode current collector portion 141 in the first direction Y is less than or equal to 600 mm, optionally 100 mm to 600 mm, optionally 400 mm to 600 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm or the range composed of any two of the above values.

[0172] As Figure 9 shown, D is any point in the negative electrode current collector portion 141. D is located at a position between the two edges of the negative electrode current collector portion 141, and the distance between D and the negative electrode tab 112 on the closest side in the first direction Y is d 1 , and the distance between D and the negative electrode tab 112 on the other side is d 2 , d 2 is greater than d 1 , d 1 is less than or equal to 300 mm.

[0173] In the embodiments of the present application, by regulating the distance between any point in the negative electrode current collector portion 141 and the negative electrode tab 112 closest to this point in the first direction Y to be less than or equal to 300 mm, the electron transmission path is shorter, each tab bears less current, the current distribution is more uniform, the lithium ion deintercalation or intercalation is more uniform, and the risk of lithium deposition can be further reduced.

[0174] Optionally, when the battery cell 7 is in a 100% charged state, the ratio of the thickness of the single-sided negative electrode film layer 142 to the thickness of the negative electrode current collector portion 141 is 12.5 to 19.5. For example, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5 or the range composed of any two of the above values.

[0175] When the ratio of the thickness of the single-sided negative electrode film layer 142 to the thickness of the negative electrode current collector portion 141 is within the above range, the energy density of the battery cell 7 can be improved.

[0176] [Stacked electrode assembly] As Figure 10 and Figure 11 shown, when the electrode assembly 10 is of a stacked structure, the positive electrode plate 13, the negative electrode plate 14 and the separator 15 form the electrode assembly 10 through a stacking process, and the positive electrode plate 13, the negative electrode plate 14 and the separator 15 are stacked. Figure 10In the figure, X represents the thickness direction of the electrode assembly 10. In the case of a stacked structure, the thickness direction of the electrode assembly 10 is parallel to the thickness directions of the positive electrode tab 13 and the negative electrode tab 14.

[0177] Along the second direction Z, the distance between any point in the positive current collector 131 and the positive tab 111 closest to that point is less than or equal to 300 mm, and can be optionally less than or equal to 200 mm. Exemplarily, along the second direction Z, the distance between any point in the positive current collector 131 and the positive tab 111 closest to that point is 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm, or a range composed of any two of the above values.

[0178] The positive tab 111 can be one or more. Along the second direction Z, the distance between any point in the positive current collector 131 and the positive tab 111 closest to that point can be the distance along the second direction Z between any point in the positive current collector 131, such as point E, and the positive tab 111 closest to point E.

[0179] Optionally, the single-sided coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 ; it can be optionally 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; it can be optionally 200 mg / 1540.25 mm 2 to 360 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 、210 mg / 1540.25 mm 2 、220 mg / 1540.25 mm 2 、230 mg / 1540.25 mm 2 、240 mg / 1540.25 mm 2 、250 mg / 1540.25 mm 2 、260 mg / 1540.25 mm 2 、270 mg / 1540.25 mm 2 、280 mg / 1540.25 mm 2 、290 mg / 1540.25 mm 2 、300 mg / 1540.25 mm 2, 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 360 mg / 1540.25 mm 2 , 370 mg / 1540.25 mm 2 , 400 mg / 1540.25 mm 2 or a range composed of any two of the above values.

[0180] When the single-sided coating weight of the positive electrode film layer 132 is within the above range, the heat generation amount per unit area of the positive electrode tab 13 will not be too large, and the energy density of the battery cell 7 can be improved while taking it into account.

[0181] The positive electrode tab 111 is provided as at least one, and optionally at least two. When the positive electrode tab 111 is provided as at least two, at least two positive electrode tabs 111 can be provided on both sides of the positive electrode current collector 131 along the first direction Y.

[0182] Optionally, when there are two positive electrode tabs 111, the two positive electrode tabs 111 are provided on both sides of the positive electrode current collector 131.

[0183] Optionally, along the first direction Y, the distance between the third point in the positive electrode current collector 131 and the positive electrode tab 111 closest to the third point is less than or equal to 300 mm, less than or equal to 200 mm, such as 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm or a range composed of any two of the above values.

[0184] As Figure 11 shown, when there is one positive electrode tab 111, F is any point in the positive electrode current collector 131, F is located at a position between the two edges of the positive electrode current collector 131, and the distance between F and the positive electrode tab 111 along the first direction Y is f 1 .

[0185] In some embodiments, when all the positive electrode tabs 111 are located on the same side of the positive electrode current collector 131, the dimension of the positive electrode current collector 131 in the first direction Y is less than or equal to 300 mm, and can be optionally 100 mm to 300 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm or the range composed of any two of the above values. For example, one positive electrode tab 111 is provided, and one positive electrode tab 111 is disposed on one side of the positive electrode current collector 131 in the first direction Y.

[0186] As Figure 12 shown, when there are multiple positive electrode tabs 111, two can be optionally selected. The two positive electrode tabs 111 are respectively disposed on both sides of the positive electrode current collector 131 in the first direction Y. F is any point in the positive electrode current collector 131, and F is located at a position between the two edges of the positive electrode current collector 131. The distance between it and the nearest positive electrode tab 111 in the first direction Y is f 1 , and the distance from the other positive electrode tab 111 is f 2 , f 2 is greater than f 1 , then f 1 is less than or equal to 300 mm.

[0187] In some embodiments, when there are two positive electrode tabs 111, the two positive electrode tabs 111 are disposed on both sides of the positive electrode current collector 131. The dimension of the positive electrode current collector 131 in the first direction Y is less than or equal to 600 mm, and can be optionally 100 mm to 600 mm, and can be optionally 400 mm to 600 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm or the range composed of any two of the above values.

[0188] Figure 12 In which S 1 represents the dimension of the positive electrode current collector 131 in the first direction Y.

[0189] When the positive electrode sheet 13 meets the above conditions, the electron transmission path is shorter, the current borne between the tabs is smaller, the current distribution is more uniform, the lithium ion deintercalation or intercalation is more uniform, and the risk of lithium deposition can be reduced.

[0190] Optionally, when the battery cell 7 is at 100% state of charge, the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive electrode current collector portion 131 is 3.5 to 7.0, such as 3.5, 3.6, 3.8, 4, 4.2, 4.5, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0 or the range composed of any two of the above values.

[0191] When the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive electrode current collector portion 131 is within the above range, the energy density of the battery cell 7 can be improved.

[0192] As Figure 13 shown, the negative electrode tab 112 is provided as at least one, and can be optionally at least two. When the negative electrode tab 112 is provided as at least two, the at least two negative electrode tabs 112 can be provided on both sides of the negative electrode current collector portion 141.

[0193] Along the second direction Z, the distance between any point in the negative electrode current collector portion 141 and the negative electrode tab 112 closest to this point along the second direction Z is less than or equal to 300 mm, and can be optionally less than or equal to 200 mm. Exemplarily, the distance between any point in the negative electrode current collector portion 141 and the negative electrode tab 112 closest to this point along the second direction Z is 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm or the range composed of any two of the above values.

[0194] The negative electrode tab 112 can be one or more, and the distance between any point in the negative electrode current collector portion 141 and the negative electrode tab 112 closest to this point along the second direction Z can be the distance between any point in the negative electrode current collector portion 141, such as point G, and the negative electrode tab 112 closest to point G along the second direction Z.

[0195] Optionally, the single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 and can be optionally 90 mg / 1540.25 mm 2 to 164 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm 2 、96 mg / 1540.25 mm 2, 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 112 mg / 1540.25 mm 2 , 114 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 116 mg / 1540.25 mm 2 , 118 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 142 mg / 1540.25 mm 2 , 145 mg / 1540.25 mm 2 , 148 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 152 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 164 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 Or a range composed of any two of the above values.

[0196] When the single-sided coating weight of the negative electrode film layer 142 is within the above range, the heat generation per unit area of the negative electrode plate 14 will not be excessive, and the energy density of the battery cell 7 can be improved while taking it into account.

[0197] Optionally, when the battery cell 7 is at 100% state of charge, the ratio of the thickness of the single-sided negative electrode film layer 142 to the thickness of the negative electrode current collector part 141 is 10.5 to 17.5. For example, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5 or the range composed of any two of the above values.

[0198] When the ratio of the thickness of the single-sided negative electrode film layer 142 to the thickness of the negative electrode current collector part 141 is within the above range, the energy density of the battery cell 7 can be improved.

[0199] Optionally, when there are two negative electrode tabs 112, the two negative electrode tabs 112 are arranged on both sides of the negative electrode current collector part 141.

[0200] In some embodiments, along the first direction Y, the distance between the fourth point in the negative electrode current collector part 141 and the negative electrode tab 112 closest to the fourth point is less than or equal to 300 mm. For example, 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm or the range composed of any two of the above values.

[0201] As Figure 13 shown, when there is one negative electrode tab 112, H is any point in the negative electrode current collector part 141, H is located at a position between the two edges of the negative electrode current collector part 141, and the distance between it and the negative electrode tab 112 along the first direction H is h 1 , h 1 is less than or equal to 300 mm.

[0202] In some embodiments, when all the negative electrode tabs 112 are located on the same side of the negative electrode current collector part 141, the dimension of the negative electrode current collector part 141 along the first direction Y is less than or equal to 300 mm, and can be optionally 100 mm to 300 mm. For example, 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm or the range composed of any two of the above values.

[0203] As Figure 14 shown, when there are multiple negative electrode tabs 112, optionally two, the two negative electrode tabs 112 are respectively arranged on both sides of the negative electrode current collector part 141 along the first direction Y, H is any point in the negative electrode current collector part 141, H is located at a position between the two edges of the negative electrode current collector part 141, and the distance between it and the negative electrode tab 112 on the closest side along the first direction H is h 1, the distance from the other negative electrode tab 112 is h 2 , h 2 greater than h 1 , then h 1 is less than or equal to 300 mm.

[0204] In some embodiments, when all the negative electrode tabs 112 are located on both sides of the negative electrode current collector portion 141, the dimension of the negative electrode current collector portion 141 along the first direction Y is less than or equal to 600 mm, and can be selected from 100 mm to 600 mm, and can be selected from 400 mm to 600 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm or the range composed of any two of the above values.

[0205] As Figure 14 shown, the dimension of the negative electrode current collector portion 141 along the first direction Y is S 2 .

[0206] In the embodiments of the present application, by controlling the distance between any point in the negative electrode current collector portion 141 and the negative electrode tab 112 closest to this point along the first direction Y to be less than or equal to 300 mm, the electron transmission path is shorter, the current borne by each tab is smaller, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium deposition can be further reduced.

[0207] Regardless of whether the electrode assembly 10 is a wound structure or a stacked structure, in some embodiments, the dimension of the end face of the positive electrode tab 111 connected to the positive electrode current collector portion 131 along the second direction Z is 20 mm to 100 mm. For example, the dimension of the end face of the positive electrode tab 111 connected to the positive electrode current collector portion 131 along the second direction Z is 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm or the range composed of any two of the above values. Figure 11 where L 1 represents the dimension of the end face of the positive electrode tab 111 connected to the positive electrode current collector portion 131 along the second direction Z. When the positive electrode tab 111 satisfies the above range, the current-carrying area is larger and the current-carrying capacity is stronger, and the risk of lithium deposition can be further reduced.

[0208] Regardless of whether the electrode assembly 10 is a wound structure or a stacked structure, in some embodiments, the dimension of the negative electrode tab 112 connected to the end face of the negative current collector 141 along the second direction Z is 20 mm to 100 mm. For example, the length of the connection region between the negative electrode tab 112 and the negative current collector 141 is 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, or a range composed of any two of the above values. Figure 13 In Figure 13 , L2 represents the dimension of the end face of the negative electrode tab 112 connected to the negative current collector 141 along the second direction Z. When the negative electrode tab 112 satisfies the above range, the current-carrying area is relatively large, the current-carrying capacity is relatively strong, and the risk of lithium plating can be further reduced.

[0209] [Positive electrode tab] The positive electrode tab includes a positive current collector and a positive electrode film layer provided on at least one surface of the positive current collector and including a positive electrode active material. For example, the positive current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive current collector.

[0210] The upper charge limit voltage and the lower discharge cut-off voltage of the battery cell vary depending on the positive electrode active material. For example, when the phosphate material includes lithium iron phosphate, the upper charge limit voltage can be 3.65 V and the lower discharge cut-off voltage can be 2.0 V. Also, when the phosphate material includes lithium manganese iron phosphate, the upper charge limit voltage can be 4.3 V and the lower discharge cut-off voltage can be 2.0 V. Next, taking the upper charge limit voltage of 3.65 V and the lower discharge cut-off voltage of 2.0 V as an example, the state of the battery cell is described as follows: In the embodiments of the present application, the 100% state of charge (SOC) and the 0% state of charge (SOC) of the battery cell are defined as follows. The battery cell is charged at a constant current charging rate of 0.33C to the upper charge limit 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.

[0211] In some embodiments, when the battery cell is in the 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 , and can be optionally 2.55 g / cm 3 to 2.70 g / cm 3 . Exemplarily, when the battery cell is in the 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3, 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 or a range composed of any two of the above values.

[0212] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the positive electrode active materials in the positive electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation during rapid 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 charging rate performance.

[0213] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) can be detected by the following method. Disassemble the positive electrode sheet from the battery cell at 100% SOC and measure the compaction density of the positive electrode film layer. For example, take 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), punch it into small round pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive electrode film layer of the above weighed positive electrode sheet, weigh the weight of the positive electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode sheet - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode sheet - the thickness H0 of the positive electrode current collector, 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.

[0214] In some embodiments, the powder resistivity of the positive electrode active material is from 1 Ω•cm to 27.5 Ω•cm, optionally less than or equal to 20 Ω•cm, and optionally less than or equal to 11 Ω•cm. Exemplarily, the powder resistivity of the positive electrode active material can be 27.5 Ω•cm, 20 Ω•cm, 19 Ω•cm, 18 Ω•cm, 17 Ω•cm, 16 Ω•cm, 15 Ω•cm, 14 Ω•cm, 13 Ω•cm, 12 Ω•cm, 11 Ω•cm, 10 Ω•cm, 9 Ω•cm, 8 Ω•cm, 7 Ω•cm, 6 Ω•cm, 5 Ω•cm, 4 Ω•cm, 3 Ω•cm, 2 Ω•cm, 1 Ω•cm or the range composed of any two of the above values.

[0215] The relatively low powder resistivity of the positive electrode active material results in a relatively low resistance of the positive electrode sheet and less heat generation of the battery cell.

[0216] In the embodiments of the present application, the powder resistivity of the material has the meaning well-known in the art and can be detected by the methods and equipment well-known in the art. For example, according to the test standard GB / T30835-2014, a PRCD1100 powder resistivity meter is used for testing.

[0217] In some embodiments, the powder compaction density of the positive electrode active material under 30000 N is 2.46 g / cm 3 to 2.8 g / cm 3 . Exemplarily, the powder compaction density of the positive electrode active material under 30000 N is 2.46 g / cm 3 , 2.47 g / cm 3 , 2.48 g / cm 3 , 2.49 g / cm 3 , 2.5 g / cm 3 , 2.51 g / cm 3 , 2.55 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 or the range composed of any two of the above values.

[0218] When the powder compaction density of the positive electrode active material under 30,000 N 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 closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0219] In the embodiments of the present application, the powder compaction density of the material has a well-known meaning in the art, and can be detected by methods and equipment well-known in the art. Detection is carried out 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 a mold with a bottom area of 1.327 cm 2 in the UTM7305 type electronic pressure testing machine, pressurize to 3000 kg (equivalent to 30,000 N), keep the pressure for 30 s, then release the pressure, keep it for 10 s, and then record and calculate the powder compaction density of the positive electrode active material under the action of 30,000 N.

[0220] In some embodiments, the charging specific capacity of the positive electrode active material at a 0.1C rate is 150 mAh / g to 170 mAh / g, and can be optionally 157 mAh / g to 170 mAh / g. Exemplarily, the charging specific 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 the range composed of any two of the above values.

[0221] When the charging specific 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.

[0222] In the embodiments of the present application, the specific capacity of the active material has a well-known meaning in the art, and can be tested by equipment and methods well-known in the art. The test method of the initial coulomb efficiency and the initial discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be adopted. Using metallic lithium as the negative electrode and the sample electrode sheet containing the above materials as the positive electrode, a half-button battery is assembled. Under the condition of 23°C ± 2°C, the half-button battery is placed on a battery tester or other test equipment with the same performance, and the charge-discharge capacity is obtained through charging and discharging at a 0.1C rate, and then the capacity is divided by the mass of the active material of the electrode sheet to obtain the charging specific capacity parameter.

[0223] In some embodiments, the mass ratio of the lithium-containing phosphate with an olivine structure in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%. It can be considered that the positive electrode active material of the present application is a lithium-containing phosphate system with an olivine structure. When the mass ratio of the lithium-containing phosphate with an olivine structure is less than 100%, the positive electrode active material can further include common positive electrode active materials, such as at least one of lithium-containing transition metal oxides, for example, but not limited to. Examples of the lithium-containing transition metal oxides can include but 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.

[0224] Optionally, the mass ratio of the lithium-containing phosphate with an olivine structure in the positive electrode active material is 100%.

[0225] In the embodiments of the present application, the lithium-containing phosphate with an olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium-containing phosphate with an olivine structure includes phosphate particles and a coating layer. The coating layer coats the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

[0226] By surface coating the coating layer on the phosphate particles, the conductivity of the lithium-containing phosphate with an olivine structure can be improved, the powder resistivity of the material can be reduced, and it is beneficial to the migration rate of lithium ions, improving the fast charging ability of the battery and reducing the heat generation of the battery cell.

[0227] In some embodiments, the phosphate particles include a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z 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 cyclic stability of the phosphate particles is relatively excellent, which is beneficial to improving the cyclic performance of the battery cell.

[0228] Exemplarily, the phosphate particles include LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 or one or more of them. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. Regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., 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 applied to the battery system, after charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will fluctuate, and the above situations are all within the protection scope of the present application.

[0229] In some embodiments, the coating layer includes a fast ion conductor with the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0 ≤ d ≤ 1, 0 < x 2 <5, 0 < y 2 <4.

[0230] Exemplarily, the fast ion conductor is a material having a NASICON structure, such as including lithium iron titanium phosphate Li 2 FeTi(PO 4 ) 3 , lithium iron zirconium phosphate Li 2 FeZr(PO 4 ) 3 , lithium iron tin phosphate Li 2 FeSn(PO 4 ) 3 or one or more of them.

[0231] The fast ion conductor having a NASICON structure is a material with ultrafast ion conduction ability, having rich three-dimensional lithium ion diffusion and transport channels, and having advantages such as high ion conduction efficiency and strong structural stability during multiple de-lithiation and lithiation processes. Coating the surface of phosphate particles with a fast ion conductor containing a NASICON structure can significantly improve the transport rate of lithium ions during multiple de-lithiation / embedding in the positive electrode, improve the ion conductivity of the positive electrode active material, improve the fast charging ability of the battery cell, and in addition, can also improve the specific capacity and the energy density of the corresponding battery cell.

[0232] In some embodiments, the coating layer further includes elemental carbon.

[0233] The elemental carbon and the fast ion conductor can be arranged in layers. For example, the elemental carbon serves as an independent carbon coating layer, and the fast ion conductor serves as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Or, 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 elemental carbon and the fast ion conductor can also be arranged in the same layer.

[0234] Optionally, the carbon coating layer can be formed by carbonizing an organic carbon source (such as glucose, polyethylene glycol, etc.) on the surface of the fast ion conductor layer. The carbon coating layer can partially coat the fast ion conductor layer or can completely coat the fast ion conductor layer. The setting of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, make up for the defect of poor electronic conduction performance of the phosphate particles, and improve the energy density of the battery cell. Specifically, the setting of the carbon coating layer endows the positive electrode active material of the present application with the following advantages: The carbon coating layer in the positive electrode active material of the present application provides a suitable channel for the transport of electrons, can significantly improve the conduction rate of electrons during multiple de-lithiation and lithiation processes, improve the electronic conductivity of the lithium-containing phosphate, improve the charging ability of the corresponding battery cell, and can also improve the energy density.

[0235] The carbon coating layer of the positive electrode active material of this application has a loose and porous structure, which enables the electrolyte to come into full and effective contact with the lithium-containing phosphate, thereby improving the lithium ion transport rate at the phase interface and enhancing the charging capacity of the battery cell.

[0236] Coating a layer of carbon coating on the surface of the lithium-containing phosphate can not only improve the conductivity of the lithium-containing phosphate, but also enhance the structural stability of the positive electrode active material, effectively alleviating the iron dissolution phenomenon of the positive electrode active material during the 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 this application uses lithium-containing phosphate as the base material, giving full play to the advantages of low cost, high reliability in use, and good cycle stability of the lithium-containing phosphate. At the same time, the coating layer (fast ion conductor layer and carbon coating layer) is used to solve the disadvantages of poor electronic conductivity and ion conductivity. The battery cell prepared from the positive electrode active material of this application can improve the energy density of the battery cell on the premise of excellent cycle performance. In the embodiments of this application, the content of elements in the positive electrode active material has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After the battery cell is discharged to 0% state of charge (SOC) and the positive electrode plate is disassembled, it is washed with DMC and dried, then impurities are removed by high-temperature calcination. Weigh 0.4 g of the positive electrode active material, add 10 ml (50% concentration) of aqua regia to it. Then place it on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is made up to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0237] In some embodiments, the graphitization degree of the positive electrode active material is from 0.15 to 0.32, and can be optionally from 0.19 to 0.26. Exemplarily, the graphitization degree of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32 or a range composed of any two of the above values.

[0238] 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 plate, and thus reduce the heat generation of the battery cell.

[0239] In the embodiments of the present application, the higher the graphitization degree of the material, the lower the degree of disorder, and the test can be carried out according to the general rules of X-ray diffraction analysis method in JIS / K 0131-1996 test standard.

[0240] In some embodiments, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g to 18m 2 / g.

[0241] Optionally, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 7.5m 2 / g to 14m 2 / g.

[0242] Exemplarily, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or the range composed of any two of the above values.

[0243] Exemplarily, the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14m 2 / g, 15m 2 / g, 16m 2 / g, 17m 2 / g, 18m 2 / g or the range composed of any two of the above values.

[0244] 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, the conductivity of the lithium-containing phosphate with olivine structure can be significantly improved, which is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the rapid charging ability and energy density of the battery monomer.

[0245] In the embodiments of the present application, the specific surface area of the material has the meaning well-known in the art, and can be detected by devices and methods well-known in the art. For example, it can be detected according to the test standard GB / T 19587-2017. Taking the positive electrode active material as a sample, the specific surface area is tested by a Tri-Star 3020 specific surface area and pore size analyzer of Micromeritics Company in the United States.

[0246] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm.

[0247] Exemplarily, Dv50 of the positive electrode active material can be 1 µm, 1.1 µm, 1.15 µm, 1.2 µm, 1.25 µm, 1.3 µm, 1.35 µm, 1.4 µm, 1.45 µm, 1.5 µm, 1.55 µm, 1.6 µm, 1.65 µm, 1.7 µm, 1.75 µm, 1.8 µm, 1.85 µm, 1.9 µm, 1.95 µm, 2 µm or a range composed of any two of the above values.

[0248] Exemplarily, Dv10 of the positive electrode active material can be 0.4 µm, 0.45 µm, 0.5 µm, 0.55 µm, 0.6 µm, 0.65 µm, 0.7 µm or a range composed of any two of the above values.

[0249] The particle size of the positive electrode active material is relatively small, the lithium deintercalation and intercalation paths of lithium ions in the positive electrode active material are short, and the heat generation is less. Moreover, the particle size of the above positive electrode active material is not too small, and basically no agglomeration occurs during the processing and preparation process, making the performance of the positive electrode active material stable.

[0250] In the embodiments of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% in the volume distribution. It can be detected by devices and methods well-known in the art. For example, taking the positive electrode active material as a sample, according to the test standard GB / T 19077-2016, the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer.

[0251] When the positive electrode active material includes other materials in addition to the lithium phosphate with an olivine structure, the volume distribution particle size of the positive electrode active material refers to the volume distribution particle size of all positive electrode active materials.

[0252] In some embodiments, the lithium-containing phosphate in the olivine structure is granular. The lithium-containing phosphate in the olivine structure includes secondary particles, and the secondary particles include a plurality of primary particles. 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 composed of any two of the above values.

[0253] The average particle size of the primary particles is relatively small, the lithium deintercalation / insertion path of lithium ions in the cathode active material is short, and the heat generation is less.

[0254] In the embodiments of the present application, the secondary particles refer to aggregated particles formed by the aggregation of two or more primary particles. The primary particles and the secondary particles can be easily distinguished by experimental means (such as taking SEM images using a scanning electron microscope), and the average particle size of the primary particles can be obtained by testing in the SEM images of the scanning electron microscope. The SEM test parameters can be set as follows: the working voltage (EHT) is 10.00 kV, the InLens detector is used, the working distance is 4.6 mm, and the magnification is 1000X.

[0255] In some embodiments, the cathode film layer further includes one or more of a ternary material, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, lithium citrate, lithium nickelate, and lithium ferrate. The above materials can be used as a lithium supplement agent, which can supplement lithium ions to the cathode film layer, make up for the irreversible lithium ion loss in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0256] 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.

[0257] 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 or at least one of them.

[0258] 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 the range composed 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 to the positive electrode film layer, make up for the irreversible lithium ion loss in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0259] The lithium supplement can be in the same layer as the positive electrode active material or in different layers. When the lithium supplement and the positive electrode active material are in different layers, the lithium supplement can be in the lithium supplement layer, and the positive electrode active material can be in the positive electrode active material layer. In other words, the positive electrode film layer includes a lithium supplement layer and a positive electrode active material layer. The positive electrode active material layer can be disposed on at least one side of the positive electrode current collector, and the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer can be located between the lithium supplement layer and the positive electrode current collector. Optionally, the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. During the cyclic charge and discharge process of the battery cell, the lithium supplement in the lithium supplement layer can be gradually released into the system to make up for the lithium loss of the battery system.

[0260] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. There is no particular limitation on the type of the positive electrode conductive agent in the embodiments of the present application. 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%.

[0261] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. There is no particular limitation on the type of the positive electrode binder in the embodiments of the present application. 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 fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0262] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0263] In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05 to 0.3. Exemplarily, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, or a range composed of any two of the above values.

[0264] When the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is within the above range, the rapid charging ability and energy density of the battery cell can be improved.

[0265] In some embodiments, the thickness of the positive current collector is 10 μm to 15 μm, optionally 12 μm to 15 μm. Exemplarily, the thickness of the positive current collector is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm or a range composed of any two of the above values.

[0266] When the thickness of the positive current collector is within the above range, the current-carrying capacity of the positive current collector is relatively excellent, and it can enable the battery cell to have a relatively high energy density.

[0267] In the embodiments of the present application, the thicknesses of the positive electrode film layer and the positive current collector have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, the thickness of the positive electrode plate is measured with a micrometer, the film layer on the surface of the positive current collector is removed, and the thickness of the positive current collector is measured with a micrometer. When the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode plate minus the thickness of the positive current collector. When the positive electrode film layer is coated on both sides, the thickness of the positive electrode film layer is (the thickness of the positive electrode plate minus the thickness of the positive current collector) / 2.

[0268] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive current collector and then drying and cold-pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0269] The positive electrode plate does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode plate of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive current collector and the positive electrode film layer and disposed on the surface of the positive current collector. In some other embodiments, the positive electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0270] In some embodiments, the positive electrode plate further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the positive electrode film layer and the positive current collector. The positive electrode conductive layer can further improve the conductive performance of the positive electrode plate and reduce the heat generation of the positive electrode plate, thereby reducing the heat generation of the battery cell.

[0271] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. Exemplarily, the thickness of the positive electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or a range composed of any two of the above values.

[0272] 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 while taking into account.

[0273] In the embodiments of the present application, the thickness of the positive electrode conductive layer has the meaning well known in the art and can be detected by using the equipment and methods well known in the art. For example, tomographic scanning is performed on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0274] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0275] 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 composed of any two of the above values.

[0276] 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 sheet and reducing the heat generation amount of the battery cell.

[0277] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. Exemplarily, 50%, 60%, 65%, 70% or a range composed of any two of the above values.

[0278] 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 fluorinated acrylate resins. The positive electrode binder in the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector portion and the positive electrode film layer and improve the structural stability of the positive electrode sheet.

[0279] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector portion and a negative electrode film layer provided on at least one surface of the negative electrode current collector portion and including a negative electrode active material. For example, the negative electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector portion.

[0280] In some embodiments, when the battery cell is in a 100% charged state, the compaction density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 , and can be optionally 1.25 g / cm3 to 1.36 g / cm 3 。Exemplarily, the tap density of the negative electrode film layer of the battery cell at 100% state of charge is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 , 1.28 g / cm 3 , 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.36 g / cm 3 or a range composed of any two of the above values.

[0281] When the tap density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative electrode active material in the negative electrode film layer is stacked relatively tightly and the contact resistance between particles is relatively small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0282] In the embodiments of the present application, the tap density of the negative electrode film layer of the battery cell at 100% state of charge has the meaning well known in the art and can be detected by using the equipment and methods well known in the art. The detection method is the same as the tap density test method of the positive electrode film layer described above.

[0283] In some embodiments, the powder resistivity of the negative electrode active material is from 0.005 Ω·cm to 0.043 Ω·cm, and can be 0.04 Ω·cm. Exemplarily, the powder resistivity of the negative electrode active material can be 0.043 Ω·cm, 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm or a range composed of any two of the above values.

[0284] The relatively low powder resistivity of the negative electrode active material makes the resistance of the negative electrode sheet relatively low and the heat generation of the battery cell less.

[0285] In the embodiments of the present application, the powder resistivity of the negative electrode active material has the meaning well known in the art and can be detected by using the equipment and methods well known in the art. The detection method is the same as the powder resistivity test method of the positive electrode active material described above.

[0286] In some embodiments, the tap density of the powder of the negative electrode active material under a pressure of 20000 N is 1.5 g / cm 3 to 1.85 g / cm 3, optionally 1.55 g / cm 3 to 1.65 g / cm 3 . Exemplarily, the powder compaction density of the negative electrode active material under a pressure of 20000 N is 1.5 g / cm 3 , 1.55 g / cm 3 , 1.6 g / cm 3 , 1.65 g / cm 3 , 1.7 g / cm 3 , 1.75 g / cm 3 , 1.8 g / cm 3 , 1.85 g / cm 3 or a range composed of any two of the above values.

[0287] When the powder compaction density of the negative electrode active material under 20000 N is within the above range, the energy density of the battery cell can be improved, and since the negative electrode active material in the negative electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0288] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art, and can be detected by methods and equipment well-known in the art, and detected according to 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 a mold with a bottom area of 1.327 cm 2 in a UTM7305 type electronic pressure testing machine, pressurized to 2000 kg (equivalent to 20000 N), kept under pressure for 30 s, then depressurized, kept for 10 s, and then the powder compaction density of the negative electrode active material under a force of 20000 N is recorded and calculated.

[0289] In some embodiments, the charging specific capacity of the negative electrode active material at a 0.1C rate is 350 mAh / g to 480 mAh / g. Exemplarily, the charging specific capacity of the negative electrode active material at a 0.1C rate is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g or a range composed of any two of the above values.

[0290] When the charging specific 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.

[0291] In the embodiments of the present application, the charging specific capacity of the negative electrode active material at a rate of 0.1C is a meaning well-known in the art, and can be detected by devices and methods well-known in the art. The detection method is the same as the charging specific capacity test method of the positive electrode active material at a rate of 0.1C described above.

[0292] In some embodiments, the negative electrode active material includes a carbon-based material. The carbon-based material has high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass percentage 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%.

[0293] 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. When the two are used in combination, the battery cell has excellent cycle performance.

[0294] 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 composed of any two of the above values.

[0295] When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet and the battery cell, and can improve the fast charging performance of the battery cell.

[0296] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer. The artificial graphite includes secondary particles, and the secondary particles include a plurality of primary particles. The carbon coating layer covers the surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon. Amorphous carbon refers to a transition carbon material with a very low degree of graphitization crystallization and an approximate amorphous form (or no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0297] The artificial graphite includes secondary particles. There are more migration paths for lithium ions in the artificial graphite, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions. The carbon coating layer has more end faces and defects, resulting in a larger number of sites where lithium ions can be intercalated and deintercalated, making the electrical conductivity of the carbon coating layer excellent and capable of reducing the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0298] 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 composed of any two of the above values.

[0299] When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode sheet can be further reduced, and the heat generation of the battery cell can be reduced.

[0300] In the embodiments of the present application, the graphite particles can be prepared by methods well-known in the art. For example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and after carbonization treatment, forming a carbon coating layer on at least part of the surface of the artificial graphite particles.

[0301] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of the coal tar pitch and the petroleum pitch is below 250°C.

[0302] Optionally, the carbonization treatment temperature is 700°C to 1800°C. Optionally, the carbonization treatment temperature is 1000°C to 1300°C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized, and a coating layer containing amorphous carbon can be formed on at least part of the surface of the artificial graphite.

[0303] Optionally, the carbonization treatment time is 1h to 6h.

[0304] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include graphite particles, or the carbon-based material may include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0305] 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.

[0306] Optionally, based on the mass of the negative electrode active material, the mass content of silicon element in the silicon-based material is 0.3% to 10.0%, and may be optionally 1% to 6%. Exemplarily, the mass content of silicon element in the silicon-based material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10% or any range composed of any two of the above values.

[0307] When the mass content of silicon element in the silicon-based material is within the above range, the capacity of the negative electrode active material can be increased, and the energy density of the battery cell can be improved.

[0308] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0309] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0310] In this application, the qualitative and quantitative determination of each substance or element can be detected by suitable equipment and methods known to those skilled in the art. 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.

[0311] For example, this application can perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material in combination with the general rules of X-ray diffraction analysis method JIS / K0131-1996.

[0312] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). There are voids between flake structures in the SEM cross-sectional view of natural graphite, while the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or they can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, while only 2H phase exists in the XRD spectrum of artificial graphite.

[0313] In the embodiments of this application, the negative electrode film layer includes at least one layer of film layer, which can be a single-layer film layer or at least two-layer film layers. Optionally, the negative electrode film layer includes at least two-layer film layers.

[0314] When 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 further includes a silicon-based material. When adopting a single-layer film layer, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm to 13.5 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm or the range composed of any two of the above values.

[0315] When 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. 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.

[0316] 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 disposed on the surface of the negative electrode current collector. The carbon-based material in the first negative electrode film layer includes graphite particles. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector. The carbon-based material in the second negative electrode film layer includes graphite particles. The graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer can be the same or different.

[0317] The interface between the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0318] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0319] The negative electrode film layer includes at least two film layers, and layer-by-layer coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences between the first negative electrode film layer and the second negative electrode film layer, the pore differences of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission can be reduced, and the fast charging performance of the battery cell can be improved.

[0320] 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 improving the compaction density of the negative electrode film layer. When the negative electrode active material includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0321] The difference in particle sizes between the first negative electrode film layer and the second negative electrode film layer can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode film layer is usually relatively high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can also improve the problem of lithium deposition on the surface layer of the negative electrode plate.

[0322] Optionally, the negative electrode active material in the first negative electrode film layer is granular, and its volume average particle size Dv50 is from 9.5 μm to 18.5 μm, optionally from 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 composed 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 from 9.5 μm to 18.5 μm, optionally from 9.5 μm to 14.6 μm.

[0323] 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, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0324] Optionally, the negative electrode active material in the second negative electrode film layer is granular, and its volume average particle size Dv50 is from 7.8 μm to 14.3 μm, optionally from 7.8 μm to 11.3 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm or a range composed 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 from 7.8 μm to 14.3 μm, optionally from 7.8 μm to 11.3 μm.

[0325] 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, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the other hand, the negative electrode active material in the second negative electrode film layer with the above volume average particle size range and the negative electrode active material in the first negative electrode film layer cooperate to facilitate the construction of the 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.

[0326] In the embodiments of the present application, the volume average particle size Dv50 of the negative electrode active material has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. The detection method is the same as the volume average particle size Dv50 test method of the positive electrode active material described above.

[0327] Optionally, the tapped density of the carbon-based material in the first negative electrode film layer is less than or equal to the tapped density of the carbon-based material in the second negative electrode film layer. The tapped density can reflect the packing density of the active material in the film layer. When the tapped density of the carbon-based material in the second negative electrode film layer is greater than that in the first negative electrode film layer, the second negative electrode film layer is more densely packed, improving the energy density of the battery cell. The first negative electrode film layer is relatively sparsely packed with richer pores, which can enhance the fast charging performance of the battery cell. When the negative electrode active material includes graphite particles, the tapped density of the graphite particles in the first negative electrode film layer is less than or equal to the tapped density of the graphite particles in the second negative electrode film layer.

[0328] Optionally, the tapped density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 , for example, 0.82 g / cm 3 , 0.85 g / cm 3 , 0.88 g / cm 3 , 0.90 g / cm 3 , 0.92 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 or the range composed of any two of the above values. When the tapped 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.

[0329] Optionally, the tapped density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 , for example, 0.90 g / cm 3 , 0.92 g / cm 3, 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 , 1.22 g / cm 3 , 1.23 g / cm 3 , 1.24 g / cm 3 , 1.25 g / cm 3 Or a range composed of any two of the above values. When the tap density of the carbon-based material in the second negative electrode film layer is within a suitable range, the energy density of the battery cell can be improved.

[0330] In the embodiments of the present application, the tap density of the material has the meaning well known in the art and can be measured by instruments and methods known in the art. For example, reference can be made to GB / T5162-2006 and a powder tap density tester can be used for measurement. The test instrument can be BT-301 produced by Dandong BETTER.

[0331] Optionally, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7 to 7:3, and can be optionally 4:6 to 6:4. Exemplarily, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7, 4:6, 5:5, 6:4, 7:3 or a range composed of any two of the above values. By adjusting the thickness ratio of the first negative electrode film layer and the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging ability of the battery cell can be improved.

[0332] In some embodiments, after the battery cell has undergone 10 full charge test 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 composed 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 ability of the battery cell can be improved.

[0333] In some embodiments, after the battery cell undergoes 10 full charge test 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 any range composed of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, it is possible to regulate and increase the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer, reduce the tortuosity of lithium ion transport, and improve the fast charging ability of the battery cell.

[0334] In the embodiments of the present application, for example, taking the battery charging upper limit voltage of 3.65 V and the battery discharge cut-off voltage of 2.0 V as an example for illustration, The specific steps of the BOL full charge test are as follows: At 25 °C, charge at a charging rate of 0.33 C of the battery nominal capacity to 3.65 V, then charge at a constant voltage of 3.65 V to 0.05 C, stand for 10 min, then discharge at a discharge rate of 0.33 C to 2.0 V, stand for 10 min. The above one charge and discharge is one cycle, and cycle 10 times. Then charge at a charging rate of 0.33 C of the nominal capacity to 3.65 V, and then charge at a constant voltage of 3.65 V to 0.05 C to obtain the BOL full charge state. In the BOL full charge state, disassemble the negative electrode plate, use a tomography electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode plate, distinguish the two regions according to the interface between the first negative electrode film layer and the second negative electrode film layer, and measure the thickness of the two respectively. For example, measure the thickness of 10 positions of the first negative electrode film layer, calculate its average value 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 its average value as the average value of the second negative electrode film layer.

[0335] In some embodiments, after the full charge test at the end of life (EOL) of the battery cell, the thickness of the first negative electrode film layer is 15 μm to 70 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or a range composed 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 regulate and increase the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transport, and improve the fast charging ability of the battery cell.

[0336] In some embodiments, after the full charge test at the end of life (EOL) of the battery cell, the thickness of the second negative electrode film layer is 15 μm to 70 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or a range composed 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 regulate and increase the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transport, and improve the fast charging ability of the battery cell.

[0337] In the embodiments of the present application, for example, taking the battery charging upper limit voltage of 3.65 V and the battery discharge cut-off voltage of 2.0 V as an example for illustration, The specific steps for the EOL full charge test are as follows: At 60 °C, charge at a charging rate of 0.33C of the battery's nominal capacity until 3.65V, then perform constant voltage charging at 3.65V until 0.05C, let it stand for 10 minutes, then discharge at a discharge rate of 0.33C until 2.0V, and let it stand for 10 minutes. The above one charge and discharge cycle is repeated until the battery capacity decays to 80% of the nominal capacity and the test stops. Then, at 25 °C, charge at a constant current of 0.33C until 3.65V, and perform constant voltage charging at a rate of 0.05C until 3.65V, which is the EOL full charge state. In the EOL full charge state, disassemble the negative electrode sheet, use a tomography scanning electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode sheet, distinguish the regions of the first negative electrode film layer and the second negative electrode film layer according to their interfaces, and measure their thicknesses respectively. For example, measure the thicknesses at 10 positions of the first negative electrode film layer, calculate their average value as the average value of the first negative electrode film layer, measure the thicknesses at 10 positions of the second negative electrode film layer, and calculate their average value as the average value of the second negative electrode film layer.

[0338] In some embodiments, when the negative electrode film layer adopts a single-layer film layer (different from the above double-layer film layer), the negative electrode film layer further 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 composed of any two of the above values. The lithium element in the lithium-containing binder can exist in ionic form, which can increase the number of free-moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the lithium ion insertion / extraction rate, and enhance the fast charging performance of the battery cell. Optionally, the negative electrode film layer can 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 (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0339] Optionally, the mass content of lithium element in the lithium-containing binder is 3% to 10%. Exemplarily, the mass content of lithium element in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values. The mass content of lithium element is calculated based on the mass of the lithium-containing binder. When the mass content of lithium element is within the above range, the number of free-moving lithium ions 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, improve the lithium ion insertion / extraction rate, and enhance the fast charging performance of the battery cell.

[0340] Exemplarily, the lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer, and the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0341] The lithium-containing binder of the above materials can provide a certain amount of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during the charge and discharge process, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0342] In some other embodiments, when the negative electrode film layer adopts at least two layers of film layers, the negative electrode film layer further includes a lithium-containing binder.

[0343] 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.

[0344] The mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the number of freely movable lithium ions provided by the second lithium-containing binder for the second negative electrode film layer is relatively more, which can further improve the fast charging performance of the battery cell.

[0345] 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 the range composed of any two of the above values. The lithium element in the first lithium-containing binder can exist in the form of ions, which can increase the number of freely movable lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0346] Optionally, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. Exemplarily, the mass content of lithium element in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values. When the mass content of lithium element is within the above range, the number of free-moving lithium ions 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, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0347] Exemplarily, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, and the lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-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 2-hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0348] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during the charge and discharge process, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0349] 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 composed 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 free-moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0350] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0351] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. Exemplarily, the mass content of lithium element in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range composed of any two of the above values. When the mass content of lithium element is within the above range, the number of free-moving lithium ions 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, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0352] Exemplarily, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, and the lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-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 2-hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0353] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during the charge and discharge process, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0354] 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 independently include 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).

[0355] 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.

[0356] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. 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%.

[0357] In some embodiments, the negative electrode film layer may further optionally 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%.

[0358] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include a thickener, a dispersant, etc., for example, 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%.

[0359] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0360] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. Exemplarily, the thickness of the negative electrode current collector is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm or a range composed of any two of the above values.

[0361] When the thickness of the negative electrode current collector is within the above range, the current-carrying capacity of the negative electrode current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0362] In the embodiments of the present application, the thickness of the negative electrode current collector has the meaning well known in the art, and can be detected by using the equipment and methods well known in the art. For example, the film layer on the surface of the negative electrode current collector is washed away with a solvent, and the thickness of the negative electrode current collector is measured with a micrometer.

[0363] The negative electrode film layer is usually formed by coating a negative electrode slurry on a negative electrode current collector part and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing negative electrode active materials, optional conductive agents, optional binders, and other optional additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0364] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the embodiment of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector part and the negative electrode film layer and disposed on the surface of the negative electrode current collector part. In some other embodiments, the negative electrode plate of the embodiment of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0365] 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 collector part. 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.

[0366] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. Exemplarily, the thickness of the negative electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or a range composed of any two of the above values.

[0367] When the thickness of the negative electrode conductive layer is within the above range, it 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, and can also take into account the improvement of the energy density of the battery cell.

[0368] In the embodiment of the present application, the thickness of the negative electrode conductive layer has the meaning well-known in the art, can be detected by equipment and methods well-known in the art, and can adopt the test method of the negative electrode conductive layer in the foregoing text.

[0369] 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 plate 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 part and the negative electrode film layer and improve the structural stability of the negative electrode plate.

[0370] In some embodiments, the negative electrode conductive layer also optionally includes other additives. As an example, the other additives can include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0371] 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 composed of any two of the above values.

[0372] Exemplarily, 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.

[0373] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%. Exemplarily, 60%, 65%, 70%, 75%, 80% or a range composed of any two of the above values.

[0374] Exemplarily, the negative electrode binder includes one or more of styrene-butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0375] In some embodiments, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05 to 1.30, and can be optionally 1.07 to 1.15. Exemplarily, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3 or a range composed of any two of the above values.

[0376] When the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is within the above range, there are sufficient sites in the negative electrode film layer for lithium insertion, which can reduce the risk of lithium plating and is beneficial to rapid charging.

[0377] In the embodiments of the present application, the meaning of the CB value is well-known in the art, and it can be detected by using well-known equipment and methods in the art. For example, the capacity of the negative electrode film layer per unit area and the capacity of the positive electrode film layer per unit area are calculated respectively, and then the ratio of the two is calculated to obtain the CB value.

[0378] Specifically, taking the battery charging upper limit voltage of 3.65V and the battery discharge cut-off voltage of 2.0V as an example for illustration, The capacity of the positive electrode film layer per unit area refers to the actual de-lithiation capacity of the positive electrode active material. The test method is as follows: Disassemble the battery in a PRS340 / 11-119-11 Braun glove box, take the positive electrode plate, and assemble it into a CR2430 type half-button battery of positive electrode-lithium sheet. The area of the positive electrode plate used is amm 2 , where the electrolyte uses 1mol / L LiPF 6In a solution with EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then the assembled half-button battery is left standing for 3 h. The test is carried out at 25°C. First, charge (discharge lithium) at 0.1C in the voltage range of 2.0 V to 3.65 V, and then discharge (intercalate lithium) at 0.05C to 2.0 V. Cycle 2 times. The discharge capacity of the second cycle is recorded as Y mAh. The actual length of the positive electrode plate of the battery design is b mm, the width is c mm, and the number of sides d of the positive active material coated on the positive current collector part. Then the capacity of the positive electrode film layer per unit area = Y / (a × b × c × d).

[0379] Specifically, the capacity of the negative electrode film layer per unit area refers to the actual lithium intercalation capacity of the negative active material. The test method is as follows: Disassemble the battery in a PRS340 / 11 - 119 - 11 Braun glove box, take the negative electrode plate, and assemble it into a CR2430 type half-button battery of negative electrode - lithium sheet. The area of the negative electrode plate used is f mm 2 , where the electrolyte uses 1 mol / L LiPF 6 In a solution with EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then the assembled half-button battery is left standing for 3 h. The test is carried out at 25°C. First, discharge (intercalate lithium) at 0.1C in the voltage range of 2 V - 0 V, and then charge (discharge lithium) at 0.05C to 2 V. Cycle 2 times. The discharge capacity of the second cycle is recorded as Z mAh. The actual length of the negative electrode plate of the battery design is h mm, the width is i mm, and the number of sides d of the negative active material coated on the negative current collector part. Then the lithium intercalation capacity of the negative electrode = Z / (f × h × i × d). In the embodiments of the present application, the separator includes a base film with a porous structure.

[0380] 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.

[0381] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0382] In some embodiments, the porosity of the base film is 20% to 70%, and can be 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 composed of any two of the above values.

[0383] When the porosity of the base film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0384] In the embodiments of the present application, the porosity refers to the percentage of the internal pore volume in the separator occupying the total volume of the separator. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin Separator for Battery Cell". It should be noted that in the actual testing process, the testing process may be slightly different from the standard according to the differences in testing instruments, testing errors, and in order to eliminate the influence on the porosity test as much as possible, so as to obtain a more accurate test value.

[0385] In some embodiments, the thickness of the base film is 6 μm to 12 μm, and can be 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 the range composed of any two of the above values.

[0386] When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0387] In the embodiments of the present application, the separator can be a base film. Optionally, the separator further includes a functional layer disposed on at least one side of the base film. The functional layer can include inorganic particles to improve the heat resistance of the separator. Optionally, the functional layer is disposed on both sides of the base film.

[0388] 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 and includes first inorganic particles. The second functional layer is located on the other side of the base film and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0389] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator.

[0390] Optionally, the first functional layer can include a binder, and can optionally include at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0391] Optionally, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0392] In the embodiments of the present application, the meaning of the thickness of the base film is the meaning well-known in the art, and the well-known meaning and equipment in the art can be used for detection. For example, a newly prepared separator film can be taken as a sample, or a battery cell that has been discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, the separator film is obtained from the battery cell, and after drying the separator film, it is used as a sample. The separator film is cut off 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 separator film and its respective layers.

[0393] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers. Optionally, the acrylate copolymers include acrylate-acrylonitrile-acrylamide-propylene copolymers. The acrylate copolymers have excellent adhesion properties and relatively high adhesion stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as a molar ratio of 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0394] The second inorganic particles in the composite particles make it difficult for the non-fluoropolymer particles to adhere to each other due to the high-temperature treatment during the granulation process, resulting in pores in the composite particles, which is beneficial to the transport of lithium ions, improving the ionic conductivity of the separator film. Moreover, the second inorganic particles can also increase the compression modulus of the composite particles. During the charge and discharge process, the composite particles are not easily deformed, making the structure of the separator film more stable, which can improve the kinetic performance of the battery cell and enhance the fast charging performance. Optionally, compared with the first functional layer, the second functional layer is disposed closer to the negative electrode tab. Since the composite particles are not easily deformed, the separator film basically does not cause side effects such as extrusion to the negative electrode tab, making the kinetic performance of the negative electrode tab stable. Correspondingly, the first functional layer is disposed closer to the positive electrode tab.

[0395] Optionally, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Optionally, the second inorganic particles include silicon oxide. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer and can cooperate with the non-fluoropolymer to form composite particles, further improving the cycle stability and kinetic performance of the separator film, and improving the cycle performance and fast charging performance of the battery cell.

[0396] 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.

[0397] 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.

[0398] 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.

[0399] 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.

[0400] 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.

[0401] Test: On an electrochemical workstation, at 10-1 ~10 6 It is tested within the frequency range of -1 ~10 Hz to obtain the separator resistance Rb, and the ionic conductivity σ (unit: mS / cm) is calculated by the following formula, σ = L / (R b ×S) where: R b is the separator resistance, and L and S are the thickness and area of the separator to be measured, respectively.

[0402] [Electrolyte] In some embodiments, the battery cell further includes an electrolyte.

[0403] During the charge and discharge process of the battery cell, active ions such as lithium ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0404] In the embodiments of the present application, the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, and may be optionally 15 mS / cm to 20 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm or the range composed of any two of the above values.

[0405] 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 can improve the fast charging performance of the battery cell.

[0406] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and it can be detected by using the equipment and methods well known in the art, for example, tested with reference to the industry standard HG-T 4067-2015.

[0407] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. Exemplarily, 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 the range composed of any two of the above values.

[0408] When the viscosity 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.

[0409] In the embodiments of the present application, the viscosity of the electrolyte has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, it can be detected according to GB / T10247-2008.

[0410] 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 composed of any two of the above values.

[0411] 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.

[0412] In the embodiments of the present application, the density of the electrolyte has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, it can be tested with reference to GB / T 2013-2010.

[0413] 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.

[0414] In some embodiments, the organic solvent includes a chain carboxylic acid ester solvent, and the mass content of the chain carboxylic acid ester solvent relative to the mass of the organic solvent is greater than or equal to 5% and less than or equal to 75%, optionally greater than or equal to 10% and less than or equal to 75%, optionally 30% to 70%, optionally 50% to 70%. Exemplarily, the mass content of the chain carboxylic acid ester solvent is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or a range composed of any two of the above values.

[0415] 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.

[0416] In some embodiments, the chain carboxylic acid ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1 comprises a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 comprises a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0417] The above-mentioned chain carboxylic ester solvents have relatively high conductivity, which is beneficial to improving the rapid charging ability of battery monomers.

[0418] Optionally, R 1 comprises a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 1 comprises a hydrogen atom, a halogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0419] Optionally, R 2 comprises a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 2 comprises a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0420] In the above 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.

[0421] 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.

[0422] Exemplarily, the chain carboxylic ester solvents include one or more of the compounds represented by Formula I-1 to Formula I-8,

[0423] In some embodiments, the organic solvent further includes a carbonate solvent.

[0424] 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-mentioned carbonate solvents and chain carboxylic ester solvents are used in combination, so that the conductivity of the electrolyte at room temperature is improved, which is beneficial to the migration of lithium ions.

[0425] Further optionally, the mass content of the carbonate solvent in the organic solvent is 30% to 70%, and may be optionally 30% to 50%. Exemplarily, the mass content of the carbonate solvent in the organic solvent is 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70% or a range composed of any two of the above values. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0426] Exemplarily, 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 30% to 50%.

[0427] In some embodiments, the electrolyte further contains additives. The additives may include negative electrode film-forming additives, may also include positive electrode film-forming additives, and may further include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature power performance of the battery, etc.

[0428] In some embodiments, the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives, and may be optionally at least two. The above additives can improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to enhancing the fast charging performance of the battery cell and improving the cycle performance.

[0429] In some embodiments, the mass content of the additives in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. Exemplarily, the mass content of the additives in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values.

[0430] The additives with the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to enhancing the fast charging performance of the battery cell and improving the cycle performance.

[0431] Exemplarily, the carbonate additives include one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0432] Exemplarily, the sulfur-containing additives include one or more of ethylene sulfate DTD, bis(ethylene sulfate) 2-DTD, butene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methyl methanedisulfonate MMDS.

[0433] Optionally, the lithium salt additives include lithium difluorophosphate LiPO2 F 2 , one or more of lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF 4 , and lithium bis(oxalato)borate LiBOB.

[0434] Optionally, the mass content of vinylene carbonate VC in the electrolyte is 0.5% to 9%, and may be optionally 2% to 6%.

[0435] Optionally, the mass content of fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%, and may be optionally 0.5% to 3%.

[0436] 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%.

[0437] 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%.

[0438] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of a fluorosulfonylimide salt and lithium hexafluorophosphate LiPF 6 . The above lithium salts are easy to dissociate, which is beneficial to the rapid migration of lithium ions, and the electrolyte system is relatively stable and not easily decomposed, which can improve the cycle performance of the battery cell.

[0439] Optionally, the fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0440] 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 is 0.5 mol / L to 1.0 mol / L.

[0441] Exemplarily, 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 6 is 0.7 mol / L.

[0442] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.5 mol / L.

[0443] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.8 mol / L.

[0444] Optionally, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF 6 is from 0.2 to 1.0, and can be optionally from 0.2 to 0.5. Exemplarily, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range composed of any two of the above values.

[0445] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentration in the electrolyte have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, reference can be made to the standard JY / T 020-1996 "General Rules for Ion Chromatography Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salt concentration in the electrolyte by ion chromatography analysis method. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a discharged battery (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample, and detected by ion chromatography analysis method.

[0446] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, reference can be made to GB / T 9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a discharged battery (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample, and detected by ion chromatography analysis method.

[0447] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified, and chain carboxylic ester solvents and carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as the constituent components of the organic solvent. Based on the mass of the organic solvent being 100%, the mass content of each component is calculated. Use carbonate additives (such as vinylene carbonate, fluoroethylene carbonate), sulfur-containing additives, and lithium salt additives as additives for the electrolyte. Based on the mass of the electrolyte being 100%, calculate the mass content of each component.

[0448] In some embodiments, the battery cell satisfies: 2.45 g / Ah ≤ d / A ≤ 3.5 g / Ah, optionally 2.45 g / Ah ≤ d / A ≤ 3.3 g / Ah, where 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. Exemplarily, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah, or a range composed of any two of the above values.

[0449] d / A can reflect the liquid retention ability of the electrolyte. When d / A is within the above range, the electrolyte can play a better wetting role on the positive electrode plate and the negative electrode plate, and can also improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the fast charging ability of the battery cell.

[0450] In the embodiments of the present application, d / A of the battery cell can be understood as the liquid retention coefficient, and can be detected by using equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharge as 2.0 V in accordance with GB / T31486-2015 "Power Battery Electrical Performance Requirements and Test Methods for Electric Vehicles" for illustration. At 25 °C, charge the battery cell at 0.33C to 3.65V, then charge at constant voltage to 0.05C, and then discharge at 0.33C constant current to 2.0V. Take the released capacity A as the denominator, weigh the battery cell as M0, then disassemble the positive electrode plate, the negative electrode plate, the separator, and the electrolyte, where the free electrolyte is in a bag. Put all the above solid components into an oven at 60 °C and bake for more than 4 hours (including but not limited to the positive electrode plate, the negative electrode plate, the separator, and other mechanical parts of the disassembled battery cell that contribute to M0), and then weigh all the components of the battery cell as M1. 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.

[0451] In some embodiments, the positive electrode plate, the separator, and the negative electrode plate can be made into an electrode assembly by a winding process and / or a stacking process.

[0452] In some embodiments, the battery cell 7 can include a housing 20.

[0453] In some embodiments, the housing 20 of the battery cell 7 can be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The housing 20 of the battery cell 7 can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0454] The housing 20 is a hollow structure, and the housing 20 can be used to encapsulate the above-mentioned electrode assembly 10 and electrolyte.

[0455] The preparation method of the battery cell 7 according to the embodiments 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 the electrode assembly 10 through a winding process and / or a stacking process. The electrode assembly 10 is placed in the housing 20, and after drying, the electrolyte is injected. After processes such as vacuum packaging, standing, formation, and shaping, the battery cell 7 is obtained.

[0456] In some embodiments, the housing 20 includes a housing body 21 and an end cap 22. The housing body 21 has an opening, and the end cap 22 covers the opening.

[0457] The shape of the housing body 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical housing can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid housing can be selected. Optionally, both the electrode assembly 10 and the housing body 21 are cuboid structures.

[0458] In some embodiments, the base material of the housing body 21 includes steel. Steel has high mechanical strength and is not easily deformed, which can improve the service reliability of the battery cell 7. In the embodiments of the present application, the base material refers to the material with the highest proportion in the housing body 21.

[0459] Optionally, the thickness of the housing body 21 is from 0.1 mm to 0.5 mm, and can be selected from 0.2 mm to 0.35 mm. Exemplarily, the thickness of the housing body 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm or the range composed of any two of the above values. When the thickness of the housing body 21 is within the above range, the mechanical strength of the housing body 21 is high, which can improve the service reliability of the battery cell 7; and the housing body 21 occupies less space and there is more internal space in the housing body 21, which is beneficial to improving the energy density of the battery cell 7.

[0460] From the appearance of the electrode assembly 10, the electrode assembly 10 includes a main body portion 12 and electrode tabs 11. The electrode tabs 11 include a positive electrode tab 111 and a negative electrode tab 112, and the positive electrode tab 111 and the negative electrode tab 112 protrude from the main body portion 12.

[0461] The positive electrode tab 111 and the negative electrode tab 112 can extend from the same side of the main body 12, or can extend from opposite sides respectively.

[0462] Optionally, the number of positive electrode tabs 111 located on the same side of the main body 12 is at least one, optionally at least two. At least two positive electrode tabs 111 can increase the current-carrying capacity of the positive electrode tab 111.

[0463] Optionally, the number of negative electrode tabs 112 located on the same side of the main body 12 is at least one, optionally at least two. At least two negative electrode tabs 112 can increase the current-carrying capacity of the negative electrode tab 112.

[0464] In some embodiments, the battery cell 7 further includes a positive terminal 31, and the positive terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 are welded. The positive terminal 31 and the positive electrode tab 111 can be connected through an adapter, or can be connected without using an adapter; optionally, the positive terminal 31 and the positive electrode tab 111 are not connected through an adapter, that is, the positive terminal 31 and the positive electrode tab 111 are directly welded, which can reduce the resistance at the connection, and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0465] In some embodiments, the battery cell 7 further includes a negative terminal 32, and the negative terminal 32 is electrically connected to the negative electrode tab 112. Optionally, the negative terminal 32 and the negative electrode tab 112 are welded. The negative terminal 32 and the negative electrode tab 112 can be connected through an adapter, or can be connected without using an adapter; optionally, the negative terminal 32 and the negative electrode tab 112 are not connected through an adapter, that is, the negative terminal 32 and the negative electrode tab 112 are directly welded, which can reduce the resistance at the connection, and is beneficial to reducing the overall internal resistance of the battery cell 7. When the negative electrode tab 112 is the negative electrode tab, the negative terminal 32 is the positive terminal.

[0466] Optionally, the number of positive terminals 31 located on the same side of the main body 12 is at least one, optionally at least two. At least two positive terminals 31 can increase the current-carrying capacity of the positive terminal 31.

[0467] Further optionally, the current-carrying area of a single positive terminal 31 is 150 mm 2 to 1000 mm 2 , optionally 200 mm 2 to 1000 mm 2 . The current-carrying area of the positive terminal 31 on one side refers to the sum of the current-carrying areas of all positive terminals 31 located on the same side of the main body 12. The current-carrying area of the positive terminal 31 can be understood as the cross-sectional area of the positive terminal 31, and this cross-section is perpendicular to the thickness direction of the end cover 22.

[0468] Exemplarily, the overcurrent area of the single-sided positive terminal 31 can be 150 mm 2 , 200 mm 2 , 210 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 , 850 mm 2 , 900 mm 2 , 950 mm 2 , 1000 mm 2 or a range composed of any two of the above values.

[0469] Optionally, the number of negative terminals 32 on the same side of the main body 12 is at least one, optionally at least two. At least two negative terminals 32 can increase the overcurrent capacity of the negative terminals 32.

[0470] Further optionally, the overcurrent area of the single-sided negative terminal 32 is 150 mm 2 to 1000 mm 2 , optionally 200 mm 2 to 1000 mm 2 , and the overcurrent area of the single-sided negative terminal 32 refers to the sum of the overcurrent areas of all negative terminals 32 on the same side of the main body 12. The overcurrent area of the negative terminal 32 can be understood as the cross-sectional area of the negative terminal 32, and this cross-section is perpendicular to the thickness direction of the end cover 22.

[0471] Exemplarily, the overcurrent area of the single-sided negative terminal 32 can be 150 mm 2 , 200 mm 2 , 210 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 , 850 mm 2 , 900 mm 2 , 950 mm 2 , 1000 mm 2 or a range formed by any two of the above values.

[0472] As Figure 15 shown, in some embodiments of the present application, the battery cells 7 according to the implementation manners of the present application can be assembled into a battery module 6. The number of battery cells 7 included 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.

[0473] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, in parallel, or in a series-parallel combination. A series-parallel combination means that there are both series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series, in parallel, or in a series-parallel combination together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodation part of the battery module 6. Of course, it is also possible that the multiple battery cells 7 are first connected in series, in parallel, or in a series-parallel combination to form battery modules 6, and then the multiple battery modules 6 are connected in series, in parallel, or in a series-parallel combination to form a whole and are accommodated in the accommodation part. Optionally, the battery module 6 can further include an accommodation part having an accommodation space, and the multiple battery cells 7 are accommodated in the accommodation space.

[0474] As Figure 16 shown, in some implementation manners, the above battery module 6 can be further assembled into a battery pack 2. The number of battery modules 6 included in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device herein can be the battery module 6 or the battery pack 2.

[0475] The battery pack 2 can include a box body 5 and multiple battery modules 6 disposed in the box body 5. The box body 5 includes a first box body part 5a and a second box body part 5b. The box body 5 has an accommodation space 5c. The first box body part 5a is used to cover the second box body part 5b and form a closed space for accommodating the battery modules 6. The multiple battery modules 6 can be arranged in the box body 5 in any manner.

[0476] 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 jointly define a receiving space 5c for receiving battery cells. The second box body part 5b can be a hollow structure with one end open, the first box body part 5a is a plate-like structure, and 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 receiving space 5c. The first box body part 5a and the second box body part 5b can also both be hollow structures 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 receiving space 5c. Of course, the first box body part 5a and the second box body part 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0477] To improve the sealing performance after the connection between the first box body part 5a and the second box body part 5b, a sealing member can also be provided between the first box body part 5a and the second box body part 5b, such as sealant, sealing ring, etc.

[0478] Assume that the first box body part 5a covers the top of the second box body part 5b. The first box body part 5a can also be called the upper box cover, and the second box body part 5b can also be called the lower box body. 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 where the battery pack 2 is located is 30°C.

[0479] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge (SOC) to 80% state of charge (SOC), the temperature of the external environment where the battery pack 2 is located is 30°C.

[0480] In some embodiments, during 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, it includes multiple charging steps. The difference between the maximum state of charge of any charging step and the maximum state of charge of its adjacent charging step is less than or equal to 5% state of charge, such as 1% state of charge, 1.5% state of charge, 2% state of charge, 2.5% state of charge, 3% state of charge, 3.5% state of charge, 4% state of charge, 4.5% state of charge, 5% state of charge, or a range composed of any two of the above values.

[0481] The battery pack 2 or any battery cell that makes up the battery pack 2 includes multiple charging steps from a state of charge (SOC) of 10% to 40%. For any one of the charging steps, it can be charged at any rate between 5C and 10C. The charging rate corresponding to each charging step can be any value among 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value within the range composed of any two of the above values.

[0482] The battery pack 2 or any battery cell that makes up the battery pack 2 also includes multiple charging steps from a state of charge (SOC) of 40% to 80%. The charging rate of any one of the charging steps is less than the charging rate of any one of the charging steps from a state of charge (SOC) of 10% to 40%, and the charging rate of the step when charging to 80% state of charge is any value between 2.5C and 5C. For example, it can be 2.7C.

[0483] Exemplarily, the charging steps of the battery pack 2 or any battery cell that makes up the battery pack 2 from 10% to 80% can be carried out in the following manner: 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.

[0484] In some embodiments, the charging time of the battery pack 2 or any battery cell that makes up the battery pack 2 from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, optionally 5 min to 10.5 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, such as 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 the range composed of any two of the above values. In some embodiments, the volumetric energy density of the battery cell is 390 Wh / L to 500 Wh / L, optionally 410 Wh / L to 470 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, 480 Wh / L, 490 Wh / L, 500 Wh / L or the range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0485] In the embodiments of the present application, the volumetric energy density of the battery cell has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharging as 2.0 V as an example for illustration. Place the battery cell at 25°C, charge it at a constant current of 0.33C to 3.65 V, then charge it at a constant voltage until 0.05C, discharge it at a constant current of 0.33C to 2.0 V, and record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulating film outside the shell), calculate the volume V0 of the single battery cell, unit: L, and the volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0486] electric device In the second aspect of the embodiments of the present application, an electrical device is provided. The electrical device includes the battery device of the embodiments of the present application, such as a battery cell, a battery module, or a battery pack. The battery cell, the battery module, or the battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical 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. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or an extended-range electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle, and a spaceship, etc. The electric toy includes a stationary or mobile electric toy, for example, a game console, an electric vehicle 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, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact drill, a concrete vibrator, and a power planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices. The electrical device can select a battery cell, a battery module, or a battery pack according to its usage requirements.

[0487] Figure 17 It is a schematic diagram of an electrical device 1 as an example. The electrical 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 electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0488] A battery pack 2 is provided inside the electrical device 1. The battery pack 2 can be provided at the bottom, the head, or the tail of the electrical device 1. The battery pack 2 can be used for power supply of the electrical device 1. For example, the battery pack 2 can be used as the operating power source of the electrical device 1 and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1.

[0489] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery pack 2 to supply power to the motor 4. For example, it is used for the working power requirements during the start, navigation, and driving of the electrical device 1.

[0490] Another example of the electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires being thin and light, and a battery cell can be used as the power source.

[0491] The charging process of the electrical device can select the following charging methods: Charge from 10% SOC to 15% SOC at a constant current of 5.0C, Charge from 15% SOC to 20% SOC at a constant current of 5.0C, Charge from 20% SOC to 25% SOC at a constant current of 5.0C, Charge from 25% SOC to 30% SOC at a constant current of 5.0C, Charge from 30% SOC to 35% SOC at a constant current of 5.0C, Charge from 35% SOC to 40% SOC at a constant current of 5.0C, Charge from 40% SOC to 45% SOC at a constant current of 4.6C, Charge from 45% SOC to 50% SOC at a constant current of 4.3C, Charge from 50% SOC to 55% SOC at a constant current of 4.0C, Charge from 55% SOC to 60% SOC at a constant current of 3.7C, Charge from 60% SOC to 65% SOC at a constant current of 3.4C, Charge from 65% SOC to 70% SOC at a constant current of 3.1C, Charge from 70% SOC to 75% SOC at a constant current of 2.9C, Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0492] In some embodiments, the charging time of the electrical device from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, and can be optionally 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, such as 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 the range composed of any two of the above values.

[0493] The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0494] Example 1-1 1. Preparation of the positive electrode sheet The positive electrode sheet includes a positive current collector, a positive conductive layer on the positive current collector, and a positive electrode film layer. The positive current collector is an aluminum foil with a thickness of 10 μm.

[0495] The positive electrode conductive layer on the positive electrode current collector is a film layer formed by uniformly mixing a positive electrode conductive agent, superconducting carbon, a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), and then coating and drying on the surface of the current collector. The thickness is 1 μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0496] The positive electrode film layer is formed by uniformly coating a positive electrode paste (with a solvent of N-methylpyrrolidone, NMP) on the surface of the positive electrode conductive layer, followed by 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, with a weight ratio of 97:2:1.

[0497] The positive electrode active material includes lithium iron phosphate and a coating layer. The coating layer coats the surface of the lithium iron phosphate. The coating layer includes lithium iron titanium phosphate, Li 2 FeTi(PO 4 ) 3 and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0498] 2. Preparation of the negative electrode plate The negative electrode plate includes a negative electrode current collector, a negative electrode conductive layer on the negative electrode current collector, and a negative electrode film layer. The negative electrode current collector is a copper foil with a thickness of 5 μm.

[0499] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing a negative electrode conductive agent, superconducting carbon, a negative electrode binder, styrene-butadiene rubber (SBR), a thickening agent, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, and then coating and drying on the surface of the negative electrode current collector. 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 thickening agent in the negative electrode conductive layer is 5%.

[0500] The negative electrode film layer is formed by uniformly coating a negative electrode paste (with a solvent of deionized water) on the surface of the negative electrode conductive layer, followed by drying and cold pressing.

[0501] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0502] The first negative electrode film layer comprises graphite particles, conductive agent acetylene black, a first lithium-containing binder (lithium acrylate - acrylonitrile - acrylamide - 2 - hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2 - hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene - butadiene rubber, and thickening agent sodium carboxymethyl cellulose in a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium element in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer, and the carbon coating layer coats the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0503] The second negative electrode film layer comprises graphite particles, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate - acrylonitrile - acrylamide - 2 - hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2 - hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene - butadiene rubber, and thickening agent sodium carboxymethyl cellulose in a mass ratio of 97.5:0.5:0.5:0.5:1. The mass content of lithium element in the second lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer, and the carbon coating layer coats the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0504] 3. Separator The separator includes a base film, and the base film is a 7 - μm polyethylene film layer with a porosity of 42%.

[0505] 4. Preparation of electrolyte The electrolyte includes organic solvents, lithium salts and additives.

[0506] The organic solvents include 60% chain carboxylic ester solvents (ethyl acetate) and 40% carbonate solvents (30% ethylene carbonate EC, and the rest is dimethyl carbonate). The mass content of each component in the organic solvents is calculated based on the mass of the organic solvents.

[0507] Based on the mass of the electrolyte, the mass content of the additives is 6.5%, and it includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES and lithium difluoro(oxalato)borate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0508] The lithium salt includes 1 mol / L lithium hexafluorophosphate LiPF 6 .

[0509] 5. Preparation of battery cell Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and obtain an electrode assembly through the lamination process; place the electrode assembly in an outer packaging shell, inject electrolyte after drying, and go through processes such as vacuum packaging, standing, formation, and shaping to obtain a battery cell.

[0510] Example 1-2 A battery cell was prepared using a method similar to that of Example 1-1. Different from Example 1-1, the dimensions of the positive current collector along the first direction and the dimensions of the negative current collector along the first direction were adjusted.

[0511] Examples 1-3 and 1-4 A battery cell was prepared using a method similar to that of Example 1-1. Different from Example 1-1, the single-sided coating weight of the positive electrode film layer was adjusted, and the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive current collector changed accordingly; The single-sided coating weight of the negative electrode film layer was adjusted, and the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative current collector changed accordingly.

[0512] Comparative Example 1-1 A battery cell was prepared using a method similar to that of Example 1-1. Different from Example 1-1, the dimensions of the positive current collector along the first direction and the dimensions of the negative current collector along the first direction were adjusted.

[0513] Comparative Examples 1-2 and 1-3 A battery cell was prepared using a method similar to that of Example 1-1. Different from Example 1-1, the single-sided coating weight of the positive electrode film layer was adjusted, and the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive current collector changed accordingly; The single-sided coating weight of the negative electrode film layer was adjusted, and the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative current collector changed accordingly.

[0514] Comparative Example 1-4 A battery cell was prepared using a method similar to that of Example 1-1. Different from Example 1-1, the dimension of the positive current collector along the second direction was adjusted to 380 mm, and the dimension of the negative current collector along the second direction was adjusted to 385 mm.

[0515] Performance Test 1. Lithium deposition area test of the battery cell After each battery pack of each example was cycled 20 times according to its respective 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 lithium deposition area (grayish-white area) was observed, and the lithium deposition area was measured. The lithium deposition degree is as follows: No lithium deposition: Lithium deposition area < 0.05%.

[0516] Slight lithium plating: the area of lithium plating < 2%.

[0517] Severe lithium plating: the area of lithium plating ≥ 2%.

[0518] Charge the battery cell at the temperature of the external environment of 30 °C. The charging steps include the following steps: Constant current 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.

[0519] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0520] The discharging strategy is as follows: constant current discharge at 0.33C to the cut-off voltage, such as 2.0V.

[0521] Test results The test results are shown in Table 1.

[0522] Table 1

[0523] On both sides of the positive current collector in Table 1, a positive tab is provided respectively, and on both sides of the negative current collector, a negative tab is provided respectively.

[0524] For Examples 1-1 to Comparative Example 1-3, the dimension of the positive current collector along the second direction Z is 300mm, and the dimension of the negative current collector along the second direction Z is 305mm. For any point in the positive current collector, such as Figure 12 point E in [diagram] and the distance e between the tab and the point along the second direction is less than 300mm. For any point in the negative current collector, such as Figure 14 point G in [diagram] and the distance g between the tab and the point along the second direction is less than 300mm.

[0525] As Figure 12 shown, the dimension of the positive current collector along the first direction Y is S 1 . For any point in the positive current collector, such as point F, the distance f between the point and the nearest positive tab along the first direction Y 1 is less than or equal to 300mm.

[0526] For example, in Example 1-1, the distance between any point in the positive current collector and the nearest positive tab along the first direction Y is less than or equal to 450mm / 2 = 225mm.

[0527] In Comparative Example 1-1, the distance between any point in the positive current collector and the nearest positive tab along the first direction Y is less than or equal to 780mm / 2 = 390mm, which is greater than 300mm.

[0528] As Figure 14 shown, the dimension of the negative current collector along the first direction Y is S 2 . For any point in the negative current collector, such as point H, the distance h between the point and the nearest negative tab along the first direction Y 1 is less than or equal to 300mm.

[0529] For example, in Example 1-1, the distance between any point in the positive current collector and the nearest positive tab along the first direction Y is less than or equal to 450mm / 2 = 225mm.

[0530] In Comparative Example 1-4, for any point in the positive current collector, such as Figure 12 point E in [diagram] to the distance e between the nearest positive tab along the second direction Z is greater than 300mm.

[0531] Any point in the negative current collector part, for example Figure 14 The distance g from point G to the nearest negative tab along the second direction Z in is greater than 300 mm.

[0532] In Comparative Example 1-1, the tab spacing is relatively large, resulting in a long electron transmission path, uneven current distribution, and easier lithium deposition. In Comparative Examples 1-2 and 1-3, although the tab spacing is not too long, in Comparative Example 1-2, the single-sided coating weight of the positive electrode film layer is relatively small, resulting in a relatively small volume energy density of the battery cell, which may not meet the energy density requirements. In Comparative Example 1-3, the single-sided coating weight of the positive electrode film layer is relatively large. Although the volume energy density of the battery cell is relatively high, due to the large coating weight, the electron movement path is long and the risk of lithium deposition is high. In Comparative Example 1-4, along the second direction, the electron transmission path is long, the current distribution is uneven, and lithium deposition is likely to occur.

[0533] In the embodiment of the present application, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 When, the volume energy density of the battery cell is relatively high; and the tab spacing is set so that the electron transmission path is short, the current borne between the tabs is small, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium deposition can be reduced; thereby enabling both the energy density and the use reliability of the battery cell 7 to be improved.

[0534] Example 2-1 1. Preparation of the positive electrode plate The positive electrode plate includes a positive current collector, a positive conductive layer on the positive current collector, and a positive electrode film layer. The positive current collector is an aluminum foil with a thickness of 10 μm.

[0535] The positive conductive layer on the positive current collector is a film layer formed by uniformly mixing a positive conductive agent, superconducting carbon, a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone NMP, and then coating and drying on the surface of the current collector. The thickness is 1 μm, and the mass content of the positive conductive agent in the positive conductive layer is 40%, and the mass content of the positive binder is 60%.

[0536] The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode slurry (solvent is N-methylpyrrolidone NMP) on the surface of the positive conductive layer, followed by 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 with a weight ratio of 97:2:1.

[0537] The positive electrode active material includes lithium iron phosphate and a coating layer. The coating layer covers the surface of the lithium iron phosphate. The coating layer includes lithium2 FeTi(PO 4 ) 3 and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0538] The single-sided coating weight of the positive electrode film layer is 300 mg / 1540.25 mm 2 .

[0539] 2. Preparation of the negative electrode sheet The negative electrode sheet includes a negative electrode current collector, a negative electrode conductive layer on the negative electrode current collector, and a negative electrode film layer. The negative electrode current collector is a copper foil with a thickness of 5 μm.

[0540] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing a negative electrode conductive agent, superconducting carbon, a negative electrode binder, styrene-butadiene rubber (SBR), a thickening agent, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, and then coating and drying on the surface of the negative electrode current collector. 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 thickening agent in the negative electrode conductive layer is 5%.

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

[0542] The single-sided coating weight of the negative electrode film layer is 138 mg / 1540.25 mm 2 .

[0543] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0544] The first negative electrode film layer includes graphite particles, conductive agent acetylene black, a first lithium-containing binder (copolymer of lithium acrylate - acrylonitrile - acrylamide - 2-hydroxyethyl acrylate, where the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 2-hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose, with a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium element in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer, and the carbon coating layer covers the surface of the artificial graphite, with a mass content of 3.5%.

[0545] The second negative electrode film layer includes graphite particles, conductive agent acetylene black, second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, where the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose. The mass content of lithium element in the second lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer covers the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0546] 3. Separator The separator includes a base film, which is a 7-μm polyethylene film layer with a porosity of 42%.

[0547] 4. Preparation of electrolyte The electrolyte includes organic solvents, lithium salts and additives.

[0548] The organic solvents include 60% chain carboxylic ester solvents (ethyl acetate) and 40% carbonate solvents (30% ethylene carbonate EC, 10% dimethyl carbonate). The mass content of each component in the organic solvents is calculated based on the mass of the organic solvents.

[0549] Based on the mass of the electrolyte, the mass content of the additives is 6.5%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES and lithium difluorooxalate borate LiDFOB with a mass ratio of 5:0.5:0.5:0.5.

[0550] The lithium salt includes 1 mol / L lithium hexafluorophosphate LiPF 6 .

[0551] 5. Preparation of battery cell Stack the above-mentioned positive electrode plate, separator, and negative electrode plate in sequence, with the separator between the positive electrode plate and the negative electrode plate to play an isolation role, and obtain an electrode assembly through a winding process; place the electrode assembly in an outer packaging shell, inject the electrolyte after drying, and go through processes such as vacuum packaging, standing, forming, and shaping to obtain a battery cell. The compaction density of the positive electrode film layer at 100% SOC is 2.72 g / cm 3 , and the compaction density of the negative electrode film layer at 100% SOC is 1.26 g / cm 3 .

[0552] Examples 2-2 to 2-4 Battery cells are prepared by a method similar to that of Example 2-1. Different from Example 2-1, the spacing between adjacent positive electrode tabs and the spacing between adjacent negative electrode tabs are adjusted.

[0553] Examples 2-5 and 2-6 The battery single cells were prepared by a method similar to that of Example 2-1. Different from Example 2-1, the single-sided coating weight of the positive electrode film layer was adjusted, and the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector part changed accordingly; The single-sided coating weight of the negative electrode film layer was adjusted, and the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector part changed accordingly.

[0554] Comparative Example 2-1 The battery single cells were prepared by a method similar to that of Example 2-1. Different from Example 2-1, the distance between two adjacent positive electrode tabs and the distance between two adjacent negative electrode tabs were adjusted.

[0555] Comparative Example 2-2 The battery single cells were prepared by a method similar to that of Example 2-1. Different from Example 2-1, the single-sided coating weight of the positive electrode film layer was adjusted, and the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector part changed accordingly; The single-sided coating weight of the negative electrode film layer was adjusted, and the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector part changed accordingly.

[0556] Test results The test results are shown in Table 2.

[0557] Table 2

[0558] The distance between two adjacent positive electrode tabs refers to the distance in the second direction Z. For example Figure 5 the distance between two adjacent positive electrode tabs in, the distance between two adjacent positive electrode tabs is less than or equal to 600 mm, and the distance from any point in the positive electrode current collector part to the positive electrode tab closest to that point in the second direction Y is less than or equal to 300 mm. For example, in Example 2-1, the distance between two adjacent positive electrode tabs is 150 mm, and the distance from any point in the positive electrode current collector part to the positive electrode tab closest to that point in the second direction Y is less than or equal to 150 mm / 2 = 75 mm. For example a 2 less than or equal to 75 mm, the edge A of the positive electrode current collector part 1 and the distance a between the positive electrode tab 1 less than or equal to 150 mm.

[0559] The distance between two adjacent negative electrode tabs refers to the distance in the second direction Z. For example Figure 7The distance between two adjacent negative electrode tabs is less than or equal to 600 mm, and the distance from any point in the negative current collector to the nearest negative electrode tab along the second direction Y is less than or equal to 300 mm. For example, in Example 2-1, the distance between two adjacent negative electrode tabs is less than 150 mm, and the distance from any point in the negative current collector to the nearest negative electrode tab along the second direction is less than or equal to 150 mm / 2 = 75 mm, such as b 2 Less than or equal to 75 mm, the edge B of the negative current collector 1 The distance b between the negative electrode tab 1 Less than or equal to 150 mm.

[0560] In Comparative Example 2-1, the distance between two adjacent positive electrode tabs is 700 mm, and the distance from any point in the positive current collector to the nearest positive electrode tab along the second direction can reach 700 mm / 2 = 350 mm, which is greater than 300 mm.

[0561] In Comparative Example 2-1, the distance between two adjacent negative electrode tabs is 700 mm, and the distance from any point in the negative current collector to the nearest negative electrode tab along the second direction can reach 700 mm / 2 = 350 mm, which is greater than 300 mm.

[0562] As can be seen from Table 2, in Comparative Example 2-1, the tab spacing is relatively large, resulting in a longer electron transport path, uneven current distribution, and easier lithium deposition. Although the tab spacing in Comparative Example 2-2 is not set too long, the single-sided coating weight of the positive electrode film layer in Comparative Example 2-2 is relatively small, resulting in a relatively small volume energy density of the battery cell, which may not meet the energy density requirements.

[0563] In the embodiments of the present application, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 To 400 mg / 1540.25 mm 2 When the volume energy density of the battery cell is relatively high; and the tab spacing is set so that the electron transport path is shorter, the current borne between the tabs is smaller, the current distribution is more uniform, and the lithium ions are more evenly extracted or inserted, which can reduce the risk of lithium deposition; thereby enabling the energy density and use reliability of the battery cell to be improved simultaneously.

[0564] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principle, and scope of the present application.

Claims

1. A battery cell, characterized in that: The invention comprises an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode film layer, a positive electrode current collector and at least one positive electrode tab, wherein the positive electrode film layer is arranged on at least one side of the positive electrode current collector along the thickness direction of the positive electrode sheet, and the positive electrode tab is arranged on at least one side of the positive electrode current collector along the first direction, wherein: The positive electrode film layer includes a positive electrode active material, the positive electrode active material includes an olivine structured lithium-containing material, and the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 400mg / 1540.25mm 2 , Along the second direction, the distance between the first point of the positive current collector and the positive electrode tab closest to the first point is less than or equal to 300 mm, the first point is any point of the positive current collector, and the first direction, the second direction and the thickness direction of the positive electrode sheet are perpendicular to each other.

2. The battery cell according to claim 1, characterized in that: The positive electrode tab is provided in one or more portions, and all the positive electrode tabs are provided on the same side of the positive electrode current collecting portion along the first direction. The size of the positive electrode current collecting portion along the first direction is 100 mm to 300 mm.

3. The battery cell according to claim 1, characterized in that: The positive electrode tabs are provided in plurality, and the plurality of positive electrode tabs are provided on both sides of the positive electrode current collecting portion along the first direction, and the size of the positive electrode current collecting portion along the first direction is 100 mm to 600 mm.

4. The battery cell according to claim 1, characterized in that: The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 ; and / or The thickness of the positive electrode current collector is 10 μm to 15 μm.

5. The battery cell according to claim 1, characterized in that: The electrode assembly further includes a negative electrode sheet, which includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode tab, wherein the negative electrode film layer is disposed on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is disposed on at least one side of the negative electrode current collector along the first direction, wherein: The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material. Along the second direction, a distance between a second point of the negative electrode current collecting portion and the negative electrode tab closest to the second point is less than or equal to 300 mm, and the second point is any point of the negative electrode current collecting portion.

6. The battery cell according to claim 5, characterized in that: The negative electrode tab is provided in one or more portions, and all the negative electrode tabs are provided on the same side of the negative electrode current collecting portion along the first direction. The dimension of the negative electrode current collecting portion along the first direction is 100 mm to 300 mm.

7. The battery cell according to claim 5, characterized in that: The negative electrode tabs are provided in plurality, and the plurality of negative electrode tabs are provided on both sides of the negative electrode current collecting portion along the first direction. The dimension of the negative electrode current collecting portion along the first direction is 100 mm to 600 mm.

8. The battery cell according to claim 5, characterized in that: The single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 Up to 170mg / 1540.25mm 2 ; and / or The thickness of the negative electrode current collector is 4 μm to 6 μm.

9. The battery cell according to claim 1, characterized in that: The electrode assembly is of a wound structure, and the positive electrode tabs are provided in plurality, and the plurality of positive electrode tabs are arranged relatively to each other along the thickness direction of the electrode assembly.

10. The battery cell according to claim 9, characterized in that: Along the second direction, a distance between the first point of the positive electrode current collecting portion and the positive electrode tab closest to the first point is less than or equal to 200 mm.

11. The battery cell according to claim 9, characterized in that: When the battery cell is in a 100% charged state, the ratio of the thickness of the positive electrode film layer on one side to the thickness of the positive electrode current collecting portion is 4.8 to 8.6; and / or The single-sided coating weight of the positive electrode film layer is 280 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 .

12. The battery cell according to claim 9, characterized in that: The electrode assembly comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode film layer, a negative electrode current collector and at least one negative electrode tab, the negative electrode film layer is arranged on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is arranged on at least one side of the negative electrode current collector along the first direction, wherein: When the battery cell is in a 100% charged state, the ratio of the thickness of the negative electrode film layer on one side to the thickness of the negative electrode current collecting portion is 12.5 to 19.5; and / or The negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a carbon-based material, and the single-side coating weight of the negative electrode film layer is 125 mg / 1540.25 mm 2 Up to 170mg / 1540.25mm 2 .

13. The battery cell according to claim 1, characterized in that: The electrode assembly is a laminated structure, and the positive electrode tab is arranged on at least one side of the positive electrode current collecting portion.

14. The battery cell according to claim 13, characterized in that: The positive electrode tabs are provided in plurality, and the plurality of positive electrode tabs are provided on both sides of the positive electrode current collecting portion along the first direction, and the size of the positive electrode current collecting portion along the first direction is 400 mm to 600 mm; and / or The electrode assembly includes a negative electrode sheet, which includes a negative electrode film layer, a negative electrode current collecting portion and at least one negative electrode tab, the negative electrode film layer is arranged on at least one side of the negative electrode current collecting portion along the thickness direction, the negative electrode tab is arranged in plurality, and the plurality of negative electrode tabs are arranged on both sides of the negative electrode current collecting portion along the first direction, and the size of the negative electrode current collecting portion along the first direction is 400 mm to 600 mm.

15. The battery cell according to claim 13, characterized in that: When the battery cell is in a 100% charged state, the ratio of the thickness of the positive electrode film layer on one side to the thickness of the positive electrode current collecting portion is 3.5 to 7.0; and / or The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 360mg / 1540.25mm 2 .

16. The battery cell according to claim 13, characterized in that: The electrode assembly comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode film layer, a negative electrode current collector and at least one negative electrode tab, the negative electrode film layer is arranged on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is arranged on at least one side of the negative electrode current collector along the first direction, wherein: When the battery cell is in a 100% charged state, the ratio of the thickness of the negative electrode film layer on one side to the thickness of the negative electrode current collecting portion is 10.5 to 17.5; and / or The negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a carbon-based material, and the single-side coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 Up to 164mg / 1540.25mm 2 .

17. The battery cell according to claim 1, characterized in that: The olivine-structured lithium-containing material is an olivine-structured lithium-containing phosphate; 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.

18. The battery cell according to claim 17, 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.

19. The battery cell according to claim 17, 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.

20. The battery cell according to claim 17, characterized in that: The graphitization degree of the lithium-containing phosphate with an olivine structure is 0.15 to 0.

32.

21. The battery cell according to claim 17, 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 of the olivine structure is 5m 2 / g to 18m 2 / g.

22. The battery cell according to claim 17, characterized in that: The lithium-containing phosphate with olivine structure is in granular form, and its volume distribution particle size satisfies: 1µm≤Dv50≤2µm, 0.4µm≤Dv10≤0.7µm.

23. 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 positive electrode film layer and the positive electrode current collecting portion.

24. The battery cell according to claim 23, characterized in that: The thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

25. The battery cell according to claim 23, 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.

26. The battery cell according to claim 1, characterized in that: The electrode assembly comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode film layer, a negative electrode current collector and a negative electrode tab, the negative electrode film layer is arranged on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is arranged on at least one side of the negative electrode current collector along the first direction, wherein: The negative electrode film layer includes a negative electrode active material, 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%.

27. The battery cell according to claim 26, 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.

28. The battery cell according to claim 27, characterized in that: The mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles.

29. The battery cell according to claim 26, characterized in that: The negative electrode film layer comprises: a first negative electrode film layer, disposed on the surface of the negative electrode current collecting portion, wherein the first negative electrode film layer comprises a carbon-based material, and A second negative electrode film layer is connected to a side of the first negative electrode film layer away from the negative electrode current collecting portion, wherein the second negative electrode film layer comprises a carbon-based material. The carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently include graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

30. The battery cell according to claim 29, characterized in that The carbon-based material in the first negative electrode film layer also includes natural graphite.

31. The battery cell according to claim 29, characterized in that: 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.

32. The battery cell according to claim 31, characterized in that: 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 3 , and / or 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 .

33. The battery cell according to claim 29, characterized in that: The volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm, and / or The volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm.

34. The battery cell according to claim 29, characterized in that 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. 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.

35. The battery cell according to claim 34, characterized in that: 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%, and / or 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%.

36. The battery cell according to claim 34, characterized in that The mass content of lithium in the first lithium-containing binder is 3% to 10%, and / or The mass content of lithium element in the second lithium-containing binder is 3% to 10%.

37. The battery cell according to claim 34, characterized in that The first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from 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%; and / or 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%.

38. The battery cell according to claim 26, characterized in that The negative electrode active material further comprises a silicon-based material, and the mass content of silicon element in the silicon-based material is 0.3% to 10.0%, based on the mass of the negative electrode active material.

39. The battery cell according to claim 26, characterized in that 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.

40. The battery cell according to claim 39 is characterized in that: The thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

41. The battery cell according to claim 39, 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.

42. The battery cell according to claim 1, characterized in that The electrode assembly includes a separator, the separator includes a base film with a porous structure, and the porosity of the base film is 20% to 70%; and / or The base film has a thickness of 6 μm to 12 μm.

43. The battery cell according to claim 42, 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.

44. The battery cell according to claim 43, characterized in that The non-fluorinated polymer particles include acrylic copolymers.

45. The battery cell according to claim 43, 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.

46. ​​The battery cell according to claim 43, 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.

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

48. The battery cell according to claim 47, characterized in that The electrolyte includes an organic solvent, the organic solvent includes a carboxylate solvent, the carboxylate solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent in the organic solvent is 5% to 75%.

49. The battery cell according to claim 48, characterized in that The mass content of the chain carboxylic acid ester solvent in the organic solvent is 30% to 70%.

50. The battery cell according to claim 48, 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.

51. The battery cell according to claim 50, characterized in that R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group or a C1 to C3 halogenated alkyl group, and / or R2 includes C1 to C3 alkyl or C1 to C3 halogenated alkyl.

52. The battery cell according to claim 51, characterized in that The chain carboxylic acid ester solvent includes one or more of the compounds represented by formula I-1 to the compounds represented by formula I-8, 。 53. The battery cell according to claim 48, 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.

54. The battery cell according to claim 53, characterized in that The carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

55. The battery cell according to claim 53, characterized in that The mass content of the carbonate solvent in the organic solvent is 30% to 70%.

56. The battery cell according to claim 47, 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.

57. The battery cell according to claim 56, characterized in that The carbonate additive includes one or more of vinylene carbonate, 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).

58. The battery cell according to claim 56, characterized in that The mass content of the additive in the electrolyte is 1% to 10%.

59. The battery cell according to claim 58, characterized in that The mass content of the additive in the electrolyte is 2% to 8%.

60. The battery cell according to claim 47, 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.

61. The battery cell according to claim 60, characterized in that The fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

62. The battery cell according to claim 61, characterized in that The lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate. The molar concentration of the lithium bis(fluorosulfonyl)imide is 0.2 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate is 0.5 mol / L to 1.0 mol / L.

63. The battery cell according to claim 62, characterized in that The ratio of the molar concentration of the lithium bis(fluorosulfonyl)imide to the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.2 to 1.

0.

64. The battery cell according to claim 1, characterized in that The battery cell includes a case that accommodates the electrode assembly, the case includes steel, and a thickness of the case is 0.1 mm to 0.5 mm.

65. The battery cell according to claim 64, characterized in that The thickness of the shell is 0.2 mm to 0.35 mm.

66. The battery cell according to claim 1, characterized in that The battery cell further includes a positive terminal, and the positive electrode tab is directly welded to the positive terminal.

67. The battery cell according to claim 1, characterized in that The charging time of the battery cell from 10% state of charge to 80% state of charge is 5 minutes to 10.5 minutes.

68. A battery device, characterized in that: Comprising the battery cell according to any one of claims 1 to 67.

69. The battery device according to claim 68, characterized in that The charging time of the battery device from a 10% state of charge to an 80% state of charge is 5 minutes to 10.5 minutes.

70. An electrical device, characterized in that: Comprising a battery device as described in claim 68.

Images