Battery cell, battery device and electrical device

Abstract

The present application relates to a battery cell, a battery device, and an electrical device. The battery cell 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 portion, and a positive electrode tab. The positive electrode film layer is disposed on at least one side of the positive electrode current collector portion 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 portion along the 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, and 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 the second direction, the distance between the first point of the positive electrode current collector portion 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 portion. The first direction, the second direction, and the thickness direction of the positive electrode tab are perpendicular to each other pairwise. The present application can reduce the risk of lithium deposition in the battery cell and improve the reliability of the battery cell in use.

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 thus 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 of 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 portion, 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 portion 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 portion 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 portion 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 portion. 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 portion and the positive electrode tab closest to this 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 provided on the same side of the positive electrode current collector along the first direction. The size 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 extraction or insertion is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and usage 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 provided on both sides of the positive electrode current collector along the first direction. The size 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 extraction or insertion is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and usage 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 tab, and the negative electrode tab includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode tab. The negative electrode film layer is provided on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is provided 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 extraction or insertion is more uniform, and the risk of lithium plating can be reduced; thereby enabling the energy density and usage 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 provided on the same side of the negative electrode current collector along the first direction. The size of the negative electrode current collector along the first direction is 100 mm to 300 mm. Each negative electrode tab bears a 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 tabs are provided as multiple, and the multiple negative electrode tabs are provided on both sides of the negative electrode current collector along the first direction. The size of the negative electrode current collector along the first direction is 100 mm to 600 mm. Each negative electrode tab bears a 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 electrode current collector is 4 μm to 6 μm. 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 high energy density.

[0017] In some embodiments, the electrode assembly is of a wound structure, and the positive electrode tabs are provided as multiple, and the multiple positive electrode tabs are oppositely arranged along the thickness direction of the electrode assembly. The multiple positive electrode tabs are oppositely arranged along the thickness direction of the electrode assembly, which is beneficial for connecting the positive electrode tabs and the positive electrode adapter.

[0018] In some embodiments, along the second direction, the distance between the first point of the positive electrode 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 small. By adjusting the setting position of the positive electrode tabs, 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 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 electrode 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 electrode 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 the improvement of 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 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 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 the improvement of 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 current collector.

[0024] In some embodiments, a plurality of positive electrode tabs are provided, and the plurality of positive electrode tabs are disposed on both sides of the positive current collector along the first direction. The size of the positive 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 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, a plurality of negative electrode tabs are provided, 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 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 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 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 2To 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 of olivine structure includes phosphate particles and a coating layer. The coating layer coats the phosphate particles, and the coating layer contains one or more elements among 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 of 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, reducing 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 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The phosphate particles have relatively excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0033] In some embodiments, the coating layer includes a compound with the general formula Li 3-d Fe 2-d M2d (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. Coating the fast ion conductor on the surface of the phosphate particles can significantly improve the transport rate of lithium ions during multiple deintercalation / insertion at the positive electrode, improve the ionic conductivity of the positive electrode active material, thereby increasing the specific capacity, and further increasing 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, and may be 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 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g to 18m 2 / g, and may be optionally 7.5m 2 / g to 14m 2 / g.

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

[0037] In some embodiments, the lithium-containing phosphate with olivine structure is in particulate form, 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 process, so that the performance of the positive electrode active material is stable.

[0038] In some embodiments, the lithium-containing phosphate with olivine structure is in particulate form, the lithium-containing phosphate with olivine structure includes secondary particles, and the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 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, and the carbon-based material includes graphite particles. The graphitization degree of the graphite particles is 92.0% to 94.5%. When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent conductivity, can reduce the heat generation of the negative electrode tab and the battery cell, and can 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 where lithium ions can be inserted and extracted is more, and the conductivity of the carbon coating layer is 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 diameter Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle diameter Dv50 of the graphite particles in the second negative electrode film layer.

[0048] Thus, there are differences in the particle sizes in the first negative electrode film layer and the second negative electrode film layer in the embodiments of the present application, which 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 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, the fast charging performance of the battery cell can be improved.

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

[0053] In some embodiments, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm. When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the above range, the fast charging performance can be improved.

[0054] 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.

[0055] 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.

[0056] 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 freely movable lithium ions provided by the second lithium-containing binder for the second negative electrode film layer is relatively large, which can further improve the fast charging performance of the battery cell.

[0057] 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 intercalation and deintercalation rate of lithium ions can be improved, and the fast charging performance of the battery cell can be improved.

[0058] In some embodiments, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, and may be selected from 3% to 8%. When the mass content of lithium element is within the above range, the number of freely movable lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance 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.

[0059] 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 intercalation and deintercalation rate of lithium ions is improved, and the fast charging performance of the battery cell is improved.

[0060] In some embodiments, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, and may be selected from 3% to 8%. When the mass content of lithium element is within the above range, the number of freely movable lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance 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.

[0061] 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%.

[0062] 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 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.

[0063] 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%.

[0064] 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 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.

[0065] 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.

[0066] In some embodiments, the negative electrode plate further comprises 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.

[0067] 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 conductive performance of the negative electrode plate and reduce the heat generation of the negative electrode plate, thereby reducing the heat generation amount of the battery cell.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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, which can improve the heat resistance of the separator.

[0076] In some embodiments, the non-fluoropolymer particles include an acrylate copolymer. The acrylate copolymer has excellent adhesion properties and a relatively high adhesion stability with the base film.

[0077] In some embodiments, the first inorganic particles include 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.

[0078] In some embodiments, the second inorganic particles include 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.

[0079] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is in the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0080] 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 in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0081] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. When the viscosity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is 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 density of the electrolyte at room temperature is 1.05 g / mL to 1.35 g / mL. When the density of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is 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.

[0083] In some embodiments, the carboxylic acid ester solvent includes 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 in the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0084] In some embodiments, the chain carboxylic acid ester solvent includes a compound represented by Formula I

[0085] Formula I,

[0086] In Formula I,

[0087] R1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group,

[0088] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0089] Thus, in the embodiments of the present application, the conductivity of the above-mentioned chain carboxylic ester solvents is relatively high, which is beneficial to improving the fast charging ability of the battery monomer.

[0090] In some embodiments, R1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0091] In some embodiments, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0092] In some embodiments, the chain carboxylic ester solvent includes one or more of the compounds shown in Formula I-1 to Formula I-8,

[0093]

[0094] 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-mentioned 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.

[0095] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate.

[0096] 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.

[0097] In some embodiments, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. 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 monomer and improving the cycle performance.

[0098] In some embodiments, the carbonate additive includes one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0099] In some embodiments, the sulfur-containing additive includes one or more of ethylene sulfate (DTD), bis(ethylene sulfate) (2-DTD), butene sulfite (BS), 1,3-propane sultone (PS), ethylene sulfite (ES), and methylene methanedisulfonate (MMDS).

[0100] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate (LiBF4), and lithium bis(oxalato)borate (LiBOB).

[0101] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, 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 enhancing the fast charging performance of the battery cell, and improves the cycle performance.

[0102] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of fluorosulfonylimide salts and lithium hexafluorophosphate (LiPF6). 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.

[0103] In some embodiments, the fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0104] In some embodiments, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6), 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 (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0105] In some embodiments, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.2 to 1.0.

[0106] In some embodiments, the matrix material of the housing includes steel, and the thickness of the housing is 0.1 mm to 0.5 mm, 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.

[0107] 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 point, which is beneficial to reducing the overall internal resistance of the battery cell.

[0108] 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 charging speed of the battery cell is relatively fast, which is more conducive to improving the fast charging ability.

[0109] 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.

[0110] 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 charging speed of the battery is relatively fast, which is more conducive to improving the fast charging ability.

[0111] 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

[0112] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces 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.

[0113] Figure 1 Schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0114] Figure 2 Explosion schematic diagram of a battery cell provided in some embodiments of the present application;

[0115] Figure 3 Schematic structural diagram of an electrode assembly in a battery cell provided in some embodiments of the present application;

[0116] Figure 4 Schematic cross-sectional structure diagram of a first electrode plate in a battery cell provided in some embodiments of the present application;

[0117] Figure 5 Schematic unfolded structure diagram of a first electrode plate in a battery cell provided in some embodiments of the present application;

[0118] Figure 6 Schematic cross-sectional structure diagram of a second electrode plate in a battery cell provided in some embodiments of the present application;

[0119] Figure 7 Schematic diagram of the unfolded structure of the second pole piece in a battery cell provided in some embodiments of the present application;

[0120] Figure 8 Schematic diagram of the unfolded structure of the first pole piece in a battery cell provided in some other embodiments of the present application;

[0121] Figure 9 Schematic diagram of the unfolded structure of the second pole piece in a battery cell provided in some other embodiments of the present application;

[0122] Figure 10 Schematic diagram of the structure of an electrode assembly in a battery cell provided in some other embodiments of the present application;

[0123] Figure 11 Schematic diagram of the structure of the first pole piece in a battery cell provided in still some other embodiments of the present application;

[0124] Figure 12 Schematic diagram of the structure of the first pole piece in a battery cell provided in still some other embodiments of the present application;

[0125] Figure 13 Schematic diagram of the structure of the second pole piece in a battery cell provided in still some other embodiments of the present application;

[0126] Figure 14 Schematic diagram of the structure of the second pole piece in a battery cell provided in still some other embodiments of the present application;

[0127] Figure 15 Schematic diagram of the structure of a battery module provided in some embodiments of the present application;

[0128] Figure 16 Schematic diagram of the structure of a battery provided in some embodiments of the present application;

[0129] Figure 17 Schematic diagram of an electrical device provided in some embodiments of the present application.

[0130] The accompanying drawings are not necessarily drawn to actual scale.

[0131] Explanation of reference numerals is as follows:

[0132] Y, the first direction; Z, the second direction;

[0133] 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, housing; 5a, first housing part; 5b, second housing part; 5c, accommodation space; 6, battery module;

[0134] 7, battery cell;

[0135] 10, electrode assembly;

[0136] 11. Tab

[0137] 111. Positive tab; 112. Negative tab

[0138] 12. Main body

[0139] 13. Positive electrode plate; 131. Positive current collector; 132. Positive electrode film layer

[0140] 14. Negative electrode plate; 141. Negative current collector; 142. Negative electrode film layer

[0141] 15. Separator

[0142] 20. Outer shell; 21. Housing; 22. End cap

[0143] 31. Positive terminal; 32. Negative terminal

[0144] 41. Positive adapter; 42. Negative adapter Detailed implementation manners

[0145] Hereinafter, embodiments of the battery cell, battery device, and electrical 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 detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy 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.

[0146] The "ranges" disclosed in this application are 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 boundaries of a particular range. The ranges defined in this way can include or exclude 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, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise stated, the numerical range "a to b" represents an abbreviated representation of any combination of real numbers 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" are fully listed in this article, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0147] If there is no special indication, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0148] If there is no special indication, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0149] If there is no special indication, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), which 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, it is mentioned that the method may further include step (c), which 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.

[0150] 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 deposition; especially when the ear pitch is too large, each ear bears a large current, resulting in an increased risk of lithium deposition.

[0151] 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 prevented from being too large, the risk of lithium plating in the battery cell is reduced, and the reliability of the battery cell in use is improved.

[0152] Battery cell

[0153] In a first aspect, an embodiment of the present application provides a battery cell.

[0154] The battery cell includes an electrode assembly. The electrode assembly includes a first electrode tab, the first electrode tab includes a first film layer, a first current collector portion, and at least one first tab. The first film layer is disposed on at least one side of the first current collector portion along the thickness direction of the first electrode tab. The first tab is disposed on at least one side of the first current collector portion along a first direction. Wherein, along a second direction, the distance between any point in the first current collector portion and the first tab closest to the point is less than or equal to 300 mm. The first direction, the second direction, and the thickness direction of the first electrode tab are perpendicular to each other in pairs.

[0155] Any point in the first current collector portion is defined as point P, and point P is arbitrarily taken in the first current collector portion.

[0156] 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.

[0157] 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.

[0158] Along 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 along the second direction.

[0159] The projection of the closest tab along the first direction partially overlaps with the projection of the first current collector portion along the first direction. In other words, the projection of the closest tab along the first direction is located within the projection of the first current collector portion along the first direction, where the first direction is parallel to the normal of the projection plane.

[0160] Point P is any point in the first current collector portion. When the projection of point P along the first direction is located within the projection of the closest tab along the first direction, it can be considered that the distance between point P and the closest tab along the second direction is 0.

[0161] When the projection of point P along the first direction is located outside the projection of the closest tab along the first direction, it can be considered that the distance between the first point and the closest tab along the second direction is greater than 0, and this distance is the distance between point P and the first edge along the second direction.

[0162] In the embodiments of the present application, the first electrode tab can be a positive electrode tab or a negative electrode tab.

[0163] 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.

[0164] 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 along 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 along the first direction Y. For the part of the positive electrode tab 111 where the active material layer is not coated, along 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

[0165] is the first direction, the Z direction is the second direction, and 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

[0166] , the area of the point is much smaller than the area of the tab, and the size of the point basically does not interfere with the measurement of the distance.

[0167] When there is one positive electrode tab 111, the distance between the first point (such as point A) in the positive electrode current collector 131 and the closest positive electrode tab 111 along the second direction Z refers to the distance between point A in the positive electrode current collector 131 and this positive electrode tab 111 along the second direction Z.

[0168] As Figure 5As shown, A1 is any point in the positive current collector 131. A1 is located at the edge of the positive current collector 131, and its distance from the closest positive tab 111 along the second direction Z is a1, where a1 is less than or equal to 300 mm.

[0169] A2 is any point in the positive current collector 131. A2 is located at a position between two edges of the positive current collector 131. Its distance from the closest positive tab 111 along the second direction Z is a2, and its distances from other positive tabs 111 are a3, a4, etc. a3 > a2, a4 > a2, and a2 is less than or equal to 300 mm.

[0170] Electrons are introduced or led out to the positive electrode film layer 132 through the positive tab 111. The coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 This makes the energy density of the battery cell 7 relatively high, but at the same time, it may increase the risk of lithium plating. However, in the embodiment of the present application, by regulating the distance between any point in the positive current collector 131 and the closest positive tab 111 along the second direction Z to be less than or equal to 300 mm, the transmission path of electrons is shorter, each tab bears less current, the current distribution is more uniform, the lithium ions are more evenly extracted or inserted, and the risk of lithium plating can be reduced. Moreover, since each tab bears less current, the heat generation of the system can be reduced, and the cycle performance of the battery cell 7 can be improved. Further, the positive active material includes a lithium-containing material with an olivine structure. 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.

[0171] In the embodiment 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 selected as 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.

[0172] As Figure 6 and Figure 7 shown, in some embodiments, the negative electrode plate 14 includes a negative electrode film layer 142, a negative current collector 141, and at least one negative tab 112. The negative electrode film layer 142 is disposed on at least one side of the negative current collector 141 along the thickness direction of the negative electrode plate 14. The negative electrode film layer 142 includes a negative active material. The negative active material includes a carbon-based material. The single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm2 to 170 mg / 1540.25 mm 2 , the negative electrode tab 112 is connected to at least one side of the negative electrode current collector 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 electrode current collector 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.

[0173] The negative electrode tab 112 can be one or more. The second point in the negative electrode current collector 141 is any point in the negative electrode current collector 141, such as point B.

[0174] When there is one negative electrode tab 112, the distance between point B and the negative electrode tab 112 closest to point B along the second direction Z refers to the distance between point B in the negative electrode current collector 141 and this negative electrode tab 112 along the second direction Z.

[0175] 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 along the second direction Z. From this, the distance between this negative electrode tab 112 and point B along the second direction Y is measured.

[0176] As Figure 7 shown, B1 is any point in the negative electrode current collector 141. B1 is located at the edge of the negative electrode current collector 141, and its distance from the negative electrode tab 112 closest to it along the second direction Z is b1, and b1 is less than or equal to 300 mm.

[0177] B2 is any point in the negative electrode current collector 141. B2 is located at a position between the two edges of the negative electrode current collector 141. Its distance from the negative electrode tab 112 closest to it along the second direction Z is b2, and its distances from other negative electrode tabs 112 are b3, b4, etc. b3 is greater than b2, b4 is greater than b2, and b2 is less than or equal to 300 mm.

[0178] 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 141 and the negative electrode tab 112 closest to this point along 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 ion deintercalation or intercalation is more uniform, and the risk of lithium deposition can be reduced.

[0179] 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 mm2 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 tab 14 will not be too large, and it can also take into account the improvement of the energy density of the battery cell 7.

[0180] [Wound Electrode Assembly]

[0181] Please continue to refer to Figures 1 to 7 , when the electrode assembly 10 is of 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.

[0182] When at least two positive electrode ears 111 are provided, the at least two positive electrode ears 111 are arranged oppositely in the thickness direction of the electrode assembly 10. The closer to the start end of winding, the smaller the distance between two adjacent positive electrode ears 111, which is beneficial to connecting the positive electrode ear 111 and the positive electrode adapter 41. Figure 3 In [the figure], X represents the thickness direction of the electrode assembly 10.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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 mm2 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 the range formed by any two of the above values.

[0187] 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.

[0188] In some embodiments, along the first direction Y, the distance between the third point in the positive electrode current collector portion 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 in the positive electrode current collector portion 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 the range formed by any two of the above values.

[0189] When all the positive electrode tabs 111 are located on the same side of the positive electrode current collector part 131, along the first direction Y, the distance between any point (such as point C) in the positive electrode current collector part 131 and the positive electrode tab 111 closest to point C refers to the distance between point C in the positive electrode current collector part 131 and the positive electrode tab 111 along the first direction Y. Figure 5 As shown in Figure 5 , c1 represents the distance between point C and the positive electrode tab 111 along the first direction Y.

[0190] In some embodiments, when all the positive electrode tabs 111 are located on the same side of the positive electrode current collector part 131, the dimension of the positive electrode current collector part 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 Figure 5 , R1 represents the dimension of the positive electrode current collector part 131 along the first direction Y.

[0191] When the positive electrode tabs 111 are located on both sides of the positive electrode current collector part 131, along the first direction Y, the distance between any point (such as point C) in the positive electrode current collector part 131 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.

[0192] In some embodiments, when the positive electrode tabs 111 are located on both sides of the positive electrode current collector part 131, the dimension of the positive electrode current collector part 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.

[0193] As Figure 8 shown, C is any point in the positive electrode current collector part 131. C is located at a position between the two edges of the positive electrode current collector part 131. The distance between C and the positive electrode tab 111 on the closest side along the first direction Y is c1, and the distance between C and the positive electrode tab 111 on the other side is c2. c2 is greater than c1, and c1 is less than or equal to 300 mm.

[0194] In the embodiments of the present application, by controlling the distance between any point in the positive current collector 131 and the positive tab 111 closest to this point along 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.

[0195] Optionally, when the battery cell 7 is in a 100% charged state, 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.

[0196] 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.

[0197] When at least two negative tabs 112 are provided, the at least two negative tabs 112 are arranged opposite to each other along the thickness direction of the electrode assembly 10, and the distance between adjacent two negative tabs 112 is smaller closer to the winding start end, which is beneficial to connecting the negative tab 112 and the negative adapter 42.

[0198] When at least two negative tabs 112 are provided, the at least two negative tabs 112 are arranged opposite to each other along the thickness direction of the electrode assembly 10, which is beneficial to connecting the negative tab 112 and the negative adapter 42.

[0199] Optionally, the at least two negative tabs 112 are provided on the same side of the negative current collector 141.

[0200] As Figure 9 shown, optionally, the at least two negative tabs 112 can also be provided on both sides of the negative current collector 141.

[0201] Along the second direction Z, the distance between any point in the negative current collector 141 and the negative tab 112 closest to this point along the second direction Z is less than or equal to 300 mm, and can optionally be less than or equal to 200 mm. Exemplarily, the distance between any point in the negative current collector 141 and the negative 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 a range composed of any two of the above values.

[0202] 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 optionally be 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 mm 2 , 170 mg / 1540.25 mm 2 or a range formed by any two of the above values.

[0203] 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 it can also take into account the improvement of the energy density of the battery cell 7.

[0204] In some embodiments, along the first direction Y, the distance between the fourth point in the negative electrode current collector portion 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 portion 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.

[0205] When the negative electrode tab 112 is located on the same side of the negative electrode current collector portion 141, the distance along the first direction Y between any point (such as point D) in the negative electrode current collector portion 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 portion 141 and the negative electrode tab 112. Figure 7 As shown in, d1 is the distance along the first direction Y between point D and the negative electrode tab 112.

[0206] In some embodiments, when all the negative electrode tabs 112 are located on the same side of the negative electrode current collector 141, the dimension of the negative electrode current collector 141 in 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 7 R2 shown in Figure 7 represents the dimension of the negative electrode current collector 141 in the first direction Y.

[0207] When the negative electrode tabs 112 are located on both sides of the negative electrode current collector 141, the distance between any point (such as point D) in the negative electrode current collector 141 and the negative electrode tab 112 closest to point D in the first direction Y refers to the distance between the negative electrode tab 112 closest to point D in the first direction Y among the negative electrode tabs 112 on both sides and point D.

[0208] In some embodiments, when all the negative electrode tabs 112 are located on both sides of the negative electrode current collector 141, the dimension of the negative electrode current collector 141 in 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.

[0209] As Figure 9 shown, D is any point in the negative electrode current collector 141. D is located at a position between the two edges of the negative electrode current collector 141. The distance between D and the negative electrode tab 112 on the closest side in the first direction Y is d1, and the distance between D and the negative electrode tab 112 on the other side is d2. d2 is greater than d1, and d1 is less than or equal to 300 mm.

[0210] In the embodiments of the present application, by controlling the distance between any point in the negative electrode current collector 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 extraction or insertion is more uniform, and the risk of lithium deposition can be further reduced.

[0211] Optionally, when the battery cell 7 is in a 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 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.

[0212] 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.

[0213] [Stacked electrode assembly]

[0214] As Figure 10 and Figure 11 shown, when the electrode assembly 10 is of a stacked structure, the positive electrode tab 13, the negative electrode tab 14 and the separator 15 are formed into the electrode assembly 10 through a stacking process, and the positive electrode tab 13, the negative electrode tab 14 and the separator 15 are stacked. Figure 10 In 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 direction of the positive electrode tab 13 and the thickness direction of the negative electrode tab 14.

[0215] Along the second direction Z, the distance between any point in the positive electrode current collector portion 131 and the positive electrode tab 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 electrode current collector portion 131 and the positive electrode tab 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.

[0216] The positive electrode tab 111 can be one or more. Along the second direction Z, the distance between any point in the positive electrode current collector portion 131 and the positive electrode tab 111 closest to this point can be the distance along the second direction Z between any point in the positive electrode current collector portion 131, such as point E, and the positive electrode tab 111 closest to point E.

[0217] 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; Optionally, it can be 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.

[0218] 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 it can take into account the improvement of the energy density of the battery cell 7.

[0219] 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.

[0220] 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.

[0221] Optionally, along the first direction Y, the distance between the third point in the positive current collector 131 and the positive 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 the range composed of any two of the above values.

[0222] As Figure 11 shown, when there is one positive tab 111, F is any point in the positive current collector 131, F is located at a position between the two edges of the positive current collector 131, and the distance between F and the positive tab 111 along the first direction Y is f1.

[0223] In some embodiments, when all the positive tabs 111 are located on the same side of the positive current collector 131, the dimension of the positive current collector 131 along 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, when there is one positive tab 111, one positive tab 111 is arranged on one side of the positive current collector 131 along the first direction Y.

[0224] As Figure 12 shown, when there are multiple positive tabs 111, which can be two, the two positive tabs 111 are respectively arranged on both sides of the positive current collector 131 along the first direction Y. F is any point in the positive current collector 131, F is located at a position between the two edges of the positive current collector 131, the distance between it and the positive tab 111 on the closest side along the first direction Y is f1, and the distance between it and the positive tab 111 on the other side is f2. If f2 is greater than f1, then f1 is less than or equal to 300 mm.

[0225] In some embodiments, when there are two positive tabs 111, the two positive tabs 111 are arranged on both sides of the positive current collector 131, the dimension of the positive current collector 131 along the first direction Y is less than or equal to 600 mm, and can be optionally 100 mm to 600 mm, or 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.

[0226] Figure 12 Among them, S1 represents the dimension of the positive current collector portion 131 along the first direction Y.

[0227] When the positive electrode sheet 13 satisfies 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 plating can be reduced.

[0228] Optionally, when the battery cell 7 is in a 100% charged state, the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive 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.

[0229] When the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive current collector portion 131 is within the above range, the energy density of the battery cell 7 can be improved.

[0230] As Figure 13 shown, the negative electrode tab 112 is provided as at least one, and can be selected as at least two. When the negative electrode tab 112 is provided as at least two, at least two negative electrode tabs 112 can be provided on both sides of the negative current collector portion 141.

[0231] Along the second direction Z, the distance between any point in the negative 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 selected as less than or equal to 200 mm. Exemplarily, the distance between any point in the negative 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.

[0232] The negative electrode tab 112 can be one or more. The distance between any point in the negative 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 current collector portion 141, such as point G, and the negative electrode tab 112 closest to point G along the second direction Z.

[0233] 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 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 mm2 Or a range composed of any two of the above values.

[0234] 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 taken into account and improved.

[0235] 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 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 a range composed of any two of the above values.

[0236] When the ratio of the thickness of the single-sided negative electrode film layer 142 to the thickness of the negative electrode current collector 141 is within the above range, the energy density of the battery cell 7 can be improved.

[0237] 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 141.

[0238] 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. 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 a range composed of any two of the above values.

[0239] As Figure 13 shown, when there is one negative electrode tab 112, H is any point in the negative electrode current collector 141. H is located at a position between the two edges of the negative electrode current collector 141, and the distance between it and the negative electrode tab 112 along the first direction H is h1, and h1 is less than or equal to 300 mm.

[0240] In some embodiments, when all the negative electrode tabs 112 are located on the same side of the negative electrode current collector 141, the dimension 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. 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 a range composed of any two of the above values.

[0241] As Figure 14As shown, when there are multiple negative electrode tabs 112, two can be selected. 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, and H is located at a position between the two edges of the negative electrode current collector part 141. The distance between H and the negative electrode tab 112 on the closest side along the first direction H is h1, and the distance between H and the negative electrode tab 112 on the other side is h2. If h2 is greater than h1, then h1 is less than or equal to 300 mm.

[0242] In some embodiments, when all the negative electrode tabs 112 are located on both sides of the negative electrode current collector part 141, the size of the negative electrode current collector part 141 along the first direction Y is less than or equal to 600 mm, and can be selected from 100 mm to 600 mm, or can be selected from 400 mm to 600 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, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm or a range composed of any two of the above values.

[0243] As Figure 14 shown, the size of the negative electrode current collector part 141 along the first direction Y is S2.

[0244] In the embodiments of the present application, by adjusting the distance between any point in the negative electrode current collector part 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 transmission path of electrons 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.

[0245] Regardless of whether the electrode assembly 10 is a wound structure or a stacked structure, in some embodiments, the size of the end face of the positive electrode tab 111 connected to the positive electrode current collector part 131 along the second direction Z is 20 mm to 100 mm. For example, the size of the end face of the positive electrode tab 111 connected to the positive electrode current collector part 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 a range composed of any two of the above values. Figure 11 In the figure, L1 represents the size of the end face of the positive electrode tab 111 connected to the positive electrode current collector part 131 along the second direction Z. When the positive electrode tab 111 meets 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.

[0246] 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 meets 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.

[0247] [Positive electrode plate]

[0248] The positive electrode plate 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 any one or both of the two opposite surfaces of the positive current collector.

[0249] The upper charging limit voltage and the lower discharging cut-off voltage of the battery cell are different according to the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper charging limit voltage can be 3.65 V and the lower discharging cut-off voltage can be 2.0 V. Also, for example, when the phosphate material includes lithium manganese iron phosphate, the upper charging limit voltage can be 4.3 V and the lower discharging cut-off voltage can be 2.0 V. Next, taking the upper charging limit voltage of 3.65 V and the lower discharging cut-off voltage of 2.0 V as an example, the state of the battery cell will be described: 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.

[0250] The battery cell is charged at a constant current charging rate of 0.33C to the upper charging 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 discharging rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0251] In some embodiments, when the battery cell is at 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 3Exemplarily, when the battery cell is at 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.

[0252] When the tap density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. And because the positive electrode active materials in the positive electrode film layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during fast charging. Therefore, by adjusting the tap density of the positive electrode film layer to a reasonable range, the battery cell has both high energy density and high charge rate performance.

[0253] In the embodiments of the present application, the tap 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% state of charge (SOC), and measure the tap density of the positive electrode film layer. For example, take a single-sided coated positive electrode sheet (if it is a double-sided coated electrode 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 part, 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 part) / 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 part, and the tap 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.

[0254] 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 a range composed of any two of the above values.

[0255] 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.

[0256] 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 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.

[0257] 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 a range composed of any two of the above values.

[0258] When the powder compaction density of the positive electrode active material is within the above range under 30,000 N, 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.

[0259] 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. Detection is carried out in accordance with 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, pressurized to 3000 kg (equivalent to 30,000 N), kept under pressure for 30 s, then the pressure is released, kept for 10 s, and then the powder compaction density of the positive electrode active material under the action of 30,000 N is recorded and calculated.

[0260] 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.

[0261] 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.

[0262] In the embodiments of the present application, the specific capacity of the active material has the meaning well-known in the art and can be tested by equipment and methods well-known in the art. The test method of the first Coulomb efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 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 cell is assembled. Under the condition of 23°C ± 2°C, the half-button cell 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 charging specific capacity parameter is obtained by dividing the capacity by the mass of the active material of the electrode sheet.

[0263] In some embodiments, the mass percentage 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 percentage of the lithium-containing phosphate with an olivine structure is less than 100%, the positive electrode active material may further include common positive electrode active materials, for example, it may include but is not limited to at least one of lithium-containing transition metal oxides. Examples of the lithium-containing transition metal oxides may include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their respective modified compounds.

[0264] Optionally, the mass percentage of the lithium-containing phosphate with an olivine structure in the positive electrode active material is 100%.

[0265] 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 covers the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

[0266] By surface coating the phosphate particles with a 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, improving the fast charging ability of the battery and reducing the heat generation of the battery cell.

[0267] 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 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The phosphate particles have relatively excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0268] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The battery cell will be accompanied by the deintercalation and consumption of active ions such as Li during the charging and discharging process, and the molar content of Li in the battery cell is different when it is discharged to different states. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after the charge and discharge cycle. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiment of the present application, the molar content of oxygen O is only a theoretical state value. The release of lattice oxygen will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will fluctuate. The above situations are all within the scope of protection of the present application.

[0269] In some embodiments, the coating layer includes a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor M2 includes one or more elements of Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x2<5, 0<y2<4.

[0270] Exemplarily, the fast ion conductor is a material having a NASICON structure, for example, including one or more of lithium iron titanium phosphate Li2FeTi(PO4)3, lithium iron zirconium phosphate Li2FeZr(PO4)3, and lithium iron tin phosphate Li2FeSn(PO4)3.

[0271] Fast ion conductors with NASICON structures are materials with ultrafast ion conduction capabilities, rich three-dimensional lithium ion diffusion and transmission channels, and have the advantages of high ion conduction efficiency and strong structural stability during multiple lithium removal and insertion processes. Coating fast ion conductors with NASICON structures on the surface of phosphate particles can significantly increase the transmission rate of lithium ions during multiple lithium removal / insertion at the positive terminal, improve the ionic conductivity of the positive electrode active material, and improve the fast charging capability of the battery cell. In addition, it can also increase the gram capacity and the energy density of the corresponding battery cell.

[0272] In some embodiments, the coating layer further includes carbon.

[0273] The carbon element and the fast ion conductor can be arranged in layers. For example, the carbon element 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 coat 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 coat the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0274] 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 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 single battery.

[0275] Specifically, the setting of the carbon coating layer endows the cathode active material of the present application with the following advantages:

[0276] The carbon coating layer in the cathode active material of the present application provides a suitable channel for the transmission of electrons, can significantly improve the conduction rate of electrons during multiple de-lithiation and intercalation processes, improve the electronic conductivity of lithium-containing phosphates, improve the charging ability of the corresponding single battery, and can also improve the energy density.

[0277] The carbon coating layer of the cathode active material of the present application has loose pores, which enables the electrolyte to come into full and effective contact with the lithium-containing phosphates, thereby increasing the transmission rate of lithium ions at the phase interface and improving the charging ability of the single battery.

[0278] Coating a layer of carbon coating layer on the surface of the lithium-containing phosphates can not only improve the conductivity of the lithium-containing phosphates, but also improve the structural stability of the cathode active material, effectively alleviate the iron dissolution phenomenon of the cathode active material during the long-term storage and cyclic use of the single battery, thereby improving the cycle life of the single battery.

[0279] The cathode active material of the present application is based on lithium-containing phosphates, giving full play to the advantages of low cost, high use reliability, and good cycle stability of lithium-containing phosphates. At the same time, the coating layers (fast ion conductor layer and carbon coating layer) are used to solve the disadvantages of poor electronic conductivity and ion conductivity. The single battery prepared from the cathode active material of the present application can improve the energy density of the single battery on the premise of excellent cycle performance.

[0280] In the embodiments of the present 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 discharging the battery cell to 0% state of charge (SOC) and disassembling the positive electrode plate, it is cleaned with DMC and dried, and then after removing impurities by high-temperature calcination, 0.4 g of the positive electrode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0281] In some embodiments, the graphitization degree of the positive electrode active material is from 0.15 to 0.32, and may 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.

[0282] 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.

[0283] In the embodiments of the present application, the higher the graphitization degree of the material, the lower the degree of disorder, and it can be tested according to the general rules of X-ray diffraction analysis method of JIS / K 0131-1996.

[0284] 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 5 m 2 / g to 18 m 2 / g.

[0285] 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 7.5 m 2 / g to 14 m 2 / g.

[0286] 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 a range composed of any two of the above values.

[0287] Exemplarily, the specific surface area of the lithium-containing phosphate in the olivine structure is 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g, 16 m 2 / g, 17 m 2 / g, 18 m 2 / g or a range composed of any two of the above values.

[0288] 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 transport 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 in the olivine structure can be significantly improved, which is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate in the olivine structure, and can improve the rapid charging ability and energy density of the battery cell.

[0289] 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 the equipment and methods well-known in the art. For example, it is detected according to the test standard GB / T 19587-2017. The positive electrode active material is used as a sample, and the specific surface area is tested by a Tri-Star 3020 specific surface area and pore size analyzer of Micromeritics, USA.

[0290] 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.

[0291] 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.

[0292] Exemplarily, the Dv10 of the positive electrode active material can be 0.4 µm, 0.45 µm, 0.5 µm, 0.55 µm, 0.6 µm, 0.65 µm, 0.7 µm, or a range composed of any two of the above values.

[0293] The particle size of the positive electrode active material is relatively small, the lithium insertion / extraction 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 process, so that the performance of the positive electrode active material is stable.

[0294] 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 using equipment 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, etc.

[0295] When the positive electrode active material includes other materials in addition to the lithium-containing 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.

[0296] In some embodiments, the lithium-containing phosphate with an olivine structure is in particulate form. The lithium-containing phosphate with an 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.

[0297] The average particle size of the primary particles is relatively small, the lithium insertion / extraction path of lithium ions in the positive electrode active material is short, and the heat generation is less.

[0298] 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 image 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.

[0299] In some embodiments, the positive electrode film layer further includes one or more of ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium 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 positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0300] Optionally, the ternary material includes Li x3 A y3 Ni a3 Co b3 Mn c M3 (1-a3-b3-c3) Y3 z3 , where 0 < x3 ≤ 2.1, 0 < y3 ≤ 2.1, and 0.9 ≤ x3 + y3 ≤ 2.1, 0 ≤ a3 ≤ 1, 0 ≤ b3 ≤ 1, 0 ≤ c3 ≤ 1, and 0.1 ≤ a3 + b3 + c3 ≤ 1, 1.8 ≤ z3 ≤ 3.5, A includes one or several of Na, K, and Mg, M3 includes one or several 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, Ce, and Y3 includes one or several of O and F.

[0301] Exemplarily, the ternary material includes at least one of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2.

[0302] In some embodiments, the mass content of the lithium supplement agent in the positive electrode film layer is 0.5% to 5%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range composed of any two of the above values. When the mass content of the lithium supplement agent 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.

[0303] The lithium supplement agent can be in the same layer as the positive electrode active material or in different layers. When the lithium supplement agent and the positive electrode active material are in different layers, the lithium supplement agent can be in 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 agent in the lithium supplement layer can be gradually released into the system to make up for the lithium loss in the battery system.

[0304] 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%.

[0305] 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%.

[0306] In some embodiments, the positive current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy foils 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).

[0307] In some embodiments, the ratio of the thickness of the positive current collector to the thickness of the single-sided positive electrode film layer is from 0.05 to 0.3. Exemplarily, the ratio of the thickness of the positive 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.

[0308] When the ratio of the thickness of the positive current collector to the thickness of the single-sided positive electrode film layer is within the above range, the fast charging ability and energy density of the battery cell can be improved.

[0309] In some embodiments, the thickness of the positive current collector is from 10 μm to 15 μm, and may be optionally from 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.

[0310] 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 the battery cell can have a high energy density.

[0311] 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.

[0312] The positive electrode film layer is usually formed by coating a positive electrode paste on a positive electrode current collector, followed by drying and cold pressing. The positive electrode paste is typically 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.

[0313] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the present application embodiment further includes a positive electrode conductive layer disposed on the surface of the positive electrode current collector and sandwiched between the positive electrode current collector and the positive electrode film layer. In some other embodiments, the positive electrode sheet of the present application embodiment further includes a protective layer covering the surface of the positive electrode film layer.

[0314] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode sheet, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell.

[0315] 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.

[0316] When the thickness of the positive electrode conductive layer is within the above range, it can further improve the conductivity of the positive electrode sheet, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell, and can also take into account improving the energy density of the battery cell.

[0317] 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 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.

[0318] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0319] 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.

[0320] 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 of the battery cell.

[0321] 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.

[0322] 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.

[0323] [Negative electrode sheet]

[0324] 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.

[0325] In some embodiments, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 , optionally 1.25 g / cm 3 to 1.36 g / cm 3 . Exemplarily, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 , 1.28 g / cm 3 , 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.36 g / cm 3 or a range composed of any two of the above values.

[0326] 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, and since the negative electrode active materials in the negative 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 heat generation.

[0327] In the embodiments of the present application, the tap density of the negative electrode film layer in the 100% charged state of the battery cell has the meaning well known in the art, and can be detected by 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.

[0328] 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 optionally 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 the range composed of any two of the above values.

[0329] The relatively low powder resistivity of the negative electrode active material results in a relatively low resistance of the negative electrode sheet, and less heat generation of the battery cell.

[0330] 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 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.

[0331] In some embodiments, the tap density of the powder of the negative electrode active material under a pressure of 20,000 N is 1.5 g / cm 3 to 1.85 g / cm 3 , and can be optionally 1.55 g / cm 3 to 1.65 g / cm 3 . Exemplarily, the tap density of the powder of the negative electrode active material under a pressure of 20,000 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 the range composed of any two of the above values.

[0332] When the tap density of the powder of the negative electrode active material under 20,000 N is within the above range, the energy density of the battery cell can be improved, and since the negative electrode active materials 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.

[0333] In the embodiments of the present application, the powder compacting 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 is 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 compacting density of the negative electrode active material under the action of 20000 N is recorded and calculated.

[0334] In some embodiments, the charging specific capacity of the negative electrode active material at a rate of 0.1C is 350 mAh / g to 480 mAh / g. Exemplarily, the charging specific capacity of the negative electrode active material at a rate of 0.1C 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 the range composed of any two of the above values.

[0335] When the charging specific capacity of the negative electrode active material at a rate of 0.1C is within the above range, the energy density of the battery cell is relatively high.

[0336] In the embodiments of the present application, the charging specific capacity of the negative electrode active material at a rate of 0.1C has the meaning well-known in the art and can be detected by equipment 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.

[0337] In some embodiments, the negative electrode active material includes a carbon-based material, and the carbon-based material has high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass ratio 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%.

[0338] 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 cycle performance of the battery cell is relatively excellent.

[0339] 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.

[0340] When the graphitization degree of the graphite particles is within the above range, the electrical conductivity of the graphite particles is relatively excellent, which 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.

[0341] 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, and amorphous carbon refers to a transition carbon material with a very low degree of graphitization crystallization, similar to an 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.

[0342] 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, so that the number of sites where lithium ions can be deintercalated is more, making the electrical conductivity of the carbon coating layer relatively excellent, and can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0343] 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.

[0344] 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 sheet and the heat generation of the battery cell.

[0345] 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 then forming a carbon coating layer on at least part of the surface of the artificial graphite particles after carbonization treatment.

[0346] 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 coal tar pitch and petroleum pitch is below 250°C.

[0347] Optionally, the carbonization temperature is from 700°C to 1800°C. Optionally, the carbonization temperature is from 1000°C to 1300°C. When the carbonization temperature is within a suitable range, the organic carbon source can be carbonized, and a coating layer containing amorphous carbon is formed on at least a part of the surface of the artificial graphite.

[0348] Optionally, the carbonization time is from 1 h to 6 h.

[0349] 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.

[0350] In some embodiments, the negative electrode active material may further include a silicon-based material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0351] Optionally, based on the mass of the negative electrode active material, the mass content of silicon element in the silicon-based material is from 0.3% to 10.0%, and may be from 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.

[0352] 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 improved, and the energy density of the battery cell is improved.

[0353] 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.

[0354] 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.

[0355] The qualitative and quantitative analysis of various substances or elements in this application 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 analysis, or several detection methods can be used in combination for qualitative or quantitative determination.

[0356] For example, this application can combine the General Rules for X-ray Diffraction Analysis of JIS / K0131-1996 to conduct X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0357] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). There are gaps between flaky 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 the XRD spectrum of artificial graphite only has 2H phase.

[0358] In the embodiment of this application, the negative electrode film layer includes at least one layer of film layer, which can be a single layer of film layer or at least two layers of film layer. Optionally, the negative electrode film layer includes at least two layers of film layer.

[0359] When the negative electrode film layer adopts a single layer of film layer, the negative electrode active material in the negative electrode film layer includes carbon-based material, and optionally also includes silicon-based material. When adopting a single layer of film layer, the volume average particle diameter Dv50 of the negative electrode active material is 8.2 μm to 13.5 μm. Exemplarily, the volume average particle diameter 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.

[0360] When the negative electrode film layer adopts at least two layers of film layer, the negative electrode active material in the negative electrode film layer includes carbon-based material, and optionally also includes silicon-based material. The silicon-based material can be located in one of the at least two layers of film layer or in at least two of the at least two layers of film layer. The negative electrode film layer can include two layers of film layer, three layers of film layer, four layers of film layer, or even more layers of film layer.

[0361] 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 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 portion. 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 may be the same or different.

[0362] The interface between the first negative electrode film layer and the second negative electrode film layer may be regular or irregular, and is optionally irregular.

[0363] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0364] The negative electrode film layer includes at least two film layers. Layered 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.

[0365] 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.

[0366] The difference in particle size 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 sheet.

[0367] Optionally, the negative 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 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.

[0368] When the volume average particle size Dv50 of the negative active material in the first negative electrode film layer is within the above range, on the one hand, 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.

[0369] Optionally, the negative 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 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.

[0370] When the volume average particle size Dv50 of the negative active material in the second negative electrode film layer is within the above range, on the one hand, 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 further hand, the cooperation of the negative active material in the second negative electrode film layer and the negative active material in the first negative electrode film layer within the above volume average particle size range is beneficial to constructing the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, and improving the fast charging performance of the battery cell.

[0371] 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 test method for the volume average particle size Dv50 of the positive electrode active material described above.

[0372] 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, which improves the energy density of the battery cell. The first negative electrode film layer is relatively sparsely packed with richer pores, which can improve 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.

[0373] 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 , such as 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.

[0374] 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 , such as 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.

[0375] 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 the 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 BET.

[0376] 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.

[0377] 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.

[0378] 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 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 gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be regulated and increased, the tortuosity of lithium ion transport can be reduced, and the fast charging ability of the battery cell can be improved.

[0379] In the embodiments of the present application, 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,

[0380] The specific steps of the BOL full charge test are as follows: At 25 °C, charge at a charging rate of 0.33C of the nominal capacity of the battery to 3.65 V, then charge at a constant voltage of 3.65 V to 0.05C, stand for 10 min, then discharge at a discharging rate of 0.33C 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 0.33C of the nominal capacity to 3.65 V, and then charge at a constant voltage of 3.65 V to 0.05C to obtain the BOL full charge state. In the BOL full charge state, disassemble the negative electrode plate, use a tomographic scanning electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode plate, distinguish the two regions according to the interface between the first negative electrode film layer and the second negative electrode film layer, measure the thicknesses of the two respectively. For example, measure the thicknesses of 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 of 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.

[0381] In some embodiments, after the battery cell undergoes a full charge test at the end of its life (End Of Life, EOL), 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.

[0382] In some embodiments, after the battery cell undergoes a full charge test at the end of its life (End Of Life, EOL), 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.

[0383] 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,

[0384] 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 nominal capacity until 3.65V, then perform constant voltage charging at 3.65V until 0.05C, let it stand for 10 min, then discharge at a discharge rate of 0.33C until 2.0V, and let it stand for 10 min. 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 plate, and use a tomography scanning electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode plate. Distinguish the regions of the first negative electrode film layer and the second negative electrode film layer according to the interface between them, 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.

[0385] In some embodiments, when the negative electrode film layer adopts a single-layer film layer (different from the above-mentioned 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 an 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, increase the intercalation and deintercalation rate of lithium ions, and improve 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 (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0386] 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, it can make the number of free-moving lithium ions in the negative electrode film layer relatively large, further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0387] Exemplarily, the lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, which 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.

[0388] 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 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.

[0389] 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.

[0390] Optionally, the first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. Further optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0391] The mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides a relatively larger number of freely movable lithium ions for the second negative electrode film layer, which can further improve the fast charging performance of the battery cell.

[0392] Optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range composed of any two of the above values. The lithium element in the first lithium-containing binder can exist in the form of ions, which can increase the number of 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, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0393] 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.

[0394] 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.

[0395] 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 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.

[0396] 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.

[0397] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0398] 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 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.

[0399] 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.

[0400] 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.

[0401] In some embodiments, the first negative electrode film layer further includes a negative electrode binder, and the second negative electrode film layer further includes a negative electrode binder. The negative electrode binder in the first negative electrode film layer and the negative electrode binder in the second negative electrode film layer each independently include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0402] 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.

[0403] In some embodiments, the negative electrode film layer may optionally further 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%.

[0404] In some embodiments, the negative electrode film layer may optionally further include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0405] In some embodiments, the negative electrode film layer may optionally further include other additives. As an example, the other additives may include thickeners, dispersants, 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%.

[0406] 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).

[0407] 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.

[0408] 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 high energy density.

[0409] 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.

[0410] The negative electrode film layer is usually formed by coating a negative electrode paste on a negative electrode current collector part and then drying and cold pressing. The negative electrode paste 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.

[0411] The negative electrode plate does not exclude other additional functional layers in addition to 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.

[0412] 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.

[0413] In some embodiments, the thickness of the negative electrode conductive layer is from 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.

[0414] 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.

[0415] 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 the testing method of the negative electrode conductive layer in the foregoing can be adopted.

[0416] 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.

[0417] In some embodiments, the negative electrode conductive layer may also optionally include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethylcellulose (CMC), PTC thermistor materials, etc.

[0418] 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 the range composed of any two of the above values.

[0419] 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.

[0420] 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 the range composed of any two of the above values.

[0421] 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.

[0422] 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 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 the range composed of any two of the above values.

[0423] 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 for fast charging.

[0424] 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, calculate the capacity of the negative electrode film layer per unit area and the capacity of the positive electrode film layer per unit area respectively, and then calculate the ratio of the two to obtain the CB value.

[0425] Specifically, taking the upper limit voltage of battery charging as 3.65V and the cut-off voltage of battery discharge as 2.0V as an example for illustration,

[0426] 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 the PRS340 / 11-119-11 Braun glove box, take the positive electrode plate, assemble it into a CR2430 type half-button battery of positive electrode-lithium sheet, and the area of the positive electrode plate used is amm 2, where the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, the assembled coin cell is left standing for 3 h, and the test is carried out at 25°C. First, charge de-lithiation is carried out at a rate of 0.1C in the voltage range of 2.0V to 3.65V, and then discharge lithiation is carried out at a rate of 0.05C to 2.0V. After 2 cycles, the discharge capacity of the second cycle is recorded as Y mAh. The actual length of the positive electrode tab of the battery design is b mm, the width is c mm, and the number of sides of the positive active material coated on the positive current collector is d. Then, the capacity of the positive electrode film layer per unit area = Y / (a × b × c × d).

[0427] Specifically, the capacity of the negative electrode film layer per unit area refers to the actual lithiation 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 tab, and assemble a CR2430 type coin cell of negative electrode - lithium sheet. The area of the negative electrode tab used is f mm 2 , where the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, the assembled coin cell is left standing for 3 h, and the test is carried out at 25°C. First, discharge lithiation is carried out at a rate of 0.1C in the voltage range of 2V - 0V, and then charge de-lithiation is carried out at a rate of 0.05C to 2V. After 2 cycles, the discharge capacity of the second cycle is recorded as Z mAh. The actual length of the negative electrode tab of the battery design is h mm, the width is i mm, and the number of sides of the negative active material coated on the negative current collector is d. Then, the lithiation capacity of the negative electrode = Z / (f × h × i × d).

[0428] In the embodiments of the present application, the separator includes a base film with a porous structure.

[0429] 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.

[0430] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0431] 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.

[0432] When the porosity of the base film in the embodiment of the present application is within the above range, the migration ability of lithium ions in the isolation film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0433] In the embodiments of the present application, porosity refers to the percentage of the pore volume in the separator to the total volume of the separator. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin separator for battery monomers". It should be noted that the actual test process can be slightly different from the standard test process according to the difference in test instruments, test errors, and in order to eliminate the test influence on porosity as much as possible, so as to obtain a more accurate test value.

[0434] In some embodiments, the thickness of the base film is 6 μm to 12 μm, and optionally 6 μm to 9 μm. Exemplarily, the thickness of the base film is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range consisting of any two of the above values.

[0435] When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell and thus reduce heat generation.

[0436] In the embodiment of the present application, the isolation film may be a base film, and optionally, the isolation film further comprises a functional layer disposed on at least one side of the base film, and the functional layer may comprise inorganic particles to improve the heat resistance of the isolation film. Optionally, the functional layer is disposed on both sides of the base film.

[0437] In some embodiments, the functional layer includes a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer includes first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer includes composite particles, the composite particles include second inorganic particles and multiple non-fluoropolymer particles, the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles.

[0438] The first functional layer and the second functional layer have good heat resistance and can improve the heat resistance of the isolation film.

[0439] Optionally, the first functional layer may include a binder, optionally including at least one of a fluorine-containing binder or a polyacrylic binder, such as polyvinylidene fluoride.

[0440] Optionally, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide. The first inorganic particles can improve the heat resistance of the first functional layer.

[0441] 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 meaning well-known in the art and equipment 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 the separator film is dried and 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.

[0442] 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 copolymer includes an acrylate-acrylonitrile-acrylamide-acrylonitrile copolymer. The acrylate copolymer has excellent adhesion performance 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.

[0443] 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 transmission of lithium ions, improving the ionic conductivity of the separator film. In addition, 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, improving the kinetic performance of the battery cell and 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.

[0444] 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.

[0445] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, and optionally 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or a range composed of any two of the above values. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0446] In the embodiments of the present application, the average particle size of the second inorganic particles 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, after obtaining the separator and drying the separator as a sample, the separator is cut by 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 separator, and 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.

[0447] In some embodiments, the ionic conductivity of the separator is 0.3 mS / cm to 0.6 mS / cm. Exemplarily, the ionic conductivity of the separator 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 composed of any two of the above values.

[0448] When the ionic conductivity of the separator is within the above range, the migration ability of lithium ions in the separator can be further improved, and the fast charging performance of the battery cell can be improved.

[0449] In the embodiments of the present application, the ionic conductivity of the separator 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,

[0450] Prepare a 2025 type button battery for testing: In a vacuum glove box, put a lithium sheet into the negative electrode case of the battery, add 150 μL of electrolyte thereto, and the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then put the separator (with an area of 3.14 cm 2 , a thickness of 12 μm) so that it is close to the lithium sheet, add another 25 μL of electrolyte, and finally place the positive electrode sheet (the positive electrode sheet can be the positive electrode sheet in Example 1) thereon and seal it. Take out the assembled button battery from the vacuum glove box and place it for 24 h for the next test.

[0451] Test: Conduct the test on an electrochemical workstation within the frequency range of 10 -1 ~10 6 Hz to obtain the separator resistance Rb, and calculate the ionic conductivity σ (unit: mS / cm) through the following formula:

[0452] σ = L / (R b × S)

[0453] where: R b is the separator resistance, and L and S are the thickness and area of the separator to be measured, respectively.

[0454] [Electrolyte]

[0455] In some embodiments, the battery cell further includes an electrolyte.

[0456] 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.

[0457] In the embodiments of the present application, the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, and can 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.

[0458] 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.

[0459] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and can be detected by using equipment and methods well-known in the art, for example, tested with reference to the industry standard HG-T 4067-2015.

[0460] In some embodiments, the viscosity of the electrolyte at room temperature is from 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 a range composed of any two of the above values.

[0461] 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 can improve the fast charging performance of the battery cell.

[0462] 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.

[0463] In some embodiments, the density of the electrolyte at room temperature, such as 25 °C, is from 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.

[0464] 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 can improve the fast charging performance of the battery cell.

[0465] 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.

[0466] 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.

[0467] 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%, and 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.

[0468] 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.

[0469] In some embodiments, the chain carboxylic acid ester solvent includes a compound represented by Formula I,

[0470] Formula I,

[0471] In Formula I,

[0472] R1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group,

[0473] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0474] The above chain carboxylic acid ester solvent has a high conductivity, which is beneficial to improving the fast charging ability of the battery monomer.

[0475] Optionally, R1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0476] Optionally, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0477] 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.

[0478] 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.

[0479] Exemplarily, the chain carboxylic acid ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8,

[0480]

[0481] In some embodiments, the organic solvent further includes carbonate solvents.

[0482] Optionally, the carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Further optionally, the carbonate solvents include one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate. The above carbonate solvents and chain carboxylic acid 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.

[0483] Further optionally, the mass content of the carbonate solvents in the organic solvent is 30% to 70%, and can be 30% to 50%. Exemplarily, the mass content of the carbonate solvents 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 solvents 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.

[0484] Exemplarily, the carbonate solvents include one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate, and the mass content of the carbonate solvents is 30% to 50%.

[0485] In some embodiments, the electrolyte further contains additives. The additives can include negative electrode film-forming additives, or can include positive electrode film-forming additives, or can also include additives that can improve certain performance of the battery, 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.

[0486] In some embodiments, the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives, and can be 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 improving the fast charging performance of the battery monomer and improving the cycle performance.

[0487] 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.

[0488] The additives with the above mass contents 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.

[0489] Exemplarily, the carbonate additives include one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0490] 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 methylene methylene disulfonate (MMDS).

[0491] Optionally, the lithium salt additives include one or more of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate (LiBF4), and lithium bis(oxalate) borate (LiBOB).

[0492] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 9%, and optionally 2% to 6%.

[0493] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 4%, and optionally 0.5% to 3%.

[0494] 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%.

[0495] 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%.

[0496] 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 (LiPF6). 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.

[0497] Optionally, the fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0498] Optionally, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6). 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 (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0499] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is from 0.4 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.7 mol / L.

[0500] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.5 mol / L.

[0501] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.8 mol / L.

[0502] Optionally, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF6 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 LiPF6 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.

[0503] 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 / T020-1996 "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, freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully 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, and the free electrolyte obtained from the battery can be taken as a sample, and the ion chromatography analysis method is used for detection.

[0504] 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 / T9722-2006 "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, freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully 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, and the free electrolyte obtained from the battery can be taken as a sample, and the ion chromatography analysis method is used for detection.

[0505] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified. Chain carboxylic acid ester solvents and carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as constituent components of the organic solvent. Based on the mass of the organic solvent being 100%, the mass content of each component is calculated.

[0506] Vinylene carbonate additives (such as vinylene carbonate, fluoroethylene carbonate), sulfur-containing additives, and lithium salt additives are used as additives in the electrolyte. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0507] In some embodiments, the battery cell satisfies: 2.45 g / Ah ≤ d / A ≤ 3.5 g / Ah, and 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.

[0508] d / A can reflect the liquid retention ability of the electrolyte. When d / A is within the above range, the electrolyte can play a good 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.

[0509] 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 using equipment and methods well-known in the art. For example, taking the upper charging voltage of the battery as 3.65 V and the discharge cut-off voltage of the battery as 2.0 V as an example in accordance with GB / T 31486-2015 "Performance Requirements and Test Methods for Power Batteries for Electric Vehicles".

[0510] At 25°C, the battery cell is charged to 3.65 V at 0.33 C, then charged at a constant voltage until 0.05 C, and then discharged at a constant current of 0.33 C to 2.0 V. The discharged capacity A is used as the denominator. The battery cell is weighed as M0, and then the positive electrode plate, negative electrode plate, separator, and electrolyte are disassembled. The free electrolyte is placed in a bag. All the above solid components are placed in an oven at 60°C and baked for more than 4 hours (including but not limited to the positive electrode plate, negative electrode plate, separator, and other mechanical parts of the disassembled battery cell that contribute to M0), and then all the components of the battery cell are weighed 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.

[0511] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly by a winding process and / or a stacking process.

[0512] In some embodiments, the battery cell 7 can include a housing 20.

[0513] In some embodiments, the housing 20 of the battery cell 7 can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The 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).

[0514] The housing 20 has a hollow structure, and the housing 20 can be used to encapsulate the above-mentioned electrode assembly 10 and the electrolyte.

[0515] 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 an electrode assembly 10 by a winding process and / or a stacking process, the electrode assembly 10 is placed in the housing 20, the electrolyte is injected after drying, and after processes such as vacuum packaging, standing, formation, and shaping, the battery cell 7 is obtained.

[0516] 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.

[0517] 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 rectangular parallelepiped structure, a rectangular parallelepiped housing can be selected. Optionally, both the electrode assembly 10 and the housing body 21 are rectangular parallelepiped structures.

[0518] In some embodiments, the base material of the housing body 21 includes steel, and the mechanical strength of the steel is relatively high, not easily deformed, and can improve the use 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.

[0519] Optionally, the thickness of the housing 21 is from 0.1 mm to 0.5 mm, and may be optionally from 0.2 mm to 0.35 mm. Exemplarily, the thickness of the housing 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm or a range composed of any two of the above values. When the thickness of the housing 21 is within the above range, the mechanical strength of the housing 21 is relatively high, which can improve the reliability of use of the battery cell 7; and the housing 21 occupies less space and has more internal space, which is beneficial to improving the energy density of the battery cell 7.

[0520] Viewed from the outer shape of the electrode assembly 10, the electrode assembly 10 includes a main body portion 12 and tab portions 11. The tab portions 11 include a positive tab 111 and a negative tab 112, and the positive tab 111 and the negative tab 112 protrude from the main body portion 12.

[0521] The positive tab 111 and the negative tab 112 can extend from the same side of the main body portion 12, or can extend from opposite sides respectively.

[0522] Optionally, the number of positive tabs 111 located on the same side of the main body portion 12 is at least one, and may be optionally at least two. At least two positive tabs 111 can increase the current-carrying capacity of the positive tab 111.

[0523] Optionally, the number of negative tabs 112 located on the same side of the main body portion 12 is at least one, and may be optionally at least two. At least two negative tabs 112 can increase the current-carrying capacity of the negative tab 112.

[0524] In some embodiments, the battery cell 7 further includes a positive terminal 31, and the positive terminal 31 is electrically connected to the positive tab 111. Optionally, the positive terminal 31 and the positive tab 111 are welded. The positive terminal 31 and the positive tab 111 can be connected through an adapter, or may not use an adapter; optionally, the positive terminal 31 and the positive tab 111 do not use an adapter, that is, the positive terminal 31 and the positive 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.

[0525] 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 a negative electrode tab, the negative terminal 32 is a positive terminal.

[0526] Optionally, the number of positive terminals 31 on the same side of the main body 12 is at least one, and can be optionally at least two. At least two positive terminals 31 can increase the current-carrying capacity of the positive terminals 31.

[0527] Further optionally, the current-carrying area of a single positive terminal 31 is 150 mm 2 to 1000 mm 2 , and can be optionally 200 mm 2 to 1000 mm 2 . The current-carrying area of the positive terminals 31 on one side refers to the sum of the current-carrying areas of all the positive terminals 31 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 cap 22.

[0528] Exemplarily, the current-carrying area of the positive terminals 31 on one side 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.

[0529] Optionally, the number of negative terminals 32 on the same side of the main body 12 is at least one, optionally at least two. The at least two negative terminals 32 can increase the over-current capacity of the negative terminals 32.

[0530] Further optionally, the over-current area of the single-sided negative terminal 32 is 150 mm 2 to 1000 mm 2 , optionally 200 mm 2 to 1000 mm 2 The over-current area of the single-sided negative terminal 32 refers to the sum of the over-current areas of all the negative terminals 32 on the same side of the main body 12. The over-current 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.

[0531] Exemplarily, the over-current 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 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.

[0532] As Figure 15 shown, in some embodiments of the present application, the battery cell 7 according to the implementation manner 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.

[0533] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, in parallel, or in a combination of series and parallel. A combination of series and parallel 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 combination of series and parallel together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodating portion 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 combination of series and parallel to form battery modules 6, and then the multiple battery modules 6 are connected in series, in parallel, or in a combination of series and parallel to form a whole and are accommodated in the accommodating portion. Optionally, the battery module 6 can also include an accommodating portion with an accommodating space, and the multiple battery cells 7 are accommodated in this accommodating space.

[0534] As Figure 16 shown, in some embodiments, the above-mentioned battery module 6 can also be assembled into a battery pack 2, and the number of battery modules 6 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 either the battery module 6 or the battery pack 2.

[0535] The battery pack 2 can include a box body 5 and a plurality of battery modules 6 disposed in the box body 5. The box body 5 includes a first box body portion 5a and a second box body portion 5b. The box body 5 has an accommodating space 5c. The first box body portion 5a is used to cover the second box body portion 5b and form a closed space for accommodating the battery module 6. The plurality of battery modules 6 can be arranged in the box body 5 in any manner.

[0536] The first box body portion 5a and the second box body portion 5b are covered with each other, and the first box body portion 5a and the second box body portion 5b jointly define an accommodating space 5c for accommodating the battery cells. The second box body portion 5b can be a hollow structure with one end open, and the first box body portion 5a is a plate-like structure. The first box body portion 5a covers the opening side of the second box body portion 5b to form the box body 5 with the accommodating space 5c. The first box body portion 5a and the second box body portion 5b can also both be hollow structures with one side open, and the opening side of the first box body portion 5a covers the opening side of the second box body portion 5b to form the box body 5 with the accommodating space 5c. Of course, the first box body portion 5a and the second box body portion 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0537] To improve the sealing performance after the connection between the first box body portion 5a and the second box body portion 5b, a sealing member can also be provided between the first box body portion 5a and the second box body portion 5b, such as sealant, sealing ring, etc.

[0538] Assume that the first box body portion 5a covers the top of the second box body portion 5b. The first box body portion 5a can also be called the upper box cover, and the second box body portion 5b can also be called the lower box body.

[0539] 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% SOC, the temperature of the external environment where the battery pack 2 is located is 30°C.

[0540] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% SOC to 80% SOC, the temperature of the external environment where the battery pack 2 is located is 30°C.

[0541] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% SOC to 80% SOC, it includes multiple charging steps, and the difference between the maximum SOC of any charging step and the maximum SOC of its adjacent charging step is less than or equal to 5% SOC, such as 1% SOC, 1.5% SOC, 2% SOC, 2.5% SOC, 3% SOC, 3.5% SOC, 4% SOC, 4.5% SOC, 5% SOC, or a range composed of any two of the above values.

[0542] The charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% SOC to 40% SOC includes multiple charging steps. For any charging step, it can be charged at any rate between 5C and 10C, and 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.

[0543] The charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 40% SOC to 80% SOC also includes multiple charging steps. The charging rate of any charging step is less than the charging rate of any charging step from 10% SOC to 40% SOC, and the charging rate of the step when charging to 80% SOC is any value between 2.5C and 5C. For example, it can be 2.7C.

[0544] Exemplarily, the charging steps of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be carried out as follows:

[0545] Constant current charging at 5.0C from 10% SOC to 15% SOC,

[0546] Constant current charging at 5.0C from 15% SOC to 20% SOC,

[0547] Constant current charging at 5.0C from 20% SOC to 25% SOC,

[0548] Charge from 25% SOC to 30% SOC at a constant current of 5.0C,

[0549] Charge from 30% SOC to 35% SOC at a constant current of 5.0C,

[0550] Charge from 35% SOC to 40% SOC at a constant current of 5.0C,

[0551] Charge from 40% SOC to 45% SOC at a constant current of 4.6C,

[0552] Charge from 45% SOC to 50% SOC at a constant current of 4.3C,

[0553] Charge from 50% SOC to 55% SOC at a constant current of 4.0C,

[0554] Charge from 55% SOC to 60% SOC at a constant current of 3.7C,

[0555] Charge from 60% SOC to 65% SOC at a constant current of 3.4C,

[0556] Charge from 65% SOC to 70% SOC at a constant current of 3.1C,

[0557] Charge from 70% SOC to 75% SOC at a constant current of 2.9C,

[0558] Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0559] In some embodiments, the charging time of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, and can be 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

[0560] In some embodiments, the volumetric energy density of the battery cell is from 390 Wh / L to 500 Wh / L, and may be optionally from 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 a range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0561] 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 charging limit voltage of the battery as 3.65 V and the discharge cut-off voltage of the battery as 2.0 V as an example for illustration,

[0562] The battery cell is placed at 25 °C and charged at a constant current of 0.33 C to 3.65 V, then charged at a constant voltage to 0.05 C, and discharged at a constant current of 0.33 C to 2.0 V. 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 excluding the insulating film outside the outer shell), and calculate the volume V0 of the single battery cell, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0563] Electrical device

[0564] The second aspect of the embodiments of the present application provides an electrical device. 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, 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, a spaceship, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy, 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 planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices.

[0565] The electrical device can select battery cells, battery modules, or battery packs according to its usage requirements.

[0566] Figure 17 It is a schematic diagram of the electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the electrical device 1, a battery pack or a battery module can be adopted.

[0567] A battery pack 2 is arranged inside the electrical device 1. The battery pack 2 can be arranged at the bottom, head, or 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 supply of the electrical device 1 and can also be used as the driving power supply of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1.

[0568] 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.

[0569] Another example of an electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires a thin and light design and can use battery cells as the power source.

[0570] The charging process of the electrical device can select the following charging methods:

[0571] Charge from 10% SOC to 15% SOC at a constant current of 5.0C,

[0572] Charge from 15% SOC to 20% SOC at a constant current of 5.0C,

[0573] Charge from 20% SOC to 25% SOC at a constant current of 5.0C,

[0574] Charge from 25% SOC to 30% SOC at a constant current of 5.0C,

[0575] Charge from 30% SOC to 35% SOC at a constant current of 5.0C,

[0576] Charge from 35% SOC to 40% SOC at a constant current of 5.0C,

[0577] Charge from 40% SOC to 45% SOC at a constant current of 4.6C,

[0578] Charge from 45% SOC to 50% SOC at a constant current of 4.3C,

[0579] Charge from 50% SOC to 55% SOC at a constant current of 4.0C,

[0580] Charge from 55% SOC to 60% SOC at a constant current of 3.7C,

[0581] Charge from 60% SOC to 65% SOC at a constant current of 3.4C,

[0582] Charge from 65% SOC to 70% SOC at a constant current of 3.1C,

[0583] Charge from 70% SOC to 75% SOC at a constant current of 2.9C,

[0584] Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0585] 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.

[0586] 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 the instruments used in the examples are all commercially available.

[0587] Example 1-1

[0588] 1. Preparation of the positive electrode sheet

[0589] The positive electrode sheet includes a positive electrode current collector, a positive electrode conductive layer on the positive electrode current collector, and a positive electrode film layer. The positive electrode current collector is an aluminum foil with a thickness of 10 μm.

[0590] 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 it on the surface of the current collector and drying. The thickness is 1 μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0591] The positive electrode film layer is formed by uniformly coating a positive electrode slurry (with N-methylpyrrolidone NMP as the solvent) on the surface of the positive electrode conductive layer, followed by drying and cold pressing. The positive electrode film layer comprises a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black in a weight ratio of 97:2:1.

[0592] The positive electrode active material includes lithium iron phosphate and a coating layer. The coating layer coats the surface of the lithium iron phosphate and comprises lithium titanium iron phosphate Li2FeTi(PO4)3 and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0593] 2. Preparation of the negative electrode plate

[0594] 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.

[0595] 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 it on the surface of the negative electrode current collector and drying. 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%.

[0596] The negative electrode film layer is formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer, followed by drying and cold pressing.

[0597] 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.

[0598] The first negative electrode film layer comprises graphite particles, a conductive agent acetylene black, a first lithium-containing binder (a 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%), a negative electrode binder styrene-butadiene rubber, and a 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. The carbon coating layer coats the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0599] 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, and the carbon coating layer covers the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0600] 3. Separator

[0601] The separator includes a base film, and the base film is a 7-μm polyethylene film layer with a porosity of 42%.

[0602] 4. Preparation of electrolyte

[0603] The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0604] The organic solvent includes 60% chain carboxylic ester solvent (ethyl acetate) and 40% carbonate solvent (30% ethylene carbonate EC, and the rest is dimethyl carbonate). The mass content of each component in the organic solvent is calculated based on the mass of the organic solvent.

[0605] Based on the mass of the electrolyte, the mass content of the additive is 6.5%, and it 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.

[0606] The lithium salt includes 1 mol / L lithium hexafluorophosphate LiPF6.

[0607] 5. Preparation of battery cell

[0608] Stack the above-mentioned positive electrode plate, separator, and negative electrode plate in sequence, so that the separator is between the positive electrode plate and the negative electrode plate to play a separation role, and obtain an electrode assembly through the stacking process; place the electrode assembly in an outer packaging shell, inject the electrolyte after drying, and obtain a battery cell through processes such as vacuum packaging, standing, forming, and shaping.

[0609] Example 1-2

[0610] A battery cell is prepared by a method similar to that of Example 1-1. Different from Example 1-1, the size of the positive current collector part along the first direction and the size of the negative current collector part along the first direction are adjusted.

[0611] Example 1-3 and Example 1-4

[0612] The battery monomer was prepared by 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.

[0613] 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.

[0614] Comparative Example 1-1

[0615] The battery monomer was prepared by a method similar to that of Example 1-1. Different from Example 1-1, the size of the positive current collector along the first direction and the size of the negative current collector along the first direction were adjusted.

[0616] Comparative Examples 1-2 and 1-3

[0617] The battery monomer was prepared by 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.

[0618] 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.

[0619] Comparative Example 1-4

[0620] The battery monomer was prepared by a method similar to that of Example 1-1. Different from Example 1-1, the size of the positive current collector along the second direction was adjusted to 380 mm, and the size of the negative current collector along the second direction was adjusted to 385 mm.

[0621] Performance Test

[0622] 1. Lithium deposition area test of the battery monomer

[0623] After each battery pack of the examples was cycled 20 times according to its respective charge-discharge strategy, it was fully charged to 100% SOC according to the corresponding charging strategy. The negative electrode plate in the battery pack was disassembled, the negative electrode plate was unfolded, the lithium deposition area (grayish-white area) was observed, and the lithium deposition area was measured. The lithium deposition degree was as follows:

[0624] No lithium deposition: Lithium deposition area < 0.05%.

[0625] Slight lithium deposition: Lithium deposition area < 2%.

[0626] Severe lithium deposition: Lithium deposition area ≥ 2%.

[0627] The battery monomer was charged at a temperature of 30°C in the external environment. The charging steps included the following steps:

[0628] Charge from 0% SOC to 5% SOC at a constant current of 5.0 C;

[0629] Charge from 5% SOC to 10% SOC at a constant current of 5.0 C;

[0630] Charge from 10% SOC to 15% SOC at a constant current of 5.0 C;

[0631] Charge from 15% SOC to 20% SOC at a constant current of 5.0 C;

[0632] Charge from 20% SOC to 25% SOC at a constant current of 5.0 C;

[0633] Charge from 25% SOC to 30% SOC at a constant current of 5.0 C;

[0634] Charge from 30% SOC to 35% SOC at a constant current of 5.0 C;

[0635] Charge from 35% SOC to 40% SOC at a constant current of 5.0 C;

[0636] Charge from 40% SOC to 45% SOC at a constant current of 4.6 C;

[0637] Charge from 45% SOC to 50% SOC at a constant current of 4.3 C;

[0638] Charge from 50% SOC to 55% SOC at a constant current of 4.0 C;

[0639] Charge from 55% SOC to 60% SOC at a constant current of 3.7 C;

[0640] Charge from 60% SOC to 65% SOC at a constant current of 3.4 C;

[0641] Charge from 65% SOC to 70% SOC at a constant current of 3.1 C;

[0642] Charge from 70% SOC to 75% SOC at a constant current of 2.9 C;

[0643] Charge from 75% SOC to 80% SOC at a constant current of 2.7 C;

[0644] Charge from 80% SOC to 85% SOC at a constant current of 1.8 C;

[0645] Charge from 85% SOC to 90% SOC at a constant current of 1.3 C;

[0646] Charge from 90% SOC to 95% SOC at a constant current of 0.7 C;

[0647] Charge from 95% SOC to 98% SOC at a constant current of 0.33 C;

[0648] Charge from 98% SOC to 100% SOC at a constant current of 0.1C.

[0649] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0650] The discharging strategy is as follows: discharge at a constant current of 0.33C until the cut-off voltage, such as 2.0V.

[0651] Test results

[0652] The test results are shown in Table 1.

[0653] Table 1

[0654]

[0655] One positive electrode tab is provided on each side of the positive electrode current collector part in Table 1, and one negative electrode tab is provided on each side of the negative electrode current collector part.

[0656] For Examples 1-1 to Comparative Example 1-3, the dimension of the positive electrode current collector part along the second direction Z is 300mm, and the dimension of the negative electrode current collector part along the second direction Z is 305mm. For any point in the positive electrode current collector part, 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 electrode current collector part, 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.

[0657] As Figure 12 shown, the dimension of the positive electrode current collector part along the first direction Y is S1. For any point in the positive electrode current collector part, such as point F, the distance f1 between the point and the nearest positive electrode tab along the first direction Y is less than or equal to 300mm.

[0658] For example, in Example 1-1, the distance between any point in the positive electrode current collector part and the nearest positive electrode tab along the first direction Y is less than or equal to 450mm / 2 = 225mm.

[0659] In Comparative Example 1-1, the distance between any point in the positive electrode current collector part and the nearest positive electrode tab along the first direction Y is less than or equal to 780mm / 2 = 390mm, which is greater than 300mm.

[0660] As Figure 14 shown, the dimension of the negative electrode current collector part along the first direction Y is S2. For any point in the negative electrode current collector part, such as point H, the distance h1 between the point and the nearest negative electrode tab along the first direction Y is less than or equal to 300mm.

[0661] For example, in Example 1-1, the distance between any point in the positive electrode current collector part and the nearest positive electrode tab along the first direction Y is less than or equal to 450mm / 2 = 225mm.

[0662] In Comparative Examples 1-4,

[0663] For any point in the positive current collector portion, such as Figure 12 the distance e along the second direction Z from point E in it to the positive tab closest to it is greater than 300 mm.

[0664] For any point in the negative current collector portion, such as Figure 14 the distance g along the second direction Z from point G in it to the negative tab closest to it is greater than 300 mm.

[0665] In Comparative Example 1-1, the tab spacing is relatively large, resulting in a relatively long electron transmission path, uneven current distribution, and easier lithium deposition. In Comparative Examples 1-2 and 1-3, although the tab setting 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 relatively long and the risk of lithium deposition is relatively high. In Comparative Example 1-4, along the second direction, the electron transmission path is relatively long, the current distribution is uneven, and lithium deposition is likely to occur.

[0666] In the embodiment of the present application, when 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 the volume energy density of the battery cell is relatively high; and the tab spacing is set so that the electron transmission path is relatively short, the current borne between the tabs is small, the current distribution is more uniform, the lithium ions are more uniformly removed or inserted, and the risk of lithium deposition can be reduced; thereby enabling the energy density and service reliability of the battery cell 7 to be improved simultaneously.

[0667] Example 2-1

[0668] 1. Preparation of the positive electrode tab

[0669] The positive electrode tab includes a positive current collector, a positive electrode 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.

[0670] The positive electrode conductive layer on the positive 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, and the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0671] The positive electrode film layer is formed by uniformly coating a positive electrode slurry (with N-methylpyrrolidone NMP as the solvent) 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.

[0672] The positive electrode active material includes lithium iron phosphate and a coating layer. The coating layer coats the surface of the lithium iron phosphate and includes lithium iron titanium phosphate Li2FeTi(PO4)3 and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0673] The single-sided coating weight of the positive electrode film layer is 300 mg / 1540.25 mm 2 。

[0674] 2. Preparation of the negative electrode plate

[0675] 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.

[0676] 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%.

[0677] The negative electrode film layer is formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer, followed by drying and cold pressing.

[0678] The single-sided coating weight of the negative electrode film layer is 138 mg / 1540.25 mm 2 。

[0679] 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.

[0680] 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. 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 is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0681] 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. 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 is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0682] 3. Separator

[0683] The separator includes a base film, and the base film is a 7-μm polyethylene film layer with a porosity of 42%.

[0684] 4. Preparation of electrolyte

[0685] The electrolyte includes organic solvents, lithium salts and additives.

[0686] The organic solvents include 60% chain carboxylic ester solvents (ethyl acetate) and 40% carbonate solvents (30% ethylene carbonate EC and 10% dimethyl carbonate). The mass content of each component in the organic solvents is calculated based on the mass of the organic solvents.

[0687] 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.

[0688] The lithium salt includes 1 mol / L lithium hexafluorophosphate LiPF6.

[0689] 5. Preparation of battery cell

[0690] 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 a winding process; place the electrode assembly in an outer packaging case, inject electrolyte after drying, and obtain a battery cell through processes such as vacuum packaging, standing, formation, and shaping. 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 .

[0691] Examples 2-2 to 2-4

[0692] Prepare a battery cell using a method similar to that of Example 2-1. Different from Example 2-1, the distance between adjacent positive electrode tabs and the distance between adjacent negative electrode tabs are adjusted.

[0693] Examples 2-5 and 2-6

[0694] Prepare a battery cell using 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 is adjusted, and the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector changes accordingly;

[0695] The single-sided coating weight of the negative electrode film layer is adjusted, and the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector changes accordingly.

[0696] Comparative Example 2-1

[0697] Prepare a battery cell using a method similar to that of Example 2-1. Different from Example 2-1, the distance between adjacent positive electrode tabs and the distance between adjacent negative electrode tabs are adjusted.

[0698] Comparative Example 2-2

[0699] Prepare a battery cell using 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 is adjusted, and the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector changes accordingly;

[0700] The single-sided coating weight of the negative electrode film layer is adjusted, and the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector changes accordingly.

[0701] Test results

[0702] The test results are shown in Table 2.

[0703] Table 2

[0704]

[0705] The distance between two adjacent positive current collector tabs refers to the distance in the second direction Z. For example Figure 5 the distance between two adjacent positive current collector tabs in Figure 5 . The distance between two adjacent positive current collector tabs is less than or equal to 600 mm. The distance from any point in the positive current collector portion to the positive current collector tab closest to this 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 current collector tabs is 150 mm. The distance from any point in the positive current collector portion to the positive current collector tab closest to this point in the second direction Y is less than or equal to 150 mm / 2 = 75 mm. For example, a2 is less than or equal to 75 mm, and the distance a1 between the edge A1 of the positive current collector portion and the positive current collector tab is less than or equal to 150 mm.

[0706] The distance between two adjacent negative current collector tabs refers to the distance in the second direction Z. For example Figure 7 the distance between two adjacent negative current collector tabs in Figure 7 . The distance between two adjacent negative current collector tabs is less than or equal to 600 mm. The distance from any point in the negative current collector portion to the negative current collector tab closest to this 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 negative current collector tabs is less than 150 mm. The distance from any point in the negative current collector portion to the negative current collector tab closest to this point in the second direction is less than or equal to 150 mm / 2 = 75 mm. For example, b2 is less than or equal to 75 mm, and the distance b1 between the edge B1 of the negative current collector portion and the negative current collector tab is less than or equal to 150 mm.

[0707] In Comparative Example 2-1, the distance between two adjacent positive current collector tabs is 700 mm. The distance from any point in the positive current collector portion to the positive current collector tab closest to it in the second direction can reach 700 mm / 2 = 350 mm, which is greater than 300 mm.

[0708] In Comparative Example 2-1, the distance between two adjacent negative current collector tabs is 700 mm. The distance from any point in the negative current collector portion to the negative current collector tab closest to it in the second direction can reach 700 mm / 2 = 350 mm, which is greater than 300 mm.

[0709] As can be seen from Table 2, in Comparative Example 2-1, the tab spacing is relatively large, resulting in a longer electron transmission path, uneven current distribution, and easier lithium plating. Although the tab spacing in Comparative Example 2-2 is not 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.

[0710] 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 2When the time is right, the volumetric energy density of the battery cell is relatively high; and the spacing between the tabs 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 ions are deintercalated or intercalated more uniformly, 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.

[0711] Although the illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as a limitation of the present application, and changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A battery cell, characterized in that, including an electrode assembly, the electrode assembly including a positive electrode tab, the positive electrode tab including a positive electrode film layer, a positive current collector portion, and at least one positive electrode ear, the positive electrode film layer being disposed on at least one side of the positive current collector portion along the thickness direction of the positive electrode tab, the positive electrode ear being disposed on at least one side of the positive current collector portion 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, and 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 current collector portion and the positive electrode ear closest to the first point is less than or equal to 300 mm, the first point being any point of the positive current collector portion, the first direction, the second direction, and the thickness direction of the positive electrode tab being perpendicular to each other in pairs.

2. The battery cell according to claim 1, characterized in that, the positive electrode ear is provided as one or more, all the positive electrode ears being disposed on the same side of the positive current collector portion along the first direction, the size of the positive current collector portion along the first direction being 100 mm to 300 mm.

3. The battery cell according to claim 1, wherein, the positive electrode ear is provided as multiple, the multiple positive electrode ears being disposed on both sides of the positive current collector portion along the first direction, the size of the positive current collector portion along the first direction being 100 mm to 600 mm.

4. The battery cell according to claim 1, wherein, The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; and / or the thickness of the positive current collector portion 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 tab, the negative electrode tab including a negative electrode film layer, a negative current collector portion, and at least one negative electrode ear, the negative electrode film layer being disposed on at least one side of the negative current collector portion along the thickness direction, the negative electrode ear being disposed on at least one side of the negative current collector portion along the first direction, wherein, the negative electrode film layer includes a negative electrode active material, the negative electrode active material including a carbon-based material, along the second direction, the distance between a second point of the negative current collector portion and the negative electrode ear closest to the second point is less than or equal to 300 mm, the second point being any point of the negative current collector portion.

6. The battery cell according to claim 5, characterized in that, the negative electrode ear is provided as one or more, all the negative electrode ears being disposed on the same side of the negative current collector portion along the first direction, the size of the negative current collector portion along the first direction being 100 mm to 300 mm.

7. The battery cell according to claim 5, characterized in that, the negative electrode ear is provided as multiple, the multiple negative electrode ears being disposed on both sides of the negative current collector portion along the first direction, the size of the negative current collector portion along the first direction being 100 mm to 600 mm.

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

9. The battery cell according to claim 1, wherein the electrode assembly is of a wound structure, the positive electrode ear being provided as multiple, the multiple positive electrode ears being oppositely disposed along the thickness direction of the electrode assembly.

10. The battery cell according to claim 9, wherein, along the second direction, the distance between the first point of the positive current collector portion and the positive electrode ear closest to the first point is less than or equal to 200 mm.

11. The battery cell according to claim 9, wherein, 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 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 to 370 mg / 1540.25 mm 2 .

12. The battery cell according to claim 9, wherein The electrode assembly includes a negative electrode tab, and the negative electrode tab includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode ear. 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 ear is disposed on at least one side of the negative electrode current collector along the first direction, where 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; 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-sided coating weight of the negative electrode film layer is 125 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 .

13. The battery cell according to claim 1, wherein the electrode assembly is of a stacked structure, and the positive electrode ear is disposed on at least one side of the positive electrode current collector.

14. The battery cell according to claim 13, wherein, A plurality of positive electrode ears are provided, and the plurality of positive electrode ears are disposed on both sides of the positive electrode current collector along the first direction. The size of the positive electrode current collector along the first direction is 400 mm to 600 mm; and / or The electrode assembly includes a negative electrode tab, and the negative electrode tab includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode ear. The negative electrode film layer is disposed on at least one side of the negative electrode current collector along the thickness direction, and a plurality of negative electrode ears are provided. The plurality of negative electrode ears are disposed on both sides of the negative electrode current collector along the first direction. The size of the negative electrode current collector along the first direction is 400 mm to 600 mm.

15. The battery cell according to claim 13, wherein 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; and / or The one-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 360 mg / 1540.25 mm 2 .

16. The battery cell according to claim 13, wherein The electrode assembly includes a negative electrode tab, and the negative electrode tab includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode ear. 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 ear is disposed on at least one side of the negative electrode current collector along the first direction, where 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; 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-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 164 mg / 1540.25 mm 2 .

17. The battery cell according to claim 1, wherein the lithium-containing material with an olivine structure is a lithium-containing phosphate with an olivine structure; The lithium-containing phosphate with an olivine structure includes: phosphate particles, and a coating layer that coats the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

18. The battery cell according to claim 17, wherein, The phosphate particles comprise a compound of the general formula Li x1 A y1 Me a M b P 1-c X c Y z wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A comprises one or more of Na, K, and Mg, Me comprises one or more of Mn, Fe, Co, and Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X comprises one or more of S, Si, Cl, B, C, and N, and Y comprises one or more of O and F.

19. The battery cell according to claim 17, wherein The coating layer includes a fast ion conductor with the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , where M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0 ≤ d ≤ 1, 0 < x2 < 5, and 0 < y2 < 4.

20. The battery cell according to claim 17, wherein, 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 element in the lithium-containing phosphate with an olivine structure is 1% to 2%, The specific surface area of the lithium-containing phosphate with olivine structure is 5 m 2 / g to 18 m 2 / g.

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

23. The battery cell according to claim 1, characterized in that, The positive electrode tab further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the positive electrode film layer and the positive electrode current collector.

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

25. The battery cell according to claim 23, wherein 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 fluorinated acrylate resins.

26. The battery cell according to claim 1, characterized in that, The electrode assembly includes a negative electrode tab, and the negative electrode tab includes a negative electrode film layer, a negative electrode current collector portion, and a negative electrode tab. The negative electrode film layer is disposed on at least one side of the negative electrode current collector portion along the thickness direction, and the negative electrode tab is disposed on at least one side of the negative electrode current collector portion 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, wherein, The graphite particles include: Artificial graphite, including secondary particles, and A carbon coating layer, covering the surface of the artificial graphite.

28. The battery cell according to claim 27, wherein Based on the mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%.

29. The battery cell according to claim 26, characterized in that, The negative electrode film layer includes: A first negative electrode film layer, disposed on the surface of the negative electrode current collector portion, the first negative electrode film layer includes a carbon-based material, and A second negative electrode film layer, connected to a 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 diameter Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle diameter Dv50 of the graphite particles in the second negative electrode film layer.

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

31. The battery cell according to claim 29, wherein, The tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer.

32. The battery cell according to claim 31, wherein 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 , and / or 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 .

33. The battery cell according to claim 29, wherein, The volume average particle diameter 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 diameter 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, wherein The first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the 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, wherein, 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, wherein, The mass content of lithium element 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, wherein the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, 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, and 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%; and / or the second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, 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, and 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%.

38. The battery cell according to claim 26, wherein 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, wherein The negative electrode sheet further comprises 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 portion.

40. The battery cell according to claim 39, wherein, 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 comprises a negative electrode conductive agent, and the negative electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and / or the negative electrode conductive layer comprises a negative electrode binder, and the negative electrode binder comprises one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate and carboxymethyl chitosan.

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

43. The battery cell according to claim 42, wherein, The separator comprises a base film and a functional layer provided on at least one side of the base film, and the functional layer comprises: a first functional layer located on one side of the base film, and the first functional layer comprises first inorganic particles a second functional layer located on the other side of the base film, and the second functional layer comprises composite particles, and the composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

44. The battery cell according to claim 43, characterized in that, The non-fluoropolymer particles comprise acrylate copolymers.

45. The battery cell according to claim 43, characterized in that, The first inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide.

46. The battery cell according to claim 43, wherein, The second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide, and / or The average particle size of the second inorganic particles is 5 nm to 100 nm.

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

48. The battery cell according to claim 47, characterized in that, The electrolyte solution includes an organic solvent, the organic solvent includes a carboxylic acid ester solvent, the carboxylic acid ester solvent includes a chain carboxylic acid ester solvent, and the mass content of the chain carboxylic acid ester 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, wherein, The chain carboxylic acid ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

51. The battery cell according to claim 50, wherein R1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group, or a C1-C3 haloalkyl group, and / or R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group.

52. The battery cell according to claim 51, wherein The chain carboxylic acid ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8, 。 53. The battery cell according to claim 48, wherein 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, wherein, The carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

55. The battery cell according to claim 53, wherein, 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 solution further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive.

57. The battery cell according to claim 56, wherein, The carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate, and / or The sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate, and / or The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

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

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

60. The battery cell according to claim 47, wherein, The electrolyte solution further includes a lithium salt, and the lithium salt includes one or more of a fluorosulfonylimide salt and lithium hexafluorophosphate.

61. The battery cell according to claim 60, wherein The fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

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

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

0.

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

65. The battery cell according to claim 64, wherein, The thickness of the housing is from 0.2 mm to 0.35 mm.

66. The battery cell according to claim 1, wherein, 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 from 5 min to 10.5 min.

68. A battery device, characterized in that, It includes 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 10% state of charge to 80% state of charge is from 5 min to 10.5 min.

70. An electrical device, characterized in that, It includes the battery device according to claim 68.

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