Battery cell, battery device and electric device

Abstract

A battery cell (7), a battery (2) and an electric device (1). The battery cell (7) comprises an electrode assembly (10). The electrode assembly (10) comprises a positive electrode sheet (13). The positive electrode sheet (13) comprises a positive electrode film layer (132), a positive electrode current collecting part (131), and a positive electrode tab (111), wherein the positive electrode film layer (132) is arranged on at least one side of the positive electrode current collecting part (131) in the direction of thickness of the positive electrode sheet (13); and the positive electrode tab (111) is arranged on at least one side of the positive electrode current collecting part (131) in a first direction. The positive electrode film layer (132) comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing material of an olivine structure. The single-sided coating weight of the positive electrode film layer (132) ranges from 200 mg / 1540.25 mm2 to 400 mg / 1540.25 mm2. In a second direction, the distance between a first point on the positive electrode current collecting part (131) and the positive electrode tab (111) closest to the first point is less than or equal to 300 mm, the first point being any point on the positive electrode current collecting part (131). The first direction, the second direction, and the direction of thickness of the positive electrode sheet (13) are mutually perpendicular. The structure can reduce the risk of lithium plating in the battery cell and improve the operational reliability of the battery cell.

Description

Battery cell, battery device and electric device TECHNICAL FIELD

[0001] The present application relates to a battery cell, a battery device and an electric device. BACKGROUND

[0002] Battery cells have characteristics such as high capacity and long service life, and are therefore widely used in electronic devices such as mobile phones, notebook computers, electric vehicles, electric cars, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes and electric tools.

[0003] SUMMARY

[0004] The present application provides a battery cell, a battery device and an electric device, which can reduce the risk of lithium precipitation of the battery cell and improve the use reliability of the battery cell.

[0005] In a first aspect, the present application provides a battery cell, the battery cell comprising an electrode assembly, the electrode assembly comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode film layer, a positive electrode current collecting part and at least one positive electrode tab, the positive electrode film layer being arranged on at least one side of the positive electrode current collecting part along the thickness direction of the positive electrode sheet, the positive electrode tab being arranged on at least one side of the positive electrode current collecting part along a first direction, wherein the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprising a lithium-containing material with an olivine structure, the single-sided coating weight of the positive electrode film layer being 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 mm along a second direction, the distance between a first point of the positive electrode current collecting part and the positive electrode tab closest to the first point being less than or equal to 300 mm, the first point being any point of the positive electrode current collecting part, the first direction, the second direction and the thickness direction of the positive electrode sheet being perpendicular to each other.

[0006] Therefore, in the present application, when the single-sided coating weight of the positive electrode film layer is within the above range, the energy density of the battery cell is high; in the case of the above high energy density, by adjusting the distance between any point of the positive electrode current collecting part and the positive electrode tab closest to the point along the second direction 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, and the lithium ion extraction or insertion is more uniform, thereby reducing the risk of lithium precipitation; thus, the energy density and use reliability of the battery cell can be improved.

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

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

[0009] In some embodiments, the single-side 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-side coating weight of the positive electrode film layer is within the above range, the energy density of the battery cell can be improved.

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

[0011] In some embodiments, the electrode assembly further comprises a negative electrode tab, the negative electrode tab comprises a negative electrode film layer, a negative current collector, and at least one negative electrode tab, the negative electrode film layer is disposed on at least one side of the negative current collector along the thickness direction, and the negative electrode tab is disposed on at least one side of the negative current collector along the first direction, wherein the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprises a carbon-based material, along the second direction, the distance between the second point of the negative 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 current collector.

[0012] Thus, each negative electrode tab bears a smaller current, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium precipitation can be reduced; thereby the energy density and use reliability of the battery cell can be improved.

[0013] In some embodiments, the negative tab is provided as one or more, all of the negative tabs are arranged on the same side of the negative current collector along the first direction, and the size of the negative current collector along the first direction is 100 mm to 300 mm. Each negative tab bears a smaller current, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium precipitation can be reduced. Thus, the energy density and use reliability of the battery cell can be improved.

[0014] In some embodiments, the negative tab is provided as one or more, all of the negative tabs are arranged on the same side of the negative current collector along the first direction, and the size of the negative current collector along the first direction is 100 mm to 300 mm. Each negative tab bears a smaller current, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium precipitation can be reduced. Thus, the energy density and use reliability of the battery cell can be improved.

[0015] In some embodiments, the single-sided coating weight of the negative 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 film layer is in the above range, the energy density of the battery cell can be improved.

[0016] In some embodiments, the thickness of the negative current collector is 4 μm to 6 μm. When the thickness of the negative current collector is in the above range, the overcurrent capacity of the negative current collector is excellent, and the battery cell has a higher energy density.

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

[0018] In some embodiments, along the second direction, the distance between the first point of the positive current collector and the positive tab closest to the first point is less than or equal to 200 mm. The distance between the tabs is small, the setting position of the positive tab is adjusted, the electron transport path is short, the current borne by the tabs is small, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium precipitation can be reduced. Thus, the energy density and use reliability of the battery cell can be improved.

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

[0020] In some embodiments, the single-side 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-side coating weight of the positive electrode film layer is within the above range, the energy density of the battery cell can be improved.

[0021] In some embodiments, the ratio of the thickness of the single-side negative electrode film layer to the thickness of the negative electrode current collector is 12.5 to 19.5 when the battery cell is at 100% state of charge. When the ratio of the thickness of the single-side negative electrode film layer to the thickness of the negative electrode current collector is within the above range, the energy density of the battery cell can be improved.

[0022] In some embodiments, the single-side 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-side coating weight of the negative electrode film layer is within the above range, the energy density of the battery cell can be improved.

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

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

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

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

[0027] In some embodiments, the ratio of the thickness of the single-side positive electrode film layer to the thickness of the positive electrode current collector is 3.5 to 7.0 when the battery cell is at 100% state of charge. When the ratio of the thickness of the single-side 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.

[0028] In some embodiments, the single-side coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2to 360 mg / 1540.25 mm 2 When the single-side coating weight of the positive electrode film layer is within the above range, the energy density of the battery cell can be improved.

[0029] In some embodiments, the ratio of the thickness of the single-side negative electrode film layer to the thickness of the negative electrode current collector is 10.5 to 17.5 at 100% state of charge. When the single-side coating weight of the negative electrode film layer is within the above range, the energy density of the battery cell can be improved.

[0030] In some embodiments, the single-side 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-side coating weight of the negative electrode film layer is within the above range, the energy density of the battery cell can be improved.

[0031] In some embodiments, the olivine-structured lithium-containing phosphate includes phosphate particles and a coating layer, the coating layer coats the phosphate particles, and the coating layer contains one or more of C, Fe, Ti, Zr, Hf, Ge, and Sn. The phosphate particles are coated with the coating layer on the surface, which can improve the electrical conductivity of the olivine-structured lithium-containing phosphate, reduce the powder resistivity of the material, and facilitate the migration rate of lithium ions, thereby reducing the heat generation of the battery cell.

[0032] In some embodiments, the phosphate particles include a compound with a general formula of Li x1 A y1 Me a M b P 1-c X c Y z , wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F. The cycle stability of the phosphate particles is excellent, which is conducive to improving the cycle performance of the battery cell.

[0033] In some embodiments, the coating layer includes a compound with a general formula of Li 3-d Fe 2-d M2d (PO x2 ) y2 The fast ion conductor includes M2P2O7, M2 includes one or more elements of Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0

[0034] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, and optionally 0.19 to 0.26. When the graphitization degree of the positive electrode active material is in the above range, the conductivity of the positive electrode active material is improved, and the heat generation of the positive electrode plate is reduced, thereby reducing the heat generation of the battery cell.

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

[0036] Therefore, the material with the above mass content of carbon element and the above specific surface area is more conducive to the effective contact between the electrolyte and the olivine-structured lithium-containing phosphate, and is more conducive to the transmission of lithium ions at the phase interface.

[0037] In some embodiments, the olivine-structured lithium-containing phosphate is in a particulate form, and the volume distribution particle size satisfies 1 μm≤Dv50≤2 μm and 0.4 μm≤Dv10≤0.7 μm. The particle size of the olivine-structured lithium-containing phosphate is relatively small, the path of lithium ion deintercalation in the positive electrode active material is relatively short, and the heat generation is relatively small. In addition, the particle size of the above positive electrode active material is not too small, and agglomeration basically does not occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0038] In some embodiments, the olivine-structured lithium-containing phosphate is in a particulate form, and the olivine-structured lithium-containing phosphate includes secondary particles, the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. The average particle size of the primary particles is relatively small, the path of lithium ion deintercalation in the positive electrode active material is relatively short, and the heat generation is relatively small.

[0039] In some embodiments, the positive electrode tab further comprises a positive electrode conductive layer between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode tab, 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, the conductivity of the positive electrode tab can be further improved, the heat generation of the positive electrode tab can be reduced, thus the heat generation of the battery cell can be reduced, and the energy density of the battery cell can be improved.

[0041] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thus 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 adhesion 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 comprises 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 comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorine-containing acrylic ester resin.

[0044] In some embodiments, the negative electrode active material comprises a carbon-based material, and the carbon-based material comprises graphite particles with a graphitization degree of 92.0% to 94.5%. When the graphitization degree of the graphite particles is within the above range, the conductivity of the graphite particles is excellent, the heat generation of the negative electrode tab can be reduced, the heat generation of the battery cell can be reduced, and the rapid charging performance of the battery cell can be improved.

[0045] In some embodiments, the graphite particles comprise artificial graphite and a carbon coating layer, the artificial graphite comprises secondary particles, and the carbon coating layer is coated on the surface of the artificial graphite. The carbon coating layer has more end faces and defects, so that the number of sites capable of deintercalating lithium ions is more, 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, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode tab can be further reduced, and the heat generation of the battery cell can be reduced.

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

[0048] Thus, in the embodiments of the present application, there is a difference in particle size between the first negative electrode film layer and the second negative electrode film layer, which can improve the rapid charging performance of the battery monomer. Specifically, during rapid charging, the overpotential of the second negative electrode film layer is generally high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and improve the problem of lithium stripping on the surface 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 tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, so that the energy density of the battery monomer is improved, and the first negative electrode film layer is relatively sparse in filling, and the pores are more abundant, which can improve the rapid charging performance of the battery monomer.

[0051] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 . When the tap density of the carbon-based material in the first negative electrode film layer is within a suitable range, the rapid charging performance of the battery monomer can be improved.

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

[0055] In some embodiments, the first negative electrode film layer further comprises a first lithium-containing binder, and the second negative electrode film layer further comprises a second lithium-containing binder, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[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 second lithium-containing binder provides a relatively large number of lithium ions that can move freely in the second negative electrode film layer, which can further improve the rapid 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 in the above range, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0058] In some embodiments, the mass content of lithium in the first lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium is in the above range, the number of lithium ions that can move freely in the negative electrode film layer is relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[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 in the second lithium-containing binder is in the above range, the deintercalation rate of lithium ions is improved, and the rapid charging performance of the battery cell is improved.

[0060] In some embodiments, the mass content of lithium in the second lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium is in the above range, the number of lithium ions that can move freely in the negative electrode film layer is relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0061] In some embodiments, the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[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 rapid charging performance of the battery monomer, and is not prone to swelling during the charging and discharging process, has a stable structure, and improves the cycle performance of the negative electrode film layer during the rapid charging and discharging process.

[0063] In some embodiments, the second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[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 rapid charging performance of the battery monomer, and is not prone to swelling during the charging and discharging process, has a stable structure, and improves the cycle performance of the negative electrode film layer during the rapid charging and discharging process.

[0065] In some embodiments, the negative electrode active material further comprises a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10.0%, based on the mass of the negative electrode active material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery monomer.

[0066] In some embodiments, 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.

[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 conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery monomer.

[0068] In some embodiments, the negative electrode conductive layer comprises one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet, reducing the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the adhesion between the negative electrode current collector and the negative electrode film layer, improve the structural stability of the negative electrode sheet.

[0069] In some embodiments, the negative electrode conductive agent comprises one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0070] In some embodiments, the negative electrode binder comprises one or more of styrene butadiene rubber, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0071] In some embodiments, the separator film comprises a base film with a porous structure, and the porosity of the base film is 20% to 70%. When the porosity of the separator film in the present application is within the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0072] In some embodiments, the separator film comprises a base film with a porous structure, and the porosity of the base film is 35% to 60%. When the porosity of the separator film in the present application is within the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[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, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[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, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0075] In some embodiments, the separator film comprises a base film and a functional layer arranged on at least one side of the base film, the functional layer comprises a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer comprises first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer comprises composite particles, the composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

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

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

[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, the heat resistance and the compression modulus of the composite particles can be improved.

[0080] In some embodiments, the electrolyte has an electrical conductivity of 13 mS / cm to 20 mS / cm at room temperature. When the electrical conductivity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the rapid charging performance of the battery cell.

[0081] In some embodiments, the electrolyte has a viscosity of 2.3 mPa·s to 3.5 mPa·s at room temperature. When the viscosity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the rapid charging performance of the battery cell.

[0082] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature. When the density of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the rapid 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%, and 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] In formula I,

[0086] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group,

[0087] R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

[0088] Therefore, the chain carboxylate solvent has a high conductivity in the embodiments of the present application, which is beneficial to improving the rapid charging capability of the battery cell.

[0089] In some embodiments, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 halogenated alkyl group.

[0090] In some embodiments, R2 includes a C1 to C3 alkyl group or a C1 to C3 halogenated alkyl group.

[0091] In some embodiments, the chain carboxylate solvent includes one or more of a compound shown in formula I-1 to a compound shown in formula I-8.

[0092] 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 combination of the carbonate solvent and the chain carboxylate solvent improves the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0093] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate.

[0094] In some embodiments, the mass content of the carbonate solvent in the organic solvent is 30% to 70%, which can be 30% to 50%. The carbonate solvent with the mass content can further improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0095] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The additive can improve the interface film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0096] In some embodiments, the carbonate additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0097] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfonate DTD, bis vinyl sulfonate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methyl methylene disulfonate MMDS.

[0098] 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.

[0099] In some embodiments, the additive has a mass content of 1% to 10% in the electrolyte, which can be optionally 2% to 8%. The additive with the above mass content can effectively improve the interface film performance on the positive electrode side and / or the negative electrode side, which is conducive to improving the rapid charging performance and cycle performance of the battery cell.

[0100] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfimide salt and lithium hexafluorophosphate LiPF6. The lithium salt is easy to dissociate, which is conducive to the rapid migration of lithium ions, and the electrolyte system is relatively stable and is not easy to decompose, which can improve the cycle performance of the battery cell.

[0101] In some embodiments, the fluorine-containing sulfimide salt includes one or more of lithium bisfluorosulfimide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0102] In some embodiments, the lithium salt includes lithium bisfluorosulfimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of lithium bisfluorosulfimide 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.

[0103] In some embodiments, the ratio of the molar concentration of lithium bisfluorosulfimide to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2 to 1.0.

[0104] In some embodiments, the base material of the shell includes steel, and the thickness of the shell is 0.1 mm to 0.5 mm, which can be optionally 0.2 mm to 0.35 mm. When the thickness of the shell is in the above range, the mechanical strength of the shell is relatively high, which can improve the use reliability and cycle performance of the battery cell, and the shell occupies less space, and the internal space of the shell is relatively large, which is conducive to improving the energy density of the battery cell.

[0105] In some embodiments, the battery cell further includes a positive electrode terminal, and the positive electrode tab is directly welded to the positive electrode terminal. Direct welding can reduce the resistance at the connection, which is conducive to reducing the overall internal resistance of the battery cell.

[0106] 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 faster, and the fast charging capability is improved.

[0107] In a second aspect, the present application provides a battery device, the battery device comprising the plurality of battery cells according to any one of the embodiments of the first aspect of the present application.

[0108] 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 faster, and the fast charging capability is improved.

[0109] In a third aspect, the present application provides a power consumption device, the power consumption device comprising the battery device according to any one of the embodiments of the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0110] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0111] FIG. 1 is a structural schematic diagram of a battery cell according to some embodiments of the present application;

[0112] FIG. 2 is an exploded schematic diagram of a battery cell according to some embodiments of the present application;

[0113] FIG. 3 is a structural schematic diagram of an electrode assembly in a battery cell according to some embodiments of the present application;

[0114] FIG. 4 is a cross-sectional structural schematic diagram of a first electrode sheet in a battery cell according to some embodiments of the present application;

[0115] FIG. 5 is an unfolded structural schematic diagram of a first electrode sheet in a battery cell according to some embodiments of the present application;

[0116] FIG. 6 is a cross-sectional structural schematic diagram of a second electrode sheet in a battery cell according to some embodiments of the present application;

[0117] FIG. 7 is an unfolded structural schematic diagram of a second electrode sheet in a battery cell according to some embodiments of the present application;

[0118] FIG. 8 is an unfolded structural schematic diagram of a first electrode sheet in a battery cell according to some other embodiments of the present application;

[0119] FIG. 9 is an unfolded structural schematic diagram of a second electrode sheet in a battery cell according to some other embodiments of the present application;

[0120] FIG. 10 is a structural diagram of an electrode assembly in a battery cell according to some embodiments of the present application;

[0121] FIG. 11 is a structural diagram of a first electrode tab in a battery cell according to some embodiments of the present application;

[0122] FIG. 12 is a structural diagram of a first electrode tab in a battery cell according to some embodiments of the present application;

[0123] FIG. 13 is a structural diagram of a second electrode tab in a battery cell according to some embodiments of the present application;

[0124] FIG. 14 is a structural diagram of a second electrode tab in a battery cell according to some embodiments of the present application;

[0125] FIG. 15 is a structural diagram of a battery module according to some embodiments of the present application;

[0126] FIG. 16 is a structural diagram of a battery according to some embodiments of the present application;

[0127] FIG. 17 is a structural diagram of an electric device according to some embodiments of the present application.

[0128] The accompanying drawings are not necessarily drawn to scale.

[0129] The reference signs are explained as follows: Y, first direction; Z, second direction; 1, electric device; 2, battery; 3, controller; 4, motor; 5, case; 5a, first case portion; 5b, second case portion; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, tab portion; 111, positive electrode tab; 112, negative electrode tab; 12, main body portion; 13, positive electrode tab; 131, positive electrode current collecting portion; 132, positive electrode film layer; 14, negative electrode tab; 141, negative electrode current collecting portion; 142, negative electrode film layer; 15, separator; 20, housing; 21, case; 22, end cap; 31, positive electrode terminal; 32, negative electrode terminal; 41, positive electrode adapter; 42, negative electrode adapter. DETAILED DESCRIPTION

[0130] Hereinafter, embodiments of the battery cell, battery device, and electric device of the present application are specifically disclosed while appropriately referring to the accompanying drawings. However, there are cases where unnecessary detailed explanations are omitted. For example, there are cases where detailed explanations of matters that are already well known, repeated explanations of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following explanations are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0131] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the range, wherein each sub-range includes each and every number between (and including) the end values of the sub-range. For example, if a range is stated as 1-10, it is intended to include any and all sub-ranges between (and including) the end values of 1 and 10, e.g., 7-3, 5-1, 2-8, 9-1, etc. Also, it is specifically intended that the end number of a range include each and every number within (and including) the end number of the range, e.g., 6 is a part of a range 1-10, 1-8, 1-6, 2-6, etc. Any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the end values of 1 and 10, e.g., 7-3, 5-1, 2-8, 9-1, etc.

[0132] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated otherwise.

[0133] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, if not specifically stated otherwise.

[0134] All steps of the present application can be performed in sequence or randomly, preferably in sequence, if not specifically stated otherwise. For example, a method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0135] The battery cell includes an electrode assembly, the electrode assembly includes a positive electrode tab and a negative electrode tab, lithium ions are separated from the positive electrode tab and embedded in the negative electrode tab during charging, and the separated lithium ions may not be embedded in the negative electrode tab in time, resulting in lithium precipitation; especially in the case of excessively large tab pitch, each tab bears a large current, resulting in increased risk of lithium precipitation.

[0136] In view of the above problems, the embodiments of the present application design the system of the battery monomer, and improve the distance between the tabs, so that the current between the tabs is not too large, the risk of lithium precipitation of the battery monomer is reduced, and the use reliability of the battery monomer is improved.

[0137] Battery monomer

[0138] In a first aspect, the embodiments of the present application provide a battery monomer.

[0139] The battery monomer comprises an electrode assembly, and the electrode assembly comprises a first tab, the first tab comprising a first film layer, a first current collecting part, and at least one first tab, the first film layer being arranged on at least one side of the first current collecting part along the thickness direction of the first tab, and the first tab being arranged on at least one side of the first current collecting part along the first direction, wherein along the second direction, the distance between any point in the first current collecting part and the first tab closest to the point is less than or equal to 300 mm, and the first direction, the second direction, and the thickness direction of the first tab are perpendicular to each other.

[0140] Any point in the first current collecting part is defined as a P point, and the P point is randomly taken in the first current collecting part.

[0141] The first tab can be one or more, and in the case of multiple first tabs, the first tab closest to the P point along the second direction refers to the first tab with the smallest distance to the P point along the second direction.

[0142] The first tab closest to the P point is defined as the closest tab, and the closest tab comprises a first edge and a second edge opposite to each other along the second direction, the first edge being arranged close to the P point, and the second edge being arranged away from the P point.

[0143] Along the second direction, the distance between the P point and the first tab closest to the P point refers to the distance between the P point and the first edge along the second direction.

[0144] The projection of the closest tab along the first direction partially overlaps the projection of the first current collecting part along the first direction, in other words, the projection of the closest tab along the first direction is located in the projection of the first current collecting part along the first direction, wherein the first direction is parallel to the normal of the projection plane.

[0145] The P point is any point in the first current collecting part, and when the projection of the P point along the first direction is located in the projection of the closest tab along the first direction, it can be considered that the distance between the P point and the closest tab along the second direction is 0.

[0146] When the projection of the P point 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 the distance is the distance between the P point and the first edge along the second direction.

[0147] In the embodiments of the present application, the first electrode tab can be a positive electrode tab or a negative electrode tab.

[0148] As shown in FIGS. 1-5, the battery cell 7 includes an electrode assembly 10 including a positive electrode tab 13, a negative electrode tab 14, and a separator 15, and the electrode assembly 10 can be in a jelly-roll structure or a stacked structure.

[0149] In some embodiments, regardless of whether the electrode assembly 10 is in a jelly-roll structure or a stacked structure, 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, 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 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 a first direction Y, and the distance between a first point in the positive electrode current collector 131 and the positive electrode tab 111 closest to the first point along a second direction Z is less than or equal to 300 mm. In FIG. 4, the M direction is the thickness direction of the positive electrode tab 13, the Y direction is the first direction, and the Z direction is the second direction, and the M direction, the Y direction, and the Z direction are perpendicular to each other.

[0150] Any point in the positive electrode current collector 131 can be a point with an area, for example, the area of the point is 0.01 mm 2 The area of the point is much smaller than the area of the tab, and the size of the point does not substantially interfere with the measurement of the distance.

[0151] The positive electrode tab 111 can be one or more. In the case where the positive electrode tab 111 is one, the distance between the first point, for example, point A, in the positive electrode current collector 131 and the positive electrode tab 111 closest to the first point along the second direction Z is the distance between the point A in the positive electrode current collector 131 and the positive electrode tab 111 along the second direction Z.

[0152] In the case where the positive electrode tab 111 is more than one, the positive electrode tab 111 closest to the point A among the plurality of positive electrode tabs 111 is the positive electrode tab 111 closest to the point A along the second direction Z, and thus the distance between the positive electrode tab 111 and the point A along the second direction Z is measured.

[0153] As shown in FIG. 5, A1 is any point in the positive electrode current collector 131, A1 is located at the edge of the positive electrode current collector 131, and the distance between A1 and the positive electrode tab 111 closest to A1 along the second direction Z is a1, and a1 is less than or equal to 300 mm.

[0154] A2 is any point in the positive current collector 131, A2 is located between two edges of the positive current collector 131, and the distance of A2 from the closest positive tab 111 in the second direction Z is a2, and the distance of A2 from other positive tabs 111 is a3, a4, etc., a3 is greater than a2, a4 is greater than a2, and a2 is less than or equal to 300 mm.

[0155] Electrons are introduced or removed from the positive electrode film layer 132 through the positive tab 111, and the coating weight of the positive electrode film layer 132 is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 , so that the energy density of the battery monomer 7 is high, but at the same time, the risk of lithium precipitation may also increase; and in the embodiments of the present application, the distance of any point in the positive current collector 131 from the closest positive tab 111 in the second direction Z is less than or equal to 300 mm, so that the transmission path of the 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 precipitation can be reduced; and because each tab bears less current, the system heat generation can be reduced, and the cycle performance of the battery monomer 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 stable structure and excellent cycle stability, which is beneficial to further improve the cycle performance of the battery monomer 7.

[0156] In the embodiments 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 , which can be 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 in the above range, the heat generation per unit area of the positive electrode tab 13 will not be too large, and the energy density of the battery monomer 7 can be improved.

[0157] As shown in FIGS. 6 and 7, in some embodiments, the negative electrode tab 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 arranged on at least one side of the negative current collector 141 along the thickness direction of the negative electrode tab 14, the negative electrode film layer 142 includes a negative active material, the negative active material includes a carbon-based material, and 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 2The negative tab 112 is connected to at least one side of the negative current collector 141 along the first direction Y, and the negative active material is not arranged on the negative tab 112. Along the second direction Z, the distance between the second point in the negative current collector 14100 and the negative tab 112 closest to the second point is less than or equal to 300 mm. The thickness direction of the negative tab 14 is parallel to the thickness direction M of the positive tab 13.

[0158] The negative tab 112 can be one or more, and the second point in the negative current collector 141 is any point in the negative current collector 141, for example, point B.

[0159] When the negative tab 112 is one, the distance between the point B in the negative current collector 141 and the negative tab 112 closest to the point B along the second direction Z refers to the distance between the point B in the negative current collector 141 and the negative tab 112 along the second direction Z.

[0160] When the negative tab 112 is multiple, the negative tab 112 closest to the point B among the multiple negative tabs 112 refers to the negative tab 113 closest to the point B along the second direction Z, and the distance between the negative tab 113 and the point B along the second direction Y is measured.

[0161] As shown in FIG. 7, B1 is any point in the negative current collector 141, and B1 is located at the edge of the negative current collector 141. The distance between B1 and the negative tab 112 closest to B1 along the second direction Z is b1, and b1 is less than or equal to 300 mm.

[0162] B2 is any point in the negative current collector 141, and B2 is located between the two edges of the negative current collector 141. The distance between B2 and the negative tab 112 closest to B2 along the second direction Z is b2, and the distances between B2 and other negative 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.

[0163] When the single-side coating weight of the negative film layer 142 is within the above range, the energy density of the battery cell 7 is higher. In the case of the above high energy density, the electron is introduced or introduced through the negative tab 112. By controlling the distance between any point in the negative current collector 141 and the negative tab 112 closest to the point along the second direction Z to be less than or equal to 300 mm, the transmission path of the electron is shorter, the current between the tabs is smaller, the current distribution is more uniform, the lithium ion is more uniform, and the risk of lithium precipitation can be reduced.

[0164] In the embodiments of the present application, the single-side coating weight of the negative film layer 142 is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2When the single-sided coating weight of the negative electrode film layer 142 is within the above range, the heat generation amount within the unit area of the negative electrode tab 14 will not be too large, and the energy density of the battery monomer 7 can be improved.

[0165] [Coiled electrode assembly]

[0166] Please continue to refer to FIG. 1 to FIG. 7, when the electrode assembly 10 is in a coiled structure, the positive electrode tab 13, the separator film 15 and the negative electrode tab 14 are coiled in the same direction, and after coiling, the positive electrode tab 13 includes a plurality of positive electrode tabs 111, and the negative electrode tab 14 includes a plurality of negative electrode tabs 112.

[0167] When the positive electrode tab 111 is provided in at least two, the at least two positive electrode tabs 111 are oppositely arranged along the thickness direction of the electrode assembly 10, and the closer to the coiling starting end, the smaller the spacing between the adjacent two positive electrode tabs 111, which is conducive to connecting the positive electrode tab 111 and the positive electrode adapter 41. In FIG. 3, X represents the thickness direction of the electrode assembly 10.

[0168] Optionally, the at least two positive electrode tabs 111 are arranged on the same side of the positive electrode current collecting part 131 along the first direction Y.

[0169] As shown in FIG. 8, optionally, the at least two positive electrode tabs 111 can also be arranged on both sides of the positive electrode current collecting part 131 along the first direction Y.

[0170] Along the second direction Z, the distance between any point in the positive electrode current collecting part 131 and the positive electrode tab 111 closest to the point is less than or equal to 300 mm, and optionally less than or equal to 200 mm. For example, along the second direction Z, the distance between any point in the positive electrode current collecting part 131 and the positive electrode tab 111 closest to the point is 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm, or a range formed by any two of the above values.

[0171] 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 ; optionally 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; optionally 280 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2Exemplarily, the single-side 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 formed by any two of the above values.

[0172] When the single-side coating weight of the positive electrode film layer 132 is within the above range, the heat generation per unit area of the positive electrode tab 13 will not be too large, and the energy density of the battery monomer 7 can be improved.

[0173] In some embodiments, along the first direction Y, the distance between the third point of the positive electrode current collecting part 131 and the positive electrode tab 111 closest to the third point is less than or equal to 300 mm, and the third point is any point of the positive electrode current collecting part 131, 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 formed by any two of the above values.

[0174] In the case where all the positive electrode tabs 111 are located on the same side of the positive electrode current collector 131, the distance between any point C in the positive electrode current collector 131 and the positive electrode tab 111 closest to the point C in the first direction Y is the distance between the point C and the positive electrode tab 111 closest to the point C in the first direction Y. In FIG. 5, c1 represents the distance between the point C and the positive electrode tab 111 in the first direction Y.

[0175] In some embodiments, in the case where all the positive electrode tabs 111 are located on the same side of the positive electrode current collector 131, the dimension of the positive electrode current collector 131 in the first direction Y is less than or equal to 300 mm, and can be optionally 100 mm to 300 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, or a range defined by any two of the above values.

[0176] In the case where the positive electrode tabs 111 are located on both sides of the positive electrode current collector 131, the distance between any point C in the positive electrode current collector 131 and the positive electrode tab 111 closest to the point C in the first direction Y is the distance between the positive electrode tab 111 closest to the point C in the first direction Y and the point C among the positive electrode tabs 111 on both sides.

[0177] In some embodiments, in the case where the positive electrode tabs 111 are located on both sides of the positive electrode current collector 131, the dimension of the positive electrode current collector 131 in the first direction Y is less than or equal to 600 mm, and can be optionally 100 mm to 600 mm, and can be optionally 400 mm to 600 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, or a range defined by any two of the above values.

[0178] As shown in FIG. 8, C is any point in the positive electrode current collector 131, which is located between the two edges of the positive electrode current collector 131, and the distance between the point C and the positive electrode tab 111 closest to the point C in the first direction Y is c1, and the distance between the point 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.

[0179] The embodiments of the present application control the distance between any point in the positive electrode current collector 131 and the positive electrode tab 111 closest to the point in the first direction Y to be less than or equal to 300 mm, so that the transmission path of the 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 precipitation can be further reduced.

[0180] Optionally, the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive electrode current collector 131 at 100% state of charge is 4.8 to 8.6, for example, 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 a range between any two of the aforementioned values.

[0181] When the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive electrode current collector 131 is within the aforementioned range, the energy density of the battery cell 7 can be improved.

[0182] When the negative electrode tab 112 is provided in at least two, the at least two negative electrode tabs 112 are oppositely arranged along the thickness direction of the electrode assembly 10, and the closer to the winding starting end, the smaller the spacing between the adjacent two negative electrode tabs 112, which is conducive to connecting the negative electrode tab 112 and the negative electrode adapter 42.

[0183] When the negative electrode tab 112 is provided in at least two, the at least two negative electrode tabs 112 are oppositely arranged along the thickness direction of the electrode assembly 10, which is conducive to connecting the negative electrode tab 112 and the negative electrode adapter 42.

[0184] Optionally, the at least two negative electrode tabs 112 are arranged on the same side of the negative electrode current collector 141.

[0185] As shown in FIG. 9, optionally, the at least two negative electrode tabs 112 can also be arranged on both sides of the negative electrode current collector 141.

[0186] In the second direction Z, the spacing between any point in the negative electrode current collector 141 and the negative electrode tab 112 closest to the point in the second direction Z is less than or equal to 300 mm, and optionally less than or equal to 200 mm. For example, the spacing between any point in the negative electrode current collector 141 and the negative electrode tab 112 closest to the point in 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 between any two of the aforementioned values.

[0187] Optionally, the single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm 2to 170 mg / 1540.25 mm 2 , optionally 125 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 Exemplarily, the single-sided coating weight of the negative electrode film layer 142 is 90 mg / 1540.25 mm 2 , 96 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 112 mg / 1540.25 mm 2 , 114 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 116 mg / 1540.25 mm 2 , 118 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 142 mg / 1540.25 mm 2 , 145 mg / 1540.25 mm 2 , 148 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 152 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 165 mg / 1540.25 mm 2 , 167 mg / 1540.25 mm2 170 mg / 1540.25 mm 2 or a range consisting of any two of the aforementioned numerical values.

[0188] When the single-side coating weight of the negative electrode film layer 142 is within the above range, the heat generation amount within the unit area of the negative electrode tab 14 will not be too large, and the energy density of the battery monomer 7 can be improved.

[0189] In some embodiments, along the first direction Y, the distance between the fourth point in the negative electrode current collecting part 141 and the negative electrode tab 112 closest to the fourth point is less than or equal to 300 mm, and the fourth point is any point in the negative electrode current collecting part 141, 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 consisting of any two of the aforementioned numerical values.

[0190] When the negative electrode tab 112 is located on the same side of the negative electrode current collecting part 141, the distance between any point in the negative electrode current collecting part 141, for example, the point D, and the negative electrode tab 112 closest to the point D along the first direction Y refers to the distance between the point D and the negative electrode tab 112 along the first direction Y in the negative electrode current collecting part 141. In FIG. 7, d1 represents the distance between the point D and the negative electrode tab 112 along the first direction Y.

[0191] In some embodiments, when all the negative electrode tabs 112 are located on the same side of the negative electrode current collecting part 141, the size of the negative electrode current collecting part 141 along the first direction Y is less than or equal to 300 mm, which can be optionally 100 mm to 300 mm, for example, 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, or a range consisting of any two of the aforementioned numerical values. In FIG. 7, R2 represents the size of the negative electrode current collecting part 141 along the first direction Y.

[0192] When the negative electrode tab 112 is located on both sides of the negative electrode current collecting part 141, the distance between any point in the negative electrode current collecting part 141, for example, the point D, and the negative electrode tab 112 closest to the point D along the first direction Y refers to the distance between the negative electrode tab 112 closest to the point D along the first direction Y and the point D among the negative electrode tabs 112 on both sides.

[0193] In some embodiments, when all the negative tabs 112 are located on both sides of the negative current collector 141, the dimension of the negative current collector 141 along the first direction Y is less than or equal to 600 mm, which can be optionally 100 mm to 600 mm, and can be optionally 400 mm to 600 mm, such as 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, or a range between any two of the above values.

[0194] As shown in FIG. 9, D is any point in the negative current collector 141, which is located between the two edges of the negative current collector 141, and the distance between the point D and the nearest negative tab 112 along the first direction Y is d1, and the distance between the point D and the other negative tab 112 is d2, where d2 is greater than d1, and d1 is less than or equal to 300 mm.

[0195] In the embodiments of the present application, the distance between any point in the negative current collector 141 and the nearest negative tab 112 along the first direction Y is less than or equal to 300 mm, so that the transmission path of the 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 precipitation can be further reduced.

[0196] Optionally, the ratio of the thickness of the single-sided negative film layer 142 to the thickness of the negative current collector 141 of the battery monomer 7 at 100% state of charge is 12.5 to 19.5, such as 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, or a range between any two of the above values.

[0197] When the ratio of the thickness of the single-sided negative film layer 142 to the thickness of the negative current collector 141 is in the above range, the energy density of the battery monomer 7 can be improved.

[0198] [Stacked electrode assembly]

[0199] As shown in FIGS. 10 and 11, when the electrode assembly 10 is in a stacked structure, the positive tab 13, the negative tab 14, and the separator film 15 are stacked to form the electrode assembly 10 by a stacking process. In FIG. 10, X represents the thickness direction of the electrode assembly 10, which is parallel to the thickness direction of the positive tab 13 and the thickness direction of the negative tab 14 in the case of the stacked structure.

[0200] In the second direction Z, the distance between any point in the positive current collector 131 and the positive tab 111 closest to the point is less than or equal to 300 mm, and can be less than or equal to 200 mm. For example, in the second direction Z, the distance between any point in the positive current collector 131 and the positive tab 111 closest to the point is 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm, or a range defined by any two of the above values.

[0201] The positive tab 111 can be one or more. In the second direction Z, the distance between any point in the positive current collector 131 and the positive tab 111 closest to the point can be the distance between the point E in the positive current collector 131 and the positive tab 111 closest to the point E in the second direction Z.

[0202] Optionally, the single-sided coating weight of the positive film layer 132 is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 ; optionally 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; optionally 200 mg / 1540.25 mm 2 to 360 mg / 1540.25 mm 2 . For example, the single-sided coating weight of the positive 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 between any two of the above values.

[0203] When the single-side coating weight of the positive electrode film layer 132 is within the above range, the heat generation per unit area of the positive electrode tab 13 will not be too large, and the energy density of the battery monomer 7 can be improved.

[0204] 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, the 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.

[0205] Optionally, when the positive electrode tab 111 is two, the two positive electrode tabs 111 are provided on both sides of the positive electrode current collector 131.

[0206] Optionally, along the first direction Y, the distance between the third point in the positive electrode current collector 131 and the positive electrode tab 111 closest to the third point is less than or equal to 300 mm, less than or equal to 200 mm, such as 300 mm, 290 mm, 280 mm, 270 mm, 250 mm, 230 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 120 mm, 100 mm, 80 mm, 50 mm, 20 mm, 10 mm, 0 mm, or a range between any two of the above values.

[0207] As shown in FIG. 11, when the positive electrode tab 111 is one, F is any point in the positive electrode current collector 131, F is located between the two edges of the positive electrode current collector 131, and the distance between F and the positive electrode tab 111 along the first direction Y is f1.

[0208] In some embodiments, when all the positive electrode tabs 111 are located on the same side of the positive electrode current collector 131, the size of the positive electrode current collector 131 along the first direction Y is less than or equal to 300 mm, and 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 a range between any two of the above values. For example, the positive electrode tab 111 is provided as one, and one positive electrode tab 111 is provided on one side of the positive electrode current collector 131 along the first direction Y.

[0209] As shown in FIG. 12, when the positive electrode tab 111 is multiple, which can be two, the two positive electrode tabs 111 are respectively arranged on both sides of the positive electrode current collecting part 131 along the first direction Y. F is any point in the positive electrode current collecting part 131, which is located between the two edges of the positive electrode current collecting part 131. The distance between F and the positive electrode tab 111 closest to one side along the first direction Y is f1, and the distance between F and the positive electrode tab 111 on the other side is f2. f2 is greater than f1, and f1 is less than or equal to 300 mm.

[0210] In some embodiments, when the positive electrode tab 111 is two, the two positive electrode tabs 111 are arranged on both sides of the positive electrode current collecting part 131. The size of the positive electrode current collecting part 131 along the first direction Y is less than or equal to 600 mm, which can be 100 mm to 600 mm, or 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.

[0211] In FIG. 12, S1 represents the size of the positive electrode current collecting part 131 along the first direction Y.

[0212] When the positive electrode tab 111 meets the above conditions, the transmission path of the electron is shorter, the current between the tabs is smaller, the current distribution is more uniform, the lithium ion extraction or insertion is more uniform, and the risk of lithium precipitation can be reduced.

[0213] Optionally, the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive electrode current collecting part 131 of the battery monomer 7 under 100% state of charge is 3.5 to 7.0, for example, 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 a range composed of any two of the above values.

[0214] When the ratio of the thickness of the single-sided positive electrode film layer 132 to the thickness of the positive electrode current collecting part 131 is in the above range, the energy density of the battery monomer 7 can be improved.

[0215] As shown in FIG. 13, the negative electrode tab 112 is arranged as at least one, which can be at least two. When the negative electrode tab 112 is arranged as at least two, at least two negative electrode tabs 112 can be arranged on both sides of the negative electrode current collecting part 141.

[0216] In the second direction Z, the distance between any point in the negative current collector 141 and the closest negative tab 112 to the point in the second direction Z is less than or equal to 300 mm, and optionally less than or equal to 200 mm. Illustratively, the distance between any point in the negative current collector 141 and the closest negative tab 112 to the point in 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 defined by any two of the aforementioned values.

[0217] The negative tab 112 can be one or more, and the distance between any point in the negative current collector 141 and the closest negative tab 112 to the point in the second direction Z can be the distance between the point G in the negative current collector 141 and the closest negative tab 112 to the point G in the second direction Z.

[0218] Optionally, the single-sided coating weight of the negative film layer 142 is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 , and optionally 90 mg / 1540.25 mm 2 to 164 mg / 1540.25 mm 2 Illustratively, the single-sided coating weight of the negative 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 / 154 0.25 mm 2 , 130 mg / 154 0.25 mm 2 , 132 mg / 154 0.25 mm 2 , 135 mg / 154 0.25 mm 2 , 137 mg / 154 0.25 mm 2 , 140 mg / 154 0.25 mm 2 , 142 mg / 154 0.25 mm 2 , 145 mg / 154 0.25 mm 2 , 148 mg / 154 0.25 mm 2 , 150 mg / 154 0.25 mm 2 , 152 mg / 154 0.25 mm 2 , 155 mg / 154 0.25 mm 2 , 160 mg / 154 0.25 mm 2 , 164 mg / 154 0.25 mm 2 , 170 mg / 154 0.25 mm 2 or a range between any two of the above values.

[0219] 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 tab 14 will not be too large, and the energy density of the battery monomer 7 can be improved.

[0220] Optionally, the ratio of the thickness of the single-sided negative electrode film layer 142 to the thickness of the negative electrode current collector 141 of the battery monomer 7 at 100% state of charge 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 between any two of the above values.

[0221] 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 monomer 7 can be improved.

[0222] 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.

[0223] In some embodiments, the distance between the fourth point and the closest negative tab 112 to the fourth point in the negative current collector 141 along the first direction Y 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 between any two of the above values.

[0224] As shown in FIG. 13, when the negative tab 112 is one, H is any point in the negative current collector 141, which is located between the two edges of the negative current collector 141, and the distance between H and the negative tab 112 along the first direction Y is h1, and h1 is less than or equal to 300 mm.

[0225] In some embodiments, when all the negative tabs 112 are located on the same side of the negative current collector 141, the size of the negative current collector 141 along the first direction Y is less than or equal to 300 mm, and is optionally 100 mm to 300 mm, for example, 100 mm, 110 mm, 120 mm, 130 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm, 300 mm, or a range between any two of the above values.

[0226] As shown in FIG. 14, when the negative tabs 112 are multiple, and are optionally two, the two negative tabs 112 are respectively arranged on the two sides of the negative current collector 141 along the first direction Y, H is any point in the negative current collector 141, which is located between the two edges of the negative current collector 141, and the distance between H and the negative tab 112 on the closest side along the first direction Y is h1, and the distance between H and the negative tab 112 on the other side is h2, h2 is greater than h1, and then h1 is less than or equal to 300 mm.

[0227] In some embodiments, when all the negative tabs 112 are located on the two sides of the negative current collector 141, the size of the negative current collector 141 along the first direction Y is less than or equal to 600 mm, and is optionally 100 mm to 600 mm, and is optionally 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 between any two of the above values.

[0228] As shown in FIG. 14, the size of the negative current collector 141 along the first direction Y is S2.

[0229] The embodiment of the present application makes the transmission path of electrons shorter by regulating the distance between any point in the negative current collector 141 and the negative tab 112 closest to the point in the first direction Y to be less than or equal to 300 mm, makes the current borne by each tab smaller, makes the current distribution more uniform, makes the lithium ion extraction or intercalation more uniform, and can further reduce the risk of lithium precipitation.

[0230] In some embodiments, the dimension of the end surface of the positive current collector 131 to which the positive tab 111 is connected in the second direction Z is 20 mm to 100 mm, regardless of whether the electrode assembly 10 is a jelly-roll structure or a stacked structure. For example, the dimension of the end surface of the positive current collector 131 to which the positive tab 111 is connected in 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 defined by any two of the above values. In FIG. 11, L1 represents the dimension of the end surface of the positive current collector 131 to which the positive tab 111 is connected in the second direction Z. When the positive tab 111 satisfies the above range, the flow area is larger and the flow capacity is stronger, and the risk of lithium precipitation can be further reduced.

[0231] In some embodiments, the dimension of the end surface of the negative current collector 141 to which the negative tab 112 is connected in the second direction Z is 20 mm to 100 mm, regardless of whether the electrode assembly 10 is a jelly-roll structure or a stacked structure. For example, the length of the connection region of the negative tab 112 to 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 defined by any two of the above values. In FIG. 13, L2 represents the dimension of the end surface of the negative current collector 141 to which the negative tab 112 is connected in the second direction Z. When the negative tab 112 satisfies the above range, the flow area is larger and the flow capacity is stronger, and the risk of lithium precipitation can be further reduced.

[0232] [Positive electrode tab]

[0233] The positive electrode tab includes a positive current collector and a positive film layer disposed on at least one surface of the positive current collector and including a positive active material. For example, the positive current collector has two surfaces opposite in the thickness direction thereof, and the positive film layer is disposed on any one or both of the two opposite surfaces of the positive current collector.

[0234] The charging upper limit voltage and discharging cut-off voltage of the battery cell are different according to the positive electrode active material, for example, when the phosphate material includes lithium iron phosphate, the charging upper limit voltage can be 3.65V, and the discharging cut-off voltage can be 2.0V, for example, when the phosphate material includes lithium manganese iron phosphate, the charging upper limit voltage can be 4.3V, and the discharging cut-off voltage can be 2.0V, and then taking the charging upper limit voltage of 3.65V and the discharging cut-off voltage of 2.0V as an example, the state of the battery cell is explained: 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,

[0235] The battery cell is charged to the charging upper limit voltage at a constant current charging rate of 0.33C, and then charged to 0.05C at a constant voltage, corresponding to the state of 100% SOC of the battery cell, and the battery cell is discharged to the cut-off voltage at a constant current discharging rate of 0.33C, corresponding to the state of 0% SOC of the battery cell.

[0236] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge SOC is 2.50g / cm 3 to 2.80g / cm 3 , and optionally 2.55g / cm 3 to 2.70g / cm 3 . For example, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge SOC is 2.50g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.56g / cm 3 , 2.57g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.72g / cm 3 , 2.75g / cm 3 , 2.78g / cm 3 , 2.80g / cm 3 , or a range composed of any two of the above values.

[0237] When the compaction density of the positive electrode film layer is in the above range, the energy density of the battery cell can be improved, and the positive electrode active material in the positive electrode film layer is packed more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation under fast charging. Therefore, by adjusting the compaction density of the positive electrode film layer to a reasonable range, the battery cell has high energy density and high charging rate performance.

[0238] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) can be detected by the following method. The positive electrode sheet of the battery cell at 100% state of charge (SOC) is disassembled, the compaction density of the positive electrode film layer is measured, for example, a single-coated positive electrode sheet (if it is a double-coated sheet, the positive electrode film layer on one side can be wiped off first), a small disc with an area of S1 is punched, weighed, recorded as M1, and its thickness H1 is measured. Then the positive electrode film layer of the above weighed positive electrode sheet is wiped off, the weight of the positive electrode current collecting part is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight of the positive electrode sheet M1 - the weight of the positive electrode current collecting part M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode sheet H1 - the thickness of the positive electrode current collecting part H0, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0239] In some embodiments, the powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm, optionally, less than or equal to 20 Ω·cm, optionally, less than or equal to 11 Ω·cm. For example, the powder resistivity of the positive electrode active material can be 27.5 Ω·cm, 20 Ω·cm, 19 Ω·cm, 18 Ω·cm, 17 Ω·cm, 16 Ω·cm, 15 Ω·cm, 14 Ω·cm, 13 Ω·cm, 12 Ω·cm, 11 Ω·cm, 10 Ω·cm, 9 Ω·cm, 8 Ω·cm, 7 Ω·cm, 6 Ω·cm, 5 Ω·cm, 4 Ω·cm, 3 Ω·cm, 2 Ω·cm, 1 Ω·cm, or a range composed of any two of the above values.

[0240] The relatively low powder resistivity of the positive electrode active material makes the resistance of the positive electrode sheet relatively low, and the battery cell generates less heat.

[0241] In the embodiments of the present application, the powder resistivity of the material is the meaning known in the art, which can be detected by the methods and devices known in the art, for example, according to the test standard GB / T30835-2014, using PRCD1100 powder resistivity meter for testing.

[0242] In some embodiments, the powder compaction density of the positive electrode active material under 30000N is 2.46 g / cm 3 to 2.8 g / cm3 For example, the powder compaction density of the positive electrode active material under 30000N is 2.46g / cm 3 , 2.47g / cm 3 , 2.48g / cm 3 , 2.49g / cm 3 , 2.5g / cm 3 , 2.51g / cm 3 , 2.55g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.72g / cm 3 , 2.75g / cm 3 , 2.78g / cm 3 , 2.80g / cm 3 , or a range formed by any two of the above values.

[0243] When the powder compaction density of the positive electrode active material under 30000N is in the above range, the energy density of the battery cell can be improved, and the positive electrode active material in the positive electrode film layer can be more closely accumulated, the contact resistance between particles is smaller, which can further reduce the resistance of the pole piece, thereby reducing the heat generation.

[0244] In the embodiments of the present application, the powder compaction density of the material is the meaning known in the art, which can be detected by the method and equipment known in the art according to the test standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample, added into a mold with a bottom area of 1.327cm 2 of UTM7305 electronic pressure testing machine, pressurized to 3000kg (equivalent to 30000N), keep pressure for 30s, then release pressure, keep for 10s, then record and calculate the powder compaction density of the positive electrode active material under the action of 30000N.

[0245] In some embodiments, the charging gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g to 170 mAh / g, which can be 157 mAh / g to 170 mAh / g. Illustratively, the charging gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g, 151 mAh / g, 152 mAh / g, 153 mAh / g, 154 mAh / g, 155 mAh / g, 156 mAh / g, 157 mAh / g, 158 mAh / g, 159 mAh / g, 160 mAh / g, 161 mAh / g, 162 mAh / g, 163 mAh / g, 164 mAh / g, 165 mAh / g, 166 mAh / g, 167 mAh / g, 168 mAh / g, 169 mAh / g, 170 mAh / g, or a range between any two of the above values.

[0246] When the charging gram capacity of the positive electrode active material at 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0247] In the embodiments of the present application, the gram capacity of the active material is the meaning known in the art, which can be tested by using the devices and methods known in the art, and the test method of the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used. The half-button battery is assembled by taking lithium metal as the negative electrode and the sample electrode tab containing the above material as the positive electrode. The half-button battery is placed in a battery tester or other testing equipment with the same performance at 23℃±2℃, and the button capacity is obtained by 0.1C rate charging and discharging. Then the capacity is divided by the mass of the active material of the electrode tab to obtain the charging gram capacity parameter.

[0248] In some embodiments, the mass fraction of the olivine-structured lithium-containing phosphate in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%, and the positive electrode active material of the present application can be considered to be an olivine-structured lithium-containing phosphate system. When the mass fraction of the olivine-structured lithium-containing phosphate is less than 100%, the positive electrode active material can also include commonly used positive electrode active materials, for example, can include but is not limited to at least one of lithium-containing transition metal oxides. Examples of lithium-containing transition metal oxides can include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0249] Optionally, the mass fraction of the olivine-structured lithium-containing phosphate in the positive electrode active material is 100%.

[0250] In the embodiments of the present application, the lithium-containing phosphate with olivine structure can be phosphate particles or a material obtained after coating modification of the phosphate particles, for example, the lithium-containing phosphate with olivine structure includes phosphate particles and a coating layer, the coating layer is coated on the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge and Sn.

[0251] The phosphate particles are coated with the coating layer, which can improve the conductivity of the lithium-containing phosphate with olivine structure, reduce the powder resistivity of the material, and be beneficial to the migration rate of lithium ions, improve the rapid charging capability of the battery, and reduce the heat generation of the battery cell.

[0252] In some embodiments, the phosphate particles include a compound with a general formula of Li x1 A y1 Me a M b P 1-c X c Y z wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The cycle stability of the phosphate particles is relatively excellent, which is beneficial to improving the cycle performance of the battery cell.

[0253] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4. During the charging and discharging process, the battery cell is accompanied by the deintercalation and consumption of active ions such as Li, and the battery cell has different molar contents of Li when discharged to different states. In the enumeration of the 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, and the positive electrode active material is applied to the battery system. After charging and discharging cycles, the molar content of Li may change. In the enumeration of the positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiments of the application, the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will fluctuate, and the above-mentioned situations are all within the protection scope of the application.

[0254] In some embodiments, the coating layer includes a fast ion conductor with a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0

[0255] Exemplarily, the fast ion conductor is a material with a NASICON structure, for example, including one or more of lithium titanium iron phosphate Li2FeTi(PO4)3, lithium zirconium iron phosphate Li2FeZr(PO4)3, lithium tin iron phosphate Li2FeSn(PO4)3.

[0256] The fast ion conductor with a NASICON structure is a material with super-fast ion conduction ability, has abundant three-dimensional lithium ion diffusion and transmission channels, and has the advantages of high ion conduction efficiency and strong structural stability in multiple delithiation and lithium intercalation processes. Coating the surface of the phosphate particles with the fast ion conductor containing the NASICON structure can significantly improve the transmission rate of lithium ions in the positive electrode during multiple delithiation and lithium intercalation, improve the ion conductivity of the positive electrode active material, and improve the rapid charging capacity of the battery cell. In addition, it can also improve the specific capacity and the energy density of the corresponding battery cell.

[0257] In some embodiments, the coating layer further includes elemental carbon.

[0258] The carbon element and the fast ion conductor can be arranged in layers, for example, the carbon element as an independent carbon coating layer and the fast ion conductor as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0259] Optionally, the carbon coating layer can be coated on the surface of the fast ion conductor layer by a carbonization process of an organic carbon source (for example, glucose, polyethylene glycol, etc.). The carbon coating layer can partially coat the fast ion conductor layer or completely coat the fast ion conductor layer. The arrangement of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, compensate for the poor electronic conduction performance of the phosphate particles, and improve the energy density of the battery cell.

[0260] Specifically, the arrangement of the carbon coating layer has the following advantages for the positive electrode active material of the application:

[0261] The carbon coating layer in the positive electrode active material of the application provides a suitable channel for the transmission of electrons, can significantly improve the conduction rate of electrons in the process of multiple delithiation and lithiation, improve the electronic conductivity of the lithium-containing phosphate, and improve the charging capacity and energy density of the corresponding battery cell.

[0262] The carbon coating layer of the positive electrode active material of the application is loose and porous, which enables the electrolyte to fully and effectively contact the lithium-containing phosphate, thereby improving the transmission rate of lithium ions at the phase interface and the charging capacity of the battery cell.

[0263] Coating a carbon coating layer on the surface of the lithium-containing phosphate not only improves the electronic conductivity of the lithium-containing phosphate, but also improves the structural stability of the positive electrode active material, effectively alleviates the iron dissolution phenomenon of the positive electrode active material during long-term storage and cyclic use of the battery cell, and thus improves the cycle life of the battery cell.

[0264] The positive electrode active material of the application uses lithium-containing phosphate as a substrate, fully utilizes the advantages of low cost, high reliability, and good cycle stability of lithium-containing phosphate, and solves the disadvantages of poor electronic conductivity and ionic conductivity by using the coating layer (fast ion conductor layer and carbon coating layer). The battery cell prepared from the positive electrode active material of the application can improve the energy density of the battery cell under the premise of excellent cycle performance.

[0265] In the embodiments of the present application, the content of elements in the positive electrode active material is in the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, referring to EPA 6010D-2014, tested by inductively coupled plasma atomic emission spectrometry, and determined by plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After disassembling the positive electrode sheet from the battery monomer discharged to 0% state of charge SOC, washing and drying with DMC, and removing impurities by high temperature calcination, 0.4g of the positive electrode active material is weighed, 10ml (50% concentration) aqua regia is added thereto. Then it is placed on a 180℃ flat plate for 30min. After digestion on the flat plate, it is diluted to a volume of 100ml, and the quantitative test is carried out by the standard curve method.

[0266] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, which can be optionally 0.19 to 0.26. Illustratively, the graphitization degree of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, or a range consisting of any two of the above values.

[0267] When the graphitization degree of the positive electrode active material is in the above range, it is beneficial to improve the conductivity of the positive electrode active material and reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery monomer.

[0268] In the embodiments of the present application, the higher the graphitization degree of the material, the lower the degree of disorder, which can be tested according to the test standard JIS / K 0131-1996 X-ray diffraction analysis method general rules.

[0269] In some embodiments, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine structure lithium-containing phosphate is 5m 2 / g to 18m 2 / g.

[0270] Optionally, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine structure lithium-containing phosphate is 7.5m 2 / g to 14m 2 / g.

[0271] Illustratively, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or a range consisting of any two of the above values.

[0272] For example, the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14m 2 / g, 15m 2 / g, 16m 2 / g, 17m 2 / g, 18m 2 / g, or a range formed by any two of the above values.

[0273] The carbon element mainly exists in the form of a carbon coating layer in the coating layer, the carbon coating layer is loose and porous, which is beneficial to improve the specific surface area of the material, and is more beneficial to the effective contact between the electrolyte and the phosphate particles, and is beneficial to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is in the above range, the conductivity of the lithium-containing phosphate with olivine structure can be significantly improved, which is beneficial to improve the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the rapid charging capacity and energy density of the battery cell.

[0274] In the embodiments of the present application, the specific surface area of the material has the meaning known in the art, and can be detected by using the equipment and method known in the art, for example, the specific surface area 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 using a Tri-Star 3020 type specific surface area pore size analyzer of the Micromeritics company in the United States.

[0275] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1μm≤Dv50≤2μm, 0.4μm≤Dv10≤0.7μm.

[0276] For example, the Dv50 of the positive electrode active material can be 1μm, 1.1μm, 1.15μm, 1.2μm, 1.25μm, 1.3μm, 1.35μm, 1.4μm, 1.45μm, 1.5μm, 1.55μm, 1.6μm, 1.65μm, 1.7μm, 1.75μm, 1.8μm, 1.85μm, 1.9μm, 1.95μm, 2μm, or a range formed by any two of the above values.

[0277] Exemplarily, the Dv10 of the positive electrode active material can be 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, or a range formed by any two of the above values.

[0278] The particle size of the positive electrode active material is relatively small, the path of lithium ion deintercalation in the positive electrode active material is short, and the heat production is less. Moreover, the particle size of the positive electrode active material is not too small, and agglomeration basically does not occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0279] 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. The detection can be performed by using devices and methods known in the art. For example, the positive electrode active material is taken as a sample, the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0280] When the positive electrode active material includes not only the lithium-containing phosphate with olivine structure but also other materials, the volume distribution particle size of the positive electrode active material refers to the volume distribution particle size of all the positive electrode active materials.

[0281] In some embodiments, the lithium-containing phosphate with olivine structure is in a particulate form, the lithium-containing phosphate with olivine structure includes secondary particles, the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. Exemplarily, the average particle size of the primary particles is 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, or a range formed by any two of the above values.

[0282] The average particle size of the primary particles is relatively small, the path of lithium ion deintercalation in the positive electrode active material is short, and the heat production is less.

[0283] In the embodiments of the present application, the secondary particle refers to a particle in an agglomerated state formed by two or more primary particles. The primary particles and the secondary particles can be easily distinguished by experimental means (such as using a scanning electron microscope to take SEM images), and the average particle size of the primary particles can be obtained by SEM image testing. The SEM test parameters can be set as follows: working voltage (EHT) is 10.00 kV, InLens detector is used, working distance is 4.6 mm, and magnification is 1000X.

[0284] In some embodiments, the positive electrode film layer further comprises one or more of a ternary material, lithium phosphate, lithium dihydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, lithium citrate, lithium nickelate, and lithium ferrite. The above-mentioned materials can act as a lithium supplement, which can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and thus improve the energy density of the battery cell.

[0285] Optionally, the ternary material comprises Li x3 A y3 Ni a3 Co b3 Mn c M3(1-a3-b3-c3)Y3 z3 wherein 0

[0286] Exemplarily, the ternary material comprises LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2.

[0287] In some embodiments, the mass content of the lithium supplement agent in the positive electrode film layer is 0.5% to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two of the foregoing values. When the mass content of the lithium supplement agent is within the foregoing range, the lithium supplement agent can supplement lithium ions to the positive electrode film layer, compensate for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0288] 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 a lithium supplement layer, and the positive electrode active material can be in a positive electrode active material layer, in other words, the positive electrode film layer includes the lithium supplement layer and the positive electrode active material layer. The positive electrode active material layer can be disposed on at least one side of the positive electrode current collector, and the lithium supplement layer can be 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 between the lithium supplement layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be between the positive electrode active material layer and the positive electrode current collector, and the lithium supplement agent in the lithium supplement layer can be gradually released into the system during the cyclic charging and discharging of the battery cell, thereby compensating for the loss of lithium in the battery system.

[0289] In some embodiments, the positive electrode film layer optionally further includes a positive electrode conductive agent. The type of positive electrode conductive agent is not particularly limited in the embodiments of the present application, and as an example, the positive electrode conductive agent includes at least one of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode film layer.

[0290] In some embodiments, the positive electrode film layer optionally further includes a positive electrode binder. The type of positive electrode binder is not particularly limited in the embodiments of the present application, and as an example, the positive electrode binder can include at least one of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorine-containing acrylic ester resin. In some embodiments, the mass content of the positive electrode binder is ≤5% based on the mass of the positive electrode film layer.

[0291] In some embodiments, the positive current collector can 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 can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer can include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0292] In some embodiments, the ratio of the thickness of the positive current collector to the thickness of the single-sided positive film layer is 0.05 to 0.3. As an example, the ratio of the thickness of the positive current collector to the thickness of the single-sided positive 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 between any two of the above values.

[0293] When the ratio of the thickness of the positive current collector to the thickness of the single-sided positive film layer is in the above range, the rapid charging capability and the energy density of the battery cell can be improved.

[0294] In some embodiments, the thickness of the positive current collector is 10 μm to 15 μm, and can be 12 μm to 15 μm. As an example, 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 between any two of the above values.

[0295] When the thickness of the positive current collector is in the above range, the overcurrent capability of the positive current collector is excellent, and the battery cell can have a high energy density.

[0296] In the embodiments of the present application, the thickness of the positive film layer and the positive current collector has the meaning known in the art, and can be detected by using the devices and methods known in the art. For example, the thickness of the positive electrode sheet can be measured by using a micrometer, the thickness of the positive current collector can be measured by removing the film layer on the surface of the positive current collector, and the thickness of the positive film layer can be measured by subtracting the thickness of the positive current collector from the thickness of the positive electrode sheet when the positive film layer is single-sided coated, or by dividing the thickness of the positive electrode sheet by 2 when the positive film layer is double-sided coated.

[0297] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode current collector, and then drying and cold-pressing. The positive electrode slurry is usually formed by dispersing and uniformly stirring the positive electrode active material, the optional conductive agent, the optional binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0298] The positive electrode tab does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode tab of the embodiments of the present application further comprises a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer, and arranged on the surface of the positive electrode current collector. In some other embodiments, the positive electrode tab of the embodiments of the present application further comprises a protective layer covering the surface of the positive electrode film layer.

[0299] In some embodiments, the positive electrode tab further comprises a positive electrode conductive layer between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode tab, reduce the heat generation of the positive electrode tab, and thus reduce the heat generation of the battery cell.

[0300] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. For example, the thickness of the positive electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range defined by any two of the above values.

[0301] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode tab can be further improved, the heat generation of the positive electrode tab can be reduced, and thus the heat generation of the battery cell can be reduced, while the energy density of the battery cell can be improved.

[0302] In the embodiments of the present application, the thickness of the positive electrode conductive layer has the meaning known in the art, and can be detected by using the devices and methods known in the art, for example, by performing tomography on the positive electrode tab to directly measure the thickness of the positive electrode conductive layer.

[0303] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder.

[0304] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. For example, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or a range defined by any two of the above values.

[0305] For example, the positive electrode conductive agent comprises one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, and thus improve the conductivity of the positive electrode tab and reduce the heat generation of the battery cell.

[0306] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. Illustratively, the mass content of the positive electrode binder in the positive electrode conductive layer is 50%, 60%, 65%, 70%, or a range between any two of the above values.

[0307] Illustratively, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a polyacrylic acid, and a fluorine-containing acrylic ester resin. The positive electrode binder in the positive electrode conductive layer can improve the adhesion between the positive electrode current collector and the positive electrode film layer, and improve the structural stability of the positive electrode sheet.

[0308] [Negative electrode sheet]

[0309] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0310] In some embodiments, the compaction density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 , optionally 1.25 g / cm 3 to 1.36 g / cm 3 , at 100% state of charge of the battery cell. 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 between any two of the above values.

[0311] When the compaction density of the negative electrode film layer is within the above range, the energy density of the battery cell can be improved, and since the negative electrode active material in the negative electrode film layer is packed more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the sheet and thus reduce heat generation.

[0312] In the embodiments of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge is the meaning known in the art, which can be detected by using the devices and methods known in the art, and the detection method is as follows.

[0313] In some embodiments, the powder resistivity of the negative active material is 0.005 Ω·cm to 0.043 Ω·cm, which can be 0.04 Ω·cm. Exemplarily, the powder resistivity of the negative active material can be 0.043 Ω·cm, 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm, or a range composed of any two of the above values.

[0314] The relatively low powder resistivity of the negative active material makes the resistance of the negative electrode sheet relatively low, and the battery cell generates less heat.

[0315] In the embodiments of the present application, the powder resistivity of the negative active material is the meaning known in the art, which can be detected by using the devices and methods known in the art, and the detection method is as follows.

[0316] In some embodiments, the powder compaction density of the negative active material under a pressure of 20,000 N is 1.5 g / cm 3 to 1.85 g / cm 3 , which can be 1.55 g / cm 3 to 1.65 g / cm 3 . Exemplarily, the powder compaction density of the negative 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 a range composed of any two of the above values.

[0317] When the powder compaction density of the negative active material under a pressure of 20,000 N is in the above range, the energy density of the battery cell can be improved, and because the negative active material in the negative electrode film layer can be more tightly packed, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0318] In the embodiments of the present application, the powder compaction density of the material is the meaning known in the art, which can be detected by using the methods and devices known in the art according to the test standard GB / T24533-2009. As an example, a certain amount of negative active material is taken as a sample, which is added into a mold with a bottom area of 1.327 cm2 of a UTM7305 type electronic pressure testing machine, and is pressed to 2000 kg (equivalent to 20000 N), and is kept for 30 s, then is unloaded, and is kept for 10 s, then the powder compaction density of the negative active material under the action of 20000 N is recorded and calculated. 2

[0319] In some embodiments, the charge gram capacity of the negative active material at 0.1C rate is 350 mAh / g to 480 mAh / g. Illustratively, the charge gram capacity of the negative active material at 0.1C rate is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, or a range consisting of any two of the above values.

[0320] When the charge gram capacity of the negative active material at 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0321] In the embodiments of the present application, the charge gram capacity of the negative active material at 0.1C rate is the meaning known in the art, which can be detected by using the devices and methods known in the art, and the detection method is as the above charge gram capacity test method of the positive active material at 0.1C rate.

[0322] In some embodiments, the negative active material comprises a carbon-based material, and the cycle stability of the carbon-based material is relatively high, which can improve the cycle performance of the battery cell. Optionally, the mass ratio of the carbon-based material in the negative active material can be greater than or equal to 80% and less than or equal to 100%.

[0323] The positive active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative active material is mainly a carbon-based material system, and the two are used in combination, and the cycle performance of the battery cell is relatively excellent.

[0324] ​Optionally, the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. Illustratively, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, or a range defined by any two of the foregoing values.

[0325] When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, which can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the rapid charging performance of the battery cell.

[0326] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer, the artificial graphite includes secondary particles, the secondary particles include a plurality of primary particles, and the carbon coating layer is coated on the surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon, which refers to a transition state carbon material with a very low degree of graphitization and crystallization, and an approximate amorphous state (or a structure with no fixed shape and periodicity). In this application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0327] The artificial graphite includes secondary particles, the migration path of lithium ions in the artificial graphite is more, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions, the carbon coating layer has more end faces and defects, so that the number of sites capable of deintercalating lithium ions is more, and the electrical conductivity of the carbon coating layer is excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0328] Optionally, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. Illustratively, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range defined by any two of the foregoing values.

[0329] When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode sheet and the heat generation of the battery cell can be further reduced.

[0330] In the embodiments of the present application, the graphite particles can be prepared by methods known in the art, for example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and forming a carbon coating layer on at least part of the surface of the artificial graphite particles after carbonization treatment.

[0331] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of the coal tar pitch and the petroleum pitch is 250°C or lower.

[0332] Optionally, the carbonization treatment temperature is 700°C to 1800°C. Optionally, the carbonization treatment temperature is 1000°C to 1300°C. The carbonization treatment temperature is within a suitable range, which can carbonize the organic carbon source and form a coating layer containing amorphous carbon on at least a part of the surface of the artificial graphite.

[0333] Optionally, the carbonization treatment time is 1h to 6h.

[0334] In some embodiments, the carbon-based material can further include natural graphite. Specifically, the carbon-based material can include graphite particles, or the carbon-based material can include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0335] In some embodiments, the negative electrode active material can 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.

[0336] Optionally, the mass content of silicon element in the silicon-based material is 0.3% to 10.0%, and optionally 1% to 6%, based on the mass of the negative electrode active material. Illustratively, the mass content of silicon element in the silicon-based material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10%, or a range between any two of the above values.

[0337] The mass content of silicon element in the silicon-based material within the above range can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0338] Optionally, the silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0339] In some embodiments, the negative electrode active material, in addition to including the above-mentioned carbon-based material and optional silicon-based material, can further include at least one of a tin-based material and lithium titanate. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0340] The qualitative and quantitative detection of each substance or element in the present application can be carried out by using suitable equipment and methods known to those skilled in the art, and the relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc., and those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used for qualitative or quantitative determination.

[0341] For example, the present application can perform X-ray powder diffraction test and qualitative analysis on the negative electrode sheet or the negative electrode active material by JIS / K0131-1996 X-ray Diffraction Analysis Method General Rules.

[0342] Artificial graphite and natural graphite can be distinguished by SEM cross-sectional SEM photographs taken by scanning electron microscope SEM, there are gaps between flaky structures in the SEM cross-sectional photograph of natural graphite, the SEM cross-sectional photograph of artificial graphite is dense and has no obvious gap, or distinguished by XRD spectrum obtained by X-ray diffraction method, there are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and there is only 2H phase in the XRD spectrum of artificial graphite.

[0343] The negative electrode film layer in the embodiments of the present application includes at least one film layer, which can adopt a single layer film layer or at least two film layers. Optionally, the negative electrode film layer includes at least two film layers.

[0344] In the case of using a single layer film layer for the negative electrode film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes a silicon-based material. In the case of using a single layer film layer, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm to 13.5 μm. Illustratively, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, or a range composed of any two of the above values.

[0345] In the case of using at least two film layers for the negative electrode film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes a silicon-based material, which can be located in one of the at least two film layers or in at least two of the at least two film layers. The negative electrode film layer can include two film layers, three film layers, four film layers, or even more film layers.

[0346] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is arranged on the surface of the negative electrode current collector, the carbon-based material in the first negative electrode film layer includes graphite particles, the second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, the carbon-based material in the second negative electrode film layer includes graphite particles, and the graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer can be the same or different.

[0347] The interface of the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0348] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0349] The negative electrode film layer includes at least two film layers, and the layered coating is conducive to improving the rapid charging performance of the battery cell. In particular, when the first negative electrode film layer and the second negative electrode film layer are different, the pore difference of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission is reduced, and the rapid charging performance of the battery cell is improved.

[0350] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which is conducive to improving the compaction density of the negative electrode film layer. When the negative electrode active material includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0351] The difference in particle size in the first negative electrode film layer and the second negative electrode film layer can improve the rapid charging performance of the battery cell. Specifically, during rapid charging, the overpotential of the second negative electrode film layer is generally high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and can improve the problem of lithium extraction on the surface of the negative electrode sheet.

[0352] Optionally, the negative active material in the first negative electrode film layer is in a granular form, and the volume average particle size Dv50 of the negative active material is 9.5-18.5 μm, or 9.5-14.6 μm. For example, the volume average particle size of the negative active material 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 defined by any two of the above values. When the first negative electrode film layer comprises graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5-18.5 μm, or 9.5-14.6 μm.

[0353] 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, the solid-phase transmission path of lithium ions can be shortened, and the fast charging performance can be improved; on the other hand, the material is less likely to agglomerate during preparation, and the stability of the material can be improved.

[0354] Optionally, the negative active material in the second negative electrode film layer is in a granular form, and the volume average particle size Dv50 of the negative active material is 7.8-14.3 μm, or 7.8-11.3 μm. For example, the volume average particle size Dv50 of the negative active material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm, or a range defined by any two of the above values. When the second negative electrode film layer comprises graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8-14.3 μm, or 7.8-11.3 μm.

[0355] 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, the solid-phase transmission path of lithium ions can be shortened, and the fast charging performance can be improved; on the other hand, the material is less likely to agglomerate during preparation, and the stability of the material can be improved; and on the further hand, the negative active material in the second negative electrode film layer with the above volume average particle size range and the negative active material in the first negative electrode film layer cooperate to facilitate the construction of a gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reduce the tortuosity of lithium ion transmission, and improve the fast charging performance of the battery cell.

[0356] In the embodiments of the present application, the volume average particle size Dv50 of the negative active material has the meaning known in the art and can be detected using devices and methods known in the art, such as the volume average particle size Dv50 test method of the positive active material described above.

[0357] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. The tap density can reflect the filling density of the active material in the film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, so that the energy density of the battery cell is improved, and the first negative electrode film layer is relatively sparse in filling, and has more pores, which can improve the rapid charging performance of the battery cell. When the negative active material includes graphite particles, the tap density of the graphite particles in the first negative electrode film layer is less than or equal to the tap density of the graphite particles in the second negative electrode film layer.

[0358] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 , for example, 0.82 g / cm 3 , 0.85 g / cm 3 , 0.88 g / cm 3 , 0.90 g / cm 3 , 0.92 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 , or a range composed of any two of the above values. When the tap density of the carbon-based material in the first negative electrode film layer is within a suitable range, the rapid charging performance of the battery cell can be improved.

[0359] Optionally, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 , for example, 0.90 g / cm 3 , 0.92 g / cm 30.95 g / cm3 3 0.98 g / cm3 3 1.00 g / cm3 3 1.05 g / cm3 3 1.08 g / cm3 3 1.10 g / cm3 3 1.12 g / cm3 3 1.15 g / cm3 3 1.18 g / cm3 3 1.20 g / cm3 3 1.21 g / cm3 3 1.22 g / cm3 3 1.23 g / cm3 3 1.24 g / cm3 3 1.25 g / cm3 3 or a range defined by any two of the above. When the tap density of the carbon-based material in the second negative electrode film layer is within the appropriate range, the energy density of the battery cell can be improved.

[0360] In embodiments of the present application, the tap density of the material is the meaning known in the art, which can be measured by instruments and methods known in the art. For example, GB / T 5162-2006 can be referred to, and a powder tap density tester can be used for measurement. The testing instrument can use Dandong Bit BT-301.

[0361] Alternatively, 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, which can be 4:6 to 6:4. For example, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7, 4:6, 5:5, 6:4, 7:3, or a range defined by any two of the above. By adjusting the thickness ratio of the first negative electrode film layer and the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0362] In some embodiments, after the battery cell is subjected to a full charge test cycle of 10 cycles at the beginning of life (BOL), the thickness of the first negative electrode film layer is 15 μm to 65 μm, for example, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range defined by any two of the above. 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 rapid charging capacity of the battery cell can be improved.

[0363] In some embodiments, the thickness of the second negative electrode film layer is 15-65 μm, for example, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range defined by any two of the above values, after 10 cycles of BOL full charge test of the battery cell. When the thickness of the second negative electrode film layer is in the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be adjusted to reduce the tortuosity of lithium ion transmission and improve the rapid charging capacity of the battery cell.

[0364] In the embodiments of the present application, for example, the battery charging upper limit voltage is 3.65 V, and the battery discharging cut-off voltage is 2.0 V.

[0365] The BOL full charge test procedure is as follows: at 25°C, charge to 3.65 V at a charging rate of 0.33C of the nominal capacity of the battery, then charge to 0.05C at 3.65 V constant voltage, stand for 10 min, then discharge to 2.0 V at a discharging rate of 0.33C, stand for 10 min, the above one-time charging and discharging is one cycle, cycle for 10 times, then charge to 3.65 V at a charging rate of 0.33C of the nominal capacity, then charge to 0.05C at 3.65 V constant voltage, which is the BOL full charge state. In the BOL full charge state, the negative electrode sheet is disassembled, the thickness direction section of the middle region of the negative electrode sheet is observed using a scanning electron microscope, the two regions are distinguished according to the interface between the first negative electrode film layer and the second negative electrode film layer, and the thicknesses of the two regions are measured, for example, the thicknesses of 10 positions of the first negative electrode film layer are measured, the average value is calculated as the average value of the first negative electrode film layer, and the thicknesses of 10 positions of the second negative electrode film layer are measured, the average value is calculated as the average value of the second negative electrode film layer.

[0366] In some embodiments, after the battery cell is subjected to full-charge test at the end of life (EOL), the thickness of the first negative electrode film layer is 15-70 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, or a range defined by 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 the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the rapid charging capability of the battery cell.

[0367] In some embodiments, after the battery cell is subjected to full-charge test at the end of life (EOL), the thickness of the second negative electrode film layer is 15-70 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, or a range defined by 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 the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the rapid charging capability of the battery cell.

[0368] In the embodiments of the present application, for example, the upper limit voltage of battery charging is 3.65 V, and the discharge cut-off voltage of the battery is 2.0 V.

[0369] The EOL full charge test procedure is as follows: At 60℃, charge the battery to 3.65V at a charging rate of 0.33C (the nominal capacity), then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 10 minutes, then discharge it to 2.0V at a discharging rate of 0.33C, and let it stand for 10 minutes. One charge and discharge cycle is one cycle. The test is stopped when the battery capacity decays to 80% of the nominal capacity. Then, charge at 25°C with a constant current of 0.33C to 3.65V, and then charge at a constant voltage of 0.05C to 3.65V, which is the EOL full charge state. In the EOL full charge state, disassemble the negative electrode plate and use a tomographic scanning electron microscope to observe the cross-section of the thickness direction of the middle region of the negative electrode plate. Distinguish the two regions according to the interface of the first negative electrode film layer and the second negative electrode film layer, and measure the thickness of each. For example, measure the thickness of the first negative electrode film layer at 10 locations and calculate the average value as the average value of the first negative electrode film layer. Measure the thickness of the second negative electrode film layer at 10 locations and calculate the average value as the average value of the second negative electrode film layer.

[0370] In some embodiments, when the negative electrode film layer is a single-layer film (as opposed to the double-layer film layer described above), the negative electrode film layer further includes a lithium-containing binder. Optionally, the mass content of the lithium-containing binder relative to the negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the lithium-containing binder relative to 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 any combination of two of the above values. The lithium element in the lithium-containing binder can exist in ionic form, which can increase the number of freely moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the lithium ion insertion / extraction rate, and improve the fast charging performance of the battery cell. Optionally, the negative electrode film layer may further include a negative electrode binder, such as at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0371] Optionally, the lithium content in the lithium-containing binder is 3% to 10% by mass. For example, the lithium content in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of two of the above values. The lithium content is calculated based on the mass of the lithium-containing binder. When the lithium content is within the above range, a relatively large number of freely moving lithium ions can be achieved in the negative electrode film, further shortening the distance that lithium ions diffuse to the surface of the negative electrode film, increasing the lithium ion insertion / extraction rate, and improving the fast-charging performance of the battery cell.

[0372] Exemplarily, the lithium-containing binder comprises lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers and the hydroxyethyl acrylate monomers is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0373] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery monomer, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0374] In some other embodiments, in the case of adopting at least two film layers for the negative electrode film layer, the negative electrode film layer further comprises a lithium-containing binder.

[0375] Optionally, the first negative electrode film layer further comprises a first lithium-containing binder, and the second negative electrode film layer further comprises a second lithium-containing binder, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. 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.

[0376] The mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides a relatively large amount of freely movable lithium ions for the second negative electrode film layer, which can further improve the rapid charging performance of the battery monomer.

[0377] 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 of lithium ion diffusion to the surface of the negative electrode film layer, improve the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery monomer.

[0378] Optionally, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, or 3% to 8%. For example, the mass content of lithium element in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range defined by any two of the above values. When the mass content of lithium element is within the above range, the number of lithium ions that can freely move in the negative electrode film layer is relatively large, the distance of lithium ion diffusion to the surface of the negative electrode film layer is shortened, the deintercalation rate of lithium ions is improved, and the rapid charging performance of the battery cell is improved.

[0379] For example, the first lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, and the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0380] The lithium-containing binder described above can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0381] 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%. For example, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range defined by any two of the above values. The lithium element in the second lithium-containing binder can exist in the form of ions, which can increase the number of lithium ions that can freely move in the negative electrode film layer, shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0382] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0383] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, optionally 3% to 8%. Illustratively, the mass content of lithium element in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range formed by any two of the above values. When the mass content of lithium element is in the above range, the number of lithium ions that can freely move in the negative electrode film layer is relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0384] Illustratively, the second lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, and the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0385] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0386] 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 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).

[0387] 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.

[0388] In some embodiments, the negative electrode film layer can further optionally include a negative electrode conductive agent. The present embodiments do not have particular limitations on the type of the negative electrode conductive agent, and the negative electrode conductive agent can include, for example, at least one of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is ≤ 5% based on the total weight of the negative electrode film layer.

[0389] In some embodiments, the negative electrode film layer can further optionally include a negative electrode binder. In some embodiments, the mass content of the negative electrode binder is ≤ 5% based on the total weight of the negative electrode film layer.

[0390] In some embodiments, the negative electrode film layer can further optionally include other auxiliary agents. The other auxiliary agents can include, for example, thickening agents, dispersants, and the like, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, the mass content of the other auxiliary agents is ≤ 2% based on the total weight of the negative electrode film layer.

[0391] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As examples of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As examples, the metal material in the metal material layer can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As examples, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0392] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. For example, the thickness of the negative electrode current collector is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or a range defined by any two of the above values.

[0393] When the thickness of the negative electrode current collector is in the above range, the overcurrent capacity of the negative electrode current collector is excellent, and the battery cell can have a high energy density.

[0394] In the present embodiments, the thickness of the negative electrode current collector has the meaning known in the art and can be detected using the devices and methods known in the art, for example, by washing the film layer on the surface of the negative electrode current collector with a solvent and measuring the thickness of the negative electrode current collector with a micrometer.

[0395] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative electrode current collector, and then drying and cold-pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, the optional conductive agent, the optional binder, and other optional additives in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0396] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab of the embodiments of the present application further comprises a negative electrode conductive layer arranged between the negative electrode current collector and the negative electrode film layer and arranged on the surface of the negative electrode current collector. In some other embodiments, the negative electrode tab of the embodiments of the present application further comprises a protective layer arranged on the surface of the negative electrode film layer.

[0397] In some embodiments, the negative electrode tab further comprises a negative electrode conductive layer arranged between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode tab, reduce the heat generation of the negative electrode tab, and thus reduce the heat generation of the battery cell.

[0398] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. For example, 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 formed by any two of the above values.

[0399] When the thickness of the negative electrode conductive layer is in the above range, the conductivity of the negative electrode tab can be further improved, the heat generation of the negative electrode tab can be reduced, the heat generation of the battery cell can be reduced, and the energy density of the battery cell can be improved.

[0400] In the embodiments of the present application, the thickness of the negative electrode conductive layer has the meaning known in the art, can be detected by using the devices and methods known in the art, and can be detected by using the test method of the negative electrode conductive layer described above.

[0401] In some embodiments, the negative electrode conductive layer comprises one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode tab and reducing the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the adhesion between the negative electrode current collector and the negative electrode film layer, thereby improving the structural stability of the negative electrode tab.

[0402] In some embodiments, the negative electrode conductive layer can further comprise other additives. For example, the other additives can comprise a thickening agent, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.

[0403] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 20% to 40%. Illustratively, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or a range consisting of any two of the aforementioned values.

[0404] Illustratively, the negative electrode conductive agent includes one or more of super-p carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0405] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%. Illustratively, the mass content of the negative electrode binder is 60%, 65%, 70%, 75%, 80%, or a range consisting of any two of the aforementioned values.

[0406] Illustratively, 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.

[0407] In some embodiments, the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is 1.05 to 1.30, and optionally 1.07 to 1.15. Illustratively, the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3, or a range consisting of any two of the aforementioned values.

[0408] When the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is in the aforementioned range, there are sufficient sites in the negative electrode film layer for lithium intercalation, which can reduce the risk of lithium precipitation and is conducive to fast charging.

[0409] In the embodiments of the present application, the CB value has the meaning known in the art and can be detected using devices and methods known in the art, for example, the capacity of the unit area negative electrode film layer and the capacity of the unit area positive electrode film layer are calculated respectively, and the ratio of the two is calculated to obtain the CB value.

[0410] Specifically, taking the upper limit voltage of battery charging as 3.65V and the discharge cut-off voltage of the battery as 2.0V as an example,

[0411] The capacity of the unit area positive electrode film layer refers to the actual delithiation capacity of the positive electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the positive electrode sheet is taken out, and a CR2430 type half buckle battery of positive electrode-lithium sheet is assembled. The area of the positive electrode sheet used is amm 2The electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then the assembled half-buckle battery is left to stand for 3 h. The test is carried out at 25°C, and the capacity of the positive electrode film per unit area is Y / a*b*c*d, where Y is the discharge capacity of the second cycle, a is the length of the positive electrode tab in mm, b is the width of the positive electrode tab in mm, c is the number of surfaces of the positive electrode current collector coated with the positive electrode active material, and d is the area of the negative electrode tab in mm2.

[0412] Specifically, the capacity of the negative electrode film per unit area refers to the actual lithium intercalation capacity of the negative electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, and the negative electrode tab is taken out to assemble a CR2430 type half-buckle battery of negative electrode-lithium tab. The area of the negative electrode tab is f mm2. 2 The electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then the assembled half-buckle battery is left to stand for 3 h. The test is carried out at 25°C, and the capacity of the positive electrode film per unit area is Y / a*b*c*d, where Y is the discharge capacity of the second cycle, a is the length of the positive electrode tab in mm, b is the width of the positive electrode tab in mm, c is the number of surfaces of the positive electrode current collector coated with the positive electrode active material, and d is the area of the negative electrode tab in mm2.

[0413] In the embodiments of the present application, the separation film includes a base film with a porous structure.

[0414] 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, and is not particularly limited. When the base film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0415] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0416] In some embodiments, the porosity of the base film is 20% to 70%, and is optionally 35% to 60%. For example, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range defined by any two of the above values.

[0417] When the porosity of the base film is in the above range in the embodiments of the present application, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0418] In the embodiments of the present application, the porosity refers to the percentage of the volume of the pores in the separator film to the total volume of the separator film. The porosity can be tested according to the standard GB / T 36363-2018 “Polyolefin Separator for Battery Cell”. It should be noted that the actual testing process can be slightly different from the standard in order to eliminate the influence on the testing of the porosity as much as possible, and to obtain more accurate test values according to the differences in testing instruments, testing errors, and testing processes.

[0419] In some embodiments, the thickness of the base film is 6 μm to 12 μm, which can be optionally 6 μm to 9 μm. For example, the thickness of the base film is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range formed by any two of the above values.

[0420] When the thickness of the base film is in the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0421] In the embodiments of the present application, the separator film can be the base film. Optionally, the separator film further comprises a functional layer disposed on at least one side of the base film, and the functional layer can comprise inorganic particles to improve the heat resistance of the separator film. Optionally, the functional layer is disposed on both sides of the base film.

[0422] In some embodiments, the functional layer comprises a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer comprises first inorganic particles, the second functional layer is located on the other side of the base film, and the second functional layer comprises composite particles, the composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles, and 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.

[0423] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

[0424] Optionally, the first functional layer can comprise a binder, which can optionally comprise at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0425] Optionally, the first inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0426] In the embodiments of the present application, the thickness of the base film has the meaning known in the art, which can be detected using the meaning and equipment known in the art. For example, a newly prepared separator film can be taken as a sample, or a battery cell that has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery cell is about 0% SOC) is disassembled in reverse, a separator film is obtained from the battery cell, and the separator film is dried and taken as a sample. The separator film is cut by an ion beam cutter to form a cross section, and then the thickness of the cross section of the separator film and each layer thereof is measured using a scanning electron microscope.

[0427] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers, which optionally include acrylate-acrylonitrile-acrylamide-acryl copolymers. The acrylate copolymers have excellent bonding properties, and have high bonding 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.

[0428] The second inorganic particles in the composite particles prevent the non-fluoropolymer particles from being easily bonded due to high-temperature treatment in the granulation process, so that the composite particles have pores, which are beneficial to the transmission of lithium ions, improve the ion conductivity of the separator film, and the second inorganic particles also improve the compression modulus of the composite particles, so that the composite particles are not easily deformed during charging and discharging, making the structure of the separator film more stable, and improving the kinetic performance of the battery cell and the rapid charging performance. Optionally, the second functional layer is arranged close to the negative electrode tab, and because the composite particles are not easily deformed, the separator film does not cause side effects such as extrusion to the negative electrode tab, so that the kinetic performance of the negative electrode tab is stable. Correspondingly, the first functional layer is arranged close to the positive electrode tab.

[0429] 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 rapid charging performance of the battery cell.

[0430] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, and optionally 5 nm to 20 nm. Illustratively, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range defined by any two of the above values. When the average particle size of the second inorganic particles is within the above range, the heat resistance and compression modulus of the composite particles can be improved.

[0431] In the embodiments of the present application, the average particle size of the second inorganic particles has the meaning known in the art and can be detected by using the devices and methods known in the art. For example, after the isolation film is obtained, the isolation film is dried as a sample, the isolation film is cut by an ion beam cutter to form a cross section, and then the particle size of the second inorganic particles in the isolation film is measured by using a scanning electron microscope. The particle size of a plurality of, for example, 50, second inorganic particles is measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0432] In some embodiments, the ion conductivity of the isolation film is 0.3 mS / cm to 0.6 mS / cm. Illustratively, the ion conductivity of the isolation film is 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.45 mS / cm, 0.5 mS / cm, 0.55 mS / cm, 0.6 mS / cm, or a range defined by any two of the above values.

[0433] When the ion conductivity of the isolation film is within the above range, the migration ability of lithium ions of the isolation film can be further improved, and the rapid charging performance of the battery cell can be improved.

[0434] In the embodiments of the present application, the ion conductivity of the isolation film has the meaning known in the art and can be detected by using the devices and methods known in the art. For example,

[0435] Preparation of a 2025 type button cell for testing: In a vacuum glove box, lithium pieces were placed into a negative electrode shell, 150 μL of an electrolyte was added, the electrolyte was a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then an isolation film (area of 3.14 cm 2 , thickness of 12 μm) was placed to tightly adhere to the lithium pieces, 25 μL of an electrolyte was added, and finally a positive electrode piece (the positive electrode piece can be the positive electrode piece in Example 1) was placed thereon, and then the button cell was packaged. The assembled button cell was taken out of the vacuum glove box and placed for 24 h for the next step of testing.

[0436] Test: In an electrochemical workstation, test at a frequency range of 10 -1 ~10 6 Hz, obtain the resistance Rb of the separator film, and calculate the ion conductivity σ (unit: mS / cm) by the following formula, σ = L / (R b x S)

[0437] wherein R b is the resistance of the separator film, and L and S are the thickness and area of the separator film to be tested, respectively.

[0438] [Electrolyte]

[0439] In some embodiments, the battery cell further comprises an electrolyte.

[0440] During the charging and discharging of the battery cell, active ions such as lithium ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0441] In the embodiments of the present application, the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, which can be 15 mS / cm to 20 mS / cm. For example, the conductivity of the electrolyte at room temperature is 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm or a range formed by any two of the above values.

[0442] When the conductivity of the electrolyte at room temperature, for example 25℃, is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0443] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, for example 25℃, is the ion conductivity, which can be detected by devices and methods known in the art, for example, by referring to the industry standard HG-T 4067-2015.

[0444] In some embodiments, the electrolyte has a viscosity of 2.3 mPa-s to 3.5 mPa-s at room temperature. For example, the electrolyte has a viscosity of 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 defined by any two of the above values.

[0445] When the viscosity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0446] In the embodiments of the present application, the viscosity of the electrolyte is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, according to GB / T 10247-2008.

[0447] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature, for example, 25°C. For example, the electrolyte has a density of 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 defined by any two of the above values.

[0448] When the density of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0449] In the embodiments of the present application, the density of the electrolyte is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, according to GB / T 2013-2010.

[0450] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not particularly limited and can be selected according to actual needs.

[0451] In some embodiments, the organic solvent comprises a chain carboxylic ester solvent, and the mass content of the chain carboxylic 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%, and optionally 50% to 70%. For example, the mass content of the chain carboxylic ester solvent is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or a range defined by any two of the above values.

[0452] When the mass content of the chain carboxylic ester solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is conducive to the migration of lithium ions.

[0453] In some embodiments, the chain carboxylic ester solvent comprises a compound represented by Formula I,

[0454] In Formula I,

[0455] R1 comprises a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group,

[0456] R2 comprises a C1 to C5 alkyl group or a C1 to C5 haloalkyl group.

[0457] The chain carboxylic ester solvent described above has a high conductivity, which is conducive to improving the rapid charging capability of the battery cell.

[0458] Optionally, R1 comprises a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further optionally, R1 comprises a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0459] Optionally, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. Further optionally, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0460] In each of the above embodiments, the halogen atom comprises one or more of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and optionally, the halogen atom comprises a fluorine atom.

[0461] In each of the above embodiments, the haloalkyl group comprises one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group, and an iodoalkyl group, and optionally, the haloalkyl group comprises a fluoroalkyl group.

[0462] For example, the chain carboxylic ester solvent comprises one or more of a compound represented by Formula I-1 to a compound represented by Formula I-8,

[0463] In some embodiments, the organic solvent further comprises a carbonate solvent.

[0464] Optionally, the carbonate solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Further optionally, the carbonate solvent comprises one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The carbonate solvent and the chain carboxylic acid ester solvent are used in combination, so that the conductivity of the electrolyte at room temperature is improved, which is conducive to the migration of lithium ions.

[0465] Further optionally, the mass content of the carbonate solvent in the organic solvent is 30% to 70%, optionally 30% to 50%. Illustratively, the mass content of the carbonate solvent in the organic solvent is 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, or a range formed by any two of the above values. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte at room temperature, which is conducive to the migration of lithium ions.

[0466] Illustratively, the carbonate solvent comprises one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, and the mass content of the carbonate solvent is 30% to 50%.

[0467] In some embodiments, the electrolyte further comprises an additive. The additive can comprise a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, etc.

[0468] In some embodiments, the additive comprises one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive, optionally at least two of them. The additive can improve the performance of the interface film on the positive electrode side and / or the negative electrode side, which is conducive to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0469] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. Illustratively, the mass content of the additive in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range formed by any two of the above values.

[0470] The additive with the above mass content can effectively improve the performance of the interface film on the positive electrode side and / or the negative electrode side, which is conducive to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0471] Exemplarily, the carbonate-based additive includes one or more of vinylene carbonate VC, fluoroethylene carbonate FEC.

[0472] Exemplarily, the sulfur-containing additive includes one or more of vinyl sulfite DTD, bis vinyl sulfite 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, methyl methylsulfate MMDS.

[0473] Optionally, the lithium salt-based additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF4, lithium bis(oxalato)borate LiBOB.

[0474] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, optionally 2% to 6%.

[0475] Optionally, the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%, optionally 0.5% to 3%.

[0476] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, and the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%.

[0477] Further optionally, the mass content of the vinylene carbonate VC in the electrolyte is 2% to 6%, and the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.5% to 3%.

[0478] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfimide salt and lithium hexafluorophosphate LiPF6. The above lithium salt is easy to dissociate, is conducive to the rapid migration of lithium ions, and the electrolyte system is relatively stable and is not easy to decompose, which can improve the cycle performance of the battery cell.

[0479] Optionally, the fluorine-containing sulfimide salt includes one or more of lithium bisfluorosulfonylimide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0480] Optionally, the lithium salt includes lithium bisfluorosulfonylimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of the lithium bisfluorosulfonylimide LiFSI is 0.2 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.5 mol / L to 1.0 mol / L.

[0481] Exemplarily, the molar concentration of the lithium bisfluorosulfonylimide LiFSI is 0.4 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.7 mol / L.

[0482] For example, the molar concentration of lithium bisfluorosulfonylimide LiFSI is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.5 mol / L.

[0483] For example, the molar concentration of lithium bisfluorosulfonylimide LiFSI is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.8 mol / L.

[0484] Optionally, the ratio of the molar concentration of lithium bisfluorosulfonylimide to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2 to 1.0, optionally 0.2 to 0.5. For example, the ratio of the molar concentration of lithium bisfluorosulfonylimide 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 between any two of the above values.

[0485] In the embodiments of the present application, the types and contents of inorganic components / lithium salt in the electrolyte are the meanings known in the art, and can be detected by using the devices and methods known in the art, for example, the qualitative or quantitative analysis of the inorganic components / lithium salt in the electrolyte can be performed by ion chromatography according to the standard JY / T020-1996 "General Ion Chromatography Analysis Method". In the embodiments of the present application, the freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or the free electrolyte obtained from a battery that has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) by reverse disassembly can be taken as a sample, and the ion chromatography analysis method is used for detection.

[0486] In the embodiments of the present application, the types and contents of organic components in the electrolyte are the meanings known in the art, and can be detected by using the devices and methods known in the art, for example, the qualitative and quantitative analysis of the organic components in the electrolyte can be performed by gas chromatography according to the standard GB / T9722-2006 "General Gas Chromatography Method for Chemical Reagents". In the embodiments of the present application, the freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or the free electrolyte obtained from a battery that has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) by reverse disassembly can be taken as a sample, and the ion chromatography analysis method is used for detection.

[0487] In the embodiments of the present application, after the components in the electrolyte are quantitatively and qualitatively detected, the components are classified, and the chain carboxylic acid ester solvent, the carbonate solvent (for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate) is taken as a component of the organic solvent, and the mass content of each component is calculated based on 100% of the mass of the organic solvent,

[0488] The carbonate additive (for example, vinylene carbonate, fluoroethylene carbonate), the sulfur-containing additive and the lithium salt additive are taken as additives of the electrolyte, and the mass content of each component is calculated based on 100% of the mass of the electrolyte.

[0489] 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 units of g, and A represents the rated capacity of the battery cell, in units of Ah. Exemplarily, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah, or a range composed of any two of the above values.

[0490] d / A can reflect the liquid retention capacity of the electrolyte. When d / A is in the above range, the electrolyte can have a good infiltration effect on the positive and negative electrode sheets, and can improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the rapid charging capacity of the battery cell.

[0491] In the embodiments of the present application, d / A of the battery cell can be understood as a liquid retention coefficient, which can be detected by using devices and methods known in the art. For example, GB / T31486-2015 "Electric Performance Requirements and Test Methods for Power Accumulator for Electric Vehicles" can be used as an example to illustrate the case where the upper limit voltage of the battery is 3.65V and the discharge cut-off voltage of the battery is 2.0V.

[0492] At 25°C, the battery cell is charged to 3.65V at 0.33C, then charged to 0.05C at constant voltage, and then discharged to 2.0V at 0.33C, to obtain the discharged capacity A as the denominator. The battery cell is weighed as M0, and then the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte are disassembled, and the free electrolyte is placed in a bag. All the solid components are placed in a 60°C oven for more than 4 hours (including but not limited to the positive electrode sheet, the negative electrode sheet, the separator and other mechanical parts of the disassembled battery cell which contribute to M0), and then all the components of the battery cell are weighed as M1. The weight difference between M0 and M1 is taken as the numerator. The liquid retention coefficient is equal to the value obtained by dividing the weight difference between M0 and M1 by the capacity A.

[0493] In some embodiments, the positive electrode sheet, the separator film, and the negative electrode sheet can be made into an electrode assembly through a winding process and / or a stacking process.

[0494] In some embodiments, the battery cell 7 can include a housing 20.

[0495] 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, and the like. The housing 20 of the battery cell 7 can also be a soft pack, such as a pouch soft pack. The material of the soft pack can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0496] The housing 20 is a hollow structure, which can be used to encapsulate the electrode assembly 10 and the electrolyte as described above.

[0497] The preparation method of the battery cell 7 of the embodiments of the present application is known. In some embodiments, the positive electrode sheet, the separator film, 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 film, and the negative electrode sheet can be formed into the electrode assembly 10 through a winding process and / or a stacking process, the electrode assembly 10 can be placed in the housing 20, the electrolyte can be injected after drying, and the battery cell 7 can be obtained through processes such as vacuum packaging, standing, formation, and shaping.

[0498] In some embodiments, the housing 20 includes a shell 21 having an opening and an end cap 22 covering the opening.

[0499] The shape of the shell 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical shell can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid shell can be selected. Alternatively, the electrode assembly 10 and the shell 21 are both cuboid structures.

[0500] In some embodiments, the base material of the shell 21 includes steel, which has high mechanical strength and is not easy to deform, 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 shell 21.

[0501] Optionally, the thickness of the shell 21 is 0.1mm to 0.5mm, and optionally 0.2mm to 0.35mm. For example, the thickness of the shell 21 is 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm or a range between any two of the above values. When the thickness of the shell 21 is within the above range, the mechanical strength of the shell 21 is high, which can improve the use reliability of the battery monomer 7; and the shell 21 occupies less space, and the internal space of the shell 21 is large, which is beneficial to improve the energy density of the battery monomer 7.

[0502] From the appearance of the electrode assembly 10, the electrode assembly 10 includes a main body part 12 and a tab part 11, the tab part 11 includes a positive electrode tab 111 and a negative electrode tab 112, and the positive electrode tab 111 and the negative electrode tab 112 protrude from the main body part 12.

[0503] The positive electrode tab 111 and the negative electrode tab 112 can protrude from the same side of the main body part 12, or can protrude from opposite sides respectively.

[0504] Optionally, the number of the positive electrode tabs 111 on the same side of the main body part 12 is at least one, and optionally at least two, and the at least two positive electrode tabs 111 can increase the overcurrent capacity of the positive electrode tab 111.

[0505] Optionally, the number of the negative electrode tabs 112 on the same side of the main body part 12 is at least one, and optionally at least two, and the at least two negative electrode tabs 112 can increase the overcurrent capacity of the negative electrode tab 112.

[0506] In some embodiments, the battery monomer 7 further includes a positive electrode terminal 31, and the positive electrode terminal 31 is electrically connected with the positive electrode tab 111. Optionally, the positive electrode terminal 31 and the positive electrode tab 111 are welded, and the positive electrode terminal 31 and the positive electrode tab 111 can be connected through an adapter or without using an adapter; optionally, the positive electrode terminal 31 and the positive electrode tab 111 are not connected through an adapter, i.e. the positive electrode terminal 31 and the positive electrode tab 111 are directly welded, which can reduce the resistance at the connection, and is beneficial to reduce the overall internal resistance of the battery monomer 7.

[0507] In some embodiments, the battery cell 7 further comprises a negative terminal 32 electrically connected with the negative tab 112. Optionally, the negative terminal 32 and the negative tab 112 are welded, and the negative terminal 32 and the negative tab 112 can be connected through a jumper or without a jumper; optionally, the negative terminal 32 and the negative tab 112 are not connected through a jumper, i.e., the negative terminal 32 and the negative tab 112 are directly welded, which can reduce the resistance at the connection and is conducive to reducing the overall internal resistance of the battery cell 7. When the negative tab 112 is a negative tab, the negative terminal 32 is a positive terminal.

[0508] Optionally, the number of positive terminals 31 located on the same side of the main body part 12 is at least one, and can be at least two, and the at least two positive terminals 31 can increase the overcurrent capacity of the positive terminal 31.

[0509] Further optionally, the overcurrent area of a single positive terminal 31 is 150mm 2 to 1000mm 2 , and can be 200mm 2 to 1000mm 2 . The overcurrent area of the positive terminal 31 on one side refers to the sum of the overcurrent areas of all positive terminals 31 located on the same side of the main body part 12. The overcurrent area of the positive terminal 31 can be understood as the cross-sectional area of the positive terminal 31, which is perpendicular to the thickness direction of the end cover 22.

[0510] Exemplarily, the overcurrent area of the positive terminal 31 on one side can be 150mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 , 650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , 850mm 2 , 900mm 2 , 950mm 2 , 1000mm 2 , or a range composed of any two of the above values.

[0511] Optionally, the number of negative terminals 32 located on the same side of the main body 12 is at least one, and can be at least two. The at least two negative terminals 32 can increase the overcurrent capacity of the negative terminals 32.

[0512] Further optionally, the overcurrent area of the single-side negative terminals 32 is 150mm 2 to 1000mm 2 , and can be 200mm 2 to 1000mm 2 The overcurrent area of the single-side negative terminals 32 refers to the sum of the overcurrent areas of all the negative terminals 32 located on the same side of the main body 12. The overcurrent area of the negative terminals 32 can be understood as the cross-sectional area of the negative terminals 32, which is perpendicular to the thickness direction of the end cover 22.

[0513] Exemplarily, the overcurrent area of the single-side negative terminals 32 can be 150mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 , 650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , 850mm 2 , 900mm 2 , 950mm 2 , 1000mm 2 , or a range composed of any two of the above values.

[0514] As shown in FIG. 15, in some embodiments of the present application, the battery cell 7 according to the embodiments of the present application can be assembled into a battery module 6. The number of battery cells 7 contained in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0515] If the battery cell 7 is multiple, the multiple battery cells 7 can be connected in series or in parallel or in a mixed connection, the mixed connection 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 or in parallel or in a mixed connection, and then the whole of the multiple battery cells 7 is accommodated in the accommodating portion of the battery module 6; of course, the multiple battery cells 7 can be first connected in series or in parallel or in a mixed connection to form the battery module 6, and then the multiple battery modules 6 are connected in series or in parallel or in a mixed connection to form a whole, which is accommodated in the accommodating portion. Alternatively, the battery module 6 can further include an accommodating portion having an accommodating space, and the multiple battery cells 7 are accommodated in the accommodating space.

[0516] As shown in FIG. 16, in some embodiments, the above-mentioned battery module 6 can also be assembled into a battery pack 2, and the number of battery modules 6 contained in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. In this article, the battery device can be a battery module 6 or a battery pack 2.

[0517] In the battery pack 2, a box 5 and multiple battery modules 6 arranged in the box 5 can be included. The box 5 includes a first box portion 5a and a second box portion 5b, and the box 5 has an accommodating space 5c, the first box portion 5a is used to cover the second box portion 5b and forms a closed space for accommodating the battery module 6. The multiple battery modules 6 can be arranged in the box 5 in any manner.

[0518] The first box portion 5a and the second box portion 5b are mutually covered, and the first box portion 5a and the second box portion 5b jointly define the accommodating space 5c for accommodating the battery cell. The second box portion 5b can be a hollow structure with one end open, and the first box portion 5a is a plate-shaped structure, which is covered on the open side of the second box portion 5b to form the box 5 with the accommodating space 5c. The first box portion 5a and the second box portion 5b can also be hollow structures with one side open, and the open side of the first box portion 5a is covered on the open side of the second box portion 5b to form the box 5 with the accommodating space 5c. Of course, the first box portion 5a and the second box 5b can have various shapes, such as a cylinder, a cuboid, etc.

[0519] In order to improve the sealing performance of the first box portion 5a and the second box portion 5b after being connected, a sealing member such as sealing glue, sealing ring, etc. can be arranged between the first box portion 5a and the second box portion 5b.

[0520] Suppose that the first box portion 5a is covered on the top of the second box portion 5b, the first box portion 5a can also be called an upper box cover, and the second box portion 5b can also be called a lower box.

[0521] In some embodiments, the temperature of the environment in which the battery pack 2 or any battery cell constituting the battery pack 2 is located is 30°C during the charging process from 0% state of charge (SOC) to 100% SOC.

[0522] In some embodiments, the temperature of the environment in which the battery pack 2 or any battery cell constituting the battery pack 2 is located is 30°C during the charging process from 10% state of charge (SOC) to 80% SOC.

[0523] In some embodiments, the charging process from 10% SOC to 80% SOC of the battery pack 2 or any battery cell constituting the battery pack 2 includes a plurality of charging steps, and the difference between the maximum state of charge of any charging step and the maximum state of charge of its adjacent charging step is less than or equal to 5% SOC, for example, 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 between any two of the above values.

[0524] The charging process from 10% SOC to 40% SOC of the battery pack 2 or any battery cell constituting the battery pack 2 includes a plurality of charging steps, and for any charging step, the charging rate can be any value between 5C and 10C, and the charging rate corresponding to each charging step can be any value of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value in a range between any two of the above values.

[0525] The charging process from 40% SOC to 80% SOC of the battery pack 2 or any battery cell constituting the battery pack 2 also includes a plurality of charging steps, and 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 charging to 80% SOC is any value of 2.5C-5C, for example, it can be 2.7C.

[0526] For example, the charging steps from 10% to 80% of the battery pack 2 or any battery cell constituting the battery pack 2 can be carried out as follows:

[0527] charging from 10% SOC to 15% SOC at a constant current of 5.0C,

[0528] charging from 15% SOC to 20% SOC at a constant current of 5.0C,

[0529] charging from 20% SOC to 25% SOC at a constant current of 5.0C,

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

[0531] charged from 30% SOC to 35% SOC at 5.0C constant current,

[0532] charged from 35% SOC to 40% SOC at 5.0C constant current,

[0533] charged from 40% SOC to 45% SOC at 4.6C constant current,

[0534] charged from 45% SOC to 50% SOC at 4.3C constant current,

[0535] charged from 50% SOC to 55% SOC at 4.0C constant current,

[0536] charged from 55% SOC to 60% SOC at 3.7C constant current,

[0537] charged from 60% SOC to 65% SOC at 3.4C constant current,

[0538] charged from 65% SOC to 70% SOC at 3.1C constant current,

[0539] charged from 70% SOC to 75% SOC at 2.9C constant current,

[0540] charged from 75% SOC to 80% SOC at 2.7C constant current.

[0541] In some embodiments, the battery pack 2 or any battery cell constituting the battery pack 2 has a charging time from 10% state of charge to 80% state of charge less than or equal to 10.5 min, optionally 5 min to 10.5 min, and the battery pack 2 is at room temperature, for example 30°C, at 10% state of charge. Illustratively, the battery pack 2 has a charging time from 10% state of charge to 80% state of charge of 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min, or a range between any two of the above values.

[0542] In some embodiments, the battery cell has a volumetric energy density of 390 Wh / L to 500 Wh / L, optionally 410 Wh / L to 470 Wh / L. Illustratively, the battery cell has a volumetric energy density of 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 between any two of the above values. The battery cell has a high volumetric energy density.

[0543] In the embodiments of the present application, the volumetric energy density of the battery cell is in the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, taking the battery charging upper limit voltage of 3.65V and the battery discharging cut-off voltage of 2.0V as an example for illustration,

[0544] The battery cell is placed at 25℃, charged to 3.65V at 0.33C constant current, then charged to 0.05C at constant voltage, discharged to 2.0V at 0.33C constant current, and the discharge capacity A0 at this time is recorded, unit: Ah, the length, width and height of the battery cell are measured by using the caliper (generally calculated by the size of the shell of the battery, excluding the height of the electrode terminal, and excluding the insulating film outside the shell), the volume V0 of the battery cell is calculated, unit: L, and the volumetric energy density VED of the battery cell is (A0 x discharge platform voltage) / V0, unit: Wh / L.

[0545] Electric device

[0546] The second aspect of the embodiments of the present application provides an electric device, which comprises the battery device of the embodiments of the present application, such as a battery cell, a battery module or a battery pack. The battery cell, the battery module or the battery pack can be used as a power source of the electric device, or can be used as an energy storage unit of the electric device. The electric device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel automobile, a gas automobile or a new energy automobile, the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended electric automobile, etc., the spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc., the electric toy includes a fixed or mobile electric toy, for example, a game machine, an electric automobile toy, an electric ship toy and an electric airplane toy, etc., the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, for example, an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer, etc. The embodiments of the present application do not specially limit the above-mentioned electric device.

[0547] The electric device can select the battery cell, the battery module or the battery pack according to the use requirement thereof.

[0548] FIG. 17 is a schematic diagram of an electric device 1 as an example. The electric device 1 is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the electric device 1, a battery pack or a battery module can be used.

[0549] The internal part of the electric device 1 is provided with a battery pack 2, which can be arranged at the bottom or head or tail of the electric device 1. The battery pack 2 can be used for power supply of the electric device 1, for example, the battery pack 2 can be used as the operating power supply of the electric device 1, and also can be used as the driving power supply of the electric device 1, instead of or partially instead of fuel or natural gas to provide driving power for the electric device 1.

[0550] The electric device 1 can also include a controller 3 and a motor 4, the controller 3 is used to control the battery pack 2 to supply power for the motor 4, for example, for the working power demand of the electric device 1 during starting, navigation and driving.

[0551] As another example of the electric device can be a mobile phone, a tablet computer, a notebook computer, etc. The electric device generally requires thinning, and can use a battery monomer as a power supply.

[0552] The charging process of the electric device can select the following charging mode:

[0553] Charging from 10% SOC to 15% SOC at 5.0C constant current,

[0554] Charging from 15% SOC to 20% SOC at 5.0C constant current,

[0555] Charging from 20% SOC to 25% SOC at 5.0C constant current,

[0556] Charging from 25% SOC to 30% SOC at 5.0C constant current,

[0557] Charging from 30% SOC to 35% SOC at 5.0C constant current,

[0558] Charging from 35% SOC to 40% SOC at 5.0C constant current,

[0559] Charging from 40% SOC to 45% SOC at 4.6C constant current,

[0560] Charging from 45% SOC to 50% SOC at 4.3C constant current,

[0561] Charging from 50% SOC to 55% SOC at 4.0C constant current,

[0562] Charging from 55% SOC to 60% SOC at 3.7C constant current,

[0563] Charging from 60% SOC to 65% SOC at 3.4C constant current,

[0564] Charging from 65% SOC to 70% SOC at 3.1C constant current,

[0565] Charging from 70% SOC to 75% SOC at 2.9C constant current,

[0566] Charged from 75% SOC to 80% SOC at 2.7C constant current.

[0567] In some embodiments, the charging time of the power device from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, optionally 5 min to 10.5 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, for example 30°C. Exemplarily, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min, or a range formed by any two of the above values.

[0568] The following examples more specifically describe the disclosure of the embodiments of the present application, which are only illustrative and various modifications and changes can be made within the scope of the disclosure of the embodiments of the present application, which will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further treatment, and the instruments used in the examples are commercially available.

[0569] Example 1-1

[0570] 1. Preparation of positive electrode sheet

[0571] 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.

[0572] The positive electrode conductive layer on the positive electrode current collector is a film layer formed by uniformly mixing a positive electrode conductive agent, super carbon, and a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and then coating on the surface of the current collector and drying. The thickness of the positive electrode conductive layer is 1 μm, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0573] The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode slurry (the solvent is N-methyl pyrrolidone (NMP)) on the surface of the positive electrode conductive layer, and then drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder, polyvinylidene fluoride (PVDF), and a conductive agent, acetylene black, in a weight ratio of 97:2:1.

[0574] The positive active material includes lithium iron phosphate and a coating layer, the coating layer is coated on the surface of the lithium iron phosphate, the coating layer includes lithium iron titanium phosphate Li2FeTi(P04)3 and amorphous carbon. The Dv50 of the positive active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0575] 2. Preparation of the negative electrode tab

[0576] The negative electrode tab includes a negative current collector, a negative conductive layer on the negative current collector, and a negative film layer.

[0577] The negative conductive layer on the negative current collector is a film layer formed by uniformly mixing a negative conductive agent super carbon, a negative binder styrene butadiene rubber SBR, a thickening agent sodium carboxymethyl cellulose (CMC-Na), and a solvent water, and then coating on the surface of the negative current collector and drying, the thickness is 1 μm, the mass content of the negative conductive agent in the negative conductive layer is 35%, the mass content of the negative binder in the negative conductive layer is 60%, and the mass content of the thickening agent in the negative conductive layer is 5%.

[0578] The negative film layer includes a film layer formed by uniformly coating a negative slurry (the solvent is deionized water) on the surface of the negative conductive layer, and then drying and cold pressing.

[0579] The negative film layer includes a first negative film layer and a second negative film layer, the first negative film layer is located on the surface of the negative conductive layer, and the second negative film layer is located on the surface of the first negative film layer.

[0580] The first negative film layer includes graphite particles, a conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), a negative binder styrene butadiene rubber, and a thickening agent sodium carboxymethyl cellulose, the mass content of lithium element in the first lithium-containing binder is 4.8%, the Dv50 of the graphite particles is 11.3 μm, the graphite particles include artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0581] The second negative electrode film layer comprises graphite particles, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene butadiene rubber, 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, and the graphite particles comprise artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0582] 3. Isolation film

[0583] The isolation film comprises a base film, and the base film is a 7 μm polyethylene film layer with a porosity of 42%.

[0584] 4. Preparation of electrolyte

[0585] The electrolyte comprises an organic solvent, a lithium salt and an additive.

[0586] The organic solvent comprises 60% chain carboxylate solvents (ethyl acetate) and 40% carbonate solvents (30% ethylene carbonate EC, and the rest is dimethyl carbonate), and the mass content of each component in the organic solvent is calculated based on the mass of the organic solvent.

[0587] The mass content of the additive is 6.5% based on the mass of the electrolyte, and the additive comprises vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES and lithium difluoro(oxalato)borate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0588] The lithium salt comprises 1 mol / L lithium hexafluorophosphate LiPF6.

[0589] 5. Preparation of battery monomer

[0590] The above positive electrode sheet, isolation film and negative electrode sheet are stacked in order, the isolation film is between the positive electrode sheet and the negative electrode sheet to play a separation role, and an electrode assembly is obtained through a stacking process; the electrode assembly is placed in an outer packaging shell, electrolyte is injected after drying, and a battery monomer is obtained through processes such as vacuum packaging, standing, formation and shaping.

[0591] Example 1-2

[0592] A battery monomer is prepared by a method similar to that of Example 1-1, except that the size of the positive electrode current collector along the first direction and the size of the negative electrode current collector along the first direction are adjusted.

[0593] Example 1-3 and Example 1-4

[0594] A battery cell was prepared by a similar method to Example 1-1, except that the single-sided coating weight of the positive electrode film layer was adjusted, and the thickness ratio of the single-sided positive electrode film layer to the thickness of the positive electrode current collector was changed accordingly.

[0595] The single-sided coating weight of the negative electrode film layer was adjusted, and the thickness ratio of the single-sided negative electrode film layer to the thickness of the negative electrode current collector was changed accordingly.

[0596] Comparative Example 1-1

[0597] A battery cell was prepared by a similar method to Example 1-1, except that the size of the positive electrode current collector along the first direction and the size of the negative electrode current collector along the first direction were adjusted.

[0598] Comparative Examples 1-2 and 1-3

[0599] A battery cell was prepared by a similar method to Example 1-1, except that the single-sided coating weight of the positive electrode film layer was adjusted, and the thickness ratio of the single-sided positive electrode film layer to the thickness of the positive electrode current collector was changed accordingly.

[0600] The single-sided coating weight of the negative electrode film layer was adjusted, and the thickness ratio of the single-sided negative electrode film layer to the thickness of the negative electrode current collector was changed accordingly.

[0601] Comparative Example 1-4

[0602] A battery cell was prepared by a similar method to Example 1-1, except that the size of the positive electrode current collector along the second direction was 380 mm, and the size of the negative electrode current collector along the second direction was 385 mm.

[0603] Performance Test

[0604] 1. Lithium precipitation area test of battery cell

[0605] After each battery pack was cycled for 20 cycles according to the respective charge and discharge strategy, it was fully charged to 100% SOC according to the corresponding charging strategy, and the negative electrode sheet in the battery pack was disassembled. The negative electrode sheet was unfolded, the lithium precipitation area (gray-white area) was observed, and the lithium precipitation area was measured. The lithium precipitation degree was as follows:

[0606] No lithium precipitation: lithium precipitation area < 0.05%.

[0607] Mild lithium precipitation: lithium precipitation area < 2%.

[0608] Severe lithium precipitation: lithium precipitation area ≥ 2%.

[0609] The battery cell was charged at an external environment temperature of 30°C, and the charging steps included the following steps:

[0610] Charge from 0% SOC to 5% SOC at 5.0 C constant current;

[0611] Charge from 5% SOC to 10% SOC at 5.0 C constant current;

[0612] Charge from 10% SOC to 15% SOC at 5.0 C constant current;

[0613] Charge from 15% SOC to 20% SOC at 5.0 C constant current;

[0614] Charge from 20% SOC to 25% SOC at 5.0 C constant current;

[0615] Charge from 25% SOC to 30% SOC at 5.0 C constant current;

[0616] Charge from 30% SOC to 35% SOC at 5.0 C constant current;

[0617] Charge from 35% SOC to 40% SOC at 5.0 C constant current;

[0618] Charge from 40% SOC to 45% SOC at 4.6 C constant current;

[0619] Charge from 45% SOC to 50% SOC at 4.3 C constant current;

[0620] Charge from 50% SOC to 55% SOC at 4.0 C constant current;

[0621] Charge from 55% SOC to 60% SOC at 3.7 C constant current;

[0622] Charge from 60% SOC to 65% SOC at 3.4 C constant current;

[0623] Charge from 65% SOC to 70% SOC at 3.1 C constant current;

[0624] Charge from 70% SOC to 75% SOC at 2.9 C constant current;

[0625] Charge from 75% SOC to 80% SOC at 2.7 C constant current;

[0626] Charge from 80% SOC to 85% SOC at 1.8 C constant current;

[0627] Charge from 85% SOC to 90% SOC at 1.3 C constant current;

[0628] Charge from 90% SOC to 95% SOC at 0.7 C constant current;

[0629] Charge from 95% SOC to 98% SOC at 0.33 C constant current;

[0630] Charged from 98% SOC to 100% SOC at 0.1C constant current.

[0631] The cut-off voltage of the last charging step in the above charging steps was 3.65 V.

[0632] The discharge strategy was as follows: discharged to a cut-off voltage, for example 2.0 V, at 0.33C constant current.

[0633] Test results

[0634] The test results are shown in Table 1.

[0635] Table 1

[0636] In Table 1, one positive tab was provided on each side of the positive current collector, and one negative tab was provided on each side of the negative current collector.

[0637] The dimension of the positive current collector along the second direction Z in Example 1-1 to Comparative Example 1-3 was 300 mm, and the dimension of the negative current collector along the second direction Z was 305 mm. The distance e between any point, for example point E in FIG. 12, in the positive current collector and the tab along the second direction was less than 300 mm. The distance g between any point, for example point G in FIG. 14, in the negative current collector and the tab along the second direction was less than 300 mm.

[0638] As shown in FIG. 12, the dimension of the positive current collector along the first direction Y was S1. The distance f1 between any point, for example point F, in the positive current collector and the nearest positive tab along the first direction Y was less than or equal to 300 mm.

[0639] For example, in Example 1-1, the distance between any point in the positive current collector and the nearest positive tab along the first direction Y was less than or equal to 450 mm / 2 = 225 mm.

[0640] In Comparative Example 1-1, the distance between any point in the positive current collector and the nearest positive tab along the first direction Y was less than or equal to 780 mm / 2 = 390 mm, which was greater than 300 mm.

[0641] As shown in FIG. 14, the dimension of the negative current collector along the first direction Y was S2. The distance h1 between any point, for example point H, in the negative current collector and the nearest negative tab along the first direction Y was less than or equal to 300 mm.

[0642] For example, in Example 1-1, the distance between any point in the positive current collector and the nearest positive tab along the first direction Y was less than or equal to 450 mm / 2 = 225 mm.

[0643] In Comparative Example 1-4,

[0644] The distance e from any point in the positive current collector, such as point E in FIG. 12, to the nearest positive tab in the second direction Z is greater than 300 mm.

[0645] The distance g from any point in the negative current collector, such as point G in FIG. 14, to the nearest negative tab in the second direction Z is greater than 300 mm.

[0646] In Comparative Example 1-1, the tab distance is large, making the electron transport path longer, the current distribution uneven, and lithium precipitation more likely. In Comparative Example 1-2 and Comparative Example 1-3, although the tab distance is not too long, in Comparative Example 1-2, the single-side coating weight of the positive electrode film layer is relatively small, making the volumetric energy density of the battery cell small, which may not meet the energy density requirement. In Comparative Example 1-3, the single-side coating weight of the positive electrode film layer is relatively large, although the volumetric energy density of the battery cell is high, but due to the large coating weight, the electron movement path is long, and the risk of lithium precipitation is high. In Comparative Example 1-4, in the second direction, the electron transport path is long, the current distribution is uneven, and lithium precipitation is likely to occur.

[0647] In the embodiments of the present application, the single-side coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 , the volumetric energy density of the battery cell is relatively high; and the tab distance is set to make the electron transport path shorter, the current between the tabs smaller, the current distribution more uniform, and the lithium ion extraction or insertion more uniform, thereby reducing the risk of lithium precipitation; thus, the energy density and use reliability of the battery cell 7 can be improved.

[0648] Example 2-1

[0649] 1. Preparation of the positive electrode tab

[0650] The positive electrode tab includes a positive current collector, a positive conductive layer on the positive current collector, and a positive electrode film layer. The positive current collector is an aluminum foil with a thickness of 10 μm.

[0651] The positive conductive layer on the positive current collector is a film layer formed by uniformly mixing a positive conductive agent, super carbon, and a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and coating the mixture on the surface of the current collector and drying. The thickness of the positive conductive layer is 1 μm, the mass content of the positive conductive agent in the positive conductive layer is 40%, and the mass content of the positive binder is 60%.

[0652] The positive electrode film layer includes a film layer formed by uniformly coating a positive slurry (the solvent is N-methyl pyrrolidone (NMP)) on the surface of the positive conductive layer, and drying and cold pressing. The positive electrode film layer includes a positive active material, a binder, polyvinylidene fluoride (PVDF), and a conductive agent, acetylene black, in a weight ratio of 97:2:1.

[0653] The positive active material includes lithium iron phosphate and a coating layer, the coating layer is coated on the surface of the lithium iron phosphate, the coating layer includes lithium iron titanium phosphate Li2FeTi(P04)3 and amorphous carbon. The Dv50 of the positive active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0654] The single-side coating weight of the positive film layer is 300 mg / 1540.25 mm 2 .

[0655] 2. Preparation of the negative electrode sheet

[0656] The negative electrode sheet includes a negative current collector, a negative conductive layer on the negative current collector, and a negative film layer. The negative current collector is a copper foil with a thickness of 5 μm.

[0657] The negative conductive layer on the negative current collector is formed by uniformly mixing a negative conductive agent, a negative binder, a thickening agent, and a solvent, and then coating the mixture on the surface of the negative current collector and drying. The thickness of the negative conductive layer is 1 μm. The mass content of the negative conductive agent in the negative conductive layer is 35%. The mass content of the negative binder in the negative conductive layer is 60%. The mass content of the thickening agent in the negative conductive layer is 5%.

[0658] The negative film layer includes a film layer formed by uniformly coating a negative slurry (with deionized water as the solvent) on the surface of the negative conductive layer, and then drying and cold pressing.

[0659] The single-side coating weight of the negative film layer is 138 mg / 1540.25 mm 2 .

[0660] The negative film layer includes a first negative film layer and a second negative film layer. The first negative film layer is located on the surface of the negative conductive layer, and the second negative film layer is located on the surface of the first negative film layer.

[0661] The first negative film layer includes graphite particles, a conductive agent, a first lithium-containing binder, a negative binder, and a thickening agent, with a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer is coated on the surface of the artificial graphite. The mass content of the carbon coating layer is 3.5%.

[0662] The second negative electrode film layer comprises graphite particles, a conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), a negative electrode binder styrene butadiene rubber, and a thickening agent sodium carboxymethyl cellulose, the mass content of lithium in the second lithium-containing binder is 4.8%, the Dv50 of the graphite particles is 11.3 μm, the graphite particles comprise artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0663] 3. The separator film

[0664] The separator film comprises a base film, and the base film is a 7 μm polyethylene film layer with a porosity of 42%.

[0665] 4. Preparation of the electrolyte

[0666] The electrolyte comprises an organic solvent, a lithium salt and an additive.

[0667] The organic solvent comprises 60% of a chain carboxylic acid ester solvent (ethyl acetate) and 40% of a carbonate solvent (30% of ethylene carbonate EC and 10% of dimethyl carbonate), and the mass content of each component in the organic solvent is calculated based on the mass of the organic solvent.

[0668] The additive has a mass content of 6.5% based on the mass of the electrolyte, and the additive comprises vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES and lithium difluoro(oxalato)borate LiDFOB at a mass ratio of 5:0.5:0.5:0.5.

[0669] The lithium salt comprises 1 mol / L of lithium hexafluorophosphate LiPF6.

[0670] 5. Preparation of the battery cell

[0671] The above positive electrode sheet, the separator film and the negative electrode sheet are stacked in sequence, the separator film is arranged between the positive electrode sheet and the negative electrode sheet to play a separating role, and an electrode assembly is obtained through a winding process; the electrode assembly is placed in an outer packaging shell, electrolyte is injected after drying, and a battery cell is obtained through processes such as vacuum packaging, standing, formation and shaping, the compaction density of the positive electrode film layer is 2.72 g / cm 3 at 100% SOC, and the compaction density of the negative electrode film layer is 1.26 g / cm 3 at 100% SOC.

[0672] Examples 2-2 to 2-4

[0673] A battery cell was prepared in a similar manner to Example 2-1, except that the interval between the two adjacent positive electrode tabs and the interval between the two adjacent negative electrode tabs were adjusted.

[0674] Example 2-5 and Example 2-6

[0675] A battery cell was prepared in a similar manner to Example 2-1, except that the single-sided coating weight of the positive electrode membrane layer was adjusted, and the thickness ratio of the single-sided positive electrode membrane layer to the thickness of the positive electrode current collector was changed accordingly.

[0676] The single-sided coating weight of the negative electrode membrane layer was adjusted, and the thickness ratio of the single-sided negative electrode membrane layer to the thickness of the negative electrode current collector was changed accordingly.

[0677] Comparative Example 2-1

[0678] A battery cell was prepared in a similar manner to Example 2-1, except that the interval between the two adjacent positive electrode tabs and the interval between the two adjacent negative electrode tabs were adjusted.

[0679] Comparative Example 2-2

[0680] A battery cell was prepared in a similar manner to Example 2-1, except that the single-sided coating weight of the positive electrode membrane layer was adjusted, and the thickness ratio of the single-sided positive electrode membrane layer to the thickness of the positive electrode current collector was changed accordingly.

[0681] The single-sided coating weight of the negative electrode membrane layer was adjusted, and the thickness ratio of the single-sided negative electrode membrane layer to the thickness of the negative electrode current collector was changed accordingly.

[0682] Test Results

[0683] The test results are shown in Table 2.

[0684] Table 2

[0685] The interval between the two adjacent positive electrode tabs refers to the interval in the second direction Z, for example, the interval between the two adjacent positive electrode tabs in FIG. 5. The interval between the two adjacent positive electrode tabs is less than or equal to 600 mm, and the interval from any point in the positive electrode current collector to the positive electrode tab closest to the point in the second direction Y is less than or equal to 300 mm. For example, in Example 2-1, the interval between the two adjacent positive electrode tabs is 150 mm, and the interval from any point in the positive electrode current collector to the positive electrode tab closest to the 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 interval a1 between the edge A1 of the positive electrode current collector and the positive electrode tab is less than or equal to 150 mm.

[0686] The distance between the two adjacent negative tabs refers to the distance in the second direction Z, for example, the distance between the two adjacent negative tabs in FIG. 7, the distance between the two adjacent negative tabs is less than or equal to 600 mm, and the distance from any point in the negative current collecting part to the negative tab closest to the point in the second direction Y is less than or equal to 300 mm. For example, in Example 2-1, the distance between the two adjacent negative tabs is less than 150 mm, and the distance from any point in the negative current collecting part to the negative tab closest to the 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 negative current collecting part edge B1 and the negative tab is less than or equal to 150 mm.

[0687] In Comparative Example 2-1, the distance between the two adjacent positive tabs is 700 mm, and the distance from any point in the positive current collecting part to the positive tab closest to the point in the second direction can be up to 700 mm / 2 = 350 mm, which is greater than 300 mm.

[0688] In Comparative Example 2-1, the distance between the two adjacent negative tabs is 700 mm, and the distance from any point in the negative current collecting part to the negative tab closest to the point in the second direction can be up to 700 mm / 2 = 350 mm, which is greater than 300 mm.

[0689] As can be seen from Table 2, in Comparative Example 2-1, the tab distance is large, which makes the electron transport path longer, the current distribution uneven, and lithium precipitation more likely. Although the tab distance 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, which makes the volume energy density of the battery cell smaller, and it can not meet the energy density requirement.

[0690] In the examples of the present application, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 400 mg / 1540.25 mm 2 , the volume energy density of the battery cell is relatively high; and the distance between the tabs is set so that the electron transport path is shorter, the current between the tabs is smaller, the current distribution is more uniform, and the lithium ion extraction or insertion is more uniform, which can reduce the risk of lithium precipitation; thus, the energy density and use reliability of the battery cell can be improved.

[0691] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as a limitation of the present application, and the embodiments can be changed, replaced and modified without departing from the spirit, principles and scope of the present application.

Claims

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

2. The battery cell according to claim 1, wherein, The positive electrode tab is configured as one or more, and all the positive electrode tabs are disposed on the same side of the positive current collector along the first direction. The dimension of the positive current collector along the first direction is 100mm to 300mm.

3. The battery cell according to claim 1, wherein, The positive electrode tabs are configured in multiple ways, and the multiple positive electrode tabs 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 100mm to 600mm.

4. The battery cell according to any one of claims 1 to 3, wherein, The single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2 Up to 370mg / 1540.25mm 2 ; and / or The thickness of the positive current collector is 10 μm to 15 μm.

5. The battery cell according to any one of claims 1 to 4, wherein, The electrode assembly further includes a negative electrode sheet, which comprises a negative electrode film layer, a negative electrode current collector, and at least one negative electrode tab. The negative electrode film layer is disposed on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is disposed on at least one side of the negative electrode current collector along the first direction. The negative electrode film layer includes a negative electrode active material, which includes a carbon-based material. Along the second direction, the distance between the second point of the negative 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 current collector.

6. The battery cell according to claim 5, wherein, The negative electrode tab is configured as one or more, and all the negative electrode tabs are disposed on the same side of the negative electrode current collector along the first direction. The dimension of the negative electrode current collector along the first direction is 100mm to 300mm.

7. The battery cell according to claim 5, wherein, The negative electrode tabs are configured in multiple ways, and the multiple negative electrode tabs 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 100mm to 600mm.

8. The battery cell according to any one of claims 5 to 7, wherein, The single-sided coating weight of the negative electrode film is 90 mg / 1540.25 mm. 2 Up to 170mg / 1540.25mm 2 ; and / or The thickness of the negative electrode current collector is 4 μm to 6 μm.

9. The battery cell according to any one of claims 1 to 8, wherein, The electrode assembly has a wound structure, and multiple positive electrode tabs are provided, which are arranged opposite to each other 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 and the positive electrode tab closest to the first point is less than or equal to 200 mm.

11. The battery cell according to claim 9 or 10, wherein, When the battery cell is 100% charged, the ratio of the thickness of the positive electrode film layer on one side to the thickness of the positive electrode current collector is 4.8 to 8.6; and / or The single-sided coating weight of the positive electrode film is 280 mg / 1540.25 mm. 2 Up to 370mg / 1540.25mm 2 .

12. The battery cell according to any one of claims 9 to 11, wherein, The electrode assembly includes a negative electrode sheet, which includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode tab. The negative electrode film layer is disposed on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is disposed on at least one side of the negative electrode current collector along the first direction. When the battery cell is 100% charged, the ratio of the thickness of the negative electrode film on one side 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, which includes a carbon-based material. The single-sided coating weight of the negative electrode film layer is 125 mg / 1540.25 mm. 2 Up to 170mg / 1540.25mm 2 .

13. The battery cell according to any one of claims 1 to 8, wherein, The electrode assembly has a stacked structure, and the positive electrode tab is disposed on at least one side of the positive electrode current collector.

14. The battery cell according to claim 13, wherein, The positive electrode tabs are configured in multiple ways, and the multiple positive electrode tabs are disposed on both sides of the positive electrode current collector along the first direction. The dimension of the positive electrode current collector along the first direction is 400mm to 600mm; and / or The electrode assembly includes a negative electrode sheet, which includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode tab. The negative electrode film layer is disposed on at least one side of the negative electrode current collector along the thickness direction. Multiple negative electrode tabs are disposed on both sides of the negative electrode current collector along the first direction. The dimension of the negative electrode current collector along the first direction is 400 mm to 600 mm.

15. The battery cell according to claim 13 or 14, wherein, When the battery cell is 100% charged, the ratio of the thickness of the positive electrode film on one side to the thickness of the positive electrode current collector is 3.5 to 7.0; and / or The single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2 Up to 360mg / 1540.25mm 2 .

16. The battery cell according to any one of claims 13 to 15, wherein, The electrode assembly includes a negative electrode sheet, which includes a negative electrode film layer, a negative electrode current collector, and at least one negative electrode tab. The negative electrode film layer is disposed on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is disposed on at least one side of the negative electrode current collector along the first direction. When the battery cell is 100% charged, the ratio of the thickness of the negative electrode film on one side 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, which includes a carbon-based material. The single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm. 2 Up to 164mg / 1540.25mm 2 .

17. The battery cell according to any one of claims 1 to 16, wherein, The lithium phosphate with the olivine structure includes: Phosphate particles, and A coating layer that coats the phosphate particles, the coating layer containing one or more elements selected from C, Fe, Ti, Zr, Hf, Ge and Sn.

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

19. The battery cell according to claim 17 or 18, wherein, The coating layer includes a general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 A fast ion conductor, M2 includes one or more elements from Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x2<5, 0<y2<4.

20. The battery cell according to any one of claims 17 to 19, wherein, The degree of graphitization of the lithium phosphate with the olivine structure is 0.15 to 0.

32.

21. The battery cell according to any one of claims 17 to 20, wherein, The lithium phosphate with the olivine structure has a carbon content of 1% to 2% by mass. The specific surface area of ​​the lithium phosphate with the olivine structure is 5 m². 2 / g to 18m 2 / g.

22. The battery cell according to any one of claims 17 to 21, wherein, The lithium phosphate with the olivine structure is granular, and its volume distribution particle size satisfies: 1μm≤Dv50≤2μm, 0.4μm≤Dv10≤0.7μm.

23. The battery cell according to any one of claims 1 to 22, wherein, The positive electrode sheet further includes a positive conductive layer, which is located between the positive electrode film and the positive electrode current collector.

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 or 24, wherein, The positive electrode conductive layer includes a positive electrode conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and / or The positive electrode conductive layer includes a positive electrode binder, which includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorinated acrylate resins.

26. The battery cell according to any one of claims 1 to 25, wherein, The electrode assembly includes a negative electrode sheet, which includes a negative electrode film layer, a negative electrode current collector, and a negative electrode tab. The negative electrode film layer is disposed on at least one side of the negative electrode current collector along the thickness direction, and the negative electrode tab is disposed on at least one side of the negative electrode current collector along the first direction. The negative electrode film layer includes a negative electrode active material, which includes a carbon-based material, which 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 is applied to 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 amorphous carbon layer is 2% to 5%.

29. The battery cell according to any one of claims 26 to 28, wherein, The negative electrode film layer includes: A first negative electrode film layer is disposed on the surface of the negative electrode current collector. The first negative electrode film layer comprises a carbon-based material, and The second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, and the second negative electrode film layer comprises a carbon-based material. The carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently include graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

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

31. The battery cell according to claim 29 or 30, 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 tap density of the carbon-based material in the first negative electrode film is 0.82 g / cm³. 3 Up to 1.21 g / cm 3 , and / or The tap density of the carbon-based material in the second negative electrode film is 0.90 g / cm³. 3 Up to 1.25 g / cm 3 .

33. The battery cell according to any one of claims 29 to 32, wherein, The volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm, and / or The volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm.

34. The battery cell according to any one of claims 29 to 33, wherein, The first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder, wherein the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

35. The battery cell according to claim 34, wherein, The first lithium-containing binder has a mass content of 0.1% to 1% relative to the first negative electrode film layer, and / or The second lithium-containing binder has a mass content of 0.1% to 1% relative to the second negative electrode film layer.

36. The battery cell according to claim 34 or 35, wherein, The lithium content in the first lithium-containing binder is 3% to 10% by mass, and / or The lithium content in the second lithium-containing binder is 3% to 10% by mass.

37. The battery cell according to any one of claims 34 to 36, wherein, The first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%; and / or The second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

38. The battery cell according to any one of claims 26 to 37, wherein, The negative electrode active material also includes a silicon-based material, wherein the silicon content in the silicon-based material is 0.3% to 10.0% by mass, based on the mass of the negative electrode active material.

39. The battery cell according to any one of claims 26 to 38, wherein, The negative electrode sheet further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector.

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

42. The battery cell according to any one of claims 1 to 41, wherein, The electrode assembly includes a separating membrane, the separating membrane comprising a porous base membrane having a porosity of 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 isolation membrane includes a base membrane and a functional layer disposed on at least one side of the base membrane, the functional layer including: A first functional layer is located on one side of the base film, and the first functional layer includes first inorganic particles. The second functional layer is located on the other side of the base film. The second functional layer includes composite particles, which include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

44. The battery cell according to claim 43, wherein, The non-fluoropolymer particles include acrylate copolymers.

45. The battery cell according to claim 43 or 44, wherein, The first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

46. ​​The battery cell according to any one of claims 43 to 45, wherein, The second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide, and / or The average particle size of the second inorganic particle is 5 nm to 100 nm.

47. The battery cell according to any one of claims 1 to 46, wherein the battery cell comprises an electrolyte. The electrolyte has a viscosity of 2.3 mPa·s to 3.5 mPa·s at room temperature; and / or The electrolyte has a conductivity of 13 mS / cm to 20 mS / cm at room temperature; and / or The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature.

48. The battery cell according to claim 47, wherein, The carboxylic acid ester solvent includes chain carboxylic acid ester solvents, wherein the chain carboxylic acid ester solvent has a mass content of 5% to 75% in the organic solvent.

49. The battery cell according to claim 48, wherein, The chain-like carboxylic acid ester solvent has a mass content of 30% to 70% in the organic solvent.

50. The battery cell according to claim 48 or 49, wherein, The chain-like carboxylic acid ester solvents include compounds represented by Formula I. In formula I, R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group. R2 includes C1 to C5 alkyl or C1 to C5 haloalkyl.

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

52. The battery cell according to claim 51, wherein, The chain-like carboxylic acid ester solvents include one or more compounds from Formula I-1 to Formula I-8.

53. The battery cell according to any one of claims 48 to 52, wherein, The organic solvent also includes carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

54. The battery cell according to claim 53, wherein, The carbonate solvents include one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

55. The battery cell according to claim 53 or 54, wherein, The carbonate solvent has a mass content of 30% to 70% in the organic solvent.

56. The battery cell according to any one of claims 47 to 55, wherein, The electrolyte also includes additives, which include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives.

57. The battery cell according to claim 56, wherein, The carbonate additives include one or more of vinylene carbonate and fluoroethylene carbonate, and / or The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, vinyl sulfite, and methylene disulfonate, and / or The lithium salt additives include one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium dioxalate borate.

58. The battery cell according to claim 56 or 57, wherein, The additive is present in the electrolyte at a mass content of 1% to 10%.

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

60. The battery cell according to any one of claims 47 to 59, wherein, The electrolyte also includes lithium salts, which include one or more of fluorosulfonyl imide salts and lithium hexafluorophosphate.

61. The battery cell according to claim 60, wherein, The fluorinated sulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide and lithium bistrifluoromethylsulfonate imide.

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

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

0.

64. [Correction 02.08.2024 according to Rule 91] The battery cell according to any one of claims 1 to 63, the battery cell comprising a housing that houses the electrode assembly, the housing comprising steel, the thickness of the housing being 0.1 mm to 0.5 mm.

65. [Correction 02.08.2024 based on Rule 91] The battery cell according to claim 64, wherein, The thickness of the shell is 0.2 mm to 0.35 mm.

66. [Correction 02.08.2024 according to Rule 91] The battery cell according to any one of claims 1 to 65 further includes a positive terminal, wherein the positive electrode tab is directly welded to the positive terminal.

67. [Correction 02.08.2024 according to Rule 91] The battery cell according to any one of claims 1 to 66, wherein, The charging time for a single battery cell from 10% to 80% state of charge is 5 to 10.5 minutes.

68. [Revised according to Rule 91, 02.08.2024] A battery device comprising a battery cell as claimed in any one of claims 1 to 67.

69. [Correction 02.08.2024 according to Rule 91] The battery device according to claim 68, wherein, The charging time for the battery device from 10% state of charge to 80% state of charge is 5 min to 10.5 min.

70. [Correction 02.08.2024 according to Rule 91] An electrical device comprising a battery device as claimed in claim 68 or 69.

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