Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device, the battery monomer comprises an electrolyte, a positive pole piece and a negative pole piece, the positive pole piece comprises a positive pole current collecting part and a positive pole film layer located on at least one surface of the positive pole current collecting part and containing a positive pole active material, and the positive pole active material comprises lithium-containing phosphate of an olivine structure; the coating weight of one side of the positive electrode film layer is 200mg / 1540.25 mm < 2 > to 370mg / 1540.25 mm < 2 >, the negative electrode plate comprises a negative electrode current collecting part and a negative electrode film layer which is positioned on at least one surface of the negative electrode current collecting part and contains a negative electrode active material, the negative electrode active material comprises a carbon-based material, the conductivity of the electrolyte is 13-20mS / cm, the battery monomer is subjected to constant-current discharge from a 100% state of charge (0.33 C) to 2.0 V at 25 DEG C, and a discharge platform voltage V1 is 3.19-3.235 V. According to the invention, the fast charging performance, the energy density and the cycle performance of the battery monomer can be improved.

Description

[0001] This application claims the priority of the PCT international application PCT / CN2024 / 107009, titled "Battery Cell, Battery Device and Electrical Device", filed on July 23, 2024, the entire content of which is incorporated herein by reference. Technical Field

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

[0003] Battery cells have characteristics such as high capacity and long life, and are thus widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools, etc. Due to the great progress made in the battery field, higher requirements are put forward for the performance of batteries. The fast charging performance, energy density and cycle performance of battery cells still need to be further improved. Summary of the Invention

[0004] This application provides a battery cell, a battery device and an electrical device, which can improve the fast charging performance of the battery cell and enable the battery cell to have a relatively high energy density and cycle performance.

[0005] In a first aspect, this application proposes a battery cell. The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab, a negative electrode tab and a separator. The separator is located between the positive electrode tab and the negative electrode tab. The positive electrode tab includes a positive current collector portion and at least one surface disposed along the thickness direction of the positive electrode tab and including a positive electrode film layer containing a positive electrode active material. The positive electrode active material includes a lithium-containing phosphate with an olivine structure. The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 , the negative electrode tab includes a negative current collector portion and at least one surface disposed along the thickness direction of the negative electrode tab and including a negative electrode film layer containing a negative electrode active material. The negative electrode active material includes a carbon-based material. The conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm. In an external environment of 25°C, during the discharge process of the battery cell from 100% state of charge at a constant current rate of 0.33C to 2.0V, it has a discharge platform voltage V 1 V 1 is 3.19V to 3.235V.

[0006] Thus, in the embodiments of the present application, the positive active material in the positive electrode tab includes lithium-containing phosphate with an olivine structure, and the negative active material in the negative electrode tab includes a carbon-based material. The structure of the material system is more stable, and the cycle stability of the material system is relatively excellent; the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 , the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, which is beneficial to achieving the fast charging performance and excellent cycle performance of the battery cell; and the battery cell has a discharge platform voltage V 1 during the discharge process, making the energy density of the battery cell relatively high.

[0007] In some embodiments, the electrode assembly has a stacked structure, and the positive electrode tab, the separator, and the negative electrode tab are stacked. V 1 is 3.19 V to 3.225 V. The battery cell has a discharge platform voltage V 1 during the discharge process, making the energy density of the battery cell relatively high.

[0008] In some embodiments, the electrode assembly has a stacked structure, and the positive electrode tab further includes a positive electrode tab ear, and the positive electrode tab ear is disposed on at least one side of the positive current collector along the length direction of the positive electrode tab.

[0009] In some embodiments, the electrode assembly has a stacked structure, and the positive electrode tab ears are disposed on both sides of the positive current collector along the length direction of the positive electrode tab. The positive electrode tab ears are disposed on both sides of the positive current collector along the length direction, so that the current in the length direction of the positive current collector is evenly divided by the positive electrode tab ears on both sides. The electron transmission path is short, and the current distribution is more uniform. The delithiation state of each part of the positive electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0010] In some embodiments, the electrode assembly has a stacked structure. The size of the positive electrode film layer along the length direction of the positive electrode tab, that is, the length of the positive electrode film layer, is 200 mm to 400 mm, and V 1 is 3.20 V to 3.225 V. The positive electrode film layer with the above size in combination with the above discharge platform voltage is beneficial to further improving the energy density of the battery cell.

[0011] In some embodiments, the electrode assembly has a stacked structure, the length of the positive electrode film layer is greater than 400 mm and less than or equal to 1000 mm, and V 1 is 3.19 V to 3.218 V. The positive electrode film layer with the above size in combination with the above discharge platform voltage is beneficial to further improving the energy density of the battery cell.

[0012] In some embodiments, the electrode assembly has a wound structure, and the positive electrode sheet, the separator, and the negative electrode sheet are wound in the same direction, and V 1 is from 3.215 V to 3.235 V. The wound-structure electrode assembly in combination with the above discharge platform voltage is conducive to further improving the energy density of the battery cell.

[0013] In some embodiments, the negative active material further includes a silicon-based material, and V 1 is from 3.190 V to 3.230 V. The above negative active material in combination with the discharge platform voltage is conducive to further improving the energy density of the battery cell.

[0014] In some embodiments, the mass content of silicon element in the silicon-based material is 0.3% to 10.0% based on the mass of the negative active material. The above negative active material in combination with the discharge platform voltage is conducive to further improving the energy density of the battery cell.

[0015] In some embodiments, the electrode assembly has a stacked structure, and V 1 is from 3.190 V to 3.218 V. The stacked-structure electrode assembly in combination with the silicon-containing negative active material and the above discharge platform voltage is conducive to further improving the energy density of the battery cell.

[0016] In some embodiments, the electrode assembly has a wound structure, and V1 is from 3.210 V to 3.230 V. The wound-structure electrode assembly in combination with the silicon-containing negative active material and the above discharge platform voltage is conducive to further improving the energy density of the battery cell.

[0017] In some embodiments, when discharging the battery cell in an external environment at 25 °C, the battery cell has a discharge platform voltage V during the discharge process from 100% state of charge at a constant current of 2C to 2.0 V 2 , V 2 / V 1 is from 0.942 to 0.975. In the embodiments of the present application, the discharge platform voltages during the discharge of the battery cell at a rate of 0.33C and at a rate of 2C are similar, and the battery cell discharges relatively completely during the discharges at rates of 0.33C and 2C, and has good rate performance, which is conducive to the exertion of the energy density of the battery cell.

[0018] In some embodiments, V 2 is from 3.05 V to 3.15 V.

[0019] In some embodiments, the single-sided coating weight of the positive electrode film layer is 240 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode sheet will not be excessive, and it can also take into account the improvement of the energy density of the battery cell.

[0020] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 and can be optionally 110 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2 When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode sheet will not be excessive, and it can also take into account the improvement of the energy density of the battery cell.

[0021] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge is 2.50 g / cm 3 to 2.80 g / cm 3 When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. And because the positive active materials in the positive electrode film layer are stacked relatively tightly, the contact resistance between particles is relatively small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0022] In some embodiments, at 100% state of charge of the battery cell, the compaction density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. And because the negative active materials in the negative electrode film layer are stacked relatively tightly, the contact resistance between particles is relatively small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0023] In some embodiments, the powder resistivity of the positive active material is 1 Ω•cm to 27.5 Ω•cm. The relatively low powder resistivity of the positive active material makes the resistance of the positive electrode sheet relatively low, and the heat generation of the battery cell is less.

[0024] In some embodiments, the powder compaction density of the positive active material under 30000 N is 2.46 g / cm 3 to 2.8 g / cm 3 When the powder compaction density of the positive active material under 30000 N is within the above range, it can improve the energy density of the battery cell. And because the positive active materials in the positive electrode film layer can be stacked more tightly, the contact resistance between particles is relatively small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0025] In some embodiments, the charging specific capacity of the positive electrode active material at a rate of 0.1C is 150 mAh / g to 170 mAh / g. When the charging specific capacity of the positive electrode active material at a rate of 0.1C is within the above range, the energy density of the battery cell is relatively high.

[0026] In some embodiments, the lithium-containing phosphate of olivine structure includes phosphate particles and a coating layer. The coating layer coats the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn. By coating the surface of the phosphate particles with the coating layer, the conductivity of the lithium-containing phosphate of olivine structure can be improved, the powder resistivity of the material can be reduced, and it is beneficial to the migration rate of lithium ions and reduces the heat generation of the battery cell.

[0027] In some embodiments, the phosphate particles include a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z where 0.5 ≤ x 1 ≤ 1.3, 0 ≤ y 1 ≤ 1.3, and 0.9 ≤ x 1 + y 1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F. The phosphate particles have relatively excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0028] In some embodiments, the coating layer includes a fast ion conductor with the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0 ≤ d ≤ 1, 0 < x 2 <5, 0 < y 2< 4. Coating the surface of phosphate particles with a fast ion conductor can significantly improve the transport rate of lithium ions during multiple deintercalation / insertion at the positive electrode, enhance the ionic conductivity of the positive electrode active material, thereby increasing the specific capacity, and further improving the energy density of the corresponding battery cell.

[0029] In some embodiments, the graphitization degree of the positive electrode active material is from 0.15 to 0.32; optionally from 0.19 to 0.26. When the graphitization degree of the positive electrode active material is within the above range, it is beneficial to enhance the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell.

[0030] In some embodiments, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g to 18m 2 / g, optionally 7.5m 2 / g to 14m 2 / g.

[0031] Thus, in the embodiments of the present application, the carbon element with the above mass content in combination with the material with the above specific surface area is more conducive to the effective contact between the electrolyte and the lithium-containing phosphate with olivine structure, and is beneficial to the transport of lithium ions at the phase interface.

[0032] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1µm ≤ Dv50 ≤ 2µm, and / or 0.4µm ≤ Dv10 ≤ 0.7µm, and / or 15µm ≤ Dv99 ≤ 25µm.

[0033] The particle size of the positive electrode active material is relatively small, the deintercalation / insertion path of lithium ions in the positive electrode active material is short, and the heat generation is less; moreover, the particle size of the above positive electrode active material is not too small, and basically no agglomeration occurs during the processing and preparation, so that the performance of the positive electrode active material is stable.

[0034] In some embodiments, the lithium-containing phosphate with olivine structure is in granular form, the lithium-containing phosphate with olivine structure includes secondary particles, and the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is from 200nm to 500nm. The average particle size of the primary particles is relatively small, the deintercalation / insertion path of lithium ions in the positive electrode active material is short, and the heat generation is less.

[0035] In some embodiments, the ratio of the thickness of the positive electrode current collector part to the total thickness of the single-sided positive electrode film layer is 0.06 to 0.10. When the positive electrode sheet satisfies the above range, the thickness of the positive electrode current collector part is relatively thin, which can provide more coating space for the positive electrode film layer, thereby increasing the energy density of the battery cell and being beneficial to improving the fast charging performance of the battery cell.

[0036] In some embodiments, the positive electrode film layer further includes a first material, which includes one or more of ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrate. As a lithium supplement agent, the first material can supplement lithium ions to the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby enhancing the energy density of the battery cell.

[0037] In some embodiments, the mass content of the first material in the positive electrode film layer is 0.5% to 5%. When the mass content of the lithium supplement agent is within the above range, it can supplement lithium ions to the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby enhancing the energy density of the battery cell.

[0038] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm. When the thickness of the positive electrode current collector is within the above range, the current-carrying capacity of the positive electrode current collector is relatively excellent, and the battery cell can have a high energy density.

[0039] In some embodiments, the positive electrode plate further includes a positive electrode conductive layer, which is located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode plate and reduce the heat generation of the positive electrode plate, thereby reducing the heat generation of the battery cell.

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

[0041] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode plate and reducing the heat generation of the battery cell; the positive electrode binder in the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector and the positive electrode film layer and enhance the structural stability of the positive electrode plate.

[0042] In some embodiments, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0043] In some embodiments, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins.

[0044] In some embodiments, the powder resistivity of the negative electrode active material is from 0.005 Ω·cm to 0.043 Ω·cm. The relatively low powder resistivity of the negative electrode active material results in a relatively low resistance of the negative electrode sheet, and less heat generation in the battery cell.

[0045] In some embodiments, the powder compaction density of the negative electrode active material under 20000 N is 1.5 g / cm 3 to 1.85 g / cm 3 . When the powder compaction density of the negative electrode active material under 20000 N is within the above range, the energy density of the battery cell can be improved. Moreover, since the negative electrode active material in the negative electrode film layer can be stacked more tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0046] In some embodiments, the charging specific capacity of the negative electrode active material at a rate of 0.1 C is greater than or equal to 350 mAh / g. When the charging specific capacity of the negative electrode active material at a rate of 0.1 C is within the above range, the energy density of the battery cell is relatively high.

[0047] In some embodiments, the negative electrode active material includes a carbon-based material, the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is from 92.0% to 94.5%. When the graphitization degree of the graphite particles is within the above range, the electrical conductivity of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the fast charging performance of the battery cell.

[0048] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer, the artificial graphite includes secondary particles, and the carbon coating layer coats the surface of the artificial graphite. The carbon coating layer has more end faces and defects, so that the number of sites capable of intercalating and deintercalating lithium ions is larger, and the electrical conductivity of the carbon coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode sheet and reduce the heat generation of the battery cell.

[0049] In some embodiments, based on the mass of the graphite particles, the mass content of the carbon coating layer is from 2% to 5%. When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode sheet can be further reduced, and the heat generation of the battery cell can be reduced.

[0050] In some embodiments, the porosity of the negative electrode film layer is from 40% to 55%. When the porosity of the negative electrode film layer is within the above range, it is beneficial to improve the migration rate of lithium ions and improve the fast charging performance of the battery cell.

[0051] In some embodiments, the negative electrode film layer is a single-layer film layer, the negative electrode active material is granular, and the volume-average particle size of the negative electrode active material is 8.2 μm to 13.5 μm. When the volume-average particle size of the negative electrode active material is within the above range, the negative electrode film layer can have an excellent pore structure, which is beneficial to improving the fast charging performance of the battery cell.

[0052] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector portion. The first negative electrode film layer includes a carbon-based material. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector portion. The second negative electrode film layer includes a carbon-based material. The carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently include graphite particles, and the volume-average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume-average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0053] Thus, in the embodiments of the present application, there is a difference in the particle sizes of the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium deposition on the surface layer of the negative electrode plate.

[0054] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0055] In some embodiments, the tapped density of the carbon-based material in the first negative electrode film layer is less than or equal to the tapped density of the carbon-based material in the second negative electrode film layer. When the tapped density of the carbon-based material in the second negative electrode film layer is greater than the tapped density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, which improves the energy density of the battery cell. The first negative electrode film layer is filled relatively sparsely and has more pores, which can improve the fast charging performance of the battery cell.

[0056] In some embodiments, the tapped density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 . When the tapped density of the carbon-based material in the first negative electrode film layer is within a suitable range, the fast charging performance of the battery cell can be improved.

[0057] In some embodiments, the tapped density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3When the tap density of the carbon-based material in the second negative electrode film layer is within a suitable range, the energy density of the battery cell can be improved. In some embodiments, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm. When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the above range, the fast charging performance can be improved.

[0058] In some embodiments, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm. When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is within the above range, the tortuosity of lithium ion transport can be reduced, and the fast charging performance of the battery cell can be improved.

[0059] In some embodiments, the first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0060] Thus, in the embodiments of the present application, the mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the number of freely movable lithium ions provided by the second lithium-containing binder for the second negative electrode film layer is relatively more, which can further improve the fast charging performance of the battery cell.

[0061] In some embodiments, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. When the mass content of the first lithium-containing binder is within the above range, the insertion / extraction rate of lithium ions can be improved, and the fast charging performance of the battery cell can be improved.

[0062] In some embodiments, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. When the mass content of lithium element is within the above range, the number of freely movable lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the insertion / extraction rate of lithium ions, and improve the fast charging performance of the battery cell.

[0063] In some embodiments, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. When the mass content of lithium element in the second lithium-containing binder is within the above range, the insertion / extraction rate of lithium ions is improved, and the fast charging performance of the battery cell is improved.

[0064] In some embodiments, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, optionally 3% to 8%. When the mass content of lithium element is within the above range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0065] In some embodiments, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, and the lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is (0.3 - 0.5):(0.15 - 0.45):(0.05 - 0.2):(0.2 - 0.35).

[0066] Thus, the lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improving the fast charging performance of the battery cell; and it is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0067] In some embodiments, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, and the lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is (0.3 - 0.5):(0.15 - 0.45):(0.05 - 0.2):(0.2 - 0.35).

[0068] Thus, the lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improving the fast charging performance of the battery cell; and it is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0069] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. When the thickness of the negative electrode current collector is within the above range, the current-carrying capacity of the negative electrode current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0070] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, and the negative electrode conductive layer is located between the negative electrode film layer and the negative electrode current collector.

[0071] 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, reduce the heat generation of the negative electrode sheet, and thus reduce the heat generation of the battery cell.

[0072] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the heat generation of the battery cell; the negative electrode binder in the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector part and the negative electrode film layer and improve the structural stability of the negative electrode sheet.

[0073] In some embodiments, the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0074] In some embodiments, the negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0075] In some embodiments, the conductivity of the electrolyte at room temperature is 15 mS / cm to 20 mS / cm. When the conductivity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the fast charging performance of the battery cell.

[0076] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. When the viscosity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the fast charging performance of the battery cell.

[0077] In some embodiments, the density of the electrolyte at room temperature is 1.05 g / mL to 1.35 g / mL. When the density of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the fast charging performance of the battery cell.

[0078] 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%, and optionally 30% to 75%. 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.

[0079] In some embodiments, the chain carboxylic ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0080] Thus, in the embodiments of the present application, the above chain carboxylic ester solvent has a relatively high conductivity, which is beneficial to improving the rapid charging ability of the battery cell.

[0081] In some embodiments, R 1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0082] In some embodiments, in some embodiments, R 2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0083] In some embodiments, the chain carboxylic ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8,

[0084] 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 ethyl methyl carbonate. The above carbonate solvent and the chain carboxylic ester solvent are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0085] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0086] In some embodiments, the mass content of the carbonate solvent in the organic solvent is 25% to 95%, and can be optionally 25% to 70%. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0087] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The above additive can improve the interfacial 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.

[0088] In some embodiments, the carbonate additives include one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0089] In some embodiments, the sulfur-containing additives include one or more of ethylene sulfate (DTD), bis(ethylene sulfate) (2-DTD), butene sulfite (BS), 1,3-propane sultone (PS), ethylene sulfite (ES), and methylene methyl disulfonate (MMDS).

[0090] In some embodiments, the lithium salt additives include lithium difluorophosphate LiPO 2 F 2 , lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate LiBF 4 , and one or more of lithium bis(oxalato)borate (LiBOB).

[0091] In some embodiments, the mass content of the additives in the electrolyte is 1% to 10%, and optionally 2% to 8%. The additives with the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0092] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of fluorosulfonylimide salts and lithium hexafluorophosphate LiPF 6 . The above lithium salts are easy to dissociate, which is beneficial to the rapid migration of lithium ions; and the electrolyte system is relatively stable and not easy to decompose, which can improve the cycle performance of the battery cell.

[0093] In some embodiments, the fluorosulfonylimide salts include one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0094] In some embodiments, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate LiPF 6 , the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.5 mol / L to 1.0 mol / L.

[0095] In some embodiments, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.2 to 1.0.

[0096] In some embodiments, the thickness of the base film does not exceed 12 μm, and is optionally 5 μm to 12 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell and thus reduce heat generation.

[0097] In some embodiments, the separator membrane comprises a base film and a functional layer disposed on at least one side of the base film. The functional layer comprises a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and comprises first inorganic particles. The second functional layer is located on the other side of the base film and comprises composite particles. The composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator membrane.

[0098] In some embodiments, the non-fluoropolymer particles comprise acrylate copolymers. Acrylate copolymers have excellent adhesion properties and high adhesion stability with the base film.

[0099] In some embodiments, the first inorganic particles comprise one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above-mentioned first inorganic particles can improve the heat resistance of the first functional layer.

[0100] In some embodiments, the second inorganic particles comprise one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above-mentioned second inorganic particles can improve the heat resistance of the first functional layer.

[0101] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is in the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0102] In some embodiments, the volume energy density of the battery cell is 390 Wh / L to 550 Wh / L. The volume energy density of the battery cell is relatively high.

[0103] In some embodiments, the charging time of the battery cell from 10% state of charge to 80% state of charge is less than or equal to 12.5 min, and can be optionally 6 min to 12.5 min. The charging speed of the battery cell is relatively fast, which is more beneficial to improving the fast charging ability.

[0104] In a second aspect, the present application provides a battery device, which comprises a battery cell according to any one of the embodiments of the first aspect of the present application.

[0105] In some embodiments, the charging time of the battery device from 10% state of charge to 80% state of charge is less than or equal to 12.5 min, and can be optionally 6 min to 12.5 min. The charging speed of the battery device is relatively fast, which is more beneficial to improving the fast charging ability.

[0106] In a third aspect, the present application provides an electrical device, which includes the battery device according to any one of the embodiments of the second aspect of the present application. Description of the Drawings

[0107] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on the drawings without creative efforts.

[0108] Figure 1 It is a schematic structural diagram of a battery cell provided in some embodiments of the present application; Figure 2 It is an exploded view of a battery cell provided in some embodiments of the present application; Figure 3 It is a schematic structural diagram of a battery module provided in some embodiments of the present application; Figure 4 It is a schematic structural diagram of a battery pack provided in some embodiments of the present application; Figure 5 It is a schematic structural diagram of an electrical device provided in some embodiments of the present application.

[0109] The drawings are not necessarily drawn to actual scale.

[0110] The reference numerals are explained as follows: 1. Electrical device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box body; 5a. First box body part; 5b. Second box body part; 5c. Accommodating space; 6. Battery module; 7. Battery cell; 10. Electrode assembly; 111. Positive electrode tab; 112. Negative electrode tab; 12. Main body part; 20. Outer shell; 21. Shell; 22. End cover; 31. Positive terminal; 32. Negative terminal. Detailed Embodiments

[0111] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0112] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are understood to be anticipated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all anticipated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

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

[0114] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0115] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0116] With the development of the battery field, the performance requirements for batteries are getting higher and higher, especially the requirements for the energy density and fast charging performance of batteries are gradually increasing, while the related technologies are difficult to balance the energy density and fast charging performance of batteries.

[0117] In view of the above problems, the embodiments of this application have designed the system of the battery cell. The electrode sheet has a small resistance, which is beneficial to improving the fast charging performance of the battery cell; by adjusting the discharge voltage platform of the battery cell, the battery cell has a high energy density.

[0118] battery cell In a first aspect, an embodiment of the present application provides a battery cell.

[0119] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab, a negative electrode tab, and a separator. The separator is located between the positive electrode tab and the negative electrode tab. Among them, the positive electrode tab includes a positive current collector and at least one surface disposed along the thickness direction of the positive electrode tab and including a positive electrode active material layer containing a positive electrode active material. The positive electrode active material includes a lithium-containing phosphate in an olivine structure; the negative electrode tab includes a negative current collector and at least one surface disposed along the thickness direction of the negative electrode tab and including a negative electrode active material layer containing a negative electrode active material. The negative electrode active material includes a carbon-based material. The single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 , the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm. In a 25°C external environment, during the discharge process of the battery cell from 100% state of charge at a constant current rate of 0.33C to 2.0V, there is a discharge platform voltage V 1 , V 1 is 3.19V to 3.235V.

[0120] The positive electrode active material in the positive electrode tab can provide lithium, and lithium can be in the form of ions. Lithium ions escape from the positive electrode active material and migrate through the electrolyte to the negative electrode tab, and gain electrons at the negative electrode tab. The negative electrode active material in the negative electrode tab can receive lithium, and lithium can be embedded in the negative electrode active material in the form of a metal single substance, or form an alloy with the negative electrode active material, etc. The positive electrode active material in the positive electrode tab includes a lithium-containing phosphate in an olivine structure, and the negative electrode active material in the negative electrode tab includes a carbon-based material. The material system structure is more stable, and the cycle stability of the material system is relatively excellent; The single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 , the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, which is beneficial to achieving the fast charging performance and excellent cycle performance of the battery cell; and there is a discharge platform voltage V during the discharge process 1 , making the energy density of the battery cell relatively high.

[0121] The upper charging limit voltage and the lower discharge cut-off voltage of the battery cell vary according to the different cathode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper charging limit voltage can be 3.65V and the lower discharge cut-off voltage can be 2.0V. Another example is when the phosphate material includes lithium manganese iron phosphate, the upper charging limit voltage can be 4.3V and the lower discharge cut-off voltage can be 2.0V. Next, taking the upper charging limit voltage of 3.65V and the lower discharge cut-off voltage of 2.0V as an example, the discharge platform voltage V of the battery cell 1 will be described: Charge the battery cell at a constant current charging rate of 0.33C to the upper charging limit voltage, and then charge at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell. Discharge the battery cell at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0122] Place the battery cell at 25°C, discharge it at a constant current rate of 0.33C to 2.0V, let it stand for 30 minutes, charge it at a constant current rate of 0.33 to 3.65V, and then charge at a constant voltage of 3.65V to 0.05C. After standing for 2 hours, discharge it at a constant current rate of 0.33C to 2.0V, and record the discharge energy W, discharge capacity A0, and discharge platform voltage V at this time 1 The calculation method is W / A0. Unit of W: Wh, unit of A0: Ah.

[0123] Place the battery cell at 25°C, discharge it at a constant current rate of 0.33C to 2.0V, let it stand for 2 hours, charge it at a constant current rate of 0.33 to 3.65V, and then charge at a constant voltage of 3.65V to 0.05C. Record the charging energy W, charging capacity A0, and calculate the charging platform voltage with the method of W / A0. Unit of W: Wh, unit of A0: Ah.

[0124] In some embodiments, when discharging the battery cell in an external environment of 25°C, the battery cell has a discharge platform voltage V during the discharge process from 100% state of charge at a constant current rate of 2C to 2.0V 2 , V 2 / V 1 is from 0.942 to 0.975, such as 0.942, 0.945, 0.948, 0.950, 0.952, 0.955, 0.958, 0.960, 0.962, 0.965, 0.968, 0.970, 0.972, 0.975 or the range composed of any two of the above values.

[0125] Taking the upper charging limit voltage of 3.65V and the lower discharge cut-off voltage of 2.0V as an example, the discharge platform voltage V of the battery cell 2 will be described: Charge the battery cell at a constant current charge rate of 0.33C to the upper charge limit voltage, and then charge it at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell.

[0126] Place the battery cell at 25°C and discharge it at a constant current rate of 0.33C to 2.0V, let it stand for 30 min, charge it at a constant current rate of 0.33 to 3.65V, and then charge it at a constant voltage of 3.65V to 0.05C. After standing for 2 h, discharge it at a rate of 2C to 2.0V, and record the discharge energy W, discharge capacity A0, and discharge platform voltage V at this time. 2 The calculation method is W / A0. Unit of W: Wh, unit of A0: Ah.

[0127] As the discharge rate increases, the current is relatively large, which easily causes the polarization of the battery cell to increase during discharge, resulting in the discharge voltage decreasing to the discharge cut-off voltage in advance, making the discharge incomplete and the capacity not fully utilized; while in the embodiment of the present application, the discharge platform voltages of the battery cell during discharge at a rate of 0.33 and the battery cell during discharge at a rate of 2C are similar, and the battery cell discharges relatively completely during discharge at rates of 0.33 and 2C, with good rate performance, which is beneficial to the utilization of the energy density of the battery cell.

[0128] Optionally, V 2 can be from 3.05V to 3.15V, such as 3.05V, 3.06V, 3.07V, 3.08V, 3.09V, 3.10V, 3.11V, 3.12V, 3.13V, 3.14V, 3.15V or the range composed of any two of the above values.

[0129] The electrode assembly can be a wound electrode assembly or a stacked electrode assembly.

[0130] In some embodiments, the electrode assembly is a stacked electrode assembly, and the electrode assembly includes a positive electrode plate, a separator, and a negative electrode plate arranged in a stacked manner.

[0131] In the case where the electrode assembly is a stacked electrode assembly, V 1 is from 3.19V to 3.225V. Optionally, V 1 is from 3.200V to 3.225V. Exemplarily, the discharge platform voltage of the electrode assembly is 3.190V, 3.195V, 3.200V, 3.205V, 3.215V, 3.220V, 3.225V or the range composed of any two of the above values.

[0132] The discharge platform voltage V of the stacked electrode assembly 1When within the above range, the energy density of the battery cell can be improved, and the discharge platform voltage will not be too high. The interface side reaction rate in the battery cell is low, which is beneficial to reducing the internal resistance DCR of the battery cell and improving the fast charging performance of the battery cell.

[0133] The negative electrode active material includes a carbon-based material. Optionally, the negative electrode active material also includes a silicon-based material. In the case where the negative electrode active material includes a silicon-based material and a silicon-based material, the electrode assembly is a laminated electrode assembly. 1 The discharge platform voltage of the battery cell is relatively small, which makes the interface side reaction between the negative electrode active material and the electrolyte less and the reaction rate lower, which can improve the fast charging performance of the battery cell. And because the negative electrode active material includes silicon-based materials, the energy density of the battery cell is higher.

[0134] The positive electrode sheet also includes a positive electrode tab, which is arranged on at least one side of the positive current collector, and the positive electrode tab is arranged on at least one side of the positive current collector along the width direction of the positive electrode sheet, and optionally, the positive electrode tab is arranged on both sides of the positive current collector along the width direction of the positive electrode sheet. Alternatively, the positive electrode tab is arranged on at least one side of the positive current collector along the length direction of the positive electrode sheet, and optionally, the positive electrode tab is arranged on both sides of the positive current collector along the length direction of the positive electrode sheet.

[0135] The current transmission path in the length direction is longer, and the current distribution in the length direction is uneven. The positive electrode ears are arranged on both sides of the positive electrode current collecting part along the length direction, so that the current of the positive electrode current collecting part in the length direction is evenly divided by the positive electrode ears on both sides. The electron transmission path is shorter and the current distribution is more uniform. The lithium desorption state of each part of the positive electrode sheet is uniform, and the charging performance of the battery cell can be improved.

[0136] The negative electrode tab is arranged on at least one side of the negative current collector, and the negative electrode tab is arranged on at least one side of the negative current collector along the width direction of the negative electrode sheet, and optionally, the negative electrode tab is arranged on both sides of the negative current collector along the width direction of the negative electrode sheet. Alternatively, the negative electrode tab is arranged on at least one side of the negative current collector along the length direction of the negative electrode sheet, and optionally, the negative electrode tab is arranged on both sides of the negative current collector along the length direction of the negative electrode sheet.

[0137] The current transmission path in the length direction is longer, and the current distribution in the length direction is uneven. The negative electrode ears are arranged on both sides of the negative electrode current collecting part along the length direction, so that the current of the negative electrode current collecting part in the length direction is evenly divided by the negative electrode ears on both sides. The electron transmission path is shorter and the current distribution is more uniform. The lithium insertion state of each part of the negative electrode plate is uniform, and the charging performance of the battery cell can be improved.

[0138] Optionally, the length of the positive electrode film layer is from 200 mm to 1000 mm, such as 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, 700 mm, 750 mm, 800 mm, 850 mm, 900 mm, 950 mm, 1000 mm or a range composed of any two of the above values.

[0139] When the length of the positive electrode film layer is relatively short, such as from 200 mm to 400 mm, the coating weight of the positive electrode film layer is relatively low, which is not conducive to the improvement of energy density. In the embodiments of the present application, V 1 is from 3.20 V to 3.225 V, so that the capacity of the battery cell is more fully exerted during the discharge process, and the improvement of energy density can be further enhanced.

[0140] When the length of the positive electrode film layer is relatively long, such as greater than 400 mm and less than or equal to 1000 mm, the coating weight of the positive electrode film layer is relatively high, so that the energy density is relatively large. In this case, in combination with a discharge platform voltage of 3.19 V to 3.218 V, a relatively low interfacial side reaction rate can be taken into account, the internal resistance DCR of the battery cell can be reduced, and it is beneficial to improve the fast charging performance of the battery cell.

[0141] In the case where the electrode assembly is a wound electrode assembly, the positive electrode tab can be a whole-piece structure, the separator can be a whole-piece structure, and the negative electrode tab can be a whole-piece structure. The positive electrode tab, the separator and the negative electrode tab are wound in the same direction to form an electrode assembly.

[0142] The coating weight of the wound electrode assembly is relatively low, which is not conducive to the improvement of energy density. In the embodiments of the present application, V 1 is from 3.215 V to 3.235 V, so that the capacity of the battery cell is more fully exerted during the discharge process, and the improvement of energy density can be further enhanced.

[0143] The negative electrode active material includes a carbon-based material. Optionally, the negative electrode active material further includes a silicon-based material. In the case where the negative electrode active material includes a carbon-based material and a silicon-based material, the electrode assembly is a wound electrode assembly, V 1 is from 3.190 V to 3.230 V. The discharge platform voltage of the battery cell is relatively small, so that the interfacial side reaction between the negative electrode active material and the electrolyte is less, and the reaction rate is lower, which can improve the fast charging performance of the battery cell. Moreover, since the negative electrode active material includes a silicon-based material, the energy density of the battery cell is relatively high.

[0144] The positive electrode tab further includes a positive electrode tab, which is disposed on at least one side of the positive current collector portion. The positive electrode tab is disposed on at least one side of the positive current collector portion along the width direction of the positive electrode tab. Optionally, the positive electrode tab is disposed on both sides of the positive current collector portion along the width direction of the positive electrode tab. Alternatively, the positive electrode tab is disposed on at least one side of the positive current collector portion along the length direction of the positive electrode tab. Optionally, the positive electrode tab is disposed on both sides of the positive current collector portion along the width direction of the positive electrode tab.

[0145] The negative electrode tab is disposed on at least one side of the negative current collector portion. The negative electrode tab is disposed on at least one side of the negative current collector portion along the width direction of the negative electrode tab. Optionally, the negative electrode tab is disposed on both sides of the negative current collector portion along the width direction of the negative electrode tab. Alternatively, the negative electrode tab is disposed on at least one side of the negative current collector portion along the length direction of the negative electrode tab. Optionally, the negative electrode tab is disposed on both sides of the negative current collector portion along the width direction of the negative electrode tab.

[0146] From the perspective of appearance, the electrode assembly includes a main body portion, a positive electrode tab, and a negative electrode tab, and the positive electrode tab and the negative electrode tab protrude from the main body portion. The positive electrode tab is the part of the positive electrode tab that is not coated with the active material layer, and the negative electrode tab is the part of the negative electrode tab that is not coated with the active material layer. The positive electrode tab and the negative electrode tab are used to lead out the current in the main body portion. The positive electrode tab and the negative electrode tab can extend from the same side of the main body portion or can extend from opposite sides respectively.

[0147] Optionally, the positive electrode tab can extend from both sides of the main body portion. The current is evenly distributed in the main body portion, so that the delithiation state of each part of the positive electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0148] Optionally, the negative electrode tab can extend from both sides of the main body portion. The current is evenly distributed in the main body portion, so that the lithium intercalation state of each part of the negative electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0149] The negative active material in the embodiment of the present application includes a carbon-based material.

[0150] Optionally, the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. Exemplarily, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5% or the range composed of any two of the above values.

[0151] When the graphitization degree of the graphite particles is within the above range, the conductive performance of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode tab and the heat generation of the battery cell; and can improve the fast charging performance of the battery cell.

[0152] 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 coats the surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon, which refers to a transitional carbon material with a very low degree of graphitization crystallization and an approximately amorphous form (or no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0153] The artificial graphite includes secondary particles. There are more migration paths for lithium ions in the artificial graphite, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions. The carbon coating layer has more end faces and defects, resulting in a larger number of sites where lithium ions can be intercalated and deintercalated, making the conductivity of the carbon coating layer relatively excellent, capable of reducing the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0154] Optionally, based on the mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%. Exemplarily, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range composed of any two of the above values.

[0155] When the mass content of the carbon coating layer is within the above range, it can further reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0156] In the embodiments of the present application, the graphite particles can be prepared by methods well-known in the art. For example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and after carbonization treatment, forming a carbon coating layer on at least part of the surface of the artificial graphite particles.

[0157] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of coal tar pitch and petroleum pitch is below 250°C.

[0158] Optionally, the carbonization treatment temperature is 700°C to 1800°C. Optionally, the carbonization treatment temperature is 1000°C to 1300°C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized and a coating layer containing amorphous carbon can be formed on at least part of the surface of the artificial graphite.

[0159] Optionally, the carbonization treatment time is 1h to 6h.

[0160] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include graphite particles, or the carbon-based material may include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0161] In some embodiments, the negative electrode active material may further include a silicon-based material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell. When the negative electrode active material includes a carbon-based material and a silicon-based material, V 1 is from 3.190 V to 3.230 V. The discharge platform voltage of the battery cell is relatively small, resulting in fewer side reactions and a lower reaction rate at the interface between the negative electrode active material and the electrolyte, which can improve the fast charging performance of the battery cell. Moreover, since the negative electrode active material includes a silicon-based material, the battery cell has a relatively high energy density.

[0162] Optionally, based on the mass of the negative electrode active material, the mass content of silicon element in the silicon-based material is from 0.3% to 10.0%, and may be optionally from 1% to 6%. Exemplarily, the mass content of silicon element in the silicon-based material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10% or a range composed of any two of the above values.

[0163] When the mass content of silicon element in the silicon-based material is within the above range, the capacity of the negative electrode active material can be improved, and the energy density of the battery cell can be enhanced.

[0164] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0165] In some embodiments, in addition to the above-mentioned carbon-based material and the optional silicon-based material, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0166] In the present application, the qualitative and quantitative determination of each substance or each element can be performed using suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0167] For example, the carbon-based material in the present application can be used to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or the negative electrode active material in combination with the General Rules for X-ray Diffraction Analysis of JIS / K0131-1996.

[0168] [Positive electrode sheet] The positive electrode sheet includes a positive electrode current collector portion and a positive electrode film layer provided on at least one surface of the positive electrode current collector portion and including a positive electrode active material. For example, the positive electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposite surfaces of the positive electrode current collector portion.

[0169] In some embodiments, when the battery cell is in a 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 ; optionally 2.55 g / cm 3 to 2.70 g / cm 3 . Exemplarily, when the battery cell is in a 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 or the range composed of any two of the above values.

[0170] When the tap density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the positive electrode active materials in the positive electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0171] In the embodiments of the present application, the compaction density of the positive electrode film layer at 100% state of charge (SOC) of the battery cell has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, the battery cell is charged at a constant current charging rate of 0.33C to the cut-off voltage, left standing for 1 minute, and then continued to be charged at a constant current charging rate of 0.1C to the cut-off voltage. At this time, the battery cell is at 100% SOC, and then the positive electrode plate is disassembled to measure the compaction density of the positive electrode film layer.

[0172] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; optionally 240 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 240 mg / 1540.25 mm 2 , 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 360 mg / 1540.25 mm 2 , 370 mg / 1540.25 mm 2 or the range composed of any two of the above values.

[0173] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode plate will not be excessive, and it is possible to take into account the improvement of the energy density of the battery cell. In the embodiments of the present application, the compaction density of the positive electrode film layer in the battery cell at 100% state of charge (SOC) has the meaning well-known in the art, that is, the positive electrode plate of the battery cell at 100% SOC is disassembled, and the compaction density of the positive electrode film layer is measured. For example, a positive electrode plate with single-sided coating (if it is a double-sided coated electrode plate, one side of the positive electrode film layer can be wiped off first) is punched into small round pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the positive electrode film layer of the above-mentioned weighed positive electrode plate is wiped off, the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode plate - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode plate - the thickness H0 of the positive electrode current collector, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0174] In some embodiments, the powder resistivity of the positive electrode active material is from 1 Ω·cm to 27.5 Ω·cm, optionally less than or equal to 20 Ω·cm, and optionally less than or equal to 11 Ω·cm. Exemplarily, the powder resistivity of the positive electrode active material can be 27.5 Ω·cm, 20 Ω·cm, 19 Ω·cm, 18 Ω·cm, 17 Ω·cm, 16 Ω·cm, 15 Ω·cm, 14 Ω·cm, 13 Ω·cm, 12 Ω·cm, 11 Ω·cm, 10 Ω·cm, 9 Ω·cm, 8 Ω·cm, 7 Ω·cm, 6 Ω·cm, 5 Ω·cm, 4 Ω·cm, 3 Ω·cm, 2 Ω·cm, 1 Ω·cm or the range composed of any two of the above values.

[0175] The relatively low powder resistivity of the positive electrode active material results in a relatively low resistance of the positive electrode plate and less heat generation of the battery cell.

[0176] In the embodiments of the present application, the powder resistivity of the material has the meaning well-known in the art, and the well-known methods and equipment in the art can be used for detection. For example, according to the test standard GB / T30835-2014, a PRCD1100 powder resistivity meter is used for testing.

[0177] In some embodiments, the powder compaction density of the positive electrode active material under 30000 N is greater than or equal to 2.46 g / cm 3 , optionally 2.46 g / cm 3 to 2.8 g / cm 3 . Exemplarily, the powder compaction density of the positive electrode active material under 30000 N is 2.46 g / cm 3 , 2.47 g / cm3 , 2.48 g / cm 3 , 2.49 g / cm 3 , 2.5 g / cm 3 , 2.51 g / cm 3 , 2.55 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 or a range composed of any two of the above values.

[0178] When the powder compaction density of the positive electrode active material is within the above range under 30000 N, the energy density of the single battery can be improved. Moreover, since the positive electrode active material in the positive electrode film layer can be stacked more closely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0179] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art and can be detected by methods and equipment well-known in the art. Detection is carried out according to the test standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in a UTM7305 type electronic pressure testing machine, pressurized to 3000 kg (equivalent to 30000 N), kept under pressure for 30 s, then the pressure is released, kept for 10 s, and then the powder compaction density of the positive electrode active material under the action of 30000 N is recorded and calculated.

[0180] In some embodiments, the charging specific capacity of the positive electrode active material at a rate of 0.1C is from 150 mAh / g to 170 mAh / g, and optionally from 157 mAh / g to 170 mAh / g. Exemplarily, the charging specific capacity of the positive electrode active material at a rate of 0.1C 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 composed of any two of the above values.

[0181] When the charging specific capacity of the positive electrode active material at a rate of 0.1C is within the above range, the energy density of the battery cell is relatively high.

[0182] In the embodiments of the present application, the specific capacity of the active material has the meaning well-known in the art, and can be tested by the equipment and methods well-known in the art. The test method of the initial coulomb efficiency and the initial discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be adopted. Using metallic lithium as the negative electrode and the sample electrode sheet containing the above materials as the positive electrode, a half-button cell is assembled. Under the condition of 23°C ± 2°C, the half-button cell is placed on a battery tester or other test equipment with the same performance, and the charging and discharging are carried out at a rate of 0.1C to obtain the discharging capacity, and then the capacity is divided by the mass of the active material of the electrode sheet to obtain the charging specific capacity parameter.

[0183] In some embodiments, the mass percentage of the lithium-containing phosphate with olivine structure in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%. It can be considered that the positive electrode active material of the present application is a lithium-containing phosphate system with olivine structure. When the mass percentage of the lithium-containing phosphate with olivine structure is less than 100%, the positive electrode active material can also include common positive electrode active materials, such as at least one of lithium-containing transition metal oxides. Examples of the 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.

[0184] Optionally, the mass percentage of the lithium-containing phosphate with olivine structure in the positive electrode active material is 100%.

[0185] In the embodiments of the present application, the lithium-containing phosphate in the olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium-containing phosphate in the olivine structure includes phosphate particles and a coating layer, the coating layer covers the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

[0186] By coating the surface of the phosphate particles with a coating layer, the conductivity of the lithium-containing phosphate in the olivine structure can be improved, the powder resistivity of the material can be reduced, and it is beneficial to the migration rate of lithium ions, improving the fast charging ability of the battery and reducing the heat generation of the battery cell.

[0187] In some embodiments, the phosphate particles include a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z where 0.5 ≤ x 1 ≤ 1.3, 0 ≤ y 1 ≤ 1.3, and 0.9 ≤ x 1 + y 1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The phosphate particles have relatively excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0188] Exemplarily, the phosphate particles include one or more of LiFePO 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4 . During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. Regarding the cathode active materials LiFePO 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4In the examples of the present invention, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is used in the battery system, the molar content of Li may change after charge and discharge cycles. 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4 In the enumeration of etc., the molar content of oxygen O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In reality, the molar content of oxygen O will fluctuate. The above situations are all within the protection scope of the present application.

[0189] In some embodiments, the coating layer includes a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor M2 includes one or more elements selected from Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x 2 <5,0<y 2 <4.

[0190] Exemplarily, the fast ion conductor is a material having a NASICON structure, for example, lithium iron titanium phosphate Li 2 FeTi(PO 4 ) 3 、Lithium Zirconium Iron Phosphate Li 2 FeZr(PO 4 ) 3 、Lithium iron tin phosphate Li 2 FeSn(PO 4 ) 3 One or more of .

[0191] Fast ion conductors with NASICON structures are materials with ultrafast ion conduction capabilities, rich three-dimensional lithium ion diffusion and transmission channels, and have the advantages of high ion conduction efficiency and strong structural stability during multiple lithium removal and insertion processes. Coating fast ion conductors with NASICON structures on the surface of phosphate particles can significantly increase the transmission rate of lithium ions during multiple lithium removal / insertion at the positive terminal, improve the ionic conductivity of the positive electrode active material, and improve the fast charging capability of the battery cell. In addition, it can also increase the gram capacity and the energy density of the corresponding battery cell.

[0192] In some embodiments, the ion-conducting layer further includes carbon.

[0193] The carbon element and the fast ion conductor can be arranged in layers, for example, the carbon element is used as an independent carbon coating layer, and the fast ion conductor is used as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the core portion, 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 core portion; or the fast ion conductor layer can be coated on the surface of the core portion, 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 core portion. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0194] Optionally, the carbon coating layer can be coated on the surface of the fast ion conductor layer by a carbonization process of an organic carbon source (e.g., glucose, polyethylene glycol, etc.). The carbon coating layer can partially coat the fast ion conductor layer, or it can completely coat the fast ion conductor layer. The provision of the carbon coating layer can significantly improve the electronic conductivity of the core, make up for the defect of poor electronic conductivity of the core, and improve the energy density of the battery cell. Specifically, the provision of the carbon coating layer enables the positive electrode active material of the present application to have the following advantages: The carbon coating layer in the positive electrode active material of the present application provides a suitable channel for the transmission of electrons, which can significantly improve the conduction rate of electrons in multiple lithium de- and lithium insertion processes, improve the electronic conductivity of lithium-containing phosphates, improve the charging capacity of the corresponding battery cells, and also improve the energy density.

[0195] The carbon coating layer of the positive electrode active material of the present application is loose and porous, which enables the electrolyte to be in full and effective contact with the lithium-containing phosphate, thereby increasing the transmission rate of lithium ions at the interface and improving the charging capacity of the battery cell.

[0196] Coating a carbon coating on the surface of the lithium-containing phosphate can not only improve the conductivity of the lithium-containing phosphate, but also improve the structural stability of the positive electrode active material, effectively alleviate the iron dissolution of the positive electrode active material during long-term storage and cyclic use of the battery cell, thereby improving the cycle life of the battery cell. The positive electrode active material of the present application uses lithium-containing phosphate as a base material, giving full play to the advantages of low cost, high reliability and good cycle stability of lithium-containing phosphate, while using the ion-conducting layer (fast ion conductor layer and carbon coating layer) to solve the disadvantages of poor electronic conductivity and ion conductivity. The battery cell prepared by the positive electrode active material of the present application can improve the energy density of the battery cell while having excellent cycle performance. In the embodiments of the present application, the content of elements in the positive electrode active material has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry, and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode plate is disassembled, washed with DMC and dried, and then the binder is burned off at high temperature to obtain the positive electrode active material to be tested. Weigh 0.4 g of the positive electrode active material, and add 10 ml (50% concentration) of aqua regia to it. Then place it on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is made up to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0197] In some embodiments, the graphitization degree of the positive electrode active material is from 0.15 to 0.32, and can be optionally from 0.19 to 0.26. Exemplarily, the graphitization degree of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32 or the range composed of any two of the above values.

[0198] When the graphitization degree of the positive electrode active material is within the above range, it is beneficial to improve the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode plate, and thus reduce the heat generation of the battery cell.

[0199] In the embodiments of the present application, the graphitization degree of the material has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, it can be tested according to the test standards JIS K 0131-1996 and JB / T 4220-2011. After drying the positive electrode active material as a sample, it is tested by a Bruker D8 Discover X-ray diffractometer to obtain the interlayer spacing d of the (002) crystal plane of carbon in the positive electrode active material. 002 , and then according to the formula g=(0.344 - d 002 ) / (0.344 - 0.3354)×100%, the graphitization degree of the positive electrode active material is calculated.

[0200] In some embodiments, the mass content of carbon element in the lithium-containing phosphate with olivine structure is from 1% to 2%; the specific surface area of the lithium-containing phosphate with olivine structure is from 5 m 2 / g to 18 m 2 / g.

[0201] Optionally, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%; the specific surface area of the lithium-containing phosphate with olivine structure is 7.5 m 2 / g to 14 m 2 / g.

[0202] Exemplarily, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or the range composed of any two of the above values.

[0203] Exemplarily, the specific surface area of the lithium-containing phosphate with olivine structure is 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g, 16 m 2 / g, 17 m 2 / g, 18 m 2 / g or the range composed of any two of the above values.

[0204] The carbon element mainly exists in the coating layer in the form of a carbon coating layer. The carbon coating layer is loose and porous, which is beneficial to increasing the specific surface area of the material, more beneficial to the effective contact between the electrolyte and the phosphate particles, and beneficial to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, the conductivity of the lithium-containing phosphate with olivine structure can be significantly improved, which is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the fast charging ability and energy density of the battery monomer.

[0205] In the embodiments of the present application, the specific surface area of the material has the meaning well known in the art, and can be detected by using the equipment and methods well known in the art. For example, it is detected according to the test standard GB / T 19587-2017. The positive electrode active material is used as a sample, and the specific surface area is tested by a Tri-Star 3020 specific surface area and pore size analyzer of Micromeritics Company, USA.

[0206] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1 µm ≤ Dv50 ≤ 2 µm, and / or 0.4 µm ≤ Dv10 ≤ 0.7 µm, and / or 15 µm ≤ Dv99 ≤ 25 µm.

[0207] Exemplarily, the Dv50 of the positive electrode active material may be 1 µm, 1.1 µm, 1.15 µm, 1.2 µm, 1.25 µm, 1.3 µm, 1.35 µm, 1.4 µm, 1.45 µm, 1.5 µm, 1.55 µm, 1.6 µm, 1.65 µm, 1.7 µm, 1.75 µm, 1.8 µm, 1.85 µm, 1.9 µm, 1.95 µm, 2 µm, or a range composed of any two of the above values.

[0208] Exemplarily, the Dv10 of the positive electrode active material may be 0.4 µm, 0.45 µm, 0.5 µm, 0.55 µm, 0.6 µm, 0.65 µm, 0.7 µm, or a range composed of any two of the above values.

[0209] Exemplarily, the Dv99 of the positive electrode active material may be 15 µm, 16 µm, 17 µm, 18 µm, 19 µm, 20 µm, 21 µm, 22 µm, 23 µm, 24 µm, 25 µm, or a range composed of any two of the above values.

[0210] The particle size of the positive electrode active material is relatively small, the lithium deintercalation / insertion path of lithium ions in the positive electrode active material is short, and the heat generation is less; moreover, the particle size of the above positive electrode active material is not too small, and basically no agglomeration occurs during the processing and preparation process, so that the performance of the positive electrode active material is stable.

[0211] 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, the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% in the volume distribution, and the volume average particle size Dv99 of the material refers to the particle size corresponding to 99% in the volume distribution. It can be detected by using equipment and methods well-known in the art. For example, taking the positive electrode active material as a sample, according to the test standard GB / T 19077-2016, the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer.

[0212] When the positive electrode active material includes other materials in addition to the lithium phosphate with an olivine structure, the volume distribution particle size of the positive electrode active material refers to the volume distribution particle size of all positive electrode active materials.

[0213] In some embodiments, the lithium-containing phosphate in the olivine structure is granular. The lithium-containing phosphate in the olivine structure includes secondary particles, and the secondary particles include a plurality of primary particles. The average particle size of the primary particles is from 200 nm to 500 nm. Exemplarily, the average particle size of the primary particles is 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm or a range composed of any two of the above values.

[0214] The average particle size of the primary particles is relatively small, the lithium deintercalation / insertion path of lithium ions in the cathode active material is short, and the heat generation is less.

[0215] In the embodiments of the present application, the secondary particles refer to agglomerated particles formed by the aggregation of two or more primary particles. The primary particles and the secondary particles can be easily distinguished by experimental means (such as taking SEM images using a scanning electron microscope), and the average particle size of the primary particles can be obtained by testing in the SEM image of the scanning electron microscope. The SEM test parameters can be set as follows: the working voltage (EHT) is 10.00 kV, the InLens detector is used, the working distance is 4.6 mm, and the magnification is 1000X.

[0216] In some embodiments, the cathode film layer further includes a first material, and the first material includes one or more of ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, lithium citrate, lithium nickelate, and lithium ferrate. As a lithium supplement agent, the first material can supplement lithium ions for the cathode film layer, make up for the irreversible lithium ion loss in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0217] Optionally, the ternary material includes Li x3 A y3 Ni a3 Co b3 Mn c M3 (1-a3-b3-c3) Y3 z3 where 0 < x 3 ≤ 2.1, 0 < y 3 ≤ 2.1, and 0.9 ≤ x 3 + y 3 ≤ 2.1, 0 ≤ a 3 ≤ 1, 0 ≤ b 3 ≤ 1, 0 ≤ c 3 ≤ 1, and 0.1 ≤ a 3 + b 3 + c 3 ≤ 1, 1.8 ≤ z 3≤3.5, A includes one or more of Na, K, and Mg, M3 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, and Y3 includes one or more of O and F.

[0218] Exemplarily, the ternary material includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.80 Co 0.15 Al 0.05 O 2 at least one of.

[0219] In some embodiments, the mass content of the lithium supplement in the positive electrode film layer is 0.5% to 5%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range composed of any two of the above values. When the mass content of the lithium supplement is within the above range, it can supplement lithium ions to the positive electrode film layer, make up for the irreversible lithium ion loss in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0220] The lithium supplement can be in the same layer as the positive electrode active material or in different layers. When the lithium supplement and the positive electrode active material are in different layers, the lithium supplement can be in the lithium supplement layer, and the positive electrode active material can be in the positive electrode active material layer. In other words, the positive electrode film layer includes a lithium supplement layer and a positive electrode active material layer. The positive electrode active material layer can be disposed on at least one side of the positive electrode current collector, and the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer can be located between the lithium supplement layer and the positive electrode current collector. Optionally, the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. During the charge and discharge cycling of the battery cell, the lithium supplement in the lithium supplement layer can be gradually released into the system to make up for the lithium loss in the battery system.

[0221] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. There is no particular limitation on the type of the positive electrode conductive agent in the embodiments of the present application. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0222] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. There is no particular limitation on the type of the positive electrode binder in the embodiments of the present application. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0223] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0224] In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05 to 0.30, and may be optionally 0.06 to 0.10. Exemplarily, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3 or a range composed of any two of the above values.

[0225] When the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is within the above range, the rapid charging ability and energy density of the battery cell can be improved.

[0226] In some embodiments, the thickness of the positive current collector is from 10 μm to 15 μm, optionally from 12 μm to 15 μm. Exemplarily, the thickness of the positive current collector is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm or a range composed of any two of the above values.

[0227] When the thickness of the positive current collector is within the above range, the current-carrying capacity of the positive current collector is relatively excellent, and it can enable the battery cell to have a relatively high energy density.

[0228] In the embodiments of the present application, the thicknesses of the positive electrode film layer and the positive current collector have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, a micrometer is used to measure the thickness of the positive electrode sheet, an organic solvent such as alcohol is used to wash off the film layer on the surface of the positive current collector, and a micrometer is used to measure the thickness of the positive current collector. When the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode sheet minus the thickness of the positive current collector; when the positive electrode film layer is coated on both sides, the thickness of the positive electrode film layer is (the thickness of the positive electrode sheet minus the thickness of the positive current collector) / 2.

[0229] The positive electrode film layer is usually formed by coating a positive electrode paste on the positive current collector and then drying and cold-pressing. The positive electrode paste is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0230] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive current collector and the positive electrode film layer and disposed on the surface of the positive current collector. In some other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0231] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the positive electrode film layer and the positive current collector. The positive electrode conductive layer can further improve the conductive performance of the positive electrode sheet and reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery cell.

[0232] In some embodiments, the thickness of the positive electrode conductive layer is from 0.5 μm to 2 μm. Exemplarily, the thickness of the positive electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or a range composed of any two of the above values.

[0233] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode plate can be further improved, the heat generation of the positive electrode plate can be reduced, thereby reducing the heat generation of the battery cell; moreover, the energy density of the battery cell can be improved while taking into account.

[0234] In the embodiments of the present application, the thickness of the positive electrode conductive layer has the meaning well known in the art, and can be detected by using equipment and methods well known in the art. For example, tomographic scanning is performed on the positive electrode plate to directly measure the thickness of the positive electrode conductive layer.

[0235] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0236] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Exemplarily, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50% or a range composed of any two of the above values.

[0237] Exemplarily, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode plate and reducing the heat generation amount of the battery cell.

[0238] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. Exemplarily, 50%, 60%, 65%, 70% or a range composed of any two of the above values.

[0239] Exemplarily, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. The positive electrode binder in the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector part and the positive electrode film layer, and improve the structural stability of the positive electrode plate.

[0240] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector part and a negative electrode film layer provided on at least one surface of the negative electrode current collector part and including a negative electrode active material. For example, the negative electrode current collector part has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector part.

[0241] In some embodiments, when the battery cell is in a 100% charged state, the compaction density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 ; optionally 1.25 g / cm3 to 1.36 g / cm 3 。Exemplarily, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 , 1.28 g / cm 3 , 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.36 g / cm 3 or a range composed of any two of the above values.

[0242] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the negative electrode active material in the negative electrode film layer is stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0243] 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 has the meaning well known in the art, and can be detected by the equipment and methods well known in the art. The detection method is as described in the compaction density test method of the positive electrode film layer above.

[0244] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 , and can be selected as 110 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2 。Exemplarily, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 , 92 mg / 1540.25 mm 2 , 95 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 , 170 mg / 1540.25 mm 2 Or a range composed of any two of the above values.

[0245] When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode plate will not be excessive, and it can also take into account the improvement of the energy density of the battery cell.

[0246] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. The detection method is as described in the single-sided coating weight test method of the film layer above.

[0247] In some embodiments, the powder resistivity of the negative electrode active material is from 0.005 Ω·cm to 0.043 Ω·cm, and may be optionally 0.04 Ω·cm. Exemplarily, the powder resistivity of the negative electrode active material may be 0.043 Ω·cm, 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm or a range composed of any two of the above values.

[0248] The relatively low powder resistivity of the negative electrode active material results in a relatively low resistance of the negative electrode sheet and less heat generation of the battery cell.

[0249] In the embodiments of the present application, the powder resistivity of the negative electrode active material has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. The detection method is the same as the powder resistivity test method of the positive electrode active material described above.

[0250] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20000 N is 1.5 g / cm 3 to 1.85 g / cm 3 and may be optionally 1.55 g / cm 3 to 1.65 g / cm 3 . Exemplarily, the powder compaction density of the negative electrode active material under a pressure of 20000 N is 1.5 g / cm 3 、1.55 g / cm 3 、1.6 g / cm 3 、1.65 g / cm 3 、1.7 g / cm 3 、1.75 g / cm 3 、1.8 g / cm 3 、1.85 g / cm 3 or a range composed of any two of the above values.

[0251] When the powder compaction density of the negative electrode active material under 20000 N is within the above range, the energy density of the battery cell can be improved, and since the negative electrode active materials in the negative electrode film layer can be stacked more closely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0252] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art and can be detected by using the methods and equipment well-known in the art. Detection is carried out according to the test standard GB / T24533-2009. For example, a certain amount of the negative electrode active material is taken as a sample and added to the UTM7305 type electronic pressure testing machine with a bottom area of 1.327 cm 2In the mold, it is pressurized to 2000 kg (equivalent to 20000 N), the pressure is maintained for 30 s, then the pressure is released, and it is kept for 10 s, and then the powder compaction density of the negative electrode active material under the action of 20000 N is recorded and calculated.

[0253] In some embodiments, the charging specific capacity of the negative electrode active material at a rate of 0.1 C is from 350 mAh / g to 480 mAh / g. Exemplarily, the charging specific capacity of the negative electrode active material at a rate of 0.1 C is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g or a range composed of any two of the above values.

[0254] When the charging specific capacity of the negative electrode active material at a rate of 0.1 C is within the above range, the energy density of the battery cell is relatively high.

[0255] In the embodiments of the present application, the charging specific capacity of the negative electrode active material at a rate of 0.1 C has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art, and its detection method is the same as the charging specific capacity test method of the positive electrode active material at a rate of 0.1 C described above.

[0256] In some embodiments, the negative electrode active material includes a carbon-based material, and the carbon-based material has relatively high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass ratio of the carbon-based material in the negative electrode active material can be greater than or equal to 80% and less than or equal to 100%.

[0257] The positive electrode active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. When the two are used in combination, the cycle performance of the battery cell is relatively excellent.

[0258] Optionally, the carbon-based material includes graphite particles.

[0259] In some embodiments, the negative electrode active material may further include a silicon-based material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0260] The qualitative and quantitative analysis of various substances or elements in this application can be detected by suitable equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters from the perspective of detection accuracy, etc., to obtain more accurate detection results. One detection method can be used for qualitative or quantitative analysis, or several detection methods can be used jointly for qualitative or quantitative determination.

[0261] For example, this application can combine the general rules of X-ray diffraction analysis method in JIS / K0131-1996 to conduct X-ray powder diffraction tests and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0262] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional views taken by scanning electron microscope (SEM). There are voids between flaky structures in the SEM cross-sectional view of natural graphite, while the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps. Or they can be distinguished by the XRD spectra obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, while only 2H phase exists in the XRD spectrum of artificial graphite.

[0263] In the embodiments of this application, the negative electrode film layer includes at least one layer of film layer, which can be a single-layer film layer or at least two layers of film layers. Optionally, the negative electrode film layer includes at least two layers of film layers.

[0264] When the negative electrode film layer adopts a single-layer film layer, the negative electrode active material in the negative electrode film layer includes carbon-based materials, and optionally also includes silicon-based materials. When a single-layer film layer is adopted, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm to 13.5 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm or the range composed of any two of the above values.

[0265] When the negative electrode film layer adopts at least two layers of film layers, the negative electrode active material in the negative electrode film layer includes carbon-based materials, and optionally also includes silicon-based materials. The silicon-based materials can be located in one of the at least two layers of film layers, or in at least two of the at least two layers of film layers. The negative electrode film layer can include two layers of film layers, three layers of film layers, four layers of film layers, or even more layers of film layers.

[0266] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector portion. The carbon-based material in the first negative electrode film layer includes graphite particles. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector portion. The carbon-based material in the second negative electrode film layer includes graphite particles.

[0267] The interface between the first negative electrode film layer and the second negative electrode film layer may be regular or irregular; optionally, it is irregular.

[0268] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0269] The negative electrode film layer includes at least two film layers. Layered coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences between the first negative electrode film layer and the second negative electrode film layer, it is possible to construct pore differences in the negative electrode film layer, reduce the tortuosity of lithium ion transport, and improve the fast charging performance of the battery cell.

[0270] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which is beneficial to improving the compaction density of the negative electrode film layer. When the negative electrode active material includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0271] There are differences in the particle sizes between the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode film layer is usually relatively high. The bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transport path of lithium ions, improve the fast charging performance, and can also improve the problem of lithium deposition on the surface layer of the negative electrode plate.

[0272] Optionally, the negative active material in the first negative electrode film layer is granular, and its volume average particle size Dv50 is from 9.5 μm to 18.5 μm, and can be optionally from 9.5 μm to 14.6 μm. Exemplarily, the volume average particle size of the negative active material in the first negative electrode film layer is 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 14.6 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm or a range composed of any two of the above values. When the first negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is from 9.5 μm to 18.5 μm, and can be optionally from 9.5 μm to 14.6 μm.

[0273] When the volume average particle size Dv50 of the negative active material in the first negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance; on the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0274] Optionally, the negative active material in the second negative electrode film layer is granular, and its volume average particle size Dv50 is from 7.8 μm to 14.3 μm, and can be optionally from 7.8 μm to 11.3 μm. Exemplarily, the volume average particle size Dv50 of the negative active material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm or a range composed of any two of the above values. When the second negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is from 7.8 μm to 14.3 μm, and can be optionally from 7.8 μm to 11.3 μm.

[0275] When the volume average particle size Dv50 of the negative active material in the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance, on the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material, and on the third hand, the cooperation of the negative active material in the second negative electrode film layer and the negative active material in the first negative electrode film layer within the above volume average particle size range is beneficial to constructing the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, and improving the fast charging performance of the battery cell.

[0276] In the embodiments of the present application, the volume average particle size Dv50 of the negative electrode active material has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. The detection method is the same as the volume average particle size Dv50 test method of the positive electrode active material described above.

[0277] Optionally, the tapped density of the carbon-based material in the first negative electrode film layer is less than or equal to the tapped density of the carbon-based material in the second negative electrode film layer. The tapped density can reflect the packing density of the active material in the film layer. When the tapped density of the carbon-based material in the second negative electrode film layer is greater than that in the first negative electrode film layer, the second negative electrode film layer is more densely packed, which improves the energy density of the battery cell. The first negative electrode film layer is relatively sparsely packed and has more pores, which can improve the fast charging performance of the battery cell. When the negative electrode active material includes graphite particles, the tapped density of the graphite particles in the first negative electrode film layer is less than or equal to the tapped density of the graphite particles in the second negative electrode film layer.

[0278] Optionally, the tapped density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 , such as 0.82 g / cm 3 , 0.85 g / cm 3 , 0.88 g / cm 3 , 0.90 g / cm 3 , 0.92 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 or the range composed of any two of the above values. When the tapped density of the carbon-based material in the first negative electrode film layer is within a suitable range, the fast charging performance of the battery cell can be improved.

[0279] Optionally, the tapped density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 , such as 0.90 g / cm 3 , 0.92 g / cm 3, 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 , 1.22 g / cm 3 , 1.23 g / cm 3 , 1.24 g / cm 3 , 1.25 g / cm 3 or a range composed of any two of the above values. When the tap density of the carbon-based material in the second negative electrode film layer is within a suitable range, the energy density of the battery cell can be improved.

[0280] In the embodiments of the present application, the tap density of the material has the meaning well-known in the art and can be measured by instruments and methods known in the art. For example, reference can be made to GB / T5162-2006 and a powder tap density tester can be used for measurement. The test instrument can be BT-301 produced by Dandong BET.

[0281] Optionally, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7 to 7:3, and can be optionally 4:6 to 6:4. Exemplarily, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7, 4:6, 5:5, 6:4, 7:3 or a range composed of any two of the above values. By adjusting the thickness ratio of the first negative electrode film layer and the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging ability of the battery cell can be improved.

[0282] In some embodiments, after the battery cell undergoes 10 full charge test cycles at the beginning of life (BOL), the thickness of the first negative electrode film layer is 15 μm to 65 μm, such as 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm or a range composed of any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging ability of the battery cell can be improved.

[0283] In some embodiments, after the battery cell undergoes 10 full charge test cycles at the beginning of life (BOL), the thickness of the second negative electrode film layer is 15 μm to 65 μm, such as 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm or the range composed of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be regulated and increased, the tortuosity of lithium ion transport can be reduced, and the fast charging ability of the battery cell can be improved.

[0284] In the embodiments of the present application, for example, taking the battery charging upper limit voltage of 3.65 V and the battery discharge cut-off voltage of 2.0 V as an example for illustration, The specific steps of the BOL full charge test are as follows: At 25 °C, charge at a charging rate of 0.33 C of the battery nominal capacity to 3.65 V, then charge at a constant voltage of 3.65 V to 0.05 C, stand for 10 min, then discharge at a discharge rate of 0.33 C to 2.0 V, stand for 10 min. The above one charge and discharge is one cycle, and cycle 10 times. Then charge at a charging rate of 0.33 C of the nominal capacity to 3.65 V, and then charge at a constant voltage of 3.65 V to 0.05 C to be the BOL full charge state. In the BOL full charge state, disassemble the negative electrode plate, use a tomography electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode plate, distinguish the two regions according to the interface between the first negative electrode film layer and the second negative electrode film layer, and measure the thicknesses of the two respectively. For example, measure the thicknesses of 10 positions of the first negative electrode film layer, calculate their average value as the average value of the first negative electrode film layer, measure the thicknesses of 10 positions of the second negative electrode film layer, and calculate their average value as the average value of the second negative electrode film layer.

[0285] In some embodiments, after the battery cell undergoes a full charge test at the end of its life (End Of Life, EOL), the thickness of the first negative electrode film layer is 15 μm to 70 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or a range composed of any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the first negative electrode film layer and the second negative electrode film layer can regulate and increase the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transport, and improve the fast charging ability of the battery cell.

[0286] In some embodiments, after the battery cell undergoes a full charge test at the end of its life (End Of Life, EOL), the thickness of the second negative electrode film layer is 15 μm to 70 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or a range composed of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the first negative electrode film layer and the second negative electrode film layer can regulate and increase the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transport, and improve the fast charging ability of the battery cell.

[0287] In the embodiments of the present application, for example, taking the battery charging upper limit voltage of 3.65 V and the battery discharge cut-off voltage of 2.0 V as an example for illustration, The specific steps for the EOL full charge test are as follows: At 60 °C, charge at a charging rate of 0.33C of the battery's nominal capacity until 3.65V, then perform constant voltage charging at 3.65V until 0.05C, let it stand for 10 minutes, then discharge at a discharge rate of 0.33C until 2.0V, and let it stand for 10 minutes. One charge and discharge cycle is defined as above, and the test stops until the battery capacity decays to 80% of the nominal capacity. Then, at 25 °C, charge at a constant current of 0.33C until 3.65V, and perform constant voltage charging at a rate of 0.05C until 3.65V, which is the EOL full charge state. In the EOL full charge state, disassemble the negative electrode sheet, use a tomography scanning electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode sheet, distinguish the regions of the first negative electrode film layer and the second negative electrode film layer according to the interface between them, and measure their thicknesses respectively. For example, measure the thicknesses of 10 positions of the first negative electrode film layer, calculate their average value as the average value of the first negative electrode film layer, measure the thicknesses of 10 positions of the second negative electrode film layer, and calculate their average value as the average value of the second negative electrode film layer.

[0288] In some embodiments, when the negative electrode film layer adopts a single-layer film layer (different from the above-mentioned double-layer film layer), the negative electrode film layer further includes a lithium-containing binder. Optionally, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range composed of any two of the above values. The lithium element in the lithium-containing binder can exist in ionic form, which can increase the number of free-moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell. Optionally, the negative electrode film layer can further include a negative electrode binder. For example, the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0289] Optionally, the mass content of lithium element in the lithium-containing binder is 3% to 10%. Exemplarily, the mass content of lithium element in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values. The mass content of lithium element is calculated based on the mass of the lithium-containing binder. When the mass content of lithium element is within the above range, it can make the number of free-moving lithium ions in the negative electrode film layer relatively large, further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0290] Exemplarily, the lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, which is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is (0.3 - 0.5):(0.15 - 0.45):(0.05 - 0.2):(0.2 - 0.35). For example, the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is 0.35:0.3:0.15:0.2, or 0.4:0.2:0.1:0.3, or 0.45:0.15:0.2:0.2, etc.

[0291] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during the charge and discharge process, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0292] In some other embodiments, when the negative electrode film layer adopts at least two layers of film layers, the negative electrode film layer further includes a lithium-containing binder.

[0293] Optionally, the first negative electrode film layer further includes a first lithium-containing binder, the second negative electrode film layer further includes a second lithium-containing binder, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. Further optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0294] The mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides a relatively larger number of freely movable lithium ions for the second negative electrode film layer, which can further improve the fast charging performance of the battery cell.

[0295] 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 an ionic form, which can increase the number of freely movable lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0296] Optionally, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. Exemplarily, the mass content of lithium element in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range composed of any two of the above values. When the mass content of lithium element is within the above range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0297] Exemplarily, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, and the lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is (0.3-0.5):(0.15-0.45):(0.05-0.2):(0.2-0.35). For example, the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is 0.35:0.3:0.15:0.2, or 0.4:0.2:0.1:0.3, or 0.45:0.15:0.2:0.2, etc.

[0298] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell; and it is not easy to swell during the charge and discharge process, and the structure is stable, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0299] Optionally, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or the range composed of any two of the above values. The lithium element in the second lithium-containing binder can exist in the form of ions, which can increase the number of free-moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0300] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0301] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. Exemplarily, the mass content of lithium element in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values. When the mass content of lithium element is within the above range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0302] Exemplarily, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, and the lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is (0.3-0.5):(0.15-0.45):(0.05-0.2):(0.2-0.35). For example, the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is 0.35:0.3:0.15:0.2, or 0.4:0.2:0.1:0.3, or 0.45:0.15:0.2:0.2, etc.

[0303] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improving the fast charging performance of the battery cell; and it is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0304] In some embodiments, the first negative electrode film layer further includes a negative electrode binder, and the second negative electrode film layer further includes a negative electrode binder. The negative electrode binder in the first negative electrode film layer and the negative electrode binder in the second negative electrode film layer independently include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0305] 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.

[0306] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0307] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. There is no particular limitation on the type of the negative electrode binder in the embodiments of the present application. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0308] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include thickeners, dispersants, etc., for example, sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0309] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0310] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. Exemplarily, the thickness of the negative electrode current collector is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm or a range composed of any two of the above values.

[0311] When the thickness of the negative electrode current collector is within the above range, the current-carrying capacity of the negative electrode current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0312] In the embodiments of the present application, the thickness of the negative current collector is the meaning well-known in the art, and it can be detected by the equipment and methods well-known in the art. For example, the film layer on the surface of the negative current collector is washed away with an organic solvent such as water, and the thickness of the positive current collector is measured with a micrometer.

[0313] The negative film layer is usually formed by coating the negative electrode paste on the negative current collector and then drying and cold pressing. The negative electrode paste is usually formed by dispersing negative active materials, optional conductive agents, optional binders, and other optional additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0314] The negative electrode sheet does not exclude other additional functional layers besides the negative film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a negative conductive layer disposed on the surface of the negative current collector and sandwiched between the negative current collector and the negative film layer. In some other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative film layer.

[0315] In some embodiments, the negative electrode sheet further includes a negative conductive layer, and the negative conductive layer is located between the negative film layer and the negative current collector. The negative 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 cell.

[0316] In some embodiments, the thickness of the negative conductive layer is from 0.5 μm to 2 μm. Exemplarily, the thickness of the negative conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or a range composed of any two of the above values.

[0317] When the thickness of the negative conductive layer is within the above range, it 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 cell; and it can also take into account the improvement of the energy density of the battery cell.

[0318] In the embodiments of the present application, the thickness of the negative conductive layer is the meaning well-known in the art, and it can be detected by the equipment and methods well-known in the art, and the testing method of the negative conductive layer in the foregoing can be adopted.

[0319] In some embodiments, the negative conductive layer includes one or more of a negative conductive agent and a negative binder. The negative conductive agent in the negative conductive layer can improve the conductivity of the negative conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the heat generation of the battery cell; the negative binder in the negative conductive layer can improve the bonding performance between the negative current collector and the negative film layer and improve the structural stability of the negative electrode sheet.

[0320] In some embodiments, the negative electrode conductive layer may further optionally include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0321] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 20% to 40%. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40% or a range composed of any two of the above values.

[0322] Exemplarily, the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0323] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%. Exemplarily, 60%, 65%, 70%, 75%, 80% or a range composed of any two of the above values.

[0324] Exemplarily, the negative electrode binder includes one or more of styrene-butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0325] In some embodiments, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05 to 1.30, and may be optionally 1.07 to 1.15. Exemplarily, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3 or a range composed of any two of the above values.

[0326] When the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is within the above range, there are sufficient sites in the negative electrode film layer for lithium insertion, which can reduce the risk of lithium plating; and is beneficial for fast charging.

[0327] In the embodiments of the present application, the meaning of the CB value is well-known in the art, and it can be detected by using well-known equipment and methods in the art. For example, calculate the capacity of the negative electrode film layer per unit area and the capacity of the positive electrode film layer per unit area respectively, and then calculate the ratio of the two to obtain the CB value.

[0328] Specifically, 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. The capacity of the positive electrode film layer per unit area refers to the actual de-lithiation capacity of the positive electrode active material. The test method is as follows: Disassemble the battery in a PRS340 / 11-119-11 Braun glove box, take the positive electrode plate, and assemble it into a CR2430 type half-button battery with a positive electrode-lithium sheet. The area of the positive electrode plate used is amm 2 , where the electrolyte uses 1mol / L LiPF 6 in a solution of EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, let the assembled half-button battery stand for 3h. The test is carried out at 25°C. First, charge (Charge) and de-lithiate at a voltage range of 2.0V to 3.65V with 0.1C, and then discharge (Discharge) and intercalate lithium to 2.0V with 0.05C. Cycle 2 times, and record the discharge and charge capacity of the second cycle as YmAh. The actual length of the positive electrode plate designed for the battery is bmm, the width is cmm, and the number of sides d where the positive electrode active material is coated on the positive electrode current collector part. Then, the capacity of the positive electrode film layer per unit area = Y / a * b * c * d.

[0329] Specifically, the capacity of the negative electrode film layer per unit area refers to the actual lithium intercalation capacity of the negative electrode active material. The test method is: Disassemble the battery in a PRS340 / 11-119-11 Braun glove box, take the negative electrode plate, and assemble it into a CR2430 type half-button battery with a negative electrode-lithium sheet. The area of the negative electrode plate used is fmm 2 , where the electrolyte uses 1mol / L LiPF 6 in a solution of EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, let the assembled half-button battery stand for 3h. The test is carried out at 25°C. First, discharge (Discharge) and intercalate lithium at a voltage range of 2V - 0V with 0.1C, and then charge (Discharge) and de-lithiate to 2V with 0.05C. Cycle 2 times, and record the discharge and charge capacity of the second cycle as ZmAh. The actual length of the negative electrode plate designed for the battery is hmm, the width is imm, and the number of sides d where the negative electrode active material is coated on the negative electrode current collector part. Then, the lithium intercalation capacity of the negative electrode = Z / f * h * i * d. [Separator membrane] In the embodiments of the present application, the separator membrane includes a base membrane with a porous structure.

[0330] In some embodiments, the base membrane includes at least one of glass fiber, non-woven fabric, and polyolefin. The base membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the base membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0331] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0332] In some embodiments, the porosity of the base film is from 20% to 70%, optionally from 35% to 60%. Exemplarily, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range composed of any two of the above values.

[0333] When the porosity of the base film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0334] In the embodiments of the present application, the porosity refers to the percentage of the internal pore volume in the separator occupying the total volume of the separator. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin Separator for Battery Cell". It should be noted that in the actual testing process, a testing process slightly different from the standard can be adopted according to the differences in testing instruments, testing errors, and in order to eliminate the testing influence on the porosity as much as possible, so as to obtain a more accurate test value.

[0335] In some embodiments, the thickness of the base film is from 6μm to 12μm, optionally from 6μm to 9μm. Exemplarily, the thickness of the base film is 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm or a range composed of any two of the above values.

[0336] 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.

[0337] In the embodiments of the present application, the separator can be a base film. Optionally, the separator further includes a functional layer disposed on at least one side of the base film. The functional layer can include inorganic particles to improve the heat resistance of the separator. Optionally, the functional layer is disposed on both sides of the base film.

[0338] In some embodiments, the functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and includes first inorganic particles. The second functional layer is located on the other side of the base film and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of and / or dispersed in the non-fluoropolymer particles.

[0339] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator.

[0340] Optionally, the first functional layer may include a binder, optionally including at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0341] Optionally, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0342] In the embodiments of the present application, the meaning of the thickness of the base film is the meaning well known in the art, and it can be detected by using the meaning and equipment well known in the art. For example, a newly prepared separator can be taken as a sample, or a battery cell that has been discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, the separator is obtained from the battery cell, and the separator is dried and used as a sample. The separator is cut off with an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the thickness of the cross-section of the separator and its respective layers.

[0343] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers. Optionally, the acrylate copolymers include acrylate-acrylonitrile-acrylamide-acrylonitrile copolymers. The acrylate copolymers have excellent adhesion properties and high adhesion stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as a molar ratio of 0.35:0.3:0.15:0.2, or 0.4:0.2:0.1:0.3, or 0.45:0.15:0.2:0.2, etc.

[0344] The second inorganic particles in the composite particles make it difficult for the non-fluoropolymer particles to adhere to each other due to the high-temperature treatment in the granulation process, resulting in pores in the composite particles, which is beneficial to the transmission of lithium ions and improves the ion-conducting ability of the separator. Moreover, the second inorganic particles can also increase the compression modulus of the composite particles. During the charge and discharge process, the composite particles are not easily deformed, making the structure of the separator more stable, which can improve the kinetic performance of the battery cell and enhance the fast charging performance. Optionally, compared with the first functional layer, the second functional layer is disposed closer to the negative electrode tab. Since the composite particles are not easily deformed, the separator basically does not cause side effects such as extrusion to the negative electrode tab, making the kinetic performance of the negative electrode tab stable. Correspondingly, the first functional layer is disposed closer to the positive electrode tab.

[0345] Optionally, the second inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Optionally, the second inorganic particles include silica. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer and can form composite particles in cooperation with the non-fluoropolymer, further improving the cycle stability and kinetic performance of the separator membrane, and improving the cycle performance and fast charging performance of the battery cell.

[0346] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, and optionally 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or the range composed of any two of the above values. When the average particle size of the second inorganic particles is in the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0347] In the embodiments of the present application, the average particle size of the second inorganic particles has the meaning well known in the art and can be detected by the equipment and methods well known in the art. For example, after obtaining the separator membrane and drying the separator membrane as a sample, use an ion beam cutter to cut the separator membrane to form a cross-section. Subsequently, use a scanning electron microscope to measure the particle size of the second inorganic particles in the separator membrane, measure the particle sizes of multiple, such as 50, second inorganic particles, and calculate their average value as the average particle size of the second inorganic particles.

[0348] In some embodiments, the ionic conductivity of the separator membrane is 0.3 mS / cm to 0.6 mS / cm. Exemplarily, the ionic conductivity of the separator membrane is 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.45 mS / cm, 0.5 mS / cm, 0.55 mS / cm, 0.6 mS / cm or the range composed of any two of the above values.

[0349] When the ionic conductivity of the separator membrane is in the above range, it can further improve the migration ability of lithium ions in the separator membrane and improve the fast charging performance of the battery cell.

[0350] In the embodiments of the present application, the ionic conductivity of the separator membrane has the meaning well known in the art and can be detected by the equipment and methods well known in the art. For example, Prepare a 2025-type button battery for testing: In a vacuum glove box, place a lithium sheet in the battery negative electrode case, add 150 μL of electrolyte, and the electrolyte uses 1 mol / L LiPF 6In a solution with EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then place the separator (with an area of 3.14 cm 2 , a thickness of 12 μm) so that it closely adheres to the lithium sheet, then add 25 μL of electrolyte, and finally place the positive electrode sheet (the positive electrode sheet can be the positive electrode sheet in Example 1) on it, and encapsulate. Take out the assembled button battery from the vacuum glove box and place it for 24 h for the next test.

[0351] Test: On an electrochemical workstation, perform tests in the frequency range of 10 -1 to 10 6 Hz to obtain the separator resistance Rb, and calculate the ionic conductivity σ (unit: mS / cm) through the following formula, σ = L / (R b ×S) where: R b is the separator resistance, and L and S are the thickness and area of the separator to be measured, respectively.

[0352] [Electrolyte] In some embodiments, the battery cell further includes an electrolyte.

[0353] During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and removed back and forth 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.

[0354] In the embodiments of the present application, the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, and can be optionally 15 mS / cm to 20 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm or a range composed of any two of the above values.

[0355] When the conductivity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the fast charging performance of the battery cell.

[0356] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and can be detected by using equipment and methods well known in the art, for example, tested with reference to the industry standard HG-T 4067-2015.

[0357] In some embodiments, the viscosity of the electrolyte at room temperature is from 2.3 mPa·s to 3.5 mPa·s. Exemplarily, the viscosity of the electrolyte is 2.3 mPa·s, 2.4 mPa·s, 2.5 mPa·s, 2.6 mPa·s, 2.7 mPa·s, 2.8 mPa·s, 2.9 mPa·s, 3.0 mPa·s, 3.1 mPa·s, 3.2 mPa·s, 3.3 mPa·s, 3.4 mPa·s, 3.5 mPa·s or a range composed of any two of the above values.

[0358] When the viscosity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0359] In the embodiments of the present application, the viscosity of the electrolyte has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, it can be detected in accordance with GB / T10247-2008.

[0360] In some embodiments, the density of the electrolyte at room temperature, such as 25 °C, is from 1.05 g / mL to 1.35 g / mL. Exemplarily, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL or a range composed of any two of the above values.

[0361] When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0362] In the embodiments of the present application, the density of the electrolyte has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, it can be tested with reference to GB / T 2013-2010.

[0363] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not specifically limited and can be selected according to actual needs.

[0364] In some embodiments, the organic solvent includes a chain carboxylic acid ester solvent, and the mass content of the chain carboxylic acid ester solvent relative to the mass of the organic solvent is greater than or equal to 5% and less than or equal to 75%, and can be optionally 30% to 75%. Exemplarily, the mass content of the chain carboxylic acid ester solvent is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or a range composed of any two of the above values.

[0365] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0366] In some embodiments, the chain carboxylic acid ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0367] The above chain carboxylic acid ester solvent has a high conductivity, which is beneficial to improving the fast charging ability of the battery monomer.

[0368] Optionally, R 1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0369] Optionally, R 2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0370] In the above embodiments, the halogen atom includes one or more of a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Optionally, the halogen atom includes a fluorine atom.

[0371] In the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0372] Exemplarily, the chain carboxylic acid ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8,

[0373] In some embodiments, the organic solvent further includes a carbonate solvent.

[0374] Optionally, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Further optionally, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The above carbonate solvents and chain carboxylic acid ester solvents are used in combination, which improves the conductivity of the electrolyte at room temperature and is beneficial to the migration of lithium ions.

[0375] Further optionally, the mass content of the carbonate solvent in the organic solvent is 25% to 95%, and can be 25% to 70%. Exemplarily, the mass content of the carbonate solvent in the organic solvent is 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, 75% or a range composed of any two of the above values. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte at room temperature and is beneficial to the migration of lithium ions.

[0376] Exemplarily, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, and the mass content of the carbonate solvent is 25% to 70%.

[0377] In some embodiments, the electrolyte further contains additives. The additives can include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery performance, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature performance of the battery, additives that improve the low-temperature power performance of the battery, etc.

[0378] In some embodiments, the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives, and can be at least two. The above additives can improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery monomer and improving the cycle performance.

[0379] In some embodiments, the mass content of the additives in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. Exemplarily, the mass content of the additives in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values.

[0380] The additives with the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery monomer and improving the cycle performance.

[0381] Exemplarily, the carbonate additives include one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0382] Exemplarily, the sulfur-containing additives include one or more of ethylene sulfate (DTD), bis(ethylene sulfate) (2-DTD), butene sulfite (BS), 1,3-propane sultone (PS), ethylene sulfite (ES), and methylene methyl disulfonate (MMDS).

[0383] Optionally, the lithium salt additives include lithium difluorophosphate LiPO 2 F 2 , lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate LiBF 4 , and one or more of lithium bis(oxalato)borate (LiBOB).

[0384] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 9%, optionally 2% to 6%.

[0385] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 4%, optionally 0.5% to 3%.

[0386] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 9%, and the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 4%.

[0387] Further optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 2% to 6%, and the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.5% to 3%.

[0388] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of fluorosulfonylimide salts and lithium hexafluorophosphate LiPF 6 . The above lithium salts are easy to dissociate, which is beneficial to the rapid migration of lithium ions, and the electrolyte system is relatively stable and not easily decomposed, which can improve the cycle performance of the battery cell.

[0389] Optionally, the fluorosulfonylimide salts include one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0390] Optionally, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate LiPF 6 , the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.5 mol / L to 1.0 mol / L.

[0391] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.4 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.7 mol / L.

[0392] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.5 mol / L.

[0393] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.8 mol / L.

[0394] Optionally, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.2 to 1.0, and can be optionally 0.2 to 0.5. Exemplarily, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF 6 is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or the range composed of any two of the above values.

[0395] In the embodiments of the present application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to the standard JY / T 020-1996 "General Rules for Ion Chromatographic Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salt concentrations in the electrolyte by ion chromatography. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample, and detected by ion chromatography.

[0396] In the embodiments of the present application, the types and contents of organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to GB / T 9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample, and detected by ion chromatography.

[0397] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified. Chain carboxylic ester solvents and carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as component components of the organic solvent. Based on the mass of the organic solvent being 100%, the mass content of each component is calculated. Vinylene carbonate additives (such as vinylene carbonate and fluoroethylene carbonate), sulfur-containing additives, and lithium salt additives are used as additives in the electrolyte. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0398] In some embodiments, the battery cell satisfies: 2.45 g / Ah ≤ d / A ≤ 3.5 g / Ah, and can be optionally 2.45 g / Ah ≤ d / A ≤ 3.3 g / Ah, where d represents the mass of the electrolyte in the battery cell, in g, and A represents the rated capacity of the battery cell, in Ah. Exemplarily, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah, or a range composed of any two of the above values.

[0399] d / A can reflect the liquid retention ability of the electrolyte. When d / A is within the above range, the electrolyte can play a good wetting role on the positive electrode plate and the negative electrode plate, and can also improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the fast charging ability of the battery cell.

[0400] In the embodiments of the present application, d / A of the battery cell can be understood as the liquid retention coefficient, and can be detected by using equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharging as 2.0 V in accordance with GB / T31486-2015 "Power Battery Electrical Performance Requirements and Test Methods for Electric Vehicles" for illustration. At 25 °C, the battery cell is charged to 3.65 V at 0.33 C, then charged at a constant voltage until 0.05 C, and then discharged at a constant current of 0.33 C to 2.0 V. The discharged capacity A is used as the denominator. The battery cell is weighed as M0, and then the positive electrode plate, negative electrode plate, separator, and electrolyte are disassembled. The free electrolyte is placed in a bag. All the above solid components are placed in an oven at 60 °C and baked for more than 4 hours (including but not limited to the positive electrode plate, negative electrode plate, separator, and other mechanical parts of the disassembled battery cell that contribute to M0), and then all the components of the battery cell are weighed as M1. The weight difference between M0 and M1 is used as the numerator. The liquid retention coefficient is equal to the value obtained by dividing the weight difference d between M0 and M1 by the capacity A.

[0401] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly through a winding process and / or a stacking process.

[0402] In some embodiments, the battery cell 7 may further include a housing 20.

[0403] In some embodiments, the housing 20 of the battery cell 7 can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The housing 20 of the battery cell 7 can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0404] The housing 20 is a hollow structure, and the housing 20 can be used to encapsulate the above-mentioned electrode assembly 10 and the electrolyte.

[0405] The preparation method of the battery cell 7 according to the embodiments of the present application is well-known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte can be assembled to form the battery cell 7. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly 10 through a winding process and / or a stacking process, the electrode assembly 10 is placed in the housing 20, the electrolyte is injected after drying, and after processes such as vacuum packaging, standing, formation, and shaping, the battery cell 7 is obtained.

[0406] From the perspective of appearance, the electrode assembly 10 includes a main body portion 12, a positive electrode tab 111, and a negative electrode tab 112, and the positive electrode tab 111 and the negative electrode tab 112 protrude from the main body portion 12.

[0407] In some embodiments, the housing 20 includes a housing body 21 and an end cap 22, the housing body 21 has an opening, and the end cap 22 covers the opening.

[0408] The shape of the housing body 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical housing can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid housing can be selected. Optionally, both the electrode assembly 10 and the housing body 21 are cuboid structures.

[0409] In some embodiments, the base material of the housing body 21 includes steel, and the mechanical strength of steel is relatively high, not easily deformed, and can improve the use reliability of the battery cell 7. In the embodiments of the present application, the base material refers to the material with the highest proportion in the housing body 21.

[0410] Optionally, when the base material of the housing 21 includes steel, the thickness of the housing 21 is 0.1 mm to 0.5 mm, and can be optionally 0.2 mm to 0.35 mm. Exemplarily, the thickness of the housing 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm or a range composed of any two of the above values. When the thickness of the housing 21 is within the above range, the mechanical strength of the housing 21 is relatively high, which can improve the use reliability of the battery cell 7; and the housing 21 occupies less space and has more internal space, which is beneficial to improving the energy density of the battery cell 7.

[0411] In some embodiments, the battery cell 7 further includes a positive terminal 31, and the positive terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 are welded, and the positive terminal 31 and the positive electrode tab 111 can be connected through an adapter, or can be connected without using an adapter. When the positive electrode tab 111 is a negative electrode tab, the positive terminal 31 is a positive terminal. When the positive electrode tab 111 is a positive electrode tab, the positive terminal 31 is a negative terminal.

[0412] In some embodiments, the battery cell 7 further includes a negative terminal 32, and the negative terminal 32 is electrically connected to the negative electrode tab 112. Optionally, the negative terminal 32 and the negative electrode tab 112 are welded, and the negative terminal 32 and the negative electrode tab 112 can be connected through an adapter, or can be connected without using an adapter. When the negative electrode tab 112 is a negative electrode tab, the negative terminal 32 is a positive terminal. When the negative electrode tab 112 is a positive electrode tab, the negative terminal 32 is a negative terminal.

[0413] Optionally, the number of positive terminals 31 on the same side of the main body portion 12 is at least one, and can be optionally at least two. At least two positive terminals 31 can increase the current-carrying capacity of the positive terminals 31.

[0414] Further optionally, the current-carrying area of all the positive terminals 31 on one side is greater than or equal to 200 mm 2 , and can be optionally 200 mm 2 to 1000 mm 2 . The current-carrying area of all the positive terminals 31 on one side refers to the sum of the current-carrying areas of all the positive terminals 31 on the same side of the main body portion 12.

[0415] Optionally, the number of negative terminals 32 on the same side of the main body portion 12 is at least one, and can be optionally at least two. At least two negative terminals 32 can increase the current-carrying capacity of the negative terminals 32.

[0416] Further optionally, the current-carrying area of all the negative terminals 32 on one side is greater than or equal to 200 mm 2, optionally 200 mm 2 to 1000 mm 2 , the overcurrent area of the single-sided negative terminal 32 refers to the sum of the overcurrent areas of all the negative terminals 32 on the same side of the main body 12.

[0417] Such as Figure 3 As shown, in some embodiments of the present application, the battery cell 7 according to the implementation manner of the present application can be assembled into a battery module 6. The number of battery cells 7 included in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0418] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, in parallel, or in a series-parallel combination. A series-parallel combination means that there are both series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series, in parallel, or in a series-parallel combination together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodating part of the battery module 6; of course, it can also be that the multiple battery cells 7 are first connected in series, in parallel, or in a series-parallel combination to form battery modules 6, and then the multiple battery modules 6 are connected in series, in parallel, or in a series-parallel combination to form a whole and are accommodated in the accommodating part. Optionally, the battery module 6 can also include an accommodating part with an accommodating space, and the multiple battery cells 7 are accommodated in this accommodating space.

[0419] Such as Figure 4 As shown, in some implementation manners, the above-mentioned battery module 6 can also be assembled into a battery pack 2. The number of battery modules 6 included in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device herein can be the battery module 6 or the battery pack 2.

[0420] The battery pack 2 can include a box body 5 and a plurality of battery modules 6 arranged in the box body 5. The box body 5 includes a first box body part 5a and a second box body part 5b. The box body 5 has an accommodating space 5c. The first box body part 5a is used to cover the second box body part 5b and form a closed space for accommodating the battery module 6. The plurality of battery modules 6 can be arranged in the box body 5 in any manner.

[0421] The first box body part 5a and the second box body part 5b cover each other, and the first box body part 5a and the second box body part 5b jointly define an accommodating space 5c for accommodating the battery cell. The second box body part 5b can be a hollow structure with one end open, and the first box body part 5a is a plate-like structure. The first box body part 5a covers the opening side of the second box body part 5b to form the box body 5 with the accommodating space 5c; both the first box body part 5a and the second box body part 5b can also be hollow structures with one side open, and the opening side of the first box body part 5a covers the opening side of the second box body part 5b to form the box body 5 with the accommodating space 5c. Of course, the first box body part 5a and the second box body part 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0422] To improve the sealing performance after the connection between the first box body part 5a and the second box body part 5b, a sealing member such as sealant, sealing ring, etc. can also be provided between the first box body part 5a and the second box body part 5b.

[0423] Assume that the first box body part 5a covers the top of the second box body part 5b. The first box body part 5a can also be called the upper box cover, and the second box body part 5b can also be called the lower box body. In some embodiments, during the process of the battery pack 2 or any battery cell constituting the battery pack 2 from 0% state of charge (SOC) to 100% SOC, the temperature of the external environment where the battery pack 2 is located is room temperature, such as 30°C.

[0424] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% SOC to 80% SOC, it includes multiple charging steps. The difference between the maximum SOC of any charging step and the maximum SOC of its adjacent charging step is less than or equal to 5% SOC, such as 1% SOC, 1.5% SOC, 2% SOC, 2.5% SOC, 3% SOC, 3.5% SOC, 4% SOC, 4.5% SOC, 5% SOC, or a range composed of any two of the above values.

[0425] The charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% SOC to 40% SOC includes multiple charging steps. For any charging step, it can be charged at any rate between 5C and 10C. The charging rate corresponding to each charging step can be any value among 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value within a range composed of any two of the above values.

[0426] Exemplarily, the charging steps of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be carried out as follows: Constant current charging at 5.0C from 10% SOC to 15% SOC; Constant current charging at 5.0C from 15% SOC to 20% SOC; Constant current charging at 5.0C from 20% SOC to 25% SOC; Constant current charging at 5.0C from 25% SOC to 30% SOC; Constant current charging at 5.0C from 30% SOC to 35% SOC; Constant current charging at 5.0C from 35% SOC to 40% SOC; Constant current charging at 4.6C from 40% SOC to 45% SOC; Charge from 45% SOC to 50% SOC at a constant current of 4.3C; Charge from 50% SOC to 55% SOC at a constant current of 4.0C; Charge from 55% SOC to 60% SOC at a constant current of 3.7C; Charge from 60% SOC to 65% SOC at a constant current of 3.4C; Charge from 65% SOC to 70% SOC at a constant current of 3.1C; Charge from 70% SOC to 75% SOC at a constant current of 2.9C; Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0427] In some embodiments, the charging time of the battery pack 2 or any battery cell constituting the battery pack 2 from 20% state of charge to 80% state of charge is less than or equal to 12.5 min, optionally 6 min to 12.5 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, such as 30°C. Exemplarily, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 12.5 min, 12 min, 11.5 min, 11 min, 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 or the range composed of any two of the above values.

[0428] In some embodiments, the volumetric energy density of the battery cell is 390 Wh / L to 500 Wh / L, optionally 410 Wh / L to 470 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, 480 Wh / L, 490 Wh / L, 500 Wh / L or the range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0429] In the embodiments of the present application, the volumetric energy density of the battery cell has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.65V and the cut-off voltage of battery discharging as 2.0V as an example for illustration, The battery cell is placed at 25 °C and charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage to 0.05C, and discharged at a constant current of 0.33C to 2.0V. Record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulating film outside the outer shell), and calculate the volume V0 of the single battery cell, unit: L. The volume energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0430] electrical device The second aspect of the embodiments of the present application provides an electrical device. The electrical device includes at least one of the battery cell, battery module, or battery pack of the embodiments of the present application. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, electric tool, etc. The vehicle can be a fuel vehicle, gas vehicle, or new energy vehicle. The new energy vehicle can be a pure electric vehicle, hybrid electric vehicle, or range-extended electric vehicle, etc.; the spacecraft includes airplanes, rockets, space shuttles, and spaceships, etc.; the electric toy includes fixed or mobile electric toys, for example, game consoles, electric vehicle toys, electric ship toys, and electric airplane toys, etc.; the electric tool includes metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices. The electrical device can select the battery cell, battery module, or battery pack according to its usage requirements.

[0431] Figure 5 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, hybrid electric vehicle, plug-in hybrid electric vehicle, etc. To meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or battery module can be used.

[0432] A battery pack 2 is provided inside the electrical device 1. The battery pack 2 can be provided at the bottom, head, or tail of the electrical device 1. The battery pack 2 can be used for the power supply of the electrical device 1. For example, the battery pack 2 can be used as the operating power source of the electrical device 1 and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1.

[0433] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery pack 2 to supply power to the motor 4, for example, to meet the working power requirements during the startup, navigation, and driving of the electrical device 1.

[0434] As another example, the electrical device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electrical device generally requires being thin and light, and battery cells can be used as the power source.

[0435] The following charging methods can be selected for the charging process of the electrical device: Charge from 10% SOC to 15% SOC at a constant current of 5.0C; Charge from 15% SOC to 20% SOC at a constant current of 5.0C; Charge from 20% SOC to 25% SOC at a constant current of 5.0C; Charge from 25% SOC to 30% SOC at a constant current of 5.0C; Charge from 30% SOC to 35% SOC at a constant current of 5.0C; Charge from 35% SOC to 40% SOC at a constant current of 5.0C; Charge from 40% SOC to 45% SOC at a constant current of 4.6C; Charge from 45% SOC to 50% SOC at a constant current of 4.3C; Charge from 50% SOC to 55% SOC at a constant current of 4.0C; Charge from 55% SOC to 60% SOC at a constant current of 3.7C; Charge from 60% SOC to 65% SOC at a constant current of 3.4C; Charge from 65% SOC to 70% SOC at a constant current of 3.1C; Charge from 70% SOC to 75% SOC at a constant current of 2.9C; Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0436] In some embodiments, the charging time of the electrical device from 10% state of charge to 80% state of charge is less than or equal to 12.5 min, and can be optionally 6 min to 12.5 min. The temperature of the external environment of the battery pack 2 in the electrical device at 20% state of charge is room temperature, such as 30°C. Exemplarily, the charging time of the battery pack 2 in the electrical device from 10% state of charge to 80% state of charge is 12.5 min, 12 min, 11.5 min, 11 min, 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 or the range composed of any two of the above values.

[0437] embodiment The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and variations within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods, and can be used directly without further treatment, and the instruments used in the examples are all commercially available.

[0438] Example 1-1 Battery Cell (Wound Electrode Assembly) 1. Preparation of the Positive Electrode Plate The positive electrode plate includes a positive current collector, a positive conductive layer on the positive current collector, and a positive electrode film layer. The positive current collector is an aluminum foil with a thickness of 15 μm.

[0439] The positive conductive layer on the positive current collector is a film layer formed by uniformly mixing a positive conductive agent, superconducting carbon, a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), and then coating and drying on the surface of the current collector. The thickness is 1 μm. 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%.

[0440] The positive electrode film layer is a film layer formed by uniformly coating a positive electrode paste (solvent: N-methylpyrrolidone (NMP)) on the surface of the positive conductive layer, followed by drying and cold pressing. The positive electrode film layer includes a positive active material, a binder, polyvinylidene fluoride (PVDF), and a conductive agent, acetylene black, with a weight ratio of 97:2:1.

[0441] The positive active material includes lithium iron phosphate and a coating layer. The coating layer coats the surface of the lithium iron phosphate. The coating layer includes lithium iron titanium phosphate Li 2 FeTi(PO 4 ) 3 and amorphous carbon. The Dv50 of the positive active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0442] 2. Preparation of the Negative Electrode Plate The negative electrode plate includes a negative current collector, a negative conductive layer on the negative current collector, and a negative electrode film layer. The negative current collector is a copper foil with a thickness of 6 μm.

[0443] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing a negative electrode conductive agent of superconducting carbon, a negative electrode binder of styrene-butadiene rubber (SBR), a thickening agent of sodium carboxymethyl cellulose (CMC-Na), and a solvent of water, and then coating it on the surface of the negative electrode current collector and drying. The thickness is 1 μm. The mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickening agent in the negative electrode conductive layer is 5%. The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer, and then drying and cold pressing.

[0444] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer, and then drying and cold pressing.

[0445] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0446] The first negative electrode film layer includes graphite particles, conductive agent acetylene black, a first lithium-containing binder (a copolymer of lithium acrylate - acrylonitrile - acrylamide - 2-hydroxyethyl acrylate, where the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 2-hydroxyethyl acrylate monomer is 0.35:0.3:0.15:0.2), negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose in a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium element in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer covers the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0447] The second negative electrode film layer includes graphite particles, conductive agent acetylene black, a second lithium-containing binder (a copolymer of lithium acrylate - acrylonitrile - acrylamide - 2-hydroxyethyl acrylate, where the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 2-hydroxyethyl acrylate monomer is 0.35:0.3:0.15:0.2), negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose in a mass ratio of 97.5:0.5:0.5:0.5:1. The mass content of lithium element in the second lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer covers the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0448] 3. Separator The separator includes a base film, which is a 7-μm polyethylene film layer with a porosity of 42%.

[0449] 4. Preparation of electrolyte The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0450] The organic solvent includes 60% chain carboxylic ester solvents (ethyl acetate) and 40% carbonate solvents (30% ethylene carbonate EC and 10% dimethyl carbonate). The mass content of each component in the organic solvent is calculated based on the mass of the organic solvent.

[0451] Based on the mass of the electrolyte, the mass content of the additive is 6.5%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluorooxalate borate LiDFOB with a mass ratio of 5:0.5:0.5:0.5.

[0452] The lithium salt includes 1 mol / L lithium hexafluorophosphate LiPF 6 .

[0453] The conductivity of the electrolyte at room temperature is 16.4 mS / cm.

[0454] 5. Preparation of the battery cell Stack the above positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and obtain an electrode assembly through a winding process; place the electrode assembly in an outer packaging shell, inject the electrolyte after drying, and obtain the battery cell through processes such as vacuum packaging, standing, forming, and shaping. At 100% SOC, the tap density of the positive electrode film layer of the battery cell is 2.63 g / cm 3 , and the tap density of the negative electrode film layer is 1.26 g / cm 3 .

[0455] Comparative Example 1-1 and Comparative Example 1-2 Prepare the battery cell using a method similar to that of Example 1-1. Different from Example 1-1, the coating weights of the positive electrode film layer and the negative electrode film layer are adjusted.

[0456] Comparative Example 1-3 Prepare the battery cell using a method similar to that of Example 1-1. Different from Example 1-1, the conductivity of the electrolyte is adjusted.

[0457] Examples 1-2 to 1-6 Prepare the battery cell using a method similar to that of Example 1-1. Different from Example 1-1, at least one of the coating weights of the positive electrode film layer and the negative electrode film layer and the conductivity of the electrolyte is adjusted, as specifically shown in Table 1.

[0458] Among them, In Examples 1-4, the organic solvent in the electrolyte includes 30% chain carboxylic ester solvents (ethyl acetate) and 70% carbonate solvents (30% ethylene carbonate EC and 40% dimethyl carbonate). The mass content of each component in the organic solvent is calculated based on the mass of the organic solvent, and the conductivity is 13.1 mS / cm. In Examples 1-5, the organic solvent in the electrolyte includes 70% chain carboxylic ester solvents (methyl acetate) and 30% carbonate solvents (ethylene carbonate EC). The mass content of each component in the organic solvent is calculated based on the mass of the organic solvent, and the conductivity is 18.7 mS / cm.

[0459] In Example 1-6, the negative electrode active material further includes a silicon-based material, and the mass content of silicon element in the silicon-based material relative to the mass of the negative electrode active material is 3%.

[0460] performance test 1. Charging time of the battery cell For the battery cell of Example 1, when charging from 10% SOC to 80% SOC, the following charging steps are specifically adopted. At 30 °C, start charging from the state of 10% SOC of the battery. Constant current charge at 5.0C from 10% SOC to 15% SOC; Constant current charge at 5.0C from 15% SOC to 20% SOC; Constant current charge at 5.0C from 20% SOC to 25% SOC; Constant current charge at 5.0C from 25% SOC to 30% SOC; Constant current charge at 5.0C from 30% SOC to 35% SOC; Constant current charge at 5.0C from 35% SOC to 40% SOC; Constant current charge at 4.6C from 40% SOC to 45% SOC; Constant current charge at 4.3C from 45% SOC to 50% SOC; Constant current charge at 4.0C from 50% SOC to 55% SOC; Constant current charge at 3.7C from 55% SOC to 60% SOC; Constant current charge at 3.4C from 60% SOC to 65% SOC; Constant current charge at 3.1C from 65% SOC to 70% SOC; Constant current charge at 2.9C from 70% SOC to 75% SOC; Constant current charge at 2.7C from 75% SOC to 80% SOC.

[0461] Record the total charging time.

[0462] Based on the charging rate adjustment in Example 1, the actual rate is adjusted due to the charging time adjustment at 10% - 80% SOC for different examples.

[0463] 2. Cycling performance of battery cells At 30°C, charge the battery cell from 10% SOC to 80% SOC according to the above charging process, then charge it to 3.65V at 0.33C, let it stand for 30 min, and then discharge it to 10% SOC at 1C. This is one charge-discharge cycle. Repeat the above charge-discharge cycle 1000 times, and calculate the cycling capacity retention rate of the battery cell. The higher the cycling capacity retention rate, the better the cycling performance of the battery cell. Based on the charging rate adjustment in Example 1, the actual rate is adjusted due to the charging time adjustment at 10% - 80% SOC for different examples.

[0464] The test results are shown in Table 1.

[0465] Table 1

[0466] As can be seen from Table 1, in Comparative Example 1-1, the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 , and its coating weight is relatively small, resulting in a relatively small energy density of the battery cell; while in Comparative Example 1-2, the single-sided coating weight of the positive electrode film layer is 400 mg / 1540.25 mm 2 , and its coating weight is relatively high, which may result in a relatively large resistance to lithium-ion migration and poor fast-charging performance. In Comparative Example 1-3, the conductivity of the electrolyte is relatively small, the resistance to lithium-ion migration is relatively large, and the fast-charging performance is poor.

[0467] 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 370 mg / 1540.25 mm 2 , the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, which can make the discharge platform voltage during the discharge process of the battery cell from 100% state of charge at a constant current rate of 0.33C to 2.0V be 3.19V to 3.235V, optionally 3.215V to 3.235V, and the discharge platform voltage during the discharge process of the battery cell from 100% state of charge at a constant current rate of 2C to 2.0V be 3.05V to 3.15V. Thus, it can take into account improving the energy density, fast-charging performance, and cycling performance of the battery cell.

[0468] In Examples 1-6, since the negative electrode active material contains silicon-based materials, its energy density is significantly improved, but due to its volume expansion effect, its cycling performance may be slightly worse than that of Example 1-1.

[0469] Example 2-1 Battery Cell (Laminated Electrode Assembly) A battery cell was prepared by a method similar to that of Example 1-1. Different from Example 1-1, a laminated process was used to prepare the electrode assembly.

[0470] Examples 2-2 to 2-6 A battery cell was prepared by a method similar to that of Example 2-1. Different from Example 2-1, at least one of the coating weights of the positive electrode film layer and the negative electrode film layer and the conductivity of the electrolyte was adjusted, as specifically shown in Table 2.

[0471] The battery performance of Examples 2-1 to 2-6 was tested by a method similar to that of Example 1-1, and the test results are shown in Table 2.

[0472] Among them, in Examples 2-5 and 2-6, the negative electrode active material further included a silicon-based material, and the mass content of silicon element in the silicon-based material relative to the mass of the negative electrode active material was 3%.

[0473] Table 2

[0474] As can be seen from Table 2, 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 370 mg / 1540.25 mm 2 , the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, which can make the discharge platform voltage of the battery cell during the discharge process from 100% charged state at a constant current rate of 0.33C to 2.0V be 3.19V to 3.235V, optionally 3.19 to 3.225V, and the discharge platform voltage of the battery cell during the discharge process from 100% charged state at a constant current rate of 2C to 2.0V be 3.05V to 3.15V. Thus, it is possible to take into account improving the energy density, fast charging performance and cycle performance of the battery cell.

[0475] In Examples 2-5 and 2-6, the negative electrode active material further included a silicon-based material, and its energy density was significantly improved. However, due to its volume expansion effect, the cycle performance may be slightly worse than that of Example 2-1.

[0476] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as a limitation to the present application, and the embodiments can be changed, substituted and modified without departing from the spirit, principle and scope of the present application.

Claims

1. A battery cell, characterized in that: The invention comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet comprises a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector along the thickness direction of the positive electrode sheet and comprising a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing phosphate with an olivine structure, and the single-side coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 , The negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector along the thickness direction of the negative electrode sheet and comprising a negative electrode active material, wherein the negative electrode active material comprises a carbon-based material. The conductivity of the electrolyte at room temperature is 13mS / cm to 20mS / cm. In an external environment at 25° C., the battery cell has a discharge platform voltage V1 in the process of discharging from a 100% state of charge to 2.0V at a constant current of 0.33C rate, and V1 is 3.19V to 3.235V.

2. The battery cell according to claim 1, characterized in that: The single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 Up to 170mg / 1540.25mm 2 .

3. The battery cell according to claim 1, characterized in that: The electrode assembly is a laminated structure, the positive electrode sheet, the isolation membrane, and the negative electrode sheet are stacked, and V1 is 3.19V to 3.225V.

4. The battery cell according to claim 3, characterized in that: The positive electrode sheet further includes a positive electrode tab, and the positive electrode tab is arranged on at least one side of the positive current collecting portion along the length direction of the positive electrode sheet.

5. The battery cell according to claim 4, characterized in that: The positive electrode tabs are arranged on both sides of the positive electrode current collecting portion along the length direction of the positive electrode sheet.

6. The battery cell according to claim 3, characterized in that: The dimension of the positive electrode film layer along the length direction of the positive electrode plate is 200 mm to 400 mm, and V1 is 3.20 V to 3.225 V.

7. The battery cell according to claim 3, characterized in that: The dimension of the positive electrode film layer along the length direction is greater than 400 mm and less than or equal to 1000 mm, and V1 is 3.19V to 3.218V.

8. The battery cell according to claim 1, characterized in that: The electrode assembly is a wound structure, the positive electrode sheet, the isolation membrane, and the negative electrode sheet are wound in the same direction, and V1 is 3.215V to 3.235V.

9. The battery cell according to claim 1, characterized in that: The negative electrode active material further includes a silicon-based material, and V1 is 3.190V to 3.230V.

10. The battery cell according to claim 9, characterized in that: The mass content of silicon element in the silicon-based material is 0.3% to 10.0%, based on the mass of the negative electrode active material.

11. The battery cell according to claim 9, characterized in that: The electrode assembly is a laminated structure, and V1 is 3.190V to 3.218V.

12. The battery cell according to claim 9, characterized in that: The electrode assembly is a wound structure, and V1 is 3.210V to 3.230V.

13. The battery cell according to claim 1, characterized in that: The battery cell is discharged under an external environment of 25° C., and has a discharge platform voltage V2 during the discharge process from a 100% state of charge to 2.0V at a constant current of 2C rate, and V2 / V1 is 0.942 to 0.

975.

14. The battery cell according to claim 12, characterized in that: V2 is 3.05V to 3.15V.

15. The battery cell according to claim 1, characterized in that: The single-sided coating weight of the positive electrode film layer is 240 mg / 1540.25 mm 2 Up to 330mg / 1540.25mm 2 .

16. The battery cell according to claim 1, characterized in that: The single-sided coating weight of the negative electrode film layer is 110 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 .

17. The battery cell according to claim 1, characterized in that: The battery cell is at 100% charge state, and the compaction density of the positive electrode film layer is 2.50 g / cm 3 Up to 2.80g / cm 3 .

18. The battery cell according to claim 1, characterized in that: The compaction density of the negative electrode film layer of the battery cell is 1.15 g / cm 3 Up to 1.36g / cm 3 .

19. The battery cell according to claim 1, characterized in that: The powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm; and / or The powder compaction density of the positive electrode active material at 30000N is 2.46g / cm 3 Up to 2.8g / cm 3 ; and / or The positive electrode active material has a charge capacity of 150 mAh / g to 170 mAh / g at a charge rate of 0.1C.

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

21. The battery cell according to claim 20, characterized in that: The phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y z A compound wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F.

22. The battery cell according to claim 20, characterized in that: The coating layer includes a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor M2 includes one or more elements of Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x2<5, 0<y2<4.

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

32.

24. The battery cell according to claim 23, characterized in that: The graphitization degree of the lithium-containing phosphate with an olivine structure is 0.19 to 0.

26.

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

26. The battery cell according to claim 25, characterized in that: The specific surface area of ​​the lithium-containing phosphate with olivine structure is 7.5 m 2 / g to 14m 2 / g.

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

28. The battery cell according to claim 1, characterized in that: The lithium-containing phosphate with an olivine structure is in a granular form, and includes secondary particles. The secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm.

29. The battery cell according to claim 1, characterized in that: The ratio of the thickness of the positive electrode current collector to the total thickness of the positive electrode film layer on one side is 0.06 to 0.

10.

30. The battery cell according to claim 1, characterized in that The thickness of the positive electrode current collector is 10 μm to 15 μm.

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

32. The battery cell according to claim 31, characterized in that: The thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

33. The battery cell according to claim 31, characterized in that The positive electrode conductive layer includes a positive electrode conductive agent, and the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and / or The positive electrode conductive layer includes a positive electrode binder, and the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

34. The battery cell according to claim 1, characterized in that The positive electrode film layer also includes a first material, which includes one or more of a ternary material, lithium phosphate, dilithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate and lithium ferrite.

35. The battery cell according to claim 34, characterized in that: The mass content of the first material in the positive electrode film layer is 0.5% to 5.0%.

36. The battery cell according to claim 1, characterized in that The powder resistivity of the negative electrode active material is 0.005 Ω•cm to 0.043 Ω•cm; and / or The powder compaction density of the negative electrode active material at 20000N is 1.5g / cm 3 Up to 1.85g / cm 3 .

37. The battery cell according to claim 1, characterized in that The negative electrode active material has a charge capacity of 350 mAh / g to 480 mAh / g at a 0.1C rate.

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

39. The battery cell according to claim 38, characterized in that: The graphite particles include: Artificial graphite, including secondary particles, and The carbon coating layer is coated on the surface of the artificial graphite.

40. The battery cell according to claim 39, characterized in that The mass content of amorphous carbon in the coating layer is 2% to 5% based on the mass of the graphite particles.

41. The battery cell according to claim 1, characterized in that The porosity of the negative electrode film layer is 40% to 55%.

42. The battery cell according to claim 1, characterized in that The negative electrode film layer is a single-layer film layer, the negative electrode active material is in a granular form, and the volume average particle size of the negative electrode active material is 8.2 μm to 13.5 μm.

43. The battery cell according to claim 1, characterized in that The negative electrode film layer comprises: a first negative electrode film layer, disposed on the surface of the negative electrode current collecting portion, wherein the first negative electrode film layer comprises a carbon-based material, and A second negative electrode film layer is connected to a side of the first negative electrode film layer away from the negative electrode current collecting portion, wherein the second negative electrode film layer comprises a carbon-based material. The carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently include graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

44. The battery cell according to claim 43, characterized in that The volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm, and / or The volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm.

45. The battery cell according to claim 43, characterized in that The first negative electrode film layer also includes a first lithium-containing binder, and the second negative electrode film layer also includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

46. ​​The battery cell according to claim 45, characterized in that The mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%, and / or The mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%.

47. The battery cell according to claim 45, characterized in that The mass content of lithium in the first lithium-containing binder is 3% to 10%, and / or The mass content of lithium element in the second lithium-containing binder is 3% to 10%.

48. The battery cell according to claim 45, characterized in that The first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer and a hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the hydroxyethyl acrylate monomer is (0.3-0.5): (0.15-0.45): (0.05-0.2): (0.2-0.35); and / or The second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer and a hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the hydroxyethyl acrylate monomer is (0.3-0.5): (0.15-0.45): (0.05-0.2): (0.2-0.35).

49. The battery cell according to claim 1, characterized in that The thickness of the negative electrode current collector is 4 μm to 6 μm.

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

51. The battery cell according to claim 50, characterized in that The thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

52. The battery cell according to claim 50, characterized in that The negative electrode conductive layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and / or The negative electrode conductive layer includes a negative electrode binder, and the negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate and carboxymethyl chitosan.

53. The battery cell according to claim 1, characterized in that The conductivity of the electrolyte at room temperature is 15 mS / cm to 20 mS / cm.

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

55. The battery cell according to claim 1, characterized in that The electrolyte includes an organic solvent, the organic solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent in the organic solvent is 5% to 75%.

56. The battery cell according to claim 55, characterized in that The mass content of the chain carboxylic acid ester solvent in the organic solvent is 30% to 75%.

57. The battery cell according to claim 55, characterized in that The chain carboxylic acid ester solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

58. The battery cell according to claim 57, characterized in that R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group or a C1 to C3 halogenated alkyl group, and / or R2 includes C1 to C3 alkyl or C1 to C3 halogenated alkyl.

59. The battery cell according to claim 58, characterized in that The chain carboxylic acid ester solvent includes one or more of the compounds represented by formula I-1 to the compounds represented by formula I-8, 。 60. The battery cell according to claim 55, characterized in that The organic solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

61. The battery cell according to claim 60, characterized in that The mass content of the carbonate solvent in the organic solvent is greater than or equal to 25% and less than or equal to 95%.

62. The battery cell according to claim 1, characterized in that The electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives and lithium salt additives.

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

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

65. The battery cell according to claim 64, characterized in that The mass content of the additive in the electrolyte is 2% to 8%.

66. The battery cell according to claim 1, characterized in that The electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfonyl imide salt and lithium hexafluorophosphate.

67. The battery cell according to claim 66, characterized in that The fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

68. The battery cell according to claim 67, characterized in that The lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate. The molar concentration of the lithium bis(fluorosulfonyl)imide is 0.2 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate is 0.5 mol / L to 1.0 mol / L.

69. The battery cell according to claim 68, characterized in that The ratio of the molar concentration of the lithium bis(fluorosulfonyl)imide to the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.2 to 1.

0.

70. The battery cell according to claim 1, characterized in that The isolation film includes a base film with a porous structure, and the thickness of the base film is 5 μm to 12 μm.

71. The battery cell according to claim 70, characterized in that The isolation film further includes a functional layer disposed on at least one side of the base film, and the functional layer includes: a first functional layer, located on one side of the base film, wherein the first functional layer comprises first inorganic particles, The second functional layer is located on the other side of the base film, and the second functional layer includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

72. The battery cell according to claim 71, characterized in that The non-fluorinated polymer particles include acrylic copolymers.

73. The battery cell according to claim 71, characterized in that The first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

74. The battery cell according to claim 71, characterized in that The second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide, and / or The average particle size of the second inorganic particles is 5 nm to 100 nm.

75. The battery cell according to claim 1, characterized in that The volume energy density of the battery cell is 390Wh / L to 550Wh / L.

76. The battery cell according to claim 1, characterized in that The charging time of the battery cell from 10% state of charge to 80% state of charge is 6 minutes to 12.5 minutes.

77. A battery device, characterized in that: Comprising the battery cell as claimed in any one of claims 1 to 76.

78. The battery device according to claim 77, characterized in that The charging time of the battery device from a 10% state of charge to an 80% state of charge is 6 minutes to 12.5 minutes.

79. An electrical device, characterized in that: Comprising a battery device as described in claim 77.

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