Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device, the battery monomer comprises an electrode assembly and an electrolyte, and the electrode assembly comprises a positive pole piece, an isolating membrane and a negative pole piece which are laminated along the thickness direction; the positive pole piece comprises a positive pole lug, a positive pole current collecting part and a positive pole film layer which is arranged on the surface of the positive pole current collecting part along the thickness direction and contains a positive pole active material, and the positive pole lug is arranged on at least one side of the positive pole current collecting part; the negative pole piece comprises a negative pole lug, a negative pole current collecting part and a negative pole film layer which is arranged on the surface of the negative pole current collecting part in the thickness direction and contains a negative pole active material, the negative pole lug is arranged on at least one side of the negative pole current collecting part, and the ratio of the length to the width of the positive pole film layer is 4-20; the size of the positive electrode film layer in the length direction is 600-1200 mm; and the single-side coating weight of the negative electrode film layer is 74mg / 1540.25 mm < 2 > to 156mg / 1540.25 mm < 2 >. The reliability 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 / 106997, 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, so they are widely used in electronic devices, such as mobile phones, laptops, battery-powered vehicles, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools, etc. Due to great progress in the battery field, higher requirements are put forward for the performance of batteries. However, currently, battery cells cannot balance the improvement of energy density and fast charging performance. Summary of the Invention

[0004] This application provides a battery cell, a battery device and an electrical device, which can improve the reliability and cycling performance of the battery cell.

[0005] In a first aspect, this application proposes a battery cell. The battery cell includes an electrode assembly, and the electrode assembly includes a positive electrode tab, a separator, and a negative electrode tab stacked in the thickness direction of the battery cell; the positive electrode tab includes a positive electrode ear, a positive current collector, and a positive electrode film layer disposed on at least one surface of the positive current collector in the thickness direction and containing a positive electrode active material, and the positive electrode ear is disposed on at least one side of the positive current collector; the negative electrode tab includes a negative electrode ear, a negative current collector, and a negative electrode film layer disposed on at least one surface of the negative current collector in the thickness direction and containing a negative electrode active material, and the negative electrode ear is disposed on at least one side of the negative current collector, wherein the ratio of the length to the width of the positive electrode film layer is 4 to 20; the length of the positive electrode film layer is 600 mm to 1200 mm; the single-sided coating weight of the negative electrode film layer is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 . It should be noted that the dimension of the positive electrode film layer in the length direction is the length of the positive electrode film layer, and the dimension of the positive electrode film layer in the width direction is the width of the positive electrode film layer.

[0006] Thus, when the embodiments of this application meet the above requirements, when the ratio of the length to the width of the positive electrode film layer is within the above range and the single-sided coating weight of the negative electrode film layer is within the above range, the current distribution in the positive current collector and the negative current collector is relatively uniform, and the uniformly extracted lithium can be uniformly embedded in the negative electrode tab. The negative electrode tab is not prone to lithium deposition, which can improve the fast charging performance of the battery cell and can also improve the energy density.

[0007] In some embodiments, the width of the positive electrode film layer is from 60 mm to 150 mm. The relatively short width of the positive electrode film layer enables a shorter transmission path of electrons in the width direction, thereby improving the current uniformity in the width direction.

[0008] In some embodiments, the positive electrode tabs are disposed on both sides of the positive current collector along the length direction of the electrode assembly. By disposing the positive electrode tabs on both sides of the positive current collector along the length direction, the current in the length direction of the positive current collector is evenly divided by the positive electrode tabs on both sides, resulting in a shorter electron transmission path and a more uniform current distribution. The de-lithiation state of each part of the positive electrode plate is uniform, and the charging performance of the battery cell can be improved.

[0009] In some embodiments, there is one or more positive electrode tabs on the same side of the positive current collector. The positive electrode tab includes a first end face connected to the positive current collector. The dimension of the first end face in the width direction is W1, and the sum of the dimensions of all the first end faces in the width direction on the same side of the positive current collector is n×W1. The dimension of the positive current collector in the width direction is W2, and n×W1 / W2 is greater than or equal to 1 / 3, where n represents the number of all positive electrode tabs on the same side of the positive current collector. Optionally, n×W1 / W2 is greater than or equal to 2 / 3, where n represents the number of all positive electrode tabs on the same side of the positive current collector.

[0010] Thus, when n×W1 / W2 satisfies the above range, the current-carrying area of the positive electrode tab is relatively large, which is beneficial to improving the fast charging performance of the battery cell.

[0011] In some embodiments, the negative electrode tabs are disposed on both sides of the negative current collector along the length direction of the electrode assembly. By disposing the negative electrode tabs on both sides of the negative current collector along the length direction, the current in the length direction of the negative current collector is evenly divided by the negative electrode tabs on both sides, resulting in a shorter electron transmission path and a more uniform current distribution. 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.

[0012] In some embodiments, there is one or more negative electrode tabs on the same side of the negative current collector. The negative electrode tab includes a second end face connected to the negative current collector. The dimension of the second end face in the width direction is W3, and the sum of the dimensions of all the second end faces in the width direction on the same side of the negative current collector is m×W3. The dimension of the negative current collector in the width direction is W4, and m×W3 / W4 is greater than or equal to 1 / 3, where m represents the number of all negative electrode tabs on the same side of the negative current collector. Optionally, m×W3 / W4 is greater than or equal to 2 / 3, where m represents the number of all negative electrode tabs on the same side of the negative current collector.

[0013] Thus, when m×W3 / W4 satisfies the above range, the current-carrying area of the negative electrode tab is relatively large, which is beneficial to improving the fast charging performance of the battery cell.

[0014] In some embodiments, the positive electrode tab is disposed on at least one side of the positive electrode current collector portion in the width direction. In the positive electrode current collector portion, the electron transmission path is short, and the current distribution is more uniform. The de-lithiation state of each part of the positive electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0015] In some embodiments, the number of positive electrode tabs on the same side of the positive electrode current collector portion is one or more. The positive electrode tab includes a third end face connected to the positive electrode current collector portion, and the dimension of the third end face in the length direction is L 10 , and the sum of the dimensions of all the third end faces on the same side of the positive electrode current collector portion in the length direction is s×L 10 , the dimension of the positive electrode current collector portion in the length direction is L1, s×L 10 / L1 is greater than or equal to 1 / 3, and s represents the number of all positive electrode tabs on the same side of the positive electrode current collector portion.

[0016] Thus, the current-carrying area of the positive electrode tab is relatively large, which is beneficial to improving the fast charging performance of the battery cell.

[0017] In some embodiments, the negative electrode tab is disposed on at least one side of the negative electrode current collector portion in the width direction. In the negative electrode current collector portion, the electron transmission path is short, and the current distribution is more uniform. The de-lithiation state of each part of the negative electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0018] In some embodiments, the number of negative electrode tabs on the same side of the negative electrode current collector portion is one or more. The negative electrode tab includes a fourth end face connected to the negative electrode current collector portion, and the dimension of the fourth end face in the length direction is L 20 , and the sum of the dimensions of all the fourth end faces on the same side of the negative electrode current collector portion in the length direction is p×L 20 , the dimension of the negative electrode current collector portion in the length direction is L2, p×L 20 / L2 is greater than or equal to 1 / 3, and p represents the number of all negative electrode tabs on the same side of the negative electrode current collector portion.

[0019] Thus, the current-carrying area of the negative electrode tab is relatively large, which is beneficial to improving the fast charging performance of the battery cell.

[0020] In some embodiments, along the length direction, the dimension of the negative electrode film layer is larger than that of the positive electrode film layer, and the difference between the dimension of the negative electrode film layer and that of the positive electrode film layer is OH 1 , OH 1 is 0.5 mm to 3.0 m. The larger dimension of the negative electrode film layer than that of the positive electrode film layer can reduce the risk of lithium plating.

[0021] In some embodiments, along the width direction, the dimension of the negative electrode film layer is larger than that of the positive electrode film layer, and the difference between the dimension of the negative electrode film layer and that of the positive electrode film layer is OH 2, OH 2 is from 0.5 mm to 3.0 mm. The size of the negative electrode film layer is larger than that of the positive electrode film layer, which can reduce the risk of lithium plating.

[0022] In some embodiments, the positive electrode tab is disposed on both sides of the positive electrode current collector along the length direction, the negative electrode tab is disposed on at least one side of the negative electrode current collector along the length direction. Along the length direction of the battery cell, the size of the negative electrode film layer is larger than that of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH 1 ; along the width direction of the battery cell, the size of the negative electrode film layer is larger than that of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH 2 , where OH 1 is greater than OH 2 .

[0023] Thus, in the embodiments of the present application, OH 1 is set to be greater than OH 2 , so that the ability of the region near the negative electrode film layer to receive lithium ions in the length direction is stronger. In particular, the ability of the region of the negative electrode film layer near the negative electrode tab to receive lithium ions can be improved, the risk of lithium plating can be reduced, and the use reliability of the battery cell can be improved.

[0024] In some embodiments, the battery cell further includes a positive terminal, and the positive terminal is electrically connected to the positive electrode tab.

[0025] In some embodiments, the positive terminal is directly welded to the positive electrode tab. Direct welding of the positive terminal and the positive electrode tab can reduce the resistance at the connection, which is beneficial to reducing the overall internal resistance of the battery cell.

[0026] In some embodiments, the battery cell further includes a positive terminal, the positive terminal is connected to the positive electrode tab, and the positive terminal is one or at least two, and is preferably at least two. At least two positive terminals can increase the overall current-carrying capacity of the positive terminals.

[0027] In some embodiments, the number of positive terminals on the same side of the positive electrode current collector is at least two. At least two positive terminals can increase the overall current-carrying capacity of the positive terminals.

[0028] In some embodiments, the current-carrying area of a single positive terminal is from 200 mm 2 to 800 mm 2 . When the current-carrying area of the positive terminal satisfies the above relationship, the current-carrying capacity is relatively excellent, which is beneficial to fast charging.

[0029] In some embodiments, the battery cell further includes a negative terminal, and the negative terminal is electrically connected to the negative electrode tab.

[0030] In some embodiments, the battery cell further includes a negative terminal, which is connected to the negative electrode tab. The negative terminal is one or at least two, and preferably at least two. At least two negative terminals can increase the overall overcurrent capacity of the negative terminals.

[0031] In some embodiments, the negative terminal is directly welded to the negative electrode tab. Directly welding the negative terminal and the negative electrode tab can reduce the resistance at the connection, which is beneficial to reducing the overall internal resistance of the battery cell.

[0032] In some embodiments, the number of negative terminals on the same side of the negative current collector is at least two. At least two negative terminals can increase the overall overcurrent capacity of the negative terminals.

[0033] In some embodiments, the overcurrent area of a single negative terminal is 200 mm 2 to 800 mm 2 . When the overcurrent area of the negative terminal satisfies the above relationship, the overcurrent capacity is relatively excellent, which is beneficial to fast charging.

[0034] In some embodiments, the battery cell includes a housing that houses the electrode assembly and the electrolyte. The thickness of the housing is 0.1 mm to 0.5 mm, and preferably 0.2 mm to 0.35 mm. The housing has a relatively thin thickness, occupies less space, and can further improve the energy density of the battery cell.

[0035] In some embodiments, when the battery cell is in a 100% charged state, the compaction density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 , and preferably 2.55 g / cm 3 to 2.70 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 since the positive active material in the positive electrode film layer is stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet and thus reduce heat generation.

[0036] In some embodiments, the single-sided coating weight of the positive electrode film layer is 160 mg / 1540.25 mm 2 to 340 mg / 1540.25 mm 2 . 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 sheet will not be too large, and it can also take into account improving the energy density of the battery cell.

[0037] 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 results in a relatively low resistance of the positive electrode sheet and less heat generation of the battery cell.

[0038] In some embodiments, the powder compaction density of the positive electrode active material under 30,000 N is 2.46 g / cm 3 to 2.8 g / cm 3 . When the powder compaction density of the positive electrode active material under 30,000 N is within the above range, the energy density of the battery cell can be improved. Moreover, since the positive electrode active material in the positive electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0039] In some embodiments, the charging specific capacity of the positive electrode active material at a 0.1 C rate is 150 mAh / g to 170 mAh / g. When the charging specific capacity of the positive electrode active material at a 0.1 C rate is within the above range, the energy density of the battery cell is relatively high.

[0040] In some embodiments, the positive electrode active material includes a lithium-containing phosphate with an olivine structure. The lithium-containing phosphate with an olivine structure includes phosphate particles and a coating layer. The coating layer coats the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn. By surface coating the phosphate particles with the coating layer, the conductivity of the lithium-containing phosphate with an olivine structure can be improved, the powder resistivity of the material can be reduced, and it is beneficial to the migration rate of lithium ions, reducing the heat generation of the battery cell.

[0041] 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.

[0042] In some embodiments, the coating layer comprises a fast ion conductor with the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , where M2 comprises one or more elements selected from Ti, Zr, Hf, Ge, and Sn, 0 ≤ d ≤ 1, 0 < x 2 <5, 0 < y 2 <4. Coating the surface of the phosphate particles with the fast ion conductor can significantly improve the transmission rate of lithium ions during multiple deintercalation / insertion of lithium at the positive electrode, improve the ionic conductivity of the positive electrode active material, thereby increasing the specific capacity, and further increasing the energy density of the corresponding battery cell.

[0043] In some embodiments, the graphitization degree of the positive electrode active material is from 0.15 to 0.32, and may be optionally from 0.19 to 0.26. When the graphitization degree of the positive electrode active material is within the above range, it is beneficial to improve the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell.

[0044] In some embodiments, the mass content of carbon element in the lithium-containing phosphate with olivine structure is from 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 5 m 2 / g to 18 m 2 / g, and may be optionally from 7.5 m 2 / g to 14 m 2 / g.

[0045] Thus, in the embodiments of the present application, the carbon element with the above mass content cooperates with the material with the above specific surface area, which is more conducive to the effective contact between the electrolyte and the lithium-containing phosphate with olivine structure, and is conducive to the transmission of lithium ions at the phase interface.

[0046] In some embodiments, the lithium-containing phosphate with olivine structure is granular, and its volume distribution particle size satisfies: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm. The particle size of the lithium-containing phosphate with olivine structure is relatively small, the deintercalation / insertion path of lithium ions in the positive electrode active material is short, the heat generation is less, and the particle size of the above positive electrode active material is not too small, and basically no agglomeration occurs during the processing and preparation process, so that the performance of the positive electrode active material is stable.

[0047] In some embodiments, the lithium-containing phosphate with olivine structure is granular, and the lithium-containing phosphate with olivine structure comprises secondary particles, and the secondary particles comprise a plurality of primary particles, and the average particle size of the primary particles is from 200 nm to 500 nm. The average particle size of the primary particles is relatively small, the deintercalation / insertion path of lithium ions in the positive electrode active material is short, and the heat generation is less.

[0048] In some embodiments, the particle size of the smallest particles in the lithium-containing phosphate with an olivine structure is 0.1 μm to 0.4 μm; when the particle size of the smallest particles is within the above range, agglomeration is not likely to occur during the preparation of the positive electrode film layer.

[0049] In some embodiments, the particle size of the largest particles in the lithium-containing phosphate with an olivine structure is 15 μm to 25 μm. When the particle size of the largest particles is within the above range, the migration path of lithium ions during charge and discharge will not be too long, which can improve the fast charge and discharge performance of the battery cell.

[0050] In some embodiments, the ratio of the thickness of the positive electrode current collector part to the thickness of the single-sided positive electrode film layer is 0.05 to 0.3. When the ratio of the thickness of the positive electrode current collector part to the thickness of the single-sided positive electrode film layer is within the above range, the fast charging ability and energy density of the battery cell can be improved.

[0051] In some embodiments, the thickness of the positive electrode current collector part is 10 μm to 15 μm. When the thickness of the positive electrode current collector part is within the above range, the current-carrying capacity of the positive electrode current collector part is relatively excellent, and the battery cell can have a high energy density.

[0052] In some embodiments, the positive electrode 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, trilithium citrate, lithium nickelate, and lithium ferrate. The above first material can be used as a lithium supplement agent, which can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and thus improve the energy density of the battery cell.

[0053] In some embodiments, the mass content of the lithium supplement agent 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 for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and thus improve the energy density of the battery cell.

[0054] In some embodiments, the positive electrode plate further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the positive electrode film layer and the positive electrode current collector part. The positive electrode conductive layer can further improve the conductive performance of the positive electrode plate, reduce the heat generation of the positive electrode plate, and thus reduce the heat generation of the battery cell.

[0055] 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 conductive performance of the positive electrode plate, reduce the heat generation of the positive electrode plate, and thus reduce the heat generation of the battery cell, and can also take into account the improvement of the energy density of the battery cell.

[0056] 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 sheet, 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 part and the positive electrode film layer, and improve the structural stability of the positive electrode sheet.

[0057] 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.

[0058] 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.

[0059] In some embodiments, the powder compaction density of the negative electrode active material under 20000N is 1.5 g / cm 3 to 1.85 g / cm 3 . When the powder compaction density of the negative electrode active material under 20000N is within the above range, the energy density of the battery cell can be improved, and since the negative electrode active materials in the negative electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0060] In some embodiments, the charging specific capacity of the negative electrode active material at a 0.1C rate is greater than or equal to 350 mAh / g. When the charging specific capacity of the negative electrode active material at a 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0061] In some embodiments, the negative electrode active material includes a carbon-based material, the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. When the graphitization degree of the graphite particles is within the above range, the conductive performance of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode sheet and the battery cell, and can improve the fast charging performance of the battery cell.

[0062] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer, the artificial graphite includes secondary particles, and the carbon coating layer covers the surface of the artificial graphite. The carbon coating layer has more end faces and defects, so that the number of sites capable of intercalating and deintercalating lithium ions is larger, and the conductivity of the carbon coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0063] In some embodiments, based on the mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%. When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode sheet can be further reduced, and the heat generation of the battery cell can be reduced.

[0064] 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 materials in the first negative electrode film layer and the second negative electrode film layer each independently include graphite particles, and the volume average particle diameter Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle diameter Dv50 of the graphite particles in the second negative electrode film layer.

[0065] Thus, in the embodiments of the present application, there is a difference in the particle diameters 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 relatively high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle diameter of the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can improve the problem of lithium deposition on the surface layer of the negative electrode sheet.

[0066] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0067] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, so that the energy density of the battery cell is improved. The filling of the first negative electrode film layer is relatively sparse and the pores are richer, which can improve the fast charging performance of the battery cell.

[0068] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 . When the tap density of the carbon-based material in the first negative electrode film layer is within a suitable range, the fast charging performance of the battery cell can be improved.

[0069] In some embodiments, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 . When the tap density of the carbon-based material in the second negative electrode film layer is within a suitable range, the energy density of the battery 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.

[0070] 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.

[0071] 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.

[0072] Therefore, in the embodiments of the present application, the mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the number of freely movable lithium ions provided by the second lithium-containing binder for the second negative electrode film layer is relatively large, which can further improve the fast charging performance of the battery cell.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] In some embodiments, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. When the mass content of lithium element is within the above range, the number of 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.

[0077] In some embodiments, the first lithium-containing binder comprises 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).

[0078] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0079] In some embodiments, the second lithium-containing binder comprises 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).

[0080] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0081] In some embodiments, the negative electrode active material further comprises a silicon-based material, and the mass content of silicon element in the silicon-based material is 0.3% to 10.0% based on the mass of the negative electrode active material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0082] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. When the thickness of the negative electrode current collector is within the above range, the current-carrying capacity of the negative electrode current collector is relatively excellent, and the battery cell can have a high energy density.

[0083] In some embodiments, the negative electrode sheet further comprises a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector.

[0084] 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.

[0085] 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 and the negative electrode film layer, and improve the structural stability of the negative electrode sheet.

[0086] 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.

[0087] 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.

[0088] In some embodiments, the separator includes a base film with a porous structure, and the porosity of the base film is 20% to 70%. When the porosity of the separator in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0089] In some embodiments, the separator includes a base film with a porous structure, and the porosity of the base film is 35% to 60%. When the porosity of the separator in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0090] In some embodiments, the thickness of the base film is 6 μm to 12 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0091] In some embodiments, the thickness of the base film is 6 μm to 9 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0092] In some embodiments, the separator membrane includes a base film and a functional layer disposed on at least one side of the base film. The functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film 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 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.

[0093] In some embodiments, the non-fluoropolymer particles include acrylate copolymers. The acrylate copolymers have excellent adhesion properties and high adhesion stability with the base film.

[0094] In some embodiments, the first inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0095] In some embodiments, the second inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above second inorganic particles can improve the heat resistance of the first functional layer.

[0096] 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.

[0097] In some embodiments, the carboxylic ester solvent includes a chain carboxylic ester solvent. The mass content of the chain carboxylic ester solvent in the organic solvent is greater than or equal to 5% and less than or equal to 75%, optionally greater than or equal to 10% and less than or equal to 75%, and optionally 30% to 75%. When the mass content of the chain carboxylic 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.

[0098] 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. Thus, the chain carboxylic ester solvent in the embodiments of the present application has a high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0099] In some embodiments, R 1 comprises a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0100] In some embodiments, in some embodiments, R 2 comprises a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0101] In some embodiments, the chain carboxylic ester solvent comprises one or more of the compounds represented by Formula I-1 to Formula I-8,

[0102] In some embodiments, the organic solvent further comprises a carbonate solvent, and the carbonate solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. The above-mentioned carbonate solvent and the chain carboxylic ester solvent are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0103] In some embodiments, the carbonate solvent comprises one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate.

[0104] In some embodiments, the mass content of the carbonate solvent in the organic solvent is 25% to 95%, and may be 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.

[0105] In some embodiments, the electrolyte further comprises an additive, and the additive comprises one or more of a carbonate additive, a sulfur-containing additive and a lithium salt additive. The above additives can improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery monomer and improving the cycle performance.

[0106] In some embodiments, the carbonate additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0107] In some embodiments, the sulfur-containing additive comprises one or more of ethylene sulfate DTD, bis(ethylene sulfate) 2-DTD, butene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methylene methanedisulfonate MMDS.

[0108] In some embodiments, the lithium salt additive comprises lithium difluorophosphate LiPO 2 F 2 、lithium difluorooxalate borate LiDFOB, lithium tetrafluoroborate LiBF 4, one or more of lithium bis(oxalato)borate LiBOB.

[0109] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, and optionally 2% to 8%. The additive with the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, is beneficial to improving the fast charging performance of the battery cell, and improves the cycling performance.

[0110] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes a fluorosulfonylimide salt and lithium hexafluorophosphate LiPF 6 one or more of them. The above lithium salt is 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 cycling performance of the battery cell.

[0111] In some embodiments, the fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0112] 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.

[0113] In some embodiments, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF 6 in it is 0.2 to 1.0.

[0114] In some embodiments, the charging time of the battery cell from 20% state of charge to 80% state of charge is 6 min to 15 min. The charging speed of the battery cell is relatively fast, which is more beneficial to improving the fast charging ability.

[0115] In a second aspect, the present application proposes a battery device, and the battery device includes a plurality of battery cells according to any one of the embodiments of the first aspect of the present application.

[0116] In some embodiments, the charging time of the battery device from 20% state of charge to 80% state of charge is 6 min to 15 min. The charging speed of the battery device is relatively fast, which is more beneficial to improving the fast charging ability.

[0117] In a third aspect, the present application proposes an electrical device, and the electrical device includes the battery device according to any one of the embodiments of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0118] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the embodiments of the present application. Obviously, the accompanying drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on the accompanying drawings.

[0119] Figure 1 Structural schematic diagram of a battery cell provided in some embodiments of the present application; Figure 2 Explosion schematic diagram of a battery cell provided in some embodiments of the present application; Figure 3 Cross-sectional schematic diagram of an electrode assembly of a battery cell provided in some embodiments of the present application; Figure 4 Structural schematic diagram of a positive electrode tab of a battery cell provided in some embodiments of the present application; Figure 5 Structural schematic diagram of a negative electrode tab of a battery cell provided in some embodiments of the present application; Figure 6 Structural schematic diagram of a positive electrode tab of a battery cell provided in some other embodiments of the present application; Figure 7 Structural schematic diagram of a negative electrode tab of a battery cell provided in some other embodiments of the present application; Figure 8 Structural schematic diagram of an electrode assembly of a battery cell provided in some embodiments of the present application; Figure 9 Structural schematic diagram of a battery cell provided in some other embodiments of the present application; Figure 10 Structural schematic diagram of a battery module provided in some embodiments of the present application; Figure 11 Structural schematic diagram of a battery pack provided in some embodiments of the present application; Figure 12 Structural schematic diagram of an electrical device provided in some embodiments of the present application.

[0120] The accompanying drawings are not necessarily drawn to actual scale.

[0121] The descriptions of the reference numerals are as follows: X, thickness direction; Y, width direction; Z, length direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, box body; 5a, first box body part; 5b, second box body part; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11. Positive electrode tab; 111. Positive electrode tab ear; 1111. First end face; 1112. Third end face; 112. Positive current collector; 113. Positive electrode film layer; 12. Negative electrode tab; 121. Negative electrode tab ear; 1211. Second end face; 1212. Fourth end face; 122. Negative current collector; 123. Negative electrode film layer; 13. Separator; 20. Outer shell; 21. Housing; 211. First housing part; 212. Second housing part; 22. End cap; 31. Positive terminal; 32. Negative terminal. Detailed implementation manners

[0122] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0123] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise stated, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0124] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0125] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0126] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0127] With the development of the battery field, the requirements for the energy density and fast charging of batteries are gradually increasing. However, it has been found through research that when the energy density of the battery is increased, the increase in the transport resistance of active ions such as lithium ions makes it impossible for a single battery cell to achieve fast charging, and the energy density and fast charging ability of the battery cannot be improved simultaneously.

[0128] In view of the above problems, the embodiments of this application design a single battery cell, and improve the structural form, size of the electrode sheet and the coating weight of the film layer, so that the energy density and fast charging ability of the single battery cell can be improved simultaneously.

[0129] battery cell In a first aspect, the embodiments of this application propose a single battery cell.

[0130] As Figures 1 to 5 shown, the single battery cell 7 includes an electrode assembly 10 and an electrolyte. The electrode assembly 10 includes a positive electrode sheet 11, a separator 13 and a negative electrode sheet 12 stacked along the thickness direction X of the single battery cell 7; the positive electrode sheet 11 includes a positive electrode tab 111, a positive current collector 112 and a positive electrode film layer 113 disposed on at least one surface of the positive current collector 112 along the thickness direction X and containing a positive electrode active material, and the positive electrode tab 111 is disposed on at least one side of the positive current collector 112; the negative electrode sheet 12 includes a negative electrode tab 121, a negative current collector 122 and a negative electrode film layer 123 disposed on at least one surface of the negative current collector 122 along the thickness direction X and containing a negative electrode active material, and the negative electrode tab 121 is disposed on at least one side of the negative current collector 122. Among them, the ratio of the length to the width of the positive electrode film layer 113 is 4 to 20; the length of the positive electrode film layer 113 is 600 mm to 1200 mm; the single-sided coating weight of the negative electrode film layer 123 is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 .

[0131] The electrode assembly 10 of the embodiment of the present application is a stacked electrode assembly 10, and the positive electrode sheet 11, the separator 13 and the negative electrode sheet 12 form the electrode assembly 10 through a lamination process. The thickness direction X of the electrode assembly 10, the thickness direction of the positive electrode sheet 11 and the thickness direction of the negative electrode sheet 12 are parallel. The width direction of the electrode assembly 10, the width direction of the positive electrode sheet 11 and the width direction of the negative electrode sheet 12 are parallel. The length direction of the electrode assembly 10, the length direction of the positive electrode sheet 11 and the length direction of the negative electrode sheet 12 are parallel. The thickness direction X of the electrode assembly 10, the width direction of the electrode assembly 10 and the length direction of the electrode assembly 10 are perpendicular to each other in pairs. Y represents the width direction of the electrode assembly 10, and Z represents the length direction of the electrode assembly 10.

[0132] In the embodiment of the present application, the dimension of the positive electrode sheet 11 in the thickness direction of the battery cell 7 can be understood as the thickness of the positive electrode sheet 11. The dimension of the positive electrode sheet 11 in the length direction of the battery cell 7 can be understood as the length of the positive electrode sheet 11. The dimension of the positive electrode sheet 11 in the width direction of the battery cell 7 can be understood as the width of the positive electrode sheet 11. Figure 4 In it, the length of the positive current collector portion 112 is equal to the length of the positive electrode film layer 113. L1 can represent the length of the positive electrode film layer 113 or the length of the positive current collector portion 112. Figure 4 In it, the width of the positive current collector portion 112 is equal to the width of the positive electrode film layer 113. W2 can represent the width of the positive electrode film layer 113 or the width of the positive current collector portion 112.

[0133] In the embodiment of the present application, the dimension of the negative electrode sheet 12 in the thickness direction of the battery cell 7 can be understood as the thickness of the negative electrode sheet 12. The dimension of the negative electrode sheet 12 in the length direction of the battery cell 7 can be understood as the length of the negative electrode sheet 12. The dimension of the negative electrode sheet 12 in the width direction of the battery cell 7 can be understood as the width of the negative electrode sheet 12. Figure 5 In it, the length of the negative current collector portion 122 is equal to the length of the negative electrode film layer 123. L2 can represent the length of the negative electrode film layer 123 or the length of the negative current collector portion 122. Figure 5 In it, the width of the negative current collector portion 122 is equal to the width of the negative electrode film layer 123. W4 can represent the width of the negative electrode film layer 123 or the width of the negative current collector portion 122.

[0134] Both the positive electrode sheet 11 and the negative electrode sheet 12 have an impact on the energy density and fast charging performance of the battery cell 7. By improving the positive electrode sheet 11 and the negative electrode sheet 12, the energy density and fast charging performance of the battery cell 7 are improved. Specifically: The single-sided coating weight of the negative electrode film layer 123 is less than 74 mg / 1540.25 mm 2When the energy density of the battery cell 7 is small; the single-sided coating weight of the negative electrode film layer 123 is greater than 156 mg / 1540.25 mm 2 When the energy density of the battery cell 7 is improved, the migration path of active ions such as lithium ions in the negative electrode film layer 123 is long, which is not conducive to the fast charge and discharge of the battery cell 7; in the embodiment of the present application, the single-sided coating weight of the negative electrode film layer 123 is set to 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 ; which is conducive to balancing the fast charging performance and the energy density; When the ratio of the length to the width of the positive electrode film layer 113 is less than 4, the coating weight of the positive electrode film layer 113 is relatively small, and the energy density of the battery cell 7 is small. Increasing the ratio of the length to the width of the positive electrode film layer 113 so that the ratio of the length to the width of the positive electrode film layer 113 is less than or equal to 20, so that the length of the single battery is not too long, and the electron transmission path during the fast charging process is not too long, and the fast charging performance can be balanced while taking into account the energy density; however, as the ratio of the length to the width of the positive electrode film layer 113 further increases, the size difference between the length and the width of the positive electrode film layer 113 increases, which easily causes the current distribution in the positive electrode tab 11 to be uneven, resulting in inconsistent charging states of the positive electrode film layer 113 during the charging process, different lithium deintercalation speeds at different parts of the positive electrode film layer 113, and the lithium deintercalated from the positive electrode film layer 113 is embedded in the negative electrode tab 12, resulting in different lithium intercalation speeds in the negative electrode tab 12, which easily leads to lithium precipitation in the negative electrode tab 12; When the ratio of the length to the width of the positive electrode film layer 113 is less than or equal to 20, at least one side of the positive current collector 112 is provided with a positive electrode tab 111, and it is optional to provide positive electrode tabs 111 on both sides. The positive electrode tabs 111 can share the current with each other, and make the electron transmission path in the positive current collector 112 shorter and the current distribution more uniform. During the charging process, the positive active material at each part of the positive electrode tab 11 deintercalates lithium evenly; since at least one side of the negative current collector 122 is provided with a negative electrode tab 121, and it is optional to provide negative electrode tabs 121 on both sides. The negative electrode tabs 121 can share the current with each other, and make the electron transmission path in the negative current collector 122 shorter and the current distribution more uniform. The uniformly deintercalated lithium can be evenly embedded in the negative electrode tab 12, and the negative electrode tab 12 is not likely to precipitate lithium, and the single-sided coating weight of the negative electrode film layer 123 is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 , and the migration path of lithium ions in the negative electrode film layer 123 is relatively short, which can improve the fast charging performance of the battery cell 7.

[0135] Thus, by coordinately regulating the ratio of the length to the width of the positive electrode film layer 113 and the single-sided coating weight of the negative electrode film layer 123, it is possible to balance the improvement of the energy density and the fast charging performance of the battery cell 7.

[0136] In the embodiment of the present application, the ratio of the length to the width of the positive electrode film layer 113 is 4 to 20, for example, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20 or a range composed of any two of the above values.

[0137] In the embodiment of the present application, the length of the positive electrode film layer 113 is 600 mm to 1200 mm. Exemplarily, the length of the positive electrode film layer 113 can be 600 mm, 650 mm, 700 mm, 750 mm, 800 mm, 850 mm, 900 mm, 950 mm, 1000 mm, 1050 mm, 1100 mm, 1150 mm, 1200 mm or a range composed of any two of the above values. The relatively long length of the positive electrode film layer 113 is beneficial to increasing the coating weight of the positive electrode film layer 113 and improving the energy density of the battery cell 7.

[0138] In some embodiments, the width of the positive electrode film layer 113 is 60 mm to 150 mm. Exemplarily, the width of the positive electrode film layer 113 can be 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 115 mm, 120 mm, 125 mm, 130 mm, 135 mm, 140 mm, 145 mm, 150 mm or a range composed of any two of the above values. The relatively short width of the positive electrode film layer 113 makes the transmission path of electrons in the width direction Y shorter, and can improve the uniformity of the current in the width direction Y.

[0139] The positive electrode tab 111 is disposed on at least one side of the positive electrode current collector portion 112.

[0140] In some embodiments, the positive electrode tab 111 may be disposed on at least one side of the positive electrode current collector 112 along the length direction Z. Optionally, the positive electrode tab 111 is disposed on both sides of the positive electrode current collector 112 along the length direction Z. Since the length of the positive electrode current collector 112 is greater than the width of the positive electrode current collector 112, the current transmission path in the length direction Z is relatively long, and the current distribution in the length direction Z is uneven. The positive electrode tab 111 is disposed on both sides of the positive electrode current collector 112 along the length direction Z, so that the current in the length direction Z of the positive electrode current collector 112 is evenly divided by the positive electrode tabs 111 on both sides, the electron transmission path is shorter, and the current distribution is more uniform. The delithiation state of each part of the positive electrode plate 11 is uniform, and the charging performance of the battery cell 7 can be improved. Figure 4 It shows that the positive electrode tab 111 is disposed on both sides of the positive electrode current collector 112 along the length direction Z. With the positive electrode tabs 111 disposed on both sides, the positive electrode tabs 111 can share the current with each other, and the electron transmission path in the positive electrode current collector 112 is shorter, and the current distribution is more uniform. During the charging process, the positive active material in each part of the positive electrode plate 11 is uniformly delithiated.

[0141] When the positive electrode tab 111 is disposed on at least one side of the positive electrode current collector 112 along the length direction Z, the number of positive electrode tabs 111 on the same side of the positive electrode current collector 112 may be at least one, such as one or at least two. When the number of positive electrode tabs 111 on the same side of the positive electrode current collector 112 is at least two, the at least two positive electrode tabs 111 can increase the current-carrying area, and can evenly divide the current, improving the current uniformity in the positive electrode plate 11, which is beneficial to further improving the fast charging performance of the battery cell 7.

[0142] In some embodiments, the number of positive electrode tabs 111 on the same side of the positive electrode current collector 112 is one or more. For example, all the positive electrode tabs 111 are located on the same side of the positive electrode current collector 112 along the length direction Z, or all the positive electrode tabs 111 are respectively arranged on both sides of the positive electrode current collector 112 along the length direction Z; the positive electrode tab 111 includes a first end face 1111 connected to the positive electrode current collector 112, the dimension of the first end face 1111 along the width direction Y is W1, the sum of the dimensions of all the first end faces 1111 on the same side of the positive electrode current collector 112 is n×W1, the width of the positive electrode current collector 112 is W2, and n×W1 / W2 is greater than or equal to 1 / 3 and less than or equal to 1, and may be optionally greater than or equal to 2 / 3 and less than 1. n represents the number of all the positive electrode tabs 111 on the same side of the positive electrode current collector 112, and n is greater than or equal to 1. For example, when the number of all the positive electrode tabs 111 on the same side of the positive electrode current collector 112 is 1, n is 1; when the number of all the positive electrode tabs 111 on the same side of the positive electrode current collector 112 is 2, n is 2.

[0143] Exemplarily, n×W1 / W2 is 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9 or a range composed of any two of the above values.

[0144] When n×W1 / W2 satisfies the above range, the current-carrying area of the positive electrode tab 111 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0145] The negative electrode tab 121 is disposed on at least one side of the negative electrode current collector 122.

[0146] In some embodiments, the negative electrode tab 121 may be disposed on at least one side of the negative electrode current collector 122 along the length direction Z. Optionally, the negative electrode tab 121 is disposed on both sides of the negative electrode current collector 122 along the length direction Z. Since the length of the negative electrode current collector 122 is greater than the width of the negative electrode current collector 122, the current transmission path in the length direction Z is longer and the current distribution in the length direction Z is uneven. The negative electrode tab 121 is disposed on both sides of the negative electrode current collector 122 along the length direction Z, so that the current in the length direction Z of the negative electrode current collector 122 is evenly divided by the negative electrode tabs 121 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 12 is uniform, and the charging performance of the battery cell 7 can be improved. Figure 5 It shows that the negative electrode tab 121 is disposed on both sides of the negative electrode current collector 122 along the length direction Z.

[0147] When the negative electrode tab 121 is disposed on at least one side of the negative electrode current collector 122 along the length direction Z, the number of negative electrode tabs 121 on the same side of the negative electrode current collector 122 can be at least one, such as one or at least two. When the number of negative electrode tabs 121 on the same side of the negative electrode current collector 122 is at least two, the at least two negative electrode tabs 121 can increase the current-carrying area, and can evenly divide the current, improving the current uniformity in the negative electrode plate 12, which is beneficial to further improving the fast charging performance of the battery cell 7.

[0148] In some embodiments, there is one or more negative electrode tabs 121 on the same side of the negative electrode current collector 122. For example, all the negative electrode tabs 121 are on the same side of the negative electrode current collector 122 along the length direction Z, or all the negative electrode tabs 121 are respectively arranged on both sides of the negative electrode current collector 122 along the length direction Z; the negative electrode tab 121 includes a second end face 1211 connected to the negative electrode current collector 122, the dimension of the second end face 1211 along the width direction Y of the battery cell 7 is W3, the sum of the dimensions of all the second end faces 1211 on the same side of the negative electrode current collector 122 is m×W3, the width of the negative electrode current collector 122 is W4, m×W3 / W4 is greater than or equal to 1 / 3 and less than or equal to 1, and can be optionally greater than or equal to 2 / 3 and less than 1. m represents the number of all the negative electrode tabs 121 on the same side of the negative electrode current collector 122. For example, m is greater than or equal to 1. When the number of all the negative electrode tabs 121 on the same side of the negative electrode current collector 122 is 1, m is 1; when the number of all the negative electrode tabs 121 on the same side of the negative electrode current collector 122 is 2, m is 2.

[0149] Exemplarily, m×W3 / W4 is 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9 or a range composed of any two of the above values.

[0150] When m×W3 / W4 satisfies the above range, the current-carrying area of the negative electrode tab 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0151] As Figure 6 shown, in some embodiments, the positive electrode tab 111 can be arranged on at least one side of the positive electrode current collector 112 along the width direction Y, such as one side or both sides; optionally, the positive electrode tab 111 can be arranged on one side of the positive electrode current collector 112 along the width direction Y. When the positive electrode current collector 112 is arranged on one side of the positive electrode tab 111 along the width direction Y, the electron transmission path in the positive electrode current collector 112 is shorter, the current distribution is more uniform, and during the charging process, the lithium deintercalation of the positive active material at each part of the positive electrode plate 11 is uniform.

[0152] In the case where the positive electrode tab 111 is arranged on at least one side of the positive electrode current collector 112 along the width direction Y, there is one or more positive electrode tabs 111 on the same side of the positive electrode current collector 112. The positive electrode tab 111 includes a third end face 1112 connected to the positive electrode current collector 112, and the dimension of the third end face 1112 along the length direction Z is L 10 , the sum of the dimensions of all the third end faces 1112 on the same side of the positive electrode current collector 112 along the length direction Z is s×L 10 , the dimension of the positive electrode current collector 112 along the length direction Z is L1, s×L 10 / L1 is greater than or equal to 1 / 3, optionally greater than or equal to 2 / 3 and less than 1, and s represents the number of all the positive electrode tabs 111 on the same side of the positive electrode current collector 112.

[0153] Exemplarily, s×L 10 / L1 is 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9 or a range composed of any two of the above values.

[0154] s×L 10 When / L1 satisfies the above range, the current-carrying area of the positive electrode tab 111 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0155] Such as Figure 7 As shown, in some embodiments, the negative electrode tab 121 is disposed on at least one side of the negative electrode current collector 122 along the width direction Y, for example, one side or both sides; optionally, the negative electrode tab 121 is disposed on one side of the negative electrode current collector 122 along the width direction Y, so that the electron transmission path in the negative electrode current collector 122 is shorter, the current distribution is more uniform, and lithium deposition is not likely to occur.

[0156] When the negative electrode tab 121 is disposed on at least one side of the negative electrode current collector 122 along the width direction Y, the number of negative electrode tabs 121 on the same side of the negative electrode current collector 122 is one or more. The negative electrode tab 121 includes a fourth end face 1212 connected to the negative electrode current collector 122, and the dimension of the fourth end face 1212 along the length direction Z is L 20 , and the sum of the dimensions of all the fourth end faces 1212 on the same side of the negative electrode current collector 122 along the length direction Z is p×L 20 , the dimension of the negative electrode current collector 122 along the length direction Z is L2, p×L 20 / L2 is greater than or equal to 1 / 3, optionally greater than or equal to 2 / 3 and less than 1, and p represents the number of all the negative electrode tabs 121 on the same side of the negative electrode current collector 122.

[0157] Exemplarily, p×L 20 / L2 is 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9 or a range composed of any two of the above values.

[0158] p×L 20 When / L2 satisfies the above range, the current-carrying area of the negative electrode tab 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0159] Such as Figure 8As shown, in some embodiments, along the length direction Z of the battery cell 7, the size of the negative electrode film layer 123 is larger than that of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH 1 , OH 1 is 0.5 mm to 3.0 mm, such as 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm or the range composed of any two of the above values. Along the length direction Z, both sides of the negative electrode film layer 123 extend beyond the positive electrode film layer 113, and each side extends beyond OH 1 / 2, that is, half of the size of OH 1 , and OH Figure 8 / 2 is shown in 1 .

[0160] In some embodiments, along the width direction Y of the battery cell 7, the size of the negative electrode film layer 123 is larger than that of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH 2 , OH 2 is 0.5 mm to 3.0 mm, such as 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm or the range composed of any two of the above values. Along the width direction Y, both sides of the negative electrode film layer 123 extend beyond the positive electrode film layer 113, and each side extends beyond OH 2 / 2, that is, half of the size of OH 2 , and OH Figure 8 / 2 is shown in 2 .

[0161] In some embodiments, the positive electrode tab 111 is connected to both sides of the positive electrode current collector 112 along the length direction Z, the negative electrode tab 121 is connected to both sides of the negative electrode current collector 122 along the length direction Z. Along the length direction Z of the battery cell 7, the size of the negative electrode film layer 123 is larger than that of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH 1 ; along the width direction Y of the battery cell 7, the size of the negative electrode film layer 123 is larger than that of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH 2 , OH 1 is larger than OH 2 . Figure 8 The positive electrode tab 111 and the negative electrode tab 121 are not shown in

[0162] The negative electrode tab 121 is located on both sides of the negative electrode current collector portion 122 along the length direction Z. The width of the negative electrode current collector portion 122 is greater than the width of the negative electrode tab 121, so that the current-carrying area of the negative electrode current collector portion 122 is greater than the current-carrying area of the negative electrode tab 121. Due to the different current-carrying areas, the current density in the connection region between the negative electrode tab 121 and the negative electrode current collector portion 122 increases sharply, and problems such as lithium deposition are more likely to occur in this region; while in the embodiment of the present application, OH 1 is greater than OH 2 , so that the ability of the negative electrode film layer 123 to receive lithium ions is stronger in the length direction Z, especially the ability of the region of the negative electrode film layer 123 close to the negative electrode tab 121 to receive lithium ions can be improved, the risk of lithium deposition is reduced, and the use reliability of the battery cell 7 is improved.

[0163] In some other embodiments, the positive electrode tab 111 is connected to one side of the positive electrode current collector portion 112 along the width direction Y, and the negative electrode tab 121 is connected to one side of the negative electrode current collector portion 122 along the width direction Y. Along the width direction Y of the electrode assembly 10, the size of the negative electrode film layer 123 is greater than the size of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH 2 ; along the length direction Z of the electrode assembly 10, the size of the negative electrode film layer 123 is greater than the size of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH 1 , OH 2 is greater than OH 1 . Of course, OH 1 can also be greater than OH 2 .

[0164] The negative electrode tab 121 is located on one side of the negative electrode current collector portion 122 along the width direction Y. The length of the negative electrode current collector portion 122 is greater than the length of the negative electrode tab 121, so that the current-carrying area of the negative electrode current collector portion 122 is greater than the current-carrying area of the negative electrode tab 121. Due to the different current-carrying areas, the current density in the connection region between the negative electrode tab 121 and the negative electrode current collector portion 122 increases sharply, and problems such as lithium deposition are more likely to occur in this region; while in the embodiment of the present application, OH 2 is greater than OH 1 , so that the ability of the negative electrode film layer 123 to receive lithium ions is stronger in the width direction Y, especially the ability of the region of the negative electrode film layer 123 close to the negative electrode tab 121 to receive lithium ions can be improved, the risk of lithium deposition is reduced, and the use reliability of the battery cell 7 is improved.

[0165] Please refer to Figure 2 and Figure 9 together. In some embodiments, the battery cell 7 may include a housing 20.

[0166] 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).

[0167] The housing 20 is a hollow structure, and the housing 20 can be used to encapsulate the above-mentioned electrode assembly 10 and electrolyte.

[0168] The preparation method of the battery cell 7 according to the embodiments of the present application is well-known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte can be assembled to form the battery cell 7. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into the electrode assembly 10 through a lamination process, the electrode assembly 10 is placed in the housing 20, the electrolyte is injected after drying, and through processes such as vacuum packaging, standing, formation, and shaping, the battery cell 7 is obtained.

[0169] In some embodiments, the housing 20 includes a housing body 21 and an end cover 22. The housing body 21 has an opening, and the end cover 22 covers the opening.

[0170] 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.

[0171] In some embodiments, the material of the housing body 21 includes steel. Steel has high mechanical strength and is not easily deformed, which can improve the use reliability and cycle performance of the battery cell. Optionally, the mass ratio of steel is the highest among the materials in the housing body 21.

[0172] Optionally, the thickness of the housing body 21 is 0.1 mm to 0.5 mm, and can be 0.2 mm to 0.35 mm. Exemplarily, the thickness of the housing body 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm or the range composed of any two of the above values. When the thickness of the housing body 21 is within the above range, the housing body 21 has high mechanical strength, which can improve the use reliability and cycle performance of the battery cell 7, and the housing body 21 occupies less space and there is more internal space in the housing body 21, which is beneficial to improving the energy density of the battery cell 7.

[0173] When the housing 21 has a cuboid structure, the housing 21 includes two first housing parts 211 and two second housing parts 212. The two first housing parts 211 are arranged oppositely, and the two second housing parts 212 are arranged oppositely. The first housing part 211 is connected between the two second housing parts 212, and the area of the first housing part 211 is larger than that of the second housing part 212.

[0174] In some embodiments, the thickness of the first housing part 211 is from 0.1 mm to 0.5 mm, and optionally from 0.2 mm to 0.35 mm. The thickness of the first housing part 211 is relatively thin, and the space occupied by the housing 21 is less, which can further improve the energy density of the battery cell 7.

[0175] In some embodiments, the thickness of the second housing part 212 is from 0.1 mm to 0.5 mm, and optionally from 0.2 mm to 0.35 mm. In some embodiments, the thickness of the first housing part 211 is greater than or equal to the thickness of the second housing part 212. In some other embodiments, the thickness of the first housing part 211 is less than the thickness of the second housing part 212.

[0176] In some embodiments, the base material of the housing 21 includes steel. Steel has relatively high mechanical strength and is not easily deformed, which can improve the use reliability and cycle performance of the battery cell. In the embodiments of the present application, the base material refers to the material with the highest proportion in the housing 21.

[0177] In some embodiments, the battery cell 7 further includes a positive terminal 31, and the positive terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 are welded. The positive terminal 31 and the positive electrode tab 111 can be connected through an adapter, or can be connected without using an adapter; optionally, the positive terminal 31 and the positive electrode tab 111 are connected without using an adapter, that is, the positive terminal 31 and the positive electrode tab 111 are directly welded, which can reduce the resistance at the connection and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0178] Optionally, the number of the positive terminals 31 is at least one, and optionally at least two. For example, when the positive terminals 31 are two, the two positive terminals 31 are respectively located on both sides of the positive electrode current collector part.

[0179] Optionally, the number of the positive terminals 31 on the same side of the positive electrode current collector part 112 is at least one, and optionally at least two. At least two positive terminals 31 can increase the overall current-carrying capacity of the positive terminals 31.

[0180] Further optionally, the current-carrying area of a single positive terminal 31 is greater than or equal to 200 mm 2 and optionally from 200 mm 2 to 800 mm 2。The current-carrying area of the positive terminal 31 can be understood as the cross-sectional area of the positive terminal 31, and this cross-section is perpendicular to the thickness direction of the positive terminal 31.

[0181] Exemplarily, the current-carrying area of a single positive terminal 31 can be 200 mm 2 , 210 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 or a range composed of any two of the above values.

[0182] 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 121. Optionally, the negative terminal 32 and the negative electrode tab 121 are welded. The negative terminal 32 and the negative electrode tab 121 can be connected through an adapter, or an adapter may not be used; optionally, an adapter is not used between the negative terminal 32 and the negative electrode tab 121, that is, the negative terminal 32 and the negative electrode tab 121 are directly welded, which can reduce the resistance at the connection and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0183] Optionally, the number of negative terminals 32 is at least one, and can be at least two. For example, when there are two negative terminals 32, the two negative terminals 32 are respectively located on both sides of the negative electrode current collector part. Exemplarily, the battery cell 7 includes two positive terminals 31 and two negative terminals 32. The two positive terminals 31 are respectively located on both sides of the positive electrode current collector part, and the two negative terminals 32 are respectively located on both sides of the negative electrode current collector part. It can be understood that there is one positive terminal 31 and one negative terminal 32 on one side of the battery cell 7, and there is one positive terminal 31 and one negative terminal 32 on the other side. Figure 9 shows that the battery cell 7 includes two positive terminals 31 and two negative terminals 32.

[0184] Optionally, the number of negative terminals 32 located on the same side of the negative electrode current collector part 122 is at least one, and can be at least two. At least two negative terminals 32 can increase the current-carrying capacity of the negative terminal 32.

[0185] Further optionally, the current-carrying area of a single negative terminal 32 is greater than or equal to 200 mm 2 , and may be 200 mm 2 to 800 mm 2 . The current-carrying area of the negative terminal 32 can be understood as the cross-sectional area of the negative terminal 32, and this cross-section is perpendicular to the thickness direction of the negative terminal 32.

[0186] Exemplarily, the current-carrying area of a single negative terminal 32 can be 200 mm 2 , 210 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 or a range composed of any two of the above values.

[0187] [Positive electrode tab] The positive electrode tab includes a positive current collector portion and a positive electrode film layer provided on at least one surface of the positive current collector portion and including a positive electrode active material. For example, the positive current collector portion has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive current collector portion.

[0188] The upper charge limit voltage and the lower discharge cut-off voltage of the battery cell are different according to the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper charge limit voltage can be 3.65 V and the lower discharge cut-off voltage can be 2.0 V. Also, for example, when the phosphate material includes lithium manganese iron phosphate, the upper charge limit voltage can be 4.3 V and the lower discharge cut-off voltage can be 2.0 V. Next, taking the upper charge limit voltage of 3.65 V and the lower discharge cut-off voltage of 2.0 V as an example, the state of the battery cell will be described: In the embodiments of the present application, the 100% state of charge (SOC) and the 0% state of charge (SOC) of the battery cell are defined as follows, Charge the battery cell at a constant current charge rate of 0.33C to the upper charge voltage, then charge it 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.

[0189] In some embodiments, when the battery cell is at 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 ; optionally 2.55 g / cm 3 to 2.70 g / cm 3 . Exemplarily, when the battery cell is at 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 or a range composed of any two of the above values.

[0190] 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 active material in the positive electrode film layer is stacked relatively tightly and the contact resistance between particles is small, it can further reduce the resistance of the electrode sheet, thereby reducing heat generation during fast charging. Therefore, by adjusting the tap density of the positive electrode film layer to a reasonable range, the battery cell has both high energy density and high charging rate performance.

[0191] In some embodiments, the single-sided coating weight of the positive electrode film layer is 160 mg / 1540.25 mm 2 to 340 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer is 160 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 , 180 mg / 1540.25 mm 2, 190 mg / 1540.25 mm 2 , 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 Or a range composed of any two of the above values.

[0192] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation amount per unit area of the positive electrode plate will not be too large, and it can balance the improvement of the energy density and charging rate performance of the battery cell.

[0193] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell in the 100% state of charge (SOC) has the meaning well known in the art, that is, the positive electrode plate is disassembled from the battery cell in the 100% state of charge (SOC), and the compaction density of the positive electrode film layer is measured. For example, for a single-sided coated positive electrode plate (if it is a double-sided coated plate, one side of the positive electrode film layer can be wiped off first), it 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 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.

[0194] 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.

[0195] The relatively low powder resistivity of the positive electrode active material results in a relatively low resistance of the positive electrode sheet and less heat generation of the battery cell.

[0196] In the embodiments of the present application, the powder resistivity of the material has the meaning well-known in the art and can be detected by the methods and equipment well-known in the art. For example, according to the test standard GB / T30835-2014, a PRCD1100 powder resistivity meter is used for testing.

[0197] 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 / cm 3 , 2.48 g / cm 3 , 2.49 g / cm 3 , 2.5 g / cm 3 , 2.51 g / cm 3 , 2.55 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 or the range composed of any two of the above values.

[0198] When the powder compaction density of the positive electrode active material is within the above range under 30000N, the energy density of the battery cell can be improved. Moreover, since the positive electrode active materials in the positive electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0199] 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 the UTM7305 type electronic pressure testing machine, pressurize to 3000 kg (equivalent to 30000N), keep the pressure for 30 s, then release the pressure, keep for 10 s, and then record and calculate the powder compaction density of the positive electrode active material under the action of 30000N.

[0200] In some embodiments, the charging specific capacity of the positive electrode active material at a 0.1C rate is 150 mAh / g to 170 mAh / g. Exemplarily, the charging specific capacity of the positive electrode active material at a 0.1C rate is 150 mAh / g, 151 mAh / g, 152 mAh / g, 153 mAh / g, 154 mAh / g, 155 mAh / g, 156 mAh / g, 157 mAh / g, 158 mAh / g, 159 mAh / g, 160 mAh / g, 161 mAh / g, 162 mAh / g, 163 mAh / g, 164 mAh / g, 165 mAh / g, 166 mAh / g, 167 mAh / g, 168 mAh / g, 169 mAh / g, 170 mAh / g or the range composed of any two of the above values.

[0201] When the charging specific capacity of the positive electrode active material at a 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0202] In the embodiments of the present application, the specific capacity of the active material has the meaning well-known in the art, and can be tested by equipment and methods well-known in the art. The test method of the first coulomb efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be adopted. Using metallic lithium as the negative electrode and the sample electrode sheet containing the above materials as the positive electrode, a half-button cell is assembled. Under the condition of 23°C ± 2°C, the half-button cell is placed on a battery tester or other test equipment with the same performance, and the discharge capacity is obtained through charge and discharge at a 0.1C rate, and then the capacity is divided by the mass of the active material of the electrode sheet to obtain the charging specific capacity parameter.

[0203] In some embodiments, the mass percentage of the lithium-containing phosphate with an olivine structure in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%. It can be considered that the positive electrode active material of the present application is a lithium-containing phosphate system with an olivine structure. When the mass percentage of the lithium-containing phosphate with an olivine structure is less than 100%, the positive electrode active material can also include common positive electrode active materials, for example, it can include but is not limited to 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.

[0204] Optionally, the mass percentage of the lithium-containing phosphate with an olivine structure in the positive electrode active material is 100%.

[0205] In the embodiments of the present application, the lithium-containing phosphate with an olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium-containing phosphate with an olivine structure includes phosphate particles and a coating layer. The coating layer is coated on the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

[0206] By coating the surface of the phosphate particles with a coating layer, the conductivity of the lithium-containing phosphate with an olivine structure can be improved, the powder resistivity of the material can be reduced, and it is beneficial to the migration rate of lithium ions, improving the fast charging ability of the battery and reducing the heat generation of the battery cell.

[0207] In some embodiments, the phosphate particles include a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z where 0.5 ≤ x 1 ≤ 1.3, 0 ≤ y 1 ≤ 1.3, and 0.9 ≤ x 1 + y 1≤1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F. The cyclic stability of the phosphate particles is relatively excellent, which is beneficial to improving the cyclic performance of the battery cell.

[0208] Exemplarily, the phosphate particles include LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 or one or more of them. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. Regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., the molar content of oxygen O is only the theoretical state value. The release of oxygen from the crystal lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will show fluctuations, and all the above situations are within the protection scope of the present application.

[0209] 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.

[0210] Exemplarily, the fast ion conductor is a material having a NASICON structure, such as including lithium iron titanium phosphate Li 2 FeTi(PO 4 ) 3 , lithium iron zirconium phosphate Li 2 FeZr(PO 4 ) 3 , lithium iron tin phosphate Li 2 FeSn(PO 4 ) 3 or one or more of them.

[0211] The fast ion conductor having a NASICON structure is a material with ultrafast ion conduction ability, having rich three-dimensional lithium ion diffusion and transport channels, and having advantages such as high ion conduction efficiency and strong structural stability during multiple de-lithiation and intercalation processes. Coating the surface of phosphate particles with a fast ion conductor containing a NASICON structure can significantly improve the transport rate of lithium ions during multiple de / intercalation at the positive electrode, improve the ionic conductivity of the positive electrode active material, improve the fast charging ability of the battery monomer, and in addition, can also improve the specific capacity and the energy density of the corresponding battery monomer.

[0212] In some embodiments, the coating layer further includes elemental carbon.

[0213] The elemental carbon and the fast ion conductor can be arranged in layers. For example, the elemental carbon serves as an independent carbon coating layer, and the fast ion conductor serves as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Or, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the elemental carbon and the fast ion conductor can also be arranged in the same layer.

[0214] Optionally, the carbon coating layer can be formed by carbonizing an organic carbon source (such as glucose, polyethylene glycol, etc.) on the surface of the fast ion conductor layer. The carbon coating layer can partially coat the fast ion conductor layer or can completely coat the fast ion conductor layer. The setting of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, make up for the defect of poor electronic conduction performance of the phosphate particles, and improve the energy density of the battery monomer. Specifically, the setting of the carbon coating layer endows the positive electrode active material of the present application with the following advantages: The carbon coating layer in the positive electrode active material of the present application provides a suitable channel for the transport of electrons, can significantly improve the conduction rate of electrons during multiple de-lithiation and intercalation processes, improve the electronic conductivity of the lithium-containing phosphate, improve the charging ability of the corresponding battery monomer, and can also improve the energy density.

[0215] The carbon coating layer of the positive electrode active material of the present application is loose and porous, enabling the electrolyte to come into full and effective contact with the lithium-containing phosphate, thereby enhancing the lithium-ion transport rate at the phase interface and improving the charging capacity of the battery cell.

[0216] Coating a layer of carbon coating on the surface of the lithium-containing phosphate can not only improve the electrical conductivity of the lithium-containing phosphate but also enhance the structural stability of the positive electrode active material, effectively alleviating the iron dissolution phenomenon of the positive electrode active material during 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 is based on lithium-containing phosphate, giving full play to the advantages of low cost, high use reliability, and good cycle stability of the lithium-containing phosphate. At the same time, the coating layers (fast ion conductor layer and carbon coating layer) are used to solve the drawbacks of poor electronic and ionic conductivities. The battery cell prepared from the positive electrode active material of the present application can improve the energy density of the battery cell on the premise of 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 equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC) and disassembling the positive electrode plate, it is washed with DMC and dried, then impurities are removed by high-temperature calcination. After weighing 0.4 g of the positive electrode active material, 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is made up to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0217] In some embodiments, the graphitization degree of the positive electrode active material is from 0.15 to 0.32, and can be optionally from 0.19 to 0.26. Exemplarily, the graphitization degree of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32 or a range composed of any two of the above values.

[0218] When the graphitization degree of the positive electrode active material is within the above range, it is beneficial to improve the electrical 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.

[0219] In the embodiments of the present application, the higher the graphitization degree of the material, the lower the degree of disorder. The test can be carried out according to the general rules of X-ray diffraction analysis method in JIS / K 0131-1996 test standard.

[0220] 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.

[0221] Optionally, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 7.5m 2 / g to 14m 2 / g.

[0222] 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.

[0223] Exemplarily, the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14m 2 / g, 15m 2 / g, 16m 2 / g, 17m 2 / g, 18m 2 / g or the range composed of any two of the above values.

[0224] The carbon element mainly exists in the coating layer in the form of a carbon coating layer. The carbon coating layer is loose and porous, which is beneficial to increasing the specific surface area of the material, more beneficial to the effective contact between the electrolyte and the phosphate particles, and beneficial to the transport of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, the conductivity of the lithium-containing phosphate with olivine structure can be significantly improved, which is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the rapid charging ability and energy density of the battery cell.

[0225] In the embodiments of the present application, the specific surface area of the material has the meaning well-known in the art and can be detected by the equipment and methods well-known in the art. For example, it can be detected according to the test standard GB / T 19587-2017. Taking the positive electrode active material as a sample, the specific surface area is tested by a Tri-Star 3020 specific surface area and pore size analyzer of Micromeritics Company in the United States.

[0226] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm.

[0227] Exemplarily, Dv50 of the positive electrode active material can be 1 µm, 1.1 µm, 1.15 µm, 1.2 µm, 1.25 µm, 1.3 µm, 1.35 µm, 1.4 µm, 1.45 µm, 1.5 µm, 1.55 µm, 1.6 µm, 1.65 µm, 1.7 µm, 1.75 µm, 1.8 µm, 1.85 µm, 1.9 µm, 1.95 µm, 2 µm or a range composed of any two of the above values.

[0228] Exemplarily, Dv10 of the positive electrode active material can be 0.4 µm, 0.45 µm, 0.5 µm, 0.55 µm, 0.6 µm, 0.65 µm, 0.7 µm or a range composed of any two of the above values.

[0229] 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 does not agglomerate during the processing and preparation process, making the performance of the positive electrode active material stable.

[0230] In the embodiments of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% in the volume distribution. It can be detected by the 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.

[0231] When the positive electrode active material includes other materials in addition to the lithium phosphate with 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.

[0232] In some embodiments, the lithium-containing phosphate with an olivine structure is granular, and the lithium-containing phosphate with an olivine structure is composed of secondary particles formed by the aggregation 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.

[0233] 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.

[0234] In the embodiments of the present application, the primary particles and secondary particles are terms well known in the art. The secondary particles refer to agglomerated particles formed by the aggregation of two or more primary particles. The primary particles and 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. 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.

[0235] The cathode film layer usually includes a plurality of cathode active material particles, that is, the lithium-containing phosphate with an olivine structure is a plurality of particles, and the particle sizes of the plurality of particles are different. The plurality of particles include the smallest particle and the largest particle. The smallest particle is the particle with the smallest particle size, and the largest particle is the particle with the largest particle size. By matching the large and small particles, the compaction density of the cathode film layer can be improved, and the pore structure of the cathode film layer can be increased, so that the fast charging performance of the battery cell is improved.

[0236] In some embodiments, the particle size of the smallest particle in the lithium-containing phosphate with an olivine structure is from 0.1 μm to 0.4 μm. Exemplarily, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm or a range composed of any two of the above values. When the particle size of the smallest particle is within the above range, agglomeration is not likely to occur during the preparation of the cathode film layer 113.

[0237] In some embodiments, the particle size of the largest particles in the lithium phosphate of olivine structure is 15 μm to 25 μm. Exemplarily, it can be 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm or the range composed of any two of the above values. When the particle size of the largest particles is within the above range, the migration path of lithium ions during charge and discharge will not be too long, which can improve the fast charge and discharge performance of the battery cell.

[0238] In some embodiments, the positive electrode film layer further includes one or more of ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, lithium citrate, lithium nickelate, and lithium ferrate. The above materials can be used as lithium supplement agents. The lithium supplement agent can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0239] 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 several of Na, K, and Mg, M3 includes one or several of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and Y3 includes one or several of O and F.

[0240] 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

[0241] 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.

[0242] 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 cycle 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.

[0243] In some embodiments, the positive electrode film layer may optionally further 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%.

[0244] 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 resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0245] 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 of foils 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).

[0246] In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05 to 0.3. Exemplarily, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, or a range composed of any two of the above values.

[0247] 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.

[0248] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm, and may be optionally 12 μm to 15 μm. Exemplarily, the thickness of the positive electrode 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.

[0249] When the thickness of the positive electrode current collector is within the above range, the current-carrying capacity of the positive electrode current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0250] In the embodiments of the present application, the thicknesses of the positive electrode film layer and the positive electrode current collector are of the meanings well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, the thickness of the positive electrode plate is measured with a micrometer, the film layer on the surface of the positive electrode current collector is removed, and the thickness of the positive electrode current collector is measured with a micrometer. When the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode plate minus the thickness of the positive electrode current collector. When the positive electrode film layer is coated on both sides, the thickness of the positive electrode film layer is (the thickness of the positive electrode plate minus the thickness of the positive electrode current collector) / 2.

[0251] The positive electrode film layer is usually formed by coating a positive electrode paste on the positive electrode 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.

[0252] The positive electrode plate does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode plate of the embodiments of the present application further includes a positive electrode conductive layer disposed on the surface of the positive electrode current collector and sandwiched between the positive electrode current collector and the positive electrode film layer. In some other embodiments, the positive electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0253] In some embodiments, the positive electrode plate further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode plate, reduce the heat generation of the positive electrode plate, and thus reduce the heat generation of the battery cell.

[0254] 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.

[0255] 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, reduce the heat generation of the positive electrode plate, and thus reduce the heat generation of the battery cell, and can also take into account the improvement of the energy density of the battery cell.

[0256] In the embodiments of the present application, the thickness of the positive electrode conductive layer is of the meanings well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, the positive electrode plate is subjected to tomographic scanning to directly measure the thickness of the positive electrode conductive layer.

[0257] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0258] 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.

[0259] Exemplarily, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode plate and reducing the heat generation of the battery cell.

[0260] 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.

[0261] 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.

[0262] [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.

[0263] In some embodiments, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 ; it can be optionally 1.25 g / cm 3 to 1.36 g / cm 3 . Exemplarily, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 , 1.28 g / cm 3 , 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3, 1.36 g / cm 3 Or a range composed of any two of the above values.

[0264] 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 materials in the negative electrode film layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0265] In the embodiments of the present application, the compaction density of the negative electrode film layer of the battery cell in the 100% charged state 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 compaction density test method of the positive electrode film layer described above.

[0266] In some embodiments, the single-sided coating weight of the negative electrode film layer is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer is 74 mg / 1540.25 mm 2 , 80 mg / 1540.25 mm 2 , 85 mg / 1540.25 mm 2 , 90 mg / 1540.25 mm 2 , 95 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 mm2 、135 mg / 1540.25 mm 2 、137 mg / 1540.25 mm 2 、140 mg / 1540.25 mm 2 、145 mg / 1540.25 mm 2 、150 mg / 1540.25 mm 2 、155 mg / 1540.25 mm 2 、156 mg / 1540.25 mm 2 or a range composed of any two of the above values.

[0267] 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 the energy density of the battery cell can be improved while taking it into account.

[0268] 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 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.

[0269] In some embodiments, the powder resistivity of the negative electrode active material is from 0.005 Ω·cm to 0.043 Ω·cm, and can be 0.04 Ω·cm. Exemplarily, the powder resistivity of the negative electrode active material can be 0.043 Ω·cm, 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm or a range composed of any two of the above values.

[0270] The relatively low powder resistivity of the negative electrode active material results in a relatively low resistance of the negative electrode plate and less heat generation of the battery cell.

[0271] In the embodiments of the present application, the powder resistivity of the negative electrode active material has the meaning well known in the art, and can be detected by the equipment and methods well known in the art. The detection method is as described in the powder resistivity test method of the positive electrode active material above.

[0272] 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 can be 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.

[0273] When the powder compaction density of the negative electrode active material is within the above range under 20,000 N, the energy density of the battery cell can be improved, and since the negative electrode active material in the negative electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0274] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art, and can be detected by methods and equipment well-known in the art, and is detected according to the test standard GB / T24533-2009. As an example, a certain amount of negative electrode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in the UTM7305 type electronic pressure testing machine, pressurized to 2000 kg (equivalent to 20,000 N), kept under pressure for 30 s, then the pressure is released, kept for 10 s, and then the powder compaction density of the negative electrode active material under the action of 20,000 N is recorded and calculated.

[0275] In some embodiments, the charging specific capacity of the negative electrode active material at a 0.1C rate is 350 mAh / g to 480 mAh / g. Exemplarily, the charging specific capacity of the negative electrode active material at a 0.1C rate is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g or a range composed of any two of the above values.

[0276] When the charging specific capacity of the negative electrode active material at a 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0277] In the embodiments of the present application, the charging specific capacity of the negative electrode active material at a 0.1C rate has the meaning well-known in the art, and can be detected by 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 0.1C rate described above.

[0278] In some embodiments, the negative electrode active material includes a carbon-based material, which has high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass percentage of the carbon-based material in the negative electrode active material can be greater than or equal to 80% and less than or equal to 100%.

[0279] 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 used in combination, the battery cell has excellent cycle performance.

[0280] 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.

[0281] When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet and the battery cell, and can improve the fast charging performance of the battery cell.

[0282] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer. The artificial graphite includes secondary particles, and the secondary particles include a plurality of primary particles. The carbon coating layer covers the surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon, which refers to a transitional carbon material with a very low degree of graphitization crystallization and an approximate amorphous form (or no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0283] The artificial graphite includes secondary particles. In the artificial graphite, there are more migration paths for lithium ions, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions. The carbon coating layer has more end faces and defects, so that the number of sites where lithium ions can be intercalated and deintercalated is larger, and the electrical conductivity of the carbon coating layer is excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0284] 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 the range composed of any two of the above values.

[0285] 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.

[0286] 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 a part of the surface of the artificial graphite particles.

[0287] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of the coal tar pitch and the petroleum pitch is below 250 °C.

[0288] 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 a part of the surface of the artificial graphite.

[0289] Optionally, the carbonization treatment time is 1 h to 6 h.

[0290] 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.

[0291] 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.

[0292] Optionally, based on the mass of the negative electrode active material, the mass content of silicon element in the silicon-based material is 0.3% to 10.0%, and may be 1% to 6%. Exemplarily, the mass content of silicon element in the silicon-based material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10% or any range composed of any two of the above values.

[0293] 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 improved.

[0294] 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.

[0295] In some embodiments, in addition to the above-mentioned carbon-based materials and optional silicon-based materials, 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 materials.

[0296] In this application, the qualitative and quantitative determination of each substance or element can be detected by suitable equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0297] For example, this application can combine the General Rules for X-ray Diffraction Analysis of JIS / K0131-1996 to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or the negative electrode active material.

[0298] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). There are voids between flake structures in the SEM cross-sectional view of natural graphite, while the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, while only 2H phase exists in the XRD spectrum of artificial graphite.

[0299] 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.

[0300] 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.

[0301] When the negative electrode film layer adopts at least two film layers, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes a silicon-based material. The silicon-based material can be located in one of the at least two film layers, or can be located in at least two of the at least two film layers. The negative electrode film layer can include two film layers, three film layers, four film layers, or even more film layers.

[0302] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector. The carbon-based material in the first negative electrode film layer includes graphite particles. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector. The carbon-based material in the second negative electrode film layer includes graphite particles. The graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer can be the same or different.

[0303] The interface between the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0304] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0305] The negative electrode film layer includes at least two film layers, and layer-by-layer coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences between the first negative electrode film layer and the second negative electrode film layer, the pore differences of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission can be reduced, and the fast charging performance of the battery cell can be improved.

[0306] 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.

[0307] The difference in particle sizes between the first negative electrode film layer and the second negative electrode film layer can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode film layer is usually relatively high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can improve the problem of lithium deposition on the surface layer of the negative electrode plate.

[0308] Optionally, the negative electrode active material in the first negative electrode film layer is granular, and its volume average particle size Dv50 is from 9.5 μm to 18.5 μm, and can be optionally from 9.5 μm to 14.6 μm. Exemplarily, the volume average particle size of the negative electrode active material in the first negative electrode film layer is 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 14.6 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm or a range composed of any two of the above values. When the first negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is from 9.5 μm to 18.5 μm, and can be optionally from 9.5 μm to 14.6 μm.

[0309] When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0310] Optionally, the negative electrode active material in the second negative electrode film layer is granular, and its volume average particle size Dv50 is from 7.8 μm to 14.3 μm, and can be optionally from 7.8 μm to 11.3 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm or a range composed of any two of the above values. When the second negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is from 7.8 μm to 14.3 μm, and can be optionally from 7.8 μm to 11.3 μm.

[0311] When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the further hand, the cooperation of the negative electrode active material in the second negative electrode film layer with the volume average particle size range and the negative electrode active material in the first negative electrode film layer 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.

[0312] 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 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.

[0313] 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 packed more densely, improving the energy density of the battery cell. The first negative electrode film layer is relatively sparsely packed with richer pores, which can improve the fast charging performance of the battery cell. When the negative electrode active material includes graphite particles, the tapped density of the graphite particles in the first negative electrode film layer is less than or equal to the tapped density of the graphite particles in the second negative electrode film layer.

[0314] 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 a 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.

[0315] 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.

[0316] 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.

[0317] 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 transport can be reduced, and the fast charging ability of the battery cell can be improved.

[0318] In some embodiments, after the battery cell has undergone 10 full charge test cycles at the beginning of life (BOL), the thickness of the first negative electrode film layer is 15 μm to 65 μm, such as 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm or a range composed of any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased, the tortuosity of lithium ion transport can be reduced, and the fast charging ability of the battery cell can be improved.

[0319] In some embodiments, after the battery cell undergoes 10 full charge test cycles at the beginning of life (BOL), the thickness of the second negative electrode film layer is 15 μm to 65 μm, such as 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range composed of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be regulated and increased, the tortuosity of lithium ion transport can be reduced, and the fast charging ability of the battery cell can be improved.

[0320] In the embodiments of the present application, for example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharging as 2.0 V as an example for illustration, 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 discharging rate of 0.33 C to 2.0 V, stand for 10 min. The above one charge and discharge is one cycle, and cycle 10 times. Then charge at a charging rate of 0.33 C of the nominal capacity to 3.65 V, and then charge at a constant voltage of 3.65 V to 0.05 C to obtain the BOL full charge state. In the BOL full charge state, disassemble the negative electrode plate, use a tomography electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode plate, distinguish the two regions according to the interface between the first negative electrode film layer and the second negative electrode film layer, and measure the thickness of the two respectively. For example, measure the thickness at 10 positions of the first negative electrode film layer, calculate its average value as the average value of the first negative electrode film layer, measure the thickness at 10 positions of the second negative electrode film layer, and calculate its average value as the average value of the second negative electrode film layer.

[0321] In some embodiments, after the full charge test at the end of life (EOL) of the battery cell, the thickness of the first negative electrode film layer is 15 μm to 70 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or the 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.

[0322] In some embodiments, after the full charge test at the end of life (EOL) of the battery cell, the thickness of the second negative electrode film layer is 15 μm to 70 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or 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 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.

[0323] In the embodiments of the present application, for example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharging as 2.0 V as an example for illustration, The specific steps for the EOL full charge test are as follows: At 60 °C, charge at a charging rate of 0.33C of the battery nominal capacity until 3.65V, then charge at a constant voltage of 3.65V until 0.05C, stand for 10 min, then discharge at a discharge rate of 0.33C until 2.0V, stand for 10 min. One cycle of the above charge and discharge is considered one cycle, and the test is stopped 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 charge at a constant voltage of 0.05C until 3.65V, which is the EOL full charge state. In the EOL full charge state, disassemble the negative electrode sheet, and 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.

[0324] In some embodiments, when the negative electrode film layer adopts a single-layer film layer (different from the above double-layer film layer), the negative electrode film layer further includes a lithium-containing binder. Optionally, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range composed of any two of the above values. The lithium element in the lithium-containing binder can exist in 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, 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 may further include a negative electrode binder. For example, the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0325] 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.

[0326] Exemplarily, the lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, which is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is (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.

[0327] The lithium-containing binder of the above materials can provide a certain number of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during the charge and discharge process, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0328] In some other embodiments, when the negative electrode film layer adopts at least two film layers, the negative electrode film layer further includes a lithium-containing binder.

[0329] Optionally, the first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. Further optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0330] 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.

[0331] Optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or the range composed of any two of the above values. The lithium element in the first lithium-containing binder can exist in the form of ions, which can increase the number of freely movable lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the insertion and extraction rate of lithium ions, and improve the fast charging performance of the battery cell.

[0332] 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.

[0333] 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.

[0334] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0335] 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.

[0336] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0337] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. Exemplarily, the mass content of lithium element in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range composed of any two of the above values. When the mass content of lithium element is within the above range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the insertion / extraction rate of lithium ions, and improve the fast charging performance of the battery cell.

[0338] 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.

[0339] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0340] In some embodiments, the first negative electrode film layer further includes a negative electrode binder, and the second negative electrode film layer further includes a negative electrode binder. The negative electrode binder in the first negative electrode film layer and the negative electrode binder in the second negative electrode film layer each independently include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0341] 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.

[0342] In some embodiments, the negative electrode film layer may optionally further include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0343] In some embodiments, the negative electrode film layer may optionally further include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0344] In some embodiments, the negative electrode film layer may optionally further include other additives. As an example, the other additives may include thickeners, dispersants, etc. For example, sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0345] In some embodiments, the porosity of the negative electrode film layer is 40% to 55%. Exemplarily, the porosity of the negative electrode film layer is 40%, 45%, 50%, 55% or a range composed of any two of the above values.

[0346] When the porosity of the negative electrode film layer in the embodiments of the present application is within the above range, the migration ability of lithium ions in the negative electrode film layer can be improved, and the fast charging performance can be improved.

[0347] In the embodiments of the present application, the porosity of the negative electrode film layer can be measured by the gas displacement method according to standard GB / T24586. The porosity P = (V1 - V2) / V1 × 100%, where V1 is the apparent volume of the sample and V2 is the true volume of the sample.

[0348] In some embodiments, the negative electrode current collector portion may be a metal foil or a composite current collector portion. 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 portion 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).

[0349] In some embodiments, the thickness of the negative current collector is from 4 μm to 6 μm. Exemplarily, the thickness of the negative 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.

[0350] When the thickness of the negative current collector is within the above range, the current-carrying capacity of the negative current collector is relatively excellent, and it can enable the battery cell to have a relatively high energy density.

[0351] In the embodiments of the present application, the thickness of the negative current collector has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, the film layer on the surface of the negative current collector is washed away with a solvent, and the thickness of the negative current collector is measured with a micrometer.

[0352] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative current collector and drying and cold-pressing it. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, 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.

[0353] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the embodiments of the present application further includes a negative electrode conductive layer disposed on the surface of the negative current collector and sandwiched between the negative current collector and the negative electrode film layer. In some other embodiments, the negative electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0354] 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 current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, and thus reduce the heat generation of the battery cell.

[0355] In some embodiments, the thickness of the negative electrode conductive layer is from 0.5 μm to 2 μm. Exemplarily, the thickness of the negative electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or a range composed of any two of the above values.

[0356] When the thickness of the negative electrode conductive layer is within the above range, it can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, and thus reduce the heat generation of the battery cell, and can also take into account the improvement of the energy density of the battery cell.

[0357] In the embodiments of the present application, the thickness of the negative electrode conductive layer has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art, and the testing method of the negative electrode conductive layer in the foregoing can be adopted.

[0358] 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.

[0359] In some embodiments, the negative electrode conductive layer may also optionally include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0360] 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.

[0361] 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.

[0362] 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.

[0363] 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.

[0364] In some embodiments, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05 to 1.30, and can be optionally 1.07 to 1.15. Exemplarily, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3 or a range composed of any two of the above values.

[0365] 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.

[0366] In the embodiments of the present application, the CB value 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 capacity of the negative electrode film layer per unit area and the capacity of the positive electrode film layer per unit area are calculated respectively, and then the ratio of the two is calculated to obtain the CB value.

[0367] Specifically, 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 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, assemble it into a CR2430 type half-button battery of positive electrode-lithium sheet, and the area of the positive electrode plate used is amm 2 , and the electrolyte used is 1mol / L LiPF 6 in a solution of EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, the assembled half-button battery is left standing for 3h, and the test is carried out at 25°C. First, charge (Charge) and de-lithiate in the voltage range of 2.0V to 3.65V at 0.1C, and then discharge (Discharge) and intercalate lithium to 2.0V at 0.05C, and cycle 2 times. Take the discharge cut-off 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 of the positive electrode active material coated on the positive electrode current collector is d. Then, the capacity of the positive electrode film layer per unit area = Y / (a × b × c × d).

[0368] Specifically, the capacity of the negative electrode film layer per unit area refers to the actual 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, assemble it into a CR2430 type half-button battery of negative electrode-lithium sheet, and the area of the negative electrode plate used is fmm 2 , and the electrolyte used is 1mol / L LiPF 6 in a solution of EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, the assembled half-button battery is left standing for 3h, and the test is carried out at 25°C. First, discharge (Discharge) and intercalate lithium in the voltage range of 2V - 0V at 0.1C, and then charge (Discharge) and de-lithiate to 2V at 0.05C, and cycle 2 times. Take the discharge cut-off 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 of the negative electrode active material coated on the negative electrode current collector is d. Then, the 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.

[0369] In some embodiments, the base film comprises at least one of glass fiber, non-woven fabric, and polyolefin. The base film may be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0370] Optionally, the polyolefin comprises at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0371] 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.

[0372] When the porosity of the base film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0373] In the embodiments of the present application, the porosity refers to the percentage of the internal pore volume in the total volume of the separator. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin Separator for Battery Cells". It should be noted that in the actual testing process, the testing process may be slightly different from the standard according to the differences in testing instruments, testing errors, and in order to eliminate the influence on the porosity test as much as possible, so as to obtain a more accurate test value.

[0374] 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.

[0375] When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0376] In the embodiments of the present application, the separator may be the base film. Optionally, the separator further comprises a functional layer disposed on at least one side of the base film. The functional layer may comprise inorganic particles to improve the heat resistance of the separator. Optionally, the functional layer is disposed on both sides of the base film.

[0377] In some embodiments, the functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and includes first inorganic particles. The second functional layer is located on the other side of the base film and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0378] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator membrane.

[0379] Optionally, the first functional layer may include a binder, optionally at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0380] 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.

[0381] 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 membrane 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 membrane is obtained from the battery cell, and the separator membrane is dried and used as a sample. The separator membrane 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 membrane and its respective layers.

[0382] 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.

[0383] The second inorganic particles in the composite particles prevent the non-fluoropolymer particles from easily adhering to each other during the high-temperature treatment in the granulation process, creating pores in the composite particles, which is beneficial for the transport of lithium ions, improving the ionic conductivity of the separator membrane. Additionally, the second inorganic particles can also increase the compression modulus of the composite particles, making the composite particles less likely to deform during charge and discharge processes, resulting in a more stable structure of the separator membrane, enhancing the kinetic performance of the battery cell and the fast charging performance. Optionally, compared with the first functional layer, the second functional layer is disposed closer to the negative electrode tab. Since the composite particles are less likely to deform, the separator membrane basically does not cause side effects such as extrusion to the negative electrode tab, ensuring the stable kinetic performance of the negative electrode tab. Correspondingly, the first functional layer is disposed closer to the positive electrode tab.

[0384] Optionally, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Optionally, the second inorganic particles include silicon oxide. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer and can form composite particles in combination with the non-fluoropolymer, further improving the cycle stability and kinetic performance of the separator membrane, and enhancing the cycle performance and fast charging performance of the battery cell.

[0385] The average particle size of the second inorganic particles is from 5 nm to 100 nm, optionally from 10 nm to 100 nm, and optionally from 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or a range composed of any two of the above values. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0386] 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 using equipment and methods well-known in the art. For example, after obtaining the separator membrane and drying it 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.

[0387] In some embodiments, the ionic conductivity of the separator membrane is from 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 a range composed of any two of the above values.

[0388] When the ionic conductivity of the separator membrane is within the above range, the migration ability of lithium ions in the separator membrane can be further improved, and the fast charging performance of the battery cell can be enhanced.

[0389] 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 using 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 negative electrode case of the battery, add 150 μL of electrolyte thereto, and the electrolyte is a solution of 1 mol / L LiPF 6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then place the separator membrane (with an area of 3.14 cm 2 , a thickness of 12 μm) to make it close 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) thereon and encapsulate. Take out the assembled button battery from the vacuum glove box and place it for 24 h for the next test.

[0390] Testing: On an electrochemical workstation, perform tests in the frequency range of 10 -1 ~10 6 Hz to obtain the separator membrane 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 membrane resistance, and L and S are the thickness and area of the separator membrane to be tested, respectively.

[0391] [Electrolyte] In some embodiments, the battery cell further includes an electrolyte.

[0392] During the charge and discharge process of the battery cell, active ions are embedded and extracted 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.

[0393] In the embodiments of the present application, the conductivity of the electrolyte at room temperature is from 13 mS / cm to 20 mS / cm, and can be optionally from 15 mS / cm to 20 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm or the range composed of any two of the above values.

[0394] When the conductivity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0395] 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 the equipment and methods well-known in the art. For example, it can be tested with reference to the industry standard HG-T 4067-2015.

[0396] 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 the range composed of any two of the above values.

[0397] 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.

[0398] 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 using the equipment and methods well-known in the art. For example, it can be detected according to GB / T10247-2008.

[0399] 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 the range composed of any two of the above values.

[0400] 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.

[0401] 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.

[0402] 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.

[0403] In some embodiments, the organic solvent includes a chain carboxylic ester solvent, and the mass content of the chain carboxylic ester solvent relative to the mass of the organic solvent is greater than or equal to 5% and less than or equal to 75%, optionally greater than or equal to 10% and less than or equal to 75%, and optionally 30% to 75%. Exemplarily, the mass content of the chain carboxylic ester solvent is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or the range composed of any two of the above values.

[0404] When the mass content of the chain carboxylic ester solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0405] 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.

[0406] The above chain carboxylic ester solvent has a relatively high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0407] 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.

[0408] Optionally, R 2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R2 including C1-C2 alkyl or C1-C2 haloalkyl.

[0409] In each of 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.

[0410] In each of the above embodiments, the haloalkyl includes one or more of a fluoroalkyl, a chloroalkyl, a bromoalkyl, and an iodoalkyl. Optionally, the haloalkyl includes a fluoroalkyl.

[0411] Exemplarily, the chain carboxylic ester solvents include one or more of the compounds represented by Formula I-1 to Formula I-8.

[0412] In some embodiments, the organic solvent further includes carbonate solvents.

[0413] Optionally, the carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Further optionally, the carbonate solvents include one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The above carbonate solvents and chain carboxylic ester solvents are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0414] Further optionally, the mass content of the carbonate solvents in the organic solvent is 25% to 95%, and can be 25% to 70%. Exemplarily, the mass content of the carbonate solvents in the organic solvent is 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or a range composed of any two of the above values. The carbonate solvents with the above mass content can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0415] Exemplarily, the carbonate solvents include one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, and the mass content of the carbonate solvents is 30% to 50%.

[0416] In some embodiments, the electrolyte further contains additives. The additives can include negative electrode film-forming additives, or can include positive electrode film-forming additives, or can also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature power performance of the battery, etc.

[0417] In some embodiments, the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive, and may be at least two of them. The above additives can improve the interfacial film properties on the positive electrode side and / or the negative electrode side, which is beneficial to enhancing the fast charging performance of the battery cell and improving the cycling performance.

[0418] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. Exemplarily, the mass content of the additive in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values.

[0419] The additive with the above mass content can effectively improve the interfacial film properties on the positive electrode side and / or the negative electrode side, which is beneficial to enhancing the fast charging performance of the battery cell and improving the cycling performance.

[0420] Exemplarily, the carbonate additive includes one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0421] Exemplarily, the sulfur-containing additive includes one or more of ethylene sulfate (DTD), bis(ethylene sulfate) (2-DTD), butene sulfite (BS), 1,3-propane sultone (PS), ethylene sulfite (ES), and methylene methyl disulfonate (MMDS).

[0422] Optionally, the lithium salt additive includes lithium difluorophosphate LiPO 2 F 2 2, lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate LiBF 4 4, and lithium bis(oxalate) borate (LiBOB), one or more of them.

[0423] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 9%, and may be 2% to 6%.

[0424] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 4%, and may be 0.5% to 3%.

[0425] 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%.

[0426] 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%.

[0427] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of a fluorosulfonylimide salt and lithium hexafluorophosphate LiPF 6 among others. The above-mentioned lithium salts are easily dissociated, 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 monomer.

[0428] Optionally, the fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0429] 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.

[0430] 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.

[0431] 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.

[0432] 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.

[0433] 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 a range composed of any two of the above values.

[0434] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte have meanings well-known in the art and can be detected by devices and methods well-known in the art. For example, reference can be made to the General Rules for Ion Chromatography Analysis (JY / T 020-1996) to qualitatively or quantitatively analyze the concentration of inorganic components / lithium salts in the electrolyte by ion chromatography. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography analysis method.

[0435] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art and can be detected by devices and methods well-known in the art. For example, reference can be made to the General Rules for Gas Chromatography of Chemical Reagents (GB / T 9722-2006) to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography analysis method.

[0436] 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 the constituent components of the organic solvent. Based on the mass of the organic solvent being 100%, the mass content of each component is calculated. Carbonate additives (such as vinylene carbonate, fluoroethylene carbonate), sulfur-containing additives, and lithium salt additives are used as additives in the electrolyte. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0437] In some embodiments, the battery cell satisfies: d / A ≤ 3.5 g / Ah, and optionally 2.40 g / Ah ≤ d / A ≤ 3.3 g / Ah, where d represents the mass of the electrolyte in the battery cell, in g; 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, 2.4 g / Ah, or a range composed of any two of the above values.

[0438] 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.

[0439] In the embodiments of the present application, the d / A of the battery cell can be understood as the liquid retention coefficient, 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 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 3.65V at 0.33C, then charged at a constant voltage until 0.05C, and then discharged at a constant current of 0.33C to 2.0V. The discharged capacity A is used as the denominator. The battery cell is weighed as M0, and then the positive electrode plate, the negative electrode plate, the separator, and the electrolyte are disassembled. The free electrolyte is placed in a bag. All the above solid components are placed in an oven at 60°C for more than 4 hours (including but not limited to the positive electrode plate, the negative electrode plate, the separator, and other mechanical parts contributing to M0 of the disassembled battery cell), 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 the value obtained by dividing the weight difference d between M0 and M1 by the capacity A.

[0440] As Figure 10 shown, in some embodiments of the present application, the battery cell 7 according to the embodiments of the present application can be assembled into a battery module 6. The number of battery cells 7 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.

[0441] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, in parallel, or in a hybrid connection. A hybrid connection means that there are both series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series, in parallel, or in a hybrid connection 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 hybrid connection to form a battery module 6, and then the multiple battery modules 6 are connected in series, in parallel, or in a hybrid connection 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.

[0442] As Figure 11 shown, in some embodiments, the above 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.

[0443] The battery pack 2 may include a housing 5 and a plurality of battery modules 6 disposed in the housing 5. The housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 has a receiving space 5c. The first housing portion 5a is used to cover the second housing portion 5b and form a closed space for receiving the battery modules 6. The plurality of battery modules 6 may be arranged in the housing 5 in any manner.

[0444] The first housing portion 5a and the second housing portion 5b cover each other, and the first housing portion 5a and the second housing portion 5b jointly define a receiving space 5c for receiving battery cells. The second housing portion 5b may be a hollow structure with one end open. The first housing portion 5a is a plate-like structure. The first housing portion 5a covers the open side of the second housing portion 5b to form the housing 5 having the receiving space 5c. The first housing portion 5a and the second housing portion 5b may also both be hollow structures with one side open. The open side of the first housing portion 5a covers the open side of the second housing portion 5b to form the housing 5 having the receiving space 5c. Of course, the first housing portion 5a and the second housing portion 5b may be of various shapes, such as a cylinder, a cuboid, etc.

[0445] To improve the sealing performance after the connection between the first housing portion 5a and the second housing portion 5b, a sealing member, such as sealant, sealing ring, etc., may also be provided between the first housing portion 5a and the second housing portion 5b.

[0446] Assuming that the first housing portion 5a covers the top of the second housing portion 5b, the first housing portion 5a may also be referred to as an upper cover, and the second housing portion 5b may also be referred to as a lower housing. 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.

[0447] In some embodiments, during the process of the battery pack 2 or any battery cell constituting the battery pack 2 from 20% SOC to 80% SOC, the temperature of the external environment where the battery pack 2 is located is room temperature, such as 30°C.

[0448] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from a state of charge (SOC) of 20% to 80%, it includes multiple charging steps. The difference between the maximum SOC of any charging step and the maximum SOC of its adjacent charging step in the multiple charging steps 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.

[0449] The charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from a SOC of 20% to 40% 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.

[0450] Exemplarily, the charging steps of the battery pack 2 or any battery cell constituting the battery pack 2 from 20% to 80% can be carried out as follows: 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; Constant current charging at 4.3C from 45% SOC to 50% SOC; Constant current charging at 4.0C from 50% SOC to 55% SOC; Constant current charging at 3.7C from 55% SOC to 60% SOC; Constant current charging at 3.4C from 60% SOC to 65% SOC; Constant current charging at 3.1C from 65% SOC to 70% SOC; Constant current charging at 2.9C from 70% SOC to 75% SOC; Constant current charging at 2.7C from 75% SOC to 80% SOC.

[0451] In some embodiments, the battery pack 2 or any battery cell that makes up the battery pack 2 takes less than or equal to 15 minutes, optionally 6 minutes to 15 minutes, to go from 20% state of charge to 80% state of charge. The temperature of the external environment of the battery pack 2 at 20% state of charge is room temperature, such as 30°C. Exemplarily, the charging time of the battery pack 2 from 20% state of charge to 80% state of charge is 15 minutes, 14.5 minutes, 14 minutes, 13.5 minutes, 13 minutes, 12.5 minutes, 12 minutes, 11.5 minutes, 11 minutes, 10.5 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes or a range composed of any two of the above values.

[0452] 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 a range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0453] 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 devices 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, Place the battery cell at 25°C, charge it at a constant current of 0.33C to 3.65V, then charge it at a constant voltage until 0.05C, discharge it at a constant current of 0.33C to 2.0V, and record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and excluding the insulating film outside the outer shell), calculate the volume V0 of the single battery cell, unit: L, and the volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0454] electrical device The second aspect of the embodiments of the present application provides an electrical device, which includes at least one of the battery cells, battery modules or battery packs of the embodiments of the present application. The battery cells, battery modules or battery packs can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or an extended-range electric vehicle, etc.; the spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc.; the electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy and an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact drill, a concrete vibrator and a planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices. The electrical device can select battery cells, battery modules or battery packs according to its usage requirements.

[0455] Figure 12 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0456] A battery pack 2 is arranged inside the electrical device 1, and the battery pack 2 can be arranged at the bottom, head or tail of the electrical device 1. The battery pack 2 can be used for power supply of the electrical device 1. For example, the battery pack 2 can be used as the operating power 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.

[0457] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery pack 2 to supply power to the motor 4. For example, it is used for the working power requirements during the start, navigation and driving of the electrical device 1.

[0458] Another example of an electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires thinness and lightness, and battery cells can be used as the power source.

[0459] The charging process of the electrical device can select the following charging methods: 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.

[0460] In some embodiments, the charging time of the electrical device from 20% state of charge to 80% state of charge is less than or equal to 15 min, and can be selected from 6 min to 15 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 20% state of charge to 80% state of charge is 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 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.

[0461] 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 changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0462] Example 1 1. Preparation of the positive electrode tab The positive electrode tab includes a positive current collector, a positive conductive layer on the positive current collector, and a positive electrode film layer. The positive current collector is an aluminum foil with a thickness of 10 μm.

[0463] The positive electrode conductive layer on the positive electrode current collector is a film layer formed by uniformly mixing a positive electrode conductive agent, superconducting carbon, a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), and then coating it on the surface of the current collector and drying. The thickness is 1 μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

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

[0465] The positive electrode active material includes lithium iron phosphate and a coating layer. The coating layer coats the surface of the lithium iron phosphate. The coating layer includes lithium iron titanium phosphate, Li 2 FeTi(PO 4 ) 3 and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, the Dv10 is 0.64 μm, the particle size of the smallest particle is 0.2 μm, and the particle size of the largest particle is 18 μm.

[0466] The single-sided coating weight of the positive electrode film layer is 240 mg / 1540.25 mm 2 .

[0467] 2. Preparation of the negative electrode plate The negative electrode plate includes a negative electrode current collector, a negative electrode conductive layer on the negative electrode current collector, and a negative electrode film layer. The negative electrode current collector is a copper foil with a thickness of 5 μm.

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

[0469] The single-sided coating weight of the negative electrode film layer is 110 mg / 1540.25 mm 2 .

[0470] 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.

[0471] The first negative electrode film layer includes graphite particles, conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, where the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 2-hydroxyethyl acrylate monomer is 0.35:0.3:0.15:0.2), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose, with a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium element in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer, and the carbon coating layer covers the surface of the artificial graphite, with a mass content of 3.5%.

[0472] The second negative electrode film layer includes graphite particles, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, where the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 2-hydroxyethyl acrylate monomer is 0.35:0.3:0.15:0.2), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose, with a mass ratio of 97.5:0.5:0.5:0.5:1. The mass content of lithium element in the second lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer, and the carbon coating layer covers the surface of the artificial graphite, with a mass content of 3.5%.

[0473] 3. Separator The separator includes a base film, which is a 7-μm polyethylene film layer with a porosity of 42%.

[0474] 4. Preparation of electrolyte The electrolyte includes organic solvent, lithium salt, and additive.

[0475] The organic solvent includes 60% chain carboxylic ester solvent (ethyl acetate) and 40% carbonate solvent (30% ethylene carbonate EC, 10% dimethyl carbonate). The mass content of each component in the organic solvent is calculated based on the mass of the organic solvent.

[0476] 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.

[0477] The lithium salt includes 1 mol / L lithium hexafluorophosphate LiPF 6 .

[0478] The conductivity of the electrolyte at room temperature is 16.4 mS / cm.

[0479] 5. Preparation of Battery Cell Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining an electrode assembly. Place the electrode assembly in an outer packaging shell, inject electrolyte after drying, and obtain a battery cell through processes such as vacuum packaging, standing, formation, and shaping. The compaction density of the positive electrode film layer of the battery cell at 100% SOC is 2.65 g / cm 3 and the compaction density of the negative electrode film layer at 100% SOC is 1.26 g / cm 3 .

[0480] Comparative Example 1 and Comparative Example 2 Prepare a battery cell using a method similar to that of Example 1. Different from Example 1, the width and length of the positive electrode film layer are adjusted.

[0481] Example 2-1 and Example 2-2 Prepare a battery cell using a method similar to that of Example 1. Different from Example 1, the width of the positive electrode film layer is adjusted.

[0482] performance test 1. DC Internal Resistance DCR Test of Battery Cell The method in GB / T 31467 "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEV" can be referred to.

[0483] For example, at -20 °C, charge the battery cell at a constant current of 0.33 C to 3.65 V, let it stand for 1 min, then charge it at a constant current of 0.1 C to 3.65 V, let it stand for 30 min, discharge it at a constant current of 0.33 C to 2.0 V, and record the discharge capacity A 0 , in units of Ah, and then charge it at a constant current of 0.33 C for 0.5 A 0 Ah, and adjust the SOC to 50%.

[0484] After placing the battery cell at -20 °C for 2 h, discharge it at a constant current of 4 C for 10 s, and record ∆U 放电 , ∆I 放电 , and calculate the discharge DCR data of the lithium-ion battery through the following formula, R 放电 = ∆U 放电 / ∆I 放电 , where ∆U 放电 represents the voltage change within the first 10 s of discharge, and ∆I 放电 represents the current value within the first 10 s of discharge.

[0485] 2. Cycle Performance of Battery Cell At 30 °C, the battery cell is charged from above 20% SOC to 80% SOC according to the above charging process, then charged at 0.33C to 3.65V. After standing for 30 minutes, it is discharged at 1C to 20% SOC. This is one charge-discharge cycle. Repeat the above charge-discharge cycle 1000 times, and calculate the cycle capacity retention rate of the battery cell. The higher the cycle capacity retention rate, the better the cycle performance of the battery cell.

[0486] The charging process of the battery from 20% to 80% SOC is as follows: 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.

[0487] The test results are shown in Table 1.

[0488] Table 1

[0489] In Table 1, in each example and Comparative Example 1, The positive electrode tab is arranged on both sides of the positive current collector in the length direction, and the negative electrode tab is arranged on both sides of the negative current collector in the length direction.

[0490] The ratio of the width of the first end face of the positive electrode tab to the width of the positive current collector is 2 / 3, and the current-carrying area of the positive terminal on the same side is 314 mm 2 . The ratio of the width of the second end face of the negative electrode tab to the width of the negative current collector is 2 / 3.

[0491] The positive electrode film layer is arranged on both sides of the positive current collector in the thickness direction, and the negative electrode film layer is arranged on both sides of the negative current collector in the thickness direction.

[0492] As can be seen from Table 1, In Comparative Example 1, the ratio of the length to the width of the positive electrode film layer is less than 4, and in Comparative Example 2, the ratio of the length to the width of the positive electrode film layer is greater than 20, resulting in a relatively high internal resistance of the battery cell; moreover, excellent cycle performance and energy density cannot be balanced. In the examples of the present application, the ratio of the length to the width of the positive electrode film layer is 4 to 20, which makes the internal resistance of the battery cell smaller, is beneficial to improving the cycle performance, and can balance the improvement of the cycle performance and the energy density.

[0493] Comparative Example 3 and Comparative Example 4 The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, the single-sided coating weight of the negative electrode film layer was adjusted.

[0494] Example 3-1 and Example 3-2 The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, the single-sided coating weight of the negative electrode film layer was adjusted.

[0495] The test results are shown in Table 2.

[0496] Table 2

[0497] In Comparative Example 3, the coating weight of the negative electrode film layer is small and cannot meet the energy density requirement; in Comparative Example 4, the coating weight of the negative electrode film layer is large, resulting in a small impedance of the battery cell and poor cycling performance.

[0498] In the examples of the present application, the coating weight of the negative electrode film layer is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 , which can effectively reduce the internal resistance of the battery cell, improve the fast charging performance of the battery cell, and can also improve the cycle performance and have excellent energy density.

[0499] Example 4 The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, in Example 1, the ratio of the width of the first end face of the positive electrode tab to the width of the positive electrode current collector is 2 / 3, and the ratio of the width of the second end face of the negative electrode tab to the width of the negative electrode current collector is 2 / 3. In Example 4-1, the ratio of the width of the first end face of the positive electrode tab to the width of the positive electrode current collector is 1 / 3, and the ratio of the width of the second end face of the negative electrode tab to the width of the negative electrode current collector is 1 / 3.

[0500] Example 5 The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, in Example 1, the current-carrying area of the positive terminal is 314 mm2 , the overcurrent area of the negative terminal is 314 mm 2 . In Example 5, the overcurrent area of the positive terminal is 706 mm 2 , and the overcurrent area of the negative terminal is 706 mm 2 .

[0501] Example 6 A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the preparation of the negative electrode tab was as follows: The negative electrode tab 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 5 μm.

[0502] The negative conductive layer on the negative current collector is a film layer formed by uniformly mixing a negative conductive agent, superconducting carbon, a negative binder, styrene-butadiene rubber (SBR), a thickener, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, and then coating and drying on the surface of the negative current collector. The thickness is 1 μm. The mass content of the negative conductive agent in the negative conductive layer is 35%, the mass content of the negative binder in the negative conductive layer is 60%, and the mass content of the thickener in the negative conductive layer is 5%.

[0503] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode paste (the solvent is deionized water) on the surface of the negative conductive layer and then drying and cold pressing.

[0504] The negative electrode film layer includes a first negative electrode film layer, and the first negative electrode film layer is located on the surface of the negative conductive layer.

[0505] The first negative electrode film layer includes graphite particles, conductive agent acetylene black, a first lithium-containing binder (copolymer of lithium acrylate - acrylonitrile - acrylamide - 2-hydroxyethyl acrylate, where the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 2-hydroxyethyl acrylate monomer is 0.35:0.3:0.15:0.2), negative binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose with a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium element in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer, and the carbon coating layer covers the surface of the artificial graphite. The mass content of the carbon coating layer is 3.5%.

[0506] Comparative Example 5 A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the positive electrode tab is provided on one side of the positive current collector, and the negative electrode tab is provided on one side of the negative current collector.

[0507] The test results are shown in Table 3.

[0508] Table 3

[0509] As can be seen from Table 3, In Comparative Example 5, when the positive electrode tab is disposed on one side of the positive current collector in the length direction and the negative electrode tab is disposed on one side of the negative current collector in the length direction, the current distribution is uneven, the internal resistance of the battery cell is relatively large, and the cycle performance is poor.

[0510] When the ratio of the width of the first end face of the positive electrode tab to the width of the positive current collector is greater than or equal to 1 / 3, and the ratio of the width of the second end face of the negative electrode tab to the width of the negative current collector is greater than or equal to 1 / 3, the battery cell has a smaller internal resistance and excellent cycle performance and energy density.

[0511] The current-carrying area of the positive terminal is 200 mm 2 to 800 mm 2 , and the current-carrying area of the negative terminal is 200 mm 2 to 800 mm 2 When this is the case, the battery cell has a smaller internal resistance and excellent cycle performance and energy density.

[0512] When the negative electrode film layer is disposed on at least one side of the negative current collector, the battery cell has a smaller internal resistance and excellent cycle performance and energy density.

[0513] Although the illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A battery cell, characterized in that: The battery comprises an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet stacked in a thickness direction of the battery cell; The positive electrode sheet comprises a positive electrode tab, a positive current collecting portion, and a positive electrode film layer provided on at least one surface of the positive current collecting portion along the thickness direction and containing a positive electrode active material, wherein the positive electrode tab is provided on at least one side of the positive current collecting portion; The negative electrode sheet comprises a negative electrode tab, a negative electrode current collector, and a negative electrode film layer provided on at least one surface of the negative electrode current collector along the thickness direction and containing a negative electrode active material, wherein the negative electrode tab is provided on at least one side of the negative electrode current collector. The ratio of the size of the positive electrode film layer along the length direction of the battery cell to the size of the positive electrode film layer along the width direction of the battery cell is 4 to 20, and the size of the positive electrode film layer along the length direction is 600 mm to 1200 mm; The single-sided coating weight of the negative electrode film layer is 74 mg / 1540.25 mm 2 Up to 156mg / 1540.25mm 2 .

2. The battery cell according to claim 1, characterized in that: The dimension of the positive electrode film layer along the width direction is 60 mm to 150 mm.

3. The battery cell according to claim 1, characterized in that: The positive electrode tabs are arranged on both sides of the positive electrode current collecting portion along the length direction.

4. The battery cell according to claim 1, characterized in that: There are one or more positive electrode tabs located on the same side of the positive current collecting portion, and the positive electrode tab includes a first end face connected to the positive current collecting portion, and the size of the first end face along the width direction is W1. The sum of the sizes of all first end faces located on the same side of the positive current collecting portion along the width direction is n×W1, and the size of the positive current collecting portion along the width direction is W2, n×W1 / W2 is greater than or equal to 1 / 3, and n represents the number of all positive electrode tabs located on the same side of the positive current collecting portion.

5. The battery cell according to claim 4, characterized in that: n×W1 / W2 is greater than or equal to 2 / 3.

6. The battery cell according to claim 1, characterized in that: The negative electrode tabs are arranged on both sides of the negative electrode current collecting portion along the length direction.

7. The battery cell according to claim 6, characterized in that: There are one or more negative electrode tabs located on the same side of the negative current collecting portion, and the negative electrode tab includes a second end face connected to the negative current collecting portion, and the size of the second end face along the width direction is W3. The sum of the sizes of all second end faces located on the same side of the negative current collecting portion along the width direction is m×W3, and the size of the negative current collecting portion along the width direction is W4, m×W3 / W4 is greater than or equal to 1 / 3, and m represents the number of all negative electrode tabs located on the same side of the negative current collecting portion.

8. The battery cell according to claim 7, characterized in that: m×W3 / W4 is greater than or equal to 2 / 3.

9. The battery cell according to claim 1, characterized in that: The positive electrode tab is disposed on at least one side of the positive electrode current collecting portion along the width direction.

10. The battery cell according to claim 9, characterized in that: There are one or more positive electrode tabs located on the same side of the positive electrode current collector, and the positive electrode tab includes a third end surface connected to the positive electrode current collector, and the dimension of the third end surface along the length direction is L 10 The sum of the dimensions of all third end faces on the same side of the positive electrode current collecting portion along the length direction is s×L 10 The dimension of the positive electrode current collector along the length direction is L1, s×L 10 / L1 is greater than or equal to 1 / 3, and s represents the number of all positive electrode tabs located on the same side of the positive electrode current collecting portion.

11. The battery cell according to claim 1, characterized in that: The negative electrode tab is disposed on at least one side of the negative electrode current collecting portion along the width direction.

12. The battery cell according to claim 11, characterized in that: There are one or more negative electrode tabs located on the same side of the negative electrode current collecting portion, and the negative electrode tab includes a fourth end surface connected to the negative electrode current collecting portion, and the size of the fourth end surface along the length direction is L 20 The sum of the dimensions of all fourth end faces located on the same side of the negative electrode current collecting portion along the length direction is p×L 20 The dimension of the negative electrode current collector along the length direction is L2, p×L 20 / L2 is greater than or equal to 1 / 3, and p represents the number of all negative electrode tabs located on the same side of the negative electrode current collecting portion.

13. The battery cell according to claim 1, characterized in that: Along the length direction, the size of the negative electrode film layer is larger than that of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH1, and OH1 is 0.5 mm to 3.0 mm; and / or Along the width direction, the size of the negative electrode film layer is larger than that of the positive electrode film layer, and the size difference between the negative electrode film layer and the positive electrode film layer is OH2, and OH2 is 0.5 mm to 3.0 mm.

14. The battery cell according to claim 1, characterized in that: The positive electrode tabs are arranged on both sides of the positive electrode current collecting portion along the length direction, and the negative electrode tabs are arranged on both sides of the negative electrode current collecting portion along the length direction. Along the length direction, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH1; Along the width direction, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH2, Among them, OH1 is greater than OH2.

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

16. The battery cell according to claim 1, characterized in that: The battery cell further includes a positive terminal, which is connected to the positive electrode tab. There are one or at least two positive terminals.

17. The battery cell according to claim 16, characterized in that: There are at least two positive terminals.

18. The battery cell according to claim 15, characterized in that: The flow area of ​​a single positive terminal is 200mm 2 Up to 800mm 2 .

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

20. The battery cell according to claim 1, characterized in that: The battery cell further includes a negative terminal, which is connected to the negative electrode tab. There are one or at least two negative terminals.

21. The battery cell according to claim 20, characterized in that: There are at least two negative electrode terminals.

22. The battery cell according to claim 19, characterized in that: The flow area of ​​a single negative terminal is 200 mm 2 Up to 800mm 2 .

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

24. The battery cell according to claim 23, characterized in that: The thickness of the shell is 0.2 mm to 0.35 mm.

25. The battery cell according to claim 1, characterized in that The single-sided coating weight of the positive electrode film layer is 160 mg / 1540 mm 2 Up to 340mg / 1540 / mm 2 ; and / or The compaction density of the positive electrode film layer of the battery cell at 100% charge state is 2.50 g / cm 3 Up to 2.80g / cm 3 .

26. The battery cell according to claim 1, characterized in that: The powder resistivity of the positive electrode active material is 1Ω•cm to 27.5Ω•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.

27. The battery cell according to claim 1, characterized in that: The positive electrode active material includes a lithium-containing phosphate with an olivine structure, and the lithium-containing phosphate with an olivine structure includes: 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.

28. The battery cell according to claim 27, 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.

29. The battery cell according to claim 27, 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.

30. The battery cell according to claim 27, characterized in that: The graphitization degree of the lithium-containing phosphate with an olivine structure is 0.15 to 0.

32.

31. The battery cell according to claim 30, characterized in that: The graphitization degree of the lithium-containing phosphate with an olivine structure is 0.19 to 0.

26.

32. The battery cell according to claim 27, characterized in that: The mass content of carbon in the lithium-containing phosphate with olivine structure is 1% to 2%. The specific surface area of ​​the lithium-containing phosphate of the olivine structure is 5m 2 / g to 18m 2 / g.

33. The battery cell according to claim 32, 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.

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

35. The battery cell according to claim 27, characterized in that The smallest particle size of the lithium-containing phosphate with an olivine structure is 0.1 μm to 0.4 μm; and / or The maximum particle size of the olivine-structured lithium-containing phosphate is 15 μm to 25 μm.

36. The battery cell according to claim 1, characterized in that The ratio of the thickness of the positive electrode current collector to the thickness of the positive electrode film layer on one side is 0.05 to 0.

3.

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

38. 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.

39. 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.

40. The battery cell according to claim 39, characterized in that The mass content of the first material in the positive electrode film layer is 0.5% to 5%.

41. 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 .

42. 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 under 20000N is 1.5g / cm 3 Up to 1.85g / cm 3 ; and / or The negative electrode active material has a charge capacity of 350 mAh / g to 480 mAh / g at a charge rate of 0.1C.

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

44. The battery cell according to claim 43, 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.

45. The battery cell according to claim 44, characterized in that The mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles.

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

47. 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.

48. 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.

49. The battery cell according to claim 48, 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.

50. The battery cell according to claim 48, characterized in that The tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer.

51. The battery cell according to claim 50, characterized in that The tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 Up to 1.21g / cm 3 , and / or The tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 Up to 1.25g / cm 3 .

52. The battery cell according to claim 48, 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.

53. The battery cell according to claim 52, 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%.

54. The battery cell according to claim 52, 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%.

55. The battery cell according to claim 52, 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).

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

57. 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.

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

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

60. The battery cell according to claim 59, characterized in that The mass content of the chain carboxylic acid ester solvent in the organic solvent is 30% to 75%.

61. The battery cell according to claim 59, 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.

62. The battery cell according to claim 61, 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.

63. The battery cell according to claim 62, 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, 。 64. The battery cell according to claim 59, characterized in that The organic solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

65. The battery cell according to claim 64, characterized in that The carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

66. The battery cell according to claim 64, characterized in that The mass content of the carbonate solvent in the organic solvent is 25% to 95%.

67. The battery cell according to claim 1, characterized in that The battery cell includes an electrolyte, and the electrolyte also includes an additive. The additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive.

68. The battery cell according to claim 67, 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).

69. The battery cell according to claim 67, characterized in that The mass content of the additive in the electrolyte is 1% to 10%.

70. The battery cell according to claim 69, characterized in that The mass content of the additive in the electrolyte is 2% to 8%.

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

72. The battery cell according to claim 71, characterized in that The fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

73. The battery cell according to claim 72, 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.

74. The battery cell according to claim 73, characterized in that The ratio of the molar concentration of the lithium bis(fluorosulfonyl)imide to the molar concentration of the lithium hexafluorophosphate is 0.2 to 1.

0.

75. The battery cell according to claim 1, characterized in that The isolation membrane includes a base membrane with a porous structure, the thickness of the base membrane is 6 μm to 12 μm; and / or the porosity of the base membrane is 35% to 60%.

76. The battery cell according to claim 75, 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.

77. The battery cell according to claim 76, characterized in that The non-fluorinated polymer particles include acrylic copolymers.

78. The battery cell according to claim 76, 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; and / or 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.

79. The battery cell according to claim 76, characterized in that The average particle size of the second inorganic particles is 5 nm to 100 nm.

80. The battery cell according to claim 1, characterized in that The charging time of the battery cell from 20% state of charge to 80% state of charge is 6 minutes to 15 minutes.

81. A battery device, characterized in that: Comprising the battery cell according to any one of claims 1 to 80.

82. The battery device according to claim 81, characterized in that The charging time of the battery device from a 20% state of charge to an 80% state of charge is 6 minutes to 15 minutes.

83. An electrical device, characterized in that: Comprising a battery device as described in claim 81.

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