Battery cell, battery device and electric device

Abstract

A battery cell, a battery device and an electric device. The battery cell (7) comprises an electrode assembly (10) and an electrolyte, and the electrode assembly (10) comprises a positive electrode sheet (11), a separator (13) and a negative electrode sheet (12), which are stacked in its own direction of thickness, wherein the positive electrode sheet (11) comprises a positive electrode tab (111), a positive electrode current-collecting portion (112), and a positive electrode film layer (113) arranged on a surface of the positive electrode current-collecting portion (112) in the direction of thickness and containing a positive electrode active material, the positive electrode tab (111) being arranged on at least one side of the positive electrode current-collecting portion (112); the negative electrode sheet (12) comprises a negative electrode tab (121), a negative electrode current-collecting portion (122), and a negative electrode film layer (123) arranged on a surface of the negative electrode current-collecting portion (122) in the direction of thickness and containing a negative electrode active material, the negative electrode tab (121) being arranged on at least one side of the negative electrode current-collecting portion (122); the ratio of the length to the width of the positive electrode film layer (113) ranges from 4 to 20; the dimension of the positive electrode film layer (113) in the direction of length ranges from 600 mm to 1200 mm; and the single-sided coating weight of the negative electrode film layer (123) ranges from 74 mg / 1540.25 mm2 to 156 mg / 1540.25 mm2. The usage reliability and cycle performance of the battery cell can be improved.

Description

Battery cell, battery device and electric device TECHNICAL FIELD

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

[0002] Battery cells have characteristics of high capacity and long service life, and are widely used in electronic devices such as mobile phones, notebook computers, electric vehicles, electric cars, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes and electric tools. Due to great progress in the field of batteries, higher requirements are put forward for the performance of batteries. However, the battery cell cannot improve the energy density and the rapid charging performance at the same time.

[0003] SUMMARY

[0004] The present application provides a battery cell, a battery device and an electric device, which can improve the use reliability and cycle performance of the battery cell.

[0005] In a first aspect, the present application provides a battery cell, the battery cell comprising an electrode assembly, the electrode assembly comprising a positive electrode sheet, a separator film and a negative electrode sheet stacked along a thickness direction of the battery cell; the positive electrode sheet comprising a positive electrode tab, a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector along the thickness direction and containing a positive electrode active material, the positive electrode tab being provided on at least one side of the positive electrode current collector; the negative electrode sheet comprising 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, the negative electrode tab being provided on at least one side of the negative electrode current collector, wherein a ratio of a length to a 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; and a single-sided coating weight of the negative electrode film layer is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 It should be noted that the size of the positive electrode film layer along the length direction is the length of the positive electrode film layer, and the size of the positive electrode film layer along the width direction is the width of the positive electrode film layer.

[0006] Therefore, when the length to width ratio of the positive electrode film layer is in the above range and the single-sided coating weight of the negative electrode film layer is in the above range, the current distribution in the positive electrode current collector and the negative electrode current collector is more uniform, the lithium uniformly extracted can be uniformly embedded in the negative electrode sheet, the negative electrode sheet is less likely to occur lithium precipitation, the rapid charging performance of the battery cell can be improved, and the energy density can be improved.

[0007] In some embodiments, the width of the positive electrode film layer is 60 mm to 150 mm. The width of the positive electrode film layer is relatively short, so that the electron transport path in the width direction is short, and the uniformity of the current in the width direction can be improved.

[0008] In some embodiments, the positive electrode tabs are arranged on both sides of the positive electrode current collector along the length direction of the electrode assembly. The positive electrode tabs are arranged on both sides of the positive electrode current collector along the length direction, so that the current in the length direction of the positive electrode current collector is evenly distributed to the positive electrode tabs on both sides, the electron transport path is short, the current distribution is more uniform, the delithiation state of the positive electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0009] In some embodiments, the positive electrode tabs on the same side of the positive electrode current collector are one or more, the positive electrode tab includes a first end surface connected to the positive electrode current collector, the size of the first end surface along the width direction is W1, the size of all the first end surfaces on the same side of the positive electrode current collector along the width direction is n*W1, the size of the positive electrode current collector along the width direction is W2, n*W1 / W2 is greater than or equal to 1 / 3, and n represents the number of all the positive electrode tabs on the same side of the positive electrode current collector. Optionally, n*W1 / W2 is greater than or equal to 2 / 3, and n represents the number of all the positive electrode tabs on the same side of the positive electrode current collector.

[0010] Therefore, when n*W1 / W2 satisfies the above range, the overcurrent area of the positive electrode tab is relatively large, which is beneficial to improve the rapid charging performance of the battery cell.

[0011] In some embodiments, the negative electrode tabs are arranged on both sides of the negative electrode current collector along the length direction of the electrode assembly. The negative electrode tabs are arranged on both sides of the negative electrode current collector along the length direction, so that the current in the length direction of the negative electrode current collector is evenly distributed to the negative electrode tabs on both sides, the electron transport path is short, the current distribution is more uniform, the lithium intercalation state of the negative electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0012] In some embodiments, the negative electrode tabs on the same side of the negative electrode current collector are one or more, the negative electrode tab includes a second end surface connected to the negative electrode current collector, the size of the second end surface along the width direction is W3, the size of all the second end surfaces on the same side of the negative electrode current collector along the width direction is m*W3, the size of the negative electrode current collector along the width direction is W4, m*W3 / W4 is greater than or equal to 1 / 3, and m represents the number of all the negative electrode tabs on the same side of the negative electrode current collector. Optionally, m*W3 / W4 is greater than or equal to 2 / 3, and m represents the number of all the negative electrode tabs on the same side of the negative electrode current collector.

[0013] Therefore, when m*W3 / W4 satisfies the above range, the overcurrent area of the negative electrode tab is relatively large, which is beneficial to improve the rapid charging performance of the battery cell.

[0014] In some embodiments, the positive electrode tabs are arranged on at least one side of the positive electrode current collector in the width direction. The electron transport path in the positive electrode current collector is shorter, and the current distribution is more uniform, the delithiation state of the positive electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0015] In some embodiments, the positive electrode tabs on the same side of the positive electrode current collector are one or more, and the positive electrode tab includes a third end surface connected to the positive electrode current collector, the dimension of the third end surface in the length direction is L 10 , and the sum of the dimensions of all third end surfaces on the same side of the positive electrode current collector in the length direction is s*L 10 , the dimension of the positive electrode current collector in the length direction is L1, and 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.

[0016] Therefore, the flow area of the positive electrode tab is relatively large, which is conducive to improving the rapid charging performance of the battery cell.

[0017] In some embodiments, the negative electrode tabs are arranged on at least one side of the negative electrode current collector in the width direction. The electron transport path in the negative electrode current collector is shorter, and the current distribution is more uniform, the delithiation state of the negative electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0018] In some embodiments, the negative electrode tabs on the same side of the negative electrode current collector are one or more, and the negative electrode tab includes a fourth end surface connected to the negative electrode current collector, the dimension of the fourth end surface in the length direction is L 20 , and the sum of the dimensions of all fourth end surfaces on the same side of the negative electrode current collector in the length direction is p*L 20 , the dimension of the negative electrode current collector in the length direction is L2, and 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.

[0019] Therefore, the flow area of the negative electrode tab is relatively large, which is conducive to improving the rapid charging performance of the battery cell.

[0020] In some embodiments, in the length direction, the dimension of the negative electrode film layer is greater than the dimension of the positive electrode film layer, and the difference between the dimension of the negative electrode film layer and the dimension of the positive electrode film layer is OH1, and OH1 is 0.5 mm to 3.0 m. The dimension of the negative electrode film layer is greater than the dimension of the positive electrode film layer, which can reduce the risk of lithium precipitation.

[0021] In some embodiments, the size of the negative electrode film layer is greater than the size of the positive electrode film layer in the width direction, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH2, OH2 is 0.5 mm to 3.0 mm. The size of the negative electrode film layer being greater than the size of the positive electrode film layer can reduce the risk of lithium precipitation.

[0022] In some embodiments, the positive electrode tabs are arranged on both sides of the positive electrode current collecting part in the length direction, the negative electrode tabs are arranged on at least one side of the negative electrode current collecting part in the length direction, the size of the negative electrode film layer is greater than the size of the positive electrode film layer in the length direction of the battery monomer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH1; the size of the negative electrode film layer is greater than the size of the positive electrode film layer in the width direction of the battery monomer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH2, wherein OH1 is greater than OH2.

[0023] Therefore, the embodiments of the present application set OH1 to be greater than OH2, so that the ability of the negative electrode film layer to receive lithium ions in the length direction is stronger, especially the ability of the area of the negative electrode film layer close to the negative electrode tab to receive lithium ions is improved, the risk of lithium precipitation is reduced, and the use reliability of the battery monomer is improved.

[0024] In some embodiments, the battery monomer further comprises a positive electrode terminal, and the positive electrode terminal is electrically connected with the positive electrode tab.

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

[0026] In some embodiments, the battery monomer further comprises a positive electrode terminal, and the positive electrode terminal is connected with the positive electrode tab. The positive electrode terminal can be one or at least two, and can be at least two. At least two positive electrode terminals can increase the overall current-carrying capacity of the positive electrode terminal.

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

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

[0029] In some embodiments, the battery monomer further comprises a negative electrode terminal, and the negative electrode terminal is electrically connected with the negative electrode tab.

[0030] In some embodiments, the battery cell further comprises a negative terminal, the negative terminal is connected with the negative tab, and the negative terminal is one or at least two, and optionally at least two. The at least two negative terminals can increase the overall current-carrying capacity of the negative terminals.

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

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

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

[0034] In some embodiments, the battery cell comprises a shell, the shell contains the electrode assembly and the electrolyte, and the thickness of the shell is 0.1mm to 0.5mm, and optionally 0.2mm to 0.35mm. The thickness of the shell is relatively thin, the space occupied by the shell is relatively small, and the energy density of the battery cell can be further improved.

[0035] In some embodiments, under a 100% state of charge, the compaction density of the positive film layer of the battery cell is 2.50g / cm 3 to 2.80g / cm 3 , and optionally 2.55g / cm 3 to 2.70g / cm 3 . When the compaction density of the positive film layer is in the above range, it is conducive to improving the energy density of the battery cell; and because the positive active material in the positive film layer is packed relatively tightly, the contact resistance between particles is relatively small, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0036] In some embodiments, the single-side coating weight of the positive film layer is 160mg / 1540.25mm 2 to 340mg / 1540.25mm 2 . When the single-side coating weight of the positive film layer is in the above range, the heat generation per unit area of the positive electrode sheet will not be too large, and the energy density of the battery cell can be improved.

[0037] In some embodiments, the powder resistivity of the positive active material is 1Ω·cm to 27.5Ω·cm. The relatively low powder resistivity of the positive active material makes the resistance of the positive electrode sheet relatively low, and the battery cell generates less heat.

[0038] In some embodiments, the powder compaction density of the positive electrode active material under 30000N is 2.46g / cm3 to 2.8g / cm3. 3 to 2.8g / cm3 3 When the powder compaction density of the positive electrode active material under 30000N is in the above range, the energy density of the battery cell can be improved, and the positive electrode active material in the positive electrode film layer can be more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0039] In some embodiments, the charge gram capacity of the positive electrode active material under 0.1C rate is 150mAh / g to 170mAh / g. When the charge gram capacity of the positive electrode active material under 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0040] In some embodiments, the olivine structure lithium-containing phosphate includes phosphate particles and a coating layer, the coating layer coats the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge and Sn. The phosphate particles are coated with the coating layer on the surface, which can improve the conductivity of the olivine structure lithium-containing phosphate, reduce the powder resistivity of the material, and facilitate the migration rate of lithium ions, thereby reducing the heat generation of the battery cell.

[0041] In some embodiments, the phosphate particles include a compound with a general formula of Li x1 A y1 Me a M b P 1-c X c Y z , wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F. The cycle stability of the phosphate particles is relatively excellent, which is conducive to improving the cycle performance of the battery cell.

[0042] In some embodiments, the coating layer includes a compound with a general formula of Li 3-d Fe 2-d M2d (PO x2 ) y2 The fast ion conductor includes M2PO4, M2 includes one or more elements of Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0

[0043] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, and optionally 0.19 to 0.26. When the graphitization degree of the positive electrode active material is in the above range, the conductivity of the positive electrode active material is improved, and the heat generation of the positive electrode plate is reduced, thereby reducing the heat generation of the battery cell.

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

[0045] Therefore, the material with the above mass content of carbon elements and the above specific surface area is more conducive to the effective contact between the electrolyte and the olivine-structured lithium-containing phosphate, and is conducive to the transmission of lithium ions at the phase interface.

[0046] In some embodiments, the olivine-structured lithium-containing phosphate is in a particulate form, and the volume distribution particle size satisfies 1μm≤Dv50≤2μm and 0.4μm≤Dv10≤0.7μm. The particle size of the olivine-structured lithium-containing phosphate is relatively small, the path of lithium ions in the positive electrode active material is relatively short, and the heat generation is relatively small. In addition, the particle size of the above positive electrode active material is not too small, and agglomeration basically does not occur in the process of preparation and processing, so that the performance of the positive electrode active material is stable.

[0047] In some embodiments, the olivine-structured lithium-containing phosphate is in a particulate form, and the olivine-structured lithium-containing phosphate includes secondary particles, the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200nm to 500nm. The average particle size of the primary particles is relatively small, the path of lithium ions in the positive electrode active material is relatively short, and the heat generation is relatively small.

[0048] In some embodiments, the particle size of the smallest particles in the olivine-structured lithium-containing phosphate is 0.1μm to 0.4μm. When the particle size of the smallest particles is in the above range, agglomeration does not easily occur in the process of preparing and forming the positive electrode film layer.

[0049] In some embodiments, the largest particle in the lithium-containing olivine-structured phosphate has a particle size of 15 μm to 25 μm. When the largest particle has a particle size in the above range, the migration path of lithium ions during charging and discharging is not too long, and the rapid charging and discharging performance of the battery cell can be improved.

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

[0051] In some embodiments, the thickness of the positive current collector is 10 μm to 15 μm. When the thickness of the positive current collector is in the above range, the overcurrent capability of the positive current collector is excellent, and the battery cell has a high energy density.

[0052] In some embodiments, the positive film layer further comprises a first material, and the first material comprises one or more of a ternary material, lithium phosphate, lithium dihydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metavanadate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. The above first material can serve as a lithium supplement, can supplement lithium ions for the positive 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 in the positive film layer is 0.5% to 5%. When the mass content of the lithium supplement is in the above range, lithium ions can be supplemented for the positive film layer, the irreversible loss of lithium ions in the system can be made up, the capacity can be improved, and thus the energy density of the battery cell can be improved.

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

[0055] In some embodiments, the thickness of the positive conductive layer is 0.5 μm to 2 μm. When the thickness of the positive conductive layer is in the above range, the conductivity of the positive electrode sheet can be further improved, the heat generation of the positive electrode sheet can be reduced, the heat generation of the battery cell can be reduced, and the energy density of the battery cell can be improved.

[0056] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet, reducing the heat generation of the battery cell, and the positive electrode binder in the positive electrode conductive layer can improve the adhesion between the positive electrode current collector and the positive electrode film layer, thereby improving the structural stability of the positive electrode sheet.

[0057] In some embodiments, the positive electrode conductive agent comprises one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0058] In some embodiments, the positive electrode binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a polyacrylic acid, and a fluorine-containing acrylic ester resin.

[0059] In some embodiments, the powder compaction density of the negative electrode active material at 20,000 N is 1.5 g / cm 3 to 1.85 g / cm 3 When the powder compaction density of the negative electrode active material at 20,000 N is within the above range, the energy density of the battery cell can be improved, and the negative electrode active material in the negative electrode film layer can be more tightly packed, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0060] In some embodiments, the charge gram capacity of the negative electrode active material at a 0.1C rate is greater than or equal to 350 mAh / g. When the charge gram 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 comprises a carbon-based material, and the carbon-based material comprises 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 rapid charging performance of the battery cell.

[0062] In some embodiments, the graphite particles comprise artificial graphite and a carbon coating layer, the artificial graphite comprises secondary particles, and the carbon coating layer is coated on the surface of the artificial graphite. The carbon coating layer has more end faces and defects, so that the number of sites capable of deintercalating lithium ions is more, and the conductive performance 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, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. When the mass content of the carbon coating layer is in 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 arranged on the surface of the negative electrode current collector, the first negative electrode film layer includes a carbon-based material, the second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, the second negative electrode film layer includes a carbon-based material, the carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently includes graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0065] Therefore, in the embodiments of the present application, there is a difference in particle size between the first negative electrode film layer and the second negative electrode film layer, which can improve the rapid charging performance of the battery cell. Specifically, during rapid charging, the overpotential of the second negative electrode film layer is usually high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and improve the problem of lithium extraction 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 more densely packed, so that the energy density of the battery cell is improved, and the first negative electrode film layer is relatively sparse in packing, with more pores, which can improve the rapid 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 in the appropriate range, the rapid 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 in the appropriate range, the energy density of the battery cell can be improved.

[0070] In some embodiments, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 pm to 18.5 pm. When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is in the above range, the rapid charging performance can be improved.

[0071] In some embodiments, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 pm to 14.3 pm. When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is in the above range, the rapid charging performance of the battery cell can be improved.

[0072] In some embodiments, the first negative electrode film layer further comprises a first lithium-containing binder, and the second negative electrode film layer further comprises a second lithium-containing binder, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0073] Thus, in the embodiments of the present application, the mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides a relatively large number of lithium ions that can move freely in the second negative electrode film layer, which can further improve the rapid charging performance of the battery cell.

[0074] In some embodiments, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. When the mass content of the first lithium-containing binder is in the above range, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0075] In some embodiments, the mass content of lithium in the first lithium-containing binder is 3% to 10%, and optionally 3% to 8%. When the mass content of lithium is in the above range, the number of lithium ions that can move freely in the negative electrode film layer is relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0076] In some embodiments, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. When the mass content of lithium in the second lithium-containing binder is in the above range, the deintercalation rate of lithium ions is improved, and the rapid charging performance of the battery cell is improved.

[0077] In some embodiments, the mass content of lithium in the second lithium-containing binder is 3% to 10%, and optionally 3% to 8%. When the mass content of lithium is in the above range, the number of lithium ions that can move freely in the negative electrode film layer is relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0078] In some embodiments, the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0079] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery monomer, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0080] In some embodiments, the second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0081] Thus, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery monomer, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0082] In some embodiments, the negative active material further comprises a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10.0%, based on the mass of the negative active material. The introduction of the silicon-based material can improve the capacity of the negative active material and increase the energy density of the battery monomer.

[0083] In some embodiments, the thickness of the negative current collector is 4 μm to 6 μm. When the thickness of the negative current collector is in the above range, the overcurrent capacity of the negative current collector is excellent, and the battery monomer has a high energy density.

[0084] In some embodiments, the negative electrode sheet further comprises a negative conductive layer, and the negative conductive layer is located between the negative electrode film layer and the negative current collector.

[0085] In some embodiments, the thickness of the negative conductive layer is 0.5 μm to 2 μm. The negative conductive layer can further improve the conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery monomer.

[0086] In some embodiments, the negative electrode conductive layer comprises one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet, reducing the heat generation of the battery cell, and the negative electrode binder in the negative electrode conductive layer can improve the adhesion between the negative electrode current collector and the negative electrode film layer, thereby improving the structural stability of the negative electrode sheet.

[0087] In some embodiments, the negative electrode conductive agent comprises one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the negative electrode binder comprises one or more of styrene-butadiene rubber, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0089] In some embodiments, the separator film comprises a base film with a porous structure, and the porosity of the base film is 20% to 70%. When the porosity of the separator film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0090] In some embodiments, the separator film comprises a base film with a porous structure, and the porosity of the base film is 35% to 60%. When the porosity of the separator film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0091] In some embodiments, the thickness of the base film is 6 μm to 12 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0092] In some embodiments, the thickness of the base film is 6 μm to 9 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0093] In some embodiments, the separator film comprises a base film and a functional layer arranged on at least one side of the base film, the functional layer comprises a first functional layer and a second functional layer, the first functional layer is arranged on one side of the base film, the first functional layer comprises first inorganic particles, the second functional layer is arranged on the other side of the base film, the second functional layer comprises composite particles, the composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

[0094] In some embodiments, the non-fluoropolymer particles include an acrylate copolymer. The acrylate copolymer has excellent adhesion properties, and has high adhesion stability with the base film.

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

[0096] In some embodiments, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above second inorganic particles can improve the heat resistance of the first functional layer.

[0097] In some embodiments, the average particle diameter of the second inorganic particles is 5 nm to 100 nm. When the average particle diameter of the second inorganic particles is in the above range, the heat resistance and the compression modulus of the composite particles can be improved.

[0098] In some embodiments, the carboxylate solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate 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 carboxylate solvent is in the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0099] In some embodiments, the chain carboxylate solvent includes a compound represented by Formula I,

[0100] In Formula I,

[0101] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group, and R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group. In this way, the above chain carboxylate solvent in the embodiments has a relatively high conductivity, which is beneficial to improving the rapid charging capability of the battery cell.

[0102] In some embodiments, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 halogenated alkyl group.

[0103] In some embodiments, R2 includes a C1 to C3 alkyl group or a C1 to C3 halogenated alkyl group.

[0104] In some embodiments, the chain carboxylate solvent includes one or more of a compound represented by Formula I-1 to a compound represented by Formula I-8,

[0105] 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 methyl ethyl carbonate. The carbonate solvent and the chain carboxylic acid ester solvent are used in combination, so that the conductivity of the electrolyte is improved, and the migration of lithium ions is facilitated.

[0106] In some embodiments, the carbonate solvent comprises one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate.

[0107] In some embodiments, the mass content of the carbonate solvent in the organic solvent is 25% to 95%, or optionally 25% to 70%. The carbonate solvent in the above mass content can further improve the conductivity of the electrolyte, and facilitate the migration of lithium ions.

[0108] 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 additive can improve the interface film performance on the positive electrode side and / or the negative electrode side, facilitate the improvement of the rapid charging performance of the battery cell, and improve the cycle performance.

[0109] In some embodiments, the carbonate additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0110] In some embodiments, the sulfur-containing additive comprises one or more of vinyl sulfonate DTD, bis vinyl sulfonate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, vinyl sulfite ES, and methyl methylene disulfonate MMDS.

[0111] In some embodiments, the lithium salt additive comprises one or more of lithium difluorophosphate LiPO2F2, lithium difluoro oxalate borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bisoxalate borate LiBOB.

[0112] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, or optionally 2% to 8%. The additive in the above mass content can effectively improve the interface film performance on the positive electrode side and / or the negative electrode side, facilitate the improvement of the rapid charging performance of the battery cell, and improve the cycle performance.

[0113] In some embodiments, the electrolyte further comprises a lithium salt, and the lithium salt comprises one or more of a fluorine-containing sulfonimide salt and lithium hexafluorophosphate LiPF6. The lithium salt is easy to dissociate, facilitates the rapid migration of lithium ions, and the electrolyte system is relatively stable and is not easy to decompose, which can improve the cycle performance of the battery cell.

[0114] In some embodiments, the fluorine-containing sulfimide salt comprises one or more of lithium bisfluorosulfimide (LiFSI), lithium bis-trifluoromethanesulfonamide (LiTFSI).

[0115] In some embodiments, the lithium salt comprises lithium bisfluorosulfimide (LiFSI) and lithium hexafluorophosphate (LiPF6), the molar concentration of lithium bisfluorosulfimide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0116] In some embodiments, the ratio of the molar concentration of lithium bisfluorosulfimide (LiFSI) to the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.2 to 1.0.

[0117] 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, and the battery cell has a faster charging speed, which is more conducive to improving the rapid charging capability.

[0118] 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, and the battery cell has a faster charging speed, which is more conducive to improving the rapid charging capability.

[0119] 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 battery device has a faster charging speed, which is more conducive to improving the rapid charging capability.

[0120] 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 battery device has a faster charging speed, which is more conducive to improving the rapid charging capability. BRIEF DESCRIPTION OF DRAWINGS

[0121] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0122] FIG. 1 is a structural schematic diagram of a battery cell provided by some embodiments of the present application;

[0123] FIG. 2 is an exploded schematic diagram of a battery cell provided by some embodiments of the present application;

[0124] FIG. 3 is a cross-sectional schematic diagram of an electrode assembly of a battery cell provided by some embodiments of the present application;

[0125] FIG. 4 is a structural schematic diagram of a positive electrode sheet of a battery cell provided by some embodiments of the present application;

[0126] FIG. 5 is a structural diagram of a negative electrode tab of a battery cell according to some embodiments of the present application;

[0127] FIG. 6 is a structural diagram of a positive electrode tab of a battery cell according to some embodiments of the present application;

[0128] FIG. 7 is a structural diagram of a negative electrode tab of a battery cell according to some embodiments of the present application;

[0129] FIG. 8 is a structural diagram of an electrode assembly of a battery cell according to some embodiments of the present application;

[0130] FIG. 9 is a structural diagram of a battery cell according to some embodiments of the present application;

[0131] FIG. 10 is a structural diagram of a battery module according to some embodiments of the present application;

[0132] FIG. 11 is a structural diagram of a battery pack according to some embodiments of the present application;

[0133] FIG. 12 is a structural diagram of an electric device according to some embodiments of the present application.

[0134] The accompanying drawings are not necessarily drawn to scale.

[0135] The reference signs are explained as follows:

[0136] X: thickness direction; Y: width direction; Z: length direction

[0137] 1: electric device; 2: battery pack; 3: controller; 4: motor; 5: case; 5a: first case portion; 5b: second case portion; 5c: accommodation space; 6: battery module

[0138] 7: battery cell

[0139] 10: electrode assembly

[0140] 11: positive electrode tab; 111: positive electrode tab; 1111: first end surface; 1112: third end surface; 112: positive electrode current collector; 113: positive electrode film layer

[0141] 12: negative electrode tab; 121: negative electrode tab; 1211: second end surface; 1212: fourth end surface; 122: negative electrode current collector; 123: negative electrode film layer

[0142] 13: separator

[0143] 20: housing; 21: case; 211: first case portion; 212: second case portion

[0144] 22: end cap

[0145] 31: positive terminal; 32: negative terminal. DETAILED DESCRIPTION

[0146] Hereinafter, embodiments of the battery cell, the battery device, and the electric device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters that are well known, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0147] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this manner can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., 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 particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise stated, a numerical range "a to b" indicates a shorthand way of describing all of the real combinations of a to b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all of the real numbers between "0 to 5" have been listed herein, and "0 to 5" is merely a shorthand way of describing these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0148] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0149] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0150] If not otherwise specified, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, a method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any sequence. For example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0151] With the development of the battery field, the requirements for the energy density and fast charging of the battery are gradually improved, but it is found through research that, in the case of improving the energy density of the battery, the increase of the transmission resistance of active ions such as lithium ions makes the battery monomer unable to realize fast charging, and the energy density and fast charging capability of the battery cannot be improved at the same time.

[0152] In view of the above problems, the embodiments of the present application design the battery monomer, improve the structure form, size and coating weight of the film layer of the pole piece, so that the energy density and fast charging capability of the battery monomer can be improved at the same time.

[0153] Battery monomer

[0154] In a first aspect, the embodiments of the present application provide a battery monomer.

[0155] As shown in FIGS. 1-5, the battery monomer 7 comprises an electrode assembly 10 and an electrolyte, the electrode assembly 10 comprises a positive pole piece 11, a separator film 13 and a negative pole piece 12 stacked along the thickness direction X of the battery monomer 7; the positive pole piece 11 comprises a positive pole lug 111, a positive current collecting part 112 and a positive film layer 113 containing positive active material and arranged on at least one surface of the positive current collecting part 112 along the thickness direction X, and the positive pole lug 111 is arranged on at least one side of the positive current collecting part 112; the negative pole piece 12 comprises a negative pole lug 121, a negative current collecting part 122 and a negative film layer 123 containing negative active material and arranged on at least one surface of the negative current collecting part 122 along the thickness direction X, and the negative pole lug 121 is arranged on at least one side of the negative current collecting part 122, wherein the ratio of the length to the width of the positive film layer 113 is 4-20; the length of the positive film layer 113 is 600-1200 mm; the single-sided coating weight of the negative film layer 123 is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 .

[0156] The electrode assembly 10 of the embodiments of the present application is a laminated electrode assembly 10, and the positive electrode tab 11, the separator 13, and the negative electrode tab 12 are formed into the electrode assembly 10 through a lamination process. The thickness direction X of the electrode assembly 10, the thickness direction of the positive electrode tab 11, and the thickness direction of the negative electrode tab 12 are parallel, the width direction of the electrode assembly 10, the width direction of the positive electrode tab 11, and the width direction of the negative electrode tab 12 are parallel, and the length direction of the electrode assembly 10, the length direction of the positive electrode tab 11, and the length direction of the negative electrode tab 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, Y represents the width direction of the electrode assembly 10, and Z represents the length direction of the electrode assembly 10.

[0157] In the embodiments of the present application, the size of the positive electrode tab 11 along the thickness direction of the battery cell 7 can be understood as the thickness of the positive electrode tab 11. The size of the positive electrode tab 11 along the length direction of the battery cell 7 can be understood as the length of the positive electrode tab 11. The size of the positive electrode tab 11 along the width direction of the battery cell 7 can be understood as the width of the positive electrode tab 11. In FIG. 4, the length of the positive current collector portion 112 is equal to the length of the positive film layer 113, and L1 can represent the length of the positive film layer 113 or the length of the positive current collector portion 112. In FIG. 4, the width of the positive current collector portion 112 is equal to the width of the positive film layer 113, and W2 can represent the width of the positive film layer 113 or the width of the positive current collector portion 112.

[0158] In the embodiments of the present application, the size of the negative electrode tab 12 along the thickness direction of the battery cell 7 can be understood as the thickness of the negative electrode tab 12. The size of the negative electrode tab 12 along the length direction of the battery cell 7 can be understood as the length of the negative electrode tab 12. The size of the negative electrode tab 12 along the width direction of the battery cell 7 can be understood as the width of the negative electrode tab 12. In FIG. 5, the length of the negative current collector portion 122 is equal to the length of the negative film layer 123, and L2 can represent the length of the negative film layer 123 or the length of the negative current collector portion 122. In FIG. 5, the width of the negative current collector portion 122 is equal to the width of the negative film layer 123, and W4 can represent the width of the negative film layer 123 or the width of the negative current collector portion 122.

[0159] Both the positive electrode tab 11 and the negative electrode tab 12 have an impact on the energy density and the fast charging performance of the battery cell 7, and by improving the positive electrode tab 11 and the negative electrode tab 12, the energy density and the fast charging performance of the battery cell 7 are improved, specifically:

[0160] The single-side coating weight of the negative film layer 123 is less than 74 mg / 1540.25 mm 2The energy density of the battery cell 7 is small; the single-side coating weight of the negative electrode film layer 123 is greater than 156 mg / 1540.25 mm 2 Although 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 rapid charging and discharging of the battery cell 7; and in the embodiments of the present application, the single-side 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 rapid charging performance and energy density;

[0161] When the length-width ratio 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 length-width ratio of the positive electrode film layer 113, so that the length-width ratio of the positive electrode film layer 113 is less than or equal to 20, is conducive to increasing the coating weight of the positive electrode film layer 113 and improving the energy density of the battery cell 7; but as the length-width ratio of the positive electrode film layer 113 further increases, the size difference between the length and width of the positive electrode film layer 113 increases, which easily causes uneven current distribution in the positive electrode sheet 11, resulting in non-uniform charging state of the positive electrode film layer 113 during the charging process, different lithium extraction speeds of the positive electrode film layer 113, and different lithium extraction speeds of the negative electrode sheet 12, which easily leads to lithium precipitation of the negative electrode sheet 12;

[0162] When the length-width ratio 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 the positive electrode tab 111, which can be optionally provided with the positive electrode tab 111 on both sides. The positive electrode tab 111 can share the current with each other, and the electron transmission path in the positive current collector 112 is relatively short, and the current distribution is more uniform, so that the positive electrode active material in the positive electrode sheet 11 is uniformly extracted during the charging process. Because at least one side of the negative current collector 122 is provided with the negative electrode tab 121, which can be optionally provided with the negative electrode tab 121 on both sides, the negative electrode tab 121 can share the current with each other, and the electron transmission path in the negative current collector 122 is relatively short, and the current distribution is more uniform, so that the uniformly extracted lithium can be uniformly embedded in the negative electrode sheet 12, and the negative electrode sheet 12 is not prone to lithium precipitation, and the single-side coating weight of the negative electrode film layer 123 is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 , the migration path of lithium ions in the negative electrode film layer 123 is relatively short, which can improve the rapid charging performance of the battery cell 7.

[0163] Thus, by cooperatively regulating the ratio of the length and width of the positive electrode film layer 113 and the single-sided coating weight of the negative electrode film layer 123, the energy density and the rapid charging performance of the battery cell 7 can be improved.

[0164] In embodiments of the present application, the ratio of the length and 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 between any two of the aforementioned values.

[0165] In embodiments of the present application, the length of the positive electrode film layer 113 is 600 mm to 1200 mm, for example, 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 between any two of the aforementioned values. The length of the positive electrode film layer 113 is relatively long, which is conducive to increasing the coating weight of the positive electrode film layer 113 and improving the energy density of the battery cell 7.

[0166] In some embodiments, the width of the positive electrode film layer 113 is 60 mm to 150 mm, for example, 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 between any two of the aforementioned values. The width of the positive electrode film layer 113 is relatively short, which makes the transmission path of electrons in the width direction Y shorter and improves the uniformity of the current in the width direction Y.

[0167] The positive electrode tab 111 is disposed on at least one side of the positive electrode current collector 112.

[0168] 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 length direction Z, and optionally, the positive electrode tab 111 is arranged 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 longer, the current distribution in the length direction Z is uneven, and the positive electrode tab 111 arranged on both sides of the positive electrode current collector 112 along the length direction Z can evenly divide the current of the positive electrode current collector 112 in the length direction Z, the electron transmission path is shorter, and the current distribution is more uniform, the delithiation state of the positive electrode tab 11 is uniform, and the charging performance of the battery cell 7 can be improved. FIG. 4 shows that the positive electrode tab 111 is arranged on both sides of the positive electrode current collector 112 along the length direction Z. The positive electrode tab 111 arranged on both sides can share the current with each other, and the electron transmission path in the positive electrode current collector 112 is shorter, the current distribution is more uniform, and the delithiation of the positive electrode active material in the positive electrode tab 11 is uniform during the charging process.

[0169] 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 length direction Z, the number of positive electrode tabs 111 on the same side of the positive electrode current collector 112 can be at least one, for example, 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, at least two positive electrode tabs 111 can increase the current flow area and evenly divide the current, thereby improving the current uniformity in the positive electrode tab 11 and further improving the rapid charging performance of the battery cell 7.

[0170] 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 positive electrode tabs 111 are arranged on the same side of the positive electrode current collector 112 along the length direction Z, or all positive electrode tabs 111 are arranged on both sides of the positive electrode current collector 112 along the length direction Z; the positive electrode tab 111 comprises a first end surface 1111 connected to the positive electrode current collector 112, the size of the first end surface 1111 along the width direction Y is W1, the size of all first end surfaces 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, n*W1 / W2 is greater than or equal to 1 / 3 and less than or equal to 1, and optionally greater than or equal to 2 / 3 and less than 1, n represents the number of all positive electrode tabs 111 on the same side of the positive electrode current collector 112, n is greater than or equal to 1, for example, when the number of all 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 positive electrode tabs 111 on the same side of the positive electrode current collector 112 is 2, n is 2.

[0171] 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 formed by any two of the above values.

[0172] When n*W1 / W2 satisfies the above range, the overcurrent area of the positive tab 111 is relatively large, which is beneficial to improve the rapid charging performance of the battery monomer 7.

[0173] The negative tab 121 is arranged on at least one side of the negative current collecting part 122.

[0174] In some embodiments, the negative tab 121 can be arranged on at least one side of the negative current collecting part 122 along the length direction Z, and optionally, the negative tab 121 is arranged on both sides of the negative current collecting part 122 along the length direction Z. Since the length of the negative current collecting part 122 is greater than the width of the negative current collecting part 122, the current transmission path in the length direction Z is longer, and the current distribution in the length direction Z is uneven. Arranging the negative tab 121 on both sides of the negative current collecting part 122 along the length direction Z makes the current in the length direction Z of the negative current collecting part 122 evenly distributed by the negative tabs 121 on both sides, the electronic transmission path is shorter, and the current distribution is more uniform, the lithium intercalation state of the negative tab 12 is uniform, and the charging performance of the battery monomer 7 can be improved. FIG. 5 shows that the negative tab 121 is arranged on both sides of the negative current collecting part 122 along the length direction Z.

[0175] In the case where the negative tab 121 is arranged on at least one side of the negative current collecting part 122 along the length direction Z, the number of negative tabs 121 on the same side of the negative current collecting part 122 can be at least one, for example, one or at least two. When the number of negative tabs 121 on the same side of the negative current collecting part 122 is at least two, the at least two negative tabs 121 can increase the overcurrent area and evenly distribute the current, improve the current uniformity in the negative tab 12, and be beneficial to further improve the rapid charging performance of the battery monomer 7.

[0176] In some embodiments, the negative tabs 121 located on the same side of the negative current collector 122 are one or more, for example, all the negative tabs 121 are located on the same side of the negative current collector 122 along the length direction Z, or all the negative tabs 121 are arranged on both sides of the negative current collector 122 along the length direction Z; the negative tab 121 comprises a second end surface 1211 connected to the negative current collector 122, the size of the second end surface 1211 along the width direction Y of the battery cell 7 is W3, the size of all the second end surfaces 1211 located on the same side of the negative current collector 122 is added to m*W3, the width of the negative current collector 122 is W4, m*W3 / W4 is greater than or equal to 1 / 3 and less than or equal to 1, which can be greater than or equal to 2 / 3 and less than 1, m represents the number of all the negative tabs 121 located on the same side of the negative current collector 122, for example, m is greater than or equal to 1, when the number of all the negative tabs 121 located on the same side of the negative current collector 122 is 1, m is 1; when the number of all the negative tabs 121 located on the same side of the negative current collector 122 is 2, m is 2.

[0177] For example, 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.

[0178] When m*W3 / W4 meets the above range, the flow area of the negative tab 121 is relatively large, which is beneficial to improve the rapid charging performance of the battery cell 7.

[0179] As shown in FIG. 6, in some embodiments, the positive tab 111 can be arranged on at least one side of the positive current collector 112 along the width direction Y, for example, one side or both sides; optionally, the positive tab 111 can be arranged on one side of the positive current collector 112 along the width direction Y. Arranging the positive tab 111 on one side of the positive current collector 112 along the width direction Y makes the electron transport path in the positive current collector 112 shorter, and the current distribution more uniform, so that the positive active material in the positive tab 11 is uniformly delithiated during the charging process.

[0180] In the case where the positive tab 111 is arranged on at least one side of the positive current collector 112 along the width direction Y, the positive tabs 111 located on the same side of the positive current collector 112 are one or more, and the positive tab 111 comprises a third end surface 1112 connected to the positive current collector 112, the size of the third end surface 1112 along the length direction Z is L 10 , the size of all the third end surfaces 1112 located on the same side of the positive current collector 112 along the length direction Z is added to s*L 10 , the size of the positive current collector 112 along the length direction Z is L1, and s*L 10 / L1 is greater than or equal to 1 / 3, can be greater than or equal to 2 / 3, and less than 1, where s represents the number of all positive electrode tabs 111 located on the same side of the positive current collector 112.

[0181] For example, s*L 10 / L1 is a range of 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 any two of the above values.

[0182] s*L 10 When L1 meets the above range, the overcurrent area of ​​the positive electrode tab 111 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0183] As shown in Figure 7, 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, such as 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 transport path in the negative electrode current collector 122 is shorter, the current distribution is more uniform, and lithium plating is less likely to occur.

[0184] 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, there are one or more negative electrode tabs 121 located on the same side of the negative electrode current collector 122. 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 The sum of the dimensions of all 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 negative electrode current collector 122 has a length dimension of L2 along the Z direction, p*L 20 / L2 is greater than or equal to 1 / 3, can be greater than or equal to 2 / 3, and less than 1, where p represents the number of all negative electrode tabs 121 located on the same side of the negative electrode current collector 122.

[0185] For example, p*L 20 / L2 is a range of 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 any two of the above values.

[0186] p*L 20 When L2 meets the above range, the overcurrent area of ​​the negative electrode tab 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0187] As shown in Figure 8, 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 the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH1, which is 0.5 mm to 3.0 mm, for example, 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 any combination of 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, each side exceeding OH1 / 2, that is, half the size of OH1, which is shown in Figure 8.

[0188] 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 the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH2, where OH2 is 0.5 mm to 3.0 mm, for example, 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 any combination of 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, each side exceeding OH2 / 2, i.e., half the size of OH2, as shown in Figure 8.

[0189] In some embodiments, the positive electrode tab 111 is connected to both sides of the positive current collector 112 along the length direction Z, and the negative electrode tab 121 is connected to both sides of the negative 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 the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH1. Along the width direction Y of the battery cell 7, the size of the negative electrode film layer 123 is larger than the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH2, where OH1 is greater than OH2. The positive electrode tab 111 and the negative electrode tab 121 are not shown in Figure 8.

[0190] The negative electrode tab 121 is located on both sides of the negative electrode current collector 122 along the length direction Z. The width of the negative electrode current collector 122 is greater than the width of the negative electrode tab 121, which makes the current flow area of ​​the negative electrode current collector 122 greater than that of the negative electrode tab 121. Due to the difference in current flow area, the current density in the connection area between the negative electrode tab 121 and the negative electrode current collector 122 increases sharply, making it easier for lithium plating and other problems to occur in this area. However, in the embodiment of this application, OH1 is set to be greater than OH2, which makes the ability of the negative electrode film layer 123 to receive lithium ions in the length direction Z stronger. In particular, it can improve the ability of the negative electrode film layer 123 to receive lithium ions in the area near the negative electrode tab 121, reduce the risk of lithium plating, and improve the reliability of the battery cell 7.

[0191] In other embodiments, the positive electrode tab 111 is connected to one side of the positive current collector 112 along the width direction Y, and the negative electrode tab 121 is connected to one side of the negative current collector 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 larger than the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH2. Along the length direction Z of the electrode assembly 10, the size of the negative electrode film layer 123 is larger than the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH1, where OH2 is greater than OH1. Of course, OH1 can also be greater than OH2.

[0192] The negative electrode tab 121 is located on one side of the negative electrode current collector 122 along the width direction Y. The length of the negative electrode current collector 122 is greater than the length of the negative electrode tab 121, which makes the current-passing area of ​​the negative electrode current collector 122 greater than the current-passing area of ​​the negative electrode tab 121. Due to the difference in current-passing area, the current density in the connection area between the negative electrode tab 121 and the negative electrode current collector 122 increases sharply, making it easier for lithium plating and other problems to occur in this area. However, in the embodiment of this application, OH2 is set to be greater than OH1, which makes the ability of the negative electrode film layer 123 to receive lithium ions in the width direction Y stronger. In particular, it can improve the ability of the negative electrode film layer 123 to receive lithium ions in the area near the negative electrode tab 121, reduce the risk of lithium plating, and improve the reliability of the battery cell 7.

[0193] Please refer to Figures 2 and 9 together. In some embodiments, the battery cell 7 may include a housing 20.

[0194] In some embodiments, the casing 20 of the battery cell 7 can be a rigid casing, such as a hard plastic casing, an aluminum casing, a steel casing, etc. The casing 20 of the battery cell 7 can also be a pouch, such as a pouch-type pouch. The material of the pouch can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0195] The outer shell 20 is a hollow structure, and the outer shell 20 can be used to encapsulate the electrode assembly 10 and the electrolyte.

[0196] The method for preparing the battery cell 7 according to the embodiments of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell 7. As an example, the positive electrode, the separator, and the negative electrode can be stacked to form an electrode assembly 10. The electrode assembly 10 is placed in a housing 20, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, the battery cell 7 is obtained.

[0197] In some embodiments, the housing 20 includes a housing 21 and an end cap 22, the housing 21 having an opening and the end cap 22 closing the opening.

[0198] The shape of the housing 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 21 are cuboid structures.

[0199] In some embodiments, the casing 21 is made of steel, which has high mechanical strength, is not easily deformed, and can improve the reliability and cycle performance of the battery cells. Optionally, steel is the material with the highest mass percentage in the casing 21.

[0200] Optionally, the thickness of the casing 21 is 0.1 mm to 0.5 mm, and optionally 0.2 mm to 0.35 mm. For example, the thickness of the casing 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 any combination of two of the above values. When the thickness of the casing 21 is within the above range, the mechanical strength of the casing 21 is high, which can improve the reliability and cycle performance of the battery cell 7. Furthermore, the casing 21 occupies less space, and the internal space of the casing 21 is larger, which is beneficial to improving the energy density of the battery cell 7.

[0201] When the shell 21 has a cuboid structure, the shell 21 includes two first shell parts 211 and two second shell parts 212. The two first shell parts 211 are arranged opposite to each other, and the two second shell parts 212 are arranged opposite to each other. The first shell parts 211 are connected between the two second shell parts 212, and the area of ​​the first shell parts 211 is larger than the area of ​​the second shell parts 212.

[0202] In some embodiments, the thickness of the first housing portion 211 is 0.1 mm to 0.5 mm, optionally 0.2 mm to 0.35 mm. The thinner thickness of the first housing portion 211 results in less space occupied by the housing 21, which can further improve the energy density of the battery cell 7.

[0203] In some embodiments, the thickness of the second shell portion 212 is 0.1 mm to 0.5 mm, optionally 0.2 mm to 0.35 mm.

[0204] In some embodiments, the thickness of the first shell portion 211 is greater than or equal to the thickness of the second shell portion 212. In other embodiments, the thickness of the first shell portion 211 is less than the thickness of the second shell portion 212.

[0205] In some embodiments, the base material of the casing 21 includes steel. Steel has high mechanical strength, is not easily deformed, and can improve the reliability and cycle performance of the battery cell. In the embodiments of this application, the base material refers to the material with the highest proportion of material in the casing 21.

[0206] In some embodiments, the battery cell 7 further includes a positive terminal 31, which is electrically connected to a positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 are welded together, and the positive terminal 31 and the positive electrode tab 111 can be connected by an adapter, or they can be connected without an adapter. Optionally, the positive terminal 31 and the positive electrode tab 111 are directly welded together without an adapter, which can reduce the resistance at the connection point and help reduce the overall internal resistance of the battery cell 7.

[0207] Optionally, the number of positive terminals 31 is at least one, and can be at least two. For example, when there are two positive terminals 31, the two positive terminals 31 are located on both sides of the positive current collector.

[0208] Optionally, the number of positive terminals 31 located on the same side of the positive current collector 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.

[0209] Further optionally, the flow area of ​​a single positive terminal 31 is greater than or equal to 200 mm². 2 200mm is optional 2 Up to 800mm 2 The flow area of ​​the positive terminal 31 can be understood as the cross-sectional area of ​​the positive terminal 31, which is perpendicular to the thickness direction of the positive terminal 31.

[0210] For example, the flow area of ​​a single positive terminal 31 can be 200 mm². 2 210mm 2 250mm2 280mm 2 300mm 2 320mm 2 350mm 2 380mm 2 400mm 2 450mm 2 500mm 2 550mm 2 600mm 2 650mm 2 700mm 2 750mm 2 800mm 2 Or a range consisting of any two of the above values.

[0211] In some embodiments, the battery cell 7 further includes a negative terminal 32, which is electrically connected to the negative electrode tab 121. Optionally, the negative terminal 32 and the negative electrode tab 121 are welded together, and the negative terminal 32 and the negative electrode tab 121 can be connected by an adapter, or they can be connected without an adapter. Optionally, the negative terminal 32 and the negative electrode tab 121 are directly welded together without an adapter, which can reduce the resistance at the connection point and help reduce the overall internal resistance of the battery cell 7.

[0212] Optionally, the number of negative terminals 32 is at least one, and optionally at least two. For example, when there are two negative terminals 32, the two negative terminals 32 are located on opposite sides of the negative current collector. Exemplarily, the battery cell 7 includes two positive terminals 31 and two negative terminals 32. The two positive terminals 31 are located on opposite sides of the positive current collector, and the two negative terminals 32 are located on opposite sides of the negative current collector. This can be understood as the battery cell 7 having one positive terminal 31 and one negative terminal 32 on one side, and one positive terminal 31 and one negative terminal 32 on the other side. Figure 9 shows the battery cell 7 including two positive terminals 31 and two negative terminals 32.

[0213] Optionally, the number of negative terminals 32 located on the same side of the negative current collector 122 is at least one, and optionally at least two. At least two negative terminals 32 can increase the current carrying capacity of the negative terminals 32.

[0214] Further optionally, the flow area of ​​a single negative terminal 32 is greater than or equal to 200 mm². 2 200mm is optional 2 Up to 800mm 2 The flow area of ​​the negative terminal 32 can be understood as the cross-sectional area of ​​the negative terminal 32, which is perpendicular to the thickness direction of the negative terminal 32.

[0215] For example, the flow area of ​​a single negative terminal 32 can be 200 mm². 2 210mm 2 250mm 2 280mm 2 300mm 2 320mm 2 350mm 2 380mm 2 400mm 2 450mm 2 500mm 2 550mm 2 600mm 2 650mm 2 700mm 2 750mm 2 800mm 2 Or a range consisting of any two of the above values.

[0216] [Positive electrode plate]

[0217] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0218] The upper limit voltage for charging and the lower limit voltage for discharging a single battery cell vary depending on the positive electrode active material. For example, when the phosphate material includes lithium iron phosphate, the upper limit voltage for charging can be 3.65V and the lower limit voltage for discharging can be 2.0V. Similarly, when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage for charging can be 4.3V and the lower limit voltage for discharging can be 2.0V. Taking a charging upper limit voltage of 3.65V and a discharging lower limit voltage of 2.0V as an example, the state of a single battery cell will be described as follows: In this embodiment, the 100% state of charge (SOC) and the 0% state of charge (SOC) of a single battery cell are defined as follows...

[0219] The battery cell is charged at a constant current charging rate of 0.33C to the upper limit of the charging voltage, and then charged at a constant voltage to 0.05C, which corresponds to the 100% SOC state of the battery cell. The battery cell is then discharged at a constant current discharging rate of 0.33C to the cutoff voltage, which corresponds to the 0% SOC state of the battery cell.

[0220] In some embodiments, the compaction density of the positive electrode film layer is 2.50 g / cm³ when the battery cell is at 100% state of charge (SOC). 3 Up to 2.80 g / cm 3; 2.55g / cm³ is optional 3 Up to 2.70 g / cm 3 For example, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film is 2.50 g / cm³. 3 2.52g / cm 3 2.55g / cm 3 2.56 g / cm 3 2.57g / cm 3 2.58g / cm 3 2.60g / cm 3 2.62 g / cm 3 2.65g / cm 3 2.68g / cm 3 2.70 g / cm 3 2.72 g / cm 3 2.75g / cm 3 2.78g / cm 3 2.80g / cm 3 Or a range consisting of any two of the above values.

[0221] When the compaction density of the positive electrode film is within the aforementioned range, it is beneficial to improve the energy density of the battery cell. Furthermore, because the positive electrode active material in the positive electrode film is densely packed, the contact resistance between particles is low, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during fast charging. Therefore, by adjusting the compaction density of the positive electrode film to a reasonable range, the battery cell can achieve both high energy density and high charging rate performance.

[0222] In some embodiments, the single-sided coating weight of the positive electrode film is 160 mg / 1540.25 mm. 2 Up to 340mg / 1540.25mm 2 For example, the single-sided coating weight of the positive electrode film is 160 mg / 1540.25 mm. 2 170mg / 1540.25mm 2 180mg / 1540.25mm 2 190mg / 1540.25mm 2 200mg / 1540.25mm 2 210mg / 1540.25mm 2 220mg / 1540.25mm 2 230mg / 1540.25mm 2 240mg / 1540.25mm 2 250mg / 1540.25mm 2260mg / 1540.25mm 2 270mg / 1540.25mm 2 280mg / 1540.25mm 2 290mg / 1540.25mm 2 300mg / 1540.25mm 2 310mg / 1540.25mm 2 320mg / 1540.25mm 2 330mg / 1540.25mm 2 340mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0223] When the single-sided coating weight of the positive electrode film 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 improve the energy density and charging rate performance of the battery cell.

[0224] In this embodiment, the compaction density of the positive electrode film layer of a single battery cell at 100% State of Charge (SOC) is a well-known concept in the art. This means that the positive electrode sheet is disassembled from the single battery cell at 100% SOC, and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if double-sided coated, the positive electrode film layer on one side can be wiped off first) is cut into small circular pieces with an area of ​​S1, weighed, and recorded as M1, and its thickness H1 is measured. Then, the positive electrode film layer of the weighed positive electrode sheet is wiped off, the weight of the positive current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film = (weight of the positive electrode sheet M1 - weight of the positive current collector M0) / S1, the thickness of the positive electrode film = the thickness of the positive electrode sheet H1 - the thickness of the positive current collector H0, and the compaction density of the positive electrode film = the single-sided coating weight of the positive electrode film / the thickness of the positive electrode film.

[0225] In some embodiments, the resistivity of the positive electrode active material powder 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 resistivity of the positive electrode active material powder can be 27.5 Ω·cm, 20 Ω·cm, 19 Ω·cm, 18 Ω·cm, 17 Ω·cm, 16 Ω·cm, 15 Ω·cm, 14 Ω·cm, 13 Ω·cm, 12 Ω·cm, 11 Ω·cm, 10 Ω·cm, 9 Ω·cm, 8 Ω·cm, 7 Ω·cm, 6 Ω·cm, 5 Ω·cm, 4 Ω·cm, 3 Ω·cm, 2 Ω·cm, 1 Ω·cm, or a range consisting of any two of the above values.

[0226] The powder resistivity of the positive electrode active material is relatively low, which results in relatively low resistance of the positive electrode sheet and less heat generation in the battery cell.

[0227] In the embodiments of this application, the powder resistivity of the material has a well-known meaning in the art and can be tested using methods and equipment well-known in the art, such as using a PRCD1100 powder resistivity meter according to the test standard GB / T30835-2014.

[0228] In some embodiments, the compacted density of the positive electrode active material at 30000 N is greater than or equal to 2.46 g / cm³. 3 The option is 2.46 g / cm³. 3 Up to 2.8 g / cm 3 For example, the compacted density of the positive electrode active material at 30000 N is 2.46 g / cm³. 3 2.47 g / cm 3 2.48 g / cm 3 2.49 g / cm 3 2.5g / cm 3 2.51g / cm 3 2.55g / cm 3 2.58g / cm 3 2.60g / cm 3 2.65g / cm 3 2.68g / cm 3 2.70 g / cm 3 2.72 g / cm 3 2.75g / cm 3 2.78g / cm 3 2.80g / cm 3 Or a range consisting of any two of the above values.

[0229] When the powder compaction density of the positive electrode active material at 30000N is within the above range, it can improve the energy density of the battery cell. Furthermore, since the positive electrode active material in the positive electrode film can be stacked more tightly, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0230] In the embodiments of this application, the powder compaction density of the material has a meaning known in the art and can be tested using methods and equipment known in the art, according to the testing standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample and added to a UTM7305 electronic pressure testing machine with a bottom area of ​​1.327 cm². 2In the mold, the pressure is increased to 3000 kg (equivalent to 30000 N), held for 30 s, then depressurized and held for 10 s. The compaction density of the positive electrode active material under a force of 30000 N is then recorded and calculated.

[0231] In some embodiments, the specific charge capacity of the positive electrode active material at a 0.1C rate is between 150 mAh / g and 170 mAh / g. Exemplarily, the specific charge 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 a range consisting of any two of the above values.

[0232] When the 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.

[0233] In the embodiments of this application, the specific capacity of the active material has a meaning known in the art and can be tested using equipment and methods known in the art. The test methods for the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be adopted. A half-coin cell is assembled with lithium metal as the negative electrode and a sample electrode containing the above-mentioned material as the positive electrode. The half-coin cell is tested on a battery tester or other test equipment with equivalent performance at 23℃±2℃ by charging and discharging at a rate of 0.1C to obtain the coin capacity. The capacity is then divided by the mass of the electrode active material to obtain the charging specific capacity parameter.

[0234] In some embodiments, the mass percentage of olivine-structured lithium phosphate in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%, and the positive electrode active material of this application can be considered as an olivine-structured lithium phosphate system. When the mass percentage of olivine-structured lithium phosphate is less than 100%, the positive electrode active material may also include commonly used positive electrode active materials, such as, but not limited to, at least one of lithium transition metal oxides. Examples of lithium transition metal oxides 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.

[0235] Optionally, the lithium phosphate with an olivine structure in the positive electrode active material accounts for 100% by mass.

[0236] In this application, the lithium phosphate with olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium phosphate with olivine structure includes phosphate particles and a coating layer. The coating layer is coated on the surface of the phosphate particles and contains one or more elements selected from C, Fe, Ti, Zr, Hf, Ge and Sn.

[0237] Phosphate particles, through surface coating, can improve the conductivity of lithium phosphates with olivine structure, reduce the powder resistivity of the material, facilitate the migration rate of lithium ions, improve the fast charging capability of the battery, and reduce the heat generation of the battery cell.

[0238] In some embodiments, the phosphate particles comprise the general formula Li x1 A y1 Me a M b P 1-c X c Y z The compound contains 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, where 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. Phosphate particles exhibit excellent cycle stability, which is beneficial for improving the cycle performance of battery cells.

[0239] For example, phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charging and discharging process, active ions such as Li are de-intercalated and consumed in a single battery cell, resulting in different molar contents of Li in different discharged states. In the examples of positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar contents of Li represent the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar contents of Li may change after charge-discharge cycles. In the embodiments of this application, the molar contents of oxygen (O) in the examples of positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4 are only theoretical values. Lattice oxygen release can cause changes in the molar contents of oxygen (O). In reality, the molar contents of oxygen (O) may fluctuate, and all of the above situations are within the scope of protection of this application.

[0240] In some embodiments, the coating layer includes a general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 A fast ion conductor, M2 includes one or more elements from Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x2<5, 0<y2<4.

[0241] For example, the fast ion conductor is a material having a NASICON structure, such as one or more of lithium iron phosphate (Li2FeTi(PO4)3), lithium zirconium iron phosphate (Li2FeZr(PO4)3), and lithium iron tin phosphate (Li2FeSn(PO4)3).

[0242] Fast ion conductors with a NASICON structure are materials with ultrafast ion conduction capabilities, possessing abundant three-dimensional lithium-ion diffusion and transport channels. They exhibit advantages such as high ion conduction efficiency and strong structural stability during multiple lithium delithiation and lithium intercalation processes. Coating the surface of phosphate particles with fast ion conductors containing a NASICON structure can significantly improve the lithium-ion transport rate during multiple lithium delithiation / intercalation at the positive electrode, enhance the ionic conductivity of the positive electrode active material, improve the fast charging capability of the battery cell, and further increase the specific capacity and energy density of the corresponding battery cell.

[0243] In some embodiments, the coating layer also includes all-carbon.

[0244] The carbon element and the fast ion conductor can be layered. For example, the carbon element can be an independent carbon coating layer, and the fast ion conductor can be an independent fast ion conductor layer. The carbon coating layer can be applied to the surface of the phosphate particles, and the fast ion conductor layer can be located on the surface of the carbon coating layer, i.e., the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Alternatively, the fast ion conductor layer can be applied to the surface of the phosphate particles, and the carbon coating layer can be located on the surface of the fast ion conductor layer, i.e., the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be layered together.

[0245] Optionally, the carbon coating layer can be formed by carbonizing an organic carbon source (e.g., glucose, polyethylene glycol, etc.) onto the surface of the fast ion conductor layer. The carbon coating layer can partially or completely cover the fast ion conductor layer. The carbon coating layer can significantly improve the electronic conductivity of phosphate particles, compensating for the poor electronic conductivity of phosphate particles and increasing the energy density of the battery cell.

[0246] Specifically, the carbon coating layer gives the positive electrode active material of this application the following advantages:

[0247] The carbon coating layer in the positive electrode active material of this application provides a suitable channel for electron transport, which can significantly improve the electron conduction rate during multiple lithium delithiation and lithium insertion processes, improve the electronic conductivity of lithium phosphate, improve the charging capacity of the corresponding battery cell, and also improve the energy density.

[0248] The carbon coating layer of the positive electrode active material in this application is porous, which allows the electrolyte to come into full and effective contact with the lithium phosphate, thereby improving the lithium ion transport rate at the phase interface and enhancing the charging capacity of the battery cell.

[0249] Coating the surface of lithium phosphate with a carbon coating layer can not only improve the conductivity of lithium phosphate, but also improve the structural stability of the positive electrode active material. This effectively alleviates the iron dissolution phenomenon of the positive electrode active material during long-term storage and cyclic use of battery cells, thereby improving the cycle life of battery cells.

[0250] The positive electrode active material of this application uses lithium phosphate as a substrate, fully leveraging the advantages of lithium phosphate such as low cost, high reliability, and good cycle stability. Simultaneously, it utilizes coating layers (a fast ion conductor layer and a carbon coating layer) to overcome the drawbacks of poor electronic and ionic conductivity. Battery cells prepared using the positive electrode active material of this application can improve the energy density of battery cells while maintaining excellent cycle performance.

[0251] In this embodiment, the elemental content in the positive electrode active material is defined in a way known in the art and can be detected using equipment and methods known in the art. For example, referring to EPA 6010D-2014, it can be tested by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned and dried with DMC, and then calcined at high temperature to remove impurities. 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. Then it is placed on a plate at 180°C for 30min. After digestion on the plate, the volume is adjusted to 100mL, and quantitative testing is performed using the standard curve method.

[0252] In some embodiments, the degree of graphitization of the positive electrode active material is 0.15 to 0.32, optionally 0.19 to 0.26. Exemplarily, the degree of graphitization of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, or a range consisting of any two of the above values.

[0253] When the degree of graphitization 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.

[0254] In the embodiments of this application, the higher the degree of graphitization of the material, the lower the degree of disorder, and the test can be carried out according to the general rules of X-ray diffraction analysis method JIS / K 0131-1996.

[0255] In some embodiments, the carbon content in the olivine-structured lithium phosphate is 1% to 2% by mass, and the specific surface area of ​​the olivine-structured lithium phosphate is 5 m². 2 / g to 18m 2 / g.

[0256] Optionally, the carbon content in the olivine-structured lithium phosphate is 1% to 2% by mass, and the specific surface area of ​​the olivine-structured lithium phosphate is 7.5 m². 2 / g to 14m 2 / g.

[0257] For example, the mass content of carbon in the lithium 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 any combination of two of the above values.

[0258] For example, the specific surface area of ​​lithium phosphate with an olivine structure is 5 m². 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m 2 / g、18m 2 / g or a range consisting of any two of the above values.

[0259] Carbon mainly exists in the form of a carbon coating layer. The carbon coating layer is loose and porous, which helps to increase the specific surface area of ​​the material, facilitates effective contact between the electrolyte and phosphate particles, and promotes the transport of lithium ions at the phase interface. In addition, when the mass content of carbon is within the above range, it can significantly improve the conductivity of lithium phosphate with olivine structure, which is beneficial to improving the ionic and electronic conductivity of lithium phosphate with olivine structure, and can improve the rapid charging capability and energy density of battery cells.

[0260] In the embodiments of this application, the specific surface area of ​​the material has a meaning known in the art and can be detected using equipment and methods known in the art. For example, it can be detected according to the testing standard GB / T 19587-2017, using the positive electrode active material as a sample, and the specific surface area is tested using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0261] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1μm≤Dv50≤2μm, 0.4μm≤Dv10≤0.7μm.

[0262] For example, the 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 any range of two of the above values.

[0263] For example, the Dv10 of the positive electrode active material can be 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, or any combination of two of the above values.

[0264] The positive electrode active material has a relatively small particle size, resulting in a shorter lithium ion insertion / extraction path and less heat generation. Moreover, the particle size of the positive electrode active material is not too small, so it will not agglomerate during the processing and preparation process, which makes the performance of the positive electrode active material stable.

[0265] In the embodiments of this application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% of the volume distribution, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% of the volume distribution. They can be detected using equipment and methods known in the art. For example, the positive electrode active material can be used as a sample, and the Dv50 and Dv10 of the particles can be tested using a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0266] When the positive electrode active material includes other materials besides 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.

[0267] In some embodiments, the olivine-structured lithium phosphate is in particulate form, and the olivine-structured lithium phosphate is formed from secondary particles formed by the agglomeration of primary particles, with the average particle size of the primary particles being 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 consisting of any two of the above values.

[0268] The average particle size of primary particles is relatively small, the lithium ion insertion / extraction path in the positive electrode active material is shorter, and the heat generation is less.

[0269] In the embodiments of this application, primary particles and secondary particles are terms well known in the art. Secondary particles refer to aggregated particles formed by the aggregation of two or more primary particles. Primary and secondary particles can be easily distinguished by experimental means (such as taking SEM images using a scanning electron microscope). The average particle size of primary particles can be obtained by testing in the SEM image. The SEM test parameters can be set as follows: operating voltage (EHT) of 10.00 kV, using an InLens detector, working distance of 4.6 mm, and magnification of 1000X.

[0270] The positive electrode film typically comprises multiple positive electrode active material particles, namely, lithium phosphate particles with an olivine structure. These particles vary in size, including minimum and maximum particles. The combination of particles of different sizes increases the compaction density of the positive electrode film and enhances its porosity, thereby improving the fast-charging performance of the battery cell.

[0271] In some embodiments, the minimum particle size of the lithium phosphate containing the 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 any combination of two of the above values. When the minimum particle size is within the above range, agglomeration is less likely to occur during the preparation of the positive electrode film 113.

[0272] In some embodiments, the maximum particle size of the lithium phosphate with an olivine structure is between 15 μm and 25 μm, exemplarily 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, or any combination of two of the above values. When the maximum particle size is within the above range, the migration path of lithium ions during charging and discharging is not too long, which can improve the fast charge and discharge performance of the battery cell.

[0273] In some embodiments, the positive electrode film layer further includes one or more of the following: ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, lithium trilithium citrate, lithium nickel oxide, and lithium ferrite. These materials can act as lithium replenishing agents, which can replenish lithium ions to the positive electrode film layer, compensate for irreversible lithium ion losses within the system, increase capacity, and thereby improve the energy density of the battery cell.

[0274] Optionally, ternary materials include Li x3 A y3 Ni a3 Co b3 Mn c M3(1-a3-b3-c3)Y3 z3Wherein, 0 < x3 ≤ 2.1, 0 < y3 ≤ 2.1, and 0.9 ≤ x3 + y3 ≤ 2.1, 0 ≤ a3 ≤ 1, 0 ≤ b3 ≤ 1, 0 ≤ c3 ≤ 1, and 0.1 ≤ a3 + b3 + c3 ≤ 1, 1.8 ≤ z3 ≤ 3.5, A includes one or more of Na, K, and Mg, M3 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, and Y3 includes one or more of O and F.

[0275] For example, ternary materials include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 At least one of O2.

[0276] In some embodiments, the lithium replenishing agent has a mass content of 0.5% to 5% in the positive electrode film, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any combination of two of the above values. When the mass content of the lithium replenishing agent is within the above range, it can replenish lithium ions to the positive electrode film, compensate for irreversible lithium ion loss in the system, increase capacity, and thereby increase the energy density of the battery cell.

[0277] The lithium replenishing agent can be located in the same layer as the positive electrode active material or in a different layer. When the lithium replenishing agent and the positive electrode active material are in different layers, the lithium replenishing agent can be located in the lithium replenishing layer, and the positive electrode active material can be located in the positive electrode active material layer. In other words, the positive electrode film layer includes a lithium replenishing 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 replenishing layer can be located between the positive electrode active material layer and the positive electrode current collector. Alternatively, the lithium replenishing 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 replenishing layer and the positive electrode current collector. Optionally, the lithium replenishing layer can be located between the positive electrode active material layer and the positive electrode current collector. During the cycle charging and discharging of the battery cell, the lithium replenishing agent in the lithium replenishing layer can be gradually released into the system to compensate for the lithium loss of the battery system.

[0278] In some embodiments, the positive electrode film layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode film layer.

[0279] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include at least one selected from polyvinylidene fluoride, polytetrafluoroethylene, a terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, the mass content of the positive electrode binder is ≤5% based on the mass of the positive electrode film layer.

[0280] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one foil selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. A composite current collector may include a polymer base material and a metal material layer formed on at least one surface of the polymer base material. As an example, the metal material layer may include at least one selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer base material may include at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0281] In some embodiments, the ratio of the thickness of the positive current collector to the thickness of the positive electrode film on one side is 0.05 to 0.3. For example, the ratio of the thickness of the positive current collector to the thickness of the positive electrode film on one side 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 consisting of any two of the above values.

[0282] When the ratio of the thickness of the positive current collector to the thickness of the positive electrode film layer on one side is within the above range, the fast charging capability and energy density of the battery cell can be improved.

[0283] In some embodiments, the thickness of the positive current collector is 10 μm to 15 μm, optionally 12 μm to 15 μm. Exemplarily, the thickness of the positive current collector is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, or a range consisting of any two of the above values.

[0284] 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 excellent, and it can enable the battery cell to have a high energy density.

[0285] In the embodiments of this application, the thickness of the positive electrode film layer and the positive electrode current collector are known in the art and can be detected using equipment and methods known in the art. For example, the thickness of the positive electrode sheet can be measured with a micrometer, the film layer on the surface of the positive electrode current collector can be removed, and the thickness of the positive electrode current collector can be 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 sheet 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 sheet minus the thickness of the positive electrode current collector) / 2.

[0286] The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0287] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0288] In some embodiments, the positive electrode further includes a positive conductive layer located between the positive electrode film and the positive current collector. The positive conductive layer can further improve the conductivity of the positive electrode and reduce the heat generation of the positive electrode, thereby reducing the heat generation of the battery cell.

[0289] In some embodiments, the thickness of the positive electrode conductive layer is from 0.5 μm to 2 μm. For example, the thickness of the positive electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or any combination of two of the above values.

[0290] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode sheet can be further improved, the heat generation of the positive electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can also be improved.

[0291] In the embodiments of this application, the thickness of the positive electrode conductive layer has a meaning known in the art and can be detected using equipment and methods known in the art, such as performing a tomographic scan on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0292] In some embodiments, the positive conductive layer includes one or more of a positive conductive agent and a positive binder.

[0293] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. For example, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or any combination of two of the above values.

[0294] For example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet and reducing the heat generation of the battery cell.

[0295] Optionally, the positive electrode binder has a mass content of 50% to 70% in the positive electrode conductive layer. For example, 50%, 60%, 65%, 70%, or any combination of two of the above values.

[0296] For example, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. The positive electrode binder in the positive electrode conductive layer can improve the adhesion between the positive electrode current collector and the positive electrode film layer, thereby enhancing the structural stability of the positive electrode sheet.

[0297] [Negative electrode plate]

[0298] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0299] In some embodiments, the compaction density of the negative electrode film layer is 1.15 g / cm³ when the battery cell is 100% charged. 3 Up to 1.36 g / cm 3; 1.25g / cm³ is optional 3 Up to 1.36 g / cm 3 For example, the compaction density of the negative electrode film layer of a single battery cell at 100% charge is 1.15 g / cm³. 3 1.18 g / cm 3 1.20g / cm 3 1.22g / cm 3 1.25g / cm 3 1.28g / cm 3 1.3g / cm 3 1.32g / cm 3 1.35g / cm 3 1.36 g / cm 3 Or a range consisting of any two of the above values.

[0300] When the compaction density of the negative electrode film is within the above range, it is beneficial to improve the energy density of the battery cell; and because the negative electrode active material in the negative electrode film is packed more tightly, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0301] In the embodiments of this application, the compaction density of the negative electrode film layer of a single battery cell under 100% charge state has a well-known meaning in the art and can be detected using well-known equipment and methods in the art. The detection method is as described above for the compaction density test method of the positive electrode film layer.

[0302] In some embodiments, the single-sided coating weight of the negative electrode film is 74 mg / 1540.25 mm. 2 Up to 156mg / 1540.25mm 2 For example, the single-sided coating weight of the negative electrode film is 74 mg / 1540.25 mm. 2 80mg / 1540.25mm 2 85mg / 1540.25mm 2 90mg / 1540.25mm 2 95mg / 1540.25mm 2 100mg / 1540.25mm 2 102mg / 1540.25mm 2 104mg / 1540.25mm 2 105mg / 1540.25mm 2 108mg / 1540.25mm 2 110mg / 1540.25mm 2 112mg / 1540.25mm 2114mg / 1540.25mm 2 115mg / 1540.25mm 2 116mg / 1540.25mm 2 118mg / 1540.25mm 2 120mg / 1540.25mm 2 122mg / 1540.25mm 2 125mg / 1540.25mm 2 128mg / 1540.25mm 2 130mg / 1540.25mm 2 132mg / 1540.25mm 2 135mg / 1540.25mm 2 137mg / 1540.25mm 2 140mg / 1540.25mm 2 145mg / 1540.25mm 2 150mg / 1540.25mm 2 155mg / 1540.25mm 2 156mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0303] When the single-sided coating weight of the negative electrode film is within the above range, the heat generation per unit area of ​​the negative electrode sheet will not be too large, and the energy density of the battery cell can be improved at the same time.

[0304] In the embodiments of this application, the single-sided coating weight of the negative electrode film layer has a meaning known in the art and can be detected using equipment and methods known in the art, such as the single-sided coating weight test method of the film layer described above.

[0305] In some embodiments, the resistivity of the negative electrode active material powder is from 0.005 Ω·cm to 0.043 Ω·cm, optionally 0.04 Ω·cm. Exemplarily, the resistivity of the negative electrode active material powder 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 consisting of any two of the above values.

[0306] The powder resistivity of the negative electrode active material is relatively low, which results in relatively low resistance of the negative electrode sheet and less heat generation in the battery cell.

[0307] In the embodiments of this application, the powder resistivity of the negative electrode active material has a well-known meaning in the art and can be detected using equipment and methods well-known in the art, such as the powder resistivity test method for the positive electrode active material described above.

[0308] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.5 g / cm³. 3 Up to 1.85 g / cm 3 1.55g / cm³ is an optional value. 3 Up to 1.65 g / cm 3 For example, the compacted density of the negative electrode active material powder under a pressure of 20000N is 1.5 g / cm³. 3 1.55g / cm 3 1.6g / cm 3 1.65g / cm 3 1.7g / cm 3 1.75g / cm 3 1.8g / cm 3 1.85g / cm 3 Or a range consisting of any two of the above values.

[0309] When the powder compaction density of the negative electrode active material at 20000N is within the above range, it can improve the energy density of the battery cell. Furthermore, since the negative electrode active material in the negative electrode film can be stacked more tightly, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0310] In this application, the powder compaction density of the material has a meaning known in the art and can be tested using methods and equipment known in the art, according to the testing standard GB / T24533-2009. As an example, a certain amount of negative electrode active material is taken as a sample and added to a UTM7305 electronic pressure testing machine with a base area of ​​1.327 cm². 2 In the mold, the pressure is increased to 2000 kg (equivalent to 20000 N), held for 30 s, then depressurized and held for 10 s. The compaction density of the negative electrode active material under a force of 20000 N is then recorded and calculated.

[0311] In some embodiments, the specific charge capacity of the negative electrode active material at a 0.1C rate is between 350 mAh / g and 480 mAh / g. Exemplarily, the specific charge 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 consisting of any two of the above values.

[0312] When the charge 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.

[0313] In the embodiments of this application, the charging capacity of the negative electrode active material at a rate of 0.1C is a well-known concept in the art and can be detected using well-known equipment and methods in the art. The detection method is as described above for the charging capacity test method of the positive electrode active material at a rate of 0.1C.

[0314] 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%.

[0315] The positive electrode active material of this application is mainly a lithium phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. When used together, the cycle performance of the battery cell is excellent.

[0316] Optionally, the carbon-based material includes graphite particles with a graphitization degree of 92.0% to 94.5%. Exemplarily, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, or a range consisting of any two of the above values.

[0317] When the degree of graphitization of graphite particles is within the above range, the graphite particles have excellent electrical conductivity, which can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the fast charging performance of the battery cell.

[0318] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer. The artificial graphite includes secondary particles, which in turn include multiple primary particles. The carbon coating layer coats the surface of the artificial graphite. The carbon in the carbon coating layer is primarily amorphous carbon, which refers to transitional carbon materials with a very low degree of graphitization and crystallization, exhibiting an approximately amorphous morphology (or lacking a fixed shape and periodic structural regularity). In this application, amorphous carbon refers to the product of carbonization treatment of an organic carbon source.

[0319] Artificial graphite includes secondary particles. There are more migration paths for lithium ions in artificial graphite, and the migration paths in primary particles are shorter, which can improve the migration rate of lithium ions. The carbon coating layer has more end faces and defects, which increases the number of sites where lithium ions can be inserted and extracted, resulting in better conductivity of the carbon coating layer. This can reduce the internal resistance of the negative electrode and reduce the heat generation of the battery cell.

[0320] Optionally, the carbon coating content is 2% to 5% by mass, based on the mass of the graphite particles. For example, the carbon coating content is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any range of two of the above values.

[0321] When the mass content of the carbon coating is within the above range, it can further reduce the internal resistance of the negative electrode and reduce the heat generation of the battery cell.

[0322] In the embodiments of this application, the graphite particles can be prepared using methods known in the art, such as: providing artificial graphite and an organic carbon source, mixing the two, and then carbonizing them to form a carbon coating layer on at least a portion of the surface of the artificial graphite particles.

[0323] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum asphalt, phenolic resin, and coconut shell. More preferably, the organic carbon source includes petroleum asphalt. Optionally, the softening point of coal tar pitch or petroleum asphalt is below 250°C.

[0324] Optionally, the carbonization temperature is between 700°C and 1800°C. Optionally, the carbonization temperature is between 1000°C and 1300°C. Within a suitable range, the carbonization temperature allows the organic carbon source to be carbonized, forming a coating layer containing amorphous carbon on at least a portion of the surface of the artificial graphite.

[0325] Optionally, the carbonization treatment time is 1 hour to 6 hours.

[0326] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include graphite particles, or it may include both graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0327] In some embodiments, the negative electrode active material may also include a silicon-based material. The introduction of silicon-based materials can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0328] 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%, optionally 1% to 6%. Exemplarily, the mass content of silicon element in the silicon-based material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10%, or a range consisting of any two of the above values.

[0329] When the mass content of silicon in silicon-based materials is within the above range, it can improve the capacity of the negative electrode active material, thereby improving the energy density of the battery cell.

[0330] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy.

[0331] In some embodiments, the negative electrode active material may include, in addition to the carbon-based materials and optionally silicon-based materials described above, at least one of tin-based materials and lithium titanate. Tin-based materials may include at least one of elemental tin, tin oxides, and tin alloys.

[0332] The qualitative and quantitative analysis of each substance or element in this application can be performed using suitable equipment and methods known to those skilled in the art. Relevant testing methods can be referenced from domestic and international testing standards and enterprise standards. Furthermore, those skilled in the art can adaptively modify certain testing steps / instrument parameters from the perspective of testing accuracy to obtain more accurate results. One testing method can be used for qualitative or quantitative analysis, or several testing methods can be used in combination for qualitative or quantitative determination.

[0333] For example, this application can combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis to perform X-ray powder diffraction tests and qualitative analysis on negative electrode sheets or negative electrode active materials.

[0334] Artificial graphite and natural graphite can be distinguished by SEM cross-sectional images taken by scanning electron microscope (SEM). Natural graphite has gaps between the sheet-like structures in its SEM cross-section, while artificial graphite has a dense structure with no obvious gaps. Alternatively, they can be distinguished by XRD patterns obtained by X-ray diffraction. Natural graphite has obvious 2H and 3R phases in its XRD pattern, while artificial graphite only has the 2H phase in its XRD pattern.

[0335] In the embodiments of this application, the negative electrode film layer includes at least one film layer, which can be a single film layer or at least two film layers. Optionally, the negative electrode film layer includes at least two film layers.

[0336] When a single-layer negative electrode film is used, the negative electrode active material in the negative electrode film includes a carbon-based material, and optionally also includes a silicon-based material. When a single-layer film is used, the volume average particle size Dv50 of the negative electrode active material is from 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 a range consisting of any two of the above values.

[0337] When the negative electrode film layer comprises 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 may be located in one of the at least two film layers, or in at least two of the at least two film layers. The negative electrode film layer may include two film layers, three film layers, four film layers, or even more film layers.

[0338] 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 away from the negative electrode current collector. The carbon-based material in the second negative electrode film layer also includes graphite particles. The graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer may be the same or different.

[0339] The interface between the first negative electrode film and the second negative electrode film can be regular or irregular, and can optionally be irregular.

[0340] Optionally, the carbon-based material in the first negative electrode film layer may also include natural graphite.

[0341] The negative electrode film consists of at least two layers, and layered coating is beneficial for improving the fast charging performance of the battery cell. In particular, when there are differences between the first and second negative electrode films, it can create porosity differences in the negative electrode films, reduce the tortuosity of lithium-ion transport, and improve the fast charging performance of the battery cell.

[0342] 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. More preferably, 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 for increasing 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.

[0343] The difference in particle size between the first and second negative electrode layers can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode layer is usually higher, and the bottleneck of fast charging is mainly in the second negative electrode layer. However, in the embodiments of this application, the particle size of the second negative electrode layer is relatively small, which can shorten the solid-phase transport path of lithium ions, improve fast charging performance, and improve the problem of lithium deposition on the surface of the negative electrode sheet.

[0344] Optionally, the negative electrode active material in the first negative electrode film layer is particulate, and its volume average particle size Dv50 is 9.5 μm to 18.5 μm, optionally 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 consisting 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 9.5 μm to 18.5 μm, and can be selected as 9.5 μm to 14.6 μm.

[0345] When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the above range, it can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during the preparation process, which can improve the stability of the material.

[0346] Optionally, the negative electrode active material in the second negative electrode film layer is particulate, and its volume average particle size Dv50 is 7.8 μm to 14.3 μm, optionally 7.8 μm to 11.3 μm. For example, 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 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 7.8 μm to 14.3 μm, and can be selected as 7.8 μm to 11.3 μm.

[0347] When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film is within the above-mentioned range, it can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during the preparation process, which can improve the stability of the material. Furthermore, the combination of the negative electrode active material in the second negative electrode film within the above-mentioned volume average particle size range and the negative electrode active material in the first negative electrode film is conducive to building a gradient porosity difference between the second negative electrode film and the first negative electrode film, reducing the tortuosity of lithium ion transport, and improving the fast charging performance of the battery cell.

[0348] In the embodiments of this application, the volume average particle size Dv50 of the negative electrode active material has a meaning known in the art and can be detected using equipment and methods known in the art, such as the volume average particle size Dv50 test method for positive electrode active materials described above.

[0349] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. Tap density reflects the compactness of the active material within the film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than that in the first negative electrode film layer, the second negative electrode film layer is more densely packed, thus increasing the energy density of the battery cell. Conversely, the first negative electrode film layer is relatively sparsely packed with more pores, which improves the fast-charging performance of the battery cell. When the negative electrode active material includes graphite particles, the tap density of the graphite particles in the first negative electrode film layer is less than or equal to that in the second negative electrode film layer.

[0350] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm³. 3 Up to 1.21 g / cm3 For example, 0.82 g / cm³ 3 0.85g / cm 3 0.88g / cm 3 0.90g / cm 3 0.92g / cm 3 0.95g / cm 3 0.98g / cm 3 1.00g / cm 3 1.05g / cm 3 1.08g / cm 3 1.10 g / cm 3 1.12 g / cm 3 1.15g / cm 3 1.18 g / cm 3 1.20g / cm 3 1.21 g / cm 3 Or it can be a range consisting of any two of the above values. When the tap density of the carbon-based material in the first negative electrode film is within a suitable range, it can improve the fast charging performance of the battery cell.

[0351] Optionally, the tap density of the carbon-based material in the second negative electrode film is 0.90 g / cm³. 3 Up to 1.25 g / cm 3 For example, 0.90 g / cm³ 3 0.92g / cm 3 0.95g / cm 3 0.98g / cm 3 1.00g / cm 3 1.05g / cm 3 1.08g / cm 3 1.10 g / cm 3 1.12 g / cm 3 1.15g / cm 3 1.18 g / cm 3 1.20g / cm 3 1.21 g / cm 3 1.22g / cm 3 1.23g / cm 3 1.24 g / cm 3 1.25g / cm 3 Or it can be a range consisting of any two of the above values. When the tap density of the carbon-based material in the second negative electrode film is within a suitable range, it can improve the energy density of the battery cell.

[0352] In the embodiments of this application, the tap density of the material has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined using a powder tap density tester according to GB / T5162-2006. The testing instrument can be the Dandong Baite BT-301.

[0353] Optionally, the thickness ratio of the second negative electrode film to the first negative electrode film is 3:7 to 7:3, and optionally 4:6 to 6:4. For example, the thickness ratio of the second negative electrode film to the first negative electrode film is 3:7, 4:6, 5:5, 6:4, 7:3, or any range of two of the above values. By adjusting the thickness ratio of the first and second negative electrode films, the gradient porosity difference between the upper and lower layers can be further increased, reducing the tortuosity of lithium-ion transport and improving the fast charging capability of the battery cell.

[0354] In some implementations, after 10 full-charge cycles during the Beginning of Life (BOL) test, the thickness of the first negative electrode film layer in a single battery cell is between 15 μm and 65 μm, for example, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or any combination of two of the above values. When the thickness of the first negative electrode film layer is within the above range, it can increase the gradient porosity difference between the first and second negative electrode film layers, reduce the tortuosity of lithium-ion transport, and improve the fast-charging capability of the battery cell.

[0355] In some implementations, after 10 full-charge cycles during the Beginning of Life (BOL) test, the thickness of the second negative electrode film is between 15 μm and 65 μm, for example, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or any combination of two of the above values. When the thickness of the second negative electrode film is within the above range, the gradient porosity difference between the first and second negative electrode films can be increased, reducing lithium-ion transport tortuosity and improving the fast-charging capability of the battery cell.

[0356] In this embodiment, for example, a battery charging upper limit voltage of 3.65V and a battery discharging cutoff voltage of 2.0V will be used for explanation.

[0357] The BOL full charge test procedure is as follows: At 25℃, charge the battery to 3.65V at a charging rate of 0.33C (the nominal capacity), then charge it to 0.05C at a constant voltage of 3.65V, let it rest for 10 minutes, then discharge it to 2.0V at a discharging rate of 0.33C, let it rest for 10 minutes. One charge-discharge cycle constitutes one cycle; complete 10 cycles. Then charge the battery to 3.65V again at a charging rate of 0.33C (the nominal capacity), and then charge it to 0.05C at a constant voltage of 3.65V. With the BOL fully charged, the negative electrode sheet is disassembled. A tomographic scanning electron microscope is used to observe the cross-section of the thickness direction in the middle region of the negative electrode sheet. The two regions are distinguished according to the interface between the first negative electrode film layer and the second negative electrode film layer. The thickness of each is measured separately. For example, the thickness of the first negative electrode film layer is measured at 10 locations, and the average value is calculated as the average value of the first negative electrode film layer. The thickness of the second negative electrode film layer is measured at 10 locations, and the average value is calculated as the average value of the second negative electrode film layer.

[0358] In some embodiments, after a full-charge test at the end of life (EOL) of the battery cell, the thickness of the first negative electrode film is between 15 μm and 70 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, or any combination of two of the above values. When the thickness of the first negative electrode film is within the above range, the first and second negative electrode films can be modulated to increase the gradient porosity difference between the upper and lower layers, reduce the tortuosity of lithium-ion transport, and improve the fast charging capability of the battery cell.

[0359] In some embodiments, after the battery cell undergoes an end-of-life (EOL) full-charge test, the thickness of the second negative electrode film is between 15 μm and 70 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, or any combination of two of the above values. When the thickness of the second negative electrode film is within the above range, the first and second negative electrode films can be modulated to increase the gradient porosity difference between the upper and lower layers, reduce the tortuosity of lithium-ion transport, and improve the fast charging capability of the battery cell.

[0360] In this embodiment, for example, a battery charging upper limit voltage of 3.65V and a battery discharging cutoff voltage of 2.0V will be used for explanation.

[0361] The EOL full charge test procedure is as follows: At 60℃, charge the battery to 3.65V at a charging rate of 0.33C (the nominal capacity), then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 10 minutes, then discharge it to 2.0V at a discharging rate of 0.33C, and let it stand for 10 minutes. One charge and discharge cycle is one cycle. The test is stopped when the battery capacity decays to 80% of the nominal capacity. Then, charge at 25°C with a constant current of 0.33C to 3.65V, and then charge at a constant voltage of 0.05C to 3.65V, which is the EOL full charge state. In the EOL full charge state, disassemble the negative electrode plate and use a tomographic scanning electron microscope to observe the cross-section of the thickness direction of the middle region of the negative electrode plate. Distinguish the two regions according to the interface of the first negative electrode film layer and the second negative electrode film layer, and measure the thickness of each. For example, measure the thickness of the first negative electrode film layer at 10 locations and calculate the average value as the average value of the first negative electrode film layer. Measure the thickness of the second negative electrode film layer at 10 locations and calculate the average value as the average value of the second negative electrode film layer.

[0362] In some embodiments, when the negative electrode film layer is a single-layer film (as opposed to the double-layer film layer described above), the negative electrode film layer further includes a lithium-containing binder. Optionally, the mass content of the lithium-containing binder relative to the negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the lithium-containing binder relative to the negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any combination of two of the above values. The lithium element in the lithium-containing binder can exist in ionic form, which can increase the number of freely moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the lithium ion insertion / extraction rate, and improve the fast charging performance of the battery cell. Optionally, the negative electrode film layer may further include a negative electrode binder, such as at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0363] Optionally, the lithium content in the lithium-containing binder is 3% to 10% by mass. For example, the lithium content in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of two of the above values. The lithium content is calculated based on the mass of the lithium-containing binder. When the lithium content is within the above range, a relatively large number of freely moving lithium ions can be achieved in the negative electrode film, further shortening the distance that lithium ions diffuse to the surface of the negative electrode film, increasing the lithium ion insertion / extraction rate, and improving the fast-charging performance of the battery cell.

[0364] For example, lithium-containing binders include lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymers, which are derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, wherein the molar ratio of lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0365] The lithium-containing binder of the above-mentioned material can provide a certain number of lithium ions to the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charging and discharging, with a stable structure, which improves the cycle performance of the negative electrode film layer during fast charging and discharging.

[0366] In other embodiments, where the negative electrode film layer comprises at least two layers, the negative electrode film layer further includes a lithium-containing binder.

[0367] 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, wherein the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. More 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.

[0368] The second lithium-containing binder has a relatively high mass content in the second negative electrode film layer. The second lithium-containing binder provides a relatively larger number of freely movable lithium ions to the second negative electrode film layer, which can further improve the fast charging performance of the battery cell.

[0369] Optionally, the mass content of the first lithium-containing binder relative to the first negative electrode film layer is 0.1% to 1%. For example, the mass content of the first lithium-containing binder relative to 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 any combination of two of the above values. The lithium element in the first lithium-containing binder can exist in ionic form, which can increase the number of freely moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the lithium ion insertion / extraction rate, and improve the fast charging performance of the battery cell.

[0370] Optionally, the lithium content in the first lithium-containing binder is 3% to 10% by mass, and optionally 3% to 8%. For example, the lithium content in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of two of the above values. When the lithium content is within the above range, a relatively large number of freely moving lithium ions can be achieved in the negative electrode film layer, further shortening the distance that lithium ions diffuse to the surface of the negative electrode film layer, increasing the lithium ion insertion / extraction rate, and improving the fast charging performance of the battery cell.

[0371] For example, the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0372] The lithium-containing binder of the above-mentioned material can provide a certain number of lithium ions to the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charging and discharging, with a stable structure, which improves the cycle performance of the negative electrode film layer during fast charging and discharging.

[0373] Optionally, the mass content of the second lithium-containing binder relative to the second negative electrode film layer is 0.1% to 1%. For example, the mass content of the second lithium-containing binder relative to the 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 any combination of two of the above values. The lithium element in the second lithium-containing binder can exist in ionic form, which can increase the number of freely moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the lithium ion insertion / extraction rate, and improve the fast charging performance of the battery cell.

[0374] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0375] Optionally, the lithium content in the second lithium-containing binder is 3% to 10% by mass, and optionally 3% to 8%. For example, the lithium content in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of two of the above values. When the lithium content is within the above range, a relatively large number of freely moving lithium ions can be achieved in the negative electrode film layer, further shortening the distance that lithium ions diffuse to the surface of the negative electrode film layer, increasing the lithium ion insertion / extraction rate, and improving the fast charging performance of the battery cell.

[0376] For example, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0377] The lithium-containing binder of the above-mentioned material can provide a certain number of lithium ions to the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during charging and discharging, with a stable structure, which improves the cycle performance of the negative electrode film layer during fast charging and discharging.

[0378] 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, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0379] 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.

[0380] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0381] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. In some embodiments, the mass content of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0382] In some embodiments, the negative electrode film layer may optionally include other additives. As examples, other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of other additives is ≤2% based on the total weight of the negative electrode film layer.

[0383] In some embodiments, the porosity of the negative electrode film is 40% to 55%. Exemplarily, the porosity of the negative electrode film is 40%, 45%, 50%, 55%, or any combination of two of the above values.

[0384] When the porosity of the negative electrode film layer in the embodiments of this application is within the above-mentioned range, it can enhance the migration ability of lithium ions in the negative electrode film layer and improve fast charging performance.

[0385] In the embodiments of this application, the porosity of the negative electrode film can be measured using the gas displacement method according to standard GB / T24586. Porosity P = (V1-V2) / V1*100%, where V1 is the apparent volume of the sample and V2 is the actual volume of the sample.

[0386] In some embodiments, the negative current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one foil selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. A composite current collector may include a polymer base material and a metal material layer formed on at least one surface of the polymer base material. As an example, the metal material layer may include at least one selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer base material may include at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0387] In some embodiments, the thickness of the negative current collector is 4 μm to 6 μm. For example, the thickness of the negative current collector is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or any combination of two of the above values.

[0388] 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 excellent, and it can enable the battery cell to have a high energy density.

[0389] In the embodiments of this application, the thickness of the negative electrode current collector has a meaning known in the art and can be detected using equipment and methods known in the art. For example, the film layer on the surface of the negative electrode current collector can be washed away with a solvent, and the thickness of the negative electrode current collector can be measured with a micrometer.

[0390] The negative electrode film is typically formed by coating a negative electrode slurry onto the negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0391] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0392] In some embodiments, the negative electrode sheet further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery cell.

[0393] In some embodiments, the thickness of the negative electrode conductive layer is from 0.5 μm to 2 μm. For example, the thickness of the negative electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or any combination of two of the above values.

[0394] When the thickness of the negative electrode conductive layer is within the above range, the conductivity of the negative electrode sheet can be further improved, the heat generation of the negative electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can also be improved.

[0395] In the embodiments of this application, the thickness of the negative electrode conductive layer has a meaning known in the art and can be detected using equipment and methods known in the art, such as the test method for the negative electrode conductive layer described above.

[0396] 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, thereby improving the structural stability of the negative electrode sheet.

[0397] In some embodiments, the negative electrode conductive layer may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0398] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 20% to 40%. For example, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or any combination of two of the above values.

[0399] For example, 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.

[0400] Optionally, the negative electrode binder has a mass content of 60% to 80% in the negative electrode conductive layer. For example, 60%, 65%, 70%, 75%, 80%, or any range of two of the above values.

[0401] For example, 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.

[0402] In some embodiments, the ratio CB of the capacity of the negative electrode film per unit area to the capacity of the positive electrode film per unit area in a single battery cell is from 1.05 to 1.30, and optionally from 1.07 to 1.15. Exemplarily, the ratio CB of the capacity of the negative electrode film per unit area to the capacity of the positive electrode film per unit area in a single 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 of any two of the above values.

[0403] When the ratio CB of the capacity of the negative electrode film per unit area to the capacity of the positive electrode film per unit area in a single battery cell is within the above range, there are sufficient sites in the negative electrode film for lithium insertion, which can reduce the risk of lithium plating and facilitate fast charging.

[0404] In the embodiments of this application, the CB value has a well-known meaning in the art and can be detected using well-known equipment and methods in the art. For example, the capacity of the negative electrode film per unit area and the capacity of the positive electrode film per unit area can be calculated respectively, and the ratio between the two can be calculated to obtain the CB value.

[0405] Specifically, this explanation will be based on an example where the upper limit of battery charging voltage is 3.65V and the battery discharge cutoff voltage is 2.0V.

[0406] The capacity per unit area of ​​the positive electrode film refers to the actual lithium-depleting capacity of the positive electrode active material. The testing method is as follows: The battery is disassembled in a Braun glove box (PRS340 / 11-119-11), the positive electrode sheet is removed, and assembled into a CR2430 model semi-button battery with a positive electrode and lithium sheet. The positive electrode sheet area used is a mm². 2 The electrolyte used was a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). The assembled semi-coin cells were then left to stand for 3 hours. The test was conducted at 25°C. The cells were first charged at 0.1C in the voltage range of 2.0V to 3.65V to remove lithium, and then discharged at 0.05C to insert lithium to 2.0V. This cycle was repeated twice. The discharge coin capacity of the second cycle was recorded as YmAh. The actual battery design had a positive electrode length of bmm and a width of cmm. The number of surfaces of the positive electrode active material coated on the positive electrode current collector was d. Therefore, the capacity of the positive electrode film per unit area was Y / a*b*c*d.

[0407] Specifically, the capacity per unit area of ​​the negative electrode film refers to the actual lithium intercalation capacity of the negative electrode active material. The testing method is as follows: The battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode sheet is removed, and it is assembled into a CR2430 model semi-button battery with a negative electrode and lithium sheet. The area of ​​the negative electrode sheet used is fmm². 2 The electrolyte used was a 1 mol / L LiPF6 solution in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). The assembled semi-coin cells were then left to stand for 3 hours. The test was conducted at 25°C. Lithium insertion was first performed by discharging at 0.1C in the voltage range of 2V-0V, followed by lithium extraction by charging at 0.05C to 2V. This cycle was repeated twice. The discharge capacity of the second cycle was recorded as ZmAh. The actual battery design had a negative electrode length of h mm and a width of i mm. The number of surfaces of the negative electrode active material coated on the negative electrode current collector was d. Therefore, the lithium insertion capacity of the negative electrode was Z / f*h*i*d.

[0408] [Isolation membrane]

[0409] In this embodiment, the separator includes a porous base membrane.

[0410] In some embodiments, the base film includes at least one of glass fiber, nonwoven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0411] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0412] In some embodiments, the porosity of the base membrane is 20% to 70%, optionally 35% to 60%. Exemplarily, the porosity of the base membrane is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range of two of the above values.

[0413] When the porosity of the base film in the embodiments of this application is within the above-mentioned range, it can enhance the migration ability of lithium ions in the separator, further reduce the internal resistance of the battery cell, and thus reduce heat generation.

[0414] In this embodiment, porosity refers to the percentage of the volume of the pores in the separator to the total volume of the separator. Porosity can be tested according to the standard GB / T 36363-2018 "Polyolefin Separators for Battery Cells". It should be noted that the actual testing process may differ slightly from the standard due to differences in testing instruments, testing errors, and to minimize the impact on porosity testing, in order to obtain more accurate test values.

[0415] In some embodiments, the thickness of the base film is 6 μm to 12 μm, optionally 6 μm to 9 μm. Exemplarily, the thickness of the base film is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or any range of two of the above values.

[0416] When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell and thus reduce heat generation.

[0417] In this embodiment, the separator can be a base film. Optionally, the separator further includes a functional layer disposed on at least one side of the base film. The functional layer may include inorganic particles to improve the heat resistance of the separator. Optionally, the functional layer is disposed on both sides of the base film.

[0418] In some embodiments, the functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and includes first inorganic particles. The second functional layer is located on the other side of the base film and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0419] The first and second functional layers have good heat resistance, which can improve the heat resistance of the separator.

[0420] Optionally, the first functional layer may include an adhesive, optionally including at least one of a fluorinated adhesive or a polyacrylic adhesive, such as polyvinylidene fluoride.

[0421] 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. These first inorganic particles can improve the heat resistance of the first functional layer.

[0422] In the embodiments of this application, the thickness of the base film has a meaning known in the art and can be detected using known meanings and equipment. For example, a newly prepared separator can be taken as a sample, or a battery cell that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is about 0% SOC) can be disassembled in reverse, the separator can be obtained from the battery cell, and the separator can be dried and used as a sample. The separator can be cut with an ion beam cutter to form a cross section, and then the thickness of the separator and its various layers can be measured using a scanning electron microscope.

[0423] In the second functional layer, the non-fluorinated polymer particles refer to polymers that are non-fluorinated polymers. For example, non-fluorinated polymer particles include acrylate copolymers. Optionally, acrylate copolymers include acrylate-acrylonitrile-acrylamide-propylene copolymers. Acrylate copolymers have excellent adhesion properties and high adhesion stability to the base film. The molar ratio of each monomer in the copolymer can be arbitrary, for example, a molar ratio of 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0424] The second inorganic particle in the composite particles prevents the non-fluoropolymer particles from sticking together due to the high-temperature treatment during granulation. This creates porosity within the composite particles, facilitating lithium-ion transport and enhancing the ion-conductivity of the separator. Furthermore, the second inorganic particle increases the compressive modulus of the composite particles, reducing their deformation during charging and discharging, resulting in a more stable separator structure and improved kinetic performance of the battery cells, as well as faster charging performance. Optionally, compared to the first functional layer, the second functional layer is positioned closer to the negative electrode. Because the composite particles are less prone to deformation, the separator exerts minimal pressure or other side effects on the negative electrode, ensuring stable kinetic performance of the negative electrode. Correspondingly, the first functional layer is positioned closer to the positive electrode.

[0425] 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. These second inorganic particles can improve the heat resistance of the second functional layer and can combine with non-fluoropolymers to form composite particles, further improving the cycle stability and kinetic performance of the separator, and improving the cycle performance and fast-charging performance of the battery cells.

[0426] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, or optionally 5 nm to 20 nm. For example, 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 any combination of 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 compressive modulus of the composite particles.

[0427] In the embodiments of this application, the average particle size of the second inorganic particles has a meaning known in the art and can be detected using equipment and methods known in the art. For example, after obtaining the separator membrane, the separator membrane is dried and used as a sample. The separator membrane is cut with an ion beam cutter to form a cross-section. Subsequently, the particle size of the second inorganic particles in the separator membrane is measured using a scanning electron microscope. The particle size of multiple, such as 50, second inorganic particles is measured, and their average value is calculated as the average particle size of the second inorganic particles.

[0428] In some embodiments, the ionic conductivity of the separator is from 0.3 mS / cm to 0.6 mS / cm. Exemplarily, the ionic conductivity of the separator is 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.45 mS / cm, 0.5 mS / cm, 0.55 mS / cm, 0.6 mS / cm, or a range consisting of any two of the above values.

[0429] When the ionic conductivity of the separator is within the above range, the lithium-ion migration ability of the separator can be further improved, thereby enhancing the fast charging performance of the battery cell.

[0430] In this application embodiment, the ionic conductivity of the separator has a meaning known in the art and can be detected using equipment and methods known in the art, for example,

[0431] Preparation of the 2025-type button cell for testing: In a vacuum glove box, a lithium sheet was placed in the negative electrode case of the battery, and 150 μL of electrolyte was added. The electrolyte was a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, a separator (with an area of ​​3.14 cm²) was placed inside. 2 The electrode (12 μm thick) is tightly attached to the lithium sheet, then 25 μL of electrolyte is added, and finally the positive electrode (which can be the positive electrode from Example 1) is placed on top and sealed. The assembled button cell is removed from the vacuum glove box and left to stand for 24 hours for further testing.

[0432] Test: At an electrochemical workstation, at 10 -1 ~10 6 The isolation film resistance Rb was obtained by testing within a frequency range of Hz, and the ionic conductivity σ (unit: mS / cm) was calculated using the following formula.

[0433] σ=L / (R b ×S)

[0434] Where: R b Let L be the resistance of the isolation membrane, and S be the thickness and area of ​​the isolation membrane under test, respectively.

[0435] Electrolyte

[0436] In some implementations, the battery cell also includes an electrolyte.

[0437] During the charging and discharging process of a single battery cell, active ions are inserted and extracted back and forth between the positive and negative electrode plates, while the electrolyte plays a role in conducting active ions between the positive and negative electrode plates.

[0438] In this embodiment of the application, the conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm, optionally 15 mS / cm to 20 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm, or any range of two of the above values.

[0439] 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.

[0440] In the embodiments of this application, the conductivity of the electrolyte at room temperature, such as 25°C, is the ionic conductivity, which can be detected using equipment and methods known in the art, such as by referring to industry standard HG-T 4067-2015.

[0441] In some embodiments, the viscosity of the electrolyte at room temperature is from 2.3 mPa·s to 3.5 mPa·s. Exemplarily, the viscosity of the electrolyte is 2.3 mPa·s, 2.4 mPa·s, 2.5 mPa·s, 2.6 mPa·s, 2.7 mPa·s, 2.8 mPa·s, 2.9 mPa·s, 3.0 mPa·s, 3.1 mPa·s, 3.2 mPa·s, 3.3 mPa·s, 3.4 mPa·s, 3.5 mPa·s, or a range consisting of any two of the above values.

[0442] 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.

[0443] In the embodiments of this application, the viscosity of the electrolyte has a meaning known in the art and can be detected using equipment and methods known in the art, such as in accordance with GB / T10247-2008.

[0444] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature, such as 25°C. Exemplarily, the electrolyte density is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, or a range of any two of the above values.

[0445] When the electrolyte density 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.

[0446] In the embodiments of this application, the density of the electrolyte has a meaning known in the art and can be detected using equipment and methods known in the art, such as referring to GB / T 2013-2010 for testing.

[0447] Electrolytes consist of organic solvents and electrolyte salts. The types of organic solvents and electrolyte salts are not specifically limited and can be selected according to actual needs.

[0448] In some embodiments, the organic solvent includes a chain carboxylic acid ester solvent, wherein the mass content of the chain carboxylic acid ester solvent relative to the organic solvent is greater than or equal to 5% and less than or equal to 75%, optionally greater than or equal to 10% and less than or equal to 75%, optionally from 30% to 75%. Exemplarily, the mass content of the chain carboxylic acid ester solvent is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or a range of any two of the above values.

[0449] When the mass content of chain carboxylic acid ester solvents is within the above range, the viscosity of the electrolyte system is relatively low, which is conducive to the migration of lithium ions.

[0450] When the mass content of chain carboxylic acid ester solvents is within the above range, the viscosity of the electrolyte system is relatively low, which is conducive to the migration of lithium ions.

[0451] In some embodiments, the chain carboxylic acid ester solvent includes compounds represented by Formula I.

[0452] In formula I,

[0453] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0454] R2 includes C1 to C5 alkyl or C1 to C5 haloalkyl.

[0455] The aforementioned chain-like carboxylic acid ester solvents have high conductivity, which is beneficial for improving the fast charging capability of battery cells.

[0456] Optionally, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0457] Optionally, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. More optionally, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0458] In the above embodiments, the halogen atom includes one or more of fluorine, chlorine, bromine and iodine atoms, and optionally, the halogen atom includes fluorine atom.

[0459] In the above embodiments, the halogenated alkyl group includes one or more of fluoroalkyl, chloroalkyl, bromoalkyl and iodoalkyl groups, and optionally, the halogenated alkyl group includes fluoroalkyl.

[0460] For example, the chain carboxylic acid ester solvent includes one or more compounds of formula I-1 to formula I-8.

[0461] In some embodiments, the organic solvent also includes carbonate solvents.

[0462] Optionally, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. More preferably, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate. The combined use of the above-mentioned carbonate solvents and chain carboxylic acid ester solvents improves the conductivity of the electrolyte, which is beneficial for lithium ion migration.

[0463] Further optionally, the carbonate solvent in the organic solvent has a mass content of 25% to 95%, optionally 25% to 70%. Exemplarily, the mass content of the carbonate solvent in the organic solvent is 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any combination of two of the above values. The carbonate solvent at the above mass content can further improve the conductivity of the electrolyte at room temperature, which is beneficial for lithium ion migration.

[0464] For example, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, and the carbonate solvent content is 30% to 50% by mass.

[0465] In some embodiments, the electrolyte also contains additives, which may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0466] In some embodiments, the additive comprises one or more of carbonate additives, sulfur-containing additives, and lithium salt additives, optionally at least two. These additives can improve the interfacial film performance on the positive and / or negative electrode sides, which is beneficial for improving the fast-charging performance of individual battery cells and enhancing cycle performance.

[0467] In some embodiments, the additive has a mass content of 1% to 10% in the electrolyte, optionally 2% to 8%, and more preferably 3.5% to 8%. Exemplarily, the additive has a mass content of 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% in the electrolyte, or a range of any two of the above values.

[0468] The additives mentioned above can effectively improve the interfacial film performance on the positive and / or negative electrode sides, which is beneficial to improving the fast charging performance of battery cells and improving cycle performance.

[0469] For example, carbonate additives include one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0470] For example, sulfur-containing additives include one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butenyl sulfite BS, 1,3-propanesulfonate lactone PS, vinyl sulfite ES, and methylene disulfonate MMDS.

[0471] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate (LiBF4), and lithium dioxalate borate (LiBOB).

[0472] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 9%, and optionally 2% to 6%.

[0473] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 4%, and optionally 0.5% to 3%.

[0474] 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%.

[0475] 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%.

[0476] In some embodiments, the electrolyte salt includes a lithium salt, which includes one or more of fluorosulfonylimide salts and lithium hexafluorophosphate (LiPF6). These lithium salts are readily dissociated, facilitating rapid lithium-ion migration, and the electrolyte system is relatively stable and not easily decomposed, thus improving the cycle performance of the battery cells.

[0477] Optionally, the fluorosulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide (LiFSI) and lithium bistrifluoromethanesulfonate (LiTFSI).

[0478] Optionally, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6), wherein the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is from 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is from 0.5 mol / L to 1.0 mol / L.

[0479] For example, 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 (LiPF6) is 0.7 mol / L.

[0480] For example, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L.

[0481] For example, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.8 mol / L.

[0482] Optionally, the molar ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate (LiPF6) is from 0.2 to 1.0, and optionally from 0.2 to 0.5. Exemplarily, the molar ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate (LiPF6) is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range of any two of the above values.

[0483] In the embodiments of this application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte are well-known in the art and can be detected using well-known equipment and methods. For example, the concentrations of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography using the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography analysis.

[0484] In the embodiments of this application, the types and contents of organic components in the electrolyte are defined in the art and can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography.

[0485] In this embodiment, after quantitative and qualitative detection of each component in the electrolyte, the components are classified. Chain-like carboxylic acid ester solvents and carbonate solvents (e.g., ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate) are considered as components of the organic solvent. The mass content of each component is calculated with the mass of the organic solvent representing 100%.

[0486] Carbonate additives (such as vinylene carbonate and fluoroethylene carbonate), sulfur-containing additives, and lithium salt additives are used as additives in the electrolyte. The mass content of each component is calculated based on the mass of the electrolyte as 100%.

[0487] In some embodiments, the battery cell satisfies: d / A ≤ 3.5 g / Ah, optionally 2.40 g / Ah ≤ d / A ≤ 3.3 g / Ah, where d represents the mass of electrolyte in the battery cell in grams (g), and A represents the rated capacity of the battery cell in Ah. Exemplarily, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah, 2.4 g / Ah, or a range of any two of the above values.

[0488] d / A reflects the electrolyte's liquid retention capacity. When d / A is within the above range, the electrolyte can effectively wet the positive and negative electrode plates and improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the fast charging capability of the battery cell.

[0489] In the embodiments of this application, the d / A ratio of a single battery cell can be understood as the liquid retention coefficient, which can be tested using equipment and methods known in the art. For example, it can be described using GB / T31486-2015 "Electrical Performance Requirements and Test Methods for Power Batteries for Electric Vehicles", taking a battery charging upper limit voltage of 3.65V and a battery discharge cut-off voltage of 2.0V as an example.

[0490] At 25°C, the battery cell is charged to 3.65V at 0.33C, then charged at a constant voltage to 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. Then, the positive electrode, negative electrode, separator, and electrolyte are disassembled, with the free electrolyte remaining in a bag. All the solid components are placed in a 60°C oven and baked for at least 4 hours (including but not limited to the positive electrode, negative electrode, separator, and other mechanical parts of the disassembled battery cell that contribute to M0). Then, all components of the battery cell are weighed again as M1, with the weight difference between M0 and M1 as the numerator. The liquid retention coefficient is equal to the weight difference d between M0 and M1 divided by the capacity A.

[0491] As shown in Figure 10, in some embodiments of this application, the battery cell 7 according to the implementation of this application can be assembled into a battery module 6. The number of battery cells 7 contained in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0492] If there are multiple battery cells 7, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that some battery cells 7 are connected in series while others are connected in parallel. Multiple battery cells 7 can be directly connected in series, parallel, or in a mixed configuration, and then the entire assembly of the multiple battery cells 7 is housed within the housing of the battery module 6. Alternatively, multiple battery cells 7 can first be connected in series, parallel, or in a mixed configuration to form the battery module 6, and then the multiple battery modules 6 can be connected in series, parallel, or in a mixed configuration to form a whole, which is then housed within the housing. Optionally, the battery module 6 may also include a housing with a accommodating space, within which multiple battery cells 7 are housed.

[0493] As shown in Figure 11, in some embodiments, the battery module 6 can also be assembled into a battery pack 2, and the number of battery modules 6 contained in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device described herein can be either a battery module 6 or a battery pack 2.

[0494] The battery pack 2 may include a housing 5 and a plurality of battery modules 6 disposed within the housing 5. The housing 5 includes a first housing portion 5a and a second housing portion 5b, and 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 accommodating the battery modules 6. The plurality of battery modules 6 can be arranged in the housing 5 in any manner.

[0495] The first housing portion 5a and the second housing portion 5b overlap each other, and together they define a receiving space 5c for accommodating a single battery cell. The second housing portion 5b can be a hollow structure with one open end, and the first housing portion 5a can be a plate-like structure. The first housing portion 5a covers the open side of the second housing portion 5b to form a housing 5 with the receiving space 5c. Alternatively, both the first housing portion 5a and the second housing portion 5b can be hollow structures with one open side, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the receiving space 5c. Of course, the first housing portion 5a and the second housing portion 5b can be of various shapes, such as cylinders, cuboids, etc.

[0496] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0497] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0498] In some embodiments, during the process of the battery pack 2 or any individual battery cell constituting the battery pack 2 from 0% state of charge to 100% state of charge (SOC), the temperature of the external environment in which the battery pack 2 is located is room temperature, for example, 30°C.

[0499] In some embodiments, during the process of the battery pack 2 or any individual battery cell constituting the battery pack 2 increasing from 20% SOC to 80% SOC, the ambient temperature of the external environment in which the battery pack 2 is located is room temperature, for example, 30°C.

[0500] In some embodiments, the charging process of the battery pack 2 or any individual battery cell comprising the battery pack 2 from 20% state of charge to 80% state of charge includes multiple charging steps. The difference between the maximum state of charge of any charging step and the maximum state of charge of its adjacent charging step is less than or equal to 5% state of charge, such as 1% state of charge, 1.5% state of charge, 2% state of charge, 2.5% state of charge, 3% state of charge, 3.5% state of charge, 4% state of charge, 4.5% state of charge, 5% state of charge, or any range of any two of the above values.

[0501] The battery pack 2 or any individual battery cell comprising the battery pack 2 includes multiple charging steps from 20% state of charge to 40% state of charge. For any charging step, the battery can be charged at any rate between 5C and 10C. The charging rate corresponding to each charging step can be any value of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, or 10C, or a value within the range of any two of the above values.

[0502] For example, the charging steps from 20% to 80% for the battery pack 2 or any individual battery cell comprising the battery pack 2 can be performed as follows:

[0503] Charge from 20% SOC to 25% SOC at a constant current of 5.0C;

[0504] Charge from 25% SOC to 30% SOC at a constant current of 5.0C;

[0505] Charge from 30% SOC to 35% SOC at a constant current of 5.0C;

[0506] Charge from 35% SOC to 40% SOC at a constant current of 5.0C;

[0507] Charge from 40% SOC to 45% SOC at a constant current of 4.6C;

[0508] Charge from 45% SOC to 50% SOC at a constant current of 4.3C;

[0509] Charge from 50% SOC to 55% SOC at a constant current of 4.0C;

[0510] Charge from 55% SOC to 60% SOC at a constant current of 3.7C;

[0511] Charge from 60% SOC to 65% SOC at a constant current of 3.4C;

[0512] Charge from 65% SOC to 70% SOC at a constant current of 3.1C;

[0513] Charge from 70% SOC to 75% SOC at a constant current of 2.9C;

[0514] Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0515] In some embodiments, the charging time for the battery pack 2 or any individual battery cell comprising the battery pack 2 from 20% state of charge to 80% state of charge is less than or equal to 15 minutes, optionally ranging from 6 minutes to 15 minutes. The ambient temperature of the battery pack 2 at 20% state of charge is room temperature, for example, 30°C. Exemplarily, the charging time for 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 of any two of the above values.

[0516] In some embodiments, the volumetric energy density of the battery cell is from 390 Wh / L to 500 Wh / L, optionally from 410 Wh / L to 470 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, 480 Wh / L, 490 Wh / L, 500 Wh / L, or a range of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0517] In the embodiments of this application, the volumetric energy density of a single battery cell has a meaning known in the art and can be detected using equipment and methods known in the art. For example, the following description uses a battery charging upper limit voltage of 3.65V and a battery discharging cutoff voltage of 2.0V as an example.

[0518] Place the battery cell at 25°C and charge it to 3.65V with a constant current of 0.33C, then charge it to 0.05C with a constant voltage, and discharge it to 2.0V with a constant current of 0.33C. Record the discharge capacity A0 at this point, in Ah. Use calipers to measure the length, width, and height of the battery cell (generally calculated based on the battery casing dimensions, excluding the height of the electrode terminals and the insulating film outside the casing). Calculate the volume of the battery cell V0, in L. The volumetric energy density of the battery cell VED = (A0 × discharge plateau voltage) / V0, in Wh / L.

[0519] Electrical appliances

[0520] A second aspect of this application provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack described in this application. The battery cell, battery module, or battery pack can be the power source of the electrical device or the energy storage unit of the electrical device. The electrical device can be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, or power tool, etc. Vehicles can be gasoline-powered vehicles, natural gas-powered vehicles, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.; spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-described electrical device.

[0521] Electrical devices can be equipped with individual battery cells, battery modules, or battery packs depending on their usage requirements.

[0522] Figure 12 is a schematic diagram of an example electrical device 1. This electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 1, a battery pack or battery module can be used.

[0523] The electrical device 1 is equipped with a battery pack 2, which can be located at the bottom, head, or tail of the electrical device 1. The battery pack 2 can be used to supply power to the electrical device 1. For example, the battery pack 2 can serve as the operating power source for the electrical device 1, and can also serve as the driving power source for the electrical device 1, replacing or partially replacing fuel oil or natural gas to provide driving power for the electrical device 1.

[0524] Electrical device 1 may also include controller 3 and motor 4. Controller 3 is used to control battery pack 2 to supply power to motor 4, for example, to meet the power needs of electrical device 1 during startup, navigation and driving.

[0525] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0526] The following charging methods can be selected for the charging process of electrical devices:

[0527] Charge from 20% SOC to 25% SOC at a constant current of 5.0C;

[0528] Charge from 25% SOC to 30% SOC at a constant current of 5.0C;

[0529] Charge from 30% SOC to 35% SOC at a constant current of 5.0C;

[0530] Charge from 35% SOC to 40% SOC at a constant current of 5.0C;

[0531] Charge from 40% SOC to 45% SOC at a constant current of 4.6C;

[0532] Charge from 45% SOC to 50% SOC at a constant current of 4.3C;

[0533] Charge from 50% SOC to 55% SOC at a constant current of 4.0C;

[0534] Charge from 55% SOC to 60% SOC at a constant current of 3.7C;

[0535] Charge from 60% SOC to 65% SOC at a constant current of 3.4C;

[0536] Charge from 65% SOC to 70% SOC at a constant current of 3.1C;

[0537] Charge from 70% SOC to 75% SOC at a constant current of 2.9C;

[0538] Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0539] In some embodiments, the charging time for the electrical device from 20% state of charge to 80% state of charge is less than or equal to 15 minutes, optionally ranging from 6 minutes to 15 minutes, and the ambient temperature of the battery pack 2 in the electrical device at 20% state of charge is room temperature, for example, 30°C. Exemplarily, the charging time for the battery pack 2 in the electrical device 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 of any two of the above values.

[0540] Example

[0541] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0542] Example 1

[0543] 1. Preparation of positive electrode sheet

[0544] The positive electrode includes a positive current collector, a positive conductive layer on the positive current collector, and a positive film layer. The positive current collector is an aluminum foil with a thickness of 10 μm.

[0545] The positive electrode conductive layer on the positive electrode current collector is a film formed by uniformly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride (PVDF), and the solvent N-methylpyrrolidone (NMP), coating it on the surface of the current collector, and drying it. 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%.

[0546] The positive electrode film layer comprises a film layer formed by uniformly coating a positive electrode slurry (solvent being N-methylpyrrolidone, NMP) onto the surface of a positive electrode conductive layer, followed by drying and cold pressing. The positive electrode film layer comprises positive electrode active material, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black in a weight ratio of 97:2:1.

[0547] The positive electrode active material includes lithium iron phosphate and a coating layer. The coating layer is coated on the surface of the lithium iron phosphate and includes lithium titanium iron phosphate (Li2FeTi(PO4)3) and amorphous carbon. The positive electrode active material has a Dv50 of 1.6 μm, a Dv10 of 0.64 μm, a minimum particle size of 0.2 μm, and a maximum particle size of 18 μm.

[0548] The single-sided coating weight of the positive electrode film is 240 mg / 1540.25 mm. 2 .

[0549] 2. Preparation of negative electrode sheet

[0550] The negative electrode includes a negative current collector, a negative conductive layer on the negative current collector, and a negative film layer. The negative current collector is a copper foil with a thickness of 5μm.

[0551] The negative electrode conductive layer on the negative electrode current collector is a film formed by uniformly mixing superconducting carbon, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), and water, and then coating it onto the surface of the negative electrode current collector and drying it. 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 thickener in the negative electrode conductive layer is 5%.

[0552] The negative electrode film layer comprises a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) onto the surface of a negative electrode conductive layer, followed by drying and cold pressing.

[0553] The single-sided coating weight of the negative electrode film is 110 mg / 1540.25 mm. 2 .

[0554] 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.

[0555] The first negative electrode film layer comprises graphite particles in a mass ratio of 96.5:0.5:0.5:1.5:1, conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose. The lithium content in the first lithium-containing binder is 4.8% by mass. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer coats the surface of the artificial graphite, and the carbon coating layer has a mass content of 3.5%.

[0556] The second negative electrode film layer comprises graphite particles in a mass ratio of 97.5:0.5:0.5:0.5:1, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose. The lithium content in the second lithium-containing binder is 4.8% by mass. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer coats the surface of the artificial graphite, and the carbon coating layer has a mass content of 3.5%.

[0557] 3. Separating membrane

[0558] The separator includes a base membrane, which is a 7μm polyethylene film layer with a porosity of 42%.

[0559] 4. Preparation of electrolyte

[0560] The electrolyte consists of organic solvents, lithium salts, and additives.

[0561] The organic solvents include 60% chain carboxylic acid ester solvents (ethyl acetate) and 40% carbonate solvents (30% ethylene carbonate EC, 10% dimethyl carbonate). The mass content of each component in the organic solvents is calculated based on the mass of the organic solvents.

[0562] Based on the mass of the electrolyte, the additive content is 6.5%, which includes vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfite (ES), and lithium difluorooxalate borate (LiDFOB) in a mass ratio of 5:0.5:0.5:0.5.

[0563] The lithium salts include 1 mol / L lithium hexafluorophosphate (LiPF6).

[0564] The electrolyte has a conductivity of 16.4 mS / cm at room temperature.

[0565] 5. Preparation of battery cells

[0566] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, thus obtaining the electrode assembly. The electrode assembly is then placed in an outer packaging shell, dried, and injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a battery cell is obtained. The compaction density of the positive electrode film layer in the battery cell at 100% SOC is 2.65 g / cm³. 3 The compaction density of the negative electrode film at 100% SOC is 1.26 g / cm³. 3 .

[0567] Comparative Example 1 and Comparative Example 2

[0568] Battery cells were prepared using a method similar to that of Example 1, except that the width and length of the positive electrode film were adjusted.

[0569] Examples 2-1 and 2-2

[0570] Battery cells were prepared using a method similar to that of Example 1, except that the width of the positive electrode film was adjusted.

[0571] Performance testing

[0572] 1. DC internal resistance (DCR) test of individual battery cells

[0573] You can refer to the methods in GB / T 31467 "Performance Test Specification for High-Power Lithium-ion Power Batteries for HEVs".

[0574] For example, at -20℃, charge a single battery cell to 3.65V with a constant current of 0.33C, let it stand for 1 minute, then charge it to 3.65V with a constant current of 0.1C, let it stand for 30 minutes, and then discharge it to 2.0V with a constant current of 0.33C. Record the discharge capacity A0 at this point in Ah. Then charge it to 0.5A0Ah with a constant current of 0.33C and adjust the SOC to 50%.

[0575] After placing the battery cell at -20℃ for 2 hours, it was discharged at a constant current of 4C for 10 seconds, and ΔU was recorded. 放电 ΔI 放 电 The discharge DCR data of lithium-ion batteries can be calculated using the following formula, R. 放电 =ΔU 放电 / ΔI 放电 ,

[0576] Wherein, ΔU 放电 ΔI represents the voltage change within 10 seconds of the start of discharge. 放电 This indicates the current value within 10 seconds of the start of discharge.

[0577] 2. Cycle performance of individual battery cells

[0578] At 30°C, the battery cell is charged from 20% SOC to 80% SOC using the above charging process, then charged at 0.33C to 3.65V, left to stand for 30 minutes, and then discharged at 1C to 20% SOC. This constitutes one charge-discharge cycle. The above charge-discharge cycle is repeated 1000 times. The cycle capacity retention rate of the battery cell is calculated. The higher the cycle capacity retention rate, the better the cycle performance of the battery cell.

[0579] The battery charging process from 20% to 80% SOC is as follows:

[0580] Charge from 20% SOC to 25% SOC at a constant current of 5.0C;

[0581] Charge from 25% SOC to 30% SOC at a constant current of 5.0C;

[0582] Charge from 30% SOC to 35% SOC at a constant current of 5.0C;

[0583] Charge from 35% SOC to 40% SOC at a constant current of 5.0C;

[0584] Charge from 40% SOC to 45% SOC at a constant current of 4.6C;

[0585] Charge from 45% SOC to 50% SOC at a constant current of 4.3C;

[0586] Charge from 50% SOC to 55% SOC at a constant current of 4.0C;

[0587] Charge from 55% SOC to 60% SOC at a constant current of 3.7C;

[0588] Charge from 60% SOC to 65% SOC at a constant current of 3.4C;

[0589] Charge from 65% SOC to 70% SOC at a constant current of 3.1C;

[0590] Charge from 70% SOC to 75% SOC at a constant current of 2.9C;

[0591] Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0592] The test results are shown in Table 1.

[0593] Table 1

[0594] In Table 1, in each embodiment and Comparative Example 1,

[0595] The positive electrode tabs are located on both sides of the positive current collector along the length direction, and the negative electrode tabs are located on both sides of the negative current collector along the length direction.

[0596] 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 electrode on the same side is 314 mm². 2 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.

[0597] The positive electrode film layer is disposed on both sides of the thickness direction of the positive electrode current collector, and the negative electrode film layer is disposed on both sides of the thickness direction of the negative electrode current collector.

[0598] As can be seen from Table 1,

[0599] In Comparative Example 1, the length-to-width ratio of the positive electrode film is less than 4, and in Comparative Example 2, the length-to-width ratio is greater than 20, resulting in higher internal resistance of the battery cell and an inability to achieve both excellent cycle performance and energy density. In contrast, the length-to-width ratio of the positive electrode film in the embodiments of this application is between 4 and 20, resulting in lower internal resistance of the battery cell, which is beneficial for improving cycle performance and allows for a balance between improved cycle performance and energy density.

[0600] Comparative Example 3 and Comparative Example 4

[0601] Battery cells were prepared using a method similar to that of Example 1, except that the single-sided coating weight of the negative electrode film was adjusted.

[0602] Examples 3-1 and 3-2

[0603] Battery cells were prepared using a method similar to that of Example 1, except that the single-sided coating weight of the negative electrode film was adjusted.

[0604] The test results are shown in Table 2.

[0605] Table 2

[0606] In Comparative Example 3, the coating weight of the negative electrode film is too small, which cannot meet the energy density requirements; in Comparative Example 4, the coating weight of the negative electrode film is too large, which results in a lower impedance of the battery cell and poorer cycle life.

[0607] In this embodiment, the coating weight of the negative electrode film is 74 mg / 1540.25 mm. 2 Up to 156mg / 1540.25mm 2 It can effectively reduce the internal resistance of individual battery cells, improve the fast charging performance of individual battery cells, and improve cycle performance and have excellent energy density.

[0608] Example 4

[0609] Battery cells were prepared using a method similar to that of Example 1. The difference is that in Example 1, the ratio of the width of the first end face of the positive electrode tab to the width of the positive current collector was 2 / 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 was also 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 current collector was 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 was also 1 / 3.

[0610] Example 5

[0611] The battery cells were prepared using a method similar to that of Example 1, except that the current-carrying area of ​​the positive terminal in Example 1 was 314 mm². 2 The current-carrying area of ​​the negative terminal is 314 mm². 2 In Example 5, the flow area of ​​the positive terminal is 706 mm². 2 The current-carrying area of ​​the negative terminal is 706 mm². 2 .

[0612] Example 6

[0613] Battery cells were prepared using a method similar to that of Example 1, except that the negative electrode sheet was prepared as follows:

[0614] The negative electrode includes a negative current collector, a negative conductive layer on the negative current collector, and a negative film layer. The negative current collector is a copper foil with a thickness of 5μm.

[0615] The negative electrode conductive layer on the negative electrode current collector is a film formed by uniformly mixing the negative electrode conductive agent superconducting carbon, the negative electrode binder styrene-butadiene rubber SBR, the thickener sodium carboxymethyl cellulose (CMC-Na) and the solvent water, coating it on the surface of the negative electrode current collector and drying it. The thickness is 1μm. The negative electrode conductive agent has a mass content of 35% in the negative electrode conductive layer, the negative electrode binder has a mass content of 60% in the negative electrode conductive layer, and the thickener has a mass content of 5% in the negative electrode conductive layer.

[0616] The negative electrode film layer comprises a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) onto the surface of a negative electrode conductive layer, followed by drying and cold pressing.

[0617] The negative electrode film layer includes a first negative electrode film layer, which is located on the surface of the negative electrode conductive layer.

[0618] The first negative electrode film layer comprises graphite particles in a mass ratio of 96.5:0.5:0.5:1.5:1, conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose. The lithium content in the first lithium-containing binder is 4.8% by mass. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer coats the surface of the artificial graphite, and the carbon coating layer has a mass content of 3.5%.

[0619] Comparative Example 5

[0620] The battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 is that the positive electrode tab is disposed on one side of the positive electrode current collector, and the negative electrode tab is disposed on one side of the negative electrode current collector.

[0621] The test results are shown in Table 3.

[0622] Table 3

[0623] As shown in Table 3,

[0624] In Comparative Example 5, when the positive electrode tab is located on one side of the positive current collector along the length direction and the negative electrode tab is located on one side of the negative current collector along the length direction, the current distribution is uneven, the internal resistance of the battery cell is relatively large, and the cycle life is poor.

[0625] 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 small internal resistance and excellent cycle performance and energy density.

[0626] The positive terminal has a flow area of ​​200 mm². 2 Up to 800mm 2 The current-passing area of ​​the negative terminal is 200 mm². 2 Up to 800mm 2 At that time, the battery cells have low internal resistance and excellent cycle performance and energy density.

[0627] When the negative electrode film layer is disposed on at least one side of the negative electrode current collector, the battery cell has a small internal resistance and excellent cycle performance and energy density.

[0628] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and 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, comprising an electrode assembly, the electrode assembly comprising a positive electrode tab, a separator film and a negative electrode tab stacked along a thickness direction of the battery cell; the positive electrode tab comprising a positive electrode lug, a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector along the thickness direction and comprising a positive electrode active material, the positive electrode lug being provided on at least one side of the positive electrode current collector; the negative electrode tab comprising a negative electrode lug, 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 comprising a negative electrode active material, the negative electrode lug being provided on at least one side of the negative electrode current collector, wherein, a ratio of a dimension of the positive electrode film layer along a length direction of the battery cell to a dimension of the positive electrode film layer along a width direction of the battery cell is 4 to 20, the dimension of the positive electrode film layer along the length direction being 600 mm to 1200 mm; The single-side coating weight of the negative electrode film layer is 74 mg / 1540.25 mm 2 to 156 mg / 1540.25 mm 2 .

2. The battery cell of claim 1, wherein, the dimension of the positive electrode film layer along the width direction being 60 mm to 150 mm.

3. The battery cell of claim 1 or 2, wherein, the positive electrode lug is provided on both sides of the positive electrode current collector along the length direction.

4. The battery cell of claim 4, wherein, the positive electrode lug on the same side of the positive electrode current collector is one or more, the positive electrode lug comprising a first end surface connected to the positive electrode current collector, a dimension of the first end surface along the width direction being W1, a sum of dimensions of all first end surfaces on the same side of the positive electrode current collector along the width direction being n*W1, a dimension of the positive electrode current collector along the width direction being W2, n*W1 / W2 being greater than or equal to 1 / 3, n representing a number of all positive electrode lugs on the same side of the positive electrode current collector.

5. The battery cell of claim 4, wherein, n*W1 / W2 is greater than or equal to 2 / 3.

6. The battery cell of any one of claims 1 to 5, wherein, the negative electrode lug is provided on both sides of the negative electrode current collector along the length direction.

7. The battery cell of claim 6, wherein, the negative electrode lug on the same side of the negative electrode current collector is one or more, the negative electrode lug comprising a second end surface connected to the negative electrode current collector, a dimension of the second end surface along the width direction being W3, a sum of dimensions of all second end surfaces on the same side of the negative electrode current collector along the width direction being m*W3, a dimension of the negative electrode current collector along the width direction being W4, m*W3 / W4 being greater than or equal to 1 / 3, m representing a number of all negative electrode lugs on the same side of the negative electrode current collector.

8. The battery cell of claim 7, wherein, m*W3 / W4 is greater than or equal to 2 / 3.

9. The battery cell of any one of claims 1-8, wherein, the positive electrode lug is provided on at least one side of the positive electrode current collector along the width direction.

10. The battery cell of claim 9, wherein, The positive electrode tabs located on the same side of the positive electrode current collecting part are one or more, and the positive electrode tabs include a third end surface connected to the positive electrode current collecting part, and the dimension of the third end surface along the length direction is L 10 The dimensions of all third end surfaces located on the same side of the positive electrode current collecting part along the length direction are added to be s*L 10 The dimension of the positive electrode current collecting part along the length direction is L1, and 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 part.

11. The battery cell of any one of claims 1-10, wherein, the negative electrode lug is provided on at least one side of the negative electrode current collector along the width direction.

12. The battery cell of claim 11, wherein, The negative electrode tabs located on the same side of the negative electrode current collecting portion are one or more, and the negative electrode tabs include a fourth end surface connected to the negative electrode current collecting portion, and the dimension of the fourth end surface along the length direction is L 20 The dimensions of all the fourth end surfaces located on the same side of the negative electrode current collecting portion along the length direction add up to p*L 20 The dimension of the negative electrode current collecting portion along the length direction is L2, and p*L 20 / L2 is greater than or equal to 1 / 3, and p represents the number of all the negative electrode tabs located on the same side of the negative electrode current collecting portion. 13.The battery cell according to any one of claims 1 to 12, wherein, along the length direction, a dimension of the negative electrode film layer is greater than a dimension of the positive electrode film layer, and a difference between the dimension of the negative electrode film layer and the dimension of the positive electrode film layer is OH1, OH1 being 0.5 mm to 3.0 mm; and / or along the width direction, the dimension of the negative electrode film layer is greater than the dimension of the positive electrode film layer, and a difference between the dimension of the negative electrode film layer and the dimension of the positive electrode film layer is OH2, OH2 being 0.5 mm to 3.0 mm. ​ 14. The battery cell according to any one of claims 1 to 13, wherein, the positive electrode tab is disposed on both sides of the positive electrode current collector along the length direction, and the negative electrode tab is disposed on both sides of the negative electrode current collector along the length direction, along the length direction, the size of the negative electrode film layer is greater 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 greater 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, wherein OH1 is greater than OH2.

15. The battery cell according to any one of claims 1 to 14, further comprising a positive electrode terminal directly welded with the positive electrode tab.

16. The battery cell of any one of claims 1-15, wherein, The battery cell further comprises a positive electrode terminal connected with the positive electrode tab, and the positive electrode terminal is one or at least two.

17. The battery cell of claim 16, wherein, The positive electrode terminal is at least two.

18. The battery cell of any one of claims 15-17, wherein, The overcurrent area of the single positive terminal is 200mm 2 up to 800mm 2 .

19. The battery cell according to any one of claims 1 to 18, further comprising a negative electrode terminal directly welded with the negative electrode tab.

20. The battery cell of any one of claims 1-19, wherein, The battery cell further comprises a negative electrode terminal connected with the negative electrode tab, and the negative electrode terminal is one or at least two.

21. The battery cell of claim 20, wherein, The negative electrode terminal is at least two.

22. The battery cell of any one of claims 19-21, wherein, The overcurrent area of the single negative terminal is 200mm 2 to 800mm 2 .

23. The battery cell according to any one of claims 1 to 22, comprising a housing accommodating the electrode assembly, and the thickness of the housing is 0.1 mm to 0.5 mm.

24. The battery cell of claim 23, wherein, The thickness of the housing is 0.2 mm to 0.35 mm.

25. The battery cell according to any one of claims 1 to 24, wherein, The single-side coating weight of the positive electrode film layer is 160 mg / 1540 mm 2 to 340 mg / 1540 / mm 2 ; and / or The compaction density of the positive electrode film layer of the battery cell at 100% state of charge is 2.50 g / cm 3 to 2.80 g / cm 3 .

26. The battery cell of any one of claims 1-25, wherein, the powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm; and / or The powder compaction density of the positive electrode active material at 30000 N is 2.46 g / cm 3 to 2.8 g / cm 3 ; and / or the charge gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g to 170 mAh / g.

27. The battery cell of any one of claims 1-26, wherein, The lithium-containing phosphate of olivine structure comprises: phosphate particles, and a coating layer covering the phosphate particles, the coating layer containing one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

28. The battery cell of claim 27, wherein, The phosphate particles include a compound of a general formula of Li x1 A y1 Me a M b P 1-c X c Y z , wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F.

29. The battery cell of claim 27 or 28, wherein, The coating layer includes a general formula of Li 3-d Fe 2- d M2 d (PO x2 ) y2 a fast ion conductor, M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0 30. The battery cell of any one of claims 27-29, wherein, The graphitization degree of the lithium-containing phosphate of olivine structure is 0.15 to 0.

32.

31. The battery cell of claim 30, wherein, The graphitization degree of the lithium-containing phosphate of olivine structure is 0.19 to 0.

26.

32. The battery cell of any one of claims 27-31, wherein, The mass content of carbon element in the lithium-containing phosphate of olivine structure is 1% to 2%, The lithium-containing phosphate of olivine structure has a specific surface area of 5 m 2 / g to 18 m 2 / g.

33. The battery cell of claim 32, wherein, The lithium-containing phosphate of olivine structure has a specific surface area of 7.5 m 2 / g to 14 m 2 / g.

34. The battery cell of any one of claims 27-33, wherein, The lithium-containing phosphate of olivine structure is in a particulate form, and the volume distribution particle size of the lithium-containing phosphate of olivine structure satisfies: 1 μm≤Dv50≤2 μm, 0.4 μm≤Dv10≤0.7 μm.

35. The battery cell of any one of claims 27-34, wherein, The particle size of the smallest particles in the lithium-containing phosphate of olivine structure is 0.1 μm to 0.4 μm; and / or The particle size of the largest particles in the lithium-containing phosphate of olivine structure is 15 μm to 25 μm.

36. The battery cell of any one of claims 1-35, wherein, 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 of any one of claims 1-36, wherein, The thickness of the positive electrode current collector is 10 μm to 15 μm.

38. The battery cell of any one of claims 1-37, wherein, The positive electrode tab further includes a positive electrode conductive layer, the positive electrode conductive layer being located between the positive electrode film layer and the positive electrode current collector.

39. The battery cell of any one of claims 1-38, wherein, The positive electrode film layer further includes a first material, the first material including one or more of a ternary material, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite.

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

41. The battery cell of any one of claims 1 to 40, wherein, The compacted density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 .

42. The battery cell of any one of claims 1-41, wherein, 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 active material at 20000N is 1.5g / cm 3 to 1.85g / cm 3 ; and / or the charge gram capacity of the negative electrode active material at a 0.1C rate is 350 mAh / g to 480 mAh / g.

43. The battery cell of any one of claims 1-42, wherein, The negative electrode active material includes a carbon-based material, the carbon-based material including graphite particles, the graphite particles having a graphitization degree of 92.0% to 94.5%.

44. The battery cell of claim 43, wherein, The graphite particles include: artificial graphite including secondary particles, and a carbon coating layer coated on a surface of the artificial graphite.

45. The battery cell of claim 44, wherein, The mass content of the amorphous carbon layer is 2% to 5% based on the mass of the graphite particles.

46. The battery cell of any one of claims 1-45, wherein, The porosity of the negative electrode film layer is 40% to 55%.

47. The battery cell of any one of claims 1-46, wherein, The negative electrode film layer is a single-layer film layer, the negative electrode active material is particulate, and the volume average particle diameter of the negative electrode active material is 8.2 μm to 13.5 μm.

48. The battery cell of any one of claims 1-46, wherein, The negative electrode film layer includes: a first negative electrode film layer disposed on a surface of the negative electrode current collector, the first negative electrode film layer including a carbon-based material, and a second negative electrode film layer connected to a side of the first negative electrode film layer facing away from the negative electrode current collector, the second negative electrode film layer including a carbon-based material, the carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently include graphite particles, and the volume average particle diameter Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle diameter Dv50 of the graphite particles in the second negative electrode film layer.

49. The battery cell of claim 48, wherein, the volume average particle diameter Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm, and / or the volume average particle diameter Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm.

50. The battery cell of claim 48 or 49, wherein, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer.

51. The battery cell of claim 50, wherein, 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 , and / or 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 .

52. The battery cell of any one of claims 48-51, wherein, the first negative electrode film layer further includes a first lithium-containing binder, the second negative electrode film layer further includes a second lithium-containing binder, and the mass content of the first lithium-containing binder with respect 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 with respect to the mass of the second negative electrode film layer.

53. The battery cell of claim 52, wherein, the mass content of the first lithium-containing binder with respect 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 with respect to the mass of the second negative electrode film layer is 0.1% to 1%.

54. The battery cell of claim 52 or 53, wherein, a mass content of lithium element in the first lithium-containing binder is 3% to 10%, and / or a mass content of lithium element in the second lithium-containing binder is 3% to 10%.

55. The battery cell of any one of claims 52 to 54, wherein, the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers in a molar ratio of 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%; and / or the second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers in a molar ratio of 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. a thickness of the negative current collector is 4 pm to 6 pm.

56. The battery cell of any one of claims 1-55, wherein, the negative electrode tab further comprises a negative conductive layer between the negative film layer and the negative current collector.

57. The battery cell of any one of claims 1-56, wherein, 58. The battery cell of any one of claims 1 to 57, wherein, an electrical conductivity of the electrolyte at room temperature is 13 mS / cm to 20 mS / cm; and / or a viscosity of the electrolyte at room temperature is 2.3 mPa-s to 3.5 mPa-s; and / or a density of the electrolyte at room temperature is 1.05 g / mL to 1.35 g / mL.

59. The battery cell of any one of claims 1 to 58, comprising an electrolyte, the electrolyte comprising an organic solvent, the organic solvent comprising a chain carboxylic acid ester-based solvent, a mass content of the chain carboxylic acid ester-based solvent in the organic solvent is 5% to 75%. a mass content of the chain carboxylic acid ester-based solvent in the organic solvent is 30% to 75%.

60. The battery cell of claim 59, wherein, in Formula I, 61. The battery cell of claim 59 or 60, wherein, The chain carboxylate-based solvent includes a compound represented by Formula I, R1comprises a hydrogen atom, a halogen atom, a C1to C5alkyl group, or a C1to C5haloalkyl group, R2comprises a C1to C5alkyl group or a C1to C5haloalkyl group.

62. The battery cell of claim 61, wherein, R1comprises a hydrogen atom, a halogen atom, a C1to C3alkyl group, or a C1to C3haloalkyl group, and / or R2comprises a C1to C3alkyl group or a C1to C3haloalkyl group. the organic solvent further comprises a carbonate-based solvent, the carbonate-based solvent comprising one or more of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

63. The battery cell of claim 62, wherein, The chain carboxylate-based solvent includes one or more of compounds represented by Formula I-1 to Formula I-8, 64. The battery cell of any one of claims 59-63, wherein, the carbonate-based solvent comprises one or more of vinyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

65. The battery cell of claim 64, wherein, ​ 66. The battery cell of claim 64 or 65, wherein, The mass content of the carbonate-based solvent in the organic solvent is 25% to 95%.

67. The battery cell of any one of claims 1-66, wherein, The electrolyte further comprises an additive, and the additive comprises one or more of a carbonate-based additive, a sulfur-containing additive, and a lithium salt-based additive.

68. The battery cell of claim 67, wherein, The carbonate-based additive comprises one or more of vinylene carbonate, fluoroethylene carbonate, and / or The sulfur-containing additive comprises one or more of vinyl sulfonate, bis vinyl sulfonate, butylene sulfite, 1,3-propane sulfonate, vinyl sulfite, and methyl bisulfite, and / or The lithium salt-based additive comprises one or more of lithium difluorophosphate, lithium difluoro oxalate borate, lithium tetrafluoroborate, and lithium bis-oxalate borate.

69. The battery cell of claim 67 or 68, wherein, The mass content of the additive in the electrolyte is 1% to 10%.

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

71. The battery cell of any one of Claims 1-70, wherein, The electrolyte further comprises a lithium salt, and the lithium salt comprises one or more of a fluorine-containing sulfonimide salt and lithium hexafluorophosphate.

72. The battery cell of claim 71, wherein, The fluorine-containing sulfonimide salt comprises one or more of lithium bisfluorosulfonimide and lithium bistrifluoromethylsulfonimide.

73. The battery cell of claim 72, wherein, The lithium salt comprises lithium bisfluorosulfonimide and lithium hexafluorophosphate, the molar concentration of the lithium bisfluorosulfonimide 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 of claim 73, wherein, The ratio of the molar concentration of the lithium bisfluorosulfonimide to the molar concentration of the lithium hexafluorophosphate is 0.2 to 1.

0.

75. The battery cell of any one of Claims 1-74, wherein, The separator film comprises a base film of a porous structure, the thickness of the base film is 6 μm to 12 μm, and / or the porosity of the base film is 35% to 60%.

76. The battery cell of claim 75, wherein, The separator film further comprises a functional layer provided on at least one side of the base film, and the functional layer comprises: a first functional layer on one side of the base film, the first functional layer comprising first inorganic particles, a second functional layer on the other side of the base film, the second functional layer comprising composite particles, the composite particles comprising second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles being attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles.

77. The battery cell of claim 76, wherein, The non-fluoropolymer particles comprise an acrylate copolymer.

78. The battery cell of claim 76 or 77, wherein, The first inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide, and / or The second inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

79. The battery cell of any one of claims 76-78, wherein, The average particle size of the second inorganic particles is 5 nm to 100 nm.

80. The battery cell of any one of claims 1 to 79, having a charge time from 20% state of charge to 80% state of charge of 6 min to 15 min.

81. A battery device comprising the battery cell of any one of claims 1 to 80.

82. The battery device of claim 81, wherein, The battery device has a charge time from 20% state of charge to 80% state of charge of 6 min to 15 min.

83. An electrical device comprising the battery of claim 81 or 82.

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