Battery cell, battery device, and electric device

Abstract

A battery cell, a battery device and an electric device. The battery cell comprises an electrode assembly, and the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet which are stacked in the thickness direction of the battery cell; the positive electrode sheet comprises a positive electrode tab, a positive electrode current collecting portion, and a positive electrode film layer provided on at least one surface of the positive electrode current collecting portion in the thickness direction and comprising a positive electrode active material, the positive electrode tab is provided on at least one side of the positive electrode current collecting portion, and the positive electrode active material comprises a lithium-containing phosphate having an olivine structure; and the negative electrode sheet comprises a negative electrode tab, a negative electrode current collecting portion, and a negative electrode film layer provided on at least one surface of the negative electrode current collecting portion in the thickness direction and comprising a negative electrode active material, and the negative electrode tab is provided on at least one side of the negative electrode current collecting portion, wherein the ratio of the length to the width of the positive electrode film layer is from 2.66 to 7.5, and the single-side coating weight of the negative electrode film layer is from 90 mg / 1540.25 mm2 to 170 mg / 1540.25 mm2. The rapid charging performance and cycle performance of battery cells can be improved.

Description

Battery cell, battery device and power utilization device TECHNICAL FIELD

[0001] The present application relates to a battery cell, a battery device and a power utilization 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 a power utilization 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 and an electrolyte, 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 positive electrode active material comprising a lithium-containing phosphate with an olivine structure; 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 size of the positive electrode film layer along a length direction of the battery cell to a size of the positive electrode film layer along a width direction of the battery cell is 2.66 to 7.5; a single-side coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 .

[0006] Therefore, when the ratio of the length and the width of the positive electrode film layer is in the above range and the single-side 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 relatively uniform, the lithium uniformly discharged can be uniformly embedded in the negative electrode sheet, the negative electrode sheet is less likely to cause 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 length of the positive electrode film layer is 200 mm to 590 mm. The length of the positive electrode film layer is relatively long, which is conducive to increasing the coating weight of the positive electrode film layer and improving the energy density of the battery cell.

[0008] In some embodiments, the width of the positive electrode film layer is 80 mm to 210 mm. The width of the positive electrode film layer is relatively short, so that the transmission path of electrons in the width direction is relatively short, and the uniformity of the current in the width direction can be improved.

[0009] In some embodiments, the positive electrode tab is arranged on at least one side of the positive electrode current collecting part along the length direction of the battery cell, and optionally, the positive electrode tab is arranged on both sides of the positive electrode current collecting part along the length direction of the battery cell. The positive electrode tab is arranged on both sides of the positive electrode current collecting part along the length direction, so that the current in the length direction of the positive electrode current collecting part is evenly distributed by the positive electrode tabs on both sides, the transmission path of electrons is relatively short, 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.

[0010] In some embodiments, the positive electrode tab on the same side of the positive electrode current collecting part is one or more, the positive electrode tab comprises a first end surface connected to the positive electrode current collecting part, 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 collecting part along the width direction is n*W1, the size of the positive electrode current collecting part 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 collecting part. 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 collecting part.

[0011] 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.

[0012] In some embodiments, the negative electrode tab is arranged on at least one side of the negative electrode current collecting part along the length direction of the battery cell, and optionally, the negative electrode tab is arranged on both sides of the negative electrode current collecting part along the length direction of the battery cell. The negative electrode tab is arranged on both sides of the negative electrode current collecting part along the length direction, so that the current in the length direction of the negative electrode current collecting part is evenly distributed by the negative electrode tabs on both sides, the transmission path of electrons is relatively short, and the current distribution is more uniform, the lithiation state of the negative electrode tab is uniform, and the charging performance of the battery cell can be improved.

[0013] In some embodiments, the negative electrode tab on the same side of the negative electrode current collecting part is one or more, the negative electrode tab comprises a second end surface connected to the negative electrode current collecting part, 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 collecting part along the width direction is m*W3, the size of the negative electrode current collecting part 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 collecting part. 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 collecting part.

[0014] Thus, when m*W3 / W4 satisfies the above range, the flow area of the negative tab is relatively large, which is beneficial to improve the rapid charging performance of the battery cell.

[0015] In some embodiments, the positive tab is arranged on at least one side of the positive current collecting part along the length direction, the negative tab is arranged on at least one side of the negative current collecting part along the length direction, the size of the negative film layer is greater than the size of the positive film layer along the length direction of the battery cell, and the difference between the size of the negative film layer and the size of the positive film layer is OH1; the size of the negative film layer is greater than the size of the positive film layer along the width direction of the battery cell, and the difference between the size of the negative film layer and the size of the positive film layer is OH2, wherein OH1 is greater than OH2.

[0016] Thus, the embodiments of the present application set OH1 to be greater than OH2, so that the ability of the negative film layer close to the negative tab to receive lithium ions in the length direction is stronger, especially the ability of the area of the negative film layer close to the negative tab to receive lithium ions is improved, the risk of lithium precipitation is reduced, and the use reliability of the battery cell is improved.

[0017] In some embodiments, OH1 is 0.5 mm to 3.0 mm.

[0018] In some embodiments, OH2 is 0.5 mm to 3.0 mm.

[0019] In some embodiments, the battery cell further comprises a positive terminal, and the positive terminal is electrically connected with the positive tab.

[0020] In some embodiments, the positive terminal is directly welded with the positive tab. Directly welding the positive terminal and the positive tab can reduce the resistance at the connection, which is beneficial to reduce the overall internal resistance of the battery cell.

[0021] In some embodiments, the number of positive terminals located on the same side of the positive current collecting part is at least two. At least two positive terminals can increase the overall flow capacity of the positive terminals.

[0022] In some embodiments, the battery cell further comprises at least one positive terminal, and the flow area of all the positive terminals located on the same side of the positive current collecting part is 150 mm 2 to 1000 mm 2 . When the flow area of the positive terminal satisfies the above relationship, the flow capacity is relatively excellent, which is beneficial to rapid charging.

[0023] In some embodiments, the battery cell further comprises a negative terminal, and the negative terminal is electrically connected with the negative tab.

[0024] In some embodiments, the negative terminal is directly welded with the negative tab. 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.

[0025] 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 overcurrent capacity of the negative terminals.

[0026] In some embodiments, the battery cell further comprises at least one negative terminal, and the overcurrent area of all negative terminals located on the same side of the negative current collector is 150 mm 2 to 1000 mm 2 . When the overcurrent area of the negative terminal satisfies the above relationship, the overcurrent capacity is relatively excellent, which is conducive to rapid charging.

[0027] In some embodiments, the battery cell comprises a shell, the shell accommodating the electrode assembly and the electrolyte, and the thickness of the shell is 0.1 mm to 0.5 mm, which can be optionally 0.2 mm to 0.35 mm. The thickness of the shell is relatively thin, and the shell occupies less space, which can further improve the energy density of the battery cell.

[0028] In some embodiments, the battery cell is under 100% state of charge, and the single-sided coating weight of the negative film layer is 110 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2 . When the compaction density of the negative film layer is in the above range, it is conducive to improving the energy density of the battery cell, and because the negative active material in the negative film layer is packed more tightly, the contact resistance between particles is smaller, which can further reduce the resistance of the pole piece, thereby reducing heat generation.

[0029] In some embodiments, the battery cell is under 100% state of charge, and the compaction density of the positive film layer is 2.50 g / cm 3 to 2.80 g / cm 3 , which can be optionally 2.55 g / cm 3 to 2.70 g / 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 more tightly, the contact resistance between particles is smaller, which can further reduce the resistance of the pole piece, thereby reducing heat generation.

[0030] In some embodiments, the single-sided coating weight of the positive film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 , which can be optionally 240 mg / 1540.25 mm 2to 330 mg / 1540.25 mm 2 When the single-side coating weight of the positive electrode film layer is in the above range, the heat generation per unit area of the positive electrode tab will not be too large, and the energy density of the battery cell can be improved.

[0031] In some embodiments, the powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm. The powder resistivity of the positive electrode active material is relatively low, so that the resistance of the positive electrode tab is relatively low, and the heat generation of the battery cell is less.

[0032] In some embodiments, the powder compaction density of the positive electrode active material under 30000 N is 2.46 g / cm 3 to 2.8 g / cm 3 When the powder compaction density of the positive electrode active material under 30000 N is in the above range, the energy density of the battery cell can be improved, and because the positive electrode active material in the positive electrode film layer can be more closely packed, the contact resistance between particles is small, which can further reduce the resistance of the tab and thus reduce the heat generation.

[0033] In some embodiments, the charge gram capacity of the positive electrode active material under 0.1C rate is 150 mAh / g to 170 mAh / 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.

[0034] In some embodiments, the lithium-containing phosphate of olivine structure includes phosphate particles and a coating layer, the coating layer coats the phosphate particles, and the coating layer contains one or more 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 lithium-containing phosphate of olivine structure, reduce the powder resistivity of the material, and facilitate the migration rate of lithium ions, thereby reducing the heat generation of the battery cell.

[0035] In some embodiments, the phosphate particles include 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 comprises one or more of Na, K, Mg, Me comprises one or more of Mn, Fe, Co, Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X comprises one or more of S, Si, Cl, B, C, N, and Y comprises 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.

[0036] In some embodiments, the coating layer comprises a compound of the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 ) 2 In some embodiments, the graphite degree of the positive active material is 0.15 to 0.32, and can be 0.19 to 0.26. When the graphite degree of the positive active material is in the above range, the conductivity of the positive active material is improved, and the heat generation of the positive plate is reduced, thereby reducing the heat generation of the battery cell.

[0037] In some embodiments, the graphite degree of the positive active material is 0.15 to 0.32, and can be 0.19 to 0.26. When the graphite degree of the positive active material is in the above range, the conductivity of the positive active material is improved, and the heat generation of the positive plate is reduced, thereby reducing the heat generation of the battery cell.

[0038] In some embodiments, the mass content of carbon element in the olivine-structured lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine-structured lithium-containing phosphate is 5m 2 / g to 18m 2 / g, and can be 7.5m 2 / g to 14m 2 / g.

[0039] Therefore, the material with the above mass content of carbon element and the above specific surface area in the embodiments of the present application 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.

[0040] In some embodiments, the lithium-containing olivine-structured phosphate is in a particulate form, and the volume distribution particle size satisfies 1 μm≤Dv50≤2 μm and 0.4 μm≤Dv10≤0.7 μm. The particle size of the lithium-containing olivine-structured phosphate is relatively small, the lithium ion has a short deintercalation path in the positive electrode active material, and the heat generation is less. Moreover, the particle size of the positive electrode active material is not too small, and the agglomeration is unlikely to occur in the process of preparation and production, so that the performance of the positive electrode active material is stable.

[0041] In some embodiments, the lithium-containing olivine-structured phosphate is in a particulate form, and the lithium-containing olivine-structured phosphate includes secondary particles, and the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. The average particle size of the primary particles is relatively small, the lithium ion has a short deintercalation path in the positive electrode active material, and the heat generation is less.

[0042] In some embodiments, the particle size of the smallest particles in the lithium-containing olivine-structured phosphate is 0.1 μm to 0.4 μm. When the particle size of the smallest particles is in the above range, the agglomeration is unlikely to occur in the process of preparation and production of the positive electrode film layer.

[0043] In some embodiments, the particle size of the largest particles in the lithium-containing olivine-structured phosphate is 15 μm to 25 μm. When the particle size of the largest particles is in the above range, the migration path of the lithium ion is not too long in the process of charging and discharging, and the rapid charging and discharging performance of the battery cell can be improved.

[0044] In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05 to 0.3. When the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is in the above range, the rapid charging capability and the energy density of the battery cell can be improved.

[0045] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm. When the thickness of the positive electrode current collector is in the above range, the overcurrent capability of the positive electrode current collector is excellent, and the battery cell has a high energy density.

[0046] In some embodiments, the positive electrode film layer further includes a first material, and the first material includes 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 manganite, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. The first material can be used as a lithium supplement, and can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and thus improve the energy density of the battery cell.

[0047] In some embodiments, the lithium replenishing agent has a mass content of 0.5% to 5% in the positive electrode film. 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.

[0048] 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.

[0049] In some embodiments, the thickness of the positive electrode conductive layer is from 0.5 μm to 2 μm. When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode 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 at the same time, the energy density of the battery cell can be improved.

[0050] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet and reducing the heat generation of the battery cell. The positive electrode binder in the positive electrode conductive layer can improve the adhesion between the positive electrode current collector and the positive electrode film layer, thereby improving the structural stability of the positive electrode sheet.

[0051] In some embodiments, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0052] In some embodiments, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins.

[0053] 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 The option is 1.25g / cm³. 3 Up to 1.36 g / cm 3 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. Furthermore, since 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.

[0054] In some embodiments, the powder compaction density of the negative active material at 20000N is 1.5g / cm3 to 1.85g / cm3. 3 to 1.85g / cm3 3 When the powder compaction density of the negative active material at 20000N is within the above range, the energy density of the battery cell can be improved, and the negative active material in the negative 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.

[0055] In some embodiments, the charge gram capacity of the negative active material at 0.1C rate is greater than or equal to 350mAh / g. When the charge gram capacity of the negative active material at 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0056] In some embodiments, the negative active material comprises a carbon-based material, 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 electrical conductivity of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the rapid charging performance of the battery cell.

[0057] 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 electrical conductivity of the carbon coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0058] In some embodiments, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode sheet and the heat generation of the battery cell can be further reduced.

[0059] In some embodiments, the negative film layer comprises a first negative film layer and a second negative film layer, the first negative film layer is arranged on the surface of the negative current collector, the first negative film layer comprises a carbon-based material, the second negative film layer is connected to the side of the first negative film layer away from the negative current collector, the second negative film layer comprises a carbon-based material, and the carbon-based material in the first negative film layer and the carbon-based material in the second negative film layer each independently comprises graphite particles, and the volume average particle size Dv50 of the graphite particles in the first negative film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative film layer.

[0060] Therefore, the particle size in the first negative electrode film layer and the second negative electrode film layer in the embodiments of the present application is different, which can improve the rapid charging performance of the battery monomer. Specifically, in the rapid charging process, the overpotential of the second negative electrode film layer is generally high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. However, the particle size in the second negative electrode film layer in the embodiments of the present application 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 of the negative electrode sheet.

[0061] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0062] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, so that the energy density of the battery monomer is improved, and the first negative electrode film layer is relatively sparse, and the pores are more abundant, which can improve the rapid charging performance of the battery monomer.

[0063] 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 monomer can be improved.

[0064] 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 monomer can be improved.

[0065] In some embodiments, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm. When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is in the above range, the rapid charging performance can be improved.

[0066] In some embodiments, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm. When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is in the above range, the rapid charging performance of the battery monomer can be improved.

[0067] 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.

[0068] 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 free lithium ions for the second negative electrode film layer, which can further improve the rapid charging performance of the battery cell.

[0069] In some embodiments, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. When the mass content of the first lithium-containing binder is within the above range, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0070] In some embodiments, the mass content of lithium in the first lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium is within the above range, the number of free lithium ions in the negative electrode film layer can be relatively large, the distance of lithium ion diffusion to the surface of the negative electrode film layer can be further shortened, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0071] 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 within the above range, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0072] In some embodiments, the mass content of lithium in the second lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium is within the above range, the number of free lithium ions in the negative electrode film layer can be relatively large, the distance of lithium ion diffusion to the surface of the negative electrode film layer can be further shortened, the deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0073] In some embodiments, the first lithium-containing binder comprises lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0074] 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, and has a stable structure, so that the cycle performance of the negative electrode film layer during rapid charging and discharging is improved.

[0075] In some embodiments, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer 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%.

[0076] 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, and has a stable structure, so that the cycle performance of the negative electrode film layer during rapid charging and discharging is improved.

[0077] In some embodiments, the negative active material further includes 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.

[0078] 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 flow capacity of the negative current collector is excellent, and the battery monomer has a high energy density.

[0079] In some embodiments, the negative electrode sheet further includes a negative conductive layer between the negative electrode film layer and the negative current collector.

[0080] 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.

[0081] In some embodiments, the negative conductive layer includes one or more of a negative conductive agent and a negative binder. The negative conductive agent in the negative conductive layer can improve the conductivity of the negative conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the heat generation of the battery monomer, and the negative binder in the negative conductive layer can improve the adhesion between the negative current collector and the negative electrode film layer and improve the structural stability of the negative electrode sheet.

[0082] In some embodiments, the negative electrode conductive agent includes one or more of super-p carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] In some embodiments, the negative electrode binder includes one or more of styrene butadiene rubber, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0084] In some embodiments, the separator film includes a base film with a porous structure, and the porosity of the base film is 20% to 70%. When the porosity of the separator film is in the above range, the migration ability of lithium ions in the separator film is improved, and the internal resistance of the battery cell is further reduced, thereby reducing heat generation.

[0085] In some embodiments, the separator film includes a base film with a porous structure, and the porosity of the base film is 35% to 60%. When the porosity of the separator film is in the above range, the migration ability of lithium ions in the separator film is improved, and the internal resistance of the battery cell is further reduced, thereby reducing heat generation.

[0086] In some embodiments, the thickness of the base film is 6 μm to 12 μm. When the thickness of the base film is in the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell is further reduced, thereby reducing heat generation.

[0087] In some embodiments, the thickness of the base film is 6 μm to 9 μm. When the thickness of the base film is in the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell is further reduced, thereby reducing heat generation.

[0088] In some embodiments, the separator film includes a base film and a functional layer disposed on at least one side of the base film, the functional layer includes a first functional layer and a second functional layer, the first functional layer is located on one side of the base film, the first functional layer includes first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer includes composite particles, the composite particles include second inorganic particles and 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.

[0089] In some embodiments, the non-fluoropolymer particles include an acrylate copolymer. The acrylate copolymer has excellent adhesion, and has high adhesion stability with the base film.

[0090] 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.

[0091] 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.

[0092] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is in the above range, the heat resistance and the compression modulus of the composite particles can be improved.

[0093] In some embodiments, the carboxylic acid ester-based solvent includes a chain carboxylic acid ester-based solvent, and the mass content of the chain carboxylic acid ester-based solvent in the organic solvent is greater than or equal to 5% and less than or equal to 75%, optionally greater than or equal to 10% and less than or equal to 75%, optionally 30% to 70%, and optionally 50% to 70%. When the mass content of the chain carboxylic acid ester-based solvent is in the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0094] In some embodiments, the chain carboxylic acid ester-based solvent includes a compound represented by Formula I,

[0095] In Formula I,

[0096] 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 carboxylic acid ester-based solvent in the embodiments of the present application has a relatively high conductivity, which is beneficial to improving the rapid charging capability of the battery cell.

[0097] 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.

[0098] In some embodiments, R2 includes a C1 to C3 alkyl group or a C1 to C3 halogenated alkyl group.

[0099] In some embodiments, the chain carboxylic acid ester-based solvent includes one or more of a compound represented by Formula I-1 to a compound represented by Formula I-8,

[0100] 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 combination of the above-mentioned carbonate solvent and chain carboxylic ester solvent can improve the conductivity of the electrolyte, and facilitate the migration of lithium ions.

[0101] In some embodiments, the carbonate solvent comprises one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate.

[0102] In some embodiments, the mass content of the carbonate solvent in the organic solvent is 30% to 70%, or 30% to 50%. The above-mentioned mass content of the carbonate solvent can further improve the conductivity of the electrolyte, and facilitate the migration of lithium ions.

[0103] In some embodiments, the electrolyte further comprises an additive, and the additive comprises one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The above-mentioned additive can improve the performance of the interface film on the positive electrode side and / or the negative electrode side, improve the rapid charging performance of the battery cell, and improve the cycle performance.

[0104] In some embodiments, the carbonate additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0105] 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, ethylene sulfite ES, and methyl methylene disulfonate MMDS.

[0106] 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.

[0107] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, or 2% to 8%. The above-mentioned mass content of the additive can effectively improve the performance of the interface film on the positive electrode side and / or the negative electrode side, improve the rapid charging performance of the battery cell, and improve the cycle performance.

[0108] 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 above-mentioned 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.

[0109] In some embodiments, the fluorine-containing sulfimide salt includes one or more of lithium bisfluorosulfimide (LiFSI), lithium bis-trifluoromethanesulfonamide (LiTFSI).

[0110] In some embodiments, the lithium salt includes lithium bisfluorosulfimide (LiFSI) and lithium hexafluorophosphate (LiPF6), the molar concentration of lithium bisfluorosulfimide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0111] 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.

[0112] In some embodiments, the base material of the shell includes steel, and the thickness of the shell is 0.1 mm to 0.5 mm, and optionally 0.2 mm to 0.35 mm. When the thickness of the shell is in the above range, the mechanical strength of the shell is relatively high, which can improve the use reliability and cycle performance of the battery monomer, and the shell occupies less space, and the internal space of the shell is relatively large, which is conducive to improving the energy density of the battery monomer.

[0113] In some embodiments, the battery monomer further includes an electrode terminal, and the electrode assembly includes a tab portion, and the tab portion is directly welded to the electrode terminal. Direct welding can reduce the resistance at the connection, which is conducive to reducing the overall internal resistance of the battery monomer.

[0114] In some embodiments, the charging time of the battery monomer from 20% state of charge to 80% state of charge is 5 min to 12.5 min. The charging speed of the battery monomer is relatively fast, which is more conducive to improving the rapid charging capability.

[0115] In the second aspect, the present application provides a battery device, which includes a plurality of battery monomers according to any one of the embodiments of the first aspect of the present application.

[0116] In some embodiments, the charging time of the battery device from 20% state of charge to 80% state of charge is 5 min to 12.5 min. The charging speed of the battery device is relatively fast, which is more conducive to improving the rapid charging capability.

[0117] In the third aspect, the present application provides a power consumption device, which includes a battery device according to any one of the embodiments of the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0118] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings described below are only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the drawings.

[0119] Fig. 1 is a structural schematic diagram of a battery cell provided by some embodiments of the present application;

[0120] Fig. 2 is an exploded schematic diagram of a battery cell provided by some embodiments of the present application;

[0121] Fig. 3 is a sectional schematic diagram of an electrode assembly of a battery cell provided by some embodiments of the present application;

[0122] Fig. 4 is a structural schematic diagram of a positive electrode sheet of a battery cell provided by some embodiments of the present application;

[0123] Fig. 5 is a structural schematic diagram of a negative electrode sheet of a battery cell provided by some embodiments of the present application;

[0124] Fig. 6 is a structural schematic diagram of an electrode assembly of a battery cell provided by some embodiments of the present application;

[0125] Fig. 7 is a structural schematic diagram of a battery module provided by some embodiments of the present application;

[0126] Fig. 8 is a structural schematic diagram of a battery pack provided by some embodiments of the present application;

[0127] Fig. 9 is a structural schematic diagram of an electric device provided by some embodiments of the present application.

[0128] The drawings are not necessarily drawn according to the actual scale.

[0129] The following is a description of the reference signs: X, thickness direction; Y, width direction; Z, length direction; 1, electric device; 2, battery pack; 3, controller; 4, motor; 5, box; 5a, first box part; 5b, second box part; 5c, containing space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, positive electrode sheet; 111, positive electrode tab; 1111, first end face; 112, positive electrode current collecting part; 113, positive electrode film layer; 12, negative electrode sheet; 121, negative electrode tab; 1211, second end face; 122, negative electrode current collecting part; 123, negative electrode film layer; 13, separator; 20, outer shell; 21, shell; 211, first shell part 211; 212, second shell part; 22, end cover; 31, positive electrode terminal; 32, negative electrode terminal. DETAILED DESCRIPTION

[0130] Hereinafter, specific embodiments of the battery cell, the battery device, and the electric device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, 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 to enable those skilled in the art to sufficiently understand the present application, and are not intended to limit the subject matter recited in the claims.

[0131] The ranges disclosed herein are defined by their lower and upper limits. Ranges that include both a lower limit and an upper limit are defined by selecting a lower limit and an upper limit. The ranges can be either 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 a range is listed as 60 to 120 and 80 to 110, it is understood that a range of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if a minimum range value of 1 is listed and a maximum range value of 3 is listed, then the following ranges are all contemplated: 1 to 3, 1 to 2, 1 to 3, 2 to 3, 2 to 2, and 2 to 3. In this application, unless otherwise indicated, a numerical range "a to b" means a range of any combination of values between the lower value "a" and the upper value "b" where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" have been listed herein, and "0 to 5" is merely a shorthand for listing all of those values. Also, when a parameter is stated to be 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.

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

[0133] 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.

[0134] If not specifically stated, all steps of the present application can be performed in sequence or randomly, and 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 order. For example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0135] 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 ability of the battery cannot be improved at the same time.

[0136] In view of the above problems, the battery monomer is designed in the embodiments of the present application, and the structure form, size and coating weight of the film layer of the pole piece are improved, so that the energy density and fast charging ability of the battery monomer can be improved at the same time.

[0137] Battery monomer

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

[0139] As shown in FIGS. 1-5, the battery monomer 7 includes an electrode assembly 10 and an electrolyte, the electrode assembly 10 includes a positive pole piece 11, a separator film 13 and a negative pole piece 12 which are stacked in the thickness direction of the battery monomer 7; the positive pole piece 11 includes a positive pole lug 111, a positive current collecting part 112 and a positive film layer 113 containing a positive active material and arranged on at least one surface of the positive current collecting part 112 in the thickness direction, the positive pole lug 111 is arranged on at least one side of the positive current collecting part 112, and the positive active material includes lithium-containing olivine phosphate; the negative pole piece 12 includes a negative pole lug 121, a negative current collecting part 122 and a negative film layer 123 containing a negative active material and arranged on at least one surface of the negative current collecting part 122 in the thickness direction, the negative pole lug 121 is arranged on at least one side of the negative current collecting part 122, wherein the ratio of the size of the positive film layer 113 along the length direction of the battery monomer to the size of the positive film layer 113 along the width direction of the battery monomer is 2.66-7.5; the single-sided coating weight of the negative film layer 123 is 90 mg / 1540.25 mm 2 170 mg / 1540.25 mm 2 .

[0140] The electrode assembly 10 of the embodiment of the present application is a stacked electrode assembly 10, and the positive electrode tab 11, the separator 13, and the negative electrode tab 12 form the electrode assembly 10 through a lamination process. The thickness direction of the battery cell 7, the thickness direction 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 battery cell 7, 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 battery cell 7, 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 of the battery cell 7, the width direction of the electrode assembly 10, and the length direction of the battery cell 7 are perpendicular to each other, X represents the thickness direction of the battery cell 7, Y represents the width direction of the battery cell 7, and Z represents the length direction of the battery cell 7.

[0141] In the embodiment 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 112 is equal to the length of the positive film layer 113, and L1 can represent the length of the positive film layer 113. In FIG. 4, the width of the positive current collector 112 is equal to the width of the positive film layer 113, and W2 can represent the width of the positive film layer 113.

[0142] In the embodiment 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 122 is equal to the length of the negative film layer 123, and L2 can represent the length of the negative film layer 123. In FIG. 5, the width of the negative current collector 122 is equal to the width of the negative film layer 123, and W4 can represent the width of the negative film layer 123.

[0143] Both the positive electrode tab 11 and the negative electrode tab 12 have an influence on the energy density and the rapid 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 rapid charging performance of the battery cell 7 can be improved, specifically:

[0144] When the length-to-width ratio of the positive electrode film layer 113 is less than 2.66, the coating weight of the positive electrode film layer 113 is relatively small, and the energy density of the battery monomer 7 is relatively small. Increasing the length-to-width ratio of the positive electrode film layer 113 and making the length-to-width ratio of the positive electrode film layer 113 less than or equal to 7.5 can increase the coating weight of the positive electrode film layer 113 to a certain extent and improve the energy density of the battery monomer 7. However, as the length-to-width ratio of the positive electrode film layer 113 further increases, the size difference between the length and the width of the positive electrode film layer 113 increases, which easily causes uneven current distribution in the positive electrode sheet 11, resulting in uneven charging state of the positive electrode film layer 113 during charging, different lithium stripping speeds at different positions of the positive electrode film layer 113, different lithium intercalation speeds in the negative electrode sheet 12, and easy lithium precipitation in the negative electrode sheet 12. Therefore, the length-to-width ratio of the positive electrode film layer 113 should not be greater than 7.5. When the length-to-width ratio of the positive electrode film layer is 2.66 to 7.5, the electron transmission path in the positive electrode current collecting part 112 is short, the current distribution is more uniform, and the fast charging performance is improved.

[0145] When the single-side coating weight of the negative electrode film layer 123 is less than 90 mg / 1540.25 mm 2 , the energy density of the battery monomer 7 is relatively small. When the single-side coating weight of the negative electrode film layer 123 is greater than 170 mg / 1540.25 mm 2 , the energy density of the battery monomer 7 is improved, but 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 monomer 7. In the embodiments of the present application, the single-side coating weight of the negative electrode film layer 123 is set to 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 , which can improve the energy density of the battery monomer 7.

[0146] Therefore, by synergistically controlling the length-to-width ratio of the positive electrode film layer 113 and the single-side coating weight of the negative electrode film layer 123, the energy density and the fast charging performance of the battery monomer 7 can be improved.

[0147] In the embodiments of the present application, the length-to-width ratio of the positive electrode film layer 113 is 2.66 to 7.5, for example, 2.66, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.5, 6, 6.5, 7, 7.5, or a range formed by any two of the above values.

[0148] In some embodiments, the length of the positive electrode film layer 113 is 200 mm to 590 mm. For example, the length of the positive electrode film layer 113 can be 200 mm, 250 mm, 280 mm, 300 mm, 320 mm, 350 mm, 380 mm, 400 mm, 420 mm, 450 mm, 480 mm, 500 mm, 520 mm, 530 mm, 550 mm, 560 mm, 570 mm, 590 mm, or a range defined by any two of the above values. The relatively long length of the positive electrode film layer 113 is conducive to increasing the coating weight of the positive electrode film layer 113 and improving the energy density of the battery monomer 7.

[0149] In some embodiments, the width of the positive electrode film layer 113 is 80 mm to 210 mm. For example, the width of the positive electrode film layer 113 can be 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, 155 mm, 160 mm, 165 mm, 170 mm, 175 mm, 180 mm, 185 mm, 190 mm, 195 mm, 200 mm, 205 mm, 210 mm, or a range defined by any two of the above values. The relatively short width of the positive electrode film layer 113 makes the transmission path of the electrons in the width direction Y shorter, which can improve the uniformity of the current in the width direction Y.

[0150] The positive electrode tab 111 is arranged on at least one side of the positive electrode current collector 112, and can be arranged on both sides of the positive electrode current collector 112. The positive electrode tab 111 can be arranged on both sides of the positive electrode current collector 112 in the length direction Z, or arranged on both sides of the positive electrode current collector 112 in the width direction Y. Optionally, the positive electrode tab 111 is arranged on both sides of the positive electrode current collector 112 in the length direction Z. FIG. 4 shows that the positive electrode tab 111 is arranged on both sides of the positive electrode current collector 112 in the length direction Z.

[0151] Since the length of the positive electrode current collector 112 is greater than the width of the positive electrode current collector 112, the transmission path of the current in the length direction Z is longer, and the distribution of the current in the length direction Z is uneven. Arranging the positive electrode tab 111 on both sides of the positive electrode current collector 112 in the length direction Z makes the current in the length direction Z of the positive electrode current collector 112 evenly distributed by the positive electrode tabs 111 on both sides, the transmission path of the electrons is shorter, and the distribution of the current is more uniform. The delithiation state of the positive electrode tab 11 is uniform, and the charging performance of the battery monomer 7 can be improved.

[0152] The negative tab 121 is arranged on at least one side of the negative current collecting part 122, and can be arranged on both sides of the negative current collecting part 122, can be arranged on both sides of the negative current collecting part 122 along the length direction Z, or arranged on both sides of the negative current collecting part 122 along the width direction Y; or the negative tab 121 is arranged on both sides of the negative current collecting part 122 along the length direction Z. 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.

[0153] 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, the current distribution in the length direction Z is uneven, and the negative tab 121 is arranged on both sides of the negative current collecting part 122 along the length direction Z, so that the current in the length direction Z of the negative current collecting part 122 is evenly divided by the negative tab 121 on both sides, the electron 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 cell 7 can be improved.

[0154] The number of positive tabs 111 on the same side of the positive current collecting part 112 can be at least one, for example, one or at least two. When the number of positive tabs 111 on the same side of the positive current collecting part 112 is at least two, at least two positive tabs 111 can increase the current flow area and evenly divide the current, thereby improving the current uniformity in the positive tab 11 and further improving the rapid charging performance of the battery cell 7.

[0155] In some embodiments, the positive tabs 111 on the same side of the positive current collecting part 112 are one or more, for example, all the positive tabs 111 are on the same side of the positive current collecting part 112 along the length direction Z, the positive tab 111 includes a first end surface 1111 connected to the positive current collecting part 112, the size of the first end surface 1111 along the width direction Y is W1, the size of all the first end surfaces 1111 on the same side of the positive current collecting part 112 is n*W1, the width of the positive current collecting part 112 is W2, n*W1 / W2 is greater than or equal to 1 / 3 and less than or equal to 1, and can be greater than or equal to 2 / 3 and less than 1, n represents the number of all positive tabs 111 on the same side of the positive current collecting part 112, n is greater than or equal to 1, for example, when the number of all positive tabs 111 on the same side of the positive current collecting part 112 is 1, n is 1; when the number of all positive tabs 111 on the same side of the positive current collecting part 112 is 2, n is 2.

[0156] For example, 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.

[0157] 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.

[0158] The number of the negative tabs 121 located on the same side of the negative current collector 122 can be at least one, for example, one or at least two. When the number of the negative tabs 121 located on the same side of the negative current collector 122 is at least two, the at least two negative tabs 121 can increase the overcurrent area and can divide the current, thereby improving the current uniformity in the negative tab 12 and being beneficial to further improve the rapid charging performance of the battery monomer 7.

[0159] 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, 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 monomer 7 is W3, the size of all the second end surfaces 1211 located on the same side of the negative current collector 122 is 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.

[0160] 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.

[0161] When m*W3 / W4 satisfies the above range, the overcurrent area of the negative tab 121 is relatively large, which is beneficial to improve the rapid charging performance of the battery monomer 7.

[0162] As shown in FIG. 6, in some embodiments, the positive tab 111 is connected to at least one side of the positive current collector 112 along the length direction Z, the negative tab 121 is connected to at least one side of the negative current collector 122 along the length direction Z, along the length direction Z of the battery monomer 7, the size of the negative film layer 123 is greater than the size of the positive film layer 113, and the difference between the size of the negative film layer 123 and the size of the positive film layer 113 is OH1; along the width direction Y of the battery monomer 7, the size of the negative film layer 123 is greater than the size of the positive film layer 113, and the difference between the size of the negative film layer 123 and the size of the positive film layer 113 is OH2, OH1 is greater than OH2.

[0163] The negative tab 121 is located at at least one side of the negative current collector 122 along the length direction Z, and the width of the negative current collector 122 is greater than the width of the negative tab 121, so that the flow area of the negative current collector 122 is greater than the flow area of the negative tab 121. Due to the difference in flow area, the current density of the connection area of the negative tab 121 and the negative current collector 122 increases sharply, and problems such as lithium precipitation are more likely to occur in this area. The present application sets OH1 to be greater than OH2, so that the ability to receive lithium ions in the length direction Z near the negative film layer 123 is stronger, especially the ability to receive lithium ions in the area near the negative tab 121 of the negative film layer 123 is improved, the risk of lithium precipitation is reduced, and the use reliability of the battery monomer 7 is improved.

[0164] Exemplarily, OH1 is 0.5mm to 3.0mm, for example, 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3.0mm or a range composed of any two of the above values. Along the length direction Z, the negative film layer 123 exceeds the positive film layer 113 on both sides, and each side exceeds OH1 / 2, i.e., half the size of OH1, which is shown in FIG. 6.

[0165] Exemplarily, OH2 is 0.5mm to 3.0mm, for example, 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3.0mm or a range composed of any two of the above values. Along the width direction Y, the negative film layer 123 exceeds the positive film layer 113 on both sides, and each side exceeds OH2 / 2, i.e., half the size of OH2, which is shown in FIG. 6.

[0166] In other embodiments, the positive tab 111 is connected to the positive current collector 112 at at least one side along the width direction Y, and the negative tab 121 is connected to the negative current collector 122 at at least one side along the width direction Y. Along the width direction Y of the battery monomer 7, the size of the negative film layer 123 is greater than the size of the positive film layer 113, and the difference between the size of the negative film layer 123 and the size of the positive film layer 113 is OH3. Along the length direction Z of the battery monomer 7, the size of the negative film layer 123 is greater than the size of the positive film layer 113, and the difference between the size of the negative film layer 123 and the size of the positive film layer 113 is OH4, and OH3 is greater than OH4.

[0167] The negative tab 121 is located on at least one side of the negative current collector 122 along the width direction Y, and the length of the negative current collector 122 is greater than the length of the negative tab 121, so that the flow area of the negative current collector 122 is greater than the flow area of the negative tab 121. Due to the difference in flow area, the current density of the connection area between the negative tab 121 and the negative current collector 122 increases sharply, and problems such as lithium precipitation are more likely to occur in this area. The present application embodiment sets OH3 to be greater than OH4, so that the ability to receive lithium ions in the width direction Y near the negative film layer 123 is stronger, especially the ability to receive lithium ions in the area near the negative tab 121 of the negative film layer 123 is improved, the risk of lithium precipitation is reduced, and the use reliability of the battery monomer 7 is improved.

[0168] Exemplarily, OH3 is 0.5mm to 3.0mm, for example, 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3.0mm, or a range composed of any two of the above values.

[0169] Exemplarily, OH3 is 0.5mm to 3.0mm, for example, 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3.0mm, or a range composed of any two of the above values.

[0170] In some embodiments, the battery monomer 7 can include a shell 20.

[0171] In some embodiments, the shell 20 of the battery monomer 7 can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The shell 20 of the battery monomer 7 can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0172] The shell 20 is a hollow structure, which can be used to package the above-mentioned electrode assembly 10 and electrolyte.

[0173] The preparation method of the battery monomer 7 of the present application embodiment is known. In some embodiments, the positive electrode tab, the separator, the negative electrode tab, and the electrolyte can be assembled to form the battery monomer 7. As an example, the positive electrode tab, the separator, and the negative electrode tab can be formed into an electrode assembly 10 through a lamination process, the electrode assembly 10 is placed in the shell 20, and after drying, the electrolyte is injected. After vacuum packaging, standing, formation, shaping, and other processes, the battery monomer 7 is obtained.

[0174] In some embodiments, the shell 20 includes a shell body 21 and an end cover 22, the shell body 21 has an opening, and the end cover 22 covers the opening.

[0175] The shape of the shell 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is in a cylindrical structure, a cylindrical shell can be selected; if the electrode assembly 10 is in a cuboid structure, a cuboid shell can be selected. Alternatively, the electrode assembly 10 and the shell 21 are both in a cuboid structure.

[0176] In some embodiments, the material of the shell 21 includes steel, which has high mechanical strength and is not easy to deform, thereby improving the use reliability and cycle performance of the battery monomer. Alternatively, the mass percentage of steel is the highest in the material of the shell 21.

[0177] Alternatively, the thickness of the shell 21 is 0.1 mm to 0.5 mm, which can be 0.2 mm to 0.35 mm. For example, the thickness of the shell 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm or a range composed of any two of the above values. When the thickness of the shell 21 is in the above range, the mechanical strength of the shell 21 is high, which can improve the use reliability and cycle performance of the battery monomer 7, and the shell 21 occupies less space, the internal space of the shell 21 is larger, which is beneficial to improve the energy density of the battery monomer 7.

[0178] When the shell 21 is in 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 oppositely arranged, the two second shell parts 212 are oppositely arranged, the first shell part 211 is connected between the two second shell parts 212, and the area of the first shell part 211 is greater than that of the second shell part 212.

[0179] In some embodiments, the thickness of the first shell part 211 is 0.1 mm to 0.5 mm, which can be 0.2 mm to 0.35 mm. The thickness of the first shell part 211 is thin, the shell 21 occupies less space, which can further improve the energy density of the battery monomer 7.

[0180] In some embodiments, the thickness of the second shell part 212 is 0.1 mm to 0.5 mm, which can be 0.2 mm to 0.35 mm.

[0181] In some embodiments, the thickness of the first shell part 211 is greater than or equal to the thickness of the second shell part 212. In other embodiments, the thickness of the first shell part 211 is less than the thickness of the second shell part 212.

[0182] In some embodiments, the base material of the shell 21 includes steel, which has high mechanical strength and is not easy to deform, thereby improving the use reliability and cycle performance of the battery monomer. In the embodiments of the present application, the base material refers to the material with the highest percentage in the shell 21.

[0183] In some embodiments, the battery cell 7 further comprises a positive terminal 31 electrically connected with the positive tab 111. Optionally, the positive terminal 31 and the positive tab 111 are welded, and the positive terminal 31 and the positive tab 111 can be connected through an adapter or without an adapter; optionally, the positive terminal 31 and the positive tab 111 are not connected through an adapter, i.e., the positive terminal 31 and the positive tab 111 are directly welded, which can reduce the resistance at the connection and is conducive to reducing the overall internal resistance of the battery cell 7.

[0184] Optionally, the number of positive terminals 31 located on the same side of the positive current collecting part 112 is at least one, and can be at least two, and the at least two positive terminals 31 can increase the overall current carrying capacity of the positive terminal 31.

[0185] Further optionally, the current carrying area of the single-side positive terminal 31 is 150mm 2 to 1000mm 2 , and can be 200mm 2 to 1000mm 2 . The current carrying area of the single-side positive terminal 31 refers to the sum of the current carrying areas of all positive terminals 31 located on the same side of the positive current collecting part 112. The current carrying 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.

[0186] Exemplarily, the current carrying area of the single-side positive terminal 31 can be 150mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 , 650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , 850mm 2 , 900mm 2 , 950mm 2 , 1000mm 2 , or a range composed of any two of the above values.

[0187] In some embodiments, the battery cell 7 further comprises a negative terminal 32 electrically connected with the negative tab 121. Optionally, the negative terminal 32 and the negative tab 121 are welded, and the negative terminal 32 and the negative tab 121 can be connected through an adapter or without an adapter; optionally, the negative terminal 32 and the negative tab 121 are not connected through an adapter, i.e., the negative terminal 32 and the negative tab 121 are directly welded, which can reduce the resistance at the connection and is conducive to reducing the overall internal resistance of the battery cell 7.

[0188] Optionally, the number of negative terminals 32 located on the same side of the negative current collecting part 122 is at least one, and can be at least two, and the at least two negative terminals 32 can increase the overcurrent capacity of the negative terminal 32.

[0189] Further optionally, the overcurrent area of the single-side negative terminal 32 is 150mm 2 to 1000mm 2 , and can be 200mm 2 to 1000mm 2 The overcurrent area of the single-side negative terminal 32 refers to the sum of the overcurrent areas of all negative terminals 32 located on the same side of the negative current collecting part 122. The overcurrent 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.

[0190] Exemplarily, the overcurrent area of the single-side negative terminal 32 can be 150mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 , 650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , 850mm 2 , 900mm 2 , 950mm 2 , 1000mm 2 , or a range composed of any two of the above values.

[0191] [Positive electrode sheet]

[0192] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0193] The charging upper limit voltage and the discharging cut-off voltage of the battery cell differ depending on the positive electrode active material. For example, when the phosphate-based material includes lithium iron phosphate, the charging upper limit voltage can be 3.65 V, and the discharging cut-off voltage can be 2.0 V. For another example, when the phosphate-based material includes lithium manganese iron phosphate, the charging upper limit voltage can be 4.3 V, and the discharging cut-off voltage can be 2.0 V. Next, taking the charging upper limit voltage of 3.65 V and the discharging cut-off voltage of 2.0 V as examples, the state of the battery cell is described as follows: In the embodiments of the present application, the 100% state of charge (SOC) and the 0% state of charge (SOC) of the battery cell are defined as follows,

[0194] The battery cell is charged to the charging upper limit voltage at a constant current charging rate of 0.33 C, and then charged to 0.05 C at a constant voltage, corresponding to the state of 100% SOC of the battery cell. The battery cell is discharged to the cut-off voltage at a constant current discharging rate of 0.33 C, corresponding to the state of 0% SOC of the battery cell.

[0195] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) is 2.50 g / cm 3 to 2.80 g / cm 3 , and optionally 2.55 g / cm 3 to 2.70 g / cm 3 . For example, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) is 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm3 2.80 g / cm3 3 or a range consisting of any two of the aforementioned values.

[0196] When the compaction density of the positive electrode film layer is within the above range, the energy density of the battery monomer can be improved, and the positive electrode active material in the positive electrode film layer is packed more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the pole piece, thereby reducing the heat generation under fast charging. Therefore, by adjusting the compaction density of the positive electrode film layer to a reasonable range, the battery monomer has high energy density and high charging rate performance.

[0197] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 , and optionally 240 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 . For example, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 240 mg / 1540.25 mm 2 , 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 360 mg / 1540.25 mm 2 , 370 mg / 1540.25 mm 2 or a range consisting of any two of the aforementioned values.

[0198] When the single-sided coating weight of the positive electrode film layer is in the above range, the heat generation per unit area of the positive electrode tab will not be too large, and the energy density and charge rate performance of the battery cell can be improved.

[0199] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) can be detected by the following method. The positive electrode tab of the battery cell at 100% SOC is disassembled, the compaction density of the positive electrode film layer is measured, for example, the single-sided coated positive electrode tab (if it is a double-sided coated tab, the positive electrode film layer on one side can be wiped off first), a small disc with an area of S1 is punched out, weighed, recorded as M1, and its thickness H1 is measured. Then the positive electrode film layer of the above weighed positive electrode tab is wiped off, the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight of the positive electrode tab M1 - the weight of the positive electrode current collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode tab H1 - the thickness of the positive electrode current collector H0, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0200] In some embodiments, the powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm, optionally, less than or equal to 20 Ω·cm, optionally, less than or equal to 11 Ω·cm. For example, the powder resistivity of the positive electrode active material can be 27.5 Ω·cm, 20 Ω·cm, 19 Ω·cm, 18 Ω·cm, 17 Ω·cm, 16 Ω·cm, 15 Ω·cm, 14 Ω·cm, 13 Ω·cm, 12 Ω·cm, 11 Ω·cm, 10 Ω·cm, 9 Ω·cm, 8 Ω·cm, 7 Ω·cm, 6 Ω·cm, 5 Ω·cm, 4 Ω·cm, 3 Ω·cm, 2 Ω·cm, 1 Ω·cm, or a range defined by any two of the above values.

[0201] The relatively low powder resistivity of the positive electrode active material makes the resistance of the positive electrode tab relatively low, and the battery cell generates less heat.

[0202] In the embodiments of the present application, the powder resistivity of the material is the meaning known in the art, which can be detected by the methods and devices known in the art, for example, according to the test standard GB / T30835-2014, using PRCD1100 powder resistivity meter for testing.

[0203] In some embodiments, the powder compaction density of the positive electrode active material under 30000N is 2.46g / cm 3 to 2.8g / cm 3 . For example, the powder compaction density of the positive electrode active material under 30000N is 2.46g / cm 3 , 2.47g / cm3 2.48 g / cm 3 2.49 g / cm 3 2.5 g / cm 3 2.51 g / cm 3 2.55 g / cm 3 2.58 g / cm 3 2.60 g / cm 3 2.65 g / cm 3 2.68 g / cm 3 2.70 g / cm 3 2.72 g / cm 3 2.75 g / cm 3 2.78 g / cm 3 2.80 g / cm 3 or a range between any two of the above values.

[0204] When the powder compaction density of the positive active material at 30000N is within the above range, the energy density of the battery cell can be improved, and the positive 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.

[0205] In the embodiments of the present application, the powder compaction density of the material is the meaning known in the art, which can be detected by the methods and devices known in the art according to the test standard GB / T24533-2009. For example, a certain amount of positive active material is taken as a sample, added into a mold with a bottom area of 1.327 cm 2 of the UTM7305 electronic pressure testing machine, pressurized to 3000kg (equivalent to 30000N), keep pressure for 30s, then release pressure, keep for 10s, then record and calculate the powder compaction density of the positive active material under the action of 30000N force.

[0206] In some embodiments, the charging gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g to 170 mAh / g, which can be 157 mAh / g to 170 mAh / g. Illustratively, the charging gram capacity of the positive electrode active material at 0.1C rate is 150 mAh / g, 151 mAh / g, 152 mAh / g, 153 mAh / g, 154 mAh / g, 155 mAh / g, 156 mAh / g, 157 mAh / g, 158 mAh / g, 159 mAh / g, 160 mAh / g, 161 mAh / g, 162 mAh / g, 163 mAh / g, 164 mAh / g, 165 mAh / g, 166 mAh / g, 167 mAh / g, 168 mAh / g, 169 mAh / g, 170 mAh / g, or a range between any two of the above values.

[0207] When the charging gram capacity of the positive electrode active material at 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0208] In the embodiments of the present application, the gram capacity of the active material is the meaning known in the art, which can be tested by using the devices and methods known in the art, and the test method of the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used. The half-button battery is assembled by taking lithium metal as the negative electrode and the sample electrode tab containing the above material as the positive electrode. The half-button battery is placed in a battery tester or other testing equipment with the same performance at 23℃±2℃, and the button capacity is obtained by 0.1C rate charging and discharging. Then the capacity is divided by the mass of the active material of the electrode tab to obtain the charging gram capacity parameter.

[0209] In some embodiments, the mass fraction of the olivine-structured lithium-containing phosphate in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%, and the positive electrode active material of the present application can be considered to be an olivine-structured lithium-containing phosphate system. When the mass fraction of the olivine-structured lithium-containing phosphate is less than 100%, the positive electrode active material can also include commonly used positive electrode active materials, for example, can include but is not limited to at least one of lithium-containing transition metal oxides. Examples of lithium-containing transition metal oxides can include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0210] Optionally, the mass fraction of the olivine-structured lithium-containing phosphate in the positive electrode active material is 100%.

[0211] In the embodiments of the present application, the lithium-containing phosphate with olivine structure can be phosphate particles or a material obtained after coating modification of the phosphate particles, for example, the lithium-containing phosphate with olivine structure includes phosphate particles and a coating layer, the coating layer is coated on the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge and Sn.

[0212] The phosphate particles are coated with the coating layer, which can improve the conductivity of the lithium-containing phosphate with olivine structure, reduce the powder resistivity of the material, and be beneficial to the migration rate of lithium ions, improve the rapid charging capability of the battery, and reduce the heat generation of the battery cell.

[0213] 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 The compound has a general formula of Li A Me M P X Y, wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K and Mg, Me includes one or more of Mn, Fe, Co and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce, X includes one or more of S, Si, Cl, B, C and N, and Y includes one or more of O and F. The cycle stability of the phosphate particles is relatively excellent, which is beneficial to improving the cycle performance of the battery cell.

[0214] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charging and discharging process, the battery cell is accompanied by the deintercalation and consumption of active ions such as Li, and the battery cell has different molar contents of Li when discharged to different states. In the enumeration of the positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, and the like, the molar content of Li is the initial state of the material, that is, the state before feeding, and the positive electrode active material is applied to the battery system. After the charging and discharging cycle, the molar content of Li may change. In the enumeration of the positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, and the like in the embodiments of the present application, the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will fluctuate, and the above-mentioned situations are all within the protection scope of the present application.

[0215] In some embodiments, the coating layer includes a fast ion conductor with a general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2 , M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0

[0216] Exemplarily, the fast ion conductor is a material with a NASICON structure, for example, including one or more of lithium titanium iron phosphate Li2FeTi(PO4)3, lithium zirconium iron phosphate Li2FeZr(PO4)3, and lithium tin iron phosphate Li2FeSn(PO4)3.

[0217] The fast ion conductor with a NASICON structure is a material with super-fast ion conduction ability, has abundant three-dimensional lithium ion diffusion and transmission channels, and has the advantages of high ion conduction efficiency and strong structural stability in multiple delithiation and lithium intercalation processes. Coating the surface of the phosphate particles with the fast ion conductor containing the NASICON structure can significantly improve the transmission rate of lithium ions in the positive electrode during multiple delithiation and lithium intercalation, improve the ion conductivity of the positive electrode active material, and improve the rapid charging capacity of the battery cell. In addition, it can also improve the specific capacity and the energy density of the corresponding battery cell.

[0218] In some embodiments, the coating layer further includes elemental carbon.

[0219] The carbon element and the fast ion conductor can be arranged in layers, for example, the carbon element as an independent carbon coating layer and the fast ion conductor as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0220] Optionally, the carbon coating layer can be coated on the surface of the fast ion conductor layer by a carbonization process of an organic carbon source (for example, glucose, polyethylene glycol, etc.). The carbon coating layer can partially coat the fast ion conductor layer or completely coat the fast ion conductor layer. The arrangement of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, compensate for the poor electronic conductivity of the phosphate particles, and improve the energy density of the battery cell.

[0221] Specifically, the arrangement of the carbon coating layer has the following advantages for the positive electrode active material of the application:

[0222] The carbon coating layer in the positive electrode active material of the application provides a suitable channel for the transmission of electrons, can significantly improve the conduction rate of electrons during multiple delithiation and lithiation processes, improve the electronic conductivity of the lithium-containing phosphate, and improve the charging capacity and energy density of the corresponding battery cell.

[0223] The carbon coating layer of the positive electrode active material of the application has a loose and porous structure, which enables the electrolyte to fully and effectively contact the lithium-containing phosphate, thereby improving the transmission rate of lithium ions at the phase interface and improving the charging capacity of the battery cell.

[0224] Coating a carbon coating layer on the surface of the lithium-containing phosphate not only improves the electronic conductivity of the lithium-containing phosphate, but also improves the structural stability of the positive electrode active material, effectively alleviates the iron dissolution phenomenon of the positive electrode active material during long-term storage and cyclic use of the battery cell, and thus improves the cycle life of the battery cell.

[0225] The positive electrode active material of the application uses lithium-containing phosphate as a substrate, fully utilizes the advantages of low cost, high reliability, and good cycle stability of lithium-containing phosphate, and solves the disadvantages of poor electronic conductivity and ionic conductivity by using the coating layer (fast ion conductor layer and carbon coating layer). The battery cell prepared from the positive electrode active material of the application can improve the energy density of the battery cell under the premise of excellent cycle performance.

[0226] In the embodiments of the present application, the content of elements in the positive electrode active material is in the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, referring to EPA 6010D-2014, tested by inductively coupled plasma atomic emission spectrometry, and determined by plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After disassembling the positive electrode sheet from the battery monomer discharged to 0% state of charge SOC, washing and drying with DMC, and removing impurities by high temperature calcination, 0.4g of the positive electrode active material is weighed, 10ml (50% concentration) aqua regia is added thereto. Then it is placed on a 180℃ flat plate for 30min. After digestion on the flat plate, it is diluted to a volume of 100ml, and the quantitative test is carried out by the standard curve method.

[0227] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, which can be optionally 0.19 to 0.26. Illustratively, the graphitization degree of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, or a range consisting of any two of the above values.

[0228] When the graphitization degree of the positive electrode active material is in the above range, it is beneficial to improve the conductivity of the positive electrode active material and reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery monomer.

[0229] In the embodiments of the present application, the higher the graphitization degree of the material, the lower the degree of disorder, which can be tested according to the test standard JIS / K 0131-1996 X-ray diffraction analysis method general rules.

[0230] In some embodiments, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine structure lithium-containing phosphate is 5m 2 / g to 18m 2 / g.

[0231] Optionally, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1% to 2%, and the specific surface area of the olivine structure lithium-containing phosphate is 7.5m 2 / g to 14m 2 / g.

[0232] Illustratively, the mass content of carbon element in the olivine structure lithium-containing phosphate is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or a range consisting of any two of the above values.

[0233] For example, the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14m 2 / g, 15m 2 / g, 16m 2 / g, 17m 2 / g, 18m 2 / g, or a range formed by any two of the above values.

[0234] The carbon element mainly exists in the form of a carbon coating layer in the coating layer, the carbon coating layer is loose and porous, which is beneficial to improve the specific surface area of the material, and is more beneficial to the effective contact between the electrolyte and the phosphate particles, and is beneficial to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is in the above range, the conductivity of the lithium-containing phosphate with olivine structure can be significantly improved, which is beneficial to improve the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the rapid charging capacity and energy density of the battery cell.

[0235] In the embodiments of the present application, the specific surface area of the material has the meaning known in the art, and can be detected by using the devices and methods known in the art, for example, according to the test standard GB / T 19587-2017, taking the positive electrode active material as a sample, and using a Tri-Star 3020 type specific surface area pore size analyzer of the United States Micromeritics company to test the specific surface area.

[0236] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1μm≤Dv50≤2μm, 0.4μm≤Dv10≤0.7μm.

[0237] For example, the Dv50 of the positive electrode active material can be 1μm, 1.1μm, 1.15μm, 1.2μm, 1.25μm, 1.3μm, 1.35μm, 1.4μm, 1.45μm, 1.5μm, 1.55μm, 1.6μm, 1.65μm, 1.7μm, 1.75μm, 1.8μm, 1.85μm, 1.9μm, 1.95μm, 2μm, or a range formed by any two of the above values.

[0238] Exemplarily, the Dv10 of the positive electrode active material can be 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, or a range formed by any two of the above values.

[0239] The particle size of the positive electrode active material is relatively small, the path of lithium ion deintercalation in the positive electrode active material is short, and the heat production is less. Moreover, the particle size of the positive electrode active material is not too small, and agglomeration basically does not occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0240] In the embodiments of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% in the volume distribution. The Dv50 and Dv10 of the particles can be detected by using devices and methods known in the art, for example, the positive electrode active material is taken as a sample, the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0241] When the positive electrode active material includes not only the lithium-containing phosphate with olivine structure but also other materials, the volume distribution particle size of the positive electrode active material refers to the volume distribution particle size of all the positive electrode active materials.

[0242] In some embodiments, the lithium-containing phosphate with olivine structure is in a particulate form, and the lithium-containing phosphate with olivine structure is a secondary particle formed by agglomeration of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. Exemplarily, the average particle size of the primary particles is 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, or a range formed by any two of the above values.

[0243] The average particle size of the primary particles is relatively small, the path of lithium ion deintercalation in the positive electrode active material is short, and the heat production is less.

[0244] In the embodiments of the present application, the primary particles and the secondary particles are terms known in the art, and the secondary particle refers to an agglomerated particle formed by agglomeration of two or more primary particles. The primary particles and the secondary particles can be easily distinguished by experimental means (such as using a scanning electron microscope to take SEM images), and the average particle size of the primary particles can be obtained by SEM testing. The SEM testing parameters can be set as follows: working voltage (EHT) is 10.00 kV, InLens detector is used, working distance is 4.6 mm, and magnification is 1000X.

[0245] The plurality of particles of the olivine-structured lithium-containing phosphate in the positive electrode film layer 113 have different particle sizes, and include minimum particles and maximum particles. The minimum particles are particles having the smallest particle size, and the maximum particles are particles having the largest particle size. By matching the sizes of the particles, the compaction density of the positive electrode film layer 113 can be improved, and the pore structure of the positive electrode film layer 113 can be increased, so that the rapid charging performance of the battery monomer 7 is improved.

[0246] In some embodiments, the particle size of the minimum particles in the olivine-structured lithium-containing phosphate is 0.1 μm to 0.4 μm, for example, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, or a range defined by any two of the above values. When the particle size of the minimum particles is in the above range, agglomeration is less likely to occur during the preparation of the positive electrode film layer 113.

[0247] In some embodiments, the particle size of the maximum particles in the olivine-structured lithium-containing phosphate is 15 μm to 25 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, or a range defined by any two of the above values. When the particle size of the maximum particles is 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 monomer can be improved.

[0248] In some embodiments, the positive electrode film layer further includes 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 materials can act as a lithium supplement, which can supplement lithium ions for the positive electrode film layer, make up for the loss of irreversible lithium ions in the system, increase the capacity, and thus improve the energy density of the battery monomer.

[0249] Optionally, the ternary material includes 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 comprises one or more of Na, K, Mg, M3 comprises 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, Ce, and Y3 comprises one or more of O, F.

[0250] Exemplarily, the ternary material comprises LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2.

[0251] In some embodiments, the mass content of the lithium supplement agent in the positive electrode film layer is 0.5% to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two of the foregoing values. When the mass content of the lithium supplement agent is in the foregoing range, the lithium supplement agent can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0252] The lithium supplement agent can be located in the same layer as the positive electrode active material, or can be located in different layers. When the lithium supplement agent and the positive electrode active material are located in different layers, the lithium supplement agent can be located in a lithium supplement layer, and the positive electrode active material can be located in a positive electrode active material layer, in other words, the positive electrode film layer comprises the lithium supplement layer and the positive electrode active material layer. The positive electrode active material layer can be arranged on at least one side of the positive electrode current collector, and the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be arranged on at least one side of the positive electrode current collector, and the positive electrode active material layer can be located between the lithium supplement layer and the positive electrode current collector. Optionally, the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector, and during the cyclic charging and discharging process of the battery cell, the lithium supplement agent in the lithium supplement layer can be gradually released into the system to make up for the loss of lithium in the battery system.

[0253] In some embodiments, the positive electrode film layer further optionally comprises a positive electrode conductive agent. The embodiments of the present application do not have particular limitations on the type of positive electrode conductive agent, which may, for example, include at least one of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode film layer.

[0254] In some embodiments, the positive electrode film layer further optionally comprises a positive electrode binder. The embodiments of the present application do not have particular limitations on the type of positive electrode binder, which may, for example, include at least one 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. In some embodiments, the mass content of the positive electrode binder is ≤5% based on the mass of the positive electrode film layer.

[0255] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As an example of a metal foil, at least one foil of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer can include at least one of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0256] In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05 to 0.3. For example, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, or a range defined by any two of the aforementioned values.

[0257] When the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is within the aforementioned range, the rapid charging capability and the energy density of the battery cell can be improved.

[0258] In some embodiments, the thickness of the cathode current collector is 10-15 μm, optionally 12-15 μm. Illustratively, the thickness of the cathode 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 defined by any two of the above values.

[0259] When the thickness of the cathode current collector is within the above range, the cathode current collector has excellent flow capacity, and the battery cell has high energy density.

[0260] In the embodiments of the present application, the thickness of the cathode film layer and the cathode current collector has the meaning known in the art, and can be detected by using the devices and methods known in the art. For example, the thickness of the cathode electrode sheet is measured by using a micrometer, the thickness of the cathode current collector is measured by using a micrometer after removing the film layer on the surface of the cathode current collector, the thickness of the cathode film layer is the thickness of the cathode electrode sheet minus the thickness of the cathode current collector when the cathode film layer is coated on one side, and the thickness of the cathode film layer is (the thickness of the cathode electrode sheet minus the thickness of the cathode current collector) / 2 when the cathode film layer is coated on both sides.

[0261] The cathode film layer is usually formed by coating a cathode slurry on the cathode current collector, drying, and cold pressing. The cathode slurry is usually formed by dispersing the cathode active material, optionally the conductive agent, optionally the binder, and any other components in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0262] The cathode electrode sheet does not exclude other additional functional layers in addition to the cathode film layer. For example, in some embodiments, the cathode electrode sheet of the embodiments of the present application further comprises a cathode conductive layer disposed between the cathode current collector and the cathode film layer and arranged on the surface of the cathode current collector. In some other embodiments, the cathode electrode sheet of the embodiments of the present application further comprises a protective layer arranged on the surface of the cathode film layer.

[0263] In some embodiments, the cathode electrode sheet further comprises a cathode conductive layer arranged between the cathode film layer and the cathode current collector. The cathode conductive layer can further improve the conductivity of the cathode electrode sheet and reduce the heat generation of the cathode electrode sheet, thereby reducing the heat generation of the battery cell.

[0264] In some embodiments, the thickness of the cathode conductive layer is 0.5-2 μm. Illustratively, the thickness of the cathode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range defined by any two of the above values.

[0265] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode tab can be further improved, the heat generation of the positive electrode tab can be reduced, the heat generation of the battery monomer can be reduced, and the energy density of the battery monomer can be improved.

[0266] In the embodiments of the present application, the thickness of the positive electrode conductive layer has the meaning known in the art and can be detected by using the devices and methods known in the art, for example, by tomography of the positive electrode tab to directly measure the thickness of the positive electrode conductive layer.

[0267] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder.

[0268] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. For example, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or a range formed by any two of the above values.

[0269] For example, the positive electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode tab and reducing the heat generation of the battery monomer.

[0270] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. For example, the mass content of the positive electrode binder is 50%, 60%, 65%, 70%, or a range formed by any two of the above values.

[0271] For example, the positive electrode binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorine-containing acrylic ester resin. 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 tab.

[0272] [Negative electrode tab]

[0273] The negative electrode tab comprises a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two opposite surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0274] In some embodiments, the compaction density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3; optionally 1.25 g / cm 3 to 1.36 g / cm 3 . Illustratively, the compacted density of the negative film layer of the battery cell at 100% state of charge is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 , 1.28 g / cm 3 , 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.36 g / cm 3 or a range between any two of the above values.

[0275] When the compacted density of the negative film layer is within the above range, the energy density of the battery cell can be improved; and since the negative active material in the negative film layer is packed more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0276] In the embodiments of the present application, the compacted density of the negative film layer of the battery cell at 100% state of charge is the meaning known in the art, which can be detected by using the devices and methods known in the art, and the detection method is as described above for the compacted density of the positive film layer.

[0277] In some embodiments, the single-sided coating weight of the negative film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 , optionally 110 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2 . Illustratively, the single-sided coating weight of the negative film layer is 90 mg / 1540.25 mm 2 , 92 mg / 1540.25 mm 2 , 95 mg / 1540.25 mm 2 , 96 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2112 mg / 15 40.25 mm 2 114 mg / 15 40.25 mm 2 115 mg / 15 40.25 mm 2 116 mg / 15 40.25 mm 2 118 mg / 15 40.25 mm 2 120 mg / 15 40.25 mm 2 122 mg / 15 40.25 mm 2 125 mg / 15 40.25 mm 2 128 mg / 15 40.25 mm 2 130 mg / 15 40.25 mm 2 132 mg / 15 40.25 mm 2 135 mg / 15 40.25 mm 2 137 mg / 15 40.25 mm 2 140 mg / 15 40.25 mm 2 142 mg / 15 40.25 mm 2 145 mg / 15 40.25 mm 2 148 mg / 15 40.25 mm 2 150 mg / 15 40.25 mm 2 152 mg / 15 40.25 mm 2 155 mg / 15 40.25 mm 2 160 mg / 15 40.25 mm 2 165 mg / 15 40.25 mm 2 170 mg / 15 40.25 mm 2 or a range between any two of the above values.

[0278] When the single-side coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode tab will not be too large, and the energy density of the battery monomer can be improved.

[0279] In the embodiments of the present application, the single-side coating weight of the negative electrode film layer has the meaning known in the art, and can be detected by using the devices and methods known in the art, and the detection method is as described in the foregoing test method for the single-side coating weight of the film layer.

[0280] In some embodiments, the powder resistivity of the negative active material is 0.005 Ω·cm to 0.043 Ω·cm, optionally 0.04 Ω·cm. Illustratively, the powder resistivity of the negative active material can be 0.043 Ω·cm, 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm, or a range defined by any two of the above values.

[0281] The relatively low powder resistivity of the negative active material results in a relatively low resistance of the negative electrode sheet, and less heat generation of the battery cell.

[0282] In the embodiments of the present application, the powder resistivity of the negative active material is in the meaning known in the art, and can be detected by using the devices and methods known in the art, such as the powder resistivity test method of the positive active material described above.

[0283] In some embodiments, the powder compaction density of the negative active material under a pressure of 20000 N is 1.5 g / cm 3 to 1.85 g / cm 3 , optionally 1.55 g / cm 3 to 1.65 g / cm 3 . Illustratively, the powder compaction density of the negative active material under a pressure of 20000 N is 1.5 g / cm 3 , 1.55 g / cm 3 , 1.6 g / cm 3 , 1.65 g / cm 3 , 1.7 g / cm 3 , 1.75 g / cm 3 , 1.8 g / cm 3 , 1.85 g / cm 3 , or a range defined by any two of the above values.

[0284] When the powder compaction density of the negative active material under a pressure of 20000 N is in the above range, the energy density of the battery cell can be improved, and the negative active material in the negative electrode film layer can be more tightly packed, the contact resistance between particles is smaller, and the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0285] In the embodiments of the present application, the powder compaction density of the material is in the meaning known in the art, and can be detected by using the methods and devices known in the art according to the test standard GB / T24533-2009. As an example, a certain amount of negative active material is taken as a sample, and a UTM7305 electronic pressure testing machine with a bottom area of 1.327 cm 2The negative active material is placed in a mold, and is pressed to 2000kg (equivalent to 20000N), and is kept for 30s, then is unloaded, and is kept for 10s, then the powder compaction density of the negative active material under the action of 20000N is recorded and calculated.

[0286] In some embodiments, the charging gram capacity of the negative active material at 0.1C rate is 350mAh / g to 480mAh / g. Illustratively, the charging gram capacity of the negative active material at 0.1C rate is 350mAh / g, 355mAh / g, 360mAh / g, 365mAh / g, 370mAh / g, 375mAh / g, 380mAh / g, 385mAh / g, 390mAh / g, 395mAh / g, 400mAh / g, 410mAh / g, 420mAh / g, 430mAh / g, 440mAh / g, 450mAh / g, 460mAh / g, 470mAh / g, 480mAh / g, or a range consisting of any two of the above.

[0287] When the charging gram capacity of the negative active material at 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0288] In the embodiments of the present application, the charging gram capacity of the negative active material at 0.1C rate is the meaning known in the art, which can be detected by using the devices and methods known in the art, and the detection method is as described above in the charging gram capacity test method of the positive active material at 0.1C rate.

[0289] In some embodiments, the negative active material comprises a carbon-based material, and the cycle stability of the carbon-based material is relatively high, which can improve the cycle performance of the battery cell. Optionally, the mass percentage of the carbon-based material in the negative active material can be greater than or equal to 80% and less than or equal to 100%.

[0290] The positive active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative active material is mainly a carbon-based material system, and the two are used in combination, and the cycle performance of the battery cell is relatively excellent.

[0291] Optionally, the carbon-based material comprises graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. Illustratively, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, or a range consisting of any two of the above.

[0292] When the graphitization degree of the graphite particles is in the above range, the conductivity of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the rapid charging performance of the battery cell.

[0293] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer, the artificial graphite includes secondary particles, the secondary particles include a plurality of primary particles, and the carbon coating layer is coated on a surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon, which refers to a transition state carbon material with a very low degree of graphitization crystallization and an approximate amorphous state (or a structure with no fixed shape and periodicity). In this application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0294] The artificial graphite includes secondary particles, the migration path of lithium ions in the artificial graphite is more, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions. The carbon coating layer has more end faces and defects, so that the number of sites capable of deintercalating lithium ions is more, and the conductivity of the carbon coating layer is more excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0295] Optionally, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. Illustratively, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range composed of any two of the above values.

[0296] When the mass content of the carbon coating layer is in the above range, the internal resistance of the negative electrode sheet and the heat generation of the battery cell can be further reduced.

[0297] In the embodiments of the present application, the graphite particles can be prepared by methods known in the art, for example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and forming a carbon coating layer on at least part of the surface of the artificial graphite particles after carbonization treatment.

[0298] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of the coal tar pitch and the petroleum pitch is 250°C or lower.

[0299] Optionally, the carbonization treatment temperature is 700°C to 1800°C. Optionally, the carbonization treatment temperature is 1000°C to 1300°C. When the carbonization treatment temperature is in a suitable range, the organic carbon source can be carbonized, and a coating layer containing amorphous carbon can be formed on at least part of the surface of the artificial graphite.

[0300] Optionally, the carbonization treatment time is 1h to 6h.

[0301] In some embodiments, the carbon-based material can also include natural graphite. Specifically, the carbon-based material can include graphite particles, or the carbon-based material can include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0302] 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.

[0303] 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.

[0304] When the mass content of silicon in silicon-based materials is within the above range, it can increase the capacity of the negative electrode active material, thereby improving the energy density of the battery cell.

[0305] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy.

[0306] 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.

[0307] 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.

[0308] For example, this application can combine the general rules of X-ray diffraction analysis in JIS / K0131-1996 to perform X-ray powder diffraction tests and qualitative analysis on negative electrode sheets or negative electrode active materials.

[0309] The artificial graphite and the natural graphite can be distinguished by a scanning electron microscope (SEM) cross-section image taken by the SEM, wherein the SEM cross-section image of the natural graphite has gaps between flaky structures, and the SEM cross-section image of the artificial graphite is dense and has no obvious gaps, or distinguished by an X-ray diffraction (XRD) spectrum obtained by an XRD method, wherein the XRD spectrum of the natural graphite has obvious 2H phase and 3R phase, and the XRD spectrum of the artificial graphite only has 2H phase.

[0310] The negative electrode film layer in the embodiments of the present application includes at least one film layer, which can be a single-layer film layer or at least two film layers. Optionally, the negative electrode film layer includes at least two film layers.

[0311] In the case of using a single-layer film layer for the negative electrode film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally, a silicon-based material. In the case of using a single-layer film layer, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm to 13.5 μm. 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 formed by any two of the above values.

[0312] In the case of using at least two film layers for the negative electrode film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally, a silicon-based material, which can be located in one of the at least two film layers or at least two of the at least two film layers. The negative electrode film layer can include two film layers, three film layers, four film layers, or even more film layers.

[0313] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is arranged on the surface of the negative electrode current collector, the carbon-based material in the first negative electrode film layer includes graphite particles, the second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, the carbon-based material in the second negative electrode film layer includes graphite particles, and the graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer can be the same or different.

[0314] The interface of the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and optionally, irregular.

[0315] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0316] The negative electrode film layer includes at least two film layers, and the layered coating is conducive to improving the rapid charging performance of the battery cell. In particular, when the first negative electrode film layer and the second negative electrode film layer are different, the pore difference of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission is reduced, and the rapid charging performance of the battery cell is improved.

[0317] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which is conducive to improving the compaction density of the negative electrode film layer. When the negative electrode active material includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0318] The particle size difference in the first negative electrode film layer and the second negative electrode film layer can improve the rapid charging performance of the battery cell. Specifically, during the rapid charging process, the overpotential of the second negative electrode film layer is generally high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and improve the problem of lithium extraction on the surface of the negative electrode sheet.

[0319] Optionally, the negative electrode active material in the first negative electrode film layer is in a particle form, and the volume average particle size Dv50 thereof is 9.5 μm to 18.5 μm, which can be 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 formed by 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, which can be 9.5 μm to 14.6 μm.

[0320] 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, on the one hand, the solid-phase transmission path of lithium ions can be shortened, and the rapid charging performance can be improved. On the other hand, the material is not prone to agglomeration during preparation, and the stability of the material can be improved.

[0321] Optionally, the volume average particle size Dv50 of the negative active material in the second negative film layer is 7.8 μm to 14.3 μm, or 7.8 μm to 11.3 μm. For example, the volume average particle size Dv50 of the negative active material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm, or a range defined by any two of the above values. When the second negative film layer comprises graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative film layer is 7.8 μm to 14.3 μm, or 7.8 μm to 11.3 μm.

[0322] When the volume average particle size Dv50 of the negative active material in the second negative film layer is within the above range, on the one hand, the solid-phase transmission path of lithium ions can be shortened, and the rapid charging performance can be improved. On the other hand, the material is less likely to agglomerate during preparation, and the stability of the material can be improved. On the other hand, the negative active material in the second negative film layer and the negative active material in the first negative film layer cooperate to facilitate the construction of a gradient pore difference between the second negative film layer and the first negative film layer, reduce the tortuosity of lithium ion transmission, and improve the rapid charging performance of the battery cell.

[0323] In the embodiments of the present application, the volume average particle size Dv50 of the negative active material has the meaning known in the art, and can be detected by using the devices and methods known in the art. The detection method is as described above in the volume average particle size Dv50 test method of the positive active material.

[0324] Optionally, the tap density of the carbon-based material in the first negative film layer is less than or equal to the tap density of the carbon-based material in the second negative film layer. The tap density can reflect the filling density of the active material in the film layer. When the tap density of the carbon-based material in the second negative film layer is greater than the tap density of the carbon-based material in the first negative film layer, the second negative film layer is more densely packed, so that the energy density of the battery cell is improved, and the first negative film layer is relatively sparse in filling, and the pores are more abundant, which can improve the rapid charging performance of the battery cell. When the negative active material comprises graphite particles, the tap density of the graphite particles in the first negative film layer is less than or equal to the tap density of the graphite particles in the second negative film layer.

[0325] Optionally, the tap density of the carbon-based material in the first negative film layer is 0.82 g / cm 3 to 1.21 g / cm3 for example 0.82 g / cm 3 , 0.85 g / cm 3 , 0.88 g / cm 3 , 0.90 g / cm 3 , 0.92 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 or a range between any two of the above values. The tap density of the carbon-based material in the first negative electrode film layer, when in a suitable range, can improve the fast charging performance of the battery cell.

[0326] Optionally, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 , for example 0.90 g / cm 3 , 0.92 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 , 1.22 g / cm 3 , 1.23 g / cm 3 , 1.24 g / cm 3 , 1.25 g / cm 3 or a range between any two of the above values. The tap density of the carbon-based material in the second negative electrode film layer, when in a suitable range, can improve the energy density of the battery cell.

[0327] In the embodiments of the present application, the tap density of the material is the meaning known in the art, which can be measured by instruments and methods known in the art. For example, GB / T 5162-2006 can be referred to, and a powder tap density tester can be used for measurement. The testing instrument can be Dandong Bitai BT-301.

[0328] Optionally, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7 to 7:3, and optionally 4:6 to 6:4. For example, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7, 4:6, 5:5, 6:4, 7:3, or a range composed of any two of the above values. By adjusting the thickness ratio of the first negative electrode film layer and the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0329] In some embodiments, after the battery cell is subjected to a full charge test cycle for 10 cycles at the beginning of life (BOL), the thickness of the first negative electrode film layer is 15 μm to 65 μm, for example, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range composed of any two of the above values. When the thickness of the first negative electrode film layer is in the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0330] In some embodiments, after the battery cell is subjected to a full charge test cycle for 10 cycles at the beginning of life (BOL), the thickness of the second negative electrode film layer is 15 μm to 65 μm, for example, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range composed of any two of the above values. When the thickness of the second negative electrode film layer is in the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be adjusted to increase, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0331] In the embodiments of the present application, for example, the upper limit voltage of battery charging is 3.65 V, and the discharge cut-off voltage of the battery is 2.0 V.

[0332] The BOL full charge test procedure is as follows: at 25°C, charge at a charge rate of 0.33C of the nominal capacity of the battery to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, stand for 10 min, then discharge at a discharge rate of 0.33C to 2.0V, stand for 10 min, the above one charge-discharge is one cycle, cycle for 10 cycles, then charge at a charge rate of 0.33C of the nominal capacity of the battery to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, which is the BOL full charge state, in the BOL full charge state, disassemble the negative electrode sheet, use a scanning electron microscope to observe the cross section in the thickness direction of the middle region of the negative electrode sheet, distinguish the two regions according to the interface between the first negative electrode film layer and the second negative electrode film layer, and measure the thicknesses of the two regions respectively, for example, measure the thicknesses of 10 positions of the first negative electrode film layer respectively, calculate the average value as the average value of the first negative electrode film layer, and measure the thicknesses of 10 positions of the second negative electrode film layer, calculate the average value as the average value of the second negative electrode film layer.

[0333] In some embodiments, after the battery cell is subjected to the End Of Life (EOL) full charge test, the thickness of the first negative electrode film layer is 15-70 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, or a range consisting of any two of the above values. When the thickness of the first negative electrode film layer is in the above range, the first negative electrode film layer and the second negative electrode film layer can regulate the increase of the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the rapid charging capacity of the battery cell.

[0334] In some embodiments, after the battery cell is subjected to the End Of Life (EOL) full charge test, the thickness of the second negative electrode film layer is 15-70 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, or a range consisting of any two of the above values. When the thickness of the second negative electrode film layer is in the above range, the first negative electrode film layer and the second negative electrode film layer can regulate the increase of the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the rapid charging capacity of the battery cell.

[0335] In the embodiments of the present application, for example, the battery charging upper limit voltage is 3.65V, and the battery discharging cut-off voltage is 2.0V.

[0336] The EOL full charge test procedure is as follows: at 60°C, charge to 3.65V at a charging rate of 0.33C of the nominal capacity of the battery, then charge to 0.05C at a constant voltage of 3.65V, stand for 10min, then discharge to 2.0V at a discharging rate of 0.33C, stand for 10min, the above one charge-discharge is one cycle, until the battery capacity decays to 80% of the nominal capacity to stop the test. Then charge to 3.65V at a constant current of 0.33C at 25°C, and charge to 3.65V at a constant voltage of 0.05C, which is the EOL full charge state. In the EOL full charge state, the negative electrode sheet is disassembled, and the thickness direction cross section of the middle region of the negative electrode sheet is observed using a scanning electron microscope. The first negative electrode film layer and the second negative electrode film layer are distinguished according to the interface, and the thicknesses of the two regions are measured, for example, the thicknesses of 10 positions of the first negative electrode film layer are measured, and the average value is calculated as the average value of the first negative electrode film layer. The thicknesses of 10 positions of the second negative electrode film layer are measured, and the average value is calculated as the average value of the second negative electrode film layer.

[0337] In some embodiments, in the case of using a single-layer film layer (different from the above-mentioned double-layer film layer) for the negative electrode film layer, the negative electrode film layer further comprises a lithium-containing binder. Optionally, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1% to 1%. Illustratively, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range composed of any two of the above values. The lithium element in the lithium-containing binder can exist in ionic form, which can increase the number of lithium ions that can move freely in the negative electrode film layer, shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, increase the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery monomer. Optionally, the negative electrode film layer can further comprise a negative electrode binder, for example, the negative electrode binder comprises at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0338] Optionally, the mass content of lithium element in the lithium-containing binder is 3% to 10%. Illustratively, the mass content of lithium element in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the above values. When the mass content of lithium element is within the above range, the number of lithium ions that can freely move in the negative electrode film layer is relatively large, 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.

[0339] Illustratively, the lithium-containing binder comprises lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, and the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0340] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0341] In some other embodiments, when the negative electrode film layer comprises at least two film layers, the negative electrode film layer further comprises a lithium-containing binder.

[0342] Optionally, the first negative electrode film layer further comprises a first lithium-containing binder, and the second negative electrode film layer further comprises a second lithium-containing binder, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. Further optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0343] 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 freely move in the second negative electrode film layer, which can further improve the rapid charging performance of the battery cell.

[0344] Optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. Illustratively, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range defined by any two of the foregoing. The lithium element in the first lithium-containing binder can exist in the form of ions, can increase the number of lithium ions that move freely in the negative electrode film layer, can shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, can increase the deintercalation rate of lithium ions, and can improve the rapid charging performance of the battery cell.

[0345] Optionally, the mass content of the lithium element in the first lithium-containing binder is 3% to 10%, or 3% to 8%. Illustratively, the mass content of the lithium element in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range defined by any two of the foregoing. When the mass content of the lithium element is in the foregoing range, the number of lithium ions that move freely in the negative electrode film layer can be relatively large, the distance of lithium ion diffusion to the surface of the negative electrode film layer can be further shortened, the deintercalation rate of lithium ions can be increased, and the rapid charging performance of the battery cell can be improved.

[0346] Illustratively, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0347] The lithium-containing binder of the foregoing material can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and not easily swell during the charging and discharging process, thereby improving the structural stability and the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0348] Optionally, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. Illustratively, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range defined by any two of the foregoing. The lithium element in the second lithium-containing binder can exist in ionic form, which can increase the number of lithium ions that can move freely in the negative electrode film layer, shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, increase the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0349] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0350] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, or 3% to 8%. Illustratively, the mass content of lithium element in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range defined by any two of the foregoing. When the mass content of lithium element is within the foregoing range, the number of lithium ions that can move freely in the negative electrode film layer can be relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, increase the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0351] Illustratively, the second lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0352] The lithium-containing binder described above can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during the charging and discharging process, has a stable structure, and thus the cycle performance of the negative electrode film layer during rapid charging and discharging is improved.

[0353] In some embodiments, the first negative electrode film layer further comprises a negative electrode binder, and the second negative electrode film layer further comprises 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 comprises at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0354] 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.

[0355] In some embodiments, the negative electrode film layer further optionally comprises a negative electrode conductive agent. The type of the negative electrode conductive agent is not particularly limited in the embodiments of the present application. As an example, the negative electrode conductive agent can comprise at least one of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0356] In some embodiments, the negative electrode film layer further optionally comprises 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.

[0357] In some embodiments, the negative electrode film layer further optionally comprises other auxiliary agents. As an example, the other auxiliary agents can comprise thickening agents, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of the other auxiliary agents is ≤2% based on the total weight of the negative electrode film layer.

[0358] In some embodiments, the porosity of the negative electrode film layer is 40% to 55%. Exemplarily, the porosity of the negative electrode film layer is 40%, 45%, 50%, 55%, or a range composed of any two of the above.

[0359] When the porosity of the negative electrode film layer in the embodiments of the present application is within the above range, the migration ability of lithium ions in the negative electrode film layer can be improved, and the rapid charging performance can be improved.

[0360] In the embodiments of the present application, the porosity of the negative electrode film layer can be measured by the gas displacement method according to the standard GB / T24586. The porosity P = (V1-V2) / V1*100%, wherein V1 is the apparent volume of the sample, and V2 is the true volume of the sample.

[0361] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy foils can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0362] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. As an example, the thickness of the negative electrode current collector is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or a range between any two of the above values.

[0363] When the thickness of the negative electrode current collector is in the above range, the overcurrent capacity of the negative electrode current collector is excellent, and the battery cell can have a high energy density.

[0364] In the embodiments of the present application, the thickness of the negative electrode current collector has the meaning known in the art and can be detected by using the devices and methods known in the art, for example, the thickness of the negative electrode current collector can be measured by using a micrometer after the solvent is used to wash off the film layer on the surface of the negative electrode current collector.

[0365] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, the optional conductive agent, the optional binder, and other optional additives in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0366] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab of the embodiments of the present application further 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 some other embodiments, the negative electrode tab of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0367] In some embodiments, the negative electrode tab further comprises a negative electrode conductive layer between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode tab, reduce the heat generation of the negative electrode tab, and thus reduce the heat generation of the battery cell.

[0368] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 pm to 2 pm. For example, the thickness of the negative electrode conductive layer can be 0.5 pm, 0.8 pm, 1 pm, 1.2 pm, 1.5 pm, 1.6 pm, 1.8 pm, 2 pm, or a range defined by any two of the above values.

[0369] When the thickness of the negative electrode conductive layer is within the above range, the conductivity of the negative electrode tab can be further improved, the heat generation of the negative electrode tab can be reduced, and thus the heat generation of the battery cell can be reduced, while the energy density of the battery cell can be improved.

[0370] In the embodiments of the present application, the thickness of the negative electrode conductive layer has the meaning known in the art, can be detected by using the devices and methods known in the art, and can be detected by using the test method of the negative electrode conductive layer described above.

[0371] 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, and thus improve the conductivity of the negative electrode tab and reduce the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the adhesion between the negative electrode current collector and the negative electrode film layer, and thus improve the structural stability of the negative electrode tab.

[0372] In some embodiments, the negative electrode conductive layer can optionally further comprise other auxiliary agents. For example, the other auxiliary agents can include thickening agents, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0373] 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 a range defined by any two of the above values.

[0374] For example, the negative electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0375] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%. For example, the mass content of the negative electrode binder is 60%, 65%, 70%, 75%, 80%, or a range defined by any two of the above values.

[0376] Exemplarily, the negative electrode binder comprises 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.

[0377] In some embodiments, the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is 1.05 to 1.30, which can be optionally 1.07 to 1.15. Exemplarily, the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3, or a range formed by any two of the above values.

[0378] When the ratio CB of the capacity of the unit area negative electrode film layer to the capacity of the unit area positive electrode film layer in the battery cell is in the above range, there are sufficient sites for lithium insertion in the negative electrode film layer, which can reduce the risk of lithium precipitation and is conducive to fast charging.

[0379] In the embodiments of the present application, the CB value has the meaning known in the art and can be detected by using the devices and methods known in the art, for example, the capacity of the unit area negative electrode film layer and the capacity of the unit area positive electrode film layer are calculated respectively, and the ratio of the two is calculated to obtain the CB value.

[0380] Specifically, taking the upper limit voltage of battery charging as 3.65V and the discharge cut-off voltage of the battery as 2.0V as an example,

[0381] The capacity of the unit area positive electrode film layer refers to the actual delithiation capacity of the positive electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the positive electrode sheet is taken out, and a CR2430 half buckle type battery of positive electrode-lithium sheet is assembled. The area of the positive electrode sheet used is a*b*c d mm 2 wherein the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then the assembled half buckle type battery is left for 3h, the test is carried out at 25℃, 0.1C is used to charge (Charge) delithiation in the voltage range of 2.0V to 3.65V, then 0.05C is used to discharge (Discharge) lithium intercalation to 2.0V, and the discharge capacity of the second cycle is taken as Y mAh. The actual battery design positive electrode sheet length is b mm, the width is c mm, and the number of positive electrode active material coated on the positive electrode current collector is d. Therefore, the capacity of the unit area positive electrode film layer = Y / a*b*c*d.

[0382] Specifically, the capacity of the negative electrode film layer per unit area refers to the actual lithium intercalation capacity of the negative electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode sheet is taken out, and a CR2430 type half-buckle battery of negative electrode-lithium sheet is assembled. The area of the negative electrode sheet used is fmm 2 wherein the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then the assembled half-buckle battery is left to stand for 3 h, the test is carried out at 25°C, 0.1C is used to discharge lithium intercalation at a voltage interval of 2V-0V, then 0.05C is used to charge lithium deintercalation to 2V, and the discharge capacity of the second cycle is taken as Z mAh. The actual battery design negative electrode sheet length is h mm, the width is i mm, the negative electrode active material is coated on the negative electrode current collector, and the number of faces d is then the negative electrode lithium intercalation capacity = Z / f*h*i*d.

[0383] [Separator film]

[0384] In the embodiments of the present application, the separator film comprises a base film with a porous structure.

[0385] In some embodiments, the base film comprises at least one of glass fiber, non-woven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the base film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0386] Optionally, the polyolefin comprises at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0387] In some embodiments, the porosity of the base film is 20% to 70%, and optionally 35% to 60%. For example, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range between any two of the above values.

[0388] When the porosity of the base film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0389] In the embodiments of the present application, the porosity refers to the percentage of the pore volume in the separator film to the total volume of the separator film. The porosity can be tested according to the standard GB / T 36363-2018 "Polyolefin Separator for Battery Cell". It should be noted that the actual test process can be slightly different from the standard in order to obtain more accurate test values, according to the differences between test instruments, test errors, and in order to eliminate the influence on the test of the porosity as much as possible.

[0390] In some embodiments, the thickness of the base film is 6-12 μm, optionally 6-9 μm. For example, the thickness of the base film is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range defined by any two of the above values.

[0391] When the thickness of the base film is in 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, thereby reducing the heat generation.

[0392] In the embodiments of the present application, the separator film can be the base film. Optionally, the separator film further comprises a functional layer disposed on at least one side of the base film. The functional layer can comprise inorganic particles to improve the heat resistance of the separator film. Optionally, the functional layer is disposed on both sides of the base film.

[0393] In some embodiments, the functional layer comprises a first functional layer and a second functional layer. The first functional layer is disposed on one side of the base film, and the first functional layer comprises first inorganic particles. The second functional layer is disposed on the other side of the base film, and the second functional layer comprises composite particles. The composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles. 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.

[0394] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

[0395] Optionally, the first functional layer can comprise a binder, optionally at least one of a fluorine-containing binder or a polyacrylic acid binder, for example, polyvinylidene fluoride.

[0396] Optionally, the first inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0397] In the embodiments of the present application, the thickness of the base film has the meaning known in the art, and can be detected using the meaning and equipment known in the art. For example, a newly prepared separator film can be taken as a sample, or a battery cell that has been fully discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the separator film is obtained from the battery cell and dried as a sample. The separator film is cut off using an ion beam cutting instrument to form a cross section, and then the thickness of the cross section of the separator film and each layer thereof is measured using a scanning electron microscope.

[0398] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers, which optionally include acrylate-acrylonitrile-acrylamide-acryl copolymers. The acrylate copolymers have excellent bonding properties and high bonding stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as 35%:30%:15%:20%, or 40%:20%:10%:30%, or 45%:15%:20%:20%, and the like.

[0399] The second inorganic particles in the composite particles prevent the non-fluoropolymer particles from being easily bonded due to high-temperature treatment during the granulation process, so that the composite particles have pores, which are beneficial to the transmission of lithium ions and improve the ion conductivity of the separator film. In addition, the second inorganic particles can also improve the compression modulus of the composite particles, so that the composite particles are less likely to deform during charging and discharging, making the structure of the separator film more stable and improving the kinetic performance of the battery cell and the rapid charging performance. Optionally, the second functional layer is arranged close to the negative electrode tab, and because the composite particles are less likely to deform, the separator film is less likely to cause side effects such as extrusion to the negative electrode tab, making the kinetic performance of the negative electrode tab stable. Correspondingly, the first functional layer is arranged close to the positive electrode tab.

[0400] Optionally, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Optionally, the second inorganic particles include silicon oxide. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer and cooperate with the non-fluoropolymer to form composite particles, further improving the cycle stability and kinetic performance of the separator film and the cycle performance and rapid charging performance of the battery cell.

[0401] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, and optionally 5 nm to 20 nm. 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 a range formed by any two of the above values. When the average particle size of the second inorganic particles is in the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0402] In the embodiments of the present application, the average particle size of the second inorganic particles is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, after the separator film is obtained and dried, the separator film is cut by an ion beam cutter to form a cross section, and then the particle size of the second inorganic particles in the separator film is measured by using a scanning electron microscope, the particle size of a plurality of, for example, 50, second inorganic particles is measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0403] In some embodiments, the ionic conductivity of the separator film is 0.3 mS / cm to 0.6 mS / cm. Illustratively, the ionic conductivity of the separator film is 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.45 mS / cm, 0.5 mS / cm, 0.55 mS / cm, 0.6 mS / cm, or a range consisting of any two of the above values.

[0404] When the ionic conductivity of the separator film is in the above range, the migration ability of lithium ions of the separator film can be further improved, and the rapid charging performance of the battery cell can be improved.

[0405] In the embodiments of the present application, the ionic conductivity of the separator film is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example,

[0406] Preparation of a 2025 type button cell for testing: in a vacuum glove box, lithium pieces are placed into a negative electrode shell, 150 μL of an electrolyte is added, the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), a separator film (area of 3.14 cm 2 , thickness of 12 μm) is placed to tightly adhere to the lithium pieces, 25 μL of an electrolyte is added, and finally a positive electrode piece (the positive electrode piece can be the positive electrode piece in Example 1) is placed thereon, and then the button cell is packaged. The assembled button cell is taken out of the vacuum glove box and placed for 24 h for the next step of testing.

[0407] Test: in an electrochemical workstation, a test is performed in a frequency range of 10 -1 ~ 10 6 Hz, the resistance Rb of the separator film is obtained, and the ionic conductivity σ (unit: mS / cm) is calculated by the following formula,

[0408] σ = L / (R b × S)

[0409] wherein R b is the resistance of the separator film, and L and S are the thickness and area of the separator film to be tested, respectively.

[0410] [Electrolyte]

[0411] In some embodiments, the battery cell further comprises an electrolyte.

[0412] During the charging and discharging of the battery cell, active ions such as lithium ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role of conducting the active ions between the positive electrode sheet and the negative electrode sheet.

[0413] In embodiments of the present application, the electrolyte has an electrical conductivity of 13 mS / cm to 20 mS / cm at room temperature, which can be 15 mS / cm to 20 mS / cm. For example, the electrolyte has an electrical conductivity of 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm or a range between any two of the above values at room temperature.

[0414] When the electrolyte has an electrical conductivity in the above range at room temperature, for example 25°C, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0415] In embodiments of the present application, the electrical conductivity of the electrolyte at room temperature, for example 25°C, is ionic conductivity, which can be detected by using devices and methods known in the art, for example, by referring to industry standard HG-T 4067-2015.

[0416] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. For example, 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 between any two of the above values.

[0417] When the viscosity of the electrolyte at room temperature, for example 25°C, is in the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the rapid charging performance of the battery cell.

[0418] In embodiments of the present application, the viscosity of the electrolyte is the meaning known in the art, which can be detected by using devices and methods known in the art, for example, by referring to GB / T 10247-2008.

[0419] In some embodiments, the density of the electrolyte is 1.05 g / mL to 1.35 g / mL at room temperature, for example, 25°C. Illustratively, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, or a range between any two of the aforementioned values.

[0420] When the density of the electrolyte is in the aforementioned 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 the heat generation and improving the rapid charging performance of the battery cell.

[0421] In the embodiments of the present application, the density of the electrolyte is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, by referring to GB / T 2013-2010 for testing.

[0422] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not particularly limited and can be selected according to actual needs.

[0423] In some embodiments, the organic solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent relative to the mass of the organic solvent is greater than or equal to 5% and less than or equal to 75%, which can be greater than or equal to 10% and less than or equal to 75%, which can be 30% to 70%, which can be 50% to 70%. Illustratively, the mass content of the chain carboxylate solvent is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or a range between any two of the aforementioned values.

[0424] When the mass content of the chain carboxylate solvent is in the aforementioned range, the viscosity of the electrolyte system is relatively small, which is conducive to the migration of lithium ions.

[0425] In some embodiments, the chain carboxylate solvent includes a compound shown in Formula I,

[0426] In Formula I,

[0427] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group,

[0428] R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

[0429] The chain carboxylate solvent described above has a relatively high conductivity, which is conducive to improving the rapid charging capacity of the battery cell.

[0430] 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.

[0431] Optionally, R2 includes a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. Further optionally, R2 includes a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0432] In each of the above embodiments, the halogen atom includes one or more of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Optionally, the halogen atom includes a fluorine atom.

[0433] In each of the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group, and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0434] Illustratively, the chain carboxylate-based solvent includes one or more of a compound represented by Formula I-1 to a compound represented by Formula I-8,

[0435] In some embodiments, the organic solvent further includes a carbonate-based solvent.

[0436] Optionally, the carbonate-based solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Further optionally, the carbonate-based solvent includes one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate. The above carbonate-based solvent and chain carboxylate-based solvent are used in combination, so that the conductivity of the electrolyte at room temperature is improved, which is conducive to the migration of lithium ions.

[0437] Further optionally, the mass content of the carbonate-based solvent in the organic solvent is 30% to 70%, which can be 30% to 50%. Illustratively, the mass content of the carbonate-based solvent in the organic solvent is 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, or a range composed of any two of the above values. The above mass content of the carbonate-based solvent can further improve the conductivity of the electrolyte at room temperature, which is conducive to the migration of lithium ions.

[0438] Illustratively, the carbonate-based solvent includes one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate, and the mass content of the carbonate-based solvent is 30% to 50%.

[0439] In some embodiments, the electrolyte further comprises an additive, which can include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, and the like.

[0440] In some embodiments, the additive comprises one or more, optionally at least two, of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The additive is capable of improving the interface film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0441] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. Illustratively, the mass content of the additive in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the foregoing values.

[0442] The additive in the above mass content is capable of effectively improving the interface film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0443] Illustratively, the carbonate additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0444] Illustratively, the sulfur-containing additive comprises one or more of vinyl sulfite DTD, bis vinyl sulfite 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methyl methylene disulfite MMDS.

[0445] Optionally, the lithium salt additive comprises one or more of lithium difluorophosphate LiPO2F2, lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bis(oxalato)borate LiBOB.

[0446] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, and optionally 2% to 6%.

[0447] Optionally, the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%, and optionally 0.5% to 3%.

[0448] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, and the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%.

[0449] Further optionally, the mass content of the vinylene carbonate VC in the electrolyte is 2% to 6%, and the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.5% to 3%.

[0450] In some embodiments, the electrolyte salt comprises a lithium salt, the lithium salt comprises one or more of a fluorine-containing sulfimide salt and lithium hexafluorophosphate LiPF6. The above lithium salt is prone to dissociation, is conducive to the rapid migration of lithium ions, and the electrolyte system is relatively stable and is not prone to decomposition, thereby improving the cycle performance of the battery cell.

[0451] Optionally, the fluorine-containing sulfimide salt comprises one or more of lithium bisfluorosulfimide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0452] Optionally, the lithium salt comprises lithium bisfluorosulfimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of the lithium bisfluorosulfimide LiFSI is 0.2 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.5 mol / L to 1.0 mol / L.

[0453] Illustratively, the molar concentration of the lithium bisfluorosulfimide LiFSI is 0.4 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.7 mol / L.

[0454] Illustratively, the molar concentration of the lithium bisfluorosulfimide LiFSI is 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.5 mol / L.

[0455] Illustratively, the molar concentration of the lithium bisfluorosulfimide LiFSI is 0.2 mol / L, and the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.8 mol / L.

[0456] Optionally, the ratio of the molar concentration of the lithium bisfluorosulfimide LiFSI to the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.2 to 1.0, and optionally 0.2 to 0.5. Illustratively, the ratio of the molar concentration of the lithium bisfluorosulfimide LiFSI to the molar concentration of the lithium hexafluorophosphate LiPF6 is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range composed of any two of the above values.

[0457] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt in the electrolyte are in the meanings known in the art, and can be detected by using the devices and methods known in the art, for example, the qualitative or quantitative analysis of the inorganic components / lithium salt in the electrolyte can be performed by ion chromatography according to the standard JY / T020-1996 "General Ion Chromatography Analysis Method". In the embodiments of the present application, the newly prepared electrolyte can be taken as the sample, the free electrolyte of the fresh battery can be taken as the sample, or the free electrolyte obtained from the battery which has been discharged to the lower limit cut-off voltage so that the charged state of the battery is about 0% SOC can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0458] In the embodiments of the present application, the types and contents of the organic components in the electrolyte are in the meanings known in the art, and can be detected by using the devices and methods known in the art, for example, the qualitative and quantitative analysis of the organic components in the electrolyte can be performed by gas chromatography according to the standard GB / T9722-2006 "General Gas Chromatography Method for Chemical Reagents". In the embodiments of the present application, the newly prepared electrolyte can be taken as the sample, the free electrolyte of the fresh battery can be taken as the sample, or the free electrolyte obtained from the battery which has been discharged to the lower limit cut-off voltage so that the charged state of the battery is about 0% SOC can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0459] In the embodiments of the present application, after the quantitative and qualitative detection of each component in the electrolyte, each component is classified, the chain carboxylic acid ester solvent, the carbonate solvent (for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate) is taken as the constituent component of the organic solvent, and the mass content of each component is calculated based on 100% of the mass of the organic solvent.

[0460] The carbonate additive (for example, vinylene carbonate, fluoroethylene carbonate), the sulfur-containing additive and the lithium salt additive are taken as the additive of the electrolyte, and the mass content of each component is calculated based on 100% of the mass of the electrolyte.

[0461] In some embodiments, the battery cell satisfies: 2.45 g / Ah≤d / A≤3.5 g / Ah, which can be optionally 2.45 g / Ah≤d / A≤3.3 g / Ah, wherein d represents the mass of the electrolyte in the battery cell, in units of g, and A represents the rated capacity of the battery cell, in units of Ah. Exemplarily, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah, or a range composed of any two of the above values.

[0462] The d / A can reflect the liquid retention capability of the electrolyte. When the d / A is within the above range, the electrolyte can have a good infiltration effect on the positive and negative electrode plates, and can improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the rapid charging capability of the battery cell.

[0463] In the embodiments of the present application, the d / A of the battery cell can be understood as a liquid retention coefficient, which can be detected by using devices and methods known in the art. For example, the battery charging upper limit voltage is 3.65V, and the battery discharging cut-off voltage is 2.0V, which is described by taking GB / T31486-2015 "Performance requirements and test methods for power storage batteries for electric vehicles" as an example,

[0464] At 25°C, the battery cell is charged to 3.65V at 0.33C, then constant voltage charged to 0.05C, and then discharged to 2.0V at 0.33C to obtain the discharged capacity A as the denominator. The battery cell is weighed as M0, then the positive electrode plate, negative electrode plate, separator and electrolyte are disassembled, and the free electrolyte is placed in a bag. All the solid components are placed in a 60°C oven for more than 4 hours (including but not limited to the positive electrode plate, negative electrode plate, separator, and other mechanical parts of the disassembled battery cell), then all the components of the battery cell are weighed as M1, and the weight difference between M0 and M1 is taken as the numerator. The liquid retention coefficient is equal to the value obtained by dividing the weight difference between M0 and M1 by the capacity A.

[0465] As shown in FIG. 7, in some embodiments of the present application, the battery cell 7 according to the embodiments of the present application can be assembled into a battery module 6. The number of battery cells 7 contained in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0466] If the battery cell 7 is multiple, the multiple battery cells 7 can be connected in series or parallel or mixed connection. The mixed connection means that there are both series connection and parallel connection among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series or parallel or mixed connection together, and then the whole of the multiple battery cells 7 is accommodated in the accommodation part of the battery module 6; of course, the multiple battery cells 7 can be first connected in series or parallel or mixed connection to form a battery module 6, and then the multiple battery modules 6 are connected in series or parallel or mixed connection to form a whole, which is accommodated in the accommodation part. Alternatively, the battery module 6 can further include an accommodation part having an accommodation space, and the multiple battery cells 7 are accommodated in the accommodation space.

[0467] As shown in FIG. 8, in some embodiments, the above-mentioned battery module 6 can also be assembled into a battery pack 2. 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 a battery module 6 or a battery pack 2.

[0468] The battery pack 2 can include a case 5 and a plurality of battery modules 6 disposed in the case 5. The case 5 includes a first case portion 5a and a second case portion 5b, and has a receiving space 5c, the first case portion 5a is used to cover the second case portion 5b and forms a closed space for receiving the battery modules 6. The plurality of battery modules 6 can be arranged in the case 5 in any manner.

[0469] The first case portion 5a and the second case portion 5b are mutually covered, and the first case portion 5a and the second case portion 5b together define a receiving space 5c for receiving battery cells. The second case portion 5b can be a hollow structure with one end open, and the first case portion 5a is a plate-shaped structure, which is covered on the open side of the second case portion 5b to form the case 5 with the receiving space 5c. The first case portion 5a and the second case portion 5b can also be hollow structures with one side open, and the open side of the first case portion 5a is covered on the open side of the second case portion 5b to form the case 5 with the receiving space 5c. Of course, the first case portion 5a and the second case portion 5b can be various shapes, such as a cylinder, a cuboid, etc.

[0470] In order to improve the sealing performance of the first case portion 5a and the second case portion 5b after connection, a sealing member such as sealing glue, sealing ring, etc. can be arranged between the first case portion 5a and the second case portion 5b.

[0471] Assuming that the first case portion 5a covers the top of the second case portion 5b, the first case portion 5a can also be referred to as an upper case cover, and the second case portion 5b can also be referred to as a lower case.

[0472] In some embodiments, during the process from 0% state of charge SOC to 100% state of charge SOC of the battery pack 2 or any battery cell constituting the battery pack 2, the temperature of the external environment in which the battery pack 2 is located is room temperature, for example 30°C.

[0473] In some embodiments, during the process from 20% state of charge SOC to 80% state of charge SOC of the battery pack 2 or any battery cell constituting the battery pack 2, the temperature of the external environment in which the battery pack 2 is located is room temperature, for example 30°C.

[0474] In some embodiments, during the charging process from 20% state of charge to 80% state of charge of the battery pack 2 or any battery cell constituting the battery pack 2, a plurality of charging steps are included, and the difference between the maximum state of charge of any charging step and the maximum state of charge of its adjacent charging step is less than or equal to 5% state of charge, for example 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 a range composed of any two of the above values.

[0475] The battery pack 2 or any battery cell constituting the battery pack 2 comprises a plurality of charging steps from 20% state of charge to 40% state of charge, for any charging step, the charging rate can be any value between 5C to 10C, each charging step corresponding charging rate can be any value of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value in the range between any two of the above values.

[0476] The battery pack 2 or any battery cell constituting the battery pack 2 also comprises a plurality of charging steps from 40% state of charge to 80% state of charge, for any charging step, the charging rate is less than the charging rate of any charging step from 20% state of charge to 40% state of charge, and the charging rate of the step charging to 80% state of charge is any value of 2.5C to 5C, for example, it can be 2.7C.

[0477] Exemplarily, the charging steps of the battery pack 2 or any battery cell constituting the battery pack 2 from 20% to 80% can be carried out as follows:

[0478] charging from 20% SOC to 25% SOC at 5.0C constant current;

[0479] charging from 25% SOC to 30% SOC at 5.0C constant current;

[0480] charging from 30% SOC to 35% SOC at 5.0C constant current;

[0481] charging from 35% SOC to 40% SOC at 5.0C constant current;

[0482] charging from 40% SOC to 45% SOC at 4.6C constant current;

[0483] charging from 45% SOC to 50% SOC at 4.3C constant current;

[0484] charging from 50% SOC to 55% SOC at 4.0C constant current;

[0485] charging from 55% SOC to 60% SOC at 3.7C constant current;

[0486] charging from 60% SOC to 65% SOC at 3.4C constant current;

[0487] charging from 65% SOC to 70% SOC at 3.1C constant current;

[0488] charging from 70% SOC to 75% SOC at 2.9C constant current;

[0489] charging from 75% SOC to 80% SOC at 2.7C constant current.

[0490] 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 12.5 minutes, optionally ranging from 5 minutes to 12.5 minutes, and the ambient temperature of the battery pack 2 at 20% state of charge is 25°C to 35°C. Exemplarily, the charging time for the battery pack 2 from 20% state of charge to 80% state of charge is 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, 5.5 minutes, 5 minutes, or a range of any two of the above values.

[0491] 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.

[0492] 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.

[0493] 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.

[0494] Electrical appliances

[0495] The second aspect of the embodiments of the present application provides a power utilization device, which comprises at least one of the battery cell, the battery module or the battery pack of the embodiments of the present application. The battery cell, the battery module or the battery pack can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric vehicle, a hybrid electric vehicle or a range extended electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer, etc. The embodiments of the present application do not specially limit the above power utilization device.

[0496] The power utilization device can select the battery cell, the battery module or the battery pack according to the use requirement.

[0497] FIG. 9 is a schematic diagram of a power utilization device 1 as an example. The power utilization device 1 is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the power utilization device 1, the battery pack or the battery module can be used.

[0498] The power utilization device 1 is internally provided with the battery pack 2, which can be arranged at the bottom, the head or the tail of the power utilization device 1. The battery pack 2 can be used for power supply of the power utilization device 1, for example, the battery pack 2 can be used as an operating power supply of the power utilization device 1, and can also be used as a driving power supply of the power utilization device 1, instead of or partially instead of fuel or natural gas to provide driving power for the power utilization device 1.

[0499] The power utilization device 1 can further include a controller 3 and a motor 4, and the controller 3 is used to control the battery pack 2 to supply power to the motor 4, for example, to meet the working power requirement of the power utilization device 1 during starting, navigation and driving.

[0500] The power utilization device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power utilization device usually requires thinning, and the battery cell can be used as a power supply.

[0501] The charging process of the power utilization device can select the following charging mode:

[0502] Charging from 20% SOC to 25% SOC at 5.0C constant current;

[0503] Charging from 25% SOC to 30% SOC at 5.0C constant current;

[0504] Charge from 30% SOC to 35% SOC at 5.0C constant current;

[0505] Charge from 35% SOC to 40% SOC at 5.0C constant current;

[0506] Charge from 40% SOC to 45% SOC at 4.6C constant current;

[0507] Charge from 45% SOC to 50% SOC at 4.3C constant current;

[0508] Charge from 50% SOC to 55% SOC at 4.0C constant current;

[0509] Charge from 55% SOC to 60% SOC at 3.7C constant current;

[0510] Charge from 60% SOC to 65% SOC at 3.4C constant current;

[0511] Charge from 65% SOC to 70% SOC at 3.1C constant current;

[0512] Charge from 70% SOC to 75% SOC at 2.9C constant current;

[0513] Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0514] In some embodiments, the charging time of the electrical device from 20% state of charge to 80% state of charge is less than or equal to 12.5 min, optionally 5 min to 12.5 min, and the temperature of the external environment of the battery pack 2 at 20% state of charge is room temperature, for example 30°C. Illustratively, the charging time of the battery pack 2 from 20% state of charge to 80% state of charge is 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min, or a range consisting of any two of the above values.

[0515] Examples

[0516] The following examples describe the present application in more detail, which are only used for illustrative purposes, because various modifications and changes within the scope of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further purification, and the instruments used in the examples are commercially available.

[0517] Example 1

[0518] 1. Preparation of positive electrode sheet

[0519] The positive electrode sheet 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.

[0520] The positive conductive layer on the positive current collector is a film layer formed by uniformly mixing a positive conductive agent, super carbon, and a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and then coating the mixture on the surface of the current collector and drying. The thickness of the positive conductive layer is 1 μm, the mass content of the positive conductive agent in the positive conductive layer is 40%, and the mass content of the positive binder is 60%.

[0521] The positive film layer includes a film layer formed by uniformly coating a positive slurry (solvent: N-methyl pyrrolidone (NMP)) on the surface of the positive conductive layer, and then drying and cold pressing. The positive film layer includes a positive active material, a binder, polyvinylidene fluoride (PVDF), and a conductive agent, acetylene black, in a weight ratio of 97:2:1.

[0522] The positive active material includes lithium iron phosphate and a coating layer. The coating layer is coated on the surface of the lithium iron phosphate and includes lithium titanium iron phosphate, Li2FeTi(PO4)3, and amorphous carbon. The Dv50 of the positive active material is 1.6 μm, the Dv10 is 0.64 μm, the smallest particle has a particle size of 0.2 μm, and the largest particle has a particle size of 18 μm.

[0523] The single-sided coating weight of the positive film layer is 300 mg / 1540.25 mm 2 .

[0524] 2. Preparation of negative electrode sheet

[0525] The negative electrode sheet includes a negative current collector, a negative conductive layer on the negative current collector, and a negative film layer. The negative current collector is a copper foil with a thickness of 5 μm.

[0526] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing a negative electrode conductive agent, a negative electrode binder, a thickening agent, and a solvent, and then coating the mixture on the surface of the negative electrode current collector and drying it. The thickness of the negative electrode conductive layer 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%. The mass content of the thickening agent in the negative electrode conductive layer is 5%.

[0527] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer, and then drying and cold pressing it.

[0528] The single-side coating weight of the negative electrode film layer is 138 mg / 1540.25 mm 2 .

[0529] 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.

[0530] The first negative electrode film layer includes graphite particles, a conductive agent, a first lithium-containing binder, a negative electrode binder, and a thickening agent, with a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer is coated on the surface of the artificial graphite. The mass content of the carbon coating layer is 3.5%.

[0531] The second negative electrode film layer includes graphite particles, a conductive agent, a second lithium-containing binder, a negative electrode binder, and a thickening agent, with a mass ratio of 97.5:0.5:0.5:0.5:1. The mass content of lithium in the second lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer is coated on the surface of the artificial graphite. The mass content of the carbon coating layer is 3.5%.

[0532] 3. Separation film

[0533] The separation film includes a base film. The base film is a 7 μm polyethylene film layer. The porosity of the base film is 42%.

[0534] 4. Preparation of electrolyte

[0535] The electrolyte comprises an organic solvent, a lithium salt and an additive.

[0536] The organic solvent comprises 60% of a chain carboxylate solvent (ethyl acetate) and 40% of a carbonate solvent (30% of ethylene carbonate EC, 10% of dimethyl carbonate), the mass content of each component in the organic solvent being calculated based on the mass of the organic solvent.

[0537] The additive has a mass content of 6.5% based on the mass of the electrolyte, and comprises vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES and lithium difluoro(oxalato)borate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0538] The lithium salt comprises 1 mol / L of lithium hexafluorophosphate LiPF6.

[0539] The electrolyte has an electrical conductivity of 16.4 mS / cm at room temperature.

[0540] 5. Preparation of battery monomer

[0541] The above positive electrode sheet, separator and negative electrode sheet are stacked in order with the separator between the positive electrode sheet and the negative electrode sheet to play a separating role, to obtain an electrode assembly, the electrode assembly is placed in an outer packaging shell, electrolyte is injected after drying, and the battery monomer is obtained after vacuum packaging, standing, formation, shaping and other processes, the compaction density of the positive electrode film layer of the battery monomer is 2.72 g / cm 3 at 100% SOC, and the compaction density of the negative electrode film layer is 1.26 g / cm 3 at 100% SOC.

[0542] Comparative Example 1 and Comparative Example 2

[0543] The battery monomer is prepared by a method similar to that of Example 1, except that the width of the positive electrode film layer is adjusted.

[0544] Example 2-1 and Example 2-2

[0545] The battery monomer is prepared by a method similar to that of Example 1, except that the width of the positive electrode film layer is adjusted.

[0546] Performance test

[0547] 1. Direct current internal resistance DCR test of battery monomer

[0548] The method can refer to that in GB / T 31467 "Performance Test Specification for High Power Lithium-ion Power Battery for HEV".

[0549] 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%.

[0550] 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 ,

[0551] Where, 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.

[0552] 2. Number of cycles required for a single battery cell to reach 80% SOH

[0553] At 30°C, the battery cell is charged at a constant current of 1C to the charging cutoff voltage of 3.65V, and then discharged at a constant current of 1C to 2.0V. 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.

[0554] The test results are shown in Table 1.

[0555] Table 1

[0556] In Table 1, in each embodiment and Comparative Example 1,

[0557] 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.

[0558] 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.

[0559] 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.

[0560] As can be seen from Table 1,

[0561] The ratio of the length to the width of the positive electrode film layer in Comparative Example 1 is less than 2.66, and the ratio of the length to the width of the positive electrode film layer in Comparative Example 2 is greater than 7.5, and the internal resistance of the battery cell is high; and the excellent cycle performance and energy density cannot be considered. In the present application, the ratio of the length to the width of the positive electrode film layer is 2.66 to 7.5, so that the internal resistance of the battery cell is small, which is beneficial to improve the cycle performance, and the cycle performance and energy density can be considered.

[0562] Comparative Example 3 and Comparative Example 4

[0563] The battery cell was prepared by using the similar method as in Example 1, and the difference from Example 1 is that the single-sided coating weight of the negative electrode film layer was adjusted.

[0564] Example 3-1 and Example 3-2

[0565] The battery cell was prepared by using the similar method as in Example 1, and the difference from Example 1 is that the single-sided coating weight of the negative electrode film layer was adjusted.

[0566] The test results are shown in Table 2.

[0567] Table 2

[0568] In Comparative Example 3, the coating weight of the negative electrode film layer is small, which cannot meet the requirement of energy density; in Comparative Example 4, the coating weight of the negative electrode film layer is large, so that the impedance of the battery cell is small and the cycle is poor.

[0569] In the present application, the coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 , which can effectively reduce the internal resistance of the battery cell, improve the rapid charging performance of the battery cell, and improve the cycle performance and have excellent energy density.

[0570] Example 4

[0571] The battery cell was prepared by using the similar method as in Example 1, and the difference from Example 1 is that the ratio of the width of the first end surface of the positive electrode tab to the width of the positive current collector is 1 / 3. The ratio of the width of the second end surface of the negative electrode tab to the width of the negative current collector is 1 / 3.

[0572] Example 5

[0573] The battery cell was prepared by using the similar method as in Example 1, and the difference from Example 1 is that the negative electrode tab is prepared as follows:

[0574] The negative electrode tab includes a negative current collector, a negative electrode conductive layer on the negative current collector, and a negative electrode film layer, and the negative current collector is a copper foil with a thickness of 5 μm.

[0575] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing a negative electrode conductive agent, super carbon, a negative electrode binder, styrene butadiene rubber SBR, a thickening agent, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, and then coating on the surface of the negative electrode current collector and drying. The thickness of the negative electrode conductive layer is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickening agent in the negative electrode conductive layer is 5%.

[0576] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, and then drying and cold pressing.

[0577] The single-side coating weight of the negative electrode film layer is 138 mg / 1540.25 mm 2 .

[0578] The negative electrode film layer includes a first negative electrode film layer, and the first negative electrode film layer is located on the surface of the negative electrode conductive layer.

[0579] The first negative electrode film layer includes graphite particles, a conductive agent, acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), a negative electrode binder, styrene butadiene rubber, and a thickening agent, sodium carboxymethyl cellulose, in a mass ratio of 96.5:0.5:0.5:1.5:1. The mass content of lithium in the first lithium-containing binder is 4.8%, the Dv50 of the graphite particles is 11.3 μm, the graphite particles include artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%.

[0580] Example 6

[0581] The battery cell is prepared by using a method similar to that of Example 1, except that the positive electrode tab is arranged on one side of the positive electrode current collector, and the negative electrode tab is arranged on one side of the negative electrode current collector.

[0582] The test results are shown in Table 3.

[0583] Table 3

[0584] As can be seen from Table 3,

[0585] When the ratio of the width of the first end surface of the positive electrode tab to the width of the positive electrode current collector is greater than or equal to 1 / 3, and the ratio of the width of the second end surface of the negative electrode tab to the width of the negative electrode current collector is greater than or equal to 1 / 3, the battery cell has a smaller internal resistance, and has excellent cycle performance and energy density.

[0586] When the positive tab is arranged on at least one side of the positive current collecting part and the negative tab is arranged on at least one side of the negative current collecting part, the battery monomer has a small internal resistance and excellent cycle performance and energy density.

[0587] When the negative film layer is arranged on at least one side of the negative current collecting part, the battery monomer has a small internal resistance and excellent cycle performance and energy density.

[0588] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as limiting the present application, and the embodiments can be changed, replaced and modified without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell, comprising an electrode assembly, the electrode assembly comprising a positive electrode, a separator, and a negative electrode stacked along the thickness direction of the battery cell; The positive electrode sheet includes a positive electrode tab, a positive electrode current collector, and a positive electrode film layer disposed 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 is disposed on at least one side of the positive electrode current collector, and the positive electrode active material includes a lithium phosphate with an olivine structure. The negative electrode sheet includes a negative electrode tab, a negative electrode current collector, and a negative electrode film layer containing a negative electrode active material disposed on at least one surface of the negative electrode current collector along the thickness direction. The negative electrode tab is disposed on at least one side of the negative electrode current collector. in, The ratio of the dimension of the positive electrode film along the length of the battery cell to the dimension of the positive electrode film along the width of the battery cell is 2.66 to 7.5; the single-sided coating weight of the negative electrode film is 90 mg / 1540.25 mm. 2 Up to 170mg / 1540.25mm 2 .

2. The battery cell according to claim 1, wherein, The length of the positive electrode film is 200 mm to 590 mm.

3. The battery cell according to claim 1 or 2, wherein, The width of the positive electrode film is 80 mm to 210 mm.

4. The battery cell according to any one of claims 1 to 3, wherein, The positive electrode tab is disposed on at least one side of the positive current collector along the length direction.

5. The battery cell according to claim 4, wherein, The positive electrode tabs are disposed on both sides of the positive current collector along the length direction.

6. The battery cell according to claim 4 or 5, wherein, There are one or more positive electrode tabs located on the same side of the positive current collector. Each positive electrode tab includes a first end face connected to the positive current collector. The dimension of the first end face along the width direction is W1. The sum of the dimensions of all the first end faces located on the same side of the positive current collector along the width direction is n*W1. The dimension of the positive current collector along the width direction is W2. n*W1 / W2 is greater than or equal to 1 / 3, where n represents the number of all positive electrode tabs located on the same side of the positive current collector.

7. The battery cell according to claim 6, wherein, n*W1 / W2 is greater than or equal to 2 / 3.

8. The battery cell according to any one of claims 1 to 7, wherein, The negative electrode tab is disposed on at least one side of the negative electrode current collector along the length direction.

9. The battery cell according to claim 8, wherein, The negative electrode tabs are disposed on both sides of the negative electrode current collector along the length direction.

10. The battery cell according to claim 8 or 9, wherein, There are one or more negative electrode tabs located on the same side of the negative electrode current collector. Each negative electrode tab includes a second end face connected to the negative electrode current collector. The dimension of the second end face along the width direction is W3. The sum of the dimensions of all the second end faces located on the same side of the negative electrode current collector along the width direction is m*W3. The dimension of the negative electrode current collector along the width direction is W4. m*W3 / W4 is greater than or equal to 1 / 3, where m represents the number of all negative electrode tabs located on the same side of the negative electrode current collector.

11. The battery cell according to claim 10, wherein, m*W3 / W4 is greater than or equal to 2 / 3.

12. The battery cell according to any one of claims 1 to 11, wherein, The positive electrode tab is disposed on at least one side of the positive current collector along the length direction, and the negative electrode tab is disposed on at least one side of the negative current collector along the length direction. Along the length direction, the size of the negative electrode film is larger than the size of the positive electrode film, and the size difference between the negative electrode film and the positive electrode film is OH1; Along the width direction, the size of the negative electrode film is larger than the size of the positive electrode film, and the size difference between the negative electrode film and the positive electrode film is OH2. Among them, OH1 is greater than OH2.

13. The battery cell according to claim 12, wherein, OH1 is 0.5 mm to 3.0 mm; and / or OH2 is 0.5 mm to 3.0 mm.

14. The battery cell according to any one of claims 1 to 13, wherein the battery cell further comprises a positive terminal, the positive terminal being directly welded to the positive electrode tab.

15. The battery cell according to any one of claims 1 to 14, wherein the battery cell further comprises a positive terminal, and the number of positive terminals located on the same side of the positive current collector is at least two.

16. The battery cell according to any one of claims 1 to 15, wherein the battery cell further comprises at least one positive terminal, and the current-passing area of ​​all the positive terminals located on the same side of the positive current collector is 150 mm². 2 Up to 1000mm 2 .

17. The battery cell according to any one of claims 1 to 16, wherein the battery cell further comprises a negative terminal, the negative terminal being directly welded to the negative electrode tab.

18. The battery cell according to any one of claims 1 to 17, wherein, The battery cell also includes a negative terminal, and the number of negative terminals located on the same side of the negative current collector is at least two.

19. The battery cell according to any one of claims 1 to 18, wherein, The battery cell also includes at least one negative terminal, and the current-passing area of ​​all the negative terminals located on the same side of the negative current collector is 150 mm². 2 Up to 1000mm 2 .

20. The battery cell according to any one of claims 1 to 19, the battery cell comprising a housing that accommodates the electrode assembly, the thickness of the housing being 0.1 mm to 0.5 mm.

21. The battery cell according to claim 20, wherein, The thickness of the shell is 0.2 mm to 0.35 mm.

22. The battery cell according to any one of claims 1 to 21, wherein, The single-sided coating weight of the negative electrode film is 110 mg / 1540.25 mm. 2 Up to 150mg / 1540.25mm 2 .

23. The battery cell according to any one of claims 1 to 22, wherein, When the battery cell is 100% charged, the compaction density of the positive electrode film is 2.50 g / cm³. 3 Up to 2.80 g / cm 3 , and / or The single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2 Up to 370mg / 1540.25mm 2 .

24. The battery cell according to any one of claims 1 to 23, wherein, The resistivity of the positive electrode active material powder is from 1 Ω·cm to 27.5 Ω·cm; and / or The compacted density of the positive electrode active material at 30000N is 2.46 g / cm³. 3 Up to 2.8 g / cm 3 ; and / or The positive electrode active material has a charging capacity of 150 mAh / g to 170 mAh / g at a 0.1C rate.

25. The battery cell according to any one of claims 1 to 24, wherein, The lithium phosphate with the olivine structure includes: Phosphate particles, and A coating layer that coats the phosphate particles, the coating layer containing one or more elements selected from C, Fe, Ti, Zr, Hf, Ge and Sn.

26. The battery cell according to claim 25, wherein, The phosphate particles include those with the general formula Li x1 A y1 Me a M b P 1-c X c Y z The compound, wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F.

27. The battery cell according to claim 25 or 26, wherein, The coating layer includes a general formula Li 3-d Fe 2- d M2 d (PO x2 ) y2 A fast ion conductor, M2 includes one or more elements from Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x2<5, 0<y2<4.

28. The battery cell according to any one of claims 25 to 27, wherein, The degree of graphitization of the lithium phosphate with the olivine structure is 0.15 to 0.

32.

29. The battery cell according to claim 28, wherein, The degree of graphitization of the lithium phosphate with the olivine structure is 0.19 to 0.

26.

30. The battery cell according to any one of claims 25 to 29, wherein, The lithium phosphate with the olivine structure has a carbon content of 1% to 2% by mass. The specific surface area of ​​the lithium phosphate with the olivine structure is 5 m². 2 / g to 18m 2 / g.

31. The battery cell according to claim 30, wherein, The specific surface area of ​​the lithium phosphate with the olivine structure is 7.5 m². 2 / g to 14m 2 / g.

32. The battery cell according to any one of claims 25 to 31, wherein, The lithium phosphate with olivine structure is granular, and the volume distribution particle size of the lithium phosphate with olivine structure satisfies: 1μm≤Dv50≤2μm, 0.4μm≤Dv10≤0.7μm.

33. The battery cell according to any one of claims 25 to 32, wherein, The smallest particle size in the lithium phosphate with the olivine structure is 0.1 μm to 0.4 μm; and / or The maximum particle size of the lithium phosphate containing the olivine structure is 15 μm to 25 μm.

34. The battery cell according to any one of claims 1 to 33, wherein, The ratio of the thickness of the positive current collector to the thickness of the positive electrode film layer on one side is 0.05 to 0.

3.

35. The battery cell according to any one of claims 1 to 34, wherein, The thickness of the positive current collector is 10 μm to 15 μm.

36. The battery cell according to any one of claims 1 to 35, wherein, The positive electrode sheet further includes a positive conductive layer, which is located between the positive electrode film and the positive electrode current collector.

37. The battery cell according to any one of claims 1 to 36, wherein, The positive electrode film layer further includes a first material, which 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 metamanganate, lithium tartrate, lithium trilithium citrate, lithium nickelate, and lithium ferrite.

38. The battery cell according to claim 37, wherein, The first material has a mass content of 0.5% to 5% in the positive electrode film layer.

39. The battery cell according to any one of claims 1 to 38, wherein, When the battery cell is 100% charged, the compaction density of the negative electrode film is 1.15 g / cm³. 3 Up to 1.36 g / cm 3 .

40. The battery cell according to any one of claims 1 to 39, wherein, The resistivity of the negative electrode active material powder is from 0.005 Ω·cm to 0.043 Ω·cm.

41. The battery cell according to any one of claims 1 to 40, wherein, The compacted density of the negative electrode active material at 20000N is 1.5 g / cm³. 3 Up to 1.85 g / cm 3 .

42. The battery cell according to any one of claims 1 to 41, wherein, The specific capacity of the negative electrode active material at a 0.1C rate is 350mAh / g to 480mAh / g.

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

44. The battery cell according to claim 43, wherein, The graphite particles include: Artificial graphite, including secondary particles, and A carbon coating layer is applied to the surface of the artificial graphite.

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

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

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

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

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

50. The battery cell according to 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 according to claim 50, wherein, The tap density of the carbon-based material in the first negative electrode film is 0.82 g / cm³. 3 Up to 1.21 g / cm 3 , and / or The tap density of the carbon-based material in the second negative electrode film is 0.90 g / cm³. 3 Up to 1.25 g / cm 3 .

52. The battery cell according to any one of claims 48 to 51, wherein, The first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder, wherein the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

53. The battery cell according to claim 52, wherein, The first lithium-containing binder has a mass content of 0.1% to 1% relative to the first negative electrode film layer, and / or The second lithium-containing binder has a mass content of 0.1% to 1% relative to the second negative electrode film layer.

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

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

56. The battery cell according to any one of claims 1 to 55, wherein, The thickness of the negative electrode current collector is 4 μm to 6 μm.

57. The battery cell according to any one of claims 1 to 56, wherein, The negative electrode sheet further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector.

58. The battery cell according to any one of claims 1 to 57, wherein, The electrolyte has a conductivity of 13 mS / cm to 18.5 mS / cm at room temperature; and / or The electrolyte has a viscosity of 2.3 mPa·s to 3.5 mPa·s at room temperature; and / or The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature.

59. The battery cell according to any one of claims 1 to 58, wherein the battery cell comprises an electrolyte, the electrolyte comprises an organic solvent, the organic solvent comprises a chain carboxylic acid ester solvent, and the chain carboxylic acid ester solvent has a mass content of 5% to 75% in the organic solvent.

60. The battery cell according to claim 59, wherein, The chain-like carboxylic acid ester solvent has a mass content of 30% to 70% in the organic solvent.

61. The battery cell according to claim 59 or 60, wherein, The chain-like carboxylic acid ester solvents include compounds represented by Formula I. In formula I, R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group. R2 includes C1 to C5 alkyl or C1 to C5 haloalkyl.

62. The battery cell according to claim 61, wherein, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group or a C1 to C3 haloalkyl group, and / or R2 includes C1 to C3 alkyl or C1 to C3 haloalkyl.

63. The battery cell according to claim 62, wherein, The chain-like carboxylic acid ester solvents include one or more compounds from Formula I-1 to Formula I-8.

64. The battery cell according to any one of claims 59 to 63, wherein, The organic solvent also includes carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

65. The battery cell according to claim 64, wherein, The carbonate solvents include one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

66. The battery cell according to claim 64 or 65, wherein, The carbonate solvent has a mass content of 30% to 70% in the organic solvent.

67. The battery cell according to any one of claims 1 to 66, wherein, The electrolyte also includes additives, which include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives.

68. The battery cell according to claim 67, wherein, The carbonate additives include one or more of vinylene carbonate and fluoroethylene carbonate, and / or The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, vinyl sulfite, and methylene disulfonate, and / or The lithium salt additives include one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium dioxalate borate.

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

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

71. The battery cell according to any one of claims 1 to 70, wherein, The electrolyte also includes lithium salts, which include one or more of fluorosulfonyl imide salts and lithium hexafluorophosphate.

72. The battery cell according to claim 71, wherein, The fluorinated sulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide and lithium bistrifluoromethylsulfonate imide.

73. The battery cell according to claim 72, wherein, The lithium salt comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, wherein the molar concentration of lithium bis(fluorosulfonyl)imide is from 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate is from 0.5 mol / L to 1.0 mol / L.

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

0.

75. The battery cell according to any one of claims 1 to 74, wherein, The isolation membrane comprises a porous base membrane with a thickness of 6 μm to 12 μm; and / or the porosity of the base membrane is 35% to 60%.

76. The battery cell according to claim 75, wherein, The isolation membrane further includes a functional layer disposed on at least one side of the base membrane, the functional layer comprising: A first functional layer is located on one side of the base film, and the first functional layer includes first inorganic particles. The second functional layer is located on the other side of the base film. The second functional layer includes composite particles, which include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

77. The battery cell according to claim 76, wherein, The non-fluoropolymer particles include acrylate copolymers.

78. The battery cell according to claim 76 or 77, wherein, The first inorganic particles comprise one or more of the following: silicon dioxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium dioxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide; and / or The second inorganic particle includes one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

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

80. The battery cell according to any one of claims 1 to 79, wherein, The charging time for the battery device from 20% to 80% state of charge is 5 minutes to 12.5 minutes.

81. A battery device comprising a battery cell as claimed in any one of claims 1 to 80.

82. The battery device according to claim 81, wherein, The charging time for the battery from 20% to 80% state of charge is 5 minutes to 12.5 minutes.

83. An electrical device comprising the battery device as described in claim 81 or 82.

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