Battery monomer, battery device, power utilization device and energy storage device

Abstract

The invention provides a battery monomer, a battery device, a power utilization device and an energy storage device. The size of the positive electrode active material layer in the length direction of the electrode assembly is 300 mm to 950 mm; in the length direction of the electrode assembly, the difference value between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1, and OH1 is larger than 1 mm and smaller than 5 mm; in the width direction of the electrode assembly, the difference value between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH2, and OH2 is larger than 1 mm and smaller than or equal to 4 mm; based on the total mass of the electrolyte, the mass ratio of the carboxylic ester solvent is 8%-57%, and the mass ratio of the fluorine-containing sulfimide lithium salt is 3%-8%. The battery monomer gives consideration to improvement of energy density, fast charge performance, cycle stability under fast charge and safety performance, and comprehensive improvement of battery performance is realized.

Description

[0001] This application claims the priority of the international patent application PCT / CN2025 / 086858 titled "Battery Cell, Battery Device, Electrical Device, and Energy Storage Device" filed on April 2, 2025, and the entire content of this application is incorporated herein by reference. Technical Field

[0002] This application relates to the technical field of battery cells, and particularly to a battery cell, an electrical device, and an energy storage device. Background Art

[0003] In recent years, battery cells have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0004] With the dual increase in the market's demand for the driving range and charging efficiency of electrical devices, higher requirements are also put forward for the energy density, fast charging performance, etc. of battery cells. However, while achieving the improvement of the above performances, the deterioration of cycle stability is often brought about, which has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This application is made in view of the above problems, and its purpose is to provide a battery cell, a battery device, an electrical device, and an energy storage device, in which the battery cell takes into account the improvement of energy density, fast charging performance, cycle stability under fast charging, and safety performance, and realizes the comprehensive improvement of battery performance.

[0006] In a first aspect of this application, a battery cell is provided, including an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet stacked in sequence. The positive electrode sheet includes a positive current collector and a positive active material layer provided on at least one side of the positive current collector. The positive current collector includes a positive current collecting portion and a positive electrode tab, and the positive electrode tab is provided at at least one end of the positive current collecting portion extending along the length direction of the electrode assembly; the negative electrode sheet includes a negative current collector and a negative active material layer provided on at least one side of the negative current collector. The negative current collector includes a negative current collecting portion and a negative electrode tab, and the negative electrode tab is provided at at least one end of the negative current collecting portion extending along the length direction of the electrode assembly; wherein, the positive active material layer includes a positive active material, and the positive active material includes a lithium-containing phosphate with an olivine structure; the size of the positive active material layer along the length direction of the electrode assembly is 300 mm to 950 mm; along the length direction of the electrode assembly, the size of the negative active material layer is larger than the size of the positive active material layer, and the difference between the size of the negative active material layer and the size of the positive active material layer is OH 1 OH 1is greater than 1 mm and less than 5 mm; along the width direction of the electrode assembly, the size of the negative electrode active material layer is greater than that of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH 2 , OH 2 is greater than 1 mm and less than or equal to 4 mm; the electrolyte includes a solvent and a lithium-containing electrolyte salt, the solvent includes a carboxylate solvent, and the lithium-containing electrolyte salt includes a lithium fluorosulfonylimide salt; based on the total mass of the electrolyte, the mass ratio of the carboxylate solvent is 8% to 57%, and the mass ratio of the lithium fluorosulfonylimide salt is 3% to 8%.

[0007] The lithium-containing phosphate with an olivine structure has the advantages of low cost and good life. Combining the design of the laminated electrode assembly with the size of the positive electrode active material layer in the above range along the length direction of the electrode assembly and the tab being located on the short side helps to improve the internal space utilization rate of the battery cell, improve the problem of low energy density of the battery cell when the lithium-containing phosphate is used as the positive electrode active material, shorten the current transmission path from the active material to the tab at the same time, reduce the internal resistance of the battery, and enable the battery cell to have excellent fast charging performance and energy density. However, as the charging rate of the battery cell increases, the current density in the area near the tab is high and the temperature rise is large, resulting in a faster lithium ion migration rate than other parts, and the negative electrode active material layer is prone to lithium dendrite formation near the tab. The battery cell of the embodiment of the present application passes through OH 1 's design improves the ability of the negative electrode active material layer, especially the negative electrode active material layer in the area near the tab, to accept active ions in the length direction, and makes the distance between the positive electrode active material layer and the tab side farther. The current distribution of the active material layer in the area near the tab is more uniform, resulting in a lower temperature rise, thereby comprehensively improving the lithium deposition problem of the negative electrode plate; through OH 2 's design helps to reduce the probability of the separator shrinking due to heat and causing the positive and negative electrodes to overlap and then an internal short circuit in the battery; while improving the cycle stability of the battery cell, controlling OH 1 , OH 2The value is within the above range, enabling the battery cell to have excellent energy density. Carboxylate solvents have the advantages of low viscosity and high ionic conductivity, which are beneficial to the infiltration of the electrolyte into the negative active material layer and the fast charge insertion and extraction of active ions in the negative active material layer, thereby further improving the lithium plating problem of the negative electrode sheet. However, their activity is relatively high, and they are prone to decomposition and gas generation under high-rate currents. Therefore, by further reasonably controlling the mass ratio of carboxylate solvents in the electrolyte within the above range, the electrolyte has both good conductivity and stability, which is conducive to the further comprehensive improvement of the fast charge performance and cycle stability of the battery cell. Fluorosulfonylimide salts are prone to dissociation in carboxylate solvents, which is beneficial to further improving the conductivity of the electrolyte. Moreover, fluorosulfonylimide salts have high thermochemical stability and are not easily decomposed by heat. In addition, fluorosulfonylimide salts can participate in the formation of the solid electrolyte interface film (SEI film) on the surface of the negative active material, which helps to improve the thermal stability of the SEI film, reduce the impedance of the SEI film, and further reduce the risk of lithium plating in the battery under high-rate currents. However, with the increase in the temperature of the battery cell, fluorosulfonylimide salts will undergo violent decomposition at a certain temperature threshold, releasing a large amount of heat and sharply increasing the risk of thermal runaway of the battery. This safety risk is more significant in fast-charging batteries. Therefore, by further reasonably controlling the mass ratio of lithium fluorosulfonylimide salts in the electrolyte within the above range, the electrolyte has both good conductivity and stability, further improving the fast charge performance and cycle stability while reducing the risk of thermal runaway of the battery cell, and enabling the battery cell to have excellent safety performance. In the embodiments of the present application, through the mutual cooperation between the electrode assembly and the electrolyte, lithium ions can cooperate with each other during the liquid-phase and solid-phase transmission processes, enabling the battery cell to have excellent energy density, a reduced risk of lithium plating during fast charging, an improved cycle life, and safety performance, thus achieving a comprehensive improvement in battery performance.

[0008] In any embodiment, OH 1 is greater than or equal to 1.5 mm and less than or equal to 4 mm.

[0009] In any embodiment, OH 2 is greater than or equal to 1.5 mm and less than or equal to 3 mm.

[0010] OH 1 、OH 2 Within the above range, while improving the cycle stability of the battery cell, it is beneficial to further improve the energy density of the battery cell.

[0011] In any embodiment, OH 1 ≥OH 2 .

[0012] Control OH 1 ≥OH 2, while improving the cycle stability during the fast charging process of the battery cell, it is beneficial to further improve the energy density of the battery cell.

[0013] In any implementation, the size of the positive electrode active material layer in the length direction of the battery cell is 400 mm to 650 mm.

[0014] When the size of the positive electrode active material layer in the length direction of the battery cell is within the above range, the battery cell takes into account excellent fast charging performance, cycle stability during fast charging, and energy density.

[0015] In any implementation, the size of the positive electrode active material layer in the width direction of the electrode assembly is 90 mm to 130 mm.

[0016] When the size of the positive electrode active material layer in the width direction of the electrode assembly is within the above range, combined with the size of the positive electrode active material layer in the length direction, while improving the energy density of the battery cell, it is beneficial for the battery cell to match the usage requirements of different specifications of electrical devices.

[0017] In any implementation, the size of the negative electrode active material layer in the length direction of the electrode assembly is 400 mm to 658 mm.

[0018] In any implementation, the size of the negative electrode active material layer in the width direction of the electrode assembly is 90 mm to 130 mm.

[0019] When the size of the negative electrode active material layer in the length direction and width direction of the electrode assembly is within the above range, matching the design of the positive electrode active material layer is beneficial to comprehensively improve the energy density, fast charging performance, and cycle stability during fast charging of the battery cell.

[0020] In any implementation, the positive electrode tab is disposed at one end of the positive electrode current collector extending along the length direction of the electrode assembly, and the negative electrode tab is disposed at one end of the negative electrode current collector extending along the length direction of the electrode assembly.

[0021] The above tab arrangement helps to improve the weight energy density of the battery cell.

[0022] In any implementation, the positive electrode tabs are disposed at both ends of the positive electrode current collector extending along the length direction of the electrode assembly, and the negative electrode tabs are disposed at both ends of the negative electrode current collector extending along the length direction of the electrode assembly.

[0023] In any implementation, the size of the positive electrode active material layer in the length direction of the electrode assembly is 650 mm to 950 mm, the positive electrode tabs are disposed at both ends of the positive electrode current collector extending along the length direction of the electrode assembly, and the negative electrode tabs are disposed at both ends of the negative electrode current collector extending along the length direction of the electrode assembly.

[0024] The above tab tab setting helps to improve the overcurrent capacity of the battery cell, alleviate the situation of lithium plating caused by the decomposition of the electrolyte and uneven current distribution on the tab side due to excessive temperature during fast charging on the tab side, thereby improving the fast charging performance of the battery cell and the cycle stability under fast charging, and is particularly suitable for improving the cycle stability of a battery cell with the length dimension of the positive active material layer in the range of 650 mm to 950 mm under fast charging.

[0025] In any embodiment, the ratio of the width of the positive tab to the width of the positive current collector is 0.25 to 1.

[0026] In any embodiment, the ratio of the width of the negative tab to the width of the negative current collector is 0.25 to 1.

[0027] The ratio of the width of the tab to the width of the current collector within the above range helps to improve the overcurrent capacity of the battery cell, improve the fast charging performance of the battery cell and the cycle stability under fast charging.

[0028] In any embodiment, based on the total mass of the electrolyte, the mass fraction of lithium fluorosulfonylimide salt is 4% to 8%.

[0029] The mass fraction of lithium fluorosulfonylimide salt within the above range can further balance the fast charging performance, cycle stability under fast charging and safety performance of the battery cell.

[0030] In any embodiment, the lithium fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI, lithium bis(trifluoromethanesulfonyl)imide LiTFSI, and lithium perfluorobutanesulfonylimide LiFNFSI.

[0031] In any embodiment, the lithium-containing electrolyte salt further includes lithium hexafluorophosphate LiPF 6 , based on the total mass of the electrolyte, the total mass fraction of lithium hexafluorophosphate LiPF 6 and lithium fluorosulfonylimide salt is 10% to 18%.

[0032] The lithium-containing electrolyte salt further includes lithium hexafluorophosphate LiPF 6 can reduce the risk of thermal runaway of the battery cell, keep the risk within a controllable range, and further improve the safety performance of the battery cell. The total mass fraction of lithium hexafluorophosphate LiPF 6 and lithium fluorosulfonylimide salt within the above range in the electrolyte can further balance the fast charging performance, cycle stability under fast charging and safety performance of the battery cell.

[0033] In any embodiment, based on the total mass of the electrolyte, the ratio of the mass fraction of lithium hexafluorophosphate LiPF 6 to the mass fraction of lithium fluorosulfonylimide salt is 0.9:1 to 4:1.

[0034] In the electrolyte, the ratio of the mass fraction of lithium hexafluorophosphate LiPF 6 to the mass fraction of lithium fluorosulfonylimide salt within the above range enables the battery cell to further balance the fast charging performance, cycle stability under fast charging, and safety performance of the battery cell.

[0035] In any embodiment, the carboxylic ester solvent has the general structural formula of R ' -COO-R '' wherein R ' includes one or more of a hydrogen atom, a halogen atom, a C 1 -C 5 alkyl group, and a C 1 -C 5 haloalkyl group, and R '' includes one or more of a C 1 -C 5 alkyl group and a C 1 -C 5 haloalkyl group.

[0036] In any embodiment, the carboxylic ester solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0037] In any embodiment, the solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0038] The carbonate solvent has a high dielectric constant, which can increase the dissociation rate of lithium ions and anions in the lithium-containing electrolyte salt, and further comprehensively improve the fast charging performance of the battery cell and the cycle stability under fast charging.

[0039] In any embodiment, based on the total mass of the electrolyte, the mass fraction of the carbonate solvent is 18% to 75%.

[0040] Since the carbonate solvent has a relatively large viscosity, as the content of the carbonate solvent increases, the viscosity of the electrolyte will also increase to some extent, which has a negative impact on the conductivity of the electrolyte. By reasonably controlling the mass fraction of the carbonate solvent within the above range, the electrolyte has an appropriate viscosity and a good dissociation rate, thereby comprehensively improving the conductivity of the electrolyte, which is beneficial to further enhancing the fast charging performance of the battery cell and the cycle stability under fast charging.

[0041] In any embodiment, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives.

[0042] In any embodiment, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives, wherein the ethylene carbonate derivative includes the compound shown in Formula III, Formula III R 1 、R 2 、R 3 、R 4 each independently includes one or more of a hydrogen atom, a halogen atom, a C 1 -C 5 alkyl group and a C 1 -C 5 haloalkyl group, and R 1 、R 2 、R 3 、R 4 are not simultaneously hydrogen atoms. Optionally, the carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

[0043] The carbonate additive can evolve into an organic component in the SEI film, improving the toughness of the SEI film, thereby further enhancing the stability of the SEI film during the cycling of the battery cell and further reducing the interfacial impedance on the negative electrode side, which is beneficial to further improving the cycling life and fast charging performance of the battery cell.

[0044] In any embodiment, the sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, ethylene sulfite, methylene bis(methanesulfonate), and 1,3-propane sultone.

[0045] Sulfur-containing additives often have a relatively high potential. The sulfur-containing additives added to the electrolyte will react preferentially during formation or subsequent cycling and evolve into sulfur-containing components in the SEI film. The SEI film formed by the carbonate additive has poor high-temperature stability, which is not conducive to the stability of the battery cell in a high-temperature environment. The presence of sulfur elements in the SEI film can further improve the thermal stability of the SEI film at high temperatures and further reduce the interfacial impedance on the negative electrode side, which is beneficial to further improving the cycling stability and fast charging performance of the battery cell.

[0046] In any embodiment, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0047] Lithium salt additives can evolve into inorganic components in the SEI film, improving the rigidity and thermal stability of the SEI film, further enhancing the stability of the SEI film, further reducing the interfacial impedance on the negative electrode side, and thus further improving the cycle stability and fast charging performance of the battery. Moreover, the above lithium salt additives can also form a cathode electrolyte interface film (CEI film) on the surface of the cathode active material, thereby further improving the cycle stability of the battery cell.

[0048] In any embodiment, based on the total mass of the electrolyte, the mass fraction of the carbonate additive is 3% to 8%.

[0049] When the mass fraction of the carbonate additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the stability of the SEI film and the maintenance of an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0050] In any embodiment, based on the total mass of the electrolyte, the mass fraction of vinylene carbonate is 2% to 5%.

[0051] Vinylene carbonate VC has a reduction potential close to that of carboxylic ester solvents, which can inhibit the reaction activity of carboxylic ester solvents and improve the cycle life of the battery cell. However, if the content of vinylene carbonate VC is too high, it will lead to an increase in the interfacial impedance and charge transfer impedance of the battery, which is not conducive to the fast charging performance of the battery cell. When the mass fraction of vinylene carbonate VC is within the above range, the battery can achieve excellent cycle life and fast charging performance.

[0052] In any embodiment, based on the total mass of the electrolyte, the mass fraction of ethylene carbonate derivatives is 0% to 4%.

[0053] In any embodiment, based on the total mass of the electrolyte, the mass fraction of ethylene carbonate derivatives is 1.5% to 3.5%.

[0054] Ethylene carbonate derivatives can also form a film on the surface of the negative electrode at a relatively high potential and have a low interfacial impedance and charge transfer impedance. When the mass fraction of ethylene carbonate derivatives is within the above range, the battery cell can achieve excellent fast charging performance and cycle life. By adding vinylene carbonate VC and ethylene carbonate derivatives in combination in the electrolyte, the fast charging performance and cycle stability of the battery cell can be comprehensively improved.

[0055] In any embodiment, based on the total mass of the electrolyte, the mass fraction of sulfur-containing additives is 0% to 2%.

[0056] In any embodiment, based on the total mass of the electrolyte, the mass fraction of sulfur-containing additives is 0.5% to 2%.

[0057] When the mass percentage of the sulfur-containing additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the thermal stability of the SEI film at high temperatures and maintain an appropriate viscosity of the electrolyte, further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0058] In any embodiment, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0% to 1%.

[0059] In any embodiment, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.2% to 1%.

[0060] When the mass percentage of the lithium salt additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the stability of the SEI film and maintain an appropriate viscosity of the electrolyte, further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0061] In any embodiment, the positive electrode active material includes: lithium-containing phosphate in an olivine structure, and a coating layer located on at least a part of the surface of the lithium-containing phosphate, and the coating layer contains carbon elements.

[0062] The coating layer containing carbon elements is beneficial to improving the electronic conductivity of the lithium-containing phosphate, improving the solid-phase transmission rate of electrons, and thus further improving the energy density and fast charging performance of the battery cell.

[0063] In any embodiment, based on the total mass of the positive electrode active material, the mass percentage of carbon elements is 0.8% to 2.3%.

[0064] Based on the total mass of the positive electrode active material, when the mass percentage of carbon elements is within the above range, the lithium-containing phosphate has both excellent electronic conductivity and specific capacity, further comprehensively improving the energy density and fast charging performance of the battery cell.

[0065] In any embodiment, the coating layer further includes a component represented by Formula I, Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I, where 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn. Optionally, M1 is +4 valent.

[0066] The component shown in Formula I is a fast ion conductor with a NASICON structure, whose ionic conductivity is close to or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has rich three-dimensional lithium ion diffusion and transport channels, and has the advantages of high ion conduction efficiency and strong structural stability during multiple de-lithiation and intercalation processes. The coating layer on the surface of the lithium-containing phosphate includes a fast ion conductor with a NASICON structure, which can significantly improve the transport rate of lithium ions during multiple de-intercalation / intercalation at the positive electrode, improve the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0067] In any embodiment, the lithium-containing phosphate includes a component shown in Formula II, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X includes one or more of S, Si, Cl, B, C, N, P; Y includes one or more of O and F.

[0068] The lithium-containing phosphate with an olivine structure having the above components has good structural stability, can reduce the loss during fast charging, and further improve the fast charging performance and cycle stability of the battery cell.

[0069] In any embodiment, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, and modified forms of any one of the foregoing substances, wherein the modified forms include one or more of doping modification and coating modification.

[0070] In any embodiment, the tap density of the positive electrode active material layer is 2.50 g / cm 3 to 2.80 g / cm 3 .

[0071] The positive electrode active material layer with a tap density within the above range can further achieve the balance between the fast charging performance and the energy density of the battery cell.

[0072] In any embodiment, the single-sided coating mass of the positive electrode active material layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 .

[0073] The positive electrode active layer with the single-sided coating mass of the positive electrode active material layer within the above range can further effectively balance the fast charging performance and energy density of the battery cell.

[0074] In any embodiment, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0075] The positive electrode current collector has a relatively low thickness, enabling further improvement of the energy density of the battery cell.

[0076] In any embodiment, the positive electrode plate further includes a positive electrode conductive layer located between the positive electrode active material layer and the positive electrode current collector, and the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm; and / or the negative electrode plate further includes a negative electrode conductive layer located between the negative electrode current collector and at least one side of the negative electrode active material layer, and the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

[0077] The provision of the positive electrode conductive layer and / or the negative electrode conductive layer is beneficial to improving the electronic conductivity of the battery cell plate and further improving the fast charging performance of the battery cell.

[0078] In any embodiment, the positive electrode conductive layer includes a conductive agent and a positive electrode binder, the negative electrode conductive layer includes a conductive agent and a negative electrode binder, the conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and 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.

[0079] In any embodiment, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material.

[0080] In any embodiment, the carbon-based material includes one or more of graphite and hard carbon.

[0081] In any embodiment, the carbon-based material includes composite graphite particles, the composite graphite particles include graphite body particles and a carbon coating layer covering at least part of the surface of the graphite body particles, the graphite body particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0082] Secondary particles refer to particles formed by the aggregation of two or more primary particles. The composite graphite particles include secondary particles and an amorphous carbon-containing surface coating layer, which is beneficial to the infiltration of the electrolyte in the negative electrode active layer of the electrode sheet and the improvement of the solid-phase transport ability of active ions, contributing to the further improvement of the fast charging performance of the battery cell.

[0083] In any embodiment, based on the total mass of the composite graphite particles, the mass ratio of amorphous carbon is 2% to 5%.

[0084] When the content of amorphous carbon is within a suitable range, the composite graphite material can have a high specific capacity while also having a high solid-phase transport ability of active ions, which is beneficial to comprehensively improving the energy density and fast charging performance of the battery cell.

[0085] In any embodiment, the volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 13.5 μm.

[0086] When the volume average particle size Dv50 of the composite graphite particles is within the above range, the solid-phase migration path of lithium ions is shortened while taking into account the lower reactivity, thus taking into account the fast charging ability and cycle life of the battery cell.

[0087] In any embodiment, the negative electrode active material further includes a silicon-based material, and the silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy.

[0088] In any embodiment, the silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

[0089] In any embodiment, based on the total mass of the negative electrode active material layer, the mass ratio of silicon element is 0.5% to 5%.

[0090] The introduction of the silicon-based material is beneficial to further improving the energy density of the battery cell. Based on the total mass of the negative electrode active material layer, when the mass ratio of silicon element is within the above mass range, the energy density and cycle stability of the battery cell can be taken into account.

[0091] In any embodiment, the single-sided coating mass of the negative electrode active material layer is 90 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 .

[0092] The single-sided coating mass of the negative electrode active material layer can be tested by a method similar to that of the single-sided coating mass of the positive electrode active material layer described above.

[0093] The negative electrode active material layer with a single-sided coating quality within the above range can cooperate with the positive electrode active material layer to achieve a balance between the energy density of the battery cell and the fast charging performance.

[0094] In any embodiment, the porosity of the separator is 20% to 70%, and can be optionally 35% to 60%.

[0095] The porosity of the separator within the above range is beneficial to further balance the energy density, fast charging performance, and cycle stability of the battery cell.

[0096] In any embodiment, the separator includes: a base film; a first functional layer located on at least one side of the base film, the first functional layer including a first inorganic substance; and a second functional layer located on the side of the first functional layer away from the base film, the second functional layer including a second inorganic substance and non-fluoropolymer particles.

[0097] In any embodiment, the non-fluoropolymer particles include acrylate copolymers.

[0098] In any embodiment, the first inorganic substance and the second inorganic substance each independently 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.

[0099] The inorganic particles can improve the wettability of the first functional layer and the second functional layer to the electrolyte and the heat resistance, and further comprehensively improve the fast charging performance, cycle stability, and safety performance of the battery cell. The non-fluoropolymer particles can improve the processing performance and stability of the separator, and avoid internal short circuit caused by the movement of the separator in the battery cell, thereby further improving the cycle stability and safety performance of the battery cell.

[0100] In any embodiment, the thickness of the base film is 4 μm to 12 μm, and can be optionally 5 μm to 9 μm.

[0101] The thickness of the base film within the above range is beneficial to further balance the energy density, fast charging performance, and cycle stability of the battery cell.

[0102] In any embodiment, the battery cell includes a housing and a cover assembly, the cover assembly is disposed at at least one end of the housing, the housing and the cover assembly define a receiving cavity, and the electrode assembly is disposed in the receiving cavity. The wall thickness of the housing on the large surface of the battery cell is 0.1 mm to 0.5 mm.

[0103] In some embodiments, the wall thickness of the housing on the large surface of the battery cell is 0.2 mm to 0.35 mm.

[0104] The wall thickness of the housing on the large surface of the battery cell within the above range is beneficial to further improve the energy density of the battery cell.

[0105] In any implementation, the cover plate assembly includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly and the second cover plate assembly are arranged at both ends in the length direction or the width direction of the housing. The first cover plate assembly includes a first cover plate and a first electrode terminal, and the second cover plate assembly includes a second cover plate and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite.

[0106] Thereby, during charging, the temperature rise of the battery cell is reduced and the impedance of the battery cell is reduced, which is beneficial to the improvement of the fast charging performance, cycle life and safety performance of the battery cell.

[0107] In any implementation, the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S, and it satisfies 150mm 2 ≤S≤1000mm 2 .

[0108] When the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is within the above range, it is beneficial to improve the over-current capacity of the battery cell, reduce the heat generation of the electrode terminal, reduce the internal resistance of the battery cell, and thus improve the fast charging performance and cycle stability of the battery cell.

[0109] The second aspect of the present application provides a battery device, including the battery cell provided in the first aspect of the present application. The battery device includes at least one of a battery module, a battery pack, and an energy storage battery.

[0110] The third aspect of the present application further provides an electrical device, and the electrical device includes the battery cell provided in the first aspect of the present application.

[0111] The fourth aspect of the present application further provides an energy storage device, and the energy storage device includes the battery cell provided in the first aspect of the present application. Description of the Drawings

[0112] Figure 1 is a schematic diagram of a positive electrode plate and a negative electrode plate according to an embodiment of the present application; Figure 2A is a schematic diagram of a positive electrode plate according to an embodiment of the present application; Figure 2B is a schematic diagram of a negative electrode plate according to an embodiment of the present application; Figure 3 is a schematic diagram of a positive electrode current collector according to an embodiment of the present application; Figure 4 is a schematic diagram of a positive electrode current collector according to an embodiment of the present application; Figure 5 is a schematic diagram of a negative electrode current collector according to an embodiment of the present application; Figure 6 is a schematic diagram of a negative electrode current collector according to an embodiment of the present application; Figure 7 It is a schematic structural diagram of a separator of an embodiment of the present application; Figure 8 It is a schematic structural diagram of a battery cell of an embodiment of the present application; Figure 9 It is a schematic diagram of an electrical device using the battery cell of an embodiment of the present application as a power source.

[0113] Description of reference numerals: 1 Battery cell; 11 Housing; 111 Housing of the large surface of the battery cell; 12 Electrode assembly; 121 Positive electrode tab; 1211 Positive current collector; 1212 Positive active material layer; 12110 Positive current collecting part; 12111 Positive electrode tab; 122 Negative electrode tab; 1221 Negative current collector; 1222 Negative active material layer; 12210 Negative current collecting part; 12211 Negative electrode tab; 123 Separator; 1231 Base film; 1232 First functional layer; 1233 Second functional layer; First electrode terminal 131, Second electrode terminal 132, Third electrode terminal 133, Fourth electrode terminal 134. Detailed description of specific embodiments

[0114] Hereinafter, embodiments of the battery cell, the electrical device for the battery device, and the energy storage device of the present application specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0115] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the specific range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0116] If there is no special instruction, all the embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0117] If there is no special instruction, all the technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0118] If there is no special instruction, all the steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0119] If there is no special instruction, the "including" and "comprising" mentioned in this application mean open-ended or can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can also only include or comprise the listed components.

[0120] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or present) and B is false (or absent); A is false (or absent) while B is true (or present); or both A and B are true (or present).

[0121] Adopting a laminated electrode assembly with an increased length of a single electrode assembly and an ear tab extending from the short side helps to improve the energy density of a battery cell. However, the above electrode assembly design causes the area near the ear tab of the battery cell to have a large current density and a large temperature rise under fast charging conditions, which in turn leads to lithium plating on the negative electrode and electrolyte decomposition, and is not conducive to the cycle stability of the battery.

[0122] Based on this, a first aspect of the present application provides a battery cell, including an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a separator, and a negative electrode plate stacked in sequence. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector. The positive electrode current collector includes a positive electrode current collecting portion and a positive electrode ear tab, and the positive electrode ear tab is provided at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly; the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector. The negative electrode current collector includes a negative electrode current collecting portion and a negative electrode ear tab, and the negative electrode ear tab is provided at at least one end of the negative electrode current collecting portion extending along the length direction of the electrode assembly; wherein, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure; the size of the positive electrode active material layer along the length direction of the electrode assembly is 300 mm to 950 mm; along the length direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH 1 , OH 1 is greater than 1 mm and less than 5 mm; along the width direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH 2 , OH 2 is greater than 1 mm and less than or equal to 4 mm; the electrolyte includes a solvent and a lithium-containing electrolyte salt, the solvent includes a carboxylic acid ester solvent, and the lithium-containing electrolyte salt includes a lithium fluorosulfonylimide salt; based on the total mass of the electrolyte, the mass percentage of the carboxylic acid ester solvent is 8% to 57%, and the mass percentage of the lithium fluorosulfonylimide salt is 3% to 8%.

[0123] The lithium-containing phosphate with olivine structure is an active material with an olivine structure including lithium ions and phosphate groups. The types of the positive electrode active materials can be tested by any publicly known method in the art. As an example, phase analysis methods such as X-ray diffraction method (XRD) can be combined with elemental analysis methods such as energy spectrum and XPS for analysis.

[0124] In this application, referring to Figure 1 , the electrode assembly 12 includes a positive electrode tab 121, a separator 123, and a negative electrode tab 122 that are sequentially stacked. The positive electrode tab 121 includes a positive electrode current collector 1211 and a positive electrode active material layer 1212 disposed on at least one side of the positive electrode current collector 1211. The negative electrode tab 122 includes a negative electrode current collector 1221 and a negative electrode active material layer 1222 disposed on at least one side of the negative electrode current collector 1221; along the length direction of the electrode assembly 12, the size of the positive electrode active material layer 1212 is OH 11 , the size of the negative electrode active material layer 1222 is OH 21 , and the difference in size between the negative electrode active material layer 1222 and the positive electrode active material layer 1212 is OH 1 =OH 21 -OH 11 ; referring to Figure 2A and Figure 2B , along the width direction of the electrode assembly, the size of the positive electrode active material layer 1212 is OH 12 , the size of the negative electrode active material layer 1222 is OH 22 , and the difference in size between the negative electrode active material layer 1222 and the positive electrode active material layer 1212 is OH 1 =OH 22 -OH 12 , and the size can be measured with a ruler.

[0125] In some embodiments, referring to Figure 3 , the positive electrode current collector 1211 includes a positive electrode current collecting portion 12110 and a positive electrode tab 12111, and the positive electrode tab 12111 is disposed at one end of the positive electrode current collecting portion 12110 extending along the length direction of the electrode assembly.

[0126] In some embodiments, referring to Figure 4 , the positive electrode tab 12111 is disposed at both ends of the positive electrode current collecting portion 12110 extending along the length direction of the electrode assembly.

[0127] In some embodiments, referring to Figure 5 , the negative electrode current collector 1221 includes a negative electrode current collecting portion 12210 and a negative electrode tab 12211, and the negative electrode tab 12211 is disposed at one end of the negative electrode current collecting portion 12210 extending along the length direction of the electrode assembly.

[0128] In some embodiments, referring to Figure 6 , the negative electrode tab 12211 is disposed at both ends of the negative current collector portion 12210 extending along the length direction of the electrode assembly.

[0129] In some embodiments, the size of the positive active material layer along the length direction of the electrode assembly can be 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, 700 mm, 750 mm, 800 mm, 850 mm, 900 mm, 950 mm, or a numerical range between any two of them.

[0130] In some embodiments, OH 1 can be 1.1 mm, 1.3 mm, 1.5 mm, 1.7 mm, 1.9 mm, 2.1 mm, 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm, 3.1 mm, 3.3 mm, 3.5 mm, 3.7 mm, 3.9 mm, 4.1 mm, 4.3 mm, 4.5 mm, 4.7 mm, 4.9 mm, or a numerical range between any two of them.

[0131] In some embodiments, OH 2 can be 1.1 mm, 1.3 mm, 1.5 mm, 1.7 mm, 1.9 mm, 2.1 mm, 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm, 3.1 mm, 3.3 mm, 3.5 mm, 3.7 mm, 3.9 mm, 4 mm, or a numerical range between any two of them.

[0132] The types and masses of the solvent and the lithium-containing electrolyte salt in the electrolyte can be obtained by detecting the electrolyte through methods well-known to those skilled in the art. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell is taken as a sample, and ion chromatography analysis method is used for detection. The types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, qualitative and quantitative analysis of the organic components of the electrolyte can be carried out by gas chromatography with reference to GB / T 9722-2023 General Rules for Gas Chromatography of Chemical Reagents. The types and contents of the inorganic components / lithium salts in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, qualitative or quantitative analysis of the inorganic components / lithium salts of the electrolyte can be carried out by ion chromatography analysis method with reference to the standard JY / T 020-2002 General Rules for Ion Chromatography Analysis Method.

[0133] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the carboxylate solvent can be 8%, 15%, 22%, 29%, 36%, 43%, 50%, 57%, or a numerical range between any two of them.

[0134] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the lithium fluorosulfonylimide salt can be 3%, 4%, 5%, 6%, 7%, 8%, or a numerical range between any two of them.

[0135] The lithium phosphate with an olivine structure has the advantages of low cost and good lifespan. Combining with the design of the laminated electrode assembly with the size of the positive electrode active material layer in the above range along the length direction of the electrode assembly and the tab being led out from the short side, it helps to improve the internal space utilization rate of the battery cell, improve the problem of low energy density of the battery cell when the lithium phosphate is used as the positive electrode active material, shorten the current transmission path from the active material to the tab at the same time, reduce the internal resistance of the battery, and enable the battery cell to have excellent fast charging performance and energy density. However, as the charging rate of the battery cell increases, the current density in the area near the tab is high and the temperature rise is large, making the lithium ion migration rate faster than other parts, and the negative electrode active material layer is prone to generate lithium dendrites near the tab. The battery cell of the embodiment of the present application passes OH 1 's design improves the ability of the negative electrode active material layer, especially the negative electrode active material layer in the area near the tab, to receive active ions in the length direction, and makes the distance between the positive electrode active material layer and the tab side farther. The current distribution of the active material layer in the area near the tab is more uniform, resulting in a lower temperature rise, thus comprehensively improving the problem of lithium deposition on the negative electrode plate; through OH 2 's design helps to reduce the probability of the separator shrinking due to heat and causing the positive and negative electrodes to overlap, and then resulting in an internal short circuit of the battery; while improving the cycle stability of the battery cell, controlling OH 1 、OH 2The value is within the above range, enabling the battery cell to have excellent energy density. Carboxylate solvents have the advantages of low viscosity and high ionic conductivity, which are beneficial to the infiltration of the electrolyte into the negative active material layer and the fast charge insertion and extraction of active ions in the negative active material layer, thereby further improving the lithium plating problem of the negative electrode sheet. However, they have high activity and are prone to decompose and generate gas under high-rate current. Therefore, by further reasonably controlling the mass ratio of carboxylate solvents in the electrolyte within the above range, the electrolyte has both good conductivity and stability, which is conducive to the further comprehensive improvement of the fast charging performance and cycle stability of the battery cell. Fluorosulfonylimide salts are prone to dissociation in carboxylate solvents, which is beneficial to further improving the conductivity of the electrolyte. Moreover, fluorosulfonylimide salts have high thermochemical stability and are not easily decomposed by heat. In addition, fluorosulfonylimide salts can participate in the formation of the solid electrolyte interface film (SEI film) on the surface of the negative active material, which helps to improve the thermal stability of the SEI film, reduce the impedance of the SEI film, and further reduce the risk of lithium plating in the battery under high-rate current. However, with the increase in the temperature of the battery cell, fluorosulfonylimide salts will decompose violently at a certain temperature threshold, releasing a large amount of heat and sharply increasing the risk of thermal runaway of the battery. This safety risk is more significant in fast-charging batteries. Therefore, by further reasonably controlling the mass ratio of lithium fluorosulfonylimide salt in the electrolyte within the above range, the electrolyte has both good conductivity and stability, further improving the fast charging performance and cycle stability while reducing the risk of thermal runaway of the battery cell, and the battery cell has excellent safety performance. Through the mutual cooperation between the electrode assembly and the electrolyte in the embodiments of the present application, lithium ions can cooperate with each other during the liquid-phase transmission and solid-phase transmission processes, and the battery cell has excellent energy density, a reduced risk of lithium plating during fast charging, an improved cycle life, and safety performance, achieving a comprehensive improvement in battery performance.

[0136] In some embodiments, OH 1 is greater than or equal to 1.5 mm and less than or equal to 4 mm.

[0137] In some embodiments, OH 2 is greater than or equal to 1.5 mm and less than or equal to 3 mm.

[0138] OH 1 、OH 2 Within the above range, while improving the cycle stability of the battery cell, it is beneficial to further improve the energy density of the battery cell.

[0139] In some embodiments, OH 1 ≥OH 2 .

[0140] Control OH 1 ≥OH 2, while improving the cycle stability during the fast charging of the battery cell, it is beneficial to further improve the energy density of the battery cell.

[0141] In some embodiments, the size of the positive electrode active material layer in the length direction of the battery cell is 400 mm to 650 mm.

[0142] When the size of the positive electrode active material layer in the length direction of the battery cell is within the above range, the battery cell takes into account excellent fast charging performance, cycle stability during fast charging, and energy density.

[0143] In some embodiments, the size of the positive electrode active material layer in the width direction of the electrode assembly is 90 mm to 130 mm.

[0144] In some embodiments, the size of the positive electrode active material layer in the width direction of the electrode assembly can be 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, or the numerical range between any two of them.

[0145] When the size of the positive electrode active material layer in the width direction of the electrode assembly is within the above range, combined with the size of the positive electrode active material layer in the length direction, while improving the energy density of the battery cell, it is beneficial for the battery cell to match the usage requirements of different specifications of electrical devices.

[0146] In some embodiments, the size of the negative electrode active material layer in the length direction of the electrode assembly is 400 mm to 658 mm.

[0147] In some embodiments, the size of the negative electrode active material layer in the length direction of the electrode assembly can be 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 658 mm, or the numerical range between any two of them.

[0148] In some embodiments, the size of the negative electrode active material layer in the width direction of the electrode assembly is 90 mm to 130 mm.

[0149] In some embodiments, the size of the negative electrode active material layer in the width direction of the electrode assembly can be 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, or the numerical range between any two of them.

[0150] When the sizes of the negative electrode active material layer in the length direction and width direction of the electrode assembly are within the above ranges and match the design of the positive electrode active material layer, it is beneficial for the comprehensive improvement of the energy density, fast charging performance, and cycle stability during fast charging of the battery cell.

[0151] In some embodiments, refer to Figure 3, the positive electrode tab 12111 is disposed at one end of the positive current collector portion 12110 extending along the length direction of the electrode assembly.

[0152] In some embodiments, referring to Figure 5 , the negative electrode tab 12211 is disposed at one end of the negative current collector portion 12210 along the length direction of the electrode assembly.

[0153] The above tab arrangement helps to improve the weight energy density of the battery cell.

[0154] In some embodiments, referring to Figure 4 , the positive electrode tab 12111 is disposed at both ends of the positive current collector portion 12110 extending along the length direction of the electrode assembly.

[0155] In some embodiments, referring to Figure 6 , the negative electrode tab 12211 is disposed at both ends of the negative current collector portion 12210 along the length direction of the electrode assembly.

[0156] In some embodiments, the size of the positive active material layer along the length direction of the electrode assembly is 650 mm to 950 mm. The positive electrode tab is disposed at both ends of the positive current collector portion extending along the length direction of the electrode assembly, and the negative electrode tab is disposed at both ends of the negative current collector portion along the length direction of the electrode assembly.

[0157] The above tab arrangement helps to improve the over-current capacity of the battery cell, alleviate the situation of electrolyte decomposition and uneven current distribution caused by too high temperature at the tab side during fast charging, resulting in lithium deposition at the tab side, thereby improving the fast charging performance of the battery cell and the cycle stability under fast charging, especially suitable for improving the cycle stability of the battery cell with the length size of the positive active material layer in the range of 650 mm to 950 mm under fast charging.

[0158] In some embodiments, the ratio of the width of the positive electrode tab to the width of the positive current collector portion is 0.25 to 1.

[0159] In some embodiments, the ratio of the width of the negative electrode tab to the width of the negative current collector portion is 0.25 to 1.

[0160] In some embodiments, the ratio of the width of the positive electrode tab to the width of the positive current collector portion or the ratio of the width of the negative electrode tab to the width of the negative current collector portion can be 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, 1 or any value range between any two of them.

[0161] The ratio of the width of the tab to the width of the current collector portion within the above range helps to improve the over-current capacity of the battery cell, and improve the fast charging performance of the battery cell and the cycle stability under fast charging.

[0162] In some embodiments, based on the total mass of the electrolyte, the mass fraction of lithium fluorosulfonylimide salt is 4% to 8%.

[0163] When the mass fraction of the lithium fluorosulfonylimide salt is within the above range, the fast charging performance, cycle stability under fast charging, and safety performance of the battery cell can be further balanced.

[0164] In some embodiments, the lithium fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium perfluorobutanesulfonylimide (LiFNFSI).

[0165] In some embodiments, the lithium-containing electrolyte salt further includes lithium hexafluorophosphate (LiPF 6 , and based on the total mass of the electrolyte, the total mass fraction of lithium hexafluorophosphate (LiPF 6 and the lithium fluorosulfonylimide salt is 10% to 18%.

[0166] In some embodiments, based on the total mass of the electrolyte, the total mass fraction of lithium hexafluorophosphate (LiPF 6 and the lithium fluorosulfonylimide salt can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or any value range between any two of them.

[0167] The lithium-containing electrolyte salt further includes lithium hexafluorophosphate (LiPF 6 can reduce the risk of thermal runaway of the battery cell, keep the risk within a controllable range, and further improve the safety performance of the battery cell. When the total mass fraction of lithium hexafluorophosphate (LiPF 6 and the lithium fluorosulfonylimide salt in the electrolyte is within the above range, the battery cell can further balance the fast charging performance, cycle stability under fast charging, and safety performance.

[0168] In some embodiments, based on the total mass of the electrolyte, the ratio of the mass fraction of lithium hexafluorophosphate (LiPF 6 to the mass fraction of the lithium fluorosulfonylimide salt is 0.9:1 to 4:1.

[0169] In some embodiments, based on the total mass of the electrolyte, the ratio of the mass fraction of lithium hexafluorophosphate (LiPF 6 to the mass fraction of the lithium fluorosulfonylimide salt can be 0.9:1, 1:1, 1.3:1, 1.6:1, 1.9:1, 2.2:1, 2.5:1, 2.8:1, 3.1:1, 3.4:1, 3.7:1, 4:1, or any value range between any two of them.

[0170] In the electrolyte, lithium hexafluorophosphate (LiPF 6A battery cell in which the ratio of the mass fraction of [substance] to the mass fraction of lithium fluorosulfonimide salt is within the above range can further balance the fast charging performance, cycle stability under fast charging, and safety performance of the battery cell.

[0171] In some embodiments, the carboxylic ester solvent has the general structural formula of R ' -COO-R '' where R ' includes one or more of a hydrogen atom, a halogen atom, a C 1 -C 5 alkyl group, and a C 1 -C 5 haloalkyl group, and R '' includes one or more of a C 1 -C 5 alkyl group and a C 1 -C 5 haloalkyl group.

[0172] "C 1 -C 5 alkyl group" refers to an unbranched or branched alkyl group having 1 - 5 carbon atoms; including but not limited to one or more of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl.

[0173] "C 1 -C 5 haloalkyl group" refers to an unbranched or branched alkyl group having 1 - 5 carbon atoms in which at least one hydrogen atom is replaced by a halogen, including but not limited to one or more of chloroalkyl, bromoalkyl, and iodoalkyl.

[0174] "Halogen" refers to the elements in Group VIIA of the periodic table of chemical elements. Specifically, halogens include elements such as fluorine, chlorine, bromine, iodine, or astatine.

[0175] In some embodiments, the carboxylic ester solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0176] In some embodiments, the solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0177] Carbonate solvents have a high dielectric constant, which can increase the dissociation rate of lithium ions and anions in lithium-containing electrolyte salts, and further comprehensively improve the fast charging performance of battery cells and the cycle stability under fast charging.

[0178] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent is 18% to 75%.

[0179] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent can be 18%, 30%, 40%, 50%, 60%, 70%, 75% or the numerical range between any two of them.

[0180] Since carbonate solvents have a relatively high viscosity, as the content of carbonate solvents increases, the viscosity of the electrolyte will also increase, which has a negative impact on the conductivity of the electrolyte. By reasonably controlling the mass percentage of the carbonate solvent within the above range, the electrolyte has an appropriate viscosity and a good dissociation rate, thus achieving a comprehensive improvement in the conductivity of the electrolyte, which is beneficial to further improving the fast charging performance of battery cells and the cycle stability under fast charging.

[0181] In some embodiments, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives.

[0182] Additives refer to components with relatively low content in the electrolyte, generally with a mass percentage in the electrolyte not exceeding 10%. They have the characteristics of strong pertinence and small dosage, and can significantly optimize a certain aspect of the battery performance without changing the production process.

[0183] In this application, carbonate additives refer to compounds and their derivatives including carbonate groups (-O-CO-O-), and mixtures containing the above compounds and their derivatives.

[0184] The components of the additive can be tested by any well-known method in the art. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell is taken as a sample, and ion chromatography analysis method is used for detection. The types and contents of organic components in the electrolyte are well-known meanings in the art, and can be detected by well-known equipment and methods in the art. For example, reference can be made to GB / T9722-2023 "General Rules for Chemical Reagents - Gas Chromatography" to qualitatively and quantitatively analyze the organic components of the electrolyte by gas chromatography. The types and contents of inorganic components / lithium salts in the electrolyte are well-known meanings in the art, and can be detected by well-known equipment and methods in the art. For example, reference can be made to the standard JY / T020-2002 "General Rules for Ion Chromatography Analysis Method" to qualitatively or quantitatively analyze the inorganic components / lithium salts of the electrolyte by ion chromatography analysis method.

[0185] In some embodiments, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Among them, the ethylene carbonate derivative includes the compound shown in Formula III. Formula III R 1 、R 2 、R 3 、R 4 each independently includes one or more of a hydrogen atom, a halogen atom, a C 1 -C 5 alkyl and a C 1 -C 5 haloalkyl, and R 1 、R 2 、R 3 、R 4 are not simultaneously hydrogen atoms. Optionally, the carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

[0186] The carbonate additive can evolve into organic components in the SEI film, improve the toughness of the SEI film, thereby further improving the stability of the SEI film during the cycling process of the battery cell, further reducing the interfacial impedance on the negative electrode side, and being beneficial to further improving the cycling life and fast charging performance of the battery cell.

[0187] In some embodiments, the sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, ethylene sulfite, methylene methanedisulfonate, and 1,3-propane sultone.

[0188] Sulfur-containing additives often have a relatively high potential. The sulfur-containing additives added to the electrolyte will react preferentially during formation or subsequent cycling, evolving into sulfur-containing components in the SEI film. The SEI film formed by carbonate additives has poor high-temperature stability, which is not conducive to the stability of the battery cell in a high-temperature environment. The SEI film contains sulfur elements, which can further improve the thermal stability of the SEI film at high temperatures, further reduce the interfacial impedance on the negative electrode side, and is beneficial to further improving the cycle stability and fast charging performance of the battery cell.

[0189] In some embodiments, the lithium salt additives include one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

[0190] The lithium salt additives can evolve into inorganic components in the SEI film, improve the rigidity and thermal stability of the SEI film, further enhance the stability of the SEI film, further reduce the interfacial impedance on the negative electrode side, thereby further enhancing the cycle stability and fast charging performance of the battery. Moreover, the above lithium salt additives can also form a cathode electrolyte interface film (CEI film) on the surface of the cathode active material, thereby further enhancing the cycle stability of the battery cell.

[0191] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate additives is 3% to 8%.

[0192] Based on the total mass of the electrolyte, the mass percentage of the additives can be measured by any well-known method in the art. As an example, the measurement method for the mass percentage of the solvent and lithium-containing electrolyte salt in the electrolyte described above can be used for measurement. It should be understood that since the additives in the electrolyte will be consumed to some extent during formation and cycling, generating relevant components in the SEI film and / or CEI film, the mass percentage of the additives in the electrolyte may be slightly lower than the initial added mass percentage of the additives in the electrolyte.

[0193] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate additives can be 3%, 4%, 5%, 6%, 7%, 8% or any numerical range between any two of them.

[0194] When the mass percentage of the carbonate additives in the electrolyte is within the above range, it is beneficial to balance the improvement of the stability of the SEI film and the maintenance of an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0195] In some embodiments, based on the total mass of the electrolyte, the mass percentage of vinylene carbonate is 2% to 5%.

[0196] In some embodiments, based on the total mass of the electrolyte, the mass fraction of vinylene carbonate may be 2%, 3%, 4%, 5% or any value range between any two of them.

[0197] Vinylene carbonate (VC) has a reduction potential close to that of carboxylate solvents, which can inhibit the reaction activity of carboxylate solvents and improve the cycle life of battery cells. However, if the content of vinylene carbonate (VC) is too high, it will lead to an increase in the interfacial impedance and charge transfer impedance of the battery, which is not conducive to the fast charging performance of battery cells. When the mass fraction of vinylene carbonate (VC) is within the above range, the battery can achieve both excellent cycle life and fast charging performance.

[0198] In some embodiments, based on the total mass of the electrolyte, the mass fraction of ethylene carbonate derivatives is 0% to 4%.

[0199] In some embodiments, based on the total mass of the electrolyte, the mass fraction of ethylene carbonate derivatives is 1.5% to 3.5%.

[0200] In some embodiments, based on the total mass of the electrolyte, the mass fraction of ethylene carbonate derivatives may be 0.5%, 1%, 2%, 3%, 4% or any value range between any two of them.

[0201] It should be noted that as the battery cell is charged and discharged, when the addition amount of ethylene carbonate derivatives is small, after disassembling the battery cell to obtain the electrolyte and testing the content of ethylene carbonate derivatives by gas chromatography, the content may be 0%. It can be understood that in some embodiments, the ethylene carbonate derivatives added to the electrolyte are completely converted into organic components in the SEI film during the formation process. In some embodiments, there are still ethylene carbonate derivatives remaining in the electrolyte, which form a reinforcing effect on the SEI film during the subsequent cycle process of the battery cell.

[0202] Ethylene carbonate derivatives can also form a film on the surface of the negative electrode at a relatively high potential and have a low interfacial impedance and charge transfer impedance. When the mass fraction of ethylene carbonate derivatives is within the above range, the battery cell can achieve both excellent fast charging performance and cycle life. By adding vinylene carbonate (VC) and ethylene carbonate derivatives in combination in the electrolyte, the fast charging performance and cycle stability of the battery cell can be comprehensively improved.

[0203] In some embodiments, based on the total mass of the electrolyte, the mass fraction of sulfur-containing additives is 0% to 2%.

[0204] In some embodiments, based on the total mass of the electrolyte, the mass fraction of sulfur-containing additives is 0.5% to 2%.

[0205] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the sulfur-containing additive can be 0.5%, 1%, 1.5%, 2% or any value range between any two of them.

[0206] It should be noted that since the additives in the electrolyte will be consumed to some extent during the formation and charge-discharge cycling processes, generating relevant components in the SEI film and / or CEI film, when the content of the sulfur-containing additive and the lithium salt additive is tested by gas chromatography after disassembling the battery cell to obtain the electrolyte, the content may be 0%.

[0207] Specifically, taking the case where the mass content of the sulfur-containing additive is 0% as an example, it may be that the freshly prepared electrolyte does not contain the sulfur-containing additive, or the electrolyte obtained after disassembling the battery cell does not contain the sulfur-containing additive. This situation may be that the freshly prepared electrolyte does not contain the sulfur-containing additive, or a small amount of the sulfur-containing additive is added, but it participates in the film-forming reaction of the SEI film during the formation process of the battery cell, resulting in a mass content of 0% of the sulfur-containing additive during the detection process. Optionally, the freshly prepared electrolyte includes the sulfur-containing additive.

[0208] Furthermore, for adding certain substances, such as additives, to the electrolyte, due to the characteristic that the additive plays a role by participating in the film formation on the surface of the active material, the content of the additive in the electrolyte of the battery cell is related to the formation, different battery life cycles or different battery storage states. Therefore, there may be a difference in the content of the additive between the freshly prepared electrolyte and the electrolyte obtained by reverse-disassembling the battery cell. However, those skilled in the art can know the approximate range of the content of the relevant substances in the corresponding freshly prepared electrolyte according to the performance expression level (such as the number of cycles) and the residual content of the battery cell. Similarly, those skilled in the art can also know the approximate range of the content of the non-freshly prepared (i.e., reverse) according to the content of the freshly prepared additive, based on the performance requirements and storage environment of the battery cell.

[0209] Therefore, the additive content mentioned in the technical solution of the present application can be the content of the additive actively added to the freshly prepared electrolyte, or the content of the residual additive detected by reverse according to the actual battery state.

[0210] It can be understood that in some embodiments, the sulfur-containing additive added to the electrolyte is completely converted into the sulfur-containing component in the SEI film during the formation process, and the added amount of the sulfur-containing additive in the electrolyte can be inferred by X-ray photoelectron spectroscopy (XPS) testing of the negative electrode material. In some embodiments, there is still a sulfur-containing additive remaining in the electrolyte, which forms a reinforcing effect on the SEI film during the subsequent cycling process of the battery cell.

[0211] In this application, the X-ray photoelectron spectroscopy (XPS) of the anode material can be tested by any well-known method in the art. As an example, after disassembling the battery cell, the anode electrode is cleaned with a solvent such as dimethyl carbonate (DMC) more than three times, and then powder is scraped for sampling. The obtained powder sample of the anode material is adhered to a conductive substrate, and X-ray photoelectron spectroscopy is performed using an X-ray photoelectron spectrometer (such as AXIS ULTRA). The scanning rate and time of the X-ray source are adjusted to make it focused and detect elements and functional groups at a depth of 5 nm to 10 nm from the surface of the anode material, and an X-ray photoelectron spectroscopy (XPS) spectrum of the sample is obtained, and the elemental characteristic peaks are analyzed in the spectrum.

[0212] When the mass percentage of the sulfur-containing additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the thermal stability of the SEI film at high temperatures and maintain an appropriate viscosity of the electrolyte, and further comprehensively improve the cycle life and fast charging performance of the battery cell.

[0213] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0% to 1%.

[0214] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.2% to 1%.

[0215] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.2%, 0.4%, 0.6%, 0.8%, 1% or any value range between any two of them.

[0216] It can be understood that in some embodiments, the lithium salt additive added to the electrolyte is completely converted into inorganic components in the SEI film and / or CEI film during the formation process. In some embodiments, there is still a residue of the lithium salt additive in the electrolyte, which forms a reinforcing effect on the SEI film and / or CEI film during the subsequent cycling process of the battery cell.

[0217] When the mass percentage of the lithium salt additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the stability of the SEI film and maintain an appropriate viscosity of the electrolyte, and further comprehensively improve the cycle life and fast charging performance of the battery cell.

[0218] In some embodiments, the positive electrode active material includes: lithium-containing phosphate with an olivine structure, and a coating layer located on at least a part of the surface of the lithium-containing phosphate, and the coating layer contains carbon elements.

[0219] The coating layer contains carbon elements, which is beneficial to improving the electronic conductivity of the lithium-containing phosphate, improving the solid-phase transmission rate of electrons, and thus further improving the energy density and fast charging performance of the battery cell.

[0220] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of carbon element is 0.8% to 2.3%.

[0221] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of carbon element can be 0.8%, 1.1%, 1.4%, 1.7%, 2.0%, 2.3% or the numerical range between any two of them.

[0222] Based on the total mass of the positive electrode active material, the mass percentage of carbon element is within the above range, so that the lithium-containing phosphate has both excellent electronic conductivity and specific capacity, and further comprehensively improves the energy density and fast charging performance of the battery cell.

[0223] In some embodiments, the coating layer further includes the component shown in Formula I, Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I, where 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn. Optionally, M1 is +4 valence.

[0224] In some embodiments, d1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or the numerical range between any two of them, m1 can be optionally 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or the numerical range between any two of them, and n1 can be optionally 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4 or the numerical range between any two of them.

[0225] In some embodiments, the component shown in Formula I includes Li 2 FeTi(PO 4 ) 3 , Li 2 FeZr(PO 4 ) 3 , Li 2 FeSn(PO 4 ) 3 or one or more of them.

[0226] It should be noted that the coating layer can be a single-layer structure or a multi-layer structure. That is to say, the carbon-containing components in the coating layer and the components shown in Formula I can be in a mixed phase or can be arranged in layers.

[0227] The phase structure in the coating layer can be characterized by any well-known method in the art. For example, by characterizing the positive electrode active material through a transmission electron microscope, it can be seen that there are different phase structures in the coating layer and the matrix of the positive electrode active material. Combining the diffraction pattern and energy spectrum analysis can determine the components of the coating layer.

[0228] The component shown in Formula I is a fast ion conductor with a NASICON structure, whose ionic conductivity is close to or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has rich three-dimensional lithium-ion diffusion and transport channels and has advantages such as high ion conduction efficiency and strong structural stability during multiple lithium deintercalation and intercalation processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly improve the transport rate of lithium ions during multiple deintercalation / intercalation at the positive electrode end, improve the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0229] In some embodiments, the lithium-containing phosphate includes a component shown in Formula II, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X includes one or more of S, Si, Cl, B, C, N, P; Y includes one or more of O, F.

[0230] In some embodiments, x1 can be optionally 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, or a numerical range between any two of them; y1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, or a numerical range between any two of them; x1 + y1 can be optionally 0.9, 1, 1.1, 1.2, 1.3, or a numerical range between any two of them; a1 can be optionally 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, or a numerical range between any two of them; b1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a numerical range between any two of them; a1 + b1 can be optionally 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, or a numerical range between any two of them; c1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a numerical range between any two of them; z1 can be optionally 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, or a numerical range between any two of them.

[0231] The lithium-containing phosphate with olivine structure having the above components has good structural stability, can reduce the loss during fast charging, and further improve the fast charging performance and cycle stability of the battery cell.

[0232] In some embodiments, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, and modified forms of any one of the foregoing substances, wherein the modified forms include one or more of doping modification and coating modification.

[0233] In some embodiments, the tap density of the positive electrode active material layer is 2.50 g / cm 3 to 2.80 g / cm 3 .

[0234] In the present application, the tap density of the positive electrode active material layer has the meaning well-known in the art and can be tested by methods known in the art. For example, the battery cell is charged at a constant current charging rate of 0.33C to the cut-off voltage (such as 3.65V), left standing for 1 min, and then charged at a constant voltage of 3.65V until the current is less than 0.05C. At this time, the battery cell is in a fully charged state, and then the positive electrode plate is disassembled to measure the tap density of the positive electrode active material layer. The tap density of the positive electrode active material layer is the single-sided coating mass of the positive electrode active material layer after disassembly divided by the single-sided thickness of the positive electrode active material layer.

[0235] "The single-sided coating mass of the positive electrode active material layer" refers to the mass of the positive electrode active material layer per unit area on the side of the current collector.

[0236] In this application, the single-sided coating mass of the positive electrode active material layer can be tested by methods known in the art. For example, a positive electrode plate can be taken from a disassembled battery (if it is a double-sided coated positive electrode plate, the positive electrode active material layer on one side can be wiped off first), punched into small round pieces with an area of S1, weighed, and recorded as M1. Then, wipe off the positive electrode active material layer of the above-mentioned weighed positive electrode plate, weigh the mass of the positive electrode current collector, and record it as M0. The single-sided coating weight of the positive electrode plate = (M1 - M0) / S1.

[0237] The thickness of the positive electrode active material layer has the meaning well-known in the art and can be tested by methods known in the art. For example, it can be tested using a micrometer (such as Mitutoyo 293-100 type with an accuracy of 0.1 μm). It can be understood that when the battery cell is in a fully charged state, the compaction density of the positive electrode active material layer is different from the designed value of the battery cell compaction density. Affected by actual operations, when the battery cell is in a fully charged state, the compaction density of the positive electrode active material layer is often slightly lower than the designed value of the battery cell compaction density.

[0238] In some embodiments, the compaction density of the positive electrode active material layer can be 2.50 g / cm 3 、2.55 g / cm 3 、2.60 g / cm 3 、2.68 g / cm 3 、2.70 g / cm 3 、2.75 g / cm 3 、2.80 g / cm 3 or any value range between any two of them.

[0239] The positive electrode active material layer with a compaction density within the above range can further achieve the balance between the fast charging performance and energy density of the battery cell.

[0240] In some embodiments, the single-sided coating mass of the positive electrode active material layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 .

[0241] In some embodiments, the single-sided coating mass of the positive electrode active material 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 numerical range between any two of them.

[0242] The positive electrode active material layer with a single-sided coating mass within the above range can further effectively balance the fast charging performance and energy density of the battery cell.

[0243] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0244] The material of the positive electrode current collector and / or the negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery cell and has conductivity. The current collector includes metal foils with a pure metal content of over 95%, such as at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, and nickel foil. It also includes alloy foils of at least two main metals. For example, alloy foils made of at least two main elements among copper, aluminum, nickel, titanium, and iron can be used. It can also include copper, aluminum cadmium alloy, iron, or stainless steel, etc. surface-treated with carbon, nickel, titanium, silver, copper, etc. In addition, the binding force with the negative electrode active material can be enhanced by forming fine concavities and convexities on the surface, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics.

[0245] In some embodiments, the thickness of the positive electrode current collector can be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a numerical range between any two of them.

[0246] The positive electrode current collector has a lower thickness, enabling further improvement in the energy density of the battery cell.

[0247] In some embodiments, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0248] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0249] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer located between the positive electrode active material layer and the positive electrode current collector, and the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm; and / or the negative electrode sheet further includes a negative electrode conductive layer located between the negative electrode current collector and at least one side of the negative electrode active material layer, and the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

[0250] In some embodiments, the thickness of the positive electrode conductive layer or the negative electrode conductive layer may be 0.5 µm, 0.6 µm, 0.7 µm, 0.8 µm, 0.9 µm, 1.0 µm, 1.1 µm, 1.2 µm, 1.3 µm, 1.4 µm, 1.5 µm, 1.6 µm, 1.7 µm, 1.8 µm, 1.9 µm, 2.0 µm, or a numerical range between any two of them.

[0251] The provision of the positive electrode conductive layer and / or the negative electrode conductive layer is beneficial to improving the electronic conductivity of the battery single electrode sheet and further improving the fast charging performance of the battery single body.

[0252] In some embodiments, the positive electrode conductive layer includes a conductive agent and a positive electrode binder, the negative electrode conductive layer includes a conductive agent and a negative electrode binder, the conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and the positive electrode binder includes one or more of polyvinylidene difluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins.

[0253] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material.

[0254] In some embodiments, the carbon-based material includes one or more of graphite and hard carbon.

[0255] In some embodiments, the carbon-based material includes composite graphite particles. The composite graphite particles include graphite matrix particles and a carbon coating layer covering at least a part of the surface of the graphite matrix particles. The graphite matrix particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0256] The secondary particles refer to particles formed by aggregation of two or more primary particles. The composite graphite particles including secondary particles and the surface coating layer including amorphous carbon are beneficial to the infiltration of the electrolyte in the negative electrode active layer of the electrode sheet and the improvement of the solid-phase transport ability of active ions, which helps to further improve the fast charging performance of the battery cell.

[0257] In some embodiments, based on the total mass of the composite graphite particles, the mass percentage of amorphous carbon is 2% to 5%.

[0258] In some embodiments, based on the total mass of the composite graphite particles, the mass percentage of amorphous carbon can be 2%, 3%, 4%, 5% or the numerical range between any two of them.

[0259] When the content of amorphous carbon is within a suitable range, the composite graphite material can have a high specific capacity while also having a high solid-phase transport ability of active ions, which is beneficial to further comprehensively improving the energy density and fast charging performance of the battery cell.

[0260] In some embodiments, the negative electrode active material layer may further optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0261] In some embodiments, the negative electrode active material layer may further optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0262] In some embodiments, the volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 13.5 μm.

[0263] "Volume average particle size Dv50" has a well-known meaning in the art, which respectively represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured by instruments and methods known in the art. For example, it can be conveniently measured by referring to GB / T 19077-2016 Laser diffraction method for particle size distribution and using a laser particle size analyzer. The test instrument can be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK. The composite graphite particles can be freshly prepared or obtained by scraping powder from the negative electrode active material layer after disassembling the battery cell. For example, discharge the battery to 0% SOC, then disassemble and take the negative electrode plate, scrape a certain amount of powder on the electrode plate with a blade, then use deionized water to wash and shake it repeatedly for 5 to 10 times, dry it, sinter it in a tubular furnace at 400 °C for 2 h, and after sintering, take an appropriate amount of the sample to be tested (the sample concentration should ensure a light transmittance of 8% - 12%), add deionized water, and at the same time perform ultrasonic dispersion to ensure that the sample is completely dispersed, and then measure the sample according to the GB / T 19077-2016 / ISO 13320:2009 standard.

[0264] In some embodiments, the volume average particle size Dv50 of the composite graphite particles is 9.5 μm, 10.5 μm, 11.5 μm, 12.5 μm, 13.5 μm or the numerical range between any two of them.

[0265] When the volume average particle size Dv50 of the composite graphite particles is within the above range, while shortening the solid-phase migration path of lithium ions, it also takes into account the lower reaction activity, thereby taking into account the fast charging ability and cycle life of the battery cell.

[0266] In some embodiments, the negative electrode active material further includes a silicon-based material, and the silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy.

[0267] In some embodiments, the silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

[0268] In some embodiments, based on the total mass of the negative electrode active material layer, the mass percentage of silicon element is 0.5% to 5%.

[0269] The qualitative and quantitative determination of each substance or element in this application can be detected by suitable equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination. Based on the total mass of the negative electrode active material layer, the mass percentage of silicon element has the meaning well-known in the art and can be tested by methods known in the art. For example, the negative electrode plate is placed in a solvent such as water and soaked, the negative electrode active material is separated from the negative electrode current collector, and each substance in the negative electrode active material layer is obtained by suction filtration and used as a test sample. The test sample is analyzed by an inductively coupled plasma - emission spectrometer of model ICAP7400 from Thermo Fisher Scientific Company, USA, with reference to the standard of GB / T30902 - 2014, and the silicon element content can be obtained.

[0270] In some embodiments, based on the total mass of the negative electrode active material layer, the mass content of silicon element can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5% or any value range between any two of them.

[0271] The introduction of silicon-based materials is beneficial to further improve the energy density of the battery cell. Based on the total mass of the negative electrode active material layer, when the mass percentage of silicon element is within the above mass range, the energy density and cycle stability of the battery cell can be taken into account.

[0272] In some embodiments, the single-sided coating mass of the negative electrode active material layer is 90 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 .

[0273] The single-sided coating mass of the negative electrode active material layer can be tested by a method similar to that of the single-sided coating mass of the positive electrode active material layer described above.

[0274] In some embodiments, the single-sided coating mass of the negative electrode active material layer can be 90 mg / 1540.25 mm 2 、100 mg / 1540.25 mm 2 、110 mg / 1540.25 mm 2 、120 mg / 1540.25 mm 2 、130 mg / 1540.25 mm 2 、140 mg / 1540.25 mm 2 or any value range between any two of them.

[0275] The negative electrode active material layer with a single-sided coating quality within the above range can form a cooperation with the positive electrode active material layer to achieve a balance between the energy density of the battery cell and the fast charging performance.

[0276] In some embodiments, the porosity of the separator is 20% to 70%, and can be optionally 35% to 60%.

[0277] In this application, the porosity refers to the percentage of the internal pore volume in the separator occupying the total volume of the separator. The porosity can be tested in accordance with the standard GB / T 36363-2018 "Polyolefin Separator for Battery Cells". It should be noted that in the actual testing process, due to differences in testing instruments, testing errors, and in order to eliminate the influence on the porosity test as much as possible, a testing process slightly different from the standard can be adopted to obtain a more accurate test value.

[0278] In some embodiments, the porosity of the separator can be 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or the numerical range between any two of them.

[0279] The porosity of the separator within the above range is beneficial to further balance the energy density, fast charging performance and cycle stability of the battery cell.

[0280] In some embodiments, referring to Figure 7 , the separator 123 includes: a base film 1231; a first functional layer 1232 located on at least one side of the base film 1231, and the first functional layer 1232 includes a first inorganic substance; a second functional layer 1233 located on the side of the first functional layer 1232 away from the base film 1231, and the second functional layer 1232 includes a second inorganic substance and non-fluoropolymer particles.

[0281] In some embodiments, the non-fluoropolymer particles include acrylate copolymers.

[0282] In some embodiments, the first inorganic substance and the second inorganic substance each independently include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide.

[0283] The inorganic particles can improve the wettability of the first functional layer and the second functional layer to the electrolyte and the heat resistance, and further comprehensively improve the fast charging performance, cycle stability and safety performance of the battery cell. The non-fluoropolymer particles can improve the processing performance and stability of the separator, and avoid internal short circuit caused by the movement of the separator in the battery cell, thereby further improving the cycle stability and safety performance of the battery cell.

[0284] In some embodiments, the base film comprises one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film may be a single-layer film or a multi-layer composite film, without particular limitation.

[0285] In some embodiments, the thickness of the base film is from 4 μm to 12 μm, and optionally from 5 μm to 9 μm.

[0286] In this application, the thickness of the base film can be tested by a micrometer.

[0287] In some embodiments, the thickness of the base film can be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or a numerical range between any two of them.

[0288] The thickness of the base film within the above range is beneficial to further balance the energy density, fast charging performance, and cycle stability of the battery cell.

[0289] In some embodiments, referring to Figure 8 , the battery cell 1 includes a housing 11 and a cover plate assembly. The cover plate assembly is disposed at at least one end of the housing 11. The housing 11 and the cover plate assembly define a receiving cavity. The electrode assembly is disposed in the receiving cavity. The wall thickness of the housing 111 of the large surface of the battery cell is from 0.1 mm to 0.5 mm.

[0290] In some embodiments, the wall thickness of the housing of the large surface of the battery cell is from 0.2 mm to 0.35 mm.

[0291] In some embodiments, the wall thickness of the housing of the large surface of the battery cell can be 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 numerical range between any two of them.

[0292] The wall thickness of the housing of the large surface of the battery cell within the above range is beneficial to further improve the energy density of the battery cell.

[0293] In some embodiments, the cover plate assembly includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly and the second cover plate assembly are disposed at both ends in the length direction or the width direction of the housing. The first cover plate assembly includes a first cover plate and a first electrode terminal. The second cover plate assembly includes a second cover plate and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite.

[0294] In some embodiments, referring to Figure 9, the battery cell 1 includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly includes a first cover plate, a first electrode terminal 131, and a third electrode terminal 133. The polarities of the first electrode terminal 131 and the third electrode terminal 133 are opposite. The second cover plate assembly includes a second cover plate, a second electrode terminal 132, and a fourth electrode terminal 134. The polarities of the second electrode terminal 132 and the fourth electrode terminal 134 are opposite.

[0295] Thus, during charging, the temperature rise of the battery cell is reduced and the impedance of the battery cell is decreased, which is beneficial to the improvement of the fast charging performance, cycle life, and safety performance of the battery cell.

[0296] In some embodiments, the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S, and 150 mm 2 ≤ S ≤ 1000 mm 2 .

[0297] In this application, the minimum cross-sectional area of the first electrode terminal refers to the minimum cross-sectional area of the first electrode terminal along the direction perpendicular to the current flow direction, and the minimum cross-sectional area of the second electrode terminal refers to the minimum cross-sectional area of the second electrode terminal along the direction perpendicular to the current flow direction.

[0298] In this application, when testing the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal, it can be calculated according to the shape of the minimum cross-section and its area calculation formula. For example, if the minimum cross-section of the electrode terminal is circular, the minimum cross-sectional area can be obtained by measuring the radius of the circle. If the minimum cross-section is square, the minimum cross-sectional area can be obtained by measuring the length and width of the square.

[0299] In some embodiments, the minimum cross-sectional area S of the first electrode terminal and / or the second electrode terminal can be 150 mm 2 , 300 mm 2 , 450 mm 2 , 600 mm 2 , 750 mm 2 , 900 mm 2 , 1000 mm 2 etc., or can be a range composed of any of the above values.

[0300] When the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is within the above range, it is beneficial to improve the over-current capacity of the battery cell, reduce the heat generation of the electrode terminal, reduce the internal resistance of the battery cell, and thus improve the fast charging performance and cycle stability of the battery cell.

[0301] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator can be made into an electrode assembly by a lamination process.

[0302] In some embodiments, a battery cell may include an outer package. The outer package may be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0303] In some embodiments, the outer package of the battery cell may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package of the battery cell may also be a soft package, such as a pouch soft package. The material of the soft package may be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. may be enumerated.

[0304] This application has no particular limitation on the shape of the battery cell, and it may be square or any other shape. For example, Figure 8 is a battery cell 1 with a square structure as an example.

[0305] In some embodiments, referring to Figure 8 , the outer package may include a housing 11 and a cover plate assembly. Among them, the housing 11 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate assembly can be disposed on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator may form an electrode assembly through a lamination process. The electrode assembly is encapsulated in the receiving cavity. The electrolyte infiltrates in the electrode assembly. The number of electrode assemblies included in the battery cell 1 may be one or more, and those skilled in the art can select according to specific actual needs.

[0306] In some embodiments, the battery cells can be assembled into a battery module. The number of battery cells included in the battery module may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0307] Optionally, the battery module may further include a housing having a receiving space, and a plurality of battery cells are received in the receiving space.

[0308] In some embodiments, the above-mentioned battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0309] The second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application. The battery device includes at least one of a battery module, a battery pack, and an energy storage battery.

[0310] In addition, a third aspect of the present application further provides an electrical device, which includes the battery cell provided by the first aspect of the present application. The battery cell, battery module or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0311] As the electrical device, the battery cell, battery module or battery pack can be selected according to its usage requirements.

[0312] Figure 9 Here is an example of an electrical device. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery cell, a battery pack or battery module can be used.

[0313] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thin and light design, and a battery cell can be used as the power source.

[0314] The embodiments of the present application also provide an energy storage device using a battery as the power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system, etc.

[0315] Embodiment In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0316] For those not specified in the embodiments in terms of specific techniques or conditions, the techniques or conditions described in the literature in the art or according to the product specifications are followed. For the reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0317] Embodiment 1 (1) Preparation of the positive electrode plate The positive electrode plate includes a positive current collector, a positive conductive layer on the positive current collector, and a positive active material layer. The positive current collector is an aluminum foil with a thickness of 13 μm.

[0318] The positive conductive layer on the positive current collector is an active material layer formed by uniformly mixing a positive conductive agent, superconducting carbon, a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), and then coating the mixture on the surface of the current collector and drying it. The thickness of the positive conductive layer is 1 μm. In the positive conductive layer, the mass content of the positive conductive agent is 40%, and the mass content of the positive binder is 60%.

[0319] Mix the positive active material, the binder polyvinylidene fluoride, and the conductive agent acetylene black in a ratio of 97:2:1. Then add the solvent N-methylpyrrolidone (NMP) and stir to form a positive electrode paste. Among them, the positive active material includes lithium iron phosphate, and the lithium iron phosphate has a coating layer. The coating layer coats the surface of the lithium iron phosphate particles. The coating layer includes lithium 2 FeTi(PO 4 ) 3 and carbon element, and the mass content of the carbon element is 1.12%.

[0320] Uniformly coat the positive conductive paste on the aluminum foil of the positive current collector. The thickness of the aluminum foil of the positive current collector is 13 µm; after drying, a positive conductive layer is obtained; then uniformly coat the positive electrode paste on the positive conductive layer, and after drying and cold pressing, a positive electrode plate is obtained. Among them, the single-sided coating weight of the positive active material layer is 270 mg / 1540.25 mm 2 。

[0321] (2)Preparation of the negative electrode plate The negative electrode plate includes a negative current collector, a negative conductive layer on the negative current collector, and a negative active material layer. The negative current collector is a copper foil with a thickness of 5 μm; The negative conductive layer on the negative current collector is an active material layer formed by uniformly mixing a negative conductive agent, superconducting carbon, a negative binder, styrene-butadiene rubber (SBR), a thickening agent, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, and then coating the mixture on the surface of the negative current collector and drying it. The thickness of the negative conductive layer is 1 μm. In the negative conductive layer, the mass content of the negative conductive agent is 35%, the mass content of the negative binder is 60%, and the mass content of the thickening agent is 5%; The negative active material layer includes a first negative active material layer and a second negative active material layer. The first negative active material layer is located on the surface of the negative conductive layer, and the second negative active material layer is located on the surface of the first negative active material layer; The first negative electrode active material layer comprises composite graphite particles, silicon-carbon material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 93:3.5:0.5:2:1, and the Dv50 of the composite graphite particles is 11.3 μm; the second negative electrode active material layer comprises composite graphite particles, silicon-carbon material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 94:3.5:0.5:1:1, and the Dv50 of the composite graphite particles is 11.3 μm; The silicon content in the silicon-carbon material accounts for 48%. Based on the total mass of the negative electrode active material layer, the mass fraction of silicon element is 1.68%. The composite graphite particles include graphite body particles and a carbon coating layer covering at least part of the surface of the graphite body particles. The carbon coating layer includes amorphous carbon, and based on the total mass of the composite graphite particles, the mass fraction of amorphous carbon is 3.5%.

[0322] The first negative electrode slurry is uniformly coated on the negative electrode conductive layer of the negative electrode current collector copper foil and dried; the second negative electrode slurry is coated on the surface of the dried first negative electrode slurry, and after drying and cold pressing, a negative electrode plate is obtained. Among them, the thickness ratio of the first active material layer to the second active material layer is 1:1; the single-sided coating weight of the negative electrode active material layer is 111 mg / 1540.25 mm 2 。

[0323] (3)Preparation of electrolyte The electrolyte includes a solvent, a lithium-containing electrolyte salt, and an additive.

[0324] The solvent includes a chain carboxylic acid ester solvent (22% ethyl acetate and 19.7% methyl acetate) with a mass fraction of 41.7%, 27.3% ethylene carbonate, and 6.7% dimethyl carbonate. The mass fractions of the components in the solvent are calculated based on the total mass of the electrolyte; Based on the total mass of the electrolyte, the total mass content of the additive is 9.3%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluorooxalate borate LiDFOB with a mass ratio of 4:2.5:2:0.8; Based on the total mass of the electrolyte, the lithium-containing electrolyte salt includes 5% lithium bis(fluorosulfonyl)imide LiFSI and 10% lithium hexafluorophosphate LiPF 6 。

[0325] (4)Preparation of separator The separator membrane includes a base film and a functional layer. The base film is a polyethylene film layer with a thickness of 5 μm, and the porosity of the separator membrane is 42%. The functional layer includes a first functional layer and a second functional layer. The first functional layer is a film layer formed by coating alumina particles and the binder polyvinylidene fluoride on one side of the base film, with a thickness of 1 μm. The average particle size of the alumina particles is 10 nm. The second functional layer is a film layer formed by coating composite particles composed of polyacrylate and calcium oxide particles dispersed on the polyacrylate on the surface of the first functional layer, with a thickness of 5 μm. The average particle size of the calcium oxide particles is 10 nm.

[0326] (5)Preparation of battery cell Stack the above-mentioned positive electrode plate, separator membrane, and negative electrode plate in sequence, with the separator membrane placed between the positive electrode plate and the negative electrode plate to play an isolation role. The positive electrode plate and the negative electrode plate each have a single-sided tab. The positive and negative electrode terminals are located on both sides of the battery cell in the length direction. The ratio of the width of the positive and negative electrode tabs to the width of the current collector part is 0.5, obtaining a stacked electrode assembly. Place the electrode assembly in a housing, inject electrolyte after drying, and obtain the battery cell through processes such as vacuum packaging, standing, formation, and shaping. Among them, the size of the positive active material layer along the length direction of the electrode assembly is 400 mm, OH 1 is 4 mm; the size of the positive active material layer along the width direction of the electrode assembly is 96 mm, OH 2 is 3 mm. The housing is an aluminum shell. The wall thickness of the housing on the large surface of the battery cell is 0.35 mm. The compaction density of the positive active material layer under the fully charged state of the battery is 2.75 g / cm 3 , and the compaction density of the negative active material layer is 1.26 g / cm 3 .

[0327] Examples 1 - 5 The preparation methods of Examples 1 - 5 are basically the same as those of Example 1, except that some parameters in the battery cell are adjusted, as shown in Table 1 specifically.

[0328] Example 6 The preparation method of Example 6 is basically the same as that of Example 3, except that both sides of the positive electrode plate and the negative electrode plate have tabs, and the ratio of the width of the positive and negative electrode tabs to the width of the current collector part is 1 / 3, as shown in Table 1 specifically.

[0329] Examples 7 - 8 The preparation methods of Examples 7 - 8 are basically the same as those of Example 6, except that some parameters in the battery cell are adjusted, as shown in Table 1 specifically.

[0330] Examples 9 - 10 The preparation methods of Examples 9 - 10 are basically the same as those of Example 1, except that some parameters in the battery cell are adjusted, as shown in Table 1 specifically.

[0331] Examples 11 - 12 The preparation methods of Examples 11 - 12 are basically the same as that of Example 1, except that the composition of the solvent in the electrolyte is adjusted, and the content of the carbonate additive changes accordingly, as shown in Table 2 specifically. Among them, the single - side coating mass of the positive active material layer in Example 11 is 243 mg / 1540.25 mm 2 , and the single - side coating mass of the negative active material layer is 100 mg / 1540.25 mm 2 .

[0332] Examples 13 - 14 The preparation methods of Examples 13 - 14 are basically the same as that of Example 1, except that the composition of the lithium - containing electrolyte salt in the electrolyte is adjusted, as shown in Table 2 specifically.

[0333] Examples 15 - 16 The preparation methods of Examples 15 - 16 are basically the same as that of Example 1, except that the composition of the additives in the electrolyte is adjusted, and the content of dimethyl carbonate changes accordingly, as shown in Table 2 specifically.

[0334] Example 17 The preparation method of Example 17 is basically the same as that of Example 1, except that the negative active material does not include silicon - based materials, specifically as follows: The first negative active material layer includes composite graphite particles, conductive agent acetylene black, binder styrene - butadiene rubber, and thickener sodium carboxymethyl cellulose with a mass ratio of 96.5:0.5:2:1. The Dv50 of the composite graphite particles is 11.3 μm; The second negative active material layer includes composite graphite particles, conductive agent acetylene black, binder styrene - butadiene rubber, and thickener sodium carboxymethyl cellulose with a mass ratio of 97.5:0.5:1:1. The Dv50 of the composite graphite particles is 11.3 μm; The first negative electrode slurry is uniformly coated on the negative conductive layer of the negative electrode current collector copper foil and dried; the second negative electrode slurry is coated on the surface of the dried first negative electrode slurry, and after drying and cold pressing, a negative electrode plate is obtained. Among them, the thickness ratio of the first active material layer to the second active material layer is 1:1; based on the total mass of the negative active material layer, the single - side coating mass of the negative active material layer is 111 mg / 1540.25 mm 2 . Since the negative electrode does not contain silicon, among them, the single - side coating mass of the positive active material layer is 240 mg / 1540.25 mm 2 .

[0335] Comparative Examples 1 - 8 The preparation methods of Comparative Examples 1-8 were basically the same as that of Example 1, except that some parameters in the battery cells were adjusted, as specifically shown in Tables 1 and 2. Among them, the single-sided coating mass of the positive electrode plate in Comparative Example 5 was 196 mg / 1540.25 mm 2 , and the single-sided coating mass of the negative electrode plate was 80 mg / 1540.25 mm 2 .

[0336] Test method 1. Number of cycles for the battery cell to decay to 90% SOH in Cycle Process 1 at 30°C The battery cell was charged and discharged cyclically at 30°C. The charging steps included the following steps: Constant current charging at 5.0C from 0% SOC to 5% SOC; Constant current charging at 5.0C from 5% SOC to 10% SOC; Constant current charging at 5.0C from 10% SOC to 15% SOC; Constant current charging at 5.0C from 15% SOC to 20% SOC; Constant current charging at 5.0C from 20% SOC to 25% SOC; Constant current charging at 5.0C from 25% SOC to 30% SOC; Constant current charging at 5.0C from 30% SOC to 35% SOC; Constant current charging at 5.0C from 35% SOC to 40% SOC; Constant current charging at 4.6C from 40% SOC to 45% SOC; Constant current charging at 4.3C from 45% SOC to 50% SOC; Constant current charging at 4.0C from 50% SOC to 55% SOC; Constant current charging at 3.7C from 55% SOC to 60% SOC; Constant current charging at 3.4C from 60% SOC to 65% SOC; Constant current charging at 3.1C from 65% SOC to 70% SOC; Constant current charging at 2.9C from 70% SOC to 75% SOC; Constant current charging at 2.7C from 75% SOC to 80% SOC; Constant current charging at 1.8C from 80% SOC to 85% SOC; Constant current charging at 1.3C from 85% SOC to 90% SOC; Constant current charging at 0.7C from 90% SOC to 95% SOC; Constant current charging at 0.33C from 95% SOC to 98% SOC; Charge from 98% SOC to 100% SOC at a constant current of 0.1C.

[0337] The protection voltage of the battery in the above charging steps is 3.65V. If the voltage reaches 3.65V in the corresponding charging step, it will automatically jump to the next step. The cut-off voltage of the last charging step is 3.65V.

[0338] The discharging strategy is as follows: discharge at a constant current of 1C to the cut-off voltage of 3.1V.

[0339] This is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., Cn / C0×100%) is 90%, and record the number of cycles. The more cycles, the better the cycle performance of the battery cell during the fast charging process.

[0340] 2. Number of cycles for the battery cell to decay to 90% SOH in Cycle Process 2 at 30℃ Perform charge-discharge cycles on the battery cell at 30℃. The charging steps include the following steps: Charge from 0% SOC to 5% SOC at a constant current of 8.0C; Charge from 5% SOC to 10% SOC at a constant current of 8.0C; Charge from 10% SOC to 15% SOC at a constant current of 8.0C; Charge from 15% SOC to 20% SOC at a constant current of 8.0C; Charge from 20% SOC to 25% SOC at a constant current of 7.5C; Charge from 25% SOC to 30% SOC at a constant current of 7.0C; Charge from 30% SOC to 35% SOC at a constant current of 6.6C; Charge from 35% SOC to 40% SOC at a constant current of 6.2C; Charge from 40% SOC to 45% SOC at a constant current of 5.8 C; Charge from 45% SOC to 50% SOC at a constant current of 5.4C; Charge from 50% SOC to 55% SOC at a constant current of 5.0C; Charge from 55% SOC to 60% SOC at a constant current of 4.6C; Charge from 60% SOC to 65% SOC at a constant current of 4.3C; Charge from 65% SOC to 70% SOC at a constant current of 3.8C; Charge from 70% SOC to 75% SOC at a constant current of 3.5C; Charge from 75% SOC to 80% SOC at a constant current of 3.3C; Charge from 80% SOC to 85% SOC at a constant current of 2.2C; Charge from 85% SOC to 90% SOC at a constant current of 1.6C; Charge from 90% SOC to 95% SOC at a constant current of 0.9C; Charge from 95% SOC to 98% SOC at a constant current of 0.4C; Charge from 98% SOC to 100% SOC at a constant current of 0.2C.

[0341] The protection voltage of the battery in the above charging steps is 3.65V. If the voltage reaches 3.65V in the corresponding charging step, it will automatically jump to the next step, and the cut-off voltage of the last charging step is 3.65V.

[0342] The discharge strategy is as follows: Discharge at a constant current of 1C to the cut-off voltage of 3.1V.

[0343] This is a charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., Cn / C0×100%) is 90%, and record the number of cycles. The more the number of cycles, the better the cycle performance of the battery cell during the fast charging process.

[0344] 3. Volume energy density Place the battery cell at 25°C, charge it at a constant current of 0.33C to 3.65V, then charge it at a constant voltage to 0.05C, and let it stand for 30 minutes; discharge it at a constant current of 0.33C to 2.0V, and record the discharge capacity A0 at this time, unit: Ah; use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulating film outside the shell), and calculate the volume V0 of the single battery, unit: L; the volume energy density VED of the battery cell = (A0×discharge platform voltage) / V0, unit: Wh / L.

[0345] 4. Parameter test method for battery thermal runaway: ① Charge adjustment: At 25°C, charge the lithium-ion battery at a constant current of 0.33C to 3.65V, and let it stand for 1 minute; then charge it at a constant current of 0.1C to 3.65V to adjust the charge of the battery to 100% SOC state.

[0346] ② Overcharge to thermal runaway test: Place the battery with a test fixture and a fixture force of 3000N, and then charge it at a constant current of 1C rate until the battery cell reaches thermal runaway. After the battery cools down to room temperature, observe the state of the thermally runaway battery cell. If fire or explosion occurs, the thermal runaway boundary deteriorates.

[0347] Test results Table 1

[0348] Table 2

[0349] Table 3

[0350] Table 4

[0351] From the comparison between the embodiments and comparative examples of the present application, it can be seen that the positive electrode tab is disposed at at least one end of the positive current collector portion extending along the length direction of the electrode assembly, and the size of the positive active material layer along the length direction of the electrode assembly is 300 mm to 950 mm; along the length direction of the electrode assembly, the size of the negative active material layer is larger than that of the positive active material layer, and the difference between the size of the negative active material layer and the size of the positive active material layer is OH 1 , OH 1 is greater than 1 mm and less than 5 mm; along the width direction of the electrode assembly, the size of the negative active material layer is larger than that of the positive active material layer, and the difference between the size of the negative active material layer and the size of the positive active material layer is OH 2 , OH 2 is greater than 1 mm and less than or equal to 4 mm; based on the total mass of the electrolyte, the mass fraction of the carboxylic acid ester solvent is 8% to 57%, and the mass fraction of the lithium fluorosulfonylimide salt is 3% to 8%. The battery cell takes into account the improvement of the energy density, fast charging performance, cycle stability under fast charging, and safety performance of the battery cell, and realizes the comprehensive improvement of the battery performance.

[0352] From the comparison between Examples 1 and 3 and Examples 2 and 4, and the comparison between Examples 6 and 8 and Example 7, it can be seen that the size of the positive active material layer along the length direction of the electrode assembly is 400 mm to 650 mm, and the battery cell of the active material layer takes into account the improvement of the energy density and cycle stability under fast charging of the battery cell.

[0353] From Examples 1-8, it can be seen that the size of the positive active material layer along the width direction of the electrode assembly is 90 mm to 130 mm, and the battery cell has excellent energy density and cycle stability under fast charging.

[0354] From the comparison between Example 3 and Examples 6, Example 4 and Example 7, and Example 5 and Example 8, it can be seen that when the positive electrode tab and the negative electrode tab are disposed at both ends along the length direction of the electrode assembly, it helps to further improve the cycle stability of the battery cell under fast charging, and is particularly suitable for improving the cycle stability of the battery cell with the length dimension of the positive active material layer in the range of 650 mm - 950 mm under fast charging.

[0355] From the comparison between Examples 1, 9 and Example 10, it can be seen that 1.5 ≤ OH 1≤4, 1.5≤OH 2 ≤3, the energy density of the battery cell is further improved while taking into account the cycle stability under good fast charging.

[0356] As can be seen from Examples 1, 11, and 12, based on the total mass of the electrolyte, the mass fraction of the carbonate solvent is 18% to 70%. While the battery cell has excellent cycle stability under fast charging, it also takes into account excellent energy density.

[0357] As can be seen from Examples 1, 11, and 12, based on the total mass of the electrolyte, the mass fraction of the carbonate additive is 3% to 8%. While the battery cell has excellent cycle stability under fast charging, it also takes into account excellent energy density.

[0358] As can be seen from Examples 1, 11, and 12, based on the total mass of the electrolyte, the mass fraction of vinylene carbonate is 2% to 5%. While the battery cell has excellent cycle stability under fast charging, it also takes into account excellent energy density.

[0359] As can be seen from the comparison between Example 1 and Examples 13 and 14, based on the total mass of the electrolyte, the mass fraction of lithium fluorosulfonylimide salt is 4% to 8%, and the cycle stability of the battery cell under fast charging is further improved.

[0360] As can be seen from Examples 1, 9 - 11, the mass fraction ratio of lithium hexafluorophosphate LiPF 6 to the mass fraction of lithium fluorosulfonylimide salt is 0.9:1 to 4:1, and the battery cell has excellent energy density and cycle stability under fast charging.

[0361] As can be seen from Examples 1 and 15, the mass fraction of the sulfur - containing additive is 0.5% to 2%, and the battery cell has excellent energy density and cycle stability under fast charging.

[0362] As can be seen from Examples 1 and 16, the mass fraction of the lithium - salt - containing additive is 0.2% to 1%, and the battery cell has excellent energy density and cycle stability under fast charging.

[0363] As can be seen from the comparison between Example 1 and Example 17, including silicon - based materials in the negative electrode active material is beneficial to further improve the energy density of the battery cell while taking into account excellent cycle stability under fast charging.

[0364] It should be noted that the present disclosure is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same effect as the technical idea within the scope of the technical solution of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope not departing from the gist of the present disclosure, various modifications that can be conceived by those skilled in the art to the embodiments, and other forms constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present disclosure.

Claims

1. A battery cell, characterized in that: The invention comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet which are stacked in sequence, wherein the positive electrode sheet comprises a positive current collector and a positive active material layer which is arranged on at least one side of the positive current collector, wherein the positive current collector comprises a positive current collector and a positive electrode tab, wherein the positive electrode tab is arranged on at least one end of the positive current collector extending along the length direction of the electrode assembly; wherein the negative electrode sheet comprises a negative current collector and a negative active material layer which is arranged on at least one side of the negative current collector, wherein the negative current collector comprises a negative current collector and a negative electrode tab, wherein the negative electrode tab is arranged on at least one end of the negative current collector extending along the length direction of the electrode assembly; Wherein, the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing phosphate with an olivine structure; The dimension of the positive electrode active material layer along the length direction of the electrode assembly is 300 mm to 950 mm; Along the length direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH1, and OH1 is larger than 1 mm and smaller than 5 mm; along the width direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH2, and OH2 is larger than 1 mm and smaller than or equal to 4 mm; The electrolyte includes a solvent and a lithium-containing electrolyte salt, the solvent includes a carboxylate solvent, and the lithium-containing electrolyte salt includes a fluorine-containing sulfonyl imide lithium salt; based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent is 8% to 57%, and the mass proportion of the fluorine-containing sulfonyl imide lithium salt is 3% to 8%.

2. The battery cell according to claim 1, characterized in that: OH1 is greater than or equal to 1.5 mm and less than or equal to 4 mm.

3. The battery cell according to any one of claims 1 to 2, characterized in that: OH2 is greater than or equal to 1.5 mm and less than or equal to 3 mm.

4. The battery cell according to any one of claims 1 to 2, characterized in that: OH1≥OH2.

5. The battery cell according to any one of claims 1 to 2, characterized in that: The dimension of the positive electrode active material layer along the length direction of the battery cell is 400 mm to 650 mm.

6. The battery cell according to any one of claims 1 to 2, characterized in that: The dimension of the positive electrode active material layer along the width direction of the electrode assembly is 90 mm to 130 mm.

7. The battery cell according to any one of claims 1 to 2, characterized in that: The dimension of the negative electrode active material layer along the length direction of the electrode assembly is 400 mm to 658 mm.

8. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode active material layer has a dimension of 90 mm to 130 mm along a width direction of the electrode assembly.

9. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode tab is arranged at one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly, and the negative electrode tab is arranged at one end of the negative electrode current collecting portion extending along the length direction of the electrode assembly.

10. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode tabs are arranged at both ends of the positive electrode current collecting portion extending along the length direction of the electrode assembly, and the negative electrode tabs are arranged at both ends of the negative electrode current collecting portion along the length direction of the electrode assembly.

11. The battery cell according to any one of claims 1 to 2, characterized in that: The dimension of the positive electrode active material layer along the length direction of the electrode assembly is 650 mm to 950 mm, the positive electrode tabs are arranged at both ends of the positive electrode collecting part extending along the length direction of the electrode assembly, and the negative electrode tabs are arranged at both ends of the negative electrode collecting part along the length direction of the electrode assembly.

12. The battery cell according to any one of claims 1 to 2, characterized in that: The ratio of the width of the positive electrode tab to the width of the positive electrode current collecting portion is 0.25 to 1; and / or, The ratio of the width of the negative electrode tab to the width of the negative electrode current collecting portion is 0.25 to 1.

13. The battery cell according to any one of claims 1 to 2, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the fluorinated sulfonyl imide lithium salt is 4% to 8%.

14. The battery cell according to any one of claims 1 to 2, characterized in that: The fluorine-containing lithium sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI, lithium bis(trifluoromethanesulfonyl)imide LiTFSI, and lithium perfluorobutylsulfonyl imide LiFNFSI.

15. The battery cell according to any one of claims 1 to 2, characterized in that: The lithium-containing electrolyte salt also includes lithium hexafluorophosphate LiPF6. Based on the total mass of the electrolyte, the total mass of the lithium hexafluorophosphate LiPF6 and the fluorine-containing sulfonyl imide lithium salt accounts for 10% to 18%.

16. The battery cell according to claim 15, characterized in that: Based on the total mass of the electrolyte, the ratio of the mass proportion of lithium hexafluorophosphate LiPF6 to the mass proportion of the fluorinated sulfonyl imide lithium salt is 0.9:1 to 4:

1.

17. The battery cell according to any one of claims 1 to 2, characterized in that: The carboxylic acid ester solvent has R ' -COO-R '' The general structural formula is ' Including one or more of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, C1-C5 halogenated alkyl groups, R '' Includes one or more of C1-C5 alkyl, C1-C5 halogenated alkyl.

18. The battery cell according to any one of claims 1 to 2, characterized in that: The carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

19. The battery cell according to any one of claims 1 to 2, characterized in that: The solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

20. The battery cell according to claim 19, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the carbonate solvent is 18% to 75%.

21. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives.

22. The battery cell according to claim 21, characterized in that: The carbonate additive includes one or more of vinylene carbonate and vinyl carbonate derivatives. Wherein, the ethylene carbonate derivative includes a compound represented by formula III, Formula III R1, R2, R3, and R4 each independently include one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 halogenated alkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time; The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, vinyl sulfite, methylene disulfonate, and 1,3-propane sultone; and / or, The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

23. The battery cell according to claim 22, characterized in that: The carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

24. The battery cell according to claim 21, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 3% to 8%.

25. The battery cell according to any one of claims 22 to 23, characterized in that: Based on the total mass of the electrolyte, the mass proportion of vinylene carbonate is 2% to 5%.

26. The battery cell according to any one of claims 22 to 23, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 0% to 4%.

27. The battery cell according to any one of claims 22 to 23, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 1.5% to 3.5%.

28. The battery cell according to claim 21, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0% to 2%.

29. The battery cell according to claim 21, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0.5% to 2%.

30. The battery cell according to claim 21, characterized in that Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

31. The battery cell according to claim 21, characterized in that Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% to 1%.

32. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode active material comprises: Lithium-containing phosphates with an olivine structure, and A coating layer is located on at least a portion of the surface of the lithium-containing phosphate, and the coating layer contains carbon.

33. The battery cell according to claim 32, characterized in that: Based on the total mass of the positive electrode active material, the mass proportion of the carbon element is 0.8% to 2.3%.

34. The battery cell according to claim 32, characterized in that: The coating layer also includes a component as shown in Formula I, Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I Among them, 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, M1 includes one or more of Ti, Zr, Hf, Ge, Sn, and M1 has a valence of +4.

35. The battery cell according to claim 32, characterized in that The lithium-containing phosphate comprises a component as shown in Formula II, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II Among them, 0.5≤x1≤1.3, 0≤y1≤1.3, 0.9≤x1+y1≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z1≤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, N and P; Y includes one or more of O and F.

36. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate and any modified forms of the foregoing substances, wherein the modified form includes one or more of doping modification and coating modification.

37. The battery cell according to any one of claims 1 to 2, characterized in that: The compaction density of the positive electrode active material layer is 2.50 g / cm 3 Up to 2.80g / cm 3 .

38. The battery cell according to any one of claims 1 to 2, characterized in that: The single-sided coating mass of the positive electrode active material layer is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 .

39. The battery cell according to any one of claims 1 to 2, characterized in that: The thickness of the positive electrode current collector is 10 μm to 15 μm.

40. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode plate also includes a positive conductive layer, which is located between the positive active material layer and the positive current collector, and the thickness of the positive conductive layer is 0.5 μm to 2 μm; and / or, the negative electrode plate also includes a negative conductive layer, which is located between the negative current collector and the negative active material layer on at least one side, and the thickness of the negative conductive layer is 0.5 μm to 2 μm.

41. The battery cell according to claim 40, characterized in that The positive electrode conductive layer includes a conductive agent and a positive electrode binder, and the negative electrode conductive layer includes a conductive agent and a negative electrode binder. The conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

42. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material.

43. The battery cell according to claim 42, characterized in that The carbon-based material includes one or more of graphite and hard carbon.

44. The battery cell according to claim 42, characterized in that The carbon-based material comprises composite graphite particles, wherein the composite graphite particles comprise graphite main particles and a carbon coating layer coated on at least a portion of the surface of the graphite main particles, the graphite main particles comprise secondary particles, and the carbon coating layer comprises amorphous carbon.

45. The battery cell according to claim 44, characterized in that Based on the total mass of the composite graphite particles, the mass proportion of amorphous carbon is 2% to 5%.

46. ​​The battery cell according to claim 44 or 45, characterized in that: The volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 13.5 μm.

47. The battery cell according to claim 42, characterized in that The negative electrode active material further includes a silicon-based material, and the silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy.

48. The battery cell according to claim 47, characterized in that The silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

49. The battery cell according to claim 47 or 48, characterized in that: Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 0.5% to 5%.

50. The battery cell according to any one of claims 1 to 2, characterized in that: The single-sided coating mass of the negative electrode active material layer is 90 mg / 1540.25 mm 2 Up to 140mg / 1540.25mm 2 .

51. The battery cell according to any one of claims 1 to 2, characterized in that: The porosity of the isolation film is 20% to 70%.

52. The battery cell according to any one of claims 1 to 2, characterized in that: The porosity of the isolation film is 35% to 60%.

53. The battery cell according to any one of claims 1 to 2, characterized in that: The isolation film comprises: Basement membrane; A first functional layer, located on at least one side of the base film, wherein the first functional layer comprises a first inorganic substance; The second functional layer is located on a side of the first functional layer away from the base film, and the second functional layer includes a second inorganic substance and non-fluorine polymer particles.

54. The battery cell according to claim 53, characterized in that The non-fluorinated polymer particles include acrylic copolymers.

55. The battery cell according to claim 53, characterized in that The first inorganic substance and the second inorganic substance each independently 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.

56. The battery cell according to claim 53, characterized in that The base film has a thickness of 4 μm to 12 μm.

57. The battery cell according to claim 56, characterized in that The base film has a thickness of 5 μm to 9 μm.

58. The battery cell according to any one of claims 1 to 2, characterized in that: The battery cell comprises a shell and a cover assembly, wherein the cover assembly is arranged at at least one end of the shell, the shell and the cover assembly define a receiving cavity, the electrode assembly is arranged in the receiving cavity, and the shell wall thickness of the large surface of the battery cell is 0.1 mm to 0.5 mm.

59. The battery cell according to claim 58, characterized in that The shell wall thickness of the large surface of the battery cell is 0.2 mm to 0.35 mm.

60. The battery cell according to claim 58, characterized in that The cover plate assembly includes a first cover plate assembly and a second cover plate assembly, the first cover plate assembly and the second cover plate assembly are arranged at both ends of the length direction or the width direction of the shell, the first cover plate assembly includes a first cover plate and a first electrode terminal, the second cover plate assembly includes a second cover plate and a second electrode terminal, and the polarities of the first electrode terminal and the second electrode terminal are opposite.

61. The battery cell according to claim 60, characterized in that The minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal is S and meets the requirement of 150 mm 2 ≤S≤1000mm 2 .

62. A battery device, characterized in that: Comprising the battery monomer described in any one of claims 1 to 61, the battery device is at least one of a battery module, a battery pack, and an energy storage battery.

63. An electrical device, characterized in that: Comprising the battery device of claim 62.

64. An energy storage device, characterized in that: Comprising the battery device of claim 62, wherein the battery device is used to store electrical energy.

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