Battery cell, battery device, power-consuming device, and energy storage device

Abstract

The present application provides a battery cell, a battery device, an electrical device, and an energy storage device. The size of the positive electrode active material layer along the length direction of the electrode assembly is 300mm to 950mm; along the length direction of the electrode assembly, the size difference between the negative electrode active material layer and the positive electrode active material layer is OH1, OH1 is greater than 1mm and less than 5mm; along the width direction of the electrode assembly, the size difference between the negative electrode active material layer and the positive electrode active material layer is OH2, OH2 is greater than 1mm and less than or equal to 4mm; based on the total mass of the electrolyte, the mass proportion of the carboxylic acid ester solvent is 8% to 57%, and the mass proportion of the fluorinated sulfonyl imide lithium salt is 3% to 8%. The battery cell takes into account the improvement of energy density, fast charging performance, cycle stability under fast charging, and safety performance, thereby achieving a comprehensive improvement in battery performance.

Description

[0001] This application claims priority to international patent application PCT / CN2025 / 086858, filed on April 2, 2025, entitled “Battery Cell, Battery Device, Electrical Device and Energy Storage Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the technical field of battery cells, and in particular 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 stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0004] With the market's increasing demands for both the range and recharge efficiency of electric devices, higher requirements are being placed on the energy density and fast-charging performance of battery cells. However, achieving these performance improvements often results in a deterioration in cycle stability, which has become a technical problem that urgently needs to be addressed in this field. Summary of the Invention

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

[0006] The first aspect of the present application provides a battery cell, comprising an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence, the positive electrode sheet comprising a positive electrode collector and a positive electrode active material layer arranged on at least one side of the positive electrode collector, the positive electrode collector comprising a positive electrode collector portion and a positive electrode tab, the positive electrode tab being arranged at at least one end of the positive electrode collector extending along the length direction of the electrode assembly; the negative electrode sheet comprising a negative electrode collector and a negative electrode active material layer arranged on at least one side of the negative electrode collector, the negative electrode collector comprising a negative electrode collector portion and a negative electrode tab, the negative electrode tab being arranged at at least one end of the negative electrode collector extending along the length direction of the electrode assembly; wherein the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing phosphate with an olivine structure; the positive electrode active material layer extends along the length direction of the electrode assembly The size of the electrode assembly is 300mm to 950mm along the length direction; 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 size difference between the negative active material layer and the positive active material layer is OH1, and OH1 is larger than 1mm and smaller than 5mm; 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 size difference between the negative active material layer and the positive active material layer is OH2, and OH2 is larger than 1mm and less than or equal to 4mm; 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 of the carboxylate solvent accounts for 8% to 57%, and the mass of the fluorine-containing sulfonyl imide lithium salt accounts for 3% to 8%.

[0007] Lithium-containing phosphates with an olivine structure have the advantages of low cost and long life. When combined with a laminated electrode assembly design where the dimensions of the positive electrode active material layer along the length of the electrode assembly are within the aforementioned range and the tabs are located on the short side, this helps improve the internal space utilization of the battery cells and address the low energy density of the battery cells when lithium-containing phosphates are used as the positive electrode active material. This also shortens the current transmission path from the active material to the tabs, reducing the battery's internal resistance and enabling the battery cells to achieve both excellent fast-charging performance and energy density. However, as the charge rate of the battery cells increases, the current density and temperature rise near the tabs are high, resulting in faster lithium ion migration than in other areas, making it easier for lithium dendrites to form near the tabs in the negative electrode active material layer. The battery cell of the embodiment of the present application improves the ability of the negative electrode active material layer, especially the negative electrode active material layer near the tab area, to accept active ions in the length direction through the design of OH1, and makes the distance between the positive electrode active material layer and the tab side farther, and the current distribution of the active material layer near the tab area is more uniform, so that the temperature rise is reduced, thereby comprehensively improving the lithium plating problem of the negative electrode plate; the design of OH2 helps to reduce the probability of the positive and negative electrodes overlapping due to thermal shrinkage of the isolation membrane and subsequent internal short circuit of the battery; while improving the cycle stability of the battery cell, the values of OH1 and OH2 are controlled within the above range, so that the battery cell has excellent energy density. Carboxylate solvents offer the advantages of low viscosity and high ionic conductivity, facilitating electrolyte wetting of the negative electrode active material layer and the rapid insertion and removal of active ions from the negative electrode active material layer, thereby further alleviating lithium plating issues in the negative electrode. However, their high activity makes them susceptible to decomposition and gassing at high current rates. Therefore, by rationally controlling the mass fraction of carboxylate solvents in the electrolyte within the above range, the electrolyte achieves both good conductivity and stability, further improving the fast-charging performance and cycling stability of the battery cells. Fluorinated sulfonyl imide salts readily dissociate in carboxylate solvents, further enhancing electrolyte conductivity. Furthermore, fluorinated sulfonyl imide salts exhibit high thermochemical stability and are not susceptible to thermal decomposition. Furthermore, fluorinated sulfonyl imide salts can participate in the formation of the solid electrolyte interface (SEI) film on the surface of the negative electrode active material, helping to enhance the thermal stability of the SEI film and reduce its impedance, further mitigating the risk of lithium plating at high current rates. However, as the temperature of the battery cells rises, the fluorinated sulfonyl imide salt will undergo violent decomposition below a certain temperature threshold, releasing a large amount of heat, sharply increasing the risk of thermal runaway in the battery. This safety risk is even more significant in fast-charging batteries. Therefore, by further rationally controlling the mass percentage of the fluorinated sulfonyl imide lithium salt in the electrolyte within the above range, the electrolyte has good conductivity and stability, further improving fast-charging performance and cycle stability while reducing the risk of thermal runaway in the battery cells, thus maintaining excellent safety performance in the battery cells.The embodiments of the present application enable lithium ions to cooperate with each other during liquid-phase and solid-phase transmission through the mutual cooperation between the electrode assembly and the electrolyte. The battery cells have excellent energy density, reduced risk of lithium plating during fast charging, improved cycle life, and safety performance, thereby achieving a comprehensive improvement in battery performance.

[0008] In any embodiment, OH1 is greater than or equal to 1.5 mm and less than or equal to 4 mm.

[0009] In any embodiment, OH2 is greater than or equal to 1.5 mm and less than or equal to 3 mm.

[0010] When OH1 and OH2 are within the above range, the cycle stability of the battery cell is improved and the energy density of the battery cell is further improved.

[0011] In any embodiment, OH1 ≥ OH2.

[0012] Controlling OH1≥OH2 improves the cycle stability of the battery cell during fast charging and is conducive to further improving the energy density of the battery cell.

[0013] In any embodiment, the dimension of the positive electrode active material layer along the length direction of the battery cell is 400 mm to 650 mm.

[0014] The size of the positive electrode active material layer along the length direction of the battery cell is within the above range, and the battery cell has excellent fast charging performance, cycle stability during fast charging, and energy density.

[0015] In any embodiment, the dimension of the positive electrode active material layer along the width direction of the electrode assembly is 90 mm to 130 mm.

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

[0017] In any embodiment, the dimension of the negative electrode active material layer along the length direction of the electrode assembly is 400 mm to 658 mm.

[0018] In any embodiment, the dimension of the negative electrode active material layer along the width direction of the electrode assembly is 90 mm to 130 mm.

[0019] When the dimensions of the negative electrode active material layer along the length and width directions of the electrode assembly are within the above range, matching the design of the positive electrode active material layer is beneficial to the comprehensive improvement of the battery cell energy density, fast charging performance and cycle stability during fast charging.

[0020] In any embodiment, the positive electrode tab is provided 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 provided at one end of the negative electrode current collecting portion extending along the length direction of the electrode assembly.

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

[0022] In any embodiment, the positive electrode tabs are provided 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 provided at both ends of the negative electrode current collecting portion extending along the length direction of the electrode assembly.

[0023] In any embodiment, the size 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 portion extending along the length direction of the electrode assembly, and the negative electrode tabs are arranged at both ends of the negative electrode collecting portion extending along the length direction of the electrode assembly.

[0024] The above-mentioned tab setting helps to improve the overcurrent capacity of the battery cell, alleviate the situation where the temperature on the tab side is too high during fast charging, causing electrolyte decomposition and uneven current distribution to cause lithium deposition on the tab side, thereby improving the fast charging performance of the battery cell and the cycle stability under fast charging. It is particularly suitable for improving the cycle stability of battery cells with a positive electrode active material layer length ranging from 650mm to 950mm under fast charging.

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

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

[0027] The ratio of the width of the tab to the width of the current collecting portion being within the above range helps to enhance the current carrying capacity of the battery cell, and improves 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 proportion of the fluorinated sulfonyl imide lithium salt is 4% to 8%.

[0029] The mass proportion of the fluorinated sulfonyl imide lithium salt is within the above range, which can further take into account the fast charging performance, cycle stability and safety performance of the battery cell under fast charging.

[0030] In any embodiment, the fluorine-containing lithium sulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide LiFSI, lithium bistrifluoromethanesulfonyl imide LiTFSI, and lithium perfluorobutylsulfonyl imide LiFNFSI.

[0031] In any embodiment, the lithium-containing electrolyte salt further includes lithium hexafluorophosphate LiPF6, and the total mass of the lithium hexafluorophosphate LiPF6 and the fluorinated sulfonyl imide lithium salt accounts for 10% to 18% based on the total mass of the electrolyte.

[0032] Lithium-containing electrolyte salts that also include lithium hexafluorophosphate (LiPF6) can reduce the risk of thermal runaway in battery cells, keeping the risk reduction within a controllable range and further improving the safety performance of the battery cells. Battery cells with a combined mass ratio of lithium hexafluorophosphate (LiPF6) and fluorinated sulfonyl imide salts in the electrolyte within the aforementioned range can further balance the battery cells' fast-charging performance, cycling stability under fast-charging conditions, and safety performance.

[0033] In any embodiment, 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.

[0034] A battery cell in which the ratio of the mass proportion of lithium hexafluorophosphate LiPF6 to the mass proportion of fluorinated sulfonyl imide lithium salt in the electrolyte is within the above range can further take into account the fast charging performance, cycle stability under fast charging and safety performance of the battery cell.

[0035] In any embodiment, the carboxylate solvent has R ' -COO-R '' The general structural formula, where R ' Including one or more of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, C1-C5 haloalkyl groups, R '' Including one or more of C1-C5 alkyl, C1-C5 halogenated alkyl.

[0036] In any embodiment, 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.

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

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

[0040] Due to the high viscosity of carbonate solvents, increasing the carbonate solvent content increases the electrolyte viscosity, negatively impacting the electrolyte's conductivity. By properly controlling the mass percentage of carbonate solvents within the aforementioned range, the electrolyte achieves both an appropriate viscosity and a good dissociation rate, thereby achieving a comprehensive improvement in electrolyte conductivity, which is beneficial for further enhancing the fast-charging performance of battery cells and the cycling stability under fast charging.

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

[0042] In any embodiment, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives.

[0043] Among them, the ethylene carbonate derivatives include compounds represented by formula III,

[0044] Formula III

[0045] 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 haloalkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time. Optionally, the carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

[0046] Carbonate additives can evolve into organic components in the SEI film, improving the toughness of the SEI film, thereby further improving the stability of the SEI film during the battery cell cycle and further reducing the interfacial impedance on the negative electrode side, which is beneficial to further improve the cycle life and fast charging performance of the battery cell.

[0047] In any embodiment, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, vinyl sulfite, methylene disulfonate, and 1,3 propane sultone.

[0048] Sulfur-containing additives often have a higher potential. Sulfur-containing additives added to the electrolyte will preferentially react 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 detrimental to the stability of the battery cells in high-temperature environments. The presence of sulfur in the SEI film can further enhance the thermal stability of the SEI film at high temperatures and further reduce the interfacial impedance on the negative electrode side, which is beneficial for further improving the cycling stability and fast-charging performance of the battery cells.

[0049] In any embodiment, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0050] Lithium salt additives can evolve into inorganic components in the SEI film, increasing the rigidity and thermal stability of the SEI film, further improving the stability of the SEI film and further reducing the interfacial impedance on the negative electrode side, thereby further improving the battery's cycle stability and fast charging performance. Furthermore, these lithium salt additives can form a positive electrode electrolyte interface film (CEI film) on the surface of the positive electrode active material, further improving the cycle stability of the battery cell.

[0051] In any embodiment, based on the total mass of the electrolyte, the carbonate additive accounts for 3% to 8% by mass.

[0052] The mass proportion of carbonate additives in the electrolyte is within the above range, which is beneficial to both improving the stability of the SEI film and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0053] In any embodiment, based on the total mass of the electrolyte, the mass proportion of vinylene carbonate is 2% to 5%.

[0054] Vinylene carbonate (VC) has a similar reduction potential to carboxylate solvents, which can inhibit the reactivity of carboxylate solvents and improve the cycle life of battery cells. However, excessive VC content can increase the battery's interfacial impedance and charge transfer impedance, hindering the fast-charging performance of the battery cells. A VC mass percentage within the above range ensures that the battery achieves both excellent cycle life and fast-charging performance.

[0055] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 0% to 4%.

[0056] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 1.5% to 3.5%.

[0057] Ethylene carbonate derivatives can also form films on the negative electrode surface at higher potentials and exhibit low interfacial and charge transfer resistance. The mass percentage of ethylene carbonate derivatives within the aforementioned range enables the battery cells to achieve both excellent fast-charging performance and cycle life. By combining vinylene carbonate (VC) and ethylene carbonate derivatives in the electrolyte, the fast-charging performance and cycle stability of the battery cells can be comprehensively improved.

[0058] In any embodiment, the mass proportion of the sulfur-containing additive is 0% to 2% based on the total mass of the electrolyte.

[0059] In any embodiment, the mass proportion of the sulfur-containing additive is 0.5% to 2% based on the total mass of the electrolyte.

[0060] The mass proportion of sulfur-containing additives in the electrolyte is within the above range, which is beneficial to both improving the thermal stability of the SEI film at high temperatures and maintaining an appropriate viscosity of the electrolyte, and further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0061] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

[0062] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% to 1%.

[0063] The mass proportion of lithium salt additives in the electrolyte is within the above range, which is beneficial to both improving the stability of the SEI film and maintaining an appropriate viscosity of the electrolyte, and further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0064] In any embodiment, the positive electrode active material includes: an olivine-structured lithium-containing phosphate, and a coating layer, wherein the coating layer is located on at least a portion of the surface of the lithium-containing phosphate, and the coating layer contains carbon.

[0065] The coating layer contains carbon elements, which is beneficial to improving the electronic conductivity of lithium-containing phosphates and improving the solid-phase transmission rate of electrons, thereby further improving the energy density and fast charging performance of the battery cells.

[0066] In any embodiment, the mass proportion of carbon element is 0.8% to 2.3% based on the total mass of the positive electrode active material.

[0067] Based on the total mass of the positive electrode active material, the mass proportion of the carbon element is within the above range, so that the lithium-containing phosphate has both excellent electronic conductivity and gram capacity, further comprehensively improving the energy density and fast charging performance of the battery cell.

[0068] In any embodiment, the coating layer further comprises a component as shown in Formula I,

[0069] Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I,

[0070] Wherein, 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, M1 includes one or more of Ti, Zr, Hf, Ge, and Sn, and optionally, M1 has a valence of +4.

[0071] The component shown in Formula I is a fast ion conductor with a NASICON structure. Its ionic conductivity approaches or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has abundant three-dimensional lithium ion diffusion and transport channels, and has advantages such as high ion conduction efficiency and strong structural stability during multiple lithium de- and lithium insertion processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly increase the lithium ion transmission rate during multiple lithium de- and lithium insertion at the positive terminal, improve the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0072] In any embodiment, the lithium-containing phosphate comprises a component as shown in Formula II,

[0073] Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II,

[0074] 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; and Y includes one or more of O and F.

[0075] The lithium-containing phosphate with an olivine structure having the above components has good structural stability, can reduce the loss during the fast charging process, and further improve the fast charging performance and cycle stability of the battery cell.

[0076] 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 of the foregoing substances, wherein the modified form includes one or more of doping modification and coating modification.

[0077] In any embodiment, the compaction density of the positive electrode active material layer is 2.50 g / cm 3 to 2.80g / cm 3 .

[0078] The positive electrode active material layer with a compaction density within the above range can further achieve a balance between the fast charging performance and energy density of the battery cell.

[0079] In any embodiment, the coating mass of the positive electrode active material layer on one side is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 .

[0080] The positive electrode active material layer having a single-side coating mass within the above range can further effectively balance the fast charging performance and energy density of the battery cell.

[0081] In any embodiment, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0082] The positive electrode current collector has a relatively low thickness, which enables further improvement in the energy density of the battery cell.

[0083] In any embodiment, the positive electrode plate further includes a positive electrode conductive layer, which is 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, which is located between the negative electrode current collector and the negative electrode active material layer on at least one side, and the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

[0084] 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 pole piece, and is beneficial to further improving the fast charging performance of the battery cell.

[0085] 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 superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. One or more of the positive electrode binder includes polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylate resin.

[0086] 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.

[0087] In any embodiment, the carbon-based material includes one or more of graphite and hard carbon.

[0088] In any embodiment, the carbon-based material includes composite graphite particles, the composite graphite particles include graphite particles and a carbon coating layer coated on at least a portion of the surface of the graphite particles, the graphite particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0089] Secondary particles are particles formed by the aggregation of two or more primary particles. Composite graphite particles, including secondary particles and a surface coating including amorphous carbon, facilitate the infiltration of electrolyte into the negative electrode active layer of the electrode and enhance the solid-phase transport capacity of active ions, contributing to further improvement in the fast-charging performance of battery cells.

[0090] In any embodiment, the amorphous carbon accounts for 2% to 5% by mass based on the total mass of the composite graphite particles.

[0091] When the content of amorphous carbon is within an appropriate range, the composite graphite material can have a high gram capacity while also having a high active ion solid-phase transport ability, which is conducive to further comprehensive improvement of the energy density and fast charging performance of the battery cell.

[0092] In any embodiment, the composite graphite particles have a volume average particle size Dv50 of 9.5 μm to 13.5 μm.

[0093] The volume average particle size Dv50 of the composite graphite particles is within the above range, which shortens the solid phase migration path of lithium ions while taking into account lower reaction activity, thereby taking into account the fast charging capability and cycle life of the battery cell.

[0094] 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.

[0095] In any embodiment, the silicon-based material includes one or more of silicon-carbon materials, silicon-oxygen materials, and silicon-nitrogen materials.

[0096] In any embodiment, the mass ratio of silicon element is 0.5% to 5% based on the total mass of the negative electrode active material layer.

[0097] The introduction of silicon-based materials helps further improve the energy density of battery cells. Based on the total mass of the negative electrode active material layer, the silicon mass percentage is within the above mass range, achieving a balance between the energy density and cycle stability of the battery cells.

[0098] In any embodiment, the coating mass of the negative electrode active material layer on one side is 90 mg / 1540.25 mm 2 Up to 140mg / 1540.25mm 2 .

[0099] The single-side coating quality of the negative electrode active material layer can be tested by a method similar to the single-side coating quality of the positive electrode active material layer described above.

[0100] The negative electrode active material layer with a single-side coating mass within the above range can cooperate with the positive electrode active material layer to achieve a balance between the energy density and fast charging performance of the battery cell.

[0101] In any embodiment, the porosity of the separator is 20% to 70%, and optionally 35% to 60%.

[0102] The porosity of the isolation membrane within the above range is beneficial for further taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0103] In any embodiment, the isolation membrane includes: a base membrane; a first functional layer located on at least one side of the base membrane, the first functional layer including a first inorganic substance; a second functional layer located on a side of the first functional layer away from the base membrane, the second functional layer including a second inorganic substance and non-fluoropolymer particles.

[0104] In any embodiment, the non-fluoropolymer particles include an acrylate copolymer.

[0105] 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.

[0106] Inorganic particles enhance the electrolyte wettability and heat resistance of the first and second functional layers, further improving the battery's fast-charging performance, cycling stability, and safety. Non-fluoropolymer particles enhance the processability and stability of the separator, preventing internal short circuits caused by the separator's movement within the battery cell, further improving the battery's cycling stability and safety.

[0107] In any embodiment, the base film has a thickness of 4 μm to 12 μm, optionally 5 μm to 9 μm.

[0108] The thickness of the base film within the above range is beneficial for further taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0109] In any embodiment, the battery cell includes a shell and a cover assembly, the cover assembly is arranged at at least one end of the shell, the shell and the cover assembly define a accommodating cavity, the electrode assembly is arranged in the accommodating cavity, and the shell wall thickness of the large surface of the battery cell is 0.1mm to 0.5mm.

[0110] In any of the embodiments, the housing wall thickness of the battery cell on the large surface is 0.2 mm to 0.35 mm.

[0111] The shell wall thickness of the large surface of the battery cell is within the above range, which is conducive to further improving the energy density of the battery cell.

[0112] In any embodiment, 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 shell in the length direction or the width direction, 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.

[0113] Therefore, the temperature rise of the battery cell and the impedance of the battery cell are reduced during charging, which is beneficial to improving the fast charging performance, cycle life and safety performance of the battery cell.

[0114] In any embodiment, the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S and satisfies 150 mm 2 ≤S≤1000mm 2 .

[0115] The minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is within the above range, which is beneficial to improving the current carrying capacity of the battery cell, reducing the heat generation of the electrode terminal, and reducing the internal resistance of the battery cell, thereby improving the fast charging performance and cycle stability of the battery cell.

[0116] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device comprises at least one of a battery module, a battery pack, and an energy storage battery.

[0117] The third aspect of the present application further provides an electrical device, which includes the battery cell provided in the first aspect of the present application.

[0118] The fourth aspect of the present application further provides an energy storage device, which includes the battery cell provided in the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0119] Figure 1 Schematic diagram of a positive electrode sheet and a negative electrode sheet according to an embodiment of the present application;

[0120] Figure 2A Schematic diagram of a positive electrode sheet according to one embodiment of the present application;

[0121] Figure 2B is a schematic diagram of a negative electrode sheet according to one embodiment of the present application;

[0122] Figure 3 Schematic diagram of a positive electrode current collector according to one embodiment of the present application;

[0123] Figure 4Schematic diagram of a positive electrode current collector according to one embodiment of the present application;

[0124] Figure 5 is a schematic diagram of a negative electrode current collector according to one embodiment of the present application;

[0125] Figure 6 is a schematic diagram of a negative electrode current collector according to one embodiment of the present application;

[0126] Figure 7 Schematic diagram of the structure of an isolation membrane according to one embodiment of the present application;

[0127] Figure 8 is a schematic structural diagram of a battery cell according to an embodiment of the present application;

[0128] Figure 9 FIG2 is a schematic diagram of an electrical device using a battery cell according to an embodiment of the present application as a power source.

[0129] Description of reference numerals:

[0130] 1 battery cell; 11 housing; 111 housing of the large surface of the battery cell; 12 electrode assembly; 121 positive electrode sheet; 1211 positive electrode current collector; 1212 positive electrode active material layer; 12110 positive electrode current collecting portion; 12111 positive electrode tab; 122 negative electrode sheet; 1221 negative electrode current collector; 1222 negative electrode active material layer; 12210 negative electrode current collecting portion; 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

[0131] Below, the embodiments of the battery cell, battery device, power supply device and energy storage device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0132] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0133] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0134] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0135] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0136] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0137] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0138] Using a laminated electrode assembly with increased length and tabs on the short side helps improve the energy density of battery cells. However, this electrode assembly design makes it prone to high current density and temperature rise near the tabs during fast charging, which can lead to lithium deposition at the negative electrode and electrolyte decomposition, compromising the battery's cycling stability.

[0139] Based on this, the first aspect of the present application provides a battery cell, 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 electrode active material layer arranged on at least one side of the positive current collector, the positive current collector includes a positive current collecting part and a positive electrode tab, the positive electrode tab is arranged at at least one end of the positive current collecting part extending along the length direction of the electrode assembly; the negative electrode sheet includes a negative current collector and a negative electrode active material layer arranged on at least one side of the negative current collector, the negative current collector includes a negative current collecting part and a negative electrode tab, the negative electrode tab is arranged at at least one end of the negative current collecting part extending along the length direction of the electrode assembly; wherein, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes a lithium-containing phosphate with an olivine structure; the positive electrode active material layer extends along the length of the electrode assembly The dimension in the longitudinal direction is 300mm to 950mm; along the length direction of the electrode assembly, the dimension of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the dimension difference between the negative electrode active material layer and the positive electrode active material layer is OH1, and OH1 is larger than 1mm and smaller than 5mm; along the width direction of the electrode assembly, the dimension of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the dimension difference between the negative electrode active material layer and the positive electrode active material layer is OH2, and OH2 is larger than 1mm and smaller than or equal to 4mm; 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 fluorine-containing sulfonyl imide lithium salt; based on the total mass of the electrolyte, the mass of the carboxylic acid ester solvent accounts for 8% to 57%, and the mass of the fluorine-containing sulfonyl imide lithium salt accounts for 3% to 8%.

[0140] Olivine-structured lithium-containing phosphates are active materials with an olivine structure that include lithium ions and phosphate groups. The type of positive electrode active material can be determined by any method known in the art. For example, phase analysis methods such as X-ray diffraction (XRD) can be combined with elemental analysis methods such as energy dispersive spectroscopy and XPS.

[0141] In this application, reference Figure 1 The electrode assembly 12 includes a positive electrode sheet 121, a separator 123 and a negative electrode sheet 122 stacked in sequence. The positive electrode sheet 121 includes a positive electrode current collector 1211 and a positive electrode active material layer 1212 provided on at least one side of the positive electrode current collector 1211. The negative electrode sheet 122 includes a negative electrode current collector 1221 and a negative electrode active material layer 1222 provided 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 The difference between the size of the negative electrode active material layer 1222 and the size of the positive electrode active material layer 1212 is OH1=OH 21 -OH 11 ;refer 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 The difference between the size of the negative electrode active material layer 1222 and the size of the positive electrode active material layer 1212 is OH1=OH 22 -OH 12 , the size can be measured with a ruler.

[0142] In some embodiments, reference Figure 3 The positive electrode current collector 1211 includes a positive electrode current collecting portion 12110 and a positive electrode tab 12111 . 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.

[0143] In some embodiments, reference Figure 4 The positive electrode tabs 12111 are arranged at both ends of the positive electrode current collecting portion 12110 extending along the length direction of the electrode assembly.

[0144] In some embodiments, reference Figure 5 The negative electrode current collector 1221 includes a negative electrode current collecting portion 12210 and a negative electrode tab 12211 . 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.

[0145] In some embodiments, reference Figure 6 The negative electrode tabs 12211 are arranged at both ends of the negative electrode current collecting portion 12210 extending along the length direction of the electrode assembly.

[0146] In some embodiments, the dimension of the positive electrode active material layer along the length direction of the electrode assembly can be 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, 750mm, 800mm, 850mm, 900mm, 950mm or any numerical range therebetween.

[0147] In some embodiments, OH1 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 any range therebetween.

[0148] In some embodiments, OH2 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 any range therebetween.

[0149] The types and qualities of the solvent and lithium-containing electrolyte salt in the electrolyte can be obtained by testing the electrolyte using methods known to those skilled in the art. In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery 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 reversely disassembled, and the free electrolyte obtained from the battery cell is used as a sample for detection using an ion chromatography analysis method. The types and contents of organic components in the electrolyte are well known in the art and can be detected using equipment and methods known in the art. For example, the organic components of the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography with reference to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents". The types and contents of inorganic components / lithium salts in the electrolyte are well known in the art and can be detected using equipment and methods known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-2002 "General Rules for Ion Chromatography Analysis Methods".

[0150] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent can be 8%, 15%, 22%, 29%, 36%, 43%, 50%, 57%, or any range therebetween.

[0151] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the fluorinated sulfonyl imide lithium salt may be 3%, 4%, 5%, 6%, 7%, 8%, or any range therebetween.

[0152] Lithium-containing phosphates with an olivine structure have the advantages of low cost and long life. When combined with a laminated electrode assembly design where the dimensions of the positive electrode active material layer along the length of the electrode assembly are within the aforementioned range and the tabs are located on the short side, this helps improve the internal space utilization of the battery cells and address the low energy density of the battery cells when lithium-containing phosphates are used as the positive electrode active material. This also shortens the current transmission path from the active material to the tabs, reducing the battery's internal resistance and enabling the battery cells to achieve both excellent fast-charging performance and energy density. However, as the charge rate of the battery cells increases, the current density and temperature rise near the tabs are high, resulting in faster lithium ion migration than in other areas, making it easier for lithium dendrites to form near the tabs in the negative electrode active material layer. The battery cell of the embodiment of the present application improves the ability of the negative electrode active material layer, especially the negative electrode active material layer near the tab area, to accept active ions in the length direction through the design of OH1, and makes the distance between the positive electrode active material layer and the tab side farther, and the current distribution of the active material layer near the tab area is more uniform, so that the temperature rise is reduced, thereby comprehensively improving the lithium plating problem of the negative electrode plate; the design of OH2 helps to reduce the probability of the positive and negative electrodes overlapping due to thermal shrinkage of the isolation membrane and subsequent internal short circuit of the battery; while improving the cycle stability of the battery cell, the values of OH1 and OH2 are controlled within the above range, so that the battery cell has excellent energy density. Carboxylate solvents offer the advantages of low viscosity and high ionic conductivity, facilitating electrolyte wetting of the negative electrode active material layer and the rapid insertion and removal of active ions from the negative electrode active material layer, thereby further alleviating lithium plating issues in the negative electrode. However, their high activity makes them susceptible to decomposition and gassing at high current rates. Therefore, by rationally controlling the mass fraction of carboxylate solvents in the electrolyte within the above range, the electrolyte achieves both good conductivity and stability, further improving the fast-charging performance and cycling stability of the battery cells. Fluorinated sulfonyl imide salts readily dissociate in carboxylate solvents, further enhancing electrolyte conductivity. Furthermore, fluorinated sulfonyl imide salts exhibit high thermochemical stability and are not susceptible to thermal decomposition. Furthermore, fluorinated sulfonyl imide salts can participate in the formation of the solid electrolyte interface (SEI) film on the surface of the negative electrode active material, helping to enhance the thermal stability of the SEI film and reduce its impedance, further mitigating the risk of lithium plating at high current rates. However, as the temperature of the battery cells rises, the fluorinated sulfonyl imide salt will undergo violent decomposition below a certain temperature threshold, releasing a large amount of heat, sharply increasing the risk of thermal runaway in the battery. This safety risk is even more significant in fast-charging batteries. Therefore, by further rationally controlling the mass percentage of the fluorinated sulfonyl imide lithium salt in the electrolyte within the above range, the electrolyte has good conductivity and stability, further improving fast-charging performance and cycle stability while reducing the risk of thermal runaway in the battery cells, thus maintaining excellent safety performance in the battery cells.The embodiments of the present application enable lithium ions to cooperate with each other during liquid-phase and solid-phase transmission through the mutual cooperation between the electrode assembly and the electrolyte. The battery cells have excellent energy density, reduced risk of lithium plating during fast charging, improved cycle life, and safety performance, thereby achieving a comprehensive improvement in battery performance.

[0153] In some embodiments, OH1 is greater than or equal to 1.5 mm and less than or equal to 4 mm.

[0154] In some embodiments, OH2 is greater than or equal to 1.5 mm and less than or equal to 3 mm.

[0155] When OH1 and OH2 are within the above range, the cycle stability of the battery cell is improved and the energy density of the battery cell is further improved.

[0156] In some embodiments, OH1 ≥ OH2.

[0157] Controlling OH1≥OH2 improves the cycle stability of the battery cell during fast charging and is conducive to further improving the energy density of the battery cell.

[0158] In some embodiments, the dimension of the positive electrode active material layer along the length direction of the battery cell is 400 mm to 650 mm.

[0159] The size of the positive electrode active material layer along the length direction of the battery cell is within the above range, and the battery cell has excellent fast charging performance, cycle stability during fast charging, and energy density.

[0160] In some embodiments, the positive electrode active material layer has a dimension in a width direction of the electrode assembly of 90 mm to 130 mm.

[0161] In some embodiments, the dimension of the positive electrode active material layer along the width direction of the electrode assembly may be 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, or any range of values therebetween.

[0162] When the dimension of the positive electrode active material layer along the width direction of the electrode assembly is within the above range, combined with the dimension of the positive electrode active material layer in the length direction, the energy density of the battery cell is improved while facilitating the battery cell to match the usage requirements of electrical devices of different specifications.

[0163] In some embodiments, the negative electrode active material layer has a length in the range of 400 mm to 658 mm along the length direction of the electrode assembly.

[0164] In some embodiments, the dimension of the negative electrode active material layer along the length direction of the electrode assembly may be 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 658 mm, or any range therebetween.

[0165] In some embodiments, the negative electrode active material layer has a dimension in a width direction of the electrode assembly of 90 mm to 130 mm.

[0166] In some embodiments, the dimension of the negative electrode active material layer along the width direction of the electrode assembly may be 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, or any range therebetween.

[0167] When the dimensions of the negative electrode active material layer along the length and width directions of the electrode assembly are within the above range, matching the design of the positive electrode active material layer is beneficial to the comprehensive improvement of the battery cell energy density, fast charging performance and cycle stability during fast charging.

[0168] In some embodiments, reference Figure 3 The positive electrode tab 12111 is arranged at one end of the positive electrode current collecting portion 12110 extending along the length direction of the electrode assembly.

[0169] In some embodiments, reference Figure 5 The negative electrode tab 12211 is arranged at one end of the negative electrode current collecting portion 12210 along the length direction of the electrode assembly.

[0170] The above-mentioned tab arrangement helps to improve the weight energy density of the battery cell.

[0171] In some embodiments, reference Figure 4 The positive electrode tabs 12111 are arranged at both ends of the positive electrode current collecting portion 12110 extending along the length direction of the electrode assembly.

[0172] In some embodiments, reference Figure 6 The negative electrode tabs 12211 are arranged at both ends of the negative electrode current collecting portion 12210 along the length direction of the electrode assembly.

[0173] In some embodiments, the size 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.

[0174] The above-mentioned tab setting helps to improve the overcurrent capacity of the battery cell, alleviate the situation where the temperature on the tab side is too high during fast charging, causing electrolyte decomposition and uneven current distribution to cause lithium deposition on the tab side, thereby improving the fast charging performance of the battery cell and the cycle stability under fast charging. It is particularly suitable for improving the cycle stability of battery cells with a positive electrode active material layer length ranging from 650mm to 950mm under fast charging.

[0175] In some embodiments, a ratio of the width of the positive electrode tab to the width of the positive electrode current collector is 0.25 to 1.

[0176] In some embodiments, a ratio of the width of the negative electrode tab to the width of the negative electrode current collector is 0.25 to 1.

[0177] In some embodiments, the ratio of the width of the positive electrode tab to the width of the positive electrode current collector or the ratio of the width of the negative electrode tab to the width of the negative electrode current collector can be 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, 1, or any range therebetween.

[0178] The ratio of the width of the tab to the width of the current collecting portion being within the above range helps to enhance the current carrying capacity of the battery cell, and improves the fast charging performance of the battery cell and the cycle stability under fast charging.

[0179] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the fluorinated sulfonyl imide lithium salt is 4% to 8%.

[0180] The mass proportion of the fluorinated sulfonyl imide lithium salt is within the above range, which can further take into account the fast charging performance, cycle stability and safety performance of the battery cell under fast charging.

[0181] In some embodiments, the fluorine-containing lithium sulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide LiFSI, lithium bistrifluoromethanesulfonyl imide LiTFSI, and lithium perfluorobutylsulfonyl imide LiFNFSI.

[0182] In some embodiments, the lithium-containing electrolyte salt further includes lithium hexafluorophosphate LiPF6, and based on the total mass of the electrolyte, the total mass of the lithium hexafluorophosphate LiPF6 and the fluorinated sulfonyl imide lithium salt accounts for 10% to 18%.

[0183] In some embodiments, based on the total mass of the electrolyte, the total mass proportion of lithium hexafluorophosphate LiPF6 and fluorinated sulfonyl imide lithium salt can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or any numerical range therebetween.

[0184] Lithium-containing electrolyte salts that also include lithium hexafluorophosphate (LiPF6) can reduce the risk of thermal runaway in battery cells, keeping the risk reduction within a controllable range and further improving the safety performance of the battery cells. Battery cells with a combined mass ratio of lithium hexafluorophosphate (LiPF6) and fluorinated sulfonyl imide salts in the electrolyte within the aforementioned range can further balance the battery cells' fast-charging performance, cycling stability under fast-charging conditions, and safety performance.

[0185] In some embodiments, based on the total mass of the electrolyte, the mass ratio of lithium hexafluorophosphate LiPF6 to the mass ratio of the fluorinated sulfonyl imide lithium salt is 0.9:1 to 4:1.

[0186] In some embodiments, based on the total mass of the electrolyte, the ratio of the mass proportion of lithium hexafluorophosphate LiPF6 to the mass proportion of fluorinated sulfonyl imide lithium 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 numerical range therebetween.

[0187] A battery cell in which the ratio of the mass proportion of lithium hexafluorophosphate LiPF6 to the mass proportion of fluorinated sulfonyl imide lithium salt in the electrolyte is within the above range can further take into account the fast charging performance, cycle stability under fast charging and safety performance of the battery cell.

[0188] In some embodiments, the carboxylate solvent has R ' -COO-R '' The general structural formula, where R ' Including one or more of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, C1-C5 haloalkyl groups, R '' Including one or more of C1-C5 alkyl, C1-C5 halogenated alkyl.

[0189] "C1-C5 alkyl" refers to an unbranched or branched alkyl group having 1 to 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, and 1-ethylpropyl.

[0190] “C1-C5 haloalkyl” refers to an unbranched or branched alkyl group having 1 to 5 carbon atoms in which at least one hydrogen atom is substituted by a halogen, including but not limited to one or more of chloroalkyl, bromoalkyl, and iodoalkyl.

[0191] "Halogen" refers to an element of Group VIIA of the periodic table of chemical elements. Specifically, halogen includes fluorine, chlorine, bromine, iodine or astatine.

[0192] In some embodiments, 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.

[0193] 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.

[0194] Carbonate solvents have a high dielectric constant, which can increase the dissociation rate of lithium ions and anions in lithium-containing electrolyte salts, thereby further comprehensively improving the fast charging performance of battery cells and the cycle stability under fast charging.

[0195] In some embodiments, based on the total mass of the electrolyte, the carbonate solvent accounts for 18% to 75% by mass.

[0196] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the carbonate solvent can be 18%, 30%, 40%, 50%, 60%, 70%, 75% or any range therebetween.

[0197] Due to the high viscosity of carbonate solvents, increasing the carbonate solvent content increases the electrolyte viscosity, negatively impacting the electrolyte's conductivity. By properly controlling the mass percentage of carbonate solvents within the aforementioned range, the electrolyte achieves both an appropriate viscosity and a good dissociation rate, thereby achieving a comprehensive improvement in electrolyte conductivity, which is beneficial for further enhancing the fast-charging performance of battery cells and the cycling stability under fast charging.

[0198] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive.

[0199] Additives refer to components with low content in the electrolyte, which generally account for no more than 10% of the mass of the electrolyte. They are highly targeted and used in small amounts, and can significantly optimize the performance of a certain aspect of the battery without changing the production process.

[0200] In the present application, carbonate additives refer to compounds including carbonate groups (—O—CO—O—) and their derivatives, as well as mixtures containing the above compounds and their derivatives.

[0201] The components of the additives can be obtained by testing using any method known in the art. In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the battery cell has a charged state of approximately 0% SOC) can be reversely disassembled and the free electrolyte obtained from the battery cell can be used as a sample for testing using ion chromatography. The types and contents of organic components in the electrolyte are well known in the art and can be tested using equipment and methods known in the art. For example, reference can be made to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents" to conduct qualitative and quantitative analysis of the organic components of the electrolyte by gas chromatography. The types and contents of inorganic components / lithium salts in the electrolyte are well known in the art and can be detected using equipment and methods known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-2002 "General Rules for Ion Chromatography Analysis Methods".

[0202] In some embodiments, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives.

[0203] Among them, the ethylene carbonate derivatives include compounds represented by formula III,

[0204] Formula III

[0205] 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 haloalkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time. Optionally, the carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

[0206] Carbonate additives can evolve into organic components in the SEI film, improving the toughness of the SEI film, thereby further improving the stability of the SEI film during the battery cell cycle and further reducing the interfacial impedance on the negative electrode side, which is beneficial to further improve the cycle life and fast charging performance of the battery cell.

[0207] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl bissulfate, butylene sulfite, vinyl sulfite, methylene disulfonate, and 1,3 propane sultone.

[0208] Sulfur-containing additives often have a higher potential. Sulfur-containing additives added to the electrolyte will preferentially react 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 detrimental to the stability of the battery cells in high-temperature environments. The presence of sulfur in the SEI film can further enhance the thermal stability of the SEI film at high temperatures and further reduce the interfacial impedance on the negative electrode side, which is beneficial for further improving the cycling stability and fast-charging performance of the battery cells.

[0209] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0210] Lithium salt additives can evolve into inorganic components in the SEI film, increasing the rigidity and thermal stability of the SEI film, further improving the stability of the SEI film and further reducing the interfacial impedance on the negative electrode side, thereby further improving the battery's cycle stability and fast charging performance. Furthermore, these lithium salt additives can form a positive electrode electrolyte interface film (CEI film) on the surface of the positive electrode active material, further improving the cycle stability of the battery cell.

[0211] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 3% to 8%.

[0212] Based on the total mass of the electrolyte, the mass proportion of the additive can be measured using any method known in the art. As an example, the mass proportion of the solvent and lithium-containing electrolyte salt in the electrolyte can be measured using the test method described above. It should be understood that since the additive in the electrolyte will be consumed during the formation and circulation process to form relevant components in the SEI film and / or CEI film, the mass proportion of the additive in the electrolyte may be slightly lower than the initial mass proportion of the additive in the electrolyte.

[0213] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the carbonate additive may be 3%, 4%, 5%, 6%, 7%, 8%, or any range therebetween.

[0214] The mass proportion of carbonate additives in the electrolyte is within the above range, which is beneficial to both improving the stability of the SEI film and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0215] In some embodiments, based on the total mass of the electrolyte, the mass proportion of vinylene carbonate is 2% to 5%.

[0216] In some embodiments, based on the total mass of the electrolyte, the mass proportion of vinylene carbonate can be 2%, 3%, 4%, 5%, or any range therebetween.

[0217] Vinylene carbonate (VC) has a similar reduction potential to carboxylate solvents, which can inhibit the reactivity of carboxylate solvents and improve the cycle life of battery cells. However, excessive VC content can increase the battery's interfacial impedance and charge transfer impedance, hindering the fast-charging performance of the battery cells. A VC mass percentage within the above range ensures that the battery achieves both excellent cycle life and fast-charging performance.

[0218] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 0% to 4%.

[0219] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 1.5% to 3.5%.

[0220] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative can be 0.5%, 1%, 2%, 3%, 4% or any range therebetween.

[0221] It should be noted that as the battery cells charge and discharge, when the amount of ethylene carbonate derivative added is relatively low, the ethylene carbonate derivative content may be 0% when the electrolyte is obtained by gas chromatography after disassembling the battery cells. It is understood that in some embodiments, the ethylene carbonate derivative added to the electrolyte is completely converted into organic components in the SEI film during the formation process. In some embodiments, ethylene carbonate derivatives remain in the electrolyte, reinforcing the SEI film during subsequent battery cell cycling.

[0222] Ethylene carbonate derivatives can also form films on the negative electrode surface at higher potentials and exhibit low interfacial and charge transfer resistance. The mass percentage of ethylene carbonate derivatives within the aforementioned range enables the battery cells to achieve both excellent fast-charging performance and cycle life. By combining vinylene carbonate (VC) and ethylene carbonate derivatives in the electrolyte, the fast-charging performance and cycle stability of the battery cells can be comprehensively improved.

[0223] In some embodiments, the mass proportion of the sulfur-containing additive is 0% to 2% based on the total mass of the electrolyte.

[0224] In some embodiments, the mass proportion of the sulfur-containing additive is 0.5% to 2% based on the total mass of the electrolyte.

[0225] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive may be 0.5%, 1%, 1.5%, 2%, or any range therebetween.

[0226] It should be noted that since the additives in the electrolyte will be consumed during the formation and charge-discharge cycle to generate relevant components in the SEI film and / or CEI film, after disassembling the battery cell to obtain the electrolyte, when testing the content of sulfur-containing additives and lithium salt additives by gas chromatography, the content may be 0%.

[0227] Specifically, taking the case where the mass content of a sulfur-containing additive is 0% as an example, this could be because no sulfur-containing additives were added to the freshly prepared electrolyte, or because the electrolyte obtained after disassembling the battery cell does not contain sulfur-containing additives. In this case, it could be that the freshly prepared electrolyte did not contain sulfur-containing additives, or it could be that a small amount of sulfur-containing additives was added but participated in the SEI film formation reaction during the battery cell formation process, resulting in a mass content of 0% during the test. Alternatively, the freshly prepared electrolyte does contain sulfur-containing additives.

[0228] Furthermore, regarding the addition of certain substances, such as additives, to the electrolyte, the content of additives in the battery cell electrolyte is related to the formation process, different battery life cycles, or different battery storage conditions due to the additives' role in film formation on the surface of the active material. Therefore, the additive content in a freshly prepared electrolyte may differ from that in an electrolyte obtained by reverse disassembling a battery cell. However, those skilled in the art can determine the approximate content range of the relevant substances in the fresh electrolyte based on the performance level of the battery cell (such as the number of cycles) and residual content. Similarly, those skilled in the art can also determine the approximate content range of the corresponding non-freshly prepared (i.e., after reverse disassembly) electrolyte based on the content of the freshly prepared additives, the performance requirements for the battery cell, the storage environment, etc.

[0229] Therefore, the additive content mentioned in the technical solution of the present application can be the content of the additive actively added to the fresh electrolyte, or it can be the content of the residual additive detected by reverse detection based on the actual battery status.

[0230] It is understood that in some embodiments, the sulfur-containing additive added to the electrolyte is completely converted into sulfur-containing components in the SEI film during the formation process. The amount of sulfur-containing additive added to the electrolyte can be inferred by X-ray photoelectron spectroscopy (XPS) testing of the negative electrode material. In some embodiments, the sulfur-containing additive may remain in the electrolyte, reinforcing the SEI film during subsequent battery cell cycling.

[0231] In this application, X-ray photoelectron spectroscopy (XPS) of the negative electrode material can be tested by any method known in the art. As an example, after disassembling the battery cell, the negative electrode plate is cleaned with a solvent such as dimethyl carbonate (DMC) three or more times, and then a powder sample is scraped off. The resulting negative electrode material powder is adhered to a conductive substrate and X-ray photoelectron spectroscopy is performed using an X-ray photoelectron spectrometer (such as AXIS ULTRA). The scan rate and time of the X-ray source are adjusted to focus and detect elements and functional groups at a depth of 5nm to 10nm from the surface of the negative electrode material. The X-ray photoelectron spectroscopy (XPS) spectrum of the sample is obtained, and the characteristic element peaks in the spectrum are analyzed.

[0232] The mass proportion of sulfur-containing additives in the electrolyte is within the above range, which is beneficial to both improving the thermal stability of the SEI film at high temperatures and maintaining an appropriate viscosity of the electrolyte, and further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0233] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

[0234] In some embodiments, the mass proportion of the lithium salt additive is 0.2% to 1% based on the total mass of the electrolyte.

[0235] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2%, 0.4%, 0.6%, 0.8%, 1%, or any range therebetween.

[0236] It is 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, the lithium salt additive still remains in the electrolyte, which strengthens the SEI film and / or CEI film during subsequent battery cell cycling.

[0237] The mass proportion of lithium salt additives in the electrolyte is within the above range, which is beneficial to both improving the stability of the SEI film and maintaining an appropriate viscosity of the electrolyte, and further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0238] In some embodiments, the positive electrode active material includes: an olivine-structured lithium-containing phosphate, and a coating layer, wherein the coating layer is located on at least a portion of the surface of the lithium-containing phosphate, and the coating layer contains carbon.

[0239] The coating layer contains carbon elements, which is beneficial to improving the electronic conductivity of lithium-containing phosphates and improving the solid-phase transmission rate of electrons, thereby further improving the energy density and fast charging performance of the battery cells.

[0240] In some embodiments, based on the total mass of the positive electrode active material, the mass proportion of carbon element is 0.8% to 2.3%.

[0241] In some embodiments, based on the total mass of the positive electrode active material, the mass proportion of carbon element may be 0.8%, 1.1%, 1.4%, 1.7%, 2.0%, 2.3%, or any range therebetween.

[0242] Based on the total mass of the positive electrode active material, the mass proportion of the carbon element is within the above range, so that the lithium-containing phosphate has both excellent electronic conductivity and gram capacity, further comprehensively improving the energy density and fast charging performance of the battery cell.

[0243] In some embodiments, the coating layer further comprises a component as shown in Formula I,

[0244] Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I,

[0245] Wherein, 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, M1 includes one or more of Ti, Zr, Hf, Ge, and Sn, and optionally, M1 has a valence of +4.

[0246] In some embodiments, d1 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any range therebetween, m1 can be selected as 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 any range therebetween, and n1 can be selected as 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 any range therebetween.

[0247] In some embodiments, the component represented by Formula I includes one or more of Li2FeTi(PO4)3, Li2FeZr(PO4)3, and Li2FeSn(PO4)3.

[0248] It should be noted that the coating layer can be a single-layer structure or a multi-layer structure, that is, the carbon-containing component in the coating layer and the component shown in Formula I can be a mixed phase or can be arranged in layers.

[0249] The physical structure of the coating layer can be characterized by any method known in the art. For example, by characterizing the positive electrode active material through transmission electron microscopy, it can be seen that the coating layer and the matrix of the positive electrode active material have different physical structures. Combining diffraction patterns and energy spectrum analysis, the composition of the coating layer can be judged.

[0250] The component shown in Formula I is a fast ion conductor with a NASICON structure. Its ionic conductivity approaches or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has abundant three-dimensional lithium ion diffusion and transport channels, and has advantages such as high ion conduction efficiency and strong structural stability during multiple lithium de- and lithium insertion processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly increase the lithium ion transmission rate during multiple lithium de- and lithium insertion at the positive terminal, improve the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0251] In some embodiments, the lithium-containing phosphate includes a component as shown in Formula II,

[0252] Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II,

[0253] 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; and Y includes one or more of O and F.

[0254] In some embodiments, x1 can be selected as 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any range therebetween, y1 can be selected as 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 any range therebetween, x1+y1 can be selected as 0.9, 1, 1.1, 1.2, 1.3 or any range therebetween, a1 can be selected as 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any range therebetween, b1 can be selected as wherein a1+b1 is 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any range therebetween; c1 is 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any range therebetween; z1 is 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 any range therebetween.

[0255] The lithium-containing phosphate with an olivine structure having the above components has good structural stability, can reduce the loss during the fast charging process, and further improve the fast charging performance and cycle stability of the battery cell.

[0256] 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 of the foregoing substances, wherein the modified form includes one or more of doping modification and coating modification.

[0257] In some embodiments, the compaction density of the positive electrode active material layer is 2.50 g / cm 3 to 2.80g / cm 3 .

[0258] In this application, the compacted density of the positive electrode active material layer has a meaning well known in the art and can be tested using methods known in the art. For example, a battery cell is charged at a constant current charge rate of 0.33C to a cutoff voltage (e.g., 3.65V), left to stand for 1 minute, and then charged at a constant voltage of 3.65V to a current less than 0.05C. At this point, the battery cell is fully charged. The positive electrode sheet is then disassembled and the compacted density of the positive electrode active material layer is measured. The compacted density of the positive electrode active material layer is the single-sided coating mass of the positive electrode active material layer measured after disassembly / the single-sided thickness of the positive electrode active material layer.

[0259] The “mass of the positive electrode active material layer coated on one side” refers to the mass of the positive electrode active material layer per unit area on one side of the current collector.

[0260] In this application, the single-sided coating quality of the positive electrode active material layer can be tested using methods known in the art. For example, the positive electrode sheet can be taken from the disassembled battery (if it is a double-sided coated positive electrode sheet, the positive electrode active material layer on one side can be wiped off first), punched into small discs with an area of S1, and the mass is measured and recorded as M1. Then, the positive electrode active material layer of the weighed positive electrode sheet is wiped off, and the mass of the positive electrode current collector is weighed and recorded as M0. The single-sided coating weight of the positive electrode sheet = (M1-M0) / S1.

[0261] The thickness of the positive electrode active material layer is well known in the art and can be measured using methods known in the art, such as using a micrometer (e.g., Mitutoyo 293-100, with an accuracy of 0.1 μm). It is understood that when a battery cell is fully charged, the compaction density of the positive electrode active material layer differs from the design compaction density of the battery cell. Due to actual operational influences, the compaction density of the positive electrode active material layer when a battery cell is fully charged is often slightly lower than the design compaction density of the battery cell.

[0262] In some embodiments, the compaction density of the positive electrode active material layer may be 2.50 g / cm 3 , 2.55g / cm 3 , 2.60g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.75g / cm 3 , 2.80g / cm 3 or any range of values between them.

[0263] The positive electrode active material layer with a compaction density within the above range can further achieve a balance between the fast charging performance and energy density of the battery cell.

[0264] In some embodiments, 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 .

[0265] In some embodiments, the single-sided coating mass of the positive electrode active material layer is 200 mg / 1540.25 mm 2 、210mg / 1540.25mm 2 、220mg / 1540.25mm 2 、230mg / 1540.25mm 2、240mg / 1540.25mm 2 、250mg / 1540.25mm 2 、260mg / 1540.25mm 2 、270mg / 1540.25mm 2 、280mg / 1540.25mm 2 、290mg / 1540.25mm 2 、300mg / 1540.25mm 2 、310mg / 1540.25mm 2 、320mg / 1540.25mm 2 、330mg / 1540.25mm 2 、340mg / 1540.25mm 2 、350mg / 1540.25mm 2 、360mg / 1540.25mm 2 、370mg / 1540.25mm 2 or any range of values between them.

[0266] The positive electrode active material layer having a single-side coating mass within the above range can further effectively balance the fast charging performance and energy density of the battery cell.

[0267] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0268] The materials for the positive and / or negative electrode current collectors are not particularly limited, as long as they do not cause chemical changes in the battery cells and are conductive. The current collectors include metal foils with a pure metal content of 95% or more, such as at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, and nickel foil. They also include alloy foils containing at least two main elements, such as copper, aluminum, nickel, titanium, and iron. They can also include copper, aluminum-cadmium alloys, iron, or stainless steel surface-treated with carbon, nickel, titanium, silver, or copper. Furthermore, fine concave-convex surfaces can be formed to enhance the binding force with the negative electrode active material. The current collectors can be used in various forms, such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0269] In some embodiments, the thickness of the positive electrode current collector may be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any range therebetween.

[0270] The positive electrode current collector has a relatively low thickness, which enables further improvement in the energy density of the battery cell.

[0271] In some embodiments, the positive electrode active material layer may further optionally include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0272] In some embodiments, the positive electrode active material layer may further include a conductive agent. For 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.

[0273] In some embodiments, the positive electrode plate further includes a positive electrode conductive layer, which is 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, which is located between the negative electrode current collector and the negative electrode active material layer on at least one side, and the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

[0274] In some embodiments, the thickness of the positive electrode conductive layer or the negative electrode conductive layer can be 0.5µm, 0.6µm, 0.7µm, 0.8µm, 0.9µm, 1.0µm, 1.1µm, 1.2µm, 1.3µm, 1.4µm, 1.5µm, 1.6µm, 1.7µm, 1.8µm, 1.9µm, 2.0µm, or any range therebetween.

[0275] 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 pole piece, and is beneficial to further improving the fast charging performance of the battery cell.

[0276] In some embodiments, 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, and the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylate resin.

[0277] In some embodiments, the negative active material layer includes a negative active material, and the negative active material includes a carbon-based material.

[0278] In some embodiments, the carbon-based material includes one or more of graphite and hard carbon.

[0279] In some embodiments, the carbon-based material includes composite graphite particles, the composite graphite particles include graphite particles and a carbon coating layer coated on at least a portion of the surface of the graphite particles, the graphite particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0280] Secondary particles are particles formed by the aggregation of two or more primary particles. Composite graphite particles, including secondary particles and a surface coating including amorphous carbon, facilitate the infiltration of electrolyte into the negative electrode active layer of the electrode and enhance the solid-phase transport capacity of active ions, contributing to further improvement in the fast-charging performance of battery cells.

[0281] In some embodiments, the amorphous carbon accounts for 2% to 5% by weight based on the total weight of the composite graphite particles.

[0282] In some embodiments, the mass percentage of amorphous carbon based on the total mass of the composite graphite particles may be 2%, 3%, 4%, 5%, or any range therebetween.

[0283] When the content of amorphous carbon is within an appropriate range, the composite graphite material can have a high gram capacity while also having a high active ion solid-phase transport ability, which is conducive to further comprehensive improvement of the energy density and fast charging performance of the battery cell.

[0284] In some embodiments, the negative electrode active material layer may further 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).

[0285] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0286] In some embodiments, the composite graphite particles have a volume average particle size Dv50 of 9.5 μm to 13.5 μm.

[0287] "Volume average particle size Dv50" is well known in the art and represents the particle size corresponding to the 50% cumulative volume distribution percentage of a material. It can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, as per GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK. The composite graphite particles can be freshly prepared or scraped from the negative electrode active material layer after disassembly of a battery cell. For example, discharge the battery to 0% SOC, then disassemble and take out the negative electrode, scrape a certain amount of powder on the electrode with a blade, and then use deionized water to clean it repeatedly by shaking for 5 to 10 times. After drying, sinter it in a tube furnace at 400°C for 2 hours. After sintering, take an appropriate amount of the sample to be tested (the sample concentration can ensure 8%-12% shading), add deionized water, and ultrasonically disperse it to ensure that the sample is completely dispersed. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0288] 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 any range therebetween.

[0289] The volume average particle size Dv50 of the composite graphite particles is within the above range, which shortens the solid phase migration path of lithium ions while taking into account lower reaction activity, thereby taking into account the fast charging capability and cycle life of the battery cell.

[0290] 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.

[0291] In some embodiments, the silicon-based material includes one or more of a silicon-carbon material, a silicon-oxygen material, and a silicon-nitrogen material.

[0292] In some embodiments, the mass proportion of silicon element is 0.5% to 5% based on the total mass of the negative electrode active material layer.

[0293] The qualitative and quantitative determination of each substance or element in this application can be carried out using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single 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 proportion of silicon element has a meaning well known in the art and can be tested using methods known in the art. For example, the negative electrode plate is placed in a solvent such as water for immersion, the negative electrode active material is separated from the negative electrode current collector, and the various substances in the negative electrode active material layer are obtained by filtration. This is used as a test sample. The test sample is analyzed using an ICAP7400 model inductively coupled plasma-emission spectrometer from Thermo Fisher Scientific, USA, and in accordance with the GB / T30902-2014 standard to obtain the silicon element content.

[0294] 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 numerical range therebetween.

[0295] The introduction of silicon-based materials helps further improve the energy density of battery cells. Based on the total mass of the negative electrode active material layer, the silicon mass percentage is within the above mass range, achieving a balance between the energy density and cycle stability of the battery cells.

[0296] In some embodiments, the single-side coating mass of the negative electrode active material layer is 90 mg / 1540.25 mm 2 Up to 140mg / 1540.25mm 2 .

[0297] The single-side coating quality of the negative electrode active material layer can be tested by a method similar to the single-side coating quality of the positive electrode active material layer described above.

[0298] In some embodiments, the single-side coating mass of the negative electrode active material layer can be 90 mg / 1540.25 mm 2 、100mg / 1540.25mm 2 、110mg / 1540.25mm 2 、120mg / 1540.25mm 2 、130mg / 1540.25mm 2 、140mg / 1540.25mm 2 or any range of values between them.

[0299] The negative electrode active material layer with a single-side coating mass within the above range can cooperate with the positive electrode active material layer to achieve a balance between the energy density and fast charging performance of the battery cell.

[0300] In some embodiments, the porosity of the separator is 20% to 70%, and optionally 35% to 60%.

[0301] In this application, porosity refers to the percentage of the pore volume within the separator to the total volume of the separator. Porosity can be tested according to the standard GB / T 36363-2018, "Polyolefin Separators for Battery Cells." It should be noted that the actual testing process may vary slightly from the standard to obtain a more accurate test value, depending on instrument differences, test errors, and to minimize the impact of porosity on the test.

[0302] In some embodiments, the porosity of the separator may be 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range therebetween.

[0303] The porosity of the isolation membrane within the above range is beneficial for further taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0304] In some embodiments, reference Figure 7 The isolation film 123 includes: a base film 1231; a first functional layer 1232, located on at least one side of the base film 1231, the first functional layer 1232 includes a first inorganic substance; a second functional layer 1233, located on a side of the first functional layer 1232 away from the base film 1231, the second functional layer 1232 includes a second inorganic substance and non-fluoropolymer particles.

[0305] In some embodiments, the non-fluoropolymer particles include an acrylate copolymer.

[0306] In some embodiments, the first inorganic material and the second inorganic material 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.

[0307] Inorganic particles enhance the electrolyte wettability and heat resistance of the first and second functional layers, further improving the battery's fast-charging performance, cycling stability, and safety. Non-fluoropolymer particles enhance the processability and stability of the separator, preventing internal short circuits caused by the separator's movement within the battery cell, further improving the battery's cycling stability and safety.

[0308] In some embodiments, the base film comprises one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film can be a single-layer film or a multi-layer composite film, without particular limitation.

[0309] In some embodiments, the base film has a thickness of 4 μm to 12 μm, optionally 5 μm to 9 μm.

[0310] In the present application, the thickness of the base film can be tested by a micrometer.

[0311] In some embodiments, the thickness of the base film may be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any range therebetween.

[0312] The thickness of the base film within the above range is beneficial for further taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0313] In some embodiments, reference Figure 8 The battery cell 1 includes a shell 11 and a cover assembly. The cover assembly is arranged at at least one end of the shell 11. The shell 11 and the cover assembly define an accommodating cavity. The electrode assembly is arranged in the accommodating cavity. The wall thickness of the shell 111 on the large surface of the battery cell is 0.1mm to 0.5mm.

[0314] In some embodiments, the thickness of the shell wall of the battery cell's large surface is 0.2 mm to 0.35 mm.

[0315] In some embodiments, the shell wall thickness of the large surface of the battery cell may 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 any range of values therebetween.

[0316] The shell wall thickness of the large surface of the battery cell is within the above range, which is conducive to further improving the energy density of the battery cell.

[0317] In some embodiments, the cover plate assembly includes a first cover plate assembly and a second cover plate assembly, and the first cover plate assembly and the second cover plate assembly are arranged at both ends of the length direction or width direction of the shell, 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, and the polarities of the first electrode terminal and the second electrode terminal are opposite.

[0318] In some embodiments, reference Figure 9The 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.

[0319] Therefore, the temperature rise of the battery cell and the impedance of the battery cell are reduced during charging, which is beneficial to improving the fast charging performance, cycle life and safety performance of the battery cell.

[0320] In some embodiments, the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S and meets 150mm 2 ≤S≤1000mm 2 .

[0321] 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, 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.

[0322] In the present application, when testing the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal, the minimum cross-sectional area can be calculated based on the shape of the minimum cross-sectional area and the area calculation formula thereof. For example, if the minimum cross-sectional area 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-sectional area is square, the minimum cross-sectional area can be obtained by measuring the length and width of the square.

[0323] In some embodiments, the minimum cross-sectional area S of the first electrode terminal and / or the second electrode terminal may 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 within the range of any of the above numerical values.

[0324] The minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is within the above range, which is beneficial to improving the current carrying capacity of the battery cell, reducing the heat generation of the electrode terminal, and reducing the internal resistance of the battery cell, thereby improving the fast charging performance and cycle stability of the battery cell.

[0325] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a lamination process.

[0326] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0327] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0328] The present application has no particular restrictions on the shape of the battery cell, which can be square or any other shape. For example, Figure 8 The battery cell 1 is a square structure as an example.

[0329] In some embodiments, reference Figure 8 The outer packaging may include a shell 11 and a cover assembly. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover assembly can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly through a lamination process. The electrode assembly is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly. The number of electrode assemblies contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0330] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0331] Optionally, the battery module may further include a housing having an accommodation space, wherein the plurality of battery cells are accommodated in the accommodation space.

[0332] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0333] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device comprises at least one of a battery module, a battery pack, and an energy storage battery.

[0334] In addition, the third aspect of the present application further provides an electrical device, comprising the battery cell provided in the first aspect of the present application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0335] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0336] Figure 9 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cells in this device, a battery pack or battery module can be used.

[0337] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0338] An embodiment of the present application also provides an energy storage device that uses a battery as a power source. The energy storage device may 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.

[0339] Example

[0340] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0341] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0342] Example 1

[0343] (1) Preparation of positive electrode

[0344] The positive electrode sheet includes a positive electrode current collector, a positive electrode conductive layer on the positive electrode current collector, and a positive electrode active material layer. The positive electrode current collector is an aluminum foil with a thickness of 13 μm.

[0345] The positive electrode conductive layer on the positive electrode current collector is an active material layer formed by evenly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride (PVDF) and the solvent N-methylpyrrolidone NMP, and then coating it on the current collector surface and drying it. The thickness is 1μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0346] The positive electrode active material, the binder polyvinylidene fluoride, and the conductive agent acetylene black are mixed in a ratio of 97:2:1, and then the solvent N-methylpyrrolidone (NMP) is added and stirred into a positive electrode slurry, wherein the positive electrode active material includes lithium iron phosphate, and the lithium iron phosphate has a coating layer, which is coated on the surface of the lithium iron phosphate particles. The coating layer includes lithium iron titanium phosphate Li2FeTi(PO4)3 and carbon element, and the mass content of the carbon element is 1.12%.

[0347] The positive electrode conductive slurry is evenly coated on the positive electrode current collector aluminum foil, the thickness of the positive electrode current collector aluminum foil is 13µm; after drying, the positive electrode conductive layer is obtained; the positive electrode slurry is evenly coated on the positive electrode conductive layer, dried, and cold pressed to obtain the positive electrode sheet. The single-sided coating weight of the positive electrode active material layer is 270mg / 1540.25mm 2 .

[0348] (2) Preparation of negative electrode sheet

[0349] The negative electrode sheet includes a negative electrode current collector, a negative electrode conductive layer on the negative electrode current collector, and a negative electrode active material layer. The negative electrode current collector is a copper foil with a thickness of 5 μm.

[0350] The negative electrode conductive layer on the negative electrode current collector is an active material layer formed by uniformly mixing superconducting carbon as a negative electrode conductive agent, styrene-butadiene rubber (SBR) as a negative electrode binder, sodium carboxymethyl cellulose (CMC-Na) as a thickener, and solvent water, and then coating and drying on the surface of the negative electrode current collector. The thickness is 1 μm, and the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0351] The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer is located on the surface of the negative electrode conductive layer, and the second negative electrode active material layer is located on the surface of the first negative electrode active material layer;

[0352] The first negative electrode active material layer includes composite graphite particles, silicon-carbon material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in 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 includes composite graphite particles, silicon-carbon material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 94:3.5:0.5:1:1, and the Dv50 of the composite graphite particles is 11.3 μm;

[0353] The silicon-carbon material contains 48% silicon. Based on the total mass of the negative electrode active material layer, the silicon content accounts for 1.68% by mass. The composite graphite particles include graphite particles and a carbon coating layer coated on at least a portion of the surface of the graphite particles. The carbon coating layer includes amorphous carbon, which accounts for 3.5% by mass of the total mass of the composite graphite particles.

[0354] The first negative electrode slurry is evenly 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, dried, and cold pressed to obtain a negative electrode sheet. The thickness ratio of the first active material layer and 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 .

[0355] (3) Preparation of electrolyte

[0356] The electrolyte solution includes a solvent, a lithium-containing electrolyte salt, and additives.

[0357] The solvent includes 41.7% by weight of a chain carboxylic acid ester solvent (22% ethyl acetate and 19.7% methyl acetate), 27.3% ethylene carbonate, and 6.7% dimethyl carbonate. The mass proportion of each component in the solvent is calculated based on the total mass of the electrolyte;

[0358] 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, vinyl sulfite ES and lithium difluorooxalatoborate LiDFOB in a mass ratio of 4:2.5:2:0.8;

[0359] Based on the total mass of the electrolyte, the lithium-containing electrolyte salt includes 5% by mass of lithium bis(fluorosulfonyl)imide LiFSI and 10% by mass of lithium hexafluorophosphate LiPF6.

[0360] (4) Preparation of isolation membrane

[0361] The isolation membrane includes a base membrane and a functional layer. The base membrane is a polyethylene film layer with a thickness of 5 μm and a porosity of 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 aluminum oxide particles and a binder polyvinylidene fluoride on one side of the base membrane. The thickness is 1 μm, and the average particle size of the aluminum oxide particles is 10 nm. The second functional layer is a film layer formed by coating composite particles formed by polyacrylate and calcium oxide particles dispersed on polyacrylate on the surface of the first functional layer. The thickness is 5 μm, and the average particle size of the calcium oxide particles is 10 nm.

[0362] (5) Preparation of battery cells

[0363] The above-mentioned positive electrode sheets, separators, and negative electrode sheets are stacked in order, so that the separator is placed between the positive electrode sheets and the negative electrode sheets to play an isolating role. The positive electrode sheets and the negative electrode sheets have tabs on one side respectively, and the positive and negative poles are located on both sides of the length direction of the battery cell. The ratio of the width of the positive and negative pole tabs to the width of the current collector is 0.5 to obtain a laminated electrode assembly. The electrode assembly is placed in a shell, and after drying, the electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained. Among them, the size of the positive active material layer along the length direction of the electrode assembly is 400mm, and OH1 is 4mm; the size of the positive active material layer along the width direction of the electrode assembly is 96mm, and OH2 is 3mm. The shell is an aluminum shell, and the shell wall thickness of the large surface of the battery cell is 0.35mm. The compaction density of the positive active material layer when the battery is fully charged is 2.75g / cm 3 The compaction density of the negative electrode active material layer is 1.26 g / cm 3 .

[0364] Examples 1-5

[0365] The preparation methods of Examples 1-5 are basically the same as that of Example 1, except that some parameters in the battery cells are adjusted, as shown in Table 1.

[0366] Example 6

[0367] The preparation method of Example 6 is basically the same as that of Example 3, except that tabs are provided on both sides of the positive electrode sheet and the negative electrode sheet, and the ratio of the width of the positive and negative electrode tabs to the width of the current collecting portion is 1 / 3, as shown in Table 1.

[0368] Examples 7-8

[0369] The preparation methods of Examples 7-8 are basically the same as those of Example 6, except that some parameters in the battery cells are adjusted, as shown in Table 1.

[0370] Examples 9-10

[0371] The preparation methods of Examples 9-10 are basically the same as those of Example 1, except that some parameters in the battery cells are adjusted, as shown in Table 1.

[0372] Examples 11-12

[0373] The preparation method of Examples 11-12 is 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 is changed accordingly, as shown in Table 2. The single-sided coating mass of the positive electrode active material layer of Example 11 is 243 mg / 1540.25 mm 2 The single-sided coating mass of the negative electrode active material layer is 100 mg / 1540.25 mm 2 .

[0374] Examples 13-14

[0375] The preparation methods of Examples 13-14 are basically the same as those of Example 1, except that the composition of the lithium electrolyte salt in the electrolyte is adjusted, as shown in Table 2.

[0376] Examples 15-16

[0377] The preparation methods of Examples 15-16 are basically the same as those 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.

[0378] Example 17

[0379] The preparation method of Example 17 is substantially the same as that of Example 1, except that the negative electrode active material does not include a silicon-based material, as follows:

[0380] The first negative electrode active material layer includes composite graphite particles, acetylene black as a conductive agent, styrene-butadiene rubber as a binder, and sodium carboxymethyl cellulose as a thickener in a mass ratio of 96.5:0.5:2:1, wherein the Dv50 of the composite graphite particles is 11.3 μm;

[0381] The second negative electrode active material layer includes composite graphite particles, acetylene black as a conductive agent, styrene butadiene rubber as a binder, and sodium carboxymethyl cellulose as a thickener in a mass ratio of 97.5:0.5:1:1, wherein the Dv50 of the composite graphite particles is 11.3 μm;

[0382] The first negative electrode slurry is evenly 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, dried, and cold pressed to obtain a negative electrode sheet. The thickness ratio of the first active material layer and the second active material layer is 1:1; based on the total mass of the negative electrode active material layer, the single-side coating mass of the negative electrode active material layer is 111 mg / 1540.25 mm 2Since the negative electrode does not contain silicon, the single-sided coating mass of the positive electrode active material layer is 240 mg / 1540.25 mm 2 .

[0383] Comparative Examples 1-8

[0384] The preparation methods of Comparative Examples 1-8 are basically the same as those of Example 1, except that some parameters of the battery cells are adjusted, as shown in Tables 1 and 2. The single-side coating mass of the positive electrode sheet of Comparative Example 5 is 196 mg / 1540.25 mm 2 The single-sided coating mass of the negative electrode is 80mg / 1540.25mm 2 .

[0385] Test Method

[0386] 1. 30℃ cycle process 1 cycle decay to 90% SOH cycle number

[0387] The battery cells were subjected to charge and discharge cycles at 30°C. The charging step included the following steps:

[0388] Charge from 0% SOC to 5% SOC at 5.0C constant current;

[0389] Charge from 5% SOC to 10% SOC at 5.0C constant current;

[0390] Charge from 10% SOC to 15% SOC at 5.0C constant current;

[0391] Charge from 15% SOC to 20% SOC at 5.0C constant current;

[0392] Charge from 20% SOC to 25% SOC at 5.0C constant current;

[0393] Charge from 25% SOC to 30% SOC at 5.0C constant current;

[0394] Charge from 30% SOC to 35% SOC at 5.0C constant current;

[0395] Charge from 35% SOC to 40% SOC at 5.0C constant current;

[0396] Charge from 40% SOC to 45% SOC at 4.6C constant current;

[0397] Charge from 45% SOC to 50% SOC at 4.3C constant current;

[0398] Charge from 50% SOC to 55% SOC at 4.0C constant current;

[0399] Charge from 55% SOC to 60% SOC at 3.7C constant current;

[0400] Charge from 60% SOC to 65% SOC at 3.4C constant current;

[0401] Charge from 65% SOC to 70% SOC at 3.1C constant current;

[0402] Charge from 70% SOC to 75% SOC at 2.9C constant current;

[0403] Charge from 75% SOC to 80% SOC at 2.7C constant current;

[0404] Charge from 80% SOC to 85% SOC at 1.8C constant current;

[0405] Charge from 85% SOC to 90% SOC at 1.3C constant current;

[0406] Charge from 90% SOC to 95% SOC at 0.7C constant current;

[0407] Charge from 95% SOC to 98% SOC at 0.33C constant current;

[0408] Charge from 98% SOC to 100% SOC at 0.1C constant current.

[0409] 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.

[0410] The discharge strategy is as follows: discharge at a constant current of 1C to a cut-off voltage of 3.1V.

[0411] This is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., Cn / C0 × 100%) reaches 90%. Record the number of cycles. A higher number of cycles indicates better cycling performance during fast charging of the battery cell.

[0412] 2. The number of cycles required for the 2-cycle decay to 90% SOH at 30℃

[0413] The battery cells were subjected to charge and discharge cycles at 30°C. The charging step included the following steps:

[0414] Charge from 0% SOC to 5% SOC at 8.0C constant current;

[0415] Charge from 5% SOC to 10% SOC at 8.0C constant current;

[0416] Charge from 10% SOC to 15% SOC at 8.0C constant current;

[0417] Charge from 15% SOC to 20% SOC at 8.0C constant current;

[0418] Charge from 20% SOC to 25% SOC at 7.5C constant current;

[0419] Charge from 25% SOC to 30% SOC at 7.0C constant current;

[0420] Charge from 30% SOC to 35% SOC at 6.6C constant current;

[0421] Charge from 35% SOC to 40% SOC at 6.2C constant current;

[0422] Charge from 40% SOC to 45% SOC at 5.8 C constant current;

[0423] Charge from 45% SOC to 50% SOC at 5.4C constant current;

[0424] Charge from 50% SOC to 55% SOC at 5.0C constant current;

[0425] Charge from 55% SOC to 60% SOC at 4.6C constant current;

[0426] Charge from 60% SOC to 65% SOC at 4.3C constant current;

[0427] Charge from 65% SOC to 70% SOC at 3.8C constant current;

[0428] Charge from 70% SOC to 75% SOC at 3.5C constant current;

[0429] Charge from 75% SOC to 80% SOC at 3.3C constant current;

[0430] Charge from 80% SOC to 85% SOC at 2.2C constant current;

[0431] Charge from 85% SOC to 90% SOC at 1.6C constant current;

[0432] Charge from 90% SOC to 95% SOC at 0.9C constant current;

[0433] Charge from 95% SOC to 98% SOC at 0.4C constant current;

[0434] Charge from 98% SOC to 100% SOC at 0.2C constant current.

[0435] 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.

[0436] The discharge strategy is as follows: discharge at a constant current of 1C to a cut-off voltage of 3.1V.

[0437] This is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., Cn / C0 × 100%) reaches 90%. Record the number of cycles. A higher number of cycles indicates better cycling performance during fast charging of the battery cell.

[0438] 3. Volumetric energy density

[0439] Place the battery cell at 25°C, charge it to 3.65V at a constant current of 0.33C, then charge it to 0.05C at a constant voltage, and let it rest for 30 minutes; discharge it to 2.0V at a constant current of 0.33C, and record the discharge capacity A0 at this time, in Ah; use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the battery casing size, excluding the electrode terminal height and the insulating film outside the casing), and calculate the volume of the single cell V0, in L; the battery cell volume energy density VED = (A0 × discharge platform voltage) / V0, in Wh / L.

[0440] 4. Parameter test method for battery thermal runaway:

[0441] ① Charge adjustment: At 25°C, charge the lithium-ion battery to 3.65V at a constant current of 0.33C and let it stand for 1 minute; then charge it to 3.65V at a constant current of 0.1C and adjust the battery to 100% SOC.

[0442] ② Overcharge to thermal runaway test: Place the battery in a test fixture with a clamp force of 3000N and charge at a constant current rate of 1C until the cell experiences thermal runaway. After the battery cools to room temperature, observe the state of the thermal runaway cell. If fire or explosion occurs, the thermal runaway boundary has deteriorated.

[0443] Test results

[0444] Table 1

[0445]

[0446] Table 2

[0447]

[0448] Table 3

[0449]

[0450] Table 4

[0451]

[0452] According to the comparison between the embodiments of the present application and the comparative example, it can be seen that the positive electrode tab is arranged at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly, and the size of the positive electrode active material layer along the length direction of the electrode assembly is 300mm to 950mm; 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 greater than 1mm and less than 5mm; 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 greater than 1mm and less than or equal to 4mm; based on the total mass of the electrolyte, the mass proportion of the carboxylic acid ester solvent is 8% to 57%, and the mass proportion of the fluorinated sulfonyl imide lithium 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, thereby achieving a comprehensive improvement in battery performance.

[0453] From the comparison between Examples 1 and 3 and Examples 2 and 4, and between Examples 6 and 8 and Example 7, it can be seen that the size of the positive electrode active material layer along the length direction of the electrode assembly is 400 mm to 650 mm, and the active material layer battery cell takes into account the improvement of the energy density of the battery cell and the cycle stability under fast charging.

[0454] As can be seen from Examples 1-8, the size of the positive electrode 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.

[0455] From the comparison between Example 3 and Example 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 arranged 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 a positive electrode active material layer length size in the range of 650mm-950mm under fast charging.

[0456] From the comparison between Examples 1 and 9 and Example 10, it can be seen that 1.5≤OH1≤4, 1.5≤OH2≤3, the energy density of the battery cell is further improved while taking into account good cycle stability under fast charging.

[0457] It can be seen from Examples 1, 11, and 12 that, based on the total mass of the electrolyte, the mass proportion of the carbonate solvent is 18% to 70%, and the battery cell has excellent cycle stability under fast charging while also having excellent energy density.

[0458] It can be seen from Examples 1, 11, and 12 that, based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 3% to 8%, and the battery cell has excellent cycle stability under fast charging while also having excellent energy density.

[0459] It can be seen from Examples 1, 11, and 12 that based on the total mass of the electrolyte, the mass proportion of vinylene carbonate is 2% to 5%, and the battery cell has excellent cycle stability under fast charging while also having excellent energy density.

[0460] From the comparison between Example 1 and Examples 13 and 14, it can be seen that the mass proportion of the fluorinated sulfonyl imide lithium salt is 4% to 8% based on the total mass of the electrolyte, and the cycle stability of the battery cell under fast charging is further improved.

[0461] It can be seen from Examples 1 and 9-11 that the mass ratio of lithium hexafluorophosphate LiPF6 to the mass ratio of fluorinated sulfonyl imide lithium salt is 0.9:1 to 4:1, and the battery cell has excellent energy density and cycle stability under fast charging.

[0462] It can be seen from Examples 1 and 15 that the mass proportion of the sulfur-containing additive is 0.5% to 2%, and the battery cell has excellent energy density and cycle stability under fast charging.

[0463] It can be seen from Examples 1 and 16 that the mass proportion of the lithium salt additive is 0.2% to 1%, and the battery cell has excellent energy density and cycle stability under fast charging.

[0464] From the comparison between Example 1 and Example 17, it can be seen that the inclusion of silicon-based materials in the negative electrode active material is beneficial to further improving the energy density of the battery cell while also taking into account excellent cycle stability under fast charging.

[0465] It should be noted that the present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present disclosure, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present disclosure. In addition, without departing from the scope of the present disclosure, other methods of constructing the embodiments by applying various modifications that can be imagined by those skilled in the art and 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 stacked in sequence, the positive electrode sheet comprises a positive current collector and a positive electrode active material layer arranged on at least one side of the positive current collector, the positive current collector comprises a positive current collecting portion and a positive electrode tab, the positive electrode tab being arranged at at least one end of the positive current collecting portion extending along the length direction of the electrode assembly; the negative electrode sheet comprises a negative current collector and a negative electrode active material layer arranged on at least one side of the negative current collector, the negative current collector comprises a negative current collecting portion and a negative electrode tab, the negative electrode tab being arranged at at least one end of the negative 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 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 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 size difference between the negative electrode active material layer and the positive electrode active material layer is OH2, and OH2 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 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, wherein: 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 positive electrode active material layer has a dimension in a width direction of the electrode assembly of 90 mm to 130 mm.

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

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 in a width direction of the electrode assembly of 90 mm to 130 mm.

9. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode tab is provided 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 provided 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 size of the positive electrode active material layer along the length direction of the electrode assembly is 650mm to 950mm, 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 further includes lithium hexafluorophosphate LiPF6. Based on the total mass of the electrolyte, the total mass of the lithium hexafluorophosphate LiPF6 and the fluorinated 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 mass ratio of lithium hexafluorophosphate LiPF6 to the mass ratio 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, where R ' Including one or more of hydrogen atoms, halogen atoms, C1-C5 alkyl groups, C1-C5 haloalkyl groups, R '' Including 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 an additive, and the additive includes a carbonate additive.

22. The battery cell according to claim 21, characterized in that 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 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 haloalkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time.

23. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte further includes an additive, and the additive includes a sulfur-containing additive.

24. The battery cell according to claim 23, characterized in that The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, vinyl sulfite, methylene disulfonate, and 1,3-propane sultone.

25. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte further includes an additive, and the additive includes a lithium salt additive.

26. The battery cell according to claim 25, characterized in that The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

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

28. 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%.

29. The battery cell according to claim 22, characterized in that Based on the total mass of the electrolyte, the mass proportion of the vinylene carbonate is 2% to 5%.

30. The battery cell according to claim 22, wherein: Based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 0% to 4%.

31. The battery cell according to claim 30, 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%.

32. The battery cell according to claim 23, characterized in that Based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0% to 2%.

33. The battery cell according to claim 32, characterized in that Based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0.5% to 2%.

34. The battery cell according to claim 25, characterized in that Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

35. The battery cell according to claim 34, characterized in that Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% to 1%.

36. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode active material includes: 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.

37. The battery cell according to claim 36, 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%.

38. The battery cell according to claim 36, characterized in that The coating layer further comprises 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, and Sn, and M1 has a valence of +4.

39. The battery cell according to claim 36, characterized in that The lithium-containing phosphate includes 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; and Y includes one or more of O and F.

40. 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 modified forms of any of the foregoing substances, wherein the modified form includes one or more of doping modification and coating modification.

41. 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 to 2.80g / cm 3 .

42. 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 .

43. 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.

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

45. The battery cell according to claim 44, 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, carbon 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.

46. 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.

47. The battery cell according to claim 46, characterized in that The carbon-based material includes one or more of graphite and hard carbon.

48. The battery cell according to claim 46, characterized in that The carbon-based material includes composite graphite particles, which include graphite particles and a carbon coating layer coated on at least a portion of the surface of the graphite particles. The graphite particles include secondary particles, and the carbon coating layer includes amorphous carbon.

49. The battery cell according to claim 48, characterized in that Based on the total mass of the composite graphite particles, the mass proportion of amorphous carbon is 2% to 5%.

50. The battery cell according to claim 48 or 49, characterized in that: The volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 13.5 μm.

51. The battery cell according to claim 46, 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.

52. The battery cell according to claim 51, characterized in that The silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

53. The battery cell according to claim 51 or 52, 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%.

54. 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 .

55. The battery cell according to any one of claims 1 to 2, characterized in that The isolation film has a porosity of 20% to 70%.

56. 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%.

57. The battery cell according to any one of claims 1 to 2, characterized in that The isolation film includes: 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.

58. The battery cell according to claim 57, characterized in that The non-fluoropolymer particles include acrylic copolymers.

59. The battery cell according to claim 57, 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.

60. The battery cell according to claim 57, wherein: The base film has a thickness of 4 μm to 12 μm.

61. The battery cell according to claim 60, characterized in that The base film has a thickness of 5 μm to 9 μm.

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

63. The battery cell according to claim 62, characterized in that The shell wall thickness of the large surface of the battery cell is 0.2 mm to 0.35 mm.

64. The battery cell according to claim 62, 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 shell in the length direction or the width direction, 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.

65. The battery cell according to claim 64, 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 150mm 2 ≤S≤1000mm 2 .

66. A battery device, characterized in that The battery device comprises the battery cell according to any one of claims 1 to 65, and is a battery module.

67. A battery device, characterized in that The battery device comprises the battery cell according to any one of claims 1 to 65, and is a battery pack.

68. A battery device, characterized in that The battery device comprises the battery monomer according to any one of claims 1 to 65, and is an energy storage battery.

69. An electrical device, characterized in that: A battery device comprising the battery device of any one of claims 66 to 68.

70. An energy storage device, characterized in that A battery device comprising the battery device of any one of claims 66 to 68, wherein the battery device is used to store electrical energy.

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