Battery cell, battery device, power consumption 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 compaction density of the positive electrode active material layer is 2.65 g / cm 3 to 2.8 g / cm 3 , and the size of the positive electrode active material layer along the length direction of the electrode assembly is 300 mm to 950 mm; the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. The battery cell takes into account the improvement of energy density, fast charging performance, and cycle stability, and realizes the comprehensive improvement of battery performance.

Description

[0001] This application claims the priority of PCT International Application PCT / CN2025 / 086890 titled "Battery Cell, Battery Device, Electrical Device, and Energy Storage Device" filed on April 2, 2025, and the entire content of this application is incorporated into this application by reference. Technical Field

[0002] This application relates to the technical field of battery cells, and particularly to a battery cell, a battery device, 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 hydraulic, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0004] With the dual increase in the market's demand for the cruising range and charging efficiency of electrical devices, higher requirements have also been put forward for the energy density of battery cells. However, while improving the energy density performance, it often brings about the deterioration of fast charging performance and cycle stability, which has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

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

[0006] The first aspect of this application provides a battery cell, including an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a separator, and a negative electrode plate that are sequentially stacked. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector. 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. Among them, the tap density of the positive electrode active material layer is 2.65 g / cm 3 to 2.8 g / cm 3 , and the size of the positive electrode active material layer along the length direction of the electrode assembly is 300 mm to 950 mm; the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s.

[0007] Lithium-containing phosphates with an olivine structure have the advantages of low cost and long life. When used with a laminated electrode assembly design in which the dimensions of the positive electrode active material layer along the length direction of the electrode assembly are within the above-mentioned range and the compaction density is within the above-mentioned range, it helps to improve the internal space utilization of the battery cell, improve the problem of low energy density of the battery cell when lithium-containing phosphate is used as the positive electrode active material, and at the same time make the internal resistance of the battery cell appropriate, so that the battery cell has both excellent energy density and fast charging performance. However, the above-mentioned electrode assembly design makes the distance for the electrolyte to infiltrate the positive and negative electrode active material layers longer, increases the resistance, and reduces the porosity of the active material layer, making it difficult for the electrolyte to infiltrate the active material layer in the length direction, which in turn leads to the problem of "bridge breaking" in the lithium ion transmission path during the cycle. As the charging rate of the battery cell increases, it is easy to cause severe lithium deposition at the negative electrode, which in turn leads to cycle drop. The battery cells of the embodiments of the present application, by ensuring that the viscosity of the electrolyte is within the above-mentioned range, help improve the wettability of the electrolyte to the positive and negative electrode active material layers, thereby alleviating the problem of the electrolyte having difficulty wetting the active material layers in the longitudinal direction, and slowing down the degree of lithium deposition in the battery cells under fast-charging conditions. At the same time, the electrolyte has good conductivity, stability, and dissociation rate, thereby enabling the battery cells to achieve both excellent cycle stability and fast-charging performance. The embodiments of the present application, through the interaction between the positive electrode sheet and the electrolyte, enable the battery cells to achieve both excellent energy density, fast-charging performance, and cycle life.

[0008] In any embodiment, the compaction density of the positive electrode active material layer is 2.75 g / cm 3 Up to 2.8g / cm 3 .

[0009] The positive electrode active material layer with a compaction density within the above range enables the battery cell to have excellent cycle stability and fast charging performance, while the energy density is further improved.

[0010] In any embodiment, the dimension of the positive electrode active material layer along the length direction of the electrode assembly is 400 mm to 650 nm.

[0011] The size of the positive electrode active material layer along the length direction of the electrode assembly is within the above range, and the battery cell has excellent energy density, cycle stability and fast charging performance.

[0012] In any embodiment, the electrolyte includes a first solvent, the viscosity η of the first solvent at room temperature is 0.3 mPa·s to 0.6 mPa·s, and the mass proportion of the first solvent based on the total mass of the electrolyte is 8% to 60%.

[0013] The first solvent with a viscosity η within the above range has both excellent stability and low viscosity. When the mass percentage of the first solvent is within the above range, it helps to reduce the viscosity of the electrolyte, improve the conductivity of the electrolyte, and at the same time take into account the stability of the electrolyte, thus being beneficial to the further comprehensive improvement of the fast charging performance and cycle stability of the battery cell.

[0014] In any embodiment, based on the total mass of the electrolyte, the mass percentage of the first solvent is 30% to 60%.

[0015] When the mass percentage of the first solvent is within the above range, it is beneficial to further reduce the viscosity of the electrolyte, improve the conductivity of the electrolyte. While the battery cell has excellent cycle stability, the fast charging performance is further improved.

[0016] In any embodiment, the first solvent includes carboxylic ester solvents.

[0017] Carboxylic ester solvents have the advantages of low viscosity and high ionic conductivity, which are beneficial to the wetting of the positive and negative electrode active material layers by the electrolyte and the rapid insertion and extraction of active ions in the negative electrode active material layer, thus further improving the fast charging performance of the battery cell.

[0018] In any embodiment, the carboxylic ester solvent has the structural general formula of R ， -COO-R ，， where R ， includes one or more of a hydrogen atom, a halogen atom, an alkyl group with 1 to 5 carbon atoms, and a halogenated alkyl group with 1 to 5 carbon atoms, and R ，， includes one or more of an alkyl group with 1 to 5 carbon atoms and a halogenated alkyl group with 1 to 5 carbon atoms.

[0019] In any embodiment, the carboxylic ester solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0020] In any embodiment, the electrolyte further includes a second solvent, and the second solvent includes carbonate solvents. The carbonate solvents include one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0021] Carbonate solvents have a high dielectric constant, which can increase the dissociation rate of lithium ions and anions in the lithium-containing electrolyte salt, and further improve the fast charging performance of the battery cell.

[0022] In any embodiment, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent is 18% to 75%.

[0023] Since carbonate solvents have relatively high viscosities, as the content of carbonate solvents increases, the viscosity of the electrolyte will also increase to some extent, which has a negative impact on the conductivity of the electrolyte. By reasonably controlling the mass ratio of carbonate solvents within the above range, the electrolyte has both appropriate viscosity and good dissociation rate, thereby comprehensively improving the conductivity of the electrolyte, which is beneficial to further enhancing the fast charging performance and cycle stability of the battery cell.

[0024] In any embodiment, the electrolyte includes a lithium-containing electrolyte salt. Based on the total mass of the electrolyte, the mass ratio of the lithium-containing electrolyte salt in the electrolyte is 10% to 18%.

[0025] When the molar concentration of the lithium-containing electrolyte salt in the electrolyte is within the above range, it is beneficial to balance the wettability and ionic conductivity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0026] In any embodiment, the lithium-containing electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6).

[0027] LiFSI is prone to dissociation in the electrolyte solvent, and LiFSI has a smaller molecular weight compared to other types of fluorosulfonylimide salts (such as lithium bis(trifluoromethylsulfonyl)imide, LiTFSI). Therefore, it is beneficial to increase the conductivity of the electrolyte while reducing the viscosity of the electrolyte. Moreover, LiFSI has good thermal stability and is not prone to decomposition during cyclic use, which can reduce the generation of hydrogen fluoride during battery cycling and the probability of side reactions occurring at the negative electrode, thereby further comprehensively improving the cycle stability and fast charging performance of the battery cell. However, as the temperature of the battery cell increases, LiFSI will undergo violent decomposition at a certain temperature threshold, releasing a large amount of heat and sharply increasing the risk of thermal runaway of the battery. This safety risk is more significant in fast charging batteries. The lithium-containing electrolyte salt also includes LiPF6, which can reduce the risk of thermal runaway of the battery cell, keeping the risk within a controllable range, thereby improving the safety performance of the battery cell.

[0028] In any embodiment, based on the total mass of the electrolyte, the mass ratio of lithium bis(fluorosulfonyl)imide (LiFSI) in the electrolyte is 4% to 8%.

[0029] When the mass ratio of lithium bis(fluorosulfonyl)imide (LiFSI) is within the above range, the battery cell has excellent fast charging performance, cycle stability, and safety performance.

[0030] In any embodiment, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, lithium salt additives, and fluorobenzene additives.

[0031] In any embodiment, the carbonate additives include one or more of vinylene carbonate and ethylene carbonate derivatives,

[0032] wherein the ethylene carbonate derivatives include the compounds shown in Formula III,

[0033] Formula III

[0034] R1, R2, R3, and R4 each independently include one or more of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R1, R2, R3, and R4 are not simultaneously hydrogen atoms. Optionally, the carbonate additives include one or more of vinylene carbonate and fluoroethylene carbonate.

[0035] The carbonate additives can evolve into organic components in the SEI film, improving the toughness of the SEI film, thereby enhancing the stability of the SEI film during the cycling of the battery cell and reducing the interfacial impedance on the negative electrode side, reducing the side reactions between the electrolyte and the negative electrode active material layer and then reducing gas generation, which is beneficial to further improving the cycling, storage life, and fast charging performance of the battery cell.

[0036] In any embodiment, the sulfur-containing additives include one or more of ethylene sulfate, bis(ethylene sulfate), 1,3-propane sultone, butene sulfite, ethylene sulfite, and methylene methanedisulfonate.

[0037] Sulfur-containing additives often have a relatively high potential, and the sulfur-containing additives added to the electrolyte will react preferentially during formation or subsequent cycling and evolve into sulfur-containing inorganic components in the SEI film. The SEI film formed by carbonate additives has poor high-temperature stability, which is not conducive to the stability of the battery cell in a high-temperature environment. The presence of sulfur elements in the SEI film can further improve the thermal stability of the SEI film at high temperatures and further reduce the interfacial impedance on the negative electrode side, which is beneficial to further improving the cycling stability and fast charging performance of the battery cell.

[0038] In any embodiment, the lithium salt additives include one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0039] The lithium salt additives can evolve into inorganic components in the SEI film, further improving the rigidity and thermal stability of the SEI film, thereby further enhancing the cycling stability and fast charging performance of the battery. And the above-mentioned lithium salt additives can also form a cathode electrolyte interface film (CEI film) on the surface of the cathode active material, thereby further enhancing the cycling stability of the battery cell.

[0040] In any embodiment, the fluorobenzene additives include one or more of fluorobenzene and its derivatives.

[0041] Fluorobenzene additives help improve the wettability of the electrolyte to the positive and negative electrode active material layers, thereby further improving the cycle stability and fast charging performance of the battery cell.

[0042] In any embodiment, based on the total mass of the electrolyte, the mass fraction of the carbonate additive is 3% to 8%.

[0043] When the mass fraction of the carbonate additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the stability of the SEI film and maintain an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0044] In any embodiment, based on the total mass of the electrolyte, the mass fraction of vinylene carbonate is 2% to 5%.

[0045] Vinylene carbonate VC has a reduction potential close to that of carboxylic ester solvents, which can inhibit the reaction activity of carboxylic ester solvents and improve the cycle life of the battery cell. However, too high a content of vinylene carbonate VC will lead to an increase in the battery interface impedance and charge transfer impedance, which is not conducive to the fast charging performance of the battery cell. When the mass fraction of vinylene carbonate VC is within the above range, the battery can achieve excellent cycle life and fast charging performance.

[0046] In any embodiment, based on the total mass of the electrolyte, the mass fraction of ethylene carbonate derivatives is 0% to 4%.

[0047] In any embodiment, based on the total mass of the electrolyte, the mass fraction of ethylene carbonate derivatives is 1.5% to 3.5%.

[0048] Ethylene carbonate derivatives can also form a film on the negative electrode surface at a relatively high potential and have a low interface impedance and charge transfer impedance. When the mass fraction of ethylene carbonate derivatives is within the above range, the battery cell can achieve excellent fast charging performance and cycle life. By adding vinylene carbonate VC and ethylene carbonate derivatives in combination in the electrolyte, the fast charging performance and cycle stability of the battery cell can be comprehensively improved.

[0049] In any embodiment, based on the total mass of the electrolyte, the mass fraction of sulfur-containing additives is 0% to 2%.

[0050] In any embodiment, based on the total mass of the electrolyte, the mass fraction of sulfur-containing additives is 0.5% to 2%.

[0051] When the mass fraction of sulfur-containing additives in the electrolyte is within the above range, it is beneficial to balance the improvement of the thermal stability of the SEI film at high temperatures and maintain an appropriate viscosity of the electrolyte, further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0052] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

[0053] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% to 1%.

[0054] When the mass proportion of the lithium salt additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the stability of the SEI film and the maintenance of the appropriate viscosity of the electrolyte, and further comprehensively improve the cycle life and fast charging performance of the battery cell.

[0055] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the fluorobenzene additive is 0.1% to 1%.

[0056] When the mass proportion of the fluorobenzene additive in the electrolyte is within the above range, it is beneficial to balance the wettability of the electrolyte and the maintenance of the appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0057] In any embodiment, the negative electrode plate includes a negative current collector and a negative active material layer provided on at least one side of the negative current collector, and the compaction density of the negative active material layer is 1.20 g / cm 3 to 1.50 g / cm 3 .

[0058] The negative active material layer with a compaction density within the above range can further achieve the balance of the energy density, fast charging performance and cycle stability of the battery cell.

[0059] In any embodiment, the positive current collector includes a positive current collecting part and a positive electrode tab, and the positive electrode tab is provided at at least one end of the positive current collecting part extending along the length direction of the electrode assembly or at least one side of the positive current collecting part extending along the width direction of the electrode assembly.

[0060] In any embodiment, the negative current collector includes a negative current collecting part and a negative electrode tab, and the negative electrode tab is provided at at least one end of the negative current collecting part extending along the length direction of the electrode assembly or at least one side of the negative current collecting part extending along the width direction of the electrode assembly.

[0061] In any embodiment, the size of the positive active material layer along the length direction of the electrode assembly is 650 mm to 950 mm, and the positive electrode tab is provided at both ends of the positive current collecting part extending along the length direction of the electrode assembly or at least one side of the positive current collecting part extending along the width direction of the electrode assembly.

[0062] The above tab design helps to improve the overcurrent capacity of the battery cell, alleviate the situation of electrolyte decomposition and uneven current distribution caused by excessive temperature on the tab side during fast charging, resulting in lithium plating on the tab side, thereby improving the fast charging performance and cycle stability of the battery cell. It is especially suitable for improving the fast charging performance of battery cells with the length dimension of the positive active material layer in the range of 650 mm to 950 mm, while taking into account excellent volumetric energy density.

[0063] In any embodiment, the positive tab is disposed at at least one end of the positive current collector extending along the length direction of the electrode assembly, and the ratio of the width of the positive tab to the width of the positive current collector is 0.25 to 1; and / or, the ratio of the width of the negative tab to the width of the negative current collector is 0.25 to 1.

[0064] In any embodiment, the positive tab is disposed at at least one side of the positive current collector extending along the width direction of the electrode assembly, and the ratio of the width of the positive tab to the length of the positive current collector is 0.25 to 1; and / or, the ratio of the width of the negative tab to the length of the negative current collector is 0.25 to 1.

[0065] The width of the tab within the above range helps to improve the overcurrent capacity of the battery cell, and improve the fast charging performance and cycle stability of the battery cell.

[0066] In any embodiment, along the length direction of the electrode assembly, the size of the negative active material layer is larger than the size of the positive active material layer, and the difference between the size of the negative active material layer and the size of the positive active material layer is OH1; along the width direction of the electrode assembly, the size of the negative active material layer is larger than the size of the positive active material layer, and the difference between the size of the negative active material layer and the size of the positive active material layer is OH2, where OH1 is 1.0 mm to 4.0 mm; and / or, OH2 is 1.0 mm to 3.0 mm.

[0067] As the charging rate of the battery cell increases, the current density and temperature rise are high in the area near the tab, making it easy for the negative active material layer to generate lithium dendrites near the tab. Through the design of OH1 and OH2 in the battery cell of the embodiment of the present application, the ability of the negative active material layer, especially the negative active material layer in the area near the tab, to accept active ions in the length direction is improved, and the distance between the positive active material layer and the tab side becomes farther. The current distribution in the active material layer near the tab is more uniform, resulting in a lower temperature rise. Thus, the lithium plating problem of the negative electrode plate is comprehensively improved, and at the same time, the probability of the separator shrinking due to heat and causing the positive and negative electrodes to overlap and then an internal short circuit in the battery is reduced. While the fast charging performance and cycle stability of the battery cell are improved, controlling the values of OH1 and OH2 within the above range enables the battery cell to have excellent energy density.

[0068] In any embodiment, OH1 is greater than or equal to OH2.

[0069] Controlling OH1 ≥ OH2 can improve the cycle stability of the battery cell while being beneficial to further improving the energy density of the battery cell.

[0070] In any embodiment, the positive electrode active material includes: a lithium-containing phosphate, and a coating layer located on at least a part of the surface of the lithium-containing phosphate, and the coating layer contains carbon elements.

[0071] The coating layer containing carbon elements is beneficial to improving the electronic conductivity of the lithium-containing phosphate, improving the solid-phase transmission rate of electrons, and thus further improving the energy density and fast charging performance of the battery cell.

[0072] In any embodiment, based on the total mass of the positive electrode active material, the mass ratio of carbon elements is 0.8% to 2.3%.

[0073] Based on the total mass of the positive electrode active material, when the mass ratio of carbon elements is within the above range, the lithium-containing phosphate has both excellent electronic conductivity and specific capacity, further comprehensively improving the energy density and fast charging performance of the battery cell.

[0074] In any embodiment, the coating layer further includes a component shown in Formula I,

[0075] Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I,

[0076] where 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn. Optionally, M1 is +4 valent.

[0077] The component shown in Formula I is a fast ion conductor with a NASICON structure, whose ionic conductivity is close to or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has rich three-dimensional lithium ion diffusion and transmission channels and has advantages such as high ionic conduction efficiency and strong structural stability during multiple lithium deintercalation and intercalation processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly improve the transmission rate of lithium ions during multiple deintercalation / intercalation at the positive electrode end, improve the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0078] In any embodiment, the lithium-containing phosphate includes a component shown in Formula II,

[0079] Li x1 A y1 Mea1 M b1 P 1-c1 X c1 Y z1 Formula II

[0080] wherein, 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, N, and P; Y includes one or more of O and F.

[0081] The lithium-containing phosphate with olivine structure having the above components has good structural stability, can reduce the loss during fast charging, and further improve the fast charging performance and cycle stability of the battery cell.

[0082] In any embodiment, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, and modified forms of any one of the foregoing substances, wherein the modified forms include one or more of doping modification and coating modification.

[0083] In any embodiment, the powder compaction density of the positive electrode active material under 30,000 N is 2.55 g / cm 3 to 2.75 g / cm 3 .

[0084] The positive electrode active material with a powder compaction density within a suitable range can make the positive electrode active material layer have a high compaction density, thereby enabling the battery cell to have a high energy density.

[0085] In any embodiment, the single-sided coating mass of the positive electrode active material layer is 220 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 .

[0086] The positive electrode active material layer with a single-sided coating mass within the above range can further effectively balance the fast charging performance and energy density of the battery cell.

[0087] In any embodiment, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0088] The positive electrode current collector has a relatively low thickness, which enables further improvement in the energy density of the battery cell.

[0089] 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.

[0090] 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.

[0091] 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, 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.

[0092] 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.

[0093] In any embodiment, the carbon-based material includes one or more of graphite and hard carbon.

[0094] 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.

[0095] Secondary particles are particles formed by the aggregation of two or more primary particles. Composite graphite particles, including secondary particles and a surface coating layer including amorphous carbon, further improve the electrolyte's wettability in the negative electrode active material layer and enhance the solid-phase transport capacity of active ions, contributing to further improvements in the battery's cycle stability and fast-charging performance.

[0096] In any embodiment, the amorphous carbon accounts for 2% to 5% by mass based on the total mass of the composite graphite particles.

[0097] When the content of amorphous carbon is within a suitable range, the composite graphite material can have a high specific capacity while also having a high active ion solid-phase transport ability, which is beneficial to further comprehensively improving the energy density and fast charging performance of the battery cell.

[0098] In any embodiment, the volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 14.5 μm.

[0099] When the volume average particle size Dv50 of the composite graphite particles is within the above range, the solid-phase migration path of lithium ions is shortened while taking into account the lower reaction activity, thereby taking into account the fast charging ability and cycle life of the battery cell.

[0100] 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.

[0101] In any embodiment, the silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

[0102] In any embodiment, based on the total mass of the negative electrode active material layer, the mass ratio of silicon element is 0.5% to 5.0%.

[0103] The introduction of the silicon-based material is beneficial to further improving the energy density of the battery cell. Based on the total mass of the negative electrode active material layer, when the mass ratio of silicon element is within the above mass range, the energy density and cycle stability of the battery cell can be taken into account.

[0104] In any embodiment, the single-sided coating mass of the negative electrode active material layer is 100 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 .

[0105] The negative electrode active material layer with a single-sided coating mass within the above range can form a cooperation with the positive electrode active material layer to achieve a balance between the energy density and fast charging performance of the battery cell.

[0106] In any embodiment, the porosity of the separator is 20% to 70%, and can be optionally 35% to 60%.

[0107] The porosity of the separator within the above range is beneficial to further taking into account the energy density, fast charging performance, and cycle stability of the battery cell.

[0108] In any embodiment, the separator includes: a base film; a first functional layer located on at least one side of the base film, and the first functional layer includes a first inorganic substance; a second functional layer located on the side of the first functional layer away from the base film, and the second functional layer includes a second inorganic substance and non-fluoropolymer particles.

[0109] In any embodiment, the non-fluoropolymer particles include an acrylate copolymer.

[0110] In any embodiment, the first inorganic substance and the second inorganic substance each independently include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

[0111] The inorganic particles can improve the wettability of the first functional layer and the second functional layer with respect to the electrolyte and the heat resistance, and further comprehensively improve the fast charging performance, cycle stability, and safety performance of the battery cell. The non-fluoropolymer particles can improve the processability and stability of the separator, and prevent the separator from moving in the battery cell to cause internal short circuit, thereby further improving the cycle stability and safety performance of the battery cell.

[0112] In any embodiment, the thickness of the base film is 4 μm to 12 μm, and may be optionally 5 μm to 9 μm.

[0113] The thickness of the base film within the above range is beneficial to further taking into account the energy density, fast charging performance, and cycle stability of the battery cell.

[0114] In any embodiment, the battery cell includes a housing and a cover assembly. The cover assembly is disposed at at least one end of the housing. The housing and the cover assembly define a receiving cavity. The electrode assembly is disposed in the receiving cavity. The wall thickness of the housing on the large surface of the battery cell is 0.2 mm to 0.5 mm.

[0115] The wall thickness of the housing on the large surface of the battery cell within the above range is beneficial to further improving the energy density of the battery cell.

[0116] In any embodiment, the cover assembly includes a first cover assembly and a second cover assembly. The first cover assembly and the second cover assembly are disposed at two ends of the housing in the length direction or the width direction. The first cover assembly includes a first cover and a first electrode terminal. The second cover assembly includes a second cover and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite.

[0117] Thereby, during charging, the temperature rise of the battery cell is reduced and the impedance of the battery cell is reduced, which is beneficial to the improvement of the fast charging performance, cycle life, and safety performance of the battery cell.

[0118] 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≤1000 mm 2 .

[0119] When the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is within the above range, it is beneficial to improve the over-current capacity of the battery cell, reduce the heat generation of the electrode terminal, and reduce the internal resistance of the battery cell, thereby improving the fast charging performance and cycle stability of the battery cell.

[0120] In any implementation, the volume energy density of the battery cell is 430 Wh / L to 530 Wh / L.

[0121] In any implementation, the volume energy density of the battery cell is 430 Wh / L to 470 Wh / L.

[0122] This battery cell has a high energy density at the same time and can meet the demand for improving the endurance mileage of the electrical device.

[0123] In any implementation, the liquid injection coefficient of the battery cell is 2.2 g / Ah to 3.0 g / Ah.

[0124] When the liquid injection coefficient is within the above range, the cycle stability and energy density of the battery cell can be taken into account.

[0125] The second aspect of the present application provides a battery device, including the battery cell provided by the first aspect of the present application. The battery device includes at least one of a battery module, a battery pack, and an energy storage battery.

[0126] The third aspect of the present application further provides an electrical device, and the electrical device includes the battery cell provided by the first aspect of the present application.

[0127] The fourth aspect of the present application further provides an energy storage device, and the energy storage device includes the battery cell provided by the first aspect of the present application. Description of the Drawings

[0128] Figure 1 is a schematic diagram of a positive electrode plate and a negative electrode plate according to an embodiment of the present application;

[0129] Figure 2 is a schematic diagram of a positive electrode plate and a negative electrode plate according to an embodiment of the present application;

[0130] Figure 3 is a schematic diagram of a positive electrode current collector according to an embodiment of the present application;

[0131] Figure 4 is a schematic diagram of a positive electrode current collector according to an embodiment of the present application;

[0132] Figure 5 is a schematic diagram of a positive electrode current collector according to an embodiment of the present application;

[0133] Figure 6 is a schematic diagram of a positive electrode current collector according to an embodiment of the present application;

[0134] Figure 7 It is a schematic diagram of the negative electrode current collector of an embodiment of the present application;

[0135] Figure 8 It is a schematic diagram of the negative electrode current collector of an embodiment of the present application;

[0136] Figure 9 It is a schematic diagram of the negative electrode current collector of an embodiment of the present application;

[0137] Figure 10 It is a schematic diagram of the negative electrode current collector of an embodiment of the present application;

[0138] Figure 11 It is a schematic structural diagram of the separator of an embodiment of the present application;

[0139] Figure 12 It is a schematic structural diagram of a battery cell of an embodiment of the present application;

[0140] Figure 13 It is a schematic diagram of an electrical device using a battery cell of an embodiment of the present application as a power source.

[0141] Description of reference numerals:

[0142] 1 Battery cell; 11 Housing; 111 Housing of the large surface of the battery cell; 12 Electrode assembly; 121 Positive electrode plate; 1211 Positive electrode current collector; 1212 Positive electrode active material layer; 12110 Positive electrode current collecting part; 12111 Positive electrode tab; 122 Negative electrode plate; 1221 Negative electrode current collector; 1222 Negative electrode active material layer; 12210 Negative electrode current collecting part; 12211 Negative electrode tab; 123 Separator; 1231 Base film; 1232 First functional layer; 1233 Second functional layer; First electrode terminal 131, Second electrode terminal 132, Third electrode terminal 133, Fourth electrode terminal 134. Detailed embodiments

[0143] Hereinafter, embodiments of the battery cell, battery device, electrical device, and energy storage device of the present application will be specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying 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.

[0144] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0145] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0146] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0147] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0148] If there is no special instruction, the "including" and "comprising" mentioned in this application mean open-ended or can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can also mean that only the listed components are included or comprised.

[0149] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or 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).

[0150] Adopting a stacked electrode assembly with an increased length of a single electrode assembly and a high-compaction-density electrode design helps to improve the energy density of a single battery cell. However, the above electrode assembly design makes it difficult for the electrolyte to infiltrate in the length direction of the electrode sheet, resulting in a problem of cyclic voltage drop in the single battery cell.

[0151] Based on this, a first aspect of this application provides a single battery cell, including an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet that are sequentially stacked. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure. Among them, the compaction density of the positive electrode active material layer is 2.65 g / cm 3 to 2.8 g / cm 3 , and the size of the positive electrode active material layer along the length direction of the electrode assembly is 300 mm to 950 mm; the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s.

[0152] The lithium-containing phosphate with an olivine structure is an active material with an olivine structure including lithium ions and phosphate groups. The type of the positive electrode active material can be tested by any well-known method in the art. As an example, methods such as X-ray diffraction (XRD) for phase analysis combined with elemental analysis methods such as energy spectrum and XPS can be used for analysis.

[0153] In this application, the compaction density of the positive electrode active material layer has the meaning well-known in the art and can be tested by known methods in the art. For example, the single battery cell is placed at 25°C and charged at a constant current charging rate of 0.33C to the cut-off voltage (such as 3.65V), left standing for 1 min, and then charged at a constant voltage of 3.65V until the current is less than 0.05C. At this time, the single battery cell is in a fully charged state, and then the positive electrode sheet is disassembled to measure the compaction density of the positive electrode active material layer. The compaction 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.

[0154] In this application, the "single-sided coating mass of the positive electrode active material layer" refers to the mass of the positive electrode active material layer per unit area on one side of the current collector.

[0155] In this application, the single-sided coating mass of the positive electrode active material layer can be tested by methods known in the art. For example, the positive electrode plate can be taken from the disassembled battery (if it is a double-sided coated positive electrode plate, the positive electrode active material layer on one side can be wiped off first), punched into small round pieces with an area of S1, weighed, and recorded as M1. Then, wipe off the positive electrode active material layer of the positive electrode plate after weighing above, weigh the mass of the positive electrode current collector, and record it as M0. The single-sided coating mass of the positive electrode plate = (M1 - M0) / S1.

[0156] The thickness of the positive electrode active material layer has the meaning well known in the art and can be tested by methods known in the art. For example, it can be tested with a micrometer (such as Mitutoyo 293-100 type with an accuracy of 0.1 μm). It can be understood that when the battery cell is in a fully charged state, the compaction density of the positive electrode active material layer is different from the designed value of the battery cell compaction density. Affected by actual operations, when the battery cell is in a fully charged state, the compaction density of the positive electrode active material layer is often slightly lower than the designed value of the battery cell compaction density.

[0157] In some embodiments, the compaction density of the positive electrode active material layer can be 2.65 g / cm 3 、2.67 g / cm 3 、2.69 g / cm 3 、2.71 g / cm 3 、2.73 g / cm 3 、2.75 g / cm 3 、2.77 g / cm 3 、2.80 g / cm 3 or any value range between any two of them.

[0158] In this application, referring to Figure 1 , the electrode assembly 12 includes a positive electrode plate 121, a separator 123, and a negative electrode plate 122 stacked in sequence. The positive electrode plate 121 includes a positive electrode current collector 1211 and a positive electrode active material layer 1212 disposed on at least one side of the positive electrode current collector 1211. Along the length direction of the electrode assembly 12, the size of the positive electrode active material layer 1212 is OH 11 , and the size can be measured with a ruler.

[0159] In some embodiments, the size of the positive electrode active material layer along the length direction of the electrode assembly is 300 nm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 950 mm or any value range between any two of them.

[0160] In this application, "room temperature" refers to 25 ± 3°C.

[0161] In this application, the viscosity of the electrolyte at room temperature has the meaning well-known in the art and can be measured by methods known in the art. For example, the rotational method provided in the national standard GB / T 10247-2008 "Viscosity Measurement Method" can be referred to. Specifically, a certain mass of the electrolyte sample is placed in a sample container and placed in a hydrothermal bath for constant-temperature static placement for 10 to 20 minutes. After the sample temperature is the same as the hydrothermal temperature, a rotational viscometer with the instrument model DV-2TLV produced by Brookfield Company and a viscosity measurement accuracy of ±1% of the full scale is used for testing. When the 18th rotor rotates continuously in the sample at a constant speed of 70 r, the shear force generated causes the spring to generate torque, and the torque is proportional to the viscosity, obtaining the viscosity value. Five samples are tested, and the viscosity is the average value of the five samples. Before testing, the sample cup and the rotor are rinsed with the electrolyte sample and kept at the temperature to be measured. The testing equipment meets the following testing environmental conditions: 1. External environment of the equipment: temperature is 15 to 28 °C, humidity is RH < 80%; 2. Internal environment of the equipment: 2 / 3 of the sample container is immersed in a water bath, the medium is water, and the water is used to keep the sample at a constant temperature, and the hydrothermal temperature is 25 ± 3 °C.

[0162] In some embodiments, the viscosity of the electrolyte at room temperature can be 2.3 mPa·s, 2.5 mPa·s, 2.7 mPa·s, 2.9 mPa·s, 3.1 mPa·s, 3.3 mPa·s, 3.5 mPa·s or the numerical range between any two of them.

[0163] Lithium-containing phosphates with an olivine structure have the advantages of low cost and long life. When used with a laminated electrode assembly design in which the dimensions of the positive electrode active material layer along the length direction of the electrode assembly are within the above-mentioned range and the compaction density is within the above-mentioned range, it helps to improve the internal space utilization of the battery cell, improve the problem of low energy density of the battery cell when lithium-containing phosphate is used as the positive electrode active material, and at the same time make the internal resistance of the battery cell appropriate, so that the battery cell has both excellent energy density and fast charging performance. However, the above-mentioned electrode assembly design makes the distance for the electrolyte to infiltrate the positive and negative electrode active material layers longer, increases the resistance, and reduces the porosity of the active material layer, making it difficult for the electrolyte to infiltrate the active material layer in the length direction, which in turn leads to the problem of "bridge breaking" in the lithium ion transmission path during the cycle. As the charging rate of the battery cell increases, it is easy to cause severe lithium deposition at the negative electrode, which in turn leads to cycle drop. The battery cells of the embodiments of the present application, by ensuring that the viscosity of the electrolyte is within the above-mentioned range, help improve the wettability of the electrolyte to the positive and negative electrode active material layers, thereby alleviating the problem of the electrolyte having difficulty wetting the active material layers in the longitudinal direction, and slowing down the degree of lithium deposition in the battery cells under fast-charging conditions. At the same time, the electrolyte has good conductivity, stability, and dissociation rate, thereby enabling the battery cells to achieve both excellent cycle stability and fast-charging performance. The embodiments of the present application, through the interaction between the positive electrode sheet and the electrolyte, enable the battery cells to achieve both excellent energy density, fast-charging performance, and cycle life.

[0164] In some embodiments, the compaction density of the positive electrode active material layer is 2.75 g / cm 3 Up to 2.8g / cm 3 .

[0165] The positive electrode active material layer with a compaction density within the above range enables the battery cell to have excellent cycle stability and fast charging performance, while the energy density is further improved.

[0166] In some embodiments, the size of the positive electrode active material layer along the length direction of the electrode assembly is 400 mm to 650 nm.

[0167] The size of the positive electrode active material layer along the length direction of the electrode assembly is within the above range, and the battery cell has excellent energy density, cycle stability and fast charging performance.

[0168] In some embodiments, the electrolyte includes a first solvent, the viscosity η of the first solvent at room temperature is 0.3 mPa·s to 0.6 mPa·s, and the mass proportion of the first solvent based on the total mass of the electrolyte is 8% to 60%.

[0169] The types and quality of solvents in the electrolyte can be obtained by detecting the electrolyte through methods well-known to those skilled in the art. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, free electrolyte from a fresh battery can be taken as a sample, or a discharged battery cell (discharged to the discharge cut-off voltage such that the charged state of the battery cell is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell can be taken as a sample, and detected by ion chromatography analysis method. The types and contents of organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to GB / T 9722-2023 "General Rules for Chemical Reagents - Gas Chromatography" to qualitatively and quantitatively analyze the organic components of the electrolyte by gas chromatography. The types and contents of inorganic components / lithium salts in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to the standard JY / T 020-2002 "General Rules for Ion Chromatography Analysis Method" to qualitatively or quantitatively analyze the inorganic components / lithium salts of the electrolyte by ion chromatography analysis method.

[0170] The viscosity of the first solvent at room temperature can be tested by a method similar to the viscosity of the electrolyte described above at room temperature.

[0171] In some embodiments, the viscosity η of the first solvent can be 0.3 mPa·s, 0.35 mPa·s, 0.4 mPa·s, 0.45 mPa·s, 0.5 mPa·s, 0.55 mPa·s, 0.6 mPa·s or the numerical range between any two of them.

[0172] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the first solvent can be 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or the numerical range between any two of them.

[0173] The first solvent with a viscosity η in the above range has both excellent stability and low viscosity. When the mass percentage of the first solvent is in the above range, it helps to reduce the viscosity of the electrolyte, improve the conductivity of the electrolyte, and at the same time take into account the stability of the electrolyte, thereby being beneficial to the further comprehensive improvement of the fast charging performance and cycle stability of the battery cell.

[0174] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the first solvent is 30% to 60%.

[0175] When the mass percentage of the first solvent is in the above range, it is beneficial to further reduce the viscosity of the electrolyte, improve the conductivity of the electrolyte. While the battery cell has excellent cycle stability, the fast charging performance is further improved.

[0176] In some embodiments, the first solvent includes a carboxylic acid ester solvent.

[0177] The carboxylic acid ester solvent has the advantages of low viscosity and high ionic conductivity, which is beneficial to the infiltration of the electrolyte into the positive and negative active material layers and the rapid insertion and extraction of active ions in the negative active material layer, thereby further improving the fast charging performance of the battery cell.

[0178] In some embodiments, the carboxylic acid ester solvent has the general structural formula of R ， -COO-R ，， where R ， includes one or more of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R ，， includes one or more of an alkyl group having 1 to 5 carbon atoms and a halogenated alkyl group having 1 to 5 carbon atoms.

[0179] "Alkyl group having 1 to 5 carbon atoms" 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, 1-ethylpropyl.

[0180] "Halogenated alkyl group having 1 to 5 carbon atoms" refers to an unbranched or branched alkyl group having 1 to 5 carbon atoms in which at least one hydrogen atom is replaced by a halogen, including but not limited to one or more of a chloroalkyl group, a bromoalkyl group, and an iodoalkyl group.

[0181] "Halogen" refers to the elements in Group VIIA of the periodic table of chemical elements. Specifically, halogens include elements such as fluorine, chlorine, bromine, iodine, or astatine.

[0182] In some embodiments, the carboxylic acid ester solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0183] In some embodiments, the electrolyte further includes a second solvent, and the second solvent 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.

[0184] The carbonate solvent has a high dielectric constant, which can increase the dissociation rate of lithium ions and anions in the lithium-containing electrolyte salt, and further improve the fast charging performance of the battery cell.

[0185] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent is 18% to 75%.

[0186] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent can be 18%, 30%, 40%, 50%, 60%, 75% or any value range between any two of them.

[0187] Since the carbonate solvent has a relatively high viscosity, as the content of the carbonate solvent increases, the viscosity of the electrolyte will also increase, which has a negative impact on the conductivity of the electrolyte. By reasonably controlling the mass percentage of the carbonate solvent within the above range, the electrolyte has an appropriate viscosity and a good dissociation rate, thereby comprehensively improving the conductivity of the electrolyte, which is beneficial to further improving the fast charging performance and cycle stability of the battery cell.

[0188] In some embodiments, the electrolyte includes a lithium-containing electrolyte salt. Based on the total mass of the electrolyte, the mass percentage of the lithium-containing electrolyte salt in the electrolyte is 10% to 18%.

[0189] The type and mass of the lithium-containing electrolyte salt in the electrolyte can be obtained by testing the electrolyte by methods well known to those skilled in the art. As an example, the testing method for the type and mass of the solvent in the electrolyte described above can be used for testing.

[0190] In some embodiments, the mass percentage of the lithium-containing electrolyte salt in the electrolyte is 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or any value range between any two of them.

[0191] When the molar concentration of the lithium-containing electrolyte salt in the electrolyte is within the above range, it is beneficial to balance the wettability and ionic conductivity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0192] In some embodiments, the lithium-containing electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6).

[0193] LiFSI is prone to dissociation in the electrolyte solvent, and LiFSI has a smaller molecular weight compared to other types of fluorosulfonylimide salts (such as lithium bis(trifluoromethanesulfonyl)imide LiTFSI). This is conducive to improving the conductivity of the electrolyte while reducing the viscosity of the electrolyte. Moreover, LiFSI has good thermal stability and is not prone to decomposition during the recycling process, which can reduce the generation of hydrogen fluoride during battery cycling and the probability of side reactions occurring at the negative electrode, thereby further comprehensively improving the cycle stability and fast charging performance of the battery cell. However, as the temperature of the battery cell increases, LiFSI will undergo violent decomposition at a certain temperature threshold, releasing a large amount of heat and sharply increasing the risk of thermal runaway of the battery. This safety risk is more significant in fast charging batteries. The lithium-containing electrolyte salt also includes lithium hexafluorophosphate LiPF6, which can reduce the risk of thermal runaway of the battery cell, keeping the risk within a controllable range, thereby improving the safety performance of the battery cell.

[0194] In some embodiments, based on the total mass of the electrolyte, the mass percentage of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is 4% to 8%.

[0195] In some embodiments, based on the total mass of the electrolyte, the mass percentage of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is 4%, 5%, 6%, 7%, 8% or the numerical range between any two of them.

[0196] When the mass percentage of lithium bis(fluorosulfonyl)imide LiFSI is within the above range, the battery cell takes into account excellent fast charging performance, cycle stability, and safety performance.

[0197] In some embodiments, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, lithium salt additives, and fluorobenzene additives.

[0198] Additives refer to components with relatively low content in the electrolyte. Generally, the mass percentage in the electrolyte does not exceed 10%. They have the characteristics of strong pertinence and small dosage, and can significantly optimize a certain aspect of the battery performance without changing the production process.

[0199] In the present application, carbonate additives refer to compounds containing a carbonate group (-O-CO-O-) and their derivatives, as well as mixtures containing the above compounds and their derivatives.

[0200] In the present application, fluorobenzene additives refer to organic compounds and their derivatives in which one or more hydrogen atoms on the benzene ring are replaced by fluorine atoms, as well as mixtures containing the above compounds and their derivatives.

[0201] The types of additives in the electrolyte can be obtained by testing the electrolyte through methods well-known to those skilled in the art. As an example, the testing methods for the types and masses of solvents in the electrolyte described above can be used for testing.

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

[0203] Among them, the ethylene carbonate derivatives include the compounds shown in Formula III.

[0204] Formula III

[0205] R1, R2, R3, and R4 each independently include one or more of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R1, R2, R3, and R4 are not simultaneously hydrogen atoms. Optionally, the carbonate additives include one or more of vinylene carbonate and fluoroethylene carbonate.

[0206] The carbonate additives can evolve into organic components in the SEI film, improve the toughness of the SEI film, thereby improving the stability of the SEI film during the cycling process of the battery cell and reducing the interfacial impedance on the negative electrode side, reducing the side reactions between the electrolyte and the negative electrode active material layer and then reducing gas generation, which is beneficial to further improving the cycling, storage life, and fast charging performance of the battery cell.

[0207] In some embodiments, the sulfur-containing additives include one or more of ethylene sulfate, bis(ethylene sulfate), 1,3-propane sultone, butene sulfite, ethylene sulfite, and methylene methanedisulfonate.

[0208] The sulfur-containing additives often have a relatively high potential. The sulfur-containing additives added to the electrolyte will react preferentially during formation or subsequent cycling processes and evolve into sulfur-containing inorganic components in the SEI film. The SEI film formed by carbonate additives has poor high-temperature stability, which is not conducive to the stability of the battery cell in a high-temperature environment. The presence of sulfur elements in the SEI film can further improve the thermal stability of the SEI film at high temperatures and further reduce the interfacial impedance on the negative electrode side, which is beneficial to further improving the cycling stability and fast charging performance of the battery cell.

[0209] In some embodiments, the lithium salt additives include one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

[0210] Lithium salt additives can evolve into inorganic components in the SEI film, further improving the rigidity and thermal stability of the SEI film, thereby further enhancing the cycle stability and fast charging performance of the battery. Moreover, the above-mentioned lithium salt additives can also form a cathode electrolyte interface film (CEI film) on the surface of the cathode active material, thereby further enhancing the cycle stability of the battery cell.

[0211] In some embodiments, the fluorobenzene additives include one or more of fluorobenzene and its derivatives.

[0212] The fluorobenzene additives help to improve the wettability of the electrolyte to the positive and negative active material layers, thereby further improving the cycle stability and fast charging performance of the battery cell.

[0213] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate additive is 3% to 8%.

[0214] Based on the total mass of the electrolyte, the mass percentage of the additive can be measured by any well-known method in the art. As an example, the measurement method of the mass percentage of the solvent and the lithium-containing electrolyte salt in the electrolyte described above can be used for measurement. It should be understood that since the additives in the electrolyte will be consumed to some extent during formation and cycling, generating the relevant components in the SEI film and / or CEI film, the mass percentage of the additive in the electrolyte may be slightly lower than the initial added mass percentage of the additive in the electrolyte.

[0215] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate additive can be 3%, 4%, 5%, 6%, 7%, 8% or any numerical range between any two of them.

[0216] When the mass percentage of the carbonate additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the stability of the SEI film and the maintenance of the appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0217] In some embodiments, based on the total mass of the electrolyte, the mass percentage of vinylene carbonate is 2% to 5%.

[0218] In some embodiments, based on the total mass of the electrolyte, the mass percentage of vinylene carbonate can be 2%, 3%, 4%, 5% or any numerical range between any two of them.

[0219] Vinylene carbonate (VC) has a reduction potential close to that of carboxylic ester solvents, which can inhibit the reactivity of carboxylic ester solvents and improve the cycle life of battery cells. However, if the content of VC is too high, it will increase the interfacial impedance and charge transfer impedance of the battery, which is not conducive to the fast charging performance of battery cells. When the mass ratio of VC is within the above range, the battery can achieve both excellent cycle life and fast charging performance.

[0220] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the ethylene carbonate derivative is 0% to 4%.

[0221] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the ethylene carbonate derivative is 1.5% to 3.5%.

[0222] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the ethylene carbonate derivative can be 0.5%, 1%, 2%, 3%, 4% or any value range between any two of them.

[0223] It should be noted that as the battery cell is charged and discharged, when the addition amount of the ethylene carbonate derivative is small, after disassembling the battery cell to obtain the electrolyte and testing the content of the ethylene carbonate derivative by gas chromatography, the content may be 0%. It can be understood that in some embodiments, the ethylene carbonate derivative added to the electrolyte is completely converted into the organic components in the SEI film during the formation process. In some embodiments, there is still ethylene carbonate derivative remaining in the electrolyte, which forms a reinforcing effect on the SEI film during the subsequent cycle process of the battery cell.

[0224] The ethylene carbonate derivative can also form a film on the surface of the negative electrode at a relatively high potential and has a low interfacial impedance and charge transfer impedance. When the mass ratio of the ethylene carbonate derivative is within the above range, the battery cell can achieve both excellent fast charging performance and cycle life. By adding VC and the ethylene carbonate derivative in combination in the electrolyte, the fast charging performance and cycle stability of the battery cell can be comprehensively improved.

[0225] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the sulfur-containing additive is 0% to 2%.

[0226] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the sulfur-containing additive is 0.5% to 2%.

[0227] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the sulfur-containing additive can be 0.5%, 1%, 1.5%, 2% or any value range between any two of them.

[0228] It should be noted that, since the additives in the electrolyte will be somewhat consumed during formation and charge-discharge cycling, generating the relevant components in the SEI film and / or CEI film, when the content of sulfur-containing additives and lithium salt additives is tested by gas chromatography after disassembling the battery cell to obtain the electrolyte, the content may be 0%.

[0229] Specifically, taking the case where the mass content of the sulfur-containing additive is 0% as an example, it may be that the freshly prepared electrolyte does not contain the sulfur-containing additive, or that the electrolyte obtained after disassembling the battery cell does not contain the sulfur-containing additive. This situation may be that the freshly prepared electrolyte does not contain the sulfur-containing additive, or that a small amount of the sulfur-containing additive is added, but it participates in the film-forming reaction of the SEI film during the formation of the battery cell, resulting in a mass content of 0% for the sulfur-containing additive during the detection. Optionally, the freshly prepared electrolyte includes the sulfur-containing additive.

[0230] Furthermore, for adding certain substances in the electrolyte, such as additives, due to the characteristic that the additives play a role by participating in the film formation on the surface of the active material, the content of the additives in the electrolyte of the battery cell is related to formation, different battery life cycles or different battery storage states. Therefore, there may be a difference in the content of the additives between the freshly prepared electrolyte and the electrolyte obtained by reverse-disassembling the battery cell. However, those skilled in the art can know the approximate range of the content of the relevant substances in the corresponding freshly prepared electrolyte according to the performance expression level (such as the number of cycles) and the residual content of the battery cell. Similarly, those skilled in the art can also know the approximate range of the content of the non-freshly prepared (i.e., reverse) according to the content of the freshly prepared additives, based on the performance requirements of the battery cell, the storage environment, etc.

[0231] Therefore, the additive content mentioned in the technical solution of this application can be the content of the additives actively added to the freshly prepared electrolyte, or the content of the residual additives detected by reverse according to the actual battery state.

[0232] It can be understood that, in some embodiments, the sulfur-containing additives added in the electrolyte are completely converted into the sulfur-containing components in the SEI film during formation, and the addition amount of the sulfur-containing additives in the electrolyte can be inferred by X-ray photoelectron spectroscopy (XPS) testing of the negative electrode material. In some embodiments, there are still sulfur-containing additives remaining in the electrolyte, which form a reinforcing effect on the SEI film during the subsequent cycling of the battery cell.

[0233] In this application, the X-ray photoelectron spectroscopy (XPS) of the negative electrode material can be tested by any well-known method 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) more than three times, and then powder is scraped for sampling. The obtained negative electrode material sample 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 scanning rate and time of the X-ray source are adjusted to make it focused and detect elements and functional groups at a depth of 5 nm to 10 nm from the surface of the negative electrode material, and an X-ray photoelectron spectroscopy (XPS) spectrum of the sample is obtained. The elemental characteristic peaks are analyzed in the spectrum.

[0234] When the mass percentage of the sulfur-containing additive in the electrolyte is within the above range, it is beneficial to balance 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.

[0235] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0% to 1%.

[0236] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.2% to 1%.

[0237] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.2%, 0.4%, 0.�%, 0.8%, 1% or any numerical range between any two of them.

[0238] It can be understood that in some embodiments, the lithium salt additive added to the electrolyte is completely converted into inorganic components in the SEI film and / or CEI film during the formation process. In some embodiments, there is still residual lithium salt additive in the electrolyte, which forms a reinforcing effect on the SEI film and / or CEI film during the subsequent cycle of the battery cell.

[0239] When the mass percentage of the lithium salt additive in the electrolyte is within the above range, it is beneficial to balance enhancing 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.

[0240] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the fluorobenzene additive is 0.1% to %.

[0241] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the fluorobenzene additive is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or any numerical range between any two of them.

[0242] The mass proportion of fluorobenzene additives in the electrolyte is within the above range, which is beneficial to taking into account the wettability of the electrolyte and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0243] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and the compaction density of the negative electrode active material layer is 1.20 g / cm 3 Up to 1.50g / cm 3 .

[0244] The compaction density of the negative electrode active material layer can be tested by a method similar to the compaction density of the positive electrode active material layer described above.

[0245] In some embodiments, the compaction density of the negative electrode active material layer is 1.20 g / cm 3 , 1.25g / cm 3 , 1.30g / cm 3 , 1.35g / cm 3 , 1.40g / cm 3 , 1.45g / cm 3 , 1.50g / cm 3 or any range of values between them.

[0246] The negative electrode active material layer with a compaction density within the above range can further achieve a balance among the energy density, fast charging performance and cycle stability of the battery cell.

[0247] In some embodiments, the positive electrode current collector includes a positive electrode current collecting portion and a positive electrode tab, and the positive electrode tab is disposed at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly or at least one side extending along the width direction of the electrode assembly.

[0248] 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.

[0249] The above-mentioned tab arrangement helps to improve the weight energy density of the battery cell.

[0250] 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.

[0251] The above tab design helps to improve the over-current capacity of the battery cell, alleviate the situation of lithium deposition caused by excessive temperature on the tab side during fast charging, which leads to electrolyte decomposition and uneven current distribution on the tab side, thereby improving the fast charging performance and cycle stability of the battery cell. It is especially applicable to improving the fast charging performance of battery cells with the length dimension of the positive active material layer in the range of 650 mm to 950 mm, while taking into account excellent volumetric energy density.

[0252] In some embodiments, referring to Figure 5 , the positive tab 12111 is disposed on one side of the positive current collector 12110 extending along the width direction of the electrode assembly.

[0253] In some embodiments, referring to Figure 6 , the positive tab 12111 is disposed on both sides of the positive current collector 12110 extending along the width direction of the electrode assembly.

[0254] The above tab design helps to further improve the over-current capacity of the battery cell, thereby further improving the fast charging performance and cycle stability of the battery cell. It is especially applicable to improving the fast charging performance of battery cells with the length dimension of the positive active material layer in the range of 650 mm to 950 mm.

[0255] In some embodiments, the negative current collector includes a negative current collector portion and a negative tab, and the negative tab is disposed at at least one end of the negative current collector portion extending along the length direction of the electrode assembly or at least one side of the negative current collector portion extending along the width direction of the electrode assembly.

[0256] In some embodiments, referring to Figure 7 , the negative current collector 1221 includes a negative current collector portion 12210 and a negative tab 12211, and the negative tab 12211 is disposed at one end of the negative current collector portion 12210 extending along the length direction of the electrode assembly.

[0257] In some embodiments, referring to Figure 8 , the negative tab 12211 is disposed at both ends of the negative current collector portion 12210 extending along the length direction of the electrode assembly.

[0258] In some embodiments, referring to Figure 9 , the negative tab 12211 is disposed on one side of the negative current collector portion 12210 extending along the width direction of the electrode assembly.

[0259] In some embodiments, referring to Figure 10 , the negative tab 12211 is disposed on both sides of the negative current collector portion 12210 extending along the width direction of the electrode assembly.

[0260] In some embodiments, the size of the positive electrode active material layer in the length direction of the electrode assembly is 650 mm to 950 mm, and the positive electrode tab is disposed at both ends of the positive current collector portion extending in the length direction of the electrode assembly or at least one side extending in the width direction of the electrode assembly.

[0261] In some embodiments, referring to Figure 3 and 4 , the positive electrode tab is disposed at at least one end of the positive current collector portion extending in the length direction of the electrode assembly, and the ratio of the width of the positive electrode tab to the width of the positive current collector portion is 0.25 to 1.

[0262] In some embodiments, referring to Figure 7 and 8 , the negative electrode tab is disposed at at least one end of the negative current collector portion extending in the length direction of the electrode assembly, and the ratio of the width of the negative electrode tab to the width of the negative current collector portion is 0.25 to 1.

[0263] In some embodiments, referring to Figure 5 and 6 , the positive electrode tab is disposed at at least one side of the positive current collector portion extending in the width direction of the electrode assembly, and the ratio of the width of the positive electrode tab to the length of the positive current collector portion is 0.25 to 1.

[0264] In some embodiments, referring to Figure 9 and 10 , the negative electrode tab is disposed at at least one side of the negative current collector portion extending in the width direction of the electrode assembly, and the ratio of the width of the negative electrode tab to the length of the negative current collector portion is 0.25 to 1.

[0265] In some embodiments, the ratio of the width of the positive electrode tab to the width of the positive current collector portion or the ratio of the width of the negative electrode tab to the width of the negative current collector portion can be 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, 1 or the numerical range between any two of them.

[0266] When the width of the tab is within the above range, it helps to improve the over-current capacity of the battery cell, and improve the fast charging performance and cycle stability of the battery cell.

[0267] In some embodiments, along the length direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1; along the width direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH2, where OH1 is 1.0 mm to 4.0 mm; and / or, OH2 is 1.0 mm to 3.0 mm.

[0268] In this application, referring to Figure 1 , 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 OH1 between the size of the negative electrode active material layer 1222 and the size of the positive electrode active material layer 1212 is OH 21 -OH 11 ; referring to Figure 2 , 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 OH1 between the size of the negative electrode active material layer 1222 and the size of the positive electrode active material layer 1212 is OH 22 -OH 12 , and the size can be measured with a ruler.

[0269] In some embodiments, OH1 can be 1.0 mm, 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, 4.0 mm or the numerical range between any two of them.

[0270] In some embodiments, OH2 can be 1.0 mm, 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, 3.0 mm or the numerical range between any two of them.

[0271] As the charging rate of the battery cell increases, the current density in the area near the tab is high and the temperature rise is large, making it easy for the negative electrode active material layer to generate lithium dendrites near the tab. The battery cell of the embodiment of this application improves the ability of the negative electrode active material layer, especially the negative electrode active material layer in the area near the tab, to receive active ions in the length direction through the design of OH1 and OH2, and makes the distance between the positive electrode active material layer and the tab side farther. The current distribution of the active material layer in the area near the tab is more uniform, resulting in a reduced temperature rise. Thus, the lithium deposition problem of the negative electrode plate is comprehensively improved. At the same time, the probability of the separator shrinking due to heat and causing the positive and negative electrodes to overlap and then resulting in an internal short circuit of the battery is reduced. While the fast charging performance and cycle stability of the battery cell are improved, by controlling the values of OH1 and OH2 within the above range, the battery cell can achieve excellent energy density.

[0272] In some embodiments, OH1 is greater than or equal to OH2.

[0273] Controlling OH1≥OH2 can improve the cycle stability of the battery cell while being beneficial to further improving the energy density of the battery cell.

[0274] In some embodiments, the positive electrode active material includes: a lithium-containing phosphate, and a coating layer located on at least a part of the surface of the lithium-containing phosphate, and the coating layer contains carbon elements.

[0275] The coating layer contains carbon elements, which is beneficial to improving the electronic conductivity of the lithium-containing phosphate, improving the solid-phase transport rate of electrons, and thus further improving the energy density and fast charging performance of the battery cell.

[0276] In some embodiments, based on the total mass of the positive electrode active material, the mass ratio of carbon elements is 0.8% to 2.3%.

[0277] In some embodiments, based on the total mass of the positive electrode active material, the mass ratio of carbon elements can be 0.8%, 1.1%, 1.4%, 1.7%, 2.0%, 2.3% or the numerical range between any two of them.

[0278] Based on the total mass of the positive electrode active material, when the mass ratio of carbon elements is within the above range, the lithium-containing phosphate has both excellent electronic conductivity and specific capacity, further comprehensively improving the energy density and fast charging performance of the battery cell.

[0279] In some embodiments, the coating layer further includes a component shown in Formula I,

[0280] Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I,

[0281] where 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn. Optionally, M1 is +4 valent.

[0282] In some embodiments, d1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a numerical range between any two of them, m1 can be optionally 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or a numerical range between any two of them, and n1 can be optionally 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4 or a numerical range between any two of them.

[0283] In some embodiments, the component shown in Formula I includes one or more of Li2FeTi(PO4)3, Li2FeZr(PO4)3, and Li2FeSn(PO4)3.

[0284] It should be noted that the coating layer can be a single-layer structure or a multi-layer structure. That is to say, the carbon-containing component in the coating layer and the component shown in Formula I can be a mixed phase or a layered arrangement.

[0285] The phase structure in the coating layer can be characterized by any well-known method in the art. For example, by characterizing the positive electrode active material through a transmission electron microscope, it can be seen that there are different phase structures in the coating layer and the matrix of the positive electrode active material. Combining the diffraction pattern and energy spectrum analysis can judge the components of the coating layer.

[0286] The component shown in Formula I is a fast ion conductor with a NASICON structure, whose ionic conductivity is close to or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has rich three-dimensional lithium ion diffusion and transport channels and has advantages such as high ion conduction efficiency and strong structural stability during multiple de-lithiation and intercalation processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly improve the transport rate of lithium ions during multiple de-intercalation / intercalation at the positive electrode end, improve the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0287] In some embodiments, the lithium-containing phosphate includes the component shown in Formula II,

[0288] Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II,

[0289] Among them, 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, N, and P; Y includes one or more of O and F.

[0290] In some embodiments, x1 can be selected from 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or the numerical range between any two of them, y1 can be selected from 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 the numerical range between any two of them, x1 + y1 can be selected from 0.9, 1, 1.1, 1.2, 1.3 or the numerical range between any two of them, a1 can be selected from 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or the numerical range between any two of them, b1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or the numerical range between any two of them, a1 + b1 can be selected from 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or the numerical range between any two of them, c1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or the numerical range between any two of them, z1 can be selected from 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or the numerical range between any two of them.

[0291] The lithium-containing phosphate with an olivine structure having the above components has good structural stability, can reduce the loss during fast charging, and further improve the fast charging performance and cycle stability of the battery cell.

[0292] 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 forms include one or more of doping modification and coating modification.

[0293] In some embodiments, the powder compaction density of the positive electrode active material under 30000N is 2.55 g / cm 3 to 2.75 g / cm3 .

[0294] The powder compaction density of the positive electrode active material under 30000N is a meaning well-known in the art and can be measured by instruments and methods known in the art. For example, it can be measured with reference to GB / T 24533-2019 through an electronic pressure testing machine (such as the UTM7305 type electronic pressure testing machine). The exemplary test method is as follows: Weigh 1g of the positive electrode active material powder, add it to a mold with a bottom area of 1.327 cm 2 , apply pressure up to 30000N, keep the pressure for 30s, then release the pressure, keep it for 10s, and then record and calculate the powder compaction density of the material under a pressure of 30000N.

[0295] In some embodiments, the powder compaction density of the positive electrode active material under 30000N is 2.55 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.70 g / cm 3 , 2.75 g / cm 3 or the numerical range between any two of them.

[0296] The positive electrode active material with a powder compaction density within a suitable range can make the positive electrode active material layer have a higher compaction density, thereby enabling the battery cell to have a higher energy density.

[0297] In some embodiments, the single-sided coating mass of the positive electrode active material layer is from 220 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 .

[0298] In some embodiments, the single-sided coating mass of the positive electrode active material layer is 220 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 240 mg / 1540.25 mm 2 , 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2, 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 360 mg / 1540.25 mm 2 , 370 mg / 1540.25 mm 2 or the numerical range between any two of them.

[0299] The positive electrode active material layer with the single-sided coating mass within the above range can further effectively balance the fast charging performance and energy density of the battery cell. [[ID=?]] [[ID=?]]

[0300] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm. [[ID=?]] [[ID=?]]

[0301] The material of the positive electrode current collector and / or the negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery cell and has conductivity. The current collector includes a metal foil with a pure metal content of more than 95%, such as at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, and nickel foil. It also includes an alloy foil of at least two main metals. For example, an alloy foil made of at least two main elements among copper, aluminum, nickel, titanium, and iron can be used. It can also include copper, aluminum cadmium alloy, iron, or stainless steel, etc. surface-treated with carbon, nickel, titanium, silver, copper, etc. In addition, the bonding force with the negative electrode active material can be enhanced by forming fine concavities and convexities on the surface, and it can be used in various forms such as film, sheet, foil, mesh, porous body, foam, and non-woven fabric. [[ID=?]] [[ID=?]]

[0302] In some embodiments, the thickness of the positive electrode current collector can be 10 µm, 11 µm, 12 µm, 13 µm, 14 µm, 15 µm or the numerical range between any two of them. [[ID=?]] [[ID=?]]

[0303] The positive electrode current collector has a lower thickness, enabling further improvement of the energy density of the battery cell. [[ID=?]] [[ID=?]]

[0304] In some embodiments, the positive electrode active material layer may optionally further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. [[ID=?]] [[ID=?]]

[0305] In some embodiments, the positive electrode active material layer may optionally further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. [[ID=?]] [[ID=?]]

[0306] In some embodiments, the positive electrode tab further includes a positive electrode conductive layer located between the positive electrode active material layer and the positive electrode current collector, and the thickness of the positive electrode conductive layer is from 0.5 μm to 2 μm; and / or the negative electrode tab further includes a negative electrode conductive layer located between the negative electrode current collector and at least one side of the negative electrode active material layer, and the thickness of the negative electrode conductive layer is from 0.5 μm to 2 μm.

[0307] In some embodiments, the thickness of the positive electrode conductive layer or the negative electrode conductive layer can be 0.5 µm, 0.6 µm, 0.7 µm, 0.8 µm, 0.9 µm, 1.0 µm, 1.1 µm, 1.2 µm, 1.3 µm, 1.4 µm, 1.5 µm, 1.6 µm, 1.7 µm, 1.8 µm, 1.9 µm, 2.0 µm or a numerical range between any two of them.

[0308] The provision of the positive electrode conductive layer and / or the negative electrode conductive layer is beneficial to improving the electronic conductivity of the battery single cell tab and further improving the fast charging performance of the battery single cell.

[0309] In some embodiments, the positive electrode conductive layer includes a conductive agent and a positive electrode binder, the negative electrode conductive layer includes a conductive agent, 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 resins.

[0310] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material.

[0311] In some embodiments, the carbon-based material includes one or more of graphite and hard carbon.

[0312] In some embodiments, the carbon-based material includes composite graphite particles, the composite graphite particles include graphite body particles and a carbon coating layer covering at least part of the surface of the graphite body particles, the graphite body particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0313] The secondary particles refer to particles formed by the aggregation of two or more primary particles. The composite graphite particles including secondary particles and the surface coating layer including amorphous carbon are beneficial to further improving the wetting performance of the electrolyte in the negative electrode active material layer and the improvement of the solid-phase transport ability of active ions, and contribute to the further improvement of the cycle stability and fast charging performance of the battery single cell.

[0314] In some embodiments, based on the total mass of the composite graphite particles, the mass fraction of amorphous carbon is 2% to 5%.

[0315] In some embodiments, based on the total mass of the composite graphite particles, the mass fraction of amorphous carbon can be 2%, 3%, 4%, 5%, or any value range between any two of them.

[0316] When the content of amorphous carbon is within a suitable range, the composite graphite material can have a high specific capacity while also having a high active ion solid-phase transport ability, which is beneficial to further comprehensively improving the energy density and fast charging performance of the battery cell.

[0317] In some embodiments, the negative electrode active material layer may further optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0318] In some embodiments, the negative electrode active material layer may further optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0319] In some embodiments, the volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 14.5 μm.

[0320] The "volume average particle size Dv50" has the meaning well-known in the art, which respectively represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured by instruments and methods known in the art. For example, it can be conveniently measured by referring to GB / T19077-2016 Laser diffraction method for particle size distribution and using a laser particle size analyzer. The test instrument can be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK. The composite graphite particles can be freshly prepared or scraped from the negative electrode active material layer after disassembling the battery cell. For example, discharge the battery to 0% SOC, then disassemble to take the negative electrode plate, scrape a certain amount of powder on the electrode plate with a blade, then use deionized water to wash and shake it repeatedly 5 to 10 times, dry it, sinter it in a tube furnace at 400 °C for 2 h, after sintering, take an appropriate amount of the sample to be measured (the sample concentration ensures a light transmittance of 8% - 12%), add deionized water, and disperse it ultrasonically at the same time to ensure that the sample is completely dispersed, and then measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0321] 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, 14.5 μm, or a numerical range between any two of them.

[0322] When the volume-average particle size Dv50 of the composite graphite particles is within the above range, the solid-phase migration path of lithium ions is shortened while maintaining relatively low reactivity, thereby taking into account both the fast charging ability and the cycle life of the battery cell.

[0323] 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.

[0324] In some embodiments, the silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

[0325] In some embodiments, based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 0.5% to 5.0%.

[0326] In this application, the qualitative and quantitative determination of each substance or element can be detected by suitable equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change some detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination. Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element has the well-known meaning in the art and can be tested by methods known in the art. For example, the negative electrode plate is placed in a solvent such as water for soaking, the negative electrode active material is separated from the negative electrode current collector, and each substance in the negative electrode active material layer is obtained by filtration and used as a test sample. The test sample is analyzed by an inductively coupled plasma - emission spectrometer of model ICAP7400 from Thermo Fisher Scientific Company, USA, with reference to the standard of GB / T30902-2014, and the silicon element content can be obtained.

[0327] 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 a numerical range between any two of them.

[0328] The introduction of the silicon-based material is beneficial to further improve the energy density of the battery cell. When the mass proportion of silicon element is within the above mass range based on the total mass of the negative electrode active material layer, the energy density and cycle stability of the battery cell can be taken into account.

[0329] In some embodiments, the coating mass of the negative electrode active material layer on one side is 100 mg / 1540.25 mm 2 Up to 140mg / 1540.25mm 2 .

[0330] 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.

[0331] In some embodiments, the single-side coating mass of the negative electrode active material layer can be 100 mg / 1540.25 mm 2 、110mg / 1540.25mm 2 、120mg / 1540.25mm 2 、130mg / 1540.25mm 2 、140mg / 1540.25mm 2 or any range of values between them.

[0332] 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.

[0333] In some embodiments, the porosity of the separator is 20% to 70%, and optionally 35% to 60%.

[0334] 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.

[0335] In some embodiments, the porosity of the separator may be 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range therebetween.

[0336] 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.

[0337] In some embodiments, reference Figure 11, the separator 123 includes: a base film 1231; a first functional layer 1232 located on at least one side of the base film 1231, and the first functional layer 1232 includes a first inorganic substance; a second functional layer 1233 located on the side of the first functional layer 1232 away from the base film 1231, and the second functional layer 1232 includes a second inorganic substance and non-fluoropolymer particles.

[0338] In some embodiments, the non-fluoropolymer particles include acrylate copolymers.

[0339] In some embodiments, each of the first inorganic substance and the second inorganic substance independently includes one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

[0340] The inorganic particles can improve the wettability of the first functional layer and the second functional layer to the electrolyte and the heat resistance, and further comprehensively improve the fast charging performance, cycle stability, and safety performance of the battery cell. The non-fluoropolymer particles can improve the processing performance and stability of the separator, and avoid internal short circuit caused by the movement of the separator in the battery cell, thereby further improving the cycle stability and safety performance of the battery cell.

[0341] In some embodiments, the thickness of the base film is 4 μm to 12 μm, and can be optionally 5 μm to 9 μm.

[0342] In some embodiments, the thickness of the base film can be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or the numerical range between any two of them.

[0343] In some embodiments, the base film includes 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.

[0344] The thickness of the base film within the above range is beneficial to further balance the energy density, fast charging performance, and cycle stability of the battery cell.

[0345] In some embodiments, referring to Figure 12 , the battery cell 1 includes a housing 11 and a cover plate assembly. The cover plate assembly is disposed at at least one end of the housing 11. The housing 11 and the cover plate assembly define a receiving cavity. The electrode assembly is disposed in the receiving cavity. The wall thickness of the housing 111 of the large surface of the battery cell is 0.2 mm to 0.5 mm.

[0346] In some embodiments, the wall thickness of the housing of the large surface of the battery cell can be 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or the numerical range between any two of them.

[0347] When the wall thickness of the housing is within the above range, it is beneficial to further improve the energy density of the battery cell.

[0348] In some embodiments, the cover plate assembly includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly and the second cover plate assembly are disposed at both ends in the length direction or the width direction of the housing. The first cover plate assembly includes a first cover plate and a first electrode terminal, and the second cover plate assembly includes a second cover plate and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite.

[0349] In some embodiments, referring to Figure 12 , the battery cell 1 includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly includes a first cover plate, a first electrode terminal 131, and a third electrode terminal 133. The polarities of the first electrode terminal 131 and the third electrode terminal 133 are opposite. The second cover plate assembly includes a second cover plate, a second electrode terminal 132, and a fourth electrode terminal 134. The polarities of the second electrode terminal 132 and the fourth electrode terminal 134 are opposite.

[0350] Thereby, during charging, the temperature rise of the battery cell is reduced and the impedance of the battery cell is reduced, which is beneficial to the improvement of the fast charging performance, cycle life, and safety performance of the battery cell.

[0351] In some embodiments, the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S, and it satisfies 150 mm 2 ≤ S ≤ 1000 mm 2 .

[0352] In this application, the minimum cross-sectional area of the first electrode terminal refers to the minimum cross-sectional area of the first electrode terminal along the direction perpendicular to the current flow direction, and the minimum cross-sectional area of the second electrode terminal refers to the minimum cross-sectional area of the second electrode terminal along the direction perpendicular to the current flow direction.

[0353] In this application, when testing the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal, it can be calculated according to the shape of the minimum cross-section and its area calculation formula. For example, if the minimum cross-section of the electrode terminal is circular, the minimum cross-sectional area can be obtained by measuring the radius of the circle. If the minimum cross-section is square, the minimum cross-sectional area can be obtained by measuring the length and width of the square.

[0354] In some embodiments, the minimum cross-sectional area S of the first electrode terminal and / or the second electrode terminal can be 150 mm 2 , 300 mm 2 , 450 mm 2 , 600 mm 2 , 750 mm 2 , 900 mm 2, 1000 mm 2 etc., or can be a range composed of any of the above values.

[0355] When the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is within the above range, it is beneficial to improve the over-current capacity of the battery cell, reduce the heat generation of the electrode terminal, reduce the internal resistance of the battery cell, thereby improving the fast charging performance and cycle stability of the battery cell.

[0356] In some embodiments, the volumetric energy density of the battery cell is 430 Wh / L to 530 Wh / L.

[0357] In some embodiments, the volumetric energy density of the battery cell is 430 Wh / L to 470 Wh / L.

[0358] The volumetric energy density of the battery cell can be tested by any well-known method in the art. As an example, the battery cell is placed at 25 °C, charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage to 0.05C, and left standing for 30 min; discharged at a constant current of 0.33C to 2.0V, and record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminal and the insulating film outside the outer shell), and calculate the volume V0 of the single battery cell, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0359] In some embodiments, the volumetric energy density of the battery cell can be selected as 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, 480 Wh / L, 490 Wh / L, 500 Wh / L, 510 Wh / L, 520 Wh / L, 530 Wh / L or the numerical range between any two of them.

[0360] This battery cell simultaneously has a high energy density and can meet the demand for improving the cruising range of the electrical device.

[0361] In some embodiments, the liquid injection coefficient of the battery cell is 2.2 g / Ah to 3.0 g / Ah.

[0362] The liquid injection coefficient of a battery cell refers to the ratio of the mass of the electrolyte inside the battery cell to the battery capacity. The liquid injection coefficient of a battery cell can be measured by any well-known method in the art. Exemplarily, the mass of the electrolyte in the battery cell can be measured by the following method: Weigh the battery, and record the mass as M0. Disassemble the battery cell and pour out the free electrolyte. Take out the internal electrode assembly and separate the positive electrode plate, negative electrode plate, separator, and mechanical parts. Immerse and clean the positive electrode plate, negative electrode plate, separator, and mechanical parts with dimethyl carbonate (DMC) solvent for 24h - 48h, and soak repeatedly for more than 3 times. Place the aforementioned positive electrode plate, negative electrode plate, separator, and mechanical parts in an oven at 100°C for more than 24h until completely dried. Weigh the dried positive electrode plate, negative electrode plate, separator, and mechanical parts, and record the mass as M1. Thus, the mass of the electrolyte in the battery cell is (M0 - M1). The liquid injection coefficient is calculated by (M0 - M1) / the rated capacity of the battery cell. The rated capacity is the nominal capacity of the battery, or charge at a charging rate of 0.33C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, let it stand for 10min, and then discharge at a discharge rate of 0.33C to 2.0V. Take the discharge capacity of the battery cell as the rated capacity.

[0363] In some embodiments, the liquid injection coefficient of the battery cell can be selected as 2.2g / Ah, 2.3g / Ah, 2.4g / Ah, 2.5g / Ah, 2.6g / Ah, 2.7g / Ah, 2.8g / Ah, 2.9g / Ah, 3.0g / Ah, or any value range between any two of them.

[0364] When the liquid injection coefficient is within the above range, the cycle stability and energy density of the battery cell can be taken into account.

[0365] In some embodiments, the positive electrode plate, negative electrode plate, and separator can be made into an electrode assembly by a stacking process.

[0366] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0367] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0368] This application does not particularly limit the shape of the battery cell, and it can be square or any other shape. For example, Figure 12 is a battery cell 1 with a square structure as an example.

[0369] In some embodiments, referring to Figure 1 , the outer package may include a housing 11 and a cover plate assembly. Among them, the housing 11 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate assembly can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can be formed into an electrode assembly by a winding process or a laminating process. The electrode assembly is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly. The number of electrode assemblies included in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0370] In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells included in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0371] Optionally, the battery module may further include a housing having a receiving space, and a plurality of battery cells 1 are received in the receiving space.

[0372] In some embodiments, the above battery module can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0373] A second aspect of the present application provides a battery device, including the battery cell provided in the first aspect of the present application. The battery device includes at least one of a battery module, a battery pack, and an energy storage battery.

[0374] In addition, a third aspect of the present application further provides an electrical device, and the electrical device includes the battery cell provided in the first aspect of the present application. The battery cell, the battery module or the battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0375] As the electrical device, the battery cell, the battery module or the battery pack can be selected according to its usage requirements.

[0376] Figure 13 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery cell, a battery pack or a battery module can be used.

[0377] The device as another example can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a single battery cell can be used as the power source.

[0378] The embodiment of the present application also provides an energy storage device using a battery as the power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system, etc.

[0379] Embodiment

[0380] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in combination with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes a limitation to the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0381] For those not specified with specific technologies or conditions in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For the reagents or instruments not specified with the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0382] Embodiment 1

[0383] (1) Preparation of the positive electrode plate

[0384] The positive electrode plate includes a positive current collector, a positive conductive layer on the positive current collector, and a positive active material layer. The positive current collector is an aluminum foil with a thickness of 12 μm.

[0385] The positive conductive layer on the positive current collector is an active material layer formed by uniformly mixing a positive conductive agent, superconducting carbon, a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), and then coating and drying on the surface of the current collector. The thickness is 1 μm. The mass content of the positive conductive agent in the positive conductive layer is 40%, and the mass content of the positive binder is 60%.

[0386] Mix the positive active material, the binder polyvinylidene fluoride, and the conductive agent acetylene black in a ratio of 97:2:1, and then add the solvent N-methylpyrrolidone (NMP) and stir to form a positive electrode paste. Among them, the positive active material includes lithium iron phosphate, and the lithium iron phosphate has a coating layer. The coating layer covers the surface of the lithium iron phosphate particles. The coating layer includes lithium iron titanium phosphate Li2FeTi(PO4)3 and carbon element. The mass content of the carbon element is 1.12%. The powder compaction density of the lithium iron phosphate material under 30,000 N is 2.65 g / cm3 .

[0387] The positive conductive paste is evenly coated on the positive current collector aluminum foil, and after drying, a positive conductive layer is obtained; then the positive paste is evenly coated on the positive conductive layer, and after drying and cold pressing, a positive electrode plate is obtained. Among them, the single-sided coating mass of the positive active material layer is 263 mg / 1540.25 mm 2 .

[0388] (2) Preparation of the negative electrode plate

[0389] The negative electrode plate includes a negative current collector, a negative conductive layer on the negative current collector, and a negative active material layer. The negative current collector is a copper foil with a thickness of 5 μm;

[0390] The negative conductive layer on the negative current collector is an active material layer formed by uniformly mixing a negative conductive agent superconducting carbon, a negative binder styrene-butadiene rubber SBR, a thickener sodium carboxymethyl cellulose (CMC-Na), and a solvent water, coating it on the surface of the negative current collector, and drying. The thickness is 1 μm. The mass content of the negative conductive agent in the negative conductive layer is 35%, the mass content of the negative binder in the negative conductive layer is 60%, and the mass content of the thickener in the negative conductive layer is 5%;

[0391] The negative active material layer includes a negative active material, a conductive agent acetylene black, a negative binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose with a mass ratio of 96.5:0.5:2:1. The negative active material includes composite graphite particles. The composite graphite particles include a graphite body particle and a carbon coating layer covering at least part of the surface of the graphite body particle. The carbon coating layer includes amorphous carbon. Based on the total mass of the composite graphite particles, the mass ratio of amorphous carbon is 3.5%; the Dv50 of the composite graphite particles is 11.3 μm. The negative paste is evenly coated on the negative conductive layer of the negative current collector copper foil, and after drying and cold pressing, a negative electrode plate is obtained. The single-sided coating mass of the negative active material layer is 120 mg / 1540.25 mm 2 .

[0392] (3) Preparation of the electrolyte

[0393] The electrolyte includes a solvent, a lithium-containing electrolyte salt, and an additive.

[0394] The solvent includes ethyl acetate (the first solvent) with a mass ratio of 39.0%, ethylene carbonate EC with a mass content of 27.3%, and dimethyl carbonate DMC (the second solvent) with a mass content of 11.7%. The mass ratio of each component in the solvent is calculated based on the total mass of the electrolyte;

[0395] Based on the total mass of the electrolyte, the total mass content of the additives is 7%, which includes vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), and lithium difluoro(oxalato)borate (LiDFOB) with a mass ratio of 4:1.5:1:0.5;

[0396] The lithium-containing electrolyte salt includes 5% by mass of lithium bis(fluorosulfonyl)imide (LiFSI) and 10% by mass of lithium hexafluorophosphate (LiPF6). The mass ratio of the lithium-containing electrolyte salt is calculated based on the total mass of the electrolyte; the viscosity of the electrolyte at room temperature is 2.70 mPa·s.

[0397] (4) Preparation of the separator

[0398] The separator includes a base film and a functional layer. The base film includes a polyethylene film layer with a thickness of 5 μm, and the porosity of the separator is 42%;

[0399] 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 the binder polyvinylidene fluoride on one side of the base film, with a thickness of 1 μm and an average particle size of 10 nm for the aluminum oxide particles; the second functional layer is a film layer formed by coating a composite particle of polyacrylate and calcium oxide particles dispersed on the polyacrylate on the surface of the first functional layer, with a thickness of 5 μm and an average particle size of 10 nm for the calcium oxide particles.

[0400] (5) Preparation of the battery cell

[0401] Stack the above positive electrode plate, separator, and negative electrode plate in sequence, with the separator placed between the positive electrode plate and the negative electrode plate to play an isolation role. The tabs are provided at both ends of the current collector portion extending along the length direction of the electrode assembly. The ratio of the width of the positive and negative tabs to the width of the current collector portion is 1 / 3, obtaining a stacked electrode assembly. Place the electrode assembly in a housing, inject the electrolyte after drying, with a filling coefficient of 2.45 g / Ah, and obtain the battery cell through processes such as vacuum packaging, standing, formation, and shaping. Among them, the size of the positive active material layer along the length direction of the electrode assembly is 630 mm, the size along the width direction of the electrode assembly is 95 mm, OH1 is 4 mm, and OH2 is 3 mm. The housing is an aluminum shell, and the wall thickness of the housing on the large surface of the battery cell is 0.35 mm. The energy density of the battery cell is 460 Wh / L. The compaction density of the positive active material layer in the fully charged state is 2.75 g / cm 3 , and the compaction density of the negative active material layer in the fully charged state is 1.35 g / cm 3 .

[0402] Examples 1 - 13

[0403] The preparation methods of Examples 1-13 are basically the same as that of Example 1, except that some parameters in the battery cell are adjusted, as specifically shown in Tables 1 and 2. Among them, the single-sided coating mass of the positive active material layer in Example 7 is 220 mg / 1540.25 mm 2 , and the single-sided coating mass of the negative active material layer is 100 mg / 1540.25 mm 2 .

[0404] Example 14

[0405] The preparation method of Example 14 is basically the same as that of Example 1, except that the negative active material includes a silicon-based material, specifically as follows:

[0406] The negative active material layer includes a negative active material, a silicon-carbon material, a conductive agent acetylene black, a negative binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose with a mass ratio of 94.7:1.8:0.5:2:1. The negative active material includes composite graphite particles, and the Dv50 of the composite graphite particles is 11.3 μm. The single-sided coating mass of the negative active material layer is 113 mg / 1540.25 mm 2 , and based on the total mass of the negative active material layer, the mass fraction of silicon element is 0.86%.

[0407] Comparative Examples 1-6

[0408] The preparation methods of Comparative Examples 1-6 are basically the same as that of Example 1, except that some parameters in the battery cell are adjusted, as specifically shown in Tables 1 and 2.

[0409] Testing method

[0410] 1. Fast charging performance

[0411] At 30 °C, after the battery cells are cycled 200 times according to the following charge and discharge strategies respectively, and then fully charged to 100% SOC according to the corresponding charging strategy, the negative electrode plate is disassembled, the negative electrode plate is unfolded, the lithium deposition area (grayish-white area) is observed, and the lithium deposition area is measured. The lithium deposition degree is as follows:

[0412] No lithium deposition: The percentage of the lithium deposition area in the area of the negative active material layer < 0.05%.

[0413] Slight lithium deposition: The percentage of the lithium deposition area in the area of the negative active material layer < 2%.

[0414] Severe lithium deposition: The percentage of the lithium deposition area in the area of the negative active material layer ≥ 2%.

[0415] Charge the battery cell, and the charging steps include the following steps:

[0416] Charge from 0% SOC to 40% SOC at a constant current of 5.0C; charge from 40% SOC to 45% SOC at a constant current of 4.6C; charge from 45% SOC to 50% SOC at a constant current of 4.3C; charge from 50% SOC to 55% SOC at a constant current of 4.0C; charge from 55% SOC to 60% SOC at a constant current of 3.7C; charge from 60% SOC to 65% SOC at a constant current of 3.4C; charge from 65% SOC to 70% SOC at a constant current of 3.1C; charge from 70% SOC to 75% SOC at a constant current of 2.9C; charge from 75% SOC to 80% SOC at a constant current of 2.7C; charge from 80% SOC to 85% SOC at a constant current of 1.8C; charge from 85% SOC to 90% SOC at a constant current of 1.3C; charge from 90% SOC to 95% SOC at a constant current of 0.7C; charge from 95% SOC to 98% SOC at a constant current of 0.33C; charge from 98% SOC to 100% SOC at a constant current of 0.1C.

[0417] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0418] The discharging strategy is as follows: discharge at a constant current of 0.33C to the cut-off voltage, for example, 2.0V.

[0419] When performing charge and discharge tests on the battery cell, the battery cell can be assembled in a battery device, and the required charge and discharge strategies can be regulated through the battery management system for testing.

[0420] 2. Volume energy density

[0421] Place the battery cell at 25°C, charge it at a constant current of 0.33C to 3.65V, then charge it at a constant voltage to 0.05C, and let it stand for 30 min; discharge it at a constant current of 0.33C to 2.0V, and record the discharge capacity A0 at this time, unit: Ah; use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulation film outside the shell), and calculate the volume V0 of the single battery cell, unit: L; the volume energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0422] 3. Cycle performance

[0423] At 60°C, charge the battery cell at a constant current of 0.8C to the charge cut-off voltage of 3.6V, then charge it at a constant current of 0.1C to the charge cut-off voltage of 3.65V, and let it stand for 30 min; discharge it at a constant current of 1C to 3.1V, and let it stand for 30 min. This is one charge and discharge cycle. Repeat the above charge and discharge cycle steps until the cycle capacity retention rate (i.e., C n(( / C0×100%)) is 80%, and record the number of circulation cycles. The more the number of circulation cycles, the better the cycle performance of the battery cell.

[0424] Test results

[0425] Table 1

[0426]

[0427] Table 2

[0428]

[0429] From the comparison between the embodiments and the comparative examples of the present application, it can be seen that the compaction density of the positive electrode active material layer is 2.65 g / cm 3 to 2.8 g / cm 3 , and the size of the positive electrode active material layer along the length direction of the electrode assembly is 300 mm to 950 mm; the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s, which can take into account the improvement of the energy density, fast charging performance, and cycle stability of the battery cell, and realize the comprehensive improvement of the battery performance.

[0430] From the comparison between Example 1, 3 and Example 2, it can be seen that the compaction density of the positive electrode active material layer is 2.75 g / cm 3 to 2.8 g / cm 3 , while the battery cell has excellent cycle stability and fast charging performance, the energy density is further improved.

[0431] From the comparison between Example 1 and Example 4, 5, 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 battery cell takes into account excellent energy density, cycle stability and fast charging performance and is further improved.

[0432] From Example 1, 6, it can be seen that the electrolyte includes a first solvent with a viscosity η of 0.3 mPa·s to 0.6 mPa·s, and the battery cell has excellent energy density, fast charging performance and cycle stability.

[0433] From Example 1, 7-10, it can be seen that the mass ratio of the carboxylic acid ester solvent is 8% to 60%, and the battery cell has excellent energy density, fast charging performance and cycle stability.

[0434] From the comparison between Example 1, 8, 9 and Example 7, it can be seen that based on the total mass of the electrolyte, the mass ratio of the first solvent is 30% to 60%, and while the battery cell has excellent cycle stability and fast charging performance, the volume energy density is further improved.

[0435] As can be seen from Examples 1, 7 - 10, when the mass ratio of the carbonate solvent is 18% to 75%, the battery cell has excellent energy density, fast charging performance, and cycle stability.

[0436] As can be seen from Examples 1, 10, and 11, based on the total mass of the electrolyte, when the mass ratio of the carbonate additive is 3% to 8%, the battery cell takes into account excellent cycle stability, fast charging performance, and energy density.

[0437] As can be seen from Examples 1 and 12, based on the total mass of the electrolyte, when the mass ratio of the sulfur - containing additive is 0.5% to 2% and the mass ratio of the lithium salt additive is 0.2% to 1%, the battery cell takes into account excellent cycle stability, fast charging performance, and energy density.

[0438] As can be seen from the comparison between Example 13 and Example 1, the inclusion of fluorobenzene - based additives in the electrolyte is beneficial to further improving the cycle stability and fast charging performance of the battery cell.

[0439] As can be seen from the comparison between Example 14 and Example 1, 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 taking into account excellent fast charging performance and cycle stability.

[0440] It should be noted that the present disclosure is not limited to the above - mentioned embodiments. The above - mentioned embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the scope of the technical solution of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope not departing from the gist of the present disclosure, various modifications that can be thought of by those skilled in the art to the embodiments, and other ways constructed by combining some of the constituent elements of the embodiments are also included in the scope of the present disclosure.

Claims

1. A battery cell, wherein, It includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet that are stacked in sequence. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes one or more of lithium iron phosphate with an olivine structure and its modified forms. The modified forms include one or more of doping modification and coating modification. Among them, the tap density of the positive electrode active material layer is 2.65 g / cm 3 to 2.8 g / cm 3 , and the size of the positive electrode active material layer in the length direction of the electrode assembly is 300 mm to 950 mm; the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s.

2. The battery cell according to claim 1, wherein, The tap density of the positive active material layer is 2.75 g / cm 3 to 2.8 g / cm 3 .

3. The battery cell according to claim 1 or 2, wherein, The size of the positive electrode active material layer in the length direction of the electrode assembly is 400 mm to 650 nm.

4. The battery cell according to claim 1, wherein The electrolyte includes a first solvent, the viscosity η of the first solvent at room temperature is 0.3 mPa·s to 0.6 mPa·s, and based on the total mass of the electrolyte, the mass percentage of the first solvent is 8% to 60%.

5. The battery cell according to claim 4, wherein, Based on the total mass of the electrolyte, the mass percentage of the first solvent is 30% to 60%.

6. The battery cell according to claim 4 or 5, wherein The first solvent includes a carboxylic acid ester solvent.

7. The battery cell according to claim 6, wherein, The carboxylic ester solvent has R ， -COO-R ，， as the general structural formula, where R ， includes one or more of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R ，， includes one or more of an alkyl group having 1 to 5 carbon atoms and a halogenated alkyl group having 1 to 5 carbon atoms.

8. The battery cell according to claim 6, wherein, The carboxylic acid ester solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

9. The battery cell according to claim 1, wherein, The electrolyte further includes a second solvent, the second solvent 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.

10. The battery cell according to claim 9, wherein, Based on the total mass of the electrolyte, the mass percentage of the carbonate solvent is 18% to 75%.

11. The battery cell according to claim 1, wherein, The electrolyte includes a lithium-containing electrolyte salt, and based on the total mass of the electrolyte, the mass percentage of the lithium-containing electrolyte salt in the electrolyte is 10% to 18%.

12. The battery cell according to claim 11, wherein, The lithium-containing electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium hexafluorophosphate LiPF6.

13. The battery cell according to claim 12, wherein, Based on the total mass of the electrolyte, the mass percentage of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is 4% to 8%.

14. The battery cell according to claim 1, wherein, The electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, a lithium salt additive, and a fluorobenzene additive.

15. The battery cell according to claim 14, wherein, The carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Among them, the ethylene carbonate derivative includes the compound shown in Formula Ⅲ. Formula III R1, R2, R3, and R4 each independently include one or more of a hydrogen atom, a halogen atom, an alkyl group with 1 to 5 carbon atoms, and a halogenated alkyl group with 1 to 5 carbon atoms, and R1, R2, R3, and R4 are not simultaneously hydrogen atoms.

16. The battery cell according to claim 15, wherein, The carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate. The sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), 1,3-propane sultone, butylene sulfite, ethylene sulfite, and methylene bis(sulfonic acid) methyl ester. The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate; and / or The fluorobenzene additive includes one or more of fluorobenzene and its derivatives.

17. The battery cell according to claim 14 or 15, wherein, Based on the total mass of the electrolyte, the mass percentage of the carbonate additive is 3% to 8%.

18. The battery cell according to claim 14, wherein, The carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Based on the total mass of the electrolyte, the mass percentage of vinylene carbonate is 2% to 5%.

19. The battery cell according to claim 14, wherein, The carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Based on the total mass of the electrolyte, the mass percentage of the ethylene carbonate derivative is 0% to 4%.

20. The battery cell according to claim 14, wherein, The carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Based on the total mass of the electrolyte, the mass percentage of the ethylene carbonate derivative is 1.5% to 3.5%.

21. The battery cell according to claim 14, wherein, Based on the total mass of the electrolyte, the mass percentage of the sulfur-containing additive is 0% to 2%.

22. The battery cell according to claim 14, wherein, Based on the total mass of the electrolyte, the mass percentage of the sulfur-containing additive is 0.5% to 2%.

23. The battery cell according to claim 14, wherein, Based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0% to 1%.

24. The battery cell according to claim 14, wherein, Based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.2% to 1%.

25. The battery cell according to claim 14, wherein, Based on the total mass of the electrolyte, the mass content of the fluorobenzene additive is 26. The battery cell according to claim 1, wherein, The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector, and the tap density of the negative electrode active material layer is 1.20 g / cm 3 to 1.50 g / cm 3 .

27. The battery cell according to claim 26, wherein, ​ 28. The battery cell according to claim 27, wherein, ​ 29. The battery cell according to claim 27 or 28, wherein, ​ 30. The battery cell according to claim 27 or 28, wherein, ​ 31. The battery cell according to claim 26, wherein, ​ 32. The battery cell according to claim 31, wherein, ​ 33. The battery cell according to claim 1, wherein, ​ ​ ​ 34. The battery cell according to claim 33, wherein, ​ 35. The battery cell according to claim 33 or 34, wherein, ​ Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I Among them, 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn.

36. The battery cell according to claim 35, wherein, M1 is +4 valence.

37. The battery cell according to claim 33, wherein, The lithium-containing phosphate includes a component shown in Formula II. Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II Among them, 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, N, and P; Y includes one or more of O and F.

38. The battery cell according to claim 1, wherein, The positive electrode active material further includes one or more of lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, and modified forms of any one of the foregoing substances, wherein the modified forms include one or more of doping modification and coating modification.

39. The battery cell according to claim 1, wherein, The powder tap density of the positive electrode active material under 30,000 N is 2.55 g / cm 3 to 2.75 g / cm 3 .

40. The battery cell according to claim 1, wherein The single-sided coating mass of the positive electrode active material layer is 220 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 .

41. The battery cell according to claim 1, wherein, The thickness of the positive electrode current collector is 10 μm to 15 μm.

42. The battery cell according to claim 1, wherein, The positive electrode sheet further includes a positive electrode conductive layer, the positive electrode conductive layer 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 sheet further includes a negative electrode conductive layer, the negative electrode conductive layer is located between the negative electrode current collector and at least one side of the negative electrode active material layer, and the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

43. The battery cell according to claim 42, wherein, The positive electrode conductive layer includes a conductive agent and a positive electrode binder, the negative electrode conductive layer includes a conductive agent, the conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins.

44. The battery cell according to claim 1, wherein, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material.

45. The battery cell according to claim 44, wherein, The carbon-based material includes one or more of graphite and hard carbon.

46. The battery cell according to claim 44 or 45, wherein The carbon-based material includes composite graphite particles, the composite graphite particles include graphite body particles and a carbon coating layer coated on at least a part of the surface of the graphite body particles, the graphite body particles include secondary particles, and the carbon coating layer includes amorphous carbon.

47. The battery cell according to claim 46, wherein, Based on the total mass of the composite graphite particles, the mass ratio of the amorphous carbon is 2% to 5%.

48. The battery cell according to claim 46, wherein, The volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 14.5 μm.

49. The battery cell according to claim 44, wherein, 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.

50. The battery cell according to claim 49, wherein, The silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

51. The battery cell according to claim 44 or 45, wherein, Based on the total mass of the negative electrode active material layer, the mass ratio of silicon element is 0.5% to 5.0%.

52. The battery cell according to claim 1, wherein, The negative electrode plate includes a negative current collector and a negative active material layer provided on at least one side of the negative current collector, and the single-sided coating mass of the negative active material layer is 100 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 .

53. The battery cell according to claim 1, wherein, The porosity of the separator is 20% to 70%.

54. The battery cell according to claim 53, wherein, The porosity of the separator is 35% to 60%.

55. The battery cell according to claim 1, wherein, The separator includes: a base film; a first functional layer located on at least one side of the base film, and the first functional layer includes a first inorganic substance; a second functional layer located on the side of the first functional layer away from the base film, and the second functional layer includes a second inorganic substance and non-fluoropolymer particles.

56. The battery cell according to claim 55, wherein, The non-fluoropolymer particles include acrylate copolymers.

57. The battery cell according to claim 55 or 56, wherein, 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.

58. The battery cell according to claim 55, wherein, The thickness of the base film is 4 μm to 12 μm.

59. The battery cell according to claim 55, wherein, The thickness of the base film is 5 μm to 9 μm.

60. The battery cell according to claim 1, wherein, The battery cell includes a housing and a cover assembly. The cover assembly is disposed at at least one end of the housing. The housing and the cover assembly define a receiving cavity, and the electrode assembly is disposed in the receiving cavity. The wall thickness of the housing on the large surface of the battery cell is 0.2 mm to 0.5 mm.

61. The battery cell according to claim 60, wherein, The cover assembly includes a first cover assembly and a second cover assembly. The first cover assembly and the second cover assembly are disposed at both ends of the housing in the length direction or the width direction. The first cover assembly includes a first cover and a first electrode terminal, and the second cover assembly includes a second cover and a second electrode terminal. The polarities of the first electrode terminal and the second electrode terminal are opposite.

62. The battery cell according to claim 61, wherein, The minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is S, and it satisfies 150 mm 2 ≤ S ≤ 1000 mm 2 .

63. The battery cell according to claim 1, wherein, The volume energy density of the battery cell is 430 Wh / L to 530 Wh / L.

64. The battery cell according to claim 1, wherein, The volume energy density of the battery cell is 430 Wh / L to 470 Wh / L.

65. The battery cell according to claim 1, wherein, The liquid injection coefficient of the battery cell is 2.2 g / Ah to 3.0 g / Ah.

66. A battery device, wherein, Including the battery cell according to any one of claims 1 to 65, the battery device is at least one of a battery module, a battery pack, and an energy storage battery.

67. An electrical device, characterized in that, Including the battery device according to claim 66.

68. A energy storage device, characterized in that, Including the battery device according to claim 66, and the battery device is used for storing electric energy.

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