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

Abstract

The invention provides a battery monomer, a battery device, a power utilization device and an energy storage device. The 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 in the length direction of the electrode assembly is 300 mm to 950 mm; the viscosity of the electrolyte at the normal temperature ranges from 2.3 mPa * s to 3.5 mPa * s. And the battery monomer gives consideration to improvement of energy density, fast charging performance and cycling stability, and comprehensive improvement of battery performance is realized.

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, the entire content of which is incorporated herein 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 hydroelectric, 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 are also put forward for the energy density of battery cells, etc. 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 tab, a separator, and a negative electrode tab stacked in sequence. The positive electrode tab 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 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] The lithium-containing phosphate with olivine structure has the advantages of low cost and good lifespan. Coupled with the design of the laminated electrode assembly where the size of the positive electrode active material layer along the length direction of the electrode assembly is within the above range and the compaction density is within the above range, it helps to improve the internal space utilization rate of the battery cell, solve the problem of relatively low energy density of the battery cell when using the lithium-containing phosphate as the positive electrode active material, and at the same time make the internal resistance of the battery cell appropriate, enabling the battery cell to have excellent energy density and fast charging performance. However, the above electrode assembly design makes the distance for the electrolyte to infiltrate the positive and negative electrode active material layers longer and the resistance greater, and the porosity of the active material layer decreases, resulting in difficulties in electrolyte infiltration in the length direction of the active material layer. Furthermore, during the cycling process, there is an easy "broken bridge" situation in the lithium-ion transmission path, and with the increase of the charging rate of the battery cell, serious lithium deposition on the negative electrode is likely to occur, leading to cycling degradation. By making the viscosity of the electrolyte within the above range in the battery cell of the embodiment of the present application, it helps to improve the wettability of the electrolyte to the positive and negative electrode active material layers, thus solving the problem of difficult electrolyte infiltration in the length direction of the active material layer. While slowing down the degree of lithium deposition under fast charging conditions, the electrolyte also has good conductivity, stability and dissociation rate, so that the battery cell has excellent cycle stability and fast charging performance. Through the mutual cooperation between the positive electrode plate and the electrolyte in the embodiment of the present application, the battery cell has 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 to 2.8 g / 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 further improving the energy density.

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

[0011] When the size of the positive electrode active material layer along the length direction of the electrode assembly is within the above range, 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 based on the total mass of the electrolyte, the mass percentage of the first solvent is 8% to 60%.

[0013] The first solvent with a viscosity η within the above range has both excellent stability and low viscosity. The mass percentage of the first solvent within the above range 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 ，， wherein R ， includes one or more of a hydrogen atom, a halogen atom, an alkyl group of C 1 ~C 5 , a halogenated alkyl group of C 1 ~C 5 , and R ，， includes one or more of an alkyl group of C 1 ~C 5 , a halogenated alkyl group of C 1 ~C 5 .

[0019] In any embodiment, the carboxylic ester solvents include 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 proportion of the carbonate solvent is 18% to 75%.

[0023] Since carbonate solvents have a large viscosity, the electrolyte viscosity will increase with the increase of carbonate solvent content, which will have a negative impact on the conductivity of the electrolyte. By reasonably controlling the mass proportion of carbonate solvents within the above range, the electrolyte has both suitable viscosity and good dissociation rate, thereby achieving a comprehensive improvement in the electrolyte conductivity, which is conducive to further improving the fast charging performance and cycle stability of battery cells.

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

[0025] When the molar concentration of the lithium electrolyte salt in the electrolyte is within the above range, it is beneficial to take into account both the wettability and ion 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 lithium bis(fluorosulfonyl)imide LiFSI, lithium hexafluorophosphate LiPF 6 One or more of .

[0027] LiFSI is easy to dissociate in the electrolyte solvent, and the molecular weight of LiFSI is smaller than that of other types of fluorinated sulfonyl imide salts (such as lithium bis(trifluoromethanesulfonyl)imide LiTFSI), which is beneficial to improve the conductivity of the electrolyte while reducing the viscosity of the electrolyte. LiFSI has good thermal stability and is not easy to decompose during recycling. It can reduce the production of hydrogen fluoride during the battery cycle and reduce the probability of negative electrode side reactions, thereby further comprehensively improving the cycle stability and fast charging performance of the battery cell. However, with the increase in the temperature of the battery cell, LiFSI will undergo violent decomposition and release a large amount of heat at a certain temperature threshold, which will sharply increase the risk of thermal runaway of the battery. This safety risk is more significant in fast-charging batteries. Lithium-containing electrolyte salts also include lithium hexafluorophosphate LiPF 6 The risk of thermal runaway of battery cells can be reduced to a controllable range, thereby improving the safety performance of battery cells.

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

[0029] The mass proportion of lithium bis(fluorosulfonyl)imide LiFSI is within the above range, and the battery cells have excellent fast charging performance, cycle stability and safety performance.

[0030] In any embodiment, 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.

[0031] In any embodiment, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Among them, the ethylene carbonate derivative includes the compound shown in Formula III. Formula III R 1 、R 2 、R 3 、R 4 Each independently includes one or more of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R 1 、R 2 、R 3 、R 4 are not simultaneously hydrogen atoms. Optionally, the carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

[0032] The carbonate additive can evolve into an organic component 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 reaction 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.

[0033] In any embodiment, the sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), 1,3-propane sultone, butene sulfite, ethylene sulfite, and methylene bis(methanesulfonate).

[0034] The sulfur-containing additive often has a relatively high potential. The sulfur-containing additive added to the electrolyte will react preferentially during formation or subsequent cycling and evolve into a sulfur-containing inorganic component in the SEI film. The SEI film formed by the carbonate additive has poor high-temperature stability, which is not conducive to the stability of the battery cell in a high-temperature environment. The SEI film contains sulfur elements, which 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.

[0035] In any embodiment, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0036] 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 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.

[0037] In any embodiment, the fluorobenzene additives include one or more of fluorobenzene and its derivatives.

[0038] 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.

[0039] In any embodiment, based on the total mass of the electrolyte, the mass percentage of the carbonate additive is 3% to 8%.

[0040] 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 maintain an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0041] In any embodiment, based on the total mass of the electrolyte, the mass percentage of vinylene carbonate is 2% to 5%.

[0042] 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 percentage of vinylene carbonate VC is within the above range, the battery can achieve excellent cycle life and fast charging performance.

[0043] In any embodiment, based on the total mass of the electrolyte, the mass percentage of ethylene carbonate derivatives is 0% to 4%.

[0044] In any embodiment, based on the total mass of the electrolyte, the mass percentage of ethylene carbonate derivatives is 1.5% to 3.5%.

[0045] Ethylene carbonate derivatives can also form a film on the surface of the negative electrode at a relatively high potential and have a low interface impedance and charge transfer impedance. When the mass percentage 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.

[0046] In any embodiment, based on the total mass of the electrolyte, the mass percentage of the sulfur-containing additive is 0% to 2%.

[0047] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0.5% to 2%.

[0048] When the mass proportion 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.

[0049] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

[0050] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% to 1%.

[0051] When the mass proportion 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.

[0052] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the fluorobenzene additive is 0.1% to 1%.

[0053] 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 maintain an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0054] In any embodiment, the negative electrode tab 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 .

[0055] 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.

[0056] 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.

[0057] 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.

[0058] In any embodiment, 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 electrode current collector extending in the length direction of the electrode assembly or at least one side extending in the width direction of the electrode assembly.

[0059] The above-mentioned tab setting helps to improve the over-current capacity of the battery cell, alleviate the situation of lithium plating caused by electrolyte decomposition and uneven current distribution on the tab side due to excessive temperature on the tab side during fast charging, thereby improving the fast charging performance and cycle stability of the battery cell, especially applicable to improving the fast charging performance of battery cells with the length dimension of the positive electrode active material layer in the range of 650 mm to 950 mm, while taking into account excellent volumetric energy density.

[0060] In any embodiment, the positive electrode tab is disposed at at least one end of the positive electrode current collector 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 electrode current collector is 0.25 to 1; and / or, the ratio of the width of the negative electrode tab to the width of the negative electrode current collector is 0.25 to 1.

[0061] In any embodiment, the positive electrode tab is disposed at at least one side of the positive electrode current collector 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 electrode current collector is 0.25 to 1; and / or, the ratio of the width of the negative electrode tab to the length of the negative electrode current collector is 0.25 to 1.

[0062] The width of the tab within the above range helps to improve the over-current capacity of the battery cell, and improve the fast charging performance and cycle stability of the battery cell.

[0063] In any embodiment, along the length direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH 1 ; along the width direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH 2 , where OH 1 is 1.0 mm to 4.0 mm; and / or, OH 2 is 1.0 mm to 3.0 mm.

[0064] 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 electrode active material layer to generate lithium dendrites near the tab. The battery cell of the embodiment of the present application passes through OH 1 , OH 2The design improves the ability of the negative electrode active material layer, especially the negative electrode active material layer near the tab area, to receive active ions in the length direction, and makes the distance between the positive electrode active material layer and the tab side farther. The current distribution of the active material layer near the tab area is more uniform, resulting in a lower 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, the values of OH 1 and OH 2 are controlled within the above range, enabling the battery cell to have excellent energy density.

[0065] In any implementation, OH 1 is greater than or equal to OH 2 .

[0066] Controlling OH 1 ≥OH 2 improves the cycle stability of the battery cell and is beneficial to further improving the energy density of the battery cell.

[0067] In any implementation, the positive electrode active material includes: lithium-containing phosphate, and a coating layer located on at least part of the surface of the lithium-containing phosphate, and the coating layer contains carbon elements.

[0068] The coating layer containing carbon elements is beneficial to improving the electronic conductivity of the lithium-containing phosphate and improving the solid-phase transmission rate of electrons, thereby further improving the energy density and fast charging performance of the battery cell.

[0069] In any implementation, based on the total mass of the positive electrode active material, the mass proportion of carbon elements is 0.8% to 2.3%.

[0070] Based on the total mass of the positive electrode active material, the mass proportion of carbon elements within the above range enables the lithium-containing phosphate to have excellent electronic conductivity and specific capacity, and further comprehensively improves the energy density and fast charging performance of the battery cell.

[0071] In any implementation, the coating layer further includes a component shown in Formula I, Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I, where 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn. Optionally, M1 is +4 valent.

[0072] The component shown in Formula I is a fast ion conductor with a NASICON structure, whose ionic conductivity is close to or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has rich three-dimensional lithium ion diffusion and transport channels and has the advantages of high ion conduction efficiency and strong structural stability during multiple lithium deintercalation and intercalation processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly improve the transport rate of lithium ions during multiple deintercalation / intercalation at the positive electrode end, improve the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0073] In any embodiment, the lithium-containing phosphate includes a component shown in Formula II, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II, 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.

[0074] 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.

[0075] 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.

[0076] In any embodiment, the powder compaction density of the positive electrode active material under 30000 N is 2.55 g / cm 3 to 2.75 g / cm 3 .

[0077] The cathode active material with a powder compaction density within a suitable range can make the cathode active material layer have a high compaction density, thereby enabling the battery cell to have a high energy density.

[0078] In any embodiment, the single-sided coating mass of the cathode active material layer is 220 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 .

[0079] The cathode active material layer with the single-sided coating mass of the cathode active material layer within the above range can further effectively balance the fast charging performance and energy density of the battery cell.

[0080] In any embodiment, the thickness of the cathode current collector is 10 μm to 15 μm.

[0081] The cathode current collector has a low thickness, enabling further improvement in the energy density of the battery cell.

[0082] In any embodiment, the cathode electrode sheet further includes a cathode conductive layer located between the cathode active material layer and the cathode current collector, and the thickness of the cathode conductive layer is 0.5 μm to 2 μm; and / or the anode electrode sheet further includes an anode conductive layer located between the anode current collector and at least one side of the anode active material layer, and the thickness of the anode conductive layer is 0.5 μm to 2 μm.

[0083] The provision of the cathode conductive layer and / or the anode conductive layer is beneficial to improving the electronic conductivity of the battery cell electrode sheet and further improving the fast charging performance of the battery cell.

[0084] In any embodiment, the cathode conductive layer includes a conductive agent and a cathode binder, the anode 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 cathode 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.

[0085] In any embodiment, the anode active material layer includes an anode active material, and the anode active material includes a carbon-based material.

[0086] In any embodiment, the carbon-based material includes one or more of graphite and hard carbon.

[0087] In any embodiment, 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.

[0088] The secondary particles refer to particles formed by aggregation of two or more primary particles. The composite graphite particles including secondary particles and the surface coating layer including amorphous carbon are beneficial to 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 cell.

[0089] In any embodiment, based on the total mass of the composite graphite particles, the mass ratio of the amorphous carbon is 2% to 5%.

[0090] When the content of the amorphous carbon is within a suitable range, the composite graphite material can have a high specific capacity while also having a high solid-phase transport ability of active ions, which is beneficial to further comprehensively improving the energy density and fast charging performance of the battery cell.

[0091] In any embodiment, the volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 14.5 μm.

[0092] When the volume average particle size Dv50 of the composite graphite particles is within the above range, while shortening the solid-phase migration path of lithium ions, the lower reaction activity is taken into account, so as to take into account the fast charging ability and cycle life of the battery cell.

[0093] 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.

[0094] In any embodiment, the silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

[0095] In any embodiment, based on the total mass of the negative electrode active material layer, the mass ratio of the silicon element is 0.5% to 5.0%.

[0096] 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 the silicon element is within the above mass range, the energy density and cycle stability of the battery cell can be taken into account.

[0097] 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 .

[0098] The negative electrode active material layer with a single-sided coating quality within the above range can cooperate with the positive electrode active material layer to achieve a balance between the energy density and fast charging performance of the battery cell.

[0099] In any embodiment, the porosity of the separator is 20% to 70%, and can be optionally 35% to 60%.

[0100] The porosity of the separator within the above range is beneficial to further balance the energy density, fast charging performance and cycle stability of the battery cell.

[0101] In any embodiment, the separator includes: a base film; a first functional layer located on at least one side of the base film, the first functional layer including a first inorganic substance; a second functional layer located on the side of the first functional layer away from the base film, the second functional layer including a second inorganic substance and non-fluoropolymer particles.

[0102] In any embodiment, the non-fluoropolymer particles include acrylate copolymers.

[0103] In any embodiment, the first inorganic substance and the second inorganic substance each independently include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide.

[0104] The inorganic particles can improve the wettability and heat resistance of the first functional layer and the second functional layer to the electrolyte, 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 performance of the separator, avoid internal short circuit caused by the movement of the separator in the battery cell, and thus further improve the cycle stability and safety performance of the battery cell.

[0105] In any embodiment, the thickness of the base film is 4μm to 12μm, and can be optionally 5μm to 9μm.

[0106] 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.

[0107] In any embodiment, the battery cell includes a housing and a cover assembly, the cover assembly is arranged at at least one end of the housing, the housing and the cover assembly define a receiving cavity, and the electrode assembly is arranged in the receiving cavity. The wall thickness of the housing on the large surface of the battery cell is 0.2mm to 0.5mm.

[0108] The wall thickness of the housing on the large surface of the battery cell within the above range is beneficial to further improve the energy density of the battery cell.

[0109] In any implementation, the cover plate assembly includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly and the second cover plate assembly are disposed at two 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.

[0110] Thus, during charging, the temperature rise of the battery cell is reduced and the impedance of the battery cell is decreased, which is beneficial to the improvement of the fast charging performance, cycle life, and safety performance of the battery cell.

[0111] In any implementation, 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 .

[0112] 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 overcurrent capacity of the battery cell, reduce the heat generation of the electrode terminal, and decrease the internal resistance of the battery cell, thereby improving the fast charging performance and cycle stability of the battery cell.

[0113] In any implementation, the volumetric energy density of the battery cell is from 430 Wh / L to 530 Wh / L.

[0114] In any implementation, the volumetric energy density of the battery cell is from 430 Wh / L to 470 Wh / L.

[0115] This battery cell simultaneously has a high energy density and can meet the demand for improving the endurance mileage of the electrical device.

[0116] In any implementation, the liquid injection coefficient of the battery cell is from 2.2 g / Ah to 3.0 g / Ah.

[0117] When the liquid injection coefficient is within the above range, the cycle stability and energy density of the battery cell can be balanced.

[0118] The second aspect of the present application provides a battery device, including the battery cell provided in the first aspect of the present application. The battery device includes at least one of a battery module, a battery pack, and an energy storage battery.

[0119] The third aspect of the present application further provides an electrical device, and the electrical device includes the battery cell provided in the first aspect of the present application.

[0120] The fourth aspect of the present application further provides an energy storage device, and the energy storage device includes the battery cell provided in the first aspect of the present application. Description of the Drawings

[0121] Figure 1Schematic diagram of the positive electrode plate and negative electrode plate according to an embodiment of the present application; Figure 2 Schematic diagram of the positive electrode plate and negative electrode plate according to an embodiment of the present application; Figure 3 Schematic diagram of the positive electrode current collector according to an embodiment of the present application; Figure 4 Schematic diagram of the positive electrode current collector according to an embodiment of the present application; Figure 5 Schematic diagram of the positive electrode current collector according to an embodiment of the present application; Figure 6 Schematic diagram of the positive electrode current collector according to an embodiment of the present application; Figure 7 Schematic diagram of the negative electrode current collector according to an embodiment of the present application; Figure 8 Schematic diagram of the negative electrode current collector according to an embodiment of the present application; Figure 9 Schematic diagram of the negative electrode current collector according to an embodiment of the present application; Figure 10 Schematic diagram of the negative electrode current collector according to an embodiment of the present application; Figure 11 Schematic diagram of the structure of the separator according to an embodiment of the present application; Figure 12 Schematic diagram of the structure of the battery cell according to an embodiment of the present application; Figure 13 Schematic diagram of an electrical device using the battery cell as a power source according to an embodiment of the present application.

[0122] Description of reference numerals: 1 Battery cell; 11 Housing; 111 Housing of the large surface of the battery cell; 12 Electrode assembly; 121 Positive electrode 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 implementation manners

[0123] 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 details are omitted. For example, there may be cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by 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 recited in the claims.

[0124] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range 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 the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when a certain parameter is expressed as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0125] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0126] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0127] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0128] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application mean open-ended or may also be closed-ended. For example, the "comprising" and "including" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0129] Unless otherwise specified, in this application, the term "or" is inclusive. 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) while B is true (or exists); or both A and B are true (or exist).

[0130] 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 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 battery cell.

[0131] Based on this, a first aspect of this application provides a battery cell, including an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet stacked in sequence. The positive electrode sheet includes a positive 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 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.

[0132] The lithium-containing phosphate with olivine structure is an active material with olivine structure including lithium ions and phosphate groups. The types of the positive electrode active materials can be tested by any well-known method in the art. As an example, methods for phase analysis such as X-ray diffraction method (XRD) can be combined with elemental analysis methods such as energy spectrum and XPS for analysis.

[0133] In this application, the tap density of the positive electrode active material layer has the meaning well-known in the art and can be tested by methods known in the art. For example, the battery cell is placed at 25 °C and charged at a constant current charge rate of 0.33C until the cut-off voltage (such as 3.65V), then left standing for 1 min, and charged at a constant voltage of 3.65V until the current is less than 0.05C. At this time, the battery cell is in a fully charged state. Then, the positive electrode plate is disassembled, and the tap density of the positive electrode active material layer is measured. The tap 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.

[0134] 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.

[0135] In this application, the single-sided coating mass of the positive electrode active material layer can be tested by methods known in the art. For example, a positive electrode plate can be taken from the disassembled battery (if it is a positive electrode plate with double-sided coating, 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, the positive electrode active material layer of the above-mentioned weighed positive electrode plate is wiped off, and the mass of the positive electrode current collector is weighed and recorded as M0. The single-sided coating mass of the positive electrode plate = (M1 - M0) / S1.

[0136] 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 by a micrometer (such as Mitutoyo 293-100 type with an accuracy of 0.1μm). It can be understood that when the battery cell is in a fully charged state, the tap density of the positive electrode active material layer is different from the designed value of the tap density of the battery cell. Affected by actual operations, when the battery cell is in a fully charged state, the tap density of the positive electrode active material layer is often slightly lower than the designed value of the tap density of the battery cell.

[0137] In some embodiments, the tap 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 / cm3 、 2.80 g / cm 3 or the numerical range between any two of them.

[0138] In this application, with reference to Figure 1 , the electrode assembly 12 includes a positive electrode tab 121, a separator 123, and a negative electrode tab 122 that are stacked in sequence. The positive electrode tab 121 includes a positive current collector 1211 and a positive active material layer 1212 disposed on at least one side of the positive current collector 1211. Along the length direction of the electrode assembly 12, the size of the positive active material layer 1212 is OH 11 , and the size can be measured with a ruler.

[0139] In some embodiments, the size of the positive 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 the numerical range between any two of them.

[0140] In this application, "room temperature" refers to 25 ± 3°C.

[0141] In this application, the viscosity of the electrolyte at room temperature has the meaning well-known in the art and can be tested 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 and static settlement for 10 - 20 min. After the sample temperature is the same as the hydrothermal temperature, a rotational viscometer produced by Brookfield Corporation with the instrument model DV-2TLV and a viscosity measurement accuracy of ±1% of the full scale is used for testing. When the 18th rotor rotates continuously at a constant speed of 70 r in the sample, the shear force causes a torque on the spring. The torque is proportional to the viscosity, and the viscosity value is obtained. Five samples of the test sample are tested, and the viscosity is the average value of the five samples. Before the test, the sample cup and the rotor are rinsed with the electrolyte sample and kept at the temperature to be measured. The test equipment meets the following test environmental conditions: 1. Equipment external environment: temperature is 15 - 28°C, humidity is RH < 80%; 2. Equipment internal environment: 2 / 3 of the sample container is immersed in the 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.

[0142] 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.

[0143] 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 range and the compaction density is within the above 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 serious lithium precipitation at the negative electrode, which in turn leads to cycle diving. The battery cell of the embodiment of the present application helps to improve the wettability of the electrolyte to the positive and negative electrode active material layers by making the viscosity of the electrolyte within the above range, thereby improving the problem of the difficulty of the electrolyte in wetting the active material layer in the length direction, slowing down the lithium precipitation degree of the battery cell under fast charging conditions, while the electrolyte has good conductivity, stability and dissociation rate, so that the battery cell has both excellent cycle stability and fast charging performance. The embodiment of the present application makes the battery cell have excellent energy density, fast charging performance and cycle life through the mutual cooperation between the positive electrode sheet and the electrolyte.

[0144] 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 .

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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 is 8% to 60% based on the total mass of the electrolyte.

[0149] 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, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery monomer that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery monomer is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery monomer is taken as a sample, and ion chromatography analysis method is used for detection. 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 / T9722-2023 General Rules for Gas Chromatography of Chemical Reagents 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 / T020-2002 General Rules for Ion Chromatography Analysis Method to qualitatively or quantitatively analyze the inorganic components / lithium salts of the electrolyte by ion chromatography analysis method.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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 monomer.

[0154] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the first solvent is 30% to 60%.

[0155] 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 monomer has excellent cycle stability, the fast charging performance is further improved.

[0156] In some embodiments, the first solvent includes a carboxylate solvent.

[0157] The carboxylate 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.

[0158] In some embodiments, the carboxylate solvent has the general structural formula of R ， -COO-R ，， wherein 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 1 ~C 5 alkyl group, C 1 ~C 5 one or more of the halogenated alkyl groups, and R ，， includes C 1 ~C 5 alkyl group, C 1 ~C 5 one or more of the halogenated alkyl groups.

[0159] "C 1 ~C 5 alkyl group" 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.

[0160] "C 1 ~C 5 halogenated alkyl group" 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.

[0161] "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.

[0162] In some embodiments, the carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0163] 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.

[0164] Carbonate solvents have a high dielectric constant, which can increase the dissociation rate of lithium ions and anions in lithium-containing electrolyte salts, and further improve the fast charging performance of battery cells.

[0165] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate solvent is 18% to 75%.

[0166] 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.

[0167] Due to the relatively high viscosity of carbonate solvents, as the content of carbonate solvents increases, the viscosity of the electrolyte will also increase, which has a negative impact on the conductivity of the electrolyte. By reasonably controlling the mass percentage of the carbonate solvent within the above range, the electrolyte has an appropriate viscosity and a good dissociation rate, thereby comprehensively improving the conductivity of the electrolyte, which is beneficial to further improving the fast charging performance and cycle stability of battery cells.

[0168] 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%.

[0169] 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.

[0170] 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.

[0171] 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 battery cells.

[0172] In some embodiments, the lithium-containing electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF 6 among others.

[0173] 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 increasing the conductivity of the electrolyte while reducing its viscosity. 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 LiPF 6 It is possible to 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.

[0174] 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%.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] Additives refer to components with relatively low content in the electrolyte, generally with a mass percentage in the electrolyte not exceeding 10%. They have the characteristics of strong pertinence and small dosage, and can significantly optimize a certain aspect of the battery performance without changing the production process.

[0179] In this 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.

[0180] In this 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.

[0181] The types of additives in the electrolyte can be obtained by detecting 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.

[0182] In some embodiments, the carbonate additives include one or more of vinylene carbonate and ethylene carbonate derivatives. Among them, the ethylene carbonate derivatives include the compounds shown in Formula III. Formula III R 1 、R 2 、R 3 、R 4 each independently includes one or more of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R 1 、R 2 、R 3 、R 4 are not simultaneously hydrogen atoms. Optionally, the carbonate additives include one or more of vinylene carbonate and fluoroethylene carbonate.

[0183] 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.

[0184] 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.

[0185] Sulfur-containing additives often have a relatively high potential. The sulfur-containing additives added to the electrolyte will react preferentially during formation or subsequent cycling and evolve into sulfur-containing 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.

[0186] In some embodiments, the lithium salt additives include one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

[0187] 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 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.

[0188] In some embodiments, the fluorobenzene additives include one or more of fluorobenzene and its derivatives.

[0189] 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.

[0190] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate additive is 3% to 8%.

[0191] 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 for 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 addition mass percentage of the additive in the electrolyte.

[0192] 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 value range between any two of them.

[0193] 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.

[0194] In some embodiments, based on the total mass of the electrolyte, the mass percentage of vinylene carbonate is 2% to 5%.

[0195] 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 value range between any two of them.

[0196] 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 lead to an increase in the interfacial impedance and charge transfer impedance of the battery, which is not conducive to the fast charging performance of battery cells. When the mass ratio of VC is within the above range, the battery can achieve both excellent cycle life and fast charging performance.

[0197] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the ethylene carbonate derivative is 0% to 4%.

[0198] 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%.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the sulfur-containing additive is 0% to 2%.

[0203] In some embodiments, based on the total mass of the electrolyte, the mass ratio of the sulfur-containing additive is 0.5% to 2%.

[0204] 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.

[0205] It should be noted that during the formation and charge-discharge cycling process, the additives in the electrolyte will be consumed to some extent to form the relevant components in the SEI film and / or CEI film. When the electrolyte is obtained by disassembling the battery cell and the contents of the sulfur-containing additives and lithium salt additives are tested by gas chromatography, the content may be 0%.

[0206] Specifically, taking the case where the mass content of the sulfur-containing additive is 0% as an example, it may be that the freshly prepared electrolyte does not contain the sulfur-containing additive, or the electrolyte obtained after disassembling the battery cell does not contain the sulfur-containing additive. This situation may be that the freshly prepared electrolyte does not contain the sulfur-containing additive, or a small amount of the sulfur-containing additive is added, but it participates in the film-forming reaction of the SEI film during the formation process of the battery cell, resulting in a mass content of 0% of the sulfur-containing additive during the detection process. Optionally, the freshly prepared electrolyte includes the sulfur-containing additive.

[0207] Furthermore, for adding certain substances, such as additives, to the electrolyte, due to the characteristic that the additives participate in the film formation on the surface of the active material and play a role, the content of the additives in the electrolyte of the battery cell is related to the formation, different battery life cycles, or different battery storage states. Therefore, there may be a difference in the content of the 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 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) electrolyte according to the content of the freshly prepared additives, the performance requirements of the battery cell, the storage environment, etc.

[0208] Therefore, the content of the additives 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.

[0209] It can be understood that in some embodiments, the sulfur-containing additives added to the electrolyte are completely converted into the sulfur-containing components in the SEI film during the formation process, and the amount of the sulfur-containing additives added to the electrolyte can be inferred by testing the X-ray photoelectron spectroscopy (XPS) of the negative electrode material. In some embodiments, there are still sulfur-containing additives remaining in the electrolyte, which play a role in strengthening the SEI film during the subsequent cycling process of the battery cell.

[0210] 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 sheet is cleaned with a solvent such as dimethyl carbonate (DMC) more than three times, and then powder is scraped for sampling. The obtained powder sample of the negative electrode material is adhered to a conductive substrate, and X-ray photoelectron spectroscopy is performed using an X-ray photoelectron spectrometer (such as AXIS ULTRA). The scanning rate and time of the X-ray source are adjusted to focus and detect elements and functional groups at a depth of 5 nm to 10 nm from the surface of the negative electrode material, and the X-ray photoelectron spectroscopy (XPS) spectrum of the sample is obtained. The elemental characteristic peaks are analyzed in the spectrum.

[0211] When the mass percentage of the sulfur-containing additive in the electrolyte is within the above range, it is beneficial to balance the improvement of the thermal stability of the SEI film at high temperatures and maintain an appropriate viscosity of the electrolyte, further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0212] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0% to 1%.

[0213] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.2% to 1%.

[0214] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.2%, 0.4%, 0.6%, 0.8%, 1% or any numerical range between any two of them.

[0215] It can be understood that, in some embodiments, the lithium salt additive added to the electrolyte is completely converted into inorganic components in the SEI film and / or CEI film during the formation process. In some embodiments, there is still a residue of the lithium salt additive in the electrolyte, which forms a reinforcing effect on the SEI film and / or CEI film during the subsequent cycling process of the battery cell.

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

[0217] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the fluorobenzene additive is 0.1% to 1%.

[0218] 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.

[0219] When the mass percentage of the fluorobenzene additive in the electrolyte is within the above range, it is beneficial to balance the wettability of the electrolyte and maintain an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0220] In some embodiments, the negative electrode tab 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 .

[0221] The compaction density of the negative active material layer can be tested by a method similar to that of the compaction density of the positive active material layer described above.

[0222] In some embodiments, the compaction density of the negative active material layer is 1.20 g / cm 3 , 1.25 g / cm 3 , 1.30 g / cm 3 , 1.35 g / cm 3 , 1.40 g / cm 3 , 1.45 g / cm 3 , 1.50 g / cm 3 or any numerical range between any two of them.

[0223] The negative 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.

[0224] In some embodiments, the positive current collector includes a positive current collecting portion and a positive tab, and the positive tab is provided at at least one end extending along the length direction of the electrode assembly or at least one side extending along the width direction of the electrode assembly.

[0225] In some embodiments, referring to Figure 3 , the positive current collector 1211 includes a positive current collecting portion 12110 and a positive tab 12111, and the positive tab 12111 is provided at one end of the positive current collecting portion 12110 extending along the length direction of the electrode assembly.

[0226] The above tab setting helps to improve the weight energy density of the battery cell.

[0227] In some embodiments, referring to Figure 4 , the positive tab 12111 is provided at both ends of the positive current collecting portion 12110 extending along the length direction of the electrode assembly.

[0228] The above tab design helps to improve the overcurrent capacity of the battery cell, relieve the situation of excessive temperature on the tab side during fast charging, which causes electrolyte decomposition and uneven current distribution, 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.

[0229] 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.

[0230] 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.

[0231] The above tab design helps to further improve the overcurrent capacity of the battery cell, thereby further 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] When the width of the tab is within the above range, it helps to improve the overcurrent capacity of the battery cell, and improve the fast charging performance and cycle stability of the battery cell.

[0244] 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 OH 1 ; along the width direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH 2 , where OH 1 is 1.0 mm to 4.0 mm; and / or, OH2 is from 1.0 mm to 3.0 mm.

[0245] In this application, with reference 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 in size between the negative electrode active material layer 1222 and the positive electrode active material layer 1212 is OH 1 =OH 21 -OH 11 ; with reference 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 in size between the negative electrode active material layer 1222 and the positive electrode active material layer 1212 is OH 1 =OH 22 -OH 12 , and the size can be measured with a ruler.

[0246] In some embodiments, OH 1 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.

[0247] In some embodiments, OH 2 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.

[0248] 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 passes through OH 1 , OH 2The design improves the ability of the negative electrode active material layer, especially the negative electrode active material layer in the region near the tab, to receive active ions in the length direction, and makes the distance between the positive electrode active material layer and the tab side farther. The current distribution of the active material layer in the region near the tab is more uniform, resulting in a lower 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 an internal short circuit in the battery is reduced. While the fast charging performance and cycle stability of the battery cell are improved, the values of OH 1 and OH 2 are controlled within the above range, enabling the battery cell to have excellent energy density.

[0249] In some embodiments, OH 1 is greater than or equal to OH 2 .

[0250] By controlling OH 1 ≥OH 2 , while improving the cycle stability of the battery cell, it is beneficial to further improve the energy density of the battery cell.

[0251] In some embodiments, the positive electrode active material includes: 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.

[0252] The coating layer containing carbon elements is beneficial to improving the electronic conductivity of the lithium-containing phosphate and improving the solid-phase transmission rate of electrons, thereby further improving the energy density and fast charging performance of the battery cell.

[0253] 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%.

[0254] 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 any numerical range between any two of them.

[0255] Based on the total mass of the positive electrode active material, the mass ratio of carbon elements within the above range enables the lithium-containing phosphate to have both excellent electronic conductivity and specific capacity, further comprehensively improving the energy density and fast charging performance of the battery cell.

[0256] In some embodiments, the coating layer further includes a component shown in Formula I, Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I, Among them, 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4, M1 includes one or more of Ti, Zr, Hf, Ge, Sn, and optionally, M1 is +4 valent.

[0257] In some embodiments, d1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or the numerical range between any two of them, m1 can be optionally 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or the numerical range between any two of them, and n1 can be optionally 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4 or the numerical range between any two of them.

[0258] In some embodiments, the component shown in Formula I includes Li 2 FeTi(PO 4 ) 3 , Li 2 FeZr(PO 4 ) 3 , Li 2 FeSn(PO 4 ) 3 or one or more of them.

[0259] 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 can be arranged in layers.

[0260] 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.

[0261] 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 ion conduction efficiency and strong structural stability during multiple lithium deintercalation and intercalation processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly improve the 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 monomer.

[0262] In some embodiments, the lithium-containing phosphate comprises components as shown in Formula II, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula II, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A comprises one or more of Na, K, and Mg; Me comprises one or more of Mn, Fe, Co, and Ni; M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X comprises one or more of S, Si, Cl, B, C, N, and P; Y comprises one or more of O and F.

[0263] In some embodiments, x1 can be optionally 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or a numerical range between any two of them, y1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or a numerical range between any two of them, x1 + y1 can be optionally 0.9, 1, 1.1, 1.2, 1.3 or a numerical range between any two of them, a1 can be optionally 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or a numerical range between any two of them, b1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5 or a numerical range between any two of them, a1 + b1 can be optionally 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or a numerical range between any two of them, c1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5 or a numerical range between any two of them, and z1 can be optionally 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or a numerical range between any two of them.

[0264] 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.

[0265] 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.

[0266] In some embodiments, the powder tap density of the positive electrode active material under 30000N is 2.55 g / cm 3 to 2.75 g / cm 3 .

[0267] The powder tap density of the positive electrode active material under 30000N has a well-known meaning in the art and can be measured by instruments and methods known in the art. For example, reference can be made to GB / T 24533-2019 and measured by an electronic pressure testing machine (such as a UTM7305 type electronic pressure testing machine). An exemplary test method is as follows: Weigh 1 g 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 30 s, then release the pressure, keep it for 10 s, and then record and calculate the powder tap density of the material under 30000N pressure.

[0268] In some embodiments, the powder tap 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 a numerical range between any two of them.

[0269] The positive electrode active material with a powder tap density within a suitable range can make the positive electrode active material layer have a higher tap density, thereby enabling the battery cell to have a higher energy density.

[0270] In some embodiments, 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 .

[0271] 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.

[0272] 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.

[0273] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0274] 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 electrical conductivity. The current collector includes metal foils 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, and also includes alloy foils of at least two main metals. For example, alloy foils made of at least two main elements among copper, aluminum, nickel, titanium, and iron can be used. It can also include copper, aluminum cadmium alloy, iron, or stainless steel, etc. surface-treated with carbon, nickel, titanium, silver, copper, etc. In addition, the 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 films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0275] 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.

[0276] The positive electrode current collector has a lower thickness, enabling further improvement in the energy density of the battery cell.

[0277] In some embodiments, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0278] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0279] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer located between the positive electrode active material layer and the positive electrode current collector, and the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm; and / or the negative electrode sheet further includes a negative electrode conductive layer located between the negative electrode current collector and at least one side of the negative electrode active material layer, and the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

[0280] In some embodiments, the thickness of the positive electrode conductive layer or the negative electrode conductive layer may be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, or a numerical range between any two of them.

[0281] The provision of the positive electrode conductive layer and / or the negative electrode conductive layer is beneficial to improving the electronic conductivity of the battery single electrode sheet and further improving the fast charging performance of the battery single body.

[0282] 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 difluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins.

[0283] 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.

[0284] In some embodiments, the carbon-based material includes one or more of graphite and hard carbon.

[0285] In some embodiments, the carbon-based material includes composite graphite particles, the composite graphite particles include graphite matrix particles and a carbon coating layer covering at least a part of the surface of the graphite matrix particles, the graphite matrix particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0286] The secondary particles refer to particles aggregated by 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 cell.

[0287] In some embodiments, based on the total mass of the composite graphite particles, the mass proportion of the amorphous carbon is 2% to 5%.

[0288] In some embodiments, based on the total mass of the composite graphite particles, the mass proportion of the amorphous carbon can be 2%, 3%, 4%, 5% or the numerical range between any two of them.

[0289] When the content of the amorphous carbon is within a suitable range, the composite graphite material can have a high specific capacity while also having a high solid-phase transport ability of active ions, which is beneficial to further comprehensively improving the energy density and fast charging performance of the battery cell.

[0290] 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).

[0291] 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.

[0292] In some embodiments, the volume average particle size Dv50 of the composite graphite particles is 9.5 μm to 14.5 μm.

[0293] "Volume average particle size Dv50" has a well-known meaning in the art, which respectively represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured by instruments and methods known in the art. For example, it can be conveniently measured with a laser particle size analyzer with reference to GB / T 19077-2016 Laser diffraction method for particle size distribution. The test instrument can be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK. The composite graphite particles can be freshly prepared or obtained by scraping powder from the negative electrode active material layer after disassembling a single battery cell. For example, discharge the battery to 0% SOC, then disassemble and take the negative electrode plate, scrape a certain amount of powder on the electrode plate with a blade, then use deionized water to wash and shake it repeatedly for 5 - 10 times, dry it, sinter it in a tubular furnace at 400 °C for 2 h, and after sintering, take an appropriate amount of the sample to be 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 / T 19077-2016 / ISO 13320:2009 standard.

[0294] 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 the numerical range between any two of them.

[0295] When the volume average particle size Dv50 of the composite graphite particles is within the above range, while shortening the solid-phase migration path of lithium ions, it also takes into account the lower reactivity, thereby taking into account the fast charging ability and cycle life of the single battery cell.

[0296] 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.

[0297] In some embodiments, the silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

[0298] 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%.

[0299] The qualitative and quantitative determination of each substance or element in this application can be detected by suitable equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change some detection steps / instrument parameters from the perspective of detection accuracy, etc., 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 meaning well-known in the art and can be tested by methods known in the art. For example, the negative electrode plate is placed in a solvent such as water and soaked, the negative electrode active material is separated from the negative electrode current collector, and each substance in the negative electrode active material layer is obtained by suction filtration and used as a test sample. The test sample is analyzed by an inductively coupled plasma - emission spectrometer of model ICAP7400 from Thermo Fisher Scientific Company in the United States, and with reference to the standard of GB / T30902 - 2014, the silicon element content can be obtained.

[0300] In some embodiments, based on the total mass of the negative electrode active material layer, the mass content of silicon element can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5% or any value range between any two of them.

[0301] The introduction of silicon-based materials is beneficial to further improve the energy density of the battery cell. Based on the total mass of the negative electrode active material layer, when the mass proportion of silicon element is within the above mass range, the energy density and cycle stability of the battery cell can be taken into account.

[0302] In some embodiments, 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 .

[0303] The single-sided coating mass of the negative electrode active material layer can be tested by a method similar to that of the single-sided coating mass of the positive electrode active material layer described above.

[0304] In some embodiments, the single-sided coating mass of the negative electrode active material layer can be 100 mg / 1540.25 mm 2 、110 mg / 1540.25 mm 2 、120 mg / 1540.25 mm 2 、130 mg / 1540.25 mm 2 、140 mg / 1540.25 mm 2 or any value range between any two of them.

[0305] The negative electrode active material layer with a single-sided coating quality within the above range can cooperate with the positive electrode active material layer to achieve a balance between the energy density and fast charging performance of the battery cell.

[0306] In some embodiments, the porosity of the separator is 20% to 70%, and may be optionally 35% to 60%.

[0307] In this application, the porosity refers to the percentage of the internal pore volume in the separator occupying the total volume of the separator. The porosity can be tested in accordance with the standard GB / T 36363-2018 "Polyolefin Separator for Battery Cells". It should be noted that in the actual testing process, due to differences in testing instruments, testing errors, and in order to eliminate the influence on the porosity test as much as possible, a testing process slightly different from the standard can be adopted to obtain a more accurate test value.

[0308] In some embodiments, the porosity of the separator can be 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or any value range between any two of them.

[0309] The porosity of the separator within the above range is beneficial to further balance the energy density, fast charging performance, and cycle stability of the battery cell.

[0310] In some embodiments, referring to 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.

[0311] In some embodiments, the non-fluoropolymer particles include acrylate copolymers.

[0312] In some embodiments, the first inorganic substance and the second inorganic substance each independently include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

[0313] Inorganic particles can improve the wettability and heat resistance of the first functional layer and the second functional layer to the electrolyte, and further comprehensively improve the fast charging performance, cycle stability, and safety performance of the battery cell. Non-fluoropolymer particles can improve the processing performance 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.

[0314] In some embodiments, the thickness of the base film is 4μm to 12μm, and may be optionally 5μm to 9μm.

[0315] In some embodiments, the thickness of the base film can be 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, or any value range between any two of them.

[0316] 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.

[0317] 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.

[0318] In some embodiments, referring to Figure 12 , the battery cell 1 includes a housing 11 and a cover assembly. The cover assembly is disposed at at least one end of the housing 11. The housing 11 and the cover assembly define a receiving cavity. The electrode assembly is disposed within 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.

[0319] 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 any value range between any two of them.

[0320] The wall thickness of the housing within the above range is beneficial to further improve the energy density of the battery cell.

[0321] In some embodiments, 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 in the length direction or the width direction of the housing. 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.

[0322] In some embodiments, referring to Figure 12 , the battery cell 1 includes a first cover assembly and a second cover assembly. The first cover assembly includes a first cover, 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 assembly includes a second cover, 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.

[0323] Thereby, during charging, the temperature rise of the battery cell and the impedance of the battery cell are reduced, which is beneficial to the improvement of the fast charging performance, cycle life, and safety performance of the battery cell.

[0324] 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 .

[0325] 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.

[0326] 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.

[0327] 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.

[0328] When the minimum cross-sectional area of the first electrode terminal and / or the second electrode terminal is within the above range, it is beneficial to improve the over-current capacity of the battery cell, reduce the heat generation of the electrode terminal, reduce the internal resistance of the battery cell, and thus improve the fast charging performance and cycle stability of the battery cell.

[0329] In some embodiments, the volume energy density of the battery cell is 430 Wh / L to 530 Wh / L.

[0330] In some embodiments, the volume energy density of the battery cell is 430 Wh / L to 470 Wh / L.

[0331] 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 and 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 the discharge capacity A0 at this time is recorded, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulating film outside the shell), and calculate the volume V0 of the single battery cell, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0332] 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 any value range between any two of them.

[0333] This battery cell simultaneously has a high energy density and can meet the demand for increasing the cruising range of the electrical device.

[0334] In some embodiments, the liquid injection coefficient of the battery cell is from 2.2 g / Ah to 3.0 g / Ah.

[0335] The liquid injection coefficient of the 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 the battery cell can be obtained by testing through any well-known method in the art. Exemplarily, the mass of the electrolyte in the battery cell can be obtained through 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 24 h to 48 h, and soak repeatedly 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 24 h 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, leave standing for 10 min, and then discharge at a discharge rate of 0.33C to 2.0V, and use the discharge capacity of the battery cell as the rated capacity.

[0336] In some embodiments, the liquid injection coefficient of the battery cell can be selected as 2.2 g / Ah, 2.3 g / Ah, 2.4 g / Ah, 2.5 g / Ah, 2.6 g / Ah, 2.7 g / Ah, 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah or the numerical range between any two of them.

[0337] 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.

[0338] In some embodiments, the positive electrode plate, negative electrode plate and separator can be made into an electrode assembly by a stacking process.

[0339] In some embodiments, the battery cell can include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0340] 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, polybutylene succinate, etc. can be listed.

[0341] 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.

[0342] In some embodiments, referring to Figure 1 , the outer package can include a housing 11 and a cover plate assembly. Among them, the housing 11 can 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, negative electrode plate and separator can form an electrode assembly by a winding process or a stacking process. The electrode assembly is encapsulated in the receiving cavity. The electrolyte infiltrates in the electrode assembly. The number of electrode assemblies contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0343] In some embodiments, the battery cells can be assembled into a battery module. The number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0344] Optionally, the battery module can further include an outer shell having a receiving space, and a plurality of battery cells 1 are received in the receiving space.

[0345] In some embodiments, the above battery modules can also be assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0346] 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.

[0347] In addition, 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. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0348] As the electrical device, the battery cell, battery module, or battery pack can be selected according to its usage requirements.

[0349] 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.

[0350] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a battery cell can be used as the power source.

[0351] The embodiments of the present application further provide an energy storage device using a battery as the power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system, etc.

[0352] Embodiment In order to make the technical problems, technical solutions, and beneficial effects solved by the present application clearer, the present application will be further described in detail below with reference to embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of 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 belong to the scope of protection of the present application.

[0353] In the examples where specific technologies or conditions are not specified, they shall be in accordance with the technologies or conditions described in the literature in this field or in accordance with the product specifications. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchases.

[0354] Example 1 (1) Preparation of the positive electrode sheet The positive electrode sheet 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.

[0355] 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%.

[0356] Mix the positive active material, binder polyvinylidene fluoride, and conductive agent acetylene black in a ratio of 97:2:1. Then add the solvent N-methylpyrrolidone (NMP) and stir to form a positive electrode slurry. 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 Li 2 FeTi(PO 4 ) 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 / cm 3 .

[0357] Uniformly coat the positive conductive slurry on the aluminum foil of the positive current collector, and after drying, obtain the positive conductive layer; then uniformly coat the positive electrode slurry on the positive conductive layer, and after drying and cold pressing, obtain the positive electrode sheet. Among them, the single-sided coating mass of the positive active material layer is 263 mg / 1540.25 mm 2 .

[0358] (2) Preparation of the negative electrode sheet The negative electrode sheet includes a negative current collector, a negative conductive layer on the negative current collector, and a negative active material layer. The negative current collector is a copper foil with a thickness of 5 μm; The negative conductive layer on the negative current collector is an active material layer formed by uniformly mixing a negative conductive agent, superconducting carbon, a negative binder, styrene-butadiene rubber (SBR), a thickener, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, and then coating and drying on the surface of the negative current collector. 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%; The negative electrode active material layer comprises a negative electrode active material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickening agent, with a mass ratio of 96.5:0.5:2:1. The negative electrode active material includes composite graphite particles, which include graphite body particles and a carbon coating layer covering at least a part of the surface of the graphite body particles. The carbon coating layer includes amorphous carbon, and based on the total mass of the composite graphite particles, the mass ratio of amorphous carbon is 3.5%; the Dv50 of the composite graphite particles is 11.3 μm. The negative electrode slurry is uniformly coated on the negative electrode conductive layer of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode plate is obtained. The single-sided coating mass of the negative electrode active material layer is 120 mg / 1540.25 mm 2 。

[0359] (3)Preparation of the electrolyte The electrolyte includes a solvent, a lithium-containing electrolyte salt, and an additive

[0360] 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 ratios of the components in the solvent are calculated based on the total mass of the electrolyte Based on the total mass of the electrolyte, the total mass content of the additive is 7%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluorooxalate borate LiDFOB with a mass ratio of 4:1.5:1:0.5 The lithium-containing electrolyte salt includes lithium bis(fluorosulfonyl)imide LiFSI with a mass ratio of 5% and lithium hexafluorophosphate LiPF 6 , and 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

[0361] (4)Preparation of the separator 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% The functional layer includes a first functional layer and a second functional layer. The first functional layer is a film layer formed by coating alumina particles and 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 alumina particles; the second functional layer is a film layer formed by coating a composite particle composed of polyacrylate and calcium oxide particles dispersed on the polyacrylate on the surface of the first functional layer, with a thickness of 5 μm and an average particle size of 10 nm for the calcium oxide particles

[0362] (5)Preparation of the battery cell Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet 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 electrolyte after drying, with a liquid injection coefficient of 2.45 g / Ah, and obtain a battery cell through processes such as vacuum packaging, standing, forming, 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, OH 1 is 4 mm, OH 2 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 of the battery 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 .

[0363] Examples 1 - 13 The preparation methods of Examples 1 - 13 are basically the same as those of Example 1, except that some parameters in the battery cell are adjusted, as shown in Tables 1 and 2 specifically. 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 .

[0364] Example 14 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: The negative active material layer includes negative active material, silicon-carbon material, conductive agent acetylene black, negative binder styrene-butadiene rubber, and thickener carboxymethyl cellulose sodium 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 proportion of silicon element is 0.86%.

[0365] Comparative Examples 1 - 6 The preparation methods of Comparative Examples 1 - 6 are basically the same as those of Example 1, except that some parameters in the battery cell are adjusted, as shown in Tables 1 and 2 specifically.

[0366] Testing Methods 1. Fast Charging Performance At 30°C, after cycling the battery cells 200 times according to the following charge-discharge strategies respectively, fully charge them to 100% SOC according to the corresponding charging strategy, disassemble the negative electrode plate, unfold the negative electrode plate, observe the lithium deposition area (grayish-white area), and measure the lithium deposition area. The degree of lithium deposition is as follows: No lithium deposition: The percentage of the lithium deposition area in the area of the negative electrode active material layer < 0.05%.

[0367] Slight lithium deposition: The percentage of the lithium deposition area in the area of the negative electrode active material layer < 2%.

[0368] Severe lithium deposition: The percentage of the lithium deposition area in the area of the negative electrode active material layer ≥ 2%.

[0369] Charge the battery cell, and the charging steps include the following steps: Charge at a constant current of 5.0C from 0% SOC to 40% SOC; charge at a constant current of 4.6C from 40% SOC to 45% SOC; charge at a constant current of 4.3C from 45% SOC to 50% SOC; charge at a constant current of 4.0C from 50% SOC to 55% SOC; charge at a constant current of 3.7C from 55% SOC to 60% SOC; charge at a constant current of 3.4C from 60% SOC to 65% SOC; charge at a constant current of 3.1C from 65% SOC to 70% SOC; charge at a constant current of 2.9C from 70% SOC to 75% SOC; charge at a constant current of 2.7C from 75% SOC to 80% SOC; charge at a constant current of 1.8C from 80% SOC to 85% SOC; charge at a constant current of 1.3C from 85% SOC to 90% SOC; charge at a constant current of 0.7C from 90% SOC to 95% SOC; charge at a constant current of 0.33C from 95% SOC to 98% SOC; charge at a constant current of 0.1C from 98% SOC to 100% SOC.

[0370] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0371] The discharge strategy is as follows: Discharge at a constant current of 0.33C to the cut-off voltage, such as 2.0V.

[0372] When performing charge-discharge tests on the battery cell above, the battery cell can be assembled in a battery device, and the required charge-discharge strategies can be regulated through a battery management system for testing.

[0373] 2. Volume energy density Place the battery cell at 25°C, charge it at a constant current of 0.33C to 3.65V, then charge it at a constant voltage to 0.05C, and let it stand for 30 min; discharge it at a constant current of 0.33C to 2.0V, and record the discharge capacity A at this time 0, unit: Ah; Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulating film outside the shell), and calculate the volume V of the single cell battery 0 , unit L; The volume energy density VED of the battery cell = (A 0 × discharge platform voltage) / V 0 , unit Wh / L.

[0374] 3. Cycling performance At 60°C, charge the battery cell at a constant current of 0.8C until the charging cut-off voltage of 3.6V, then charge it at a constant current of 0.1C until the charging cut-off voltage of 3.65V, and let it stand for 30 minutes; discharge it at a constant current of 1C to 3.1V and let it stand for 30 minutes. This is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., C n / C 0 × 100%) is 80%, and record the number of cycles. The more cycles, the better the cycling performance of the battery cell.

[0375] Test results Table 1

[0376] Table 2

[0377] According to the comparison between the examples and comparative examples of the present application, the compaction density of the positive active material layer is 2.65 g / cm 3 to 2.8 g / cm 3 , and the size of the positive 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 cycling stability of the battery cell, and achieve the comprehensive improvement of battery performance.

[0378] From the comparison between Examples 1 and 3 and Example 2, it can be seen that the compaction density of the positive active material layer is 2.75 g / cm 3 to 2.8 g / cm 3 , while the battery cell has excellent cycling stability and fast charging performance, the energy density is further improved.

[0379] From the comparison between Example 1 and Examples 4 and 5, it can be seen that the size of the positive active material layer along the length direction of the electrode assembly is 400 mm to 650 mm, and the battery cell takes into account excellent energy density, cycling stability, and fast charging performance and is further improved.

[0380] As can be seen from Examples 1 and 6, 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.

[0381] As can be seen from Examples 1 and 7-10, the mass percentage of the carboxylic ester solvent is 8% to 60%, and the battery cell has excellent energy density, fast charging performance, and cycle stability.

[0382] As can be seen from the comparison between Examples 1, 8, 9 and Example 7, based on the total mass of the electrolyte, the mass percentage of the first solvent is 30% to 60%. While the battery cell has excellent cycle stability and fast charging performance, the volumetric energy density is further improved.

[0383] As can be seen from Examples 1 and 7-10, the mass percentage of the carbonate solvent is 18% to 75%, and the battery cell has excellent energy density, fast charging performance, and cycle stability.

[0384] As can be seen from Examples 1, 10, and 11, based on the total mass of the electrolyte, the mass percentage of the carbonate additive is 3% to 8%, and the battery cell takes into account excellent cycle stability, fast charging performance, and energy density.

[0385] As can be seen from Examples 1 and 12, based on the total mass of the electrolyte, the mass percentage of the sulfur-containing additive is 0.5% to 2%, and the mass percentage 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.

[0386] As can be seen from the comparison between Example 13 and Example 1, the inclusion of fluorobenzene additives in the electrolyte is beneficial to the further improvement of the cycle stability and fast charging performance of the battery cell.

[0387] 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 the further improvement of the energy density of the battery cell, while taking into account excellent fast charging performance and cycle stability.

[0388] It should be noted that the present disclosure is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same constitution and the same effect as the technical idea within the scope of the technical solution of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope not departing from the gist of the present disclosure, various modifications that can be conceived by those skilled in the art and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present disclosure.

Claims

1. A battery cell, wherein: The invention comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing phosphate with an olivine structure, wherein the compaction density of the positive electrode active material layer is 2.65 g / cm 3 Up to 2.8g / cm 3 , and the dimension 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.

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

3. The battery cell according to claim 1 or 2, wherein: The size of the positive electrode active material layer along 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 proportion 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 proportion of the first solvent is 30% to 60%.

6. The battery cell according to claim 4 or 5, wherein: The first solvent includes a carboxylate solvent.

7. The battery cell according to claim 6, wherein: The carboxylic acid ester solvent has R ， -COO-R ，， The general structural formula is ， Including one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, a C1-C5 halogenated alkyl group, R ，， Includes one or more of C1~C5 alkyl and C1~C5 halogenated alkyl.

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

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 proportion 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 the mass proportion of the lithium-containing electrolyte salt in the electrolyte is 10% to 18% based on the total mass of the electrolyte.

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 proportion 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 additives, and the additives include one or more of carbonate additives, sulfur-containing additives, lithium salt additives, and fluorobenzene additives.

15. The battery cell according to claim 14, wherein: The carbonate additive includes one or more of vinylene carbonate and vinyl carbonate derivatives. Wherein, the ethylene carbonate derivative includes a compound represented by formula III, Formula III R1, R2, R3, and R4 each independently include one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 halogenated alkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time.

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 vinyl sulfate, vinyl disulfate, 1,3-propane sultone, butylene sulfite, vinyl sulfite, and methylene disulfonate; The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate); and / or, The fluorobenzene additives include one or more 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 proportion 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 vinylene carbonate derivatives. Based on the total mass of the electrolyte, the mass proportion 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 proportion 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 proportion 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 proportion 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 proportion 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 proportion 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 proportion 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 0.1% to 1%.

26. 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 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 .

27. The battery cell according to claim 26, wherein: The positive electrode collector comprises a positive electrode collector and a positive electrode tab, wherein the positive electrode tab is arranged at at least one end of the positive electrode collector extending along the length direction of the electrode assembly or at least one side extending along the width direction of the electrode assembly; and / or, the negative electrode collector comprises a negative electrode collector and a negative electrode tab, wherein the negative electrode tab is arranged at at least one end of the negative electrode collector extending along the length direction of the electrode assembly or at least one side extending along the width direction of the electrode assembly.

28. The battery cell according to claim 27, wherein: The dimension of the positive electrode active material layer along the length direction of the electrode assembly is 650 mm to 950 mm, and the positive electrode tabs are arranged at both ends of the positive electrode current collecting portion extending along the length direction of the electrode assembly or at least one side extending along the width direction of the electrode assembly.

29. The battery cell according to claim 27 or 28, wherein: The positive electrode tab is arranged at at least one end of the positive electrode collecting portion extending along the length direction of the electrode assembly, and the ratio of the width of the positive electrode tab to the width of the positive electrode collecting portion is 0.25 to 1; and / or the ratio of the width of the negative electrode tab to the width of the negative electrode collecting portion is 0.25 to 1.

30. The battery cell according to claim 27 or 28, wherein: The positive electrode tab is arranged on at least one side of the positive electrode current collecting portion extending along the width direction of the electrode assembly, and the ratio of the width of the positive electrode tab to the length of the positive electrode current collecting portion is 0.25 to 1; and / or, the ratio of the width of the negative electrode tab to the length of the negative electrode current collecting portion is 0.25 to 1.

31. The battery cell according to claim 26, wherein: Along the length direction of the electrode assembly, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH1; along the width direction of the electrode assembly, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH2, wherein OH1 is 1.0 mm to 4.0 mm; and / or OH2 is 1.0 mm to 3.0 mm.

32. The battery cell according to claim 31, wherein: OH1 is greater than or equal to OH2.

33. The battery cell according to claim 1, wherein: The positive electrode active material comprises: The olivine-structured lithium-containing phosphate, and A coating layer is located on at least a portion of the surface of the lithium-containing phosphate, and the coating layer contains carbon.

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

35. The battery cell according to claim 33 or 34, wherein: The coating layer also includes a component as shown in Formula I, Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula I Among them, 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn.

36. The battery cell according to claim 35, wherein: M1 has a valence of +4.

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

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

39. The battery cell according to claim 1, wherein: The powder compaction density of the positive electrode active material at 30000N is 2.55g / cm 3 Up to 2.75g / 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 Up to 370mg / 1540.25mm 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 plate also includes a positive electrode conductive layer, which is located between the positive electrode active material layer and the positive electrode collector, and the thickness of the positive electrode conductive layer is 0.5μm to 2μm; and / or the negative electrode plate also includes a negative electrode conductive layer, which is located between the negative electrode collector and the negative electrode active material layer on at least one side, and the thickness of the negative electrode conductive layer is 0.5μm to 2μm.

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 fluorine-containing acrylic resin.

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 disposed on at least one side of the negative electrode current collector. 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 comprises composite graphite particles, wherein the composite graphite particles comprise graphite main particles and a carbon coating layer coated on at least a portion of the surface of the graphite main particles, the graphite main particles comprise secondary particles, and the carbon coating layer comprises amorphous carbon.

47. The battery cell according to claim 46, wherein: Based on the total mass of the composite graphite particles, the mass proportion 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 proportion of silicon element is 0.5% to 5.0%.

52. 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 disposed on at least one side of the negative electrode current collector, and the single-sided coating mass of the negative electrode active material layer is 100 mg / 1540.25 mm 2 Up to 140mg / 1540.25mm 2 .

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

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

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

56. The battery cell according to claim 55, wherein: The non-fluorinated polymer particles include acrylic 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 base film has a thickness of 4 μm to 12 μm.

59. The battery cell according to claim 55, wherein: The base film has a thickness of 5 μm to 9 μm.

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

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

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 meets the requirement of 150 mm 2 ≤S≤1000mm 2 .

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

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

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

66. A battery device, wherein: Comprising the battery monomer described in 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: A battery device comprising the battery device of claim 66.

68. An energy storage device, characterized in that: Comprising the battery device of claim 66, wherein the battery device is used to store electrical energy.

Images