Battery cells, battery devices, power consumption devices and energy storage devices

Abstract

The present application provides a battery cell, a battery device, an electric device and an energy storage device. The single-sided coating mass of the negative electrode active material layer is 80 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 Based on the total mass of the negative electrode active material layer, silicon accounts for 0.5% to 5% by mass; the viscosity of the electrolyte at room temperature is 2.3 to 3.5 mPa·s. The battery cells achieve comprehensive improvements in energy density, fast-charging performance, and cycle stability, achieving enhanced battery performance.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to PCT patent application PCT / CN2025 / 086882, entitled “Battery Cell, Battery Device, Electrical Device and Energy Storage Device,” filed on April 2, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of battery cells, and in particular to a battery cell, a battery device, an electrical device, and an energy storage device. Background Art

[0004] In recent years, battery cells have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0005] With the market's increasing demands for both the range of electric devices and the efficiency of recharging, higher requirements are being placed on the energy density of battery cells. However, while achieving improved energy density performance, this often leads to deterioration in cycle stability and fast-charging performance, which has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery device, an electrical device and an energy storage device. The battery cell takes into account the improvement of energy density, fast charging performance and cycle stability to achieve comprehensive performance improvement.

[0007] The first aspect of the present application provides a battery cell, including an electrode assembly and an electrolyte, wherein the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, the separator is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged 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; the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer arranged 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 80 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 The negative electrode active material layer includes a negative electrode active material, which includes a silicon-based material. Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 0.5% to 5%; the viscosity of the electrolyte at room temperature is 2.3mPa·s to 3.5mPa·s.

[0008] Lithium-containing phosphates with an olivine structure offer the advantages of low cost and long lifespan. When used with silicon-based materials containing silicon-containing negative electrodes with high specific capacity, they can improve the low energy density of battery cells when lithium-containing phosphates are used as the positive electrode active material. However, silicon-based materials undergo significant volume changes during cycling, which in turn leads to significant volume expansion of the negative electrode electrode and increased expansion force within the battery cell. The increased compressive force on the electrode squeezes out the electrolyte in the positive and negative active material layers, making it difficult to reabsorb it. The loss of electrolyte in the active material layer can lead to "bridge" failure in the lithium-ion transmission pathway and severe lithium deposition at the negative electrode, which in turn causes battery cell cycle lifespan to plummet, negatively impacting the fast-charging performance and cycle life of the battery cells. The battery cell of the embodiment of the present application can reduce the content of silicon-based materials per unit area and shorten the lithium ion diffusion path while taking into account the energy density by ensuring that the single-sided coating mass of the negative electrode active material layer is within the above range, thereby reducing the volume expansion of the negative electrode plate and the amount of electrolyte extruded, reducing internal resistance, and improving the cycle stability and fast charging performance of the battery cell; further, by controlling the viscosity of the electrolyte within the above range, the electrolyte has good conductivity, stability and dissociation rate while helping to improve the electrolyte's ability to wet the active material layer, thereby improving the reabsorption of the extruded electrolyte, which is beneficial to further improve the cycle stability and fast charging performance of the battery cell. The battery cell of the embodiment of the present application achieves excellent energy density, cycle life and fast charging performance through the mutual cooperation between the negative electrode plate and the electrolyte.

[0009] In any embodiment, the coating mass of the negative electrode active material layer on one side is 110 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 .

[0010] When the single-side coating quality of the negative electrode active material layer is within the above range, the battery cell has excellent cycle life and fast charging performance, while the energy density is further improved.

[0011] In any embodiment, the mass ratio of silicon element is 1.6% to 5% based on the total mass of the negative electrode active material layer.

[0012] When the mass proportion of silicon element is within the above range, the battery cell has excellent cycle life and fast charging performance, while the energy density is further improved.

[0013] In any embodiment, the silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy, and may be a silicon-carbon material.

[0014] The carbon material in the silicon-carbon material helps to alleviate the volume expansion of the silicon material, thereby taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0015] In any embodiment, based on the total mass of the silicon-carbon material, the mass proportion of silicon element in the silicon-carbon material is 40% to 80%.

[0016] In any embodiment, the volume average particle size Dv50 of the silicon-carbon material is 5.0 μm to 12.5 μm.

[0017] Silicon-carbon materials with a volume average particle size within the above range shorten the solid-phase migration path of lithium ions while taking into account lower reaction activity, thereby taking into account the fast charging capability and cycle life of the battery cell.

[0018] In any embodiment, the specific surface area of ​​the silicon carbon material is 3.1 m 2 / g to 3.6m 2 / g.

[0019] Silicon-carbon materials with a specific surface area within the above range shorten the solid-phase migration path of lithium ions while taking into account lower reaction activity, thereby taking into account the fast charging capability and cycle life of the battery cell.

[0020] In any embodiment, the powder compaction density of the silicon carbon material at 25000N is 0.7g / cm 3 to 1.2g / cm 3 .

[0021] Silicon-carbon materials with a powder compaction density within the above range have no negative impact on the compaction density of the negative electrode sheet and do not deteriorate the energy density of the battery cell.

[0022] In any embodiment, the negative electrode active material further includes a carbon-based material.

[0023] In any embodiment, the carbon-based material includes one or more of graphite and hard carbon, and can be graphite.

[0024] In any embodiment, the carbon-based material includes composite graphite particles, the composite graphite particles include graphite particles and a carbon coating layer coated on at least a portion of the surface of the graphite particles, the graphite particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0025] Secondary particles are particles formed by the aggregation of two or more primary particles. Composite graphite particles, including secondary particles and a surface coating layer including amorphous carbon, further improve the electrolyte's wettability in the negative electrode active material layer and enhance the solid-phase transport capacity of active ions, contributing to enhanced fast-charging performance and cycle stability of battery cells.

[0026] In any embodiment, the amorphous carbon accounts for 2% to 5% by mass based on the total mass of the composite graphite particles.

[0027] When the content of amorphous carbon is within an appropriate range, the composite graphite material can have a high gram capacity while also having a high active ion solid-phase transport ability, which is conducive to further comprehensive improvement of the energy density and fast charging performance of the battery cell.

[0028] In any embodiment, the composite graphite particles have a volume average particle size Dv50 of 8.5 μm to 16.5 μm.

[0029] The composite graphite particles with a volume average particle size within the above range shorten the solid phase migration path of lithium ions while taking into account low reaction activity, thereby taking into account the fast charging capability and cycle life of the battery cell.

[0030] In any embodiment, the compaction density of the negative electrode active material layer is 1.10 g / cm 3 Up to 1.50g / cm 3 .

[0031] The negative electrode active material layer with a compaction density within the above range allows the battery to have excellent energy density while further improving the fast charging performance and cycle stability of the battery cell.

[0032] In any embodiment, the dimension of the negative electrode active material layer along the length direction of the electrode assembly is 200 mm to 650 mm.

[0033] The design of a laminated electrode assembly in which the dimension of the negative electrode active material layer along the length direction of the electrode assembly is within the above range is beneficial for taking into account the energy density, cycle stability and fast charging performance of the battery cell.

[0034] In any embodiment, the electrolyte includes a first solvent, the viscosity η of the first solvent at room temperature is 0.3 mPa·s to 0.6 mPa·s, and the mass proportion of the first solvent based on the total mass of the electrolyte is 8% to 60%.

[0035] The first solvent with a viscosity η within the above range has both excellent stability and low viscosity. The mass proportion of the first solvent within the above range helps to reduce the viscosity of the electrolyte, improve the conductivity of the electrolyte, and take into account the stability of the electrolyte, thereby facilitating further comprehensive improvement of the fast charging performance and cycle stability of the battery cell.

[0036] In any embodiment, the mass proportion of the first solvent is 30% to 60% based on the total mass of the electrolyte.

[0037] When the mass proportion of the first solvent is within the above range, the viscosity of the electrolyte is further reduced while the electrolyte has good stability and conductivity, which is beneficial to further improve the cycle stability of the battery cell.

[0038] In any embodiment, the first solvent includes a carboxylate solvent.

[0039] Carboxylate solvents have the advantages of low viscosity and high ionic conductivity, which are conducive 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 cycle stability and fast charging performance of the battery cell.

[0040] In any embodiment, the carboxylate solvent has a general structural formula of R'-COO-R", wherein R' includes one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R' includes one or more of a C1-C5 alkyl group and a C1-C5 haloalkyl group.

[0041] In any embodiment, the carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0042] In any embodiment, 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.

[0043] Carbonate solvents have a high dielectric constant. Carbonate solvents can easily form a solvation structure with lithium ions in lithium-containing electrolyte salts to increase the dissociation rate of lithium ions and anions in lithium-containing electrolyte salts, thereby further improving the fast charging performance of battery cells.

[0044] In any embodiment, based on the total mass of the electrolyte, the carbonate solvent accounts for 18% to 75% by mass.

[0045] Due to the high viscosity of carbonate solvents, increasing the carbonate solvent content increases the electrolyte viscosity, negatively impacting the electrolyte's conductivity. By properly controlling the carbonate solvent mass percentage within the above range, the electrolyte achieves optimal viscosity, conductivity, and good dissociation rate and wettability, which improves the overall kinetic performance and cycling stability of the battery cells.

[0046] In any embodiment, the electrolyte includes a lithium-containing electrolyte salt, and the lithium-containing electrolyte salt accounts for 10% to 18% by mass of the electrolyte based on the total mass of the electrolyte.

[0047] 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 ionic conductivity of the electrolyte, thereby further comprehensively improving the cycle stability and fast charging performance of the battery cell.

[0048] In any embodiment, the lithium-containing electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6).

[0049] LiFSI is easy to dissociate in the electrolyte solvent, and LiFSI has a smaller molecular weight than other types of fluorinated sulfonyl imide salts (such as lithium bis(trifluoromethanesulfonyl)imide LiTFSI), which is beneficial for improving 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 battery cycling 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, 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. Lithium-containing electrolyte salts also include lithium hexafluorophosphate LiPF6, which can reduce the risk of thermal runaway of the battery cell, reducing the risk to a controllable range, thereby improving the safety performance of the battery cell.

[0050] 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%.

[0051] The battery cell having the molar concentration of lithium bis(fluorosulfonyl)imide in the electrolyte within the above range can take into account the dynamic performance, cycle stability and safety performance of the battery cell.

[0052] 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.

[0053] In any embodiment, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives, wherein the ethylene carbonate derivative includes the compound shown in Formula I,

[0054] Formula I

[0055] R1, R2, R3, and R4 each independently include one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time. Optionally, the carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

[0056] Carbonate additives can evolve into organic components in the SEI film, which is beneficial to improving the toughness of the SEI film, reducing the probability of SEI film rupture due to volume changes of silicon-based materials and causing side reactions between the electrolyte and silicon-based materials, reducing battery gas production and reducing the interfacial impedance on the negative electrode side, which is beneficial to further improve the cycle, storage life and fast charging performance of battery cells.

[0057] In any embodiment, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl bissulfate, 1,3 propane sultone, butylene sulfite, vinyl sulfite, and methylene disulfonate.

[0058] Sulfur-containing additives often have a higher potential. Sulfur-containing additives added to the electrolyte will preferentially react during formation or subsequent cycling, evolving into sulfur-containing inorganic components in the SEI film. The SEI film formed by carbonate additives has poor high-temperature stability, which is detrimental to the stability of the battery cells in high-temperature environments. The presence of sulfur in the SEI film can further enhance the thermal stability of the SEI film at high temperatures and further reduce the interfacial impedance on the negative electrode side, thereby further improving the cycling stability and fast-charging performance of the battery cells.

[0059] In any embodiment, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0060] Lithium salt additives can evolve into inorganic components in the SEI film, further improving the rigidity and stability of the SEI film, thereby further enhancing the battery's cycling stability and fast-charging performance. Furthermore, these lithium salt additives can form a positive electrode electrolyte interface film (CEI film) on the surface of the positive electrode active material, further improving the cycling stability of the battery cell.

[0061] In any embodiment, the fluorobenzene additive includes one or more fluorobenzene and its derivatives.

[0062] Fluorobenzene additives help improve the wettability of the electrolyte to the positive and negative electrode active material layers, thereby further improving the cycle stability and fast charging performance of the battery cells.

[0063] In any embodiment, based on the total mass of the electrolyte, the carbonate additive accounts for 3% to 8% by mass.

[0064] The mass proportion of carbonate additives in the electrolyte is within the above range, which takes into account both improving the stability of the SEI film and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0065] In any embodiment, based on the total mass of the electrolyte, the mass proportion of vinylene carbonate is 2% to 5%.

[0066] Vinylene carbonate (VC) has a similar reduction potential to carboxylate solvents, which can inhibit the reactivity of carboxylate solvents and improve the cycle life of battery cells. However, excessive VC content can increase the battery's interfacial impedance and charge transfer impedance, hindering the fast-charging performance of the battery cells. A VC mass percentage within the above range ensures that the battery achieves both excellent cycle life and fast-charging performance.

[0067] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 0% to 4%.

[0068] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 1.5% to 3.5%.

[0069] Ethylene carbonate derivatives can also form films on the negative electrode surface at higher potentials and exhibit low interfacial and charge transfer resistance. The mass percentage of ethylene carbonate derivatives within the aforementioned range enables the battery cells to achieve both excellent fast-charging performance and cycle life. By combining vinylene carbonate (VC) and ethylene carbonate derivatives in the electrolyte, the fast-charging performance and cycle stability of the battery cells can be comprehensively improved.

[0070] In any embodiment, the mass proportion of the sulfur-containing additive is 0% to 2% based on the total mass of the electrolyte.

[0071] In any embodiment, the mass proportion of the sulfur-containing additive is 0.5% to 2% based on the total mass of the electrolyte.

[0072] The mass proportion of the sulfur-containing additive in the electrolyte is within the above range, which takes into account both improving the thermal stability of the SEI film at high temperature and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0073] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

[0074] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% to 1%.

[0075] The mass proportion of lithium salt additives in the electrolyte is within the above range, which takes into account both improving the stability of the SEI film and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0076] In any embodiment, the mass content of the fluorobenzene additive is 0.1% to 1% based on the total mass of the electrolyte.

[0077] The mass proportion of fluorobenzene additives in the electrolyte is within the above range, taking into account the wettability of the electrolyte and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0078] 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 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 the size of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH2, wherein OH1 is 1.0 mm to 4.0 mm; and / or OH2 is 1.0 mm to 3.0 mm.

[0079] As the charge rate of a battery cell increases, the current density near the tab increases, leading to a large temperature rise. This makes the negative electrode active material layer susceptible to the formation of lithium dendrites near the tab. The design of OH1 and OH2 improves the ability of the negative electrode active material layer, especially the layer near the tab, to accept active ions along its length. This also increases the distance between the positive electrode active material layer and the tab, resulting in a more uniform current distribution and lower temperature rise. This comprehensively improves the lithium deposition problem in the negative electrode sheet and reduces the probability of overlap between the positive and negative electrodes due to thermal shrinkage of the separator, which could lead to internal battery short circuits. This improves the fast-charging performance and cycle stability of the battery cell while controlling the OH1 and OH2 values ​​within the above range, ensuring that the battery cell also has excellent energy density.

[0080] In any embodiment, OH1 is greater than or equal to OH2.

[0081] Controlling OH1 to be greater than OH2 improves the cycle stability of the battery cell and is conducive to further improving the energy density of the battery cell.

[0082] In any embodiment, the positive electrode collector includes a positive electrode current collecting portion and a positive electrode tab, and the positive electrode tab is arranged at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly or at least one side extending along the width direction of the electrode assembly; and / or, the negative electrode collector includes a negative electrode current collecting portion and a negative electrode tab, and the negative electrode tab is arranged at at least one end of the negative 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.

[0083] In any embodiment, the dimension of the negative electrode active material layer along the length direction of the electrode assembly is greater than 500 mm, and the negative electrode tabs are arranged at both ends of the negative 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.

[0084] The above-mentioned tab setting helps to improve the overcurrent capacity of the battery cell, alleviate the situation where the temperature on the tab side is too high during fast charging, causing electrolyte decomposition and uneven current distribution to cause lithium deposition on the tab side, thereby improving the fast charging performance and cycle stability of the battery cell. It is especially suitable for improving the fast charging performance of battery cells with an active material layer length greater than 500mm, while taking into account excellent volume energy density.

[0085] In any embodiment, the positive electrode tab is arranged at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly, and the ratio of the width of the positive electrode tab to the width of the positive electrode current collecting portion is 0.25 to 1; and / or, the ratio of the width of the negative electrode tab to the width of the negative electrode current collecting portion is 0.25 to 1.

[0086] In any embodiment, 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.

[0087] The width of the tab is within the above range, which helps to improve the current capacity of the battery cell and improve the fast charging performance and cycle stability of the battery cell.

[0088] In any embodiment, the positive electrode active material includes: an olivine-structured lithium-containing phosphate, and a coating layer, wherein the coating layer is located on at least a portion of the surface of the lithium-containing phosphate, and the coating layer contains carbon.

[0089] The coating layer contains carbon elements, which is beneficial to improving the electronic conductivity of lithium-containing phosphates and improving the solid-phase transmission rate of electrons, thereby further improving the energy density and fast charging performance of the battery cells.

[0090] In any embodiment, the mass proportion of carbon element is 0.8% to 2.3% based on the total mass of the positive electrode active material.

[0091] Based on the total mass of the positive electrode active material, the mass proportion of the carbon element is within the above range, so that the lithium-containing phosphate has both excellent electronic conductivity and gram capacity, further comprehensively improving the energy density and fast charging performance of the battery cell.

[0092] In any embodiment, the coating layer further comprises a component as shown in Formula II,

[0093] Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1Formula II, wherein 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, M1 includes one or more of Ti, Zr, Hf, Ge, and Sn, and optionally, M1 has a valence of +4.

[0094] The component represented by Formula II is a fast ion conductor with a NASICON structure. Its ionic conductivity approaches or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has abundant three-dimensional lithium ion diffusion and transport channels, and has advantages such as high ion conduction efficiency and strong structural stability during multiple lithium de- and lithium insertion processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly increase the lithium ion transmission rate during multiple lithium de- and lithium insertion at the positive terminal, enhance the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0095] In any embodiment, the lithium-containing phosphate comprises a component as shown in Formula III,

[0096] Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula III, 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; and Y includes one or more of O and F.

[0097] The lithium-containing phosphate with an olivine structure having the above components has good structural stability, can reduce the loss during the fast charging process, and further improve the fast charging performance and cycle stability of the battery cell.

[0098] In any embodiment, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate and modified forms of any of the foregoing substances, wherein the modified form includes one or more of doping modification and coating modification.

[0099] In any embodiment, the powder compaction density of the positive electrode active material at 30,000 N is 2.45 g / cm 3Up to 2.75g / cm 3 .

[0100] The positive electrode active material with a powder compaction density within an appropriate range can make the positive electrode active material layer have a higher compaction density, thereby making the battery cell have a higher energy density.

[0101] In any embodiment, the compaction density of the positive electrode active material layer is 2.5 g / cm 3 to 2.83g / cm 3 .

[0102] The positive electrode active material layer with a compaction density within the above range can further achieve a balance among the energy density, fast charging performance and cycle stability of the battery cell.

[0103] In any embodiment, the coating mass of the positive electrode active material layer on one side is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 .

[0104] The positive electrode active material layer having a single-side coating mass within the above range can further effectively balance the fast charging performance and energy density of the battery cell.

[0105] In any embodiment, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0106] The positive electrode current collector has a relatively low thickness, which enables further improvement in the energy density of the battery cell.

[0107] In any embodiment, the negative electrode plate further includes a negative electrode conductive layer, which is located between the negative electrode current collector and the negative electrode active material layer on at least one side, and the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm; and / or, the positive electrode plate further includes a positive electrode conductive layer, which is located between the positive electrode active material layer and the positive electrode current collector, and the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

[0108] The provision of the positive electrode conductive layer and / or the negative electrode conductive layer is beneficial to improving the electronic conductivity of the battery cell pole piece, and is beneficial to further improving the fast charging performance of the battery cell.

[0109] In any embodiment, the negative electrode conductive layer includes a conductive agent, the positive electrode conductive layer includes a conductive agent and a positive electrode binder, the conductive agent includes superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. One or more of the positive electrode binder includes polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin. One or more.

[0110] In any embodiment, the separator has a porosity of 20% to 70%.

[0111] In any embodiment, the separator has a porosity of 35% to 60%.

[0112] The porosity of the isolation membrane within the above range is beneficial for further taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0113] In any embodiment, the isolation membrane includes a base membrane; a first functional layer located on at least one side of the base membrane, the first functional layer including a first inorganic substance; a second functional layer located on a side of the first functional layer away from the base membrane, the second functional layer including a second inorganic substance and a non-fluoropolymer.

[0114] In any embodiment, the non-fluoropolymer particles include an acrylate copolymer.

[0115] 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.

[0116] Inorganic particles enhance the electrolyte wettability and heat resistance of the first and second functional layers, further improving the battery's fast-charging performance, cycling stability, and safety. Non-fluoropolymer particles enhance the processability and stability of the separator, preventing internal short circuits caused by the separator's movement within the battery cell, further improving the battery's cycling stability and safety.

[0117] In any embodiment, the base film has a thickness of 4 μm to 12 μm, optionally 5 μm to 9 μm.

[0118] The thickness of the base film within the above range is beneficial for further taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0119] In any embodiment, the battery cell includes a shell and a cover assembly, the cover assembly is arranged at at least one end of the shell, the shell and the cover assembly define a accommodating cavity, the electrode assembly is arranged in the accommodating cavity, and the shell wall thickness of the large surface of the battery cell is 0.1mm to 0.5mm.

[0120] In any embodiment, the housing wall thickness of the battery cell on the large surface is 0.2 mm to 0.35 mm.

[0121] The shell wall thickness of the large surface of the battery cell is within the above range, which is conducive to further improving the energy density of the battery cell.

[0122] In any embodiment, the cover plate assembly includes a first cover plate assembly and a second cover plate assembly, the first cover plate assembly and the second cover plate assembly are arranged at both ends of the shell in the length direction or the width direction, the first cover plate assembly includes a first cover plate and a first electrode terminal, the second cover plate assembly includes a second cover plate and a second electrode terminal, and the polarities of the first electrode terminal and the second electrode terminal are opposite.

[0123] Therefore, the temperature rise of the battery cell and the impedance of the battery cell are reduced during charging, which is beneficial to improving the fast charging performance, cycle life and safety performance of the battery cell.

[0124] In any embodiment, the minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal is S and satisfies 150 mm 2 ≤S≤1000mm 2 .

[0125] The minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal is within the above range, which is beneficial to improving the current carrying capacity of the battery cell, reducing the heat generation of the electrode terminal, and reducing the internal resistance of the battery cell, thereby improving the fast charging performance and cycle stability of the battery cell.

[0126] In any embodiment, the volume energy density of the battery cell is greater than 440 Wh / L and less than or equal to 530 Wh / L.

[0127] In any embodiment, the volumetric energy density of the battery cell is 450 Wh / L to 510 Wh / L.

[0128] The battery cell also has a high energy density, which can meet the demand for increased driving range of electrical devices.

[0129] In any embodiment, the filling factor of the battery cell is 2.2 g / Ah to 3 g / Ah.

[0130] The filling coefficient within the above range can take into account both the cycle stability and energy density of the battery cell.

[0131] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device comprises at least one of a battery module, a battery pack, and an energy storage battery.

[0132] The third aspect of the present application further provides an electrical device, which includes the battery cell provided in the first aspect of the present application.

[0133] The fourth aspect of the present application further provides an energy storage device, which includes the battery cell provided in the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0134] Figure 1 Schematic diagram of a positive electrode sheet and a negative electrode sheet according to an embodiment of the present application;

[0135] Figure 2 Schematic diagram of a positive electrode sheet and a negative electrode sheet according to an embodiment of the present application;

[0136] Figure 3 Schematic diagram of a positive electrode current collector according to one embodiment of the present application;

[0137] Figure 4 Schematic diagram of a positive electrode current collector according to one embodiment of the present application;

[0138] Figure 5 Schematic diagram of a positive electrode current collector according to one embodiment of the present application;

[0139] Figure 6 Schematic diagram of a positive electrode current collector according to one embodiment of the present application;

[0140] Figure 7 is a schematic diagram of a negative electrode current collector according to one embodiment of the present application;

[0141] Figure 8 is a schematic diagram of a negative electrode current collector according to one embodiment of the present application;

[0142] Figure 9 is a schematic diagram of a negative electrode current collector according to one embodiment of the present application;

[0143] Figure 10 is a schematic diagram of a negative electrode current collector according to one embodiment of the present application;

[0144] Figure 11 Schematic diagram of the structure of an isolation membrane according to one embodiment of the present application;

[0145] Figure 12 is a schematic structural diagram of a battery cell according to an embodiment of the present application;

[0146] Figure 13 FIG2 is a schematic diagram of an electrical device using a battery cell according to an embodiment of the present application as a power source.

[0147] Description of reference numerals:

[0148] 1 battery cell; 11 housing; 111 housing of the large surface of the battery cell; 12 electrode assembly; 121 positive electrode sheet; 1211 positive electrode current collector; 1212 positive electrode active material layer; 12110 positive electrode current collecting portion; 12111 positive electrode tab; 122 negative electrode sheet; 1221 negative electrode current collector; 1222 negative electrode active material layer; 12210 negative electrode current collecting portion; 12211 negative electrode tab; 123 separator; 1231 base film; 1232 first functional layer; 1233 second functional layer; first electrode terminal 131, second electrode terminal 132, third electrode terminal 133, fourth electrode terminal 134. DETAILED DESCRIPTION

[0149] Below, the embodiments of the battery cells, battery devices, electrical devices and energy storage devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0150] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0151] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0152] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0153] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0154] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0155] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0156] Silicon-based materials have a high theoretical specific capacity. As negative electrode active materials, they help to improve the energy density of battery cells. However, silicon-based materials will undergo significant volume changes during the cycle, which will lead to a large volume expansion of the silicon-containing negative electrode sheets and an increase in the expansion force of the battery cell. The increased extrusion pressure on the positive and negative electrode sheets makes the electrolyte in the active material layer squeezed out and difficult to reabsorb, resulting in a cycle water drop problem in the battery cells.

[0157] Based on this, the first aspect of the present application provides a battery cell, including an electrode assembly and an electrolyte, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, the separator is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer arranged on at least one side of the positive electrode collector, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure; the negative electrode sheet includes a negative electrode collector and a negative electrode active material layer arranged on at least one side of the negative electrode collector, and the single-sided coating mass of the negative electrode active material layer is 80mg / 1540.25mm 2 Up to 150mg / 1540.25mm 2 The negative electrode active material layer includes a negative electrode active material, which includes a silicon-based material. Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 0.5% to 5%; the viscosity of the electrolyte at room temperature is 2.3mPa·s to 3.5mPa·s.

[0158] Olivine-structured lithium-containing phosphates are active materials with an olivine structure that include lithium ions and phosphate groups. The type of positive electrode active material can be determined by any method known in the art. For example, phase analysis methods such as X-ray diffraction (XRD) can be combined with elemental analysis methods such as energy dispersive spectroscopy and XPS.

[0159] In the present application, “the coating mass of the negative electrode active material layer on one side” refers to the mass of the negative electrode active material layer per unit area on one side of the current collector.

[0160] In this application, the single-sided coating quality of the negative electrode active material layer can be tested using methods known in the art. For example, the negative electrode sheet can be removed from the disassembled battery (if the negative electrode sheet is coated on both sides, the negative electrode active material layer can be wiped off on one side first), punched into small discs with an area of ​​S1, and the mass of each disc is measured and recorded as M1. The negative electrode active material layer of the weighed negative electrode sheet is then wiped off, and the mass of the negative electrode current collector is weighed and recorded as M0. The single-sided coating quality of the negative electrode sheet = (M1-M0) / S1.

[0161] In some embodiments, the single-sided coating mass of the negative electrode active material layer can be 80 mg / 1540.25 mm 2 、90mg / 1540.25mm 2 、100mg / 1540.25mm 2 、110mg / 1540.25mm 2 、120mg / 1540.25mm 2 、130mg / 1540.25mm 2 、140mg / 1540.25mm 2、150mg / 1540.25mm 2 or any range of values ​​between them.

[0162] The qualitative and quantitative determination of each substance or element in this application can be performed using appropriate equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and international testing standards, domestic and international enterprise standards, etc. Those skilled in the art may also adapt certain detection steps / instrument parameters to achieve more accurate detection results based on detection accuracy. A single detection method can be used for qualitative or quantitative determination, or a combination of several detection methods can be used for qualitative or quantitative determination. In this application, the mass fraction of silicon based on the total mass of the negative electrode active material layer can be measured using methods known in the art. For example, the negative electrode sheet is immersed in a solvent such as water, the negative electrode active material is separated from the negative electrode current collector, and the various substances in the negative electrode active material layer are filtered to obtain a test sample. The test sample is analyzed using an ICAP7400 inductively coupled plasma-optical emission spectrometer from Thermo Fisher Scientific, USA, in accordance with GB / T30902-2014 standard to determine the silicon content.

[0163] 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%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any numerical range therebetween.

[0164] In this application, "normal temperature" refers to 25±3°C.

[0165] The viscosity of an electrolyte at room temperature is well known in the art and can be measured using methods known in the art. For example, the rotational method provided in the national standard GB / T 10247-2008, "Viscosity Measurement Method," can be used. Specifically, a certain mass of electrolyte sample is placed in a sample container and placed in a hydrothermal constant temperature for 10-20 minutes. Once the sample temperature matches the hydrothermal temperature, the viscosity is measured using a Brookfield DV2TLV rotational viscometer. A No. 18 rotor rotates continuously in the sample at a constant speed of 70 rpm. The shear force exerted on the spring generates torque, which is proportional to the viscosity. The viscosity value is obtained by testing five samples, and the average viscosity of the five samples is taken. The test equipment meets the following test environmental conditions: 1. External environment: Temperature 15-28°C, humidity RH <80%; 2. Internal environment: The sample container is two-thirds submerged in a water bath containing water, which is used to maintain the sample temperature, and the hydrothermal temperature is 25±3°C.

[0166] In some embodiments, the viscosity of the electrolyte at room temperature may be 2.3 mPa·s, 2.4 mPa·s, 2.5 mPa·s, 2.6 mPa·s, 2.7 mPa·s, 2.8 mPa·s, 2.9 mPa·s, 3.0 mPa·s, 3.1 mPa·s, 3.2 mPa·s, 3.3 mPa·s, 3.4 mPa·s, 3.5 mPa·s or any range of values ​​therebetween.

[0167] Lithium-containing phosphates with an olivine structure offer the advantages of low cost and long lifespan. When used with silicon-based materials containing silicon-containing negative electrodes with high specific capacity, they can improve the low energy density of battery cells when lithium-containing phosphates are used as the positive electrode active material. However, silicon-based materials undergo significant volume changes during cycling, which in turn leads to significant volume expansion of the negative electrode electrode and increased expansion force within the battery cell. The increased compressive force on the electrode squeezes out the electrolyte in the positive and negative active material layers, making it difficult to reabsorb it. The loss of electrolyte in the active material layer can lead to "bridge" failure in the lithium-ion transmission pathway and severe lithium deposition at the negative electrode, which in turn causes battery cell cycle lifespan to plummet, negatively impacting the fast-charging performance and cycle life of the battery cells. The battery cell of the embodiment of the present application can reduce the content of silicon-based materials per unit area and shorten the lithium ion diffusion path while taking into account the energy density by ensuring that the single-sided coating mass of the negative electrode active material layer is within the above range, thereby reducing the volume expansion of the negative electrode plate and the amount of electrolyte extruded, reducing internal resistance, and improving the cycle stability and fast charging performance of the battery cell; further, by controlling the viscosity of the electrolyte within the above range, the electrolyte has good conductivity, stability and dissociation rate while helping to improve the electrolyte's ability to wet the active material layer, thereby improving the reabsorption of the extruded electrolyte, which is beneficial to further improve the cycle stability and fast charging performance of the battery cell. The battery cell of the embodiment of the present application achieves excellent energy density, cycle life and fast charging performance through the mutual cooperation between the negative electrode plate and the electrolyte.

[0168] In some embodiments, the single-side coating mass of the negative electrode active material layer is 110 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 .

[0169] When the single-side coating quality of the negative electrode active material layer is within the above range, the battery cell has excellent cycle life and fast charging performance, while the energy density is further improved.

[0170] In some embodiments, based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 1.6% to 5%.

[0171] When the mass proportion of silicon element is within the above range, the battery cell has excellent cycle life and fast charging performance, while the energy density is further improved.

[0172] In some embodiments, the silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy, and may be a silicon-carbon material.

[0173] The carbon material in the silicon-carbon material helps to alleviate the volume expansion of the silicon material, thereby taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0174] In some embodiments, based on the total mass of the silicon-carbon material, the mass proportion of silicon element in the silicon-carbon material is 40% to 80%.

[0175] In some embodiments, based on the total mass of the silicon-carbon material, the mass proportion of silicon element in the silicon-carbon material can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or any numerical range therebetween.

[0176] In some embodiments, the volume average particle size Dv50 of the silicon-carbon material is 5.0 μm to 12.5 μm.

[0177] In this application, "volume average particle size Dv50" has a well-known meaning in the art and represents the particle size corresponding to the cumulative volume distribution percentage of a material reaching 50%. It can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0178] In some embodiments, the volume average particle size Dv50 of the silicon carbon material can be 5.0 μm, 5.6 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, 11.0 μm, 11.5 μm, 12.0 μm, 12.5 μm or any numerical range therebetween.

[0179] Silicon-carbon materials with a volume average particle size within the above range shorten the solid-phase migration path of lithium ions while taking into account lower reaction activity, thereby taking into account the fast charging capability and cycle life of the battery cell.

[0180] In some embodiments, the specific surface area of ​​the silicon carbon material is 3.1 m 2 / g to 3.6m 2 / g.

[0181] In this application, specific surface area has a meaning well known in the art and can be tested using methods known in the art. The determination method can refer to GB / T19587-2017, using the nitrogen adsorption specific surface area analysis test method and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, USA.

[0182] In some embodiments, the specific surface area of ​​the silicon carbon material can be 3.1 m 2 / g, 3.15m 2 / g, 3.2m 2 / g, 3.25m 2 / g, 3.3m 2 / g, 3.35m 2 / g, 3.4m 2 / g, 3.45m 2 / g, 3.5m 2 / g, 3.55m 2 / g, 3.6m 2 / g or any range of values ​​between them.

[0183] Silicon-carbon materials with a specific surface area within the above range shorten the solid-phase migration path of lithium ions while taking into account lower reaction activity, thereby taking into account the fast charging capability and cycle life of the battery cell.

[0184] In some embodiments, the powder compaction density of the silicon carbon material at 25000N is 0.7g / cm 3 to 1.2g / cm 3 .

[0185] The compaction density of silicon-carbon material powder at 25000N is well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using an electronic pressure testing machine (such as the UTM7305 electronic pressure testing machine) in accordance with GB / T 24533-2019. An exemplary test method is as follows: 1g of silicon-carbon material powder is weighed and added to a container with a bottom area of ​​1.327cm 2 In the mold, pressurize to 25000N, hold the pressure for 30s, then release the pressure, hold for 10s, and then record and calculate the powder compaction density of the material under the pressure of 25000N.

[0186] In some embodiments, the powder compaction density of the silicon carbon material at 25000N can be 0.7g / cm 3 , 0.75g / cm 3 , 0.8g / cm3 , 0.85g / cm 3 , 0.9g / cm 3 , 0.95g / cm 3 , 1.0g / cm 3 , 1.05g / cm 3 , 1.1g / cm 3 , 1.15g / cm 3 , 1.2g / cm 3 or any range of values ​​between them.

[0187] Silicon-carbon materials with a powder compaction density within the above range have no negative impact on the compaction density of the negative electrode sheet and do not deteriorate the energy density of the battery cell.

[0188] In some embodiments, the negative electrode active material further includes a carbon-based material.

[0189] In some embodiments, the carbon-based material includes one or more of graphite and hard carbon, and can be graphite.

[0190] In some embodiments, the carbon-based material includes composite graphite particles, the composite graphite particles include graphite particles and a carbon coating layer coated on at least a portion of the surface of the graphite particles, the graphite particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0191] Secondary particles are particles formed by the aggregation of two or more primary particles. Composite graphite particles, including secondary particles and a surface coating layer including amorphous carbon, further improve the electrolyte's wettability in the negative electrode active material layer and enhance the solid-phase transport capacity of active ions, contributing to enhanced fast-charging performance and cycle stability of battery cells.

[0192] In some embodiments, the amorphous carbon accounts for 2% to 5% by weight based on the total weight of the composite graphite particles.

[0193] In some embodiments, the mass percentage of amorphous carbon based on the total mass of the composite graphite particles may be 2%, 3%, 4%, 5%, or any range therebetween.

[0194] When the content of amorphous carbon is within an appropriate range, the composite graphite material can have a high gram capacity while also having a high active ion solid-phase transport ability, which is conducive to further comprehensive improvement of the energy density and fast charging performance of the battery cell.

[0195] In some embodiments, the composite graphite particles have a volume average particle size Dv50 of 8.5 μm to 16.5 μm.

[0196] "Volume average particle size Dv50" is well known in the art and represents the particle size corresponding to the 50% cumulative volume distribution percentage of a material. It can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, as per GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK. The composite graphite particles can be freshly prepared or scraped from the negative electrode active material layer after disassembly of a battery cell. For example, discharge the battery to 0% SOC, then disassemble and take out the negative electrode, scrape a certain amount of powder on the electrode with a blade, and then use deionized water to clean it repeatedly by shaking for 5 to 10 times. After drying, sinter it in a tube furnace at 400°C for 2 hours. After sintering, take an appropriate amount of the sample to be tested (the sample concentration can ensure 8%-12% shading), add deionized water, and ultrasonically disperse it to ensure that the sample is completely dispersed. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0197] In some embodiments, the volume average particle size Dv50 of the composite graphite particles may be 8.5 μm, 9.5 μm, 10.5 μm, 11.5 μm, 12.5 μm, 13.5 μm, 14.5 μm, 15.5 μm, 16.5 μm, or any range therebetween.

[0198] The composite graphite particles with a volume average particle size within the above range shorten the solid phase migration path of lithium ions while taking into account low reaction activity, thereby taking into account the fast charging capability and cycle life of the battery cell.

[0199] In some embodiments, the compaction density of the negative electrode active material layer is 1.10 g / cm 3 Up to 1.50g / cm 3 .

[0200] The compacted density of the negative electrode active material layer is well known in the art and can be measured using methods known in the art. For example, a battery cell is placed at 25°C and charged at a constant current of 0.33C to 3.65V. Then, it is charged at a constant voltage of 3.65V to 0.05C. At this point, the battery cell is fully charged. The negative electrode sheet is then disassembled and the compacted density of the negative electrode active material layer is measured. The compacted density of the negative electrode active material layer is calculated as the single-sided coating mass of the negative electrode active material layer divided by the single-sided thickness of the negative electrode active material layer, as measured after disassembly.

[0201] The thickness of the negative electrode active material layer is well known in the art and can be measured using methods known in the art, such as using a micrometer (e.g., Mitutoyo 293-100, with an accuracy of 0.1 μm). It is understood that when a battery cell is fully charged, the compaction density of the negative electrode active material layer will differ from the design compaction density of the battery cell. Due to actual operational influences, the compaction density of the negative electrode active material layer when a battery cell is fully charged is often slightly lower than the design compaction density of the battery cell.

[0202] In some embodiments, the compaction density of the negative electrode active material layer may be 1.10 g / cm 3 , 1.15g / cm 3 , 1.20g / cm 3 , 1.25g / cm 3 , 1.30g / cm 3 , 1.35g / cm 3 , 1.40g / cm 3 , 1.45g / cm 3 , 1.50g / cm 3 or any range of values ​​between them.

[0203] The negative electrode active material layer with a compaction density within the above range allows the battery to have excellent energy density while further improving the fast charging performance and cycle stability of the battery cell.

[0204] In some embodiments, the electrode assembly is a laminate structure.

[0205] In some embodiments, reference Figure 1 The negative electrode sheet 122 includes a negative electrode current collector 1221 and a positive electrode active material layer 1222 arranged on at least one side of the negative electrode current collector 1221. The size of the negative electrode active material layer 1222 along the length direction of the electrode assembly is 200 mm to 650 mm, and the size can be measured with a ruler.

[0206] In some embodiments, the dimension of the negative electrode active material layer along the length direction of the electrode assembly may be 200 nm, 250 nm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, or any range therebetween.

[0207] The design of a laminated electrode assembly in which the dimension of the negative electrode active material layer along the length direction of the electrode assembly is within the above range is beneficial for taking into account the energy density, cycle stability and fast charging performance of the battery cell.

[0208] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0209] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0210] In some embodiments, the electrolyte includes a first solvent, the viscosity η of the first solvent at room temperature is 0.3 mPa·s to 0.6 mPa·s, and the mass proportion of the first solvent based on the total mass of the electrolyte is 8% to 60%.

[0211] The type and quality of the solvent in the electrolyte can be obtained by testing the electrolyte by methods known to those skilled in the art. In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is approximately 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery cell is used as a sample, which is tested by ion chromatography. The type and content of the organic components in the electrolyte are well known in the art and can be tested by equipment and methods well known in the art. For example, the organic components of the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography with reference to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents". The types and contents of inorganic components / lithium salts in the electrolyte are well known in the art and can be detected using equipment and methods known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-2002 "General Rules for Ion Chromatography Analysis Methods".

[0212] The viscosity of the first solvent at room temperature can be tested by a method similar to the viscosity of the electrolyte at room temperature described above.

[0213] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the first solvent can be 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or any numerical range therebetween.

[0214] In some embodiments, the viscosity η of the first solvent may 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 any range therebetween.

[0215] The first solvent with a viscosity η within the above range has both excellent stability and low viscosity. The mass proportion of the first solvent within the above range helps to reduce the viscosity of the electrolyte, improve the conductivity of the electrolyte, and take into account the stability of the electrolyte, thereby facilitating further comprehensive improvement of the fast charging performance and cycle stability of the battery cell.

[0216] In some embodiments, the first solvent accounts for 30% to 60% by mass based on the total mass of the electrolyte.

[0217] When the mass proportion of the first solvent is within the above range, the viscosity of the electrolyte is further reduced while the electrolyte has good stability and conductivity, which is beneficial to further improve the cycle stability of the battery cell.

[0218] In some embodiments, the first solvent includes a carboxylate solvent.

[0219] Carboxylate solvents have the advantages of low viscosity and high ionic conductivity, which are conducive 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 cycle stability and fast charging performance of the battery cell.

[0220] In some embodiments, the carboxylate solvent has a general structural formula of R'-COO-R'', wherein R' includes one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R'' includes one or more of a C1-C5 alkyl group and a C1-C5 haloalkyl group.

[0221] "C1-C5 alkyl" refers to an unbranched or branched alkyl group having 1 to 5 carbon atoms; including but not limited to one or more of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, and 1-ethylpropyl.

[0222] “C1-C5 haloalkyl” refers to an unbranched or branched alkyl group having 1 to 5 carbon atoms in which at least one hydrogen atom is substituted by a halogen, including but not limited to one or more of chloroalkyl, bromoalkyl, and iodoalkyl.

[0223] "Halogen" refers to an element of Group VIIA of the periodic table of chemical elements. Specifically, halogen includes fluorine, chlorine, bromine, iodine or astatine.

[0224] 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.

[0225] In some embodiments, 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.

[0226] Carbonate solvents have a high dielectric constant. Carbonate solvents can easily form a solvation structure with lithium ions in lithium-containing electrolyte salts to increase the dissociation rate of lithium ions and anions in lithium-containing electrolyte salts, thereby further improving the fast charging performance of battery cells.

[0227] In some embodiments, based on the total mass of the electrolyte, the carbonate solvent accounts for 18% to 75% by mass.

[0228] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the carbonate solvent can be 18%, 20%, 30%, 40%, 50%, 60%, 70%, 75% or any range therebetween.

[0229] Due to the high viscosity of carbonate solvents, increasing the carbonate solvent content increases the electrolyte viscosity, negatively impacting the electrolyte's conductivity. By properly controlling the carbonate solvent mass percentage within the above range, the electrolyte achieves optimal viscosity, conductivity, and good dissociation rate and wettability, which improves the overall kinetic performance and cycling stability of the battery cells.

[0230] In some embodiments, the electrolyte includes a lithium-containing electrolyte salt, and the lithium-containing electrolyte salt accounts for 10% to 18% by mass of the electrolyte based on the total mass of the electrolyte.

[0231] The type and quality of the lithium electrolyte salt in the electrolyte can be obtained by testing the electrolyte using methods known to those skilled in the art. As an example, the type and quality of the solvent in the electrolyte can be tested using the test method described above.

[0232] In some embodiments, the mass percentage of the lithium electrolyte salt in the electrolyte can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or any range therebetween.

[0233] 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 ionic conductivity of the electrolyte, thereby further comprehensively improving the cycle stability and fast charging performance of the battery cell.

[0234] In some embodiments, the lithium-containing electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6).

[0235] LiFSI is easy to dissociate in the electrolyte solvent, and LiFSI has a smaller molecular weight than other types of fluorinated sulfonyl imide salts (such as lithium bis(trifluoromethanesulfonyl)imide LiTFSI), which is beneficial for improving 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 battery cycling 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, 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. Lithium-containing electrolyte salts also include lithium hexafluorophosphate LiPF6, which can reduce the risk of thermal runaway of the battery cell, reducing the risk to a controllable range, thereby improving the safety performance of the battery cell.

[0236] In some embodiments, based on the total mass of the electrolyte, the mass proportion of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is 4% to 8%.

[0237] In some embodiments, based on the total mass of the electrolyte, the mass proportion of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte may be 4%, 5%, 6%, 7%, 8%, or any range therebetween.

[0238] The battery cell having the molar concentration of lithium bis(fluorosulfonyl)imide in the electrolyte within the above range can take into account the dynamic performance, cycle stability and safety performance of the battery cell.

[0239] In some embodiments, 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.

[0240] Additives refer to components with low content in the electrolyte, which generally account for no more than 10% of the mass of the electrolyte. They are highly targeted and used in small amounts, and can significantly optimize the performance of a certain aspect of the battery without changing the production process.

[0241] In the present application, carbonate additives refer to compounds including carbonate groups (—O—CO—O—) and their derivatives, as well as mixtures containing the above compounds and their derivatives.

[0242] In the present application, fluorobenzene additives refer to organic compounds and their derivatives in which one or more hydrogen atoms on the benzene ring are replaced by fluorine atoms, as well as mixtures containing the above compounds and their derivatives.

[0243] The type of additive in the electrolyte can be determined by testing the electrolyte using methods known to those skilled in the art. For example, the type and quality of the solvent in the electrolyte can be determined using the aforementioned testing method.

[0244] In some embodiments, the carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives, wherein the ethylene carbonate derivative includes the compound shown in Formula I,

[0245] Formula I

[0246] R1, R2, R3, and R4 each independently include one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time. Optionally, the carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

[0247] Carbonate additives can evolve into organic components in the SEI film, which is beneficial to improving the toughness of the SEI film, reducing the probability of SEI film rupture due to volume changes of silicon-based materials and causing side reactions between the electrolyte and silicon-based materials, reducing battery gas production and reducing the interfacial impedance on the negative electrode side, which is beneficial to further improve the cycle, storage life and fast charging performance of battery cells.

[0248] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl bissulfate, 1,3 propane sultone, butylene sulfite, vinyl sulfite, and methylene disulfonate.

[0249] Sulfur-containing additives often have a higher potential. Sulfur-containing additives added to the electrolyte will preferentially react during formation or subsequent cycling, evolving into sulfur-containing inorganic components in the SEI film. The SEI film formed by carbonate additives has poor high-temperature stability, which is detrimental to the stability of the battery cells in high-temperature environments. The presence of sulfur in the SEI film can further enhance the thermal stability of the SEI film at high temperatures and further reduce the interfacial impedance on the negative electrode side, thereby further improving the cycling stability and fast-charging performance of the battery cells.

[0250] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0251] Lithium salt additives can evolve into inorganic components in the SEI film, further improving the rigidity and stability of the SEI film, thereby further enhancing the battery's cycling stability and fast-charging performance. Furthermore, these lithium salt additives can form a positive electrode electrolyte interface film (CEI film) on the surface of the positive electrode active material, further improving the cycling stability of the battery cell.

[0252] In some embodiments, the fluorobenzene additive includes one or more of fluorobenzene and its derivatives.

[0253] Fluorobenzene additives help improve the wettability of the electrolyte to the positive and negative electrode active material layers, thereby further improving the cycle stability and fast charging performance of the battery cells.

[0254] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 3% to 8%.

[0255] Based on the total mass of the electrolyte, the mass proportion of the additive can be measured using any method known in the art. As an example, the mass proportion of the solvent and lithium-containing electrolyte salt in the electrolyte can be measured using the test method described above. It should be understood that since the additive in the electrolyte will be consumed during the formation and circulation process to form relevant components in the SEI film and / or CEI film, the mass proportion of the additive in the electrolyte may be slightly lower than the initial mass proportion of the additive in the electrolyte.

[0256] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the carbonate additive can be selected to be 3%, 4%, 5%, 6%, 7%, 8% or any range therebetween.

[0257] The mass proportion of carbonate additives in the electrolyte is within the above range, which takes into account both improving the stability of the SEI film and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0258] In some embodiments, based on the total mass of the electrolyte, the mass proportion of vinylene carbonate is 2% to 5%.

[0259] In some embodiments, based on the total mass of the electrolyte, the mass proportion of vinylene carbonate can be 2%, 3%, 4%, 5%, or any range therebetween.

[0260] Vinylene carbonate (VC) has a similar reduction potential to carboxylate solvents, which can inhibit the reactivity of carboxylate solvents and improve the cycle life of battery cells. However, excessive VC content can increase the battery's interfacial impedance and charge transfer impedance, hindering the fast-charging performance of the battery cells. A VC mass percentage within the above range ensures that the battery achieves both excellent cycle life and fast-charging performance.

[0261] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 0% to 4%.

[0262] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 1.5% to 3.5%.

[0263] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative can be 0.5%, 1%, 2%, 3%, 4% or any range therebetween.

[0264] It should be noted that as the battery cells charge and discharge, when the amount of ethylene carbonate derivative added is relatively low, the ethylene carbonate derivative content may be 0% when the electrolyte is obtained by gas chromatography after disassembling the battery cells. It is understood that in some embodiments, the ethylene carbonate derivative added to the electrolyte is completely converted into organic components in the SEI film during the formation process. In some embodiments, ethylene carbonate derivatives remain in the electrolyte, reinforcing the SEI film during subsequent battery cell cycling.

[0265] Ethylene carbonate derivatives can also form films on the negative electrode surface at higher potentials and exhibit low interfacial and charge transfer resistance. The mass percentage of ethylene carbonate derivatives within the aforementioned range enables the battery cells to achieve both excellent fast-charging performance and cycle life. By combining vinylene carbonate (VC) and ethylene carbonate derivatives in the electrolyte, the fast-charging performance and cycle stability of the battery cells can be comprehensively improved.

[0266] In some embodiments, the mass proportion of the sulfur-containing additive is 0% to 2% based on the total mass of the electrolyte.

[0267] In some embodiments, the mass proportion of the sulfur-containing additive is 0.5% to 2% based on the total mass of the electrolyte.

[0268] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive may be 0.5%, 1%, 1.5%, 2%, or any range therebetween.

[0269] It should be noted that since the additives in the electrolyte will be consumed during the formation and charge-discharge cycle to generate relevant components in the SEI film and / or CEI film, after disassembling the battery cell to obtain the electrolyte, when testing the content of sulfur-containing additives and lithium salt additives by gas chromatography, the content may be 0%.

[0270] Specifically, taking the case where the mass content of a sulfur-containing additive is 0% as an example, this could be because no sulfur-containing additives were added to the freshly prepared electrolyte, or because the electrolyte obtained after disassembling the battery cell does not contain sulfur-containing additives. In this case, it could be that the freshly prepared electrolyte did not contain sulfur-containing additives, or it could be that a small amount of sulfur-containing additives was added but participated in the SEI film formation reaction during the battery cell formation process, resulting in a mass content of 0% during the test. Alternatively, the freshly prepared electrolyte does contain sulfur-containing additives.

[0271] Furthermore, regarding the addition of certain substances, such as additives, to the electrolyte, the content of additives in the battery cell electrolyte is related to the formation process, different battery life cycles, or different battery storage conditions due to the additives' role in film formation on the surface of the active material. Therefore, the additive content in a freshly prepared electrolyte may differ from that in an electrolyte obtained by reverse disassembling a battery cell. However, those skilled in the art can determine the approximate content range of the relevant substances in the fresh electrolyte based on the performance level of the battery cell (such as the number of cycles) and residual content. Similarly, those skilled in the art can also determine the approximate content range of the corresponding non-freshly prepared (i.e., after reverse disassembly) electrolyte based on the content of the freshly prepared additives, the performance requirements for the battery cell, the storage environment, etc.

[0272] Therefore, the additive content mentioned in the technical solution of the present application can be the content of the additive actively added to the fresh electrolyte, or it can be the content of the residual additive detected by reverse detection based on the actual battery status.

[0273] It is understood that in some embodiments, the sulfur-containing additive added to the electrolyte is completely converted into sulfur-containing components in the SEI film during the formation process. The amount of sulfur-containing additive added to the electrolyte can be inferred by X-ray photoelectron spectroscopy (XPS) testing of the negative electrode material. In some embodiments, the sulfur-containing additive may remain in the electrolyte, reinforcing the SEI film during subsequent battery cell cycling.

[0274] In this application, X-ray photoelectron spectroscopy (XPS) of the negative electrode material can be tested by any method known in the art. As an example, after disassembling the battery cell, the negative electrode plate is cleaned with a solvent such as dimethyl carbonate (DMC) three or more times, and then a powder sample is scraped off. The resulting negative electrode material powder is adhered to a conductive substrate and X-ray photoelectron spectroscopy is performed using an X-ray photoelectron spectrometer (such as AXIS ULTRA). The scan rate and time of the X-ray source are adjusted to focus and detect elements and functional groups at a depth of 5nm to 10nm from the surface of the negative electrode material. The X-ray photoelectron spectroscopy (XPS) spectrum of the sample is obtained, and the characteristic element peaks in the spectrum are analyzed.

[0275] The mass proportion of the sulfur-containing additive in the electrolyte is within the above range, which takes into account both improving the thermal stability of the SEI film at high temperature and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0276] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

[0277] In some embodiments, the mass proportion of the lithium salt additive is 0.2% to 1% based on the total mass of the electrolyte.

[0278] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the lithium salt additive can be selected to be 0.2%, 0.4%, 0.6%, 0.8%, 1% or any range therebetween.

[0279] It is understood that in some embodiments, the lithium salt additive added to the electrolyte is completely converted into inorganic components in the SEI film and / or CEI film during the formation process. In some embodiments, the lithium salt additive still remains in the electrolyte, which strengthens the SEI film and / or CEI film during subsequent battery cell cycling.

[0280] The mass proportion of lithium salt additives in the electrolyte is within the above range, which takes into account both improving the stability of the SEI film and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0281] In some embodiments, the mass content of the fluorobenzene additive is 0.1% to 1% based on the total mass of the electrolyte.

[0282] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the fluorobenzene additive can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or any numerical range therebetween.

[0283] The mass proportion of fluorobenzene additives in the electrolyte is within the above range, taking into account the wettability of the electrolyte and maintaining an appropriate viscosity of the electrolyte, thereby further comprehensively improving the cycle life and fast charging performance of the battery cell.

[0284] 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 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 the size of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH2, wherein OH1 is 1.0 mm to 4.0 mm; and / or OH2 is 1.0 mm to 3.0 mm.

[0285] In this application, reference 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 between the size of the negative electrode active material layer 1222 and the size of the positive electrode active material layer 1212 is OH1=OH 21 -OH 11 ;refer to Figure 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 between the size of the negative electrode active material layer 1222 and the size of the positive electrode active material layer 1212 is OH1=OH 22 -OH 12 , the size can be measured with a ruler.

[0286] In some embodiments, OH1 can be selected as 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 any range therebetween.

[0287] In some embodiments, OH2 can be selected as 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 any range therebetween.

[0288] As the charge rate of a battery cell increases, the current density near the tab increases, leading to a large temperature rise. This makes the negative electrode active material layer susceptible to the formation of lithium dendrites near the tab. The design of OH1 and OH2 improves the ability of the negative electrode active material layer, especially the layer near the tab, to accept active ions along its length. This also increases the distance between the positive electrode active material layer and the tab, resulting in a more uniform current distribution and lower temperature rise. This comprehensively improves the lithium deposition problem in the negative electrode sheet and reduces the probability of overlap between the positive and negative electrodes due to thermal shrinkage of the separator, which could lead to internal battery short circuits. This improves the fast-charging performance and cycle stability of the battery cell while controlling the OH1 and OH2 values ​​within the above range, ensuring that the battery cell also has excellent energy density.

[0289] In some embodiments, OH1 is greater than or equal to OH2.

[0290] Controlling OH1 to be greater than OH2 improves the cycle stability of the battery cell and is conducive to further improving the energy density of the battery cell.

[0291] In some embodiments, the positive electrode current collector includes a positive electrode current collecting portion and a positive electrode tab, and the positive electrode tab is disposed at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly or at least one side extending along the width direction of the electrode assembly.

[0292] In some embodiments, reference Figure 3 The positive electrode current collector 1211 includes a positive electrode current collecting portion 12110 and a positive electrode tab 12111 . The positive electrode tab 12111 is disposed at one end of the positive electrode current collecting portion 12110 extending along the length direction of the electrode assembly.

[0293] The above-mentioned tab arrangement helps to improve the weight energy density of the battery cell.

[0294] In some embodiments, reference Figure 4 The positive electrode tabs 12111 are arranged at both ends of the positive electrode current collecting portion 12110 extending along the length direction of the electrode assembly.

[0295] The above-mentioned tab setting helps to improve the overcurrent capacity of the battery cell, alleviate the situation where the temperature on the tab side is too high during fast charging, causing electrolyte decomposition and uneven current distribution to cause lithium deposition on the tab side, thereby improving the fast charging performance and cycle stability of the battery cell. It is especially suitable for improving the fast charging performance of battery cells with an active material layer length greater than 500mm, while taking into account excellent volume energy density.

[0296] In some embodiments, reference Figure 5 The positive electrode tab 12111 is arranged on one side of the positive electrode current collecting portion 12110 extending along the width direction of the electrode assembly.

[0297] In some embodiments, reference Figure 6 The positive electrode tabs 12111 are arranged on both sides of the positive electrode current collecting portion 12110 extending along the width direction of the electrode assembly.

[0298] The above-mentioned tab setting helps to further improve the current carrying capacity of the battery cell, thereby further improving the fast charging performance and cycle stability of the battery cell, and is particularly suitable for improving the fast charging performance of the battery cell with an active material layer length greater than 500 mm.

[0299] In some embodiments, the negative electrode current collector includes a negative electrode current collecting portion and a negative electrode tab, and the negative electrode tab is disposed at at least one end of the negative 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.

[0300] In some embodiments, reference Figure 7 The negative electrode current collector 1221 includes a negative electrode current collecting portion 12210 and a negative electrode tab 12211 . The negative electrode tab 12211 is disposed at one end of the negative electrode current collecting portion 12210 extending along the length direction of the electrode assembly.

[0301] In some embodiments, reference Figure 8 The negative electrode tabs 12211 are arranged at both ends of the negative electrode current collecting portion 12210 extending along the length direction of the electrode assembly.

[0302] In some embodiments, reference Figure 9 The negative electrode tab 12211 is arranged on one side of the negative electrode current collecting portion 12210 extending along the width direction of the electrode assembly.

[0303] In some embodiments, reference Figure 10 The negative electrode tabs 12211 are arranged on both sides of the negative electrode current collecting portion 12210 extending along the width direction of the electrode assembly.

[0304] In some embodiments, the dimension of the negative active material layer along the length direction of the electrode assembly is greater than 500 mm, and the negative electrode tabs are arranged at both ends of the negative 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.

[0305] In some embodiments, reference Figure 3 and 4 The positive electrode tab is arranged at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly, and the ratio of the width of the positive electrode tab to the width of the positive electrode current collecting portion is 0.25 to 1.

[0306] In some embodiments, reference Figure 7 and 8The negative electrode tab is arranged at at least one end of the negative electrode current collecting portion extending along the length direction of the electrode assembly, and the ratio of the width of the negative electrode tab to the width of the negative electrode current collecting portion is 0.25 to 1.

[0307] In some embodiments, reference Figure 5 and 6 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.

[0308] In some embodiments, reference Figure 9 and 10 The negative electrode tab is arranged on at least one side of the negative electrode current collecting portion extending along the width direction of the electrode assembly, and 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.

[0309] In some embodiments, the ratio of the width of the positive electrode tab to the width of the positive electrode current collector or the ratio of the width of the negative electrode tab to the width of the negative electrode current collector can be 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, 1, or any range therebetween.

[0310] The width of the tab is within the above range, which helps to improve the current capacity of the battery cell and improve the fast charging performance and cycle stability of the battery cell.

[0311] In some embodiments, the positive electrode active material includes: an olivine-structured lithium-containing phosphate, and a coating layer, wherein the coating layer is located on at least a portion of the surface of the lithium-containing phosphate, and the coating layer contains carbon.

[0312] The coating layer contains carbon elements, which is beneficial to improving the electronic conductivity of lithium-containing phosphates and improving the solid-phase transmission rate of electrons, thereby further improving the energy density and fast charging performance of the battery cells.

[0313] In some embodiments, based on the total mass of the positive electrode active material, the mass proportion of carbon element is 0.8% to 2.3%.

[0314] In some embodiments, based on the total mass of the positive electrode active material, the mass proportion of the carbon element can be selected to be 0.8%, 1.1%, 1.4%, 1.7%, 2.0%, 2.3% or any numerical range therebetween.

[0315] Based on the total mass of the positive electrode active material, the mass proportion of the carbon element is within the above range, so that the lithium-containing phosphate has both excellent electronic conductivity and gram capacity, further comprehensively improving the energy density and fast charging performance of the battery cell.

[0316] In some embodiments, the coating layer further comprises a component as shown in Formula II,

[0317] Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula II, wherein 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, M1 includes one or more of Ti, Zr, Hf, Ge, and Sn, and optionally, M1 has a valence of +4.

[0318] In some embodiments, d1 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any range therebetween, m1 can be selected as 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or any range therebetween, and n1 can be selected as 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4 or any range therebetween.

[0319] In some embodiments, the component represented by Formula II includes one or more of Li2FeTi(PO4)3, Li2FeZr(PO4)3, and Li2FeSn(PO4)3.

[0320] It should be noted that the coating layer can be a single-layer structure or a multi-layer structure, that is, the carbon-containing component in the coating layer and the component shown in Formula II can be a mixed phase or can be arranged in layers.

[0321] The physical structure of the coating layer can be characterized by any method known in the art. For example, by characterizing the positive electrode active material through transmission electron microscopy, it can be seen that the coating layer and the matrix of the positive electrode active material have different physical structures. Combining diffraction patterns and energy spectrum analysis, the composition of the coating layer can be judged.

[0322] The component represented by Formula II is a fast ion conductor with a NASICON structure. Its ionic conductivity approaches or exceeds that of conductive liquids such as electrolyte solutions or molten salts. It has abundant three-dimensional lithium ion diffusion and transport channels, and has advantages such as high ion conduction efficiency and strong structural stability during multiple lithium de- and lithium insertion processes. The coating layer on the surface of the lithium-containing phosphate contains a fast ion conductor with a NASICON structure, which can significantly increase the lithium ion transmission rate during multiple lithium de- and lithium insertion at the positive terminal, enhance the ionic conductivity of the positive electrode active material, and further improve the energy density and fast charging performance of the battery cell.

[0323] In some embodiments, the lithium-containing phosphate includes a component as shown in Formula III,

[0324] Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula III, 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; and Y includes one or more of O and F.

[0325] In some embodiments, x1 can be selected as 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any range therebetween, y1 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any range therebetween, x1+y1 can be selected as 0.9, 1, 1.1, 1.2, 1.3 or any range therebetween, a1 can be selected as 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any range therebetween, b1 can be selected as wherein a1+b1 is 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any range therebetween; c1 is 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any range therebetween; z1 is 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or any range therebetween.

[0326] The lithium-containing phosphate with an olivine structure having the above components has good structural stability, can reduce the loss during the fast charging process, and further improve the fast charging performance and cycle stability of the battery cell.

[0327] In some embodiments, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, and modified forms of any of the foregoing substances, wherein the modified form includes one or more of doping modification and coating modification.

[0328] In some embodiments, the powder compaction density of the positive electrode active material at 30,000 N is 2.45 g / cm 3 Up to 2.75g / cm 3 .

[0329] The compaction density of the positive electrode active material powder at 30,000 N is well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using an electronic pressure tester (such as the UTM7305 electronic pressure tester) in accordance with GB / T 24533-2019. An exemplary test method is as follows: Weigh 1 g of the positive electrode active material powder and add a pressure gauge with a bottom area of ​​1.327 cm 2 In the mold, pressurize to 30000N, hold the pressure for 30s, then release the pressure, hold for 10s, and then record and calculate the powder compaction density of the material under 30000N pressure.

[0330] In some embodiments, the powder compaction density of the positive electrode active material at 30,000 N may be 2.45 g / cm 3 , 2.50g / cm 3 , 2.55g / cm 3 , 2.60g / cm 3 , 2.65g / cm 3 , 2.70g / cm 3 , 2.75g / cm 3 or any range of values ​​between them.

[0331] The positive electrode active material with a powder compaction density within an appropriate range can make the positive electrode active material layer have a higher compaction density, thereby making the battery cell have a higher energy density.

[0332] In some embodiments, the compaction density of the positive electrode active material layer is 2.5 g / cm 3 to 2.83g / cm 3 .

[0333] The compaction density of the positive electrode active material layer can be tested by a method similar to the compaction density of the negative electrode active material layer described above.

[0334] In some embodiments, the compaction density of the positive electrode active material layer may be 2.50 g / cm 3 , 2.53g / cm 3, 2.55g / cm 3 , 2.57g / cm 3 , 2.59g / cm 3 , 2.61g / cm 3 , 2.63g / cm 3 , 2.65g / cm 3 , 2.67g / cm 3 , 2.69g / cm 3 , 2.71g / cm 3 , 2.73g / cm 3 , 2.75g / cm 3 , 2.77g / cm 3 , 2.79g / cm 3 , 2.81g / cm 3 , 2.83g / cm 3 or any range of values ​​between them.

[0335] The positive electrode active material layer with a compaction density within the above range can further achieve a balance among the energy density, fast charging performance and cycle stability of the battery cell.

[0336] In some embodiments, the single-sided coating mass of the positive electrode active material layer is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 .

[0337] The single-side coating quality of the positive electrode active material layer can be tested by a method similar to the single-side coating quality of the negative electrode active material layer described above.

[0338] In some embodiments, the single-sided coating mass of the positive electrode active material layer can be 230 mg / 1540.25 mm 2 、240mg / 1540.25mm 2 、250mg / 1540.25mm 2 、260mg / 1540.25mm 2 、270mg / 1540.25mm 2 、280mg / 1540.25mm 2 、290mg / 1540.25mm 2 、300mg / 1540.25mm 2 、310mg / 1540.25mm 2 、320mg / 1540.25mm 2 、330mg / 1540.25mm 2 、340mg / 1540.25mm 2、350mg / 1540.25mm 2 、360mg / 1540.25mm 2 、370mg / 1540.25mm 2 or any range of values ​​between them.

[0339] The positive electrode active material layer having a single-side coating mass within the above range can further effectively balance the fast charging performance and energy density of the battery cell.

[0340] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0341] The materials for the positive and / or negative electrode current collectors are not particularly limited, as long as they do not cause chemical changes in the battery cells and are conductive. The current collectors include metal foils with a pure metal content of 95% or more, such as at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, and nickel foil. They also include alloy foils containing at least two main elements, such as copper, aluminum, nickel, titanium, and iron. They can also include copper, aluminum-cadmium alloys, iron, or stainless steel surface-treated with carbon, nickel, titanium, silver, or copper. Furthermore, fine concave-convex surfaces can be formed to enhance the binding force with the negative electrode active material. The current collectors can be used in various forms, such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0342] In some embodiments, the thickness of the positive electrode current collector may be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any range therebetween.

[0343] The positive electrode current collector has a relatively low thickness, which enables further improvement in the energy density of the battery cell.

[0344] In some embodiments, the positive electrode active material layer may further optionally include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0345] In some embodiments, the positive electrode active material layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0346] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, which is located between the negative electrode current collector and the negative electrode active material layer on at least one side, and the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm; and / or, the positive electrode plate further includes a positive electrode conductive layer, which is located between the positive electrode active material layer and the positive electrode current collector, and the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

[0347] In some embodiments, the thickness of the positive electrode conductive layer or the negative electrode conductive layer may be 0.5µm, 0.6µm, 0.7µm, 0.8µm, 0.9µm, 1.0µm, 1.1µm, 1.2µm, 1.3µm, 1.4µm, 1.5µm, 1.6µm, 1.7µm, 1.8µm, 1.9µm, 2.0µm or any range therebetween.

[0348] The provision of the positive electrode conductive layer and / or the negative electrode conductive layer is beneficial to improving the electronic conductivity of the battery cell pole piece, and is beneficial to further improving the fast charging performance of the battery cell.

[0349] In some embodiments, the negative electrode conductive layer includes a conductive agent, the positive electrode conductive layer includes a conductive agent and a positive electrode binder, the conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylate resin.

[0350] In some embodiments, the separator has a porosity of 20% to 70%.

[0351] In some embodiments, the separator has a porosity of 35% to 60%.

[0352] In some embodiments, the porosity of the isolation membrane may be 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range therebetween.

[0353] In this application, porosity refers to the percentage of the pore volume within the separator to the total volume of the separator. Porosity can be tested according to the standard GB / T 36363-2018, "Polyolefin Separators for Battery Cells." It should be noted that the actual testing process may vary slightly from the standard to obtain a more accurate test value, depending on instrument differences, test errors, and to minimize the impact of porosity on the test.

[0354] The porosity of the isolation membrane within the above range is beneficial for further taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0355] In some embodiments, reference Figure 11 The isolation film 123 includes a base film 1231; a first functional layer 1232 is 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 is located on a side of the first functional layer away from the base film 1231, and the second functional layer 1232 includes a second inorganic substance and a non-fluoropolymer.

[0356] In some embodiments, the non-fluoropolymer particles include an acrylate copolymer.

[0357] In some embodiments, the first inorganic material and the second inorganic material each independently include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

[0358] Inorganic particles enhance the electrolyte wettability and heat resistance of the first and second functional layers, further improving the battery's fast-charging performance, cycling stability, and safety. Non-fluoropolymer particles enhance the processability and stability of the separator, preventing internal short circuits caused by the separator's movement within the battery cell, further improving the battery's cycling stability and safety.

[0359] In some embodiments, the base film comprises one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film can be a single-layer film or a multi-layer composite film, without particular limitation.

[0360] In some embodiments, the base film has a thickness of 4 μm to 12 μm, optionally 5 μm to 9 μm.

[0361] In some embodiments, the thickness of the base film may be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any range therebetween.

[0362] The thickness of the base film within the above range is beneficial for further taking into account the energy density, fast charging performance and cycle stability of the battery cell.

[0363] In some embodiments, reference Figure 12 The battery cell 1 includes a shell 11 and a cover assembly. The cover assembly is arranged at at least one end of the shell 11. The shell 11 and the cover assembly define an accommodating cavity. The electrode assembly is arranged in the accommodating cavity. The wall thickness of the shell 111 on the large surface of the battery cell is 0.1mm to 0.5mm.

[0364] In some embodiments, the wall thickness of the shell 111 of the large surface of the battery cell is 0.2 mm to 0.35 mm.

[0365] In some embodiments, the shell wall thickness of the battery cell's major surface can be 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or any range therebetween. A shell wall thickness of the battery cell's major surface within the aforementioned range is beneficial for further improving the battery cell's energy density.

[0366] In some embodiments, the cover plate assembly includes a first cover plate assembly and a second cover plate assembly, and the first cover plate assembly and the second cover plate assembly are arranged at both ends of the length direction or width direction of the shell, the first cover plate assembly includes a first cover plate and a first electrode terminal, and the second cover plate assembly includes a second cover plate and a second electrode terminal, and the polarities of the first electrode terminal and the second electrode terminal are opposite.

[0367] In some embodiments, reference Figure 12 The battery cell 1 includes a first cover plate assembly and a second cover plate assembly. The first cover plate assembly includes a first cover plate, a first electrode terminal 131, and a third electrode terminal 133. The polarities of the first electrode terminal 131 and the third electrode terminal 133 are opposite. The second cover plate assembly includes a second cover plate, a second electrode terminal 132 and a fourth electrode terminal 134. The polarities of the second electrode terminal 132 and the fourth electrode terminal 134 are opposite.

[0368] Therefore, the temperature rise of the battery cell and the impedance of the battery cell are reduced during charging, which is beneficial to improving the fast charging performance, cycle life and safety performance of the battery cell.

[0369] In some embodiments, 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 .

[0370] In this application, the minimum cross-sectional area of ​​the first electrode terminal refers to the minimum cross-sectional area of ​​the first electrode terminal along the direction perpendicular to the current flow, and the minimum cross-sectional area of ​​the second electrode terminal refers to the minimum cross-sectional area of ​​the second electrode terminal along the direction perpendicular to the current flow.

[0371] In the present application, when testing the minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal, the minimum cross-sectional area can be calculated based on the shape of the minimum cross-sectional area and the area calculation formula thereof. For example, if the minimum cross-sectional area of ​​the electrode terminal is circular, the minimum cross-sectional area can be obtained by measuring the radius of the circle; if the minimum cross-sectional area is square, the minimum cross-sectional area can be obtained by measuring the length and width of the square.

[0372] In some embodiments, the minimum cross-sectional area S of the first electrode terminal and / or the second electrode terminal may be 150 mm 2 , 300 mm 2 , 450 mm 2 , 600 mm 2 , 750 mm 2 , 900 mm 2 , 1000 mm 2 etc., or can be within the range of any of the above numerical values.

[0373] The minimum cross-sectional area of ​​the first electrode terminal and / or the second electrode terminal is within the above range, which is beneficial to improving the current carrying capacity of the battery cell, reducing the heat generation of the electrode terminal, and reducing the internal resistance of the battery cell, thereby improving the fast charging performance and cycle stability of the battery cell.

[0374] In some embodiments, the volume energy density of the battery cell is greater than 440 Wh / L and less than or equal to 530 Wh / L.

[0375] In some embodiments, the volumetric energy density of the battery cell is 450 Wh / L to 510 Wh / L.

[0376] The volumetric energy density of a battery cell can be tested by any method known in the art. As an example, place the battery cell at 25°C, charge it to 3.65V at a constant current of 0.33C, then charge it to 0.05C at a constant voltage, and let it rest for 30 minutes. Discharge it to 2.0V at a constant current of 0.33C, and record the discharge capacity A0 at this time in Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the dimensions of the battery casing, excluding the height of the electrode terminals and the insulating film outside the casing), and calculate the volume of the single cell V0 in L. The volumetric energy density of the battery cell VED = (A0 × discharge platform voltage) / V0 in Wh / L.

[0377] In some embodiments, the volumetric energy density of the battery cell may be selected as 441Wh / L, 450Wh / L, 460Wh / L, 470Wh / L, 480Wh / L, 490Wh / L, 500Wh / L, 510Wh / L, 520Wh / L, 530Wh / L or any range therebetween.

[0378] The battery cell also has a high energy density, which can meet the demand for increased driving range of electrical devices.

[0379] In some embodiments, the battery cell has a filling factor of 2.2 g / Ah to 3 g / Ah.

[0380] The filling factor of a battery cell refers to the ratio of the mass of the electrolyte within the cell to the battery capacity. The filling factor of a battery cell can be measured using any method known in the art. For example, the mass of the electrolyte in a battery cell can be measured using the following method: Weigh the battery, and record the mass as M0. Disassemble the battery cell and pour out the free electrolyte. Remove the internal electrode assembly and separate the positive and negative electrode sheets, separators, and mechanical components. Soak and clean the positive and negative electrode sheets, separators, and mechanical components in dimethyl carbonate (DMC) for 24 to 48 hours, repeated three or more times. Place the positive and negative electrode sheets, separators, and mechanical components in a 100°C oven for at least 24 hours until completely dried. Weigh the dried positive and negative electrode sheets, separators, and mechanical components, and record the mass as M1. The mass of the electrolyte in the battery cell is thus calculated as (M0 - M1). The filling coefficient is calculated as (M0-M1) / rated capacity of the battery cell. The rated capacity is the nominal capacity of the battery, or the discharge capacity of the battery cell after charging to 3.65V at a charge rate of 0.33C, then charging to 0.05C at a constant voltage of 3.65V, letting it rest for 10 minutes, and then discharging to 2.0V at a discharge rate of 0.33C.

[0381] In some embodiments, the battery cell filling coefficient may be 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 g / Ah, or any range therebetween.

[0382] The filling coefficient within the above range can take into account both the cycle stability and energy density of the battery cell.

[0383] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0384] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0385] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 12 The battery cell 1 is a square structure as an example.

[0386] In some embodiments, reference Figure 12, the outer packaging may include a shell 11 and a cover assembly. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover assembly can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly through a winding process or a lamination process. The electrode assembly is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly. The number of electrode assemblies contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0387] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0388] Optionally, the battery module may further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0389] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0390] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device comprises at least one of a battery module, a battery pack, and an energy storage battery.

[0391] In addition, the third aspect of the present application further provides an electrical device, comprising the battery cell provided in the first aspect of the present application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0392] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0393] Figure 13 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cells in this device, a battery pack or battery module can be used.

[0394] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0395] An embodiment of the present application also provides an energy storage device that uses a battery as a power source. The energy storage device may be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0396] Example

[0397] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0398] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0399] Example 1

[0400] (1) Preparation of negative electrode sheet

[0401] The negative electrode sheet includes a negative electrode current collector, a negative electrode conductive layer on the negative electrode current collector, and a negative electrode active material layer. The negative electrode current collector is a copper foil with a thickness of 5 μm.

[0402] The negative electrode conductive layer on the negative electrode current collector is an active material layer formed by uniformly mixing superconducting carbon as a negative electrode conductive agent, styrene-butadiene rubber (SBR) as a negative electrode binder, sodium carboxymethyl cellulose (CMC-Na) as a thickener, and solvent water, and then coating and drying on the surface of the negative electrode current collector. The thickness is 1 μm, and the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0403] The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer is located on the surface of the negative electrode conductive layer, and the second negative electrode active material layer is located on the surface of the first negative electrode active material layer;

[0404] The first negative electrode active material layer includes composite graphite particles, silicon-carbon material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 93:3.5:0.5:2:1. The silicon content in the silicon-carbon material is 48%, the volume average particle size Dv50 of the silicon-carbon material is 8.8 μm, and the specific surface area of ​​the silicon-carbon material is 3.4 m 2 / g, the powder compaction density of silicon carbon material under 25000N is 0.92 g / cm 3 , the Dv50 of composite graphite particles is 11.3 μm;

[0405] The second negative electrode active material layer includes composite graphite particles, silicon-carbon material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 94:3.5:0.5:1:1. The silicon content in the silicon-carbon material is 48%, the volume average particle size Dv50 of the silicon-carbon material is 8.8 μm, and the specific surface area of ​​the silicon-carbon material is 3.4 m 2 / g, the powder compaction density of silicon carbon material under 25000N is 0.92 g / cm 3 The Dv50 of the composite graphite particles is 11.3 μm; the composite graphite particles include graphite body particles and a carbon coating layer coated on at least a portion 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 proportion of amorphous carbon is 3.5%.

[0406] The first negative electrode slurry is evenly coated on the negative electrode conductive layer of the negative electrode current collector copper foil and dried; the second negative electrode slurry is coated on the surface of the dried first negative electrode slurry, dried, and cold pressed to obtain a negative electrode sheet. The thickness ratio of the first active material layer to the second active material layer is 1:1; the mass proportion of silicon element is 1.68% based on the total mass of the negative electrode active material layer; the single-side coating weight of the negative electrode active material layer is 111mg / 1540.25mm 2 .

[0407] (2) Preparation of positive electrode

[0408] The positive electrode sheet includes a positive electrode current collector, a positive electrode conductive layer on the positive electrode current collector, and a positive electrode active material layer. The positive electrode current collector is an aluminum foil with a thickness of 12 μm.

[0409] The positive electrode conductive layer on the positive electrode current collector is an active material layer formed by evenly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride (PVDF) and the solvent N-methylpyrrolidone NMP, and then coating it on the current collector surface and drying it. The thickness is 1μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0410] The positive electrode active material, the binder polyvinylidene fluoride, and the conductive agent acetylene black are mixed in a ratio of 97:2:1, and then the solvent N-methylpyrrolidone (NMP) is added and stirred to form a positive electrode slurry, wherein the positive electrode active material includes lithium iron phosphate, and the lithium iron phosphate has a coating layer, which is coated on the surface of the lithium iron phosphate particles. The coating layer includes lithium iron titanium phosphate Li2FeTi(PO4)3 and carbon element, and the mass content of the carbon element is 1.12%. The powder compaction density of the lithium iron phosphate material under 30000N is 2.65g / cm 3 .

[0411] The positive electrode conductive slurry is evenly coated on the positive electrode current collector aluminum foil, and dried to obtain the positive electrode conductive layer; the positive electrode slurry is then evenly coated on the positive electrode conductive layer, dried, and cold pressed to obtain the positive electrode sheet. The single-sided coating weight of the positive electrode active material layer is 270 mg / 1540.25 mm 2 .

[0412] (3) Preparation of electrolyte

[0413] The electrolyte solution includes a solvent, a lithium-containing electrolyte salt, and additives.

[0414] The solvent includes 22% by weight of ethyl acetate and 19.7% by weight of methyl acetate (a first solvent), 27.3% by weight of ethylene carbonate, and 6.7% by weight of dimethyl carbonate (a second solvent), and the weight ratio of each component in the solvent is calculated based on the total weight of the electrolyte;

[0415] Based on the total mass of the electrolyte, the total mass content of the additive is 9.3%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, vinyl sulfite ES and lithium difluorooxalatoborate LiDFOB in a mass ratio of 4:2.5:2:0.8;

[0416] Based on the total mass of the electrolyte, the lithium-containing electrolyte salt includes 5% by mass of lithium bis(fluorosulfonyl)imide LiFSI and 10% by mass of lithium hexafluorophosphate LiPF6; the viscosity of the electrolyte at room temperature is 2.58 mPa·s.

[0417] (4) Preparation of isolation membrane

[0418] The isolation film includes a base film and a functional layer. The base film is a 5μm polyethylene film layer, and the porosity of the isolation film is 42%;

[0419] The functional layer includes a first functional layer and a second functional layer. The first functional layer is a film layer formed by coating aluminum oxide particles and binder polyvinylidene fluoride on one side of the base film, with a thickness of 1 μm and an average particle size of the aluminum oxide particles of 10 nm; the second functional layer is a film layer formed by coating composite particles formed by 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 the calcium oxide particles of 10 nm.

[0420] (5) Preparation of battery cells

[0421] The above-mentioned positive electrode sheets, separators, and negative electrode sheets are stacked in order, so that the separator is placed between the positive electrode sheets and the negative electrode sheets to play an isolating role. The tabs are set at both ends of the current collecting part 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 collecting part is 1 / 3 to obtain a laminated electrode assembly. The electrode assembly is placed in a shell, and after drying, the electrolyte is injected with an injection coefficient of 2.45g / Ah. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained. Among them, the size of the positive electrode active material layer along the length direction of the electrode assembly is 630mm, and OH1 is 4mm; the size of the positive electrode material layer along the width direction of the electrode assembly is 95mm, and OH2 is 3mm. The shell is an aluminum shell, and the shell wall thickness of the large surface of the battery cell is 0.35mm. The energy density of the battery cell is 460Wh / L, and the compaction density of the negative electrode active material layer is 1.26g / cm 3 The compaction density of the positive electrode active material layer is 2.75g / cm 3 .

[0422] Example 2-3

[0423] The preparation method of Example 2-3 is basically the same as that of Example 1, except that the mass ratio of silicon element in the first negative electrode active material layer and the second negative electrode active material layer is adjusted, the mass of the composite graphite particles is changed accordingly, and the single-sided coating quality of the positive electrode active material layer is adjusted accordingly, as shown in Tables 1 and 2.

[0424] Examples 4-5

[0425] The preparation method of Example 4-5 is basically the same as that of Example 1, except that the coating mass on one side of the negative electrode active material layer is adjusted, and the coating mass on one side of the positive electrode active material layer is adjusted accordingly, as shown in Tables 1 and 2.

[0426] Examples 6-9

[0427] The preparation methods of Examples 6-9 are basically the same as those of Example 1, except that the mass ratios of the first solvent and the second solvent are adjusted, and the viscosity of the electrolyte changes accordingly, as shown in Tables 1 and 2.

[0428] Example 10

[0429] The preparation method of Example 10 is basically the same as that of Example 1, except that the type of lithium electrolyte salt in the electrolyte is adjusted, and the viscosity of the electrolyte changes accordingly, as shown in Tables 1 and 2.

[0430] Examples 11-14

[0431] The preparation methods of Examples 11-14 are basically the same as those of Example 1, except that the mass ratio of the lithium electrolyte salt in the electrolyte and the amount of additives added are adjusted, the amount of solvent is adjusted accordingly, and the viscosity of the electrolyte changes accordingly, as shown in Tables 1 and 2.

[0432] Comparative Examples 1-6

[0433] The preparation methods of Comparative Examples 1-6 are basically the same as those of Example 1, except that some parameters in the battery cells are adjusted, as shown in Tables 1 and 2.

[0434] Test Method

[0435] 1. Fast charging performance

[0436] At 30°C, the battery cells were cycled 200 times according to the following charge and discharge strategies, and then fully charged to 100% SOC according to the corresponding charging strategy. The negative electrode sheet was disassembled and unfolded to observe the lithium deposition area (gray-white area) and measure the lithium deposition area. The degree of lithium deposition is as follows:

[0437] No lithium plating: The percentage of lithium plating area to the negative electrode active material layer area is less than 0.05%.

[0438] Slight lithium deposition: The percentage of lithium deposition area to the negative electrode active material layer area is less than 2%.

[0439] Severe lithium plating: The percentage of lithium plating area to the negative electrode active material layer area is ≥2%.

[0440] The battery cells are charged, and the charging steps include the following steps:

[0441] Charge from 0% SOC to 40% SOC at 5.0C constant current; charge from 40% SOC to 45% SOC at 4.6C constant current; charge from 45% SOC to 50% SOC at 4.3C constant current; charge from 50% SOC to 55% SOC at 4.0C constant current; charge from 55% SOC to 60% SOC at 3.7C constant current; charge from 60% SOC to 65% SOC at 3.4C constant current; charge from 65% SOC to 70% SOC at 3.1C constant current; and Charge from 70% SOC to 75% SOC at 2.9C constant current; charge from 75% SOC to 80% SOC at 2.7C constant current; charge from 80% SOC to 85% SOC at 1.8C constant current; charge from 85% SOC to 90% SOC at 1.3C constant current; charge from 90% SOC to 95% SOC at 0.7C constant current; charge from 95% SOC to 98% SOC at 0.33C constant current; charge from 98% SOC to 100% SOC at 0.1C constant current.

[0442] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0443] The discharge strategy is as follows: discharge at a constant current of 0.33C to a cut-off voltage, for example, 2.0V.

[0444] When performing charge and discharge tests on battery cells, the battery cells can be assembled in a battery device, and the required charge and discharge strategies can be controlled by the battery management system for testing.

[0445] 2. Volumetric energy density

[0446] Place the battery cell at 25°C, charge it to 3.65V at a constant current of 0.33C, then charge it to 0.05C at a constant voltage, and let it rest for 30 minutes; discharge it to 2.0V at a constant current of 0.33C, and record the discharge capacity A0 at this time, in Ah; use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the battery casing size, excluding the electrode terminal height and the insulating film outside the casing), and calculate the volume of the single cell V0, in L; the battery cell volume energy density VED = (A0 × discharge platform voltage) / V0, in Wh / L.

[0447] 3. Cycle performance

[0448] At 60°C, charge the battery cell at a constant current of 0.8C to a charge cut-off voltage of 3.6V, then charge at a constant current of 0.1C to a charge cut-off voltage of 3.65V, and let it rest for 30 minutes; discharge at a constant current of 1C to 3.1V, and let it rest for 30 minutes. This is one charge and discharge cycle. Repeat the above charge and discharge cycle steps until the cycle capacity retention rate (i.e., C n / C0×100%) is 80%, and the number of cycles is recorded. The more cycles, the better the cycling performance of the battery cell.

[0449] Test results

[0450] Table 1

[0451]

[0452] Table 2

[0453]

[0454] According to the comparison between the embodiment of the present application and the comparative example, the single-side coating mass of the negative electrode active material layer in the battery cell is 80 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 0.5% to 5%, and the viscosity of the electrolyte at room temperature is 2.3mPa·s to 3.5mPa·s, which can take into account the improvement of the energy density, fast charging performance and cycle stability of the battery cell, and achieve a comprehensive improvement in battery performance.

[0455] From the comparison between Examples 1 and 3 and Example 2, it can be seen that based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 1.6% to 5%. While the battery cell has excellent fast charging performance and cycle stability, the energy density is further improved.

[0456] From Examples 1, 5 and 4, it can be seen that the coating mass of the negative electrode active material layer on one side is 110 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 While the battery cells have excellent fast charging performance and cycle stability, the energy density is further improved.

[0457] As can be seen from the embodiment, the electrolyte includes the 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.

[0458] It can be seen from Examples 1 and 6-9 that, based on the total mass of the electrolyte, the mass proportion of the first solvent is 8%-60%, and the mass proportion of the second solvent is 18% to 75%, and the battery cell has excellent energy density, fast charging performance and cycle stability.

[0459] From the comparison between Examples 1, 8, and 9 and Example 7, it can be seen that the mass of the first solvent accounts for 30% to 60% based on the total mass of the electrolyte. The battery cell has excellent energy density and cycle stability, and the fast charging performance is further improved.

[0460] From the comparison between Examples 1 and 10, it can be seen that the lithium-containing electrolyte salt includes LiFSI, which is beneficial to further reduce the viscosity of the electrolyte, and the fast charging performance and cycle stability of the battery cell are further improved.

[0461] It can be seen from Examples 1, 11, and 12 that the mass proportion of lithium electrolyte salt in the electrolyte is 10% to 18%, and the battery cell has excellent energy density, fast charging performance, and cycle stability.

[0462] It can be seen from Examples 1, 11, and 12 that, based on the total mass of the electrolyte, the mass proportion of the carbonate additive added is 3% to 8%, and the battery cell has excellent energy density, fast charging performance, and cycle stability.

[0463] It can be seen from Examples 1 and 13 that, based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0.5% to 2%, and the mass proportion of the lithium salt additive is 0.2%-1%. The battery cell has excellent energy density, fast charging performance and cycle stability.

[0464] From the comparison between Example 14 and Example 1, it can be seen that the electrolyte includes fluorobenzene additives, which is beneficial to further improve the cycle stability and fast charging performance of the battery cell.

[0465] It should be noted that the present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present disclosure, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present disclosure. In addition, within the scope of the present disclosure, various modifications that can be imagined by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements of the embodiments are also included in the scope of the present disclosure.

Claims

1. A battery cell, characterized in that: The invention comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing phosphate with an olivine structure; The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector. The single-side coating mass of the negative electrode active material layer is 80 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 , The negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a silicon-based material, and the mass proportion of silicon element is 0.5% to 5% based on the total mass of the negative electrode active material layer; The viscosity of the electrolyte at room temperature is greater than or equal to 2.5 mPa·s and less than 2.9 mPa·s, and the room temperature refers to 22°C~28°C; the electrolyte includes a first solvent, the first solvent includes a carboxylate solvent, and the mass proportion of the first solvent based on the total mass of the electrolyte is 30% to 60%; the electrolyte also includes an additive, the additive includes a carbonate additive, and the mass proportion of the carbonate additive based on the total mass of the electrolyte is 4% to 8%.

2. The battery cell according to claim 1, wherein: The single-sided coating mass of the negative electrode active material layer is 110 mg / 1540.25 mm 2 Up to 150 mg / 1540.25 mm 2 .

3. The battery cell according to claim 1, wherein: Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 1.6% to 5%.

4. The battery cell according to claim 1, wherein: The silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and silicon alloy.

5. The battery cell according to claim 4, characterized in that The silicon-based material includes a silicon-carbon material.

6. The battery cell according to claim 4, characterized in that The silicon-carbon material satisfies at least one of the following conditions: (1) Based on the total mass of the silicon-carbon material, the mass proportion of silicon element in the silicon-carbon material is 40% to 80%; (2) The volume average particle size Dv50 of the silicon-carbon material is 5.0 μm to 12.5 μm; (3) The specific surface area of ​​the silicon-carbon material is 3.1 m 2 / g to 3.6m 2 / g; (4) The powder compaction density of the silicon-carbon material under 25000N is 0.7g / cm 3 to 1.2g / cm 3 .

7. The battery cell according to claim 1, characterized in that The negative electrode active material also includes a carbon-based material.

8. The battery cell according to claim 7, characterized in that The carbon-based material includes one or more of graphite and hard carbon.

9. The battery cell according to claim 7, characterized in that: The carbon-based material includes graphite.

10. The battery cell according to claim 7, characterized in that The carbon-based material includes composite graphite particles, which include graphite particles and a carbon coating layer coated on at least a portion of the surface of the graphite particles. The graphite particles include secondary particles, and the carbon coating layer includes amorphous carbon.

11. The battery cell according to claim 10, characterized in that Based on the total mass of the composite graphite particles, the mass proportion of the amorphous carbon is 2% to 5%.

12. The battery cell according to claim 10 or 11, characterized in that: The volume average particle size Dv50 of the composite graphite particles is 8.5 μm to 16.5 μm.

13. The battery cell according to claim 1, characterized in that The compaction density of the negative electrode active material layer is 1.10 g / cm 3 Up to 1.50g / cm 3 .

14. The battery cell according to claim 1, characterized in that The negative electrode active material layer has a dimension of 200 mm to 650 mm along the length direction of the electrode assembly.

15. The battery cell according to claim 1, characterized in that The viscosity η of the first solvent at room temperature is 0.3 mPa·s to 0.6 mPa·s.

16. The battery cell according to claim 1, characterized in that The carboxylate solvent has a general structural formula of R'-COO-R'', wherein R' includes one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R'' includes one or more of a C1-C5 alkyl group and a C1-C5 haloalkyl group.

17. The battery cell according to claim 1, characterized in that The carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

18. The battery cell according to claim 1, characterized in that The electrolyte further includes a second solvent, which includes a carbonate solvent. The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

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

20. The battery cell according to claim 1, characterized in that The electrolyte solution includes a lithium-containing electrolyte salt, and the lithium-containing electrolyte salt accounts for 10% to 18% by mass of the electrolyte solution based on the total mass of the electrolyte solution.

21. The battery cell according to claim 20, characterized in that The lithium-containing electrolyte salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6).

22. The battery cell according to claim 21, characterized in that Based on the total mass of the electrolyte, the mass proportion of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is 4% to 8%.

23. The battery cell according to claim 1, characterized in that The additives include one or more of sulfur-containing additives, lithium salt additives and fluorobenzene additives.

24. The battery cell according to claim 23, characterized in that The carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Wherein, the ethylene carbonate derivative includes the compound shown in formula I, Formula I R1, R2, R3, and R4 each independently include one or more of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time; 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 additive includes one or more of fluorobenzene and its derivatives.

25. The battery cell according to claim 1, characterized in that The carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate.

26. The battery cell according to claim 1, characterized in that The carbonate additive includes vinylene carbonate; based on the total mass of the electrolyte, the mass proportion of the vinylene carbonate is 2% to 5%.

27. The battery cell according to claim 1, characterized in that The carbonate additive includes an ethylene carbonate derivative; based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 0% to 4%.

28. The battery cell according to claim 1, characterized in that The carbonate additive includes an ethylene carbonate derivative; based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate derivative is 1.5% to 3.5%.

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

30. The battery cell according to claim 23, characterized in that Based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0.5% to 2%.

31. The battery cell according to claim 23, characterized in that Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0% to 1%.

32. The battery cell according to claim 23, characterized in that Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.2% to 1%.

33. The battery cell according to claim 23, characterized in that Based on the total mass of the electrolyte, the mass proportion of the fluorobenzene additive is 0.1% to 1%.

34. The battery cell according to claim 1, characterized in that Along the length direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH1; Along the width direction of the electrode assembly, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH2, Wherein, the OH1 is 1.0 mm to 4.0 mm; and / or, The OH2 is 1.0 mm to 3.0 mm.

35. The battery cell according to claim 34, characterized in that The OH1 is greater than or equal to the OH2.

36. The battery cell according to claim 1, characterized in that The positive electrode collector includes a positive electrode current collecting portion and a positive electrode tab, and the positive electrode tab is arranged at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly or at least one side extending along the width direction of the electrode assembly; and / or, the negative electrode collector includes a negative electrode current collecting portion and a negative electrode tab, and the negative electrode tab is arranged at at least one end of the negative 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.

37. The battery cell according to claim 36, characterized in that The dimension of the negative electrode active material layer along the length direction of the electrode assembly is greater than 500 mm, and the negative electrode tabs are arranged at both ends of the negative 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.

38. The battery cell according to claim 36, characterized in that The positive electrode tab is arranged at at least one end of the positive electrode current collecting portion extending along the length direction of the electrode assembly, and the ratio of the width of the positive electrode tab to the width of the positive electrode current collecting portion is 0.25 to 1; and / or, the ratio of the width of the negative electrode tab to the width of the negative electrode current collecting portion is 0.25 to 1.

39. The battery cell according to claim 36, characterized in that 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.

40. The battery cell according to claim 1, wherein The positive electrode active material includes: Lithium-containing phosphates with an olivine structure, and A coating layer is located on at least a portion of the surface of the lithium-containing phosphate, and the coating layer contains carbon.

41. The battery cell according to claim 40, characterized in that Based on the total mass of the positive electrode active material, the mass proportion of carbon element is 0.8% to 2.3%.

42. The battery cell according to claim 40, characterized in that The coating layer further comprises a component as shown in Formula II, Li 3-d1 Fe 2-d1 M1 d1 (PO m1 ) n1 Formula II Among them, 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M1 includes one or more of Ti, Zr, Hf, Ge, and Sn.

43. The battery cell according to claim 42, characterized in that M1 has a valence of +4.

44. The battery cell according to claim 40, characterized in that The lithium-containing phosphate includes a component as shown in Formula III, Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula III Among them, 0.5≤x1≤1.3, 0≤y1≤1.3, 0.9≤x1+y1≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z1≤5; A includes one or more of Na, K and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, N, and P; and Y includes one or more of O and F.

45. The battery cell according to claim 1, characterized in that The positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate and modified forms thereof, wherein the modified form includes one or more of doping modification and coating modification.

46. ​​The battery cell according to claim 1, characterized in that The powder compaction density of the positive electrode active material at 30000N is 2.45g / cm 3 Up to 2.75g / cm 3 .

47. The battery cell according to claim 1, characterized in that The compaction density of the positive electrode active material layer is 2.5 g / cm 3 to 2.83g / cm 3 .

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

49. The battery cell according to claim 1, characterized in that The thickness of the positive electrode current collector is 10 μm to 15 μm.

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

51. The battery cell according to claim 50, characterized in that The negative electrode conductive layer includes a conductive agent, the positive electrode conductive layer includes a conductive agent and a positive electrode binder, the conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene 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.

52. The battery cell according to claim 1, characterized in that The isolation film has a porosity of 20% to 70%.

53. The battery cell according to claim 52, characterized in that The porosity of the isolation film is 35% to 60%.

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

55. The battery cell according to claim 54, characterized in that The non-fluorine polymer includes an acrylic copolymer.

56. The battery cell according to claim 54, characterized in that The first inorganic substance and the second inorganic substance 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.

57. The battery cell according to claim 54, characterized in that The base film has a thickness of 4 μm to 12 μm.

58. The battery cell according to claim 54, characterized in that The base film has a thickness of 5 μm to 9 μm.

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

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

61. The battery cell according to claim 59, characterized in that The cover plate assembly includes a first cover plate assembly and a second cover plate assembly, the first cover plate assembly and the second cover plate assembly are arranged at both ends of the shell in the length direction or the width direction, the first cover plate assembly includes a first cover plate and a first electrode terminal, the second cover plate assembly includes a second cover plate and a second electrode terminal, and the polarities of the first electrode terminal and the second electrode terminal are opposite.

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

63. The battery cell according to claim 1, characterized in that The volume energy density of the battery cell is greater than 440Wh / L and less than or equal to 530Wh / L.

64. The battery cell according to claim 63, characterized in that The volume energy density of the battery cell is 450Wh / L to 510Wh / L.

65. The battery cell according to claim 1, characterized in that The battery cell has a liquid injection coefficient of 2.2 g / Ah to 3.0 g / Ah.

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

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 The battery device of claim 66 is used to store electrical energy.

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