Battery cell, battery device and electrical device

Abstract

The present application relates to a battery cell, a battery device and an electrical device. The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate and a negative electrode plate. The positive electrode film layer of the positive electrode plate includes a lithium-containing phosphate. The negative electrode film layer of the negative electrode plate includes a carbon-based material and a silicon-based material. The electrolyte includes ethylene carbonate and a cyclic carbonate additive. The cyclic carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Among them, the mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.5% to 5%. The mass content of ethylene carbonate in the electrolyte is 20% to 40%. The mass content of the cyclic carbonate additive in the electrolyte is 2% to 8%. The present application can improve the cycle performance of the battery cell.

Description

[0001] This application claims the priority of International Patent Application PCT / CN2025 / 082771 titled "Battery Cell, Battery Device and Electrical Device" filed on March 14, 2025, the entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to a battery cell, a battery device and an electrical device. Background Art

[0003] Battery cells have characteristics such as high capacity and long life, and thus are widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, and electric tools, etc. With the development of the application fields of lithium-ion batteries, higher requirements are put forward for the performance of battery cells, such as the cycling performance of battery cells at high energy density. Summary of the Invention

[0004] This application provides a battery cell, a battery device and an electrical device, which can improve the cycling performance of the battery cell at high energy density.

[0005] In a first aspect, this application proposes a battery cell. The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab includes a positive current collector and a positive electrode film layer provided on at least one side of the positive current collector. The positive electrode film layer includes a lithium-containing phosphate. The negative electrode tab includes a negative current collector and a negative electrode film layer provided on at least one side of the negative current collector. The negative electrode film layer includes a carbon-based material and a silicon-based material. The electrolyte includes ethylene carbonate and a cyclic carbonate additive. The cyclic carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. Among them, the mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.5% to 5%; the mass content of ethylene carbonate in the electrolyte is 20% to 40%; the mass content of the cyclic carbonate additive in the electrolyte is 2% to 8%.

[0006] Thus, in the embodiments of the present application, regulating the mass content of silicon elements can improve the energy density of a battery cell; by regulating the components of the electrolyte, the cycle performance of the battery cell can be improved. Specifically, the electrolyte includes ethylene carbonate and cyclic carbonate additives. A part of the ethylene carbonate can act synergistically with the cyclic carbonate additives to participate in the formation of a solid electrolyte interface (SEI) film on the negative electrode side, optimizing the mechanical properties and protective properties of the SEI film, effectively alleviating the volume expansion on the negative electrode side, and effectively alleviating the side reactions on the negative electrode side, thus improving the cycle performance of the battery cell; another part of the ethylene carbonate can be used as a solvent, which can improve the stability of the electrolyte; moreover, ethylene carbonate has a high dielectric constant and strong ability to dissociate ions, which is beneficial to lithium ion transport. At a certain current density, lithium ions can quickly embed into the negative electrode film layer and combine with electrons, reducing the risk of lithium deposition on the surface of the negative electrode film layer and improving the cycle performance of the battery cell; by further regulating the mass content of ethylene carbonate and the mass content of cyclic carbonate additives, it is beneficial to uniformly infiltrate the negative electrode sheet, reduce the risk of lithium deposition on the surface of the negative electrode film layer, and the film-forming impedance of the SEI film will not be too high, which is beneficial to the fast charging of the battery cell, and can further reduce the risk of lithium deposition on the surface of the negative electrode film layer and improve the cycle performance of the battery cell.

[0007] In some embodiments, the mass content of ethylene carbonate in the electrolyte is 20% to 35%. When the mass content of ethylene carbonate is within the above range, it is beneficial to further improve the cycle performance of the battery cell.

[0008] In some embodiments, the mass content of vinylene carbonate in the electrolyte is 1.5% to 5%. When the mass content of vinylene carbonate is within the above range, a dense SEI film containing organic components can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reactions on the negative electrode side and take into account the improvement of the cycle performance of the battery cell at high energy density.

[0009] In some embodiments, the mass content of ethylene carbonate derivatives in the electrolyte is 0 to 4%, and can be optionally 1.5% to 3.5%. The ethylene carbonate derivatives and ethylene carbonate act together, and the ethylene carbonate derivatives can further optimize the components of the SEI film, reduce the impedance of the SEI film, and effectively improve the cycle performance of the battery cell at high energy density.

[0010] In some embodiments, the ethylene carbonate derivatives include the compound shown in Formula A,

[0011] Formula A,

[0012] In Formula A, Q1, Q2, Q3, and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and at least one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0013] The above ethylene carbonate derivative can more effectively improve the cycling performance of a battery cell at high energy density.

[0014] In some embodiments, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom or a C1-C5 haloalkyl group. The ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side, which can make the impedance of the film layer low while protecting the negative electrode active material, and can more effectively improve the cycling performance of the battery cell at high energy density.

[0015] In some embodiments, the ethylene carbonate derivative includes one or more of the compounds represented by Formula A-1 to the compounds represented by Formula A-3.

[0016] 。

[0017] The above materials can further improve the cycling performance of the battery cell at high energy density.

[0018] In some embodiments, the electrolyte further includes a linear ester solvent. The linear ester solvent includes one or more of a linear carboxylic acid ester solvent and a linear carbonate solvent. The mass content of the linear ester solvent in the electrolyte is 45% to 65%. The linear ester solvent with the above mass content is beneficial to improving the cycling performance and fast charging performance of the battery cell.

[0019] In some embodiments, the linear carboxylic acid ester solvent includes a compound represented by Formula I.

[0020] Formula I

[0021] In Formula I,

[0022] R1 includes a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0023] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0024] The above linear carboxylic acid ester solvent has a low viscosity, improves the fast charging ability of the battery cell at high energy density, reduces the risk of lithium plating during fast charging, and improves the cycling performance of the battery cell.

[0025] In some embodiments, the linear carboxylic ester solvent includes one or more of the compounds represented by Formula I-1 to the compounds represented by Formula I-12.

[0026]

[0027] The above materials can further improve the cycling performance of the battery cell at high energy density.

[0028] In some embodiments, the linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The above materials can further improve the cycling performance of the battery cell at high energy density.

[0029] In some embodiments, the linear ester solvent includes a linear carbonate solvent, and the mass content of the cyclic carbonate additive is 2% to 5%. The above electrolyte system is beneficial to further improve the cycling performance of the battery cell.

[0030] In some embodiments, the linear ester solvent includes a linear carboxylic ester solvent with a mass content > 0 and a linear carbonate solvent with a mass content ≥ 0, and the mass content of the cyclic carbonate additive is 3.5% to 8%. The above electrolyte system is beneficial to further improve the cycling performance of the battery cell.

[0031] In some embodiments, the electrolyte includes an electrolyte lithium salt, and the mass content of the electrolyte lithium salt in the electrolyte is 10% to 18%. The electrolyte lithium salt with the above mass content can improve the cycling performance of the battery cell.

[0032] In some embodiments, the electrolyte lithium salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6). The above electrolyte lithium salt can improve the cycling performance of the battery cell.

[0033] In some embodiments, the mass content of lithium bis(fluorosulfonyl)imide (LiFSI) in the electrolyte is 4% to 6%. When the mass content of lithium bis(fluorosulfonyl)imide is within the above range, the mass content of lithium hexafluorophosphate can be reduced, resulting in a decrease in the acid content and side reactions in the electrolyte, and improving the cycling performance of the battery cell.

[0034] In some embodiments, the electrolyte further includes a sulfur-containing additive with a mass content of 0 to 2% in the electrolyte, optionally 0.5% to 2%; the sulfur-containing additive includes one or more of vinylene sulfate, bis(vinylsulfonyl)ethylene, 1,3-propane sultone, butene sulfite, ethylene sulfite, and methylene methanedisulfonate; the sulfur-containing additive and the cyclic carbonate additive cooperate to form a film, which can optimize the film layer components of the SEI film and improve the high-temperature cycling performance of the battery cell at high energy density.

[0035] In some embodiments, the electrolyte further includes a lithium salt additive with a mass content of 0 to 1% in the electrolyte, optionally 0.2% to 1%; the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. The lithium salt additive and the cyclic carbonate additive cooperate to form a film, which can optimize the film layer components of the SEI film and improve the cycling performance of the battery monomer at high energy density.

[0036] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.8% to 3%. When the mass content of silicon element is within the above range, the energy density and cycling performance of the battery monomer can be improved.

[0037] In some embodiments, the silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material; optionally, the silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material. Optionally, the silicon-based material includes silicon-carbon material. The specific capacity of the above materials is relatively high, which is beneficial to improving the energy density of the battery monomer.

[0038] In some embodiments, based on the mass of the silicon-based material, the mass content of silicon element is 40% to 80%; when the silicon-based material meets the above conditions, the energy density and cycling performance of the battery monomer can be further improved.

[0039] In some embodiments, the volume average particle size Dv50 of the silicon-based material is 5.0 μm to 12.5 μm; when the silicon-based material meets the above conditions, the energy density and cycling performance of the battery monomer can be further improved.

[0040] In some embodiments, the specific surface area of the silicon-based material is 3.1 m 2 / g to 3.6 m 2 / g; when the silicon-based material meets the above conditions, the energy density and cycling performance of the battery monomer can be further improved.

[0041] In some embodiments, the powder compaction density of the silicon-based material under 25000N is 0.7 g / cm 3 to 1.2 g / cm 3 . When the silicon-based material meets the above conditions, the energy density and cycling performance of the battery monomer can be further improved.

[0042] In some embodiments, the carbon-based material includes graphite particles, the graphite particles include graphite body particles and a negative electrode coating layer coated on the surface of the graphite body particles, the graphite body particles include secondary particles, and the negative electrode coating layer includes carbon element. The conductivity of the negative electrode coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode sheet, reduce the heat generation of the battery monomer, and improve the cycling performance of the battery monomer at high energy density.

[0043] In some embodiments, the graphite bulk particles include one or more of artificial graphite and natural graphite.

[0044] In some embodiments, the carbon content of the negative electrode coating is 2% to 5% by mass, based on the mass of the graphite particles. When the carbon content of the negative electrode coating is within this range, the internal resistance of the negative electrode sheet can be further reduced, the heat generation of the battery cell can be reduced, and the cycling performance of the battery cell at high energy density can be improved.

[0045] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is disposed on the surface of the negative electrode current collector, and the second negative electrode film layer is disposed on the side of the first negative electrode film layer facing away from the negative electrode current collector. The volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer, wherein at least one of the first negative electrode film layer and the second negative electrode film layer includes a silicon-based material. In the embodiments of the present application, the particle size of the carbon-based material in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve fast charging performance, and can improve the problem of lithium plating on the surface of the negative electrode sheet, thereby improving cycle performance.

[0046] In some embodiments, the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer is 8.5 μm to 14.5 μm; when the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and enable lithium ions to quickly gain electrons on the negative electrode side, reduce the risk of lithium plating, and improve the cycle performance.

[0047] In some embodiments, the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is 9.8 μm to 16.8 μm. When the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is within this range, the solid-phase transport path of lithium ions can be shortened, thereby improving fast charging performance. Furthermore, the material is less likely to agglomerate during the preparation process, thereby improving the stability of the material and the cycle performance.

[0048] In some embodiments, the silicon-based material is located in the first negative electrode film layer. The second negative electrode film layer can effectively alleviate the volume expansion of the silicon-based material in the first negative electrode film layer, thereby improving the cycle performance of the battery cell.

[0049] In some embodiments, the negative electrode layer has a compaction density of 1.10 g / cm2 at 100% state of charge. 3 Up to 1.50g / cm 3 When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density and cycle performance of the battery cell.

[0050] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 . When the single-sided coating weight of the negative electrode film layer is within the above range, it is beneficial to improve the energy density and cycling performance of the battery cell.

[0051] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm. When the thickness of the negative electrode current collector is within the above range, the thickness of the negative electrode current collector is relatively thin, which is beneficial to improve the volumetric energy density of the battery cell.

[0052] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, the negative electrode conductive layer is located between the negative electrode current collector and the negative electrode film layer, the negative electrode conductive layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The negative electrode conductive layer can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, thereby reducing the heat generation of the battery cell, and improving the fast charging performance and high-temperature cycling performance of the battery cell.

[0053] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. When the thickness of the negative electrode conductive layer is within the above range, it can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, thereby reducing the heat generation of the battery cell, and can also take into account improving the energy density of the battery cell.

[0054] In some embodiments, the lithium-containing phosphate includes phosphate particles and a positive electrode coating layer, the positive electrode coating layer is located on at least part of the surface of the phosphate particles, and the positive electrode coating layer contains carbon elements. By surface coating the phosphate particles with the positive electrode coating layer, the conductivity of the lithium-containing phosphate can be improved, which is beneficial to the migration rate of lithium ions, improves the fast charging ability of the battery, and reduces the heat generation of the battery cell, improving the cycling performance of the battery cell.

[0055] In some embodiments, based on the mass of the lithium-containing phosphate, the mass content of carbon elements is 0.8% to 2.3%. When the mass content of carbon elements is within the above range, the conductivity of the lithium-containing phosphate can be significantly improved, which is beneficial to improving the ionic conductivity and electronic conductivity of the lithium-containing phosphate, and can improve the fast charging ability of the battery cell at high energy density.

[0056] In some embodiments, the positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn. The above positive electrode coating layer can improve the ionic conductivity of the positive electrode active material, improve the fast charging ability of the battery cell, and in addition, can also improve the specific capacity and the energy density of the corresponding battery cell.

[0057] In some embodiments, the phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. The cycle stability of the above materials is relatively excellent, and can improve the cycle performance of the battery cell.

[0058] In some embodiments, the lithium-containing phosphate includes a material with the general formula Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ 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, Hf, Ge, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F. The cycle stability of the above materials is relatively excellent, and can improve the cycle performance of the battery cell.

[0059] In some embodiments, the powder compaction density of the positive electrode active material under 30,000 N is 2.46 g / cm 3 to 2.85 g / cm 3 . When the powder compaction density of the positive electrode active material under 30,000 N is within the above range, the energy density and cycle performance of the battery cell can be improved.

[0060] In some embodiments, when the battery cell is in a 100% SOC charged state, the compaction density of the positive electrode film layer is 2.5 g / cm 3 to 2.8 g / cm 3 . When the compaction density of the positive electrode film layer is within the above range, the energy density and cycle performance of the battery cell can be improved.

[0061] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 350 mg / 1540.25 mm 2 . When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode plate will not be too large, and the cycle performance of the battery cell at high energy density can be improved.

[0062] In some embodiments, the thickness of the positive current collector is 10 μm to 15 μm. When the thickness of the positive current collector is within the above range, the thickness of the positive current collector is relatively thin, which is beneficial to improving the volume energy density of the battery cell.

[0063] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer. The positive electrode conductive layer is located between the positive current collector and the positive electrode film layer. The positive electrode conductive layer includes a positive electrode conductive agent, and the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive layer can further improve the electrical conductivity of the positive electrode sheet and reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery cell.

[0064] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. When the thickness of the positive electrode conductive layer is within the above range, it can further improve the electrical conductivity of the positive electrode sheet, reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery cell, and can improve the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0065] In some embodiments, the electrode assembly further includes a separator. The separator is located between the positive electrode sheet and the negative electrode sheet. The thickness of the separator is 5 μm to 12 μm. When the thickness of the separator is within the above range, the migration path of lithium ions in the separator is shorter, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0066] In some embodiments, the porosity of the separator is 20% to 70%. When the porosity of the separator is within the above range, it can improve the migration ability of lithium ions in the separator, can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0067] In some embodiments, the separator further includes a base film and a functional layer provided on the base film. The functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film, and the first functional layer includes first inorganic particles. The second functional layer is located on the other side of the base film, and the second functional layer includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator.

[0068] In some embodiments, the non-fluoropolymer particles include acrylate copolymers. Acrylate copolymers have excellent adhesion properties and relatively high adhesion stability to the base film.

[0069] In some embodiments, the first inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide; the first inorganic particles are beneficial to improving the heat resistance and compression modulus of the separator membrane.

[0070] In some embodiments, the average particle size of the first inorganic particles is 5 nm to 100 nm. When the average particle size of the first inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the separator membrane.

[0071] In some embodiments, the second inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The second inorganic particles can improve the heat resistance of the second functional layer and can form composite particles in cooperation with the non-fluoropolymer, further improving the cycle stability and kinetic performance of the separator membrane and improving the cycle performance and fast charging performance of the battery cell.

[0072] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0073] In some embodiments, the positive electrode tab and the negative electrode tab are stacked along the thickness direction of the battery cell; the electrode assembly further includes a positive electrode ear and a negative electrode ear. The positive electrode ear is connected to at least one side of the positive current collector along the length direction of the battery cell, and the negative electrode ear is connected to at least one side of the negative current collector along the length direction of the battery cell; along the length direction of the battery cell, the size of the negative electrode film layer is larger than that of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH1; along the width direction of the battery cell, the size of the negative electrode film layer is larger than that of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH2, where OH1 is greater than OH2. When the battery cell meets the above conditions, the risk of lithium plating can be reduced, and the use reliability of the battery cell can be improved.

[0074] In some embodiments, OH1 is 1 mm to 4 mm; and / or OH2 is 1 mm to 3 mm. When the battery cell meets the above conditions, the risk of lithium plating can be reduced, and the use reliability of the battery cell can be improved.

[0075] In some embodiments, the positive electrode ear and the negative electrode ear are disposed at the same end along the length direction of the electrode assembly, which is beneficial to improving the energy density of the battery cell.

[0076] In some embodiments, the positive electrode ear and the negative electrode ear are respectively disposed at both ends along the length direction of the electrode assembly, shortening the electron transmission path and improving the fast charging ability of the battery cell.

[0077] In some embodiments, the battery cell includes a housing that houses an electrode assembly and an electrolyte. The housing has a cuboid structure and includes two first side walls that are oppositely arranged and two second side walls that are oppositely arranged. The two first side walls are connected by the second side walls. The cross-sectional area of the first side wall perpendicular to its own thickness direction is larger than the cross-sectional area of the second side wall perpendicular to its own thickness direction. The thickness of the first side wall is from 0.1 mm to 0.5 mm, and optionally from 0.2 mm to 0.35 mm. The first side wall has a relatively high mechanical strength, which can improve the reliability and cycling performance of the battery cell.

[0078] In some embodiments, the volumetric energy density of the battery cell is from 450 Wh / L to 530 Wh / L, so that the battery cell has a relatively high energy density.

[0079] In a second aspect, the present application provides a battery device, which includes a plurality of battery cells according to any one of the embodiments in the first aspect of the present application.

[0080] In a third aspect, the present application provides an electrical device, which includes the battery device according to any one of the embodiments in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the drawings.

[0082] Figure 1 It is a schematic structural diagram of a battery cell provided in some embodiments of the present application.

[0083] Figure 2 It is an exploded schematic diagram of a battery cell provided in some embodiments of the present application.

[0084] Figure 3 It is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0085] Figure 4 It is a schematic structural diagram of a positive electrode plate of a battery cell provided in some embodiments of the present application.

[0086] Figure 5 It is a schematic structural diagram of a positive electrode plate of a battery cell provided in some other embodiments of the present application.

[0087] Figure 6 It is a schematic structural diagram of a negative electrode plate of a battery cell provided in some embodiments of the present application.

[0088] Figure 7 Schematic structural diagram of the negative electrode tab of a battery cell provided for some other embodiments of the present application

[0089] Figure 8 Top view structural diagram of an electrode assembly of a battery cell provided for some embodiments of the present application

[0090] Figure 9 Schematic structural diagram of a battery module provided for some embodiments of the present application

[0091] Figure 10 Schematic structural diagram of a battery pack provided for some embodiments of the present application

[0092] Figure 11 Schematic structural diagram of an electrical device provided for some embodiments of the present application

[0093] The drawings are not necessarily drawn to actual scale.

[0094] Explanation of reference numerals is as follows:

[0095] X, thickness direction; Y, width direction; Z, length direction

[0096] 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, housing; 5a, first housing part; 5b, second housing part; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, positive electrode tab; 111, positive electrode tab ear; 112, positive electrode current collector; 12, negative electrode tab; 121, negative electrode tab ear; 122, negative electrode current collector; 13, separator; 14, main body part; 20, outer shell; 21, housing; 211, first side wall; 212, second side wall; 22, end cap; 31, positive terminal; 32, negative terminal. Detailed description of specific embodiments

[0097] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid 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 recited in the claims.

[0098] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0099] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0100] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0101] If there is no special instruction, all steps of the present application can be carried out sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0102] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab includes a positive current collector and a positive electrode film layer provided on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material. The negative electrode tab includes a negative current collector and a negative electrode film layer provided on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material.

[0103] The positive electrode active material includes lithium-containing phosphate, and the specific capacity of the positive electrode active material is relatively low, resulting in a relatively low volume energy density of the battery cell.

[0104] In order to improve the volumetric energy density of a battery cell, a silicon-based material is introduced into the negative active material. The silicon-based material has a relatively high specific capacity per gram, which increases the overall specific capacity per gram of the negative active material. The main bottleneck in improving the volumetric energy density of the battery cell lies in the positive electrode film layer. By reducing the occupied space of the negative electrode film layer and increasing the occupied space of the positive electrode film layer, the volumetric energy density of the battery cell can be improved, enabling the battery cell to have a relatively high volumetric energy density.

[0105] However, due to the large volume change of the silicon-based material during the charge and discharge process of the battery cell, the solid electrolyte interface (SEI) film on the negative electrode side is repeatedly damaged, leading to an exacerbation of the side reactions on the negative electrode side, deteriorating the cycling performance of the battery cell, and resulting in poor cycling performance of the battery cell at high volumetric energy density.

[0106] The embodiments of the present application rationally design the system of the battery cell, which can take into account and improve the cycling performance of the battery cell at high energy density. Specifically,

[0107] First, the silicon element of the silicon-based material is regulated within an appropriate range, and the mass content of the silicon element is not too high, which can alleviate the degree of volume change to a certain extent.

[0108] Second, the electrolyte includes ethylene carbonate and a cyclic carbonate additive. The cyclic carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. A part of the ethylene carbonate can cooperate with the cyclic carbonate additive to participate in the formation of the SEI film on the negative electrode side, optimizing the mechanical properties and protective properties of the SEI film, effectively alleviating the volume expansion on the negative electrode side, and having a not-too-high impedance, which can effectively alleviate the side reactions on the negative electrode side and improve the cycling performance of the battery cell.

[0109] Another part of the ethylene carbonate can be used as a solvent. Since the boiling point of ethylene carbonate is relatively high and it is not easily decomposed at the operating temperature of the battery cell, it can improve the stability of the electrolyte. Moreover, ethylene carbonate has a high dielectric constant and strong ability to dissociate ions, which is beneficial to lithium ion transport. At a certain current density, lithium ions can quickly embed into the negative electrode film layer and combine with electrons, reducing the risk of lithium deposition on the surface of the negative electrode film layer and improving the cycling performance of the battery cell.

[0110] By further regulating the mass content of ethylene carbonate and the mass content of cyclic carbonate additives, the mass content of ethylene carbonate will not be too high, and the viscosity of the electrolyte will not be too high, which is beneficial to uniformly infiltrate the negative electrode sheet, reduce the risk of lithium plating on the surface of the negative electrode film layer, and improve the cycling performance of the battery cell; the mass content of cyclic carbonate additives will not be too high, so that the film-forming impedance of the SEI film will not be too high, which is beneficial to the rapid charging of the battery cell, can further reduce the risk of lithium plating on the surface of the negative electrode film layer, and improve the cycling performance of the battery cell.

[0111] Therefore, the embodiments of the present application can improve the cycling performance of the battery cell at high energy density.

[0112] Battery cell

[0113] In a first aspect, an embodiment of the present application provides a battery cell.

[0114] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate; the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material and a silicon-based material;

[0115] The electrolyte includes ethylene carbonate and cyclic carbonate additives. The cyclic carbonate additives include one or more of vinylene carbonate and ethylene carbonate derivatives,

[0116] wherein,

[0117] The mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.5% to 5%;

[0118] The mass content of ethylene carbonate in the electrolyte is 20% to 40%;

[0119] The mass content of cyclic carbonate additives in the electrolyte is 2% to 8%.

[0120] The positive electrode active material includes a lithium-containing phosphate, and the negative electrode active material includes a silicon-based material with a mass content of silicon element greater than or equal to 0.5%, which can make the battery cell have a relatively high volumetric energy density;

[0121] As the mass content of silicon increases, the volumetric energy density of the battery cell further increases. However, due to the large volume change of the silicon-based material during the charge and discharge process of the battery cell, the solid electrolyte interface (SEI) film on the negative electrode side is repeatedly damaged, leading to an exacerbation of the side reactions on the negative electrode side, deteriorating the cycling performance of the battery cell and resulting in poor cycling performance of the battery cell at high volumetric energy density.

[0122] Therefore, in the embodiments of the present application, on the one hand, the mass content of silicon is regulated to be less than or equal to 5%, so that the mass content of silicon is not too high, which can alleviate the degree of volume change to a certain extent;

[0123] In the embodiments of the present application, on the other hand, the cycling performance of the battery cell is improved by regulating the components of the electrolyte. Specifically, the electrolyte includes ethylene carbonate with a mass content of greater than or equal to 20% and a cyclic carbonate additive with a mass content of greater than or equal to 2%. The cyclic carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. A part of the ethylene carbonate can cooperate with the cyclic carbonate additive to participate in the formation of the SEI film on the negative electrode side, optimizing the mechanical properties and protective properties of the SEI film, effectively alleviating the volume expansion on the negative electrode side, and effectively alleviating the side reactions on the negative electrode side, thus improving the cycling performance of the battery cell;

[0124] Another part of the ethylene carbonate can be used as a solvent. Since the boiling point of ethylene carbonate is relatively high and it is not easily decomposed at the operating temperature of the battery cell, it can improve the stability of the electrolyte. Moreover, ethylene carbonate has a high dielectric constant and strong ability to dissociate ions, which is beneficial to the transmission of lithium ions. At a certain current density, lithium ions can quickly embed into the negative electrode film layer and combine with electrons, reducing the risk of lithium metal plating on the surface of the negative electrode film layer and improving the cycling performance of the battery cell;

[0125] By further regulating the mass content of ethylene carbonate and the mass content of the cyclic carbonate additive, the mass content of ethylene carbonate is not too high, for example, less than or equal to 40%, so that the viscosity of the electrolyte is not too high, which is beneficial to uniformly wetting the negative electrode plate and reducing the risk of lithium metal plating on the surface of the negative electrode film layer, thus improving the cycling performance of the battery cell; the mass content of the cyclic carbonate additive is not too high, for example, less than or equal to 8%, so that the film-forming impedance of the SEI film is not too high, which is beneficial to the fast charging of the battery cell, can further reduce the risk of lithium metal plating on the surface of the negative electrode film layer, and improve the cycling performance of the battery cell.

[0126] Therefore, the embodiments of the present application can improve the cycling performance of the battery cell at high energy density.

[0127] [Electrolyte]

[0128] The battery cell includes an electrolyte. During the charge and discharge process of the battery cell, active ions such as lithium ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0129] The electrolyte includes an organic solvent, an additive, and an electrolyte salt.

[0130] In an embodiment of the present application, the electrolyte includes ethylene carbonate, and the mass content of ethylene carbonate in the electrolyte is 20% to 40%; it can be optionally 20% to 35%.

[0131] Exemplarily, the mass content of ethylene carbonate is 20%, 25%, 30%, 35%, 40% or a range composed of any two of the above values.

[0132] Ethylene carbonate can form an SEI film component containing organic components (such as polyether substances) and inorganic components on the negative electrode side. Acting synergistically with cyclic carbonate additives, it can optimize the components of the SEI film and improve the protective effect on the negative electrode side.

[0133] When the mass content of ethylene carbonate is too low, the SEI film formed on the negative electrode side is too thin, the protective strength is weakened, the volume change of the silicon-based material on the negative electrode side cannot be effectively alleviated, and the side reactions on the negative electrode side are still relatively serious; when the mass content of ethylene carbonate is greater than or equal to 20%, the protective strength of the SEI film is enhanced, the volume expansion on the negative electrode side can be effectively alleviated, and the side reactions on the negative electrode side can be effectively alleviated, improving the cycle performance of the battery cell;

[0134] When the mass content of ethylene carbonate is too high, the viscosity of the electrolyte is too high, the fluidity of the electrolyte is poor, the wetting of the negative electrode plate is uneven, and lithium deposition is likely to occur on the surface of the negative electrode film layer; while the mass content of vinylene carbonate in the embodiment of the present application is not too high, for example, less than or equal to 40%, the viscosity of the electrolyte is not too high, which is beneficial to uniformly wet the negative electrode plate, reduce the risk of lithium deposition on the surface of the negative electrode film layer, and improve the cycle performance of the battery cell.

[0135] In some embodiments, the organic solvent further includes a linear ester solvent. The linear ester solvent has a small viscosity, making the viscosity of the electrolyte small, which is beneficial to improving the wetting performance of the electrolyte on the electrode plate and improving the cycle performance of the battery cell. Moreover, the linear ester solvent can increase the transmission rate of lithium ions in the electrolyte, thereby being beneficial to improving the fast charging performance of the battery cell.

[0136] In some embodiments, the linear ester solvent includes one or more of linear carboxylic acid ester solvents and linear carbonate solvents, and the mass content of the linear ester solvent in the electrolyte is 45% to 65%, such as 45%, 50%, 55%, 60%, 65%, or a range composed of any two of the above values. The linear ester solvent with the above mass content is beneficial to improving the cycle performance and fast charging performance of the battery cell.

[0137] Exemplarily, the linear carboxylic acid ester solvent includes a compound represented by Formula I,

[0138] Formula I,

[0139] In Formula I,

[0140] R1 includes a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group,

[0141] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0142] The above linear carboxylic acid ester solvent has a low viscosity, improves the fast charging ability of the battery cell at high energy density, reduces the risk of lithium deposition during fast charging, and improves the cycle performance of the battery cell.

[0143] Optionally, R1 includes a hydrogen atom, a C1-C3 alkyl group, or a C1-C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a C1-C2 alkyl group, or a C1-C2 haloalkyl group.

[0144] Optionally, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0145] In the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group, and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0146] Exemplarily, the linear carboxylic acid ester solvent includes one or more of the compounds represented by Formula I-1 to the compounds represented by Formula I-12,

[0147]

[0148] The above materials can further improve the cycle performance of the battery cell at high energy density.

[0149] Exemplarily, the linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The above materials can further improve the cycle performance of the battery cell at high energy density.

[0150] In the embodiments of the present application, the electrolyte further includes an additive, the additive includes a cyclic carbonate additive, and the mass content of the cyclic carbonate additive in the electrolyte is 2% to 8%.

[0151] Exemplarily, the mass content of the cyclic carbonate additive is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8% or a range composed of any two of the above values.

[0152] When the mass content of the cyclic carbonate additive is less than 2%, the film layer formed on the negative electrode side is relatively thin, which is not conducive to the protection of the negative electrode active material; as the mass content of the cyclic carbonate additive increases, the film-forming effect on the negative electrode side is more excellent, which can play an excellent protective role on the negative electrode active material, reduce the side reactions on the negative electrode side, and improve the cycle performance; however, as the mass content of the cyclic carbonate additive further increases, the impedance of the SEI film formed on the negative electrode side is relatively high, which is not conducive to fast charging and may cause lithium deposition during the cycling process, deteriorating the cycle performance; therefore, the mass content of the cyclic carbonate additive in the embodiments of the present application is regulated to 2% to 8%, which can effectively improve the cycle performance of the battery cell at high energy density.

[0153] In some embodiments, the mass content of vinylene carbonate in the electrolyte is 1.5% to 5%, such as 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range composed of any two of the above values. When the mass content of vinylene carbonate is within the above range, a dense SEI film containing organic components can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reactions on the negative electrode side and take into account the improvement of the cycle performance of the battery cell at high energy density.

[0154] Vinylene carbonate can form an SEI film rich in organic components on the negative electrode side. During the cycling process of the battery cell, the volume change of the negative electrode active material basically does not cause the SEI film to break; moreover, vinylene carbonate and ethylene carbonate act synergistically. Ethylene carbonate can increase the inorganic components in the SEI film, improve the mechanical properties of the SEI film, further enhance the stability of the SEI film, play a more effective protective role on the negative electrode active material, and further improve the cycle performance of the battery cell.

[0155] In some embodiments, the mass content of ethylene carbonate derivative in the electrolyte is 0 to 4%, and can be optionally 1.5% to 3.5%.

[0156] For example, the mass content of the ethylene carbonate derivative in the electrolyte is 0, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or a range composed of any two of the above values.

[0157] Taking the case where the mass content of the ethylene carbonate derivative is 0 as an example,

[0158] it may be that the freshly prepared electrolyte does not contain an ethylene carbonate derivative,

[0159] or the electrolyte obtained after disassembling the battery cell does not contain an ethylene carbonate derivative. This situation may be that the freshly prepared electrolyte does not contain an ethylene carbonate derivative, or a small amount of ethylene carbonate derivative is added, but it participates in the film-forming reaction of the SEI film during the formation process of the battery cell, resulting in a mass content of 0 for the ethylene carbonate derivative during the detection process.

[0160] Optionally, the freshly prepared electrolyte includes an ethylene carbonate derivative.

[0161] Furthermore, for adding certain substances, such as additives, to the electrolyte, due to the characteristics of the additives participating in the film formation on the surface of the active material, the content of the additives in the electrolyte of the battery cell is related to the state after formation, different battery life cycles, or different battery storage states. Therefore, there may be a difference in the content of the additives between the freshly prepared electrolyte and the electrolyte obtained by reverse disassembling the battery. However, those skilled in the art can know the approximate range of the content of the relevant substances in the corresponding freshly prepared electrolyte according to the performance expression level (such as the number of cycles), residual content, etc. of the battery cell. Similarly, those skilled in the art can also know the approximate range of the content of the non-freshly prepared (i.e., reverse) according to the content of the freshly prepared additives, based on the performance requirements of the battery cell, storage environment, etc.

[0162] Therefore, the content of the additives mentioned in the technical solution of the present application can be the content of the additives actively added to the freshly prepared electrolyte, or the content of the residual additives detected by reverse according to the actual battery state.

[0163] The ethylene carbonate derivative and ethylene carbonate act together. The ethylene carbonate derivative can further optimize the components of the SEI film, reduce the impedance of the SEI film, and effectively improve the cycling performance of the battery cell at high energy density. When the ethylene carbonate derivative includes an optional fluorine atom, it can increase the fluorine element content of the SEI film, enhance the mechanical strength of the SEI film, effectively relieve the volume expansion of the silicon-based material, reduce the risk of SEI film breakage, and further improve the cycling performance of the battery cell.

[0164] In some embodiments, the linear ester solvent includes a linear carbonate solvent, and the mass content of the cyclic carbonate additive is 2% to 5%. Optionally, the linear ester solvent is a linear carbonate solvent, and the mass content of the cyclic carbonate additive is 2% to 5%. The above electrolyte system is beneficial to further improving the cycling performance of the battery cell.

[0165] In some other embodiments, the linear ester solvent includes a linear carboxylic acid ester solvent with a mass content > 0 and a linear carbonate solvent with a mass content ≥ 0, and the mass content of the cyclic carbonate additive is 3.5% to 8%. The above electrolyte system is beneficial to further improving the cycling performance of the battery cell.

[0166] Exemplarily, the linear ester solvent is a linear carboxylic acid ester solvent, and the mass content of the cyclic carbonate additive is 3.5% to 8%.

[0167] Exemplarily, the linear ester solvent is a mixed solvent of a linear carboxylic acid ester solvent and a linear carbonate solvent, and the mass content of the cyclic carbonate additive is 3.5% to 8%.

[0168] In the embodiments of the present application, the ethylene carbonate derivative means that at least one hydrogen atom of ethylene carbonate is substituted, and the substituent group can be one, two, three, or four, etc.

[0169] Exemplarily, the ethylene carbonate derivative includes the compound shown in Formula A,

[0170]

[0171] Formula A,

[0172] In Formula A, Q1, Q2, Q3, and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not simultaneously hydrogen atoms.

[0173] Q1, Q2, Q3, and Q4 are not simultaneously hydrogen atoms. In other words, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0174] Exemplarily, one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and the rest are hydrogen atoms. Exemplarily, at least two of Q1, Q2, Q3, and Q4 include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group. Exemplarily, at least three of Q1, Q2, Q3, and Q4 include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group. Exemplarily, Q1, Q2, Q3, and Q4 each independently include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0175] Optionally, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom or a C1-C5 haloalkyl group. The halogen atom includes a fluorine atom, a bromine atom, a chlorine atom, etc., and may be a fluorine atom. The C1-C5 haloalkyl group includes a C1-C5 fluoroalkyl group, a C1-C5 bromoalkyl group, a C1-C5 chloroalkyl group, etc., and may be a fluorine atom. For example, the C1-C5 fluoroalkyl group includes fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, or fluoropentyl.

[0176] When the ethylene carbonate derivative includes a fluorine atom, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side. On the basis of protecting the negative electrode active material, the impedance of the film layer can be lower, and the cycle performance of the battery cell at high energy density can be improved more effectively.

[0177] For example, the ethylene carbonate derivative includes one or more of the compounds shown in Formula A-1 to the compounds shown in Formula A-6.

[0178]

[0179] The above materials can further improve the high-temperature cycle performance of the battery cell at high energy density.

[0180] Optionally, the ethylene carbonate derivative includes one or more of the compounds shown in Formula A-1 to the compounds shown in Formula A-3. Further optionally, the ethylene carbonate derivative includes the compound shown in Formula A-1.

[0181] In some embodiments, the additive further includes one or more of a sulfur-containing additive and a lithium salt additive, and may be at least two. The above additives can improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0182] In some embodiments, the electrolyte includes a sulfur-containing additive with a mass content of 0 to 2% in the electrolyte. For example, the mass content of the sulfur-containing additive is 0, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0% or a range composed of any two of the above values. Optionally, the mass content of the sulfur-containing additive in the electrolyte is 0.5% to 2%. The sulfur-containing additive and the cyclic carbonate additive cooperate to participate in film formation, which can optimize the film layer components of the SEI film. The sulfur-containing additive can participate in the formation of an SEI film rich in inorganic substances, and the inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI film, and improve the high-temperature cycle performance of the battery cell at high energy density.

[0183] Exemplarily, the sulfur-containing additive includes one or more of vinylene sulfate DTD, bis(vinylsulfonyl)ethylene 2-DTD, 1,3-propanesultone, butene sulfite BS, ethylene sulfite ES, and methylene methanedisulfonate MMDS.

[0184] In some embodiments, the electrolyte includes a lithium salt additive with a mass content of 0 to 1% in the electrolyte. For example, the mass content of the lithium salt additive is 0, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or a range composed of any two of the above values. Optionally, the mass content of the lithium salt additive in the electrolyte is 0.2% to 1%. The lithium salt additive and the cyclic carbonate additive cooperate to form a film, which can optimize the film layer components of the SEI film. The lithium salt additive can participate in the formation of an SEI film rich in inorganic substances, and the inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI film, and improve the cycling performance of the battery cell at high energy density.

[0185] Exemplarily, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bis(oxalato)borate LiBOB.

[0186] In some embodiments, the electrolyte salt includes an electrolyte lithium salt, and the mass content of the electrolyte lithium salt in the electrolyte is 10% to 18%. For example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or a range composed of any two of them. The above electrolyte lithium salt can improve the cycling performance of the battery cell.

[0187] Optionally, the electrolyte lithium salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium hexafluorophosphate LiPF6. Optionally, the electrolyte lithium salt includes lithium bis(fluorosulfonyl)imide LiFSI and lithium hexafluorophosphate LiPF6. The above electrolyte lithium salt can improve the cycling performance of the battery cell.

[0188] In some embodiments, the mass content of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is 4% to 6%. For example, 4%, 4.5%, 5%, 5.5%, 6% or a range composed of any two of them. When the mass content of lithium bis(fluorosulfonyl)imide LiFSI is within the above range, the mass content of lithium hexafluorophosphate can be reduced, so that the acid production content in the electrolyte is reduced and the side reactions are reduced, and the cycling performance of the battery cell can be improved.

[0189] In the embodiments of the present application, the types and contents of the inorganic components / electrolyte lithium salts in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to the standard JY / T 0575-2020 "General Rules for Ion Chromatography Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / electrolyte lithium salts in the electrolyte by ion chromatography analysis methods. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or the battery monomer that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery monomer is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery monomer can be taken as a sample for detection by ion chromatography analysis methods.

[0190] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography.

[0191] [Negative electrode plate]

[0192] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0193] The charge upper limit voltage and discharge cut-off voltage of the battery monomer vary depending on the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the charge upper limit voltage can be 3.65V and the discharge cut-off voltage can be 2.0V. Another example is that when the phosphate material includes lithium manganese iron phosphate, the charge upper limit voltage can be 4.2V and the discharge cut-off voltage can be 2.0V. Next, taking the charge upper limit voltage of 3.65V and the discharge cut-off voltage of 2.0V as an example, the state of the battery monomer will be described: In the embodiments of the present application, the 100% state of charge SOC and 0% state of charge SOC of the battery monomer are defined as follows,

[0194] The battery monomer is charged at a constant current charge rate of 0.33C to the charge upper limit voltage, and then charged at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery monomer. The battery monomer is discharged at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery monomer.

[0195] In the embodiments of the present application, the negative electrode active material includes a silicon-based material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery monomer.

[0196] The mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.5% to 5%; optionally 0.8% to 3%.

[0197] Exemplarily, the mass content of silicon element is 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5% or a range composed of any two of the above values. When the mass content of silicon element is within the above range, the energy density and cycle performance of the battery cell can be improved.

[0198] Optionally, the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon material, and silicon-nitrogen material. The specific capacity of the above materials is relatively high, which is beneficial to improving the energy density of the battery cell.

[0199] Further optionally, the silicon-based material may include one or more of silicon oxide, silicon-carbon material, and silicon-nitrogen material. Even further optionally, the silicon-based material may include silicon-carbon material. The above materials have relatively good cycle stability during the cycling process of the battery cell, which is beneficial to taking into account the improvement of the energy density and cycle performance of the battery cell.

[0200] Exemplarily, the silicon-carbon material may include a porous carbon skeleton and silicon disposed in the porous carbon skeleton, and the silicon may be nano-silicon. The nano-silicon can be deposited in the porous carbon skeleton by methods such as chemical vapor deposition, and the specific process parameters can be the parameters well known in the art.

[0201] When the silicon-based material includes one or more of silicon oxide, silicon-carbon material, and silicon-nitrogen material; especially when the silicon-based material includes silicon-carbon material, the silicon-based material can further improve the energy density and cycle performance of the battery cell by improving at least one parameter among the mass content of silicon element, volume average particle size, specific surface area, powder compact density, etc.

[0202] Exemplarily, based on the mass of the silicon-based material, the mass content of silicon element is 40% to 80%, such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or a range composed of any two of the above values.

[0203] Exemplarily, the volume average particle size Dv50 of the silicon-based material is 5.0 μm to 12.5 μm, such as 5.0 μm, 5.5 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 a range composed of any two of the above values.

[0204] In the embodiments of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, and can be detected by using equipment and methods well-known in the art. For example, taking the positive electrode active material as a sample, according to the test standard GB / T 19077-2016, the Dv50 of the particles is tested by a Mastersizer 2000E laser particle size analyzer, etc.

[0205] Exemplarily, the specific surface area of the silicon-based material is 3.1 m 2 / g to 3.6 m 2 / g, such as 3.1 m 2 / g, 3.2 m 2 / g, 3.3 m 2 / g, 3.4 m 2 / g, 3.5 m 2 / g, 3.6 m 2 / g or the range composed of any two of the above values.

[0206] In the embodiments of the present application, the specific surface area of the material has the meaning well-known in the art and can be detected by using equipment and methods well-known in the art. For example, it is detected according to the test standard GB / T 19587-2017. Taking the positive electrode active material as a sample, the specific surface area is tested by a Tri-Star 3020 specific surface area and pore size analyzer of Micromeritics Corporation of the United States.

[0207] Exemplarily, the powder compaction density of the silicon-based material under 25000 N is 0.7 g / cm 3 to 1.2 g / cm 3 , such as 0.7 g / cm 3 , 0.8 g / cm 3 , 0.9 g / cm 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 or the range composed of any two of the above values.

[0208] When the powder compaction density of the silicon-based material under 25000 N is within the above range, the energy density of the battery cell can be improved, and since the negative electrode active materials in the negative electrode film layer can be stacked more closely and the contact resistance between particles is smaller, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation and improving the cycle performance of the battery cell at high energy density.

[0209] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art, and can be detected by methods and equipment well-known in the art, and is detected according to the test standard GB / T24533-2009. As an example, a certain amount of negative electrode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in a UTM7305 type electronic pressure testing machine, pressurized to 2500 kg (equivalent to 25000 N), held for 30 s, then depressurized, held for 10 s, and then the powder compaction density of the negative electrode active material under the action of 25000 N is recorded and calculated.

[0210] In the embodiments of the present application, the negative electrode active material further includes a carbon-based material, and the carbon-based material includes graphite particles. The graphite particles have relatively high cycle stability and can improve the cycle performance of the battery cell. The positive electrode active material of the present application is mainly a lithium-containing phosphate system, and the negative electrode active material is mainly a graphite and silicon-based material system. When used in combination, the energy density of the battery cell of the lithium-containing phosphate system can be improved, and the battery cell life can be taken into account at the same time.

[0211] In some embodiments, the graphite particles include graphite body particles and a negative electrode coating layer. The graphite body particles include secondary particles, and the secondary particles include a plurality of primary particles. The negative electrode coating layer coats the surface of the graphite body particles, and the negative electrode coating layer includes carbon elements. The carbon in the negative electrode coating layer is mainly amorphous carbon. Amorphous carbon refers to a transition carbon material with a very low degree of graphitization crystallization and an approximate amorphous form (or no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0212] The graphite body particles include secondary particles. The migration path of lithium ions in the graphite body particles is relatively long, and the migration path in the primary particles is relatively short, which can improve the migration rate of lithium ions. The negative electrode coating layer has more end faces and defects, so that the number of sites capable of intercalating and deintercalating lithium ions is more, and the conductivity of the negative electrode coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the cycle performance of the battery cell at high energy density.

[0213] Exemplarily, the graphite body particles include one or more of artificial graphite and natural graphite, and may be artificial graphite.

[0214] Optionally, based on the mass of the graphite particles, the mass content of the carbon element in the negative electrode coating layer is 2% to 5%. Exemplarily, the mass content of the carbon element in the negative electrode coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range composed of any two of the above values.

[0215] When the mass content of carbon element in the negative electrode coating layer is within the above range, the internal resistance of the negative electrode sheet can be further reduced, the heat generation of the battery cell can be reduced, and the cycling performance of the battery cell at high energy density can be improved.

[0216] When the powder resistivity of the graphite particles is within the above range, the resistance of the negative electrode sheet is relatively low, which is beneficial to reducing the internal resistance of the negative electrode sheet, reducing the heat generation of the battery cell, and improving the cycling performance of the battery cell at high energy density.

[0217] In the embodiments of the present application, the graphite particles can be prepared by methods well-known in the art. Taking artificial graphite as an example of the graphite body particles, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and after carbonization treatment, forming a negative electrode coating layer on at least a part of the surface of the artificial graphite particles.

[0218] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of coal tar pitch and petroleum pitch is below 250 °C.

[0219] Optionally, the carbonization treatment temperature is 700 °C to 1800 °C. Optionally, the carbonization treatment temperature is 1000 °C to 1300 °C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized and a negative electrode coating layer containing amorphous carbon can be formed on at least a part of the surface of the artificial graphite.

[0220] Optionally, the carbonization treatment time is 1 h to 6 h.

[0221] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include graphite particles, or the carbon-based material may include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0222] In some embodiments, in addition to the above-mentioned carbon-based material and silicon-based material, the negative electrode active material may further include one or more of a tin-based material and lithium titanate. The tin-based material may include one or more of elemental tin, tin oxide, and tin alloy material.

[0223] In the present application, the qualitative and quantitative determination of each substance or each element can be carried out by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change some detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0224] For example, the mass content of silicon in the negative electrode film layer has the meaning well-known in the art and can be detected by the equipment and methods well-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 each substance in the negative electrode film layer is obtained by suction filtration and used as a test sample. The mass content of silicon can be obtained by using an inductively coupled plasma-emission spectrometer of model ICAP7400 from Thermo Fisher Scientific Company in the United States and referring to the standard of GB / T30902-2014.

[0225] For example, the present application can also perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or the negative electrode active material in combination with the general rules of JIS / K0131-1996 X-ray diffraction analysis method.

[0226] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by a scanning electron microscope (SEM). There are voids between the flaky structures in the SEM cross-sectional view of natural graphite, while the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or they can be distinguished by the XRD spectrum obtained by the X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, while only the 2H phase exists in the XRD spectrum of artificial graphite.

[0227] In the embodiments of the present application, the negative electrode film layer includes at least one layer of film layer, and a single-layer film layer can be used, or at least two layers of film layers can be used. The negative electrode film layer can include two layers of film layers, three layers of film layers, four layers of film layers, or even more layers of film layers.

[0228] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector, and the carbon-based material in the first negative electrode film layer includes graphite particles. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector, and the carbon-based material in the second negative electrode film layer includes graphite particles.

[0229] The negative electrode film layer includes at least two layers of film layers, and layer-by-layer coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences between the first negative electrode film layer and the second negative electrode film layer, the pore differences of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission can be reduced, and the fast charging performance of the battery cell can be improved.

[0230] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which is beneficial to improving the tap density of the negative electrode film layer. When the negative electrode active material includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0231] There are differences in the particle sizes of the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, the overpotential of the second negative electrode film layer is usually relatively high, and the bottleneck of charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can improve the problem of lithium deposition on the surface layer of the negative electrode sheet and improve the cycle performance.

[0232] Optionally, the negative electrode active material in the first negative electrode film layer is in the form of particles, and its volume average particle size Dv50 is from 9.8 μm to 16.8 μm, for example, 9.8 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 16.8 μm or the range composed of any two of the above values. When the first negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is from 9.8 μm to 16.8 μm.

[0233] When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material and improve the cycle performance.

[0234] Optionally, the negative electrode active material in the second negative electrode film layer is in the form of particles, and its volume average particle size Dv50 is from 8.5 μm to 14.5 μm, for example, 8.5 μm, 9.0 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm or the range composed of any two of the above values. When the second negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is from 8.5 μm to 14.5 μm.

[0235] When the volume average particle diameter Dv50 of the negative electrode active material in the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the other hand, the negative electrode active material in the second negative electrode film layer with the above volume average particle diameter range cooperates with the negative electrode active material in the first negative electrode film layer, which is beneficial to constructing the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, enabling lithium ions to quickly gain electrons and precipitate on the negative electrode side, reducing the risk of lithium precipitation, and improving the cycle performance.

[0236] In some embodiments, at least one of the first negative electrode film layer and the second negative electrode film layer includes a silicon-based material.

[0237] Exemplarily, the first negative electrode film layer includes a silicon-based material. The second negative electrode film layer can effectively relieve the volume expansion of the silicon-based material in the first negative electrode film layer and improve the cycle performance of the battery cell.

[0238] Exemplarily, the second negative electrode film layer includes a silicon-based material.

[0239] Exemplarily, both the first negative electrode film layer and the second negative electrode film layer include a silicon-based material, and this setting method is beneficial to improving the energy density of the battery cell.

[0240] In some embodiments, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.10 g / cm 3 to 1.50 g / cm 3 . Exemplarily, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.10 g / cm 3 、1.15 g / cm 3 、1.20 g / cm 3 、1.22 g / cm 3 、1.25 g / cm 3 、1.28 g / cm 3 、1.3 g / cm 3 、1.32 g / cm 3 、1.35 g / cm 3 、1.40 g / cm 3 、1.45 g / cm 3 、1.50 g / cm 3 or the range composed of any two of the above values.

[0241] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative electrode active materials in the negative electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation and the amount of gas generated by the decomposition of carboxylic ester solvents due to heat accumulation, and improving the cycle performance of the battery cell.

[0242] In the embodiments of the present application, the compaction density of the negative electrode film layer in the 100% charged state of the battery cell has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. The detection method is the same as that for the compaction density of the positive electrode film layer.

[0243] In some embodiments, the single-sided coating weight of the negative electrode film layer is from 90 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 , 92 mg / 1540.25 mm 2 , 95 mg / 1540.25 mm 2 , 96 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 112 mg / 1540.25 mm 2 , 114 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 116 mg / 1540.25 mm 2 , 118 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2, 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 Or a range composed of any two of the above values.

[0244] When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode sheet will not be too large, and it can take into account improving the cycling performance of the battery cell at high energy density.

[0245] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer has the meaning well-known in the art, and can be detected by equipment and methods well-known in the art. Disassemble the negative electrode sheet of the battery cell in the 100% state of charge (SOC), measure the compaction density of the negative electrode film layer. For example, take a single-sided coated negative electrode sheet (if it is a double-sided coated sheet, the negative electrode film layer on one side can be wiped off first), punch it into small round pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the negative electrode film layer of the above weighed negative electrode sheet, weigh the weight of the negative electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the negative electrode film layer = (the weight M1 of the negative electrode sheet - the weight M0 of the negative electrode current collector) / S1, the thickness of the negative electrode film layer = the thickness H1 of the negative electrode sheet - the thickness H0 of the negative electrode current collector, and the compaction density of the negative electrode film layer = the single-sided coating weight of the negative electrode film layer / the thickness of the negative electrode film layer.

[0246] In some embodiments, the negative electrode film layer further includes a negative electrode binder, and the negative electrode binder includes one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤ 5%.

[0247] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤ 5%.

[0248] In some embodiments, the negative electrode film layer may also optionally include other additives. As an example, the other additives may include thickeners, dispersants, etc. For example, sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0249] In some embodiments, the negative electrode current collector may be made of a metal foil or a composite current collector. As an example of the metal foil, one or more foils of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0250] The negative electrode film layer is usually formed by coating a negative electrode slurry on a negative electrode current collector and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing negative electrode active materials, optional conductive agents, optional binders, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0251] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm, such as 4 μm, 5 μm, 6 μm, or a range composed of any two of the above values. When the thickness of the negative electrode current collector is within the above range, the thickness of the negative electrode current collector is relatively thin, which is beneficial to improving the volume energy density of the battery cell.

[0252] The negative electrode plate does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the embodiments of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0253] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, and the negative electrode conductive layer is located between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, thereby reducing the heat generation of the battery cell, and improving the fast charging performance and high temperature cycling performance of the battery cell.

[0254] In some embodiments, the thickness of the negative electrode conductive layer is from 0.5 μm to 2 μm. Exemplarily, the thickness of the negative electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range composed of any two of the above values.

[0255] When the thickness of the negative electrode conductive layer is within the above range, it can further improve the conductivity of the negative electrode sheet, reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery cell, and can also take into account the improvement of the energy density of the battery cell.

[0256] In the embodiments of the present application, the thickness of the negative electrode conductive layer has the meaning well-known in the art, and can be detected by equipment and methods well-known in the art. For example, tomography is performed on the negative electrode sheet to directly measure the thickness of the negative electrode conductive layer.

[0257] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent of the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the heat generation of the battery cell. The negative electrode binder of the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector and the negative electrode film layer, and improve the structural stability of the negative electrode sheet.

[0258] In some embodiments, the negative electrode conductive layer may also optionally include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0259] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is from 20% to 40%. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or a range composed of any two of the above values.

[0260] Exemplarily, the negative electrode conductive agent of the negative electrode conductive layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0261] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is from 60% to 80%. Exemplarily, 60%, 65%, 70%, 75%, 80%, or a range composed of any two of the above values.

[0262] Exemplarily, the negative electrode binder of the negative electrode conductive layer includes one or more of styrene-butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0263] [Positive electrode sheet]

[0264] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0265] In the embodiments of the present application, the lithium-containing phosphate can be phosphate particles with an olivine structure; or a material obtained by coating and modifying the phosphate particles. For example, the lithium-containing phosphate includes phosphate particles and a positive electrode coating layer, and the positive electrode coating layer coats at least a part of the surface of the phosphate particles, and the positive electrode coating layer contains carbon elements.

[0266] By coating the surface of the phosphate particles with a positive electrode coating layer, the conductivity of the lithium-containing phosphate can be improved, which is beneficial to the migration rate of lithium ions, improves the fast charging ability of the battery, reduces the heat generation of the battery cell, and improves the cycle performance of the battery cell.

[0267] Examples of the phosphate particles may include, but are not limited to, one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. The above materials have excellent cycle stability and can improve the cycle performance of the battery cell.

[0268] In some embodiments, the lithium-containing phosphate includes a material with the general formula Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ 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, Hf, Ge, and Ce; X includes one or more of Cl, C, N, and P; Y includes one or more of O and F.

[0269] The lithium-containing phosphate has excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0270] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur. The molar content of Li is different when the battery cell is discharged to different states. In the listing of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of Li is the initial state of the material, that is, the state before feeding. When the cathode active material is applied to the battery system, after charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, in the listing of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of oxygen O is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will fluctuate. The above situations are all within the protection scope of the present application.

[0271] In some embodiments, the mass content of carbon element in the lithium-containing phosphate is 0.8% to 2.3%. Exemplarily, the mass content of carbon element in the lithium-containing phosphate is 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.3% or the range composed of any two of the above values.

[0272] The carbon element mainly exists in the cathode coating layer in the form of a carbon coating layer. The carbon coating layer is loose and porous, which is beneficial to increasing the specific surface area of the material, more beneficial to the effective contact between the electrolyte and the phosphate particles, and beneficial to the transport of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, the conductivity of the lithium-containing phosphate can be significantly improved, which is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate, and can improve the fast charging ability of the battery cell at high energy density.

[0273] In some embodiments, the cathode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

[0274] In some embodiments, the cathode coating layer includes a compound with the general formula Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 , where 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M3 includes one or more of Ti, Zr, Hf, Ge, and Sn.

[0275] Li 3-d1 Fe 2-d1 M3 d1 (PO m1 )n1 The compound is a fast ion conductor having a NASICON structure, for example, one or more of lithium iron titanium phosphate Li2FeTi(PO4)3, lithium iron zirconium phosphate Li2FeZr(PO4)3, and lithium iron tin phosphate Li2FeSn(PO4)3.

[0276] Fast ion conductors with a NASICON structure are materials with ultrafast ion conduction capabilities. They possess abundant three-dimensional lithium ion diffusion and transport channels, and have advantages such as high ion conduction efficiency and strong structural stability during multiple lithium de- and lithium insertion processes. Coating a fast ion conductor containing a NASICON structure on the surface of phosphate particles can significantly increase the lithium ion transmission rate during multiple lithium de- and lithium insertion processes at the positive terminal, improve the ionic conductivity of the positive electrode active material, and enhance the rapid charging capability of the battery cell. In addition, it can also increase the specific capacity and the energy density of the corresponding battery cell.

[0277] The carbon element and the fast ion conductor can be arranged in layers. For example, the carbon element serves as an independent carbon coating layer, and the fast ion conductor serves as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer facing away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer facing away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0278] Optionally, a carbon coating can be formed by carbonizing an organic carbon source (e.g., glucose, polyethylene glycol, etc.) and coating the surface of the fast ion conductor layer. The carbon coating can partially or completely cover the fast ion conductor layer. The carbon coating can significantly improve the electronic conductivity of the phosphate particles, compensating for their poor electronic conductivity and increasing the energy density of the battery cell.

[0279] The cathode active material of this application, based on a lithium-containing phosphate, leverages the advantages of lithium-containing phosphates: low cost, high reliability, and excellent cycling stability. Furthermore, the cathode coating (a fast ion conductor layer and a carbon coating) addresses the drawbacks of poor electronic and ionic conductivity. Battery cells prepared with this cathode active material can improve the energy density of the battery while maintaining excellent cycling performance.

[0280] In the embodiments of the present application, the content of elements in the positive electrode active material has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry, and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode plate is disassembled, washed with DMC and dried, and then after removing impurities by high-temperature calcination, 0.4 g of the positive electrode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0281] In some embodiments, the powder tap density of the positive electrode active material under 30000 N is 2.46 g / cm 3 to 2.85 g / cm 3 .

[0282] Exemplarily, the powder tap density of the positive electrode active material under 30000 N is 2.46 g / cm 3 , 2.47 g / cm 3 , 2.48 g / cm 3 , 2.49 g / cm 3 , 2.5 g / cm 3 , 2.51 g / cm 3 , 2.55 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.8 g / cm 3 , 2.85 g / cm 3 Or a range composed of any two of the above values.

[0283] When the powder tap density of the positive electrode active material under 30000 N is within the above range, the energy density of the battery cell can be improved, and since the positive electrode active material in the positive electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode plate, thereby reducing heat generation and improving the cycle performance of the battery cell at high energy density.

[0284] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art, and can be detected by methods and equipment well-known in the art. Detection is carried out according to the test standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in a UTM7305 type electronic pressure testing machine, pressurized to 3000 kg (equivalent to 30000 N), kept under pressure for 30 s, then the pressure is released, kept for 10 s, and then the powder compaction density of the positive electrode active material under the action of 30000 N is recorded and calculated.

[0285] In some embodiments, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film layer is 2.5 g / cm 3 to 2.8 g / cm 3 . Exemplarily, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film layer is 2.5 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.75 g / cm 3 , 2.8 g / cm 3 or a range composed of any two of the above values.

[0286] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the positive electrode active materials in the positive electrode film layer are stacked relatively closely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation during fast charging and improving the cycle performance of the battery cell at high energy density.

[0287] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 350 mg / 1540.25 mm 2 , such as 200 mg / 1540.25 mm 2, 210 mg / 1540.25 mm², 220 mg / 1540.25 mm², 230 mg / 1540.25 mm², 240 mg / 1540.25 mm², 250 mg / 1540.25 mm², 260 mg / 1540.25 mm², 270 mg / 1540.25 mm², 280 mg / 1540.25 mm², 290 mg / 1540.25 mm², 300 mg / 1540.25 mm², 310 mg / 1540.25 mm², 350 mg / 1540.25 mm², or a range composed of any two of the above values.

[0288] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation amount per unit area of the positive electrode plate will not be too large, improving the cycling performance of the battery cell at high energy density.

[0289] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell in the 100% state of charge (SOC) can be detected by the following method. The positive electrode plate is disassembled from the battery cell, and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode plate (if it is a double-sided coated plate, one side of the positive electrode film layer can be wiped off first) is punched into small circular pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the positive electrode film layer of the above-mentioned weighed positive electrode plate is wiped off, the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode plate - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode plate - the thickness H0 of the positive electrode current collector, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0290] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The embodiments of the present application do not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode 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. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0291] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of the positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0292] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, one or more foils of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0293] The positive electrode film layer is usually formed by coating a positive electrode paste on the positive electrode current collector and then drying and cold pressing. The positive electrode paste is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0294] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a range composed of any two of the above values. When the thickness of the positive electrode current collector is within the above range, the thickness of the positive electrode current collector is relatively thin, which is beneficial to improving the volumetric energy density of the battery cell.

[0295] The positive electrode tab does not exclude other additional functional layers other than the positive electrode film layer. For example, in some embodiments, the positive electrode tab of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In some other embodiments, the positive electrode tab of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0296] In some embodiments, the positive electrode tab further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode tab and reduce the heat generation of the positive electrode tab, thereby reducing the heat generation of the battery cell.

[0297] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. Exemplarily, the thickness of the positive electrode conductive layer may be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range composed of any two of the above values.

[0298] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode sheet can be further improved, the heat generation of the positive electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the fast charging performance and high-temperature cycling performance of the battery cell at high energy density can be improved.

[0299] In the embodiments of the present application, the thickness of the positive electrode conductive layer has the meaning well known in the art and can be detected by using the equipment and methods well known in the art. For example, tomographic scanning is performed on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0300] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0301] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Exemplarily, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50% or a range composed of any two of the above values.

[0302] Exemplarily, the positive electrode conductive agent of the positive electrode conductive layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent of the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet and reducing the heat generation amount of the battery cell.

[0303] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. Exemplarily, 50%, 60%, 65%, 70% or a range composed of any two of the above values.

[0304] Exemplarily, the positive electrode binder of the positive electrode conductive layer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. The positive electrode binder of the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector and the positive electrode film layer and improve the structural stability of the positive electrode sheet.

[0305] [Separator membrane]

[0306] In the embodiments of the present application, the separator membrane is disposed between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet and the negative electrode sheet.

[0307] In some embodiments, the porosity of the separator membrane is 20% to 7%, and can be optionally 35% to 60%. Exemplarily, the porosity of the separator membrane is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range composed of any two of the above values.

[0308] When the porosity of the isolation membrane in the embodiment of the present application is within the above range, the migration ability of lithium ions in the isolation membrane can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation and improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0309] In the embodiments of this application, porosity refers to the percentage of the pore volume of the separator to the total volume of the separator. Porosity can be tested in accordance with the standard GB / T36363-2018, "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 testing.

[0310] In some embodiments, the isolation film has a thickness of 5 μm to 12 μm. For example, the base film has a thickness of 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range consisting of any two of the above values.

[0311] When the thickness of the isolation membrane is within the above range, the migration path of lithium ions in the isolation membrane is shorter, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0312] In the embodiment of the present application, the isolation membrane includes a base membrane with a porous structure.

[0313] Optionally, the porosity of the base film is 20% to 70%, optionally 35% to 60%.

[0314] In some embodiments, the base film comprises one or more of glass fiber, non-woven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0315] Optionally, the polyolefin includes one or more of polyethylene, polypropylene and polyvinylidene fluoride.

[0316] In the embodiment of the present application, the isolation membrane may be a base membrane. Optionally, the isolation membrane further includes a functional layer disposed on at least one side of the base membrane. The functional layer may include inorganic particles to enhance the heat resistance of the isolation membrane. Optionally, the functional layer is disposed on both sides of the base membrane.

[0317] In some embodiments, the functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and includes first inorganic particles. The second functional layer is located on the other side of the base film and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0318] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator membrane.

[0319] Optionally, the first functional layer may include a binder, optionally including one or more of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0320] Optionally, the first inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0321] Optionally, the average particle size of the first inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, optionally 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or a range composed of any two of the above values. When the average particle size of the first inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0322] In the embodiments of the present application, the meaning of the thickness of the base film is the meaning well-known in the art, and it can be detected by using the meaning and equipment well-known in the art. For example, a newly prepared separator membrane can be taken as a sample, or a battery cell that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, the separator membrane is obtained from the battery cell, and the separator membrane is dried and used as a sample. The separator membrane is cut off with an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the thickness of the cross-section of the separator membrane and each of its layers.

[0323] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers. Optionally, the acrylate copolymers include acrylate-acrylonitrile-acrylamide-propylene copolymers. The acrylate copolymers have excellent adhesion properties and relatively high adhesion stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0324] The second inorganic particles in the composite particles prevent the non-fluoropolymer particles from sticking to each other due to the high-temperature treatment during the granulation process, creating pores in the composite particles, which is beneficial for the transport of lithium ions and improves the ionic conductivity of the separator membrane. Additionally, the second inorganic particles can also increase the compression modulus of the composite particles. During charge and discharge processes, the composite particles are less likely to deform, making the structure of the separator membrane more stable, enhancing the kinetic performance of the battery cell, and improving the fast charging performance. Optionally, compared with the first functional layer, the second functional layer is disposed closer to the negative electrode tab. Since the composite particles are less likely to deform, the separator membrane basically does not cause side effects such as extrusion to the negative electrode tab, ensuring the stable kinetic performance of the negative electrode tab. Correspondingly, the first functional layer is disposed closer to the positive electrode tab.

[0325] Optionally, the second inorganic particles 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. Optionally, the second inorganic particles include silicon oxide. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer and form composite particles in combination with the non-fluoropolymer, further enhancing the cycle stability and kinetic performance of the separator membrane, and improving the cycle performance and fast charging performance of the battery cell.

[0326] The average particle size of the second inorganic particles is from 5 nm to 100 nm, optionally from 10 nm to 100 nm, and optionally from 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or a range composed of any two of the above values. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0327] In the embodiments of the present application, the average particle size of the second inorganic particles has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, after obtaining the separator membrane and drying the separator membrane as a sample, the separator membrane is cut by an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the particle size of the second inorganic particles in the separator membrane, and the particle sizes of multiple, for example, 50, second inorganic particles are measured, and the average value thereof is calculated as the average particle size of the second inorganic particles.

[0328] In some embodiments, the positive electrode sheet, the separator membrane, and the negative electrode sheet can be made into an electrode assembly through a winding process and / or a stacking process.

[0329] Figure 1 and Figure 2 shows a schematic structural diagram of a battery cell.

[0330] In some embodiments, the battery cell 7 may include a housing 20.

[0331] The housing 20 can be in various shapes, such as a cylinder, a cuboid, etc. The shape of the housing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylinder structure, the housing 20 can be selected as a cylinder structure. If the electrode assembly 10 is a cuboid structure, the housing 20 can be selected as a cuboid structure. Optionally, the electrode assembly 10 is a cuboid structure.

[0332] The material of the housing 20 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not make special limitations thereon. Optionally, the inner wall of the housing 20 may further include an insulating layer, and the insulating layer can separate the housing 20 and the electrode assembly 10. The material of the insulating layer can be selected from the materials commonly used in the art and is not specially limited herein.

[0333] The electrode assembly 10 accommodated in the housing 20 can be one or more.

[0334] In some embodiments, the housing 20 includes a housing body 21 and an end cap 22. The housing body 21 has an opening, and the end cap 22 covers the opening. The housing body 21 accommodates the electrode assembly 10 and the electrolyte.

[0335] In some embodiments, the material of the housing body 21 includes one or more of aluminum and steel, and steel can be selected. Steel has high mechanical strength and is not easily deformed, which can improve the use reliability and cycle performance of the battery cell. Optionally, the mass ratio of steel is the highest among the materials in the housing body 21.

[0336] Optionally, the thickness of the housing 21 is from 0.1 mm to 0.5 mm. Exemplarily, the thickness of the housing 21 is 0.1 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.5 mm or a range composed of any two of the above values. When the thickness of the housing 21 is within the above range, the mechanical strength of the housing 21 is relatively high, which can improve the use reliability and cycling performance of the battery cell 7, and the housing 21 occupies less space and has more internal space, which is beneficial to improving the energy density of the battery cell 7.

[0337] Optionally, the housing 21 has a cuboid structure. The housing 21 includes two first side walls 211 arranged oppositely and two second side walls 212 arranged oppositely. The two first side walls 211 are connected by the second side walls 212. The cross-sectional area of the first side wall 211 perpendicular to its own thickness direction is larger than the cross-sectional area of the second side wall 212 perpendicular to its own thickness direction. The thickness of the first side wall 211 is from 0.1 mm to 0.5 mm; further optionally from 0.2 mm to 0.35 mm.

[0338] The cross-sectional area of the first side wall 211 is relatively large. When its thickness is within the above range, the mechanical strength of the first side wall 211 is relatively high, which can improve the use reliability and cycling performance of the battery cell 7, and the housing 21 occupies less space and has more internal space, which is beneficial to improving the energy density of the battery cell 7.

[0339] Next, the electrode assembly 10 will be described by taking the stacked structure as an example.

[0340] The electrode assembly 10 includes a positive electrode tab 11, a negative electrode tab 12, and a separator 13 stacked along the thickness direction X of the battery cell 7.

[0341] As Figure 2 and Figure 3 shown, from the perspective of the appearance of the electrode assembly 10, the electrode assembly 10 includes a main body portion 14, a positive electrode tab 111, and a negative electrode tab 121. The positive electrode tab 111 and the negative electrode tab 121 protrude from the main body portion 14. The positive electrode tab 111 and the negative electrode tab 121 are used to lead out the current of the main body portion 14.

[0342] The part of the positive electrode tab 11 where the active material layer is not coated is the positive electrode tab 111. The active material coated on the positive electrode current collector in the positive electrode tab 11 constitutes the positive electrode film layer. The positive electrode film layer and the positive electrode current collector coated with the active material are part of the main body portion 14.

[0343] The negative part of the negative electrode tab 12 where the active material layer is not coated is the negative electrode tab 121. The active material coated on the negative electrode current collector in the negative electrode tab 12 constitutes the negative electrode film layer. The negative electrode film layer and the negative electrode current collector coated with the active material are part of the main body portion 14.

[0344] The main body portion 14 may further include a separator membrane 13, and the separator membrane 13 is located between the positive electrode tab and the negative electrode tab.

[0345] The positive electrode tab 111 and the negative electrode tab 121 may extend from the same side of the main body portion 14, or may extend from opposite sides respectively. Figure 2 and Figure 3 It shows the case where the positive electrode tab 111 is disposed on the same side and the negative electrode tab 121 is disposed on the same side. Exemplarily, the positive electrode tab 111 and the negative electrode tab 121 are disposed at the same end along the length direction Z of the electrode assembly 10.

[0346] Of course, the positive electrode tab 111 and the negative electrode tab 121 may also extend from opposite sides respectively. For example, the positive electrode tab 111 and the negative electrode tab 121 are disposed at both ends along the length direction Z of the electrode assembly 10.

[0347] In some embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collector along the length direction Z of the battery cell 7, and the negative electrode tab 121 is connected to at least one side of the negative electrode current collector along the length direction Z of the battery cell.

[0348] Such as Figure 4 shown, for example, the positive electrode tab 111 is connected to one side of the positive electrode current collector 112 along the length direction Z of the battery cell 7.

[0349] Such as Figure 5 shown, for example, the positive electrode tab 111 is connected to both sides of the positive electrode current collector 112 along the length direction Z of the battery cell 7.

[0350] Such as Figure 6 shown, for example, the negative electrode tab 121 is connected to one side of the negative electrode current collector 122 along the length direction Z of the battery cell 7.

[0351] Such as Figure 7 shown, for example, the negative electrode tab 121 is connected to both sides of the negative electrode current collector 122 along the length direction Z of the battery cell 7.

[0352] Such as Figure 8 shown, in some embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collector 112 along the length direction Z, the negative electrode tab 121 is connected to at least one side of the negative electrode current collector 122 along the length direction Z, along the length direction Z of the battery cell 7, the size of the negative electrode film layer 123 is larger than the size of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH1; along the width direction Y of the battery cell 7, the size of the negative electrode film layer 123 is larger than the size of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH2, and OH1 is greater than OH2.

[0353] The negative electrode tab 121 is located on at least one side of the negative electrode current collector 122 along the length direction Z. The current density in the connection region between the negative electrode tab 121 and the negative electrode current collector 122 increases sharply, and problems such as lithium deposition are more likely to occur in this region. In the embodiment of the present application, OH1 is set to be greater than OH2, so that the ability of the negative electrode film layer 123 to receive lithium ions in the length direction Z is stronger, especially the ability of the region of the negative electrode film layer 123 close to the negative electrode tab 121 to receive lithium ions can be improved, the risk of lithium deposition can be reduced, and the use reliability of the battery cell 7 can be improved.

[0354] Exemplarily, OH1 is from 1 mm to 4 mm, such as 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm, 3.5 mm, 4 mm or the range composed of any two of the above values. Along the length direction Z, both sides of the negative electrode film layer 123 exceed the positive electrode film layer 113, and each side exceeds OH1 / 2, that is, half of the size of OH1. Figure 8 OH1 / 2 is shown in.

[0355] Exemplarily, OH2 is from 1 mm to 3 mm, such as 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm or the range composed of any two of the above values. Along the width direction Y, both sides of the negative electrode film layer 123 exceed the positive electrode film layer 113, and each side exceeds OH2 / 2, that is, half of the size of OH2. Figure 8 OH2 / 2 is shown in.

[0356] In some other embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collector 112 along the width direction Y, and the negative electrode tab 121 is connected to at least one side of the negative electrode current collector 122 along the width direction Y.

[0357] Optionally, the number of the positive electrode tabs 111 on the same side of the main body 14 is at least one, optionally at least two. At least two positive electrode tabs 111 can increase the current-carrying capacity of the positive electrode tab 111.

[0358] Optionally, the number of the negative electrode tabs 121 on the same side of the main body 14 is at least one, optionally at least two. At least two negative electrode tabs 121 can increase the current-carrying capacity of the negative electrode tab 121.

[0359] In some embodiments, the battery cell 7 further includes a positive terminal 31. The positive terminal 31 is arranged on the outer shell 20 and can be arranged on the housing 21 or the end cover 22.

[0360] The positive terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 are welded. The positive terminal 31 and the positive electrode tab 111 can be connected through an adapter, or can be connected without using an adapter. Optionally, the positive terminal 31 and the positive electrode tab 111 are connected without using an adapter, that is, the positive terminal 31 and the positive electrode tab 111 are directly welded, which can reduce the resistance at the connection and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0361] In some embodiments, the battery cell 7 further includes a negative terminal 32, and the negative terminal 32 is disposed on the housing 20 and can be disposed on the housing 21 or the end cap 22.

[0362] The negative terminal 32 is electrically connected to the negative electrode tab 121. Optionally, the negative terminal 32 and the negative electrode tab 121 are welded. The negative terminal 32 and the negative electrode tab 121 can be connected through an adapter, or can be connected without using an adapter. Optionally, the negative terminal 32 and the negative electrode tab 121 are connected without using an adapter, that is, the negative terminal 32 and the negative electrode tab 121 are directly welded, which can reduce the resistance at the connection and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0363] Optionally, the number of positive terminals 31 on the same side of the main body 14 is at least one, and can be at least two. At least two positive terminals 31 can increase the current-carrying capacity of the positive terminal 31.

[0364] Optionally, the number of negative terminals 32 on the same side of the main body 14 is at least one, and can be at least two. At least two negative terminals 32 can increase the current-carrying capacity of the negative terminal 32.

[0365] As Figure 9 shown, the battery cell 7 of the embodiment of the present application can be assembled into a battery module 6. The number of battery cells 7 included in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0366] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, parallel or in a hybrid connection. A hybrid connection means that there are both series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series, parallel or in a hybrid connection together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodation part of the battery module 6. Of course, it can also be that multiple battery cells 7 are first connected in series, parallel or in a hybrid connection to form a battery module 6, and then multiple battery modules 6 are connected in series, parallel or in a hybrid connection to form a whole and are accommodated in the accommodation part. Optionally, the battery module 6 can further include an accommodation part having an accommodation space, and the multiple battery cells 7 are accommodated in the accommodation space.

[0367] The multiple battery cells 7 of the battery module 6 can be electrically connected through busbar components to achieve parallel, series, or hybrid connection of the multiple battery cells 7 of the battery module 6. The busbar components can be one or more, and each busbar component is used to electrically connect at least two battery cells 7.

[0368] As Figure 10 shown, in some embodiments, the above battery module 6 can also be assembled into a battery pack 2, and the number of battery modules 6 included in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device herein can be a battery module 6, a battery pack 2, or a battery cell 7, and the battery cell 7 can be the smallest unit constituting the battery device.

[0369] The battery pack 2 can include a box body 5 and a plurality of battery modules 6 provided in the box body 5. The box body 5 includes a first box body part 5a and a second box body part 5b. The box body 5 has an accommodation space 5c. The first box body part 5a is used to cover the second box body part 5b and form a closed space for accommodating the battery module 6. The plurality of battery modules 6 can be arranged in the box body 5 in any manner.

[0370] The first box body part 5a and the second box body part 5b cover each other, and the first box body part 5a and the second box body part 5b jointly define an accommodation space 5c for accommodating the battery cells. The second box body part 5b can be a hollow structure with one end open, and the first box body part 5a is a plate-like structure. The first box body part 5a covers the opening side of the second box body part 5b to form the box body 5 with the accommodation space 5c. The first box body part 5a and the second box body part 5b can also both be hollow structures with one side open, and the opening side of the first box body part 5a covers the opening side of the second box body part 5b to form the box body 5 with the accommodation space 5c. Of course, the first box body part 5a and the second box body part 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0371] To improve the sealing performance after the connection between the first box body part 5a and the second box body part 5b, a sealing member, such as a sealant, a sealing ring, etc., can also be provided between the first box body part 5a and the second box body part 5b.

[0372] Assuming that the first box body part 5a covers the top of the second box body part 5b, the first box body part 5a can also be referred to as an upper box cover, and the second box body part 5b can also be referred to as a lower box body.

[0373] Electrical device

[0374] The second aspect of the embodiments of the present application provides an electrical device, which includes the battery device of the embodiments of the present application, such as a battery cell, a battery module or a battery pack. The battery cell, the battery module or the battery pack can be used as the power supply of the electrical device or as the energy storage unit of the electrical device. The electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or an extended-range electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact drill, a concrete vibrator and a planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices.

[0375] The electrical device can select a battery cell, a battery module or a battery pack according to its usage requirements.

[0376] Figure 11 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0377] A battery pack 2 is arranged inside the electrical device 1. The battery pack 2 can be arranged at the bottom, the head or the tail of the electrical device 1. The battery pack 2 can be used for supplying power to the electrical device 1. For example, the battery pack 2 can be used as the operating power supply of the electrical device 1 and can also be used as the driving power supply of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1.

[0378] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery pack 2 to supply power to the motor 4. For example, it is used for the working power requirements during the start, navigation and driving of the electrical device 1.

[0379] Another example of an electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. Such an electrical device usually requires being thin and light, and a battery cell can be used as the power supply.

[0380] Embodiment

[0381] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0382] Example 1

[0383] 1. Preparation of positive electrode sheet

[0384] The positive electrode sheet includes a positive electrode current collector, a positive electrode film layer and a positive electrode conductive layer. The positive electrode film layer is arranged on both sides of the positive electrode current collector. The positive electrode conductive layer is located between the positive electrode current collector and the positive electrode film layer. The positive electrode current collector is 13μm aluminum foil.

[0385] The positive conductive layer on the positive electrode current collector is a film 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 surface of the positive electrode current collector and drying it. The thickness is 1 μm. 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%.

[0386] The positive electrode film layer includes a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) uniformly coated on the surface of the positive electrode conductive layer, and a film layer formed after drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride PVDF, and a conductive agent acetylene black in a weight ratio of 97:2:1.

[0387] The positive electrode active material includes lithium iron phosphate particles and a positive electrode coating layer. The positive electrode coating layer is coated on the surface of the lithium iron phosphate particles. The positive electrode coating layer includes lithium iron titanium phosphate Li2FeTi(PO4)3 and carbon. The mass content of carbon element is 1.12%.

[0388] The powder compaction density of the positive electrode active material at 30000N is 2.75g / cm 3 .

[0389] The single-sided coating weight of the positive electrode film is 323mg / 1540.25mm 2 .

[0390] 2. Preparation of negative electrode sheet

[0391] 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 film layer. The negative electrode current collector is a copper foil with a thickness of 6 μm.

[0392] The negative conductive layer on the negative current collector is a film layer formed by uniformly mixing a negative conductive agent superconducting carbon, a negative binder styrene-butadiene rubber SBR, a thickener sodium carboxymethyl cellulose CMC-Na, and a solvent water, coating it on the surface of the negative current collector, and drying. The thickness is 1 μm. The mass content of the negative conductive agent in the negative conductive layer is 35%, the mass content of the negative binder in the negative conductive layer is 60%, and the mass content of the thickener in the negative conductive layer is 5%.

[0393] The negative film layer includes a first negative film layer and a second negative film layer. The first negative film layer is located on the surface of the negative conductive layer, and the second negative film layer is located on the surface of the first negative film layer.

[0394] The first negative film layer is a film layer formed by uniformly coating a first negative electrode slurry (solvent is water) on the surface of the positive conductive layer, followed by drying and cold pressing. The first negative film layer includes 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-carbon material is silicon carbide, and the mass content of silicon in the silicon-carbon material is 48%. The Dv50 of the silicon-carbon material is 8.8 μm, and the Dv50 of the graphite particles is 11.3 μm. The graphite particles include graphite body particles and a negative coating layer coated on the surface of the graphite body particles. The graphite body particles include secondary particles, and the negative coating layer includes carbon element with a mass content of 2.5%. The graphite body particles are artificial graphite.

[0395] The second negative film layer is a film layer formed by uniformly coating the first negative electrode slurry (solvent is water) on the surface of the first negative film layer, followed by drying and cold pressing. The second negative film layer includes graphite particles, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 96.5:0.5:2:1. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include graphite body particles and a negative coating layer coated on the surface of the graphite body particles. The graphite body particles include secondary particles, and the negative coating layer includes carbon element with a mass content of 2.5%. The graphite body particles are artificial graphite.

[0396] The thickness ratio of the first negative film layer to the second negative film layer is 1:1. The mass content of silicon element in the negative film layer is 0.84%.

[0397] The single-sided coating weight of the negative film layer is 130 mg / 1540.25 mm 2 。

[0398] 3. Separator

[0399] The separator includes a base film and functional layers provided on both sides of the base film. The base film includes 7 μm polyethylene PE, and the porosity of the separator is 42%.

[0400] The functional layer includes a first functional layer and a second functional layer. The first functional layer is a film layer formed by coating alumina particles and a binder polyvinylidene fluoride on one side of a base film, with a thickness of 1 μm and an average particle size of the alumina particles of 10 nm.

[0401] The second functional layer is a film layer formed by coating composite particles composed of polyacrylate and silica particles dispersed on the polyacrylate on the other side of the base film, with a thickness of 1 μm and an average particle size of the silica particles of 10 nm.

[0402] 4. Preparation of electrolyte

[0403] The electrolyte includes an organic solvent, an electrolyte lithium salt, and an additive.

[0404] After mixing the components of each organic solvent, the electrolyte lithium salt and the additive are added to prepare the electrolyte.

[0405] The organic solvent includes ethylene carbonate EC with a mass content of 27.3%, ethyl acetate with a mass content of 22%, methyl acetate with a mass content of 19.7%, and dimethyl carbonate DMC with a mass content of 6.7%. The mass ratio of each component in the solvent is calculated based on the total mass of the electrolyte;

[0406] Based on the total mass of the electrolyte, the additive includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluorooxalate borate LiDFOB with a mass ratio of 4:2.5:2:0.8;

[0407] The electrolyte lithium salt includes lithium hexafluorophosphate LiPF6 with a mass content of 15%.

[0408] 5. Preparation of battery cell

[0409] The above positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining a stacked electrode assembly. The electrode assembly is placed in a housing, and positive and negative terminals are provided on the housing. After baking, the electrolyte is injected, and through processes such as vacuum packaging, standing, forming, and shaping, a battery cell is obtained.

[0410] The liquid injection coefficient of the battery cell is 2.5 g / Ah.

[0411] The compaction density of the positive electrode film layer of the battery cell at 100% SOC is 2.75 / cm 3 and the compaction density of the negative electrode film layer at 100% SOC is 1.25 g / cm 3 .

[0412] The housing includes an aluminum shell with a cuboid structure. The thickness of the large surface shell of the battery cell is 0.3 mm, and the large surface shell of the battery cell refers to the thickness of the first side wall of the shell.

[0413] Among them, the size of the positive electrode film layer in the length direction of the battery cell is 630 mm, and OH1 is 4 mm;

[0414] The size of the positive electrode film layer in the width direction of the battery cell is 95 mm, and OH2 is 3 mm.

[0415] The energy density of the battery cell is 453 Wh / L.

[0416] Examples 2-1 and 2-2

[0417] The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, the components and mass contents of the solvent were adjusted.

[0418] Examples 3-1 to 3-3

[0419] The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, the mass content of vinylene carbonate was adjusted, and with the change of the mass content of vinylene carbonate, the mass content of dimethyl carbonate was synchronously adjusted.

[0420] Examples 4-1 and 4-2

[0421] The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, the mass content of fluoroethylene carbonate was adjusted, and with the change of the mass content of fluoroethylene carbonate, the mass content of dimethyl carbonate was synchronously adjusted.

[0422] Example 5

[0423] The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, the types of cyclic carbonate additives were adjusted.

[0424] Comparative Examples 1-1 and 1-2

[0425] The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, the components and mass contents of the solvent were adjusted.

[0426] Comparative Examples 2-1 to 2-3

[0427] The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, the mass contents of vinylene carbonate and fluoroethylene carbonate were adjusted, and with the change of the mass contents of vinylene carbonate and fluoroethylene carbonate, the mass content of dimethyl carbonate was synchronously adjusted.

[0428] Performance Test

[0429] 1. The volume energy density of the battery cell

[0430] The battery cells of the examples and comparative examples were placed at 25°C and charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V to 0.05C, and left standing for 30 min; discharged at a constant current of 0.33C to 2.0V, and the discharge capacity A0 at this time was recorded, unit: Ah; the length, width, and height of the battery cell were measured using a caliper, and the volume V0 of the battery cell was calculated, unit: L; the volume energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0431] 2. Cycling performance of the battery cell

[0432] At 60°C, the battery cell was charged at a constant current of 0.8C to the charge cut-off voltage of 3.6V, then charged at a constant current of 0.1C to the charge cut-off voltage of 3.65V, and left standing for 30 min; discharged at a constant current of 1C to 3.1V, and left standing for 30 min. This was one charge-discharge cycle, and the above charge-discharge cycle steps were repeated until the cycle capacity retention rate (i.e., Cn / C0 × 100%) was 70%, and the number of cycle turns was recorded. The more cycle turns, the better the cycling performance of the battery cell.

[0433] The test results are shown in Table 1.

[0434] Table 1

[0435]

[0436] In Table 1,

[0437] Ethyl acetate 22 means that the mass content of ethyl acetate in the electrolyte is 22%;

[0438] Methyl acetate 19.7 means that the mass content of methyl acetate in the electrolyte is 19.7%;

[0439] Methyl acetate 13.7 means that the mass content of methyl acetate in the electrolyte is 13.7%;

[0440] Methyl acetate 3.7 means that the mass content of methyl acetate in the electrolyte is 3.7%.

[0441] The addition amount of ethylene carbonate EC in Comparative Example 1-1 was too low, and the SEI film formed on the negative electrode side could not provide good protection for the negative electrode active material, and the side reactions on the negative electrode side were relatively intense, especially the side reactions at high temperatures were more intense, deteriorating the high-temperature cycling performance of the battery cell.

[0442] The addition amount of ethylene carbonate EC in Comparative Example 1-2 was too high, resulting in too high viscosity of the electrolyte, which was not conducive to uniformly wetting the negative electrode plate, increasing the risk of lithium layer separation in the negative electrode film, and shortening the cycle life of the battery cell.

[0443] In the embodiments of the present application, the mass content of ethylene carbonate is set within a reasonable range. For example, the mass contents in Embodiment 1, Embodiment 2-1, and Embodiment 2 are 20% to 40%. On the one hand, ethylene carbonate can participate in the film-forming reaction of the SEI film on the negative electrode side with cyclic carbonate additives, effectively relieve the volume expansion on the negative electrode side, and effectively relieve the side reactions on the negative electrode side, improving the cycle performance of the battery cell. On the other hand, it makes the viscosity of the electrolyte not too high, which is beneficial to uniformly wet the negative electrode plate, reduces the risk of lithium deposition on the surface of the negative electrode film layer, and improves the cycle performance of the battery cell.

[0444] In Comparative Example 2-1 and Comparative Example 2-2, the mass content of the cyclic carbonate additive is too low, and the SEI film formed on the negative electrode side cannot play a good protective role for the negative electrode active material, and the side reactions on the negative electrode side are relatively intense, especially the side reactions at high temperatures are more intense, deteriorating the high-temperature cycle performance of the battery cell.

[0445] In Comparative Example 2-3, the mass content of the cyclic carbonate additive is too high, resulting in too high impedance of the SEI film, which is not conducive to the rapid charging of the battery cell. At the same current density, the risk of lithium deposition on the negative electrode film layer increases, shortening the cycle life of the battery cell.

[0446] In Embodiment 3-1 to Embodiment 3-3, the mass content of vinylene carbonate is adjusted so that the mass content of the cyclic carbonate additive is within an appropriate range, which can participate in the film-forming reaction of the SEI film on the negative electrode side synergistically with ethylene carbonate, effectively relieve the volume expansion on the negative electrode side, and effectively relieve the side reactions on the negative electrode side, improving the cycle performance of the battery cell.

[0447] In Embodiment 4-1 to Embodiment 4-3, the mass content of fluoroethylene carbonate is adjusted so that the mass content of fluoroethylene carbonate is within an appropriate range, which can participate in the film-forming reaction of the SEI film on the negative electrode side synergistically with ethylene carbonate, effectively relieve the volume expansion on the negative electrode side, and effectively relieve the side reactions on the negative electrode side, improving the cycle performance of the battery cell. The high-temperature stability of fluoroethylene carbonate is poor. As the mass content of fluoroethylene carbonate increases, partial decomposition of fluoroethylene carbonate may occur, which may reduce the protective effect on the negative electrode side to a certain extent.

[0448] Using ethylene carbonate derivatives of different materials, such as fluoroethylene carbonate and difluoroethylene carbonate, can effectively improve the high-temperature cycle performance of the battery cell.

[0449] Embodiment 6-1 and Embodiment 6-2

[0450] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the mass content of the sulfur-containing additive was adjusted, and with the adjustment of the mass content of the sulfur-containing additive, the mass content of dimethyl carbonate was synchronously adjusted.

[0451] Examples 6-3 and 6-4

[0452] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the mass content of the lithium salt additive was adjusted, and with the adjustment of the mass content of the lithium salt additive, the mass content of dimethyl carbonate was synchronously adjusted.

[0453] The test results are shown in Table 2.

[0454] Table 2

[0455]

[0456] As can be seen from Table 2,

[0457] In Examples 6-1 and 6-2, the mass content of the sulfur-containing additive was adjusted, and the mass content of the sulfur-containing additive was 0.5% to 2.0%, which could further optimize the components of the SEI film, enhance the protection effect on the negative electrode side and relieve the expansion of the silicon-based material, and improve the high-temperature cycle performance of the battery monomer.

[0458] In Examples 6-3 and 6-4, the mass content of the lithium salt additive was adjusted, and the mass content of the lithium salt additive was 0.2% to 1.0%, which could further optimize the components of the SEI film, enhance the protection effect on the negative electrode side and relieve the expansion of the silicon-based material, and improve the high-temperature cycle performance of the battery monomer.

[0459] Examples 7-1 to 7-3

[0460] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the mass content of silicon element in the negative electrode film layer was adjusted.

[0461] Example 8

[0462] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the type of silicon-based material was adjusted.

[0463] Example 9

[0464] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the preparation process of the negative electrode plate was adjusted, and the negative electrode film layer adopted a single-layer film layer. Specifically:

[0465] The negative electrode film layer includes a negative electrode film layer, and the negative electrode film layer is located on the surface of the negative electrode conductive layer;

[0466] The negative electrode film layer is a film layer formed by uniformly coating a negative electrode slurry (with water as the solvent) on the surface of the positive electrode conductive layer and then drying and cold pressing. The first negative electrode film layer includes graphite particles, silicon carbide material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 95.75:1.75:0.5:1:1. The silicon carbide material is silicon carbide, and the mass content of silicon element in the silicon carbide material is 48%.

[0467] Example 10

[0468] A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the preparation process of the negative electrode plate was adjusted, specifically the distribution position of the silicon-based material was adjusted. The silicon-based material is located in the first negative electrode film layer and the second negative electrode film layer. Specifically:

[0469] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer;

[0470] The first negative electrode film layer is a film layer formed by uniformly coating a first negative electrode slurry (with water as the solvent) on the surface of the positive electrode conductive layer and then drying and cold pressing. The first negative electrode film layer includes graphite particles, silicon carbide material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 95.75:1.75:0.5:1:1. The silicon carbide material is silicon carbide, and the mass content of silicon element in the silicon carbide material is 48%;

[0471] The second negative electrode film layer is a film layer formed by uniformly coating the first negative electrode slurry (with water as the solvent) on the surface of the first negative electrode film layer and then drying and cold pressing. The second negative electrode film layer includes graphite particles, conductive agent acetylene black, binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 95.75:1.75:0.5:1:1.

[0472] Example 11

[0473] A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the preparation process of the negative electrode plate was adjusted, specifically the distribution position of the silicon-based material was adjusted. The silicon-based material is located in the second negative electrode film layer. Specifically:

[0474] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer;

[0475] The first negative electrode film layer is a film layer formed by uniformly coating the surface of the positive electrode conductive layer with the first negative electrode paste (the solvent is water), followed by drying and cold pressing. The first negative electrode film layer includes graphite particles, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 96.5:0.5:2:1.

[0476] The second negative electrode film layer is a film layer formed by uniformly coating the surface of the first negative electrode film layer with the first negative electrode paste (the solvent is water), followed by drying and cold pressing. The second negative electrode film layer includes 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-carbon material is silicon carbide, and the mass content of silicon element in the silicon-carbon material is 48%.

[0477] The test results are shown in Table 3.

[0478] Table 3

[0479]

[0480] In Table 3,

[0481] Compared with Comparative Example 3-1, in the embodiment of the present application, introducing a silicon-based material into the negative electrode film layer can significantly improve the energy density of the battery cell; however, if the addition amount of the silicon-based material is too much, such as Comparative Example 3-2, although the energy density of the battery cell is high, the volume expansion of the silicon-based material is excessive, deteriorating the cycle performance.

[0482] In Embodiment 1, Embodiments 7-1 to 7-3 of the present application, the mass content of silicon element of the silicon-based material in the negative electrode film layer is appropriate, such as 0.5% to 5.00%, and can be selected as 0.8% to 3%. This enables the battery cell to have a relatively high energy density, and at a high energy density, through the synergistic effect of ethylene carbonate and cyclic carbonate additives in the electrolyte, the volume expansion of the silicon-based material can be effectively alleviated, improving the cycle performance of the battery cell.

[0483] The silicon-based material has various distribution forms, such as in Embodiment 1, Embodiment 9, Embodiment 10, and Embodiment 11, etc. Compared with other embodiments, in Embodiment 1, the silicon-based material is disposed in the first negative electrode film layer, so that the entire second negative electrode film layer can play a certain inhibitory role in the volume expansion of the first negative electrode film layer, reducing the overall volume expansion of the negative electrode film layer and effectively improving the cycle performance of the battery cell.

[0484] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as a limitation of the present application, and changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principle, and scope of the present application.

Claims

1. A battery cell, characterized in that, It includes an electrode assembly and an electrolyte, wherein the electrode assembly includes a positive electrode sheet and a negative electrode sheet; The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, wherein the positive electrode film layer includes a lithium-containing phosphate; The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector, wherein the negative electrode film layer includes a carbon-based material and a silicon-based material; The electrolyte includes ethylene carbonate and a cyclic carbonate additive, wherein the cyclic carbonate additive includes one or more of vinylene carbonate and ethylene carbonate derivatives. in, The mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.5% to 5%; The mass content of the ethylene carbonate in the electrolyte is 20% to 40%; The mass content of the cyclic carbonate additive in the electrolyte is 2% to 8%.

2. The battery cell according to claim 1, characterized in that, The mass content of the ethylene carbonate in the electrolyte is 20% to 35%.

3. The battery cell according to claim 1 or 2, characterized in that, The mass content of the vinylene carbonate in the electrolyte is 1.5% to 5%.

4. The battery cell according to any one of claims 1 to 2, characterized in that, The mass content of the ethylene carbonate derivative in the electrolyte is 0 to 4%.

5. The battery cell according to claim 4, wherein, The mass content of the ethylene carbonate derivative in the electrolyte is 1.5% to 3.5%.

6. The battery cell according to any one of claims 1 to 2, characterized in that, The ethylene carbonate derivatives include compounds shown in formula A, Formula A, In Formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and at least one of Q1, Q2, Q3, Q4 includes a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

7. The battery cell according to claim 6, characterized in that, At least one of Q1, Q2, Q3, and Q4 includes a halogen atom, or a C1 to C5 halogenated alkyl group.

8. The battery cell according to any one of claims 1 to 2, characterized in that, The ethylene carbonate derivatives include one or more compounds represented by formula A-1 to formula A-3. 。 9. The battery cell according to any one of claims 1 to 2, characterized in that, The electrolyte further includes a linear ester solvent, which includes one or more of a linear carboxylate solvent and a linear carbonate solvent. The mass content of the linear ester solvent in the electrolyte is 45% to 65%.

10. The battery cell according to claim 9, wherein The linear carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

11. The battery cell according to claim 9, wherein, The linear carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-12, 。 12. The battery cell according to claim 9, characterized in that, The linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

13. The battery cell according to claim 9, characterized in that The linear ester solvent includes a linear carbonate solvent; The mass content of the cyclic carbonate additive is 2% to 5%.

14. The battery cell according to claim 9, characterized in that The linear ester solvents include linear carboxylate solvents with a mass content greater than 0 and linear carbonate solvents with a mass content greater than or equal to 0; The mass content of the cyclic carbonate additive is 3.5% to 8%.

15. The battery cell according to any one of claims 1 to 2, characterized in that, The electrolyte includes an electrolyte lithium salt, and the mass content of the electrolyte lithium salt in the electrolyte is 10% to 18%.

16. The battery cell according to claim 15, wherein The electrolyte lithium salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium hexafluorophosphate LiPF6.

17. The battery cell according to claim 16, wherein, The mass content of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is 4% to 6%.

18. The battery cell according to any one of claims 1 to 2, characterized in that the electrolyte further includes a sulfur-containing additive with a mass content of 0 to 2% in the electrolyte, and the sulfur-containing additive includes one or more of vinylene sulfate, divinylene sulfate, 1,3-propane sultone, butylene sulfite, ethylene sulfite, methylene methanedisulfonate; and / or the electrolyte further includes a lithium salt additive with a mass content of 0 to 1% in the electrolyte, and the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium bis(oxalato)borate.

19. The battery cell according to claim 18, characterized in that the mass content of the sulfur-containing additive in the electrolyte is 0.5% to 2%; and / or the mass content of the lithium salt additive in the electrolyte is 0.2% to 1%.

20. The battery cell according to any one of claims 1 to 2, characterized in that, The mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.8% to 3%.

21. The battery cell according to any one of claims 1 to 2, characterized in that, The silicon-based material includes one or more of elemental silicon, silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

22. The battery cell according to claim 21, wherein The silicon-based material includes one or more of silicon-carbon material, silicon-oxygen material, and silicon-nitrogen material.

23. The battery cell according to claim 22, characterized in that, The silicon-based material includes silicon-carbon material.

24. The battery cell according to claim 22 or 23, characterized in that based on the mass of the silicon-based material, the mass content of the silicon element is 40% to 80%; and / or the volume average particle size Dv50 of the silicon-based material is 5.0 μm to 12.5 μm; and / or The specific surface area of the silicon-based material is 3.1 m 2 / g to 3.6 m 2 / g; and / or The powder compaction density of the silicon-based material under 25,000 N is 0.7 g / cm 3 to 1.2 g / cm 3 .

25. The battery cell according to any one of claims 1 to 2, characterized in that, the carbon-based material includes graphite particles, the graphite particles include graphite body particles and a negative electrode coating layer coated on the surface of the graphite body particles, the graphite body particles include secondary particles, and the negative electrode coating layer includes carbon element.

26. The battery cell according to claim 25, wherein The graphite body particles include one or more of artificial graphite and natural graphite.

27. The battery cell according to claim 25, characterized in that, Based on the mass of the graphite particles, the mass content of the carbon element in the negative electrode coating layer is 2% to 5%.

28. The battery cell according to any one of claims 1 to 2, characterized in that The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector, and the second negative electrode film layer is disposed on the side of the first negative electrode film layer away from the negative electrode current collector. The volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer. Wherein, at least one of the first negative electrode film layer and the second negative electrode film layer includes a silicon-based material.

29. The battery cell according to claim 28, wherein The volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer is 8.5 μm to 14.5 μm; and / or The volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer is 9.8 μm to 16.8 μm.

30. The battery cell according to claim 28, wherein, The silicon-based material is located in the first negative electrode film layer.

31. The battery cell according to any one of claims 1 to 2, characterized in that, When the battery cell is in a 100% charged state, the compaction density of the negative electrode film layer is 1.10 g / cm 3 to 1.50 g / cm 3 .

32. The battery cell according to any one of claims 1 to 2, characterized in that, The single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 .

33. The battery cell according to any one of claims 1 to 2, characterized in that, The thickness of the negative current collector is 4 μm to 6 μm.

34. The battery cell according to any one of claims 1 to 2, characterized in that, The negative electrode sheet further includes a negative conductive layer, the negative conductive layer is located between the negative current collector and the negative film layer, the negative conductive layer includes a negative conductive agent, and the negative 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.

35. The battery cell according to claim 34, wherein, The thickness of the negative conductive layer is 0.5 μm to 2 μm.

36. The battery cell according to any one of claims 1 to 2, characterized in that, The lithium-containing phosphate includes: phosphate particles, and a positive electrode coating layer, the positive electrode coating layer is located on at least a part of the surface of the phosphate particles, and the positive electrode coating layer contains carbon elements.

37. The battery cell according to claim 36, wherein Based on the mass of the lithium-containing phosphate, the mass content of the carbon element is 0.8% to 2.3%.

38. The battery cell according to claim 36, wherein, The positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

39. The battery cell according to claim 36, wherein, The phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

40. The battery cell according to any one of claims 1 to 2, characterized in that, The lithium-containing phosphate includes a material having a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 wherein Wherein, 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ 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, Hf, Ge, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

41. The battery cell according to any one of claims 1 to 2, characterized in that, The positive electrode film layer includes a positive electrode active material, and the powder compaction density of the positive electrode active material is 2.46 g / cm 3 to 2.85 g / cm 3 .

42. The battery cell according to any one of claims 1 to 2, characterized in that, When the battery cell is in a 100% SOC state of charge, the tap density of the positive electrode film layer is 2.5 g / cm 3 to 2.8 g / cm 3 .

43. The battery cell according to any one of claims 1 to 2, characterized in that, The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 350 mg / 1540.25 mm 2 .

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

45. The battery cell according to any one of claims 1 to 2, characterized in that, The positive electrode sheet further includes a positive conductive layer, the positive conductive layer is located between the positive current collector and the positive film layer, the positive conductive layer includes a positive conductive agent, and the positive 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.

46. The battery cell according to claim 45, characterized in that, The thickness of the positive conductive layer is 0.5 μm to 2 μm.

47. The battery cell according to any one of claims 1 to 2, characterized in that, The electrode assembly further includes a separator, the separator is located between the positive electrode sheet and the negative electrode sheet, and the thickness of the separator is 4 μm to 12 μm.

48. The battery cell according to claim 47, characterized in that, The porosity of the separator is 20% to 70%.

49. The battery cell according to claim 47, wherein, The separator further includes a base film and a functional layer provided on the base film, and the functional layer includes: a first functional layer, located on one side of the base film, and the first functional layer includes first inorganic particles, a second functional layer, located on the other side of the base film, and the second functional layer includes composite particles, the composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

50. The battery cell according to claim 49, characterized in that, The non-fluoropolymer particles include acrylate copolymers.

51. The battery cell according to claim 49 or 50, characterized in that, The first inorganic particles 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; and / or The average particle size of the first inorganic particles is 5 nm to 100 nm.

52. The battery cell according to any one of claims 49 to 50, characterized in that, The second inorganic particles 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, and / or The average particle size of the second inorganic particles is 5 nm to 100 nm.

53. The battery cell according to any one of claims 1 to 2, characterized in that, The positive electrode sheet and the negative electrode sheet are stacked along the thickness direction of the battery cell; The electrode assembly further includes a positive electrode tab and a negative electrode tab. The positive electrode tab is connected to at least one side of the positive electrode current collector along the length direction of the battery cell, and the negative electrode tab is connected to at least one side of the negative electrode current collector along the length direction of the battery cell; Along the length direction of the battery cell, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH1; Along the width direction of the battery cell, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH2, wherein, OH1 is greater than OH2.

54. The battery cell according to claim 53, wherein, OH1 is 1 mm to 4 mm; and / or OH2 is 1 mm to 3 mm.

55. The battery cell according to claim 53, characterized in that, The positive electrode tab and the negative electrode tab are arranged at the same end along the length direction of the electrode assembly; and / or The positive electrode tab and the negative electrode tab are respectively arranged at both ends of the electrode assembly along the length direction.

56. The battery cell according to any one of claims 1 to 2, characterized in that, The battery cell includes a housing, the housing accommodates the electrode assembly and the electrolyte, the housing is a cuboid structure, the housing includes two first side walls arranged opposite to each other and two second side walls arranged opposite to each other, the two first side walls are connected by the second side walls, the cross-sectional area of the first side wall perpendicular to its own thickness direction is larger than the cross-sectional area of the second side wall perpendicular to its own thickness direction, and the thickness of the first side wall is 0.1 mm to 0.5 mm.

57. The battery cell according to claim 56, wherein The thickness of the first side wall is 0.2 mm to 0.35 mm.

58. The battery cell according to any one of claims 1 to 2, characterized in that, The volume energy density of the battery cell is 450 Wh / L to 530 Wh / L.

59. A battery device, characterized in that, Including the battery cell according to any one of claims 1 to 58.

60. An electrical device, characterized in that, Including the battery device according to claim 59.

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