Battery monomer, battery device and electric device

Abstract

The invention discloses a battery monomer, a battery device and a power utilization device. A positive active material of a positive pole piece of the battery monomer comprises lithium-containing phosphate with an olivine structure, and the single-side coating weight of a positive film layer is 180mg / 1540.25 mm < 2 > to 380mg / 1540.25 mm < 2 >; the negative pole piece comprises a negative pole film layer, the negative pole film layer comprises a negative pole active material, the negative pole active material comprises a silicon-based material, and based on the mass of the negative pole active material, the mass content of the silicon element is 0.3%-10.0%; the electrolyte comprises a first additive, the first additive comprises at least one of vinylene carbonate and an ethylene carbonate derivative, the mass content of the first additive is 1%-12% based on the total mass of the electrolyte, and the compaction density of the positive electrode film layer is 2.50 g / cm < 3 >-2.80 g / cm < 3 > when the battery monomer is in a 100% state of charge.

Description

[0001] This application claims the priority of PCT International Application PCT / CN2024 / 125833 entitled "Battery and Electrical Device" filed on October 18, 2024, 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] Lithium-ion batteries have characteristics such as high capacity and long life, and are thus widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, and power tools, etc. With the development of the application fields of lithium-ion batteries, higher requirements are put forward for the performance of lithium-ion batteries, such as fast charging performance, energy density, etc. Summary of the Invention

[0004] In view of the above problems, this application provides a battery cell, a battery device, and an electrical device, which can not only improve the energy density of the battery cell, but also take into account good cycle performance and fast charging performance (hereinafter referred to as fast charge performance).

[0005] In a first aspect, this application provides a battery cell, including an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab, a negative electrode tab, and a separator. The separator is located between the positive electrode tab and the negative electrode tab. The positive electrode tab 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 with an olivine structure. The single-sided coating weight of the positive electrode film layer is 180 mg / 1540.25 mm 2 ~380 mg / 1540.25 mm 2 ; The negative electrode tab 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 silicon-based material. Based on the mass of the negative electrode active material, the mass content of silicon element is 0.3% - 10.0%; The electrolyte includes a first additive. The first additive includes at least one of vinylene carbonate and ethylene carbonate derivatives. Based on the total mass of the electrolyte, the mass content of the first additive is 1% - 12%. Among them, the ethylene carbonate derivative includes a compound represented by Formula I. Formula I R 1 、R 2 、R 3 、R4 Each independently includes any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a haloalkyl group having 1 to 5 carbon atoms, and R 1 , R 2 , R 3 , R 4 are not simultaneously hydrogen atoms.

[0006] In the present application, the positive electrode active material of the battery cell includes a lithium-containing phosphate having an olivine structure, which has excellent structural stability. By matching the positive electrode film layer with a high coating weight with the negative electrode film layer containing a certain amount of silicon element, while ensuring an increase in the energy density of the battery cell, the fast charging performance of the battery cell can be effectively improved; at the same time, the electrolyte of the battery cell contains a first additive of vinylene carbonate and / or a vinylene carbonate derivative, and the mass content of the first additive is controlled within a suitable range, which can form a SEI film with a moderate thickness, enhanced flexibility and stability at the silicon-containing negative electrode interface, ensuring that the silicon-containing negative electrode interface has both good stability and low impedance, thereby enabling the battery cell to have both a high energy density, excellent fast charging performance and good cycle performance.

[0007] In summary, in the present application, by synergistically controlling the single-sided coating weight of the positive electrode film layer, the mass content of silicon element in the negative electrode active material, the positive electrode active material including a lithium-containing phosphate having an olivine structure, and the type and mass content of additives in the electrolyte within a suitable range, the fast charging performance, cycle performance and energy density of the battery cell can be balanced.

[0008] In any embodiment, based on the mass of the negative electrode active material, the mass content of silicon element is 0.3% to 6.0%.

[0009] When the mass content of silicon element in the silicon-based material is within a suitable range, while increasing the energy density of the battery cell, it can also reduce the influence of excessive silicon element on the cycle performance of the battery cell, and balance the energy density and cycle performance of the battery cell.

[0010] In any embodiment, at least one of R 1 , R 2 , R 3 , R 4 contains a fluorine atom.

[0011] R 1 , R 2 , R 3 , R 4 Vinylene carbonate derivatives in which at least one of them is a fluorine atom are prone to ring opening and form a SEI film containing more organic substances on the negative electrode surface, which is beneficial to improving the flexibility of the overall SEI film, achieving the purpose of improving the stability of the SEI film and the negative electrode interface during the cycle, and improving the cycle performance of the battery cell. In any embodiment, the ethylene carbonate derivative includes one or more of fluorinated ethylene carbonate, difluoroethylene carbonate, and trifluoromethyl ethylene carbonate.

[0012] A suitable ethylene carbonate derivative additive can form an SEI film containing more organic substances on the negative electrode side, which is beneficial to improving the flexibility of the overall SEI film, achieving the purpose of improving the stability of the interface between the SEI film and the negative electrode during the cycling process, improving the cycling performance of the battery cell. At the same time, the SEI film formed by the participation of fluorinated ethylene carbonate, difluoroethylene carbonate, and trifluoromethyl ethylene carbonate has a low impedance, which is also beneficial to improving the fast charging performance of the battery cell.

[0013] In any embodiment, the battery cell satisfies the following relationship: 0.025 ≤ A / B ≤ 6, and preferably 0.035 ≤ A / B ≤ 2.5, where A is the mass content of silicon element, based on the mass of the negative electrode active material; B is the mass content of the first additive, based on the total mass of the electrolyte.

[0014] When the ratio of the mass content of silicon element in the negative electrode active material to the mass content of the first additive in the electrolyte is within a suitable range, through the synergistic effect of silicon element and the first additive in the negative electrode, it is possible to improve the energy density of the battery cell while also taking into account the cycling performance of the battery cell.

[0015] In any embodiment, based on the mass of the negative electrode active material, the mass content of silicon element in the negative electrode active material is 0.3% - 3%; Based on the total mass of the electrolyte, the mass content of the first additive is 2% - 7.5%.

[0016] In a system with a relatively low silicon element content, the damage to the SEI film during the cycling process of the battery cell is relatively small. By controlling the mass content of the first additive within a suitable range to form an SEI film with a suitable thickness, while improving the stability of the interface between the SEI film and the negative electrode and the cycling performance of the battery cell, it is also possible to achieve a low impedance at the negative electrode interface, which is beneficial to improving the fast charging performance of the battery cell, and is more suitable for use scenarios with higher requirements for the cycling performance and fast charging performance of the battery cell.

[0017] In any embodiment, based on the mass of the negative electrode active material, the mass content of silicon element in the negative electrode active material is greater than 3% and less than or equal to 6%; Based on the total mass of the electrolyte, the mass content of the first additive is 3% - 10%.

[0018] In a system with a relatively high silicon element content, the damage to the SEI film during the cycling of the battery cell is relatively severe. By controlling the mass content of the first additive within a suitable range, an SEI film with a suitable thickness is formed, achieving the purpose of improving the stability of the SEI film and the negative electrode interface and enhancing the cycling performance of the battery cell, which is more suitable for usage scenarios with higher requirements for the cycling performance and energy density of the battery cell.

[0019] In any embodiment, the lithium-containing phosphate with an olivine structure includes: a lithium-containing phosphate matrix, and a coating layer located on at least a part of the surface of the lithium-containing phosphate matrix, and the coating layer contains carbon elements. The lithium-containing phosphate with an olivine structure including a carbon coating layer can improve the electrical conductivity of the material, which is beneficial to enhancing the fast charging performance of the battery cell.

[0020] In any embodiment, based on the mass of the lithium-containing phosphate with an olivine structure, the mass content of carbon elements is 0.8% - 2.3%.

[0021] By controlling the mass content of carbon elements in the coating layer within a suitable range, while improving the electrical conductivity of the material and the fast charging performance of the battery, the specific capacity of the material can also be taken into account, taking into account both the fast charging performance and the energy density of the battery cell.

[0022] In any embodiment, the battery cell satisfies the following relationship: 0.08 ≤ C / B ≤ 1.15, wherein, C is the mass content of carbon elements, based on the mass of the lithium-containing phosphate with an olivine structure; B is the mass content of the first additive, based on the total mass of the electrolyte.

[0023] By controlling the mass content of carbon elements in the lithium-containing phosphate with an olivine structure and the mass content of the first additive in the electrolyte within a suitable range, it is possible to improve the electrical conductivity of the material, enhance the fast charging performance of the battery cell, and at the same time improve the cycling stability of the material and the cycling performance of the battery cell.

[0024] In any embodiment, the coating layer further includes Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 substance, wherein, 0 ≤ d1 ≤ 1, 3 ≤ m1 ≤ 5, 2 ≤ n1 ≤ 4; M3 includes one or more of Ti, Zr, Hf, Ge, Sn, and optionally, M3 is +4 valent.

[0025] The coating layer includes Li 3-d1 Fe 2-d1 M3d1 (PO m1 ) n1 A substance that has excellent ionic conductivity, can significantly improve the transport rate of lithium ions deintercalation / insertion in the material, enhance the ionic conductivity of the overall material, and is beneficial to improving the fast charging performance of the battery.

[0026] In any embodiment, the lithium-containing phosphate matrix includes a compound 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, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; where A includes at least one of Na, K, and Mg; Me includes at least one of Mn, Fe, Co, and Ni; M includes at least one of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes at least one of S, Si, Cl, B, C, N, and P; Y includes at least one of O and F.

[0027] In any embodiment, the lithium-containing phosphate matrix includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, and modified forms of any one of the foregoing substances, where the modified forms include one or more of doping modification and coating modification.

[0028] In any embodiment, the powder compaction density of the positive electrode active material under 30000N is 2.43 g / cm 3 ~2.85 g / cm 3 , and can be optionally 2.48 g / cm 3 ~2.80 g / cm 3 .

[0029] When the powder compaction density of the positive electrode active material under 30000N is within the above range, it can improve the energy density of the battery cell, 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 sheet and is also beneficial to improving the fast charging performance of the battery cell.

[0030] In any embodiment, when the battery cell is in a 100% state of charge, the tap density of the positive electrode film layer is 2.50 g / cm 3 ~2.80 g / cm 3 .

[0031] When the tap density of the positive electrode film layer is within a suitable range, the battery cell has a high energy density.

[0032] In any embodiment, the negative electrode active material includes a carbon-based material, and the carbon-based material includes graphite.

[0033] Graphite has good electrical conductivity and cycle stability, which is beneficial to improving the fast charging performance and cycle performance of the battery cell.

[0034] In any embodiment, the graphite includes composite graphite particles, the composite graphite particles include graphite body particles and a carbon coating layer coated on the surface of the graphite body particles, the graphite body particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0035] The secondary particles have excellent ion transport performance, which is beneficial to the insertion and extraction of lithium ions and to improving the ionic conductivity of the material. In addition, the carbon coating layer includes amorphous carbon, which can improve the electrical conductivity of the composite graphite particles. The secondary particles in the core and the coating layer of amorphous carbon jointly improve the electron conduction performance and ion conduction performance of the material, which helps to improve the fast charging performance of the battery cell.

[0036] In any embodiment, the composite graphite particles satisfy at least one of the following conditions: (1) Based on the total mass of the composite graphite particles, the mass content of amorphous carbon is 2% - 5%; (2) The powder resistivity of the composite graphite particles is 0.005 Ω•cm - 0.04 Ω•cm.

[0037] Controlling the mass content of amorphous carbon in the composite graphite particles within a suitable range can improve the electrical conductivity of the material and the fast charging performance of the battery.

[0038] The powder resistivity of the composite graphite particles is small, and the composite graphite particles have excellent electrical conductivity, which is beneficial to improving the fast charging performance of the battery cell.

[0039] In any embodiment, there are a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed between the current collector and the second negative electrode film layer, and both the first negative electrode film layer and the second negative electrode film layer include the composite graphite particles.

[0040] In any embodiment, the volume average particle diameter Dv50 of the composite graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle diameter Dv50 of the composite graphite particles in the second negative electrode film layer.

[0041] During the fast charging process of the battery cell, the overpotential of the second negative electrode film layer away from the current collector is usually higher. The bottleneck in the negative electrode film layer that affects the fast charging performance of the battery cell mainly lies in the second negative electrode film layer. The present application controls the particle size of the composite graphite particles in the second negative electrode film layer to be relatively smaller, which can shorten the transmission path of lithium ions, improve the lithium ion transmission performance of the second negative electrode film layer, and improve the fast charging performance of the battery cell.

[0042] In any embodiment, the volume average particle size Dv50 of the composite graphite particles in the first negative electrode film layer is 8.5 μm to 14.8 μm, and / or, The volume average particle size Dv50 of the composite graphite particles in the second negative electrode film layer is 7.8 μm to 12.8 μm.

[0043] Controlling the particle size of the composite graphite particles in the first negative electrode film layer and / or the second negative electrode film layer within a suitable range can shorten the transmission path of lithium ions in the negative electrode film layer and improve the fast charging performance of the battery cell.

[0044] In any embodiment, based on the total thickness of the first negative electrode film layer and the second negative electrode film layer, the thickness of the second negative electrode film layer accounts for 30% to 70%.

[0045] The thickness ratio of the second negative electrode film layer is within an appropriate range, which can take into account the contribution of the second negative electrode film layer to the fast charging performance of the battery and the contribution of the first negative electrode film layer to the energy density of the battery, thereby obtaining a battery cell with excellent fast charging performance and high energy density.

[0046] In any embodiment, the negative electrode plate also includes a negative electrode conductive layer, which is located between the negative electrode current collector and the negative electrode film layer on at least one side, and the negative electrode conductive layer includes a conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0047] By providing a negative electrode conductive layer containing a conductive agent between the current collector and the negative electrode film layer, the conductivity of the negative electrode plate can be improved and the fast charging performance of the battery cell can be improved.

[0048] In any embodiment, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

[0049] By controlling the thickness of the negative electrode conductive layer within an appropriate range, both the fast charging performance and the energy density of the battery cell can be taken into account.

[0050] In any embodiment, the compaction density of the negative electrode film layer of the battery cell at 100% charge state is 1.15 g / cm 3 ~1.45g / cm 3 , and / or, The single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 ~135 mg / 1540.25 mm 2 .

[0051] When the single-sided coating weight or the compaction density of the negative electrode film layer is within a suitable range, it is beneficial to improve the fast charging performance of the battery cell.

[0052] In any embodiment, the electrolyte further includes an organic solvent, and the organic solvent includes one or more of a first organic solvent and a second organic solvent. Among them, the first organic solvent includes at least one of a cyclic carbonate and a linear carbonate, and may be selected as a cyclic carbonate. The second organic solvent includes R 5 -COO-R 6 , wherein, R5 includes any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R6 includes any one of an alkyl group having 1 to 5 carbon atoms and a halogenated alkyl group having 1 to 5 carbon atoms.

[0053] The first organic solvent of the cyclic carbonate and the linear carbonate has a relatively high dielectric constant and excellent ionic conductivity, which is beneficial to improving the conductivity of the electrolyte. The second organic solvent has a low viscosity, which is beneficial to improving the conductivity of the electrolyte. The electrolyte contains the first organic solvent and / or the second organic solvent, which is beneficial to improving the migration of lithium ions and improving the fast charging performance of the battery cell.

[0054] In any embodiment, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate; and / or The linear carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; and / or The second organic solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0055] In any embodiment, based on the total mass of the electrolyte, the mass content of the first organic solvent is 20% to 72%.

[0056] A suitable content of the first organic solvent of the cyclic carbonate and the linear carbonate can further improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions and improves the fast charging performance of the battery cell.

[0057] In any embodiment, the electrolyte further includes a second additive, and the second additive includes one or more of a sulfur-containing additive and a lithium salt additive.

[0058] Sulfur-containing additives and lithium salt additives can improve the interfacial film properties on the positive electrode side and / or the negative electrode side, improve the interfacial chemistry between the positive electrode and / or the negative electrode and the electrolyte, and enhance the fast charging performance and cycling performance of the battery.

[0059] In any embodiment, the sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate; and / or, The lithium salt additives include one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0060] In any embodiment, the electrolyte further includes a lithium salt, and the lithium salt includes one or two of fluorosulfonylimide salts and lithium hexafluorophosphate.

[0061] Fluorosulfonylimide salts and lithium hexafluorophosphate are easy to dissociate, which is beneficial to the rapid migration of lithium ions, beneficial to improving the fast charging performance of the battery monomer, and fluorosulfonylimide salts and lithium hexafluorophosphate are relatively stable in the electrolyte system, which can enhance the cycling performance of the battery monomer.

[0062] In any embodiment, the fluorosulfonylimide salt includes one or two of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

[0063] In any embodiment, the lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, and the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate is 0.2 to 1.0.

[0064] In any embodiment, the molar concentration of lithium bis(fluorosulfonyl)imide is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate is 0.5 mol / L to 1.2 mol / L.

[0065] In any embodiment, the separator satisfies at least one of the following conditions: (1) The thickness of the separator is 4 μm to 12 μm, and can be selected as 5 μm to 9 μm; (2) The porosity of the separator is 20% to 70%, and can be selected as 35% to 60%.

[0066] When the thickness of the separator is within a suitable range, the migration path of lithium ions in the separator is shorter, which can reduce the internal resistance of the battery monomer and improve the fast charging performance of the battery monomer.

[0067] When the porosity of the separator is within a suitable range, it can enhance the migration rate of lithium ions in the separator, reduce the internal resistance of the battery monomer, and improve the fast charging performance of the battery monomer.

[0068] In any implementation, the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 min to 10.5 min.

[0069] The battery cell has a fast charging speed and excellent fast charging performance.

[0070] In any implementation, the volumetric energy density of the battery cell is 395 Wh / L to 530 Wh / L.

[0071] In a second aspect, the present application provides a battery device including the battery cell of the first aspect.

[0072] In any implementation, the charging time of the battery device from 10% state of charge to 80% state of charge is 5 min to 10.5 min.

[0073] The battery device has a fast charging speed and excellent fast charging performance.

[0074] In a third aspect, the present application provides an electrical device including the battery device of the second aspect. Description of the Drawings

[0075] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the embodiments of the present application will be briefly introduced below. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on the drawings without creative efforts.

[0076] Figure 1 is a schematic diagram of a battery cell according to an embodiment of the present application; Figure 2 is Figure 1 an exploded view of the battery cell according to an embodiment of the present application shown in Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application; Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application; Figure 5 is Figure 4 an exploded view of the battery pack according to an embodiment of the present application shown in Figure 6 is a schematic diagram of an electrical device using the battery cell as a power source according to an embodiment of the present application.

[0077] Description of the Reference Numerals: 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed Embodiments

[0078] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0079] Hereinafter, the battery, the method for injecting electrolyte into the battery, the electrolyte and its preparation method, and the electrical device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where the detailed description of well-known matters and the repeated description of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0080] 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 range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0081] 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.

[0082] 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.

[0083] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0084] With the continuous expansion of the application fields of lithium-ion batteries, higher requirements are also put forward for their energy density and fast charging performance. In order to improve the energy density of the battery, generally, the coating surface density of the positive electrode film layer and the negative electrode film layer is increased. However, as the coating surface density of the positive electrode film layer and the negative electrode film layer increases, the migration path of lithium ions becomes longer, and the internal resistance of the battery is larger, affecting the fast charging performance of the battery. In particular, a high coating surface density of the negative electrode film layer will seriously affect the fast charging performance of the battery cell. It is very difficult to balance the energy density and fast charging performance of the battery cell only by adjusting the coating weights of the positive electrode and the negative electrode.

[0085] In view of the above problems, this application reasonably designs the system of the battery cell, achieving a balance between energy density and fast charging performance. Specifically, by reasonably matching the coating surface density of the positive electrode plate, the silicon content of the negative electrode material, and the additives in the electrolyte, while improving the energy density, the fast charging performance and cycle performance of the battery can also be balanced.

[0086] [Battery cell] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate and a separator. The separator is located between the positive electrode plate and the negative electrode plate. 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. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a lithium-containing phosphate with an olivine structure. The single-sided coating weight of the positive electrode film layer is 180 mg / 1540.25 mm 2 to 380 mg / 1540.25 mm 2 ; 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. The negative electrode film layer includes a negative electrode active material. The negative electrode active material includes a silicon-based material. Based on the mass of the negative electrode active material, the mass content of silicon element is 0.3% - 10.0%. The electrolyte includes a first additive, the first additive includes at least one of vinylene carbonate and ethylene carbonate derivatives, and based on the total mass of the electrolyte, the mass content of the first additive is 1% to 12%. Wherein, the ethylene carbonate derivative includes the compound shown in Formula I Formula I R 1 、R 2 、R 3 、R 4 each independently includes any one of a hydrogen atom, a halogen atom, an alkyl group with 1 to 5 carbon atoms, and a halogenated alkyl group with 1 to 5 carbon atoms, and R 1 、R 2 、R 3 、R 4 are not simultaneously hydrogen atoms.

[0087] In some embodiments, the single-sided coating weight of the positive electrode film layer is 180 mg / 1540.25 mm 2 ~380 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer is 180 mg / 1540.25 mm 2 、190 mg / 1540.25 mm 2 、200 mg / 1540.25 mm 2 、210 mg / 1540.25 mm 2 、220 mg / 1540.25 mm 2 、230 mg / 1540.25 mm 2 、240 mg / 1540.25 mm 2 、250 mg / 1540.25 mm 2 、260 mg / 1540.25 mm 2 、270 mg / 1540.25 mm 2 、280 mg / 1540.25 mm 2 、290 mg / 1540.25 mm 2 、300 mg / 1540.25 mm 2 、310 mg / 1540.25 mm 2 、320 mg / 1540.25 mm 2 、330 mg / 1540.25 mm 2 、340 mg / 1540.25 mm 2 、350 mg / 1540.25 mm 2 、360 mg / 1540.25 mm 2, 370 mg / 1540.25 mm 2 , 380 mg / 1540.25 mm 2 Or a range composed of any two of the above values.

[0088] In the embodiments of the present application, the single-sided coating areal density of the positive electrode film layer of the battery cell can be detected by the following method. For example, take a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), punch it into small circular pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive electrode film layer of the above-mentioned weighed positive electrode sheet, weigh the weight of the positive electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode sheet - the weight M0 of the positive electrode current collector) / S1.

[0089] In the embodiments of the present application, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. Here, the elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material can refer to both the silicon-based material and the form of silicon element in the negative electrode sheet in the battery after formation. Here, the silicon oxide SiO x , 0 < x ≤ 2 because the bonding mode between silicon atoms and oxygen atoms in the negative electrode film layer is diverse and can be SiO, SiO 1.2 , or SiO 2 and at least one of other possible silicon oxides. Here, the silicon-carbon composite can refer to the form of silicon element in the negative electrode sheet in the battery after formation. The silicon-carbon composite can also be a silicon-carbon composite formed by certain chemical reactions between silicon element and carbon element in the battery cell. The silicon-carbon composite can also be formed by physical mixing of silicon and carbon. For example, the carbon includes a porous framework, and the silicon is located in the pores of the porous framework and can also be located on the surface of the porous framework. The silicon-carbon composite can also be a carbon layer coated on the surface of silicon.

[0090] In some embodiments, based on the mass of the negative electrode active material, the mass content of silicon element is 0.3% - 10.0%. Exemplarily, the mass content of silicon element is 0.3%, 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%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10% or a range composed of any two of the above values.

[0091] The qualitative and quantitative determination of each substance or element in the present application can be detected by suitable equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain 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.

[0092] For example, the mass content of silicon element in 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. For example, the negative electrode sheet is placed in a solvent such as water for soaking to separate the negative electrode active material 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 test sample is analyzed by an ICAP7400 model inductively coupled plasma - emission spectrometer of Thermo Fisher Scientific Company in the United States, and the silicon element content can be obtained with reference to the GB / T30902 - 2014 standard.

[0093] In some embodiments, based on the total mass of the electrolyte, the mass content of the first additive is 1% - 12%. Exemplarily, the mass content of the first additive is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or a range composed of any two of the above values.

[0094] The type and content of the first additive in the electrolyte can be obtained by detecting the electrolyte through methods well-known to those skilled in the art. For example, the composition of the electrolyte can be measured by liquid chromatography, ultraviolet spectrophotometry, ultraviolet-visible spectrophotometry, etc. Exemplarily, an ion chromatograph (IC) is used to test the content of inorganic substances in the electrolyte. A quantitative electrolyte is weighed (the dilution concentration is in the middle of the standard curve), fixed volume is made to 100 mL with ultrapure water, and the ion chromatograph automatically injects samples for detection to test the ion chromatogram of inorganic substances. According to the peak position of the chromatogram, the corresponding types of inorganic substances are compared, and the percentage of the content of the corresponding inorganic ions is calculated according to the peak area. The above free electrolyte is diluted 3 to 10 times with acetonitrile to obtain a diluted electrolyte to be tested. Using a GC-MS 3100 gas chromatograph for organic components, the above diluted electrolyte is placed in the instrument for full-scan qualitative analysis. The inlet temperature is 250 °C, and the scanning range is 35 μm to 270 μm. After the test is completed, the total ion current chromatogram of each organic substance is obtained. According to the peak position of the chromatogram, the corresponding types of organic substances are compared, and the percentage of the content of each organic substance is calculated according to the peak area. The mass of the first additive measured is divided by the mass of the electrolyte sample to obtain the mass content of the first additive in the electrolyte of the battery cell. It can be understood that the mass content of the first additive in the electrolyte of the battery cell is slightly lower than the added mass content of the first additive in the electrolyte of the battery cell.

[0095] In this article, the term "halogen atom" includes one or more of fluorine atom, chlorine atom, bromine atom, and iodine atom.

[0096] In this article, the term "C1-C5 alkyl" refers to a straight-chain or branched-chain hydrocarbon chain group composed only of carbon and hydrogen atoms, without unsaturation in the group, having from one to five carbon atoms, and attached to the rest of the molecule through a single bond. As examples, it includes but is not limited to methyl, ethyl, propyl, isopropyl, 2-methyl-1-propyl, 2-methyl-2-propyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-3-butyl, 2,2-dimethyl-1-propyl, 2-methyl-1-pentyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, neopentyl.

[0097] In this article, the term "C1-C5 haloalkyl" refers to a C1-C5 alkyl in which at least one hydrogen atom is replaced by a halogen atom. As examples, it includes but is not limited to: -CF 3 ,-CF 2 CH 2 ,-CF 2 CH 2 CH 3 ,-CF 2 CF 2 CH 2 CH 3 ,-CF2 CH 2 CH 2 CH 2 CH 3 。

[0098] In this application, the positive electrode film layer with a high coating weight is matched with the negative electrode film layer containing silicon elements. While improving the energy density of the battery cell, it can also reduce the coating weight of the negative electrode film layer, thereby enhancing the fast charging performance of the battery cell. At the same time, controlling the mass content of silicon elements in the negative electrode film layer within a suitable range can take into account the cycle performance of the battery cell while improving the energy density of the battery cell. However, when introducing silicon-containing materials into the negative electrode active material, the volume of the silicon material expands and contracts significantly during the charge and discharge process of the battery cell, and the SEI film on the negative electrode side is easily damaged, exposing a fresh interface. The electrolyte continues to undergo a reduction reaction on the interface, consuming the electrolyte and active lithium, affecting the cycle and storage performance of the battery cell. To address this problem, in this application, a first additive of vinylene carbonate and / or ethylene carbonate derivatives is added to the electrolyte. Vinylene carbonate and ethylene carbonate derivatives can preferentially participate in the formation of the SEI film on the negative electrode side over other components in the electrolyte, and the organic matter content in the film formed by vinylene carbonate and ethylene carbonate derivatives is relatively high, which is beneficial to improving the overall flexibility of the SEI film, improving the stability of the SEI film and the negative electrode interface during the cycle, reducing the reaction between the negative electrode active material and the electrolyte, reducing the consumption of lithium ions, and improving the cycle performance and storage performance of the battery cell. Additionally, controlling the mass content of the first additive within a suitable range can improve the flexibility and stability of the SEI film while controlling the thickness of the SEI film within a suitable range, thereby simultaneously achieving the stability and low impedance of the negative electrode interface and taking into account the cycle performance and fast charging performance of the battery cell. In addition, the positive electrode active material includes lithium phosphate with an olivine structure, which has excellent structural stability and improves the cycle performance of the battery cell.

[0099] In summary, by synergistically controlling the single-sided coating weight of the positive electrode film layer, the mass content of silicon elements in the negative electrode active material, the positive electrode active material including lithium phosphate with an olivine structure, the type and mass content of additives in the electrolyte within a suitable range, this application can achieve a balance among the fast charging performance, cycle performance, and energy density of the battery cell.

[0100] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed 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 disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0101] In some embodiments, based on the mass of the negative electrode active material, the mass content of silicon element is 0.3% to 6.0%, and can be optionally 0.3%, 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%, 5.2%, 5.5%, 5.8%, 6% or a range composed of any two of the above values.

[0102] When the mass content of silicon element in the silicon-based material is within a suitable range, it can improve the energy density of the battery cell while reducing the influence of excessive silicon element on the cycle performance of the battery cell, taking into account both the energy density and cycle performance of the battery cell.

[0103] In some embodiments, the battery cell satisfies the following relationship: 0.025 ≤ A / B ≤ 6, and can be optionally 0.035 ≤ A / B ≤ 2.5, where A is the mass content of the silicon element, based on the mass of the negative electrode active material; B is the mass content of the first additive, based on the total mass of the electrolyte.

[0104] In some embodiments, the value of A / B can be optionally 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0 or a range composed of any two of the above values.

[0105] When the ratio of the mass content of silicon element in the negative electrode active material to the mass content of the first additive in the electrolyte is within a suitable range, through the synergistic effect of the silicon element in the negative electrode active material and the first additive, it can improve the energy density of the battery cell while taking into account the cycle performance of the battery cell.

[0106] In some embodiments, based on the mass of the negative electrode active material, the mass content of the silicon element is 0.3% to 3%; Based on the total mass of the electrolyte, the mass content of the first additive is 2% to 7.5%.

[0107] In some embodiments, the mass content of silicon element in the negative electrode active material can be optionally 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3% or a range composed of any two of the above values; The mass content of the first additive in the electrolyte can be optionally 2%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7%, 7.5% or a range composed of any two of the above values.

[0108] In a system with a relatively low silicon element content, the damage to the SEI film during the cycling of the battery cell is relatively small. By controlling the mass content of the first additive within a suitable range to form an SEI film with a suitable thickness, while improving the stability of the SEI film and the negative electrode interface and enhancing the cycling performance of the battery cell, a low impedance at the negative electrode interface can also be achieved, which is beneficial to improving the fast charging performance of the battery cell and is more suitable for usage scenarios with higher requirements for the cycling performance and fast charging performance of the battery cell.

[0109] In some embodiments, based on the mass of the negative electrode active material, the mass content of the silicon element is greater than 3% and less than or equal to 6%; Based on the total mass of the electrolyte, the mass content of the first additive is 3% - 10%.

[0110] In some embodiments, the mass content of the silicon element in the negative electrode active material can be optionally 3.1%, 3.5%, 3.8%, 4.0%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6% or a range composed of any two of the above values; The mass content of the first additive in the electrolyte can be optionally 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0% or a range composed of any two of the above values.

[0111] In a system with a relatively high silicon element content, the damage to the SEI film during the cycling of the battery cell is relatively severe. By controlling the mass content of the first additive within a suitable range to form an SEI film with a suitable thickness, the purpose of improving the stability of the SEI film and the negative electrode interface and enhancing the cycling performance of the battery cell can be achieved, and it is more suitable for usage scenarios with higher requirements for the cycling performance and energy density of the battery cell.

[0112] In some embodiments, the negative electrode active material includes a carbon-based material, and the carbon-based material includes graphite.

[0113] Graphite has good electrical conductivity and cycling stability, which is beneficial to improving the fast charging performance and cycling performance of the battery cell.

[0114] In some embodiments, based on the mass of the negative electrode active material, the mass proportion of the carbon-based material can be greater than or equal to 80% and less than 100%.

[0115] In some embodiments, the graphite includes composite graphite particles, the composite graphite particles include graphite matrix particles and a carbon coating layer coated on the surface of the graphite matrix particles, the graphite matrix particles include secondary particles, and the carbon coating layer includes amorphous carbon.

[0116] A secondary particle refers to a particle formed by aggregation of two or more primary particles.

[0117] In this context, amorphous carbon refers to a transitional carbon material with a very low degree of graphitization crystallization, approximating an amorphous form (or having no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product obtained by carbonizing an organic carbon source, which has more end faces and defects and more lithium-ion sites.

[0118] The secondary particles can improve the migration rate of lithium ions, enhance the transport performance of lithium ions, facilitate the insertion and extraction of lithium ions, and contribute to improving the ionic conductivity of the material. In addition, since the carbon coating layer includes amorphous carbon, it can improve the conductivity of the composite graphite particles. The secondary particles in the core and the amorphous carbon coating layer together improve the electron-conducting and ion-conducting properties of the material, which helps to improve the fast-charging performance of the battery cell.

[0119] In the embodiments of the present application, the composite graphite particles can be prepared by methods well known in the art. For example, the preparation method includes: providing graphite matrix particles (which can be artificial graphite) and an organic carbon source, mixing the two, and after carbonization treatment, forming a carbon coating layer on at least part of the surface of the graphite matrix particles to obtain the composite graphite particles in the embodiments.

[0120] 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 the coal tar pitch and petroleum pitch is below 250°C.

[0121] Optionally, the carbonization treatment temperature is from 700°C to 1800°C. Optionally, the carbonization treatment temperature is from 1000°C to 1300°C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized and a coating layer containing amorphous carbon can be formed on at least part of the surface of the graphite matrix particles. Optionally, the carbonization treatment time is from 1 h to 6 h.

[0122] In some embodiments, based on the total mass of the composite graphite particles, the mass content of the amorphous carbon is 2% - 5%, and can be optionally 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range composed of any two of the above values.

[0123] Controlling the mass content of the amorphous carbon in the composite graphite particles within a suitable range can improve the conductivity of the material and the fast-charging performance of the battery.

[0124] In some embodiments, the powder resistivity of the composite graphite particles is 0.005 Ω·cm - 0.04 Ω·cm, and may be optionally 0.01 Ω·cm, 0.015 Ω·cm, 0.020 Ω·cm, 0.025 Ω·cm, 0.03 Ω·cm, 0.04 Ω·cm, or a range composed of any two of the above values.

[0125] In the embodiments of the present application, the powder resistivity of the material has the meaning well-known in the art, and can be detected by methods and equipment well-known in the art. For example, according to the test standard GB / T30835-2014, a PRCD1100 powder resistivity meter is used for testing.

[0126] The powder resistivity of the composite graphite particles is small, and the composite graphite particles have excellent electrical conductivity, which is beneficial to improving the fast charging performance of the battery cell.

[0127] In the embodiments of the present application, the negative electrode film layer includes at least one film layer, and a single film layer can be used, or at least two film layers can be used. Optionally, the negative electrode film layer includes at least two film layers.

[0128] When the negative electrode film layer uses a single film layer, the negative electrode active material in the negative electrode film layer includes graphite and a silicon-based material. Optionally, the negative electrode active material includes composite graphite particles and a silicon-based material. When using a single film layer, the volume average particle size Dv50 of the composite graphite particles is 8.2 μm to 13.5 μm. Exemplarily, the volume average particle size Dv50 of the composite graphite particles is 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, or a range composed of any two of the above values.

[0129] When the negative electrode film layer uses at least two film layers, the negative electrode active material in the negative electrode film layer includes graphite and a silicon-based material. Optionally, the negative electrode active material includes composite graphite particles and a silicon-based material. The silicon-based material can be located in one of the at least two film layers, or can be located in at least two of the at least two film layers. The composite graphite particles can be located in one of the at least two film layers, or can be located in at least two of the at least two film layers. The negative electrode film layer can include two film layers, three film layers, four film layers, or even more film layers.

[0130] 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 located between the current collector and the second negative electrode film layer. The silicon-based material can be located in the first negative electrode film layer and / or the second negative electrode film layer. The composite graphite particles can be located in the first negative electrode film layer and / or the second negative electrode film layer.

[0131] The interface between the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0132] The negative electrode film layer includes at least two 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, it is possible to construct pore differences in the negative electrode film layer, reduce the tortuosity of lithium ion transport, and improve the fast charging performance of the battery cell.

[0133] In some embodiments, both the first negative electrode film layer and the second negative electrode film layer include composite graphite particles.

[0134] Both the first negative electrode film layer and the second negative electrode film layer include composite graphite particles, which can improve the fast charging performance of the battery cell.

[0135] In some embodiments, the volume average particle size Dv50 of the composite graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the composite graphite particles in the second negative electrode film layer.

[0136] 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 active material as a sample, according to the test standard GB / T19077-2016, the Dv50 of the particles is tested by a Mastersizer2000E type laser particle size analyzer.

[0137] During the fast charging process of the battery cell, the overpotential of the second negative electrode film layer far from the current collector is usually relatively high. The bottleneck affecting the fast charging performance of the battery cell in the negative electrode film layer mainly lies in the second negative electrode film layer. In the present application, controlling the particle size of the composite graphite particles in the second negative electrode film layer to be relatively smaller can shorten the lithium ion transport path, improve the lithium ion transport performance of the second negative electrode film layer, and improve the fast charging performance of the battery cell.

[0138] In some embodiments, the volume average particle size Dv50 of the composite graphite particles in the first negative electrode film layer is 8.5 μm to 14.8 μm, and can be optionally 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, 14.8 μm or a range composed of any two of the above values.

[0139] In some embodiments, the volume average particle size Dv50 of the composite graphite particles in the second negative electrode film layer is 7.8 μm to 12.8 μm, and may be optionally 7.8 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 12.8 μm, or a range composed of any two of the above values.

[0140] Controlling the particle size of the graphite particles in the first negative electrode film layer and / or the second negative electrode film layer within a suitable range can, on the one hand, 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. Furthermore, the negative electrode active materials in the second negative electrode film layer and the negative electrode active materials in the first negative electrode film layer with the above volume average particle size range cooperate to facilitate the construction of the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reduce the tortuosity of lithium ion transmission, and improve the fast charging performance of the battery cell.

[0141] In some embodiments, based on the total thickness of the first negative electrode film layer and the second negative electrode film layer, the thickness ratio of the second negative electrode film layer is 30% to 70%, and may be optionally 30%, 40%, 50%, 60%, 70%, or a range composed of any two of the above values.

[0142] When the thickness ratio of the second negative electrode film layer is within a suitable range, by adjusting the thickness ratio of the first negative electrode film layer and the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging performance of the battery cell can be improved.

[0143] In some embodiments, when the battery cell is in a 100% charged state, the thickness of the first negative electrode film layer is 15 μm to 65 μm, such as 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range composed of any two of the above values.

[0144] When the thickness of the first negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging performance of the battery cell can be improved.

[0145] In some embodiments, when the battery cell is in a 100% state of charge, the thickness of the second negative electrode film layer is 15 μm to 65 μm, such as 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, or a range composed of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be regulated and increased, the tortuosity of lithium ion transport can be reduced, and the fast charging performance of the battery cell can be improved.

[0146] In the embodiments of the present application, when the battery cell is in a 100% state of charge, the test steps for the first negative electrode film layer and the second negative electrode film layer are as follows: The battery cell is charged to 3.65 V at a constant current of 0.33C, and then continues to be charged at a constant voltage of 3.65 V until 0.05C, and then the charging is stopped. At this time, the state of the battery is the 100% state of charge. The negative electrode pole piece of the battery cell in the 100% state of charge is disassembled, and a cross-section in the thickness direction of the middle area of the negative electrode pole piece is observed using a tomography electron microscope. The regions of the two are distinguished according to the interface between the first negative electrode film layer and the second negative electrode film layer, and the thicknesses of the two are measured respectively. For example, the thicknesses of 10 positions of the first negative electrode film layer are measured respectively, and the average value is calculated as the average value of the first negative electrode film layer. The thicknesses of 10 positions of the second negative electrode film layer are measured, and the average value is calculated as the average value of the second negative electrode film layer.

[0147] In some embodiments, the negative electrode film layer may further 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 at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0148] 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%.

[0149] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder.

[0150] In some embodiments, the negative electrode binder 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.

[0151] In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0152] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0153] In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0154] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil 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 at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0155] 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.

[0156] 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 present application embodiment 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 other embodiments, the negative electrode plate of the present application embodiment further includes a protective layer covering the surface of the negative electrode film layer.

[0157] 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 at least one side of the negative electrode film layer, the negative electrode conductive layer includes a conductive agent, and the conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0158] By providing a negative electrode conductive layer containing a conductive agent between the current collector and the negative electrode film layer, the conductivity of the negative electrode plate can be improved, and the fast charging performance of the battery cell can be improved.

[0159] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm, and may be optionally 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.

[0160] 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 using the equipment and methods well-known in the art, and the testing methods of the first negative electrode film layer or the second negative electrode film layer in the foregoing text can be referred to.

[0161] Controlling the thickness of the negative electrode conductive layer within a suitable range can take into account the fast charging performance and energy density of the battery cell.

[0162] In some embodiments, the negative electrode conductive layer includes a negative electrode conductive layer binder.

[0163] The binder in 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.

[0164] In some embodiments, the negative electrode conductive layer binder 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.

[0165] In some embodiments, when the battery cell is in a 100% charged state, the compaction density of the negative electrode film layer is 1.15 g / cm 3 ~1.45 g / cm 3 , exemplarily, when the battery cell is in a 100% charged state, the compaction density of the negative electrode film layer is 1.15 g / cm 3 , 1.18 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 , 1.36 g / cm 3 , 1.38 g / cm 3 , 1.4 g / cm 3 , 1.42 g / cm 3 , 1.45 g / cm 3 or a range composed of any two of the above values.

[0166] In the embodiments of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge (SOC) can be detected by the following method: charge the battery cell at a constant current of 0.33C to 3.65V, and then continue to charge at a constant voltage of 3.65V until the current is 0.05C, and then stop charging. At this time, the state of the battery is the 100% state of charge. Disassemble the negative electrode plate of the battery cell at 100% SOC, and measure the compaction density of the negative electrode film layer. Take the negative electrode plate with single-sided coating (if it is a double-sided coated electrode plate, one side of the negative electrode film layer 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-mentioned weighed negative electrode plate, 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 plate - 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 plate - 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.

[0167] When the compaction density of the negative electrode film layer is within a suitable range, it is beneficial to improve the fast charging performance of the battery cell.

[0168] In some embodiments, the single-sided coating weight of the negative electrode film layer is 70mg / 1540.25mm 2 ~135mg / 1540.25mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer is 70mg / 1540.25mm 2 、75mg / 1540.25mm 2 、80mg / 1540.25mm 2 、85mg / 1540.25mm 2 、90mg / 1540.25mm 2 、92mg / 1540.25mm 2 、95mg / 1540.25mm 2 、96mg / 1540.25mm 2 、100mg / 1540.25mm 2 、102mg / 1540.25mm 2 、104mg / 1540.25mm 2 、105mg / 1540.25mm 2 、108mg / 1540.25mm 2 、110mg / 1540.25mm 2 、112mg / 1540.25mm 2 、114mg / 1540.25mm 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 Or a range composed of any two of the above values.

[0169] When the single-sided coating weight of the negative electrode film layer is within a suitable range, it is beneficial to improve the fast charging performance of the battery cell.

[0170] [Positive electrode tab] The positive electrode tab 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 either or both of the two opposite surfaces of the positive electrode current collector.

[0171] In some embodiments, the mass ratio of the lithium-containing phosphate with an olivine structure in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%. It can be considered that the positive electrode active material of the present application is a lithium-containing phosphate system with an olivine structure. When the mass ratio of the lithium-containing phosphate with an olivine structure is less than 100%, the positive electrode active material may further include common positive electrode active materials, such as at least one of lithium-containing transition metal oxides. Examples of the lithium-containing transition metal oxides may include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0172] In some embodiments, the mass ratio of the lithium-containing phosphate with an olivine structure in the positive electrode active material is 100%.

[0173] In some embodiments, the lithium-containing phosphate with an olivine structure includes: A lithium-containing phosphate matrix, and A coating layer, the coating layer is located on at least part of the surface of the lithium-containing phosphate matrix, and the coating layer contains carbon elements.

[0174] The lithium-containing phosphate with olivine structure includes a carbon coating layer, which is loose and porous, conducive to increasing the specific surface area of the material, more conducive to the effective contact between the electrolyte and the phosphate particles, conducive to the transport of lithium ions at the phase interface, capable of improving the electrical conductivity of the material, and conducive to improving the fast charging performance of the battery cell.

[0175] In some embodiments, the lithium-containing phosphate matrix includes a compound 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, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; where A includes at least one of Na, K, and Mg; Me includes at least one of Mn, Fe, Co, and Ni; M includes at least one of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes at least one of S, Si, Cl, B, C, N, and P; Y includes at least one of O and F.

[0176] In some embodiments, x1 can be selected from 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3 or a range composed of any two of the above values.

[0177] In some embodiments, y1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3 or a range composed of any two of the above values.

[0178] In some embodiments, x1 + y1 can be selected from 0.9, 1.0, 1.1, 1.2, 1.3 or a range composed of any two of the above values.

[0179] In some embodiments, a1 can be selected from 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range composed of any two of the above values.

[0180] In some embodiments, b1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or a range composed of any two of the above values.

[0181] In some embodiments, a1 + b1 can be optionally 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or a range composed of any two of the above values.

[0182] In some embodiments, c1 can be optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a range composed of any two of the above values.

[0183] In some embodiments, z1 can be optionally 3.0, 3.5, 4.0, 4.5, 5.0, or a range composed of any two of the above values.

[0184] The lithium-containing phosphate with olivine structure has good cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0185] In some embodiments, the lithium-containing phosphate matrix includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate, and modified forms of any one of the foregoing substances, wherein the modified forms include one or more of doping modification and coating modification.

[0186] During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. Regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiFe 1-x Mn x PO 4 (0 < x < 1), LiNiPO 4 , LiCoPO 4 etc., the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiFe 1-x Mn x PO 4 (0 < x < 1), LiCoPO 4 etc., the molar content of oxygen is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of oxygen will fluctuate. The above situations are all within the protection scope of the present application.

[0187] In some embodiments, based on the mass of the lithium-containing phosphate with an olivine structure, the mass content of carbon element is 0.8% - 2.3%, and it can be optionally 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.3% or the range composed of any two of the above values.

[0188] Generally, infrared absorption is used to measure the carbon content in the material, such as an infrared carbon and sulfur instrument, or an indirect carbon determination method. The latter can refer to the content on pages 3 - 4 of the national standard GB / T 3521 - 2008 (Methods for Chemical Analysis of Graphite).

[0189] Controlling the mass content of carbon element in the coating layer within a suitable range can not only improve the conductivity of the material and the fast charging performance of the battery, but also take into account the specific capacity of the material, as well as the fast charging performance and energy density of the battery cell.

[0190] In some embodiments, the battery cell satisfies the following relationship: 0.08 ≤ C / B ≤ 1.15, where C is the mass content of carbon element, based on the mass of the lithium-containing phosphate with an olivine structure; B is the mass content of the first additive, based on the total mass of the electrolyte.

[0191] In some embodiments, the value of C / B can be optionally 0.08, 0.10, 0.12, 0.15, 0.18, 0.2, 0.25, 0.30, 0.35, 0.40, 0.45, 0.5, 0.55, 0.60, 0.65, 0.70, 0.75, 0.8, 0.85, 0.90, 1.0, 1.05, 1.10, 1.15 or the range composed of any two of the above values.

[0192] As described above, the carbon element in the carbon coating layer can improve the effective contact between the electrolyte and the phosphate particles and enhance the conductivity of the material. However, while the porous carbon coating layer improves the infiltration performance of the electrolyte, it also brings side reactions between the phosphate particles and the electrolyte, consuming lithium ions and affecting the cycle performance of the battery cell. The first additive in the electrolyte helps to form a CEI film layer on the positive electrode side, reducing the possibility of side reactions between the electrolyte and the positive electrode active material, improving the stability of the positive electrode interface, and enhancing the cycle performance of the battery cell.

[0193] By controlling the mass content of carbon element and the mass content of the first additive in the lithium-containing phosphate with an olivine structure within a suitable range, through their synergistic effect, the present application can not only improve the conductivity of the material and the fast charging performance of the battery cell, but also take into account the cycle stability of the material and the cycle performance of the battery.

[0194] In some embodiments, the coating layer further comprises Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 substances, where 0 ≤ d1 ≤ 1, 0 ≤ m1 ≤ 5, 0 ≤ n1 ≤ 4; M3 comprises one or more elements of Ti, Zr, Hf, Ge, Sn, and optionally, M3 is +4 valent.

[0195] In some embodiments, the coating layer further comprises Li 2 FeTi(PO 4 ) 3 , Li 2 FeZr(PO 4 ) 3 , Li 2 FeSn(PO 4 ) 3 or more of them.

[0196] In some embodiments, the carbon element and Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 substances can be arranged in layers. For example, the carbon element serves as an independent carbon coating layer, and Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 substances serve as an independent fast ion conductor layer. The carbon coating layer can coat 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 away from the phosphate particles. Or, the fast ion conductor layer can coat 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 away from the phosphate particles. Of course, the carbon element and Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 substances can also be arranged in the same layer.

[0197] The coating layer comprises Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 , which has excellent ion conductivity, and together with the carbon element with excellent conductivity in the coating layer, improves the conductivity and ion conductivity of the material, which is beneficial to improving the fast charging performance of the battery.

[0198] 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 equipment and methods well-known in the art. For example, referring to EPA6010D-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) and disassembling the positive electrode plate, it is cleaned with DMC and dried. After that, 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 made up to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0199] In some embodiments, the powder compaction density of the positive electrode active material under 30,000 N is 2.43 g / cm 3 ~2.85 g / cm 3 , optionally 2.43 g / cm 3 , 2.44 g / cm 3 , 2.45 g / cm 3 , 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 , 2.78 g / cm 3 , 2.80 g / cm 3 , 2.85 g / cm 3 Or a range composed of any two of the above values.

[0200] When the powder compaction density of the positive electrode active material under 30,000 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 and the contact resistance between particles is small, the resistance of the electrode plate can be further reduced, which is also beneficial to improving the fast charging performance of the battery cell.

[0201] 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 in accordance with the test standard GB / T24533-2009. For example, a certain amount of the 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.

[0202] In some embodiments, when the battery cell is in a 100% charged state, the compaction density of the positive electrode film layer is 2.50 g / cm 3 ~2.80 g / cm 3 , optionally 2.50 g / cm 3 , 2.55 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.70 g / cm 3 , 2.75 g / cm 3 , 2.80 g / cm 3 or a range composed of any two of the above values.

[0203] In the embodiments of the present application, the compaction density of the positive electrode film layer when the battery cell is in a 100% charged state has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. The detection method is the same as the compaction density test method of the negative electrode film layer described above.

[0204] When the compaction density of the positive electrode film layer is within a suitable range, the battery cell has a high energy density.

[0205] In some embodiments, the positive electrode film layer may also optionally include a positive electrode conductive agent. There is no particular limitation on the type of the positive electrode conductive agent in the embodiments of the present application. As an example, the positive electrode conductive agent includes at least one 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%.

[0206] In some embodiments, the positive electrode film layer may also optionally include a positive electrode binder. The present application embodiment has no particular restrictions on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0207] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, at least one foil 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 at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0208] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this. The positive electrode plate does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode plate of the embodiment of the present application also includes a positive conductive layer sandwiched between the positive electrode collector and the positive electrode film layer and arranged on the surface of the positive electrode collector. In some other embodiments, the positive electrode plate of the embodiment of the present application also includes a protective layer covering the surface of the positive electrode film layer.

[0209] [Electrolyte] During the charge and discharge process of a battery cell, active ions such as lithium ions are embedded and released back and forth between the positive electrode and the negative electrode, and the electrolyte plays the role of conducting the active ions between the positive electrode and the negative electrode.

[0210] In an embodiment of the present application, the electrolyte includes a first additive, the first additive includes at least one of vinylene carbonate and a vinyl carbonate derivative, and the mass content of the first additive is 1% to 12% based on the total mass of the electrolyte. Wherein, the ethylene carbonate derivative includes the compound shown in formula I, Formula I R 1 、R 2 、R 3 、R 4 each independently includes any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and a halogenated alkyl group having 1 to 5 carbon atoms, and R 1 、R 2 、R 3 、R 4 are not simultaneously hydrogen atoms.

[0211] A first additive of vinylene carbonate and / or a vinylene carbonate derivative is added to the electrolyte. Vinylene carbonate and the vinylene carbonate derivative can preferentially participate in the formation of the SEI film on the negative electrode side over other components in the electrolyte, and the organic matter content in the film formed by vinylene carbonate and the vinylene carbonate derivative is relatively high, which is beneficial to improving the overall flexibility of the SEI film, can improve the stability of the interface between the SEI film and the negative electrode during the cycling process, reduce the reaction between the negative electrode active material and the electrolyte, reduce the consumption of lithium ions, and improve the cycling performance and storage performance of the battery cell. Additionally, controlling the mass content of the first additive within a suitable range can improve the flexibility and stability of the SEI film while also controlling the thickness of the SEI film within a suitable range, thereby simultaneously achieving the stability and low impedance of the negative electrode interface and taking into account the cycling performance and fast charging performance of the battery cell.

[0212] In some embodiments, R 1 、R 2 、R 3 、R 4 at least one contains a fluorine atom.

[0213] R 1 、R 2 、R 3 、R 4 The vinylene carbonate derivative in which at least one of R

[0214] is a fluorine atom is prone to ring opening and forms an SEI film containing more organic matter on the negative electrode surface, which is beneficial to improving the flexibility of the overall SEI film, achieving the purpose of improving the stability of the interface between the SEI film and the negative electrode during the cycling process, and improving the cycling performance of the battery cell.

[0215] A suitable ethylene carbonate derivative additive can form a SEI film containing a large amount of organic matter on the negative electrode side, which can improve the overall flexibility of the SEI film, achieve the purpose of improving the stability of the interface between the SEI film and the negative electrode during the cycling process, improve the cycling performance of the battery cell, and at the same time, the SEI film formed by fluoroethylene carbonate, difluoroethylene carbonate, and trifluoromethyl ethylene carbonate has a low impedance, which is also beneficial to improving the fast charging performance of the battery cell.

[0216] In some embodiments, the electrolyte further includes an organic solvent, and the organic solvent includes one or more of a first organic solvent and a second organic solvent. Among them, the first organic solvent includes at least one of a cyclic carbonate and a linear carbonate, and may be a cyclic carbonate. The second organic solvent includes R 5 -COO-R 6 , Among them, R 5 includes any one of a hydrogen atom, a halogen atom, an alkyl group with 1 to 5 carbon atoms, and a halogenated alkyl group with 1 to 5 carbon atoms, and R 6 includes any one of an alkyl group with 1 to 5 carbon atoms and a halogenated alkyl group with 1 to 5 carbon atoms.

[0217] The first organic solvent of the cyclic carbonate and the linear carbonate has a relatively high dielectric constant and excellent ionic conductivity, which is beneficial to improving the conductivity of the electrolyte. The second organic solvent has a low viscosity, which is beneficial to improving the conductivity of the electrolyte. The electrolyte contains the first organic solvent and / or the second organic solvent, which is beneficial to improving the migration of lithium ions and the fast charging performance of the battery cell.

[0218] In some embodiments, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate.

[0219] In some embodiments, the linear carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0220] In some embodiments, the second organic solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0221] In some embodiments, based on the total mass of the electrolyte, the mass content of the first organic solvent is 20% to 72%, and may be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 72% or a range composed of any two of the above values.

[0222] The first organic solvent with appropriate contents of cyclic carbonate and chain carbonate can further improve the conductivity of the electrolyte, facilitate the migration of lithium ions, and improve the fast charging performance of the battery cell.

[0223] The types and masses of solvents in the electrolyte can be obtained by detecting the electrolyte through methods well-known to those skilled in the art. For example, the composition of the electrolyte can be measured by liquid chromatography, ultraviolet spectrophotometry, ultraviolet-visible spectrophotometry, etc. Exemplarily, disassemble the battery cell, obtain the free electrolyte from the battery cell, dilute the free electrolyte in the battery cell with acetonitrile by 3 to 10 times to obtain the electrolyte dilution to be tested. Use a GC-MS 3100 organic component gas chromatograph, place the above electrolyte dilution in the instrument for full-scan qualitative analysis, with the injection port temperature at 250 °C and the scanning range: 35 μm to 270 μm. After the test is completed, obtain the total ion current chromatogram of each organic substance, compare the corresponding organic substance types according to the peak positions in the chromatogram, and calculate the percentage of the corresponding content of each organic substance according to the peak areas.

[0224] In some embodiments, the electrolyte further includes a second additive, and the second additive includes one or more of sulfur-containing additives and lithium salt additives.

[0225] Additives refer to components with relatively low contents in the electrolyte, generally with a mass ratio in the electrolyte not exceeding 10%. They have the characteristics of strong pertinence and small dosage, and can significantly optimize a certain aspect of the battery performance without changing the production process.

[0226] Sulfur-containing additives and lithium salt additives can improve the interfacial film performance on the positive electrode side and / or negative electrode side, improve the interfacial chemistry between the positive electrode and / or negative electrode and the electrolyte, and improve the fast charging performance and cycling performance of the battery.

[0227] In some embodiments, the sulfur-containing additive includes one or more of vinylene sulfate, divinylene sulfate, butene sultone, 1,3-propane sultone, ethylene sulfite, and methylene methyl disulfonate.

[0228] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

[0229] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or two of fluorosulfonylimide salts and lithium hexafluorophosphate.

[0230] Fluorosulfonylimide salts and lithium hexafluorophosphate are easy to dissociate, which is beneficial to the rapid migration of lithium ions and beneficial to improving the fast charging performance of the battery cell. Moreover, fluorosulfonylimide salts and lithium hexafluorophosphate are relatively stable in the electrolyte system and can improve the cycling performance of the battery cell.

[0231] In some embodiments, the fluorosulfonylimide salt includes one or both of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

[0232] In some embodiments, the lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, and the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate is 0.2 to 1.0, and can be optionally 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.

[0233] In some embodiments, the molar concentration of lithium bis(fluorosulfonyl)imide is 0.2 mol / L to 0.5 mol / L, and can be optionally 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.40 mol / L, 0.45 mol / L, 0.5 mol / L or a range composed of any two of the above values; The molar concentration of lithium hexafluorophosphate is 0.5 mol / L to 1.2 mol / L, and can be optionally 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.2 mol / L or a range composed of any two of the above values.

[0234] [Separator membrane] The electrode assembly includes a separator membrane disposed between the positive electrode and the negative electrode.

[0235] The present application does not particularly limit the type of the separator membrane, and any publicly known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0236] As an example, the main material of the separator membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator membrane.

[0237] In some embodiments, the thickness of the separator membrane is 4 μm to 12 μm, and can be optionally 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm or a range composed of any two of the above values.

[0238] In the embodiments of the present application, the thickness of the isolation membrane has a meaning well known in the art, and can be detected using the meanings and equipment well known in the art. For example, a newly prepared isolation membrane can be taken as a sample, or a battery cell that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery's charged state is approximately 0% SOC) can be reversely disassembled, the isolation membrane can be obtained from the battery cell and the isolation membrane can be dried as a sample, the isolation membrane can be cut with an ion beam cutter to form a cross section, and then the thickness of the isolation membrane can be measured using a scanning electron microscope.

[0239] When the thickness of the isolation membrane is within an appropriate range, the migration path of lithium ions in the isolation membrane is shorter, which can reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0240] In some embodiments, the porosity of the isolation membrane is 20% to 70%, which can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range consisting of any two of the above values.

[0241] In the embodiments of the present application, porosity refers to the percentage of the pore volume in the separator to the total volume of the separator. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin separator for battery monomers". It should be noted that the actual test process can be slightly different from the standard test process according to the difference in test instruments, test errors, and in order to eliminate the test influence on porosity as much as possible, so as to obtain a more accurate test value.

[0242] When the porosity of the isolation membrane is within an appropriate range, the migration rate of lithium ions in the isolation membrane can be increased, the internal resistance of the battery cell can be reduced, and the fast charging performance of the battery cell can be improved.

[0243] In some embodiments, the battery cell is configured to have a charging time of 5 min to 10.5 min from a 10% state of charge to an 80% state of charge, which can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 10.5 min or a range consisting of any two of the above values.

[0244] In some embodiments, the charging process of the battery cell from 10% state of charge to 80% state of charge includes multiple charging steps, and the maximum state of charge of any charging step in the multiple charging steps is The difference between the maximum state of charge in the state and the adjacent charging step is less than or equal to 5% state of charge, such as 1% state of charge, 1.5% state of charge, 2% state of charge, 2.5% state of charge, 3% state of charge, 3.5% state of charge, 4% state of charge, 4.5% state of charge, 5% state of charge, or any point value in the range consisting of any two of the above values.

[0245] The battery cell includes multiple charging steps from 10% state of charge (SOC) to 40% SOC. For any charging step, it can be charged at any rate between 5C and 10C. The charging rate corresponding to each charging step can be any value among 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value within the range composed of any two of the above values.

[0246] The battery cell also includes multiple charging steps from 40% SOC to 80% SOC. The charging rate of any charging step is less than that of any charging step from 10% SOC to 40% SOC, and the charging rate of the step when charging to 80% SOC is any value between 2.5C and 7C. Exemplarily, the charging steps of the battery cell from 10% SOC to 80% SOC can be carried out as follows: Constant current charging at 7.0C from 10% SOC to 15% SOC; Constant current charging at 7.0C from 15% SOC to 20% SOC; Constant current charging at 7.0C from 20% SOC to 25% SOC; Constant current charging at 6.6C from 25% SOC to 30% SOC; Constant current charging at 6.2C from 30% SOC to 35% SOC; Constant current charging at 5.7C from 35% SOC to 40% SOC; Constant current charging at 5.2C from 40% SOC to 45% SOC; Constant current charging at 4.8C from 45% SOC to 50% SOC; Constant current charging at 4.6C from 50% SOC to 55% SOC; Constant current charging at 4.4C from 55% SOC to 60% SOC; Constant current charging at 4.2C from 60% SOC to 65% SOC; Constant current charging at 3.9C from 65% SOC to 70% SOC; Constant current charging at 3.5C from 70% SOC to 75% SOC; Constant current charging at 3.0C from 75% SOC to 80% SOC.

[0247] The charging speed of the battery cell is relatively fast, and the battery cell has excellent fast charging performance.

[0248] In some embodiments, the volumetric energy density of the battery cell is 395 Wh / L to 530 Wh / L, and may be optionally 395 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, 480 Wh / L, 490 Wh / L, 500 Wh / L, 510 Wh / L, 520 Wh / L, 530 Wh / L or a range composed of any two of the above values.

[0249] The battery cell has a relatively high volumetric energy density.

[0250] In the embodiments of the present application, the volumetric energy density of the battery cell has the meaning well-known in the art and can be detected by devices and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharging as 2.0 V as an example, the battery cell is placed at 25 °C, charged at a constant current of 0.33 C to 3.65 V, then charged at a constant voltage until 0.05 C, and discharged at a constant current of 0.33 C to 2.0 V. Record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and excluding the insulating film outside the outer shell), and calculate the volume V0 of the single battery cell, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0251] [Battery device] In some embodiments, the positive electrode sheet, negative electrode sheet, and separator can be made into an electrode assembly by a winding process or a stacking process.

[0252] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0253] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0254] The present application does not particularly limit the shape of the battery cell, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 is a battery cell 5 with a square structure as an example.

[0255] In some embodiments, referring to Figure 2, the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0256] In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells included in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0257] Figure 3 is a battery module 4 as an example. Refer to Figure 3 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0258] Optionally, the battery module 4 can further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0259] In some embodiments, the above battery module can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0260] Figure 4 and Figure 5 is a battery pack 1 as an example. Refer to Figure 4 and Figure 5 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 and form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0261] In addition, the present application also provides an electrical device, which includes at least one of the battery cells, battery modules, or battery packs provided by the present application. The battery cells, battery modules, or battery packs can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0262] As the electrical device, the battery cells, battery modules, or battery packs can be selected according to its usage requirements.

[0263] Figure 6 This is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high-power and high-energy density requirements of the battery cells for this electrical device, a battery pack or a battery module can be adopted.

[0264] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinness and lightness, and a battery cell can be used as the power source.

[0265] I. Preparation method of the embodiment The following embodiments more specifically describe the content disclosed in the embodiments of the present application. These embodiments are only for illustrative purposes, because various modifications and changes are obvious to those skilled in the art within the scope of the content disclosed in the embodiments of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the embodiments are commercially available.

[0266] Example 1 (1) Preparation of the positive electrode plate The positive electrode plate includes a positive current collector, a positive conductive layer on the positive current collector, and a positive electrode film layer. The positive current collector is an aluminum foil with a thickness of 13 μm.

[0267] The positive conductive layer on the positive current collector is a film layer formed by uniformly mixing a positive conductive agent, superconducting carbon, a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), and then coating it on the surface of the current collector and drying. The thickness is 1 μm. The mass content of the positive conductive agent in the positive conductive layer is 40%, and the mass content of the positive binder is 60%.

[0268] The positive electrode film layer is formed by uniformly coating a positive electrode slurry (with N-methylpyrrolidone NMP as the solvent) on the surface of the positive electrode conductive layer, followed by 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 with a weight ratio of 97:2:1.

[0269] The positive electrode active material includes lithium iron phosphate, which has a coating layer covering the surface of the lithium iron phosphate particles. The coating layer includes lithium 2 FeTi(PO 4 ) 3 and carbon element, and the mass content of the carbon element is 1.12%.

[0270] The single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 .

[0271] (2) Preparation of the negative electrode plate The negative electrode plate 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 5 μm.

[0272] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing a negative electrode conductive agent superconducting carbon, a negative electrode binder styrene-butadiene rubber SBR, a thickener sodium carboxymethyl cellulose (CMC-Na), and a solvent water, and then coating and drying on the surface of the negative electrode current collector. The thickness is 1 μm. The mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0273] The negative electrode film layer is formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer, followed by drying and cold pressing.

[0274] The single-sided coating weight of the negative electrode film layer is 95 mg / 1540.25 mm 2 .

[0275] 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.

[0276] The first negative electrode film layer includes composite graphite particles, silicon-carbon composite materials, a conductive agent acetylene black, a binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose with a mass ratio of 91.5:5:0.5:2:1. The Dv50 of the composite graphite particles is 11.3 μm.

[0277] The second negative electrode film layer includes composite graphite particles, silicon-carbon composite materials, conductive agent acetylene black, binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 92.5:5:0.5:1:1. The Dv50 of the composite graphite particles is 11.3 μm.

[0278] Among them, the thickness ratio of the first film layer to the second film layer is 50%:50%.

[0279] (3) Separator The separator includes a base film, which is a 7-μm polyethylene film layer with a porosity of 42%.

[0280] (4) Preparation of electrolyte The electrolyte includes organic solvents, lithium salts, a first additive, and a second additive.

[0281] The organic solvents include 39.0% by mass of chain carboxylic ester solvents (ethyl acetate) and 39.0% by mass of carbonate solvents (27.3% by mass of ethylene carbonate EC and 11.7% by mass of dimethyl carbonate). The mass content of each component in the organic solvents is calculated based on the mass of the electrolyte.

[0282] Based on the mass of the electrolyte, the total mass content of the first additive and the second additive is 7%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluorooxalate borate LiDFOB with a mass ratio of 5:1:0.5:0.5.

[0283] The lithium salt includes 4.5% by mass of lithium bis(fluorosulfonyl)imide LiFSI and 10.5% by mass of lithium hexafluorophosphate LiPF 6 , and the mass content of the lithium salt is calculated based on the mass of the electrolyte.

[0284] (5) Preparation of battery cell Stack the above-mentioned positive electrode plate, separator, and negative electrode plate in sequence, with the separator placed between the positive electrode plate and the negative electrode plate to play an isolation role, obtaining an electrode assembly. Place the electrode assembly in an outer packaging shell, inject the electrolyte after drying, and go through processes such as vacuum packaging, standing, forming, and shaping to obtain the battery cell. Examples 2 - 5 Compared with Example 1, Examples 2 - 5 adjusted the single-sided coating weight of the positive electrode film layer and the mass content of the silicon-carbon composite material in the first negative electrode film layer and the second negative electrode film layer of the negative electrode film layer. For specific parameters, refer to Table 3 and Table 4.

[0285] Examples 6 - 9 Compared with Example 1, in Examples 6-9, the mass contents of ethylene carbonate, dimethyl carbonate, ethyl acetate, and the first additive in the electrolyte and the mass contents of the silicon-carbon composite material in the first negative electrode film layer and the second negative electrode film layer in the negative electrode film layer were adjusted. For specific parameters, see Table 3 and Table 4.

[0286] Examples 10-12 Compared with Example 1, in Examples 10-12, the mass content of carbon element in the lithium iron phosphate coating layer was adjusted. For specific parameters, see Table 3 and Table 4.

[0287] Example 13 Compared with Example 1, in Example 13, the single-sided coating weight of the positive electrode film layer and the negative electrode film layer and the mass contents of ethylene carbonate, dimethyl carbonate, ethyl acetate, and the first additive in the electrolyte were adjusted. For specific parameters, see Table 3 and Table 4.

[0288] Comparative Example 1 Compared with Example 1, in Comparative Example 1, the single-sided coating weights of the positive electrode film layer and the negative electrode film layer were adjusted and the negative electrode film layer did not contain the silicon-carbon composite material. For specific parameters, see Table 3 and Table 4.

[0289] Comparative Example 2 Compared with Example 1, in Comparative Example 2, the single-sided coating weight of the positive electrode film layer and the mass contents of the silicon-carbon composite material in the first negative electrode film layer and the second negative electrode film layer in the negative electrode film layer were adjusted. For specific parameters, see Table 3 and Table 4.

[0290] Comparative Examples 3-4 Compared with Example 1, in Comparative Examples 3-4, the mass contents of ethylene carbonate, dimethyl carbonate, ethyl acetate, and the first additive in the electrolyte were adjusted. For specific parameters, see Table 3 and Table 4.

[0291] II. Performance tests.

[0292] 1. The charging time of the battery cell from 10% SOC to 80% SOC. The following charging steps were specifically adopted. Taking the battery cell of Example 1 as an example: At 30 °C, charging was carried out from the 10% SOC state of the battery cell. Constant current charging at 7.0C from 10% SOC to 15% SOC; Constant current charging at 7.0C from 15% SOC to 20% SOC; Constant current charging at 7.0C from 20% SOC to 25% SOC; Constant current charging at 7.0C from 25% SOC to 30% SOC; Constant current charging at 6.2C from 30% SOC to 35% SOC; Charge from 35% SOC to 40% SOC at a constant current of 5.7C; Charge from 40% SOC to 45% SOC at a constant current of 5.2C; Charge from 45% SOC to 50% SOC at a constant current of 4.8C; Charge from 50% SOC to 55% SOC at a constant current of 4.6C; Charge from 55% SOC to 60% SOC at a constant current of 4.4C; Charge from 60% SOC to 65% SOC at a constant current of 4.2C; Charge from 65% SOC to 70% SOC at a constant current of 3.9C; Charge from 70% SOC to 75% SOC at a constant current of 3.5C; Charge from 75% SOC to 80% SOC at a constant current of 3.0C; Record the total charging time.

[0293] The slight differences in the charging times of the battery cells in different embodiments and comparative examples from 10% to 80% SOC can be obtained by slightly adjusting the above charging rates. Generally, the charging rate gradually decreases from low SOC to high SOC. The specific charging rate for different SOC intervals is as follows: At 25°C, charge the battery cell at a constant current of 1 / 3C until the charging cut-off voltage of 3.65V, then charge at a constant voltage until the current is 0.05C, let it stand for 5 minutes, and then discharge at a constant current of 1 / 3C until the discharge cut-off voltage of 2V. Record its actual capacity as C. Then charge the battery cell successively at constant currents of 0.5C, 1.0C, 1.5C, 2.0C, 2.5C, 3.0C, 3.5C, 4.0C, 4.5C, 5.0C, 5.5C, 6.0C, 6.5C, 7.0C, 7.5C, 8.0C, 8.5C, 9.0C, 9.5C, 10.0C until the full-battery charging cut-off voltage of 3.65V or the 0mV lithium plating potential (whichever comes first). After each charging is completed, discharge at 1C until the full-battery discharge cut-off voltage of 2V. Record the negative electrode potentials corresponding to 10%, 15%, 20%, 25%, 30%... 80% SOC (State of Charge) at different charging rates, plot the rate-negative electrode potential curves at different SOC states, and obtain the charging rates corresponding to the 0mV lithium plating potential at different SOC states by linear fitting. This charging rate is the charging rate adopted for the corresponding SOC interval during the above charging time test. Among them, the maximum rate that the mechanical components of the battery cell can withstand for charging from 10% SOC to 15% SOC is 7C. For the specific charging rates, refer to Table 1 and Table 2.

[0294] Table 1

[0295] Table 2

[0296] 2. Capacity retention rate of the battery cell at 30°C after 1000 cycles At 30°C, charge the battery cell starting from 0% SOC. Charge it to 100% SOC at the rates corresponding to the following different SOCs, then continue to charge at a constant current of 0.33C until 3.65V, let it stand for 30 min, and then discharge at a constant current of 1C until 2.0V. This is one charge-discharge cycle. Record the capacity C0 after the first cycle; repeat the above charge-discharge cycle steps until 1000 cycles, and record the capacity Cn corresponding to the 1000th cycle. The capacity retention rate of the battery at 30°C after 1000 cycles = Cn / C0 × 100%. The higher the capacity retention rate, the better the cycling performance of the battery cell. The charging process from 0% SOC to 100% SOC is as follows: Taking the battery cell of Example 1 as an example: Charge at a constant current of 1C from 0% SOC to 10% SOC; Charge at a constant current of 7.0C from 10% SOC to 15% SOC; Charge at a constant current of 7.0C from 15% SOC to 20% SOC; Charge at a constant current of 7.0C from 20% SOC to 25% SOC; Charge at a constant current of 7.0C from 25% SOC to 30% SOC; Charge at a constant current of 6.2C from 30% SOC to 35% SOC; Charge at a constant current of 5.7C from 35% SOC to 40% SOC; Charge at a constant current of 5.2C from 40% SOC to 45% SOC; Charge at a constant current of 4.8C from 45% SOC to 50% SOC; Charge at a constant current of 4.6C from 50% SOC to 55% SOC; Charge at a constant current of 4.4C from 55% SOC to 60% SOC; Charge at a constant current of 4.2C from 60% SOC to 65% SOC; Charge at a constant current of 3.9C from 65% SOC to 70% SOC; Charge at a constant current of 3.5C from 70% SOC to 75% SOC; Charge at a constant current of 3.0C from 75% SOC to 80% SOC; Charge at a constant current of 0.33C from 80% SOC to 100% SOC.

[0297] The slight differences in the charging time of the battery cells in different embodiments and comparative examples at 10% - 80% SOC can be obtained by slightly adjusting the above charging rate. Generally, the charging rate gradually decreases from low SOC to high SOC. For specific charging rates, refer to Table 1 and Table 2.

[0298] 3. The test steps for the volume energy density (VED) of the battery cell are as follows: Place the battery cells of the embodiments and comparative examples at 25°C, charge them at a constant current of 0.33C to 3.65V, then charge them at a constant voltage of 3.65V to 0.05C, and let them stand for 30 minutes; discharge them at a constant current of 0.33C to 2.0V, and record the discharge capacity A0 at this time, unit: Ah; use a caliper to measure the length, width, and height of the battery cell, and calculate the volume V0 of the single battery cell, unit: L; the volume energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0299] III. Analysis of the test results of each embodiment and comparative example Prepare each embodiment and comparative example according to the above method, and measure various performance parameters. The results are shown in the following table.

[0300] Table 3

[0301] Table 4

[0302] (863cls@60% SOH in Comparative Example 3 means that after the battery cell in Comparative Example 3 is cycled 863 times, the capacity retention rate is only 60%) According to the above results, the battery cells in Embodiments 1 - 13 include an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is located between the positive electrode plate and the negative electrode plate. The positive electrode plate 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 positive electrode active material includes a lithium phosphate with an olivine structure. The single-sided coating weight of the positive electrode film layer is 180mg / 1540.25mm 2 ~380mg / 1540.25mm 2 ; the negative electrode plate 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. The negative electrode active material includes a silicon-based material. Based on the mass of the negative electrode active material, the mass content of silicon element is 0.3% - 10.0%; the electrolyte includes a first additive. The first additive includes vinylene carbonate and / or fluoroethylene carbonate. The mass content of the first additive is 1% - 12%.

[0303] As can be seen from the comparison between Examples 1-13 and Comparative Example 1, compared with simply adjusting the single-sided coating weight of the positive electrode film layer and the single-sided coating weight of the negative electrode film layer, by adjusting the single-sided coating weight of the positive electrode film layer and the content of silicon-based elements in the negative electrode film layer, the present application can improve the energy density of the battery cell while taking into account the fast charging performance of the battery cell.

[0304] As can be seen from the comparison between Examples 1-13 and Comparative Example 2, controlling the mass content of silicon element in the silicon-based material to be 0.3% - 10.0% can improve the cycling performance and fast charging performance of the battery cell.

[0305] As can be seen from the comparison between Examples 1-13 and Comparative Examples 3-4, controlling the mass content of the first additive to be 1% - 12% can improve the cycling performance of the battery cell while also taking into account the fast charging performance of the battery cell.

[0306] As can be seen from the comparison between Examples 1-4 and Example 5, when the mass content of silicon element in the silicon-based material is 0.3% - 6.0%, the cycling performance and fast charging performance of the battery cell can be further improved.

[0307] As can be seen from Examples 1-3, 6-7, 10-13, when the mass content of silicon element in the negative active material is 0.3% - 3% and the mass content of the first additive in the electrolyte is 2% - 7%, the battery cell has excellent cycling performance and fast charging performance.

[0308] As can be seen from Examples 4-5, 8-9, when the mass content of silicon element in the negative active material is greater than 3% and less than or equal to 6% and the mass content of the first additive in the electrolyte is 3% - 10%, the battery cell has a high volumetric energy density.

[0309] As can be seen from Examples 1-13, when the ratio of the mass content A of silicon element in the silicon-based material to the mass content B of the first additive is 0.025 - 6, the battery cell has a high energy density, excellent cycling performance and fast charging performance.

[0310] As can be seen from Examples 1, 10-12, based on the mass of the lithium-containing carbonate based on the olivine structure, when the mass content of carbon element is 0.8% - 2.3%, the battery cell takes into account excellent cycling performance and fast charging performance.

[0311] As can be seen from Examples 1, 13, the electrolyte includes a first organic solvent of ethylene carbonate and dimethyl carbonate and a second organic solvent of ethyl acetate, and based on the total mass of the electrolyte, the mass content of the first organic solvent is 20% - 72%, and the battery cell has excellent cycling performance and fast charging performance.

Claims

1. A battery cell, characterized in that: The invention comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing phosphate with an olivine structure. The single-sided coating weight of the positive electrode film layer is 180 mg / 1540.25 mm 2 Up to 380mg / 1540.25mm 2 ; The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a silicon-based material, and the mass content of silicon element is 0.3% to 10.0% based on the mass of the negative electrode active material; The electrolyte includes a first additive, the first additive includes at least one of vinylene carbonate and a vinyl carbonate derivative, and the mass content of the first additive is 1% to 12% based on the total mass of the electrolyte. Wherein, the ethylene carbonate derivative includes the compound shown in formula I, Formula I R1, R2, R3, and R4 are each independently a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 halogenated alkyl group, and R1, R2, R3, and R4 are not hydrogen atoms at the same time. The battery cell is at 100% charge state, and the compaction density of the positive electrode film layer is 2.50 g / cm 3 ~2.80g / cm 3 .

2. The battery cell according to claim 1, characterized in that: Based on the mass of the negative electrode active material, the mass content of the silicon element is 0.3% to 6.0%.

3. The battery cell according to claim 1 or 2, characterized in that: At least one of R1, R2, R3, and R4 contains a fluorine atom.

4. The battery cell according to claim 1, characterized in that: The ethylene carbonate derivatives include one or more of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoromethylethylene carbonate.

5. The battery cell according to claim 1, characterized in that: The battery cell satisfies the following relationship: 0.025≤A / B≤6, Wherein A is the mass content of the silicon element, based on the mass of the negative electrode active material; B is the mass content of the first additive, based on the total mass of the electrolyte.

6. The battery cell according to claim 1, characterized in that: The battery cell satisfies the following relationship: 0.035≤A / B≤2.5, Wherein A is the mass content of the silicon element, based on the mass of the negative electrode active material; B is the mass content of the first additive, based on the total mass of the electrolyte.

7. The battery cell according to claim 1, characterized in that: Based on the mass of the negative electrode active material, the mass content of the silicon element is 0.3% to 3%; Based on the total mass of the electrolyte, the mass content of the first additive is 2% to 7.5%.

8. The battery cell according to claim 1, characterized in that: Based on the mass of the negative electrode active material, the mass content of the silicon element is greater than 3% and less than or equal to 6%; Based on the total mass of the electrolyte, the mass content of the first additive is 3% to 10%.

9. The battery cell according to claim 1, characterized in that: The lithium-containing phosphate of the olivine structure comprises: A lithium phosphate matrix, and The coating layer is located on at least a portion of the surface of the lithium-phosphate matrix, and the coating layer contains carbon elements.

10. The battery cell according to claim 9, characterized in that: Based on the mass of the lithium-containing phosphate with an olivine structure, the mass content of the carbon element is 0.8% to 2.3%.

11. The battery cell according to claim 9 or 10, characterized in that: The battery cell satisfies the following relationship: 0.08≤C / B≤1.15, Wherein, C is the mass content of the carbon element, based on the mass of the lithium-containing phosphate with an olivine structure; B is the mass content of the first additive, based on the total mass of the electrolyte.

12. The battery cell according to claim 9, characterized in that: The coating layer also includes Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 of substances, Among them, 0≤d1≤1, 3≤m1≤5, 2≤n1≤4; M3 includes one or more of Ti, Zr, Hf, Ge, and Sn.

13. The battery cell according to claim 12, characterized in that: M3 has a valence of +4.

14. The battery cell according to claim 9, characterized in that: The lithium-containing phosphate matrix includes a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 The compound Among them, 0.5≤x1≤1.3, 0≤y1≤1.3, 0.9≤x1+y1≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z1≤5; Among them, A includes at least one of Na, K and Mg; Me includes at least one of Mn, Fe, Co and Ni; M includes at least one of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce; X includes at least one of S, Si, Cl, B, C, N and P; Y includes at least one of O and F.

15. The battery cell according to claim 9, characterized in that: The lithium-phosphate matrix includes lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, lithium cobalt phosphate and one or more modified forms of any one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate and lithium cobalt phosphate, wherein the modified form includes one or more of doping modification and coating modification.

16. The battery cell according to claim 1, characterized in that: The powder compaction density of the positive electrode active material at 30000N is 2.43g / cm 3 ~2.85g / cm 3 .

17. The battery cell according to claim 16, characterized in that: The powder compaction density of the positive electrode active material at 30000N is 2.48g / cm 3 ~2.80g / cm 3 .

18. The battery cell according to claim 1, characterized in that: The negative electrode active material includes a carbon-based material, and the carbon-based material includes graphite.

19. The battery cell according to claim 18, characterized in that: The graphite comprises composite graphite particles, wherein the composite graphite particles comprise graphite main particles and a carbon coating layer coated on the surface of the graphite main particles, the graphite main particles comprise secondary particles, and the carbon coating layer comprises amorphous carbon.

20. The battery cell according to claim 19, characterized in that: The composite graphite particles satisfy at least one of the following conditions: (1) Based on the total mass of the composite graphite particles, the mass content of the amorphous carbon is 2% to 5%; (2) The powder resistivity of the composite graphite particles is 0.005Ω•cm-0.04Ω•cm.

21. The battery cell according to claim 19, 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 arranged between the current collector and the second negative electrode film layer, and the first negative electrode film layer and the second negative electrode film layer both include the composite graphite particles.

22. The battery cell according to claim 21, characterized in that: The volume average particle size Dv50 of the composite graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the composite graphite particles in the second negative electrode film layer.

23. The battery cell according to claim 22, characterized in that: The volume average particle size Dv50 of the composite graphite particles in the first negative electrode film layer is 8.5 μm to 14.8 μm, and / or, The volume average particle size Dv50 of the composite graphite particles in the second negative electrode film layer is 7.8 μm to 12.8 μm.

24. The battery cell according to claim 21, characterized in that: Based on the total thickness of the first negative electrode film layer and the second negative electrode film layer, the thickness of the second negative electrode film layer accounts for 30% to 70%.

25. The battery cell according to claim 1, characterized in that The negative electrode plate also includes a negative electrode conductive layer, which is located between the negative electrode current collector and the negative electrode film layer on at least one side. The negative electrode conductive layer includes a conductive agent, and the conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

26. The battery cell according to claim 25, characterized in that: The thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

27. The battery cell according to claim 1, characterized in that: The compaction density of the negative electrode film layer of the battery cell is 1.15 g / cm 3 ~1.45g / cm 3 , and / or, The single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 Up to 135mg / 1540.25mm 2 .

28. The battery cell according to claim 1, characterized in that: The electrolyte further includes an organic solvent, and the organic solvent includes one or more of a first organic solvent and a second organic solvent. Wherein, the first organic solvent includes at least one of a cyclic carbonate and a chain carbonate, and can be a cyclic carbonate; The second organic solvent comprises R5-COO-R6, Wherein, R5 includes any one of a hydrogen atom, a halogen atom, a C1~C5 alkyl group, and a C1~C5 halogenated alkyl group, and R6 includes any one of a C1~C5 alkyl group and a C1~C5 halogenated alkyl group.

29. The battery cell according to claim 28, characterized in that: The first organic solvent is a cyclic carbonate.

30. The battery cell according to claim 29, characterized in that The cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate and butylene carbonate; and / or, The linear carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; and / or, The second organic solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

31. The battery cell according to claim 29 or 30, characterized in that: Based on the total mass of the electrolyte, the mass content of the first organic solvent is 20% to 72%.

32. The battery cell according to claim 1, characterized in that The electrolyte further includes a second additive, and the second additive includes one or more of a sulfur-containing additive and a lithium salt additive.

33. The battery cell according to claim 32, characterized in that: The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylene disulfonate; and / or, The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

34. The battery cell according to claim 1, characterized in that The electrolyte further includes a lithium salt, and the lithium salt includes one or both of a fluorine-containing sulfonyl imide salt and lithium hexafluorophosphate.

35. The battery cell according to claim 34, characterized in that: The fluorine-containing sulfonyl imide salt includes one or both of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

36. The battery cell according to claim 35, characterized in that The lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, and the ratio of the molar concentration of the lithium bis(fluorosulfonyl)imide to the molar concentration of the lithium hexafluorophosphate is 0.2-1.

0.

37. The battery cell according to claim 36, characterized in that: The molar concentration of the lithium bis(fluorosulfonyl)imide is 0.2 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate is 0.5 mol / L to 1.2 mol / L.

38. The battery cell according to claim 1, characterized in that The isolation film satisfies at least one of the following conditions: (1) The thickness of the isolation film is 4 μm to 12 μm; (2) The porosity of the isolation membrane is 20% to 70%.

39. The battery cell according to claim 38, characterized in that The isolation film satisfies at least one of the following conditions: (1) The thickness of the isolation film is 5 μm to 9 μm; (2) The porosity of the isolation membrane is 35% to 60%.

40. The battery cell according to claim 1, characterized in that The battery cell is configured such that the charging time from a 10% state of charge to an 80% state of charge is 5 minutes to 10.5 minutes.

41. The battery cell according to claim 1, characterized in that The volume energy density of the battery cell is 395Wh / L~530Wh / L.

42. A battery device, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 41.

43. The battery device according to claim 42, characterized in that The battery device is configured such that the charging time from a 10% state of charge to an 80% state of charge is 5 minutes to 10.5 minutes.

44. An electrical device, characterized in that: A battery device comprising claim 42 or 43.

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