Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device, the battery monomer comprises an electrode assembly and an electrolyte, and the electrode assembly comprises a positive pole piece and a negative pole piece; the positive pole piece comprises a positive pole current collecting part and a positive pole film layer; the positive pole film layer comprises lithium-containing phosphate with an olivine structure; the negative pole piece comprises a negative pole current collecting part and a negative pole film layer, and the negative pole film layer comprises a carbon-based material; the electrolyte comprises a carboxylic ester solvent, a first additive and fluorine-containing lithium sulfimide, and the mass content of the carboxylic ester solvent is 8%-60%; the total mass content of the first additive is 2.5%-10%, the first additive comprises 1, 3-propane sultone with the mass content larger than or equal to 0, an ethylene carbonate derivative with the mass content larger than or equal to 0 and vinylene carbonate with the mass content larger than 0, and the ethylene carbonate derivative comprises a compound shown in the formula A; the mass content of the fluorine-containing lithium sulfimide is 4%-8%. According to the invention, the rapid charging performance and the cycle performance of the battery monomer can be improved. # imgabs0 # formula A

Description

[0001] This application claims the priority of the international application PCT / CN2025 / 078570 titled "Battery Cell, Battery Device and Electrical Device" filed on February 21, 2025, and the entire content of this application 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 thus are widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, and electric tools, etc. With the development of the application fields of lithium-ion batteries, higher requirements are put forward for the performance of lithium-ion batteries, such as fast charging performance, cycling performance, etc. Summary of the Invention This application provides a battery cell, a battery device and an electrical device, which can reduce the heat generation of the battery cell and improve the fast charging performance and cycling performance of the battery cell.

[0004] In a first aspect, this application provides a battery cell. The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab; the positive electrode tab includes a positive current collector part and a positive electrode film layer provided on at least one side of the positive current collector part, and the positive electrode film layer includes a lithium-containing phosphate with an olivine structure; the negative electrode tab includes a negative current collector part and a negative electrode film layer provided on at least one side of the negative current collector part, and the negative electrode film layer includes a carbon-based material; the electrolyte includes a carboxylic acid ester solvent, a first additive and a lithium salt. Among them, based on the mass of the electrolyte, the mass content of the carboxylic acid ester solvent is 8% to 60%; based on the mass of the electrolyte, the total mass content of the first additive is 2.5% to 10%, and the first additive includes 1,3-propane sultone with a mass content ≥0, a carbonic acid ethylene ester derivative with a mass content ≥0, and vinylene carbonate with a mass content >0. The carbonic acid ethylene ester derivative includes a compound represented by Formula A, Formula A, In Formula A, Q 1 , Q 2 , Q 3 and Q 4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q 1 , Q 2 , Q 3 , Q 4 are not simultaneously hydrogen atoms; The lithium salt includes lithium fluorosulfonylimide, and the mass content of lithium fluorosulfonylimide in the electrolyte is 4% to 8%.

[0005] Thus, in the embodiments of the present application, the positive electrode active material includes lithium-containing phosphate in an olivine structure, and the negative electrode active material includes a carbon-based material. The above material system has relatively excellent cycle stability; the electrolyte includes lithium fluorosulfonylimide, and lithium fluorosulfonylimide has good water stability and is not likely to react with water to produce acid, which can improve the stability of the solid electrolyte interface film (SEI film), reduce the consumption and usage amount of additives; the electrolyte includes a carboxylic ester solvent and a first additive, and the first additive includes vinylene carbonate. The reaction potentials of vinylene carbonate and the carboxylic ester solvent are close, and there is a competitive reaction with the carboxylic ester solvent during the film formation process. When the mass content of vinylene carbonate is appropriate, it is beneficial for vinylene carbonate to participate in film formation on the negative electrode side, and vinylene carbonate can form a dense organic film, making it difficult for the carboxylic ester solvent to penetrate the organic film to the negative electrode active material, thereby alleviating the side reaction between the carboxylic ester solvent and the negative electrode active material, reducing gas generation, and improving the high-temperature cycle performance; the mass content of the first additive is not too high, so that the impedance of the SEI film is relatively low, which is beneficial for improving the fast charging ability; further, when the mass content of the carboxylic ester solvent is within an appropriate range, it can further alleviate the side reaction with the negative electrode active material, and can reduce the viscosity of the electrolyte, increase the migration rate of lithium ions in the electrolyte, and improve the fast charging ability of the battery cell. Therefore, the embodiments of the present application can improve the fast charging ability and cycle performance of the battery cell.

[0006] In some embodiments, the mass content of lithium fluorosulfonylimide in the electrolyte is 4% to 6%. When the mass content of lithium fluorosulfonylimide is within the above range, it can improve the cycle performance and fast charging performance of the battery cell.

[0007] In some embodiments, lithium fluorosulfonylimide includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and lithium perfluorobutanesulfonylimide. The above materials can improve the cycle performance and fast charging performance of the battery cell.

[0008] In some embodiments, the lithium salt further includes lithium hexafluorophosphate, and the ratio of the mass content of lithium fluorosulfonylimide to the mass content of lithium hexafluorophosphate is 0.3 to 1.0, and can be selected as 0.4 to 0.8, based on the mass of the electrolyte. The above lithium salt system has excellent ionic conductivity, and can reduce the side reaction on the negative electrode side, and improve the cycle performance and fast charging performance of the battery cell.

[0009] In some embodiments, the mass content of lithium hexafluorophosphate in the electrolyte is 8% to 12%. When the mass content of lithium hexafluorophosphate is within the above range, the ionic conductivity of the electrolyte is relatively excellent, which is beneficial for improving the fast charging performance of the battery cell.

[0010] In some embodiments, the mass content of the first additive is 3% to 7.5%, which can further improve the fast charging ability, cycling performance, and use reliability of the battery cell.

[0011] In some embodiments, the mass content of vinylene carbonate in the electrolyte is 2% to 5%. When the mass content of vinylene carbonate is within the above range, a dense SEI film can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reactions on the negative electrode side and balance the improvement of the cycling performance and fast charging ability of the battery cell.

[0012] In some embodiments, the mass content of 1,3 - propanesultone in the electrolyte is 0 to 0.5%, and can be optionally 0 to 0.3%. When the mass content of 1,3 - propanesultone is within the above range, the impedance of the formed SEI film will not be too high, which can reduce the impedance on the basis of alleviating side reactions and improve the fast charging performance and high - temperature cycling performance of the battery cell.

[0013] In some embodiments, the mass content of ethylene carbonate derivatives in the electrolyte is 0 to 4.0%, and can be optionally 1.5% to 3.5%. Ethylene carbonate derivatives can form a film preferentially, optimize the components of the SEI film, reduce the impedance of the SEI film, and effectively improve the fast charging performance and cycling performance of the battery cell.

[0014] In some embodiments, Q 1 、Q 2 、Q 3 and Q 4 at least one of them includes a halogen atom or a C1 - C5 haloalkyl group. When the ethylene carbonate derivative includes a fluorine atom, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side. On the basis of protecting the negative electrode active material, the impedance of the film layer is low, which can more effectively balance the improvement of the high - temperature cycling performance and fast charging performance of the battery cell.

[0015] In some embodiments, the ethylene carbonate derivative includes at least one of the compounds shown by Formula A - 1 to the compounds shown by Formula A - 3,

[0016] The above materials can further improve the high - temperature cycling performance and fast charging performance of the battery cell.

[0017] In some embodiments, the carboxylic ester solvent includes the compound shown by Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a C1 - C5 alkyl group or a C1 - C5 haloalkyl group, R 2 including C1-C5 alkyl or C1-C5 haloalkyl.

[0018] The above-mentioned chain carboxylic ester solvents have low viscosity, improve the fast charging ability of battery cells, reduce the risk of lithium deposition under fast charging, and improve the reliability of battery cell use.

[0019] In some embodiments, the carboxylic ester solvent includes one or more of the compounds shown in Formula I-1 to the compounds shown in Formula I-12.

[0020] The above materials can further improve the fast charging performance of battery cells.

[0021] In some embodiments, the electrolyte further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 18% to 70%. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions and improves the fast charging ability of battery cells.

[0022] In some embodiments, the carbonate solvent includes cyclic carbonates, and the cyclic carbonates include one or more of ethylene carbonate, propylene carbonate, and butylene carbonate; the above materials can further improve the fast charging performance of battery cells.

[0023] In some embodiments, the carbonate solvent includes linear carbonates, and the linear carbonates include one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The above materials can further improve the fast charging performance of battery cells.

[0024] In some embodiments, the electrolyte includes a sulfur-containing additive with a mass content of 0 to 2% in the electrolyte. Optionally, the mass content of the sulfur-containing additive is 0.5% to 2%. The sulfur-containing additive includes one or more of vinylene sulfate, bis(vinylsulfate), butylene sulfite, ethylene sulfite, and methylene methyl disulfonate. The sulfur-containing additive and the first additive cooperate to participate in film formation, which can optimize the film layer components of the SEI film. The sulfur-containing additive can participate in the formation of an SEI film rich in inorganic substances, and the inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI film, and improve the high-temperature cycle performance of battery cells.

[0025] In some embodiments, the electrolyte includes a lithium salt additive with a mass content of 0 to 1% in the electrolyte. Optionally, the mass content of the lithium salt additive is 0.2% to 1%. The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate. The salt additive and the first additive cooperate to form a film, which can optimize the film layer components of the SEI film. The lithium salt additive can participate in the formation of an SEI film rich in inorganic substances, and the inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI film, and improve the high-temperature cycling performance of the battery cell.

[0026] In some embodiments, the lithium-containing phosphate in the olivine structure includes phosphate particles and a cathode coating layer. The cathode coating layer is located on at least part of the surface of the phosphate particles, and the cathode coating layer contains carbon elements. By coating the surface of the phosphate particles with the cathode coating layer, the conductivity of the lithium-containing phosphate in the olivine structure can be improved, which is beneficial to the migration rate of lithium ions, improves the fast charging ability of the battery, and reduces the heat generation of the battery cell, and improves the high-temperature cycling performance of the battery cell.

[0027] In some embodiments, based on the mass of the lithium-containing phosphate in the olivine structure, the mass content of carbon elements is 0.8% to 2.3%. When the mass content of carbon elements is within the above range, the conductivity of the lithium-containing phosphate in the olivine structure can be significantly improved, which is beneficial to improving the ionic conductivity and electronic conductivity of the lithium-containing phosphate in the olivine structure, and can improve the fast charging ability of the battery cell.

[0028] In some embodiments, the cathode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn. The material containing the above elements can improve the ionic conductivity of the cathode active material, improve the fast charging ability of the battery cell, and in addition, can also improve the specific capacity and the energy density of the corresponding battery cell.

[0029] In some embodiments, the phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. The above materials have excellent cycle stability and can improve the cycle performance of the battery cell.

[0030] In some embodiments, the lithium-containing phosphate includes a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1Compounds, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5, 0 ≤ c1 ≤ 0.5, 3 ≤ z1 ≤ 5, A includes 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 Cl, C, and N; Y includes at least one of O and F. The above materials have excellent cycling stability and can improve the cycling performance of battery cells.

[0031] In some embodiments, the powder tap density of the positive electrode active material under 30,000 N is 2.43 g / cm 3 to 2.85 g / cm 3 . When the powder tap density of the positive electrode active material under 30,000 N is within the above range, it can improve the energy density of the battery cell. And because the positive electrode active materials in the positive electrode film layer can be stacked more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the high-temperature cycling performance and fast charging performance of the battery cell.

[0032] In some embodiments, at 0% SOC state of charge of the battery cell, the tap density of the positive electrode film layer is 2.46 g / cm 3 to 2.8 g / cm 3 ; when the tap density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. And because the positive electrode active materials in the positive electrode film layer are stacked more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during fast charging and improving the high-temperature cycling performance and fast charging performance of the battery cell.

[0033] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 350 mg / 1540.25 mm 2 . When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode sheet will not be too large, improving the high-temperature cycling performance and fast charging performance of the battery cell.

[0034] In some embodiments, the positive electrode tab further includes a positive electrode conductive layer located between the positive electrode current collector portion and the positive electrode film layer. The positive electrode conductive layer includes a positive electrode conductive agent, and the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive layer can further improve the electrical conductivity of the positive electrode tab and reduce the heat generation of the positive electrode tab, thereby reducing the heat generation of the battery cell.

[0035] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. When the thickness of the positive electrode conductive layer is within the above range, it can further improve the electrical conductivity of the positive electrode tab, reduce the heat generation of the positive electrode tab, thereby reducing the heat generation of the battery cell, and can improve the high-temperature cycle performance of the battery cell.

[0036] In some embodiments, the graphite particles include graphite body particles and a negative electrode coating layer coated on the surface of the graphite body particles. The graphite body particles include secondary particles, and the negative electrode coating layer includes carbon elements. The graphite body particles include secondary particles, and there are more migration paths for lithium ions in the graphite body particles and shorter migration paths in the primary particles, which can improve the migration rate of lithium ions. The negative electrode coating layer has more end faces and defects, so that the number of sites capable of intercalating and deintercalating lithium ions is larger, making the electrical conductivity of the negative electrode coating layer relatively excellent, which can reduce the internal resistance of the negative electrode tab, reduce the heat generation of the battery cell, and improve the fast charging performance and high-temperature cycle performance of the battery cell.

[0037] In some embodiments, the graphite body particles include at least one of artificial graphite and natural graphite.

[0038] In some embodiments, based on the total mass of the graphite particles, the mass content of carbon elements in the negative electrode coating layer is 2% to 5%. When the mass content of carbon elements in the negative electrode coating layer is within the above range, it can further reduce the internal resistance of the negative electrode tab, reduce the heat generation of the battery cell, and can improve the high-temperature cycle performance of the battery cell.

[0039] In some embodiments, the negative electrode film layer further includes a silicon-based material, and the mass content of silicon elements in the negative electrode film layer is 0.3% to 5.0%. When the mass content of silicon elements in the silicon-based material is within the above range, it can improve the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0040] In some embodiments, the powder compaction density of the negative electrode active material under 20000 N is 1.4 g / cm 3 to 1.8 g / cm 3When the powder compaction density of the negative electrode active material is within the above range under 20,000 N, the energy density of the battery cell can be improved. Moreover, due to the closer packing of the negative electrode active material in the negative electrode film layer, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the high-temperature cycle performance of the battery cell.

[0041] In some embodiments, when the battery cell is in the 0% state of charge, the compaction density of the negative electrode film layer is 1.30 g / cm 3 to 1.55 g / cm 3 When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, due to the closer packing of the negative electrode active material in the negative electrode film layer, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and reducing the amount of gas generated by the decomposition of carboxylic ester solvents due to heat accumulation, and improving the high-temperature cycle performance of the battery cell.

[0042] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode sheet will not be too large, and it can also take into account the improvement of the high-temperature cycle performance of the battery cell.

[0043] In some embodiments, the negative electrode sheet further includes a negative electrode conductive layer, which is located between the negative electrode current collector and the negative electrode film layer. The negative electrode conductive layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The negative electrode conductive layer can further improve the conductivity of the negative electrode sheet, reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery cell, and improving the fast charging performance and high-temperature cycle performance of the battery cell.

[0044] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. When the thickness of the negative electrode conductive layer is within the above range, it can further improve the conductivity of the negative electrode sheet, reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery cell, and can also take into account the improvement of the energy density of the battery cell.

[0045] In some embodiments, the electrode assembly further includes a separator, which is located between the positive electrode sheet and the negative electrode sheet. The separator includes a base film, and the thickness of the base film is 4 μm to 12 μm; and / or the porosity of the base film is 20% to 70%. When the base film meets the above range, it can improve the migration ability of lithium ions in the separator, further reduce the internal resistance of the battery cell, thereby reducing heat generation, and improving the fast charging performance and high-temperature cycle performance of the battery cell.

[0046] In some embodiments, the separator membrane further includes a functional layer disposed on at least one side of the base membrane. The functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base membrane and includes first inorganic particles. The second functional layer is located on the other side of the base membrane and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator membrane.

[0047] In some embodiments, the non-fluoropolymer particles include acrylate copolymers. Acrylate copolymers have excellent adhesion properties and high adhesion stability with the base membrane.

[0048] In some embodiments, the first inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide; the first inorganic particles have good heat resistance, which is beneficial to improving the heat resistance and compression modulus of the composite particles.

[0049] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the first inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0050] In some embodiments, the second inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The second inorganic particles have good heat resistance, which is beneficial to improving the heat resistance and compression modulus of the composite particles.

[0051] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0052] In some embodiments, the positive electrode tab and the negative electrode tab are stacked along the thickness direction of the battery cell; the electrode assembly further includes a positive electrode ear and a negative electrode ear. The positive electrode ear is connected to at least one side of the positive current collector along the length direction of the battery cell, and the negative electrode ear is connected to at least one side of the negative current collector along the length direction of the battery cell; along the length direction of the battery cell, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH 1 ; along the width direction of the battery cell, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH 2 wherein, OH1 Greater than OH 2 .

[0053] Thus, the embodiment of the present application sets OH 1 Greater than OH 2 , so that the ability of the negative electrode film layer to receive lithium ions in the length direction is stronger, especially the ability of the area of the negative electrode film layer close to the negative electrode tab to receive lithium ions can be improved, the risk of lithium precipitation can be reduced, and the use reliability of the battery cell can be improved.

[0054] In some embodiments, OH 1 is 1.0 mm to 4.0 mm; and / or OH 2 is 1.0 mm to 3.0 mm. When the battery cell meets the above conditions, the risk of lithium precipitation can be reduced, and the use reliability of the battery cell can be improved.

[0055] In some embodiments, the battery cell further includes at least one positive terminal, and the current-carrying area of all the positive terminals on the same side of the positive current collector is 150 mm 2 to 1000 mm 2 ; when the current-carrying area of the positive terminal meets the above range, the current-carrying capacity is strong, the internal resistance can be reduced, and the heat generation can be reduced, which is beneficial to improving the fast charging performance and high-temperature cycling performance of the battery cell.

[0056] In some embodiments, the battery cell further includes at least one negative terminal, and the current-carrying area of all the negative terminals on the same side of the negative current collector is 150 mm 2 to 1000 mm 2 . When the current-carrying area of the negative terminal meets the above range, the current-carrying capacity is strong, the internal resistance can be reduced, and the heat generation can be reduced, which is beneficial to improving the fast charging performance and high-temperature cycling performance of the battery cell.

[0057] In some embodiments, the battery cell includes a housing that houses the electrode assembly and the electrolyte, and the thickness of the housing is 0.1 mm to 0.5 mm. When the thickness of the housing is within the above range, the mechanical strength of the housing is high, the use reliability and cycling performance of the battery cell can be improved, and the housing occupies less space and there is more internal space in the housing, which is beneficial to improving the energy density of the battery cell.

[0058] In a second aspect, the present application provides a battery device, and the battery device includes a plurality of battery cells according to any one of the embodiments of the first aspect of the present application.

[0059] In some embodiments, the charging time of the battery device from 10% state of charge to 80% state of charge is 5 min to 15 min. The charging speed of the battery device is fast, which is more beneficial to improving the fast charging ability.

[0060] In a third aspect, the present application provides an electrical device, which includes the battery device according to any one of the embodiments of the second aspect of the present application. Description of the Drawings

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below 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.

[0062] Figure 1 It is a schematic structural diagram of a battery cell provided in some embodiments of the present application. Figure 2 It is an exploded schematic diagram of a battery cell provided in some embodiments of the present application. Figure 3 It is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application. Figure 4 It is a schematic structural diagram of a positive electrode tab of a battery cell provided in some embodiments of the present application. Figure 5 It is a schematic structural diagram of a positive electrode tab of a battery cell provided in some other embodiments of the present application. Figure 6 It is a schematic structural diagram of a negative electrode tab of a battery cell provided in some embodiments of the present application. Figure 7 It is a schematic structural diagram of a negative electrode tab of a battery cell provided in some other embodiments of the present application. Figure 8 It is a top view structural schematic diagram of an electrode assembly of a battery cell provided in some embodiments of the present application. Figure 9 It is a schematic structural diagram of a battery module provided in some embodiments of the present application. Figure 10 It is a schematic structural diagram of a battery pack provided in some embodiments of the present application. Figure 11 It is a schematic structural diagram of an electrical device provided in some embodiments of the present application.

[0063] The drawings are not necessarily drawn to actual scale.

[0064] The description of the reference numerals is as follows: 1. Electrical device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box body; 5a. First box body part; 5b. Second box body part; 5c. Accommodating space; 6. Battery module; 7. Battery cell; 10. Electrode assembly; 11. Positive electrode tab; 111. Positive electrode ear; 112. Positive electrode current collector; 113. Positive electrode film layer; 12. Negative electrode tab; 121. Negative electrode ear; 122. Negative electrode current collector; 123. Negative electrode film layer; 13. Separator; 14. Main body; 20. Outer shell; 21. Housing; 22. End cap; 31. Positive terminal; 32. Negative terminal. Detailed implementation manners

[0065] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to 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.

[0066] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The ranges defined in this way can include 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 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when a certain parameter is expressed as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0067] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0068] 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 new technical solutions.

[0069] 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 also 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 also include steps (a), (c), and (b), or may also include steps (c), (a), and (b), etc.

[0070] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. Trace water contained in the battery cell may cause the lithium salt in the electrolyte to decompose to produce hydrofluoric acid HF. The hydrofluoric acid may erode the solid electrolyte interface film (SEI film) on the negative electrode side. On the one hand, a large amount of additives are required to repair the SEI film; on the other hand, the interface stability on the negative electrode side is poor, side reactions are serious, gas generation is aggravated, and the cycle is deteriorated. Under fast charging conditions, the above problems are further aggravated, which is not conducive to the fast charging of the battery cell and the improvement of the cycle performance.

[0071] In view of the above problems, the embodiments of this application reasonably design the system of the battery cell, which can take into account the improvement of the cycle performance and the fast charging ability of the battery cell; specifically, the positive electrode active material includes lithium-containing phosphate with an olivine structure, and the negative electrode active material includes a carbon-based material. The above material system has relatively excellent cycle stability; The electrolyte includes lithium fluorosulfonylimide. Lithium fluorosulfonylimide has good water stability and is not likely to react with water to produce acid, which can improve the stability of the solid electrolyte interface film (SEI film) and reduce the consumption and usage amount of additives; The electrolyte includes a carboxylic ester solvent and a first additive. The first additive includes vinylene carbonate. The reaction potential of vinylene carbonate and the carboxylic ester solvent is close. There is a competitive reaction with the carboxylic ester solvent during the film-forming process. When the mass content of vinylene carbonate is appropriate, it is beneficial for vinylene carbonate to participate in film formation on the negative electrode side, and vinylene carbonate can form a dense organic film, making it difficult for the carboxylic ester solvent to penetrate the organic film to the negative electrode active material, thereby alleviating the side reaction between the carboxylic ester solvent and the negative electrode active material, reducing gas generation, and improving the high-temperature cycle performance; the mass content of the first additive is not too high, so that the impedance of the SEI film is relatively low, which is beneficial to improving the fast charging ability; Furthermore, when the mass content of the carboxylic ester solvent is within an appropriate range, it can further alleviate the side reaction with the negative electrode active material, and can reduce the viscosity of the electrolyte, improve the migration rate of lithium ions in the electrolyte, and improve the fast charging ability of the battery cell.

[0072] Therefore, the embodiments of the present application can improve the fast charging ability and cycling performance of battery cells.

[0073] Battery cell In a first aspect, embodiments of the present application provide a battery cell.

[0074] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a lithium-containing phosphate in an olivine structure. The negative electrode tab includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a carbon-based material. The electrolyte includes a carboxylic ester additive, a first additive, and a lithium salt. Wherein, Based on the mass of the electrolyte, the mass content of the carboxylic ester solvent is 8% to 60%. Based on the mass of the electrolyte, the total mass content of the first additive is 2.5% to 10%. The first additive includes 1,3-propane sultone with a mass content ≥ 0, a derivative of ethylene carbonate with a mass content ≥ 0, and vinylene carbonate with a mass content > 0. The derivative of ethylene carbonate includes a compound represented by Formula A. Formula A In Formula A, Q 1 、Q 2 、Q 3 and Q 4 each independently includes any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q 1 、Q 2 、Q 3 、Q 4 are not simultaneously hydrogen atoms. The lithium salt includes lithium fluorosulfonylimide, and the mass content of lithium fluorosulfonylimide in the electrolyte is 4% to 8%.

[0075] The positive electrode active material includes a lithium-containing phosphate in an olivine structure, and the negative electrode active material includes graphite particles. The above material system has excellent cycling stability; the electrolyte also includes a carboxylic ester solvent with a mass content greater than or equal to 8%, which can reduce the viscosity of the electrolyte and further improve the migration rate of lithium ions in the electrolyte, thereby improving the fast charging ability of the battery cell. However, lithium-containing phosphates may contain crystal water. During the cycling or storage of the battery cell, the crystal water reacts with the lithium salt, causing the lithium salt to decompose and generate hydrofluoric acid. Hydrofluoric acid can corrode the solid electrolyte interface film (SEI film) on the negative electrode side, resulting in damage to the SEI film. The carboxylate solvent in the electrolyte can penetrate through the SEI film to the negative electrode active material and react with the negative electrode active material, deteriorating the cycle performance. As the SEI film is damaged, the first additive in the electrolyte needs to be continuously consumed to form a new SEI film to protect the negative electrode active material. The embodiment of the present application further includes lithium fluorosulfonylimide with a mass content greater than or equal to 4%. On the one hand, when the mass content of lithium fluorosulfonylimide is greater than or equal to 4%, the hydrolysis stability of lithium fluorosulfonylimide is relatively excellent, and it is not easy to react with water to generate hydrofluoric acid, which can reduce the total production amount of hydrofluoric acid in the electrolyte and alleviate the erosion risk of hydrofluoric acid to the SEI film. Therefore, when the mass content of the first additive is greater than or equal to 2.5%, the SEI film can be effectively repaired, playing an excellent protective role for the negative electrode active material. On the other hand, when the mass content of lithium fluorosulfonylimide is less than or equal to 8%, the transmission rate of lithium ions in the electrolyte including lithium fluorosulfonylimide is relatively fast, which is beneficial to the rapid transmission and infiltration of lithium ions and can improve the fast charging performance. However, due to the more serious side reaction between the carboxylate solvent and the negative electrode active material and the increased gas generation under fast charging, on the one hand, the embodiment of the present application limits the carboxylate solvent to be less than or equal to 60%. On the other hand, a first additive is added to the electrolyte. The first additive includes vinylene carbonate. The reaction potential of vinylene carbonate is close to that of the carboxylate solvent, and there is a competitive reaction with the carboxylate solvent. When the mass content of vinylene carbonate is appropriate, it is beneficial for vinylene carbonate to participate in forming a dense organic film on the negative electrode side, making it difficult for the carboxylate solvent to penetrate through the organic film to the negative electrode active material, thereby alleviating the side reaction between the carboxylate solvent and the negative electrode active material and reducing the gas generation amount. Moreover, since the first additive is within an appropriate content range, the film impedance formed by it on the negative electrode side is relatively low, which is beneficial to improving the fast charging ability of the battery cell.

[0076] Therefore, the embodiment of the present application can improve the fast charging ability and cycle performance of the battery cell.

[0077] [Electrolyte] In some embodiments, the battery cell further includes an electrolyte.

[0078] During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0079] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not specifically limited and can be selected according to actual needs.

[0080] The electrolyte salt includes a lithium salt, and the lithium salt includes lithium bis(fluorosulfonyl)imide. The mass content of lithium bis(fluorosulfonyl)imide in the electrolyte is 4% to 8%, such as 4%, 5%, 6%, 7%, 8% or a range composed of any two of the above values. Optionally, the mass content of lithium bis(fluorosulfonyl)imide in the electrolyte is 4% to 6%. When the mass content of lithium bis(fluorosulfonyl)imide is within the above range, the cycle performance and fast charging performance of the battery cell can be improved.

[0081] Optionally, the lithium bis(fluorosulfonyl)imide includes at least one of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and lithium perfluorobutanesulfonylimide. The above materials can improve the cycle performance and fast charging performance of the battery cell.

[0082] In some embodiments, the lithium salt further includes lithium hexafluorophosphate. The ratio of the mass content of lithium bis(fluorosulfonyl)imide to the mass content of lithium hexafluorophosphate is 0.3 to 1.0, and can be optionally 0.4 to 0.8, based on the mass of the electrolyte.

[0083] Exemplarily, the ratio of the mass content of lithium bis(fluorosulfonyl)imide to the mass content of lithium hexafluorophosphate is 0.3, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0 or a range composed of any two of the above values.

[0084] The above lithium salt system has excellent ionic conductivity, can reduce side reactions on the negative electrode side, and improve the cycle performance and fast charging performance of the battery cell.

[0085] In some embodiments, the mass content of lithium hexafluorophosphate in the electrolyte is 8% to 12%, such as 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12% or a range composed of any two of the above values. When the mass content of lithium hexafluorophosphate is within the above range, the ionic conductivity of the electrolyte is relatively excellent, which is beneficial to improving the fast charging performance of the battery cell.

[0086] The organic solvents include carboxylate solvents, and the mass content of the carboxylate solvents in the electrolyte is 8% to 60%. Exemplarily, the mass content of the carboxylate solvents is 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or a range composed of any two of the above values. When the mass content of the carboxylate solvents is greater than or equal to 8%, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions; when the mass content of the carboxylate solvents is less than or equal to 60%, the side reaction between the carboxylate solvents and the negative electrode active material is relatively small, which is beneficial to improving the cycling performance.

[0087] In some embodiments, the carboxylate solvents may include at least one of chain carboxylate solvents and cyclic carboxylate solvents, and may be optionally a chain carboxylate solvent. The chain carboxylate solvent has a lower viscosity and can further improve the migration rate of lithium ions and the fast charging ability of the battery cell.

[0088] Due to the lower viscosity of the chain carboxylate solvent and better fluidity, it is more conducive to the rapid infiltration of the electrode sheet. Under fast charging conditions, local lithium deposition is not likely to occur on the surface of the negative electrode sheet, improving the reliability of the battery cell.

[0089] Exemplarily, the carboxylate solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0090] The above-mentioned chain carboxylate solvent has a lower viscosity, which is beneficial to improving the fast charging ability of the battery cell.

[0091] Optionally, R 1 includes a hydrogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 1 includes a hydrogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0092] Optionally, R 2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0093] In the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0094] Exemplarily, the carboxylic ester solvent includes one or more of the compounds represented by Formula I-1 to the compounds represented by Formula I-12.

[0095] The above materials can further improve the fast charging performance of the battery cell.

[0096] In some embodiments, the organic solvent further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 18% to 70%. Exemplarily, the mass content of the carbonate solvent in the electrolyte is 18%, 20%, 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, 65%, 70% or a range composed of any two of the above values. The carbonate solvent with the above mass content can further increase the conductivity of the electrolyte at room temperature, facilitate the migration of lithium ions, and enhance the fast charging ability of the battery cell.

[0097] Optionally, the carbonate solvent includes at least one of a cyclic carbonate and a chain carbonate.

[0098] Exemplarily, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate. The above materials can further improve the fast charging performance of the battery cell.

[0099] Exemplarily, the chain carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The above materials can further improve the fast charging performance of the battery cell.

[0100] In the embodiments of the present application, the electrolyte further includes an additive, the additive includes a first additive, and the first additive includes 1,3-propane sultone with a mass content ≥0, a derivative of ethylene carbonate with a mass content ≥0, and vinylene carbonate with a mass content >0.

[0101] In the embodiments of the present application, the total mass content of the first additive is 2.5% to 10%, such as 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or a range composed of any two of the above values.

[0102] When the mass content of the first additive is less than 2.5%, the film layer formed on the negative electrode side is relatively thin, which is not conducive to the protection of the negative electrode active material. As the mass content of the first additive increases, the film-forming effect on the negative electrode side is more excellent, which can play an excellent protective role for the negative electrode active material, reduce the risk of carboxylic ester solvents penetrating the SEI film and entering the negative electrode film layer, reduce side reactions on the negative electrode side, reduce the gas generation amount, and improve the high-temperature cycle performance. However, as the mass content of the first additive further increases, the impedance of the SEI film formed on the negative electrode side is relatively high, which is not conducive to fast charging. Therefore, the mass content of the first additive in the embodiment of the present application is adjusted to 2.5% to 10%, which can balance the improvement of the cycle performance and fast charging performance of the battery cell. Optionally, the mass content of the first additive is 3% to 7.5%, which can further improve the cycle performance and fast charging performance of the battery cell. Optionally, the mass content of the first additive in the freshly prepared electrolyte is 3% to 7.5%. The freshly prepared electrolyte can be understood as the electrolyte that has not participated in processes such as formation.

[0103] The first additive includes vinylene carbonate with a mass content > 0. In other words, vinylene carbonate is an essential component of the electrolyte.

[0104] In the case where the mass content of 1,3 - propanesultone is 0 and the mass content of the ethylene carbonate derivative is 0, the first additive may only include vinylene carbonate, and the mass content of vinylene carbonate may be 2.5% to 10%; Specifically, taking the case where the mass content of the ethylene carbonate derivative is 0 as an example, it may be that the freshly prepared electrolyte does not add the ethylene carbonate derivative, or the electrolyte obtained after disassembling the battery cell does not contain the ethylene carbonate derivative. This situation may be that the freshly prepared electrolyte does not add the ethylene carbonate derivative, or a small amount of the ethylene carbonate derivative is added, but it participates in the film-forming reaction of the SEI film during the formation process of the battery cell, resulting in a mass content of 0 for the ethylene carbonate derivative during the detection process. Optionally, the freshly prepared electrolyte includes the ethylene carbonate derivative.

[0105] Furthermore, for the addition of certain substances, such as additives, to the electrolyte, the content of additives in the electrolyte of the battery cell is related to the formation, different battery life cycles or different battery storage states due to the characteristics of the additives participating in the film formation on the surface of the active material. Therefore, the additives in the freshly prepared electrolyte may differ from the additives in the electrolyte obtained by reverse disassembling the battery cell. However, those skilled in the art can know the approximate range of the content of the relevant substances in the fresh electrolyte corresponding to the performance expression level of the battery cell (such as the number of cycles), residual content, etc. Similarly, those skilled in the art can also know the approximate range of the content of the non-freshly prepared (i.e., after reverse) electrolyte according to the content of the freshly prepared additives, the performance requirements for the battery cell, the storage environment, etc.

[0106] Therefore, the additive content mentioned in the technical solution of the present application can be the content of the additive actively added to the fresh electrolyte, or it can be the content of the residual additive detected by reverse detection based on the actual battery status.

[0107] In some embodiments, the mass content of vinylene carbonate in the electrolyte is 2% to 5%, such as 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the above values. When the mass content of vinylene carbonate is within the above range, a dense SEI film containing organic components can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reaction on the negative electrode side, and improve the cycle performance and fast charging capability of the battery monomer.

[0108] The first additive may include 1,3-propane sultone in a mass content of >0, or the first additive may include an ethylene carbonate derivative in a mass content of >0, or the first additive may include 1,3-propane sultone and an ethylene carbonate derivative.

[0109] 1,3-Propane sultone, ethylene carbonate derivatives and vinylene carbonate are combined to form a dense film layer with relatively low impedance, which reduces gas production and improves the cycle performance and fast charging performance of the battery monomer.

[0110] In some embodiments, the mass content of 1,3-propane sultone in the electrolyte is 0 to 0.5%, for example, 0, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or a range consisting of any two of the above values. Optionally, the mass content of 1,3-propane sultone in the electrolyte is 0 to 0.3%.

[0111] When the mass content of 1,3 - propanesultone is 0, it means that 1,3 - propanesultone can be not added to the freshly prepared electrolyte, or the electrolyte obtained after disassembling the battery monomer does not contain 1,3 - propanesultone. Generally speaking, since the consumption of 1,3 - propanesultone during the film - forming process is less, the mass content of 1,3 - propanesultone in the freshly prepared electrolyte is slightly greater than that in the electrolyte after disassembly.

[0112] Both 1,3 - propanesultone and vinylene carbonate can form a dense SEI film on the negative electrode side, which can effectively alleviate the risk of carboxylic ester solvents penetrating the SEI film and reacting with the negative electrode active material.

[0113] When the mass content of 1,3 - propanesultone is greater than 0 and less than or equal to 0.5%, the impedance of the formed SEI film will not be too high, which can reduce the impedance on the basis of alleviating side reactions and improve the fast - charging performance and high - temperature cycling performance of the battery monomer.

[0114] Exemplarily, the mass content of 1,3 - propanesultone in the electrolyte is 0% to 0.3%; the mass content of vinylene carbonate in the electrolyte is 2% to 5%.

[0115] In some embodiments, the mass content of ethylene carbonate derivatives in the electrolyte is 0 to 4.0%, such as 0, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4.0% or the range composed of any two of the above values. Optionally, the mass content of ethylene carbonate derivatives in the electrolyte is 1.5% to 3.5%.

[0116] Optionally, the freshly prepared electrolyte includes ethylene carbonate derivatives, and in the freshly prepared electrolyte, the mass content of ethylene carbonate derivatives is greater than 0. Ethylene carbonate derivatives form films preferentially. After adding a certain content of ethylene carbonate derivatives to the freshly prepared electrolyte, due to the large consumption of ethylene carbonate derivatives during the film - forming stage, the battery monomer obtained after disassembly may not be able to detect ethylene carbonate derivatives either.

[0117] Vinylene carbonate continuously participates in the formation of the SEI film during the cycling of the battery monomer, alleviating the risk of carboxylic ester solvents penetrating the SEI film. However, the organic component content of this SEI film is relatively high, resulting in a relatively high impedance of the SEI film; while ethylene carbonate derivatives can form films preferentially, optimize the components of the SEI film, reduce the impedance of the SEI film, and effectively improve the fast - charging performance and cycling performance of the battery monomer. And because the lithium salt includes lithium fluorosulfonylimide, the thermal stability of the electrolyte is relatively high, which can alleviate the problem of poor high - temperature cycling of high - content ethylene carbonate derivatives and further improve the fast - charging performance and cycling performance of the battery monomer.

[0118] Exemplarily, the mass content of vinylene carbonate in the electrolyte is 2% to 5%; the mass content of ethylene carbonate derivative in the electrolyte is 1.5% to 3.5%.

[0119] Exemplarily, the mass content of 1,3 - propane sultone in the electrolyte is 0% to 0.3%; the mass content of vinylene carbonate in the electrolyte is 2% to 5%; the mass content of ethylene carbonate derivative in the electrolyte is 1.5% to 3.5%.

[0120] Under fast charging, the above three types of substances jointly participate in the formation of the SEI film. The low - content 1,3 - propane sultone can reinforce the SEI film, and vinylene carbonate can further reinforce the film - forming process, reducing the risk of carboxylic ester solvents penetrating the SEI film and improving the high - temperature cycling performance of the battery cell; the appropriate content of ethylene carbonate derivative can reduce the film - forming impedance and improve the fast - charging performance, and the mass content of the ethylene carbonate derivative is not too high, which can reduce the risk of high - temperature decomposition and further improve the high - temperature cycling performance of the battery cell; thus, the fast - charging performance and high - temperature cycling performance of the battery cell are improved.

[0121] In the embodiments of the present application, the ethylene carbonate derivative means that at least one hydrogen atom of ethylene carbonate is substituted, and the substitution group can be one, two, three, four, etc.

[0122] Exemplarily, the ethylene carbonate derivative includes the compound shown in Formula A, Formula A, In Formula A, Q 1 、Q 2 、Q 3 and Q 4 each independently includes any one of a hydrogen atom, a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group, and Q 1 、Q 2 、Q 3 、Q 4 are not simultaneously hydrogen atoms.

[0123] Q 1 、Q 2 、Q 3 、Q 4 are not simultaneously hydrogen atoms. In other words, at least one of Q 1 、Q 2 、Q 3 、Q 4 includes a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group.

[0124] Exemplarily, Q 1 、Q 2 、Q3 , Q 4 One of them includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and the rest are hydrogen atoms.

[0125] Exemplarily, Q 1 , Q 2 , Q 3 , Q 4 At least two of them include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0126] Exemplarily, Q 1 , Q 2 , Q 3 , Q 4 At least three of them include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0127] Exemplarily, Q 1 , Q 2 , Q 3 , Q 4 Each independently includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0128] Optionally, at least one of Q 1 , Q 2 , Q 3 and Q 4 includes a halogen atom or a C1-C5 haloalkyl group. The halogen atom includes a fluorine atom, a bromine atom, or a chlorine atom, etc., and can be optionally a fluorine atom. The C1-C5 haloalkyl group includes a C1-C5 fluoroalkyl group, a C1-C5 bromoalkyl group, or a C1-C5 chloroalkyl group, etc., and can be optionally a fluorine atom. For example, the C1-C5 fluoroalkyl group includes fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, or fluoropentyl.

[0129] When the ethylene carbonate derivative includes a fluorine atom, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side, and on the basis of protecting the negative electrode active material, the impedance of the film layer is low, and it can more effectively balance the improvement of the cycle performance and fast charging performance of the battery cell.

[0130] For example, the ethylene carbonate derivative includes at least one of the compounds shown by Formula A-1 to the compounds shown by Formula A-6,

[0131] The above materials can further improve the high-temperature cycle performance and fast charging performance of the battery cell.

[0132] Optionally, the ethylene carbonate derivative includes at least one of the compounds represented by Formula A-1 to the compounds represented by Formula A-3. Further optionally, the ethylene carbonate derivative includes the compound represented by Formula A-1.

[0133] In some embodiments, the electrolyte further includes a second additive with a mass content greater than or equal to 0. The second additive includes at least one of a sulfur-containing additive and a lithium salt additive.

[0134] Exemplarily, the sulfur-containing additive includes one or more of vinylene sulfate DTD, bis(vinylsulfonyl)ethylene 2-DTD, butene sulfite BS, ethylene sulfite ES, and methylene methyl disulfonate MMDS.

[0135] Exemplarily, the lithium salt additive includes lithium difluorophosphate LiPO 2 F 2 , lithium difluorooxalate borate LiDFOB, lithium tetrafluoroborate LiBF 4 , and one or more of lithium bis(oxalato)borate LiBOB.

[0136] In some embodiments, the electrolyte includes a sulfur-containing additive with a mass content of 0 to 2% in the electrolyte. Optionally, the mass content of the sulfur-containing additive is 0.5% to 2%. The sulfur-containing additive and the first additive cooperate to participate in film formation, which can optimize the film layer components of the SEI film. The sulfur-containing additive can participate in the formation of an SEI film rich in inorganic substances, and the inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI film, and improve the high-temperature cycling performance of the battery cell.

[0137] Exemplarily, the mass content of the sulfur-containing additive in the electrolyte is 0 to 2%, such as 0, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 2% or a range composed of any two of the above values.

[0138] In some embodiments, the electrolyte includes a lithium salt additive with a mass content of 0 to 1% in the electrolyte. Optionally, the mass content of the lithium salt additive is 0.2% to 1%. The lithium salt additive and the first additive cooperate to participate in film formation, which can optimize the film layer components of the SEI film. The lithium salt additive can participate in the formation of an SEI film rich in inorganic substances, and the inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI film, and improve the high-temperature cycling performance of the battery cell.

[0139] Exemplarily, the mass content of the lithium salt additive in the electrolyte is 0 to 1%, such as 0, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or a range composed of any two of the above values.

[0140] When the mass content of the second additive is 0, it means that the second additive may not be added to the freshly prepared electrolyte, or when the addition amount of the second additive is small, the second additive cannot be detected in the electrolyte obtained after disassembling the battery cell.

[0141] In the embodiments of the present application, the types and contents of inorganic components / lithium salts in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to the standard JY / T 020-1996 "General Rules for Ion Chromatographic Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is about 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery cell can be taken as a sample, and detected by ion chromatography.

[0142] In the embodiments of the present application, the types and contents of organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to GB / T 9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography.

[0143] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector part and a negative electrode film layer provided on at least one surface of the negative electrode current collector part and including a negative electrode active material. For example, the negative electrode current collector part has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector part.

[0144] The charge upper limit voltage and discharge cut-off voltage of the battery cell vary depending on the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the charge upper limit voltage can be 3.65V and the discharge cut-off voltage can be 2.0V. Another example is that when the phosphate material includes lithium manganese iron phosphate, the charge upper limit voltage can be 4.2V and the discharge cut-off voltage can be 2.0V. Next, taking the charge upper limit voltage of 3.65V and the discharge cut-off voltage of 2.0V as an example, the state of the battery cell is described as follows: In the embodiments of the present application, the 100% state of charge SOC and 0% state of charge SOC of the battery cell are defined as follows. The battery cell is charged at a constant current charge rate of 0.33C to the charge upper limit voltage, and then charged at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell. The battery cell is discharged at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0145] In the embodiments of the present application, the negative electrode film layer includes at least one film layer, which can be a single film layer or 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.

[0146] In the embodiments of the present application, the negative electrode active material includes a carbon-based material, and the carbon-based material includes graphite particles. The graphite particles have high cycle stability and can improve the cycle performance of the battery cell. The positive electrode active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. When used in combination, the battery cell has excellent cycle performance.

[0147] The volume average particle size Dv50 of the graphite particles is from 8.5 μm to 13.5 μm, such as 8.5 μm, 9 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.5 μm or the range composed of any two of the above values. Optionally, the volume average particle size Dv50 of the graphite particles is from 9.5 μm to 13 μm.

[0148] The relatively small volume average particle size of the graphite particles results in a shorter solid-phase migration path for lithium ions and can improve the fast charging ability of the battery cell. However, under fast charging conditions, the side reaction between the small-sized graphite particles and the carboxylic ester solvent in the electrolyte is relatively intense. The electrolyte is further added with a first additive, which can preferentially form a film on the negative electrode side, play an excellent protective role for the negative electrode active material, reduce the risk of side reactions occurring on the negative electrode side, and improve the cycle performance of the battery cell.

[0149] 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 it can be detected by using the equipment and methods well-known in the art. For example, taking the negative electrode active material as a sample, according to the test standard GB / T 19077-2016, the Dv50 of the particles is tested by a Mastersizer 2000E laser particle size analyzer, etc.

[0150] In some embodiments, the graphite particles include graphite body particles and a negative electrode coating layer. The graphite body particles include secondary particles, and the secondary particles include a plurality of primary particles. The negative electrode coating layer coats the surface of the graphite body particles, and the negative electrode coating layer includes carbon elements. The carbon in the negative electrode coating layer is mainly amorphous carbon. Amorphous carbon refers to a transition carbon material with a very low degree of graphitization crystallization and an approximate amorphous form (or no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0151] The graphite matrix particles include secondary particles. There are more migration paths for lithium ions in the graphite matrix particles, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions. The negative electrode coating layer has more end faces and defects, resulting in a larger number of sites where lithium ions can be intercalated and deintercalated, making the conductivity of the negative electrode coating layer relatively excellent. It can reduce the internal resistance of the negative electrode plate, reduce the heat generation of the battery cell, and improve the fast charging performance and high-temperature cycle performance of the battery cell.

[0152] Exemplarily, the graphite matrix particles include at least one of artificial graphite and natural graphite, and may be artificial graphite.

[0153] Optionally, based on the mass of the graphite particles, the mass content of carbon element in the negative electrode coating layer is 2% to 5%. Exemplarily, the mass content of carbon element in the negative electrode coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or the range composed of any two of the above values.

[0154] When the mass content of carbon element in the negative electrode coating layer is within the above range, it can further reduce the internal resistance of the negative electrode plate, reduce the heat generation of the battery cell, and improve the high-temperature cycle performance of the battery cell.

[0155] In the embodiments of the present application, the graphite particles can be prepared by methods well known in the art. Taking the graphite matrix particles as artificial graphite as an example for illustration, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and after carbonization treatment, forming a negative electrode coating layer on at least part of the surface of the artificial graphite particles.

[0156] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of coal tar pitch and petroleum pitch is below 250°C.

[0157] Optionally, the carbonization treatment temperature is 700°C to 1800°C. Optionally, the carbonization treatment temperature is 1000°C to 1300°C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized and a negative electrode coating layer containing amorphous carbon can be formed on at least part of the surface of the artificial graphite.

[0158] Optionally, the carbonization treatment time is 1h to 6h.

[0159] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include graphite particles, or the carbon-based material may include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0160] In some embodiments, the negative electrode active material may further include a silicon-based material. The introduction of the silicon-based material can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0161] Optionally, based on the mass of the negative electrode film layer, the mass content of silicon element in the silicon-based material is 0.3% to 5%. Exemplarily, the mass content of silicon element in the silicon-based material 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% or a range composed of any two of the above values.

[0162] When the mass content of silicon element in the silicon-based material is within the above range, the capacity of the negative electrode active material can be increased, and the energy density of the battery cell can be improved.

[0163] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0164] In some embodiments, in addition to the above-mentioned carbon-based material and optionally the silicon-based material, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0165] In this application, the qualitative and quantitative determination of each substance or each element can be detected by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change some detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0166] For example, this application can perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or the negative electrode active material in combination with JIS / K0131-1996 General Rules for X-ray Diffraction Analysis.

[0167] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). There are voids between flaky structures in the SEM cross-sectional view of natural graphite, and the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and only 2H phase exists in the XRD spectrum of artificial graphite.

[0168] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.4 g / cm 3 to 1.8 g / cm 3 . Exemplarily, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.4 g / cm 3 , 1.5 g / cm 3 , 1.55 g / cm 3 , 1.6 g / cm 3 , 1.65 g / cm 3 , 1.7 g / cm 3 , 1.75 g / cm 3 , 1.8 g / cm 3 or a range composed of any two of the above values.

[0169] When the powder compaction density of the negative electrode active material under 20,000 N is within the above range, the energy density of the battery cell can be improved. Moreover, since the negative electrode active material in the negative electrode film layer can be stacked more closely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation and improving the high-temperature cycle performance of the battery cell.

[0170] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art and can be detected by methods and equipment well-known in the art, and is detected according to the test standard GB / T24533-2009. As an example, a certain amount of negative electrode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in a UTM7305 type electronic pressure testing machine, pressurized to 2000 kg (equivalent to 20,000 N), kept under pressure for 30 s, then depressurized, kept for 10 s, and then the powder compaction density of the negative electrode active material under a force of 20,000 N is recorded and calculated.

[0171] In some embodiments, when the battery cell is in a 0% state of charge, the compaction density of the negative electrode film layer is 1.30 g / cm 3 to 1.55 g / cm 3 . Exemplarily, when the battery cell is in a 0% state of charge, the compaction density of the negative electrode film layer is 1.30 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.40 g / cm 3 , 1.45 g / cm 3 , 1.50 g / cm 3 , 1.55 g / cm 3 or a range composed of any two of the above values.

[0172] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative active material in the negative electrode film layer is stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation and the amount of gas generated by the decomposition of carboxylic ester solvents due to heat accumulation, and improving the high-temperature cycle performance of the battery cell.

[0173] In the embodiments of the present application, the compaction density of the negative electrode film layer in the 0% state of charge of the battery cell has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. The detection method is the same as the compaction density test method of the positive electrode film layer described above.

[0174] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 140 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 , 92 mg / 1540.25 mm 2 , 95 mg / 1540.25 mm 2 , 96 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 112 mg / 1540.25 mm 2 , 114 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 116 mg / 1540.25 mm 2 , 118 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2, 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 Or a range composed of any two of the above values.

[0175] When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation amount per unit area of the negative electrode plate is not too large, and the high-temperature cycling performance of the battery cell can be improved.

[0176] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. The negative electrode plate of the battery cell in the 0% state of charge (SOC) is disassembled, and the compaction density of the negative electrode film layer is measured. For example, a single-sided coated negative electrode plate (if it is a double-sided coated plate, one side of the negative electrode film layer can be wiped off first) is punched into small round pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the negative electrode film layer of the above-mentioned weighed negative electrode plate is wiped off, the weight of the negative electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. 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.

[0177] In some embodiments, the negative electrode film layer further includes a negative electrode binder, and the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0178] In some embodiments, the negative electrode film layer may optionally further 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. 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%.

[0179] In some embodiments, the negative electrode film layer may optionally further 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. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0180] In some embodiments, the negative electrode current collector part can adopt 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 can be used. The composite current collector can 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 can 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 can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0181] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative electrode current collector part and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0182] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the embodiments of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector part and the negative electrode film layer and disposed on the surface of the negative electrode current collector part. In some other embodiments, the negative electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0183] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, and the negative electrode conductive layer is located between the negative electrode film layer and the negative electrode current collector part. The negative electrode conductive layer can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, thereby reducing the heat generation of the battery cell, and improving the fast charging performance and high-temperature cycle performance of the battery cell.

[0184] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. Exemplarily, the thickness of the negative electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range composed of any two of the above values.

[0185] When the thickness of the negative electrode conductive layer is within the above range, it can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, thereby reducing the heat generation of the battery cell, and can also take into account the improvement of the energy density of the battery cell.

[0186] 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. For example, tomographic scanning of the negative electrode plate can be performed to directly measure the thickness of the negative electrode conductive layer.

[0187] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent of the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode tab and reducing the heat generation of the battery cell. The negative electrode binder of the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector part and the negative electrode film layer, and improve the structural stability of the negative electrode tab.

[0188] In some embodiments, the negative electrode conductive layer may optionally further include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0189] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 20% to 40%. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40% or a range composed of any two of the above values.

[0190] Exemplarily, the negative electrode conductive agent of the negative electrode conductive layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0191] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%. Exemplarily, 60%, 65%, 70%, 75%, 80% or a range composed of any two of the above values.

[0192] Exemplarily, the negative electrode binder of the negative electrode conductive layer includes one or more of styrene-butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0193] [Positive electrode tab] The positive electrode tab includes a positive electrode current collector part and a positive electrode film layer provided on at least one surface of the positive electrode current collector part and including a positive electrode active material. For example, the positive electrode current collector part has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector part.

[0194] The electrode assembly according to the embodiments of the present application can be a wound electrode assembly or a stacked electrode assembly, and is preferably a stacked electrode assembly.

[0195] In the case where the electrode assembly is of a wound structure, the positive electrode tab and the negative electrode tab are wound in the same direction.

[0196] In the case where the electrode assembly is of a stacked structure, there are a plurality of positive electrode tabs and a plurality of negative electrode tabs, and the plurality of positive electrode tabs and the plurality of negative electrode tabs are stacked in the thickness direction of the battery cell.

[0197] The carboxylate ester solvent has a relatively low viscosity, and the mass content of the carboxylate ester solvent is 8% to 60%. It can quickly infiltrate the electrode sheet in the length direction, making the reaction degree of the electrode sheet more consistent in the length direction. When active ions migrate to the negative electrode sheet, problems such as lithium deposition are not likely to occur, which is beneficial to improving the use reliability of the battery cell.

[0198] In the embodiments of the present application, the lithium-containing phosphate in the olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium-containing phosphate in the olivine structure includes phosphate particles and a positive electrode coating layer. The positive electrode coating layer coats at least part of the surface of the phosphate particles, and the positive electrode coating layer contains carbon elements.

[0199] By surface coating the positive electrode coating layer on the phosphate particles, the conductivity of the lithium-containing phosphate in the olivine structure can be improved, which is beneficial to the migration rate of lithium ions, improves the fast charging ability of the battery, and reduces the heat generation of the battery cell, thereby improving the high-temperature cycle performance of the battery cell.

[0200] Examples of the phosphate particles may include, but are not limited to, one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. The cycle stability of the above materials is relatively excellent, which can improve the cycle performance of the battery cell.

[0201] In some embodiments, the lithium-containing phosphate 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, 0.5 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5, 0 ≤ c1 ≤ 0.5, 3 ≤ z1 ≤ 5, A includes 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 Cl, C, N, and P; Y includes at least one of O and F.

[0202] The cycle stability of the phosphate particles is relatively excellent, which is beneficial to improving the cycle performance of the battery cell.

[0203] Exemplarily, the phosphate particles include LiFePO 4 、LiMnPO4 , LiNiPO 4 , LiCoPO 4 or more. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur. The molar content of Li is different when the battery cell is discharged to different states. Regarding the cathode active material LiFePO 4 , LiMnPO 4 , 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 cathode active material is applied to the battery system, after charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, regarding the cathode active material LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., the molar content of oxygen O is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will fluctuate. The above situations are all within the protection scope of the present application.

[0204] In some embodiments, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 0.8% to 2.3%. Exemplarily, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.3% or the range composed of any two of the above values.

[0205] The carbon element mainly exists in the cathode coating layer in the form of a carbon coating layer. The carbon coating layer is loose and porous, which is beneficial to increasing the specific surface area of the material, more beneficial to the effective contact between the electrolyte and the phosphate particles, and beneficial to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, it can significantly improve the conductivity of the lithium-containing phosphate with olivine structure, is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the rapid charging ability and energy density of the battery cell.

[0206] In some embodiments, the cathode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

[0207] In some embodiments, the cathode coating layer includes a general formula of Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1A compound wherein 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M3 includes one or more of Ti, Zr, Hf, Ge, and Sn.

[0208] Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 The compound is a fast ion conductor having a NASICON structure, for example, one or more of lithium iron titanium phosphate Li2FeTi(PO4)3, lithium iron zirconium phosphate Li2FeZr(PO4)3, and lithium iron tin phosphate Li2FeSn(PO4)3.

[0209] Fast ion conductors with NASICON structures are materials with ultrafast ion conduction capabilities, rich three-dimensional lithium ion diffusion and transmission channels, and have the advantages of high ion conduction efficiency and strong structural stability during multiple lithium removal and insertion processes. Coating fast ion conductors with NASICON structures on the surface of phosphate particles can significantly increase the transmission rate of lithium ions during multiple lithium removal / insertion at the positive terminal, improve the ionic conductivity of the positive electrode active material, and improve the fast charging capability of the battery cell. In addition, it can also increase the gram capacity and the energy density of the corresponding battery cell.

[0210] The carbon element and the fast ion conductor can be arranged in layers, for example, the carbon element is used as an independent carbon coating layer, and the fast ion conductor is used as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0211] Optionally, the carbon coating layer can be coated on the surface of the fast ion conductor layer by a carbonization process of an organic carbon source (e.g., glucose, polyethylene glycol, etc.). The carbon coating layer can partially coat the fast ion conductor layer, or it can completely coat the fast ion conductor layer. The provision of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, make up for the defect of poor electronic conductivity of the phosphate particles, and improve the energy density of the battery cell. The positive electrode active material of the present application uses lithium-containing phosphate as a base material, giving full play to the advantages of low cost, high reliability and good cycle stability of lithium-containing phosphate, while using the positive electrode coating layer (fast ion conductor layer and carbon coating layer) to solve the disadvantages of poor electronic conductivity and ion conductivity. The battery cell prepared by the positive electrode active material of the present application can improve the energy density of the battery cell while having excellent cycle performance. 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 EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry, and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode plate is disassembled, washed with DMC and dried, and then after removing impurities by high-temperature calcination, 0.4 g of the positive electrode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0212] In some embodiments, the powder compaction density of the positive electrode active material under 30000 N is 2.43 g / cm 3 to 2.85 g / cm 3 .

[0213] Exemplarily, the powder compaction density of the positive electrode active material under 30000 N is 2.43 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 the range composed of any two of the above values.

[0214] When the powder compaction density of the positive electrode active material under 30000 N is within the above range, the energy density of the battery cell can be improved, and since the positive electrode active material in the positive electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode plate, thereby reducing heat generation and improving the high-temperature cycle performance and fast charging performance of the battery cell.

[0215] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art, and can be detected by methods and equipment well-known in the art. Detection is carried out according to the test standard GB / T24533-2009. For example, a certain amount of cathode 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 cathode active material under the action of 30000 N is recorded and calculated.

[0216] In some embodiments, when the battery cell is in the 0% state of charge (SOC), the compaction density of the cathode film layer is 2.46 g / cm 3 to 2.80 g / cm 3 . Exemplarily, when the battery cell is in the 0% state of charge (SOC), the compaction density of the cathode film layer is 2.46 g / cm 3 , 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.75 g / cm 3 , 2.80 g / cm 3 or a range composed of any two of the above values.

[0217] When the compaction density of the cathode film layer is within the above range, it is beneficial to improve the energy density of the battery cell, and since the cathode active material in the cathode film layer is stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation during fast charging and improving the high-temperature cycle performance and fast charging performance of the battery cell.

[0218] In some embodiments, the single-sided coating weight of the cathode film layer is 200 mg / 1540.25 mm 2 to 350 mg / 1540.25 mm 2, such as 200 mg / 1540.25 mm², 210 mg / 1540.25 mm², 220 mg / 1540.25 mm², 230 mg / 1540.25 mm², 240 mg / 1540.25 mm², 250 mg / 1540.25 mm², 260 mg / 1540.25 mm², 270 mg / 1540.25 mm², 280 mg / 1540.25 mm², 290 mg / 1540.25 mm², 300 mg / 1540.25 mm², 310 mg / 1540.25 mm², 320 mg / 1540.25 mm², 330 mg / 1540.25 mm², 340 mg / 1540.25 mm², 350 mg / 1540.25 mm² or a range composed of any two of the above values.

[0219] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation amount per unit area of the positive electrode plate will not be too large, improving the high-temperature cycle performance and fast charging performance of the battery cell.

[0220] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell at 0% state of charge (SOC) can be detected by the following method. Disassemble the positive electrode plate from the battery cell at 0% SOC and measure the compaction density of the positive electrode film layer. For example, take a single-sided coated positive electrode plate (if it is a double-sided coated plate, one side of the positive electrode film layer can be wiped off first), 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 positive electrode film layer of the above weighed positive electrode plate, 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 plate - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode plate - the thickness H0 of the positive electrode current collector, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0221] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The embodiments of the present application do not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes 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%.

[0222] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. There is no particular limitation on the type of the positive electrode binder in the embodiments of the present application. 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 fluorinated acrylate resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0223] In some embodiments, the positive electrode current collector part may adopt a metal foil or a composite current collector. As an example of the 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).

[0224] The positive electrode film layer is usually formed by coating a positive electrode paste on the positive electrode current collector part and then drying and cold pressing. The positive electrode paste is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0225] The positive electrode tab does not exclude other additional functional layers other than the positive electrode film layer. For example, in some embodiments, the positive electrode tab of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector part and the positive electrode film layer and disposed on the surface of the positive electrode current collector part. In some other embodiments, the positive electrode tab of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0226] In some embodiments, the positive electrode tab further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the positive electrode film layer and the positive electrode current collector part. The positive electrode conductive layer can further improve the conductivity of the positive electrode tab, reduce the heat generation of the positive electrode tab, thereby reducing the heat generation of the battery cell, and can improve the fast charging performance and high temperature cycle performance of the battery cell.

[0227] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. Exemplarily, the thickness of the positive electrode conductive layer may be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range composed of any two of the above values.

[0228] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode sheet can be further improved, the heat generation of the positive electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved while taking into account.

[0229] In the embodiments of the present application, the thickness of the positive electrode conductive layer has the meaning well known in the art and can be detected by using the equipment and methods well known in the art. For example, tomographic scanning of the positive electrode sheet can be performed to directly measure the thickness of the positive electrode conductive layer.

[0230] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0231] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Exemplarily, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50% or a range composed of any two of the above values.

[0232] Exemplarily, the positive electrode conductive agent of the positive electrode conductive layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent of the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet and reducing the heat generation amount of the battery cell.

[0233] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. Exemplarily, 50%, 60%, 65%, 70% or a range composed of any two of the above values.

[0234] Exemplarily, the positive electrode binder of the positive electrode conductive layer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. The positive electrode binder of the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector part and the positive electrode film layer and improve the structural stability of the positive electrode sheet.

[0235] [Separator membrane] In the embodiments of the present application, the separator membrane is disposed between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet and the negative electrode sheet.

[0236] In the embodiments of the present application, the separator membrane includes a base membrane with a porous structure.

[0237] In some embodiments, the base film comprises at least one of glass fiber, non-woven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0238] Optionally, the polyolefin comprises at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0239] In some embodiments, the porosity of the base film is 20% to 70%, optionally 35% to 60%. Exemplarily, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range composed of any two of the above values.

[0240] When the porosity of the base film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, the internal resistance of the battery cell can be further reduced, thereby reducing heat generation and improving the fast charging performance and high-temperature cycling performance of the battery cell.

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

[0242] In some embodiments, the thickness of the base film is 6μm to 12μm, optionally 6μm to 9μm. Exemplarily, the thickness of the base film is 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm or a range composed of any two of the above values.

[0243] When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, the internal resistance of the battery cell can be further reduced, thereby reducing heat generation and improving the fast charging performance and high-temperature cycling performance of the battery cell.

[0244] In the embodiments of the present application, the separator can be the base film. Optionally, the separator further comprises a functional layer disposed on at least one side of the base film. The functional layer can include inorganic particles to improve the heat resistance of the separator. Optionally, the functional layer is disposed on both sides of the base film.

[0245] In some embodiments, the functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and includes first inorganic particles. The second functional layer is located on the other side of the base film and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0246] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator membrane.

[0247] Optionally, the first functional layer may include a binder, optionally at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0248] Optionally, the first inorganic particles include one or more of silica, alumina, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0249] Optionally, the average particle size of the first inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, optionally 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or a range composed of any two of the above values. When the average particle size of the first inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0250] In the embodiments of the present application, the meaning of the thickness of the base film is well-known in the art, and it can be detected by using the well-known meaning and equipment in the art. For example, a newly prepared separator membrane can be taken as a sample, or a battery cell that has been discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, the separator membrane is obtained from the battery cell, and the separator membrane is dried and used as a sample. The separator membrane is cut off with an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the thickness of the cross-section of the separator membrane and its respective layers.

[0251] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers. Optionally, the acrylate copolymers include acrylate-acrylonitrile-acrylamide-propylene copolymers. The acrylate copolymers have excellent adhesion properties and relatively high adhesion stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0252] The second inorganic particles in the composite particles prevent the non-fluoropolymer particles from sticking to each other due to the high-temperature treatment during the granulation process, creating pores in the composite particles, which is beneficial for the transport of lithium ions and improves the ionic conductivity of the separator. Moreover, the second inorganic particles can also increase the compression modulus of the composite particles. During the charge and discharge process, the composite particles are not easily deformed, making the structure of the separator more stable, improving the kinetic performance of the battery monomer, and enhancing the fast charging performance. Optionally, compared with the first functional layer, the second functional layer is arranged closer to the negative electrode tab. Since the composite particles are not easily deformed, the separator basically does not cause side effects such as extrusion to the negative electrode tab, ensuring the stable kinetic performance of the negative electrode tab. Correspondingly, the first functional layer is arranged closer to the positive electrode tab.

[0253] Optionally, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Optionally, the second inorganic particles include silicon oxide. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer and form composite particles in combination with the non-fluoropolymer, further improving the cycle stability and kinetic performance of the separator, as well as the cycle performance and fast charging performance of the battery monomer.

[0254] The average particle size of the second inorganic particles is from 5 nm to 100 nm, optionally from 10 nm to 100 nm, and optionally from 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or any range composed of any two of the above values. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0255] In the embodiments of the present application, the average particle size of the second inorganic particles has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, after obtaining the separator membrane and drying the separator membrane as a sample, the separator membrane is cut by an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the particle size of the second inorganic particles in the separator membrane, and the particle sizes of multiple, such as 50, second inorganic particles are measured, and the average value thereof is calculated as the average particle size of the second inorganic particles.

[0256] In some embodiments, the positive electrode sheet, the separator membrane, and the negative electrode sheet can be made into an electrode assembly through a winding process and / or a stacking process.

[0257] Figure 1 and Figure 2 shows a schematic structural diagram of a battery cell.

[0258] In some embodiments, the battery cell 7 may include a housing 20.

[0259] The housing 20 can be of various shapes, such as a cylinder, a cuboid, etc. The shape of the housing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is of a cylindrical structure, the housing 20 can be selected as a cylindrical structure. If the electrode assembly 10 is of a cuboid structure, the housing 20 can be selected as a cuboid structure. Optionally, the electrode assembly 10 is of a cuboid structure.

[0260] The material of the housing 20 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not make special restrictions thereon. Optionally, the inner wall of the housing 20 may further include an insulating layer, and the insulating layer can separate the housing 20 from the electrode assembly 10. The material of the insulating layer can be selected from the materials commonly used in the art and is not specially restricted herein.

[0261] The electrode assembly 10 accommodated in the housing 20 can be one or more.

[0262] In some embodiments, the housing 20 includes a housing body 21 and an end cover 22. The housing body 21 has an opening, and the end cover 22 covers the opening. The electrode assembly 10 and the electrolyte are accommodated in the housing body 21.

[0263] In some embodiments, the material of the housing body 21 includes steel, and the mechanical strength of the steel is relatively high and it is not easily deformed, which can improve the use reliability and cycle performance of the battery cell. Optionally, the mass ratio of the steel is the highest among the materials in the housing body 21.

[0264] Optionally, the thickness of the housing 21 is from 0.1 mm to 0.5 mm, and may be optionally from 0.2 mm to 0.35 mm. Exemplarily, the thickness of the housing 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or a range composed of any two of the above values. When the thickness of the housing 21 is within the above range, the mechanical strength of the housing 21 is relatively high, which can improve the use reliability and cycling performance of the battery cell 7, and the housing 21 occupies less space and has more internal space, which is beneficial to improving the energy density of the battery cell 7.

[0265] Next, taking the electrode assembly 10 as a stacked structure as an example for illustration, As Figure 2 and Figure 3 shown, from the external shape of the electrode assembly 10, the electrode assembly 10 includes a main body portion 14, a positive electrode tab 111, and a negative electrode tab 121. The positive electrode tab 111 and the negative electrode tab 121 protrude from the main body portion 14. The positive electrode tab 111 and the negative electrode tab 121 are used to lead out the current of the main body portion 14.

[0266] The portion of the positive electrode plate 11 where the active material layer is not coated is the positive electrode tab 111. The active material coated on the positive current collector portion 112 of the positive electrode plate 11 constitutes the positive electrode film layer 113. The positive electrode film layer 113 and the positive current collector portion 112 coated with the active material are part of the main body portion 14.

[0267] The portion of the negative electrode plate 12 where the active material layer is not coated is the negative electrode tab 121. The active material coated on the negative current collector portion 122 of the negative electrode plate 12 constitutes the negative electrode film layer 123. The negative electrode film layer 123 and the negative current collector portion 122 coated with the active material are part of the main body portion 14.

[0268] The main body portion 14 may further include a separator 13. The separator 13 is located between the positive electrode plate 11 and the negative electrode plate 12. The positive electrode plate 11 and the negative electrode plate 12 are stacked along the thickness direction X of the battery cell.

[0269] The positive electrode tab 111 and the negative electrode tab 121 may extend from the same side of the main body portion 14, or may extend from opposite sides respectively.

[0270] In some embodiments, the positive electrode tab 111 is connected to at least one side of the positive current collector portion 112 along the length direction Z of the battery cell, and the negative electrode tab 121 is connected to at least one side of the negative current collector portion 122 along the length direction Z of the battery cell.

[0271] As Figure 4 shown, for example, the positive electrode tab 111 is connected to one side of the positive current collector portion 112 along the length direction Z of the battery cell.

[0272] As Figure 5 shown, for example, the positive electrode tab 111 is connected to both sides of the positive current collector 112 along the length direction Z of the battery cell.

[0273] As Figure 6 shown, for example, the negative electrode tab 121 is connected to one side of the negative current collector 122 along the length direction Z of the battery cell.

[0274] As Figure 7 shown, for example, the negative electrode tab 121 is connected to both sides of the negative current collector 122 along the length direction Z of the battery cell.

[0275] As Figure 8 shown, in some embodiments, the positive electrode tab 111 is connected to at least one side of the positive current collector 112 along the length direction Z, the negative electrode tab 121 is connected to at least one side of the negative current collector 122 along the length direction Z. Along the length direction Z of the battery cell 7, the size of the negative electrode film layer 123 is larger than that of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH 1 ; along the width direction Y of the battery cell 7, the size of the negative electrode film layer 123 is larger than that of the positive electrode film layer 113, and the difference between the size of the negative electrode film layer 123 and the size of the positive electrode film layer 113 is OH 2 , OH 1 is greater than OH 2 .

[0276] The negative electrode tab 121 is located on at least one side of the negative current collector 122 along the length direction Z. The current density in the connection region between the negative electrode tab 121 and the negative current collector 122 increases sharply, and problems such as lithium deposition are more likely to occur in this region; while in the embodiment of the present application, OH 1 is greater than OH 2 , so that the ability of the negative electrode film layer 123 to receive lithium ions is stronger in the length direction Z, especially the ability of the region of the negative electrode film layer 123 close to the negative electrode tab 121 to receive lithium ions can be improved, the risk of lithium deposition is reduced, and the use reliability of the battery cell 7 is improved.

[0277] Exemplarily, OH 1 is from 0.5 mm to 3.0 mm, such as 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm or the range composed of any two of the above values. Along the length direction Z, both sides of the negative electrode film layer 123 exceed the positive electrode film layer 113, and each side exceeds OH 1 / 2, that is, half of the size of OH 1 , Figure 8 shows OH 1 / 2.

[0278] Exemplarily, OH 2 is from 0.5 mm to 3.0 mm, such as 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm or a range composed of any two of the above values. Along the width direction Y, both sides of the negative electrode film layer 123 extend beyond the positive electrode film layer 113, and each side extends beyond OH 2 / 2, that is, OH 2 half of the size, Figure 8 OH is shown in 2 / 2.

[0279] In some other embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collector 112 along the width direction Y, and the negative electrode tab 121 is connected to at least one side of the negative electrode current collector 122 along the width direction Y.

[0280] Optionally, the number of positive electrode tabs 111 on the same side of the main body 14 is at least one, optionally at least two. At least two positive electrode tabs 111 can increase the current-carrying capacity of the positive electrode tab 111.

[0281] Optionally, the number of negative electrode tabs 121 on the same side of the main body 14 is at least one, optionally at least two. At least two negative electrode tabs 121 can increase the current-carrying capacity of the negative electrode tab 121.

[0282] In some embodiments, the battery cell 7 further includes a positive terminal 31. The positive terminal 31 is disposed on the outer shell 20 and can be disposed on the housing 21 or the end cover 22.

[0283] The positive terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 are welded. The positive terminal 31 and the positive electrode tab 111 can be connected through an adapter, or can be connected without using an adapter. Optionally, the positive terminal 31 and the positive electrode tab 111 are directly welded without using an adapter, which can reduce the resistance at the connection and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0284] In some embodiments, the battery cell 7 further includes a negative terminal 32. The negative terminal 32 is disposed on the outer shell 20 and can be disposed on the housing 21 or the end cover 22.

[0285] The negative terminal 32 is electrically connected to the negative electrode tab 121. Optionally, the negative terminal 32 and the negative electrode tab 121 are welded. The negative terminal 32 and the negative electrode tab 121 can be connected through an adapter, or can be connected without using an adapter. Optionally, no adapter is used to connect the negative terminal 32 and the negative electrode tab 121, that is, the negative terminal 32 and the negative electrode tab 121 are directly welded, which can reduce the resistance at the connection point and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0286] Optionally, the number of positive terminals 31 on the same side of the main body 14 is at least one, and can be at least two. At least two positive terminals 31 can increase the current-carrying capacity of the positive terminals 31.

[0287] Further optionally, the current-carrying area of the positive terminals 31 on one side is 150 mm 2 to 1000 mm 2 and can be 200 mm 2 to 1000 mm 2 The current-carrying area of the positive terminals 31 on one side refers to the sum of the current-carrying areas of all the positive terminals 31 on the same side of the main body 14. The current-carrying area of the positive terminals 31 can be understood as the cross-sectional area of the positive terminals 31, and this cross-section is perpendicular to the thickness direction of the end cover 22. When the current-carrying area of the positive terminals 31 on one side meets the above range, the current-carrying capacity is relatively strong, which can reduce the internal resistance and heat generation, and is beneficial to improving the fast charging performance and high-temperature cycle performance of the battery cell 7.

[0288] Exemplarily, the current-carrying area of the positive terminals 31 on one side can be 150 mm 2 、200 mm 2 、210 mm 2 、250 mm 2 、280 mm 2 、300 mm 2 、320 mm 2 、350 mm 2 、380 mm 2 、400 mm 2 、450 mm 2 、500 mm 2 、550 mm 2 、600 mm 2 、650 mm 2 、700 mm 2 、750 mm 2 、800 mm 2 、850 mm 2 、900 mm 2 、950 mm 2 、1000 mm 2 or a range composed of any two of the above values.

[0289] Optionally, the number of negative terminals 32 on the same side of the main body 14 is at least one, optionally at least two. The at least two negative terminals 32 can increase the overcurrent capacity of the negative terminals 32.

[0290] Further optionally, the overcurrent area of the unilateral negative terminal 32 is 150 mm 2 to 1000 mm 2 , optionally 200 mm 2 to 1000 mm 2 The overcurrent area of the unilateral negative terminal 32 refers to the sum of the overcurrent areas of all negative terminals 32 on the same side of the main body 14. The overcurrent area of the negative terminal 32 can be understood as the cross-sectional area of the negative terminal 32, and this cross-section is perpendicular to the thickness direction of the end cover 22. When the overcurrent area of the unilateral negative terminal 32 meets the above range, the overcurrent capacity is strong, the internal resistance can be reduced, and the heat generation can be reduced, which is beneficial to improving the fast charging performance and high-temperature cycling performance of the battery cell 7.

[0291] Exemplarily, the overcurrent area of the unilateral negative terminal 32 can be 150 mm 2 , 200 mm 2 , 210 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 , 850 mm 2 , 900 mm 2 , 950 mm 2 , 1000 mm 2 or a range composed of any two of the above values.

[0292] As Figure 9 shown, the battery cell 7 of the embodiment of the present application can be assembled into a battery module 6. The number of battery cells 7 included in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0293] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, in parallel, or in a combined series-parallel connection. A combined series-parallel connection means that among the multiple battery cells 7, there are both series and parallel connections. The multiple battery cells 7 can be directly connected in series, in parallel, or in a combined series-parallel connection together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodating part of the battery module 6. Of course, it is also possible that the multiple battery cells 7 are first connected in series, in parallel, or in a combined series-parallel connection to form battery modules 6, and then the multiple battery modules 6 are connected in series, in parallel, or in a combined series-parallel connection to form a whole and are accommodated in the accommodating part. Optionally, the battery module 6 can also include an accommodating part with an accommodating space, and the multiple battery cells 7 are accommodated in this accommodating space.

[0294] The multiple battery cells 7 of the battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or combined series-parallel connection of the multiple battery cells 7 of the battery module 6. The busbar component can be one or more, and each busbar component is used to electrically connect at least two battery cells 7.

[0295] As Figure 10 shown, in some embodiments, the above-mentioned battery module 6 can also be assembled into a battery pack 2, and the number of battery modules 6 included in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device in this article can be a battery module 6, a battery pack 2, or a battery cell 7, and the battery cell 7 can be the smallest unit constituting the battery device.

[0296] The battery pack 2 can include a box body 5 and multiple battery modules 6 arranged on the box body 5. The box body 5 includes a first box body part 5a and a second box body part 5b. The box body 5 has an accommodating space 5c. The first box body part 5a is used to cover the second box body part 5b and form a closed space for accommodating the battery module 6. The multiple battery modules 6 can be arranged in the box body 5 in any manner.

[0297] The first box body part 5a and the second box body part 5b cover each other, and the first box body part 5a and the second box body part 5b jointly define an accommodating space 5c for accommodating the battery cells. The second box body part 5b can be a hollow structure with one end open, and the first box body part 5a is a plate-like structure. The first box body part 5a covers the open side of the second box body part 5b to form the box body 5 with the accommodating space 5c. The first box body part 5a and the second box body part 5b can also both be hollow structures with one side open, and the open side of the first box body part 5a covers the open side of the second box body part 5b to form the box body 5 with the accommodating space 5c. Of course, the first box body part 5a and the second box body part 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0298] To improve the sealing performance after the connection between the first box body part 5a and the second box body part 5b, a sealing member such as sealant, sealing ring, etc. can also be provided between the first box body part 5a and the second box body part 5b.

[0299] Assume that the first box body part 5a covers the top of the second box body part 5b. The first box body part 5a can also be called the upper box cover, and the second box body part 5b can also be called the lower box body. In some embodiments, during the charging process of the battery pack 2 or any battery cell that makes up the battery pack 2 from a 0% state of charge (SOC) to a 100% state of charge (SOC), the temperature of the external environment where the battery pack 2 is located is 30°C.

[0300] In some embodiments, during the charging process of the battery pack 2 or any battery cell that makes up the battery pack 2 from a 10% state of charge (SOC) to an 80% state of charge (SOC), the temperature of the external environment where the battery pack 2 is located is 30°C.

[0301] In some embodiments, during the charging process of the battery pack 2 or any battery cell that makes up the battery pack 2 from a 10% state of charge to an 80% state of charge, it includes multiple charging steps. The difference between the maximum state of charge of any charging step and the maximum state of charge of its 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 the range composed of any two of the above values.

[0302] The charging process of the battery pack 2 or any battery cell that makes up the battery pack 2 from a 10% state of charge to a 40% state of charge includes multiple charging steps. For any charging step, it can be charged at any rate between 4C and 10C. The charging rate corresponding to each charging step can be any value among 4C, 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or the value of the range composed of any two of the above values.

[0303] Exemplarily, the charging steps of the battery pack 2 or any battery cell that makes up the battery pack 2 from 10% to 80% can be carried out as follows: Constant current charging at 5.0C from 10% SOC to 15% SOC, Constant current charging at 5.0C from 15% SOC to 20% SOC, Constant current charging at 5.0C from 20% SOC to 25% SOC, Constant current charging at 5.0C from 25% SOC to 30% SOC, Charge from 30% SOC to 35% SOC at a constant current of 5.0C, Charge from 35% SOC to 40% SOC at a constant current of 5.0C, Charge from 40% SOC to 45% SOC at a constant current of 4.6C, Charge from 45% SOC to 50% SOC at a constant current of 4.3C, Charge from 50% SOC to 55% SOC at a constant current of 4.0C, Charge from 55% SOC to 60% SOC at a constant current of 3.7C, Charge from 60% SOC to 65% SOC at a constant current of 3.4C, Charge from 65% SOC to 70% SOC at a constant current of 3.1C, Charge from 70% SOC to 75% SOC at a constant current of 2.9C, Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0304] In some embodiments, the charging time of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge is 5 min to 15 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, such as 30°C. Exemplarily, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 15 min, 14 min, 13 min, 12 min, 11 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min or a range composed of any two of the above values.

[0305] Power consumption device The second aspect of the embodiments of the present application provides an electrical device, which includes the battery device of the embodiments of the present application, such as a battery cell, a battery module or a battery pack. The battery cell, the battery module or the battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or an extended-range electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact electric drill, a concrete vibrator and a planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices. The electrical device can select a battery cell, a battery module or a battery pack according to its usage requirements.

[0306] Figure 11 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device 1, a battery pack or a battery module can be adopted.

[0307] A battery pack 2 is arranged inside the electrical device 1. The battery pack 2 can be arranged at the bottom, the head or the tail of the electrical device 1. The battery pack 2 can be used for power supply of the electrical device 1. For example, the battery pack 2 can be used as the operating power source of the electrical device 1 and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1.

[0308] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery pack 2 to supply power to the motor 4. For example, it is used for the working power requirements during the start, navigation and driving of the electrical device 1.

[0309] Another example of the electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires thin and light design, and a battery cell can be used as the power source.

[0310] The charging process of the electrical device can select the following charging methods: Charge from 10% SOC to 15% SOC at a constant current of 5.0C, Charge from 15% SOC to 20% SOC at a constant current of 5.0C, Charge from 20% SOC to 25% SOC at a constant current of 5.0C, Charge from 25% SOC to 30% SOC at a constant current of 5.0C, Charge from 30% SOC to 35% SOC at a constant current of 5.0C, Charge from 35% SOC to 40% SOC at a constant current of 5.0C, Charge from 40% SOC to 45% SOC at a constant current of 4.6C, Charge from 45% SOC to 50% SOC at a constant current of 4.3C, Charge from 50% SOC to 55% SOC at a constant current of 4.0C, Charge from 55% SOC to 60% SOC at a constant current of 3.7C, Charge from 60% SOC to 65% SOC at a constant current of 3.4C, Charge from 65% SOC to 70% SOC at a constant current of 3.1C, Charge from 70% SOC to 75% SOC at a constant current of 2.9C, Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0311] In some embodiments, the charging time of the electrical device from 10% state of charge to 80% state of charge is 5 min to 15 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, such as 30°C. Exemplarily, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 15 min, 14 min, 13 min, 12 min, 11 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min or the range composed of any two of the above values.

[0312] Embodiment The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0313] Example 1-1 1. Preparation of the positive electrode sheet The positive electrode plate includes a positive current collector part, a positive electrode film layer, and a positive electrode conductive layer. The positive electrode film layer is disposed on both sides of the positive current collector part, and the positive electrode conductive layer is located between the positive current collector part and the positive electrode film layer. The positive current collector part is aluminum foil.

[0314] The positive electrode conductive layer on the positive current collector part is a film layer formed by uniformly coating a mixture of a positive electrode conductive agent, superconducting carbon, a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), on the surface of the positive current collector part and drying it. The thickness is 1 μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0315] The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode paste (with a solvent of N-methylpyrrolidone, NMP) on the surface of the positive electrode conductive layer and drying and cold pressing it. 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.

[0316] The positive electrode active material includes lithium iron phosphate particles and a positive electrode coating layer. The positive electrode coating layer coats the surface of the lithium iron phosphate particles. The positive electrode coating layer includes lithium iron titanium phosphate (Li2FeTi(PO4)3) and carbon element, and the mass content of the carbon element is 1.12%.

[0317] The powder compaction density of the positive electrode active material under 30000 N is 2.55 g / cm 3 。

[0318] The single-sided coating weight of the positive electrode film layer is 263 mg / 1540.25 mm 2 。

[0319] The length of the positive electrode film layer is 610 mm, and the width is 110 mm.

[0320] 2. Preparation of the negative electrode plate The negative electrode plate includes a negative current collector part, a negative electrode film layer, and a negative electrode conductive layer. The negative electrode film layer is disposed on both sides of the negative current collector part, and the negative electrode conductive layer is located between the negative current collector part and the negative electrode film layer. The negative current collector part is copper foil.

[0321] The negative electrode conductive layer on the negative current collector part is a film layer formed by uniformly coating a mixture of a negative electrode conductive agent, superconducting carbon, a negative electrode binder, styrene-butadiene rubber (SBR), a thickening agent, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, on the surface of the negative current collector part and drying it. 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 thickening agent in the negative electrode conductive layer is 5%.

[0322] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode paste (with a solvent of deionized water) on the surface of the negative electrode conductive layer and drying and cold pressing it.

[0323] The negative electrode film layer comprises a negative electrode active material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickener, with a mass ratio of 96.5:0.5:2:1. The graphite particles include artificial graphite and a negative electrode coating layer, and the negative electrode coating layer is coated on the surface of the artificial graphite. The mass content of carbon element in the negative electrode coating layer is 3.5%. The Dv50 of the graphite particles is 11.3 μm.

[0324] The powder compaction density of the negative electrode active material under 20000 N is 1.6 g / cm 3 。

[0325] The single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 。

[0326] The length of the negative electrode film layer is 4 mm greater than the length of the positive electrode film layer, and the width of the negative electrode film layer is 3 mm greater than the length of the positive electrode film layer.

[0327] 3. Separator The separator includes a base film and functional layers provided on both sides of the base film. The base film includes a 7-μm polyethylene film layer with a porosity of 42%; The functional layer includes a first functional layer and a second functional layer. The first functional layer includes alumina particles and polyvinylidene fluoride as a binder. The first functional layer is a film layer formed by coating a first slurry on one side of the base film, with a thickness of 1 μm, and the average particle size of the alumina particles is 10 nm; among them, the first slurry includes alumina particles and polyvinylidene fluoride as a binder; The second functional layer is a composite particle formed by polyacrylate and calcium oxide particles dispersed on the polyacrylate. The second functional layer is a film layer formed by coating a second slurry on the other side of the base film, with a thickness of 5 μm, and the average particle size of the calcium oxide particles is 10 nm; the second slurry includes the composite particles.

[0328] 4. Preparation of electrolyte The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0329] After mixing the components of each organic solvent, a lithium salt and an additive are added to prepare the electrolyte.

[0330] The organic solvent includes a chain carboxylic ester solvent (ethyl acetate) with a mass content of 39.0%, ethylene carbonate with a mass content of 27.3%, and dimethyl carbonate with a mass content of 11.7%. The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0331] The mass content of the additive is 6%, and it includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluorooxalate borate LiDFOB with a mass ratio of 3:2:0.5:0.5.

[0332] The lithium salt includes lithium bis(fluorosulfonyl)imide LiFSI with a mass content of 6% and lithium hexafluorophosphate LiPF with a mass content of 10%. 6 , and the mass content of the lithium salt is calculated based on the mass of the electrolyte solution.

[0333] 5. Preparation of the battery cell Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining a stacked electrode assembly. Place the electrode assembly in a housing, and positive and negative terminals are provided on the housing. After baking, inject the electrolyte solution, and through processes such as vacuum packaging, standing, formation, aging, down-bin, and shaping, obtain the battery cell. Among them, the battery cell is baked for 12 h. After baking, the water content of the positive electrode sheet is 356 ppm; The liquid injection coefficient of the battery cell is 2.9 g / Ah.

[0334] The compaction density of the positive electrode film layer of the battery cell at 0% SOC is 2.7 g / cm 3 , and the compaction density of the negative electrode film layer at 0% SOC is 1.41 g / cm 3 .

[0335] The housing is an aluminum shell with a cuboid structure, and the thickness of the face with the largest area of the cuboid structure is 0.5 mm.

[0336] Among them, the current-carrying area of the positive terminal on the same side is 640 mm 2 , and the current-carrying area of the negative terminal on the same side is 640 mm 2 .

[0337] Examples 1-2 and 1-3 Prepare the battery cell using a method similar to that of Example 1. Different from Example 1, the mass content of the lithium salt components is adjusted, as shown in Table 1 specifically.

[0338] Example 1-4 Prepare the battery cell using a method similar to that of Example 1. Different from Example 1, the material of the lithium fluorosulfonylimide is adjusted, and lithium bis(trifluoromethylsulfonyl)imide LiTFSI is used.

[0339] Example 1-5 Prepare the battery cell using a method similar to that of Example 1. Different from Example 1, the baking time of the battery cell is adjusted to 1 h, and the water content of the positive electrode film layer is 1638 ppm.

[0340] Example 1-6 The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the baking time of the battery monomer was adjusted to 4 h, and the water content of the positive electrode film layer was 782 ppm.

[0341] Examples 2-2 to 2-10 The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the components and component contents of the first additive were adjusted. Among them, the mass content of dimethyl carbonate was adjusted accordingly according to the adjustment of other components. For example, if the mass content of the first additive and lithium fluorosulfonylimide increased by 1% compared with Example 1, the mass content of dimethyl carbonate decreased by 1% compared with Example 1. Specifically, as shown in Table 1.

[0342] Example 3 The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the material of the ethylene carbonate derivative was adjusted, and difluoroethylene carbonate was used.

[0343] Comparative Examples 1-1 to 1-3 The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the components and component contents of the first additive were adjusted. Among them, the mass content of dimethyl carbonate was adjusted accordingly according to the adjustment of other components. For example, if the mass content of the first additive increased by 1% compared with Example 1, the mass content of dimethyl carbonate decreased by 1% compared with Example 1. Specifically, as shown in Table 1.

[0344] Comparative Example 1-4 The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the mass content of lithium fluorosulfonylimide was adjusted; among them, the mass content of dimethyl carbonate was adjusted accordingly according to the adjustment of other components. For example, if the mass content of lithium fluorosulfonylimide increased by 1% compared with Example 1, the mass content of dimethyl carbonate decreased by 1% compared with Example 1.

[0345] The baking time of the battery monomer was also adjusted to 1 h, and the water content of the positive electrode film layer was 1638 ppm.

[0346] Performance test 1. DC internal resistance DCR test of battery monomer The method of GB / T 31467 "Performance Test Specification for High-power Lithium-ion Power Batteries for HEV" can be referred to.

[0347] For example, at room temperature, the battery cell is charged at a constant current of 0.33 C to 3.65 V, then charged at a constant voltage of 3.65 V to 0.05 C, left standing for 30 min, discharged at a constant current of 0.33 C to 2.0 V, and the discharge capacity A at this time is recorded. 0 , in units of Ah, and then charged at a constant current of 0.33 C for 0.5 A 0 Ah, and the SOC is adjusted to 50%.

[0348] After the battery cell is placed at -20 °C for 2 h, it is discharged at a constant current of 1 C for 10 s, and ∆U is recorded. 放电 、∆I 放电 , and the discharge DCR data of the lithium-ion battery is calculated through the following formula, R 放电 =∆U 放电 / ∆I 放电 , where ∆U 放电 represents the voltage change within 10 s from the start of discharge, and ∆I 放电 represents the current value within 10 s from the start of discharge.

[0349] 2. Number of cycles for the battery cell to cycle to 70% SOH At 60 °C, the battery cell is charged at a constant current of 0.8 C to the charging cut-off voltage of 3.6 V, then charged at a constant current of 0.1 C to the charging cut-off voltage of 3.65 V, and left standing for 30 min; discharged at a constant current of 1 C to 2.83 V, and left standing for 30 min. This is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., Cn / C0×100%) is 70%, and record the number of cycles. The more cycles, the better the cycle performance of the battery cell.

[0350] 3. Lithium plating situation test of the battery cell At 30 °C, after each battery cell of each example is cycled 200 times according to its respective charge-discharge strategy, it is fully charged to 100% SOC according to the corresponding charging strategy, the negative electrode plate is disassembled, the negative electrode plate is unfolded, the lithium plating area (grayish-white area) is observed, and the lithium plating area is measured. The degree of lithium plating is as follows: No lithium plating: Lithium plating area < 0.05%.

[0351] Slight lithium plating: Lithium plating area < 2% and ≥ 0.05%.

[0352] Severe lithium plating: Lithium plating area ≥ 2%.

[0353] The battery cell is charged, and the charging steps include the following steps: Charge from 0% SOC to 5% SOC at a constant current of 5.0 C; Charge from 5% SOC to 10% SOC at a constant current of 5.0 C; Charge from 10% SOC to 15% SOC at a constant current of 5.0C; Charge from 15% SOC to 20% SOC at a constant current of 5.0C; Charge from 20% SOC to 25% SOC at a constant current of 5.0C; Charge from 25% SOC to 30% SOC at a constant current of 5.0C; Charge from 30% SOC to 35% SOC at a constant current of 5.0C; Charge from 35% SOC to 40% SOC at a constant current of 5.0C; Charge from 40% SOC to 45% SOC at a constant current of 4.6C; Charge from 45% SOC to 50% SOC at a constant current of 4.3C; Charge from 50% SOC to 55% SOC at a constant current of 4.0C; Charge from 55% SOC to 60% SOC at a constant current of 3.7C; Charge from 60% SOC to 65% SOC at a constant current of 3.4C; Charge from 65% SOC to 70% SOC at a constant current of 3.1C; Charge from 70% SOC to 75% SOC at a constant current of 2.9C; Charge from 75% SOC to 80% SOC at a constant current of 2.7C; Charge from 80% SOC to 85% SOC at a constant current of 1.8C; Charge from 85% SOC to 90% SOC at a constant current of 1.3C; Discharge at a constant current of 0.7C to the cut-off voltage, e.g., 2.0V. Charge from 95% SOC to 98% SOC at a constant current of 0.33C; Charge from 98% SOC to 100% SOC at a constant current of 0.1C.

[0354] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0355] The discharging strategy is as follows: Discharge at a constant current of 0.33C to the cut-off voltage, e.g., 2.0V.

[0356] When performing charge and discharge tests on the battery cell, the battery cell can be assembled in a battery device, and the required charge and discharge strategies can be adjusted through the battery management system for testing.

[0357] The test results are shown in Table 1.

[0358] Table 1

[0359] In Table 1, VC represents vinylene carbonate; PS represents 1,3 - propane sultone; For Comparative Examples 1 - 4, lithium bis(fluorosulfonyl)imide with a relatively low mass content was used. Since the water content in the positive electrode film layer in Comparative Examples 1 - 4 was relatively high, the water content in the positive electrode film layer was 1638 ppm, and the mass content of lithium hexafluorophosphate was relatively high, resulting in a relatively high amount of acid produced by the decomposition of lithium hexafluorophosphate. The hydrofluoric acid HF generated may damage the SEI film, leading to a reduction in the protective performance of the SEI film for the negative active material, an exacerbation of the side reaction between the carboxylic ester solvent and the negative active material, and deterioration of the cycle.

[0360] In Examples 1 - 5, a relatively high content of lithium bis(fluorosulfonyl)imide was used, which can reduce the usage amount of lithium hexafluorophosphate, thereby reducing the amount of acid produced and improving the cycle performance and fast charging performance of the battery cell.

[0361] Compared with Examples 1 - 5, the water content in the positive electrode film layer of Examples 1 - 1 and Examples 1 - 6 is relatively less. Under the condition of using the same electrolyte composition, the less the water content, the less the acid production, the lower the risk of erosion to the SEI film, and the more significant the improvement effect on the cycle performance and fast charging performance of the battery cell.

[0362] The lithium salts in Examples 1 - 1 to Examples 1 - 6 of the present application include 4% to 8% of lithium bis(fluorosulfonyl)imide, which can reduce the usage amount of lithium hexafluorophosphate, thereby reducing the amount of acid produced, alleviating the risk of erosion of hydrofluoric acid to the SEI film. The SEI film does not need to be repeatedly repaired, which can reduce the usage amount of additives, making the impedance of the SEI film relatively low, and can improve the high - temperature cycle performance and fast charging performance of the battery cell. When lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate are used in combination, and the ratio of the mass content of lithium bis(fluorosulfonyl)imide to the mass content of the lithium hexafluorophosphate is 0.3 to 1.0, and can be selected as 0.4 to 0.8, the electrolyte has excellent ionic conductivity, and can reduce the side reaction on the negative electrode side, improving the cycle performance and fast charging performance of the battery cell.

[0363] When different materials are selected for the lithium bis(fluorosulfonyl)imide, such as lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide LiTFSI (used in Examples 1 - 5), it can improve the high - temperature cycle performance and fast charging performance of the battery cell.

[0364] Compared with Example 1 - 3, when the addition amount of lithium bis(fluorosulfonyl)imide is too high, for example, greater than 8%, a large amount of energy may accumulate in the battery cell during thermal runaway, resulting in a large amount of energy release and deterioration of the reliability of the battery cell in use.

[0365] The addition amount of the first additive in the electrolytes of Comparative Example 1-1 and Comparative Example 1-3 is too low. For example, the addition amount of vinylene carbonate is too low, and even the electrolyte of Comparative Example 1-3 does not contain vinylene carbonate. Although the impedance of the SEI film on the negative electrode side is relatively low, due to the relatively poor protection effect of the SEI film, carboxylic ester solvents are prone to side reactions with the negative electrode active material at high temperatures, deteriorating the high-temperature cycle and possibly causing lithium deposition.

[0366] The addition amount of the first additive in the electrolyte of Comparative Example 1-2 is too high. For example, the addition amount of vinylene carbonate is too high. Vinylene carbonate can form a dense SEI film composed of organic components on the negative electrode side, alleviating the side reaction between carboxylic ester solvents and the negative electrode active material. However, due to the too high impedance of the SEI film, it is not conducive to the rapid migration of lithium ions, making it impossible for the battery cell to be quickly charged.

[0367] While the addition amount of the first additive in the electrolyte of the embodiment of the present application is within an appropriate range, and its mass content is 2.5% to 10%. The reaction potentials of vinylene carbonate in the first additive and carboxylic ester solvents are close, and there is a competitive reaction with carboxylic ester solvents. Vinylene carbonate can participate in the formation of a dense SEI film on the negative electrode side, making it difficult for carboxylic ester solvents to penetrate the SEI film to reach the graphite particles, thereby alleviating the side reaction between carboxylic ester solvents and graphite particles and reducing the gas generation amount; moreover, because the first additive is within an appropriate content, the film impedance formed by it on the negative electrode side is relatively small, which is beneficial to improving the high-temperature cycle performance and reducing the risk of lithium deposition.

[0368] Example 2-2: The data in Table 1 were obtained by detecting and analyzing the components of the electrolyte. In this case, the battery cell has not undergone the formation process. After the electrolyte component test and analysis, it is assembled into a battery cell, and then the performance test is carried out; it should be noted that Example 2-2 uses the electrolyte of the unformed battery cell as a sample, and based on the mass of the electrolyte being 100%, the mass contents of the components in the first additive and the components in the lithium salt are calculated.

[0369] In Example 2-1, the free electrolyte in the battery cell after processes such as formation, aging, and warehousing was detected and analyzed to obtain the data in Table 1. The components of the fresh electrolyte of the battery cell are as shown in Example 2-2; it can be seen from the data in Table 1 that through processes such as formation, vinylene carbonate, 1,3-propane sultone, and fluoroethylene carbonate are all consumed and participate in the film-forming reaction of the SEI film on the negative electrode side, and an SEI film with relatively low impedance can be obtained, improving the fast charging performance, high-temperature cycle performance, and service reliability of the battery cell.

[0370] It should be noted that in Example 2-1, the free electrolyte of the battery monomer after processes such as formation was used as the sample, and with the mass of the electrolyte being 100%, the mass contents of the components in the first additive and the components in the lithium salt were calculated.

[0371] In Example 2-3 and Example 2-4, by regulating the mass contents of vinylene carbonate, 1,3-propane sultone, and fluoroethylene carbonate in the freshly prepared electrolyte, an SEI film with relatively low impedance can be obtained, improving the fast charging performance, high-temperature cycling performance, and service reliability of the battery monomer.

[0372] In Example 1-1, Example 2-5, and Example 2-6, by regulating the mass content of 1,3-propane sultone, as the mass content of 1,3-propane sultone increases, the components of the SEI film can be optimized, improving the protection effect of the SEI film, which is beneficial to the improvement of the high-temperature cycling performance; however, the impedance of the SEI film also increases appropriately, which may slightly deteriorate the fast charging performance of the battery monomer. In view of this, the mass content of 1,3-propane sultone is 0 to 0.5%, and can be selected as 0% to 0.3%, so as to balance the improvement of the high-temperature cycling performance and fast charging performance of the battery monomer.

[0373] In Example 1-1, Example 2-7 to Example 2-10, by regulating the mass content of fluoroethylene carbonate, as the mass content of fluoroethylene carbonate increases, the components of the SEI film can be optimized, reducing the impedance of the SEI film, which is beneficial to the rapid migration of lithium ions and improving the fast charging performance of the battery monomer; however, at high temperatures, the stability of fluoroethylene carbonate is poor, and it is easy to decompose to produce acid, damaging the SEI film and deteriorating the protection effect on the negative electrode active material, resulting in a possible slight deterioration of the high-temperature cycling performance. In view of this, the mass content of the ethylene carbonate derivative in the electrolyte is 0 to 4.0%, and can be selected as 1.5% to 3.5%, so as to balance the improvement of the high-temperature cycling performance and fast charging performance of the battery monomer.

[0374] Using ethylene carbonate derivatives of different materials, such as fluoroethylene carbonate and difluoroethylene carbonate (used in Example 3), can effectively improve the high-temperature cycling performance and fast charging performance of the battery monomer.

[0375] Example 4-1 and Example 4-2 The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the components and mass contents of the carboxylic ester solvent and the carbonate solvent were adjusted. Among them, in Example 4-1, the ethylene carbonate was 3%, 1,3-propane sultone was 0.5%, fluoroethylene carbonate FEC was 1.5%, and the mass content of the first additive was 5%. In Example 4-2, the ethylene carbonate is 3%, the 1,3-propane sultone is 0.5%, the fluoroethylene carbonate FEC is 1.5%, and the mass content of the first additive is 5%.

[0376] Specifically, it is shown in Table 2 as follows.

[0377] Example 5 A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the material of the carboxylic ester solvent and the mass content of the carbonate solvent were adjusted. Among them, in Example 5, the ethylene carbonate is 6%, the 1,3-propane sultone is 0.5%, the fluoroethylene carbonate FEC is 1.5%, and the mass content of the first additive is 8.0%.

[0378] Specifically, it is shown in Table 2 as follows.

[0379] Examples 6-1 to 6-3 A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the components and mass content of the second additive were adjusted. Among them, in Example 6-1, the mass content of dimethyl carbonate was also adjusted. Specifically, it is shown in Table 2 as follows.

[0380] Comparative Examples 2-1 to 2-2 A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the components and mass content of the carboxylic ester solvent and the carbonate solvent were adjusted. Specifically, it is shown in Table 2 as follows.

[0381] The test results are shown in Table 2 as follows.

[0382] Table 2

[0383] In Table 2, EA represents ethyl acetate; MA represents methyl acetate; EC represents ethylene carbonate; DMC represents dimethyl carbonate; ES represents ethylene sulfite; DTD represents ethylene sulfate; LiDFOB represents lithium difluorooxalate borate; LiPO 2 F 2 represents lithium difluorophosphate; EC: 27.3 means that the mass content of EC is 27.3%.

[0384] The meanings of other examples are explained as above and will not be elaborated here.

[0385] The mass content of the carboxylate solvent in the electrolyte of Comparative Example 2-1 is relatively low, resulting in a relatively high viscosity and impedance of the electrolyte, which is not conducive to the rapid wetting of the electrode sheet. The wettability of different parts of the electrode sheet is different, leading to different discharge degrees of the electrode sheet, which may cause local lithium deposition on the negative electrode side and deteriorate the cycle performance.

[0386] The mass content of the carboxylate solvent in the electrolyte of Comparative Example 2-2 is relatively high, resulting in a relatively low viscosity and impedance of the electrolyte, which is conducive to rapid charging. However, at high temperatures, the side reaction between the carboxylate solvent and the negative electrode active material is relatively serious, deteriorating the high-temperature cycle performance and possibly causing lithium deposition on the negative electrode side.

[0387] Through testing, Examples 1-1, 1-2 to 3 of this application basically do not show lithium deposition.

[0388] Examples 4-1 and 4-2 can reduce the viscosity of the electrolyte and improve the migration rate of lithium ions in the electrolyte by adjusting the mass content of the carboxylate solvent within an appropriate range, such as 8% to 60%. And in combination with the first additive, it can alleviate side reactions, improve high-temperature cycling, and reduce the risk of lithium deposition.

[0389] Carboxylate solvents made of different materials, such as ethyl acetate and methyl acetate, can improve the rapid charging performance and high-temperature cycle performance. For example, the carboxylate solvent in Example 5 includes methyl acetate. In combination with an appropriate content of the first additive, it can improve the film-forming performance of the SEI film while reducing the viscosity of the electrolyte, reduce the internal resistance of the battery cell, and improve the rapid charging performance of the battery cell. And because the SEI film can effectively protect the negative electrode active material, it can alleviate side reactions and improve the high-temperature cycle performance. However, due to the relatively high boiling point of ethyl acetate and relatively good stability at high temperatures, the high-temperature cycle performance of Example 1 is more excellent than that of Example 5.

[0390] Examples 6-1 to 6-3, by using second additives made of different materials, can further optimize the components of the SEI film, reduce the internal resistance of the battery cell, and improve the rapid charging performance and high-temperature cycle performance of the battery cell.

[0391] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principle, and scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises an electrode assembly and an electrolyte, and the electrode assembly comprises a positive electrode sheet and a negative electrode sheet; The positive electrode sheet comprises a positive current collecting portion and a positive electrode film layer disposed on at least one side of the positive current collecting portion, wherein the positive electrode film layer comprises a lithium-containing phosphate having an olivine structure; The negative electrode plate comprises a negative electrode current collecting portion and a negative electrode film layer disposed on at least one side of the negative electrode current collecting portion, wherein the negative electrode film layer comprises a carbon-based material; The electrolyte includes a carboxylic acid ester solvent, a first additive and a lithium salt, in, Based on the mass of the electrolyte, the mass content of the carboxylic acid ester solvent is 8% to 60%; Based on the mass of the electrolyte, the total mass content of the first additive is 2.5% to 10%, and the first additive includes 1,3-propane sultone with a mass content of ≥0, a vinyl carbonate derivative with a mass content of ≥0, and vinylene carbonate with a mass content of >0, and the vinyl carbonate derivative includes a compound shown in formula A, Formula A, In Formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time; The lithium salt includes fluorinated lithium sulfonyl imide, and the mass content of the fluorinated lithium sulfonyl imide in the electrolyte is 4% to 8%.

2. The battery cell according to claim 1, characterized in that: The mass content of the fluorinated lithium sulfonyl imide in the electrolyte is 4% to 6%.

3. The battery cell according to claim 1 or 2, characterized in that: The fluorine-containing lithium sulfonyl imide includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide and lithium perfluorobutylsulfonyl imide.

4. The battery cell according to claim 1, characterized in that: The lithium salt further includes lithium hexafluorophosphate, and the ratio of the mass content of the fluorinated lithium sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.3 to 1.0, based on the mass of the electrolyte.

5. The battery cell according to claim 4, characterized in that: The ratio of the mass content of the fluorinated lithium sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.4 to 0.8, based on the mass of the electrolyte.

6. The battery cell according to claim 4, characterized in that: The mass content of lithium hexafluorophosphate in the electrolyte is 8% to 12%.

7. The battery cell according to claim 1, characterized in that: The mass content of the first additive is 3% to 7.5%.

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

9. The battery cell according to claim 1, characterized in that: The mass content of 1,3-propane sultone in the electrolyte is 0 to 0.5%.

10. The battery cell according to claim 9, characterized in that: The mass content of 1,3-propane sultone in the electrolyte is 0 to 0.3%.

11. The battery cell according to claim 1, characterized in that: The mass content of the ethylene carbonate derivative in the electrolyte is 0 to 4.0%.

12. The battery cell according to claim 11, characterized in that: The mass content of the ethylene carbonate derivative in the electrolyte is 1.5% to 3.5%.

13. The battery cell according to claim 1, characterized in that: At least one of Q1, Q2, Q3 and Q4 includes a halogen atom, or a C1 to C5 halogenated alkyl group.

14. The battery cell according to claim 1, characterized in that: The ethylene carbonate derivative includes at least one of the compounds represented by formula A-1 to the compounds represented by formula A-3, 。 15. The battery cell according to claim 1, characterized in that: The carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

16. The battery cell according to claim 15, characterized in that: The carboxylic acid ester solvent includes one or more of the compounds represented by formula I-1 to the compounds represented by formula I-12, 。 17. The battery cell according to claim 1, characterized in that: The electrolyte further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 18% to 70%.

18. The battery cell according to claim 17, characterized in that: The carbonate solvent includes cyclic carbonate, and the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate; and / or, The carbonate solvent includes chain carbonate, and the chain carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

19. The battery cell according to claim 1, characterized in that: The electrolyte includes a sulfur-containing additive in an amount of 0 to 2% by mass in the electrolyte, wherein the sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, vinyl sulfite, and methylene disulfonate; and / or The electrolyte includes a lithium salt additive with a mass content of 0 to 1% in the electrolyte, and the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

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

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

22. The battery cell according to claim 21, characterized in that: The mass content of the carbon element is 0.8% to 2.3% based on the mass of the olivine-structured lithium-containing phosphate.

23. The battery cell according to claim 21, characterized in that: The positive electrode coating layer also includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

24. The battery cell according to claim 21, characterized in that: The phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

25. The battery cell according to claim 1, characterized in that The lithium-containing phosphate 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, 0.5≤x1+y1≤1.3, 0.9≤a1≤1.5, 0≤b1≤0.5, 0.9≤a1+b1≤1.5, 0≤c1≤0.5, 3≤z1≤5, A includes 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.

26. The battery cell according to claim 1, characterized in that: The positive electrode sheet includes a positive electrode active material, and the positive electrode active material has a powder compaction density of 2.43 g / cm at 30000 N. 3 Up to 2.85g / cm 3 .

27. The battery cell according to claim 1, characterized in that: The compaction density of the positive electrode film layer of the battery cell at 0% charge state is 2.46 g / cm 3 Up to 2.8g / cm 3 ; and / or The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 350mg / 1540.25mm 2 .

28. The battery cell according to claim 1, characterized in that: The positive electrode plate also includes a positive electrode conductive layer, which is located between the positive electrode current collecting portion and the positive electrode film layer. The positive electrode conductive layer includes a positive electrode 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.

29. The battery cell according to claim 28, characterized in that: The thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

30. The battery cell according to claim 1, characterized in that The carbon-based material includes graphite particles, the graphite particles include graphite body particles and a negative electrode coating layer coated on the surface of the graphite body particles, the graphite body particles include secondary particles, and the negative electrode coating layer includes carbon elements.

31. The battery cell according to claim 30, characterized in that: The graphite bulk particles include at least one of artificial graphite and natural graphite.

32. The battery cell according to claim 30, characterized in that The mass content of carbon element in the negative electrode coating layer is 2% to 5% based on the mass of the graphite particles.

33. The battery cell according to claim 1, characterized in that: The negative electrode film layer further comprises a silicon-based material, and the mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.3% to 5.0%.

34. The battery cell according to claim 1, characterized in that The negative electrode plate includes a negative electrode active material, and the powder compaction density of the negative electrode active material under 20000N is 1.4g / cm 3 Up to 1.8g / cm 3 .

35. The battery cell according to claim 1, characterized in that The compaction density of the negative electrode film layer of the battery cell at 0% charge state is 1.30 g / cm 3 Up to 1.55g / cm 3 , and / or, The single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 Up to 140mg / 1540.25mm 2 .

36. 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 collecting portion and the negative electrode film layer. The negative electrode conductive layer includes a negative electrode 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.

37. The battery cell according to claim 36, characterized in that: The thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

38. The battery cell according to claim 1, characterized in that The electrode assembly further includes a separator, which is located between the positive electrode plate and the negative electrode plate. The separator includes a base film, the base film has a thickness of 4 μm to 12 μm, and / or a porosity of 20% to 70%.

39. The battery cell according to claim 38, characterized in that The isolation film further includes a functional layer disposed on at least one side of the base film, and the functional layer includes: a first functional layer, located on one side of the base film, wherein the first functional layer comprises first inorganic particles, The second functional layer is located on the other side of the base film, and the second functional layer includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

40. The battery cell according to claim 39, characterized in that The non-fluorinated polymer particles include acrylic copolymers.

41. The battery cell according to claim 39 or 40, characterized in that: The first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide; and / or the first inorganic particles have an average particle size of 5 nm to 100 nm.

42. The battery cell according to claim 39, characterized in that The second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide and tin oxide, and / or the average particle size of the second inorganic particles is 5 nm to 100 nm.

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

44. The battery cell according to claim 43, characterized in that OH1 is 1.0 mm to 4.0 mm; and / or OH2 is 1.0 mm to 3.0 mm.

45. The battery cell according to claim 1, characterized in that The battery cell also includes at least one positive terminal, and the flow area of ​​all the positive terminals on the same side of the positive current collecting portion is 150mm 2 Up to 1000mm 2 ; and / or The battery cell also includes at least one negative terminal, and the flow area of ​​all the negative terminals on the same side of the negative current collecting portion is 150mm 2 Up to 1000mm 2 .

46. ​​The battery cell according to claim 1, characterized in that The battery cell includes a case that accommodates the electrode assembly and the electrolyte, and a thickness of the case is 0.1 mm to 0.5 mm.

47. A battery device, characterized in that: The battery device includes the battery cell according to any one of claims 1 to 46.

48. The battery device according to claim 47, characterized in that The battery device is configured to charge from a 10% state of charge to an 80% state of charge in a time range of 5 minutes to 15 minutes.

49. An electrical device, characterized in that: The electrical device comprises a battery device as claimed in claim 47 or 48.

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