Battery cell, battery device, and electrical device

Abstract

The present application relates to a battery cell, a battery device and an electrical device. The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab includes a positive current collector portion and a positive electrode film layer, and the positive electrode film layer includes a lithium-containing phosphate with an olivine structure. The negative electrode tab includes a negative current collector portion and a negative electrode film layer, and the negative electrode film layer includes a carbon-based material. The electrolyte includes a carboxylate solvent, a first additive and lithium fluorosulfonimide. The mass content of the carboxylate solvent is 8% to 60%. 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 the compound shown in Formula A. The mass content of lithium fluorosulfonimide is 4% to 8%. The present application can improve the fast charging performance and cycling performance of the battery cell. #imgabs0# Formula A.

Description

[0001] This application claims the priority of International Application PCT / CN2025 / 078570 titled "Battery Cell, Battery Device and Electric Appliance" 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 electric appliance. 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

[0004] This application provides a battery cell, a battery device and an electric appliance, which can reduce the heat generation of the battery cell and improve the fast charging performance and cycling performance of the battery cell.

[0005] In a first aspect, this application provides a battery cell, which 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, and the positive electrode film layer includes a lithium-containing phosphate with 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, and the negative electrode film layer includes a carbon-based material; the electrolyte includes a carboxylic ester solvent, a first additive and a lithium salt. Among them, 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%, 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. The derivative of ethylene carbonate includes a compound represented by Formula A,

[0006] Formula A,

[0007] In Formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q1, Q2, Q3, Q4 are not simultaneously hydrogen atoms;

[0008] The lithium salt includes lithium fluorosulfonylimide, and the mass content of lithium fluorosulfonylimide in the electrolyte is 4% to 8%.

[0009] Accordingly, 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 prone 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 reach 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.

[0010] 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.

[0011] 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.

[0012] 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, optionally 0.4 to 0.8, based on the mass of the electrolyte. 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.

[0013] 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.

[0014] In some embodiments, the mass content of the first additive is 3% to 7.5%, which can further improve the fast charging ability, cycle performance and use reliability of the battery cell.

[0015] 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 cycle performance and fast charging ability of the battery cell.

[0016] In some embodiments, the mass content of 1,3 - propane sultone in the electrolyte is 0 to 0.5%, and can be optionally 0 to 0.3%. When the mass content of 1,3 - propane sultone 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 cycle performance of the battery cell.

[0017] 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, can optimize the components of the SEI film, reduce the impedance of the SEI film, and effectively improve the fast charging performance and cycle performance of the battery cell.

[0018] In some embodiments, at least one of Q1, Q2, Q3 and Q4 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 relatively low, and it can more effectively balance the improvement of the high - temperature cycle performance and fast charging performance of the battery cell.

[0019] 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,

[0020] 。

[0021] The above materials can further improve the high - temperature cycle performance and fast charging performance of the battery cell.

[0022] In some embodiments, the carboxylic ester solvent includes the compound shown by formula I,

[0023] Formula I,

[0024] In formula I,

[0025] R1 includes a hydrogen atom, a C1 - C5 alkyl group or a C1 - C5 haloalkyl group,

[0026] R2 includes C1-C5 alkyl or C1-C5 haloalkyl.

[0027] The above-mentioned chain carboxylic ester solvents have low viscosity, improve the rapid charging ability of the battery cell, reduce the risk of lithium precipitation under rapid charging, and improve the service reliability of the battery cell.

[0028] 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.

[0029]

[0030] The above materials can further improve the rapid charging performance of the battery cell.

[0031] 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 increase the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions and improves the rapid charging ability of the battery cell.

[0032] 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 rapid charging performance of the battery cell.

[0033] 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 rapid charging performance of the battery cell.

[0034] 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(vinylene sulfate), 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 the battery cell.

[0035] 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(oxalato)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.

[0036] In some embodiments, the lithium-containing phosphate with an 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 surface-coating the phosphate particles with the cathode coating layer, the conductivity of the lithium-containing phosphate with an 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 cycling performance of the battery cell.

[0037] In some embodiments, based on the mass of the lithium-containing phosphate with an 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 with an olivine structure can be significantly improved, which is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate with an olivine structure, and can improve the fast charging ability of the battery cell.

[0038] 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.

[0039] 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.

[0040] 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 cycle stability of the above materials is relatively excellent, and it can improve the cycle performance of the battery cell.

[0041] In some embodiments, the powder compaction density of the positive electrode active material under 30000N is 2.43 g / cm 3 to 2.85 g / cm 3 . When the powder compaction density of the positive electrode active material under 30000N is within the above range, it can improve the energy density of the battery cell, and since the positive electrode active 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 cycle performance and fast charging performance of the battery cell.

[0042] In some embodiments, when the battery cell is in the 0% SOC state of charge, the compaction density of the positive electrode film layer is 2.46 g / cm 3 to 2.8 g / cm 3 ; when the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell, and since 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 cycle performance and fast charging performance of the battery cell.

[0043] 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 cycle performance and fast charging performance of the battery cell.

[0044] In some embodiments, the positive electrode tab further includes a positive electrode conductive layer, which is 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 conductivity of the positive electrode tab, reduce the heat generation of the positive electrode tab, and thus reduce the heat generation of the battery cell.

[0045] 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 conductivity of the positive electrode tab, reduce the heat generation of the positive electrode tab, and thus reduce the heat generation of the battery cell, and can improve the high-temperature cycle performance of the battery cell.

[0046] 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 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, so that the number of sites where lithium ions can be deintercalated is larger, and the conductivity of the negative electrode coating layer is 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.

[0047] In some embodiments, the graphite body particles include at least one of artificial graphite and natural graphite.

[0048] 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.

[0049] 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.

[0050] 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, since the negative electrode active material in the negative electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the high-temperature cycle performance of the battery cell.

[0051] 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 When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative electrode active material in the negative electrode film layer is stacked more closely, the contact resistance between particles is small, 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.

[0052] 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 is not too large, and the high-temperature cycle performance of the battery cell can be improved while taking it into account.

[0053] In some embodiments, the negative electrode sheet further includes a negative electrode conductive layer. The negative electrode conductive layer is located between the negative electrode current collector and the negative electrode film layer. The negative electrode conductive layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The negative electrode conductive layer can further improve the conductivity of the negative electrode 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.

[0054] 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, the conductivity of the negative electrode sheet can be further improved, the heat generation of the negative 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 it into account.

[0055] In some embodiments, the electrode assembly further includes a separator. The separator is located between the positive electrode sheet and the negative electrode sheet. The 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, 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 the fast charging performance and high-temperature cycle performance of the battery cell can be improved.

[0056] In some embodiments, the separator membrane further includes a functional layer disposed on at least one side of the base film. The functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and 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. 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.

[0057] In some embodiments, the non-fluoropolymer particles include acrylate copolymers. Acrylate copolymers have excellent adhesion properties and high adhesion stability to the base film.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] In some embodiments, the positive electrode plate and the negative electrode plate are stacked along the thickness direction of the battery cell; the electrode assembly further includes a positive electrode tab and a negative electrode tab. The positive electrode tab is connected to at least one side of the positive current collector along the length direction of the battery cell, and the negative electrode tab is connected to at least one side of the negative current collector along the length direction of the battery cell; along the length direction of the battery cell, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH1; along the width direction of the battery cell, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH2, where OH1 is greater than OH2.

[0063] Therefore, in the embodiment of the present application, OH1 is set to be greater than OH2, so that the ability of the negative electrode film layer 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 deposition can be reduced, and the reliability of the battery cell in use can be improved.

[0064] In some embodiments, OH1 is 1.0 mm to 4.0 mm; and / or OH2 is 1.0 mm to 3.0 mm. When the battery cell meets the above conditions, the risk of lithium deposition can be reduced, and the reliability of the battery cell in use can be improved.

[0065] 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.

[0066] 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.

[0067] 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 relatively high, the reliability of the battery cell in use and the cycling performance 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.

[0068] In a second aspect, the present application provides a battery device, which includes a plurality of battery cells according to any one of the embodiments in the first aspect of the present application.

[0069] 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 relatively fast, which is more beneficial to improving the fast charging ability.

[0070] In a third aspect, the present application provides an electrical device, which includes the battery device according to any one of the embodiments in the second aspect of the present application. Description of the Drawings

[0071] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the drawings.

[0072] Figure 1 It is a schematic structural diagram of a battery cell provided in some embodiments of the present application.

[0073] Figure 2 It is an exploded view of a battery cell provided in some embodiments of the present application.

[0074] Figure 3 It is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0075] Figure 4 It is a schematic structural diagram of a positive electrode plate of a battery cell provided in some embodiments of the present application.

[0076] Figure 5 It is a schematic structural diagram of a positive electrode plate of a battery cell provided in some other embodiments of the present application.

[0077] Figure 6 It is a schematic structural diagram of a negative electrode plate of a battery cell provided in some embodiments of the present application.

[0078] Figure 7 It is a schematic structural diagram of a negative electrode plate of a battery cell provided in some other embodiments of the present application.

[0079] Figure 8 It is a schematic top view structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0080] Figure 9 It is a schematic structural diagram of a battery module provided in some embodiments of the present application.

[0081] Figure 10 It is a schematic structural diagram of a battery pack provided in some embodiments of the present application.

[0082] Figure 11 It is a schematic structural diagram of an electrical device provided in some embodiments of the present application.

[0083] The drawings are not necessarily drawn to actual scale.

[0084] The descriptions of the reference numerals are as follows:

[0085] 1. Electrical device; 2. Battery pack; 3. Controller; 4. Motor; 5. Housing; 5a. First housing part; 5b. Second housing part; 5c. Accommodation space; 6. Battery module;

[0086] 7. Battery cell; 10. Electrode assembly; 11. Positive electrode tab; 111. Positive electrode ear; 112. Positive current collector part; 113. Positive electrode film layer; 12. Negative electrode tab; 121. Negative electrode ear; 122. Negative current collector part; 123. Negative electrode film layer; 13. Separator; 14. Main body part; 20. Outer shell; 21. Housing; 22. End cap; 31. Positive terminal; 32. Negative terminal. Detailed implementation manners

[0087] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0088] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where 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. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0089] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0090] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0091] Unless otherwise specified, all steps of this application can be carried out in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. 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 can include steps (a), (b) and (c), or can also include steps (a), (c) and (b), or can also include steps (c), (a) and (b), etc.

[0092] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate and a negative electrode plate. 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.

[0093] 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 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;

[0094] The electrolyte includes lithium fluorosulfonimide. Lithium fluorosulfonimide has good water stability and is not prone 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;

[0095] The electrolyte includes a carboxylic acid ester solvent and a first additive. The first additive includes vinylene carbonate. The reaction potential of vinylene carbonate and the carboxylic acid ester solvent is close. There is a competitive reaction with the carboxylic acid ester solvent during the film formation process. The mass content of vinylene carbonate is appropriate, which 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 acid ester solvent to penetrate the organic film to the negative electrode active material. Thus, the side reaction between the carboxylic acid ester solvent and the negative electrode active material is alleviated, gas generation is reduced, and the high-temperature cycle performance is improved; 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;

[0096] Furthermore, when the mass content of the carboxylic acid ester solvent is within an appropriate range, the side reaction with the negative electrode active material can be further alleviated, the viscosity of the electrolyte can be reduced, the migration rate of lithium ions in the electrolyte can be increased, and the rapid charging ability of the battery cell can be improved.

[0097] Therefore, the embodiments of the present application can improve the rapid charging ability and cycling performance of the battery cell.

[0098] Battery cell

[0099] In a first aspect, an embodiment of the present application provides a battery cell.

[0100] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate and a negative electrode plate. The positive electrode plate 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.

[0101] The negative electrode plate 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.

[0102] The electrolyte includes a carboxylic acid ester additive, a first additive, and a lithium salt.

[0103] Among them,

[0104] Based on the mass of the electrolyte, the mass content of the carboxylic acid ester solvent is 8% to 60%.

[0105] 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.

[0106] Formula A

[0107] In Formula A, Q1, Q2, Q3, and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not simultaneously hydrogen atoms.

[0108] The lithium salt includes lithium fluorosulfonylimide. The mass content of lithium fluorosulfonylimide in the electrolyte is 4% to 8%.

[0109] The positive electrode active material includes lithium-containing phosphate with an olivine structure, and the negative electrode active material includes graphite particles. The above material system has excellent cycle stability; the electrolyte also includes a carboxylic acid ester solvent with a mass content of greater than or equal to 8%, which can reduce the viscosity of the electrolyte, further improve the migration rate of lithium ions in the electrolyte, and thus improve the fast charging ability of the battery cell;

[0110] However, the lithium-containing phosphate 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 carboxylic acid ester solvent in the electrolyte can penetrate the SEI film to the negative electrode active material and react with the negative electrode active material, deteriorating the cycle; 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;

[0111] The embodiment of the present application further includes lithium fluorosulfonylimide with a mass content of greater than or equal to 4%. On the one hand, the mass content of lithium fluorosulfonylimide is greater than or equal to 4%, and the hydrolysis stability of lithium fluorosulfonylimide is relatively excellent. It is not easy to react with water to generate hydrofluoric acid, which can reduce the total amount of hydrofluoric acid generated in the electrolyte and alleviate the erosion risk of hydrofluoric acid to the SEI film. Thus, 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, lithium fluorosulfonylimide with a mass content of less than or equal to 8% has a relatively fast transmission rate of lithium ions in the electrolyte including lithium fluorosulfonylimide, which is beneficial to the rapid transmission and infiltration of lithium ions and can improve the fast charging performance;

[0112] However, due to the more serious side reaction between the carboxylic acid ester solvent and the negative electrode active material under fast charging, the gas generation intensifies. On the one hand, the embodiment of the present application limits the carboxylic acid ester 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 carboxylic acid ester solvent, and there is a competitive reaction with the carboxylic acid ester solvent. With an appropriate mass content of vinylene carbonate, it is beneficial for vinylene carbonate to participate in the formation of a dense organic film on the negative electrode side, making it difficult for the carboxylic acid ester solvent to penetrate the organic film to the negative electrode active material, thereby alleviating the side reaction between the carboxylic acid ester solvent and the negative electrode active material 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 low, which is beneficial to improving the fast charging ability of the battery cell.

[0113] Therefore, the embodiment of the present application can improve the fast charging ability and cycle performance of the battery cell.

[0114] [Electrolyte]

[0115] In some embodiments, the battery cell further includes an electrolyte solution.

[0116] During the charge and discharge process of the battery cell, active ions such as lithium ions are intercalated and deintercalated back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte solution plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0117] The electrolyte solution 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.

[0118] The electrolyte salt includes a lithium salt, and the lithium salt includes lithium fluorosulfonylimide. The mass content of lithium fluorosulfonylimide in the electrolyte solution 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 fluorosulfonylimide in the electrolyte solution is 4% to 6%. When the mass content of lithium fluorosulfonylimide is within the above range, the cycle performance and fast charging performance of the battery cell can be improved.

[0119] Optionally, the lithium fluorosulfonylimide includes at least one of lithium bis(fluorosulfonyl)imide LiFSI, lithium bis(trifluoromethanesulfonyl)imide LiTFSI, and lithium perfluorobutanesulfonylimide. The above materials can improve the cycle performance and fast charging performance of the battery cell.

[0120] In some embodiments, the lithium salt further includes lithium hexafluorophosphate, and 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 0.4 to 0.8, based on the mass of the electrolyte solution.

[0121] 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.

[0122] 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.

[0123] In some embodiments, the mass content of lithium hexafluorophosphate in the electrolyte solution 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 solution is relatively excellent, which is beneficial to improving the fast charging performance of the battery cell.

[0124] 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 cycle performance.

[0125] 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 solvents have lower viscosity, which can further improve the migration rate of lithium ions and enhance the fast charging ability of the battery monomer.

[0126] Due to the lower viscosity of the chain carboxylate solvents and better fluidity, it is more beneficial to quickly infiltrate 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 use reliability of the battery monomer.

[0127] Exemplarily, the carboxylate solvents include the compounds shown in Formula I,

[0128] Formula I,

[0129] In Formula I,

[0130] R1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group,

[0131] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0132] The above-mentioned chain carboxylate solvents have lower viscosity, which is beneficial to enhancing the fast charging ability of the battery monomer.

[0133] Optionally, R1 includes a hydrogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0134] Optionally, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0135] 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.

[0136] Exemplarily, 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.

[0137]

[0138] The above materials can further improve the fast charging performance of the battery cell.

[0139] 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.

[0140] Optionally, the carbonate solvent includes at least one of a cyclic carbonate and a chain carbonate.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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 the 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.

[0146] The first additive includes vinylene carbonate with a mass content > 0. In other words, vinylene carbonate is an essential component of the electrolyte.

[0147] In the case where the mass content of 1,3-propane sultone 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%.

[0148] Specifically, taking the case where the mass content of the ethylene carbonate derivative is 0 as an example,

[0149] it may be that the freshly prepared electrolyte does not contain the ethylene carbonate derivative,

[0150] 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 contain 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.

[0151] Further, regarding the addition of certain substances, such as additives, to the electrolyte, due to the characteristic that the additives function by participating in the film formation on the surface of the active material, the content of the additives in the electrolyte of a single battery cell is related to formation, different battery life cycles, or different battery storage states. Therefore, there may be a difference in the content of the additives between the freshly prepared electrolyte and the electrolyte obtained from reverse-disassembling a single battery cell. However, those skilled in the art can know the approximate range of the content of the relevant substances in the corresponding freshly prepared electrolyte based on the performance expression level (such as the number of cycles) of the single battery cell, the residual content, etc. Similarly, those skilled in the art can also know the approximate range of the corresponding non-freshly prepared (i.e., reverse) content based on the content of the freshly prepared additives, according to the performance requirements of the single battery cell, the storage environment, etc.

[0152] Therefore, the additive content mentioned in the technical solution of this application can be the content of the additives actively added to the freshly prepared electrolyte, or the content of the residual additives detected by reverse according to the actual battery state.

[0153] 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 the range composed of any two of the above values. When the mass content of vinylene carbonate is within the above range, a dense SEI film containing organic components can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reactions on the negative electrode side and balance the improvement of the cycle performance and fast charging ability of the single battery cell.

[0154] The first additive may include 1,3 - propane sultone with a mass content > 0, or the first additive may include a vinylene carbonate derivative with a mass content > 0, or the first additive may include 1,3 - propane sultone and a vinylene carbonate derivative.

[0155] 1,3 - propane sultone, vinylene carbonate derivative, and vinylene carbonate cooperate to form a dense and relatively low - impedance film layer, reduce the gas generation amount, and improve the cycle performance and fast charging performance of the single battery cell.

[0156] In some embodiments, the mass content of 1,3 - propane sultone in the electrolyte is 0 to 0.5%, such as 0, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5% or the range composed of any two of the above values. Optionally, the mass content of 1,3 - propane sultone in the electrolyte is 0 to 0.3%.

[0157] When the mass content of 1,3 - propane sultone is 0, it means that 1,3 - propane sultone can be not added to the freshly prepared electrolyte, or the electrolyte obtained after disassembling the battery cell does not contain 1,3 - propane sultone. Generally speaking, due to the less consumption of 1,3 - propane sultone during the film - forming process, the mass content of 1,3 - propane sultone in the freshly prepared electrolyte is slightly greater than that in the electrolyte after disassembly.

[0158] Both 1,3 - propane sultone 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.

[0159] When the mass content of 1,3 - propane sultone 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 cell.

[0160] 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%.

[0161] In some embodiments, the mass content of ethylene carbonate derivative 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 derivative in the electrolyte is 1.5% to 3.5%.

[0162] Optionally, the freshly prepared electrolyte includes ethylene carbonate derivative, and in the freshly prepared electrolyte, the mass content of ethylene carbonate derivative is greater than 0. Ethylene carbonate derivative forms a film preferentially. After adding a certain content of ethylene carbonate derivative to the freshly prepared electrolyte, due to the large consumption of ethylene carbonate derivative during the film - forming stage, the ethylene carbonate derivative may not be detected in the battery cell obtained after disassembly.

[0163] Vinylene carbonate continuously participates in the formation of the SEI film during the cycling of the battery cell, 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 derivative 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. 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 a high content of ethylene carbonate derivative and further improve the fast - charging performance and cycling performance of the battery cell.

[0164] 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%.

[0165] 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%.

[0166] Under fast charging, the above three types of substances jointly participate in the formation of the SEI film. It can reinforce the SEI film through a low content of 1,3 - propane sultone, and vinylene carbonate can further reinforce the film - forming, reduce the risk of carboxylic acid ester solvents penetrating the SEI film, and improve the high - temperature cycling performance of the battery cell; an appropriate content of ethylene carbonate derivative can reduce the film - forming impedance, 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.

[0167] 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 substituting group can be one, two, three, four, etc.

[0168] Exemplarily, the ethylene carbonate derivative includes the compound shown in Formula A,

[0169] Formula A,

[0170] In Formula A, Q1, Q2, Q3, and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group, and Q1, Q2, Q3, Q4 are not simultaneously hydrogen atoms.

[0171] Q1, Q2, Q3, Q4 are not simultaneously hydrogen atoms. In other words, at least one of Q1, Q2, Q3, Q4 includes a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group.

[0172] Exemplarily, one of Q1, Q2, Q3, Q4 includes a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group, and the rest are hydrogen atoms.

[0173] Exemplarily, at least two of Q1, Q2, Q3, Q4 include a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group.

[0174] Exemplarily, at least three of Q1, Q2, Q3, Q4 include a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group.

[0175] Exemplarily, each of Q1, Q2, Q3, and Q4 independently includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0176] Optionally, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom or a C1-C5 haloalkyl group. The halogen atom includes a fluorine atom, a bromine atom, or a chlorine atom, etc., and may be a fluorine atom. The C1-C5 haloalkyl group includes a C1-C5 fluoroalkyl group, a C1-C5 bromoalkyl group, or a C1-C5 chloroalkyl group, etc., and may be a fluorine atom. For example, the C1-C5 fluoroalkyl group includes fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, or fluoropentyl.

[0177] 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 can be lower, and it can more effectively balance the improvement of the cycle performance and fast charging performance of the battery cell.

[0178] For example, the ethylene carbonate derivative includes at least one of the compounds shown in Formula A-1 to the compounds shown in Formula A-6.

[0179] 。

[0180] 。

[0181] The above materials can further improve the high-temperature cycle performance and fast charging performance of the battery cell.

[0182] Optionally, the ethylene carbonate derivative includes at least one of the compounds shown in Formula A-1 to the compounds shown in Formula A-3. Further optionally, the ethylene carbonate derivative includes the compound shown in Formula A-1.

[0183] 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.

[0184] Exemplarily, the sulfur-containing additive includes one or more of vinylene sulfate DTD, bis(vinylene sulfate) 2-DTD, butylene sulfite BS, ethylene sulfite ES, and methylene methylene disulfonate MMDS.

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

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte have the meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography analysis method. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, 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 analysis method.

[0192] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to GB / T 9722-2006 General Rules for Gas Chromatography of Chemical Reagents to qualitatively and quantitatively analyze the organic components of the electrolyte by gas chromatography.

[0193] [Negative electrode plate]

[0194] The negative electrode plate includes a negative electrode current collector portion and a negative electrode film layer provided on at least one surface of the negative electrode current collector portion and including a negative electrode active material. For example, the negative electrode current collector portion 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 portion.

[0195] The upper charge limit voltage and the lower discharge cut-off voltage of the battery cell vary depending on the positive electrode active material. For example, when the phosphate material includes lithium iron phosphate, the upper charge limit voltage can be 3.65 V and the lower discharge cut-off voltage can be 2.0 V. Another example is that when the phosphate material includes lithium manganese iron phosphate, the upper charge limit voltage can be 4.2 V and the lower discharge cut-off voltage can be 2.0 V. Next, taking the upper charge limit voltage of 3.65 V and the lower discharge cut-off voltage of 2.0 V as an example, the state of the battery cell will be described: In the embodiments of the present application, the 100% state of charge (SOC) and 0% SOC of the battery cell are defined as follows.

[0196] The battery cell is charged at a constant current charge rate of 0.33C to the upper charge 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.

[0197] In the embodiments of the present application, the negative electrode film layer includes at least one layer of film layer, and a single-layer film layer can be used, or at least two layers of film layers can be used. The negative electrode film layer can include two layers of film layers, three layers of film layers, four layers of film layers, or even more layers of film layers.

[0198] 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 the two are used in combination, the cycle performance of the battery cell is relatively excellent.

[0199] 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.

[0200] The volume average particle size of the graphite particles is relatively small, so that the solid-phase migration path of lithium ions is short, which 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 on 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.

[0201] In the embodiments of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, and can be detected by using 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.

[0202] In some embodiments, the graphite particles include a graphite body particle and a negative electrode coating layer. The graphite body particle includes secondary particles, and the secondary particles include a plurality of primary particles. The negative electrode coating layer coats the surface of the graphite body particle, 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.

[0203] The graphite body particle includes secondary particles. There are many migration paths of lithium ions in the graphite body particle, and the migration path in the primary particle is short, which can improve the migration rate of lithium ions. The negative electrode coating layer has many end faces and defects, so that the number of sites where lithium ions can be intercalated and deintercalated is more, and the conductivity of the negative electrode coating layer is relatively excellent, which 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.

[0204] Exemplarily, the graphite body particle includes at least one of artificial graphite and natural graphite, and may be artificial graphite.

[0205] 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.

[0206] When the mass content of carbon element in the negative electrode coating layer is within the above range, the internal resistance of the negative electrode sheet can be further reduced, the heat generation of the battery cell can be reduced, and the high-temperature cycling performance of the battery cell can be improved.

[0207] In the embodiments of the present application, the graphite particles can be prepared by methods well known in the art. Taking artificial graphite as an example of the graphite body particles, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and after carbonization treatment, forming a negative electrode coating layer on at least part of the surface of the artificial graphite particles.

[0208] 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.

[0209] 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.

[0210] Optionally, the carbonization treatment time is 1h to 6h.

[0211] 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.

[0212] 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.

[0213] 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 the range composed of any two of the above values.

[0214] When the mass content of silicon element in the silicon-based material is within the above range, the capacity of the anode active material can be improved, and the energy density of the battery cell can be enhanced.

[0215] 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.

[0216] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, the anode 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.

[0217] In this application, the qualitative and quantitative determination of each substance or element can be detected by suitable equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used jointly for qualitative or quantitative determination.

[0218] For example, this application can combine the General Rules for X-ray Diffraction Analysis of JIS / K0131-1996 to conduct X-ray powder diffraction testing and qualitative analysis on the anode electrode or anode active material.

[0219] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). In the SEM cross-sectional view of natural graphite, there are voids between the flaky structures. The SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or they can be distinguished by the XRD spectrum obtained by X-ray diffraction method. In the XRD spectrum of natural graphite, obvious 2H phase and 3R phase exist, while the XRD spectrum of artificial graphite only has 2H phase.

[0220] In some embodiments, the powder compaction density of the anode active material under a pressure of 20000N is 1.4 g / cm 3 to 1.8 g / cm 3 . Exemplarily, the powder compaction density of the anode active material under a pressure of 20000N 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 the range composed of any two of the above values.

[0221] When 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, since the negative electrode active material in the negative 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 cycle performance of the battery cell.

[0222] 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), held for 30 s, then depressurized, held for 10 s, and then the powder compaction density of the negative electrode active material under the action of 20,000 N is recorded and calculated.

[0223] 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 the range composed of any two of the above values.

[0224] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative electrode active material in the negative electrode film layer is 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 can reduce the amount of gas generated by the decomposition of carboxylic ester solvents due to heat accumulation, and improve the high-temperature cycle performance of the battery cell.

[0225] In the embodiments of the present application, the compaction density of the negative electrode film layer when the battery cell is in a 0% state of charge has the meaning well-known in the art, and can be detected by equipment and methods well-known in the art, and its detection method is the same as the compaction density test method of the positive electrode film layer described above.

[0226] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2To 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.

[0227] 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 plate will not be too large, and the high-temperature cycling performance of the battery cell can be improved.

[0228] 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 the equipment and methods well-known in the art. Disassemble the negative electrode plate of the battery monomer in the 0% state of charge (SOC), measure the compaction density of the negative electrode film layer. For example, take the negative electrode plate with single-sided coating (if it is a double-sided coated electrode plate, first wipe off the negative electrode film layer on one side), punch it into small round pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the negative electrode film layer of the weighed negative electrode plate, weigh the weight of the negative electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the negative electrode film layer = (the weight M1 of the negative electrode plate - the weight M0 of the negative electrode current collector) / S1, the thickness of the negative electrode film layer = the thickness H1 of the negative electrode plate - the thickness H0 of the negative electrode current collector, and the compaction density of the negative electrode film layer = the single-sided coating weight of the negative electrode film layer / the thickness of the negative electrode film layer.

[0229] 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%.

[0230] In some embodiments, the negative electrode film layer may optionally further include a negative electrode conductive agent. The embodiments of the present application do not particularly limit the type of the negative electrode conductive agent. 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%.

[0231] 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%.

[0232] In some embodiments, the negative current collector portion may employ a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0233] The negative electrode film layer is usually formed by coating a negative electrode paste on the negative current collector portion and then drying and cold pressing. The negative electrode paste is usually formed by dispersing negative electrode active materials, optional conductive agents, optional binders, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0234] The negative electrode plate does not exclude other additional functional layers in addition to 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 disposed on the surface of the negative current collector portion and sandwiched between the negative current collector portion and the negative electrode film layer. 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.

[0235] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer located between the negative electrode film layer and the negative current collector portion. 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.

[0236] 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 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.

[0237] 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.

[0238] 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 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.

[0239] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent of the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the heat generation of the battery cell. The negative electrode binder of the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector part and the negative electrode film layer, and improve the structural stability of the negative electrode sheet.

[0240] In some embodiments, the negative electrode conductive layer may also optionally include other additives. By way of example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0241] 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.

[0242] 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.

[0243] 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.

[0244] 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.

[0245] [Positive electrode sheet]

[0246] The positive electrode sheet 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.

[0247] The electrode assembly of the embodiments of the present application can be a wound electrode assembly or a stacked electrode assembly, and is preferably a stacked electrode assembly.

[0248] In the case where the electrode assembly is of a wound structure, the positive electrode sheet and the negative electrode sheet are wound in the same direction.

[0249] In the case where the electrode assembly is of a stacked structure, both the positive electrode sheet and the negative electrode sheet are multiple, and the multiple positive electrode sheets and the multiple negative electrode sheets are stacked in the thickness direction of the battery cell.

[0250] Carboxylate solvents have low viscosity, and the mass content of carboxylate solvents is 8% to 60%. They 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 reliability of the battery cell during use.

[0251] 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.

[0252] By coating the surface of the phosphate particles with a positive electrode 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, enhances the fast charging ability of the battery, reduces the heat generation of the battery cell, and improves the high-temperature cycle performance of the battery cell.

[0253] 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.

[0254] 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.

[0255] The cycle stability of the phosphate particles is relatively excellent, which is beneficial to improving the cycle performance of the battery cell.

[0256] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charge and discharge process of the battery cell, the insertion and extraction of active ions such as Li will occur, along with consumption. The molar content of Li in the battery cell is different when it is discharged to different states. In the listing of cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of Li is the initial state of the material, that is, the state before feeding. When the cathode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, in the listing of cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of oxygen O is only the theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In fact, the molar content of oxygen O will fluctuate, and the above situations are all within the protection scope of the present application.

[0257] 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.

[0258] The carbon element mainly exists in the cathode coating layer in the form of a carbon coating layer. The carbon coating layer is loose and porous, which is beneficial to increasing the specific surface area of the material, more beneficial to the effective contact between the electrolyte and the phosphate particles, and beneficial to the transport of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, it can significantly improve the conductivity of the lithium-containing phosphate with olivine structure, which is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the fast charging ability and energy density of the battery cell.

[0259] In some embodiments, the cathode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

[0260] In some embodiments, the cathode coating layer includes a compound with the general formula Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 , where 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M3 includes one or more of Ti, Zr, Hf, Ge, and Sn.

[0261] 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.

[0262] Fast ion conductors with a NASICON structure are materials with ultrafast ion conduction capabilities. They possess abundant three-dimensional lithium ion diffusion and transport channels, and exhibit advantages such as high ion conduction efficiency and strong structural stability during multiple lithium de- and intercalation processes. Coating phosphate particles with a fast ion conductor containing a NASICON structure can significantly increase the lithium ion transport rate at the positive electrode during multiple lithium de- and intercalation processes, improving the ionic conductivity of the positive electrode active material and the rapid charging capability of the battery cell. Furthermore, it can increase the specific capacity and the energy density of the corresponding battery cell.

[0263] The carbon element and the fast ion conductor can be arranged in layers. For example, the carbon element serves as an independent carbon coating layer, and the fast ion conductor serves as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer facing away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer facing away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0264] Optionally, a carbon coating can be formed by carbonizing an organic carbon source (e.g., glucose, polyethylene glycol, etc.) and coating the surface of the fast ion conductor layer. The carbon coating can partially or completely cover the fast ion conductor layer. The carbon coating can significantly improve the electronic conductivity of the phosphate particles, compensating for their poor electronic conductivity and increasing the energy density of the battery cell.

[0265] The cathode active material of this application, based on a lithium-containing phosphate, leverages the advantages of lithium-containing phosphates: low cost, high reliability, and excellent cycling stability. Furthermore, the cathode coating (a fast ion conductor layer and a carbon coating) addresses the drawbacks of poor electronic and ionic conductivity. Battery cells prepared with this cathode active material can improve the energy density of the battery while maintaining excellent cycling performance.

[0266] 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) and disassembling the positive electrode plate, it is cleaned with DMC, dried, and then calcined at high temperature to remove impurities. Then, 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.

[0267] In some embodiments, the powder tap density of the positive electrode active material under 30000 N is 2.43 g / cm 3 to 2.85 g / cm 3 .

[0268] Exemplarily, the powder tap 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 a range composed of any two of the above values.

[0269] When the powder tap density of the positive electrode active material under 30000 N is within the above range, the energy density of the battery cell can be improved, and since the positive electrode active material in the positive electrode film layer can be stacked more closely and the contact resistance between particles is smaller, the resistance of the electrode plate can be further reduced, thereby reducing heat generation and improving the high-temperature cycle performance and fast charging performance of the battery cell.

[0270] 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.

[0271] 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 the range composed of any two of the above values.

[0272] 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 and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation during fast charging and improving the high-temperature cycle performance and fast charging performance of the battery cell.

[0273] 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.

[0274] 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 sheet will not be too large, improving the high-temperature cycle performance and fast charging performance of the battery cell.

[0275] 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 sheet 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 sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), punch it into small circular pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive electrode film layer of the above weighed positive electrode sheet, weigh the weight of the positive electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode sheet - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode sheet - 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.

[0276] 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 have any particular limitations on 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%.

[0277] 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%.

[0278] In some embodiments, the positive electrode current collector portion 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).

[0279] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode current collector portion and then drying and cold pressing. The positive electrode slurry 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.

[0280] 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 portion and the positive electrode film layer and disposed on the surface of the positive electrode current collector portion. 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.

[0281] 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 portion. 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 amount of the battery cell, and can improve the fast charging performance and high temperature cycle performance of the battery cell.

[0282] 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.

[0283] 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.

[0284] In the embodiments of the present application, the thickness of the positive electrode conductive layer has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, tomographic scanning is performed on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0285] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0286] 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 the range composed of any two of the above values.

[0287] 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.

[0288] 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 the range composed of any two of the above values.

[0289] 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.

[0290] [Separator membrane]

[0291] 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.

[0292] In the embodiments of the present application, the separator membrane includes a base membrane with a porous structure.

[0293] In some embodiments, the base film comprises at least one of glass fiber, non-woven fabric, and polyolefin. The base film may 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 may be the same or different, without particular limitation.

[0294] Optionally, the polyolefin includes at least one of polyethylene, polypropylene and polyvinylidene fluoride.

[0295] 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 consisting of any two of the above values.

[0296] When the porosity of the base film in the embodiment of the present application is within the above range, the migration ability of lithium ions in the isolation membrane can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation and improving the fast charging performance and high-temperature cycle performance of the battery cell.

[0297] In the embodiments of this application, porosity refers to the percentage of the pore volume of the separator's base membrane to the total volume of the separator's base membrane. Porosity can be tested in accordance with the standard GB / T36363-2018, "Polyolefin Separators for Battery Cells." It should be noted that the actual testing process may vary slightly from the standard due to differences in testing instrumentation, testing errors, and to minimize the impact of porosity testing, in order to obtain a more accurate test value.

[0298] In some embodiments, the base film has a thickness of 6 μm to 12 μm, optionally 6 μm to 9 μm. For example, the base film has a thickness of 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range consisting of any two of the above values.

[0299] When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance and high-temperature cycle performance of the battery cell.

[0300] In the embodiment of the present application, the isolation membrane may be a base membrane. Optionally, the isolation membrane further includes a functional layer disposed on at least one side of the base membrane. The functional layer may include inorganic particles to enhance the heat resistance of the isolation membrane. Optionally, the functional layer is disposed on both sides of the base membrane.

[0301] 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.

[0302] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator membrane.

[0303] 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.

[0304] 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.

[0305] 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.

[0306] 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 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.

[0307] 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.

[0308] The second inorganic particles in the composite particles prevent the non-fluoropolymer particles from sticking to each other due to the high-temperature treatment during the granulation process, creating pores in the composite particles, which is beneficial for the transport of lithium ions and improves the ionic conductivity of the separator membrane. Additionally, the second inorganic particles can also increase the compression modulus of the composite particles. During the charge and discharge process, the composite particles are less likely to deform, making the structure of the separator membrane more stable, improving the kinetic performance of the battery cell, 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 less likely to deform, the separator membrane basically does not cause side effects such as extrusion to the negative electrode tab, ensuring the stable kinetic performance of the negative electrode tab. Correspondingly, the first functional layer is arranged closer to the positive electrode tab.

[0309] 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 can form composite particles in combination with the non-fluoropolymer, further improving the cycle stability and kinetic performance of the separator membrane, and enhancing the cycle performance and fast charging performance of the battery cell.

[0310] 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.

[0311] In the embodiments of the present application, the average particle size of the second inorganic particles has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, after obtaining the separator membrane and drying the separator membrane as a sample, the separator membrane is cut by an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the particle size of the second inorganic particles in the separator membrane, and the particle sizes of multiple, for example, 50 second inorganic particles are measured, and the average value thereof is calculated as the average particle size of the second inorganic particles.

[0312] 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.

[0313] Figure 1 and Figure 2 shows a schematic structural diagram of a battery cell.

[0314] In some embodiments, the battery cell 7 may include a housing 20.

[0315] 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.

[0316] 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 and the electrode assembly 10. The material of the insulating layer can be selected from the materials commonly used in the art and is not specially restricted herein.

[0317] The electrode assembly 10 accommodated in the housing 20 can be one or more.

[0318] In some embodiments, the housing 20 includes a housing body 21 and an end cap 22. The housing body 21 has an opening, and the end cap 22 covers the opening. The electrode assembly 10 and the electrolyte are accommodated in the housing body 21.

[0319] 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.

[0320] 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.

[0321] Next, taking the laminated structure of the electrode assembly 10 as an example for illustration,

[0322] 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, and 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.

[0323] The portion of the positive electrode plate 11 without the active material layer coated is the positive electrode tab 111. The active material coated on the positive electrode 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 electrode current collector portion 112 coated with the active material are part of the main body portion 14.

[0324] The portion of the negative electrode plate 12 without the active material layer coated is the negative electrode tab 121. The active material coated on the negative electrode 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 electrode current collector portion 122 coated with the active material are part of the main body portion 14.

[0325] 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, and the positive electrode plate 11 and the negative electrode plate 12 are stacked in the thickness direction X of the battery cell.

[0326] 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.

[0327] In some embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode 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 electrode current collector portion 122 along the length direction Z of the battery cell.

[0328] As Figure 4As shown, for example, the positive electrode tab 111 is connected to one side of the positive current collector 112 along the length direction Z of the battery cell.

[0329] 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.

[0330] 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.

[0331] 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.

[0332] 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 OH1; 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 OH2, and OH1 is greater than OH2.

[0333] 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, OH1 is set to be greater than OH2, so that the ability of the negative electrode film layer 123 to receive lithium ions is stronger near the negative electrode film layer 123 along the length direction Z. In particular, the ability of the region of the negative electrode film layer 123 near the negative electrode tab 121 to receive lithium ions can be improved, the risk of lithium deposition can be reduced, and the use reliability of the battery cell 7 can be improved.

[0334] Exemplarily, OH1 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 extend beyond the positive electrode film layer 113, and each side extends beyond OH1 / 2, that is, half of the size of OH1. Figure 8 OH1 / 2 is shown in

[0335] Exemplarily, OH2 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 OH2 / 2, that is, half of the size of OH2. Figure 8 OH2 / 2 is shown in .

[0336] 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.

[0337] Optionally, the number of positive electrode tabs 111 on the same side of the main body portion 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.

[0338] Optionally, the number of negative electrode tabs 121 on the same side of the main body portion 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.

[0339] In some embodiments, the battery cell 7 further includes a positive terminal 31. The positive terminal 31 is disposed on the outer casing 20 and can be disposed on the housing 21 or the end cap 22.

[0340] 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.

[0341] In some embodiments, the battery cell 7 further includes a negative terminal 32. The negative terminal 32 is disposed on the outer casing 20 and can be disposed on the housing 21 or the end cap 22.

[0342] The negative terminal 32 is electrically connected to the negative electrode tab 121. Optionally, the negative terminal 32 and the negative electrode tab 121 are welded. The negative terminal 32 and the negative electrode tab 121 can be connected through an adapter, or can be connected without using an adapter. Optionally, the negative terminal 32 and the negative electrode tab 121 are 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.

[0343] Optionally, the number of positive extreme terminals 31 on the same side of the main body 14 is at least one, optionally at least two. At least two positive extreme terminals 31 can increase the overcurrent capacity of the positive extreme terminals 31.

[0344] Further optionally, the overcurrent area of the single-sided positive extreme terminal 31 is 150 mm 2 to 1000 mm 2 optionally 200 mm 2 to 1000 mm 2 The overcurrent area of the single-sided positive extreme terminal 31 refers to the sum of the overcurrent areas of all positive extreme terminals 31 on the same side of the main body 14. The overcurrent area of the positive extreme terminal 31 can be understood as the cross-sectional area of the positive extreme terminal 31, and this cross-section is perpendicular to the thickness direction of the end cover 22. When the overcurrent area of the single-sided positive extreme terminal 31 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 cycle performance of the battery cell 7.

[0345] Exemplarily, the overcurrent area of the single-sided positive extreme terminal 31 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 the range composed of any two of the above values.

[0346] Optionally, the number of negative extreme terminals 32 on the same side of the main body 14 is at least one, optionally at least two. At least two negative extreme terminals 32 can increase the overcurrent capacity of the negative extreme terminals 32.

[0347] Further optionally, the overcurrent area of the single-sided negative extreme terminal 32 is 150 mm 2 to 1000 mm 2, optionally 200 mm 2 to 1000 mm 2 The over-current area of the single-sided negative terminal 32 refers to the sum of the over-current areas of all negative terminals 32 on the same side of the main body 14. The over-current 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 over-current area of the single-sided negative terminal 32 meets the above range, the over-current capacity is strong, the internal resistance can be reduced, 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.

[0348] Exemplarily, the over-current area of the single-sided 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 , 75 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.

[0349] 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.

[0350] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, parallel or in a combined series-parallel connection. A combined series-parallel connection means that there are both series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series, parallel or in a combined series-parallel connection together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodation part of the battery module 6. Of course, it is also possible that the multiple battery cells 7 are first connected in series, parallel or in a combined series-parallel connection to form battery modules 6, and then the multiple battery modules 6 are connected in series, parallel or in a combined series-parallel connection to form a whole and are accommodated in the accommodation part. Optionally, the battery module 6 can also include an accommodation part with an accommodation space, and the multiple battery cells 7 are accommodated in this accommodation space.

[0351] 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.

[0352] As Figure 10 shown, in some embodiments, the above battery module 6 can also be assembled into a battery pack 2, and the number of battery modules 6 included in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device 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 that makes up the battery device.

[0353] The battery pack 2 can include a box body 5 and a plurality of 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 accommodation space 5c. The first box body part 5a is used to cover the second box body part 5b and form a closed space for accommodating the battery module 6. The multiple battery modules 6 can be arranged in the box body 5 in any manner.

[0354] The first box body part 5a and the second box body part 5b cover each other, and the first box body part 5a and the second box body part 5b jointly define an accommodation space 5c for accommodating the battery cells. The second box body part 5b can be a hollow structure with one end open, and the first box body part 5a is a plate-like structure. The first box body part 5a covers the open side of the second box body part 5b to form a box body 5 with an accommodation space 5c. The first box body part 5a and the second box body part 5b can also both be hollow structures with one side open, and the open side of the first box body part 5a covers the open side of the second box body part 5b to form a box body 5 with an accommodation space 5c. Of course, the first box body part 5a and the second box body part 5b can be in various shapes, such as a cylinder, a cuboid, etc.

[0355] 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.

[0356] 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.

[0357] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from the 0% state of charge (SOC) to the 100% state of charge (SOC), the temperature of the external environment where the battery pack 2 is located is 30°C.

[0358] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from the 10% state of charge (SOC) to the 80% state of charge (SOC), the temperature of the external environment where the battery pack 2 is located is 30°C.

[0359] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from the 10% state of charge to the 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.

[0360] The battery pack 2 or any battery cell constituting the battery pack 2 from the 10% state of charge to the 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 of 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.

[0361] Exemplarily, the charging steps of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be carried out in the following manner:

[0362] Constant current charging at 5.0C from 10% SOC to 15% SOC,

[0363] Constant current charging at 5.0C from 15% SOC to 20% SOC,

[0364] Constant current charging at 5.0C from 20% SOC to 25% SOC,

[0365] Charge from 25% SOC to 30% SOC at a constant current of 5.0C.

[0366] Charge from 30% SOC to 35% SOC at a constant current of 5.0C.

[0367] Charge from 35% SOC to 40% SOC at a constant current of 5.0C.

[0368] Charge from 40% SOC to 45% SOC at a constant current of 4.6C.

[0369] Charge from 45% SOC to 50% SOC at a constant current of 4.3C.

[0370] Charge from 50% SOC to 55% SOC at a constant current of 4.0C.

[0371] Charge from 55% SOC to 60% SOC at a constant current of 3.7C.

[0372] Charge from 60% SOC to 65% SOC at a constant current of 3.4C.

[0373] Charge from 65% SOC to 70% SOC at a constant current of 3.1C.

[0374] Charge from 70% SOC to 75% SOC at a constant current of 2.9C.

[0375] Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0376] 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 the range composed of any two of the above values.

[0377] Electrical device

[0378] A 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 drill, a concrete vibrator and a planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices.

[0379] The electrical device can select a battery cell, a battery module or a battery pack according to its usage requirements.

[0380] Figure 11 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0381] 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.

[0382] The electrical device 1 can also 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.

[0383] Another example of an electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires being thin and light, and a battery cell can be used as the power source.

[0384] The charging process of the electrical device can select the following charging methods:

[0385] Charge from 10% SOC to 15% SOC at a constant current of 5.0C,

[0386] Charge from 15% SOC to 20% SOC at a constant current of 5.0C,

[0387] Charge from 20% SOC to 25% SOC at a constant current of 5.0C,

[0388] Charge from 25% SOC to 30% SOC at a constant current of 5.0C,

[0389] Charge from 30% SOC to 35% SOC at a constant current of 5.0C,

[0390] Charge from 35% SOC to 40% SOC at a constant current of 5.0C,

[0391] Charge from 40% SOC to 45% SOC at a constant current of 4.6C,

[0392] Charge from 45% SOC to 50% SOC at a constant current of 4.3C,

[0393] Charge from 50% SOC to 55% SOC at a constant current of 4.0C,

[0394] Charge from 55% SOC to 60% SOC at a constant current of 3.7C,

[0395] Charge from 60% SOC to 65% SOC at a constant current of 3.4C,

[0396] Charge from 65% SOC to 70% SOC at a constant current of 3.1C,

[0397] Charge from 70% SOC to 75% SOC at a constant current of 2.9C,

[0398] Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0399] 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 a range composed of any two of the above values.

[0400] Embodiment

[0401] 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 the instruments used in the examples are all commercially available.

[0402] Example 1-1

[0403] 1. Preparation of the positive electrode sheet

[0404] The positive electrode sheet includes a positive current collector, 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, and the positive electrode conductive layer is located between the positive current collector and the positive electrode film layer. The positive current collector is aluminum foil.

[0405] The positive electrode conductive layer on the positive current collector is a film layer formed by uniformly mixing a positive electrode conductive agent, superconducting carbon, a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), and then coating and drying on the surface of the positive current collector. 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%.

[0406] The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode slurry (with a solvent of N-methylpyrrolidone, NMP) on the surface of the positive electrode conductive layer, followed by drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder, polyvinylidene fluoride (PVDF), and a conductive agent, acetylene black, in a weight ratio of 97:2:1.

[0407] 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%.

[0408] The powder compaction density of the positive electrode active material under 30000 N is 2.55 g / cm 3 .

[0409] The single-sided coating weight of the positive electrode film layer is 263 mg / 1540.25 mm 2 .

[0410] The length of the positive electrode film layer is 610 mm, and the width is 110 mm.

[0411] 2. Preparation of the negative electrode sheet

[0412] The negative electrode plate includes a negative current collector, 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, and the negative electrode conductive layer is located between the negative current collector and the negative electrode film layer. The negative current collector is a copper foil.

[0413] The negative electrode conductive layer on the negative current collector is a film layer formed by uniformly mixing a negative electrode conductive agent, superconducting carbon, a negative electrode binder, styrene-butadiene rubber (SBR), a thickening agent, carboxymethyl cellulose sodium (CMC-Na), and a solvent, water, and then coating the mixture on the surface of the negative current collector 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 is 60%, and the mass content of the thickening agent is 5%.

[0414] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode conductive layer and then drying and cold pressing it.

[0415] The negative electrode film layer includes a negative electrode active material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickening agent carboxymethyl cellulose sodium in a mass ratio of 96.5:0.5:2:1. The graphite particles include artificial graphite and a negative electrode coating layer. The negative electrode coating layer covers the surface of the artificial graphite, and 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.

[0416] The powder compaction density of the negative electrode active material under 20000 N is 1.6 g / cm 3 。

[0417] The single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 。

[0418] 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.

[0419] 3. Separator

[0420] The separator includes a base film and functional layers disposed on both sides of the base film. The base film includes a 7-μm polyethylene film layer with a porosity of 42%;

[0421] The functional layer includes a first functional layer and a second functional layer. The first functional layer includes alumina particles and a binder, polyvinylidene fluoride. 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. The average particle size of the alumina particles is 10 nm. Among them, the first slurry includes alumina particles and a binder, polyvinylidene fluoride;

[0422] 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 the second slurry on the other side of the base film. The thickness is 5 μm and the average particle size of the calcium oxide particles is 10 nm. The second slurry includes composite particles.

[0423] 4. Preparation of electrolyte

[0424] The electrolyte includes an organic solvent, lithium salt and additives.

[0425] After mixing the components of the organic solvents, lithium salt and additives are added to prepare an electrolyte solution.

[0426] The organic solvent includes a chain carboxylic acid ester solvent (ethyl acetate) with a mass content of 39.0%, ethylene carbonate 27.3% and dimethyl carbonate 11.7%, and the mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0427] The mass content of the additive is 6%, and the additive includes vinylene carbonate VC, fluoroethylene carbonate FEC, vinyl sulfite ES and lithium difluorooxalatoborate LiDFOB in a mass ratio of 3:2:0.5:0.5.

[0428] The lithium salt includes lithium bis(fluorosulfonyl)imide LiFSI with a mass content of 6% and lithium hexafluorophosphate LiPF6 with a mass content of 10%. The mass content of the lithium salt is calculated based on the mass of the electrolyte.

[0429] 5. Preparation of battery cells

[0430] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive electrode sheet and the negative electrode sheet to provide isolation, to obtain a laminated electrode assembly. The electrode assembly is placed in a housing, on which a positive terminal and a negative terminal are provided. After baking, an electrolyte is injected. After vacuum packaging, standing, forming, aging, unloading, and shaping, a battery cell is obtained. The battery cell is baked for 12 hours. After baking, the water content of the positive electrode sheet is 356 ppm.

[0431] The battery cell filling coefficient is 2.9g / Ah.

[0432] The compaction density of the positive electrode film layer of the battery cell at 0% SOC is 2.7g / cm 3 The compaction density of the negative electrode film at 0% SOC is 1.41g / cm 3 .

[0433] The outer shell is an aluminum shell with a rectangular structure, and the thickness of the largest surface of the rectangular structure is 0.5 mm.

[0434] Among them, the flow area of the positive terminal on the same side is 640mm2 , the over-current area of the negative terminal on the same side is 640 mm 2 .

[0435] Examples 1-2 and 1-3

[0436] The battery monomers were prepared by a method similar to that of Example 1. Different from Example 1, the mass content of the lithium salt component was adjusted, as shown in Table 1 specifically.

[0437] Example 1-4

[0438] The battery monomers were prepared by a method similar to that of Example 1. Different from Example 1, the material of lithium fluorosulfonylimide was adjusted, and lithium bis(trifluoromethylsulfonyl)imide LiTFSI was used.

[0439] Example 1-5

[0440] The battery monomers were prepared by a method similar to that of Example 1. Different from Example 1, the baking time of the battery monomers was adjusted to 1 h, and the water content of the positive electrode film layer was 1638 ppm.

[0441] Example 1-6

[0442] The battery monomers were prepared by a method similar to that of Example 1. Different from Example 1, the baking time of the battery monomers was adjusted to 4 h, and the water content of the positive electrode film layer was 782 ppm.

[0443] Examples 2-2 to 2-10

[0444] The battery monomers were 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. As shown in Table 1 specifically.

[0445] Example 3

[0446] The battery monomers were prepared by a method similar to that of Example 1. Different from Example 1, the material of ethylene carbonate derivative was adjusted, and difluoroethylene carbonate was used.

[0447] Comparative Examples 1-1 to 1-3

[0448] The battery single cells were 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, it is shown in Table 1.

[0449] Comparative Examples 1-4

[0450] The battery single cells were 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.

[0451] The baking time of the battery single cell was also adjusted to 1 h, and the water content of the positive electrode film layer was 1638 ppm.

[0452] Performance test

[0453] 1. DC internal resistance DCR test of the battery single cell

[0454] The method of GB / T 31467 "Performance Test Specification for High Power Lithium Ion Power Batteries for HEV" can be referred to.

[0455] For example, at room temperature, the battery single cell was charged to 3.65 V at a constant current of 0.33 C, 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 A0 at this time was recorded, with the unit of Ah. Then, it was charged at a constant current of 0.33 C for 0.5A0 Ah to adjust the SOC to 50%.

[0456] After the battery single cell was placed at -20 °C for 2 h, it was discharged at a constant current of 1 C for 10 s, and ∆U was recorded 放电 , ∆I 放电 , and the discharge DCR data of the lithium ion battery was calculated through the following formula, R 放电 = ∆U 放电 / ∆I 放电 ,

[0457] Among them, ∆U 放电 represents the voltage change within the first 10 s of discharge, and ∆I 放电 represents the current value within the first 10 s of discharge.

[0458] 2. Number of cycles for the battery single cell to cycle to 70% SOH

[0459] At 60 °C, the battery cell is charged at a constant current of 0.8C until the charging cut-off voltage of 3.6V, then charged at a constant current of 0.1C until the charging cut-off voltage of 3.65V, and left standing for 30 min; discharged at a constant current of 1C until 2.83V, 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.

[0460] 3. Test on the lithium plating situation of the battery cell

[0461] 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:

[0462] No lithium plating: lithium plating area < 0.05%.

[0463] Slight lithium plating: lithium plating area < 2% and ≥ = 0.05%.

[0464] Severe lithium plating: lithium plating area ≥ 2%.

[0465] Charge the battery cell. The charging steps include the following steps:

[0466] Charge at a constant current of 5.0C from 0% SOC to 5% SOC;

[0467] Charge at a constant current of 5.0C from 5% SOC to 10% SOC;

[0468] Charge at a constant current of 5.0C from 10% SOC to 15% SOC;

[0469] Charge at a constant current of 5.0C from 15% SOC to 20% SOC;

[0470] Charge at a constant current of 5.0C from 20% SOC to 25% SOC;

[0471] Charge at a constant current of 5.0C from 25% SOC to 30% SOC;

[0472] Charge at a constant current of 5.0C from 30% SOC to 35% SOC;

[0473] Charge at a constant current of 5.0C from 35% SOC to 40% SOC;

[0474] Charge at a constant current of 4.6C from 40% SOC to 45% SOC;

[0475] Charge at a constant current of 4.3C from 45% SOC to 50% SOC;

[0476] Charge from 50% SOC to 55% SOC at a constant current of 4.0C;

[0477] Charge from 55% SOC to 60% SOC at a constant current of 3.7C;

[0478] Charge from 60% SOC to 65% SOC at a constant current of 3.4C;

[0479] Charge from 65% SOC to 70% SOC at a constant current of 3.1C;

[0480] Charge from 70% SOC to 75% SOC at a constant current of 2.9C;

[0481] Charge from 75% SOC to 80% SOC at a constant current of 2.7C;

[0482] Charge from 80% SOC to 85% SOC at a constant current of 1.8C;

[0483] Charge from 85% SOC to 90% SOC at a constant current of 1.3C;

[0484] Charge from 90% SOC to 95% SOC at a constant current of 0.7C;

[0485] Charge from 95% SOC to 98% SOC at a constant current of 0.33C;

[0486] Charge from 98% SOC to 100% SOC at a constant current of 0.1C.

[0487] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0488] The discharging strategy is as follows: discharge at a constant current of 0.33C to the cut-off voltage, such as 2.0V.

[0489] When performing charge and discharge tests on the battery cell above, the battery cell can be assembled in the battery device, and the required charge and discharge strategies can be regulated through the battery management system for testing.

[0490] The test results are shown in Table 1.

[0491] Table 1

[0492]

[0493] In Table 1, VC represents vinylene carbonate; PS represents 1,3 - propanesultone;

[0494] Comparative Examples 1-4 used lithium bis(fluorosulfonyl)imide with a relatively low mass content. 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 generated by the decomposition of lithium hexafluorophosphate. The hydrofluoric acid HF generated might damage the SEI film, leading to a reduction in the protective performance of the SEI film for the negative active material, exacerbating the side reaction between the carboxylic ester solvent and the negative active material, and deteriorating the cycle performance.

[0495] Examples 1-5 used a relatively high content of lithium bis(fluorosulfonyl)imide, which could reduce the usage amount of lithium hexafluorophosphate, thereby reducing the amount of acid generated and improving the cycle performance and fast charging performance of the battery monomer.

[0496] Compared with Examples 1-5, the water content in the positive electrode film layer of Examples 1-1 and Examples 1-6 was relatively less. Under the condition of using the same electrolyte composition, the less the water content, the less the acid generated, 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 monomer.

[0497] The lithium salts in Examples 1-1 to 1-6 of the present application included 4% to 8% of lithium bis(fluorosulfonyl)imide, which could reduce the usage amount of lithium hexafluorophosphate, thereby reducing the amount of acid generated, alleviating the erosion risk of hydrofluoric acid to the SEI film. The SEI film did not need to be repeatedly repaired, which could reduce the usage amount of additives, making the impedance of the SEI film relatively low, and improving the high-temperature cycle performance and fast charging performance of the battery monomer. When lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate were used in combination, and the ratio of the mass content of lithium fluorosulfonylimide to the mass content of the lithium hexafluorophosphate was 0.3 to 1.0, and optionally 0.4 to 0.8, the electrolyte had excellent ionic conductivity, and could reduce the side reaction on the negative electrode side, improving the cycle performance and fast charging performance of the battery monomer.

[0498] Lithium fluorosulfonylimide of different materials was selected, such as lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide LiTFSI (used in Example 1-5), which could improve the high-temperature cycle performance and fast charging performance of the battery monomer.

[0499] Compared with Example 1-3, when the addition amount of lithium bis(fluorosulfonyl)imide was too high, such as greater than 8%, the battery monomer might accumulate a large amount of energy during thermal runaway, resulting in a large amount of energy release and deteriorating the use reliability of the battery monomer.

[0500] 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 triggering lithium deposition.

[0501] 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.

[0502] 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 potential of vinylene carbonate in the first additive is close to that of carboxylic ester solvents, 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 the graphite particles, thereby alleviating the side reaction between carboxylic ester solvents and graphite particles and reducing the gas generation amount. Moreover, since the first additive is within an appropriate content, the film impedance formed 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.

[0503] In 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 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 are calculated.

[0504] In Example 2-1, the data in Table 1 were obtained by detecting and analyzing the free electrolyte in the battery cell after processes such as formation, aging, and warehousing. 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.

[0505] 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.

[0506] 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.

[0507] 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 optionally 0% to 0.3%, so as to balance the improvement of the high-temperature cycling performance and fast charging performance of the battery monomer.

[0508] 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, making the high-temperature cycling performance may deteriorate slightly. In view of this, the mass content of the ethylene carbonate derivative in the electrolyte is 0 to 4.0%, and can be optionally 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.

[0509] 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.

[0510] Example 4-1 and Example 4-2

[0511] 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 acid ester solvent and the carbonate solvent were adjusted.

[0512] 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%.

[0513] In Example 4-2, ethylene carbonate is 3%, 1,3-propane sultone is 0.5%, fluoroethylene carbonate FEC is 1.5%, and the mass content of the first additive is 5%.

[0514] Specifically, it is shown in Table 2 as follows.

[0515] Example 5

[0516] A battery monomer 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, ethylene carbonate is 6%, 1,3-propane sultone is 0.5%, fluoroethylene carbonate FEC is 1.5%, and the mass content of the first additive is 8.0%.

[0517] Specifically, it is shown in Table 2 as follows.

[0518] Examples 6-1 to 6-3

[0519] A battery monomer 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.

[0520] Comparative Examples 2-1 to 2-2

[0521] A battery monomer 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.

[0522] The test results are shown in Table 2 as follows.

[0523] Table 2

[0524]

[0525] In Table 2, EA represents ethyl acetate; MA represents methyl acetate;

[0526] EC represents ethylene carbonate; DMC represents dimethyl carbonate;

[0527] ES represents ethylene sulfite;

[0528] DTD represents ethylene sulfate;

[0529] LiDFOB represents lithium difluorooxalate borate;

[0530] LiPO2F2 represents lithium difluorophosphate;

[0531] EC: 27.3, indicating that the mass content of EC is 27.3%.

[0532] The meanings of other examples are the same as the above explanations and will not be elaborated here.

[0533] The mass content of the carboxylic ester solvent in the electrolyte of Comparative Example 2-1 is relatively low, resulting in a relatively high viscosity and impedance of the electrolyte, and it is not conducive to the rapid infiltration of the electrode sheet. The wettability of each part 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.

[0534] The mass content of the carboxylic ester solvent in the electrolyte of Comparative Example 2-2 is relatively high, making the viscosity of the electrolyte small and the impedance small, which is conducive to rapid charging. However, at high temperatures, the side reaction between the carboxylic ester 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.

[0535] Examples 1-1, 1-2 to 3 of this application are tested and basically no lithium deposition occurs.

[0536] 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 carboxylic ester 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.

[0537] Using different materials for the carboxylic ester solvent, such as ethyl acetate and methyl acetate, can improve the fast charging performance and high-temperature cycling performance. For example, the carboxylic ester 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 fast 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 cycling performance. However, due to the relatively high boiling point of ethyl acetate and relatively good stability at high temperatures, the high-temperature cycling performance of Example 1 is more excellent than that of Example 5.

[0538] Examples 6-1 to 6-3, using different materials for the second additive, can further optimize the components of the SEI film, reduce the internal resistance of the battery cell, and improve the fast charging performance and high-temperature cycling performance of the battery cell.

[0539] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as a limitation of this application, and changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principle, and scope of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes an electrode assembly and an electrolyte, and the electrode assembly includes a positive electrode sheet and a negative electrode sheet; The positive electrode sheet includes a positive current collector portion and a positive electrode film layer provided on at least one side of the positive current collector portion, and the positive electrode film layer includes a lithium-containing phosphate with an olivine structure; The negative electrode sheet includes a negative current collector portion and a negative electrode film layer provided on at least one side of the negative current collector portion, and the negative electrode film layer includes a carbon-based material; The electrolyte includes a carboxylic ester solvent, 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 carbonic acid ethylene ester derivative with a mass content ≥0, and vinylene carbonate with a mass content >0, and the carbonic acid ethylene ester 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-C5 alkyl group, or a C1-C5 haloalkyl group, and Q1, Q2, Q3, and Q4 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%; 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, based on the mass of the electrolyte.

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

3. The battery cell according to claim 1 or 2, characterized in that, The lithium fluorosulfonylimide includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and lithium perfluorobutanesulfonylimide.

4. The battery cell according to claim 1 or 2, characterized in that, The ratio of the mass content of lithium fluorosulfonylimide to the mass content of lithium hexafluorophosphate is 0.4 to 0.8, based on the mass of the electrolyte.

5. The battery cell according to claim 1 or 2, characterized in that, The mass content of lithium hexafluorophosphate in the electrolyte is 8% to 12%.

6. The battery cell according to claim 1 or 2, characterized in that, The mass content of the first additive is 3% to 7.5%.

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

8. The battery cell according to claim 1 or 2, characterized in that, The mass content of 1,3-propane sultone in the electrolyte is 0 to 0.5%.

9. The battery cell according to claim 8, wherein, The mass content of 1,3-propane sultone in the electrolyte is 0 to 0.3%.

10. The battery cell according to claim 1 or 2, characterized in that, The mass content of the carbonic acid ethylene ester derivative in the electrolyte is 0 to 4.0%.

11. The battery cell according to claim 10, wherein, The mass content of the carbonic acid ethylene ester derivative in the electrolyte is 1.5% to 3.5%.

12. The battery cell according to claim 1 or 2, characterized in that, At least one of Q1, Q2, Q3, and Q4 includes a halogen atom or a C1-C5 haloalkyl group.

13. The battery cell according to claim 1 or 2, characterized in that, The carbonic acid ethylene ester derivative includes at least one of a compound shown in Formula A-1 to a compound shown in Formula A-3, 。 14. The battery cell according to claim 1 or 2, characterized in that, The carboxylic ester solvent includes a compound shown in Formula I, Formula I In Formula I, R1 includes a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

15. The battery cell according to claim 14, wherein The carboxylic ester solvent includes one or more of a compound shown in Formula I-1 to a compound shown in Formula I-12, 。 16. The battery cell according to claim 1 or 2, 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%.

17. The battery cell according to claim 16, wherein, The carbonate solvent includes cyclic carbonates, and the cyclic carbonates include one or more of ethylene carbonate, propylene carbonate, and butylene carbonate; and / or, The carbonate solvent includes linear carbonates, and the linear carbonates include one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

18. The battery cell according to claim 1 or 2, characterized in that, The electrolyte includes a sulfur-containing additive with a mass content of 0 to 2% in the electrolyte, and the sulfur-containing additive includes one or more of vinylene sulfate, bis(vinylene sulfate), butylene sulfite, ethylene sulfite, and methylene methyl 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 difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

19. The battery cell according to claim 18, 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%.

20. The battery cell according to claim 1 or 2, characterized in that, The lithium-containing phosphate with an olivine structure includes: phosphate particles, and a positive electrode coating layer located on at least a part of the surface of the phosphate particles, and the positive electrode coating layer contains carbon.

21. The battery cell according to claim 20, characterized in that, Based on the mass of the lithium-containing phosphate with an olivine structure, the mass content of the carbon element is 0.8% to 2.3%.

22. The battery cell according to claim 20, wherein The positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

23. The battery cell according to claim 20, 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.

24. The battery cell according to claim 1 or 2, characterized in that, 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 wherein Wherein, 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5, 0 ≤ c1 ≤ 0.5, 3 ≤ z1 ≤ 5, A includes 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.

25. The battery cell according to claim 1 or 2, characterized in that, The positive electrode sheet includes a positive electrode active material, and the powder compaction density of the positive electrode active material under 30,000 N is 2.43 g / cm 3 to 2.85 g / cm 3 .

26. The battery cell according to claim 1 or 2, characterized in that, When the battery cell is in a 0% state of charge, the tap density of the positive electrode film layer is 2.46 g / cm 3 to 2.8 g / cm 3 ; and / or 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 .

27. The battery cell according to claim 1 or 2, characterized in that, The positive electrode tab further includes a positive electrode conductive layer located between the positive electrode current collector part and the positive electrode film layer, and 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, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

28. The battery cell according to claim 27, wherein The thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

29. The battery cell according to claim 1 or 2, characterized in that, The carbon-based material includes graphite particles, the graphite particles include graphite body particles and a negative electrode coating layer coated on the surface of the graphite body particles, the graphite body particles include secondary particles, and the negative electrode coating layer contains carbon.

30. The battery cell according to claim 29, wherein The graphite body particles include at least one of artificial graphite and natural graphite.

31. The battery cell according to claim 29, wherein Based on the mass of the graphite particles, the mass content of carbon element in the negative electrode coating layer is 2% to 5%.

32. The battery cell according to claim 1 or 2, characterized in that, The negative electrode film layer further includes a silicon-based material, and the mass content of silicon element in the negative electrode film layer is 0.3% to 5.0%.

33. The battery cell according to claim 1 or 2, characterized in that, The negative electrode sheet includes a negative active material, and the powder compaction density of the negative active material under 20,000 N is 1.4 g / cm 3 to 1.8 g / cm 3 .

34. The battery cell according to claim 1 or 2, characterized in that, 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 , and / or, 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 .

35. The battery cell according to claim 1 or 2, characterized in that, The negative electrode sheet further includes a negative electrode conductive layer, the negative electrode conductive layer is located between the negative electrode current collector portion 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, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

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

37. The battery cell according to claim 1 or 2, characterized in that, The electrode assembly further includes a separator, the separator is located between the positive electrode sheet and the negative electrode sheet, 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%.

38. The battery cell according to claim 37, wherein The separator further includes a functional layer provided 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, and the first functional layer includes first inorganic particles. A second functional layer, located on the other side of the base film, and the second functional layer includes composite particles, the composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

39. The battery cell according to claim 38, wherein, The non-fluoropolymer particles include acrylate copolymers.

40. The battery cell according to claim 38 or 39, characterized in that, The first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide; and / or the average particle size of the first inorganic particles is 5 nm to 100 nm.

41. The battery cell according to claim 38 or 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.

42. The battery cell according to claim 1 or 2, characterized in that, The positive electrode sheet and the negative electrode sheet are stacked along the thickness direction of the battery cell. The electrode assembly further includes a positive electrode tab and a negative electrode tab, the positive electrode tab is connected to at least one side of the positive electrode current collector 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 collector 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 the size of the positive electrode film layer, and the difference between the size of the negative electrode film layer and the size of the positive electrode film layer is OH2, where OH1 is greater than OH2.

43. The battery cell according to claim 42, wherein OH1 is 1.0 mm to 4.0 mm; and / or OH2 is 1.0 mm to 3.0 mm.

44. The battery cell according to claim 1 or 2, characterized in that, The battery cell further includes at least one positive terminal, and the current-carrying area of all the positive terminals located on the same side of the positive current collector is 150 mm 2 to 1000 mm 2 ; and / or The battery cell further includes at least one negative terminal, and the current-carrying area of all the negative terminals located on the same side of the negative current collector is 150 mm 2 to 1000 mm 2 .

45. The battery cell according to claim 1 or 2, characterized in that, The battery cell includes a housing that houses the electrode assembly and the electrolyte, and the thickness of the housing is from 0.1 mm to 0.5 mm.

46. A battery device, characterized in that, The battery device includes the battery cell according to any one of claims 1 to 45.

47. The battery device according to claim 46, characterized in that, The battery device is configured such that the charging time from a state of charge of 10% to a state of charge of 80% is from 5 min to 15 min.

48. An electrical device, characterized in that, The electrical device includes the battery device according to claim 46 or 47.

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