Battery cells, battery devices, and power-consuming devices

Abstract

This 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 sheet and a negative electrode sheet. The positive electrode sheet includes an olivine-structured lithium-containing phosphate. The negative electrode sheet includes graphite particles. The electrolyte includes a carboxylate solvent and a first additive. The thickness of a single negative electrode film layer is 50 to 75 μm, and the volume average particle size of the graphite particles is 8.5 to 13.5 μm. Based on the mass of the electrolyte, the mass content of the carboxylate solvent is 8% to 60%, and the total mass content of the first additive is 3% to 10%. The first additive includes 1,3-propane sultone (at least 0%), an ethylene carbonate derivative (at least 0%), and vinylene carbonate (at least 3%). The ethylene carbonate derivative includes the compound represented by Formula A. This application can improve the fast charging performance and cycling performance of the battery cell at high energy density. #imgabs0# Formula A.

Description

[0001] This application claims priority to international patent application PCT / CN2025 / 078556, filed on February 21, 2025, entitled “Battery Cell, Battery Device, and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

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

[0003] Battery cells, with their high capacity and long lifespan, are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric cars, electric aircraft, electric ships, and power tools. With the development of lithium-ion battery applications, higher requirements are being placed on the performance of battery cells, such as their fast charging performance at high energy density, cycle performance, and reliability. Summary of the Invention

[0004] The present application provides a battery cell, a battery device, and an electrical device, which can improve the fast charging performance and cycle performance and usage reliability of the battery cell at high energy density.

[0005] In the first aspect, the present application proposes a battery cell, the battery cell comprising an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode sheet and a negative electrode sheet; the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer comprising an olivine-structured lithium-containing phosphate; the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer comprising graphite particles; the electrolyte comprising a carboxylic acid ester solvent and a first additive, wherein the thickness of the single-side negative electrode film layer is The volume average particle size of the graphite particles is 50 μm to 75 μm, and the volume average particle size of the graphite particles is 8.5 μm to 13.5 μm; 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 3% to 10%, and the first additive includes 1,3-propane sultone with a mass content of ≥0, an ethylene carbonate derivative with a mass content of ≥0, and vinylene carbonate with a mass content of ≥3%, and the ethylene carbonate derivative 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 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time.

[0008] Therefore, in the embodiment of the present application, the thickness of the negative electrode film layer is within an appropriate range, which can make the energy density of the battery cell relatively high. The electrolyte includes a carboxylic acid ester solvent with an appropriate mass content, which can reduce the viscosity of the electrolyte and increase the migration rate of lithium ions in the electrolyte; the volume average particle size of the graphite particles is relatively small, so that the solid phase migration path of lithium ions in the graphite particles is shorter, which can increase the migration rate of lithium ions in the liquid phase and the solid phase, thereby improving the fast charging capability of the battery cell; the carboxylic acid ester solvent will not be too high, and the volume average particle size of the graphite particles will not be too small, which alleviates side reactions; on the other hand, the thickness of the negative electrode film layer will not be too high, which reduces the viscosity of the graphite particles. The coating amount of ink particles can alleviate side reactions; on the other hand, a first additive is added to the electrolyte, and the first additive includes vinylene carbonate. The reaction potential of vinylene carbonate and carboxylic acid ester solvents is close, and there is a competitive reaction with the carboxylic acid ester solvents. Vinylene carbonate can participate in the formation of a dense solid electrolyte interface membrane SEI film containing organic components on the negative electrode side, making it difficult for the carboxylic acid ester solvent to penetrate the SEI film to the graphite particles, thereby alleviating the side reaction between the carboxylic acid ester solvent and the graphite particles and reducing the gas production; and because the first additive is within an appropriate content, the membrane impedance formed on the negative electrode side will not be too large, and the fast charging performance will basically not be deteriorated. Therefore, the embodiments of the present application can improve the fast charging capability and cycle performance of the battery cell at high energy density and the reliability of use.

[0009] In some embodiments, the mass content of the first additive is 3.5% to 8%, which can further improve the fast charging capability and cycle performance and reliability of the battery cell at high energy density.

[0010] In some embodiments, the mass content of vinylene carbonate in the electrolyte is 3% to 8%. 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 side reactions on the negative electrode side and improve the cycle performance and fast charging capability of the battery cell at high energy density.

[0011] In some embodiments, the mass content of 1,3-propane sultone in the electrolyte is 0 to 0.5%, and optionally 0.05 to 0.5%. 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 while mitigating side reactions, thereby improving the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0012] In some embodiments, the weight content of the ethylene carbonate derivative in the electrolyte is 0 to 3.5%, and optionally 0.5 to 1.5%. The ethylene carbonate derivative can preferentially form a film, optimize the composition 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 at high energy density.

[0013] In some embodiments, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom or a C1 to C5 haloalkyl group. When the ethylene carbonate derivative includes a fluorine atom, the ethylene carbonate derivative can form a film rich in F and Li on the negative electrode side. This can protect the negative electrode active material while reducing the impedance of the film, effectively improving both the high-temperature cycling performance and the fast charging performance of the battery cell at high energy density.

[0014] In some embodiments, the ethylene carbonate derivative includes at least one of the compounds represented by formula A-1 to the compounds represented by formula A-3.

[0015] .

[0016] The above materials can further improve the high-temperature cycle performance and fast charging performance of battery cells at high energy density.

[0017] In some embodiments, the carboxylate solvent includes a compound represented by Formula I,

[0018] Formula I,

[0019] In Formula I,

[0020] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0021] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0022] The aforementioned chain carboxylate solvents have a low viscosity, thereby improving the rapid charging capability of the battery cells at high energy density, reducing the risk of lithium plating during rapid charging, and improving the reliability of the battery cells.

[0023] In some embodiments, the carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-12.

[0024]

[0025] The above materials can further improve the fast charging performance of battery cells at high energy density.

[0026] In some embodiments, the electrolyte further comprises a carbonate solvent, with the carbonate solvent comprising 18% to 70% by weight of the electrolyte. This carbonate solvent content can further improve the electrolyte's room temperature conductivity, facilitate lithium ion migration, and enhance the rapid charging capability of the battery cells at high energy density.

[0027] In some embodiments, the carbonate solvent includes a cyclic carbonate, and 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 at high energy density.

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

[0029] In some embodiments, the electrolyte includes a sulfur-containing additive in an amount of 0 to 2% by weight of the electrolyte. Optionally, the amount of the sulfur-containing additive is 0.5 to 2% by weight. The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, vinyl sulfite, and methylene disulfonate. The sulfur-containing additive and the first additive cooperate in film formation, thereby optimizing the film composition of the SEI film. The sulfur-containing additive participates in the formation of an inorganic-rich SEI film. The inorganic substances can enhance the high-temperature and high-voltage stability of the SEI film, thereby improving the high-temperature cycling performance of the battery cell.

[0030] In some embodiments, the electrolyte includes a lithium salt additive in an amount of 0 to 1% by weight. Optionally, the lithium salt additive has an amount of 0.2 to 1% by weight, and the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate). The salt additive and the first additive cooperate in film formation, optimizing the composition of the SEI film. The lithium salt additive contributes to the formation of an inorganic-rich SEI film. The inorganics enhance the high-temperature and high-voltage stability of the SEI film, thereby improving the high-temperature cycling performance of the battery cell.

[0031] In some embodiments, the thickness of a single negative electrode film layer is 50 μm to 65 μm. When the thickness of a single negative electrode film layer is within this range, while increasing the energy density of the battery cell, the lithium ion transmission path is shortened, which is beneficial for improving the fast charging performance of the battery cell, thereby improving the high-temperature cycling performance and fast charging performance of the battery cell at high energy density.

[0032] In some embodiments, the volume average particle size of the graphite particles is 9.5 μm to 13 μm. The relatively small volume average particle size of the graphite particles shortens the solid phase migration path of lithium ions, thereby improving the fast charging capability of the battery cell.

[0033] In some embodiments, the graphite particles include graphite particles and a negative electrode coating layer coated on the surface of the graphite particles, the graphite particles include secondary particles, and the negative electrode coating layer includes carbon. The graphite particles include secondary particles, the graphite particles have more migration paths for lithium ions, and the migration paths in the primary particles are shorter, which can increase the migration rate of lithium ions. The negative electrode coating layer has more end faces and defects, which increases the number of sites for lithium ion insertion and extraction, making the negative electrode coating layer more conductive, reducing the internal resistance of the negative electrode plate, reducing the heat generation of the battery cell, and improving the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0034] In some embodiments, the graphite bulk particles include at least one of artificial graphite and natural graphite.

[0035] In some embodiments, the carbon content of the negative electrode coating is 2% to 5% by mass, based on the total mass of the graphite particles. When the carbon content of the negative electrode coating is within this range, the internal resistance of the negative electrode plate can be further reduced, the heat generation of the battery cell can be reduced, and the high-temperature cycling performance of the battery cell at high energy density can be improved.

[0036] In some embodiments, the negative electrode film layer further comprises a silicon-based material, wherein the mass content of silicon in the negative electrode film layer is 0.3% to 5%. A silicon content within the above range can increase the capacity of the negative electrode active material, thereby improving the energy density of the battery cell.

[0037] In some embodiments, the powder compaction density of the negative electrode active material at 20,000 N is 1.4 g / cm 3 to 1.8g / cm 3 When the powder compaction density of the negative electrode active material at 20,000N is within the above range, the energy density of the battery cell can be improved. Furthermore, since the negative electrode active material in the negative electrode film layer can be more densely packed, 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 at high energy density.

[0038] In some embodiments, the compaction density of the negative electrode film layer of the battery cell at 0% state of charge is 1.30 g / cm 3 Up to 1.55g / 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 of the negative electrode film layer is densely packed, the contact resistance between particles is small, 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 acid ester solvents due to heat accumulation, thereby improving the high-temperature cycle performance of the battery cell.

[0039] In some embodiments, the single-side coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 Up to 140mg / 1540.25mm 2 When the coating weight of the negative electrode film on one side is within the above range, the heat generated per unit area of ​​the negative electrode sheet will not be too large, and the high-temperature cycle performance of the battery cell at high energy density can be improved.

[0040] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, which is located between the negative current collector and the negative electrode film layer. The negative electrode conductive layer includes a negative electrode conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The negative electrode conductive layer can further enhance the conductivity of the negative electrode plate, reduce heat generation of the negative electrode plate, and thus reduce heat generation of the battery cell, thereby improving the fast charging performance and high-temperature cycling performance of the battery cell.

[0041] 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 plate can be further improved, the heat generation of the negative electrode plate can be reduced, and thus the heat generation of the battery cell can be reduced, while also improving the energy density of the battery cell.

[0042] In some embodiments, the thickness of the positive electrode film layer on one side is 50 μm to 65 μm. When the thickness of the positive electrode film layer on one side is within the above range, the thickness of the positive electrode film layer is thinner, which shortens the transmission path of lithium ions and is conducive to improving the fast charging performance of the battery cell.

[0043] In some embodiments, the positive and negative electrode sheets are stacked along the thickness of the battery cell, and the positive electrode film layer has a dimension of 200 mm to 650 mm along the length of the battery cell. When the dimension of the positive electrode film layer along the length of the battery cell is within this range, a relatively large amount of positive electrode film is applied, which helps to increase the energy density of the battery cell. Furthermore, the electron transmission path is not excessively long, which helps to improve the fast charging capability of the battery cell.

[0044] In some embodiments, the olivine-structured lithium-containing phosphate includes phosphate particles and a positive electrode coating layer. The positive electrode coating layer is located on at least a portion of the surface of the phosphate particles and contains carbon. The positive electrode coating layer coated on the surface of the phosphate particles can enhance the conductivity of the olivine-structured lithium-containing phosphate, facilitate the migration rate of lithium ions, improve the fast charging capability of the battery, reduce heat generation in the battery cells, and improve the high-temperature cycling performance of the battery cells.

[0045] In some embodiments, the mass content of carbon is 0.8% to 2.3% based on the mass of the olivine-structured lithium-containing phosphate. A carbon content within this range can significantly improve the conductivity of the olivine-structured lithium-containing phosphate, thereby enhancing the ionic and electronic conductivities of the olivine-structured lithium-containing phosphate and improving the rapid charging capability of the battery cell at high energy density.

[0046] In some embodiments, the positive electrode coating layer further comprises one or more elements selected from the group consisting of Fe, Ti, Zr, Hf, Ge, and Sn. Materials containing these elements can enhance the ionic conductivity of the positive electrode active material, improve the rapid charging capability of the battery cell, and increase the specific capacity and energy density of the corresponding battery cell.

[0047] 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. These materials have excellent cycle stability and can improve the cycle performance of battery cells.

[0048] In some embodiments, the lithium-containing phosphate comprises a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Compounds, 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 comprises at least one of Na, K, and Mg; Me comprises at least one of Mn, Fe, Co, and Ni; M comprises 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 comprises at least one of Cl, C, and N; and Y comprises at least one of O and F. The above materials have excellent cycle stability and can improve the cycle performance of battery cells.

[0049] In some embodiments, the powder compaction density of the positive electrode active material at 30,000 N is 2.43 g / cm 3 Up to 2.85g / cm 3When the powder compaction density of the positive electrode active material at 30,000N is within the above range, the energy density of the battery cell can be improved. Moreover, since the positive electrode active material in the positive electrode film layer can be more densely packed, 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 at high energy density.

[0050] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 0% SOC is 2.46 g / cm 3 to 2.80g / 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. Moreover, since the positive electrode active material of the positive electrode film layer is stacked relatively densely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation under fast charging and improving the high-temperature cycle performance and fast charging performance of the battery cell under high energy density.

[0051] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 350mg / 1540.25mm 2 When the single-side 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, thereby improving the high-temperature cycle performance and fast charging performance of the battery cell at high energy density.

[0052] In some embodiments, the positive electrode plate further includes a positive conductive layer, which is located between the positive current collector and the positive electrode film layer. The positive conductive layer includes a positive conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive conductive layer can further improve the conductivity of the positive electrode plate, reduce heat generation of the positive electrode plate, and thus reduce heat generation of the battery cell.

[0053] 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, the conductivity of the positive electrode plate can be further improved, and the heat generation of the positive electrode plate can be reduced, thereby reducing the heat generation of the battery cell, and improving the high-temperature cycling performance of the battery cell at high energy density.

[0054] In some embodiments, the electrode assembly further includes a separator, which is positioned between the positive and negative electrode sheets. The separator includes a base film having a thickness of 4 to 12 μm and / or a porosity of 20% to 70%. When the base film meets the above ranges, the migration of lithium ions through the separator can be enhanced, further reducing the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance and high-temperature cycling performance of the battery cell at high energy density.

[0055] In some embodiments, the isolation membrane further includes a functional layer disposed on at least one side of the base membrane, the functional layer including a first functional layer and a second functional layer, the first functional layer being located on one side of the base membrane and including first inorganic particles, the second functional layer being located on the other side of the base membrane and including composite particles, the composite particles including second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles being attached to the surface of the non-fluoropolymer particles and / or dispersed within the non-fluoropolymer particles. The first and second functional layers have good heat resistance, thereby improving the heat resistance of the isolation membrane.

[0056] In some embodiments, the non-fluorinated polymer particles include acrylic copolymers, which have excellent bonding properties and high bonding stability with the base film.

[0057] In some embodiments, 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; the first inorganic particles have good heat resistance, which is beneficial to improving the heat resistance and compression modulus of the composite particles.

[0058] 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.

[0059] In some embodiments, 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. The second inorganic particles have good heat resistance, which is beneficial to improving the heat resistance and compression modulus of the composite particles.

[0060] 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.

[0061] In some embodiments, the positive electrode sheets and the negative electrode sheets are stacked along the thickness direction of the battery cell; the electrode assembly further comprises a positive electrode tab and a negative electrode tab, the positive electrode tab is connected to at least one side of the positive electrode collecting portion along the length direction of the battery cell, and the negative electrode tab is connected to at least one side of the negative electrode collecting portion along the length direction of the battery cell; along the length direction of the battery cell, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the size difference between the negative electrode film layer and 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 size difference between the negative electrode film layer and the positive electrode film layer is OH2, wherein OH1 is larger than OH2.

[0062] 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 negative electrode film layer to receive lithium ions in the area close to the negative electrode tab, thereby reducing the risk of lithium plating and improving the reliability of the battery cell.

[0063] 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 plating can be reduced and the reliability of the battery cell can be improved.

[0064] In some embodiments, the battery cell further includes at least one positive terminal, and the flow area of ​​all positive terminals on the same side of the positive current collecting portion is 150 mm 2 Up to 1000mm 2 When the overflow area of ​​the positive terminal meets the above range, the overflow capacity is strong, which can reduce the internal resistance and reduce the heat generation, which is beneficial to improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0065] In some embodiments, the battery cell further includes at least one negative terminal, and the flow area of ​​all negative terminals on the same side of the negative current collecting portion is 150 mm 2 Up to 1000mm 2 When the negative terminal's overflow area meets the above range, the overflow capacity is strong, which can reduce internal resistance and heat generation, and is beneficial to improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0066] In some embodiments, a battery cell includes a housing that houses an electrode assembly and an electrolyte, and the housing has a thickness of 0.1 mm to 0.5 mm. When the housing thickness is within this range, the housing has high mechanical strength, which can improve the reliability and cycle performance of the battery cell. Furthermore, the housing occupies less space, leaving more space inside the housing, which is beneficial for improving the energy density of the battery cell.

[0067] In a second aspect, the present application proposes a battery device, which includes a plurality of battery cells according to any embodiment of the first aspect of the present application.

[0068] In some embodiments, the battery device can be charged from a 10% state of charge to an 80% state of charge in a time range of 5 to 15 minutes. The faster the charging speed of the battery device, the better the improvement in fast charging capability.

[0069] In a third aspect, the present application proposes an electrical device, which includes a battery device according to any embodiment of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0071] Figure 1 This is a schematic diagram of the structure of a battery cell provided in some embodiments of the present application.

[0072] Figure 2 Schematic diagram of an explosion of a battery cell provided in some embodiments of the present application,

[0073] Figure 3 This is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0074] Figure 4 This is a schematic structural diagram of the positive electrode sheet of a battery cell provided in some embodiments of the present application.

[0075] Figure 5 This is a schematic structural diagram of the positive electrode sheet of a battery cell provided in some other embodiments of the present application.

[0076] Figure 6 This is a schematic structural diagram of the negative electrode sheet of a battery cell provided in some embodiments of the present application.

[0077] Figure 7 This is a schematic structural diagram of the negative electrode sheet of a battery cell provided in some other embodiments of the present application.

[0078] Figure 8 This is a schematic diagram of a top view of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0079] Figure 9 This is a schematic diagram of the structure of the battery module provided in some embodiments of the present application.

[0080] Figure 10 This is a schematic diagram of the structure of the battery pack provided in some embodiments of the present application.

[0081] Figure 11 It is a schematic diagram of the structure of an electrical device provided in some embodiments of the present application.

[0082] The drawings are not necessarily drawn to scale.

[0083] The following are the descriptions of the reference numerals:

[0084] 1. Power-consuming device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box; 5a. First box portion; 5b. Second box portion; 5c. Accommodation space; 6. Battery module;

[0085] 7. Battery cell; 10. Electrode assembly;

[0086] 11. Positive electrode sheet; 111. Positive electrode tab; 112. Positive electrode current collector; 113. Positive electrode film layer;

[0087] 12. Negative electrode sheet; 121. Negative electrode tab; 122. Negative electrode current collector; 123. Negative electrode film layer;

[0088] 13. Isolation membrane; 14. Main body; 20. Outer shell; 21. Shell; 22. End cap; 31. Positive terminal; 32. Negative terminal.

[0089] In the drawings, direction X is the thickness direction or stacking direction of the battery cells. DETAILED DESCRIPTION

[0090] Below, the embodiments of the battery cells, battery devices, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0091] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. 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 can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0092] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0093] 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.

[0094] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0095] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. The negative electrode sheet includes a negative electrode active material. At the negative electrode side interface, the negative electrode active material and the electrolyte may undergo side reactions, worsening the cycle. As the charging rate of the battery cell increases, the side reactions at the negative electrode side interface are further intensified, causing the cycle to further worsen, which is not conducive to fast charging.

[0096] In view of the above problems, the embodiments of the present application rationally design a battery cell system, which can improve both the cycle performance and fast charging capability of high-energy-density battery cells. Specifically, the thickness of the negative electrode film layer within an appropriate range can make the energy density of the battery cell relatively high. The positive electrode active material includes an olivine-structured lithium-containing phosphate, and the negative electrode active material includes graphite particles. The above material system has excellent cycle stability.

[0097] During the charging process, active ions such as lithium ions migrate from the positive electrode plate to the negative electrode plate through the electrolyte. The electrolyte includes a carboxylic acid ester solvent with an appropriate mass content, which can reduce the viscosity of the electrolyte and increase the migration rate of lithium ions in the electrolyte. The volume average particle size of the graphite particles is relatively small, which makes the solid phase migration path of lithium ions in the graphite particles shorter, and can increase the migration rate of lithium ions in the liquid phase and solid phase, thereby improving the fast charging capability of the battery cell. Due to the low viscosity of the electrolyte, the fluidity is better, which is more conducive to the rapid infiltration of the electrode plate. Under fast charging conditions, local lithium deposition is less likely to occur on the surface of the negative electrode plate, which can improve the reliability of the battery cell.

[0098] However, under fast charging, the side reaction between carboxylate solvents and graphite particles is more serious, and gas production is aggravated. On the one hand, the embodiment of the present application limits the carboxylate solvent to not too high and the volume average particle size of the graphite particles to not too small, thereby alleviating the side reaction; on the other hand, the thickness of the negative electrode film layer is not too high, thereby reducing the coating amount of the graphite particles and alleviating the side reaction; on the other hand, a first additive is added to the electrolyte, and the first additive includes vinylene carbonate. The reaction potential of vinylene carbonate and carboxylate solvents is close, and there is a competitive reaction with the carboxylate solvent. Vinylene carbonate can participate in the formation of a dense solid electrolyte interface membrane SEI membrane containing organic components on the negative electrode side, making it difficult for the carboxylate solvent to penetrate the SEI membrane to the graphite particles, thereby alleviating the side reaction between the carboxylate solvent and the graphite particles and reducing gas production; and since the first additive is within an appropriate content, the membrane impedance formed on the negative electrode side will not be too large, and basically will not deteriorate the fast charging performance.

[0099] Therefore, the embodiments of the present application can improve the fast charging capability, cycle performance and reliability of battery cells at high energy density.

[0100] battery cells

[0101] In a first aspect, an embodiment of the present application provides a battery cell.

[0102] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a lithium-containing phosphate with an olivine structure. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material. The negative electrode active material includes graphite particles. The electrolyte includes an organic solvent and a first additive.

[0103] The thickness of the negative electrode film layer on one side is 50 μm to 75 μm, and the volume average particle size of the graphite particles is 8.5 μm to 13.5 μm;

[0104] The organic solvent includes a carboxylic acid ester additive, and the mass content of the carboxylic acid ester solvent in the electrolyte is 8% to 60%;

[0105] Based on the mass of the electrolyte, the total mass content of the first additive is 3% to 10%, and the first additive includes 1,3-propane sultone with a mass content greater than or equal to 0, an ethylene carbonate derivative with a mass content greater than or equal to 0, and vinylene carbonate with a mass content greater than or equal to 3%, and the ethylene carbonate derivative 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 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time.

[0108] The thickness of the negative electrode film layer on one side is greater than or equal to 50 μm, which can make the energy density of the battery cell relatively high; the positive electrode active material includes an olivine-structured lithium-containing phosphate, and the negative electrode active material includes graphite particles. The above material system has excellent cycle stability;

[0109] During the charging process, active ions such as lithium ions migrated from the positive electrode plate to the negative electrode plate through the electrolyte. The electrolyte 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 and increase the migration rate of lithium ions in the electrolyte; the volume average particle size of the graphite particles is relatively small, for example, less than or equal to 13.5 μm, so that the solid phase migration path of lithium ions in the graphite particles is shorter, which can increase the migration rate of lithium ions in the liquid phase and the solid phase, thereby improving the fast charging capability of the battery cell; due to the low viscosity of the electrolyte, the fluidity is better, which is more conducive to the rapid infiltration of the electrode plate. Under fast charging conditions, local lithium deposition is less likely to occur on the surface of the negative electrode plate, which can improve the reliability of the battery cell;

[0110] However, under fast charging, the side reaction between the carboxylate solvent and the graphite particles is more serious, and the gas production is aggravated. On the one hand, the embodiment of the present application limits the carboxylate solvent to less than or equal to 60%, and the volume average particle size of the graphite particles is greater than or equal to 8.5μm, so that the active area of ​​the graphite particles will not be too large, which can alleviate the side reaction; on the other hand, the thickness of the negative electrode film layer is thinned so that the thickness of the single-side negative electrode film layer is less than or equal to 75μm, thereby reducing the coating amount of the graphite particles and reducing the total amount participating in the reaction, thereby alleviating the side reaction; on the other hand, a first additive is added to the electrolyte, the first additive includes vinylene carbonate, the reaction potential of vinylene carbonate and the carboxylate solvent is close, and there is a competitive reaction with the carboxylate solvent. Vinylene carbonate can participate in the formation of a dense SEI film containing organic components on the negative electrode side, making it difficult for the carboxylate solvent to penetrate the SEI film to the graphite particles, thereby alleviating the side reaction between the carboxylate solvent and the graphite particles, reducing gas production, and improving high-temperature cycle performance; and because the first additive is within an appropriate content, the membrane impedance formed on the negative electrode side will not be too large, and basically will not deteriorate the fast charging performance.

[0111] Therefore, the embodiments of the present application can improve the fast charging capability, cycle performance and reliability of battery cells at high energy density.

[0112] [Electrolyte]

[0113] Battery cells contain electrolytes. During the charge and discharge process of the battery cells, active ions such as lithium ions are inserted and removed back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting the active ions between the positive and negative electrodes.

[0114] The electrolyte solution includes an organic solvent and an electrolyte salt.

[0115] The organic solvent includes a carboxylate solvent, and the mass content of the carboxylate solvent in the electrolyte is 8% to 60%. For example, the mass content of the carboxylate solvent is 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range consisting of any two of the above values. When the mass content of the carboxylate solvent is greater than or equal to 8%, the viscosity of the electrolyte system is relatively small, which is conducive to the migration of lithium ions; when the mass content of the carboxylate solvent is less than or equal to 60%, the side reaction between the carboxylate solvent and the negative electrode active material is relatively small, which is conducive to improving the cycle performance.

[0116] In some embodiments, the carboxylate solvent may include at least one of a linear carboxylate solvent and a cyclic carboxylate solvent, with the linear carboxylate solvent being preferred. The linear carboxylate solvent has a lower viscosity, which can further increase the migration rate of lithium ions and enhance the fast charging capability of the battery cell.

[0117] Since chain carboxylate solvents have lower viscosity and better fluidity, they are more conducive to rapid wetting of the electrode. Under fast charging conditions, local lithium deposition is less likely to occur on the surface of the negative electrode, thereby improving the reliability of the battery cell.

[0118] Illustratively, the carboxylate solvent includes a compound represented by Formula I,

[0119] Formula I,

[0120] In Formula I,

[0121] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0122] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0123] The aforementioned chain carboxylate solvents have a low viscosity, thereby improving the rapid charging capability of the battery cells at high energy density, reducing the risk of lithium plating during rapid charging, and improving the reliability of the battery cells.

[0124] Alternatively, R1 includes a hydrogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further alternatively, R1 includes a hydrogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0125] Alternatively, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. Further alternatively, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0126] In each of the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Alternatively, the haloalkyl group includes a fluoroalkyl group.

[0127] Illustratively, the carboxylate solvent includes one or more of the compounds represented by Formula I-1 to the compounds represented by Formula I-12.

[0128]

[0129] The above materials can further improve the fast charging performance of battery cells at high energy density.

[0130] In some embodiments, the organic solvent further comprises a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 18% to 70%. For example, 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 consisting of any two of the above values. The above mass content of carbonate solvent can further improve the conductivity of the electrolyte at room temperature, facilitate the migration of lithium ions, and enhance the fast charging capability of the battery cell at high energy density.

[0131] Optionally, the carbonate solvent includes at least one of a cyclic carbonate and a chain carbonate.

[0132] For example, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate. These materials can further improve the fast charging performance of the battery cell at high energy density.

[0133] For example, the chain carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. These materials can further improve the fast charging performance of the battery cell at high energy density.

[0134] In an embodiment 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, an ethylene carbonate derivative with a mass content ≥0, and vinylene carbonate with a mass content ≥3.

[0135] In an embodiment of the present application, the total mass content of the first additive is 3% to 10%, for example, 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 consisting of any two of the above values.

[0136] When the weight content of the first additive is less than 3%, the film formed on the negative electrode side is relatively thin, which is not conducive to protecting the negative electrode active material. As the weight content of the first additive increases, the film formation effect on the negative electrode side is more excellent, which can provide excellent protection for the negative electrode active material, reduce the risk of carboxylic acid ester solvents penetrating the SEI film into the negative electrode film layer, reduce side reactions on the negative electrode side, reduce gas production, and improve high-temperature cycling performance. However, as the weight content of the first additive further increases, the SEI film formed on the negative electrode side has higher impedance, which is not conducive to fast charging. Therefore, in embodiments of the present application, the weight content of the first additive is controlled to be 3% to 10%, which can achieve both improved cycling performance and fast charging performance of the battery cell at high energy density. Alternatively, the weight content of the first additive is 3.5% to 8%, which can further improve the cycling performance and fast charging performance of the battery cell at high energy density. Optionally, the weight content of the first additive in the freshly prepared electrolyte is 3.5% to 8%. Freshly prepared electrolyte can be understood as electrolyte that has not yet undergone formation or other steps.

[0137] The first additive includes vinylene carbonate with a mass content of ≥3. In other words, vinylene carbonate is an essential component of the electrolyte.

[0138] When the mass content of 1,3-propane sultone is 0 and the mass content of the vinyl carbonate derivative is 0, the first additive may include only vinylene carbonate, and the mass content of the vinylene carbonate may be 3% to 10%.

[0139] Specifically, taking the case where the mass content of the ethylene carbonate derivative is 0 as an example,

[0140] It can be that the freshly prepared electrolyte does not contain any ethylene carbonate derivatives.

[0141] Alternatively, the electrolyte obtained after disassembling the battery cell does not contain an ethylene carbonate derivative. This may be because the freshly prepared electrolyte does not contain an ethylene carbonate derivative, or because a small amount of an ethylene carbonate derivative was added but participated in the SEI film formation reaction during the battery cell formation process, resulting in an ethylene carbonate derivative mass content of zero during testing. Alternatively, the freshly prepared electrolyte includes an ethylene carbonate derivative.

[0142] Furthermore, regarding the addition of certain substances, such as additives, to the electrolyte, the content of additives in the battery cell electrolyte is related to the formation process, different battery life cycles, or different battery storage conditions due to the additives' role in film formation on the surface of the active material. Therefore, the additive content in a freshly prepared electrolyte may differ from that in an electrolyte obtained by reverse disassembling a battery cell. However, those skilled in the art can determine the approximate content range of the relevant substances in the fresh electrolyte based on the performance level of the battery cell (such as the number of cycles) and residual content. Similarly, those skilled in the art can also determine the approximate content range of the corresponding non-freshly prepared (i.e., after reverse disassembly) electrolyte based on the content of the freshly prepared additives, the performance requirements for the battery cell, the storage environment, etc.

[0143] Therefore, the additive content mentioned in the technical solution of the present application can be the content of the additive actively added to the fresh electrolyte, or it can be the content of the residual additive detected by reverse detection based on the actual battery status.

[0144] In some embodiments, the mass content of vinylene carbonate in the electrolyte is 3% to 8%, for example 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8% or a range consisting of any two of the above values. When the mass content of vinylene carbonate is within the above range, a dense SEI film containing organic components can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reaction on the negative electrode side, while improving the cycle performance and fast charging capability of the battery cell at high energy density. Optionally, the mass content of vinylene carbonate in the electrolyte is 3% to 6%.

[0145] The first additive may include 1,3-propane sultone in a mass content greater than 0, or the first additive may include an ethylene carbonate derivative in a mass content greater than 0, or the first additive may include 1,3-propane sultone and an ethylene carbonate derivative.

[0146] 1,3-Propane sultone, ethylene carbonate derivatives and vinylene carbonate are combined to form a dense and relatively low-impedance film layer, which reduces gas production and improves the cycle performance and fast charging performance of battery cells at high energy density.

[0147] In some embodiments, the mass content of 1,3-propane sultone in the electrolyte is 0 to 0.5%, for example, 0, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or a range consisting of any two of the foregoing values. Optionally, the mass content of 1,3-propane sultone in the electrolyte is 0.05% to 0.5%.

[0148] When the mass content of 1,3-propane sultone is 0, it means that 1,3-propane sultone does not need to be 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 low consumption of 1,3-propane sultone during the film formation process, the mass content of 1,3-propane sultone in the freshly prepared electrolyte is slightly higher than that in the disassembled electrolyte.

[0149] 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 acid ester solvents penetrating the SEI film and reacting with the negative electrode active material.

[0150] 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, and the impedance can be reduced on the basis of alleviating side reactions, thereby improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0151] Illustratively, the mass content of 1,3-propane sultone in the electrolyte is 0.05% to 0.5%; the mass content of vinylene carbonate in the electrolyte is 3% to 6%.

[0152] In some embodiments, the weight content of the ethylene carbonate derivative in the electrolyte is 0 to 3.5%, for example, 0, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or a range consisting of any two of the foregoing values. Alternatively, the weight content of the ethylene carbonate derivative in the electrolyte is 0.5% to 1.5%.

[0153] Optionally, the freshly prepared electrolyte includes an ethylene carbonate derivative, and the mass content of the ethylene carbonate derivative in the freshly prepared electrolyte is greater than 0. The ethylene carbonate derivative preferentially forms a film. After adding a certain amount of the ethylene carbonate derivative to the freshly prepared electrolyte, due to the large amount of ethylene carbonate derivative consumed during the film formation stage, the ethylene carbonate derivative may not be detected in the battery cells obtained after disassembly.

[0154] Vinylene carbonate continuously participates in the formation of SEI film during the battery cell cycle, alleviating the risk of carboxylic acid ester solvents penetrating the SEI film. However, the organic component content of the SEI film is relatively high, which makes the impedance of the SEI film relatively high. Ethylene carbonate derivatives can form films preferentially, optimize the components of the SEI film, reduce the impedance of the SEI film, and effectively improve the fast charging performance and cycle performance of the battery cell at high energy density.

[0155] Illustratively, the mass content of vinylene carbonate in the electrolyte is 3% to 6%; the mass content of vinylene carbonate derivatives in the electrolyte is 0.5% to 1.5%.

[0156] Illustratively, the mass content of 1,3-propane sultone in the electrolyte is 0.05% to 0.5%; the mass content of vinylene carbonate in the electrolyte is 3% to 6%; and the mass content of vinylene carbonate in the electrolyte is 0.5% to 1.5%.

[0157] Under fast charging, the above three types of substances jointly participate in the formation of the SEI film, which can not only strengthen the SEI film through a low content of 1,3-propane sultone, but also vinylene carbonate can further strengthen the film formation, reduce the risk of carboxylic acid ester solvents penetrating the SEI film, and improve the high-temperature cycle performance of the battery cell; an appropriate content of vinyl carbonate derivatives can reduce the film formation impedance and improve the fast charging performance, and the mass content of vinyl carbonate derivatives will not be too high, which can reduce the risk of high-temperature decomposition and further improve the high-temperature cycle performance of the battery cell; thereby improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0158] In the embodiment of the present application, the ethylene carbonate derivative refers to ethylene carbonate in which at least one hydrogen atom is substituted, and the substituted group may be one, two, three or four.

[0159] Exemplarily, the ethylene carbonate derivatives include compounds represented by formula A,

[0160] Formula A,

[0161] In formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time.

[0162] Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time. In other words, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group.

[0163] Illustratively, one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and the rest are hydrogen atoms.

[0164] Illustratively, at least two of Q1, Q2, Q3, and Q4 include a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0165] Illustratively, at least three of Q1, Q2, Q3, and Q4 include a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0166] Illustratively, Q1, Q2, Q3, and Q4 each independently include a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0167] Alternatively, at least one of Q1, Q2, Q3 and Q4 includes a halogen atom or a C1 to C5 haloalkyl group. The halogen atom includes a fluorine atom, a bromine atom or a chlorine atom, and may be a fluorine atom. The C1 to C5 haloalkyl group includes a C1 to C5 fluoroalkyl group, a C1 to C5 bromoalkyl group or a C1 to C5 chloroalkyl group, and may be a fluorine atom. For example, the C1 to C5 fluoroalkyl group includes a fluoromethyl group, a fluoroethyl group, a fluoropropyl group, a fluorobutyl group or a fluoropentyl group.

[0168] When the ethylene carbonate derivative includes fluorine atoms, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side, which can reduce the impedance of the film layer while protecting the negative electrode active material, and can more effectively improve the high-temperature cycle performance and fast charging performance of the battery cell at high energy density.

[0169] For example, the ethylene carbonate derivative includes at least one of the compounds represented by formula A-1 to the compounds represented by formula A-6,

[0170]

[0171] The above materials can further improve the high-temperature cycle performance and fast charging performance of battery cells at high energy density.

[0172] Optionally, the ethylene carbonate derivative includes at least one of the compounds represented by formula A-1 to the compounds represented by formula A-3. Further optionally, the ethylene carbonate derivative includes the compound represented by formula A-1.

[0173] In some embodiments, the electrolyte further includes a second additive having a mass content greater than or equal to 0, and the second additive includes at least one of a sulfur-containing additive and a lithium salt additive.

[0174] For example, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butylene sulfite BS, vinyl sulfite ES, and methylene disulfonate MMDS.

[0175] Illustratively, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluorooxalatoborate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bis(oxalatoborate) LiBOB.

[0176] In some embodiments, the electrolyte includes a sulfur-containing additive in an amount of 0 to 2% by weight of the electrolyte, and optionally, the amount of the sulfur-containing additive is 0.5 to 2% by weight. The sulfur-containing additive and the first additive cooperate in film formation, thereby optimizing the film composition of the SEI film. The sulfur-containing additive can participate in the formation of an inorganic-rich SEI film, and the inorganic substances can enhance the high-temperature and high-voltage stability of the SEI film, thereby improving the high-temperature cycling performance of the battery cell.

[0177] Illustratively, the mass content of the sulfur-containing additive in the electrolyte is 0 to 2%, for example, 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 consisting of any two of the above values.

[0178] In some embodiments, the electrolyte includes a lithium salt additive in an amount of 0 to 1% by weight of the electrolyte. Optionally, the amount of the lithium salt additive is 0.2 to 1% by weight. The lithium salt additive and the first additive cooperate in film formation, thereby optimizing the film composition of the SEI film. The lithium salt additive can participate in the formation of an inorganic-rich SEI film. The inorganic matter can enhance the high-temperature and high-voltage stability of the SEI film, thereby improving the high-temperature cycling performance of the battery cell.

[0179] Illustratively, 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 consisting of any two of the above values.

[0180] 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 amount of the second additive added is small, the second additive cannot be detected in the electrolyte obtained after disassembling the battery cell.

[0181] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes lithium hexafluorophosphate (LiPF6). Optionally, the electrolyte further includes a fluorinated sulfonyl imide lithium salt, which can improve the cycle performance of the battery cell.

[0182] Optionally, the fluorine-containing lithium sulfonyl imide includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0183] In some embodiments, the mass content of the lithium salt is 10% to 16%.

[0184] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis methods in accordance with the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the battery cell has a charged state of approximately 0% SOC) can be reversely disassembled and the free electrolyte obtained from the battery cell can be used as a sample for detection using ion chromatography analysis methods.

[0185] In the embodiment of the present application, the types and contents of the organic components in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the organic components of the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography with reference to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0186] [Negative electrode]

[0187] The negative electrode sheet includes a negative current collector and a negative electrode film layer comprising a negative electrode active material disposed on at least one surface of the negative current collector. For example, the negative current collector may have two opposing surfaces in the thickness direction of the negative current collector, and the negative electrode film layer may be disposed on either or both of the two opposing surfaces of the negative current collector.

[0188] In an embodiment of the present application, the thickness of the negative electrode film layer on one side is 50 μm to 75 μm, for example, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, or a range consisting of any two of the above values. Optionally, the thickness of the negative electrode film layer on one side is 50 μm to 65 μm.

[0189] When the thickness of the single-sided negative electrode film layer is within the above range, the thickness of the negative electrode film layer is moderate. On the basis of improving the energy density of the battery cell, the amount of negative electrode active material added to the negative electrode film layer is relatively small, which can effectively reduce the total amount of side reactions, thereby reducing the gas production and improving the high-temperature cycle performance of the battery cell; and the lithium ion transmission path is shorter, which is conducive to improving the fast charging performance of the battery cell, thereby improving the high-temperature cycle performance and fast charging performance of the battery cell at high energy density.

[0190] In the embodiment of the present application, the thickness of the single-sided negative electrode film layer has a meaning well known in the art. For example, it can be detected using equipment and methods well known in the art. For example, a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the battery cell has a charged state of approximately 0% SOC) is reversely disassembled, and the negative electrode pole piece obtained from the battery cell is used as a sample, and the thickness of the negative electrode pole piece is measured using a micrometer; then the negative electrode film layer on the surface of the negative electrode current collector is washed away with a solvent, and the thickness of the negative electrode current collector is measured using a micrometer. In the case where the negative electrode film layer is coated on one side, the thickness of the negative electrode pole piece minus the thickness of the negative electrode current collector is the thickness of the negative electrode film layer; or, in the case where the negative electrode film layer is coated on both sides, the thickness of the negative electrode pole piece minus the thickness of the negative electrode current collector is the total thickness of the negative electrode film layers on both sides, and the total thickness of the negative electrode film layers on both sides divided by 2 is the thickness of the single-sided negative electrode film layer.

[0191] The upper limit of charge voltage and the cut-off voltage of discharge of the battery cell vary depending on the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper limit of charge voltage can be 3.65V and the cut-off voltage of discharge can be 2.0V. For another example, when the phosphate material includes lithium manganese iron phosphate, the upper limit of charge voltage can be 4.2V and the cut-off voltage of discharge can be 2.0V. Next, taking the upper limit of charge voltage of 3.65V and the cut-off voltage of discharge of 2.0V as an example, the state of the battery cell is explained: In the embodiment of the present application, the 100% state of charge SOC and 0% state of charge SOC of the battery cell are defined as follows:

[0192] The battery cell is charged at a constant current charge rate of 0.33C to the upper limit of the charge 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.

[0193] In the embodiment of the present application, the negative electrode film layer includes at least one film layer, which can be a single film layer or at least two film layers. The negative electrode film layer can include two film layers, three film layers, four film layers, or even more film layers.

[0194] In the embodiments of the present application, the negative electrode active material comprises a carbon-based material, which includes graphite particles. Graphite particles have high cycling stability and can improve the cycling performance of the battery cell. The positive electrode active material of the present application is primarily an olivine-structured lithium-containing phosphate system, and the negative electrode active material is primarily a carbon-based material system. The combination of the two results in excellent cycling performance for the battery cell.

[0195] The volume average particle size Dv50 of the graphite particles is 8.5 μm to 13.5 μm, for example, 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 a range consisting of any two of the foregoing values. Optionally, the volume average particle size Dv50 of the graphite particles is 9.5 μm to 13 μm.

[0196] The volume average particle size of the graphite particles is relatively small, which makes the solid-phase migration path of lithium ions shorter, and can improve the fast charging capability of the battery cell; however, under fast charging conditions, the side reaction between the small-sized graphite particles and the carboxylic acid ester solvent in the electrolyte is more 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 on the negative electrode side, and improve the cycle performance of the battery cell.

[0197] In the embodiment 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, which can be detected using equipment and methods known in the art. For example, the negative electrode active material is used as a sample and the Dv50 of the particles is tested using a Mastersizer 2000E laser particle size analyzer in accordance with the test standard GB / T 19077-2016.

[0198] In some embodiments, the graphite particles include primary graphite particles and a negative electrode coating layer, wherein the primary graphite particles include secondary particles, each of which includes a plurality of primary particles. The negative electrode coating layer is coated on the surface of the primary graphite particles, and the negative electrode coating layer includes carbon. The carbon in the negative electrode coating layer is primarily amorphous carbon, which refers to a transitional carbon material with a very low degree of graphitization and crystallization, resulting in a nearly amorphous morphology (or lacking a fixed shape and periodic structural regularity). In this application, amorphous carbon refers to the product of carbonization of an organic carbon source.

[0199] The graphite body particles include secondary particles. There are more migration paths for lithium ions in the graphite body particles, and the migration paths in the primary particles are shorter, which can improve the migration rate of lithium ions. The negative electrode coating layer has more end faces and defects, which increases the number of sites that can be used to deintercalate and deintercalate lithium ions, making the conductivity of the negative electrode coating layer better, 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 at high energy density.

[0200] Exemplarily, the graphite body particles include at least one of artificial graphite and natural graphite, and artificial graphite can be selected.

[0201] Optionally, the carbon content of the negative electrode coating layer is 2% to 5% by mass based on the mass of the graphite particles. Exemplarily, the carbon content of the negative electrode coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the foregoing values.

[0202] When the mass content of carbon elements in the negative electrode coating layer is within the above range, the internal resistance of the negative electrode plate can be further reduced, the heat generation of the battery cell can be reduced, and the high-temperature cycle performance of the battery cell under high energy density can be improved.

[0203] In an embodiment of the present application, the graphite particles can be prepared by methods known in the art. Taking the graphite body particles as artificial graphite as an example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and forming a negative electrode coating layer on at least a portion of the surface of the artificial graphite particles after carbonization treatment.

[0204] Optionally, the organic carbon source includes one or more of coal tar, petroleum tar, phenolic resin, and coconut shell. Further, optionally, the organic carbon source includes petroleum tar. Optionally, the softening point of the coal tar or petroleum tar is below 250°C.

[0205] Optionally, the carbonization treatment temperature is 700° C. to 1800° C. Optionally, the carbonization treatment temperature is 1000° C. to 1300° C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized and a negative electrode coating layer containing amorphous carbon can be formed on at least a portion of the surface of the artificial graphite.

[0206] Optionally, the carbonization treatment time is 1 hour to 6 hours.

[0207] 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.

[0208] In some embodiments, the negative electrode active material may include not only graphite particles but also silicon-based materials. The introduction of silicon-based materials can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0209] Optionally, based on the mass of the negative electrode film layer, the mass content of silicon in the silicon-based material is 0.3% to 5.0%, optionally 1% to 5%. Exemplarily, the mass content of silicon in the silicon-based material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, or a range consisting of any two of the above values.

[0210] When the mass content of silicon in the silicon-based material is within the above range, the capacity of the negative electrode active material can be increased, thereby improving the energy density of the battery cell.

[0211] Alternatively, the silicon-based material may include at least one of elemental silicon, silicon oxide, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy material.

[0212] In some embodiments, the negative electrode active material may include at least one of a tin-based material and lithium titanate in addition to the aforementioned carbon-based material and optionally a silicon-based material. The tin-based material may include at least one of elemental tin, tin oxide, and a tin alloy.

[0213] The qualitative and quantitative properties of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0214] For example, the present application may combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis Methods to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0215] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flake structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0216] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.4 g / cm 3 to 1.8g / cm 3 For example, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.4 g / cm 3 , 1.5g / cm 3 , 1.55g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 , 1.75g / cm 3 , 1.8g / cm 3 Or a range consisting of any two of the above values.

[0217] When the powder compaction density of the negative electrode active material at 20,000 N is within the above range, the energy density of the battery cell can be improved. Moreover, since the negative electrode active material of the negative electrode film layer can be stacked more densely and the contact resistance between particles is smaller, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation and improving the high-temperature cycle performance of the battery cell at high energy density.

[0218] In the embodiments of the present application, the powder compaction density of the material is a well-known meaning in the art and can be tested using methods and equipment known in the art in accordance with the test standard GB / T24533-2009. As an example, a certain amount of negative electrode active material is taken as a sample and placed in a UTM7305 electronic pressure testing machine with a bottom area of ​​1.327 cm 2 The mold was pressurized to 2000 kg (equivalent to 20000 N), maintained for 30 seconds, then released and maintained for 10 seconds, and then the powder compaction density of the negative electrode active material under a force of 20000 N was recorded and calculated.

[0219] In some embodiments, the compaction density of the negative electrode film layer of the battery cell at 0% state of charge is 1.30 g / cm 3 Up to 1.55g / cm 3 For example, the compaction density of the negative electrode film layer of the battery cell at 0% state of charge is 1.30 g / cm 3 , 1.32g / cm 3 , 1.35g / cm 3 , 1.40g / cm 3 , 1.45g / cm 3 , 1.50g / cm 3 , 1.55g / cm 3 Or a range consisting of any two of the above values.

[0220] 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 of the negative electrode film layer is stacked relatively densely, the contact resistance between particles is small, 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 acid ester solvents due to heat accumulation, thereby improving the high-temperature cycle performance of the battery cell.

[0221] In the embodiment of the present application, the compaction density of the negative electrode film layer of the battery cell at 0% charge state has a meaning well known in the art and can be detected using 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 mentioned above.

[0222] In some embodiments, the single-side coating weight of the negative electrode film layer is 90 mg / 1540.25 mm2 Up to 140mg / 1540.25mm 2 For example, the coating weight of the negative electrode film on one side is 90 mg / 1540.25 mm 2 、92mg / 1540.25mm 2 、95mg / 1540.25mm 2 、96mg / 1540.25mm 2 、100mg / 1540.25mm 2 、102mg / 1540.25mm 2 、104mg / 1540.25mm 2 、105mg / 1540.25mm 2 、108mg / 1540.25mm 2 、110mg / 1540.25mm 2 、112mg / 1540.25mm 2 、114mg / 1540.25mm 2 、115mg / 1540.25mm 2 、116mg / 1540.25mm 2 、118mg / 1540.25mm 2 、120mg / 1540.25mm 2 、122mg / 1540.25mm 2 、125mg / 1540.25mm 2 、128mg / 1540.25mm 2 、130mg / 1540.25mm 2 、132mg / 1540.25mm 2 、135mg / 1540.25mm 2 、137mg / 1540.25mm 2 、140mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0223] When the single-side coating weight of the negative electrode film layer is within the above range, the heat generated per unit area of ​​the negative electrode sheet will not be too large, and the high-temperature cycle performance of the battery cell at high energy density can be improved.

[0224] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer has a meaning well known in the art and can be tested using equipment and methods well known in the art. For example, a negative electrode sheet is disassembled from a battery cell at 0% state of charge (SOC) to determine the compaction density of the negative electrode film layer. For example, a single-sided coated negative electrode sheet (if a double-sided coated sheet, the negative electrode film layer on one side can be wiped off first) is punched into small discs with an area of ​​S1. The discs are weighed and recorded as M1, and their thickness H1 is measured. The negative electrode film layer of the weighed negative electrode sheet is then wiped off, and the weight of the negative current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the negative electrode film layer = (weight of the negative electrode sheet M1 - weight of the negative current collector M0) / S1. The thickness of the negative electrode film layer = thickness of the negative electrode sheet H1 - thickness of the negative current collector H0. The compaction density of the negative electrode film layer = single-sided coating weight of the negative electrode film layer / thickness of the negative electrode film layer.

[0225] In some embodiments, the negative electrode film layer further includes a negative electrode binder. The negative electrode binder includes at least one of styrene-butadiene rubber (SBR), a water-soluble unsaturated resin SR-1B, a water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the weight content of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0226] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of negative electrode conductive agent. For 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, the weight content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0227] In some embodiments, the negative electrode film layer may also optionally include other additives. Examples of these additives include thickeners, dispersants, and the like, such as sodium carboxymethylcellulose (CMC-Na) and PTC thermistor materials. In some embodiments, the weight content of these additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0228] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0229] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0230] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the present application further includes a negative conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0231] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further enhance the conductivity of the negative electrode plate, reduce heat generation of the negative electrode plate, and thus reduce heat generation of the battery cell, thereby improving the fast charging performance and high-temperature cycling performance of the battery cell.

[0232] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. For example, the thickness of the negative electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range consisting of any two of the above values.

[0233] 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.

[0234] In the embodiment of the present application, the thickness of the negative electrode conductive layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, for example, by performing a tomographic scan on the negative electrode sheet to directly measure the thickness of the negative electrode conductive layer.

[0235] 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 in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode pole piece and reducing the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector and the negative electrode film layer, thereby improving the structural stability of the negative electrode pole piece.

[0236] In some embodiments, the negative electrode conductive layer may further include other additives, such as thickeners, sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0237] Optionally, the negative electrode conductive agent of the negative electrode conductive layer has a mass content of 20% to 40% in the negative electrode conductive layer. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or a range consisting of any two of the above values.

[0238] Illustratively, 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.

[0239] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%, illustratively 60%, 65%, 70%, 75%, 80%, or a range consisting of any two of the above values.

[0240] Illustratively, 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, aqueous acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0241] [Positive electrode]

[0242] The positive electrode sheet includes a positive current collector and a positive electrode film layer comprising a positive electrode active material and disposed on at least one surface of the positive current collector. For example, the positive current collector may have two opposing surfaces in the thickness direction of the positive current collector, and the positive electrode film layer may be disposed on one or both of the two opposing surfaces of the positive current collector.

[0243] In some embodiments, the thickness of a single-sided positive electrode film layer is 50 μm to 65 μm, such as 50 μm, 55 μm, 60 μm, 65 μm, or a range consisting of any two of the above values.

[0244] When the thickness of the positive electrode film layer on one side is within the above range, the thickness of the positive electrode film layer is thinner, so that the transmission path of lithium ions is shorter, which is beneficial to improving the fast charging performance of the battery cell.

[0245] In the embodiment of the present application, the thickness of the single-sided positive electrode film layer has a well-known meaning in the art and can be detected using equipment and methods well-known in the art, for example, the thickness detection method of the negative electrode film layer can be used for detection.

[0246] The electrode assembly of the embodiment of the present application may be a wound electrode assembly or a laminated electrode assembly, and may be optionally a laminated electrode assembly.

[0247] When the electrode assembly is a wound structure, the positive electrode sheet and the negative electrode sheet are wound in the same direction.

[0248] In the case where the electrode assembly is a laminated structure, there are multiple positive electrode sheets and multiple negative electrode sheets, and the multiple positive electrode sheets and the multiple negative electrode sheets are stacked along the thickness direction of the battery cell.

[0249] In some embodiments, the dimension of the positive electrode film layer along the length of the battery cell is 200 mm to 650 mm, such as 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, or a range consisting of any two of the foregoing values. For example, in the case of a laminated electrode assembly, the dimension of the positive electrode film layer along the length of the battery cell is 200 mm to 650 mm. The dimension of the positive electrode film layer along the length of the battery cell can be understood as the length of the positive electrode film layer, i.e., the length of the positive electrode film layer is 200 mm to 650 mm.

[0250] When the size of the positive electrode film layer along the length direction of the battery cell is within the above range, the coating amount of the positive electrode film layer is relatively large, which is beneficial to improving the energy density of the battery cell; and the electron transmission path will not be too long, which is beneficial to improving the fast charging capability of the battery cell.

[0251] The viscosity of carboxylic acid ester solvents is relatively low, and the mass content of carboxylic acid ester solvents is 8% to 60%. They can quickly soak the electrode in the length direction, making the reaction degree of the electrode more consistent in the length direction. When the active ions migrate to the negative electrode, lithium plating and other problems are less likely to occur, which is beneficial to improving the reliability of the battery cell.

[0252] In an embodiment of the present application, the lithium-containing phosphate with an olivine structure may be phosphate particles, or a material obtained by coating and modifying the phosphate particles. For example, the lithium-containing phosphate with an olivine structure includes phosphate particles and a positive electrode coating layer, the positive electrode coating layer is coated on at least a portion of the surface of the phosphate particles, and the positive electrode coating layer contains carbon elements.

[0253] By coating the surface of the positive electrode coating layer, the phosphate particles can enhance the conductivity of the lithium-containing phosphate with an olivine structure, which is beneficial to the migration rate of lithium ions, improves the fast charging capability of the battery, reduces the heat generation of the battery cell, and improves the high-temperature cycle performance of the battery cell.

[0254] Examples of phosphate particles 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. These materials have excellent cycle stability and can improve the cycle performance of battery cells.

[0255] In some embodiments, the lithium-containing phosphate comprises a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 A compound, 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 Cl, C, N and P; and Y includes at least one of O and F.

[0256] Phosphate particles have excellent cycle stability, which is beneficial to improving the cycle performance of battery cells.

[0257] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The battery cells are accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cells is different when discharged to different states. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiment of the present application, the molar content of oxygen O is only a theoretical state value. Lattice oxygen release will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate. The above situations are all within the scope of protection of the present application.

[0258] In some embodiments, the mass content of carbon in the olivine-structured lithium-containing phosphate is 0.8% to 2.3%. For example, the mass content of carbon in the olivine-structured lithium-containing phosphate is 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.3%, or a range consisting of any two of the foregoing values.

[0259] The carbon element is mainly present in the positive electrode coating 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 conducive to effective contact between the electrolyte and phosphate particles, and conducive to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, it can significantly improve the conductivity of the olivine-structured lithium-containing phosphate, which is beneficial to improving the ionic conductivity and electronic conductivity of the olivine-structured lithium-containing phosphate, and can improve the rapid charging capability of the battery cell at high energy density.

[0260] In some embodiments, the positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

[0261] In some embodiments, the positive electrode coating layer includes a general formula of Li 3-d1 Fe 2-d1 M3 d1 (PO m1 ) n1 A compound, wherein 0≤d1≤1, 3≤m1≤5, 2≤n1≤4, and M3 includes one or more of Ti, Zr, Hf, Ge, and Sn.

[0262] 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.

[0263] 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.

[0264] 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.

[0265] 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.

[0266] 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.

[0267] In the embodiments of this application, the element content in the positive electrode active material has a meaning well known in the art and can be measured using equipment and methods well known in the art. For example, in accordance with EPA 6010D-2014, it can be measured by inductively coupled plasma atomic emission spectrometry (ICP-OES, Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned with DMC, dried, and calcined at high temperature to remove impurities. Then, 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. The sample is then placed on a plate at 180°C for 30 minutes. After digestion on the plate, the volume is adjusted to 100ml, and quantitative analysis is performed using a standard curve method.

[0268] In some embodiments, the powder compaction density of the positive electrode active material at 30,000 N is 2.43 g / cm 3 Up to 2.85g / cm 3 .

[0269] For example, the powder compaction density of the positive electrode active material at 30000N is 2.43g / cm 3 , 2.47g / cm 3 , 2.48g / cm 3 , 2.49g / cm 3 , 2.5g / cm 3 , 2.51g / cm 3 , 2.55g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.72g / cm 3 , 2.75g / cm 3 , 2.78g / cm 3 , 2.80g / cm 3 , 2.85g / cm 3 Or a range consisting of any two of the above values.

[0270] When the powder compaction density of the positive electrode active material at 30,000N is within the above range, the energy density of the battery cell can be improved. Moreover, since the positive electrode active material of the positive electrode film layer can be stacked more densely and the contact resistance between particles is smaller, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation and improving the high-temperature cycle performance and fast charging performance of the battery cell at high energy density.

[0271] In the embodiment of the present application, the powder compaction density of the material is a well-known meaning in the art and can be tested using methods and equipment known in the art. For example, a certain amount of positive electrode active material is taken as a sample and added to a UTM7305 electronic pressure testing machine with a bottom area of ​​1.327 cm 2 The mold was pressurized to 3000 kg (equivalent to 30000 N), maintained for 30 seconds, then released and maintained for 10 seconds, and then the powder compaction density of the positive electrode active material under a force of 30000 N was recorded and calculated.

[0272] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 0% state of charge SOC is 2.46 g / cm 3 to 2.80g / cm 3 For example, when the battery cell is at 0% state of charge (SOC), the compaction density of the positive electrode film is 2.46 g / cm 3 , 2.50g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.56g / cm 3 , 2.57g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.75g / cm 3 , 2.80g / cm 3 Or a range consisting of any two of the above values.

[0273] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the positive electrode active material of the positive electrode film layer is stacked more densely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation under fast charging and improving the high-temperature cycle performance and fast charging performance of the battery cell under high energy density.

[0274] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 350mg / 1540.25mm 2, such as 200mg / 1540.25mm², 210mg / 1540.25mm², 220mg / 1540.25mm², 230mg / 1540.25mm², 240mg / 1540.25mm², 250mg / 1540.25mm², 260mg / 1540.25mm², 270mg / 1540.25mm², 280mg / 1540.25mm², 290mg / 1540.25mm², 300mg / 1540.25mm², 310mg / 1540.25mm², 320mg / 1540.25mm², 330mg / 1540.25mm², 340mg / 1540.25mm², 350mg / 1540.25mm² or a range consisting of any two of the above values.

[0275] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, thereby improving the high-temperature cycle performance and fast charging performance of the battery cell at high energy density.

[0276] In the embodiments of the present application, the compaction density of the positive electrode film layer of a battery cell at 0% state of charge (SOC) can be tested using the following method: The positive electrode sheet of the battery cell at 0% state of charge (SOC) is disassembled and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first) is punched into small discs with an area of ​​S1. The discs are weighed and recorded as M1, and their thickness H1 is measured. The positive electrode film layer of the weighed positive electrode sheet is then wiped off, and the weight of the positive current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (weight of the positive electrode sheet M1 - weight of the positive current collector M0) / S1. The thickness of the positive electrode film layer = thickness of the positive electrode sheet H1 - thickness of the positive current collector H0. The compaction density of the positive electrode film layer = single-sided coating weight of the positive electrode film layer / thickness of the positive electrode film layer.

[0277] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application embodiment does not particularly limit the type of positive electrode conductive agent. For example, the positive 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, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode film layer.

[0278] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and at least one of a fluorine-containing acrylic resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0279] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0280] The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0281] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0282] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer, which is located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode sheet, reduce the heat generated by the positive electrode sheet, and thus reduce the heat generated by the battery cell.

[0283] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. For example, the thickness of the positive electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a range consisting of any two of the above values.

[0284] 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 improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0285] In the embodiment of the present application, the thickness of the positive electrode conductive layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, for example, performing a tomographic scan on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0286] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0287] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Exemplarily, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or a range consisting of any two of the above values.

[0288] Illustratively, 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 heat generation in the battery cell.

[0289] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%, illustratively, 50%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0290] Illustratively, the positive electrode binder of the positive conductive layer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorine-containing acrylate resin. The positive electrode binder of the positive conductive layer can improve the bonding performance between the positive electrode current collector and the positive electrode film layer, thereby improving the structural stability of the positive electrode sheet.

[0291] [Isolation film]

[0292] In the embodiment of the present application, the isolation film is arranged between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet from the negative electrode sheet.

[0293] In the embodiment of the present application, the isolation membrane includes a base membrane with a porous structure.

[0294] 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.

[0295] Optionally, the polyolefin includes at least one of polyethylene, polypropylene and polyvinylidene fluoride.

[0296] 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.

[0297] In the embodiment of the present application, when the porosity of the base film is within the above range, the migration ability of lithium ions in the isolation membrane can be enhanced, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation and improving the fast charging performance and high-temperature cycle performance of the battery cell at high energy density.

[0298] 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.

[0299] In some embodiments, the base film has a thickness of 4 μm to 12 μm, optionally 6 μm to 9 μm. For example, the base film has a thickness of 4 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range consisting of any two of the above values.

[0300] 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 at high energy density.

[0301] 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.

[0302] 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, the first functional layer includes first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer includes composite particles, the composite particles include second inorganic particles and multiple 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.

[0303] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the isolation film.

[0304] Optionally, the first functional layer may include a binder, optionally including at least one of a fluorine-containing binder or a polyacrylic binder, such as polyvinylidene fluoride.

[0305] Optionally, 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. The first inorganic particles can improve the heat resistance of the first functional layer.

[0306] Optionally, the average particle size of the first inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, or 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 consisting 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.

[0307] In the embodiments of the present application, the thickness of the base film has a meaning well known in the art, and can be tested using the meanings and equipment well known in the art. For example, a newly prepared isolation membrane can be taken as a sample, or a battery cell that has been discharged (discharged to the lower cut-off voltage so that the battery's charged state is approximately 0% SOC) can be reversely disassembled, and the isolation membrane can be obtained from the battery cell. The isolation membrane is dried and used as a sample, and the isolation membrane is cut 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 isolation membrane and its various layers.

[0308] The non-fluorinated polymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluorinated polymer particles include an acrylic copolymer. Optionally, the acrylic copolymer includes an acrylate-acrylonitrile-acrylamide-propylene copolymer. Acrylic copolymers have excellent bonding properties and high bonding 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.

[0309] The second inorganic particles in the composite particles make it difficult for the non-fluoropolymer particles to adhere to each other due to the high temperature treatment during the granulation process, so that the composite particles have pores, which is conducive to the transmission of lithium ions and improves the ion conductivity of the separator. The second inorganic particles can also increase the compression modulus of the composite particles. During the charge and discharge process, the composite particles are not easily deformed, making the structure of the separator more stable, which can improve the dynamic performance of the battery cell and improve the fast charging performance. Optionally, compared to the first functional layer, the second functional layer is arranged close to the negative electrode sheet. Since the composite particles are not easily deformed, the separator basically does not cause side effects such as extrusion on the negative electrode sheet, which stabilizes the dynamic performance of the negative electrode sheet. Accordingly, the first functional layer is arranged close to the positive electrode sheet.

[0310] 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. These second inorganic particles can enhance the heat resistance of the second functional layer and can form composite particles with non-fluoropolymers to further improve the cycle stability and dynamic performance of the separator, thereby improving the cycle performance and fast charging performance of the battery cell.

[0311] The average particle size of the second 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 consisting 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.

[0312] In the embodiment of the present application, the average particle size of the second inorganic particles has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, after obtaining the isolation film and drying the isolation film as a sample, the isolation film is cut with 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 isolation film. The particle sizes of multiple, for example, 50, second inorganic particles are measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0313] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0314] Figure 1 and Figure 2 A schematic structural diagram of a battery cell is shown.

[0315] In some embodiments, the battery cell 7 may include a housing 20 .

[0316] The housing 20 can have a variety of shapes, such as a cylinder, a rectangular parallelepiped, etc. The shape of the housing 20 can be determined based on the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, the housing 20 can be a cylindrical structure. If the electrode assembly 10 has a rectangular parallelepiped structure, the housing 20 can be a rectangular parallelepiped structure. Alternatively, the electrode assembly 10 has a rectangular parallelepiped structure.

[0317] The housing 20 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the present embodiment does not impose any particular restrictions on this. Optionally, the inner wall of the housing 20 may further include an insulating layer, which can separate the housing 20 from the electrode assembly 10. The material of the insulating layer can be selected from materials commonly used in the art and is not particularly limited here.

[0318] There may be one or more electrode assemblies 10 housed in the housing 20 .

[0319] In some embodiments, the housing 20 includes a shell 21 and an end cap 22 . The shell 21 has an opening, and the end cap 22 covers the opening. The shell 21 accommodates the electrode assembly 10 and the electrolyte.

[0320] In some embodiments, the housing 21 is made of steel, which has high mechanical strength and is not easily deformed, thereby improving the reliability and cycle performance of the battery cells. Optionally, steel accounts for the largest proportion of the housing 21 by mass.

[0321] Optionally, the thickness of the shell 21 is 0.1mm to 0.5mm, and optionally 0.2mm to 0.35mm. For example, the thickness of the shell 21 is 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, or a range consisting of any two of the above values. When the thickness of the shell 21 is within the above range, the mechanical strength of the shell 21 is high, which can improve the reliability and cycle performance of the battery cell 7. In addition, the shell 21 occupies less space, and the internal space of the shell 21 is more, which is conducive to improving the energy density of the battery cell 7.

[0322] Next, the electrode assembly 10 is described as a laminated structure.

[0323] like Figure 2 and Figure 3 As shown, the electrode assembly 10 includes a main body 14, a positive electrode tab 111, and a negative electrode tab 121. The positive electrode tab 111 and the negative electrode tab 121 protrude from the main body 14. The positive electrode tab 111 and the negative electrode tab 121 are used to draw current from the main body 14.

[0324] The portion of the positive electrode sheet 11 that is not coated with the active material layer is the positive electrode tab 111 , and the active material coated on the positive electrode current collecting portion 112 of the positive electrode sheet 11 constitutes the positive electrode film layer 113 . The positive electrode film layer 113 and the positive electrode current collecting portion 112 coated with the active material are part of the main body 14 .

[0325] The portion of the negative electrode sheet 12 not coated with the active material layer is the negative electrode tab 121 , and the active material coated on the negative electrode current collecting portion 122 of the negative electrode sheet 12 constitutes the negative electrode film layer 123 . The negative electrode film layer 123 and the negative electrode current collecting portion 122 coated with the active material are part of the main body 14 .

[0326] The main body 14 may further include a separator 13 , which is located between the positive electrode sheet 11 and the negative electrode sheet 12 .

[0327] The positive electrode tab 111 and the negative electrode tab 121 may extend from the same side of the main body 14 , or may extend from opposite sides thereof.

[0328] In some embodiments, the positive electrode tab 111 is connected to at least one side of the positive current collecting portion 112 along the length direction Z of the battery cell 7 , and the negative electrode tab 121 is connected to at least one side of the negative current collecting portion 122 along the length direction Z of the battery cell.

[0329] like Figure 4 As shown, for example, the positive electrode tab 111 is connected to one side of the positive electrode current collecting portion 112 along the length direction Z of the battery cell 7 .

[0330] like Figure 5 As shown, for example, the positive electrode tabs 111 are connected to both sides of the positive electrode current collecting portion 112 along the longitudinal direction Z of the battery cell 7 .

[0331] like Figure 6 As shown, for example, the negative electrode tab 121 is connected to one side of the negative electrode current collecting portion 122 along the longitudinal direction Z of the battery cell 7 .

[0332] like Figure 7 As shown, for example, the negative electrode tabs 121 are connected to both sides of the negative electrode current collecting portion 122 along the longitudinal direction Z of the battery cell 7 .

[0333] like Figure 8 As shown, in some embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode collecting portion 112 along the length direction Z, and the negative electrode tab 121 is connected to at least one side of the negative electrode collecting portion 122 along the length direction Z. Along the length direction Z of the battery cell 7, the size of the negative electrode film layer 123 is larger than the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH1; along the width direction Y of the battery cell 7, the size of the negative electrode film layer 123 is larger than the size of the positive electrode film layer 113, and the size difference between the negative electrode film layer 123 and the positive electrode film layer 113 is OH2, and OH1 is larger than OH2.

[0334] The negative electrode tab 121 is located on at least one side of the negative electrode current collecting portion 122 along the length direction Z. The current density in the connection area between the negative electrode tab 121 and the negative electrode current collecting portion 122 increases sharply, and lithium deposition and other problems are more likely to occur in this area. In the embodiment of the present application, OH1 is set to be greater than OH2, so that the ability of the area near the negative electrode film layer 123 to receive lithium ions in the length direction Z is stronger, especially the ability of the area near the negative electrode tab 121 of the negative electrode film layer 123 to receive lithium ions, thereby reducing the risk of lithium deposition and improving the reliability of the battery cell 7.

[0335] Exemplarily, OH1 is 1.0 mm to 4.0 mm, such as 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm, 3.5 mm, 4.0 mm, or a range consisting 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, each side extending beyond OH1 / 2, that is, half the size of OH1. Figure 8 OH1 / 2 is shown in FIG.

[0336] Exemplarily, OH2 is 1.0 mm to 3.0 mm, such as 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm, or a range consisting of any two of the above values. In the width direction Y, both sides of the negative electrode film layer 123 extend beyond the positive electrode film layer 113, each side extending beyond OH2 / 2, i.e., half the size of OH2. Figure 8 OH2 / 2 is shown in FIG.

[0337] In other embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collecting portion 112 along the width direction Y, and the negative electrode tab 121 is connected to at least one side of the negative electrode current collecting portion 122 along the width direction Y.

[0338] Optionally, the number of the positive electrode tabs 111 located on the same side of the main body 14 is at least one, and optionally at least two. At least two positive electrode tabs 111 can increase the current capacity of the positive electrode tab 111 .

[0339] Optionally, the number of the negative electrode tabs 121 located on the same side of the main body 14 is at least one, and optionally at least two. At least two negative electrode tabs 121 can increase the current capacity of the negative electrode tabs 121 .

[0340] In some embodiments, the battery cell 7 further includes a positive terminal 31 , which is disposed on the outer shell 20 , and may be disposed on the housing 21 or the end cover 22 .

[0341] 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 may be connected via an adapter or may not be connected via an adapter. Optionally, the positive terminal 31 and the positive electrode tab 111 are connected without an adapter, that is, the positive terminal 31 and the positive electrode tab 111 are directly welded, which can reduce the resistance at the connection point and help reduce the overall internal resistance of the battery cell 7.

[0342] In some embodiments, the battery cell 7 further includes a negative terminal 32 , which is disposed on the outer shell 20 , and may be disposed on the housing 21 or the end cover 22 .

[0343] 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 may be connected via an adapter or may not be connected via an adapter. Optionally, the negative terminal 32 and the negative electrode tab 121 are connected without an adapter, that is, the negative terminal 32 and the negative electrode tab 121 are directly welded, which can reduce the resistance at the connection and help reduce the overall internal resistance of the battery cell 7.

[0344] Optionally, the number of the positive terminals 31 located on the same side of the main body 14 is at least one, and optionally at least two. At least two positive terminals 31 can increase the current capacity of the positive terminal 31 .

[0345] Alternatively, the flow area of ​​the single-side positive terminal 31 is 150 mm 2 Up to 1000mm 2 , 200mm is optional 2 Up to 1000mm 2 The flow area of ​​a single-sided positive terminal 31 refers to the sum of the flow areas of all positive terminals 31 located on the same side of the main body 14. The flow area of ​​a positive terminal 31 can be understood as the cross-sectional area of ​​the positive terminal 31, with this cross-section perpendicular to the thickness of the end cap 22. When the flow area of ​​a single-sided positive terminal 31 meets the above range, the flow capacity is strong, internal resistance can be reduced, and heat generation can be reduced, which is beneficial for improving the fast charging performance and high-temperature cycling performance of the battery cell 7 at high energy density.

[0346] For example, the flow area of ​​the single-sided positive terminal 31 can be 150 mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 、650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , 850mm 2 , 900mm 2 , 950mm 2 , 1000mm 2 Or a range consisting of any two of the above values.

[0347] Optionally, the number of the negative terminals 32 located on the same side of the main body 14 is at least one, and optionally at least two. At least two negative terminals 32 can increase the current capacity of the negative terminal 32 .

[0348] Alternatively, the flow area of ​​the single-side negative terminal 32 is 150 mm 2 Up to 1000mm2 , 200mm is optional 2 Up to 1000mm 2 The flow area of ​​a single-sided negative terminal 32 refers to the sum of the flow areas of all negative terminals 32 located on the same side of the main body 14. The flow area of ​​a negative terminal 32 can be understood as the cross-sectional area of ​​the negative terminal 32, with this cross-section perpendicular to the thickness of the end cap 22. When the flow area of ​​a single-sided negative terminal 32 meets the above range, the flow capacity is strong, internal resistance is reduced, and heat generation is reduced, which is beneficial for improving the fast charging performance and high-temperature cycling performance of the battery cell 7 at high energy density.

[0349] For example, the flow area of ​​the single-side negative terminal 32 may be 150 mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 450mm 2 , 500mm 2 , 550mm 2 , 600mm 2 、650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , 850mm 2 , 900mm 2 , 950mm 2 , 1000mm 2 Or a range consisting of any two of the above values.

[0350] like Figure 9 As shown, the battery cells 7 of the embodiment of the present application can be assembled into a battery module 6. The number of battery cells 7 contained 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.

[0351] If there are multiple battery cells 7, they can be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections within the battery cells 7. Multiple battery cells 7 can be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 7 is housed within the housing of the battery module 6. Alternatively, multiple battery cells 7 can be first connected in series, in parallel, or in a hybrid connection to form a battery module 6, and then the battery modules 6 are further connected in series, in parallel, or in a hybrid connection to form a single unit and housed within the housing. Optionally, the battery module 6 may further include a housing portion having a storage space, and the multiple battery cells 7 are housed within the storage space.

[0352] The multiple battery cells 7 of the battery module 6 can be electrically connected via a busbar to achieve parallel, series, or mixed connection of the multiple battery cells 7 of the battery module 6. There can be one or more busbars, each of which is used to electrically connect at least two battery cells 7.

[0353] like Figure 10 As shown, in some embodiments, the battery modules 6 can be assembled into a battery pack 2. The number of battery modules 6 in the battery pack 2 can be adjusted based on the application and capacity of the battery pack. The battery device herein can be a battery module 6, a battery pack 2, or a battery cell 7. A battery cell 7 is the smallest unit that constitutes a battery device.

[0354] The battery pack 2 may include a housing 5 and a plurality of battery modules 6 disposed within the housing 5. The housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 defines a receiving space 5c. The first housing portion 5a covers the second housing portion 5b and forms an enclosed space for receiving the battery modules 6. The plurality of battery modules 6 may be arranged within the housing 5 in any manner.

[0355] The first housing portion 5a and the second housing portion 5b overlap each other, and together they define a storage space 5c for accommodating the battery cells. The second housing portion 5b can be a hollow structure with one end open. The first housing portion 5a is a plate-like structure, and the first housing portion 5a overlaps the open side of the second housing portion 5b to form the housing 5 with the storage space 5c. Alternatively, both the first housing portion 5a and the second housing portion 5b can be hollow structures with one end open, and the open side of the first housing portion 5a overlaps the open side of the second housing portion 5b to form the housing 5 with the storage space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0356] In order to improve the sealing performance after the first box body portion 5a and the second box body portion 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body portion 5a and the second box body portion 5b.

[0357] Assuming that the first box portion 5a covers the top of the second box portion 5b, the first box portion 5a can also be called an upper box cover, and the second box portion 5b can also be called a lower box.

[0358] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 0% state of charge (SOC) to 100% state of charge (SOC), the temperature of the external environment of the battery pack 2 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 10% state of charge (SOC) to 80% state of charge (SOC), the temperature of the external environment of the battery pack 2 is 30° C.

[0360] In some embodiments, the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge includes multiple charging steps, and 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 a range consisting of any two of the above values.

[0361] The battery pack 2 or any battery cell constituting the battery pack 2 includes multiple charging steps from a 10% state of charge to a 40% state of charge. 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 a value within a range consisting of any two of the above values.

[0362] For example, the charging step of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be performed as follows:

[0363] Charge from 10% SOC to 15% SOC at 5.0C constant current.

[0364] Charge from 15% SOC to 20% SOC at 5.0C constant current.

[0365] Charge from 20% SOC to 25% SOC at 5.0C constant current.

[0366] Charge from 25% SOC to 30% SOC at 5.0C constant current.

[0367] Charge from 30% SOC to 35% SOC at 5.0C constant current.

[0368] Charge from 35% SOC to 40% SOC at 5.0C constant current.

[0369] Charge from 40% SOC to 45% SOC at 4.6C constant current.

[0370] Charge from 45% SOC to 50% SOC at 4.3C constant current.

[0371] Charge from 50% SOC to 55% SOC at 4.0C constant current.

[0372] Charge from 55% SOC to 60% SOC at 3.7C constant current.

[0373] Charge from 60% SOC to 65% SOC at 3.4C constant current.

[0374] Charge from 65% SOC to 70% SOC at 3.1C constant current.

[0375] Charge from 70% SOC to 75% SOC at 2.9C constant current.

[0376] Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0377] 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 minutes to 15 minutes, and the temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, for example, 30° C. Exemplarily, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 15 minutes, 14 minutes, 13 minutes, 12 minutes, 11 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5.5 minutes, 5 minutes, or a range consisting of any two of the above values.

[0378] Electrical devices

[0379] According to a second aspect of the embodiments of the present application, there is provided an electrical device, which includes a battery device according to the embodiments of the present application, such as a battery cell, a battery module, or a battery pack. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, 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 vehicle, or an extended-range vehicle. The spacecraft includes an airplane, a rocket, a space shuttle, and a spacecraft. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator, and an electric planer. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0380] The electrical device can select battery cells, battery modules or battery packs according to its usage requirements.

[0381] Figure 11 1 is a schematic diagram of an exemplary electric device 1. The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 1, a battery pack or battery module may be used.

[0382] A battery pack 2 is disposed within the electrical device 1. The battery pack 2 can be located at the bottom, top, or rear of the electrical device 1. The battery pack 2 can be used to power the electrical device 1. For example, the battery pack 2 can serve as the operating power source of the electrical device 1 or 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.

[0383] The electric device 1 may further include a controller 3 and a motor 4 . The controller 3 is used to control the battery pack 2 to supply power to the motor 4 , for example, to meet the power requirements of the electric device 1 during startup, navigation, and driving.

[0384] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0385] The following charging methods can be selected for the charging process of the electrical device:

[0386] Charge from 10% SOC to 15% SOC at 5.0C constant current.

[0387] Charge from 15% SOC to 20% SOC at 5.0C constant current.

[0388] Charge from 20% SOC to 25% SOC at 5.0C constant current.

[0389] Charge from 25% SOC to 30% SOC at 5.0C constant current.

[0390] Charge from 30% SOC to 35% SOC at 5.0C constant current.

[0391] Charge from 35% SOC to 40% SOC at 5.0C constant current.

[0392] Charge from 40% SOC to 45% SOC at 4.6C constant current.

[0393] Charge from 45% SOC to 50% SOC at 4.3C constant current.

[0394] Charge from 50% SOC to 55% SOC at 4.0C constant current.

[0395] Charge from 55% SOC to 60% SOC at 3.7C constant current.

[0396] Charge from 60% SOC to 65% SOC at 3.4C constant current.

[0397] Charge from 65% SOC to 70% SOC at 3.1C constant current.

[0398] Charge from 70% SOC to 75% SOC at 2.9C constant current.

[0399] Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0400] In some embodiments, the charging time of the electrical device from 10% state of charge to 80% state of charge is 5 minutes to 15 minutes, 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 minutes, 14 minutes, 13 minutes, 12 minutes, 11 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5.5 minutes, 5 minutes, or a range consisting of any two of the above values.

[0401] Example

[0402] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0403] Example 1

[0404] 1. Preparation of positive electrode sheet

[0405] The positive electrode sheet includes a positive current collecting part, a positive electrode film layer and a positive electrode conductive layer. The positive electrode film layer is arranged on both sides of the positive current collecting part, and the positive electrode conductive layer is located between the positive current collecting part and the positive electrode film layer. The positive electrode current collecting part is aluminum foil.

[0406] The positive electrode conductive layer on the positive electrode current collecting part is a film layer formed by evenly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride PVDF and the solvent N-methylpyrrolidone NMP, and then coating it on the surface of the positive electrode current collecting part and drying it. The thickness is 1 μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0407] The positive electrode film layer includes a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) uniformly coated on the surface of the positive electrode conductive layer, and a film layer formed after drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride PVDF, and a conductive agent acetylene black in a weight ratio of 97:2:1.

[0408] The positive electrode active material includes lithium iron phosphate particles and a positive electrode coating layer. The positive electrode coating layer is coated on the surface of the lithium iron phosphate particles. The positive electrode coating layer includes lithium iron titanium phosphate Li2FeTi(PO4)3 and carbon. The mass content of carbon element is 1.12%.

[0409] The powder compaction density of the positive electrode active material at 30000N is 2.55g / cm 3 .

[0410] The single-sided coating weight of the positive electrode film is 263mg / 1540.25mm 2 .

[0411] The length of the positive electrode film layer is 610 mm and the width is 110 mm.

[0412] 2. Preparation of negative electrode sheet

[0413] The negative electrode plate includes a negative current collecting part, a negative electrode film layer and a negative electrode conductive layer. The negative electrode film layer is arranged on both sides of the negative current collecting part, and the negative electrode conductive layer is located between the negative current collecting part and the negative electrode film layer. The negative electrode current collecting part is copper foil.

[0414] The negative electrode conductive layer on the negative electrode current collecting part is a film layer formed by evenly mixing the negative electrode conductive agent superconducting carbon, the negative electrode binder styrene-butadiene rubber SBR, the thickener sodium carboxymethyl cellulose CMC-Na and the solvent water, and then coating it on the surface of the negative electrode current collecting part and drying it. The thickness is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0415] The negative electrode film layer includes a film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, drying, and cold pressing.

[0416] The negative electrode film layer comprises a negative electrode active material, a conductive agent, acetylene black, a negative electrode binder, and a thickener, sodium carboxymethyl cellulose, in a mass ratio of 96.5:0.5:2:1. The graphite particles comprise artificial graphite and a negative electrode coating layer, which is coated on the surface of the artificial graphite. The carbon content of the negative electrode coating layer is 3.5% by mass. The Dv50 of the graphite particles is 11.3μm.

[0417] The powder compaction density of the negative electrode active material at 20000N is 1.6g / cm 3 .

[0418] The single-sided coating weight of the negative electrode film is 120mg / 1540.25mm 2 .

[0419] The negative electrode film is 4mm longer than the positive electrode film, and 3mm wider than the positive electrode film. After being fabricated into a battery cell, the cell was disassembled and tested at 0% SOC, revealing a negative electrode film thickness of 55μm.

[0420] 3. Isolation film

[0421] The isolation film includes a base film and functional layers arranged on both sides of the base film. The base film includes a 7μm polyethylene film layer with a porosity of 42%;

[0422] The functional layer includes a first functional layer and a second functional layer. The first functional layer includes aluminum oxide particles and a binder, polyvinylidene fluoride. The first functional layer is a film layer formed by applying a first slurry on one side of the base film. The thickness of the first functional layer is 1 μm, and the average particle size of the aluminum oxide particles is 10 nm. The first slurry includes aluminum oxide particles and a binder, polyvinylidene fluoride.

[0423] 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.

[0424] 4. Preparation of electrolyte

[0425] The electrolyte includes an organic solvent, lithium salt and additives.

[0426] After mixing the components of the organic solvents, lithium salt and additives are added to prepare an electrolyte solution.

[0427] The organic solvent includes a chain carboxylic acid ester solvent (ethyl acetate) with a mass content of 39%, ethylene carbonate EC of 27.3% and dimethyl carbonate of 11.7%. The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0428] The mass content of the additive is 6%, and the additive includes vinylene carbonate VC, 1,3-propane sultone, fluoroethylene carbonate FEC, vinyl sulfite ES and lithium difluorooxalatoborate LiDFOB in a mass ratio of 4:0.2:0.8:0.5:0.5.

[0429] The lithium salt includes lithium hexafluorophosphate LiPF6 with a mass content of 16%, and the mass content of the lithium salt is calculated based on the mass of the electrolyte.

[0430] 5. Preparation of battery cells

[0431] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, to obtain a laminated electrode assembly. The electrode assembly is placed in a shell, on which a positive terminal and a negative terminal are provided. After baking, the electrolyte is injected, and the battery cell is obtained through processes such as vacuum packaging, standing, formation, aging, storage, and shaping.

[0432] The battery cell injection coefficient is 2.9g / Ah.

[0433] The compaction density of the positive electrode film layer of the battery cell at 0% SOC is 2.70g / cm 3 The compaction density of the negative electrode film at 0% SOC is 1.41g / cm 3 .

[0434] The outer shell is an aluminum shell with a rectangular parallelepiped structure, and the shell thickness corresponding to the surface with the largest area of ​​the rectangular parallelepiped structure is 0.5 mm.

[0435] Among them, the flow area of ​​the positive terminal on the same side is 640mm 2, the negative terminal on the same side has a flow area of ​​640mm 2 .

[0436] Example 2-2 to Example 2-11

[0437] Battery cells were prepared using a method similar to that of Example 1. Unlike Example 1, the composition and content of the first additive were adjusted. The mass content of dimethyl carbonate was adjusted accordingly with the adjustment of the first additive. For example, if the mass content of the first additive increased by 1% compared to Example 1, the mass content of dimethyl carbonate decreased by 1% compared to Example 1. The details are shown in Table 1.

[0438] Example 3

[0439] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the material of the ethylene carbonate derivative was adjusted, as shown in Table 1.

[0440] Comparative Example 1-1 to Comparative Example 1-3

[0441] Battery cells were prepared using a method similar to that of Example 1. Unlike Example 1, the composition and content of the first additive were adjusted. The mass content of dimethyl carbonate was adjusted accordingly with the adjustment of the first additive. For example, if the mass content of the first additive increased by 1% compared to Example 1, the mass content of dimethyl carbonate decreased by 1% compared to Example 1. The details are shown in Table 1.

[0442] Performance Testing

[0443] 1. DC internal resistance DCR test of battery cells

[0444] You can refer to the method in GB / T 31467 "Performance test specification for high-power lithium-ion power batteries for HEV".

[0445] For example, at room temperature, charge the battery cell to 3.65V at a constant current of 0.33C, then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 30 minutes, and discharge it to 2.0V at a constant current of 0.33C. Record the discharge capacity A0 at this time in Ah, and then charge it for 0.5A0Ah at a constant current of 0.33C to adjust the SOC to 50%.

[0446] After the battery cell is placed at -20 ℃ for 2 hours, it is discharged at a constant current of 1C for 10 seconds and ∆U is recorded. 放电 , ∆I 放电 , the discharge DCR data of lithium-ion batteries is calculated by the following formula, R 放电 =∆U 放电 / ∆I 放电 ,

[0447] Where ∆U 放电 Indicates the voltage change within 10s after the discharge starts, ∆I 放电 Indicates the current value within 10 seconds after the start of discharge.

[0448] 2. Number of cycles of battery cells until SOH reaches 70%

[0449] At 60°C, charge the battery cell at a constant current of 0.8C to a charge cutoff voltage of 3.6V. Then, charge it at a constant current of 0.1C to a charge cutoff voltage of 3.65V and let it rest for 30 minutes. Discharge it at a constant current of 1C to 2.83V and let it rest for 30 minutes. This constitutes one charge-discharge cycle. Repeat these charge-discharge cycles until the cycle capacity retention (i.e., Cn / C0 × 100%) reaches 70%. Record the number of cycles. A higher number of cycles indicates better cycling performance of the battery cell.

[0450] 3. Test of lithium deposition of battery cells

[0451] At 30°C, the battery cells of each embodiment were cycled 200 times according to their respective charge and discharge strategies, and then fully charged to 100% SOC according to the corresponding charging strategy. The negative electrode sheets were disassembled and unfolded to observe the deterioration area (gray-white area). The deterioration area was measured. The deterioration degree was as follows:

[0452] No lithium deposition: lithium deposition area <0.05%.

[0453] Slight lithium deposition: lithium deposition area is less than 2% and greater than or equal to 0.05%.

[0454] Severe lithium deposition: lithium deposition area ≥2%.

[0455] The battery cells are charged, and the charging steps include the following steps:

[0456] Charge from 0% SOC to 5% SOC at 5.0C constant current;

[0457] Charge from 5% SOC to 10% SOC at 5.0C constant current;

[0458] Charge from 10% SOC to 15% SOC at 5.0C constant current;

[0459] Charge from 15% SOC to 20% SOC at 5.0C constant current;

[0460] Charge from 20% SOC to 25% SOC at 5.0C constant current;

[0461] Charge from 25% SOC to 30% SOC at 5.0C constant current;

[0462] Charge from 30% SOC to 35% SOC at 5.0C constant current;

[0463] Charge from 35% SOC to 40% SOC at 5.0C constant current;

[0464] Charge from 40% SOC to 45% SOC at 4.6C constant current;

[0465] Charge from 45% SOC to 50% SOC at 4.3C constant current;

[0466] Charge from 50% SOC to 55% SOC at 4.0C constant current;

[0467] Charge from 55% SOC to 60% SOC at 3.7C constant current;

[0468] Charge from 60% SOC to 65% SOC at 3.4C constant current;

[0469] Charge from 65% SOC to 70% SOC at 3.1C constant current;

[0470] Charge from 70% SOC to 75% SOC at 2.9C constant current;

[0471] Charge from 75% SOC to 80% SOC at 2.7C constant current;

[0472] Charge from 80% SOC to 85% SOC at 1.8C constant current;

[0473] Charge from 85% SOC to 90% SOC at 1.3C constant current;

[0474] Charge from 90% SOC to 95% SOC at 0.7C constant current;

[0475] Charge from 95% SOC to 98% SOC at 0.33C constant current;

[0476] Charge from 98% SOC to 100% SOC at 0.1C constant current.

[0477] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0478] The discharge strategy is as follows: discharge at a constant current of 0.33C to a cut-off voltage, for example, 2.0V.

[0479] When performing charge and discharge tests on battery cells, the battery cells can be assembled in a battery device, and the required charge and discharge strategies can be controlled by the battery management system for testing.

[0480] The test results are shown in Table 1.

[0481] Table 1

[0482]

[0483] In Table 1,

[0484] VC stands for vinylene carbonate;

[0485] PS stands for 1,3-propane sultone;

[0486] FEC stands for monofluoroethylene carbonate or fluoroethylene carbonate;

[0487] DFEC stands for bisfluoroethylene carbonate.

[0488] The amount of the first additive added to the electrolytes of Comparative Examples 1-1 and 1-3 is too low, for example, the amount of vinylene carbonate added is too low, or even the electrolytes of Comparative Examples 1-3 do not contain vinylene carbonate. Although the impedance of the SEI film on the negative electrode side is relatively low, due to the relatively poor protective effect of the SEI film, the carboxylic acid ester solvent is prone to side reactions with the negative electrode active material at high temperatures, worsening high-temperature cycling and possibly causing lithium precipitation.

[0489] The amount of the first additive added to the electrolyte of Comparative Example 1-2 is too high, for example, the amount of vinylene carbonate added is too high. Vinylene carbonate can form a dense SEI film of organic components on the negative electrode side, alleviating the side reaction between the carboxylate solvent and the negative electrode active material. However, due to the high impedance of the SEI film, it is not conducive to the rapid migration of lithium ions, making it impossible to quickly charge the battery cell.

[0490] The amount of the first additive added to the electrolyte of the embodiment of the present application is within an appropriate range, and its mass content is 3% to 10%. The reaction potential of the vinylene carbonate in the first additive and the carboxylate solvent is close, and there is a competitive reaction with the carboxylate solvent. The vinylene carbonate can participate in the formation of a dense SEI film on the negative electrode side, making it difficult for the carboxylate solvent to penetrate the SEI film to the graphite particles, thereby alleviating the side reaction between the carboxylate solvent and the graphite particles and reducing the gas production; and because the first additive is within an appropriate content, the membrane impedance formed on the negative electrode side is relatively small, which is beneficial to improving high-temperature cycle performance and reducing the risk of lithium plating.

[0491] In Example 2-2, the electrolyte components were tested and analyzed to obtain the data in Table 1. In this case, the battery cells had not yet undergone the formation process. After the electrolyte components were tested and analyzed, they were assembled into battery cells and then subjected to performance testing. It should be noted that in Example 2-2, the electrolyte of the unformed battery cells was used as a sample, and the mass of the electrolyte was taken as 100% to calculate the mass content of each component in the first additive.

[0492] In Example 2-1, the free electrolyte in the battery cell after the formation, aging, and storage processes was detected and analyzed to obtain the data in Table 1. The components of the fresh electrolyte of the battery cell are shown in Example 2-2. It can be seen from the data in Table 1 that after the formation and other processes, 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, thereby obtaining a SEI film with relatively low impedance, thereby improving the fast charging performance, high-temperature cycle performance, and reliability of the battery cell.

[0493] It should be noted that Example 2-1 uses the free electrolyte of the battery cell after treatment such as formation as a sample, and the mass content of each component in the first additive is calculated with the mass of the electrolyte being 100%.

[0494] By regulating the mass content of vinylene carbonate, 1,3-propane sultone, and fluoroethylene carbonate in the freshly prepared electrolyte, Examples 2-3 to 2-5 can obtain a SEI film with relatively low impedance, thereby improving the fast charging performance, high-temperature cycling performance, and reliability of the battery cell.

[0495] Examples 2-6, 2-7, and 2-11 control the mass content of 1,3-propane sultone. Increasing the mass content of 1,3-propane sultone optimizes the SEI film composition, improves the SEI film's protective properties, and contributes to improved high-temperature cycling performance. However, the SEI film's impedance also increases, potentially slightly reducing the battery's rapid charging performance. Therefore, the mass content of 1,3-propane sultone is between 0 and 0.5%, and can be optionally between 0.05 and 0.5%, to achieve both improved high-temperature cycling performance and rapid charging performance.

[0496] In Examples 1, 2-8, and 2-11, by regulating the mass content of fluoroethylene carbonate, increasing the mass content of fluoroethylene carbonate can optimize the composition of the SEI film, reduce the impedance of the SEI film, facilitate the rapid migration of lithium ions, and improve the rapid charging performance of the battery cell. However, at high temperatures, fluoroethylene carbonate has poor stability and easily decomposes to produce acid that damages the SEI film, deteriorating the protective effect of the negative electrode active material and possibly slightly worsening the high-temperature cycling performance. In view of this, the mass content of the ethylene carbonate derivative in the electrolyte is 0 to 3.5%, optionally 0.1% to 1.5%, and further optionally 0.5% to 1.5%, thereby improving both the high-temperature cycling performance and the rapid charging performance of the battery cell.

[0497] The use of ethylene carbonate derivatives made of different materials, such as fluoroethylene carbonate and difluoroethylene carbonate, can effectively improve the high-temperature cycle performance and fast charging performance of battery cells.

[0498] Example 4-1 and Example 4-2

[0499] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the components and mass contents of the carboxylate solvent and the carbonate solvent were adjusted.

[0500] In Example 4-1, the content of ethylene carbonate is 3%, the content of 1,3-propane sultone is 0.5%, the content of fluoroethylene carbonate FEC is 1.5%, and the mass content of the first additive is 5%.

[0501] In Example 4-2, the content of ethylene carbonate is 3%, the content of 1,3-propane sultone is 0.5%, the content of fluoroethylene carbonate FEC is 1.5%, and the mass content of the first additive is 5%.

[0502] The details are shown in Table 2.

[0503] Example 5

[0504] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the material of the carboxylate solvent and the mass content of the carbonate solvent were adjusted.

[0505] In Example 5, the content of ethylene carbonate is 6%, the content of 1,3-propane sultone is 0.5%, the content of fluoroethylene carbonate FEC is 1.5%, and the mass content of the first additive is 8.0%.

[0506] The details are shown in Table 2.

[0507] Example 6-1 to Example 6-3

[0508] Battery cells were prepared using a method similar to that of Example 1. Unlike Example 1, the composition and mass content of the second additive were adjusted. The mass content of dimethyl carbonate was adjusted accordingly with the additive. For example, if the mass content of the additive increased by 1% compared to Example 1, the mass content of dimethyl carbonate decreased by 1% compared to Example 1. The details are shown in Table 2.

[0509] Comparative Example 2-1 to Comparative Example 2-2

[0510] Battery cells were prepared using a method similar to that of Example 1. Unlike Example 1, the composition and mass content of the carboxylate and carbonate solvents were adjusted. The mass content of dimethyl carbonate was adjusted accordingly with the additives. For example, if the mass content of the additive increased by 1% compared to Example 1, the mass content of dimethyl carbonate decreased by 1%. The details are shown in Table 2.

[0511] The test results are shown in Table 2.

[0512] Table 2

[0513]

[0514] In Table 2, EA represents ethyl acetate; MA represents methyl acetate;

[0515] EC stands for ethylene carbonate; DMC stands for dimethyl carbonate;

[0516] ES stands for ethylene sulfite;

[0517] DTD stands for diethylene sulfate;

[0518] LiDFOB stands for lithium difluorooxalatoborate;

[0519] LiPO2F2 represents lithium difluorophosphate;

[0520] EC: 27.3, means that the mass content of EC is 27.3%.

[0521] The meanings of other examples are the same as explained above and will not be repeated here.

[0522] The mass content of the carboxylate solvent in the electrolyte of Comparative Example 2-1 is relatively low, which makes the viscosity of the electrolyte higher, the impedance higher, and is not conducive to the rapid infiltration of the electrode. The wettability of different parts of the electrode is different, resulting in different degrees of discharge of the electrode, which may cause local lithium deposition on the negative electrode side and deterioration of the cycle.

[0523] The mass content of the carboxylate solvent in the electrolyte of Comparative Example 2-2 is relatively high, which makes the viscosity of the electrolyte smaller and the impedance smaller, which is conducive to fast charging; however, at high temperatures, the side reaction between the carboxylate solvent and the negative electrode active material is more serious, which deteriorates the high-temperature cycle performance and may cause lithium lateral deposition at the negative electrode.

[0524] Due to the relatively low mass content of the carboxylate solvent in Example 4-1, the migration rate of lithium ions in the electrolyte is slow, resulting in a slight risk of lithium deposition at a constant current density. Increasing the mass content of the carboxylate solvent can reduce the viscosity of the electrolyte and increase the migration rate of lithium ions in the electrolyte. Furthermore, when combined with an appropriate amount of the first additive, it can mitigate side reactions, improve high-temperature cycling, and reduce the risk of lithium deposition.

[0525] Examples 4-1 and 4-2 of the present application can reduce the viscosity of the electrolyte and increase the migration rate of lithium ions in the electrolyte by adjusting the mass content of the carboxylic acid ester solvent within an appropriate range, for example, 8% to 60%; and when combined with an appropriate content of the first additive, they can alleviate side reactions, improve high-temperature cycles, and reduce the risk of lithium plating.

[0526] Carboxylate ester solvents made of various materials, such as ethyl acetate and methyl acetate, can improve both fast-charging performance and high-temperature cycling performance. For example, the carboxylate ester solvent in Example 5 includes methyl acetate, which, combined with a high content of the first additive, can reduce electrolyte viscosity while improving the SEI film formation, lowering the internal resistance of the battery cells and enhancing the fast-charging performance of the battery cells. Furthermore, because the SEI film effectively protects the negative electrode active material, it can mitigate side reactions and improve high-temperature cycling performance. However, due to the relatively high boiling point of ethyl acetate and its relatively good stability at high temperatures, Example 1 exhibits superior high-temperature cycling performance compared to Example 5.

[0527] In Examples 6-1 to 6-3, the use of second additives made of different materials can further optimize the components of the SEI film, reduce the internal resistance of the battery cell, and improve the fast charging performance and high-temperature cycle performance of the battery cell.

[0528] Example 7-1 and Example 7-2

[0529] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the thickness of the negative electrode film layer on one side was adjusted, as shown in Table 3.

[0530] Example 8-1 and Example 8-2

[0531] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size of the graphite particles in the negative electrode film layer was adjusted, as shown in Table 3.

[0532] Example 9

[0533] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the composition of the negative electrode active material of the negative electrode film layer was adjusted. The negative electrode active material also included silicon oxide, a silicon-based material. The mass content of silicon in the negative electrode film layer was 1.5%.

[0534] Comparative Example 3-1 and Comparative Example 3-2

[0535] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the thickness of the negative electrode film layer on one side was adjusted, as shown in Table 3.

[0536] Comparative Example 3-3 and Comparative Example 3-4

[0537] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size of the graphite particles in the negative electrode film layer was adjusted, as shown in Table 3.

[0538] The test results are shown in Table 3.

[0539] Table 3

[0540]

[0541] The thickness of the single-sided negative electrode film layer of Comparative Example 3-1 is relatively thin, and the lithium ion transmission path is shorter, which is beneficial to reducing the internal resistance of the battery cell and improving the fast charging performance; however, the energy density of the battery cell is low and may not meet the energy density requirements.

[0542] The thickness of the single-sided negative electrode film layer of Comparative Example 3-2 is relatively thick, and the energy density of the battery cell is relatively high, but it makes the lithium ion transmission path longer and the internal resistance of the battery cell higher, which is not conducive to fast charging and high-temperature cycling under high energy density.

[0543] The moderate thickness of the negative electrode film layers in Examples 1, 7-1, and 7-2 allows the battery cells to achieve both high energy density and a short lithium ion migration path, improving the rapid charging performance of the battery cells. Furthermore, the addition of appropriate amounts of the carboxylate solvent and the first additive effectively further improves the rapid charging performance and high-temperature cycling performance of the battery cells at high energy density. The energy density of Example 1 is 410Wh / L.

[0544] The volume average particle size of the graphite particles in Comparative Example 3-3 is relatively small, and the lithium ion transmission path in the solid phase is short, which is beneficial to improving the fast charging performance of the battery cell. However, the graphite particles have relatively more active surfaces, which aggravates the side reactions and worsens the high-temperature cycle.

[0545] The graphite particles in Comparative Examples 3-4 have a relatively large volume average particle size, relatively less active surface area, relatively fewer side reactions, and relatively excellent high-temperature cycle performance; however, the lithium ion transmission path in the solid phase is longer, which is not conducive to the fast charging performance of the battery cell.

[0546] The volume average particle size of the graphite particles in Example 8-1 and Example 8-2 is moderate, which can shorten the solid-phase transmission path of lithium ions while reducing the degree of side reactions, thereby improving the fast charging capability and high-temperature cycle performance of the battery cells.

[0547] The negative electrode film layer of Example 9 also includes silicon with a mass content of 1.5%. Silicon can effectively improve the energy density of the battery cell; however, due to the large volume expansion of silicon-based materials during the charging and discharging process, the side reactions on the negative electrode side are more than those in Example 1, and the high-temperature cycle is slightly deteriorated.

[0548] Under a preset high energy density, when the negative electrode film layer includes a silicon-based material, a relatively thin negative electrode film layer can be used, which can shorten the migration path of lithium ions and is conducive to improving the fast charging capability.

[0549] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A battery cell, characterized in that: It includes an electrode assembly and an electrolyte, wherein the electrode assembly includes a positive electrode sheet and a negative electrode sheet; The positive electrode plate includes a positive current collecting portion and a positive electrode film layer provided on at least one side of the positive current collecting portion, wherein the positive electrode film layer includes a lithium-containing phosphate having an olivine structure; The negative electrode plate includes a negative electrode current collecting portion and a negative electrode film layer provided on at least one side of the negative electrode current collecting portion, wherein the negative electrode film layer includes graphite particles; The electrolyte includes a carboxylic acid ester solvent and a first additive, in, The thickness of the negative electrode film layer on one side is 50 μm to 75 μm, and the volume average particle size of the graphite particles is 8.5 μm to 13.5 μm; Based on the mass of the electrolyte, the mass content of the carboxylic acid ester solvent is 8% to 60%; Based on the mass of the electrolyte, the total mass content of the first additive is 3% to 10%, and the first additive includes 1,3-propane sultone with a mass content of ≥0, an ethylene carbonate derivative with a mass content of ≥0, and vinylene carbonate with a mass content of ≥3%, wherein the ethylene carbonate derivative includes a compound represented by formula A. Formula A, In formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not hydrogen atoms at the same time.

2. The battery cell according to claim 1, wherein: The mass content of the first additive is 3.5% to 8%.

3. The battery cell according to claim 1 or 2, characterized in that: The mass content of the vinylene carbonate in the electrolyte is 3% to 8%.

4. The battery cell according to any one of claims 1 to 2, characterized in that: The mass content of the 1,3-propane sultone in the electrolyte is 0 to 0.5%.

5. The battery cell according to claim 4, characterized in that The mass content of the 1,3-propane sultone in the electrolyte is 0.05% to 0.5%.

6. The battery cell according to any one of claims 1 to 2, characterized in that: The mass content of the ethylene carbonate derivative in the electrolyte is 0 to 3.5%.

7. The battery cell according to claim 6, characterized in that The mass content of the ethylene carbonate derivative in the electrolyte is 0.5% to 1.5%.

8. The battery cell according to any one of claims 1 to 2, characterized in that: At least one of Q1, Q2, Q3, and Q4 includes a halogen atom, or a C1 to C5 halogenated alkyl group.

9. The battery cell according to any one of claims 1 to 2, characterized in that: The ethylene carbonate derivative includes at least one of the compounds represented by formula A-1 to the compounds represented by formula A-3, 。 10. The battery cell according to any one of claims 1 to 2, characterized in that: The carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

11. The battery cell according to claim 10, characterized in that The carboxylic acid ester solvent includes one or more compounds represented by formula I-1 to formula I-12, 。 12. The battery cell according to any one of claims 1 to 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%.

13. The battery cell according to claim 12, characterized in that: The carbonate solvent includes cyclic carbonate, and the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate; and / or, The carbonate solvent includes chain carbonate, and the chain carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

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

15. The battery cell according to claim 14, 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%.

16. The battery cell according to any one of claims 1 to 2, characterized in that: The thickness of the negative electrode film layer on one side is 50 μm to 65 μm.

17. The battery cell according to any one of claims 1 to 2, characterized in that: The volume average particle size of the graphite particles is 9.5 μm to 13 μm.

18. The battery cell according to any one of claims 1 to 2, characterized in that: The graphite particles include graphite main particles and a negative electrode coating layer coated on the surface of the graphite main particles. The graphite main particles include secondary particles, and the negative electrode coating layer includes carbon elements.

19. The battery cell according to claim 18, characterized in that The graphite bulk particles include at least one of artificial graphite and natural graphite.

20. The battery cell according to claim 18, characterized in that The mass content of carbon element in the negative electrode coating layer is 2% to 5% based on the total mass of the graphite particles.

21. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode film layer further comprises a silicon-based material, and the mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.3% to 5%.

22. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode plate includes a negative electrode active material, and the powder compaction density of the negative electrode active material under 20000N is 1.4g / cm 3 to 1.8g / cm 3 .

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

24. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode plate also includes a negative electrode conductive layer, which is located between the negative electrode current collecting portion and the negative electrode film layer. The negative electrode conductive layer includes a negative electrode conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

25. The battery cell according to claim 24, characterized in that The thickness of the negative electrode conductive layer is 0.5 μm to 2 μm.

26. The battery cell according to any one of claims 1 to 2, characterized in that: The thickness of the positive electrode film layer on one side is 50 μm to 65 μm.

27. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode sheet and the negative electrode sheet are stacked along the thickness direction of the battery cell, and the size of the positive electrode film layer along the length direction of the battery cell is 200 mm to 650 mm.

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

29. The battery cell according to claim 28, characterized in that The mass content of the carbon element is 0.8% to 2.3% based on the mass of the olivine-structured lithium-containing phosphate.

30. The battery cell according to claim 28, characterized in that The positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn.

31. The battery cell according to claim 28, 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.

32. The battery cell according to any one of claims 1 to 2, characterized in that: The lithium-containing phosphate includes a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Compounds Among them, 0.5≤x1≤1.3, 0≤y1≤1.3, 0.5≤x1+y1≤1.3, 0.9≤a1≤1.5, 0≤b1≤0.5, 0.9≤a1+b1≤1.5, 0≤c1≤0.5, 3≤z1≤5, A includes at least one of Na, K and Mg; Me includes at least one of Mn, Fe, Co and Ni; M includes at least one of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce; X includes at least one of Cl, C, N; and Y includes at least one of O and F.

33. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode plate includes a positive electrode active material, and the powder compaction density of the positive electrode active material under 30000N is 2.43g / cm 3 Up to 2.85g / cm 3 .

34. The battery cell according to any one of claims 1 to 2, characterized in that: The battery cell is at 0% SOC state of charge, and the compaction density of the positive electrode film layer is 2.46 g / cm 3 to 2.80g / cm 3 and / or The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 350mg / 1540.25mm 2 .

35. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode plate also includes a positive electrode conductive layer, which is located between the positive electrode current collecting portion and the positive electrode film layer. The positive electrode conductive layer includes a positive electrode conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

36. The battery cell according to claim 35, characterized in that The thickness of the positive electrode conductive layer is 0.5 μm to 2 μm.

37. The battery cell according to any one of claims 1 to 2, characterized in that: The electrode assembly further includes a separator, which is located between the positive electrode plate and the negative electrode plate. The separator includes a base film, the base film has a thickness of 4 μm to 12 μm, and / or a porosity of 20% to 70%.

38. The battery cell according to claim 37, characterized in that The isolation film further includes a functional layer disposed on at least one side of the base film, the functional layer including: A first functional layer is located on one side of the base film, and the first functional layer includes first inorganic particles. The second functional layer is located on the other side of the base film, and the second functional layer includes composite particles. The composite particles include second inorganic particles and multiple 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.

39. The battery cell according to claim 38, characterized in that The non-fluoropolymer particles include acrylic 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 first inorganic particles have an average particle size of 5 nm to 100 nm.

41. The battery cell according to any one of claims 38 to 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 any one of claims 1 to 2, characterized in that: The positive electrode sheet and the negative electrode sheet are stacked along the thickness direction of the battery cell; The electrode assembly further includes a positive electrode tab and a negative electrode tab, wherein the positive electrode tab is connected to at least one side of the positive electrode current collecting portion along the length direction of the battery cell, and the negative electrode tab is connected to at least one side of the negative electrode current collecting portion along the length direction of the battery cell; Along the length direction of the battery cell, the size of the negative electrode film layer is larger than the size of the positive electrode film layer, and the size difference between the negative electrode film layer and the positive electrode film layer is OH1; Along the width direction of the battery cell, the size of the negative electrode film layer is larger than that of the positive electrode film layer, and the size difference between the negative electrode film layer and the positive electrode film layer is OH2, wherein OH1 is larger than OH2.

43. The battery cell according to claim 42, characterized in that 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 any one of claims 1 to 2, characterized in that The battery cell further comprises at least one positive terminal, and the flow area of ​​all the positive terminals on the same side of the positive current collecting portion is 150 mm 2 Up to 1000mm 2 and / or The battery cell further comprises at least one negative terminal, and the flow area of ​​all the negative terminals on the same side of the negative current collecting portion is 150 mm 2 Up to 1000mm 2 .

45. The battery cell according to any one of claims 1 to 2, characterized in that The battery cell includes a case that accommodates the electrode assembly and the electrolyte, and the case has a thickness of 0.1 mm to 0.5 mm.

46. ​​A battery device, characterized in that A battery cell comprising 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 to charge from a 10% state of charge to an 80% state of charge in a time range of 5 minutes to 15 minutes.

48. An electrical device, characterized in that: Comprising a battery device as claimed in claim 46 or 47.

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