Battery cells, battery devices, and power-consuming devices

Abstract

The present application relates to a battery cell, a battery device, and an electrical device. The battery cell includes a housing assembly, an electrolyte, and an electrode assembly. The electrode assembly includes a positive electrode portion and a negative electrode portion. The positive electrode portion includes a positive electrode active material layer containing a lithium phosphate having an olivine structure. The positive electrode tab of the electrode assembly and the positive terminal of the housing assembly are connected via a positive electrode adapter. The negative electrode tab of the electrode assembly and the negative terminal are connected via a negative electrode adapter. The total area of ​​the positive electrode connection region of the positive electrode tab is 150 to 600 mm. 2 The total area of ​​the negative connection area of ​​the negative tab is 150 to 600 mm 2 The electrolyte includes 8% to 30% by weight of a carboxylic acid ester solvent and 0.05% to 0.5% by weight of lithium fluorosulfonate, and the battery cell has an AC internal resistance of 0.15 to 0.4 Ω. This application can balance the energy density, fast charging, and reliability of the battery cell.

Description

[0001] This application claims priority to international patent application PCT / CN2025 / 101070, filed on June 13, 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 battery cell applications, higher performance requirements are being placed on battery cells, such as the need to balance energy density, fast charging, and reliability. Summary of the Invention

[0004] The present application provides a battery cell, a battery device, and an electrical device that can take into account the energy density, fast charging, and reliability of the battery cell.

[0005] In the first aspect, the present application proposes a battery cell, which includes an electrolyte, an electrode assembly, a shell assembly and a transition assembly, the shell assembly includes a shell and a terminal assembly arranged on the shell, the terminal assembly includes a positive terminal and a negative terminal; the transition assembly includes a positive electrode adapter and a negative electrode adapter; the electrolyte and the electrode assembly are accommodated in the shell, the electrode assembly includes a main body and a pole ear part, the main body includes a positive electrode part, a negative electrode part and a separator arranged in a stacked manner, the positive electrode part includes a positive electrode collector and a positive electrode active material layer arranged on at least one side of the positive electrode collector, and the negative electrode part includes a negative electrode collector and a negative electrode active material layer arranged on at least one side of the negative electrode collector The electrode tab includes a positive electrode tab and a negative electrode tab, the positive electrode tab is connected to at least one side of the positive electrode current collector along the first direction, the positive electrode tab and the positive electrode terminal are connected through a positive electrode adapter, the positive electrode tab includes a positive electrode connection area, the positive electrode connection area is the area of ​​the positive electrode tab connected to the positive electrode adapter, the negative electrode tab is connected to at least one side of the negative electrode current collector along the first direction, the negative electrode tab and the negative electrode terminal are connected through a negative electrode adapter, the negative electrode tab includes a negative electrode connection area, the negative electrode connection area is the area of ​​the negative electrode tab connected to the negative electrode adapter, wherein the first direction is parallel to the length direction of the battery cell, or the first direction is parallel to the width direction of the battery cell,

[0006] in,

[0007] The positive electrode active material layer includes an olivine-structured lithium-containing phosphate.

[0008] The size of the housing along the length of the battery cell is 190mm to 650mm;

[0009] The thickness of the positive electrode adapter is 1.5mm to 2.5mm, and the thickness of the negative electrode adapter is 1.2mm to 2.5mm;

[0010] The total area of ​​the positive connection area is 150mm 2 Up to 600mm 2 , the total area of ​​the negative connection area is 150mm 2 Up to 600mm 2 ;

[0011] The electrolyte comprises a carboxylate solvent and lithium fluorosulfonate, wherein the mass content of the carboxylate solvent in the electrolyte is 8% to 30%, and the mass content of the lithium fluorosulfonate in the electrolyte is 0.05% to 0.5%;

[0012] The AC internal resistance of the battery cell is 0.15Ω to 0.4Ω.

[0013] By rationally designing the length of the battery cell shell, the present application can not only make the battery cell have a relatively high energy density, but also regulate the cross-linking internal resistance within a reasonable range, so that the heat generation inside the battery cell will not be too high;

[0014] The connection area between the positive and negative tabs and the positive and negative electrode adapters is relatively large, which makes the positive and negative tabs have excellent current flow capacity; and the thickness of the positive and negative electrode adapters is relatively thick, which makes the positive electrode adapter have excellent current flow capacity, improves the electron transmission capacity, and generates less heat, and the reliability of the battery cell is higher.

[0015] The electrolyte includes appropriate amounts of carboxylic acid ester solvents and lithium fluorosulfonate, which can improve the conductivity of lithium ions. Through the coordinated regulation of mechanical structures and electrolytes, the conductivity of electrons and ions can be comprehensively improved, which can effectively improve the fast charging capability of battery cells.

[0016] The above comprehensive design strategy can effectively balance the fast charging capability, energy density and reliability of battery cells.

[0017] In some embodiments, the outer shell has a length along the length of the battery cell that is greater than or equal to 190 mm and less than 300 mm, and the AC internal resistance IMPB of the battery cell is between 0.15 Ω and 0.3 Ω. By adjusting the outer shell length and the AC internal resistance IMPB, the battery cell can effectively balance the fast charging capability, energy density, and reliability of the battery cell.

[0018] In some embodiments, the outer shell has a length along the length of the battery cell that is greater than or equal to 300 mm and less than 450 mm, and the AC internal resistance IMPB of the battery cell is between 0.2 Ω and 0.35 Ω. The combined control of the outer shell length and the AC internal resistance IMPB can effectively balance the fast charging capability, energy density, and reliability of the battery cell.

[0019] In some embodiments, the outer shell has a length along the length of the battery cell that is greater than or equal to 450 mm and less than or equal to 650 mm, and the AC internal resistance IMPB of the battery cell is between 0.25 Ω and 0.4 Ω. The combined control of the outer shell length and the AC internal resistance IMPB can effectively balance the fast charging capability, energy density, and reliability of the battery cell.

[0020] In some embodiments, the carboxylate solvent includes a compound represented by Formula I,

[0021] Formula I,

[0022] In Formula I,

[0023] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0024] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0025] The above-mentioned carboxylic acid ester solvents are beneficial to the migration of lithium ions and are beneficial to improving the fast charging capability of battery cells.

[0026] In some embodiments, the carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate. These carboxylate solvents facilitate the migration of lithium ions and improve the fast charging capability of the battery cells.

[0027] In some embodiments, the carboxylate solvent includes one or more of methyl acetate and ethyl acetate. The carboxylate solvent is beneficial to the migration of lithium ions and is beneficial to improving the fast charging capability of the battery cell.

[0028] In some embodiments, the electrolyte further includes a carbonate solvent, with the carbonate solvent comprising 45% to 75% by weight in the electrolyte. This carbonate solvent content can further increase the conductivity of the electrolyte, facilitate lithium ion migration, and improve the fast charging capability and reliability of the battery cells.

[0029] In some embodiments, the carbonate solvent includes a cyclic carbonate solvent, and the mass content of the cyclic carbonate solvent in the electrolyte is 25% to 35%; the cyclic carbonate solvent with the above mass content can better dissolve lithium salts, improve the conductivity of the electrolyte, and facilitate rapid charging of the battery cell.

[0030] In some embodiments, the carbonate solvent includes a linear carbonate solvent, and the weight content of the linear carbonate solvent in the electrolyte is 18% to 45%. The linear carbonate solvent in this weight content has a relatively low viscosity, which can reduce the overall viscosity of the electrolyte, increase the ion migration rate, and facilitate rapid charging of the battery cells.

[0031] In some embodiments, the cyclic carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate; the cyclic carbonate solvents of the above materials can better dissolve lithium salts, improve the conductivity of the electrolyte, and facilitate rapid charging of the battery cells.

[0032] In some embodiments, the linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. These linear carbonate solvents have relatively low viscosity, which can reduce the overall viscosity of the electrolyte, increase ion migration rate, and facilitate rapid charging of the battery cells.

[0033] In some embodiments, the electrolyte further includes an unsaturated ester additive, with the unsaturated ester additive comprising 0.05% to 3% by weight of the electrolyte. The unsaturated ester additive includes one or more of vinylene carbonate, vinyl ethylene carbonate, allyl ethyl carbonate, and fluorocarbonate additives. Unsaturated ester additives can form a dense solid electrolyte interface film on the negative electrode side without excessively high film impedance, facilitating a balance between the fast-charging performance and reliability of the battery cell.

[0034] In some embodiments, the mass content of the unsaturated ester additive in the electrolyte is 1% to 3%. When the mass content of the unsaturated ester additive is within the above range, it can effectively balance the fast charging performance and reliability of the battery cell.

[0035] In some embodiments, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 2%. When the mass content of the unsaturated ester additive is within the above range, it can effectively balance the fast charging performance and reliability of the battery cell.

[0036] In some embodiments, the fluorocarbonate additive includes one or more of fluoroethylene carbonate, bisfluoroethylene carbonate, and trifluoromethylethylene carbonate. Fluorinated carbonate additives can form a film rich in fluorine and lithium on the negative electrode side. This can protect the negative electrode active material and reduce interfacial gas generation while lowering the impedance of the film, effectively improving both the fast charging capability and reliability of the battery cell.

[0037] In some embodiments, the electrolyte further includes a sulfur-containing additive in an amount of 0% to 2% by weight. The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylene dimethylsulfonate. The sulfur-containing additive can optimize the composition of the SEI film, enhance interfacial stability, and reduce gas production caused by interfacial side reactions, thereby ensuring both the fast charging capability and reliability of the battery cell.

[0038] In some embodiments, the sulfur-containing additive is present in an amount of 0.5% to 2% by weight based on the mass of the electrolyte. This amount of sulfur-containing additive can optimize the composition of the SEI film, enhance interfacial stability, and reduce gas production caused by interfacial side reactions, while maintaining both the fast charging capability and reliability of the battery cell.

[0039] In some embodiments, the electrolyte further includes a lithium salt additive at a concentration of 0.1% to 1% by weight. The lithium salt additive includes one or more of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), and lithium difluorooxalatoborate. These lithium salt additives can optimize the composition of the SEI film, enhance interfacial stability, and reduce gas production caused by interfacial side reactions, thereby ensuring both the fast charging capability and reliability of the battery cell.

[0040] In some embodiments, the silane-based additive comprises 0.05% to 1% by weight of the electrolyte, and the silane-based additive includes one or more of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and trimethylfluorosilane. When the silane-based additive is present within this range, both the reliability and fast charging capability of the battery cell can be achieved.

[0041] In some embodiments, the mass content of the silane-based additive in the electrolyte is 0.1% to 0.5%. When the mass content of the silane-based additive is within the above range, both the reliability and fast charging capability of the battery cell can be taken into account.

[0042] In some embodiments, the silane-based additive includes one or more of tris(trimethylsilyl)phosphate and trimethylfluorosilane. These materials are more conducive to balancing the reliability and fast charging capability of the battery cell.

[0043] In some embodiments, the electrolyte further comprises a lithium salt, and the lithium salt has a mass content of 10% to 18% in the electrolyte. The above content of lithium salt can improve the fast charging capability and reliability of the battery cell.

[0044] In some embodiments, the lithium salt includes one or more of lithium fluorine-containing sulfonyl imide and lithium hexafluorophosphate. The above content of lithium salt can improve the fast charging capability and reliability of the battery cell.

[0045] In some embodiments, the fluorinated lithium sulfonyl imide includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide. These materials more readily dissociate lithium ions, improving the electrolyte's conductivity and thermal stability, balancing rapid charging and operational reliability of the battery cells.

[0046] In some embodiments, the mass content of lithium hexafluorophosphate in the electrolyte is 8% to 12%. Lithium hexafluorophosphate helps improve the conductivity of the electrolyte and has good solubility in organic solvents, making the electrolyte system more stable.

[0047] In some embodiments, the mass content of fluorinated lithium sulfonyl imide in the electrolyte is 3% to 8%. When the mass content of fluorinated lithium sulfonyl imide is within the above range, the thermal stability of the electrolyte can be improved while taking into account the fast charging and reliability of the battery cell.

[0048] In some embodiments, the single-side coating weight of the positive electrode active material layer is 250 mg / 1540.25 mm 2 Up to 320mg / 1540.25mm 2 When the single-side coating weight of the positive electrode active material layer is within the above range, it is beneficial to take into account the energy density, reliability and fast charging capability of the battery cell.

[0049] In some embodiments, the compacted density of the positive electrode active material layer is 2.6 g / cm 3 Up to 2.8g / cm 3 When the compaction density of the positive electrode active material layer is within the above range, it is beneficial to take into account the energy density, reliability and fast charging capability of the battery cell.

[0050] In some embodiments, the lithium-containing phosphate includes phosphate particles and a positive electrode coating layer. The positive electrode coating layer is located on at least a portion of the surface of the phosphate particles and contains carbon. The positive electrode coating layer on the surface of the phosphate particles can improve the conductivity of the lithium-containing phosphate, facilitate the migration rate of lithium ions, and enhance the rapid charging capability of the battery cells. It also reduces heat generation in the battery cells and the risk of high-temperature decomposition and gas generation of the electrolyte, thereby ensuring both the rapid charging capability and reliability of the battery cells.

[0051] In some embodiments, the mass content of carbon is 0.8% to 2.3% based on the mass of the lithium-containing phosphate. When the mass content of carbon is within this range, the conductivity of the lithium-containing phosphate can be significantly improved, which is beneficial for enhancing the ionic and electronic conductivities of the lithium-containing phosphate, and can improve the rapid charging capability of the battery cell at high energy density.

[0052] In some embodiments, the positive electrode coating layer further comprises one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn. These elements are beneficial for improving the fast charging capability of the lithium-containing phosphate.

[0053] 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. Lithium-containing phosphates have excellent stability during cycling and can extend the service life of battery cells.

[0054] 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 comprises one or more of Na, K, and Mg; Me comprises one or more of Mn, Fe, Co, and Ni; M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X comprises one or more of Cl, C, and N; and Y comprises one or more of O and F. The lithium-containing phosphate has excellent stability during cycling and can extend the service life of the battery cell.

[0055] In some embodiments, the positive electrode active material layer includes a positive electrode conductive agent, which can improve the conductivity of the positive electrode active material layer, thereby facilitating the improvement of the fast charging capability of the battery cell.

[0056] In some embodiments, the positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, superconducting carbon, conductive graphite, acetylene black, Ketjen black, carbon dots, graphene and carbon nanofibers; the positive electrode conductive agent can improve the conductivity of the positive electrode active material layer, which is beneficial to improving the fast charging capability of the battery cell.

[0057] In some embodiments, the mass content of the positive electrode conductive agent in the positive electrode active material layer is 0.1% to 1.2%. This mass content of the positive electrode conductive agent can not only improve the conductivity of the positive electrode active material layer, but also increase the mass proportion of other substances, such as the positive electrode active material, thereby achieving a balance between the fast charging capability and energy density of the battery cell.

[0058] In some embodiments, the positive electrode portion further includes a positive electrode conductive layer, which is located between the positive electrode current collector and the positive electrode active material layer. The positive electrode conductive layer can further improve the conductivity of the positive electrode portion and reduce heat generation in the positive electrode portion, thereby reducing heat generation in the battery cell and reducing high-temperature gas generation in the electrolyte, thereby ensuring both fast charging capability and reliability of the battery cell.

[0059] In some embodiments, the positive electrode conductive layer includes a first conductive agent, which includes one or more of conductive carbon black, carbon nanotubes, superconducting carbon, conductive graphite, acetylene black, Ketjen black, carbon dots, graphene and carbon nanofibers; the first 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 part, reducing the heat generation of the battery cell, reducing the high-temperature gas generation of the electrolyte, and can take into account the fast charging capability and reliability of the battery cell.

[0060] In some embodiments, the positive electrode conductive layer includes a first binder, and the first binder 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 first binder of the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector and the positive electrode active material layer, thereby improving the structural stability of the positive electrode portion.

[0061] In some embodiments, the single-side coating weight of the negative electrode active material layer is 110 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 When the single-side coating weight of the negative electrode active material layer is within the above range, the energy density, reliability and fast charging capability of the battery cell can be taken into consideration.

[0062] In some embodiments, the compaction density of the negative electrode active material layer is 1.2 g / cm 3 Up to 1.6g / cm 3 When the compaction density of the negative electrode active material layer is within the above range, the energy density, reliability and fast charging capability of the battery cell can be taken into account.

[0063] In some embodiments, the negative electrode active material layer includes graphite particles. Graphite particles have high stability during cycling and can extend the service life of the battery cell.

[0064] In some embodiments, the negative electrode portion further includes a negative electrode conductive layer, which is located between the negative electrode current collector and the negative electrode active material layer. The negative electrode conductive layer can further improve the conductivity of the negative electrode portion and reduce the heat generation of the negative electrode portion, thereby reducing the heat generation of the battery cell and reducing the high-temperature gas generation of the electrolyte, thereby taking into account the fast charging capability and reliability of the battery cell.

[0065] In some embodiments, the negative electrode conductive layer includes a second 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 second conductive agent of the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode part, reducing the heat generation of the battery cell, and reducing the high-temperature gas generation of the electrolyte, and can take into account the fast charging capability and reliability of the battery cell.

[0066] In some embodiments, the negative electrode conductive layer includes a second binder comprising one or more of styrene-butadiene rubber, a water-soluble unsaturated resin, a water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The second binder in the negative electrode conductive layer can improve the bonding between the negative electrode current collector and the negative electrode active material layer, thereby enhancing the structural stability of the negative electrode portion.

[0067] In some embodiments, the porosity of the separator is 20% to 70%. When the porosity of the separator is within the above range, the migration ability of lithium ions in the separator can be improved, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can balance the fast charging capability and reliability of the battery cell.

[0068] In some embodiments, the separator includes a base film having a thickness of 4 μm to 12 μm. When the base film thickness is within this range, the migration path of lithium ions through the separator is shorter, further reducing the internal resistance of the battery cell. Furthermore, the separator occupies less space overall, thereby improving both the fast charging capability and energy density of the battery cell.

[0069] In some embodiments, the isolation film includes a base film and a first functional layer disposed on at least one side of the base film, wherein the first functional layer includes inorganic particles. The inorganic particles can improve the heat resistance of the isolation film.

[0070] In some embodiments, the separator includes a base film and a second functional layer disposed on at least one side of the base film, wherein the second functional layer includes a fluorine-containing binder. The second functional layer can prevent short circuits between the positive and negative electrodes, thereby improving the reliability of the battery cell.

[0071] In some embodiments, the second functional layer is located on a side of the first functional layer away from the base film. The second functional layer can prevent short circuits between the positive and negative electrodes, thereby improving the reliability of the battery cell.

[0072] In some embodiments, the 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 inorganic particles can improve the heat resistance of the isolation film.

[0073] In some embodiments, the average particle size of the inorganic particles is 5 nm to 100 nm. When the average particle size of the inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the isolation film.

[0074] In some embodiments, the positive electrode tab is connected to one side of the positive electrode current collector along the width of the battery cell, and the negative electrode tab is connected to one side of the negative electrode current collector along the width of the battery cell, with the positive and negative electrode tabs located on the same side of the electrode assembly. This arrangement shortens the electron transmission path, reduces resistance, and reduces heat generation, balancing the fast charging capability and reliability of the battery cell with the energy density of the battery cell.

[0075] In some embodiments, along the first direction, the negative electrode active material layer is larger than the positive electrode active material layer, and the difference between the negative electrode active material layer and the positive electrode active material layer is OH1, where OH1 is 1.3 mm to 5 mm. This configuration can balance the reliability and energy density of the battery cell.

[0076] In some embodiments, along the second direction, the negative electrode active material layer is larger than the positive electrode active material layer, and the difference between the negative electrode active material layer and the positive electrode active material layer is OH2. The second direction and the first direction are perpendicular to the thickness direction of the battery cell, and OH2 is 1.5 mm to 4 mm. This configuration can balance the reliability and energy density of the battery cell.

[0077] In some embodiments, OH1 is 1.8 mm to 4.2 mm; and / or OH2 is 1.5 mm to 3.5 mm. This configuration can balance the reliability and energy density of the battery cell.

[0078] In some embodiments, along a first direction, the negative electrode active material layer is larger than the positive electrode active material layer, and the difference between the two is OH1. Along a second direction, the negative electrode active material layer is larger than the positive electrode active material layer, and the difference between the two is OH2. The second and first directions are perpendicular to the thickness of the battery cell, the first direction is parallel to the width of the battery cell, and OH1 is less than or equal to OH2. This configuration balances the reliability and energy density of the battery cell.

[0079] In some embodiments, the battery cell includes a housing that accommodates an electrode assembly and an electrolyte. The housing includes a shell and an end cap. The shell includes an opening. The end cap covers the opening. The terminal assembly is disposed on the end cap.

[0080] In some embodiments, the housing is a rectangular parallelepiped structure, comprising two opposing first walls and two opposing second walls, the two first walls connected by the second wall, the cross-sectional area of ​​the first wall perpendicular to its thickness being greater than the cross-sectional area of ​​the second wall perpendicular to its thickness, the thickness of the first wall being 0.3 mm to 0.5 mm, and / or the thickness of the second wall being 0.5 mm to 0.7 mm. When the housing meets these conditions, the battery cell can achieve both operational reliability and energy density.

[0081] In some embodiments, the battery cell further includes a positive electrode reinforcement member, which is connected to at least the positive electrode connection region and is located on a side of the positive electrode tab facing away from the positive electrode adapter.

[0082] Therefore, the embodiment of the present application makes the positive electrode tab less prone to cracks or even breakage through the reinforcing effect of the positive electrode reinforcement, further improves the structural stability of the positive electrode tab, and can improve the current flow capacity of the positive electrode tab and the fast charging capability of the battery cell.

[0083] In some embodiments, the battery cell further includes a negative electrode reinforcement, which is connected to at least the negative electrode connection region and is located on a side of the negative electrode tab facing away from the negative electrode adapter.

[0084] Therefore, the embodiment of the present application makes the negative electrode tab less prone to cracks or even breakage through the reinforcing effect of the negative electrode reinforcement, further improves the structural stability of the negative electrode tab, and can improve the current flow capacity of the negative electrode tab and improve the fast charging capability of the battery cell.

[0085] In some embodiments, the positive electrode tab includes aluminum or an aluminum alloy; the positive electrode reinforcement includes aluminum or an aluminum alloy; the connection between the positive electrode tab and the positive electrode reinforcement is more stable, and the internal resistance at the connection is smaller, which is conducive to improving the fast charging capability of the battery cell.

[0086] In some embodiments, the negative electrode tab includes copper or a copper alloy; the negative electrode reinforcement includes copper or a copper alloy; the connection between the negative electrode tab and the negative electrode reinforcement is more stable, and the internal resistance at the connection is smaller, which is conducive to improving the fast charging capability of the battery cell.

[0087] In some embodiments, the ratio of the total cross-sectional area of ​​the positive electrode reinforcement perpendicular to the thickness direction thereof to the total area of ​​the positive electrode connection region is 1.0 to 1.5.

[0088] When the ratio of the total cross-sectional area of ​​the positive electrode reinforcement perpendicular to its own thickness direction to the total area of ​​the positive electrode connection region is within the above range, the current flow capacity between the positive electrode tab and the positive electrode adapter can be improved, thereby improving the fast charging capability of the battery cell.

[0089] In some embodiments, the total cross-sectional area of ​​the positive electrode reinforcement perpendicular to its own thickness direction is 320 mm 2 Up to 1600mm 2 .

[0090] When the total cross-sectional area of ​​the positive electrode reinforcement perpendicular to its own thickness direction is within the above range, the current flow capacity between the positive electrode tab and the positive electrode adapter can be improved, thereby improving the fast charging capability of the battery cell.

[0091] In some embodiments, the positive electrode reinforcement includes a first reinforcement portion and a second reinforcement portion. The first reinforcement portion is welded to the positive electrode connection region; the second reinforcement portion surrounds and is connected to the first reinforcement portion. The first reinforcement portion reinforces the positive electrode connection region, and the second reinforcement portion is connected to the first reinforcement portion to enhance the overall structural stability of the positive electrode reinforcement, thereby firmly reinforcing the positive electrode connection region and improving the current flow capacity of the positive electrode connection region, thereby improving the rapid charging capability of the battery cell.

[0092] In some embodiments, the thickness of the second reinforcement portion is 0.1 mm to 0.8 mm. When the thickness of the negative electrode reinforcement is within the above range, the fast charging capability and the reliability of the battery cell can be improved.

[0093] In some embodiments, the battery cell further includes a positive electrode thermal insulator located between the positive electrode connection region and the main body, and covering at least the positive electrode connection region. The positive electrode thermal insulator can mitigate the risk of heat transfer to the main body, reduce the adverse effects of heat on the main body, enhance the structural stability of the main body, and reduce the risk of electrolyte decomposition and gassing, thereby improving the reliability of the battery cell.

[0094] In some embodiments, the battery cell further includes a negative electrode thermal insulator located between the negative electrode connection region and the main body, and covering at least the negative electrode connection region. The negative electrode thermal insulator can mitigate the risk of heat transfer to the main body, reduce the adverse effects of heat on the main body, enhance the structural stability of the main body, and reduce the risk of electrolyte decomposition and gassing, thereby improving the reliability of the battery cell.

[0095] In some embodiments, the thickness of the portion of the positive electrode thermal insulator located opposite the positive electrode connection region is 1 mm to 4 mm. The positive electrode connection region generates relatively more heat, and the relatively thick positive electrode thermal insulator can more effectively mitigate heat transfer and improve the reliability of the battery cell.

[0096] In some embodiments, the positive electrode thermal insulation member includes a first thermal insulation layer and a second thermal insulation layer disposed continuously, with at least portions of the first and second thermal insulation layers overlapping, and both covering at least the positive electrode connection region. This multi-layer coverage can more effectively mitigate heat diffusion toward the main body and electrolyte, improving the reliability of the battery cell.

[0097] In some embodiments, the thickness of the first thermal insulation layer is 0.5 mm to 2.0 mm. When the thickness of the first thermal insulation layer is within the above range, it can effectively alleviate the diffusion of heat toward the main body and the electrolyte, thereby improving the reliability of the battery cell.

[0098] In some embodiments, the thickness of the second thermal insulation layer is 0.5 mm to 2.0 mm. When the thickness of the second thermal insulation layer is within the above range, it can effectively alleviate the diffusion of heat toward the main body and the electrolyte, thereby improving the reliability of the battery cell.

[0099] In some embodiments, the positive electrode tab is connected to a portion of the positive electrode adapter, and the positive electrode thermal insulator is connected to another portion of the positive electrode adapter. The connection between the positive electrode thermal insulator and the positive electrode adapter provides a more stable connection and more effective thermal insulation. Furthermore, the positive electrode thermal insulator can cover at least a portion of the positive electrode adapter, providing a wider coverage area, further facilitating the thermal insulation of the positive electrode thermal insulator and improving the reliability of the battery cell.

[0100] In some embodiments, the positive electrode thermal insulator is welded to the positive electrode adapter, which makes the connection between the positive electrode thermal insulator and the positive electrode adapter more stable.

[0101] In some embodiments, the positive electrode thermal insulator comprises one or more of polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polycarbonate. These materials offer excellent thermal insulation, effectively mitigating the risk of heat transfer to the battery cell and electrolyte, reducing the adverse effects of heat on the battery cell and electrolyte, and thereby improving the reliability of the battery cell.

[0102] In some embodiments, the polyolefin includes one or more of polyethylene, polypropylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, and polytetrafluoroethylene. These materials have good thermal insulation effects and can more effectively improve the reliability of battery cells.

[0103] 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.

[0104] In some embodiments, the battery device further includes a heat barrier covering at least one of the two first walls of the battery cell. The heat barrier can mitigate heat transfer to adjacent battery cells, reduce the risk of thermal runaway in adjacent battery cells, and improve the reliability of the battery device.

[0105] 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 12.5 minutes. The battery device has a short charging time and excellent fast charging capability.

[0106] In some embodiments, the maximum charging rate of the battery device is 5 C to 12 C. The battery device can be charged at a higher rate, which is beneficial for fast charging of the battery device.

[0107] 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

[0108] 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.

[0109] Figure 1 A schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0110] Figure 2 An exploded schematic diagram of a battery cell provided in some embodiments of the present application;

[0111] Figure 3 A schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application;

[0112] Figure 4 Schematic diagram of an exploded view of a battery cell provided in some other embodiments of the present application;

[0113] Figure 5 for Figure 4 An enlarged schematic diagram of a battery cell at position A is shown;

[0114] Figure 6 for Figure 4 Another enlarged schematic diagram of the battery cell at position A shown;

[0115] Figure 7 for Figure 4 Another enlarged schematic diagram of the battery cell at position A shown;

[0116] Figure 8 A schematic structural diagram of an end cover, etc. of a battery cell provided in some embodiments of the present application;

[0117] Figure 9 A schematic structural diagram of a positive electrode adapter, a positive electrode tab, and a positive electrode reinforcement of a battery cell provided in some embodiments of the present application;

[0118] Figure 10 Schematic diagram of the structure of the positive electrode adapter, positive electrode tab and positive electrode reinforcement of the battery cell provided in other embodiments of the present application;

[0119] Figure 11 Schematic diagram of the structure of the positive electrode adapter, positive electrode tab and positive electrode thermal insulation of the battery cell provided in other embodiments of the present application;

[0120] Figure 12 Schematic diagram of the structure of the positive electrode adapter, positive electrode tab and positive electrode thermal insulation of the battery cell provided in other embodiments of the present application;

[0121] Figure 13 A schematic structural diagram of a battery cell provided in some other embodiments of the present application;

[0122] Figure 14 for Figure 13 An enlarged schematic diagram of a battery cell at position B is shown;

[0123] Figure 15 A schematic structural diagram of a positive electrode thermal insulation member of a battery cell provided in some embodiments of the present application;

[0124] Figure 16 A schematic structural diagram of a positive electrode thermal insulation member of a battery cell provided in other embodiments of the present application;

[0125] Figure 17 A schematic structural diagram of an electrode assembly of a battery cell provided in other embodiments of the present application;

[0126] Figure 18 A schematic structural diagram of the positive electrode portion of a battery cell provided in some embodiments of the present application;

[0127] Figure 19 A schematic structural diagram of the positive electrode portion of a battery cell provided in some other embodiments of the present application;

[0128] Figure 20 A schematic structural diagram of the negative electrode portion of a battery cell provided in some embodiments of the present application;

[0129] Figure 21 A schematic structural diagram of the negative electrode portion of a battery cell provided in other embodiments of the present application;

[0130] Figure 22 A schematic structural diagram of the positive electrode portion of a battery cell provided in some embodiments of the present application;

[0131] Figure 23 A schematic structural diagram of a positive electrode portion of a battery cell provided in some other embodiments of the present application;

[0132] Figure 24 A schematic structural diagram of the negative electrode portion of a battery cell provided in some embodiments of the present application;

[0133] Figure 25 A schematic structural diagram of the negative electrode portion of a battery cell provided in other embodiments of the present application;

[0134] Figure 26 A schematic top view of an electrode assembly of a battery cell provided in some embodiments of the present application;

[0135] Figure 27 A schematic diagram of the structure of a battery pack provided in some embodiments of the present application;

[0136] Figure 28 A schematic diagram of the structure of a battery module provided in some embodiments of the present application;

[0137] Figure 29 It is a schematic diagram of the structure of an electrical device provided in some embodiments of the present application.

[0138] The drawings are not necessarily drawn to scale.

[0139] The following are the descriptions of the reference numerals:

[0140] M, first direction; N, second direction;

[0141] X, thickness direction of the battery cell; Y, width direction of the battery cell; Z, length direction of the battery cell;

[0142] 1. Power-consuming device; 2. Battery pack; 3. Controller; 4. Motor; 5. Housing; 5a. First housing portion; 5b. Second housing portion; 5c. Accommodation space; 6. Battery module; 7. Battery cell;

[0143] 70. Housing assembly;

[0144] 10. Electrode assembly;

[0145] 11. Positive electrode;

[0146] 111, positive electrode tab; 1111, positive electrode connection region; 1111a, sub-region; 1111b, unit region;

[0147] 112. positive electrode current collector; 113. positive electrode active material layer;

[0148] 12. Negative electrode portion; 121. Negative electrode tab; 122. Negative electrode current collector; 123. Negative electrode active material layer;

[0149] 13. Isolation film;

[0150] 14. Main body;

[0151] 151. Positive electrode adapter; 152. Negative electrode adapter;

[0152] 16. Positive electrode reinforcement; 160. First sub-reinforcement; 161. First reinforcement portion; 162. Second reinforcement portion;

[0153] 17. Positive electrode thermal insulation member; 171. First thermal insulation layer; 172. Second thermal insulation layer;

[0154] 20. Shell;

[0155] 21. Housing; 211. First wall; 212. Second wall;

[0156] 22. End cover; 220. Pressure relief mechanism; 221. Weak part;

[0157] 30. Terminal assembly; 31. Positive terminal; 32. Negative terminal;

[0158] 40. Heat-resistant parts. DETAILED DESCRIPTION

[0159] 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.

[0160] " 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.

[0161] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0162] 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.

[0163] 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.

[0164] In the design of lithium iron phosphate fast-charging stacked batteries, the alternating current impedance of battery (IMPB) is a key factor affecting fast-charging performance and reliability. IMPB reflects the balance between internal heat generation and heat dissipation in the battery cell during fast charging. A reasonable IMPB value can effectively reduce internal heat generation in the battery cell during fast charging, thereby improving the reliability of the battery cell. However, if the IMPB is too high, the battery cell will generate excessive heat during fast charging, which can easily lead to problems such as thermal runaway and significantly deteriorate the reliability of the battery cell.

[0165] To solve this problem, this application comprehensively optimizes key parameters such as the battery cell shell length, adapter thickness, tab and adapter area, and electrolyte composition based on the overall battery system.

[0166] By rationally designing the length of the battery cell shell, the battery cell can have a relatively high energy density, and the IMPB can be controlled within a reasonable range, so that the heat generation inside the battery cell will not be too high. At the same time, by increasing the thickness of the adapter, increasing the connection area between the tab and the adapter, and improving the ion conductivity of the electrolyte (specifically achieved by adding carboxylic acid ester solvents and lithium fluorosulfonate), the comprehensive conduction rate of electrons and ions is further optimized, and heat generation is reduced, which can take into account the improvement of the fast charging performance and functional reliability of the battery cell.

[0167] The above comprehensive design strategy can effectively balance the fast charging capability, energy density and reliability of battery cells.

[0168] battery cells

[0169] In a first aspect, an embodiment of the present application provides a battery cell.

[0170] The battery cell includes an electrolyte, a shell assembly, a switching assembly and an electrode assembly. The shell assembly includes a shell and a terminal assembly provided on the shell. The terminal assembly includes a positive terminal and a negative terminal. The electrolyte and the electrode assembly are accommodated in the shell. The switching assembly includes a positive electrode switching piece and a negative electrode switching piece.

[0171] The electrode assembly includes a main body and a tab portion.

[0172] The main body includes a positive electrode portion, a negative electrode portion and a separator arranged in a stacked manner, the positive electrode portion includes a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, and the negative electrode portion includes a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector;

[0173] The tabs include the positive tab and the negative tab.

[0174] The positive electrode tab is connected to at least one side of the positive electrode current collector along the first direction. The positive electrode tab and the positive electrode terminal are connected through a positive electrode adapter. The positive electrode tab includes a positive electrode connection area, which is an area of ​​the positive electrode tab connected to the positive electrode adapter.

[0175] The negative electrode tab is connected to at least one side of the negative electrode current collector along the first direction, the negative electrode tab and the negative electrode terminal are connected through a negative electrode adapter, and the negative electrode tab includes a negative electrode connection area, which is the area of ​​the negative electrode tab connected to the negative electrode adapter, wherein the first direction is parallel to the length direction of the battery cell, or the first direction is parallel to the width direction of the battery cell.

[0176] in,

[0177] The positive electrode active material layer includes an olivine-structured lithium-containing phosphate.

[0178] The size of the housing along the length of the battery cell is 190mm to 650mm;

[0179] The thickness of the positive electrode adapter is 1.5mm to 2.5mm, and the thickness of the negative electrode adapter is 1.2mm to 2.5mm;

[0180] The total area of ​​the positive connection area is 150mm 2 Up to 600mm 2 , the total area of ​​the negative connection area is 150mm 2 Up to 600mm 2 ;

[0181] The electrolyte comprises a carboxylate solvent and lithium fluorosulfonate, wherein the mass content of the carboxylate solvent in the electrolyte is 8% to 30%, and the mass content of the lithium fluorosulfonate in the electrolyte is 0.05% to 0.5%;

[0182] The AC internal resistance IMPB of the battery cell is 0.15Ω to 0.4Ω.

[0183] By rationally designing the length of the battery cell housing, the present application can not only make the battery cell have a relatively high energy density, but also control the IMPB within a reasonable range so that the heat generation inside the battery cell will not be too high.

[0184] The connection area between the positive and negative tabs and the positive and negative electrode adapters is relatively large, which makes the positive and negative tabs have excellent current flow capacity; and the thickness of the positive and negative electrode adapters is relatively thick, which makes the positive electrode adapter have excellent current flow capacity, improves the electron transmission capacity, and generates less heat, and the reliability of the battery cell is higher.

[0185] The electrolyte includes appropriate amounts of carboxylic acid ester solvents and lithium fluorosulfonate, which can improve the conductivity of lithium ions. Through the coordinated regulation of mechanical structures and electrolytes, the conductivity of electrons and ions can be comprehensively improved, which can effectively improve the fast charging capability of battery cells.

[0186] The above comprehensive design strategy can effectively balance the fast charging capability, energy density and reliability of battery cells.

[0187] In the embodiment of the present application, the AC internal resistance IMPB of the battery cell is 0.15Ω, 0.20Ω, 0.25Ω, 0.30Ω, 0.35Ω, 0.40Ω, or a range consisting of any two of the above values.

[0188] The AC internal resistance IMPB of a battery cell is related to the size of the shell, the material of the positive and negative active materials, the mass content of the binder and conductive agent in the positive and negative active material layers, the coating weight of the positive and negative active materials, the compaction density, and the composition of the electrolyte.

[0189] The AC internal resistance IMPB of a battery cell can be tested using equipment and methods known in the art. For example, the battery cell is charged to 40% SOC, and at 25±3°C, a Tonghui battery AC low resistance tester TH2523 is used. The test probes on the tester are placed on the positive and negative terminals of the battery cell respectively. The tester passes a 1kHz AC constant current source, and then the AC impedance value on the tester is read, which is the IMPB value.

[0190] Figure 1 and Figure 2 A schematic structural diagram of a battery cell is shown.

[0191] like Figure 1 and Figure 2 As shown, in some embodiments, the battery cell 7 may include a housing assembly 70 , which includes a housing 20 and a terminal assembly 30 .

[0192] In some embodiments, the dimension of the housing 20 along the lengthwise direction Z of the battery cell 7 is 190 mm to 650 mm, for example, 100 mm, 150 mm, 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. The dimension of the housing 20 along the lengthwise direction Z of the battery cell 7 can be understood as the length of the housing 20. Figure 1 KL shown in denoted by : represents the length of the housing 20 .

[0193] When the size of the outer shell 20 along the length direction Z of the battery cell 7 meets the above range, the size of the outer shell 20 will not be too short, and the energy density of the battery cell 7 will be relatively high; the size of the outer shell 20 will not be too long, so that the electron transmission path is relatively short, which is conducive to improving the fast charging capability of the battery cell 7, thereby being able to take into account both the energy density and the fast charging capability of the battery cell 7.

[0194] As the length of the shell 20 increases, the amount of active material that can be carried on the main body increases, which is beneficial to increasing the energy density of the battery cell 7; however, the ohmic resistance of the main body increases, which makes the AC internal resistance IMPB tend to increase, and the heat generation increases, which is not conducive to the rapid charging and reliability of the battery cell 7.

[0195] The embodiment of the present application can effectively balance the fast charging capability, energy density and reliability of the battery cell by jointly regulating the length of the shell 20 and the AC internal resistance IMPB.

[0196] Exemplarily, the dimension of the housing 20 along the length direction Z of the battery cell 7 is greater than or equal to 190 mm and less than 300 mm, and the AC internal resistance IMPB of the battery cell is 0.15Ω to 0.3Ω.

[0197] Exemplarily, the dimension of the housing 20 along the length direction Z of the battery cell 7 is greater than or equal to 300 mm and less than 450 mm, and the AC internal resistance IMPB of the battery cell is 0.2Ω to 0.35Ω.

[0198] Exemplarily, the dimension of the housing 20 along the length direction Z of the battery cell 7 is greater than or equal to 450 mm and less than or equal to 650 mm, and the AC internal resistance IMPB of the battery cell is 0.25Ω to 0.4Ω.

[0199] 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.

[0200] 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.

[0201] In some embodiments, the material of the housing 21 includes one or more of aluminum and steel, with steel being preferred. Steel has high mechanical strength and is less prone to deformation, thereby improving the reliability of the battery cells. Optionally, the material of the housing 21 includes steel, and steel accounts for the largest proportion of the material in the housing 21 by mass.

[0202] 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.

[0203] Optionally, the housing 21 has a rectangular parallelepiped structure and includes two opposing first walls 211 and two opposing second walls 212. The two first walls 211 are connected by the second wall 212, and the cross-sectional area of ​​the first wall 211 perpendicular to its thickness is greater than the cross-sectional area of ​​the second wall 212 perpendicular to its thickness. In the rectangular parallelepiped structure, the first wall 211 can be understood as the large surface of the housing 21, and the second wall 212 can be understood as the side surface of the housing 21.

[0204] Optionally, the thickness of the first wall 211 is 0.3 mm to 0.5 mm, such as 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or a range consisting of any two of the above values.

[0205] The cross-sectional area of ​​the first wall 211 is relatively large. When its thickness is within the above range, the mechanical strength of the first wall 211 is relatively high, which can improve the reliability of the battery cell 7. In addition, the shell 21 occupies less space as a whole, and the internal space of the shell 21 is larger, which is conducive to improving the energy density of the battery cell 7, so that the battery cell 7 can take into account both reliability and energy density.

[0206] Optionally, the thickness of the second wall 212 is 0.5 mm to 0.7 mm, such as 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, or a range consisting of any two of the above values. The relatively thick thickness of the second wall 212 can improve the mechanical strength of the second wall 212, making the housing 21 more stable during the cycle.

[0207] In some embodiments, the housing 20 is provided with a pressure relief mechanism 220. Optionally, the end cover 22 is provided with a pressure relief mechanism 220. For example, the pressure relief mechanism 220 can be an explosion-proof valve, or a weak portion formed by thinning a local area of ​​the end cover 22.

[0208] When short circuits, overcharge, or other events occur, the electrolyte and active materials react, releasing gas and heat. The pressure relief mechanism 220 is configured to deform when the internal pressure or temperature of the housing 20 reaches a pressure relief threshold, allowing the interior of the housing 20 to communicate with the exterior, thereby releasing the pressure or temperature within the housing 20. Deformation of the pressure relief mechanism 220 includes, but is not limited to, rupture and melting. The pressure relief threshold may depend on the materials of one or more of the positive and negative electrodes, electrolyte, and separator within the battery cell 7.

[0209] In the embodiment of the present application, the deformation of the pressure relief mechanism 220 may be triggered by the internal pressure of the housing 20 , or by the internal temperature of the housing 20 , or may be triggered jointly by the internal pressure and internal temperature of the housing 20 .

[0210] As an example, as gas accumulates within the housing 20, the internal pressure of the housing 20 may reach or even exceed a pressure relief threshold. When the internal pressure of the housing 20 reaches the threshold, the pressure relief mechanism 220 deforms under the action of the internal pressure, allowing the interior space of the housing 20 to communicate with the external space, allowing the gas inside the housing 20 to be discharged, thereby reducing the risk of explosion of the battery cell 7.

[0211] For example, when the electrolyte and active material react and rapidly release heat, the internal temperature of the housing 20 increases, which in turn causes the internal pressure of the housing 20 to increase. When the internal temperature of the housing 20 reaches a threshold, the pressure relief mechanism 220 deforms under the influence of temperature and pressure, allowing the internal space of the housing 20 to communicate with the external space, allowing the gas inside the housing 20 to be discharged, thereby reducing the risk of explosion of the battery cell 7.

[0212] When the internal pressure or temperature of the shell 20 reaches a threshold, the embodiment of the present application can utilize the deformation of the pressure relief mechanism 220 to connect the internal space of the shell 20 with the external space, thereby releasing the internal gas and internal pressure of the shell 20 and reducing the risk of explosion of the battery cell 7.

[0213] Optionally, the pressure relief mechanism 220 includes a weak portion 221 .

[0214] Optionally, the base material of the weak portion 221 includes steel or aluminum.

[0215] The terminal assembly 30 includes a positive terminal 31 and a negative terminal 32. The positive terminal 31 is provided on the housing 20, and can be provided on the housing 21 or the end cap 22. The negative terminal 32 is provided on the housing 20, and can be provided on the housing 21 or the end cap 22.

[0216] The battery cell 7 also includes an electrode assembly 10. One or more electrode assemblies 10 may be housed within the housing 20. For example, the electrode assembly 10 may be a laminated structure, with the positive electrode portion, separator, and negative electrode portion stacked along the thickness of the battery cell. Two laminated electrode assemblies are stacked within the housing 20. Laminated electrode assemblies can help increase the energy density of the battery cell.

[0217] like Figure 2 and Figure 3 As shown, the electrode assembly 10 includes a main body 14 and a tab portion. The tab portion is connected to the main body 14 and extends out of the main body 14 along a first direction. The first direction is parallel to the length direction Z of the battery cell 7, or the first direction is parallel to the width direction Y of the battery cell 7. Figure 2 and Figure 3 As shown in FIG, the first direction is parallel to the width direction Y of the battery cell 7 , and the tab portion is connected to the main body portion 14 and protrudes from the main body portion 14 along the width direction Y of the battery cell 7 .

[0218] The main body 14 includes a positive electrode portion and a negative electrode portion. The positive electrode portion includes a positive electrode collector 112 and a positive electrode active material layer 113 disposed on at least one side of the positive electrode collector 112 . The negative electrode portion includes a negative electrode collector 122 and a negative electrode active material layer 123 disposed on at least one side of the negative electrode collector 122 .

[0219] Specifically,

[0220] The portion of the positive electrode portion 11 not coated with the active material layer is the positive electrode tab 111. The active material coated on the positive electrode current collector 112 in the positive electrode portion 11 constitutes the positive electrode active material layer 113. The positive electrode active material layer 113 and the positive electrode current collector 112 coated with the active material are part of the main body 14, which is defined as the positive electrode portion.

[0221] The portion of the negative electrode portion 12 not coated with the active material layer is the negative electrode tab 121. The active material coated on the negative electrode current collector 122 in the negative electrode portion 12 constitutes the negative electrode active material layer 123. The negative electrode active material layer 123 and the negative electrode current collector 122 coated with the active material are part of the main body 14, which is defined as the negative electrode portion.

[0222] The main body portion 14 may further include a separator 13 , which is located between the positive electrode portion 11 and the negative electrode portion 12 .

[0223] 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 lead the current out of the main body 14 .

[0224] The positive terminal 31 is electrically connected to the positive tab 111 , and the positive terminal 31 and the positive tab 111 are connected via a positive adapter 151 . For example, the positive terminal 31 and the positive tab 111 are welded via the positive adapter 151 .

[0225] The thickness of the positive electrode adapter 151 is 1.5 mm to 2.5 mm, such as 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, or a range consisting of any two of the above values.

[0226] When the thickness of the positive electrode adapter 151 is too small, the mechanical strength of the positive electrode adapter 151 is poor and the current flow capacity is poor; when the thickness of the positive electrode adapter 151 is too thick, although the current flow capacity of the positive electrode adapter 151 is relatively good, it is difficult to connect it with the positive electrode tab 111 and is easy to peel off.

[0227] When the thickness of the positive electrode adapter 151 is within the above range, the current flow capacity and connection stability can be effectively improved, and the fast charging capability and use reliability of the battery cell 7 can be effectively balanced.

[0228] The negative terminal 32 is electrically connected to the negative electrode tab 121 , and the negative terminal 32 and the negative electrode tab 121 are connected via a negative electrode adapter 152 . For example, the negative terminal 32 and the negative electrode tab 121 are welded via the negative electrode adapter 152 .

[0229] The thickness of the negative electrode adapter 152 is 1.2 mm to 2.5 mm, such as 1.2 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, or a range consisting of any two of the above values.

[0230] When the thickness of the negative electrode adapter 152 is too small, the mechanical strength of the negative electrode adapter 152 is poor and the current flow capacity is poor; when the thickness of the positive electrode adapter 151 is too thick, although the current flow capacity of the negative electrode adapter 152 is relatively good, it is difficult to connect it to the positive electrode tab 111 and is easy to peel off.

[0231] When the thickness of the negative electrode adapter 152 is within the above range, the current capacity and connection stability can be effectively improved, and the fast charging capability and usage reliability of the battery cell 7 can be effectively balanced.

[0232] [Positive electrode tab]

[0233] like Figures 4 and 5As shown, the positive electrode tab 111 includes a positive electrode connection area 1111, which is the area of ​​the positive electrode tab 111 that is connected to the positive electrode adapter 151. For example, when the positive electrode tab 111 is welded to the positive electrode adapter 151, the positive electrode connection area 1111 is the weld mark area of ​​the positive electrode tab 111. In order to more clearly illustrate the positive electrode connection area 1111 of the positive electrode tab 111, Figure 4 and Figure 5 The middle positive electrode tab 111 is the unfolded tab. After entering the shell, the positive electrode tab 111 can be bent into a shape similar to Figure 4 In the structural form of another electrode tab, the shaded portion on the positive electrode tab 111 represents the positive electrode connection area 1111. In the embodiment of the present application, the positive electrode tab 111 also includes a non-connection area, and the positive electrode connection area 1111 and the non-connection area are continuously arranged. For example, the positive electrode connection area 1111 is a weld print area, and the non-connection area is a non-weld print area.

[0234] Optionally, the positive electrode connection region 1111 includes one or more sub-regions 1111 a .

[0235] like Figure 5 As shown, when the positive electrode connection region 1111 includes a sub-region 1111a, the positive electrode tab 111 may be multiple pieces, and the multiple positive electrode tabs 111 are bent together and then connected to the positive electrode adapter 151 together, such as by welding.

[0236] like Figure 6 As shown, when the positive electrode connection region 1111 includes multiple sub-regions 1111a, the positive electrode tabs 111 may be multiple pieces, and after the multiple pieces of positive electrode tabs 111 are bent together, they are connected to the positive electrode adapter 151 through the multiple sub-regions 1111a.

[0237] like Figure 7 and Figure 8 As shown, in the case where the positive electrode connection area 1111 includes multiple sub-areas 1111a, the positive electrode tabs 111 may be multiple pieces, and the multiple pieces of positive electrode tabs 111 are divided into two groups, each group of positive electrode tabs 111 includes at least two positive electrode tabs 111, each group of positive electrode tabs 111 are individually bent, and after bending, they are respectively connected to the positive electrode adapter 151, and each group of positive electrode tabs 111 can be connected to the positive electrode adapter 151 through one sub-area 1111a or multiple sub-areas 1111a.

[0238] Optionally, the positive electrode connection region 1111 includes one or more sub-regions 1111a. Further optionally, the positive electrode connection region 1111 includes multiple sub-regions 1111a, and the multiple sub-regions 1111a are arranged relatively along the thickness direction of the electrode assembly 10. Specifically, after the positive electrode tab 111 is bent into the shell, the multiple sub-regions 1111a are arranged relatively along the thickness direction of the electrode assembly 10. Exemplarily, the positive electrode connection region 1111 includes two sub-regions 1111a. In this embodiment of the present application, the thickness direction of the electrode assembly 10 is parallel to the thickness direction of the battery cell 7.

[0239] The multiple sub-regions 1111a are beneficial to improving the connection stability between the positive electrode tab 111 and the positive electrode adapter 151, and improving the current flow capacity of the positive electrode tab 111 and the positive electrode adapter 151, thereby improving the fast charging capability of the battery cell 7.

[0240] Optionally, the sub-region 1111a includes one or more unit regions 1111b. Further optionally, the sub-region 1111a includes multiple unit regions 1111b, and the multiple unit regions 1111b are relatively arranged in a direction perpendicular to the thickness direction of the electrode assembly 10. Specifically, after the positive electrode tab 111 is bent into the shell, the multiple unit regions 1111b are relatively arranged in a direction perpendicular to the thickness direction of the electrode assembly 10.

[0241] The multiple unit regions 1111b are beneficial to improving the connection stability between the positive electrode tab 111 and the positive electrode adapter 151, as well as improving the current carrying capacity of the positive electrode tab 111 and the positive electrode adapter 151, thereby improving the fast charging capability of the battery cell 7.

[0242] When the positive electrode tab 111 and the positive electrode adapter 151 are connected by welding, the positive electrode connection region 1111 is the welding region of the positive electrode tab 111. The subregion 1111a constitutes a component of the welding region, and the unit region 1111b constitutes a component of the subregion 1111a.

[0243] For example, the total area of ​​the positive electrode connection region 1111 is 150 mm 2 Up to 600mm 2 , such as 150 mm², 200 mm², 300 mm², 400 mm², 500 mm², 600 mm², or a range consisting of any two of the above values. The total area of ​​the positive electrode connection area 1111 refers to the sum of the areas of all sub-areas 1111a; or the sum of the areas of all unit areas 1111b. Alternatively, the total area of ​​the connection area between the positive electrode adapter 151 and the positive electrode tab 111 is 150 mm². 2 Up to 600mm 2 .

[0244] When the area of ​​the positive electrode connection region 1111 is within the above range, it is beneficial to improve the connection stability between the positive electrode tab 111 and the positive electrode adapter 151, and improve the current flow capacity of the positive electrode tab 111 and the positive electrode adapter 151, thereby improving the fast charging capability of the battery cell.

[0245] [Positive electrode reinforcement]

[0246] like Figure 8 and Figure 9 As shown, in some embodiments, the battery cell further includes a positive electrode reinforcement 16, which is connected to the positive electrode tab 111. Specifically, the positive electrode reinforcement 16 is connected to at least the positive electrode connection region 1111. Optionally, the positive electrode reinforcement 16 is located on a side of the positive electrode tab 111 facing away from the positive electrode adapter 151. Figure 9 The positive electrode connection region 1111 shown in FIG. 1 includes four unit regions 1111 b .

[0247] The positive electrode reinforcement 16 is connected to at least the positive electrode connection area 1111 , which can be understood as the positive electrode reinforcement 16 being connected to the positive electrode connection area 1111 , or the positive electrode reinforcement 16 being connected not only to the positive electrode connection area 1111 but also to the remaining area of ​​the positive electrode tab 111 .

[0248] When the positive electrode tab 111 is welded to the positive electrode adapter 151, during the welding process, the positive electrode reinforcement 16 is set on the surface of the positive electrode tab 111, and the positive electrode reinforcement 16 is at least partially melted and welded to the positive electrode tab 111 and the positive electrode adapter 151, thereby strengthening the strength of the connection between the positive electrode tab 111 and the positive electrode adapter 151; and when the thickness of the positive electrode tab 111 is relatively thin, the reinforcing effect of the positive electrode reinforcement 16 makes it less likely for the positive electrode tab 111 to crack or even break, and the structure is more stable. It can also improve the current capacity of the positive electrode tab 111, and improve the fast charging capability and reliability of the battery cell 7.

[0249] During the charge and discharge cycle of the battery cell 7, the volume of the active material layer expands or contracts, which may cause the current collector to undergo a certain deformation, and the connection between the positive electrode tab 111 and the positive electrode adapter 151 may cause cracks or even breakage; the positive electrode reinforcement 16 can enhance the mechanical strength of the connection between the positive electrode tab 111 and the positive electrode adapter 151, enhance the structural stability; and enhance the flow capacity between the positive electrode tab 111 and the positive electrode adapter 151, thereby improving the fast charging capability and reliability of the battery cell 7.

[0250] Optionally, the ratio of the total cross-sectional area of ​​the positive reinforcement 16 perpendicular to its thickness direction to the total area of ​​the positive connection region 1111 is 1.0 to 1.5, such as 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range consisting of any two of the above values.

[0251] When the ratio of the total cross-sectional area of ​​the positive electrode reinforcement 16 perpendicular to its own thickness direction to the total area of ​​the positive electrode connection area 1111 is within the above range, the current flow capacity between the positive electrode tab 111 and the positive electrode adapter 151 can be further improved, thereby improving the fast charging capability and usage reliability of the battery cell 7.

[0252] The ratio of the cross-sectional area of ​​the positive electrode reinforcement 16 perpendicular to its thickness to the area of ​​the positive electrode connection region 1111 can represent the extent to which the positive electrode reinforcement 16 covers the positive electrode connection region 1111. For example, when the ratio is 1.0, the positive electrode reinforcement 16 and the positive electrode connection region 1111 have the same area, and the positive electrode reinforcement 16 can completely cover the positive electrode connection region 1111. When the ratio is greater than 1.0, the positive electrode reinforcement 16 not only covers the positive electrode connection region 1111 but also extends beyond the positive electrode connection region 1111, thereby further strengthening the connection strength of the positive electrode connection region 1111.

[0253] For example, the total cross-sectional area of ​​the positive electrode reinforcement 16 perpendicular to its thickness direction is 320 mm 2 Up to 1600mm 2 , for example 300 mm², 400 mm², 500 mm², 600 mm², 700 mm², 800 mm², 900 mm², 1000 mm², 1100 mm², 1200 mm², 1300 mm², 1400 mm², 1500 mm², 1600 mm² or a range consisting of any two of the above values.

[0254] When the cross-sectional area of ​​the positive electrode reinforcement 16 perpendicular to its own thickness direction is within the above range, it is beneficial to enhance the coverage of the positive electrode connection area 1111, improve the structural strength of the connection between the positive electrode tab 111 and the positive electrode adapter 151, and further improve the current flow capacity between the positive electrode tab 111 and the positive electrode adapter 151, thereby improving the fast charging capability of the battery cell 7.

[0255] When the positive electrode connection region 1111 includes two subregions 1111a, and each subregion 1111a includes two unit regions 1111b, that is, when the positive electrode connection region 1111 includes four unit regions 1111b, the four unit regions 1111b are independently spaced apart, and of course, the four unit regions 1111b can also be connected; the positive electrode reinforcement 16 covers the four unit regions 1111b, and the positive electrode reinforcement 16 can include four first sub-reinforcers 160. A first sub-reinforcer 160 can be provided in each of the four unit regions 1111b to cover the unit region 1111b. Of course, the positive electrode reinforcement 16 can also include two first sub-reinforcers 160, each covering one subregion 1111a.

[0256] For example, the cross-sectional area of ​​the first sub-reinforcement member 160 perpendicular to its own thickness direction is 80 mm 2 Up to 400mm 2 , such as 50 mm², 100 mm², 150 mm², 200 mm², 250 mm², 300 mm², 350 mm², 400 mm², or a range consisting of any two of the above values. The total cross-sectional area of ​​the four first sub-reinforcers 160 is the total cross-sectional area of ​​the positive electrode reinforcement 16 .

[0257] like Figure 9 and Figure 10 As shown, in some embodiments, the positive electrode reinforcement 16 includes a first reinforcement portion 161 and a second reinforcement portion 162. The first reinforcement portion 161 is connected to the positive electrode connection region 1111; the second reinforcement portion 162 is disposed around the first reinforcement portion 161 and connected to the first reinforcement portion 161. When the positive electrode reinforcement 16 includes multiple first sub-reinforcements 160, each first sub-reinforcement 160 can include a first reinforcement portion 161 and a second reinforcement portion 162. Optionally, the first reinforcement portion 161 is welded to the positive electrode connection region 1111.

[0258] The first reinforcement portion 161 covers the positive electrode connection area 1111, and the first reinforcement portion 161 can play a role in reinforcing the positive electrode connection area 1111. The second reinforcement portion 162 is connected to the first reinforcement portion 161, which can improve the overall structural stability of the positive electrode reinforcement 16, thereby firmly reinforcing the positive electrode connection area 1111 and improving the current flow capacity of the positive electrode connection area 1111, thereby improving the fast charging capability of the battery cell.

[0259] Optionally, the first reinforcement portion 161 and the second reinforcement portion 162 are an integrated structure, so that the strength of the positive electrode reinforcement 16 is higher.

[0260] Optionally, there may be a clear boundary between the first reinforcement portion 161 and the second reinforcement portion 162; for example, during the welding process, the first reinforcement portion 161 is welded to the positive electrode tab 111, and the second reinforcement portion 162 may not melt and may be a sheet-like structure.

[0261] Optionally, the second reinforcement portion 162 may not be connected to the positive electrode tab 111 , for example, the two may be tightly fitted together, or a gap may be left between the two.

[0262] Optionally, the thickness of the positive electrode reinforcement 16 is 0.1 mm to 0.8 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, or a range consisting of any two of the above values.

[0263] When the thickness of the positive electrode reinforcement 16 is within the above range, the overall mechanical strength of the positive electrode reinforcement 16 is higher, which can enhance the reinforcement effect on the positive electrode connection area 1111 and the current carrying capacity, while improving the fast charging capability and reliability of the battery cell.

[0264] Optionally, the thickness of the second reinforcement portion 162 is 0.1 mm to 0.8 mm, such as 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, or a range consisting of any two of the above values.

[0265] When the thickness of the second reinforcement portion 162 is within the above range, the mechanical strength of the second reinforcement portion 162 is relatively high, so that the overall mechanical strength of the positive electrode reinforcement 16 is relatively high, which can enhance the reinforcement effect and current flow capacity of the positive electrode connection area 1111, while improving the fast charging capability and reliability of the battery cell.

[0266] Optionally, the positive electrode tab 111 includes aluminum or an aluminum alloy, and the positive electrode reinforcement 16 is a metal reinforcement, which may optionally include aluminum or an aluminum alloy. This makes the connection between the positive electrode tab 111 and the positive electrode reinforcement 16 more stable and the internal resistance at the connection smaller, which is beneficial to improving the fast charging capability of the battery cell.

[0267] [Positive electrode thermal insulation]

[0268] like Figures 10 to 15 As shown, in some embodiments, the battery cell 7 further includes a positive electrode thermal insulator 17, which is located between the positive electrode connection region 1111 and the main body 14 and at least covers the positive electrode connection region 1111. In the case where the battery cell 7 further includes an optional positive electrode reinforcement 16, the positive electrode thermal insulator 17 is also located between the positive electrode reinforcement 16 and the main body 14.

[0269] The positive electrode connection area 1111 may generate a lot of heat during the charging and discharging process of the battery cell 7, and the positive electrode insulation 17 can alleviate the risk of heat transfer to the main body 14, reduce the adverse effects of heat on the main body 14, such as possible damage to the isolation membrane, etc., improve the structural stability of the main body 14, and reduce the risk of electrolyte decomposition and gas production, thereby improving the reliability of the battery cell 7.

[0270] Optionally, the positive electrode thermal insulator 17 also covers at least a portion of the positive electrode adapter 151 .

[0271] Further optionally, the positive electrode tab 111 is connected to a portion of the positive electrode adapter 151, and the positive electrode thermal insulator 17 is connected to another portion of the positive electrode adapter 151. The positive electrode tab 111 and the positive electrode thermal insulator 17 are respectively connected to different portions of the positive electrode adapter 151. Although the positive electrode adapter 151 is artificially divided into one portion and another portion, there is no clear boundary between the two portions, and the positive electrode adapter 151 can be an integrated structure.

[0272] Alternatively, the positive electrode thermal insulator 17 is welded to the positive electrode adapter 151. This provides a more stable connection between the positive electrode thermal insulator 17 and the positive electrode adapter 151, effectively mitigating the risk of heat transfer to the main body 14 and reducing the risk of electrolyte decomposition and gas generation, thereby improving the reliability of the battery cell 7.

[0273] In some embodiments, the positive electrode thermal insulation member 17 includes multiple thermal insulation layers, each of which covers at least the positive electrode connection region 1111 .

[0274] Multiple layers of thermal insulation layers can be stacked along the thickness direction of the positive electrode thermal insulation component 17. Covering the positive electrode connection area 1111 with multiple layers of thermal insulation layers can more effectively alleviate the diffusion of heat toward the main body 14 and the electrolyte, reduce the risk of high-temperature decomposition and gas production of the electrolyte, and improve the reliability of the battery cell 7.

[0275] like Figure 15 and Figure 16 As shown, in other embodiments, the positive electrode thermal insulator 17 includes a first thermal insulation layer 171 and a second thermal insulation layer 172 disposed continuously. The first thermal insulation layer 171 and the second thermal insulation layer 172 at least partially overlap, and both the first thermal insulation layer 171 and the second thermal insulation layer 172 at least cover the positive electrode connection area 1111. When the positive electrode thermal insulator 17 is unfolded, the second thermal insulation layer 172 can be located on both sides of the first thermal insulation layer 171. After the positive electrode thermal insulator 17 is placed in the casing, the second thermal insulation layer 172 is bent to partially overlap the first thermal insulation layer 171.

[0276] Optionally, the first thermal insulation layer 171 also covers the non-connected area of ​​the positive electrode tab 111. Further optionally, the second thermal insulation layer 172 also covers the non-connected area of ​​the positive electrode tab 111.

[0277] The positive electrode connection area 1111 generates more heat. The first thermal insulation layer 171 and the second thermal insulation layer 172 cover the positive electrode connection area 1111. The multi-layer covering can more effectively alleviate the diffusion of heat toward the main body 14 and the electrolyte, thereby improving the reliability of the battery cell 7.

[0278] Exemplarily, the thickness of the first thermal insulation layer 171 is 0.5 mm to 2.0 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, or a range consisting of any two of the foregoing values. When the thickness of the first thermal insulation layer 171 is within the foregoing range, it can effectively reduce heat dissipation toward the main body 14 and the electrolyte, thereby improving the reliability of the battery cell 7.

[0279] Exemplarily, the thickness of the second thermal insulation layer 172 is 0.5 mm to 2.0 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, or a range consisting of any two of the foregoing values. When the thickness of the second thermal insulation layer 172 is within the foregoing range, it can effectively reduce heat dissipation toward the main body 14 and the electrolyte, thereby improving the reliability of the battery cell 7.

[0280] For example, the thickness of the portion of the positive electrode thermal insulator 17 located opposite the positive electrode connection region 1111 is 1 mm to 4 mm, such as 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, or a range consisting of any two of these values. The positive electrode connection region 1111 generates relatively more heat, and the relatively thick positive electrode thermal insulator 17 can more effectively mitigate heat transfer, thereby improving the reliability of the battery cell 7. Figure 14 and Figure 15 GH1 shown in FIG. 1 represents the thickness of a portion of the positive electrode heat insulator 17 disposed opposite the positive electrode connection region 1111. GH2 represents the thickness of the remaining portion of the positive electrode heat insulator 17, for example, 0.5 mm to 2.0 mm.

[0281] Illustratively, the positive electrode thermal insulator 17 comprises one or more of polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polycarbonate. These materials offer excellent thermal insulation, effectively mitigating the risk of heat transfer to the main body 14 and the electrolyte, reducing the adverse effects of heat on these components, and thereby improving the reliability of the battery cell 7.

[0282] For example, the polyolefin includes one or more of polyethylene, polypropylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, and polytetrafluoroethylene.

[0283] [Negative electrode tab]

[0284] The negative electrode tab 121 includes a negative electrode connection region, which is the region of the negative electrode tab 121 connected to the negative electrode adapter 152. For example, when the negative electrode tab 121 and the negative electrode adapter 152 are welded, the negative electrode connection region is the weld mark region of the negative electrode tab 121.

[0285] The total area of ​​the negative connection area is 150mm 2 Up to 600mm 2 , such as 150 mm², 200 mm², 300 mm², 400 mm², 500 mm², 600 mm², or a range consisting of any two of the above values. The total area of ​​the negative connection area refers to the sum of the areas of all negative connection areas.

[0286] When the area of ​​the negative electrode connection region is within the above range, it is beneficial to improve the connection stability between the negative electrode tab 121 and the negative electrode adapter 152, and improve the flow capacity of the negative electrode tab 121 and the negative electrode adapter 152, thereby improving the fast charging capability of the battery cell.

[0287] In some embodiments, the negative electrode tab 121 includes a non-connected region of the negative electrode tab 121 . Exemplarily, the non-connected region is a non-weld print region.

[0288] Optionally, the battery cell further includes a negative electrode reinforcement, which is connected to the negative electrode tab and at least connected to the negative electrode connection region. Optionally, the negative electrode reinforcement is located on a side of the negative electrode tab away from the negative electrode adapter.

[0289] The negative electrode reinforcement being connected to at least the negative electrode connection region can be understood as the negative electrode reinforcement being connected to the negative electrode connection region, or the negative electrode reinforcement being connected not only to the negative electrode connection region but also to the remaining region of the negative electrode tab.

[0290] During the welding process, the negative electrode reinforcement is arranged on the surface of the negative electrode tab, and the negative electrode reinforcement is at least partially melted and welded to the negative electrode tab and the negative electrode adapter, thereby strengthening the strength of the connection between the negative electrode tab and the negative electrode adapter; and when the thickness of the negative electrode tab is relatively thin, the reinforcing effect of the negative electrode reinforcement makes it less likely for the negative electrode tab to crack or even break, further improving the structural stability and overcurrent capacity of the negative electrode tab, and improving the fast charging capability and reliability of the battery cell.

[0291] During the charge and discharge cycle of the battery cell, the active material layer expands or contracts in volume, which may cause the current collector to undergo certain deformation, and may cause cracks or even breakage at the connection between the negative electrode tab and the negative electrode adapter; the negative electrode reinforcement can improve the mechanical strength of the connection between the negative electrode tab and the negative electrode adapter, improve the structural stability and current flow capacity, and improve the fast charging capability and reliability of the battery cell.

[0292] The negative electrode tab includes copper or copper alloy, and the negative electrode reinforcement is a metal reinforcement, which can optionally include copper or copper alloy. This makes the connection between the negative electrode tab and the negative electrode reinforcement more stable and the internal resistance at the connection smaller, which is conducive to improving the fast charging capability of the battery cell.

[0293] The structure of the negative electrode tab is similar to that of the positive electrode tab and will not be described in detail here.

[0294] The relevant parameters of the negative electrode connection area are similar to the relevant parameters of the positive electrode connection area and will not be repeated here.

[0295] The relevant parameters of the negative electrode reinforcement are similar to those of the positive electrode reinforcement and will not be further described here.

[0296] In some embodiments, the battery cell further includes a negative electrode thermal insulator, which is located between the negative electrode connection region and the main body and covers at least the negative electrode connection region. If the battery cell further includes an optional negative electrode reinforcement, the negative electrode thermal insulator is also located between the negative electrode reinforcement and the main body.

[0297] The structure, size and material of the negative electrode thermal insulation are similar to those of the positive electrode thermal insulation, and will not be described in detail here.

[0298] Next, the tab arrangement will be described using the electrode assembly 10 as a laminated structure as an example.

[0299] like Figure 17 As shown, the electrode assembly 10 includes a positive electrode portion 11 , a negative electrode portion 12 , and a separator 13 , which are stacked along a thickness direction X of the battery cell.

[0300] 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. Figure 17 FIG. 4 shows a situation where the positive electrode tab 111 and the negative electrode tab 121 are arranged on the same side.

[0301] 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 .

[0302] 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 .

[0303] In some embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collector 112 along a first direction M. The first direction M is parallel to the length direction Z of the battery cell, or the first direction M is parallel to the width direction Y of the battery cell.

[0304] In some embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collector 112 along the length direction Z of the battery cell.

[0305] like Figure 18 As shown, for example, the positive electrode tab 111 is connected to one side of the positive electrode current collector 112 along the length direction Z of the battery cell.

[0306] like Figure 19 As shown, for example, the positive electrode tabs 111 are connected to both sides of the positive electrode current collector 112 along the length direction Z of the battery cell.

[0307] In some embodiments, the negative electrode tab 121 is connected to at least one side of the negative electrode current collector 122 along a first direction M, and the first direction M is parallel to the length direction Z of the battery cell, or the first direction M is parallel to the width direction Y of the battery cell.

[0308] like Figure 20 As shown, for example, the negative electrode tab 121 is connected to one side of the negative electrode current collector 122 along the length direction Z of the battery cell.

[0309] like Figure 21 As shown, for example, the negative electrode tabs 121 are connected to both sides of the negative electrode current collector 122 along the length direction Z of the battery cell.

[0310] In other embodiments, the positive electrode tab 111 is connected to at least one side of the positive electrode current collector 112 along the width direction Y. This arrangement shortens the electron transmission path, reduces resistance, and reduces heat generation, which is beneficial for balancing the fast charging capability and reliability of the battery cell.

[0311] like Figure 22As shown, for example, the positive electrode tab 111 is connected to one side of the positive electrode current collector 112 along the width direction Y of the battery cell.

[0312] like Figure 23 As shown, for example, the positive electrode tabs 111 are connected to both sides of the positive electrode current collector 112 along the width direction Y of the battery cell.

[0313] In other embodiments, the negative electrode tab 121 is connected to at least one side of the negative electrode current collector 122 along the width direction Y. This arrangement shortens the electron transmission path, reduces resistance, and reduces heat generation, which helps to balance the fast charging capability and reliability of the battery cell.

[0314] like Figure 24 As shown, for example, the negative electrode tab 121 is connected to one side of the negative electrode current collector 122 along the width direction Y of the battery cell.

[0315] like Figure 25 As shown, for example, the negative electrode tabs 121 are connected to both sides of the negative electrode current collector 122 along the width direction Y of the battery cell.

[0316] For example, the positive electrode tab 111 is connected to one side of the positive electrode current collector 112 along the width direction Y of the battery cell, and the negative electrode tab 121 is connected to one side of the negative electrode current collector 122 along the width direction Y of the battery cell. The positive electrode tab 111 and the negative electrode tab 121 are located on the same side of the electrode assembly 10. This arrangement shortens the electron transmission path, reduces resistance, and reduces heat generation, thereby balancing the fast charging capability and reliability of the battery cell with the energy density of the battery cell.

[0317] like Figure 26 As shown, in some embodiments, the positive electrode tab is connected to at least one side of the positive electrode current collector along the first direction M, and the negative electrode tab is connected to at least one side of the negative electrode current collector along the first direction M. Along the first direction M, the size of the negative electrode active material layer 123 is larger than the size of the positive electrode active material layer 113, and the size difference between the negative electrode active material layer 123 and the positive electrode active material layer 113 is OH1; along the second direction N, the size of the negative electrode active material layer 123 is larger than the size of the positive electrode active material layer 113, and the size difference between the negative electrode active material layer 123 and the positive electrode active material layer 113 is OH2, OH1 is greater than OH2, or OH1 is less than or equal to OH2, wherein the second direction N is perpendicular to the first direction M and the thickness direction of the battery cell.

[0318] When the first direction M is parallel to the width direction Y of the battery cell, the second direction N is parallel to the length direction Z of the battery cell. When the first direction M is parallel to the length direction Z of the battery cell, the second direction N is parallel to the width direction Y of the battery cell.

[0319] When the first direction M is parallel to the length direction Z of the battery cell 7, the negative electrode tab is located on at least one side of the negative electrode collector along the first direction M, and the current density in the connection area between the negative electrode tab and the negative electrode collector increases sharply, and problems such as lithium plating are more likely to occur in this area; and the embodiment of the present application sets OH1 to be greater than OH2, so that the negative electrode active material layer 123 has a stronger ability to receive lithium ions in the first direction M, especially can improve the ability of the negative electrode active material layer 123 to receive lithium ions in the area close to the negative electrode tab, reduce the risk of lithium plating, and improve the reliability of the battery cell.

[0320] When the first direction M is parallel to the width direction Y of the battery cell 7 , the embodiment of the present application sets OH1 to be less than or equal to OH2 , which can reduce excessive redundancy of the negative electrode active material layer 123 in the first direction M and improve the energy density of the battery cell 7 .

[0321] Exemplarily, OH1 is 1.3 mm to 5 mm, such as 1.3 mm, 1.5 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3.0 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, or a range consisting of any two of the above values; alternatively, OH1 is 1.8 mm to 4.2 mm. Along the first direction M, both sides of the negative electrode active material layer 123 may extend beyond the positive electrode active material layer 113, with each side extending beyond OH1 / 2, that is, half the size of OH1. Figure 26 OH1 / 2 is shown in FIG.

[0322] Exemplarily, OH2 is 1.5 mm to 4 mm, for example, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm, 3.5 mm, 4 mm, or a range consisting of any two of the above values; optionally, OH2 is 1.5 mm to 3.5 mm. Along the second direction N, both sides of the negative electrode active material layer 123 may extend beyond the positive electrode active material layer 113, with each side extending beyond OH2 / 2, that is, half the size of OH2. Figure 26 OH2 / 2 is shown in FIG.

[0323] [Electrolyte]

[0324] In an embodiment of the present application, the mass content of the carboxylate solvent in the electrolyte is 8% to 30%, for example, 8%, 10%, 15%, 20%, 25%, 30% or a range consisting of any two of the above values.

[0325] Too low a carboxylate ester solvent content slows ion migration in the electrolyte, hindering rapid charging of the battery cells. Too high a carboxylate ester solvent content increases the risk of gassing from interfacial side reactions at the negative electrode, leading to swelling and pressure relief in the battery cells and worsening reliability.

[0326] When the mass content of the carboxylic acid ester solvent is within the above range, it is beneficial to the migration of lithium ions and can improve the fast charging capability and use reliability of the battery cell.

[0327] In some embodiments, the carboxylate-based solvent comprises a linear carboxylate-based solvent.

[0328] Optionally, the carboxylate solvent includes a compound represented by formula I,

[0329] Formula I,

[0330] In Formula I,

[0331] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0332] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0333] The above-mentioned carboxylic acid ester solvents are beneficial to the migration of lithium ions and are beneficial to improving the fast charging capability of battery cells.

[0334] 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.

[0335] 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.

[0336] 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.

[0337] Illustratively, the carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0338] Optionally, the carboxylate solvent includes one or more of methyl acetate and ethyl acetate.

[0339] In some embodiments, the organic solvent further comprises a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 45% to 75%, for example, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, or a range consisting of any two of the foregoing values. The above mass content of the carbonate solvent can further improve the conductivity of the electrolyte, facilitate the migration of lithium ions, and improve the fast charging capability and reliability of the battery cell.

[0340] Optionally, the carbonate solvent includes one or more of a cyclic carbonate solvent and a linear carbonate solvent. Cyclic carbonate solvents have a higher dielectric constant, can better dissolve lithium salts, improve the conductivity of the electrolyte, and are beneficial to the rapid charging of battery cells. Linear carbonate solvents have a lower viscosity, can reduce the overall viscosity of the electrolyte, increase the ion migration rate, and are beneficial to the rapid charging of battery cells. The use of cyclic carbonate solvents and linear carbonate solvents together can increase the dielectric constant of the electrolyte and reduce the viscosity, thereby improving the rapid charging of battery cells.

[0341] Further optionally, the mass content of the cyclic carbonate solvent in the electrolyte is 25% to 35%, for example, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or a range consisting of any two of the foregoing values. The above mass content of the cyclic carbonate solvent can better dissolve the lithium salt, improve the conductivity of the electrolyte, and facilitate rapid charging of the battery cell.

[0342] Illustratively, the cyclic carbonate-based solvent includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate.

[0343] Further optionally, the weight content of the linear carbonate solvent in the electrolyte is 18% to 45%, for example, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or a range consisting of any two of the foregoing values. The linear carbonate solvent in the above weight content has a low viscosity, can reduce the overall viscosity of the electrolyte, increase the ion migration rate, and facilitate rapid charging of the battery cells.

[0344] Illustratively, the linear carbonate-based solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0345] In some embodiments, the electrolyte further includes an unsaturated ester additive, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 3%, and the unsaturated ester additive includes one or more of vinylene carbonate, vinyl ethylene carbonate, allyl ethyl carbonate and fluorocarbonate additives.

[0346] When the mass content of the unsaturated ester additive is within the above range, it can optimize the components of the solid electrolyte interface SEI film on the negative electrode side, improve the density of the SEI film, and reduce the risk of premature decomposition of the carboxylic acid ester solvent on the negative electrode side, so that the battery cell can reduce gas production while taking into account the fast charging performance, thereby improving the reliability of the battery cell.

[0347] Optionally, the unsaturated ester additives include vinylene carbonate and fluorocarbonate additives. Fluorinated carbonate additives and vinylene carbonate work together, and fluorocarbonate additives can further optimize the components of the SEI film, reduce the impedance of the SEI film, increase the internal resistance of the battery cell, and effectively improve the fast charging capability of the battery cell at high energy density. Fluorinated carbonate additives can form a film 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 reducing the gas production at the interface, and can more effectively take into account the improvement of the fast charging capability and reliability of the battery cell.

[0348] For example, the fluorocarbonate additive includes one or more of fluoroethylene carbonate, bisfluoroethylene carbonate, and trifluoromethylethylene carbonate.

[0349] Illustratively, the unsaturated ester additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0350] Illustratively, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 3%, for example, 0.05%, 0.15%, 0.25%, 0.35%, 0.45%, 0.55%, 0.65%, 0.75%, 0.85%, 0.95%, 1.05%, 1.15%, 1.25%, 1.35%, 1.45%, 1.55%, 1.65%, 1.75%, 1.85%, 1.95%, 2.05%, 2.15%, 2.25%, 2.35%, 2.45%, 2.55%, 2.65%, 2.75%, 2.85%, 2.95%, 3.00%, or a range consisting of any two of the above values.

[0351] When the mass content of the unsaturated ester additive is within the above range, a dense and relatively low-impedance SEI film can be formed on the negative electrode side, thereby providing excellent protection for the negative electrode side, reducing the gas production caused by interfacial side reactions, and taking into account the fast charging capability and reliability of the battery cell.

[0352] When certain substances, such as additives, are added to the electrolyte, their content in the electrolyte of the battery cell is related to the post-formation period, 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. However, those skilled in the art can determine the approximate content range of the relevant substances in the fresh electrolyte based on the performance expression level of the battery cell (such as the number of cycles), residual content, etc. Similarly, those skilled in the art can also 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.

[0353] 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.

[0354] Illustratively, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 3%, for example, 0.05%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3% or a range consisting of any two of the above values.

[0355] When the mass content of the unsaturated ester additive is within the above range, an excellent SEI film can be formed on the negative electrode side, which can improve the interface stability of the negative electrode side. In addition, the impedance of the SEI film is small, and the internal resistance of the battery cell is small, thereby improving the reliability and fast charging performance of the battery cell.

[0356] For example, the mass content of unsaturated ester additives in the electrolyte is 1% to 3%, which can be understood as the unsaturated ester additive content of the freshly prepared electrolyte. When the mass content of the unsaturated ester additive is within the above range, it can more effectively take into account the reliability and fast charging performance of the battery cell.

[0357] For example, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 2%, which can be understood as obtaining the content of the unsaturated ester additive in the electrolyte of the battery cell after formation. When the mass content of the unsaturated ester additive is within the above range, it can more effectively take into account the reliability and fast charging performance of the battery cell.

[0358] As the cycle and storage time of battery cells increases, the unsaturated ester additives are continuously consumed, and their mass content shows a downward trend. The changes in the mass content of unsaturated ester additives in different life cycles of battery cells are as follows:

[0359] In the fresh electrolyte, the mass content of unsaturated ester additives is 1%;

[0360] The mass content of unsaturated ester additives in battery cells stored in the lower warehouse for 3 months is about 0.26%;

[0361] When the battery cells are stored in the lower warehouse for 3 to 6 months, the mass content of unsaturated ester additives is about 0.12%;

[0362] When the battery cells are stored in the lower warehouse for 6 to 12 months, the mass content of the unsaturated ester additive is approximately 0.05%.

[0363] In the fresh electrolyte, the mass content of unsaturated ester additives is 2%;

[0364] The mass content of unsaturated ester additives in battery cells stored in the lower warehouse for 3 months is about 0.83%;

[0365] When the battery cells are stored in the lower warehouse for 3 to 6 months, the mass content of unsaturated ester additives is about 0.60%;

[0366] When the battery cells are stored in the lower warehouse for 6 to 12 months, the mass content of the unsaturated ester additive is approximately 0.42%.

[0367] In the fresh electrolyte, the mass content of unsaturated ester additives is 3%;

[0368] The mass content of unsaturated ester additives in battery cells stored in the lower warehouse for 3 months is about 1.56%;

[0369] When the battery cells are stored in the lower warehouse for 3 to 6 months, the mass content of unsaturated ester additives is about 1.28%;

[0370] When the battery cells are stored in the lower warehouse for 6 to 12 months, the mass content of unsaturated ester additives is approximately 1.03%.

[0371] In an embodiment of the present application, the electrolyte further includes lithium fluorosulfonate, and the mass content of lithium fluorosulfonate in the electrolyte is 0.05% to 0.5%, for example, 0.05%, 0.15%, 0.25%, 0.35%, 0.45%, 0.5 or a range consisting of any two of the above values.

[0372] When the mass content of lithium fluorosulfonate is too low, the ion transport capacity of the electrolyte is relatively poor; when the mass content of lithium fluorosulfonate is too high, the impedance of the SEI film formed on the negative electrode side is too high, which increases the internal resistance of the battery cell and is not conducive to the rapid charging of the battery cell.

[0373] Lithium fluorosulfonate LiSO3F can provide high ionic conductivity. When combined with carboxylic acid ester solvents, it can promote the transport of lithium ions in the electrolyte. Lithium fluorosulfonate can also form a SEI film on the negative electrode side that includes inorganic components with low impedance, improving the stability of the negative electrode interface, which is beneficial to improving both the fast charging performance and the reliability of the battery cell.

[0374] In some embodiments, the electrolyte includes a lithium salt additive having a mass content of 0.1% to 1% in the electrolyte, for example, the mass content of the lithium salt additive is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or a range consisting of any two of the above values.

[0375] Lithium salt additives can optimize the membrane components of the SEI membrane. Lithium salt additives participate in the formation of an inorganic-rich SEI membrane. Inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI membrane. The electrolyte is not easily decomposed and gasified, thereby improving the reliability of the battery cell.

[0376] Illustratively, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium tetrafluoroborate LiBF4, lithium bis(oxalatoborate) LiBOB, and lithium difluorooxalatoborate LiDFOB.

[0377] In some embodiments, the electrolyte includes a silane-based additive. Optionally, the mass content of the silane-based additive in the electrolyte is 0.05% to 1%, for example, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range consisting of any two of the foregoing values. Optionally, the mass content of the silane-based additive in the electrolyte is 0.1% to 0.5%.

[0378] Silane-based additives can combine with trace water in the electrolyte, reduce the generation of hydrofluoric acid HF, slow down the side interface reaction on the negative electrode side caused by HF acid destroying the SEI film, reduce the gas production of the electrolyte, reduce the internal pressure of the battery cell, and improve the reliability of the battery cell.

[0379] In some embodiments, the silane-based additive includes one or more of tris(trimethylsilyl)phosphate (TMSP), tris(trimethylsilyl)borate (TMSB), and trimethylfluorosilane. Alternatively, the silane-based additive includes one or more of tris(trimethylsilyl)phosphate (TMSP) and trimethylfluorosilane. These materials are more conducive to balancing the reliability and fast charging capabilities of the battery cells.

[0380] In some embodiments, the electrolyte further comprises a sulfur-containing additive in an amount of 0 to 2% by weight of the electrolyte, for example, the amount of the sulfur-containing additive is 0, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or a range consisting of any two of the foregoing values. Optionally, the amount of the sulfur-containing additive in the electrolyte is 0.5% to 2%.

[0381] Sulfur-containing additives can optimize the membrane components of the SEI film. Sulfur-containing additives participate in the formation of an inorganic-rich SEI film. Inorganic substances can improve the high-temperature stability and high-pressure stability of the SEI film, improve the interface stability, reduce the gas production caused by interface side reactions, and take into account the fast charging capability and reliability of the battery cell.

[0382] For example, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butylene sulfite BS, 1,3 propane sultone, vinyl sulfite ES, and methylene disulfonate MMDS.

[0383] When the mass content of sulfur-containing additives is 0,

[0384] It can be that the freshly prepared electrolyte does not contain sulfur additives.

[0385] Alternatively, the electrolyte obtained after disassembling the battery cell does not contain sulfur-containing additives. This may be because the freshly prepared electrolyte does not contain sulfur-containing additives, or a small amount of sulfur-containing additives may be added, but the sulfur-containing additives participate in the SEI film formation reaction during the battery cell formation process, resulting in a mass content of the sulfur-containing additives of zero during the test.

[0386] In some embodiments, the electrolyte includes a lithium salt, and the lithium salt has a weight content of 10% to 18% in the electrolyte, such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or any combination thereof. Such a lithium salt content can improve the fast charging capability and reliability of the battery cell.

[0387] Optionally, the lithium salt comprises one or more of a fluorinated lithium sulfonyl imide and lithium hexafluorophosphate. Further, the lithium salt comprises a fluorinated lithium sulfonyl imide and lithium hexafluorophosphate. These lithium salts readily dissociate, facilitating rapid lithium ion migration. Furthermore, the electrolyte system is relatively stable and less susceptible to decomposition and gassing, thereby enhancing the rapid charging capability and reliability of the battery cells.

[0388] Exemplarily, the fluorinated lithium sulfonyl imide includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI). For example, the fluorinated lithium sulfonyl imide includes lithium bis(fluorosulfonyl)imide (LiFSI). These materials more easily dissociate lithium ions, improving the conductivity of the electrolyte and enhancing the thermal stability of the electrolyte, thereby ensuring both fast charging and reliable operation of the battery cells.

[0389] Optionally, the mass content of the fluorinated lithium sulfonyl imide in the electrolyte is 3% to 8%, for example, 3%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or any combination thereof. When the mass content of the fluorinated lithium sulfonyl imide is within the above range, the thermal stability of the electrolyte can be improved, while ensuring both fast charging and reliability of the battery cells.

[0390] Optionally, the mass content of lithium hexafluorophosphate in the electrolyte is 8% to 12%, for example, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, or any combination thereof. Lithium hexafluorophosphate improves the conductivity of the electrolyte and has good solubility in organic solvents, making the electrolyte system more stable.

[0391] In the embodiments of the present application, the types and contents of the inorganic components / electrolyte lithium salts in the electrolyte have well-known meanings in the art and can be detected using equipment and methods well-known in the art. For example, the inorganic components / electrolyte lithium salts in the electrolyte can be qualitatively or quantitatively analyzed with reference to the standards JY / T 0575-2020 "General Rules for Ion Chromatography Analysis Methods" and GB / T 6040-2019 "General Rules for Infrared Spectroscopy 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.

[0392] 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 / T 9722-2023 "General Rules for Gas Chromatography of Chemical Reagents".

[0393] [Positive electrode]

[0394] The positive electrode portion includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector and comprising a positive electrode active material. For example, the positive electrode current collector has two opposing sides in its thickness direction, and the positive electrode active material layer is disposed on either or both sides of the positive electrode current collector.

[0395] In an embodiment of the present application, the lithium-containing phosphate can be phosphate particles having an olivine structure; or a material obtained by coating and modifying phosphate particles. For example, the lithium-containing phosphate 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.

[0396] By coating the surface of the phosphate particles with a positive electrode coating layer, the conductivity of the lithium-containing phosphate can be improved, which is beneficial to the migration rate of lithium ions, improves the fast charging capability of the battery cells, reduces the heat generation of the battery cells, and reduces the risk of high-temperature decomposition and gas production of the electrolyte, taking into account the fast charging capability and reliability of the battery cells.

[0397] 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 service life of battery cells.

[0398] 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 z1A material, wherein 0.5≤x1≤1.3, 0≤y1≤1.3, 0.5≤x1+y1≤1.3, 0.9≤a1≤1.5, 0≤b1≤0.5, 0.9≤a1+b1≤1.5, 0≤c1≤0.5, 3≤z1≤5, A includes one or more of Na, K and Mg; Me includes one or more of Mn, Fe, Co and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Hf, Ge and Ce; X includes one or more of Cl, C and N; and Y includes one or more of O and F.

[0399] Lithium-containing phosphates have excellent stability during the cycle process and can increase the service life of battery cells.

[0400] 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.

[0401] In some embodiments, the mass content of carbon in the lithium-containing phosphate is 0.8% to 2.3%. For example, the mass content of carbon in the lithium-containing phosphate is 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.3%, or a range consisting of any two of the foregoing values.

[0402] 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 lithium-containing phosphate, which is beneficial to improving the ionic conductivity and electronic conductivity of the lithium-containing phosphate, and can improve the rapid charging capability of the battery cell at high energy density.

[0403] In some embodiments, the positive electrode coating layer further comprises one or more elements of Fe, Ti, Zr, Hf, Ge, and Sn. These elements are beneficial for improving the fast charging capability of the lithium-containing phosphate.

[0404] 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.

[0405] 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.

[0406] 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.

[0407] 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.

[0408] 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 enhancing the rapid charging capability of the battery cell.

[0409] The positive electrode active material of the present application uses lithium-containing phosphate as a base material, fully utilizing the advantages of lithium-containing phosphate, such as low cost, high reliability in use, and good cycle stability, while at the same time utilizing the positive electrode coating layer (fast ion conductor layer and carbon coating layer) to solve the disadvantages of poor electronic conductivity and ionic conductivity.

[0410] 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, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode portion is disassembled, cleaned with dimethyl carbonate (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 material 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.

[0411] In some embodiments, the specific surface area of ​​the olivine-structured lithium-containing phosphate is 9 m 2 / g to 15m 2 / g, for example 9m 2 / g、10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g、15m 2 / g or a range consisting of any two of the above values.

[0412] The specific surface area of ​​the lithium-containing phosphate with an olivine structure is within the above range, which is beneficial to the transmission of lithium ions at the interface between the lithium-containing phosphate and the electrolyte, improves the ion conductivity, and enhances the fast charging capability of the battery cell.

[0413] In the embodiments of the present application, the specific surface area of ​​the material has a meaning well known in the art and can be tested using equipment and methods well known in the art. For example, according to the test standard GB / T 19587-2017, the specific surface area of ​​the lithium-containing phosphate is tested using a Tri-Star 3020 specific surface area pore size analyzer produced by Micromeritics, USA.

[0414] In some embodiments, the mass content of the olivine-structured lithium-containing phosphate in the positive electrode active material layer is 96.8% to 97.8%, for example, 96.8%, 97%, 97.5%, 97.8% or a range consisting of any two of the above values.

[0415] When the mass content of the lithium-containing phosphate in the positive electrode active material layer satisfies the above range, the capacity of the positive electrode active material layer can be increased, thereby improving the energy density of the battery cell.

[0416] In the embodiments of the present application, the mass content of the positive electrode active material has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, after discharging the battery cell to 0% state of charge (SOC), the positive electrode portion is disassembled (if it is a double-sided coated electrode sheet, the positive electrode active material layer on one side can be wiped off first), and the mass content of the positive electrode active material in the positive electrode active material layer is calculated according to the following steps:

[0417] Step 1: Weigh the total weight of the container and filter membrane as m0;

[0418] Step 2: Combine n pieces of positive electrode with a total mass of m2 and a concentration of 25 wt % concentrated hydrochloric acid in a container, with a mass ratio of the positive electrode portion to the concentrated hydrochloric acid being 1:8, and then placing the container on a hot plate for primary heating digestion at 180° C. for 20 minutes to obtain a primary digestion solution with a volume of approximately 2.5 mL; vacuum filtering the primary digestion solution through a filter membrane, and rinsing the filtered residue with 200 mL of water to obtain a rinsed filter residue; and weighing the weight of a single positive electrode current collector after removing the positive electrode active material layer as m1;

[0419] Step 3: Mix the filter residue after washing in step 2 with a concentration of 36 wt% concentrated hydrochloric acid in a container, with the mass ratio of the filter residue to the concentrated hydrochloric acid being 1:5, and then the container was placed on a hot plate for secondary heating digestion at 230°C for 10 minutes to obtain a secondary digestion solution with a volume of about 5 mL;

[0420] Step 4: Filter the secondary digestion solution through the filter membrane in step 2, and rinse the filtered residue with 200 mL of water;

[0421] Step 5: Repeat steps 3 and 4 until the filtrate is a colorless and transparent solution to obtain a product residue, bake the product residue at 90°C for 10 hours, and then place it in a desiccator to dry for 1 hour;

[0422] Step 6: Weigh the total weight of the container, product residue and filter membrane as m3. Based on the obtained m0, m1, m2 and m3, calculate the content of positive electrode active material in the positive electrode part according to the formula W t , the calculation formula is:

[0423] .

[0424] In some embodiments, the resistivity of the lithium phosphate-containing powder is 1 Ω•cm to 15 Ω•cm, for example, 1 Ω•cm, 2 Ω•cm, 3 Ω•cm, 4 Ω•cm, 5 Ω•cm, 6 Ω•cm, 7 Ω•cm, 8 Ω•cm, 9 Ω•cm, 10 Ω•cm, 11 Ω•cm, 12 Ω•cm, 13 Ω•cm, 14 Ω•cm, 15 Ω•cm, or a range consisting of any two of the above values.

[0425] The powder resistivity of the positive electrode active material is relatively low, which makes the resistance of the positive electrode relatively low, the internal resistance of the battery cell is low, and the heat generation is less. It can improve the stability of the electrolyte and reduce the high-temperature gas production, which is beneficial to taking into account the fast charging capability and reliability of the battery cell.

[0426] In an embodiment of the present application, the powder resistivity of the positive electrode active material may be the powder resistivity of the positive electrode active material at 8 MPa, which may be tested using methods and equipment known in the art, such as according to the test standard GB / T30835-2014. For example, an appropriate amount of material is placed in a tablet press to prepare a sheet sample, wherein the pressure of the tablet press is 8 MPa, i.e., the sheet sample is subjected to a pressure of 8 MPa; a powder resistivity tester, such as Yuanneng Technology PRCD1100, is connected to both ends of the sample, and the resistivity data of the sample is tested and used as the powder resistivity. Moisture has a significant impact on the test results. During the test, the material can be placed in a sealing device, such as aluminum foil, for sealing before testing.

[0427] In some embodiments, the powder compaction density of the positive electrode active material at 30,000 N is 2.53 g / cm3 to 2.80g / cm 3 .

[0428] For example, the powder compaction density of the positive electrode active material at 30000N is 2.53g / 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 , 2.80g / cm 3 Or a range consisting of any two of the above values.

[0429] 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 in the positive electrode active material layer can be stacked more densely and the contact resistance between particles is smaller, the resistance of the electrode sheet can be further reduced, the internal resistance of the battery cell can be reduced, and heat generation and high-temperature gas production can be reduced, which is beneficial to taking into account the energy density, fast charging capability and reliability of the battery cell.

[0430] In the embodiment of the present application, the powder compaction density of the material has a meaning well known in the art and can be tested using methods and equipment well 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.

[0431] In some embodiments, the compacted density of the positive electrode active material layer is 2.6 g / cm 3 Up to 2.8g / cm 3 For example, the compaction density of the positive electrode active material layer is 2.60 g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.75g / cm 3 , 2.8g / cm 3Or a range consisting of any two of the above values.

[0432] The compaction density of the positive electrode active material layer may be the compaction density of the positive electrode active material layer at a state of charge (SOC) of the battery cell of 100%.

[0433] When the compaction density of the positive electrode active material layer is within the above range, it is beneficial to improve the energy density of the battery cell. Furthermore, because the positive electrode active material in the positive electrode active material layer is densely packed, the contact resistance between particles is low, which can further reduce the resistance of the electrode sheet, reduce the internal resistance of the battery cell, and improve the fast charging capability of the battery cell. Furthermore, when the resistance is low, the heat generation within the battery cell is low, the electrolyte stability is high, and the amount of high-temperature gas generated can be reduced, which is beneficial to improving the reliability of the battery cell, thereby balancing the energy density, reliability, and fast charging capability of the battery cell.

[0434] In some embodiments, the single-side coating weight of the positive electrode active material layer is 250 mg / 1540.25 mm 2 Up to 320mg / 1540.25mm 2 , for example, 250mg / 1540.25mm², 260mg / 1540.25mm², 270mg / 1540.25mm², 280mg / 1540.25mm², 290mg / 1540.25mm², 300mg / 1540.25mm², 310mg / 1540.25mm², 320mg / 1540.25mm² or a range consisting of any two of the above values.

[0435] When the single-sided coating weight of the positive electrode active material layer is within the above range, the heat generated per unit area of ​​the positive electrode portion will not be too large, which is beneficial for taking into account the energy density, fast charging capability and reliability of the battery cell.

[0436] The upper charge voltage limit and discharge cutoff voltage of a battery cell vary depending on the positive electrode active material. For example, when the phosphate material includes lithium iron phosphate, the upper charge voltage limit may be 3.65V, and the discharge cutoff voltage may be 2.0V. Another example is when the phosphate material includes lithium manganese iron phosphate, the upper charge voltage limit may be 4.2V, and the discharge cutoff voltage may be 2.0V.

[0437] Next, the state of the battery cell is described by taking the charging upper limit voltage of 3.65V and the discharge cut-off voltage of 2.0V as an example: 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:

[0438] 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.

[0439] In the embodiments of the present application, the compacted density and single-sided coating weight of the positive electrode active material layer can be tested using the following method: disassemble the positive electrode portion from the battery cell, for example, take a single-sided coated positive electrode portion (if it is a double-sided coated electrode, the positive electrode active material layer on one side can be wiped off first), punch it into a small disc with an area of ​​S1, weigh it, record it as M1, and measure its thickness H1. Then, wipe off the positive electrode active material layer of the weighed positive electrode portion, weigh the positive electrode current collector, record it as M0, and measure its thickness H0.

[0440] The coating weight of the positive electrode active material layer on one side=(the weight of the positive electrode portion M1 - the weight of the positive electrode current collector M0) / S1.

[0441] In some embodiments, the positive electrode active material layer may also optionally include a positive electrode conductive agent. The present embodiments do not specifically limit the type of positive electrode conductive agent. For example, the positive electrode conductive agent may include one or more of conductive carbon black, carbon nanotubes, superconducting carbon, conductive graphite, acetylene black, Ketjen black, carbon dots, graphene, and carbon nanofibers. The positive electrode conductive agent can enhance the conductivity of the positive electrode active material layer, thereby improving the fast charging capability of the battery cell.

[0442] Optionally, based on the mass of the positive electrode active material layer, the mass content of the positive electrode conductive agent is 0.1% to 1.2%, for example, 0.1%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, or a range consisting of any two of the foregoing values. When the mass content of the positive electrode conductive agent is within the foregoing range, the mass proportion of other substances, such as the positive electrode active material, can be increased while improving the conductivity of the positive electrode active material layer, thereby achieving a balance between the fast charging capability and energy density of the battery cell.

[0443] In some embodiments, the positive electrode active material layer may further optionally include a first binder. The embodiment of the present application does not particularly limit the type of the first binder. As an example, the first binder may include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and one or more fluorine-containing acrylic resins. In some embodiments, based on the mass of the positive electrode active material layer, the mass content of the first binder is ≤5%.

[0444] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying, and cold pressing. 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 may be, but is not limited to, N-methylpyrrolidone (NMP).

[0445] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As examples of metal foils, one or more foils of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0446] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 13 μm, for example, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, or a range consisting of any two of the foregoing values. When the thickness of the positive electrode current collector is within the foregoing range, the thickness of the positive electrode current collector is relatively thin, which helps to increase the space occupied by the positive electrode active material layer, thereby increasing the volume energy density of the battery cell.

[0447] In the embodiment of the present application, the thickness of the positive electrode current collector has a well-known meaning 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 positive electrode portion to directly measure the thickness of the positive electrode current collector.

[0448] The positive electrode portion does not exclude other additional functional layers in addition to the positive electrode active material layer. For example, in some embodiments, the positive electrode portion 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 active material layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode portion of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode active material layer.

[0449] In some embodiments, the positive electrode portion further includes a positive electrode conductive layer, which is located between the positive electrode active material layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode portion and reduce heat generation in the positive electrode portion, thereby reducing heat generation in the battery cell and reducing high-temperature gas generation in the electrolyte, thereby ensuring both fast charging capability and reliability of the battery cell.

[0450] In some embodiments, the thickness of the single-sided positive electrode conductive layer is 0.5 μm to 2 μm. For example, the thickness of the single-sided 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.

[0451] When the thickness of the single-sided positive electrode conductive layer is within the above range, the space it occupies is relatively small, which is beneficial to increasing the space occupied by the positive electrode active material layer; and the positive electrode conductive layer can further improve the conductivity of the positive electrode part, reduce the heat generation of the positive electrode part, thereby reducing the heat generation of the battery cell, and reducing the gas production caused by high-temperature decomposition of the electrolyte, which can take into account the energy density, fast charging capability and reliability of the battery cell.

[0452] A positive electrode conductive layer is provided on at least one side of the positive electrode current collector, for example, a positive electrode conductive layer is provided on one side of the positive electrode current collector, or positive electrode conductive layers are provided on both sides of the positive electrode current collector; the thickness of the above-mentioned single-sided positive electrode conductive layer refers to the thickness of the positive electrode conductive layer located on one side of the positive electrode current collector.

[0453] In the embodiment of the present application, the thickness of the positive electrode conductive layer has a well-known meaning 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 portion to directly measure the thickness of the positive electrode conductive layer.

[0454] In some embodiments, the positive electrode conductive layer includes one or more of a first conductive agent and a first binder.

[0455] Optionally, the mass content of the first conductive agent in the positive electrode conductive layer is 30% to 55%. Exemplarily, the mass content of the first conductive agent is 30%, 35%, 40%, 45%, 50%, 55%, or a range consisting of any two of the above values.

[0456] Illustratively, the first conductive agent of the positive electrode conductive layer includes one or more of conductive carbon black, carbon nanotubes, superconducting carbon, conductive graphite, acetylene black, Ketjen black, carbon dots, graphene, and carbon nanofibers. The first 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 portion, reducing heat generation in the battery cell, and reducing high-temperature gas generation in the electrolyte, thereby ensuring both the fast charging capability and operational reliability of the battery cell.

[0457] Optionally, the mass content of the first binder in the positive electrode conductive layer is 40% to 70%. Exemplarily, the mass content of the first binder is 40%, 45%, 50%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0458] Illustratively, the first binder of the positive electrode 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 first binder of the positive electrode conductive layer can enhance the bonding between the positive electrode current collector and the positive electrode active material layer, improve the structural stability of the positive electrode portion, and enhance the reliability of the battery cell.

[0459] In some embodiments, the positive electrode conductive layer further includes a hydroxide, for example, the hydroxide may include one or more of calcium hydroxide and magnesium hydroxide. Optionally, the hydroxide also includes calcium hydroxide. Calcium hydroxide and the like can neutralize acidic substances in the positive electrode active material layer, reducing the risk of acidic substances corroding the positive electrode current collector, further reducing internal resistance, and improving the fast charging capability of the battery cell.

[0460] Optionally, the mass content of the hydroxide in the positive electrode conductive layer is 1% to 5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the foregoing values. A hydroxide mass content within the foregoing range can effectively neutralize acidic substances in the positive electrode active material layer, reducing the risk of acidic substances corroding the positive electrode current collector, further reducing internal resistance, and improving the fast charging capability of the battery cell.

[0461] [Negative electrode]

[0462] The negative electrode portion includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two opposing sides in its thickness direction, and the negative electrode active material layer is disposed on either or both sides of the negative electrode current collector.

[0463] In some embodiments, the mass content of the negative electrode active material in the negative electrode active material layer is 96.5% to 97.8%, for example, 96.5%, 97%, 97.5%, 98%, 98.5%, or a range consisting of any two of the foregoing values.

[0464] When the mass content of the negative electrode active material in the negative electrode active material layer satisfies the above range, the capacity of the negative electrode active material layer can be increased, thereby increasing the energy density of the battery cell.

[0465] In some embodiments, the negative electrode active material includes a silicon-based material. The introduction of the silicon-based material can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0466] The silicon content of the silicon-based material in the negative electrode active material layer is 0.5% to 5% by mass, and optionally 0.8% to 3% by mass. For example, the silicon content is 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, or a range consisting of any two of the foregoing values.

[0467] When the mass content of silicon is within the above range, the energy density of the battery cell can be improved; the degree of interface side reactions can be reduced, the amount of high-temperature gas production can be reduced, and the reliability of the battery cell can be improved.

[0468] Alternatively, the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon material, and silicon-nitrogen material. These materials have a high specific capacity, which is beneficial for improving the energy density of the battery cell.

[0469] Alternatively, the silicon-based material may include one or more of silicon oxide, silicon-carbon material, and silicon-nitrogen material. Even more preferably, the silicon-based material may include silicon-carbon material. These materials exhibit relatively good cycling stability during the battery cell cycle and are beneficial for improving both the energy density and reliability of the battery cell.

[0470] For example, the silicon-carbon material may include a porous carbon skeleton and silicon disposed within the porous carbon skeleton, wherein the silicon may be nano-silicon. The nano-silicon may be deposited within the porous carbon skeleton using methods such as chemical vapor deposition, and the specific process parameters may be parameters known in the art. For example, the silicon-carbon material may include silicon carbide.

[0471] When the silicon-based material includes one or more of silicon oxide, silicon-carbon material, and silicon-nitrogen material; especially when the silicon-based material includes silicon-carbon material, the silicon-based material can further improve the energy density, reliability of use, and fast charging capability of the battery cell by improving at least one parameter such as the mass content of the silicon element, the volume average particle size, the specific surface area, and the powder compaction density.

[0472] Illustratively, based on the mass of the silicon-based material, the mass content of silicon element is 40% to 80%, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or a range consisting of any two of the above values.

[0473] Exemplarily, the volume average particle size Dv50 of the silicon-based material is 5.0 μm to 12.5 μm, for example, 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, 11.0 μm, 11.5 μm, 12.0 μm, 12.5 μm or a range consisting of any two of the above values.

[0474] 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, and can be detected using equipment and methods known in the art. For example, the material to be tested 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 19077-2024.

[0475] For example, the specific surface area of ​​the silicon-based material is 3.1 m 2 / g to 3.6m 2 / g, for example 3.1m 2 / g, 3.2m 2 / g, 3.3m 2 / g, 3.4m 2 / g, 3.5m 2 / g, 3.6m 2 / g or a range consisting of any two of the above values.

[0476] In the embodiments of the present application, the specific surface area of ​​a material has a meaning well known in the art and can be tested using equipment and methods well known in the art. For example, the test standard GB / T 19587-2017 is used for testing, and the material to be tested is used as a sample, and the specific surface area is tested using a Tri-Star 3020 specific surface area pore size analyzer produced by Micromeritics, USA.

[0477] For example, the powder compaction density of silicon-based materials at 25000N is 0.7g / cm 3 to 1.2g / cm 3 , for example 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 Or a range consisting of any two of the above values.

[0478] When the powder compaction density of the silicon-based material at 25000N 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 active material layer can be stacked more densely and the contact resistance between particles is smaller, the resistance of the electrode can be further reduced, thereby reducing heat generation, reducing high-temperature gas production, and improving the reliability and fast charging capability of the battery cell at high energy density.

[0479] In the embodiments of the present application, the powder compaction density of the material has a meaning known in the art and can be tested using methods and equipment known in the art and in accordance with the test standard GB / T 24533-2019. As an example, a certain amount of the material to be tested is taken as a sample and placed in a UTM7305 electronic pressure testing machine with a bottom area of ​​1.327 cm 2 In the mold, pressurize to 2500kg (equivalent to 25000N), maintain pressure for 30s, then release the pressure, maintain for 10s, and then record and calculate the powder compaction density of the material to be tested under a force of 25000N.

[0480] In the embodiments of the present application, the negative electrode active material also includes a carbon-based material, which includes graphite particles. Graphite particles have high stability during cycling and can extend the service life of the battery cells. The positive electrode active material of the present application is primarily a lithium-containing phosphate system, while the negative electrode active material is primarily a graphite and silicon-based material system. The combination of the two can effectively improve the energy density of lithium-containing phosphate battery cells.

[0481] In the case where the negative electrode active material includes a silicon-based material and a carbon-based material, the total mass content of the silicon-based material and the carbon-based material in the negative electrode active material layer is 96.5% to 97.8%.

[0482] 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.

[0483] The graphite main particles include secondary particles. There are more migration paths for lithium ions in the graphite main 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, so that there are more sites for lithium ions to be inserted and removed, making the conductivity of the negative electrode coating layer better, which can reduce the internal resistance of the negative electrode part, reduce the heat generation of the battery cell, reduce the high-temperature gas generation, and improve the reliability and fast charging capability of the battery cell at high energy density.

[0484] Illustratively, the graphite body particles include one or more of artificial graphite and natural graphite, and artificial graphite can be selected.

[0485] 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.

[0486] 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 portion can be further reduced, the heat generation of the battery cell can be reduced, the high-temperature gas generation can be reduced, and the reliability and fast charging capability of the battery cell under high energy density can be improved.

[0487] In some embodiments, the powder resistivity of the graphite particles is 0.005 Ω·cm to 0.04 Ω·cm, for example, 0.005 Ω·cm, 0.01 Ω·cm, 0.015 Ω·cm, 0.02 Ω·cm, 0.025 Ω·cm, 0.03 Ω·cm, 0.035 Ω·cm, 0.04 Ω·cm, or a range consisting of any two of the foregoing values.

[0488] When the powder resistivity of the graphite particles is within the above range, the resistance of the negative electrode portion is relatively low, which is beneficial to reducing the internal resistance of the negative electrode portion, reducing the heat generation of the battery cell, reducing the amount of high-temperature gas generation, and improving the reliability and fast charging capability of the battery cell at high energy density.

[0489] In the embodiment of the present application, the powder resistivity of the graphite particles may be the powder resistivity of the graphite particles at 150 MPa. The test method of the powder resistivity may refer to the test method of the powder resistivity of the positive electrode active material.

[0490] In some embodiments, the volume average particle size Dv50 of the graphite particles is 8.5 μm to 14.8 μm, for example, 8.5 μm, 9.0 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 14.8 μm, or a range consisting of any two of these values. When the Dv50 of the graphite particles is within the above range, the solid-phase transport path of lithium ions can be shortened, thereby improving fast charging capability. Furthermore, the active surface area is not excessively large, thereby reducing gas generation from interfacial side reactions, lowering internal pressure, and improving the reliability of the battery cell.

[0491] 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.

[0492] 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.

[0493] 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.

[0494] Optionally, the carbonization treatment time is 1 hour to 6 hours.

[0495] 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.

[0496] In some embodiments, the negative electrode active material may include, in addition to the carbon-based material and silicon-based material, one or more of a tin-based material and lithium titanate. The tin-based material may include one or more of elemental tin, tin oxide, and a tin alloy.

[0497] 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.

[0498] For example, the mass content of silicon in the negative electrode active material layer has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, a newly prepared negative electrode portion is 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 charge state of approximately 0% SOC) is reversely disassembled to remove the negative electrode portion, and the negative electrode portion is immersed in a solvent such as water. The negative electrode active material is separated from the negative electrode current collector, and the various substances in the negative electrode active material layer are filtered out and used as a test sample. The test sample is tested using an ICAP7400 model inductively coupled plasma-optical emission spectrometer from Thermo Fisher Scientific, USA, in accordance with the GB / T30902-2014 standard to obtain the mass content of silicon.

[0499] For example, the present application may also combine JIS / K0131-1996 X-ray diffraction analysis method general rules to perform X-ray powder diffraction test and qualitative analysis on the negative electrode part or the negative electrode active material.

[0500] 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.

[0501] In the embodiment of the present application, the negative electrode active material layer includes at least one film layer, which can be a single film layer or at least two film layers. The negative electrode active material layer can include two film layers, three film layers, four film layers, or even more film layers.

[0502] In some embodiments, the negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer is arranged on the surface of the negative electrode current collector, the carbon-based material in the first negative electrode active material layer includes graphite particles, and the second negative electrode active material layer is connected to the side of the first negative electrode active material layer away from the negative electrode current collector, and the carbon-based material in the second negative electrode active material layer includes graphite particles.

[0503] The negative electrode active material layer comprises at least two film layers. Layered coating helps improve the rapid charging capability and energy density of the battery cell. In particular, when the first and second negative electrode active material layers are differentiated, the pore structure of the negative electrode active material layers can be differentiated, reducing the tortuosity of lithium-ion transport and improving the rapid charging capability of the battery cell.

[0504] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active material layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active material layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active material layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active material layer, which is beneficial for improving the compaction density of the negative electrode active material layer. When the negative electrode active material includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode active material layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode active material layer.

[0505] There is a difference in the particle size between the first negative electrode active material layer and the second negative electrode active material layer, which can improve the fast charging capability of the battery cell. Specifically, the overpotential of the second negative electrode active material layer is usually higher, and the charging bottleneck mainly lies in the second negative electrode active material layer. In the embodiment of the present application, the particle size of the second negative electrode active material layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging capability, and improve the problem of lithium plating on the surface of the negative electrode, thereby improving the reliability of the battery cell.

[0506] Optionally, the negative electrode active material in the first negative electrode active material layer is in a granular form, and its volume average particle size Dv50 is 8.5 μm to 14.8 μm. When the first negative electrode active material layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode active material layer is 8.5 μm to 14.8 μm.

[0507] When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active material layer is within the above range, on the one hand, the solid phase transmission path of lithium ions can be shortened and the fast charging capability can be improved; on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material and increase the service life.

[0508] Optionally, the negative electrode active material in the second negative electrode active material layer is in a granular form, and its volume average particle size Dv50 is 8.5 μm to 14.8 μm. When the second negative electrode active material layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative electrode active material layer is 8.5 μm to 14.8 μm.

[0509] When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active material layer is within the above range, on the one hand, the solid phase transmission path of lithium ions can be shortened, thereby improving the fast charging capability; on the other hand, the material is not easily agglomerated during the preparation process, thereby improving the stability of the material; and on still another hand, the combination of the negative electrode active material in the second negative electrode active material layer within the above volume average particle size range and the negative electrode active material in the first negative electrode active material layer is beneficial to constructing a gradient pore difference between the second negative electrode active material layer and the first negative electrode active material layer, thereby reducing the tortuosity of lithium ion transmission, allowing lithium ions to quickly obtain electrons and precipitate on the negative electrode side, thereby reducing the risk of lithium precipitation and improving the reliability of the battery cell.

[0510] In some embodiments, at least one of the first negative active material layer and the second negative active material layer includes a silicon-based material.

[0511] For example, the first negative electrode active material layer includes a silicon-based material. The second negative electrode active material layer can effectively alleviate the volume expansion of the silicon-based material of the first negative electrode active material layer, alleviate interface side reactions, reduce high-temperature gas production, and improve the reliability of the battery cell.

[0512] Illustratively, the second negative electrode active material layer includes a silicon-based material. This configuration is beneficial for improving the energy density of the battery cell.

[0513] Illustratively, both the first negative electrode active material layer and the second negative electrode active material layer include silicon-based materials. This configuration is beneficial for improving the energy density of the battery cell.

[0514] In some embodiments, based on the total thickness of the negative electrode active material layer, the thickness of the second negative electrode active material layer accounts for 30% to 70%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range consisting of any two of the above values.

[0515] By adjusting the thickness ratio of the first negative electrode active material layer and the second negative electrode active material layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging capability of the battery cell can be improved.

[0516] In the embodiment of the present application, the thickness of the first negative electrode active material layer and the second negative electrode active material layer has a meaning well known in the art and can be detected by methods well known in the art. For example, the negative electrode portion is used as a sample, sliced ​​along the thickness direction of the negative electrode active material layer, and then photographed using a scanning electron microscope (SEM) to obtain an SEM cross-sectional image, distinguish the interface between the first negative electrode active material layer and the second negative electrode active material layer, and calculate the thickness of each film layer.

[0517] In some embodiments, the compaction density of the negative electrode active material layer is 1.2 g / cm3 Up to 1.6g / cm 3 For example, the compaction density of the negative electrode active material layer is 1.2 g / cm 3 , 1.22g / cm 3 , 1.25g / cm 3 , 1.28g / cm 3 , 1.3g / 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 , 1.6g / cm 3 Or a range consisting of any two of the above values.

[0518] When the compaction density of the negative electrode active material layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative electrode active materials in the negative electrode active material layer are stacked relatively densely and the contact resistance between particles is relatively small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation, and reducing the amount of gas generated by the decomposition of linear carboxylic acid ester solvents due to heat accumulation, while improving the fast charging capability and reliability of the battery cell.

[0519] The compaction density of the negative electrode active material layer is the compaction density of the negative electrode active material layer of the battery cell at 100% state of charge (SOC).

[0520] In the embodiment of the present application, the compaction density of the negative electrode active material layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, such as the compaction density test method for the positive electrode active material layer.

[0521] In some embodiments, the single-side coating weight of the negative electrode active material layer is 110 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 For example, the coating weight of the negative electrode active material layer on one side is 110 mg / 1540.25 mm 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 、145mg / 1540.25mm 2 、150mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0522] When the coating weight on one side of the negative electrode active material layer is within the above range, the energy density, reliability in use, and fast charging capability of the battery cell can be achieved at the same time.

[0523] In the embodiment of the present application, the single-sided coating weight of the negative electrode active material layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, such as the single-sided coating weight test method for the positive electrode active material layer.

[0524] In some embodiments, the negative electrode active material layer further includes a second binder comprising one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resins (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 second binder is ≤5% based on the total weight of the negative electrode active material layer.

[0525] In some embodiments, the negative electrode active material layer further includes a second conductive agent. The present embodiments do not particularly limit the type of the second conductive agent. For example, the second conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the weight content of the second conductive agent is ≤5% based on the total weight of the negative electrode active material layer.

[0526] In some embodiments, the negative electrode active material layer further includes 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 active material layer.

[0527] The negative electrode active material layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, drying, and cold pressing. 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.

[0528] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As examples of metal foils, one or more foils of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0529] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm, for example, 4 μm, 5 μm, 6 μm, or a range consisting of any two of the foregoing values. When the thickness of the negative electrode current collector is within the foregoing range, the thickness of the negative electrode current collector is relatively thin, which is beneficial for improving the volumetric energy density of the battery cell.

[0530] The negative electrode portion does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in certain embodiments, the negative electrode portion of the present invention further includes a negative conductive layer disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode active material layer. In other embodiments, the negative electrode portion of the present invention further includes a protective layer covering the surface of the negative electrode active material layer.

[0531] In some embodiments, the negative electrode portion further includes a negative electrode conductive layer, which is located between the negative electrode active material layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode portion and reduce heat generation in the negative electrode portion, thereby reducing heat generation in the battery cell and reducing high-temperature gas generation in the electrolyte, thereby ensuring both fast charging capability and reliability of the battery cell.

[0532] In some embodiments, the thickness of the negative electrode conductive layer on one side is 0.5 μm to 2 μm. For example, the thickness of the negative electrode conductive layer on one side 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.

[0533] When the thickness of the single-sided negative electrode conductive layer is within the above range, the space it occupies is relatively small, which is beneficial to increasing the space occupied by the negative electrode active material layer; and the negative electrode conductive layer can further improve the conductivity of the negative electrode part, reduce the heat generation of the negative electrode part, thereby reducing the heat generation of the battery cell, and can take into account the energy density, fast charging capability and reliability of the battery cell.

[0534] A negative electrode conductive layer is provided on at least one side of the negative electrode current collector, for example, a negative electrode conductive layer is provided on one side of the negative electrode current collector, or negative electrode conductive layers are provided on both sides of the negative electrode current collector; the thickness of the above-mentioned single-sided negative electrode conductive layer refers to the thickness of the negative electrode conductive layer located on one side of the negative electrode current collector.

[0535] In the embodiment of the present application, the thickness of the negative electrode conductive layer has a well-known meaning 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 portion to directly measure the thickness of the negative electrode conductive layer.

[0536] In some embodiments, the negative electrode conductive layer includes one or more of a second conductive agent and a second binder.

[0537] In some embodiments, the negative electrode conductive layer may further include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, and the like.

[0538] Optionally, the mass content of the second conductive agent in the negative electrode conductive layer is 20% to 40%. Exemplarily, the mass content of the second conductive agent is 20%, 25%, 30%, 35%, 40%, or a range consisting of any two of the above values.

[0539] Illustratively, the second conductive agent in 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. This second 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 portion, reducing heat generation in the battery cell, and reducing high-temperature gas generation in the electrolyte, thereby ensuring both rapid charging capability and operational reliability of the battery cell.

[0540] Optionally, the mass content of the second binder in the negative electrode conductive layer is 60% to 80%. Exemplarily, the mass content of the second binder is 60%, 65%, 70%, 75%, 80%, or a range consisting of any two of the above values.

[0541] Illustratively, the second binder for the negative electrode conductive layer includes one or more of styrene-butadiene rubber (SBR), a water-soluble unsaturated resin (SR-1B), a water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The second binder for the negative electrode conductive layer can enhance the bonding between the negative electrode current collector and the negative electrode active material layer, improve the structural stability of the negative electrode portion, and enhance the reliability of the battery cell.

[0542] [Isolation film]

[0543] In the embodiment of the present application, the isolation film is provided between the positive electrode portion and the negative electrode portion to isolate the positive electrode portion from the negative electrode portion.

[0544] In some embodiments, the porosity of the isolation membrane is 20% to 70%, optionally 35% to 60%. For example, the porosity of the isolation membrane is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0545] When the porosity of the isolation membrane in the embodiment of the present application is within the above range, the migration ability of lithium ions in the isolation membrane can be improved, the internal resistance of the battery cell can be further reduced, thereby reducing heat generation, and taking into account the fast charging capability and reliability of the battery cell.

[0546] In the embodiments of this application, porosity refers to the percentage of the pore volume of the separator to the total volume of the separator. Porosity can be tested according to the standard GB / T36363-2018, Polyolefin Separators for Battery Cells. It should be noted that the actual testing process may vary slightly from the standard to obtain a more accurate test value, depending on instrument differences, test errors, and to minimize the impact of porosity testing.

[0547] In the embodiment of the present application, the isolation membrane includes a base membrane with a porous structure.

[0548] In some embodiments, the base film comprises one or more of glass fiber, nonwoven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0549] Optionally, the polyolefin includes one or more of polyethylene, polypropylene and polyvinylidene fluoride.

[0550] In some embodiments, the base film has a thickness of 4 μm to 12 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, 11 μm, 12 μm, or a range consisting of any two of the above values.

[0551] When the thickness of the base film is within the above range, the migration path of lithium ions in the isolation membrane is shorter, which can further reduce the internal resistance of the battery cell and make the isolation membrane occupy less space as a whole, thereby improving the fast charging capability and energy density of the battery cell.

[0552] In the embodiments of the present application, the thickness of the film layer has a meaning commonly known in the art, and can be detected using the meanings and equipment commonly 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 discharge cut-off voltage so that the charged state of the battery cell 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.

[0553] In some embodiments, the isolation film may be a base film.

[0554] In some embodiments, the separator further includes a first functional layer disposed on at least one side of the base film. The first functional layer may include inorganic particles to enhance the separator's heat resistance and improve the reliability of the battery cell. Optionally, the first functional layer is disposed on both sides of the base film. Specifically, the first functional layer is disposed on both sides of the base film along the thickness of the separator.

[0555] Illustratively, the 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. These inorganic particles can improve the heat resistance of the first functional layer and enhance the reliability of the battery cell.

[0556] Exemplarily, the average particle size of the inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, or optionally 5 nm to 20 nm. For example, the average particle size of the 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 inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the separator, thereby improving the reliability of the battery cell.

[0557] In the embodiment of the present application, the average particle size of the 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 membrane and drying the isolation membrane as a sample, 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 particle size of the inorganic particles in the isolation membrane. The particle size of multiple, for example, 50, inorganic particles is measured, and the average value is calculated as the average particle size of the particles.

[0558] Optionally, the first functional layer may further include a binder. Optionally, the binder includes one or more of a fluorine-containing binder or a polyacrylic binder. Specifically, the fluorine-containing binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and a tetrafluoroethylene-hexafluoropropylene copolymer. The polyacrylic binder includes one or more of polyacrylic acid and a fluorine-containing acrylic resin.

[0559] In some embodiments, the isolation membrane also includes a second functional layer arranged on at least one side of the base membrane. The second functional layer may include a binder. The binder can enhance the bonding ability of adjacent film layers in the isolation membrane, reduce the risk of short circuit between the negative electrode and the positive electrode, and enhance the reliability of the battery cell.

[0560] Optionally, the second functional layer is disposed on both sides of the base film. Specifically, the second functional layer is disposed on both sides of the base film along the thickness direction of the isolation film itself.

[0561] Optionally, the binder of the second functional layer may include one or more of a fluorine-containing binder or a polyacrylic acid binder. Further optionally, the binder may include a fluorine-containing binder. Specifically, the fluorine-containing binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. The polyacrylic acid binder includes one or more of polyacrylic acid and fluorine-containing acrylic resins. The binder of the second functional layer can prevent short circuiting of the positive and negative electrodes and improve the reliability of the battery cell.

[0562] Further optionally, the second functional layer is located on a side of the first functional layer away from the base film.

[0563] For example, the separator includes a first functional layer and a second functional layer, wherein the first functional layer is located on both sides of the base film, and the second functional layer is located on one side of the base film, and is located on the side of the first functional layer away from the base film. In this case, the second functional layer can be located near the negative electrode portion.

[0564] Exemplarily, the isolation film includes a first functional layer and a second functional layer, the first functional layer is located on both sides of the base film, and the second functional layer is located on both sides of the base film and on a side of the first functional layer away from the base film.

[0565] The positive electrode portion, the separator, and the negative electrode portion can be formed into an electrode assembly through a lamination process.

[0566] The battery cell of the present application is applicable to various battery devices and electrical devices using the battery cell.

[0567] For example, the power-consuming device may be a mobile phone, portable device, laptop computer, electric vehicle, electric toy, electric tool, vehicle, ship, spacecraft, etc. Alternatively, for example, the power-consuming device may be a spacecraft, including an airplane, rocket, space shuttle, and spacecraft.

[0568] A battery device may include one or more battery cell assemblies to provide voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or in series via a busbar.

[0569] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0570] As an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing multiple battery cells to form an independent module. As an example, the battery module may be formed by bundling multiple battery cells with a cable tie.

[0571] like Figure 27 As shown, in some embodiments, the battery device may be a battery pack 2 , which includes a box 5 and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the box 5 .

[0572] As an example, the battery cell assembly may also be housed in the box body 5 by directly fixing a plurality of battery cells to the box body 5 .

[0573] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b, which define a storage space 5c. The first housing portion 5a and the second housing portion 5b engage to form a closed space within the housing 5 for accommodating the battery cell assembly. "Enclosed" here means covered or closed, and can be either sealed or unsealed. The first housing portion 5a can be a top cover or a bottom plate.

[0574] As an example, the box body 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly.

[0575] In some embodiments, the box 5 can be used as a part of the chassis structure of the vehicle. For example, part of the box 5 can become at least a part of the floor of the vehicle, or part of the box 5 can become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0576] As an example, the battery cell assembly may be a battery module 6 , and the battery cell assembly may be accommodated in the box body 5 by fixing the battery module 6 in the box body 5 .

[0577] like Figure 28 As shown, the battery module 6 includes a plurality of battery cells 7 .

[0578] In some embodiments, the battery device further includes a heat resistor 40, which covers at least one of the two first walls 211 of the battery cell 7. Optionally, the heat resistor 40 covers both first walls 211. For example, the battery module 6 includes the heat resistor 40. The heat resistor 40 can mitigate heat transfer to adjacent battery cells 7, reducing the risk of thermal runaway in adjacent battery cells 7 and improving the reliability of the battery device.

[0579] In some embodiments, the heat-resisting element 40 comprises a thermal insulation material, which may include one or more of aerogel, foam, polyurethane, and silicone rubber. These materials offer excellent thermal insulation properties, effectively mitigating heat diffusion, reducing the risk of thermal runaway between adjacent battery cells, and improving the reliability of the battery device.

[0580] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% state of charge (SOC), the temperature of the external environment in which the battery device is located is room temperature. In the embodiments of the present application, room temperature refers to any temperature between 15° C. and 35° C., for example, 25° C.

[0581] In some embodiments, during the charging process of the battery device or any battery cell 7 constituting the battery device from 10% state of charge (SOC) to 80% state of charge (SOC), the temperature of the external environment of the battery device is room temperature, such as 25° C.

[0582] In some embodiments, the battery device or any battery cell 7 constituting the battery device includes multiple charging steps from 10% state of charge to 80% state of charge, and the maximum charging rate in the multiple charging steps is 5C to 12C, for example, any value of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, 11C and 12C, or a value in the range consisting of any two of the above values.

[0583] For example, the charging step of the battery device or any battery cell 7 constituting the battery device from 10% SOC to 80% SOC may be performed as follows:

[0584] Charge from 10% SOC to 15% SOC at 8.00C constant current;

[0585] Charge from 15% SOC to 20% SOC at 8.00C constant current;

[0586] Charge from 20% SOC to 25% SOC at 8.00C constant current;

[0587] Charge from 25% SOC to 30% SOC at 8.00C constant current;

[0588] Charge from 30% SOC to 35% SOC at 7.50C constant current;

[0589] Charge from 35% SOC to 40% SOC at 6.87C constant current;

[0590] Charge from 40% SOC to 45% SOC at 6.38C constant current;

[0591] Charge from 45% SOC to 50% SOC at 5.95C constant current;

[0592] Charge from 50% SOC to 55% SOC at 5.53C constant current;

[0593] Charge from 55% SOC to 60% SOC at 5.14C constant current;

[0594] Charge from 60% SOC to 65% SOC at 4.76C constant current;

[0595] Charge from 65% SOC to 70% SOC at 4.36C constant current;

[0596] Charge from 70% SOC to 75% SOC at 3.94C constant current;

[0597] Charge from 75% SOC to 80% SOC at 3.57C constant current.

[0598] In some embodiments, the charging time of the battery device or any battery cell 7 constituting the battery device from a 10% state of charge to an 80% state of charge is 5 minutes to 12.5 minutes, and the ambient temperature of the battery device at a 10% state of charge is room temperature, for example, 25° C. Exemplarily, the charging time of the battery device from a 10% state of charge to an 80% state of charge is 12.5 minutes, 12 minutes, 11.5 minutes, 11 minutes, 10.5 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5 minutes, or a range consisting of any two of the foregoing values.

[0599] Electrical devices

[0600] A second aspect of the embodiments of the present application provides an electrical device.

[0601] For example, the power-consuming device may be a mobile phone, portable device, laptop computer, electric vehicle, electric toy, electric tool, vehicle, ship, spacecraft, etc. Alternatively, for example, the power-consuming device may be a spacecraft, including an airplane, rocket, space shuttle, and spacecraft.

[0602] Figure 29 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.

[0603] A battery device is disposed within the electrical device 1, and the battery device can be disposed at the bottom, head, or tail of the electrical device 1. The battery device can be used to power the electrical device 1. For example, the battery device can serve as an operating power source for the electrical device 1, and can also serve as a driving power source for the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1. Figure 1 The battery device shown in FIG. 1 is a battery pack 2 .

[0604] The electric device 1 may further include a controller 3 and a motor 4 . The controller 3 is used to control the battery device to supply power to the motor 4 , for example, to meet the power requirements of the electric device 1 during startup, navigation, and driving.

[0605] Example

[0606] 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.

[0607] Example 1

[0608] 1. Preparation of the positive electrode

[0609] The positive electrode part includes a positive electrode collector, a positive electrode active material layer and a positive electrode conductive layer. The positive electrode active material layer is arranged on both sides of the positive electrode collector. The positive electrode conductive layer is located between the positive electrode collector and the positive electrode active material layer. The positive electrode collector is 12.5μm aluminum foil.

[0610] The positive electrode conductive layer on the positive electrode current collector includes a first conductive agent, superconducting carbon, a first binder, polyvinylidene fluoride (PVDF), and a calcium hydroxide solvent, N-methylpyrrolidone (NMP), which are evenly mixed and then coated on the surface of the positive electrode current collector and dried to form a film layer with a thickness of 1 μm. The mass content of the first conductive agent in the positive electrode conductive layer is 43%, the mass content of the first binder is 55%, and the mass content of calcium hydroxide is 2%.

[0611] The positive electrode active material layer includes a film layer formed by uniformly coating the positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on the surface of the positive electrode conductive layer, drying, and cold pressing. The positive electrode active material 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.

[0612] 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 in the positive electrode active material is 1.12%.

[0613] The single-side coating weight of the positive electrode active material layer is 283 mg / 1540.25 mm 2 .

[0614] 2. Preparation of the negative electrode

[0615] The negative electrode portion includes a negative electrode current collector, a negative electrode conductive layer on the negative electrode current collector, and a negative electrode active material layer. The negative electrode active material layer is arranged on both sides of the negative electrode current collector, and the negative electrode conductive layer is located between the negative electrode current collector and the negative electrode active material layer. The negative electrode current collector is a copper foil with a thickness of 4.5 μm.

[0616] The negative electrode conductive layer on the negative electrode current collector includes a second conductive agent, superconducting carbon, a second binder, styrene-butadiene rubber (SBR), a thickener, sodium carboxymethyl cellulose (CMC-Na), and solvent water, which are uniformly mixed and then coated on the surface of the negative electrode current collector and dried to form a film layer with a thickness of 1 μm. The mass content of the second conductive agent in the negative electrode conductive layer is 35%, the mass content of the second binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%;

[0617] The negative electrode active material layer includes graphite particles, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 97:0.5:1.5:1, and the Dv50 of the graphite particles is 11.3 μm; the graphite particles include graphite body particles and a negative electrode coating layer coated on the surface of the graphite body particles, the graphite body particles include secondary particles, the negative electrode coating layer includes carbon elements, the mass content of the carbon element in the negative electrode coating layer in the graphite particles is 2.5%, and the graphite body particles are artificial graphite.

[0618] The single-side coating weight of the negative electrode active material layer is 130 mg / 1540.25 mm 2 .

[0619] 3. Isolation film

[0620] The isolation film includes a base film, a first functional layer and a second functional layer. The base film includes 7μm polyethylene PE, and the porosity of the isolation film is 42%;

[0621] The first functional layer is a film layer formed by coating aluminum oxide particles and a binder polyvinylidene fluoride on both sides of the base film, with a thickness of 1 μm and an average particle size of the aluminum oxide particles of 10 nm;

[0622] The second functional layer is a film layer formed by coating polyvinylidene fluoride on the first functional layer, and the thickness of the second functional layer is 1 μm.

[0623] 4. Preparation of electrolyte

[0624] The electrolyte includes an organic solvent, an electrolyte lithium salt and additives.

[0625] After mixing the components of the organic solvents, electrolyte lithium salt and additives are added to prepare an electrolyte solution.

[0626] The organic solvent includes ethyl acetate EA with a mass content of 18%, dimethyl carbonate DMC with a mass content of 31.85%, and ethylene carbonate EC with a mass content of 30%. The mass proportion of each component in the solvent is calculated based on the total mass of the electrolyte;

[0627] Based on the total mass of the electrolyte, the electrolyte also includes 1% by mass of vinylene carbonate VC, 0.7% by mass of fluoroethylene carbonate FEC, 0.5% by mass of tris(trimethylsilyl) phosphate TMSP, 2% by mass of vinyl sulfate DTD, 0.8% by mass of lithium difluorooxalatoborate LiDFOB, and 0.15% by mass of lithium fluorosulfonate LiSO3F;

[0628] The electrolyte lithium salt includes 10% by mass of lithium hexafluorophosphate LiPF6 and 5% by mass of lithium bis(fluorosulfonyl)imide LiFSI.

[0629] 5. Preparation of battery cells

[0630] The positive electrode part, separator, and negative electrode part are stacked in order, with the separator placed between the positive electrode part and the negative electrode part 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 (if necessary, multiple injections can be performed), and after vacuum packaging, standing, formation, shaping and other processes, a battery cell is obtained.

[0631] The compaction density of the positive electrode active material layer of the battery cell is 2.65 / cm 3 The compaction density of the negative electrode active material layer is 1.3 g / cm 3 ;

[0632] An explosion-proof valve is provided on the end cover of the battery cell housing.

[0633] Example 2-1 to Example 2-3

[0634] A battery cell was prepared using a method similar to that of Example 1, except that the length of the outer shell was adjusted.

[0635] Comparative Example 1

[0636] A battery cell was prepared using a method similar to that of Example 1, except that the length of the outer shell was adjusted.

[0637] Example 3-1 and Example 3-2

[0638] 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 positive electrode adapter and the thickness of the negative electrode adapter were adjusted.

[0639] Comparative Example 2-1 and Comparative Example 2-2

[0640] 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 positive electrode adapter and the thickness of the negative electrode adapter were adjusted.

[0641] Example 4-1 and Example 4-2

[0642] 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 positive electrode adapter and the thickness of the negative electrode adapter were adjusted.

[0643] Comparative Example 3

[0644] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the total area of ​​the positive electrode connection region and the total area of ​​the negative electrode connection region were adjusted.

[0645] Performance Testing

[0646] 1. DC internal resistance DCR test of battery cells

[0647] At room temperature, charge the battery cell to 3.65V at a constant current of 0.33C, let it stand for 1 min, then charge it to 3.65V at a constant current of 0.1C, let it stand for 30 min, and discharge it to 2.0V at a constant current of 0.33C. Record the discharge capacity A0 at this time in Ah. Then charge it at a constant current of 0.33C for 0.5A0Ah and adjust the SOC to 50%.

[0648] After the battery cell was placed at -20℃ for 2 hours, it was discharged at a constant current of 4C for 10 seconds and the ∆U 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 ,

[0649] 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.

[0650] 2. AC internal resistance of battery cell IMPB

[0651] Charge the battery cell at a constant current of 0.33C to 40% state of charge (SOC). At 25±3°C, use the Tonghui Battery AC Low Resistance Tester TH2523. Place the test probes on the tester on the positive and negative terminals of the battery cell respectively. The tester passes a 1kHz AC constant current source, and then reads the AC impedance value on the tester, which is the IMPB value.

[0652] 3. Temperature of the explosion-proof valve of the battery cell during fast charging

[0653] Attach a temperature sensor to the explosion-proof valve on the end cap of a battery cell. Then place the battery cell in a charger / discharger and charge it according to the following fast-charging strategy. Monitor the temperature changes of the temperature sensor probe during charging until charging is completed. Then, record the highest temperature at the explosion-proof valve of the battery cell during fast charging.

[0654] The charging process includes the following steps:

[0655] Charge from 0% SOC to 30% SOC at 8.0C constant current; charge from 30% SOC to 35% SOC at 7.5C constant current; charge from 35% SOC to 40% SOC at 6.87C constant current; charge from 40% SOC to 45% SOC at 6.38C constant current; charge from 45% SOC to 50% SOC at 5.95C constant current; charge from 50% SOC to 55% SOC at 5.53C constant current; charge from 55% SOC to 60% SOC at 5.14C constant current; charge from 60% SOC to 60% SOC at 4.76C constant current. Charge from 65% SOC to 65% SOC at a constant current of 4.36C; charge from 65% SOC to 70% SOC at a constant current of 3.94C; charge from 70% SOC to 75% SOC at a constant current of 3.57C; charge from 75% SOC to 80% SOC at a constant current of 2.82C; charge from 80% SOC to 85% SOC at a constant current of 2.45C; charge from 85% SOC to 90% SOC at a constant current of 1.4C; charge from 90% SOC to 95% SOC at a constant current of 0.33C; charge from 95% SOC to 98% SOC or 3.6V at a constant current of 0.1C.

[0656] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0657] The test results are shown in Table 1.

[0658] Table 1

[0659]

[0660] When the shell length is too short, the production process is difficult to produce battery cells.

[0661] As the length of the shell increases, the active material increases, which is beneficial to increasing the energy density of the battery cell; however, the ohmic resistance of the main body increases, which makes the AC internal resistance IMPB tend to increase. The increase in internal resistance and heat generation is not conducive to the rapid charging and reliability of the battery cell.

[0662] Embodiments 1, 2-1 and 2-3 of the present application can effectively balance the fast charging capability, energy density and reliability of the battery cells by jointly regulating the length of the shell and the AC internal resistance IMPB.

[0663] In the case of comparative example 2-1 where the thickness of the positive and negative electrode adapter is too small, the mechanical strength of the positive and negative electrode adapter is poor, and the current carrying capacity is poor; in the case of comparative example 2-2 where the thickness of the positive and negative electrode adapter is too thick, although the current carrying capacity of the positive and negative electrode adapter is relatively excellent, it is difficult to connect it with the positive and negative electrode tabs and it is easy to peel off, which reduces the reliability of the battery cell.

[0664] The thickness of the positive and negative electrode adapters of Example 3-1 and Example 3-2 is within an appropriate range, which can effectively improve the current flow capacity and connection stability, reduce internal resistance and heat generation, and effectively balance the fast charging capability and usage reliability of the battery cell.

[0665] In Comparative Example 3, the area of ​​the positive electrode connection region is too small, resulting in too small a welding area between the positive electrode tab and the positive electrode adapter, poor current carrying capacity of the positive electrode tab, increased heat generation, and increased internal resistance, which is not conducive to rapid charging and reliability of the battery cell; the area of ​​the negative electrode connection region is too small, resulting in too small a welding area between the negative electrode tab and the negative electrode adapter, poor current carrying capacity of the negative electrode tab, increased heat generation, and increased internal resistance, which is not conducive to rapid charging and reliability of the battery cell.

[0666] When the area of ​​the positive electrode connection region of Example 4-1 and Example 4-2 is within the above range, it is beneficial to improve the connection stability of the positive electrode tab and the positive electrode adapter, as well as improve the flow capacity of the positive electrode tab and the positive electrode adapter; when the area of ​​the negative electrode connection region is within the above range, it is beneficial to improve the connection stability of the negative electrode tab and the negative electrode adapter, as well as improve the flow capacity of the negative electrode tab and the negative electrode adapter, thereby improving the fast charging capability of the battery cell.

[0667] Example 5-1 and Example 5-2

[0668] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass content of ethyl acetate and the mass content of dimethyl carbonate in the electrolyte were adjusted.

[0669] Comparative Example 4-1 and Comparative Example 3-2

[0670] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass content of ethyl acetate and the mass content of dimethyl carbonate in the electrolyte were adjusted.

[0671] Example 6-1 and Example 6-2

[0672] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass content of lithium fluorosulfonate in the electrolyte was adjusted.

[0673] Comparative Example 5-1 and Comparative Example 5-2

[0674] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass content of lithium fluorosulfonate in the electrolyte was adjusted.

[0675] The test results are shown in Table 2.

[0676] Table 2

[0677]

[0678] EA represents ethyl acetate; DMC represents dimethyl carbonate; LISO3F represents lithium fluorosulfonate.

[0679] The carboxylate ester solvent content in Comparative Example 4-1 is too low, resulting in slow ion migration in the electrolyte and hindering rapid charging of the battery cells. The carboxylate ester solvent content in Comparative Example 4-2 is too high, increasing the risk of high-temperature gas generation due to interfacial side reactions on the negative electrode side.

[0680] In Examples 5-1 and 5-2 of the present application, by limiting the mass content of the carboxylic acid ester solvent within an appropriate range and combining it with an appropriate amount of unsaturated ester additive, on the basis of improving the ion migration rate in the electrolyte and improving fast charging, it can also reduce gas production, lower internal pressure, improve overcharge performance, and enhance the reliability of battery cells.

[0681] In Comparative Example 5-1, lithium fluorosulfonate is not added to the electrolyte, the internal resistance of the electrolyte is high, and the ion transmission capacity of the electrolyte is relatively poor; in Comparative Example 5-2, when the mass content of lithium fluorosulfonate in the electrolyte is too high, the impedance of the SEI film formed on the negative electrode side is too high, which increases the internal resistance of the battery cell, which is not conducive to the rapid charging of the battery cell.

[0682] The lithium fluorosulfonate in Example 6-1 and Example 6-2 can provide high ionic conductivity, and its combination with carboxylic acid ester solvents can promote the transmission of lithium ions in the electrolyte; and lithium fluorosulfonate can also form an SEI film including inorganic components with low impedance on the negative electrode side, thereby improving the stability of the negative electrode interface, which is beneficial to improving both the fast charging performance and the reliability of the battery cell.

[0683] 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: include: A housing assembly, comprising a housing and a terminal assembly disposed on the housing, the terminal assembly comprising a positive terminal and a negative terminal; A transfer assembly, including a positive transfer component and a negative transfer component; as well as An electrolyte and an electrode assembly are contained in the housing, wherein the electrode assembly comprises: a main body portion, comprising a positive electrode portion, a negative electrode portion, and a separator arranged in a stacked manner, wherein the positive electrode portion comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, and the negative electrode portion comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector; The electrode tab portion 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 collector along the first direction, the positive electrode tab and the positive terminal are connected through the positive electrode adapter, the positive electrode tab includes a positive electrode connection area, and the positive electrode connection area is the area of ​​the positive electrode tab connected to the positive electrode adapter, the negative electrode tab is connected to at least one side of the negative electrode current collector along the first direction, the negative electrode tab and the negative terminal are connected through the negative electrode adapter, the negative electrode tab includes a negative electrode connection area, and the negative electrode connection area is the area of ​​the negative electrode tab connected to the negative electrode adapter, wherein the first direction is parallel to the length direction of the battery cell, or the first direction is parallel to the width direction of the battery cell, in, The positive electrode active material layer includes an olivine-structured lithium-containing phosphate, The size of the housing along the length direction of the battery cell is 190 mm to 650 mm; The thickness of the positive electrode adapter is 1.5 mm to 2.5 mm, and the thickness of the negative electrode adapter is 1.2 mm to 2.5 mm; The total area of ​​the positive electrode connection area is 150 mm 2 Up to 600mm 2 The total area of ​​the negative electrode connection area is 150mm 2 Up to 600mm 2 ; The electrolyte comprises a carboxylate solvent and lithium fluorosulfonate, wherein the mass content of the carboxylate solvent in the electrolyte is 8% to 30%, and the mass content of the lithium fluorosulfonate in the electrolyte is 0.05% to 0.5%; The AC internal resistance of the battery cell is 0.15Ω to 0.4Ω.

2. The battery cell according to claim 1, wherein: The size of the housing along the length direction of the battery cell is greater than or equal to 190 mm and less than 300 mm, and the AC internal resistance of the battery cell is 0.15Ω to 0.3Ω.

3. The battery cell according to claim 1, wherein: The size of the housing along the length direction of the battery cell is greater than or equal to 300 mm and less than 450 mm, and the AC internal resistance of the battery cell is 0.2Ω to 0.35Ω.

4. The battery cell according to claim 1, wherein: The size of the housing along the length direction of the battery cell is greater than or equal to 450 mm and less than or equal to 650 mm, and the AC internal resistance of the battery cell is 0.25Ω to 0.4Ω.

5. The battery cell according to any one of claims 1 to 4, 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.

6. The battery cell according to claim 5, characterized in that The carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate and ethyl butyrate.

7. The battery cell according to claim 6, characterized in that The carboxylate solvent includes one or more of methyl acetate and ethyl acetate.

8. The battery cell according to claim 1, wherein: The electrolyte further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 45% to 75%.

9. The battery cell according to claim 8, characterized in that The carbonate solvent includes a cyclic carbonate solvent, and the mass content of the cyclic carbonate solvent in the electrolyte is 25% to 35%; and / or The carbonate solvent includes a linear carbonate solvent, and the mass content of the linear carbonate solvent in the electrolyte is 18% to 45%.

10. The battery cell according to claim 9, characterized in that The cyclic carbonate solvent includes one or more of ethylene carbonate, propylene carbonate and butylene carbonate; and / or The linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

11. The battery cell according to claim 1, characterized in that The electrolyte also includes an unsaturated ester additive, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 3%, and the unsaturated ester additive includes one or more of vinylene carbonate, vinyl ethylene carbonate, allyl ethyl carbonate and fluorocarbonate additives.

12. The battery cell according to claim 11, characterized in that The mass content of the unsaturated ester additive in the electrolyte is 1% to 3%.

13. The battery cell according to claim 11, characterized in that The mass content of the unsaturated ester additive in the electrolyte is 0.05% to 2%.

14. The battery cell according to claim 11, characterized in that The fluorocarbonate additive includes one or more of fluoroethylene carbonate, bisfluoroethylene carbonate and trifluoromethylethylene carbonate.

15. The battery cell according to claim 1, characterized in that The electrolyte further includes a sulfur-containing additive in an amount of 0% to 2% by mass in the electrolyte, wherein the sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite and methylene disulfonate.

16. The battery cell according to claim 15, characterized in that Based on the mass of the electrolyte, the mass content of the sulfur-containing additive is 0.5% to 2%.

17. The battery cell according to claim 1, characterized in that The electrolyte further includes a lithium salt additive with a mass content of 0.1% to 1% in the electrolyte, and the lithium salt additive includes one or more of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate) and lithium difluorooxalatoborate.

18. The battery cell according to claim 1, characterized in that The electrolyte further includes a silane-based additive, which includes one or more of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and trimethylfluorosilane. The mass content of the silane-based additive in the electrolyte is 0.05% to 1%.

19. The battery cell according to claim 18, characterized in that The mass content of the silane-based additive in the electrolyte is 0.1% to 0.5%; and / or The silane-based additive includes one or more of tris(trimethylsilyl)phosphate and trimethylfluorosilane.

20. The battery cell according to claim 1, characterized in that The electrolyte further includes a lithium salt, and the mass content of the lithium salt in the electrolyte is 10% to 18%.

21. The battery cell according to claim 20, characterized in that The lithium salt includes one or more of lithium fluorine-containing sulfonyl imide and lithium hexafluorophosphate.

22. The battery cell according to claim 21, characterized in that The fluorine-containing lithium sulfonyl imide includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

23. The battery cell according to claim 21, characterized in that The mass content of the fluorinated lithium sulfonyl imide in the electrolyte is 3% to 8%.

24. The battery cell according to claim 21, characterized in that The mass content of the lithium hexafluorophosphate in the electrolyte is 8% to 12%.

25. The battery cell according to claim 1, characterized in that The single-side coating weight of the positive electrode active material layer is 250 mg / 1540.25 mm 2 Up to 320mg / 1540.25mm 2 .

26. The battery cell according to claim 1, characterized in that The compaction density of the positive electrode active material layer is 2.6 g / cm 3 Up to 2.8g / cm 3 .

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

28. The battery cell according to claim 27, characterized in that Based on the mass of the lithium-containing phosphate, the mass content of the carbon element is 0.8% to 2.3%.

29. The battery cell according to claim 27, characterized in that The positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge and Sn.

30. The battery cell according to claim 27, wherein: The phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate and lithium cobalt phosphate.

31. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 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 one or more of Na, K and Mg; Me includes one or more of Mn, Fe, Co and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce; X includes one or more of Cl, C and N; and Y includes one or more of O and F.

32. The battery cell according to claim 1, characterized in that The positive electrode active material layer includes a positive electrode conductive agent, The positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, superconducting carbon, conductive graphite, acetylene black, Ketjen black, carbon dots, graphene and carbon nanofibers; and / or The positive electrode conductive agent has a mass content of 0.1% to 1.2% in the positive electrode active material layer.

33. The battery cell according to claim 1, characterized in that The positive electrode portion further includes a positive electrode conductive layer, wherein the positive electrode conductive layer is located between the positive electrode current collector and the positive electrode active material layer. The positive electrode conductive layer includes a first conductive agent, wherein the first conductive agent includes one or more of conductive carbon black, carbon nanotubes, superconducting carbon, conductive graphite, acetylene black, Ketjen black, carbon dots, graphene and carbon nanofibers; and / or The positive electrode conductive layer includes a first binder, which includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

34. The battery cell according to claim 1, characterized in that The porosity of the negative electrode active material layer is 30% to 45%.

35. The battery cell according to claim 1, characterized in that The single-side coating weight of the negative electrode active material layer is 110 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 .

36. The battery cell according to claim 1, characterized in that The compaction density of the negative electrode active material layer is 1.2 g / cm 3 Up to 1.6g / cm 3 .

37. The battery cell according to claim 1, characterized in that The negative electrode active material layer includes graphite particles.

38. The battery cell according to claim 1, characterized in that The negative electrode portion further includes a negative electrode conductive layer, wherein the negative electrode conductive layer is located between the negative electrode current collector and the negative electrode active material layer. The negative electrode conductive layer includes a second conductive agent, and the second conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers; and / or The negative electrode conductive layer includes a second binder, and the second binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate and carboxymethyl chitosan.

39. The battery cell according to claim 1, wherein: The porosity of the isolation membrane is 20% to 70%; and / or The isolation film includes a base film, and the base film has a thickness of 4 μm to 12 μm.

40. The battery cell according to claim 1, wherein The isolation film includes a base film and a first functional layer disposed on at least one side of the base film, wherein the first functional layer includes inorganic particles.

41. The battery cell according to claim 1, characterized in that The isolation film includes a base film and a second functional layer disposed on at least one side of the base film, wherein the second functional layer includes a fluorine-containing binder.

42. The battery cell according to claim 41, characterized in that The isolation film includes a base film and a first functional layer disposed on at least one side of the base film, wherein the first functional layer includes inorganic particles; and the second functional layer is located on a side of the first functional layer away from the base film.

43. The battery cell according to claim 40 or 42, characterized in that: The 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 inorganic particles is 5 nm to 100 nm.

44. The battery cell according to claim 1, characterized in that The positive electrode tab is connected to one side of the positive electrode current collector along the width direction of the battery cell; The negative electrode tab is connected to one side of the negative electrode current collector along the width direction of the battery cell. Wherein, the positive electrode tab and the negative electrode tab are located on the same side of the electrode assembly.

45. The battery cell according to claim 1, characterized in that Along the first direction, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH1, and OH1 is 1.3 mm to 5 mm; and / or Along the second direction, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH2. The second direction and the first direction are perpendicular to the thickness direction of the battery cell, and OH2 is 1.5mm to 4mm.

46. ​​The battery cell according to claim 45, characterized in that OH1 is 1.8 mm to 4.2 mm; and / or OH2 is 1.5 mm to 3.5 mm.

47. The battery cell according to claim 1, characterized in that Along the first direction, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH1. Along the second direction, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer, and the size difference between the negative electrode active material layer and the positive electrode active material layer is OH2. The second direction and the first direction are perpendicular to the thickness direction of the battery cell. The first direction is parallel to the width direction of the battery cell, and OH1 is less than or equal to OH2.

48. The battery cell according to claim 1, characterized in that The housing includes a shell and an end cover, the shell includes an opening, and the end cover covers the opening. The shell is a rectangular parallelepiped structure, comprising two first walls and two second walls arranged opposite to each other, the two first walls being connected by the second wall, the cross-sectional area of ​​the first wall perpendicular to its own thickness direction being larger than the cross-sectional area of ​​the second wall perpendicular to its own thickness direction. The thickness of the first wall is 0.3 mm to 0.5 mm; and / or The thickness of the second wall is 0.5 mm to 0.7 mm.

49. The battery cell according to claim 1, characterized in that The battery cell further includes a positive electrode reinforcement member, wherein the positive electrode reinforcement member is at least connected to the positive electrode connection area and is located on a side of the positive electrode tab away from the positive electrode adapter; and / or The battery cell further includes a negative electrode reinforcement member, which is connected to at least the negative electrode connection region and is located on a side of the negative electrode tab away from the negative electrode adapter.

50. The battery cell according to claim 49, characterized in that The positive electrode tab comprises aluminum or an aluminum alloy; the positive electrode reinforcement comprises aluminum or an aluminum alloy; or The negative electrode tab comprises copper or a copper alloy; the negative electrode reinforcement comprises copper or a copper alloy.

51. The battery cell according to claim 49, characterized in that The ratio of the total cross-sectional area of ​​the positive electrode reinforcement perpendicular to the thickness direction thereof to the total area of ​​the positive electrode connection region is 1.0 to 1.

5.

52. The battery cell according to claim 49, characterized in that The total cross-sectional area of ​​the positive electrode reinforcement perpendicular to its own thickness direction is 320 mm 2 Up to 1600mm 2 .

53. The battery cell according to claim 49, characterized in that The positive electrode reinforcement comprises: a first reinforcement portion, welded to the positive electrode connection region; and The second reinforcement portion is disposed around the first reinforcement portion and connected to the first reinforcement portion.

54. The battery cell according to claim 53, characterized in that The second reinforcement portion has a thickness of 0.1 mm to 0.8 mm.

55. The battery cell according to claim 1, characterized in that The battery cell further includes a positive electrode thermal insulator, the positive electrode thermal insulator is located between the positive electrode connection area and the main body and at least covers the positive electrode connection area; and / or The battery cell further includes a negative electrode thermal insulator, which is located between the negative electrode connection region and the main body and covers at least the negative electrode connection region.

56. The battery cell according to claim 55, characterized in that The thickness of the portion of the positive electrode thermal insulation member opposite to the positive electrode connection region is 1 mm to 4 mm.

57. The battery cell according to claim 55, characterized in that The positive electrode thermal insulation member includes a first thermal insulation layer and a second thermal insulation layer that are continuously arranged. The first thermal insulation layer and the second thermal insulation layer at least partially overlap, and both the first thermal insulation layer and the second thermal insulation layer at least cover the positive electrode connection area.

58. The battery cell according to claim 57, characterized in that The thickness of the first thermal insulation layer is 0.5 mm to 2.0 mm; and / or The thickness of the second heat insulation layer is 0.5 mm to 2.0 mm.

59. The battery cell according to claim 55, characterized in that The positive electrode tab is connected to a portion of the positive electrode adapter, and the positive electrode thermal insulation component is connected to another portion of the positive electrode adapter.

60. The battery cell according to claim 59, characterized in that The positive electrode heat insulation component is welded to the positive electrode adapter.

61. The battery cell according to claim 55, characterized in that The positive electrode thermal insulator includes one or more of polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polycarbonate.

62. The battery cell according to claim 61, characterized in that The polyolefin includes one or more of polyethylene, polypropylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride and polytetrafluoroethylene.

63. A battery device, characterized in that A battery cell comprising the battery cell according to any one of claims 1 to 62.

64. The battery device according to claim 63, characterized in that The battery device further includes a heat resistor covering at least one of the two first walls of the battery cell.

65. The battery device according to claim 63, characterized in that The battery device has a charging time from 10% state of charge to 80% state of charge of 5 minutes to 12.5 minutes.

66. The battery device according to claim 63, characterized in that The maximum charging rate of the battery device is 5C to 12C.

67. An electrical device, characterized in that: Comprising a battery device as claimed in any one of claims 63 to 66.

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