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 an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet includes a lithium-containing phosphate with an olivine structure. The negative electrode sheet includes graphite particles. The volume average particle size Dv50 of the graphite particles is 8.5 μm to 13.5 μm. The interstitial electrolyte amount A of the battery cell satisfies: A=A T ‑A1‑A2‑A3, 0.5g / Ah≤A≤1.4g / Ah; A T "A1" represents the amount of electrolyte in the battery cell; "A2" represents the amount of electrolyte in the positive electrode active material layer; "A3" represents the amount of electrolyte in the separator; the electrolyte comprises 25% to 35% by weight of ethylene carbonate and 0.05% to 6% by weight of an unsaturated ester additive. This application achieves both rapid charging and operational reliability for the battery cell.

Description

[0001] This application claims priority to international patent application PCT / CN2025 / 101025, entitled “Battery Cell, Battery Device, and Electrical Device,” filed on June 13, 2025, 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 for them to balance fast charging and reliability. Summary of the Invention

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

[0005] In a first aspect, the present application provides a battery cell, which includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet 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. The negative electrode sheet 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.

[0006] in,

[0007] The positive electrode active material layer includes a lithium-containing phosphate with an olivine structure, and the negative electrode active material layer includes graphite particles, wherein the volume average particle size Dv50 of the graphite particles is 8.5 μm to 13.5 μm;

[0008] The interstitial electrolyte volume A of the battery cell satisfies: A=A T -A1-A2-A3, 0.5g / Ah≤A≤1.4g / Ah;

[0009] A T Indicates the amount of electrolyte in the battery cell, its unit is g / Ah;

[0010] A1 represents the amount of electrolyte in the positive electrode active material layer, and its unit is g / Ah;

[0011] A2 represents the amount of electrolyte in the negative electrode active material layer, and its unit is g / Ah;

[0012] A3 represents the amount of electrolyte in the separator, and its unit is g / Ah;

[0013] The electrolyte includes ethylene carbonate, and the mass content of ethylene carbonate in the electrolyte is 20% to 35%;

[0014] The electrolyte also includes unsaturated ester additives, the mass content of the unsaturated ester additives in the electrolyte is 0.05% to 6%, and the unsaturated ester additives include one or more of vinylene carbonate, vinyl ethylene carbonate, allyl ethyl carbonate and fluorocarbonate additives.

[0015] This application synergistically regulates the mass content of ethylene carbonate (EC) and the particle size of graphite particles in the electrolyte. Ethylene carbonate (EC) can effectively improve the conductivity of the electrolyte. Graphite with an appropriate particle size can not only increase the solid-phase migration rate of lithium ions and improve the fast charging capability of battery cells, but also effectively balance the reaction activity between the graphite particles and the electrolyte.

[0016] In order to further slow down the interfacial side reactions on the negative electrode side, the electrolyte adjusts the amount of interstitial electrolyte and the content of unsaturated ester additives so that the total equivalent of unsaturated ester additives is relatively high, but not too high. More unsaturated ester additives can participate in the film formation and consumption of the SEI layer of the solid electrolyte interface on the negative electrode side, but the impedance of the SEI film will not be too high, which can effectively delay the time for the solvent in the electrolyte to react with small-particle graphite particles, thereby slowing down the gas production during long-term circulation, further reducing the risk of pressure release of battery cells, and improving the reliability of battery cells.

[0017] In some embodiments, the interstitial electrolyte volume A of the battery cell is 0.8 g / Ah to 1.3 g / Ah. When the interstitial electrolyte volume A of the battery cell meets the above conditions, the reliability and fast charging capability of the battery cell can be more effectively taken into account.

[0018] In some embodiments, the amount of electrolyte in the battery cell is A T When the amount of electrolyte in the battery cell is within the above range, the electrolyte components can be maintained at an appropriate level during the cycle and storage of the battery cell, which is beneficial for balancing the reliability and fast charging performance of the battery cell.

[0019] In some embodiments, the amount of electrolyte A1 in the positive electrode active material layer is 0.6 g / Ah to 1.0 g / Ah. When the amount of electrolyte in the positive electrode active material layer is within the above range, the electrolyte more fully infiltrates the positive electrode active material layer, which facilitates the rapid migration of lithium ions in the positive electrode active material layer, reduces transmission resistance, reduces the internal resistance of the battery cell, and improves the fast charging performance of the battery cell.

[0020] In some embodiments, the amount of electrolyte A2 in the negative electrode active material layer is 0.7 g / Ah to 1.0 g / Ah. When the amount of electrolyte in the negative electrode active material layer is within this range, the electrolyte more fully infiltrates the negative electrode active material layer, which facilitates the rapid migration of lithium ions in the negative electrode active material layer, reduces transmission resistance, reduces the internal resistance of the battery cell, and improves the fast charging performance of the battery cell.

[0021] In some embodiments, the amount of electrolyte A3 in the separator is 0.1 g / Ah to 0.3 g / Ah. When the amount of electrolyte in the separator is within this range, the electrolyte more fully infiltrates the negative electrode active material layer, facilitating rapid migration of lithium ions in the separator, reducing transmission resistance, lowering the internal resistance of the battery cell, and improving the fast charging performance of the battery cell.

[0022] In some embodiments, a battery cell includes a housing that houses an electrode assembly and an electrolyte, and the housing is provided with a pressure relief mechanism. When the internal pressure or temperature of the housing reaches a pressure relief threshold, the pressure relief mechanism deforms, allowing the interior of the housing to communicate with the exterior, thereby releasing the pressure or temperature within the housing.

[0023] In some embodiments, the mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 0.05% and less than 1.5%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 80% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell. The battery cell can be cycled until the current capacity decays to 85% of the nominal capacity, and the battery cell has a relatively long service life.

[0024] In some embodiments, the mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 1.5% and less than 3%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 70% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell. The battery cell can be cycled until the current capacity decays to 75% of the nominal capacity, and the battery cell has a relatively long service life.

[0025] In some embodiments, the mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 3% and less than 4.5%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 60% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell. The battery cell can be cycled until the current capacity decays to 65% of the nominal capacity, and the battery cell has a relatively long service life.

[0026] In some embodiments, the unsaturated ester additive comprises 4.5% to 6% by weight of the electrolyte, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 50% SOH, where SOH represents the ratio of the current battery cell capacity to the nominal capacity of the battery cell. The battery cell can be cycled until the current battery cell capacity decays to 55% of the nominal capacity, resulting in a relatively long battery cell life.

[0027] 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.

[0028] In some embodiments, the housing includes a shell and an end cap, the shell has an opening, the end cap covers the opening, the shell accommodates the electrode assembly and the electrolyte, and the end cap is provided with a pressure relief mechanism.

[0029] In some embodiments, the pressure relief mechanism includes a weakened portion.

[0030] In some embodiments, the mass content of ethylene carbonate in the electrolyte is 25% to 35%. When the content of ethylene carbonate is within the above range, the conductivity of the electrolyte can be increased and the fast charging capability of the battery cell can be improved.

[0031] In some embodiments, the electrolyte includes a carboxylate solvent, and the mass content of the carboxylate solvent in the electrolyte is 8% to 30%. The carboxylate solvent is conducive to the migration of lithium ions and helps improve the fast charging capability of the battery cell.

[0032] In some embodiments, the carboxylate solvent includes a compound represented by Formula I,

[0033] Formula I,

[0034] In Formula I,

[0035] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0036] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] In some embodiments, the electrolyte 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] In some embodiments, the electrolyte further includes a lithium salt additive at a concentration of 0.2% to 1.5% by weight. The lithium salt additive includes one or more of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, and lithium fluorosulfonate. 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] In some embodiments, the electrolyte further comprises a lithium salt, wherein the mass content of the lithium salt in the electrolyte is 10% to 18%. The above-mentioned content of lithium salt can improve the fast charging capability and reliability of the battery cell.

[0049] In some embodiments, the lithium salt includes one or more of lithium fluorinated sulfonyl imide and lithium hexafluorophosphate. These lithium salts are easily dissociated, facilitating the rapid migration of lithium ions. Furthermore, the electrolyte system is relatively stable and less susceptible to decomposition and gas production, thereby enhancing the rapid charging capability and reliability of the battery cells.

[0050] 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.

[0051] In some embodiments, the fluorinated lithium sulfonyl imide comprises 3% to 8% by weight of the electrolyte. This material more readily dissociates lithium ions, improving the electrolyte's conductivity and thermal stability, ensuring both rapid charging and reliable operation of the battery cells.

[0052] 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.

[0053] In some embodiments, the porosity of the negative electrode active material layer is 30% to 45%. When the porosity of the negative electrode active material layer is within the above range, the negative electrode active material layer has sufficient spatial sites to absorb the electrolyte, and the electrolyte more fully infiltrates the negative electrode active material layer, which is conducive to the rapid migration of lithium ions in the negative electrode active material layer, reduces transmission resistance, reduces the internal resistance of the battery cell, and improves the fast charging performance of the battery cell.

[0054] In some embodiments, the porosity of the positive electrode active material layer is 23% to 33%. When the porosity of the positive electrode active material layer is within the above range, the positive electrode active material layer has sufficient spatial sites to absorb the electrolyte, and the electrolyte more fully infiltrates the positive electrode active material layer, which is conducive to the rapid migration of lithium ions in the positive electrode active material layer, reduces transmission resistance, reduces the internal resistance of the battery cell, and improves the fast charging performance of the battery cell.

[0055] 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.

[0056] 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.

[0057] In some embodiments, the graphite particles include graphite main particles and a negative electrode coating layer coated on the surface of the graphite main particles, the graphite main particles include secondary particles, and the negative electrode coating layer includes carbon elements.

[0058] When the graphite particles meet the above conditions, they can improve both the reliability and fast charging capability of the battery cells.

[0059] In some embodiments, the graphite bulk particles include at least one of artificial graphite and natural graphite; when the graphite particles meet the above conditions, both the reliability and fast charging capability of the battery cell can be improved.

[0060] In some embodiments, the carbon content of the negative electrode coating is 2% to 5% by mass based on the mass of the graphite particles. When the graphite particles meet the above conditions, both the reliability and fast charging capability of the battery cell can be improved.

[0061] In some embodiments, the graphite particles include artificial graphite, which can improve both the reliability and fast charging capability of the battery cell.

[0062] 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 disposed on the negative electrode current collector; the second negative electrode active material layer is disposed on a side of the first negative electrode active material layer away from the negative electrode current collector. Both the first negative electrode active material layer and the second negative electrode active material layer include graphite particles. The negative electrode active material layer comprises at least two film layers, which helps improve the fast charging capability of the battery cell.

[0063] In some embodiments, the negative electrode plate 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 plate, reduce the heat generation of the negative electrode plate, thereby reducing the heat generation of the battery cell, and reducing the high-temperature gas generation of the electrolyte, which can take into account the fast charging capability and reliability of the battery cell.

[0064] In some embodiments, the negative electrode conductive layer includes a negative electrode conductive agent, which includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers; the negative electrode conductive 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 plate, 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.

[0065] In some embodiments, the negative electrode conductive layer includes a negative electrode binder, which includes 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 negative electrode 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 sheet.

[0066] 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 the heat generation of the battery cells and the risk of high-temperature decomposition and gas generation of the electrolyte, thereby ensuring both the rapid charging capability and the reliability of the battery cells.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] In some embodiments, the positive electrode sheet further includes a positive conductive layer, which is located between the positive current collector and the positive active material layer. The positive conductive layer can further improve the conductivity of the positive electrode sheet and reduce heat generation, 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.

[0075] In some embodiments, the positive electrode conductive layer includes a positive electrode 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 positive electrode conductive agent of the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet, 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.

[0076] In some embodiments, the positive electrode conductive layer includes a positive electrode binder, which includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorine-containing acrylate resin. The positive electrode binder in 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 sheet.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] In some embodiments, the electrode assembly is a laminated structure, with the positive electrode sheet, separator, and negative electrode sheet stacked along the thickness direction of the battery cell. The laminated electrode assembly is beneficial for improving the energy density of the battery cell.

[0085] In some embodiments, the positive electrode sheet includes at least one positive electrode tab, which is connected to at least one side of the positive electrode current collector along a first direction parallel to the width of the battery cell or the length of the battery cell. This arrangement shortens the electron transmission path, reduces resistance, and reduces heat generation, thereby ensuring both the fast charging capability and reliability of the battery cell.

[0086] In some embodiments, the negative electrode plate includes at least one negative electrode tab, which is connected to at least one side of the negative electrode current collector along a first direction parallel to the width of the battery cell or the length of the battery cell. This arrangement shortens the electron transmission path, reduces resistance, and reduces heat generation, thereby ensuring both the fast charging capability and reliability of the battery cell.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] In some embodiments, a battery cell includes a housing that houses an electrode assembly and an electrolyte. The housing includes a shell and an end cap. The shell includes an opening, and the end cap is engaged with the opening. The length of the housing along the length of the battery cell is 190 mm to 650 mm. When the length of the housing along the length of the battery cell falls within the above range, both the energy density and the fast charging capability of the battery cell can be achieved.

[0093] In some embodiments, 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; when the size of the housing along the length direction of the battery cell meets the above range, it is beneficial to improve the fast charging capability of the battery cell.

[0094] In some embodiments, the size of the shell along the length direction of the battery cell is greater than or equal to 300 mm and less than 450 mm; when the size of the shell along the length direction of the battery cell meets the above range, the energy density and fast charging capability of the battery cell can be taken into account.

[0095] In some embodiments, the size of the outer shell along the length of the battery cell is greater than or equal to 450 mm and less than or equal to 650 mm. When the size of the outer shell along the length of the battery cell meets the above range, it is beneficial to improve the energy density of the battery cell.

[0096] 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.

[0097] In some embodiments, a battery cell includes a first electrode terminal and a first adapter; an electrode assembly includes a tab portion and a main body portion, the tab portion is connected to the main body portion and extends out of the main body portion along a first direction, the tab portion includes a first tab, the first tab and the first electrode terminal are connected via a first adapter, the first tab includes a first region, the first region is a region of the first tab connected to the first adapter, wherein the first tab is a positive tab or a negative tab, and the total area of ​​the first region is 160 mm 2 Up to 1000mm 2 ,

[0098] The main body includes a positive electrode portion, a negative electrode portion, and a separator. The positive electrode portion includes a positive current collector and a positive electrode active material layer disposed on at least one side of the positive current collector. The negative electrode portion includes a negative current collector and a negative electrode active material layer disposed on at least one side of the negative current collector. When the area of ​​the first region is within the above range, the fast charging capability of the battery cell can be improved.

[0099] In some embodiments, the battery cell further includes a first reinforcement member, which is connected to at least the first region and is located on a side of the first tab facing away from the first adapter. Thus, the first reinforcement member, through the reinforcement effect of the first reinforcement member, makes the first tab less susceptible to cracking or even breaking, further improving the structural stability of the first tab, and can also enhance the current carrying capacity of the first tab, thereby improving the rapid charging capability of the battery cell.

[0100] In some embodiments, a ratio of a total cross-sectional area of ​​the first reinforcement perpendicular to its thickness direction to a total area of ​​the first region is 1.0 to 1.5.

[0101] When the ratio of the total cross-sectional area of ​​the first reinforcement perpendicular to its own thickness direction to the total area of ​​the first region is within the above range, the current flow capacity between the first tab and the first adapter can be improved, thereby improving the fast charging capability of the battery cell.

[0102] In some embodiments, the total cross-sectional area of ​​the first reinforcement perpendicular to its own thickness direction is 320 mm 2 Up to 1600mm 2 .

[0103] When the total cross-sectional area of ​​the first reinforcement perpendicular to its own thickness direction is within the above range, the current flow capacity between the first tab and the first adapter can be improved, thereby improving the fast charging capability of the battery cell.

[0104] In some embodiments, the first reinforcement member includes a first reinforcement portion and a second reinforcement portion. The first reinforcement portion is welded to the first region; the second reinforcement portion surrounds and connects to the first reinforcement portion. The first reinforcement portion reinforces the first region, and the second reinforcement portion is connected to the first reinforcement portion to enhance the overall structural stability of the first reinforcement member, thereby firmly reinforcing the first region and improving the current carrying capacity of the first region, thereby improving the rapid charging capability of the battery cell.

[0105] In some embodiments, the thickness of the second reinforcement portion is 0.1 mm to 0.8 mm. When the thickness of the second reinforcement portion is within the above range, the fast charging capability and the reliability of the battery cell can be improved.

[0106] In some embodiments, the first electrode tab is a positive electrode tab, and the positive electrode tab includes aluminum or an aluminum alloy; the first reinforcement includes aluminum or an aluminum alloy; the connection between the positive electrode tab and the first 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.

[0107] In some embodiments, the first electrode tab is a negative electrode tab, which includes copper or a copper alloy; the first reinforcement includes copper or a copper alloy; the connection between the negative electrode tab and the first 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.

[0108] In some embodiments, the battery cell further includes a first thermal insulator positioned between the first region and the main body and covering at least the first region. The first 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.

[0109] In some embodiments, the thickness of the portion of the first thermal insulation member disposed opposite the first region is 1 mm to 4 mm. The first region generates relatively more heat, and the relatively thick first thermal insulation member can more effectively mitigate heat transfer and improve the reliability of the battery cell.

[0110] In some embodiments, the first thermal insulation member includes a first thermal insulation layer and a second thermal insulation layer disposed continuously, with at least portions of the first thermal insulation layer overlapping, and both the first thermal insulation layer and the second thermal insulation layer covering at least the first region. This multi-layer coverage can more effectively mitigate heat diffusion toward the main body and electrolyte, thereby improving the reliability of the battery cell.

[0111] 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.

[0112] 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.

[0113] In some embodiments, the first tab is connected to a portion of the first adapter, and the first thermal insulator is connected to another portion of the first adapter. The connection of the first thermal insulator to the first adapter provides a more stable connection and more effective thermal insulation. Furthermore, the first thermal insulator can cover at least a portion of the first adapter, providing a wider coverage area for the first thermal insulator, further facilitating the thermal insulation of the first thermal insulator and improving the reliability of the battery cell.

[0114] In some embodiments, the first thermal insulation member and the first transition member are welded together, thereby making the connection between the first thermal insulation member and the first transition member more stable.

[0115] In some embodiments, the first thermal insulation member 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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

[0122] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces 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.

[0123] Figure 1 This is a schematic diagram of the structure of a battery cell provided in some embodiments of the present application.

[0124] Figure 2 This is a schematic diagram of an exploded view of a battery cell provided in some embodiments of the present application.

[0125] Figure 3 This is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0126] Figure 4 Schematic diagram of an exploded view of a battery cell provided in some other embodiments of the present application,

[0127] Figure 5 for Figure 4 An enlarged schematic diagram of a battery cell at position A is shown;

[0128] Figure 6 for Figure 4 Another enlarged schematic diagram of the battery cell at position A shown;

[0129] Figure 7 for Figure 4 Another enlarged schematic diagram of the battery cell at position A shown;

[0130] Figure 8 A schematic structural diagram of an end cover, etc. of a battery cell provided in some embodiments of the present application;

[0131] Figure 9 A schematic structural diagram of a first adapter, a first tab, and a first reinforcement member of a battery cell provided in some embodiments of the present application;

[0132] Figure 10 Schematic diagram of the structure of the first adapter, the first tab, and the first reinforcement of the battery cell provided in other embodiments of the present application;

[0133] Figure 11 Schematic diagram of the structure of the first adapter, the first tab, and the first thermal insulation member of the battery cell provided in other embodiments of the present application;

[0134] Figure 12 Schematic diagram of the structure of the first adapter, the first tab, and the first thermal insulation member of the battery cell provided in other embodiments of the present application;

[0135] Figure 13 A schematic structural diagram of a battery cell provided in some other embodiments of the present application;

[0136] Figure 14 for Figure 13 An enlarged schematic diagram of a battery cell at position B is shown;

[0137] Figure 15 A schematic structural diagram of a first thermal insulation member of a battery cell provided in some embodiments of the present application;

[0138] Figure 16 A schematic structural diagram of a first thermal insulation member of a battery cell provided in some other embodiments of the present application;

[0139] Figure 17 A schematic structural diagram of an electrode assembly of a battery cell provided in other embodiments of the present application;

[0140] Figure 18 This is a schematic structural diagram of the positive electrode sheet of a battery cell provided in some embodiments of the present application.

[0141] Figure 19 This is a schematic structural diagram of the positive electrode sheet of a battery cell provided in some other embodiments of the present application.

[0142] Figure 20 This is a schematic structural diagram of the negative electrode sheet of a battery cell provided in some embodiments of the present application.

[0143] Figure 21 This is a schematic structural diagram of the negative electrode sheet of a battery cell provided in some other embodiments of the present application.

[0144] Figure 22 This is a schematic structural diagram of the positive electrode sheet of a battery cell provided in some embodiments of the present application.

[0145] Figure 23 This is a schematic structural diagram of the positive electrode sheet of a battery cell provided in some other embodiments of the present application.

[0146] Figure 24 This is a schematic structural diagram of the negative electrode sheet of a battery cell provided in some embodiments of the present application.

[0147] Figure 25 This is a schematic structural diagram of the negative electrode sheet of a battery cell provided in some other embodiments of the present application.

[0148] Figure 26 This is a schematic diagram of a top view of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0149] Figure 27 A schematic diagram of the structure of a battery pack provided in some embodiments of the present application is shown.

[0150] Figure 28 This is a schematic diagram of the structure of the battery module provided in some embodiments of the present application.

[0151] Figure 29 It is a schematic diagram of the structure of an electrical device provided in some embodiments of the present application.

[0152] The drawings are not necessarily drawn to scale.

[0153] The following are the descriptions of the reference numerals:

[0154] M, first direction; N, second direction;

[0155] X, thickness direction of the battery cell; Y, width direction of the battery cell; Z, length direction of the battery cell;

[0156] 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;

[0157] 10. Electrode assembly;

[0158] 110, first tab;

[0159] 11. Positive electrode;

[0160] 111, positive electrode tab; 1111, first region; 1111a, sub-region; 1111b, unit region;

[0161] 112. positive electrode current collector; 113. positive electrode active material layer;

[0162] 12. Negative electrode sheet; 121. Negative electrode tab; 122. Negative electrode current collector; 123. Negative electrode active material layer;

[0163] 13. Isolation film;

[0164] 14. Main body;

[0165] 150, first adapter; 151, positive adapter; 152, negative adapter;

[0166] 16. First reinforcement member; 160. First sub-reinforcement member; 161. First reinforcement portion; 162. Second reinforcement portion;

[0167] 17. First thermal insulation member; 171. First thermal insulation layer; 172. Second thermal insulation layer;

[0168] 20. Shell;

[0169] 21. Housing; 211. First wall; 212. Second wall;

[0170] 22. End cover; 220. Pressure relief mechanism; 221. Weak part;

[0171] 30. First electrode terminal; 31. Positive electrode terminal; 32. Negative electrode terminal;

[0172] 40. Heat-resistant parts. DETAILED DESCRIPTION

[0173] 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.

[0174] " 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.

[0175] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0176] 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.

[0177] 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.

[0178] The gram capacity of lithium iron phosphate is relatively low, resulting in a relatively poor energy density of the battery cell. In related technologies, in order to improve the fast charging capability of the battery cell, it may be necessary to sacrifice the reliability of the battery cell.

[0179] The fast-charging lithium iron phosphate battery has a high internal temperature rise during the fast charging process, which makes the electrolyte less stable and easily decomposes and produces gas, causing the battery cell to swell in volume and release pressure, affecting the reliability of the battery cell.

[0180] In view of the above problems,

[0181] This application achieves a dual improvement in fast charging capability and reliability by comprehensively regulating the positive and negative electrode materials, electrolyte composition, and interstitial electrolyte volume of the battery cells. Specifically,

[0182] The smaller the graphite particle size, the more conducive it is to fast charging. However, its reaction activity with the electrolyte is stronger, which easily triggers side reactions on the negative electrode side, resulting in increased consumption of additives and solvents in the electrolyte. The rate of side reactions is closely related to the particle size of the graphite particles. The smaller the particle size, the higher the side reaction rate and the more severe the gas production.

[0183] Part of the electrolyte is distributed in the pores of the active material layer of the electrode assembly and the pores of the separator, while the other part is free in the interstitial part of the electrode assembly. During the long-term cycle of the battery cell, the electrolyte in the pores is gradually consumed, and the electrolyte in the interstitial part is then replenished to the pores. The more electrolyte in the interstitial part (defined as the interstitial electrolyte amount), the higher the total equivalent (i.e., added mass) of each component in the electrolyte. For example, the greater the interstitial electrolyte amount, the higher the total equivalent of the solvent that undergoes side reactions in the electrolyte, and the more severe the gas production.

[0184] In order to balance the fast charging performance and reliability of battery cells, the present application synergistically regulates the mass content of ethylene carbonate (EC) and the particle size of graphite particles in the electrolyte. Ethylene carbonate (EC) can effectively improve the conductivity of the electrolyte, and graphite with an appropriate particle size can not only increase the solid-phase migration rate of lithium ions and improve the fast charging capability of battery cells, but also effectively balance the reaction activity between graphite particles and the electrolyte.

[0185] In order to further slow down the interfacial side reactions on the negative electrode side, the electrolyte adjusts the amount of interstitial electrolyte and the content of unsaturated ester additives so that the total equivalent of unsaturated ester additives is relatively high, but not too high. More unsaturated ester additives can participate in the film formation and consumption of the SEI layer of the solid electrolyte interface on the negative electrode side, but the impedance of the SEI film will not be too high, which can effectively delay the time for the solvent in the electrolyte to react with small-particle graphite particles, thereby slowing down the gas production during long-term circulation, further reducing the risk of pressure release of battery cells, and improving the reliability of battery cells.

[0186] Through the above-mentioned comprehensive regulation, the battery cells not only achieve an improvement in fast charging capability, but also significantly enhance their reliability in use.

[0187] battery cells

[0188] In a first aspect, an embodiment of the present application provides a battery cell.

[0189] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a separator and a negative electrode sheet. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer disposed on at least one side of the positive electrode collector. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer disposed on at least one side of the negative electrode collector.

[0190] The positive electrode active material layer includes a lithium-containing phosphate with an olivine structure, and the negative electrode active material layer includes graphite particles, wherein the volume average particle size Dv50 of the graphite particles is 8.5 μm to 13.5 μm;

[0191] The interstitial electrolyte volume A of the battery cell satisfies: A=A T -A1-A2-A3, 0.5g / Ah≤A≤1.4g / Ah;

[0192] A T Indicates the amount of electrolyte in the battery cell, its unit is g / Ah;

[0193] A1 represents the amount of electrolyte in the positive electrode active material layer, and its unit is g / Ah;

[0194] A2 represents the amount of electrolyte in the negative electrode active material layer, and its unit is g / Ah;

[0195] A3 represents the amount of electrolyte in the separator, and its unit is g / Ah;

[0196] The electrolyte includes ethylene carbonate, and the mass content of ethylene carbonate in the electrolyte is 20% to 35%;

[0197] The electrolyte also includes unsaturated ester additives, the mass content of the unsaturated ester additives in the electrolyte is 0.05% to 6%, and the unsaturated ester additives include one or more of vinylene carbonate, vinyl ethylene carbonate, allyl ethyl carbonate and fluorocarbonate additives.

[0198] The smaller the graphite particle size, the more conducive it is to fast charging. However, its reaction activity with the electrolyte is stronger, which can easily trigger side reactions and increase the consumption of additives and solvents in the electrolyte. The rate of side reactions is closely related to the particle size of the graphite particles. The smaller the particle size, the higher the side reaction rate and the more severe the gas production.

[0199] Part of the electrolyte is distributed in the pores of the active material layer of the electrode assembly and the pores of the separator, while the other part is free in the interstitial part of the electrode assembly. During the long-term cycle of the battery cell, the electrolyte in the pores is gradually consumed, and the electrolyte in the interstitial part is then replenished to the pores. The more electrolyte in the interstitial part (defined as the interstitial electrolyte amount), the higher the total equivalent (i.e., added mass) of each component in the electrolyte. For example, the greater the interstitial electrolyte amount, the higher the total equivalent of the solvent that undergoes side reactions in the electrolyte, and the more severe the gas production.

[0200] In order to balance the fast charging performance and reliability of battery cells, the present application synergistically regulates the mass content of ethylene carbonate (EC) and the particle size of graphite particles in the electrolyte. Ethylene carbonate (EC) can effectively improve the conductivity of the electrolyte, and graphite with an appropriate particle size can not only increase the solid-phase migration rate of lithium ions and improve the fast charging capability of battery cells, but also effectively balance the reaction activity between graphite particles and the electrolyte.

[0201] In order to further slow down the interfacial side reactions on the negative electrode side, the electrolyte adjusts the amount of interstitial electrolyte and the content of unsaturated ester additives so that the total equivalent of unsaturated ester additives is relatively high, but not too high. More unsaturated ester additives can participate in the film formation and consumption of the SEI layer of the solid electrolyte interface on the negative electrode side, but the impedance of the SEI film will not be too high, which can effectively delay the time for the solvent in the electrolyte to react with small-particle graphite particles, thereby slowing down the gas production during long-term circulation, further reducing the risk of pressure release of battery cells, and improving the reliability of battery cells.

[0202] Through the above-mentioned comprehensive regulation, the battery cells not only achieve an improvement in fast charging capability, but also significantly enhance their reliability in use.

[0203] Battery cells contain electrolytes. During the charge and discharge process of the battery cells, active ions such as lithium ions are inserted and removed back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting the active ions between the positive and negative electrodes.

[0204] After the electrolyte is injected into the battery cell, it participates in the formation of the interface film on the positive and negative electrode sides, and some of the electrolyte will be consumed, and the remaining electrolyte will be free inside the battery cell.

[0205] A portion of the free electrolyte is absorbed in the porous pores inside the electrode assembly, such as the pores of the positive electrode active material layer, the pores of the negative electrode active material layer and the pores of the isolation membrane; another portion of the electrolyte fills the gaps between the membrane layers in the electrode assembly, such as the gap between the positive electrode plate and the isolation membrane, the gap between the negative electrode plate and the isolation membrane, etc., and may also fill the gap between the electrode assembly and the outer shell of the battery cell. This portion of the electrolyte is defined as the interstitial electrolyte.

[0206] The amount of interstitial electrolyte A is too much. Although the amount of carboxylic acid ester solvent used inside the battery cell is large and the internal resistance of the battery cell is low, the electrolyte occupies too much space, resulting in less residual space inside the battery cell and no extra space for gas production. The internal pressure of the battery cell is relatively high, resulting in a higher risk of premature pressure release of the battery cell, which is not conducive to the reliability of the battery cell.

[0207] If the amount of interstitial electrolyte A is too small, the content of unsaturated ester additives in the battery cell may be too low, and the carboxylic ester solvent may react prematurely on the negative electrode side, resulting in increased gas production and a high risk of premature pressure release in the battery cell, which is not conducive to the reliability of the battery cell.

[0208] In the embodiment of the present application, by regulating the amount of interstitial electrolyte A to meet 0.5g / Ah≤A≤1.4g / Ah, and coordinating the components of the electrolyte, the amount of carboxylic acid ester solvent added to the battery cell is appropriate, which is beneficial to making the internal resistance of the battery cell relatively low, and can allow more unsaturated ester additives to participate in the film formation and consumption of the solid electrolyte interface SEI layer on the negative electrode side, and can effectively avoid the carboxylic acid ester solvent from having side reactions on the negative electrode side too early, thereby slowing down the gas production phenomenon, reducing the risk of pressure release of the battery cell, and taking into account the reliability of the battery cell and the fast charging performance.

[0209] Exemplarily, the interstitial electrolyte amount A is 0.5 g / Ah, 0.6 g / Ah, 0.7 g / Ah, 0.8 g / Ah, 0.9 g / Ah, 1.0 g / Ah, 1.1 g / Ah, 1.2 g / Ah, 1.3 g / Ah, 1.4 g / Ah, or a range consisting of any two of the above values.

[0210] Optionally, the interstitial electrolyte amount A satisfies 0.8 g / Ah to 1.3 g / Ah, which can more effectively balance the reliability and fast charging capability of the battery cell.

[0211] The amount of electrolyte in the gap A and the amount of electrolyte in the battery cell A T The amount of electrolyte in the positive electrode active material layer A1, the amount of electrolyte in the negative electrode active material layer A2, and the amount of electrolyte in the separator A3 satisfy: A = A T -A1-A2-A3.

[0212] In some embodiments, the amount of electrolyte in the battery cell is A T 2.4 g / Ah to 3.3 g / Ah, for example, 2.4 g / Ah, 2.5 g / Ah, 2.6 g / Ah, 2.7 g / Ah, 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah, 3.1 g / Ah, 3.2 g / Ah, 3.3 g / Ah, or a range consisting of any two of the foregoing values.

[0213] When the amount of electrolyte in the battery cell is within the above range, the electrolyte components can be maintained at an appropriate content during the cycle and storage of the battery cell, which is beneficial for balancing the reliability and fast charging performance of the battery cell.

[0214] The amount of electrolyte in a battery cell refers to the ratio of the mass of the electrolyte inside the battery cell to the rated capacity of the battery cell, which can be obtained by testing methods known in the art, for example,

[0215] Weigh the battery cell, denoting its mass as M0. Disassemble the battery cell and pour out the electrolyte. Remove the internal electrode assembly and separate the positive and negative electrode sheets, separators, and mechanical components (e.g., the insulating film covering the electrode assembly). Soak and clean the positive and negative electrode sheets, separators, and mechanical components in dimethyl carbonate (DMC) for 24 to 48 hours, repeating this soaking process at least three times. Place the positive and negative electrode sheets, separators, and mechanical components in a 100°C oven for at least 24 hours until completely dried. Weigh the dried positive and negative electrode sheets, separators, and mechanical components, denoting their mass as M1. The resulting mass of the electrolyte inside the battery cell is M0-M1.

[0216] The rated capacity of a battery cell can be calculated using the nominal capacity of the battery cell, or by charging the battery cell at a constant current of 0.33C to an upper limit of charge voltage, for example, 3.65V, and then charging at a constant voltage of 3.65V to 0.05C, leaving it at a charge upper limit voltage, for example, 3.65V, letting it stand for 1 hour, and then discharging at a discharge rate of 0.33C to a discharge cut-off voltage, for example, 2.0V, with the discharge capacity of the battery cell as the nominal capacity.

[0217] In some embodiments, the amount of electrolyte A1 in the positive electrode active material layer is 0.6 g / Ah to 1.0 g / Ah, for example, 0.6 g / Ah, 0.65 g / Ah, 0.7 g / Ah, 0.75 g / Ah, 0.8 g / Ah, 0.85 g / Ah, 0.9 g / Ah, 0.95 g / Ah, 1.0 g / Ah or a range consisting of any two of the above values.

[0218] The amount of electrolyte A1 in the positive electrode active material layer refers to the amount of electrolyte absorbed inside the positive electrode active material layer. When the amount of electrolyte in the positive electrode active material layer is within the above range, the electrolyte can more fully penetrate the positive electrode active material layer, which is beneficial to the rapid migration of lithium ions in the positive electrode active material layer, reduces transmission resistance, reduces the internal resistance of the battery cell, and improves the fast charging performance of the battery cell.

[0219] The positive electrode active material layer includes a positive electrode active material, an optional conductive agent, and an optional binder. During the formation of the positive electrode active material layer, the accumulation of particles forms a porous structure, so that the positive electrode active material layer has a certain pore volume and solid volume.

[0220] The amount of electrolyte in the positive electrode active material layer A1 = (pore volume of the positive electrode active material layer × density of the electrolyte) / nominal capacity of the battery cell, where the unit of pore volume is mL and the unit of electrolyte density is g / cm3 , the nominal capacity of the battery cell is in Ah;

[0221] The pore volume of the positive electrode active material layer = length of the positive electrode active material layer × width of the positive electrode active material layer × total thickness of the positive electrode active material layer × porosity of the positive electrode active material layer / 1000, where the length of the positive electrode active material layer is in mm, the width of the positive electrode active material layer is in mm, and the total thickness of the positive electrode active material layer is in mm. If the positive electrode active material layer is coated on one side, the total thickness of the positive electrode active material layer is the thickness of the single-sided positive electrode active material layer; if the positive electrode active material layer is coated on both sides, the total thickness of the positive electrode active material layer is the total thickness of the double-sided positive electrode active material layer.

[0222] In the embodiments of the present application, the density of the electrolyte refers to the density at room temperature, for example, 15°C to 35°C, specifically 25°C, and can be tested using equipment and methods known in the art, for example, with reference to GB / T 2013-2010.

[0223] Optionally, the density of the electrolyte at 25°C is 1.05 g / cm 3 Up to 1.35g / cm 3 For example, 1.05g / cm 3 , 1.10g / cm 3 , 1.15g / cm 3 , 1.2g / cm 3 , 1.25g / cm 3 , 1.3g / cm 3 , 1.35g / cm 3 Or a range consisting of any two of the above values.

[0224] When the density of the electrolyte is within the above range, it is beneficial for lithium ions to migrate quickly in the positive electrode active material layer, can further reduce the internal resistance of the battery cell, and can improve the fast charging performance of the battery cell.

[0225] In the embodiments of the present application, the nominal capacity of a battery cell refers to the theoretical capacity that the battery cell can provide at a standard discharge current and ambient temperature. It can usually be obtained by consulting the product specifications of the battery cell; it can also be obtained by the following test methods:

[0226] Charge the battery cell at a constant current of 0.33C to the upper limit of charging voltage, for example, 3.65V, then charge at a constant voltage of 0.05C at the upper limit of charging voltage, for example, 3.65V, let it stand for 1 hour, and then discharge at a discharge rate of 0.33C to the discharge cutoff voltage, for example, 2.0V. The discharge capacity of the battery cell is used as the nominal capacity.

[0227] Optionally, the porosity of the positive electrode active material layer is 23% to 33%, for example, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33% or a range consisting of any two of the above values.

[0228] When the porosity of the positive electrode active material layer is within the above range, the positive electrode active material layer has sufficient spatial sites to absorb the electrolyte, and the electrolyte infiltrates the positive electrode active material layer more fully, which is conducive to the rapid migration of lithium ions in the positive electrode active material layer, reduces transmission resistance, reduces the internal resistance of the battery cell, and improves the fast charging performance of the battery cell.

[0229] In the embodiments of the present application, porosity refers to the percentage of the pore volume of the positive electrode active material layer to the total volume of the positive electrode active material layer. Porosity can be tested according to standard GB / T 24586-2009. The positive electrode sheet is disassembled from a battery cell at 100% state of charge (SOC). The positive electrode sheet is repeatedly washed with dimethyl carbonate (DMC) solvent for more than three times until the electrolyte in the positive electrode sheet is completely washed out. The positive electrode sheet is then dried in an oven at 100°C for more than 12 hours. The positive electrode sheet is then cut into multiple discs.

[0230] In a dry room, use tweezers to select >20 discs with good appearance and no powdering on the edges and place them into the sample cup. Record the number of discs and calculate the apparent volume.

[0231] Place the sample cup containing the sample in the true density tester. The volume of the sample cup is 3.5 cm 3 Helium is used as the analytical gas. In a closed test system, helium is introduced according to the program. By detecting the pressure of the gas in the sample chamber and expansion chamber, the true volume is calculated according to Bohr's law (PV=nRT), thereby obtaining the porosity of the sample to be tested.

[0232] In some embodiments, the amount of electrolyte A2 in the negative electrode active material layer is 0.7 g / Ah to 1.0 g / Ah, for example, 0.7 g / Ah, 0.75 g / Ah, 0.8 g / Ah, 0.85 g / Ah, 0.9 g / Ah, 0.95 g / Ah, 1.0 g / Ah, or a range consisting of any two of the above values.

[0233] The amount of electrolyte A2 in the negative electrode active material layer refers to the amount of electrolyte absorbed in the negative electrode active material layer. When the amount of electrolyte in the negative electrode active material layer is within the above range, the electrolyte can more fully penetrate the negative electrode active material layer, which is beneficial to the rapid migration of lithium ions in the negative electrode active material layer, reduces transmission resistance, reduces the internal resistance of the battery cell, and improves the fast charging performance of the battery cell.

[0234] The negative electrode active material layer includes a negative electrode active material, an optional conductive agent, and an optional binder. During the formation of the negative electrode active material layer, the accumulation of particles forms a porous structure, so that the negative electrode active material layer has a certain pore volume and solid volume.

[0235] The amount of electrolyte in the negative electrode active material layer A2 = (pore volume of the negative electrode active material layer × density of the electrolyte) / nominal capacity of the battery cell, where the unit of pore volume is mL and the unit of electrolyte density is g / cm 3 , the nominal capacity of the battery cell is in Ah;

[0236] The pore volume of the negative electrode active material layer = length of the negative electrode active material layer × width of the negative electrode active material layer × total thickness of the negative electrode active material layer × porosity of the negative electrode active material layer / 1000, where the length of the negative electrode active material layer is in mm, the width of the negative electrode active material layer is in mm, and the total thickness of the negative electrode active material layer is in mm. If the negative electrode active material layer is coated on one side, the total thickness of the negative electrode active material layer is the thickness of the single-sided negative electrode active material layer; if the negative electrode active material layer is coated on both sides, the total thickness of the negative electrode active material layer is the total thickness of the double-sided negative electrode active material layer.

[0237] Optionally, the porosity of the negative electrode active material layer is 30% to 45%, for example 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 above values.

[0238] When the porosity of the negative electrode active material layer is within the above range, the negative electrode active material layer has sufficient spatial sites to absorb the electrolyte, and the electrolyte infiltrates the negative electrode active material layer more fully, which is conducive to the rapid migration of lithium ions in the negative electrode active material layer, reduces transmission resistance, reduces the internal resistance of the battery cell, and improves the fast charging performance of the battery cell.

[0239] In the embodiment of the present application, the porosity of the negative electrode active material layer refers to the porosity test method of the positive electrode active material layer, which will not be repeated here.

[0240] In some embodiments, the amount of electrolyte A3 in the separator is 0.1 g / Ah to 0.3 g / Ah, such as 0.1 g / Ah, 0.15 g / Ah, 0.2 g / Ah, 0.25 g / Ah, 0.3 g / Ah, or a range consisting of any two of the above values.

[0241] The amount of electrolyte A3 in the isolation membrane is the amount of electrolyte absorbed in the isolation membrane. When the amount of electrolyte in the isolation membrane is within the above range, the electrolyte can more fully penetrate the negative electrode active material layer, which is beneficial to the rapid migration of lithium ions in the isolation membrane, reduce transmission resistance, reduce the internal resistance of the battery cell, and improve the fast charging performance of the battery cell.

[0242] The isolation membrane includes a base membrane and an optional functional layer. During the formation of the isolation membrane, a porous structure may be formed inside the isolation membrane, so that the isolation membrane has a certain pore volume and solid volume.

[0243] The amount of electrolyte in the separator A3 = (pore volume of separator × density of electrolyte) / nominal capacity of battery cell, where the unit of pore volume is mL and the unit of electrolyte density is g / cm 3 , the nominal capacity of the battery cell is in Ah;

[0244] The pore volume of the separator=the length of the separator×the width of the separator×the thickness of the separator×the porosity of the separator / 1000, wherein the length of the separator is in mm, the width of the separator is in mm, and the total thickness of the separator is in mm.

[0245] 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.

[0246] 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.

[0247] 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 standard GB / T36363-2018. Discharge the battery cell at a 0.33C rate to a discharge cutoff voltage, for example, 2.0V. With the battery cell at a 0% state of charge (SOC), disassemble the separator and repeatedly clean the separator with dimethyl carbonate (DMC) solvent three or more times until the electrolyte is completely washed out. The separator is then dried in a 100°C oven for at least 12 hours, which is then used as a sample for testing.

[0248] [Electrolyte]

[0249] In an embodiment of the present application, the electrolyte includes ethylene carbonate, and the mass content of ethylene carbonate in the electrolyte is 20% to 35%, for example, 20%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% or a range consisting of any two of the above values.

[0250] When the mass content of ethylene carbonate is too low, the conductivity of the electrolyte is low and the internal resistance of the battery cell is large;

[0251] When the mass content of ethylene carbonate is too high, the viscosity of the electrolyte increases, the conductivity deteriorates, and the internal resistance of the battery cell is large, which is not conducive to the rapid charging of the battery cell.

[0252] By controlling the content of ethylene carbonate EC in the electrolyte, the electrolyte has a higher dielectric constant, can better dissolve lithium salts, improve the conductivity of the electrolyte, can improve the conductivity of the electrolyte, and improve the fast charging capability of the battery cell.

[0253] Optionally, the mass content of ethylene carbonate in the electrolyte is 25% to 35%. When the content of ethylene carbonate is within the above range, the conductivity of the electrolyte can be increased, thereby improving the fast charging capability of the battery cell.

[0254] In some embodiments, 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.

[0255] 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.

[0256] In some embodiments, the carboxylate-based solvent comprises a linear carboxylate-based solvent.

[0257] Optionally, the carboxylate solvent includes a compound represented by formula I,

[0258] Formula I,

[0259] In Formula I,

[0260] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0261] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0262] If the carboxylate ester solvent content is too low, the electrolyte viscosity is too high, resulting in slower ion migration in the electrolyte and hindering rapid charging of the battery cells. If the carboxylate ester solvent content is too high, the risk of gassing from the negative electrode interface side reactions is increased. During rapid charging of the battery cells, the side reactions between the carboxylate ester solvent and the negative electrode active material are exacerbated, increasing gas production and internal pressure. This increases the risk of battery cell swelling and deteriorates reliability.

[0263] When the mass content of the carboxylate solvent is within the above range, it is beneficial to the migration of lithium ions and can improve the reliability of the battery cell under fast charging.

[0264] 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.

[0265] 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.

[0266] 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.

[0267] 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.

[0268] 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.

[0269] Optionally, the carboxylate solvent includes one or more of methyl acetate and ethyl acetate.

[0270] In some embodiments, the electrolyte includes a linear carbonate solvent. Linear carbonate solvents have a low viscosity, which can reduce the overall viscosity of the electrolyte, increase ion migration rate, and facilitate rapid charging of the battery cells. The combined use of ethylene carbonate and linear carbonate solvents can increase the dielectric constant of the electrolyte and reduce viscosity, thereby improving rapid charging of the battery cells.

[0271] 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.

[0272] Illustratively, the linear carbonate-based solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0273] In an embodiment of the present application, the electrolyte further includes an unsaturated ester additive, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 6%, and the unsaturated ester additive includes one or more of vinylene carbonate, vinyl ethylene carbonate, allyl ethyl carbonate and fluorocarbonate additives.

[0274] During the circulation and use of battery cells, the unsaturated ester additives in the electrolyte are consumed first and participate in the formation of a dense SEI film on the negative electrode side. In this process, the gas production is relatively small, so that the internal pressure of the battery cell remains basically unchanged; as time goes by, the unsaturated ester additives are gradually consumed, and the carboxylic ester solvents undergo side reactions on the negative electrode side, causing the gas production to increase sharply, which may lead to excessive internal pressure and cause the battery cell to depressurize.

[0275] When the mass content of the unsaturated ester additive is too low, it is completely consumed prematurely on the negative electrode side, causing the carboxylate solvent to decompose in large quantities in the early stage of the battery cell cycle, resulting in premature pressure release and a greater risk of use.

[0276] The mass content of unsaturated ester additives is too high, which makes the SEI film impedance formed on the negative electrode side too large, the internal resistance of the battery cell too high, the kinetic performance is poor, and lithium plating is prone to occur, resulting in poor fast charging performance and reliability of the battery cell.

[0277] 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, reduce the risk of premature decomposition of the carboxylic ester solvent on the negative electrode side, and increase the pressure relief threshold, 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.

[0278] 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.

[0279] For example, the fluorocarbonate additive includes one or more of fluoroethylene carbonate, bisfluoroethylene carbonate, and trifluoromethylethylene carbonate.

[0280] Illustratively, the unsaturated ester additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0281] Illustratively, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 6%, 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%, 3.50%, 4.00%, 4.50%, 5.00%, 5.50%, 6%, or a range consisting of any two of the above values.

[0282] 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.

[0283] 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.

[0284] For example, the mass content of unsaturated ester additives in the electrolyte is 1% to 6%, 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.

[0285] For example, the mass content of the unsaturated ester additive in the electrolyte is 0.2% to 5%, 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.

[0286] 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:

[0287] In fresh electrolyte, the mass content of unsaturated ester additives is 1% to 6%;

[0288] The mass content of unsaturated ester additives in battery cells stored in the lower warehouse for one month is about 0.2% to 5%;

[0289] The mass content of unsaturated ester additives in battery cells stored in the lower warehouse for 3 months is about 0.1% to 4%;

[0290] During the 6-month storage period of the battery cells in the lower warehouse, the mass content of the unsaturated ester additives is approximately 0.07% to 3.5%.

[0291] During 12 months of storage in the lower warehouse of battery cells, the mass content of unsaturated ester additives is approximately 0.05% to 3%.

[0292] The mass content of unsaturated ester additives is related to the pressure relief threshold of the pressure relief mechanism of the battery cell. As the mass content of the unsaturated ester additives increases, the protection of the negative electrode side increases, the risk of premature decomposition and gas production of the carboxylic ester solvent decreases, the pressure relief threshold increases, and the risk of premature pressure relief decreases, which is beneficial to improving the reliability of the battery cell.

[0293] Illustratively, the mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 0.05% and less than 1.5%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 80% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell.

[0294] In the above example, the battery cell is charged and discharged in cycles, and the battery cell can be cycled at least until the capacity of the current battery cell decays to 80% of the nominal capacity, and the pressure relief mechanism can release the pressure, so the service life of the battery cell is relatively long.

[0295] For example, the battery cell can be cycled until the capacity of the current battery cell decays to 80% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 75% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 70% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 65% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 50% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 45% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 40% of the nominal capacity, and the pressure relief mechanism releases pressure.

[0296] Illustratively, the mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 1.5% and less than 3%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 70% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell.

[0297] In the above example, the battery cell is charged and discharged in cycles, and the battery cell can be cycled at least until the capacity of the current battery cell decays to 70% of the nominal capacity, and the pressure relief mechanism can release the pressure, so the service life of the battery cell is relatively long.

[0298] For example, the battery cell can be cycled until the capacity of the current battery cell decays to 70% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 65% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 50% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 45% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 40% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 30% of the nominal capacity, and the pressure relief mechanism releases pressure.

[0299] Illustratively, the mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 3% and less than 4.5%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 60% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell.

[0300] In the above example, the battery cell is charged and discharged in cycles, and the battery cell can be cycled at least until the capacity of the current battery cell decays to 60% of the nominal capacity, and the pressure relief mechanism can release the pressure, so the service life of the battery cell is relatively long.

[0301] For example, the battery cell can be cycled until the capacity of the current battery cell decays to 60% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 50% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 45% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 40% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 30% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 20% of the nominal capacity, and the pressure relief mechanism releases pressure.

[0302] Illustratively, the mass content of the unsaturated ester additive in the electrolyte is 4.5% to 6%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 50% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell.

[0303] In the above example, the battery cell is charged and discharged in cycles, and the battery cell can be cycled at least until the capacity of the current battery cell decays to 50% of the nominal capacity, and the pressure relief mechanism can release the pressure, so the service life of the battery cell is relatively long.

[0304] For example, the battery cell can be cycled until the capacity of the current battery cell decays to 50% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 45% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 40% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 30% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 20% of the nominal capacity, and the pressure relief mechanism releases pressure; or, the battery cell can be cycled until the capacity of the current battery cell decays to 10% of the nominal capacity, and the pressure relief mechanism releases pressure.

[0305] 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%.

[0306] 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.

[0307] 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.

[0308] When the mass content of sulfur-containing additives is 0,

[0309] It can be that the freshly prepared electrolyte does not contain sulfur additives.

[0310] Alternatively, the electrolyte obtained after disassembling the battery cell does not contain sulfur-containing additives. This situation may be that 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, making the mass content of the sulfur-containing additives zero during the detection process.

[0311] In some embodiments, the electrolyte includes a lithium salt additive having a mass content of 0.2% to 1.5% in the electrolyte, for example, the mass content of the lithium salt additive is 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5% or a range consisting of any two of the above values.

[0312] Lithium salt additives can optimize the membrane components of the SEI film. Lithium salt additives participate in the formation of an inorganic-rich SEI film. Inorganic substances can improve the high-temperature and high-voltage stability of the SEI film, making the electrolyte less likely to decompose and produce gas, thereby improving the reliability of battery cells at high energy density.

[0313] Illustratively, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium tetrafluoroborate LiBF4, lithium bis(oxalatoborate) LiBOB, lithium difluorooxalatoborate LiDFOB, and lithium fluorosulfonate LiSO3F.

[0314] 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%.

[0315] 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.

[0316] 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.

[0317] 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 reliability of the battery cell under fast charging.

[0318] 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 improving the reliability of the battery cell during rapid charging.

[0319] 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 can more easily dissociate lithium ions, improving the conductivity of the electrolyte and enhancing the thermal stability of the electrolyte, thereby improving the reliability of the battery cells during rapid charging.

[0320] Optionally, the fluorinated lithium sulfonyl imide content 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 fluorinated lithium sulfonyl imide content is within the above range, it can enhance the thermal stability of the electrolyte and improve the reliability of the battery cell under rapid charging.

[0321] 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 and improving the reliability of the battery cells under fast charging.

[0322] 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.

[0323] 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".

[0324] [Positive electrode]

[0325] The positive electrode sheet 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.

[0326] 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.

[0327] 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.

[0328] 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.

[0329] 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 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.

[0330] Lithium-containing phosphates have excellent stability during the cycle process and can increase the service life of battery cells.

[0331] 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.

[0332] 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.

[0333] 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.

[0334] 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.

[0335] 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.

[0336] 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.

[0337] 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.

[0338] 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.

[0339] 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.

[0340] 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.

[0341] 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 sheet 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 sample is then placed on a plate at 180°C for 30 minutes. After digestion on the plate, the volume is adjusted to 100ml, and quantitative analysis is performed using a standard curve method.

[0342] 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.

[0343] 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.

[0344] 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.

[0345] 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.

[0346] 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.

[0347] 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 plate is disassembled (if it is a double-sided coated plate, 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:

[0348] Step 1: Weigh the total weight of the container and filter membrane as m0;

[0349] 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 sheet 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;

[0350] 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;

[0351] Step 4: Filter the secondary digestion solution through the filter membrane in step 2, and rinse the filtered residue with 200 mL of water;

[0352] 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;

[0353] 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 sheet according to the formula W t , the calculation formula is:

[0354] .

[0355] 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.

[0356] The powder resistivity of the positive electrode active material is relatively low, which makes the resistance of the positive electrode sheet relatively low, the internal resistance of the battery cell 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.

[0357] 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.

[0358] In some embodiments, the powder compaction density of the positive electrode active material at 30,000 N is 2.53 g / cm 3 to 2.80g / cm 3 .

[0359] 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.

[0360] 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.

[0361] 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.

[0362] 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 3 Or a range consisting of any two of the above values.

[0363] 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%.

[0364] 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.

[0365] 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.

[0366] 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 sheet will not be too large, which is beneficial for taking into account the energy density, fast charging capability and reliability of the battery cell.

[0367] 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.

[0368] 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:

[0369] 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.

[0370] 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 sheet from the battery cell, for example, take a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode active material layer on one side can be wiped off first), punch it into small discs 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 sheet, weigh the positive electrode current collector, record it as M0, and measure its thickness H0.

[0371] The coating weight of the positive electrode active material layer on one side = (the weight of the positive electrode sheet M1 - the weight of the positive electrode current collector M0) / S1.

[0372] 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.

[0373] 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.

[0374] In some embodiments, the positive electrode active material layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and 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 positive electrode binder is ≤5%.

[0375] 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).

[0376] 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).

[0377] 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.

[0378] 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 sheet to directly measure the thickness of the positive electrode current collector.

[0379] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode active material layer. For example, in some embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode active material layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode active material layer.

[0380] In some embodiments, the positive electrode sheet further includes a positive conductive layer, which is located between the positive electrode active material layer and the positive electrode current collector. The positive conductive layer can further improve the conductivity of the positive electrode sheet and reduce heat generation of the positive electrode sheet, thereby reducing heat generation of the battery cell and reducing high-temperature gas generation of the electrolyte, thereby ensuring both the fast charging capability and reliability of the battery cell.

[0381] 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.

[0382] 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 plate, reduce the heat generation of the positive electrode plate, thereby reducing the heat generation of the battery cell, and reducing the gas production of high-temperature decomposition of the electrolyte, which can take into account the energy density, fast charging capability and reliability of the battery cell.

[0383] 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.

[0384] In the embodiment of the present application, the thickness of the positive electrode conductive layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, for example, performing a tomographic scan on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0385] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0386] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 55%. Exemplarily, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, 55%, or a range consisting of any two of the above values.

[0387] Illustratively, the positive electrode 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 positive electrode conductive agent of the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet, 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.

[0388] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 40% to 70%. Exemplarily, the mass content of the positive electrode binder is 40%, 45%, 50%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0389] Illustratively, the positive electrode binder of the positive conductive layer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorinated acrylic resin. The positive electrode binder of the positive conductive layer can enhance the bonding between the positive current collector and the positive active material layer, improve the structural stability of the positive electrode sheet, and enhance the reliability of the battery cell.

[0390] 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.

[0391] 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.

[0392] [Negative electrode]

[0393] The negative electrode sheet 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.

[0394] 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.

[0395] 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.

[0396] 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.

[0397] 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.

[0398] 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.

[0399] 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.

[0400] 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.

[0401] 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.

[0402] 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.

[0403] 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.

[0404] 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.

[0405] 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.

[0406] 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, 3.5m2 / g, 3.6m 2 / g or a range consisting of any two of the above values.

[0407] 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.

[0408] 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.

[0409] 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.

[0410] 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.

[0411] 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.

[0412] 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%.

[0413] 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.

[0414] 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, which increases the number of sites for lithium ion insertion and extraction, making the conductivity of the negative electrode coating layer better, which can reduce the internal resistance of the negative electrode plate, reduce the heat generation of the battery cell, reduce the high-temperature gas generation, and improve the reliability and fast charging capability of the battery cell at high energy density.

[0415] Illustratively, the graphite body particles include one or more of artificial graphite and natural graphite, and artificial graphite can be selected.

[0416] 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.

[0417] When the mass content of carbon elements in the negative electrode coating layer is within the above range, the internal resistance of the negative electrode plate can be further reduced, the heat generation of the battery cell can be reduced, 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.

[0418] 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.

[0419] When the powder resistivity of the graphite particles is within the above range, the resistance of the negative electrode plate is relatively low, which is beneficial to reducing the internal resistance of the negative electrode plate, reducing the heat generation of the battery cell, reducing the high-temperature gas generation, and improving the reliability and fast charging capability of the battery cell at high energy density.

[0420] 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.

[0421] In some embodiments, the volume average particle size Dv50 of the graphite particles is 8.5 μm to 13.5 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, or a range consisting of any two of the foregoing values.

[0422] When the Dv50 of graphite particles is too small, although the solid-phase transmission path of lithium ions in the graphite particles is short, its active surface is large, the side reaction gas production is aggravated, and the internal pressure increases, which is not conducive to the reliability of the battery cell.

[0423] When the Dv50 of the graphite particles is too large, the solid-phase transmission path of lithium ions in the graphite particles is long, which is not conducive to rapid charging of the battery cells.

[0424] When the Dv50 of the graphite particles is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging capability. On the other hand, the active surface will not be too large, which can reduce the gas production of interfacial side reactions, reduce the internal pressure, and improve the reliability of the battery cell.

[0425] 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.

[0426] 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.

[0427] 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.

[0428] Optionally, the carbonization treatment time is 1 hour to 6 hours.

[0429] 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.

[0430] 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.

[0431] 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.

[0432] 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 plate 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 charged state of approximately 0% SOC) is reversely disassembled to remove the negative electrode plate, and the negative electrode plate is placed in a solvent such as water for immersion. 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.

[0433] For example, the present application may also combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis Methods to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0434] 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.

[0435] 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.

[0436] 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.

[0437] 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.

[0438] 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.

[0439] There is a difference in 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 sheet, thereby improving the reliability of the battery cell.

[0440] 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 13.5 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 13.5 μm.

[0441] 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.

[0442] 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 13.5 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 13.5 μm.

[0443] 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.

[0444] 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.

[0445] 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.

[0446] 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.

[0447] 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.

[0448] 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.

[0449] 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.

[0450] 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 have meanings well known in the art and can be detected by methods well known in the art. For example, the negative electrode sheet is used as a sample, sliced ​​along the thickness direction of the negative electrode active material layer, and then photographed with 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.

[0451] 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 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.

[0452] 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.

[0453] 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).

[0454] 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.

[0455] 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.

[0456] 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.

[0457] 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.

[0458] In some embodiments, the negative electrode active material layer further includes a negative electrode binder, which includes one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the weight content of the negative electrode binder is ≤5% based on the total weight of the negative electrode active material layer.

[0459] In some embodiments, the negative electrode active material layer further includes a negative electrode conductive agent. The present application embodiment does not particularly limit the type of negative electrode conductive agent. As an example, the negative electrode 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 negative electrode conductive agent is ≤5% based on the total weight of the negative electrode active material layer.

[0460] 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.

[0461] 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.

[0462] 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).

[0463] 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.

[0464] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in certain embodiments, the negative electrode sheet of the present application further includes a negative conductive layer sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode active material layer.

[0465] In some embodiments, the negative electrode plate further includes a negative conductive layer, which is located between the negative electrode active material layer and the negative electrode current collector. The negative conductive layer can further improve the conductivity of the negative electrode plate and reduce heat generation, 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.

[0466] 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.

[0467] 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 plate, reduce the heat generation of the negative electrode plate, and thus reduce the heat generation of the battery cell, which can take into account the energy density, fast charging capability and reliability of the battery cell.

[0468] 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.

[0469] In the embodiment of the present application, the thickness of the negative electrode conductive layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, for example, by performing a tomographic scan on the negative electrode sheet to directly measure the thickness of the negative electrode conductive layer.

[0470] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder.

[0471] 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.

[0472] Optionally, the negative electrode conductive agent of the negative electrode conductive layer has a mass content of 20% to 40% in the negative electrode conductive layer. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or a range consisting of any two of the above values.

[0473] Illustratively, the negative electrode conductive agent of the negative electrode conductive layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The negative electrode conductive agent of the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode pole piece, reducing heat generation in the battery cell, and reducing high-temperature gas generation in the electrolyte, thereby ensuring both the fast charging capability and reliability of the battery cell.

[0474] Optionally, the negative electrode binder content of the negative electrode conductive layer is 60% to 80% by mass. Exemplarily, the negative electrode binder content is 60%, 65%, 70%, 75%, 80% by mass, or a range consisting of any two of the above values.

[0475] Illustratively, the negative electrode binder of the negative conductive layer includes one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The negative electrode binder of the negative 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 sheet, and enhance the reliability of the battery cell.

[0476] [Isolation film]

[0477] In the embodiment of the present application, the isolation film is arranged between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet from the negative electrode sheet.

[0478] In the embodiment of the present application, the isolation membrane includes a base membrane with a porous structure.

[0479] 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.

[0480] Optionally, the polyolefin includes one or more of polyethylene, polypropylene and polyvinylidene fluoride.

[0481] 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.

[0482] 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.

[0483] 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.

[0484] In some embodiments, the isolation film may be a base film.

[0485] 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.

[0486] 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.

[0487] 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.

[0488] 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.

[0489] 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.

[0490] 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.

[0491] 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.

[0492] 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 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.

[0493] Further optionally, the second functional layer is located on a side of the first functional layer away from the base film.

[0494] 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 close to the negative electrode plate.

[0495] 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.

[0496] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0497] Optionally, the electrode assembly is a laminated structure, with the positive electrode sheet, separator, and negative electrode sheet stacked along the thickness direction of the battery cell. The laminated electrode assembly is beneficial for improving the energy density of the battery cell.

[0498] Figure 1 and Figure 2 A schematic structural diagram of a battery cell is shown.

[0499] like Figure 1 and Figure 2 As shown, in some embodiments, the battery cell 7 may include a housing 20 .

[0500] 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.

[0501] 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.

[0502] 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.

[0503] 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 .

[0504] 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.

[0505] For example, the size 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. When the size of the housing 20 along the length direction Z of the battery cell 7 meets the above range, it is more conducive to improving the fast charging capability of the battery cell 7.

[0506] For example, the size 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. When the size of the housing 20 along the length direction Z of the battery cell 7 meets the above range, the energy density and fast charging capability of the battery cell 7 can be taken into account.

[0507] For example, the size 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. When the size of the housing 20 along the length direction Z of the battery cell 7 meets the above range, it is more conducive to improving the energy density of the battery cell 7.

[0508] 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.

[0509] 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.

[0510] 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.

[0511] 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.

[0512] 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.

[0513] 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. Exemplarily, the pressure relief mechanism 220 can be an explosion-proof valve, or a weak portion 221 formed by thinning a local area of ​​the end cover 22.

[0514] 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 electrode sheets, electrolyte, and separator within the battery cell 7.

[0515] 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 .

[0516] 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.

[0517] 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.

[0518] 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.

[0519] Optionally, the pressure relief mechanism 220 includes a weak portion 221 .

[0520] Optionally, the base material of the weak portion 221 includes steel or aluminum.

[0521] The battery cell 7 further includes an electrode assembly 10 , and there may be one or more electrode assemblies 10 housed in the housing 20 . For example, the electrode assembly 10 is a laminated structure, and two laminated electrode assemblies are stacked and disposed in the housing 20 .

[0522] In some embodiments, the battery cell 7 further includes a first electrode terminal and a second electrode terminal, one of which is a positive electrode terminal 31 and the other is a negative electrode terminal 32 .

[0523] Optionally, the positive terminal 31 is provided on the outer shell 20 , and may be provided on the housing 21 or the end cover 22 .

[0524] Optionally, the negative terminal 32 is provided on the outer shell 20 , and may be provided on the housing 21 or the end cover 22 .

[0525] 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 .

[0526] 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 .

[0527] Specifically,

[0528] The portion of the positive electrode sheet 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 sheet 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.

[0529] The portion of the negative electrode sheet 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 sheet 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.

[0530] The main body 14 may further include a separator 13 , which is located between the positive electrode sheet 11 and the negative electrode sheet 12 .

[0531] The tab portion includes a first tab and a second tab, one of which is the positive tab 111 and the other is the negative tab 121. When the first tab is the positive tab 111, the second tab is the negative tab 121. When the first tab is the negative tab 121, the second tab is the positive tab 111.

[0532] 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 .

[0533] The first electrode terminal is electrically connected to the first tab. Optionally, the first electrode terminal and the first tab may be connected via a first adapter, or may be connected without the first adapter. When the first tab is the positive tab 111, the first adapter is the positive tab adapter 151. When the first tab is the negative tab 121, the first adapter is the negative tab adapter 152.

[0534] The second electrode terminal is electrically connected to the second electrode tab. Optionally, the second electrode terminal and the second electrode tab may be connected via a second adapter, or may not be connected using a second adapter. If the second electrode tab is the positive electrode tab 111, the second adapter is the positive electrode adapter 151. If the second electrode tab is the negative electrode tab 121, the second adapter is the negative electrode adapter 152.

[0535] Illustratively, the positive terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 may be connected via a positive electrode adapter 151. For example, the positive terminal 31 and the positive electrode tab 111 are welded via the positive electrode adapter 151.

[0536] Illustratively, the negative terminal 32 is electrically connected to the negative electrode tab 121. Optionally, the negative terminal 32 and the negative electrode tab 121 may be 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.

[0537] [First Tab]

[0538] like Figures 4 and 5 As shown, in some embodiments, the first tab 110 includes a first region 1111, which is the region of the first tab 110 connected to the first adapter 150. For example, the first tab 110 is a positive tab, and when the positive tab is welded to the positive adapter, the first region 1111 is the weld mark region of the positive tab. In order to more clearly illustrate the first region 1111 of the first tab 110, Figure 4 and Figure 5 The first tab 110 is the tab after expansion. After entering the shell, the first tab 110 can be bent into a shape similar to Figure 4 In the embodiment of the present application, the first tab 110 further includes a second region, wherein the first region 1111 and the second region are continuously arranged. For example, the first region 1111 is a weld imprint region, and the second region is a non-weld imprint region.

[0539] Optionally, the first region 1111 includes one or more sub-regions 1111 a .

[0540] like Figure 5As shown, when the first region 1111 includes a sub-region 1111 a , the first tab 110 may be multiple pieces, and the multiple pieces of first tabs 110 are bent together and then connected to the first adapter 150 , for example, by welding.

[0541] like Figure 6 As shown, when the first region 1111 includes multiple sub-regions 1111 a , the first tab 110 may be multiple pieces, and the multiple first tabs 110 are bent together and connected to the first adapter 150 through the multiple sub-regions 1111 a .

[0542] like Figure 7 and Figure 8 As shown, in the case where the first region 1111 includes multiple sub-regions 1111a, the first pole tabs 110 may be multiple pieces, and the multiple pieces of first pole tabs 110 are divided into two groups, each group of first pole tabs 110 includes at least two pieces of first pole tabs 110, each group of first pole tabs 110 is bent separately, and after bending, they are respectively connected to the first adapter 150, and each group of first pole tabs 110 can be connected to the first adapter 150 through one sub-region 1111a or multiple sub-regions 1111a.

[0543] When the first region 1111 includes multiple subregions 1111a, the multiple subregions 1111a are arranged relative to each other along the thickness direction of the electrode assembly 10. Specifically, after the first tab 110 is inserted into the casing and bent, the multiple subregions 1111a are arranged relative to each other along the thickness direction of the electrode assembly 10. For example, the first region 1111 includes two subregions 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.

[0544] The multiple sub-regions 1111 a are beneficial to improving the connection stability between the first electrode tab 110 and the first adapter 150 , and improving the current carrying capacity of the first electrode tab 110 and the first adapter 150 , thereby improving the fast charging capability of the battery cell 7 .

[0545] 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 first electrode ear 110 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.

[0546] The multiple unit regions 1111 b are beneficial to improving the connection stability between the first electrode tab 110 and the first adapter 150 , as well as improving the flow capacity of the first electrode tab 110 and the first adapter 150 , thereby improving the fast charging capability of the battery cell 7 .

[0547] When the first tab 110 and the first adapter 150 are connected by welding, the first region 1111 is the welding region of the first tab 110. The subregion 1111a constitutes a component of the welding region, and the unit region 1111b constitutes a component of the subregion 1111a.

[0548] For example, the total area of ​​the first region 1111 is 160 mm 2 Up to 1000mm 2 , such as 160 mm², 200 mm², 300 mm², 400 mm², 500 mm², 600 mm², 700 mm², 800 mm², 900 mm², 1000 mm² or a range consisting of any two of the above values. The total area of ​​the first region 1111 refers to the sum of the areas of all sub-regions 1111a; or the sum of the areas of all unit regions 1111b. Alternatively, the total area of ​​the connection area of ​​the first adapter 150 with the first tab 110 is 160 mm². 2 Up to 1000mm 2 .

[0549] When the area of ​​the first region 1111 is within the above range, it is beneficial to improve the connection stability between the first electrode tab 110 and the first adapter 150, and improve the current carrying capacity of the first electrode tab 110 and the first adapter 150, thereby improving the fast charging capability of the battery cell.

[0550] [First reinforcement member]

[0551] like Figure 8 and Figure 9 As shown, in some embodiments, the battery cell further includes a first reinforcement 16 , which is connected to the first tab 110 . Specifically, the first reinforcement 16 is connected to at least the first region 1111 .

[0552] Optionally, the first reinforcement 16 is located on a side of the first tab 110 facing away from the first adapter 150 .

[0553] Figure 9 The first region 1111 shown in FIG. 1 includes four unit regions 1111 b .

[0554] The first reinforcement 16 being connected to at least the first region 1111 can be understood as the first reinforcement 16 being connected to the first region 1111 , or the first reinforcement 16 being connected not only to the first region 1111 but also to the rest of the first tab 110 .

[0555] When the first pole tab 110 is welded to the first adapter 150, during the welding process, the first reinforcement 16 is arranged on the surface of the first pole tab 110, and the first reinforcement 16 is at least partially melted and fused to the first pole tab 110 and the first adapter 150, thereby strengthening the strength of the connection between the first pole tab 110 and the first adapter 150; and when the thickness of the first pole tab 110 is relatively thin, the reinforcement effect of the first reinforcement 16 makes it less likely for the first pole tab 110 to crack or even break, and the structure is more stable. It can also improve the current carrying capacity of the first pole tab 110, and improve the fast charging capability and reliability of the battery cell 7.

[0556] During the charge and discharge cycle of the battery cell 7, the active material layer expands or contracts in volume, which may cause the current collector to undergo a certain deformation, and may cause cracks or even breakage at the connection between the first pole tab 110 and the first adapter 150; the first reinforcement 16 can enhance the mechanical strength of the connection between the first pole tab 110 and the first adapter 150, enhance the structural stability; and enhance the flow capacity between the first pole tab 110 and the first adapter 150, thereby improving the fast charging capability and reliability of the battery cell 7.

[0557] Optionally, the ratio of the total cross-sectional area of ​​the first reinforcement 16 perpendicular to its own thickness direction to the total area of ​​the first region 1111 is 1.0 to 1.5, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range consisting of any two of the above values.

[0558] When the ratio of the total cross-sectional area of ​​the first reinforcement 16 perpendicular to its own thickness direction to the total area of ​​the first region 1111 is within the above range, the current flow capacity between the first tab 110 and the first adapter 150 can be further improved, thereby improving the fast charging capability and usage reliability of the battery cell 7.

[0559] The ratio of the cross-sectional area of ​​the first reinforcement 16 perpendicular to its own thickness direction to the area of ​​the first region 1111 can represent the extent to which the first reinforcement 16 covers the first region 1111. For example, when the ratio is 1.0, the areas of the first reinforcement 16 and the first region 1111 are the same, and the first reinforcement 16 can completely cover the first region 1111. When the ratio is greater than 1.0, the first reinforcement 16 not only covers the first region 1111, but also exceeds the first region 1111, which can further strengthen the connection strength of the first region 1111.

[0560] For example, the total cross-sectional area of ​​the first reinforcement 16 perpendicular to its own 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.

[0561] When the cross-sectional area of ​​the first reinforcement 16 perpendicular to its own thickness direction is within the above range, it is beneficial to enhance the coverage of the first region 1111, improve the structural strength of the connection between the first pole tab 110 and the first adapter 150, and further improve the flow capacity between the first pole tab 110 and the first adapter 150, thereby improving the fast charging capability of the battery cell 7.

[0562] When the first region 1111 includes two subregions 1111a, and each subregion 1111a includes two unit regions 1111b, that is, when the first region 1111 includes four unit regions 1111b, the four unit regions 1111b are independently spaced apart and arranged. Of course, the four unit regions 1111b can also be connected. The first reinforcement 16 covers the four unit regions 1111b, and the first reinforcement 16 can include four first sub-reinforcements 160. In each of the four unit regions 1111b, a first sub-reinforcement 160 can be provided to cover the unit region 1111b. Of course, the first reinforcement 16 can also include two first sub-reinforcements 160, each covering one subregion 1111a.

[0563] 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-reinforcements 160 is the total cross-sectional area of ​​the first reinforcement 16 .

[0564] like Figure 9 and Figure 10 As shown, in some embodiments, the first reinforcement member 16 includes a first reinforcement portion 161 and a second reinforcement portion 162. The first reinforcement portion 161 is connected to the first 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 first reinforcement member 16 includes multiple first sub-reinforcements 160, each first sub-reinforcement member 160 can include a first reinforcement portion 161 and a second reinforcement portion 162. Optionally, the first reinforcement portion 161 is welded to the first region 1111.

[0565] The first reinforcement portion 161 covers the first area 1111, and the first reinforcement portion 161 can reinforce the first area 1111. The second reinforcement portion 162 is connected to the first reinforcement portion 161, and can improve the overall structural stability of the first reinforcement 16, thereby firmly reinforcing the first area 1111 and improving the current flow capacity of the first area 1111, thereby improving the fast charging capability of the battery cell.

[0566] Optionally, the first reinforcement portion 161 and the second reinforcement portion 162 are an integrated structure, so that the strength of the first reinforcement member 16 is higher.

[0567] Optionally, there may be a clear boundary between the first reinforcement portion 161 and the second reinforcement portion 162 ; for example, during welding, the first reinforcement portion 161 is welded to the first tab 110 , while the second reinforcement portion 162 may not melt and may be a sheet-like structure.

[0568] Optionally, the second reinforcement portion 162 may not be connected to the first electrode tab 110 , for example, the two may be tightly fitted together, or a gap may be left between the two.

[0569] Optionally, the thickness of the first 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.

[0570] When the thickness of the first reinforcement 16 is within the above range, the overall mechanical strength of the first reinforcement 16 is higher, which can enhance the reinforcement effect and current carrying capacity of the first region 1111 , while improving the fast charging capability and reliability of the battery cell.

[0571] 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.

[0572] 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 first reinforcement 16 is relatively high, which can enhance the reinforcement effect and current flow capacity of the first area 1111, while improving the fast charging capability and reliability of the battery cell.

[0573] When the first electrode tab 110 is a positive electrode tab, optionally, the positive electrode tab includes aluminum or an aluminum alloy, and the first reinforcement 16 is a metal reinforcement, optionally including aluminum or an aluminum alloy, thereby making the connection between the positive electrode tab and the first reinforcement 16 more stable and the internal resistance at the connection smaller, which is conducive to improving the fast charging capability of the battery cell.

[0574] When the first electrode tab 110 is a negative electrode tab, optionally, the negative electrode tab includes copper or a copper alloy, and the first reinforcement 16 is a metal reinforcement, optionally including copper or a copper alloy, thereby making the connection between the negative electrode tab and the first reinforcement 16 more stable and the internal resistance at the connection smaller, which is conducive to improving the fast charging capability of the battery cell.

[0575] In some embodiments, the second tab includes a third region, where the third region is a region of the second tab connected to the second adapter.

[0576] Optionally, the battery cell further includes a second reinforcement member connected to the second tab and covering at least a third area. When the second tab is welded to the second adapter, the third area is a weld mark area of ​​the second tab.

[0577] The second reinforcement member at least covering the third area can be understood as the second reinforcement member covering the third area, or the second reinforcement member not only covers the third area but also extends beyond the third area.

[0578] During the welding process, the second reinforcement is arranged on the surface of the second pole lug, and the second reinforcement is at least partially melted and welded to the second pole lug and the second adapter, thereby strengthening the strength of the connection between the second pole lug and the second adapter; and when the thickness of the second pole lug is relatively thin, the reinforcing effect of the second reinforcement makes it less likely for the second pole lug to crack or even break, further improving the structural stability and current carrying capacity of the second pole lug, and improving the fast charging capability and reliability of the battery cell.

[0579] 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 second pole tab and the second adapter; the second reinforcement can enhance the mechanical strength of the connection between the second pole tab and the second adapter, improve the structural stability and current carrying capacity, and enhance the rapid charging capability and reliability of the battery cell.

[0580] The relevant parameters of the third area are similar to the relevant parameters of the first area 1111 and are not described in detail here.

[0581] The relevant parameters of the second reinforcement member are similar to the relevant parameters of the first reinforcement member 16 and will not be described in detail here.

[0582] [First thermal insulation member]

[0583] like Figures 10 to 15 As shown, in some embodiments, the battery cell 7 further includes a first thermal insulation member 17, which is located between the first region 1111 and the main body 14 and covers at least the first region 1111. If the battery cell 7 further includes an optional first reinforcement member 16, the first thermal insulation member 17 is also located between the first reinforcement member 16 and the main body 14.

[0584] The first region 1111 may generate high heat during the charging and discharging process of the battery cell 7, and the first thermal insulation component 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.

[0585] Optionally, the first thermal insulation member 17 also covers at least a portion of the first adapter 150 .

[0586] Further optionally, the first electrode tab 110 is electrically connected to the first electrode terminal 30, the first electrode tab 110 is connected to a portion of the first adapter 150, and the first thermal insulator 17 is connected to another portion of the first adapter 150. The first electrode tab 110 and the first thermal insulator 17 are respectively connected to different portions of the first adapter 150. Although the first adapter 150 is artificially divided into one portion and another portion, there is no clear boundary between the two portions, and the two portions can be an integrated structure.

[0587] Further optionally, the first thermal insulator 17 is welded to the first adapter 150. This provides a more stable connection between the first thermal insulator 17 and the first adapter 150, more effectively mitigating the risk of heat transfer to the main body 14 and reducing the risk of electrolyte decomposition and gas production, thereby improving the reliability of the battery cell 7.

[0588] In some embodiments, the first thermal insulation member 17 includes multiple thermal insulation layers, each thermal insulation layer covering at least the first region 1111 .

[0589] Multiple layers of thermal insulation layers can be stacked along the thickness direction of the first thermal insulation component 17. Covering the first 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.

[0590] like Figure 15 and Figure 16As shown, in other embodiments, the first thermal insulation element 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 cover at least the first region 1111. When the first thermal insulation element 17 is unfolded, the second thermal insulation layer 172 can be located on both sides of the first thermal insulation layer 171. After the first thermal insulation element 17 is inserted into the shell, the second thermal insulation layer 172 bends and partially overlaps with the first thermal insulation layer 171.

[0591] Optionally, the first thermal insulation layer 171 also covers the first adapter 150. Further optionally, the second thermal insulation layer 172 also covers the first adapter 150.

[0592] The first region 1111 generates more heat, and the first thermal insulation layer 171 and the second thermal insulation layer 172 cover the first region 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 .

[0593] 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.

[0594] 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.

[0595] For example, the thickness of the portion of the first thermal insulation member 17 opposite the first 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 first region 1111 generates relatively more heat, and the relatively thick first thermal insulation member 17 can more effectively mitigate heat transfer, thereby improving the reliability of the battery cell 7. Figure 14 and Figure 15 GH1 shown in the figure represents the thickness of a portion of the first thermal insulation member 17 disposed opposite to the first region 1111. GH2 represents the thickness of the remaining portion of the first thermal insulation member 17, for example, 0.5 mm to 2.0 mm.

[0596] Illustratively, the first 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 the main body 14 and the electrolyte, and thereby improving the reliability of the battery cell 7.

[0597] For example, the polyolefin includes one or more of polyethylene, polypropylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, and polytetrafluoroethylene.

[0598] In some embodiments, the battery cell further includes a second thermal insulator, which is located between the third region of the second tab and the main body 14 and covers at least the third region. If the battery cell further includes an optional second reinforcement member, the second thermal insulator is also located between the second reinforcement member and the main body 14.

[0599] The structure, size and material of the second thermal insulation member are similar to those of the first thermal insulation member 17 and will not be described in detail here.

[0600] Next, the tab arrangement will be described using the electrode assembly 10 as a laminated structure as an example.

[0601] like Figure 17 As shown, the electrode assembly 10 includes a positive electrode sheet 11 , a negative electrode sheet 12 and a separator 13 stacked along a thickness direction X of the battery cell.

[0602] 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.

[0603] 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 .

[0604] 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 .

[0605] 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.

[0606] 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.

[0607] 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.

[0608] 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.

[0609] 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.

[0610] 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.

[0611] 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.

[0612] 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.

[0613] like Figure 22 As 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.

[0614] like Figure 23As 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.

[0615] 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.

[0616] 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.

[0617] 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.

[0618] 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.

[0619] 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.

[0620] 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.

[0621] 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.

[0622] 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 .

[0623] 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.

[0624] 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.

[0625] The battery cell of the present application is applicable to various battery devices and electrical devices using the battery cell.

[0626] 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.

[0627] 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.

[0628] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0629] 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.

[0630] 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 .

[0631] 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 .

[0632] 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.

[0633] 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.

[0634] 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.

[0635] 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 .

[0636] like Figure 28 As shown, the battery module 6 includes a plurality of battery cells 7 .

[0637] 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.

[0638] 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.

[0639] 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.

[0640] 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.

[0641] 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.

[0642] 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:

[0643] Charge from 10% SOC to 15% SOC at 8.00C constant current;

[0644] Charge from 15% SOC to 20% SOC at 8.00C constant current;

[0645] Charge from 20% SOC to 25% SOC at 8.00C constant current;

[0646] Charge from 25% SOC to 30% SOC at 8.00C constant current;

[0647] Charge from 30% SOC to 35% SOC at 7.50C constant current;

[0648] Charge from 35% SOC to 40% SOC at 6.87C constant current;

[0649] Charge from 40% SOC to 45% SOC at 6.38C constant current;

[0650] Charge from 45% SOC to 50% SOC at 5.95C constant current;

[0651] Charge from 50% SOC to 55% SOC at 5.53C constant current;

[0652] Charge from 55% SOC to 60% SOC at 5.14C constant current;

[0653] Charge from 60% SOC to 65% SOC at 4.76C constant current;

[0654] Charge from 65% SOC to 70% SOC at 4.36C constant current;

[0655] Charge from 70% SOC to 75% SOC at 3.94C constant current;

[0656] Charge from 75% SOC to 80% SOC at 3.57C constant current.

[0657] 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.

[0658] Electrical devices

[0659] A second aspect of the embodiments of the present application provides an electrical device.

[0660] 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.

[0661] Figure 291 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.

[0662] 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 .

[0663] 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.

[0664] Example

[0665] 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.

[0666] Example 1

[0667] 1. Preparation of positive electrode sheet

[0668] The positive electrode sheet 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.

[0669] The positive conductive layer on the positive current collector is a film layer formed by evenly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride PVDF, calcium hydroxide and the solvent N-methylpyrrolidone NMP, and then coating it on the surface of the positive electrode collector and drying it. The thickness is 1 μm. The mass content of the positive electrode conductive agent in the positive conductive layer is 43%, the mass content of the positive electrode binder is 55%, and the mass content of calcium hydroxide is 2%.

[0670] 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.

[0671] 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%.

[0672] The single-side coating weight of the positive electrode active material layer is 283 mg / 1540.25 mm 2 .

[0673] 2. Preparation of negative electrode sheet

[0674] The negative electrode sheet 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.

[0675] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing a negative electrode conductive agent superconducting carbon, a negative electrode binder styrene-butadiene rubber (SBR), a thickener sodium carboxymethyl cellulose (CMC-Na), and a solvent water, and then coating it on the surface of the negative electrode current collector and drying it. The thickness is 1 μm, and the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%;

[0676] The negative electrode active material layer includes graphite particles, a conductive agent acetylene black, a binder styrene-butadiene rubber, and a 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 element, the mass content of carbon element in the graphite particles is 2.5%, and the graphite body particles are artificial graphite.

[0677] The single-side coating weight of the negative electrode active material layer is 130 mg / 1540.25 mm 2 .

[0678] 3. Isolation film

[0679] 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%;

[0680] 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;

[0681] 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.

[0682] 4. Preparation of electrolyte

[0683] The electrolyte includes an organic solvent, an electrolyte lithium salt and additives.

[0684] After mixing the components of the organic solvents, electrolyte lithium salt and additives are added to prepare an electrolyte solution.

[0685] 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;

[0686] 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;

[0687] The electrolyte lithium salt includes 10% by mass of lithium hexafluorophosphate LiPF6 and 5% by mass of lithium bis(fluorosulfonyl)imide LiFSI.

[0688] 5. Preparation of battery cells

[0689] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, to obtain a laminated electrode assembly. The electrode assembly is placed in a shell, on which a positive terminal and a negative terminal are provided. After baking, the electrolyte is injected, and after vacuum packaging, standing, formation, shaping and other processes, a battery cell is obtained.

[0690] The compaction density of the positive electrode active material layer of the battery cell is 2.65 / cm 3 The porosity of the positive electrode active material layer is 26.4%, and the compaction density of the negative electrode active material layer is 1.3 g / cm 3 , the porosity of the negative electrode active material layer is 42.5%;

[0691] The amount of electrolyte A1 in the positive electrode active material layer is 0.8 g / Ah;

[0692] The amount of electrolyte A2 in the negative electrode active material layer is 0.9 g / Ah;

[0693] The amount A3 of the electrolyte in the separator is 0.2 g / Ah.

[0694] The length of the battery cell is 200mm, and the volume energy density of the battery cell is 415Wh / L.

[0695] Example 2-1 to Example 2-4

[0696] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the amount of interstitial electrolyte and the amount of electrolyte injected were adjusted.

[0697] Comparative Example 1-1 and Comparative Example 1-2

[0698] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the amount of interstitial electrolyte and the amount of electrolyte injected were adjusted.

[0699] Performance Testing

[0700] 1. DC internal resistance DCR test of battery cells

[0701] At 25°C, charge the battery cell to 3.65 V at a constant current of 0.33 C, let it stand for 1 min, then charge it to 3.65 V at a constant current of 0.1 C, let it stand for 30 min, and discharge it to 2.0 V at a constant current of 0.33 C. Record the discharge capacity A0 at this time in Ah, and then charge it at a constant current of 0.33 C for 0.5A0Ah and adjust the SOC to 50%.

[0702] 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 ,

[0703] 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.

[0704] 2. Battery cell pressure relief threshold test

[0705] Test the attenuation SOH (State of Health) of battery cells that are cyclically gassed and depressurized at high temperatures. Specifically:

[0706] After the battery cell completes the capacity test, weld the gas production pipeline to the battery cell liquid injection port and connect the pressure gauge.

[0707] The battery cell was placed in a 55°C constant temperature box, charged to 3.65 V at a constant current of 0.5 C, then charged to 3.65 V at a constant current of 0.1 C, left to stand for 10 min, and discharged to 2.8 V at a constant current of 1 C. The discharge capacity D0 was recorded. This was considered a cycle until the pressure relief mechanism of the battery cell was opened. The discharge capacity D1 at this time was recorded, and the capacity decay at this time was calculated as D1 / D0×100%. The percentage of the battery capacity decay to the nominal capacity was the pressure relief threshold.

[0708] When the pressure relief mechanism releases pressure, the greater the SOH is, the fewer cycles of the battery cell are. That is, when the number of cycles is small, the gas production inside the battery cell is high, the side reaction is serious, and the life of the battery cell is short.

[0709] 3. Volume energy density of battery cells

[0710] The battery cells of the embodiment and comparative example were placed at 25°C, charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V to 0.05C, and allowed to stand for 30 minutes; discharged at a constant current of 0.33C to 2.0V, and the discharge capacity A0 at this time was recorded in Ah; the length, width, and height of the battery cell were measured with a caliper, and the volume V0 of the battery cell was calculated in L; the volume energy density of the battery cell, VED, was calculated as (A0×discharge platform voltage) / V0 in Wh / L.

[0711] The test results are shown in Table 1.

[0712] Table 1

[0713]

[0714] In comparative example 1-1, the amount of interstitial electrolyte A is too small, and the impedance of the SEI film formed on the negative electrode side is low, which makes the internal resistance of the battery cell smaller. However, it may cause the content of unsaturated ester additives in the battery cell to be too low, and the carboxylic ester solvent will react with the negative electrode side too early, resulting in increased gas production. The risk of premature pressure relief of the battery cell is high, and the pressure relief threshold is greater than 85% SOH, which is not conducive to the reliability of the battery cell.

[0715] In comparative example 1-2, the amount of interstitial electrolyte A is too much. Although the amount of carboxylic acid ester solvent used inside the battery cell is relatively large and the internal resistance of the battery cell is relatively low, the electrolyte occupies too much space, resulting in less residual space inside the battery cell and no extra space for gas production. The internal pressure of the battery cell is relatively high, resulting in a higher risk of premature pressure relief of the battery cell. The pressure relief threshold is greater than 85% SOH, which is not conducive to the reliability of the battery cell.

[0716] In Example 1, Example 2-1 to Example 2-4, by adjusting the interstitial electrolyte amount A to meet 0.5g / Ah≤A≤1.4g / Ah, and matching the components of the electrolyte, further matching, the electrolyte amount A in the battery cell T The concentration of unsaturated ester additives is 2.4 g / Ah to 3.3 g / Ah, which can enable more unsaturated ester additives to participate in the film formation and consumption of the solid electrolyte interface SEI layer on the negative electrode side, and can effectively avoid the premature side reactions of carboxylic acid ester solvents on the negative electrode side, thereby slowing down the gas production phenomenon, reducing the risk of pressure release of the battery cell, and taking into account the reliability and fast charging performance of the battery cell.

[0717] Example 2-5 and Example 2-6

[0718] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the amount of interstitial electrolyte and the amount of electrolyte injected were adjusted.

[0719] The test results are shown in Table 2.

[0720] Table 2

[0721]

[0722] In Examples 2-5 and 2-6, by regulating the porosity and compaction density of the positive electrode active material layer, the porosity and compaction density of the negative electrode active material layer, and the porosity of the isolation membrane, the interstitial electrolyte amount A can be effectively regulated to meet 0.5g / Ah≤A≤1.4g / Ah, thereby reducing the pressure release risk of the battery cell, taking into account the reliability and fast charging performance of the battery cell, and the battery cell has excellent energy density.

[0723] Example 3-1 to Example 3-3

[0724] 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 ethylene carbonate and the mass content of dimethyl carbonate in the electrolyte were adjusted.

[0725] Comparative Example 3-1 and Comparative Example 3-2

[0726] 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 ethylene carbonate and the mass content of dimethyl carbonate in the electrolyte were adjusted.

[0727] Example 4-1 and Example 4-2

[0728] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size Dv50 of the graphite particles in the electrolyte was adjusted.

[0729] Comparative Example 4-1 and Comparative Example 4-2

[0730] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size Dv50 of the graphite particles in the electrolyte was adjusted.

[0731] Example 5-1 to Example 5-4

[0732] 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 the unsaturated ester additive in the electrolyte was adjusted.

[0733] Comparative Example 5-1 and Comparative Example 5-2

[0734] 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 the unsaturated ester additive in the electrolyte was adjusted.

[0735] Example 5-5

[0736] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the type of unsaturated ester additive in the electrolyte was adjusted, and the unsaturated ester additive was bis(fluoroethylene carbonate) DFEC.

[0737] The test results are shown in Table 3.

[0738] Table 3

[0739]

[0740] EC stands for ethylene carbonate; DMC stands for dimethyl carbonate; and VC stands for vinylene carbonate.

[0741] As a cyclic ester, ethylene carbonate EC has a higher degree of dissociation with lithium salts and a stronger coordination ability. Increasing the EC content within a certain range is helpful to improve the conductivity. In the case of comparative example 3-1, when the mass content of ethylene carbonate EC is too low, the dissociation degree with lithium salts is poor, and the internal resistance of the battery cell increases. However, ethylene carbonate EC also has a certain film-forming effect. If the EC content is too low and the linear ester content is too high, the film formation is poor during the cycle or storage process, the side reactions increase, the gas production increases, and the internal pressure increases, resulting in a higher pressure release threshold of the battery cell.

[0742] The mass content of ethylene carbonate in Comparative Example 3-2 is too high, the viscosity of the electrolyte increases, and the internal resistance of the battery cell increases, which is not conducive to the rapid charging of the battery cell.

[0743] In Examples 3-1 to 3-3 of the present application, by limiting the mass content of ethylene carbonate within an appropriate range and combining it with an appropriate amount of unsaturated ester additives, not only can the ion migration rate in the electrolyte be increased to improve fast charging, but it can also reduce gas production, lower internal pressure, and improve the reliability of battery cells.

[0744] The volume average particle size Dv50 of the graphite particles in comparative example 4-1 is relatively low. Although the solid phase transmission path of lithium ions is relatively short, the interfacial activity is relatively high and the side reaction gas production is intense, resulting in a high risk of premature pressure release of the battery cell, which is not conducive to the reliability of the battery cell.

[0745] The volume average particle size Dv50 of the graphite particles in Comparative Example 4-2 is relatively high, the solid phase transmission path of lithium ions is relatively long, and the internal resistance of the battery cell is relatively high, which is not conducive to rapid charging of the battery cell.

[0746] The volume average particle size Dv50 of the graphite particles in Example 4-1 and Example 4-2 is within an appropriate range. When combined with unsaturated ester additives, they can not only increase the lithium ion migration rate and improve fast charging, but also reduce gas production, lower internal pressure, and improve the reliability of battery cells.

[0747] When the mass content of the unsaturated ester additive in comparative example 5-1 is too low, the film-forming effect on the negative electrode side is poor, and it cannot provide excellent protection for the negative electrode active material layer, so that side reactions may still occur between the negative electrode active material and the solvent, resulting in an increase in the internal pressure of the battery cell, which is not conducive to the reliability of the battery cell.

[0748] However, as the mass content of the unsaturated ester additive increases, for example, the unsaturated ester additive in Example 5-2 can form a dense SEI film on the negative electrode side, effectively reducing the risk of side reactions between the negative electrode active material and the solvent; but the impedance of the SEI film formed by it is too high, which is not conducive to the rapid charging of the battery cell.

[0749] When the mass content of the unsaturated ester additives in Examples 5-1 to 5-4 is within the above range, it can effectively protect the negative electrode active material layer, alleviate interfacial side reactions, and reduce the impedance of the SEI film, thereby effectively taking into account both the reliability of the battery cell and the fast charging performance.

[0750] Various fluorocarbonate additives can effectively balance the reliability and fast charging performance of battery cells. For example, the ethylene carbonate derivative of Example 1 includes FEC, and the ethylene carbonate derivative of Example 5-5 includes DFEC. These materials can effectively balance the reliability and fast charging performance of battery cells.

[0751] 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: The invention comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet, wherein the positive electrode sheet comprises 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 the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein: The positive electrode active material layer includes a lithium-containing phosphate with an olivine structure, and the negative electrode active material layer includes graphite particles, wherein the volume average particle size Dv50 of the graphite particles is 8.5 μm to 13.5 μm; The interstitial electrolyte volume A of the battery cell satisfies: A=A T -A1-A2-A3, 0.5g / Ah≤A≤1.4g / Ah; A T Indicates the amount of electrolyte in the battery cell, the unit is g / Ah; A1 represents the amount of electrolyte in the positive electrode active material layer, and its unit is g / Ah; A2 represents the amount of electrolyte in the negative electrode active material layer, and its unit is g / Ah; A3 represents the amount of electrolyte in the separator, and its unit is g / Ah; The electrolyte comprises ethylene carbonate, and the mass content of the ethylene carbonate in the electrolyte is 20% to 35%; The electrolyte further includes an unsaturated ester additive, the mass content of the unsaturated ester additive in the electrolyte is 0.05% to 6%, and the unsaturated ester additive includes one or more of vinylene carbonate, vinyl ethylene carbonate, allyl ethyl carbonate and fluorocarbonate additives.

2. The battery cell according to claim 1, wherein: The interstitial electrolyte amount A of the battery cell is 0.8 g / Ah to 1.3 g / Ah.

3. The battery cell according to claim 1 or 2, characterized in that: The amount of electrolyte A in the battery cell T 2.4g / Ah to 3.3g / Ah.

4. The battery cell according to claim 1, wherein: The amount A1 of the electrolyte in the positive electrode active material layer is 0.6 g / Ah to 1.0 g / Ah.

5. The battery cell according to claim 1, characterized in that The amount A2 of the electrolyte in the negative electrode active material layer is 0.7 g / Ah to 1.0 g / Ah.

6. The battery cell according to claim 1, characterized in that The amount A3 of the electrolyte in the separator is 0.1 g / Ah to 0.3 g / Ah.

7. The battery cell according to claim 1, characterized in that The battery cell includes a shell, the shell contains the electrode assembly and the electrolyte, and the shell is provided with a pressure relief mechanism.

8. The battery cell according to claim 7, characterized in that The mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 0.05% and less than 1.5%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 80% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell.

9. The battery cell according to claim 7, characterized in that The mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 1.5% and less than 3%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 70% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell.

10. The battery cell according to claim 7, characterized in that The mass content of the unsaturated ester additive in the electrolyte is greater than or equal to 3% and less than 4.5%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 60% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell.

11. The battery cell according to claim 7, characterized in that The mass content of the unsaturated ester additive in the electrolyte is 4.5% to 6%, and the pressure relief threshold of the pressure relief mechanism is less than or equal to 50% SOH, where SOH represents the ratio of the current capacity of the battery cell to the nominal capacity of the battery cell.

12. The battery cell according to claim 1, wherein The fluorocarbonate additive includes one or more of fluoroethylene carbonate, bisfluoroethylene carbonate and trifluoromethylethylene carbonate.

13. The battery cell according to claim 7, characterized in that The outer shell includes a shell and an end cover. The shell has an opening. The end cover covers the opening. The shell accommodates the electrode assembly and the electrolyte. The pressure relief mechanism is provided on the end cover. The pressure relief mechanism includes a weak portion.

14. The battery cell according to claim 1, characterized in that The mass content of the ethylene carbonate in the electrolyte is 25% to 35%.

15. The battery cell according to claim 1, characterized in that The electrolyte comprises a carboxylate solvent, wherein the mass content of the carboxylate solvent in the electrolyte is 8% to 30%; and / or The electrolyte further includes a linear carbonate solvent, and the mass content of the linear carbonate solvent in the electrolyte is 18% to 45%.

16. The battery cell according to claim 15, 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.

17. The battery cell according to claim 16, 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.

18. The battery cell according to claim 17, characterized in that The carboxylate solvent includes one or more of methyl acetate and ethyl acetate.

19. The battery cell according to claim 15, characterized in that The linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

20. 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.

21. The battery cell according to claim 20, characterized in that Based on the mass of the electrolyte, the mass content of the sulfur-containing additive is 0.5% to 2%.

22. The battery cell according to claim 1, characterized in that The electrolyte further includes a lithium salt additive with a mass content of 0.2% to 1.5% in the electrolyte, and the lithium salt additive includes one or more of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate and lithium fluorosulfonate.

23. 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%.

24. The battery cell according to claim 23, 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.

25. 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%.

26. The battery cell according to claim 25, characterized in that The lithium salt includes one or more of lithium fluorine-containing sulfonyl imide and lithium hexafluorophosphate.

27. The battery cell according to claim 26, characterized in that The fluorine-containing lithium sulfonyl imide includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide; and / or The mass content of the fluorinated lithium sulfonyl imide in the electrolyte is 3% to 8%; and / or The mass content of the lithium hexafluorophosphate in the electrolyte is 8% to 12%.

28. The battery cell according to claim 1, characterized in that The porosity of the negative electrode active material layer is 30% to 45%; and / or The positive electrode active material layer has a porosity of 23% to 33%.

29. 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 and / or 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 .

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

31. The battery cell according to claim 30, characterized in that The graphite bulk particles include at least one of artificial graphite and natural graphite; and / or The mass content of carbon element in the negative electrode coating layer is 2% to 5% based on the mass of the graphite particles.

32. The battery cell according to claim 31, characterized in that The graphite bulk particles include artificial graphite.

33. The battery cell according to claim 1, characterized in that The negative electrode active material layer includes: a first negative electrode active material layer, disposed on the negative electrode current collector; The second negative electrode active material layer is provided on a side of the first negative electrode active material layer away from the negative electrode current collector. Wherein, both the first negative electrode active material layer and the second negative electrode active material layer include the graphite particles.

34. The battery cell according to claim 1, characterized in that The negative electrode plate 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 includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers; and / or The negative electrode conductive layer includes a negative electrode binder, and the negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate and carboxymethyl chitosan.

35. 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.

36. The battery cell according to claim 35, characterized in that The mass content of the carbon element is 0.8% to 2.3% based on the mass of the lithium-containing phosphate; and / or The positive electrode coating layer further includes one or more elements of Fe, Ti, Zr, Hf, Ge and Sn.

37. The battery cell according to claim 35, characterized in that The phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate and lithium cobalt phosphate.

38. 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.

39. The battery cell according to claim 1, wherein: The positive electrode active material layer includes a positive electrode conductive agent, and 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.

40. The battery cell according to claim 1, wherein The positive electrode sheet 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 includes a positive electrode conductive agent, and 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 layer includes a positive electrode 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.

41. The battery cell according to claim 1, characterized in that 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.

42. The battery cell according to claim 1, 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.

43. 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.

44. The battery cell according to claim 43, 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.

45. The battery cell according to claim 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.

46. ​​The battery cell according to claim 1, characterized in that The electrode assembly is a laminated structure, and the positive electrode sheet, the separator, and the negative electrode sheet are stacked along the thickness direction of the battery cell.

47. The battery cell according to claim 46, characterized in that The positive electrode sheet includes at least one positive electrode tab, and the positive electrode tab is connected to at least one side of the positive electrode collector along a first direction, and the first direction is parallel to the width direction of the battery cell or the first direction is parallel to the length direction of the battery cell; and / or The negative electrode sheet includes at least one negative electrode tab connected to at least one side of the negative electrode collector along a first direction, wherein the first direction is parallel to the width direction of the battery cell or the first direction is parallel to the length direction of the battery cell.

48. The battery cell according to claim 47, 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.

49. The battery cell according to claim 47, 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.

50. The battery cell according to claim 49, characterized in that OH1 is 1.8 mm to 4.2 mm; and / or OH2 is 1.5 mm to 3.5 mm.

51. The battery cell according to claim 47, 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.

52. The battery cell according to claim 1, characterized in that The battery cell includes a housing that houses the electrode assembly and the electrolyte. The outer shell includes a shell and an end cover. The shell includes an opening. The end cover covers the opening. The size of the outer shell along the length direction of the battery cell is 190 mm to 650 mm.

53. The battery cell according to claim 52, characterized in that The dimension of the housing along the length direction of the battery cell is greater than or equal to 190 mm and less than 300 mm; or The dimension of the housing along the length direction of the battery cell is greater than or equal to 300 mm and less than 450 mm; or A dimension of the housing along a length direction of the battery cell is greater than or equal to 450 mm and less than or equal to 650 mm.

54. The battery cell according to claim 52, characterized in that The housing is a rectangular parallelepiped structure, comprising two first walls and two second walls disposed 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 thickness direction being larger than the cross-sectional area of ​​the second wall perpendicular to its thickness direction, and the thickness of the first wall being 0.3 mm to 0.5 mm; and / or The thickness of the second wall is 0.5 mm to 0.7 mm.

55. The battery cell according to claim 1, characterized in that The battery cell includes a first electrode terminal and a first adapter; The electrode assembly includes a tab portion and a main body portion, wherein the tab portion is connected to the main body portion and extends out of the main body portion along a first direction, the tab portion includes a first tab, the first tab and the first electrode terminal are connected via a first adapter, the first tab includes a first region, and the first region is the region of the first tab connected to the first adapter, wherein the first tab is a positive tab or a negative tab, and the total area of ​​the first region is 160 mm 2 Up to 1000mm 2 ,in, The main body includes a positive electrode portion, a negative electrode portion and a separator. The positive electrode portion includes a positive electrode collector and a positive electrode active material layer arranged on at least one side of the positive electrode collector. The negative electrode portion includes a negative electrode collector and a negative electrode active material layer arranged on at least one side of the negative electrode collector.

56. The battery cell according to claim 55, characterized in that The battery cell further includes a first reinforcement member, which is connected to at least the first region and is located on a side of the first tab facing away from the first adapter.

57. The battery cell according to claim 56, characterized in that The ratio of the total cross-sectional area of ​​the first reinforcement perpendicular to the thickness direction thereof to the total area of ​​the first region is 1.0 to 1.

5.

58. The battery cell according to claim 56, characterized in that The total cross-sectional area of ​​the first reinforcement perpendicular to its own thickness direction is 320 mm 2 Up to 1600mm 2 .

59. The battery cell according to claim 56, characterized in that The first reinforcement member comprises: a first reinforcement portion welded to the first region; and The second reinforcement portion is disposed around the first reinforcement portion and connected to the first reinforcement portion.

60. The battery cell according to claim 59, characterized in that The second reinforcement portion has a thickness of 0.1 mm to 0.8 mm.

61. The battery cell according to claim 56, characterized in that The first electrode tab is a positive electrode tab, and the positive electrode tab comprises aluminum or an aluminum alloy; the first reinforcement comprises aluminum or an aluminum alloy; or The first electrode tab is a negative electrode tab, and the negative electrode tab includes copper or a copper alloy; the first reinforcement includes copper or a copper alloy.

62. The battery cell according to claim 55, characterized in that The battery cell further includes a first thermal insulation member located between the first region and the main body and covering at least the first region.

63. The battery cell according to claim 62, characterized in that The thickness of the portion of the first thermal insulation component opposite to the first region is 1 mm to 4 mm.

64. The battery cell according to claim 62, characterized in that The first thermal insulation component 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 first area.

65. The battery cell according to claim 64, 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 thermal insulation layer is 0.5 mm to 2.0 mm.

66. The battery cell according to claim 62, characterized in that The first electrode tab is connected to a portion of the first adapter, and the first thermal insulation member is connected to another portion of the first adapter.

67. The battery cell according to claim 66, characterized in that The first heat insulating component is welded to the first adapter component.

68. The battery cell according to claim 62, characterized in that The first thermal insulation member includes one or more of polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polycarbonate.

69. The battery cell according to claim 68, characterized in that The polyolefin includes one or more of polyethylene, polypropylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride and polytetrafluoroethylene.

70. A battery device, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 69.

71. The battery device according to claim 70, characterized in that The battery device further includes a heat resistor covering at least one of the two first walls of the battery cell.

72. The battery device according to claim 70, 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.

73. The battery device according to claim 70, characterized in that The maximum charging rate of the battery device is 5C to 12C.

74. An electrical device, characterized in that: Comprising a battery device as claimed in any one of claims 70 to 73.

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