Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive pole piece and a negative pole piece, the positive pole piece comprises lithium-containing phosphate; the negative pole piece comprises graphite particles; the electrolyte comprises a carboxylic ester solvent, a linear carbonic ester solvent and an additive, the mass content of the carboxylic ester solvent is 10%-30%, and the mass content of the linear carbonic ester solvent is 10%-50%; the mass content of the additive is 3%-9%, the additive comprises 1, 3-propane sultone with the mass content larger than or equal to 0, an ethylene carbonate derivative with the mass content larger than or equal to 0 and vinylene carbonate with the mass content larger than 0, and the ethylene carbonate derivative comprises a compound shown in the formula A; q1, Q2, Q3 and Q4 each independently comprise any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, and Q1, Q2, Q3 and Q4 are not hydrogen atoms at the same time. # imgabs0 # formula A is shown in the specification.

Description

[0001] This application claims the priority of the international patent application PCT / CN2025 / 078578 titled "Battery Cell, Battery Device and Electric Appliance" filed on February 21, 2025, the entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to a battery cell, a battery device and an electric appliance. Background Art

[0003] Battery cells have characteristics such as high capacity and long life, and are therefore widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, and power tools, etc. With the development of the application fields of lithium-ion batteries, higher requirements are put forward for the performance of battery cells, such as the fast charging performance, cycle performance and use reliability of battery cells at high energy density. Summary of the Invention

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

[0005] In a first aspect, this application provides a battery cell, which includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab stacked along the thickness direction of the battery cell; the positive electrode tab includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, and the positive electrode film layer includes a lithium-containing phosphate with an olivine structure; the negative electrode tab includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, and the negative electrode film layer includes graphite particles. The electrolyte includes a carboxylate solvent, a linear carbonate solvent and an additive. Among them, based on the mass of the electrolyte, the mass content of the carboxylate solvent is 10% to 30%, and the mass content of the linear carbonate solvent is 10% to 50%; the mass content of the additive is 3% to 9%, and the additive includes 1,3-propane sultone with a mass content ≥0, a derivative of ethylene carbonate with a mass content ≥0, and vinylene carbonate with a mass content >0. The derivative of ethylene carbonate includes a compound represented by Formula A. Formula A In Formula A, Q 1 , Q 2 , Q 3 and Q 4 each independently includes any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q 1 , Q 2 , Q 3 , Q 4 are not simultaneously hydrogen atoms.

[0006] Thus, during the charging process of the present application embodiment, active ions such as lithium ions migrating out of the positive electrode plate migrate through the electrolyte to the negative electrode plate. The electrolyte includes a carboxylic ester solvent, which can reduce the viscosity of the electrolyte and improve the migration rate of lithium ions in the electrolyte. As the mass content of the carboxylic ester solvent increases, the viscosity of the electrolyte decreases, the conductivity increases, and the migration rate of lithium ions in the electrolyte can be further improved, which is beneficial to the improvement of the fast charging performance. However, as the mass content of the carboxylic ester solvent further increases, the side reaction between the carboxylic ester solvent and the negative active material becomes more serious and the gas generation increases. The electrolyte also includes a linear carbonate solvent. The addition of the linear carbonate solvent can enable the electrolyte to have a relatively high conductivity and improve the migration rate of lithium ions even when the addition amount of the carboxylic ester solvent is relatively low. Moreover, since the mass content of the carboxylic ester solvent is relatively low, the side reaction is slowed down and the gas generation amount is reduced. Further, the electrolyte further includes an additive. The additive includes vinylene carbonate. The reaction potential of vinylene carbonate is close to that of the carboxylic ester solvent, and there is a competitive reaction with the carboxylic ester solvent. Vinylene carbonate can participate in the formation of a dense solid electrolyte interface film (SEI film) containing organic components on the negative electrode side, making it difficult for the carboxylic ester solvent to penetrate the SEI film to the negative active material, thereby further alleviating the side reaction between the carboxylic ester solvent and the negative active material and further reducing the gas generation amount. Moreover, since the additive is within an appropriate content range, the film impedance formed on the negative electrode side will not be too large and will basically not deteriorate the fast charging performance. Therefore, the present application embodiment can improve the fast charging ability and cycling performance of the battery cell. In some embodiments, the mass content of the additive is 5% to 8%. When the mass content of the additive is within the above range, the cycling performance and fast charging performance of the battery cell can be further improved.

[0007] In some embodiments, the mass content of vinylene carbonate is 0.8% to 7%, and can be optionally 2% to 6%. When the mass content of vinylene carbonate is within the above range, a dense SEI film containing organic components can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reaction on the negative electrode side and take into account the improvement of the cycling performance and fast charging ability of the battery cell.

[0008] In some embodiments, the mass content of 1,3 - propanesultone in the electrolyte is 0 to 0.5%. When the mass content of 1,3 - propanesultone is within the above range, the impedance of the formed SEI film will not be too high, which can reduce the impedance on the basis of alleviating the side reaction and improve the fast charging performance and cycling performance of the battery cell.

[0009] In some embodiments, the mass content of the ethylene carbonate derivative in the electrolyte is 0 to 2.55%. The ethylene carbonate derivative can preferentially form a film, optimize the components of the SEI film, reduce the impedance of the SEI film, and effectively improve the fast charging performance and cycling performance of the battery cell.

[0010] In some embodiments, Q 1 , Q 2 , Q 3 and Q 4 at least one of them includes a halogen atom or a C1-C5 haloalkyl group. When the ethylene carbonate derivative contains a fluorine atom, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side. On the basis of protecting the negative electrode active material, the impedance of the film layer is relatively low, and it can more effectively balance the improvement of the cycling performance and fast charging performance of the battery cell.

[0011] In some embodiments, the ethylene carbonate derivative includes at least one of the compounds represented by Formula A-1 to the compounds represented by Formula A-3.

[0012] The above materials can further improve the cycling performance and fast charging performance of the battery cell.

[0013] In some embodiments, the conductivity of the electrolyte is 11 mS / cm to 14 mS / cm. The relatively high conductivity of the electrolyte is beneficial to improving the fast charging performance of the battery cell.

[0014] In some embodiments, the carboxylic ester solvent includes at least one of ethyl acrylate, propyl acetate, ethyl propionate, ethyl formate, propyl formate, ethyl acetate, and butyl propionate. The above materials have relatively low viscosities and can further improve the fast charging performance of the battery cell.

[0015] In some embodiments, the linear carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The above materials have relatively low viscosities, can increase the conductivity of the electrolyte at room temperature, and enhance the fast charging ability of the battery cell.

[0016] In some embodiments, the electrolyte further includes a cyclic carbonate solvent, and the mass content of the cyclic carbonate solvent in the electrolyte is 20% to 50%. The cyclic carbonate solvent has excellent desolvation ability, can enable lithium ions to be quickly released from the solvation structure at the positive and negative electrode interfaces, and enhance the transport rate of lithium ions at the interfaces, thereby further enhancing the fast charging ability of the battery cell.

[0017] In some embodiments, the cyclic carbonate solvents include at least one of ethylene carbonate, propylene carbonate, and butylene carbonate. The above materials have excellent desolvation ability, can improve the transport rate of lithium ions at the interface, and thus further improve the fast charging ability of the battery cell.

[0018] In some embodiments, the electrolyte further includes a lithium salt additive, and the lithium salt additive includes at least one of lithium difluorophosphate, lithium fluorosulfonate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. The above additives can improve the performance of the SEI film on the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycling performance.

[0019] In some embodiments, the mass content of the lithium salt additive in the electrolyte is 0.02% to 0.5%. The lithium salt additive and the additive cooperate to participate in film formation, which can optimize the film layer components of the SEI film. The lithium salt additive can participate in the formation of an SEI film rich in inorganic substances, and the inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI film, and improve the cycling performance of the battery cell.

[0020] In some embodiments, when the battery cell is in the 0% state of charge, the compaction density of the negative electrode film layer is 1.30 g / cm 3 to 1.52 g / cm 3 . When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative electrode active materials in the negative electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation, and the amount of gas generated by the decomposition of the carboxylate solvent due to heat accumulation can be reduced, improving the cycling performance of the battery cell.

[0021] In some embodiments, the single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 to 180 mg / 1540.25 mm 2 . When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode sheet will not be too large, and the cycling performance of the battery cell can be improved.

[0022] In some embodiments, the graphite particles include graphite body particles and a negative electrode coating layer coated on the surface of the graphite body particles. The graphite body particles include secondary particles, and the negative electrode coating layer includes carbon elements.

[0023] In some embodiments, the graphite body particles include at least one of artificial graphite and natural graphite.

[0024] In some embodiments, the graphitization degree of the graphite particles is 90% to 94%. When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, can reduce the heat generation of the negative electrode plate, reduce the heat generation of the battery cell, and can improve the fast charging performance of the battery cell.

[0025] In some embodiments, the volume average particle size Dv50 of the graphite particles is 7 μm to 15 μm. The volume average particle size of the graphite particles is relatively small, which shortens the solid phase migration path of lithium ions and improves the fast charging capability of the battery cell.

[0026] In some embodiments, the thickness of the negative electrode coating layer is 100 nm to 500 nm. When the thickness of the negative electrode coating layer is within the above range, the conductivity of the graphite particles can be further improved, the internal resistance of the negative electrode sheet can be reduced, the heat generation of the battery cell can be reduced, and the cycle performance of the battery cell can be improved.

[0027] In some embodiments, the negative electrode film layer further comprises a silicon-based material, and the mass content of silicon in the negative electrode film layer is 0.5% to 10.0%. The mass content of silicon in the silicon-based material is within the above range, which can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0028] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is arranged on the surface of the negative electrode collecting portion; the second negative electrode film layer is arranged on the side of the first negative electrode film layer away from the negative electrode collecting portion, wherein the first negative electrode film layer and the second negative electrode film layer both include graphite particles, and the average longest diameter of the graphite particles of the first negative electrode film layer is greater than or equal to the average longest diameter of the graphite particles of the second negative electrode film layer.

[0029] Therefore, there is a difference in the particle size between the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiment of the present application, the particle size of the second negative electrode film layer is relatively small, which can shorten the solid phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium plating on the surface of the negative electrode plate.

[0030] In some embodiments, the average longest diameter of the graphite particles of the first negative electrode film layer is 7 μm to 18 μm. When the average longest diameter of the graphite particles of the first negative electrode film 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 performance 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.

[0031] In some embodiments, the average longest diameter of the graphite particles in the second negative electrode film layer is 6 μm to 10 μm. When the average longest diameter of the graphite particles in the second negative electrode film layer is within the above range, on the one hand, the solid-phase transport path of lithium ions can be shortened, improving the fast charging performance. On the other hand, the materials are not prone to agglomeration during the preparation process, enhancing the stability of the materials. Additionally, the negative electrode active materials in the second negative electrode film layer with the above particle size range cooperate with the negative electrode active materials in the first negative electrode film layer, facilitating the construction of a gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transport, and improving the fast charging performance of the battery cell.

[0032] In some embodiments, the ratio of the thickness of the second negative electrode film layer to the thickness of the negative electrode film layer is 0.3 to 0.7. By adjusting the thickness ratio of the first negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transport can be reduced, and the fast charging ability of the battery cell can be improved.

[0033] In some embodiments, when the battery cell is in the 0% SOC state of charge, the tap density of the positive electrode film layer is 2.3 g / cm 3 to 2.6 g / cm 3 ; when the tap density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell, and since the positive electrode active materials in the positive electrode film layer are stacked relatively closely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation during fast charging and improving the cycle performance and fast charging performance of the battery cell.

[0034] In some embodiments, the single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 . When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode sheet will not be excessive, improving the cycle performance and fast charging performance of the battery cell.

[0035] In some embodiments, the lithium-containing phosphate includes at least one of primary particles and secondary particles, the secondary particles include a plurality of primary particles, and the secondary particles are spherical and / or spherical-like. The migration path of lithium ions in the primary particles is short, which can improve the migration rate of lithium ions; moreover, the secondary particles are spherical and / or spherical-like, resulting in more migration paths, which can further improve the migration rate of lithium ions and improve the fast charging performance of the battery cell.

[0036] In some embodiments, the average longest diameter of the primary particles is 300 nm to 800 nm. When the average longest diameter of the primary particles is within the above range, the solid-phase transport distance of lithium ions is short, which can further improve the migration rate of lithium ions and improve the fast charging performance of the battery cell.

[0037] In some embodiments, the average particle size of the secondary particles is 5 μm to 15 μm. When the average particle size of the secondary particles is within the above range, the solid-phase transport distance of lithium ions is short, which can further improve the migration rate of lithium ions and improve the fast charging performance of the battery cell.

[0038] In some embodiments, the lithium-containing phosphate includes phosphate particles and a cathode additive element located in the phosphate particles, and the cathode additive element includes at least one element of aluminum, vanadium, titanium, and niobium. The above-mentioned cathode additive element can improve the crystal structure stability of the cathode active material, improve the pressure resistance of the lithium-containing phosphate, be beneficial to improving the compaction density of the cathode film layer, and improving the energy density and cycle performance of the battery cell.

[0039] In some embodiments, the mass content of aluminum element in the lithium-containing phosphate is 200 ppm to 2500 ppm. When the mass content of aluminum element is within the above range, it can improve the pressure resistance of the lithium-containing phosphate, be beneficial to improving the compaction density of the cathode film layer, and improving the energy density and cycle performance of the battery cell.

[0040] In some embodiments, the mass content of vanadium element in the lithium-containing phosphate is 300 ppm to 2000 ppm. When the mass content of vanadium element is within the above range, it is beneficial to improving the compaction density of the cathode film layer, and improving the energy density and cycle performance of the battery cell.

[0041] In some embodiments, the mass content of titanium element in the lithium-containing phosphate is 1500 ppm to 3500 ppm. When the mass content of titanium element is within the above range, it can further improve the crystal structure of the cathode active material and improve the cycle performance.

[0042] In some embodiments, the mass content of niobium element in the lithium-containing phosphate is 300 ppm to 2000 ppm. When the mass content of niobium element is within the above range, it can further improve the crystal structure of the cathode active material and improve the cycle performance.

[0043] In some embodiments, the phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. The cycle stability of the above materials is relatively excellent, which can improve the cycle performance of the battery cell.

[0044] In some embodiments, the lithium-containing phosphate includes a general formula of Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1Compounds, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5, 0 ≤ c1 ≤ 0.5, 3 ≤ z1 ≤ 5, A includes at least one of Na, K, and Mg; Me includes at least one of Mn, Fe, Co, and Ni; M includes at least one of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes at least one of Cl, C, and N; Y includes at least one of O and F. The lithium-containing phosphate has excellent cycling stability, which is beneficial to improving the cycling performance of the battery cell.

[0045] In some embodiments, the positive electrode tab includes at least one positive electrode tab ear, and at least one positive electrode tab ear is connected to the positive electrode current collector and extends out of the positive electrode current collector along the length direction of the battery cell. This setting method is beneficial to reducing the occupied space of the tab ear and improving the energy density of the battery cell.

[0046] In some embodiments, the negative electrode tab includes at least one negative electrode tab ear, and at least one negative electrode tab ear is connected to the negative electrode current collector and extends out of the negative electrode current collector along the length direction of the battery cell. This setting method is beneficial to reducing the occupied space of the tab ear and improving the energy density of the battery cell.

[0047] In some embodiments, the positive electrode tab satisfies: n*W1 / W2 is 0.9 to 1.0; n represents the number of all positive electrode tab ears on the same side of the positive electrode current collector; W1 represents the average size of the positive electrode tab ear along the width direction of the battery cell; W2 represents the size of the positive electrode current collector along the width direction.

[0048] Thus, when n*W1 / W2 satisfies the above range, the current-carrying area of the positive electrode tab ear is relatively large, which is beneficial to improving the fast charging performance of the battery cell.

[0049] In some embodiments, the negative electrode tab satisfies: m*W3 / W4 is 0.9 to 1.0; m represents the number of all negative electrode tab ears on the same side of the negative electrode current collector; W3 represents the average size of the negative electrode tab ear along the width direction of the battery cell; W4 represents the size of the negative electrode current collector along the width direction.

[0050] Thus, when m*W3 / W4 satisfies the above range, the current-carrying area of the negative electrode tab ear is relatively large, which is beneficial to improving the fast charging performance of the battery cell.

[0051] In some embodiments, the battery cell further includes a positive terminal and a positive current collector adapter. The positive terminal is disposed on at least one side of the electrode assembly along the width direction of the battery cell, and the positive terminal is connected to the positive tab through the positive current collector adapter. Through the connection of the positive current collector adapter, the overcurrent capacity between the positive terminal and the positive tab can be improved, and the fast charging capacity of the battery cell can be improved.

[0052] In some embodiments, the battery cell further includes a negative terminal and a negative current collector adapter. The negative terminal is disposed on at least one side of the electrode assembly along the width direction, and the negative terminal is connected to the negative tab through the negative current collector adapter. Through the connection of the negative current collector adapter, the overcurrent capacity between the negative terminal and the negative tab can be improved, and the fast charging capacity of the battery cell can be improved.

[0053] In some embodiments, the thickness of the positive current collector adapter is 1.25 mm to 3.00 mm; the thickness of the positive current collector adapter is relatively thick, and the overcurrent capacity is relatively excellent, which can further improve the fast charging capacity of the battery cell.

[0054] In some embodiments, the thickness of the negative current collector adapter is 1.50 mm to 2.50 mm. The thickness of the negative current collector adapter is relatively thick, and the overcurrent capacity is relatively excellent, which can further improve the fast charging capacity of the battery cell.

[0055] In some embodiments, the positive current collector adapter includes a first positive current collector adapter portion and a second positive current collector adapter portion. The first positive current collector adapter portion is connected to the positive tab, the second positive current collector adapter portion is connected to the first positive current collector adapter portion and protrudes from the first positive current collector adapter portion along the length direction, and the second positive current collector adapter portion is connected to the positive terminal; the ratio of the dimension of the first positive current collector adapter portion along the width direction to the width of the battery cell is 0.2 to 0.5; when the ratio of the dimension of the first positive current collector adapter portion along the width direction to the width of the battery cell is within the above range, the path for electrons to transfer from the positive tab to the positive terminal through the positive current collector adapter is relatively short, which can improve the fast charging capacity of the battery cell 7.

[0056] In some embodiments, the ratio of the dimension of the second positive current collector adapter portion along the length direction to the length of the battery cell is 0.05 to 0.2. When the ratio of the dimension of the second positive current collector adapter portion along the length direction to the length of the battery cell is within the above range, the path for electrons to transfer from the positive tab to the positive terminal through the positive current collector adapter is relatively short, which can improve the fast charging capacity of the battery cell.

[0057] In some embodiments, the negative electrode adapter includes a first negative electrode adapter portion and a second negative electrode adapter portion. The first negative electrode adapter portion is connected to the negative electrode tab, the second negative electrode adapter portion is connected to the first negative electrode adapter portion and protrudes from the first negative electrode adapter portion in the length direction, and the second negative electrode adapter portion is connected to the negative terminal; the ratio of the dimension of the first negative electrode adapter portion in the width direction to the width of the battery cell is 0.2 to 0.5; when the ratio of the dimension of the first negative electrode adapter portion in the width direction to the width of the battery cell is within the above range, the path for electrons to be transmitted from the negative electrode tab through the negative electrode adapter to the negative terminal is relatively short, which can improve the fast charging ability of the battery cell.

[0058] In some embodiments, the ratio of the dimension of the second negative electrode adapter portion in the length direction to the length of the battery cell is 0.05 to 0.2. When the ratio of the dimension of the second negative electrode adapter portion in the length direction to the length of the battery cell is within the above range, the path for electrons to be transmitted from the negative electrode tab through the negative electrode adapter to the negative terminal is relatively short, which can improve the fast charging ability of the battery cell.

[0059] In some embodiments, the length of the battery cell is 200 mm to 400 mm; when the length of the battery cell is within the above range, it is beneficial to improve the energy density of the battery cell; and the transmission path of electrons in the length direction is not too long, which is beneficial to improving the fast charging ability of the battery cell.

[0060] In some embodiments, the width of the battery cell is 80 mm to 130 mm; when the width of the battery cell is within the above range, it is beneficial to improve the energy density of the battery cell; and the transmission path of electrons in the width direction is not too long, which is beneficial to improving the fast charging ability of the battery cell.

[0061] In some embodiments, the thickness of the battery cell is 25 mm to 60 mm. When the thickness of the battery cell is within the above range, it is beneficial for the battery cell to quickly release internal heat, slow down the risk of electrolyte decomposition caused by heat accumulation, and improve the cycle performance of the battery cell.

[0062] In a second aspect, the present application provides a battery device, which includes one or more battery cells according to any one of the embodiments of the first aspect of the present application.

[0063] In a third aspect, the present application provides an electrical device, which includes the battery device according to any one of the embodiments of the second aspect of the present application. Description of the Drawings

[0064] To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for the embodiments of the present application will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on the accompanying drawings.

[0065] Figure 1 Schematic diagram of the structure of a battery cell provided by some embodiments of the present application, Figure 2 Explosion diagram of a battery cell provided by some embodiments of the present application, Figure 3 Schematic diagram of the structure of the electrode assembly of a battery cell provided by some embodiments of the present application, Figure 4 Schematic diagram of the structure of the positive electrode tab of a battery cell provided by some embodiments of the present application, Figure 5 Schematic diagram of the structure of the positive electrode tab of a battery cell provided by some other embodiments of the present application, Figure 6 Schematic diagram of the structure of the positive electrode tab of a battery cell provided by some other embodiments of the present application, Figure 7 Schematic diagram of the structure of the positive electrode tab of a battery cell provided by some other embodiments of the present application, Figure 8 Schematic diagram of the structure of the negative electrode tab of a battery cell provided by some embodiments of the present application, Figure 9 Schematic diagram of the structure of the negative electrode tab of a battery cell provided by some other embodiments of the present application, Figure 10 Explosion diagram of a battery cell provided by some other embodiments of the present application, Figure 11 Schematic diagram of the structure of the positive electrode adapter of a battery cell provided by some embodiments of the present application, Figure 12 Schematic diagram of the structure of the negative electrode adapter of a battery cell provided by some embodiments of the present application, Figure 13 Schematic diagram of the structure of a battery module provided by some embodiments of the present application, Figure 14 Schematic diagram of the structure of a battery pack provided by some embodiments of the present application, Figure 15 Schematic diagram of an electrical device provided by some embodiments of the present application.

[0066] The accompanying drawings are not necessarily drawn to actual scale.

[0067] Explanation of the reference numerals in the drawings is as follows: X, thickness direction; Y, width direction; Z, length direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, housing; 5a, first housing part; 5b, second housing part; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, positive electrode tab; 111, positive electrode ear; 1111, first end; 112, positive electrode current collector; 12, negative electrode tab; 121, negative electrode ear; 1211, second end; 122, negative electrode current collector; 13, separator; 20, outer shell; 21, housing; 22, end cap; 31, positive terminal; 32, negative terminal; 41, positive electrode adapter; 411, first positive electrode adapter part; 412, second positive electrode adapter part; 42, negative electrode adapter; 421, first negative electrode adapter part; 422, second negative electrode adapter part. Detailed implementation manners

[0068] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0069] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0070] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0071] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0072] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0073] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab. The negative electrode tab includes a negative active material. At the negative electrode side interface, a side reaction may occur between the negative active material and the electrolyte, deteriorating the cycle; as the charging rate of the battery cell increases, the side reaction at the negative electrode side interface further intensifies, causing the cycle to deteriorate further, which is not conducive to fast charging.

[0074] In view of the above problems, the embodiments of the present application reasonably design the system of the battery cell, which can take into account improving the cycle performance and fast charging ability of the battery cell; specifically, the positive electrode active material includes lithium-containing phosphate in an olivine structure, and the negative electrode active material includes graphite particles. The above material system has relatively excellent cycle stability; During the charging process, active ions such as lithium ions migrating out of the positive electrode plate migrate to the negative electrode plate through the electrolyte. The electrolyte includes a carboxylic acid ester solvent, which can reduce the viscosity of the electrolyte and improve the migration rate of lithium ions in the electrolyte; as the mass content of the carboxylic acid ester solvent increases, the viscosity of the electrolyte decreases, the conductivity increases, and the migration rate of lithium ions in the electrolyte can be further improved, which is beneficial to the improvement of the fast charging performance; however, as the mass content of the carboxylic acid ester solvent further increases, the side reaction between the carboxylic acid ester solvent and the negative electrode active material becomes more serious, and the gas generation increases; The electrolyte also includes a linear carbonate solvent. The addition of the linear carbonate solvent can enable the electrolyte to have a relatively high conductivity and improve the migration rate of lithium ions even when the addition amount of the carboxylic acid ester solvent is relatively low; moreover, since the mass content of the carboxylic acid ester solvent is relatively low, the side reaction is slowed down and the gas generation amount is reduced; Furthermore, the electrolyte also includes an additive. The additive includes vinylene carbonate. The reaction potential of vinylene carbonate is close to that of the carboxylic acid ester solvent, and there is a competitive reaction with the carboxylic acid ester solvent. Vinylene carbonate can participate in the formation of a dense solid electrolyte interface film (SEI film) containing organic components on the negative electrode side, making it difficult for the carboxylic acid ester solvent to penetrate the SEI film to the negative electrode active material, thereby further alleviating the side reaction between the carboxylic acid ester solvent and the negative electrode active material and further reducing the gas generation amount; moreover, since the additive is within an appropriate content, the film impedance formed on the negative electrode side will not be too large and will basically not deteriorate the fast charging performance.

[0075] Therefore, the embodiments of the present application can improve the fast charging ability and cycle performance of the battery cell.

[0076] battery cell In a first aspect, the embodiments of the present application propose a battery cell.

[0077] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate and a negative electrode plate. The positive electrode plate and the negative electrode plate are stacked along the thickness direction of the battery cell; the positive electrode plate includes a positive electrode current collector part and a positive electrode film layer provided on at least one side of the positive electrode current collector part. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes lithium-containing phosphate in an olivine structure; the negative electrode plate includes a negative electrode current collector part and a negative electrode film layer provided on at least one side of the negative electrode current collector part. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite particles; The electrolyte includes an organic solvent and an additive. Among them, the organic solvent includes a carboxylic acid ester solvent and a linear carbonate solvent. The mass content of the carboxylic acid ester solvent in the electrolyte is 10% to 30%, and the mass content of the linear carbonate solvent is 10% to 50%. Based on the mass of the electrolyte, the mass content of the additive is 3% to 9%. The additive includes 1,3 - propanesultone with a mass content ≥0, a ethylene carbonate derivative with a mass content ≥0, and vinylene carbonate with a mass content >0. The ethylene carbonate derivative includes the compound shown in Formula A, Formula A, In Formula A, Q 1 、Q 2 、Q 3 and Q 4 each independently includes any one of a hydrogen atom, a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group, and Q 1 、Q 2 、Q 3 、Q 4 are not simultaneously hydrogen atoms.

[0078] The positive electrode active material includes lithium - containing phosphate with an olivine structure, and the negative electrode active material includes graphite particles. The cycle stability of the above material system is relatively excellent; During the charging process, active ions such as lithium ions migrating out of the positive electrode plate migrate through the electrolyte to the negative electrode plate. The electrolyte includes a carboxylic acid ester solvent with a mass content greater than or equal to 10%, which can reduce the viscosity of the electrolyte, improve the migration rate of lithium ions in the electrolyte, and improve the fast charging ability of the battery monomer; As the mass content of the carboxylic acid ester solvent increases, the viscosity of the electrolyte decreases, the conductivity increases, and the migration rate of lithium ions in the electrolyte can be further improved, which is beneficial to the improvement of the fast charging performance; however, as the mass content of the carboxylic acid ester solvent further increases, the side reaction between the carboxylic acid ester solvent and the negative electrode active material becomes more serious, and the gas generation increases; The electrolyte also includes a linear carbonate solvent. The addition of 10% to 50% of the linear carbonate solvent can enable the electrolyte to have a relatively high conductivity and improve the migration rate of lithium ions even when the addition amount of the carboxylic acid ester solvent is relatively low; moreover, since the mass content of the carboxylic acid ester solvent is relatively low, for example, less than or equal to 30%, it can slow down the side reaction on the negative electrode side and reduce the gas generation amount; Furthermore, the electrolyte further includes an additive, and the additive includes vinylene carbonate. The reaction potential of vinylene carbonate is close to that of the carboxylic acid ester solvent, and there is a competitive reaction with the carboxylic acid ester solvent. Vinylene carbonate can participate in the formation of a dense solid electrolyte interface membrane (SEI membrane) containing organic components on the negative electrode side, making it difficult for the carboxylic acid ester solvent to penetrate the SEI membrane to the negative electrode active material, thereby further alleviating the side reaction between the carboxylic acid ester solvent and the negative electrode active material and further reducing the gas generation amount. Moreover, since the additive is within an appropriate content, the film impedance formed on the negative electrode side will not be too large and will basically not deteriorate the fast charging performance.

[0079] Therefore, the embodiments of the present application can improve the fast charging ability and cycling performance of the battery cell.

[0080] [Electrolyte] The battery cell includes an electrolyte. During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0081] In some embodiments, the conductivity of the electrolyte is from 11 mS / cm to 14 mS / cm. Exemplarily, the conductivity of the electrolyte is 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, 14 mS / cm or a range composed of any two of the above values.

[0082] When the conductivity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0083] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and it can be detected by using equipment and methods well-known in the art, such as testing with reference to the industry standard HG-T 4067-2015.

[0084] The electrolyte includes an organic solvent and an electrolyte salt.

[0085] The organic solvent includes a carboxylic acid ester solvent, and the mass content of the carboxylic acid ester solvent in the electrolyte is from 10% to 30%. Exemplarily, the mass content of the carboxylic acid ester solvent is 10%, 15%, 20%, 25%, 30% or a range composed of any two of the above values. When the mass content of the carboxylic acid ester solvent is greater than or equal to 10%, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions; when the mass content of the carboxylic acid ester solvent is less than or equal to 30%, the side reaction between the carboxylic acid ester solvent and the negative electrode active material is relatively small, which is beneficial to improving the cycling performance.

[0086] In some embodiments, the carboxylic acid ester solvent may include at least one of a linear carbonate solvent and a cyclic carboxylic acid ester solvent, and may optionally be a linear carbonate solvent. The linear carbonate solvent has a lower viscosity, which can further improve the migration rate of lithium ions and enhance the fast charging ability of the battery cell.

[0087] Due to the lower viscosity of the linear carbonate solvent, it has better fluidity and is more conducive to the rapid infiltration of the electrode sheet. Under fast charging conditions, local lithium deposition is not likely to occur on the surface of the negative electrode sheet, improving the reliability of the battery cell during use.

[0088] Exemplarily, the carboxylic acid ester solvent includes at least one of ethyl acrylate, propyl acetate, ethyl propionate, ethyl formate, propyl formate, ethyl acetate, and butyl propionate, and may optionally be ethyl acrylate.

[0089] The above materials have a lower viscosity, which can further improve the fast charging performance of the battery cell.

[0090] In the embodiments of the present application, the organic solvent further includes a linear carbonate solvent, and the mass content of the linear carbonate solvent in the electrolyte is 10% to 50%. Exemplarily, the mass content of the linear carbonate solvent in the electrolyte is 10%, 15%, 20%, 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50% or a range composed of any two of the above values.

[0091] The linear carbonate solvent with the above mass content can further increase the conductivity of the electrolyte at room temperature, facilitate the migration of lithium ions, and enhance the fast charging ability of the battery cell.

[0092] Exemplarily, the linear carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and may optionally be dimethyl carbonate.

[0093] The above materials have a relatively low viscosity, which can increase the conductivity of the electrolyte at room temperature and enhance the fast charging ability of the battery cell.

[0094] In some embodiments, the organic solvent further includes cyclic carbonate solvents, and the mass content of the cyclic carbonate solvents in the electrolyte is 20% to 50%. Exemplarily, the mass content of the cyclic carbonate solvents in the electrolyte is 20%, 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50% or a range composed of any two of the above values. The cyclic carbonate solvents have excellent desolvation ability, which can enable lithium ions to be quickly released from the solvation structure at the positive and negative electrode interfaces, improve the transport rate of lithium ions at the interfaces, and thus further improve the fast charging ability of the battery cell.

[0095] Exemplarily, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate, and may be ethylene carbonate. The above materials have excellent desolvation ability, which can improve the transport rate of lithium ions at the interfaces, and thus further improve the fast charging ability of the battery cell.

[0096] In the embodiments of the present application, the electrolyte further includes additives, and the additives include 1,3 - propanesultone with a mass content ≥0, ethylene carbonate derivatives with a mass content ≥0, and vinylene carbonate with a mass content >0.

[0097] In the embodiments of the present application, the mass content of the additives is 3% to 9%, for example, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9% or a range composed of any two of the above values.

[0098] When the mass content of the additives is less than 3%, the film layer formed on the negative electrode side is relatively thin, which is not conducive to the protection of the negative electrode active material; as the mass content of the additives increases, the film - forming effect on the negative electrode side is more excellent, which can play an excellent protective role for the negative electrode active material, reduce the risk of carboxylic ester solvents penetrating the SEI film into the negative electrode film layer, reduce the side reactions on the negative electrode side, reduce the gas generation amount, and improve the cycle performance; however, as the mass content of the additives further increases, the impedance of the SEI film formed on the negative electrode side is relatively high, which is not conducive to fast charging; therefore, the mass content of the additives in the embodiments of the present application is regulated to 3% to 9%, which can balance the improvement of the cycle performance and fast charging performance of the battery cell. Optionally, the mass content of the additives is 5% to 8%, which can further improve the cycle performance and fast charging performance of the battery cell.

[0099] The additives include vinylene carbonate with a mass content >0, in other words, vinylene carbonate is an essential component of the electrolyte.

[0100] When the mass contents of 1,3 - propanesultone and ethylene carbonate derivatives are 0, it means the sum of the mass content of 1,3 - propanesultone and the mass content of ethylene carbonate derivatives is 0. In this case, the additive may only include vinylene carbonate, and the mass content of vinylene carbonate may be 3% to 9%. Specifically, taking the case where the mass content of ethylene carbonate derivatives is 0 as an example, it may be that ethylene carbonate derivatives are not added to the freshly prepared electrolyte, or the electrolyte obtained after disassembling the battery cell does not contain ethylene carbonate derivatives. This situation may be that ethylene carbonate derivatives are not added to the freshly prepared electrolyte, or a small amount of ethylene carbonate derivatives are added, but they participate in the film - forming reaction of the SEI film during the formation process of the battery cell, resulting in a mass content of 0 for ethylene carbonate derivatives during the detection process. Optionally, the freshly prepared electrolyte includes ethylene carbonate derivatives.

[0101] Furthermore, for adding certain substances, such as additives, to the electrolyte, due to the characteristic that additives play a role by participating in the film - forming on the surface of the active material, the content of additives in the electrolyte of the battery cell is related to formation, different battery life cycles, or different battery storage states. Therefore, there may be a difference in the content of additives between the freshly prepared electrolyte and the electrolyte obtained by reverse - disassembling the battery cell. However, those skilled in the art can know the approximate range of the content of relevant substances in the corresponding freshly prepared electrolyte according to the performance expression level (such as the number of cycles) and residual content of the battery cell. Similarly, those skilled in the art can also know the approximate range of the content of the non - freshly prepared (i.e., reverse) according to the content of the freshly prepared additives, based on the performance requirements of the battery cell, storage environment, etc.

[0102] Therefore, the additive content mentioned in the technical solution of this application can be the content of additives actively added to the freshly prepared electrolyte, or the content of residual additives detected by reverse according to the actual battery state.

[0103] In some embodiments, the mass content of vinylene carbonate in the electrolyte is 0.8% to 7%, such as 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7% or the range composed of any two of the above values. When the mass content of vinylene carbonate is within the above range, a dense SEI film containing organic components can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reactions on the negative electrode side and take into account the improvement of the cycle performance and fast - charging ability of the battery cell. Optionally, the mass content of vinylene carbonate in the electrolyte is 2% to 6%.

[0104] The additive further includes at least one of 1,3 - propanesultone and ethylene carbonate derivative with a mass content > 0. The additive may include 1,3 - propanesultone, or the additive may include an ethylene carbonate derivative, or the additive may include 1,3 - propanesultone and an ethylene carbonate derivative.

[0105] In some embodiments, the mass content of 1,3 - propanesultone in the electrolyte is 0 to 0.5%, such as 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or a range composed of any two of the above values.

[0106] When the mass content of 1,3 - propanesultone is 0, it means that 1,3 - propanesultone may not be added to the freshly prepared electrolyte, or the electrolyte obtained after disassembling the battery cell does not contain 1,3 - propanesultone. Generally, since the consumption of 1,3 - propanesultone during the film - forming process is less, the mass content of 1,3 - propanesultone in the freshly prepared electrolyte is slightly greater than that in the electrolyte after disassembly.

[0107] Both 1,3 - propanesultone and vinylene carbonate can form a dense SEI film on the negative electrode side, which can effectively alleviate the risk of carboxylic ester solvents penetrating the SEI film and reacting with the negative electrode active material.

[0108] When the mass content of 1,3 - propanesultone is greater than 0 and less than or equal to 0.5%, the impedance of the formed SEI film will not be too high, which can reduce the impedance on the basis of alleviating side reactions and improve the fast - charging performance and cycling performance of the battery cell.

[0109] In some embodiments, the mass content of the ethylene carbonate derivative in the electrolyte is 0 to 2.55%, such as 0, 0.5%, 1%, 1.5%, 2%, 2.5%, 2.55% or a range composed of any two of the above values. Optionally, the freshly prepared electrolyte includes an ethylene carbonate derivative, and in the freshly prepared electrolyte, the mass content of the ethylene carbonate derivative is greater than 0. The ethylene carbonate derivative forms a film preferentially. After adding a certain content of the ethylene carbonate derivative to the freshly prepared electrolyte, due to the large consumption of the ethylene carbonate derivative during the film - forming stage, the ethylene carbonate derivative may not be detected in the battery cell obtained after disassembly.

[0110] Vinylene carbonate continuously participates in the formation of the SEI film during the cycling of the battery cell, alleviating the risk of carboxylic ester solvents penetrating the SEI film. However, the organic component content of this SEI film is relatively high, resulting in a relatively high impedance of the SEI film. Ethylene carbonate derivatives can form a film preferentially, optimize the components of the SEI film, reduce the impedance of the SEI film, and effectively improve the fast charging performance and cycling performance of the battery cell.

[0111] Under fast charging, the above three substances jointly participate in the formation of the SEI film. It can not only reinforce the SEI film with a low content of 1,3 - propanesultone, but also vinylene carbonate can further reinforce the film formation, reducing the risk of carboxylic ester solvents penetrating the SEI film and improving the cycling performance of the battery cell. An appropriate content of ethylene carbonate derivatives can reduce the film - forming impedance and improve the fast - charging performance, and the mass content of ethylene carbonate derivatives will not be too high, reducing the risk of high - temperature decomposition and further improving the cycling performance of the battery cell. Thus, the fast - charging performance and cycling performance of the battery cell are improved.

[0112] In the embodiments of the present application, the ethylene carbonate derivative refers to that at least one hydrogen atom of ethylene carbonate is substituted, and the substituting group can be one, two, three, or four, etc.

[0113] Exemplarily, the ethylene carbonate derivative includes the compound shown in Formula A, Formula A, In Formula A, Q 1 、Q 2 、Q 3 and Q 4 each independently includes any one of a hydrogen atom, a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group, and Q 1 、Q 2 、Q 3 、Q 4 are not simultaneously hydrogen atoms.

[0114] Q 1 、Q 2 、Q 3 、Q 4 are not simultaneously hydrogen atoms. In other words, at least one of Q 1 、Q 2 、Q 3 、Q 4 includes a halogen atom, a C1 - C5 alkyl group, or a C1 - C5 haloalkyl group.

[0115] Exemplarily, Q 1 、Q 2 、Q 3 、Q 4One of them includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and the rest are hydrogen atoms.

[0116] Exemplarily, Q 1 , Q 2 , Q 3 , Q 4 At least two of them include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0117] Exemplarily, Q 1 , Q 2 , Q 3 , Q 4 At least three of them include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0118] Exemplarily, Q 1 , Q 2 , Q 3 , Q 4 Each independently includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0119] Optionally, at least one of Q 1 , Q 2 , Q 3 and Q 4 includes a halogen atom or a C1-C5 haloalkyl group. The halogen atom includes a fluorine atom, a bromine atom, or a chlorine atom, etc., and can be optionally a fluorine atom. The C1-C5 haloalkyl group includes a C1-C5 fluoroalkyl group, a C1-C5 bromoalkyl group, or a C1-C5 chloroalkyl group, etc., and can be optionally a fluorine atom. For example, the C1-C5 fluoroalkyl group includes fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, or fluoropentyl.

[0120] In the case where the ethylene carbonate derivative includes a fluorine atom, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side, and on the basis of protecting the negative electrode active material, the impedance of the film layer is relatively low, and it can more effectively balance the improvement of the cycle performance and the fast charging performance of the battery cell.

[0121] For example, the ethylene carbonate derivative includes at least one of the compounds shown by Formula A-1 to the compounds shown by Formula A-6,

[0122] The above materials can further improve the cycle performance and the fast charging performance of the battery cell.

[0123] Optionally, the ethylene carbonate derivative includes at least one of the compounds shown by Formula A-1 to the compounds shown by Formula A-3, and further optionally, the ethylene carbonate derivative includes the compound shown by Formula A-1.

[0124] In some embodiments, the additive further includes a lithium salt additive, and the lithium salt additive includes at least one of lithium difluorophosphate, lithium fluorosulfonate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate. The above additives can improve the performance of the SEI film on the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0125] In some embodiments, the mass content of the lithium salt additive in the electrolyte is 0.02% to 0.5%, such as 0.02%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50% or the range composed of any two of the above values. The lithium salt additive and the additive cooperate to form a film, which can optimize the film layer components of the SEI film. The lithium salt additive can participate in the formation of an SEI film rich in inorganic substances, and the inorganic substances can improve the high-temperature stability and high-voltage stability of the SEI film, and improve the cycle performance of the battery cell.

[0126] Exemplarily, the lithium salt additive includes lithium difluorophosphate, and the mass content of lithium difluorophosphate in the electrolyte is 0.02% to 0.5%.

[0127] Exemplarily, the lithium salt additive includes lithium fluorosulfonate, and the mass content of lithium fluorosulfonate in the electrolyte is 0.02% to 0.5%.

[0128] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes lithium hexafluorophosphate LiPF 6 . Optionally, the electrolyte further includes a lithium fluorosulfonylimide salt, which can improve the cycle performance of the battery cell.

[0129] Optionally, the lithium fluorosulfonylimide includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0130] In some embodiments, the mass content of the lithium salt is 5% to 18%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or the range composed of any two of the above values.

[0131] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte have meanings well-known in the art, and can be detected by using equipment and methods well-known in the art. For example, reference can be made to the standard JY / T 020-1996 "General Rules for Ion Chromatography Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography analysis methods. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell can be taken as a sample and detected by ion chromatography analysis methods.

[0132] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by using equipment and methods well-known in the art. For example, reference can be made to GB / T 9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography.

[0133] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector portion and a negative electrode film layer provided on at least one surface of the negative electrode current collector portion and including a negative electrode active material. For example, the negative electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector portion.

[0134] The charge upper limit voltage and discharge cut-off voltage of the battery cell vary depending on the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the charge upper limit voltage can be 3.65V and the discharge cut-off voltage can be 2.0V. Another example is that when the phosphate material includes lithium manganese iron phosphate, the charge upper limit voltage can be 4.2V and the discharge cut-off voltage can be 2.0V. Next, taking the charge upper limit voltage of 3.65V and the discharge cut-off voltage of 2.0V as an example, the state of the battery cell is described as follows: In the embodiments of the present application, the 100% state of charge SOC and 0% state of charge SOC of the battery cell are defined as follows. The battery cell is charged at a constant current charge rate of 0.33C to the charge upper limit voltage, and then charged at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell. The battery cell is discharged at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0135] In some embodiments, when the battery cell is in the 0% state of charge, the compaction density of the negative electrode film layer is 1.30 g / cm 3 to 1.52 g / cm 3. Exemplarily, the compaction density of the negative electrode film layer at 0% state of charge of the battery cell is 1.30 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.40 g / cm 3 , 1.45 g / cm 3 , 1.50 g / cm 3 , 1.52 g / cm 3 or a range composed of any two of the above values.

[0136] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the negative electrode active materials in the negative electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation and the amount of gas generated by the decomposition of carboxylic ester solvents due to heat accumulation, and improving the cycle performance of the battery cell.

[0137] In some embodiments, the single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 to 180 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 145 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 165 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 , 175 mg / 1540.25 mm 2 , 180 mg / 1540.25 mm 2Or a range composed of any two of the above values. Optionally, the single-sided coating weight of the negative electrode film layer is 125 mg / 1540.25 mm 2 to 160 mg / 1540.25 mm 2 .

[0138] When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode plate will not be too large, which can improve the cycling performance of the battery cell.

[0139] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer has the meaning well-known in the art, and can be detected by the equipment and methods well-known in the art. Disassemble the negative electrode plate of the battery cell in the 0% state of charge (SOC), and measure the compaction density of the negative electrode film layer. For example, take a single-sided coated negative electrode plate (if it is a double-sided coated plate, the negative electrode film layer on one side can be wiped off first), punch it into small round pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the negative electrode film layer of the above-mentioned weighed negative electrode plate, weigh the weight of the negative electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the negative electrode film layer = (the weight M1 of the negative electrode plate - the weight M0 of the negative electrode current collector) / S1, the thickness of the negative electrode film layer = the thickness H1 of the negative electrode plate - the thickness H0 of the negative electrode current collector, and the compaction density of the negative electrode film layer = the single-sided coating weight of the negative electrode film layer / the thickness of the negative electrode film layer.

[0140] In the embodiments of the present application, the negative electrode active material includes a carbon-based material, and the carbon-based material includes graphite particles. The graphite particles have high cycle stability and can improve the cycling performance of the battery cell. The positive electrode active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. When the two are used in combination, the cycling performance of the battery cell is relatively excellent.

[0141] In some embodiments, the graphitization degree of the graphite particles is 90% to 94%. Exemplarily, the graphitization degree of the graphite particles is 90%, 91%, 92.0%, 92.5%, 93%, 93.5%, 94% or a range composed of any two of the above values.

[0142] When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, can reduce the heat generation of the negative electrode plate and the battery cell, and can improve the fast charging performance of the battery cell.

[0143] In some embodiments, the volume average particle size Dv50 of the graphite particles is from 7 μm to 15 μm, such as 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm or a range composed of any two of the above values.

[0144] The volume average particle size of the graphite particles is relatively small, resulting in a shorter solid-phase migration path for lithium ions, which can improve the fast charging ability of the battery cell. However, under fast charging conditions, the active surface of the small-sized graphite particles is relatively large, and the side reaction with carboxylic ester solvents in the electrolyte is relatively intense. The electrolyte is further added with additives, which can preferentially form a film on the negative electrode side, play an excellent protective role for the negative electrode active material, reduce the risk of side reactions occurring on the negative electrode side, and improve the cycle performance of the battery cell.

[0145] In the embodiments of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, and can be detected by using equipment and methods well-known in the art. For example, taking the negative electrode active material as a sample, according to the test standard GB / T 19077-2016, the Dv50 of the particles is tested by a Mastersizer 2000E laser particle size analyzer, etc.

[0146] In some embodiments, the graphite particles include graphite body particles and a negative electrode coating layer. The graphite body particles include secondary particles, and the secondary particles include a plurality of primary particles. The negative electrode coating layer covers the surface of the graphite body particles, and the negative electrode coating layer includes carbon elements. The carbon in the negative electrode coating layer is mainly amorphous carbon, and amorphous carbon refers to a transition carbon material with a very low degree of graphitization crystallization, approximately an amorphous form (or no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0147] The graphite body particles include secondary particles. There are more migration paths for lithium ions in the graphite body particles, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions. The negative electrode coating layer has more end faces and defects, resulting in a larger number of sites where lithium ions can be intercalated and deintercalated, making the conductivity of the negative electrode coating layer relatively excellent, capable of reducing the internal resistance of the negative electrode sheet, reducing the heat generation of the battery cell, and improving the fast charging performance and cycle performance of the battery cell.

[0148] Exemplarily, the graphite body particles include at least one of artificial graphite and natural graphite, and may be artificial graphite.

[0149] Optionally, the thickness of the negative electrode coating layer is from 100 nm to 500 nm. Exemplarily, the thickness of the negative electrode coating layer is 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a range composed of any two of the above values.

[0150] When the thickness of the negative electrode coating layer is within the above range, the conductivity of the graphite particles can be further improved, the internal resistance of the negative electrode sheet can be reduced, the heat generation of the battery cell can be reduced, and the cycle performance of the battery cell can be improved.

[0151] In the embodiments of the present application, the graphite particles can be prepared by methods well known in the art. Taking the artificial graphite as the graphite body particles as an example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and after carbonization treatment, forming a negative electrode coating layer on at least part of the surface of the artificial graphite particles.

[0152] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening points of coal tar pitch and petroleum pitch are below 250 °C.

[0153] Optionally, the carbonization treatment temperature is from 700 °C to 1800 °C. Optionally, the carbonization treatment temperature is from 1000 °C to 1300 °C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized and a negative electrode coating layer containing amorphous carbon can be formed on at least part of the surface of the artificial graphite.

[0154] Optionally, the carbonization treatment time is from 1 h to 6 h.

[0155] 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.

[0156] In some embodiments, in addition to including graphite particles, the negative electrode active material may further include a silicon-based material. The introduction of the silicon-based material can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0157] Optionally, based on the mass of the negative electrode film layer, the mass content of silicon element in the silicon-based material is 0.5% to 10.0%. Exemplarily, the mass content of silicon element in the silicon-based material 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%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10% or a range composed of any two of the above values.

[0158] When the mass content of silicon element in the silicon-based material is within the above range, the capacity of the negative electrode active material can be improved, and the energy density of the battery cell can be improved.

[0159] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0160] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0161] In this application, the qualitative and quantitative determination of each substance or each element can be detected by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change some detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0162] For example, this application can combine the general rules of X-ray diffraction analysis method in JIS / K0131-1996 to perform X-ray powder diffraction test and qualitative analysis on the negative electrode plate or the negative electrode active material.

[0163] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by scanning electron microscope (SEM). There are voids between the flake structures in the SEM cross-section of natural graphite, and the SEM cross-section of artificial graphite is dense and has no obvious gaps, or can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and only 2H phase exists in the XRD spectrum of artificial graphite.

[0164] In the embodiments of the present application, the negative electrode film layer includes at least one film layer, which can be a single-layer film layer or at least two-layer film layers. The negative electrode film layer can include two-layer film layers, three-layer film layers, four-layer film layers, or even more film layers. Optionally, the negative electrode film layer includes at least two-layer film layers.

[0165] When the negative electrode film layer is a single-layer film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes a silicon-based material.

[0166] When the negative electrode film layer is at least two-layer film layers, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes a silicon-based material. The silicon-based material can be located in one of the at least two-layer film layers or in at least two of the at least two-layer film layers. The negative electrode film layer can include two-layer film layers, three-layer film layers, four-layer film layers, or even more film layers.

[0167] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector. The carbon-based material in the first negative electrode film layer includes graphite particles. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector. The carbon-based material in the second negative electrode film layer includes graphite particles. The graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer can be the same or different.

[0168] The interface between the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and optionally is irregular.

[0169] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0170] The negative electrode film layer includes at least two-layer film layers. Layered coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences between the first negative electrode film layer and the second negative electrode film layer, it is possible to construct pore differences in the negative electrode film layer, reduce the tortuosity of lithium ion transport, and improve the fast charging performance of the battery cell.

[0171] Optionally, both the first negative electrode film layer and the second negative electrode film layer include graphite particles, and the average longest diameter of the graphite particles in the first negative electrode film layer is greater than or equal to the average longest diameter of the graphite particles in the second negative electrode film layer. Further optionally, the average longest diameter of the graphite particles in the first negative electrode film layer is greater than the average longest diameter of the graphite particles in the second negative electrode film layer.

[0172] There are differences in the particle sizes of the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer is usually relatively high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can also improve the problem of lithium deposition on the surface layer of the negative electrode sheet.

[0173] Optionally, the average longest diameter of the graphite particles in the first negative electrode film layer is 7 μm to 18 μm. Exemplarily, the average longest diameter of the graphite particles in the first negative electrode film layer is 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 14.6 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm or the range composed of any two of the above values.

[0174] When the average longest diameter of the graphite particles in the first negative electrode film layer 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 performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0175] Optionally, the average longest diameter of the graphite particles in the second negative electrode film layer is 6 μm to 10 μm. Exemplarily, the average longest diameter of the graphite particles in the second negative electrode film layer is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm or the range composed of any two of the above values.

[0176] When the average longest diameter of the graphite particles in the second negative electrode film layer 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 performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the further hand, the negative electrode active materials in the second negative electrode film layer with the above particle size range cooperate with the negative electrode active materials in the first negative electrode film layer, which is beneficial to constructing the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, and improving the fast charging performance of the battery cell.

[0177] Optionally, the ratio of the thickness of the second negative electrode film layer to the thickness of the negative electrode film layer is 0.3 to 0.7. Exemplarily, the ratio of the thickness of the second negative electrode film layer to the thickness of the negative electrode film layer is 0.3, 0.4, 0.5, 0.6, 0.7 or a range composed of any two of the above values. By adjusting the thickness ratio of the first negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium-ion transport can be reduced, and the fast charging ability of the battery cell can be improved.

[0178] In the embodiment of the present application, the negative electrode sheet is cut along the thickness direction of the sheet to expose the cut surface of the negative electrode film layer, which can also be understood as the cross-section of the negative electrode film layer along its own thickness direction. By performing a scanning electron microscope (SEM) test on the cut surface of the negative electrode film layer, the longest diameter of the graphite particles is determined. For example, the "longest diameter" of the particles refers to the longest straight line passing through the center point of the particle and extending to the outer periphery of the particle.

[0179] In the cross-section of the negative electrode film layer along its own thickness direction, the longest diameters of all the graphite particles in the cross-section are statistically counted, and the average value thereof is the average longest diameter.

[0180] In the cross-section of the negative electrode film layer along its own thickness direction, the sizes of the second negative electrode film layer and the negative electrode film layer are measured, and the size ratio of the second negative electrode film layer is calculated.

[0181] In some embodiments, the negative electrode film layer further includes a negative electrode binder, and the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0182] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The embodiment of the present application does not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0183] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0184] In some embodiments, the negative electrode current collector portion may employ a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0185] The negative electrode film layer is generally formed by coating a negative electrode slurry on the negative electrode current collector portion and then drying and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0186] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application embodiment further includes a negative electrode conductive layer disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer. In some other embodiments, the negative electrode plate of the present application embodiment further includes a protective layer covering the surface of the negative electrode film layer.

[0187] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer located between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode plate, reduce the heat generation of the negative electrode plate, thereby reducing the heat generation of the battery cell, and improving the fast charging performance and cycling performance of the battery cell.

[0188] [Positive Electrode Plate] The positive electrode plate includes a positive electrode current collector portion and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0189] In some embodiments, at 0% state of charge (SOC) of the battery cell, the tap density of the positive electrode film layer is 2.3 g / cm 3 to 2.6 g / cm 3 . Exemplarily, at 0% state of charge (SOC) of the battery cell, the tap density of the positive electrode film layer is 2.3 g / cm 3 , 2.35 g / cm 3 , 2.4 g / cm 3, 2.45 g / cm 3 , 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 or a range composed of any two of the above values. Optionally, when the battery cell is at 0% state of charge (SOC), the compaction density of the positive electrode film layer is 2.4 g / cm 3 to 2.55 g / cm 3 .

[0190] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the positive electrode active materials in the positive electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation during fast charging and improving the cycle performance and fast charging performance of the battery cell.

[0191] In some embodiments, the single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 , such as 250 mg / 1540.25 mm², 260 mg / 1540.25 mm², 270 mg / 1540.25 mm², 280 mg / 1540.25 mm², 290 mg / 1540.25 mm², 300 mg / 1540.25 mm², 310 mg / 1540.25 mm², 320 mg / 1540.25 mm², 330 mg / 1540.25 mm² or a range composed of any two of the above values. Optionally, the single-sided coating weight of the positive electrode film layer is 275 mg / 1540.25 mm 2 to 320 mg / 1540.25 mm 2 .

[0192] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode sheet will not be too large, improving the cycle performance and fast charging performance of the battery cell.

[0193] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell at 0% state of charge (SOC) can be detected by the following method. Disassemble the positive electrode plate of the battery cell at 0% SOC, and measure the compaction density of the positive electrode film layer. For example, take a positive electrode plate with single-sided coating (if it is a double-sided coated electrode plate, the positive electrode film layer on one side can be wiped off first), punch it into small round pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive electrode film layer of the positive electrode plate after weighing above, weigh the weight of the positive electrode current collector part, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode plate - the weight M0 of the positive electrode current collector part) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode plate - the thickness H0 of the positive electrode current collector part, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0194] In some embodiments, the lithium-containing phosphate includes at least one of primary particles and secondary particles. The secondary particles include a plurality of primary particles. In other words, the secondary particles are formed by the aggregation of a plurality of primary particles, and the secondary particles are spherical and / or quasi-spherical.

[0195] The migration path of lithium ions in the primary particles is short, which can improve the migration rate of lithium ions; moreover, the secondary particles are spherical and / or quasi-spherical, resulting in more migration paths, which can further improve the migration rate of lithium ions and improve the fast charging performance of the battery cell.

[0196] In some embodiments, the average longest diameter of the primary particles is from 300 nm to 800 nm, such as 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm or a range composed of any two of the above values. When the average longest diameter of the primary particles is within the above range, the solid-phase transmission distance of lithium ions is short, which can further improve the migration rate of lithium ions and improve the fast charging performance of the battery cell.

[0197] In some embodiments, the average particle size of the secondary particles is from 5 μm to 15 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or a range composed of any two of the above values. When the average particle size of the secondary particles is within the above range, the solid-phase transmission distance of lithium ions is short, which can further improve the migration rate of lithium ions and improve the fast charging performance of the battery cell.

[0198] In the embodiments of the present application, the positive electrode sheet is cut along the thickness direction of the sheet to expose the cut surface of the positive electrode film layer, which can also be understood as the cross-section of the positive electrode film layer along its own thickness direction. By performing a scanning electron microscope (SEM) test on the cut surface of the positive electrode film layer, the average longest diameter of the primary particles of the lithium-containing phosphate and the average particle diameter of the secondary particles are determined. For example, the "longest diameter" of a particle refers to the longest straight line passing through the center point of the particle and extending to the outer periphery of the particle.

[0199] In the cross-section of the positive electrode film layer along its own thickness direction, the longest diameters of the primary particles of each lithium-containing phosphate in the cross-section are counted, and the average value of the longest diameters of the primary particles of each lithium-containing phosphate is calculated; then, the average value of the longest diameters of, for example, 50 primary particles of lithium-containing phosphate is counted as the average longest diameter.

[0200] In the cross-section of the positive electrode film layer along its own thickness direction, the particle diameters of all the secondary particles of the lithium-containing phosphate in the cross-section are counted, and the average value of the particle diameters of the secondary particles of the lithium-containing phosphate is calculated as the average particle diameter of the secondary particles.

[0201] In the embodiments of the present application, the lithium-containing phosphate of the olivine structure can be phosphate particles or a material obtained by modifying them. For example, the lithium-containing phosphate of the olivine structure includes phosphate particles and positive electrode additive elements. The positive electrode additive elements are located in the phosphate particles, which can be located inside the phosphate particles or coated on the surface of the phosphate particles. The positive electrode additive elements contain at least one element of aluminum (Al), vanadium (V), titanium (Ti), and niobium (Nb).

[0202] The above-mentioned positive electrode additive elements can improve the crystal structure stability of the positive electrode active material, enhance the pressure resistance of the lithium-containing phosphate, and are beneficial to improving the compaction density of the positive electrode film layer, as well as enhancing the energy density and cycle performance of the battery cell.

[0203] In some embodiments, the mass content of aluminum element in the lithium-containing phosphate is from 200 ppm to 2500 ppm, such as 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm or the range composed of any two of the above values. When the mass content of the aluminum element is within the above range, it can improve the pressure resistance of the lithium-containing phosphate, which is beneficial to enhancing the compaction density of the positive electrode film layer, as well as enhancing the energy density and cycle performance of the battery cell.

[0204] In some embodiments, the mass content of vanadium element in the lithium-containing phosphate is from 300 ppm to 2000 ppm, such as 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm or a range composed of any two of the above values. When the mass content of the vanadium element is within the above range, it is beneficial to improve the compaction density of the positive electrode film layer and improve the energy density and cycling performance of the battery cell.

[0205] In some embodiments, the mass content of titanium element in the lithium-containing phosphate is from 1500 ppm to 3500 ppm, such as 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3100 ppm, 3200 ppm, 3300 ppm, 3400 ppm, 3500 ppm or a range composed of any two of the above values. When the mass content of the titanium element is within the above range, it can further improve the crystal structure of the positive electrode active material and improve the cycling performance.

[0206] In some embodiments, the mass content of niobium element in the lithium-containing phosphate is from 300 ppm to 2000 ppm, such as 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm or a range composed of any two of the above values. When the mass content of the niobium element is within the above range, it can further improve the crystal structure of the positive electrode active material and improve the cycling performance.

[0207] Examples of the phosphate particles may include, but are not limited to, phosphate particles including one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. The cycling stability of the above materials is relatively excellent, and it can improve the cycling performance of the battery cell.

[0208] In some embodiments, the lithium-containing phosphate includes a general formula of Li x1 A y1 Me a1 Mb1 P 1-c1 X c1 Y z1 a compound of, wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5, 0 ≤ c1 ≤ 0.5, 3 ≤ z1 ≤ 5, A includes at least one of Na, K and Mg; Me includes at least one of Mn, Fe, Co and Ni; M includes at least one of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce; X includes at least one of Cl, C, N and P; Y includes at least one of O and F.

[0209] The lithium-containing phosphate has excellent cycling stability, which is beneficial to improving the cycling performance of the battery cell.

[0210] Exemplarily, the phosphate particles include LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 or more. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. Regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., the molar content of oxygen O is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will fluctuate, and the above situations are all within the protection scope of the present application.

[0211] In the embodiments of the present application, the content of elements in the positive electrode active material has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode plate is disassembled, washed with DMC, dried, and then calcined at high temperature to remove impurities. Then, 0.4 g of the positive electrode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0212] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The embodiments of the present application do not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0213] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of the positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0214] In some embodiments, the positive electrode current collector part may be made of a metal foil or a composite current collector part. As an example of the metal foil, at least one foil of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy can be used. The composite current collector part may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0215] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0216] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiment of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiment of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0217] [Isolation film] In the embodiment of the present application, the isolation film is disposed between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet from the negative electrode sheet.

[0218] In some embodiments, the porosity of the isolation membrane is 20% to 70%, optionally 35% to 60%. Exemplarily, 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.

[0219] When the porosity of the separator in the embodiment of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0220] In the embodiments of the present application, porosity refers to the percentage of the pore volume in the separator to the total volume of the separator. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin separator for battery monomers". It should be noted that the actual test process can be slightly different from the standard test process according to the difference in test instruments, test errors, and in order to eliminate the test influence on porosity as much as possible, so as to obtain a more accurate test value.

[0221] In some embodiments, the thickness of the isolation film is 4 μm to 12 μm, and can be 5 μm to 9 μm. For example, the thickness of the base film is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range consisting of any two of the above values.

[0222] When the thickness of the separator is within the above range, the migration path of lithium ions in the separator is shorter, which can further reduce the internal resistance of the battery cell and thus reduce heat generation.

[0223] In the embodiments of the present application, the separator membrane may be a base film. Optionally, the separator membrane further includes a functional layer disposed on at least one side of the base film. The functional layer may include inorganic particles to improve the heat resistance of the separator membrane. Optionally, the functional layer is disposed on both sides of the base film.

[0224] In some embodiments, the base film includes at least one of glass fiber, non-woven fabric, and polyolefin. The base film may be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0225] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0226] In some embodiments, the functional layer may include a binder, optionally including at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0227] In some embodiments, the functional layer may include inorganic particles. The inorganic particles may 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 above inorganic particles can improve the heat resistance of the functional layer.

[0228] In the embodiments of the present application, the meaning of the thickness of the separator membrane is well-known in the art. Detection can be carried out using the well-known meaning and equipment in the art. For example, a newly prepared separator membrane can be taken as a sample, or a battery cell that has been discharged (discharged to the discharge cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, the separator membrane is obtained from the battery cell, and the separator membrane is dried and used as a sample. The separator membrane is cut off with an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the thickness of the cross-section of the separator membrane and its respective layers.

[0229] In some embodiments, the positive electrode plate, the separator membrane, and the negative electrode plate can be made into an electrode assembly by a stacking process.

[0230] Figure 1 and Figure 2 shows a schematic structural diagram of a battery cell.

[0231] In some embodiments, the battery cell 7 may include a housing 20.

[0232] The outer shell 20 can be of various shapes, such as a cylinder, a cuboid, etc. The shape of the outer shell 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylinder structure, the outer shell 20 can be selected as a cylinder structure. If the electrode assembly 10 is a cuboid structure, the outer shell 20 can be selected as a cuboid structure. Optionally, the electrode assembly 10 is a cuboid structure.

[0233] The material of the outer shell 20 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not make special restrictions on this. Optionally, the inner wall of the outer shell 20 can further include an insulating layer, and the insulating layer can separate the outer shell 20 and the electrode assembly 10. The material of the insulating layer can be selected from the commonly used materials in the art and is not specially restricted here.

[0234] The electrode assembly 10 accommodated in the outer shell 20 can be one or more.

[0235] In some embodiments, the outer shell 20 includes a housing 21 and an end cap 22. The housing 21 has an opening, and the end cap 22 covers the opening. The electrode assembly 10 and the electrolyte are accommodated in the housing 21.

[0236] In some embodiments, the material of the housing 21 includes steel. Steel has relatively high mechanical strength and is not easily deformed, which can improve the service reliability and cycle performance of the battery cell. Optionally, the mass ratio of steel is the highest among the materials in the housing 21.

[0237] In some embodiments, the length of the battery cell 7 is 200 mm to 400 mm, such as 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, 250 mm, 260 mm, 270 mm, 280 mm, 290 mm, 300 mm, 310 mm, 320 mm, 330 mm, 340 mm, 350 mm, 360 mm, 370 mm, 380 mm, 390 mm, 400 mm or the range composed of any two of the above values. When the length of the battery cell 7 is within the above range, it is beneficial to improve the energy density of the battery cell 7; moreover, the transmission path of electrons in the length direction will not be too long, which is beneficial to improving the fast charging ability of the battery cell 7. Figure 1 Z1 shown in it represents the length of the battery cell 7.

[0238] The electrolyte has relatively high conductivity, small viscosity, and excellent fluidity. It can quickly infiltrate the electrode sheet in the length direction, making the reaction degree of the electrode sheet more consistent in the length direction. When the active ions migrate to the negative electrode sheet 12, problems such as lithium deposition are not likely to occur, which is beneficial to improving the service reliability and cycle performance of the battery cell 7.

[0239] In some embodiments, the width of the battery cell 7 is from 80 mm to 130 mm, such as 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, or a range composed of any two of the above values. When the width of the battery cell 7 is within the above range, it is beneficial to improve the energy density of the battery cell 7; moreover, the transmission path of electrons in the width direction will not be too long, which is beneficial to improving the fast charging ability of the battery cell 7. Figure 1 Y1 shown in Figure 1 represents the width of the battery cell 7.

[0240] In some embodiments, the thickness of the battery cell 7 is from 25 mm to 60 mm, such as 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, or a range composed of any two of the above values. When the thickness of the battery cell 7 is within the above range, it is beneficial for the battery cell 7 to quickly release internal heat, slow down the risk of electrolyte decomposition due to heat accumulation, and improve the cycle performance of the battery cell 7. Figure 1 X1 shown in Figure 1 represents the thickness of the battery cell 7.

[0241] Next, taking the electrode assembly 10 as a stacked structure as an example for illustration, As Figure 3 shown, when the electrode assembly 10 is a stacked structure, there are multiple positive electrode plates 11 and multiple negative electrode plates 12, and the multiple positive electrode plates 11 and the multiple negative electrode plates 12 are stacked along the thickness direction X of the battery cell 7. Optionally, the electrode assembly 10 further includes a separator 13, and the separator 13 is located between the positive electrode plate 11 and the negative electrode plate 12.

[0242] In some embodiments, as Figure 4 shown, the positive electrode plate 11 includes at least one positive electrode tab 111, and at least one positive electrode tab 111 is connected to the positive current collector 112 and extends out of the positive current collector 112 along the length direction Z of the battery cell 7. This setting method is beneficial to reducing the occupied space of the tabs and improving the energy density of the battery cell.

[0243] For example, at least one positive electrode tab 111 can be arranged on the same side of the positive current collector 112 along the length direction Z.

[0244] Again, for example, as Figure 5 shown, in the same positive electrode plate 11, there are multiple positive electrode tabs 111, and the multiple positive electrode tabs 111 can be arranged on both sides of the positive current collector 112 along the length direction Z. The positive electrode tabs 111 are arranged on both sides of the positive current collector 112, which can shorten the transmission path of electrons in the length direction Z, improve the electron transmission rate, and improve the fast charging ability of the battery cell 7.

[0245] As Figure 5 andFigure 6 As shown, in some embodiments, the positive electrode tab 11 satisfies: n*W1 / W2 is 0.9 to 1.0; n represents the number of all positive electrode tabs 111 on the same side of the positive electrode current collector 112; W1 represents the average dimension of the positive electrode tab 111 in the width direction Y; W2 represents the dimension of the positive electrode current collector 112 in the width direction Y.

[0246] Exemplarily, n*W1 / W2 is 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00 or a range composed of any two of the above values.

[0247] When n*W1 / W2 satisfies the above range, the current-carrying area of the positive electrode tab 111 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0248] W1 represents the average dimension of the positive electrode tab 111 in the width direction Y.

[0249] When the positive electrode tab 111 has a special-shaped structure, for example, along the length direction Z, the dimension of the positive electrode tab 111 in the width direction Y gradually increases. In this case, the dimensions of the positive electrode tab 111 in the width direction Y at multiple locations can be measured, and thus the average dimension of the positive electrode tab 111 in the width direction Y can be calculated. Of course, the dimensions of the positive electrode tab 111 in the width direction Y at each location can be the same value. In this case, this value can be used as the average dimension of the positive electrode tab 111.

[0250] The positive electrode tab 111 can be one or more. For example, n is 1 to 4. When there are multiple positive electrode tabs 111 on the same side of the positive electrode current collector 112, after measuring the average dimensions of each positive electrode tab 111 respectively, the average dimension of the positive electrode tab 111 can be calculated by adding the average dimensions and dividing by the number of positive electrode tabs 111.

[0251] The positive electrode tab 111 is connected to the positive electrode current collector 112. The positive electrode tab 111 includes a first end 1111 connected to the positive electrode current collector 112. When n*W1 / W2 satisfies the above range, it means that the cross-section of the first end 1111 along the thickness direction of the positive electrode tab 111 itself is relatively large, the contact surface between the positive electrode tab 111 and the positive electrode current collector 112 is relatively large, the current-carrying capacity of the positive electrode tab 111 is strong, and the fast charging performance and cycle performance of the battery cell 7 can be improved.

[0252] Optionally, the positive electrode tab 111 and the positive electrode current collector 112 are of an integral structure, so that the internal resistance of the positive electrode tab 11 is relatively low, and the cycle performance of the battery cell 7 can be further improved.

[0253] As Figure 7 shown, in some other embodiments, at least one positive current collector tab 111 may also be connected to the positive current collector portion 112 and extend out of the positive current collector portion 112 along the width direction Y of the battery cell 7.

[0254] As Figure 8 and Figure 9 shown, in some embodiments, the negative electrode plate 12 includes at least one negative current collector tab 121, and at least one negative current collector tab 121 is connected to the negative current collector portion 122 and extends out of the negative current collector portion 122 along the length direction Z of the battery cell 7. Of course, at least one negative current collector tab 121 may also be connected to the negative current collector portion 122 and extend out of the negative current collector portion 122 along the width direction Y of the battery cell 7.

[0255] For example, as Figure 8 shown, at least one negative current collector tab 121 may be disposed on the same side of the negative current collector portion 122 along the length direction Z.

[0256] Again for example, as Figure 9 shown, in the same negative electrode plate 12, there are multiple negative current collector tabs 121, and the multiple negative current collector tabs 121 may be disposed on both sides of the negative current collector portion 122 along the length direction Z. The negative current collector tabs 121 are disposed on both sides of the negative current collector portion 122, which can shorten the electron transmission path in the length direction Z, improve the electron transmission rate, and improve the fast charging ability of the battery cell 7.

[0257] In some embodiments, the negative electrode plate 12 satisfies: m*W3 / W4 is 0.9 to 1.0; m represents the number of all negative current collector tabs 121 on the same side of the negative current collector portion 122; W3 represents the average size of the negative current collector tab 121 along the width direction Y; W4 represents the size of the negative current collector portion 122 along the width direction Y.

[0258] Exemplarily, m*W3 / W4 is 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00 or a range composed of any two of the above values.

[0259] When m*W3 / W4 satisfies the above range, the current-carrying area of the negative current collector tab 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0260] W3 represents the average size of the negative current collector tab 121 along the width direction Y. The negative current collector tab 121 may be one or more. For example, m is 1 to 4. In the case where there are multiple negative current collector tabs 121, the average size can be calculated by measuring the sizes of each negative current collector tab 121 with a micrometer.

[0261] The negative electrode tab 121 is connected to the negative electrode current collector portion 122. The negative electrode tab 121 includes a second end 1211 connected to the negative electrode current collector portion 122. When n*W3 / W4 satisfies the above range, it means that the cross-section of the second end 1211 along the thickness direction of the negative electrode tab 121 itself is relatively large, the contact surface between the negative electrode tab 121 and the negative electrode current collector portion 122 is relatively large, the current-carrying capacity of the negative electrode tab 121 is strong, and the fast charging performance and cycle performance of the battery cell 7 can be improved.

[0262] Optionally, the negative electrode tab 121 and the negative electrode current collector portion 122 are of an integral structure, so that the internal resistance of the negative electrode plate 12 is relatively low, and the fast charging performance and cycle performance of the battery cell 7 can be further improved.

[0263] As Figure 10 shown, in some embodiments, the battery cell 7 further includes a positive terminal 31. The positive terminal 31 is disposed on the outer casing 20 and can be disposed on the housing 21 or the end cap 22.

[0264] The positive terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive terminal 31 and the positive electrode tab 111 are welded. The positive terminal 31 and the positive electrode tab 111 can be connected through a positive electrode adapter 41, or can be directly welded without using a positive electrode adapter. The direct welding of the positive terminal 31 and the positive electrode tab 111 can reduce the resistance at the connection, which is beneficial to reducing the overall internal resistance of the battery cell 7.

[0265] Optionally, the positive terminal 31 is disposed on at least one side of the electrode assembly 10 along the width direction Y of the battery cell 7. The positive terminal 31 and the positive electrode tab 111 are connected through a positive electrode adapter 41. Through the connection of the positive electrode adapter 41, the current-carrying capacity between the positive terminal 31 and the positive electrode tab 111 can be improved, and the fast charging ability of the battery cell 7 can be improved.

[0266] Optionally, the thickness of the positive electrode adapter 41 is 1.25 mm to 3.00 mm, such as 1.25 mm, 1.50 mm, 1.75 mm, 2.00 mm, 2.25 mm, 2.50 mm, 2.75 mm, 3.00 mm or a range composed of any two of the above values. The positive electrode adapter 41 has a relatively thick thickness and excellent current-carrying capacity, and can further improve the fast charging ability of the battery cell 7.

[0267] Exemplarily, the material of the positive electrode adapter 41 may include aluminum, copper, aluminum alloy, copper alloy, etc.

[0268] As Figure 10 and Figure 11As shown, optionally, the positive electrode adapter 41 includes a first positive electrode adapter portion 411 and a second positive electrode adapter portion 412. The first positive electrode adapter portion 411 is connected to the positive electrode tab 111, and the second positive electrode adapter portion 412 is connected to the first positive electrode adapter portion 411 and protrudes from the first positive electrode adapter portion 411 along the length direction Z. The second positive electrode adapter portion 412 is connected to the positive terminal 31. Through the first positive electrode adapter portion 411 and the second positive electrode adapter portion 412, the positive electrode tab 111 can be electrically connected to the positive terminal 31, and the current-carrying capacity between the positive electrode tab 111 and the positive terminal 31 can be improved, and the fast charging ability of the battery cell 7 can be improved.

[0269] Optionally, the ratio of the dimension of the first positive electrode adapter portion 411 in the width direction Y to the width of the battery cell 7 is 0.2 to 0.5, such as 0.2, 0.3, 0.4, 0.5 or the range composed of any two of the above values. When the ratio of the dimension of the first positive electrode adapter portion 411 in the width direction Y to the width of the battery cell 7 is within the above range, the path for electrons to be transmitted from the positive electrode tab 111 through the positive electrode adapter 41 to the positive terminal 31 is relatively short, and the fast charging ability of the battery cell 7 can be improved. Figure 11 As shown, Y2 represents the dimension of the first positive electrode adapter portion 411 in the width direction Y, and Y2 / Y1 represents the ratio of the dimension of the first positive electrode adapter portion 411 in the width direction Y to the width of the battery cell 7.

[0270] Optionally, the ratio of the dimension of the second positive electrode adapter portion 412 in the length direction Z to the length of the battery cell 7 is 0.05 to 0.2, such as 0.05, 0.1, 0.15, 0.2 or the range composed of any two of the above values. When the ratio of the dimension of the second positive electrode adapter portion 412 in the length direction Z to the length of the battery cell 7 is within the above range, the path for electrons to be transmitted from the positive electrode tab 111 through the positive electrode adapter 41 to the positive terminal 31 is relatively short, and the fast charging ability of the battery cell 7 can be improved. Figure 11 As shown, Z2 represents the dimension of the first positive electrode adapter portion 411 in the length direction Z, and Z2 / Z1 represents the ratio of the dimension of the second positive electrode adapter portion 412 in the length direction Z to the length of the battery cell 7.

[0271] In some embodiments, the battery cell 7 further includes a negative terminal 32, and the negative terminal 32 is disposed on the housing 20 and can be disposed on the housing 21 or the end cap 22.

[0272] The negative terminal 32 is electrically connected to the negative electrode tab 121. Optionally, the negative terminal 32 and the negative electrode tab 121 are welded. The negative terminal 32 and the negative electrode tab 121 can be connected through an adapter, or can be directly welded without using an adapter, which can reduce the resistance at the connection and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0273] Optionally, the negative terminal 32 is disposed on at least one side of the electrode assembly 10 along the width direction Y of the battery cell 7, and the negative terminal 32 is connected to the negative tab 121 through the positive transfer member 41. Through the connection of the negative transfer member 42, the overcurrent capacity between the negative terminal 32 and the negative tab 121 can be improved, and the fast charging capacity of the battery cell 7 can be improved.

[0274] Optionally, the thickness of the negative transfer member 42 is 1.25 mm to 3.00 mm, such as 1.25 mm, 1.50 mm, 1.75 mm, 2.00 mm, 2.25 mm, 2.50 mm, 2.75 mm, 3.00 mm or a range composed of any two of the above values. The negative transfer member 42 has a relatively thick thickness and excellent overcurrent capacity, which can further improve the fast charging capacity of the battery cell 7.

[0275] Exemplarily, the material of the negative transfer member 42 may include aluminum, copper, aluminum alloy, copper alloy, etc.

[0276] As Figure 12 shown, optionally, the negative transfer member 42 includes a first negative transfer portion 421 and a second negative transfer portion 422. The first negative transfer portion 421 is connected to the negative tab 121, the second negative transfer portion 422 is connected to the first negative transfer portion 421 and protrudes from the first negative transfer portion 421 along the length direction Z, and the second negative transfer portion 422 is connected to the negative terminal 32. Through the first negative transfer portion 421 and the second negative transfer portion 422, the negative tab 121 and the negative terminal 32 can be electrically connected, and the overcurrent capacity between the two can be improved, and the fast charging capacity of the battery cell 7 can be improved.

[0277] Optionally, the ratio of the dimension of the first negative transfer portion 421 along the width direction Y to the width of the battery cell 7 is 0.2 to 0.5, such as 0.2, 0.3, 0.4, 0.5 or a range composed of any two of the above values. When the ratio of the dimension of the first negative transfer portion 421 along the width direction Y to the width of the battery cell 7 is within the above range, the path for electrons to transfer from the negative tab 121 to the negative terminal 32 through the negative transfer member 42 is relatively short, which can improve the fast charging capacity of the battery cell 7. Figure 12 As shown, Y3 represents the dimension of the first negative transfer portion 421 along the width direction Y, and Y3 / Y1 represents the ratio of the dimension of the first negative transfer portion 421 along the width direction Y to the width of the battery cell 7.

[0278] Optionally, the ratio of the dimension of the second negative electrode connecting portion 422 in the length direction Z to the length of the battery cell 7 is 0.05 to 0.2, such as 0.05, 0.1, 0.15, 0.2, or a range composed of any two of the above values. When the ratio of the dimension of the second negative electrode connecting portion 422 in the length direction Z to the length of the battery cell 7 is within the above range, the path for electrons to transfer from the negative electrode tab 121 to the negative terminal 32 through the negative electrode connecting member 42 is relatively short, which can improve the fast charging ability of the battery cell 7. Figure 12 As shown, Z3 represents the dimension of the second negative electrode connecting portion 422 in the length direction Z, and Z3 / Z1 represents the ratio of the dimension of the second negative electrode connecting portion 422 in the length direction Z to the length of the battery cell 7.

[0279] As Figure 13 shown, the battery cell 7 of the embodiment of the present application can be assembled into a battery module 6. The number of battery cells 7 included in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0280] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, parallel, or in a mixed connection. A mixed connection means that there are both series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series, parallel, or in a mixed connection together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodating portion of the battery module 6. Of course, it can also be that the multiple battery cells 7 are first connected in series, parallel, or in a mixed connection to form a battery module 6, and then the multiple battery modules 6 are connected in series, parallel, or in a mixed connection to form a whole and are accommodated in the accommodating portion. Optionally, the battery module 6 can further include an accommodating portion having an accommodating space, and the multiple battery cells 7 are accommodated in the accommodating space.

[0281] The multiple battery cells 7 of the battery module 6 can be electrically connected through a bus bar component to achieve parallel, series, or mixed connection of the multiple battery cells 7 of the battery module 6. The bus bar component can be one or more, and each bus bar component is used to electrically connect at least two battery cells 7.

[0282] As Figure 14 shown, in some embodiments, the above battery module 6 can be further assembled into a battery pack 2. The number of battery modules 6 included in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device herein can be a battery module 6, a battery pack 2, or a battery cell 7, and the battery cell 7 can be the smallest unit constituting the battery device.

[0283] The battery pack 2 may include a box body 5 and a plurality of battery modules 6 disposed in the box body 5. The box body 5 includes a first box body portion 5a and a second box body portion 5b. The box body 5 has an accommodation space 5c. The first box body portion 5a is used to cover the second box body portion 5b and form a closed space for accommodating the battery modules 6. The plurality of battery modules 6 may be arranged in the box body 5 in any manner.

[0284] The first box body portion 5a and the second box body portion 5b cover each other, and the first box body portion 5a and the second box body portion 5b jointly define an accommodation space 5c for accommodating battery cells. The second box body portion 5b may be a hollow structure with one end open. The first box body portion 5a is a plate-like structure. The first box body portion 5a covers the opening side of the second box body portion 5b to form the box body 5 with the accommodation space 5c. The first box body portion 5a and the second box body portion 5b may also both be hollow structures with one side open. The opening side of the first box body portion 5a covers the opening side of the second box body portion 5b to form the box body 5 with the accommodation space 5c. Of course, the first box body portion 5a and the second box body 5b may be of various shapes, such as a cylinder, a cuboid, etc.

[0285] To improve the sealing performance after the connection between the first box body portion 5a and the second box body portion 5b, a sealing member, such as sealant, sealing ring, etc., may also be provided between the first box body portion 5a and the second box body portion 5b.

[0286] Assuming that the first box body portion 5a covers the top of the second box body portion 5b, the first box body portion 5a may also be referred to as the upper box cover, and the second box body portion 5b may also be referred to as the lower box body. electric device In a second aspect of the embodiments of the present application, an electrical device is provided. The electrical device includes the battery device of the embodiments of the present application, such as battery cells, battery modules or battery packs. The battery cells, battery modules or battery packs may be used as the power source of the electrical device or may also be used as the energy storage unit of the electrical device. The electrical device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid electric vehicle or an extended-range electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric vehicle toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, such as an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact electric drill, a concrete vibrator and a power planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices. The electrical device can select battery cells, battery modules or battery packs according to its usage requirements.

[0287] Figure 15 It is a schematic diagram of the electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high-power and high-energy-density requirements of the electrical device 1, battery packs or battery modules can be adopted.

[0288] A battery pack 2 is arranged inside the electrical device 1, and the battery pack 2 can be arranged at the bottom, head or tail of the electrical device 1. The battery pack 2 can be used to supply power to the electrical device 1. For example, the battery pack 2 can be used as the operating power supply of the electrical device 1 and can also be used as the driving power supply of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1.

[0289] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery pack 2 to supply power to the motor 4. For example, it is used for the working power requirements during the start-up, navigation and driving of the electrical device 1.

[0290] As another example, the electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires being thin and light, and battery cells can be adopted as the power source.

[0291] embodiment The following embodiments more specifically describe the content disclosed in the embodiments of the present application. These embodiments are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the embodiments are all commercially available.

[0292] Embodiment 1 1. Preparation of the positive electrode plate The positive electrode plate includes a positive current collector part and a positive electrode film layer. The positive electrode film layer is arranged on both sides of the positive current collector part, and the positive current collector part is an aluminum foil.

[0293] The positive electrode film layer is formed by uniformly coating the surface of the positive current collector part with a positive electrode slurry (the solvent is N-methylpyrrolidone NMP), followed by drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF) and a conductive agent acetylene black with a weight ratio of 97:2:1.

[0294] The positive electrode active material includes lithium iron phosphate particles and positive electrode additive elements located in the lithium iron phosphate particles. The positive electrode additive elements include Al, V, Ti, and Nb. The mass content of the positive electrode additive elements is 1500 ppm, and the mass ratio of the addition of the four elements is 1:1:1:1.

[0295] The lithium-containing phosphate includes primary particles and secondary particles formed by the aggregation of primary particles. The secondary particles are spherical and / or quasi-spherical. In the cross-section along the thickness direction of the positive electrode film layer, the average longest diameter of the primary particles is 600 nm, and the average particle size of the secondary particles is 10 μm.

[0296] The single-sided coating weight of the positive electrode film layer is 290 mg / 1540.25 mm 2 。

[0297] 2. Preparation of the negative electrode plate The negative electrode plate includes a negative electrode current collector part and a negative electrode film layer. The negative electrode film layer is disposed on both sides of the negative electrode current collector part, and the negative electrode current collector part is a copper foil.

[0298] The negative electrode film layer is formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode current collector part and then drying and cold pressing.

[0299] The first negative electrode film layer is disposed on the surface of the negative electrode current collector part. It includes a negative electrode active material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose with a mass ratio of 96.5:0.5:2:1. The negative electrode active material includes graphite particles and silicon oxide. The graphite particles include artificial graphite and a negative electrode coating layer. The negative electrode coating layer covers the surface of the artificial graphite. The negative electrode coating layer includes carbon elements. The graphitization degree of the graphite particles is 92.5%, and the volume average particle size of the graphite particles is 8.5 μm.

[0300] The second negative electrode film layer is disposed on the surface of the negative electrode current collector part. It includes a negative electrode active material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose with a mass ratio of 96.5:0.5:2:1. The negative electrode active material includes graphite particles and silicon oxide. The graphite particles include artificial graphite and a negative electrode coating layer. The negative electrode coating layer covers the surface of the artificial graphite. The mass content of carbon elements in the negative electrode coating layer is 2%. The graphitization degree of the graphite particles is 92.5%, and the volume average particle size of the graphite particles is 7 μm.

[0301] The mass content of silicon element in the negative electrode film layer is 0.7%.

[0302] In the cross-section along the thickness direction of the negative electrode film layer, the average longest diameter of the graphite particles in the first negative electrode film layer is 11.5 μm, the thickness of the negative electrode coating layer of the graphite particles in the first negative electrode film layer is 200 nm, the average longest diameter of the graphite particles in the second negative electrode film layer is 10 μm, and the thickness of the negative electrode coating layer of the graphite particles in the second negative electrode film layer is 200 nm.

[0303] The single-sided coating weight of the negative electrode film layer is 130 mg / 1540.25 mm 2 。

[0304] 3. Separator The separator is a 7-μm polyethylene film layer with a porosity of 35%.

[0305] 4. Preparation of electrolyte The electrolyte includes organic solvents, lithium salts, and additives. After mixing the components of each organic solvent, lithium salts and additives are added to prepare the electrolyte.

[0306] The organic solvents include 16.3% by mass of carboxylic ester solvents, 35.7% of linear carbonate solvents, and 26.3% of cyclic carbonate solvents.

[0307] The mass content of the additive is 6.4%, which includes vinylene carbonate VC, 1,3-propane sultone, and fluoroethylene carbonate FEC with a mass ratio of 4:0.4:2.

[0308] The electrolyte also includes 0.2% lithium difluorophosphate and 0.1% lithium fluorosulfonate.

[0309] The lithium salt includes 15% by mass of lithium hexafluorophosphate LiPF 6 。

[0310] The conductivity of the electrolyte is 12.8 ms / cm.

[0311] 5. Preparation of battery cell Stack the above positive electrode plate, separator, and negative electrode plate in sequence, with the separator placed between the positive electrode plate and the negative electrode plate to play an isolation role, obtaining a stacked electrode assembly. Place the electrode assembly in a housing, with positive and negative terminals provided on the housing. After baking, inject the electrolyte, and through processes such as vacuum packaging, standing, formation, and shaping, obtain the battery cell.

[0312] The compaction density of the positive electrode film layer of the battery cell at 0% SOC is 2.52 g / cm 3 , and the compaction density of the negative electrode film layer at 0% SOC is 1.35 g / cm 3 。

[0313] The aluminum shell has a cuboid structure, and the thickness of the shell corresponding to the face with the largest area of the cuboid structure is 0.5 mm.

[0314] Examples 2-1 to 2-5 The battery monomers were prepared by a method similar to that of Example 1. Different from Example 1, in Examples 2-1 to 2-4, the mass contents of the solvents were adjusted; in Example 2-5, the material of the solvent was adjusted.

[0315] Comparative Examples 1-1 and 1-2 The battery monomers were prepared by a method similar to that of Example 1. Different from Example 1, the mass contents of the solvents were adjusted.

[0316] Performance test 1. Fast charging test of battery monomers At 25 °C, the battery monomers were charged from 0% state of charge (SOC) to 10% SOC at a constant current of 0.33C; charged from 10% SOC to 15% SOC at a constant current of 5.0C; charged from 15% SOC to 20% SOC at a constant current of 4.6C; charged from 20% SOC to 35% SOC at a constant current of 4.2C; charged from 35% SOC to 45% SOC at a constant current of 3.8C; charged from 45% SOC to 50% SOC at a constant current of 3.6C; charged from 50% SOC to 60% SOC at a constant current of 3.4C; charged from 60% SOC to 70% SOC at a constant current of 3.0C; charged from 70% SOC to 75% SOC at a constant current of 2.8C; charged from 75% SOC to 80% SOC at a constant current of 2.4C; Record the fast charging time of the battery monomers from 10% SOC to 80% SOC.

[0317] 2. Number of cycles for the battery monomers to reach 80% SOH At 25 °C, the battery monomers were charged at a constant current of 1C to the charging cut-off voltage of 3.65V, then charged at a constant current of 0.05C to the charging cut-off voltage of 3.65V, and left standing for 30 min; discharged at a constant current of 1C to 2.5V and left standing for 30 min. This is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., Cn / C0×100%) reaches 80%, and record the number of cycles. The more the number of cycles, the better the cycle performance of the battery monomers.

[0318] When performing charge and discharge tests on battery cells, the battery cells can be assembled in a battery device, and the required charge and discharge strategies can be regulated through a battery management system for testing.

[0319] The test results are shown in Table 1.

[0320] Table 1

[0321] In Table 1, EA represents ethyl acetate; EP represents ethyl propionate; DMC represents dimethyl carbonate; DEC represents diethyl carbonate; in Example 1, Examples 2-1 to 2-4, Comparative Example 1-1 and Comparative Example 1-2, the mass ratio of DMC to DEC is 1:1; EMC represents ethyl methyl carbonate; in Example 2-5, the mass ratio of EMC to DEC is 1:1; EC represents ethylene carbonate.

[0322] The components of the electrolytes of the examples and comparative examples were detected. The mass content of the carboxylic ester solvent in the electrolyte of Comparative Example 1-1 is relatively low. Although the introduction of the linear carbonate solvent can reduce the viscosity of the electrolyte to a certain extent, the overall viscosity of the electrolyte is still relatively high and the impedance is high, which is not conducive to fast charging.

[0323] The electrolyte of Comparative Example 1-2 also includes a certain content of linear carbonate. Although it can appropriately reduce the additives of the carboxylic ester solvent, the mass content of the carboxylic ester solvent in Comparative Example 1-2 is still relatively high, making the viscosity of the electrolyte small and the impedance small, which is conducive to fast charging; however, the side reaction between the carboxylic ester solvent and the negative electrode active material is relatively serious, deteriorating the cycle performance.

[0324] By adjusting the mass content of the carboxylic ester solvent within an appropriate range, such as 10% to 30%, and cooperating with 10% to 50% of the linear carbonate solvent in the examples of the present application, the viscosity of the electrolyte can be reduced and the migration rate of lithium ions in the electrolyte can be increased; moreover, the use of the carboxylic ester solvent in combination with the linear carbonate solvent makes the mass content of the carboxylic ester solvent not too high, which can alleviate the side reaction between the carboxylic ester solvent and the negative electrode active material; and the electrolyte also includes additives, which can form an excellent and low-impedance solid electrolyte interface film (SEI film) on the negative electrode side, which can further alleviate the side reaction, improve the cycle performance and enhance the fast charging ability.

[0325] Examples 2-1 to 2-5. By adjusting the mass contents of the carboxylic acid ester solvents and the linear carbonate solvents, the conductivity can be adjusted. With the increase in conductivity, it is beneficial to the migration of lithium ions in the electrolyte, which can improve the fast charging performance of the battery cell and shorten the charging time.

[0326] For example, in Examples 1, 2-1, and 2-2, with the increase in the mass content of the carboxylic acid ester solvents, the conductivity of the electrolyte increases, the migration rate of lithium ions in the electrolyte accelerates, which can improve the fast charging performance of the battery cell and shorten the charging time. However, due to the increase in the mass content of the carboxylic acid ester solvents, the side reaction degree on the negative electrode side is greater, which can deteriorate the cycle performance to a certain extent.

[0327] In Examples 2-3 and 2-4, with the increase in the mass content of the linear carbonate solvents, the conductivity of the electrolyte also has a certain increase, which can improve the fast charging performance of the battery cell and shorten the charging time.

[0328] The carboxylic acid ester solvents are suitable for different materials, and the linear carbonate solvents are suitable for different materials. For example, Example 2-5 and Example 1 use solvent materials of different materials, which can also play a role in improving the fast charging and cycle performance of the battery cell.

[0329] Examples 3-1 to 3-8 The battery cells were prepared by a method similar to that of Example 1. Different from Example 1, one of the material and mass content of the additive was adjusted, and the mass content of the organic solvent was adjusted accordingly according to the adjustment of the mass content of components such as the additive. For example, if the increase in the mass content of the additive is 1%, the decrease in the mass content of the organic solvent is 1%, and the mass ratio of each component in the organic solvent remains unchanged, as shown in Table 2 specifically; Among them, the electrolyte of Example 3-8 does not contain lithium difluorophosphate and lithium fluorosulfonate.

[0330] The test results are shown in Table 2.

[0331] Table 2

[0332] In Table 2, VC represents vinylene carbonate; PS represents 1,3-propane sultone; FEC represents fluoroethylene carbonate; DFEC represents difluoroethylene carbonate; The addition amount of the additive in the electrolyte of Comparative Example 2-1 is too low. For example, the addition amount of vinylene carbonate is too low. Although the impedance of the SEI film on the negative electrode side is relatively low, due to the relatively poor protection effect of the SEI film, the carboxylate solvent is likely to have a side reaction with the negative electrode active material, deteriorating the cycle performance.

[0333] The addition amount of the additive in the electrolyte of Comparative Example 2-2 is too high. For example, the addition amount of vinylene carbonate is too high. Vinylene carbonate can form a dense SEI film of organic components on the negative electrode side, alleviating the side reaction between the carboxylate solvent and the negative electrode active material. However, due to the too high impedance of the SEI film, it is not conducive to the rapid migration of lithium ions, resulting in a longer charging time for the battery cell.

[0334] While the addition amount of the additive in the electrolyte of the embodiment of the present application is within an appropriate range, and its mass content is 3% to 9%. The reaction potentials of vinylene carbonate and the carboxylate solvent in the additive are close, and there is a competitive reaction with the carboxylate solvent. Vinylene carbonate can participate in the formation of a dense SEI film on the negative electrode side, making it difficult for the carboxylate solvent to penetrate the SEI film to the graphite particles, thereby alleviating the side reaction between the carboxylate solvent and the graphite particles and reducing the gas generation amount; moreover, since the additive is within an appropriate content, the impedance of the film formed on the negative electrode side is relatively small, which is beneficial to improving the cycle performance and reducing the risk of lithium plating.

[0335] In Examples 3-1 to 3-8, by regulating the mass contents of vinylene carbonate, 1,3-propanesultone, and ethylene carbonate derivatives, an SEI film with relatively low impedance can be obtained, improving the fast charging performance and cycle performance of the battery cell.

[0336] In Example 1, Example 3-1, and Example 3-2, as the mass content of vinylene carbonate increases, the protection performance on the negative electrode side is improved, which is beneficial to improving the cycle performance; however, the impedance of the SEI film increases and the fast charging time increases.

[0337] In Example 1, Example 3-3, and Example 3-4, by regulating the mass content of 1,3-propanesultone, as the mass content of 1,3-propanesultone increases, the components of the SEI film can be optimized, and the protection effect of the SEI film can be improved, which is beneficial to the improvement of the cycle performance; however, the impedance of the SEI film also increases appropriately, which may slightly deteriorate the fast charging performance of the battery cell. In view of this, the mass content of 1,3-propanesultone is 0 to 0.5%, and can be optionally 0.2% to 0.5% to balance the improvement of the cycle performance and fast charging performance of the battery cell.

[0338] Examples 1, 3 - 5, and 3 - 6 regulate the mass content of fluoroethylene carbonate. As the mass content of fluoroethylene carbonate increases, the components of the SEI film can be optimized, the impedance of the SEI film can be reduced, which is beneficial to the rapid migration of lithium ions and improves the rapid charging performance of the battery cell. However, as the mass content of fluoroethylene carbonate increases, the protective performance on the negative electrode side is more excellent, but the impedance of the formed SEI film will also increase accordingly, resulting in an increase in the charging time. In view of this, the mass content of ethylene carbonate derivatives in the electrolyte is 0 to 2.55% to balance the improvement of the cycle performance and rapid charging performance of the battery cell.

[0339] When the electrolyte includes fluoroethylene carbonate, the mass content of vinylene carbonate can be appropriately reduced, which is beneficial to balancing the improvement of the cycle performance and rapid charging performance of the battery cell.

[0340] Using ethylene carbonate derivatives of different materials, such as fluoroethylene carbonate and difluoroethylene carbonate, can effectively improve the cycle performance and rapid charging performance of the battery cell.

[0341] Compared with Example 3 - 8, Example 1 also includes lithium fluorosulfonate and lithium difluorophosphate, which can further optimize the components of the SEI film on the negative electrode side, improve the protective performance on the negative electrode side, and improve the cycle performance.

[0342] Examples 4 - 1 and 4 - 2 The battery cells were prepared using a method similar to that of Example 1. Different from Example 1, Example 4 - 1 adjusted the single - side coating weight of the positive and negative electrode film layers; Example 4 - 2 adjusted the compaction density of the positive and negative electrode film layers.

[0343] The test results are shown in Table 3.

[0344] Table 3

[0345] Compared with Example 1, the single - side coating weight of the positive and negative electrode film layers in Example 4 - 1 is smaller, resulting in a relatively lower energy density of the battery cell. The migration path of lithium ions in the positive and negative electrode film layers is shortened, which is more conducive to achieving rapid charging and shortening the charging time. Moreover, due to the reduction of the single - side coating weight, the total amount of active materials participating in the side reactions on the negative electrode side is reduced, which is beneficial to improving the cycle performance.

[0346] The compaction density of the positive and negative electrode film layers in Example 4 - 2 increases, resulting in a relatively higher energy density of the battery cell. However, the migration resistance of lithium ions in the positive and negative electrode film layers increases, resulting in an increase in the charging time. Moreover, due to the increase in the compaction density, the total amount of active materials participating in the side reactions on the negative electrode side increases, and the cycle performance deteriorates slightly.

[0347] Example 5 A battery cell was prepared using a preparation method similar to that of Example 1. Different from Example 1, the volume average particle size of the graphite particles was adjusted.

[0348] Example 6 A battery cell was prepared using a preparation method similar to that of Example 1. Different from Example 1, the negative electrode film layer of Example 6 included a single-layer film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode current collector, followed by drying and cold pressing.

[0349] The negative electrode film layer was disposed on the surface of the negative electrode current collector and included a negative electrode active material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 96.5:0.5:2:1. The negative electrode active material included graphite particles and silicon oxide. The graphite particles included artificial graphite and a negative electrode coating layer. The negative electrode coating layer coated the surface of the artificial graphite. The mass content of carbon element in the negative electrode coating layer was 2%. The graphitization degree of the graphite particles was 92.5%. The volume average particle size of the graphite particles was 8.5 μm. The mass content of silicon element in the negative electrode film layer was 0.7%.

[0350] Example 7 A battery cell was prepared using a preparation method similar to that of Example 1. Different from Example 1, the mass content of silicon element in the negative electrode film layer was adjusted to 3.0%.

[0351] Example 8 A battery cell was prepared using a preparation method similar to that of Example 1. Different from Example 1, the particle size of the lithium-containing phosphate was adjusted.

[0352] Example 9 A battery cell was prepared using a preparation method similar to that of Example 1. Different from Example 1, no positive electrode additive element was added to the lithium-containing phosphate.

[0353] Example 10 A battery cell was prepared using a preparation method similar to that of Example 1. Different from Example 1, the type and mass content of the positive electrode additive element of the lithium-containing phosphate were adjusted.

[0354] The test results are shown in Table 4.

[0355] Table 4

[0356] The volume average particle size of the graphite particles in Example 1 and Example 5 is different. As the volume average particle size of the graphite particles decreases, the solid-phase transport path of lithium ions is shortened, which is beneficial to shortening the fast charging time and improving the fast charging performance of the battery; however, the active surface area of the graphite particles may be larger, resulting in more side reactions and slightly deteriorating the cycle performance of the battery.

[0357] Example 6 uses a single-layer negative electrode film layer. Compared with the single-layer negative electrode film layer, the double-layer film layer of Example 1 is more conducive to constructing a pore structure, improving the fast charging ability of the battery cell, and shortening the fast charging time; due to the relatively large particle size of the graphite particles in Example 6, the exposed active surface can be reduced, improving the cycle performance.

[0358] The mass content of silicon element in the negative electrode film layer of Example 1 and Example 7 is different. As the mass content of silicon element increases, the volume energy density of the battery cell increases, but the side reactions on the negative electrode side intensify, deteriorating the cycle; moreover, due to the repeated expansion of the silicon-based material during charge and discharge, the SEI film needs to be continuously repaired, which may increase the impedance of the SEI film and possibly increase the fast charging time of the battery cell.

[0359] The particle size of the lithium-containing phosphate in Example 1 and Example 8 is different. As the particle size decreases, the solid-phase transport path of lithium ions is shortened, which is beneficial to shortening the fast charging time and improving the fast charging performance of the battery; however, the active surface area of the lithium-containing phosphate may be larger, resulting in more side reactions and slightly deteriorating the cycle performance of the battery.

[0360] Compared with the lithium-containing phosphate in Example 9 without adding a positive electrode additive element, the lithium-containing phosphates in Example 1 and Example 10 are added with a positive electrode additive element, which can improve the cycle stability of the lithium-containing phosphate and enhance the cycle performance; with the appropriate increase of the positive electrode additive element, the improvement effect is more excellent.

[0361] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as limitations on this application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, and scope of this application.

Claims

1. A battery cell, characterized in that: It includes an electrode assembly and an electrolyte, wherein the electrode assembly includes a positive electrode sheet and a negative electrode sheet stacked in a thickness direction of the battery cell; The positive electrode sheet comprises a positive current collecting portion and a positive electrode film layer disposed on at least one side of the positive current collecting portion, wherein the positive electrode film layer comprises a lithium-containing phosphate having an olivine structure; The negative electrode sheet comprises a negative electrode current collecting portion and a negative electrode film layer disposed on at least one side of the negative electrode current collecting portion, wherein the negative electrode film layer comprises graphite particles; The electrolyte comprises a carboxylic acid ester solvent, a linear carbonate solvent and an additive, Wherein, based on the mass of the electrolyte, The mass content of the carboxylate solvent is 10% to 30%, and the mass content of the linear carbonate solvent is 10% to 50%; The mass content of the additive is 3% to 9%, and the additive includes 1,3-propane sultone with a mass content of ≥0, a vinyl carbonate derivative with a mass content of ≥0, and vinylene carbonate with a mass content of >0, and the vinyl carbonate derivative includes a compound shown in formula A, Formula A, In formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, Q4 are not hydrogen atoms at the same time.

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

3. The battery cell according to any one of claims 1 to 2, characterized in that: The mass content of the vinylene carbonate is 0.8% to 7%.

4. The battery cell according to claim 3, characterized in that: The mass content of the vinylene carbonate is 2% to 6%.

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

6. The battery cell according to any one of claims 1 to 2, characterized in that: The mass content of the ethylene carbonate derivative in the electrolyte is 0 to 2.55%.

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

8. The battery cell according to any one of claims 1 to 2, characterized in that: The ethylene carbonate derivative includes at least one of the compounds represented by formula A-1 to the compounds represented by formula A-3, 。 9. The battery cell according to any one of claims 1 to 2, characterized in that: The conductivity of the electrolyte is 11 ms / cm to 14 ms / cm.

10. The battery cell according to any one of claims 1 to 2, characterized in that: The carboxylate solvent includes at least one of ethyl acrylate, propyl acetate, ethyl propionate, ethyl formate, propyl formate, ethyl acetate, and butyl propionate; and / or The linear carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

11. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte further includes a cyclic carbonate solvent, and the mass content of the cyclic carbonate solvent in the electrolyte is 20% to 50%.

12. The battery cell according to claim 11, characterized in that: The cyclic carbonate solvent includes at least one of ethylene carbonate, propylene carbonate and butylene carbonate.

13. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte further includes a lithium salt additive, and the lithium salt additive includes at least one of lithium difluorophosphate, lithium fluorosulfonate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

14. The battery cell according to claim 13, characterized in that: The mass content of the lithium salt additive in the electrolyte is 0.02% to 0.5%.

15. The battery cell according to any one of claims 1 to 2, characterized in that: The compaction density of the negative electrode film layer of the battery cell at 0% charge state is 1.30 g / cm 3 Up to 1.52g / cm 3 , and / or, The single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 Up to 180mg / 1540.25mm 2 .

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

17. The battery cell according to claim 16, characterized in that: The graphite bulk particles include at least one of artificial graphite and natural graphite.

18. The battery cell according to claim 16, characterized in that: The graphite particles have a degree of graphitization of 90% to 94%; and / or The volume average particle size Dv50 of the graphite particles is 7 μm to 15 μm; and / or The thickness of the negative electrode coating layer is 100nm to 500nm.

19. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode film layer further comprises a silicon-based material, and the mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.5% to 10.0%.

20. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode film layer comprises: A first negative electrode film layer is disposed on the surface of the negative electrode current collecting portion; The second negative electrode film layer is arranged on a side of the first negative electrode film layer away from the negative electrode current collecting portion, Wherein, both the first negative electrode film layer and the second negative electrode film layer include graphite particles, and the average longest diameter of the graphite particles of the first negative electrode film layer is greater than or equal to the average longest diameter of the graphite particles of the second negative electrode film layer.

21. The battery cell according to claim 20, characterized in that: The average longest diameter of the graphite particles of the first negative electrode film layer is 7 μm to 18 μm; and / or The average longest diameter of the graphite particles of the second negative electrode film layer is 6 μm to 10 μm.

22. The battery cell according to claim 20, characterized in that: The ratio of the thickness of the second negative electrode film layer to the thickness of the negative electrode film layer is 0.3 to 0.

7.

23. The battery cell according to any one of claims 1 to 2, characterized in that: The compaction density of the positive electrode film layer of the battery cell at 0% SOC is 2.3 / cm 3 Up to 2.6g / cm 3 ; and / or The single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 Up to 330mg / 1540.25mm 2 .

24. The battery cell according to any one of claims 1 to 2, characterized in that: The lithium-containing phosphate includes at least one of primary particles and secondary particles, the secondary particles include a plurality of primary particles, and the secondary particles are spherical and / or quasi-spherical.

25. The battery cell according to claim 24, characterized in that: The average longest diameter of the primary particles is 300 nm to 800 nm; and / or The average particle size of the secondary particles is 5 μm to 15 μm.

26. The battery cell according to any one of claims 1 to 2, characterized in that: The lithium-containing phosphate comprises: Phosphate particles, and The positive electrode additive element is located in the phosphate particles, and the positive electrode additive element includes at least one element selected from the group consisting of aluminum, vanadium, titanium and niobium.

27. The battery cell according to claim 26, characterized in that: The mass content of aluminum element in the lithium-containing phosphate is 200 ppm to 2500 ppm; and / or The mass content of vanadium in the lithium-containing phosphate is 300 ppm to 2000 ppm; and / or The mass content of titanium in the lithium-containing phosphate is 1500 ppm to 3500 ppm; and / or The mass content of niobium element in the lithium-containing phosphate is 300 ppm to 2000 ppm.

28. The battery cell according to claim 26, 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.

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

30. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode sheet comprises at least one positive electrode tab, wherein the at least one positive electrode tab is connected to the positive electrode current collecting portion and extends out of the positive electrode current collecting portion along the length direction of the battery cell; and / or The negative electrode plate includes at least one negative electrode tab, and the at least one negative electrode tab is connected to the negative electrode current collecting portion and extends out of the negative electrode current collecting portion along the length direction of the battery cell.

31. The battery cell according to claim 30, characterized in that: The positive electrode sheet satisfies: n*W1 / W2 is 0.9 to 1.0; n represents the number of all positive electrode tabs located on the same side of the positive electrode current collector; W1 represents the average size of the positive electrode tab along the width direction of the battery cell; W2 represents the dimension of the positive electrode current collecting portion along the width direction; and / or The negative electrode sheet satisfies: m*W3 / W4 is 0.9 to 1.0; m represents the number of all negative electrode tabs located on the same side of the negative electrode current collecting portion; W3 represents the average size of the negative electrode tab along the width direction of the battery cell; W4 represents the dimension of the negative electrode current collecting portion along the width direction.

32. The battery cell according to claim 30, characterized in that The battery cell further comprises a positive terminal and a positive electrode adapter, wherein the positive terminal is arranged on at least one side of the electrode assembly along the width direction of the battery cell, and the positive terminal is connected to the positive electrode tab via the positive electrode adapter; and / or The battery cell further includes a negative terminal and a negative electrode adapter. The negative terminal is disposed on at least one side of the electrode assembly along the width direction. The negative terminal is connected to the negative electrode tab through the negative electrode adapter.

33. The battery cell according to claim 32, characterized in that: The thickness of the positive electrode adapter is 1.25 mm to 3.00 mm; and / or The thickness of the negative electrode adapter is 1.50 mm to 2.50 mm.

34. The battery cell according to claim 32, characterized in that: The positive electrode adapter comprises a first positive electrode adapter portion and a second positive electrode adapter portion, the first positive electrode adapter portion is connected to the positive electrode tab, the second positive electrode adapter portion is connected to the first positive electrode adapter portion and protrudes from the first positive electrode adapter portion along the length direction, and the second positive electrode adapter portion is connected to the positive terminal; The ratio of the dimension of the first positive electrode transition portion along the width direction to the width of the battery cell is 0.2 to 0.5; and / or The ratio of the dimension of the second positive electrode transition portion along the length direction to the length of the battery cell is 0.05 to 0.

2.

35. The battery cell according to any one of claims 32 to 34, characterized in that: The negative electrode adapter comprises a first negative electrode adapter portion and a second negative electrode adapter portion, the first negative electrode adapter portion is connected to the negative electrode tab, the second negative electrode adapter portion is connected to the first negative electrode adapter portion and protrudes from the first negative electrode adapter portion along the length direction, and the second negative electrode adapter portion is connected to the negative terminal; The ratio of the dimension of the first negative electrode transition portion along the width direction to the width of the battery cell is 0.2 to 0.5; and / or The ratio of the dimension of the second negative electrode transition portion along the length direction to the length of the battery cell is 0.05 to 0.

2.

36. The battery cell according to any one of claims 1 to 2, characterized in that: The length of the battery cell is 200 mm to 400 mm; and / or The width of the battery cell is 80 mm to 130 mm; and / or The thickness of the battery cell is 25 mm to 60 mm.

37. A battery device, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 36.

38. An electrical device, characterized in that: Comprising a battery device as claimed in claim 37.

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