Battery cell, battery device, and electrical device

Abstract

The present application relates to a battery cell, a battery device, and an electrical device. The battery cell includes a positive electrode plate and a negative electrode plate; the positive electrode plate includes a lithium-containing phosphate; the negative electrode plate includes graphite particles; the electrolyte includes a carboxylic acid ester solvent, a linear carbonate solvent, and an additive. The mass content of the carboxylic acid ester 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 ethylene carbonate derivative with a mass content ≥ 0, and vinylene carbonate with a mass content > 0. The ethylene carbonate derivative includes a compound represented by Formula A. In Formula A, Q1, Q2, Q3, and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not simultaneously hydrogen atoms. #imgabs0# Formula A.

Description

[0001] This application claims the priority of International Patent Application PCT / CN2025 / 078578 titled "Battery Cell, Battery Device and Electrical Device" 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 electrical device. Background Art [[ID=⑨]]

[0003] Battery cells have characteristics such as high capacity and long life, and are thus widely used in electronic devices, such as mobile phones, laptop computers, battery-powered vehicles, electric vehicles, electric aircraft, 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 electrical device, 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 in 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.

[0006] The electrolyte includes a carboxylic acid ester solvent, a linear carbonate solvent and an additive. Among them, based on the mass of the electrolyte, the mass content of the carboxylic acid ester solvent is 10% to 30%, 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.

[0007] Formula A

[0008] In Formula A, Q1, Q2, Q3 and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q1, Q2, Q3, Q4 are not simultaneously hydrogen atoms.

[0009] Thus, during the charging process of the embodiments of the present application, 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 also 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 embodiments of the present application can improve the fast charging ability and cycle performance of the battery cell.

[0010] In some embodiments, the mass content of the additive is 5% to 8%. When the mass content of the additive is within the above range, the cycle performance and fast charging performance of the battery cell can be further improved.

[0011] 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 cycle performance and fast charging ability of the battery cell.

[0012] In some embodiments, the mass content of 1,3 - propane sultone in the electrolyte is 0 to 0.5%. When the mass content of 1,3 - propane sultone is within the above range, the impedance of the formed SEI film will not be too high, which can reduce the impedance on the basis of alleviating the side reaction and improve the fast charging performance and cycle performance of the battery cell.

[0013] 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, can 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.

[0014] In some embodiments, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom or a C1-C5 haloalkyl group. When the ethylene carbonate derivative includes a fluorine atom, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side, 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 cycling performance and fast charging performance of the battery cell.

[0015] 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.

[0016] 。

[0017] The above materials can further improve the cycling performance and fast charging performance of the battery cell.

[0018] 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.

[0019] 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.

[0020] 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 and can increase the conductivity of the electrolyte at room temperature and enhance the fast charging ability of the battery cell.

[0021] 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 improve the transport rate of lithium ions at the interfaces, thereby further enhancing the fast charging ability of the battery cell.

[0022] 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, which can improve the transport rate of lithium ions at the interface, thereby further improving the fast charging ability of the battery cell.

[0023] 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(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.

[0024] 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 cycle performance of the battery cell.

[0025] In some embodiments, when the battery cell is in a 0% state of charge, the compaction density of the negative electrode film layer is 1.30 g / cm 3 to 1.52 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, and since the negative 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 carboxylic ester solvent due to heat accumulation can be reduced, improving the cycle performance of the battery cell.

[0026] 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 cycle performance of the battery cell can be improved.

[0027] 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.

[0028] In some embodiments, the graphite body particles include at least one of artificial graphite and natural graphite.

[0029] In some embodiments, the graphite particles have a degree of graphitization of 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 heat generation of the negative electrode plate and the battery cell, and can improve the fast charging performance of the battery cell.

[0030] In some embodiments, the volume average particle size Dv50 of the graphite particles is 7 μm to 15 μm. The relatively small volume average particle size of the graphite particles shortens the solid phase migration path of lithium ions, thereby improving the fast charging capability of the battery cell.

[0031] In some embodiments, the thickness of the negative electrode coating is 100 nm to 500 nm. When the thickness of the negative electrode coating 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.

[0032] In some embodiments, the negative electrode film layer further comprises a silicon-based material, wherein the mass content of silicon in the negative electrode film layer is 0.5% to 10.0%. A silicon content in the silicon-based material within this range can increase the capacity of the negative electrode active material, thereby improving the energy density of the battery cell.

[0033] 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 current 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 current 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.

[0034] 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 sheet.

[0035] In some embodiments, the average longest diameter of the graphite particles in the first negative electrode film layer is 7 μm to 18 μm. When the average longest diameter of the graphite particles in the first negative electrode film layer is within this range, the solid-phase transport path of lithium ions can be shortened, thereby improving fast charging performance. Furthermore, the material is less likely to agglomerate during the preparation process, thereby improving material stability.

[0036] 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, which can improve the stability of the materials. On the other 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 transport, and improving the fast charging performance of the battery cell.

[0037] 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.

[0038] 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 tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation under fast charging and improving the cycle performance and fast charging performance of the battery cell.

[0039] 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 too large, improving the cycle performance and fast charging performance of the battery cell.

[0040] 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 quasi-spherical. 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.

[0041] 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.

[0042] 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.

[0043] 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 cathode additive element can improve the crystal structure stability of the cathode active material, improve the pressure resistance of the lithium-containing phosphate, is beneficial to improving the compaction density of the cathode film layer, and improving the energy density and cycle performance of the battery cell.

[0044] 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, is beneficial to improving the compaction density of the cathode film layer, and improving the energy density and cycle performance of the battery cell.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] In some embodiments, the phosphate particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate. The above materials have excellent cycle stability and can improve the cycle performance of the battery cell.

[0049] 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 z1A compound, wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5, 0 ≤ c1 ≤ 0.5, 3 ≤ z1 ≤ 5, A includes at least one of Na, K, and Mg; Me includes at least one of Mn, Fe, Co, and Ni; M includes at least one of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes at least one of Cl, C, and N; Y includes at least one of O and F. The lithium-containing phosphate has excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0050] 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 arrangement is beneficial to reducing the occupied space of the tab ears and improving the energy density of the battery cell.

[0051] 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 arrangement is beneficial to reducing the occupied space of the tab ears and improving the energy density of the battery cell.

[0052] In some embodiments, the positive electrode tab satisfies that n * W1 / W2 is from 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.

[0053] 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.

[0054] In some embodiments, the negative electrode tab satisfies that m * W3 / W4 is from 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.

[0055] 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.

[0056] In some embodiments, the battery cell further includes a positive terminal and a positive transfer member. 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 transfer member. Through the connection of the positive transfer member, 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.

[0057] In some embodiments, the battery cell further includes a negative terminal and a negative transfer member. 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 transfer member. Through the connection of the negative transfer member, 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.

[0058] In some embodiments, the thickness of the positive transfer member is 1.25 mm to 3.00 mm; the thickness of the positive transfer member is relatively thick, and the overcurrent capacity is relatively excellent, which can further improve the fast charging capacity of the battery cell.

[0059] In some embodiments, the thickness of the negative transfer member is 1.50 mm to 2.50 mm. The thickness of the negative transfer member is relatively thick, and the overcurrent capacity is relatively excellent, which can further improve the fast charging capacity of the battery cell.

[0060] In some embodiments, the positive transfer member includes a first positive transfer portion and a second positive transfer portion. The first positive transfer portion is connected to the positive tab, the second positive transfer portion is connected to the first positive transfer portion and protrudes from the first positive transfer portion along the length direction, and the second positive transfer portion is connected to the positive terminal; the ratio of the dimension of the first positive transfer 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 transfer 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 transfer member is relatively short, which can improve the fast charging capacity of the battery cell 7.

[0061] In some embodiments, the ratio of the dimension of the second positive transfer 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 transfer 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 transfer member is relatively short, which can improve the fast charging capacity of the battery cell.

[0062] 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 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 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 the internal heat, slow down the risk of electrolyte decomposition caused by heat accumulation, and improve the cycle performance of the battery cell.

[0067] 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.

[0068] 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

[0069] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the drawings.

[0070] Figure 1 Schematic diagram of the structure of a battery cell provided by some embodiments of the present application

[0071] Figure 2 Explosion diagram of a battery cell provided by some embodiments of the present application

[0072] Figure 3 Schematic diagram of the structure of the electrode assembly of a battery cell provided by some embodiments of the present application

[0073] Figure 4 Schematic diagram of the structure of the positive electrode tab of a battery cell provided by some embodiments of the present application

[0074] Figure 5 Schematic diagram of the structure of the positive electrode tab of a battery cell provided by other embodiments of the present application

[0075] Figure 6 Schematic diagram of the structure of the positive electrode tab of a battery cell provided by other embodiments of the present application

[0076] Figure 7 Schematic diagram of the structure of the positive electrode tab of a battery cell provided by other embodiments of the present application

[0077] Figure 8 Schematic diagram of the structure of the negative electrode tab of a battery cell provided by some embodiments of the present application

[0078] Figure 9 Schematic diagram of the structure of the negative electrode tab of a battery cell provided by other embodiments of the present application

[0079] Figure 10 Explosion diagram of a battery cell provided by other embodiments of the present application

[0080] Figure 11 Schematic diagram of the structure of the positive electrode adapter of a battery cell provided by some embodiments of the present application

[0081] Figure 12 Schematic diagram of the structure of the negative electrode adapter of a battery cell provided by some embodiments of the present application

[0082] Figure 13 Schematic diagram of the structure of a battery module provided by some embodiments of the present application

[0083] Figure 14 Schematic diagram of the structure of the battery pack provided for some embodiments of the present application

[0084] Figure 15 Schematic diagram of the structure of the electrical device provided for some embodiments of the present application

[0085] The drawings are not necessarily drawn to actual scale

[0086] The reference numerals are explained as follows

[0087] X, thickness direction; Y, width direction; Z, length direction

[0088] 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

[0089] 7, battery cell

[0090] 10, electrode assembly

[0091] 11, positive electrode tab; 111, positive electrode ear; 1111, first end; 112, positive electrode current collector part

[0092] 12, negative electrode tab; 121, negative electrode ear; 1211, second end; 122, negative electrode current collector part

[0093] 13, separator

[0094] 20, outer shell; 21, housing; 22, end cap

[0095] 31, positive terminal; 32, negative terminal

[0096] 41, positive electrode adapter; 411, first positive electrode adapter part; 412, second positive electrode adapter part

[0097] 42, negative electrode adapter; 421, first negative electrode adapter part; 422, second negative electrode adapter part Detailed embodiments

[0098] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims

[0099] 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 real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when 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.

[0100] 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.

[0101] 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.

[0102] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0103] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate and a negative electrode plate. The negative electrode plate includes a negative electrode active material. At the negative electrode side interface, a side reaction may occur between the negative electrode 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, making the cycle deteriorate further, which is not conducive to fast charging.

[0104] In view of the above problems, the embodiments of the present application reasonably design the system of the battery cell, which can balance the improvement of 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, and the above material system has relatively excellent cycle stability;

[0105] 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 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 electrode active material becomes more serious and the gas generation increases;

[0106] 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;

[0107] 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 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 electrode active material, thereby further alleviating the side reaction between the carboxylic 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.

[0108] Therefore, the embodiments of the present application can improve the fast charging ability and cycle performance of the battery cell.

[0109] Battery cell

[0110] In a first aspect, the embodiments of the present application provide a battery cell.

[0111] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode tab and a negative electrode tab, and the positive electrode tab and the negative electrode tab are stacked along the thickness direction of the battery cell; the positive electrode tab includes a positive current collector portion and a positive electrode film layer disposed on at least one side of the positive current collector portion. The positive electrode film layer includes a positive active material, and the positive active material includes a lithium-containing phosphate in an olivine structure; the negative electrode tab includes a negative current collector portion and a negative electrode film layer disposed on at least one side of the negative current collector portion. The negative electrode film layer includes a negative active material, and the negative active material includes graphite particles;

[0112] 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%;

[0113] Based on the mass of the electrolyte, the mass content of the additive is 3% to 9%. The additive includes 1,3-propane sultone 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 a compound shown in Formula A,

[0114] Formula A,

[0115] In Formula A, Q1, Q2, Q3, and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not simultaneously hydrogen atoms.

[0116] The positive active material includes a lithium-containing phosphate in an olivine structure, and the negative active material includes graphite particles. The above material system has relatively excellent cycle stability;

[0117] During the charging process, active ions such as lithium ions migrating out of the positive electrode tab migrate through the electrolyte into the negative electrode tab. 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 cell;

[0118] 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 active material becomes more serious, and the gas generation increases;

[0119] The electrolyte also includes linear carbonate solvents. The addition of 10% to 50% of linear carbonate solvents can enable the electrolyte to have a relatively high conductivity and improve the migration rate of lithium ions even when the addition amount of carboxylate solvents is relatively low. Moreover, since the mass content of carboxylate solvents is relatively low, for example, less than or equal to 30%, it can slow down the side reactions on the negative electrode side and reduce the gas generation amount.

[0120] Furthermore, the electrolyte also includes additives. The additives include vinylene carbonate. The reaction potential of vinylene carbonate is close to that of carboxylate solvents, and there is a competitive reaction with carboxylate solvents. 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 carboxylate solvents to penetrate the SEI film to the negative electrode active material, thereby further alleviating the side reactions between carboxylate solvents and negative electrode active materials and further reducing the gas generation amount. Moreover, when the additives are within an appropriate content range, the film impedance formed by them on the negative electrode side will not be too large and will basically not deteriorate the fast charging performance.

[0121] Therefore, the embodiments of the present application can improve the fast charging ability and cycling performance of battery cells.

[0122] [Electrolyte]

[0123] 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.

[0124] In some embodiments, the conductivity of the electrolyte is 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 the range composed of any two of the above values.

[0125] 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.

[0126] 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 the equipment and methods well-known in the art. For example, it can be tested with reference to the industry standard HG-T 4067-2015.

[0127] The electrolyte includes organic solvents and electrolyte salts.

[0128] The organic solvents include carboxylate solvents, and the mass content of the carboxylate solvents in the electrolyte is 10% to 30%. Exemplarily, the mass content of the carboxylate solvents is 10%, 15%, 20%, 25%, 30% or the range composed of any two of the above values. When the mass content of the carboxylate solvents 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 carboxylate solvents is less than or equal to 30%, the side reactions between the carboxylate solvents and the negative electrode active material are relatively few, which is beneficial to improving the cycle performance.

[0129] In some embodiments, the carboxylate solvents may include at least one of linear carbonate solvents and cyclic carboxylate solvents, and may be selected as linear carbonate solvents. The linear carbonate solvents have lower viscosity, can further improve the migration rate of lithium ions, and enhance the fast charging ability of the battery cell.

[0130] Due to the lower viscosity of the linear carbonate solvents, they have better fluidity and are more conducive to the rapid infiltration of the electrode sheets. 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 in use.

[0131] Exemplarily, the carboxylate solvents include at least one of ethyl acrylate, propyl acetate, ethyl propionate, ethyl formate, propyl formate, ethyl acetate, butyl propionate, and may be selected as ethyl acrylate.

[0132] The above materials have lower viscosity and can further improve the fast charging performance of the battery cell.

[0133] In the embodiments of the present application, the organic solvents further include linear carbonate solvents, and the mass content of the linear carbonate solvents in the electrolyte is 10% to 50%. Exemplarily, the mass content of the linear carbonate solvents in the electrolyte is 10%, 15%, 20%, 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50% or the range composed of any two of the above values.

[0134] The linear carbonate solvents with the above mass content can further increase the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions and enhances the fast charging ability of the battery cell.

[0135] Exemplarily, the linear carbonate solvents include at least one of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, and may be selected as dimethyl carbonate.

[0136] The above materials have relatively low viscosity, can increase the conductivity of the electrolyte at room temperature, and enhance the fast charging ability of the battery cell.

[0137] In some embodiments, the organic solvent further includes a cyclic carbonate solvent, and the mass content of the cyclic carbonate solvent in the electrolyte is 20% to 50%. Exemplarily, the mass content of the cyclic carbonate solvent 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 solvent has excellent desolvation ability, which can enable lithium ions to be quickly released from the solvation structure at the positive and negative electrode interfaces, improving the transport rate of lithium ions at the interfaces, and thus further enhancing the fast charging ability of the battery cell.

[0138] Exemplarily, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate, and may be ethylene carbonate.

[0139] The above materials have excellent desolvation ability, which can improve the transport rate of lithium ions at the interfaces, and thus further enhance the fast charging ability of the battery cell.

[0140] In the embodiments of the present application, the electrolyte further includes an additive, 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.

[0141] In the embodiments of the present application, the mass content of the additive is 3% to 9%, such as 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.

[0142] When the mass content of the additive 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 additive increases, the film-forming effect on the negative electrode side is more excellent, which can play an excellent protective role for the negative electrode active material, reduce the risk of carboxylic ester solvents penetrating the SEI film 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 additive further increases, the impedance of the SEI film formed on the negative electrode side is relatively high, which is not conducive to fast charging; therefore, the mass content of the additive 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 additive is 5% to 8%, which can further improve the cycle performance and fast charging performance of the battery cell.

[0143] The additive includes vinylene carbonate with a mass content >0, in other words, vinylene carbonate is an essential component of the electrolyte.

[0144] When the mass contents of 1,3 - propanesultone and ethylene carbonate derivatives are 0, it means the sum of the mass contents of 1,3 - propanesultone and ethylene carbonate derivatives is 0. In this case, the additive may only include vinylene carbonate, and the mass content of vinylene carbonate can be 3% to 9%.

[0145] Specifically, taking the case where the mass content of ethylene carbonate derivatives is 0 as an example,

[0146] it can be that no ethylene carbonate derivatives are added to the freshly prepared electrolyte,

[0147] or the electrolyte obtained after disassembling the battery cell does not contain ethylene carbonate derivatives. This situation may be that no ethylene carbonate derivatives are 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.

[0148] Furthermore, for adding certain substances, such as additives, to the electrolyte, due to the characteristic that the additives play a role by participating in the film - forming on the surface of the active material, the content of the 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 the 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 the relevant substances in the corresponding freshly prepared electrolyte based on the performance expression level (such as the number of cycles), residual content, etc. 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) based on the content of the freshly prepared additives, according to the performance requirements of the battery cell, storage environment, etc.

[0149] Therefore, the additive content mentioned in the technical solution of this application can be the content of the additives actively added to the freshly prepared electrolyte, or the content of the residual additives detected by reverse according to the actual battery state.

[0150] In some embodiments, the mass content of vinylene carbonate in the electrolyte is from 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 a range composed of any two of the above values. When the mass content of vinylene carbonate is within the above range, a dense SEI film containing organic components can be formed on the negative electrode side, and the impedance of the SEI film is relatively low, which can reduce the side reactions on the negative electrode side and balance the improvement of the cycle performance and fast charging ability of the battery cell. Optionally, the mass content of vinylene carbonate in the electrolyte is from 2% to 6%.

[0151] The additive further includes at least one of 1,3 - propane sultone and ethylene carbonate derivative with a mass content > 0. The additive may include 1,3 - propane sultone, or the additive may include an ethylene carbonate derivative, or the additive may include 1,3 - propane sultone and an ethylene carbonate derivative.

[0152] In some embodiments, the mass content of 1,3 - propane sultone in the electrolyte is from 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.

[0153] When the mass content of 1,3 - propane sultone is 0, it means that 1,3 - propane sultone may not be added to the freshly prepared electrolyte, or the electrolyte obtained after disassembling the battery cell does not contain 1,3 - propane sultone. Generally speaking, since the consumption of 1,3 - propane sultone during the film - forming process is less, the mass content of 1,3 - propane sultone in the freshly prepared electrolyte is slightly greater than that in the electrolyte after disassembly.

[0154] Both 1,3 - propane sultone and vinylene carbonate can form a dense SEI film on the negative electrode side, which can effectively alleviate the risk of carboxylic ester solvents penetrating the SEI film and reacting with the negative electrode active material.

[0155] When the mass content of 1,3 - propane sultone is greater than 0 and less than or equal to 0.5%, the impedance of the formed SEI film will not be too high, which can reduce the impedance on the basis of alleviating side reactions and improve the fast charging performance and cycle performance of the battery cell.

[0156] In some embodiments, the mass content of the ethylene carbonate derivative in the electrolyte is from 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.

[0157] Optionally, the freshly prepared electrolyte includes ethylene carbonate derivatives. In the freshly prepared electrolyte, the mass content of the ethylene carbonate derivatives is greater than 0. The ethylene carbonate derivatives preferentially form a film. After adding a certain content of ethylene carbonate derivatives to the freshly prepared electrolyte, due to the large consumption of the ethylene carbonate derivatives during the film-forming stage, the ethylene carbonate derivatives may not be detectable in the battery cells obtained after disassembly.

[0158] Vinylene carbonate continuously participates in the formation of the SEI film during the cycling of the battery cells, alleviating the risk of carboxylic ester solvents penetrating the SEI film. However, the organic component content of this SEI film is relatively high, resulting in a relatively high impedance of the SEI film; while the ethylene carbonate derivatives can preferentially form a film, can 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 cells.

[0159] Under fast charging, the above three substances jointly participate in the formation of the SEI film. It can not only reinforce the SEI film through a low content of 1,3-propane sultone, and vinylene carbonate can further reinforce the film-forming, reducing the risk of carboxylic ester solvents penetrating the SEI film and improving the cycling performance of the battery cells; an appropriate content of ethylene carbonate derivatives can reduce the film-forming impedance and improve the fast charging performance, and the mass content of the ethylene carbonate derivatives is not too high, which can reduce the risk of thermal decomposition at high temperature and further improve the cycling performance of the battery cells; thereby improving the fast charging performance and cycling performance of the battery cells.

[0160] In the embodiments of the present application, the ethylene carbonate derivatives refer to at least one hydrogen atom of ethylene carbonate being substituted, and the substituting groups can be one, two, three, four, etc.

[0161] Exemplarily, the ethylene carbonate derivatives include the compounds shown in Formula A,

[0162] Formula A,

[0163] In Formula A, Q1, Q2, Q3, and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not simultaneously hydrogen atoms.

[0164] Q1, Q2, Q3, and Q4 are not simultaneously hydrogen atoms. In other words, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0165] Exemplarily, one of Q1, Q2, Q3, and Q4 includes a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and the rest are hydrogen atoms.

[0166] Exemplarily, at least two of Q1, Q2, Q3, and Q4 include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0167] Exemplarily, at least three of Q1, Q2, Q3, and Q4 include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0168] Exemplarily, Q1, Q2, Q3, and Q4 each independently include a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group.

[0169] Optionally, at least one of Q1, Q2, Q3, and Q4 includes a halogen atom or a C1-C5 haloalkyl group. The halogen atom includes a fluorine atom, a bromine atom, or a chlorine atom, etc., and may be a fluorine atom. The C1-C5 haloalkyl group includes a C1-C5 fluoroalkyl group, a C1-C5 bromoalkyl group, or a C1-C5 chloroalkyl group, etc., and may be a fluorine atom. For example, the C1-C5 fluoroalkyl group includes fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, or fluoropentyl.

[0170] When the ethylene carbonate derivative includes a fluorine atom, the ethylene carbonate derivative can form a film layer rich in F and Li on the negative electrode side, which can make the impedance of the film layer lower while protecting the negative electrode active material, and can more effectively balance the improvement of the cycle performance and fast charging performance of the battery cell.

[0171] 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.

[0172]

[0173] The above materials can further improve the cycle performance and fast charging performance of the battery cell.

[0174] 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. Further optionally, the ethylene carbonate derivative includes the compound shown by Formula A-1.

[0175] In some embodiments, the additive further includes a lithium salt additive. 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 SEI film performance on the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0176] In some embodiments, the mass content of the lithium salt additive in the electrolyte is from 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 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 cycle performance of the battery cell.

[0177] Exemplarily, the lithium salt additive includes lithium difluorophosphate, and the mass content of lithium difluorophosphate in the electrolyte is from 0.02% to 0.5%.

[0178] Exemplarily, the lithium salt additive includes lithium fluorosulfonate, and the mass content of lithium fluorosulfonate in the electrolyte is from 0.02% to 0.5%.

[0179] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes lithium hexafluorophosphate LiPF6. Optionally, the electrolyte further includes a lithium fluorosulfonylimide salt, which can improve the cycle performance of the battery cell.

[0180] Optionally, the lithium fluorosulfonylimide includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0181] In some embodiments, the mass content of the lithium salt is from 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.

[0182] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte have the meanings well known in the art, and can be detected by equipment and methods well known in the art. For example, reference can be made to the standard JY / T020-1996 "General Rules for Ion Chromatographic Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography analysis method. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or the battery cell that has been discharged (discharged to the discharge cut-off voltage so that the charged state of the battery cell is about 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 method.

[0183] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to GB / T 9722-2006 General Rules for Gas Chromatography of Chemical Reagents to qualitatively and quantitatively analyze the organic components of the electrolyte by gas chromatography.

[0184] [Negative electrode plate]

[0185] 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.

[0186] The upper charge limit voltage and the discharge cut-off voltage of the battery cell are different according to the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper charge limit voltage can be 3.65 V and the discharge cut-off voltage can be 2.0 V. Another example is that when the phosphate material includes lithium manganese iron phosphate, the upper charge limit voltage can be 4.2 V and the discharge cut-off voltage can be 2.0 V. Next, taking the upper charge limit voltage of 3.65 V and the discharge cut-off voltage of 2.0 V as an example, the state of the battery cell will be described: In the embodiments of the present application, the 100% state of charge (SOC) and 0% SOC of the battery cell are defined as follows.

[0187] The battery cell is charged at a constant current charging rate of 0.33C to the upper charge limit voltage, and then charged at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell. The battery cell is discharged at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0188] 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, 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 、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 the range composed of any two of the above values.

[0189] 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 active material in the negative electrode film layer is stacked relatively closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, 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.

[0190] 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 2 or 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 .

[0191] 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, which can improve the cycle performance of the battery cell.

[0192] 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 using the equipment and methods well-known in the art. Disassemble the negative electrode sheet 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 the negative electrode sheet with single-sided coating (if it is a double-sided coated sheet, 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 weighed negative electrode sheet, 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 sheet - 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 sheet - 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.

[0193] In the embodiments of the present application, the negative electrode active material includes carbon-based materials, and the carbon-based materials include graphite particles. The graphite particles have relatively high cycle stability and can improve the cycle performance of the battery cell. The positive electrode active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. When used in combination, the battery cell has relatively excellent cycle performance.

[0194] 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.

[0195] When the graphitization degree of the graphite particles is within the above range, the graphite particles have relatively excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet and the battery cell, and can improve the fast charging performance of the battery cell.

[0196] In some embodiments, the volume average particle size Dv50 of the graphite particles is 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.

[0197] The volume average particle size of the graphite particles is relatively small, resulting in a short 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 large, and the side reaction with carboxylic ester solvents in the electrolyte is relatively intense. The electrolyte is further added with an additive, which can form a film preferentially 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.

[0198] 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.

[0199] In some embodiments, the graphite particles include a graphite body particle and a negative electrode coating layer. The graphite body particle includes secondary particles, and the secondary particles include a plurality of primary particles. The negative electrode coating layer is coated on the surface of the graphite body particle, and the negative electrode coating layer includes carbon elements. The carbon in the negative electrode coating layer is mainly amorphous carbon, and amorphous carbon refers to a transition carbon material with a very low degree of graphitization crystallization and an approximate amorphous form (or no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0200] The graphite body particle includes secondary particles. There are many migration paths for lithium ions in the graphite body particle, and the migration path in the primary particle is short, which can improve the migration rate of lithium ions. The negative electrode coating layer has many end faces and defects, so that the number of sites capable of intercalating and deintercalating lithium ions is more, 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.

[0201] Exemplarily, the graphite body particle includes at least one of artificial graphite and natural graphite, and may be artificial graphite.

[0202] Optionally, the thickness of the negative electrode coating layer is 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.

[0203] When the thickness of the negative electrode coating layer is within the above range, it can further improve the conductivity of the graphite particles, reduce the internal resistance of the negative electrode sheet, reduce the heat generation of the battery cell, and can improve the cycle performance of the battery cell.

[0204] In the embodiments of the present application, the graphite particles can be prepared by methods well-known in the art. Taking artificial graphite as an example of the graphite body particles, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and after carbonization treatment, forming a negative electrode coating layer on at least a part of the surface of the artificial graphite particles.

[0205] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of coal tar pitch and petroleum pitch is below 250°C.

[0206] 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 a part of the surface of the artificial graphite.

[0207] Optionally, the carbonization treatment time is from 1 h to 6 h.

[0208] 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.

[0209] In some embodiments, in addition to graphite particles, the negative electrode active material may further include a silicon-based material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0210] Optionally, based on the mass of the negative electrode film layer, the mass content of silicon element in the silicon-based material is from 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 any range composed of any two of the above values.

[0211] 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.

[0212] 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.

[0213] In some embodiments, in addition to the above-mentioned carbon-based materials and optional silicon-based materials, 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.

[0214] The qualitative and quantitative determination of each substance or element in this application can be detected by suitable equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used jointly for qualitative or quantitative determination.

[0215] 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 testing and qualitative analysis on the negative electrode sheet or the negative electrode active material.

[0216] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). There are voids between flaky structures in the SEM cross-sectional view of natural graphite, while the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or they can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, while only 2H phase exists in the XRD spectrum of artificial graphite.

[0217] In the embodiments of this application, the negative electrode film layer includes at least one layer of film layer, which can be a single-layer film layer or at least two layers of film layers. The negative electrode film layer can include two layers of film layers, three layers of film layers, four layers of film layers, or even more layers of film layers. Optionally, the negative electrode film layer includes at least two layers of film layers.

[0218] When the negative electrode film layer adopts a single-layer film layer, the negative electrode active material in the negative electrode film layer includes carbon-based materials, and optionally also includes silicon-based materials.

[0219] When the negative electrode film layer adopts at least two layers of film layers, the negative electrode active material in the negative electrode film layer includes carbon-based materials, and optionally also includes silicon-based materials. The silicon-based materials can be located in one of the at least two layers of film layers, or can be located in at least two of the at least two layers of film layers. The negative electrode film layer can include two layers of film layers, three layers of film layers, four layers of film layers, or even more layers of film layers.

[0220] 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 portion. 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 portion. 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 may be the same or different.

[0221] The interface between the first negative electrode film layer and the second negative electrode film layer may be regular or irregular, and optionally is irregular.

[0222] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0223] The negative electrode film layer includes at least two 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, the pore differences of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission can be reduced, and the fast charging performance of the battery cell can be improved.

[0224] 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.

[0225] There are differences in the particle sizes in 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 fast charging, 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 improve the problem of lithium deposition on the surface layer of the negative electrode plate.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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 third hand, the negative electrode active material in the second negative electrode film layer with the above particle size range cooperates with the negative electrode active material 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.

[0230] 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 the 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 transmission can be reduced, and the fast charging ability of the battery cell can be improved.

[0231] In the embodiment of the present application, the negative electrode plate is cut along the thickness direction of the plate 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 particle refers to the longest straight line passing through the center point of the particle and extending to the outer periphery of the particle.

[0232] 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 analyzed, and the average value calculated is the average longest diameter.

[0233] 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.

[0234] 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 (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0235] In some embodiments, the negative electrode film layer may optionally further include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. 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%.

[0236] In some embodiments, the negative electrode film layer may optionally further include other additives. As an example, the other additives may include a thickener, a dispersant, 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%.

[0237] In some embodiments, the negative electrode current collector part may adopt a metal foil or a composite current collector part. 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 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 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).

[0238] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative electrode current collector part and then drying and cold pressing. The negative electrode slurry is usually 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.

[0239] The negative electrode tab does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode tab of the embodiment of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode tab of the embodiment of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0240] In some embodiments, the negative electrode tab further includes a negative electrode conductive layer, and the negative electrode conductive layer is 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 tab, reduce the heat generation of the negative electrode tab, thereby reducing the heat generation of the battery cell, and improving the fast charging performance and cycle performance of the battery cell.

[0241] [Positive electrode tab]

[0242] The positive electrode tab includes a positive electrode current collector 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.

[0243] In some embodiments, when the battery cell is in the 0% state of charge (SOC), the tap density of the positive electrode film layer is 2.3 g / cm 3 to 2.6 g / cm 3 . Exemplarily, when the battery cell is in the 0% state of charge (SOC), 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 in the 0% state of charge (SOC), the tap density of the positive electrode film layer is 2.4 g / cm 3 to 2.55 g / cm 3 .

[0244] 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 active material in the positive electrode film layer is stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during rapid charging and improving the cycle performance and rapid charging performance of the battery cell.

[0245] 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 the 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 .

[0246] 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 is not too large, improving the cycle performance and rapid charging performance of the battery cell.

[0247] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell at 0% state of charge (SOC) can be detected by the following method. Disassemble the positive electrode sheet from the battery cell at 0% SOC, and measure the compaction density of the positive electrode film layer. For example, take a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, one side of the positive electrode film layer 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 above weighed positive electrode sheet, weigh the weight of the positive current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode sheet - the weight M0 of the positive current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode sheet - the thickness H0 of the positive current collector, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0248] 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 spherical-like.

[0249] 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.

[0250] 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 the 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.

[0251] 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 the 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.

[0252] 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 containing lithium phosphate and the average particle size 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.

[0253] In the cross-section of the positive electrode film layer along its own thickness direction, the longest diameters of the primary particles containing lithium phosphate in the cross-section are counted, and the average value of the longest diameters of the primary particles containing lithium phosphate is calculated; then the average value of the longest diameters of, for example, 50 primary particles containing lithium phosphate is counted as the average longest diameter.

[0254] In the cross-section of the positive electrode film layer along its own thickness direction, the particle sizes of all the secondary particles containing lithium phosphate in the cross-section are counted, and the average value of the particle sizes of the secondary particles containing lithium phosphate is calculated as the average particle size of the secondary particles.

[0255] In the embodiments of the present application, the lithium-containing phosphate of olivine structure can be phosphate particles or a material obtained by modifying them. For example, the lithium-containing phosphate of olivine structure includes phosphate particles and a cathode additive element. The cathode additive element is located in the phosphate particles, and can be located inside the phosphate particles or coated on the surface of the phosphate particles. The cathode additive element contains at least one element of aluminum (Al), vanadium (V), titanium (Ti), and niobium (Nb).

[0256] The above-mentioned cathode additive element can improve the crystal structure stability of the cathode active material, enhance the pressure resistance of the lithium-containing phosphate, and is beneficial to improving the compaction density of the cathode film layer, as well as enhancing the energy density and cycle performance of the battery cell.

[0257] In some embodiments, the mass content of aluminum element in the lithium-containing phosphate is 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 aluminum element is within the above range, it can improve the pressure resistance of the lithium-containing phosphate, and is beneficial to improving the compaction density of the cathode film layer, as well as enhancing the energy density and cycle performance of the battery cell.

[0258] In some embodiments, the mass content of vanadium element in the lithium-containing phosphate is 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 the range composed of any two of the above values. 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, as well as enhancing the energy density and cycle performance of the battery cell.

[0259] 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, the crystal structure of the positive electrode active material can be further improved, and the cycle performance can be improved.

[0260] 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, the crystal structure of the positive electrode active material can be further improved, and the cycle performance can be improved.

[0261] 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 above materials have excellent cycle stability and can improve the cycle performance of the battery cell.

[0262] 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 z1A compound, wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, 0.5 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5, 0 ≤ c1 ≤ 0.5, 3 ≤ z1 ≤ 5, A includes at least one of Na, K, and Mg; Me includes at least one of Mn, Fe, Co, and Ni; M includes at least one of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes at least one of Cl, C, N, and P; Y includes at least one of O and F.

[0263] The lithium-containing phosphate has excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0264] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur. The molar content of Li is different when the battery cell is discharged to different states. In the enumeration of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of Li is the initial state of the material, that is, the state before feeding. When the cathode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, in the enumeration of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of oxygen O is only the theoretical state value, and 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.

[0265] In the embodiments of the present application, the content of elements in the cathode 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 atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After the battery cell is discharged to 0% state of charge (SOC) and the cathode electrode sheet is disassembled, it is cleaned with DMC and dried, and then after high-temperature calcination to remove impurities, 0.4 g of the cathode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a 180 °C flat plate 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.

[0266] In some embodiments, the positive electrode film layer may optionally further include a positive electrode conductive agent. There is no particular limitation on the type of the positive electrode conductive agent in the embodiments of the present application. 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%.

[0267] In some embodiments, the positive electrode film layer may optionally further include a positive electrode binder. There is no particular limitation on the type of the positive electrode binder in the embodiments of the present application. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0268] In some embodiments, the positive electrode current collector part can adopt a metal foil or a composite current collector. As an example of the metal foil, at least one foil of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy can be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0269] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode current collector part and then drying and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0270] The positive electrode plate does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode plate of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector part and the positive electrode film layer and disposed on the surface of the positive electrode current collector part. In some other embodiments, the positive electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0271] [Separator membrane]

[0272] In the embodiments of the present application, the separator membrane is disposed between the positive electrode plate and the negative electrode plate to isolate the positive electrode plate and the negative electrode plate.

[0273] In some embodiments, the porosity of the separator membrane is from 20% to 70%, optionally from 35% to 60%. Exemplarily, the porosity of the separator membrane is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range composed of any two of the above values.

[0274] When the porosity of the separator membrane in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator membrane can be improved, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0275] In the embodiments of the present application, the porosity refers to the percentage of the internal pore volume of the separator membrane occupying the total volume of the separator membrane. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin Separator for Battery Cell". It should be noted that in the actual testing process, the testing process slightly different from the standard can be adopted according to the differences in testing instruments, testing errors, and in order to eliminate the influence on the porosity test as much as possible, so as to obtain a more accurate test value.

[0276] In some embodiments, the thickness of the separator membrane is from 4 μm to 12 μm, optionally from 5 μm to 9 μm. Exemplarily, 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 composed of any two of the above values.

[0277] When the thickness of the separator membrane is within the above range, the migration path of lithium ions in the separator membrane is shorter, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0278] In the embodiments of the present application, the separator membrane can 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 can 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.

[0279] In some embodiments, the base film includes at least one of glass fiber, non-woven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0280] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0281] 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.

[0282] In some embodiments, the functional layer may include inorganic particles, and 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.

[0283] In the embodiments of the present application, the meaning of the thickness of the separator is the meaning well known in the art, and it can be detected by using the meaning and equipment well known in the art. For example, a newly prepared separator 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 is obtained from the battery cell, and the separator is dried and used as a sample. The separator is cut off by 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 and its respective layers.

[0284] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly by a stacking process.

[0285] Figure 1 and Figure 2 shows a schematic structural diagram of a battery cell.

[0286] In some embodiments, the battery cell 7 may include a housing 20.

[0287] The housing 20 can be in various shapes, such as a cylinder, a cuboid, etc. The shape of the housing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, the housing 20 can be selected as a cylindrical structure. If the electrode assembly 10 is a cuboid structure, the housing 20 can be selected as a cuboid structure. Optionally, the electrode assembly 10 is a cuboid structure.

[0288] The material of the housing 20 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not make special restrictions on this. Optionally, the inner wall of the housing 20 may further include an insulating layer, and the insulating layer can separate the housing 20 and the electrode assembly 10. The material of the insulating layer can be selected from the materials commonly used in the art and is not specifically limited here.

[0289] One or more electrode assemblies 10 accommodated in the housing 20 may be included.

[0290] In some embodiments, the housing 20 includes a housing body 21 and an end cap 22. The housing body 21 has an opening, and the end cap 22 covers the opening. The housing body 21 accommodates the electrode assembly 10 and the electrolyte.

[0291] In some embodiments, the housing 21 is made of steel, which has high mechanical strength and is not easily deformed, thereby improving the reliability and cycle performance of the battery cells. Optionally, steel accounts for the largest proportion of the housing 21 by mass.

[0292] 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, or 400 mm, or a range consisting of any two of the foregoing values. When the length of the battery cell 7 is within the foregoing range, the energy density of the battery cell 7 is increased, and the electron transmission path in the length direction is not excessively long, which is beneficial for improving the fast charging capability of the battery cell 7. Figure 1 Z1 shown in represents the length of the battery cell 7 .

[0293] The electrolyte has relatively high conductivity, low viscosity, and excellent fluidity. It can quickly infiltrate the electrode in the length direction, so that the reaction degree of the electrode in the length direction is relatively consistent. When the active ions migrate to the negative electrode 12, lithium plating and other problems are not likely to occur, which is beneficial to improving the reliability and cycle performance of the battery cell 7.

[0294] In some embodiments, the width of the battery cell 7 is between 80 mm and 130 mm, for example, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, or a range consisting of any two of these values. When the width of the battery cell 7 is within this range, the energy density of the battery cell 7 is increased. Furthermore, the electron transmission path in the width direction is not excessively long, which improves the fast charging capability of the battery cell 7. Figure 1 Y1 shown in FIG. 7 represents the width of the battery cell 7 .

[0295] In some embodiments, the thickness of the battery cell 7 is between 25 mm and 60 mm, for example, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, or a range consisting of any two of the foregoing values. When the thickness of the battery cell 7 is within the foregoing range, it facilitates rapid heat release from the battery cell 7, reduces the risk of electrolyte decomposition due to heat accumulation, and improves the cycle performance of the battery cell 7. Figure 1 X1 shown in represents the thickness of the battery cell 7 .

[0296] Next, the electrode assembly 10 is described as a laminated structure.

[0297] As Figure 3 shown, when the electrode assembly 10 is of 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.

[0298] In some embodiments, as Figure 4 shown, the positive electrode plate 11 includes at least one positive electrode tab 111, and the 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.

[0299] For example, the 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.

[0300] 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 electron transmission path in the length direction Z, improve the electron transmission rate, and improve the fast charging ability of the battery cell 7.

[0301] As Figure 5 and Figure 6 shown, in some embodiments, the positive electrode plate 11 satisfies: n*W1 / W2 is 0.9 to 1.0;

[0302] n represents the number of all positive electrode tabs 111 on the same side of the positive current collector 112;

[0303] W1 represents the average size of the positive electrode tab 111 along the width direction Y;

[0304] W2 represents the size of the positive current collector 112 along the width direction Y.

[0305] 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.

[0306] 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.

[0307] W1 represents the average dimension of the positive electrode tab 111 in the width direction Y.

[0308] 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 the average value of the dimensions of the positive electrode tab 111 in the width direction Y can be calculated therefrom. Of course, the dimensions of the positive electrode tab 111 in the width direction Y at each location can be the same value, and in this case, this value can be used as the average dimension of the positive electrode tab 111.

[0309] There can be one or more positive electrode tabs 111. For example, n ranges from 1 to 4. When there are multiple positive electrode tabs 111 on the same side of the positive current collector 112, the average dimension of each positive electrode tab 111 can be measured respectively, and then the sum of the average dimensions is divided by the number of positive electrode tabs 111 to calculate the average dimension of the positive electrode tabs 111.

[0310] The positive electrode tab 111 is connected to the positive current collector 112. The positive electrode tab 111 includes a first end 1111 connected to the positive 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 current collector 112 is relatively large, the current-carrying capacity of the positive electrode tab 111 is strong, and the fast charging performance and cycling performance of the battery cell 7 can be improved.

[0311] Optionally, the positive electrode tab 111 and the positive current collector 112 are of an integral structure, so that the internal resistance of the positive electrode plate 11 is low, and the cycling performance of the battery cell 7 can be further improved.

[0312] As Figure 7 shown, in some other embodiments, at least one positive electrode tab 111 can also be connected to the positive current collector 112 and extend out of the positive current collector 112 along the width direction Y of the battery cell 7.

[0313] As Figure 8 and Figure 9 shown, in some embodiments, the negative electrode plate 12 includes at least one negative electrode tab 121, and at least one negative electrode tab 121 is connected to the negative current collector 122 and extends out of the negative current collector 122 along the length direction Z of the battery cell 7. Of course, at least one negative electrode tab 121 can also be connected to the negative current collector 122 and extend out of the negative current collector 122 along the width direction Y of the battery cell 7.

[0314] For example, as Figure 8 shown, at least one negative electrode tab 121 can be disposed on the same side of the negative current collector 122 along the length direction Z.

[0315] For another example, as Figure 9 shown, in the same negative electrode tab 12, there are multiple negative electrode tabs 121, and the multiple negative electrode tabs 121 can be arranged on both sides of the negative electrode current collector 122 along the length direction Z. The negative electrode tabs 121 are arranged on both sides of the negative electrode current collector 122, which can shorten the transmission path of electrons in the length direction Z, improve the electron transmission rate, and enhance the fast charging ability of the battery cell 7.

[0316] In some embodiments, the negative electrode tab 12 satisfies: m*W3 / W4 is 0.9 to 1.0;

[0317] m represents the number of all negative electrode tabs 121 on the same side of the negative electrode current collector 122;

[0318] W3 represents the average size of the negative electrode tab 121 along the width direction Y;

[0319] W4 represents the size of the negative electrode current collector 122 along the width direction Y.

[0320] 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.

[0321] When m*W3 / W4 satisfies the above range, the current-carrying area of the negative electrode tab 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0322] W3 represents the average size of the negative electrode tab 121 along the width direction Y. The negative electrode tab 121 can be one or more. For example, m is 1 to 4. When there are multiple negative electrode tabs 121, the average size can be calculated by measuring the sizes of each negative electrode tab 121 with a micrometer.

[0323] The negative electrode tab 121 is connected to the negative electrode current collector 122. The negative electrode tab 121 includes a second end 1211 connected to the negative electrode current collector 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 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.

[0324] Optionally, the negative electrode tab 121 and the negative electrode current collector 122 are of an integral structure, so that the internal resistance of the negative electrode tab 12 is low, and the fast charging performance and cycle performance of the battery cell 7 can be further improved.

[0325] For example Figure 10As shown, in some embodiments, the battery cell 7 further includes a positive terminal 31, which is disposed on the outer casing 20 and can be disposed on the housing 21 or the end cap 22.

[0326] 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 the connection without the positive electrode adapter can be adopted, and the positive terminal 31 and the positive electrode tab 111 are directly welded, which can reduce the resistance at the connection and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0327] 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, and the positive terminal 31 and the positive electrode tab 111 are connected through the positive electrode adapter 41. Through the connection of the positive electrode adapter 41, the overcurrent capacity between the positive terminal 31 and the positive electrode tab 111 can be improved, and the fast charging capacity of the battery cell 7 can be improved.

[0328] Optionally, the thickness of the positive electrode adapter 41 is from 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 the range composed of any two of the above values. The thickness of the positive electrode adapter 41 is relatively thick, and the overcurrent capacity is relatively excellent, which can further improve the fast charging capacity of the battery cell 7.

[0329] Exemplarily, the material of the positive electrode adapter 41 can include aluminum, copper, aluminum alloy, copper alloy, etc.

[0330] As [[ID=1,16]] Figure 10 and Figure 11 shown, optionally, the positive electrode adapter 41 includes a first positive electrode transfer portion 411 and a second positive electrode transfer portion 412. The first positive electrode transfer portion 411 is connected to the positive electrode tab 111, the second positive electrode transfer portion 412 is connected to the first positive electrode transfer portion 411 and protrudes from the first positive electrode transfer portion 411 along the length direction Z, and the second positive electrode transfer portion 412 is connected to the positive terminal 31. Through the first positive electrode transfer portion 411 and the second positive electrode transfer portion 412, the positive electrode tab 111 and the positive terminal 31 can be electrically connected, and the overcurrent capacity between the positive electrode tab 111 and the positive terminal 31 can be improved, and the fast charging capacity of the battery cell 7 can be improved.

[0331] Optionally, the ratio of the dimension of the first positive electrode transfer part 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 a range composed of any two of the above values. When the ratio of the dimension of the first positive electrode transfer part 411 in 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 positive electrode tab 111 to the positive terminal 31 through the positive electrode transfer member 41 is relatively short, which can improve the fast charging ability of the battery cell 7. Figure 11 As shown, Y2 represents the dimension of the first positive electrode transfer part 411 in the width direction Y, and Y2 / Y1 represents the ratio of the dimension of the first positive electrode transfer part 411 in the width direction Y to the width of the battery cell 7.

[0332] Optionally, the ratio of the dimension of the second positive electrode transfer part 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 a range composed of any two of the above values. When the ratio of the dimension of the second positive electrode transfer part 412 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 positive electrode tab 111 to the positive terminal 31 through the positive electrode transfer member 41 is relatively short, which can improve the fast charging ability of the battery cell 7. Figure 11 As shown, Z2 represents the dimension of the first positive electrode transfer part 411 in the length direction Z, and Z2 / Z1 represents the ratio of the dimension of the second positive electrode transfer part 412 in the length direction Z to the length of the battery cell 7.

[0333] In some embodiments, the battery cell 7 further includes a negative terminal 32, and the negative terminal 32 is disposed on the outer shell 20, and can be disposed on the housing 21 or the end cap 22.

[0334] 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 a transfer member, or can be directly welded without using a transfer member, which can reduce the resistance at the connection and is beneficial to reducing the overall internal resistance of the battery cell 7.

[0335] Optionally, the negative terminal 32 is disposed on at least one side of the electrode assembly 10 in the width direction Y of the battery cell 7, and the negative terminal 32 and the negative electrode tab 121 are connected through the positive electrode transfer member 41. Through the connection of the negative electrode transfer member 42, the overcurrent capacity between the negative terminal 32 and the negative electrode tab 121 can be improved, and the fast charging ability of the battery cell 7 can be improved.

[0336] Optionally, the thickness of the negative electrode adapter 42 is from 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 electrode adapter 42 has a relatively thick thickness and excellent overcurrent capacity, which can further improve the fast charging capacity of the battery cell 7.

[0337] Exemplarily, the material of the negative electrode adapter 42 may include aluminum, copper, aluminum alloy, copper alloy, etc.

[0338] As Figure 12 shown, optionally, the negative electrode adapter 42 includes a first negative electrode adapter portion 421 and a second negative electrode adapter portion 422. The first negative electrode adapter portion 421 is connected to the negative electrode tab 121, and the second negative electrode adapter portion 422 is connected to the first negative electrode adapter portion 421 and protrudes from the first negative electrode adapter portion 421 along the length direction Z. The second negative electrode adapter portion 422 is connected to the negative terminal 32. Through the first negative electrode adapter portion 421 and the second negative electrode adapter portion 422, the negative electrode tab 121 and the negative terminal 32 can be electrically connected, and the overcurrent capacity of the two can be improved, thereby improving the fast charging capacity of the battery cell 7.

[0339] Optionally, the ratio of the dimension of the first negative electrode adapter portion 421 along the width direction Y to the width of the battery cell 7 is from 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 electrode adapter 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 electrode tab 121 to the negative terminal 32 through the negative electrode adapter 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 electrode adapter portion 421 along the width direction Y, and Y3 / Y1 represents the ratio of the dimension of the first negative electrode adapter portion 421 along the width direction Y to the width of the battery cell 7.

[0340] Optionally, the ratio of the dimension of the second negative electrode adapter portion 422 along the length direction Z to the length of the battery cell 7 is from 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 adapter portion 422 along 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 adapter 42 is relatively short, which can improve the fast charging capacity of the battery cell 7. Figure 12 As shown, Z3 represents the dimension of the second negative electrode adapter portion 422 along the length direction Z, and Z3 / Z1 represents the ratio of the dimension of the second negative electrode adapter portion 422 along the length direction Z to the length of the battery cell 7.

[0341] 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.

[0342] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, in parallel, or in a combined series-parallel connection. A combined series-parallel connection means that there are both series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series, in parallel, or in a combined series-parallel connection together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodation part of the battery module 6. Of course, it can also be that the multiple battery cells 7 are first connected in series, in parallel, or in a combined series-parallel connection to form battery modules 6, and then the multiple battery modules 6 are connected in series, in parallel, or in a combined series-parallel connection to form a whole and are accommodated in the accommodation part. Optionally, the battery module 6 can also include an accommodation part with an accommodation space, and the multiple battery cells 7 are accommodated in this accommodation space.

[0343] The multiple battery cells 7 of the battery module 6 can be electrically connected through a busbar component to achieve series, parallel, or combined series-parallel connection of the multiple battery cells 7 of the battery module 6. The busbar component can be one or more, and each busbar component is used to electrically connect at least two battery cells 7.

[0344] As Figure 14 shown, in some embodiments, the above battery module 6 can also be 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 the battery module 6, or the battery pack 2, or the battery cell 7, and the battery cell 7 can be the smallest unit constituting the battery device.

[0345] The battery pack 2 can include a box body 5 and a plurality of battery modules 6 disposed on the box body 5. The box body 5 includes a first box body part 5a and a second box body part 5b. The box body 5 has an accommodation space 5c. The first box body part 5a is used to cover the second box body part 5b and form a closed space for accommodating the battery module 6. The plurality of battery modules 6 can be arranged in the box body 5 in any manner.

[0346] The first box body part 5a and the second box body part 5b cover each other, and the first box body part 5a and the second box body part 5b jointly define a receiving space 5c for receiving battery cells. The second box body part 5b can be a hollow structure with one end open, and the first box body part 5a is a plate-like structure. The first box body part 5a covers the open side of the second box body part 5b to form a box body 5 with a receiving space 5c. The first box body part 5a and the second box body part 5b can also both be hollow structures with one side open, and the open side of the first box body part 5a covers the open side of the second box body part 5b to form a box body 5 with a receiving space 5c. Of course, the first box body part 5a and the second box body 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0347] To improve the sealing performance after the connection between the first box body part 5a and the second box body part 5b, a sealing member can also be provided between the first box body part 5a and the second box body part 5b, such as sealant, sealing ring, etc.

[0348] Assume that the first box body part 5a covers the top of the second box body part 5b. The first box body part 5a can also be called the upper box cover, and the second box body part 5b can also be called the lower box body.

[0349] Electrical device

[0350] 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 can be used as the power source of the electrical device or can also be used as the energy storage unit of the electrical device. The electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or an extended-range electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc. The electric toy includes fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, electric airplane toys, etc. The electric tool includes metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators and electric planers, etc. The embodiments of the present application do not impose special restrictions on the above-mentioned electrical devices.

[0351] The electrical device can select battery cells, battery modules or battery packs according to its usage requirements.

[0352] Figure 15It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0353] A battery pack 2 is arranged inside the electrical device 1, and the battery pack 2 can be arranged at the bottom, the head or the tail of the electrical device 1. The battery pack 2 can be used for power supply of the electrical device 1. For example, the battery pack 2 can be used as the operating power 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.

[0354] 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, navigation and driving of the electrical device 1.

[0355] 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 a battery cell can be adopted as the power source.

[0356] Embodiment

[0357] 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 are obvious to those skilled in the art within the scope of the content disclosed in the embodiments of the present application. 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.

[0358] Example 1

[0359] 1. Preparation of the positive electrode tab

[0360] The positive electrode tab includes a positive electrode current collector part and a positive electrode film layer. The positive electrode film layer is arranged on both sides of the positive electrode current collector part, and the positive electrode current collector part is an aluminum foil.

[0361] The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode paste (the solvent is N-methylpyrrolidone NMP) on the surface of the positive electrode current collector part and 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.

[0362] 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 four elements added is 1:1:1:1.

[0363] The lithium-containing phosphate includes primary particles and secondary particles formed by the aggregation of the 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 diameter of the secondary particles is 10 μm.

[0364] The single-sided coating weight of the positive electrode film layer is 290 mg / 1540.25 mm 2 。

[0365] 2. Preparation of the negative electrode sheet

[0366] The negative electrode sheet 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.

[0367] The negative electrode film layer is formed by uniformly coating a negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector part and then drying and cold pressing.

[0368] 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, a conductive agent acetylene black, a negative electrode binder styrene-butadiene rubber, and a thickening agent 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 diameter of the graphite particles is 8.5 μm.

[0369] 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, a conductive agent acetylene black, a negative electrode binder styrene-butadiene rubber, and a thickening agent 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 diameter of the graphite particles is 7 μm.

[0370] The mass content of silicon element in the negative electrode film layer is 0.7%.

[0371] 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.

[0372] The single-sided coating weight of the negative electrode film layer is 130 mg / 1540.25 mm 2 。

[0373] 3. Separator

[0374] The separator is a 7-μm polyethylene film layer with a porosity of 35%.

[0375] 4. Preparation of electrolyte

[0376] 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.

[0377] The organic solvents include 16.3% by mass of carboxylate solvents, 35.7% of linear carbonate solvents, and 26.3% of cyclic carbonate solvents.

[0378] 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.

[0379] The electrolyte also includes 0.2% lithium difluorophosphate and 0.1% lithium fluorosulfonate.

[0380] The lithium salt includes 15% by mass of lithium hexafluorophosphate LiPF6.

[0381] The conductivity of the electrolyte is 12.8 ms / cm.

[0382] 5. Preparation of battery cell

[0383] 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.

[0384] 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 。

[0385] 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.

[0386] Examples 2-1 to 2-5

[0387] Battery monomers were prepared using 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.

[0388] Comparative Examples 1-1 and 1-2

[0389] Battery monomers were prepared using a method similar to that of Example 1. Different from Example 1, the mass contents of the solvents were adjusted.

[0390] Performance test

[0391] 1. Quick charging test of battery monomers

[0392] At 25 °C, the battery monomers

[0393] were charged from 0% state of charge (SOC) to 10% SOC at a constant current of 0.33C;

[0394] were charged from 10% SOC to 15% SOC at a constant current of 5.0C;

[0395] were charged from 15% SOC to 20% SOC at a constant current of 4.6C;

[0396] were charged from 20% SOC to 35% SOC at a constant current of 4.2C;

[0397] were charged from 35% SOC to 45% SOC at a constant current of 3.8C;

[0398] were charged from 45% SOC to 50% SOC at a constant current of 3.6C;

[0399] were charged from 50% SOC to 60% SOC at a constant current of 3.4C;

[0400] were charged from 60% SOC to 70% SOC at a constant current of 3.0C;

[0401] were charged from 70% SOC to 75% SOC at a constant current of 2.8C;

[0402] were charged from 75% SOC to 80% SOC at a constant current of 2.4C;

[0403] Record the quick charging time of the battery monomers from 10% SOC to 80% SOC.

[0404] 2. Number of cycles for the battery monomers to cycle to 80% SOH

[0405] At 25 °C, the battery cell is charged at a constant current of 1C to a charging cut-off voltage of 3.65V, then charged at a constant current of 0.05C to a 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%) is 80%, and record the number of cycles. The more cycles, the better the cycle performance of the battery cell.

[0406] When performing charge-discharge tests on the battery cell above, the battery cell can be assembled in a battery device, and the required charge-discharge strategy can be regulated through the battery management system for testing.

[0407] The test results are shown in Table 1.

[0408] Table 1

[0409]

[0410] In Table 1,

[0411] EA represents ethyl acetate;

[0412] EP represents ethyl propionate;

[0413] DMC represents dimethyl carbonate;

[0414] 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;

[0415] EMC represents ethyl methyl carbonate; in Example 2-5, the mass ratio of EMC to DEC is 1:1;

[0416] EC represents ethylene carbonate.

[0417] Detect the components of the electrolytes of the examples and comparative examples.

[0418] 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 relatively high, which is not conducive to fast charging.

[0419] The electrolytes of Comparative Examples 1-2 also include a certain content of linear carbonates. Although it can reduce the additives of carboxylic ester solvents appropriately, the mass content of carboxylic ester solvents in Comparative Examples 1-2 is still relatively high, resulting in a relatively low viscosity and impedance of the electrolyte, which is beneficial for fast charging. However, the side reaction between the carboxylic ester solvent and the negative electrode active material is relatively serious, deteriorating the cycle performance.

[0420] In the embodiments of the present application, 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, 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 can prevent the mass content of the carboxylic ester solvent from being too high, alleviating the side reaction between the carboxylic ester solvent and the negative electrode active material. In addition, the electrolyte also includes additives, which can form an excellent and low-impedance solid electrolyte interface film (SEI film) on the negative electrode side, further alleviating the side reaction, improving the cycle performance, and enhancing the fast charging ability.

[0421] In Examples 2-1 to 2-5, by adjusting the mass content of the carboxylic ester solvent and the linear carbonate solvent, the conductivity can be adjusted. With the increase in conductivity, it is beneficial for the migration of lithium ions in the electrolyte, and the fast charging performance of the battery cell can be improved, shortening the charging time.

[0422] For example, in Example 1, Example 2-1, and Example 2-2, with the increase in the mass content of the carboxylic ester solvent, the conductivity of the electrolyte increases, the migration rate of lithium ions in the electrolyte accelerates, and the fast charging performance of the battery cell can be improved, shortening the charging time. However, due to the increase in the mass content of the carboxylic ester solvent, the degree of side reaction on the negative electrode side is greater, which can deteriorate the cycle performance to a certain extent.

[0423] In Examples 2-3 and 2-4, with the increase in the mass content of the linear carbonate solvent, the conductivity of the electrolyte also increases to a certain extent, improving the fast charging performance of the battery cell and shortening the charging time.

[0424] The carboxylic ester solvent is suitable for different materials, and the linear carbonate solvent is suitable for different materials. For example, Example 2-5 and Example 1 use different solvent materials, which can also improve the fast charging and cycle performance of the battery cell.

[0425] Examples 3-1 to 3-8

[0426] The battery monomer was 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 was 1%, the decrease in the mass content of the organic solvent was 1%, and the mass ratio of each component in the organic solvent remained unchanged, as shown in Table 2 specifically;

[0427] Among them, the electrolytes of Examples 3-8 did not contain lithium difluorophosphate and lithium fluorosulfonate.

[0428] The test results are shown in Table 2.

[0429] Table 2

[0430]

[0431] In Table 2,

[0432] VC represents vinylene carbonate;

[0433] PS represents 1,3-propane sultone;

[0434] FEC represents fluoroethylene carbonate;

[0435] DFEC represents difluoroethylene carbonate;

[0436] For Comparative Example 2-1, the addition amount of the additive in the electrolyte was too low. For example, the addition amount of vinylene carbonate was too low. Although the impedance of the SEI film on the negative electrode side was relatively low, due to the relatively poor protection effect of the SEI film, the carboxylic ester solvent was likely to have a side reaction with the negative electrode active material, deteriorating the cycle.

[0437] For Comparative Example 2-2, the addition amount of the additive in the electrolyte was too high. For example, the addition amount of vinylene carbonate was too high. Vinylene carbonate could form a dense SEI film composed of organic components on the negative electrode side, alleviating the side reaction between the carboxylic ester solvent and the negative electrode active material. However, due to the too high impedance of the SEI film, it was not conducive to the rapid migration of lithium ions, resulting in a longer charging time for the battery monomer.

[0438] For the electrolyte of the embodiment of the present application, the addition amount of the additive is within an appropriate range, and its mass content is 3% to 9%. The reaction potentials of vinylene carbonate and the carboxylic ester solvent in the additive are close, and there is a competitive reaction with the carboxylic ester solvent. Vinylene carbonate can participate in the formation of a dense SEI film on the negative electrode side, making it difficult for the carboxylic ester solvent to penetrate the SEI film to the graphite particles, thereby alleviating the side reaction between the carboxylic ester solvent and the graphite particles and reducing the gas generation amount; moreover, since the additive is within an appropriate content, the film impedance formed on the negative electrode side is relatively small, which is conducive to improving the cycle performance and reducing the risk of lithium deposition.

[0439] Examples 3-1 to 3-8 can obtain an SEI film with relatively low impedance by regulating the mass contents of vinylene carbonate, 1,3-propane sultone, and ethylene carbonate derivatives, thereby improving the fast charging performance and cycling performance of the battery cells.

[0440] In Examples 1, 3-1, and 3-2, as the mass content of vinylene carbonate increases, the protective performance on the negative electrode side is improved, which is beneficial to improving the cycling performance; however, the impedance of the SEI film increases and the fast charging time increases.

[0441] In Examples 1, 3-3, and 3-4, by regulating the mass content of 1,3-propane sultone, as the mass content of 1,3-propane sultone increases, the components of the SEI film can be optimized, the protective effect of the SEI film can be improved, which is beneficial to the improvement of the cycling performance; however, the impedance of the SEI film also increases appropriately, which may slightly deteriorate the fast charging performance of the battery cells. In view of this, the mass content of 1,3-propane sultone is 0 to 0.5%, and can be selected as 0.2% to 0.5% to balance the improvement of the cycling performance and fast charging performance of the battery cells.

[0442] In Examples 1, 3-5, and 3-6, by regulating the mass content of fluoroethylene carbonate, as the mass content of fluoroethylene carbonate increases, the components of the SEI film can be optimized, the impedance of the SEI film can be reduced, which is beneficial to the rapid migration of lithium ions and improves the fast charging performance of the battery cells; 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 cycling performance and fast charging performance of the battery cells.

[0443] 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 cycling performance and fast charging performance of the battery cells.

[0444] Using ethylene carbonate derivatives of different materials, such as fluoroethylene carbonate and difluoroethylene carbonate, can effectively improve the cycling performance and fast charging performance of the battery cells.

[0445] 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 cycling performance.

[0446] Examples 4-1 and 4-2

[0447] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1,

[0448] In Example 4-1, the single-sided coating weight of the positive and negative electrode film layers was adjusted;

[0449] In Example 4-2, the compaction density of the positive and negative electrode film layers was adjusted.

[0450] The test results are shown in Table 3.

[0451] Table 3

[0452]

[0453] Compared with Example 1, the single-sided coating weight of the positive and negative electrode film layers in Example 4-1 was smaller, resulting in a relatively lower energy density of the battery monomer. The migration path of lithium ions in the positive and negative electrode film layers was shortened, which was more conducive to achieving fast charging and shortening the charging time. Moreover, due to the reduction of the single-sided coating weight, the total amount of active materials participating in the side reactions on the negative electrode side decreased, which was beneficial to improving the cycling performance.

[0454] In Example 4-2, the compaction density of the positive and negative electrode film layers increased, resulting in a relatively higher energy density of the battery monomer. However, the migration resistance of lithium ions in the positive and negative electrode film layers increased, resulting in a longer 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 increased, and the cycling performance deteriorated slightly.

[0455] Example 5

[0456] The battery monomer was prepared by a preparation method similar to that of Example 1. Different from Example 1, the volume average particle size of the graphite particles was adjusted.

[0457] Example 6

[0458] The battery monomer was prepared by a preparation method similar to that of Example 1. Different from Example 1, the negative electrode film layer in 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 and then drying and cold pressing.

[0459] 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 thickener carboxymethyl cellulose sodium 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%.

[0460] Example 7

[0461] The battery single cells were prepared by 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%.

[0462] Example 8

[0463] The battery single cells were prepared by a preparation method similar to that of Example 1. Different from Example 1, the particle size of the lithium-containing phosphate was adjusted.

[0464] Example 9

[0465] The battery single cells were prepared by 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.

[0466] Example 10

[0467] The battery single cells were prepared by 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.

[0468] The test results are shown in Table 4.

[0469] Table 4

[0470]

[0471] 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 possibly slightly deteriorating the cycle performance of the battery.

[0472] 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 single 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.

[0473] 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 single 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 single cell.

[0474] The particle sizes of the lithium-containing phosphates in Example 1 and Example 8 are different. As the particle size decreases, the solid-phase transport path of lithium ions shortens, 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 a possible increase in side reactions and a slight deterioration of the battery's cycle performance.

[0475] Compared with the lithium-containing phosphate in Example 9 without adding a cathode additive element, the lithium-containing phosphates in Example 1 and Example 10 are added with a cathode additive element, which can improve the cycle stability of the lithium-containing phosphate and enhance the cycle performance. With the appropriate increase of the cathode additive element, the improvement effect is more excellent.

[0476] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principle, and scope of the present application.

Claims

1. A battery cell, characterized in that, It includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate and a negative electrode plate stacked along the thickness direction of the battery cell. The positive electrode plate includes a positive current collector portion and a positive electrode film layer provided on at least one side of the positive current collector portion. The positive electrode film layer includes a lithium-containing phosphate with an olivine structure. The negative electrode plate includes a negative current collector portion and a negative electrode film layer provided on at least one side of the negative current collector portion. The negative electrode film layer includes graphite particles. The electrolyte includes a carboxylate 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%. The additive includes 1,3-propane sultone 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 a compound represented by Formula A. Formula A, In Formula A, Q1, Q2, Q3, and Q4 each independently include any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and Q1, Q2, Q3, and Q4 are not simultaneously hydrogen atoms.

2. The battery cell according to claim 1, wherein, 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 the 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-C5 haloalkyl 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 a compound represented by Formula A-1 to a compound 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, 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. 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. The lithium salt additive includes at least one of lithium difluorophosphate, lithium fluorosulfonate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

14. The battery cell according to claim 13, wherein, 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, When the battery cell is at 0% state of charge, the tap density of the negative electrode film layer is 1.30 g / cm 3 to 1.52 g / cm 3 , and / or, 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 .

16. The battery cell according to any one of claims 1 to 2, characterized in that, 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.

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

18. The battery cell according to claim 16, wherein the graphitization degree of the graphite particles is 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 100 nm to 500 nm.

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

20. The battery cell according to any one of claims 1 to 2, characterized in that, The negative electrode film layer includes: a first negative electrode film layer disposed on the surface of the negative electrode current collector portion; a second negative electrode film layer disposed on a side of the first negative electrode film layer facing away from the negative electrode current collector 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 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.

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

22. The battery cell according to claim 20, wherein, 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, When the battery cell is at a state of charge (SOC) of 0%, the tap density of the positive electrode film layer is 2.3 / cm 3 to 2.6 g / cm 3 ; and / or 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 .

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 includes: phosphate particles, and a positive electrode additive element located in the phosphate particles, the positive electrode additive element includes at least one element 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 [[ID= ​ ​ 28. The battery cell according to claim 26, wherein ​ 29. The battery cell according to any one of claims 1 to 2, characterized in that, The lithium-containing phosphate includes a compound having the general formula Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 , ​ ​ ​ The positive electrode tab includes at least one positive electrode tab ear, and the at least one positive electrode tab ear is connected to the positive current collector and extends out of the positive current collector along the length direction of the battery cell; and / or The negative electrode tab includes at least one negative electrode tab ear, and the at least one negative electrode tab ear is connected to the negative current collector and extends out of the negative current collector along the length direction of the battery cell.

31. The battery cell according to claim 30, wherein, The positive electrode tab satisfies that 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 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 current collector along the width direction; and / or The negative electrode tab satisfies that 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 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 current collector along the width direction.

32. The battery cell according to claim 30, characterized in that, The battery cell further includes a positive terminal and a positive 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 electrode tab ear through the positive adapter; and / or The battery cell further includes a negative terminal and a negative 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 electrode tab ear through the negative adapter.

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

34. The battery cell according to claim 32, wherein The positive adapter includes a first positive adapter portion and a second positive adapter portion. The first positive adapter portion is connected to the positive electrode tab ear, the second positive adapter portion is connected to the first positive adapter portion and protrudes from the first positive adapter portion along the length direction, and the second positive adapter portion is connected to the positive terminal; the ratio of the size of the first positive adapter portion along the width direction to the width of the battery cell is 0.2 to 0.5; and / or the ratio of the size of the second positive adapter 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 adapter includes a first negative adapter portion and a second negative adapter portion. The first negative adapter portion is connected to the negative electrode tab ear, the second negative adapter portion is connected to the first negative adapter portion and protrudes from the first negative adapter portion along the length direction, and the second negative adapter portion is connected to the negative terminal; the ratio of the size of the first negative adapter portion along the width direction to the width of the battery cell is 0.2 to 0.5; and / or the ratio of the size of the second negative adapter 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, wherein the length of the battery cell is 200 mm to 400 mm; and / or The width of the battery cell is from 80 mm to 130 mm; and / or The thickness of the battery cell is from 25 mm to 60 mm.

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

38. An electrical device, characterized in that, Comprising the battery device according to claim 37.

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