Battery cells, battery devices, and power-consuming devices

Abstract

The present disclosure provides a battery cell, a battery device, and an electric device. The battery cell includes an electrode assembly. Along the extension direction of the tab connection edge of the positive electrode main body, the total width of the positive electrode tab accounts for 50%-100% of the total size of the tab connection edge. Along the extension direction of the tab connection edge of the negative electrode main body, the total width of the negative electrode tab accounts for 50%-100% of the total size of the tab connection edge. The coating weight of a single layer of negative electrode active material is 0.1g / 1540.25mm 2 ‑0.145 g / 1540.25 mm 2 The electrolyte includes at least one of dimethyl carbonate and a linear carboxylate, wherein the linear carboxylate has a structural formula of R1-COO-R2, and R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl groups; based on the total mass of the organic solvent, the mass fraction of the first solvent is 4%-72%.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to PCT patent application No. PCT / CN2024 / 107376 filed on July 24, 2024, and incorporates its entirety into this document. Technical Field

[0003] The present application relates to the field of battery technology, and in particular, to battery cells, battery devices, and electrical devices. Background Art

[0004] Lithium-ion battery cells are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, and electric vehicles. As the scope of battery cell applications gradually expands, the market is also placing higher demands on battery performance. However, current batteries still have many shortcomings in their application, and their fast-charging performance needs to be further improved.

[0005] It should be noted that the above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0006] In the first aspect of the present application, the present application proposes a battery cell, comprising: an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode current collector comprises a positive electrode main body and at least one positive electrode ear portion, the ear connection edge of the positive electrode main body is connected to the positive electrode ear portion, and along the direction in which the ear connection edge extends, the total width of the positive electrode ear portion accounts for The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode current collector comprises a negative electrode main body and at least one negative electrode ear portion. The ear connection edge of the negative electrode main body is connected to the negative electrode ear portion. Along the direction in which the ear connection edge extends, the total width of the negative electrode ear portion accounts for 50%-100% of the total size of the ear connection edge of the negative electrode main body. The coating weight of a single layer of the negative electrode active material layer is 0.1g / 1540.25mm 2 -0.145 g / 1540.25 mm 2The electrolyte comprises an organic solvent, including a first solvent, the first solvent comprising at least one of dimethyl carbonate and a linear carboxylic acid ester, wherein the linear carboxylic acid ester has the structural formula R1-COO-R2, and R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl groups; the mass fraction of the first solvent is 4%-72% based on the total mass of the electrolyte. This can effectively improve the fast-charging performance of the battery cell and enhance the performance of the battery cell under fast-charging conditions.

[0007] In some embodiments, the total width of the positive electrode tab is 40 mm to 160 mm; and / or the total width of the negative electrode tab is 40 mm to 160 mm; and / or the width of the positive electrode tab is 40 mm to 160 mm; and / or the width of the negative electrode tab is 40 mm to 160 mm. As a result, the positive and negative electrode tabs have larger flow areas and better heat dissipation capabilities.

[0008] In some embodiments, the positive electrode tab and the negative electrode tab are located on the same side of the positive electrode body, or the positive electrode tab and the negative electrode tab are located on opposite sides of the positive electrode body. This simplifies external circuit connections and assembly processes.

[0009] In some embodiments, the positive electrode current collector includes the positive electrode body and multiple positive electrode tabs, with at least two of the positive electrode tabs located on opposite sides of the positive electrode body; and / or the negative electrode current collector includes the negative electrode body and multiple negative electrode tabs, with at least two of the negative electrode tabs located on opposite sides of the negative electrode body. This can provide more uniform heat distribution and reduce tab deformation caused by excessive force on one side.

[0010] In some embodiments, the positive electrode current collector includes the positive electrode body and a plurality of spaced-apart positive electrode tabs; and / or the negative electrode current collector includes the negative electrode body and a plurality of spaced-apart negative electrode tabs. This can shorten the electron transmission path and reduce battery heat generation.

[0011] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.135g / 1540.25mm 2 As a result, the battery cell has a higher volume energy density.

[0012] In some embodiments, the battery takes 7 minutes to 15 minutes to charge from 10% SOC to 80% SOC, thereby providing the battery cell with excellent fast charging performance.

[0013] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145g / 1540.25mm 2 As a result, the battery cell has a higher volume energy density.

[0014] In some embodiments, the battery takes 20 minutes to charge from 10% SOC to 80% SOC, thereby providing the battery cell with excellent fast charging performance.

[0015] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located at least on one side of the negative electrode current collector, and the compaction density of the negative electrode active material layer is 1.2g / cm3-1.5g / cm 3 This helps improve the fast charging performance of battery cells.

[0016] In some embodiments, the negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, and the mass fraction of silicon in the negative electrode active material is 0.1%-7%. This can improve the mass energy density of the battery cell.

[0017] In some embodiments, the mass fraction of silicon in the negative electrode active material is 1%-5%, thereby further improving the mass energy density of the battery cell.

[0018] In some embodiments, the negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer stacked together, the first negative electrode active material layer being located on the side closest to the negative electrode current collector, the Dv50 of the first negative electrode active material in the first negative electrode active material layer being 9.2 μm-18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer being 7.2 μm-15.5 μm. This can significantly improve the fast charging performance and energy density of the battery cell.

[0019] In some embodiments, the conductivity of the electrolyte is 10 ms / cm-20 ms / cm, thereby helping to improve the fast charging performance of the battery cell.

[0020] In some embodiments, the mass fraction of the first solvent is 16%-72% based on the total mass of the electrolyte, thereby improving the fast charging performance of the battery cell.

[0021] In some embodiments, the mass fraction of the linear carboxylate is 32%-68% based on the total mass of the electrolyte, thereby effectively reducing the viscosity of the electrolyte and improving the fast charging performance of the battery.

[0022] In some embodiments, the electrolyte further includes a first lithium salt additive, comprising at least one of a fluorine-containing borate and a fluorine-containing phosphate, and the mass fraction of the first lithium salt additive is 0.05%-0.5% based on the total mass of the electrolyte. This can effectively reduce the internal resistance of the battery cell.

[0023] In some embodiments, the first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalatophosphate, lithium difluorooxalatoborate, and lithium tetrafluoroborate, thereby facilitating the formation of a low-resistance solid electrolyte film on the surface of the negative electrode active material.

[0024] In some embodiments, the mass fraction of the first lithium salt additive is 0.1%-0.3% based on the total mass of the electrolyte, thereby helping to reduce the cost of battery cells.

[0025] In some embodiments, the organic solvent further comprises a second solvent, wherein the second solvent comprises at least one of ethylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate. This helps to improve the cycle life of the battery cells.

[0026] In some embodiments, the second solvent includes diethyl carbonate, and the content of the diethyl carbonate is not less than 12% based on the total mass of the electrolyte.

[0027] In some embodiments, the electrolyte further includes a non-lithium salt additive, wherein the non-lithium salt additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate. This helps form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0028] In some embodiments, the carbonate additive includes at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and vinyl ethylene carbonate, thereby facilitating the formation of a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0029] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the vinylene carbonate is 0.5%-2.5%, and / or the mass fraction of the fluoroethylene carbonate is 0.05%-2%. This helps form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0030] In some embodiments, the sulfate ester additive includes at least one of 4,4-ethylene sulfate, vinyl bissulfate, vinyl trisulfate, and 1,3-propane sultone.

[0031] In some embodiments, the mass fraction of the non-lithium salt additive is 0.05%-3% based on the total mass of the electrolyte, thereby helping to reduce the cost of battery cells.

[0032] In some embodiments, the electrolyte further includes a second lithium salt additive, comprising at least one of lithium bis(oxalatoborate), lithium difluorobis(oxalatophosphate), lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate. This facilitates the formation of a solid electrolyte membrane with high ionic conductivity on the surface of the negative electrode active material.

[0033] In some embodiments, the electrolyte further includes a lithium salt, wherein the lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass fraction of the lithium salt is greater than or equal to 13% based on the total mass of the electrolyte. This helps to improve the conductivity of the electrolyte.

[0034] In some embodiments, the electrolyte lithium salt includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide in the electrolyte is (1.2-2): 1. This helps further improve the conductivity of the electrolyte.

[0035] In some embodiments, the compaction density of the positive electrode active material layer is 2.2 g / cm 3 -2.6g / cm 3 This helps improve the fast charging performance and energy density of battery cells.

[0036] In some embodiments, the positive electrode active material layer includes a positive electrode active material comprising a core portion comprising an olivine-structured lithium-containing phosphate, and a coating layer coated on the surface of the olivine-structured lithium-containing phosphate, the coating layer containing one or more elements selected from the group consisting of C, Fe, Ti, Zr, Hf, Ge, and Sn. This helps improve the structural stability and ionic conductivity of the positive electrode active material.

[0037] In some embodiments, the olivine-structured lithium-containing phosphate includes a general formula of Li x1 A y1 Me a M1 b P 1-c X c Y zA compound wherein 0.5≤x1≤1.3, 0≤y1≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A comprises one or more of Na, K, and Mg; Me comprises one or more of Mn, Fe, Co, and Ni; M1 comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X comprises one or more of S, Si, Cl, B, C, and N; and Y comprises one or more of O and F. This helps to improve the ionic and electronic conductivity of the core.

[0038] In some embodiments, the coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15-0.32, thereby helping to improve the electronic conductivity of the positive electrode active material.

[0039] In some embodiments, in a cross-section of the positive electrode active material layer along the thickness direction, the positive electrode active material includes an olivine-structured lithium-containing phosphate with a longest diameter of 1 μm to 3 μm and an olivine-structured lithium-containing phosphate with a shortest diameter of 0.1 μm to 0.3 μm. This helps to increase the energy density of the battery cell.

[0040] In some embodiments, the positive electrode active material satisfies at least one of the following conditions: the Dv50 particle size of the positive electrode active material is 1 μm to 5 μm; the Dv10 particle size of the positive electrode active material is 0.4 μm to 0.7 μm; and the positive electrode active material is a primary particle or a quasi-single crystal particle. Thus, the larger particle size of the positive electrode active material is beneficial for improving the energy density of the battery cell.

[0041] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, including at least one of lithium ferrite, lithium nickelate, lithium nickel copperate, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, and lithium nickel cobalt manganate. This helps to improve the cycle life of the battery cells.

[0042] In some embodiments, the length of the battery cell is L, the width of the battery cell is H, and the value of L is 4 to 10 times the value of H. In this way, the volume utilization of the battery can be effectively improved, and the overall energy density of the battery can be improved.

[0043] In some embodiments, the value of L is 4 to 7 times the value of H. This helps the battery cell to have both higher energy density and lower internal resistance.

[0044] In some embodiments, L is 400 mm to 1000 mm, and / or H is 80 mm to 160 mm.

[0045] In some embodiments, a housing is further included, wherein the electrode assembly is located within the housing. The housing includes two first housing walls disposed opposite each other, and a surrounding wall connecting the two first housing walls. The surrounding wall includes two second housing walls disposed opposite each other along the length of the first housing wall, and two third housing walls disposed opposite each other along the width of the first housing wall. Electrode terminals are provided on the second housing walls, and the positive electrode tab and the negative electrode tab are electrically connected to the electrode terminals on the two second housing walls, respectively. A folding structure is provided between the second housing wall electrically connected to the positive electrode tab and the positive electrode body, and the folding structure is configured to fold the plurality of positive electrode tabs together. This facilitates the fixing of the positive electrode tabs and the welding between the positive electrode tabs and the electrode posts.

[0046] In some embodiments, the edge of the positive electrode sheet is chamfered along the length direction of the first shell wall, thereby facilitating rapid assembly of the electrode assembly.

[0047] In some embodiments, a liquid injection hole is provided on the second shell wall connected to the negative electrode ear portion, thereby facilitating the injection of electrolyte.

[0048] In some embodiments, the injection hole and the pressure relief portion of the housing are located on different second housing walls, and the pressure relief portion is configured to release pressure inside the housing, thereby reducing corrosion of the pressure relief portion by the electrolyte during the injection process.

[0049] In some embodiments, the electrode terminal is provided with at least one mounting hole, through which the pole is passed and riveted to the pole lug, thereby helping to reduce the volume and weight of the battery cell and improve the energy density of the battery cell.

[0050] In some embodiments, the electrode terminal is provided with at least two mounting holes, and each pole is passed through the mounting holes and riveted to the pole lug, thereby helping to improve the current carrying capacity of the pole.

[0051] In some embodiments, the diameter of the pole is 3 mm to 8 mm. Thus, the pole has both high current capacity and low space occupation.

[0052] In some embodiments, the post riveted to the positive electrode tab and the post riveted to the negative electrode tab are staggered in the longitudinal direction of the first shell wall. Alternatively, the post riveted to the positive electrode tab and the post riveted to the negative electrode tab are arranged diagonally in the longitudinal direction of the first shell wall. This helps to improve the volumetric energy density of the assembled battery module or battery pack.

[0053] In some embodiments, the pole and the tab are electrically connected via an adapter, thereby significantly improving the welding quality and connection reliability between the pole and the tab.

[0054] In some embodiments, the pole and the tab are directly electrically connected, thereby helping to reduce the structural complexity inside the battery cell, helping to reduce the volume of the battery cell and improve the energy density.

[0055] In some embodiments, the distance between the two first shell walls is D, and D is less than or equal to 30 mm, thereby facilitating rapid heat dissipation of the battery cell.

[0056] In some embodiments, D is 10 mm to 25 mm. Thus, the battery cell has higher mechanical strength and better heat dissipation capability.

[0057] In some embodiments, the thickness of the first shell wall and the third shell wall are independently less than or equal to 0.5 mm, thereby increasing the volume energy density of the battery cell.

[0058] In some embodiments, the first shell wall and the third shell wall include at least one of an aluminum shell and a steel shell, thereby improving the mechanical strength of the battery cell.

[0059] In some embodiments, the first shell wall and the third shell wall are steel shells, and the wall thickness of the steel shells is 0.1 mm-0.5 mm, thereby effectively alleviating the volume expansion of the battery cells during the charging and discharging process.

[0060] In some embodiments, the first shell wall and the third shell wall are aluminum shells, and the thickness of the aluminum shells is 0.3 mm to 0.4 mm, thereby effectively improving the mass energy density of the battery cell.

[0061] In some embodiments, the first shell wall and the third shell wall are formed by bending and welding aluminum plates, and the weld is located at the connection between the first shell wall and the third shell wall, thereby reducing leakage of the electrolyte.

[0062] In some embodiments, a side support plate is provided between the electrode assembly and the first shell wall, thereby helping to improve the structural stability of the battery cell.

[0063] In some embodiments, at least one of the second shell walls is provided with a pressure relief portion configured to release pressure within the shell. The orthographic projection of the pressure relief portion on the second shell wall is 7%-15% of the area of the second shell wall. This facilitates rapid release of excess pressure gas within the battery cell through the pressure relief portion when excessive pressure is present.

[0064] In some embodiments, the capacity of the battery is Q, the ratio of the area of the orthographic projection of the pressure relief portion on the second shell wall to Q is greater than or equal to 1.1, the unit of Q is Ah, and the unit of the area is mm 2 This helps to quickly release the overpressure gas inside the battery cell.

[0065] In a second aspect of the present application, a battery device is provided, comprising the aforementioned battery cell, wherein the battery device comprises at least one of a battery module, a battery pack, and an energy storage device. Thus, the battery device has all the features and advantages of the aforementioned battery cell, which will not be further elaborated here.

[0066] In a third aspect of the present application, an electrical device is provided, comprising the aforementioned battery cell. Thus, the electrical device has all the features and advantages of the aforementioned battery cell, which will not be elaborated herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0068] Figure 1 This is a schematic structural diagram of an electrode assembly manufactured using a lamination process according to one embodiment of the present application;

[0069] Figure 2 This is a schematic structural diagram of a positive electrode current collector according to one embodiment of the present application;

[0070] Figure 3 This is a schematic structural diagram of a positive electrode current collector according to another embodiment of the present application;

[0071] Figure 4 This is a schematic structural diagram of a positive electrode current collector according to another embodiment of the present application;

[0072] Figure 5 This is a schematic structural diagram of a positive electrode current collector according to another embodiment of the present application;

[0073] Figure 6 This is a schematic structural diagram of an electrode assembly manufactured using a winding process according to an embodiment of the present application;

[0074] Figure 7This is a schematic structural diagram of a battery cell according to an embodiment of the present application;

[0075] Figure 8 This is a partial structural diagram of a housing according to an embodiment of the present application;

[0076] Figure 9 This is a partial structural diagram of a housing according to another embodiment of the present application;

[0077] Figure 10 This is a partial structural diagram of a housing according to another embodiment of the present application;

[0078] Figure 11 This is a partial structural diagram of a housing according to another embodiment of the present application;

[0079] Figure 12 This is a partial structural diagram of a housing according to another embodiment of the present application;

[0080] Figure 13 This is a partial structural diagram of a housing according to another embodiment of the present application;

[0081] Figure 14 This is a partial structural diagram of a housing according to another embodiment of the present application;

[0082] Figure 15 This is a schematic structural diagram of an electrical device according to an embodiment of the present application.

[0083] Description of reference numerals:

[0084] 11 positive electrode main body; 12 positive electrode ear; 21 negative electrode main body; 22 negative electrode ear;

[0085] 101 first shell wall; 102 second shell wall; 103 third shell wall; 104 pressure relief portion; 105 pole; 106 retracted structure; 107 liquid injection hole; 108 adapter plate. DETAILED DESCRIPTION

[0086] The following describes the embodiments of the present application in detail. Examples of the embodiments are shown in the accompanying drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary lengthiness in the following description and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0087] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0088] The terms "include" and "have" in the description and claims of this application and any variations thereof are open expressions, that is, including the contents specified in this application but not excluding other contents.

[0089] In the description of this application, all numbers disclosed herein are approximate, regardless of whether the word "about" or "approximately" is used. The value of each number may vary by less than 10% or by a reasonable difference considered by a person skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0090] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0091] In the description of this application, it should be understood that the terms "length", "width", "thickness", "up", "down", "front", "back", "left", "right", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0092] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the technical features indicated. "First feature" and "second feature" may include one or more of the features.

[0093] In the description of this application, “plurality” means two or more.

[0094] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0095] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0096] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0097] Improving the fast-charging performance of batteries allows users to recharge their devices in a shorter time, reducing charging wait times and improving the overall user experience. However, the chemical reaction rate within the battery cells accelerates during fast charging, causing the battery to generate more heat. Sustained high temperatures accelerate the aging of battery materials, particularly electrolyte decomposition and degradation of positive electrode active materials, thereby shortening the battery's cycle life. Furthermore, the current flowing through the tab during fast charging is also relatively high, placing high demands on the maximum current that the tab can carry.

[0098] When the coating weight of a single negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.145g / 1540.25mm 2When the coating weight of the single-layer negative electrode active material layer is high, and the thickness of the negative electrode active material layer located on the surface of the negative electrode current collector is moderate and uniform, the lithium ion transmission path in the negative electrode active material layer is short, and the negative electrode active material can be quickly embedded and de-embedded during the charge and discharge process. At the same time, the battery cell has a high energy density and is suitable for battery cells with high fast charging performance requirements. Furthermore, by using a tab portion with a total width that accounts for 50%-100% of the total dimension of the tab connecting edge of the corresponding main body in the positive and negative current collectors, the current conduction path on the tab can be effectively increased. Therefore, when the battery is rapidly charged and discharged, a higher current can pass through the tab portion, which can meet the performance requirements for the current carrying capacity of the tab portion under fast charging conditions. At the same time, the larger cross-sectional area of the tab portion can reduce its resistance, thereby reducing the heat generation and accumulation of the base of the tab portion. Therefore, the tab portion that meets the above requirements can withstand higher currents while reducing the generation and accumulation of heat within the battery cell and providing a larger surface area for heat dissipation, thereby enhancing the heat dissipation effect of the tab portion and helping the battery cell maintain a relatively low system temperature during fast charging. Furthermore, the first solvent has a higher electrical conductivity due to its lower viscosity, which can effectively reduce the internal resistance of the battery cell, but at the same time has the characteristic of a lower boiling point. When the aforementioned battery cell can maintain a relatively low system temperature under fast charging conditions, the heat loss of the first solvent caused by the higher temperature rise of the battery cell can be effectively reduced, so that the first solvent can stably and fully exert its advantage of higher electrical conductivity, thereby reducing the heat generation of the battery cell during the fast charging process, increasing the output power under fast charging conditions, and further improving the fast charging performance of the battery cell.

[0099] The present application can improve the energy density of the battery cell and its performance under fast charging conditions by adopting a suitable coating weight of the negative active material layer and a suitable amount of the first solvent. However, in the fast charging scenario, a large amount of heat is easily generated and accumulated inside the battery cell, which causes the first solvent with a lower boiling point to produce gas, release acid, and other adverse effects that are not conducive to the fast charging performance of the battery. By combining a pole ear structure with a larger flow area, the temperature rise of the battery cell during the fast charging process can be effectively slowed down, and the occurrence of the above-mentioned adverse effects of the high-conductivity, low-boiling-point first solvent in the fast charging scenario can be alleviated, so that the internal resistance of the battery cell is lower, the heat generation of the battery cell under fast charging conditions is alleviated, the output power is improved, and the performance under fast charging conditions is better.

[0100] In the first aspect of the present application, the present application proposes a battery cell, referring to Figures 1-6, comprising: an electrode assembly, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode current collector comprises a positive electrode main body 11 and at least one positive electrode ear portion 12, the ear connection edge of the positive electrode main body 11 is connected to the positive electrode ear portion 12, and along the extension direction of the ear connection edge of the positive electrode main body 11, the total width W1 of the positive electrode ear portion 12 accounts for the total size V1 of the ear connection edge of the positive electrode main body 11 50%-100%, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector, the negative electrode current collector includes a negative electrode main body 21 and at least one negative electrode ear portion 22, the ear connection edge of the negative electrode main body 21 is connected to the negative electrode ear portion 22, along the extension direction of the ear connection edge of the negative electrode main body 21, the total width W2 of the negative electrode ear portion 22 accounts for 50%-100% of the total dimension V2 of the ear connection edge of the negative electrode main body 21, wherein the coating weight of a single layer of the negative electrode active material layer is 0.1g / 1540.25mm 2 -0.145g / 1540.25mm 2 The electrolyte comprises an organic solvent, the organic solvent comprising a first solvent, the first solvent comprising at least one of dimethyl carbonate and a linear carboxylic acid ester, wherein the linear carboxylic acid ester has a structural formula satisfying R1-COO-R2, with R1 and R2 independently selected from a C1-C5 alkyl group or a halogenated alkyl group; the mass fraction of the first solvent is 4%-72% based on the total mass of the electrolyte. Thus, by adopting an appropriate coating weight of the negative electrode active material layer, the energy density of the battery cell and its performance under fast charging conditions can be improved. Furthermore, by adopting a larger tab structure, the current carrying capacity of the tab can be effectively improved, and the temperature rise of the battery cell during fast charging can be mitigated. Furthermore, the use of a first solvent with high conductivity and a low boiling point can further reduce the internal resistance of the battery cell, thereby mitigating heat generation of the battery cell under fast charging conditions, increasing output power, improving the fast charging performance of the battery cell, and enhancing the performance of the battery cell under fast charging conditions.

[0101] It can be understood that the positive electrode active material layer is located on at least one side of the positive electrode main body of the positive electrode collector, and the negative electrode active material layer is located on at least one side of the negative electrode main body of the negative electrode collector.

[0102] As an example, the widths of the positive electrode ear and the negative electrode ear can be the same. When the lengths of the ear connection edges of the positive electrode current collector and the negative electrode current collector are also the same, the ratio of the total width of the positive electrode ear 12 to the total size of the ear connection edge of the positive electrode main body 11 along the direction in which the ear connection edge of the positive electrode main body 11 extends is the same as the ratio of the total width of the negative electrode ear 22 to the total size of the ear connection edge of the negative electrode main body 21 along the direction in which the ear connection edge of the negative electrode main body 21 extends.

[0103] It should be noted that when the electrode assembly is prepared by the lamination process, the electrode assembly may include multiple layers of continuously arranged positive electrode sheet / separator / negative electrode sheet / separator structure. At this time, the ratio of the total width W1 of the positive electrode ear portion 12 to the total dimension V1 of the ear connection side of the positive electrode main body 11 corresponds to the ratio of the width of the ear portion to the side length of the main body in any positive electrode sheet. Similarly, the ratio of the total width W2 of the negative electrode ear portion 22 to the total dimension V2 of the ear connection side of the negative electrode main body 21 corresponds to the ratio of the width of the ear portion to the side length of the main body in any negative electrode sheet. When the electrode assembly is prepared by the winding process, the electrode assembly only includes one layer of positive electrode sheet, one layer of A layer of isolation film and a layer of negative electrode plate, wherein the positive electrode plate has multiple positive electrode ears 12. At this time, the ratio of the total width of the aforementioned positive electrode ears 12 to the total size of the electrode ear connection edge of the positive electrode main body 11 corresponds to the ratio of the sum of the widths of all positive electrode ears to the side length of the positive electrode main body. Similarly, the ratio of the total width of the aforementioned negative electrode ears 22 to the total size of the electrode ear connection edge of the negative electrode main body 21 corresponds to the ratio of the sum of the widths of all negative electrode ears to the side length of the negative electrode main body.

[0104] As an example, along the width direction of the positive electrode body 11 , the total width W1 of the positive electrode ear 12 may account for 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the total width V1 of the positive electrode body 11 .

[0105] As an example, along the width direction of the negative electrode body 21 , the total width W2 of the negative electrode ear 22 may account for 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the total width V2 of the negative electrode body 21 .

[0106] When the battery cell is charged and discharged at a high rate, the current and voltage inside the battery cell will increase accordingly, and the current passing through the tab will increase. A larger tab area means lower resistance. On the one hand, according to Ohm's law, at the same voltage, a tab with a larger area can carry a higher current, that is, it has a stronger current capacity. On the other hand, when the resistance of the tab is small, the heat generated by the resistance loss after the current flows through the tab can be reduced, which reduces the heat generation of the battery under high current and indirectly improves the heat dissipation efficiency of the battery. At this time, the lower boiling point of the first solvent significantly reduces the adverse effects on the performance of the battery cell, and the first solvent can give full play to the advantages of improving the conductivity of the electrolyte and improving the fast charging capability of the battery cell.

[0107] In some embodiments, the dimension of the tab-connecting edge of the positive electrode body 11 can be larger than its dimension in the length direction, or the dimension of the tab-connecting edge of the positive electrode body 11 can be equal to its dimension in the length direction, or the dimension of the tab-connecting edge of the positive electrode body 11 can be smaller than its dimension in the length direction. That is, the positive electrode tab 12 can be located on the long side of the positive electrode body 11 or on the short side of the positive electrode body 11. Similarly, the negative electrode tab 22 can be located on the long side of the negative electrode body 21 or on the short side of the negative electrode body 21.

[0108] In some embodiments, the total width W1 of the positive electrode ear portion 12 may be 40 mm to 160 mm.

[0109] As an example, W1 may be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or 160 mm.

[0110] Similarly, in some embodiments, the total width W2 of the negative electrode ear portion 22 may also be 40 mm-160 mm.

[0111] As an example, W2 may be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or 160 mm.

[0112] When the total widths of the positive electrode ear and the negative electrode ear are respectively within the aforementioned ranges, the flow area of the ear is larger, which can effectively improve the flow capacity of the ear and alleviate the temperature rise of the battery cell during fast charging. Then, a first solvent with high conductivity and low boiling point can be used to further reduce the internal resistance of the battery cell, thereby alleviating the heat generation of the battery cell under fast charging conditions, improving the fast charging performance of the battery cell, and improving the performance of the battery cell under fast charging conditions.

[0113] In some embodiments, the width W3 of the positive electrode ear portion 12 may be 40 mm to 160 mm.

[0114] As an example, W1 may be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or 160 mm.

[0115] Similarly, in some embodiments, the width W4 of the negative electrode ear portion 22 may be 40 mm-160 mm.

[0116] As an example, W2 may be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or 160 mm.

[0117] As an example, refer to Figure 4 When the electrode assembly is prepared using a lamination process, the total width W1 of the positive electrode ear 12 corresponds to the total width of multiple positive electrode ears 12 after the positive electrode sheets, negative electrode sheets and isolation membranes are stacked. Similarly, the total width W2 of the negative electrode ear 22 corresponds to the total width of multiple negative electrode ears 22 after the positive electrode sheets, negative electrode sheets and isolation membranes are stacked.

[0118] As an example, refer to Figure 6 When the electrode assembly is prepared by a winding process, the total width W1 of the aforementioned positive electrode ear 12 corresponds to the total width of multiple positive electrode ears 12 stacked after the positive electrode sheet, the negative electrode sheet and the separator are wound. Similarly, the total width W2 of the aforementioned negative electrode ear 22 corresponds to the total width of multiple negative electrode ears 22 stacked after the positive electrode sheet, the negative electrode sheet and the separator are wound.

[0119] In some embodiments, the positive electrode tab 12 and the negative electrode tab 22 are located on the same side of the positive electrode body 11. For electrode assemblies produced using a lamination process or a winding process, the positive electrode body 11 is arranged parallel to the negative electrode body 21, so the positive electrode tab 12 and the negative electrode tab 22 are also located on the same side of the negative electrode body 21. This simplifies the connection of external circuits and the assembly process.

[0120] In some embodiments, the positive electrode tab 12 and the negative electrode tab 22 are located on opposite sides of the positive electrode body 11. For electrode assemblies obtained using a lamination process or a winding process, the positive electrode body 11 is arranged parallel to the negative electrode body 21, and the positive electrode tab 12 and the negative electrode tab 22 are also located on both sides of the negative electrode body 21. This can provide more uniform heat distribution and reduce tab deformation caused by excessive force on one side.

[0121] In some embodiments, reference Figure 2 The positive electrode current collector includes the positive electrode body 11 and multiple positive electrode tabs 12, with at least two of the positive electrode tabs 12 located on opposite sides of the positive electrode body 11. Similarly, the negative electrode current collector includes the negative electrode body and multiple negative electrode tabs, with at least two of the negative electrode tabs located on opposite sides of the negative electrode body. This provides more uniform heat distribution and reduces tab deformation caused by excessive force on one side.

[0122] In some embodiments, reference Figure 3 The positive electrode current collector includes a positive electrode main body 11 and a plurality of positive electrode tabs 12 spaced apart along the length direction of the positive electrode current collector. Similarly, the negative electrode current collector may also include a negative electrode main body 21 and a plurality of negative electrode tabs 22 spaced apart along the length direction of the negative electrode current collector.

[0123] When the positive electrode current collector includes multiple positive electrode ears 12 and the negative electrode current collector includes multiple negative electrode ears 22, the transmission path of electrons between the positive electrode ears and the negative electrode ears is shorter, which can reduce battery heat generation and improve fast charging performance.

[0124] Reference below Figures 1-6 The specific embodiments are described as follows:

[0125] refer to Figure 1 In some specific embodiments, using a lamination process to prepare an electrode assembly, the positive electrode sheet used is rectangular. In this case, one of the two short sides of the positive current collector has a positive electrode tab 12 extending along the length of the positive current collector. The width of the positive electrode tab is W3, and the total dimension V1 of the tab-connecting edges of the positive electrode main body is the width of the positive current collector. Similarly, the corresponding negative electrode current collector can also have a similar structure. In this case, one of the two short sides of the negative current collector has a negative electrode tab extending along the length of the negative current collector. The width of the negative electrode tab is W4, and the total dimension V2 of the tab-connecting edges of the negative electrode main body is the width of the negative current collector.

[0126] refer to Figure 2In some specific embodiments, using a lamination process to prepare an electrode assembly, the positive electrode sheet used is rectangular. In this case, the short sides of the positive electrode current collector each have a positive electrode tab 12 extending along the length of the positive electrode current collector, with the two positive electrode tabs 12 extending in opposite directions. The width W3 of the multiple positive electrode tabs 12 can be the same or different, and the total dimension V1 of the tab-connecting edges of the positive electrode main body is the width of the positive electrode current collector. Similarly, the corresponding negative electrode current collector can also have a similar structure. In this case, the width W4 of the multiple negative electrode tabs can be the same or different, and the total dimension V2 of the tab-connecting edges of the negative electrode main body is the width of the negative electrode current collector.

[0127] refer to Figure 3 In some specific embodiments, taking the lamination process as an example, the positive electrode sheet used is rectangular. In this case, one of the long sides of the positive electrode current collector has multiple positive electrode tabs 12 extending along the width direction of the positive electrode current collector. The multiple positive electrode tabs 12 are spaced apart along the length direction of the positive electrode current collector, wherein the width of each positive electrode tab can be the same or different. Taking three positive electrode tabs as an example, the widths of the three positive electrode tabs 12 are L1, L2, and L3, respectively. L1, L2, and L3 can be all the same, all different, or any two of them can be the same. In this case, the total width W1 of the positive electrode tabs is the sum of the widths of the multiple positive electrode tabs, that is, W1 = L1 + L2 + L3. The total dimension V1 of the tab-connecting edges of the positive electrode main body is the length of the positive electrode current collector. Similarly, the corresponding negative electrode current collector may also have a similar structure. In this case, the total width W2 of the negative electrode ear portion is the sum of the widths of the multiple negative electrode ear portions, and the width of the negative electrode body portion is the length of the negative electrode current collector.

[0128] refer to Figure 4 In some specific embodiments, in an electrode assembly manufactured using a lamination process, multiple positive electrode tabs 12 are staggered (adjacent positive electrode tabs at least partially overlap). In this case, the total width W1 of the positive electrode tabs 12 corresponds to the total width of the stacked positive electrode tabs 12 after the positive electrode sheets, negative electrode sheets, and separator are stacked. Similarly, multiple negative electrode tabs 22 are staggered (adjacent negative electrode tabs at least partially overlap). The total width W2 of the negative electrode tabs 22 corresponds to the total width of the stacked negative electrode tabs 22 after the positive electrode sheets, negative electrode sheets, and separator are stacked.

[0129] refer to Figure 5In some specific embodiments, taking the winding process as an example, the corresponding positive electrode current collector can have multiple positive electrode tabs 12 extending perpendicularly to the long side of the positive electrode body 11 after horizontal expansion. The width W3 of each positive electrode tab can be the same or different. Similarly, the corresponding negative electrode current collector can also have a similar structure, and the width W4 of each negative electrode tab can be the same or different.

[0130] refer to Figure 6 In some specific embodiments, in the electrode assembly produced by the winding process, the positive electrode current collector and the negative electrode current collector have the following Figure 5 In the structure shown, the total width W1 of the aforementioned positive electrode ear portion 12 corresponds to the total width of multiple positive electrode ear portions 12 stacked after the positive electrode sheet, the negative electrode sheet and the separator are wound (adjacent positive electrode ear portions at least partially overlap). Similarly, the total width W2 of the aforementioned negative electrode ear portion 22 corresponds to the total width of multiple negative electrode ear portions 22 stacked after the positive electrode sheet, the negative electrode sheet and the separator are wound (adjacent negative electrode ear portions at least partially overlap).

[0131] As an example, the coating weight of a single layer of the negative electrode active material layer may be 0.1 g / 1540.25 mm 2 、0.105g / 1540.25mm 2 、0.115g / 1540.25mm 2 , 0.12g / 1540.25mm 2 , 0.125g / 1540.25mm 2 、0.13g / 1540.25mm 2 , 0.135g / 1540.25mm 2 、0.14g / 1540.25mm 2 、0.145g / 1540.25mm 2 .

[0132] As an example, the coating weight of a single layer of the negative electrode active material layer can be tested by the following method: the coating weight can be obtained by wiping the negative electrode active material layer on the negative electrode sheet and calculating the difference in mass before and after wiping.

[0133] In some embodiments, the organic solvent includes a first solvent comprising at least one of dimethyl carbonate (DMC) and a linear carboxylic acid ester, wherein the linear carboxylic acid ester has a structural formula of R1-COO-R2, where R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl groups. This can effectively reduce the viscosity of the electrolyte.

[0134] The viscosity of the aforementioned first solvent is low, which in turn makes the overall viscosity of the electrolyte with an organic solvent as the main body low. The intermolecular interaction force in the low-viscosity electrolyte is weaker, and the movement between molecules is freer, which accelerates the diffusion and migration of lithium ions in the electrolyte. Furthermore, when the battery cell is rapidly charged and discharged, concentration polarization will occur inside the battery. When the ion migration rate of the electrolyte is high, the concentration polarization inside the battery can be alleviated. The aforementioned low-viscosity electrolyte can effectively reduce concentration polarization by increasing the ion migration rate, thereby improving the fast charging performance of the battery.

[0135] For example, the viscosity of an electrolyte can be measured using the following method: Viscosity is measured using a viscometer. Referencing the national standard GB / T10247-2008, "Methods for Measuring Viscosity," the following applies: At a certain temperature, when a rotor rotates continuously at a constant speed within a sample, the shear force exerted on the rotor causes a spring to generate torque. This torque is proportional to the viscosity, resulting in the viscosity value.

[0136] In some embodiments, the linear carboxylate includes at least one of ethyl formate, isopropyl formate, ethyl acetate (EA), methyl acetate, propyl acetate, and methyl propionate, thereby further reducing the viscosity of the electrolyte.

[0137] Linear carboxylates have good lithium salt solubility, which can improve the conductivity of the electrolyte, accelerate the migration rate of lithium ions within the battery, and enhance the battery's charge and discharge efficiency. Linear carboxylates also exhibit good thermal and oxidative stability at high temperatures, helping to improve battery stability under fast charging conditions and reduce the risk of thermal runaway.

[0138] In some embodiments, the mass fraction of the first solvent is 16%-72% based on the total mass of the electrolyte, thereby improving the fast charging performance of the battery cell.

[0139] As an example, based on the total mass of the electrolyte, the mass fraction of the first solvent can be 4%, 8%, 12%, 16%, 20%, 24%, 28%, 32%, 36%, 40%, 44%, 48%, 52%, 56%, 60%, 64%, 68% or 72%.

[0140] As the mass fraction of the first solvent increases, the viscosity of the electrolyte gradually decreases, and the fast charging performance of the battery is further improved.

[0141] As an example, the quantitative test of the first solvent can be obtained by the following test method: referring to the standard GB / T9722-2006, the organic components in the electrolyte can be quantitatively analyzed by gas chromatography.

[0142] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the linear carboxylic acid ester is 32%-68%.

[0143] As an example, the mass fraction of the linear carboxylic acid ester may be 32%, 36%, 40%, 44%, 48%, 52%, 56%, 60%, 64% or 68% based on the total mass of the electrolyte.

[0144] Linear carboxylic acid esters have a relatively low viscosity. When the mass fraction of the linear carboxylic acid esters is within the above range based on the total mass of the electrolyte, the liquid phase transmission resistance of lithium ions can be further reduced, thereby improving the fast charging performance and cycle performance of the battery cell.

[0145] As an example, the quantitative analysis of the linear carboxylic acid ester can be obtained by testing using the following method: referring to the standard GB / T9722-2006, the organic components in the electrolyte can be quantitatively analyzed by gas chromatography.

[0146] It is understood that, in general, the electrolyte includes an organic solvent and a lithium salt (including electrolyte lithium salt and lithium salt additives). Based on the total mass of the electrolyte, the mass fraction of the organic solvent is about 80%, and the rest can be lithium salt and / or additives.

[0147] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.135g / 1540.25mm 2 As a result, the battery cell has a higher volume energy density.

[0148] When the coating weight of a single negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.135g / 1540.25mm 2 At this time, the thickness of the negative electrode active material layer is relatively thin, and the distance that lithium ions need to diffuse in the negative electrode active material layer is relatively short, thereby accelerating the transmission of lithium ions and improving the fast charging performance of the battery. For example, the time it takes to charge the battery cell from 10% SOC to 80% SOC using the negative electrode sheet that meets the aforementioned coating weight is 7 minutes to 15 minutes. As a result, the battery cell has better fast charging performance.

[0149] Taking a car as an example, in actual usage scenarios, the state of charge (SOC) of a car's battery is usually between 10% and 80%. Therefore, when the battery charging time within this SOC range is short, the user's waiting time for charging can be reduced, greatly improving the user experience.

[0150] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145g / 1540.25mm 2 As a result, the battery cell has a higher volume energy density.

[0151] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145g / 1540.25mm 2 When the above-mentioned positive electrode sheets are used to assemble a battery cell, the volume energy density can be 410Wh / L-430Wh / L. Therefore, the battery cell has a higher volume energy density.

[0152] When the coating weight of a single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145g / 1540.25mm 2 When the negative electrode active material layer is thicker, the negative electrode active material can provide more lithium ion deintercalation sites, which helps to improve the energy density of the battery.

[0153] In some embodiments, the battery cell takes 20 minutes to charge from 10% SOC to 80% SOC, thereby providing the battery cell with excellent fast charging performance.

[0154] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located at least on one side of the negative electrode current collector, and the compaction density of the negative electrode active material layer is 1.2g / cm3-1.5g / cm 3 This helps improve the fast charging performance of battery cells.

[0155] As an example, the compaction density of the negative electrode active material layer can be 1.2 g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 or 1.5g / cm 3 .

[0156] When the compaction density of the negative electrode active material layer is within the aforementioned range, the compaction density of the negative electrode active material layer is relatively moderate. At this time, the lithium ion deintercalation rate of the negative electrode plate is faster, which is beneficial to improving the fast charging performance of the battery.

[0157] As an example, the test method for the compaction density of the negative electrode active material layer may be consistent with the test method for the compaction density of the positive electrode active material layer, and will not be described in detail here.

[0158] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, roller pressing (such as cold pressing process) and other processes, a negative electrode active material layer can be formed to obtain a negative electrode sheet. The compaction density of the aforementioned negative electrode active material layer refers to the compaction density of the negative electrode active material layer after roller pressing. Specifically, the compaction density of the negative electrode active material layer after roller pressing and formation treatment, the compaction density of the negative electrode active material layer when the battery cell is in a fully charged state or fully discharged state, and the compaction density of the negative electrode active material layer after the battery cell has been left standing for a long time are all within the aforementioned range.

[0159] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0160] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0161] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0162] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0163] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0164] In some embodiments, the negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, and the mass fraction of silicon in the negative electrode active material is 0.1%-7%. This can improve the mass energy density of the battery cell.

[0165] Silicon has a theoretical specific capacity of up to 4200 mAh / g, far exceeding that of graphite. Adding silicon-containing materials to the negative electrode active material can effectively improve the battery's mass energy density. Furthermore, pure silicon undergoes a significant volume expansion (up to 300% or more) upon lithium ion insertion, causing the SEI (solid electrolyte interface) to rupture and reorganize, consuming the electrolyte and active lithium ions, and ultimately reducing the battery's cycle life. By controlling the silicon mass fraction in the silicon-containing material to 0.1%-7%, the battery's mass energy density can be improved by leveraging silicon's extremely high theoretical specific capacity while also mitigating the volume expansion and contraction of the silicon-containing material during charge and discharge.

[0166] As an example, the mass fraction of silicon in the silicon-containing material is 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5% or 7%.

[0167] As an example, the silicon-containing material may be a silicon-carbon material.

[0168] In some embodiments, the mass fraction of silicon in the silicon-containing material is 1%-5%, thereby further improving the mass energy density of the battery cell.

[0169] As an example, the mass fraction of silicon in the silicon-containing material can be measured using the following method: Reference can be made to standards YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015. Specifically, the measurement can be performed using an ICP inductively coupled plasma optical emission spectrometer according to the manufacturer's instructions.

[0170] In some embodiments, the negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer stacked together, the first negative electrode active material layer being located on the side closest to the negative electrode current collector, the Dv50 of the first negative electrode active material in the first negative electrode active material layer being 9.2 μm-18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer being 7.2 μm-15.5 μm. This can significantly improve the fast charging performance and energy density of the battery cell.

[0171] When the Dv50 particle size of the first negative electrode active material and the second negative electrode active material is within the aforementioned range, the particle size of the second negative electrode active material is smaller than that of the first negative electrode active material, and the particle size of the particles in the first negative electrode active material layer is larger, which can provide more lithium deintercalation sites and improve the battery capacity; the particle size of the particles in the second negative electrode active material layer is smaller, and the lithium ion deintercalation rate is faster, which helps to improve the fast charging performance of the battery.

[0172] In some embodiments, the conductivity of the electrolyte is 10 ms / cm-20 ms / cm, thereby helping to improve the fast charging performance of the battery cell.

[0173] As an example, the conductivity of the electrolyte may be 10 ms / cm, 11 ms / cm, 12 ms / cm, 13 ms / cm, 14 ms / cm, 15 ms / cm, 16 ms / cm, 17 ms / cm, 18 ms / cm, 19 ms / cm, or 20 ms / cm.

[0174] When the conductivity of the electrolyte is within the range, the electrolyte can conduct lithium ions more effectively, thereby effectively reducing the internal resistance of the battery, helping to improve the fast charging performance of the battery, and reducing the battery temperature rise caused by the resistance thermal effect during the charging and discharging process, reducing the thermal stress inside the battery cell, and thus improving the battery performance under high power.

[0175] As an example, the conductivity of the electrolyte can be directly measured using a conductivity meter using a method known in the art.

[0176] In some embodiments, the electrolyte further includes a first lithium salt additive, comprising at least one of a fluorine-containing borate and a fluorine-containing phosphate, and the mass fraction of the first lithium salt additive is 0.05%-0.5% based on the total mass of the electrolyte. This can effectively reduce the internal resistance of the battery cell.

[0177] As an example, based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive may be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0178] By adding a lithium salt additive comprising at least one of a fluorine-containing borate and a fluorine-containing phosphate to the electrolyte of the battery cell, a low-resistance SEI film containing boron and phosphorus atoms is formed on the surface of the negative electrode active material, effectively reducing the internal resistance of the battery cell, thereby enabling the battery cell to have both high energy density and fast charging performance. When the mass fraction of the first lithium salt additive is within the aforementioned range, the first lithium salt additive facilitates the formation of a low-resistance SEI film on the surface of the negative electrode active material, while the required amount is relatively low, thus helping to reduce the cost of the electrolyte.

[0179] As an example, the mass fraction of the first lithium salt additive, based on the total mass of the electrolyte, can be determined by removing the free electrolyte from the finished battery and measuring the content of the first lithium salt additive using ion chromatography. The concentration of the first lithium salt additive in the electrolyte can be quantitatively analyzed using ion chromatography analysis in accordance with standard JY / T020-1996.

[0180] In some embodiments, the first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalatophosphate, lithium difluorooxalatoborate, and lithium tetrafluoroborate, thereby facilitating the formation of a low-resistance solid electrolyte film on the surface of the negative electrode active material.

[0181] The first lithium salt additive itself has a high ionic conductivity, which can increase the migration rate of lithium ions in the electrolyte; further, the first lithium salt additive can form a stable and dense low-resistance SEI film on the surface of the negative electrode active material during the first charge, which can not only reduce the side reactions between the negative electrode active material and the electrolyte, but also reduce the internal resistance of the battery.

[0182] In some embodiments, the mass fraction of the first lithium salt additive is 0.1%-0.3% based on the total mass of the electrolyte, thereby helping to reduce the cost of battery cells.

[0183] The amount of the first lithium salt additive in the electrolyte is related to the migration distance of lithium ions between the positive and negative electrodes. When the migration distance of lithium ions between the positive and negative electrodes is longer, the amount of the first lithium salt additive in the electrolyte needs to be increased accordingly to reduce the internal resistance of the battery and alleviate the increase in internal resistance caused by the longer migration distance of lithium ions. When the mass fraction of the first lithium salt additive in the electrolyte is within the aforementioned range, the battery cell can achieve both low internal resistance and low manufacturing cost.

[0184] In some embodiments, the organic solvent further includes a second solvent, and the second solvent includes at least one of ethylene carbonate, ethylene carbonate (EC), propylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, and fluoroethylene carbonate. This helps improve the cycle life of the battery cells.

[0185] The aforementioned second solvent has a wide electrochemical stability window and can remain stable even in a high voltage environment, thereby reducing its own decomposition in the electrochemical reaction and improving the cycle life of the battery cell.

[0186] In some embodiments, the second solvent includes diethyl carbonate, and the mass fraction of the diethyl carbonate is greater than or equal to 12% based on the total mass of the electrolyte, thereby helping to further improve the cycle life of the battery cell.

[0187] Diethyl carbonate has suitable viscosity and boiling point, which helps to adjust the physical properties of the electrolyte, so that the electrolyte has suitable viscosity and better low-temperature performance.

[0188] In some embodiments, the electrolyte further includes a non-lithium salt additive, wherein the non-lithium salt additive includes a sulfate additive and a carbonate additive, thereby facilitating the formation of a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0189] Carbonate non-lithium salt additives containing double bonds help to form a SEI film with good flexibility on the surface of the negative electrode active material, which can slow down the destruction of the interface film caused by the volume expansion of the negative electrode active material during the cyclic charge and discharge process, improve the cycle stability of the battery cell, and increase the cycle life.

[0190] In some embodiments, the carbonate additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and vinylethylene carbonate, thereby facilitating the formation of a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0191] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the vinylene carbonate is 0.5%-2.5%, and / or the mass fraction of the fluoroethylene carbonate is 0.05%-2%. This helps form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0192] As an example, based on the total mass of the electrolyte, the mass fraction of the vinylene carbonate is 0.5%, 1%, 1.5%, 2.0% or 2.5%.

[0193] As an example, based on the total mass of the electrolyte, the mass fraction of the fluoroethylene carbonate is 0.05%, 0.1%, 0.5%, 1%, 1.5% or 2.0%.

[0194] It is understandable that because carbonate-based non-lithium salt additives containing double bonds participate in the formation of the SEI film on the surface of the negative electrode active material during the formation process and are thereby partially consumed, the actual detected amount of these substances in the battery cell will be slightly less than their added amount. For example, based on the total mass of the electrolyte, when the added amount of vinylene carbonate is 2.0%, its actual detected amount in the battery cell is approximately 0.87%; based on the total mass of the electrolyte, when the added amount of fluoroethylene carbonate is 1.3%, its actual detected amount in the battery cell is approximately 0.05%.

[0195] In some embodiments, the sulfate ester additive includes at least one of 4,4-ethylene sulfate, vinyl bissulfate, vinyl trisulfate, and 1,3-propane sultone.

[0196] In some embodiments, the mass fraction of the non-lithium salt additive is 0.05%-3% based on the total mass of the electrolyte, thereby helping to reduce the cost of battery cells.

[0197] In some embodiments, the electrolyte further includes a second lithium salt additive, comprising at least one of lithium bis(oxalatoborate), lithium difluorobis(oxalatophosphate), lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate. This facilitates the formation of a solid electrolyte membrane with high ionic conductivity on the surface of the negative electrode active material.

[0198] The second lithium salt additive can form a dense and stable interfacial film on the surface of the negative electrode active material in preference to the organic solvent, inhibiting the oxidative decomposition of the organic solvent at the negative electrode, and reducing the consumption of active lithium due to the side reactions between the negative electrode active material and the electrolyte; effectively preventing direct contact between the organic solvent and the negative electrode active material, and the presence of the interfacial film also helps to reduce the dissolution of transition metals from the negative electrode active material.

[0199] In some embodiments, the electrolyte further includes a lithium salt, wherein the lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass fraction of the lithium salt is greater than or equal to 13% based on the total mass of the electrolyte. This helps to improve the conductivity of the electrolyte.

[0200] As an example, based on the total mass of the electrolyte, the mass fraction of the lithium salt in the electrolyte is 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 21%, 23%, 24% or 25%.

[0201] When the mass fraction of the electrolyte lithium salt is within the aforementioned range based on the total mass of the electrolyte, the electrolyte has both high ionic conductivity and low viscosity. The electrolyte lithium salt releases lithium ions upon dissolution in an organic solvent. The lithium ions form a solvated structure with the electrolyte, increasing the conductivity of the electrolyte and facilitating the rapid migration of lithium ions within the electrolyte.

[0202] In some embodiments, the electrolyte lithium salt includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide in the electrolyte is (1.2-2): 1. This helps further improve the conductivity of the electrolyte.

[0203] Compared with lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide has better electrical conductivity, thermal stability, and hydrolysis resistance, but lithium bis(fluorosulfonyl)imide has the problem of difficulty in fully dissociating. Lithium hexafluorophosphate has an advantage in commercial production and application maturity, and has a lower production cost. When the electrolyte lithium salt includes both lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate can promote better dissociation of lithium bis(fluorosulfonyl)imide, improve the performance of the electrolyte, and thus improve the battery cycle life and fast charging performance.

[0204] As an example, the mass ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide in the electrolyte can be tested by the following method: the concentration of inorganic components in the electrolyte can be quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-1996.

[0205] As an example, the mass ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide in the electrolyte may be 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1.

[0206] In some embodiments, the compaction density of the positive electrode active material layer is 2.2 g / cm 3 -2.6g / cm 3 This helps improve the fast charging performance and energy density of battery cells.

[0207] As an example, the compaction density of the positive electrode active material layer may be 2.2 g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 or 2.6g / cm 3 .

[0208] When the compaction density of the positive electrode active material layer is within the aforementioned range, the compaction density of the positive electrode active material layer is relatively moderate, and the positive electrode sheet has a relatively high energy density.

[0209] As an example, the compacted density of the positive electrode active material layer can be measured by dividing the mass and thickness of the positive electrode active material layer. The mass and thickness of the positive electrode active material layer can be determined by wiping the positive electrode active material layer on the positive electrode sheet and calculating the difference in mass and thickness before and after wiping.

[0210] In some embodiments, the positive electrode sheet can be prepared by dispersing the positive electrode active material, conductive agent, binder and any other components in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, roller pressing (such as cold pressing process) and other processes, a positive electrode active material layer can be formed to obtain a positive electrode sheet.

[0211] The aforementioned compacted density of the positive electrode active material layer refers to the compacted density of the positive electrode active material layer after roller pressing. Specifically, the compacted density of the positive electrode active material layer after roller pressing and formation treatment, the compacted density of the positive electrode active material layer when the battery cell is fully charged or fully discharged, and the compacted density of the positive electrode active material layer after the battery cell has been left unattended for an extended period of time are all within the aforementioned ranges.

[0212] In some embodiments, the positive electrode active material layer includes a positive electrode active material comprising a core portion comprising an olivine-structured lithium-containing phosphate, and a coating layer coated on the surface of the olivine-structured lithium-containing phosphate, the coating layer containing one or more elements selected from the group consisting of C, Fe, Ti, Zr, Hf, Ge, and Sn. This helps improve the structural stability and ionic conductivity of the positive electrode active material.

[0213] Lithium-containing phosphates with an olivine structure combine low cost with high theoretical specific capacity, helping to increase the energy density of battery cells. Furthermore, the olivine structure maintains good crystal integrity during charge and discharge, reducing structural stress and extending the battery's cycle life. The coating effectively alleviates the poor electronic and ionic conductivity of lithium-containing phosphates with an olivine structure, improving the specific capacity of the cathode active material and the compacted density of the powder.

[0214] In some embodiments, the olivine-structured lithium-containing phosphate includes a general formula of Li x1 A y1 Me a M1 b P 1-c X c Y zA compound wherein 0.5≤x1≤1.3, 0≤y1≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A comprises one or more of Na, K, and Mg; Me comprises one or more of Mn, Fe, Co, and Ni; M1 comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X comprises one or more of S, Si, Cl, B, C, and N; and Y comprises one or more of O and F. This helps to improve the ionic and electronic conductivity of the core.

[0215] When the lithium-containing phosphate with an olivine structure satisfies the aforementioned general formula, its advantages over ternary materials are fully utilized to improve the high temperature resistance and structural stability of the battery cells prepared therefrom, thereby reducing the manufacturing cost of the battery cells.

[0216] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for the positive electrode active materials refer to the initial state of the material, i.e., the state before addition. When the positive electrode active material is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0217] In the list of positive electrode active materials for lithium-ion batteries in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0218] In some embodiments, the coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15-0.32, thereby helping to improve the electronic conductivity of the positive electrode active material.

[0219] The provision of the carbon layer can significantly improve the electronic conductivity of the lithium-containing phosphate with an olivine structure, make up for the defect of poor electronic conductivity of the lithium-containing phosphate with an olivine structure, and improve the capacity of the battery cell.

[0220] As an example, the degree of graphitization of the carbon layer may be 0.15, 0.17, 0.19, 0.21, 0.23, 0.25, 0.27, 0.29, 0.31, or 0.32.

[0221] When the degree of graphitization of the carbon layer falls within the aforementioned range, the arrangement of carbon atoms in the carbon layer is relatively disordered, with numerous lattice defects, resulting in a lack of a complete graphite lattice. Consequently, the electronic conductivity is slightly lower than that of carbon materials with higher degrees of graphitization. Carbon layers with a more disordered arrangement of carbon atoms typically have a higher specific surface area, which facilitates sufficient contact between the core and the electrolyte, improving the efficiency of lithium ion transfer at the interface between the two phases.

[0222] As an example, the graphitization degree of the carbon layer can be tested by the following method: the graphitization degree can be determined by the lattice parameters of the carbon crystal using the XRD diffraction method with reference to the standards JB / T4220-2011 and JISK0131-1996.

[0223] In some embodiments, in a cross-section of the positive electrode active material layer along the thickness direction, the positive electrode active material includes an olivine-structured lithium-containing phosphate with a longest diameter of 1 μm to 3 μm and an olivine-structured lithium-containing phosphate with a shortest diameter of 0.1 μm to 0.3 μm. This helps to increase the energy density of the battery cell.

[0224] As an example, in a cross section of the positive electrode active material layer along a thickness direction, the positive electrode active material includes an olivine-structured lithium-containing phosphate having a longest diameter of 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm.

[0225] As an example, in a cross section of the positive electrode active material layer along a thickness direction, the positive electrode active material includes an olivine-structured lithium-containing phosphate having a shortest diameter of 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, or 0.3 μm.

[0226] In some embodiments, the positive electrode active material has a Dv50 particle size of 1 μm to 5 μm.

[0227] As an example, the Dv50 particle size of the positive active material may be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm.

[0228] In some embodiments, the positive electrode active material has a Dv10 particle size of 0.4 μm to 0.7 μm.

[0229] As an example, the Dv10 particle size of the positive electrode active material may be 0.4 μm, 0.5 μm, 0.6 μm, or 0.7 μm.

[0230] When the Dv50 particle size and Dv10 particle size of the positive electrode active material are within the aforementioned range, the overall particle size distribution of the positive electrode active material is relatively reasonable, which is beneficial to improving the powder compaction density of the positive electrode active material, and then beneficial to improving the electrode compaction density of the positive electrode sheet, and ultimately improving the volume energy density of the battery cell.

[0231] The aforementioned Dv50 particle size refers to the particle size corresponding to when the cumulative volume distribution percentage of the particles reaches 50%.

[0232] The aforementioned Dv10 particle size refers to the particle size corresponding to when the cumulative volume distribution percentage of the particles reaches 10%.

[0233] As an example, the particle size of the positive electrode active material can be measured using laser diffraction particle size analysis. Specifically, the particle size of the positive electrode active material can be measured using a laser particle size analyzer (eg, Malvern-Master-Size-3000) in accordance with standard GB / T19077-2016.

[0234] In some embodiments, the positive electrode active material is a primary particle or a single crystal-like particle. Thus, the particle size of the positive electrode active material is larger, which is beneficial to improving the energy density of the battery cell.

[0235] When the positive electrode active material is in the form of primary particles or quasi-single crystal particles, a larger particle size helps increase its powder compaction density. Furthermore, under similar particle size distributions, a larger primary particle size of the positive electrode active material increases the powder compaction density of the positive electrode active material, which helps improve the volumetric energy density of the battery cell.

[0236] In some embodiments, the positive electrode active material is a mixture of primary and secondary particles. The primary particles can increase the powder compaction density of the positive electrode active material, while the secondary particles can improve the ionic conductivity of the positive electrode active material. This combination of primary and secondary particles can collectively improve the battery's volumetric energy density and fast-charging capability.

[0237] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, including at least one of lithium ferrite, lithium nickelate, lithium nickel copperate, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, and lithium nickel cobalt manganate. This helps to improve the cycle life of the battery cells.

[0238] When a battery is first charged, a SEI film forms on the surface of the negative electrode active material. The SEI's rupture and recombination during the charge-discharge cycle also cause irreversible lithium ion consumption, resulting in reduced initial battery efficiency and capacity loss. The addition of lithium-rich materials can pre-replenish this lost lithium during battery preparation, reducing or eliminating capacity decay caused by lithium loss and extending the battery's cycle life.

[0239] In some embodiments, the lithium-rich material includes at least one of lithium ferrite, lithium nickelate, and lithium oxalate. Thus, after the lithium-rich material releases lithium ions during the formation process, the residual product can improve and reduce the internal resistance of the positive electrode active material, improve the DC impedance of the battery, and increase the battery's charge and discharge efficiency.

[0240] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0241] In some embodiments, the positive electrode active material layer may further include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0242] In some embodiments, the positive electrode active material layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0243] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0244] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0245] In some embodiments, the length of the battery cell is L, the width of the battery cell is H, and the value of L is 4 to 10 times the value of H. In this way, the volume utilization of the battery can be effectively improved, and the overall energy density of the battery can be improved.

[0246] By flattening and extending the battery cells into a thin and long shape, the long strips of battery cells are arranged and combined to form a battery pack, eliminating the intermediate module structure, which can effectively improve the volume utilization of the battery pack and increase the overall energy density of the battery cells.

[0247] As an example, the value of L can be 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times, 9 times, 9.5 times, or 10 times the value of H.

[0248] When the proportional relationship between the values of L and H is within the above range, it helps to improve the volume utilization of the battery pack formed by the assembly of battery cells, and in the event of a collision or external impact, the force on the battery cells is more uniform and dispersed, effectively reducing the risk of short circuit.

[0249] In some embodiments, the value of L is 4 to 7 times the value of H. This helps the battery cell to have both higher energy density and lower internal resistance.

[0250] In some embodiments, L is 400 mm to 1000 mm, and / or H is 80 mm to 160 mm.

[0251] As an example, L may be 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, 700 mm, 750 mm, 800 mm, 850 mm, 900 mm, 950 mm, or 1000 mm.

[0252] As an example, H may be 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or 160 mm.

[0253] When L and H are within the above numerical ranges, the size of the battery cell is moderate, which is conducive to transfer and rapid assembly, and the transmission path of lithium ions in the battery cell is relatively short, and the internal resistance of the battery cell is small.

[0254] In some embodiments, reference Figures 1-8 , further comprising a housing, wherein the electrode assembly is located within the housing, the housing comprising two first housing walls 101 disposed opposite each other, and a surrounding wall connecting the two first housing walls 101, the surrounding wall comprising: two second housing walls 102 disposed opposite each other along the length direction of the first housing wall 101, and two third housing walls 103 disposed opposite each other along the width direction of the first housing wall 101, the second housing walls 102 being provided with electrode terminals, the positive electrode ears 12 and the negative electrode ears 22 being electrically connected to the electrode terminals on the two second housing walls 102, respectively, wherein a folding structure 106 is provided between the second housing wall 102 electrically connected to the positive electrode ears 12 and the positive electrode body 11, the folding structure 106 being configured to fold the plurality of positive electrode ears 12 together. This facilitates the fixing of the positive electrode ears and the welding between the positive electrode sheet and the electrode post 105.

[0255] refer to Figure 4 and Figure 5 Leading the positive electrode tab 12 and negative electrode tab 22 of the battery cell out of the two second shell walls of the housing, i.e., out of the opposite sides, facilitates more efficient arrangement of the battery cells within a limited space and facilitates the formation of efficient series and parallel connections of multiple battery cells within the battery pack. This also reduces the space occupied by connectors between battery cells, thereby improving the volumetric energy density of the battery pack. To increase the volumetric energy density, a lamination process can be used to form an electrode assembly, in which each positive electrode sheet has a corresponding positive electrode tab, and each negative electrode sheet has a corresponding negative electrode tab. To achieve current convergence, all positive electrode tabs 12 and negative electrode tabs 22 need to be brought together and then electrically connected to the corresponding electrode terminals.

[0256] Typically, aluminum foil is used for the positive electrode current collector, and copper foil is used for the negative electrode current collector. Because copper foil is soft and prone to breakage, the negative electrode tab must first be welded to the corresponding post on the second shell wall, then installed into the enclosure formed by the first and third shell walls. Finally, the positive electrode tab must be welded to the corresponding post on the second shell wall. To reduce the risk of inverted insertion of the positive electrode tab during welding to the corresponding second shell wall, which could cause an internal short circuit in the battery cell, multiple positive electrode tabs can be secured using a retractable structure to prevent inverted insertion and facilitate welding of the positive electrode tab to the lower seat of the post.

[0257] In some embodiments, the edge of the positive electrode sheet is chamfered along the length of the first shell wall 101. This facilitates quick assembly of the electrode assembly and reduces the risk of the separator being pierced when the electrode assembly is inserted into the shell.

[0258] In some embodiments, a liquid injection hole is provided on the second shell wall 102 connected to the negative electrode ear portion 22, thereby facilitating the injection of electrolyte.

[0259] Since the second shell wall connected to the positive electrode ear is provided with a retracting structure for retracting the positive electrode ear, in order to make the second shell wall have higher mechanical strength, the injection hole is provided on the second shell wall 102 connected to the negative electrode ear 22.

[0260] In some embodiments, reference Figure 9 and Figure 10 The injection hole 107 and the pressure relief portion 104 of the housing are located on different second housing walls 102. The pressure relief portion 104 is configured to release the pressure inside the housing. This can reduce corrosion of the pressure relief portion 104 by the electrolyte during the injection process.

[0261] Since the electrolyte will corrode the pressure relief portion when the electrolyte is injected into the battery cell through the injection hole, the injection hole and the pressure relief portion of the shell should be located on different second side walls.

[0262] In some embodiments, see Figure 11 The electrode terminal is provided with at least one mounting hole, and the pole 105 is passed through the mounting hole and riveted to the pole ear. This helps to reduce the volume and weight of the battery cell and improve the energy density of the battery cell.

[0263] Achieving electrical connection through a single pole can reduce connection points, simplify the production and assembly process, require fewer materials and processing steps, and reduce costs.

[0264] In some embodiments, reference Figure 9 and Figure 10 The electrode terminal is provided with at least two mounting holes, and each pole 105 is passed through the mounting holes and riveted to the pole ear portion, thereby helping to improve the current carrying capacity of the pole 105.

[0265] Achieving electrical connection through bipolar columns can disperse current, reduce local overheating, and improve the battery's fast charging performance.

[0266] In some embodiments, the diameter of the pole 105 is 3 mm to 8 mm. Thus, the pole 105 has both high current capacity and low space occupation.

[0267] As an example, the diameter of the pole may be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm or 8 mm.

[0268] When the pole diameter is within the above range, the pole has a stronger current-carrying capacity and a lower internal resistance, which can reduce heat generation.

[0269] In some embodiments, reference Figure 12 The pole post 105 riveted to the positive electrode tab 12 and the pole post 105 riveted to the negative electrode tab are staggered along the length of the first shell wall 101. Optionally, the pole post 105 riveted to the positive electrode tab and the pole post 105 riveted to the negative electrode tab are arranged diagonally along the length of the first shell wall 101. This helps to more efficiently arrange battery cells in a limited space and improve the volume energy density of the assembled battery module or battery pack.

[0270] In some embodiments, reference Figure 13 The pole 105 and the tab are electrically connected via the adapter 108. This significantly improves the welding quality and connection reliability between the pole 105 and the tab.

[0271] When the electrical connection between the pole and the lug is achieved through the adapter, the shape and size of the adapter can be adjusted as needed to adapt to different distances and positions. The welding process of the adapter has fewer defects, which can help distribute the current more evenly, reduce local overheating and potential difference, and improve the service life of the battery.

[0272] In some embodiments, reference Figure 14 The pole 105 is directly electrically connected to the tab, thereby reducing the structural complexity of the battery cell, reducing the volume of the battery cell, and increasing the energy density.

[0273] When the pole and the tab are directly electrically connected, the connector is eliminated, the internal structure of the battery cell is simplified, the assembly steps are reduced, and the overall manufacturing cost is reduced.

[0274] In some embodiments, the battery cells can be directly assembled into a battery pack, eliminating the need for a battery module and increasing the battery's energy density. A battery pack can contain one or more battery cells, with those skilled in the art selecting the specific number based on the application and capacity of the battery pack.

[0275] In some embodiments, the distance between the two first shell walls 101 is D, which is less than or equal to 30 mm, thereby facilitating rapid heat dissipation of the battery cell.

[0276] Because under fast charging conditions, the charging current and voltage flowing through the battery cell will increase accordingly, according to Joule's law, the heat generated will also increase significantly. For long battery cells, the first shell wall is the surface with the largest area of the battery cell, so the heat dissipation effect of the battery cell close to the first shell wall is better. However, in the thickness direction of the battery cell, that is, in the width direction of the third shell wall, the heat diffusion inside the battery cell is slow. When the distance D between the two first shell walls 101 is within the aforementioned range, the heat dissipation effect of the battery cell in the thickness direction is better, which is conducive to achieving good heat dissipation under fast charging and improving the fast charging performance of the battery cell.

[0277] In some embodiments, D is 10 mm to 25 mm. Thus, the battery cell has higher mechanical strength and better heat dissipation capability.

[0278] As an example, D may be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, or 30 mm.

[0279] In some embodiments, the thickness of the first shell wall 101 and the third shell wall 103 are independently less than or equal to 0.5 mm, thereby increasing the volume energy density of the battery cell.

[0280] When the thickness of the first shell wall 101 and the third shell wall 103 is within the aforementioned range, the shell wall is thinner and the weight of the shell is lighter, which is beneficial to improving the mass energy density and volume energy density of the battery cell.

[0281] As an example, the thicknesses of the first shell wall 101 and the third shell wall 103 may be the same.

[0282] In some embodiments, the first shell wall 101 and the third shell wall 103 include at least one of an aluminum shell and a steel shell, thereby improving the mechanical strength of the battery cell.

[0283] At the same thickness, the mechanical strength of the steel shell is greater than that of the aluminum shell, which can better restrain the electrode assembly and alleviate the expansion of the battery cell during charging and discharging.

[0284] At the same thickness, the density of the aluminum shell is lighter than that of the steel shell, the weight of the shell is further reduced, and the mass energy density of the battery cell is further improved.

[0285] In some embodiments, the first shell wall 101 and the third shell wall 103 are steel shells with a wall thickness of 0.1 mm to 0.5 mm, thereby effectively alleviating the volume expansion of the battery cell during the charge and discharge process.

[0286] In some embodiments, the first shell wall 101 and the third shell wall 103 are aluminum shells, and the thickness of the aluminum shells is 0.3 mm to 0.4 mm, thereby effectively improving the mass energy density of the battery cell.

[0287] In some embodiments, the first shell wall 101 and the third shell wall 103 are formed by bending and welding aluminum plates, and the weld is located at the connection between the first shell wall 101 and the third shell wall 103. This can reduce leakage of the electrolyte.

[0288] The aluminum shell obtained by bending and laser welding the aluminum plate has an excellent sealing effect, which can effectively prevent electrolyte leakage, improve the stability of the internal environment of the battery cell, and improve the cycle life of the battery cell.

[0289] In some embodiments, when the organic solvent in the electrolyte is mainly a low-viscosity solvent, the electrolyte as a whole also exhibits a lower viscosity. Low-viscosity electrolytes are prone to decomposition and gas production during high-rate charge and discharge, causing the battery cells to swell. The weld, as a mechanical weak point, may crack under extreme circumstances. In order to prevent rapid deterioration caused by electrolyte leakage after the weld cracks, the weld can be located at the junction of the third shell wall and the first shell wall away from the ground, so that after the weld cracks, the electrolyte is still not easy to flow out of the battery cell, effectively suppressing the rapid deterioration of the battery condition.

[0290] In some embodiments, a side support plate is provided between the electrode assembly and the first shell wall 101, thereby helping to improve the structural stability of the battery cell.

[0291] The side support plate can block direct contact between the pole piece and the shell, reducing damage to the pole piece caused by the rounded corners at the edge of the inner wall of the shell.

[0292] In some embodiments, at least one of the second shell walls 102 is provided with a pressure relief portion 104, which is configured to release pressure within the shell. The orthographic projection of the pressure relief portion 104 on the second shell wall 102 is 7%-15% of the area of the second shell wall 102. This facilitates rapid release of excess pressure gas within the battery cell through the pressure relief portion 104 when the pressure within the battery cell is excessive.

[0293] As an example, the area of the pressure relief portion may be 155 mm 2 , the area of the second shell wall can be 1920mm 2 .

[0294] When the area of the orthographic projection of the pressure relief portion 104 on the second shell wall 102 is within the aforementioned range, the pressure relief portion can respond quickly when the internal pressure of the battery cell suddenly increases and rupture to release the internal pressure; it also occupies less space on the second shell wall, making it convenient to arrange other structural components on the second shell wall.

[0295] In some embodiments, the capacity of the battery cell is Q, the area of the positive projection of the pressure relief portion 104 on the second shell wall 102 is P, the ratio of P to Q is greater than or equal to 1.1, the unit of Q is Ah, and the unit of P is mm 2 This helps to quickly release the overpressure gas inside the battery cell.

[0296] When the capacity of a battery cell is large, the content of low-viscosity electrolyte inside the battery is correspondingly high, resulting in a high gas production per unit time during high-rate charge and discharge. Furthermore, lithium bis(fluorosulfonyl)imide also undergoes a gas-producing side reaction with the fully charged negative electrode active material layer. Therefore, a larger pressure relief portion is required to provide more venting space, allowing for rapid response to the initial surge in internal pressure within the battery cell, rupturing and releasing the internal pressure. When the ratio of P to Q falls within the aforementioned range, the pressure relief portion's area matches the battery capacity, meeting the pressure relief requirements of the corresponding capacity battery cell.

[0297] In some embodiments, both second shell walls may be provided with a pressure relief portion. The ratio between the area of the pressure relief portion and the area of the second shell wall can be referred to the above content.

[0298] In a second aspect of the present application, a battery device is provided, including the aforementioned battery cell. The battery device may be a battery module, a battery pack, an energy storage device, etc. Therefore, the battery device has all the features and advantages of the aforementioned battery cell, which will not be described in detail here.

[0299] In a third aspect of the present application, an electrical device is provided, comprising the aforementioned battery cell. Thus, the electrical device has all the features and advantages of the aforementioned battery cell, which will not be elaborated herein.

[0300] The aforementioned battery cells or battery packs can be used as power sources or energy storage units for electrical devices. These devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0301] As the electrical device, a battery cell or a battery pack can be selected according to its usage requirements.

[0302] Figure 15 This is an example of an electric device. This electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the electric device, a battery pack can be used.

[0303] The present invention will be described below by way of specific examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are determined according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments not specified by manufacturer are all commercially available conventional products.

[0304] Example 1

[0305] 1) Preparation of positive electrode sheet

[0306] The positive electrode sheet consists of a positive electrode current collector aluminum foil and a positive electrode active material layer. The positive electrode active material layer is formed by evenly coating the surface of the positive electrode current collector aluminum foil with a positive electrode slurry (solvent: N-methylpyrrolidone), drying it, and cold pressing it to form a film. The positive electrode active material layer comprises the positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.4:1.1. The positive electrode active material is lithium iron phosphate containing aluminum, titanium, and vanadium. The mass fractions of aluminum, titanium, and vanadium are 0.012%, 0.025%, and 0.025%, respectively. In a cross section of the positive electrode active material layer along the thickness direction, the positive electrode active material includes an olivine-structured lithium-containing phosphate with a longest diameter of 2.5 μm and an olivine-structured lithium-containing phosphate with a shortest diameter of 0.2 μm. The total width of the positive electrode ear accounts for 50% of the total width of the positive electrode body. The coating weight of the single-layer positive electrode active material layer is 0.283 g / 1540.25 mm 2 The compaction density of the positive electrode active material layer is 2.45 g / cm 3 .

[0307] 2) Preparation of negative electrode sheet

[0308] The negative electrode sheet includes a negative electrode current collector copper foil and a negative electrode active material layer. The negative electrode active material layer includes a film layer formed by evenly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector copper foil, drying, and cold pressing. The negative electrode active material layer includes a negative electrode active material, a binder styrene-butadiene rubber (SBR), a thickener sodium carboxymethyl cellulose (CMC-Na), and a conductive agent carbon black (Super P) in a weight ratio of 96.2:1.8:1.2:0.8. The negative electrode active material is a single layer of graphite. The Dv50 particle size of the negative electrode active material is 10.5μm, wherein the total width of the negative electrode ear accounts for 50% of the total width of the negative electrode main body, wherein the coating weight of the single layer of negative electrode active material layer is 0.127g / 1540.25mm 2 The compaction density of the negative electrode active material layer is 1.45 g / cm 3 .

[0309] 3) Isolation film

[0310] The isolation film is a porous polypropylene PP film.

[0311] 4) Preparation of electrolyte

[0312] The organic solvent substances in the electrolyte are EA / DMC / EC=10 / 55 / 35 in proportion, and the electrolyte lithium salt in the electrolyte is lithium hexafluorophosphate with a mass content of 12.5%.

[0313] 5) Battery preparation

[0314] The lithium-ion battery includes a housing, an electrode assembly, and an electrolyte. The electrode assembly and electrolyte are located within the housing. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The electrode assembly is a wound electrode assembly, with the separator disposed between the positive and negative electrode sheets. The battery cell has a length (L) of 510m, a width (H) of 120mm, and a thickness (D) of 16mm.

[0315] The differences between the remaining embodiments and embodiment 1 are shown in Tables 1 to 5.

[0316] Table 1

[0317]

[0318] Table 2

[0319]

[0320] Table 3

[0321]

[0322] Table 4

[0323]

[0324] Table 5

[0325]

[0326] Comparative Example 1

[0327] Comparative Example 1 is consistent with Example 1, except that the total width of the positive electrode ear accounts for 30% of the total width of the positive electrode body, the total width of the negative electrode ear accounts for 30% of the total width of the negative electrode body, and the coating weight of the single-layer positive electrode active material layer is 0.25g / 1540.25mm 2 The coating weight of the single-layer negative electrode active material layer is 0.1g / 1540.25mm 2 The organic solvent substances in the electrolyte and their proportions are EA / EC=90 / 10.

[0328] Comparative Example 2

[0329] Comparative Example 2 is consistent with Example 1, except that the coating weight of the single-layer positive electrode active material layer is 0.3g / 1540.25mm 2 The coating weight of the single-layer negative electrode active material layer is 0.145g / 1540.25mm 2 The organic solvent substances in the electrolyte and their proportions are DMC / EC=60 / 40.

[0330] Comparative Example 3

[0331] Comparative Example 3 is consistent with Example 1, except that the total width of the positive electrode ear accounts for 100% of the total width of the positive electrode body, the total width of the negative electrode ear accounts for 100% of the total width of the negative electrode body, and the coating weight of the single-layer positive electrode active material layer is 0.31g / 1540.25mm 2 The coating weight of the single-layer negative electrode active material layer is 0.16g / 1540.25mm 2 The organic solvent substances in the electrolyte and their proportions are EA / EC=90 / 10.

[0332] The fast charging performance of the batteries in Examples 1-10 and Comparative Examples 1-3 was tested using the following method. The test results are shown in Table 1-1.

[0333] Charging time test: ① Voltage calibration: 1) Prepare a laminated three-electrode battery with the positive electrode sheet, negative electrode sheet, separator, and electrolyte in the embodiment or comparative example, and let it stand at 25°C for 30 minutes; 2) Charge the battery cell at 0.33C at 25°C to a charge cut-off voltage of 3.65V, and continue to charge at the charge cut-off voltage until the current reaches 0.05C and the charge is cut off (where C represents the rated capacity of the battery cell); 3) Let it stand at 25°C for 1 hour; 4) Discharge the battery cell at 0.33C at 25°C to a discharge cut-off voltage of 2.5V, and record the total discharge capacity C0 released by the battery cell; 5) Let it stand at 25°C for 1 hour. ② Room temperature charging test: 1) Prepare a laminated three-electrode battery with the positive electrode sheet, negative electrode sheet, separator, and electrolyte in the embodiment or comparative example, and let it stand for 30 minutes; 2) 0.33C0 DC discharge to the discharge cut-off voltage of 2.5V, which corresponds to 0% SOC; 3) Let it stand for 5 minutes; 4) 5C0 constant current charge to the negative electrode potential of 0V, read the capacity C1 at this time, which corresponds to C1 / C0SOC; 5) Let it stand for 5 minutes; 6) 4.5C0 constant current charge to the negative electrode potential of 0V, read the capacity C2 at this time, which corresponds to C2 / C0SOC; 7) Let it stand for 5 minutes; 8) 4C0 constant current charge to the negative electrode potential of 0V, read the capacity C3 at this time, which corresponds to C3 / C0SOC; 9) Let it stand for 5 minutes; 10) 3C0 constant current charge to the negative electrode potential of 0V, read the capacity C4 at this time, which corresponds to C4 / C0SOC; 11) Let it stand for 5 minutes; 12) 2C0 constant current charge 13) Let stand for 5 minutes; 14) Charge with a constant current of 1C0 until the negative electrode potential is 0V and read the capacity C6, which corresponds to C6 / C0SOC; 15) Let stand for 5 minutes; 16) Charge with a constant current of 0.8C0 until the negative electrode potential is 0V and read the capacity C7, which corresponds to C7 / C0SOC; 17) Let stand for 5 minutes; 18) Charge with a constant current of 0.5C0 until the negative electrode potential is 0V and read the capacity C8, which corresponds to C8 / C0SOC; 19) Let stand for 5 minutes; 20) Charge with a constant current of 0.33C0 until the negative electrode potential is 0V and read the capacity C9 (also known as C0), which corresponds to 100% SOC. The required charging time is calculated by adding the total charging time from 10% SOC to 80% SOC.

[0334] Temperature rise test: Place a temperature sensing wire at any position on the battery cell top cover to monitor the top cover temperature, and then perform the following charging process on the battery cell:

[0335] 1) The battery cells of the embodiment or comparative example were discharged at 0.33C DC to a discharge cut-off voltage of 2.5V, which corresponds to 0% SOC;

[0336] 2) Let the battery rest for 5 minutes, then charge at a constant current of 5C to C1 / CSOC (C1 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell);

[0337] 3) Let the battery rest for 5 minutes, then charge at a constant current of 4.5C to C2 / CSOC (C2 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell);

[0338] 4) Let stand for 5 minutes, then charge at a constant current of 4C to C3 / CSOC (the value of C3 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell);

[0339] 5) Let stand for 5 minutes, then charge at a constant current of 3C to C4 / CSOC (the value of C4 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell);

[0340] 6) Let stand for 5 minutes, then charge at a constant current of 2C to C5 / CSOC (the value of C5 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell);

[0341] 7) Let stand for 5 minutes, then charge at a constant current of 1C to C6 / CSOC (the value of C6 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell);

[0342] 8) Let stand for 5 minutes, then charge at a constant current of 0.8C to C7 / CSOC (the value of C7 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell);

[0343] 9) Let the battery rest for 5 minutes, then charge at a constant current of 0.5C to C8 / CSOC (the value of C8 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell);

[0344] 10) Let it rest for 5 minutes, then charge at a constant current of 0.33C to C9 / CSOC (the value of C9 is the capacity corresponding to the negative electrode analysis window of the laminated three-electrode battery test, and C represents the rated capacity of the battery cell). At this point, the battery cell reaches a fully charged state, that is, 100% SOC;

[0345] Monitor and record the temperature rise of the battery cells when charging from 10% SOC to 80% SOC.

[0346] The battery cells in Example 1 and Examples 11-13 were subjected to cycle performance tests using the following test methods. The test results are shown in Table 1-2.

[0347] Cycle life: At 45°C, charge the battery cell at a constant current of 1C to a cut-off voltage of 3.65V, then charge it at a constant voltage of 0.05C, leave it for 10 minutes, and discharge it at a constant current of 1C to 2.5V. Repeat this step until the capacity retention rate decays to 80% and the number of cycles at this time is recorded.

[0348] Table 1-1

[0349]

[0350] Table 1-2

[0351]

[0352] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, wherein: include: An electrode assembly, comprising a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, wherein: The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector. The positive electrode current collector includes a positive electrode main body and at least one positive electrode ear. The ear connection edge of the positive electrode main body is connected to the positive electrode ear. Along the direction in which the ear connection edge extends, the total width of the positive electrode ear accounts for 50%-100% of the total size of the ear connection edge of the positive electrode main body. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode current collector includes a negative electrode main body and at least one negative electrode ear. The ear connection edge of the negative electrode main body is connected to the negative electrode ear. Along the direction in which the ear connection edge extends, the total width of the negative electrode ear accounts for 50%-100% of the total size of the ear connection edge of the negative electrode main body. The coating weight of a single layer of the negative electrode active material layer is 0.1g / 1540.25mm 2 -0.145 g / 1540.25 mm 2 , An electrolyte, the electrolyte comprising an organic solvent, the organic solvent comprising a first solvent, the first solvent comprising at least one of dimethyl carbonate and a linear carboxylic acid ester, wherein the linear carboxylic acid ester has a structural formula satisfying R1-COO-R2, R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl groups; based on the total mass of the electrolyte, the mass fraction of the first solvent is 4%-72%.

2. The battery cell according to claim 1, wherein: The total width of the positive electrode ear is 40mm-160mm; and / or the total width of the negative electrode ear is 40mm-160mm; and / or the width of the positive electrode ear is 40mm-160mm; and / or the width of the negative electrode ear is 40mm-160mm.

3. The battery cell according to claim 1 or 2, wherein: The positive electrode ear and the negative electrode ear are located on the same side of the positive electrode main body, or the positive electrode ear and the negative electrode ear are located on two opposite sides of the positive electrode main body.

4. The battery cell according to claim 1, wherein: The positive electrode current collector includes the positive electrode main body and multiple positive electrode ear portions, and at least two of the positive electrode ear portions are located on two opposite sides of the positive electrode main body; and / or, the negative electrode current collector includes the negative electrode main body and multiple negative electrode ear portions, and at least two of the negative electrode ear portions are located on two opposite sides of the negative electrode main body.

5. The battery cell according to claim 1, wherein The positive electrode current collector includes the positive electrode main body and a plurality of positive electrode tabs arranged at intervals; and / or the negative electrode current collector includes the negative electrode main body and a plurality of negative electrode tabs arranged at intervals. The battery cell according to claim 1 , wherein: The coating weight of the single layer of the negative electrode active material layer is 0.1g / 1540.25mm 2 -0.135g / 1540.25mm 2 .

7. The battery cell according to claim 6, wherein: The time for charging the battery from 10% SOC to 80% SOC is 7 min-15 min.

8. The battery cell according to claim 1, wherein The coating weight of the single layer of the negative electrode active material layer is 0.136g / 1540.25mm 2 -0.145g / 1540.25mm 2 .

9. The battery cell according to claim 8, wherein: The time for charging the battery from 10% SOC to 80% SOC is 20 min-30 min.

10. The battery cell according to claim 1, wherein The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located at least on one side of the negative electrode current collector, and the compaction density of the negative electrode active material layer is 1.2g / cm3-1.5g / cm 3 .

11. The battery cell according to claim 10, wherein: The negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, and the mass fraction of silicon in the negative electrode active material is 0.1%-7%.

12. The battery cell according to claim 11, wherein: The mass fraction of silicon in the negative electrode active material is 1%-5%.

13. The battery cell according to claim 10, wherein: The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer arranged in a stacked manner, the first negative electrode active material layer is located on a side close to the negative electrode current collector, the Dv50 of the first negative electrode active material in the first negative electrode active material layer is 9.2μm-18.5μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2μm-15.5μm.

14. The battery cell according to claim 1, wherein The conductivity of the electrolyte is 10 ms / cm-20 ms / cm.

15. The battery cell according to claim 1, wherein Based on the total mass of the electrolyte, the mass fraction of the first solvent is 16%-72%.

16. The battery cell according to claim 1, wherein Based on the total mass of the electrolyte, the mass fraction of the linear carboxylic acid ester is 32%-68%.

17. The battery cell according to claim 1, wherein The electrolyte further includes a first lithium salt additive, which includes at least one of a fluorine-containing borate and a fluorine-containing phosphate. Based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive is 0.05%-0.5%.

18. The battery cell according to claim 17, wherein: The first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalatophosphate, lithium difluorooxalatoborate, and lithium tetrafluoroborate.

19. The battery cell according to claim 17, wherein: Based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive is 0.1%-0.3%.

20. The battery cell according to claim 1, wherein The organic solvent further includes a second solvent, and the second solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

21. The battery cell according to claim 20, wherein: The second solvent includes diethyl carbonate, and the mass fraction of the diethyl carbonate is greater than or equal to 12% based on the total mass of the electrolyte.

22. The battery cell according to claim 1, wherein The electrolyte further includes non-lithium salt additives, and the non-lithium salt additives include sulfate additives and carbonate additives.

23. The battery cell according to claim 22, wherein: The carbonate additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate.

24. The battery cell according to claim 23, wherein: Based on the total mass of the electrolyte, the mass fraction of the vinylene carbonate is 0.5%-2.5%, and / or the mass fraction of the fluoroethylene carbonate is 0.05%-2%.

25. The battery cell according to claim 22, wherein: The sulfate ester additive includes at least one of 4,4-ethylene sulfate, vinyl disulfate, vinyl cyclotrisulfate, and 1,3-propane sultone.

26. The battery cell according to claim 22, wherein Based on the total mass of the electrolyte, the mass fraction of the non-lithium salt additive is 0.05%-3%.

27. The battery cell according to claim 1, wherein The electrolyte further includes a second lithium salt additive, which includes at least one of lithium bis(oxalatoborate), lithium difluorobis(oxalatophosphate), lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate.

28. The battery cell according to claim 1, wherein The electrolyte further includes an electrolyte lithium salt, which includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Based on the total mass of the electrolyte, the mass fraction of the electrolyte lithium salt is greater than or equal to 13%.

29. The battery cell according to claim 28, wherein The electrolyte lithium salt includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide in the electrolyte is (1.2-2):

1.

30. The battery cell according to claim 1, wherein The compaction density of the positive electrode active material layer is 2.2 g / cm 3 -2.6g / cm 3 .

31. The battery cell according to claim 1, wherein The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes: a core portion comprising an olivine-structured lithium-containing phosphate, and The coating layer is coated on the surface of the lithium-containing phosphate with an olivine structure, and the coating layer contains one or more elements selected from the group consisting of C, Fe, Ti, Zr, Hf, Ge, and Sn.

32. The battery cell according to claim 31, wherein The lithium-containing phosphate of the olivine structure includes the general formula Li x1 A y1 Me a M1 b P 1-c X c Y z A compound wherein 0.5≤x1≤1.3, 0≤y1≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M1 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F.

33. The battery cell according to claim 31 or 32, wherein: The coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15-0.

32.

34. The battery cell according to claim 31, wherein In a cross section of the positive electrode active material layer along a thickness direction, the positive electrode active material includes an olivine-structured lithium-containing phosphate with a longest diameter of 1 μm to 3 μm and an olivine-structured lithium-containing phosphate with a shortest diameter of 0.1 μm to 0.3 μm.

35. The battery cell according to claim 31, wherein The positive electrode active material satisfies at least one of the following conditions: The Dv50 particle size of the positive electrode active material is 1 μm-5 μm; The Dv10 particle size of the positive electrode active material is 0.4 μm-0.7 μm; The positive electrode active material is a primary particle or a single crystal-like particle.

36. The battery cell according to claim 31, wherein The positive electrode active material layer also includes a lithium-rich material, and the lithium-rich material includes at least one of lithium ferrite, lithium nickelate, lithium nickel copperate, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, and lithium nickel cobalt manganate.

37. The battery cell according to claim 1, wherein: The length of the battery cell is L, the width of the battery cell is H, and the value of L is 4 to 10 times the value of H.

38. The battery cell according to claim 37, wherein: The value of L is 4 to 7 times the value of H.

39. The battery cell according to claim 37 or 38, wherein: L is 400mm-1000mm, and / or H is 80mm-160mm.

40. The battery cell according to claim 1, wherein It also includes a shell, the electrode assembly is located in the shell, the shell includes two first shell walls arranged opposite to each other, and a surrounding wall connecting the two first shell walls, the surrounding wall includes: two second shell walls arranged opposite to each other along the length direction of the first shell wall, two third shell walls arranged opposite to each other along the width direction of the first shell wall, the second shell walls are provided with electrode terminals, the positive electrode ear and the negative electrode ear are electrically connected to the electrode terminals on the two second shell walls respectively, wherein a retraction structure is provided between the second shell wall electrically connected to the positive electrode ear and the positive electrode main body, and the retraction structure is configured to retract the multiple positive electrode ears.

41. The battery cell according to claim 40, wherein: In the length direction of the first shell wall, the edge of the positive electrode plate is chamfered.

42. The battery cell according to claim 40 or 41, wherein: A liquid injection hole is provided on the second shell wall connected to the negative electrode ear.

43. The battery cell according to claim 42, wherein: The liquid injection hole and the pressure relief portion of the shell are located on different second shell walls, and the pressure relief portion is configured to release the pressure inside the shell.

44. The battery cell according to claim 40, wherein At least one mounting hole is provided on the electrode terminal, and the pole is passed through the mounting hole and riveted to the pole ear.

45. The battery cell according to claim 40, wherein The electrode terminal is provided with at least two mounting holes, and each pole is passed through the mounting hole and riveted to the pole ear portion.

46. The battery cell according to claim 44 or 45, wherein: The diameter of the pole is 3mm-8mm.

47. The battery cell according to claim 44 or 45, wherein: The pole riveted to the positive electrode tab and the pole riveted to the negative electrode tab are staggered in the length direction of the first shell wall.

48. The battery cell according to claim 44 or 45, wherein: The pole riveted to the positive electrode tab and the pole riveted to the negative electrode tab are arranged diagonally in the longitudinal direction of the first shell wall.

49. The battery cell according to claim 44 or 45, wherein: The pole and the tab are electrically connected via a transition piece.

50. The battery cell according to claim 44 or 45, wherein: The pole and the tab are directly electrically connected.

51. The battery cell according to claim 40, wherein The distance between the two first shell walls is D, which is less than or equal to 30 mm.

52. The battery cell according to claim 51, wherein D is 10mm-25mm.

53. The battery cell according to claim 40, wherein The thickness of the first shell wall and the third shell wall are independently less than or equal to 0.5 mm.

54. The battery cell according to claim 53, wherein: The first shell wall and the third shell wall include at least one of an aluminum shell and a steel shell.

55. The battery cell according to claim 54, wherein The first shell wall and the third shell wall are steel shells, and the wall thickness of the steel shells is 0.1mm-0.5mm.

56. The battery cell according to claim 54, wherein: The first shell wall and the third shell wall are aluminum shells, and the wall thickness of the aluminum shells is 0.3mm-0.4mm.

57. The battery cell according to claim 56, wherein: The first shell wall and the third shell wall are obtained by bending and welding aluminum plates, and the welding seam is located at the connection between the first shell wall and the third shell wall.

58. The battery cell according to claim 40, wherein: A side support plate is provided between the electrode assembly and the first shell wall.

59. The battery cell according to claim 40, wherein At least one of the second shell walls is provided with a pressure relief portion, which is configured to release the pressure inside the shell, and the area of the positive projection of the pressure relief portion on the second shell wall is 7%-15% of the area of the second shell wall.

60. The battery cell according to claim 59, wherein The capacity of the battery is Q, the ratio of the area of the orthographic projection of the pressure relief portion on the second shell wall to Q is greater than or equal to 1.1, the unit of Q is Ah, and the unit of the area is mm 2 .

61. A battery device, wherein: The battery device comprises a battery cell according to any one of claims 1 to 60, wherein the battery device comprises at least one of a battery module, a battery pack, and an energy storage device.

62. An electrical device, wherein: A battery cell comprising the battery cell according to any one of claims 1 to 60.

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