Battery cell, battery device and electric device

Abstract

The present disclosure provides a battery cell and an electric device. The battery cell comprises: an electrode assembly, wherein in the width direction of a positive electrode body portion, the total width of a positive electrode tab portion accounts for 50%-100% of the total width of the positive electrode body portion, and in the width direction of a negative electrode body portion, the total width of a negative electrode tab portion accounts for 50%-100% of the total width of the negative electrode body portion, wherein the coating weight of a single-layer negative electrode active material layer is 0.1 g / 1540.25 mm2-0.145 g / 1540.25 mm2; and an electrolyte comprising an organic solvent, wherein the organic solvent includes a first solvent, and the first solvent comprises at least one of dimethyl carbonate and a linear carboxylic ester; the structural formula of the linear carboxylic ester satisfies R1-COO-R2, wherein R1 and R2 are each independently selected from C1-C5 alkyl or haloalkyl; and on the basis of the total mass of the organic solvent, the mass fraction of the first solvent is 4%-72%.

Description

Battery cells, battery packs, electrical devices

[0001] Cross-reference to related applications

[0002] This application claims priority to PCT patent application No. PCT / CN2024 / 107376, filed on July 24, 2024, the entirety of which is incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, specifically to battery cells, battery devices, and electrical devices. Background Technology

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

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

[0006] Application content

[0007] In a first aspect, this application proposes a battery cell comprising: an electrode assembly, the electrode assembly including a positive electrode, a negative electrode, and a separator between the positive and negative electrode, wherein the positive electrode includes a positive current collector and a positive active material layer located on at least one side of the positive current collector, the positive current collector including a positive electrode body portion and at least one positive electrode tab portion, the positive electrode body portion being connected to the positive electrode tab portion, and the total width of the positive electrode tab portion accounting for a certain percentage along the width direction of the positive electrode body portion. The positive electrode body portion accounts for 50%-100% of the total width. 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 body portion and at least one negative electrode tab portion. The negative electrode body portion and the negative electrode tab portion are connected. Along the width direction of the negative electrode body portion, the total width of the negative electrode tab portion accounts for 50%-100% of the total width of the negative electrode body portion. The coating weight of a single layer of the negative electrode active material layer is 0.1g / 1540.25mm. 2 -0.145g / 1540.25mm 2The electrolyte comprises an organic solvent, which includes a 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, and R1 and R2 are independently selected from C1-C5 alkyl or haloalkyl groups; based on the total mass of the electrolyte, the mass fraction of the first solvent is 4%-72%. This effectively improves the fast-charging performance of the battery cell and enhances its performance under fast-charging conditions.

[0008] In some embodiments, the total width of the positive electrode portion is 40mm-160mm; and / or, the total width of the negative electrode portion is 40mm-160mm; and / or, the width of the positive electrode portion is 40mm-160mm; and / or, the width of the negative electrode portion is 40mm-160mm. Therefore, the current-carrying area of ​​the positive and negative electrode portions is relatively large, resulting in superior heat dissipation capabilities.

[0009] 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 the connection of external circuitry and the assembly process.

[0010] In some embodiments, the positive current collector includes the positive electrode body and a plurality of positive electrode tabs, with at least two positive electrode tabs located on opposite sides of the positive electrode body; and / or, the negative current collector includes the negative electrode body and a plurality of negative electrode tabs, with at least two negative electrode tabs located on opposite sides of the negative electrode body. This provides a more uniform heat distribution and reduces tab deformation caused by excessive force on one side.

[0011] In some embodiments, the positive current collector includes the positive electrode body portion and a plurality of spaced-apart positive electrode tabs; and / or, the negative current collector includes the negative electrode body portion and a plurality of spaced-apart negative electrode tabs. This shortens the electron transport path and reduces battery heat generation.

[0012] In some embodiments, the coating weight of a single layer of the negative electrode active material is 0.1 g / 1540.25 mm. 2 -0.135g / 1540.25mm 2 Therefore, the battery cell has a high volumetric energy density.

[0013] In some embodiments, the battery takes 7-15 minutes to charge from 10% SOC to 80% SOC. Therefore, the battery cell exhibits superior fast-charging performance.

[0014] In some embodiments, the coating weight of a single layer of the negative electrode active material is 0.136 g / 1540.25 mm. 2 -0.145g / 1540.25mm 2 Therefore, the battery cell has a high volumetric energy density.

[0015] In some embodiments, the battery takes 20-30 minutes to charge from 10% SOC to 80% SOC. Therefore, the battery cell exhibits superior fast-charging performance.

[0016] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer located at least on one side of the negative current collector, wherein the compaction density of the negative active material layer is 1.2 g / cm³. 3 -1.5cm 3 This helps improve the fast-charging performance of individual battery cells.

[0017] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which includes a silicon-containing material, wherein 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.

[0018] In some embodiments, the mass fraction of silicon in the negative electrode active material is 1%-5%. This can further improve the mass energy density of the battery cell.

[0019] 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 is 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 is 9.2 μm-18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2 μm-15.5 μm. This significantly improves the fast-charging performance and energy density of the battery cell.

[0020] In some embodiments, the conductivity of the electrolyte is 10 ms / cm to 20 ms / cm. This helps to improve the fast-charging performance of the battery cells.

[0021] In some embodiments, the mass fraction of the first solvent is 16%-72% based on the total mass of the electrolyte. This can improve the fast-charging performance of the battery cell.

[0022] In some embodiments, the mass fraction of the linear carboxylic acid ester is 32%-68% based on the total mass of the electrolyte. This effectively reduces the viscosity of the electrolyte and improves the fast-charging performance of the battery.

[0023] In some embodiments, the electrolyte further includes a first lithium salt additive, which includes at least one of fluoroborate and fluorophosphate, and the mass fraction of the first lithium salt additive is 0.05%-0.5% based on the total mass of the electrolyte. This effectively reduces the internal resistance of the battery cell.

[0024] In some embodiments, the first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalate phosphate, lithium difluorooxalate borate, and lithium tetrafluoroborate. This facilitates the formation of a low-resistance solid electrolyte film on the surface of the negative electrode active material.

[0025] 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. This helps to reduce the cost of the battery cell.

[0026] In some embodiments, the organic solvent further includes a second solvent, the second solvent comprising at least one of ethylene carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butyl carbonate. This helps to improve the cycle life of the battery cell.

[0027] In some embodiments, the second solvent comprises diethyl carbonate, and the content of diethyl carbonate is not less than 12% based on the total mass of the electrolyte.

[0028] In some embodiments, the electrolyte further includes non-lithium salt additives, including at least one of vinylene carbonate, fluoroethylene carbonate, and ethylene ethylene carbonate. This facilitates the formation of a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0029] In some embodiments, the carbonate additive includes at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and ethylene ethylene carbonate. This facilitates the formation of a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0030] In some embodiments, the mass fraction of vinylene carbonate is 0.5%-2.5% based on the total mass of the electrolyte, and / or the mass fraction of fluoroethylene carbonate is 0.05%-2%. This facilitates the formation of a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0031] In some embodiments, the sulfate ester additive includes at least one of 4,4-vinyl sulfate, ethylene disulfate, cyclotrisulfate, and 1,3-propanesulfonate lactone.

[0032] In some embodiments, the non-lithium salt additive has a mass fraction of 0.05%-3% based on the total mass of the electrolyte. This helps to reduce the cost of individual battery cells.

[0033] In some embodiments, the electrolyte further includes a second lithium salt additive, which includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate. This facilitates the formation of a solid electrolyte film with high ionic conductivity on the surface of the negative electrode active material.

[0034] In some embodiments, the electrolyte further includes an electrolyte lithium salt, which includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the mass fraction of the electrolyte 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.

[0035] In some embodiments, the electrolyte lithium salt comprises lithium hexafluorophosphate and lithium difluorosulfonylimide, wherein the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide in the electrolyte is (1.2-2):1. This helps to further improve the conductivity of the electrolyte.

[0036] In some embodiments, the compaction density of the positive electrode active material layer is 2.2 g / cm³. 3 -2.6g / cm 3 This helps improve the fast-charging performance and energy density of individual battery cells.

[0037] In some embodiments, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprising: a core comprising a lithium phosphate with an olivine structure, and a coating layer covering the surface of the lithium phosphate with the olivine structure, the coating layer containing one or more elements selected from C, Fe, Ti, Zr, Hf, Ge, and Sn. This helps to improve the structural stability and ionic conductivity of the positive electrode active material.

[0038] In some embodiments, the lithium phosphate with the olivine structure includes those of the general formula Li x1 A y1 Me a M1 b P 1-c X c Y zThe compound contains the following components: 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. This contributes to improving the ionic and electronic conductivity of the core.

[0039] In some embodiments, the coating layer comprises a carbon layer having a graphitization degree of 0.15-0.32. This helps to improve the electronic conductivity of the positive electrode active material.

[0040] In some embodiments, in a cross-section along the thickness direction of the positive electrode active material layer, the positive electrode active material comprises a lithium phosphate with an olivine structure having a longest diameter of 1 μm-3 μm and a lithium phosphate with an olivine structure having a shortest diameter of 0.1 μm-0.3 μm. This is beneficial for improving the energy density of the battery cell.

[0041] 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-5 μm; the Dv10 particle size of the positive electrode active material is 0.4 μm-0.7 μm; and the positive electrode active material is a primary particle or a near-monocrystalline particle. Therefore, a larger particle size of the positive electrode active material is beneficial for improving the energy density of the battery cell.

[0042] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, which includes at least one of lithium ferrite, lithium nickel oxide, lithium nickel copper oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, lithium trilithium citrate, and lithium nickel cobalt manganese oxide. This helps to improve the cycle life of the battery cell.

[0043] In some embodiments, the length of the battery cell is L, and the width of the battery cell is H, where L is 4 to 10 times the value of H. This effectively improves the volume utilization rate of the battery and increases its overall energy density.

[0044] In some embodiments, the value of L is 4 to 7 times the value of H. This helps the battery cell to have both high energy density and low internal resistance.

[0045] In some embodiments, L is 400mm-1000mm, and / or H is 80mm-160mm.

[0046] In some embodiments, a housing is further included, within which the electrode assembly is located. The housing includes two first shell walls disposed opposite each other, and a surrounding wall connecting the two first shell walls. The surrounding wall includes two second shell walls disposed opposite each other along the length direction of the first shell walls, and two third shell walls disposed opposite each other along the width direction of the first shell walls. Electrode terminals are provided on the second shell walls. The positive electrode tab and the negative electrode tab are electrically connected to the electrode terminals on the two second shell walls, respectively. A closing structure is provided between the second shell wall electrically connected to the positive electrode tab and the positive electrode body. The closing structure is configured to close the plurality of positive electrode tabs. This facilitates the fixing of the positive electrode tab and the welding between the positive electrode plate and the electrode post.

[0047] In some embodiments, the edges of the positive electrode sheet are chamfered along the length of the first shell wall. This facilitates rapid assembly of the electrode assembly.

[0048] In some embodiments, a liquid injection hole is provided on the second shell wall connected to the negative electrode tab. This facilitates the injection of electrolyte.

[0049] In some embodiments, the injection port and the pressure relief portion of the housing are located on different second shell walls, and the pressure relief portion is configured to release pressure inside the housing. This reduces the corrosion of the pressure relief portion by the electrolyte during injection.

[0050] In some embodiments, the electrode terminal has at least one mounting hole, through which the electrode post passes and is riveted to the tab. This helps to reduce the volume and weight of the battery cell and increase its energy density.

[0051] In some embodiments, the electrode terminal has at least two mounting holes, and each electrode post passes through the mounting hole and is riveted to the electrode tab. This helps to improve the current carrying capacity of the electrode post.

[0052] In some embodiments, the diameter of the electrode post is 3mm-8mm. Therefore, the electrode post combines high current-carrying capacity with low space occupation.

[0053] In some embodiments, the terminal post riveted to the positive electrode tab and the terminal post riveted to the negative electrode tab are staggered along the length of the first housing wall. Optionally, the terminal post riveted to the positive electrode tab and the terminal post riveted to the negative electrode tab are diagonally arranged along the length of the first housing wall. This helps to improve the volumetric energy density of the assembled battery module or battery pack.

[0054] In some embodiments, the electrode post and the electrode tab are electrically connected via an adapter plate. This significantly improves the welding quality and connection reliability between the electrode post and the electrode tab.

[0055] In some embodiments, the terminal post and the tab are directly electrically connected. This helps reduce the structural complexity inside the battery cell, reduces the battery cell size, and increases energy density.

[0056] In some embodiments, the distance between the two first shell walls is D, where D is less than or equal to 30 mm. This facilitates rapid heat dissipation from the battery cell.

[0057] In some embodiments, D is 10mm-25mm. As a result, the battery cell has high mechanical strength and excellent heat dissipation capability.

[0058] In some embodiments, the thicknesses of the first shell wall and the third shell wall are each independently less than or equal to 0.5 mm. This can improve the volumetric energy density of the battery cell.

[0059] In some embodiments, the first shell wall and the third shell wall comprise at least one of an aluminum shell and a steel shell. This can improve the mechanical strength of the battery cell.

[0060] In some embodiments, the first and third shell walls are made of steel, and the wall thickness of the steel shell is 0.1mm-0.5mm. This effectively mitigates the volume expansion of individual battery cells during charging and discharging.

[0061] In some embodiments, the first and third shell walls are made of aluminum, and the wall thickness of the aluminum shell is 0.3 mm to 0.4 mm. This effectively improves the gravimetric energy density of the battery cell.

[0062] In some embodiments, the first shell wall and the third shell wall are formed by bending and welding aluminum plates, with the weld seam located at the junction of the first shell wall and the third shell wall. This reduces electrolyte leakage.

[0063] In some embodiments, a side support plate is provided between the electrode assembly and the first housing wall. This helps to improve the structural stability of the battery cell.

[0064] In some embodiments, at least one of the second housing walls is provided with a pressure relief section, which is configured to release pressure inside the housing. The area of ​​the pressure relief section projected onto the second housing wall is 7%-15% of the area of ​​the second housing wall. This facilitates the rapid release of overpressure gas inside the battery cell when the internal pressure is too high.

[0065] In some embodiments, the battery capacity is Q, the ratio of the area of ​​the pressure relief portion projected onto 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 rapidly release overpressure gas inside the battery cell.

[0066] A second aspect of this application provides a battery device comprising the aforementioned battery cell, wherein the battery device includes at least one of a battery module, a battery pack, and an energy storage device. Thus, this battery device possesses all the features and advantages of the aforementioned battery cell, which will not be elaborated further here.

[0067] In a third aspect, this application proposes an electrical device comprising the aforementioned battery cell. Therefore, this electrical device possesses all the features and advantages of the aforementioned battery cell, which will not be repeated here. Attached Figure Description

[0068] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0069] Figure 1 is a schematic diagram of the structure of an electrode assembly fabricated using a lamination process according to an embodiment of this application;

[0070] Figure 2 is a schematic diagram of the structure of a positive current collector according to an embodiment of this application;

[0071] Figure 3 is a schematic diagram of the structure of the positive electrode current collector according to another embodiment of this application;

[0072] Figure 4 is a schematic diagram of the structure of the positive electrode current collector according to another embodiment of this application;

[0073] Figure 5 is a schematic diagram of the structure of the positive electrode current collector according to another embodiment of this application;

[0074] Figure 6 is a schematic diagram of the structure of an electrode assembly manufactured by a winding process according to an embodiment of this application;

[0075] Figure 7 is a schematic diagram of the structure of a battery cell according to an embodiment of this application;

[0076] Figure 8 is a partial structural schematic diagram of the housing according to an embodiment of this application;

[0077] Figure 9 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0078] Figure 10 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0079] Figure 11 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0080] Figure 12 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0081] Figure 13 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0082] Figure 14 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0083] Figure 15 is a schematic diagram of the structure of an electrical device according to an embodiment of this application.

[0084] Explanation of reference numerals in the attached figures:

[0085] 11 Positive electrode main body; 12 Positive electrode tab; 21 Negative electrode main body; 22 Negative electrode tab;

[0086] 101 First shell wall; 102 Second shell wall; 103 Third shell wall; 104 Pressure relief section; 105 Pole post; 106 Closing structure; 107 Injection hole; 108 Adapter plate. Detailed Implementation

[0087] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0088] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0089] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0090] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0091] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0092] In the description of this application, it should be understood that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and 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, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0093] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "First feature" and "second feature" may include one or more of the indicated feature.

[0094] In the description of this application, "multiple" means two or more.

[0095] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0096] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0097] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0098] Improving battery fast-charging performance allows users to quickly replenish a device's power, reducing charging wait time and enhancing the overall user experience. However, fast charging accelerates the chemical reaction rate within individual battery cells, leading to increased heat generation. This sustained high temperature environment accelerates the aging of battery materials, particularly electrolyte decomposition and degradation of the positive electrode active material, thus shortening the battery's cycle life. Furthermore, the larger current flowing through the tabs during fast charging places higher demands on the maximum current capacity of the tabs.

[0099] When the coating weight of a single-layer negative electrode active material layer is 0.1g / 1540.25mm 2 -0.145g / 1540.25mm 2At this stage, the coating weight of the single-layer negative electrode active material layer is relatively high, and the thickness and uniformity of the negative electrode active material layer on the surface of the negative electrode current collector are moderate. The transport path of lithium ions in the negative electrode active material layer is relatively short, allowing for rapid insertion and extraction of the negative electrode active material during charging and discharging. Simultaneously, the battery cell has a high energy density, making it suitable for battery cells with high requirements for fast charging performance. Furthermore, by using tabs in both the positive and negative electrode current collectors with a total width accounting for 50%-100% of the total width of the corresponding main body, the current conduction path on the tabs can be effectively increased. Therefore, when the battery is charged and discharged quickly, the current that can pass through the tabs is higher, meeting the performance requirements for current carrying capacity of the tabs under fast charging conditions. At the same time, the larger cross-sectional area of ​​the tabs can reduce their resistance, thereby reducing heat generation at the root of the tabs. Thus, the tabs that meet the aforementioned requirements can withstand greater current while reducing the generation and accumulation of heat inside the battery cell and providing a larger surface area for heat dissipation, thereby enhancing the heat dissipation effect of the tabs and helping the battery cell maintain a relatively low system temperature during fast charging. Furthermore, the first solvent has high electrical conductivity due to its low viscosity, which can effectively reduce the internal resistance of the battery cell. At the same time, it has a low 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 high temperature rise of the battery cell can be effectively reduced. This allows the first solvent to stably and fully utilize its high electrical conductivity, thereby reducing the heat generation of the battery cell during fast charging, increasing the output power under fast charging conditions, and further improving the fast charging performance of the battery cell.

[0100] This application improves the energy density of a battery cell and its performance under fast charging conditions by using a suitable coating weight of the negative electrode active material layer and a suitable amount of the first solvent. However, in fast charging scenarios, a large amount of heat is easily generated and accumulated inside the battery cell, which leads to the first solvent with a low boiling point producing gas and releasing acid, which is detrimental to the battery's fast charging performance. By combining the tab structure with a large flow area, the temperature rise of the battery cell during fast charging can be effectively reduced, and the aforementioned adverse effects of the high conductivity and low boiling point first solvent in fast charging scenarios can be alleviated. This results in a lower internal resistance of the battery cell, which reduces heat generation under fast charging conditions, improves output power, and enhances performance under fast charging conditions.

[0101] In a first aspect, this application proposes a battery cell, referring to Figures 1-6, comprising: an electrode assembly, the electrode assembly including a positive electrode, a negative electrode, and a separator between the positive and negative electrode, wherein the positive electrode includes a positive current collector and a positive active material layer located on at least one side of the positive current collector, the positive current collector including a positive electrode body portion 11 and at least one positive electrode tab portion 12, the positive electrode body portion 11 being connected to the positive electrode tab portion 12, and the total width W1 of the positive electrode tab portion 12 along the width direction of the positive electrode body portion 11 accounting for... The positive electrode body 11 has a total width V1 of 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 body 21 and at least one negative electrode tab 22. The negative electrode body 21 is connected to the negative electrode tab 22. Along the width direction of the negative electrode body 21, the total width W2 of the negative electrode tab 22 accounts for 50%-100% of the total width V2 of the negative electrode body 21. 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, which includes a 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, and R1 and R2 are independently selected from C1-C5 alkyl or haloalkyl groups; the mass fraction of the first solvent is 4%-72% based on the total mass of the electrolyte. Therefore, by using a suitable negative electrode active material layer coating weight, the energy density of the battery cell and its performance under fast charging conditions can be improved. Furthermore, by using 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 alleviated. Furthermore, the use of a first solvent with high conductivity and low boiling point can further reduce the internal resistance of the battery cell, thereby alleviating heat generation under fast charging conditions, increasing output power, improving the fast charging performance of the battery cell, and enhancing its overall performance under fast charging conditions.

[0102] It is understood that the positive electrode active material layer is located on at least one side of the positive electrode body of the positive electrode current collector, and the negative electrode active material layer is located on at least one side of the negative electrode body of the negative electrode current collector.

[0103] As an example, the widths of the positive electrode tab and the negative electrode tab can be the same. When the widths 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 tab 12 to the total width of the positive electrode main body 11 along the width direction of the positive electrode main body 11 is the same as the ratio of the total width of the negative electrode tab 22 to the total width of the negative electrode main body 21 along the width direction of the negative electrode main body 21.

[0104] It should be noted that when the electrode assembly is fabricated using a stacking process, the electrode assembly may include a multilayer continuously arranged positive electrode / isolation film / negative electrode / isolation film structure. At this time, the ratio of the total width W1 of the aforementioned positive electrode tab 12 to the total width V1 of the positive electrode body 11 corresponds to the ratio of the width of the tab to the width of the body in any positive electrode sheet. Similarly, the ratio of the total width W2 of the aforementioned negative electrode tab 22 to the total width V2 of the negative electrode body 21 corresponds to the ratio of the width of the tab to the width of the body in any negative electrode sheet. When the electrode assembly is prepared by a winding process, the electrode assembly includes only one positive electrode sheet, one separator film, and one negative electrode sheet. The positive electrode sheet has multiple positive electrode tabs 12. At this time, the ratio of the total width of the aforementioned positive electrode tab 12 to the total width of the positive electrode body 11 corresponds to the ratio of the sum of the widths of all positive electrode tabs to the width of the positive electrode body. Similarly, the ratio of the total width of the aforementioned negative electrode tab 22 to the total width of the negative electrode body 21 corresponds to the ratio of the sum of the widths of all negative electrode tabs to the width of the negative electrode body.

[0105] As an example, along the width direction of the positive electrode body portion 11, the total width W1 of the positive electrode tab portion 12 can account for 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% of the total width V1 of the positive electrode body portion 11.

[0106] As an example, along the width direction of the negative electrode body portion 21, the total width W2 of the negative electrode tab portion 22 can account for 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% of the total width V2 of the negative electrode body portion 21.

[0107] When a battery cell undergoes high-rate charging and discharging, both the internal current and voltage increase accordingly, leading to a greater current flowing through the tabs. A larger tab area implies lower resistance. Firstly, according to Ohm's law, at the same voltage, a larger tab area can handle a higher current, meaning stronger overcurrent capability. Secondly, lower tab resistance reduces heat generation due to resistive losses as current flows through the tab, lowering heat generation under high current and indirectly improving the battery's heat dissipation efficiency. At this point, the lower boiling point of the first solvent significantly reduces its adverse effects on the battery cell's performance, allowing the first solvent to fully leverage its advantages in improving electrolyte conductivity and enhancing the battery cell's fast-charging capability.

[0108] In some embodiments, the dimension of the positive electrode body portion 11 in the width direction may be greater than its dimension in the length direction, or the dimension of the positive electrode body portion 11 in the width direction may be equal to its dimension in the length direction, or the dimension of the positive electrode body portion 11 in the width direction may be smaller than its dimension in the length direction. That is, the positive electrode tab 12 may be located on the long side of the positive electrode body portion 11 or on the short side of the positive electrode body portion 11. Similarly, the negative electrode tab 22 may be located on the long side of the negative electrode body portion 21 or on the short side of the negative electrode body portion 21.

[0109] In some embodiments, the total width W1 of the positive electrode tab 12 can be 40mm-160mm.

[0110] As an example, W1 can be 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or 160mm.

[0111] Similarly, in some embodiments, the total width W2 of the negative electrode tab 22 can also be 40mm-160mm.

[0112] As an example, W2 can be 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or 160mm.

[0113] When the total width of the positive and negative electrode tabs is within the aforementioned range, the current-carrying area of ​​the tabs is larger, which can effectively improve the current-carrying capacity of the tabs, alleviate the temperature rise of the battery cell during fast charging, and further reduce the internal resistance of the battery cell by using a first solvent with high conductivity and low boiling point, thereby alleviating the heat generation of the battery cell under fast charging conditions, improving the fast charging performance of the battery cell, and enhancing the performance of the battery cell under fast charging conditions.

[0114] In some embodiments, the width W3 of the positive electrode tab 12 can be 40mm-160mm.

[0115] As an example, W1 can be 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or 160mm.

[0116] Similarly, in some embodiments, the width W4 of the negative electrode tab 22 can be 40mm-160mm.

[0117] As an example, W2 can be 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or 160mm.

[0118] As an example, referring to Figure 4, when the electrode assembly is fabricated using a stacking process, the total width W1 of the positive electrode tab 12 corresponds to the total width of the multiple positive electrode tabs 12 after the positive electrode sheet, negative electrode sheet and separator are stacked. Similarly, the total width W2 of the negative electrode tab 22 corresponds to the total width of the multiple negative electrode tabs 22 after the positive electrode sheet, negative electrode sheet and separator are stacked.

[0119] As an example, referring to Figure 6, when the electrode assembly is fabricated using a winding process, the total width W1 of the aforementioned positive electrode tab 12 corresponds to the total width of the stacked positive electrode tabs 12 after the positive electrode sheet, negative electrode sheet, and separator are wound. Similarly, the total width W2 of the aforementioned negative electrode tab 22 corresponds to the total width of the stacked negative electrode tabs 22 after the positive electrode sheet, negative electrode sheet, and separator are wound.

[0120] 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 obtained by lamination or winding processes, the positive electrode body 11 is arranged parallel to the negative electrode body 21. Therefore, 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.

[0121] 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 lamination or winding processes, 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 opposite sides of the negative electrode body 21. This provides a more uniform heat distribution and reduces tab deformation caused by excessive force on one side.

[0122] In some embodiments, referring to FIG2, the positive current collector includes the positive electrode body 11 and a plurality of positive electrode tabs 12, with at least two positive electrode tabs 12 located on opposite sides of the positive electrode body 11. Similarly, the negative current collector may include the negative electrode body and a plurality of negative electrode tabs, with at least two negative electrode tabs located on opposite sides of the negative electrode body. This provides a more uniform heat distribution and reduces tab deformation caused by excessive force on one side.

[0123] In some embodiments, referring to FIG3, the positive current collector includes a positive electrode body portion 11 and a plurality of positive electrode tabs 12 spaced apart along the length direction of the positive current collector. Similarly, the negative current collector may also include a negative electrode body portion 21 and a plurality of negative electrode tabs 22 spaced apart along the length direction of the negative current collector.

[0124] When the positive current collector includes multiple positive electrode tabs 12 and the negative current collector includes multiple negative electrode tabs 22, the electron transport path between the positive electrode tabs and the negative electrode tabs is shorter, which can reduce battery heat generation and improve fast charging performance.

[0125] The specific embodiments are described below with reference to Figures 1-6:

[0126] Referring to Figure 1, in some specific embodiments, taking the fabrication of an electrode assembly using a stacking process as an example, the positive electrode sheet used is rectangular. In this case, one of the short sides of the positive current collector has a positive electrode tab 12 extending along the length direction of the positive current collector. The width of the positive electrode tab is W3, and the total width V1 of the positive electrode body is the width of the positive current collector. Similarly, the corresponding negative current collector can also have a similar structure. In this case, one of the short sides of the negative current collector has a negative electrode tab extending along the length direction of the negative current collector. The width of the negative electrode tab is W4, and the total width V2 of the negative electrode body is the width of the negative current collector.

[0127] Referring to Figure 2, in some specific embodiments, taking the fabrication of an electrode assembly using a stacking process as an example, the positive electrode sheet used is rectangular. In this case, the short sides of the positive current collector each have a positive electrode tab 12 extending along the length direction of the positive current collector, and the two positive electrode tabs 12 extend in opposite directions. The width W3 of the multiple positive electrode tabs 12 can be the same or different, and the total width V1 of the positive electrode body is the width of the positive current collector. Similarly, the corresponding negative 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 width V2 of the negative electrode body is the width of the negative current collector.

[0128] Referring to Figure 3, in some specific embodiments, taking the electrode assembly fabricated using a stacking process as an example, the positive electrode sheet used is rectangular. In this case, one of the long sides of the positive current collector has multiple positive electrode tabs 12 extending along the width direction of the positive current collector. The multiple positive electrode tabs 12 are spaced apart along the length direction of the positive current collector. 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 all be the same, all be different, or any two 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, i.e., W1 = L1 + L2 + L3, and the total width V1 of the positive electrode body is the length of the positive current collector. Similarly, the corresponding negative electrode current collector can also have a similar structure. In this case, the total width W2 of the negative electrode tab is the sum of the widths of multiple negative electrode tabs, and the width of the negative electrode body is the length of the negative electrode current collector.

[0129] Referring to Figure 4, in some specific embodiments, in the electrode assembly fabricated using a stacking 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 multiple positive electrode tabs 12 after the positive electrode sheet, negative electrode sheet, and separator are stacked. Similarly, multiple negative electrode tabs 22 are staggered (adjacent negative electrode tabs at least partially overlap), and the total width W2 of the negative electrode tabs 22 corresponds to the total width of the multiple negative electrode tabs 22 after the positive electrode sheet, negative electrode sheet, and separator are stacked.

[0130] Referring to Figure 5, in some specific embodiments, taking the electrode assembly fabricated using a winding process as an example, the corresponding positive current collector, when stretched horizontally, can have multiple positive electrode tabs 12 extending along a direction perpendicular to the long side of the positive electrode body 11. The width W3 of each positive electrode tab can be the same or different. Similarly, the corresponding negative current collector can also have a similar structure, and the width W4 of each negative electrode tab can be the same or different.

[0131] Referring to Figure 6, in some specific embodiments, in the electrode assembly manufactured by the winding process, the positive current collector and the negative current collector have the structure shown in Figure 5. The total width W1 of the aforementioned positive electrode tab 12 corresponds to the total width of the stacked positive electrode tabs 12 after the positive electrode sheet, negative electrode sheet and separator are wound (adjacent positive electrode tabs at least partially overlap). Similarly, the total width W2 of the aforementioned negative electrode tab 22 corresponds to the total width of the stacked negative electrode tabs 22 after the positive electrode sheet, negative electrode sheet and separator are wound (adjacent negative electrode tabs at least partially overlap).

[0132] As an example, the coating weight of a single layer of the negative electrode active material can 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 .

[0133] As an example, the coating weight of a single layer of the negative electrode active material can be obtained 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.

[0134] 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 satisfying R1-COO-R2, and R1 and R2 are independently selected from C1-C5 alkyl or haloalkyl groups. This effectively reduces the viscosity of the electrolyte.

[0135] The aforementioned first solvent has a low viscosity, which in turn results in a low overall viscosity of the electrolyte, which is primarily composed of organic solvents. In a low-viscosity electrolyte, the intermolecular forces are weaker, allowing for freer molecular movement. This accelerates the diffusion and migration of lithium ions within the electrolyte. Furthermore, during rapid charging and discharging of individual battery cells, concentration polarization occurs within the battery. A higher ion migration rate in the electrolyte can alleviate this concentration polarization. Therefore, the aforementioned low-viscosity electrolyte can effectively reduce concentration polarization by increasing the ion migration rate, thereby improving the battery's fast-charging performance.

[0136] As an example, the viscosity of the electrolyte can be tested using the following method: the viscosity is measured using a viscometer. Referring to the national standard GB / T10247-2008 "Methods for Viscosity Measurement": at a certain temperature, when a rotor rotates continuously at a constant speed in a sample, the shear force it experiences causes a spring to generate torque. The torque is proportional to the viscosity, thus yielding the viscosity value.

[0137] In some embodiments, the linear carboxylic acid ester includes at least one selected from ethyl formate, isopropyl formate, ethyl acetate (EA), methyl acetate, propyl acetate, and methyl propionate. This further reduces the viscosity of the electrolyte.

[0138] Linear carboxylic acid esters exhibit good lithium salt solubility, which can improve the conductivity of the electrolyte, accelerate the migration rate of lithium ions inside the battery, and enhance the battery's charge and discharge efficiency. Furthermore, linear carboxylic acid esters demonstrate good thermal and oxidation stability at high temperatures, which helps improve battery stability under fast charging conditions and reduces the risk of thermal runaway.

[0139] In some embodiments, the mass fraction of the first solvent is 16%-72% based on the total mass of the electrolyte. This can improve the fast-charging performance of the battery cell.

[0140] 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%.

[0141] 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.

[0142] As an example, the quantitative test of the first solvent can be performed by the following method: the organic components in the electrolyte can be quantitatively analyzed by gas chromatography, referring to the standard GB / T9722-2006.

[0143] In some embodiments, the mass fraction of the linear carboxylic acid ester is 32%-68% based on the total mass of the electrolyte.

[0144] As an example, based on the total mass of the electrolyte, the mass fraction of the linear carboxylic acid ester can be 32%, 36%, 40%, 44%, 48%, 52%, 56%, 60%, 64%, or 68%.

[0145] Linear carboxylic acid esters have low viscosity. When the mass fraction of the linear carboxylic acid ester is within the above range based on the total mass of the electrolyte, it can further reduce the liquid phase transport resistance of lithium ions and improve the fast charging performance and cycle performance of the battery cell.

[0146] As an example, the quantitative analysis of the linear carboxylic acid ester can be obtained by the following method: the organic components in the electrolyte can be quantitatively analyzed by gas chromatography, referring to the standard GB / T9722-2006.

[0147] Understandably, electrolytes typically consist of organic solvents and lithium salts (including electrolyte lithium salts and lithium salt additives). Based on the total mass of the electrolyte, the organic solvents comprise approximately 80% by mass, with the remainder being lithium salts and / or additives.

[0148] In some embodiments, the coating weight of a single layer of the negative electrode active material is 0.1 g / 1540.25 mm. 2 -0.135g / 1540.25mm 2 Therefore, the battery cell has a high volumetric energy density.

[0149] When the coating weight of a single-layer negative electrode active material layer is 0.1g / 1540.25mm 2 -0.135g / 1540.25mm 2 At this time, the thickness of the negative electrode active material layer is relatively thin, and the diffusion distance required for lithium ions within the negative electrode active material layer is shorter, thereby accelerating lithium ion transport and improving the battery's fast-charging performance. For example, the battery cell using a negative electrode sheet that meets the aforementioned coating weight takes 7-15 minutes to charge from 10% SOC to 80% SOC. Therefore, the battery cell exhibits superior fast-charging performance.

[0150] Taking automobiles as an example of electrical devices, in actual use scenarios, the state of charge (SOC) of a car battery is usually between 10% and 80%. Therefore, when the charging time of the battery within this SOC range is short, the user's waiting time for charging can be reduced, which greatly improves the user experience.

[0151] In some embodiments, the coating weight of a single layer of the negative electrode active material is 0.136 g / 1540.25 mm. 2 -0.145g / 1540.25mm 2 Therefore, the battery cell has a high volumetric energy density.

[0152] In some embodiments, the coating weight of a single layer of the negative electrode active material is 0.136 g / 1540.25 mm. 2 -0.145g / 1540.25mm 2 When assembled using the aforementioned positive electrode plates, the volumetric energy density of the battery cell can be 410Wh / L-430Wh / L. Therefore, the battery cell possesses a high volumetric energy density.

[0153] When the coating weight of a single layer of the negative electrode active material is 0.136 g / 1540.25 mm... 2 -0.145g / 1540.25mm 2 When the negative electrode active material layer is thicker, there are more lithium-ion insertion / extraction sites that the negative electrode active material can provide, which helps to improve the energy density of the battery.

[0154] In some embodiments, the battery cell takes 20-30 minutes to charge from 10% SOC to 80% SOC. Therefore, the battery cell exhibits superior fast-charging performance.

[0155] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer located at least on one side of the negative current collector, wherein the compaction density of the negative active material layer is 1.2 g / cm³. 3 -1.5cm 3 This helps improve the fast-charging performance of individual battery cells.

[0156] As an example, the compaction density of the negative electrode active material layer can be 1.2 g / cm³. 3 1.3g / cm 3 1.4g / cm 3 Or 1.5g / cm 3 .

[0157] 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 insertion / extraction rate of the negative electrode sheet is relatively fast, which is beneficial to improving the fast charging performance of the battery.

[0158] As an example, the test method for the compaction density of the negative electrode active material layer can be the same as that for the test method for the compaction density of the positive electrode active material layer, and will not be elaborated here.

[0159] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then performing processes such as drying and rolling (e.g., cold pressing) to form a negative electrode active material layer, thus obtaining the negative electrode sheet. The aforementioned compaction density of the negative electrode active material layer refers to the compaction density of the negative electrode active material layer after rolling treatment. Specifically, the compaction density of the negative electrode active material layer after rolling and formation treatment, the compaction density of the negative electrode active material layer when the battery cell is in a fully charged or fully discharged state, and the compaction density of the negative electrode active material layer after the battery cell has been left to stand for a long time are all within the aforementioned range.

[0160] 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, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0161] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. 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, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional 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.

[0162] In some embodiments, the negative electrode active material layer may optionally 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).

[0163] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0164] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0165] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which includes a silicon-containing material, wherein 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.

[0166] Silicon boasts a theoretical specific capacity as high as 4200 mAh / g, far exceeding that of graphite. Adding silicon-containing materials to the negative electrode active material can effectively improve the battery's energy density. However, pure silicon undergoes significant volume expansion (over 300%) after lithium-ion insertion, causing the SEI (solid electrolyte membrane) to rupture and reorganize, consuming electrolyte and active lithium ions, ultimately leading to a decrease in battery cycle life. By controlling the silicon mass fraction in the silicon-containing material to 0.1%-7%, the extremely high theoretical specific capacity of silicon can be utilized to improve the battery's energy density, while also helping to mitigate the volume expansion and contraction of the silicon-containing material during charge and discharge processes.

[0167] 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%.

[0168] As an example, silicon-containing materials can be silicon-carbon materials.

[0169] In some embodiments, the silicon content in the silicon-containing material is 1%-5% by mass. This can further improve the gravimetric energy density of the battery cell.

[0170] As an example, the mass fraction of silicon in silicon-containing materials can be determined by the following methods: Refer to standards YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015. Specifically, an ICP (Inductively Coupled Plasma) emission spectrometer can be used, and the measurement can be performed according to the manufacturer's instructions.

[0171] 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 is 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 is 9.2 μm-18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2 μm-15.5 μm. This significantly improves the fast-charging performance and energy density of the battery cell.

[0172] 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. The larger particle size of the particles in the first negative electrode active material layer can provide more lithium insertion / extraction sites and improve battery capacity. The smaller particle size of the particles in the second negative electrode active material layer results in a faster lithium ion insertion / extraction rate, which helps to improve the fast charging performance of the battery.

[0173] In some embodiments, the conductivity of the electrolyte is 10 ms / cm to 20 ms / cm. This helps to improve the fast-charging performance of the battery cells.

[0174] As an example, the conductivity of the electrolyte can 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.

[0175] When the conductivity of the electrolyte is within a certain range, the electrolyte can conduct lithium ions more effectively, thereby effectively reducing the internal resistance of the battery, which helps to improve the fast charging performance of the battery, and reduce the temperature rise of the battery caused by the resistive heating effect during charging and discharging, reduce the thermal stress inside the battery cell, and thus improve the battery performance at high power.

[0176] As an example, the conductivity of the electrolyte can be directly obtained by measuring it with a conductivity meter using methods known in the art.

[0177] In some embodiments, the electrolyte further includes a first lithium salt additive, which includes at least one of fluoroborate and fluorophosphate, and the mass fraction of the first lithium salt additive is 0.05%-0.5% based on the total mass of the electrolyte. This effectively reduces the internal resistance of the battery cell.

[0178] As an example, based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0179] By adding at least one lithium salt additive, selected from fluoroborate and fluorophosphate, to the electrolyte of a battery cell, a low-resistance SEI film containing boron and phosphorus atoms can be formed on the surface of the negative electrode active material. This effectively reduces the internal resistance of the battery cell, resulting in a battery cell with 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 contributes to the formation of a low-resistance SEI film on the surface of the negative electrode active material, while requiring a smaller amount, thus helping to reduce the cost of the electrolyte.

[0180] As an example, based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive can be obtained by testing as follows: Take out the free electrolyte from the finished battery and test 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, referring to standard JY / T020-1996.

[0181] In some embodiments, the first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalate phosphate, lithium difluorooxalate borate, and lithium tetrafluoroborate. This facilitates the formation of a low-resistance solid electrolyte film on the surface of the negative electrode active material.

[0182] The first lithium salt additive itself has high ionic conductivity, which can increase the migration rate of lithium ions in the electrolyte. Furthermore, 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 reduce the side reactions between the negative electrode active material and the electrolyte, and also reduce the internal resistance of the battery.

[0183] 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. This helps to reduce the cost of the battery cell.

[0184] 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 long, 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 battery internal resistance caused by the long 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.

[0185] In some embodiments, the organic solvent further includes a second solvent, the second solvent comprising 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, butyl carbonate, and fluoroethylene carbonate. This helps to improve the cycle life of the battery cell.

[0186] The aforementioned second solvent has a wide electrochemical stability window and can remain stable even under high voltage conditions, thereby reducing its own decomposition in electrochemical reactions and improving the cycle life of the battery cell.

[0187] In some embodiments, the second solvent comprises diethyl carbonate, wherein the mass fraction of diethyl carbonate is greater than or equal to 12% based on the total mass of the electrolyte. This contributes to further improving the cycle life of the battery cell.

[0188] Diethyl carbonate has suitable viscosity and boiling point, which helps to adjust the physical properties of the electrolyte, giving it suitable viscosity and better low-temperature performance.

[0189] In some embodiments, the electrolyte further includes non-lithium salt additives, including sulfate ester additives and carbonate additives. This helps to form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0190] Carbonate-based non-lithium salt additives containing double bonds help form a flexible SEI film on the surface of the negative electrode active material, which can slow down the damage to the interfacial film caused by the volume expansion of the negative electrode active material during charge and discharge cycles, improve the cycle stability of the battery cell, and increase cycle life.

[0191] In some embodiments, the carbonate additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and ethylene ethylene carbonate. This facilitates the formation of a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0192] In some embodiments, the mass fraction of vinylene carbonate is 0.5%-2.5% based on the total mass of the electrolyte, and / or the mass fraction of fluoroethylene carbonate is 0.05%-2%. This facilitates the formation of a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0193] 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%.

[0194] 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%.

[0195] It is understandable that, since carbonate 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, they are partially consumed. Therefore, the actual detected amount of these substances in a single 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 a single 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 a single battery cell is approximately 0.05%.

[0196] In some embodiments, the sulfate ester additive includes at least one of 4,4-vinyl sulfate, ethylene disulfate, cyclotrisulfate, and 1,3-propanesulfonate lactone.

[0197] In some embodiments, the non-lithium salt additive has a mass fraction of 0.05%-3% based on the total mass of the electrolyte. This helps to reduce the cost of individual battery cells.

[0198] In some embodiments, the electrolyte further includes a second lithium salt additive, which includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate. This facilitates the formation of a solid electrolyte film with high ionic conductivity on the surface of the negative electrode active material.

[0199] The second lithium salt additive can preferentially form a dense and stable interface film on the surface of the negative electrode active material before organic solvents, inhibiting the oxidative decomposition of organic solvents on the negative electrode, reducing the consumption of active lithium due to side reactions between the negative electrode active material and the electrolyte; effectively preventing direct contact between organic solvents and negative electrode active materials, and the presence of the interface film also helps to reduce the dissolution of transition metals from the negative electrode active material.

[0200] In some embodiments, the electrolyte further includes an electrolyte lithium salt, which includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the mass fraction of the electrolyte 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.

[0201] As an example, based on the total mass of the electrolyte, the mass fraction of lithium salt in the electrolyte is 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 21%, 23%, 24%, or 25%.

[0202] When the mass fraction of the lithium salt in the electrolyte is within the aforementioned range based on the total mass of the electrolyte, the electrolyte exhibits both high ionic conductivity and low viscosity. After the lithium salt dissolves in an organic solvent, it releases lithium ions. These lithium ions form a solvated structure with the electrolyte, increasing the electrolyte's conductivity and facilitating rapid migration of lithium ions within the electrolyte.

[0203] In some embodiments, the electrolyte lithium salt comprises lithium hexafluorophosphate and lithium difluorosulfonylimide, wherein the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide in the electrolyte is (1.2-2):1. This helps to further improve the conductivity of the electrolyte.

[0204] Lithium difluorosulfonylimide (Li₂F₃) exhibits superior conductivity, thermal stability, and hydrolysis resistance compared to Li₂F₃. However, Li₂F₃ suffers from difficulty in achieving sufficient dissociation. Li₂F₃, on the other hand, has an advantage in commercial production and application maturity, and lower production costs. When the electrolyte lithium salt comprises both Li₂F₃ and Li₂F₃, Li₂F₃ can promote better dissociation of Li₂F₃, improving electrolyte performance and consequently enhancing battery cycle life and fast-charging performance.

[0205] As an example, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide in the electrolyte can be obtained by the following method: the concentration of inorganic components in the electrolyte can be quantitatively analyzed by ion chromatography with reference to standard JY / T020-1996.

[0206] As an example, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide in the electrolyte can 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.

[0207] In some embodiments, the compaction density of the positive electrode active material layer is 2.2 g / cm³. 3 -2.6g / cm 3 This helps improve the fast-charging performance and energy density of individual battery cells.

[0208] As an example, the compaction density of the positive electrode active material layer can be 2.2 g / cm³. 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 Or 2.6g / cm 3 .

[0209] 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 at this time the positive electrode sheet has a high energy density.

[0210] As an example, the compaction density of the positive electrode active material layer can be obtained by measuring the mass and thickness of the positive electrode active material layer and dividing by the result. The mass and thickness of the positive electrode active material layer can be obtained 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.

[0211] 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 (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then performing processes such as drying and rolling (e.g., cold pressing) to form a positive electrode active material layer, thereby obtaining the positive electrode sheet.

[0212] The aforementioned compaction density of the positive electrode active material layer refers to the compaction density of the positive electrode active material layer after roll forming. Specifically, the compaction density of the positive electrode active material layer after roll forming and formation, the compaction density of the positive electrode active material layer when the battery cell is in a fully charged or fully discharged state, and the compaction density of the positive electrode active material layer after the battery cell has been left to stand for a long time are all within the aforementioned range.

[0213] In some embodiments, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprising: a core comprising a lithium phosphate with an olivine structure, and a coating layer covering the surface of the lithium phosphate with the olivine structure, the coating layer containing one or more elements selected from C, Fe, Ti, Zr, Hf, Ge, and Sn. This helps to improve the structural stability and ionic conductivity of the positive electrode active material.

[0214] Lithium phosphates with an olivine structure combine low cost with high theoretical specific capacity, which helps improve the energy density of individual battery cells. Furthermore, the olivine structure maintains good crystal integrity during charge and discharge, reducing structural stress and extending battery cycle life. The coating layer can effectively mitigate the poor electronic and ionic conductivity inherent in olivine-structured lithium phosphates, improving the specific capacity and powder compaction density of the positive electrode active material.

[0215] In some embodiments, the lithium phosphate with the olivine structure includes those of the general formula Li x1 A y1 Me a M1 b P 1-c X c Y z The compound contains the following components: 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. This contributes to improving the ionic and electronic conductivity of the core.

[0216] When lithium phosphates with an olivine structure satisfy the aforementioned general formula, their advantages for ternary materials can be fully utilized to improve the high-temperature resistance and structural stability of battery cells made from them, thereby reducing the manufacturing cost of battery cells.

[0217] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Li content changes when the positive electrode active material is applied to the battery system.

[0218] In the examples of positive electrode active materials for lithium-ion batteries in this application, the molar content of O is only a theoretical state value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0219] In some embodiments, the coating layer comprises a carbon layer having a graphitization degree of 0.15-0.32. This helps to improve the electronic conductivity of the positive electrode active material.

[0220] The addition of a carbon layer can significantly improve the electronic conductivity of lithium phosphates with an olivine structure, compensate for the poor electronic conductivity of lithium phosphates with an olivine structure, and improve the capacity utilization of individual battery cells.

[0221] As an example, the degree of graphitization of the carbon layer can be 0.15, 0.17, 0.19, 0.21, 0.23, 0.25, 0.27, 0.29, 0.31 or 0.32.

[0222] When the degree of graphitization of the carbon layer is within the aforementioned range, the arrangement of carbon atoms in the carbon layer is relatively disordered, with more lattice defects and no complete graphite lattice is formed. The electronic conductivity is slightly lower compared to carbon materials with a higher degree of graphitization. Carbon layers with a relatively disordered arrangement of carbon atoms typically have a higher specific surface area, which facilitates sufficient contact between the core and the electrolyte, improving lithium-ion transport efficiency at the two-phase interface.

[0223] As an example, the degree of graphitization of the carbon layer can be tested using the following method: The degree of graphitization can be determined by XRD diffraction based on the lattice parameters of the carbon crystal, referring to standards JB / T4220-2011 and JISK0131-1996.

[0224] In some embodiments, in a cross-section along the thickness direction of the positive electrode active material layer, the positive electrode active material comprises a lithium phosphate with an olivine structure having a longest diameter of 1 μm-3 μm and a lithium phosphate with an olivine structure having a shortest diameter of 0.1 μm-0.3 μm. This is beneficial for improving the energy density of the battery cell.

[0225] As an example, in a cross-section along the thickness direction of the positive electrode active material layer, the positive electrode active material comprises a lithium phosphate with an olivine structure having a longest diameter of 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm.

[0226] As an example, in a cross-section along the thickness direction of the positive electrode active material layer, the positive electrode active material comprises a lithium phosphate with an olivine structure having a shortest diameter of 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, or 0.3 μm.

[0227] In some embodiments, the Dv50 particle size of the positive electrode active material is 1μm-5μm.

[0228] As an example, the Dv50 particle size of the positive electrode active material can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm.

[0229] In some embodiments, the Dv10 particle size of the positive electrode active material is 0.4 μm-0.7 μm.

[0230] As an example, the Dv10 particle size of the positive electrode active material can be 0.4 μm, 0.5 μm, 0.6 μm or 0.7 μm.

[0231] When the Dv50 and Dv10 particle sizes of the positive electrode active material are within the aforementioned range, the overall particle size distribution of the positive electrode active material is more reasonable, which is conducive to improving the powder compaction density of the positive electrode active material, and in turn, to improving the electrode compaction density of the positive electrode sheet, and ultimately improving the volumetric energy density of the battery cell.

[0232] The aforementioned Dv50 particle size refers to the particle size corresponding to a cumulative volume distribution percentage of 50%.

[0233] The aforementioned Dv10 particle size refers to the particle size corresponding to a cumulative volume distribution percentage of 10%.

[0234] As an example, the particle size of the positive electrode active material can be determined using laser diffraction particle size analysis. Specifically, the particle size of the positive electrode active material can be determined using a laser particle size analyzer (e.g., Malvern-Master-Size-3000) in accordance with standard GB / T19077-2016.

[0235] In some embodiments, the positive electrode active material is a primary particle or a near-single-crystal particle. Therefore, the larger particle size of the positive electrode active material is beneficial for improving the energy density of the battery cell.

[0236] When the positive electrode active material is a primary particle or a near-monocrystalline particle, a larger particle size helps to increase its powder compaction density. Furthermore, with similar particle size distribution, the larger the primary particle size of the positive electrode active material, the greater the powder compaction density, which is beneficial for improving the volumetric energy density of the battery cell.

[0237] In some embodiments, the positive electrode active material is a mixture of primary and secondary particles. The primary particles increase the powder compaction density of the positive electrode active material, while the secondary particles enhance its ionic conductivity. The combined use of primary and secondary particles jointly improves the battery's volumetric energy density and fast-charging capability.

[0238] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, which includes at least one of lithium ferrite, lithium nickel oxide, lithium nickel copper oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, lithium trilithium citrate, and lithium nickel cobalt manganese oxide. This helps to improve the cycle life of the battery cell.

[0239] During the first charge of a battery, an SEI film forms on the surface of the negative electrode active material. The breakdown and recombination of the SEI during charge-discharge cycles both cause irreversible lithium-ion consumption, leading to reduced efficiency and capacity loss in the first cycle. Adding lithium-rich materials can pre-replenish this lost lithium during battery manufacturing, mitigating or eliminating capacity decay caused by lithium loss and extending the battery's cycle life.

[0240] In some embodiments, the lithium-rich material includes at least one of lithium iron ferrite, lithium nickel oxide, and lithium oxalate. Thus, after the lithium-rich material releases lithium ions through a formation process, the residual products 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 power.

[0241] In some embodiments, the positive 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 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 (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0242] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0243] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0244] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven 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.

[0245] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0246] In some embodiments, the length of the battery cell is L, and the width of the battery cell is H, where L is 4 to 10 times the value of H. This effectively improves the volume utilization rate of the battery and increases its overall energy density.

[0247] By flattening and elongating individual battery cells to form a thin and long shape, these elongated battery cells can be arranged and combined directly to form a battery pack. This eliminates the need for intermediate module structures, effectively improving the volume utilization rate of the battery pack and increasing the overall energy density of the individual battery cells.

[0248] 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.

[0249] When the ratio between the values ​​of L and H is within the above range, it helps to improve the volume utilization rate of the battery pack formed by assembling individual battery cells. Furthermore, when a collision or external impact occurs, the force on the individual battery cells is more uniform and dispersed, effectively reducing the risk of short circuits.

[0250] In some embodiments, the value of L is 4 to 7 times the value of H. This helps the battery cell to have both high energy density and low internal resistance.

[0251] In some embodiments, L is 400mm-1000mm, and / or H is 80mm-160mm.

[0252] As an example, L can be 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, 750mm, 800mm, 850mm, 900mm, 950mm or 1000mm.

[0253] As an example, H can be 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or 160mm.

[0254] When L and H are within the above-mentioned value range, the size of the battery cell is moderate, which facilitates transfer and rapid assembly, and the transport path of lithium ions within the battery cell is relatively short, resulting in low internal resistance of the battery cell.

[0255] In some embodiments, referring to Figures 1-8, a housing is further included, within which the electrode assembly is located. The housing includes two opposing first housing walls 101 and a surrounding wall connecting the two first housing walls 101. The surrounding wall includes two opposing second housing walls 102 along the length direction of the first housing walls 101 and two opposing third housing walls 103 along the width direction of the first housing walls 101. Electrode terminals are provided on the second housing walls 102. The positive electrode tab 12 and the negative electrode tab 22 are electrically connected to the electrode terminals on the two second housing walls 102, respectively. A closing structure 106 is provided between the second housing wall 102 electrically connected to the positive electrode tab 12 and the positive electrode body 11. The closing structure 106 is configured to close the plurality of positive electrode tabs 12. This facilitates the fixing of the positive electrode tabs and the welding between the positive electrode sheet and the electrode post 105.

[0256] Referring to Figures 4 and 5, the positive electrode tab 12 and negative electrode tab 22 of the battery cell are led out from the two second shell walls of the casing, i.e., opposite-side tabs. This helps to arrange the battery cells more efficiently in a limited space and facilitates the formation of efficient series and parallel structures of multiple battery cells inside the battery pack. It also reduces the space occupied by the connectors between battery cells and improves the volumetric energy density of the battery pack. To improve the volumetric energy density, a lamination process can be used to form the electrode assembly. In this assembly, each positive electrode has a corresponding positive electrode tab, and each negative electrode has a corresponding negative electrode tab. To achieve current collection, all the positive electrode tabs 12 and negative electrode tabs 22 need to be collected and then electrically connected to the corresponding electrode terminals.

[0257] Typically, aluminum foil is used for the positive current collector and copper foil for the negative current collector. Because copper foil is relatively soft and prone to breakage, the negative electrode tab must first be welded to the corresponding post on the second shell wall before being installed into the enclosure structure formed by the first and third shell walls. Finally, the positive electrode tab is welded to the corresponding post on the second shell wall. To reduce the risk of reverse insertion of the positive electrode tab during welding to the corresponding second shell wall, which could lead to an internal short circuit in the battery cell, multiple positive electrode tabs can be fixed using a collapsible structure. This reduces the risk of reverse insertion and facilitates welding the positive electrode tab to the post base.

[0258] In some embodiments, the edge of the positive electrode sheet is chamfered along the length of the first housing wall 101. This facilitates rapid assembly of the electrode assembly and reduces the risk of the electrode assembly puncturing the separator during housing insertion.

[0259] In some embodiments, the second shell wall 102 connected to the negative electrode tab 22 is provided with an injection hole. This facilitates the injection of electrolyte.

[0260] Since a closing structure for closing the positive electrode tab is provided on the second shell wall connected to the positive electrode tab, in order to make the second shell wall have high mechanical strength, the liquid injection hole is provided on the second shell wall 102 connected to the negative electrode tab 22.

[0261] In some embodiments, referring to Figures 9 and 10, the injection port 107 and the pressure relief portion 104 of the housing are located on different second shell walls 102, and the pressure relief portion 104 is configured to release pressure inside the housing. This reduces the corrosion of the pressure relief portion 104 by the electrolyte during injection.

[0262] Since the electrolyte will corrode the pressure relief section when it is injected into the battery cell through the injection hole, the injection hole and the pressure relief section of the casing should be located on different second side walls.

[0263] In some embodiments, referring to FIG11, the electrode terminal is provided with at least one mounting hole, and the electrode post 105 passes through the mounting hole and is riveted to the electrode tab. This helps to reduce the volume and weight of the battery cell and increase its energy density.

[0264] Using a single pole to achieve electrical connection reduces connection points, simplifies the production and assembly process, and requires fewer materials and processing steps, resulting in lower costs.

[0265] In some embodiments, referring to Figures 9 and 10, the electrode terminal is provided with at least two mounting holes, and each electrode post 105 passes through the mounting hole and is riveted to the electrode tab. This helps to improve the current carrying capacity of the electrode post 105.

[0266] Using bipolar terminals for electrical connection can disperse current, reduce localized overheating, and improve the battery's fast-charging performance.

[0267] In some embodiments, the diameter of the electrode post 105 is 3mm-8mm. Therefore, the electrode post 105 combines high current-carrying capacity with low space occupation.

[0268] As an example, the diameter of the pole can be 3mm, 4mm, 5mm, 6mm, 7mm or 8mm.

[0269] When the diameter of the electrode is within the above range, the electrode has a strong current-carrying capacity and low internal resistance, which can reduce heat generation.

[0270] In some embodiments, referring to FIG12, the terminal post 105 riveted to the positive electrode tab 12 and the terminal post 105 riveted to the negative electrode tab are staggered along the length direction of the first housing wall 101. Optionally, the terminal post 105 riveted to the positive electrode tab and the terminal post 105 riveted to the negative electrode tab are diagonally arranged along the length direction of the first housing wall 101. This helps to arrange battery cells more efficiently in a limited space and improve the volumetric energy density of the assembled battery module or battery pack.

[0271] In some embodiments, referring to FIG13, the electrode post 105 and the electrode tab are electrically connected via an adapter piece 108. This significantly improves the welding quality and connection reliability between the electrode post 105 and the electrode tab.

[0272] When using an adapter plate to achieve electrical connection between the terminal post and the tab, the shape and size of the adapter plate can be adjusted as needed to adapt to different distances and positions. Furthermore, the welding process of the adapter plate has fewer defects, which can help to distribute the current more evenly, reduce local overheating and potential difference, and improve the battery's lifespan.

[0273] In some embodiments, referring to FIG14, the terminal post 105 is directly electrically connected to the tab. This helps to reduce the structural complexity inside the battery cell, helps to reduce the size of the battery cell, and increases the energy density.

[0274] When the terminals and tabs are directly electrically connected, the connectors are eliminated, simplifying the internal structure of the battery cell, reducing assembly steps, and lowering the overall manufacturing cost.

[0275] In some embodiments, the aforementioned battery cells can be directly assembled into a battery pack, eliminating the need for a battery module structure and increasing the energy density of the battery. The battery pack may contain one or more battery cells, the specific number of which can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0276] In some embodiments, the distance between the two first shell walls 101 is D, where D is less than or equal to 30 mm. This facilitates rapid heat dissipation from the battery cell.

[0277] Under fast charging conditions, both the charging current and voltage flowing through the battery cell increase accordingly, leading to a significant increase in heat generation according to Joule's law. For elongated battery cells, the first shell wall has the largest surface area, resulting in better heat dissipation near it. However, heat diffusion within the battery cell is slower along its thickness, i.e., along the width of the third shell wall. When the distance D between the two first shell walls 101 is within the aforementioned range, the heat dissipation in the thickness direction is better, which facilitates efficient heat dissipation during fast charging and improves the fast charging performance of the battery cell.

[0278] In some embodiments, D is 10mm-25mm. As a result, the battery cell has high mechanical strength and excellent heat dissipation capability.

[0279] As an example, D can be 5mm, 10mm, 15mm, 20mm, 25mm or 30mm.

[0280] In some embodiments, the thicknesses of the first shell wall 101 and the third shell wall 103 are each independently less than or equal to 0.5 mm. This can improve the volumetric energy density of the battery cell.

[0281] 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 shell is lighter, which is beneficial to improving the mass energy density and volumetric energy density of the battery cell.

[0282] As an example, the thickness of the first shell wall 101 and the third shell wall 103 can be the same.

[0283] In some embodiments, the first shell wall 101 and the third shell wall 103 comprise at least one of an aluminum shell and a steel shell. This can improve the mechanical strength of the battery cell.

[0284] At the same thickness, steel shells have greater mechanical strength than aluminum shells, which can better confine the electrode components and alleviate the expansion of individual battery cells during charging and discharging.

[0285] At the same thickness, aluminum casing is lighter than steel casing, further reducing the weight of the casing and improving the energy density of the battery cells.

[0286] In some embodiments, the first shell wall 101 and the third shell wall 103 are steel shells with a wall thickness of 0.1mm-0.5mm. This effectively mitigates the volume expansion of individual battery cells during charging and discharging.

[0287] In some embodiments, the first shell wall 101 and the third shell wall 103 are aluminum shells with a wall thickness of 0.3mm-0.4mm. This effectively improves the gravimetric energy density of the battery cell.

[0288] In some embodiments, the first shell wall 101 and the third shell wall 103 are formed by bending and welding aluminum plates, with the weld seam located at the junction of the first shell wall 101 and the third shell wall 103. This reduces electrolyte leakage.

[0289] The aluminum shell obtained by bending and laser welding aluminum plates has 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.

[0290] In some embodiments, when the organic solvent in the electrolyte is predominantly a low-viscosity solvent, the electrolyte as a whole also exhibits a low viscosity. Low-viscosity electrolytes are prone to decomposition and gas generation during high-rate charge and discharge, leading to expansion of the battery cells. Welds, as mechanically weak points, may crack under extreme conditions. To prevent rapid deterioration caused by electrolyte leakage after weld cracking, the weld can be located at the junction of the third shell wall and the first shell wall, away from the ground. This prevents electrolyte leakage from the battery cells even after weld cracking, effectively suppressing rapid battery deterioration.

[0291] In some embodiments, a side support plate is provided between the electrode assembly and the first housing wall 101. This helps to improve the structural stability of the battery cell.

[0292] Side support plates can prevent direct contact between the electrode and the housing, reducing damage to the electrode caused by the rounded corners at the edges of the inner wall of the housing.

[0293] In some embodiments, at least one of the second housing walls 102 is provided with a pressure relief portion 104, which is configured to release pressure inside the housing. The area of ​​the pressure relief portion 104 projected onto the second housing wall 102 is 7%-15% of the area of ​​the second housing wall 102. This helps to quickly release overpressure gas inside the battery cell when the internal pressure is too high.

[0294] As an example, the area of ​​the pressure relief section can be 155 mm². 2 The area of ​​the second shell wall can be 1920 mm². 2 .

[0295] When the area of ​​the pressure relief part 104 projected onto the second shell wall 102 is within the aforementioned range, the pressure relief part can respond quickly and rupture to release the internal pressure when the internal pressure of the battery cell increases suddenly; it also occupies less space on the second shell wall, making it convenient to install other structural components on the second shell wall.

[0296] In some embodiments, the capacity of the battery cell is Q, the area of ​​the pressure relief section 104 projected onto 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 rapidly release overpressure gas inside the battery cell.

[0297] When the capacity of a single battery cell is large, the content of low-viscosity electrolyte inside the battery is correspondingly high, resulting in a large amount of gas generation per unit time during high-rate charge and discharge. Furthermore, lithium difluorosulfonylimide can also undergo gas-generating side reactions with the negative electrode active material layer under full charge. Therefore, a larger pressure relief section is needed to provide more venting space, allowing for a rapid response to the initial surge in internal pressure of the battery cell, enabling rupture and release of internal pressure. When the ratio of P to Q is within the aforementioned range, the area of ​​the pressure relief section matches the battery capacity, meeting the pressure relief requirements of the corresponding capacity battery cell.

[0298] In some embodiments, pressure relief portions may be provided on both second shell walls. The ratio between the area of ​​the pressure relief portion and the area of ​​the second shell wall can be referred to the foregoing.

[0299] In a second aspect, this application proposes a battery device including the aforementioned battery cell. The battery device can be a battery module, battery pack, energy storage device, etc. Therefore, this battery device possesses all the features and advantages of the aforementioned battery cell, which will not be repeated here.

[0300] In a third aspect, this application proposes an electrical device comprising the aforementioned battery cell. Therefore, this electrical device possesses all the features and advantages of the aforementioned battery cell, which will not be repeated here.

[0301] The aforementioned battery cells or battery packs can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is 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 and satellites, energy storage systems, etc.

[0302] As the electrical device, a single battery cell or a battery pack can be selected according to its usage requirements.

[0303] Figure 15 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this device, a battery pack can be used.

[0304] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0305] Example 1

[0306] 1) Preparation of positive electrode sheet

[0307] The positive electrode sheet includes a positive current collector aluminum foil and a positive active material layer. The positive active material layer comprises a film formed by uniformly coating the surface of the positive current collector aluminum foil with a positive electrode slurry (solvent being N-methylpyrrolidone), followed by drying and cold pressing. The positive active material layer includes positive active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.4:1.1. The positive active material is lithium iron phosphate containing aluminum, titanium, and vanadium, wherein the mass fractions of aluminum, titanium, and vanadium are 0.012%, 0.025%, and 0.025%, respectively. In the cross-section along the thickness direction of the positive electrode active material layer, the positive electrode active material includes lithium phosphate with an olivine structure having a longest diameter of 2.5 μm and lithium phosphate with an olivine structure having a shortest diameter of 0.2 μm. The total width of the positive electrode tabs accounts for 50% of the total width of the positive electrode body. The coating weight of a single layer of positive electrode active material is 0.283 g / 1540.25 mm. 2 The compaction density of the positive electrode active material layer is 2.45 g / cm³. 3 .

[0308] 2) Preparation of negative electrode sheet

[0309] The negative electrode sheet comprises a negative current collector copper foil and a negative active material layer. The negative active material layer consists of a film formed by uniformly coating the surface of the negative current collector copper foil with a negative electrode slurry (solvent being deionized water), followed by drying and cold pressing. The negative active material layer comprises negative active material in a weight ratio of 96.2:1.8:1.2:0.8, styrene-butadiene rubber (SBR) as a binder, sodium carboxymethyl cellulose (CMC-Na) as a thickener, and carbon black (Super P) as a conductive agent. The negative active material is a single layer of graphite. The Dv50 particle size of the negative active material is 10.5 μm. The total width of the negative electrode tab accounts for 50% of the total width of the negative electrode body. The coating weight of the single-layer negative active material layer is 0.127 g / 1540.25 mm. 2 The compaction density of the negative electrode active material layer is 1.45 g / cm³. 3 .

[0310] 3) Separating membrane

[0311] The separator is a porous polypropylene (PP) membrane.

[0312] 4) Preparation of electrolyte

[0313] The organic solvent in the electrolyte has a ratio of EA / DMC / EC = 10 / 55 / 35, and the electrolyte lithium salt in the electrolyte is lithium hexafluorophosphate with a mass content of 12.5%.

[0314] 5) Battery manufacturing

[0315] A lithium-ion battery includes a casing, electrode components, and an electrolyte. The electrode components and electrolyte are housed within the casing. The electrode components include a positive electrode, a negative electrode, and a separator. The electrode components are of a wound type, and the separator is disposed between the positive and negative electrode components. The length L of a single battery cell is 510 mm, the width H is 120 mm, and the thickness D is 16 mm.

[0316] The differences between the other embodiments and Embodiment 1 are shown in Tables 1-5.

[0317] Table 1

[0318] Table 2

[0319] Table 3

[0320] Table 4

[0321] Table 5

[0322] Comparative Example 1

[0323] Comparative Example 1 is consistent with Example 1, except that the total width of the positive electrode tab accounts for 30% of the total width of the positive electrode body, the total width of the negative electrode tab accounts for 30% of the total width of the negative electrode body, and the coating weight of a single layer of positive electrode active material is 0.25 g / 1540.25 mm. 2 The coating weight of a single-layer negative electrode active material layer is 0.1g / 1540.25mm. 2 The organic solvent in the electrolyte has a ratio of EA / EC = 90 / 10.

[0324] Comparative Example 2

[0325] Comparative Example 2 is the same as Example 1, except that the coating weight of the single-layer positive electrode active material layer is 0.3 g / 1540.25 mm. 2 The coating weight of a single-layer negative electrode active material layer is 0.145g / 1540.25mm. 2 The organic solvent in the electrolyte has a ratio of DMC / EC = 60 / 40.

[0326] Comparative Example 3

[0327] Comparative Example 3 is consistent with Example 1, except that the total width of the positive electrode tab is 100% of the total width of the positive electrode body, the total width of the negative electrode tab is 100% of the total width of the negative electrode body, and the coating weight of a single layer of positive electrode active material is 0.31 g / 1540.25 mm. 2 The coating weight of a single-layer negative electrode active material layer is 0.16g / 1540.25mm. 2 The organic solvent in the electrolyte has a ratio of EA / EC = 90 / 10.

[0328] Fast charging performance tests were conducted on the batteries in Examples 1-10 and Comparative Examples 1-3. The test methods are as follows, and the test results are shown in Table 1-1.

[0329] Charging time test: ① Voltage calibration: 1) The positive electrode, negative electrode, separator, and electrolyte in the example or comparative example are used to prepare a stacked three-electrode battery, and it is placed at 25℃ for 30 min; 2) At 25℃, the battery cell is charged at 0.33C to the charging cutoff voltage of 3.65V, and then constant voltage charging is continued at the charging cutoff voltage until the current is 0.05C, and the charging is cut off (where C represents the rated capacity of the battery cell); 3) Place it at 25℃ for 1 h; 4) At 25℃, the battery cell is discharged at 0.33C to the discharge cutoff voltage of 2.5V, and the total discharge capacity C0 of the battery cell is recorded; 5) Place it at 25℃ for 1 h. ② Room temperature charging test: 1) Prepare a stacked three-electrode battery using the positive electrode, negative electrode, separator, and electrolyte from the examples or comparative examples, and let it stand for 30 minutes; 2) Discharge with 0.33C0 DC to the discharge cutoff voltage of 2.5V, at which point the SOC is 0%; 3) Let it stand for 5 minutes; 4) Charge with 5C0 constant current until the negative electrode potential is 0V, and read the capacity C1 at this point, which corresponds to C1 / C0SOC; 5) Let it stand for 5 minutes; 6) Charge with 4.5C0 constant current until the negative electrode potential is 0V, and read the capacity C2 at this point, which corresponds to C2 / C0SOC; 7) Let it stand for 5 minutes; 8) Charge with 4C0 constant current until the negative electrode potential is 0V, and read the capacity C3 at this point, which corresponds to C3 / C0SOC; 9) Let it stand for 5 minutes; 10) Charge with 3C0 constant current until the negative electrode potential is 0%... V, read the current capacity C4, corresponding to C4 / C0SOC; 11) Let stand for 5 minutes; 12) Charge with 2C0 constant current until the negative electrode potential is 0V, read the current capacity C5, corresponding to C5 / C0SOC; 13) Let stand for 5 minutes; 14) Charge with 1C0 constant current until the negative electrode potential is 0V, read the current capacity C6, corresponding to C6 / C0SOC; 15) Let stand for 5 minutes; 16) Charge with 0.8C0 constant current until the negative electrode potential is 0V, read the current capacity C7, corresponding to C7 / C0SOC; 17) Let stand for 5 minutes; 18) Charge with 0.5C0 constant current until the negative electrode potential is 0V, read the current capacity C8, corresponding to C8 / C0SOC; 19) Let stand for 5 minutes; 20) Charge with 0.33C0 constant current until the negative electrode potential is 0V. Read the current capacity C9 (also known as C0), which corresponds to 100% SOC. The required charging time is obtained by summing the total charging time from 10% SOC to 80% SOC.

[0330] Temperature rise test: A temperature sensing wire is placed at any position on the top cover of the battery cell to monitor the temperature of the top cover. Then, the battery cell is charged as follows:

[0331] 1) Discharge the individual cells of the examples or comparative examples at 0.33C DC to the discharge cutoff voltage of 2.5V, at which point the state of charge (SOC) is 0%.

[0332] 2) Let stand for 5 minutes, then charge at a constant current of 5C to C1 / CSOC (the value of C1 is the capacity corresponding to the negative electrode cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell).

[0333] 3) Let stand for 5 minutes, then charge at a constant current of 4.5C to C2 / CSOC (the value of C2 is the capacity corresponding to the negative electrode cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell).

[0334] 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 cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell).

[0335] 5) Let stand for 5 minutes, then charge at 3C constant current to C4 / CSOC (C4 is the capacity corresponding to the negative electrode cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell).

[0336] 6) Let stand for 5 minutes, then charge at a constant current of 2C to C5 / CSOC (C5 is the capacity corresponding to the negative electrode cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell).

[0337] 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 cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell).

[0338] 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 cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell).

[0339] 9) Let stand for 5 minutes, then charge at a constant current of 0.5C to C8 / CSOC (C8 is the capacity corresponding to the negative electrode cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell).

[0340] 10) Let stand 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 cleavage window when testing the stacked three-electrode battery, and C represents the rated capacity of the battery cell). At this time, the battery cell reaches the fully charged state, that is, 100% SOC.

[0341] Monitor and record the temperature rise of individual battery cells as they charge from 10% SOC to 80% SOC.

[0342] Cyclic performance tests were conducted on the individual cells in Examples 1 and 11-13. The test methods are as follows, and the test results are shown in Tables 1-2.

[0343] Cycle life: At 45℃, charge the battery cell at a constant current of 1C to the cutoff voltage of 3.65V, then charge at a constant voltage to 0.05C, let it rest for 10 minutes, and discharge at a constant current of 1C to 2.5V. Repeat this process until the capacity retention rate decays to 80% and the number of cycles is recorded.

[0344] Table 1-1

[0345] Table 1-2

[0346] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, wherein, The battery comprises: an electrode assembly comprising a positive electrode tab, a negative electrode tab, and a separator film between the positive electrode tab and the negative electrode tab, wherein the positive electrode tab comprises a positive electrode current collector and a positive electrode active material layer on at least one side of the positive electrode current collector, the positive electrode current collector comprises a positive electrode main body part and at least one positive electrode tab part, the positive electrode main body part is connected to the positive electrode tab part, and the total width of the positive electrode tab part accounts for 50%-100% of the total width of the positive electrode main body part in the width direction of the positive electrode main body part, The negative electrode tab 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 part and at least one negative electrode tab part, the negative electrode main body part is connected with the negative electrode tab part, along the width direction of the negative electrode main body part, the total width of the negative electrode tab part accounts for 50%-100% of the total width of the negative electrode main body part, 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 , an electrolyte comprising an organic solvent, the organic solvent comprising a first solvent, the first solvent comprising at least one of dimethyl carbonate and linear carboxylate, wherein the structural formula of the linear carboxylate satisfies R1-COO-R2, R1 and R2 are independently selected as C1-C5 alkyl or halogenated alkyl; and the mass fraction of the first solvent is 4%-72% based on the total mass of the electrolyte.

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

3. The battery cell of claim 1 or 2, wherein, The positive electrode tab part and the negative electrode tab part are located on the same side of the positive electrode main body part, or the positive electrode tab part and the negative electrode tab part are located on opposite sides of the positive electrode main body part.

4. The battery cell of any one of claims 1-3, wherein, The positive electrode current collector comprises the positive electrode main body part and a plurality of positive electrode tab parts, and at least two positive electrode tab parts are located on opposite sides of the positive electrode main body part; and / or, the negative electrode current collector comprises the negative electrode main body part and a plurality of negative electrode tab parts, and at least two negative electrode tab parts are located on opposite sides of the negative electrode main body part.

5. The battery cell of any one of claims 1-4, wherein, The positive electrode current collector comprises the positive electrode main body part and a plurality of positive electrode tab parts arranged at intervals; and / or, the negative electrode current collector comprises the negative electrode main body part and a plurality of negative electrode tab parts arranged at intervals.

6. The battery cell of any one of claims 1-5, wherein, The coating weight of the single layer of the negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.135 g / 1540.25 mm 2 .

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

8. The battery cell of any one of claims 1-5, wherein, The coating weight of the single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2 .

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

10. The battery cell of any one of claims 1-9, wherein, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer at least on one side of the negative electrode current collector, the negative electrode active material layer having a compaction density of 1.2 g / cm 3 -1.5 cm 3 .

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

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

13. The battery cell of claim 10, wherein, The negative electrode active material layer comprises a first negative electrode active material layer and a second negative electrode active material layer arranged in a stack, the first negative electrode active material layer is located on the 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 of any one of claims 1-13, wherein, The conductivity of the electrolyte is 10ms / cm-20ms / cm.

15. The battery cell of any one of claims 1-14, wherein, The mass fraction of the first solvent is 16% to 72% based on the total mass of the electrolyte.

16. The battery cell of any one of claims 1-15, wherein, The mass fraction of the linear carboxylic acid ester is 32% to 68% based on the total mass of the electrolyte.

17. The battery cell of any one of claims 1-16, wherein, The electrolyte further comprises a first lithium salt additive, the first lithium salt additive comprises 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% to 0.5% based on the total mass of the electrolyte.

18. The battery cell of claim 17, wherein, The first lithium salt additive comprises at least one of lithium difluorophosphate, lithium difluoro oxalate phosphate, lithium difluoro oxalate borate, lithium tetrafluoroborate.

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

20. The battery cell of any one of claims 1-19, wherein, The organic solvent further comprises a second solvent, the second solvent comprises at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate.

21. The battery cell of claim 20, wherein, The second solvent comprises 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 of any one of claims 1-21, wherein, The electrolyte further comprises a non-lithium salt additive, the non-lithium salt additive comprises a sulfuric acid ester additive and a carbonic acid ester additive.

23. The battery cell of claim 22, wherein, The carbonic acid ester additive comprises at least one of vinylene carbonate, fluoro-vinylene carbonate, and vinyl ethylene carbonate.

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

25. The battery cell of claim 22, wherein, The sulfuric acid ester additive comprises at least one of 4,4 vinyl sulfite, bis vinyl sulfite, cyclic tris vinyl sulfite, and 1,3-propane sultone.

26. The battery cell of any one of claims 22-25, wherein, The mass fraction of the non-lithium salt additive is 0.05% to 3% based on the total mass of the electrolyte.

27. The battery cell of any one of claims 1-26, wherein, The electrolyte further comprises a second lithium salt additive, the second lithium salt additive comprises at least one of lithium bis-oxalate borate, lithium difluoro di-oxalate phosphate, lithium tetrafluoro oxalate phosphate, lithium bis-trifluoromethanesulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate.

28. The battery cell of any one of claims 1-27, wherein, The electrolyte further comprises an electrolyte lithium salt, the electrolyte lithium salt comprises at least one of lithium hexafluorophosphate and lithium bis-fluorosulfonylimide, and the mass fraction of the electrolyte lithium salt is greater than or equal to 13% based on the total mass of the electrolyte.

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

1.

30. The battery cell of any one of claims 1-29, wherein, The compacted density of the positive electrode active material layer is 2.2 g / cm 3 - 2.6 g / cm 3 .

31. The battery cell of any one of claims 1-30, wherein, The positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises: a core portion comprising an olivine-structured lithium-containing phosphate, and a coating layer covering a surface of the olivine-structured lithium-containing phosphate, the coating layer containing one or more elements selected from C, Fe, Ti, Zr, Hf, Ge, and Sn.

32. The battery cell of claim 31, wherein, The lithium-containing phosphate of olivine structure comprises a compound of general formula Li x1 A y1 Me a M1 b P 1-c X c Y z 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, Mg; Me comprises one or more of Mn, Fe, Co, 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, Ce; X comprises one or more of S, Si, Cl, B, C, N; Y comprises one or more of O, F.

33. The battery cell of claim 31 or 31, wherein, The coating layer comprises a carbon layer, and the graphitization degree of the carbon layer is 0.15 to 0.

32.

34. The battery cell of any one of claims 31-33, wherein, In a cross section of the positive electrode active material layer in a thickness direction, the positive electrode active material includes lithium-containing phosphate of olivine structure with a longest diameter of 1 μm-3 μm, and lithium-containing phosphate of olivine structure with a shortest diameter of 0.1 μm-0.3 μm.

35. The battery cell of any one of claims 31-34, 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 quasi-single crystal particle.

36. The battery cell of any one of claims 31-35, wherein, The positive electrode active material layer further includes a lithium-rich material, the 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, lithium citrate, lithium nickel cobalt manganese acid.

37. The battery cell of any one of claims 1-36, wherein, The length of the battery cell is L, the width of the battery cell is H, the value of L is 4-10 times the value of H.

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

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

40. The battery cell of any one of claims 1-39, wherein, Further comprising a shell, the electrode assembly is located in the shell, the shell comprises two first shell walls arranged oppositely, and a surrounding wall connecting the two first shell walls, the surrounding wall comprises two second shell walls arranged oppositely along the length direction of the first shell wall, and two third shell walls arranged oppositely along the width direction of the first shell wall, the electrode terminals are arranged on the second shell wall, and the positive tab part and the negative tab part are respectively electrically connected with the electrode terminals on the two second shell walls, wherein the second shell wall electrically connected with the positive tab part is provided with a folding structure between the positive tab part and the positive main body part, and the folding structure is configured to fold the plurality of positive tab parts.

41. The battery cell of claim 40, wherein, A chamfer is arranged at the edge of the positive electrode tab in the length direction of the first shell wall.

42. The battery cell of claim 40 or 41, wherein, The second shell wall connected with the negative tab part is provided with a liquid injection hole.

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

44. The battery cell of any one of claims 40-43, wherein, At least one mounting hole is arranged on the electrode terminal, and a pole is arranged in the mounting hole and riveted with the tab part.

45. The battery cell of any one of claims 40-43, wherein, At least two mounting holes are arranged on the electrode terminal, and each pole is arranged in the mounting hole and riveted with the tab part.

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

47. The battery cell of claim 44 or 45, wherein, The poles riveted with the positive tab part and the poles riveted with the negative tab part are arranged in a staggered manner in the length direction of the first shell wall, and optionally, the poles riveted with the positive tab part and the poles riveted with the negative tab part are arranged diagonally in the length direction of the first shell wall.

48. The battery cell of claim 44 or 45, wherein, The pole and the tab are electrically connected through a conversion sheet.

49. The battery cell of claim 44 or 45, wherein, The pole and the tab are directly electrically connected.

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

51. The battery cell of claim 50, wherein, D is 10 mm-25 mm.

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

53. The battery cell of claim 52, wherein, The first shell wall and the third shell wall comprise at least one of an aluminum shell and a steel shell.

54. The battery cell of claim 53, 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.

55. The battery cell of claim 53, 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.

56. The battery cell of claim 55, wherein, The first shell wall and the third shell wall are obtained by bending and welding an aluminum plate, and the weld of the welding is located at the connection of the first shell wall and the third shell wall.

57. The battery cell of claim 40, wherein, A side supporting plate is arranged between the electrode assembly and the first shell wall.

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

59. The battery cell of claim 58, wherein, The capacity of the battery is Q, and 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 being Ah, and the unit of the area being mm 2 .

60. A battery device, wherein, The battery device comprises at least one of a battery module, a battery pack, and an energy storage device.

61. An electrical device, comprising: The battery device comprises at least one of a battery module, a battery pack, and an energy storage device. The battery device comprises at least one of a battery module, a battery pack, and an energy storage device.

Images