Battery cell, battery device, and electric device

Abstract

The present disclosure provides a battery cell, a battery device, and an electric device. The length of the battery cell is L, and the width of the battery cell is H, wherein the value of L is four to ten times the value of H. The battery cell comprises an electrolyte, a first lithium salt additive in the electrolyte comprises at least one of fluoroborate and fluorophosphate, and the mass fraction of the first lithium salt additive is 0.01%-0.5%.

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 / 107375, 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 batteries 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 batteries 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] Summary of the Invention

[0007] In a first aspect, this application proposes a battery cell with a length of L and a width of H, where L is 4 to 10 times the value of H. The battery cell includes an electrolyte comprising an organic solvent and a first lithium salt additive, wherein the first lithium salt additive comprises at least one of a fluoroborate and a fluorophosphate, and the mass fraction of the first lithium salt additive is 0.01%-0.5% based on the total mass of the electrolyte. Therefore, the addition of the first lithium salt additive can effectively reduce the internal resistance of the battery cell, enabling the battery cell to possess both high energy density and fast-charging performance.

[0008] 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.

[0009] In some embodiments, L is 400mm-1000mm, and / or H is 80mm-160mm.

[0010] 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.

[0011] In some embodiments, the mass fraction of the first lithium salt additive in the electrolyte is 0.05%-0.5%, optionally 0.1%-0.3%. This helps to reduce the cost of the battery cell.

[0012] 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.

[0013] In some embodiments, the organic solvent 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. This effectively reduces the viscosity of the electrolyte.

[0014] In some embodiments, the linear carboxylic acid ester includes at least one selected from ethyl formate, isopropyl formate, ethyl acetate, methyl acetate, propyl acetate, and methyl propionate. This further reduces the viscosity of the electrolyte.

[0015] In some embodiments, the mass fraction of the linear carboxylic acid ester is 32%-68% based on the total mass of the electrolyte.

[0016] In some embodiments, the mass fraction of the first solvent is greater than or equal to 4% based on the total mass of the organic solvent and the total mass of the electrolyte; alternatively, the mass fraction of the first solvent is 16%-80% based on the total mass of the electrolyte.

[0017] In some embodiments, the organic solvent further includes a second solvent, the second solvent comprising at least one of 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.

[0018] In some embodiments, the second solvent comprises diethyl carbonate, and the content of diethyl carbonate is not less than 15% based on the total mass of the organic solvent.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] In some embodiments, the device further includes a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer located at least on one side of the positive current collector, the positive active material layer having a compaction density of 2.2 g / cm³. 3 -2.6g / cm 3 This helps improve the fast-charging performance of individual battery cells.

[0025] In some embodiments, the positive electrode active material layer comprises a positive electrode active material, which includes a lithium phosphate with an olivine structure or a modified material thereof. This helps to improve the cycle life of the battery cell.

[0026] In some embodiments, the olivine-structured lithium phosphate or its modified material comprises: a core comprising the olivine-structured lithium phosphate, and a coating layer covering the surface of the olivine-structured lithium phosphate, 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.

[0027] In some embodiments, the lithium phosphate with the olivine structure includes those of the general formula Li x Ay Me a M b P 1-c X c Y z The compound contains compounds in which 0.5 ≤ x ≤ 1.3, 0 ≤ y ≤ 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; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, which includes one or more 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.

[0032] In some embodiments, the device further includes a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative active material layer located at least on one side of the negative current collector, the negative active material layer having a compaction density of 1.2 g / cm³. 3 -1.5cm3 This helps improve the fast-charging performance of individual battery cells.

[0033] In some embodiments, the coating weight of a single layer of the negative electrode active material is greater than or equal to 0.1 g / 1540.25 mm. 2 .

[0034] In some embodiments, the coating weight of a single layer of the negative electrode active material is 0.1 g / 1540.25 mm. 2 -0.145g / 1540.25mm 2 Therefore, the negative electrode active material layer possesses both superior lithium-ion insertion / extraction rates and high energy density.

[0035] 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.

[0036] In some embodiments, the battery cell takes 7-15 minutes to charge from 10% SOC to 80% SOC. Therefore, the battery cell exhibits superior fast-charging performance.

[0037] 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.

[0038] 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.

[0039] 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 of the battery cell.

[0040] In some embodiments, the negative electrode active material layer comprises a negative electrode active material, which includes a silicon-containing material, wherein the mass fraction of silicon in the silicon-containing material is 0.1%-7%. This can improve the mass energy density of the battery cell.

[0041] 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.

[0042] In some embodiments, the device further includes a housing comprising two first shell walls disposed opposite to each other, and a surrounding wall connecting the two first shell walls. The surrounding wall includes two second shell walls disposed opposite to each other along the length direction of the first shell walls, and two third shell walls disposed opposite to each other along the width direction of the first shell walls. 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.

[0043] In some embodiments, D is 10mm-25mm. As a result, the battery cell has high mechanical strength and excellent heat dissipation capability.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] In some embodiments, the capacity of the battery cell is Q, the area of ​​the pressure relief portion projected onto the second shell wall 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.

[0052] In some embodiments, 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 includes a positive electrode body and at least one positive electrode tab, with the positive electrode body connected to the positive electrode tab. The negative electrode includes a negative current collector and a negative active material layer located on at least one side of the negative current collector. The negative current collector includes a negative electrode body and at least one negative electrode tab, with the negative electrode body connected to the negative electrode tab. Electrode terminals are provided on the second shell wall. The positive electrode tab and the negative electrode tab are electrically connected to the electrode terminals on two separate parts of the second shell wall. 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 together multiple positive electrode tabs. This facilitates the fixing of the positive electrode tab and the welding between the positive electrode and the electrode post.

[0053] 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.

[0054] In some embodiments, along the width direction of the positive electrode body, the total width of the positive electrode tab accounts for 30%-100% of the total width of the positive electrode body; and / or, along the width direction of the negative electrode body, the total width of the negative electrode tab accounts for 30%-100% of the total width of the negative electrode body. This effectively improves the current-carrying capacity of the tab.

[0055] In some embodiments, the size of the positive electrode tab is 50%-80% of the size of the positive electrode body in the width direction of the positive electrode body. Therefore, the positive electrode tab has superior heat dissipation capability.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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

[0066] 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:

[0067] Figure 1 is a schematic diagram of the structure of a battery cell according to an embodiment of this application;

[0068] Figure 2 is a schematic diagram of the structure of a positive current collector according to an embodiment of this application;

[0069] Figure 3 is a schematic diagram of the negative electrode current collector according to an embodiment of this application;

[0070] Figure 4 is a partial structural schematic diagram of the housing according to an embodiment of this application;

[0071] Figure 5 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0072] Figure 6 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0073] Figure 7 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0074] Figure 8 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0075] Figure 9 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0076] Figure 10 is a partial structural schematic diagram of the housing according to another embodiment of this application;

[0077] Figure 11 is a schematic diagram of the structure of an electrical device according to an embodiment of this application.

[0078] Explanation of reference numerals in the attached figures:

[0079] 11 Positive electrode main body; 12 Positive electrode tab; 21 Negative electrode main body; 22 Negative electrode tab;

[0080] 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

[0081] 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.

[0082] 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).

[0083] 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.

[0084] 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%.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] In the description of this application, "multiple" means two or more.

[0089] 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.

[0090] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0091] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0092] By flattening and elongating individual battery cells to form a thin and elongated shape, these elongated cells can be directly arranged to form a battery pack, eliminating the need for intermediate module structures. This effectively improves the volume utilization of the battery pack and increases the energy density of individual battery cells. Furthermore, when the electrode assembly is formed using a stacking process, the positive and negative electrodes of the battery cell are positioned on opposite sides along its length. This results in a significantly longer lithium-ion transport path within the battery cell—the distance lithium ions travel between the positive and negative electrodes. Consequently, the longer lithium-ion transport path increases the migration resistance of lithium ions in the electrolyte, increases the internal resistance of the battery cell, and significantly affects the charge / discharge efficiency and instantaneous power output capability of the battery cell. Specifically, the charge / discharge efficiency of a battery cell reflects its energy utilization rate during the charge / discharge process, i.e., the ratio of actual usable energy to input or theoretical energy. Low charge / discharge efficiency indicates that the battery cell generates a large amount of heat and internal stress during charge / discharge, thus accelerating battery cell aging. Instantaneous power output capability refers to the maximum energy output rate that a single battery cell can provide within a short period of time. When the instantaneous power output capability of a battery cell is weak, it is difficult for the battery cell to charge and discharge with a large current in a short time, resulting in poor fast-charging performance. By adding lithium salt additives, namely at least one of fluoroborate and fluorophosphate, to the electrolyte of the battery cell, a low-resistance SEI film (solid electrolyte membrane) containing boron and phosphorus atoms can be formed on the surface of the negative electrode active material, effectively reducing the internal resistance of the battery cell and enabling the battery cell to have both high energy density and fast-charging performance.

[0093] This application limits the relative values ​​of battery length and width to a reasonable range and further controls the content of electrolyte additives, so that the battery has both high packing efficiency and good fast charging performance.

[0094] In a first aspect, this application proposes a battery cell. Referring to FIG1, the battery cell has a length of L and a width of H, where L is 4 to 10 times the value of H. The battery cell includes an electrolyte comprising an organic solvent and a first lithium salt additive. The first lithium salt additive includes at least one of fluoroborate and fluorophosphate, and the mass fraction of the first lithium salt additive is 0.01%-0.5% based on the total mass of the electrolyte. Therefore, the addition of the first lithium salt additive can effectively reduce the internal resistance of the battery cell, thereby enabling the battery cell to have superior charge / discharge efficiency and instantaneous power output capability, thus allowing the battery cell to possess both high energy density and fast charging performance.

[0095] During the charging and discharging process of a single battery cell, active ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. The separator, placed between the positive and negative electrode plates, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] In some embodiments, L is 400mm-1000mm, and / or H is 80mm-160mm.

[0100] As an example, L can be 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, 750mm, 800mm, 850mm, 900mm, 950mm or 1000mm.

[0101] As an example, H can be 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or 160mm.

[0102] 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.

[0103] In this embodiment of the application, the dimensions of the battery cell do not include the dimensions of the terminal posts that protrude from the main body of the battery cell.

[0104] 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%.

[0105] When the mass fraction of the first lithium salt additive is within the aforementioned range, the first lithium salt additive helps to form a low-resistance SEI film on the surface of the negative electrode active material, and at the same time, the amount used is small, which helps to reduce the cost of the electrolyte.

[0106] In some embodiments, when the aspect ratio L / H of the battery cell is high, the amount of the first lithium salt additive can be increased within the aforementioned range, thereby helping the battery cell to have both superior energy density and fast charging performance.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] In some embodiments, the mass fraction of the first lithium salt additive in the electrolyte is 0.05%-0.5%, optionally 0.1%-0.3%. This helps to reduce the cost of the battery cell.

[0111] 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.

[0112] Electrolyte

[0113] 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.

[0114] 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.

[0115] 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.

[0116] As an example, the conductivity of the electrolyte can be directly measured using a conductivity meter.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] In some embodiments, the mass fraction of the linear carboxylic acid ester is 40%-85% based on the total mass of the organic solvent.

[0123] As an example, based on the total mass of the organic solvent, the mass fraction of the linear carboxylic acid ester can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%.

[0124] 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 organic solvent, it can further reduce the liquid phase transport resistance of lithium ions and improve the fast charging performance and cycle performance of battery cells.

[0125] In this application, the organic solvent in the electrolyte is defined as: organic substances with a mass fraction greater than or equal to 5% based on the total mass of the electrolyte.

[0126] As an example, based on the total mass of the organic solvent, the mass fraction 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 with reference to standard GB / T9722-2006.

[0127] In some embodiments, the mass fraction of the first solvent is greater than or equal to 5% based on the total mass of the organic solvent.

[0128] As an example, based on the total mass of the organic solvent, the mass fraction of the first solvent can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%.

[0129] 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.

[0130] As an example, based on the total mass of the organic solvent, the mass fraction of the first solvent can be obtained by the following method: the organic components in the electrolyte can be quantitatively analyzed by gas chromatography with reference to standard GB / T9722-2006.

[0131] In some embodiments, the mass fraction of the first solvent is 20%-100% based on the total mass of the organic solvent.

[0132] 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 solvent comprises approximately 80% by mass, with the remainder being lithium salts. Therefore, even when the first solvent comprises 100% by mass based on the total mass of the organic solvent, the lithium salt content in the electrolyte is approximately 20%. In this case, the electrolyte can still provide a sufficient amount of lithium ions to migrate between the positive and negative electrodes of the battery cell.

[0133] In some embodiments, the organic solvent further includes a second solvent, the second solvent comprising at least one of ethylene carbonate (EC), propylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butyl carbonate. This helps to improve the cycle life of the battery cell.

[0134] 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.

[0135] In some embodiments, the second solvent comprises diethyl carbonate, and the content of diethyl carbonate is not less than 15% based on the total mass of the organic solvent.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] In some embodiments, the non-lithium salt additives include vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0140] 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.

[0141] 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%.

[0142] 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%.

[0143] 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%.

[0144] 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.

[0145] 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.

[0146] 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%.

[0147] When the mass fraction of 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.

[0148] When lithium salts in electrolytes dissolve in organic solvents, they release lithium ions. These lithium ions then form a solvated structure with the electrolyte, increasing the conductivity of the electrolyte and facilitating the rapid migration of lithium ions within it.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] [Positive electrode plate]

[0153] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer located at least on one side of the positive current collector, wherein the compaction density of the positive active material layer is 2.2 g / cm³. 3 -2.6g / cm 3 This helps improve the fast-charging performance of individual battery cells.

[0154] 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 .

[0155] 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.

[0156] 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.

[0157] 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 a 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, thus obtaining the positive electrode sheet. The aforementioned compaction density of the positive electrode active material layer refers to the compaction density of the positive electrode active material layer after rolling treatment. Specifically, the compaction density of the positive electrode active material layer after rolling and formation treatment, 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.

[0158] In some embodiments, the positive electrode active material layer comprises a positive electrode active material, which includes a lithium phosphate with an olivine structure or a modified material thereof. This helps to improve the cycle life of the battery cell.

[0159] Lithium phosphates with an olivine structure combine low cost with high theoretical specific capacity, which helps to improve the energy density of battery cells. Furthermore, the olivine structure can maintain good crystal integrity during charging and discharging, reducing structural stress and extending the cycle life of the battery.

[0160] In some embodiments, the olivine-structured lithium phosphate or its modified material comprises: a core comprising the olivine-structured lithium phosphate, and a coating layer covering the surface of the olivine-structured lithium phosphate, 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.

[0161] The coating layer can effectively alleviate the poor electronic and ionic conductivity of lithium phosphates with olivine structure, and improve the specific capacity and powder compaction density of the positive electrode active material.

[0162] In some embodiments, the lithium phosphate with the olivine structure includes those of the general formula Li x A y Me a M b P 1-c X c Y z The compound contains compounds in which 0.5 ≤ x ≤ 1.3, 0 ≤ y ≤ 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; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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.

[0174] In some embodiments, the Dv50 particle size of the positive electrode active material is 1μm-5μm.

[0175] 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.

[0176] In some embodiments, the Dv10 particle size of the positive electrode active material is 0.4 μm-0.7 μm.

[0177] 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.

[0178] 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.

[0179] The aforementioned Dv50 particle size refers to the particle size corresponding to a cumulative volume distribution percentage of 50%.

[0180] The aforementioned Dv10 particle size refers to the particle size corresponding to a cumulative volume distribution percentage of 10%.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, which includes one or more 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.

[0186] 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.

[0187] 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.

[0188] 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.).

[0189] 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.

[0190] 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.

[0191] [Negative electrode plate]

[0192] 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.

[0193] As an example, the compaction density of the negative electrode active material layer can be 1.2 g / cm³. 3 1.3g / cm3 1.4g / cm 3 Or 1.5g / cm 3 .

[0194] 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.

[0195] 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.

[0196] 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.

[0197] In some embodiments, the coating weight of a single layer of the negative electrode active material is greater than or equal to 0.1 g / 1540.25 mm. 2 .

[0198] 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 .

[0199] When the coating weight of a single layer of negative electrode active material is within the aforementioned range, the thickness of the negative electrode active material layer on the surface of the negative electrode current collector is moderate and the uniformity is high. The transport path of lithium ions in the negative electrode active material layer is short, and the negative electrode active material can be quickly inserted and extracted during charging and discharging, thereby improving the battery's fast charging and discharging capability.

[0200] 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.

[0201] In some embodiments, the coating weight of a single layer of the negative electrode active material is 0.1 g / 1540.25 mm. 2 -0.145g / 1540.25mm 2 Therefore, the negative electrode active material layer possesses both superior lithium-ion insertion / extraction rates and high energy density.

[0202] 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 When using the aforementioned positive electrode assembly, the volumetric energy density of the battery cell can be 380Wh / L-405Wh / L. Therefore, the battery cell exhibits a high volumetric energy density.

[0203] 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.

[0204] Taking a car as an example, in practical use, the state of charge (SOC) of a car battery is typically between 10% and 80%. Therefore, when the charging time within this SOC range is short, it reduces the user's waiting time for charging, greatly improving the user experience. Specifically, when the charging time from 10% SOC to 80% SOC is 7-15 minutes, the battery cell in this SOC range has equivalent fast charging performance of 4C-6C.

[0205] 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.

[0206] 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.

[0207] 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. Specifically, when the battery cell takes 20-30 minutes to charge from 10% SOC to 80% SOC, it has an equivalent fast-charging performance of 2.2C-4C within that SOC range.

[0208] Test Method: At 25℃, the battery was treated as follows: 1) Rest for 30 min; 2) Discharge to 2.5V using 0.33Cn DC; 3) Pause; 4) Rest for 120 min; 5) Charge to 10%CnAh using 0.33Cn constant current; 6) Charge to 5%CnAh using 6.45Cn constant current; 7) Charge to 5%CnAh using 5.33Cn constant current; 8) Charge to 5%CnAh using 4.5Cn constant current; 9) Charge to 5%CnAh using 3.98Cn constant current; 10) Charge to 5%CnAh using 3.55Cn constant current; 11) Charge to 5%CnAh using 3.25Cn constant current; 12) Charge to 5%CnAh using 3.02Cn constant current; 13) Charge to 5%CnAh using 2.83Cn constant current. 14) Charge to 5% CnAh using a constant current of 2.66Cn; 15) Charge to 5% CnAh using a constant current of 2.49Cn; 16) Charge to 5% CnAh using a constant current of 2.33Cn; 17) Charge to 5% CnAh using a constant current of 2.14Cn; 18) Charge to 5% CnAh using a constant current of 1.94Cn; 19) Charge to 5% CnAh using a constant current of 1.71Cn; 20) Charge to 3.65V using a constant current of 0.33Cn, then charge to 0.05C using a constant voltage; 21) Let stand for 120 min; 22) Repeat steps 2)-21) 50 times; 23) Let stand for 120 min; 24) Charge to 3.65V using a constant current of 0.33Cn, then charge to 0.05C using a constant voltage. After the test, disassemble the battery cells and observe the lithium plating. Specifically, for the negative electrode sheet, lithium deposition can be avoided if at least one of the following conditions is met: ① The maximum area of ​​a single lithium deposition region is no greater than 5mm × 5mm; ② The number of lithium deposition regions is no more than 5 per negative electrode sheet; ③ The total lithium deposition area is no greater than 100mm². 2 / Battery.

[0209] 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 of the battery cell.

[0210] When the Dv50 of the first negative electrode active material and the second negative electrode active material are 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.

[0211] In some embodiments, the negative electrode active material layer comprises a negative electrode active material, which includes a silicon-containing material, wherein the mass fraction of silicon in the silicon-containing material is 0.1%-7%. This can improve the mass energy density of the battery cell.

[0212] 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, leading to SEI breakdown and recombination, consumption of electrolyte and active lithium ions, and ultimately, 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 mitigating the volume expansion and contraction of the silicon-containing material during charge and discharge processes.

[0213] 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%.

[0214] As an example, silicon-containing materials can be silicon-carbon materials.

[0215] 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.

[0216] 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.

[0217] 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.).

[0218] 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.

[0219] 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).

[0220] 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.

[0221] 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)).

[0222] [Isolation membrane]

[0223] 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.

[0224] 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.

[0225] In some embodiments, referring to FIG1, the housing includes two first shell walls 101 disposed opposite to each other, and a surrounding wall connecting the two first shell walls 101. The surrounding wall includes two second shell walls 102 disposed opposite to each other along the length direction of the first shell walls 101, and two third shell walls 103 disposed opposite to each other along the width direction of the first shell walls 101. The distance between the two first shell walls 101 is D, which is the thickness of the battery cell, and D is less than or equal to 30 mm. This facilitates rapid heat dissipation of the battery cell.

[0226] 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 is the surface with the largest 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 is beneficial for achieving good heat dissipation during fast charging and improving the fast charging performance of the battery cell.

[0227] In some embodiments, D is 10mm-25mm. As a result, the battery cell has high mechanical strength and excellent heat dissipation capability.

[0228] As an example, D can be 5mm, 10mm, 15mm, 20mm, 25mm or 30mm.

[0229] 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.

[0230] 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.

[0231] As an example, the thickness of the first shell wall 101 and the third shell wall 103 can be the same.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] 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 .

[0244] 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.

[0245] 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.

[0246] 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.

[0247] In some embodiments, referring to Figures 2-4, the positive electrode sheet 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 includes a positive electrode body portion 11 and at least one positive electrode tab portion 12, and the positive electrode body portion 11 is connected to the positive electrode tab portion 12. The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one side of the negative current collector. The negative current collector includes a negative electrode body portion 21 and at least one negative electrode tab portion 22, and the negative electrode body portion 21 is connected to the negative electrode tab portion 22. Electrode terminals are provided on the second shell wall 102. The positive electrode tab portion 12 and the negative electrode tab portion 22 are electrically connected to the electrode terminals on the two second shell walls 102, respectively. A closing structure 106 is provided between the second shell wall 102 electrically connected to the positive electrode tab portion 12 and the positive electrode body portion 11. The closing structure 106 is configured to close the plurality of positive electrode tab portions 12. This facilitates the fixing of the positive electrode tab and the welding between the positive electrode plate and the electrode post 105.

[0248] By extending the positive electrode tab 12 and negative electrode tab 22 of the battery cell from the two second shell walls 102 of the housing respectively (i.e., opposite-side tabs), it is possible to arrange the battery cells more efficiently in a limited space. This also facilitates the formation of efficient series and parallel connections between multiple battery cells within the battery pack, while reducing the space occupied by connectors between battery cells and increasing the volumetric energy density of the battery pack. To further improve the volumetric energy density, a lamination process can be used to form the electrode 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 positive and negative electrode tabs need to be collected separately and then electrically connected to their corresponding electrode terminals.

[0249] Typically, referring to Figure 4, the positive current collector uses aluminum foil, and the negative current collector uses copper foil. Because copper foil is relatively soft and prone to breakage, the negative electrode tab needs to be welded to the corresponding post on the second shell wall before being installed in 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 12 can be fixed using the collapsible structure 106. This reduces the risk of reverse insertion and facilitates welding of the positive electrode tab to the post base.

[0250] 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.

[0251] In some embodiments, along the width direction of the positive electrode body portion 11, the total width of the positive electrode tab portion 12 accounts for 30%-100% of the total width of the positive electrode body portion 11; and / or, along the width direction of the negative electrode body portion 21, the total width of the negative electrode tab portion 22 accounts for 30%-100% of the total width of the negative electrode body portion 21. This effectively improves the current-carrying capacity of the tab.

[0252] 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 battery heat dissipation efficiency. At this point, the lower boiling point of the first solvent significantly reduces its adverse effects on battery performance, allowing it to fully leverage its advantages in improving electrolyte conductivity and enhancing the fast-charging capability of the battery cell.

[0253] It should be noted that, for battery cells that meet the aforementioned L / H ratio, when the electrode assembly is fabricated using a stacking process, the electrode assembly may include a multi-layered, continuously arranged positive electrode / separator / negative electrode / separator structure. 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 width of the tab to the width of the body in any positive electrode sheet. 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 width of the tab to the width of the body in any negative electrode sheet. When the electrode assembly is prepared using 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 tabs. 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.

[0254] In some embodiments, the size of the positive electrode tab 12 is 50%-80% of the size of the positive electrode body 11 along the width direction of the positive electrode body. Therefore, the positive electrode tab has superior heat dissipation capability.

[0255] In some embodiments, referring to FIG5, the second shell wall 102 connected to the negative electrode tab 22 is provided with an injection hole 107. This facilitates the injection of electrolyte.

[0256] Since a gathering structure 106 for gathering 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 107 is provided on the second shell wall 102 connected to the negative electrode tab 22.

[0257] In some embodiments, referring to Figures 5-7, the injection hole 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.

[0258] Since the electrolyte will corrode the pressure relief part when it is injected into the battery cell through the injection hole 107, the injection hole 107 and the pressure relief part of the housing should be located on different second side walls.

[0259] In some embodiments, pressure relief portions 104 may be provided on both second shell walls 102. The ratio between the area of ​​the pressure relief portion and the area of ​​the second shell wall can be referred to the foregoing.

[0260] In some embodiments, referring to FIG7, 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.

[0261] 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.

[0262] In some embodiments, referring to Figures 5 and 6, 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.

[0263] Using bipolar terminals for electrical connection can disperse current, reduce local overheating, and improve the battery's fast charging performance.

[0264] 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.

[0265] As an example, the diameter of the pole can be 3mm, 4mm, 5mm, 6mm, 7mm or 8mm.

[0266] 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.

[0267] In some embodiments, referring to FIG8, 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.

[0268] In some embodiments, referring to FIG9, 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.

[0269] When the electrical connection between the terminal post and the tab is achieved through the adapter piece 108, the shape and size of the adapter piece 108 can be adjusted as needed to adapt to different distances and positions. Moreover, the welding process of the adapter piece 108 has fewer defects, which can help to distribute the current more evenly, reduce local overheating and potential difference, and improve the battery's service life.

[0270] In some embodiments, referring to FIG10, the terminal post 105 is directly electrically connected to the tab. This helps to reduce the structural complexity inside the battery cell, reduce the size of the battery cell, and increase the energy density.

[0271] 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.

[0272] In some embodiments, the aforementioned battery cells can also be directly assembled into a battery pack, eliminating the need for a battery module structure and improving the energy density of the battery. The battery pack may contain one or more battery cells, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0273] 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.

[0274] 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.

[0275] 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.

[0276] As the electrical device, a single battery cell or a battery pack can be selected according to its usage requirements.

[0277] Figure 11 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.

[0278] 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.

[0279] Example 1

[0280] 1) Preparation of positive electrode sheet

[0281] 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 a cross-section along the thickness direction of the positive active material layer, the positive 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.

[0282] 2) Preparation of negative electrode sheet

[0283] 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.

[0284] 3) Separating membrane

[0285] The separator is a porous polypropylene (PP) membrane.

[0286] 4) Preparation of electrolyte

[0287] The composition of the electrolyte is shown in Tables 1, 2 and 3. Except for the first lithium salt additive in Example 9, which is lithium difluorooxalate borate (LIDFOB), the first lithium salt additive in the other examples is lithium difluorophosphate.

[0288] 5) Battery manufacturing

[0289] A lithium-ion battery includes a casing, electrode components, and an electrolyte. The electrode components and electrolyte are disposed within the casing. The electrode components include a positive electrode, a negative electrode, and a separator, with the separator disposed between the positive and negative electrode. The thickness D of a single battery cell is 16 mm.

[0290] For the differences between the other embodiments and comparative examples and Embodiment 1, please refer to Tables 1, 2 and 3.

[0291] Table 1

[0292] In the examples and comparative examples recorded in Table 1: the organic solvents and their mass ratios in the electrolyte were all DMC / EMC / EC = 30 / 35 / 35; the lithium electrolyte salt was lithium hexafluorophosphate with a mass content of 12.5%; and the coating weight of the single-layer positive electrode active material layer was 0.283 g / 1540.25 mm. 2 The compaction density of the positive electrode active material layer is 2.45 g / cm³. 3 The coating weight of a single-layer negative electrode active material layer is 0.127g / 1540.25mm. 2 The compaction density of the negative electrode active material layer is 1.45 g / cm³. 3 .

[0293] The power density and volumetric energy density of the battery cells in the examples and comparative examples in Table 1 were tested, and the test results are shown in Table 1-1. The test methods are as follows:

[0294] Volumetric energy density: At 25℃, the battery cell is discharged at a constant current of 0.33C to 2.5V; after resting for 5 minutes, it is charged at a constant current of 0.33C to the upper limit cutoff voltage of 3.65V, then charged at a constant voltage to a current of 0.05C, rested for 5 minutes, and discharged at a constant current of 0.33C to the cutoff voltage of 2.5V. The discharge capacity C0 and discharge energy E0 are recorded at this point. Volumetric energy density = discharge energy E0 / battery cell volume L.

[0295] Power density: At 25℃, the battery cell is charged at a constant current of 0.33C to the cutoff voltage of 3.65V, then charged at a constant voltage to a current of 0.05C, and left to stand for 10 minutes; it is then discharged at a constant current of 0.33C0 to adjust the SOC of the battery cell to 50%, and the voltage U1 is recorded at this time. Then, it is discharged with a pulse of 3C0 for 30s, and the voltage after discharge is recorded as U2. The corresponding DC resistance R = (U1-U2) / 3C0, the power W = 2.5*(U1-2.5) / R, and the power density P = W / E0.

[0296] Table 1-1

[0297] Table 2

[0298] In the embodiments described in Table 2: the length L of each battery cell is 510 mm, the width H of each battery cell is 120 mm, the electrolyte lithium salt is lithium hexafluorophosphate with a mass content of 12.5%, the mass fraction of the first lithium salt additive is 0.22% based on the total mass of the electrolyte, and the coating weight of the single-layer positive electrode active material layer is 0.283 g / 1540.25 mm. 2 The compaction density of the positive electrode active material layer is 2.45 g / cm³. 3 The coating weight of a single-layer negative electrode active material layer is 0.127g / 1540.25mm. 2 The compaction density of the negative electrode active material layer is 1.45 g / cm³. 3 .

[0299] The power density and volumetric energy density of the battery cells in the embodiments in Table 2 were tested, and the test results are shown in Table 2-1.

[0300] Table 2-1

[0301] Table 3

[0302] In the embodiments described in Table 3: the length L of each battery cell is 510 mm, the width H of each battery cell is 120 mm, the organic solvent in the electrolyte and the mass ratio are DMC / EMC / EC = 30 / 35 / 35, the electrolyte lithium salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide in the electrolyte is 2:1, the concentration of electrolyte lithium salt in the electrolyte is 1 mol / L, and the mass fraction of the first lithium salt additive is 0.22% based on the total mass of the electrolyte.

[0303] The rate performance and volumetric energy density of the battery cells in the examples in Table 3 were tested, and the test results are shown in Table 3-1.

[0304] 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 0V, and read the capacity C4 at this point. 11) Let stand for 5 minutes; 12) Charge with 2C0 at a constant current until the negative electrode potential is 0V, and read the capacity C5 at this time, which corresponds to C5 / C0SOC; 13) Let stand for 5 minutes; 14) Charge with 1C0 at a constant current until the negative electrode potential is 0V, and read the capacity C6 at this time, which corresponds to C6 / C0SOC; 15) Let stand for 5 minutes; 16) Charge with 0.8C0 at a constant current until the negative electrode potential is 0V, and read the capacity C7 at this time, which corresponds to C7 / C0SOC; 17) Let stand for 5 minutes; 18) Charge with 0.5C0 at a constant current until the negative electrode potential is 0V, and read the capacity C8 at this time, which corresponds to C8 / C0SOC; 19) Let stand for 5 minutes; 20) Charge with 0.33C0 at a constant current until the negative electrode potential is 0V, and read the capacity C9 (i.e., C0), which corresponds to 100%SOC. The required charging time is obtained by summing the total charging time from 10% SOC to 80% SOC.

[0305] Table 3-1

[0306] 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, a length of the battery cell is L, and a width of the battery cell is H, the value of L is 4 to 10 times the value of H; the battery cell comprises an electrolyte, the electrolyte comprises an organic solvent and 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 a mass fraction of the first lithium salt additive is 0.01%-0.5% based on a total mass of the electrolyte.

2. The battery cell of claim 1, wherein, The value of L is 4 to 7 times the value of H.

3. The battery cell of claim 1 or 2, wherein, L is 400mm-1000mm, and / or, H is 80mm-160mm.

4. The battery cell of any one of claims 1-3, wherein, The first lithium salt additive comprises at least one of lithium difluorophosphate, lithium difluoro oxalate phosphate, lithium difluoro oxalate borate, and lithium tetrafluoroborate.

5. The battery cell of any one of claims 1-4, wherein, The mass fraction of the first lithium salt additive in the electrolyte is 0.05%-0.5%, and optionally 0.1%-0.3%.

6. The battery cell of any one of claims 1-5, wherein, The conductivity of the electrolyte is 10ms / cm-20ms / cm.

7. The battery cell of any one of claims 1-6, wherein, The organic solvent comprises a first solvent, the first solvent comprises at least one of dimethyl carbonate and linear carboxylic acid ester, wherein a structural formula of the linear carboxylic acid ester satisfies R1-COO-R2, R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl.

8. The battery cell of claim 7, wherein, The linear carboxylic acid ester comprises at least one of ethyl formate, isopropyl formate, ethyl acetate, methyl acetate, propyl acetate, and methyl propionate.

9. The battery cell of claim 7 or 8, wherein, A mass fraction of the linear carboxylic acid ester is 32%-68% based on a total mass of the electrolyte.

10. The battery cell of any one of claims 7-9, wherein, A mass fraction of the first solvent is greater than or equal to 4% based on a total mass of the electrolyte, and optionally, a mass fraction of the first solvent is 16%-80% based on a total mass of the electrolyte.

11. The battery cell of any one of claims 1-10, 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, and butylene carbonate.

12. The battery cell of claim 11, wherein, The second solvent comprises diethyl carbonate, and a content of the diethyl carbonate is not less than 12% based on a total mass of the electrolyte.

13. The battery cell of any one of claims 1-12, wherein, The electrolyte further comprises a non-lithium salt additive, the non-lithium salt additive comprises at least one of vinylene carbonate, fluoro-vinylene carbonate, and vinyl ethylene carbonate.

14. The battery cell of claim 13, wherein, A mass fraction of the vinylene carbonate is 0.5%-2.5% based on a total mass of the electrolyte, and / or, a mass fraction of the fluoro-vinylene carbonate is 0.05%-2% based on a total mass of the electrolyte.

15. The battery cell of any one of claims 1-14, 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.

16. The battery cell of any one of claims 1-15, wherein, The electrolyte further comprises an electrolyte lithium salt, the electrolyte lithium salt comprises at least one of lithium hexafluorophosphate and lithium bis-fluorosulfonyl imide, and a mass fraction of the electrolyte lithium salt is greater than or equal to 13% based on a total mass of the electrolyte.

17. The battery cell of claim 16, wherein, The electrolyte lithium salt includes lithium hexafluorophosphate and lithium bisfluorosulfonimide, and the mass ratio of the lithium hexafluorophosphate to the lithium bisfluorosulfonimide in the electrolyte is (1.2-2):

1.

18. The battery cell of any one of claims 1-17, wherein, Further comprising a positive electrode tab including a positive electrode current collector and a positive electrode active material layer at least on one side of the positive electrode current collector, the positive electrode active material layer having a compacted density of 2.2 g / cm 3 -2.6 g / cm 3 .

19. The battery cell of claim 18, wherein, The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure or a modified material thereof.

20. The battery cell of claim 19, wherein, The lithium-containing phosphate with an olivine structure or the modified material thereof includes: a core including a lithium-containing phosphate with an olivine structure, and a coating layer covering the surface of the lithium-containing phosphate with an olivine structure, and the coating layer contains one or more elements selected from C, Fe, Ti, Zr, Hf, Ge, and Sn.

21. The battery cell of claim 20, wherein, The lithium-containing phosphate of olivine structure comprises a compound of general formula Li x A y Me a M b P 1-c X c Y z wherein 0.5≤x≤1.3, 0≤y≤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; M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X comprises one or more of S, Si, Cl, B, C, N; Y comprises one or more of O, F.

22. The battery cell of claim 20, wherein, The coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15-0.

32.

23. The battery cell of any one of claims 19-21, wherein, In a cross section of the positive electrode active material layer along the thickness direction, the positive electrode active material includes a lithium-containing phosphate with an olivine structure with a longest diameter of 1-3 μm, and a lithium-containing phosphate with an olivine structure with a shortest diameter of 0.1-0.3 μm.

24. The battery cell of any one of claims 19-23, 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 1-5 μm. The Dv10 particle size of the positive electrode active material is 0.4-0.7 μm. The positive electrode active material is a primary particle or a quasi-single crystal particle.

25. The battery cell of any one of claims 18-24, wherein, The positive electrode active material layer further includes a lithium-rich material, and the lithium-rich material includes one or more of lithium iron oxide, 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 metamanganate, lithium tartrate, and trilithium citrate.

26. The battery cell of any one of claims 1-25, wherein, Further comprising a negative electrode sheet including 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 compacted density of 1.2 g / cm 3 -1.5 cm 3 .

27. The battery cell of claim 26, wherein, The coating weight of the single layer of the negative electrode active material layer is greater than or equal to 0.1 g / 1540.25 mm 2 .

28. The battery cell of claim 27, wherein, The coating weight of the single layer of the negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2 .

29. The battery cell of claim 27, 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 .

30. The battery cell of claim 29, wherein, The time for charging the battery cell from 10% SOC to 80% SOC is 7-15 min.

31. The battery cell of claim 27, 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 .

32. The battery cell of claim 31, wherein, The time for charging the battery cell from 10% SOC to 80% SOC is 20-30 min.

33. The battery cell of any one of claims 26-32, wherein, The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer arranged in a stacked manner, the first negative electrode active material layer is located on 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 9.2-18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2-15.5 μm.

34. The battery cell of any one of claims 26-33, wherein, The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a silicon-containing material, and the mass fraction of silicon in the silicon-containing material is 0.1%-7%.

35. The battery cell of claim 34, wherein, The mass fraction of silicon in the silicon-containing material is 1%-5%.

36. The battery cell of any one of claims 1-35, wherein, Further including a shell, the shell includes two first shell walls arranged oppositely, and a surrounding wall connecting the two first shell walls, the surrounding wall includes 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, wherein the distance between the two first shell walls is D, and D is less than or equal to 30 mm.

37. The battery cell of claim 36, wherein, D is 10-25 mm.

38. The battery cell of claim 36 or 37, wherein, The thickness of the first shell wall and the third shell wall is independently less than or equal to 0.5 mm.

39. The battery cell of claim 38, wherein, The first shell wall and the third shell wall comprise at least one of an aluminum shell and a steel shell.

40. The battery cell of claim 39, 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.

41. The battery cell of claim 39, 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.

42. The battery cell of claim 41, 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.

43. The battery cell of any one of claims 36-42, wherein, A side supporting plate is arranged between the electrode assembly and the first shell wall.

44. The battery cell of any one of claims 36-43, 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.

45. The battery cell of claim 44, wherein, The capacity of the battery cell is Q, the area of the orthographic projection of the pressure relief portion on the second shell wall 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 .

46. The battery cell of any one of claims 36-45, wherein, The positive electrode tab comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, and the positive electrode current collector comprises a positive electrode main body and at least one positive electrode tab, and the positive electrode main body is connected with the positive electrode tab. The second shell wall is provided with an electrode terminal, and the positive electrode tab and the negative electrode tab are respectively electrically connected with the electrode terminals on the two second shell walls, wherein the second shell wall electrically connected with the positive electrode tab is provided with a folding structure between the positive electrode main body and the second shell wall, and the folding structure is configured to fold the plurality of positive electrode tabs.

47. The battery cell of claim 46, wherein, Along the length direction of the first shell wall, a chamfer is arranged at the edge of the positive electrode tab.

48. The battery cell of claim 46 or 47, wherein, Along the width direction of the positive electrode main body, the total width of the positive electrode tab is 30%-100% of the total width of the positive electrode main body; and / or, along the width direction of the negative electrode main body, the total width of the negative electrode tab is 30%-100% of the total width of the negative electrode main body.

49. The battery cell of claim 48, wherein, Along the width direction of the positive electrode main body, the size of the positive electrode tab is 50%-80% of the size of the positive electrode main body.

50. The battery cell of any one of claims 46-49, wherein, The second shell wall connected with the negative electrode tab is provided with a liquid injection hole.

51. The battery cell of claim 50, wherein, The liquid injection hole and the pressure relief portion of the shell are located on different second shell walls, and the pressure relief portion is configured to be able to release the pressure inside the shell.

52. The battery cell of any one of claims 46-51, wherein, The electrode terminal is provided with at least one mounting hole, and the pole is arranged in the mounting hole and riveted with the tab.

53. The battery cell of any one of claims 46-51, wherein, The electrode terminal is provided with at least two mounting holes, and each pole is arranged in the mounting hole and riveted with the tab.

54. The battery cell of claim 52 or 53, wherein, The diameter of the pole is 3mm-8mm.

55. The battery cell of any one of claims 52-54, wherein, The poles riveted with the positive electrode tabs and the poles riveted with the negative electrode tabs are arranged in a staggered manner along the length direction of the first shell wall, and optionally, the poles riveted with the positive electrode tabs and the poles riveted with the negative electrode tabs are arranged in a diagonal manner along the length direction of the first shell wall.

56. The battery cell of any one of claims 52-55, wherein, The pole and the tab are electrically connected through an adapter plate.

57. The battery cell of any one of claims 52-56, wherein, The pole and the tab are directly electrically connected.

58. A battery device, wherein, The battery device includes at least one of a battery module, a battery pack, an energy storage device.

59. An electrical device, comprising: The battery device includes at least one of a battery module, a battery pack, an energy storage device.

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