Battery cell, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device, the battery monomer comprises a positive pole piece, an isolating membrane, a negative pole piece and an electrolyte, the positive pole piece and the negative pole piece are laminated, and the isolating membrane is arranged between the positive pole piece and the negative pole piece; the positive pole piece comprises a positive pole main body part and a positive pole lug part, and the ratio of the long side size to the short side size of the positive pole main body part is (3-8): 1; the negative pole piece comprises a negative pole main body part and a negative pole lug part, the long side of the negative pole main body part exceeds the edge of the long side of the positive pole main body part by 2mm-9mm, and the long side of the isolating membrane exceeds the edge of the long side of the negative pole main body part by 2mm-10mm; the electrolyte comprises a solvent, and the solvent comprises one or more of dimethyl carbonate and linear carboxylic ester with a structure as shown in a formula (1); in the formula (1), R1 and R2 respectively and independently comprise C1-C5 alkyl or halogenated alkyl. The battery monomer has relatively high energy density, relatively good cycle performance and relatively low self-discharge.

Description

[0001] This application is a divisional application of the invention patent application filed on June 20, 2025, with application number 202510831242.3 and invention title "Battery cell, battery device and power consumption device". Technical Field

[0002] This application relates to the field of battery technology, and in particular to a battery cell, a battery device, and an electrical device. Background Technology

[0003] In recent years, as the application scope of secondary batteries has become increasingly wide, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles and electric vehicles.

[0004] With the significant advancements in rechargeable batteries, higher performance requirements have been placed on them. Developing a battery with high energy density, good cycle performance, and low self-discharge is a key focus for those skilled in the art. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery device and an electrical device, wherein the battery cell has a high energy density, good cycle performance and low self-discharge.

[0006] To achieve the above objectives, a first aspect of this application provides a battery cell, including a positive electrode, a separator, a negative electrode, and an electrolyte, wherein the positive electrode and the negative electrode are stacked, and the separator is disposed between the positive electrode and the negative electrode.

[0007] The positive electrode plate includes a positive electrode body and a positive electrode tab connected to the positive electrode body, wherein the ratio of the long side dimension to the short side dimension of the positive electrode body is (3~8):1;

[0008] The negative electrode plate includes a negative electrode body and a negative electrode tab connected to the negative electrode body. The long side of the negative electrode body extends 2mm to 9mm beyond the long side edge of the positive electrode body, and the long side of the separator extends 2mm to 10mm beyond the long side edge of the negative electrode body.

[0009] The electrolyte includes a first solvent, which includes one or more of dimethyl carbonate and linear carboxylic acid esters having the structure shown in formula (1);

[0010] R1-(C=O)-O-R2 equation (1);

[0011] R1 and R2 each independently include C1 to C5 alkyl or haloalkyl groups.

[0012] By controlling the ratio of the long side dimension to the short side dimension of the positive electrode body to be (3~8):1, when a stacked battery is formed using a positive electrode with a large aspect ratio, the battery space occupied by the tabs can be reduced, which is beneficial to improving the energy density of the battery cell. By using one or more of dimethyl carbonate and linear carboxylic acid esters with the structure shown in formula (1) as solvents in the electrolyte, the solvent has a low viscosity and is beneficial to improving the conductivity of the electrolyte, which can improve the problem of insufficient electrolyte wetting in stacked batteries with large aspect ratios, thereby enabling the battery cell to achieve good cycle performance. By adopting a specific overhang setting in the negative electrode and the separator, the long side of the negative electrode body extends 2mm~9mm beyond the long side edge of the positive electrode body, and the long side of the separator extends 2mm~10mm beyond the long side edge of the negative electrode body; this can effectively reduce the battery self-discharge caused by misalignment of the positive and negative electrode plates due to gas generation by low viscosity solvent, thereby enabling the battery cell to achieve low self-discharge. This application achieves a battery cell with not only high energy density, but also good cycle performance and low self-discharge through the synergistic combination of the above factors, by setting the aspect ratio of the electrode, the electrolyte solvent, and the overhang of the negative electrode and the separator.

[0013] In any embodiment, the ratio of the long side dimension to the short side dimension of the positive electrode body is (4~6):1. This is beneficial for the battery cell to better balance higher energy density, better cycle performance, and lower self-discharge.

[0014] In any embodiment, the long side of the negative electrode body extends 3mm to 6mm beyond the long side edge of the positive electrode body; the long side of the separator extends 3mm to 7mm beyond the long side edge of the negative electrode body. This allows the battery cell to better balance higher energy density, better cycle performance, and lower self-discharge.

[0015] In any embodiment, the linear carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate. This helps to improve the problem of insufficient electrolyte wetting in stacked cells with large electrode aspect ratios, thereby enabling battery cells to achieve both high energy density and good cycle performance.

[0016] In any embodiment, the mass fraction of the first solvent is 10% to 60% based on the mass of the electrolyte. This is beneficial for the electrolyte to have suitable viscosity and high conductivity, which helps to improve the problem of insufficient electrolyte wetting in stacked batteries with large electrode aspect ratios, and allows the battery cells to better balance cycle performance.

[0017] In any embodiment, the mass fraction of the first solvent is 15% to 35% based on the mass of the electrolyte. This allows the battery cell to better balance higher energy density, better cycle performance, and lower self-discharge.

[0018] In any embodiment, the electrolyte has a conductivity of 9.5 mS / cm to 20 mS / cm at room temperature. This is beneficial for the electrolyte to have a relatively high conductivity. Controlling the conductivity of the electrolyte within this range is beneficial for improving the cycle performance of the battery cells.

[0019] In any embodiment, the electrolyte has a conductivity of 10 mS / cm to 16 mS / cm at room temperature. This is beneficial for further improving the cycle performance of the battery cells.

[0020] In any embodiment, the electrolyte further includes a lithium salt, which includes one or more of lithium hexafluorophosphate and lithium bisfluorosulfonylimide; the total mass fraction of the lithium hexafluorophosphate and / or the lithium bisfluorosulfonylimide is 12% to 18% based on the mass of the electrolyte. This is beneficial for improving the conductivity of the electrolyte and enhancing the cycle performance and kinetic performance of the battery cells.

[0021] In any embodiment, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (1.2~3):1. This is beneficial for improving the conductivity of the electrolyte, alleviating the problem of insufficient electrolyte wetting in stacked batteries with large electrode aspect ratios, and improving the cycle performance and kinetic performance of the battery cells.

[0022] In any embodiment, the electrolyte further includes additives, including one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propanesulfonate lactone. This optimizes the SEI film, allowing the battery cell to better balance cycle performance and kinetic performance.

[0023] In any embodiment, the mass fraction of the additive is less than or equal to 5% based on the mass of the electrolyte. This is more conducive to enabling the battery cell to better balance cycle performance and kinetic performance.

[0024] In any embodiment, the mass fraction of the additive is 0.5% to 3% based on the mass of the electrolyte. This helps to better balance cycle performance and kinetic performance in the battery cell.

[0025] In any embodiment, the positive electrode tab is connected to the short side of the positive electrode body, and the negative electrode tab is connected to the short side of the negative electrode body. This is beneficial for improving the energy density of the battery cell.

[0026] In any embodiment, the battery cell further includes a pouch casing, within which the positive electrode, separator, negative electrode, and electrolyte are disposed. The thickness of the pouch casing is 70 μm to 200 μm. This not only improves the energy density of the battery cell but also gives the casing greater strength, mitigating the problem of the pouch casing expanding due to gas generation by the low-viscosity solvent during cycling.

[0027] In any embodiment, the negative electrode body includes a negative electrode current collector and a negative electrode film layer. The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer disposed on the negative electrode current collector, with the first negative electrode film layer located between the negative electrode current collector and the second negative electrode film layer. Both the first and second negative electrode film layers include graphite. The average longest diameter of the graphite in the first negative electrode film layer is 7μm~18μm, and the average longest diameter of the graphite in the second negative electrode film layer is 6μm~10μm. Furthermore, the average longest diameter of the graphite in the first negative electrode film layer is greater than the average longest diameter of the graphite in the second negative electrode film layer. This allows the battery cell to better balance fast charging performance and energy density.

[0028] In any embodiment, the graphite in the first negative electrode film layer and the second negative electrode film layer independently comprises a graphite particle body and an amorphous carbon coating layer disposed on the surface of the graphite particle body, wherein the thickness of the amorphous carbon coating layer is 100nm~500nm. This is beneficial for further improving the conductivity of the graphite particles and further enhancing the kinetic performance of the battery.

[0029] In any embodiment, the graphitization degree of the graphite in the first negative electrode film layer and the second negative electrode film layer is independently 90%~94%. This is more conducive to improving the specific capacity of the negative electrode and the energy density of the battery.

[0030] In any embodiment, the single-sided coating surface density of the negative electrode film is 0.13 g / 1540.25 mm. 2 ~0.22g / 1540.25mm 2 This allows battery cells to better balance fast charging performance and energy density.

[0031] In any embodiment, the compaction density of the negative electrode sheet is 1.3 g / cc to 1.52 g / cc. This helps the battery cell to better balance fast charging performance and energy density.

[0032] In any embodiment, the positive electrode body includes a positive electrode current collector and a positive electrode film layer. The positive electrode film layer is disposed on the positive electrode current collector, and the positive electrode film layer includes a lithium-containing transition metal phosphate. The lithium-containing transition metal phosphate includes one or more of the following elements by mass: aluminum (200ppm-2500ppm), vanadium (300ppm-2000ppm), and titanium (1500ppm-3500ppm). This is beneficial for improving the fast-charging performance, cycle performance, and / or energy density of the battery cell.

[0033] In any embodiment, the positive electrode body further includes a base coating layer disposed between the positive electrode current collector and the positive electrode film layer. The base coating layer includes a conductive agent and has a thickness of 0.5 μm to 3 μm. This helps to reduce the internal resistance of the battery and improve its dynamic performance.

[0034] In any embodiment, the single-sided coating areal density of the positive electrode film is 0.33 g / 1540.25 mm. 2 ~0.45g / 1540.25mm 2 This allows battery cells to better balance fast charging performance and energy density.

[0035] In any embodiment, the compaction density of the positive electrode sheet is 2.3 g / cc to 2.65 g / cc. This helps the battery cell to better balance fast charging performance and energy density.

[0036] A second aspect of this application also provides a battery device, including the battery cell of the first aspect of this application.

[0037] A third aspect of this application also provides an electrical device, including one or more of the battery cell of the first aspect of this application and the battery device of the second aspect of this application.

[0038] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0039] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0040] Figure 1 This is a top view schematic diagram of the stacked positive electrode, separator and negative electrode in a battery cell according to an embodiment of this application;

[0041] Figure 2 This is a schematic diagram of the structure of the positive electrode sheet in a battery cell according to an embodiment of this application;

[0042] Figure 3 This is a schematic diagram of the structure of the negative electrode sheet in a battery cell according to an embodiment of this application.

[0043] Figure 4 This is a schematic diagram of a battery device according to an embodiment of this application, used as a power source for an electrical device.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1. Positive electrode plate; 2. Separator membrane; 3. Negative electrode plate; 11. Positive electrode body; 12. Positive electrode tab; 31. Negative electrode body; 32. Negative electrode tab; 6. Electrical device. Detailed Implementation

[0046] Hereinafter, embodiments of the battery cell, battery device, and power-consuming device of this application are described in detail with appropriate reference to the accompanying drawings. However, some unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy 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.

[0047] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be independently included or excluded, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 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 also 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 "a~b" 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" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0048] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0050] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0051] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] In this application, open-ended technical features or solutions described using terms such as "containing," "including," or "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3" and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0053] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0054] Currently, due to the significant advancements in rechargeable batteries, higher performance requirements have been placed on them. Developing a battery with high energy density that also exhibits good cycle performance and low self-discharge is one of the key areas of focus for those skilled in the art.

[0055] Based on this, please refer to Figure 1 , Figure 2 and Figure 3 The first aspect of this application provides a battery cell, which is a stacked battery cell. The battery cell includes a positive electrode 1, a separator 2, a negative electrode 3, and an electrolyte. The positive electrode 1 and the negative electrode 3 are stacked, and the separator 2 is disposed between the positive electrode 1 and the negative electrode 3.

[0056] The positive electrode 1 includes a positive electrode body 11 and a positive electrode tab 12 connected to the positive electrode body 11. The long side dimension of the positive electrode body 11 is (e.g., Figure 2 (as shown in d1) and the short side dimension (as shown in d1) Figure 2 The ratio of the two electrodes (as shown in d2) is (3~8):1; the negative electrode plate 3 includes a negative electrode body portion 31 and a negative electrode tab portion 32 connected to the negative electrode body portion 31. The long side of the negative electrode body portion 31 extends beyond the long side edge of the positive electrode body portion 11 (i.e., overhang, as shown in d2). Figure 1 The length of the separator 2 (as shown in L1) is 2mm to 9mm, and the long side of the separator 2 extends beyond the edge of the long side of the negative electrode body 31 (i.e., overhang). Figure 1 The diameter of the electrolyte (as shown in L2) is 2 mm to 10 mm; the electrolyte includes a first solvent, which includes one or more of dimethyl carbonate and linear carboxylic acid esters having the structure shown in formula (1);

[0057] R1-(C=O)-O-R2 equation (1);

[0058] In formula (1), R1 and R2 each independently include C1 to C5 alkyl or haloalkyl groups.

[0059] In this application, the positive electrode body portion 11 is the main body portion of the positive electrode sheet 1, and this area is mainly used to set the positive electrode film layer, and an insulating coating can be set at its edge; the positive electrode tab portion 12 refers to the conductive area extending from the positive electrode body portion 11 for connecting to an external circuit, and an insulating coating can be set at the root of the positive electrode tab portion 12; the long side of the positive electrode body portion 11 refers to the side with a longer length in the plane where the positive electrode body portion 11 is located, and the short side of the positive electrode body portion 11 refers to the side with a shorter length in the plane where the positive electrode body portion 11 is located; similarly, the negative electrode body portion 31 is the main body portion of the negative electrode sheet 3, and this area is mainly used to set the negative electrode film layer; the negative electrode tab portion 32 refers to the conductive area extending from the negative electrode body portion 31 for connecting to an external circuit; the long side of the negative electrode body portion 31 refers to the side with a longer length in the plane where the negative electrode body portion 31 is located, and the short side of the negative electrode body portion 31 refers to the side with a shorter length in the plane where the negative electrode body portion 31 is located. The long and short side dimensions of the positive electrode main body 11 and the negative electrode main body 31 can be directly measured after disassembling the stacked battery.

[0060] The distance by which the long side of the negative electrode main body 31 extends beyond the edge of the long side of the positive electrode main body 11, the distance by which the long side of the separator 2 extends beyond the edge of the long side of the negative electrode main body 31, the dimensions of the long and short sides of the positive electrode main body 11, and the dimensions of the long and short sides of the negative electrode main body 31 can all be tested using conventional methods in the art.

[0061] As an example, the stacked battery can be disassembled, and multiple (e.g., 10) test points can be selected at intervals along both sides of the long side of the positive electrode main body 11. The distance at each test point from the long side of the negative electrode main body 31 to the edge of the long side of the positive electrode main body 11 can be measured, and then the average value can be calculated. This average value can be considered as the distance from the long side of the negative electrode main body 31 to the edge of the long side of the positive electrode main body 11. Similarly, multiple (e.g., 10) test points can be selected at intervals along both sides of the long side of the negative electrode main body 31, and the distance at each test point from the long side of the separator 2 to the edge of the long side of the negative electrode main body 31 can be measured. Then the average value can be calculated, and this average value can be considered as the distance from the long side of the separator 2 to the edge of the long side of the negative electrode main body 31.

[0062] In this application, the types and contents of organic components in the electrolyte can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography, referring to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography.

[0063] In the embodiments of this application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the concentrations of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis using standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography analysis.

[0064] In the embodiments of this application, after quantitative and qualitative detection of each component in the electrolyte, the solvent composition and mass content of each solvent in the electrolyte can be determined.

[0065] The aforementioned battery cell, by controlling the ratio of the long side dimension to the short side dimension of the positive electrode body 11 of the positive electrode 1 to be (3~8):1, and using this positive electrode 1 with a large aspect ratio to form a stacked battery, can reduce the battery space occupied by the tabs, which is beneficial to improving the energy density of the battery cell. However, when the aspect ratio of the electrode in the stacked battery is large, the penetration path of the electrolyte along the length of the battery is longer, which can easily lead to insufficient electrolyte wetting in some areas of the electrode, affecting the cycle performance of the battery. By using one or more of dimethyl carbonate and linear carboxylic acid esters with the structure shown in formula (1) as the first solvent in the electrolyte, the first solvent has a low viscosity and is beneficial to improving the conductivity of the electrolyte, which can improve the problem of insufficient electrolyte wetting in stacked batteries with large aspect ratios of the electrode, thereby enabling the battery cell to achieve better cycle performance. However, electrolyte solvents containing dimethyl carbonate and / or linear carboxylic acid esters with the structure shown in formula (1) are prone to gas generation during battery cycling, which may lead to misalignment of the positive and negative electrode plates in the stacked battery, causing battery self-discharge. To address this, this application employs a specific overhang arrangement in the negative electrode plate 3 and the separator 2, such that the long side of the negative electrode body 31 extends 2mm to 9mm beyond the long side edge of the positive electrode body 11, and the long side of the separator 2 extends 2mm to 10mm beyond the long side edge of the negative electrode body 31. This effectively reduces battery self-discharge caused by misalignment of the positive and negative electrode plates, thus enabling the battery cell to achieve a lower self-discharge. This application, through the synergistic effect of the electrode aspect ratio, electrolyte solvent, and the overhang arrangement of the negative electrode plate 3 and the separator 2, enables the battery cell to not only have a high energy density but also good cycle performance and low self-discharge.

[0066] It is understandable that the ratio of the long side dimension to the short side dimension of the positive electrode body 11 can be 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, 5:1, 5.2:1, 5.5:1, 5.8:1, 6:1, 6.2:1, 6.5:1, 6.8:1, 7:1, 7.2:1, 7.5:1, 7.8:1, 8:1, and any ratio within the range formed by any two of the above ratios. The length of the long side of the negative electrode main body 31 extending beyond the edge of the long side of the positive electrode main body 11 can be 2mm, 2.2mm, 2.5mm, 2.8mm, 3mm, 3.2mm, 3.5mm, 3.8mm, 4mm, 4.2mm, 4.5mm, 4.8mm, 5mm, 5.2mm, 5.5mm, 5.8mm, 6mm, 6.2mm, 6.5mm, 6.8mm, 7mm, 7.2mm, 7.5mm, 7.8mm, 8mm, 8.2mm, 8.5mm, 8.8mm, 9mm, or any value within the range formed by any two of the above values. The length of the separator 2 extending beyond the edge of the long side of the negative electrode body 31 can be 2mm, 2.2mm, 2.5mm, 2.8mm, 3mm, 3.2mm, 3.5mm, 3.8mm, 4mm, 4.2mm, 4.5mm, 4.8mm, 5mm, 5.2mm, 5.5mm, 5.8mm, 6mm, 6.2mm, 6.5mm, 6.8mm, 7mm, 7.2mm, 7.5mm, 7.8mm, 8mm, 8.2mm, 8.5mm, 8.8mm, 9mm, 9.2mm, 9.5mm, 9.8mm, 10mm, or any value within the range formed by any two of the above values.

[0067] In some embodiments, the ratio of the long side dimension to the short side dimension of the positive electrode body 11 is (4~6):1. Controlling the ratio of the long side dimension to the short side dimension of the positive electrode body 11 within the above range is beneficial for the battery cell to better balance higher energy density, better cycle performance, and lower self-discharge.

[0068] In some embodiments, the long side of the negative electrode main body 31 extends 3mm to 6mm beyond the long side edge of the positive electrode main body 11; the long side of the separator 2 extends 3mm to 7mm beyond the long side edge of the negative electrode main body 31. This overhang design, with the long side of the negative electrode main body 31 relative to the long side of the positive electrode main body 11 and the long side of the separator 2 relative to the long side of the negative electrode main body 31, allows the battery cell to better balance higher energy density, better cycle performance, and lower self-discharge.

[0069] In some embodiments, the linear carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate. These linear carboxylic acid esters have low viscosity, which is beneficial for electrolyte wetting and improves the problem of insufficient electrolyte wetting in stacked batteries with large electrode aspect ratios. This allows the battery cells to achieve both high energy density and good cycle performance.

[0070] In some embodiments, the mass fraction of the first solvent is 10% to 60% based on the mass of the electrolyte. Controlling the mass fraction of the first solvent in the electrolyte within the above range is beneficial for the electrolyte to have suitable viscosity and high conductivity, which helps to improve the problem of insufficient electrolyte wetting in stacked cells with large electrode aspect ratios, and enables the battery cells to better balance cycle performance.

[0071] Understandably, the mass fraction of the first solvent can be, but is not limited to, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, or any value within the range formed by any two of the above values. The electrolyte may include dimethyl carbonate but not linear carboxylic acid esters, may include linear carboxylic acid esters but not dimethyl carbonate, or may include both dimethyl carbonate and linear carboxylic acid esters.

[0072] Furthermore, in some embodiments, the mass fraction of the first solvent is 15% to 35% based on the mass of the electrolyte. Controlling the mass fraction of the first solvent in the electrolyte within the above range is beneficial for enabling the battery cell to better balance higher energy density, better cycle performance, and lower self-discharge.

[0073] In some embodiments, the electrolyte has a conductivity of 9.5 mS / cm to 20 mS / cm at room temperature. Adding dimethyl carbonate and / or linear carboxylic acid esters as solvents to the electrolyte helps to achieve a higher conductivity. Controlling the electrolyte conductivity within the above range is beneficial for improving the cycle performance of the battery cells.

[0074] It is understood that the conductivity of the electrolyte at room temperature can be, but is not limited to, 9.5 mS / cm, 10 mS / cm, 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm, or any value within the range formed by any two of the above values. Room temperature typically refers to 20℃ to 25℃.

[0075] In some specific examples, the electrolyte has a conductivity of 10 mS / cm to 16 mS / cm at room temperature.

[0076] In some embodiments, the electrolyte further includes a lithium salt, including one or more of lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI); the total mass fraction of lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide is 12% to 18% by mass of the electrolyte.

[0077] By combining lithium hexafluorophosphate and lithium difluorosulfonylimide as lithium salts, and controlling the total mass fraction of lithium hexafluorophosphate and / or lithium difluorosulfonylimide within the above-mentioned range, it is beneficial to improve the conductivity of the electrolyte and enhance the cycle performance and kinetic performance of the battery cells.

[0078] Understandably, the total mass fraction of lithium hexafluorophosphate and / or lithium difluorosulfonylimide in the electrolyte can be, but is not limited to, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, and any value within the range formed by any two of the above values.

[0079] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (1.2~3):1. Controlling the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide within this range is beneficial for improving the conductivity of the electrolyte, alleviating the problem of insufficient electrolyte wetting in stacked cells with large electrode aspect ratios, and improving the cycle performance and kinetic performance of the battery cells. Understandably, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide can be, but is not limited to, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, and any ratio within the range formed by any two of the above ratios.

[0080] In some embodiments, the electrolyte further includes additives, including one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesulfonate lactone (PS). Adding these additives to the electrolyte optimizes the SEI (Solid Electrolyte Interface) membrane, which helps the battery cell better balance cycle performance and kinetic performance.

[0081] In some embodiments, the mass fraction of the additive is less than or equal to 5% based on the mass of the electrolyte. Excessive use of the additive will increase the impedance of the battery cell. In the stacked battery with a large aspect ratio of the electrodes in this application, the use of the above-mentioned additive at a mass fraction of less than 5% of the electrolyte is more conducive to enabling the battery cell to better balance cycle performance and kinetic performance.

[0082] Understandably, the mass fraction of the additive in the electrolyte can be, but is not limited to, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, and any value within the range formed by any two of the above values.

[0083] Furthermore, in some specific examples, the mass fraction of the additive is 0.5% to 3% based on the mass of the electrolyte. This helps to better balance cycle performance and kinetic performance in the battery cell.

[0084] In some embodiments, the positive electrode tab 12 is connected to the short side of the positive electrode main body 11, and the negative electrode tab 32 is connected to the short side of the negative electrode main body 31. Thus, placing the positive electrode tab 12 on one side of the short side of the positive electrode main body 11 and the negative electrode tab 32 on one side of the short side of the negative electrode main body 31 is more beneficial for improving the energy density of the battery cell compared to a design where the tabs are placed on the long side.

[0085] In some embodiments, the battery cell further includes a pouch casing, with the positive electrode 1, separator 2, negative electrode 3, and electrolyte disposed within the pouch casing. The thickness of the pouch casing is 70 μm to 200 μm. That is, the battery cell of this application can be a pouch battery cell. Controlling the thickness of the pouch casing within the above range is beneficial for improving the energy density of the battery cell and also enables the casing to have greater strength, mitigating the problem of the pouch casing expanding due to gas generation during cycling by low-viscosity solvents.

[0086] Understandably, the thickness of the soft-pack shell can be, but is not limited to, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, and any value within the range formed by any two of the above values.

[0087] In some specific examples, the material of the soft-pack shell can be plastic. Further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0088] In some embodiments, the negative electrode body 31 includes a negative electrode current collector and a negative electrode film layer. The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer disposed on the negative electrode current collector, with the first negative electrode film layer located between the negative electrode current collector and the second negative electrode film layer. Both the first and second negative electrode film layers include graphite. The average longest diameter of the graphite in the first negative electrode film layer is 7 μm to 18 μm, and the average longest diameter of the graphite in the second negative electrode film layer is 6 μm to 10 μm. Furthermore, the average longest diameter of the graphite in the first negative electrode film layer is greater than the average longest diameter of the graphite in the second negative electrode film layer.

[0089] By employing a two-layer structure for the negative electrode film, the average length of the longest diameter of graphite in the first and second negative electrode films is controlled within the aforementioned range, and the average length of the longest diameter of graphite in the first negative electrode film is made greater than that in the second negative electrode film. The second negative electrode film, located at the top, uses graphite with a smaller particle size, which provides more lithium-ion insertion sites, making it easier for lithium ions to be inserted from the electrolyte into the negative electrode film, thus improving the fast-charging performance of the battery cell. The first negative electrode film, located at the bottom, uses graphite with a larger particle size, which helps to increase the compaction density of the negative electrode film, allowing the battery cell to better balance fast-charging performance and energy density.

[0090] It is understandable that the average value of the longest diameter of graphite in the first negative electrode film layer can be 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, or any value within the range formed by any two of the above values; the average value of the longest diameter of graphite in the second negative electrode film layer can be 6μm, 7μm, 8μm, 9μm, 10μm, or any value within the range formed by any two of the above values.

[0091] The method for testing the average longest diameter is as follows: 500 graphite particles are randomly selected from the scanning electron microscope (SEM) image, and the longest diameter of each graphite particle is measured and averaged. The longest diameter of a graphite particle refers to the maximum length dimension that can be measured in all possible measurement directions of the particle in the above SEM image.

[0092] Furthermore, the ratio of the thickness of the second negative electrode film to the total thickness of the negative electrode sheet can be 30% to 70%.

[0093] In some embodiments, the graphite in the first and second negative electrode layers each independently comprises a graphite particle body and an amorphous carbon coating layer disposed on the surface of the graphite particle body, the thickness of the amorphous carbon coating layer being 100 nm to 500 nm. That is, the graphite in the first negative electrode layer may include an amorphous carbon coating layer, the graphite in the second negative electrode layer may include an amorphous carbon coating layer, or both the graphite in the first and second negative electrode layers may include an amorphous carbon coating layer. By providing an amorphous carbon coating layer of the aforementioned thickness on the graphite surface, it is beneficial to further improve the conductivity of the graphite particles and further improve the kinetic performance of the battery.

[0094] Understandably, the thickness of the amorphous carbon coating layer on the surface of the graphite particle can be, but is not limited to, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 280nm, 300nm, 320nm, 350nm, 380nm, 400nm, 420nm, 450nm, 480nm, 500nm, and any value within the range formed by any two of the above values.

[0095] Furthermore, the graphite in the first negative electrode film layer and the second negative electrode film layer can each be artificial graphite, or a mixture of artificial graphite and natural graphite.

[0096] In some embodiments, the graphitization degree of graphite in the first and second negative electrode layers is independently 90% to 94%. Graphite with the above-mentioned graphitization degree is more conducive to lithium-ion intercalation, which is beneficial to improving the specific capacity of the negative electrode and the energy density of the battery.

[0097] In some embodiments, the areal density of the negative electrode film coating on one side is 0.13 g / 1540.25 mm. 2 ~0.22g / 1540.25mm 2 Controlling the surface area density of the negative electrode film layer on one side within the aforementioned range helps to better balance fast-charging performance and energy density in a single battery cell. Understandably, the surface area density of the negative electrode film layer on one side can be, but is not limited to, 0.13 g / 1540.25 mm. 2 0.14g / 1540.25mm 2 0.15g / 1540.25mm 2 0.16g / 1540.25mm 2 0.17g / 1540.25mm 2 0.18g / 1540.25mm 2 0.19g / 1540.25mm 2 0.20g / 1540.25mm 2 0.21g / 1540.25mm 2 0.22g / 1540.25mm 2 And any value within the range formed by any two of the above values.

[0098] Optionally, the surface density of the negative electrode film coating on one side is 0.14 g / 1540.25 mm. 2 ~0.195g / 1540.25mm 2 .

[0099] In some embodiments, the compaction density of the negative electrode sheet is 1.3 g / cc to 1.52 g / cc. Controlling the compaction density of the negative electrode sheet within this range helps to better balance fast-charging performance and energy density in the battery cell. Understandably, the compaction density of the negative electrode sheet can be, but is not limited to, 1.3 g / cc, 1.31 g / cc, 1.32 g / cc, 1.33 g / cc, 1.34 g / cc, 1.35 g / cc, 1.36 g / cc, 1.37 g / cc, 1.38 g / cc, 1.39 g / cc, 1.4 g / cc, 1.41 g / cc, 1.42 g / cc, 1.43 g / cc, 1.44 g / cc, 1.45 g / cc, 1.46 g / cc, 1.47 g / cc, 1.48 g / cc, 1.49 g / cc, 1.50 g / cc, 1.51 g / cc, 1.52 g / cc, and any value within the range formed by any two of the above values.

[0100] Alternatively, the compaction density of the negative electrode sheet is 1.35 g / cc to 1.50 g / cc.

[0101] In some embodiments, the positive electrode body 11 includes a positive electrode current collector and a positive electrode film layer. The positive electrode film layer is disposed on the positive electrode current collector and includes a lithium-containing transition metal phosphate. The lithium-containing transition metal phosphate includes one or more of the following elements by mass: aluminum with a content of 200ppm to 2500ppm, vanadium with a content of 300ppm to 2000ppm, and titanium with a content of 1500ppm to 3500ppm.

[0102] Adding aluminum in the above-mentioned amounts to lithium-containing transition metal phosphates can improve the electronic conductivity of the cathode active material, thereby enhancing the fast-charging and cycle performance of the battery cell. Adding vanadium in the above-mentioned amounts to lithium-containing transition metal phosphates can improve the specific capacity of the cathode active material, which in turn can improve the energy density of the battery cell. Adding titanium in the above-mentioned amounts to lithium-containing transition metal phosphates can improve the crystal structure stability of the cathode active material, thereby enhancing the cycle performance of the battery cell.

[0103] Understandably, the aluminum content in lithium-containing transition metal phosphates can be, but is not limited to, 200 ppm, 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2500 ppm, or any value within the range formed by any two of the above values; the vanadium content in lithium-containing transition metal phosphates can be, but is not limited to, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, or any value within the range formed by any two of the above values. The content of titanium in lithium transition metal phosphates can be, but is not limited to, 1500ppm, 1800ppm, 2000ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm, and any value within the range formed by any two of the above values;

[0104] In some embodiments, the positive electrode body 11 further includes a base coating layer disposed between the positive electrode current collector and the positive electrode film layer. The base coating layer includes a conductive agent and has a thickness of 0.5 μm to 3 μm. In stacked cells with a large aspect ratio of the electrodes, the distance that electrons travel from the positive electrode body 11 to the positive electrode tab 12 is relatively long, resulting in a relatively high internal resistance (DCR) of the battery cell. By providing the aforementioned base coating layer between the positive electrode current collector and the positive electrode film layer, it is beneficial to reduce the battery's internal resistance and improve the battery's dynamic performance.

[0105] Understandably, the thickness of the base coating can be, but is not limited to, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.2μm, 1.5μm, 1.8μm, 2.0μm, 2.2μm, 2.5μm, 2.8μm, 3μm, and any value within the range formed by any two of the above values.

[0106] In some embodiments, the areal density of the positive electrode film coating on one side is 0.33 g / 1540.25 mm. 2 ~0.45g / 1540.25mm 2 Controlling the surface density of the positive electrode film coating on one side within the aforementioned range helps to better balance fast-charging performance and energy density in a single battery cell. Understandably, the surface density of the positive electrode film coating on one side can be, but is not limited to, 0.33 g / 1540.25 mm. 2 0.34g / 1540.25mm2 0.35g / 1540.25mm 2 0.36g / 1540.25mm 2 0.37g / 1540.25mm 2 0.38g / 1540.25mm 2 0.39g / 1540.25mm 2 0.40g / 1540.25mm 2 0.41g / 1540.25mm 2 0.42g / 1540.25mm 2 0.43g / 1540.25mm 2 0.44g / 1540.25mm 2 0.45g / 1540.25mm 2 And any value within the range formed by any two of the above values.

[0107] Optionally, the surface density of the positive electrode film coating on one side is 0.30 g / 1540.25 mm. 2 ~0.40g / 1540.25mm 2 .

[0108] In some embodiments, the compaction density of the positive electrode sheet is 2.3 g / cc to 2.65 g / cc. Controlling the compaction density of the positive electrode sheet within this range helps the battery cell better balance fast-charging performance and energy density. Understandably, the compaction density of the positive electrode sheet can be, but is not limited to, 2.3 g / cc, 2.32 g / cc, 2.35 g / cc, 2.38 g / cc, 2.4 g / cc, 2.42 g / cc, 2.45 g / cc, 2.48 g / cc, 2.5 g / cc, 2.52 g / cc, 2.55 g / cc, 2.58 g / cc, 2.6 g / cc, 2.62 g / cc, 2.65 g / cc, and any value within the range formed by any two of the above values.

[0109] Alternatively, the compaction density of the positive electrode sheet is 2.35 g / cc to 2.6 g / cc.

[0110] In some embodiments, the thickness ratio of the positive electrode 1 to the positive current collector is (10~20):1, and the thickness ratio of the negative electrode 3 to the negative current collector is (15~25):1. Thus, the positive current collector accounts for a smaller proportion of the thickness in the positive electrode 1, and the negative current collector accounts for a smaller proportion of the thickness in the negative electrode 3, which is beneficial for further improving the energy density of the battery cell.

[0111] A second aspect of this application provides a battery device comprising the battery cell of the first aspect of this application.

[0112] Multiple battery cells can be interconnected and arranged in a specific order, then directly housed within a housing to assemble a battery device. Alternatively, one or more battery cells can be first assembled into a battery module, then multiple battery modules can be interconnected to form a whole, and finally the entire battery module can be housed within a housing to form a battery device.

[0113] In some specific examples, the battery device is a battery module, which may include one or more of the aforementioned battery cells. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module. Within the battery module, multiple battery cells can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other arbitrary manner. Furthermore, these multiple battery cells can be secured using fasteners.

[0114] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells are housed.

[0115] In some specific examples, the battery device is a battery pack further assembled from multiple of the above-mentioned battery modules. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0116] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0117] A third aspect of this application provides an electrical device comprising one or more of the battery cells of the first aspect and the battery devices of the second aspect of this application.

[0118] The battery cell and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0119] Unless otherwise specified, the battery components, material types or contents mentioned apply to both lithium-ion and sodium-ion batteries.

[0120] In one embodiment of this application, a battery cell is provided.

[0121] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0122] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0123] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0124] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0125] In some embodiments, the positive electrode active material may comprise a positive electrode active material known in the art for use in batteries.

[0126] As a non-limiting example, the positive electrode active material of a lithium-ion battery may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium-containing transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium-containing transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.85 Co 0.1 Al 0.05 O2.

[0127] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0128] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0129] As a non-limiting example, the positive electrode active material of a sodium-ion battery may include one or more of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0130] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si; n represents (YO4). n- The price state.

[0131] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si, and n represents (YO4). n- The valence state; halogens can be one or more of F, Cl and Br.

[0132] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO)y ) m+ And a class of compounds with optional halide anions. Y can be one or more of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; halogens can be one or more of F, Cl and Br.

[0133] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (where M' is one or more of V, Fe, Mn and Ni), and Na3(VO4) y )2(PO4)2F 3-2y One or more of (0≤y≤1).

[0134] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. Transition metals can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds include, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently one or more of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0135] The weight ratio of the positive electrode active material in the positive electrode film is 80% to 100% by weight, based on the total weight of the positive electrode film.

[0136] In some embodiments, the positive electrode film layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. The binder accounts for 0% to 20% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[0137] In some embodiments, the positive electrode film may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0% to 20% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0138] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive 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 on both sides of the positive current collector, drying it and then cold pressing it through a cold rolling mill to form the positive electrode sheet.

[0139] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0140] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0141] 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0142] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries.

[0143] As a non-limiting example, the negative electrode active material of a lithium-ion battery may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more 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.

[0144] As a non-limiting example, the negative electrode active material of a sodium-ion battery is typically a hard carbon material, a two-dimensional metal carbide, or a nitride. Preferably, the negative electrode active material of a sodium-ion secondary battery is typically a hard carbon material.

[0145] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may include one or more 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).

[0146] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0147] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0148] 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 (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of the negative electrode current collector, and then obtaining the negative electrode sheet after processes such as drying and cold pressing. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector.

[0149] The electrolyte has the function of conducting ions between the positive and negative electrode plates.

[0150] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0151] In some embodiments, the electrolyte salt of the lithium-ion battery includes lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI); it may also include one or more of lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonylimide) (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0152] In some embodiments, the solvent includes one or more of dimethyl carbonate (DMC) and linear carboxylic acid esters having the structure shown in formula (1); R1-(C=O)-O-R2 of formula (1); wherein R1 and R2 each independently include a C1-C5 alkyl or haloalkyl group. It may also include one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0153] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0154] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation.

[0155] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0156] In some implementations, the positive electrode, negative electrode, and separator are fabricated into an electrode assembly using a stacking process.

[0157] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0158] In some embodiments, the outer packaging of the battery cell can be a flexible package, such as a pouch. The material of the flexible package can be plastic, and further, non-limiting examples of plastics can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0159] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions are inserted and extracted back and forth between the positive and negative electrode plates. The electrolyte plays a role in conducting active ions between the positive and negative electrode plates.

[0160] In addition, this application also provides an electrical device, which includes at least one of the battery cells or battery devices provided in this application. The battery cells or battery devices can be used as the power source for the electrical device or as the energy storage unit of 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.

[0161] As an electrical device, you can choose between individual battery cells or battery packs based on your usage requirements.

[0162] Figure 4 Here is an example of an electrical device 6. This electrical 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 electrical device, a battery device can be used.

[0163] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0164] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0165] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0166] Example 1:

[0167] (1) Preparation of positive electrode sheet

[0168] Lithium iron phosphate (LFP) positive electrode active material, Super P conductive agent, and PVDF binder are mixed at a mass ratio of 97:1:2, and N-methylpyrrolidone solvent is added and stirred evenly to obtain a positive electrode slurry. Aluminum foil is used as the positive electrode current collector. The positive electrode current collector includes a positive electrode body and a positive electrode tab connected to the positive electrode body. The positive electrode tab is connected to the short side of the positive electrode body.

[0169] A primer slurry containing PVDF and conductive carbon is coated on both sides of the positive electrode body of the positive electrode current collector. After curing, a primer layer with a thickness of 1 μm is formed. The mass ratio of PVDF to conductive carbon in the primer slurry is 1:5. The positive electrode slurry prepared above is uniformly coated on the primer layer on both sides of the positive electrode body. After drying, cold pressing, and slitting, the positive electrode sheet is obtained.

[0170] The ratio of the long side dimension to the short side dimension of the positive electrode body is 5:1. The compaction density of the positive electrode body is 2.5 g / cc, and the single-sided coating surface density is 0.4 g / 1540.25 mm. 2 .

[0171] (2) Preparation of negative electrode sheet

[0172] Artificial graphite, conductive agent Super P, thickener sodium carboxymethyl cellulose, and binder styrene-butadiene rubber were mixed in a mass ratio of 96:1:1.2:1.8, and then deionized water was added as a solvent. The mixture was stirred until homogeneous to obtain the first negative electrode slurry. The average longest diameter of the artificial graphite was 12 μm. The artificial graphite consisted of graphite particles and an amorphous carbon coating layer with a thickness of 200 nm on the surface of the graphite particles. The graphitization degree of the artificial graphite was 92%.

[0173] Copper foil is used as the negative electrode current collector. The negative electrode current collector includes a negative electrode body and a negative electrode tab connected to the negative electrode body. The negative electrode tab is connected to the short side of the negative electrode body. The first negative electrode slurry prepared above is uniformly coated on both sides of the negative electrode body, dried, and cold-pressed to obtain the first negative electrode film layer. The single-sided coating surface density of the first negative electrode film layer is 0.1 g / 1540.25 mm². 2 .

[0174] Artificial graphite, conductive agent Super P, thickener sodium carboxymethyl cellulose, and binder styrene-butadiene rubber were mixed at a mass ratio of 96:1:1.2:1.8, and then deionized water was added as a solvent. The mixture was stirred until homogeneous to obtain the second negative electrode slurry. The average longest diameter of the artificial graphite was 8 μm. The artificial graphite consisted of graphite particles and an amorphous carbon coating layer with a thickness of 200 nm on the surface of the graphite particles. The graphitization degree of the artificial graphite was 92%.

[0175] The second negative electrode slurry prepared above was uniformly coated onto the first negative electrode film layer on both sides of the negative electrode body. After drying and cold pressing, the second negative electrode film layer was obtained; after slitting, the negative electrode sheet was obtained. The surface density of the second negative electrode film layer on one side was 0.1 g / 1540.25 mm². 2 The total single-sided coating density of the negative electrode film is 0.2 g / 1540.25 mm. 2 The compaction density of the negative electrode sheet is 1.42 g / cc.

[0176] (3) Separating membrane

[0177] A polyethylene film with a thickness of 7μm was used as the separator.

[0178] (4) Electrolyte

[0179] In an argon-atmospheric glove box with a water content <10 ppm, dimethyl carbonate, ethylene carbonate, and methyl acetate were mixed to obtain an organic solvent, and dried lithium salts LiPF6 and LiFSI were added. Fluoroethylene carbonate (1% by mass) was added to the above solution as an additive to obtain the electrolyte. Based on the mass of the electrolyte, the total mass fraction of dimethyl carbonate and methyl acetate was 50%, and the volume ratio of dimethyl carbonate to methyl acetate was 1:1; the sum of the mass fractions of LiPF6 and LiFSI was 18%, and the mass ratio of LiPF6 to LiFSI was 2:1. The conductivity of the electrolyte at 25°C was 15 mS / cm.

[0180] (5) Battery assembly

[0181] The prepared positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to provide isolation, resulting in a stacked bare cell. The long side of the negative electrode body extends 5mm beyond the long side of the positive electrode body, forming an overhang region. Similarly, the long side of the separator extends 5mm beyond the long side of the negative electrode body, also forming an overhang region. The stacked bare cell is placed in a 100μm thick polypropylene soft-pack casing, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery cell is obtained.

[0182] Example 2:

[0183] This embodiment is basically the same as embodiment 1, except that in step (1), by adjusting the length of the positive electrode sheet, the ratio of the long side dimension to the short side dimension of the positive electrode body is 3:1, while the short side dimension of the positive electrode body remains unchanged.

[0184] Example 3:

[0185] This embodiment is basically the same as embodiment 1, except that in step (1), by adjusting the length of the positive electrode sheet, the ratio of the long side dimension to the short side dimension of the positive electrode body is 8:1, while the short side dimension of the positive electrode body remains unchanged.

[0186] Example 4:

[0187] This embodiment is basically the same as embodiment 1, except that: in step (5), the long side of the negative electrode body extends 2mm beyond the long side edge of the positive electrode body to form an overhang area; the long side of the separator extends 2mm beyond the long side edge of the negative electrode body to form an overhang area.

[0188] Example 5:

[0189] This embodiment is basically the same as embodiment 1, except that: in step (5), the long side of the negative electrode body extends 7mm beyond the long side edge of the positive electrode body to form an overhang area; the long side of the separator extends 10mm beyond the long side edge of the negative electrode body to form an overhang area.

[0190] Example 6:

[0191] This embodiment is basically the same as Example 1, except that in step (4), ethylene carbonate, methyl acetate and ethyl acetate are mixed to obtain an organic solvent, and dried lithium salts LiPF6 and LiFSI are added; fluoroethylene carbonate with a mass content of 0.3% is added to the above solution as an additive to obtain an electrolyte. The total mass fraction of methyl acetate and ethyl acetate in the electrolyte is 20%, and the volume ratio of methyl acetate to ethyl acetate is 1:1; the sum of the mass fractions of LiPF6 and LiFSI is 12%, and the mass ratio of LiPF6 to LiFSI is 1.2:1. The conductivity of the electrolyte at 25℃ is 10 mS / cm.

[0192] Example 7:

[0193] This embodiment is basically the same as embodiment 1, except that in step (2), by adjusting the types of artificial graphite in the first negative electrode slurry and the second negative electrode slurry, the average length of the artificial graphite in the first negative electrode film layer is 18 μm and the average length of the artificial graphite in the second negative electrode film layer is 10 μm.

[0194] Example 8:

[0195] This embodiment is basically the same as embodiment 1, except that: in step (2), the average length of the longest diameter of the artificial graphite in the first negative electrode slurry is 8 μm; and the average length of the longest diameter of the artificial graphite in the second negative electrode slurry is 6 μm.

[0196] Comparative Example 1:

[0197] This comparative example is basically the same as Example 1, except that in step (5), the long side of the negative electrode body extends 1 mm beyond the long side edge of the positive electrode body to form an overhang region; the long side of the separator extends 1 mm beyond the long side edge of the negative electrode body to form an overhang region.

[0198] Comparative Example 2:

[0199] This comparative example is basically the same as Example 1, except that in step (1), by adjusting the length of the positive electrode sheet, the ratio of the long side dimension to the short side dimension of the positive electrode body is 10:1, while the short side dimension of the positive electrode body remains unchanged.

[0200] Comparative Example 3:

[0201] This comparative example is basically the same as Example 1, except that in step (4), ethylene carbonate and propylene carbonate are mixed in a volume ratio of 1:1 to obtain an organic solvent.

[0202] Test method:

[0203] (1) Energy density test

[0204] Charge the battery cell at 0.33C to 3.65V at 25℃, then charge it at a constant voltage of 3.65V to 0.05C; let it stand for 5 minutes; discharge it at 0.33C to 2V, and record the total discharge capacity C0 and the total discharge energy E0 of the battery cell, in Wh.

[0205] The length, width, and thickness of each battery cell are measured, and the volume is calculated and denoted as V, with the unit being L;

[0206] Battery cell volumetric energy density = E0 / V, unit: Wh / L.

[0207] (2) Cyclic performance test

[0208] Step 1: Charge the battery cell at 25 ℃ at 0.33C to 3.65V, then charge it at 3.65V constant voltage to 0.05C; let it stand for 5 minutes; discharge it at 0.33C to 2V, and record the capacity at this time as C0 (this step is the actual initial capacity test).

[0209] Step 2: Charge the battery to 3.45V at 0.5C0 and to 3.65V at 0.33C0; let it stand for 10 minutes; discharge it to 2V at 1C0 and to 2V at 0.33C until the capacity decays to less than or equal to 80% of the initial capacity, and record the number of cycles at this point.

[0210] (3) Battery self-discharge performance test

[0211] The battery cells were left to stand at room temperature for 1 hour. The initial open circuit voltage (OCV) of the cells was measured using a 6.5-digit digital multimeter and recorded as OCV1. After the test, the cells were left to stand at 45°C for 120 hours, then at room temperature for 1 hour. The open circuit voltage was measured again and recorded as OCV2. The self-discharge rate was calculated using the formula: (OCV2 - OCV1) / 120. Ten cells were measured, and the average value was taken.

[0212] (4) Test of film coating surface density

[0213] The coating surface density was tested using the following method: a punch cut of 1540.25 mm. 2 Fifteen electrodes and 15 current collectors (from the same production batch as the electrodes) were weighed, and their average mass was calculated. The average mass of the electrodes is M1 (in g), and the average mass of the current collectors is M2 (in g). When the film layer is applied to both sides of the current collector, the surface density of the coating on one side is: (M1-M2) / 2S.

[0214] (5) Electrode compaction density test

[0215] Disassemble the 0% SOC battery cell to extract the electrode sheet, and punch it to 1540.25mm. 2 Take a small circular sheet and measure its weight M and thickness L; take another electrode sheet, remove the film layer from the surface, and cut the remaining empty current collector foil into 1540.25mm pieces. 2 The mass M0 of the air current collector foil is measured using a small circular piece. The compaction density PD = (M-M0) / 1.54025 / (L-L0), where L0 is the thickness of the current collector foil.

[0216] (6) Average value test of the longest diameter of graphite

[0217] In the scanning electron microscope (SEM) image of the negative electrode film, 500 graphite particles were randomly selected, and the longest diameter of each graphite particle was measured and averaged. The longest diameter of the graphite particle refers to the maximum length dimension that can be measured in all possible measurement directions of the particle in the above SEM image.

[0218] The parameters and performance data of the battery cells in the above embodiments and comparative examples are shown in Table 1. In Table 1, " / " indicates that the cell does not exist.

[0219] Table 1

[0220]

[0221] As shown in Table 1, the battery cells of each embodiment of this application have high energy density, while also possessing good cycle performance and low self-discharge. Compared with Example 1, Comparative Example 1 has a smaller distance between the long side of the negative electrode body and the long side of the positive electrode body, and a smaller distance between the long side of the separator and the long side of the negative electrode body, resulting in decreased cycle performance and significantly increased self-discharge. Compared with Example 1, Comparative Example 2 has an excessively large ratio of the long side dimension to the short side dimension of the positive electrode body, which, although improving the energy density of the battery cell, significantly reduces cycle performance, making it difficult to balance cycle performance. Compared with Example 1, Comparative Example 3 does not use dimethyl carbonate and linear carboxylic acid esters with the structure of formula (1) in the electrolyte solvent, resulting in a significant decrease in the cycle performance of the battery cell.

[0222] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0223] 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 stacked battery cell, characterized in that, The device includes a flexible outer shell, a positive electrode, a separator, a negative electrode, and an electrolyte. The positive and negative electrode are stacked, the separator is disposed between the positive and negative electrode, and the positive electrode, the separator, the negative electrode, and the electrolyte are disposed inside the flexible outer shell. The positive electrode plate includes a positive electrode body and a positive electrode tab connected to the positive electrode body, wherein the ratio of the long side dimension to the short side dimension of the positive electrode body is (3~8):1; The negative electrode plate includes a negative electrode body and a negative electrode tab connected to the negative electrode body. The long side of the negative electrode body extends 2mm to 9mm beyond the long side edge of the positive electrode body, and the long side of the separator extends 2mm to 10mm beyond the long side edge of the negative electrode body. The electrolyte includes a first solvent, which includes one or more of dimethyl carbonate and linear carboxylic acid esters having the structure shown in formula (1); R1-(C=O)-O-R2 equation (1); R1 and R2 each independently include C1 to C5 alkyl or haloalkyl groups.

2. The stacked battery cell according to claim 1, characterized in that, The ratio of the long side dimension to the short side dimension of the positive electrode body is (4~6):

1.

3. The stacked battery cell according to claim 1 or 2, characterized in that, The long side of the negative electrode main body extends 3mm to 6mm beyond the long side edge of the positive electrode main body; and / or, the long side of the separator extends 3mm to 7mm beyond the long side edge of the negative electrode main body.

4. The stacked battery cell according to any one of claims 1 to 3, characterized in that, The linear carboxylic acid esters include one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

5. The stacked battery cell according to any one of claims 1 to 4, characterized in that, The mass fraction of the first solvent is 10% to 60% based on the mass of the electrolyte.

6. The stacked battery cell according to claim 5, characterized in that, The mass fraction of the first solvent is 15% to 35% based on the mass of the electrolyte.

7. The stacked battery cell according to any one of claims 1 to 6, characterized in that, The electrolyte has a conductivity of 10 mS / cm to 16 mS / cm at room temperature.

8. The stacked battery cell according to any one of claims 1 to 7, characterized in that, The electrolyte further includes lithium salts, including one or more of lithium hexafluorophosphate and lithium difluorosulfonylimide; the total mass fraction of the lithium hexafluorophosphate and / or the lithium difluorosulfonylimide is 12% to 18% based on the mass of the electrolyte.

9. The stacked battery cell according to claim 8, characterized in that, The mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (1.2~3):

1.

10. The stacked battery cell according to any one of claims 1 to 9, characterized in that, The electrolyte also includes additives, which include one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propanesulfonate lactone.

11. The stacked battery cell according to claim 10, characterized in that, The mass fraction of the additive is less than or equal to 5% based on the mass of the electrolyte.

12. The stacked battery cell according to claim 11, characterized in that, The mass fraction of the additive is 0.5% to 3% based on the mass of the electrolyte.

13. The stacked battery cell according to any one of claims 1 to 12, characterized in that, The positive electrode tab is connected to the short side of the positive electrode body, and the negative electrode tab is connected to the short side of the negative electrode body.

14. The stacked battery cell according to any one of claims 1 to 13, characterized in that, The thickness of the soft outer shell is 70μm~200μm.

15. The stacked battery cell according to any one of claims 1 to 14, characterized in that, The negative electrode body includes a negative electrode current collector and a negative electrode film layer. The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer disposed on the negative electrode current collector. The first negative electrode film layer is located between the negative electrode current collector and the second negative electrode film layer. Both the first negative electrode film layer and the second negative electrode film layer include graphite. The average longest diameter of the graphite in the first negative electrode film layer is 7μm~18μm, and the average longest diameter of the graphite in the second negative electrode film layer is 6μm~10μm. The average longest diameter of the graphite in the first negative electrode film layer is greater than the average longest diameter of the graphite in the second negative electrode film layer.

16. The stacked battery cell according to claim 15, characterized in that, The graphite in the first negative electrode film layer and the second negative electrode film layer each independently includes a graphite particle body and an amorphous carbon coating layer disposed on the surface of the graphite particle body, wherein the thickness of the amorphous carbon coating layer is 100nm~500nm.

17. The stacked battery cell according to claim 15 or 16, characterized in that, The graphitization degree of the graphite in the first negative electrode film layer and the second negative electrode film layer is independently 90%~94%.

18. The stacked battery cell according to any one of claims 15 to 17, characterized in that, The single-sided coating surface density of the negative electrode film is 0.13 g / 1540.25 mm. 2 ~0.22g / 1540.25mm 2 .

19. The stacked battery cell according to any one of claims 1 to 18, characterized in that, The compaction density of the negative electrode sheet is 1.3 g / cc to 1.52 g / cc.

20. The stacked battery cell according to any one of claims 1 to 19, characterized in that, The positive electrode body includes a positive electrode current collector and a positive electrode film layer. The positive electrode film layer is disposed on the positive electrode current collector. The positive electrode film layer includes a lithium-containing transition metal phosphate. The lithium-containing transition metal phosphate includes one or more of the following elements: aluminum with a mass content of 200ppm to 2500ppm, vanadium with a mass content of 300ppm to 2000ppm, and titanium with a mass content of 1500ppm to 3500ppm.

21. The stacked battery cell according to claim 20, characterized in that, The positive electrode body also includes a base coating layer, which is disposed between the positive electrode current collector and the positive electrode film layer. The base coating layer includes a conductive agent and has a thickness of 0.5 μm to 3 μm.

22. The stacked battery cell according to claim 20 or 21, characterized in that, The single-sided coating surface density of the positive electrode film is 0.33 g / 1540.25 mm. 2 ~0.45g / 1540.25mm 2 .

23. The stacked battery cell according to any one of claims 1 to 22, characterized in that, The compaction density of the positive electrode sheet is 2.3 g / cc to 2.65 g / cc.

24. A battery device, characterized in that, Includes any one of the stacked battery cells according to claims 1 to 23.

25. An electrical appliance, characterized in that, It includes one or more of the stacked battery cells according to any one of claims 1 to 23 and the battery device according to claim 24.

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