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

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly relates to a battery cell, a battery device, and an electrical device. Background Art

[0002] In recent years, with the increasingly wide application scope of secondary batteries, secondary batteries are widely used in energy storage power systems such as hydroelectric power stations, thermal power stations, wind power stations, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, and electric vehicles.

[0003] Due to the great development of secondary batteries, higher requirements are also put forward for the performance of secondary batteries. Seeking a battery with a relatively high energy density, good cycle performance, and low self-discharge is one of the key concerns of those skilled in the art. Summary of the Invention

[0004] The present application is made in view of the above problems, and its purpose is to provide a battery cell, a battery device, and an electrical device, where the battery cell has a relatively high energy density, good cycle performance, and low self-discharge.

[0005] To achieve the above purpose, a first aspect of the present application provides a battery cell, including a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. The positive electrode plate and the negative electrode plate are stacked, and the separator is disposed between the positive electrode plate and the negative electrode plate;

[0006] The positive electrode plate includes a positive electrode main body portion and a positive electrode tab connected to the positive electrode main body portion. The ratio of the long side dimension to the short side dimension of the positive electrode main body portion is (3 to 8):1;

[0007] The negative electrode plate includes a negative electrode main body portion and a negative electrode tab connected to the negative electrode main body portion. The long side of the negative electrode main body portion extends 2 mm to 9 mm beyond the long side edge of the positive electrode main body portion, and the long side of the separator extends 2 mm to 10 mm beyond the long side edge of the negative electrode main body portion;

[0008] The electrolyte includes a first solvent, and the first solvent includes one or more of dimethyl carbonate and a linear carboxylic acid ester having the structure shown in formula (1);

[0009] R1-(C=O)-O-R2 formula (1);

[0010] Wherein, R1 and R2 each independently include an alkyl or haloalkyl group having 1 to 5 carbon atoms.

[0011] By controlling the ratio of the long side dimension to the short side dimension of the positive electrode main body portion of the positive electrode tab to be (3 to 8):1, when forming a laminated battery using the positive electrode tab with a relatively large aspect ratio, the battery space occupied by the tab portion can be made relatively smaller, which is beneficial to improving the energy density of the battery cell. By using one or more of dimethyl carbonate and a linear carboxylic acid ester having the structure shown in formula (1) as solvents in the electrolyte, this solvent has a relatively low viscosity and is beneficial to improving the conductivity of the electrolyte, and can improve the problem of insufficient infiltration of the electrolyte in the laminated battery with a relatively large aspect ratio of the electrode tab, so that the battery cell can take into account good cycling performance. By adopting a specific overhang setting in the negative electrode tab and the separator, the long side of the negative electrode main body portion extends 2 mm to 9 mm beyond the long side edge of the positive electrode main body portion, and the long side of the separator extends 2 mm to 10 mm beyond the long side edge of the negative electrode main body portion; it can preferably reduce the self-discharge of the battery caused by the misalignment of the positive and negative electrode tabs due to gas generation by the low-viscosity solvent, so that the battery cell can take into account a relatively low self-discharge. Through the aspect ratio of the electrode tab, the electrolyte solvent, and the overhang setting of the negative electrode tab and the separator, through the synergistic cooperation of the above factors, the battery cell not only has a relatively high energy density, but also has good cycling performance and a relatively low self-discharge.

[0012] In any embodiment, the ratio of the long side dimension to the short side dimension of the positive electrode main body portion is (4 to 6):1. In this way, it is beneficial for the battery cell to better take into account a relatively high energy density, good cycling performance, and a relatively low self-discharge.

[0013] In any embodiment, the long side of the negative electrode main body portion extends 3 mm to 6 mm beyond the long side edge of the positive electrode main body portion; the long side of the separator extends 3 mm to 7 mm beyond the long side edge of the negative electrode main body portion. In this way, it is beneficial for the battery cell to better take into account a relatively high energy density, good cycling performance, and a relatively low self-discharge.

[0014] 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. In this way, it is beneficial to improve the problem of insufficient infiltration of the electrolyte in the laminated battery with a relatively large aspect ratio of the electrode tab, so that it is beneficial for the battery cell to take into account good cycling performance while having a relatively large energy density.

[0015] In any embodiment, based on the mass of the electrolyte, the mass fraction of the first solvent is 10% to 60%. In this way, it is beneficial for the electrolyte to have a suitable viscosity and a relatively high conductivity, beneficial to improving the problem of insufficient infiltration of the electrolyte in the laminated battery with a relatively large aspect ratio of the electrode tab, and enabling the battery cell to better take into account the cycling performance.

[0016] In any embodiment, based on the mass of the electrolyte, the mass fraction of the first solvent is 15% to 35%. In this way, it is beneficial for the battery cell to better balance higher energy density, better cycling performance, and lower self-discharge.

[0017] In any embodiment, the conductivity of the electrolyte at room temperature is 9.5 mS / cm to 20 mS / cm. In this way, it is beneficial for the electrolyte to have a relatively high conductivity. Controlling the conductivity of the electrolyte within the above range is beneficial to improving the cycling performance of the battery cell.

[0018] In any embodiment, the conductivity of the electrolyte at room temperature is 10 mS / cm to 16 mS / cm. In this way, it is beneficial to further improve the cycling performance of the battery cell.

[0019] In any embodiment, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide; based on the mass of the electrolyte, the total mass fraction of the lithium hexafluorophosphate and / or the lithium bis(fluorosulfonyl)imide is 12% to 18%. In this way, it is beneficial to increase the conductivity of the electrolyte and improve the cycling performance and kinetic performance of the battery cell.

[0020] In any embodiment, the mass ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide is (1.2 to 3):1. In this way, it is beneficial to increase the conductivity of the electrolyte, improve the problem of insufficient infiltration of the electrolyte in the stacked battery with a relatively large aspect ratio of the electrode sheet, and improve the cycling performance and kinetic performance of the battery cell.

[0021] In any embodiment, the electrolyte further includes an additive, and the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3 - propane sultone. In this way, the SEI film can be optimized, which is beneficial for the battery cell to better balance the cycling performance and the kinetic performance.

[0022] In any embodiment, based on the mass of the electrolyte, the mass fraction of the additive is less than or equal to 5%. In this way, it is more beneficial for the battery cell to better balance the cycling performance and the kinetic performance.

[0023] In any embodiment, based on the mass of the electrolyte, the mass fraction of the additive is 0.5% to 3%. In this way, it is beneficial for the battery cell to better balance the cycling performance and the kinetic performance.

[0024] 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. In this way, it is beneficial to increase the energy density of the battery cell.

[0025] In any embodiment, the battery cell further includes a soft-pack outer shell, and the positive electrode plate, the separator, the negative electrode plate and the electrolyte are disposed inside the soft-pack outer shell. The thickness of the soft-pack outer shell is 70 μm to 200 μm. In this way, it is beneficial to improve the energy density of the battery cell; and it can also make the outer shell have greater strength and improve the problem that the soft-pack outer shell bulges due to gas generation during the cycle of the low-viscosity solvent.

[0026] In any embodiment, the negative electrode main body portion 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 value of the longest diameter of the graphite in the first negative electrode film layer is 7 μm to 18 μm, and the average value of the longest diameter of the graphite in the second negative electrode film layer is 6 μm to 10 μm, and the average value of the longest diameter of the graphite in the first negative electrode film layer is greater than the average value of the longest diameter of the graphite in the second negative electrode film layer. In this way, it is beneficial to enable the battery cell to better balance the fast charging performance and the energy density.

[0027] In any embodiment, 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. The thickness of the amorphous carbon coating layer is 100 nm to 500 nm. In this way, it is beneficial to further improve the conductivity of the graphite particles and further improve the kinetic performance of the battery.

[0028] In any embodiment, the graphitization degree of the graphite in the first negative electrode film layer and the second negative electrode film layer is each independently 90% to 94%. In this way, it is more beneficial to improve the negative electrode specific capacity and the battery energy density.

[0029] In any embodiment, the single-sided coating areal density of the negative electrode film layer is 0.13 g / 1540.25 mm 2 ~0.22 g / 1540.25 mm 2 . In this way, it is beneficial to enable the battery cell to better balance the fast charging performance and the energy density.

[0030] In any embodiment, the compaction density of the negative electrode plate is 1.3 g / cc to 1.52 g / cc. In this way, it is beneficial to enable the battery cell to better balance the fast charging performance and the energy density.

[0031] In any embodiment, the positive electrode main body portion 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 aluminum element with a mass content of 200 ppm to 2500 ppm, vanadium element with a mass content of 300 ppm to 2000 ppm, and titanium element with a mass content of 1500 ppm to 3500 ppm. Thus, it is beneficial to improve the fast charging performance, cycle performance, and / or energy density of the battery cell.

[0032] In any embodiment, the positive electrode main body portion further includes a bottom coating layer. The bottom coating layer is disposed between the positive electrode current collector and the positive electrode film layer. The bottom coating layer includes a conductive agent, and the thickness of the bottom coating layer is 0.5 μm to 3 μm. Thus, it is beneficial to reduce the internal resistance of the battery and improve the kinetic performance of the battery.

[0033] In any embodiment, the single-sided coating areal density of the positive electrode film layer is 0.33 g / 1540.25 mm 2 ~0.45 g / 1540.25 mm 2 。Thus, it is beneficial for the battery cell to better balance the fast charging performance and the energy density.

[0034] In any embodiment, the compaction density of the positive electrode plate is 2.3 g / cc to 2.65 g / cc. Thus, it is beneficial for the battery cell to better balance the fast charging performance and the energy density.

[0035] The second aspect of the present application further provides a battery device, including the battery cell of the first aspect of the present application.

[0036] The third aspect of the present application further provides an electrical device, including one or more of the battery cell of the first aspect of the present application and the battery device of the second aspect of the present application.

[0037] Details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the specification, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To better describe and illustrate the embodiments or examples provided by the present application, one or more drawings can be referred to. 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, and the currently understood best mode of these applications. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0039] Figure 1A top view schematic diagram of the superposition of the positive electrode plate, the separator, and the negative electrode plate in a battery cell according to an embodiment of the present application;

[0040] Figure 2 A schematic structural diagram of the positive electrode plate in a battery cell according to an embodiment of the present application;

[0041] Figure 3 A schematic structural diagram of the negative electrode plate in a battery cell according to an embodiment of the present application;

[0042] Figure 4 A schematic diagram of an electrical device using the battery device according to an embodiment of the present application as a power source.

[0043] Description of reference numerals:

[0044] 1. Positive electrode plate; 2. Separator; 3. Negative electrode plate; 11. Positive electrode main body; 12. Positive electrode tab; 31. Negative electrode main body; 32. Negative electrode tab; 6. Electrical device. Detailed embodiments

[0045] Hereinafter, embodiments of the battery cell, the battery device, and the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where non-essential details are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0046] 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, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or exclude the end values. Any end value can be independently included or excluded, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are also listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to listing the parameter as integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when stating that a certain parameter is an integer selected from "2 to 10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0047] In this application, when it comes to "multiple", "diverse", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0048] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0049] Referring to "embodiment" herein means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment or implementation manner of this application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. The same understanding applies to "implementation manner" mentioned herein.

[0050] Those skilled in the art can understand that in the methods of various embodiments or examples, the written order of each step does not mean a strict execution order that constitutes any limitation to the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Without special instructions, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0051] In this application, in an open technical feature or technical solution described by words such as "containing", "including", "comprising", etc., without other instructions, additional members other than the listed members are not excluded, and it can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that also includes additional members outside the listed members. For example, A includes a1, a2 and a3. Without other instructions, it may also include other members or may not include additional members, and it can be regarded as providing both a feature or solution of "A is composed of a1, a2 and a3" and a feature or solution of "A not only includes a1, a2 and a3, but also includes other members". In this application, without other instructions, A (such as B) means that B is a non-limiting example in A, and it can be understood that A is not limited to B.

[0052] In this application, "optionally", "optional", "option" mean that it can be there or not, that is, it refers to any one of two parallel options of "yes" or "no". If "optional" appears multiple times in a technical solution, without special instructions and without contradictions or mutual restrictions, each "optional" is independent of each other.

[0053] Currently, due to the great development of secondary batteries, higher requirements are also put forward for the performance of secondary batteries. Seeking a battery with a relatively high energy density and capable of having good cycle performance and low self-discharge is one of the key concerns of those skilled in the art.

[0054] Based on this, please refer to Figure 1 、 Figure 2 and Figure 3 , the first aspect of this application provides a battery cell, the battery cell is a laminated battery, the battery cell includes a positive electrode plate 1, a separator 2, a negative electrode plate 3 and an electrolyte, the positive electrode plate 1 and the negative electrode plate 3 are stacked, and the separator 2 is disposed between the positive electrode plate 1 and the negative electrode plate 3.

[0055] Among them, the positive electrode tab 1 includes a positive electrode main body portion 11 and a positive electrode tab ear portion 12 connected to the positive electrode main body portion 11. The long side dimension of the positive electrode main body portion 11 (as shown by d1 in Figure 2 etc.) and the short side dimension (as shown by d2 in Figure 2 etc.) have a ratio of (3 - 8):1; the negative electrode tab 3 includes a negative electrode main body portion 31 and a negative electrode tab ear portion 32 connected to the negative electrode main body portion 31. The long side of the negative electrode main body portion 31 extends beyond the long side edge of the positive electrode main body portion 11 (i.e., overhang, as shown by L1 in Figure 1 etc.) by 2 mm to 9 mm, and the long side of the separator 2 extends beyond the long side edge of the negative electrode main body portion 31 (i.e., overhang, as shown by L2 in Figure 1 etc.) by 2 mm to 10 mm; the electrolyte includes a first solvent, and the first solvent includes one or more of dimethyl carbonate and a linear carboxylic acid ester having the structure shown in formula (1);

[0056] R1-(C=O)-O-R2 Formula (1);

[0057] In formula (1), R1 and R2 each independently include an alkyl or haloalkyl group having 1 to 5 carbon atoms.

[0058] In this application, the positive electrode main body portion 11 is the main part of the positive electrode tab 1. In this area, the positive electrode film layer is mainly set, and an insulating coating can be set at its edge; the positive electrode tab ear portion 12 refers to the conductive area extending from the positive electrode main body portion 11 for connecting an external circuit, and an insulating coating can be set at the root of the positive electrode tab ear portion 12; the long side of the positive electrode main body portion 11 refers to the side with a longer length in the plane where the positive electrode main body portion 11 is located, and the short side of the positive electrode main body portion 11 refers to the side with a shorter length in the plane where the positive electrode main body portion 11 is located; similarly, the negative electrode main body portion 31 is the main part of the negative electrode tab 3. In this area, the negative electrode film layer is mainly set; the negative electrode tab ear portion 32 refers to the conductive area extending from the negative electrode main body portion 31 for connecting an external circuit; the long side of the negative electrode main body portion 31 refers to the side with a longer length in the plane where the negative electrode main body portion 31 is located, and the short side of the negative electrode main body portion 31 refers to the side with a shorter length in the plane where the negative electrode main body portion 31 is located. The long side dimension and short side dimension of the positive electrode main body portion 11 and the negative electrode main body portion 31 can be directly measured by disassembling the laminated battery.

[0059] The distance that the long side of the negative electrode main body portion 31 extends beyond the long side edge of the positive electrode main body portion 11, the distance that the long side of the separator 2 extends beyond the long side edge of the negative electrode main body portion 31, the long side dimension and short side dimension of the positive electrode main body portion 11, and the long side dimension and short side dimension of the negative electrode main body portion 31 can all be tested by conventional methods in the art.

[0060] Exemplarily, the laminated battery can be disassembled. A plurality of (e.g., 10) test points are respectively selected at intervals along the two long sides of the positive electrode main body 11, and the distance by which the long side of the negative electrode main body 31 exceeds the long side edge of the positive electrode main body 11 at each test point is measured, and then the average value is calculated. This average value can be regarded as the distance by which the long side of the negative electrode main body 31 exceeds the long side edge of the positive electrode main body 11. Similarly, a plurality of (e.g., 10) test points are respectively selected at intervals along the two long sides of the negative electrode main body 31, and the distance by which the long side of the separator 2 exceeds the long side edge of the negative electrode main body 31 at each test point is measured, and then the average value is calculated. This average value can be regarded as the distance by which the long side of the separator 2 exceeds the long side edge of the negative electrode main body 31.

[0061] In the present application, the types and contents of the organic components in the electrolyte can be detected by using equipment and methods well-known in the art. For example, reference can be made to GB / T9722-2006 General Rules for Gas Chromatography of Chemical Reagents to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery is taken as a sample and detected by ion chromatography analysis method.

[0062] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentration in the electrolyte have meanings well-known in the art and can be detected by using equipment and methods well-known in the art. For example, reference can be made to the standard JY / T020-1996 General Rules for Ion Chromatography Analysis Method to qualitatively or quantitatively analyze the inorganic components / lithium salt concentration in the electrolyte by ion chromatography analysis method. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery is taken as a sample and detected by ion chromatography analysis method.

[0063] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, the solvent components in the electrolyte and the mass content of each solvent can be determined.

[0064] For the above-mentioned battery cell, by controlling the ratio of the long side dimension to the short side dimension of the positive electrode main body portion 11 of the positive electrode tab 1 to be in the range of (3 to 8):1, and forming a stacked battery using the positive electrode tab 1 with a relatively large aspect ratio of length to width, the battery space occupied by the tab portion can be made relatively smaller, which is beneficial to improving the energy density of the battery cell. However, when the aspect ratio of the length to width of the stacked battery electrode tab is relatively large, the penetration path of the electrolyte along the battery length direction is longer, and it is easy to occur that the electrolyte infiltration in some areas of the electrode tab is insufficient, which affects the cycle performance of the battery. By using one or more of dimethyl carbonate and the linear carboxylic acid ester having the structure shown in formula (1) as the first solvent in the electrolyte, the above-mentioned first solvent has a lower viscosity and is beneficial to improving the conductivity of the electrolyte, and can improve the problem of insufficient electrolyte infiltration in the stacked battery with a relatively large aspect ratio of the electrode tab length to width, so that the battery cell can take into account better cycle performance. However, the electrolyte solvent of dimethyl carbonate and / or the linear carboxylic acid ester having the structure shown in formula (1) is prone to gas generation during the battery cycle, which may cause the positive and negative electrode tabs in the stacked battery to be misaligned, resulting in battery self-discharge. In response to this, in this application, a specific overhang setting is adopted in the negative electrode tab 3 and the separator 2, so that the long side of the negative electrode main body portion 31 extends beyond the long side edge of the positive electrode main body portion 11 by 2 mm to 9 mm, and the long side of the separator 2 extends beyond the long side edge of the negative electrode main body portion 31 by 2 mm to 10 mm; in this way, the battery self-discharge caused by the misalignment of the positive and negative electrode tabs can be better reduced, so that the battery cell can take into account a lower self-discharge. Through the aspect ratio of the electrode tab, the electrolyte solvent, and the overhang setting of the negative electrode tab 3 and the separator 2, through the synergistic cooperation of the above factors, the battery cell not only has a high energy density, but also has good cycle performance and low self-discharge.

[0065] It can be understood that the ratio of the long side dimension to the short side dimension of the positive electrode main 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 dimension by which the long side of the negative electrode main body 31 extends beyond the long side edge of the positive electrode main body 11 can be 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4 mm, 4.2 mm, 4.5 mm, 4.8 mm, 5 mm, 5.2 mm, 5.5 mm, 5.8 mm, 6 mm, 6.2 mm, 6.5 mm, 6.8 mm, 7 mm, 7.2 mm, 7.5 mm, 7.8 mm, 8 mm, 8.2 mm, 8.5 mm, 8.8 mm, 9 mm, and any value within the range formed by any two of the above values. The dimension by which the long side of the separator 2 extends beyond the long side edge of the negative electrode main body 31 can be 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4 mm, 4.2 mm, 4.5 mm, 4.8 mm, 5 mm, 5.2 mm, 5.5 mm, 5.8 mm, 6 mm, 6.2 mm, 6.5 mm, 6.8 mm, 7 mm, 7.2 mm, 7.5 mm, 7.8 mm, 8 mm, 8.2 mm, 8.5 mm, 8.8 mm, 9 mm, 9.2 mm, 9.5 mm, 9.8 mm, 10 mm, and any value within the range formed by any two of the above values.

[0066] In some embodiments, the ratio of the long side dimension to the short side dimension of the positive electrode main body 11 is (4 to 6):1. Controlling the ratio of the long side dimension to the short side dimension of the positive electrode main body 11 within the above range is beneficial for enabling the battery cell to better balance higher energy density, better cycle performance, and lower self-discharge.

[0067] In some embodiments, the long side of the negative electrode main body 31 extends 3 mm to 6 mm beyond the long side edge of the positive electrode main body 11; the long side of the separator 2 extends 3 mm to 7 mm beyond the long side edge of the negative electrode main body 31. Thus, adopting the overhang design with the above dimensions for 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 is beneficial for enabling the battery cell to better balance higher energy density, better cycle performance, and lower self-discharge.

[0068] In some of these embodiments, the linear carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate. The linear carboxylic acid esters of the above types have a low viscosity, which is beneficial to the infiltration of the electrolyte and can improve the problem of insufficient infiltration of the electrolyte in the stacked battery with a large aspect ratio of the electrode sheet. Therefore, when the battery monomer has a large energy density, it can take into account good cycle performance.

[0069] In some of these embodiments, based on the mass of the electrolyte, the mass fraction of the first solvent is 10% - 60%. Controlling the mass fraction of the first solvent in the electrolyte within the above range is beneficial to making the electrolyte have a suitable viscosity and a high conductivity, and is beneficial to improving the problem of insufficient infiltration of the electrolyte in the stacked battery with a large aspect ratio of the electrode sheet, enabling the battery monomer to better take into account the cycle performance.

[0070] It can be understood that 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%, and any value within the range formed by any two of the above values. The electrolyte may include dimethyl carbonate but not include linear carboxylic acid esters, or may include linear carboxylic acid esters but not include dimethyl carbonate, or may include both dimethyl carbonate and linear carboxylic acid esters at the same time.

[0071] Furthermore, in some of these embodiments, based on the mass of the electrolyte, the mass fraction of the first solvent is 15% - 35%. Controlling the mass fraction of the first solvent in the electrolyte within the above range is beneficial to enabling the battery monomer to better take into account a high energy density, good cycle performance, and low self-discharge.

[0072] In some of these embodiments, the conductivity of the electrolyte at room temperature is 9.5 mS / cm - 20 mS / cm. Adding dimethyl carbonate and / or linear carboxylic acid esters as solvents to the electrolyte is beneficial to making the electrolyte have a large conductivity. Controlling the conductivity of the electrolyte within the above range is beneficial to improving the cycle performance of the battery monomer.

[0073] It can be 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, and any value within the range formed by any two of the above values. Among them, room temperature usually refers to 20°C to 25°C.

[0074] In some specific examples, the conductivity of the electrolyte at room temperature is 10 mS / cm to 16 mS / cm.

[0075] In some of these embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI); based on the mass of the electrolyte, the total mass fraction of lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide is 12% to 18%.

[0076] By compounding lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide as the lithium salt and controlling the total mass fraction of lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide within the above range, it is beneficial to improve the conductivity of the electrolyte and the cycling performance and kinetic performance of the battery cell.

[0077] It can be understood that the total mass fraction of lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide 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.

[0078] In some of these embodiments, the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide is (1.2 to 3):1. Controlling the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide within the above range is conducive to improving the conductivity of the electrolyte, improving the problem of insufficient electrolyte infiltration in the stacked battery with a relatively large aspect ratio of the electrode sheet, and improving the cycle performance and kinetic performance of the battery monomer. It can be understood that the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide 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.

[0079] In some of these embodiments, the electrolyte further includes an additive, and the additive includes one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3 - propane sultone (PS). By adding the above additives to the electrolyte, the SEI (Solid Electrolyte Interface) film can be optimized, which is conducive to enabling the battery monomer to better balance the cycle performance and kinetic performance.

[0080] In some of these embodiments, based on the mass of the electrolyte, the mass fraction of the additive is less than or equal to 5%. Excessive use of the additive will increase the impedance of the battery monomer. In the stacked battery with a relatively large aspect ratio of the electrode sheet in this application, using the above additives with a mass fraction of less than 5% of the electrolyte mass is more conducive to enabling the battery monomer to better balance the cycle performance and kinetic performance.

[0081] It can be understood that 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.

[0082] Furthermore, in some specific examples, based on the mass of the electrolyte, the mass fraction of the additive is 0.5% to 3%. In this way, it is conducive to enabling the battery monomer to better balance the cycle performance and kinetic performance.

[0083] In some of these 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. In this way, the positive electrode tab 12 is arranged on one side of the short side of the positive electrode main body 11, and the negative electrode tab 32 is arranged on one side of the short side of the negative electrode main body 31. Compared with the solution of arranging the tab on the long side, it is more beneficial to improve the energy density of the battery cell.

[0084] In some of these embodiments, the battery cell further includes a soft package shell. The positive electrode plate 1, the separator 2, the negative electrode plate 3 and the electrolyte are arranged inside the soft package shell, and the thickness of the soft package shell is 70 μm to 200 μm. That is, the battery cell of the present application can be a soft package battery cell. Controlling the thickness of the soft package shell within the above range is beneficial to improving the energy density of the battery cell; and can also make the shell have greater strength, and improve the problem that the soft package shell bulges due to gas generation caused by low-viscosity solvents during the circulation process.

[0085] It can be understood that the thickness of the soft package shell can be, but is not limited to, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, and any value within the range formed by any two of the above values.

[0086] In some specific examples, the material of the soft package shell can be plastic. Further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0087] In some of these embodiments, the negative electrode main 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 arranged 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 value of the longest diameter of the graphite in the first negative electrode film layer is 7 μm to 18 μm, and the average value of the longest diameter of the graphite in the second negative electrode film layer is 6 μm to 10 μm, and the average value of the longest diameter of the graphite in the first negative electrode film layer is greater than the average value of the longest diameter of the graphite in the second negative electrode film layer.

[0088] By arranging the negative electrode film layer in a two-layer structure of upper and lower layers, controlling the average value of the longest diameters of the graphite in the first negative electrode film layer and the second negative electrode film layer within the above range, and making the average value of the longest diameters of the graphite in the first negative electrode film layer greater than the average value of the longest diameters of the graphite in the second negative electrode film layer; using graphite with a smaller particle size in the second negative electrode film layer located above can provide more lithium ion insertion sites, making it easier for lithium ions to be inserted into the negative electrode film layer from the electrolyte, which is beneficial to improving the fast charging performance of the battery cell; using graphite with a larger particle size in the first negative electrode film layer located below is beneficial to improving the compaction density of the negative electrode film layer, enabling the battery cell to better balance the fast charging performance and energy density.

[0089] It can be understood that the average value of the longest diameters of the graphite in the first negative electrode film layer can be 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, and any value within the range formed by any two of the above values; the average value of the longest diameters of the graphite in the second negative electrode film layer can be 6μm, 7μm, 8μm, 9μm, 10μm, and any value within the range formed by any two of the above values.

[0090] Among them, the test method for the average value of the longest diameter is: in the scanning electron microscope (SEM) image, randomly select 500 graphite particles, measure the longest diameter of each graphite particle, and then take the average value. 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.

[0091] Furthermore, the ratio of the thickness of the second negative electrode film layer to the total thickness of the negative electrode sheet can be 30% - 70%.

[0092] In some embodiments, 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 provided on the surface of the graphite particle body, and the thickness of the amorphous carbon coating layer is 100nm - 500nm. That is, the graphite in the first negative electrode film layer can include an amorphous carbon coating layer, the graphite in the second negative electrode film layer can include an amorphous carbon coating layer, or the graphite in both the first negative electrode film layer and the second negative electrode film layer includes an amorphous carbon coating layer. By providing the amorphous carbon coating layer with the above thickness on the surface of the graphite, it is beneficial to further improve the conductivity of the graphite particles and further improve the kinetic performance of the battery.

[0093] Understandably, the thickness of the amorphous carbon coating layer on the surface of the graphite particle body can be, but is not limited to, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, and any value within the range formed by any two of the above values.

[0094] Further, the graphite in the first negative electrode film layer and the second negative electrode film layer can be independently artificial graphite, or a mixture of artificial graphite and natural graphite.

[0095] In some embodiments, the graphitization degree of the graphite in the first negative electrode film layer and the second negative electrode film layer is independently 90% - 94%. Using graphite with the above graphitization degree is more conducive to the insertion of lithium ions and is beneficial to improving the specific capacity of the negative electrode and the energy density of the battery.

[0096] In some embodiments, the single - side coating areal density of the negative electrode film layer is 0.13 g / 1540.25 mm 2 ~0.22 g / 1540.25 mm 2 . Controlling the single - side coating areal density of the negative electrode film layer within the above range is beneficial for the battery monomer to better balance the fast - charging performance and energy density. Understandably, the single - side coating areal density of the negative electrode film layer can be, but is not limited to, 0.13 g / 1540.25 mm 2 、0.14 g / 1540.25 mm 2 、0.15 g / 1540.25 mm 2 、0.16 g / 1540.25 mm 2 、0.17 g / 1540.25 mm 2 、0.18 g / 1540.25 mm 2 、0.19 g / 1540.25 mm 2 、0.20 g / 1540.25 mm 2 、0.21 g / 1540.25 mm 2 、0.22 g / 1540.25 mm 2 and any value within the range formed by any two of the above values.

[0097] Further optionally, the single - side coating areal density of the negative electrode film layer is 0.14 g / 1540.25 mm 2 ~0.195 g / 1540.25 mm 2 .

[0098] In some of these embodiments, the compaction density of the negative electrode tab is 1.3 g / cc to 1.52 g / cc. Controlling the compaction density of the negative electrode tab within the above range is conducive to enabling the battery cell to better balance the fast charging performance and energy density. Understandably, the compaction density of the negative electrode tab 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.

[0099] Further optionally, the compaction density of the negative electrode tab is 1.35 g / cc to 1.50 g / cc.

[0100] In some of these embodiments, the positive electrode main body 11 includes a positive electrode current collector and a positive electrode film layer. The positive electrode film layer is provided 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 aluminum element with a mass content of 200 ppm to 2500 ppm, vanadium element with a mass content of 300 ppm to 2000 ppm, and titanium element with a mass content of 1500 ppm to 3500 ppm.

[0101] By adding the above content of aluminum element to the lithium-containing transition metal phosphate, it is conducive to improving the electronic conductivity of the positive electrode active material and improving the fast charging performance and cycling performance of the battery cell; by adding the above content of vanadium element to the lithium-containing transition metal phosphate, it is conducive to increasing the specific capacity of the positive electrode active material, and thus conducive to increasing the energy density of the battery cell; by adding the above content of titanium element to the lithium-containing transition metal phosphate, it is conducive to improving the crystal structure stability of the positive electrode active material, thereby enhancing the cycling performance of the battery cell.

[0102] Understandably, the content of aluminum element in the lithium-containing transition metal phosphate 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, and any value within the range formed by any two of the above values; the content of vanadium element in the lithium-containing transition metal phosphate 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, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, and any value within the range formed by any two of the above values; the content of titanium element in the lithium-containing transition metal phosphate can be, but is not limited to, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2500 ppm, 2800 ppm, 3000 ppm, 3200 ppm, 3500 ppm, and any value within the range formed by any two of the above values.

[0103] In some embodiments, the positive electrode main body 11 further includes a bottom coating, which is disposed between the positive electrode current collector and the positive electrode film layer. The bottom coating includes a conductive agent, and the thickness of the bottom coating is 0.5 μm to 3 μm. In a stacked battery with a relatively large aspect ratio of the electrode length to width, the distance for electrons to transfer from the positive electrode main body 11 to the positive electrode tab 12 is relatively long, resulting in a relatively large internal resistance (DCR) of the battery cell; by providing the above bottom coating between the positive electrode current collector and the positive electrode film layer, it is beneficial to reduce the battery internal resistance and improve the kinetic performance of the battery.

[0104] Understandably, the thickness of the bottom coating can be, but is not limited to, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, and any value within the range formed by any two of the above values.

[0105] In some embodiments, the single-sided coating areal density of the positive electrode film layer is 0.33 g / 1540.25 mm 2 ~0.45 g / 1540.25 mm 2 . Controlling the single-sided coating areal density of the positive electrode film layer within the above range is beneficial for the battery cell to better balance the fast charging performance and energy density. Understandably, the single-sided coating areal density of the positive electrode film layer can be, but is not limited to, 0.33 g / 1540.25 mm 2 、0.34 g / 1540.25 mm2 、0.35 g / 1540.25 mm 2 、0.36 g / 1540.25 mm 2 、0.37 g / 1540.25 mm 2 、0.38 g / 1540.25 mm 2 、0.39 g / 1540.25 mm 2 、0.40 g / 1540.25 mm 2 、0.41 g / 1540.25 mm 2 、0.42 g / 1540.25 mm 2 、0.43 g / 1540.25 mm 2 、0.44 g / 1540.25 mm 2 、0.45 g / 1540.25 mm 2 and any value within the range formed by any two of the above values.

[0106] Further optionally, the single-sided coating areal density of the positive electrode film layer is 0.30 g / 1540.25 mm 2 ~0.40 g / 1540.25 mm 2 .

[0107] In some embodiments, the tap density of the positive electrode plate is 2.3 g / cc to 2.65 g / cc. Controlling the tap density of the positive electrode plate within the above range is beneficial to better balance the fast charging performance and energy density of the battery cell. Understandably, the tap density of the positive electrode plate 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.

[0108] Further optionally, the tap density of the positive electrode plate is 2.35 g / cc to 2.6 g / cc.

[0109] In some embodiments, the ratio of the thickness of the positive electrode plate 1 to the thickness of the positive electrode current collector is (10~20):1, and the ratio of the thickness of the negative electrode plate 3 to the thickness of the negative electrode current collector is (15~25):1. In this way, the thickness of the positive electrode current collector in the positive electrode plate 1 accounts for a relatively small proportion, and the thickness of the negative electrode current collector in the negative electrode plate 3 accounts for a relatively small proportion, which is beneficial to further improve the energy density of the battery cell.

[0110] The second aspect of the present application provides a battery device, which includes the battery cell of the first aspect of the present application.

[0111] After a plurality of battery cells are interconnected and arranged in a certain order, they can be directly placed in a box body, thereby assembling to form a battery device. Alternatively, one or more battery cells can be first formed into a battery module, and then a plurality of battery modules are interconnected to form an integral body, and finally the whole of the battery modules is placed in a box body to form a battery device.

[0112] In some specific examples, the battery device is a battery module, and the battery module may include one or more of the above-mentioned battery cells. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module. In the battery module, a plurality of battery cells can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other way. Further, the plurality of battery cells can be fixed by fasteners.

[0113] Optionally, the battery module may further include a housing having an accommodation space, and a plurality of battery cells are accommodated in the accommodation space.

[0114] In some specific examples, the battery device is a battery pack further assembled from a plurality of the above-mentioned battery modules. The number of battery modules included 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.

[0115] The battery pack may include a battery box and a plurality of battery modules disposed in the battery box. The battery box includes an upper box body and a lower box body. The upper box body can cover the lower box body and form a closed space for accommodating the battery modules. The plurality of battery modules can be arranged in the battery box in any way.

[0116] The third aspect of the present application provides an electrical device, which includes one or more of the battery cell of the first aspect of the present application and the battery device of the second aspect.

[0117] The battery cell and the electrical device of the present application will be described below with appropriate reference to the accompanying drawings.

[0118] Unless otherwise specified, the components, types of materials or contents of the battery mentioned are applicable to both lithium-ion batteries and sodium-ion batteries.

[0119] In an embodiment of the present application, a battery cell is provided.

[0120] Under normal circumstances, a battery cell includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0121] The positive electrode plate includes a positive current collector and a positive electrode film layer provided on at least one surface of the positive current collector.

[0122] As a non-limiting example, the positive current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposite surfaces of the positive current collector.

[0123] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can 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 a polymer material substrate. In the positive current collector, non-limiting examples of the metal material can include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the positive current collector, non-limiting examples of the polymer material substrate can include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0124] In some embodiments, the positive electrode active material can include positive electrode active materials known in the art for batteries.

[0125] 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, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of a battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of the 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 the lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 ), etc.; non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.1 Al 0.05 O2.

[0126] Understandably, during the charge and discharge process of the battery, the insertion and extraction and consumption of lithium (Li) will occur, and the content of Li in the positive electrode plate varies when the battery is discharged to different states. In the enumeration of the positive electrode materials in this application, unless otherwise specified, the content of Li is the initial state of the material. When the positive electrode material is applied to the positive electrode plate in the battery system, after charge and discharge cycles, the content of Li in the positive electrode material contained in the plate usually changes. Among them, the content of Li can be measured by molar content, but it is not limited to this. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before being fed into the positive electrode slurry. It can be understood that new materials obtained by appropriate modification based on the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0127] In the enumeration of the positive electrode materials in this application, the content of oxygen (O) is only the theoretical state value, and the release of oxygen from the crystal lattice will cause changes in the molar content of oxygen, and the actual content of O will show fluctuations. Among them, the content of O can be measured by molar content, but it is not limited to this.

[0128] As a non-limiting example, the positive electrode active material of a sodium-ion battery may include one or more of the following materials: one or more of sodium transition metal oxides, polyanion-type compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as the positive electrode active material of a sodium-ion battery can also be used.

[0129] As an alternative technical solution of this application, the polyanion-type compound can be a type of compound having sodium ions, transition metal ions, and a tetrahedral (YO4) n- anion unit. 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 the valence state of (YO4) n- .

[0130] The polyanion-type compound can also be a type of compound having sodium ions, transition metal ions, a tetrahedral (YO4) n- anion unit, and a halogen anion. 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 the valence state of (YO4) n- ; the halogen can be one or more of F, Cl, and Br.

[0131] The polyanion-type compound can also be a type of compound having sodium ions, a tetrahedral (YO4) n- anion unit, a polyhedral unit (ZOy ) m+ and a class of compounds of optional halogen anions. Y can be one or more of P, S, and Si, and n represents the valence state of (YO4) n- ; Z represents a transition metal, which can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents the valence state of (ZO y ) m+ ; The halogen can be one or more of F, Cl, and Br.

[0132] Polyanionic compounds such as NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM’PO4F (M’ is one or more of V, Fe, Mn, and Ni), and Na3(VO y )2(PO4)2F 3-2y (0 ≤ y ≤ 1).

[0133] Prussian blue compounds can be a class of compounds having sodium ions, transition metal ions, and cyanide ions (CN - ). The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds such as Na a Me b Me’ c (CN)6, where 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.

[0134] The weight ratio of the positive electrode active material in the positive electrode film layer is 80 wt% to 100 wt%, based on the total weight of the positive electrode film layer.

[0135] In some embodiments, the positive electrode film layer may further optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0 wt% to 20 wt%, based on the total weight of the positive electrode film layer.

[0136] In some embodiments, the positive electrode film layer may further 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 weight ratio of the conductive agent in the positive electrode film layer is 0 wt% to 20 wt%, based on the total weight of the positive electrode film layer.

[0137] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate described above, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, coating the positive electrode slurry on both surfaces of the positive electrode current collector, and forming the positive electrode plate after drying and cold pressing by a cold rolling mill.

[0138] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0139] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0140] In some of these embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer material base layer 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. Among them, in the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0141] In some of these embodiments, the negative electrode active material can be a negative electrode active material for batteries well-known in the art.

[0142] 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. The silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0143] As a non-limiting example, the negative electrode active material of a sodium-ion battery is generally hard carbon material, two-dimensional metal carbides or nitrides. Preferably, the negative electrode active material of a sodium-ion secondary battery is generally hard carbon material.

[0144] In some embodiments, the negative electrode film layer may optionally further 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).

[0145] In some embodiments, the negative electrode film layer may optionally further 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.

[0146] In some embodiments, the negative electrode film layer may optionally further include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0147] In some embodiments, the negative electrode plate can be prepared in the following manner: the components for preparing the negative electrode plate, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained. 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 two surfaces of the negative electrode current collector.

[0148] The electrolyte has the function of conducting ions between the positive electrode plate and the negative electrode plate.

[0149] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0150] In some embodiments, the electrolyte salt of the lithium-ion battery includes lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI); it may also include one or more of lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0151] In some embodiments, the solvent includes one or more of dimethyl carbonate (DMC) and a linear carboxylic acid ester having the structure shown in formula (1); R1-(C=O)-O-R2 Formula (1); wherein, R1 and R2 each independently include an alkyl or haloalkyl group having 1 to 5 carbon atoms. It may also include one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl 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).

[0152] In some embodiments, the battery cell further includes a separator. The present application does not have any particular limitations on the type of separator, and any well-known porous separator with good chemical stability and mechanical stability can be selected.

[0153] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without any particular limitations. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without any particular limitations.

[0154] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and can be selected as 12 μm to 20 μm.

[0155] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator are made into an electrode assembly by a stacking process.

[0156] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0157] In some embodiments, the outer packaging of the battery cell can be a soft pack, such as a pouch soft pack. The material of the soft pack can be plastic. Further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0158] In the present application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy into each other. Further, generally, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the charging and discharging process of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0159] In addition, the present application also provides an electrical device, which includes at least one of the battery cell or the battery device provided by the present application. The battery cell and the battery device can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but are not limited thereto.

[0160] As an electrical device, the battery cell or the battery device can be selected according to its usage requirements.

[0161] Figure 4 Shown is an electrical device 6 as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery, a battery device can be adopted.

[0162] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a battery cell can be adopted as the power source.

[0163] In order to make the technical problems, technical solutions, and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes a limitation to the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0164] For those not specified in the embodiments, the techniques or conditions shall be in accordance with those described in the literature in this field or the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0165] Example 1:

[0166] (1) Preparation of the positive electrode sheet

[0167] The positive electrode active material lithium iron phosphate (LFP), the conductive agent Super P, and the binder PVDF are mixed at a mass ratio of 97:1:2, and the solvent N-methylpyrrolidone is added and stirred evenly to obtain the positive electrode paste. Aluminum foil is used as the positive electrode current collector, and the positive electrode current collector includes a positive electrode main body portion and a positive electrode tab portion connected to the positive electrode main body portion, and the positive electrode tab portion is connected to the short side of the positive electrode main body portion.

[0168] A primer paste containing PVDF and conductive carbon is coated on both surfaces of the positive electrode main body portion of the positive electrode current collector, and after curing, a primer layer with a thickness of 1 μm is formed. The mass ratio of PVDF to conductive carbon in the primer paste is 1:5. The above-prepared positive electrode paste is evenly coated on the primer layer on both surfaces of the positive electrode main body portion, and after drying, cold pressing, and slitting, the positive electrode sheet is obtained.

[0169] Among them, the ratio of the long side dimension to the short side dimension of the positive electrode main body of the positive electrode sheet is 5:1. The compaction density of the positive electrode sheet is 2.5 g / cc, and the single-sided coating areal density is 0.4 g / 1540.25 mm 2 .

[0170] (2) Preparation of the negative electrode sheet

[0171] After mixing artificial graphite, the conductive agent Super P, the thickening agent sodium carboxymethyl cellulose, and the binder styrene-butadiene rubber at a mass ratio of 96:1:1.2:1.8, deionized water is added as the solvent and stirred evenly to obtain the first negative electrode paste; among them, the average value of the longest diameter of the artificial graphite is 12 μm; the artificial graphite includes a graphite particle body and an amorphous carbon coating layer with a thickness of 200 nm provided on the surface of the graphite particle body. The graphitization degree of the artificial graphite is 92%.

[0172] Copper foil is used as the negative electrode current collector, and the negative electrode current collector includes a negative electrode main body portion and a negative electrode tab portion connected to the negative electrode main body portion, and the negative electrode tab portion is connected to the short side of the negative electrode main body portion. The above-prepared first negative electrode paste is evenly coated on both surfaces of the negative electrode main body portion, dried, and cold pressed to obtain the first negative electrode film layer; the single-sided coating areal density of the first negative electrode film layer is 0.1 g / 1540.25 mm 2 .

[0173] After mixing artificial graphite, conductive agent Super P, thickening agent sodium carboxymethyl cellulose, and binder styrene-butadiene rubber according to a mass ratio of 96:1:1.2:1.8, deionized water as a solvent was added and stirred evenly to obtain the second negative electrode slurry; among them, the average value of the longest diameter of the artificial graphite was 8 μm; the artificial graphite included a graphite particle body and an amorphous carbon coating layer with a thickness of 200 nm provided on the surface of the graphite particle body. The graphitization degree of the artificial graphite was 92%.

[0174] The second negative electrode slurry prepared above was evenly coated on the first negative electrode film layer on both sides of the surface of the negative electrode main body, dried and cold-pressed to obtain the second negative electrode film layer; after slitting, the negative electrode sheet was obtained. The single-sided coating areal density of the second negative electrode film layer was 0.1 g / 1540.25 mm 2 . The total single-sided coating areal density of the negative electrode film layer was 0.2 g / 1540.25 mm 2 . The compaction density of the negative electrode sheet was 1.42 g / cc.

[0175] (3)Separator

[0176] A polyethylene film with a thickness of 7 μm was used as the separator.

[0177] (4)Electrolyte

[0178] In a glove box with an argon atmosphere where the water content < 10 ppm, dimethyl carbonate, ethylene carbonate, and methyl acetate were mixed to obtain an organic solvent, and dry lithium salts LiPF6 and LiFSI were added. Fluoroethylene carbonate with a mass content of 1% was added as an additive to the above solution to obtain the electrolyte. Among them, 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 and methyl acetate was 1:1; the sum of the mass fractions of LiPF6 and LiFSI was 18%, and the mass ratio of LiPF6 and LiFSI was 2:1. The conductivity of the electrolyte at 25 °C was 15 mS / cm.

[0179] (5)Battery assembly

[0180] The positive electrode sheet, separator, and negative electrode sheet prepared above were stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining a stacked bare battery cell; moreover, the long side of the negative electrode main body exceeded the long side edge of the positive electrode main body by 5 mm to form an overhang region; the long side of the separator exceeded the long side edge of the negative electrode main body by 5 mm to form an overhang region. The stacked bare battery cell was placed in a soft package shell made of polypropylene with a thickness of 100 μm, dried and then injected with the electrolyte, and after processes such as vacuum packaging, standing, forming, and shaping, a lithium battery monomer was obtained.

[0181] Example 2:

[0182] This embodiment is basically the same as Embodiment 1, except that: in step (1), by adjusting the length of the positive electrode plate, the ratio of the long side dimension to the short side dimension of the positive electrode main body of the positive electrode plate is 3:1, and the short side dimension of the positive electrode main body remains unchanged.

[0183] Embodiment 3:

[0184] This embodiment is basically the same as Embodiment 1, except that: in step (1), by adjusting the length of the positive electrode plate, the ratio of the long side dimension to the short side dimension of the positive electrode main body of the positive electrode plate is 8:1, and the short side dimension of the positive electrode main body remains unchanged.

[0185] Embodiment 4:

[0186] This embodiment is basically the same as Embodiment 1, except that: in step (5), the long side of the negative electrode main body extends 2 mm beyond the long side edge of the positive electrode main body to form an overhang region; the long side of the separator extends 2 mm beyond the long side edge of the negative electrode main body to form an overhang region.

[0187] Embodiment 5:

[0188] This embodiment is basically the same as Embodiment 1, except that: in step (5), the long side of the negative electrode main body extends 7 mm beyond the long side edge of the positive electrode main body to form an overhang region; the long side of the separator extends 10 mm beyond the long side edge of the negative electrode main body to form an overhang region.

[0189] Embodiment 6:

[0190] This embodiment is basically the same as Embodiment 1, except that: in step (4), ethylene carbonate, methyl acetate and ethyl acetate are mixed to obtain an organic solvent, and dry lithium salts LiPF6 and LiFSI are added; 0.3% by mass of fluoroethylene carbonate is added as an additive to the above solution to obtain an electrolyte. Among them, 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 °C is 10 mS / cm.

[0191] Embodiment 7:

[0192] 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 artificial graphite in the second negative electrode slurry, the average value of the longest diameter of the artificial graphite in the first negative electrode film layer is 18 μm and the average value of the longest diameter of the artificial graphite in the second negative electrode film layer is 10 μm.

[0193] Example 8:

[0194] This example is basically the same as Example 1, except that: in step (2), the average value of the longest diameter of artificial graphite in the first negative electrode paste is 8 μm; the average value of the longest diameter of artificial graphite in the second negative electrode paste is 6 μm.

[0195] Comparative Example 1:

[0196] This comparative example is basically the same as Example 1, except that: in step (5), an overhang region is formed by making the long side of the negative electrode main body part exceed the long side edge of the positive electrode main body part by 1 mm; an overhang region is formed by making the long side of the separator exceed the long side edge of the negative electrode main body part by 1 mm.

[0197] Comparative Example 2:

[0198] This comparative example is basically the same as Example 1, except that: in step (1), by adjusting the length of the positive electrode plate, the ratio of the long side dimension to the short side dimension of the positive electrode main body part of the positive electrode plate is 10:1, and the short side dimension of the positive electrode main body part remains unchanged.

[0199] Comparative Example 3:

[0200] This comparative example is basically the same as Example 1, except that: in step (4), an organic solvent is obtained by mixing ethylene carbonate and propylene carbonate according to a volume ratio of 1:1.

[0201] Testing method:

[0202] (1) Energy density test

[0203] Charge the battery cell at 0.33C to 3.65V at 25 °C, and then perform constant voltage charging at 3.65V until 0.05C; let it stand for 5 minutes; discharge it at 0.33C to 2 V, and record the total discharge capacity C0 of the battery cell. The total discharge energy is E0, unit: Wh;

[0204] Measure the length, width and thickness of the battery cell, and calculate the volume denoted as V, unit: L;

[0205] The volume energy density of the battery cell = E0 / V, unit: Wh / L.

[0206] (2) Cycle performance test

[0207] First step: Charge the battery cell at 0.33C to 3.65V at 25 °C, and then perform constant voltage charging at 3.65V until 0.05C; let it stand for 5 minutes; discharge it at 0.33C to 2 V, and record the capacity at this time denoted as C0 (this step is the initial capacity of the actual test);

[0208] Step 2: Then charge the battery at 0.5C0 to 3.45V and at 0.33C0 to 3.65V; let it stand for 10 minutes; discharge it at 1C0 to 2V and at 0.33C to 2V until the capacity decays to less than or equal to 80% of the initial capacity, and record the number of cycles at this time.

[0209] (3)Self-discharge performance test of the battery

[0210] Let the battery cell stand for 1h at room temperature, and use a 6 1 / 2-digit digital multimeter to measure the initial open circuit voltage (Open Circuit Voltage, OCV) value of the battery cell, denoted as OCV1; after the test, let the battery cell stand for 120h at 45°C and then for 1h at room temperature, and measure the open circuit voltage value again, denoted as OCV2, and calculate the self-discharge rate. The calculation formula for the self-discharge rate is: (OCV2 - OCV1) / 120. Measure 10 battery cells and take the average value.

[0211] (4)Test of coating surface density of the film layer

[0212] The coating surface density is tested using the following method: Punch 15 pieces each of a 1540.25mm 2 pole piece and current collector (from the same production batch as the current collector used for the pole piece), weigh them, and take the average value. The average value of the pole piece mass is M1 (unit: g), and the average value of the current collector mass is M2 (unit: g); when the film layer is set on both sides of the current collector, the unilateral coating surface density is: (M1 - M2) / 2S.

[0213] (5)Test of compaction density of the pole piece

[0214] Disassemble the 0% SOC battery monomer to obtain the pole piece, and punch it into small round pieces with a diameter of 1540.25mm 2 Measure the weight M and thickness L of the small round pieces; take another layer of the pole piece, wipe off the film layer on the surface to leave only the empty current collector foil, and also punch it into small round pieces with a diameter of 1540.25mm 2 Measure the mass M0 of the empty current collector foil, then the compaction density PD = (M - M0) / 1.54025 / (L - L0), where L0 is the thickness of the current collector foil.

[0215] (6)Test of average value of the longest diameter of graphite

[0216] In the scanning electron microscope (SEM) image of the negative electrode film layer, randomly select 500 graphite particles, measure the longest diameter of each graphite particle, and then take the average value. Among them, 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.

[0217] 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 non-existence.

[0218] Table 1

[0219]

[0220] As can be seen from Table 1, the battery cells of the embodiments of the present application have a high energy density, and at the same time have good cycle performance and low self-discharge. Compared with Example 1, in Comparative Example 1, the distance by which the long side of the negative electrode main body exceeds the long side edge of the positive electrode main body is too small, and the distance by which the long side of the separator exceeds the long side edge of the negative electrode main body is too small, resulting in a decrease in the cycle performance of the battery cell and a significant increase in self-discharge. Compared with Example 1, in Comparative Example 2, the ratio of the long side dimension to the short side dimension of the positive electrode main body of the positive electrode sheet is too large. Although the energy density of the battery cell is increased to some extent, the cycle performance is significantly decreased, and it is difficult to balance the cycle performance. Compared with Example 1, in Comparative Example 3, dimethyl carbonate and the linear carboxylic acid ester having the structure of formula (1) are not used in the electrolyte solvent, resulting in a significant decrease in the cycle performance of the battery cell.

[0221] The descriptions of the above embodiments tend to emphasize the differences between the embodiments. Their similarities can be referred to each other. For the sake of brevity, they will not be elaborated herein.

[0222] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same function and effect as the technical idea within the technical solution scope of the present application are all included in the technical scope of the present application. In addition, within the scope of not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that, It includes a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte. The positive electrode sheet and the negative electrode sheet are stacked, and the separator is disposed between the positive electrode sheet and the negative electrode sheet; The positive electrode sheet includes a positive electrode main body portion and a positive electrode tab connected to the positive electrode main body portion. The ratio of the long side dimension to the short side dimension of the positive electrode main body portion is (3 to 8):1; The negative electrode sheet includes a negative electrode main body portion and a negative electrode tab connected to the negative electrode main body portion. The long side of the negative electrode main body portion extends 2 mm to 9 mm beyond the long side edge of the positive electrode main body portion, and the long side of the separator extends 2 mm to 10 mm beyond the long side edge of the negative electrode main body portion; The electrolyte includes a first solvent, and the first solvent includes one or more of dimethyl carbonate and a linear carboxylic acid ester having the structure shown in formula (1); R1-(C=O)-O-R2 Formula (1); Wherein, R1 and R2 each independently include an alkyl or haloalkyl group having 1 to 5 carbon atoms.

2. The battery cell according to claim 1, wherein, The ratio of the long side dimension to the short side dimension of the positive electrode main body portion is (4 to 6):

1.

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

4. The battery cell according to claim 1, wherein, The linear carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate and isopropyl formate.

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

6. The battery cell according to claim 5, wherein Based on the mass of the electrolyte, the mass fraction of the first solvent is 15% to 35%.

7. The battery cell according to any one of claims 1 to 4 and 6, characterized in that, The conductivity of the electrolyte at room temperature is 10 mS / cm to 16 mS / cm.

8. The battery cell according to any one of claims 1 to 4 and 6, characterized in that, The electrolyte further includes a lithium salt, and the lithium salt includes one or more of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide; based on the mass of the electrolyte, the total mass fraction of the lithium hexafluorophosphate and / or the lithium bis(fluorosulfonyl)imide is 12% to 18%.

9. The battery cell according to claim 8, wherein The mass ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide is (1.2 to 3):

1.

10. The battery cell according to any one of claims 1 to 4, 6, and 9, characterized in that The electrolyte further includes an additive, and the additive includes one or more of vinylene carbonate, fluoroethylene carbonate and 1,3-propane sultone.

11. The battery cell according to claim 10, wherein, Based on the mass of the electrolyte, the mass fraction of the additive is less than or equal to 5%.

12. The battery cell according to claim 11, wherein, Based on the mass of the electrolyte, the mass fraction of the additive is 0.5% to 3%.

13. The battery cell according to any one of claims 1 to 4, 6, 9, and 11 to 12, characterized in that, The positive electrode tab is connected to the short side of the positive electrode main body portion, and the negative electrode tab is connected to the short side of the negative electrode main body portion.

14. The battery cell according to any one of claims 1 to 4, 6, 9, 11 to 12, characterized in that, The battery cell further includes a soft package shell. The positive electrode sheet, the separator, the negative electrode sheet and the electrolyte are disposed in the soft package shell, and the thickness of the soft package shell is 70 μm to 200 μm.

15. The battery cell according to any one of claims 1 to 4, 6, 9, and 11 to 12, characterized in that, The negative electrode main body portion 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, and 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 value of the longest diameter of the graphite in the first negative electrode film layer is 7 μm to 18 μm, and the average value of the longest diameter of the graphite in the second negative electrode film layer is 6 μm to 10 μm. Moreover, the average value of the longest diameter of the graphite in the first negative electrode film layer is greater than the average value of the longest diameter of the graphite in the second negative electrode film layer.

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

17. The battery cell according to claim 15, wherein The graphitization degree of the graphite in both the first negative electrode film layer and the second negative electrode film layer is independently 90% to 94%.

18. The battery cell according to claim 15, wherein, The single-sided coating areal density of the negative electrode film layer is 0.13 g / 1540.25 mm 2 ~0.22 g / 1540.25 mm 2 .

19. The battery cell according to any one of claims 1 to 4, 6, 9, 11 to 12, and 16 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 battery cell according to any one of claims 1 to 4, 6, 9, 11 to 12, and 16 to 18, characterized in that The positive electrode main body includes a positive electrode current collector and a positive electrode film layer. The positive electrode film layer is provided on the positive electrode current collector. The positive electrode film layer includes a lithium-containing transition metal phosphate, and the lithium-containing transition metal phosphate includes one or more of aluminum element with a mass content of 200 ppm to 2500 ppm, vanadium element with a mass content of 300 ppm to 2000 ppm, and titanium element with a mass content of 1500 ppm to 3500 ppm.

21. The battery cell according to claim 20, characterized in that, The positive electrode main body further includes a bottom coating layer. The bottom coating layer is provided between the positive electrode current collector and the positive electrode film layer. The bottom coating layer includes a conductive agent, and the thickness of the bottom coating layer is 0.5 μm to 3 μm.

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

23. The battery cell according to any one of claims 1 to 4, 6, 9, 11 to 12, 16 to 18, 21 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, Including the battery cell according to any one of claims 1 to 23.

25. An electrical device, characterized in that, Including one or more of the battery cell according to any one of claims 1 to 23 and the battery device according to claim 24.

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