Battery monomer, preparation method thereof, battery and power utilization device

Abstract

The invention provides a battery monomer, a preparation method thereof, a battery and a power utilization device, the battery monomer comprises a shell, an electrode assembly and an electrolyte, and the electrode assembly comprises a positive pole piece and a negative pole piece. The electrode assembly comprises a main body part and a tab part extending out from one end of the main body part along a first direction X, the size of the negative pole piece is marked as H0 along the first direction X, the maximum size of the negative pole piece is marked as Hmax, the units are mm, H0 is smaller than or equal to Hmax, and Hmax is equal to 299.5 * (1-1 / Cap)-180.8 * D-5. 83 * eta-7.66 * P1-1.83 * P2. The parameters are defined in the description.

Description

Battery cell, preparation method thereof, battery and power-consuming device Technical Field

[0001] The present application relates to a battery cell, a preparation method thereof, a battery and an electrical device. Background Art

[0002] In recent years, batteries have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. High capacity is an irreversible trend in future battery development. Currently, the specific capacity and compaction density of the electrode materials used in batteries are difficult to significantly improve, making battery size design particularly critical. The above statements are intended only to provide background information related to this application and do not necessarily constitute prior art.

[0003] Summary of the Invention

[0004] The present application provides a battery cell, a preparation method thereof, a battery and an electrical device, which can enable the battery to have a long cycle life.

[0005] In a first aspect, the present application provides a battery cell, comprising a housing, an electrode assembly, and an electrolyte. The electrode assembly comprises a positive electrode sheet and a negative electrode sheet. The electrode assembly comprises a main body and an electrode ear extending from one end of the main body along a first direction X. Along the first direction X, the dimension of the negative electrode sheet is denoted as H0, and the maximum dimension of the negative electrode sheet is denoted as H. max , the unit is mm, then H0≤H max , and H max =299.5×(1-1 / Cap)-180.8×D-5.83×η-7.66×P1-1.83×P2. Cap is the initial capacity of the battery cell, and Cap≥350Ah; D is the depth of use of the battery cell, D=(initial capacity of the battery cell - guaranteed capacity of the battery cell) / initial capacity of the battery cell; η is the viscosity of the electrolyte, in mPa·s; P1 is the compacted density of the negative electrode sheet, in g / cm 3 ; P2 is the compaction density of the positive electrode sheet, in g / cm 3 .

[0006] Along the first direction X, the size H0 (ie, the actual size) of the negative electrode sheet of the battery cell provided by the present application is less than or equal to the maximum size H of the negative electrode sheet. max This can reduce the probability of insufficient electrolyte back-absorption, and can also enable the battery to have high capacity and high stability during long-term cycle charge and discharge, thereby enabling the battery to have a long cycle life.

[0007] In any embodiment, D is 20%-50%.

[0008] In any embodiment, η is 2-5 mPa·s.

[0009] In any embodiment, P1 is 1.0-2.5 g / cm 3 , optional 1.4-1.8g / cm 3 .

[0010] In any embodiment, P2 is 2.0-4.0 g / cm 3 , optional 2.2-2.7g / cm 3 .

[0011] In any embodiment, 0.8H max ≤H0≤H max , optionally, 0.88H max ≤H0≤H max .

[0012] In any embodiment, the electrode assembly is a flat body or a rectangular parallelepiped, and there are one or more electrode assemblies. The multiple electrode assemblies are arranged along the third direction Z. The size of the electrode assembly along the first direction X is denoted as H1, the size of the electrode assembly along the second direction Y is denoted as W1, and the size of the electrode assembly along the third direction Z is denoted as T1. All units are in mm, and then H1 = H0; 0.05 ≤ T1 / W1 ≤ 1; 0.1 ≤ H1 / W1 ≤ 10. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other. Adjusting T1 / W1 and H1 / W1 within the above ranges facilitates high battery capacity.

[0013] In any embodiment, 0.5≤H1 / W1≤1.5.

[0014] In any embodiment, the battery cell is a rectangular parallelepiped. The dimensions of the battery cell along the first direction X are denoted as H, along the second direction Y as W, and along the third direction Z as T, all in mm. Then, 0.05 ≤ T / W ≤ 1, and 0.1 ≤ H / W ≤ 10. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other. Adjusting the T / W and H / W ratios within the above ranges facilitates achieving a high battery capacity.

[0015] In any embodiment, 0.15≤T / W≤0.4.

[0016] In any embodiment, 0.5≤H / W≤1.5.

[0017] In any embodiment, 0 < H–H1 ≤ 20 mm. Thereby, the capacity and energy density of the battery can be improved.

[0018] In any embodiment, 0 < W–W1 ≤ 25 mm. Thereby, the capacity and energy density of the battery can be improved.

[0019] In any embodiment, W is 20 - 600 mm, and optionally 200 - 300 mm. By adjusting the size W of the battery cell along the second direction Y within the above range, it is beneficial to balance the current density on the surface of the negative electrode sheet and reduce the probability of local lithium deposition, thereby being beneficial to improving the cycle life and reliability of the battery.

[0020] In any embodiment, T is 10 - 100 mm, and optionally 50 - 80 mm. By adjusting the size T of the battery cell along the third direction Z within the above range, it is beneficial for the battery to dissipate heat better, and is beneficial to reducing the adverse effect of the increase in the battery operating temperature on the battery capacity, thereby enabling the battery to have a long cycle life.

[0021] In any embodiment, along the first direction X, the size of the positive electrode sheet is denoted as H′, then 0 ≤ H0–H′ ≤ 5 mm. Along the first direction X, the size of the negative electrode sheet is greater than or equal to that of the positive electrode sheet, thereby improving the capacity and energy density of the battery and reducing the lithium deposition problem.

[0022] In any embodiment, the porosity of the negative electrode sheet is 10 - 45%%, and optionally 18 - 40%. By adjusting the porosity of the negative electrode sheet, it is beneficial to improve the electrolyte wettability of the negative electrode sheet, thereby enabling the battery to have a long cycle life.

[0023] In any embodiment, the porosity of the positive electrode sheet is 10 - 45%, and optionally 18 - 40%. By adjusting the porosity of the positive electrode sheet, it is beneficial to improve the electrolyte wettability of the positive electrode sheet, thereby enabling the battery to have a long cycle life.

[0024] In any embodiment, the electrode assembly further includes a separator. Along the first direction X, the size of the separator is denoted as H″, then 0 < H″–H0 ≤ 10 mm. Along the first direction X, the size of the separator is greater than that of the negative electrode sheet, thereby reducing the probability of short - circuit between the positive and negative electrodes.

[0025] In any embodiment, the battery cell includes a lithium secondary battery cell.

[0026] In any embodiment, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate.

[0027] In any embodiment, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes one or more of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds, and the modification method includes doping modification and / or surface coating modification.

[0028] In any embodiment, the positive electrode active material includes one or more of a lithium-containing phosphate and a modifying compound.

[0029] When the positive electrode active material includes one or more of a lithium-containing phosphate and a modified compound, the probability of insufficient electrolyte reabsorption can be further reduced. Furthermore, the battery can exhibit higher capacity utilization and greater stability during long-term charge and discharge cycles, thereby extending the battery's cycle life. Furthermore, the battery can have a greater depth of use and can effectively delay, or even prevent, the accelerated decline in battery capacity.

[0030] The second aspect of the present application provides a method for preparing a battery cell, comprising the following steps: providing a negative electrode sheet, a separator, a positive electrode sheet and an electrolyte, wherein the compacted density of the negative electrode sheet is denoted as P1, and the unit is g / cm 3 The compacted density of the positive electrode is recorded as P2, and the unit is g / cm 3 , the viscosity of the electrolyte is recorded as η, in units of mPa·s, along the first direction X, the size of the negative electrode sheet is recorded as H0, in units of mm, and H0≤299.5×(1-1 / Cap)-180.8×D-5.83×η-7.66×P1-1.83×P2, Cap is the initial capacity of the battery cell, and Cap≥350Ah, D is the usage depth of the battery cell, D=(initial capacity of the battery cell-guaranteed capacity of the battery cell) / initial capacity of the battery cell; the negative electrode sheet, the separator and the positive electrode sheet are stacked in sequence to form an electrode assembly, the electrode assembly comprising a main body and a pole ear portion extending from one end of the main body along the first direction X; the electrode assembly is placed in a shell, and the electrolyte is injected to obtain a battery cell.

[0031] In any embodiment, the electrode assembly is a wound electrode assembly or a laminated electrode assembly.

[0032] A third aspect of the present application provides a battery, comprising the battery cell of the first aspect of the present application or the battery cell prepared by the method of the second aspect of the present application.

[0033] A fourth aspect of the present application provides an electrical device comprising the battery of the third aspect of the present application, wherein the battery is used to provide electrical energy.

[0034] The battery provided in the present application may have a long cycle life, and the electrical device provided in the present application includes the battery provided in the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0036] FIG1 is a schematic diagram of the dimensions of an electrode assembly provided in some embodiments of the present application.

[0037] FIG2 is a schematic diagram of the dimensions of electrode assemblies provided in other embodiments of the present application.

[0038] FIG3 is a schematic structural diagram of a battery cell provided in some embodiments of the present application.

[0039] FIG4 is an exploded schematic diagram of a battery cell provided in some embodiments of the present application.

[0040] FIG5 is a schematic structural diagram of a battery module provided in some embodiments of the present application.

[0041] FIG6 is a schematic structural diagram of a battery pack provided in some embodiments of the present application.

[0042] FIG. 7 is an exploded schematic diagram of the battery pack shown in FIG. 4 .

[0043] FIG8 is a schematic diagram of an electrical device provided in some embodiments of the present application.

[0044] FIG9 is a cycle curve diagram of the battery cell prepared in Example 1.

[0045] FIG10 is a cycle curve diagram of the battery cell prepared in Comparative Example 1.

[0046] FIG11 is a cycle curve diagram of the battery cell prepared in Comparative Example 2.

[0047] In the accompanying drawings, which are not necessarily drawn to scale, the reference numerals are as follows: 1, battery pack; 2, first housing; 3, second housing; 4, battery module; 5, battery cell; 51, housing; 52, electrode assembly; 521, main body; 522, tab; 523, current collecting member; 53, end cap assembly; 531, electrode terminal. DETAILED DESCRIPTION

[0048] Below, the battery cells, methods for preparing the same, batteries, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0049] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0051] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0052] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0053] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0054] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0055] Unless otherwise specified, in this application, the terms "first", "second", "third", etc. are used to distinguish different objects rather than to describe a specific order or a primary-secondary relationship.

[0056] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0057] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0058] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack, etc. A battery cell is the smallest unit that makes up a battery, which can independently realize the function of charging and discharging. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in mixed connection through a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a case and battery cells, and the battery cells or battery modules are housed in the case. In some embodiments, the case may serve as part of the chassis structure of the vehicle. For example, part of the case may become at least part of the floor of the vehicle, or part of the case may become at least part of the crossbeam and longitudinal beam of the vehicle.

[0059] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0060] The battery cells provided in the embodiments of the present application include lithium secondary battery cells.

[0061] The battery cell provided in the embodiments of the present application includes a housing, an electrode assembly, and an electrolyte.

[0062] The electrode assembly comprises a main body and a tab extending from one end of the main body along a first direction X. The main body is the core component of the electrode assembly that performs the charge and discharge functions, and the tab is used to conduct the current generated by the main body. In some embodiments, there may be two tabs, defined as a positive electrode tab and a negative electrode tab, respectively. The positive and negative electrode tabs may extend from the same end of the main body or from opposite ends of the main body.

[0063] Figure 1 is a schematic diagram of the dimensions of electrode assemblies provided in some embodiments of the present application. Figure 2 is a schematic diagram of the dimensions of electrode assemblies provided in other embodiments of the present application. As shown in Figure 1, two electrode ears 522 extend from the same end of the main body 521 of the electrode assembly 52. ​​As shown in Figure 2, the two electrode ears 522 extend from opposite ends of the main body 521 of the electrode assembly 52.

[0064] Along the first direction X, the size of the negative electrode sheet in the electrode assembly is recorded as H0, and the maximum size of the negative electrode sheet is recorded as H max , the unit is mm, then H0≤H max , and H max =299.5×(1-1 / Cap)-180.8×D-5.83×η-7.66×P1-1.83×P2.

[0065] Cap is the initial capacity of the battery cell, and Cap ≥ 350Ah.

[0066] D is the battery cell's depth of use, D = (battery cell's initial capacity - battery cell's guaranteed capacity) / battery cell's initial capacity. The battery cell's guaranteed capacity can be obtained from the battery cell's product specifications.

[0067] η is the viscosity of the electrolyte, in mPa·s.

[0068] P1 is the compaction density of the negative electrode sheet, in g / cm 3 .

[0069] P2 is the compaction density of the positive electrode sheet, in g / cm 3 .

[0070] In order to balance the energy density and cost of the battery, the amount of electrolyte injected is usually not too large. However, as the number of charge and discharge cycles of the battery increases, the active lithium inside the battery is continuously consumed. Most of the consumed active lithium accumulates on the surface of the negative electrode active material particles in the form of side reaction products, which will cause the gaps between the negative electrode active material particles to continue to decrease, and thus cause the negative electrode plate's ability to absorb the electrolyte to deteriorate. The deterioration of the negative electrode plate's ability to absorb the electrolyte will lead to poor electrolyte wettability of the negative electrode plate, and will also make the lithium ion transmission path longer and the battery interface impedance increase. As a result, after the battery capacity decays to a certain extent, the capacity decay rate increases rapidly, resulting in a shorter cycle life of the battery.

[0071] Furthermore, as demands for energy storage battery capacity continue to rise, battery usage depth will also increase, requiring batteries with higher initial capacities. However, as battery usage depth increases, the time at which capacity decay accelerates, impacting the battery's cycle life. Furthermore, the gram capacity and coating weight of current battery electrode materials are difficult to significantly improve, making battery size design particularly critical.

[0072] The size design of the negative electrode plate not only affects the capacity of the battery, but also affects the cycle life of the battery. The inventors have found that for high-capacity batteries (initial capacity Cap ≥ 350Ah), along the first direction X, the negative electrode plate has a maximum size (or critical size) H max , the actual size H0 of the negative electrode exceeds the maximum size H max After that, the electrolyte wettability of the negative electrode plate is poor and the electrolyte absorption is insufficient, which leads to poor cycle performance of the battery. Especially when the battery is deeply discharged, the battery capacity is prone to accelerated decay, and the battery quickly reaches the usage depth D, which leads to a short cycle life of the battery.

[0073] The inventors further studied and found that along the first direction X, the maximum size H of the negative electrode sheet max It is related to the initial capacity of the battery cell, the depth of use of the battery cell, the viscosity of the electrolyte, the compaction density of the negative electrode sheet, and the compaction density of the positive electrode sheet. As the depth of use of the battery cell increases, the maximum size H of the negative electrode sheet increases. max becomes smaller; the viscosity of the electrolyte increases, and the maximum size H of the negative electrode sheet max The compaction density of the negative electrode sheet increases, the porosity of the negative electrode sheet decreases, the electrolyte's wetting ability and resorption ability deteriorate, and the maximum size H of the negative electrode sheet increases. max The compaction density of the positive electrode sheet increases, the porosity of the positive electrode sheet decreases, the electrolyte's wetting ability and resorption ability deteriorate, and the maximum size H of the negative electrode sheet increases. max Become smaller.

[0074] The inventors further discovered that for high-capacity batteries (initial capacity Cap≥350Ah), along the first direction X, the maximum dimension H of the negative electrode sheet is max Satisfies the following relationship: H max =299.5×(1-1 / Cap)-180.8×D-5.83×η-7.66×P1-1.83×P2.

[0075] Along the first direction X, the size H0 (ie, the actual size) of the negative electrode sheet of the battery cell provided in the embodiment of the present application is less than or equal to the maximum size H of the negative electrode sheet. max This can reduce the probability of insufficient electrolyte back-absorption, and can also enable the battery to have high capacity and high stability during long-term charge and discharge cycles, thereby enabling the battery to have a long cycle life. In particular, the battery cells provided by the embodiments of the present application can have a large depth of use.

[0076] Along the first direction X, the maximum dimension H of the negative electrode sheet max It can be calculated by the above formula.

[0077] The dimension H0 of the negative electrode tab along the first direction X can be obtained by measurement. During testing, the negative electrode tab can be removed from a fully charged battery cell and its width can be measured using a tape measure or other tool. The measurements can be taken at multiple random points (e.g., five or more) and the average value calculated.

[0078] In some embodiments, the depth of use D of the battery cell can be 10%-50%, optionally 20%-50%. For example, the depth of use D of the battery cell can be 10%, 20%, 30%, 40%, 50%, or a range consisting of any of the above values, and the embodiments of the present application are not limited to this. When the depth of use D of the battery cell increases, the time when the capacity of the battery cell accelerates to decay is advanced, and the size H0 of the negative electrode sheet of the battery cell is less than or equal to the maximum size H of the negative electrode sheet. max , which can delay the time when the capacity of the battery cell decays at an accelerated rate, or even avoid the accelerated capacity decay of the battery cell, thereby enabling the battery to have high capacity and high stability during long-term cycle charge and discharge, and thus enabling the battery to have a long cycle life.

[0079] In some embodiments, the viscosity η of the electrolyte may be 2-5 mPa·s. For example, the viscosity η of the electrolyte may be 2 mPa·s, 3 mPa·s, 4 mPa·s, 5 mPa·s, or any range thereof, and the present invention is not limited thereto.

[0080] In some embodiments, the compaction density P1 of the negative electrode sheet can be 1.0-2.5 g / cm 3 For example, the compaction density P1 of the negative electrode sheet can be 1.0 g / cm 3 , 1.2g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , or a range composed of any of the above numerical values, which is not limited by the embodiments of the present application. The compaction density of the negative electrode sheet is related to the composition of the negative electrode sheet, for example, it is related to parameters such as the type, structure and content ratio of the negative electrode active material. By adjusting the composition of the negative electrode sheet, the compaction density of the negative electrode sheet can be adjusted. Optionally, the compaction density P1 of the negative electrode sheet can be 1.4-1.8g / cm 3 .

[0081] In some embodiments, the compaction density P2 of the positive electrode sheet can be 2.0-4.0 g / cm3 For example, the compaction density P2 of the positive electrode sheet can be 2.0 g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 , 2.7g / cm 3 , 2.8g / cm 3 , 2.9g / cm 3 , 3.0g / cm 3 , 3.1g / cm 3 , 3.2g / cm 3 , 3.3g / cm 3 , 3.4g / cm 3 , 3.5g / cm 3 , 3.6g / cm 3 , 3.7g / cm 3 , 3.8g / cm 3 , 3.9g / cm 3 , 4.0g / cm 3 , or a range composed of any of the above numerical values, which is not limited by the embodiments of the present application. The compaction density of the positive electrode sheet is related to the composition of the positive electrode sheet, for example, it is related to parameters such as the type, structure and content ratio of the positive electrode active material. By adjusting the composition of the positive electrode sheet, the compaction density of the positive electrode sheet can be adjusted. Optionally, the compaction density P2 of the positive electrode sheet can be 2.2-2.7g / cm 3 .

[0082] In some embodiments, 0.8H max ≤H0≤H max , optionally, 0.88H max ≤H0≤H max , 0.91H max ≤H0≤H max , 0.94H max ≤H0≤H max , 0.97H max ≤H0≤H max , 0.98H max ≤H0≤H max , 0.99H max ≤H0≤H max By further adjusting the size H0 of the negative electrode and the maximum size H max The relationship between the two can make the battery have both long cycle life and high capacity.

[0083] In some embodiments, the electrode assembly further includes a separator, which is located between the positive electrode sheet and the negative electrode sheet to prevent internal short circuits in the battery cell.

[0084] The battery cell may be cylindrical or rectangular, and may also be a soft-pack structure, which is not limited in the embodiments of the present application.

[0085] Figure 3 is a schematic diagram of the structure of a battery cell provided in some embodiments of the present application. Figure 4 is a schematic diagram of the exploded structure of a battery cell provided in some embodiments of the present application.

[0086] As shown in FIG3 and FIG4 , the battery cell 5 provided in some embodiments of the present application is a rectangular parallelepiped. The battery cell 5 includes a shell 51 , an electrode assembly 52 , an electrolyte (not shown) and an end cap assembly 53 .

[0087] The housing 51 has an opening. The end cap assembly 53 covers the opening of the housing 51 to form a receiving chamber for receiving the electrode assembly 52 and the electrolyte.

[0088] In some embodiments, the end cap assembly 53 includes an end cap that covers the opening of the housing 51. The end cap can have various structures, such as a plate-like structure, a hollow structure with one end open, etc. For example, in FIG4 , the housing 51 is a rectangular parallelepiped structure, and the end cap is a plate-like structure that covers the opening at the top of the housing 51.

[0089] The end cap can be made of an insulating material (e.g., plastic) or a conductive material (e.g., metal). When the end cap is made of a conductive material, the end cap assembly can further include an insulating member located on the side of the end cap facing the electrode assembly 52 to insulate the end cap from the electrode assembly 52.

[0090] In some embodiments, the end cap assembly 53 may further include an electrode terminal 531 mounted on the end cap. There may be two electrode terminals 531, each defined as a positive electrode terminal and a negative electrode terminal. Both the positive electrode terminal and the negative electrode terminal are used to electrically connect to the electrode assembly 52 to output the electrical energy generated by the electrode assembly 52.

[0091] In some embodiments, the shell 51 is a hollow structure with an opening on one side, and the end cover assembly 53 covers the opening of the shell 51 to form a receiving cavity for accommodating the electrode assembly 52 and the electrolyte.

[0092] In other embodiments, the housing 51 is a hollow structure with two opposing openings, and the battery cell 5 includes two end cap assemblies 53. Each end cap assembly 53 covers one opening of the housing 51 to form a chamber for accommodating the electrode assembly 52 and the electrolyte. In this structure, one end cap assembly 53 may be provided with two electrode terminals while the other end cap assembly 53 is not provided with an electrode terminal, or both end cap assemblies 53 may each be provided with an electrode terminal.

[0093] The pole ear portion 522 is used to electrically connect to the electrode terminal 531. The pole ear portion 522 can be directly connected to the electrode terminal 531 by welding or other methods, or it can be indirectly connected to the electrode terminal 531 through other components. For example, as shown in Figure 4, the electrode assembly 52 also includes a current collecting member 523, which is used to electrically connect the electrode terminal 531 and the pole ear portion 522. There are two current collecting members 523, and the two current collecting members are defined as a positive current collecting member and a negative current collecting member, respectively. The positive current collecting member is used to electrically connect the positive electrode terminal and the positive pole ear portion, and the negative current collecting member is used to electrically connect the negative electrode terminal and the negative pole ear portion. When the battery cell 5 is provided with multiple electrode assemblies 52, the positive current collecting members of the multiple electrode assemblies 52 can be provided as a whole, and the negative current collecting members of the multiple electrode assemblies 52 can be provided as a whole.

[0094] The number of electrode assemblies contained in a battery cell may be one or more. For example, in FIG4 , there are two electrode assemblies.

[0095] The electrode assembly can be a wound electrode assembly or a laminated electrode assembly, which is not limited in the present embodiment. For example, in FIG4 , the electrode assembly is a wound electrode assembly.

[0096] The shape of the electrode assembly can be a cylinder, a flat body or a rectangular parallelepiped, which is not limited in the present embodiment. For example, in FIG4 , the electrode assembly is a flat body.

[0097] In some embodiments, the electrode assembly may be a wound electrode assembly. The positive electrode sheet, negative electrode sheet, and separator are all in a strip-like structure. For example, the positive electrode sheet, separator, and negative electrode sheet may be stacked in sequence and wound two or more times to form the electrode assembly.

[0098] In other embodiments, the electrode assembly may be a laminated electrode assembly. Specifically, the electrode assembly includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, wherein the positive electrode sheets and the negative electrode sheets are alternately stacked, and the stacking direction is parallel to the thickness direction of the positive electrode sheets and the thickness direction of the negative electrode sheets.

[0099] In some embodiments, the electrode assembly can be a flat body or a rectangular parallelepiped. The size of the electrode assembly along the first direction X is recorded as H1, the size of the electrode assembly along the second direction Y is recorded as W1, and the size of the electrode assembly along the third direction Z is recorded as T1. The units are all mm, then H1=H0, 0.05≤T1 / W1≤1, 0.1≤H1 / W1≤10.

[0100] Optionally, 0.5≤H1 / W1≤1.5.

[0101] The first direction X, the second direction Y, and the third direction Z are perpendicular to each other. The first direction X can be defined as the height direction of the battery cell, the second direction Y can be defined as the width direction of the battery cell, and the third direction Z can be defined as the thickness direction of the battery cell.

[0102] As shown in Figures 1 and 2, the dimension H1 of the electrode assembly 52 refers to the dimension of the main body 521 of the electrode assembly 52 in the first direction X. In the embodiment of the present application, the dimension H1 of the electrode assembly is defined as the dimension H0 of the negative electrode tab. The dimension W1 of the electrode assembly refers to the dimension of the main body 521 of the electrode assembly in the second direction Y.

[0103] The number of electrode assemblies included in a battery cell may be one or more, and the multiple electrode assemblies are arranged along the third direction Z. The size T1 of the electrode assembly 52 refers to the size of the main body 521 of one electrode assembly 52 in the third direction Z.

[0104] The dimensions of the electrode assembly in the first direction, the second direction, and the third direction may affect the capacity of the battery. Adjusting T1 / W1 and H1 / W1 within the above ranges is beneficial for the battery to have a high capacity.

[0105] Along the second direction Y, the dimension W1 of the electrode assembly can be measured by a laser thickness gauge. During the test, 3-5 points can be randomly selected and the average value can be taken.

[0106] Along the third direction Z, the dimension T1 of the electrode assembly can be measured by a laser thickness gauge. During the test, 9 points can be randomly selected and the average value can be taken.

[0107] In some embodiments, the battery cell may be a rectangular parallelepiped. The size of the battery cell along the first direction X is denoted as H, the size of the battery cell along the second direction Y is denoted as W, and the size of the battery cell along the third direction Z is denoted as T. The units are all mm, and 0.05≤T / W≤1, 0.1≤H / W≤10.

[0108] The first direction X, the second direction Y, and the third direction Z are perpendicular to each other pairwise. The first direction X can be defined as the height direction of the battery cell, the second direction Y can be defined as the width direction of the battery cell, and the third direction Z can be defined as the thickness direction of the battery cell. The dimensions of the battery cell in the first, second, and third directions will affect the capacity of the battery. Adjusting T / W and H / W within the above ranges is beneficial for the battery to have a high capacity.

[0109] Optionally, 0.15 ≤ T / W ≤ 0.4.

[0110] Optionally, 0.5 ≤ H / W ≤ 1.5.

[0111] In some embodiments, W can be 20 - 600 mm, optionally 200 - 300 mm. By adjusting the dimension W of the battery cell along the second direction Y within the above range, it is beneficial to balance the current density on the surface of the negative electrode plate and reduce the probability of local lithium plating, thereby being beneficial to improving the cycle life and reliability of the battery.

[0112] In some embodiments, T can be 10 - 100 mm, optionally 50 - 80 mm. By adjusting the dimension T of the battery cell along the third direction Z within the above range, it is beneficial for the battery to dissipate heat better, beneficial to reducing the adverse effect of the increase in the battery operating temperature on the battery capacity, and thus the battery can have a long cycle life.

[0113] As shown in Figure 3, along the first direction X, the dimension H of the battery cell refers to the dimension of the main body part (excluding the electrode terminals) of the battery cell in the first direction X. For example, it can be the distance between the upper surface of the end cap of the battery cell and the outer side of the bottom surface of the housing.

[0114] Along the first direction X, the dimension H of the battery cell can be measured by a laser thickness gauge. When testing, 3 - 5 points can be randomly selected and then the average value is taken.

[0115] Along the second direction Y, the dimension W of the battery cell can be measured by a laser thickness gauge. When testing, 3 - 5 points can be randomly selected and then the average value is taken.

[0116] Along the third direction Z, the dimension T of the battery cell can be measured by a laser thickness gauge. When testing, 9 points can be randomly selected and then the average value is taken.

[0117] In some embodiments, 0 < H – H1 ≤ 20 mm. The dimensional difference between the battery cell and the electrode assembly in the first direction is small, thereby improving the capacity and energy density of the battery.

[0118] In some embodiments,

[0119] In some embodiments, along the first direction X, the size of the positive electrode sheet in the electrode assembly is denoted as H′, and 0 ≤ H0–H′ ≤ 5 mm. Along the first direction X, the size of the negative electrode sheet is greater than or equal to the size of the positive electrode sheet, whereby the capacity and energy density of the battery can be increased, and the problem of lithium deposition can also be reduced.

[0120] In some embodiments, along the first direction X, the size of the separator in the electrode assembly is denoted as H″, and 0 < H″–H0 ≤ 10 mm. Along the first direction X, the size of the separator is greater than the size of the negative electrode sheet, whereby the probability of short circuit between the positive electrode and the negative electrode can be reduced.

[0121] In some embodiments, the porosity of the negative electrode sheet can be 10-45%, and optionally 18-40%. By adjusting the porosity of the negative electrode sheet, it is beneficial to improve the electrolyte wettability of the negative electrode sheet, whereby the battery can have a long cycle life.

[0122] In some embodiments, the porosity of the positive electrode sheet can be 10-45%, and optionally 18-40%. By adjusting the porosity of the positive electrode sheet, it is beneficial to improve the electrolyte wettability of the positive electrode sheet, whereby the battery can have a long cycle life.

[0123] In some embodiments, the porosity of the separator can be 10-90%, and optionally 25-60%.

[0124] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. The negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0125] The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can adopt materials well-known in the art. As an example, the negative electrode active material can include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials can include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based materials can include one or more of elemental tin, tin oxide, and tin alloy materials.

[0126] In some embodiments, the negative electrode active material layer may also optionally include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent can include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the negative electrode active material layer may further optionally include a negative electrode binder. The present application does not particularly limit the type of negative electrode binder. As an example, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0128] In some embodiments, the negative electrode active material layer may further include other auxiliary agents. For example, the other auxiliary agents may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0129] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0130] The negative electrode active material layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0131] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in some embodiments, the negative electrode plate may further include a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode active material layer.

[0132] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode current collector has two surfaces that face each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0133] The positive electrode active material layer includes a positive electrode active material, which may be a material known in the art. For example, the positive electrode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates, and modified compounds thereof.

[0134] Examples of the lithium transition metal oxide may include 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, lithium nickel cobalt aluminum oxide, and modified compounds thereof.

[0135] Examples of lithium-containing phosphates may include 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 iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and modified compounds thereof.

[0136] In some embodiments, the positive electrode active material may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333),LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622),LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 One or more of O2, LiFePO4 and LiMnPO4.

[0137] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0138] In some embodiments, the positive electrode active material may include one or more of a lithium-containing phosphate and a modified compound. The inventors further discovered that when the positive electrode active material includes one or more of a lithium-containing phosphate and a modified compound, by further using a battery having the negative electrode sheet size provided in the embodiment of the present application (i.e., the actual size H0 of the negative electrode sheet is less than or equal to the maximum size H0 of the negative electrode sheet), the positive electrode active material may include one or more of a lithium-containing phosphate and a modified compound. max), can better reduce the probability of insufficient electrolyte back-absorption, and can also make the battery have higher capacity and higher stability during long-term cycle charge and discharge, so that the battery can have a longer cycle life. In addition, the above-mentioned positive electrode sheet (that is, the positive electrode active material includes one or more of lithium-containing phosphate and modified compounds) and the negative electrode sheet (that is, the actual size H0 of the negative electrode sheet is less than or equal to the maximum size H of the negative electrode sheet) are used. max ) batteries can also have a greater depth of use, and can better delay the time when the battery capacity decays at an accelerated rate, or even avoid the accelerated decay of the battery capacity.

[0139] In some embodiments, the positive electrode active material layer may further include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. As examples, the positive electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] In some embodiments, the positive electrode active material layer may further optionally include a positive electrode binder. The present application does not particularly limit the type of positive electrode binder. As an example, the positive electrode 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 fluorine-containing acrylic resin.

[0141] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0142] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0143] The electrolyte includes lithium salt and solvent.

[0144] The lithium salt may include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0145] In some embodiments, the concentration of the lithium salt in the electrolyte may be 0.7-1.8 mol / L, optionally 0.8-1.4 mol / L, or 0.9-1.2 mol / L.

[0146] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, the solvent can include one or more of cyclic carbonates, chain carbonates, carboxylates, sulfones, etc. Alternatively, the solvent can include cyclic carbonates and chain carbonates.

[0147] As an example, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE). Alternatively, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC).

[0148] More optionally, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC) and one or more of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC).

[0149] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0150] In some embodiments, the additive may include vinylene carbonate (VC). Optionally, the weight content of vinylene carbonate (VC) is less than or equal to 5% of the total weight of the electrolyte, and optionally less than or equal to 3% of the total weight of the electrolyte.

[0151] The separator is placed between the positive and negative electrodes to prevent short circuits between the positive and negative electrodes while allowing lithium ions to pass through. This application does not specifically limit the type of separator; any known porous separator with good chemical and mechanical stability can be used.

[0152] In some embodiments, the material of the isolation membrane can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different.

[0153] The viscosity of the electrolyte is well known in the art and can be measured using methods and instruments known in the art. For example, a viscometer can be used to measure the viscosity according to the viscosity measurement method in GB / T 10247-2008. The test temperature is 25°C.

[0154] The electrolyte can be sampled and analyzed during the preparation process of the battery cell, or can be sampled and analyzed from the prepared battery cell (such as the battery cell after formation or the battery cell leaving the factory).

[0155] The compacted density of the negative electrode and the positive electrode is a well-known meaning in the art, and can be tested using methods and instruments known in the art. The compacted density of the electrode = the surface density of the active material layer / the thickness of the active material layer. The thickness of the active material layer is a well-known meaning in the art, and can be tested using methods and instruments known in the art, for example, it can be tested using a micrometer. The surface density of the active material layer is a well-known meaning in the art, and can be tested using methods and instruments known in the art. For example, a single-sided coated and cold-pressed electrode can be taken (if it is a double-sided coated electrode, the active material layer on one side can be wiped off first), punched into small discs with an area of ​​S1, weighed, and recorded as M1; then the active material layer of the weighed electrode is wiped off, and the weight of the current collector is weighed, recorded as M0; the surface density of the active material layer = (M1-M0) / S1.

[0156] The porosity of the negative electrode and the positive electrode is well known in the art and can be tested using methods and instruments known in the art. An exemplary test method is as follows: take a single-sided coated and cold-pressed electrode (if it is a double-sided coated electrode, the active material layer on one side can be wiped off first), punch it into small disc samples of a certain area, and calculate the apparent volume V1 of the electrode; refer to GB / T 24586-2009, use an inert gas (such as helium or nitrogen) as the medium, adopt the gas replacement method, and use a true density tester to measure the true volume V2 of the electrode. The porosity of the electrode = (V1-V2) / V1×100%. Multiple pieces (such as 30 pieces) of electrode samples with good appearance and no powder falling on the edges can be taken for testing, and the results are averaged, thereby improving the accuracy of the test results. The testing instrument can be a Micromeritics AccuPyc II 1340 true density tester.

[0157] The porosity of the separator is well known in the art and can be tested using methods and instruments known in the art. For example, the test can be performed with reference to GB / T 36276-2018.

[0158] The initial capacity of a battery cell is a well-known term in the art and can be tested using methods and instruments known in the art. An exemplary test method is as follows: at 25°C, allow the battery cell (e.g., a formed battery cell or a factory-produced battery cell) to rest for 30 minutes, then discharge it at a constant current of 1 / 3C to the lower cutoff voltage. The initial capacity Cap of the battery cell is then tested as follows: first, allow the battery cell to rest for 30 minutes, then charge it at a constant current of 1 / 3C to the upper cutoff voltage, then charge it at a constant voltage until the current is less than 0.05C. The resulting capacity is recorded as the battery cell's charge capacity. Allow the battery cell to rest for 30 minutes, then discharge it at a constant current of 1 / 3C to the lower cutoff voltage. The resulting capacity is recorded as the battery cell's charge capacity. Repeat this process twice. The average of the three discharge capacities is taken as the battery cell's initial capacity Cap.

[0159] An embodiment of the present application also provides a method for preparing the above-mentioned battery cell.

[0160] The method comprises the following steps: providing a negative electrode sheet, a separator, a positive electrode sheet and an electrolyte, wherein the compaction density of the negative electrode sheet is denoted as P1, and the unit is g / cm 3 The compacted density of the positive electrode is recorded as P2, and the unit is g / cm 3, the viscosity of the electrolyte is recorded as η, and the unit is mPa·s. The size of the negative electrode sheet along the first direction X is recorded as H0, and the unit is mm, and H0≤299.5×(1-1 / Cap)-180.8×D-5.83×η-7.66×P1-1.83×P2, Cap is the initial capacity of the battery cell, and Cap≥350Ah, D is the usage depth of the battery cell, D=(initial capacity of the battery cell-guaranteed capacity of the battery cell) / initial capacity of the battery cell; the negative electrode sheet, the separator and the positive electrode sheet are stacked in sequence to form an electrode assembly, the electrode assembly includes a main body and a pole ear portion extending from one end of the main body along the first direction X; the electrode assembly is placed in a shell, and the electrolyte is injected to obtain a battery cell.

[0161] The battery assembly may be a wound electrode assembly or a laminated electrode assembly, which is not limited in the embodiments of the present application.

[0162] FIG5 is a schematic structural diagram of a battery module provided in some embodiments of the present application.

[0163] As shown in FIG5 , in some embodiments, battery cells 5 can be assembled into a battery module 4. In a battery module 4, there can be one or more battery cells 5 , and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module 4.

[0164] If there are multiple battery cells 5, they can be connected in series, in parallel, or in a hybrid configuration. A hybrid configuration refers to a combination of series and parallel connections within the battery cells 5. Multiple battery cells 5 can be directly connected in series, in parallel, or in a hybrid configuration. Alternatively, multiple battery cells 5 can be first connected in series, in parallel, or in a hybrid configuration to form a battery module 4, and then multiple battery modules 4 can be connected in series, in parallel, or in a hybrid configuration to form a complete unit. Multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Alternatively, they can be arranged in any other configuration. Furthermore, the multiple battery cells 5 can be secured using fasteners.

[0165] Figure 6 is a schematic diagram of the structure of a battery pack provided in some embodiments of the present application. Figure 7 is an exploded schematic diagram of the battery pack shown in Figure 6.

[0166] As shown in Figures 6 and 7, in some embodiments, the above-mentioned battery modules 4 can also be assembled into a battery pack 1. The number of battery modules 4 contained in the battery pack 1 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 1.

[0167] In some embodiments, the battery pack 1 includes multiple battery modules 4 and a housing. When there are multiple battery cells 5, the battery cells 5 are first connected in series, parallel, or in a hybrid fashion to form the battery module 4. The battery modules 4 are then connected in series, parallel, or in a hybrid fashion to form a single unit, which is then housed in the housing.

[0168] The multiple battery cells 5 in the battery module 4 can be electrically connected via a busbar component to achieve parallel connection, series connection, or mixed connection of the multiple battery cells 5 in the battery module 4 .

[0169] The box body is used to accommodate the battery cells 5, and the box body can be of various structures. In some embodiments, the box body can include a first box body portion 2 and a second box body portion 3, the first box body portion 2 and the second box body portion 3 covering each other, and the first box body portion 2 and the second box body portion 3 together define a second storage space for accommodating the battery cells 5. The second box body portion 3 can be a hollow structure with one end open, the first box body portion 2 is a plate-shaped structure, and the first box body portion 2 covers the open side of the second box body portion 3 to form a box body with a second storage space; the first box body portion 2 and the second box body portion 3 can also be a hollow structure with one side open, and the open side of the first box body portion 2 covers the open side of the second box body portion 3 to form a box body with a second storage space. Of course, the first box body portion 2 and the second box body portion 3 can be of various shapes, for example, cylinders, cuboids, etc.

[0170] In order to improve the sealing performance after the first box body 2 and the second box body 3 are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body 2 and the second box body 3.

[0171] Assuming that the first box body 2 covers the top of the second box body 3, the first box body 2 can also be called an upper box cover, and the second box body 3 can also be called a lower box.

[0172] In some embodiments, multiple battery cells 5 can also be directly assembled into a battery pack 1 .

[0173] The embodiments of the present application also provide an electrical device, which includes a battery provided in the embodiments of the present application, and the battery is used to provide electrical energy. The battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0174] The electrical device can select a specific type of battery, such as a battery cell, a battery module, or a battery pack, according to its usage requirements.

[0175] Figure 8 is a schematic diagram of an exemplary electrical device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's high power and high energy density requirements, a battery pack or battery module can be used as a power source.

[0176] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0177] Example

[0178] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0179] Example 1

[0180] Preparation of positive electrode

[0181] The positive electrode active material LiFePO4, the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) are thoroughly stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 97:1:2 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on both surfaces of the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet. The coating weight of a single side of the positive electrode sheet is 0.302mg / 1540.25mm 2 The compaction density P2 of the positive electrode is 2.4g / cm 3 .

[0182] Preparation of negative electrode sheet

[0183] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were mixed in an appropriate amount of deionized water at a weight ratio of 95:2:1:2 to form a uniform negative electrode slurry. The negative electrode slurry was evenly coated on both surfaces of the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet. The coating weight of a single side of the negative electrode sheet is 0.139mg / 1540.25mm 2 The compaction density P1 of the negative electrode is 1.5g / cm 3 .

[0184] Preparation of electrolyte

[0185] Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:3:1 to create an organic solvent. Thoroughly dried LiPF6 was then dissolved in the organic solvent to create an electrolyte solution with a concentration of 1 mol / L. Vinylene carbonate (VC) was then added to a concentration of 2% of the total electrolyte weight. The electrolyte viscosity was 3 mPa·s.

[0186] Preparation of isolation membrane

[0187] A porous polyethylene film (7 μm thick) was used as the separator.

[0188] Preparation of battery cells

[0189] The negative electrode sheet, separator, and positive electrode sheet are stacked and wound in sequence to form an electrode assembly. The two electrode assemblies are placed in a casing, dried, injected with electrolyte, packaged, and then subjected to formation and other processes to produce a battery cell. The width of the negative electrode sheet is 175mm (the width of the negative electrode sheet is equal to the dimension H0 of the negative electrode sheet along the first direction X), the width of the positive electrode sheet is 172mm (the dimension along the first direction X), and the width of the separator is 181mm (the dimension along the first direction X). The corresponding final battery cell dimensions are 69.3mm × 275mm × 188.7mm (T × W × H).

[0190] At 25°C, the prepared battery cell was allowed to rest for 30 minutes, then discharged at a 1 / 3C constant current to 2.5V. The initial capacity (Cap) of the battery cell was then tested as follows. First, the battery cell was allowed to rest for 30 minutes, then charged at a 1 / 3C constant current to 3.65V. Then, the constant voltage charge was continued until the current was less than 0.05C. The resulting capacity was recorded as the battery cell's charge capacity. After the battery cell was allowed to rest for 30 minutes, it was discharged at a 1 / 3C constant current to 2.5V. The resulting capacity was recorded as the battery cell's charge capacity. This cycle was repeated twice. The average of the three discharge capacities was taken as the battery cell's initial capacity (Cap).

[0191] The initial capacity Cap of the battery cell prepared in Example 1 is 405 Ah.

[0192] The prepared battery cells were left to rest for 30 minutes at 25°C before being tested as follows: The cells were discharged to 2.5V at a constant power of 0.5P (648W). After 6 hours of rest, they were charged to 3.65V at a constant power of 0.5P (648W). After 10 minutes of rest, the above steps were repeated until the battery capacity decayed to 50% of its initial capacity (Cap), i.e., the battery's depth of use (D) reached 50%.

[0193] Figure 9 is a cycle curve diagram of the battery cell prepared in Example 1. As can be seen from Figure 9, when the capacity of the battery cell decays to 50% SOH, there is no obvious accelerated capacity decay.

[0194] Comparative Example 1

[0195] The preparation method and testing method of the battery cell are similar to those in Example 1, except that the width dimensions of the negative electrode sheet, the positive electrode sheet, and the separator are different.

[0196] The width of the negative electrode sheet is 200 mm, the width of the positive electrode sheet is 197 mm, and the width of the separator is 206 mm.

[0197] The dimensions of the battery cell are 60.3mm×275mm×213.7mm.

[0198] The initial capacity Cap of the battery cell is 405Ah.

[0199] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0200] Figure 10 is a cycle curve of the battery cell prepared in Comparative Example 1. As can be seen from Figure 10, the battery cell capacity decays to 70% SOH. Due to the oversized design of the negative electrode plate, the battery cell capacity begins to decay rapidly. When the battery cell capacity decays to 65% SOH, the battery cell capacity decay further accelerates. After about 1300 cycles, the battery cell capacity rapidly decays to 50% SOH.

[0201] Comparative Example 2

[0202] The preparation method and testing method of the battery cell are similar to those in Example 1, except that the width dimensions of the negative electrode sheet, the positive electrode sheet, and the separator are different.

[0203] The width of the negative electrode sheet is 230 mm, the width of the positive electrode sheet is 227 mm, and the width of the separator is 236 mm.

[0204] The dimensions of the battery cell are 52.5mm×275mm×243.7mm.

[0205] The initial capacity Cap of the battery cell is 450Ah.

[0206] The charge and discharge power in the battery cell cycle test is 0.5P (720W).

[0207] Figure 11 is a cycle curve of the battery cell prepared in Comparative Example 2. As can be seen from Figure 11, the battery cell capacity decays to 75% SOH. Due to the oversized size of the negative electrode plate, the battery cell capacity begins to decay rapidly, and after about 1500 cycles, the battery cell capacity rapidly decays to 50% SOH.

[0208] It can be seen from Table 1 and Figures 9 to 11 that under the conditions of the same initial capacity of the battery cells and the same usage depth D, by adjusting the width of the negative electrode sheet (i.e., the dimension H0 of the negative electrode sheet along the first direction) to be less than or equal to the maximum dimension H max , H max =299.5×(1-1 / Cap)-180.8×D-5.83×η-7.66×P1-1.83×P2, which can make the battery cell have a longer cycle life.

[0209] Example 2-1

[0210] Except for the different electrolytes, the preparation method and testing method of the battery cell were similar to those in Example 1. The results are shown in Table 2.

[0211] Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3.4:2.6:1 to create an organic solvent. Thoroughly dried LiPF6 was then dissolved in the organic solvent to create an electrolyte solution with a concentration of 1.05 mol / L. Vinylene carbonate (VC) was then added to a concentration of 2.5% by weight of the total electrolyte solution. The viscosity of the electrolyte was 4 mPa·s.

[0212] The width of the negative electrode sheet is 169 mm, the width of the positive electrode sheet is 166 mm, and the width of the separator is 175 mm.

[0213] The dimensions of the battery cell are 71.6mm×275mm×182.7mm.

[0214] The initial capacity Cap of the battery cell is 405Ah.

[0215] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0216] Example 2-2

[0217] Except for the different electrolytes, the preparation method and testing method of the battery cell were similar to those in Example 1. The results are shown in Table 2.

[0218] Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3.6:2.4:1 to create an organic solvent. Thoroughly dried LiPF6 was dissolved in the organic solvent to create an electrolyte solution with a concentration of 1.1 mol / L. Vinylene carbonate (VC) was then added to a concentration of 3% of the total electrolyte weight. The electrolyte viscosity was 5 mPa·s.

[0219] The width of the negative electrode sheet is 163 mm, the width of the positive electrode sheet is 160 mm, and the width of the separator is 169 mm.

[0220] The dimensions of the battery cell are 74.0mm×275mm×176.7mm.

[0221] The initial capacity Cap of the battery cell is 405Ah.

[0222] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0223] Example 2-3

[0224] Except for the different electrolytes, the preparation method and testing method of the battery cell were similar to those in Example 1. The results are shown in Table 2.

[0225] Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 2.7:3.3:1 to create an organic solvent. Thoroughly dried LiPF6 was then dissolved in the organic solvent to create an electrolyte solution with a concentration of 0.9 mol / L. Vinylene carbonate (VC) was then added to a concentration of 1% by weight of the total electrolyte solution. The viscosity of the electrolyte was 2 mPa·s.

[0226] The width of the negative electrode sheet is 180 mm, the width of the positive electrode sheet is 177 mm, and the width of the separator is 186 mm.

[0227] The dimensions of the battery cell are 67.5mm×275mm×193.7mm.

[0228] The initial capacity Cap of the battery cell is 405Ah.

[0229] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0230] As shown in Table 2, the viscosity of the electrolyte is different, and the maximum size H of the negative electrode sheet along the first direction is max Different, by adjusting the width of the negative electrode sheet (ie, the size H0 of the negative electrode sheet along the first direction), and making it less than or equal to the maximum size H max , both can make the battery monomer have a good cycle life.

[0231] Example 3-1

[0232] Except for the preparation of the negative electrode sheet, the preparation method and testing method of the battery cell are similar to those of Example 1. The results are shown in Table 3.

[0233] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were mixed in an appropriate amount of deionized water at a weight ratio of 95:2:1:2 to form a uniform negative electrode slurry. The negative electrode slurry was evenly coated on both surfaces of the negative electrode current collector copper foil. After drying and cold pressing, the negative electrode sheet was obtained. The coating weight of the negative electrode sheet on one side was 0.139 mg / 1540.25 mm 2 The compaction density P1 of the negative electrode is 1.65g / cm 3 .

[0234] The width of the negative electrode sheet is 168 mm, the width of the positive electrode sheet is 165 mm, and the width of the separator is 174 mm.

[0235] The dimensions of the battery cell are 72.0mm×275mm×181.7mm.

[0236] The initial capacity Cap of the battery cell is 405Ah.

[0237] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0238] Example 3-2

[0239] Except for the preparation of the negative electrode sheet, the preparation method and testing method of the battery cell are similar to those of Example 1. The results are shown in Table 3.

[0240] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were mixed in an appropriate amount of deionized water at a weight ratio of 95:2:1:2 to form a uniform negative electrode slurry. The negative electrode slurry was evenly coated on both surfaces of the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet. The coating weight of a single side of the negative electrode sheet is 0.139mg / 1540.25mm 2 The compaction density P1 of the negative electrode is 1.8g / cm 3 .

[0241] The width of the negative electrode sheet is 172mm, the width of the positive electrode sheet is 169mm, and the width of the separator is 178mm.

[0242] The dimensions of the battery cell are 70.4mm×275mm×185.7mm.

[0243] The initial capacity Cap of the battery cell is 405Ah.

[0244] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0245] Example 3-3

[0246] Except for the preparation of the negative electrode sheet, the preparation method and testing method of the battery cell are similar to those of Example 1. The results are shown in Table 3.

[0247] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were mixed in an appropriate amount of deionized water at a weight ratio of 95:2:1:2 to form a uniform negative electrode slurry. The negative electrode slurry was evenly coated on both surfaces of the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet. The coating weight of a single side of the negative electrode sheet is 0.139mg / 1540.25mm 2 The compaction density P1 of the negative electrode is 1.4g / cm 3 .

[0248] The width of the negative electrode sheet is 173mm, the width of the positive electrode sheet is 170mm, and the width of the separator is 179mm.

[0249] The dimensions of the battery cell are 70.0mm×275mm×186.7mm.

[0250] The initial capacity Cap of the battery cell is 405Ah.

[0251] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0252] As shown in Table 3, the compaction density of the negative electrode sheet is different, and the maximum size H of the negative electrode sheet along the first direction is max Different, by adjusting the width of the negative electrode sheet (ie, the size H0 of the negative electrode sheet along the first direction), and making it less than or equal to the maximum size H max , both can make the battery monomer have a good cycle life.

[0253] Example 4-1

[0254] Except for the preparation of the positive electrode sheet, the preparation method and testing method of the battery cell are similar to those of Example 1. The results are shown in Table 4.

[0255] The positive electrode active material LiFePO4, the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) are thoroughly stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 97:1:2 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on both surfaces of the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet. The coating weight of a single side of the positive electrode sheet is 0.302mg / 1540.25mm2 The compaction density P2 of the positive electrode is 2.7g / cm 3 .

[0256] The width of the negative electrode sheet is 173mm, the width of the positive electrode sheet is 170mm, and the width of the separator is 179mm.

[0257] The dimensions of the battery cell are 70.0mm×275mm×186.7mm.

[0258] The initial capacity Cap of the battery cell is 405Ah.

[0259] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0260] Example 4-2

[0261] Except for the preparation of the positive electrode sheet, the preparation method and testing method of the battery cell are similar to those of Example 1. The results are shown in Table 4.

[0262] The positive electrode active material LiFePO4, the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) are thoroughly stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 97:1:2 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on both surfaces of the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet. The coating weight of a single side of the positive electrode sheet is 0.302mg / 1540.25mm 2 The compaction density P2 of the positive electrode is 2.2g / cm 3 .

[0263] The width of the negative electrode sheet is 170 mm, the width of the positive electrode sheet is 167 mm, and the width of the separator is 176 mm.

[0264] The dimensions of the battery cell are 71.2mm×275mm×183.7mm.

[0265] The initial capacity Cap of the battery cell is 405Ah.

[0266] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0267] As shown in Table 4, the compaction density of the positive electrode sheet is different, and the maximum size H of the negative electrode sheet along the first direction is max Different, by adjusting the width of the negative electrode sheet (ie, the size H0 of the negative electrode sheet along the first direction), and making it less than or equal to the maximum size H max , both can make the battery monomer have a good cycle life.

[0268] Example 5-1

[0269] Except for the different widths of the negative electrode sheet, the positive electrode sheet, and the separator, the preparation and testing methods of the battery cell were similar to those of Example 1. The results are shown in Table 5.

[0270] The width of the negative electrode sheet is 170 mm, the width of the positive electrode sheet is 167 mm, and the width of the separator is 176 mm.

[0271] The dimensions of the battery cell are 71.2mm x 275mm x 183.7mm, and the initial capacity of the battery cell is 405Ah.

[0272] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0273] Example 5-2

[0274] Except for the different widths of the negative electrode sheet, the positive electrode sheet, and the separator, the preparation and testing methods of the battery cell were similar to those of Example 1. The results are shown in Table 5.

[0275] The width of the negative electrode sheet is 165mm, the width of the positive electrode sheet is 162mm, and the width of the separator is 171mm.

[0276] The dimensions of the battery cell are 73.2mm x 275mm x 178.7mm, and the initial capacity of the battery cell is 405Ah.

[0277] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0278] Example 5-3

[0279] Except for the different widths of the negative electrode sheet, the positive electrode sheet, and the separator, the preparation and testing methods of the battery cell were similar to those of Example 1. The results are shown in Table 5.

[0280] The width of the negative electrode sheet is 160 mm, the width of the positive electrode sheet is 157 mm, and the width of the separator is 166 mm.

[0281] The dimensions of the battery cell are 75.3mm x 275mm x 173.7mm, and the initial capacity of the battery cell is 405Ah.

[0282] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0283] Example 5-4

[0284] Except for the different widths of the negative electrode sheet, the positive electrode sheet, and the separator, the preparation and testing methods of the battery cell were similar to those of Example 1. The results are shown in Table 5.

[0285] The width of the negative electrode sheet is 155mm, the width of the positive electrode sheet is 152mm, and the width of the separator is 161mm.

[0286] The dimensions of the battery cell are 77.5mm x 275mm x 168.7mm, and the initial capacity of the battery cell is 405Ah.

[0287] The charge and discharge power in the battery cell cycle test is 0.5P (648W).

[0288] As can be seen from Table 5, the width of the negative electrode sheet (i.e., the dimension H0 of the negative electrode sheet along the first direction) is adjusted to the maximum dimension H max The ratio can make the battery have both high capacity and long cycle life.

[0289] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, comprising: A housing; An electrode assembly, comprising a positive electrode tab and a negative electrode tab; And An electrolyte, Wherein, The electrode assembly includes a main body and an ear portion extending from one end of the main body along a first direction X. Along the first direction X, the size of the negative electrode sheet is denoted as H0, and the maximum size of the negative electrode sheet is denoted as H max , the unit is mm, then H0≤H max , and H max =299.5×(1-1 / Cap)-180.8×D-5.83×η-7.66×P1-1.83×P2, Cap is the initial capacity of the battery cell, and Cap ≥ 350 Ah; D is the depth of discharge of the battery cell, D = (Initial capacity of the battery cell - Warranty capacity of the battery cell) / Initial capacity of the battery cell; η is the viscosity of the electrolyte, with the unit of mPa·s; P1 is the compaction density of the negative electrode sheet, in g / cm 3 ; P2 is the compaction density of the positive electrode sheet, in g / cm 3 .

2. The battery cell according to claim 1, wherein, D is 20% - 50%; and / or, η is 2 - 5 mPa·s; and / or, P1: 1.0-2.5g / cm 3 , optional 1.4-1.8g / cm 3 and / or, P2: 2.0-4.0g / cm 3 , optional: 2.2-2.7g / cm 3 .

3. The battery cell according to claim 1 or 2, wherein: 0.8H max ≤H0≤H max , optionally, 0.88H max ≤H0≤H max .

4. The battery cell according to any one of claims 1 to 3, wherein: The electrode assembly is a flat body or a cuboid, the number of the electrode assemblies is one or more, the multiple electrode assemblies are arranged along the third direction Z, along the first direction X, the size of the electrode assembly is denoted as H1, along the second direction Y, the size of the electrode assembly is denoted as W1, along the third direction Z, the size of the one electrode assembly is denoted as T1, with the unit of mm for all, then H1 = H0; 0.05 ≤ T1 / W1 ≤ 1; 0.1 ≤ H1 / W1 ≤ 10, optionally, 0.5 ≤ H1 / W1 ≤ 1.5; The first direction X, the second direction Y, and the third direction Z are perpendicular to each other in pairs.

5. The battery cell according to any one of claims 1 to 4, wherein: The battery cell is a cuboid, along the first direction X, the size of the battery cell is denoted as H, along the second direction Y, the size of the battery cell is denoted as W, along the third direction Z, the size of the battery cell is denoted as T, with the unit of mm for all, then 0.05 ≤ T / W ≤ 1, optionally, 0.15 ≤ T / W ≤ 0.4; 0.1 ≤ H / W ≤ 10, optionally, 0.5 ≤ H / W ≤ 1.5; The first direction X, the second direction Y, and the third direction Z are perpendicular to each other in pairs.

6. The battery cell according to claim 5, wherein, 0 < H – H1 ≤ 20 mm; and / or, 0 < W – W1 ≤ 25 mm.

7. The battery cell according to claim 5 or 6, wherein, W is 20 - 600 mm, optionally 200 - 300 mm; and / or, T is 10 - 100 mm, optionally 50 - 80 mm.

8. The battery cell according to any one of claims 1 to 7, wherein: Along the first direction X, the size of the positive electrode tab is denoted as H′, then 0 ≤ H0 – H′ ≤ 5 mm.

9. The battery cell according to any one of claims 1 - 8, wherein, The porosity of the negative electrode tab is 10 - 45%%, optionally 18 - 40%; and / or, The porosity of the positive electrode tab is 10 - 45%, optionally 18 - 40%.

10. The battery cell according to any one of claims 1 to 9, wherein: The electrode assembly further comprises a separator, along the first direction X, the size of the separator is denoted as H″, then 0 < H″ – H0 ≤ 10 mm.

11. The battery cell according to any one of claims 1 to 10, wherein: The battery cell comprises a lithium secondary battery cell.

12. The battery cell according to any one of claims 1 - 11, wherein, The negative electrode tab comprises a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate; and / or, The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes one or more of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Optionally, the positive electrode active material includes one or more of lithium-containing phosphates and modified compounds, and the modification method includes doping modification and / or surface coating modification.

13. A method for preparing a battery cell, comprising the following steps: A negative electrode sheet, a separator, a positive electrode sheet and an electrolyte are provided. The compaction density of the negative electrode sheet is recorded as P1, and the unit is g / cm 3 The compaction density of the positive electrode sheet is recorded as P2, and the unit is g / cm 3 , the viscosity of the electrolyte is recorded as η, in mPa·s, along the first direction X, the size of the negative electrode sheet is recorded as H0, in mm, and H0≤299.5×(1-1 / Cap)-180.8×D-5.83×η-7.66×P1-1.83×P2, Cap is the initial capacity of the battery cell, and Cap≥350Ah, D is the depth of use of the battery cell, D=(initial capacity of the battery cell-guaranteed capacity of the battery cell) / initial capacity of the battery cell; The negative electrode sheet, the isolation membrane and the positive electrode sheet are stacked in sequence to form an electrode assembly, wherein the electrode assembly includes a main body and a pole ear extending from one end of the main body along a first direction X; the electrode assembly is placed in a shell, and the electrolyte is injected to obtain a battery cell.

14. The method according to claim 13, wherein: The electrode assembly is a wound electrode assembly or a laminated electrode assembly.

15. A battery comprising the battery cell according to any one of claims 1 to 12 or the battery cell prepared by the method according to any one of claims 13 to 14.

16. An electrical device comprising the battery according to claim 15, wherein the battery is used to provide electrical energy.

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