Battery monomer and 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, and belongs to the technical field of lithium batteries. The battery cell comprises an electrode assembly, the electrode assembly comprises a separation membrane, the separation membrane comprises a first region and a second region, the first region is closer to the end of the electrode assembly than the second region, and the ionic conductivity of the second region is smaller than that of the first region. According to the battery monomer, the ionic conductivity of the second region of the isolating membrane is smaller than that of the first region, and the first region is closer to the end part of the electrode assembly than the second region, so that the reaction rates of different regions in the battery monomer can be controlled, and the reaction rate of the second region closer to the middle part of the battery monomer is reduced; the temperature is reduced, and the performance degradation is reduced, so that the aim of promoting different areas to approach to be consistent in reaction temperature and performance degradation is achieved under the working conditions of low-rate charging and high-power discharging of the single battery, and the cycle performance and the service life of the single battery are effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a battery cell and a preparation method thereof, a battery and an electrical device. Background Art

[0002] In recent years, as the application scope of lithium-ion batteries has become more and more extensive, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As lithium-ion batteries have made great progress, higher requirements have been put forward for their power, energy density and cycle performance.

[0003] As lithium batteries continue to develop towards high power and high energy density, capacity decay has become the main limiting factor of lithium batteries. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell and a preparation method thereof, a battery and an electrical device, which can improve the cycle performance and service life of the battery cell.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a battery cell, which includes: an electrode assembly, the electrode assembly includes a positive electrode plate, a negative electrode plate and a separator, the electrode assembly has two opposite ends, the electrode assembly includes a pole ear, the pole ear is located at the end, the separator is arranged between the positive electrode plate and the negative electrode plate, the separator includes a first region and a second region, the first region is closer to the end than the second region, and the ionic conductivity of the second region is less than the ionic conductivity of the first region.

[0006] Therefore, during the operation of the battery cell, since the heat in the middle of the battery cell cannot be effectively conducted, the temperature in the middle of the battery cell is higher than the temperature at the edge of the battery cell. The battery cell of the present application makes the ionic conductivity of the second region of the isolation membrane smaller than the ionic conductivity of the first region, wherein the first region is closer to the end of the electrode assembly than the second region, that is, the second region is closer to the middle of the battery cell than the first region, thereby being able to control the reaction rates of different regions inside the battery cell. The reaction rate of the second region closer to the middle of the battery cell is reduced, the temperature is lowered, and the performance attenuation is reduced, so that the battery cell can achieve the purpose of promoting the reaction temperature and performance attenuation of different regions to be close to each other under the conditions of low-rate charging and high-power discharging, thereby effectively improving the cycle performance and service life of the battery cell.

[0007] In any embodiment, the difference between the ionic conductivity of the first region and the ionic conductivity of the second region is 0.02mS / cm to 0.6mS / cm. By making the difference between the ionic conductivity of the first region and the ionic conductivity of the second region within the above range, it is beneficial to control the ionic conduction rates of different regions in the battery cell to be close to the same under the condition of low-rate charging and high-power discharging of the battery cell, thereby effectively improving the cycle performance and service life of the battery cell.

[0008] In any embodiment, the separator includes a coating material, and the coating material of the first region is the same as the coating material of the second region, and the compaction density of the second region is greater than the compaction density of the first region. Under the premise that the coating materials of different regions of the separator are the same, the battery cell of the present application can achieve different ion conductivities in different regions by changing the compaction density of different regions of the separator.

[0009] In any embodiment, the isolation membrane also includes a third region, the first region and the third region are respectively close to the two ends of the electrode assembly, the second region is located between the first region and the third region, and the ion conductivity of the second region is less than the ion conductivity of the third region. The battery cell of the present application is divided into three regions by the isolation membrane, wherein the second region is a region closer to the middle of the battery cell, and the first region and the third region are regions closer to the end of the electrode assembly, and further by making the ion conductivity of the second region smaller than the first region and the third region close to the edge of the battery cell, the reaction rate of different regions inside the battery cell can be controlled, and the reaction rate of the second region closer to the middle of the battery cell is reduced, so that the battery cell can achieve the purpose of promoting the reaction temperature and performance attenuation of different regions to be close to each other under the condition of low-rate charging and high-power discharging, thereby effectively improving the cycle performance and service life of the battery cell.

[0010] In any embodiment, the two opposite ends of the electrode assembly are respectively the first end and the second end, the direction extending from the first end to the second end is the height direction of the electrode assembly, the first region, the second region and the third region are sequentially distributed along the height direction of the electrode assembly, and the ratio of the dimensions of the first region, the second region and the third region along the height direction of the electrode assembly is 10-40:50-60:10-40. By making the ratio of the dimensions of the first region, the second region and the third region along the height direction of the electrode assembly within the above range, different regions can be further subdivided according to the temperature of the battery cell when it is working, so that different regions can be more accurately controlled to be close to each other in terms of reaction temperature and performance attenuation.

[0011] In any embodiment, the difference between the ionic conductivity of the first region and the ionic conductivity of the second region is 0.06mS / cm to 0.3mS / cm, and / or; the difference between the ionic conductivity of the third region and the ionic conductivity of the second region is 0.02mS / cm to 0.2mS / cm. By making the difference between the ionic conductivity of the first region and the ionic conductivity of the second region and / or the difference between the ionic conductivity of the third region and the ionic conductivity of the second region within the above range, the reaction rate of different regions inside the battery cell can be controlled more accurately, so that the battery cell can achieve the purpose of promoting the reaction temperature and performance attenuation of different regions to be close to each other under the condition of low-rate charging and high-power discharging.

[0012] In any embodiment, the tabs include a positive tab and a negative tab disposed at the first end, and the dimension of the first region along the height direction of the electrode assembly is smaller than the dimension of the third region along the height direction of the electrode assembly. There is a certain amount of free space near the first region close to the positive tab and the negative tab and it is at the edge, and its heat dissipation is better than that of the third region without free space nearby, so the temperature of the first region is the lowest compared to the temperature of the second region and the third region during the operation of the battery cell, and when dividing the regions, by making the dimension of the first region along the height direction of the electrode assembly smaller than the dimension of the third region along the height direction of the electrode assembly, different regions can be further subdivided according to the temperature of the battery cell when it is operating, so that different regions can be more accurately controlled to be close to the same in reaction temperature and performance attenuation.

[0013] In any embodiment, the ratio of the dimensions of the first region, the second region and the third region along the height direction of the electrode assembly is 25-35:45-55:35-45, the ionic conductivity of the second region is smaller than the ionic conductivity of the third region, and the ionic conductivity of the third region is smaller than the ionic conductivity of the first region. When the ratio of the dimensions of the first region, the second region, and the third region along the height direction of the electrode assembly is within the above range, there is a certain amount of free space near the first region close to the positive electrode tab and the negative electrode tab and it is at the edge position, and its heat dissipation is better, so the temperature of the first region is the lowest compared to the temperatures of the second and third regions during the operation of the battery cell, and the performance attenuation is the smallest. Although there is no free space near the third region, it is also at the edge position, so the temperature and performance attenuation of the third region during the operation of the battery cell are between the first and third regions. By making the ionic conductivity of the second region smaller than the ionic conductivity of the third region, and the ionic conductivity of the third region smaller than the ionic conductivity of the first region, the difference in reaction rates between the first region, the second region, and the third region can be reduced, so that the battery cell can achieve the purpose of promoting the reaction temperature and performance attenuation of different regions to be close to each other under the conditions of low-rate charging and high-power discharging, thereby effectively improving the cycle performance and service life of the battery cell.

[0014] In any embodiment, the ionic conductivity of the first region is 0.3mS / cm to 0.9mS / cm, and / or the ionic conductivity of the second region is 0.4mS / cm to 0.95mS / cm. By making the ionic conductivity of the first region and / or the ionic conductivity of the second region within the above range, and satisfying that the ionic conductivity of the second region is less than that of the first region, the cycle performance and service life of the battery cell can be effectively improved.

[0015] The second aspect of the present application provides a method for preparing a battery cell, which includes: setting a coating material on the surface of a base film to form an isolation membrane, so that the isolation membrane includes a first region and a second region, and the ion conductivity of the second region is less than the ion conductivity of the first region, assembling the positive electrode plate, the negative electrode plate and the isolation membrane into an electrode assembly, the electrode assembly has two opposite ends, the electrode assembly includes a pole ear, the pole ear is located at the end, so that the first region is closer to the end than the second region.

[0016] Therefore, the preparation method of the battery cell of the present application is to form an isolation membrane having a first region and a second region by setting a coating material on the surface of the base film, and the ionic conductivity of the second region is less than that of the first region. Among them, the first region is closer to the end of the electrode assembly than the second region, that is, the second region is closer to the middle of the battery cell than the first region, so that the reaction rate of different regions inside the battery cell can be controlled, and the reaction rate of the second region closer to the middle of the battery cell is reduced, the temperature is reduced, and the performance attenuation is reduced, so that the battery cell can achieve the purpose of promoting the reaction temperature and performance attenuation of different regions to be close to each other under the condition of low-rate charging and high-power discharging, thereby effectively improving the cycle performance and service life of the battery cell.

[0017] In any embodiment, the first region and the second region are sequentially distributed along the width direction of the isolation membrane, and the coating material is firstly arranged in the first region and the second region of the base film, and the first coating layer is formed after drying, and then the coating material is arranged in the second region, and the second coating layer is formed after drying, and the isolation membrane is obtained by roller compaction. The preparation method of the battery cell of the present application makes the first region only include the first coating layer, and the second region includes the first coating layer and the second coating layer, and then the compaction density of the second region is greater than the compaction density of the first region by roller compaction, thereby obtaining an isolation membrane having an ion conductivity of the first region greater than that of the second region.

[0018] In any embodiment, the isolation membrane also includes a third region, and the ion conductivity of the third region is less than that of the first region. The first region, the second region, and the third region are sequentially distributed along the width direction of the isolation membrane. The coating material is first set in the first region, the second region, and the third region of the base membrane, and the first coating is formed after drying. Then the coating material is set in the second region and the third region, and the coating material is set again in the second region, and the second coating and the third coating are formed after drying. The isolation membrane is obtained by roller compaction. The preparation method of the battery cell of the present application makes the first region include only the first coating, the third region includes the first coating and the second coating, and the second region includes the first coating, the second coating, and the third coating. Then, the compaction density of the second region is greater than the compaction density of the third region and greater than the compaction density of the first region by roller compaction, thereby obtaining an isolation membrane having an ion conductivity of the first region greater than that of the third region and greater than that of the second region.

[0019] In any embodiment, the thickness of the first coating layer is 0.1 μm to 2 μm, and / or the thickness of the second coating layer is 1 μm to 4 μm, and / or the thickness of the third coating layer is 1 μm to 3 μm.

[0020] By making the thickness of the first coating, the second coating and the third coating within the above-mentioned range, the difference between the ionic conductivity of the first region and the ionic conductivity of the second region can be made to be 0.04mS / cm to 0.6mS / cm, and the difference between the ionic conductivity of the third region and the ionic conductivity of the second region can be made to be 0.04mS / cm to 0.6mS / cm.

[0021] In any embodiment, the pressure of the pressing roller is 10 MPa to 50 MPa. By setting the pressure of the pressing roller within the above range, the ion conductivity of the first region can be 0.3 mS / cm to 0.9 mS / cm and the ion conductivity of the second region can be 0.4 mS / cm to 0.95 mS / cm, which is beneficial for forming a battery cell.

[0022] A third aspect of the present application provides a battery, which includes the battery cell in the above embodiment or a battery cell manufactured according to the method for manufacturing the battery cell in the above embodiment.

[0023] A fourth aspect of the present application provides an electrical device, which includes the battery in the above embodiment, and the battery is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a battery cell according to an embodiment of the present application.

[0025] Figure 2 yes Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown.

[0026] Figure 3 It is a schematic diagram of the isolation membrane of the first embodiment of the present application.

[0027] Figure 4 It is a schematic diagram of an isolation membrane according to a second embodiment of the present application.

[0028] Figure 5 It is a schematic diagram of an isolation membrane according to a third embodiment of the present application.

[0029] Figure 6 It is a schematic diagram of an isolation membrane according to a fourth embodiment of the present application.

[0030] Figure 7 It is a schematic diagram of an electrode assembly according to one embodiment of the present application.

[0031] Figure 8 is a schematic diagram of an electrode assembly according to another embodiment of the present application.

[0032] Fig. 9 It is a schematic diagram of a process for preparing an isolation membrane according to an embodiment of the present application.

[0033] Fig.10 It is a top view of the isolation film preparation process according to one embodiment of the present application.

[0034] Fig.11 It is a schematic cross-sectional view of the isolation membrane in the width direction through the front edge of the pressure roller according to one embodiment of the present application.

[0035] Fig.12 It is a schematic cross-sectional view of an isolation membrane in one embodiment of the present application after being pressed by a roller along the width direction.

[0036] Fig.13 is a schematic diagram of a battery module according to an embodiment of the present application.

[0037] Fig.14 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0038] Fig.15 yes Fig.14 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0039] Fig.16 It is a schematic diagram of an electrical device using a battery cell according to an embodiment of the present application as a power source.

[0040] Description of reference numerals:

[0041] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 521 isolation membrane; 5211 first area; 5212 second area; 5213 other areas; 5214 third area; 522 tab; 5221 positive pole tab; 5222 negative pole tab; 523 end; 53 cover plate. DETAILED DESCRIPTION

[0042] Below, a battery cell and its preparation method, battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0043] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it 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.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means 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.

[0047] As lithium batteries continue to develop towards high power and high energy density, the heat in the middle of the battery cell cannot be effectively conducted, so that the temperature in the middle of the battery cell is always higher than the temperature of other edges when the battery cell is working. This causes the reaction rate in the middle of the battery cell to be the fastest and the capacity decay to be the fastest, and lithium ions are preferentially released. As the number of cycles increases, lithium plating in the middle of the battery cell becomes more serious and the number of side reactions increases, which leads to an increase in the proportion of irreversible reactions in the middle of the battery cell, thereby accelerating the capacity decay.

[0048] Based on this, the present application proposes a battery cell and a method for preparing the same, a battery and an electrical device. The present application and optional implementation methods are described in more detail below.

[0049] According to some embodiments of the present application, please refer to Figures 1 to 5 , Figure 1 is a schematic diagram of a battery cell 5 according to an embodiment of the present application; Figure 2 yes Figure 1 An exploded view of a battery cell 5 according to an embodiment of the present application is shown; Figure 3 is a schematic diagram of an isolation film 521 according to a first embodiment of the present application; Figure 4 is a schematic diagram of an isolation film 521 according to a second embodiment of the present application; Figure 5 It is a schematic diagram of an isolation film 521 according to a third embodiment of the present application.

[0050] The present application provides a battery cell 5, which includes: an electrode assembly 52, the electrode assembly 52 includes a positive electrode sheet, a negative electrode sheet and a separator 521, the electrode assembly 52 has two opposite ends 523, the electrode assembly 22 includes a pole ear 522, the pole ear 522 is located at the end 523, the separator 521 is arranged between the positive electrode sheet and the negative electrode sheet, the separator 521 includes a first region 5211 and a second region 5212, the first region 5211 is closer to the end 523 than the second region 5212, and the ionic conductivity of the second region 5212 is less than the ionic conductivity of the first region 5211.

[0051] The electrode assembly 52 is a structure made of a positive electrode sheet, a negative electrode sheet and a separator 521 through a winding process or a lamination process.

[0052] In some embodiments, the battery cell 5 may include an outer packaging, which may be used to encapsulate the electrode assembly 52 and the electrolyte.

[0053] In some embodiments, the outer packaging of the battery cell 5 may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell 5 may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0054] The present application has no particular limitation on the shape of the battery cell 5, which may be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0055] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film 521 can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0056] The first region 5211 is a region closer to the end portion 523 than the second region 5212 , and the second region 5212 is a region farther from the end portion 523 than the first region 5211 .

[0057] It should be noted that the positions of the first region 5211 and the second region 5212 are relative, the isolation film 521 can be divided into the first region 5211 and the second region 5212, and the isolation film 521 can also include other regions 5213 in addition to the first region 5211 and the second region 5212. The shapes and sizes of the first region 5211 and the second region 5212 can be determined according to actual conditions.

[0058] For example, see Figure 3 The isolation film 521 as a whole is divided into a first area 5211 and a second area 5212 , wherein the second area 5212 is a circular area located in the middle of the isolation film 521 , and the first area 5211 is an annular area surrounding the second area 5212 .

[0059] See also Figure 4 The isolation film 521 as a whole is divided into a first area 5211 and a second area 5212 , wherein the second area 5212 is a rectangular area located in the middle of the isolation film 521 , and the first area 5211 is an annular area surrounding the second area 5212 .

[0060] See also Figure 5 The isolation film 521 includes a first region 5211, a second region 5212 and other regions 5213, wherein the first region 5211 is a region located in the middle of the isolation film 521, the second region 5212 is an annular region surrounding the first region 5211, and the other region 5213 is an annular region surrounding the second region 5212.

[0061] Optionally, the isolation film 521 is divided into a plurality of temperature rise regions. When the battery cell 5 is in working state, different temperature rise regions have different temperature rises. The first region 5211 is the region with the highest temperature rise, and the second region 5212 is the region with the lowest temperature rise.

[0062] The ionic conductivity of different regions of the isolation membrane 521 can be measured by the following method:

[0063] S1. The isolation film 521 is cut into small isolation films 521 of a certain area and vacuum-baked at 60°C for 12h;

[0064] S2. After baking, the isolation film 521 is assembled in the mold and transferred to the instrument;

[0065] S3. Perform vacuuming and aeration steps to remove relevant air and moisture in the sample;

[0066] S4. Quantitatively and automatically inject liquid (300 μL, 1M LiPF6, EMC:EC:DMC=1:1:1) into each channel, and let it stand for a certain period of time after the injection is completed;

[0067] S5. After standing still, an impedance test is performed using an EIS module of a multi-channel ionic conductivity test system;

[0068] S6. Complete the assembly and testing of 1 to 4 layers of isolation membranes 521 respectively, use automatic fitting software, and fit the obtained EIS as the baseline, and the intersection of the impedance and the X-axis is Rs. Fit the EIS test results of the n-layer isolation membrane 521 to obtain the resistance Rs(n) of the n-layer isolation membrane 521, and calculate the ionic conductivity of different regions of the isolation membrane 521.

[0069] During the operation of the battery cell 5, since the heat in the middle of the battery cell 5 cannot be effectively conducted, the temperature in the middle of the battery cell 5 is higher than the temperature at the edge of the battery cell 5. The battery cell 5 of the present application makes the ionic conductivity of the second area 5212 of the isolation membrane 521 less than the ionic conductivity of the first area 5211, wherein the first area 5211 is closer to the end 523 of the electrode assembly 52 than the second area 5212, that is, the second area 5212 is closer to the middle of the battery cell 5 than the first area 5211, so that the reaction rates of different areas inside the battery cell 5 can be controlled, and the reaction rate of the second area 5212 closer to the middle of the battery cell 5 is reduced, the temperature is reduced, and the performance attenuation is reduced, so that the battery cell 5 can achieve the purpose of promoting the reaction temperature and performance attenuation of different areas to be close to each other under the conditions of low-rate charging and high-power discharging, thereby effectively improving the cycle performance and service life of the battery cell 5.

[0070] In some embodiments, the difference between the ionic conductivity of the first region 5211 and the ionic conductivity of the second region 5212 is 0.02 mS / cm to 0.6 mS / cm.

[0071] As an example, the difference between the ionic conductivity of the first region 5211 and the ionic conductivity of the second region 5212 can be 0.02mS / cm, 0.03mS / cm, 0.04mS / cm, 0.05mS / cm, 0.08mS / cm, 0.1mS / cm, 0.2mS / cm, 0.3mS / cm, 0.4mS / cm, 0.5mS / cm or 0.6mS / cm.

[0072] Optionally, the difference between the ionic conductivity of the first region 5211 and the ionic conductivity of the second region 5212 is 0.08 mS / cm to 0.4 mS / cm.

[0073] By making the difference between the ionic conductivity of the first region 5211 and the ionic conductivity of the second region 5212 within the above range, it is beneficial to control the ionic conduction rates of different regions in the battery cell 5 to be close to the same under the conditions of low-rate charging and high-power discharging of the battery cell 5, thereby effectively improving the cycle performance and service life of the battery cell 5.

[0074] In some embodiments, the isolation film 521 includes a coating material, and the coating material of the first region 5211 is the same as the coating material of the second region 5212 , and the compaction density of the second region 5212 is greater than the compaction density of the first region 5211 .

[0075] Compacted density refers to the ratio of surface density to material thickness, and surface density refers to mass per unit area. The first region 5211 and the second region 5212 of the isolation film 521 of the present application have the same thickness, and the compacted density of the second region 5212 is greater than the compacted density of the first region 5211, that is, the surface density of the first region 5211 is greater than the surface density of the second region 5212, and the mass per unit area of ​​the first region 5211 is greater than the mass per unit area of ​​the second region 5212.

[0076] The compacted density can be measured by the following method:

[0077] First, take a compacted diaphragm of a fixed area S, obtain the weight M of the diaphragm (including the coating material) by weighing, then subtract the weight m of the base film, and measure the thickness H of the diaphragm. After subtracting the thickness h of the base film, calculate the compaction density: D (compaction density) = (Mm) / (S*(Hh).

[0078] On the premise that the coating materials of different regions of the isolation membrane 521 are the same, the battery cell 5 of the present application can achieve different ion conductivities in different regions by changing the compaction density of different regions of the isolation membrane 521 .

[0079] See also Figure 6 , Figure 6 Schematic diagram of the isolation membrane 521 of the fourth embodiment of the present application. In some embodiments, the isolation membrane 521 further includes a third region 5214, the first region 5211 and the third region 5214 are respectively close to the two ends 523 of the electrode assembly 52, the second region 5212 is located between the first region 5211 and the third region 5214, and the ion conductivity of the second region 5212 is less than the ion conductivity of the third region 5214.

[0080] The battery cell 5 of the present application is divided into three areas by the isolation membrane 521, wherein the second area 5212 is the area closer to the middle of the battery cell 5, and the first area 5211 and the third area 5214 are the areas closer to the end 523 of the electrode assembly 52, and further by making the ionic conductivity of the second area 5212 smaller than the first area 5211 and the third area 5214 close to the edge of the battery cell 5, the reaction rates of different areas inside the battery cell 5 can be controlled, and the reaction rate of the second area 5212 closer to the middle of the battery cell 5 is reduced, so that the battery cell 5 can achieve the purpose of promoting the reaction temperature and performance attenuation of different areas to be close to each other under the conditions of low-rate charging and high-power discharging, thereby effectively improving the cycle performance and service life of the battery cell 5.

[0081] In some embodiments, the two opposite ends 523 of the electrode assembly 52 are respectively the first end and the second end, the direction extending from the first end to the second end is the height direction of the electrode assembly 52, the first region 5211, the second region 5212 and the third region 5214 are distributed in sequence along the height direction of the electrode assembly 52, and the ratio of the dimensions of the first region 5211, the second region 5212 and the third region 5214 along the height direction of the electrode assembly 52 is 10~40:50~60:10~40.

[0082] In such Figure 6 In the illustrated embodiment, the first region 5211 , the second region 5212 , and the third region 5214 are all rectangles distributed in sequence along the height direction of the electrode assembly 52 .

[0083] As an example, the dimensions of the first region 5211, the second region 5212, and the third region 5214 along the height direction of the electrode assembly 52 may be 10:60:30, 10:50:40, 20:50:30, 20:60:20, 30:50:20, 30:60:20, or 40:50:10.

[0084] By making the ratio of the dimensions of the first region 5211, the second region 5212 and the third region 5214 along the height direction of the electrode assembly 52 within the above range, different regions can be further subdivided according to the temperature of the battery cell 5 during operation, so that different regions can be more accurately controlled to be consistent in reaction temperature and performance attenuation.

[0085] In some embodiments, the difference between the ionic conductivity of the first region 5211 and the ionic conductivity of the second region 5212 is 0.06mS / cm to 0.3mS / cm, and / or; the difference between the ionic conductivity of the third region 5214 and the ionic conductivity of the second region 5212 is 0.02mS / cm to 0.2mS / cm.

[0086] As an example, the difference between the ionic conductivity of the first region 5211 and the ionic conductivity of the second region 5212 can be 0.06mS / cm, 0.08mS / cm, 0.1mS / cm, 0.15mS / cm, 0.2mS / cm, 0.25mS / cm or 0.3mS / cm, and / or; the difference between the ionic conductivity of the third region 5214 and the ionic conductivity of the second region 5212 can be 0.02mS / cm, 0.03mS / cm, 0.05mS / cm, 0.08mS / cm, 0.1mS / cm, 0.12mS / cm, 0.15mS / cm, 0.18mS / cm or 0.2mS / cm.

[0087] By making the difference between the ionic conductivity of the first region 5211 and the ionic conductivity of the second region 5212 and / or the difference between the ionic conductivity of the third region 5214 and the second region 5212 within the above-mentioned range, the reaction rates of different regions inside the battery cell 5 can be controlled more accurately, so that the battery cell 5 can achieve the purpose of promoting the reaction temperature and performance attenuation of different regions to be close to each other under the conditions of low-rate charging and high-power discharging.

[0088] See also Figure 7 , Figure 7 7 is a schematic diagram of an electrode assembly 52 of an embodiment of the present application. In some embodiments, the electrode tab 522 includes a positive electrode tab 5221 and a negative electrode tab 5222 arranged at the first end, and the size of the first region 5211 along the height direction of the electrode assembly 52 is smaller than the size of the third region 5214 along the height direction of the electrode assembly 52.

[0089] For example, the dimensions of the first region 5211 , the second region 5212 , and the third region 5214 along the height direction of the electrode assembly 52 may be 10:60:30, 10:50:40, 20:40:40, 20:50:30, or 25:45:30.

[0090] There is a certain amount of free space near the first region 5211 close to the positive electrode tab 5221 and the negative electrode tab 5222 and it is at the edge position. Its heat dissipation is better than that of the third region 5214 where there is no free space nearby. Therefore, during the operation of the battery cell 5, the temperature of the first region 5211 is the lowest compared to the temperatures of the second region 5212 and the third region 5214. When dividing the regions, by making the size of the first region 5211 along the height direction of the electrode assembly 52 smaller than the size of the third region 5214 along the height direction of the electrode assembly 52, different regions can be further subdivided according to the temperature of the battery cell 5 during operation, so that different regions can be more accurately controlled to be consistent in reaction temperature and performance attenuation.

[0091] See also Figure 8 , Figure 8 It is a schematic diagram of an electrode assembly 52 of another embodiment of the present application, in which the positive electrode ear 5221 of the electrode assembly 52 is located at the first end, the negative electrode ear 5222 is located at the second end, and the first region 5211 is close to the first end, and the third region 5214 is close to the second end. If the space of the positive electrode column is sufficient, the first region 5211 has sufficient heat dissipation space, and the size of the first region 5211 along the height direction of the electrode assembly 52 is smaller than the size of the third region 5214 along the height direction of the electrode assembly 52; if the space of the positive electrode column is insufficient, the size of the first region 5211 along the height direction of the electrode assembly 52 is equal to the size of the third region 5214 along the height direction of the electrode assembly 52.

[0092] In some embodiments, the ratio of the dimensions of the first region 5211, the second region 5212, and the third region 5214 along the height direction of the electrode assembly 52 is 25-35:45-55:35-45, the ionic conductivity of the second region 5212 is smaller than the ionic conductivity of the third region 5214, and the ionic conductivity of the third region 5214 is smaller than the ionic conductivity of the first region 5211.

[0093] Optionally, a ratio of the sizes of the first region 5211 , the second region 5212 , and the third region 5214 along the height direction of the electrode assembly 52 is 30:50:40.

[0094] When the ratio of the dimensions of the first region 5211, the second region 5212, and the third region 5214 along the height direction of the electrode assembly 52 is within the above range, there is a certain amount of free space near the first region 5211 close to the positive electrode tab 5221 and the negative electrode tab 5222 and it is at the edge position, and its heat dissipation is good. Therefore, during the operation of the battery cell 5, the temperature of the first region 5211 is the lowest compared to the temperatures of the second region 5212 and the third region 5214, and the performance attenuation is the smallest. Although there is no free space near the third region 5214, it is also at the edge position. Therefore, during the operation of the battery cell 5, the third region 5214 is The temperature and performance attenuation of 5214 are between the first region 5211 and the third region 5214. By making the ionic conductivity of the second region 5212 smaller than the ionic conductivity of the third region 5214, and the ionic conductivity of the third region 5214 smaller than the ionic conductivity of the first region 5211, the difference in reaction rates among the first region 5211, the second region 5212 and the third region 5214 can be reduced, so that the battery cell 5 can achieve the purpose of promoting the reaction temperature and performance attenuation of different regions to be close to each other under the conditions of low-rate charging and high-power discharging, thereby effectively improving the cycle performance and service life of the battery cell 5.

[0095] In some embodiments, the ionic conductivity of the first region 5211 is 0.3 mS / cm to 0.9 mS / cm, and / or the ionic conductivity of the second region 5212 is 0.4 mS / cm to 0.95 mS / cm.

[0096] As examples, the ionic conductivity of the first region 5211 may be 0.3 mS / cm, 0.4 mS / cm, 0.5 mS / cm, 0.6 mS / cm, 0.7 mS / cm, 0.8 mS / cm or 0.9 mS / cm, and / or; the ionic conductivity of the second region 5212 may be 0.4 mS / cm, 0.5 mS / cm, 0.6 mS / cm, 0.7 mS / cm, 0.8 mS / cm, 0.9 mS / cm or 0.95 mS / cm.

[0097] By making the ionic conductivity of the first region 5211 and / or the ionic conductivity of the second region 5212 within the above range and satisfying that the ionic conductivity of the second region 5212 is less than the ionic conductivity of the first region 5211 , the cycle performance and service life of the battery cell 5 can be effectively improved.

[0098] The present application also provides a method for preparing a battery cell, which includes: setting a coating material on the surface of a base film to form an isolation membrane, so that the isolation membrane includes a first region and a second region, and the ion conductivity of the second region is less than the ion conductivity of the first region, assembling a positive electrode plate, a negative electrode plate and the isolation membrane into an electrode assembly, the electrode assembly has two opposite ends, and the electrode assembly includes a pole ear, and the pole ear is located at the end, so that the first region is closer to the end than the second region.

[0099] Wherein, the base film includes a polyolefin porous structure base film, and the polyolefin porous structure base film can be prepared by the following preparation method:

[0100] The polyolefin resin is sequentially melted, extruded, and blown into a crystalline polymer film, and the crystalline polymer film is then sequentially subjected to crystallization treatment and annealing to obtain a highly oriented multilayer structure. The multilayer structure is further stretched at a high temperature to peel off the crystal surface to form a porous structure, thereby obtaining a polyolefin porous structure base film.

[0101] The coating material includes at least one of nano zirconium oxide balls, polycarbonate, special alumina, boehmite, polymethyl methacrylate, aramid and polyvinylidene fluoride.

[0102] The preparation method of the battery cell of the present application is to form an isolation membrane having a first region and a second region by setting a coating material on the surface of the base film, and the ion conductivity of the second region is less than that of the first region. Among them, the first region is closer to the end of the electrode assembly than the second region, that is, the second region is closer to the middle of the battery cell than the first region, so that the reaction rate of different regions inside the battery cell can be controlled, and the reaction rate of the second region closer to the middle of the battery cell is reduced, the temperature is reduced, and the performance attenuation is reduced, so that the battery cell can achieve the purpose of promoting the reaction temperature and performance attenuation of different regions to be close to each other under the condition of low-rate charging and high-power discharging, thereby effectively improving the cycle performance and service life of the battery cell.

[0103] In some embodiments, the first region and the second region are distributed sequentially along the width direction of the isolation film. The coating material is firstly arranged in the first region and the second region of the base film, and a first coating layer is formed after drying. Then, the coating material is arranged in the second region, and a second coating layer is formed after drying. The isolation film is obtained by compacting with a pressure roller.

[0104] The preparation method of the battery cell of the present application makes the first region include only the first coating, while the second region includes the first coating and the second coating, and then the compaction density of the second region is made greater than the compaction density of the first region by compaction by a pressure roller, thereby obtaining an isolation membrane having an ionic conductivity of the first region greater than that of the second region.

[0105] In some embodiments, the isolation membrane also includes a third region, and the ionic conductivity of the third region is less than that of the first region. The first region, the second region, and the third region are sequentially distributed along the width direction of the isolation membrane. A coating material is firstly arranged in the first region, the second region, and the third region of the base membrane, and a first coating layer is formed after drying. Then, a coating material is arranged in the second region and the third region, and a coating material is arranged again in the second region, and a second coating layer and a third coating layer are formed after drying. The isolation membrane is obtained by compacting with a pressure roller.

[0106] See also Figures 9 to 12 , Fig. 9 is a schematic diagram of a process for preparing an isolation membrane according to an embodiment of the present application; Fig.10 is a top view of a process for preparing an isolation membrane according to an embodiment of the present application; Fig.11 This is a schematic cross-sectional view of the isolation membrane in the width direction of the front edge of the pressure roller according to one embodiment of the present application; Fig.12 This is a schematic cross-sectional view of an isolation film in a practical mode of the present application after being pressed by a roller in the width direction. The base film is first supported by a supporting roller, and a first coating sprayer is first used to spray the coating material on the first area, the second area and the third area on one side of the base film, and the solvent of the first coating is dried in an oven to form a first coating, and then a second / third coating sprayer is used to spray the coating material on the second area and the third area, and the coating material is sprayed on the second area, and the solvent of the second coating and the third coating is dried in an oven to form a second coating and a third coating, and then the first coating, the second coating and the third coating are formed in the corresponding area on the other side of the base film by the same method, and the first coating, the second coating and the third coating are compacted by a pressing roller, so that the thickness of the first area, the second area and the third area is the same, and the isolation film is obtained.

[0107] The preparation method of the battery cell of the present application makes the first region include only the first coating, the third region includes the first coating and the second coating, and the second region includes the first coating, the second coating and the third coating, and then the compaction density of the second region is greater than the compaction density of the third region and greater than the compaction density of the first region by means of a pressure roller, thereby obtaining an isolation membrane having an ionic conductivity of the first region greater than that of the third region and greater than that of the second region.

[0108] In some embodiments, the thickness of the first coating layer is 0.1 μm to 2 μm, and / or; the thickness of the second coating layer is 1 μm to 4 μm, and / or; the thickness of the third coating layer is 1 μm to 3 μm.

[0109] As an example, the thickness of the first coating layer may be 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm or 2 μm.

[0110] The thickness of the second coating layer may be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm.

[0111] The thickness of the third coating layer may be 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm.

[0112] By making the thickness of the first coating, the second coating and the third coating within the above-mentioned range, the difference between the ionic conductivity of the first region and the ionic conductivity of the second region can be made to be 0.04mS / cm to 0.6mS / cm, and the difference between the ionic conductivity of the third region and the ionic conductivity of the second region can be made to be 0.04mS / cm to 0.6mS / cm.

[0113] In some embodiments, the pressure of the pressing roller is 10 MPa to 50 MPa.

[0114] As an example, the pressure of the pressing roller may be 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, 35 MPa, 40 MPa, 45 MPa or 50 MPa.

[0115] By setting the pressure of the pressing roller within the above range, the ion conductivity of the first region can be 0.3 mS / cm to 0.9 mS / cm and the ion conductivity of the second region can be 0.4 mS / cm to 0.95 mS / cm, which is beneficial for forming a battery cell.

[0116] In addition, a battery cell and a method for preparing the same, a battery, and an electrical device of the present application are described below with appropriate reference to the accompanying drawings.

[0117] [Battery Cell]

[0118] The present application has no particular limitation on the type of battery cells. For example, the battery cells may be lithium-ion batteries, etc.

[0119] Generally, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0120] The present application has no particular restrictions on the type of the electrolyte, which can be selected according to actual needs. For example, the electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte). Battery cells using electrolytes, and some battery cells using solid electrolytes.

[0121] [Positive electrode]

[0122] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0123] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0124] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0125] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25Mn 0.25 O2 (which can also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 )、lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and at least one of its modified compounds, etc. Examples of olivine-structured lithium-containing phosphates may include but are not limited to lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon.

[0126] In some embodiments, in order to further improve the energy density of the battery cell, the cathode active material for the lithium-ion battery may include a lithium transition metal oxide having the general formula Li a Ni b Co c M d O e A f and one or more of its modified compounds. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0127] In some embodiments, by way of example, the cathode active material for the lithium-ion battery 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 Co0.15 Al 0.05 One or more of O2, LiFePO4 and LiMnPO4.

[0128] In the present application, the modified compound of each positive electrode active material mentioned above may be a compound obtained by doping and / or surface coating the positive electrode active material.

[0129] As an optional technical method of the present application, the polyanionic compound can be Li 1+x Mn 1-y A y P 1-z R z O4; wherein x is any value in the range of -0.100 to 0.100, y is any value in the range of 0.001 to 0.500, z is any value in the range of 0.001 to 0.100, A includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and R includes one or more elements selected from B, S, Si and N;

[0130] As an optional technical method of the present application, the polyanionic compound can be Li a A e Mn 1-f B f P 1-g C g O 4-n D n , wherein A includes one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from the group consisting of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements selected from the group consisting of B, S, Si, and N; D includes one or more elements selected from the group consisting of S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the second positive electrode active material is electrically neutral.

[0131] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0132] In the enumeration of the cathode material in this application, the molar content of O is only the theoretical value. Oxygen release from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0133] As an optional technical solution of this application, the polyanionic compound can be Na 4+x R 3-y P 4-m O 15 / C; where 0 < x < 0.5, 0 < y ≤ 0.5, 0 < m ≤ 0.2, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0134] As an optional technical solution of this application, the polyanionic compound can be Na x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q d , where the A element represents an alkali metal element that dopes and replaces the Na element, the M element represents a metal element that replaces the V element, the D element represents a doping element that replaces the P element, the Q element represents a doping element that replaces the F element, the D element includes at least one of Si and S, and the Q element includes at least one of Cl and O; 3.5 ≤ x ≤ 4.5, 0 ≤ a ≤ 0.15x, 0.8 ≤ y ≤ 1.1, 0 ≤ b ≤ 0.3y, 0 ≤ c ≤ 0.15, 0.8 ≤ z ≤ 1.1, 0 ≤ d ≤ 0.2z. Optionally, the A element includes at least one of K and Li; the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0135] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer formed on at least a part of the 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 can include at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries can also be used.

[0136] As an optional technical solution of this application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na xMO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 <x≤1。

[0137] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n- valence state.

[0138] Polyanionic compounds can also be those with sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds of anion units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0139] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedral unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, n represents the valence state of V; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0140] Polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0141] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a Me b Me' c(CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 <a≤2,0<b<1,0<c<1。

[0142] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0143] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0145] [Negative electrode]

[0146] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.

[0147] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0148] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0149] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0150] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0151] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0152] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0153] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0154] In other embodiments, the current collector of the negative electrode plate may generally include a current collector body and an undercoat layer, the undercoat layer may be disposed on at least one side of the current collector body, the undercoat layer substantially does not contain negative electrode active materials, and may include a small amount of carbon material, but the thickness of the coating formed by the carbon material is thin and cannot function as a negative electrode active material. In this embodiment, the negative electrode plate may be a plate without a negative electrode active material layer. For a negative electrode plate without a negative electrode active material layer, when the current collector of the negative electrode plate does not contain an undercoat layer, the film layer may be disposed on the surface of at least one side of the current collector; when the current collector of the negative electrode plate includes an undercoat layer, the film layer may be disposed on the surface of the undercoat layer on the side away from the current collector.

[0155] In some embodiments, the film layer may further include a binder, which is used to fix the additive on the negative electrode plate. The type of the binder is not particularly limited, and those skilled in the art may flexibly select the binder according to actual needs.

[0156] [Electrolytes]

[0157] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0158] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0159] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0160] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0161] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0162] [Isolation film]

[0163] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0164] In some embodiments, the material of the isolation membrane can be selected from at least one 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, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0165] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0166] Fig.13 4 is an example of a battery module. Fig.13 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0167] Optionally, the battery module 4 may further include an outer shell having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0168] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0169] Fig.14 and Fig.15 1 is a battery pack 1 as an example. Fig.14 and Fig.15 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0170] In addition, the present application also provides an electric device, which includes at least one of the battery cells, battery modules, or battery packs provided in the present application. The battery cells, battery modules, or battery packs can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0171] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0172] Fig.16The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of battery cells, a battery pack or a battery module can be used.

[0173] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0174] Example

[0175] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0176] The relevant parameters of the battery cells of Examples 1 to 10 and Comparative Examples 1 to 2 are shown in Table 1.

[0177] Table 1 Related parameters of battery cells of Examples 1 to 10 and Comparative Examples 1 to 2

[0178]

[0179]

[0180] Test method for ionic conductivity of different regions of the isolation membrane:

[0181] S1. Cut the isolation film into small isolation films of a certain area and bake them in vacuum at 60°C for 12h;

[0182] S2. After baking, the isolation film is assembled in the mold and transferred to the instrument;

[0183] S3. Perform vacuuming and aeration steps to remove relevant air and moisture in the sample;

[0184] S4. Quantitatively and automatically inject liquid (300 μL, 1M LiPF6, EMC:EC:DMC=1:1:1) into each channel, and let it stand for a certain period of time after the injection is completed;

[0185] S5. After standing still, an impedance test is performed using an EIS module of a multi-channel ionic conductivity test system;

[0186] S6. Complete the assembly and testing of 1 to 4 layers of isolation membranes respectively, use automatic fitting software, and fit the obtained EIS as the baseline, and the intersection of the impedance and the X-axis is Rs. Fitting the EIS test results of n-layer isolation membranes can obtain the resistance Rs(n) of the n-layer isolation membrane, and calculate the ionic conductivity of different regions of the isolation membrane.

[0187] Embodiments 1 to 10 of the present application provide a battery cell and a method for preparing the same, which comprises the following steps:

[0188] S1. Preparation of positive electrode sheet

[0189] The positive electrode active material lithium iron phosphate (LiFePO4), the conductive agent acetylene black, and the binder polyvinylidene fluoride are mixed in a weight ratio of 97.9:0.5:1.6 and dissolved in a solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry is then evenly coated on a 15μm aluminum foil, and after sufficient drying, cold pressing, die cutting, and slitting are performed to obtain a positive electrode sheet.

[0190] S2. Preparation of negative electrode sheet

[0191] Artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), and deionized water are mixed evenly in a weight ratio of 96.8:2:1:0.2 to prepare a negative electrode slurry, and the negative electrode slurry is evenly coated on the negative electrode collector copper foil once or multiple times, and the negative electrode sheet is obtained after drying, cold pressing, and slitting.

[0192] S3. Preparation of isolation film

[0193] The polyolefin resin is sequentially melted, extruded, and blown into a crystalline polymer film, and the crystalline polymer film is then sequentially subjected to crystallization treatment and annealing to obtain a highly oriented multilayer structure. The multilayer structure is further stretched at a high temperature to peel off the crystal surface to form a porous structure, thereby obtaining a polyolefin porous structure base film.

[0194] The base film is supported by a supporting roller, and the base film is first divided into a first area, a second area and a third area along the width direction. A first coating sprayer is used to spray a special aluminum oxide slurry on the first area, the second area and the third area on one side of the base film, and the solvent of the first coating is dried in an oven to form a first coating. A second / third coating sprayer is used to spray the coating material on the second area and the third area, and a coating material is sprayed on the second area, and the solvent of the second coating and the third coating is dried in an oven to form a second coating and a third coating. Then, the same method is used to form the first coating, the second coating and the third coating on the corresponding areas on the other side of the base film. The first coating, the second coating and the third coating are compacted by a pressure roller so that the thickness of the first area, the second area and the third area are the same, thereby obtaining an isolation film.

[0195] S4. Preparation of electrolyte

[0196] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed evenly in a volume ratio of 3:7, 1 mol / L LiPF6 lithium salt was added and dissolved in the organic solvent, and stirred evenly to obtain an electrolyte.

[0197] S5. Assembly

[0198] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare cell, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum shell and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery is then subjected to the processes of static, formation, shaping, and capacity testing in sequence to obtain a battery cell, such as Figures 1-2 shown.

[0199] Comparative Examples 1 and 2 of the present application provide a battery cell and a method for preparing the same, which comprises the following steps:

[0200] S1. Preparation of positive electrode sheet

[0201] The positive electrode active material lithium iron phosphate (LiFePO4), the conductive agent acetylene black, and the binder polyvinylidene fluoride are mixed in a weight ratio of 97.9:0.5:1.6 and dissolved in a solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry is then evenly coated on a 15μm aluminum foil, and after sufficient drying, cold pressing, die cutting, and slitting are performed to obtain a positive electrode sheet.

[0202] S2. Preparation of negative electrode sheet

[0203] Artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), and deionized water are mixed evenly in a weight ratio of 96.8:2:1:0.2 to prepare a negative electrode slurry, and the negative electrode slurry is evenly coated on the negative electrode collector copper foil once or multiple times, and the negative electrode sheet is obtained after drying, cold pressing, and slitting.

[0204] S3. Preparation of isolation film

[0205] The polyolefin resin is sequentially melted, extruded, and blown into a crystalline polymer film, and the crystalline polymer film is then sequentially subjected to crystallization treatment and annealing to obtain a highly oriented multilayer structure. The multilayer structure is further stretched at a high temperature to peel off the crystal surface to form a porous structure, thereby obtaining a polyolefin porous structure base film.

[0206] The base film is supported by a supporting roller, and a coating sprayer is used to spray a special aluminum oxide slurry on one side of the base film. The coating solvent is dried in an oven to form a coating. Then, the same method is used to form a coating on the corresponding area on the other side of the base film. The coating is compacted by a pressure roller to obtain an isolation film.

[0207] S4. Preparation of electrolyte

[0208] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed evenly in a volume ratio of 3:7, 1 mol / L LiPF6 lithium salt was added and dissolved in the organic solvent, and stirred evenly to obtain an electrolyte.

[0209] S5. Assembly

[0210] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare cell, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum shell and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery is then subjected to the processes of static, formation, shaping, and capacity testing in sequence to obtain a battery cell, such as Figures 1-2 shown.

[0211] In addition, the temperature distributions of the first region, the second region and the third region and the 200 cls capacity retention rate of the battery cells of Examples 1 to 10 and Comparative Examples 1 to 2 were measured. The results are shown in Table 2.

[0212] Among them, the test method is as follows:

[0213] The battery cell is connected to a charger and discharger and is continuously cycled at a current of 1C charging and 0.5C discharging. At the same time, temperature sensors are attached to the aluminum shells at the upper, middle and lower parts of the battery cell to sense and record temperature changes. The highest temperature is used as the standard for calculating the consistency of the battery cell (generally the temperature is highest at the end of charging). The energy that can be released by the battery cell in each cycle is taken as the capacity of the battery cell at this time, so as to calculate the capacity retention rate of the battery cell after 200cls of cycling.

[0214] Table 2 Temperature distribution of the first region, the second region and the third region of the battery cells of Examples 1 to 10 and Comparative Examples 1 to 2 and 200 cls capacity retention rate

[0215]

[0216]

[0217] It can be seen from Examples 1 to 10 that by dividing the isolation membrane into a first region, a second region, and a third region sequentially distributed along the height direction of the electrode assembly, the ratio of the dimensions of the first region, the second region, and the third region along the height direction of the electrode assembly is 10 to 40:50 to 60:10 to 40, the ionic conductivity of the first region and the third region is 0.3 mS / cm to 0.9 mS / cm, the ionic conductivity of the second region is 0.4 mS / cm to 0.95 mS / cm, and the difference between the ionic conductivity of the first region and the ionic conductivity of the second region is 0.06 mS / cm to 0.3 mS / cm, the difference between the ionic conductivity of the third region and the ionic conductivity of the second region is 0.02 mS / cm to 0.2 mS / cm, the temperature of the second region of the prepared battery cell (i.e., the temperature of the middle part of the battery cell) is 49°C to 58°C, and the 200cls capacity retention rate is 82% to 92%.

[0218] From the comparison between Comparative Example 1 and Example 1, it can be seen that Comparative Example 1 does not divide the isolation membrane into different regions, the overall ionic conductivity of the isolation membrane of Comparative Example 1 is the same as the overall ionic conductivity of the isolation membrane of Example 1, and the temperature of the second region of the prepared battery cell (i.e., the temperature in the middle of the battery cell) is as high as 64°C, which is much higher than the temperature of the second region of the battery cell of Example 1. The 200cls capacity retention rate of the battery cell of Comparative Example 1 is only 75%, which is lower than the 200cls capacity retention rate of the battery cell of Example 1.

[0219] From the comparison between Comparative Example 2 and Example 4, it can be seen that Comparative Example 2 does not divide the isolation membrane into different regions, the overall ionic conductivity of the isolation membrane of Comparative Example 2 is the same as the overall ionic conductivity of the isolation membrane of Example 4, and the temperature of the second region of the prepared battery cell (i.e., the temperature in the middle of the battery cell) is as high as 60°C, which is much higher than the temperature of the second region of the battery cell of Example 4. The 200cls capacity retention rate of the battery cell of Comparative Example 2 is only 80%, which is lower than the 200cls capacity retention rate of the battery cell of Example 4.

[0220] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell includes an electrode assembly, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, the electrode assembly has two opposite ends, the electrode assembly includes a pole ear, the pole ear is located at the end, the separator is arranged between the positive electrode sheet and the negative electrode sheet, the separator includes a first region and a second region, the first region is closer to the end than the second region, and the ion conductivity of the second region is less than the ion conductivity of the first region.

2. The battery cell according to claim 1, characterized in that: The difference between the ionic conductivity of the first region and the ionic conductivity of the second region is 0.02 mS / cm to 0.6 mS / cm.

3. The battery cell according to claim 1, characterized in that: The isolation film includes a coating material, and the coating material of the first region is the same as the coating material of the second region, and the compaction density of the second region is greater than the compaction density of the first region.

4. The battery cell according to claim 1, characterized in that: The isolation membrane also includes a third region, the first region and the third region are respectively close to the two ends of the electrode assembly, the second region is located between the first region and the third region, and the ion conductivity of the second region is less than the ion conductivity of the third region.

5. The battery cell according to claim 4, characterized in that: The two opposite ends of the electrode assembly are respectively a first end and a second end, the direction extending from the first end to the second end is a height direction of the electrode assembly, the first region, the second region and the third region are distributed in sequence along the height direction of the electrode assembly, and a size ratio of the first region, the second region and the third region along the height direction of the electrode assembly is 10~40:50~60:10~40.

6. The battery cell according to claim 5, characterized in that: The difference between the ionic conductivity of the first region and the ionic conductivity of the second region is 0.06 mS / cm to 0.3 mS / cm, and / or; The difference between the ionic conductivity of the third region and the ionic conductivity of the second region is 0.02 mS / cm to 0.2 mS / cm.

7. The battery cell according to claim 5, characterized in that: The tabs include a positive tab and a negative tab disposed at the first end, and a dimension of the first region along a height direction of the electrode assembly is smaller than a dimension of the third region along the height direction of the electrode assembly.

8. The battery cell according to claim 7, characterized in that: The ratio of the dimensions of the first region, the second region and the third region along the height direction of the electrode assembly is 25-35:45-55:35-45, the ionic conductivity of the second region is smaller than the ionic conductivity of the third region, and the ionic conductivity of the third region is smaller than the ionic conductivity of the first region.

9. The battery cell according to any one of claims 1 to 8, characterized in that: The ionic conductivity of the first region is 0.3 mS / cm to 0.9 mS / cm, and / or; The ion conductivity of the second region is 0.4 mS / cm to 0.95 mS / cm.

10. A method for preparing a battery monomer, characterized in that: The preparation method of the battery cell includes: setting a coating material on the surface of a base film to form an isolation membrane, so that the isolation membrane includes a first region and a second region, and the ion conductivity of the second region is less than the ion conductivity of the first region, assembling a positive electrode plate, a negative electrode plate and the isolation membrane into an electrode assembly, the electrode assembly has two opposite ends, the electrode assembly includes a pole ear, the pole ear is located at the end, and the first region is closer to the end than the second region.

11. The method for preparing a battery monomer according to claim 10, characterized in that: The first region and the second region are distributed in sequence along the width direction of the isolation film. The coating material is firstly arranged on the first region and the second region of the base film, and a first coating layer is formed after drying. Then, the coating material is arranged on the second region, and a second coating layer is formed after drying. The isolation film is obtained by compacting with a pressure roller.

12. The method for preparing a battery cell according to claim 10, characterized in that: The isolation membrane also includes a third region, and the ion conductivity of the third region is smaller than that of the first region. The first region, the second region and the third region are sequentially distributed along the width direction of the isolation membrane. The coating material is firstly arranged in the first region, the second region and the third region of the base membrane, and a first coating layer is formed after drying. Then, the coating material is arranged in the second region and the third region, and the coating material is arranged again in the second region, and a second coating layer and a third coating layer are formed after drying. The isolation membrane is obtained by compacting with a pressure roller.

13. The method for preparing a battery monomer according to claim 12, characterized in that: The thickness of the first coating is 0.1 μm to 2 μm, and / or; The thickness of the second coating is 1 μm to 4 μm, and / or; The thickness of the third coating layer is 1 μm to 3 μm.

14. The method for preparing a battery monomer according to any one of claims 11 to 13, characterized in that: The pressure of the pressing roller is 10MPa to 50MPa.

15. A battery, characterized in that: The battery comprises the battery cell according to any one of claims 1 to 9 or a battery cell prepared by the method for preparing a battery cell according to any one of claims 10 to 14.

16. An electrical device, characterized in that: The electrical device comprises the battery according to claim 15, and the battery is used for providing electrical energy.

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