Diaphragm, pole core, battery, battery pack and electric equipment

Abstract

The invention provides a diaphragm, a pole core, a battery, a battery pack and electric equipment. The diaphragm comprises a base membrane and a coating, the coating is arranged on at least one side surface of the base membrane, the base membrane is provided with a first area and a second area, the first area is located in the middle of the base membrane, the second area is located at the edge of the base membrane, and the surface density of the coating located in the first area is smaller than that of the coating located in the second area. The problem that the free electrolyte amount of a battery is increased when the diaphragm is processed into the battery can be solved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of battery technology, and in particular to a diaphragm, an electrode core, a battery, a battery pack, and an electrical device. Background Art

[0002] The battery includes multiple connected electrode cores, one of which includes a positive electrode plate, a negative electrode plate and a diaphragm. The diaphragm is installed between the positive electrode plate and the negative electrode plate. The diaphragm is used to prevent direct contact between the positive and negative electrodes, thereby avoiding battery short circuit.

[0003] In the related art, when the diaphragm is hot-pressed with the positive and negative electrode sheets to form a battery, the amount of free electrolyte in the battery will increase. Summary of the Invention

[0004] The present invention provides a diaphragm, a core, a battery, a battery pack and an electrical device, which can solve the problem that the amount of free electrolyte in the battery increases when the diaphragm is hot-pressed with the positive and negative electrodes to form a battery.

[0005] The embodiments of this application provide the following technical solutions:

[0006] A first aspect of an embodiment of the present application provides a diaphragm, characterized by comprising:

[0007] basement membrane;

[0008] A coating layer is provided on at least one surface of the base film;

[0009] The base film has a first region and a second region, the first region is located in the middle of the base film, and the second region is located at the edge of the base film; the surface density of the coating located in the first region is less than the surface density of the coating located in the second region.

[0010] In certain embodiments, the difference between the areal density of the coating in the second region and the areal density of the coating in the first region is 1 g / m 2 -2g / m 2 .

[0011] In certain embodiments, the surface density of the coating in the first region is 1 g / m 2 -7g / m 2 .

[0012] In certain embodiments, the coating in the second region has an area density of 2 g / m 2 -8g / m 2 .

[0013] In certain embodiments, the thickness of the coating within the first region is the same as the thickness of the coating within the second region.

[0014] In some embodiments, the second region has a first length L along a direction perpendicular to the thickness of the base film, and the first length L satisfies:

[0015] 0mm<L≤30mm.

[0016] In certain embodiments, a plurality of second regions are provided, and the plurality of second regions are located at different edges of the base film.

[0017] In some embodiments, two second regions are provided, and the two second regions are respectively located at two ends of the first region.

[0018] In certain embodiments, the coating layer is provided with two layers, and the two coating layers are provided on opposite sides of the base film.

[0019] A second aspect of an embodiment of the present application provides a pole core comprising the diaphragm described in the first aspect.

[0020] A third aspect of the embodiments of the present application provides a battery, comprising the pole core described in the second aspect.

[0021] A fourth aspect of an embodiment of the present application provides a battery pack comprising the battery described in the third aspect.

[0022] A fifth aspect of the embodiments of the present application provides an electrical device, comprising the battery described in the third aspect or the battery pack described in the fourth aspect.

[0023] In the diaphragm of this structure, the base film is used to isolate the direct contact between the positive and negative pole pieces, thereby reducing the occurrence of heat or short circuits caused by direct contact between the positive and negative pole pieces. The coating is used to improve the thermal stability of the diaphragm, thereby reducing the occurrence of pole core short circuits or pole core combustion. Alternatively, the coating can increase the mechanical strength of the diaphragm, thereby increasing the service life of the diaphragm. Alternatively, the coating can enhance the liquid retention and wettability of the diaphragm, thereby extending the cycle life of the pole core. The surface density of the coating located in the first area is less than the surface density of the coating located in the second area, which can make the surface density of the coating in the middle of the diaphragm less than the surface density of the coating at the edge of the diaphragm. During the hot pressing process of the pole core, under the same hot pressing equipment and hot pressing parameters, the connection strength between the coating in the second area and the edge area of ​​the pole piece can be made stronger, thereby improving the safety performance of the pole core. After the hot pressing is completed, the surface density of the coating located in the first area is lower, which can improve the electrolyte infiltration effect of the diaphragm and optimize the problem of increased free electrolyte amount in the battery.

[0024] Therefore, the diaphragm provided in the present application can solve the problem that when the diaphragm is hot-pressed with the positive and negative electrode sheets to form a battery cell, the amount of free electrolyte in the battery cell will increase.

[0025] In addition to the technical problems solved by the embodiments of the present application described above, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions, other technical problems that can be solved by the diaphragm, electrode core, battery, battery pack and electrical equipment provided by the embodiments of the present application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 A schematic diagram of the main structure of the diaphragm provided in an embodiment of the present application;

[0028] Figure 2 Schematic diagram of the connection structure of the diaphragm, positive electrode sheet and negative electrode sheet provided in the embodiment of the present application.

[0029] Description of reference numerals:

[0030] 100-diaphragm; 101-base film; 102-coating;

[0031] 200-positive electrode;

[0032] 300-negative electrode;

[0033] L - first length. DETAILED DESCRIPTION

[0034] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0035] It should be noted that areal density refers to the mass per unit area.

[0036] In the related technology, during the preparation process of batteries with double-sided tabs, due to the presence of edge areas on both sides of the electrode piece, the degree of fit of the middle position of the electrode piece after hot pressing is tighter than that of the two sides of the tab. This will lead to poor safety of the edge area of ​​the electrode core after hot pressing, and will make it more difficult for the middle position of the battery cell to absorb liquid when the electrode core is processed into a battery cell, that is, the electrolyte infiltration effect of the diaphragm becomes worse, which will lead to an increase in the amount of free electrolyte in the battery.

[0037] It should be noted that the thickness at the edge of the electrode is smaller than the thickness at the middle of the electrode, so as to form an edge area of ​​the electrode. The edge area of ​​the electrode is used to allow the electrolyte to migrate from the edge to the middle.

[0038] In related technologies, a diaphragm includes a base film and a coating layer. The coating layer is formed by uniformly applying a coating slurry to the surface of the base film through a coating, spraying, or dipping process. The coating then forms a uniform coating on the surface of the base film through drying and / or curing steps.

[0039] It should be noted that the coating can be polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), alumina, silica, or a combination of one or more other materials. There is no restriction here and it can be selected according to actual use requirements.

[0040] It should be noted that the spraying process is performed by using a spraying device.

[0041] It should be noted that the spraying device can be a sprayer, a coater or an ultrasonic sprayer. The nozzle of the spraying device faces the side close to the base film.

[0042] It should be noted that the positive electrode sheet, the separator and the negative electrode sheet are formed into a core by hot pressing. During the hot pressing process of the core, under the same hot pressing equipment and hot pressing parameter conditions, the greater the surface density of the coating, the greater the contact area between the coating and the positive electrode sheet or the negative electrode sheet, thereby improving the adhesion between the separator and the positive electrode sheet or the negative electrode sheet, and a larger contact area means more intermolecular forces (such as van der Waals forces, hydrogen bonds, etc.), which helps to improve the connection strength between the separator and the positive electrode sheet or the negative electrode sheet, but a larger contact area will lead to a worse wetting effect of the electrolyte.

[0043] In the diaphragm provided in the embodiment of the present application, the base film is used to isolate the direct contact between the positive electrode plate and the negative electrode plate, so as to reduce the occurrence of heat or short circuit caused by direct contact between the positive electrode plate and the negative electrode plate. The coating is used to improve the thermal stability of the diaphragm, thereby reducing the occurrence of electrode core short circuit or electrode core combustion. Alternatively, the coating can increase the mechanical strength of the diaphragm, thereby increasing the service life of the diaphragm. Alternatively, the coating can enhance the liquid retention and wettability of the diaphragm, thereby extending the cycle life of the electrode core. The surface density of the coating located in the first area is less than the surface density of the coating located in the second area, which can make the surface density of the coating in the middle of the diaphragm less than the surface density of the coating at the edge of the diaphragm. During the hot pressing process of the electrode core, under the same hot pressing equipment and hot pressing parameters, the connection area between the coating in the second area and the edge area of ​​the electrode plate can be made larger, thereby making the connection strength between the coating in the second area and the edge area of ​​the electrode plate greater, thereby improving the safety performance of the electrode core. When the pole core is processed into a battery, the surface density of the coating in the first area is smaller, which can make the connection area between the coating in the first area and the pole piece smaller, so that the electrolyte can better penetrate between the diaphragm and the pole piece in the first area, thereby providing an effective ion conduction path, helping to improve the electrolyte infiltration effect of the diaphragm and optimize the content of free electrolyte in the battery.

[0044] Therefore, the diaphragm provided in the embodiments of the present application can solve the problem that the amount of free electrolyte in the battery cell increases when the diaphragm is hot-pressed with the positive and negative electrode sheets to form a battery cell.

[0045] like Figure 1 As shown, the diaphragm 100 provided in an embodiment of the present application includes: a base film 101 and a coating 102, wherein the coating 102 is provided on at least one side surface of the base film 101, the base film 101 has a first area and a second area, the first area is located in the middle of the base film 101, and the second area is located at the edge of the base film 101, and the surface density of the coating 102 located in the first area is less than the surface density of the coating 102 located in the second area.

[0046] It should be noted that the first region is located relatively close to the middle of the base film 101, the second region is located relatively close to the edge of the base film 101, and the first region and the second region are connected.

[0047] It should be noted that, when the hot pressing of the pole core is completed, part of the second area is arranged opposite to part of the edge area of ​​the pole piece.

[0048] It should be noted that, when the hot pressing of the pole core is completed, part of the first area and part of the middle area of ​​the pole piece are arranged relative to each other.

[0049] It should be noted that the surface density of the coating 102 located in the first area can be measured by using a microscope, a thickness gauge or other measuring equipment to measure the thickness of the coating 102 in the first area along the thickness direction of the base film 101, and the surface density is calculated in combination with the material density of the coating 102, wherein the surface density of the coating 102 located in the first area is equal to the thickness of the coating 102 in the first area multiplied by the material density of the coating 102.

[0050] The microscopy method can include cutting a sample of the first region of the diaphragm 100, including the base film 101 and the coating 102, and processing the sample to obtain a flat cross-section. The cross-section of the coating 102 located in the first region can be observed using an optical or electron microscope. The thickness of the coating 102 in the first region can be measured using a scale or calibration tool provided with the microscope, or the vertical distance between the coating 102 and the base film 101 can be measured using measurement software or the microscope's built-in measurement function on the microscope image.

[0051] The thickness gauge can be used by placing the probe of the thickness gauge on the surface of the coating 102 in the first area, ensuring that the probe is perpendicular to the surface, and reading the thickness value displayed by the thickness gauge. If necessary, multiple measurements can be taken at different locations to obtain an average value.

[0052] It should be noted that the density of the coating 102 varies depending on the material of the coating. When the coating is polyvinylidene fluoride (PVDF), the density of the coating 102 is 1.78 g / cm 3 When the coating material is polyacrylonitrile (PAN), the density of the coating 102 is 1.8 g / cm 3 When the coating material is polyvinyl alcohol (PVA), the density of the coating 102 is 1.19 g / cm 3 When the coating material is aluminum oxide, the density of the coating 102 is 3.95 g / cm 3 When the coating material is silicon dioxide, the density of the coating 102 is 2.65 g / cm 3 .

[0053] Furthermore, since it is impossible to enumerate all coating materials and material densities of the coating 102 , the material densities of the coating 102 made of other materials are also within the scope of protection of the present invention.

[0054] It should be noted that the surface density of the coating 102 located in the second area can be measured by using a microscope, a thickness gauge or other measuring equipment to measure the thickness of the coating 102 in the second area along the thickness direction of the base film 101, and the surface density is calculated in combination with the material density of the coating 102, wherein the surface density of the coating 102 located in the second area is equal to the thickness of the coating 102 in the second area multiplied by the material density of the coating 102.

[0055] The microscopy method can include cutting a sample of the second region, including the base film 101 and the coating 102, from the diaphragm 100 and processing the sample to obtain a flat cross-section. The cross-section of the coating 102 located in the second region can be observed using an optical or electron microscope. The thickness of the coating 102 in the second region can be measured using a scale or calibration tool provided with the microscope. Alternatively, the vertical distance between the coating 102 and the base film 101 can be measured from the microscope image using measurement software or the microscope's built-in measurement function.

[0056] The thickness gauge can be used by placing the probe of the thickness gauge on the surface of the coating 102 in the second area, ensuring that the probe is perpendicular to the surface, and reading the thickness value displayed by the thickness gauge. If necessary, multiple measurements can be taken at different locations to obtain an average value.

[0057] It should be noted that the density of the coating 102 varies depending on the material of the coating. When the coating is polyvinylidene fluoride (PVDF), the density of the coating 102 is 1.78 g / cm 3 When the coating material is polyacrylonitrile (PAN), the density of the coating 102 is 1.8 g / cm 3 When the coating material is polyvinyl alcohol (PVA), the density of the coating 102 is 1.19 g / cm 3 When the coating material is aluminum oxide, the density of the coating 102 is 3.95 g / cm 3 When the coating material is silicon dioxide, the density of the coating 102 is 2.65 g / cm 3 .

[0058] It should be noted that the division standard between the first area and the second area is based on the surface density of the coating 102. The surface density of the coating 102 in the middle area relatively close to the base film 101 is less than the surface density of the coating 102 in the edge area relatively close to the base film 101. In this case, the coating 102 in the middle area relatively close to the base film 101 is the coating 102 in the first area, and the coating 102 in the edge area relatively close to the base film 101 is the coating 102 in the second area.

[0059] It should be noted that there are various processing methods for the surface density of the coating 102 in the first region and the second region. The processing methods for the surface density of the coating 102 in the first region and the second region are described below with examples.

[0060] In a feasible embodiment, the spray flow rate of the nozzle of the spray device in the first area is smaller than the spray flow rate of the nozzle of the spray device in the second area.

[0061] It can be understood that the spray flow rate of the nozzle of the spray device in the first area is less than the spray flow rate of the nozzle of the spray device in the second area, which can make the spraying time of the coating 102 in the first area equal to the spraying time of the coating 102 in the second area, thereby shortening the processing time of the diaphragm 100.

[0062] In another possible embodiment, the spraying time of the nozzle of the spraying device in the first area is shorter than the spraying time of the nozzle of the spraying device in the second area.

[0063] It is understandable that the spraying time of the nozzle of the spraying device in the first area is shorter than the spraying time of the nozzle of the spraying device in the second area, which can reduce the waste of the coating 102 and shorten the processing cost of the diaphragm 100.

[0064] It is understandable that there is no limitation on the processing method of the surface density of the coating 102 in the first area and the second area, and it can be selected according to actual use requirements.

[0065] like Figure 2 As shown, the difference between the surface density of the coating 102 located in the second area and the surface density of the coating 102 located in the first area provided by the embodiment of the present application is 1 g / m 2 -2g / m 2 .

[0066] It is understood that the difference between the surface density of the coating 102 located in the second region and the surface density of the coating 102 located in the first region is 1 g / m 2 -2g / m 2 , which can make the connection strength between the coating 102 in the second area of ​​the pole core after hot pressing and the edge area of ​​the pole piece stronger, thereby improving the safety of the pole core. The surface density of the coating 102 in the first area is relatively small, which can improve the problem of the increase in the amount of free electrolyte in the battery cell when the pole core is processed into a battery cell.

[0067] It should be noted that the difference between the surface density of the coating 102 located in the second region and the surface density of the coating 102 located in the first region can be 1.1 g / m 2 , 1.2g / m 2 , 1.5g / m 2 , 1.7g / m 2 , 1.9g / m 2 , or 1g / m 2 Up to 2g / m 2 Any value within the range is not restricted here and can be selected according to actual usage requirements.

[0068] It can be understood that the difference between the surface density of the coating 102 located in the second area and the surface density of the coating 102 located in the first area is the above-mentioned value, which can make the connection strength between the coating 102 in the second area and the edge area of ​​the electrode piece of the pole core after hot pressing stronger, and the surface density of the coating 102 in the first area is smaller, which can effectively improve the problem of the increase in the amount of free electrolyte in the battery cell when the pole core is processed into a battery cell, while ensuring the mechanical properties of the diaphragm.

[0069] The surface density of the coating 102 in the first region provided by the embodiment of the present application is 1 g / m 2 -7g / m 2 .

[0070] It is understood that the surface density of the coating 102 in the first region is 1 g / m 2 -7g / m 2 , which can make the surface density of the coating 102 located in the first area smaller, and can improve the problem of increased amount of free electrolyte in the battery cell when the pole core is processed into the battery cell.

[0071] It should be noted that the surface density of the coating 102 in the first region may be 2 g / m 2 , 3g / m 2 , 4g / m 2 , 5g / m 2 , 6g / m 2 , or at 1g / m 2 Up to 7g / m 2 There is no restriction on other values ​​between and , and you can select them according to your actual needs.

[0072] It can be understood that the surface density of the coating 102 located in the first area is any of the above values, which can make the surface density of the coating 102 located in the first area smaller, and can improve the problem of increased free electrolyte amount in the battery cell when the pole core is processed into a battery cell.

[0073] The surface density of the coating 102 in the second region provided by the embodiment of the present application is 2 g / m 2 -8g / m 2 .

[0074] It is understood that the surface density of the coating 102 in the second region is 2 g / m 2 -8g / m 2 During the hot pressing process of the pole core, under the same hot pressing equipment and hot pressing parameter conditions, the connection strength between the coating 102 in the second area and the edge area of ​​the pole piece can be made stronger, thereby improving the safety of the pole core.

[0075] It should be noted that the surface density of the coating 102 in the second area can be 3 g / m 2 , 4g / m 2 , 5g / m 2 , 6g / m 2 , 7g / m 2 , or at 2g / m 2 Up to 8g / m 2 There is no restriction on other values ​​between and , and you can select them according to your actual needs.

[0076] It can be understood that the surface density of the coating 102 located in the second area is any of the above-mentioned values. During the hot pressing process of the pole core, under the same hot pressing equipment and hot pressing parameter conditions, the connection strength between the coating 102 in the second area and the edge area of ​​the pole piece can be made stronger, thereby improving the safety of the pole core.

[0077] In the embodiment of the present application, the thickness of the coating 102 in the first region is the same as the thickness of the coating 102 in the second region.

[0078] It can be understood that the thickness of the coating 102 located in the first area is the same as the thickness of the coating 102 located in the second area, which can make the surface flatness of the pole core higher after hot pressing, thereby improving the stability of the pole core.

[0079] It should be noted that errors within the normal measurement range are also within the protection scope of the present invention.

[0080] It should be noted that, when the thickness of the coating 102 in the first region and the thickness of the coating 102 in the second region are the same, the surface density of the coating 102 in the first region can be made smaller than the surface density of the coating 102 in the second region by changing the material density of the coating 102 in the first region and the material density of the coating 102 in the second region.

[0081] It should be noted that the above embodiment can be achieved by making the material density of the coating 102 located in the first region smaller than the material density of the coating 102 located in the second region.

[0082] It should be noted that the thickness of the coating 102 in the first region can be measured along the thickness direction of the base film 101 using a microscope, a thickness gauge or other measuring equipment.

[0083] The microscopy method can include cutting a sample of the first region of the diaphragm 100, including the base film 101 and the coating 102, and processing the sample to obtain a flat cross-section. The cross-section of the coating 102 located in the first region can be observed using an optical or electron microscope. The thickness of the coating 102 in the first region can be measured using a scale or calibration tool provided with the microscope, or the vertical distance between the coating 102 and the base film 101 can be measured using measurement software or the microscope's built-in measurement function on the microscope image.

[0084] The thickness gauge can be used by placing the probe of the thickness gauge on the surface of the coating 102 in the first area, ensuring that the probe is perpendicular to the surface, and reading the thickness value displayed by the thickness gauge. If necessary, multiple measurements can be taken at different locations to obtain an average value.

[0085] It should be noted that the thickness of the coating 102 in the second region can be measured along the thickness direction of the base film 101 using a microscope, a thickness gauge or other measuring equipment.

[0086] The microscopy method can include cutting a sample of the second region, including the base film 101 and the coating 102, from the diaphragm 100 and processing the sample to obtain a flat cross-section. The cross-section of the coating 102 located in the second region can be observed using an optical or electron microscope. The thickness of the coating 102 in the second region can be measured using a scale or calibration tool provided with the microscope. Alternatively, the vertical distance between the coating 102 and the base film 101 can be measured from the microscope image using measurement software or the microscope's built-in measurement function.

[0087] The thickness gauge can be used by placing the probe of the thickness gauge on the surface of the coating 102 in the second area, ensuring that the probe is perpendicular to the surface, and reading the thickness value displayed by the thickness gauge. If necessary, multiple measurements can be taken at different locations to obtain an average value.

[0088] In the diaphragm 100 provided in the embodiment of the present application, the second region has a first length L along a thickness direction perpendicular to the base film 101 , and the first length L satisfies: 0 mm < L ≤ 30 mm.

[0089] It can be understood that the first length L satisfies: 0mm<L≤30mm. During the hot pressing process of the pole core, under the same hot pressing equipment and hot pressing parameter conditions, the connection strength between the coating 102 in the second area and the edge area of ​​the pole piece can be made stronger, thereby improving the safety of the pole core.

[0090] It should be noted that the first length refers to the extended length value of the second region along the thickness direction perpendicular to the base film 101 and the length direction perpendicular to the base film 101 , that is, parallel to the width direction of the base film 101 .

[0091] It should be noted that the first length can be obtained by measuring the length of the second region in a direction parallel to the width of the base film 101 .

[0092] It should be noted that, when there are two second areas, the first length L is the length of one of the second areas.

[0093] It should be noted that the value of the first length L can be 5mm, 10mm, 15mm, 20mm, 25mm or other values ​​between 0mm and 30mm. There is no limitation here and it can be selected according to actual usage requirements.

[0094] It can be understood that the value of the first length L is any of the above-mentioned values, which can make the connection strength between the coating 102 in the second area and the edge area of ​​the pole piece stronger under the same hot pressing equipment and hot pressing parameter conditions during the hot pressing process of the pole core, thereby improving the safety of the pole core.

[0095] The embodiment of the present application provides a plurality of second regions, and the plurality of second regions are located at different edges of the base film 101 .

[0096] It can be understood that increasing the number of second areas can make the connection strength between the coating in the second area and the different edge areas of the pole piece stronger during the hot pressing process of the pole core under the same hot pressing equipment and hot pressing parameters, thereby greatly improving the safety of the pole core.

[0097] It should be noted that the number of second areas can be two, three, or four, which is not limited here and can be selected according to actual usage needs.

[0098] When the number of second areas is two, the two second areas may be arranged opposite to each other or adjacent to each other.

[0099] When the number of second areas is three, the three second areas are adjacently arranged.

[0100] When there are four second areas, the four second areas are sequentially connected end to end and arranged around the first area.

[0101] It should be noted that there are two second regions, and the two second regions are respectively arranged at both ends of the first region along the thickness direction perpendicular to the base film 101 .

[0102] It can be understood that when the pole core is hot-pressed, the coating 102 located in the two second areas is respectively connected to the edge areas on both sides of the pole piece, so that the connection strength between the diaphragm 100 and the edge area of ​​the pole piece is increased, thereby improving the safety performance of the pole core.

[0103] In some embodiments, the edge region of the base film 101 corresponds to the thinned region of the electrode piece, which is used to connect the electrode tab. Therefore, the second region of the base film 101 is provided corresponding to the thinned region of the electrode piece.

[0104] It should be noted that there are many different configurations for the thickness direction of the vertical base film 101 , and the thickness direction of the vertical base film 101 will be described with examples in turn below.

[0105] In a feasible embodiment, the direction perpendicular to the thickness direction of the base film 101 may be the length direction of the base film 101 , and along the length direction of the base film 101 , the first second region, the first region and the second second region are sequentially connected and arranged.

[0106] In another feasible embodiment, the thickness direction perpendicular to the base film 101 may be the width direction of the base film 101 , and along the width direction of the base film 101 , the first second region, the first region, and the second second region are sequentially connected and arranged.

[0107] It is understandable that the specific configuration method in the thickness direction of the vertical base film 101 is not limited and can be selected according to actual use requirements.

[0108] The coating layer 102 provided in the embodiment of the present application is provided with two layers, and the two layers of coating layer 102 are respectively provided on the opposite sides of the base film 101.

[0109] It is understandable that the coating 102 on one side of the base film 101 is used to connect the positive electrode sheet 200, and the coating 102 on the other side of the base film 101 is used to connect the negative electrode sheet 300. The coating 102 in the diaphragm 100 can play a role in bonding the positive electrode sheet 200 and the negative electrode sheet 300 after hot pressing, thereby improving the connection strength between the positive electrode sheet 200 and the negative electrode sheet 300. Alternatively, the coating 102 can enhance the mechanical strength of the diaphragm 100, so that the diaphragm 100 is not easily damaged during battery operation. Alternatively, the coating 102 can also improve the permeability of the diaphragm 100, promote the transmission of lithium ions in the electrolyte, and thus improve the electrochemical performance of the battery.

[0110] It should be noted that the two coating layers 102 are disposed on two surfaces along the thickness direction of the base film 101 . Along the thickness direction of the base film 101 , the positive electrode sheet 200 , the separator 100 , and the negative electrode sheet 300 are stacked in sequence.

[0111] In addition, an embodiment of the present application provides a pole core, including a positive pole piece 200 and a negative pole piece 300 , and a separator 100 provided in any of the above embodiments, wherein the separator 100 is sandwiched between the positive pole piece 200 and the negative pole piece 300 .

[0112] The specific structure, working principle and function of the diaphragm 100 have been described in detail in the above embodiments and will not be repeated here. It should be noted that the following are multiple groups of examples and comparative examples for the process of preparing the electrode core.

[0113] An embodiment of the present application provides a battery, comprising the pole core provided by any of the above embodiments.

[0114] An embodiment of the present application provides a battery pack, comprising the battery provided by any of the above embodiments.

[0115] An embodiment of the present application also provides an electrical device, including an electrical device, a battery as described in any of the above embodiments, or a battery pack as described in any of the above embodiments, wherein the battery or battery pack is used to provide electrical energy to the electrical device.

[0116] The electrical equipment in the embodiments of the present application may be a vehicle. For example, the vehicle may be a fuel-powered vehicle, a gas-powered vehicle, or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle. Accordingly, the electrical device may be the vehicle's drive mechanism or the vehicle's control system.

[0117] In addition, the electrical equipment may also be other energy storage devices, such as mobile phones, portable devices, laptop computers, electric toys, electric tools, ships and spacecraft, etc., among which the spacecraft may include airplanes, rockets, space shuttles or spacecraft.

[0118] Since the electrical device in this embodiment includes the battery or battery pack described in any of the above embodiments, the electrical device includes the battery or battery pack structure and beneficial effects, and this embodiment will not be further elaborated here.

[0119] Hereinafter, a battery provided by the present invention is described in detail through specific embodiments.

[0120] Example 1

[0121] The method for preparing the battery of this embodiment includes the following steps:

[0122] (1) Using a sprayer, polyvinylidene fluoride (PVDF) is sprayed onto the first and second regions of the base film 101, respectively (the first and second regions are of equal width (the width of the electrode is used as the width of the first and second regions), and the second region is on both sides of the length direction of the first region and connected to the first region) and dried and cured to form a uniform coating 102 on the surface of the base film 101. The surface density of the coating 102 in the first region is controlled to be 5.5 g / m 2 The surface density of the coating 102 in the second region is 6.9 g / m 2The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 1.4 g / m 2 , the thickness of the coating 102 is 2 μm, the first length of the second region is 20 mm, and the length of the first region is 600 mm, thereby obtaining the desired diaphragm 100 .

[0123] (2) Select a traditional lithium iron phosphate positive electrode sheet and a graphite negative electrode sheet, and make a pole core by winding or stacking them with the separator 100. Weld the pole ears on the positive and negative electrode sheets respectively, and put the pole core into the aluminum-plastic film with pre-punched holes, inject the electrolyte and encapsulate it to obtain a soft-pack battery.

[0124] Example 2

[0125] The difference from Example 1 is that the surface density of the coating 102 in the first area is 5.9 g / m 2 The surface density of the coating 102 in the second region is 6.9 g / m 2 The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 1 g / m 2 The remaining steps are the same as those in Example 1.

[0126] Example 3

[0127] The difference from Example 1 is that the surface density of the coating 102 in the first area is 4.9 g / m 2 The surface density of the coating 102 in the second region is 6.9 g / m 2 The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 2 g / m 2 The remaining steps are the same as those in Example 1.

[0128] Example 4

[0129] The difference from Example 1 is that the surface density of the coating 102 in the first area is 4.4 g / m 2 The surface density of the coating 102 in the second region is 6.9 g / m 2 The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 2.5 g / m 2 The remaining steps are the same as those in Example 1.

[0130] Example 5

[0131] The difference from Example 1 is that the surface density of the coating 102 in the first area is 8 g / m 2 The surface density of the coating 102 in the second region is 9 g / m 2The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 1 g / m 2 The remaining steps are the same as those in Example 1.

[0132] Example 6

[0133] The difference from Example 1 is that the first length of the second area is 10 mm, and the length of the first area is 620 mm. The remaining steps are the same as those in Example 1.

[0134] Example 7

[0135] The difference from Example 1 is that the first length of the second area is 30 mm, and the length of the first area is 580 mm. The remaining steps are the same as those in Example 1.

[0136] Example 8

[0137] The difference from Example 1 is that the first length of the second area is 40 mm, and the length of the first area is 560 mm. The remaining steps are the same as those in Example 1.

[0138] Example 9

[0139] The difference from Example 1 is that the surface density of the coating 102 in the first area is 7 g / m 2 The surface density of the coating 102 in the second region is 8 g / m 2 The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 1 g / m 2 The first length of the second region is 20 mm, and the length of the first region is 580 mm. The remaining steps are the same as those in Example 1.

[0140] Example 10

[0141] The difference from Example 1 is that the surface density of the coating 102 in the first area is 1 g / m 2 The surface density of the coating 102 in the second region is 2 g / m 2 The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 1 g / m 2 The first length of the second region is 20 mm, and the length of the first region is 560 mm. The remaining steps are the same as those in Example 1.

[0142] Comparative Example 1

[0143] The difference from Example 1 is that the surface density of the coating 102 in the first area is 6.3 g / m 2 The surface density of the coating 102 in the second region is 6.3 g / m 2The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 0 g / m 2 The remaining steps are the same as those in Example 1.

[0144] Comparative Example 2

[0145] The difference from Example 1 is that the surface density of the coating 102 in the first area is 7.5 g / m 2 The surface density of the coating 102 in the second region is 6.0 g / m 2 The difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is -1.5 g / m 2 The remaining steps are the same as those in Example 1.

[0146] It should be noted that the materials of the positive electrode sheet 200, the negative electrode sheet 300, the base film 101 and the coating 102 in all the embodiments and comparative examples of the present application are the same.

[0147] The amount of free electrolyte in the battery cells prepared in Examples 1-10 and Comparative Examples 1-2 was tested.

[0148] It should be noted that the surface density of the coating 102 located in the first area can be measured by using a microscope, a thickness gauge or other measuring equipment to measure the thickness of the coating 102 in the first area along the thickness direction of the base film 101, and the surface density can be calculated in combination with the material density of the coating 102, wherein the surface density of the coating 102 located in the first area is equal to the thickness of the coating 102 in the first area multiplied by the material density of polyvinylidene fluoride (PVDF).

[0149] It should be noted that the material density of polyvinylidene fluoride (PVDF) is 1.78g / cm 3 .

[0150] The microscopy method can include cutting a sample of the first region of the diaphragm 100, including the base film 101 and the coating 102, and processing the sample to obtain a flat cross-section. The cross-section of the coating 102 located in the first region can be observed using an optical or electron microscope. The thickness of the coating 102 in the first region can be measured using a scale or calibration tool provided with the microscope, or the vertical distance between the coating 102 and the base film 101 can be measured using measurement software or the microscope's built-in measurement function on the microscope image.

[0151] The thickness gauge can be used by placing the probe of the thickness gauge on the surface of the coating 102 in the first area, ensuring that the probe is perpendicular to the surface, and reading the thickness value displayed by the thickness gauge. If necessary, multiple measurements can be taken at different locations to obtain an average value.

[0152] It should be noted that the surface density of the coating 102 located in the second area can be measured by using a microscope, a thickness gauge or other measuring equipment to measure the thickness of the coating 102 in the second area along the thickness direction of the base film 101, and the surface density can be calculated in combination with the material density of the coating 102, wherein the surface density of the coating 102 located in the second area is equal to the thickness of the coating 102 in the second area multiplied by the material density of polyvinylidene fluoride (PVDF).

[0153] It should be noted that the material density of polyvinylidene fluoride (PVDF) is 1.78g / cm 3 .

[0154] The microscopy method can include cutting a sample of the second region, including the base film 101 and the coating 102, from the diaphragm 100 and processing the sample to obtain a flat cross-section. The cross-section of the coating 102 located in the second region can be observed using an optical or electron microscope. The thickness of the coating 102 in the second region can be measured using a scale or calibration tool provided with the microscope. Alternatively, the vertical distance between the coating 102 and the base film 101 can be measured from the microscope image using measurement software or the microscope's built-in measurement function.

[0155] The thickness gauge can be used by placing the probe of the thickness gauge on the surface of the coating 102 in the second area, ensuring that the probe is perpendicular to the surface, and reading the thickness value displayed by the thickness gauge. If necessary, multiple measurements can be taken at different locations to obtain an average value.

[0156] It should be noted that a sample of the base film 101 and the coating 102, including both the first and second regions, is cut from the diaphragm 100 and processed to obtain a flat cross-section. The cross-section of the coating 102 in the first and second regions is observed using an optical or electron microscope. The lengths of the first and second regions are measured using a scale or calibration tool provided with the microscope, or using measurement software or the microscope's built-in measurement function on the microscope image.

[0157] It should be noted that the difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is calculated as follows: the surface density of the coating 102 in the second region minus the surface density of the coating 102 in the first region.

[0158] It should be noted that the first length of the second region can be obtained by measuring the extended length of the second region using a length measuring instrument along a direction parallel to the width of the diaphragm 100 .

[0159] It should be noted that the test method for the amount of free electrolyte in the battery cell is: take the battery cell with a 25% SOC state after capacity division, weigh it before disassembly, weigh it three times and take the average value M1, then disassemble the battery cell, take out all parts of the battery cell except the electrode core, and put them in a ziplock bag; the electrode core is disassembled into the positive electrode sheet 200, the negative electrode sheet 300, the diaphragm 100, and the structural parts. The structural parts include all parts except the electrode core, including tape, etc., which cannot be omitted; vacuum bake at 60℃ for 6h; weigh the baked positive electrode sheet 200, negative electrode sheet 300, diaphragm 100, and structural parts, and take the average value M2 after weighing three times; wherein, the amount of free electrolyte = M1-M2.

[0160] Table 1 Test data of free electrolyte content in battery cells of Examples and Comparative Examples

[0161]

[0162] As shown in Table 1, relative to Comparative Example 1 and Comparative Example 2, Examples 1 to 10 can maximize the gap between the intermediate electrode layers of the electrode core after hot pressing by making the surface density of the coating 102 located in the first region smaller than the surface density of the coating 102 located in the second region, thereby providing a path for electrolyte migration, improving the liquid absorption capacity of the electrode core, and reducing the amount of free electrolyte.

[0163] Furthermore, it can be seen from Example 4 that the difference between the surface density of the coating 102 in the second region and the surface density of the coating 102 in the first region is 1 g / m 2 -2g / m 2 , which can reduce the amount of free electrolyte, while ensuring the mechanical properties of the diaphragm and improving the safety performance of the electrode core.

[0164] Furthermore, it can be seen from Example 5 that in Examples 1-3, and Examples 6-9, by further controlling the surface density of the coating 102 in the first region to be 1 g / m 2 -7g / m 2 The surface density of the coating 102 in the second area is 2 g / m 2 -8g / m 2 , which can reduce the amount of free electrolyte and improve the liquid absorption capacity of the electrode core.

[0165] Furthermore, it can be seen from Example 8 that Examples 1 to 7, Example 9 and Example 10 further control the first length L to satisfy: 0mm<L≤30mm. When the total length of the base film 101 remains unchanged, the length of the second region can be reduced, and the length of the first region can be increased, so that the gap between the middle electrode layers of the electrode core after hot pressing can be maximized, providing a path for electrolyte migration, improving the liquid absorption capacity of the electrode core, and reducing the amount of free electrolyte.

[0166] The various embodiments or implementation methods in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referenced to each other.

[0167] It should be noted that references in this specification to "one embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not necessarily every embodiment includes that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A diaphragm, characterized in that: include: basement membrane (101); A coating layer (102) is provided on at least one surface of the base film (101); The base film (101) has a first region and a second region, the first region is located in the middle of the base film (101), and the second region is located at the edge of the base film (101); the surface density of the coating (102) located in the first region is less than the surface density of the coating (102) located in the second region.

2. The diaphragm according to claim 1, characterized in that The difference between the surface density of the coating (102) in the second region and the surface density of the coating (102) in the first region is 1 g / m 2 -2g / m 2 .

3. The diaphragm according to claim 1 or 2, characterized in that The surface density of the coating (102) in the first region is 1 g / m 2 -7g / m 2 .

4. The diaphragm according to any one of claims 1 to 3, characterized in that The surface density of the coating (102) in the second region is 2 g / m 2 -8g / m 2 .

5. The diaphragm according to any one of claims 1 to 4, characterized in that The thickness of the coating (102) in the first region is the same as the thickness of the coating (102) in the second region.

6. The diaphragm according to any one of claims 1 to 5, characterized in that Along a thickness direction perpendicular to the base film (101), the second region has a first length L, and the first length L satisfies: 0mm<L≤30mm.

7. The diaphragm according to any one of claims 1 to 6, characterized in that There are multiple second regions, and the multiple second regions are located at different edges of the base film (101).

8. The diaphragm according to claim 7, characterized in that There are two second areas, and the two second areas are located at both ends of the first area.

9. The diaphragm according to any one of claims 1 to 8, characterized in that The coating (102) is provided with two layers, and the two layers of the coating (102) are respectively provided on the opposite sides of the base film (101).

10. A pole core, characterized in that: The invention comprises the diaphragm according to any one of claims 1 to 9.

11. A battery, characterized in that: Including the pole core according to claim 10.

12. A battery pack, characterized in that: Including the battery according to claim 11.

13. An electrical device, characterized in that: Including the battery according to claim 11 or the battery pack according to claim 12.

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