Separator, battery cell and electric device

Abstract

A separator (10), a battery cell, and an electric device. The electric device comprises a battery cell. The battery cell comprises the separator (10). The separator (10) comprises a first region (11) and a second region (12). The second region (12) surrounds the first region (11), and at least a portion of the second region (12) is thinner than the first region (11) in thickness. Thus, the likelihood of lithium plating at the edge of an electrode sheet is reduced.

Description

Diaphragms, battery cells and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on February 29, 2024, with application number 202420394906.5 and titled “Diaphragm, Battery Cell and Electrical Equipment,” the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a diaphragm, a battery cell and an electrical device. Background Art

[0004] Currently, lithium-ion batteries are widely used in energy storage and electric vehicles due to their high energy density and rapid charge and discharge capabilities. In existing technologies, lithium-ion batteries are frequently charged and discharged during user use. During this process, lithium at the edge of the negative electrode facing the positive electrode diffuses into the overhang area (the portion of the negative electrode extending beyond the positive electrode in both length and width). As a result, during charging, the SOC (state of charge, the ratio of remaining capacity to battery capacity) near the edge of the negative electrode is lower than that in the middle, leading to lithium deposition at the edge of the electrode.

[0005] Summary of the Invention

[0006] The purpose of this application is to provide a diaphragm, a battery cell and an electrical device to solve the problem of lithium deposition at the edge of the electrode.

[0007] To achieve the purpose of this application, this application provides the following technical solutions:

[0008] In a first aspect, the present application provides a diaphragm including a first region and a second region, wherein the second region surrounds the first region, and the thickness of at least a portion of the second region is thinner than that of the first region.

[0009] In one embodiment, the thickness of the first region is A1, and the thickness of at least a portion of the second region is A2, satisfying: 1 μm≤A1-A2≤5 μm.

[0010] In one embodiment, the thickness of the second region is thinner than that of the first region. The thickness of the second region is A2, which satisfies: 1 μm≤A1-A2≤5 μm.

[0011] In one embodiment, the first area is a rectangle, and the first area includes a first inner edge, a second inner edge, a third inner edge and a fourth inner edge connected in sequence, and the second area includes a first outer edge, a second outer edge, a third outer edge and a fourth outer edge connected in sequence, the first inner edge is close to and parallel to the first outer edge, the second inner edge is close to and parallel to the second outer edge, the third inner edge is close to and parallel to the third outer edge, and the fourth inner edge is close to and parallel to the fourth outer edge.

[0012] In one embodiment, the length of the second inner edge is smaller than the length of the first inner edge, the thickness of the area between the first inner edge and the first outer edge is thinner than the thickness of the first area, and the thickness of the area between the third inner edge and the third outer edge is thinner than the thickness of the first area.

[0013] In one embodiment, the width of the second region is B, which satisfies: 2 mm ≤ B ≤ 20 mm.

[0014] In one embodiment, the widths of various positions in the second region are equal.

[0015] In one embodiment, the thickness A2 of the second region satisfies: 3 μm≤A2≤19 μm.

[0016] In the second aspect, the present application also provides a battery cell, comprising a positive electrode sheet and a diaphragm as described in the first aspect, wherein the positive electrode sheet and the diaphragm are stacked, and the four edges of the positive projection of the positive electrode sheet on the diaphragm exceed the four edges of the first area and are located within the second area.

[0017] In one embodiment, the positive electrode sheet and the first region are both rectangular, the positive electrode sheet includes a first edge, the first region includes a first inner edge, the second region includes a first outer edge close to the first inner edge, the first edge, the first inner edge and the first outer edge are parallel, and the first edge is located between the first inner edge and the first outer edge.

[0018] In one embodiment, a distance between the first edge and the first inner edge is C, which satisfies: 2mm≤C≤10mm.

[0019] In one embodiment, the battery cell further includes a negative electrode sheet, the negative electrode sheet is rectangular, and the negative electrode sheet includes a first negative electrode edge, and the first negative electrode edge is located between the first inner edge and the first outer edge.

[0020] In one embodiment, a distance between the first negative electrode edge and the first inner edge is D, which satisfies: 3 mm ≤ D ≤ 11 mm.

[0021] In a third aspect, the present application further provides an electrical device, comprising an electrical device and the battery cell as described in the second aspect, wherein the battery cell supplies power to the electrical device.

[0022] By setting the first area and the second area, the second area surrounds the first area, and the thickness of at least part of the second area is thinner than that of the first area. During the charging and discharging process of the battery, since the thickness of at least part of the second area of ​​the diaphragm facing the positive electrode edge is thinner than that of the first area, the ion diffusion impedance of the thinned area is reduced, the charging dynamics of the negative electrode area is improved, and the SOC difference between the edge and the middle position is reduced, thereby reducing the probability of lithium deposition at the edge of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the implementation methods or the description of the prior art. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] FIG1 is a schematic structural diagram of a battery cell according to an embodiment;

[0025] FIG2 is a schematic structural diagram of a diaphragm according to an embodiment.

[0026] Explanation of the figure marks: 10-diaphragm, 11-first region, 111-first inner edge, 112-second inner edge, 113-third inner edge, 114-fourth inner edge, 12-second region, 121-first outer edge, 122-second outer edge, 123-third outer edge, 124-fourth outer edge, B-width of the second region, 20-positive electrode sheet, 21-first edge, 22-positive electrode tab, C-distance between the first edge and the first inner edge. Specific embodiments

[0027] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be an intermediate component. When a component is referred to as being "connected to" another component, it may be directly connected to the other component or there may be an intermediate component.

[0029] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used in this application includes any and all combinations of one or more of the relevant listed items.

[0030] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0031] At present, during the charging and discharging process of the battery, the lithium at the edge of the negative electrode facing the positive electrode will diffuse to the overhang area. Therefore, during the charging process, the SOC of the negative electrode near the edge is lower than that in the middle, resulting in the occurrence of lithium deposition on the electrode.

[0032] The present application provides a diaphragm 10, as shown in Figures 1 and 2, comprising a first region 11 and a second region 12, wherein the second region 12 surrounds the first region 11, and at least a portion of the second region 12 is thinner than the first region 11. Optionally, the diaphragm 10 is made of polypropylene or polyethylene.

[0033] Specifically, the diaphragm 10 includes the first region 11 and the second region 12, which means that the first region 11 and the second region 12 are included on a plane perpendicular to the thickness direction of the diaphragm 10, and the second region 12 surrounds the first region 11, which means that the second region 12 surrounds the first region 11 on a plane perpendicular to the thickness direction of the diaphragm 10.

[0034] By setting the first area 11 and the second area 12, the second area 12 surrounds the first area 11, and the thickness of at least part of the second area 12 is thinner than that of the first area 11. During the charge and discharge process of the battery, since the thickness of the second area 12 facing the edge of the positive electrode of the diaphragm is thinner than the thickness of the first area 11, the ion diffusion impedance of the thinned area of ​​the diaphragm is reduced, the SOC difference between the edge and the middle position of the electrode is reduced, and the probability of lithium deposition at the edge of the electrode is reduced.

[0035] In one embodiment, the thickness of the first region 11 is A1, and the thickness of at least a portion of the second region 12 is A2, satisfying: 1 μm≤A1-A2≤5 μm.

[0036] Optionally, the result of A1-A2 can be, but is not limited to, 1 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 4.5 μm, or 5 μm.

[0037] Specifically, the above setting reduces the ion diffusion impedance in the thinned area of ​​the diaphragm, improves the charging dynamics of the thinned area facing the negative electrode area, reduces the SOC difference between the edge and the middle position of the electrode, and thus reduces the probability of lithium deposition at the edge of the electrode.

[0038] In one embodiment, referring to FIG. 1 and FIG. 2 , the thickness of the second region 12 is thinner than that of the first region 11 . The thickness of the second region 12 is A2 , which satisfies: 1 μm ≤ A1 − A2 ≤ 5 μm.

[0039] Specifically, the thickness of the second region 12 being thinner than the thickness of the first region 11 means that the thickness of the entire second region 12 is reduced.

[0040] Specifically, the above arrangement greatly reduces the probability of lithium deposition at the edge of the electrode.

[0041] In one embodiment, please refer to Figures 1 and 2, the first area 11 is a rectangle, and the first area 11 includes a first inner edge 111, a second inner edge 112, a third inner edge 113 and a fourth inner edge 114 connected in sequence, and the second area 12 includes a first outer edge 121, a second outer edge 122, a third outer edge 123 and a fourth outer edge 124, the first inner edge 111 is close to and parallel to the first outer edge 121, the second inner edge 112 is close to and parallel to the second outer edge 122, the third inner edge 113 is close to and parallel to the third outer edge 123, and the fourth inner edge 114 is close to and parallel to the fourth outer edge 124.

[0042] Specifically, the first region 11 being rectangular means that the first region 11 is rectangular on a plane perpendicular to the thickness direction of the diaphragm 10 .

[0043] Specifically, the first inner edge 111 is close to the first outer edge 121, the second inner edge 112 is close to the second outer edge 122, the third inner edge 113 is close to the third outer edge 123, and the fourth inner edge 114 is close to the fourth outer edge 124. The first inner edge 111, the third inner edge 113, the first outer edge 121 and the third outer edge 123 are parallel, and the second inner edge 112, the fourth inner edge 114, the second outer edge 122 and the fourth outer edge 124 are parallel.

[0044] Alternatively, the second region 12 may be composed of a plurality of rectangles. The first inner edge 111 is closer to the center of the diaphragm 10 than the first outer edge 121, the second inner edge 112 is closer to the center of the diaphragm 10 than the second outer edge 122, the third inner edge 113 is closer to the center of the diaphragm 10 than the third outer edge 123, and the fourth inner edge 114 is closer to the center of the diaphragm 10 than the fourth outer edge 124.

[0045] Specifically, the second area 12 is an area within a figure formed by the first outer edge 121 , the second outer edge 122 , the third outer edge 123 and the fourth outer edge 124 , and outside the first area 11 .

[0046] Specifically, the shape formed by the second region 12 surrounds the first region 11. Specifically, the first inner edge 111, the third inner edge 113, the first outer edge 121, and the third outer edge 123 are parallel, and the second inner edge 112, the fourth inner edge 114, the second outer edge 122, and the fourth outer edge 124 are parallel. This imposes a certain degree of standardized restrictions on the shapes of the first region 11 and the second region 12, which is conducive to the standardized production of the diaphragm 10 in large quantities.

[0047] In one embodiment, please refer to Figures 1 and 2, the length of the second inner edge 112 is less than the length of the first inner edge 111, the thickness of the area between the first inner edge 111 and the first outer edge 121 is thinner than the thickness of the first area 11, and the thickness of the area between the third inner edge 113 and the third outer edge 123 is thinner than the thickness of the first area 11.

[0048] Specifically, the above-mentioned setting preferentially thins the long side edge region of the diaphragm 10, and the area of ​​the long side edge region accounts for a larger proportion of the area of ​​the second region 12 than the area of ​​the short side edge region accounts for the area of ​​the second region 12. Preferentially thinning the long side edge region of the diaphragm 10 can, on the one hand, ensure the strength of the diaphragm, and on the other hand, increase the thinning area compared to thinning the short side edge region, further reduce the SOC difference between the edge position and the middle position of the electrode, and help reduce the complexity of the process flow and improve production efficiency.

[0049] In one embodiment, referring to FIG. 1 and FIG. 2 , the width of the second region 12 is B, which satisfies: 2 mm ≤ B ≤ 20 mm.

[0050] Optionally, the width B of the second region 12 may be, but is not limited to, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, 20 mm, etc.

[0051] Specifically, the distance between the first inner edge 111 and the first outer edge 121 is the width of the second area 12, the distance between the second inner edge 112 and the second outer edge 122 is the width of the second area 12, the distance between the third inner edge 113 and the third outer edge 123 is the width of the second area 12, and the distance between the fourth inner edge 114 and the fourth outer edge 124 is the width of the second area 12.

[0052] In one embodiment, referring to FIG. 1 and FIG. 2 , the widths of various positions of the second region 12 are equal.

[0053] Specifically, the center of the first area 11 and the center of the second area 12 coincide with each other.

[0054] Specifically, the center of the first area 11 is the intersection of the diagonals of the rectangle formed by the first inner edge 111 , the second inner edge 112 , the third inner edge 113 and the fourth inner edge 114 .

[0055] Specifically, the center of the second area 12 is the intersection of the diagonals of the rectangle formed by the first outer edge 121 , the second outer edge 122 , the third outer edge 123 and the fourth outer edge 124 .

[0056] Specifically, the above configuration is conducive to standardizing the data in the second area 12 , thereby enabling large-scale production and improving production efficiency.

[0057] In one embodiment, referring to FIG. 1 and FIG. 2 , the thickness A2 of the second region 12 satisfies: 3 μm≤A2≤19 μm.

[0058] Optionally, the thickness A2 of the second region 12 may be, but is not limited to, 3 μm, 4 μm, 5 μm, 6 μm, 10 μm, 19 μm, etc.

[0059] The present application also provides a battery cell, please refer to Figures 1 and 2, including a positive electrode sheet 20 and the aforementioned diaphragm 10, the positive electrode sheet 20 and the diaphragm 10 are stacked, and the four edges of the positive projection of the positive electrode sheet 20 on the diaphragm 10 exceed the four edges of the first area 11 and are located in the second area 12.

[0060] Specifically, in the orthographic projection of the positive electrode sheet 20 on the separator 10 , the four peripheral edges thereof exceed the four peripheral edges of the first region 11 and are located within the second region 12 .

[0061] Optionally, when the positive electrode sheet 20 and the separator 10 are both rectangular, the four edges of the positive electrode sheet 20 extend beyond the four edges of the first region 11 by the same distance.

[0062] Specifically, the above arrangement improves the positional relationship between the positive electrode sheet 20 and the separator 10 .

[0063] In one embodiment, please refer to Figure 1, the positive electrode sheet 20 and the first region 11 are both rectangular, the positive electrode sheet 20 includes a first edge 21, the first region 11 includes a first inner edge 111, and the second region 12 includes a first outer edge 121 close to the first inner edge 111. The first edge 21, the first inner edge 111 and the first outer edge 121 are parallel, and the first edge 21 is located between the first inner edge 111 and the first outer edge 121.

[0064] Specifically, the long side of the positive electrode sheet 20 , the long side of the first region 11 , and the long side of the second region 12 are all parallel, and the short side of the positive electrode sheet 20 , the short side of the first region 11 , and the short side of the second region 12 are all parallel.

[0065] Specifically, the above arrangement improves the positional relationship between the positive electrode sheet 20 and the separator 10 .

[0066] In one embodiment, referring to FIG. 1 , a distance C between the first edge 21 and the first inner edge 111 satisfies: 2 mm ≤ C ≤ 10 mm.

[0067] Optionally, the distance C between the first edge 21 and the first inner edge 111 may be, but is not limited to, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 10 mm, etc.

[0068] Optionally, the distances between the other edges of the positive electrode sheet 20 and the nearest separator edge parallel to the edge are the same. Optionally, the center of the positive electrode sheet 20 and the center of the separator 10 coincide with each other.

[0069] Optionally, the coating area density of the active material on the positive electrode sheet 20 is 50 g / m 2 (g / m2)-300g / m 2 .

[0070] Optionally, the coating area density of the active material on the positive electrode sheet 20 may be, but is not limited to, 50 g / m 2 , 60g / m 2 , 70g / m 2 , 80g / m 2 , 90g / m 2 and 300g / m 2 wait.

[0071] Optionally, the active material on the positive electrode sheet 20 is any one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide and lithium titanate.

[0072] Optionally, the compacted density of the active material on the positive electrode sheet 20 is 2.3 g / cm 3 (g / cm3)-3.0g / cm 3 .

[0073] Optionally, the compaction density of the active material on the positive electrode sheet 20 may be, but is not limited to, 2.3 g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 and 3.0g / cm 3 wait.

[0074] Optionally, the positive electrode sheet 20 includes a positive electrode current collector having an active material thereon. The positive electrode current collector includes, but is not limited to, any one of aluminum foil, carbon-coated aluminum foil, and composite aluminum foil. The active material on the positive electrode sheet 20 also includes a conductive agent and a binder. The conductive agent includes any one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, and carbon nanotubes. The binder can be one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.

[0075] Specifically, the above arrangement improves the positional relationship between the positive electrode sheet 20 and the separator 10 and reduces the probability of lithium deposition at the edge of the electrode sheet.

[0076] Optionally, referring to FIG. 1 , the battery cell further includes a positive electrode tab 22 , one end of the positive electrode tab 22 being connected to the positive electrode sheet 20 , and the other end extending out of the edge of the diaphragm 10 .

[0077] Optionally, one end of the positive electrode tab 22 is connected to the positive electrode sheet 20 , and the other end extends out of the edge of the separator 10 by 1 mm to 10 mm.

[0078] Optionally, one end of the positive electrode tab 22 is connected to the positive electrode sheet 20 , and the other end extends out of the edge of the separator 10 , which may be, but is not limited to, 1 mm, 2 mm, 3 mm, 6 mm, 8 mm, and 10 mm.

[0079] In one embodiment, the battery cell further includes a negative electrode sheet. The negative electrode sheet is rectangular and includes a first negative electrode edge. The first negative electrode edge is located between the first inner edge 111 and the first outer edge 121 .

[0080] Specifically, the above arrangement improves the positional relationship between the negative electrode sheet, the positive electrode sheet 20 and the separator 10, and reduces the probability of lithium deposition at the edges of the electrode sheets.

[0081] In one embodiment, the distance between the first negative electrode edge and the first inner edge 111 is D, which satisfies: 3 mm ≤ D ≤ 11 mm.

[0082] Optionally, the distance D between the first negative electrode edge and the first inner edge 111 can be, but is not limited to, 3 mm, 5 mm, 8 mm, and 11 mm. Optionally, the area of ​​the negative electrode sheet is larger than the area of ​​the positive electrode sheet, and the first edge 21 is closer to the center of the separator than the first negative electrode edge.

[0083] Specifically, the above arrangement reduces the probability of lithium deposition at the edge of the electrode.

[0084] Optionally, the material of the negative electrode sheet can be graphite, silicon, lithium titanate, etc. The negative electrode sheet is rectangular, and the negative electrode sheet and the separator 10 are stacked.

[0085] The present application also provides an electrical device, including an electrical device and a battery cell as described above, wherein the battery cell supplies power to the electrical device.

[0086] Optionally, the battery may be a blade battery, a block battery, a cylindrical battery, a button battery, or the like, without limitation in this application. The battery may be manufactured using lamination or winding techniques, without limitation. The housing may be made of plastic, steel, or aluminum, without limitation.

[0087] The technical solution of this application is described in detail below through specific embodiments.

[0088] Example 1

[0089] This embodiment provides a separator 10, a battery cell, and an electrical device. In the battery cell, the area of ​​the separator 10 is larger than the area of ​​the positive electrode 20. The separator 10 is made of polyethylene, and the active material on the positive electrode 20 includes lithium iron phosphate.

[0090] A separator 10 was prepared. The separator 10 included a first region 11 and a second region 12. The second region 12 surrounded the first region 11. The thickness of the second region 12 was thinner than that of the first region 11. The width of the second region 12 was equal at all locations. The thickness of the first region 11 was A1, and the thickness of the second region 12 was A2. The result of subtracting A2 from A1 was 1 μm. The width B of the second region 12 of the separator 10 was 4 mm, the thickness A1 of the first region 11 was 14 μm, and the thickness A2 of the second region 12 of the separator 10 was 13 μm. The distance C between the first edge 21 and the first inner edge 111 of the positive electrode sheet 20 was 2 mm. The coating density of the active material on the positive electrode sheet 20 was 220 g / m 2 The compacted density of the active material on the positive electrode sheet 20 is 2.6 g / cm 3 The distance D between the first negative electrode edge and the first inner edge 111 of the negative electrode sheet is 3 mm, and the coating surface density of the active material on the negative electrode sheet is 100 g / m 2 The compaction density of the active material on the negative electrode sheet is 1.6 g / cm 3 , take the separator 10, the positive electrode sheet 20 and the negative electrode sheet to prepare a cell, and assemble the cell into a battery.

[0091] Example 2

[0092] This embodiment provides a separator 10, a battery cell, and an electrical device. In the battery cell, the area of ​​the separator 10 is larger than the area of ​​the positive electrode 20. The separator 10 is made of polyethylene, and the active material on the positive electrode 20 includes lithium iron phosphate.

[0093] A separator 10 was prepared. The separator 10 included a first region 11 and a second region 12. The second region 12 surrounded the first region 11. The thickness of the second region 12 was thinner than that of the first region 11. The width of the second region 12 was equal at all locations. The thickness of the first region 11 was A1, and the thickness of the second region 12 was A2. The result of subtracting A2 from A1 was 2 μm. The width B of the second region 12 of the separator 10 was 4 mm, the thickness A1 of the first region 11 was 14 μm, and the thickness A2 of the second region 12 of the separator 10 was 12 μm. The distance C between the first edge 21 and the first inner edge 111 of the positive electrode sheet 20 was 2 mm. The coating density of the active material on the positive electrode sheet 20 was 220 g / m 2 The compacted density of the active material on the positive electrode sheet 20 is 2.6 g / cm 3 The distance D between the first negative electrode edge and the first inner edge 111 of the negative electrode sheet is 3 mm, and the coating surface density of the active material on the negative electrode sheet is 100 g / m 2 The compaction density of the active material on the negative electrode sheet is 1.6 g / cm 3 , take the separator 10, the positive electrode sheet 20 and the negative electrode sheet to prepare a cell, and assemble the cell into a battery.

[0094] Example 3

[0095] This embodiment provides a separator 10, a battery cell, and an electrical device. In the battery cell, the area of ​​the separator 10 is larger than the area of ​​the positive electrode 20. The separator 10 is made of polyethylene, and the active material on the positive electrode 20 includes lithium iron phosphate.

[0096] A separator 10 was prepared. The separator 10 included a first region 11 and a second region 12. The second region 12 surrounded the first region 11. The thickness of the second region 12 was thinner than that of the first region 11. The width of the second region 12 was equal at all locations. The thickness of the first region 11 was A1, and the thickness of the second region 12 was A2. The result of subtracting A2 from A1 was 3 μm. The width B of the second region 12 of the separator 10 was 4 mm, the thickness A1 of the first region 11 was 14 μm, and the thickness A2 of the second region 12 of the separator 10 was 11 μm. The distance C between the first edge 21 and the first inner edge 111 of the positive electrode sheet 20 was 2 mm. The coating density of the active material on the positive electrode sheet 20 was 220 g / m 2 The compacted density of the active material on the positive electrode sheet 20 is 2.6 g / cm 3 The distance between the first negative electrode edge and the first inner edge 111 of the negative electrode sheet is 3 mm, and the coating surface density of the active material on the negative electrode sheet is 100 g / m 2 The compaction density of the active material on the negative electrode sheet is 1.6 g / cm 3, take the separator 10, the positive electrode sheet 20 and the negative electrode sheet to prepare a cell, and assemble the cell into a battery.

[0097] Example 4

[0098] This embodiment provides a separator 10, a battery cell, and an electrical device. In the battery cell, the area of ​​the separator 10 is larger than the area of ​​the positive electrode 20. The separator 10 is made of polyethylene, and the active material on the positive electrode 20 includes lithium iron phosphate.

[0099] A separator 10 was prepared. The separator 10 included a first region 11 and a second region 12. The second region 12 surrounded the first region 11. The thickness of the second region 12 was thinner than that of the first region 11. The width of the second region 12 was equal at all locations. The thickness of the first region 11 was A1, and the thickness of the second region 12 was A2. The result of subtracting A2 from A1 was 4 μm. The width B of the second region 12 of the separator 10 was 4 mm, the thickness A1 of the first region 11 was 14 μm, and the thickness A2 of the second region 12 of the separator 10 was 10 μm. The distance C between the first edge 21 and the first inner edge 111 of the positive electrode sheet 20 was 2 mm. The coating density of the active material on the positive electrode sheet 20 was 220 g / m 2 The compacted density of the active material on the positive electrode sheet 20 is 2.6 g / cm 3 The distance between the first negative electrode edge and the first inner edge 111 of the negative electrode sheet is 3 mm, and the coating surface density of the active material on the negative electrode sheet is 100 g / m 2 The compaction density of the active material on the negative electrode sheet is 1.6 g / cm 3 , take the separator 10, the positive electrode sheet 20 and the negative electrode sheet to prepare a cell, and assemble the cell into a battery.

[0100] Example 5

[0101] This embodiment provides a separator 10, a battery cell, and an electrical device. In the battery cell, the area of ​​the separator 10 is larger than the area of ​​the positive electrode 20. The separator 10 is made of polyethylene, and the active material on the positive electrode 20 includes lithium iron phosphate.

[0102] A separator 10 was prepared. The separator 10 included a first region 11 and a second region 12. The second region 12 surrounded the first region 11. The thickness of the second region 12 was thinner than that of the first region 11. The width of the second region 12 was equal at all locations. The thickness of the first region 11 was A1, and the thickness of the second region 12 was A2. The result of subtracting A2 from A1 was 5 μm. The width B of the second region 12 of the separator 10 was 4 mm, the thickness A1 of the first region 11 was 14 μm, and the thickness A2 of the second region 12 of the separator 10 was 9 μm. The distance C between the first edge 21 and the first inner edge 111 of the positive electrode sheet 20 was 2 mm. The coating density of the active material on the positive electrode sheet 20 was 220 g / m 2 The compacted density of the active material on the positive electrode sheet 20 is 2.6 g / cm 3 The distance between the first negative electrode edge and the first inner edge 111 of the negative electrode sheet is 3 mm, and the coating surface density of the active material on the negative electrode sheet is 100 g / m 2 The compaction density of the active material on the negative electrode sheet is 1.6 g / cm 3 , take the separator 10, the positive electrode sheet 20 and the negative electrode sheet to prepare a cell, and assemble the cell into a battery.

[0103] Comparative Example 1

[0104] This embodiment provides a separator 10, a battery cell, and an electrical device. In the battery cell, the area of ​​the separator 10 is larger than the area of ​​the positive electrode 20. The separator 10 is made of polyethylene, and the active material on the positive electrode 20 includes lithium iron phosphate.

[0105] A separator 10 was prepared. The separator 10 included a first region 11 and a second region 12. The second region 12 surrounded the first region 11. The thickness of the second region 12 was the same as that of the first region 11. The width of the second region 12 was equal at all locations. The thickness of the first region 11 was A1, and the thickness of the second region 12 was A2. The result of subtracting A2 from A1 was 0 μm. The width B of the second region 12 of the separator 10 was 4 mm, the thickness A1 of the first region 11 was 14 μm, and the thickness A2 of the second region 12 of the separator 10 was 14 μm. The distance C between the first edge 21 and the first inner edge 111 of the positive electrode sheet 20 was 2 mm. The coating density of the active material on the positive electrode sheet 20 was 220 g / m 2 The compacted density of the active material on the positive electrode sheet 20 is 2.6 g / cm 3 The distance between the first negative electrode edge and the first inner edge 111 of the negative electrode sheet is 3 mm, and the coating surface density of the active material on the negative electrode sheet is 100 g / m 2 The compaction density of the active material on the negative electrode sheet is 1.6 g / cm 3, take the separator 10, the positive electrode sheet 20 and the negative electrode sheet to prepare a cell, and assemble the cell into a battery.

[0106] The battery test method is as follows:

[0107] Capacity retention rate after 500 cycles: Charge the battery at a constant current of 0.33C to 3.8V and let it sit for 30 minutes; then discharge it at a current of 0.33C to the discharge end voltage of 2.0V and let it sit for 30 minutes; repeat the above two steps for a total of 500 times, record the first discharge capacity as the battery discharge capacity C1, and the discharge capacity of the 500th cycle as C500; 500-cycle capacity retention rate (%) = (C500 / C1) × 100%.

[0108] Capacity retention rate after 1000 cycles: Charge the battery at a constant current of 0.33C to 3.8V and let it sit for 30 minutes; then discharge it at a current of 0.33C to the discharge end voltage of 2.0V and let it sit for 30 minutes; repeat the above two steps a total of 1000 times, record the first discharge capacity as the battery discharge capacity C1, and the discharge capacity of the 500th cycle as C1000; 1000-cycle capacity retention rate (%) = (C1000 / C1) × 100%.

[0109] Capacity retention rate after 1500 cycles: Charge the battery at a constant current of 0.33C to 3.8V and let it sit for 30 minutes; then discharge it at a current of 0.33C to the discharge end voltage of 2.0V and let it sit for 30 minutes; repeat the above two steps a total of 1500 times, record the first discharge capacity as the battery discharge capacity C1, and the discharge capacity of the 500th cycle as C1500; 1500 cycle capacity retention rate % = (C1500 / C1) × 100%.

[0110] Table 1 shows the values ​​of A1-A2 of Examples 1 to 5 and Comparative Example 1, as well as the corresponding cell capacity retention rates of Examples 1 to 5 and Comparative Example 1 after 500, 1000, and 1500 cycles of charging using the above test method, respectively.

[0111] By comparing the values ​​of A1-A2 of Examples 1 to 5 and Comparative Example 1, as well as the corresponding capacity retention rates of cyclic charging, the data in the above table illustrate that during the charge and discharge process of the battery, since the thickness of at least a portion of the second region 12 facing the edge of the positive electrode is thinner than the thickness of the first region 11, the probability of lithium deposition at the edge of the electrode is reduced.

[0112] In the description of the embodiments of the present application, it should be noted that the orientation or position relationship of indicators such as terms "first direction", "second direction", "first distance", "second distance", "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientation or position relationship of the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0113] The above disclosure is only a preferred embodiment of the present application, and certainly cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that implementing all or part of the processes of the above embodiment and making equivalent changes based on the present application still fall within the scope covered by the present application.

Claims

1. A diaphragm (10), comprising a first region (11) and a second region (12), wherein the second region (12) surrounds the first region (11), and the thickness of at least a portion of the second region (12) is thinner than the thickness of the first region (11).

2. The diaphragm (10) according to claim 1, wherein The thickness of the first region (11) is A1, and the thickness of at least a portion of the second region (12) is A2, satisfying the following: 1 μm≤A1-A2≤5 μm.

3. The diaphragm (10) according to claim 2, wherein The thickness of the second region (12) is thinner than that of the first region (11), and the thickness of the second region (12) is A2, which satisfies: 1 μm≤A1-A2≤5 μm.

4. The diaphragm (10) according to claim 1, characterized in that The first area (11) is rectangular, and the first area (11) includes a first inner edge (111), a second inner edge (112), a third inner edge (113) and a fourth inner edge (114) connected in sequence; the second area (12) includes a first outer edge (121), a second outer edge (122), a third outer edge (123) and a fourth outer edge (124) connected in sequence; the first inner edge (111) is close to and parallel to the first outer edge (121), the second inner edge (112) is close to and parallel to the second outer edge (122), the third inner edge (113) is close to and parallel to the third outer edge (123), and the fourth inner edge (114) is close to and parallel to the fourth outer edge (124).

5. The diaphragm (10) according to claim 4, wherein The length of the second inner edge (112) is smaller than the length of the first inner edge (111), the thickness of the area between the first inner edge (111) and the first outer edge (121) is thinner than the thickness of the first area (11), and the thickness of the area between the third inner edge (113) and the third outer edge (123) is thinner than the thickness of the first area (11).

6. The diaphragm (10) according to claim 4, wherein The width of the second region (12) is B, which satisfies: 2mm≤B≤20mm.

7. The diaphragm (10) according to claim 6, wherein The width of each position of the second region (12) is equal.

8. The diaphragm (10) according to claim 3, wherein The thickness A2 of the second region (12) satisfies: 3 μm≤A2≤19 μm.

9. A battery cell comprising a positive electrode sheet (20) and a diaphragm (10) according to any one of claims 1 to 8, wherein the positive electrode sheet (20) and the diaphragm (10) are stacked, and the four edges of the positive projection of the positive electrode sheet (20) on the diaphragm (10) exceed the four edges of the first area (11) and are located within the second area (12).

10. The battery cell according to claim 9, wherein: The positive electrode sheet (20) and the first region (11) are both rectangular, the positive electrode sheet (20) includes a first edge (21), the first region (11) includes a first inner edge (111), the second region (12) includes a first outer edge (121) close to the first inner edge (111), the first edge (21), the first inner edge (111) and the first outer edge (121) are parallel, and the first edge (21) is located between the first inner edge (111) and the first outer edge (121).

11. The battery cell according to claim 10, wherein: The distance between the first edge (21) and the first inner edge (111) is C, which satisfies: 2mm≤C≤10mm.

12. The battery cell according to claim 10, wherein: The battery cell further comprises a negative electrode sheet, which is rectangular and comprises a first negative electrode edge, wherein the first negative electrode edge is located between the first inner edge (111) and the first outer edge (121).

13. The battery cell according to claim 12, wherein: The distance between the first negative electrode edge and the first inner edge (111) is D, which satisfies: 3mm≤D≤11mm.

14. An electrical equipment comprising an electrical device and the battery cell according to any one of claims 9 to 13, wherein the battery cell supplies power to the electrical device.

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