Separator, method for manufacturing the same, lithium ion battery, and electric device

Abstract

The application relates to a diaphragm and a preparation method thereof, a lithium ion battery and a power utilization device. The diaphragm comprises a base film, a lithium supplementing material and a coating. The base film has opposite first and second surfaces in the thickness direction thereof, the first surface has a convex structure, the convex structure has a through hole, the second surface has a recess on the surface opposite to the convex structure, the through hole and the recess are communicated, the inner diameter of the recess at the second surface is greater than the hole diameter of the through hole, the convex structure is multiple, and the multiple convex structures are arranged at intervals; the lithium supplementing material is located in the recess; and the coating is coated on the second surface and covers the recess. The diaphragm has the functions of liquid retention and lithium supplementing, can not only inhibit the capacity attenuation of the lithium ion battery but also reduce the falling risk of the lithium supplementing material.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a separator and its preparation method, a lithium-ion battery, and an electrical device. Background Technology

[0002] The formation process is one of the key steps in lithium-ion battery manufacturing. During formation, a solid electrolyte interphase (SEI) film is formed on the surface of the negative electrode. Lithium-ion batteries consume a significant amount of active lithium to form the SEI during formation. During continuous discharge, side reactions also lead to a decrease in the number of lithium ions, making lithium-ion batteries prone to capacity decay. Membrane-based lithium replenishment technology (e.g., coating the separator with a lithium replenishing material to form a replenishing layer) can alleviate the capacity decay problem to some extent. However, the lithium replenishing material coated on the separator is prone to detachment during cyclic expansion and contraction. Summary of the Invention

[0003] Therefore, it is necessary to provide a separator with lithium replenishment function, which can not only suppress the capacity decay of lithium-ion batteries but also reduce the risk of lithium replenishment material falling off.

[0004] This invention provides a diaphragm, comprising: The base film has a first surface and a second surface opposite each other in its thickness direction. The first surface has a raised structure with a through hole. The second surface has a recess on the surface opposite the raised structure. The through hole communicates with the recess. The inner diameter of the recess at the second surface is larger than the aperture of the through hole. There are multiple raised structures, and the multiple raised structures are arranged at intervals. Lithium replenishment material, located within the recess; and A coating is applied to the second surface and covers the recess.

[0005] In one embodiment, at least one of the following conditions (a1)-(a7) is also satisfied: (a1) The base film is made of polyolefin; (a2) The thickness of the base film is 7-16 micrometers; (a3) The diameter of the through hole is 0.1-0.5 micrometers; (a4) There are multiple through holes, which are arranged at intervals, and the sum of the areas of the multiple through holes is 10%-20% of the area of ​​the outer surface of the protrusion structure; (a5) The protruding structure is spherical; (a6) The plurality of the protrusions are arranged in an array, the spacing between two adjacent rows of the protrusions is 1.5-3 times the outer diameter of the protrusions, and the spacing between two adjacent columns of the protrusions is 1.5-3 times the outer diameter of the protrusions. (a7) The outer diameter of the protrusion structure is 1-5 micrometers, and the depth of the recess is 1-4 micrometers in the arrangement direction of the first surface and the second surface.

[0006] In one embodiment, at least one of the following conditions (a1)-(a7) is also satisfied: (a1) The lithium replenishment material is a lithium salt; (a2) The median particle size Dv50 of the lithium replenishment material is 0.6-0.7 micrometers; (a3) The coating is a ceramic layer; (a4) also includes a PVDF layer, wherein the coating is provided with the PVDF layer and / or the base film is provided with the PVDF layer on one side having the protrusion structure.

[0007] In one embodiment, the coating covers the second surface.

[0008] In one embodiment, the coating includes a first coating formed on the second surface and a second coating formed on the second surface. The first coating includes a plurality of sub-coatings, which are spaced apart along the width direction of the second surface and extend along the length direction of the second surface. The second coating and the first coating together cover the second surface.

[0009] In one embodiment, at least one of the following conditions (a1)-(a8) is also satisfied: (a1) The area of ​​the first coating is 10-70% of the area of ​​the second surface; (a2) In the width direction of the second surface, the width of the sub-coating is 5-20 mm; (a3) In the width direction of the second surface, the spacing between two adjacent sub-coatings is 1.5-3 times the width of the sub-coating; (a4) The thickness of the sub-coating is 1-3 micrometers; (a5) The sub-coating is spiral-shaped, the peak-to-trough distance of the sub-coating is 10-40mm, and the turning angle of the sub-coating is 100°-150°. (a6) The thickness of the sub-coating is 0.5-1 micrometer greater than the thickness of the second coating; (a7) The porosity of the sub-coating is 40-50%; (a8) The porosity of the second coating is 30-45%.

[0010] In one embodiment, at least one of the following conditions (a1)-(a2) is also satisfied: (a1) The sub-coating is a ceramic layer, and the sub-coating includes a first-size alumina with a particle size of 500-800 nm and a porosity of 15-25%; (a2) The second coating is a ceramic layer, the second coating includes a first particle size alumina and a second particle size alumina, the particle size of the first particle size alumina is 500-800nm, the particle size of the second particle size alumina is 10-200nm, the porosity of the first particle size alumina is 15-25%, the porosity of the second particle size alumina is 2-10%, and the mass ratio of the first particle size alumina to the second particle size alumina is 1:2-2:1.

[0011] The present invention also provides a method for preparing the above-mentioned diaphragm, comprising the following steps: (1) A protruding structure is formed on the first surface of the base film, and a concave portion opposite to the protruding structure is formed on the second surface of the base film at the same time as the protruding structure is formed; (2) A through hole communicating with the recess is formed on the protruding structure; (3) Place lithium replenishment material in the recess; and (4) Form a coating covering the recess on the second surface; Wherein, at least two of steps (1), (2), and (3) are performed simultaneously; and / or When the coating comprises a first coating and a second coating, the first coating is formed first, and then the second coating is formed.

[0012] The present invention also provides a lithium-ion battery, including a positive electrode and a negative electrode, and further including the above-mentioned separator, wherein the separator is located between the positive electrode and the negative electrode, and the coating faces the negative electrode and the protrusion structure faces the positive electrode.

[0013] The present invention also provides an electrical device comprising the aforementioned lithium-ion battery.

[0014] In the aforementioned separator, a raised structure is formed on the first surface of the base film, and a recess is formed on the second surface of the base film opposite to the raised structure, allowing the lithium replenishment material to be placed within the recess. Simultaneously, a coating covering the recess is applied to the second surface of the base film, thereby encapsulating the lithium replenishment material within the recess. Furthermore, the raised structure has through-holes, so when the separator is applied to a lithium-ion battery, the lithium replenishment material (lithium ions) can be released through the through-holes and / or the coating (which has pores for lithium ions to pass through), thus replenishing the lithium-ion battery. Therefore, the aforementioned separator has a lithium replenishment function (separator lithium replenishment technology).

[0015] The aforementioned separator, when applied to lithium-ion batteries, can suppress capacity decay. Furthermore, the separator, through its coating and the interlocking protrusions and recesses, mechanically locks in the lithium replenishment material. This significantly reduces the risk of lithium replenishment material detachment and avoids the direct addition of the material to the electrolyte (electrolyte-based lithium replenishment technology). Instead, the material is released only as needed during battery cycling, achieving precise controlled release of the lithium replenishment material. This effectively reduces side reactions and significantly improves the cycle life of lithium-ion batteries.

[0016] Furthermore, when applied to lithium-ion batteries, the aforementioned separator is positioned between the positive and negative electrodes. This allows the convex structure of the separator to face the positive electrode, while the coating faces the negative electrode. The convex structure creates a space between the first surface of the base film and the positive electrode, forming a reservoir between them. This reservoir can hold electrolyte, improving electrolyte distribution and increasing electrolyte retention. Simultaneously, the electrolyte within the reservoir can store active lithium, achieving dual lithium-ion storage (the lithium-replenishing material in the recess releases lithium ions, providing one layer of storage, while the lithium ions in the electrolyte within the reservoir provide another layer), effectively suppressing lithium loss and significantly improving the capacity and stability of the lithium-ion battery. Moreover, the reservoir can buffer thermal expansion during the expansion and contraction of the lithium-ion battery. The coating facing the negative electrode can suppress thermal contraction on the negative side and lithium dendrite penetration, enhancing safety.

[0017] The overall layout of the aforementioned separator balances mechanical strength and electrochemical performance, achieving synergistic optimization of thermal stability, dendrite protection, and electrolyte distribution. Simultaneously, the lithium-ion replenishment material optimizes the lithium-ion transport path and reduces polarization effects. Therefore, this separator is suitable for high-safety lithium-ion batteries. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a perspective view of the diaphragm according to an embodiment of the present invention (view with the protruding structure facing upwards). Figure 2 This is a perspective view of the diaphragm according to an embodiment of the present invention (view with the coating facing upwards). Figure 3 for Figure 2 A side view of the diaphragm shown; Figure 4 for Figure 2 A top view of the diaphragm shown; Figure 5 For along Figure 4 A cross-sectional view of line AA in the diagram; Figure 6 For along Figure 4 A cross-sectional view of the BB line in the diagram; Figure 7 This is a flowchart of a method for preparing a diaphragm according to an embodiment of the present invention. Detailed Implementation

[0019] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0020] In the description of this application, it should be understood that, where they appear, the terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0021] Furthermore, where applicable, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0022] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," "fixing," etc., shall be interpreted broadly. For example, they may refer to a fixed connection, a detachable connection, or an integral part; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; they may refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0024] It should be noted that, if an element is described as "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is described as "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0025] like Figures 1-6As shown, an embodiment of the present invention provides a separator 10. The separator 10 includes a base film 200, a lithium replenishing material, and a coating 300. The base film 200 has a first surface 202 and a second surface 204 opposite each other in its thickness direction. The first surface 202 has a protrusion structure 210. The protrusion structure 210 has a through hole 212. The second surface 204 has a recess 220 on the surface directly opposite to the protrusion structure 210, that is, the second surface 204 has a recess 220 at the position corresponding to the protrusion structure 210. The recess 220 communicates with the through hole 212, and the inner diameter of the recess 220 at the second surface 204 is larger than the aperture of the through hole 212. There are multiple protrusion structures 210, which are arranged at intervals. Correspondingly, there are multiple recesses 220, which are arranged at intervals, and the multiple recesses 220 are one-to-one with the multiple protrusion structures 210. The lithium replenishing material is located in the recess 220. Coating 300 is applied to the second surface 204 and covers the recess 220.

[0026] In the aforementioned separator 10, a protrusion structure 210 is provided on the first surface 202 of the base film 200, and a recess 220 is provided on the second surface 204 of the base film 200 opposite to the protrusion structure 210, thereby allowing the lithium replenishment material to be placed within the recess 220. Simultaneously, a coating 300 covering the recess 220 is coated on the second surface 204 of the base film 200, thereby encapsulating the lithium replenishment material within the recess 220. Furthermore, the protrusion structure 210 has through-holes 212, so when the separator 10 is applied to a lithium-ion battery, the lithium replenishment material (lithium ions) can be released through the through-holes 212 and / or the coating 300 (which has pores for lithium ions to pass through), thereby replenishing the lithium-ion battery. Therefore, the aforementioned separator 10 has a lithium replenishment function (separator lithium replenishment technology).

[0027] The aforementioned separator 10, when applied to lithium-ion batteries, can suppress capacity decay. Furthermore, the separator 10, through the coating 300 and the cooperating protrusions 210 and recesses 220, mechanically locks in the lithium replenishment material. When applied to lithium-ion batteries, this not only significantly reduces the risk of lithium replenishment material detachment but also avoids the direct addition of the material to the electrolyte (electrolyte-based lithium replenishment technology, where the material is directly added to the electrolyte). Instead, the material is released only as needed during battery cycling, achieving precise controlled release of the lithium replenishment material, effectively reducing side reactions and significantly improving the cycle life of lithium-ion batteries.

[0028] Furthermore, the aforementioned separator 10 is applied in a lithium-ion battery. Located between the positive and negative electrodes, the separator 10 allows the raised structure 210 to face the positive electrode and the coating 300 to face the negative electrode. The raised structure 210 spacees the first surface 202 of the base film 200 from the positive electrode, forming a storage cavity between the first surface 202 and the positive electrode. This storage cavity can hold electrolyte, improving electrolyte distribution and increasing electrolyte retention. Simultaneously, the electrolyte within the storage cavity can store active lithium, thus achieving dual lithium-ion storage (the lithium replenishment material in the recess 220 releases lithium ions, constituting one level of lithium-ion storage; the lithium ions in the electrolyte within the storage cavity constitute another level of lithium-ion storage), effectively suppressing lithium loss and significantly improving the capacity and stability of the lithium-ion battery. Moreover, the storage cavity can buffer thermal expansion during the expansion-contraction process of the lithium-ion battery. The coating 300 facing the negative electrode can suppress thermal contraction on the negative side and lithium dendrite puncture, improving safety.

[0029] The overall layout of the aforementioned separator 10 balances mechanical strength and electrochemical performance, achieving synergistic optimization of thermal stability, dendrite protection, and electrolyte distribution. Simultaneously, the lithium-ion replenishment material optimizes the lithium-ion transport path and reduces polarization effects. Therefore, the aforementioned separator 10 is suitable for high-safety lithium-ion batteries.

[0030] In this embodiment, the base film 200 is made of polyolefin. Specifically, the base film 200 can be made of PE (Polyethylene) or PP (Polypropylene). The base film 200 may also include at least one PE layer and at least one PP layer, with the PE layers and PP layers arranged alternately. It is understood that in other embodiments, the material of the base film 200 is not limited to polyolefin, and may also be other insulating materials.

[0031] In this embodiment, the thickness of the base film 200 is 7-16 micrometers. This not only meets the thickness requirements of the separator 10 in lithium-ion batteries but also facilitates the formation of mutually cooperating protrusions 210 and recesses 220. Specifically, the thickness of the base film 200 can be 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 11 micrometers, 12 micrometers, 13 micrometers, 14 micrometers, 15 micrometers, or 16 micrometers. It is understood that in other embodiments, the thickness of the base film 200 can be adjusted according to actual needs.

[0032] In this embodiment, the pore size of the through-hole 212 is 0.1-0.5 micrometers. The particle size of the granular lithium replenishment material is typically greater than 0.5 micrometers. Setting the pore size of the through-hole 212 to 0.1-0.5 micrometers prevents the granular lithium replenishment material from escaping through the through-hole 212, thus achieving encapsulation of the lithium replenishment material. Simultaneously, during lithium replenishment, lithium ions (which can be generated when the lithium replenishment material comes into contact with the electrolyte) can be released through the through-hole 212. It is understood that in other embodiments, the pore size of the through-hole 212 is not limited to 0.1-0.5 micrometers, and the pore size of the through-hole 212 can vary according to the particle size of the lithium replenishment material.

[0033] In this embodiment, there are multiple through holes 212. The multiple through holes 212 are arranged at intervals. Specifically, in this embodiment, there are two through holes 212. This facilitates the release of the lithium replenishing agent. It is understood that in other embodiments, there may be only one through hole 212.

[0034] In this embodiment, the sum of the areas of the plurality of through holes 212 is 10%-20% of the area of ​​the outer surface of the protrusion structure 210. Specifically, in this embodiment, the sum of the areas of the plurality of through holes 212 can be 10%, 12%, 14%, 16%, 18%, or 20% of the area of ​​the outer surface of the protrusion structure 210. If the sum of the areas of the through holes 212 is too small, it is not conducive to the release of lithium replenishing agent, while if the sum of the areas of the through holes 212 is too large, it will affect the strength of the protrusion structure 210. Considering the above factors, the sum of the areas of the plurality of through holes 212 is set to 10%-20% of the area of ​​the outer surface of the protrusion structure 210. It can be understood that in other embodiments, the sum of the areas of the through holes 212 can be adjusted accordingly according to actual needs.

[0035] In this embodiment, the protrusion structure 210 is spherical. The spherical protrusion structure 210 has no sharp edges and will not scratch the electrode sheet. When the protrusion structure 210 is formed using a spherical mold, the spherical mold will also not scratch the base film 200. It is understood that in other embodiments, the protrusion structure 210 may also be of other shapes; for example, the end of the protrusion structure 210 away from the base film 200 may be planar.

[0036] In this embodiment, the multiple protrusions 210 are arranged in an array. This facilitates a more uniform distribution of the lithium replenishment material on the base film 200, and also forms a relatively uniformly distributed liquid storage cavity between the first surface 202 of the base film 200 and the electrode, thereby facilitating uniform electrolyte distribution and uniform buffering of thermal expansion. It is understood that in other embodiments, the multiple protrusions 210 may be arranged in other shapes or randomly.

[0037] In this embodiment, the spacing between two adjacent rows of raised structures 210 is 1.5-3 times the outer diameter of the raised structure 210. Specifically, the spacing between two adjacent rows of raised structures 210 can also be 1.5, 2, 2.5, or 3 times the outer diameter of the raised structure 210. The spacing between two adjacent columns of raised structures 210 is 1.5-3 times the outer diameter of the raised structure 210. Specifically, the spacing between two adjacent columns of raised structures 210 is 1.5, 2, 2.5, or 3 times the outer diameter of the raised structure 210. This facilitates the preparation of the base film 200. It is understood that in other embodiments, the row spacing and column spacing can be adjusted according to actual needs.

[0038] In this embodiment, the outer diameter d of the protrusion structure 210 is 1-5 micrometers. Specifically, in this embodiment, the outer diameter d of the protrusion structure 210 can be 1 micrometer, 2 micrometers, 3 micrometers, 4 micrometers, or 5 micrometers. In the arrangement direction of the first surface 202 and the second surface 204, the depth h of the recess 220 is 1-4 micrometers. Specifically, in this embodiment, in the arrangement direction of the first surface 202 and the second surface 204, the depth h of the recess 220 can be 1 micrometer, 2 micrometers, 3 micrometers, or 4 micrometers. This not only facilitates the fabrication of the separator 10 but also provides sufficient space for storing lithium replenishment material. It is understood that in other embodiments, the outer diameter of the protrusion structure 210 and the depth of the recess 220 can be adjusted according to actual needs.

[0039] In this embodiment, the lithium replenishment material is a lithium salt. Specifically, in this embodiment, the lithium replenishment material is Li₂CO₃, Li₃N, or Li₂C₄O₄. Lithium salts have high chemical stability, low sensitivity to moisture and oxygen, and the lithium replenishment depth is controllable. By selecting different lithium salts or coating designs, the lithium release amount can be precisely set, avoiding the risk of lithium plating caused by "overlithiation". It is understood that in other embodiments, the lithium replenishment material can also be metallic lithium.

[0040] In this embodiment, the median particle size Dv50 of the lithium replenishment material is 0.6-0.7 micrometers. Thus, the particle size of the lithium replenishment material can be matched with the pore size of the through-hole 212 (0.1-0.5 micrometers), and it is also more conducive to the release of lithium ions from the lithium replenishment material.

[0041] In this embodiment, the coating 300 covers the second surface 204. That is, the second surface 204 is covered by the coating 300, thereby reducing the risk of excessive current in localized areas (areas not covered by the coating 300). It is understood that in other embodiments, the coating 300 may only cover the recesses 220, and the area between the recesses 220 may not be covered by the coating 300.

[0042] In this embodiment, coating 300 is a ceramic layer. Ceramic layers typically have pores, allowing electrolyte to wet the ceramic layer, thereby storing the electrolyte (which can store active lithium and suppress lithium loss) and allowing lithium ions to pass through. Thus, the lithium replenishment material encapsulated within the recess 220 can release lithium ions both through the through-hole 212 and through the opening on the second surface 204 of the recess 220 and the ceramic layer (lithium ions can first pass through the opening of the recess 220 and then through the ceramic layer to be released to the electrode). Furthermore, when the aforementioned separator 10 is applied in a lithium-ion battery, with the protrusion structure 210 facing the positive electrode and the ceramic layer facing the negative electrode, the ceramic layer can suppress thermal shrinkage and lithium dendrite puncture on the negative electrode side, improving safety. It is understood that in other embodiments, coating 300 is not limited to a ceramic layer and can also be a coating of other materials.

[0043] In this embodiment, the porosity of the coating 300 is 30-50%. Specifically, in this embodiment, the porosity of the coating 300 can be 30%, 35%, 40%, 45%, or 50%. This facilitates the release of lithium ions and allows the coating 300 to have a high liquid absorption rate, thereby improving the electrolyte retention rate of the separator 10 and utilizing the pores to store active lithium (lithium ions in the electrolyte), significantly suppressing lithium loss. It is understood that in other embodiments, the porosity of the coating 300 can be adjusted according to actual needs.

[0044] In this embodiment, coating 300 includes a first coating 310 and a second coating 320 formed on the second surface 204. The second coating 320 and the first coating 310 together cover the second surface 204. This optimizes the mechanical strength and thermal stability of coating 300, reduces localized stress concentration, and prevents short circuits in the lithium-ion battery caused by the shrinkage of the separator 10. It is understood that in other embodiments, coating 300 may include only one coating, instead of both the first coating 310 and the second coating 320.

[0045] In this embodiment, the first coating 310 includes a plurality of sub-coatings 312. The plurality of sub-coatings 312 are arranged at intervals along the width direction of the second surface 204. The sub-coatings 312 extend along the length direction of the second surface 204. This is more conducive to optimizing the mechanical strength and thermal stability of the coating 300, reducing local stress concentration, and preventing the separator 10 from shrinking and causing a short circuit in the lithium-ion battery.

[0046] In this embodiment, there are three or more sub-coatings 312. The multiple sub-coatings 312 are evenly distributed on the second surface 204 along its width. This improves the mechanical strength and thermal stability of the coating 300, reduces local stress concentration, and prevents short circuits in the lithium-ion battery caused by the shrinkage of the separator 10. It is understood that in other embodiments, there may be two sub-coatings 312. In these embodiments, the two sub-coatings 312 are located at opposite ends of the second surface 204 along its width.

[0047] In this embodiment, the area of ​​the first coating 310 is 10-70% of the area of ​​the second surface 204. Specifically, in this embodiment, the area of ​​the first coating 310 can be 10%, 20%, 30%, 40%, 50%, 60%, or 70% of the area of ​​the second surface 204. This is more conducive to optimizing the mechanical strength and thermal stability of the coating 300, reducing local stress concentration, and preventing the separator 10 from shrinking and causing a short circuit in the lithium-ion battery.

[0048] In this embodiment, the width of the sub-coating 312 in the width direction of the second surface 204 is 5-20 mm. Specifically, in this embodiment, the width of the sub-coating 312 in the width direction of the second surface 204 can be 5 mm, 10 mm, 15 mm, or 20 mm. This not only facilitates the preparation of the first coating 310, but also optimizes the mechanical strength and thermal stability of the coating 300, reduces local stress concentration, and prevents the separator 10 from shrinking and causing a short circuit in the lithium-ion battery.

[0049] In this embodiment, the spacing between two adjacent sub-coatings 312 in the width direction of the second surface 204 is 1.5-3 times the width of the sub-coating 312. Specifically, in this embodiment, the spacing between two adjacent sub-coatings 312 in the width direction of the second surface 204 can be 1.5 times, 2 times, 2.5 times, or 3 times the width of the sub-coating 312. This not only facilitates the preparation of the first coating 310, but also optimizes the mechanical strength and thermal stability of the coating 300, reduces local stress concentration, and prevents the separator 10 from shrinking and causing a short circuit in the lithium-ion battery.

[0050] In this embodiment, the thickness of the sub-coating 312 is 1-3 micrometers. Specifically, in this embodiment, the thickness of the sub-coating 312 can be 1 micrometer, 1.5 micrometers, 2 micrometers, 2.5 micrometers, or 3 micrometers. This not only facilitates the preparation of the first coating 310, but also optimizes the mechanical strength and thermal stability of the coating 300, reduces local stress concentration, and prevents the separator 10 from shrinking and causing a short circuit in the lithium-ion battery.

[0051] In this embodiment, the sub-coating 312 is spiral-shaped. The spiral direction forms an angle with the lithium-ion migration direction, generating a vortex effect, which increases the electrolyte wetting speed, enhances the interfacial bonding force, and reduces the interfacial impedance, thereby further improving the overall performance and charge / discharge efficiency of the lithium-ion battery. Moreover, the spiral-shaped sub-coating 312 is more conducive to optimizing the mechanical strength and thermal stability of the coating 300, reducing local stress concentration, and preventing the separator 10 from shrinking and causing a short circuit in the lithium-ion battery.

[0052] When preparing coating 300, a first coating 310 can be formed by extrusion coating process first, and then a nanoscale gravure thin-layer coating process can be used to fill the gaps of sub-coating 312 to form second coating 320, thereby achieving full surface coverage of coating 300 and reducing the risk of excessive local current.

[0053] In this embodiment, the peak-to-trough distance of the sub-coating 312 is 10-40 mm. Specifically, in this embodiment, the peak-to-trough distance of the sub-coating 312 can be 10 mm, 20 mm, 30 mm, or 40 mm. This is more conducive to optimizing the mechanical strength and thermal stability of the coating 300, reducing local stress concentration, and preventing the separator 10 from shrinking and causing a short circuit in the lithium-ion battery.

[0054] In this embodiment, the turning angle of the sub-coating 312 is 100°-150°. Specifically, in this embodiment, the turning angle of the coating 312 can be 100°, 110°, 120°, 130°, 140°, or 150°. This is more conducive to optimizing the mechanical strength and thermal stability of the coating 300, reducing local stress concentration, and preventing the separator 10 from shrinking and causing a short circuit in the lithium-ion battery.

[0055] In this embodiment, the thickness of the sub-coating 312 is 0.5-1 micrometer greater than the thickness of the second coating 320. Specifically, in this embodiment, the thickness of the sub-coating 312 can be 0.5 micrometers, 0.6 micrometers, 0.7 micrometers, 0.8 micrometers, 0.9 micrometers, or 1 micrometer greater than the thickness of the second coating 320. This is more conducive to optimizing the mechanical strength and thermal stability of the coating 300, reducing local stress concentration, and preventing the separator 10 from shrinking and causing a short circuit in the lithium-ion battery. Furthermore, it is more conducive to improving the liquid retention capacity of the separator 10 and increasing the liquid absorption rate.

[0056] In this embodiment, both the sub-coating 312 and the second coating 320 are ceramic layers. The porosity of the sub-coating 312 is 40-50%. Specifically, in this embodiment, the porosity of the sub-coating 312 can be 40%, 45%, or 50%. The porosity of the second coating 320 is 30-45%. Specifically, in this embodiment, the porosity of the second coating 320 can be 30%, 35%, 40%, or 45%. This is more conducive to optimizing the mechanical strength and thermal stability of the coating 300, reducing local stress concentration, and preventing the separator 10 from shrinking and causing a short circuit in the lithium-ion battery. Furthermore, it is more conducive to improving the liquid retention capacity of the separator 10 and increasing the liquid absorption rate.

[0057] In this embodiment, the sub-coating 312 comprises alumina with a first particle size. The median particle size Dv50 of the alumina with the first particle size is 500-800 nm. Specifically, in this embodiment, the median particle size Dv50 of the alumina with the first particle size can be 500 nm, 600 nm, 700 nm, or 800 nm. The porosity of the alumina with the first particle size is 15-25% (the alumina with the first particle size is hollow porous ceramic particles with a pore size of 50-200 nm). Specifically, in this embodiment, the porosity of the alumina with the first particle size can be 15%, 20%, or 25%. Thus, it is advantageous to obtain a sub-coating 312 with a porosity of 40-50%, and it can significantly improve the mechanical strength and thermal stability of the diaphragm 10.

[0058] In this embodiment, the second coating 320 includes alumina with a first particle size and alumina with a second particle size. The particle size of the alumina with the first particle size is 500-800 nm. Specifically, in this embodiment, the median particle size Dv50 of the alumina with the first particle size can be 500 nm, 600 nm, 700 nm, or 800 nm. The median particle size Dv50 of the alumina with the second particle size is 10-200 nm. Specifically, in this embodiment, the median particle size Dv50 of the alumina with the second particle size can be 10 nm, 30 nm, 50 nm, 70 nm, 90 nm, 110 nm, 130 nm, 150 nm, 170 nm, or 200 nm. The porosity of the alumina with the first particle size is 15-25%. Specifically, in this embodiment, the porosity of the alumina with the first particle size can be 15%, 20%, or 25%. The porosity of the second-size alumina is 2-10% (the second-size alumina is hollow porous ceramic particles with a pore size of 2-100 nm). Specifically, in this embodiment, the porosity of the second-size alumina can be 2%, 4%, 6%, 8%, or 10%. The mass ratio of the first-size alumina to the second-size alumina is 1:2-2:1. Specifically, in this embodiment, the mass ratio of the first-size alumina to the second-size alumina can be 1:2, 1:1, or 2:1. This not only facilitates obtaining a second coating 320 with a porosity of 30-45%, but also allows the large-size first-size alumina to provide high hardness and corrosion resistance to the second coating 320. Furthermore, the combination of large-size first-size alumina and small-size second-size alumina can reduce the cost of the second coating 320 (smaller particle sizes result in higher costs).

[0059] In this embodiment, the separator 10 further includes a PVDF (polyvinylidene fluoride) layer 400. In some embodiments, a PVDF layer is disposed on the coating 300. In some embodiments, a PVDF layer is disposed on the protruding structure 210. In some embodiments, a PVDF layer is disposed on the coating 300. In some embodiments, a PVDF layer is disposed on the protruding structure 210 and a PVDF layer is disposed on the coating 300. The PVDF layer is an adhesive layer, thereby facilitating the bonding of the separator 10 to the electrode.

[0060] like Figure 7 As shown, the present invention also provides a method for preparing a diaphragm, comprising the following steps: In step S410, a raised structure is formed on the first surface of the base film, and at the same time the raised structure is formed, a recess is formed on the second surface of the base film that is directly opposite to the raised structure.

[0061] Step S420: A through hole communicating with the recess is formed on the protruding structure.

[0062] Step S430: Place lithium replenishment material inside the recess.

[0063] Step S440: A coating covering the recess is formed on the second surface.

[0064] In this embodiment, in step S410, a forming roller with protrusions is used to hot-press or imprint the base film. The protrusions give the first surface of the base film a raised structure while simultaneously giving the second surface of the base film a recessed portion opposite to the raised structure. Specifically, in this embodiment, the forming roller extends along the width (or length) direction of the base film, and the forming roller has multiple protrusions spaced apart along the extension direction of the forming roller. Thus, when the forming roller rolls along the length (or width) direction of the base film and stops and presses down at a certain position, multiple protrusion structures spaced apart along the width (or length) direction of the base film can be formed at once. After the forming roller stops and presses down multiple times, an array of protrusion structures can be formed on the base film.

[0065] In this embodiment, steps S410 and S420 are performed simultaneously. Specifically, in this embodiment, the protruding surface has an outwardly convex tip. While the protrusion creates a protruding structure on the first surface of the base film, the tip also creates a through-hole communicating with the recess in the protruding structure. It is understood that in other embodiments, steps S410 and S420 may not be performed simultaneously. In this case, step S410 can be completed first, and then a through-hole communicating with the recess can be formed on the protruding structure by means of laser drilling or the like.

[0066] In this embodiment, steps S410 and S430 are performed simultaneously. Specifically, in this embodiment, the protrusion of the forming roller has a cavity, and the surface of the protrusion has a discharge port communicating with the cavity. Lithium replenishment material is placed inside the cavity. Thus, when the protrusion forms the recess and when it exits from the recess, lithium replenishment material can be placed inside the recess through the discharge port, thereby achieving the simultaneous performance of steps S410 and S430. It is understood that in other embodiments, steps S410 and S430 may not be performed simultaneously. In this case, step S410 can be completed first, and then a paddle-shaped lithium replenishment material can be coated on the entire second surface of the base film. Then, a cavity-free gravure roller (imprint roller) is used to press the lithium replenishment material in the recess into the recess. Then, the second surface is scraped to remove the lithium replenishment material in other areas. After the lithium replenishment material dries, step S430 is completed.

[0067] In this embodiment, steps S410, S420, and S430 are performed simultaneously. It can be understood that in other embodiments, at least one of steps S410, S420, and S430 may be performed asynchronously.

[0068] In this embodiment, when the coating includes a first coating and a second coating, the first coating is formed first, followed by the second coating. This makes coating preparation more efficient.

[0069] The present invention also provides a lithium-ion battery. The lithium-ion battery includes a positive electrode, a negative electrode, and the separator described above. The separator is located between the positive electrode and the negative electrode, with the coating (300) facing the negative electrode and the protrusion structure (210) facing the positive electrode.

[0070] This invention also provides an electrical device. The electrical device includes the aforementioned lithium-ion battery. The aforementioned electrical device can be a vehicle, mobile phone, portable device, laptop, ship, spacecraft, electric toy, power tool, energy storage device, amusement equipment, elevator, and lifting equipment, etc. Vehicles can be gasoline-powered vehicles, natural gas-powered vehicles, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.; spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, or electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc.; energy storage devices can be energy storage walls, base station energy storage, container energy storage, etc.; amusement equipment can be a carousel, a drop tower, etc. This embodiment does not impose any special limitations on the aforementioned electrical device.

[0071] The present invention will be further described below with reference to embodiments. I. Examples and Comparative Examples Example 1 (with lithium replenishment function + spiral coating) Step 1: Treatment of the base film (1) Base film: PE film with a thickness of 9μm.

[0072] (2) Forming roller: The forming roller has multiple protrusions arranged at intervals along the extension direction of the forming roller. The surface of the protrusion has an outwardly protruding tip. The protrusion has a cavity. The surface of the protrusion has a discharge port communicating with the cavity. Lithium replenishment material is placed inside the cavity.

[0073] (3) Place the forming roller on the second surface of the base film, and make the extension direction of the forming roller parallel to the width direction of the base film. Control the forming roller to roll along the length direction of the base film and stop and press (hot press) at a preset position. After multiple stops and presses, an array of raised structures is formed on the first surface of the base film, and an array of recesses is formed on the second surface of the base film. The raised structures have through holes communicating with the recesses, and the recesses contain lithium replenishing material. The depth of the recesses is 3 μm, the outer diameter of the raised structures is 4 μm, the spacing between two adjacent rows of raised structures is twice the outer diameter of the raised structures, the spacing between two adjacent columns of raised structures is twice the outer diameter of the raised structures, the diameter of the through holes is 0.2 μm, the sum of the areas of multiple through holes is 20% of the area of ​​the outer surface of the raised structures, the lithium replenishing material is Li2CO3, and the median particle size Dv50 is 0.6 μm.

[0074] Step 2: Prepare the coating (1) Preparation of the first coating: A first-size alumina slurry is coated onto the second surface of the base film using a narrow-slit extrusion coating process, forming multiple spiral lines (sub-coatings) on the second surface of the base film. These spiral lines are spaced apart along the width direction of the second surface. After curing, the first coating is obtained. The median particle size Dv50 of the first-size alumina is 600 nm, and the porosity is 20%. The width of the spiral lines is 12.5 mm, the coating thickness is 2 μm, the horizontal distance between the peaks and troughs is 14 mm, the vertical distance is 25 mm, and the turning angle of the spiral lines is 120°. The area of ​​the first coating is 40% of the area of ​​the second surface 204. The porosity of the first coating is 50%.

[0075] (2) Preparation of the second coating: A nanoscale microgravure roller is used for reverse coating to coat the composite alumina slurry (including alumina of the first and second particle sizes) onto the area of ​​the second surface not covered by the first coating. The microgravure roller is immersed in the composite alumina slurry, and excess slurry is quantitatively scraped off by a flexible doctor blade. The composite alumina slurry cures to obtain the second coating. The thickness of the second coating is 1.5 μm, which is 0.5 μm thinner than the thickness of the spiral lines. The median particle size Dv of the first-size alumina is 600 nm, with a porosity of 20%. The median particle size Dv50 of the second-size alumina is 150 nm, with a porosity of 6%. The mass ratio of the first-size alumina to the second-size alumina is 1:1. The porosity of the second coating is 40%.

[0076] Step 3: Prepare PVDF layer: Set PVDF layers on both surfaces of the base film (that is, set PVDF layers on the raised structure and on the coating).

[0077] Example 2 (with lithium replenishment function + ordinary coating + non-compound slurry coating) Step 1: Same as in Example 1.

[0078] Step 2: Prepare the coating A narrow-slit extrusion coating process was used to coat the second surface of the base film with an alumina slurry of the first particle size. After the alumina slurry of the first particle size was cured, a coating was obtained. The median particle size Dv50 of the alumina of the first particle size was 600 nm, the porosity was 20%, the coating thickness was 2 μm, and the porosity of the first coating was 50%.

[0079] Step 3: Same as in Example 1.

[0080] That is, in Example 2, the material and thickness of the coating are the same as those of the first coating in Example 1, but the coating in Example 2 fully covers the second surface of the base film and there are no spiral lines.

[0081] Example 3 (with lithium replenishment function + ordinary coating + compound slurry coating) Step 1: Same as in Example 1.

[0082] Step 2: Prepare the coating A narrow-slit extrusion coating process was used to coat a compound alumina slurry (comprising alumina of a first and second particle sizes) onto the second surface of a base film. The coating was obtained after curing the compound alumina slurry. The first particle size alumina had a median particle size (Dv50) of 600 nm and a porosity of 20%, while the second particle size alumina had a median particle size (Dv50) of 150 nm and a porosity of 6%. The mass ratio of the first to second particle size alumina was 1:1. The coating thickness was 2 μm, and the porosity of the coating was 40%.

[0083] Step 3: Same as in Example 1.

[0084] That is, in Example 3, the material of the coating is the same as that of the second coating in Example 1, and the thickness of the coating is the same as that of the first coating in Example 1, but the coating in Example 3 fully covers the second surface of the base film.

[0085] Comparative Example 1 (without lithium replenishment function + ordinary coating) Step 1 of Example 3 is omitted. A coating is prepared on the second surface of a PE film with a thickness of 9 μm. The preparation method of the coating is the same as step 2 of Example 2. Then, PVDF layers are respectively set on the two surfaces of the base film (that is, a PVDF layer is set on the first surface of the base film and a PVDF layer is set on the coating), resulting in a separator without lithium replenishment function and without a spiral coating.

[0086] Comparative Example 2 (without lithium replenishment function + spiral coating) Step 1 of Example 1 is omitted. A coating is prepared on the second surface of a PE film with a thickness of 9 μm. The preparation method of the coating is the same as step 2 of Example 1. Then, PVDF layers are respectively set on the two surfaces of the base film (that is, a PVDF layer is set on the first surface of the base film and a PVDF layer is set on the coating), resulting in a separator without lithium replenishment function but with a spiral coating.

[0087] II. Performance tests were conducted on the diaphragms obtained in the above embodiments and comparative examples: 1. Preparation of lithium-ion batteries (1.1) Preparation of the positive electrode: Lithium iron phosphate (positive electrode active material), conductive carbon black (SP), and binder (polyvinylidene fluoride, PVDF) were mixed evenly in a mass ratio of 98:1:1 and dispersed in a solvent (N-methylpyrrolidone, NMP) to prepare a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector (carbon-coated aluminum foil) to form a positive electrode active coating. The coating was dried at 90°C in a vacuum environment for 24 hours, and then cold-pressed and slit to obtain a positive electrode sheet.

[0088] (1.2) Preparation of negative electrode: Graphite material, conductive carbon black (SP), and binder (polyvinylidene fluoride, PVDF) were mixed evenly in a mass ratio of 97:2:1 and dispersed in deionized water to prepare a negative electrode slurry. The negative electrode slurry was evenly coated on both surfaces of a copper foil and dried at 90°C under vacuum for 24 hours to obtain a negative electrode sheet.

[0089] (1.3) Assembly The positive electrode, separator, and negative electrode are wound into a cell, housed in an aluminum casing, and then processed through baking, electrolyte injection, formation, and capacity testing to create a lithium-ion battery. During electrolyte injection, the electrolyte is prepared first. Specifically, ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed organic solvent; then, thoroughly dried lithium salt LiPF6 is dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare the electrolyte.

[0090] 2. Testing of lithium-ion batteries Cycle capacity retention testing was performed on lithium-ion batteries. The cycle capacity retention test was conducted using the Newwell CT-9004-5V100A high-precision battery testing system, following GB / T31484-2015. Specifically: at 25℃, the battery cells were charged at a constant current of 0.3C to the upper limit cutoff voltage of 3.65V, and then charged at a constant voltage to a current of 0.05C. After resting for 10 minutes, the battery cells were discharged at a constant current of 0.3C to 2.5V, and the discharge capacity at this point was recorded, which is the discharge capacity C0 of the first cycle. Cycle testing was performed according to this procedure, and the capacity at the 100th and 200th cycles was recorded. This capacity retention is denoted as Cn. The capacity retention rate for n cycles was obtained using the formula Cn / C0*100%. The cycle capacity retention test results are shown in Table 1 below.

[0091] Table 1 Results of Cyclic Capacity Retention Test ; As shown in Table 1, the capacity retention rates of the lithium-ion batteries in Examples 2 and 3 after 100 cycles are 90% and 91%, respectively, which are significantly better than the 80% of Comparative Example 1. Furthermore, the capacity retention rates of the lithium-ion batteries in Examples 2 and 3 after 200 cycles are 78% and 80%, respectively, which are significantly better than the 65% of Comparative Example 1. This demonstrates that the performance of lithium-ion batteries using a separator with "lithium replenishment function + ordinary coating" (Examples 2 and 3) is significantly better than that of lithium-ion batteries using a separator without "lithium replenishment function + ordinary coating" (Comparative Example 1). This proves that the lithium replenishment function can suppress the capacity decay of lithium-ion batteries.

[0092] As shown in Table 1, the lithium-ion battery of Comparative Example 2 retains 85% of its capacity after 100 cycles, which is better than 80% of Comparative Example 1. Furthermore, the lithium-ion battery of Comparative Example 2 retains 70% of its capacity after 200 cycles, which is better than 65% of Comparative Example 1. This demonstrates that the lithium-ion battery using a separator with a "spiral coating" (Comparative Example 2) outperforms the lithium-ion battery using a separator with a "normal coating" (Comparative Example 1), thus proving that the spiral coating can suppress capacity decay in lithium-ion batteries.

[0093] As shown in Table 1, the lithium-ion battery of Example 1 has a capacity retention rate of 98% after 100 cycles, which is significantly better than 90% of Example 2 and 91% of Example 3. Furthermore, the lithium-ion battery of Example 1 has a capacity retention rate of 90% after 200 cycles, which is significantly better than 78% of Example 2 and 80% of Example 3. This demonstrates that the lithium-ion battery using a separator with "lithium replenishment function + spiral coating" (Example 1) performs significantly better than the lithium-ion batteries using a separator with "lithium replenishment function + ordinary coating" (Examples 2 and 3). This proves that the lithium replenishment function and the spiral coating work together to better suppress the capacity decay of lithium-ion batteries.

[0094] As shown in Table 1, the capacity retention rates of the lithium-ion batteries in Examples 2 and 3 after 100 cycles are 90% and 91%, respectively, which are significantly better than the 85% of Comparative Example 2. Furthermore, the capacity retention rates of the lithium-ion batteries in Examples 2 and 3 after 200 cycles are 78% and 80%, respectively, which are significantly better than the 70% of Comparative Example 2. This demonstrates that the performance of lithium-ion batteries using a separator with "lithium replenishment function + ordinary coating" (Examples 2 and 3) is significantly better than that of lithium-ion batteries using a separator without "lithium replenishment function + spiral coating" (Comparative Example 2). This proves that a single lithium replenishment function is more effective than a single spiral coating in suppressing the capacity decay of lithium-ion batteries.

[0095] As shown in Table 1, the lithium-ion battery of Example 3 has a capacity retention rate of 91% after 100 cycles, which is better than the 90% of Example 2. Furthermore, the lithium-ion battery of Example 3 has a capacity retention rate of 80% after 200 cycles, which is better than the 78% of Example 2. This indicates that the lithium-ion battery using the "composite slurry coating" separator (Example 3) performs better than the lithium-ion battery using the "non-composite slurry coating" separator (Example 3), thus proving that the composite slurry coating can suppress the capacity decay of lithium-ion batteries.

[0096] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0097] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A diaphragm, characterized in that, include: A base film (200) has a first surface (202) and a second surface (204) opposite each other in its thickness direction. The first surface (202) has a protrusion structure (210) with a through hole (212). The second surface (204) has a recess (220) on the surface opposite to the protrusion structure. The through hole (212) communicates with the recess (220). The inner diameter of the recess (220) at the second surface (204) is larger than the aperture of the through hole (212). There are multiple protrusion structures (210) arranged at intervals. A lithium replenishing material is located within the recess (220); as well as A coating (300) is applied to the second surface (204) and covers the recess (220).

2. The diaphragm as described in claim 1, characterized in that, It also satisfies at least one of the following conditions (a1)-(a7): (a1) The base film (200) is made of polyolefin; (a2) The thickness of the base film (200) is 7-16 micrometers; (a3) The aperture of the through hole (212) is 0.1-0.5 micrometers; (a4) There are multiple through holes (212), which are arranged at intervals, and the sum of the areas of the multiple through holes (212) is 10%-20% of the area of ​​the outer surface of the protruding structure (210); (a5) The protruding structure (210) is spherical; (a6) A plurality of the protrusions (210) are arranged in an array, the spacing between two adjacent rows of the protrusions (210) is 1.5-3 times the outer diameter of the protrusions (210), and the spacing between two adjacent columns of the protrusions (210) is 1.5-3 times the outer diameter of the protrusions (210). (a7) The outer diameter of the protrusion structure (210) is 1-5 micrometers, and the depth of the recess (220) is 1-4 micrometers in the arrangement direction of the first surface (202) and the second surface (204).

3. The diaphragm as described in claim 1, characterized in that, It also satisfies at least one of the following conditions (a1)-(a7): (a1) The lithium replenishment material is a lithium salt; (a2) The median particle size Dv50 of the lithium replenishment material is 0.6-0.7 micrometers; (a3) The coating (300) is a ceramic layer; (a4) also includes a PVDF layer, wherein the coating (300) is provided with the PVDF layer and / or the base film (200) is provided with the PVDF layer on one side having the protrusion structure (210).

4. The diaphragm as described in claim 1, characterized in that, The coating (300) covers the second surface (204).

5. The diaphragm as described in claim 1, characterized in that, The coating (300) includes a first coating (310) formed on the second surface (204) and a second coating (320) formed on the second surface (204). The first coating (310) includes a plurality of sub-coatings (312), which are spaced apart along the width direction of the second surface (204) and extend along the length direction of the second surface (204). The second coating (320) and the first coating (310) together cover the second surface (204).

6. The diaphragm as described in claim 5, characterized in that, It also satisfies at least one of the following conditions (a1)-(a8): (a1) The area of ​​the first coating (310) is 10-70% of the area of ​​the second surface (204); (a2) In the width direction of the second surface (204), the width of the sub-coating (312) is 5-20 mm; (a3) In the width direction of the second surface (204), the spacing between two adjacent sub-coatings (312) is 1.5-3 times the width of the sub-coating (312); (a4) The thickness of the sub-coating (312) is 1-3 micrometers; (a5) The sub-coating (312) is spiral-shaped, the peak-valley distance of the sub-coating (312) is 10-40mm, and the turning angle of the sub-coating (312) is 100°-150°. (a6) The thickness of the sub-coating (312) is 0.5-1 micrometer greater than the thickness of the second coating (320); (a7) The porosity of the sub-coating (312) is 40-50%; (a8) The porosity of the second coating (320) is 30-45%.

7. The diaphragm as described in claim 5, characterized in that, It also satisfies at least one of the following conditions (a1)-(a2): (a1) The sub-coating (312) is a ceramic layer, and the sub-coating (312) includes alumina with a first particle size of 500-800 nm and a porosity of 15-25%. (a2) The second coating (320) is a ceramic layer. The second coating (320) includes a first-size alumina and a second-size alumina. The particle size of the first-size alumina is 500-800 nm, and the particle size of the second-size alumina is 10-200 nm. The porosity of the first-size alumina is 15-25%, and the porosity of the second-size alumina is 2-10%. The mass ratio of the first-size alumina to the second-size alumina is 1:2-2:

1.

8. A method for preparing a diaphragm as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) A protruding structure is formed on the first surface of the base film, and a concave portion opposite to the protruding structure is formed on the second surface of the base film at the same time as the protruding structure is formed; (2) A through hole communicating with the recess is formed on the protruding structure; (3) Place lithium replenishing material inside the recess; as well as (4) Form a coating covering the recess on the second surface; Wherein, at least two of steps (1), (2), and (3) are performed simultaneously; and / or When the coating comprises a first coating and a second coating, the first coating is formed first, and then the second coating is formed.

9. A lithium-ion battery, comprising a positive electrode and a negative electrode, characterized in that, It also includes a separator as described in any one of claims 1-7, the separator being located between the positive electrode and the negative electrode, with the coating (300) facing the negative electrode and the protrusion structure (210) facing the positive electrode.

10. An electrical device, characterized in that, Including the lithium-ion battery as described in claim 9.

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