Composite separator, method for manufacturing the same, and battery

Abstract

This invention relates to the field of battery technology, specifically to a composite separator, its preparation method, and a battery. The composite separator includes a base film, a gel layer disposed on at least one surface of the base film along its thickness direction, and a corrosion inhibitor layer disposed on a surface of the gel layer away from the base film; the gel layer comprises a gel material; and the corrosion inhibitor layer comprises a corrosion inhibitor. The preparation method of the composite separator includes the following steps: coating a gel layer slurry onto at least one surface of the base film along its thickness direction to form a gel layer on the base film; and coating a corrosion inhibitor layer slurry onto the surface of the gel layer away from the base film to form a corrosion inhibitor layer on the gel layer, thereby obtaining the composite separator. The composite separator provided by this invention prevents dendrites from piercing it, inhibiting dendrite growth and thus increasing battery safety and extending battery cycle performance.

Description

Technical Field

[0001] This invention relates to the field of batteries, specifically to a composite separator, its preparation method, and a battery. Background Technology

[0002] As a crucial component of lithium-ion batteries, the separator directly impacts the overall battery performance. During charge-discharge cycles, dendritic lithium dendrites form, especially during fast charging where they grow rapidly. These dendrites continuously consume electrolyte and cause irreversible lithium deposition, resulting in dead lithium and low coulombic efficiency, thus affecting cycle performance. Furthermore, dendrite formation can even puncture the separator, leading to internal short circuits, thermal runaway, and potentially combustion or explosion. Optimizing the separator through coating can effectively suppress dendrite growth and prevent short circuits and thermal runaway caused by dendrites puncturing the separator. Therefore, separator coating is the most effective and economical way to address this issue. However, existing separator structures still have limitations, such as insufficient mitigation of the lithium dendrite problem, necessitating further improvements.

[0003] Therefore, this application is hereby submitted. Summary of the Invention

[0004] In view of this, the present invention aims to provide a composite separator, a method for preparing the same, and a battery, to alleviate the problem of poor battery cycle performance caused by lithium dendrite growth in the prior art.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows:

[0006] The present invention provides a composite membrane, the composite membrane comprising a base membrane, a gel layer disposed on at least one surface of the base membrane in the thickness direction, and a corrosion inhibitor layer disposed on the side surface of the gel layer away from the base membrane;

[0007] The gel layer comprises a gel material;

[0008] The corrosion inhibitor layer includes a corrosion inhibitor.

[0009] In some specific embodiments, the gel material includes at least one of agarose, polyacrylamide gel, and polyurethane gel.

[0010] In some specific embodiments, the gel layer also includes additives.

[0011] In some specific embodiments, the additive includes at least one of alcohols, esters, or amides.

[0012] In some specific embodiments, the alcohols include polyether polyols and / or diethylene glycol.

[0013] In some specific embodiments, the polyether polyol includes a first polyether polyol and a second polyether polyol.

[0014] In some specific embodiments, the functionality of the first polyether polyol is less than 3, or the functionality of the first polyether polyol is greater than 3.

[0015] In some specific embodiments, the second polyether polyol comprises poly(propylene ether) triol.

[0016] In some specific embodiments, the mass ratio of the first polyether polyol to the second polyether polyol is (2-5):1.

[0017] In some specific embodiments, the esters include acrylate monomers and / or 4,4-diphenylmethane diisocyanate.

[0018] In some specific embodiments, the acrylate monomer includes at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate.

[0019] In some specific embodiments, the amide substance includes dimethylformamide.

[0020] In some specific embodiments, the additives include polyether polyols, acrylate monomers, dimethylformamide, diethylene glycol, and 4,4-diphenylmethane diisocyanate.

[0021] In some specific embodiments, the mass ratio of the gel material, the polyether polyol, the dimethylformamide, the acrylate monomer, the 4,4-diphenylmethane diisocyanate, and the diethylene glycol is (1-5):(15-25):(0.01-0.05):(0.3-1):(5-15):(0.3-2).

[0022] In some specific embodiments, the corrosion inhibitor includes at least one of sodium oleate, hydroquinone, and methanesulfonic acid.

[0023] In some specific embodiments, the corrosion inhibitor layer also includes an adhesive.

[0024] In some specific embodiments, the adhesive includes at least one selected from polyvinylidene fluoride, polyacrylic acid, polyacrylate, polyimide, polyamide, polyvinyl alcohol, and polytetrafluoroethylene.

[0025] In some specific embodiments, the mass ratio of the corrosion inhibitor to the binder is (2-3):10.

[0026] In some specific embodiments, the area of ​​the corrosion-inhibiting layer is larger than the area of ​​the gel layer.

[0027] In some specific embodiments, along the width direction of the composite membrane, the edges on both sides of the corrosion inhibitor layer extend beyond the edges on both sides of the gel layer.

[0028] In some specific embodiments, the dimension by which one edge of the corrosion inhibitor extends beyond the corresponding edge of the gel layer is D1, and the dimension by which the other edge of the corrosion inhibitor extends beyond the corresponding other edge of the gel layer is D2, wherein D1 is 1mm to 5mm, and / or D2 is 1mm to 5mm.

[0029] In some specific implementations, D1 and D2 are equal.

[0030] In some specific embodiments, the thickness of the gel layer is 8 μm to 15 μm.

[0031] In some specific embodiments, the thickness of the corrosion inhibitor layer is 4 μm to 7 μm.

[0032] In some specific embodiments, the thickness of the base film is 2 μm to 20 μm.

[0033] In some specific embodiments, the base film includes a polyethylene base film and / or a polypropylene base film.

[0034] A second aspect of the present invention also provides a method for preparing a composite separator, comprising the following steps:

[0035] A gel layer slurry is coated onto at least one side surface of the base film along the thickness direction to form a gel layer on the base film;

[0036] A corrosion-inhibiting slurry is coated onto the surface of the gel layer away from the base film to form a corrosion-inhibiting layer on the gel layer, thereby obtaining a composite membrane.

[0037] The gel layer slurry includes a gel material;

[0038] The corrosion inhibitor slurry includes a corrosion inhibitor.

[0039] In some specific embodiments, the gel layer slurry also includes additives and water.

[0040] In some specific embodiments, the additive includes at least one of alcohols, esters, and amides.

[0041] In some specific embodiments, the alcohols include polyether polyols and / or diethylene glycol; preferably, the polyether polyols include a first polyether polyol and a second polyether polyol.

[0042] In some specific embodiments, the esters include acrylate monomers and / or 4,4-diphenylmethane diisocyanate.

[0043] In some specific embodiments, the acrylate monomer includes at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate.

[0044] In some specific embodiments, the amide substance includes dimethylformamide.

[0045] In some specific embodiments, the additives include polyether polyols, acrylate monomers, dimethylformamide, diethylene glycol, and 4,4-diphenylmethane diisocyanate.

[0046] In some specific embodiments, the preparation of the gel layer slurry includes:

[0047] A first slurry is obtained by first mixing polyether polyol, acrylate monomer, dimethylformamide, diethylene glycol, 4,4-diphenylmethane diisocyanate and water.

[0048] The gel material and water are mixed a second time to obtain a second slurry;

[0049] The first slurry is heated in the first stage, and then the second slurry is mixed in the third stage to obtain the gel layer slurry.

[0050] In some specific embodiments, the second mixing process further includes a second heating and a cooling process, wherein the final temperature of the second heating is 90-95°C and the final temperature of the cooling is 55-65°C.

[0051] In some specific embodiments, the final temperature of the first heating is 55-65°C.

[0052] In some specific embodiments, the mass ratio of the first slurry to the second slurry is (2-3):(1-2).

[0053] In some specific embodiments, the corrosion-inhibiting slurry also includes a binder.

[0054] In some specific embodiments, the coating temperature of the gel layer slurry is 45–55°C.

[0055] In some specific embodiments, the coating temperature of the corrosion-inhibiting slurry is 45–55°C.

[0056] A third aspect of the present invention also provides a battery comprising a positive electrode, a negative electrode, and a separator, wherein the separator comprises a composite separator as described above, or a composite separator prepared according to the preparation method described above.

[0057] In some specific embodiments, the corrosion inhibitor layer in the composite membrane is disposed on the negative electrode side.

[0058] The beneficial technical effects of the present invention through the above technical solution are as follows:

[0059] The separator provided by this invention employs a double-layer coating technology. An outer layer containing a corrosion inhibitor is formed on the composite separator, while an inner layer contains a gel material. The corrosion inhibitor in the outer layer exhibits corrosion inhibition properties against metals such as iron, lithium, and sodium. When dendrites grow to the separator and reach the corrosion inhibitor layer, the corrosion inhibitor can erode the dendrites, preventing them from penetrating the separator, thereby increasing battery safety and extending cycle life. Furthermore, when the corrosion inhibitor layer does not completely eliminate dendrites, the gel material in the inner layer of the composite separator enhances the mechanical properties of the inner gel layer. Dendrites will not easily penetrate the inner gel layer, thus hindering its growth. Simultaneously, dendrites that have penetrated the corrosion inhibitor layer will continue to be corroded by the corrosion inhibitor within the layer, causing their roots to break off. This prevents dendrites penetrating the outer layer from further penetrating the separator, thereby improving battery safety. In addition, the corrosion inhibitor has a certain degree of hydrophilicity, allowing it to absorb moisture generated after battery cycling, further improving the battery's electrical performance.

[0060] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0061] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0062] Figure 1 The diagram shown is a structural schematic of the composite diaphragm provided by the present invention. Detailed Implementation

[0063] This invention discloses a composite separator, its preparation method, and a battery. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0064] In the description of this invention, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0065] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0066] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0067] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0068] Unless otherwise specified, room temperature in this application refers to 10–30°C.

[0069] During battery charge-discharge cycles, dendritic lithium dendrites form. These dendrites continuously consume electrolyte and cause irreversible lithium deposition, resulting in low coulombic efficiency and impacting cycle performance. Currently, lithium dendrite growth is primarily suppressed through separator coating. However, lithium dendrites can puncture the separator, causing internal short circuits and potentially leading to thermal runaway, combustion, or explosion. Therefore, separator optimization is needed to suppress lithium dendrite growth and prevent short circuits, thermal runaway, and other dangerous situations. This necessitates the development of a slow corrosion method to eliminate dendrites, optimize the separator, improve battery safety and cycle performance, and further advance the commercialization of lithium batteries.

[0070] In view of this, this application provides a composite separator and a method for preparing the same, and also provides a battery containing the composite separator. The composite separator can erode dendrites, preventing dendrites from piercing the separator, thereby increasing the safety of the battery and extending its cycle performance. The application will now be described in detail.

[0071] [Composite diaphragm]

[0072] In some embodiments, the present invention provides a composite membrane comprising a base membrane, a gel layer disposed on at least one surface of the base membrane in the thickness direction, and a corrosion inhibitor layer disposed on the side surface of the gel layer away from the base membrane.

[0073] The gel layer includes a gel material; the corrosion inhibitor layer includes a corrosion inhibitor.

[0074] The provided composite membrane has a double-layer coating structure, in which a gel layer and a corrosion inhibitor layer are sequentially provided on the base membrane. The gel layer is located close to the base membrane and can also be called the inner layer; the corrosion inhibitor layer is located away from the base membrane and can also be called the outer layer.

[0075] In this composite membrane, the gel layer being disposed on at least one surface of the base membrane along its thickness direction means that the gel layer can be disposed on one surface of the base membrane along its own thickness direction, or on two surfaces of the base membrane along its own thickness direction. Here, "surface" can be the entire area of ​​the base membrane or a part of the base membrane; this application does not have any particular limitation in this regard, as long as the purpose of this application can be achieved.

[0076] As an example, the base film has two surfaces opposite each other in its thickness direction, and a gel layer is disposed on the two opposite surfaces of the base film. Furthermore, a corrosion inhibitor layer is disposed on the surfaces of the gel layer on both sides. It is understood that in some embodiments, the gel layer may also be stacked on one of the two surfaces of the base film. And, when the gel layer and corrosion inhibitor layer are disposed only on one surface of the base film, these layers are disposed closer to the negative electrode side to mitigate the lithium dendrite formation problem on the negative electrode side.

[0077] In this embodiment of the invention, the provided composite separator sequentially comprises a base membrane, a gel layer containing a gel material, and a corrosion inhibitor layer containing a corrosion inhibitor. This structural design effectively mitigates dendrite problems. Specifically, when dendrites grow to the point where they reach the corrosion inhibitor layer, the corrosion inhibitor in the layer can erode the dendrites, preventing them from piercing the separator and increasing battery safety and cycle life. The inner gel layer containing a gel material enhances the mechanical properties of the inner layer, further inhibiting dendrite growth. In detail:

[0078] The separator provided by this invention employs a double-layer coating technology. An outer layer containing a corrosion inhibitor is formed on the outer surface of the composite separator, while an inner layer contains a gel material. The corrosion inhibitor in the outer layer exhibits corrosion-inhibiting properties against metals such as iron, lithium, and sodium. By coating the separator with a material that inhibits the growth of these metals, dendrites (such as iron, lithium, and sodium) reach the separator and are then corroded away by the corrosion inhibitor, preventing them from penetrating the separator. This increases battery safety and extends battery cycle life. Furthermore, since the corrosion inhibitor's corrosiveness is primarily a matter of slowing down the corrosion, this invention utilizes a double-layer coating technology. The outer layer contains the corrosion inhibitor, while the inner layer contains the gel material, thus enhancing the mechanical properties of the inner layer. Therefore, even when the corrosion inhibitor layer does not completely inhibit and eliminate dendrites, the gel material in the inner layer of the composite separator can enhance the mechanical properties of the inner gel layer. Dendrites will not easily pierce the inner gel layer, thus hindering their growth. Simultaneously, dendrites that have penetrated the corrosion inhibitor layer will continue to be corroded by the corrosion inhibitor within the layer, causing their roots to break off. This prevents dendrites penetrating the outer layer from further piercing the separator, thereby improving battery safety. Furthermore, the corrosion inhibitor has a certain degree of hydrophilicity, which can absorb moisture generated after battery cycling, further improving the battery's electrical performance.

[0079] The composite separator of this invention is suitable for use in lithium-ion batteries to alleviate problems such as lithium dendrites piercing the separator and causing internal short circuits in the battery. Of course, this composite separator is also suitable for use in sodium-ion batteries or hybrid-ion batteries, not only alleviating lithium dendrite problems but also mitigating problems such as sodium dendrites and iron dendrites piercing the separator and causing internal short circuits in the battery.

[0080] In embodiments of the present invention, the term "gel material" generally refers to a soft substance between a liquid and a solid, consisting of a three-dimensional network structure (cross-linked polymer, inorganic substance or complex) and a dispersion medium (such as water, organic solvent or gas).

[0081] In this embodiment of the invention, the term "corrosion inhibitor" refers to materials that have corrosion inhibitory properties for metals such as iron, lithium, and sodium, such as sodium oleate, hydroquinone, and methanesulfonic acid.

[0082] In some embodiments, the gel material includes, but is not limited to, at least one of agarose, polyacrylamide gel and polyurethane gel, preferably agarose.

[0083] In this invention, one or more of agarose, polyacrylamide gel, and polyurethane gel can be used as gelling materials to increase mechanical properties and physically prevent dendrites not inhibited by the outer corrosion inhibitor layer from piercing the diaphragm. Preferably, agarose is selected as the gelling material, as agarose is in a solution state at high temperatures (above 90°C) and spontaneously forms a gel at room temperature (below 40°C), making it convenient to use.

[0084] In some embodiments, the gel layer also includes additives, that is, the gel layer is mainly composed of gel materials and additives.

[0085] In some embodiments, the additive includes at least one of alcohols, esters, or amides. The additive in the gel layer may include any one or a combination of at least two of alcohols, esters, or amides; preferably, the additive includes alcohols, esters, and amides. By adding an additive composed of alcohols, esters, and amides to the gel layer, the mechanical properties of the gel layer are improved, and it works synergistically with the gel material to effectively prevent dendrites not inhibited by the outer corrosion inhibition layer from piercing the diaphragm.

[0086] Preferably, the alcohol in the additive includes polyether polyols and / or diethylene glycol. That is, the alcohol may contain polyether polyols, or diethylene glycol, or both polyether polyols and diethylene glycol. In some embodiments, it is more preferred that the alcohol contains both polyether polyols and diethylene glycol, as the polyether polyols and diethylene glycol can improve the physical wettability and antistatic properties of the membrane.

[0087] Preferably, among the alcohols, the polyether polyols include a first polyether polyol and a second polyether polyol.

[0088] In some embodiments, the functionality of the first polyether polyol is less than 3, or the functionality of the first polyether polyol is greater than 3. For example, the functionality of the first polyether polyol can be 2, 4, 5, or greater than 5. As an example, the first polyether polyol can be a polyether diol, a polyether tetraol, a polyether pentaol, etc.

[0089] In some embodiments, the second polyether polyol comprises poly(propylene ether) triol.

[0090] In the aforementioned polyether polyols, the second polyether polyol is mainly a triol, while the first polyether polyol is mainly a diol, tetraol, or pentaol, excluding triols. As an example, the first polyether polyol can be one or more of the following: polyether polyols initiated by ethylene glycol, polyether polyols initiated by pentaerythritol, polyether polyols initiated by xylitol, and polyether polyols initiated by sorbitol.

[0091] In some embodiments, the mass ratio of the first polyether polyol to the second polyether polyol is (2-5):1. As an example, the mass ratio of the first polyether polyol to the second polyether polyol can be any one of 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, and 5:1, or a range between any two. Preferably, the mass ratio of the first polyether polyol to the second polyether polyol is 3:1.

[0092] Therefore, by including the first polyether polyol and polypropylene ether triol mentioned above in the polyether polyol, and keeping their ratio within the appropriate range, better application results can be obtained, which is more conducive to improving the physical properties of the composite membrane, such as wettability and antistatic properties.

[0093] Preferably, the esters in the additive include acrylate monomers and / or 4,4-diphenylmethane diisocyanate. That is, the esters may contain acrylate monomers, 4,4-diphenylmethane diisocyanate, or both. In some embodiments, it is more preferable that the esters simultaneously contain acrylate monomers and 4,4-diphenylmethane diisocyanate, so that the acrylate monomers can provide rigid support for the gel layer and enhance interfacial adhesion; and the self-healing properties of 4,4-diphenylmethane diisocyanate can dynamically repair microscopic damage.

[0094] Preferably, the acrylate monomer in the additive includes, but is not limited to, at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate and methyl methacrylate.

[0095] Preferred amides include, but are not limited to, dimethylformamide.

[0096] In some preferred embodiments, the additives include polyether polyols, acrylate monomers, dimethylformamide, diethylene glycol, and 4,4-diphenylmethane diisocyanate.

[0097] In this invention, by adding the above-mentioned additives to the composite membrane gel layer, especially by including polyether polyol, acrylate monomer, dimethylformamide, diethylene glycol, and 4,4-diphenylmethane diisocyanate simultaneously, the mechanical properties of the gel layer can be significantly improved, preventing dendrite puncture. For example, polyether polyol can enhance the mechanical strength and elasticity of the gel layer, resisting dendrite puncture; diethylene glycol can reduce the viscosity of the system, facilitating the coating process; acrylate monomer can provide rigid support for the gel layer, enhancing interfacial adhesion; and 4,4-diphenylmethane diisocyanate significantly improves the mechanical strength (such as tensile strength and puncture resistance) of the gel layer, preventing dendrite puncture.

[0098] In some embodiments, the mass ratio of gel material, polyether polyol, dimethylformamide, acrylate monomer, 4,4-diphenylmethane diisocyanate and diethylene glycol is (1-5):(15-25):(0.01-0.05):(0.3-1):(5-15):(0.3-2). As an example, the mass ratio of the gel material, polyether polyol, dimethylformamide, acrylate monomer, 4,4-diphenylmethane diisocyanate, and diethylene glycol can be any one of the following values ​​or a range between any two: 1:15:0.01:0.3:5:0.3, 1:20:0.03:0.5:10:0.5, 3:25:0.05:0.7:15:1, 5:15:0.01:0.3:5:0.3, 5:20:0.03:0.5:10:0.5, and 5:25:0.05:1:15:1.

[0099] In this invention, by controlling the amount of each additive within the above-mentioned range, it helps to improve the mechanical properties of the gel layer, and dendrites will not easily puncture the inner gel layer and thus resist the growth of the gel layer, thereby improving the safety of the battery.

[0100] In some embodiments, the corrosion inhibitor includes, but is not limited to, at least one of sodium oleate, hydroquinone, and methanesulfonic acid.

[0101] In this invention, the corrosion inhibitor can be any one or more of sodium oleate, hydroquinone, and methanesulfonic acid. Preferably, the corrosion inhibitor contains sodium oleate, hydroquinone, and methanesulfonic acid.

[0102] Therefore, by selecting sodium oleate, hydroquinone, and methanesulfonic acid as corrosion inhibitors, which have corrosion inhibitory properties for metals such as iron, lithium, and sodium, the dendrites of iron, lithium, and sodium can be inhibited, preventing the dendrites from puncturing the separator, thereby increasing the safety of the battery and extending its cycle performance.

[0103] In some embodiments, the corrosion inhibitor layer also includes a binder. That is, the corrosion inhibitor layer is mainly composed of a corrosion inhibitor and a binder.

[0104] In some embodiments, the binder includes, but is not limited to, at least one selected from polyvinylidene fluoride, polyacrylic acid, polyacrylate, polyimide, polyamide, polyvinyl alcohol, and polytetrafluoroethylene. By adding a binder to the corrosion inhibitor layer, the adhesion between the corrosion inhibitor layer and the gel layer can be increased, the structural strength of the composite membrane can be improved, and the peeling off of the corrosion inhibitor layer can be reduced or avoided.

[0105] In some embodiments, the mass ratio of corrosion inhibitor to binder is (2-3):10. As an example, the mass ratio of corrosion inhibitor to binder can be any one of 2:10, 2.2:10, 2.5:10, 2.8:10, and 3:10, or any range between the two.

[0106] In this invention, by controlling the mass ratio of corrosion inhibitor and binder within the above-mentioned range, the corrosion inhibitor can be effectively used to inhibit the corrosion of dendrites, preventing them from piercing the diaphragm, and the adhesion of the corrosion inhibitor layer can be improved.

[0107] In some embodiments, the area of ​​the corrosion-inhibiting layer is larger than the area of ​​the gel layer.

[0108] In some embodiments, such as Figure 1 As shown, along the width direction of the composite membrane, the edges of the corrosion inhibitor layer extend beyond the edges of the gel layer.

[0109] In some embodiments, the dimension by which one edge of the corrosion inhibitor extends beyond the corresponding edge of the gel layer is D1, and the dimension by which the other edge of the corrosion inhibitor extends beyond the corresponding other edge of the gel layer is D2, where D1 is 1 mm to 5 mm, and / or D2 is 1 mm to 5 mm. As an example, D1 can be any one of 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm, or a range between any two, and D2 can be any one of 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm, or a range between any two.

[0110] In some embodiments, D1 and D2 are equal.

[0111] In this invention, by adjusting the area relationship between the corrosion inhibitor layer and the gel layer within the above-mentioned range, since the viscosity of the gel layer is weaker than that of the corrosion inhibitor layer, the gel layer is completely within the surface of the corrosion inhibitor layer, which can improve the adhesion between the corrosion inhibitor layer, the gel layer and the base film.

[0112] When this composite separator is applied to a battery, the area of ​​the gel layer needs to completely cover the area of ​​the negative electrode (especially the active material layer in the negative electrode). This is because lithium dendrites generally form on the negative electrode side, especially at the edge of the negative electrode. If it cannot be completely covered, it cannot resist all the lithium dendrites. Furthermore, the corrosion inhibitor layer needs to completely cover the gel layer, and the area of ​​the corrosion inhibitor layer is preferably larger than the area of ​​the gel layer. For example, in the width direction, one edge of the corrosion inhibitor layer preferably extends beyond one edge of the gel layer by 1 mm to 5 mm, and the other edge of the corrosion inhibitor layer also preferably extends beyond one edge of the gel layer by 1 mm to 5 mm. This can improve the adhesion between the base film, the gel layer, and the corrosion inhibitor layer, and reduce or avoid the problem of insufficient adhesion caused by the viscosity of the gel layer being weaker than that of the corrosion inhibitor layer.

[0113] In some embodiments, the thickness of the gel layer is 8 μm to 15 μm. As an example, the thickness of the gel layer can be any one of 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm and 15 μm or a range between any two.

[0114] In this invention, by controlling the thickness of the gel layer within the aforementioned range, it is helpful to improve the mechanical properties of the diaphragm, enhance its puncture resistance, and inhibit dendrite penetration. If the gel layer is too thick, it will lead to an increase in interfacial impedance and reduce the conductivity of the diaphragm; if the gel layer is too thin, it will not be able to improve the mechanical properties of the diaphragm or enhance its puncture resistance.

[0115] In some embodiments, the thickness of the corrosion inhibitor layer is 4 μm to 7 μm. As an example, the thickness of the corrosion inhibitor layer can be any one of 4 μm, 5 μm, 6 μm and 7 μm or a range between any two.

[0116] In this invention, controlling the thickness of the corrosion inhibitor layer within the aforementioned range helps to improve the corrosion inhibition of dendrites, preventing them from piercing the separator, thereby increasing battery safety and extending battery cycle performance. If the corrosion inhibitor layer is too thick, it will lead to an increase in interfacial impedance and reduce the conductivity of the separator; if the corrosion inhibitor layer is too thin, it will not effectively inhibit the corrosion of dendrites.

[0117] In some embodiments, the thickness of the base film is 2 μm to 20 μm. As an example, the thickness of the base film can be any one of 2 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm and 20 μm or a range between any two.

[0118] In some embodiments, the base film includes a polyethylene base film and / or a polypropylene base film. For example, the base film can be made of polyethylene, or polypropylene, or a mixture of polyethylene and polypropylene. Of course, it is not limited to these, and this application does not have any particular limitation, as long as the purpose of this application can be achieved.

[0119] Therefore, the composite separator provided by this invention includes a base film, a corrosion inhibitor layer, and a gel layer. The corrosion inhibitor layer contains a corrosion-inhibiting material that can inhibit the erosion of dendrites, preventing them from piercing the separator, thereby increasing battery safety and extending battery cycle performance. During fast charging, lithium dendrites grow rapidly. While the corrosion inhibitor layer can inhibit the erosion of some lithium dendrites, it cannot resist a large number, allowing some to penetrate the layer. The gel layer then resists the remaining large number of lithium dendrites, keeping them on one side of the gel layer and preventing them from piercing the separator. The corrosion inhibitor layer continues to inhibit the erosion of lithium dendrites, causing them to break at the root, preventing further growth and thus preventing dendrites that have passed through the corrosion inhibitor layer from piercing the separator. Furthermore, the corrosion inhibitor layer continues to inhibit the erosion of any remaining lithium dendrites that have passed through the corrosion inhibitor layer and deposited on one side of the gel layer, thereby improving battery safety. In addition, the corrosion inhibitor has a certain degree of hydrophilicity, which can absorb moisture generated after battery cycling, further improving the battery's electrical performance. In addition, the preparation process of this composite membrane is simple and easy to industrialize.

[0120] [Preparation method of composite membrane]

[0121] In some embodiments, a second aspect of the present invention also provides a method for preparing a composite separator, comprising the following steps:

[0122] A gel layer slurry is coated onto at least one side surface of the base film along the thickness direction to form a gel layer on the base film;

[0123] The corrosion inhibitor slurry is coated on the surface of the gel layer away from the base film to form a corrosion inhibitor layer on the gel layer, thus obtaining a composite membrane;

[0124] The gel layer slurry includes gel materials;

[0125] The corrosion inhibitor slurry contains corrosion inhibitors.

[0126] In this invention, the method for preparing the composite separator includes sequentially coating a gel layer slurry and a corrosion inhibitor layer slurry onto a base membrane to form a gel layer and a corrosion inhibitor layer, thereby obtaining the composite separator. When dendrites grow to the point where they reach the corrosion inhibitor layer, the corrosion inhibitor in the corrosion inhibitor layer can erode the dendrites, preventing them from piercing the separator and increasing battery safety and extending battery cycle performance. The inner layer is provided with a gel layer containing gel material, which increases the mechanical properties of the inner layer and inhibits dendrite growth. This preparation method is simple, easy to operate, highly feasible, has low production costs, and is easy to scale up for mass production.

[0127] It should be understood that all the features and advantages described above regarding the "composite diaphragm" also apply to the "preparation method of the composite diaphragm", and will not be repeated here.

[0128] In some embodiments, the gel layer slurry also includes additives and water.

[0129] In some embodiments, the additive includes, but is not limited to, at least one of alcohols, esters, and amides.

[0130] In some embodiments, the alcohols include, but are not limited to, polyether polyols and / or diethylene glycol; preferably, the polyether polyols include a first polyether polyol and a second polyether polyol. The first polyether polyol may be a polyether polyol initiated with ethylene glycol, a polyether polyol initiated with pentaerythritol, a polyether polyol initiated with xylitol, a polyether polyol initiated with sorbitol, etc. The second polyether polyol may be a polypropylene ether triol.

[0131] In some embodiments, esters include, but are not limited to, acrylate monomers and / or 4,4-diphenylmethane diisocyanate.

[0132] In some embodiments, the acrylate monomer includes, but is not limited to, at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate.

[0133] In some embodiments, amides include, but are not limited to, dimethylformamide.

[0134] In some preferred embodiments, the additives include polyether polyols, acrylate monomers, dimethylformamide, diethylene glycol, and 4,4-diphenylmethane diisocyanate.

[0135] Exemplarily, in some embodiments, the preparation of the gel layer slurry includes:

[0136] A first slurry is obtained by first mixing polyether polyol, acrylate monomer, dimethylformamide, diethylene glycol, 4,4-diphenylmethane diisocyanate and water.

[0137] The gel material and water are mixed a second time to obtain a second slurry;

[0138] The first slurry is heated in the first stage, and then the second slurry is mixed in the third stage to obtain the gel layer slurry.

[0139] In some embodiments, the second mixing process further includes second heating and cooling, wherein the final temperature of the second heating is 90–95°C, and the final temperature of the cooling is 55–65°C. As an example, the final temperature of the second heating can be any one of 90°C, 91°C, 92°C, 93°C, 94°C, and 95°C, or a range between any two; and the final temperature of the cooling can be any one of 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, and 65°C, or a range between any two.

[0140] In this invention, when agarose is selected as the gel material, after the agarose and water are mixed for the second time, the mixture is heated to 90-95°C to dissolve the agarose, and then cooled to 55-65°C so that the agarose can spontaneously form a gel.

[0141] In some embodiments, the final temperature of the first heating is 55–65°C. As an example, the final temperature of the first heating can be any one of 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, and 65°C, or a range between any two.

[0142] In some embodiments, the mass ratio of the first slurry to the second slurry is (2-3):(1-2). As an example, the mass ratio of the first slurry to the second slurry can be any one of 2:1, 2.5:2, 3:2, and 3:1, or any range between the two.

[0143] As an example, the configuration of the gel layer slurry includes:

[0144] At room temperature, polyether polyol, acrylate monomer, dimethylformamide and diethylene glycol are mixed and dispersed, and then 4,4-diphenylmethane diisocyanate and water are added for the first mixing to obtain the first slurry;

[0145] The gel material and water are mixed a second time, heated to 90-95°C and then cooled to 55-65°C to obtain a second slurry.

[0146] Heat 2-3 parts of the first slurry to 55-65°C, and then mix it with 1-2 parts of the second slurry to obtain the gel layer slurry.

[0147] In some embodiments, the corrosion-inhibiting slurry also includes a binder.

[0148] In some embodiments, the coating temperature of the gel layer slurry is 45–55°C. As an example, the coating temperature of the gel layer slurry can be any one of 45°C, 46°C, 47°C, 48°C, 50°C, 51°C, 52°C, 53°C, 54°C, and 55°C, or a range between any two.

[0149] In some embodiments, the coating temperature of the corrosion inhibitor slurry is 45–55°C. As an example, the coating temperature of the corrosion inhibitor slurry can be any one of 45°C, 46°C, 47°C, 48°C, 50°C, 51°C, 52°C, 53°C, 54°C, and 55°C, or a range between any two.

[0150] As an example, the method for preparing the composite membrane in this invention includes the following steps:

[0151] The gel layer slurry is coated on at least one side of the base film along the thickness direction at 45-55°C, and after drying, a gel layer is formed on the base film.

[0152] The corrosion inhibitor slurry is coated on the surface of the gel layer away from the base film at 45-55℃. After drying, a corrosion inhibitor layer is formed on the gel layer, resulting in a composite membrane.

[0153] Therefore, based on the above configuration, the composite separator provided by the present invention includes a corrosion inhibitor layer containing a corrosion inhibitor and a gel layer containing a gel material. When dendrites grow to the point where the separator reaches the corrosion inhibitor layer, the corrosion inhibitor in the corrosion inhibitor layer can erode the dendrites, preventing the dendrites from piercing the separator, thus increasing the safety of the battery and extending the cycle performance of the battery. The inner layer is provided with a gel layer containing a gel material, which increases the mechanical properties of the inner layer and can inhibit the growth of dendrites.

[0154] [Battery]

[0155] A third aspect of the present invention also provides a battery comprising a positive electrode, a negative electrode, and a separator, wherein the separator comprises a composite separator as described above, or a composite separator prepared according to the preparation method described above.

[0156] In some embodiments, the corrosion inhibitor layer in the composite separator is disposed on the negative electrode side. In this invention, battery dendrites typically form on the negative electrode of the battery; placing the corrosion inhibitor layer in the composite separator close to the negative electrode can better inhibit the corrosion of dendrites.

[0157] In some embodiments, the gel layer in the composite separator completely covers the negative electrode sheet. If the gel layer in the composite separator does not completely cover the gel layer, it cannot resist all dendrites.

[0158] The battery mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can be a battery cell, or the battery can include a battery module (or battery pack), etc.

[0159] In some embodiments, the battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator between the positive and negative electrode. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited in this regard.

[0160] In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0161] In some embodiments, the battery can be a battery pack, which may include a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0162] It should be understood that multiple battery cells can be assembled into a battery module or battery pack. The number of battery cells contained in a battery module or battery pack can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module or battery pack.

[0163] In some embodiments, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0164] In the embodiments of this application, the methods for preparing battery cells or batteries are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained. Optionally, multiple battery cells can be further connected in series, parallel, or a hybrid configuration to form a battery module. Optionally, multiple battery modules can be connected in series, parallel, or a hybrid configuration to form a battery pack. Optionally, in some embodiments, multiple battery cells can also be directly assembled into a battery pack.

[0165] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0166] Example 1

[0167] The preparation of the composite membrane includes the following steps:

[0168] (1) By mass fraction, 30 parts of polyvinylidene fluoride (PVDF) and 70 parts of N-methylpyrrolidone (NMP) are mixed and dispersed to obtain a 30% polyvinylidene fluoride slurry. 6 parts of sodium oleate are added and stirred and dispersed for 120 min to obtain the corrosion inhibitor slurry.

[0169] (2) At room temperature, 15 parts by mass fraction of the first polyether polyol (functionality 2, i.e., polyether polyol with ethylene glycol as the initiator), 5 parts by mass fraction of the second polyether polyol (polypropylene ether triol), 0.5 parts by mass fraction of the methyl acrylate monomer, 0.03 parts by mass fraction of the dimethylformamide, and 1 part by mass fraction of the diethylene glycol are mixed and dissolved. Then, 10 parts by mass fraction of the 4,4-diphenylmethane diisocyanate are added for dispersion, and then 5 parts by mass fraction of the deionized water are added for dispersion to obtain the first slurry. After mixing and dispersing 5 parts by mass fraction of the agarose and 30 parts by mass fraction of the deionized water, the mixture is heated to 95°C to dissolve the agarose and then cooled to 60°C to obtain the second slurry. After heating the first slurry to 60°C, the second slurry is mixed at a mass ratio of 2:1 to obtain the gel layer slurry.

[0170] (3) The gel layer slurry is coated onto the surface of a polyethylene base film at 50°C and dried to form a gel layer with a thickness of 10 μm on the polyethylene base film; the corrosion inhibitor slurry is coated onto the surface of the gel layer at 50°C and dried to form a corrosion inhibitor layer with a thickness of 5 μm on the gel layer. The edge of the corrosion inhibitor layer extends 2 mm beyond the corresponding edge of the gel layer on one side, and the edge of the corrosion inhibitor layer extends 2 mm beyond the corresponding edge of the gel layer on the other side, thus obtaining a composite diaphragm.

[0171] Example 2

[0172] The preparation of the composite membrane differs from that in Example 1 in that:

[0173] The amount of sodium oleate used in the corrosion inhibitor layer is 7.5 parts.

[0174] Everything else is the same as in Example 1.

[0175] Example 3

[0176] The preparation of the composite membrane differs from that in Example 1 in that:

[0177] The amount of sodium oleate used in the corrosion inhibitor layer is 9 parts.

[0178] Everything else is the same as in Example 1.

[0179] Example 4

[0180] The preparation of the composite membrane differs from that in Example 1 in that:

[0181] In the corrosion inhibitor layer, hydroquinone is used as the corrosion inhibitor, and the amount of hydroquinone used is 6 parts.

[0182] Everything else is the same as in Example 1.

[0183] Example 5

[0184] The preparation of the composite membrane differs from that in Example 1 in that:

[0185] In the corrosion inhibitor layer, the corrosion inhibitors are sodium oleate, hydroquinone and methanesulfonic acid, with each of the following amounts being 2 parts: sodium oleate, hydroquinone and methanesulfonic acid.

[0186] Everything else is the same as in Example 1.

[0187] Example 6

[0188] The preparation of the composite membrane differs from that in Example 1 in that:

[0189] In the gel layer, the gel material is polyacrylamide gel.

[0190] Everything else is the same as in Example 1.

[0191] Example 7

[0192] The preparation of the composite membrane differs from that in Example 1 in that:

[0193] In step (2), the preparation of the gel layer slurry includes the following processes:

[0194] At room temperature, 10 parts by mass fraction of the first polyether polyol (functionality 2, i.e., polyether polyol with ethylene glycol as the initiator), 5 parts by mass fraction of the second polyether polyol (polypropylene ether triol), 0.3 parts by mass fraction of the methyl acrylate monomer, 0.05 parts by mass fraction of the dimethylformamide, and 0.5 parts by mass fraction of the diethylene glycol are mixed and dissolved. Then, 15 parts by mass fraction of the 4,4-diphenylmethane diisocyanate are added for dispersion, followed by 5 parts by mass fraction of the deionized water for dispersion, to obtain the first slurry. 10 parts by mass fraction of the agarose and 30 parts by mass fraction of the deionized water are mixed and dispersed, heated to 95°C to dissolve the agarose, and then cooled to 60°C to obtain the second slurry. The first slurry is heated to 60°C and then mixed with the second slurry at a mass ratio of 2:1 to obtain the gel layer slurry.

[0195] Everything else is the same as in Example 1.

[0196] Example 8

[0197] The preparation of the composite membrane differs from that in Example 1 in that:

[0198] In the gel layer, step (2) involves the following process for preparing the gel layer slurry:

[0199] At room temperature, 20 parts by mass fraction of polyether polyol (functionality 5, i.e., polyether polyol with xylitol as the initiator), 5 parts by mass fraction of second polyether polyol (polypropylene ether triol), 1 part by mass fraction of methyl acrylate monomer, 0.01 parts by mass fraction of dimethylformamide, and 1 part by mass fraction of diethylene glycol are mixed and dissolved. Then, 5 parts by mass fraction of 4,4-diphenylmethane diisocyanate are added for dispersion, followed by 5 parts by mass fraction of deionized water for dispersion, to obtain the first slurry. 2 parts by mass fraction of agarose and 30 parts by mass fraction of deionized water are mixed and dispersed, heated to 95°C to dissolve the agarose, and then cooled to 60°C to obtain the second slurry. The first slurry is heated to 60°C and then mixed with the second slurry at a mass ratio of 2:1 to obtain the gel layer slurry.

[0200] Everything else is the same as in Example 1.

[0201] Comparative Example 1

[0202] The preparation of the composite membrane differs from that in Example 1 in that:

[0203] Sodium oleate was not added to the corrosion inhibitor layer.

[0204] Everything else is the same as in Example 1.

[0205] Comparative Example 2

[0206] The preparation of the composite membrane differs from that in Example 1 in that:

[0207] No gel layer is provided in the composite diaphragm.

[0208] Battery fabrication and performance testing

[0209] 1. Battery manufacturing

[0210] Preparation of positive electrode sheet: Lithium nickel cobalt manganese oxide, conductive carbon black (SP) and binder polyvinyl chloride fluoride (PVCF) are mixed with N-methylpyrrolidone (NMP) in a mass ratio of 96:2:2 to prepare a negative electrode slurry, which is then coated on aluminum foil, dried by forced air at 100°C, and cold-pressed and slit into positive electrode sheets.

[0211] Preparation of negative electrode sheet: Graphite, conductive carbon black (SP) and binder polyvinyl chloride fluoride (PVCF) are mixed with N-methylpyrrolidone (NMP) in a mass ratio of 95:2:3 to prepare a negative electrode slurry, which is then coated on copper foil, dried by forced air at 100°C, and cold-pressed and slit into negative electrode sheets.

[0212] Battery fabrication: The positive electrode sheet, the composite separator prepared in the examples and comparative examples, and the negative electrode sheet are wound into a core, wherein the composite separator completely covers the positive and negative electrode sheets. The resulting core is then placed in a metal casing or wrapped in an aluminum-plastic film and injected with electrolyte. Finally, aluminum-cased batteries are manufactured through processes such as settling, formation, and capacity testing.

[0213] 2. Performance Testing

[0214] (1) Cyclic test: At 25℃, the battery is charged to 4.35V with constant current and constant voltage at 2C, and the cutoff condition is 0.05C; after standing for 60 minutes, it is discharged to 2.8V at 1C. The above process is continued until the capacity decays to 80% of the initial test capacity, and the number of cycles is recorded.

[0215] (2) Thermal runaway test: The entire module (1P6S) is fixed in the fixture. A heating plate is placed between each pair of batteries and each battery has a temperature sensing device. The heating plate is heated at 800W. The test is stopped when the battery experiences thermal runaway or the temperature reaches 300°C.

[0216] The test results are shown in Table 1.

[0217] Table 1

[0218] Example 1 2591 Not expired, no fire. Example 2 2635 Not expired, no fire. Example 3 2629 Not expired, no fire. Example 4 2582 Not expired, no fire. Example 5 2520 Not expired, no fire. Example 6 2405 Not expired, no fire. Example 7 2546 Not expired, no fire. Example 8 2533 Not expired, no fire. Comparative Example 1 2167 Failure, fire Comparative Example 2 2338 Failure, no fire

[0219] As shown in Table 1, the combined effect of the corrosion inhibitor layer and the gel layer is beneficial to improving the battery cycle life (Examples 1-8 are better than Comparative Examples 1-2). The corrosion inhibitor layer and the gel layer also show excellent effects in terms of battery safety. Batteries containing both corrosion inhibitor layer and gel layer did not fail, while batteries without both corrosion inhibitor layer and gel layer experienced risks such as battery failure and fire.

[0220] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite diaphragm, characterized in that, The composite membrane includes a base membrane, a gel layer disposed on at least one surface of the base membrane in the thickness direction, and a corrosion inhibitor layer disposed on the side surface of the gel layer away from the base membrane. The gel layer comprises a gel material; the gel material comprises at least one of agarose, polyacrylamide gel, and polyurethane gel. The corrosion inhibitor layer comprises a corrosion inhibitor and a binder; the corrosion inhibitor comprises at least one of sodium oleate, hydroquinone, and methanesulfonic acid; the mass ratio of the corrosion inhibitor to the binder is (2~3):10; The thickness of the corrosion-inhibiting layer is 4µm to 7µm.

2. The composite diaphragm according to claim 1, characterized in that, The gel layer also includes additives; the additives include at least one of alcohols, esters and amides.

3. The composite diaphragm according to claim 2, characterized in that, The alcohols include polyether polyols and / or diethylene glycol.

4. The composite diaphragm according to claim 3, characterized in that, The polyether polyol includes a first polyether polyol and a second polyether polyol; the first polyether polyol has a functionality of less than 3, or the first polyether polyol has a functionality of greater than 3; the second polyether polyol includes polypropylene ether triol.

5. The composite diaphragm according to claim 4, characterized in that, The mass ratio of the first polyether polyol to the second polyether polyol is (2~5):

1.

6. The composite diaphragm according to claim 2, characterized in that, The esters include acrylate monomers and / or 4,4-diphenylmethane diisocyanate.

7. The composite diaphragm according to claim 6, characterized in that, The acrylate monomers include at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate.

8. The composite diaphragm according to claim 2, characterized in that, The amides include dimethylformamide.

9. The composite diaphragm according to claim 2, characterized in that, The additives include polyether polyols, acrylate monomers, dimethylformamide, diethylene glycol, and 4,4-diphenylmethane diisocyanate; In the gel layer, the mass ratio of the gel material, the polyether polyol, the dimethylformamide, the acrylate monomer, the 4,4-diphenylmethane diisocyanate, and the diethylene glycol is (1~5):(15~25):(0.01~0.05):(0.3~1):(5~15):(0.3~2).

10. The composite diaphragm according to claim 1, characterized in that, The adhesive includes at least one of polyvinylidene fluoride, polyacrylic acid, polyacrylate, polyimide, polyamide, polyvinyl alcohol, and polytetrafluoroethylene.

11. The composite diaphragm according to claim 1, characterized in that, The area of ​​the corrosion-inhibiting layer is larger than the area of ​​the gel layer.

12. The composite diaphragm according to claim 11, characterized in that, Along the width direction of the composite membrane, the edges of the corrosion inhibitor layer extend beyond the edges of the gel layer. Wherein, the dimension by which one edge of the corrosion inhibitor layer extends beyond the corresponding edge of the gel layer is D1, and the dimension by which the other edge of the corrosion inhibitor layer extends beyond the corresponding other edge of the gel layer is D2, wherein D1 is 1mm~5mm, and / or D2 is 1mm~5mm.

13. The composite diaphragm according to claim 12, characterized in that, D1 and D2 are equal.

14. The composite diaphragm according to any one of claims 1 to 13, characterized in that, The composite diaphragm satisfies at least one of the following technical features (1) to (3): (1) The thickness of the gel layer is 8µm~15µm; (2) The thickness of the base film is 2µm~20µm; (3) The base film includes polyethylene base film and / or polypropylene base film.

15. A method for preparing the composite separator according to any one of claims 1 to 14, characterized in that, Includes the following steps: A gel layer slurry is coated onto at least one side surface of the base film along the thickness direction to form a gel layer on the base film; A corrosion-inhibiting slurry is coated onto the surface of the gel layer away from the base film to form a corrosion-inhibiting layer on the gel layer, thereby obtaining a composite membrane. The gel layer slurry includes a gel material; The corrosion inhibitor slurry includes corrosion inhibitors and binders.

16. The method for preparing the composite diaphragm according to claim 15, characterized in that, The gel layer slurry also includes additives and water; the additives include at least one of alcohols, esters and amides.

17. The method for preparing the composite diaphragm according to claim 16, characterized in that, The alcohols include polyether polyols and / or diethylene glycol.

18. The method for preparing the composite diaphragm according to claim 17, characterized in that, The polyether polyol includes a first polyether polyol and a second polyether polyol.

19. The method for preparing the composite diaphragm according to claim 16, characterized in that, The esters include acrylate monomers and / or 4,4-diphenylmethane diisocyanate.

20. The method for preparing the composite diaphragm according to claim 19, characterized in that, The acrylate monomers include at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate.

21. The method for preparing the composite diaphragm according to claim 16, characterized in that, The amides include dimethylformamide.

22. The method for preparing the composite diaphragm according to claim 16, characterized in that, The additives include polyether polyols, acrylate monomers, dimethylformamide, diethylene glycol, and 4,4-diphenylmethane diisocyanate.

23. The method for preparing the composite diaphragm according to claim 22, characterized in that, The preparation of the gel layer slurry includes: A first slurry is obtained by first mixing polyether polyol, acrylate monomer, dimethylformamide, diethylene glycol, 4,4-diphenylmethane diisocyanate and water. The gel material and water are mixed a second time to obtain a second slurry; The first slurry is heated in the first stage, and then the second slurry is mixed in the third stage to obtain the gel layer slurry.

24. The method for preparing the composite diaphragm according to claim 23, characterized in that, The second mixing process further includes a second heating and a cooling process, wherein the final temperature of the second heating is 90-95°C and the final temperature of the cooling is 55-65°C.

25. The method for preparing the composite diaphragm according to claim 23, characterized in that, The final temperature of the first heating is 55~65℃.

26. The method for preparing the composite diaphragm according to claim 23, characterized in that, The mass ratio of the first slurry to the second slurry is (2~3):(1~2).

27. The method for preparing the composite diaphragm according to any one of claims 15 to 26, characterized in that, The coating temperature of the gel layer slurry is 45~55℃; And / or, the coating temperature of the corrosion-inhibiting slurry is 45~55℃.

28. A battery comprising a positive electrode, a negative electrode, and a separator, characterized in that, The diaphragm includes the composite diaphragm as described in any one of claims 1 to 14, or the composite diaphragm prepared by the preparation method according to any one of claims 15 to 27.

29. The battery according to claim 28, characterized in that, The corrosion inhibitor layer in the composite membrane is disposed on the negative electrode side.

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