Lithium battery diaphragm, preparation method thereof and lithium battery

Abstract

The invention relates to a lithium battery diaphragm, the lithium battery diaphragm comprises a polymer base membrane and a coating arranged on at least one surface of the polymer base membrane, the material of the coating comprises composite nanoparticles and a binder which exists in the gaps of the composite nanoparticles and is used for binding the composite nanoparticles, and the binder is used for binding the composite nanoparticles to the polymer base membrane. The composite nanoparticles comprise hollow spheres and coating layers coating the hollow spheres, the hollow spheres are made of at least one of aluminum oxide, silicon dioxide and zirconium oxide, and the coating layers are made of at least two of silicon dioxide, titanium dioxide and zirconium oxide. The lithium battery diaphragm provided by the invention has high thermal stability, mechanical property and flame retardant property, and also can maintain good ion permeability.

Description

Technical Field

[0001] The present application relates to lithium batteries, and in particular to lithium battery separators. Background Art

[0002] Lithium-ion batteries, due to their lightweight and charge-discharge reliance on the movement of ions and electrons, offer higher energy per unit area and a relatively long cycle life compared to other secondary batteries. They are widely used in digital devices such as smartphones, tablets, and wearable smart devices, and are also the primary power source for electric and hybrid vehicles. In lithium-ion battery construction, the separator is a key internal component. Its primary function is to separate the positive and negative electrodes of the battery, preventing contact and short circuits. It also allows electrolyte ions to pass through. Therefore, the performance of the separator determines the battery's interface structure and internal resistance, directly impacting its capacity, cycle life, and safety. Conventional power lithium battery separators are single- or multi-layer polyolefin products stretched using dry or wet processes. Polyolefin separators have a low pore closure temperature. At temperatures between 100 and 130°C, the separator experiences significant dimensional shrinkage, posing a risk of short circuits between the positive and negative electrodes. This can lead to a brief, high temperature buildup and potentially cause battery explosion. A ceramic coating applied to one or both sides of a polyolefin separator supports the separator, preventing it from melting at high temperatures and losing its ability to separate the positive and negative electrodes, which could lead to battery explosion. However, while existing ceramic coatings improve the separator's wettability and thermal stability, enhancing the safety and cycling stability of lithium batteries and reducing the risk of explosions, they also increase the separator's Gurley value, which means it decreases its ion permeability. Summary of the Invention

[0003] The embodiments of the present application provide a lithium battery separator to solve the technical problem that the ion permeability of the existing separator deteriorates after adding a ceramic coating.

[0004] In a first aspect, an embodiment of the present application provides a lithium battery separator, comprising:

[0005] A polymer base film, and a coating provided on at least one side of the polymer base film,

[0006] The coating material includes composite nanoparticles and a binder that exists between the gaps of the composite nanoparticles and bonds the composite nanoparticles.

[0007] The composite nanoparticles include hollow spheres and a coating layer coating the hollow spheres. The hollow spheres are made of at least one of alumina, silica, and zirconia. The coating layer is made of at least two of silica, titania, and zirconia.

[0008] In some embodiments of the present application, the average particle size of the hollow spheres is 400-800 nm.

[0009] In some embodiments of the present application, the coating material further includes at least one of a dispersant, a defoaming agent, a wetting agent, a leveling agent, and a stabilizer.

[0010] In some embodiments of the present application, the binder is at least one of polymethyl acrylate, polyethyl acrylate and polyacrylamide; and / or,

[0011] The dispersant is at least one of polyethylene glycol, sodium dodecylbenzene sulfonate, sodium polymethacrylate and sodium polyacrylate; and / or,

[0012] The defoaming agent is at least one of tributyl phosphate, n-octanol, polyoxypropylene glycerol ether and polydimethylsiloxane.

[0013] In a second aspect, an embodiment of the present application provides a method for preparing a lithium battery separator, the method comprising the following steps:

[0014] providing a hollow sphere dispersion;

[0015] adding a coating layer precursor to the hollow sphere dispersion to prepare a coating layer on the surface of the hollow sphere to obtain a composite nanoparticle dispersion;

[0016] adding a binder to the composite nanoparticle dispersion to obtain a prefabricated coating;

[0017] Providing a polymer base film, and applying the prefabricated coating to at least one side of the polymer base film to form a coating to obtain the lithium battery separator.

[0018] The material of the hollow sphere is at least one of alumina, silicon dioxide and zirconium oxide, and the coating layer precursor includes at least two of tetraethyl orthosilicate, tetrabutyl titanate, tetrabutyl zirconate and titanium tetrachloride.

[0019] In some embodiments of the present application, the average particle size of the hollow spheres is 400 to 800 nm; and / or,

[0020] In the hollow sphere dispersion, the concentration of the hollow spheres is 30 wt% to 60 wt%; and / or,

[0021] The mass ratio of the coating layer precursor to the hollow sphere is 1-10:30-60.

[0022] In some embodiments of the present application, the coating material further includes at least one of a dispersant, a defoaming agent, a wetting agent, a leveling agent, and a stabilizer.

[0023] In some embodiments of the present application, the binder is at least one of polymethyl acrylate, polyethyl acrylate and polyacrylamide; and / or,

[0024] The dispersant is at least one of polyethylene glycol, sodium dodecylbenzene sulfonate, sodium polymethacrylate and sodium polyacrylate; and / or,

[0025] The defoaming agent is at least one of tributyl phosphate, n-octanol, polyoxypropylene glycerol ether and polydimethylsiloxane.

[0026] In some embodiments of the present application, the coating layer is prepared on the surface of the hollow sphere at a temperature of 10 to 30°C.

[0027] In a third aspect, an embodiment of the present application provides a lithium battery, comprising the lithium battery separator described in any embodiment of the first aspect, or the lithium battery separator prepared by the method described in any embodiment of the second aspect.

[0028] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0029] The lithium battery separator provided in the embodiment of the present application is provided with the coating on the polymer base film, the material of the coating includes composite nanoparticles, and the composite nanoparticles include hollow spheres and a coating layer covering the hollow spheres, the material of the hollow spheres is at least one of aluminum oxide, silicon dioxide, and zirconium oxide, the material of the coating layer is any at least two of silicon dioxide, titanium dioxide, and zirconium oxide, the hollow sphere structure of the core helps to adsorb electrolyte and provide a path for ion transport, thereby ensuring that the lithium battery separator has a strong ion permeability function; the material of the coating layer is any at least two of silicon dioxide, titanium dioxide, and zirconium oxide, which is beneficial to increase the stability of the hollow structure of the core, and is beneficial to increasing the stability of the hollow structure of the core, ultimately allowing the lithium battery separator to have high thermal stability, mechanical properties, and flame retardant properties while maintaining good ion permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0032] Figure 1A schematic flow chart of a method for preparing a lithium battery separator provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] Unless otherwise specified, the terms used herein should be understood as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. In the event of any conflict, the present specification shall take precedence.

[0035] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] In lithium batteries, existing separators have a technical problem of reduced ion permeability after adding a ceramic coating.

[0037] The technical solutions provided in the embodiments of this application are intended to solve the above technical problems, and the overall idea is as follows:

[0038] In a first aspect, an embodiment of the present application provides a lithium battery separator, comprising:

[0039] A polymer base film, and a coating provided on at least one side of the polymer base film,

[0040] The coating material includes composite nanoparticles and a binder that exists between the gaps of the composite nanoparticles and bonds the composite nanoparticles.

[0041] The composite nanoparticles include hollow spheres and a coating layer coating the hollow spheres. The hollow spheres are made of at least one of alumina, silica, and zirconia. The coating layer is made of at least two of silica, titania, and zirconia.

[0042] It is easy to understand that polymer-based membranes are commonly used separator materials in the field of lithium batteries, usually polyolefin membranes.

[0043] It is easy to understand that the coating layer can be provided on one side of the polymer base film, or can be provided on both sides of the polymer base film at the same time.

[0044] The composite nanoparticles have a core / shell structure, wherein the core is the hollow sphere and the shell is the coating. It should be noted that conventionally prepared or purchased nanoscale hollow materials do not possess a strictly enclosed hollow structure. Therefore, the hollow portion of the hollow sphere can absorb electrolyte, providing a path for ion transport, thereby ensuring that the lithium battery separator has a strong ion permeability.

[0045] The beneficial effect of the coating layer being made of any at least two of silicon dioxide, titanium dioxide, and zirconium oxide is that coating the core with a coating layer is beneficial to increasing the stability of the core's hollow structure, and the coating layer comprising at least two oxides is beneficial to increasing the stability of the coating layer.

[0046] The present application arranges the coating on the polymer base film, the material of the coating includes composite nanoparticles, and the composite nanoparticles include hollow spheres and a coating layer covering the hollow spheres, the material of the hollow spheres is at least one of alumina, silica, and zirconia, and the material of the coating layer is at least two of silica, titania, and zirconia. The hollow sphere structure of the core helps to adsorb electrolyte and provide a path for ion transport, thereby ensuring that the lithium battery separator has a strong ion permeability function; the material of the coating layer is at least two of silica, titania, and zirconia, which is beneficial to increase the stability of the hollow structure of the core, and ultimately enables the lithium battery separator to have high thermal stability, mechanical properties, and flame retardant properties while maintaining good ion permeability.

[0047] In some embodiments of the present application, the average particle size of the hollow spheres is 400-800 nm.

[0048] As an example, the average particle size of the hollow spheres may be 400 nm, 500 nm, 600 nm, 700 nm, or 800 nm.

[0049] In some embodiments of the present application, the coating material further includes at least one of a dispersant, a defoaming agent, a wetting agent, a leveling agent, and a stabilizer.

[0050] It is easy to understand that the coating is formed by a suspension containing the composite nanoparticles, and the dispersant, defoamer, wetting agent, leveling agent, and stabilizer are all conventional additives for inorganic nanoparticle suspensions.

[0051] In some embodiments of the present application, the binder is at least one of polymethyl acrylate, polyethyl acrylate and polyacrylamide; and / or,

[0052] The dispersant is at least one of polyethylene glycol, sodium dodecylbenzene sulfonate, sodium polymethacrylate and sodium polyacrylate; and / or,

[0053] The defoaming agent is at least one of tributyl phosphate, n-octanol, polyoxypropylene glycerol ether and polydimethylsiloxane.

[0054] In a second aspect, an embodiment of the present application provides a method for preparing a lithium battery separator, the method comprising the following steps:

[0055] S1: providing hollow sphere dispersion;

[0056] S2: adding a coating layer precursor to the hollow sphere dispersion to prepare a coating layer on the surface of the hollow sphere to obtain a composite nanoparticle dispersion;

[0057] S3: adding a binder to the composite nanoparticle dispersion to obtain a prefabricated coating;

[0058] S4: providing a polymer base film, and applying the prefabricated coating to at least one side of the polymer base film to form a coating to obtain the lithium battery separator.

[0059] The material of the hollow sphere is at least one of alumina, silicon dioxide and zirconium oxide, and the coating layer precursor includes at least two of tetraethyl orthosilicate, tetrabutyl titanate, tetrabutyl zirconate and titanium tetrachloride.

[0060] It is easy to understand that the coating layer precursor can form materials such as silicon dioxide, titanium dioxide, and zirconium oxide.

[0061] In some embodiments of the present application, the average particle size of the hollow spheres is 400 to 800 nm; and / or,

[0062] In the hollow sphere dispersion, the concentration of the hollow spheres is 30 wt% to 60 wt%; and / or,

[0063] The mass ratio of the coating layer precursor to the hollow sphere is 1-10:30-60.

[0064] As an example, the average particle size of the hollow spheres may be 400 nm, 500 nm, 600 nm, 700 nm, or 800 nm.

[0065] As an example, the concentration of the hollow spheres may be 30 wt%, 40 wt%, 50 wt%, 60 wt%.

[0066] In some embodiments of the present application, the coating material further includes at least one of a dispersant, a defoaming agent, a wetting agent, a leveling agent, and a stabilizer.

[0067] In some embodiments of the present application, the binder is at least one of polymethyl acrylate, polyethyl acrylate and polyacrylamide; and / or,

[0068] The dispersant is at least one of polyethylene glycol, sodium dodecylbenzene sulfonate, sodium polymethacrylate and sodium polyacrylate; and / or,

[0069] The defoaming agent is at least one of tributyl phosphate, n-octanol, polyoxypropylene glycerol ether and polydimethylsiloxane.

[0070] In some embodiments of the present application, the coating layer is prepared on the surface of the hollow sphere at a temperature of 10 to 30°C.

[0071] As an example, the preparation of the coating layer on the surface of the hollow sphere can be carried out at 10°C, 15°C, 20°C, 25°C, or 30°C.

[0072] In some embodiments of the present application, step S1 may be performed as follows:

[0073] Stir the hollow balls, dispersant, defoamer and water together at a stirring speed of 600-1200 r / min for 1-3 hours, and control the material temperature at 10-30°C during stirring;

[0074] Grinding the stirred material with a sand mill until the particle size of the hollow spheres reaches 400-800 nm, the grinding speed of the sand mill is 800-1500 r / min, the grinding time is 5-25 min, and the material temperature is controlled at 20-40° C. during the grinding period;

[0075] The materials that meet the particle size requirements are then de-ironed and filtered.

[0076] In some embodiments of the present application, step S2 may be performed as follows:

[0077] Maintain the material temperature at 10-30°C and the stirring speed at 150-300 r / min, take at least two substances selected from ethyl orthosilicate, tetrabutyl titanate, tetrabutyl zirconate, and titanium tetrachloride, pump them into the material at a rate of 100-300 ml / h, and react for 1-3 days.

[0078] In some embodiments of the present application, step S3 may be performed as follows:

[0079] The material temperature is maintained at 10-30° C. and the stirring speed is 150-300 r / min. A binder and at least one of a wetting agent, a leveling agent and a stabilizer are added thereto and the reaction is carried out for 3-6 hours.

[0080] In some embodiments of the present application, the stirred material is ground using a sand mill, and two stirring barrels A and B are provided on the sand mill to grind the stirred material through a double-barrel circulation mode.

[0081] That is, mixing barrel A is used as the feed tank for the first grinding. After grinding once, it enters mixing barrel B. If a second grinding is required, it is ground from B to barrel A. The grinding is repeated until the required particle size is reached.

[0082] In a third aspect, an embodiment of the present application provides a lithium battery, comprising the lithium battery separator described in any embodiment of the first aspect, or the lithium battery separator prepared by the method described in any embodiment of the second aspect.

[0083] The lithium battery is realized based on the lithium battery separator described in any embodiment of the first aspect, or the lithium battery separator prepared by the method described in any embodiment of the second aspect. The specific implementation of the lithium battery can refer to the above embodiments and common knowledge in the field. Since the lithium battery adopts part or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0084] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0085] Example 1

[0086] The present application provides a lithium battery separator, which is prepared by the following method:

[0087] In terms of mass, 49 parts of ultrapure water, 46 parts of hollow alumina, 4 parts of sodium polyacrylate, and 1 part of tributyl phosphate were poured into a stirring barrel in sequence, and the stirring speed was controlled at 800 r / min. After stirring for 2 hours, the material was pumped into a sand mill and ground for 10 minutes. During this period, the speed of the grinder was controlled at 1300 r / min. After deironing and filtering the material, an inorganic nano-dispersion with an average particle size of 600 nm was obtained.

[0088] Control the pump speed at 180 ml / h to dropwise add tetraethyl orthosilicate and tetrabutyl titanate to the inorganic nanoparticle dispersion. Stir at 15°C for 5 days at 200 r / min to obtain a composite nanoparticle dispersion. Add 85 parts of the binary oxide coating solution and 8 parts of polyethyl acrylate to the coating solution at a uniform rate. Stir for 2 days to obtain the prefabricated coating.

[0089] A separator is provided, and the prefabricated coating is sprayed onto one side of the separator to form a coating to obtain the lithium battery separator.

[0090] Example 2

[0091] The present application provides a lithium battery separator, which is prepared by the following method:

[0092] In terms of mass, 47 parts of ultrapure water, 48 parts of hollow silica, 4 parts of polyethylene glycol, and 1 part of n-octanol were poured into a stirring barrel in sequence, and the stirring speed was controlled at 900 r / min. After stirring for 2.5 hours, the material was pumped to a sand mill and ground for 15 minutes. During this period, the speed of the grinder was controlled at 1200 r / min. After deironing and filtering the material, an inorganic nano-dispersion with an average particle size of 580 nm was obtained.

[0093] Control the pump speed to 200 ml / h and dropwise add tetraethyl orthosilicate and tetrabutyl titanate to the inorganic nanoparticle dispersion. Stir at 15°C for 5 days at a stirring rate of 180 r / min to obtain a composite nanoparticle dispersion. Add 6 parts of polymethyl acrylate to 80 parts of the binary oxide coating solution at a uniform rate and stir for 1 day to obtain the prefabricated coating.

[0094] A separator is provided, and the prefabricated coating is sprayed onto one side of the separator to form a coating to obtain the lithium battery separator.

[0095] Example 3

[0096] The present application provides a lithium battery separator, which is prepared by the following method:

[0097] In terms of mass, 51 parts of ultrapure water, 45 parts of hollow alumina, 3 parts of sodium dodecylbenzenesulfonate, and 1 part of polyoxypropylene glycerol ether were poured into a stirring barrel in sequence, and the stirring speed was controlled at 600 r / min. After stirring for 2 hours, the material was pumped to a sand mill and ground for 15 minutes. During this period, the speed of the grinder was controlled at 1100 r / min. After deironing and filtering the material, an inorganic nano-dispersion with an average particle size of 650 nm was obtained.

[0098] Control the pump speed at 280 ml / h to dropwise add ethyl orthosilicate and tetrabutyl titanate to the inorganic nanoparticle dispersion. Stir at 15°C for 5 days at 300 r / min to obtain a composite nanoparticle dispersion. Add 7 parts of polyacrylamide to 90 parts of the binary oxide coating solution at a uniform rate and stir for 2 days to obtain the prefabricated coating.

[0099] A separator is provided, and the prefabricated coating is sprayed onto one side of the separator to form a coating to obtain the lithium battery separator.

[0100] Example 4

[0101] The present application provides a lithium battery separator, which is prepared by the following method:

[0102] In terms of mass, 48 parts of ultrapure water, 46 parts of hollow zirconium oxide, 5 parts of sodium polyacrylate, and 1 part of tributyl phosphate were poured into a stirring barrel in sequence, and the stirring speed was controlled at 1000 r / min. After stirring for 2 hours, the material was pumped to a sand mill and ground for 10 minutes. During this period, the speed of the grinder was controlled at 1500 r / min. After deironing and filtering the material, an inorganic nano-dispersion with an average particle size of 500 nm was obtained.

[0103] Control the pump speed to 100 ml / h and dropwise add tetraethyl orthosilicate and tetrabutyl titanate to the inorganic nanoparticle dispersion. Stir at 15°C for 5 days at a stirring rate of 300 r / min to obtain a composite nanoparticle dispersion. Add 5 parts of polymethyl acrylate to 75 parts of the binary oxide coating solution at a uniform rate and stir for 2 days to obtain the prefabricated coating.

[0104] A separator is provided, and the prefabricated coating is sprayed onto one side of the separator to form a coating to obtain the lithium battery separator.

[0105] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0106] In this application, unless otherwise stated, directional terms such as "upper" and "lower" refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of this application specification, the terms "include", "comprise", etc. mean "including but not limited to". Moreover, the terms "include", "comprise" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the phrase "include..." do not exclude the presence of other identical elements in the process, method, article or device comprising the elements. In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. For the association relationship of more than three associated objects described with "and / or", it means that any one of these three associated objects can exist alone, or any at least two of them exist at the same time. For example, for A, and / or B, and / or C, it can be represented that any one of A, B, and C exists alone, or any two of them exist at the same time, or three of them exist at the same time. In this article, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "the following at least one (individual)" or similar expressions refer to any combination of these items, including any combination of single item (individual) or plural items (individual). For example, "at least one (individual) of a, b, or c", or "at least one (individual) of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc or abc, where a, b, c can be single or multiple, respectively.

[0107] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A lithium battery separator, characterized in that: The lithium battery separator comprises: A polymer base film, and a coating provided on at least one side of the polymer base film, The coating material includes composite nanoparticles and a binder that exists between the gaps of the composite nanoparticles and bonds the composite nanoparticles. The composite nanoparticles include hollow spheres and a coating layer coating the hollow spheres. The hollow spheres are made of at least one of alumina, silica, and zirconia. The coating layer is made of at least two of silica, titania, and zirconia.

2. The lithium battery separator according to claim 1, characterized in that The average particle size of the hollow spheres is 400-800 nm.

3. The lithium battery separator according to claim 1, characterized in that The coating material further comprises at least one of a dispersant, a defoaming agent, a wetting agent, a leveling agent, and a stabilizer.

4. The lithium battery separator according to claim 3, characterized in that The binder is at least one of polymethyl acrylate, polyethyl acrylate and polyacrylamide; and / or, The dispersant is at least one of polyethylene glycol, sodium dodecylbenzene sulfonate, sodium polymethacrylate and sodium polyacrylate; and / or, The defoaming agent is at least one of tributyl phosphate, n-octanol, polyoxypropylene glycerol ether and polydimethylsiloxane.

5. A method for preparing a lithium battery separator, characterized in that: The preparation method of the lithium battery separator comprises the following steps: providing a hollow sphere dispersion; adding a coating layer precursor to the hollow sphere dispersion to prepare a coating layer on the surface of the hollow sphere to obtain a composite nanoparticle dispersion; adding a binder to the composite nanoparticle dispersion to obtain a prefabricated coating; Providing a polymer base film, and applying the prefabricated coating to at least one side of the polymer base film to form a coating to obtain the lithium battery separator. The material of the hollow sphere is at least one of alumina, silicon dioxide and zirconium oxide, and the coating layer precursor includes at least two of tetraethyl orthosilicate, tetrabutyl titanate, tetrabutyl zirconate and titanium tetrachloride.

6. The method for preparing a lithium battery separator according to claim 5, wherein: The average particle size of the hollow spheres is 400 to 800 nm; and / or, In the hollow sphere dispersion, the concentration of the hollow spheres is 30 wt% to 60 wt%; and / or, The mass ratio of the coating layer precursor to the hollow sphere is 1-10:30-60.

7. The method for preparing a lithium battery separator according to claim 5, wherein: The coating material further comprises at least one of a dispersant, a defoaming agent, a wetting agent, a leveling agent, and a stabilizer.

8. The method for preparing a lithium battery separator according to claim 6, wherein: The binder is at least one of polymethyl acrylate, polyethyl acrylate and polyacrylamide; and / or, The dispersant is at least one of polyethylene glycol, sodium dodecylbenzene sulfonate, sodium polymethacrylate and sodium polyacrylate; and / or, The defoaming agent is at least one of tributyl phosphate, n-octanol, polyoxypropylene glycerol ether and polydimethylsiloxane.

9. The method for preparing a lithium battery separator according to claim 5, wherein: The coating layer is prepared on the surface of the hollow sphere at a temperature of 10 to 30°C.

10. A lithium battery, characterized in that: The lithium battery comprises the lithium battery separator according to any one of claims 1 to 4, or the lithium battery separator prepared by the method according to any one of claims 5 to 9.

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