Battery diaphragm and preparation method thereof

Abstract

The invention provides a battery diaphragm and a preparation method thereof, the battery diaphragm comprises a base membrane and a coating layer, the coating layer is formed on at least one surface of the base membrane, the coating layer contains Li < 2 + x < alpha > F < 6 + y > beta < x-y >, alpha is a transition metal element containing Zr, beta is a halogen element containing Cl, x is greater than or equal to 0, y is greater than or equal to 0, and x is greater than or equal to y. Li2 + xalphaF6 + ybetax-y can dissociate ZrF6 < 2-> ions from a monoclinic phase under high voltage, and the ZrF6 < 2-> ions can participate in the SEI construction process and form a trigonal phase to be deposited in an SEI film, so that inorganic components in the SEI film are improved, the ionic conductivity of the SEI film is improved, and the battery impedance is reduced. Especially in a lithium metal battery, the composite material can reduce the nucleation potential, induce the nucleation of lithium metal, form a small and uniformly distributed lithium metal negative electrode, prolong the cycle life of the battery and improve the safety of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery separator and a preparation method thereof. Background Art

[0002] Lithium metal batteries, with their extremely low electrochemical reduction potential and exceedingly high theoretical specific capacity, are considered the most promising next-generation battery candidate, potentially doubling the energy density of existing lithium-ion batteries. However, the carbonate-based electrolyte systems used in lithium-ion batteries are currently incompatible with lithium metal batteries. The fundamental reason is that current commercial electrolytes are unable to form a uniform, highly ionic, and stable solid electrolyte interface on the surface of the lithium metal anode.

[0003] Defects in the SEI film not only cause the growth of lithium dendrites, posing the risk of battery explosion, but also seriously affect the cycle life of lithium metal batteries and may cause high temperatures, smoke, and even fire. How to construct an ideal solid electrolyte interface with high electronic insulation, high ionic conductivity, and high chemical stability at the interface or surface of the lithium metal anode has always been a key challenge in this research. Summary of the Invention

[0004] One object of the present invention is to provide a battery separator, comprising: a base film, and a coating layer, wherein the coating layer is formed on at least one surface of the base film, and the coating layer contains Li 2+x αF 6+y β x-y , α is a transition metal element including Zr, β is a halogen element including Cl, x≥0, y≥0, x≥y.

[0005] In a preferred embodiment, x is 0 to 0.5, and y is 0 to 0.5.

[0006] In a preferred embodiment, the Li 2+x αF 6+y β x-y It is in one or more of monoclinic phase, rhombohedral phase and rhombohedral phase.

[0007] In a preferred embodiment, the coating layer further contains heat-resistant particles, and the heat-resistant particles include one or more of aluminum oxide, boehmite, and barium sulfate.

[0008] In a preferred embodiment, the coating layer further contains a binder, and the binder includes one or more of polytetrafluoroethylene, polytetrafluoroethylene, polyacrylic acid, sodium hydroxymethyl cellulose, and styrene-butadiene rubber.

[0009] In a preferred embodiment, the binder, the Li 2+x αF 6+y βx-y , and the mass ratio between the heat-resistant particles is 1:(0.001 to 100):(0.1 to 800).

[0010] In a preferred embodiment, the base film has a thickness of 5 μm to 16 μm, and the coating layer has a thickness of 0.5 μm to 10 μm.

[0011] Another object of the present invention is to provide a lithium battery, comprising: a positive electrode, a negative electrode, and the battery separator as described above, wherein the battery separator is located between the positive electrode and the negative electrode.

[0012] In a preferred embodiment, the lithium battery is a lithium metal battery.

[0013] In a preferred embodiment, the Li 2+x αF 6+y β x-y It is in one or more of monoclinic phase, rhombohedral phase and rhombohedral phase.

[0014] Another object of the present invention is to provide a method for preparing a battery separator, which comprises: providing a slurry containing Li 2+x αF 6+y β x-y , α is a transition metal element including Zr, β is a halogen element including Cl, x≥0, y≥0, x≥y; and after applying the slurry on at least one side of the base film, drying it to obtain the battery separator.

[0015] In a preferred embodiment, the slurry further contains heat-resistant particles, and the heat-resistant particles include one or more of alumina, boehmite, and barium sulfate.

[0016] In a preferred embodiment, the slurry further contains a binder, and the binder includes one or more of polytetrafluoroethylene, polytetrafluoroethylene, polyacrylic acid, sodium hydroxymethyl cellulose, and styrene-butadiene rubber.

[0017] In a preferred embodiment, the slurry further contains a dispersion solvent, and the dispersion solvent includes one or more of deionized water, N,N-dimethylformamide, N-methylpyrrolidone, acetonitrile, ethanol, and isopropanol.

[0018] In a preferred embodiment, based on the total mass of the slurry, the Li 2+x αF 6+y β x-y The weight percentage of the heat-resistant particles is 0.01wt% to 10wt%, the weight percentage of the binder is 1wt% to 80wt%, and the balance is the dispersing solvent.

[0019] The beneficial effects of the present invention are as follows:

[0020] Lithium batteries using this separator can suppress the formation of lithium dendrites. Specifically, LZCF dissociates from the monoclinic phase (m-Li2ZrF6) to ZrF6 at high voltage. 2- Ions participate in the SEI construction process, forming a trigonal phase (t-Li2ZrF6) that is deposited in the SEI film, increasing the inorganic content in the SEI film, improving the ionic conductivity of the SEI film, and reducing battery impedance. In lithium metal batteries in particular, it can also reduce the nucleation potential, induce lithium metal nucleation, and form a small and evenly distributed lithium metal negative electrode, thereby improving the battery's cycle life and safety. DETAILED DESCRIPTION

[0021] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0022] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] The first embodiment of the present invention provides a battery separator that can be used to be positioned between a positive electrode and a negative electrode to form a lithium battery. The lithium battery can be, but is not limited to, a lithium metal battery. The battery separator includes: a base film and a coating layer, the coating layer being formed on at least one surface of the base film, the coating layer containing Li 2+x αF 6+y β x-y , α is a transition metal element including Zr, β is a halogen element including Cl, x≥0, y≥0, x≥y. It should be noted that Li 2+x αF 6+y β x-y Can be abbreviated as LZCF.

[0024] The base film may include, but is not limited to, one or more of polypropylene film, polyethylene film, polypropylene / polyethylene composite film, polyethylene terephthalate film, polyimide film, cellulose film, polyamide film, spandex film, aramid film, ceramic diaphragm, and solid electrolyte diaphragm, preferably one or more of polypropylene film and polyethylene film. The base film thickness may be, but is not limited to, 5 μm to 16 μm, preferably any value of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or 16 μm, or a range between any two values.

[0025] The coating layer can be formed on one or both surfaces of the base film, but is not limited to the coating layer. 2+x αF 6+y β x-y , α is a transition metal element including Zr, β is a halogen element including Cl, x≥0, y≥0, x≥y” are the same conditions, and the other conditions can be, but are not limited to, the same or different. The coating layer thickness can be, but is not limited to, 0.5μm to 10μm, preferably any value of 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or the range between any two values. In addition, Li 2+x αF 6+y β x-y The distribution amount of the coating layer may be, but is not limited to, more on the side away from the base film than on the side close to the base film.

[0026] x can be, but is not limited to, 0 to 0.5, preferably any value among 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a range between any two values; y can be, but is not limited to, 0 to 0.5, preferably any value among 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a range between any two values. For example, Li 2+x αF 6+y β x-y It can be but not limited to Li2ZrF6, Li 2.1 ZrCl 0.1 F6, Li 2.2 ZrCl 0.2 F6, Li 2.3 ZrCl 0.3 F6, Li 2.4 ZrCl 0.4 F6, or Li 2.5 ZrCl 0.5 F6. Li 2+x αF 6+y β x-y It can be in one or more of the following phases, but not limited to monoclinic (m-), trigonal (t-). 2+x αF 6+y β x-y Can dissociate into ZrF6 2- ions, which participate in the SEI construction process and form t-Li 2+x αF 6+y β x-yDeposited in the SEI film, it increases the inorganic components in the SEI film, improves the ionic conductivity of the SEI film, and reduces the battery impedance; in the trigonal phase, t-Li 2+x αF 6+y β x-y It can be used directly to enhance the inorganic components in the SEI film, improve the ionic conductivity of the SEI film, and reduce the battery impedance. 2+x αF 6+y β x-y It can be in monoclinic or trigonal phase, and can achieve the required performance of battery separators.

[0027] In addition, to improve the heat resistance of the battery separator, the coating layer may contain, but is not limited to, heat-resistant particles, which may include, but is not limited to, one or more of alumina, boehmite, and barium sulfate. To improve the bonding performance of the battery separator, the coating layer may contain, but is not limited to, a binder, which may include, but is not limited to, one or more of polytetrafluoroethylene, polytetrafluoroethylene, polyacrylic acid, sodium hydroxymethyl cellulose, and styrene-butadiene rubber. 2+x αF 6+y β x-y , heat-resistant particles, binder, binder, Li 2+x αF 6+y β x-y , and the mass ratio between the heat-resistant particles can be but is not limited to 1: (0.001 to 100): (0.1 to 800), preferably 1: (0.001, 0.002, 0.003, 0.004, 0.005, 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, any value or the range between any two values): (0.1, 1, 2.5, 5, 10, 25, 50, 75, 100, 200, 300, 400, 500, 600, 700, 800, any value or the range between any two values).

[0028] The second embodiment of the present invention mentions a method for preparing a battery separator, which can be used to prepare the battery separator of the first embodiment, and can also be used to prepare other battery separators not mentioned. Therefore, the method proposed in the second embodiment is not limited by the content proposed in the first embodiment, and the battery separator proposed in the first embodiment is not limited by the content proposed in the second embodiment.

[0029] First, a slurry is provided, the slurry containing Li 2+x αF 6+y β x-y, α is a transition metal element including Zr, β is a halogen element including Cl, x≥0, y≥0, x≥y. x can be, but not limited to, 0 to 0.5, preferably any value among 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a range between any two values; y can be, but not limited to, 0 to 0.5, preferably any value among 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a range between any two values. For example, Li 2+x αF 6+y β x-y It can be but not limited to Li2ZrF6, Li 2.1 ZrCl 0.1 F6, Li 2.2 ZrCl 0.2 F6, Li 2.3 ZrCl 0.3 F6, Li 2.4 ZrCl 0.4 F6, or Li 2.5 ZrCl 0.5 F6. Li 2+x αF 6+y β x-y It can be in one or more of the following phases, but not limited to monoclinic (m-), trigonal (t-). 2+x αF 6+y β x-y Can dissociate into ZrF6 2- ions, which participate in the SEI construction process and form t-Li 2+x αF 6+y β x-y Deposited in the SEI film, it increases the inorganic components in the SEI film, increases the ionic conductivity of the SEI film, and reduces the battery impedance; while in the trigonal phase, t-Li 2+x αF 6+y β x-y It can be used directly to enhance the inorganic components in the SEI film, improve the ionic conductivity of the SEI film, and reduce the battery impedance. 2+x αF 6+y β x-y It can be in monoclinic or trigonal phase, and can achieve the required performance of battery separators.

[0030] Furthermore, to enhance the heat resistance of the battery separator, the slurry may further include, but is not limited to, heat-resistant particles. Heat-resistant particles may include, but are not limited to, one or more of alumina, boehmite, and barium sulfate. To enhance the adhesion of the battery separator, the slurry may further include, but is not limited to, a binder. The binder may include, but is not limited to, one or more of polytetrafluoroethylene, polytetrafluoroethylene, polyacrylic acid, sodium hydroxymethyl cellulose, and styrene-butadiene rubber. To enhance the dispersibility or coating properties of the slurry, the slurry may further include, but is not limited to, a dispersing solvent. The dispersing solvent may include, but is not limited to, one or more of deionized water, N,N-dimethylformamide, N-methylpyrrolidone, acetonitrile, ethanol, and isopropanol.

[0031] In addition, based on the total mass of the slurry, Li 2+x αF 6+y β x-y The weight percentage of the heat-resistant particles may be, but not limited to, 0.01 wt % to 10 wt %, the weight percentage of the binder may be, but not limited to, 1 wt % to 80 wt %, the weight percentage of the binder may be, but not limited to, 0.1 wt % to 10 wt %, and the balance may be, but not limited to, the dispersion solvent; 2+x αF 6+y β x-y The weight percentage is preferably 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, 10wt% or any range between any two values, and the weight percentage of the heat-resistant particles is preferably 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt% , 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt% or any value among them, the weight percentage of the binder is preferably 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt% or any value among them, and the balance is preferably the dispersing solvent.

[0032] Next, the slurry is applied to at least one side of a base film and dried to obtain a battery separator. The base film may include, but is not limited to, one or more of polypropylene film, polyethylene film, polypropylene / polyethylene composite film, polyethylene terephthalate film, polyimide film, cellulose film, polyamide film, spandex film, aramid film, ceramic separator, and solid electrolyte separator, preferably including one or more of polyethylene film and polypropylene film. The base film thickness may be, but is not limited to, 5 μm to 16 μm, preferably any value among 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, and 16 μm, or a range between any two values.

[0033] The slurry can be applied on one or both surfaces of the base film, but is not limited to the slurry. When the slurry is applied on both surfaces of the base film, the two slurries contain Li 2+x αF 6+y β x-y , α is a transition metal element including Zr, β is a halogen element including Cl, x ≥ 0, y ≥ 0, x ≥ y" are the same conditions, and the other conditions may be, but are not limited to, the same or different. The slurry is dried to form a coating layer, and the thickness of the coating layer may be, but is not limited to, 0.5 μm to 10 μm, preferably any value among 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm, or the range between any two values.

[0034] In addition, after the slurry is coated on at least one side of the base film, the Li 2+x αF 6+y β x-y The film is distributed toward the side away from the base film and then dried to obtain a battery separator.

[0035] The present invention is illustrated by the following examples:

[0036] Example 1

[0037] 5 g of aluminum oxide, 0.01 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0038] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0039] Example 2

[0040] 5 g of aluminum oxide, 0.2 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0041] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0042] Example 3

[0043] 5 g of aluminum oxide, 10 g of m-Li 2 ZrF 6 , 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0044] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0045] Example 4

[0046] 20 g of aluminum oxide, 0.01 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0047] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0048] Example 5

[0049] 20 g of aluminum oxide, 0.2 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0050] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0051] Example 6

[0052] 20 g of aluminum oxide, 10 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0053] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0054] Example 7

[0055] 50 g of aluminum oxide, 0.01 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0056] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0057] Example 8

[0058] 50 g of aluminum oxide, 0.2 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0059] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0060] Example 9

[0061] 50 g of aluminum oxide, 10 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0062] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0063] Example 10

[0064] 50 g of aluminum oxide, 10 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0065] 50 g of aluminum oxide, 0.2 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 2.

[0066] Slurry 1 is applied on one side of a base film (PE film) and slurry 2 is applied on the other side of the base film, followed by drying to obtain a battery separator.

[0067] Example 11

[0068] Take 5g of aluminum oxide and 0.2g of m-Li 2.1 ZrCl 0.1 F6, 2 g of polyacrylic acid, and water as the balance to obtain 100 g of slurry 1.

[0069] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0070] Example 12

[0071] Take 5g of aluminum oxide and 0.2g of m-Li 2.1 ZrCl 0.1 F6, 2 g of polyacrylic acid, and water as the balance to obtain 100 g of slurry 1.

[0072] Take 5g of aluminum oxide and 0.2g of m-Li 2.1 ZrCl 0.1 F6, 2 g of polyacrylic acid, and water as the balance to obtain 100 g of slurry 2.

[0073] Slurry 1 is applied on one side of a base film (PE film) and slurry 2 is applied on the other side of the base film, followed by drying to obtain a battery separator.

[0074] Example 13

[0075] 50 g of aluminum oxide, 0.2 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0076] Take 5g of aluminum oxide and 0.2g of m-Li 2.1 ZrCl 0.1 F6, 2 g of polyacrylic acid, and water as the balance to obtain 100 g of slurry 2.

[0077] Slurry 1 is applied on one side of a base film (PE film) and slurry 2 is applied on the other side of the base film, followed by drying to obtain a battery separator.

[0078] Comparative Example 1

[0079] 50 g of aluminum oxide, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0080] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0081] Comparative Example 2

[0082] 0.2 g of m-Li2ZrF6, 2 g of polyacrylic acid, and water as the balance were taken to obtain 100 g of slurry 1.

[0083] The slurry 1 was coated on one side of the base film (PE film) and then dried to obtain a battery separator.

[0084] The preparation parameters of all examples and comparative examples are summarized in Table 1.

[0085] Table 1. Process parameters

[0086]

[0087]

[0088] Test Method

[0089] The thermal shrinkage rate is measured by high-temperature baking. The specific test conditions are a temperature of 130°C and a test time of 1 hour. TD and MD represent longitudinal thermal shrinkage and transverse thermal shrinkage, respectively. The greater the thermal shrinkage rate, the worse the thermal shrinkage of the diaphragm.

[0090] The peel strength was measured using an electronic universal testing machine. The specific test conditions were an effective length of 200 mm and an effective width of 15 mm.

[0091] The air permeability is measured by a Gurley 4320 permeability meter. The specific test method is the time it takes for 100 mL of gas to pass through the diaphragm. The larger the air permeability increment, the worse the air permeability of the diaphragm.

[0092] The diaphragm is configured with a lithium iron phosphate positive electrode, a lithium metal negative electrode and an ether electrolyte to make a full battery, and the capacity retention rate is recorded after 200 cycles at 1C / 25℃.

[0093] Referring to Table 2, a comparison of Examples 7 to 13 and Comparative Example 1 shows that the addition of functional particles does not degrade thermal shrinkage performance, but does improve capacitance retention after multiple cycles. Furthermore, looking at Examples 1 to 3 as a group, Examples 4 to 6 as a group, and Examples 7 to 9 as a group, it can be seen that the addition of functional particles improves capacitance retention after multiple cycles in a concentration-dependent manner.

[0094] Furthermore, by comparing Example 8 with Comparative Examples 1 and 2, it can be seen that the co-addition of functional particles and heat-resistant particles can synergistically improve the capacitance retention after multiple cycles and reduce the air permeability value (i.e., improve the air permeability performance).

[0095] Table 2. Physical properties of lithium metal batteries

[0096]

[0097]

[0098] The above contents involving common knowledge are not described in detail and can be understood by those skilled in the art.

[0099] The above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. The technical scope of the present invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A battery separator, characterized in that: include: A base film, and a coating layer, wherein the coating layer is formed on at least one surface of the base film, and the coating layer contains Li 2+x αF 6+y β x-y , α is a transition metal element including Zr, β is a halogen element including Cl, x≥0, y≥0, x≥y.

2. The battery separator according to claim 1, characterized in that x is 0 to 0.5, and y is 0 to 0.

5.

3. The battery separator according to claim 1, characterized in that The Li 2+x αF 6+y β x-y It is in one or more of monoclinic phase, rhombohedral phase and rhombohedral phase.

4. The battery separator according to claim 1, characterized in that The coating layer further contains heat-resistant particles, which include one or more of aluminum oxide, boehmite, and barium sulfate.

5. The battery separator according to claim 1, characterized in that The coating layer further contains a binder, which includes one or more of polytetrafluoroethylene, polytetrafluoroethylene, polyacrylic acid, sodium hydroxymethyl cellulose, and styrene-butadiene rubber.

6. The battery separator according to claim 1, characterized in that The coating layer further contains heat-resistant particles and a binder; the binder, the Li 2+x αF 6+y β x-y , and the mass ratio between the heat-resistant particles is 1:(0.001 to 100):(0.1 to 800).

7. The battery separator according to claim 1, characterized in that The base film has a thickness of 5 μm to 16 μm, and the coating layer has a thickness of 0.5 μm to 10 μm.

8. A lithium battery comprising: A positive electrode, a negative electrode, and the battery separator according to claim 1, wherein the battery separator is located between the positive electrode and the negative electrode.

9. The lithium battery according to claim 8, characterized in that It is a lithium metal battery.

10. The lithium battery according to claim 8, characterized in that The Li 2+x αF 6+y β x-y It is in one or more of monoclinic phase, rhombohedral phase and rhombohedral phase.

11. A method for preparing a battery separator, characterized in that: include: A slurry is provided, wherein the slurry contains Li 2+x αF 6+y β x-y , α is a transition metal element including Zr, β is a halogen element including Cl, x ≥ 0, y ≥ 0, x ≥ y; as well as The battery separator is obtained by coating the slurry on at least one side of a base film and then drying the base film.

12. The method for preparing a battery separator according to claim 11, wherein: The slurry further contains heat-resistant particles, and the heat-resistant particles include one or more of alumina, boehmite, and barium sulfate.

13. The method for preparing a battery separator according to claim 11, wherein: The slurry further contains a binder, which includes one or more of polytetrafluoroethylene, polytetrafluoroethylene, polyacrylic acid, sodium hydroxymethyl cellulose, and styrene-butadiene rubber.

14. The method for preparing a battery separator according to claim 11, wherein: The slurry further contains a dispersion solvent, which includes one or more of deionized water, N,N-dimethylformamide, N-methylpyrrolidone, acetonitrile, ethanol, and isopropanol.

15. The method for preparing a battery separator according to claim 11, wherein: The slurry further contains heat-resistant particles, a binder, and a dispersing solvent; based on the total mass of the slurry, the Li 2+x αF 6+y β x-y The weight percentage of the heat-resistant particles is 0.01wt% to 10wt%, the weight percentage of the binder is 1wt% to 80wt%, and the balance is the dispersing solvent.

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