Asymmetric solid electrolyte membrane, preparation method thereof and application of asymmetric solid electrolyte membrane in battery

Abstract

The invention provides an asymmetric solid electrolyte membrane and a preparation method thereof and application of the asymmetric solid electrolyte membrane in a battery, the asymmetric solid electrolyte membrane comprises a base membrane, a first coating and a second coating, the base membrane is provided with a first surface and a second surface, the second surface is opposite to the first surface, and the second surface is opposite to the first surface. The first coating is formed on the first surface of the base film and contains lithium titanium aluminum phosphate, and the second coating is formed on the second surface of the base film and contains a solid electrolyte material except the lithium titanium aluminum phosphate. In the invention, the solid electrolyte which is stable to the negative electrode is selected for coating, so that the problem that the performance of the negative electrode is degraded by LATP is solved, the overall performance of the diaphragm is improved, and the coating process is adaptive to an existing production line and does not need to be greatly modified.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separators, and particularly to an asymmetric solid electrolyte membrane, a preparation method thereof, and an application in batteries. Background Art

[0002] Lithium-ion batteries are a kind of efficient and clean energy storage device. Since their commercialization, they have been widely used in fields such as portable electronic devices, electric vehicles, and large-scale energy storage systems. Their working principle mainly depends on the reversible migration of lithium ions between the positive electrode and the negative electrode to achieve the mutual conversion between chemical energy and electrical energy. However, with the continuous expansion of application fields and the increasing market demand, higher requirements are put forward for lithium batteries in terms of energy density, safety, cycle life, etc.

[0003] Currently, alumina separators are used in traditional commercial lithium batteries, but their performance is limited. Solid electrolytes have attracted a large amount of research in recent years due to their advantages such as high ionic conductivity, good safety performance, and good stability. As the most mature, water and air stable, and relatively low-cost one currently, LATP has the fastest development progress in coating separators, and its overall performance is better than that of alumina separators. However, LATP reacts with Li, which will cause the deterioration of performance such as high-temperature storage and high-temperature cycling in some battery cell systems. Therefore, it is urgent to develop a new coating structure to improve the problem of performance deterioration when the LATP coating faces the negative electrode and to enhance the overall performance of the separator. Summary of the Invention

[0004] In the present invention, an asymmetric solid electrolyte coating structure is developed. The coating facing the positive electrode uses LATP (lithium aluminum titanium phosphate), and the coating facing the negative electrode uses other types of solid electrolyte materials. This new coating structure solves the problem of performance deterioration facing the negative electrode and enhances the overall performance of the solid electrolyte separator, providing new ideas for the development of subsequent related products.

[0005] The first aspect of the present invention is implemented as follows:

[0006] An asymmetric solid electrolyte membrane, which includes: a base membrane, a first coating, and a second coating. The base membrane has a first surface and a second surface. The second surface is opposite to the first surface. The first coating is formed on the first surface of the base membrane and contains lithium aluminum titanium phosphate, and the second coating is formed on the second surface of the base membrane and contains a solid electrolyte material other than lithium aluminum titanium phosphate.

[0007] In an embodiment of the present invention, the solid electrolyte material includes one or more of LLZO (lithium lanthanum zirconium oxide), LLZTO (lithium lanthanum zirconium tantalum oxide), LLTO (lithium lanthanum titanium oxide), LAGP (lithium germanium aluminum phosphate), Li2ZrF6, Li2ZrCl6, and Li2AlF6.

[0008] In an embodiment of the present invention, the thickness of the base film is 5 μm to 16 μm, the thickness of the first coating is 2 μm to 4 μm, and the thickness of the second coating is 2 μm to 4 μm.

[0009] In an embodiment of the present invention, the base film is one or more of a polyvinyl film and a polypropylene film.

[0010] In an embodiment of the present invention, the particle size D50 of the lithium titanium aluminum phosphate particles in the first coating is 0.1 μm to 3 μm, and the particle size D50 of the solid electrolyte material particles in the second coating is 0.1 μm to 3 μm.

[0011] The second aspect of the present invention is implemented as follows:

[0012] A battery includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode and including the asymmetric solid electrolyte membrane as described above, with the first coating facing the positive electrode and the second coating facing the negative electrode.

[0013] The third aspect of the present invention is implemented as follows:

[0014] A method for preparing an asymmetric solid electrolyte membrane includes separately coating a first slurry and a second slurry on a first surface and a second surface opposite to the first surface of a base film, where the first slurry contains lithium titanium aluminum phosphate and the second slurry contains a solid electrolyte material other than lithium titanium aluminum phosphate; and drying to obtain the asymmetric solid electrolyte membrane.

[0015] In an embodiment of the present invention, the solid electrolyte material includes one or more of LLZO (lithium lanthanum zirconium oxide), LLZTO (lithium lanthanum zirconium tantalum oxide), LLTO (lithium lanthanum titanium oxide), LAGP (lithium germanium aluminum phosphate), Li2ZrF6, Li2ZrCl6, and Li2AlF6.

[0016] In an embodiment of the present invention, the first slurry further includes one or more of a dispersion aid, a binder, and a wetting agent, and the second slurry further includes one or more of a dispersion aid, a binder, and a wetting agent.

[0017] In an embodiment of the present invention, the dispersing aid of the first slurry includes one or more of sodium polyacrylate, polyethylene oxide, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, polyether silicone copolymer, polyoxyethylene alkanolamide, and ammonium polyacrylate; the binder of the first slurry includes one or more of polymers obtained by copolymerizing acrylate, methacrylate, styrene-butadiene rubber with olefins, polymers obtained by copolymerizing styrene-butadiene rubber with esters, polymers obtained by copolymerizing nitrile rubber with olefins, and polymers obtained by copolymerizing nitrile rubber with esters; the wetting agent of the first slurry includes one or more of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene-polyoxypropylene block copolymer.

[0018] In an embodiment of the present invention, the dispersing aid of the second slurry includes one or more of sodium polyacrylate, polyethylene oxide, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, polyether silicone copolymer, polyoxyethylene alkanolamide, and ammonium polyacrylate; the binder of the second slurry includes one or more of polymers obtained by copolymerizing acrylate, methacrylate, styrene-butadiene rubber with olefins, polymers obtained by copolymerizing styrene-butadiene rubber with esters, polymers obtained by copolymerizing nitrile rubber with olefins, and polymers obtained by copolymerizing nitrile rubber with esters; the wetting agent of the second slurry includes one or more of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene-polyoxypropylene block copolymer.

[0019] In an embodiment of the present invention, the first slurry is an aqueous slurry with a solid content of 40% to 50%, a viscosity of 10 mPa·s to 50 mPa·s, and a pH of 7 to 10; the second slurry is an aqueous slurry with a solid content of 40% to 50%, a viscosity of 10 mPa·s to 50 mPa·s, and a pH of 7 to 10.

[0020] The beneficial effects of the present invention are as follows:

[0021] By selecting a solid electrolyte stable to the negative electrode for coating, the problem of the deterioration of the performance of the negative electrode by LATP is solved, the overall performance of the separator is improved, and the coating process is adapted to the existing production line without major modifications. Description of the Drawings

[0022] Figure 1 Schematically showing the asymmetric solid electrolyte membrane of the present invention. Detailed Description of the Invention

[0023] The following is a detailed description of the specific embodiments of the present invention in conjunction with the drawings. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0024] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0025] Please refer to Figure 1 , which is an asymmetric solid electrolyte membrane of the present invention, and at least includes the following structures: a base film (1), a first coating (21), and a second coating (22). The base film (1) has a first surface and a second surface. The second surface is opposite to the first surface. The first coating (21) is formed on the first surface of the base film (1) and contains lithium aluminum titanium phosphate, and the second coating (22) is formed on the second surface of the base film (1) and contains a solid electrolyte material other than lithium aluminum titanium phosphate.

[0026] The base film (1) can be one or more of a polyethylene base film and a polypropylene base film. In addition, the thickness of the base film (1) can be 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, 16 μm or the range between any two values.

[0027] The thickness of the first coating (21) can be 2 μm to 4 μm, preferably any value among 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or the range between any two values. In addition to containing lithium aluminum titanium phosphate, the first coating (21) can further include one or more of a dispersion aid, a binder, and a wetting agent. The dispersion aid can include one or more of sodium polyacrylate, polyethylene oxide, polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, sodium carboxymethylcellulose, polyether silicone copolymer, polyoxyethylene alkanolamide, and ammonium polyacrylate salt. The binder can include one or more of polymers obtained by copolymerizing acrylate, methacrylate, styrene-butadiene rubber and olefins, polymers obtained by copolymerizing styrene-butadiene rubber and esters, polymers obtained by copolymerizing nitrile rubber and olefins, and polymers obtained by copolymerizing nitrile rubber and esters. The wetting agent can include one or more of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene polyoxypropylene block copolymer. In addition, the particle size D50 of the lithium aluminum titanium phosphate particles can be 0.1 μm to 3 μm, preferably any value among 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or the range between any two values.

[0028] The thickness of the second coating (22) can be from 2 μm to 4 μm, preferably any value among 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or the range between any two of these values. The solid electrolyte material can include one or more of LLZO (lithium lanthanum zirconium oxide), LLZTO (lithium lanthanum zirconium tantalum oxide), LLTO (lithium lanthanum titanium oxide), LAGP (lithium germanium aluminum phosphate), Li2ZrF6, Li2ZrCl6, Li2AlF6. In addition to the solid electrolyte material, the second coating (22) can further include one or more of a dispersion aid, a binder, and a wetting agent. The dispersion aid can include one or more of sodium polyacrylate, polyethylene oxide, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, polyether silicone copolymer, polyoxyethylene alkanolamide, ammonium polyacrylate salt. The binder can include one or more of polymers obtained by copolymerizing acrylate, methacrylate, styrene-butadiene rubber with olefins, polymers obtained by copolymerizing styrene-butadiene rubber with esters, polymers obtained by copolymerizing nitrile rubber with olefins, polymers obtained by copolymerizing nitrile rubber with esters. The wetting agent can include one or more of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene-polyoxypropylene block copolymer. In addition, the particle size D50 of the solid electrolyte material particles can be from 0.1 μm to 3 μm, preferably any value among 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or the range between any two of these values.

[0029] When assembling the asymmetric solid electrolyte membrane of the present invention into a battery, the asymmetric solid electrolyte membrane is disposed between the positive electrode and the negative electrode, and the first coating (21) faces the positive electrode and the second coating (22) faces the negative electrode, thereby solving the problem of the deterioration of the negative electrode performance caused by LATP.

[0030] The following describes the preparation method of the asymmetric solid electrolyte membrane of the present invention. Although the above-mentioned asymmetric solid electrolyte membrane can be prepared, it should not be limited thereto. The detailed steps of the preparation method of the asymmetric solid electrolyte membrane are as follows:

[0031] First, a first slurry and a second slurry are respectively coated on a first surface and a second surface opposite to the first surface of a base film. The first slurry contains lithium aluminum titanium phosphate, and the second slurry contains a solid electrolyte material other than lithium aluminum titanium phosphate; then, it is dried to obtain an asymmetric solid electrolyte membrane.

[0032] The base film can be one or more of a polyethylene base film and a polypropylene base film. In addition, the thickness of the base film can be 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, 16 μm or the range between any two values.

[0033] The first slurry can further include one or more of a dispersion aid, a binder, and a wetting agent. The dispersion aid of the first slurry can include one or more of sodium polyacrylate, polyethylene oxide, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, polyether silicone copolymer, polyoxyethylene alkanolamide, and ammonium polyacrylate salt. The binder of the first slurry can include one or more of polymers obtained by copolymerizing acrylate, methacrylate, styrene-butadiene rubber with olefins, polymers obtained by copolymerizing styrene-butadiene rubber with esters, polymers obtained by copolymerizing nitrile rubber with olefins, and polymers obtained by copolymerizing nitrile rubber with esters. The wetting agent of the first slurry can include one or more of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene-polyoxypropylene block copolymer. Moreover, under the condition that the first slurry further includes a dispersion aid, a binder, and a wetting agent, the preparation method of the first slurry includes: adding a part of the dispersion aid to water and stirring, then adding lithium titanium aluminum phosphate and stirring to obtain a mixture; after grinding the mixture, sequentially adding another part of the dispersion aid, the binder, and the wetting agent and stirring. In addition, the first slurry can be an aqueous slurry; its solid content can be 40% to 50%, preferably any value among 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or the range between any two values; the viscosity can be 10 mPa·s to 50 mPa·s, preferably any value among 10 mPa·s, 15 mPa·s, 20 mPa·s, 25 mPa·s, 30 mPa·s, 35 mPa·s, 40 mPa·s, 45 mPa·s, 50 mPa·s or the range between any two values; the pH can be 7 to 10, preferably any value among 7, 7.5, 8, 8.5, 9, 9.5, 10 or the range between any two values. Additionally, the particle size D50 of lithium titanium aluminum phosphate can be 0.1 μm to 3 μm, preferably any value among 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or the range between any two values.

[0034] The second slurry may further include one or more of a dispersing aid, a binder, and a wetting agent. The dispersing aid of the second slurry may include one or more of sodium polyacrylate, polyethylene oxide, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, polyether silicone copolymer, polyoxyethylene alkanolamide, and ammonium polyacrylate. The binder of the second slurry may include one or more of polymers obtained by copolymerizing acrylate, methacrylate, styrene-butadiene rubber with olefins, polymers obtained by copolymerizing styrene-butadiene rubber with esters, polymers obtained by copolymerizing nitrile rubber with olefins, and polymers obtained by copolymerizing nitrile rubber with esters. The wetting agent of the second slurry may include one or more of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene-polyoxypropylene block copolymer. Moreover, under the condition that the second slurry further includes a dispersing aid, a binder, and a wetting agent, the preparation method of the second slurry includes: adding a part of the dispersing aid to water and stirring, then adding the solid electrolyte material and stirring to obtain a mixture; after grinding the mixture, sequentially adding another part of the dispersing aid, the binder, and the wetting agent and stirring. In addition, the second slurry may be an aqueous slurry; its solid content may be 40% to 50%, preferably any value among 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or the range between any two values; the viscosity may be 10 mPa·s to 50 mPa·s, preferably any value among 10 mPa·s, 15 mPa·s, 20 mPa·s, 25 mPa·s, 30 mPa·s, 35 mPa·s, 40 mPa·s, 45 mPa·s, 50 mPa·s or the range between any two values; the pH may be 7 to 10, preferably any value among 7, 7.5, 8, 8.5, 9, 9.5, 10 or the range between any two values. Additionally, the solid electrolyte material may include one or more of LLZO (lithium lanthanum zirconium oxide), LLZTO (lithium lanthanum zirconium tantalum oxide), LLTO (lithium lanthanum titanium oxide), LAGP (lithium germanium aluminum phosphate), Li2ZrF6, Li2ZrCl6, and Li2AlF6. Moreover, the particle size D50 of the solid electrolyte material may be 0.1 μm to 3 μm, preferably any value among 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or the range between any two values.

[0035] Here, the present invention is exemplarily illustrated by the following examples.

[0036] Example 1

[0037] For the separator of this example, the base film thickness is 9 μm, with double-sided coating, where one side is coated with LATP and the other side is coated with Al2O3, and the thickness of each coating is 2 μm.

[0038] Add a dispersion aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add LATP or Al2O3. After grinding, add a dispersion aid with a mass percentage of 4 wt%. Then add the glue solution and wetting agent, and stir evenly to obtain an LATP or Al2O3 slurry with a solid content of 40%. Finally, coat both sides of the base film and dry to obtain a separator with a coating structure.

[0039] When assembling the battery, the LATP coating faces the positive electrode and the Al2O3 coating faces the negative electrode.

[0040] Example 2

[0041] For the separator in this example, the base film has a thickness of 9 μm and is double-sided coated. One side is coated with LATP and the other side is coated with LLZTO, and the thickness of each coating is 2 μm.

[0042] Add a dispersion aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add LATP or LLZTO. After grinding, add a dispersion aid with a mass percentage of 4 wt%. Then add the glue solution and wetting agent, and stir evenly to obtain an LATP or LLZTO slurry with a solid content of 40%. Finally, coat both sides of the base film and dry to obtain a separator with a coating structure.

[0043] When assembling the battery, the LATP coating faces the positive electrode and the LLZTO coating faces the negative electrode.

[0044] Example 3

[0045] For the separator in this example, the base film has a thickness of 9 μm and is double-sided coated. One side is coated with LATP and the other side is coated with LLTO, and the thickness of each coating is 2 μm.

[0046] Add a dispersion aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add LATP or LLTO. After grinding, add a dispersion aid with a mass percentage of 4 wt%. Then add the glue solution and wetting agent, and stir evenly to obtain an LATP or LLTO slurry with a solid content of 40%. Finally, coat both sides of the base film and dry to obtain a separator with a coating structure.

[0047] When assembling the battery, the LATP coating faces the positive electrode and the LLTO coating faces the negative electrode.

[0048] Example 4

[0049] For the separator in this example, the base film has a thickness of 9 μm and is double-sided coated. One side is coated with LATP and the other side is coated with LLZO, and the thickness of each coating is 2 μm.

[0050] Add a dispersion aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add LATP or LLZO. After grinding, add a dispersion aid with a mass percentage of 4 wt%. Then add a glue solution and a wetting agent, and stir evenly to obtain an LATP or LLZO slurry with a solid content of 40%. Finally, coat both sides of the base film and dry to obtain a separator with a coating structure.

[0051] When assembling the battery, the LATP coating faces the positive electrode, and the LLZO coating faces the negative electrode.

[0052] Example 5

[0053] For the separator of this example, the base film has a thickness of 9 μm and is double-sided coated. One side is coated with LATP, and the other side is coated with Li2ZrF6. Each coating has a thickness of 2 μm.

[0054] Add a dispersion aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add LATP or Li2ZrF6. After grinding, add a dispersion aid with a mass percentage of 4 wt%. Then add a glue solution and a wetting agent, and stir evenly to obtain an LATP or Li2ZrF6 slurry with a solid content of 40%. Finally, coat both sides of the base film and dry to obtain a separator with a coating structure.

[0055] When assembling the battery, the LATP coating faces the positive electrode, and the Li2ZrF6 coating faces the negative electrode.

[0056] Comparative Example 1

[0057] For the separator of this comparative example, the base film has a thickness of 9 μm and is double-sided coated. One side is coated with LATP, and the other side is also coated with LATP. Each coating has a thickness of 2 μm.

[0058] Add a dispersion aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add LATP. After grinding, add a dispersion aid with a mass percentage of 4 wt%. Then add a glue solution and a wetting agent, and stir evenly to obtain an LATP slurry with a solid content of 40%. Finally, coat both sides of the base film and dry to obtain a separator with a coating structure.

[0059] When assembling the battery, the two LATP coatings face the positive electrode and the negative electrode respectively.

[0060] Comparative Example 2

[0061] For the separator of this comparative example, the base film has a thickness of 9 μm and has no coating.

[0062] Comparative Example 3

[0063] For the separator of this comparative example, the base film has a thickness of 9 μm and is double-sided coated. One side is coated with LLTO, and the other side is also coated with LLTO. Each coating has a thickness of 2 μm.

[0064] Add a dispersing aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add LLTO. After grinding, add a dispersing aid with a mass percentage of 4 wt%. Then add the glue solution and wetting agent, and stir evenly to obtain an LLTO slurry with a solid content of 40%. Finally, coat both sides of the base film and dry it to obtain a separator with a coating structure.

[0065] When assembling the battery, the two LLTO coatings face the positive electrode and the negative electrode respectively.

[0066] Comparative Example 4

[0067] For the separator of this comparative example, the thickness of the base film is 9 μm, with double-sided coatings. One side is coated with LLZO, and the other side is also coated with LLZO. The thickness of each coating is 2 μm.

[0068] Add a dispersing aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add LLZO. After grinding, add a dispersing aid with a mass percentage of 4 wt%. Then add the glue solution and wetting agent, and stir evenly to obtain an LLZO slurry with a solid content of 40%. Finally, coat both sides of the base film and dry it to obtain a separator with a coating structure.

[0069] When assembling the battery, the two LLZO coatings face the positive electrode and the negative electrode respectively.

[0070] Comparative Example 5

[0071] For the separator of this comparative example, the thickness of the base film is 9 μm, with double-sided coatings. One side is coated with Li2ZrF6, and the other side is also coated with Li2ZrF6. The thickness of each coating is 2 μm.

[0072] Add a dispersing aid with a mass percentage of 1 wt% to deionized water. After stirring evenly, add Li2ZrF6. After grinding, add a dispersing aid with a mass percentage of 4 wt%. Then add the glue solution and wetting agent, and stir evenly to obtain a Li2ZrF6 slurry with a solid content of 40%. Finally, coat both sides of the base film and dry it to obtain a separator with a coating structure.

[0073] When assembling the battery, the two Li2ZrF6 coatings face the positive electrode and the negative electrode respectively.

[0074] It should be noted that when referring to the dispersing aid, glue solution and wetting agent in the above-mentioned examples and comparative examples, the types and contents of the dispersing aid, glue solution and wetting agent used are the same. However, this is not the core spirit protected by the present invention, so it is not necessary to describe them in detail in the above-mentioned examples and comparative examples, and it is hereby specifically stated.

[0075] In Table 1, the low-temperature discharge is the capacity retention rate of 1C discharge at -20°C. The high-temperature storage is to measure the capacity retention rate and recovery rate of the battery after 7 days of high-temperature storage at 55°C. The low-temperature cycle is the number of cycles when the capacity retention rate reaches 80% at 0.5C charge and discharge at -10°C. The high-temperature cycle is the capacity retention rate of 1C charge and discharge cycle 250 times at 45°C.

[0076] Based on the fact that the performance of Examples 1 to 5 is superior to that of Comparative Examples 1 to 5, it can be seen that the asymmetric coating structure can provide better performance for the battery. Based on the fact that the performance of Examples 2 to 5 is superior to that of Example 1, it can be seen that using a solid electrolyte material with LATP and non-LATP in the asymmetric coating structure can provide better performance for the battery.

[0077] Based on the fact that the performance of Example 3 is superior to that of Comparative Examples 1 and 3, it can be seen that using LATP and LLTO in the asymmetric coating structure can provide an unexpected degree of performance for the battery. Based on the fact that the performance of Example 4 is superior to that of Comparative Examples 1 and 4, it can be seen that using LATP and LLZO in the asymmetric coating structure can provide an unexpected degree of performance for the battery. Based on the fact that the performance of Example 5 is superior to that of Comparative Examples 1 and 5, it can be seen that using LATP and Li2ZrF6 in the asymmetric coating structure can provide an unexpected degree of performance for the battery.

[0078] Table 1

[0079]

[0080] The above content related to common general knowledge will not be described in detail, and those skilled in the art can understand.

[0081] The above are only some specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. An asymmetric solid electrolyte membrane, characterized in that, Comprising: A base film, a first coating, and a second coating. The base film has a first surface and a second surface. The second surface is opposite to the first surface. The first coating is formed on the first surface of the base film and contains lithium titanium aluminum phosphate, and the second coating is formed on the second surface of the base film and contains a solid electrolyte material other than lithium titanium aluminum phosphate.

2. The asymmetric solid electrolyte membrane according to claim 1, characterized in that, The solid electrolyte material includes one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, Li2ZrF6, Li2ZrCl6, Li2AlF6.

3. The asymmetric solid electrolyte membrane according to claim 1, characterized in that, The thickness of the base film is 5 μm to 16 μm, the thickness of the first coating is 2 μm to 4 μm, and the thickness of the second coating is 2 μm to 4 μm.

4. The asymmetric solid electrolyte membrane according to claim 1, characterized in that, The base film is one or more of a polyethylene base film and a polypropylene base film.

5. The asymmetric solid electrolyte membrane according to claim 2, characterized in that, The particle size D50 of the lithium titanium aluminum phosphate particles in the first coating is 0.1 μm to 3 μm, and the particle size D50 of the solid electrolyte material particles in the second coating is 0.1 μm to 3 μm.

6. A battery, characterized in that, Comprising: A positive electrode, a negative electrode, and a separator. The separator is disposed between the positive electrode and the negative electrode and includes the asymmetric solid electrolyte membrane as described in any one of claims 1 to 5. The first coating faces the positive electrode, and the second coating faces the negative electrode.

7. A method for preparing an asymmetric solid electrolyte membrane, characterized in that, Comprising: Coating a first slurry and a second slurry respectively on a first surface of a base film and a second surface opposite to the first surface. The first slurry contains lithium titanium aluminum phosphate, and the second slurry contains a solid electrolyte material other than lithium titanium aluminum phosphate; and Drying to obtain the asymmetric solid electrolyte membrane.

8. The method for preparing the asymmetric solid electrolyte membrane according to claim 7, wherein The solid electrolyte material includes one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, Li2ZrF6, Li2ZrCl6, Li2AlF6.

9. The method for preparing an asymmetric solid electrolyte membrane according to claim 7, characterized in that, The first slurry further includes one or more of a dispersion aid, a binder, and a wetting agent, and the second slurry further includes one or more of a dispersion aid, a binder, and a wetting agent.

10. The preparation method of the asymmetric solid electrolyte membrane according to claim 9, characterized in that, The dispersion aid of the first slurry includes one or more of sodium polyacrylate, polyethylene oxide, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, polyether silicone copolymer, polyoxyethylene alkanolamide, ammonium polyacrylate salt. The binder of the first slurry includes one or more of polymers obtained by copolymerizing acrylate, methacrylate, styrene-butadiene rubber with olefins, polymers obtained by copolymerizing styrene-butadiene rubber with esters, polymers obtained by copolymerizing nitrile rubber with olefins, polymers obtained by copolymerizing nitrile rubber with esters. The wetting agent of the first slurry includes one or more of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene-polyoxypropylene block copolymer.

11. The method for preparing an asymmetric solid electrolyte membrane according to claim 9, wherein The dispersing aids of the second slurry include one or more of sodium polyacrylate, polyethylene oxide, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, polyether silicone copolymer, polyoxyethylene alkanolamide, and ammonium polyacrylate. The binders of the second slurry include one or more of polymers obtained by copolymerizing acrylate, methacrylate, styrene-butadiene rubber with olefins, polymers obtained by copolymerizing styrene-butadiene rubber with esters, polymers obtained by copolymerizing nitrile rubber with olefins, and polymers obtained by copolymerizing nitrile rubber with esters. The wetting agents of the second slurry include one or more of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene-polyoxypropylene block copolymer.

12. The method for preparing an asymmetric solid electrolyte membrane according to claim 7, characterized in that, The first slurry is an aqueous slurry with a solid content of 40% to 50%, a viscosity of 10 mPa·s to 50 mPa·s, and a pH of 7 to 10. The second slurry is an aqueous slurry with a solid content of 40% to 50%, a viscosity of 10 mPa·s to 50 mPa·s, and a pH of 7 to 10.

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