Solid-state electrolyte membrane and preparation method therefor, and all-solid-state battery

Abstract

The present application provides a solid-state electrolyte membrane and a preparation method therefor, and an all-solid-state battery. The preparation method for a solid-state electrolyte membrane comprises: subjecting an oxide solid-state electrolyte and an additive to a first grinding and mixing treatment, so as to obtain a first mixture, wherein the additive comprises at least one of a first additive and a second additive, the first additive comprises at least one of polyvinylidene fluoride and a copolymer thereof, and the second additive comprises a lithium salt and an ionic liquid; subjecting the first mixture and polytetrafluoroethylene to a second grinding and mixing treatment, so as to obtain a sheet-shaped mixture, wherein on the basis of the total mass of the sheet-shaped mixture, the content of polytetrafluoroethylene is 0.49-5.03 wt%; and rolling the sheet-shaped mixture, so as to obtain a ceramic electrolyte membrane, wherein the solid-state electrolyte membrane comprises the ceramic electrolyte membrane.

Description

Solid electrolyte membrane and preparation method thereof, and all-solid-state battery

[0001] The present application claims priority to the Chinese patent application No. 202410992454.5, filed on July 23, 2024, to the Chinese Patent Office, the whole content of the above application being incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of solid-state batteries, in particular to a solid electrolyte membrane, a preparation method of the solid electrolyte membrane, and an all-solid-state battery. BACKGROUND

[0003] With the rapid development of the new energy automobile industry, the requirement for the energy density of power batteries is getting higher and higher, and the energy density of the traditional lithium-ion battery has reached the bottleneck value, so it is an urgent need to develop a new type of lithium battery system. Replacing the graphite negative electrode of the lithium-ion battery with metal lithium can significantly improve the energy density of the battery and reduce the volume of the battery. TECHNICAL PROBLEM

[0004] However, the compatibility of metal lithium with liquid electrolyte is poor, and metal lithium is prone to form dendrites in the repeated charging and discharging process, which can easily pierce the separator and cause safety problems. Replacing the liquid electrolyte with a solid electrolyte can alleviate the lithium dendrite problem to some extent, but the common solid electrolyte has the problem of low ionic conductivity. TECHNICAL SOLUTION

[0005] The present application provides a preparation method of a solid electrolyte membrane. The preparation method of the solid electrolyte membrane comprises:

[0006] The oxide solid electrolyte and the additive are subjected to first grinding and mixing treatment to obtain a first mixture, the additive comprising at least one of a first additive and a second additive, the first additive comprising at least one of polyvinylidene fluoride and its copolymer, and the second additive comprising a lithium salt and an ionic liquid;

[0007] The first mixture and polytetrafluoroethylene are subjected to second grinding and mixing treatment to obtain a sheet-shaped mixture, and the content of the polytetrafluoroethylene is 0.49wt%-5.03wt% based on the total mass of the sheet-shaped mixture;

[0008] The sheet-shaped mixture is subjected to rolling treatment to obtain a ceramic electrolyte membrane, and the solid electrolyte membrane comprises the ceramic electrolyte membrane.

[0009] The application further provides a solid-state electrolyte film. The solid-state electrolyte film comprises a ceramic electrolyte film, the ceramic electrolyte film comprises an oxide solid-state electrolyte, an additive and polytetrafluoroethylene, the additive comprises at least one of a first additive and a second additive, the first additive comprises at least one of polyvinylidene fluoride and a copolymer of polyvinylidene fluoride, the second additive comprises a lithium salt and an ionic liquid, and the content of the polytetrafluoroethylene is 0.49 wt% to 5.03 wt% based on the total mass of the ceramic electrolyte film.

[0010] The application further provides an all-solid-state battery. The all-solid-state battery comprises a positive electrode, a negative electrode and a solid-state electrolyte film, the solid-state electrolyte film is located between the positive electrode and the negative electrode, and the solid-state electrolyte film is the above-mentioned solid-state electrolyte film. Advantages

[0011] The solid-state electrolyte film provided by the application comprises a ceramic electrolyte film, the ceramic electrolyte film comprises an oxide solid-state electrolyte, an additive and polytetrafluoroethylene, wherein the additive comprises at least one of a lithium salt + an ionic liquid, polyvinylidene fluoride and a copolymer thereof, the additive is dispersed in the oxide solid-state electrolyte, can effectively build an ion transmission channel and improve the ionic conductivity of the ceramic electrolyte film; the polytetrafluoroethylene serves as a binder, by controlling the content of the polytetrafluoroethylene in the total material to be 0.49 wt% to 5.03 wt%, the film formation can be ensured and the mechanical strength of the ceramic electrolyte film can be improved, and thus the mechanical strength of the solid-state electrolyte film is improved.

[0012] The preparation method of the solid-state electrolyte film provided in the application prepares the ceramic electrolyte film by adopting a dry forming process, which is conducive to guaranteeing the density of the ceramic electrolyte film and improving the mechanical strength of the ceramic electrolyte film. The solid-state electrolyte film comprises the ceramic electrolyte film, so that the mechanical strength of the solid-state electrolyte film is improved. Specifically, the ceramic electrolyte film is obtained by roll forming after grinding and mixing of the oxide solid-state electrolyte, the additive and the polytetrafluoroethylene. The additive is used to improve the ionic conductivity of the ceramic electrolyte film, and the polytetrafluoroethylene is used as a binder. By controlling the content of the polytetrafluoroethylene in the total material to be 0.49wt% to 5.03wt%, the film can be guaranteed to be formed, and the mechanical strength of the ceramic electrolyte film is improved. More specifically, the oxide solid-state electrolyte and the additive are subjected to first grinding and mixing treatment to form a first mixture, and then the first mixture and the polytetrafluoroethylene are subjected to second grinding and mixing treatment to form a sheet-shaped mixture, and finally the sheet-shaped mixture is roll formed to form the ceramic electrolyte film. The first grinding and mixing treatment is used to promote uniform mixing of the oxide solid-state electrolyte and the additive to improve the dispersion effect of the additive, and the second grinding and mixing treatment is used to promote fiberization of the polytetrafluoroethylene to realize film formation. The first grinding and mixing treatment and the second grinding and mixing treatment are independent of each other, which reduces the adverse effect of the fiberization of the polytetrafluoroethylene on the dispersion effect of the additive, effectively improves the homogenization of the material, so that the material can form a continuous lithium ion transmission channel after being densified by roll forming, which is conducive to improving the ionic conductivity of the ceramic electrolyte film, and further improving the ionic conductivity of the solid-state electrolyte film. BRIEF DESCRIPTION OF DRAWINGS

[0013] Fig. 1 is a flow chart of the preparation method of the solid-state electrolyte film provided in the embodiment of the application;

[0014] Fig. 2 is a scanning electron microscope image of the ceramic electrolyte film provided in Example 2 of the application;

[0015] Fig. 3 is a scanning electron microscope image of the ceramic electrolyte film provided in Comparative Example 1 of the application. Embodiment of the application

[0016] In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower positions of the device in the actual use or working state, and "inner" and "outer" refer to the outline of the device. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish sequences.

[0017] In the present application, the association relationship between the associated objects is described by "and / or", which means that there can be three kinds of relationships, for example, A and / or B can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.

[0018] In the present application, "at least one" means one or more, and "multiple" means two or more. "One or more", "at least one of the following (one)", or similar expressions, refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0019] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has 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 described range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0020] In a first aspect, referring to FIG. 1, the present application provides a preparation method of a solid-state electrolyte film. The solid-state electrolyte film includes a ceramic electrolyte film. It should be noted that the solid-state electrolyte film can be a single-layer film structure including only the ceramic electrolyte film, the solid-state electrolyte film can also be a multi-layer film structure including multiple ceramic electrolyte films, and the solid-state electrolyte film can also be a composite film structure including the ceramic electrolyte film and a polymer electrolyte film, which is not limited herein.

[0021] Specifically, the preparation method of the solid-state electrolyte film includes preparing the ceramic electrolyte film by using a dry forming process. No organic solvent is used in the dry forming process, so that the generation of pores caused by the volatilization of the organic solvent can be prevented, the density of the ceramic electrolyte film is improved, and thus the ionic conductivity of the ceramic electrolyte film is improved. The process of preparing the ceramic electrolyte film by using the dry forming process includes:

[0022] S1, performing first grinding and mixing treatment on the oxide solid-state electrolyte and the additive to obtain a first mixture.

[0023] Compared with the polymer electrolyte, the oxide solid-state electrolyte has higher ionic conductivity, wider electrochemical stability window, good thermal stability, chemical stability and mechanical strength, which is conducive to improving the performance of the ceramic electrolyte film. Optionally, the oxide solid-state electrolyte includes at least one of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium gallium oxide (LLZGO) and lithium lanthanum zirconium tantalum oxide (LLZTO). The LLZO is a garnet type, and the chemical formula is Li7La3Zr2O 12 The LLZGO is the LLZO doped with Ga elements, and the LLZTO is the LLZO doped with Ta elements.

[0024] The above-mentioned additive mainly refers to an additive for improving the ionic conductivity of the ceramic electrolyte film. In detail, the additive includes at least one of a first additive and a second additive. Exemplarily, the additive includes the first additive, or the additive includes the second additive, or the additive includes the first additive and the second additive. The first additive includes at least one of polyvinylidene fluoride and a copolymer of polyvinylidene fluoride. The polyvinylidene fluoride (PVDF) and the copolymer of polyvinylidene fluoride have a relatively high dielectric constant, which is conducive to enhancing the ion transport property of the ceramic electrolyte film. Exemplarily, the copolymer of polyvinylidene fluoride includes polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The second additive includes a lithium salt and an ionic liquid. Exemplarily, the lithium salt can be dissolved in the ionic liquid. The lithium salt can increase the lithium salt content in the ceramic electrolyte film, so that the ionic conductivity of the ceramic electrolyte film is higher, and the ionic liquid itself has a relatively high ionic conductivity, which can also improve the ionic conductivity of the ceramic electrolyte film. When the lithium salt is dissolved in the ionic liquid, the ionic liquid has a certain wetting effect, which is conducive to promoting the uniform dispersion of the lithium salt in the oxide solid-state electrolyte. Exemplarily, the lithium salt includes at least one of lithium bis(trifluoromethyl) sulfonylimide (LiTFSI), lithium bis(fluorosulfonyl) imide (LiFSI), lithium bis(perfluoroethylsulfonyl) imide (LIBETI) and lithium bis(oxalate) borate (LiBOB). Exemplarily, the ionic liquid is a pyrrole ionic liquid, such as N-propyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl) imide salt ionic liquid. Optionally, in the second additive, the lithium salt is LiTFSI, the ionic liquid is N-propyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl) imide salt ionic liquid, and the mass ratio of LiTFSI to N-propyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl) imide salt ionic liquid is (1.5-2.5):1. For example, the mass ratio of LiTFSI to N-propyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl) imide salt ionic liquid is 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1.

[0025] Generally, the first grinding and mixing process includes a grinding process, i.e., the oxide solid electrolyte and the additives are added together and are also ground, so that the additives can be more uniformly dispersed in the oxide solid electrolyte, improving homogenization, which is conducive to the formation of a continuous ion transmission path and improves the ionic conductivity of the ceramic electrolyte film. Especially when the additives include the first additive, the first additive is difficult to dissolve due to the absence of organic solvents in the dry forming process, and in this case, the first additive relies more on the grinding process to improve the dispersion effect.

[0026] In some embodiments, when the additives include the first additive and the second additive, step S1 specifically includes:

[0027] S11, grinding and mixing the oxide solid electrolyte and the first additive to obtain a dry mixture;

[0028] S12, grinding and mixing the dry mixture with the second additive to obtain a first mixture.

[0029] That is, the first additive is first ground and mixed with the oxide solid electrolyte, and then the second additive is ground and mixed with the oxide solid electrolyte. Through step-by-step grinding and mixing, the influence of the liquid second additive on the dispersion effect of the solid first additive is reduced. Since the oxide solid electrolyte and the first additive are usually dry powders, they are mixed to form a dry mixture. In other embodiments, the first mixture can also be prepared by synchronous grinding and mixing, i.e., the oxide solid electrolyte, the first additive, and the second additive are added together and are collectively ground.

[0030] In some embodiments, carboxymethyl cellulose is also added in the process of preparing the ceramic electrolyte film, specifically, carboxymethyl cellulose is added before the second additive is added, in other words, the dry mixture also contains carboxymethyl cellulose. In detail, step S1 further includes:

[0031] S13, grinding and mixing the oxide solid electrolyte with carboxymethyl cellulose.

[0032] Here, S11 and S13 are included in the preparation process of the dry mixture, and the order of S11, S12, and S13 in step S1 can be S11→S13→S12, or S13→S11→S12, or (S11+S13)→S12.

[0033] As an example, the first grinding and mixing process can be carried out at room temperature without additional temperature conditions, which is simple and convenient and helps to reduce production costs. The grinding method of the first grinding and mixing process can be manual grinding or machine grinding.

[0034] Specifically, the process of preparing the ceramic electrolyte film by the dry forming process further comprises:

[0035] S2, the first mixture is subjected to a second grinding mixing treatment with polytetrafluoroethylene to obtain a sheet-shaped mixture.

[0036] The PTFE is used as the binder in the embodiments of the present application because the PTFE can be fibrillated to form PTFE fibers by grinding treatment in the absence of organic solvents, in which the PTFE fibers collide and rub against the grinding medium (such as grinding balls or blades) to generate shear force, and the PTFE fibers can wrap and package other particulate matters in the first mixture to achieve film formation. Although the material has been preliminarily bonded to form a film sheet at this stage, the film sheet is mainly in a dispersed state and it is difficult to form a continuous large-area film layer, i.e., the obtained material is a sheet-shaped mixture.

[0037] Generally, the composition of the sheet-shaped mixture determines the composition of the final ceramic electrolyte film. The content of the PTFE in the sheet-shaped mixture will affect the mechanical properties and ionic conductivity of the ceramic electrolyte film. If the content of the PTFE in the sheet-shaped mixture is too high, it is not conducive to the transmission of ions in the ceramic electrolyte film, and if the content of the PTFE in the sheet-shaped mixture is too low, the mechanical strength of the ceramic electrolyte film will decrease, and even the film formation will be impossible. Based on the total mass of the sheet-shaped mixture, the content of the PTFE is 0.49wt% to 5.03wt%. Within this range, the ceramic electrolyte film can be well formed and has better mechanical strength and ionic conductivity. As an example, the content of the PTFE is 0.49wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt% or 5.03wt%. In addition, if the content of the PTFE in the sheet-shaped mixture is too high, it is easy to cause side reactions after the ceramic electrolyte film is assembled into a solid-state battery, resulting in a decrease in the cycle performance of the solid-state battery.

[0038] In some embodiments, based on the total mass of the sheet-shaped mixture, the content of the oxide solid-state electrolyte is 80wt% to 92wt%. Generally, the mechanical strength and ionic conductivity of the ceramic electrolyte film increase with the increase of the content of the oxide solid-state electrolyte, but the content of the oxide solid-state electrolyte is too large, which leads to the decrease of the content of other components, and the final result is the deterioration of the performance of the ceramic electrolyte film. As an example, the content of the oxide solid-state electrolyte is 80wt%, 82wt%, 84wt%, 86wt%, 88wt%, 90wt% or 92wt%.

[0039] In some embodiments, the first additive is present in an amount of 2.29 wt% to 5.71 wt% and the second additive is present in an amount of 1.71 wt% to 4.29 wt%, based on the total weight of the sheet-shaped mixture. The first additive and the second additive are mainly used to improve the ionic conductivity of the ceramic electrolyte membrane. For example, the first additive is present in an amount of 2.29 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt% or 5.71 wt%; and the second additive is present in an amount of 1.71 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt% or 4.29 wt%.

[0040] In some embodiments, the carboxymethyl cellulose is present in an amount of 2.86 wt% to 7.14 wt%, based on the total weight of the sheet-shaped mixture. The carboxymethyl cellulose is mainly used to assist film formation and improve the ductility of the membrane during subsequent rolling treatment. For example, the carboxymethyl cellulose is present in an amount of 2.86 wt%, 3.0 wt%, 4.0 wt%, 5.0 wt%, 6.0 wt%, 7.0 wt% or 7.14 wt%.

[0041] For example, the second grinding and mixing treatment can be performed at room temperature without additional temperature conditions, which is simple and convenient and helps to reduce production costs. The grinding method of the second grinding and mixing treatment can be manual grinding or machine grinding.

[0042] Specifically, the process for preparing the ceramic electrolyte membrane by the dry forming process further comprises:

[0043] S3, performing a rolling treatment on the sheet-shaped mixture to obtain a ceramic electrolyte membrane.

[0044] The purpose of the rolling treatment is to make the sheet-shaped mixture form a continuous film layer with a larger area, i.e., the ceramic electrolyte membrane. In addition, the rolling treatment can also improve the density of the ceramic electrolyte membrane and effectively form a continuous lithium ion transmission channel. Optionally, the temperature of the rolling treatment is 50°C to 100°C. At this temperature, the polytetrafluoroethylene is appropriately softened, which helps to improve the ductility of the sheet-shaped mixture and helps to form a large-area ceramic electrolyte membrane. For example, the temperature of the rolling treatment is 50°C, 60°C, 70°C, 80°C, 90°C or 100°C.

[0045] As an example, the roll-pressing process of the sheet-shaped mixture includes passing the sheet-shaped mixture through a gap between two hot pressing rollers and shaping, and the gap width between the two hot pressing rollers is 20-40 μm. It can be understood that the gap width between the two hot pressing rollers affects the thickness of the obtained ceramic electrolyte film. When the gap width between the two hot pressing rollers is 20-40 μm, the thickness of the prepared ceramic electrolyte film is 20-40 μm. As an example, the thickness of the ceramic electrolyte film is 20 μm, 25 μm, 30 μm, 35 μm or 40 μm. Alternatively, the roll-pressing process includes vertical roll-pressing process and horizontal roll-pressing process, and the roll-pressing pressure of the vertical roll-pressing process is 15-40 t, and the roll-pressing pressure of the horizontal roll-pressing process is 15-40 t.

[0046] The solid-state electrolyte film provided by the embodiments of the present application includes a ceramic electrolyte film, and the ceramic electrolyte film is prepared by using a dry forming process in the preparation method of the solid-state electrolyte film, which is conducive to guaranteeing the density of the ceramic electrolyte film. Specifically, the ceramic electrolyte film is obtained by roll-pressing after grinding and mixing the oxide solid-state electrolyte, the additive and the polytetrafluoroethylene, wherein the additive is used to improve the ionic conductivity of the ceramic electrolyte film, and the polytetrafluoroethylene is used as a binder. By controlling the content of the polytetrafluoroethylene in the total material to be 0.49-5.03 wt%, the film formation can be ensured, and the mechanical strength of the ceramic electrolyte film can be improved. More specifically, the oxide solid-state electrolyte and the additive are subjected to a first grinding and mixing process to form a first mixture, and then the first mixture and the polytetrafluoroethylene are subjected to a second grinding and mixing process to form a sheet-shaped mixture, and finally the sheet-shaped mixture is roll-pressed to form the ceramic electrolyte film. The first grinding and mixing process is used to promote the uniform mixing of the oxide solid-state electrolyte and the additive to improve the dispersion effect of the additive, and the second grinding and mixing process is used to promote the fiberization of the polytetrafluoroethylene to realize film formation. The first grinding and mixing process and the second grinding and mixing process are independent of each other, which reduces the adverse effect of the fiberization of the polytetrafluoroethylene on the dispersion effect of the additive, effectively improves the homogenization of the material, so that the material can form a continuous lithium ion transmission channel after being densified by the roll-pressing process, which is conducive to improving the ionic conductivity of the ceramic electrolyte film, and further improving the ionic conductivity of the solid-state electrolyte film.

[0047] In addition, in some embodiments, the preparation method of the solid-state electrolyte film further includes: preparing a polymer electrolyte film, and combining the polymer electrolyte film with the ceramic electrolyte film. That is, the solid-state electrolyte film further includes a polymer electrolyte film, and the polymer electrolyte film is located on one side surface of the ceramic electrolyte film.

[0048] Optionally, the polymer electrolyte film is prepared by a wet forming process, and the polymer electrolyte film is located on one side surface of the ceramic electrolyte film to obtain the solid-state electrolyte film. Here, the ceramic electrolyte film and the polymer electrolyte film can be prepared respectively and then stacked together, or the ceramic electrolyte film can be prepared first and then the polymer electrolyte film is generated on one side surface of the ceramic electrolyte film.

[0049] For example, a polymer, a lithium salt and an organic solvent are mixed to form a slurry, the slurry is coated on one side surface of the ceramic electrolyte film, and the polymer electrolyte film is formed after the slurry is solidified, thereby obtaining the solid-state electrolyte film.

[0050] When the above solid-state electrolyte film is applied to a solid-state battery, the polymer electrolyte film can correspond to the negative electrode of the solid-state battery. Compared with the ceramic electrolyte film, the polymer electrolyte film has good flexibility and can effectively construct a stable negative electrode-electrolyte interface. The ceramic electrolyte film corresponds to the positive electrode of the solid-state battery. Since the ceramic electrolyte film has a high voltage window, it can effectively alleviate the deterioration of the positive electrode interface under high voltage of the positive electrode. Therefore, the solid-state electrolyte film formed by combining the polymer electrolyte film and the ceramic electrolyte film helps to improve the cycle stability of the solid-state battery.

[0051] In a second aspect, the embodiments of the present application also provide a solid-state electrolyte film, which comprises a ceramic electrolyte film, the ceramic electrolyte film comprising an oxide solid-state electrolyte, an additive and polytetrafluoroethylene, the additive comprising at least one of a first additive and a second additive, the first additive comprising at least one of polyvinylidene fluoride and a copolymer of polyvinylidene fluoride, and the second additive comprising a lithium salt and an ionic liquid, and the content of the polytetrafluoroethylene is 0.49wt% to 5.03wt% based on the total mass of the ceramic electrolyte film.

[0052] It should be noted that the solid-state electrolyte film can be a single-layer film structure comprising only the ceramic electrolyte film, or a multi-layer film structure comprising multiple ceramic electrolyte films, or a composite film structure comprising the ceramic electrolyte film and the polymer electrolyte film, which is not limited herein.

[0053] Specifically, compared with the polymer electrolyte, the oxide solid-state electrolyte has higher ionic conductivity, wider electrochemical stability window, good thermal stability, chemical stability and mechanical strength, which is beneficial to improving the performance of the ceramic electrolyte film. Optionally, the oxide solid-state electrolyte comprises at least one of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium gallium oxide (LLZGO) and lithium lanthanum zirconium tantalum oxide (LLZTO). The LLZO is a garnet type and has a chemical formula of Li7La3Zr2O12. 12 The LLZGO is LLZO doped with Ga elements, and the LLZTO is LLZO doped with Ta elements.

[0054] The above-mentioned additive mainly refers to an additive for improving the ionic conductivity of the ceramic electrolyte membrane. In detail, the additive is dispersed in the oxide solid electrolyte, and the additive includes at least one of a first additive and a second additive. Exemplarily, the additive includes the first additive, or the additive includes the second additive, or the additive includes the first additive and the second additive. Among them, the first additive includes at least one of polyvinylidene fluoride and a copolymer of polyvinylidene fluoride. Polyvinylidene fluoride (PVDF) and the copolymer of polyvinylidene fluoride have a relatively high dielectric constant, which is conducive to enhancing the ion transport property of the ceramic electrolyte membrane. As an example, the copolymer of polyvinylidene fluoride includes polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The second additive includes a lithium salt and an ionic liquid (abbreviated as lithium salt + ionic liquid), the lithium salt can increase the lithium salt content in the ceramic electrolyte membrane, so that the ceramic electrolyte membrane has higher ionic conductivity, and the ionic liquid itself has relatively high ionic conductivity, which can also improve the ionic conductivity of the ceramic electrolyte membrane. As an example, the lithium salt includes at least one of lithium bis(trifluoromethyl) sulfonylimide (LiTFSI), lithium bis(fluorosulfonyl) imide (LiFSI), lithium bis(perfluoroethylsulfonyl) imide (LIBETI) and lithium bis(oxalate) borate (LiBOB). As an example, the ionic liquid is a pyrrole ionic liquid, for example, N-propyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl) imide salt ionic liquid. Optionally, in the second additive, the mass ratio of the lithium salt to the ionic liquid is (1.5-2.5):1. For example, the mass ratio of the lithium salt to the ionic liquid is 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1.

[0055] In the embodiments of the present application, polytetrafluoroethylene (PTFE) is a binder. Generally, in the ceramic electrolyte membrane, the content of polytetrafluoroethylene should not be too high, otherwise it is not conducive to the transmission of ions in the ceramic electrolyte membrane, and the content of polytetrafluoroethylene should not be too low, otherwise the mechanical strength of the ceramic electrolyte membrane will decrease, and even the film cannot be formed. In the embodiments of the present application, the content of polytetrafluoroethylene is 0.49wt%-5.03wt% based on the total mass of the ceramic electrolyte membrane. Within this range, the ceramic electrolyte membrane can be well formed and has better mechanical strength and ionic conductivity. As an example, the content of polytetrafluoroethylene is 0.49wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt% or 5.03wt%. In addition, if the content of polytetrafluoroethylene in the ceramic electrolyte membrane is too high, it is easy to cause side reactions after the ceramic electrolyte membrane is assembled into a solid-state battery, resulting in a decrease in the cycle performance of the solid-state battery.

[0056] In some embodiments, the content of the oxide solid state electrolyte is 80wt% to 92wt% based on the total mass of the ceramic electrolyte film. Generally, the mechanical strength and ionic conductivity of the ceramic electrolyte film increase as the content of the oxide solid state electrolyte increases, but the content of the oxide solid state electrolyte is too large to result in the decrease of the content of other components, and finally the performance of the ceramic electrolyte film deteriorates. As an example, the content of the oxide solid state electrolyte is 80wt%, 82wt%, 84wt%, 86wt%, 88wt%, 90wt% or 92wt%.

[0057] In some embodiments, the content of the first additive is 2.29wt% to 5.71wt% and the content of the second additive is 1.71wt% to 4.29wt% based on the total mass of the ceramic electrolyte film. The first additive and the second additive are mainly used to improve the ionic conductivity of the ceramic electrolyte film. As an example, the content of the first additive is 2.29wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt% or 5.71wt%; the content of the second additive is 1.71wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt% or 4.29wt%.

[0058] In some embodiments, the content of the carboxymethyl cellulose is 2.86wt% to 7.14wt% based on the total mass of the ceramic electrolyte film. The carboxymethyl cellulose is mainly used to assist film formation and improve the ductility of the film material in the subsequent rolling process. As an example, the content of the carboxymethyl cellulose is 2.86wt%, 3.0wt%, 4.0wt%, 5.0wt%, 6.0wt%, 7.0wt% or 7.14wt%.

[0059] In some embodiments, the thickness of the ceramic electrolyte film is 20μm to 40μm. As an example, the thickness of the ceramic electrolyte film is 20μm, 25μm, 30μm, 35μm or 40μm.

[0060] In some embodiments, the solid-state electrolyte film further comprises a polymer electrolyte film, the polymer electrolyte film is located on one side surface of the ceramic electrolyte film. When the above solid-state electrolyte film is applied to a solid-state battery, the polymer electrolyte film can be corresponded to the negative electrode of the solid-state battery, compared with the ceramic electrolyte film, the polymer electrolyte film has good flexibility, and can effectively construct a stable negative electrode-electrolyte interface, and the ceramic electrolyte film is corresponded to the positive electrode of the solid-state battery, because the voltage window of the ceramic electrolyte film is high, the ceramic electrolyte film can effectively alleviate the deterioration of the positive electrode interface under high voltage of the positive electrode. Therefore, the solid-state electrolyte film formed by the combination of the polymer electrolyte film and the ceramic electrolyte film helps to improve the cycle stability of the solid-state battery. Optionally, the thickness of the polymer electrolyte film is 10 μm to 20 μm. As an example, the thickness of the polymer electrolyte film is 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm.

[0061] The solid-state electrolyte film provided by the embodiments of the present application comprises a ceramic electrolyte film, the ceramic electrolyte film comprises an oxide solid-state electrolyte, an additive and polytetrafluoroethylene, wherein the additive comprises at least one of a lithium salt + an ionic liquid, a polyvinylidene fluoride and a copolymer of polyvinylidene fluoride, the additive is dispersed in the oxide solid-state electrolyte, can effectively construct an ion transmission channel, and improve the ionic conductivity of the ceramic electrolyte film; the polytetrafluoroethylene serves as a binder, by controlling the content of the polytetrafluoroethylene in the total material to be 0.49 wt% to 5.03 wt%, not only the film formation can be ensured, but also the mechanical strength of the ceramic electrolyte film can be improved.

[0062] In a third aspect, the embodiments of the present application further provide a full solid-state battery, comprising a positive electrode, a negative electrode and a solid-state electrolyte film, the solid-state electrolyte film is located between the positive electrode and the negative electrode, and the solid-state electrolyte film is the above solid-state electrolyte film.

[0063] The above solid-state electrolyte film has better ionic conductivity and mechanical strength, which is beneficial to improving the performance of the full solid-state battery.

[0064] The specific embodiments will be described in detail below.

[0065] Embodiment 1

[0066] The ceramic electrolyte film is prepared by a dry forming process, comprising:

[0067] In 0.56 g of LLZGO (content of 80 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 7.14 wt%) is added, and after grinding and mixing uniformly, 0.04 g of PVDF (polyvinylidene fluoride) (content of 5.71 wt%) is added, and after grinding and mixing uniformly, 0.03 g of LiTFSI-IL mixed solution (prepared by stirring uniformly N-propyl-N-methyl pyrrolidine bis(trifluoromethane sulfonate) imidate ionic liquid and LiTFSI in a ratio of 2:1) (content of 4.29 wt%) is added, and after grinding and mixing uniformly, 0.02 g of PTFE (content of 2.86 wt%) is added, and after grinding and mixing sufficiently, it is fiberized to obtain a sheet-shaped mixture; and the sheet-shaped mixture is rolled in a rolling machine at 70°C to obtain a ceramic electrolyte film.

[0068] Example 2

[0069] A ceramic electrolyte film is prepared by a dry forming process, including:

[0070] In 0.9 g of LLZGO (content of 86.54 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 4.81 wt%) is added, and after grinding and mixing uniformly, 0.04 g of PVDF (polyvinylidene fluoride) (content of 3.85 wt%) is added, and after grinding and mixing uniformly, 0.03 g of LiTFSI-IL mixed solution (prepared by stirring uniformly N-propyl-N-methyl pyrrolidine bis(trifluoromethane sulfonate) imidate ionic liquid and LiTFSI in a ratio of 2:1) (content of 2.88 wt%) is added, and after grinding and mixing uniformly, 0.02 g of PTFE (content of 1.92 wt%) is added, and after grinding and mixing sufficiently, it is fiberized to obtain a sheet-shaped mixture; and the sheet-shaped mixture is rolled in a rolling machine at 70°C to obtain a ceramic electrolyte film.

[0071] Example 3

[0072] A ceramic electrolyte film is prepared by a dry forming process, including:

[0073] In 1.61 g of LLZGO (content 92 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content 2.86 wt%) is added, and after grinding and mixing uniformly, 0.04 g of PVDF (polyvinylidene fluoride) (content 2.29 wt%) is added, and after grinding and mixing uniformly, 0.03 g of LiTFSI-IL mixed solution (prepared by stirring uniformly N-propyl-N-methyl pyrrolidine bis(trifluoromethane sulfonate) imidate ionic liquid and LiTFSI in a ratio of 2:1) (content 1.71 wt%) is added, and after grinding and mixing uniformly, 0.02 g of PTFE (content 1.14 wt%) is added, and after grinding and mixing sufficiently, it is fiberized to obtain a sheet-shaped mixture; the sheet-shaped mixture is rolled in a rolling machine at 70°C to obtain a ceramic electrolyte film.

[0074] Example 4

[0075] A ceramic electrolyte film is prepared by a dry forming process, including:

[0076] In 0.9 g of LLZGO (content 83.8 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content 4.66 wt%) is added, and after grinding and mixing uniformly, 0.04 g of PVDF (polyvinylidene fluoride) (content 3.72 wt%) is added, and after grinding and mixing uniformly, 0.03 g of LiTFSI-IL mixed solution (prepared by stirring uniformly N-propyl-N-methyl pyrrolidine bis(trifluoromethane sulfonate) imidate ionic liquid and LiTFSI in a ratio of 2:1) (content 2.79 wt%) is added, and after grinding and mixing uniformly, 0.054 g of PTFE (content 5.03 wt%) is added, and after grinding and mixing sufficiently, it is fiberized to obtain a sheet-shaped mixture; the sheet-shaped mixture is rolled in a rolling machine at 70°C to obtain a ceramic electrolyte film.

[0077] Example 5

[0078] A ceramic electrolyte film is prepared by a dry forming process, including:

[0079] In 0.9 g of LLZGO (content of 87.8 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 4.88 wt%) is added, and after grinding and mixing uniformly, 0.04 g of PVDF (polyvinylidene fluoride) (content of 3.9 wt%) is added, and after grinding and mixing uniformly, 0.03 g of LiTFSI-IL mixed solution (prepared by stirring uniformly N-propyl-N-methyl pyrrolidine bis(trifluoromethane sulfonate) imidate ionic liquid and LiTFSI in a ratio of 2:1) (content of 2.93 wt%) is added, and after grinding and mixing uniformly, 0.005 g of PTFE (content of 0.49 wt%) is added, and after grinding and mixing sufficiently, it is fiberized to obtain a sheet-shaped mixture; and the sheet-shaped mixture is rolled in a rolling machine at 70°C to obtain a ceramic electrolyte film.

[0080] Example 6

[0081] A ceramic electrolyte film is prepared by a dry forming process, including:

[0082] In 0.9 g of LLZGO (content of 90 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 5 wt%) is added, and after grinding and mixing uniformly, 0.03 g of LiTFSI-IL mixed solution (prepared by stirring uniformly N-propyl-N-methyl pyrrolidine bis(trifluoromethane sulfonate) imidate ionic liquid and LiTFSI in a ratio of 2:1) (content of 3 wt%) is added, and after grinding and mixing uniformly, 0.02 g of PTFE (content of 2 wt%) is added, and after grinding and mixing sufficiently, it is fiberized to obtain a sheet-shaped mixture; and the sheet-shaped mixture is rolled in a rolling machine at 70°C to obtain a ceramic electrolyte film.

[0083] Example 7

[0084] A ceramic electrolyte film is prepared by a dry forming process, including:

[0085] In 0.9 g of LLZGO (content of 90 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 5 wt%) is added, and after grinding and mixing uniformly, 0.03 g of LiTFSI-IL mixed solution (prepared by stirring uniformly N-propyl-N-methyl pyrrolidine bis(trifluoromethane sulfonate) imidate ionic liquid and LiTFSI in a ratio of 2:1) (content of 3 wt%) is added, and after grinding and mixing uniformly, 0.02 g of PTFE (content of 2 wt%) is added, and after grinding and mixing sufficiently, it is fiberized to obtain a sheet-shaped mixture; and the sheet-shaped mixture is rolled in a rolling machine at 70°C to obtain a ceramic electrolyte film.

[0086] Example 8

[0087] A ceramic electrolyte film is prepared by a dry forming process, including:

[0088] In 0.9 g of LLZGO (content of 86.54 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 4.81 wt%), 0.04 g of PVDF (polyvinylidene fluoride) (content of 3.85 wt%), 0.03 g of LiTFSI-IL mixed solution (prepared by stirring N-propyl-N-methyl pyrrolidine bis(trifluoromethanesulfonyl) imide salt ionic liquid and LiTFSI in a ratio of 2:1) (content of 2.88 wt%) and 0.02 g of PTFE (content of 1.92 wt%) were added, and the mixture was thoroughly ground to obtain a mixed material. The mixed material was rolled in a roller press at 70°C to obtain a ceramic electrolyte film.

[0089] Comparative Example 1

[0090] A ceramic electrolyte film was prepared by a dry forming process, including:

[0091] In 0.9 g of LLZGO (content of 86.54 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 4.81 wt%), 0.04 g of PVDF (polyvinylidene fluoride) (content of 3.85 wt%), 0.03 g of LiTFSI-IL mixed solution (prepared by stirring N-propyl-N-methyl pyrrolidine bis(trifluoromethanesulfonyl) imide salt ionic liquid and LiTFSI in a ratio of 2:1) (content of 2.88 wt%) and 0.02 g of PTFE (content of 1.92 wt%) were added, and the mixture was thoroughly ground to obtain a mixed material. The mixed material was rolled in a roller press at 70°C to obtain a ceramic electrolyte film.

[0092] Comparative Example 2

[0093] A ceramic electrolyte film was prepared by a dry forming process, including:

[0094] In 0.9 g of LLZGO (content of 86.54 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 4.81 wt%), 0.04 g of PVDF (polyvinylidene fluoride) (content of 3.85 wt%), 0.03 g of LiTFSI-IL mixed solution (prepared by stirring N-propyl-N-methyl pyrrolidine bis(trifluoromethanesulfonyl) imide salt ionic liquid and LiTFSI in a ratio of 2:1) (content of 2.88 wt%) and 0.02 g of PTFE (content of 1.92 wt%) were added, and the mixture was thoroughly ground to obtain a mixed material. The mixed material was rolled in a roller press at 70°C to obtain a ceramic electrolyte film.

[0095] Comparative Example 3

[0096] A ceramic electrolyte film was prepared by a dry forming process, including:

[0097] In 0.9 g of LLZGO (content of 87.89 wt%) powder, 0.05 g of CMC (carboxymethyl cellulose) (content of 4.88 wt%) was added, and after grinding and mixing uniformly, 0.04 g of PVDF (polyvinylidene fluoride) (content of 3.91 wt%) was added, and after grinding and mixing uniformly, 0.03 g of LiTFSI-IL mixed solution (prepared by stirring uniformly N-propyl-N-methyl pyrrolidine bis(trifluoromethane sulfonate) imide salt ionic liquid and LiTFSI in a ratio of 2:1) (content of 2.93 wt%) was added, and after grinding and mixing uniformly, 0.004 g of PTFE (content of 0.39 wt%) was added, and after grinding and mixing thoroughly, since the content of PTFE was too small, a sheet-shaped mixture could not be obtained.

[0098] The mass and mass percentage of each material in the above examples 1 to 8 and comparative examples 1 to 3 are shown in Table 1:

[0099] Table 1

[0100] The ceramic electrolyte films provided by examples 1 to 8 and comparative examples 1 to 2 were characterized as follows:

[0101] 1. Ion conductivity test:

[0102] The ceramic electrolyte films prepared by examples 1 to 8 and comparative examples 1 to 2 were subjected to ion conductivity test, and the specific test method was as follows: the impedance of the solid-state electrolyte was tested by an electrochemical workstation. Pt was sputtered on the surface of the solid-state electrolyte, and electrochemical impedance spectroscopy (EIS) was used for testing, and the frequency range was 105 Hz to 0.1 Hz. The ion conductivity was calculated by the formula: σ = L / RA, wherein L represents the thickness of the electrolyte, R represents the impedance, and A represents the effective contact area. The test results are shown in Table 2.

[0103] 2. Electrochemical window test:

[0104] The ceramic electrolyte films prepared by examples 1 to 8 and comparative examples 1 to 2 were subjected to electrochemical window test, and the specific test method was as follows: the solid-state electrolyte was sandwiched between a steel sheet and a lithium foil, and linear voltammetry scanning method (LSV) was used for testing, and the scanning voltage range was 2.0 V to 6.0 V, and the scanning rate was 1 mVs -1 . The results are shown in Table 2.

[0105] 3. Cycle performance test:

[0106] First, the solid-state battery was prepared according to the following steps:

[0107] (1) Preparation of positive electrode sheet: mix nickel cobalt manganese lithium (NCM) powder, super P and PVDF in a mass ratio of 8:1:1 in NMP solvent, magnetically stir uniformly to obtain positive electrode slurry. The NCM positive electrode slurry is uniformly scraped on the aluminum foil current collector by the method of flow coating, and then vacuum dried at 110°C for 48h. In order to facilitate the assembly of the battery, the prepared positive electrode sheet is cut into a circular sheet with a diameter of 12mm. The active material loading of the NCM positive electrode is 11.5mg cm -2 .

[0108] (2) Preparation of negative electrode sheet: after purchasing lithium sheet, cut into a circular sheet with a diameter of 12mm

[0109] (3) Battery assembly: CR2032 type battery shell is used to assemble the button cell in this study, and the aluminum plastic film after punching is used to assemble the soft package battery. The battery assembly is carried out in an argon-filled glove box, and the button cell assembly sequence is: positive electrode shell, positive electrode sheet, solid electrolyte, lithium foil, steel sheet, spring sheet, negative electrode shell. After completing the battery assembly, the button cell packaging machine is used for packaging. The electrolyte is sandwiched between the positive electrode sheet and the lithium strip, and the aluminum tab and the nickel tab are attached to the positive and negative electrodes respectively, and then the electrolyte is packaged in the aluminum plastic film after punching, and the vacuum packaging machine is used to complete the packaging.

[0110] The ceramic electrolyte membranes prepared in Examples 1 to 8 and Comparative Examples 1 to 2 are respectively prepared into solid-state batteries according to the above method of preparing solid-state batteries. The corresponding solid-state batteries are subjected to cycle performance test, and the specific test method is as follows: the solid-state battery is set to charge and discharge cut-off voltage of 3.0V-4.2V and charge and discharge rate of 0.33C / 1C at 26°C, and the cycle number when the capacity retention rate reaches 80% is counted, and the results are recorded in Table 2.

[0111] 4. Tensile strength test:

[0112] The ceramic electrolyte membranes prepared in Examples 1 to 8 and Comparative Examples 1 to 2 are subjected to tensile strength test, and the specific test method is as follows: the national standard for tensile test of plastic film is GB 13022-91, and the sample is placed in an environment with temperature of 23°C and humidity of 50% for 24 hours before test, and the tensile rate is 50mm / min, and the results are recorded in Table 2.

[0113] Table 2

[0114] 5. Scanning electron microscope test:

[0115] The ceramic electrolyte film prepared from Example 2 and Comparative Example 1 was taken photos by scanning electron microscope. As shown in Figure 2, the scanning electron microscope image of the ceramic electrolyte film of Example 2 of the present application, it can be seen from Figure 2 that there are less large particle materials in the film layer, and there are also less holes in the film layer, and the film layer has better compactness. As shown in Figure 3, the scanning electron microscope image of the ceramic electrolyte film of Comparative Example 1 of the present application, it can be seen from Figure 3 that there are more large particle materials in the film layer, and there are also more holes in the film layer, and the film layer has poorer compactness.

[0116] By analyzing Table 1 and Table 2, it can be seen from the comparison of Example 1 to Example 3 that, under the condition that the mass of other materials remains unchanged, by increasing the mass of LLZGO (0.56 g, 0.9 g, 1.61 g respectively), the mass percentage of LLZGO in the ceramic electrolyte film increases (80wt%, 86.54wt%, 92wt% respectively), and the ionic conductivity, electrochemical window, cycle number and tensile strength of the ceramic electrolyte film all increase first and then decrease, wherein the performance of the ceramic electrolyte film provided by Example 2 reaches the best. This is because LLZGO itself has a wider electrochemical window, better ionic conductivity and mechanical strength, and within a certain range, increasing the content of LLZGO can promote the improvement of the performance of the ceramic electrolyte film, but too large content of LLZGO will lead to the decrease of the content of other materials in the ceramic electrolyte film, and thus lead to the decrease of the performance of the ceramic electrolyte film. This shows that the performance of the ceramic electrolyte film is the result of the comprehensive action of each component.

[0117] As can be seen by comparing Comparative Example 3, Example 5, Example 2, Example 4 and Comparative Example 2, when the mass of other materials remains unchanged, by increasing the mass of PTFE (0.004 g, 0.005 g, 0.02 g, 0.054 g, 0.065 g, respectively), the mass percentage content of PTFE is increased (0.39 wt%, 0.49 wt%, 1.92 wt%, 5.03 wt%, 5.99 wt%, respectively), and ceramic electrolyte membranes can be formed except that Comparative Example 3 cannot form a film due to the excessively low content of PTFE. Further comparison shows that, in terms of mechanical strength, as the mass percentage content of PTFE increases, the tensile strength of the ceramic electrolyte membrane gradually increases, because the cohesion of the ceramic electrolyte membrane increases as the content of PTFE increases, thereby improving the mechanical strength of the ceramic electrolyte membrane. In terms of ionic conductivity, as the mass percentage content of PTFE decreases, the ionic conductivity of the ceramic electrolyte membrane first increases and then decreases, because as the content of PTFE decreases, the contents of LLZGO, PVDF and LiTFSI-IL increase, thereby improving the ionic conductivity of the ceramic electrolyte membrane; the ionic conductivity of the ceramic electrolyte membrane in Example 5 decreases because the mass percentage content of PTFE is too low, the cohesion of the ceramic electrolyte membrane is insufficient, and the particles are not tightly combined, which affects the ion transmission channel in the ceramic electrolyte membrane, and the ionic conductivity of the ceramic electrolyte membrane decreases instead. In terms of electrochemical window, as the mass percentage content of PTFE increases, the electrochemical window of the ceramic electrolyte membrane first increases and then decreases, but the values are relatively close overall and do not change much, because the electrochemical window of the ceramic electrolyte membrane is mainly affected by the main material LLZGO, and since the content of LLZGO in each ceramic electrolyte membrane does not differ much, the electrochemical window does not change significantly. In addition, in terms of cycle performance, as the mass percentage content of PTFE increases, the cycle number of the ceramic electrolyte membrane first increases and then decreases, because the mechanical strength of the ceramic electrolyte membrane increases as the mass percentage content of PTFE increases, and the cycle number of the ceramic electrolyte membrane increases, but an excessively high mass percentage content of PTFE will increase the side reactions in the solid-state battery, thereby reducing the cycle performance of the solid-state battery.

[0118] As can be seen by comparing Comparative Example 2 and Example 6, the difference between the two is that Example 6 does not contain CMC, and it is found that the ionic conductivity of the ceramic electrolyte membrane in Example 6 decreases slightly, but the tensile strength and cycle number of the ceramic electrolyte membrane decrease significantly, because CMC can improve the ductility of the film material during the preparation of the ceramic electrolyte membrane, and ultimately improve the film formation quality of the ceramic electrolyte membrane.

[0119] Comparing Example 2 and Example 7, the difference between them is that Example 7 does not contain PVDF. It is found that the ionic conductivity, mechanical strength and cycle number of the ceramic electrolyte membrane in Example 7 are all decreased.

[0120] Comparing Example 2 and Example 8, the difference between them is that Example 8 does not contain LiTFSI-IL. It is found that the ionic conductivity of the ceramic electrolyte membrane in Example 8 is significantly decreased, which shows that LiTFSI-IL has a significant promoting effect on the ionic conductivity of the ceramic electrolyte membrane. In addition, the mechanical strength and cycle number of the ceramic electrolyte membrane in Example 8 are also decreased, because the ionic liquid can provide more ions for migration in the electrolyte system, and the lack of ions will affect the cycle performance of the system when the ionic liquid is not added; at the same time, the ionic liquid also has the effect of wetting the system, and the lack of ionic liquid leads to the dryness of the whole system, and the strength is reduced.

[0121] Comparing Example 2 and Comparative Example 1, the difference between them is only the difference in preparation process, wherein Example 2 is to add CMC, PVDF and LiTFSI to LLZGO in batches and grind and mix, and finally add PTFE and grind and mix, and Comparative Example 1 is to add CMC, PVDF, LiTFSI and PTFE to LLZGO at one time and grind and mix. It is found that the ionic conductivity, mechanical strength and cycle number of the ceramic electrolyte membrane in Example 2 are all significantly higher than those of the ceramic electrolyte membrane in Comparative Example 1. Combined with FIG. 2 and FIG. 3, it can be seen that the uniformity and compactness of the ceramic electrolyte membrane obtained in Example 2 are better. This is because in the preparation process of Comparative Example 1, LLZGO, CMC, PVDF, LiTFSI and PTFE are mixed together and then ground together, and in the grinding process, PTFE will be fibrous, so that other materials are bonded together without being fully refined and dispersed, thereby causing the ionic conductivity and mechanical strength of the ceramic electrolyte membrane to be decreased, and further causing the cycle performance to be decreased.

Claims

1. A method for preparing a solid electrolyte membrane, comprising: The oxide solid electrolyte and the additives are subjected to a first grinding and mixing process to obtain a first mixture. The additives include at least one of a first additive and a second additive. The first additive includes at least one of polyvinylidene fluoride and its copolymers. The second additive includes lithium salt and ionic liquid. The first mixture is subjected to a second grinding and mixing treatment with polytetrafluoroethylene to obtain a sheet-like mixture. Based on the total mass of the sheet-like mixture, the content of polytetrafluoroethylene is 0.49 wt% to 5.03 wt%. The sheet-like mixture is subjected to roll pressing to obtain a ceramic electrolyte membrane, wherein the solid electrolyte membrane includes the ceramic electrolyte membrane.

2. The method for preparing a solid electrolyte membrane according to claim 1, wherein, The additive includes the first additive and the second additive, and the first grinding and mixing process of the oxide solid electrolyte and the additive to obtain the first mixture includes: The oxide solid electrolyte and the first additive are ground and mixed to obtain a dry mixture; The dry mixture is ground and mixed with the second additive to obtain the first mixture.

3. The method for preparing a solid electrolyte membrane according to claim 2, wherein, The preparation process of the dry mixture also includes: The oxide solid electrolyte and carboxymethyl cellulose are ground and mixed.

4. The method for preparing a solid electrolyte membrane according to claim 3, wherein, Based on the total mass of the flake mixture, the content of the oxide solid electrolyte is 80wt% to 92wt%, the content of the first additive is 2.29wt% to 5.71wt%, the content of the second additive is 1.71wt% to 4.29wt%, and the content of the carboxymethyl cellulose is 2.86wt% to 7.14wt%.

5. The method for preparing a solid electrolyte membrane according to claim 1, wherein, In the second additive, the lithium salt includes lithium bis(trifluoromethyl)sulfonylimide, and the ionic liquid includes N-propyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, wherein the mass ratio of lithium bis(trifluoromethyl)sulfonylimide to N-propyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt is (1.5-2.5):

1.

6. The method for preparing a solid electrolyte membrane according to claim 1, wherein, The oxide solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum zirconium gallium oxide, and lithium lanthanum zirconium tantalum oxide.

7. The method for preparing a solid electrolyte membrane according to claim 1, wherein, The rolling process is carried out at a temperature of 50℃ to 100℃.

8. The method for preparing a solid electrolyte membrane according to claim 1, wherein, The rolling pressure of the rolling process is 15t to 40t.

9. The method for preparing a solid electrolyte membrane according to claim 1, wherein, The lithium salt includes at least one of lithium bis(trifluoromethyl)sulfonylimide, lithium bis(fluorosulfonyl)imide, lithium bis(perfluoroethylsulfonyl)imide, and lithium bis(oxalate)borate.

10. The method for preparing a solid electrolyte membrane according to claim 1, wherein, The rolling process of the sheet mixture includes passing the sheet mixture through the gap between two hot press rollers and forming it, wherein the gap width between the two hot press rollers is 20μm to 40μm.

11. The method for preparing a solid electrolyte membrane according to claim 1, wherein, Roll forming includes vertical roll forming and horizontal roll forming.

12. The method for preparing a solid electrolyte membrane according to any one of claims 1 to 11, wherein, The method for preparing the solid electrolyte membrane further includes preparing a polymer electrolyte membrane using a wet molding process, and then placing the polymer electrolyte membrane on one side surface of the ceramic electrolyte membrane.

13. A solid electrolyte membrane comprising a ceramic electrolyte membrane, the ceramic electrolyte membrane comprising an oxide solid electrolyte, an additive, and polytetrafluoroethylene, the additive comprising at least one of a first additive and a second additive, the first additive comprising at least one of polyvinylidene fluoride and a copolymer of polyvinylidene fluoride, the second additive comprising a lithium salt and an ionic liquid, wherein the polytetrafluoroethylene content is 0.49 wt% to 5.03 wt% based on the total mass of the ceramic electrolyte membrane.

14. The solid electrolyte membrane according to claim 13, wherein, The additives include the first additive and the second additive, and the ceramic electrolyte membrane further includes carboxymethyl cellulose. Based on the total mass of the ceramic electrolyte membrane, the content of the oxide solid electrolyte is 80 wt% to 92 wt%, the content of the first additive is 2.29 wt% to 5.71 wt%, the content of the second additive is 1.71 wt% to 4.29 wt%, and the content of the carboxymethyl cellulose is 2.86 wt% to 7.14 wt%.

15. The solid electrolyte membrane according to claim 13, wherein, In the ceramic electrolyte membrane, the lithium salt includes lithium bis(trifluoromethyl)sulfonylimide, the ionic liquid includes N-propyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, and the mass ratio of the lithium salt to the lithium bis(trifluoromethyl)sulfonylimide to the N-propyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide is (1.5-2.5):

1.

16. The solid electrolyte membrane according to claim 13, wherein, The oxide solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum zirconium gallium oxide, and lithium lanthanum zirconium tantalum oxide.

17. The solid electrolyte membrane according to claim 13, wherein, The thickness of the ceramic electrolyte membrane is 20 μm to 40 μm.

18. The solid electrolyte membrane according to claim 13, wherein, The lithium salt includes at least one of lithium bis(trifluoromethyl)sulfonylimide, lithium bis(fluorosulfonyl)imide, lithium bis(perfluoroethylsulfonyl)imide, and lithium bis(oxalate)borate.

19. The solid electrolyte membrane according to any one of claims 13 to 18, wherein, The solid electrolyte membrane further includes a polymer electrolyte membrane, which is located on one side surface of the ceramic electrolyte membrane, and the thickness of the polymer electrolyte membrane is 10 μm to 20 μm.

20. An all-solid-state battery, comprising a positive electrode, a negative electrode, and a solid electrolyte membrane, wherein the solid electrolyte membrane is located between the positive electrode and the negative electrode, and the solid electrolyte membrane is prepared by the method for preparing a solid electrolyte membrane according to any one of claims 1 to 12 or is a solid electrolyte membrane according to any one of claims 13 to 19.

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