Ceramic solid-state electrolyte film flattening method

Abstract

Disclosed in the present invention are a ceramic solid-state electrolyte film and a preparation method therefor. The preparation method comprises the following steps: (1) mixing a solid-state electrolyte blank with a fiberizable polymer, fiberizing the polymer, and uniformly mixing the fiberized polymer with the solid-state electrolyte blank; (2) carrying out hot pressing treatment on the mixture obtained in step (1) to a preset thickness to obtain a solid-state electrolyte green film; and (3) carrying out high-temperature sintering on the solid-state electrolyte green film obtained in step (2) to obtain a solid-state electrolyte film. The preparation method for the solid-state electrolyte thin film of the present invention involves simplified preparation process, and the prepared solid-state electrolyte film has high content of ceramic, compact structure and high ionic conductivity.

Description

A method for planarizing ceramic solid electrolyte films Technical Field

[0001] This invention relates to a ceramic solid electrolyte film and its preparation method, including a planarization step of the electrolyte film. The invention also relates to the application of this ceramic solid electrolyte film in solid-state batteries, and to a solid-state lithium metal battery comprising this ceramic solid electrolyte film. Background Technology

[0002] With the rapid development of renewable energy sources such as solar and wind power, the demand for energy storage is also increasing. However, traditional liquid batteries have some problems, such as limited energy density, insufficient safety, short lifespan, and long charging time. These problems become particularly prominent when addressing the modern society's demand for high-performance, sustainable, and safe energy storage.

[0003] Lithium metal batteries are considered a potential solution to the energy storage problem. Lithium metal has a higher theoretical energy density and lower voltage drop, thus enabling higher energy storage density and longer driving range. However, traditional liquid lithium metal batteries suffer from safety issues due to lithium dendrite growth and the instability of the liquid electrolyte, which limits their widespread application.

[0004] Solid-state lithium metal batteries are a novel battery technology that uses a solid electrolyte instead of a traditional liquid electrolyte. The rise of ceramic solid-state electrolyte technology has solved many problems caused by liquid electrolytes. Ceramic electrolyte materials possess characteristics such as high ionic conductivity, high temperature resistance, and chemical stability, which can prevent lithium dendrite growth and improve battery safety. Furthermore, solid-state electrolytes can achieve a wider operating temperature range, thereby improving battery performance in extreme environments.

[0005] However, ceramic electrolytes require high-temperature sintering above 1000℃ during preparation. During this process, the ceramic film is prone to deformation and bending, and uneven solid electrolyte films cannot be used for battery assembly. Therefore, improving the flatness of the electrolyte film is a key aspect of the commercial application of ceramic solid electrolytes.

[0006] Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the solid electrolyte films produced by the prior art have unevenness and the uniformity of the products needs to be improved.

[0008] To address the aforementioned technical problems, this invention provides a method for preparing a solid electrolyte film. This method adds a planarization sintering step after the densification sintering step. Through planarization heat treatment, defects in the electrolyte film can be reduced while improving its flatness. The solid electrolyte film prepared by the method of this invention has a smooth surface, dense structure, and high ionic conductivity.

[0009] The first aspect of this invention provides a method for preparing a solid electrolyte thin film, characterized in that the preparation method includes the following planarization and sintering steps:

[0010] The sintered solid electrolyte film is subjected to high-temperature sintering under mechanical pressure to obtain a planarized solid electrolyte film.

[0011] In some specific embodiments, the mechanical pressure in the leveling sintering step is in the range of 1 to 500 Pa, preferably 10 to 400 Pa, more preferably 20 to 250 Pa, and even more preferably 50 to 150 Pa.

[0012] In some specific embodiments, the thickness of the sintered solid electrolyte film is 1-600 μm, preferably 5-300 μm, and more preferably 10-200 μm. According to specific embodiments, the thickness of the sintered solid electrolyte film can be 1 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 400 μm, 500 μm, 600 μm, or any thickness within the above range.

[0013] In some specific embodiments, the planarization sintering temperature is higher than the densification sintering temperature, i.e., the sintering temperature for preparing a sintered solid electrolyte film from a solid electrolyte biofilm. Specifically, the planarization sintering temperature can be 900-1400℃, preferably 1300-1350℃. The planarization sintering temperature is related to the chemical composition of the solid electrolyte.

[0014] In some specific embodiments, the heating rate of the leveling sintering is 5 to 20°C / min, preferably 10°C / min; the holding time after reaching the leveling sintering temperature is 5 to 30 minutes, preferably 10 minutes.

[0015] In some specific embodiments, the mechanical pressure is applied during the planarization sintering step by placing a sintering plate over the sintered solid electrolyte film.

[0016] In some specific embodiments, in the planarization sintering step, the planarized solid electrolyte film is obtained by high-temperature sintering with the sintered solid electrolyte film placed between two sintering plates.

[0017] In some specific embodiments, during the planarization sintering step, the surface of the sintering plate that contacts the solid electrolyte film is a flat surface.

[0018] In some embodiments, the firing plate comprises one or more materials selected from magnesium oxide, zirconium oxide, aluminum oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, or lithium titanium aluminum phosphate. In some embodiments, the material of the firing plate is magnesium oxide or a lithium-containing material, preferably the same material as the solid electrolyte film material.

[0019] In some specific embodiments, the solid electrolyte is an oxide solid electrolyte, such as an oxide solid electrolyte selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, or lithium titanium aluminum phosphate.

[0020] In some specific embodiments, the sintered solid electrolyte film is obtained through the following steps:

[0021] (1) Mixing a solid electrolyte preform with a fibrous polymer, thereby fibrousizing the polymer and uniformly mixing it with the solid electrolyte preform;

[0022] (2) The mixture obtained in step (1) is hot-pressed to a preset thickness to obtain a solid electrolyte film;

[0023] (3) The solid electrolyte membrane obtained in step (2) is sintered at high temperature to obtain the sintered solid electrolyte membrane.

[0024] In some embodiments, the fiber-forming polymer includes at least one selected from polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and polyimide (PI). In the most preferred embodiment, the fiber-forming polymer is polytetrafluoroethylene.

[0025] In some specific embodiments, in step (1), the content of the solid electrolyte preform is 80-99.9 wt%, preferably 90-99 wt%, and more preferably 95-99 wt%.

[0026] In some specific embodiments, in step (1), the content of the fiberizable polymer is 0.1-20 wt%, preferably 1-10 wt%, and more preferably 1-5 wt%.

[0027] In some specific embodiments, the method for fiberizing the polymer in step (1) is selected from at least one of the following:

[0028] (1) Grind the polymer together with the solid electrolyte preform;

[0029] (2) The polymer and the solid electrolyte preform are sheared together at high speed;

[0030] (3) The polymer is subjected to a heat stretching treatment;

[0031] (4) The polymer and the solid electrolyte preform are subjected to air jet milling.

[0032] It should be understood that the present invention does not particularly limit the method of polymer fiberization, and any method that enables the fiberization of fiberable polymers is included within the scope of the present invention.

[0033] In some specific embodiments, the hot pressing process in step (2) is performed by using a roller press for one or more hot roller presses.

[0034] In some specific embodiments, the preset thickness in step (2) is 1-1000 μm, preferably 5-500 μm, more preferably 20-300 μm, and even more preferably 50-200 μm. According to specific embodiments, the preset thickness of the solid electrolyte film can be 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 400 μm, 500 μm, 600 μm, 800 μm, 1000 μm, or any thickness within the above range.

[0035] In some specific embodiments, step (3) causes the polymer in the solid electrolyte membrane to decompose, preferably completely decompose.

[0036] In some specific embodiments, the sintering temperature in step (3) is 800–1200°C. The sintering temperature depends on the chemical composition of the solid electrolyte. For example, for LLZO, LLZTO, LLAZO, and LLGZO, the preferred sintering temperature is 1050–1200°C; for LLTO, the preferred sintering temperature is 1100–1200°C; for LAGP, the preferred sintering temperature is 800–900°C; and for LATP, the preferred sintering temperature is 900–1000°C.

[0037] In some specific embodiments, in step (3), the heating rate is 5 to 20 °C / min, preferably 10 °C / min; the sintering time is 6 to 24 hours, preferably 12 hours.

[0038] In some specific embodiments, when mixing the solid electrolyte preform with the fiberizable polymer in step (1), an excess of lithium precursor is added, wherein the lithium precursor is selected from LiOH·H2O and Li3PO4.

[0039] In some specific embodiments, the excess proportion of the lithium precursor in step (1) is 1% to 50%, wherein

[0040] When the solid electrolyte is selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, or lithium lanthanum titanium oxide, the lithium precursor is LiOH·H2O, and its molar excess ratio is 20% to 50%, preferably 30% to 50%.

[0041] When the solid electrolyte is selected from lithium aluminum germanium phosphate or lithium aluminum titanium phosphate, the lithium precursor is Li3PO4, and its molar excess ratio is 1% to 20%, preferably 5% to 15%.

[0042] In some specific embodiments, the method for preparing the solid electrolyte preform in step (1) includes the following steps:

[0043] (a1) According to the chemical composition of the solid electrolyte, the precursors of each element and the precursor of excess lithium element are mixed with solvent and then ball-milled and then dried. The precursors of lithium element are selected from LiOH·H2O and Li3PO4.

[0044] (a2) The mixture obtained in step (a1) is pre-calcined to obtain the solid electrolyte preform.

[0045] In some specific embodiments, the excess proportion of the lithium element precursor in step (a1) is 1% to 50%, wherein...

[0046] When the solid electrolyte is selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, or lithium lanthanum titanium oxide, the lithium precursor is LiOH·H2O, and its molar excess ratio is 20% to 50%, preferably 30% to 50%.

[0047] When the solid electrolyte is selected from lithium aluminum germanium phosphate or lithium aluminum titanium phosphate, the lithium precursor is Li3PO4, and its molar excess ratio is 1% to 20%, preferably 5% to 15%.

[0048] In some specific embodiments, the method for preparing a solid electrolyte film includes both adding an excess of lithium precursor in step (a1) and adding an additional excess of lithium precursor in step (1), wherein the total excess ratio of the lithium precursor in steps (a1) and (1) is 1% to 50%.

[0049] When the solid electrolyte is selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, or lithium lanthanum titanium oxide, the lithium precursor is LiOH·H2O, and the total excess ratio of its molar number is 20% to 50%, preferably 30% to 50%.

[0050] When the solid electrolyte is selected from lithium aluminum germanium phosphate or lithium aluminum titanium phosphate, the lithium precursor is Li3PO4, and the total excess of its molar number is 1% to 20%, preferably 5% to 15%.

[0051] A second aspect of the present invention provides a solid electrolyte film, which is prepared by the preparation method of the first aspect of the present invention.

[0052] The third aspect of the present invention provides the application of the solid electrolyte film of the second aspect of the present invention in solid lithium metal batteries.

[0053] A fourth aspect of the present invention provides a solid-state lithium metal battery, which includes the solid electrolyte film described in the second aspect of the present invention.

[0054] The preparation method of the solid electrolyte film of the present invention is simple. The planarization of the solid electrolyte film is completed spontaneously under pressure, forming a solid electrolyte film with a smooth surface, dense structure and high ionic conductivity. Attached Figure Description

[0055] Figure 1 shows a schematic diagram of planarization sintering using a sintering plate in the method for preparing ceramic solid electrolyte thin films according to the present invention.

[0056] Figure 2 shows a flowchart of the method for preparing ceramic solid electrolyte thin films according to the present invention.

[0057] Figure 3 shows a physical image of the solid electrolyte film of Embodiment 1 of the present invention.

[0058] Figure 4 shows a physical image of the solid electrolyte film of Comparative Example 1 of the present invention. Detailed Implementation

[0059] The present invention will be further described below through specific embodiments. Unless otherwise specified, the terminology used herein has the same meaning as commonly understood by one of ordinary skill in the art. Numerical limits or ranges stated herein include endpoints, specifically including all values ​​and subranges within the numerical limits or ranges.

[0060] The first aspect of this invention provides a method for preparing a solid electrolyte thin film, characterized in that the preparation method includes the following planarization and sintering steps:

[0061] The sintered solid electrolyte film is subjected to high-temperature sintering under mechanical pressure to obtain a planarized solid electrolyte film.

[0062] In some specific embodiments, the mechanical pressure in the leveling sintering step is in the range of 1 to 500 Pa, preferably 10 to 400 Pa, 20 to 250 Pa, and more preferably 50 to 150 Pa. According to specific embodiments, the mechanical pressure in the leveling sintering step can be approximately 1 Pa, 10 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa, 100 Pa, 110 Pa, 120 Pa, 130 Pa, 140 Pa, 150 Pa, 160 Pa, 170 Pa, 180 Pa, 190 Pa, 200 Pa, 210 Pa, 220 Pa, 230 Pa, 240 Pa, 250 Pa, 260 Pa, 270 Pa, 280 Pa, 290 Pa, 300 Pa, 350 Pa, 400 Pa, 450 Pa, 500 Pa, or any pressure within the above range. In this invention, it is not necessary to apply significant mechanical pressure to the sintered solid electrolyte film. This is because solid electrolyte films are brittle at room temperature, and excessive pressure would crush any unevenness in the film. However, solid electrolyte films soften at high temperatures, acquiring a certain degree of deformability, allowing them to gradually flatten under external pressure without breaking.

[0063] In some specific embodiments, the thickness of the sintered solid electrolyte film is 1-600 μm, preferably 5-300 μm, and more preferably 10-200 μm. According to specific embodiments, the thickness of the sintered solid electrolyte film can be approximately 1 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 400 μm, 500 μm, 600 μm, or any thickness within the above range.

[0064] In some specific embodiments, the planarization sintering temperature is higher than the densification sintering temperature, i.e., the sintering temperature for preparing a sintered solid electrolyte film from a solid electrolyte film. Specifically, the planarization sintering temperature is 900-1400℃, preferably 1300-1350℃. The planarization sintering temperature is related to the chemical composition of the solid electrolyte. For example, for LLZO, LLZTO, LLAZO, and LLGZO, the planarization sintering temperature is preferably 1200-1400℃; for LLTO, it is preferably 1300-1400℃; for LAGP, it is preferably 800-1000℃; and for LATP, it is preferably 900-1100℃. The inventors have discovered that, to achieve the planarization of the solid electrolyte film, the temperature required for secondary planarization sintering is related to the holding time; within a certain temperature range, the higher the temperature, the shorter the required holding time. In order to improve production efficiency and avoid losses caused by lithium volatilization at high temperatures, the solid electrolyte thin film preparation method of the present invention sets the planarization sintering temperature to be higher than the densification sintering temperature.

[0065] In some specific embodiments, the heating rate of the leveling sintering is 5 to 20°C / min, preferably 10°C / min; the holding time after reaching the leveling sintering temperature is 5 to 30 minutes, preferably 10 minutes.

[0066] In some specific embodiments, the mechanical pressure is applied during the planarization sintering step by placing a sintering plate over the sintered solid electrolyte film.

[0067] In some specific embodiments, the thickness of the firing plate is 0.2-10 mm, preferably 0.5-5 mm, more preferably 1-2 mm, and the mechanical pressure is generated by the gravity of the firing plate. According to specific embodiments, the thickness of the firing plate can be approximately 0.2 mm, 0.5 mm, 0.8 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any thickness within the above range.

[0068] In some specific embodiments, during the planarization sintering step, the planarized solid electrolyte film is obtained by high-temperature sintering with the sintered solid electrolyte film placed between two sintering plates. Figure 1 shows a schematic diagram of the solid electrolyte film being held between two sintering plates.

[0069] In some specific embodiments, during the planarization sintering step, the surface of the sintering plate that contacts the solid electrolyte film is a flat surface.

[0070] In this invention, during the planarization sintering step, the solid electrolyte film softens at high temperature and has a certain deformation capacity. Under the mechanical pressure applied to the flat surface it contacts, it deforms and gradually flattens to form a flat surface structure.

[0071] In some specific embodiments, the sintering plate comprises one or more materials selected from magnesium oxide, zirconium oxide, aluminum oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, or lithium titanium aluminum phosphate. In some specific embodiments, the material of the sintering plate is magnesium oxide or a lithium-containing material, preferably the same material as the solid electrolyte film material. The material of the sintering plate has a certain influence on the ionic conductivity of the prepared solid electrolyte. Lithium (e.g., Li₂O) in the solid electrolyte will volatilize at high temperatures. If the material of the sintering plate can absorb the volatilized lithium (Li₂O), it will lead to an increase in the amount of non-lithium-conducting second phase in the solid electrolyte film, thereby causing a decrease in ionic conductivity. Relatively speaking, if the material of the sintering plate itself contains more lithium, a lithium-rich atmosphere can be formed on the film surface at high temperatures, suppressing the formation of the second phase in the solid electrolyte film.

[0072] The planarization sintering step of the present invention is applicable to solid electrolyte films prepared by any known method, including tape casting and dry sintering.

[0073] The method for preparing the solid electrolyte film of the present invention does not have any particular limitation on the chemical composition of the solid electrolyte, as long as it is a ceramic solid electrolyte that can be prepared by high-temperature sintering.

[0074] In some specific embodiments, the solid electrolyte is selected from lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum zirconium aluminum oxide (LLAZO), lithium lanthanum zirconium gallium oxide (LLGZO), lithium lanthanum titanium oxide (LLTO), lithium aluminum germanium phosphate (LAGP), or lithium aluminum titanium phosphate (LATP).

[0075] In a specific embodiment, the chemical formula of lithium lanthanum zirconium oxide (LLZO) is Li7La3Zr2O. 12 ;

[0076] The chemical formula of lithium lanthanum zirconium tantalum oxide (LLZTO) is Li. 7-x La3Zr 2-x Ta x O 12 For example, when x = 0.5, the chemical formula is Li. 6.5 La3Zr 1.5Ta 0.5 O 12 When x = 0.6, the chemical formula is Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 ;

[0077] The chemical formula of lithium lanthanum zirconium aluminum oxide (LLAZO) is Li. 7-3x La3Al x Zr2O 12 For example, when x = 0.1, the chemical formula is Li. 6.7 La3Al 0.1 Zr2O 12 When x = 0.2, the chemical formula is Li. 6.4 La3Al 0.2 Zr2O 12 ;

[0078] The chemical formula of lithium lanthanum zirconium gallium oxide (LLGZO) is Li. 7-3x La3Ga x Zr2O 12 For example, when x = 0.2, the chemical formula is Li. 6.4 La3Ga 0.2 Zr2O 12 When x = 0.3, the chemical formula is Li. 6.1 La3Ga 0.3 Zr2O 12 ;

[0079] The chemical formula of lithium lanthanum titanium oxide (LLTO) is Li. 2-3x La x TiO3, for example, when x = 0.4, has the chemical formula Li. 0.8 La 0.4 TiO3, when x = 0.5, has the chemical formula Li. 0.5 La 0.5 TiO3;

[0080] Lithium aluminum germanium phosphate (LAGP) has the chemical formula Li. 1.5 Al 0.5 Ge 1.5 (PO4)3;

[0081] The chemical formula of lithium aluminum titanium phosphate (LATP) is Li. 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0082] Those skilled in the art should understand that the solid electrolytes listed above are for illustrative purposes only, and the scope of the present invention is not limited thereto. For example, electrolytes such as LLZTO and LLAZO are element-doped forms of the garnet-type solid electrolyte LLZO, and have similar properties in some respects. They can all be prepared into solid electrolyte films using the method of the present invention. Other element-doped forms of the solid electrolytes listed, as well as other solid electrolytes not listed, can also be prepared into films using the method of the present invention.

[0083] In some specific embodiments, the sintered solid electrolyte film is obtained through the following dry sintering steps:

[0084] (1) Mixing a solid electrolyte preform with a fibrous polymer, thereby fibrousizing the polymer and uniformly mixing it with the solid electrolyte preform;

[0085] (2) The mixture obtained in step (1) is hot-pressed to a preset thickness to obtain a solid electrolyte film;

[0086] (3) The solid electrolyte membrane obtained in step (2) is sintered at high temperature to obtain a solid electrolyte film.

[0087] In some specific embodiments, the basic process of preparing a solid electrolyte thin film, including dry preparation of the film, primary densification sintering, and secondary planarization sintering, is shown in Figure 2.

[0088] In some specific embodiments, the fibrillable polymer includes at least one selected from polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and polyimide (PI). In this invention, the fibrillable polymer is not particularly limited, as long as it is a polymer capable of fibrillation and decomposition at high temperatures. In the most preferred embodiment, the fibrillable polymer is polytetrafluoroethylene (PTFE). The advantage of using PTFE is its large molecular weight, which allows for the formation of longer fibrils during the fibrillation process and facilitates the formation of a polymer network during hot pressing, thus promoting the aggregation of electrolyte powder and the formation of a dense electrolyte membrane. Similarly, when using other polymers, it is advantageous to use polymers with larger molecular weights.

[0089] In some specific embodiments, in step (1), the content of the solid electrolyte preform is 80-99.9 wt%, preferably 90-99 wt%, and more preferably 95-99 wt%. For example, the content of the solid electrolyte preform can be about 80 wt%, 85 wt%, 88 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 95.5 wt%, 96 wt%, 96.5 wt%, 97 wt%, 97.5 wt%, 98 wt%, 98.5 wt%, 99 wt%, 99.5 wt%, 99.9 wt%, etc. According to the preparation method of the present invention, the higher the content of the solid electrolyte preform, the easier it is to sinter into a dense ceramic film.

[0090] In some specific embodiments, in step (1), the content of the fibrillable polymer is 0.1-20 wt%, preferably 1-10 wt%, and more preferably 1-5 wt%. For example, the content of the fibrillable polymer can be about 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 15 wt%, 20 wt%, etc. According to the preparation method of the present invention, the content of the fibrillable polymer is low, and a dense solid electrolyte film can be obtained by sintering.

[0091] In some specific embodiments, in step (1), the total content of the solid electrolyte preform and the fiberizable polymer is 100 wt%.

[0092] In some specific embodiments, the method for fiberizing the polymer in step (1) is selected from at least one of the following:

[0093] (1) Grind the polymer together with the solid electrolyte preform;

[0094] (2) The polymer and the solid electrolyte preform are sheared together at high speed;

[0095] (3) The polymer is subjected to a heat stretching treatment;

[0096] (4) The polymer and the solid electrolyte preform are subjected to air jet milling.

[0097] It should be understood that the present invention does not particularly limit the method of polymer fiberization, and any method that enables the fiberization of fiberable polymers is included within the scope of the present invention.

[0098] In some specific embodiments, the hot pressing process in step (2) involves one or more hot rolling processes using a roller press. In some preferred embodiments, in step (2), the mixture obtained in step (1) is subjected to multiple hot rolling processes under heating conditions using a roller press to gradually reduce the film thickness, thereby obtaining a solid electrolyte film with a preset thickness. The temperature of the hot rolling process is not particularly limited, as long as it is a temperature conducive to processing, such as 50-150°C, 60-120°C, 70-100°C, 75-90°C, etc.

[0099] In some specific embodiments, the preset thickness in step (2) is 1-1000 μm, preferably 5-500 μm, more preferably 20-300 μm, and even more preferably 50-200 μm. According to specific embodiments, the preset thickness of the solid electrolyte film can be approximately 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 400 μm, 500 μm, 600 μm, 800 μm, 1000 μm, or any thickness within the above range.

[0100] In some specific embodiments, step (3) causes the polymer in the solid electrolyte film to decompose, preferably completely decompose. Through the high-temperature sintering in step (3), the polymer component in the solid electrolyte film can be substantially completely decomposed, forming a solid electrolyte film that is close to 100% ceramic. This preparation method results in a dense solid electrolyte film structure and high ionic conductivity.

[0101] In some specific embodiments, the sintering temperature in step (3) is 800–1200°C. The sintering temperature depends on the chemical composition of the solid electrolyte. For example, for LLZO, LLZTO, LLAZO, and LLGZO, the preferred sintering temperature is 1050–1200°C; for LLTO, the preferred sintering temperature is 1100–1200°C; for LAGP, the preferred sintering temperature is 800–900°C; and for LATP, the preferred sintering temperature is 900–1000°C.

[0102] In some specific embodiments, in step (3), the heating rate is 5 to 20 °C / min, preferably 5 to 10 °C / min; the sintering time is 6 to 24 hours, preferably 12 hours.

[0103] Since lithium in the solid electrolyte preform will volatilize at high temperatures, in order to obtain a solid electrolyte film with the required stoichiometric ratio, it is preferable to include a portion of excess lithium in the mixture to be sintered. For example, the excess lithium can be included in the solid electrolyte preform. Alternatively, the excess lithium can be added additionally when mixing the solid electrolyte preform with the fibrous polymer in step (1).

[0104] Therefore, in some specific embodiments, when mixing the solid electrolyte preform with the fiberizable polymer in step (1), an excess of lithium precursor is added, wherein the lithium precursor is selected from LiOH·H2O and Li3PO4.

[0105] Furthermore, in some specific embodiments, the preparation method of the solid electrolyte preform in step (1) includes the following steps:

[0106] (a1) According to the chemical composition of the solid electrolyte, the precursors of each element and the precursor of excess lithium element are mixed with solvent and then ball-milled and then dried. The precursors of lithium element are selected from LiOH·H2O and Li3PO4.

[0107] (a2) The mixture obtained in step (a1) is pre-calcined to obtain the solid electrolyte preform.

[0108] In some specific embodiments, the method for preparing the solid electrolyte film includes both adding an excess of lithium precursor in step (a1) and adding an additional excess of lithium precursor in step (1). In this case, the excess proportion of the number of moles of lithium precursor in steps (a1) and (1) should be calculated together.

[0109] In the context of this invention, "excess" refers to a situation where the molar number of lithium precursors added during the preparation process exceeds the molar content of lithium in the solid electrolyte calculated based on the chemical composition of the solid electrolyte according to the molar number of other elemental precursors (e.g., lanthanum source, zirconium source, tantalum source, etc.). For example, when preparing a solid electrolyte with the chemical formula Li... 7-x La3Zr 2-x Ta x O 12 When using LLZTO solid electrolyte, if the molar ratio of lithium, lanthanum, zirconium, and tantalum elements in the lithium source, lanthanum source, zirconium source, and tantalum source is Li:La:Zr:Ta=M:3:2-x:x, then the molar ratio of lithium element in the lithium source, M, is greater than 7-x; the excess percentage is calculated as (M-(7-x)) / (7-x).

[0110] In a specific embodiment of the present invention, regardless of whether the lithium precursor is added in step (a1), in step (1), or in both steps (a1) and (1), the excess molar ratio (or total excess ratio) is 1% to 50%. According to a specific embodiment, the excess molar ratio of the lithium precursor can be approximately 1%, 3%, 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 22%, 24%, 25%, 26%, 28%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 48%, 50%, or any ratio within the above range. Specifically, when the solid electrolyte is selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, or lithium lanthanum titanium oxide, the lithium precursor is LiOH·H2O, and its molar excess ratio (or total excess ratio) is 20%–50%, preferably 30%–50%; when the solid electrolyte is selected from lithium germanium aluminum phosphate or lithium titanium aluminum phosphate, the lithium precursor is Li3PO4, and its molar excess ratio (or total excess ratio) is 1%–20%, preferably 5%–15%. The inventors have discovered that excess lithium can be added during the preparation of the solid electrolyte preform and the film formation process. When the total excess ratio is kept constant, the timing of adding the excess lithium source has virtually no impact on the technical effect.

[0111] During high-temperature heating, lithium in the crystal lattice volatilizes, causing a phase transformation and generating a second phase without lithium ions, which reduces ionic conductivity. However, providing an excess lithium source can prevent this phase transformation and improve the ionic conductivity of the prepared solid electrolyte membrane. The inventors have experimentally confirmed that, through the solid electrolyte preparation method of this invention, the aforementioned excess lithium source does not affect the phase structure of the solid electrolyte. On one hand, due to the multiple high-temperature treatment processes, a significant amount of lithium volatilizes, and the added excess lithium source can compensate for this volatilization. On the other hand, a small amount of residual lithium can form a lithium-rich phase at the grain boundaries, thereby improving the connection between solid electrolyte grains and increasing the density after sintering.

[0112] A second aspect of the present invention provides a solid electrolyte film, which is prepared by the preparation method of the first aspect of the present invention.

[0113] The third aspect of the present invention provides the application of the solid electrolyte film of the second aspect of the present invention in solid lithium metal batteries.

[0114] A fourth aspect of the present invention provides a solid-state lithium metal battery, which includes the solid electrolyte film described in the second aspect of the present invention.

[0115] Example

[0116] The present invention will be described in detail below through embodiments, which are not intended to limit the invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.

[0117] In the following examples, the PTFE used was purchased from Kejing and had a weight-average molecular weight of 10. 6 g / mol, with a median particle size of 0.3 μm.

[0118] Preparation Example 1: Preparation of LLZTO Solid Electrolyte Preform

[0119] To prepare the chemical formula Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The following raw materials were weighed according to the stoichiometric ratio and with a certain proportion of excess lithium source for the LLZTO solid electrolyte: lithium hydroxide monohydrate (LiOH·H2O), lanthanum oxide (La2O3), zirconium oxide (ZrO2) and tantalum oxide (Ta2O5).

[0120] The weighed precursor powders of each element were placed in a zirconia ball mill jar, and five times the weight of the raw material zirconia ball milling beads were added, followed by an equal mass of isopropanol. The mixture was wet-milled at 500 rpm for 3 hours to obtain a homogeneous powder. The resulting powder was then dried in an oven to completely remove the isopropanol solvent.

[0121] The dried powder was placed in a muffle furnace and calcined at 900℃ for 12 hours. The heating and cooling rates were both 5℃ / min. After cooling, LLZTO solid electrolyte powder blanks were obtained.

[0122] Preparation Example 2: Preparation of LLZTO solid electrolyte film

[0123] 95 parts by mass of the LLZTO powder blank obtained in Preparation Example 1 (LiOH·H2O was in excess by 40% during blank preparation) and 5 parts by mass of PTFE powder were weighed out, mixed evenly, and then placed in a grinder. The mixture was ground thoroughly at 200 rpm for 30 minutes to fiberize the PTFE and mix it thoroughly with the LLZTO powder, thus obtaining a mixed block of fiberized PTFE and LLZTO.

[0124] The above-mentioned mixed block was rolled multiple times at 80°C using a roller press to gradually reduce the film thickness, and finally an electrolyte film with a thickness of 100 μm was obtained.

[0125] Example 1: Preparation of LLZTO solid electrolyte film

[0126] One-step densification sintering: The LLZTO solid electrolyte green film obtained in Preparation Example 2 was placed in a magnesium oxide crucible and then placed in a muffle furnace for high-temperature sintering in air. The sintering conditions were: heating rate 10℃ / min; holding temperature: 1150℃; holding time: 12h; cooling rate 5℃ / min. After cooling, the sintered LLZTO solid electrolyte film was obtained.

[0127] Secondary leveling sintering: A magnesium oxide sintering plate measuring 60 mm long, 40 mm wide, and 1.5 mm thick is used. Depending on the size of the solid electrolyte membrane, the pressure generated by the sintering plate is approximately 50-150 Pa. The sintered LLZTO solid electrolyte membrane is placed horizontally between two magnesium oxide sintering plates and placed in a muffle furnace for a secondary high-temperature heat treatment in air. The heat treatment conditions are: heating rate 10 °C / min; holding temperature: 1320 °C; holding time: 10 min; cooling rate 5 °C / min. After cooling, a leveled LLZTO solid electrolyte membrane is obtained.

[0128] Example 2: Preparation of LLZTO solid electrolyte film

[0129] In this embodiment, except that the magnesium oxide sintering plate is replaced with an LLZTO sintering plate (the size of the sintering plate remains unchanged, the same below), a planarized LLZTO solid electrolyte film is obtained using the same steps and conditions as in Example 1. Depending on the size of the solid electrolyte film, the pressure generated by the sintering plate is approximately 75-220 Pa.

[0130] Example 3: Preparation of LLZTO solid electrolyte film

[0131] In this embodiment, except that the magnesium oxide sintering plate is replaced with an alumina sintering plate, a planarized LLZTO solid electrolyte film is obtained using the same steps and conditions as in Example 1. Depending on the size of the solid electrolyte film, the pressure generated by the sintering plate is approximately 50-150 Pa.

[0132] Example 4: Preparation of LLZTO solid electrolyte film

[0133] In this embodiment, except that the magnesium oxide sintering plate is replaced with a zirconium oxide sintering plate, a planarized LLZTO solid electrolyte film is obtained using the same steps and conditions as in Example 1. Depending on the size of the solid electrolyte film, the pressure generated by the sintering plate is approximately 80-250 Pa.

[0134] Example 5: Preparation of LLZTO solid electrolyte film

[0135] In this embodiment, except that the magnesium oxide sintering plate is replaced with an LLGZO sintering plate, a planarized LLZTO solid electrolyte film is obtained using the same steps and conditions as in Example 1. Depending on the size of the solid electrolyte film, the pressure generated by the sintering plate is approximately 70-210 Pa.

[0136] Example 6: Preparation of LLZTO solid electrolyte film

[0137] In this embodiment, except that the magnesium oxide sintering plate is replaced with an LLAZO sintering plate, a planarized LLZTO solid electrolyte film is obtained using the same steps and conditions as in Example 1. Depending on the size of the solid electrolyte film, the pressure generated by the sintering plate is approximately 65-200 Pa.

[0138] Example 7: Preparation of LLZTO solid electrolyte film

[0139] In this embodiment, except that the final thickness of the electrolyte film in Preparation Example 2 was changed to 60 μm, a planarized LLZTO solid electrolyte film was obtained using the same steps and conditions as in Example 2.

[0140] Example 8: Preparation of LLZTO solid electrolyte film

[0141] In this embodiment, except that the final thickness of the electrolyte film in Preparation Example 2 was changed to 150 μm, a planarized LLZTO solid electrolyte film was obtained using the same steps and conditions as in Example 2.

[0142] Example 9: Preparation of LATP solid electrolyte film

[0143] In this embodiment, except that the LLZTO powder preform in Preparation Example 2 was replaced with LATP powder preform, the LATP electrolyte membrane with a final thickness of 100 μm was obtained using the same steps and conditions as in Preparation Example 2.

[0144] One-step densification sintering: The above-mentioned LATP electrolyte green film was placed in a magnesium oxide crucible and then placed in a muffle furnace for high-temperature sintering in air. The sintering conditions were: heating rate 10℃ / min; holding temperature: 950℃; holding time: 12h; cooling rate 5℃ / min. After cooling, the sintered LATP solid electrolyte film was obtained.

[0145] Secondary leveling sintering: A sintering plate measuring 60 mm in length, 40 mm in width, and 1.5 mm in thickness was used. The sintered LATP solid electrolyte film was placed horizontally between two magnesium oxide sintering plates and placed in a muffle furnace for a secondary high-temperature heat treatment in air. The heat treatment conditions were: heating rate 10 °C / min; holding temperature: 1100 °C; holding time: 10 min; cooling rate 5 °C / min. After cooling, a leveled LATP solid electrolyte film was obtained.

[0146] Example 10: Preparation of LAGP solid electrolyte thin film

[0147] In this embodiment, except that the LLZTO powder preform in Preparation Example 2 was replaced with LAGP powder preform, the same steps and conditions were used to obtain an LAGP electrolyte film with a final thickness of 100 μm.

[0148] One-step densification sintering: The above-mentioned LAGP electrolyte green film was placed in a magnesium oxide crucible and then placed in a muffle furnace for high-temperature sintering in air. The sintering conditions were: heating rate 10℃ / min; holding temperature: 800℃; holding time: 6h; cooling rate 5℃ / min. After cooling, the sintered LAGP solid electrolyte film was obtained.

[0149] Secondary leveling sintering: A sintering plate measuring 60 mm in length, 40 mm in width, and 1.5 mm in thickness was used. The sintered LAGP solid electrolyte film was placed horizontally between two magnesium oxide sintering plates and placed in a muffle furnace for secondary high-temperature heat treatment in air. The heat treatment conditions were: heating rate 10 °C / min; holding temperature: 1000 °C; holding time: 10 min; cooling rate 5 °C / min. After cooling, a leveled LAGP solid electrolyte film was obtained.

[0150] Comparative Example 1: Preparation of LLZTO solid electrolyte films

[0151] In this comparative example, except that a secondary planarization sintering was not performed, an LLZTO solid electrolyte film was obtained using the same steps and conditions as in Example 1, i.e., an LLZTO solid electrolyte film that underwent only one densification sintering.

[0152] Comparative Example 2: Preparation of LATP solid electrolyte thin films

[0153] In this comparative example, except that a secondary planarization sintering was not performed, the LATP solid electrolyte film was obtained using the same steps and conditions as in Example 9, i.e., the LATP solid electrolyte film that underwent only one densification sintering.

[0154] Comparative Example 3: Preparation of LAGP Solid Electrolyte Thin Films

[0155] In this comparative example, except that a secondary planarization sintering was not performed, the LAGP solid electrolyte film was obtained using the same steps and conditions as in Example 10, i.e., the LAGP solid electrolyte film that underwent only one densification sintering.

[0156] Characterization of solid electrolytes

[0157] The solid electrolyte films prepared according to the above examples and comparative examples were visually inspected to evaluate the film formation. Physical images of the solid electrolyte films of Example 1 and Comparative Example 1 are shown in Figures 3 and 4, respectively.

[0158] The diameter and thickness of the solid electrolyte membrane were measured using a micrometer.

[0159] To test the ionic conductivity of the solid electrolyte film, Ag conductive layers were deposited on both sides of the film using a thermal evaporation coating apparatus, and the film was then encapsulated using a button cell. Subsequently, AC impedance testing was performed using an electrochemical workstation (MetrohmAutolab) at an AC voltage of 10 mV and a frequency of 10 MHz–1 Hz. After measuring the AC impedance of the solid electrolyte film, the ionic conductivity σ was calculated using the formula σ = L / RS, where L is the thickness of the electrolyte film, R is the AC impedance of the electrolyte film, and S is the area of ​​one side of the electrolyte film.

[0160] The characterization results of the solid electrolytes of Examples 1-4 and Comparative Example 1 are summarized in Table 1.

[0161] Table 1 Characterization data of solid electrolyte films

[0162] Results and Evaluation

[0163] As shown in Figure 3, the LLZTO solid electrolyte film prepared in Example 1 has high flatness and can be used for solid-state battery assembly without further mechanical processing such as polishing. In contrast, as shown in Figure 4, the LLZTO solid electrolyte film of Comparative Example 1, which has not undergone flattening treatment, exhibits bending deformation and cannot be directly used for battery assembly.

[0164] The LLZTO electrolyte films of Example 1 and Comparative Example 1 were both translucent, indicating that the electrolyte films were thin and dense, and that the thickness was basically the same, indicating that the secondary heat treatment did not have a significant impact on the density of the thin electrolyte films.

[0165] The same applies to LAGP and LATP electrolyte films, i.e., the electrolyte films that have undergone planarization treatment in Examples 9-10 have higher flatness than the electrolyte films that have not undergone planarization treatment in Comparative Examples 2-3, and their density and ionic conductivity are basically the same.

[0166] As can be seen from the ionic conductivity data in Table 1, the material of the sintering plate has a certain influence on the ionic conductivity of the electrolyte film. When lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium gallium oxide, and lithium lanthanum zirconium aluminum oxide are used as sintering plates, the resulting flattened solid electrolyte film exhibits the highest ionic conductivity because the sintering plate is a lithium-rich material with a composition similar to or the same as the solid electrolyte. When using magnesium oxide sintering plates, the ionic conductivity of the electrolyte film remains essentially unchanged during flattening because it does not react with the volatilized lithium. In contrast, when alumina or zirconium oxide, which can react with lithium, are used as sintering plates, the ionic conductivity of the electrolyte film decreases to some extent after flattening, but it is still higher than the ionic conductivity of commonly used solid electrolyte films in the prior art.

[0167] The foregoing embodiments have described exemplary implementations of the present invention, but the present invention is not limited thereto. Those skilled in the art should understand that the above embodiments are merely illustrative, and the specific implementations and examples of the present invention should not be considered as limiting the scope of the present invention. Changes and modifications can be made to the implementations within the scope of the present invention, and such changes and modifications should fall within the protection scope of the present invention.

Claims

1. A method for producing a ceramic solid electrolyte thin film, characterized by, The preparation method includes the following steps: The sintered solid electrolyte film is subjected to high-temperature sintering under mechanical pressure to obtain a planarized solid electrolyte film.

2. The production method according to claim 1, characterized by, The mechanical pressure is in the range of 1 to 500 Pa, preferably 10 to 400 Pa, more preferably 20 to 250 Pa, and even more preferably 50 to 150 Pa.

3. The production method according to claim 1 or 2, characterized by, The thickness of the sintered solid electrolyte film is 1-600 μm, preferably 5-300 μm, and more preferably 10-200 μm.

4. The production method according to any one of claims 1 to 3, characterized by, The high-temperature sintering temperature is higher than the sintering temperature at which the solid electrolyte film is prepared from the solid electrolyte biofilm.

5. The production method according to any one of claims 1 to 4, characterized by, The mechanical pressure is applied by placing a sintering plate over the sintered solid electrolyte film.

6. The production method according to claim 5, wherein The planarized solid electrolyte film is obtained by high-temperature sintering with the sintered solid electrolyte film placed between two sintering plates.

7. The production method according to claim 5 or 6, characterized by, The surface of the sintering plate that contacts the solid electrolyte film is a flat surface.

8. The production method according to claim 5 or 6, characterized by, The firing plate comprises one or more materials selected from magnesium oxide, zirconium oxide, aluminum oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, or lithium titanium aluminum phosphate.

9. The preparation method according to any one of claims 1 to 8, characterized in that, The solid electrolyte is selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, or lithium titanium aluminum phosphate.

10. The preparation method according to any one of claims 1 to 8, characterized in that, The sintered solid electrolyte film is obtained through the following steps: (1) Mixing a solid electrolyte preform with a fibrous polymer, thereby fibrousizing the polymer and uniformly mixing it with the solid electrolyte preform; (2) The mixture obtained in step (1) is hot-pressed to a preset thickness to obtain a solid electrolyte film; (3) The solid electrolyte membrane obtained in step (2) is sintered at high temperature to obtain the sintered solid electrolyte membrane.

11. The preparation method according to claim 10, characterized in that, The fiber-forming polymer includes at least one of polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, styrene-butadiene rubber, polyacrylic acid, carboxymethyl cellulose, and polyimide.

12. The preparation method according to claim 10 or 11, characterized in that, In step (1), the content of the solid electrolyte preform is 80-99.9 wt%, preferably 90-99 wt%, more preferably 95-99 wt%; and / or the content of the fiberizable polymer is 0.1-20 wt%, preferably 1-10 wt%, more preferably 1-5 wt%.

13. The preparation method according to any one of claims 10 to 12, characterized in that, The hot pressing process in step (2) is to perform one or more hot rolling processes using a roller press, and / or the preset thickness is 1-1000μm, preferably 5-500μm, more preferably 20-300μm, and even more preferably 50-200μm.

14. The preparation method according to any one of claims 10 to 13, characterized in that, Step (3) causes the polymer in the solid electrolyte membrane to decompose completely, and / or the sintering temperature in step (3) is 800-1200°C.

15. The preparation method according to any one of claims 10 to 14, characterized in that, In step (1), when the solid electrolyte preform is mixed with the fiberizable polymer, an excess of lithium precursor is added, wherein the lithium precursor is selected from LiOH·H2O and Li3PO4.

16. The preparation method according to any one of claims 10 to 15, characterized in that, The preparation method of the solid electrolyte preform in step (1) includes the following steps: (a1) According to the chemical composition of the solid electrolyte, the precursors of each element and the precursor of excess lithium element are mixed with solvent and then ball-milled and then dried. The precursors of lithium element are selected from LiOH·H2O and Li3PO4. (a2) The mixture obtained in step (a1) is pre-calcined to obtain the solid electrolyte preform.

17. The preparation method according to claim 16, characterized in that, In step (1), when mixing the solid electrolyte preform with the fibrous polymer, an excess of lithium precursor is added, wherein the total excess of the lithium precursor in steps (a1) and (1) is 1% to 50%. When the solid electrolyte is selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, or lithium lanthanum titanium oxide, the lithium precursor is LiOH·H2O, and the total excess ratio of its molar number is 20% to 50%, preferably 30% to 50%. When the solid electrolyte is selected from lithium aluminum germanium phosphate or lithium aluminum titanium phosphate, the lithium precursor is Li3PO4, and the total excess of its molar number is 1% to 20%, preferably 5% to 15%.

18. A ceramic solid electrolyte film, said ceramic solid electrolyte film being prepared by the preparation method according to any one of claims 1 to 17.

19. The application of the ceramic solid electrolyte film of claim 18 in a solid lithium metal battery.

20. A solid-state lithium metal battery comprising the ceramic solid electrolyte film of claim 18.

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