Setter plate for preparing ceramic solid-state electrolyte film

Abstract

Disclosed is a setter plate for preparing a ceramic solid-state electrolyte film. The setter plate comprises a lithium-containing ceramic layer and a high-temperature-resistant ceramic layer. The lithium-containing ceramic layer and the high-temperature-resistant ceramic layer are tightly bonded together through sintering, and the setter plate has an essentially flat surface. Also disclosed are a method for preparing the setter plate and a method for preparing a planarized solid-state electrolyte film by using the setter plate. The present invention can improve the flatness and ionic conductivity of a solid-state electrolyte film when preparing the solid-state electrolyte film by using the setter plate, thereby obtaining a solid-state electrolyte film having a flat surface, dense structure, and high ionic conductivity.

Description

Sintering plate for preparing ceramic solid electrolyte thin films Technical Field

[0001] This invention relates to a ceramic solid electrolyte thin film sintering plate and its preparation method, belonging to the field of solid-state batteries. This invention also relates to a method for preparing ceramic solid electrolyte thin films using the sintering plate. Background Technology

[0002] For decades, battery technology has been a major focus in the technology field, driving the development of wireless communications, electric transportation, wearable devices, and other areas. With the increasing demand for high-energy-density and long-life batteries, solid-state lithium metal batteries, as a new and high-performance battery technology, are gradually attracting widespread attention.

[0003] Traditional lithium-ion batteries use liquid electrolytes, which can cause fires or explosions under high temperatures or extreme conditions, limiting their use in some applications. In contrast, the rise of ceramic solid-state electrolyte technology has solved many of the 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, improve battery safety, and greatly reduce safety hazards caused by electrolyte issues. Furthermore, solid-state electrolytes can achieve a wider operating temperature range, thereby improving battery performance in extreme environments.

[0004] However, ceramic electrolytes typically require high-temperature sintering above 1000℃ during preparation. During this process, the ceramic film is prone to deformation and bending, and an uneven solid electrolyte film cannot be used for battery assembly. Therefore, an auxiliary method is needed to improve the flatness of the electrolyte film during the sintering process.

[0005] Summary of the Invention

[0006] The inventors discovered that using a sintering plate as an aid during the sintering process can effectively improve the flatness of the electrolyte film. Furthermore, using a lithium-rich material, such as garnet solid electrolyte, as the sintering plate can effectively reduce the volatilization of lithium in the electrolyte film, thereby improving the ionic conductivity of the electrolyte film. However, sintering plates made solely of solid electrolyte materials are prone to deformation during sintering, cannot be reused for extended periods, and cannot guarantee the flatness of the electrolyte film.

[0007] Therefore, the technical problem to be solved by the present invention is to improve the high-temperature stability and flatness of the sintering plate used to prepare ceramic solid electrolyte films, thereby improving the flatness of the solid electrolyte film when using the sintering plate to prepare the solid electrolyte film, and at the same time improving the ionic conductivity of the solid electrolyte film.

[0008] To address the aforementioned technical problems, this invention provides a sintering plate for preparing ceramic solid electrolyte films. The sintering plate comprises a lithium-containing ceramic layer and a high-temperature resistant ceramic layer bonded together, exhibiting resistance to high-temperature deformation and enabling the preparation of solid electrolyte films with high flatness. This invention also discloses a method for preparing the sintering plate and a method for preparing flattened solid electrolyte films using the sintering plate.

[0009] The first aspect of the present invention provides a sintering plate for preparing ceramic solid electrolyte films, characterized in that the sintering plate comprises a lithium-containing ceramic layer and a high-temperature resistant ceramic layer.

[0010] In some specific embodiments, the lithium-containing ceramic layer of the firing plate includes one or more materials 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.

[0011] In some specific embodiments, the thickness of the lithium-containing ceramic layer is 0.2-5 mm. Preferably, the thickness of the lithium-containing ceramic layer is 0.5-3 mm, and more preferably 1-2 mm.

[0012] In some specific embodiments, the high-temperature resistant ceramic layer of the firing plate includes one or more materials selected from magnesium oxide, zirconium oxide, or aluminum oxide.

[0013] In some specific embodiments, the thickness of the high-temperature resistant ceramic layer is 0.5-5 mm. Preferably, the thickness of the high-temperature resistant ceramic layer is 1-4 mm, more preferably 2-3 mm.

[0014] In some specific embodiments, the lithium-containing ceramic layer and the high-temperature resistant ceramic layer of the sintering plate are tightly bonded together by sintering to form an integrated composite sintering plate.

[0015] In some specific embodiments, the firing plate has a substantially flat surface.

[0016] In some specific embodiments, the surface of the firing plate has a shape selected from circles, ellipses, rectangles, squares, triangles, or combinations thereof.

[0017] In some specific embodiments, the surface of the firing plate has a maximum length of 2-20 cm and / or a maximum width of 2-20 cm.

[0018] The second aspect of the present invention provides a method for preparing the firing plate of the first aspect of the present invention, comprising the following steps:

[0019] (1) Polishing and grinding the sintered lithium-containing ceramic sheet;

[0020] (2) The polished lithium-containing ceramic sheets are stacked on the high-temperature resistant ceramic sheets and sintered at high temperature to obtain the sintering plate.

[0021] Through high-temperature composite sintering, lithium-containing ceramic sheets and high-temperature resistant ceramic sheets are tightly bonded together to form an integrated composite sintering plate. The lithium-containing ceramic sheets form the lithium-containing ceramic layer of the sintering plate, and the high-temperature resistant ceramic sheets form the high-temperature resistant ceramic layer of the sintering plate.

[0022] In some specific embodiments, the surface flatness of the lithium-containing ceramic sheet after polishing is ≤10μm.

[0023] In some specific embodiments, the high-temperature composite sintering temperature is 0-50°C below the melting point of the lithium-containing ceramic material. That is, the composite sintering temperature depends on the lithium-containing ceramic material. For example, for LLZO, LLZTO, LLAZO, and LLGZO, the preferred composite sintering temperature is 1250-1400°C; for LLTO, the preferred composite sintering temperature is 1300-1400°C; for LAGP, the preferred composite sintering temperature is 900-1100°C; and for LATP, the preferred composite sintering temperature is 1000-1200°C.

[0024] In this invention, the preparation method of the lithium-containing ceramic sheet is not particularly limited; it can be prepared by tape casting or by a dry method. In some specific embodiments, the sintered lithium-containing ceramic sheet is obtained through the following steps:

[0025] (a1) Mixing lithium-containing ceramic material powder with a fiberizable polymer, thereby fiberizing the polymer and uniformly mixing it with the lithium-containing ceramic material powder;

[0026] (a2) The mixture obtained in step (a1) is hot-pressed to a preset thickness to obtain a lithium-containing ceramic film;

[0027] (a3) The lithium-containing ceramic green film obtained in step (a2) is sintered at high temperature to obtain the sintered lithium-containing ceramic sheet.

[0028] 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.

[0029] In some specific embodiments, in step (a1), the powder content of the lithium-containing ceramic material is 80-99.9 wt%, preferably 90-99 wt%, and more preferably 95-99 wt%.

[0030] In some specific embodiments, in step (a1), the content of the fiberizable polymer is 0.1-20 wt%, preferably 1-10 wt%, and more preferably 1-5 wt%.

[0031] In some specific embodiments, the method for fiberizing the polymer in step (a1) is selected from at least one of the following:

[0032] (1) Grind the polymer together with the powder of the lithium-containing ceramic material;

[0033] (2) The polymer and the lithium-containing ceramic material powder are sheared together at high speed;

[0034] (3) The polymer is subjected to a heat stretching treatment;

[0035] (4) The polymer and the lithium-containing ceramic material powder are subjected to air jet milling.

[0036] 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.

[0037] In some specific embodiments, the hot pressing process in step (a2) is performed by one or more hot rolling processes using a roller press.

[0038] In some specific embodiments, the hot pressing process in step (a2) is performed by one or more hot rolling processes using a roller press.

[0039] In some specific embodiments, the preset thickness in step (a2) is 0.2-10 mm. Preferably, the preset thickness is 0.5-5 mm, and more preferably 2-4 mm.

[0040] In some specific embodiments, step (a3) ​​causes the polymer in the lithium-containing ceramic biofilm to decompose, preferably completely decompose.

[0041] In some specific embodiments, the sintering temperature in step (a3) ​​is 1000–1400°C. The sintering temperature depends on the chemical composition of the lithium-containing ceramic material. For example, for LLZO, LLZTO, LLAZO, and LLGZO, the preferred sintering temperature is 1250–1400°C; for LLTO, the preferred sintering temperature is 1300–1400°C; for LAGP, the preferred sintering temperature is 850–1000°C; and for LATP, the preferred sintering temperature is 950–1100°C.

[0042] In some specific embodiments, the sintering temperature in step (a3) ​​is lower than the composite sintering temperature in step (2).

[0043] In some specific embodiments, when mixing the lithium-containing ceramic material powder with the fiberizable polymer in step (a1), an excess of lithium precursor may be added, wherein the lithium precursor is selected from LiOH·H2O and Li3PO4. The excess molar ratio of the lithium precursor is 0% to 20%.

[0044] A third aspect of this invention provides a method for preparing a ceramic solid electrolyte thin film, comprising the following steps:

[0045] The sintered solid electrolyte film is stacked under the sintering plate of the first aspect of the present invention and then sintered at high temperature to obtain a planarized solid electrolyte film.

[0046] The lithium-containing ceramic layer of the sintering plate faces the solid electrolyte film.

[0047] By using the composite sintering plate of the present invention to assist in flattening sintering, the flatness of the solid electrolyte film can be improved, and at the same time, the ionic conductivity of the solid electrolyte film can be improved.

[0048] 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.

[0049] In some specific embodiments, the planarization sintering temperature is higher than the densification sintering temperature, i.e., the sintering temperature for preparing the sintered solid electrolyte film from the solid electrolyte film. In some specific embodiments, the sintering plate used for planarization sintering is prepared by the method of the second aspect of the present invention, and the planarization sintering temperature is lower than the composite sintering temperature in step (2) of preparing the sintering plate. Specifically, the planarization sintering temperature can be 900-1400°C, preferably 1300-1350°C. The planarization sintering temperature is related to the chemical composition of the solid electrolyte.

[0050] 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.

[0051] In some specific embodiments, the planarized solid electrolyte film is obtained by high-temperature sintering with the sintered solid electrolyte film stacked between two sintering plates.

[0052] In some specific embodiments, the surface of the sintering plate that contacts the solid electrolyte film is a flat surface.

[0053] In some embodiments, the lithium-containing ceramic layer of the sintering plate comprises the same material as the solid electrolyte film material. In a preferred embodiment, the material of the lithium-containing ceramic layer of the sintering plate is the same as the material of the solid electrolyte film.

[0054] 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.

[0055] In some specific embodiments, the sintered solid electrolyte film is obtained through the following steps:

[0056] (b1) Mixing a solid electrolyte preform with a fibrous polymer, thereby fibrousizing the polymer and uniformly mixing it with the solid electrolyte preform;

[0057] (b2) The mixture obtained in step (b1) is hot-pressed to a preset thickness to obtain a solid electrolyte film;

[0058] (b3) The solid electrolyte film obtained in step (b2) is sintered at high temperature to obtain the sintered solid electrolyte film.

[0059] In some specific embodiments, the sintered solid electrolyte film can be prepared using the same or similar methods as the sintered lithium-containing ceramic sheet.

[0060] In some specific embodiments, the preset thickness in step (b2) 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.

[0061] In some specific embodiments, the sintering temperature in step (b3) 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.

[0062] In some specific embodiments, in step (b3), the heating rate is 5 to 20 °C / min, preferably 10 °C / min; the sintering time is 6 to 24 hours, preferably 12 hours.

[0063] In some specific embodiments, when mixing the solid electrolyte preform with the fiberizable polymer in step (b1), an excess of lithium precursor is added, wherein the lithium precursor is selected from LiOH·H2O and Li3PO4.

[0064] In some specific embodiments, the excess proportion of the lithium precursor in step (b1) is 1% to 50%, wherein...

[0065] 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%.

[0066] 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%.

[0067] In some specific embodiments, the method for preparing the solid electrolyte preform in step (b1) includes the following steps:

[0068] (c1) 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.

[0069] (c2) The mixture obtained in step (c1) is pre-calcined to obtain the solid electrolyte preform.

[0070] In some specific embodiments, the excess proportion of the lithium precursor in step (c1) is 1% to 50%, wherein...

[0071] 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%.

[0072] 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%.

[0073] In some specific embodiments, the method for preparing the solid electrolyte film includes both adding an excess of lithium precursor in step (c1) and adding an additional excess of lithium precursor in step (b1), wherein the total excess proportion of the lithium precursor in steps (c1) and (b1) is 1% to 50%.

[0074] 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%.

[0075] 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%.

[0076] The fourth aspect of the present invention provides a solid electrolyte film, which is prepared by the preparation method of the third aspect of the present invention.

[0077] The fifth aspect of the present invention provides the application of the solid electrolyte film of the fourth aspect of the present invention in solid lithium metal batteries.

[0078] The sixth aspect of the present invention provides a solid-state lithium metal battery, which includes the solid electrolyte film described in the fourth aspect of the present invention.

[0079] This invention optimizes the structure of the sintering plate used to prepare ceramic solid electrolyte films by using a relatively simple preparation process. It combines a lithium-containing ceramic layer and a high-temperature resistant ceramic layer, so that the sintering plate has the properties of high-temperature deformation resistance while containing lithium-rich materials. This improves the flatness and ionic conductivity of solid electrolyte films when using the sintering plate to prepare solid electrolyte films, resulting in solid electrolyte films with flat surfaces, dense structures, and high ionic conductivity. Attached Figure Description

[0080] Figure 1 shows a schematic diagram of the structure of the sintering plate for preparing ceramic solid electrolyte films according to the present invention. Detailed Implementation

[0081] 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.

[0082] The first aspect of the present invention provides a sintering plate for preparing ceramic solid electrolyte films, characterized in that the sintering plate comprises a lithium-containing ceramic layer and a high-temperature resistant ceramic layer.

[0083] A schematic diagram of the firing plate of the present invention is shown in Figure 1, which illustrates a longitudinal section of the firing plate, including a lithium-containing ceramic layer 1 and a high-temperature resistant ceramic layer 2. It should be understood that the thicknesses of the two layered structures in the figure are merely schematic and do not imply a limitation on the thickness relationship between the two layers. In some specific embodiments, for cost considerations, the thickness of the high-temperature resistant ceramic layer 2 may be greater than the thickness of the lithium-containing ceramic layer 1.

[0084] In some specific embodiments, the lithium-containing ceramic layer 1 of the firing plate comprises one or more materials 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). In a preferred embodiment, the lithium-containing ceramic layer 1 is composed of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphate, or lithium aluminum titanium phosphate.

[0085] The above-mentioned materials are solid electrolyte materials known in the art. In a specific embodiment, the chemical formula of lithium lanthanum zirconium oxide (LLZO) is Li7La3Zr2O. 12 ;

[0086] 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 1.5 Ta 0.5 O 12 When x = 0.6, the chemical formula is Li. 6.4 La3Zr 1.4 Ta 0.6 O 12 ;

[0087] 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 ;

[0088] 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 ;

[0089] 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;

[0090] Lithium aluminum germanium phosphate (LAGP) has the chemical formula Li. 1.5 Al 0.5 Ge 1.5 (PO4)3;

[0091] The chemical formula of lithium aluminum titanium phosphate (LATP) is Li. 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0092] The inventors discovered that the material of the sintering plate has a certain impact on the ionic conductivity of the prepared solid electrolyte. Lithium (e.g., Li₂O) in the solid electrolyte volatilizes 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, thus causing a decrease in ionic conductivity. Conversely, if the sintering plate material itself is a lithium-containing ceramic material with a high lithium content, it can create a lithium-rich atmosphere on the film surface at high temperatures, suppressing the formation of the second phase in the solid electrolyte film.

[0093] In some specific embodiments, the thickness of the lithium-containing ceramic layer is 0.2-5 mm. Preferably, the thickness of the lithium-containing ceramic layer is 0.5-3 mm, more preferably 1-2 mm. According to specific embodiments, the thickness of the lithium-containing ceramic layer can be 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, or any thickness within the above ranges.

[0094] In some specific embodiments, the high-temperature resistant ceramic layer 2 of the firing plate comprises one or more materials selected from magnesium oxide, zirconium oxide, or alumina. In a preferred embodiment, the high-temperature resistant ceramic layer 2 is composed of magnesium oxide, zirconium oxide, or alumina.

[0095] In this invention, there are no particular limitations on the material of the high-temperature resistant ceramic layer, as long as it is a material that does not wrinkle, bend or deform under high temperature conditions (e.g., >1450℃).

[0096] In some specific embodiments, the thickness of the high-temperature resistant ceramic layer is 0.5-5 mm. Preferably, the thickness of the high-temperature resistant ceramic layer is 1-4 mm, more preferably 2-3 mm. According to specific embodiments, the thickness of the high-temperature resistant ceramic layer can be 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, or any thickness within the above range.

[0097] In some specific embodiments, the lithium-containing ceramic layer and the high-temperature resistant ceramic layer of the sintering plate are tightly bonded together by sintering to form an integrated composite sintering plate.

[0098] In some specific embodiments, the firing plate has a substantially flat surface. Generally speaking, the firing plate of the present invention can maintain the flatness of its surface without change after multiple high-temperature sinterings, eliminating the need for mechanical leveling treatments such as polishing after use.

[0099] In some embodiments, the surface of the firing plate has a shape selected from circles, ellipses, rectangles, squares, triangles, or combinations thereof. In a preferred embodiment, the surface of the firing plate is substantially rectangular or circular.

[0100] In some specific embodiments, the surface of the firing plate has a maximum length of 2-20 cm and / or a maximum width of 2-20 cm. In this invention, the maximum length of the firing plate surface is defined as the maximum distance between any two points on the firing plate surface, and the maximum length of the firing plate surface is defined as the maximum distance between any two points on the firing plate surface in a direction perpendicular to the maximum length. For example, when the firing plate is rectangular, the maximum length and maximum width are the length and width of the rectangle, respectively; when the firing plate is elliptical, the maximum length and maximum width are the major axis and minor axis of the ellipse, respectively.

[0101] The second aspect of the present invention provides a method for preparing the firing plate of the first aspect of the present invention, comprising the following steps:

[0102] (1) Polishing and grinding the sintered lithium-containing ceramic sheet;

[0103] (2) The polished lithium-containing ceramic sheets are stacked on the high-temperature resistant ceramic sheets and sintered at high temperature to obtain the sintering plate.

[0104] Through high-temperature composite sintering, lithium-containing ceramic sheets and high-temperature resistant ceramic sheets are tightly bonded together to form an integrated composite sintering plate, wherein the lithium-containing ceramic sheets form the lithium-containing ceramic layer 1 of the sintering plate, and the high-temperature resistant ceramic sheets form the high-temperature resistant ceramic layer 2 of the sintering plate.

[0105] In some specific embodiments, the surface flatness of the lithium-containing ceramic sheet after polishing is ≤10μm. In this invention, surface flatness is defined as the maximum value of the height difference between points on the sampled surface in the direction perpendicular to the surface. A smaller surface flatness value indicates higher surface flatness. In preferred embodiments, the surface flatness of the lithium-containing ceramic sheet after polishing is ≤9μm, ≤8μm, ≤7μm, ≤6μm, or ≤5μm.

[0106] In some specific embodiments, the high-temperature composite sintering temperature is 0-50°C below the melting point of the lithium-containing ceramic material. That is, the composite sintering temperature depends on the lithium-containing ceramic material. For example, for LLZO, LLZTO, LLAZO, and LLGZO, the preferred composite sintering temperature is 1250-1400°C; for LLTO, the preferred composite sintering temperature is 1300-1400°C; for LAGP, the preferred composite sintering temperature is 900-1100°C; and for LATP, the preferred composite sintering temperature is 1000-1200°C. In this invention, the composite sintering needs to be carried out at a temperature close to the melting point of the lithium-containing ceramic material. Its effect is similar to melting the crystalline phase on the surface of the lithium-containing ceramic sheet, allowing the lithium-rich material to penetrate into or adhere to the high-temperature resistant ceramic sheet, thereby tightly bonding the two sheets together to form an integrated composite sintering plate.

[0107] In this invention, the preparation method of the lithium-containing ceramic sheet is not particularly limited; it can be prepared by tape casting or by a dry method. In some specific embodiments, the sintered lithium-containing ceramic sheet is obtained through the following steps:

[0108] (a1) Mixing lithium-containing ceramic material powder with a fiberizable polymer, thereby fiberizing the polymer and uniformly mixing it with the lithium-containing ceramic material powder;

[0109] (a2) The mixture obtained in step (a1) is hot-pressed to a preset thickness to obtain a lithium-containing ceramic film;

[0110] (a3) The lithium-containing ceramic green film obtained in step (a2) is sintered at high temperature to obtain the sintered lithium-containing ceramic sheet.

[0111] 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.

[0112] In some specific embodiments, in step (a1), the powder content of the lithium-containing ceramic material is 80-99.9 wt%, preferably 90-99 wt%, and more preferably 95-99 wt%.

[0113] In some specific embodiments, in step (a1), the content of the fiberizable polymer is 0.1-20 wt%, preferably 1-10 wt%, and more preferably 1-5 wt%.

[0114] In some specific embodiments, the method for fiberizing the polymer in step (a1) is selected from at least one of the following:

[0115] (1) Grind the polymer together with the powder of the lithium-containing ceramic material;

[0116] (2) The polymer and the lithium-containing ceramic material powder are sheared together at high speed;

[0117] (3) The polymer is subjected to a heat stretching treatment;

[0118] (4) The polymer and the lithium-containing ceramic material powder are subjected to air jet milling.

[0119] 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.

[0120] In some specific embodiments, the hot pressing process in step (a2) is performed by one or more hot rolling processes using a roller press.

[0121] In some specific embodiments, the hot pressing process in step (a2) is performed by one or more hot rolling processes using a roller press.

[0122] In some specific embodiments, the preset thickness in step (a2) is 0.2-10 mm. Preferably, the preset thickness is 0.5-5 mm, and more preferably 2-4 mm.

[0123] In some specific embodiments, step (a3) ​​causes the polymer in the lithium-containing ceramic biofilm to decompose, preferably completely decompose.

[0124] In some specific embodiments, the sintering temperature in step (a3) ​​is 1000–1400°C. The sintering temperature depends on the chemical composition of the lithium-containing ceramic material. For example, for LLZO, LLZTO, LLAZO, and LLGZO, the preferred sintering temperature is 1250–1400°C; for LLTO, the preferred sintering temperature is 1300–1400°C; for LAGP, the preferred sintering temperature is 850–1000°C; and for LATP, the preferred sintering temperature is 950–1100°C.

[0125] In some specific embodiments, the sintering temperature in step (a3) ​​is lower than the composite sintering temperature in step (2).

[0126] In some specific embodiments, the heating rate in step (a3) ​​is 5 to 20 °C / min, preferably 10 °C / min; the holding time after reaching the sintering temperature is 5 to 30 minutes, preferably 10 minutes.

[0127] In some specific embodiments, when mixing the lithium-containing ceramic material powder with the fiberizable polymer in step (a1), an excess of lithium precursor may be added, wherein the lithium precursor is selected from LiOH·H2O and Li3PO4. The excess molar ratio of the lithium precursor is 0% to 20%.

[0128] In this invention, the preparation method of the lithium-containing ceramic sheet used to prepare the composite sintering plate is similar to the preparation method of the solid electrolyte, the main difference being that the lithium-containing ceramic sheet has a higher thickness, a higher sintering temperature, and a shorter holding time. Through the above process, a relatively dense and flat lithium-containing ceramic sheet can be prepared, which facilitates subsequent processing, and the shorter process time helps reduce production costs.

[0129] A third aspect of this invention provides a method for preparing a ceramic solid electrolyte thin film, comprising the following steps:

[0130] The sintered solid electrolyte film is stacked under the sintering plate of the first aspect of the present invention and then sintered at high temperature to obtain a planarized solid electrolyte film.

[0131] The lithium-containing ceramic layer of the sintering plate faces the solid electrolyte film.

[0132] By using the composite sintering plate of the present invention to assist in flattening sintering, the flatness of the solid electrolyte film can be improved, and at the same time, the ionic conductivity of the solid electrolyte film can be improved.

[0133] In this invention, a certain mechanical pressure is applied to the sintered solid electrolyte film by the gravity of the sintering plate, causing it to soften and deform at high temperature, and then gradually flatten under external pressure. The pressure applied by the sintering plate is not too great, which can prevent the uneven and brittle solid electrolyte film from cracking due to excessive pressure.

[0134] 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.

[0135] In some specific embodiments, the planarization sintering temperature is higher than the densification sintering temperature, i.e., the sintering temperature for preparing the sintered solid electrolyte film from the solid electrolyte film. In some specific embodiments, the sintering plate used for planarization sintering is prepared by the method of the second aspect of the present invention, and the planarization sintering temperature is lower than the composite sintering temperature in step (2) of preparing the sintering plate. 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. For example, for LLZO, LLZTO, LLAZO and LLGZO, the planarization sintering temperature is preferably 1200-1400℃; for LLTO, the planarization sintering temperature is preferably 1300-1400℃; for LAGP, the planarization sintering temperature is preferably 800-1000℃; for LATP, the planarization sintering temperature is preferably 900-1100℃. The inventors discovered through research that, in order to achieve the goal of planarizing 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 holding time required. To improve production efficiency and avoid losses due to lithium volatilization at high temperatures, the planarization sintering temperature is set higher than the densification sintering temperature in the solid electrolyte film preparation method of this invention.

[0136] 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.

[0137] In some specific embodiments, the planarized solid electrolyte film is obtained by high-temperature sintering with the sintered solid electrolyte film stacked between two sintering plates. In this embodiment, the lithium-containing ceramic layers of both sintering plates face the solid electrolyte film, i.e., the solid electrolyte film is sandwiched between the lithium-containing ceramic layers of the two sintering plates.

[0138] In some specific embodiments, the surface of the sintering plate that contacts the solid electrolyte film is a flat surface. 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, thereby forming a flat surface structure.

[0139] In some specific embodiments, the thickness of the firing plate is 0.2-10 mm, preferably 1-5 mm, more preferably 2-4 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, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any thickness within the above range.

[0140] In some specific embodiments, the lithium-containing ceramic layer of the sintering plate comprises the same material as the solid electrolyte film material. In a preferred embodiment, the material of the lithium-containing ceramic layer of the sintering plate is the same as the material of the solid electrolyte film. When the material of the solid electrolyte film is the same as that of the lithium-containing ceramic layer of the sintering plate, the influence of the intermigration of chemical elements from different lithium-rich materials on the crystal structure of the solid electrolyte film can be reduced, and adhesion between the solid electrolyte film and the sintering plate due to different melting points can also be avoided.

[0141] 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.

[0142] The planarization sintering step of this invention is applicable to solid electrolyte films prepared by any known method, including tape casting and dry sintering. The preparation method of the solid electrolyte film of this invention does not particularly limit the chemical composition of the solid electrolyte, as long as it is a ceramic solid electrolyte that can be prepared by high-temperature sintering, including but not limited to the specific electrolyte materials listed above. 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 aspects; both can be prepared into solid electrolyte films using the method of this invention. Other element-doped forms of the listed solid electrolytes, as well as other solid electrolytes not listed, can also be prepared into films using the method of this invention.

[0143] In some specific embodiments, the sintered solid electrolyte film is obtained through the following dry process:

[0144] (b1) Mixing a solid electrolyte preform with a fibrous polymer, thereby fibrousizing the polymer and uniformly mixing it with the solid electrolyte preform;

[0145] (b2) The mixture obtained in step (b1) is hot-pressed to a preset thickness to obtain a solid electrolyte film;

[0146] (b3) The solid electrolyte film obtained in step (b2) is sintered at high temperature to obtain the sintered solid electrolyte film.

[0147] That is, the above method is a method for preparing solid electrolyte films including dry film preparation, primary densification sintering, and secondary planarization sintering.

[0148] In some specific embodiments, the sintered solid electrolyte film can be prepared using the same or similar methods as the sintered lithium-containing ceramic sheet.

[0149] 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.

[0150] In some specific embodiments, in step (b1), 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.

[0151] In some specific embodiments, in step (b1), 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.

[0152] In some specific embodiments, in step (b1), the combined content of the solid electrolyte preform and the fiberizable polymer is 100 wt%.

[0153] In some specific embodiments, the method for fiberizing the polymer in step (b1) is selected from at least one of the following:

[0154] (1) Grind the polymer together with the solid electrolyte preform;

[0155] (2) The polymer and the solid electrolyte preform are sheared together at high speed;

[0156] (3) The polymer is subjected to a heat stretching treatment;

[0157] (4) The polymer and the solid electrolyte preform are subjected to air jet milling.

[0158] 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.

[0159] In some specific embodiments, the hot pressing process in step (b2) involves one or more hot rolling processes using a roller press. In some preferred embodiments, in step (b2), the mixture obtained in step (b1) is repeatedly rolled 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 favorable to processing, such as 50-150°C, 60-120°C, 70-100°C, 75-90°C, etc.

[0160] In some specific embodiments, the preset thickness in step (b2) 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.

[0161] In some specific embodiments, step (b3) causes the polymer in the solid electrolyte film to decompose, preferably completely decompose. Through the high-temperature sintering in step (b3), 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 with high ionic conductivity.

[0162] In some specific embodiments, the sintering temperature in step (b3) 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.

[0163] In some specific embodiments, in step (b3), 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.

[0164] 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 also be added additionally when mixing the solid electrolyte preform with the fibrous polymer in step (b1).

[0165] Therefore, in some specific embodiments, when mixing the solid electrolyte preform with the fiberizable polymer in step (b1), an excess of lithium precursor is added, wherein the lithium precursor is selected from LiOH·H2O and Li3PO4.

[0166] Furthermore, in some specific embodiments, the method for preparing the solid electrolyte preform in step (b1) includes the following steps:

[0167] (c1) 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.

[0168] (c2) The mixture obtained in step (c1) is pre-calcined to obtain the solid electrolyte preform.

[0169] In some specific embodiments, the method for preparing the solid electrolyte film includes both adding an excess of lithium precursor in step (c1) and adding an additional excess of lithium precursor in step (b1). In this case, the excess proportion of the number of moles of lithium precursor in steps (c1) and (b1) should be calculated together.

[0170] 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).

[0171] In a specific embodiment of the present invention, regardless of whether the lithium precursor is added in step (c1), in step (b1), or in both steps (c1) and (b1), 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.

[0172] 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.

[0173] The fourth aspect of the present invention provides a solid electrolyte film, which is prepared by the preparation method of the third aspect of the present invention.

[0174] The fifth aspect of the present invention provides the application of the solid electrolyte film of the fourth aspect of the present invention in solid lithium metal batteries.

[0175] The sixth aspect of the present invention provides a solid-state lithium metal battery, which includes the solid electrolyte film described in the fourth aspect of the present invention.

[0176] Example

[0177] 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.

[0178] 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.

[0179] Preparation Example 1: Preparation of LLZTO Solid Electrolyte Powder

[0180] 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).

[0181] 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.

[0182] The dried powder was placed in a muffle furnace and calcined at 900℃ for 12 hours, with both heating and cooling rates at 5℃ / min. After cooling, LLZTO solid electrolyte powder was obtained. This LLZTO solid electrolyte powder is used as a powder for lithium-containing ceramic materials in the preparation of sintering plates and as a solid electrolyte preform in the preparation of solid electrolyte films.

[0183] Preparation Example 2: Preparation of LLZTO Ceramic Film

[0184] 95 parts by mass of LLZTO powder obtained in Preparation Example 1 (LiOH·H2O was in excess by 20% during powder 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.

[0185] The above-mentioned mixed block was rolled multiple times at 80°C using a roller press to gradually reduce the thickness of the green film, and finally obtained an LLZTO ceramic green film (lithium-containing ceramic green film) with a thickness of 2.5 mm.

[0186] Example 1: Preparation of LLZTO-magnesium oxide sintered plate

[0187] One-time densification sintering: The LLZTO ceramic green film obtained in Preparation Example 2 was placed in a magnesium oxide crucible and placed in a muffle furnace for high-temperature sintering in air. The sintering conditions were: heating rate 10℃ / min; holding temperature: 1350℃; holding time 10min; cooling rate 5℃ / min, to obtain sintered LLZTO ceramic sheets.

[0188] Secondary composite sintering: The sintered LLZTO ceramic sheets were polished until the surface flatness was ≤10μm, and the thickness was measured to be 1mm. LLZTO ceramic sheets with a length of 60mm and a width of 40mm were stacked on top of flat magnesia ceramic sheets of the same size (magnesia sheet thickness 2mm). The sheets were placed in a muffle furnace and subjected to a secondary high-temperature heat treatment in air. The heat treatment conditions were: heating rate 10℃ / min; holding temperature: 1380℃; holding time: 10min; cooling rate 5℃ / min. After cooling, an LLZTO-magnesia composite sintering plate for preparing ceramic solid electrolyte films was obtained.

[0189] Example 2: Preparation of LLZTO-alumina sintered plate

[0190] In this embodiment, except that the magnesium oxide ceramic sheet is replaced with an alumina ceramic sheet, the LLZTO-alumina composite sintering plate is obtained using the same steps and conditions as in Example 1.

[0191] Example 3: Preparation of LLZTO-zirconia sintered plate

[0192] In this embodiment, except that the magnesium oxide ceramic sheet is replaced with a zirconium oxide ceramic sheet, the LLZTO-zirconia composite sintering plate is obtained using the same steps and conditions as in Example 1.

[0193] Example 4: Preparation of LLGZO-magnesium oxide sintered plate

[0194] In this embodiment, except that the LLZTO powder blank in Preparation Example 2 was replaced with the LLGZO powder blank, the same steps and conditions as in Preparation Example 2 were used to obtain an LLGZO ceramic film with a final thickness of 2.5 mm.

[0195] One-time densification sintering: The above-mentioned LLGZO ceramic green film is placed in a magnesium oxide crucible and placed in a muffle furnace for high-temperature sintering in air. The sintering conditions are: heating rate 10℃ / min; holding temperature: 1300℃, holding time 10min; cooling rate 5℃ / min, to obtain sintered LLGZO ceramic sheets.

[0196] Secondary composite sintering: The sintered LLGZO ceramic sheets were polished until the surface flatness was ≤10μm, and the thickness was measured to be 1mm. A 60mm long and 40mm wide LLGZO ceramic sheet was stacked on a flat 2mm thick magnesia ceramic sheet of the same size. The sheet was placed in a muffle furnace and subjected to a secondary high-temperature heat treatment in air. The heat treatment conditions were: heating rate 10℃ / min; holding temperature: 1330℃; holding time: 10min; cooling rate 5℃ / min. After cooling, an LLGZO-magnesia composite sintering plate for preparing ceramic solid electrolyte films was obtained.

[0197] Example 5: Preparation of LLAZO-magnesium oxide sintered plate

[0198] In this embodiment, except that the LLZTO powder blank in Preparation Example 2 was replaced with LLAZO powder blank, the same steps and conditions as in Preparation Example 2 were used to obtain an LLAZO ceramic film with a final thickness of 2.5 mm.

[0199] One-time densification sintering: The above-mentioned LLAZO ceramic green film is placed in a magnesium oxide crucible and placed in a muffle furnace for high-temperature sintering in air. The sintering conditions are: heating rate 10℃ / min; holding temperature: 1330℃, holding time 10min; cooling rate 5℃ / min, to obtain sintered LLAZO ceramic sheets.

[0200] Secondary composite sintering: The sintered LLAZO ceramic sheets were polished until the surface flatness was ≤10μm, and the thickness was measured to be 1mm. LLAZO ceramic sheets with a length of 60mm and a width of 40mm were stacked on top of flat magnesium oxide ceramic sheets of the same size (2mm thick). The sheets were placed in a muffle furnace and subjected to a secondary high-temperature heat treatment in air. The heat treatment conditions were: heating rate 10℃ / min; holding temperature: 1350℃; holding time: 10min; cooling rate 5℃ / min. After cooling, the LLAZO-magnesium oxide composite sintering plate for preparing ceramic solid electrolyte films was obtained.

[0201] Example 6: Preparation of LATP-magnesium oxide sintering plate

[0202] In this embodiment, except that the LLZTO powder blank in Preparation Example 2 was replaced with LATP powder blank, the LATP ceramic film with a final thickness of 2.5 mm was obtained by the same steps and conditions as in Preparation Example 2.

[0203] One-time densification sintering: The above-mentioned LATP ceramic green film is placed in a magnesium oxide crucible and placed in a muffle furnace for high-temperature sintering in air. The sintering conditions are: heating rate 10℃ / min; holding temperature: 1000℃, holding time 10min; cooling rate 5℃ / min, to obtain sintered LATP ceramic sheets.

[0204] Secondary composite sintering: The sintered LLGZO ceramic sheets were polished until the surface flatness was ≤10μm, and the thickness was measured to be 1mm. A 60mm long and 40mm wide LATP ceramic sheet was stacked on a flat 2mm thick magnesia ceramic sheet of the same size. The sheet was placed in a muffle furnace and subjected to a secondary high-temperature heat treatment in air. The heat treatment conditions were: heating rate 10℃ / min; holding temperature: 1150℃; holding time: 10min; cooling rate 5℃ / min. After cooling, an LATP-magnesia oxide composite sintering plate for preparing ceramic solid electrolyte films was obtained.

[0205] Example 7: Preparation of LAGP-magnesium oxide sintering plate

[0206] In this embodiment, except that the LLZTO powder blank in Preparation Example 2 was replaced with LAGP powder blank, the same steps and conditions as in Preparation Example 2 were used to obtain a LAGP ceramic film with a final thickness of 2.5 mm.

[0207] One-time densification sintering: The above-mentioned LAGP ceramic green film is placed in a magnesium oxide crucible and placed in a muffle furnace for high-temperature sintering in air. The sintering conditions are: heating rate 10℃ / min; holding temperature: 850℃, holding time 10min; cooling rate 5℃ / min, to obtain sintered LAGP ceramic sheets.

[0208] Secondary composite sintering: The sintered LLGZO ceramic sheets were polished until the surface flatness was ≤10μm, and the thickness was measured to be 1mm. A 60mm long and 40mm wide LAGP ceramic sheet was stacked on a flat 2mm thick magnesium oxide ceramic sheet of the same size. The sheet was placed in a muffle furnace and subjected to a secondary high-temperature heat treatment in air. The heat treatment conditions were: heating rate 10℃ / min; holding temperature: 1050℃; holding time: 10min; cooling rate 5℃ / min. After cooling, the LAGP-magnesium oxide composite sintering plate for preparing ceramic solid electrolyte films was obtained.

[0209] Comparative Example 1: Preparation of LLZTO sintering plate

[0210] In this comparative example, the LLZTO ceramic sheet is not combined with other high-temperature resistant ceramic sheets. That is, during the secondary high-temperature heat treatment, the polished LLZTO ceramic sheet is not stacked with other materials and is directly subjected to heat treatment to obtain the LLZTO firing plate.

[0211] Test Example 1: Preparation of LLZTO Solid Electrolyte Thin Films

[0212] Step 1: Preparation of LLZTO solid electrolyte film

[0213] 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.

[0214] 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.

[0215] Step 2: Primary densification sintering

[0216] The LLZTO solid electrolyte green film obtained in step one 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.

[0217] Step 3: Secondary planarization sintering: Using the sintering plates prepared in Examples 1-3 and Comparative Example 1, the sintered LLZTO solid electrolyte film obtained in Step 2 was horizontally placed between two sintering plates, ensuring that the lithium-containing ceramic layer (e.g., the LLZTO layer) of the sintering plate was in contact with the solid electrolyte film. The plate was then 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: 1320°C; holding time: 10 min; cooling rate 5°C / min. After cooling, a planarized LLZTO solid electrolyte film was obtained.

[0218] The deformation of the substrate after the experiment was observed, and the results are shown in Table 1. Simultaneously, the ionic conductivity of the prepared LLZTO solid electrolyte film was measured. The procedure was as follows: Ag conductive layers were deposited on both sides of the electrolyte film using a thermal evaporation coating instrument, and the film was encapsulated using a button cell. Subsequently, AC impedance testing was performed using an electrochemical workstation (MetrohmAutolab) with a test 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. The results of the ionic conductivity are also shown in Table 1.

[0219] Test Example 2: Preparation of LLGZO Solid Electrolyte Thin Film

[0220] In this test example, an LLGZO solid electrolyte film was prepared using a method similar to that of Test Example 1, with the following differences: the LLZTO powder blank in step one was replaced with an LLGZO powder blank; the holding temperature for the first densification sintering was changed to 1100℃; and the sintering plate prepared in Example 4 was used in the second planarization sintering, with the holding temperature changed to 1280℃. A planarized LLGZO solid electrolyte film was finally obtained. The deformation of the sintering plate after the experiment is shown in Table 1. Furthermore, the ionic conductivity of the LLGZO solid electrolyte film was tested using the same method as in Test Example 1, and the results are also shown in Table 1.

[0221] Test Example 3: Preparation of LLAZO Solid Electrolyte Thin Film

[0222] In this test example, an LLAZO solid electrolyte film was prepared using a method similar to that of Test Example 1, with the following differences: the LLAZO powder blank in step one was replaced with LLAZO powder blank; the holding temperature for the first densification sintering was changed to 1100℃; and the sintering plate prepared in Example 5 was used in the second planarization sintering, with the holding temperature changed to 1300℃. A planarized LLAZO solid electrolyte film was finally obtained. The deformation of the sintering plate after the experiment is shown in Table 1. Furthermore, the ionic conductivity of the LLAZO solid electrolyte film was tested using the same method as in Test Example 1, and the results are also shown in Table 1.

[0223] Test Example 4: Preparation of LATP Solid Electrolyte Thin Film

[0224] In this test example, an LATP solid electrolyte film was prepared using a method similar to that of Test Example 1, with the following differences: the LATP powder blank in step one was replaced with LATP powder blank; the holding temperature for the first densification sintering was changed to 950°C; and the sintering plate prepared in Example 6 was used in the second planarization sintering, with the holding temperature changed to 1100°C. A planarized LATP solid electrolyte film was finally obtained. The deformation of the sintering plate after the experiment is shown in Table 1. Furthermore, the ionic conductivity of the LATP solid electrolyte film was tested using the same method as in Test Example 1, and the results are also shown in Table 1.

[0225] Test Example 5: Preparation of LAGP Solid Electrolyte Thin Film

[0226] In this test example, a LAGP solid electrolyte film was prepared using a method similar to that of Test Example 1, with the following differences: the LAGP powder blank in step one was replaced with a LAGP powder blank; the holding temperature for the first densification sintering was changed to 800°C; and the sintering plate prepared in Example 7 was used in the second planarization sintering, with the holding temperature changed to 1000°C. A planarized LAGP solid electrolyte film was finally obtained. The deformation of the sintering plate after the experiment is shown in Table 1. Furthermore, the ionic conductivity of the LAGP solid electrolyte film was tested using the same method as in Test Example 1, and the results are also shown in Table 1.

[0227] Table 1

[0228] Results and Evaluation

[0229] As shown in Table 1, the sintering plate with the double-layer structure of the present invention will not deform after the solid electrolyte film is prepared, and can maintain the flatness of the surface. This solves the deformation problem when a single lithium-rich material is used as the sintering plate material, while also retaining the benefits of using lithium-containing ceramic materials such as LLZTO as the sintering plate material to improve the ionic conductivity of the electrolyte film.

[0230] The solid electrolyte film prepared using the sintering plate of the present invention has high flatness, and can be assembled into a solid-state battery without further mechanical processing such as polishing; moreover, the electrolyte film is semi-transparent, indicating that the electrolyte film is thin and has high density, indicating that the flattening sintering does not affect the thin density of the electrolyte film; when the electrolyte film is sintered at high temperature, it comes into contact with lithium-rich materials with the same or similar material composition, which can reduce the volatilization of lithium and the reaction between lithium active material and sintering plate material, thereby obtaining higher ionic conductivity.

[0231] 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 susceptor for preparing a thin film of a ceramic solid electrolyte, characterized by, The firing plate includes a lithium-containing ceramic layer and a high-temperature resistant ceramic layer.

2. The grilling grate of claim 1, wherein, The lithium-containing ceramic layer comprises one or more materials 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, and / or The thickness of the lithium-containing ceramic layer is 0.2-5 mm, preferably 0.5-3 mm, and more preferably 1-2 mm.

3. The firing plate according to claim 1 or 2, characterized in that, The high-temperature resistant ceramic layer comprises one or more materials selected from magnesium oxide, zirconium oxide, or aluminum oxide, and / or The thickness of the high-temperature resistant ceramic layer is 0.5-5mm, preferably 1-4mm, and more preferably 2-3mm.

4. The firing plate according to any one of claims 1 to 3, characterized in that, The lithium-containing ceramic layer and the high-temperature resistant ceramic layer are tightly bonded together by sintering, and / or The firing plate has a substantially flat surface.

5. The firing plate according to any one of claims 1 to 4, characterized in that, The surface of the firing plate has a shape selected from circles, ellipses, rectangles, squares, triangles, or combinations thereof, and / or The surface of the firing plate has a maximum length of 2-20cm and / or a maximum width of 2-20cm.

6. The method for preparing the firing plate according to any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: (1) Polishing and grinding the sintered lithium-containing ceramic sheet; (2) The polished lithium-containing ceramic sheets are stacked on the high-temperature resistant ceramic sheets and sintered at high temperature to obtain the sintering plate.

7. The preparation method according to claim 6, characterized in that, The surface flatness of the lithium-containing ceramic sheet after polishing is ≤10μm.

8. The preparation method according to claim 6 or 7, characterized in that, The high-temperature sintering temperature is 0-50°C below the melting point of the lithium-containing ceramic material.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The sintered lithium-containing ceramic sheet is obtained through the following steps: (a1) Mixing lithium-containing ceramic material powder with a fiberizable polymer, thereby fiberizing the polymer and uniformly mixing it with the lithium-containing ceramic material powder; (a2) The mixture obtained in step (a1) is hot-pressed to a preset thickness to obtain a lithium-containing ceramic film; (a3) The lithium-containing ceramic green film obtained in step (a2) is sintered at high temperature to obtain the sintered lithium-containing ceramic sheet.

10. The preparation method according to claim 9, 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, preferably polytetrafluoroethylene, and / or In step (a1), the content of the lithium-containing ceramic material powder is 80-99.9 wt%; and / or the content of the fiberizable polymer is 0.1-20 wt%.

11. The preparation method according to claim 9 or 10, characterized in that, The hot pressing process in step (a2) involves one or more hot rolling processes using a roller press, and / or the preset thickness is 0.2-10 mm, preferably 1-5 mm, and more preferably 2-4 mm.

12. The preparation method according to any one of claims 9 to 11, characterized in that, Step (a3) ​​causes the polymer in the lithium-containing ceramic film to decompose completely, and / or the sintering temperature in step (a3) ​​is 1000-1400°C.

13. A method for preparing a ceramic solid electrolyte thin film, characterized in that, The preparation method includes the following steps: The sintered solid electrolyte film is stacked under the sintering plate described in any one of claims 1 to 5 and then subjected to high-temperature sintering to obtain a flattened solid electrolyte film. The lithium-containing ceramic layer of the sintering plate faces the solid electrolyte film.

14. The preparation method according to claim 13, characterized in that, The thickness of the sintered solid electrolyte film is 1-600 μm, preferably 5-300 μm, and more preferably 10-200 μm.

15. The preparation method according to claim 13 or 14, characterized in that, The high-temperature sintering temperature is higher than the sintering temperature at which the solid electrolyte film is prepared from the solid electrolyte biofilm.

16. The preparation method according to any one of claims 13 to 15, characterized in that, The planarized solid electrolyte film is obtained by high-temperature sintering with the sintered solid electrolyte film stacked between two sintering plates.

17. The preparation method according to any one of claims 13 to 16, characterized in that, The surface of the bearing plate that contacts the solid electrolyte film is a flat surface, and / or The lithium-containing ceramic layer of the sintering plate comprises the same material as the solid electrolyte thin film material.

18. A ceramic solid electrolyte film, said ceramic solid electrolyte film being prepared by the preparation method according to any one of claims 13 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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