High-ionic-conductivity double-doped cerium-based garnet electrolyte for solid-state battery

Abstract

The invention belongs to the technical field of solid-state lithium metal batteries, and particularly relates to a double-doped cerium-based garnet electrolyte with high ionic conductivity for a solid-state battery, the chemical composition of the double-doped cerium-based garnet electrolyte is Li < 5 + x + y > La < 3 > Ce < x > Zr < y > Ta < 2-x-y > O < 12 >, xlt; 2.0, 0lt; yt; Yt; and 1.5. Compared with the prior art, the garnet material has the advantages that the problem of low room-temperature ionic conductivity of the existing garnet material is solved; the preparation temperature of the garnet electrolyte is effectively reduced; and the cost of the garnet electrolyte raw material is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state lithium metal batteries, and particularly relates to a double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries. Background Art

[0002] Lithium-ion batteries have been widely used in portable electronic devices and electric vehicles, and the requirements for energy density and long battery life are getting higher and higher. Compared with commercial electrolytes, lithium metal batteries using inorganic solid electrolytes are expected to alleviate "battery anxiety" because they have potentially higher energy density and inherently relatively better safety.

[0003] Among inorganic electrolytes, garnet-type oxide electrolytes have attracted much attention due to their high lithium-ion conductivity (>10 -4 S cm -1 ) at room temperature, thermal stability, and wide electrochemical window. The most widely studied Li 7 La 3 Zr 2 O 12 (LLZO) exists in two different polymorphs - tetragonal phase and cubic phase, and the ionic conductivity of the cubic phase is two orders of magnitude higher than that of the tetragonal phase. Heterovalent doping at the cation position, usually at the Li + or Zr 4+ site, is a common method to stabilize the cubic phase. Al 3+ and Ga 3+ ions have been used to partially replace the Li + site to stabilize the cubic phase, thereby increasing the lithium-ion conductivity of LLZO. In particular, Ga-doped LLZO derivatives exhibit an ionic conductivity exceeding 10 -3 S cm -1 at room temperature, but Ga is a rare earth element with high cost, which limits its practical application. In addition, doping of high-valence elements into the Zr 4+ position, such as Ta 5+ , Nb 5+ , and W 6+ , can also promote the disordering of the Li + sublattice by introducing lithium vacancies in the lattice, thereby promoting the stabilization of the cubic phase and rapid ionic conduction. However, compared with liquid electrolytes, their lithium-ion conductivity is still low.

[0004] Another major challenge in the practical application of garnet electrolytes is that in order to obtain dense ceramic particles, they usually need to be sintered at high temperatures (>1200 °C) for a long time, or special sintering techniques such as spark plasma sintering (SPS), hot isostatic pressing (HIP), microwave-assisted sintering, and field-assisted sintering are adopted. These methods usually result in high energy consumption and limit large-scale production. Therefore, there is an urgent need to discover garnet electrolytes with new components to improve their ionic conductivity limit and reduce the preparation temperature of material synthesis.

[0005] The present invention aims to provide a double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries, which has high ionic conductivity and a relatively mild preparation temperature. The cerium-based garnet electrolyte is optimized by double-doping design with Zr and Ta, and garnet ceramic powders and ceramic sheets with new components are obtained by solid-phase method technology. Compared with zirconium-based garnet electrolytes, cerium-based garnets have larger lattice sizes to expand the bottleneck size of ion transport; the double-doping of Zr and Ta plays a role in stabilizing the cubic phase structure of the material to enhance the ionic conductivity of the material. In addition, cerium elements are found to be able to effectively improve the density of the material and reduce the sintering temperature of the ceramic. Finally, a new component of cerium-based garnet electrolyte with high ionic conductivity at room temperature and a relatively mild preparation temperature is obtained. Summary of the Invention

[0006] The object of the present invention is to provide a double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries, which has high ionic conductivity and a relatively mild preparation temperature. The cerium-based garnet electrolyte is optimized by double-doping design with Zr and Ta, and garnet ceramic powders and ceramic sheets with new components are obtained by solid-phase method technology. Compared with zirconium-based garnet electrolytes, cerium-based garnets have larger lattice sizes to expand the bottleneck size of ion transport; the double-doping of Zr and Ta plays a role in stabilizing the cubic phase structure of the material to enhance the ionic conductivity of the material. In addition, cerium elements are found to be able to effectively improve the density of the material and reduce the sintering temperature of the ceramic. Finally, a new component of cerium-based garnet electrolyte with high ionic conductivity at room temperature and a relatively mild preparation temperature is obtained. In short, the present invention solves the problem of low room-temperature ionic conductivity of current garnet materials; effectively reduces the preparation temperature of garnet electrolytes; and effectively reduces the cost of garnet electrolyte raw materials.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries, whose chemical composition is: Li 5+x+ y La 3 Ce x Zr y Ta 2-x-y O12 , where 0.1 < x < 2.0, 0 < y < 1.5. The specific chemical composition is, for example, Li 6.32 La 3 Ce 0.66 Zr 0.66 Ta 0.68 O 12 , Li 6.35 La 3 Ce 0.45 Zr 0.9 Ta 0.65 O 12 , Li 6.367 La 3 Ce 0.273 Zr 1.092 Ta 0.36 5 O 12 , Li 6.38 La 3 Ce 0.1535 Zr 1.228 Ta 0.6185 O 12 , Li 6.25 La 3 Ce 1.25 Ta 0.75 O 12 , Li 6 La 3 CeTaO 12 .

[0009] As an improvement to the double-doped cerium-based garnet electrolyte with high ionic conductivity for the solid-state battery of the present invention, the crystal phase of the electrolyte is a cubic phase. XRD and Raman characterizations are used to ensure that the obtained phase is a cubic phase.

[0010] As an improvement to the double-doped cerium-based garnet electrolyte with high ionic conductivity for the solid-state battery of the present invention, the highest ionic conductivity of the electrolyte at 25 °C is 1.1 mS·cm -1 .

[0011] As an improvement to the double-doped cerium-based garnet electrolyte with high ionic conductivity for the solid-state battery of the present invention, 0.1 < x < 2.0.

[0012] As an improvement to the double-doped cerium-based garnet electrolyte with high ionic conductivity for the solid-state battery of the present invention, 0 < y < 1.5.

[0013] As an improvement to the double-doped cerium-based garnet electrolyte with high ionic conductivity for the solid-state battery of the present invention, its preparation method at least includes the following steps:

[0014] First step, prepare ceramic powder by solid-phase method. Mix the oxide raw materials evenly in proportion and calcine at high temperature to obtain cubic-phase double-doped cerium-based Li 5+x+y La 3 Ce x Zr y Ta 2-x-y O 12 ceramic powder;

[0015] Second step, after ball-milling the powder obtained in the first step to reduce the particle size, press it into tablets and sinter at 1050 - 1100 °C to obtain a ceramic sheet for high-performance solid-state batteries.

[0016] As an improvement to the double-doped cerium-based garnet electrolyte with high ionic conductivity for the solid-state battery of the present invention, in the first step, the oxide raw materials include a lithium source, a lanthanum source, a cerium source, a zirconium source, and a tantalum source; among them, the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium oxide, and lithium nitrate; the lanthanum source is at least one of lanthanum dioxide, lanthanum chloride, and lanthanum nitrate; the cerium source is at least one of cerium dioxide, cerium hydroxide, and cerium oxalate; the zirconium source is at least one of zirconium dioxide, zirconium nitrate, and zirconium sulfate; the tantalum source is at least one of tantalum pentoxide and tantalum oxalate. Preferably, the raw materials prepared are a mixed oxide powder of lithium carbonate, lanthanum trioxide, cerium dioxide, zirconium dioxide, and tantalum pentoxide calcined in proportion according to the chemical formula.

[0017] As an improvement to the double-doped cerium-based garnet electrolyte with high ionic conductivity for the solid-state battery of the present invention, the calcination temperature in the first step is 900 - 1000 °C, and the calcination time is 4 - 6 hours.

[0018] As an improvement to the double-doped cerium-based garnet electrolyte with high ionic conductivity for the solid-state battery of the present invention, the particle size of the particles after ball-milling in the second step is below 300 nm, and the sintering temperature is 1050 - 1100 °C.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] First, solve the problem of low ionic conductivity of the widely used LLZO-based garnet electrolyte at present. Specifically, the room-temperature ionic conductivity of LLZO materials is generally on the order of 10 -4 S·cm -1 order of magnitude. The Ga-doped LLZO derivatives exhibit an ionic conductivity exceeding 10 -3 S·cm -1 at room temperature, but Ga, as a rare earth element, has a high cost, which limits its practical application. Therefore, compared with liquid electrolytes, the ionic conductivity of LLZO and its derivatives is still low. Ce in the cerium-based garnet electrolyte 4+Due to its larger ionic radius, it can improve the ionic transport efficiency of the material. In addition, by double-doping with Zr and Ta elements, the cubic phase is stabilized, achieving a high room-temperature ionic conductivity (1.1 mS·cm at 25 degrees). -1 )

[0021] Second, solve the technical problem of the harsh preparation conditions of garnet electrolytes and effectively reduce the sintering temperature; Garnet electrolytes usually need to be sintered at high temperatures (>1200 °C) for a long time, or special sintering techniques are used. These methods usually result in high energy consumption and limit large-scale production. Cerium elements are found to be able to effectively improve the density of the material. Cubic-phase cerium-based garnet electrolyte lithium lanthanum cerium zirconium tantalum oxide can effectively reduce the sintering temperature of the material (1050 - 1100 °C).

[0022] Third, effectively reduce the raw material cost. The extraction and refining process of Zr is relatively complex, and its reserves on the earth are relatively small, resulting in a relatively high production cost and a relatively high price. While lithium lanthanum cerium zirconium tantalum oxide uses Ce as one of the main elements at the B site. Ce is one of the rare earth elements with a relatively high abundance. Its mining and extraction are relatively easy, and the market supply is relatively sufficient, so the price is relatively low. Brief Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the crystal structure of the double-doped cerium-based garnet electrolyte provided by the present invention.

[0024] Figure 2 It is an EIS diagram of the material obtained in Example 1 at different temperatures.

[0025] Figure 3 It is an EIS diagram of the material obtained in Example 2 at different temperatures.

[0026] Figure 4 It is an EIS diagram of the material obtained in Example 3 at different temperatures.

[0027] Figure 5 It is an EIS diagram of the material obtained in Example 4 at different temperatures.

[0028] Figure 6 It is an EIS diagram of the material obtained in Comparative Example 1 at different temperatures.

[0029] Figure 7 It is an EIS diagram of the material obtained in Comparative Example 2 at different temperatures.

[0030] Figure 8 It is an EIS diagram of the material obtained in Comparative Example 3 at different temperatures. Detailed Embodiments

[0031] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0032] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0033] To make the purpose, technical solution, and advantages of the present invention clearer, the following will further describe in detail the embodiments of the present invention with reference to the accompanying drawings.

[0034] Example 1

[0035] A double-doped cerium-based garnet electrolyte with high ionic conductivity for a solid-state battery provided in this embodiment has a chemical composition of: Li 6.32 La 3 Ce 0.66 Zr 0.66 Ta 0.68 O 12 , and the crystal phase of the electrolyte is a cubic phase. The schematic diagram of its crystal structure is as Figure 1 shown.

[0036] Its preparation method at least includes the following steps:

[0037] The first step is to prepare ceramic powder by the solid-phase method. Mix the oxide raw materials evenly and calcine them at a high temperature to obtain cubic-phase double-doped cerium-based Li 6.32 La 3 Ce 0.66 Zr 0.66 Ta 0.68 O 12 ceramic powder, and ensure that the phase is a cubic phase through X-ray diffraction;

[0038] The second step is to ball-mill the powder obtained in the first step to reduce the particle size, then press it and sinter it at 1050-1100 °C to obtain a ceramic sheet for a high-performance solid-state battery.

[0039] In the first step, the oxide raw materials include: lithium carbonate (25% in excess), lanthanum trioxide, zirconium dioxide, cerium dioxide, and tantalum pentoxide.

[0040] The calcination temperature in the first step is 950 °C, and the particle size of the particles after ball-milling in the second step is below 300 nanometers.

[0041] The EIS of the material obtained in this embodiment at different temperatures is as Figure 2 shown.

[0042] Example 2

[0043] This example provides a double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries, and its chemical composition is: Li 6.35 La 3 Ce 0.45 Zr 0.9 Ta 0.65 O 12 , and the crystal phase of the electrolyte is cubic phase.

[0044] Its preparation method at least includes the following steps:

[0045] The first step is to prepare ceramic powder by the solid-phase method. Mix the oxide raw materials evenly and calcine at high temperature to obtain cubic-phase double-doped cerium-based Li 6.35 La 3 Ce 0.45 Zr 0.9 Ta 0.65 O 12 ceramic powder, and ensure that the phase is cubic phase through X-ray diffraction;

[0046] The second step is to ball-mill the powder obtained in the first step to reduce the particle size, and then press and sinter at 1050-1100 °C to obtain a ceramic sheet for high-performance solid-state batteries.

[0047] In the first step, the oxide raw materials include: lithium carbonate (25% in excess), lanthanum sesquioxide, zirconium dioxide, cerium dioxide, tantalum pentoxide. The calcination temperature in the first step is 1000 °C, and the particle size of the particles after ball-milling in the second step is below 300 nanometers.

[0048] The EIS of the material obtained in this example at different temperatures is as Figure 3 shown.

[0049] Example 3

[0050] This example provides a double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries, and its chemical composition is: Li 6.367 La 3 Ce 0.273 Zr 1.092 Ta 0.365 O 12 , and the crystal phase of the electrolyte is cubic phase.

[0051] Its preparation method at least includes the following steps:

[0052] The first step is to prepare ceramic powder by the solid-phase method. Mix the oxide raw materials evenly and calcine at high temperature to obtain cubic-phase double-doped cerium-based Li 6.367 La 3 Ce 0.273 Zr1.092 Ta 0.365 O 12 Ceramic powder, ensuring the crystal phase is cubic through X-ray diffraction;

[0053] In the second step, the powder obtained in the first step is ball-milled to reduce particle size, then pressed and sintered at 1050 - 1100 °C to obtain a ceramic sheet for high-performance solid-state batteries.

[0054] In the first step, the oxide raw materials include: lithium carbonate (25% in excess), lanthanum dioxide, zirconium dioxide, cerium dioxide, and tantalum pentoxide.

[0055] The calcination temperature in the first step is 1000 °C.

[0056] In the second step, the particle size of the ball-milled particles is below 300 nanometers.

[0057] The EIS of the material obtained in this example at different temperatures is as Figure 4 shown.

[0058] Example 4

[0059] This example provides a double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries, and its chemical composition is: Li 6.38 La 3 Ce 0.1535 Zr 1.228 Ta 0.6185 O 12 , and the crystal phase of the electrolyte is cubic.

[0060] Its preparation method at least includes the following steps:

[0061] In the first step, ceramic powder is prepared by the solid-phase method. The oxide raw materials are mixed evenly in proportion and calcined at high temperature to obtain cubic-phase double-doped cerium-based Li 6.38 La 3 Ce 0.1535 Zr 1.228 Ta 0.6185 O 12 ceramic powder, ensuring the crystal phase is cubic through X-ray diffraction;

[0062] In the second step, the powder obtained in the first step is ball-milled to reduce particle size, then pressed and sintered at 1050 - 1100 °C to obtain a ceramic sheet for high-performance solid-state batteries.

[0063] In the first step, the oxide raw materials include: lithium carbonate (25% in excess), lanthanum trioxide, zirconium dioxide, cerium dioxide, and tantalum pentoxide.

[0064] The calcination temperature in the first step is 1000 °C.

[0065] The particle size of the particles after ball milling in the second step is below 300 nanometers.

[0066] The EIS of the material obtained in this example at different temperatures is as Figure 5 shown.

[0067] Comparative Example 1

[0068] This example provides Ta 5+ doped with Li 7 La 3 Ce 2 O 12 , and its chemical composition is: Li 6.25 La 3 Ce 1.25 Ta 0.75 O 12 The EIS of the material obtained in this comparative example at different temperatures is as Figure 6 shown. After ball milling the powder of this example to reduce the particles, the tablets are sintered at 1100 °C to obtain ceramic tablets for high-performance solid-state batteries.

[0069] Comparative Example 2

[0070] This comparative example provides Ta 5+ doped with Li 7 La 3 Ce 2 O 12 , and its chemical composition is: Li 6 La 3 CeTaO 12。 The EIS of the material obtained in this comparative example at different temperatures is as Figure 7 shown.

[0071] After ball milling the powder of this example to reduce the particles, the tablets are sintered at 1150 °C to obtain ceramic tablets for high-performance solid-state batteries.

[0072] Comparative Example 3

[0073] This comparative example provides Ta 5+ doped with Li 7 La 3 Zr 2 O 12 (LLZO), and its chemical composition is: Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 The EIS of the material obtained in this comparative example at different temperatures is as Figure 8As shown. After ball milling the powder of this example to reduce the particle size, it was pressed and sintered at 1250 °C to obtain a ceramic sheet for high-performance solid-state batteries.

[0074] According to the impedance value of the EIS spectrum, the thickness of the ceramic (about 900 microns) and the area of the gold paste (diameter 6.5 mm), from Figures 2 to 8 it can be calculated that:

[0075] In Experimental Example 1, the ionic conductivities of Li 6.32 La 3 Ce 0.66 Zr 0.66 Ta 0.68 O 12 materials at different temperatures are 0.81 mS·cm -1 (20.5 °C), 1.07 mS·cm -1 (25 °C), 1.88 mS·cm -1 (38.5 °C), 2.96 mS·cm -1 (49.6 °C), 4.59 mS·cm -1 (60.4 °C), 6.53 mS·cm -1 (69.4 °C), 8.92 mS·cm -1 (80.8 °C), 12.4 mS·cm -1 (92 °C).

[0076] In Experimental Example 2, the ionic conductivities of Li 6.35 La 3 Ce 0.45 Zr 0.9 Ta 0.65 O 12 materials at different temperatures are 0.85 mS·cm -1 (20.5 °C), 1.02 mS·cm -1 (25 °C), 1.91 mS·cm -1 (39.5 °C), 2.94 mS·cm -1 (48.7 °C), 4.56 mS·cm -1 (57.7 °C), 6.37 mS·cm -1 (69.1 °C), 8.89 mS·cm -1 (78.4 °C), 12.2 mS·cm -1 (86.8 °C).

[0077] In Experimental Example 3, Li 6.367 La 3 Ce 0.273 Zr 1.092 Ta 0.365 O12 The ionic conductivities of the material at different temperatures are 0.86 mS·cm -1 (21 °C), 1.04 mS·cm -1 (25 °C), 2.05 mS·cm -1 (41.1 °C), 2.96 mS·cm -1 (49.6 °C), 4.34 mS·cm -1 (59.5 °C), 6.58 mS·cm -1 (71.8 °C), 9.13 mS·cm -1 (81.5 °C), 12.6 mS·cm -1 (92.5 °C).

[0078] In Experimental Example 4, Li 6.38 La 3 Ce 0.1535 Zr 1.228 Ta 0.6185 O 12 The ionic conductivities of the material at different temperatures are 0.68 mS·cm -1 (19.8 °C), 0.94 mS·cm -1 (25 °C), 1.85 mS·cm -1 (40.5 °C), 2.83 mS·cm -1 (49.7 °C), 4.17 mS·cm -1 (61.6 °C), 6.25 mS·cm -1 (71.3 °C), 8.70 mS·cm -1 (81.8 °C), 12.1 mS·cm -1 (91.7 °C).

[0079] In Comparative Example 1, Li 6.25 La 3 Ce 1.25 Ta 0.75 O 12 The ionic conductivities of the material at different temperatures are 0.73 mS·cm -1 (20 °C), 0.87 mS·cm -1 (25 °C), 1.09 mS·cm -1 (30 °C), 1.77 mS·cm -1 (39 °C), 2.71 mS·cm -1 (49.3 °C), 4.07 mS·cm -1 (59.1 °C), 5.83 mS·cm -1 (69.3 °C), 8.19 mS·cm -1(80.8 °C), 11.4 mS·cm -1 (92.8 °C).

[0080] In Comparative Example 2, Li 6 La 3 CeTaO 12 The ionic conductivities of the material at different temperatures are 0.49 mS·cm -1 (25 °C), 1.06 mS·cm -1 (40.7 °C), 1.72 mS·cm -1 (50.3 °C), 2.76 mS·cm -1 (61.9 °C), 5.89 mS·cm -1 (80.4 °C), 7.34 mS·cm -1 (86.6 °C).

[0081] In Comparative Example 3, Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 The ionic conductivities of the material at different temperatures are 0.57 mS·cm -1 (20 °C), 0.74 mS·cm -1 (25 °C), 1.63 mS·cm -1 (38.9 °C), 2.56 mS·cm -1 (51 °C), 3.95 mS·cm -1 (62.6 °C), 5.17 mS·cm -1 (71.3 °C), 9.05 mS·cm -1 (82.8 °C), 11.2 mS·cm -1 (93.8 °C).

[0082] Test the room-temperature ionic conductivities of Test Examples 1-5 and Comparative Examples 1-3. The test method is as follows: Grind the obtained ceramic chips with a polishing machine to a thickness of about 900 microns, and polish the surface smoothly with 600, 1200, and 2000 mesh sandpapers in sequence. Brush the gold paste on both sides of the ceramic and dry it at 800 - 900 °C for 1 hour. Test the impedance on an electrochemical workstation with a test range of 1 - 13 MHz.

[0083] The test results of each example and each comparative example are shown in Table 1.

[0084] Table 1: Apparent density, room-temperature ionic conductivity, and activation energy of Experimental Examples 1-4 and Comparative Examples 1-3

[0085]

[0086] As can be seen from Table 1: Compared with the material Li in Comparative Example 3 6.4 La 3 Zr 1.4 Ta 0.6 O 12 , after adding Ce element in Examples 1 - 3, the room - temperature ionic conductivity is significantly improved, the corresponding activation energy decreases, and the material density increases to varying degrees. Compared with the single Ta doping of cerium - based garnet materials in Comparative Examples 1 and 2 5+ doping, Examples 1 - 3 adopt the double - doping method of Zr 4+ and Ta 5+ , and the room - temperature ionic conductivity is significantly improved and the results are close. Among them, the material Li in Example 1 6.32 La 3 Ce 0.66 Zr 0.66 Ta 0.68 O 12 achieves the highest room - temperature ionic conductivity (1.07 mS·cm -1 ).

[0087] According to the disclosure and teaching of the above - mentioned specification, those skilled in the art of the present invention can also make changes and modifications to the above - mentioned embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries, characterized in that: Its chemical composition is: Li 5+x+y LqCy x Zr y Ta 2-x-y O 12 , where 0.1 <x<2.0,0 < y<1.

5.

2. The double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries according to claim 1, characterized in that: The crystal phase of the electrolyte is a cubic phase.

3. The double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries according to claim 1, characterized in that: The maximum ionic conductivity of the electrolyte at 25°C is 1.1 mS / cm.

4. The double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries according to claim 1, characterized in that: 0.1<x<2.0。 5. The double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries according to claim 1, characterized in that: 0<y<1.5。 6. The double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries according to claim 1, characterized in that: The preparation method thereof comprises at least the following steps: In the first step, the ceramic powder is prepared by solid phase method. The oxide raw materials are mixed evenly in proportion and calcined at high temperature to obtain cubic phase dual-doped cerium-based Li 5+x+y LqCy x Zr y Ta 2-x-y O 12 Ceramic powder; In the second step, the powder obtained in the first step is ball-milled to reduce the particle size, and then pressed into sheets and sintered at 1050-1100°C to obtain high-performance ceramic sheets for solid-state batteries.

7. The double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries according to claim 6, characterized in that: In the first step, the oxide raw materials include a lithium source, a lanthanum source, a cerium source, a zirconium source and a tantalum source; wherein the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium oxide and lithium potassium nitrate; the lanthanum source is at least one of lanthanum dioxide, lanthanum chloride and lanthanum potassium nitrate; the cerium source is at least one of cerium dioxide, cerium hydroxide and cerium potassium oxalate; the zirconium source is at least one of zirconium dioxide, zirconium nitrate and zirconium sulfate; and the tantalum source is at least one of tantalum pentoxide and tantalum oxalate.

8. The double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries according to claim 6, characterized in that: The calcination temperature in the first step is 900-1000° C., and the calcination time is 4-6 hours.

9. The double-doped cerium-based garnet electrolyte with high ionic conductivity for solid-state batteries according to claim 6, characterized in that: The particle size of the particles after ball milling in the second step is less than 300 nm.

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