3D ultrathin self-supporting LLZO garnet solid electrolyte, preparation method and application

Abstract

The invention discloses a 3D ultrathin self-supporting LLZO garnet solid electrolyte, a preparation method and application, the structure of the 3D ultrathin self-supporting LLZO garnet solid electrolyte is divided into an upper layer, a middle layer and a lower layer, the upper layer and the lower layer are lithium lanthanum zirconium oxide (LLZO) porous layers, the middle layer is a compact LLZO solid electrolyte layer of a garnet structure, and the thickness of the middle layer is only 3-8 microns; the porous layers on the two sides serve as mechanical supporting layers of the thin and dense layers, good mechanical stability is still kept while the thickness of the middle dense layer is reduced, and compared with an existing solid electrolyte which can achieve good performance about 30 micrometers in the research report and can achieve hundreds of micrometers in the application aspect, the thickness of the electrolyte layer is greatly reduced. The prepared Ta-Al double-doped 3D ultrathin self-supporting LLZO garnet solid electrolyte has a stable self-supporting structure, relatively high ionic conductivity (1.1 * 10 <-4 > S / cm) and good cycle performance, and can stably and continuously work at room temperature (still has a capacity retention ratio of 74.6% after 100 times of charging and discharging).

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and in particular to a 3D ultra-thin self-supporting LLZO garnet solid electrolyte, a preparation method and an application thereof. Background Art

[0002] As a highly efficient secondary energy storage device, lithium-ion batteries have the advantages of high energy density, high output power, high voltage, low self-discharge, wide operating temperature range, no memory effect and environmental friendliness, and have been widely used in electric vehicles, communication equipment, transportation rails, aerospace and other fields. However, the electrolytes of commercial lithium-ion batteries are all organic liquids. Under abnormal conditions such as excessive external battery temperature or high current charging and discharging, the internal temperature of the battery rises, and the chemical reaction between the electrolyte and the electrode intensifies, posing a safety hazard of battery spontaneous combustion or even explosion.

[0003] The safety hazards of liquid electrolytes and the range anxiety caused by limited energy density are two major problems of current lithium-ion batteries. For conventional lithium-ion batteries with organic liquid electrolytes as the main body, polymer separators cannot effectively prevent chemical or physical short circuits inside the battery. Once a short circuit occurs, the dissolved active material will inevitably pass through the micropores of the polymer membrane, and high-modulus lithium dendrites will penetrate the separator, resulting in poor battery performance and safety hazards.

[0004] Solid-state electrolytes are an effective way to address the current safety hazards of lithium-ion batteries. Among them, tantalum (Ta)-doped lithium lanthanum zirconium oxide (LLZO) solid-state electrolytes with a garnet structure exhibit advantages such as high ionic conductivity, a wide electrochemical window, and high mechanical strength that is expected to prevent the penetration of lithium dendrites. However, the solid-solid contact of Li-LLZO induces high interfacial resistance, which accelerates the growth of lithium dendrites in the solid-state electrolyte. The battery still has a high short-circuit risk at low current density and low capacity. At the same time, the solid-state electrolyte needs to maintain a certain thickness to maintain sufficient mechanical strength, and an increase in the thickness of the solid-state electrolyte will increase the battery resistance and reduce the battery efficiency. In addition, the deposition and delithiation of lithium on the electrode are accompanied by volume changes. A thicker electrolyte layer also means a larger volume expansion, which can easily lead to safety hazards such as battery structural instability. Summary of the invention

[0005] The present invention introduces Ta-Al dual-doped 3D ultra-thin self-supporting LLZO garnet solid electrolyte, aiming to solve the problems of increased battery resistance, reduced battery efficiency, and battery structural instability caused by the thick electrolyte layer, as well as the risk of short circuit caused by high interface resistance induced by the solid-solid interface, thereby proposing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte, a preparation method and an application.

[0006] In order to achieve the above technical objectives, the technical solution provided by the present invention is:

[0007] A 3D ultra-thin self-supporting LLZO garnet solid electrolyte, wherein the electrolyte structure is three layers, the upper and lower layers are both LLZO porous layers, and the middle layer is a solid electrolyte layer with a dense garnet structure; the thickness of the middle layer is only 3 to 8 μm.

[0008] The present invention also provides a method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte, comprising the following steps:

[0009] Step 1: Mix the lithium source, lanthanum source, zirconium source, tantalum source and aluminum source with a ball milling solvent in a certain proportion, dry and calcine to obtain LLZO ceramic powder;

[0010] Step 2: sieve the LLZO ceramic powder in step 1 and press it into a disc, and control the thickness of the disc by pressure;

[0011] Step 3: bury the wafer in step 2 in the sacrificial powder composed of LLZO mother powder, sinter, and grind off the sacrificial powder to obtain a 3D ultra-thin self-supporting LLZO garnet solid electrolyte with high conductivity.

[0012] Furthermore, in step 1, the lithium source is any one of lithium hydroxide monohydrate and lithium carbonate; the lanthanum source is any one of lanthanum dioxide, lanthanum trioxide and lanthanum tetroxide; the zirconium source is any one of zirconium oxide and zirconium carbonate; the tantalum source is any one of tantalum pentoxide, tantalum carbide and tantalum carbonate; and the aluminum source is any one of aluminum oxide, aluminum trioxide and aluminum oxide hydrate.

[0013] Furthermore, in step 1, the molar ratio of the lithium source, the lanthanum source, the zirconium source, the tantalum source and the aluminum source is (7-x): 3: 2: x 1 :x 2 , where x, x 1 、x 2 Any value between 0.01 and 0.5 and satisfying x = x 1 +x 2 .

[0014] Furthermore, in step 1, the ball milling solvent is one or more of deionized water, alcohol, acetone, and isopropanol.

[0015] Furthermore, in step 1, the process parameters of ball milling mixing are a rotation speed of 200 to 500 rpm and a mixing time of 6 to 12 hours.

[0016] Furthermore, in step 1, the drying temperature is 50-120°C.

[0017] Furthermore, in step 1, the calcination temperature is 800-1200° C. and the calcination time is 6-12 hours.

[0018] Furthermore, in step 2, the pressure is 100-300 MPa.

[0019] Furthermore, in step 2, the diameter of the wafer is 12 mm and the thickness is 3 to 8 μm.

[0020] Furthermore, in step 3, the sintering temperature is 850-1350° C. and the sintering time is 1-6 hours.

[0021] Furthermore, in step 3, after the sacrificial powder is ground off, the total thickness of the electrolyte sheet is 1 mm.

[0022] The present invention also provides an application of a 3D ultra-thin self-supporting LLZO garnet solid electrolyte in a solid-state lithium battery

[0023] The present invention has the following beneficial effects:

[0024] 1. The structure of the present invention is divided into three layers: upper, middle and lower. The upper and lower layers are LLZO porous layers, and the middle layer is a dense garnet solid electrolyte layer. The thickness of the middle layer is only 3 to 8 μm. The porous layers on both sides serve as mechanical support layers for the thin dense layers. While reducing the thickness of the middle dense layer, it still maintains good mechanical stability. Compared with the existing research reports of about 30 microns, better performance can be achieved, and hundreds of microns in application, the thickness of the electrolyte layer of the present invention is greatly reduced.

[0025] 2. Compared with the solid-state lithium battery prepared by Ta-doped LLZO solid electrolyte, the solid-state lithium battery prepared by Ta-Al dual-doped LLZO solid electrolyte in the present invention has smaller interface resistance and higher ion conductivity. In addition, the porous layer can be used as the main body of high-load positive electrode material and lithium metal negative electrode material, the upper porous layer is in-situ composited with the positive electrode material, and the lower porous layer is in-situ composited with the lithium metal negative electrode, which provides a continuous ion transmission path while greatly reducing the interface resistance between the electrodes, and realizing the effective construction of high-performance solid electrolyte.

[0026] 3. The Ta-Al dual-doped 3D ultra-thin self-supporting LLZO garnet solid electrolyte prepared by the present invention has a stable self-supporting structure and high ionic conductivity (1.1×10 -4 S / cm) and good cycle performance, and can work stably and continuously at room temperature (the capacity retention rate is still 74.6% after 100 charge and discharge cycles). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the electrolyte structure of the present invention;

[0028] Figure 21 and 2 are XRD patterns of the LLZO ceramic powder and the solid electrolyte sheet prepared in Example 1 of the present invention, wherein (a) is the LLZO solid electrolyte sheet and (b) is the LLZO ceramic powder.

[0029] Figure 3 The SEM morphologies of the LLZO ceramic powder and the solid electrolyte sheet prepared in Example 1 of the present invention, wherein (a) is the surface of the LLZO ceramic powder, and (b) is the cross-section of the LLZO solid electrolyte.

[0030] Figure 4 The impedance spectra of the solid-state lithium batteries in Application Examples 1, 2, 3, and 4 of the present invention at room temperature are shown in FIG. 1 , wherein (a) is the solid-state lithium battery prepared in Application Example 2, (b) is the solid-state lithium battery prepared in Application Example 1, (c) is the solid-state lithium battery prepared in Application Example 3, and (d) is the solid-state lithium battery prepared in Application Example 4.

[0031] Figure 5 These are the charge / discharge test results of the solid-state lithium battery in Application Example 1 of the present invention at room temperature, where (a) is the first charge and discharge, (b) is the 10th charge and discharge, (c) is the 50th charge and discharge, and (d) is the 100th charge and discharge.

[0032] Figure 6 This is the impedance spectrum of the solid-state lithium battery in the low-frequency band in Application Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] A 3D ultra-thin self-supporting LLZO garnet solid electrolyte, the electrolyte structure is 3 layers, the upper and lower layers are both lithium lanthanum zirconium oxide porous layers, and the middle layer is a dense garnet solid electrolyte layer; the thickness of the middle layer is 3 to 8 μm, such as Figure 1 shown.

[0036] The present invention also provides a method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte, comprising the following steps:

[0037] Step 1: Mix the lithium source, lanthanum source, zirconium source, tantalum source and aluminum source in a certain proportion with a ball milling solvent, dry and calcine to obtain LLZO ceramic powder.

[0038] Specifically, the lithium source is any one of lithium hydroxide monohydrate and lithium carbonate; the lanthanum source is any one of lanthanum dioxide, lanthanum trioxide and lanthanum tetraoxide; the zirconium source is any one of zirconium oxide and zirconium carbonate; the tantalum source is any one of tantalum pentoxide, tantalum carbide and tantalum carbonate; the aluminum source is any one of aluminum oxide, aluminum trioxide and aluminum oxide hydrate; the molar ratio of the lithium source, the lanthanum source, the zirconium source, the tantalum source and the aluminum source is (7-x): 3:2:x 1 :x 2 , where x, x 1 、x 2 Any value between 0.01 and 0.5 and satisfying x = x 1 +x 2 ; The ball milling solvent is one or more of deionized water, alcohol, acetone, and isopropanol; the process parameters of ball milling mixing are a rotation speed of 200 to 500 rpm and a mixing time of 6 to 12 hours; the drying temperature is 50 to 120°C; the calcination temperature is 800 to 1200°C, and the calcination time is 6 to 12 hours.

[0039] Step 2: Screen the lithium lanthanum zirconium oxide ceramic powder described in step 1 and press it into round tablets.

[0040] Specifically, the pressure for powder tableting is 100 to 300 MPa.

[0041] Step 3: bury the wafer in step 2 in the sacrificial powder composed of LLZO mother powder, sinter, and grind off the sacrificial powder to obtain a 3D ultra-thin self-supporting LLZO garnet solid electrolyte with high conductivity.

[0042] Specifically, the sintering temperature is 850-1350° C., and the sintering time is 1-6 hours.

[0043] The present invention also provides an application of a 3D ultra-thin self-supporting LLZO garnet solid electrolyte in a solid-state lithium battery.

[0044] In the present invention, the solid electrolyte has excellent properties such as small thickness, high conductivity, and self-supporting structure. The present invention limits the preparation process parameters of the 3D ultra-thin self-supporting LLZO garnet solid electrolyte to the above range, which can make the self-supporting structure of the solid electrolyte more stable and obtain high conductivity while compressing the thickness of the electrolyte.

[0045] Example 1

[0046] Step 1: Mix lithium hydroxide monohydrate, lanthanum oxide, zirconium oxide, tantalum pentoxide and aluminum oxide in a molar ratio of 6.75:3:2:0.15:0.1 with a ball milling solvent, dry, and calcine to obtain lithium lanthanum zirconium oxide ceramic powder.

[0047] Specifically, the ball milling solvent is isopropanol, the ball milling process is a rotation speed of 300 rpm, a mixing time of 8 hours; a drying temperature of 70° C., a drying time of 12 hours; a calcination temperature of 900° C., and a calcination time of 6 hours.

[0048] Step 2: Screen the lithium lanthanum zirconium oxide ceramic powder described in step 1 and press it into round tablets.

[0049] Specifically, the lithium lanthanum zirconium oxide ceramic powder was sieved through 100 meshes and pressed into a disc with a diameter of 12 mm and a thickness of 5 μm under a uniaxial pressure of 300 MPa.

[0050] Step 3: bury the wafer in step 2 in the sacrificial powder composed of LLZO mother powder, sinter, and grind off the sacrificial powder to obtain a 3D ultra-thin self-supporting LLZO garnet solid electrolyte with high conductivity.

[0051] Specifically, the sintering temperature is 1100° C., the sintering time is 4 hours, and the total thickness of the electrolyte sheet is 1 mm.

[0052] Example 2

[0053] Step 1: Mix lithium hydroxide monohydrate, lanthanum oxide, zirconium oxide, tantalum pentoxide and aluminum oxide in a molar ratio of 6.75:3:2:0.15:0.1 with a ball milling solvent, dry, and calcine to obtain lithium lanthanum zirconium oxide ceramic powder.

[0054] Specifically, the ball milling solvent is isopropanol, the ball milling process is a rotation speed of 200 rpm, a mixing time of 6 hours; a drying temperature of 120° C., a drying time of 2 hours; a calcination temperature of 800° C., and a calcination time of 12 hours.

[0055] Step 2: Screen the lithium lanthanum zirconium oxide ceramic powder described in step 1 and press it into round tablets.

[0056] Specifically, the lithium lanthanum zirconium oxide ceramic powder was sieved through 100 meshes and pressed into a disc with a diameter of 12 mm and a thickness of 5 μm under a uniaxial pressure of 300 MPa.

[0057] Step 3: bury the wafer in step 2 in the sacrificial powder composed of LLZO mother powder, sinter, and grind off the sacrificial powder to obtain a 3D ultra-thin self-supporting LLZO garnet solid electrolyte with high conductivity.

[0058] Specifically, the sintering temperature is 850° C., the sintering time is 6 h, and the total thickness of the electrolyte sheet is 1 mm.

[0059] Example 3

[0060] Step 1: Mix lithium hydroxide monohydrate, lanthanum oxide, zirconium oxide, tantalum pentoxide and aluminum oxide in a molar ratio of 6.75:3:2:0.15:0.1 with a ball milling solvent, dry, and calcine to obtain lithium lanthanum zirconium oxide ceramic powder.

[0061] Specifically, the ball milling solvent is isopropanol, the ball milling process is a rotation speed of 500 rpm, a mixing time of 12 hours; a drying temperature of 120° C., a drying time of 2 hours; a calcination temperature of 800° C., and a calcination time of 12 hours.

[0062] Step 2: Screen the lithium lanthanum zirconium oxide ceramic powder described in step 1 and press it into round tablets.

[0063] Specifically, the lithium lanthanum zirconium oxide ceramic powder was sieved through 100 meshes and pressed into a disc with a diameter of 12 mm and a thickness of 5 μm under a uniaxial pressure of 300 MPa.

[0064] Step 3: bury the wafer in step 2 in the sacrificial powder composed of LLZO mother powder, sinter, and grind off the sacrificial powder to obtain a 3D ultra-thin self-supporting LLZO garnet solid electrolyte with high conductivity.

[0065] Specifically, the sintering temperature is 1350° C., the sintering time is 1 h, and the total thickness of the electrolyte sheet is 1 mm.

[0066] Example 4

[0067] Step 1: Mix lithium hydroxide monohydrate, lanthanum oxide, zirconium oxide and tantalum pentoxide with a ball milling solvent in a molar ratio of 6.75:3:2:0.25, dry and calcine to obtain lithium lanthanum zirconium oxide ceramic powder.

[0068] Specifically, the ball milling solvent is isopropanol, the ball milling process is a rotation speed of 300 rpm, a mixing time of 8 hours; a drying temperature of 70° C., a drying time of 12 hours; a calcination temperature of 900° C., and a calcination time of 6 hours.

[0069] Step 2: Sieve the lithium lanthanum zirconium oxide ceramic powder described in step 1 and press it into a disc.

[0070] Specifically, the lithium lanthanum zirconium oxide ceramic powder was sieved through 100 meshes and pressed into a disc with a diameter of 12 mm and a thickness of 5 μm under a uniaxial pressure of 300 MPa.

[0071] Step 3: bury the wafer in step 2 in the sacrificial powder composed of LLZO mother powder, sinter, and grind off the sacrificial powder to obtain a 3D ultra-thin self-supporting LLZO garnet solid electrolyte with high conductivity.

[0072] Specifically, the sintering temperature is 1100° C., the sintering time is 4 hours, and the total thickness of the electrolyte sheet is 1 mm.

[0073] Application Example 1

[0074] Select lithium cobalt oxide (LiCoO 2 ) electrode is used as the positive electrode, the metal lithium sheet (Li) is used as the negative electrode, the 3D ultra-thin self-supporting LLZO prepared in Example 1 is used as the electrolyte, and LiCoO is prepared 2 / LLZO / Li solid-state lithium battery, LiCoO 2 Two drops of electrolyte were added between the electrode and the LLZO electrolyte to reduce the interface impedance.

[0075] The LiCoO 2 The preparation method of the pole piece is as follows: Commercial LiCoO 2 , polyvinylidene fluoride (PVDF) and conductive carbon (SuperP) are weighed in a mass ratio of 8:1:1 and dispersed in N-methylpyrrolidone (NMP) solvent, and stirred thoroughly to obtain positive electrode slurry. The positive electrode slurry is evenly coated on a conductive aluminum foil, and after the solvent in the slurry is dried, LiCoO is obtained by mechanical punching. 2 Pole piece.

[0076] The preparation method of the electrolyte is as follows: take 1M lithium hexafluorophosphate (LiPF6) and dissolve it in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1, and stir evenly after dissolution to obtain the required electrolyte.

[0077] Application Example 2

[0078] The difference between this application example and application example 1 is that the 3D ultra-thin self-supporting LLZO prepared in Example 2 is selected as the electrolyte. The other steps and parameters are the same as those in application example 1.

[0079] Application Example 3

[0080] The difference between this application example and application example 1 is that the 3D ultra-thin self-supporting LLZO prepared in Example 3 is selected as the electrolyte. The other steps and parameters are the same as those in application example 1.

[0081] Application Example 4

[0082] The difference between this application example and application example 1 is that the 3D ultra-thin self-supporting LLZO prepared in Example 4 is selected as the electrolyte. The other steps and parameters are the same as those in application example 1.

[0083] Figure 2 The XRD patterns of the LLZO ceramic powder and solid electrolyte sheet prepared in Example 1, where (a) is the LLZO solid electrolyte sheet and (b) is the LLZO ceramic powder. It can be seen that after calcination at 1000°C, the LLZO ceramic powder is a cubic phase LLZO, and there is no impurity peak, indicating that the raw materials are fully reacted. The LLZO solid electrolyte sheet obtained after high-temperature sintering at 1100°C is still a LLZO cubic phase, the peak intensity of the diffraction peak is greatly improved, and the strongest diffraction peak appears at about 31o (the corresponding crystal plane is (420)), indicating that the crystallinity of LLZO is higher after sintering, and a preferred orientation appears on the (420) crystal plane.

[0084] Figure 3 The SEM morphology of the LLZO ceramic powder and solid electrolyte sheet prepared in Example 1, wherein (a) is the surface of the LLZO ceramic powder, and (b) is the cross section of the LLZO solid electrolyte. As can be seen from the figure, the particle size of the LLZO ceramic powder after ball milling is about 0.5-3 μm, the grain size of the LLZO solid electrolyte after sintering is about 100-200 μm, the LLZO solid electrolyte grains are closely combined, the overall density is high, and the relative density of the sintered sample reaches 94%.

[0085] Figure 4 The impedance spectra of the solid-state lithium batteries in Application Examples 1, 2, 3, and 4 at room temperature, wherein (a) is the solid-state lithium battery prepared in Application Example 2, (b) is the solid-state lithium battery prepared in Application Example 1, (c) is the solid-state lithium battery prepared in Application Example 3, and (d) is the solid-state lithium battery prepared in Application Example 4. It can be seen that when the calcination temperature is 900°C, the interface resistance of the solid-state lithium battery is the smallest, that is, the ionic conductivity of the LLZO solid electrolyte is the highest at this time. In addition, compared with the solid-state lithium battery prepared by Ta-doped LLZO solid electrolyte (Example 4), the solid-state lithium battery prepared by Ta-Al dual-doped LLZO solid electrolyte (Examples 1-3) has a smaller interface resistance, that is, the Ta-Al dual-doped LLZO solid electrolyte has a higher ionic conductivity.

[0086] Figure 5 The charge / discharge test results of the solid-state lithium battery in Application Example 1 at room temperature, where (a) is the first charge / discharge, (b) is the 10th charge / discharge, (c) is the 50th charge / discharge, and (d) is the 100th charge / discharge. It can be seen that the charge / discharge current value of the battery is 5μA / cm 2 , the charge / discharge cut-off voltage range is 2.8~4.3V. The battery shows very small polarization during the charge / discharge process, and there is an obvious charge / discharge platform during the cycle process. The first discharge specific capacity can reach 138mAh / g. After 100 cycles, the discharge platform of the battery is still very obvious, with a capacity retention rate of 74.6% (specific capacity 103mAh / g).

[0087] Figure 6 This is the impedance spectrum of the solid-state lithium battery in the low-frequency band in Application Example 1. As can be seen from the figure, the total resistance of the battery is about 6.6 kΩ. According to the fitting circuit in the figure, the ionic conductivity of the LLZO solid electrolyte can reach 1.1×10 -4 S / cm.

[0088] In summary, the solid electrolyte prepared by the present invention has excellent properties such as high electrical conductivity and the ability to work continuously at room temperature.

[0089] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0090] The above specific implementation methods are detailed descriptions of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A 3D ultra-thin self-supporting LLZO garnet solid electrolyte, characterized in that: The electrolyte structure consists of three layers, the upper and lower layers are both LLZO porous layers, and the middle layer is a dense garnet structure LLZO solid electrolyte layer; the thickness of the middle layer is only 3 to 8 μm.

2. A method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte as claimed in claim 1, characterized in that: The steps include: Step 1: Mix the lithium source, lanthanum source, zirconium source, tantalum source and aluminum source with a ball milling solvent in a certain proportion, dry and calcine to obtain LLZO ceramic powder; Step 2: sieve the LLZO ceramic powder in step 1 and press it into a disc, and control the thickness of the disc by pressure; Step 3: bury the wafer in step 2 in the sacrificial powder composed of LLZO mother powder, sinter, and grind off the sacrificial powder to obtain a 3D ultra-thin self-supporting LLZO garnet solid electrolyte with high conductivity.

3. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 1, the lithium source is any one of lithium hydroxide monohydrate and lithium carbonate; the lanthanum source is any one of lanthanum dioxide, lanthanum trioxide and lanthanum tetroxide; the zirconium source is any one of zirconium oxide and zirconium carbonate; the tantalum source is any one of tantalum pentoxide, tantalum carbide and tantalum carbonate; the aluminum source is any one of aluminum oxide, aluminum trioxide and aluminum oxide hydrate.

4. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 1, the molar ratio of the lithium source, lanthanum source, zirconium source, tantalum source and aluminum source is (7-x):3:2:x1:x2, wherein x, x1 and x2 are any values ​​between 0.01 and 0.5 and satisfy x=x1+x2.

5. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 1, the ball milling solvent is one or more of deionized water, alcohol, acetone, and isopropanol.

6. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 1, the process parameters of ball milling mixing are a rotation speed of 200 to 500 rpm and a mixing time of 6 to 12 hours.

7. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 1, the drying temperature is 50-120°C.

8. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 1, the calcination temperature is 800 to 1200° C. and the calcination time is 6 to 12 hours.

9. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 2, the pressure is 100-300 MPa.

10. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 2, the diameter of the disc is 12 mm and the thickness is 3 to 8 μm.

11. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 3, the sintering temperature is 850-1350° C. and the sintering time is 1-6 hours.

12. The method for preparing a 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 2, characterized in that: In the step 3, after the sacrificial powder is removed, the total thickness of the electrolyte sheet is 1 mm.

13. Application of the 3D ultra-thin self-supporting LLZO garnet solid electrolyte according to claim 1 in a solid-state lithium battery.

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