A w-f co-doped garnet-type solid-state electrolyte and a preparation method thereof

Abstract

This invention relates to the field of solid-state lithium metal battery technology, specifically to a W-F dual-doped garnet-type solid electrolyte and its preparation method. The method includes: weighing raw materials; wet ball milling; drying; sieving; pre-sintering; ball milling again and pressing into shape; high-temperature sintering; grinding and sieving the sintered product to obtain W-F dual-doped Li. 6.2‑y La3Zr 1.6 W 0.4 O 12‑y F y Solid electrolyte. This invention utilizes W 6+ Cations and F ‑ The dual doping modification with anions enables the synergistic regulation of the lattice structure, microstructure and ion transport performance of LLZO electrolyte, in order to overcome the bottleneck that single-element doping cannot simultaneously achieve high ionic conductivity and high stability.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium metal battery technology, specifically to a WF-doped garnet-type solid electrolyte and its preparation method. Background Technology

[0002] Garnet-type Li7La3Zr2O 12 LLZO solid-state electrolytes are considered one of the most promising electrolyte materials for solid-state lithium metal batteries due to their wide electrochemical window, high mechanical strength, and extremely low electronic conductivity. Compared to other inorganic solid-state electrolytes such as sulfides and halides, the LLZO system combines excellent intrinsic compatibility with lithium metal anodes, excellent resistance to lithium dendrite formation, and environmental friendliness. Its preparation process is mature, and its large-scale production cost is controllable, making it a core candidate material for next-generation high-safety, high-energy-density all-solid-state lithium batteries.

[0003] However, pure-phase LLZO solid electrolytes still face two major bottlenecks that severely hinder their practical application: First, the cubic phase of pure LLZO with high ionic conductivity at room temperature easily transforms spontaneously into the tetragonal phase with low conductivity, and its intrinsic room-temperature ionic conductivity is generally below 10. -5 S cm -1 Firstly, LLZO exhibits significant differences compared to commercially available liquid electrolytes; secondly, it has poor air stability and readily reacts with atmospheric H2O and CO2. + / H + The exchange reaction generates inert insulating impurity phases such as LiOH and Li2CO3 on the surface and at the grain boundaries. This not only significantly increases the grain boundary impedance and drastically reduces the ionic conductivity of the material, but also severely deteriorates the interfacial contact characteristics between the electrolyte and the lithium metal anode.

[0004] Elemental doping modification is an important means of controlling the crystal structure of LLZO and optimizing its overall electrochemical performance. Existing research has made some progress in single-doping modification of LLZO with high-valence cations at the Zr sites. For example, single doping with elements such as Ta, Ga, and W can introduce lithium vacancies through charge compensation effects, stabilizing the cubic phase and improving the room-temperature ionic conductivity of the material. Through W... 6+ Replace Zr 4+ This achieves both cubic phase stability and improved ionic conductivity. For example, CN120581681A discloses a dual-doped high-density garnet-type solid electrolyte with a chemical composition of Li. 6.4 La 3-y Yb y Zr 1.7 W 0.3 O 12Where y is 0.05~0.2, the main phase of the dual-doped high-density garnet-type solid electrolyte is a cubic garnet structure. However, single W element doping can only optimize ion transport performance and cannot improve the intrinsic chemical stability of LLZO. After long-term storage in air, the conductivity retention rate of the sample is less than 60%, which is difficult to meet the core requirement of long-term environmental stability of electrolyte for actual service of solid lithium batteries. While single anion doping can improve the stability of the material to a certain extent, it is difficult to simultaneously improve the high ionic conductivity and cannot achieve a synergistic breakthrough in performance.

[0005] In summary, existing single-lattice site doping modification techniques generally fail to achieve a synergistic breakthrough in improving the ionic conductivity and enhancing the environmental stability of LLZO electrolytes. The microscopic mechanism of dual doping of anions and cations, as well as the synergistic optimization mechanism of conductivity and stability, still require further in-depth research. LLZO-based electrolyte systems that combine high room temperature ionic conductivity with excellent air stability are yet to be developed. Summary of the Invention

[0006] To address the issues of existing LLZO-based solid electrolytes failing to simultaneously achieve high room-temperature ionic conductivity and excellent air chemical stability, as well as poor interfacial compatibility during cycling, this invention provides a WF-doped garnet-type solid electrolyte and its preparation method. 6+ Cations and F - The dual doping modification with anions enables the synergistic regulation of the lattice structure, microstructure and ion transport performance of LLZO electrolyte, in order to overcome the bottleneck that single-element doping cannot simultaneously achieve high ionic conductivity and high stability.

[0007] This invention is achieved through the following technical solution: A method for preparing a WF-doped garnet-type solid electrolyte includes: Step 1: Weigh the raw materials, including Li2CO3, La2O3, ZrO2, WO3, and LiF; Step 2: Wet ball mill the raw materials to obtain a mixed raw material; Step 3: Dry the mixed raw materials to constant weight to obtain a dried mixture; Step 4: Screen the dried mixture to obtain the screened material; Step 5: Pre-sinter the screened material to obtain pre-sintered powder; Step 6: The pre-calcined powder is ball-milled again and pressed into shape to obtain an electrolyte preform. Step 7: The electrolyte preform is sintered at high temperature to obtain the sintered product; Step 8: Grind and sieve the sintered product to obtain WF-doped Li. 6.2-y La3Zr 1.6 W 0.4 O12-y F y Solid electrolyte.

[0008] Preferably, in step 1, Li₂CO₃, La₂O₃, ZrO₂, WO₃, and LiF are disposed in accordance with Li 6.2-y La3Zr 1.6 W 0.4 O 12-y F y The stoichiometric ratios are used for mixing, where y = 0.05~0.15.

[0009] Preferably, in step 2, during wet ball milling, zirconium oxide is used as the grinding ball, anhydrous ethanol is used as the ball milling aid, and the ball milling time is 5-7 hours.

[0010] Preferably, in step 3, the drying temperature is 80~110℃.

[0011] Preferably, in step 4, a 40-mesh standard sieve is used for sieving.

[0012] Preferably, in step 5, the pre-firing treatment is carried out at a temperature of 850~950℃, a holding time of 5~7h, and a heating rate of 2~5℃ / min.

[0013] Preferably, in step 7, during the high-temperature sintering treatment, the temperature is 1180~1240℃, the holding time is 5~8h, the heating rate is 2~5℃ / min, and the sintering process adopts the same component masterbatch embedding method.

[0014] Preferably, in step 8, the grinding time is 0.5~3 hours, and a 120-mesh standard sieve is used for sieving.

[0015] A WF-doped Li₂ obtained according to the method for preparing WF-doped garnet-type solid electrolyte 6.2- y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolyte.

[0016] A solid-state lithium metal battery comprising WF-doped Li₂ obtained by the method for preparing WF-doped garnet-type solid electrolyte as described in any one of claims 1 to 8. 6.2-y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolyte; under a constant current of 0.1mA, the lithium symmetric battery of this battery can be stably cycled for more than 1300 hours, and the polarization voltage is stable within the range of ±0.2V; after being exposed to air environment for 30 days, the ionic conductivity of the solid electrolyte is as high as 90.77%.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing WF-doped garnet-type solid electrolytes using Li7La3Zr2O 12 As the matrix, fix W 6+ The doping concentration is 0.4, through F - Replace O in the crystal lattice 2- Li was synthesized at the site using a high-temperature solid-state method. 6.2-y La3Zr 1.6 W 0.4 O 12-y F y Sample. Among them, W 6+ High-valence cation doping introduces mobile lithium vacancies through charge compensation effect, thereby stabilizing the high-conductivity cubic garnet phase and optimizing the three-dimensional transport channel of lithium ions. This reduces the lithium ion migration barrier and improves the room-temperature ionic conductivity of the material. At the same time, W has a significant cost advantage over traditional doping elements such as Ta and Ga, making it more suitable for large-scale preparation and industrial application.

[0018] In addition, the highly electronegative F - Anion doping can suppress the air degradation process of LLZO at its structural source: on the one hand, F - With higher electronegativity, its introduction enhances the bonding between cations and anions in the garnet lattice framework, making the active lithium sites in the lattice more stable, thereby reducing Li... + The chemical activity of Li in the air is fundamentally inhibited. + / H + The exchange reaction prevents the formation and accumulation of insulating Li₂CO₃ impurities on the electrolyte surface; on the other hand, doping with F... - Not only can the lithium vacancy concentration within the crystal lattice be precisely controlled, but the bottleneck size of the three-dimensional diffusion channel for lithium ions can also be optimized, reducing the intrinsic migration barrier of lithium ions. Therefore, even after long-term exposure to air, it can still provide a continuous, low-resistance long-range transport channel for lithium ions, maintaining the excellent ion transport performance of the electrolyte. Simultaneously, appropriate doping with F... - It can also suppress abnormal grain growth during high-temperature sintering, which helps to refine grains and improve the density of ceramic bodies, eliminate defect sites such as grain boundary pores that preferentially support the growth of lithium dendrites, thereby enhancing the electrolyte's mechanical resistance to lithium dendrite formation.

[0019] Furthermore, this invention determines the optimal preparation process for the WF-doped LLZO system by optimizing the entire process of pre-firing temperature, sintering temperature, and holding time.

[0020] The present invention discloses a method for preparing WF-doped garnet-type solid electrolytes, yielding WF-doped Li. 6.2- y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolytes, at room temperature, can achieve an ionic conductivity of 9.86 × 10⁻⁶. -5 S cm - ¹. When Au is used as the blocking electrode, the ionic conductivity will be further increased to 2.58 × 10⁻⁶. -4 S cm - ¹ The lithium-ion migration activation energy is as low as 0.1226 eV; after 30 days of air exposure, the ionic conductivity of the sample remains as high as 90.77%, which is far superior to the single W doping system, achieving a synergistic breakthrough in high ionic conductivity and excellent air stability.

[0021] This invention discloses a solid-state lithium metal battery with excellent long-term cycle stability and resistance to lithium dendrite formation. The lithium symmetric battery assembled using the modified WF dual-doped LLZO electrolyte of this invention can stably cycle for more than 1300 hours under a constant current of 0.1mA. The polarization voltage is maintained within ±0.2V without significant drift, and the critical current density is significantly improved compared to the W single-doped system. It exhibits excellent lithium anode interface compatibility and long-term cycle performance, providing reliable support for the practical application of high-safety, high-energy-density solid-state lithium metal batteries. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for preparing a WF-doped garnet-type solid electrolyte according to the present invention; Figure 2 These are the XRD patterns of LLZWOFy ceramic powders at different pre-firing temperatures in this invention; Figure 3 These are the XRD patterns of the LLZWOFy solid electrolyte at different sintering temperatures in this invention; Figure 4 These are the cross-sectional SEM morphology and EDS elemental distribution maps of LLZWOFy electrolytes with different F doping amounts in this invention. Figure 5 These are the room temperature Nyquist impedance spectra of LLZWOFy ceramic samples at different sintering temperatures in this invention. Figure 6 These are the room temperature impedance spectra and activation energy fitting curves of the LLZWOF0.15 electrolyte at 1220℃ for different holding times in this invention; Figure 7These are the cycle performance and critical current test curves of the Li / Li6.05La3Zr1.6W0.4O11.85F0.15 / Li symmetric battery in this invention; Figure 8 These are the XRD diffraction patterns of the LLZWOF0.15 electrolyte before and after 30 days of air exposure in this invention; Figure 9 These are the room-temperature electrochemical impedance spectra of LLZWOFy electrolytes with different F doping amounts after being exposed to air for different durations in this invention. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0024] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0025] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0026] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0027] This invention discloses a method for preparing WF-doped garnet-type solid electrolytes, referring to... Figure 1 ,include: Step 1: Weigh the raw materials, including Li₂CO₃, La₂O₃, ZrO₂, WO₃, and LiF; specifically, mix Li₂CO₃ (99.99%), La₂O₃ (99.99%), ZrO₂ (99.99%), WO₃ (99.99%), and LiF (99.99%) according to the designed Li 6.2-y La3Zr 1.6 W 0.4 O 12-y F yThe stoichiometric ratios were used to prepare the mixture, with Li2CO3 in 15% excess to compensate for lithium volatilization loss during high-temperature sintering; before use, La2O3 needed to be calcined in a muffle furnace at 900℃ for 10-12 hours to remove La(OH)3 impurities generated by deliquescence; and the remaining raw materials were dried in a drying oven at 80-110℃ for 10-12 hours before use.

[0028] Step 2: Wet ball milling of the raw materials to obtain mixed raw materials. Specifically, the weighed raw materials are placed in a polytetrafluoroethylene ball mill jar, zirconium oxide is used as the grinding balls, anhydrous ethanol is used as the ball milling aid, and wet ball milling is carried out in a planetary ball mill for 5-7 hours.

[0029] Step 3: Dry the mixed raw materials at 80~110℃ to constant weight to obtain a dried mixture.

[0030] Step 4: Use a 40-mesh standard sieve to screen the dried mixture to obtain the screened material.

[0031] Step 5: Heat the screened material to 850-950℃ at a heating rate of 2-5℃ / min for 5-7 hours to obtain pre-sintered powder.

[0032] Step 6: The pre-calcined powder is ball-milled again, and polyvinyl alcohol binder is added for granulation. The granules are then pressed into shape using a tablet press and held under pressure for 50-70 seconds to obtain the electrolyte preform. Step 7: The electrolyte embryo is subjected to high-temperature sintering using the same component masterbatch embedding method to obtain the sintered product; wherein, during the high-temperature sintering treatment, the temperature is 1180~1240℃, the holding time is 5~8h, and the heating rate is 2~5℃ / min.

[0033] Step 8: After double-sided polishing and ultrasonic cleaning with anhydrous ethanol, the sintered product is ground in an agate mortar for 0.5-3 hours to obtain WF-doped LLZO powder. Then, the WF-doped LLZO powder is sieved using a 120-mesh standard sieve to obtain WF-doped Li. 6.2-y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolyte. Specifically, This invention also discloses a WF-doped Li₂ obtained according to the method for preparing WF-doped garnet-type solid electrolyte. 6.2-y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolyte.

[0034] The WF-doped Li provided by this invention 6.2-y La3Zr1.6 W 0.4 O 12-y F y Solid electrolytes utilize W 6+ With F - The co-doping of W introduces a large number of lithium vacancies through a charge compensation mechanism, which not only stabilizes the high ionic conductivity of the cubic garnet phase but also optimizes the three-dimensional lithium-ion transport channels and reduces the migration energy barrier. Furthermore, thanks to the significant cost advantage of W compared to traditional doping elements such as Ta and Ga, it can improve the adaptability to large-scale preparation and industrialization, successfully overcoming the industry pain points of low conductivity, difficulty in densification, and high cost of traditional LLZO. Ultimately, WF-doped Li₂ possesses high ionic conductivity, excellent mechanical strength, and low-cost potential. 6.2-y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolyte.

[0035] This invention also discloses a solid-state lithium metal battery comprising WF-doped Li₂ obtained by the WF-doped garnet-type solid electrolyte preparation method as described in any one of claims 1 to 8. 6.2-y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolyte; under a constant current of 0.1mA, the lithium symmetric battery of this product can cycle stably for more than 1300 hours, and the polarization voltage is stable within the range of ±0.2V; after 30 days of exposure to air, the ionic conductivity of the solid electrolyte remains as high as 90.77%.

[0036] Example 1 Step 1, Ingredients: According to the chemical formula Li 6.15 La3Zr 1.6 W 0.4 O 11.95 F 0.05 Weigh Li₂CO₃, La₂O₃, ZrO₂, WO₃, and LiF, with Li₂CO₃ in 15% excess. Step 2, Mixing: Place the weighed raw materials into a ball mill jar, use zirconium oxide as grinding balls and anhydrous ethanol as a ball milling aid, and place it in a ball mill for wet ball milling for 6 hours to obtain mixed raw materials; Step 3, Drying: Pour out the ball-milled slurry and place it in an oven to dry at 100°C until constant weight, to obtain a dried raw material mixture; Step 4, sieving: Pass the raw material mixture through a 40-mesh standard sieve to remove coarse particles and impurities, so that the obtained material has a relatively uniform particle size distribution. Step 5, pre-calcination: Place the raw material mixture in a corundum crucible and pre-calcine it in a muffle furnace at 900℃ for 6 hours with a heating rate of 5℃ / min to obtain pre-calcined powder; Step 6, pressing and molding: After ball milling the pre-calcined powder for 6 hours, add polyvinyl alcohol binder to granulate, accurately weigh 1g of granulated powder and fill it into a mold with an inner diameter of 13mm, and press it under 10MPa pressure for 60s to obtain the electrolyte preform. Step 7, sintering: The electrolyte blank is embedded with masterbatch of the same composition and sintered in a muffle furnace at 1240℃ for 6 hours with a heating rate of 5℃ / min to obtain the sintered product. Step 8, Post-processing: The sintered product is polished on both sides with 800#~5000# SiC sandpaper, ultrasonically cleaned with anhydrous ethanol, dried, and then physically ground in an agate mortar for 2 hours. It is then passed through a 120-mesh standard sieve to obtain Li with a more uniform particle size distribution. 6.15 La3Zr 1.6 W 0.4 O 11.95 F 0.05 Solid electrolyte sample.

[0037] Example 2 The difference from Example 1 is as follows: Step 1, according to the chemical formula Li 6.1 La3Zr 1.6 W 0.4 O 11.9 F 0.1 Weigh Li₂CO₃, La₂O₃, ZrO₂, WO₃, and LiF. Step 5, during pre-sintering, the temperature is 900℃ and the holding time is 6 hours; Step 7, during high-temperature sintering, the temperature is 1220℃ and the holding time is 6 hours.

[0038] Example 3 The difference from Example 1 is as follows: According to the chemical formula Li 6.05 La3Zr 1.6 W 0.4 O 11.85 F 0.15 Weigh Li₂CO₃, La₂O₃, ZrO₂, WO₃, and LiF. Step 5, during pre-sintering, the temperature is 900℃ and the holding time is 6 hours; Step 7, during high-temperature sintering, the temperature is 1220℃ and the holding time is 6 hours.

[0039] Comparative Example 1 The difference from Example 1 is as follows: Step 1, according to the chemical formula Li 6.2 La3Zr1.6 W 0.4 O 12 Weigh Li₂CO₃, La₂O₃, ZrO₂, and WO₃, without adding LiF; Step 5, during pre-sintering, the temperature is 900℃ and the holding time is 6 hours; Step 7: During the high-temperature sintering treatment, the temperature is 1200℃ and held for 6 hours. Other procedures are the same as in Example 1.

[0040] Table 1. Room temperature ionic conductivity and relative density of the solid electrolytes obtained in Examples 1-3 and Comparative Example 1

[0041] Figure 2 The XRD patterns of the powders from Examples 1-3 at different pre-calcination temperatures are shown. XRD analysis proves that all samples pre-calcined at 900℃ for 6 hours exhibit a pure cubic LLZO crystal structure, which is highly consistent with the cubic LLZO standard card (PDF#45-0109). No obvious impurity phases are generated, confirming that 900℃ is the optimal pre-calcination temperature.

[0042] Figure 3 The XRD patterns of the bulk samples in Examples 1-3 at different sintering temperatures are shown. The results show that a pure cubic garnet phase structure can be obtained at sintering temperatures of 1200℃ and above. As the amount of F doping increases, the characteristic peak of the (420) crystal plane shifts to a higher angle in a regular manner, which confirms that F- successfully enters the LLZO lattice to replace the O2- site, causing lattice shrinkage, which is in line with the Bragg diffraction law.

[0043] Figure 4 The cross-sectional SEM images and EDS elemental distribution maps of Examples 1-3 are shown. The results show that all samples formed a dense ceramic structure without obvious pores. As the F doping amount increased, the average grain size of the samples gradually decreased, confirming that F doping can suppress abnormal grain growth during high-temperature sintering. The EDS results show that the five elements La, Zr, W, O and F are uniformly distributed in the ceramic matrix without obvious local segregation, confirming that the two doping elements W and F were successfully incorporated into the LLZO lattice.

[0044] Figure 5 The room-temperature electrochemical Nyquist impedance spectra of the LLZWOFy electrolytes prepared at different sintering temperatures in Examples 1-3 are shown. All samples exhibit typical garnet impedance characteristics of high-frequency semicircular arcs and low-frequency oblique lines. The sample with y=0.15 sintered at 1220℃ has the lowest total impedance, corresponding to a room-temperature ionic conductivity of 9.86 × 10⁻⁶. -5 S cm - ¹ represents the optimal value for the dual-doped system, reflecting the synergistic regulatory effect of sintering temperature and F doping amount on ion transport performance.

[0045] Figure 6 The table shows the room temperature impedance spectra and Arrhenius fitting curves for Example 3 after different holding times at 1220℃. The sample with 6h holding time had the lowest total impedance, the best room temperature ionic conductivity, and the lowest lithium-ion migration activation energy of 0.1226eV, confirming that 6h is the optimal holding time for this system, which can achieve synergistic optimization of phase purity, densification, and ion transport performance.

[0046] Figure 7 The electrochemical performance test results of the lithium symmetric battery assembled in Example 3 show that the battery can be stably cycled for more than 1300 hours under a constant current of 0.1mA, and the polarization voltage is always stably controlled within the range of ±0.2V. There is no obvious polarization drift or short circuit failure, demonstrating excellent interface compatibility and resistance to lithium dendrite formation.

[0047] Figure 8 The XRD patterns of Examples 1-3 and Comparative Example 1 after 30 days of air exposure are shown. The results show that Comparative Example 1 exhibits obvious Li₂CO₃ characteristic impurity peaks, while no Li₂CO₃ impurity phase is formed in any of the F-doped samples, confirming that F doping can effectively suppress Li₂CO₃ impurity phase formation. + / H + The exchange reaction and the formation of insulating impurity phases fundamentally improve the air chemical stability of LLZO electrolytes.

[0048] Figure 9 The impedance evolution spectra of the electrolytes in Examples 1-3 and Comparative Example 1 after 0-30 days of air exposure are shown. With the increase of F doping amount, the increase of sample impedance with exposure time is significantly reduced. The impedance spectrum of the sample with y=0.15 after 30 days of exposure showed no obvious distortion, and the conductivity retention rate was as high as 90.77%, which directly confirms that F doping can intrinsically suppress the air degradation behavior of LLZO.

[0049] Table 2. Air stability test results of the solid electrolytes obtained in Examples 1-3 and Comparative Example 1.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing a WF-doped garnet-type solid electrolyte, characterized in that, include: Step 1: Weigh the raw materials, including Li2CO3, La2O3, ZrO2, WO3, and LiF; Step 2: Wet ball mill the raw materials to obtain a mixed raw material; Step 3: Dry the mixed raw materials to constant weight to obtain a dried mixture; Step 4: Screen the dried mixture to obtain the screened material; Step 5: Pre-sinter the screened material to obtain pre-sintered powder; Step 6: The pre-calcined powder is ball-milled again and pressed into shape to obtain an electrolyte preform. Step 7: The electrolyte preform is sintered at high temperature to obtain the sintered product; Step 8, grind and sieve the sintered product to obtain W-F co-doped Li 6.2-y La3Zr 1.6 W 0.4 O 12-y F y solid state electrolyte.

2. The method for preparing WF-doped garnet-type solid electrolyte according to claim 1, characterized in that, In step 1, Li₂CO₃, La₂O₃, ZrO₂, WO₃, and LiF are added according to the formula Li. 6.2-y La3Zr 1.6 W 0.4 O 12-y F y The stoichiometric ratios are used for mixing, where y = 0.05~0.

15.

3. The method for preparing WF-doped garnet-type solid electrolyte according to claim 1, characterized in that, In step 2, during wet ball milling, zirconium oxide is used as the grinding ball, anhydrous ethanol is used as the ball milling aid, and the ball milling time is 5-7 hours.

4. The method for preparing WF-doped garnet-type solid electrolyte according to claim 1, characterized in that, In step 3, the drying temperature is 80~110℃.

5. The method for preparing WF-doped garnet-type solid electrolyte according to claim 1, characterized in that, In step 4, a 40-mesh standard sieve is used for sieving.

6. The method for preparing WF-doped garnet-type solid electrolyte according to claim 1, characterized in that, In step 5, during the pre-firing process, the temperature is 850~950℃, the holding time is 5~7h, and the heating rate is 2~5℃ / min.

7. The method for preparing WF-doped garnet-type solid electrolyte according to claim 1, characterized in that, In step 7, during the high-temperature sintering treatment, the temperature is 1180~1240℃, the holding time is 5~8h, the heating rate is 2~5℃ / min, and the sintering process adopts the same component master powder embedding method.

8. The method for preparing WF-doped garnet-type solid electrolyte according to claim 1, characterized in that, In step 8, the grinding time is 0.5~3 hours, and a 120-mesh standard sieve is used for sieving.

9. A WF-doped Li₂ obtained by the method for preparing WF-doped garnet-type solid electrolyte according to any one of claims 1 to 8 6.2-y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolyte.

10. A solid-state lithium metal battery, characterized in that, Lithium-ionized lithium containing WF-doped garnet-type solid electrolyte obtained by the method for preparing WF-doped garnet-type solid electrolyte as described in any one of claims 1 to 8 6.2-y La3Zr 1.6 W 0.4 O 12-y F y Solid electrolyte; under a constant current of 0.1mA, the lithium symmetric battery of this battery can be stably cycled for more than 1300 hours, and the polarization voltage is stable within the range of ±0.2V; after being exposed to air environment for 30 days, the ionic conductivity of the solid electrolyte is as high as 90.77%.

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