Li-La-Zr three-site co-doped garnet solid electrolyte ceramic, and preparation method and application thereof
By using Li-La-Zr three-point co-doped garnet solid electrolyte ceramics, the problems of low ionic conductivity and poor air stability of garnet-type solid electrolytes have been solved, achieving high ionic conductivity and excellent air stability, thereby improving the cycle stability and rate performance of lithium batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TAIYUAN UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2026-05-13
- Publication Date
- 2026-06-12
AI Technical Summary
Existing garnet-type solid electrolytes suffer from low ionic conductivity and poor air stability, which limits their application and promotion in lithium batteries.
A Li-La-Zr three-site co-doping method was used to prepare Li6.25(Ga0.25)La2.5(Sr0.5)Zr1.5(Ta0.5)O12 garnet solid electrolyte ceramic. By doping trivalent gallium, divalent strontium and pentavalent tantalum at the Li, La and Zr sites, the grain boundary contact and lattice distortion were improved, and the ionic conductivity and air stability were increased.
It improves the cycle stability and rate performance of lithium-ion batteries, enhances the ionic conductivity and air stability of solid-state batteries, and promotes the safety and energy density of solid-state batteries.
Smart Images
Figure CN122187488A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of ceramics and energy storage technology, and in particular to a Li-La-Zr three-point co-doped garnet solid electrolyte ceramic, its preparation method, and its application. Background Technology
[0002] Lithium-ion batteries are characterized by high energy density, long range, and long lifespan, and are currently widely used in various new energy vehicles and mobile communications. Most lithium batteries on the market are liquid lithium batteries. While liquid electrolytes have high ionic conductivity, they also have drawbacks such as easy decomposition at high temperatures, easy leakage, and the flammability and corrosiveness of leaked electrolytes, which can easily cause fires, explosions, and other accidents, posing safety hazards. With the widespread use of new energy vehicles, there is a demand for higher safety and longer range for lithium batteries. Solid-state batteries, with their good safety performance and high energy density, have become a research hotspot. The performance of the solid electrolyte is crucial to the performance of solid-state batteries. Garnet-type solid electrolytes, with their high energy density and wide electrochemical window, are considered one of the most promising solid electrolyte materials for promoting the commercialization of all-solid-state lithium metal batteries.
[0003] However, garnet-type solid electrolytes generally suffer from low ionic conductivity and poor air stability, which severely restricts their large-scale application and industrialization. Therefore, there is a need in this field to develop a Li-La-Zr three-site co-doped garnet solid electrolyte ceramic, its preparation method, and its applications, which can effectively solve the above problems. Summary of the Invention
[0004] The purpose of this invention is to provide a Li-La-Zr three-point co-doped garnet solid electrolyte ceramic, its preparation method and application. This Li-La-Zr three-point co-doped garnet solid electrolyte ceramic has high ionic conductivity and excellent air stability, which can improve the cycle stability and rate performance of solid-state batteries.
[0005] To achieve the above objectives, the present invention provides a Li-La-Zr three-site co-doped garnet solid electrolyte ceramic, wherein the chemical formula of the Li-La-Zr three-site co-doped garnet solid electrolyte ceramic is Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 .
[0006] Preferably, the ionic conductivity of the Li-La-Zr three-site co-doped garnet solid electrolyte ceramic is 2.77 × 10⁻⁶.-4 ~3.46×10 -4 S / cm, relative density is 94%~95.9%.
[0007] This invention also provides a method for preparing the above-mentioned Li-La-Zr three-site co-doped garnet solid electrolyte ceramic, comprising the following steps: S1, according to Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 The stoichiometric ratios of each element in the mixture were determined by weighing lithium source, gallium source, lanthanum source, strontium source, zirconium source and tantalum source respectively, and then mixing them to obtain a mixture. The mixture was then ground to obtain precursor powder. S2. The precursor powder is calcined, ground, and pressed into shape to obtain an electrolyte preform. S3. After sintering the electrolyte blank, a Li-La-Zr three-point co-doped garnet solid electrolyte ceramic is obtained.
[0008] Preferably, the lithium source in S1 includes lithium carbonate and / or lithium hydroxide; the gallium source includes gallium oxide; the lanthanum source includes lanthanum oxide; the strontium source includes strontium oxide; the zirconium source includes zirconium oxide and / or zirconium oxynitrate; and the tantalum source includes tantalum oxide.
[0009] Preferably, the method described in S1 according to Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 When weighing the corresponding raw materials according to the stoichiometric ratio of each element, the lithium source is in excess by 15 wt% to compensate for the volatilization of lithium at high temperature.
[0010] Preferably, the grinding method described in S1 is wet ball milling, with a rotation speed of 400~500 r / min and a time of 8~15 h; the dispersant used in the wet ball milling includes one of isopropanol, ethanol, and methanol, and the grinding balls used are zirconia balls; the mass ratio of the mixture, dispersant, and grinding balls is 1:1~2:3~10.
[0011] Preferably, after grinding in S1, the resulting grinding slurry is dried to obtain precursor powder; the drying temperature is 60~80℃ and the time is 6~12h.
[0012] Preferably, the calcination process in S2 includes: placing the precursor powder in a muffle furnace under an air atmosphere, heating it to a target temperature, holding it at that temperature, and then cooling it to a furnace temperature ≤50°C; the heating rate is 3~6°C / min, the target temperature is 950~1100°C, the holding time is 4~8h, and the cooling rate is 1~3°C / min.
[0013] The crucible used for calcination described in S2 is a covered magnesium oxide crucible.
[0014] Preferably, the grinding method in S2 is wet ball milling, with a rotation speed of 400~500 r / min and a time of 8~15 h; the dispersant used in the wet ball milling includes one of isopropanol, ethanol, and methanol, and the grinding balls used are zirconia balls; the mass ratio of the mixture, dispersant, and grinding balls is 1:1~2:3~10.
[0015] Preferably, after grinding in S2, the resulting grinding slurry is dried and then pressed into shape; the drying temperature is 60~80℃ and the time is 6~12h.
[0016] Preferably, the pressing process in S2 is cold isostatic pressing, with a pressure of 4~8MPa, a temperature of 20~25℃, and a holding time of 2~5min.
[0017] The pressing process described in S2 is carried out in a mold, the inner diameter of which is determined according to the size of the button battery casing.
[0018] Preferably, the sintering in S3 is carried out in an air atmosphere, and the process includes pre-sintering, final sintering, and cooling performed sequentially; the pre-sintering temperature is 400~600℃, the holding time is 3~8h, and the heating rate to the pre-sintering temperature is 3~6℃ / min; the final sintering temperature is 1100~1200℃, the holding time is 4~8h, and the heating rate from the pre-sintering temperature to the final sintering temperature is 3~6℃ / min; the target cooling temperature is 18~30℃, and the cooling rate to the target cooling temperature is 2~6℃ / min.
[0019] The sintering described in S3 is carried out in a muffle furnace using a covered magnesium oxide crucible. During sintering, precursor powder can be spread evenly at the bottom of the magnesium oxide crucible to prevent the electrolyte preform from adhering to the crucible. Simultaneously, precursor powder can be covered on the surface of the electrolyte preform to prevent lithium volatilization due to high temperatures during sintering. During sintering, the Li-La-Zr 3-site co-doped garnet electrolyte particles in the electrolyte preform grow, the ceramic densifies, and the ceramic undergoes uniform shrinkage.
[0020] The present invention also provides the application of the above-mentioned Li-La-Zr three-site co-doped garnet solid electrolyte ceramic in solid-state batteries.
[0021] Preferably, the solid-state battery is a lithium-ion solid-state battery.
[0022] This invention also provides a method for preparing a lithium-ion solid-state battery, comprising the following steps: The Li-La-Zr three-point co-doped garnet solid electrolyte ceramic was successively polished, ultrasonically cleaned, and dried to serve as the electrolyte. A coin cell, i.e. a lithium-ion solid battery, was assembled in an argon-filled glove box using lithium foil as the anode and lithium iron phosphate as the cathode.
[0023] Preferably, the ultrasonic cleaning is performed in ethanol for 30-60 seconds, and the ethanol has a mass concentration of 99.7%.
[0024] The present invention has the following beneficial effects: (1) The present invention utilizes Li7La3Zr2O 12 Li-La-Zr three-site co-doped garnet solid electrolyte ceramics were prepared by simultaneously doping Li, La, and Zr sites in LLZO. 6.25 (Ga0.25)La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 .
[0025] (2) The present invention prepares Li-La-Zr three-site co-doped ceramics by adding trivalent element (gallium) to Li sites, which can promote sintering, improve the grain boundary contact of solid electrolyte, thereby increasing the density of garnet solid electrolyte, accelerating the lithium ion transport rate, and improving ionic conductivity and air stability.
[0026] (3) The present invention can improve the air stability of solid electrolyte by preparing Li-La-Zr three-site co-doped ceramics by doping divalent element (strontium) at the La site.
[0027] (4) The present invention prepares Li-La-Zr three-site co-doped ceramics by doping pentavalent elements (tantalum) at Zr sites, which can cause lattice distortion, promote the formation of lithium ion transport channels, thereby accelerating the lithium ion transport rate and improving ionic conductivity.
[0028] (5) The Li-La-Zr three-point co-doped garnet solid battery prepared using the Li-La-Zr three-point co-doped garnet solid electrolyte ceramic of the present invention can exhibit excellent cycle stability and rate performance.
[0029] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0030] Figure 1 These are XRD patterns of the garnet solid electrolyte ceramics prepared in Examples 1 and 2 and Comparative Examples 1-3 of the present invention. Figure 2 These are SEM images of the garnet solid electrolyte ceramics prepared in Examples 1 and 2 and Comparative Examples 1-3 of this invention. in, Figure 2 In the image, 'a' represents the SEM image of Example 1. Figure 2 In the image, b is the SEM image of Example 2. Figure 2 In the diagram, 'c' represents the SEM image of Comparative Example 1. Figure 2 In the diagram, d represents the SEM image of Comparative Example 2. Figure 2 In the figure, 'e' is the SEM image of Comparative Example 3; Figure 3 These are EIS diagrams of the garnet solid electrolyte ceramics prepared in Examples 1 and 2 and Comparative Examples 1-3 of this invention; in, Figure 3 In the diagram, 'a' represents the EIS diagram of Example 1. Figure 3 In the diagram, b is the EIS diagram of Example 2. Figure 3 In the diagram, 'c' represents the EIS plot of Comparative Example 1. Figure 3 In the figure, d represents the EIS plot of Comparative Example 2. Figure 3 In the diagram, 'e' represents the EIS plot of Comparative Example 3. Figure 4 These are comparison graphs of impedance changes and lithium-ion conductivity changes of garnet solid electrolyte ceramics prepared in Examples 1 and 2 and Comparative Examples 1-3 of the present invention after being exposed to air for 30 days. in, Figure 4 In the figure, 'a' is a comparison graph of impedance changes in Example 1. Figure 4 In the figure, b is a comparison graph of impedance changes in Example 2. Figure 4 In the figure, 'c' represents a comparison of impedance changes in Comparative Example 1. Figure 4 In the figure, d represents a comparison of impedance changes in Comparative Example 2. Figure 4 In the figure, 'e' represents a comparison graph of impedance changes in Comparative Example 3. Figure 4 f in the graph represents the change in lithium-ion conductivity; Figure 5 This is a constant current charge-discharge diagram of the Li-La-Zr three-site co-doped garnet solid electrolyte ceramic prepared in Example 3 of the present invention after being applied to a lithium-ion solid battery. Detailed Implementation
[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.
[0032] Example 1 This embodiment provides a Li-La-Zr three-site co-doped garnet solid electrolyte ceramic with the chemical formula Li. 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 .
[0033] The above Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 The preparation method is as follows: S1, according to Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 The stoichiometric ratios of each element were as follows: 2.124 g lithium carbonate, 0.187 g gallium oxide, 3.258 g lanthanum oxide, 0.414 g strontium oxide, 1.479 g zirconium oxide, and 0.884 g tantalum oxide were weighed and mixed to obtain a mixture. The mixture was placed on a planetary ball mill, and 75 g zirconium oxide balls and 20 mL isopropanol were added. The mixture was ball-milled at 400 r / min for 12 h to obtain a grinding slurry. The grinding slurry was placed in an oven and dried at 80 °C for 10 h to obtain the precursor powder.
[0034] S2. Place the precursor powder into a covered magnesium oxide crucible and heat it to 1000℃ in a muffle furnace at a heating rate of 5℃ / min, hold it at that temperature for 6 hours, and then cool it to below 50℃ in the furnace at a rate of 2℃ / min to obtain electrolyte powder. Pour the electrolyte powder into a planetary ball mill, add 10mL of isopropanol and 34g of zirconia balls, and ball mill at a speed of 400r / min for 12 hours to obtain a grinding slurry. Place the grinding slurry in an oven and dry it at 80℃ for 10 hours to obtain electrolyte powder. Weigh 500mg of electrolyte powder, pour it into a mold with an inner diameter of 13mm, and cold isostatically press it at 25℃ and 6MPa for 3 minutes to obtain an electrolyte preform.
[0035] S3. The electrolyte blank obtained in S2 is placed in a covered magnesium oxide crucible with precursor powder (obtained in S2) spread on the bottom, and then the precursor powder is used to cover the surface of the electrolyte blank. The blank is pre-sintered in an air atmosphere in a muffle furnace at a heating rate of 5℃ / min to 500℃ and held for 3h. Then, the blank is sintered at a heating rate of 5℃ / min to 1130℃ and held for 6h. Finally, the blank is cooled to below 50℃ in the furnace at a cooling rate of 2℃ / min to obtain Li-La-Zr three-site co-doped garnet solid electrolyte ceramic.
[0036] The Li-La-Zr three-site co-doped garnet solid electrolyte ceramic prepared in this embodiment has an ionic conductivity of 3.46 × 10⁻⁶. -4 S / cm.
[0037] Example 2 This embodiment provides a Li-La-Zr three-site co-doped garnet solid electrolyte ceramic with the chemical formula Li. 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 .
[0038] The above Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 The preparation method is as follows: S1, according to Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12The stoichiometric ratios of each element were as follows: 2.124 g lithium carbonate, 0.187 g gallium oxide, 3.258 g lanthanum oxide, 0.414 g strontium oxide, 1.479 g zirconium oxide, and 0.884 g tantalum oxide were weighed and mixed to obtain a mixture. The mixture was placed on a planetary ball mill, and 75 g zirconium oxide balls and 20 mL isopropanol were added. The mixture was ball-milled at 400 r / min for 12 h to obtain a grinding slurry. The grinding slurry was placed in an oven and dried at 80 °C for 10 h to obtain the precursor powder.
[0039] S2. Place the precursor powder into a covered magnesium oxide crucible and heat it to 1050℃ in a muffle furnace at a heating rate of 5℃ / min, hold it at that temperature for 6 hours, and then cool it to below 50℃ in the furnace at a rate of 2℃ / min to obtain electrolyte powder. Pour the electrolyte powder into a planetary ball mill, add 10mL of isopropanol and 34g of zirconia balls, and ball mill at a speed of 400r / min for 12 hours to obtain a grinding slurry. Place the grinding slurry in an oven and dry it at 80℃ for 10 hours to obtain electrolyte powder. Weigh 500mg of electrolyte powder, pour it into a mold with an inner diameter of 13mm, and cold isostatically press it at 25℃ and 6MPa for 3 minutes to obtain an electrolyte preform.
[0040] S3. The electrolyte blank obtained in S2 is placed in a covered magnesium oxide crucible with precursor powder (obtained in S2) spread on the bottom, and then the precursor powder is used to cover the surface of the electrolyte blank. The blank is pre-sintered in an air atmosphere in a muffle furnace at a heating rate of 5℃ / min to 500℃ and held for 3h. Then, the blank is pre-sintered at a heating rate of 5℃ / min to 1180℃ and held for 6h. Finally, the blank is cooled to below 50℃ in the furnace at a cooling rate of 2℃ / min to obtain Li-La-Zr three-site co-doped garnet solid electrolyte ceramic.
[0041] The Li-La-Zr three-site co-doped garnet solid electrolyte ceramic prepared in this embodiment has an ionic conductivity of 2.77 × 10⁻⁶. -4 S / cm.
[0042] Example 3 This embodiment provides a Li-La-Zr three-site co-doped garnet solid electrolyte ceramic with the chemical formula Li. 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 The preparation method is basically the same as that in Example 1, except that in S2, 1200mg of electrolyte powder is weighed and poured into a mold with an inner diameter of 20mm for cold isostatic pressing.
[0043] The Li-La-Zr three-site co-doped garnet solid electrolyte ceramic prepared in this embodiment has an ionic conductivity of 3.46 × 10⁻⁶. -4 S / cm.
[0044] Comparative Example 1 This comparative example provides a single-Li-site-doped garnet solid electrolyte ceramic with the chemical formula Li. 6.25 (Ga 0.25 La3Zr2O 12 .
[0045] The above Li 6.25 (Ga 0.25 La3Zr2O 12 The preparation method is as follows: S1, according to Li 6.25 (Ga 0.25 La3Zr2O 12 The stoichiometric ratios of each element were measured, and 2.124 g of lithium carbonate, 0.187 g of gallium oxide, 3.910 g of lanthanum oxide and 1.972 g of zirconium oxide were weighed and mixed to obtain a mixture. The mixture was placed on a planetary ball mill, and 75 g of zirconium oxide balls and 20 mL of isopropanol were added. The mixture was ball milled at 400 r / min for 12 h to obtain a grinding slurry. The grinding slurry was placed in an oven and dried at 80 °C for 10 h to obtain the precursor powder.
[0046] S2. Place the precursor powder into a covered magnesium oxide crucible and heat it to 1000℃ in a muffle furnace at a heating rate of 5℃ / min, hold it at that temperature for 6 hours, and then cool it to below 50℃ in the furnace at a rate of 2℃ / min to obtain electrolyte powder. Pour the electrolyte powder into a planetary ball mill, add 10mL of isopropanol and 34g of zirconia balls, and ball mill at a speed of 400r / min for 12 hours to obtain a grinding slurry. Place the grinding slurry in an oven and dry it at 80℃ for 10 hours to obtain electrolyte powder. Weigh 500mg of electrolyte powder, pour it into a mold with an inner diameter of 13mm, and cold isostatically press it at 25℃ and 6MPa for 3 minutes to obtain an electrolyte preform.
[0047] S3. The electrolyte blank obtained in S2 is placed in a covered magnesium oxide crucible with a precursor powder (obtained in S2) spread evenly at the bottom, and then the precursor powder is used to cover the surface of the electrolyte blank. Pre-sintering is performed in a muffle furnace under air atmosphere, with a heating rate of 5℃ / min to 500℃ and a holding time of 3 hours. Then, final sintering is performed by heating to 1130℃ at a heating rate of 5℃ / min and a holding time of 6 hours. Finally, the temperature is lowered to below 50℃ in the furnace at a cooling rate of 2℃ / min to obtain Li. 6.25 (Ga 0.25 La3Zr2O 12Garnet solid electrolyte ceramic.
[0048] The ionic conductivity of the single-Li-site-doped garnet solid electrolyte ceramic prepared in this comparative example is 3.21 × 10⁻⁶. - 5 S / cm.
[0049] Comparative Example 2 This comparative example provides a single La-site-doped garnet solid electrolyte ceramic with the chemical formula Li. 7.5 La 2.5 (Sr 0.5 Zr2O 12 .
[0050] The above Li 7.5 La 2.5 (Sr 0.5 Zr2O 12 The preparation method is as follows: S1, according to Li 7.5 La 2.5 (Sr 0.5 Zr2O 12 The stoichiometric ratios of each element were as follows: 2.549 g of lithium carbonate, 3.258 g of lanthanum oxide, 0.414 g of strontium oxide, and 1.972 g of zirconium oxide were weighed and mixed to obtain a mixture. The mixture was placed on a planetary ball mill, and 75 g of zirconium oxide balls and 20 mL of isopropanol were added. The mixture was ball-milled at 400 r / min for 12 h to obtain a grinding slurry. The grinding slurry was placed in an oven and dried at 80 °C for 10 h to obtain the precursor powder.
[0051] S2. Place the precursor powder into a covered magnesium oxide crucible and heat it to 1000℃ in a muffle furnace at a heating rate of 5℃ / min, hold it at that temperature for 6 hours, and then cool it to below 50℃ in the furnace at a rate of 2℃ / min to obtain electrolyte powder. Pour the electrolyte powder into a planetary ball mill, add 10mL of isopropanol and 34g of zirconia balls, and ball mill at a speed of 400r / min for 12 hours to obtain a grinding slurry. Place the grinding slurry in an oven and dry it at 80℃ for 10 hours to obtain electrolyte powder. Weigh 500mg of electrolyte powder, pour it into a mold with an inner diameter of 13mm, and cold isostatically press it at 25℃ and 6MPa for 3 minutes to obtain an electrolyte preform.
[0052] S3. The electrolyte blank obtained in S2 is placed in a covered magnesium oxide crucible with a precursor powder (obtained in S2) spread evenly at the bottom, and then the precursor powder is used to cover the surface of the electrolyte blank. Pre-sintering is performed in a muffle furnace under air atmosphere, with a heating rate of 5℃ / min to 500℃ and a holding time of 3 hours. Then, final sintering is performed by heating to 1130℃ at a heating rate of 5℃ / min and a holding time of 6 hours. Finally, the temperature is lowered to below 50℃ in the furnace at a cooling rate of 2℃ / min to obtain Li. 7.5 La 2.5 (Sr 0.5 Zr2O 12 Garnet solid electrolyte ceramic.
[0053] The ionic conductivity of the single-La-site-doped garnet solid electrolyte ceramic prepared in this comparative example is 1.40 × 10⁻⁶. - 6 S / cm.
[0054] Comparative Example 3 This comparative example provides a single-Zr-site-doped garnet solid electrolyte ceramic with the chemical formula Li. 6.5 La3Zr 1.5 (Ta 0.5 )O 12 .
[0055] The above Li 6.5 La3Zr 1.5 (Ta 0.5 )O 12 The preparation method is as follows: S1. Mix 2.209g lithium carbonate, 3.910g lanthanum oxide, 1.479g zirconium oxide and 0.884g tantalum oxide to obtain a mixture. Place the mixture on a planetary ball mill, add 75g zirconium oxide balls and 20mL isopropanol, and ball mill at 400r / min for 12h to obtain a grinding slurry. Place the grinding slurry in an oven and dry at 80℃ for 10h to obtain the precursor powder.
[0056] S2. Place the precursor powder into a covered magnesium oxide crucible and heat it to 1000℃ in a muffle furnace at a heating rate of 5℃ / min, hold it at that temperature for 6 hours, and then cool it to below 50℃ in the furnace at a rate of 2℃ / min to obtain electrolyte powder. Pour the electrolyte powder into a planetary ball mill, add 10mL of isopropanol and 34g of zirconia balls, and ball mill at a speed of 400r / min for 12 hours to obtain a grinding slurry. Place the grinding slurry in an oven and dry it at 80℃ for 10 hours to obtain electrolyte powder. Weigh 500mg of electrolyte powder, pour it into a mold with an inner diameter of 13mm, and cold isostatically press it at 25℃ and 6MPa for 3 minutes to obtain an electrolyte preform.
[0057] S3. The electrolyte blank obtained in S2 is placed in a covered magnesium oxide crucible with a precursor powder (obtained in S2) spread evenly at the bottom, and then the precursor powder is used to cover the surface of the electrolyte blank. Pre-sintering is performed in a muffle furnace under air atmosphere, with a heating rate of 5℃ / min to 500℃ and a holding time of 3 hours. Then, final sintering is performed by heating to 1130℃ at a heating rate of 5℃ / min and a holding time of 6 hours. Finally, the temperature is lowered to below 50℃ in the furnace at a cooling rate of 2℃ / min to obtain Li. 6.5 La3Zr 1.5 (Ta 0.5 )O 12 Garnet solid electrolyte ceramic.
[0058] The ionic conductivity of the single-Zr-site-doped garnet solid electrolyte ceramic prepared in this comparative example is 6.58 × 10⁻⁶. - 5 S / cm.
[0059] Characterization tests: X-ray diffraction analysis was performed on the garnet solid electrolyte ceramics prepared in Examples 1 and 2 and Comparative Examples 1-3. The results are as follows: Figure 1 As shown. From Figure 1 It can be seen that the garnet solid electrolyte ceramics prepared in Examples 1, 2, 1, 2 and 3 can all generate pure cubic garnet phase, indicating that each element was successfully doped to the corresponding site and that doping can promote the synthesis of cubic garnet electrolyte.
[0060] SEM observations were performed on the garnet solid electrolyte ceramics prepared in Examples 1 and 2, and Comparative Examples 1-3. The results are as follows: Figure 2 As shown. From Figure 2 It can be seen that the garnet solid electrolyte ceramics prepared in Examples 1, 2 and Comparative Example 1 have higher density and tighter grain bonding, indicating that the doping of Li sites can promote the sintering of garnet electrolytes.
[0061] The initial impedance of the garnet solid electrolyte ceramics prepared in Examples 1 and 2 and Comparative Examples 1-3 was tested, and the results are as follows: Figure 3 As shown. From Figure 3 It can be seen that the garnet solid electrolyte ceramics prepared in Examples 1 and 2 have relatively low impedance, indicating that they have strong lithium-ion transport capabilities.
[0062] Garnet solid electrolyte ceramics prepared in Examples 1 and 2, and Comparative Examples 1-3, were exposed to air for 30 days (relative humidity 40%, temperature room temperature). The impedance changes were measured using an electrochemical workstation, and the comparison with the initial impedance results is shown in the figure below. Figure 4 As shown. From Figure 4It can be seen that the garnet solid electrolyte ceramics prepared in Examples 1 and 2 show very small impedance changes over 30 days, indicating strong air stability.
[0063] Performance testing: The Li-La-Zr three-site co-doped garnet solid electrolyte ceramic prepared in Example 3 was polished with sandpaper, ultrasonically cleaned in ethanol for 45 seconds, and then dried. Using lithium sheets as blocking electrodes, a button cell was assembled in an argon-filled glove box. The cycle performance of the symmetric cell was tested using an integrated testing system, and the results are as follows: Figure 5 As shown. From Figure 5 It can be seen that the lithium-ion solid-state battery prepared in Example 3 has excellent electrochemical stability, maintaining a stability of 0.1 mA / cm². 2 It can be stably cycled for more than 1000 hours at a current density.
[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A Li-La-Zr three-site co-doped garnet solid electrolyte ceramic, characterized in that, The chemical formula of the Li-La-Zr three-site co-doped garnet solid electrolyte ceramic is Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 .
2. The Li-La-Zr three-site co-doped garnet solid electrolyte ceramic according to claim 1, characterized in that, The ionic conductivity of the Li-La-Zr three-site co-doped garnet solid electrolyte ceramic is 2.77 × 10⁻⁶. -4 ~3.46×10 -4 S / cm, relative density is 94%~95.9%.
3. A method for preparing Li-La-Zr three-site co-doped garnet solid electrolyte ceramic as described in claim 1 or 2, characterized in that, Includes the following steps: S1, according to Li 6.25 (Ga 0.25 La 2.5 (Sr 0.5 Zr 1.5 (Ta 0.5 )O 12 The stoichiometric ratios of each element in the mixture were determined by weighing lithium source, gallium source, lanthanum source, strontium source, zirconium source and tantalum source respectively, and then mixing them to obtain a mixture. The mixture was then ground to obtain precursor powder. S2. The precursor powder is calcined, ground, and pressed into shape to obtain an electrolyte preform. S3. After sintering the electrolyte blank, a Li-La-Zr three-point co-doped garnet solid electrolyte ceramic is obtained.
4. The method for preparing Li-La-Zr three-site co-doped garnet solid electrolyte ceramic according to claim 3, characterized in that, The lithium source described in S1 includes lithium carbonate and / or lithium hydroxide; the gallium source includes gallium oxide; the lanthanum source includes lanthanum oxide; the strontium source includes strontium oxide; the zirconium source includes zirconium oxide and / or zirconium oxynitrate; and the tantalum source includes tantalum oxide.
5. The method for preparing Li-La-Zr three-site co-doped garnet solid electrolyte ceramic according to claim 3, characterized in that, The grinding method described in S1 is wet ball milling, with a rotation speed of 400~500 r / min and a time of 8~15 h; The dispersant used in the wet ball milling includes one of isopropanol, ethanol, and methanol, and the milling beads used are zirconia balls. The mass ratio of the mixture, dispersant, and milling beads is 1:1~2:3~10.
6. The method for preparing Li-La-Zr three-site co-doped garnet solid electrolyte ceramic according to claim 3, characterized in that, The calcination process described in S2 includes: In an air atmosphere, the precursor powder is placed in a muffle furnace and heated to the target temperature, then held at that temperature, and then cooled to a furnace temperature of ≤50℃. The heating rate is 3~6℃ / min, the target temperature is 950~1100℃, the holding time is 4~8h, and the cooling rate is 1~3℃ / min.
7. The method for preparing Li-La-Zr three-site co-doped garnet solid electrolyte ceramic according to claim 3, characterized in that, The grinding method described in S2 is wet ball milling, with a rotation speed of 400~500 r / min and a time of 8~15 h; The dispersant used in the wet ball milling includes one of isopropanol, ethanol, and methanol, and the milling beads used are zirconia balls. The mass ratio of the mixture, dispersant, and milling beads is 1:1~2:3~10.
8. The method for preparing Li-La-Zr three-site co-doped garnet solid electrolyte ceramic according to claim 3, characterized in that, The pressing process described in S2 uses cold isostatic pressing, with a pressure of 4~8MPa, a temperature of 20~25℃, and a holding time of 2~5min.
9. The method for preparing Li-La-Zr three-site co-doped garnet solid electrolyte ceramic according to claim 3, characterized in that, The sintering described in S3 is carried out in an air atmosphere, and the process includes pre-sintering, final sintering, and cooling performed sequentially. The pre-sintering temperature is 400~600℃, the holding time is 3~8h, and the heating rate to the pre-sintering temperature is 3~6℃ / min. The final sintering temperature is 1100~1200℃, the holding time is 4~8h, and the heating rate from the pre-sintering temperature to the final sintering temperature is 3~6℃ / min. The target cooling temperature is 18~30℃, and the cooling rate to the target cooling temperature is 2~6℃ / min.
10. The application of the Li-La-Zr three-point co-doped garnet solid electrolyte ceramic according to claim 1 or 2 in solid-state batteries.