Li-zr dual-site co-doped garnet solid electrolyte ceramic and preparation method and application thereof

Abstract

The application belongs to the field of advanced ceramics and energy storage technology, and specifically discloses a Li-Zr double-site co-doped garnet solid electrolyte ceramic and a preparation method and application thereof. 0.1 Ga 0.1 )La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 ; the Li element is derived from a lithium source, the Al element is derived from an aluminum source, the Ga element is derived from a gallium source, the La element is derived from a lanthanum source, the Zr element is derived from a zirconium source, the Nb element is derived from a niobium source, and the Ta element is derived from a tantalum source. The application adopts the above Li-Zr double-site co-doped garnet solid electrolyte ceramic and the preparation method and application thereof. The Li-Zr double-site co-doped garnet solid electrolyte ceramic has high ionic conductivity and can improve the cycle stability and rate performance of a solid-state battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of advanced ceramics and energy storage technology, and particularly relates to a Li-Zr double-site co-doped garnet solid electrolyte ceramic and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries have the characteristics of high energy density, long endurance and long service life, and are widely used in various new energy vehicles and mobile communication fields. The lithium batteries widely used in the market at present are mostly liquid lithium batteries. The liquid electrolyte therein has high ionic conductivity, but also has the shortcomings of easy decomposition at high temperature, easy leakage, corrosive leakage, etc., which can easily cause fire, explosion and other accidents, and has safety hazards. With the wide use of new energy vehicles, higher safety and longer endurance time are required for lithium batteries. Solid-state batteries have the characteristics of good safety performance and high energy density, and thus become a research hotspot. The performance of solid electrolyte is the key to determining the performance of solid-state batteries. Garnet-type solid electrolyte has excellent stability and is considered to be one of the most potential solid electrolyte materials for promoting the commercialization of all-solid-state lithium metal batteries.

[0003] However, the wide application of garnet-type solid electrolyte is greatly hindered due to its low ionic conductivity. Therefore, it is necessary to develop a Li-Zr double-site co-doped garnet solid electrolyte ceramic and a preparation method and application thereof, which can effectively solve the above problems. SUMMARY

[0004] The purpose of the present application is to provide a Li-Zr double-site co-doped garnet solid electrolyte ceramic and a preparation method and application thereof. The Li-Zr double-site co-doped garnet solid electrolyte ceramic has high ionic conductivity and can improve the cycle stability and rate performance of solid-state batteries.

[0005] To achieve the above purpose, the present application provides a Li-Zr double-site co-doped garnet solid electrolyte ceramic, which has a chemical formula of Li6(Al 0.1 Ga 0.1 )La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 ; and the Li6(Al 0.1 Ga 0.1 )La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12The Li element is derived from a lithium source, the Al element is derived from an aluminum source, the Ga element is derived from a gallium source, the La element is derived from a lanthanum source, the Zr element is derived from a zirconium source, the Nb element is derived from a niobium source, and the Ta element is derived from a tantalum source.

[0006] Preferably, the lithium source includes lithium carbonate and lithium hydroxide; the aluminum source includes aluminum oxide; the gallium source includes gallium oxide; the lanthanum source includes lanthanum oxide; the zirconium source includes zirconium oxide and zirconyl nitrate; the niobium source includes niobium oxide; and the tantalum source includes tantalum oxide.

[0007] Preferably, the ion conductivity of the Li-Zr double-site co-doped garnet solid electrolyte ceramic is 2*10 -4 ~3.17*10 -4 S / cm; and the relative density of the Li-Zr double-site co-doped garnet solid electrolyte ceramic is 97-99.1%.

[0008] The application further provides a preparation method of the Li-Zr double-site co-doped garnet solid electrolyte ceramic.

[0009] Step S1, the Li-Zr double-site co-doped garnet solid electrolyte ceramic Li6(Al 0.1 Ga 0.1 )La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 is prepared according to the stoichiometric ratio of each element, and oxide powders of lithium source, aluminum source, gallium source, lanthanum source, zirconium source, niobium source and tantalum source are weighed and ball milled to obtain mixed oxide precursor powder;

[0010] Step S2, the mixed oxide precursor powder is calcined to obtain Li-Zr double-site co-doped garnet electrolyte powder, which is off-white in color and has a particle diameter of 5-20 μm;

[0011] Step S3, the Li-Zr double-site co-doped garnet electrolyte powder is subjected to secondary ball milling to obtain Li-Zr double-site co-doped garnet electrolyte powder;

[0012] Step S4, the Li-Zr double-site co-doped garnet electrolyte powder is subjected to compression molding to obtain Li-Zr double-site co-doped garnet electrolyte green body;

[0013] Step S5, the Li-Zr double-site co-doped garnet electrolyte green body is sintered to obtain the Li-Zr double-site co-doped garnet solid electrolyte ceramic.

[0014] Preferably, in step S1, the purity of the oxides of the lithium source, the aluminum source, the gallium source, the lanthanum source, the zirconium source, the niobium source and the tantalum source is greater than 99wt%; wherein the lithium source is weighed with an excess of 15wt% to compensate for the volatilization of lithium at high temperature;

[0015] In steps S1 and S3, the ball milling is wet milling, and the dispersing agent for wet milling includes isopropyl alcohol, ethanol, and methanol; the rotation speed of the ball milling is 400-450r / min, and the ball milling time is 8-15h;

[0016] The ball milling is carried out in a polytetrafluoroethylene ball milling jar, and the ball milling beads are zirconium oxide balls; the mass ratio of the total mass of the oxides of the lithium source, the aluminum source, the gallium source, the lanthanum source, the zirconium source, the niobium source and the tantalum source to the mass of the dispersing agent and the ball milling beads is 1:2:7-10.

[0017] Preferably, in steps S1 and S3, after the ball milling, the obtained slurry is dried to obtain a mixed oxide precursor powder; the drying temperature is 60-80℃, and the drying time is 6-12h.

[0018] Preferably, in step S2, the calcination temperature is 900-1100℃, and the holding time is 4-10h;

[0019] The calcination is carried out in a muffle furnace, and the used crucible is a magnesium oxide crucible with a cover; the heating rate for heating to the calcination temperature is 2-8℃ / min, and the calcination atmosphere is air atmosphere; after the calcination, the cooling is carried out to below 50℃, and the Li-Zr dual-site co-doped garnet electrolyte powder is obtained; the cooling rate is 1-3℃ / min.

[0020] Preferably, in step S4, the press forming is cold isostatic press forming; the pressure for the press forming is 4-8MPa, the temperature for the press forming is 20-25℃, and the holding time for the pressure and temperature is 2-5min.

[0021] The forming is carried out in a mold; the inner diameter of the mold is determined according to the size of the button cell shell.

[0022] Preferably, in step S5, the sintering temperature is 1100-1250℃, the holding time is 2h-7h, and the sintering atmosphere is air atmosphere; the heating rate for heating to the sintering temperature is 2-8℃ / min.

[0023] The sintering is carried out in a muffle furnace, and the used crucible is a magnesium oxide crucible with a cover. In the sintering process, a layer of Li-Zr dual-site co-doped garnet electrolyte powder is laid on the bottom of the magnesium oxide crucible, and the surface of the Li-Zr dual-site co-doped garnet electrolyte green body is covered with Li-Zr dual-site co-doped garnet electrolyte powder to prevent adhesion. In the sintering process, the Li-Zr dual-site co-doped garnet electrolyte particles grow, and the ceramic is densified; in the sintering process, the ceramic uniformly shrinks.

[0024] After sintering, the material is cooled to below 50°C at a rate of 1-3°C / min to obtain a Li-Zr dual-site co-doped garnet electrolyte ceramic, which is milky white in color.

[0025] The present invention also provides an application of Li-Zr dual-site co-doped garnet solid electrolyte ceramic in solid-state batteries, preferably in lithium-ion solid-state batteries.

[0026] Specifically, in lithium-ion solid-state batteries, the Li-Zr dual-site co-doped garnet solid electrolyte ceramic is pretreated and used as the electrolyte. A lithium sheet is used as the anode and lithium iron phosphate is used as the cathode. The mixture is then assembled into a button cell in an argon-filled glove box.

[0027] Pretreatment included sequential sanding and polishing, ultrasonic cleaning, and drying. Ultrasonic cleaning was performed in an ethanol solution. The ultrasonic cleaning time was 30 seconds to 1 minute, and the ethanol solution had a mass concentration of 99.7%.

[0028] This invention employs the aforementioned Li-Zr dual-site co-doped garnet solid electrolyte ceramic, its preparation method, and its application, with the following beneficial effects:

[0029] (1) The present invention utilizes Li7La3Zr2O 12 Li-Zr dual-site co-doped garnet solid electrolyte ceramic Li6(Al) was prepared by simultaneously doping Li and Zr sites in LLZO. 0.1 Ga 0.1 )La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 .

[0030] (2) The present invention prepares Li-Zr dual-site co-doped ceramics by adding trivalent elements (aluminum and gallium) in equal molar ratio 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.

[0031] (3) The present invention prepares Li-Zr dual-site co-doped ceramics by doping Zr sites with pentavalent elements (niobium and tantalum) in an equimolar ratio, which can cause lattice distortion, promote the formation of lithium ion transport channels, thereby accelerating the lithium ion transport rate and improving ionic conductivity.

[0032] (4) The Li-Zr dual-site co-doped garnet solid battery prepared using the Li-Zr dual-site co-doped garnet solid electrolyte ceramic of the present invention can exhibit excellent cycle stability.

[0033] The technical solutions of the present application are described in further detail below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 XRD patterns of the garnet solid electrolyte ceramics prepared in Example 1, Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the Li-Zr dual-site co-doped garnet solid electrolyte ceramic and the preparation method and application of the present application;

[0035] Figure 2 SEM images of the garnet solid electrolyte ceramics prepared in Example 1, Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the Li-Zr dual-site co-doped garnet solid electrolyte ceramic and the preparation method and application of the present application; wherein (a) is Example 1, (b) is Example 2, (c) is Comparative Example 1, (d) is Comparative Example 2, and (e) is Comparative Example 3;

[0036] Figure 3 EIS patterns of the garnet solid electrolyte ceramics prepared in Example 1 and Comparative Example 1 of the Li-Zr dual-site co-doped garnet solid electrolyte ceramic and the preparation method and application of the present application; wherein (a) is Example 1, and (b) is Comparative Example 1;

[0037] Figure 4 EIS patterns of the garnet solid electrolyte ceramics prepared in Example 1 and Comparative Example 1 of the Li-Zr dual-site co-doped garnet solid electrolyte ceramic and the preparation method and application of the present application; wherein (a) is Example 1, and (b) is Comparative Example 1;

[0038] Figure 5 Constant current charge-discharge patterns of the symmetric batteries of the garnet solid electrolyte ceramics prepared in Example 1 and Comparative Example 1 of the Li-Zr dual-site co-doped garnet solid electrolyte ceramic and the preparation method and application of the present application; wherein (a) is Example 1, and (b) is Comparative Example 1. DETAILED DESCRIPTION

[0039] The technical solutions of the present application are described in further detail below with reference to the accompanying drawings and examples.

[0040] Unless otherwise defined, technical or scientific terms used in the present application shall have the usual meaning understood by a person having ordinary skill in the art to which the present application pertains.

[0041] Example 1

[0042] A preparation method of Li-Zr dual-site co-doped garnet solid electrolyte ceramic, comprising the following steps:

[0043] Step S1, 2.040g of lithium carbonate, 0.075g of gallium oxide, 0.041g of aluminum oxide, 3.910g of lanthanum oxide, 1.577g of zirconium oxide, 0.213g of niobium oxide and 0.354g of tantalum oxide are weighed, and the above raw materials are poured into a polytetrafluoroethylene ball mill jar. According to the mass ratio of raw materials, isopropyl alcohol and zirconium oxide ball milling beads is 1:2:9, 75g of zirconium oxide balls and 20mL of isopropyl alcohol are added. Ball milling on a planetary ball mill at a speed of 400r / min for 12h. The ball-milled slurry is placed in an 80℃ oven and dried for 8h to obtain a mixed oxide precursor powder.

[0044] Step S2, the mixed oxide precursor powder is placed in a magnesium oxide crucible, heated to 1000℃ at a heating rate of 5℃ / min in a muffle furnace, calcined for 5h, and cooled to below 50℃ at a rate of 2℃ / min to obtain a Li-Zr dual-site co-doped garnet electrolyte powder.

[0045] Step S3, the obtained Li-Zr dual-site co-doped garnet electrolyte powder is poured into a polytetrafluoroethylene ball mill jar, and isopropyl alcohol and ball milling beads are added according to the mass ratio of powder, isopropyl alcohol and zirconium oxide ball milling beads is 1:1:4. Ball milling on a planetary ball mill at a speed of 400r / min for 12h. The ball-milled slurry is placed in an 80℃ oven and dried for 8h to obtain a Li-Zr dual-site co-doped garnet electrolyte powder.

[0046] Step S4, 500mg and 1000mg of the Li-Zr dual-site co-doped garnet electrolyte powder are weighed respectively, and the powders are poured into molds with inner diameters of 13mm and 18mm respectively, and are kept at a pressure of 6MPa for 3min at 25℃ to obtain Li-Zr dual-site co-doped garnet electrolyte green bodies respectively.

[0047] Step S5, a layer of Li-Zr dual-site co-doped garnet electrolyte powder is laid on the bottom of a magnesium oxide crucible, and the Li-Zr dual-site co-doped garnet electrolyte green body is placed in the magnesium oxide crucible, and the green body is covered with Li-Zr dual-site co-doped garnet electrolyte powder, and is heated to 1180℃ at a heating rate of 5℃ / min in a muffle furnace, sintered for 5h, and cooled to below 50℃ at a rate of 2℃ / min to obtain Li-Zr dual-site co-doped garnet solid electrolyte ceramic respectively.

[0048] The ion conductivity of the Li-Zr dual-site co-doped garnet solid electrolyte ceramic prepared in this example is 3.17x10 -4 S / cm.

[0049] The Li-Zr dual-site co-doped garnet solid electrolyte ceramic prepared in this example was exposed to air for 30 days (relative humidity 40%, temperature room temperature) after sintering of the 13mm green compact, and its impedance change was tested using an electrochemical workstation.

[0050] The Li-Zr dual-site co-doped garnet solid electrolyte ceramic prepared in this example was polished with sandpaper after sintering of the 18mm green compact, cleaned the surface by ultrasonic in ethanol solution for 45s, and then dried. Lithium sheet was used as the blocking electrode, and a coin cell was assembled in an argon-filled glove box, and the cycle performance of the symmetric cell was tested using an integrated test system.

[0051] Example 2

[0052] A method for preparing a Li-Zr dual-site co-doped garnet solid electrolyte ceramic, comprising the following steps:

[0053] Step S1, weigh 2.040g of lithium carbonate, 0.075g of gallium oxide, 0.041g of aluminum oxide, 3.910g of lanthanum oxide, 1.577g of zirconium oxide, 0.213g of niobium oxide and 0.354g of tantalum oxide, and pour the above raw materials into a polytetrafluoroethylene ball mill jar. According to the mass ratio of raw materials, isopropyl alcohol and zirconium oxide milling beads is 1:2:9, then add 75g of zirconium balls and 20mL of isopropyl alcohol. Ball mill on a planetary ball mill at a speed of 400r / min for 12h. Put the ball milled slurry into an 80℃ oven and dry for 12h to obtain a mixed oxide precursor powder.

[0054] Step S2, put the mixed oxide precursor powder into a magnesium oxide crucible, heat to 950℃ at a rate of 5℃ / min in a muffle furnace, calcine for 6h, and cool to below 50℃ at a rate of 2℃ / min to obtain a Li-Zr dual-site co-doped garnet electrolyte powder.

[0055] Step S3, pour the obtained Li-Zr dual-site co-doped garnet electrolyte powder into a polytetrafluoroethylene ball mill jar, and add isopropyl alcohol and milling beads according to the mass ratio of powder, isopropyl alcohol and zirconium oxide milling beads is 1:1:4. Ball mill on a planetary ball mill at a speed of 400r / min for 12h. Put the ball milled slurry into an 80℃ oven and dry for 12h to obtain a Li-Zr dual-site co-doped garnet electrolyte powder.

[0056] Step S4, weigh 500mg of the Li-Zr dual-site co-doped garnet electrolyte powder, pour the powder into a mold with an inner diameter of 13mm, and press at a pressure of 6MPa for 3min at 25℃ to obtain a Li-Zr dual-site co-doped garnet electrolyte green compact.

[0057] Step S5, a layer of Li-Zr double site co-doped garnet electrolyte powder is laid at the bottom of the magnesium oxide crucible, the Li-Zr double site co-doped garnet electrolyte green body is put into the magnesium oxide crucible, the green body is covered with Li-Zr double site co-doped garnet electrolyte powder, the temperature is raised to 1200℃ at a rate of 5℃ / min in a muffle furnace, sintering is performed for 5h, the temperature is lowered to below 50℃ at a rate of 2℃ / min, and a Li-Zr double site co-doped garnet solid-state electrolyte ceramic is obtained.

[0058] The Li-Zr double site co-doped garnet solid-state electrolyte ceramic prepared in this embodiment has an ionic conductivity of 2.06×10 -4 S / cm.

[0059] Comparative Example 1

[0060] A preparation method of a Li7La3Zr2O 12 (LLZO) solid-state electrolyte, comprising the following steps:

[0061] Step S1, 2.379g of lithium carbonate, 3.910g of lanthanum oxide and 1.972g of zirconium oxide are weighed, and the above raw materials are poured into a polytetrafluoroethylene ball mill jar. The mass ratio of the raw materials, isopropanol and zirconium oxide milling beads is 1:2:9, 75g of zirconium oxide balls and 20mL of isopropanol are further added. Ball milling is performed on a planetary ball mill at a speed of 400r / min for 12h. The milled slurry is placed in an 80℃ oven and dried for 8h to obtain a mixed oxide precursor powder.

[0062] Step S2, the mixed oxide precursor powder is put into a magnesium oxide crucible, the temperature is raised to 1000℃ at a rate of 5℃ / min in a muffle furnace, calcination is performed for 5h, the temperature is lowered to below 50℃ at a rate of 2℃ / min, and a LLZO garnet electrolyte powder is obtained.

[0063] Step S3, the obtained LLZO garnet electrolyte powder is poured into a polytetrafluoroethylene ball mill jar, and isopropanol and milling beads are added in a mass ratio of 1:1:4. Ball milling is performed on a planetary ball mill at a speed of 400r / min for 12h. The milled slurry is placed in an 80℃ oven and dried for 8h to obtain a LLZO garnet electrolyte powder.

[0064] Step S4, 500mg and 1000mg of the LLZO garnet electrolyte powder are weighed respectively, and the powders are poured into molds with inner diameters of 13mm and 18mm respectively, and are pressed at a pressure of 6MPa at 25℃ for 3min, and LLZO garnet electrolyte green bodies are obtained respectively.

[0065] Step S5, respectively, a layer of LLZO garnet electrolyte powder was laid on the bottom of the magnesium oxide crucible, and the LLZO garnet electrolyte green body was respectively put into the magnesium oxide crucible, and the green body was respectively covered with LLZO garnet electrolyte powder, and the temperature was raised to 1180℃ at a rate of 5℃ / min in a muffle furnace, sintered for 5h, and cooled to below 50℃ at a rate of 2℃ / min, to obtain LLZO garnet solid electrolyte ceramic respectively.

[0066] The ion conductivity of the LLZO garnet solid electrolyte ceramic prepared in the present comparative example was 7.92×10 -7 S / cm.

[0067] The LLZO garnet solid electrolyte ceramic after sintering of the 13mm green body prepared in the present comparative example was exposed to air for 30 days (relative humidity 40%, temperature room temperature), and the impedance change thereof was tested by using an electrochemical workstation.

[0068] The LLZO garnet solid electrolyte ceramic after sintering of the 18mm green body prepared in the present comparative example was polished with sandpaper, cleaned on the surface by ultrasonic in ethanol solution for 45s, and then dried. Lithium sheet was used as the blocking electrode, and a coin cell was assembled in an argon-filled glove box, and the cycle performance of the symmetric cell was tested by using an integrated test system.

[0069] Comparative Example 2

[0070] A single Li site doped Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 solid electrolyte and a preparation method thereof, comprising the following steps:

[0071] Step S1, 2.175g of lithium carbonate, 0.075g of gallium oxide, 0.041g of aluminum oxide, 3.910g of lanthanum oxide and 1.972g of zirconium oxide were weighed, and the above raw materials were poured into a polytetrafluoroethylene ball mill jar. According to the mass ratio of raw materials, isopropanol and zirconium oxide milling beads is 1:2:9, 75g of zirconium oxide balls and 20mL of isopropanol were added. Ball milling on a planetary ball mill at a speed of 400r / min for 12h. The milled slurry was placed in an 80℃ oven and dried for 8h to obtain a mixed oxide precursor powder.

[0072] Step S2, the mixed oxide precursor powder was put into a magnesium oxide crucible, and the temperature was raised to 1000℃ at a rate of 5℃ / min in a muffle furnace, calcined for 5h, and cooled to below 50℃ at a rate of 2℃ / min, to obtain Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12Garnet electrolyte powder.

[0073] Step S3, the obtained Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 Garnet electrolyte powder is poured into a polytetrafluoroethylene ball mill tank, and isopropanol and ball milling beads are added in a mass ratio of 1:1:4. Ball milling is performed on a planetary ball mill at a speed of 400 r / min for 12 h. The milled slurry is placed in an 80℃ oven and dried for 8 h to obtain Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 Garnet electrolyte powder.

[0074] Step S4, 500 mg of the Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 Garnet electrolyte powder is poured into a mold with an inner diameter of 13 mm, and is pressed at a pressure of 6 MPa at 25℃ for 3 min to obtain Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 Garnet electrolyte green body.

[0075] Step S5, a layer of Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 Garnet electrolyte powder is laid on the bottom of a magnesium oxide crucible, and the Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 Garnet electrolyte green body is placed in the magnesium oxide crucible, and the Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 Garnet electrolyte powder covers the green body, which is heated in a muffle furnace at a heating rate of 5℃ / min to 1180℃, sintered for 5 h, and then cooled at a rate of 2℃ / min to below 50℃ to obtain single Li-site doped Li 6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 Garnet solid-state electrolyte ceramic.

[0076] The single Li-site doped Li6.4 (Al 0.1 Ga 0.1 )La3Zr2O 12 The ionic conductivity of the garnet solid electrolyte ceramic is 3.21 x 10 -5 S / cm.

[0077] Comparative Example 3

[0078] A single Zr site-doped Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 A method for preparing a solid electrolyte, comprising the following steps:

[0079] Step S1, weigh 2.243 g of lithium carbonate, 3.910 g of lanthanum oxide, 1.577 g of zirconium oxide, 0.213 g of niobium oxide and 0.354 g of tantalum oxide, and pour the above raw materials into a polytetrafluoroethylene ball mill jar. According to the mass ratio of raw materials, isopropyl alcohol and zirconium oxide ball milling beads is 1:2:9, then add 75 g of zirconium oxide balls and 20 mL of isopropyl alcohol. Ball mill on a planetary ball mill at a speed of 400 r / min for 12 h. Put the ball-milled slurry into an 80℃ oven and dry for 8 h to obtain a mixed oxide precursor powder.

[0080] Step S2, put the mixed oxide precursor powder into a magnesium oxide crucible, heat to 1000℃ at a rate of 5℃ / min in a muffle furnace, calcine for 5 h, and cool down to below 50℃ at a rate of 2℃ / min to obtain Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 garnet electrolyte powder.

[0081] Step S3, pour the obtained Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 garnet electrolyte powder into a polytetrafluoroethylene ball mill jar, and then add isopropyl alcohol and ball milling beads in a ratio of 1:1:4 of powder, isopropyl alcohol and zirconium oxide ball milling beads. Ball mill on a planetary ball mill at a speed of 400 r / min for 12 h. Put the ball-milled slurry into an 80℃ oven and dry for 8 h to obtain LLZO garnet electrolyte powder.

[0082] Step S4, weigh 500 mg of the Li 6.6 La3Zr 1.6 (Nb 0.2 Ta0.2 )O 12 Garnet electrolyte powder, pour the powder into a mold with an inner diameter of 13 mm, keep at 25℃, 6MPa pressure for 3min, get Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 Garnet electrolyte green body.

[0083] Step S5, lay a layer of Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 Garnet electrolyte powder, pour the powder into a mold with an inner diameter of 13 mm, keep at 25℃, 6MPa pressure for 3min, get Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 Garnet electrolyte green body into a magnesia crucible, cover the green body with Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 Garnet electrolyte powder, sinter in a muffle furnace at a heating rate of 5℃ / min to 1180℃, sinter for 5h, cool down at a rate of 2℃ / min to below 50℃, get single Zr site doped Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 Garnet solid electrolyte ceramic.

[0084] The single Zr site doped Li 6.6 La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 Garnet solid electrolyte ceramic prepared by the comparative example has an ionic conductivity of 1.91×10 -5 S / cm.

[0085] The garnet solid electrolyte ceramics prepared by example 1, example 2, comparative example 1, comparative example 2 and comparative example 3 were tested for performance.

[0086] As Figure 1 shown, the garnet solid electrolyte ceramics prepared by example 1, example 2, comparative example 2 and comparative example 3 can all generate pure phase cubic garnet phase, and comparative example 1 is pure phase tetragonal garnet phase, indicating that doping can promote the synthesis of cubic phase garnet electrolyte.

[0087] As shown in Figure 2 , the density of example 1 and example 2 is higher, and the grain is more closely combined.

[0088] As shown in Figure 3 , the impedance of example 1 and example 2 is relatively small, indicating that the lithium ion transmission ability is strong.

[0089] As shown in Figure 4 , the impedance change of example 1 within 30 days is small, indicating that the air stability is strong.

[0090] As shown in Figure 5 , the electrochemical stability of example 1 is better.

[0091] Therefore, the application adopts the above-mentioned Li-Zr double-site co-doped garnet solid electrolyte ceramic and its preparation method and application. The Li-Zr double-site co-doped garnet solid electrolyte ceramic has high ionic conductivity, which can improve the cycle stability and rate performance of the solid-state battery.

[0092] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A Li-Zr dual-site co-doped garnet solid state electrolyte ceramic, characterized by: The chemical formula of the Li-Zr double-site co-doped garnet solid electrolyte ceramic is Li6(Al 0.1 Ga 0.1 )La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 ; in the Li6(Al 0.1 Ga 0.1 )La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 , the Li element is derived from a lithium source, the Al element is derived from an aluminum source, the Ga element is derived from a gallium source, the La element is derived from a lanthanum source, the Zr element is derived from a zirconium source, the Nb element is derived from a niobium source, and the Ta element is derived from a tantalum source. The Li-Zr double-site co-doped garnet solid electrolyte ceramic has an ionic conductivity of 2*10 -4 -3.17*10 -4 S / cm, and a relative density of 97-99.1%.

2. The Li-Zr dual-site co-doped garnet solid-state electrolyte ceramic of claim 1, wherein: The lithium source includes lithium carbonate and lithium hydroxide; the aluminum source includes aluminum oxide; the gallium source includes gallium oxide; the lanthanum source includes lanthanum oxide; the zirconium source includes zirconium oxide and zirconyl nitrate; the niobium source includes niobium oxide; and the tantalum source includes tantalum oxide.

3. A method for preparing a Li-Zr dual-site co-doped garnet solid-state electrolyte ceramic according to any one of claims 1-2, characterized in that, The method comprises the following steps: Step S1, according to Li-Zr double site co-doped garnet solid electrolyte ceramic Li6(Al 0.1 Ga 0.1 )La3Zr 1.6 (Nb 0.2 Ta 0.2 )O 12 The stoichiometric ratio of each element in the formula is respectively taken to ball mill the oxide powder of lithium source, aluminum source, gallium source, lanthanum source, zirconium source, niobium source and tantalum source, to obtain a mixed oxide precursor powder; Step S2, calcining the mixed oxide precursor powder to obtain a Li-Zr dual-site co-doped garnet electrolyte powder; The calcination temperature is 900-1100℃, and the holding time is 4-10h; The temperature is raised to the calcination temperature at a rate of 2-8℃ / min, and the calcination atmosphere is air; after calcination, the temperature is cooled to below 50℃ to obtain the Li-Zr dual-site co-doped garnet electrolyte powder; the cooling rate is 1-3℃ / min; Step S3, secondary ball milling the Li-Zr dual-site co-doped garnet electrolyte powder to obtain a Li-Zr dual-site co-doped garnet electrolyte powder; Step S4, cold isostatic pressing the Li-Zr dual-site co-doped garnet electrolyte powder to obtain a Li-Zr dual-site co-doped garnet electrolyte green body; Step S5, sintering the Li-Zr dual-site co-doped garnet electrolyte green body to obtain a Li-Zr dual-site co-doped garnet solid electrolyte ceramic; The sintering temperature is 1100-1250℃, the holding time is 2-7h, and the sintering atmosphere is air; the temperature is raised to the sintering temperature at a rate of 2-8℃ / min.

4. The method of claim 3, wherein the method is characterized by: In step S1, the purity of the oxides of the lithium source, the aluminum source, the gallium source, the lanthanum source, the zirconium source, the niobium source and the tantalum source is greater than 99wt%; the lithium source is weighed with an excess of 15wt%; In steps S1 and S3, the ball milling is wet milling, the dispersant for wet milling includes isopropyl alcohol, ethanol and methanol; the rotation speed of the ball milling is 400-450r / min, and the ball milling time is 8-15h; The ball milling beads are zirconium oxide balls; the mass ratio of the total mass of the oxides of the lithium source, the aluminum source, the gallium source, the lanthanum source, the zirconium source, the niobium source and the tantalum source to the mass of the dispersant and the ball milling beads is 1:2:7-10.

5. The method for preparing a Li-Zr dual-site co-doped garnet solid electrolyte ceramic according to claim 4, characterized in that: In step S1, after ball milling, the obtained slurry is dried to obtain the mixed oxide precursor powder; the drying temperature is 60-80℃, and the drying time is 6-12h.

6. The method for preparing a Li-Zr dual-site co-doped garnet solid electrolyte ceramic according to claim 4, characterized in that: In step S3, after ball milling, the obtained slurry is dried to obtain the Li-Zr dual-site co-doped garnet electrolyte powder; the drying temperature is 60-80℃, and the drying time is 6-12h.

7. The method of claim 3, wherein the method is characterized by: In step S4, the cold isostatic pressing is performed at a pressure of 4-8MPa and a temperature of 20-25℃ for 2-5min.

8. Use of the Li-Zr dual-site co-doped garnet solid electrolyte ceramic according to any one of claims 1-2 in a solid-state battery.

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