Pyrochlore nanocrystals as versatile quasi-single-source precursors to lithium conducting garnets. Issue 34 (12th August 2020) - Weller, J. Mark
Abstract : Doped pyrochlore nanocrystal reagents enable new routes to low temperature reactions and dense Li garnet ceramics. Abstract : Lithium conducting garnets are attractive solid electrolytes for solid-state lithium batteries but are difficult to process, generally requiring high reaction and sintering temperatures with long durations. In this work, we demonstrate a synthetic route to obtain Ta-doped garnet (Li6.4 La3 Zr1.4 Ta0.6 O12 ) utilizing La- and Ta-doped lanthanum zirconate (La2.4 Zr1.12 Ta0.48 O7.04 ) pyrochlore nanocrystals as quasi-single-source precursors. Via molten salt synthesis (MSS) in a highly basic flux, the pyrochlore nanocrystals transform to Li-garnet at reaction temperatures as low as 400 °C. We also show that the pyrochlore-to-garnet conversion can take place in one step using reactive sintering, resulting in densified garnet ceramics with high ionic conductivity (0.53 mS cm −1 at 21 °C) and relative density (up to 94.7%). This approach opens new avenues for lower temperature synthesis of lithium garnets using a quasi-single-source precursor and provides an alternative route to highly dense garnet solid electrolytes without requiring advanced sintering processes.