Li-ion conductivity and stability of hot-pressed LiTa2PO8 solid electrolyte for all-solid-state batteries

Abstract

Solid-state electrolyte as a crucial component in all-solid-state batteries should have high Li-ion conductivity and good stability in air. Recently, a new solid Li-ion conductor LiTa2PO8 (LTPO) with theoretical and experimental Li-ion conductivities of 35.3 and 0.25 mS/cm has been reported. Herein, we systematically investigate the ionic conductivity and chemical stability of the LTPO electrolytes sintered by conventional sintering (CS) and hot-pressing sintering (HP) methods. The effects of Li sources, sintering temperature, and the dwelling time are concerned. LTPO pellets using CH3COOLi·2H2O as the Li source sintered by CS method have a room-temperature Li-ion conductivity of 1.86 × 10–4 S/cm with an activation energy of 0.36 eV. A conductivity of 3.12 × 10–4 S/cm with an activation energy of 0.32 eV is achieved by further HP sintering. Moreover, LTPO shows excellent chemical stabilities in air, aqueous solution, and organic solvent and shows a stable cycling performance in the symmetric Li/Li cells and the all-solid-state Li/LiFePO4 batteries with the separation of a thin PEO membrane.