A strategy to improve the overall performance of the lithium ion-conducting solid electrolyte Li0.36La0.56□0.08Ti 0.97Al0.03O3

Abstract

A strategy to improve the overall performance of the lithium ion-conducting solid electrolyte (Li-CSE) Li0.36La0.56□ 0.08-Ti0.97Al0.03O3 (LLTO) is proposed. Thin layers of the electronically insulating, electrochemically stable, and low-melting Li-CSE Li3.25Ge0.25P 0.75S4 (LGPS) were coated onto LLTO powders, which resulted in oxide/sulfide composite electrolytes. The introduction of LGPS simultaneously brought about drastic reductions in the activation energies and great enhancements of the total ionic conductivities of the composite electrolytes. As the LGPS content was increased from 0 mol-% to 20 mol-%, the activation energy decreased steadily from 0.62 eV to 0.34 eV, and accordingly a total ionic conductivity as high as 1.62 × 10-4 S cm -1 was reached, almost the same as those of the excellent oxide-based Li-CSE ceramics sintered at extremely high temperatures, and a wide electrochemical window of over 6 V vs. Li+/Li was achieved. In addition, a low electronic conductivity of 2.38 × 10-9 S cm-1 at room temperature for the composite electrolyte was discovered. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.