Low-temperature sintering of Li0.33La0.55TiO3 electrolyte for all-solid-state Li batteries

Ceramic solid-state Li batteries have promising electrochemical properties. However, their device integration is hampered by the required high sintering temperature step to obtain good ionic conductivity. The sintering temperature often leads to thermal decomposition of the cathode active material. Advanced sintering techniques, such as field-assisted sintering technology/spark plasma sintering (FAST/SPS), utilizing applied mechanical pressure to achieve a lower sintering temperature and shorter dwell time, are helpful in overcoming thermal stability challenges. While thermal stability issues are overcome by a lower sintering temperature, new challenges in the form of surface impurities arise. Low-temperature sintering does not thermally decompose surface impurities which causes low grain boundary conductivity and thus low total ionic conductivity. In this work, a cleaning method and a low-temperature sintering process is exemplarily developed for Li0.33La0.55TiO3 (LLTO) and the impact of applied mechanical pressure during FAST/SPS on the total ionic conductivity and the phase stability of LLTO is revealed.