LiAlO-Assisted Low-Temperature Sintering of Dense LiLaZrO Solid Electrolyte with High Critical Current Density.

In recent years, solid electrolytes (SEs) have been developed a lot due to the superior safety of solid-state batteries (SSBs) upon liquid electrolyte-based commercial batteries. Among them, garnet-type LiLaZrO (LLZO) is one of the few SEs that is stable to lithium anode with high Li conductivity and the feasibility of preparation under ambient air, which makes it a promising candidate for fabricating SSBs. However, high sintering temperature (>1200 °C) prevents its large-scale production, further hindering its application. In this work, the LiAlO sintering aid is proposed to decrease the sintering temperature and modify the grain boundaries of LLZO ceramics. LiAlO generates in situ LiO atmosphere and molten Li-Al-O compounds at relatively low temperatures to facilitate the gas-liquid-solid material transportation among raw LLZO grains, which decreases the densification temperature over 150 °C and strengthens the grain boundaries against lithium dendrites. As an example, Ta-doped LLZO ceramics without excessive Li sintered with 2 wt % LiAlO at 1050 °C delivered high relative density > 94%, an ionic conductivity of 6.7 × 10 S cm, and an excellent critical current density (CCD) of 1.5 mA cm at room temperature. In comparison, Ta-doped LLZO with 15% excessive Li sintered at 1200 °C delivered low relative density < 89%, a low ionic conductivity of ∼2 × 10 S cm, and a poor CCD of 0.5 mA cm. Li symmetric cells and Li-LFP full cells fabricated with LiAlO-assised ceramics were stably cycled at 0.2 mA cm over 2000 h and at 0.8C over 100 cycles, respectively.