Key factors of the self-consolidation mechanism for sintering Li7La3Zr2O12 solid electrolytes

Li7La3Zr2O12 (LLZO) is a potential solid electrolyte for all-solid-state batteries owing to its high ionic conductivity and excellent stability. The self-consolidation strategy is an extremely simplified method for LLZO preparation compared to the conventional preparation methods using hot- or cold-pressing operations. Despite the absence of high-pressure assistance, the self-consolidated LLZO exhibits high density and enhanced microstructure. The self-densification mechanism of LLZO solid electrolytes is interesting and deserves further investigation. Herein, the effects of the sintering time and the inadvertently introduced Al on the self-consolidation process are systematically studied. Extending sintering time expels the sintering voids at the grain boundaries, thereby promoting grain growth. The Li atoms in the LLZO crystal structure are rearranged and adjusted to reach an optimal state. The LLZO achieves a highly dense morphology with a Li+ ion conductivity of 3.87 × 10−4 S cm−1 when the sintering time is 20 h. Notably, an Al2O3 crucible, instead of a MgO crucible, under the same sintering conditions, contributes to the LLZO self-consolidation by generating an Al-containing solid solution. This work sheds light on the key role of the solid solutions in LLZO self-consolidation, thereby inspiring an alternative optimization method for the preparation of solid electrolytes.