Preparation and Characterization of LLZO-Based Solid Electrolytes by Al2O3-Assisted Sintering

Abstract

The rapid growth of the lithium-ion battery market has led to higher requirements for the performance and stability of lithium-ion batteries. Traditional liquid organic batteries are prone to short-circuits and cause explosions and fires, posing serious safety hazards. Compared with traditional Li-ion batteries using liquid electrolytes, all-solid-state Li-ion batteries have received extensive attention due to their good stability and safety. Garnet-type solid electrolyte Li₇La₃Zr₂O₁₂ (LLZO) has high ionic conductivity and is considered to be a promising solid electrolyte. However, the synthesis of LLZO often requires high temperature, but the high temperature could lead to a large amount of lithium evaporation, thus reducing the ionic conductivity of the LLZO-based samples. Therefore, how to reduce the synthesis temperature of LLZO and improve its ionic conductivity is an important topic. Here, we synthesized solid electrolytic Li_6.1Ga_0.3La₃Zr₂O₁₂ with garnet-type structure by traditional solid-phase method and introducing Al₂O₃ as a sintering aid. Compared with the samples without sintering aid, the introduction of Al₂O₃ not only reduces the sintering temperature, but also significantly increases the ionic conductivity. It is found that adding a small amount of Al₂O₃ as an additive can reduce the sintering temperature from 1100°C to around 1050˚C. Finally, we found, when the Al₂O₃ content is 2 wt%, the room-temperature ionic conductivity is the highest at 1.28 mS/cm.