Preparation and performances of gallium-doped LLZO electrolyte with high ionic conductivity by rapid ultra-high-temperature sintering

Garnet-type Li7La3Zr2O12 (LLZO) is a promising solid-state electrolyte (SSE) for next generation lithium batteries due to its high Li+ conductivity and stability against lithium metal, especially the Li7−3xGaxLa3Zr2O12 (Ga-LLZO) is most valuable because of its high ionic conductivity (> 1 ×10−3 S cm−1). However, it is difficult to prepare high-quality Ga-LLZO by the traditional air ambient sintering. Herein, we develop a simple and efficient rapid ultra-high-temperature sintering (RUHTS) method to prepare high-conductivity Ga-LLZO ceramic SSE. It has been found that the as-prepared Ga-LLZO ceramic SSE with the composition of Li6.25Ga0.25La3Zr2O12 exhibits high relative density of 99%, good ionic conductivity of 1.48 × 10−3 S cm−1 and large critical current density of 0.5 mA cm−2 after sintering at 1200 °C for 2 min. In addition, the Ga-LLZO SSE shows good electrochemical stability and interfacial compatibility against Li metal. The assembled Li-Li symmetric cell represents a small interfacial impedance of 37 Ω cm2. In the same time, the Li/Ga-LLZO/LE+LMNCO full battery has a total impedance of 205 Ω cm2, and can deliver a first discharge capacity of 235.1 mAh g−1 at 0.5 C, and the capacity retention rate is 88.3% after 100 cycles. This indicates that the as-prepared Ga-LLZO has good application prospect in the Li-metal solid-state batteries (LMSSBs). Moreover, this method does not require the use of mother powder during preparation process, which will effectively reduce the waste of raw materials, save manufacture costs and be beneficial to quantity production of Ga-LLZO ceramic electrolyte.