Effect of Cu/Ta-codoping on the microstructure and conductivity of Li7La3Zr2O12 by flash sintering

Cubic-phase Li 7 La 3 Zr 2 O 12 (LLZO) garnet is considered as a promising solid electrolyte due to high Li-ion conductivity and good chemical stability against electrode material. However, the desired cubic-phase formation of LLZO relies on the doping elements. To further improve the electrochemical performance and control the retention of lithium, a composite solid electrolyte based on Cu and Ta co-doped LLZO was fabricated by flash sintering (FS) in the present work due to the FS process characterized short sintering times and low furnace temperature, which could effectively restrain “Li-loss”. Based on the optimized Ta-LLZO conducted in our previous study, the effects of Cu 2+ content on the ionic conductivity and sintering behavior of the doped composites were discussed. The results show that Cu 2+ doping effectively stabilized the cubic structure of the co-doped composites and simultaneously promotes sinter-ability in FS process. Moreover, it is demonstrated that the room-temperature total conductivity of the Cu and Ta co-doped LLZO solid electrolyte is improved significantly by decreasing the grain boundary resistances and improving the densifications with the increasing of Cu 2+ content. In addition, the maximum ionic conductivity of 2.83 × 10 –3 S cm −1 and relative density 96.6% of the composite with Cu 2+ doping content 0.35 mol could be reached.