The effect of a Ta, Sr co-doping strategy on physical and electrochemical properties of Li7La3Zr2O12 electrolytes

In this study, Ta single-doped Li6.4La3Zr1.4Ta0.6O12 (Ta0.6) and a series of Ta, Sr co-doped Li6.4+xLa3-xSrxZr1.4Ta0.6O12 (Ta0.6Srx, x = 0.1, 0.2, 0.3, and 0.4) electrolytes are synthesized via a two-step process. The XRD result reveals that all samples have a pure cubic phase, which indicates that Ta5+ and Sr2+ can enter the lattice of LLZO and stabilize the cubic phase. The SEM images exhibit that all samples have a dense microstructure and tight grain boundary without obvious holes. The excellent properties are achieved when the doping amount of Sr reaches 0.2 mol. Among all designed samples, the Ta0.6Sr0.2 has the highest Li+ conductivity and relative density of 8.54 × 10−4 S cm−1 and 98.79%, respectively, as well as the lowest activation energy roughly 0.302 eV. Additionally, the symmetrical cell's galvanostatic cycling data show that it has excellent cycling performance and extremely low overpotentials even after 350 cycles, indicating that it can be successfully applied to next-generation all-solid-state lithium-ion batteries (ASSLIBs).