Effect of Sr and Ta co-substitution on microstructure and ionic conductivity of cubic-Li0.5La0.5TiO3 electrolyte for applications in Li batteries

Abstract

All-solid-state lithium batteries (ASSBs) have gained significant attention in recent years because of their potential to offer higher energy density and enhanced safety compared to conventional liquid-electrolyte-based lithium-ion batteries (LIBs). Lithium lanthanum titanate (LLTO) is a promising solid electrolyte for next-generation lithium batteries owing to its high ionic conductivity of approximately 10−3 S·cm−1 at room temperature (RT). The Sr and Ta co-doped Li0.5-□La0.5−xSrxTi1−xTaxO3 perovskites were synthesized by solid-state reaction. In this study, Sr2+ and Ta5+ with larger ionic radii, were used for co-substitution in the La3+ and Ti4+ sites, respectively, to increase the bottleneck size of the A-site and expand the average bond length of the B-site on the perovskite structure (ABO3), thereby increasing the Li+ ion mobility. The LLSrxTTaxO3 (0 ≤ x ≤ 0.12) pellets have high relative densities, and high grain conductivities, where the total conductivity of LLSr0.09TTa0.09O3 reached 4.12 × 10−5 S·cm−1. Compared with the pure specimen, the total conductivities of the doped specimens are approximately more than 2.7 times at RT. The assembled semi-solid LFP/10 wt% LLSr0.09TTa0.09O3/Li full battery has a 0.1 C specific discharge capacity of 156 mAh⋅g−1 and a 1 C capacity retention rate of 86% after 290 cycles at RT.