Te doping effect on the structure and ionic conductivity of LiTa2PO8 solid electrolyte

Abstract

LiTa2PO8 (LTPO) is a new solid-state electrolyte material, which has high bulk ionic conductivity and low grain boundary ion conductivity. However, the conductivity of materials synthesized by conventional methods is much lower than the theoretically calculated values. In this work, large radius Te ion are doped at Ta (3)-site in order to enlarge the lattice parameters and increase Li content, which are beneficial for increasing ionic conductivity. The Te substitution changes the Ta surrounding environment, increases the binding capacity of Ta–O, and reduces the attraction of oxygen to lithium ions in the system. The prepared dense Li1.04Ta1.96Te0.04PO8 ceramic electrolyte exhibits a low activation energy of 0.193 eV and four times higher ion conductivity (4.5 × 10−4 S cm−1) than undoped samples. Moreover, Li1.04Ta1.96Te0.04PO8 shows a stable cycling performance in the symmetric Li/Li cells and the Li/CPE/Li1.04Ta1.96Te0.04PO8/LiFePO4 batteries with the separation of a thin PEO membrane.