Increase in ionic conductivity of NASICON-type solid electrolyte Li1.5Al0.5Ti1.5(PO4)3 by Nb2O5 doping

A NASICON-type Li1.5Al0.5Ti1.5(PO4)3 (LATP) solid electrolyte was fabricated using a novel sol–gel approach with citric acid as a complex agent. An electrochemical impedance spectroscopy analysis shows that the ionic conductivity of the LATP solid electrolyte synthesized using the sol–gel route was low (8 × 10−5 S cm−1 at 303 K), owing to its large grain boundary impedance. To improve the ionic conductivity of the LATP conducting ceramic, we incorporated Nb2O5 as a doping agent into the LATP solid electrolyte. The effects of Nb2O5 on the phase composition, microstructure, and ionic conductivity of the LATP solid electrolyte were investigated. The LATP conducting ceramic with an 8-wt% Nb2O5 doping exhibited the highest total ionic conductivity of 3.54 × 10−4 S cm−1 at 303 K, relative density of 91.7%, and lowest activation energy of 0.271 eV. The fabricated LATP solid electrolyte doped with Nb2O5 is a promising material for electrochemical devices.