The solid-state Li-ion conductor Li$_7$TaO$_6$: A combined computational and experimental study

TL;DR

This study combines computational and experimental methods to evaluate Li$_7$TaO$_6$ as a promising solid-state electrolyte with high ionic conductivity and stability for next-generation Li-ion batteries.

Contribution

It provides the first combined computational and experimental analysis of Li$_7$TaO$_6$, demonstrating its low activation barrier, high ionic conductivity, and electrochemical stability.

Findings

Low activation barrier of ~0.29 eV for ion diffusion

High ionic conductivity of 5.7×10⁻⁴ S/cm at 300 K

Evidence of a wide electrochemical stability window

Abstract

We study the oxo-hexametallate Li$_7$TaO$_6$ with first-principles and classical molecular dynamics simulations, obtaining a low activation barrier for diffusion of $\sim$0.29 eV and a high ionic conductivity of $5.7 \times 10^{-4}$ S cm$^{-1}$ at room temperature (300 K). We find evidence for a wide electrochemical stability window from both calculations and experiments, suggesting its viable use as a solid-state electrolyte in next-generation solid-state Li-ion batteries. To assess its applicability in an electrochemical energy storage system, we performed electrochemical impedance spectroscopy measurements on multicrystalline pellets, finding substantial ionic conductivity, if below the values predicted from simulation. We further elucidate the relationship between synthesis conditions and the observed ionic conductivity using X-ray diffraction, inductively coupled plasma optical emission spectrometry, and X-ray photoelectron spectroscopy, and study the effects of Zr and Mo doping.