O2− substituted Li-richened Li2ZrCl6 lattice towards superionic conductivity

Abstract

Emerging halide superionic conductors with remarkable oxidative stability and deformability, making them a potential game-changer for high-performance all-solid-state Li batteries (ASSLBs). The recently reported Li2ZrCl6 (LZC) with low cost possess great potential. However, its ionic conductivity at 25 °C is below 1 mS cm−1. Herein, we developed a Li-richened strategy to LZC by doping O2− at Cl− site via a mechanochemical method to form oxychloride electrolytes Li2+xZrCl6−xOx (0 ≤ x ≤ 1.8), resulting in high ionic conductivity up to 1.46 mS cm−1 at room temperature (RT). The experimental results and theoretical calculations (ab initio molecular dynamics simulations) demonstrate that the Li2O doping leading to a Li-richened LZC lattice effectively enhances the Li+ conductivity in solid-state electrolytes (SSEs). Significantly, an increasing O2− substitution in the Li2+xZrCl6−xOx microcrystalline framework induces a progressive structural evolution from triangular to monoclinic phases, accompanied by a redistribution of Li+. Furthermore, the ASSLBs formed by Li3.4ZrCl4.6O1.4 (LZCO) with Li-In anode and bare LiCoO2 cathode shows excellent long-term cycling stability (94 % capacity retention for 600 cycles at 1 C) and high-rate performance (105.7 mAh g−1 at 2 C). This exploratory study provides a promising strategy to facilitate the application of low-cost LZC-based SSEs for high-performance ASSLBs.