First-principles study on ultrafast Li-ion diffusion in halospinel Li2Sc2/3Cl4 through multichannels designed by aliovalent doping

Abstract

Solid electrolytes have attracted considerable interest as next-generation materials for lithium-ion batteries because their chemical stability is incomparably higher than that of conventional liquid-phase electrolytes. However, the issue of slow Li⁺ diffusion, even in advanced halide-type electrolytes, still needs to be resolved. Here, we report the design of ultrafast diffusion channels for Li ions through optimal aliovalent doping (Fe²⁺) of the halide electrolyte with a chloride framework. Both first-principles density functional theory calculations and ab initio molecular dynamics simulations consistently demonstrate that the proposed material has high chemical stability and high Li-ion conductivity. We noted that the Fe dopant creates multichannels for Li ion diffusion, which is ascribed to the favorable regulation of electrostatic interaction with the concertedly moving Li ions. Our calculations indicate that the ionic conductivity of the proposed material is up to 2.72 mS cm⁻¹, which is a very competitive value considering that conventional organic ionic conductors show values around 1.0 mS cm⁻¹. We clearly unveil the underlying mechanism of outstanding performance, which is cost-effective and may be used for fabricating even better solid electrolytes.