La-Al Intermetallic Alloy Anode for Realizing High-Energy Fluoride-Ion Battery

Abstract

An all-solid-state fluoride-ion battery is one of the promising candidates for the next-generation high-energy batteries owing to the high theoretical energy density. However, the practical capacities of anodes are significantly low compared with cathodes, and therefore it is an urgent task to develop new anode materials for fluoride-ion batteries. Here, we show that the LaAl3 alloy anode delivers a reversible high capacity of 298 mAh g−1 with only 0.66% capacity fading per cycle. By using atomic-resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy, we investigate the structural and chemical evolution of LaAl3. We find that LaAl3 is firstly decomposed into LaF3 and AlF3 nanocrystals, forming the nanoscale network of the F– ion conduction path owing to the high ionic conductivity of LaF3. In the subsequent cycles, the redox reaction of Al/AlF3 nanocrystals solely proceeds, contributing to the reversible high capacity. Our findings should open new avenues for realizing high-energy fluoride-ion batteries.