Unlocking High Capacity and Fast Na Diffusion of H CrS by Proton-Exchange Pretreatment.

This study presents a new material, "H CrS " (denotes approximate composition) formed by proton-exchange of NaCrS which has a measured capacity of 728 mAh g with significant improvements to capacity retention, sustaining over 700 mAh g during cycling experiments. This is the highest reported capacity for a transition metal sulfide electrode and outperforms the most promising proposed sodium anodes to date. H CrS exhibits a biphasic structure featuring alternating crystalline and amorphous lamella on the scale of a few nanometers.