Unlocking High Capacity and Fast Na <sup>+</sup> Diffusion of H <sub> <i>x</i> </sub> CrS <sub>2</sub> by Proton‐Exchange Pretreatment
Joseph W. Stiles, Anna L. Soltys, Xiaoyu Song, Saul H. Lapidus, Craig B. Arnold, Leslie M. Schoop
Abstract
Abstract This study presents a new material, “H x CrS 2 ” (denotes approximate composition) formed by proton‐exchange of NaCrS 2 which has a measured capacity of 728 mAh g −1 with significant improvements to capacity retention, sustaining over 700 mAh g −1 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 x CrS 2 exhibits a biphasic structure featuring alternating crystalline and amorphous lamella on the scale of a few nanometers. This unique structural motif enables reversible access to Cr redox in the material resulting in higher capacities than seen in the parent structure which features only S redox. Pretreatment by proton‐exchange offers a route to materials such as H x CrS 2 which provide fast diffusion and high capacities for sodium‐ion batteries.