Intercalation-Induced Localized Conversion Reaction in h-CuSe for Ultrafast-Rechargeable and Long-Cycling Sodium Metal Battery

Cathode materials of sodium-based batteries with high specific capacity and fast charge-discharge mode, as well as ultralong reversible cycles at wide applied temperatures, are essential for future development of advanced energy storage system. Developing transition metal selenides with intercalation features provides a new strategy for realizing the above cathode materials. Herein, this work reports a storage mechanism of sodium ion in hexagonal CuSe (h-CuSe) based on the density functional theory (DFT) guidance. This work reveals that the two-dimensional ion intercalation triggers localized redox reaction in the h-CuSe bulk phase, termed intercalation-induced localized conversion (ILC) mechanism, to stabilize the sodium storage structure by forming localized Cu₇Se₄ transition phase and adjusting the near-edge coordination state of the Cu sites to achieve high reversible capacity and ultra-long cycling life, while allowing rapid charge-discharge cycling over a wide temperature range.