Electrochemical Mg2+ Displacement Driven Reversible Copper Extrusion/Intrusion Reactions for High‐Rate Rechargeable Magnesium Batteries. (18th December 2020) - Xue, Xiaolan
Abstract: Rechargeable magnesium batteries (RMBs) based on metal Mg anodes have shown great potential owing to the abundant natural resources, high volumetric capacity, and low safety hazard. Nevertheless, the development of RMBs is hampered by the sluggish kinetics of Mg 2+ diffusion and the limited cyclability of cathode materials. Herein, nonstoichiometric copper selenide (Cu2– x Se) are synthesized via a solution‐based method and exploited as a durable cathode material based on ionic displacement mechanism for RMBs. The copper ions in the Se 2− based sub‐lattices are reversibly exchanged by Mg 2+ ions without causing lattice collapse. Owing to the same face‐centered cubic Se 2− sub‐lattices and similar unit cell size of Cu2– x Se and MgSe, the energy barrier for lattice reconstruction during cycling processes is very low, significantly improving the rate performance, structural stability, and cycle life of the Cu2– x Se cathode. Moreover, metal Cu is in situ generated during discharging, thus greatly facilitating electron transport. Comprehensive characterizations confirm that the Cu2– x Se cathode undergoes reversible copper ion extrusion/reinjection during the discharge−charge steps. This work suggests the great potential for exploring high‐performance electrode materials based on ionic displacement mechanism for advanced multivalent‐ion secondary batteries. Abstract : Nonstoichiometric copper selenide (Cu2– x Se) nanoplates are prepared via a convenient solution‐based method. The reversible displacement reaction between magnesium ions and copper ions in Se 2− sub‐lattices can effectively avert the lattice collapse of Cu2– x Se and reduce the energy barrier for lattice reconstruction, significantly improving the electrochemical performance of Cu2– x Se cathode in rechargeable magnesium batteries.