Cu₃VSe₄ Cathode for Rechargeable Magnesium Batteries: Favorable Chemical and Electronic Structures Inducing Intercalation and Displacement Reactions.

Rechargeable Mg batteries are an advantageous energy‐storage technology with low cost and high safety, but the design of high‐performance cathode materials is currently the major difficulty. Herein, a new cathode material of Cu3VSe4 is fabricated with a comprehensive consideration of the chemical and electronic structures. The intermediate band semiconductor Cu3VSe4 has a cubic crystal structure containing interlaced 3D tunnels. The V and Se atoms form chemical bonds with high covalent proportions and facilitate the charge delocalization via the V‒Se bonds. Because of these features, Cu3VSe4 provides a high capacity of 251 mAh g‒1 with co‐redox of Cu, V, and Se elements and an outstanding rate performance of 44 mAh g‒1 at 15 A g‒1. Prominently, a high mass load of 3.0 mg cm‒2 is achieved without obvious rate capability decay, which is quite favorable to pair with the high‐capacity Mg metal anode in practical application. The mechanism investigation and theoretical computation demonstrate that Cu3VSe4 undergoes first a Mg‐intercalation and then a displacement reaction, during which the crystal structure is maintained, assisting the reaction reversibility and cycling stability. These findings reveal a rational design principle of rechargeable Mg battery cathodes based on a comprehensive consideration of chemical and electronic structures. [ABSTRACT FROM AUTHOR]