Dual‐Ion Co‐Insertion Engineering for Kinetics Enhancement and Stress Regulation in Cu₃VS₄ Toward Durable Magnesium/Lithium Hybrid Batteries

Abstract Rechargeable magnesium batteries (rMBs) have tremendous development prospects in the field of energy storage, however, the strong electrostatic interactions induced by divalent Mg²⁺ give rise to the sluggish diffusion kinetics. Herein, the dual ion co‐intercalation strategy is proposed to expedite ion migration in Cu₃VS₄, achieving elevated specific capacity, transcendent rate capability, and ultra‐stable cycling capability. Kinetic analyses combined with DFT calculations indicate that the dual‐ion co‐insertion can fast charge transfer, reduce the diffusion barrier of Mg²⁺and optimize the reaction kinetics. Finite element simulations quantitatively verify that dual ion co‐intercalation contributes to alleviating magnesiation/lithiation‐induced stress in the shell layer and maintains structural integrity from a mechanical standpoint. Ex situ characterizations profoundly illustrates the multistep magnesium/lithium storage mechanisms and the evolution of structure. The proposed cation co‐intercalation strategy not only holds promise in opening new insights for high‐performance, continuously stable rMBs, but also provides inspiration for multivalent battery systems.