Engineering Heterointerface to Synergistically Regulate\nKinetics and Stress of Copper–Cobalt Selenide toward Reversible\nMagnesium/Lithium Hybrid Batteries

Metal\nchalcogenide-based cathodes are crucial for the development\nof rechargeable magnesium batteries, yet the strong electrostatic\ninteractions of Mg<sup>2</sup><sup>+</sup> result in slow ion transport\nand high polarization. The Mg<sup>2</sup><sup>+</sup>/Li<sup>+</sup> hybrid battery holds promise for enhancing the energy storage capability.\nHerein, we establish a system that utilizes (Co,Cu)­Se<sub>2</sub>/CoSe<sub><i>x</i></sub> heterostructure grown on carbon cloth as\nthe cathode and APC-LiCl as a dual-salt electrolyte to achieve high\nreversible capacity, enhanced cyclic stability, and impressive rate\nperformance. First-principles calculations and kinetic analyses are\nemployed to uncover that constructing the heterointerface stimulates\nthe formation of an intrinsic electric field and high-density electron\nflows, thereby accelerating charge transfer and ion diffusion processes.\nFinite element simulations further demonstrate that the heterostructure\neffectively alleviates stresses associated with magnesiation/lithiation\nto enhance the structural integrity of the material. Moreover, the\nmultistep reaction unveils a stepwise structural transformation pathway.\nThis study initiates a new chapter in designing heterointerface strategies\nfor advanced energy storage devices.