Authors: Hou‐an Zhang, Panfei Xiao, Changchun Hu, Donggang Tao, Daohong Zhang, Yuliang Cao, Ting Li, Fei Xu
Published: 2025-03-12
Source: Full article
AbstractRechargeable Mg batteries are an energy‐storage technology suitable for large‐scale applications, but the lack of high‐performance cathode materials is currently hindering their development. Conversion‐type cathodes break the limits of Mg‐intercalation principle, but existing structural design strategies mostly focus on morphology optimization to increase active reaction interfaces. The present study reveals that crystal structure also plays a significant role in the Mg‐storage activity of conversion reactions. Two types of CoSe2 with orthorhombic and cubic phases are synthesized from ZIF‐67 and comparatively investigated as cathode materials for RMBs. Despite exhibiting similar micromorphology and a lower specific surface area, the orthorhombic phase CoSe2 demonstrates superior Mg‐storage capacity, rate performance, lower charge transfer resistance, and higher solid‐state Mg2+ diffusion coefficients compared to the cubic phase CoSe2. Mechanism studies reveal that the conversion reaction of orthorhombic CoSe2 is more thorough and reversible, involving the redox of both cations and anions. Further theoretical computations indicate that the higher reaction activity at (010) plane of orthorhombic CoSe2, along with more active sites of Se‒Se bonds, facilitates the conversion Mg‐storage reaction via co‐redox of the cations and anions. This study underscores the importance of crystal structure in the design of conversion‐type RMB cathode materials.