Engineered hollow cubic structures CoS/NiS heterojunctions enable high-performance magnesium-ion batteries

Rechargeable magnesium-ion batteries (RMBs) demonstrate notable benefits, including higher theoretical energy density, cost-effectiveness, and improved safety characteristics, positioning them as a viable substitute for conventional energy storage solutions. Nevertheless, the ongoing development of high-performance RMBs continues to face inevitable challenges, such as unsatisfactory practical capacity, inadequate cycle durability, swift energy degradation, and a comparatively limited-service life. Herein, CoS/NiS nanomaterials with cubic-shaped morphology were prepared by a two-step metal sulfide template-free solvothermal synthesis method. The material with internal cavity structure effectively mitigates the large expansion of magnesium-ion battery cathode material due to Mg²⁺ embedding during the charging and discharging process, and provides a robustness electrode-electrolyte interface, thus greatly improving the cycle life. Besides, the introduction of Ni elements into CoS materials may form heterojunctions thereby lowering the potential barrier of the conversion reaction and improving the reaction kinetics and redox reversibility. In addition, the abundance of highly electronegative SS bonds in the CoS/NiS material, which also provides many electrochemically active sites and smooth transport paths for the embedding of Mg²⁺, leads to the reduction of its polarization and the improvement of its reaction kinetics, which makes the CoS/NiS as a RMBs cathode material with a high specific capacity and a long cycling life. Thus, this research presents a feasible and effective strategy for enhancing the Mg²⁺ storage capability of engineered CoS nanomaterials, with potential applicability and adaptability to other electrode materials.