NiCo2Se4 hierarchical microflowers of nanosheets and nanorods as pseudocapacitive Mg-storage materials

Rechargeable Mg batteries are principally based on a metallic Mg anode and a Mg-storage cathode. The high safety and low cost make them suitable for next-generation large-scale energy storage applications, while the suitable cathode materials are relatively rare. Herein, two NiCo2Se4 materials with different morphologies, microflowers consisting of nanosheets and nanorods, are prepared and employed as Mg-storage materials. The NiCo2Se4 nanosheets exhibit a Mg-storage capacity of 145 mAh g‒1, for which the charge/discharge reaction mainly occurs between NiCo2Se4 and metallic Ni0 and Co0. The thin nanosheets or nanorods structures enable rapid solid-phase Mg2+ diffusion and surface-related pseudocapacitive behaviors, of which the NiCo2Se4 nanosheets deliver a superior rate performance delivering 40 mAh g‒1 at 2000 mA g‒1. Moreover, such microflower morphology maintains the material integrity during cycling, and the NiCo2Se4 nanosheets exhibit a remarkable cycleability for 1000 cycles. This work develops a n...