Nanoporous CoSe₂ polyhedra imbedded graphene as a high-performance sodium-ion battery anode material

Sodium-ion batteries (SIBs) have emerged as promising candidates with the virtues of abundant sodium resources and low cost of sodium salts. CoSe₂ as an anode material has attracted much attention because of its high theoretical capacity. However, the low conductivity of CoSe₂ still severely hinders its application. Herein, we fabricated a graphene-crosslinked CoSe₂ polyhedron composite material (CoPG) by utilizing graphene as the conductive framework and MOF-derived CoSe₂ as the active component for energy storage. The carbon layer derived from the MOF can effectively inhibit polyselenide dissolution and, in combination with graphene, construct a double-carbon-layer conductive network that facilitates electron transport. As a result, the as-prepared CoPG3 can deliver a high reversible capacity of 565 mAh g^-1 at 0.05C. After 100 cycles, its capacity remained at 87% at 0.5C. This work provides a new insight into the relationship between the conductivity and performance of electrode materials for SIBs.