Nickel‑cobalt selenide@N-doped carbon towards high-performance anode materials for sodium-ion batteries

Sodium-ion battery is an intriguing candidate in the post‑lithium era due to the earth-abundance of sodium. Transition metal selenides, with high conductivity and theoretical capacity, have been widely used in sodium-ion batteries. However, their structures are easily crushed when assembled as the anode, resulting in rapid capacity decay and poor rate performance, limiting its commercialization. In the present work, nickel‑cobalt selenide coated by nitrogen-doped carbon is prepared to activate multi-electron redox reactions. The composite exhibits excellent rate capacity (457 mAh g−1 at 0.1 A g−1 and 296 mAh g−1 when the current density is increased to 5 A g−1) and cycling stability (300 mAh g−1 after 1800 cycles at 2 A g−1). When assembled into a sodium ion battery, a high and stable specific capacity is also realized. This work illustrates the effectiveness of in-situ carbon coating as well as the potential advantages of selenide‑carbon composite as an anode material for sodium-ion batteries.