Double Morphology of Co(9)S(8) Coated by N, S Co-doped Carbon as Efficient Anode Materials for Sodium-Ion Batteries

Co(9)S(8) is a potential anode material for its high sodium storage performance, easy accessibility, and thermostability. However, the volume expansion is a great hindrance to its development. Herein, a composite containing Co(9)S(8) nanofibers and hollow Co(9)S(8) nanospheres with N, S co-doped carbon layer (Co(9)S(8)@NSC) is successfully synthesized through a facile solvothermal process and a high-temperature carbonization. Ascribed to the carbon coating and the large specific surface area, severe volume stress can be effectively alleviated. In particular, with N and S heteroatoms introduced into the carbon layer, which is conducive to the Na(+) adsorption and diffusion on the carbon surface, Co(9)S(8)@NSC can perform more capacitive sodium storage mechanism. As a result, the electrode can exhibit a favorable reversible capacity of 226 mA h g(−1) at 5 A g(−1) and a favorable capacity retention of 83.1% at 1 A g(−1) after 800 cycles. The unique design provides an innovative thought for enhancing the sodium storage performance.