CoS@sulfur doped onion-like carbon nanocapsules with excellent cycling stability and rate capability for sodium-ion batteries

The mineral reserves of lithium severely restrict the future development and application of lithium ion batteries. Because of rich sodium reserves and the similar chemical properties between sodium and lithium, sodium-ion batteries are the promising substitute for lithium ion batteries. Sulfur doped onion-like carbon coated CoS (CoS@S-doped OLC) nanocapsules have been synthesized by the arc-discharge approach under the atmosphere of Ar, H2S and C2H5OH. The electrochemical measurements imply that the CoS@S-doped OLC nanocapsules have the potential for a superior anode materials for the rechargeable sodium ion batteries. The discharge capacity of 582 mA h g(-1) can be reached over 500 cycles with the current density of 0.1 A g(-1) and the averaged discharge capacities of 326 and 258 mA h g(-1) are remained at 8.0 and 10.0 A g(-1) for each ten cycles, respectively. The CoS@S-doped OLC nanocapsules after 500 cycles still exhibit the complete spherical shape and the doping of S in OLC shell is conductive for conductivity, ensuring the high Na+ storage performance and excellent long-term cyclability and good rate capability of CoS@S-doped OLC nanocapsules.