Se—C Bonding Promoting Fast and Durable Na⁺ Storage in Yolk–Shell SnSe₂@Se—C

Tin-based compounds have received much attention as anode materials for lithium/sodium ion batteries owing to their high theoretical capacity. However, the huge volume change usually leads to the pulverization of electrode, giving rise to a poor cycle performance, which have severely hampered their practical application. Herein, highly durable yolk–shell SnSe₂ nanospheres (SnSe₂@Se—C) are prepared by a multistep templating method, with an in situ gas-phase selenization of the SnO₂@C hollow nanospheres. During this process, Se can be doped into the carbon shell with a tunable amount and form Se—C bonds. Density functional theory calculation results reveal that the Se—C bonding can enhance the charge transfer properties as well as the binding interaction between the SnSe₂ core and the carbon shell, favoring an improved rate performance and a superior cyclability. As expected, the sample delivers reversible capacities of 441 and 406 mAh g⁻¹ after 2000 cycles at 2 and 5 A g⁻¹, respectively, as the anode material for a sodium-ion battery. Such performances are significantly better than the control sample without the Se—C bonding and also other metal selenide-based anodes, evidently showing the advantage of Se doping in the carbon shell.