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.