Facile and scalable synthesis of a sulfur, selenium and nitrogen co-doped hard carbon anode for high performance Na- and K-ion batteries

Hard carbon is the most attractive anode material for sodium/potassium-ion storage, because of its extensive resources, low cost, and environmental benignity. However, it is a great challenge to design carbon-based anodes with a high capacity and long lifespan. Herein, sulfur, selenium and nitrogen co-doped hard carbon was preparedviaa facile and scalable solid reaction and used as the anode material for sodium/potassium-ion batteries. It shows a superior sodium storage performance, with outstanding rate performance (125.9 mA h g(-1)at a high rate of 10 A g(-1)) and good cycling stability (210.4 mA h g(-1)at 1 A g(-1)after 1000 cycles), which surpass those of most reported hard carbons. When used for KIBs, it displays a high capacity of 207 mA h g(-1)at 0.1 A g(-1)after 450 cycles. An excellent rate capability (158.1 mA h g(-1)at 3 A g(-1)) and remarkable capacity retention of 143.5 mA h g(-1)after 1100 cycles at 1 A g(-1)can also be achieved. Furthermore, the kinetic analyses of Na(+)and K(+)storage reveal that the capacitive charge storage accounts for the excellent rate performance. The facile synthetic route and excellent ion storage properties make the as-prepared material a promising anode material for alkali metal ion batteries.