Sodium storage mechanism of N, S co-doped nanoporous carbon: Experimental design and theoretical evaluation

Designing carbonaceous materials with novel structure as anodes is currently an important strategy to improve the electrochemical performance for sodium-ion batteries. Herein, we report a facile and effective method to fabricate 3D porous structured carbon with N and S co-doping. As anode material, the co-doped porous carbon exhibits a high reversible capacity of 260 mA h g(-1) after 1000 charge/discharge cycles at a current density of 0.5 A g(-1). Even at a very high rate of 10 A g(-1), the capacity can still reach 172 mA h g(-1), indicative of an excellent rate capability. These results demonstrate the synergistic effect is beneficial for the sodium storage performance in N, S co-doped 3D nanoporous carbon. Furthermore, the first principles calculations further confirm the synergistic effect from N, S co-doping, which not only promotes electronegativity of carbon and enhances the absorption of Na+ ions, but also decreases the diffusion barrier for better mobility of sodium. The co-doping carbon with 3D hierarchical porous structure can greatly provide enough paths for the permeation of electrolyte, and modify the interlayer of carbon, leading to an enhanced sodium storage performance.