Decalcified fish scale-based sponge-like nitrogen-doped porous carbon for lithium-sulfur batteries

A decalcified sponge-like nitrogen-doped porous carbon (DFSC) derived from fish scales has been synthesized via decalcification, pre-carbonization, and KOH activation processes. The synthesized carbon possesses high surface area of 2520.9 m 2 g −1 , large pore volume of 1.40 cm 3 g −1 , moderate nitrogen content, and hierarchical porous structure, which was used to prepare DFSC/S composite as cathode material in lithium-sulfur (Li-S) batteries. The DFSC/S composite delivered a better discharge specific capacity of 473.9 mAh g −1 after 500 cycles at 0.1 C, and the decay rate per cycle was 0.83%. Even at a higher rate of 0.5 C, the capacity retention of DFSC/S composite was 446.3 mAh g −1 after 400 cycles. The superior performance of the DFSC/S composite was attributed to the highly porous structure, which not only can provide sufficient accommodation space, but also can improve the infiltration of electrolyte, facilitating rapid Li + ion transfer in Li-S batteries. The moderate nitrogen doping in carbon matrix can strengthen the chemical adsorption of polysulfides. Therefore, DFSC/S composite is a promising cathode material to improve the electrochemical performance of Li-S batteries.