A N,S-codoped hierarchical carbon Foam@Porous carbon composite as freestanding cathode for high-performance lithium-sulfur batteries

Lithium sulfur (Li-S) battery is considered as one of promising energy-storage devices owing to its high energy density and low cost. However, it is still a great challenge to explore stable sulfur cathode with high sulfur loading and good cycling performance. Herein, we report a facile method to prepare N,S co-doped hierarchical pore structured carbon foam @porous carbon (CF@N-SPC) through a carbonation process from resin aerogel coated melamine foam with thiourea as the source for N and S codoping. The close combination of a carbon interconnected skeleton and the resin aerogel derived carbon forms the hierarchical pore structure that improves the electron and ion transport. The prepared CF@N-SPC can be used as a freestanding cathode without a conductive additive and a binder. Due to the synergistic effect of the hierarchical pore structure and N, S codoping, the sulfur loading in the carbon foam-based cathode can reach up to 10.6 mg cm⁻². Owing to these unique merits, the CF@N-SPC/S cathode exhibits high capacity and good cycling performance: it yields a discharge capacity of 1212 mA h g⁻¹ at 0.1 C with 4.0 mg cm⁻² sulfur loading; it also exhibits a good discharge capacity of 668 mA h g⁻¹ at 0.5 C when the sulfur loading increases to 10.6 mg cm⁻², capacity retained by 72% in 200 cycles; it experiences a very small capacity decay rate of 0.05% per cycle in 700 cycles at 1 C. Our rational design and facile synthesis of the carbon foam-based freestanding cathode is promising and applicable for development of high performance Li-S batteries.