Biomass-derived porous carbon with single-atomic cobalt toward high-performance aqueous zinc-sulfur batteries at room temperature

Aqueous zinc-sulfur batteries at room temperature hold great potential for next-generation energy storage technology due to their low cost, safety and high energy density. However, slow reaction kinetics and high activation energy at the sulfur cathode pose great challenges for the practical applications. Herein, biomass-derived carbon with single-atomic cobalt sites (MMPC-Co) is synthesized as the cathode in Zn-S batteries. The catalysis of single-atom Co sites greatly promotes the transform of cathode electrolyte interface (CEI) on the cathode surface, while offering accelerated charge transfer rate for high conversion reversibility and large electrochemical surface area (ECSA) for high electrocatalytic current. Furthermore, the rich pore structure not only physically limits sulfur loss, but also accelerates the transport of zinc ions. In addition, the large pore volume of MMPC-Co is able to relieve the stress effect caused by the volume expansion of ZnS during charge/discharge cycles, thereby maintaining the stability of electrode structure. Consequently, the sulfur cathode maintains a high specific capacity of 729.96 mA h g^‑1 after 500 cycles at 4 A g^‑1, which is much better than most cathode materials reported in the literature. This work provides new insights into the design and development of room-temperature aqueous Zn-S batteries.