A new strategy for achieving high K+ storage capacity with fast kinetics: realizing covalent sulfur-rich carbon by phosphorous doping

Designing carbon anodes with rich heteroatoms and dilated graphitic interlayer spacing via a one-step synthesis process plays a vital role in accelerating the practical application of potassium ion batteries, but it is still a big challenge. Herein, P-doped S-rich mesoporous carbon (PSMC) is prepared by direct phosphate-assisted carbonization of carrageenan, and it exhibits excellent potassium storage capacity (449 mA h g−1 at 0.1 A g−1), superior rate performance (233 mA h g−1 at 2 A g−1) and long-term stability (97.3% capacity retention after 1000 cycles), due to the high sulfur doping (16.48 wt%) and the coexistence of ordered and disordered regions in the structure. Ex situ characterization, GITT and theoretical calculations reveal that the promotion of covalent sulfur can effectively increase the adsorption of K+ and enhance the K+ reaction kinetics. The proposed one-step synthesis strategy demonstrates the precise use of the composition in biomass, enabling large-scale production of high-performance anodes for K+ storage.