High-Rate and Stable K-Storage in Carbon Nanosheet Enabled by N/S Co-Doping Synergistic Effect

With the increasing demand for high-performance energy storage devices, potassium-ion batteries (PIBs) have attracted significant interest due to their large storage capacity, affordability, and high energy density. However, the large radius of potassium ions necessitates strong structural stability in the anode material to sustain long-term cycling. In this work, a self-templated nitrogen/sulfur co-doping carbon anode material was designed and synthesized using thiourea as both the doping source and template. This approach facilitated the incorporation of nitrogen and sulfur heteroatoms while creating a highly ordered structure during the carbonization process. The experimental results demonstrated that the additional S doping not only elevated the N doping level to provide more K-storage sites, which improved the specific capacity, but also increased the carbon stacking order to improve the stability of the PIBs. The N/S co-doping also encouraged the formation of a high-ionic conductivity SEI film for fast interfacial kinetics. The prepared anode demonstrated its great potential as an anode material for PIBs by delivering high capacities of 327 mAh g–1 at 50 mA g–1 and maintaining excellent cycling stability, which achieved 179 mAh g–1 after the long 2000 cycles at a high current density of 1000 mA g–1. This study provided some good ideas and methods for the development of high-performance anode materials for PIBs.