Sulfur-Doped Carbon for Potassium-Ion Battery Anode: Insight into the Doping and Potassium Storage Mechanism of Sulfur

The sulfur doping strategy has been attracting extensive interest in potassium-ion battery carbon anodes for the dual potential of improving the capacity and kinetics of carbon anodes. Understanding the doping and potassium storage mechanism of sulfur is crucial to guide the structural design and optimization of high-performance sulfur-doped carbon anodes. Herein, presenting a laboratory-synthesized sulfur-doped hard carbon (SHC) with a sulfur content of 6.4 at. % as an example, we clarify the sulfur doping mechanism and reveal the role of sulfur in potassium storage. The high sulfur content of SHC stems from the selective substitution of sulfur for carbon and the residual trace of sulfur molecular fragments after sulfurization. As a result, thanks to the multifaceted roles of doped sulfur in potassium storage, about twice as much capacity, rate capability, and cycling stability is achieved for SHC against S-free hard carbon at the same test conditions. Furthermore, potassium-ion hybrid capacitors assembled based on an SHC anode demonstrate high energy/power density (139 Wh kg-1/7.3 kW kg-1), along with an extraordinary cycling stability.KEYWORDS: potassium-ion batteries, anode, sulfur-doped carbon, doping mechanism, potassium storage mechanism

Automated summary

The sulfur doping strategy has been proven effective in improving the capacity and kinetics of carbon anodes in potassium-ion batteries. This study presents a sulfur-doped hard carbon with a high sulfur content and investigates the sulfur doping mechanism and its role in potassium storage. The results show that sulfur doping greatly enhances the performance of the carbon anode, achieving higher capacity, rate capability, and cycling stability compared to sulfur-free hard carbon.