Sulfur-doped hollow porous carbon spheres as high-performance anode materials for potassium ion batteries

Hard carbons, due to their advantages of abundant sources, stable chemical properties, and easily adjustable structure, have been widely applied as anode materials for potassium ion batteries (PIBs). However, hard carbon still suffers from low storage capacity and structural instability. Sulfur doping has been demonstrated an effective strategy to solve these issues. Here, a series of sulfur-doped hollow porous carbon spheres (SHPCS) with different S-doping amounts are facilely prepared via a direct sulfurization process by elemental sulfur. It is found that S-doping effectively modulates the nano-micro structure of SHPCS, and thereby promote the full utilization of active sites. Notably, the optimized SHPCS achieves a prominent reversible and cycling stability (454 mAh g−1 at 50 mA g−1; 211.4 mAh g−1 at 1000 mA g−1 for 1000 cycles, a capacity retention of 93.7 %). Our work provides an efficient strategy for the design of hard carbon anodes for high-performance PIBs.