Insight into Highly Graphitic Hollow Spheres for Superior Potassium Ion Batteries

Graphite is an attractive anode material for low‐cost potassium‐ion batteries (PIBs), which are highly promising in addressing the urgent demand for large‐scale energy storage systems. However, the large volume variation of graphite during the potassiation/depotassiation may lead to poor long‐term stability, which is unfavorable for commercialization. Herein, highly graphitic hollow spheres (HGHS) are designed by using D‐ribose as the carbon source and Fe‐based catalysts to address these issues, and the effect of graphitization degree on potassium storage performance is explored, which is rarely reported. Fe‐based catalysts can promote graphitization of carbon layer and function as a hard template for manufacturing hollow and spherical architecture. HGHS possess a high porosity, which provides good contact when the liquid electrolyte infiltrates throughout the material. HGHS synthesized with a suitable amount of Fe‐based catalysts display highly graphitic hollow carbon spheres and show a superior potassium storage performance (264 mAh g −1 at 100 mA g −1 ). The hollow carbon sphere structure and highly graphitic carbon layer endows HGHS with outstanding stability, retaining 87% of the capacity after 500 cycles at 200 mA g −1 . This study provides an effective strategy in designing highly graphitic hollow nanostructures for addressing the instability issues of graphite anode in PIBs.