Sulfur-doped 3D hierarchical porous carbon network toward excellent potassium-ion storage performance

Carbonaceous materials are promising anode candidates for potassium-ion batteries, but currently the unsatisfactory cycling and rate performances due to the sluggish diffusion kinetic and serious structure damage during K+ insertion/extraction limit their practical application. Herein, a series of sulfur-doped porous carbons (SPCs) were prepared via a template-assisted freeze-drying followed by the carbonization and sulfuration processes at different temperatures. Among the three as-synthesized samples, SPC-600 exhibits the highest specific capacity (407 mAh·g−1 at 0.10 A·g−1), the best rate (242 mAh·g−1 at 2.00 A·g−1) and cycling performance (286 mAh·g−1 after 800 cycles at 0.50 A·g−1). All the SPCs display higher capacities than the undoped carbon materials. The excellent electrochemical performance of SPC can be ascribed to the abundant three-dimensional porous structure together with S-doping in the disordered carbon, which is favor of providing adequate reaction active sites as well as fast ion/electron transport paths. The density functional theory (DFT) calculations further demonstrate that the sulfur-doping can promote K-ion adsorption and storage. Meanwhile, the kinetic analyses reveal that surface-induced capacitive mechanism dominates the K-ion storage process in SPCs, which contributes to ultrafast charge storage. This work provides an effective strategy for fabricating high-performance potassium-ion storage electrode materials.