Nanopore design of sulfur doped hollow carbon nanospheres for superior potassium-ion battery anodes

Sulfur doped carbonaceous materials are promising anodes for potassium-ion batteries because of their ability to bridge active sites and induce C/S electron coupling, resulting in increased ion storage capacitance. However, the large potassium ions could cause significant volume expansion and structure collapse during operation in sulfur doped carbonaceous anodes, which lead to rapidly capacity sacrifice during long-term cycling. Nanopore design for anchoring sulfur atom in carbon skeleton is a novel way to alleviate the structure collapse and maintain the cycling stability. Therefore, this study developed a controlled nanopore and sulfur doped carbon sphere structure (S-NPHCSs). In potassium-ion batteries, S-NPHCSs anode demonstrated exceptional performance with a high reversible capacity of 247 mAh·g^–1 after 50 cycles at 0.2 A·g^–1 and delivered a long cycle stability of 600 cycles at a high current density of 1.0 A·g^–1. Interconnected nanopores and doped sulfur structure not only expand the accumulation space and offer ample active sites for diffusion and adsorption of potassium ions, but also build stable channels through nanopore structure to ensure the cyclic stability. This finding provides a fundamental theory for designing nanopore structures and introducing sulfur doped carbonaceous materials to enhance capacitive potassium storage and long cycle stability.