3D Sulfur and Nitrogen Codoped Carbon Nanofiber Aerogels with Optimized Electronic Structure and Enlarged Interlayer Spacing Boost Potassium-Ion Storage

Carbonaceous materials are promising anodes for potassium-ion batteries (PIBs). However, it is hard for large K ions (1.38 angstrom) to achieve long-distance diffusion in pristine carbonaceous materials. In this work, the following are synthesized: S/N codoped carbon nanofiber aerogels (S/N-CNFAs) with optimized electronic structure by S/N codoping, enhanced interlayer spacing by S doping, and a 3D interconnected porous structure of aerogel, through a pyrolysis sustainable seaweed (Fe-alginate) aerogel strategy. Specifically, the S/N-CNFAs electrode delivers high reversible capacities of 356 and 112 mA h g(-1) at 100 and 5000 mA g(-1), respectively. The capacity reaches 168 mA h g(-1) at 2000 mA g(-1) after 1000 cycles. A full cell with a S/N-CNFAs anode and potassium prussian blue cathode displays a specific capacity of 198 mA h g(-1) at 200 mA g(-1). Density functional theory calculations indicate that S/N codoping is beneficial to synergistically improve K ions storage of S/N-CNFAs by enhancing the adsorption of K ions and reducing the diffusion barrier of K ions. This work offers a facile heteroatom doping paradigm for designing new carbonaceous anodes for high-performance PIBs.