Fast potassium migration in mesoporous carbon with ultrathin framework boosting superior rate performance for high-power potassium storage

Abstract Potassium-ion based electrochemical energy storage devices are an emerging technology for large-scale energy storage owing to the abundance of low-cost potassium resources. Nevertheless, the sluggish kinetics and substantial volume variations of anode materials lead to poor rate capability and insufficient cyclability. Herein, a mesoporous carbon with an ultrathin framework (MCUF) was designed as an anode material to achieve stable and high-power potassium storage performance. The ultrathin framework as well as its mesoporous structure synergistically realize excellent potassium storage cyclability and high-rate performance by accommodating substantial volume variations and promoting fast potassium diffusion. The potassium storage characteristics of the MCUF were revealed using electrochemical analyses, in situ XRD characterizations, and DFT calculations, identifying a surface-dominated potassium storage behavior with excellent electrochemical kinetics, high-power capability, and reversibility. Furthermore, the MCUF was used as an anode to assemble novel non-flammable potassium-ion capacitors that exhibited excellent cyclability (with a capacity retention of 89.2% after 6000 cycles), outstanding rate performance, and high energy/power densities (120.2 Wh kg−1 and 16.7 kW kg−1, respectively). Accordingly, our work affords new insights into understanding the potassium storage mechanism in carbon materials and constructing non-flammable high-safety and high-performance potassium-ion capacitors.