High-capacity and durable enabled by modulation of nitrogen doping and graphite nanodomains in Calophyllum inophyllum L. derived hard carbon anode for potassium storage

Hard carbons (HCs) are promising anode materials for potassium ion batteries (PIBs) because of their environmental benefits, cost-effectiveness, and sustainability. Nevertheless, the short lifespan, limited capacity, and poor reversibility of HCs restrict their application as PIB anodes. In this study, nitrogen doping Calophyllum inophyllum L.-derived hard carbon (NCHC-T) with a three-dimensional (3D) porous structure is created by a one-step carbonization process. The temperature effect on nitrogen doping and graphitization is systematically analyzed. The NCHC-1200, obtained at 1200 °C, exhibits high pyrrole N and pyridine N doping, with some short-range ordered graphitic nano-regions dispersed in the amorphous regions. It exhibits a high reversible capacity of 302.7 mAh g −1  at 100 mA g −1 and a capacity of 203.4 mAh g −1 after 1000 cycles at 500 mA g −1 . The enhanced potassium storage performance of NCHC-1200 can be attributed to its rich porosity, larger layer spacing, and the presence of graphite nano-regions. Furthermore, the formation of a robust solid electrolyte interface film, facilitated by the high electrolyte concentration, mitigates side reactions between the NCHC-1200 electrode and electrolyte, thereby enhancing electrochemical stability. This work gives a valuable understanding of the fabrication of high-performance PIB anodes, thus advancing the development of PIB technology.