Active sites enriched hard carbon porous nanobelts for stable and high-capacity potassium-ion storage

Hard carbon finds critical applications in potassium-ion batteries (PIBs) anodes because of its attractive advantages including low cost and high conductivity. However, the sluggish reaction kinetics and structural instability caused by large K+ intercalation/deintercalation limit their storage capability and cycling life. Herein, active sites enriched hard carbon porous nanobelts (NOCNBs) for enhanced K+ storage are constructed from mineralized shrimp shells via a self-template assisted pyrolysis strategy. The NOCNBs possess multiscale structure with hierarchical micro/meso/macro-pores, high-level pyrrolic/pyridinic-N and O dual-doping, and large interlayer spacing. Hence, the NOCNBs deliver a high capacity of 468 mAh g(-1) at 50 mA g(-1) and long cycling life (277 mAh g(-1) at 1000 mA g(-1) over 1600 cycles), representing one of the best storage capability and cycling stability among the reported carbonaceous electrodes. Density functional theory calculations and kinetic analysis demonstrate that the abundant active sites within NOCNBs can strengthen K adsorption and diffusion, facilitating capacitive-adsorbed storage. The in-situ X-ray diffraction reveals the potassium intercalation mechanism in hard carbon for the first time. Furthermore, they exhibit a superior capacity of 89 mAh g(-1) at 100 mA g(-1) for potassium dual-ion batteries (PDIBs). This work opens up a new avenue for constructing porous hard carbon to achieve excellent K+ storage.