Defective engineering and heteroatom doping construction in carbon nanobowls for achieving high-rate potassium-ion storage with long cyclic life

Abstract

Thanks to the unparalleled advantages of environmentally friendly and low-cost, carbon-based materials have been a hot research topic as potassium ion anode materials. The key to future practical applications lies in the development of carbon anode with high capability and long life. Recent studies suggest that N, O-doping can improve the ion transfer and provide abundant active sites. Herein, density functional theory calculations are carried to confirm these functions of N, O-doping and vacancy defects. The results reveal that potassium ion adsorbability is increasing in order of N-doping, O-doping, and vacancy defects. And the existence of vacancy defects and heteroatom doping induce the spontaneous migration of potassium ion. Furthermore, rich vacancy defects can inhibit the increasing of layer distance to restrain volume variation after potassium ion intercalation. Inspired by the calculations, nanobowl-like structured carbon with abundant vacancy defects and N, O heteroatoms is elaborately designed through the structural engineering. On account of the synergistic effects between vacancy defects, heteroatom doping, and unique nanobowl-like structure, the N, O-doped carbon nanobowls achieve a high capacity of 178.0 mA h g−1 over 2000 cycles at 2 A g-1 and a high-rate capability retention of 86.97 % (154.8 mA h g−1 at 10 A g-1).