Fe, N co-doped amorphous carbon as efficient electrode materials for fast and stable Na/K-storage

Abstract Carbonaceous materials are considered as one of the potential and advantageous electrode materials in both sodium ion batteries (SIBs) and potassium ion batteries (PIBs) on account of their good conductivity and excellent chemical stability. Nevertheless, the problems of poor storage capability for sodium/potassium and unsatisfactory rate capability for carbon materials have to be solved urgently. It is imperative to combine multiple methods to achieve effectively improvement performance of carbonaceous electrode materials. Herein, by rational designing, Fe, N co-doped amorphous carbon materials (Fe-N/C) are successfully prepared by calcining Fe-doped precursor Fe-Zeolitic imidazolate framework (ZIF-8). The experimental results show that singly dispersed iron atoms can function as catalyst to promote the dynamics of electrode materials, and N-doping enhances the electrical conductivity and increases active sites. Benefitting from the synergistic interaction of various modification methods, the Fe, N co-doped amorphous carbon electrode delivers a high reversible specific capacity of 215.9 and 158.6 mAh g−1 at 500 mA g−1 after 1000 cycles for SIBs and PIBs, respectively. Density functional theory calculation (DFT) shows that the Fe doped is energetically favorable for Na/K ions adsorption and favorable to the promote the sodium and potassium storage.