Regulating the coordination microenvironment of atomic bismuth sites in nitrogen-rich carbon nanosheets as anode for superior potassium-ion batteries

Carbon-based materials are recognized as anodes fulling of promise for potassium ion batteries (PIBs) due to advantages of affordable cost and high conductivity. However, they still face challenges including structural unstability and slow kinetics. It is difficult to achieve efficient potassium storage with unmodified carbonaceous anode. Herein, atomic bismuth (Bi) sites with different atom coordinations anchored on carbon nanosheets (CNSs) have been synthesized through a template method. The properties of prepared multi-doping carbon anodes Bi-N3S1/CNSs, Bi-N3P1/CNSs and Bi-N4/CNSs were probed in PIBs. The configuration Bi-N3S1 with stronger charge asymmetry exhibits superior potassium storage performance compared to Bi-N3P1 and Bi-N4 configurations. The Bi-N3S1/CNSs display a rate capacity of 129.2 mAh g−1 even at 10 A g−1 and an impressive cyclability characterized by over 5000 cycles at 5 A g−1, on account of its optimal coordination environment with more active Bi centers and K+ adsorption sites. Notably, assembled potassium-ion full cell Mg-KVO//Bi-N3S1/CNSs also shows an outstanding cycling stability, enduring 3000 cycles at 2 A g−1. Therefore, it can be demonstrated that regulating the electronic structure of metallic centre M-N4 via changing the type of ligating atom is a feasible strategy for modifying carbon anodes, on the base of co-doping metal and non-metal.