Understanding the effect of I/N dual-doped hard carbon for high performance K-ion storage

Heteroatom doping carbonaceous materials are of great significance in potassium-ion batteries. In this work, a special iodine-/ nitrogen- dual-doped hard carbon (I/N-HC) material is successfully synthesized. In contrast to single-substitutional N dopant atoms, the I dopant presents two configurations of I3− and I5− adsorbed on the surface of carbon plane. Both I-doping and N-doping could provide more K-ions storage sites. Furthermore, the enhanced interlayer distance by I-doped and strongly K-ion adsorption energy of I/N codoping (about -4.00 eV), would favor the adsorption of K ions. When used as K-ion batteries anodes, I/N-HC can be maintained a reversible capacity of 149 mAh g−1 over 400 cycles at 500 mA g−1, and an outstanding rate capability of 150 mAh g−1 at 800 mA g−1. This work offers a new type of iodine doping, and reveal the mechanism of I/N co-doping carbon materials for K-ion batteries.