Insight into the potential of M–NbS2 (M = Pd, Ti and V) monolayers as anode materials for alkali ion (Li/Na/K) batteries

Doping engineering significantly improves the electrochemical characteristics of electrode materials in alkali ion batteries. Herein, first-principles calculations were performed to systematically explore the effects of metal atom doping in NbS₂ monolayers by substituting the Nb atoms with metal M atoms (M = Pd, Ti and V) on the structural stability and electrochemical performances. The results demonstrate that M-NbS₂ monolayers can exhibit superior characteristics, including outstanding mechanical flexibility, excellent electronic conductivity, fast charge-discharge rate, low open circuit voltage and high theoretical capacity for alkali ion (Li, Na, and K) storage. Additionally, when alkali ions approach the doping sites of M-NbS₂ monolayers, the diffusion energy barriers for Li ions and Na ions can decrease significantly. More importantly, NbS₂ monolayers with metal doping can obtain the maximum theoretical capacity of 1470.87 mA h g^-1 and the lowest open circuit voltage of 0.17 V. The results of our research can provide a valuable theoretical foundation for the advancement of doped-engineering transition metal chalcogenide monolayers as anode materials in alkali ion battery applications.