Can P₃S and C₃S monolayers be used as anode materials in metal-ion batteries? An answer from first-principles study

With the urgent need for efficient energy storage devices, significant attention has been directed to researching and developing promising anode materials for metal-ion batteries. Through density functional study, we successfully predicted the electrochemical performance of P₃S and C₃S monolayers for the first time, which could be used in alkali metal (Li, Na, and K)-ion batteries. Our study examines the energetic, dynamic, and thermal stabilities of pristine monolayers. The electronic structures of the pristine nanosheets are wide-gap semiconductors. After single metalation on the monolayers, the composite systems become metallic. Charge-density difference (CDD) analysis indicates that charge transfer occurs from alkali metal atoms to the P₃S and C₃S monolayers, and Bader charge analysis quantifies the amount of charge transfer. We analyzed how readily a single adatom diffuses within the 2D structures. One example is the diffusion of K on C₃S, which has a low barrier value of 0.06 eV and seems practically barrierless. Our predicted composite systems report considerable theoretical storage capacity (C); for example, hexalayer K-adsorbed C₃S shows a storage capacity of 1182.79 mA h g^-1. The estimated open-circuit voltage (OCV) values suggest that the C₃S monolayer is a promising anode material for Li-, Na-, and K-ion batteries, whereas the P₃S monolayer is suitable as a cathode material for Li-, Na-, and K-ion batteries.