The impact of surface functional groups on MXene anode protective layer in aqueous zinc-ion batteries: Understanding the mechanism

The development of energy storage has seen a significant increase in the use of aqueous zinc-ion batteries (AZIBs) with intrinsic safety, which have become an important choice for new high-security energy storage. However, the dendrite growth and hydrogen evolution reaction (HER) on Zn anodes present a significant challenge to the commercialisation of AZIBs. The stability of Zn anodes can be effectively improved by using an anodic interfacial protective layer. The novel two-dimensional (2D) MXene material is capable of effectively inhibiting zinc dendrite growth and the HER reaction when employed as a protective layer for AZIBs anodes due to its readily adjustable properties. The surface functional groups of MXene exhibit different electrochemical properties in different electrolytes, which affects the realization of the protective function. The current understanding of the influence of these surface functional groups on the monolayer MXene as an anodic protective layer for AZIBs is incomplete. A combination of density functional theory calculations and molecular dynamics simulations was employed to investigate the electronic properties, adsorption energies for Zn2+ and H2O, free energies for HER, Zn2+ diffusion energy barriers, Zn2+ diffusion coefficients, and coordination numbers of Zn2+ with water molecules of monolayer MXene (Mo2CTx) with nine different surface functional groups were investigated. The mechanism of the impact of surface functional groups on monolayer Mo2CTx as an anodic protective layer for AZIBs was elucidated. This study will provide guidance for the extensive use of MXene materials in AZIBs to effectively enhance the anode stability and prolong the battery operation life.