Correlated migration of ions in a 2D heterostructure anode: guaranteeing a low barrier for a high site occupancy

Abstract

Two dimensional (2D) heterostructures are promising anodes for next-generation rechargeable ion batteries due to the high theoretical capacity and low ion diffusion barrier. The traditional individual diffusion theory attributes the low barrier to the weak adhesion and even energy landscape for ions in heterostructures. Following this theory, however, for a high ion occupancy (high power state of a battery) the Coulomb repulsions between ions can hinder their migrations and lead to higher diffusion barriers. In the present study, systematic calculations of ion diffusions declare that ion migrations in a heterostructure mainly obey a correlated mechanism, where the favorable chemical environments for ions, i.e. smaller adhesion variation compared to the stable sites, and large ion spacings, i.e. lower Coulomb repulsions, in diffusion processes can guarantee a low barrier for various ion occupancies. Our study provides a comprehensive understanding of the high mobility of ions in heterostructures, which can facilitate the development of 2D material based anodes.