Theoretical Investigation of 2D Layered Materials as Protective Films for Lithium and Sodium Metal Anodes

Rechargeable batteries based on lithium (sodium) metal anodes have been attracting increasing attention due to their high capacity and energy density, but the implementation of lithium (sodium) metal anode still faces many challenges, such as low Coulombic efficiency and dendrites growth. Layered materials have been used experimentally as protective films (PFs) to address these issues. In this work, the authors explore using first-principles computations the key factors that determine the properties and feasibility of various 2D layered PFs, including the defect pattern, crystalline structure, bond length, and metal proximity effect, and perform the simulations on both aspects of Li⁺ (Na⁺) ion diffusion property and mechanical stability. It is found that the introduction of defect, the increase in bond length, and the proximity effect by metal can accelerate the transfer of Li⁺ (Na⁺) ion and improve the ionic conductivity, but all of them make negative influences on the stiffness of materials against the suppression of dendrite growth and weaken both critical strains and critical stress. The results provide new insight into the interaction mechanism between Li⁺ (Na⁺) ions and PF materials at the atomic level and shed light onto exploring a variety of layered PF materials in metal anode battery systems.