Ordered double transition metal MBene: the hexagonal ScTiB2 monolayer as a superior anode material for lithium-ion batteries

Abstract

Designing excellent anode materials is the key challenge to improve the performance of lithium-ion batteries (LIBs). In this paper, by using the structure prediction method and first-principles calculations, we design the hexagonal ScTiB2 (hex-ScTiB2) monolayer, an ordered double transition metal MBene, and systematically investigated its stabilities, mechanical properties, electronic structures, and energy storage performance. The hex-ScTiB2 monolayer is stable, which shows metallic characters and excellent mechanical properties. Surprisingly, the hex-ScTiB2 monolayer demonstrates outstanding electrochemical performance for Li-ion storage, such as low diffusion barriers, suitable average open-circuit voltage, and remarkable theoretical capacity up to 937 mA h g−1. The theoretical capacity of the hex-ScTiB2 monolayer is two times larger than that of the hexagonal Ti2B2 monolayer because the structural character of out-of-plane symmetry broken elevates the adsorption ability for Li atoms. Our results demonstrate that the hex-ScTiB2 monolayer is a high-performance anode material for the LIBs, as well as prove that designing structures with double transition metal is an efficient way to improve outstanding the electrochemical performance of MBenes.