A first-principles investigation of the ScO2 monolayer as the cathode material for alkali metal-ion batteries

Abstract

Electrode host materials play a critical role in determining the electrochemical performance of the energy storage devices such as alkali metal-ion batteries. Cathode host materials are expected to provide good electronic and ionic conductivity, improved specific capacity and high discharge voltage. Two-dimensional (2D) transition metal dichalcogenides are competitive candidates as cathode materials due to their unique structure which can enhance ion diffusion and storage. In this study, a first-principles approach is used to investigate the H-ScO₂ monolayer as the cathode host material for alkali metal-ion batteries. It is found that the H-ScO₂ monolayer can deliver capacities of 348 mA h g⁻¹, 348 mA h g⁻¹ and 435 mA h g⁻¹ for Li, Na and K storage, respectively, when the cutoff voltage of the discharge process is set to 1 V. During the discharge process, the averaged open circuit voltages are 4.15 V, 3.29 V and 2.89 V for Li-ion, Na-ion and K-ion batteries, respectively. The diffusion barriers of alkali metal atoms on the ScO₂ monolayer are less than 0.43 eV. It can be inferred that the ScO₂ monolayer is helpful for achieving high-voltage and high-capacity batteries with fast diffusion kinetics. Although the pristine H-ScO₂ monolayer is a semiconductor, intermediate products during the discharge process always show half-metallic and metallic properties, which is also beneficial for increasing the electrical conductivity of the cathode.