Two-dimensional Janus BeSeCl as a potential anode material for sodium- and potassium-ion batteries

Abstract

Highly effective anode materials play an essential role in constructing and commercializing metal-ion batteries with greater energy and power density. We systematically evaluated the electrochemical characteristics of novel 2D Janus BeSeCl implementing the density functional theory. Using AIMD simulations, phonon dispersion spectra and elastic constants, the 2D BeSeCl was verified as dynamically, thermodynamically and mechanically stable. This metallic material also showed higher adsorption energy, achieving a specific capacity of 699 mAh g⁻¹ (434.26 mAh g⁻¹) for sodium-ion batteries (potassium-ion batteries). 2D BeSeCl manifested a low value of open-circuit voltage (OCV) and diffusion barrier, promoting fast ion transport and rapid diffusion. In order to alter the electrochemical performance of the SIBs and PIBs, we doped BeSeCl with aluminium (Al) and silicon (Si). After doping, the specific capacities of BeSe_0.89Al_0.11Cl and BeSe_0.89Si_0.11Cl increased to 916.87 mAh g⁻¹ (687.65 mAh g⁻¹) and 839.59 mAh g⁻¹ (534.28 mAh g⁻¹) for SIBs (PIBs), respectively. Introducing Al and Si into the pristine structure also reduced the diffusion barrier and OCV for both Na and K. Thus, our results reveal 2D BeSeCl as a highly desirable anode material for Na- and K-ion batteries.