Doped bilayer graphene for enhanced sodium-ion battery performance: a first-principles investigation

Abstract

Expanding the interlayer spacing of graphene layers has emerged as an effective strategy to enhance sodiation behavior in sodium-ion batteries. However, the optimal interlayer spacing that facilitates sodiation and maximizes electrochemical storage performance remain incompletely understood. In this study, we utilized first-principles density functional theory calculations to explore possible doping strategies aimed at modulating the interlayer spacing of bilayer graphene (BLG) to optimize its sodiation behavior. We investigated single-atom- and co-doping of BLG with various non-metal, transition metal, and metal elements. Most dopants resulted in significantly increased interlayer spacings of BLG, potentially enhancing sodiation capacity. Notably, among the systems considered, Zn–Ge co-doped BLG exhibited the highest theoretical capacity of 828 mAhg^–1, surpassing the value of pristine BLG (124 mAhg^–1). Moreover, Zn–Ge doped BLG showed a relatively low energy barrier (0.25 eV) against Na diffusion, which is desirable for facilitating rapid charge and discharge processes. These findings have implications for the design of high-performance graphene-based anode materials for sodium-ion batteries.