Bilayer construction with desired thermoelectric behavior as a promising candidate for anode materials of magnesium-ion batteries: DFT and AIMD Study on GBS2 hetero-bilayer

The development of high-performance anode materials is essential for advancing next-generation magnesium-ion batteries (MIBs), which offer superior safety, sustainability, and energy density compared to conventional lithium-ion systems. In this study, first-principles calculations were employed to systematically evaluate the novel graphdiyne /borophene hetero-bilayer (GBS 2 ) as a potential anode material for MIBs. Its structural, thermal, and electronic properties were thoroughly investigated. The GBS 2 hetero-bilayer exhibits a work function of 4.82 eV—significantly lower than graphdiyne (5.29 eV) and comparable to borophene (4.81 eV)—indicating favorable electronic characteristics for anode applications. The hexagonal hole in the interlayer region was identified as the most stable Mg adsorption site, with an optimal adsorption energy of approximately −2.0 eV that supports reversible Mg storage. Electronic structure analyses (Bader charge, PDOS, and charge density difference) confirm predominantly ionic bonding, accompanied by a substantial charge transfer of 1.62 electrons per Mg atom. Furthermore, the material demonstrates excellent kinetic performance, with low Mg diffusion barriers of 0.42 eV on the surface and 0.50 eV between layers. Although the GBS 2 hetero-bilayer can accommodate up to 37 Mg ions, its anodic performance is optimized at a loading of 21 Mg atoms. Beyond this critical concentration, Mg clustering occurs, which impairs the electrochemical performance and distinguishes true anode behavior from simple ion storage. At the optimal loading, the anode delivers a high theoretical specific capacity of 2366.42 mAhg⁻ 1 and a suitable average open-circuit voltage of 0.55 V. Thermoelectric calculations further reveal excellent electrical conductivity upon Mg intercalation, along with efficient heat dissipation, which is highly beneficial for battery thermal management. Overall, these findings establish the GBS 2 hetero-bilayer as a highly promising anode material for fast-charging, high-performance MIBs. This work also provides a strategic framework for hetero-bilayer engineering, highlighting significant advantages over monolayer structures.