Li doping effects on the electronic conductivity of WTe₂ for energy storage devices: An ab initio investigation

Transition metal dichalcogenides (TMDs) and other layered materials, also known as van der Waals (vdW) materials, are promising candidates as electrodes for solid-state battery applications. It is known that Li intercalation in these materials, e.g., MoS₂, is accompanied by a semiconducting (2H) to metallic (1T) phase transition. Another TMD, WTe₂ shows a unique opposite transition from a semi-metallic (Td) to a gapped (Td’) phase when Li is intercalated, a phenomenon only discovered very recently. These phase transitions lead to a change in the intrinsic electronic conductivity of TMDs, an important factor governing the rate-performance of the battery. Low electronic conductivity of the electrode impedes its ability to distribute the charge rapidly. Here, we employ ab initio density functional theory (DFT) and GW calculations to carefully examine the electronic structure of pristine and Li-doped bulk WTe₂ to evaluate their applicability as electrodes in energy-storage devices, and the corresponding role of Li doping in the modification of its electronic bandstructure. We discuss the effective masses and carrier densities to elucidate the nature of the charge-transport in semi-metallic WTe₂. Finally, we calculate the quasiparticle bandstructure of WTe₂.