Thermodynamics, kinetics and doping effects of Li intercalation in two-dimensional heterostructures for energy storage devices

Van der Waals (vdW) heterostructures are promising candidates for solid-state battery applications. Devices with Li intercalation in transition metal dichalcogenides (TMDs) exhibit high ionic mobility and stability during extended cycling, which can be accompanied by a phase transition in the TMD from the 2H phase to the 1T phase at high Li concentrations The mobility and concentration of the Li ions is highly sensitive to the composition of the heterostructure and its surrounding environment, but the underlying mechanism of this sensitivity—whether electronic, chemical, or structural—is unclear. Here, we use ab initio density functional theory (DFT) and GW calculations to provide atomistic insights into the thermodynamics, kinetics and doping effects of Li intercalation in bulk and monolayer TMDs encapsulated in hexagonal boron nitride (hBN). We show the effect of implicit and explicit (Li) doping on the relative stability of the 2H and 1T phases of TMDs with and without hBN encapsulation. We determine the energy barriers associated with the Li migration in the vdW gap and the concurrent 2H to 1T phase transition_. Finally, we use GW calculations to study the quasiparticle energy of the TMD and donor levels with and without the presence of hBN.