Phase engineering of layered anode materials during ion-intercalation in Van der Waal heterostructures

Transition metal dichalcogenides (TMDs) are a class of 2D materials demonstrating promising properties, such as high capacities and cycling stabilities, making them strong candidates to replace graphitic anodes in lithium-ion batteries. However, certain TMDs, for instance, MoS(2), undergo a phase transformation from 2H to 1T during intercalation that can affect the mobility of the intercalating ions, the anode voltage, and the reversible capacity. In contrast, select TMDs, for instance, NbS(2) and VS(2), resist this type of phase transformation during Li-ion intercalation. This manuscript uses density functional theory simulations to investigate the phase transformation of TMD heterostructures during Li-, Na-, and K-ion intercalation. The simulations suggest that while stacking MoS(2) layers with NbS(2) layers is unable to limit this 2H → 1T transformation in MoS(2) during Li-ion intercalation, the interfaces effectively stabilize the 2H phase of MoS(2) during Na- and K-ion intercalation. However, stacking MoS(2) layers with VS(2) is able to suppress the 2H → 1T transformation of MoS(2) during the intercalation of Li, Na, and K-ions. The creation of TMD heterostructures by stacking MoS(2) with layers of non-transforming TMDs also renders theoretical capacities and electrical conductivities that are higher than that of bulk MoS(2).