  Light chargeable metal-ion batteries using semiconductor heterostructures are
gaining enormous interest. A few such heterostructures such as MoS2/MoOy and
TiS2/TiO2 have been shown to function as photocathodes in photochargeable
Li-ion batteries, where the type II set-up has been proposed to generate
spatially separated (longer-lived) excitons upon photo-exposure. The Li
intercalated MoS2, generated during the discharge cycle of the battery,
undergoes a phase transition from the semiconducting (2H) to a metallic (1T)
phase, in contrast to its TiS2 counterpart, casting a doubt over the
photocharging process. Here, employing density functional theory based
traditional as well as unconventional computational schemes along with relevant
spectroscopic techniques, we show that in LixMoS2/MoO3 heterostructure an
underlying band gap of LixMoS2 is exposed, upto a certain value of x, due to
dispersion of electron density onto MoO3 justifying the observed photocharging.
We believe that the general concepts explored in this study will be important
in the rational design of photo-cathode materials in Li-ion batteries.
