Effects of size on water vapour absorption and regeneration in lithium chloride nanocrystals

Ionic salts have received tremendous attention for applications such as electrolytes, solar energy, and desiccants. In particular, the high surface area of desiccant materials enhanced moisture absorption capacity, making it suitable for humidity control in various environments. However, lithium chloride (LiCl) salt properties remain largely unexplored in nanocrystalline form (at a high surface to volume ratio) due to difficulty preparing and stabilising nanoparticles, despite the high tide of expectations for energy applications. In the present investigation, for the first time, nanocrystalline LiCl was prepared by a top-down approach - successive cryomilling under an inert atmosphere. Systematic investigation shows nanocrystalline LiCl undergoes rapid dissolution in the presence of moisture. The experimental results were further corroborated with Molecular Dynamics (MD) simulations using LAMMPS. The combined use of milling at room temperature (RT) and cryomilling resulted in a crystallite size of approximately 60 nm. The nanocrystalline LiCl exhibited a water uptake capability eight times faster than that of the bulk LiCl crystal. The simulations revealed that smaller crystals are more reactive because they (i) readily deform in water and (ii) have a larger fraction of atoms with lower stability. The reasons behind the high reactivity of nanocrystalline LiCl, which has not been reported in the literature, have been discussed in detail.