Unveiling the role of polypropylene interactions with lithium fluoride solutions: Insights into crystallization dynamics and membrane behaviour

Abstract

The escalating demand for lithium, driven by its pivotal role in electronic devices and lithium-ion batteries, underscores the urgent need for sustainable lithium recovery methods. Recycling lithium from spent batteries represents a promising strategy to meet this demand; however, a detailed understanding of crystallization processes in the presence of functional interfaces remains largely unexplored. In this study, we present a novel investigation into the role of polypropylene (PP) membranes in controlling the crystallization dynamics of lithium fluoride (LiF) from ionic solutions.

Using a combined computational and experimental approach, molecular dynamics (MD) simulations are performed to compare bulk crystallization with crystallization occurring at the membrane interface. Our results reveal that the membrane deeply influences the crystallization process, increasing induction times and reducing nucleation and growth rates, which indicates a more controlled and structured crystal formation. Notably, the presence of the membrane enhances the crystallinity of the formed crystals, likely due to its structuring effect on the surrounding ionic environment. To assess the impact of the ionic solution on the membrane, we further analyzed morphological parameters and conducted experimental validation. The polypropylene membrane demonstrated exceptional robustness, retaining its structural stability and hydrophobicity, as confirmed by contact angle measurements, even after prolonged exposure to the solution. Experimental trends in nucleation times, crystal morphology, and membrane behavior align closely with the computational findings, reinforcing the reliability of our results.

This study introduces a novel perspective on the interactions between membranes and crystallizing ionic systems, providing fundamental insights into the role of membrane interfaces in influencing crystallization dynamics. The findings pave the way for optimized membrane-based processes, offering valuable knowledge to advance sustainable lithium recovery technologies.