Chitosan-based materials for battery separators and polymer electrolyte membranes: A review

Chitosan has been explored as a potential and eco-friendly material for advanced battery systems because of its ionic functional groups, polarity, non-toxicity, film-forming ability, and biodegradability. Derived from natural sources, it offers a sustainable alternative to conventional synthetic separators and polymer electrolytes. The extraction method, which comprises demineralization, deproteinization, and deacetylation, varies with the source and produces different degrees of deacetylation of chitin that strongly influence its electrochemical performance. This review fills the gap by connecting chitosan extraction to its suitability and applications in energy devices, particularly as separators and polymer electrolytes. Chitosan can also be used to modify commercial separators to improve selectivity, and with further optimization, it can also serve as a standalone separator or polymer electrolyte. Its performance can be enhanced through polymer blending, appropriate crosslinking for gel polymer electrolytes, careful salt selection, and the addition of plasticizers in solid polymer electrolytes. Chitosan therefore emerges as a sustainable material candidate capable of supporting high performance in future safe energy storage applications.