Multilayered separators with core-shell structured nanocellulose-SiO2 nanocomposites for lithium-ion batteries

Multilayered porous separators consisting of cellulose nanofibers (CNF) and SiO₂ coating are fabricated for lithium-ion batteries (LIBs) as an eco-friendly alternative to conventional polyolefin separators. Employing a sol-gel synthesis method, SiO₂ nanoparticles are intricately arranged on CNF to create core-shell structured CNF-SiO₂ composites. Simple binder-free CNF-SiO₂ surface coated composite separators are obtained via alternating sequential vacuum filtration of CNF suspensions and the nanocomposite coating functional layers, resulting in bi- and tri-layered separators. CNF entangled structure determines the pore architecture of CNF-SiO₂ as a molecular template, while simultaneously tailoring the size distribution of pores and fibers within the separator, thus optimizing Li-ion transport pathways. By combining core-shell structured CNF-SiO₂ nanocomposites as a functional layer with CNF separators, the resulting multilayer separators significantly improve the electrochemical stability of LIBs due to the effective suppression of electrolyte decomposition and dendrite growth on the Li metal surface. This approach simplifies material sourcing and production processes, making it particularly attractive for large-scale manufacturing for LIBs separators from carbohydrate precursors extracted from biomass. This study highlights the potential of chemically modified cellulose-based nanostructures as high-performing upcycled separators for energy storage, resulting in their possible commercial applications.