Surface Modification of Hydrophobic Separators Using Poly(Vinyl Alcohol) Binder Enables Uniform Coating of Aqueous Slurries for Functional Separators in Lithium-Ion Batteries

Advanced batteries with specialized functions can be realized by utilizing functional separators that consist of unique functional materials coated on the surface of the separator. However, currently commercialized separators are made of polyolefin fibers, which are hydrophobic in nature, making it difficult to utilize aqueous slurries for the coating process of functional materials due to dewetting of the slurries on the separator surface. Herein, we present an intriguing fabrication method of utilizing polyvinyl alcohol (PVA) binder for in-situ surface modification of hydrophobic separator which results in favorable wetting behavior against all kinds of aqueous slurries Dynamic contact angle measurement was employed to evaluate the wettability of the modified separator surface, and near zero degree receding contact angle was measured for PVA-treated separator. As a demonstration, aqueous slurries that could not be coated on hydrophobic separator by themselves was successfully coated uniformly using PVA as a surface modifier. In addition, a ceramic-coated separator with enhanced thermal stability and adhesion strength was demonstrated with negligible deterioration of lithium-ion transport using the proposed fabrication method. Using our fabrication method, diverse functional separators using cost-effective and eco-friendly aqueous binders can be successfully fabricated for various advanced batteries with superior features