Preparation and performance of poly(vinyl alcohol) porous separator for lithium-ion batteries

Poly(vinyl alcohol) (PVA) separator with highly developed porous structure is facilely prepared by a non-solvent induced phase separation (NIPS) wet-process and investigated in lithium-ion batteries. In this method, deionized water and ethanol are used as solvent and non-solvent for PVA material, respectively, and no pore forming additives are employed. Systematical investigations including morphology characterization, porosity measurement, electrolyte contact angle testing, electrolyte uptake/retention examination, and thermal shrinkage testing are carried out. The results demonstrate that this PVA separator possesses notable features, such as uniform and porous surface morphology, symmetric interconnected porous structure all through the separator thickness, and excellent electrolyte wettability, thus resulting in superior electrolyte adsorption/retention capacity, lower thermal shrinkage, and higher ionic conductivity, in comparison to the commercial polypropylene (PP) separator. Based on the above advantages, the PVA separator exhibits better electrochemical performances, such as the discharge C-rate capability and cycling performance, as compared to PP separator. This research presents a low-cost and environment-friendly approach to prepare a high performance separator, which is demonstrated to be a good candidate for lithium-ion batteries.