Enhancing Lithium-Ion Battery Performance with Alumina-Coated Separators: Exploring the Potential of Different Alumina Particle Sizes, Coating Techniques, and Calendering

A range of techniques for the coating of high purity alumina (HPA) on porous polypropylene battery separators has been investigated. A slurry was prepared by dispersion of the alumina powder in acetone solvent and poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) as the binder to obtain an excellent adhesion to the membrane. Doctor blade, spin coating, and electro-spin coating techniques were utilized to coat a thin layer of HPA on the separator that was followed up with a calendering step to improve compactness, decrease thickness and enhance adhesion. Furthermore, the effect of HPA particle size, distribution, and the use of a calendering step on coating thickness, compactness, and electrochemical performance were investigated using three HPA sources. The doctor blade technique was found to give the most uniform coating with the best mechanical properties and high-temperature resistance. The coated separators were incorporated into lithium-ion coin cells to evaluate the rate capability and long-term cycling performance.