Aluminum Hydroxide-based Flame Retardant Composite Separator for Lithium-ion Batteries

Despite the extensive use of polyolefins, especially as the lithium-ion battery (LIB) separators, their flammability limits them for large-scale battery applications. Therefore, fabrication of flame retardant LIB separators has attracted lots of attention in recent years. In this work, composite separators were prepared by applying a ceramic-based coating layer comprising a metal hydroxide as a filler and flame retardant agent (Al(OH)3) and a P(VDF-HFP) binder to the polypropylene (PP) commercial separator. Thermal shrinkage, thickness, air permeability, porosity and flammability of fabricated ceramic-coated composite separator were investigated. The results showed that the addition of Al(OH)3 particles improved thermal shrinkage (~8%) and flame retardancy of commercial separator which can prevent dimensional changes at high temperatures and significantly increase LIBs safety. Applied 11μm ceramic-based coating layer on PP commercial separator had 76% porosity which increased the value of air permeability from 278.15 (sec 100 ml-1) to 312.8 (sec 100 ml-1) suggests much facile air permeation through the pores of commercial separator than the composite one. Furthermore, suitable electrolyte wettability of ceramic coated separator (135%) facilitates ion transport through the pores. All these characteristics make the fabricated flame retardant Al(OH)3 composite separator an appropriate candidate to ensure the safety of large-scale LIB.