Multilayered separator based on porous polyethylene layer, Al2O3 layer, and electro-spun PVdF nanofiber layer for lithium batteries

With an aim to enhance the thermal stability and electrolyte wetting of a polyethylene porous separator, an Al2O3 nano-powder layer and an electro-spun PVdF nanofiber layer were successively formed on both sides of the polyethylene separator. The Al2O3 layer provides excellent thermal stability as indicated by thermal shrinkage of only 7.8 % in area at 180 A degrees C and absence of a meltdown up to 200 A degrees C. The electrolyte uptake of the multilayer separator was increased with the thickness of the nanofiber layer. As a result, discharge capacity, rate capability, and cycle life of the lithium ion batteries employing the PVdF nanofiber layers were improved, overcompensating for a loss of performance caused by the Al2O3 layer. Therefore, the multilayer approach is highly effective in improving both the performance and safety of lithium ion batteries.