separatorCommercial aluminum oxide powder (average particlesize = 200 nm, Aldrich) was added to 8 wt% polyvinylidene fluoride(PVDF 6020 Solef) solution with N-methyl-2-pyrrolidinone solu-tion (NMP) as solvent where a ratio of Al2O3/PVDF was fixed at90/10 (wt%/wt%).