Three polyimide membranes (polymer 0CN, copolymers 0CN/2CN (50/50) and polymer 2CN), with and without-CN dipolar groups, have been prepared by electrospinning and evaluated as lithium-ion battery separators. The prepared membranes show average fiber diameters between 0.5 and 1.09 mu m and a degree of porosity of similar to 80%. The thermal stability, uptake, tortuosity and ionic conductivity values are influenced by the presence of the-CN dipolar groups in the polyimide polymer chain. The best battery performance in LFP/Li system is obtained for the OCN sample, which shows discharge capacity values of 149.7 mAh.g(-1), 146.5 mAh.g(-1) and 124.6 mAh.g(-1) at C/20, C/10 and C/5, respectively. The obtained high solution uptake, ionic conductivity values and rate capability show that these materials are promising candidates for battery separators for rechargeable lithium-ion batteries, when compared to glass microfiber separators. (C) 2016 Elsevier B.V. All rights reserved.