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 1.09μm and a degree of porosity of ~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 0CN sample, which shows discharge capacity values of 149.7mAh·g−1, 146.5mAh·g−1 and 124.6mAh·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.