The polyacrylonitrile (PAN) nanofiber-based nonwoven separators for lithium-ion batteries have been developed by electrospinning technique. Scanning electron microscopic observation showed that the electrospun PAN nanofibers had homogeneous thickness and their diameters were around 350 nm. Cyclic voltammetry revealed that the separator was electrochemically stable between 3 and 4.5 V vs Li. The cells with the PAN separators showed better cycle performance than conventional ones at a moderate rate of C/2. In the rate-capability and pulse discharging tests, the cells with the PAN-based separators exhibited superior rate-capabilities and smaller diffusion resistance at high rate test than conventional one. (c) 2007 The Electrochemical Society.