Abstract: In order to solve the problem of the low transverse tensile breaking strength of commercial polypropylene (PP) separators, polyacrylonitrile/polyurethane (PAN/TPU) oriented fiber films were prepared by electrospinning at different rotational speeds as the outer layer of separators, so that the (PAN/TPU)－PP－(PAN/TPU) sandwich structure separator is prepared. The results show that the higher the degree of orientation is, the higher the tensile strength is. Oriented separators collected at 600 r/min and 900 r/min revolutions have high first discharge specific capacities at 2 C, while the over-oriented separators cycled at high rates (900 r/min and 1200 r/min) for a long time experienced obvious capacity decay. Therefore, it is believed that reinforced PP separators with moderately oriented electrospun fibers can improve both tensile strength and electrochemical properties.

Key words: oriented reinforcing fiber; composite structure; battery separator; electrospinning