Membranes Made from Electrospun Polyacrylonitrile Nonwoven Fibers with Uniform Diameter for Lithium-Ion Battery Separators

Membranes were prepared from polyacrylonitrile (PAN) fibers with uniform diameter for lithium-ion battery separators using optimized electrospinning parameters. In this work, the coefficient of variation (CV) is proposed as one of the indexes to evaluate the uniform consistency of fiber diameter. The most uniform fibrous membrane was compared with a control group that had different uniformity. The effects of the uniformity of the fiber diameter were studied in terms of the membrane porosity, electrolyte absorption, mechanical tensile strength, and thermal stability. The membranes were assembled into coin cells with lithium cobaltite cathodes and graphite anodes, and the performance of the cells was tested. As the uniformity of the fiber diameter increased, the ionic conductivity improved and the interface resistance decreased. The proposed separator improves the discharge capacity (181 mAh·g−1 at the 0.2C rate), C-rate cycling performance, and Coulombic efficiency (99.64 %), which indicates that the uniform membrane could be a candidate for high-performance lithium-ion battery separators.