Polycarbonate/Polypropylene-conjugated Melt-blown Nonwovens: Thermal Stability and Performance as Li-ion Battery Separators

抄録

Polypropylene melt-blown nonwovens containing thick polycarbonate (PC) fibers were fabricated by a one-step extrusion process. The effects of the PC fibers on the thermal shrinkage and performance of Li-ion battery separators were assessed. PC fibers of 15–30 μm diameter were confirmed by scanning electron microscopy and X-ray computed tomography. An increase in PC fiber fraction was found to decrease the thermal shrinkage and increase the pore diameter and its distribution. The PC-containing samples showed no shrinkage under 130 ºC by thermomechanical analysis and under 100 ºC by free-end heat treatment. The PC fibers had little effect on battery performance at C-rates of 0.1–0.3. However, for C-rates of 5 and 10, a decrease in discharge capacity was observed when the PC content reached 88 %. The decrease of the discharge capacity for high C-rates may be caused by the increase in pore diameter distribution. These results demonstrate the importance of optimizing the PC fraction of nonwovens for use as Li-ion battery separators to minimize their decrease in discharge capacity while maintaining their thermal stability.