Electrospun Silicon Dioxide/poly(vinylidene fluoride) Nanofibrous Membrane Comprising a Skin Multicore-Shell Nanostructure as a New High-Heat-Resistant Separator for Lithium-Ion Polymer Batteries

Porous silicon dioxide (SiO )/poly(vinylidene fluoride) (PVdF), SiO /PVdF, and fibrous composite membranes were prepared by electrospinning a blend solution of a SiO sol-gel/PVdF. The nanofibers of the SiO /PVdF (3/7 wt. ratio) blend comprised skin and nanofibrillar structures which were obtained from the SiO component. The thickness of the SiO skin layer comprising a thin skin layer could be readily tuned depending on the weight proportions of SiO and PVdF. The composite membrane exhibited a low thermal shrinkage of ~3% for 2 h at 200 °C. In the prototype cell comprising the composite membrane, the alternating current impedance increased rapidly at ~225 °C, and the open-circuit voltage steeply decreased at ~170 °C, almost becoming 0 V at ~180 °C. After being exposed at temperatures of >270 °C, its three-dimensional network structure was maintained without the closure of the pore structure by a melt-down of the membrane.