Electrochemical properties and cycle performance of electrospun poly(vinylidene fluoride)-based fibrous membrane electrolytes for Li-ion polymer battery

Prototype cells were prepared by hot pressing of the cathode and the anode coated with poly(vinylidenefluoride-hexafluoropropylene) P(VdF-HFP) and poly(vinylidene fluoride) PVdF-based fibrous membranes, respectively. Electrochemical properties and cycle performance of them before and after hot pressing were investigated. Pressing of the fibrous membrane resulted in decrease of the apparent porosity and electrolyte uptake. The prototype cell using hot-pressed membrane electrolyte showed continuous fading of the capacity while that using non-pressing fibrous membrane almost retained the initial capacity after 100 cycles at room temperature (0.5 C rate). In the case of cycle test at 80 °C, however, the capacity was slightly decreased after the initial capacity fading of about 6.5% during the first 10 cycles due to the evaporation of liquid electrolytes. Rate performance exhibited about 97% and 72% of the full capacity at the 1 C rate and 2 C rate, respectively. The capacities at 5 C rate and 10 C rate were about 27–28% of the full capacity similarly because of the reduction of the entrapped liquid phase due to the swell of the fibrous structure.