Journal of Power Sources, Vol.263, 29-36, 2014
Influence of the porosity degree of poly(vinylidene fluoride-coh-exafluoropropylene) separators in the performance of Li-ion batteries
Polyvinylidenedifluoride-hexafluoropropylene, (P(VdF-HFP))-based polymer electrolytes, as separators for lithium batteries, were prepared through different polymer/solvent (N,N-dimethylformamide, DMF) ratios and physicochemically investigated. Scanning electron microscopy measurements have shown a homogeneously distributed porosity within the membranes, with moderately tortuous pathways, resulting in a liquid uptake up to 77 wt.% with respect to the overall weight and conduction values above 10(-3) S cm(-1) at room temperature. Prolonged cycling tests, performed on Li/Sn-C and Li/LiFePO4 half-cells based on P(VdF-HFP) polymer electrolyte separator membranes, have evidenced nominal capacities ranging from 70% to 90% of the theoretical value with very good capacity retention and charge/discharge efficiency close at 100% even at high current rates. A capacity decay is observed at high current regime, associated to the diffusion phenomena occurring within the electrode and the polymer electrolyte separator membrane. (C) 2014 Elsevier B.V. All rights reserved.
Keywords:Porous membranes;Polyvinylidenedifluoride -hexafluoropropylene;P(VdF-HFP);Lithium batteries