Role of PVME on the ionic conductivity and morphology of a TPU based electrolyte

Ionic conductivity and morphology of a two-component hybrid polymer electrolyte comprising a polymer blend, LiClO4 and propylene carbonate (PC) have been studied. The hybrid polymer electrolyte has been made by mixing LiClO4 in required proportions with a blend of thermoplastic polyurethane (TPU) and polyvinylmethylether (PVME) and then adding PC to it. TPU used in this study was a segmented urethane having a 1:1 mixture of polypropylene glycol (PPG) and polytetramethylene glycol (PTMG) as the soft segment and 4,4′-diphenyl methane diisocyanate (MDI) extended with ethylene diamine (EDA) as the hard segment. The morphology and ionic conductivity of these hybrid polymer electrolytes were studied by using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and AC impedance measurements. Electrochemical stability of the electrolyte was studied by cyclic voltammetry (CV). Blending with 20-wt% PVME leads to: (i) ∼100% increase in absorption of PC compared to pure TPU; and (ii) increase in dissolution of LiClO4 up to ∼2.0 mmol/g of the blend which was otherwise only 0.4 mmol/g in pure TPU. Room temperature ionic conductivity of the polymer electrolyte containing 1.5 mmol of LiClO4 per gram of the blend and 40% PC is 10−4 S/cm.