PREPARATION AND CHARACTERIZATION OF POLY(VINYL-SULFONE)-BASED AND POLY(VINYLIDENE-FLUORIDE)-BASED ELECTROLYTES

A novel group of polymer electrolytes based on poly(vinyl sulfone) (PVS) and poly(vinylidene fluoride) (PVdF) polymers, plasticized with highly conductive solutions of LiClO4, LiN(CF3SO2)(2) or LiAsF6 dissolved in ethylene carbonate, propylene carbonate, sulfolane, or mixtures thereof, was prepared via in situ photopolymerization and solution casting, respectively. The polymer electrolytes were characterized from conductivity and cyclic voltammetry data. It was found that solutions of Li salts in the vinyl sulfone monomer were highly conductive at room temperature with conductivities of 0.6 to 1.3 x 10(-3)Omega(-1)cm(-1) at 30 degrees C, but the conductivities decreased by about 10(3) times on polymerizing. Conversely, the conductivities increased by about 10(2) to 10(4) times on incorporating plasticizing solvents into the solid polymer electrolytes, suggesting that ionic mobility is the primary factor affecting the conductivities of solid polymer electrolytes. The highest conductivity exhibited by PVS-based electrolyte was 3.74 x 10(-4)Omega(-1)cm(-1) and that by PVdF-based electrolyte was 1.74 x 10(-3)Omega(-1)cm(-1), at 30 degrees C. The PVS-based electrolytes were found to be stable to oxidation up to potentials ranging between 4.5 and 4.8 V, while the stable potential limits for PVdF-based electrolytes were between 3.9 and 4.3 V vs. Li+/Li.