Quasi-solid polymer electrolytes using photo-cross-linked polymers. Lithium and divalent cation conductors and their applications

In this report, we will present the results on the photo-cross-linked poly-(ethylene glycol) diacrylate (PEGDA) based quasi-solid, i.e. gel, polymer electrolyte systems with lithium, magnesium and zinc trifluoromethanesulfonates [triflate; Mn(CF3SO3)n] and their preliminary applications to primary cells. The Celgard® membrane-impregnated electrolytes were prepared in the same manner as Abraham et al. [K.M. Abraham, M. Alamgir, D.K. Hoffman, J. Electrochem. Soc. 142 (1995) 683]. The precursor solutions were composed of metal triflates, ethylene carbonate, propylene carbonate, and tetraethylene glycol diacrylate. The Celgard® #3401 membrane was soaked overnight in the precursor solution, then clamped between two Pyrex glass plates and irradiated with UV light to form a gel electrolyte. The maxima of the conductivity obtained were 4.5×10−4 S cm−1 at 12 mol% for LiCF3SO3, 1.7×10−4 S cm−1 at 1 mol% for Mg(CF3SO3)2, and 2.1×10−4 S cm−1 at 4 mol% for Zn(CF3SO3)2 system, respectively. The Arrhenius plots of the conductivities are almost linear between 268 and 338 K with 15–25 kJ/mol of activation energy for conduction. The cell, LiLiCF3SO3–SPE+Celgard® #3401(CH3)4NI5+acetylene black, showed 2.86 V of OCV and could discharge up to 25% with respect to the cathode active material at a discharging current of 0.075 mA/cm2.