Polymer electrolytes based on modified natural rubber for use in rechargeable lithium batteries

Modified natural rubber (NR) polymer hosts having low transition glass temp eratures have been investigated. Three types of modified NR, namely 25% epo xidised NR (ENR-25), 50% ENR (ENR-50) and polymethyl methacrylate grafted N R (MG-49) were employed. Results are reported for ionic conductivity and th ermal properties for both unplasticised and plasticised polymer electrolyte systems. The samples were in the form of free standing films with the thic kness 0.2-0.5 mm and mixtures of ethylene carbonate (EC) and propylene carb onate (PC) were used as plasticisers. Unplasticised modified NR based syste ms exhibit ionic conductivities in 10(-6)-10(-5) S cm(-1) range at ambient temperatures. Incorporating 50-100% of EC/PC by weight to the systems yield ed mechanically stable films and ionic conductivities in 10(-4)-10(-3) S cm (-1) range at ambient temperature. The thermal event of the systems has dis played an increasing trend of transition glass temperature at elevated salt concentration whereas incorporation of EC and PC into the systems leads to marked reduction in their T-g values. (C) 2001 Elsevier Science B.V. All r ights reserved.