Studies on a New Series of Cross-Linked Polymer Electrolytes for a Lithium Secondary Battery

Abstract

We have studied cross-linked polymer electrolytes prepared by polymerization of polyethylene glycol dimethacrylate (PEGDMA) and alkyl methacrylate monomer (MMA, EMA, and BMA) in the presence of liquid electrolyte {[}1.3 M LiPF6/ethylene carbonate-diethyl carbonate or 1.3 M LiPF6/ethylene carbonate-propylene carbonate (EC-PC)]. Flexibility and ionic conductivity of the electrolyte matrix improved as the monomer content is increased and the alkyl chain of the monomer becomes shorter. As the alkyl chain length becomes long, e.g., BMA, the polymer matrix does not appear to form a homogeneous phase with a highly polar electrolyte, e.g.. LiPF6/EC-PC, resulting in reduced ionic conductivity. The polymer electrolyte containing 50 wt % MMA forms homogeneous films with good mechanical properties and gives high ionic conductivity of 3.8 x 10(-3) S/cm at room temperature. We have also studied the electrical performance and cycling performance of a Li/polymer electrolyte/LiCoO2 solid-state cell employing PEGDMA and alkyl methacrylate monomer-based polymer electrolyte. (C) 2001 The Electrochemical Society.