Studies on a new series of cross-linked polymer electrolytes for a lithiumsecondary battery

We have studied cross-linked polymer electrolytes prepared by polymerizatio n of polyethylene glycol dimethacrylate (PEGDMA) and alkyl methacrylate mon omer (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-pro pylene carbonate (EC-PC)]. Flexibility and ionic conductivity of the electr olyte matrix improved as the monomer content is increased and the alkyl cha in 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 w ith a highly polar electrolyte, e.g.. LiPF6/EC-PC, resulting in reduced ion ic conductivity. The polymer electrolyte containing 50 wt % MMA forms homog eneous films with good mechanical properties and gives high ionic conductiv ity of 3.8 x 10(-3) S/cm at room temperature. We have also studied the elec trical performance and cycling performance of a Li/polymer electrolyte/LiCo O2 solid-state cell employing PEGDMA and alkyl methacrylate monomer-based p olymer electrolyte. (C) 2001 The Electrochemical Society.