The electrochemical properties of polymer electrolytes based on polyethylene oxide (PEO) and Li[(CF3SO2)(2)N], with and without the addition of dispersed gamma-LiAlO2 powder, are reported. The results clearly indicate that the use of the gamma-LiAlO2 ceramic filler combined with the Li[(CF3SO2)(2)N] salt greatly reduces the crystallization rate and enhances the lithium/electrolyte interface stability.