Ion conducting polymer electrolytes in thin flexible forms show great technological potentials to fabricate all-solid-state mini/micro electrochemical power sources viz. batteries, fuel cells, supercapacitors etc. This book contains the synthesis and characterization of solid polymer electrolytes, is mainly focused on the objectives: to develop some new Mg2+ ion conducting solid polymer and composite polymer electrolytes using a novel solution casting technique; to characterize these materials using various models and experimental techniques; to understand the ion transport properties; subsequently, to employ these solid polymer electrolytes in the fabrication of solid state batteries and study the cell performances under constant load. This book is also provide the basic ideas of ion conduction mechanism in polymer electrolytes and also explained various models for transport phenomenon.