Polymer Electrolytes

This chapter discusses polymer electrolytes, their characterization, and their application in solid-state batteries. The concept of a material that acts as both the physical separator and the electrolyte while maintaining good contact with the electrodes through many charge/discharge cycles has motivated research on polymer electrolytes for over three decades. Beginning with poly(ethylene oxide) (PEO) as a host matrix for lithium salts, which is still the focus of many investigations, this review covers a variety of solvent (liquid)-free systems as well as plasticized or gel electrolytes. Several strategies for improving mechanical and electrical properties such as forming blends, organic/inorganic composites, or copolymerization are also described. Some of the most commonly used characterization tools are briefly discussed, including thermal analysis, X-ray diffraction, electrical impedance, and vibrational and nuclear magnetic resonance spectroscopies. Finally, a brief survey of power source applications of polymer electrolytes ranging from microbatteries to large format electric vehicle batteries is given.