A Comprehensive Review on Polymer Electrolytes for Advanced Electrochemical Energy Storage: Materials, Conductivity, and Emerging Applications

Abstract

The increasing demand for portable electronics, electric vehicles, and renewable energy systems has accelerated the development of advanced energy storage technologies with improved safety, efficiency, and sustainability. Among the key components of electrochemical energy storage devices, electrolytes play a crucial role in governing ionic transport, electrochemical stability, cycle life, and overall device performance. Conventional liquid electrolytes, although widely used in lithium-ion batteries, suffer from limitations such as leakage, flammability, and thermal instability. Polymer electrolytes have emerged as promising alternatives due to their enhanced safety, flexibility, and compatibility with solid-state energy storage systems. This review provides a comprehensive overview of solid polymer electrolytes (SPEs), gel polymer electrolytes (GPEs), and composite/hybrid polymer electrolytes (CPEs), highlighting their structures, ion transport mechanisms, advantages, and limitations. Various fabrication techniques, including solution casting, electrospinning, in-situ polymerization, and phase separation, are discussed. Particular emphasis is placed on conductivity enhancement strategies involving plasticizers, ionic liquids, nanofillers, and interfacial engineering. Key performance parameters such as ionic conductivity, cation transference number, electrochemical stability window, and mechanical and thermal stability are critically evaluated. Recent developments in biopolymer-based electrolytes and their applications in lithium-, sodium-, and zinc-ion batteries, as well as supercapacitors, are also examined. Finally, current challenges and future perspectives for developing high-performance, sustainable polymer electrolytes for next-generation energy storage devices are discussed.