Unlocking the Potential of Epoxidized Natural Rubber (ENR)-Based Polymer Electrolytes: Key Strategies, Bibliometric Insights, and Future Directions

Natural rubber (NR) and its modified forms, such as epoxidized NR (ENR), are widely used in industries due to their versatility, biodegradability, and unique elastomeric properties. ENR has recently gained attention as a sustainable alternative to synthetic polymer electrolytes (PEs) in low- to moderate-temperature electrochemical devices, including lithium-ion batteries (LIBs), supercapacitors, and proton exchange membrane fuel cells (PEMFCs). It offers advantages such as low cost, eco-friendliness, and excellent film-forming ability. However, its practical application is hindered by poor mechanical strength, low ionic conductivity, and limited thermal and chemical stability, making it unsuitable for high-temperature systems like solid oxide fuel cells (SOFCs). Advanced modification techniques─such as blending with reinforcing polymers, chemical cross-linking, graft copolymerization, and nanofiller incorporation─have been explored to overcome these limitations. These strategies significantly enhance ENR's mechanical robustness, ionic transport, and resistance to heat and solvents, improving its viability for targeted electrochemical applications. This perspective discusses recent progress in ENR-based PEs, emphasizing conductivity, moisture resistance, and long-term durability improvements. Sustainable fabrication methods are also critical to developing high-performance membranes that minimize fuel crossover while maintaining efficient ion transport. Therefore, future research should optimize ENR's electrochemical properties and thermal stability to support performance under challenging operating conditions.