Ionic liquids based polymer electrolytes for supercapacitor applications

The rising demand for inexpensive and sustainable energy storage solutions has catalized substantial research into advanced materials for supercapacitors (SCs). Ionic liquid-based polymer electrolytes (ILPEs) have emerged as potential alternatives owing to their elevated ionic conductivity, extensive electrochemical stability windows, and superior thermal stability. This review paper focuses on advancements in ILPEs for SC applications, emphasizing the interaction between ionic liquids (ILs) and polymer matrices to enhance electrochemical performance. ILs exhibit notable characteristics, such as a wide voltage range exceeding 3V, ionic conductivity greater than 10 mS cm⁻¹, and low volatility. These attributes enhance energy densities (up to 40 Wh/kg) and power densities, in addition to providing improved thermal and mechanical stability. Data indicate that ILPEs can attain specific capacitances within the 100–300 F/g range, exhibiting stable cycling performance and minimal capacitance degradation, which are essential factors for the SC mechanism. Various approaches for incorporating ILs into polymer electrolytes (PEs), including composite materials and gel-type systems, are explored. The review identifies significant challenges such as scalability and costs, noting that the high viscosity and limited ionic conductivity of ILs initially created obstacles. It also proposes optimization strategies for future SC developments.