Advancing gel polymer electrolytes for next-generation high-performance solid-state supercapacitors: A comprehensive review

Demand for flexible and wearable electronic devices increases the need for high-performance solid-state supercapacitors (SCs), which offer high power and energy densities, rate performance, lifespan, safety, and ease of fabrication. Gel polymer electrolytes (GPEs) are leading this technological revolution due to their superior ionic conductivity and safety, outperforming solid electrolytes and avoiding liquid electrolytes. Based on a thorough literature study, this comprehensive review covers hydrogels, ionogels, organogels, and redox-mediated GPEs in depth. It rigorously examines the newest methods and technical advances, emphasizing GPEs' crucial role in flexible solid-state SC development. This paper also details hydrogel electrolytes based on H⁺, Li⁺, Na⁺, K⁺, and other ions, demonstrating their versatility and adaptability in improving solid-state SC performance and application. Scientists, engineers, and technologists seeking sustainable and efficient energy storage solutions will find this state-of-the-art report invaluable. It explains GPE fundamentals, critically addresses current challenges and outlines future research directions.