Advances in Gel Biopolymer Electrolytes: Sustainable Polymers for Energy Storage Applications

Gel biopolymer electrolytes (GBEs) have emerged as a sustainable and multifunctional class of materials for next‐generation electrochemical energy storage systems. This review provides a critical and comprehensive examination of recent advances in the development, characterization, and application of GBEs, with a particular emphasis on their biodegradable origin, electrochemical functionality, and structural adaptability. Distinct from previous literature, this work integrates insights into ionic conductivity, thermal stability, and electrochemical performance while outlining how biopolymers such as chitosan, cellulose, alginate, and starch can be engineered through plasticization, crosslinking, and nanofiller incorporation to rival synthetic counterparts. Emphasis is placed on the electrochemical requirements of different applications—including supercapacitors, lithium‐ion batteries, sodium‐ion systems, and dye‐sensitized solar cells—and how GBEs can be tailored to meet device‐specific demands such as voltage stability and mechanical resilience. Furthermore, this review identifies emerging directions involving green synthesis practices, AI‐assisted formulation design, and circular economy frameworks. By mapping challenges and opportunities in GBE research, this work serves as a material‐centric and system‐oriented reference for researchers developing high‐performance, environmentally responsible polymer electrolytes.