A review on starch-based solid electrolytes and their composites for sustainable Li-ion batteries: A green pathway to...

The growing demand for sustainable energy storage has spurred the development of biodegradable polymer electrolytes as environmentally friendly alternatives to conventional systems in lithium-ion batteries (LIBs). This review systematically explores the potential of both natural (e.g., starch, cellulose, polyhydroxyalkanoates) and synthetic (e.g., polylactic acid, polyglycolic acid) biodegradable polymers, with a focused discussion on starch-based solid polymer electrolytes (SPEs). We highlight key advances in Starch-Li⁺ coordination mechanisms, plasticization (glycerol/ionic liquids), and nanofiller reinforcement (e.g., BaTiO₃), which collectively enable ionic conductivities of 10^-4-10^-3 S/cm at optimized salt concentrations (25-40 wt%). Structural modifications such as amorphization and glass transition temperature (T_g) reduction are shown to enhance ion transport while preserving biodegradability. However, critical challenges remain in achieving practical room-temperature conductivity (>10^-3 S/cm), ensuring long-term stability, and transitioning from material development to full cell testing, hurdles that must be overcome to realize the commercial viability of these sustainable electrolytes.