Gel polymer electrolytes in lithium-based batteries: Challenges, advances, and future directions

Achieving high energy density without compromising safety remains a major challenge for lithium-based batteries. Liquid electrolytes have high ionic conductivity but suffer from flammability and leakage, while solid polymer electrolytes have low room-temperature ionic conductivity but are safer and more mechanically robust. Gel polymer electrolytes (GPEs) combine the favorable ion-transport properties of liquid electrolytes with the improved safety and mechanical robustness of solid polymer electrolytes. The present review focuses on the latest developments in GPEs, such as polymer matrices, fabrication techniques (solution casting, in situ polymerization, electrospinning, and 3D printing), and composite materials with ceramic (Al 2 O 3 , SiO 2 , TiO 2 ) and carbon fillers. These materials can achieve ionic conductivities of 10 −4 –10 −3 S cm −1 , electrochemical stability windows exceeding 4.5 V, and improved resistance to lithium-dendrite growth. In addition, better fabrication methods enhance the interface between the electrodes and the electrolyte, as well as the pathways for ion transport. GPEs are used in lithium-ion, lithium-metal, lithium-sulfur, and lithium-air batteries. However, major challenges remain, including balancing ionic conductivity with mechanical strength, maintaining long-term interfacial stability, and achieving scalable production. Future research should therefore focus on multifunctional material design, interfacial optimization, scalable manufacturing, and standardized testing protocols to enable safe, high-performance lithium-based energy-storage systems.