A review of functional group selection and design strategies for gel polymer electrolytes for metal batteries

Abstract

Electrolytes are crucial for increasing the energy density of secondary batteries. However, the electrochemical instability of conventional liquid electrolytes (LE) has significantly hindered the development of battery technology, especially in terms of safety and compatibility with metal anodes. To address these challenges, gel polymer electrolytes (GPEs) - in which the liquid component is immobilized in a solid matrix - have emerged as a promising alternative. Gel polymer electrolytes combine the advantages of liquid electrolytes while addressing interfacial issues common to all-solid electrolytes. This review summarizes how specific functional groups in the polymer framework affect the physical and chemical properties of GPEs, using lithium metal batteries (LMBs) and sodium metal batteries (SMBs) as examples. In addition, we discuss the effect of these functional groups on the performance of zinc, potassium, magnesium and calcium metal batteries. Furthermore, we emphasize the synergistic effects of multiple functional groups in GPEs. Finally, we outline the main challenges and future directions for GPEs and provide insights that can guide the design of advanced electrolytes and facilitate further research into the potential of GPEs in alkali metal batteries.