Advanced Polymer Electrolytes in Solid-State Batteries

Solid-state batteries (SSBs) have been recognized as promising energy storage devices for the future due to their high energy densities and much-improved safety compared with conventional lithium-ion batteries (LIBs), whose shortcomings are widely troubled by serious safety concerns such as flammability, leakage, and chemical instability originating from liquid electrolytes (LEs). These challenges further deteriorate lithium metal batteries (LMBs) through dendrite growth and undesirable parasitic reactions. Polymer electrolytes (PEs) have been considered among the few viable options that have attracted great interest because of their inherent non-flammability, excellent flexibility, and wide electrochemical stability window. However, practical applications are seriously limited due to the relatively low ionic conductivity, mechanical instability, and short operational life cycle. This review covers the recent developments in the field and applications of polymer electrolytes in SSBs, including solid polymer electrolytes (SPEs), gel polymer electrolytes (GPEs), and composite polymer electrolytes (CPEs). The discussion comprises the key synthesis methodologies, electrochemical evaluation, and fabrication of PEs while examining lithium-ion's solvation and desolvation processes. Finally, this review highlights innovations in PEs for advanced technologies like lithium metal batteries and beyond, covering emerging trends in polymer materials and advancements in PE performance and stability to enhance commercial applications.