Gel Polymer Electrolytes for Next-Generation Lithium Batteries: A Review of Interface Engineering and In Situ Polymerization

Abstract Gel polymer electrolytes (GPEs) are emerging as a promising solution for rechargeable lithium batteries because they combine the high ionic conductivity of liquid electrolytes with the mechanical stability and enhanced safety of solid polymer systems. GPEs immobilize liquid components within a polymer matrix while maintaining efficient ionic conductivity and electrochemical performance. This review discusses how in situ polymerization has emerged as a promising fabrication strategy for developing high-performance gel polymer electrolytes (GPEs) with enhanced safety, improved interfacial compatibility, and superior electrochemical stability. It further highlights recent advancements in GPE design, with particular emphasis on electrode–electrolyte interphase engineering through cathode surface modification and structural optimization. Special emphasis is given to the formation, stability, and improvement of the electrode–electrolyte interphase, which play critical roles in suppressing electrolyte decomposition and stabilizing battery performance. Furthermore, the performance of GPEs under extreme environments, particularly low-temperature conditions, is critically discussed, including the influence of low temperature on Li+ ion transport kinetics and solid electrolyte interphase (SEI) stability. Strategies to overcome these limitations are also been summarized. In addition, advanced characterization techniques such as electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy, and transmission electron microscopy are highlighted for understanding the dynamic, chemical, and structural evolution of interphases during cycling. This review also outlines the future prospects and major challenges associated with GPEs and provides conceptual strategies for the development of safe and high-performance lithium batteries.