Tailoring Gel Polymer Electrolytes for Advancing Quasi-Solid-State Batteries

Gel polymer electrolytes (GPEs) have attracted considerable attention due to their advantageous properties, such as uniform lithium deposition, stable solid electrolyte interphase (SEI) formation, nontoxicity, nonflammability, and leak-proof characteristics. In this study, a polyvinylidene fluoride hexafluoropropylene copolymer (PVDF-HFP)-based gel polymer electrolyte is synthesized via photo-polymerization, with a focus on examining the effects of curing time on electrolyte performance. The findings reveal that UV irradiation conditions significantly influence key material and electrochemical properties of the GPEs, including lithium-ion transference number, ionic conductivity, crystallinity, morphology, and liquid electrolyte uptake. Notably, the GPE cured for 120 s exhibited optimized performance, achieving an ionic conductivity of 1.10 mS cm⁻¹ at room temperature, an expanded electrochemical voltage window of 4.38 V, and a lithium-ion transference number of 0.50. This optimized GPE enabled long-term Li plating/stripping in a Li//Li symmetric cell and demonstrated stably cycling performance in both half-cell and full-cell configurations. Overall, this study highlights the critical role of crosslinking in regulating the electrochemical performance of GPEs and provides valuable insights for the development of high-performance GPE-based quasi-solid-state batteries.