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

Abstract

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.