A PVDF-HFP-Based Gel Polymer Electrolyte onto Air Cathode by UV-Curing for Lithium–Oxygen Batteries

Abstract

Using gel polymer electrolytes (GPEs) instead of liquid electrolytes is a sensible and effective strategy for safety reasons. A GPE membrane was prepared by UV-curing using poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as the polymer substrate material and an optimized ratio. The GPE membrane exhibited good flexibility and a higher ionic conductivity (σ = 0.63 mS cm^–1). The RuO₂@C/GPE/Li (abbreviated as S-GPE) battery is employed to demonstrate the electrochemical performance of GPE. The battery exhibits an R_ct of 255.9 Ω, accompanied by a lack of cycle stability, with a cycle life of only 110 h. The results indicate that it is challenging to enhance the battery’s overall performance by solely improving the internal transfer performance of the electrolyte and ignoring the high interface impedance caused by the “solid–solid” contact at the electrolyte–electrode interface. Based on these findings, a straightforward one-step method is adopted to combine GPE with the air cathode by in situ photopolymerization and assemble it into RuO₂@C-GPE/Li (abbreviated as I-GPE) battery used to demonstrate the electrochemical performance of the integrated GPE. The R_ct value of the battery is 89.66 Ω, with a notable improvement in cycle stability. The battery’s cycle life is 940 h, which is 8.5 times that of the sandwich structure lithium–oxygen battery. The results indicate that preparing an integrated GPE by in situ photopolymerization of the electrolyte electrode is a straightforward and effective method to improve poor interfacial compatibility and can provide a theoretical basis for subsequent in-depth research.