Sulfonated PVDF-HFP and SiO₂ based quasi-solid-state composite electrolyte for Lithium-oxygen batteries

A composite quasi-solid-state electrolyte (QSE) integrating sulfonated poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and silicon dioxide (SiO₂) nanofillers is developed for lithium‑oxygen (Li-O₂) batteries. The inclusion of SiO₂ nanofillers into the host polymer matrix helps in retaining the liquid electrolyte, enhancing ionic conductivity, mechanical stability, and structural integrity. Sulfonation of PVDF-HFP improves lithium-ion transport, reduces the shuttle effect of the lithium iodide (LiI) redox mediator, and suppresses lithium dendrite growth through uniform lithium deposition. The QSE exhibits an ionic conductivity of 1.29 mS cm^-1, a lithium transference number of 0.66, and an electrochemical stability window of 5.2 V vs. Li/Li⁺ at 30 °C. Under restricted capacity conditions, the QSE-enabled Li-O₂ cells achieve a cycle life of 191 cycles, significantly outperforming liquid electrolyte-based Li-O₂ cells. Post-cycling analyses reveal effective suppression of lithium dendrite growth and anode pulverization, resulting in a stable solid electrolyte interphase. This hybrid polymer-ceramic design addresses key challenges of Li-O₂ batteries, offering improved safety, performance, and longevity. These findings establish the viability of QSEs for next-generation energy storage systems, advancing toward the practical realization of high-energy-density Li-O₂ batteries.