Flexible Lithium-Ion-Conducting Membrane with Highly Loaded Titanium Oxide Nanoparticles to Promote Charge Transfer for Lithium-Air Battery applications

This research aims to investigate a flexible composite lithium-ion conducting membrane (FCLICM) consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and high contents of titanium dioxide (TiO₂) ceramic nanoparticles. The PVDF-HFP was selected as the host polymer owing to its chemically compatible nature with lithium metal. The TiO₂ (40-60 wt.%) was incorporated into the polymer matrix to reduce charge transfer resistance (Rct). At an optimal loading of 50 wt.% TiO₂, the Rct of this dry FC-LICM was lowered by two-thirds (420 Ω, from 1609 Ω when using pristine PVDF-HFP). After being doped with an electrolyte, the FC-LICM exhibited a 45% reduction in Rct (from 141 to 76 Ω), suggesting charge transfer promotion upon the TiO₂ incorporation. The FC-LICM was assembled into hybrid electrolyte Li-air battery (HELAB). This battery can be operated for 70 h with a cut-off capacity of 500 mAh g^-1 in a passive air-breathing mode under high humidity atmosphere. A 33% reduction in the over-potential of HELAB was observed in comparison with that equipped with the pristine polymer. The present work provides a simple and facile FC-LICM preparation HELAB applications.