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

In this research, we aim to investigate a flexible composite lithium-ion-conducting membrane (FC-LICM) consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and titanium dioxide (TiO(2)) nanoparticles with a TiO(2)-rich configuration. PVDF-HFP was selected as the host polymer owing to its chemically compatible nature with lithium metal. TiO(2) (40–60 wt%) was incorporated into the polymer matrix, and the FC-LICM charge transfer resistance values (R(ct)) were reduced by two-thirds (from 1609 Ω to 420 Ω) at the 50 wt% TiO(2) loading compared with the pristine PVDF-HFP. This improvement may be attributed to the electron transport properties enabled by the incorporation of semiconductive TiO(2). After being immersed in an electrolyte, the FC-LICM also exhibited a R(ct) that was lower by 45% (from 141 to 76 Ω), suggesting enhanced ionic transfer upon the addition of TiO(2). The TiO(2) nanoparticles in the FC-LICM facilitated charge transfers for both electron transfer and ionic transport. The FC-LICM incorporated at an optimal load of 50 wt% TiO(2) was assembled into a hybrid electrolyte Li–air battery (HELAB). This battery was operated for 70 h with a cut-off capacity of 500 mAh g(−1) in a passive air-breathing mode under an atmosphere with high humidity. A 33% reduction in the overpotential of the HELAB was observed in comparison with using the bare polymer. The present work provides a simple FC-LICM approach for use in HELABs.