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 (TiO2) nanoparticles with a TiO2-rich configuration. PVDF-HFP was selected as the host polymer owing to its chemically compatible nature with lithium metal. TiO2 (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 ? to 420 ?) at the 50 wt% TiO2 loading compared with the pristine PVDF-HFP. This improvement may be attributed to the electron transport properties enabled by the incorporation of semiconductive TiO2. After being immersed in an electrolyte, the FC-LICM also exhibited a R-ct that was lower by 45% (from 141 to 76 ?), suggesting enhanced ionic transfer upon the addition of TiO2. The TiO2 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% TiO2 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.

Automated summary

The aim of this research is to investigate a flexible composite lithium-ion-conducting membrane (FC-LICM) made of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and titanium dioxide (TiO2) nanoparticles. The addition of TiO2 improved the charge transfer resistance values and enhanced the ionic transport of the FC-LICM. The FC-LICM with 50 wt% TiO2 loading was assembled into a Li-air battery, showing a reduction in overpotential and improved performance compared to the bare polymer.