A flexible composite electrolyte membrane with ultrahigh LLZTO garnet content for quasi solid state Li-air batteries

Abstract

As an alternative next-generation energy storage device, solid state Li-air battery is generally investigated due to its high energy density and safety, yet the suitable solid state electrolyte and big overpotential issues hinder its application. Herein, we develop a novel flexible composite solid state electrolyte membrane with an ultrahigh LLZTO garnet content of ~89.6 wt% (LLZTO CMs) via a facile tap casting/phase-inversion process and a simple solution infiltration method. After introducing [Li∈12-C-4][I] supramolecular filler, LLZTO CMs exhibits high ionic conductivity of 6.92 × 10−4 S cm−1 at 20 °C and 2.85 × 10−3 S cm−1 at 80 °C, outstanding compatibility with Li metal and acceptable capability against Li dendrites. When pouch quasi solid state Li-air batteries are assembled with commercial carbon cloth (without any electrocatalysts) as oxygen electrode, a lower discharge-charge voltage gap of ~600 mV and an inspired cycling stability are obtained. This study suggests that LLZTO CMs could open a new avenue for developing advanced solid state Li-air batteries.