70 wt% SiO2-loaded flexible PVDF quasi-solid-state electrolyte membrane for lithium oxygen batteries

Abstract

Unique flexible PVDF-based quasi-solid-state electrolytes (QSSEs) with PMMA-modified nanosilica additives were successfully prepared to enhance the safety, energy density, and cycling stability of lithium oxygen batteries (LOBs). With 70 wt% of nanosilica additive (SP70), the membrane exhibited remarkable Li⁺ conductivity, electrolyte uptake and mechanical strength, hindering the shuttling of anions (I⁻ and I₃⁻) and any harmful species, without any decline in physical flexibility. Iodine was added to enhance the kinetics of the oxygen evolution reaction (OER) and expedite the decomposition of the discharge product, Li₂O₂. Furthermore, the cycle life of iodine-assisted LOBs was extended from 103 cycles with pristine PVDF to 402 cycles with SP70 at 1.0 A g⁻¹ and 1000 mA h g⁻¹ charge/discharge testing conditions. The full discharge capacity was improved to 45 336 mA h g⁻¹, which was twice that of the LOB with the PVDF-only membrane.