Suppressing the Redox Shuttling Effect Based on the Anion Trapping Composite Separator Enhances the Performance of Li-O2 Batteries

Rechargeable lithium-oxygen (Li-O2) batteries are at the forefront of energy storage technology. Yet, they face critical challenges, including poor capacity, high overpotential at the oxygen cathode, inefficient lithium utilization, oxygen crossover, and the troublesome growth of lithium dendrites. This study provides an innovative solution using a graphene nanosheet (GNS) composite nickel ferrite (NiFe2O4) (NiFe2O4@GNS) catalyst and ZIF-8 particles decorated glass fiber (GF) (ZIF-8@GF) separator. Remarkably, the in situ grown ZIF-8@GF composite separator boosts higher ionic conductivity (∼2.87 × 10–3 S cm–1) and transport number (tLi+ ∼ 0.58). The modified catalyst and separator performed significantly better than the unmodified analogs in terms of specific capacity and cycling stability. In short, the device using the ZIF-8@GF separator and NiFe2O4@GNS catalyst goes up to 500 cycles without any charge polarization at 300 mA·g–1 and 500 mAh·g–1. In contrast, the corresponding cycle number for the cell with an unmodified separator even using the modified catalyst is ∼209 cycles with high charge polarization. These studies reveal that the modified separator effectively minimizes oxygen and I–/I3– redox crossover, captures anions, accelerates lithium-ion transport, and prevents the harmful intermediates (like O2– or LiO2), which can drastically degrade the organic electrolyte. Furthermore, the insulating characteristics of the ZIF-8@GF membrane deter direct electron transport to ZIF-8 nanoparticles during lithium peroxide formation, thus ensuring uninterrupted access to catalytic anion trapping sites.