High Energy Density All Solid State Asymmetric Pseudocapacitors Based on Free Standing Reduced Graphene Oxide-Co₃O₄ Composite Aerogel Electrodes

Modern flexible consumer electronics require efficient energy storage devices with flexible free-standing electrodes. We report a simple and cost-effective route to a graphene-based composite aerogel encapsulating metal oxide nanoparticles for high energy density, free-standing, binder-free flexible pseudocapacitive electrodes. Hydrothermally synthesized Co₃O₄ nanoparticles are successfully housed inside the microporous graphene aerogel network during the room temperature interfacial gelation at the Zn surface. The resultant three-dimensional (3D) rGO-Co₃O₄ composite aerogel shows mesoporous quasiparallel layer stack morphology with a high loading of Co₃O₄, which offers numerous channels for ion transport and a 3D interconnected network for high electrical conductivity. All solid state asymmetric pseudocapacitors employing the composite aerogel electrodes have demonstrated high areal energy density of 35.92 μWh/cm² and power density of 17.79 mW/cm² accompanied by excellent cycle life.