Thin Chemisorbed Polyaniline Film on Cobalt Oxide as an Electrode for Hybrid Energy Storage Devices

Abstract

AbstractElectrical charge storing electrodes and their surface modification are intensively investigated to improve the charge storability indicators in electrochemical energy storage devices. Here, the effects of a thin chemisorbed polyaniline (PANI) film on the charge storage behavior of rod‐shaped spinal‐type cobalt oxide (Co3O4) nanorods (PANI@Co3O4) are detailed for fabrication of battery–supercapacitor hybrid (BSH) devices. The PANI@Co3O4 showed larger surface area and optimum porosity properties, which contributed to ∼50 % enhanced specific charge than that in the Co3O4. The deconvoluted total charge storage gain showed more contribution to the bulk‐diffusion controlled process (battery‐type), lower ion transport resistance and Warburg impedance in the PANI@Co3O4 electrode than that in the Co3O4. Two‐sets of BSH devices are fabricated using PANI@Co3O4 as a positive electrode and mesoporous carbon (MC) and activated carbon (AC) negative electrodes in an aqueous electrolyte and benchmarked with symmetric supercapacitors fabricated using the two carbons. The PANI@Co3O4//MC device showed nearly two‐fold higher specific energy (ES) than that of PANI@Co3O4//AC. Interestingly, AC//AC symmetric supercapacitors showed two‐fold higher ES than the MC//MC device. Origin of differences in the charge storage behavior of the two types of devices are systematically analyzed and reported.