Effect of polyaniline on the performance of zinc phosphate as a battery-grade material for supercapattery

Abstract

Efficient electrochemical energy storage devices are essential to address the current energy demands, as traditional energy storage devices are unable to fulfill the global energy quest due to their low energy and power density. Therefore, a hybrid approach is used to harvest the advantages of batteries and supercapacitors in a single device known as supercapattery. Herein, a cost-efficient, sustainable, and nontoxic zinc phosphate/polyaniline composite is developed for high-performance supercapattery through hydrothermal method. The morphology, and crystallinity of the prepared zinc phosphate with polyaniline composite (Zn3(PO4)2/PANI) is examined through SEM (scanning electron microscopy), and XRD (X-ray diffraction), respectively. Initially, the performance of Zn3(PO4)2/PANI is investigated in the three-electrode testing assembly using a 1 M KOH electrolyte. These results reveal an excellent performance of Zn3(PO4)2/PANI (50/50%) compared to its counterparts (Zn3(PO4)2 and PANI). A two-electrode real device (supercapattery) was fabricated by coupling the Zn3(PO4)2/PANI with activated carbon (Zn3(PO4)2/PANI // AC), and its performance is investigated through CV, GCD, and EIS. The maximum energy density of Zn3(PO4)2/PANI // AC supercapattery is found to be 25.16 W h/kg at a power density of 850 W/kg using 1.2 A/g current density. Furthermore, the electrochemical storage mechanism of the assembled device is inspected through Dunn's model to validate theoretically the experimental results. It is found that the diffusion controlled reactions are dominant at low scan rates for charge storage, whereas the diffusion-limited reactions are found dominant at higher scan rates. This contrast in the storage mechanism is due to the time available for ions to interact with the electrode material.