Enhancement of the Potential Window of Ppy Electrodes in the Presence of a Bis(Oxamato) Nickel(II) Complex for High-Performance Supercapacitor

Abstract

Enhancing the supercapacitors’ performance relies on the increased capacitance and voltage window, which are the current key challenges for developing new materials. In this study, the mononuclear Ni^II-bis(oxamato) complex ([ⁿBu₄N]₂[Ni(opba)], 1) has been synthesized and used as a template in polypyrrole (PPy) based conductive polymer as a novel electrode material for supercapacitor applications. The surface and structural properties of PPy and PPy/1 electrodes were studied using SEM and TEM to elucidate their interactions. The results of characterization techniques revealed that complex 1 altered the morphology, creating a prominent three-dimensional globular structure in the PPy/1 hybrid material without significant chemical modification. The electrochemical properties of PPy and PPy/1 were investigated by CV, EIS, and GCD analyses. The PPy/1 electrode demonstrated intense pseudocapacitive behavior, showing a significantly widened potential window and increased current compared to the PPy electrode, resulting in enhanced energy storage capacity within the material. This improvement was evaluated by testing a symmetric supercapacitor in a coin cell architecture with an alginate-based gel acting as both electrolyte and separator. The maximum specific cell capacitance reached 41.6 F g⁻¹ at a current density of 0.2 A g⁻¹, with a remarkable capacity retention of 97 % after 1000 galvanostatic charge/discharge cycles.