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

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.