Polycrystalline phases engineered in-situ in polyaniline-graphene composite evoluting an exceptional stability and high charge storage capacity: An EIS investigative approach to evaluate material's stability

Development of electroactive materials exhibiting high performance with superior stability is crucial in the field of supercapacitors and battery research. We report on synthesis of highly stable composite of semi-polycrystalline polyaniline and graphene (SPani-graphene) and its application in supercapacitor electrodes. The electrochemical behavior and device performance of the electrodes were investigated through cyclic voltammetry (CV), galvanostatic charge-discharge GCD) and electrochemical impedance spectroscopy (EIS) in a 3-electrode and a 2-electrode (device) cell configurations, repectively. The cell specific capacitance (Cell Csp) achieved from the 2-electrode symmetric cell configuration was 525.5 F g−1 at 0.1 A g−1 using polymer gel electrolyte (PGE). The PGE in this work is xanthan gum jellied in 1 M aq. Na2SO4. The maximum energy density and power density achieved from the device was 46.7 Wh kg−1 and 16.16 kW kg−1, respectively, at 0.4 A g−1. Furthermore, the device exhibits an excellent retention of cell specific capacitance and coulombic efficiency of 97 % and 94 %, respectively, over 10,000 continuous GCD cycles, indicating an excellent rate capability as well as a promising power management. To investigate the material's electrochemical durability, a detailed EIS study has been carried out using both, 3-electrode, and 2-electrode cell configurations, before and after long cycling test (over 10,000 continuous GCD cycles). Our thorough experimentation delivers satisfactory results and has been explained in detail in the manuscript. Hereby, we propose that the EIS technique can be adopted for investigating materials' electrochemical stability, in addition to long CV and GCD cycles in the field of supercapacitors and battery research.