Porous three-dimensional (3D) structures generally improve the performance of electrodes by increasing the active surface area and the diffusion speed of electrolyte ions during charging/discharging. In past work, we created thick 3D electrode materials by electropolymerizing pyrrole (Py) in the presence of carboxylated cellulose nanocrystals.To investigate the effect of supporting electrolyte and ions on the preparation of these electrode materials, we electrodeposited polypyrrole in the presence of varying amounts of chloride anions (Cl^-) and carboxylated cellulose nanocrystals (CNC-COO^-). The deposited structure is formed by a combined effect of different nucleation and growth mechanisms induced by CNC-COO^- and by Cl^- during electropolymerization. The result is that the 3D porous structure of the PPY supported on the CNC-COO^- scaffold can be modulated by controlling the Cl^- to CNC-COO^- ratio, with a direct effect on its performance as supercapacitor electrode material. Improved performance can even be reached by combining Cl^- anions with ClO₄⁻.

The highest area capacitance reached was 1.34 F cm^-2 (142.9 F g^-1) at a current density of 2 mA cm^-2 (0.2 A g^-1). More importantly, at a high current density of 20 mA cm^-2 (2.2 A g^-1), thick (ca.130 μm), 3D, and high mass loading (9.2 mg cm^-2) Cl^-:CNC-COO^-/PPy films exhibited a high areal capacitance of 0.85 F cm^-2 (70.8 F g^-1), increasing about 16 % over CNC-COO^-/PPy films prepared in the absence of Cl^- present during electrodeposition. In addition, an aqueous Cl^-:CNC-COO-/PPy (with Cl-:CNC-COO^- = 2.0) symmetric supercapacitor had a high areal capacitance of 0.60 F cm^-2 (55.02 F g^-1) at 1 mA cm^-2 (0.10 A g^-1), an energy density of 83.38 μWh cm^-2 (7.64 Wh Kg^-1) and good cycling stability, indicating their potential in energy storage devices. In my presentation, I will go into detail into the mechanisms, characterization, and performance of electrode materials made with different Cl^-:CNC-COO^- ratios and different doping ions introduced through changes in the supporting electrolyte during electrodeposition.