Poly(ethylene oxide)–poly(propylene oxide)–poly(ethyl oxide) enhancing capacitance behavior of composite electrode material poly(o-phenylenediamine)/manganese dioxide for supercapacitor

Composite material poly(o-phenylenediamine)/manganese dioxide (PoPD/MnO2) used as supercapacitor electrode was one-step synthesized by liquid phase co-precipitation. To obtain good electrochemical performance, such as capacitance performance, rate capability and cycle stability, non-ionic surfactant P123 (poly(ethylene oxide)–poly(propylene oxide)–poly(ethyl oxide), PEO–PPO–PEO) is employed to regulate the morphology, structure and dispersity of PoPD/MnO2. As evidenced by infrared spectroscopy and X-ray diffraction, PoPD/MnO2 are all amorphous structure with weak crystallinity. It is worth noting that P123 imposes great influence on morphology, specific surface area and capacitance behavior of PoPD/MnO2. As P123 increases, PoPD/MnO2 initially presents as large irregular blocky aggregates, gradually evolves into near-spherical nanoparticles (50–80) nm, and eventually changes to the coexistence state of both. Sample PoPD/MnO2-0.8 obtained under the optimum P123 dosage 0.8 g (0.0035 mol L−1) has the largest Brunauer–Emmett–Teller specific surface area (123.2 m2 g−1) and specific capacitance (292.4 F g−1) at 500 mA g−1, much higher than that of PoPD/MnO2-0 without P123 (47.2 m2 g−1 and 62.1 F g−1). Meanwhile, the rate capability and the cycle stability of PoPD/MnO2-0.8 improve significantly as well. The equivalent series resistance, electrons transfer resistance and diffusion impedance of samples prepared with suitable amount of P123 all reduced to some extent.