Composite materials combining intrinsically conducting polymers and metal oxides suggested as electrode materials in supercapacitors are reviewed with attention to achieved stability and specific functions and effects both components contribution to the performance of the materials. With this combination, various drawbacks of metal oxide materials frequently suggested as active masses shall be remedied. The low electronic conductivity of metal oxides traditionally ameliorated by adding conducting carbon can be enhanced by intrinsically conducting polymers, but careful consideration of changes of the polymer's conductance as a function of electrode potential is required. An inherently elastic polymer can buffer the volume changes of metal oxides. Loss of active mass, in particular of metal ions, can be prevented by encapsulating the metal oxide in the polymer. Finally, the charge storage capability of the polymer itself can be utilized for enhanced storage in the composite material. Reported materials and preparation procedures are briefly presented; achieved progress as well as remaining challenges are highlighted. Suggestions for further research and development are proposed.

Composites of metal oxides and intrinsically conducting polymers as supercapacitor electrode materials: the best of both worlds?

Construction of polyaniline/carbon nanotubes-functionalized phase-change microcapsules for thermal management application of supercapacitors

Metal-organic framework derived zirconium oxide/carbon composite as an improved supercapacitor electrode

Electrochemical performances of supercapacitors from carbon-ZrO2 composites

Polyaniline/Ferric oxide (PANI/α-Fe2O3) nanocomposites were synthesized via a simple precipitation of FeCl3 using NH4OH as the precipitating agent, followed by in situ polymerization of aniline. PXRD pattern of as-synthesized nanocomposites showed characteristic peaks of α-Fe2O3 in the PANI matrix. Structural and morphological characterization confirmed the encapsulation of α-Fe2O3 nanoparticles in PANI matrix to form PANI/α-Fe2O3 nanostructures. PANI/α-Fe2O3 as an electrode material for supercapacitor exhibited a maximum specific capacitance of 974 Fg−1 at a scan rate of 2 mVs−1 using CV and Csp of 857 Fg−1 at a current density of 0.2 Ag−1 using CP. Further, the material also exhibited a high energy density of 118 Wh kg−1 with a maximum power density of 9.8 kW kg−1 and an excellent cyclic stability with capacitance retention of about 94% after 2000 cycles. These superior electrochemical results over bare PANI and α-Fe2O3 shows the PANI/α-Fe2O3 nanocomposites to be promising electrode material for high performance energy storage systems.

Synthesis of polyaniline/α-Fe2O3 nanocomposite electrode material for supercapacitor applications

Polyaniline/zirconium oxide (PANI/ZrO2) nanocomposites have been synthesized by incorporating ZrO2 nanoparticles into the PANI matrix via liquid–liquid interfacial polymerization method. The composite formation and structural changes in PANI/ZrO2 nanocomposites were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). PXRD pattern of PANI/ZrO2 nanocomposites exhibited sharp and well-defined peaks of monoclinic phase of ZrO2 in PANI matrix. SEM images of the composites showed that ZrO2 nanoparticles were dispersed in the PANI matrix. The FT-IR analysis revealed that there was strong interaction between PANI and ZrO2. AC conductivity and dielectric properties of the nanocomposites were studied in the frequency range, 50–106 Hz. AC conductivity of the nanocomposites obeyed the power law indicating the universal behaviour of disordered media. The nanocomposites showed high dielectric constant in the order of 104, which could be related to dielectric relaxation phenomenon. Further, the materials were checked for their supercapacitance performance by using cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). Among the synthesized nanocomposites, PANI/ZrO2-25 wt.% showed a higher specific capacitance of 341 F g−1 at 2 m Vs−1 and good cyclic stability with capacitance retention of about 88% even after 500 charge–discharge cycles.

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Vinny Rose Thomas

Papers

Synthesis of polyaniline/ZrO2 nanocomposites and their performance in AC conductivity and electrochemical supercapacitance