Achieving wide potential window and high capacitance for supercapacitors using different metal oxides (viz.: ZrO2, WO3 and V2O5) and their PANI/graphene composites with Na2SO4 electrolyte

Abstract

Tuning the morphology of metal oxides is a common strategy to tailor the electrochemical response of metal oxides. To further improve their applicability, electronic conductivity and subsequently enhance charge collection, metal oxides can be coated with polyaniline and/ or graphene. Potential window is an important property for device configuration. Limitations of potential window are well reported for aqueous electrolyte based supercapacitors. This manuscript investigates the possibility of getting extended potential window with high capacitance value of materials for practical applications. Metal oxides (viz.: ZrO2, WO3 and V2O5) with different morphologies and their PANI/Graphene composites have been synthesized and extended operating potential window (i.e. potential difference: 1.6 to 2.0 V) is observed using 1 M Na2SO4 as electrolyte in three electrode measurement. The metal oxide/PANI/Graphene composites show higher capacitance value compared to their corresponding metal oxides. The symmetric devices prepared using metal oxide/PANI/Graphene composites (viz.: WO3/PANI/Graphene and V2O5/PANI/Graphene) also exhibit high operating potential window (0 to 1.6-1.8 V). The highest capacitance and energy density are found for VPG//VPG symmetric device and the values are ~127 F g−1 (at a current density 1 A g−1) and ~57 W h kg−1 (corresponding power density 900 W kg−1).