Organic-inorganic hybrid ferrocene/AC as cathodes for wide temperature range aqueous Zn-ion supercapacitors

Organic and inorganic materials have their own advantages and limitations, and new properties can be displayed in organic-inorganic hybrid materials by uniformly combining the two categories of materials at small scale. The objective of this study is to hybridize activated carbon (AC) with ferrocene to obtain a new material, ferrocene/AC, as the cathode for Zn-ion hybrid supercapacitors (ZHSCs). The optimized ferrocene/AC material owns fast charge transfer kinetics and can obtain pseudo-capacitance through redox reaction. Due to the introduction of ferrocene/AC, the ZHSCs exhibit remarkable electrochemical performances relative to that using ferrocene cathode, including high discharge specific capacity of 125.1 F g^-1, high energy density (up to 44.8 Wh kg^-1 at 0.1 A g^-1) and large power density (up to 1839 W kg^-1 at 5 A g^-1). Meanwhile, the capacity retention rate remains 73.8% after 10 000 charge and discharge cycles. In particular, this cathode material can be used at low temperatures (up to -30 °C) with 60% capacity remained, which enlarges the application temperature range of ZHSCs. These results of this study can help understand new properties of organic-inorganic hybrid materials.