Fe.sub.3O.sub.4-based core/shell nanocomposites for high-performance electrochemical supercapacitors

In this work, magnetite (Fe.sub.3O.sub.4)-based core/shell composites, including Fe.sub.3O.sub.4@carbon (C), Fe.sub.3O.sub.4@polyaniline (PANI), and Fe.sub.3O.sub.4@C@PANI, are synthesized via a facile hydrothermal process. The as-prepared core/shell composites are characterized by transmission electron microscopy, X-ray diffraction powder, and Fourier transform infrared spectroscopy. The electrochemical performances of Fe.sub.3O.sub.4, Fe.sub.3O.sub.4@C, Fe.sub.3O.sub.4@PANI, and Fe.sub.3O.sub.4@C@PANI are investigated using cyclic voltammetry, galvanostatic charge-discharge measurement, and electrochemical impedance spectroscopy. The results show that the as-prepared nanomaterials are all typical pseudocapacitance capacitors. Carbon shell can significantly increase the electronic conductivity of electrode materials, reduce capacity loss, and improve the reversibility of Fe.sub.3O.sub.4. PANI coating layer can expressively enhance the specific capacitance. Synergistic effect of double shells improves the electrochemical property of Fe.sub.3O.sub.4. Fe.sub.3O.sub.4@C@PANI composites display the high capacitance of 322.5 F g.sup.-1 at 2.5 A g.sup.-1, and 87.8 % of which can still be maintained after 3000 charge-discharge cycles. The excellent electrochemical properties of Fe.sub.3O.sub.4@C@PANI evidence their potential application as supercapacitors in energy storage field.