Hierarchical porous CoFe2O4/CoFe2Se4 nanosheet as supercapacitor electrodes: Effect of selenium content and pore structure on electrochemical performance

Abstract

Improving electrode conductivity and increasing electrode specific surface area are two strategies to enhance the storage performance of supercapacitors. Generally, to improve the conductivity of the electrode, a conductive polymer is usually coated on electrode. Nevertheless, polymer covers the pore structure, thus reduce the specific surface area of electrode material, which is not conducive to electrolyte contact and electron transfer. Therefore, the selenide nanosheet layer can be precipitated from the outer layer of CoFe2O4 nanosheet by means of selenation reaction, which can not only increase conductivity of electrode, but also increase the specific surface area of electrode, which can kill two things with one stone. So, the as-prepared CoFe2O4/CoFe2Se4 porous nanosheet electrode as the positive electrode shows an outstanding specific capacity of 933.6 C g−1 (1 A g−1). The device operating voltage of an aqueous asymmetric supercapacitor is 1.6 V, the energy density is 112.2 Wh kg−1 (power density of 400 W kg−1). The aqueous asymmetric supercapacitor has good cycle life, after 4000 cycles the capacity retention is 92.1%. Based on the discussion of charging time and charging current of mechanical energy charging supercapacitor, a satisfactory result is obtained, which is beneficial to the collection and utilization of mechanical energy in practical application.