Enhanced Cyclic Stability of Cobalt Doped Bi25FeO40/BiFeO3 as an Electrode Material for a Super Long Life Symmetric Supercapacitor Device

Abstract

BiFeO3/Bi25FeO40 and cobalt doped Bi25FeO40/BiFeO3 are synthesized by a cost-efficient hydrothermal technique. Cobalt is doped at four different concentrations of 1.5, 2.5, 3.5, and 4.5 mmol in a bismuth ferrite composite (BFCO1, BFCO2, BFCO3, and BFCO4). The capacitive behavior of BFCO3 is significantly higher than those of BFO, BFCO1, BFCO2, and BFCO4 based on their structure, morphology, and electrochemical properties. XRD confirmed the formation of a rhombohedral structure of BiFeO3 and cubic crystal structure of Bi25FeO40 and cobalt doped Bi25FeO40/BiFeO3 composites. Raman modes confirm the presence of cobalt doped Bi25FeO40/BiFeO3 in BFCO3. Microsized particles of BFCO1 were broken upon increasing the concentration of cobalt ion in BFCO2, BFCO3, and BFCO4. In BFCO3, the length of the needle is 0.45 μm and breadth is 0.06 μm, which spread over the spherical-shaped particles with an average size of 0.43 μm. The surface area and average pore diameter of BFCO3 are 60.25 m2/g and 3.38 nm, which are relatively higher than the surface area and average pore diameter of BFO, BFCO1, BFCO2, and BFCO4. The capacitive behavior of BFCO3 shows a significantly higher specific capacitance of 605.16 F g–1 at a current density of 1 A g–1 under 3 M KOH as electrolyte in a three-electrode configuration. The symmetric device of BFCO3 exhibits higher specific capacitance of 176.87 F g–1, specific energy of 35.36 Wh kg–1, and specific power of 1199.43 W kg–1 at a current density of 0.5 A g–1 with super long cyclic stability of about 87% capacity retention, and the coulombic efficiency is about 96% even after 10,000 cycles.