Electrochemical performance of transition metal based CoB2O4 (B = Co and Fe) oxides as an electrode material for energy storage devices

Abstract

Improvement in the specific capacity of the spinel structures (A_xB_3−xO₄) plays a vital role for creating energy storage devices with excellent electrochemical performance. Here, we synthesized spinel structured CoB₂O₄ (B = Co, Fe) electrode materials using a simple hydrothermal method. The X-ray Diffraction (XRD) analysis confirms the phase purity and crystallinity of the synthesized materials while morphology, surface area, pore radius, oxidation states and chemical bonding is confirmed by Field Emission Scanning Electron Microscopy (FESEM), Brunauer–Emmett–Teller (BET), X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. Williamson–Hall (W–H) plots and Rietveld refinement are used to find the average crystallite size, strain, and lattice parameter of Co₃O₄ and CoFe₂O₄ compounds. The CV analysis confirms a high specific capacity of 1039 F g⁻¹ (415 C g⁻¹) for Co₃O₄ as compared to 527 F g⁻¹ (169 C g⁻¹) for CoFe₂O₄ at 2 mV s⁻¹. The dominance of the diffusion process (b = 0.59) and quantitative separation of faradaic and capacitive contribution at different scan rates are calculated for the Co₃O₄ sample. The Galvanic Charge–Discharge (GCD) analysis confirms a specific capacity of 663 F g⁻¹ (265 C g⁻¹) for Co₃O₄, which is almost 1.2 times higher than to CoFe₂O₄. The 86% capacity retention over 5000 GCD cycles and small value of charge transfer resistance (R_ct = 45 Ω) for Co₃O₄ confirm its superiority and potential to be used as a positive electrode material for practical energy storage devices.