Innovative multiphase composites of transition metal oxides for long-term stability and high energy density in storage devices

The development of an optimal material that facilitates multiple redox reactions is crucial for advancing energy storage devices. In the present study, we focused on preparing such a material through an easy and cost-effective method to achieve enhanced charge storage ability with large power. Multiphase composites based on Mn, Ce, Co, and Ni oxides were prepared via solution combustion synthesis (SCS) for supercapacitor electrode applications. Three composites, Mn–O/CeO₂ (N1), Ni–O/Co₃O₄ (N2), and Mn–O/CeO₂/Ni–O/Co₃O₄ (N3), all in equal ratios, were prepared after sintering at 700 °C for 3 h in the open air. Preliminary characterizations, including X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Raman spectroscopy, and scanning electron microscopy (SEM), were performed to investigate the structural, optical, and morphological properties of the three distinct composites. XRD analysis confirmed the presence of various phases, such as CeO₂, Mn₂O₃, Co₃O₄, NiO, Ni₂O₃, and Mn₅O₈ in the different composites, significantly influencing their physical and electrochemical behavior. With three-electrode assembly, electroanalytical tools such as cyclic voltammetry (CV), galvanic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) were utilized to divulge electrochemical properties which confirmed pseudocapacitive behavior in the synthesized electrode composites. The specific capacitance of 59.3 F/g, 91.67 F/g, and 23.14 F/g at a current density of 1 A/g were recorded for N1, N2, and N3, respectively. Having tempting results of N2 cathode, it was fabricated against activated carbon (AC) anode to form a hybrid supercapacitor device which demonstrated a specific capacitance of 78.25 F/g, a specific energy of 24.45 Wh/kg, and a large specific power of 1086.80 W/kg at 1 A/g current density, with a coulombic efficiency of 106.5% over 1000 GCD cycles.