Surfactant-assisted hydrothermal synthesis of CoMn2O4 nanostructures for efficient supercapacitors

Mixed transition metal oxides/spinels are excellent energy storage electrode materials that can deliver sizeable specific capacitance, excellent cyclic stability, and good rate capability than their single metal oxide analogues. Synthetic methods and strategies greatly influence materials' structure, morphology, and functionality. Among several strategies employed to improve the capacitance of metal oxides, the addition of surfactant is one of the simple strategies that help profoundly increase the electrode material's surface area/active sites. This study prepared a tetragonal spinel CoMn2O4 material using a simple hydrothermal approach by a surfactant, polyvinylpyrrolidone (PVP)-based morphological strategy. Electrochemical techniques such as cyclic voltammetry (CV) and galvanostatic charge/discharge cycling (GCD) were used to investigate the active material's energy storage properties. The structural and morphological properties were studied using XRD, SEM, and TEM techniques. The obtained CoMn2O4 material has unique and beautiful Indian borage shrub-like morphology. The unique morphology of CoMn2O4 material provided excellent electrochemical properties by virtue of its enhanced physicochemical properties like pore size distribution, increased surface area, and many active sites for electrolyte ions that incurred large specific and areal capacitances. Further, the significant structural integrity provides extended cycling stability (similar to 116% capacity retention) with high Coulombic efficiency of similar to 98% even after 6000 cycles without any dwindle in capacitance value. These fascinating features make CoMn2O4 a promising and optimistic pseudocapacitive electrode material.