Zinc influence on the structural manipulation of manganese-based spinel materials: A sustainable approach on the electrochemical performance of supercapacitor electrodes in aqueous media

The increasing demand for energy storage devices requires sustainable practices for implementation, functionalization and recycling procedures that enable a circular economy with minimal wastes. Zinc and manganese are non-critical raw materials with an environmentally friendly character and proven merits in several energy storage solutions, amongst which supercapacitors, important electrochemical energy storage devices able to manage high-power, however lacking energy density. In this work, we demonstrate how these materials can be combined to improve the energy storage ability of manganese-based electrodes, through a simple, low-cost, and eco-friendly chemical precipitation method. The manipulation of manganese-based spinel was performed through the introduction of zinc, developing an enhanced electrochemical response in aqueous electrolyte media. A binary Mn3O4 + ZnMn2O4 phase achieved a high specific capacitance of 238 F/g at 0.5 A/g in a 1 V potential window. This material displayed 80.5 % rate capability at 10 A/g, and excellent capacitance retention (97 %) after 5000 consecutive GCD cycles. Furthermore, the work evidences that the concentration of zinc in the ZnMn2O4 structure can enlarge the active potential window up to 1.2 V, keeping high-rate reversibility. These electrodes reached a specific capacitance of 175 F/g at 0.5 A/g, 84 % rate capability at 10 A/g, and 78 % capacitance retention after 5000 consecutive GCD cycles. A comprehensive electrochemical study was performed to extract information on the energy storage mechanisms of the developed Manganese-based materials.