Synergy between MgO and TiO2 doped with Mn2+ ions for supercapacitor applications

Supercapacitors are unique energy storage devices that bridge the gap between Li-ion batteries and conventional capacitors with higher power/energy densities, longer life cycles, and more rapid charge/discharge rates. Research efforts are concentrated on optimizing the performance of supercapacitors (SCs), addressing a crucial component of these devices: the electrode materials, which should provide large active surface areas, display high electrical conductivities, and possess stable chemical properties. To achieve this, in this study, undoped and Mn-doped MgO−TiO₂ nanocrystals and coffee-waste-derived carbon were used as electrode materials for symmetric and asymmetric supercapacitors yielding adequate performance. The structural study was performed by X-ray diffraction and Raman analysis, showing a phase mixture of tetragonal Anatase TiO₂, cubic MgO, and orthorhombic MgTi₂O₅ nanocrystals. Electron paramagnetic resonance and photoluminescence spectroscopy analysis were used to provide insight into the defective structure of the composites. The electrochemical performance was tested by cyclic voltammetry, impedance, voltage holding, and galvanostatic cycling with potential limitations. The SCs exhibited promising results for specific capacitances up to 100 and 221 F/g for symmetric and asymmetric (containing coffee-waste-derived carbon as a counter electrode) supercapacitor devices, respectively. At the same time, enhanced energy and power density values of 30.7 Wh/kg and 122.8 kW/kg were reached.