Main focus of the innovation associate in the past year was on the finding ways of extending the potential window of the hybrid electrolyte as well as finding proper gelling agents for both hybrid and organic electrolytes.
Among the reported transition metal oxides, manganese oxide is an attractive supercapacitor electrode material due to its large earth abundancy, low cost, environment benignity, well-established synthesis methods, and its OER overpotential is higher in neutral pH medium. Based on the literature survey, Na0.5MnO2 is a material that can help to improve the operating potential window of the supercapacitor in the positive range. This material can be synthesized by chemical, hydrothermal and electrochemical methods. Making a composite of this metal oxide with carbon material is helpful in order to increase the conductance of the electrode material.
In this project, after trying different methods for preparing Na0.5MnO2 we used hydrothermal method as most effective, one-step way. By compositing the Na0.5MnO2 with pistachio shell-derived carbon (PC) as positive electrode (1:1 mass ratio) and using PC as negative electrode, two-electrode supercapacitor with hybrid electrolyte showed an increase of 0.2 V in operating voltage and the cell voltage increased from 2.3 to 2.5 V. At the next step, by modifying the negative electrode material with sodium, with the purpose of pushing the hydrogen evolution reaction to the lower potentials, the cell potential increased up to 2.8 V at hybrid electrolyte. This increase in the cell voltage, resulted in about 50% increase in the energy density of the designed Na0.5MnO2-PC//Na+ doped-PC supercapacitor in comparison with the PC//PC symmetric supercapacitor.
