Figure shows the cyclic voltammogram for a battery cell using OMIM-Br as an electrolyte, measured in the bias range of -1.4 to 1.4 V, at a scan rate of 0.001 Vs -1 . The galvanostatic charge-discharge curves for the same cell measured at a current of ±60 µA are plotted in Fig. . The black, blue, yellow and green curves in the top panel correspond to the chronopotentiograms measured upon charging at a positive current of +60 µA for 0.5, 1.0, 1.5, and 2.0 hours, respectively, and the respective discharge curves. The bottom panel shows the data measured with a negative charging current of -60 µA for 0.5, 1.0, 1.5, and 2.0 hours. Figure shows the positive discharge curves for the cell with OMIM-Br measured at currents of 60, 40, 20 and 10 µA, after charging at 60 µA for 1 hour. The corresponding specific capacitances are 3.84, 4.19, 3.74, and 3.13 mAh/g, and the energy densities are 2.25, 2.74, 2.41, and 1.76 Wh/kg, as plotted in the inset.