Electrochemical performance of a high cation-deficiency Li 2Mn 4O 9/active carbon supercapacitor in LiNO 3 electrolyte

Abstract

A hybrid supercapacitor based on spinel Li 2Mn 4O 9 and activated carbon (AC) was fabricated. The electrochemical performance of the capacitor was studied by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge in different aqueous electrolytes such as 1 M LiNO 3, Li 2SO 4, NaNO 3 and KNO 3 solution. A maximum specific capacitance of 261 F g −1 was obtained for the Li 2Mn 4O 9 single electrode between 0 and 1.4 V. The Li 2Mn 4O 9/AC hybrid supercapacitor showed a sloping voltage profile from 0 to 1.4 V and delivered an energy density of 53 Wh kg −1 based on the total weight of the active electrode materials. The hybrid capacitor exhibited a desirable profile and maintained over 80% of its initial energy density after 1000 cycles, indicating that Li 2Mn 4O 9 has excellent cycling performance and structural stability in aqueous electrolyte. The hybrid supercapacitor also exhibited an excellent rate capability, even at a power density of 1250 W kg −1, it had a specific energy 29 Wh kg −1 compared with 48 Wh kg −1 at the power density of about 417 W kg −1.