Asymmetric capacitors based on TiO2 and mesoporous MnO2 electrodes using neutral aqueous electrolyte

Asymmetric capacitor based on TiO2 with the size range from 90 to 410 nm and mesoporous MnO2 (ca. 200-380 nm) electrodes has been successfully constructed and characterized in LiClO4 aqueous electrolyte. The samples of both metal oxides were fully characterized by scanning electron microscopy (SEM), Xray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), N-2 adsorption-desorption, and so on. The electrochemical capacitive performances of both electrode materials were evaluated by cyclic voltammetry and galvanostatic charge-discharge in 1 mol/L LiClO4 with a working voltage of 2.0 V. The discharge profile of the asymmetric capacitor exhibited an excellent capacitive behavior and good cycling stability after 2000 cycles. Moreover, the TiO2//MnO2 asymmetric capacitor possesses both higher energy density and power density (7.7 Wh/kg, 762.5 W/kg) than that of Maxsorb//Maxsorb symmetrical capacitor (7.0 Wh/kg, 400.0 W/kg).