Study of capacitive properties for LT-Li4Mn5O12 in hybrid supercapacitor

Spinel Li4Mn5O12 nanoparticles have been prepared by a very simple sol–gel method. Various initial conditions were studied in order to find the optimal conditions for the synthesis of pure Li4Mn5O12. X-ray diffraction results showed that spinel Li4Mn5O12 was obtained at a low temperature of 300 °C without any miscellaneous phase. Scanning electron microscope analyses indicated that the prepared Li4Mn5O12 powders had a uniform morphology with average particle size of about 50 and 100 nm. The prepared sample was firstly used as a cathode material in an asymmetric Li4Mn5O12/AC supercapacitor in aqueous electrolyte. The capacitive properties of the hybrid supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests. The results showed that Li4Mn5O12 annealed at 450 °C for 4 h exhibited the best electrochemical capacitive performance within the potential range of 0–1.4 V in 1 M Li2SO4 solution. A maximum specific capacitance of 43 F g−1 based on the total active material weight of the two electrodes was obtained for the Li4Mn5O12/AC supercapacitor at a current density of 100 mA g−1. The capacitor showed excellent cycling performance and structure stability via 1,000 cycles.