Study On Manganese Oxides Electrochemical Capacitors

Supercapacitor, also known as electrochemical capacitor,is an efficient energystorage device with the advantages of high specific capacitance,high power densityand long cycling life.Research on electrode material is one of the most effective waysto improve theirelectrochemical performance.In this paper, mesoporous manganese oxides were synthesized via a facilechemical deposition strategy. Three kinds of basic precipitants including sodiumcarbonate (Na2CO3), sodium bicarbonate (NaHCO3), and sodium hydroxide (NaOH)were employed to adjust the microstructures and surface morphologies of MnO2materials. The obtained MnO2materials display different microstructures. Greatdifferences are observed in their specific surface area and porosity properties. TheMnO2prepared with Na2CO3precipitant exhibits the optimal microstructures andsurface morphologies compared with the other two samples, contributing to their bestelectrochemical performances for supercapacitors when conducted either in the singleelectrode tests or in the capacitor measurements. Moreover, this paper also involvesInvestigation on the performance of aqueous manganese oxides electrochemicalcapacitors at low temperature.Three different crystal phases (δ,γ and α) of MnO2wereprepared by redox, solid reaction and hydrothermal routes,respectively. The δ-MnO2prepared by a redox method exhibits the best electrochemical performances as thetemperature decreased from25℃down to the extremely low temperature of35℃. Itis also an interesting discovery that the low temperature has more effect on the chargetransfer resistance than diffusion resistance. To some degree,these results haveguiding significance for the low-temperature applications of manganese oxideselectrochemical capacitors.