High performance asymmetric supercapacitor based on MnO2electrode in ionic liquid electrolyte

Abstract

In this work, the electrochemical properties of a MnO₂ nanocomposite electrode were investigated in 1-butyl-3-methyl-imidazolium hexafluorophosphate ([Bmim]PF₆)/N,N-dimethylformamide (DMF) electrolyte. The [Bmim]PF₆/DMF electrolyte with different volume fractions exhibits significant influence on the electrochemical properties of the electrode. When the volume ratio of [Bmim]PF₆ and DMF was 1 : 1, the electrode showed the best electrochemical performance. The operation potential window of the MnO₂ nanocomposite electrode in ionic liquids was 2.1 V and the specific capacitance according to the mass of MnO₂ was 523.3 F g⁻¹ at 3 A g⁻¹. Then, a high-voltage (3 V) MnO₂ asymmetric supercapacitor was successfully fabricated, using the MnO₂ nanocomposite electrode, activated carbon and [Bmim]PF₆/DMF as the positive electrode, negative electrode and electrolyte, respectively. The MnO₂ asymmetric supercapacitor displayed a maximum specific energy of 67.5 W h kg⁻¹ at a specific power of 593.8 W kg⁻¹ and a maximum specific power of 20.4 kW kg⁻¹ at a specific energy of 8.5 W h kg⁻¹. The impressive results showed that [Bmim]PF₆/DMF could be a promising electrolyte for MnO₂ supercapacitors.