Enhancement effect of Na ions on capacitive behavior of amorphous MnO₂
By Ye, Qinglan; Dong, Ruiting; Xia, Zihao; Chen, Guoren; Wang, Haili; Tan, Guojin; Jiang, Li & Wang, Fan
Published in Electrochimica Acta
2014
Abstract
Na⁺-intercalated MnO₂ is synthesized via hydrothermal reduction. For comparison, the pristine and K⁺-intercalated MnO₂ are also synthesized and characterized. Cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy methods have been carried out to study the electrochemical properties of the obtained MnO₂ electrode. Na⁺-intercalated MnO₂ electrode shows the improved Na⁺ diffusion coefficient and electrical conductivity, which is suitable for supercapacitor. A specific capacitance (based on Na⁺-intercalated MnO₂) of 295 F·g⁻¹ at a current density of 1 A·g⁻¹ is obtained in Na₂SO₄ aqueous solution. Such results suggest that pre-intercalation of alkaline cations into Mn oxides is an effective method to enhance the electrochemical activity in alkaline electrolytes. Moreover, an all-solid-state symmetric supercapacitor based on Na⁺-intercalated MnO₂ electrode is assembled and tested.