Improved asymmetric electrochemical capacitor using Zn-Co co-doped Ni(OH)(2) positive electrode material

Abstract

The performance of Ni-foam pasted Ni(OH)(2) prepared from co-precipitated Ni(OH)(2) with Zinc (Zn) and Cobalt (Co) as the positive electrode active material of an asymmetric electrochemical capacitor (EC) is studied for the enhancement of the capacitor's specific energy and power densities. A co-precipitated Ni(OH)(2)/activated carbon (AC) composite material and AC were used as a positive and negative electrode material. The AC in the positive electrode is used as an electrolyte reservoir to reduce ionic diffusion resistance regardless of charge/discharge current density. In addition, the simultaneous presence of Zn and Co ions in the Ni(OH)(2) layer improves the efficiency of the active material and reduces the resistance of the unit cell. It was observed that through the effects of the additives in the positive electrode, the asymmetric EC exhibits a high energy density with 35.7 Wh/kg, based on the active material. Furthermore, the energy density decreasing behavior at a high discharge current density was retarded.