Improved pseudocapacitive performance and cycle life of cobalt hydroxide on an electrochemically derived nano-porous Ni framework

Abstract

The pseudocapacitance and morphology of an electrodeposited cobalt hydroxide (Co(OH) 2) significantly depends on the architecture of the electrode substrate. The nano-porous Ni framework, derived from the selective dissolution of Cu from a Ni–Cu alloy, effectively promotes the electrochemical utilization of deposited Co(OH) 2 even at a high loading amount condition. The great electronic and ionic conduction within the nano-structured electrode improves the energy storage performance of Co(OH) 2 as compared to that for a conventional flat Ni substrate. In this work, the Co(OH) 2 mass specific capacitance, evaluated using cyclic voltammetry (CV), only slightly decreases from 2650 to 2470 F g −1 when the potential sweep rate is substantially increased from 5 to 200 mV s −1. The developed Ni(OH) 2/NiOOH (from the nano-porous framework) incorporates with the deposited Co(OH) 2 upon CV cycling; the mixed hydroxide shows a noticeably synergistic capacitance. Furthermore, the dissolution of Co(OH) 2 in KOH electrolyte is greatly suppressed due to the incorporation of Ni(OH) 2/NiOOH, consequently prolonging the electrode cycle life.