In Situ Growth and Electrochemical Activation of Copper-Based Nickel–Cobalt Hydroxide for High-Performance Energy Storage Devices

Herein, an effective electrochemical activation strategy is designed to enhance the overall energy storage performance of copper-based (Cu-based) nickel–cobalt hydroxide (NiCo–OH). The long-term cyclic voltammetry (CV) cycling process in an alkaline electrolyte triggered the in situ transformation from Cu-doped NiCo–OH (Cu/NiCo–OH) to electrochemically activated CuO-doped NiCo–OH (EA-CuO/NiCo–OH) on a porous Cu foam (CF) substrate, together with the significantly increased charge storage capacity. Benefiting from fast electron/ion transfer, abundant surface defects, and powerful synergistic effect contributed by the unique self-supported heterostructure, the EA-CuO/NiCo–OH electrode can achieve a high areal capacity of 4.186 C cm–2 under 5 mA cm–2, with excellent rate performance (67.5% of initial capacity under 50 mA cm–2) and long life span (84.8% of initial capacity after 5000 cycles). The as-fabricated EA-CuO/NiCo–OH//AC hybrid supercapacitor device shows a maximum energy density of 0.648 mW h cm–2 and an outstanding cycling stability (93.4% of initial capacity after 8000 cycles). The superior energy storage performance underpins the high potential of the reported electrochemical activation strategy for developing advanced Cu-based and bimetallic hydroxide-derived electrode materials.