Oxygen-vacancy-rich nickel-cobalt layered double hydroxide electrode for high-performance supercapacitors

The introduction of oxygen vacancies into electrode materials has been proven to be a valid way to enhance the electrochemical performance. However, the traditional methods to introduce oxygen vacancies require severe conditions that may be harmful to hydroxides. Herein, the oxygen vacancy-rich nickel-cobalt (NiCo) layered double hydroxide (denoted as V_o-NiCo LDH) nanowire array electrode is synthesized using the chemical reduction method. Owing to the reduction of NaBH₄ solution, we can create oxygen vacancies under milder conditions, thus avoiding any damage to the hydroxide. The as-synthesized electrode shows a specific capacitance of 1563.1 F g⁻¹ at 1 A g⁻¹, which is much higher than that of the pristine electrode (995.4 F g⁻¹ at 1 A g⁻¹). Moreover, the cycling performance and rate performance are also enhanced. The as-fabricated asymmetric supercapacitor (V_o-NiCo LDH//Fe₂O₃) is able to deliver a maximum energy density of 56.2 W h kg⁻¹ at a power density of 800 W kg⁻¹ with a voltage window of 1.6 V.