Oxygen vacancy-rich flower-like nickel cobalt layered double hydroxides for supercapacitors with ultrahigh capacity

One of the main difficulties for high-performance supercapacitors (SCs) is to design rational structures with excellent electrochemical properties. Herein, oxygen vacancy-rich nickel-cobalt layered double hydroxide, which has excellent supercapacitor performance, is prepared through an electrodeposition procedure and in situ oxidation process on nickel foam substrate. The conductivity and electrochemical properties are significantly improved by oxygen vacancies, which can be adjusted via hydrogen peroxide treatment. NiCo-LDH with oxygen vacancy (Ov-NiCo-LDH) attains a superior specific capacity of 1160 C g−1 at the current density of 1 A g−1 and shows a good capacity retention rate (61% of its original specific capacity is left at 20 A g−1). Significantly, when the power density is 1.75 kW kg−1, the energy density of the assembled symmetric supercapacitor (SSC) device is up to 216.19 Wh·kg−1. This vacancy engineering strategy is helpful to the design of active materials for energy storage devices in the future.