Fabrication of oxygen-vacancy abundant NiAl-layered double hydroxides for ultrahigh capacity supercapacitors

The manipulation of oxygen vacancies is regarded as a viable approach to enhance the electrochemical properties of electrode materials. Herein, NiAl-LDH nanosheets with rich oxygen vacancies were successfully synthesized on the surface of nickel foam <i>via</i> a conventional hydrothermal and chemical reduction strategy. The oxygen vacancies were introduced and modulated <i>via</i> NaBH₄ treatment, significantly enhancing the electrochemical properties. The oxygen-vacancy abundant NiAl-LDH electrode materials show a high capacitance of 4028 mF cm^-2 at the current density of 2 mA cm^-2 and obtain a high capacity retention of 3000 mF cm^-2 even at a current density of up to 20 mA cm^-2. In addition, the symmetric SC device achieves a notable energy density of 71.3 W h kg^-1 while operating at a power density of 2400 W kg^-1. The empirical and theoretical findings demonstrate that the incorporation of oxygen vacancies significantly contributes to the improvement of the electrochemical characteristics of LDH electrode materials. The samples discussed in this work have the potential to serve as advanced electrode materials for supercapacitors in high-capacity energy storage devices.