Preparation of Ni-Al layered double hydroxide hollow microspheres for supercapacitor electrode

In this study, Ni-Al layered double hydroxide (NiAl-LDH) hollow microspheres with a high surface area and large pore volume were prepared using Al2O3 hollow microspheres composed of Al2O3 nanosheets as templates. During a mild microwave-assisted hydrothermal process, the Al2O3 nanosheets transformed to NiAl-LDH nanosheets without any damage to the assembled hollow spherical structure. The as-prepared NiAl-LDH hollow microspheres exhibited a high specific capacitance (1578F g−1 at a current density of 1 A g−1) and good cycling performance (capacitance retention of 93.75% after 10,000 cycles). Moreover, an asymmetric supercapacitor was successfully assembled using the synthesized hollow microspheres as the positive electrode and activated carbon nanofibers as the negative electrode. The supercapacitor device achieved a relatively high energy density and power density (energy densities of 20 Wh kg−1 and 6.6 Wh kg−1 at power densities of 0.75 kW kg−1 and 11.25 kW kg−1, respectively).