Water-promoted zeolitic imidazolate framework-67 transformation to Ni-Co layered double hydroxide hollow microsphere for supercapacitor electrode material

Hollow Ni-Co layered double hydroxide (LDH) was synthesized with rhombic dodecahedral zeolitic imidazolate framework-67 (ZIF-67) as self-sacrificed template and cobalt precursor. Water was found to be very important role on the formation of Ni-Co LDH hollow microstructure. As a supercapacitor electrode material, the obtained hollow Ni-Co LDH delivered a high specific capacitance of 1530 F g(-1) at the current density of 1.0 A g(-1) and good cycle performance, which can be ascribed to its hollow mesoporous structure composed of the Ni-Co LDH nanosheets and high specific surface area. Combined with the AC negative electrodes, the assembled asymmetric supercapacitors performed an energy density of 27.5 Wh kg(-1) at the power density of 375 W kg(-1).