NiCo layered double hydroxide nanocages for high-performance asymmetric supercapacitors

Herein, well-designed NiCo layered double hydroxide (NiCo-LDH) nanocages are prepared by a simple Cu 2 O template etching method. Due to their unique hollow structures and synergistic effects, NiCo-LDH-1 (molar ratio of Ni and Co is 1 : 1) nanocages exhibit superior capacitance (1671 F g −1 @1 A g −1 ) in a three-electrode system. In addition, a supercapacitor device is prepared with NiCo-LDH-1 nanocages as the cathode and active carbon (AC) as the anode which shows a maximum energy density of 59.0 W h kg −1 @935.7 W kg −1 power density and displays high cycling stability with a capacitance retention rate of 87.1% after 10 000 cycles at 10 A g −1 . A light emitting diode was powered by the assembled supercapacitor and remained illuminated for ∼12 min. In order to understand the charge storage mechanism of supercapacitors during the electrochemical charge/discharge process, the structure of NiCo-LDH-1 was studied in detail by in situ X-Ray Diffraction (XRD). NiCo-LDH nanocages with high specific capacity, energy densities and good capacity retention are prepared with a Cu 2 O template etching method.