Morphological control and electrochemical performance of NiCo2O4@NiCo layered double hydroxide as an electrode for supercapacitors

The rational tuning of the morphologies of transition metal compounds can effectively improve their electrochemical performance. In this study, NiCo2O4@NiCo-based layered double hydroxide (NiCo-LDH) composites with sheet-, grass-, and flower-like morphologies were facilely synthesized on carbon cloth by controlling the hydrothermal reaction time. The electrochemical performances of these three types of NiCo2O4@NiCo-LDHs were investigated and compared. The grass-like NiCo2O4@NiCo-LDHs (NiCo2O4@NiCo-LDH-G) exhibited a specific capacitance of 5810 mF cm−2 at 1 mA cm−2, which is higher than that of the sheet-like NiCo2O4@NiCo-LDHs (NiCo2O4@NiCo-LDH-S) (5180 mF cm−2 at 1 mA cm−2) and flower-like NiCo2O4@NiCo-LDHs (NiCo2O4@NiCo-LDH-F) (4504 mF cm−2 at 1 mA cm−2). Owing to the interconnected network structure and reduced impact of volume expansions, NiCo2O4@NiCo-LDH-G showed a better electrochemical performance than NiCo2O4@NiCo-LDH-S and NiCo2O4@NiCo-LDH-F. NiCo2O4@NiCo-LDH-G was further investigated for use as a positive electrode in an asymmetric supercapacitor (ASC). The constructed ASC exhibited a high specific energy of 81 Wh kg−1 at 0.85 kW kg−1 and an outstanding cycling stability of 88% capacitance retention after 5000 cycles, thereby demonstrating the promising application of this system in the energy storage field.