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

Abstract

Abstract 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\xa0mA cm−2, which is higher than that of the sheet-like NiCo2O4@NiCo-LDHs (NiCo2O4@NiCo-LDH-S) (5180 mF cm−2 at 1\xa0mA cm−2) and flower-like NiCo2O4@NiCo-LDHs (NiCo2O4@NiCo-LDH-F) (4504 mF cm−2 at 1\xa0mA 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\xa0Wh kg−1 at 0.85\xa0kW 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.