Improved electrochemical stability of NixCo2x(OH)6x/NiCo2O4 electrode material

NixCo2x(OH)(6x) decorated NiCo2O4 (NixCo2x(OH)(6x)/NiCo2O4) is synthesized by hydrothermal treatment and electrochemical deposition to improve electrochemical stability of NixCo2x(OH)(6x) during charge-discharge process. NiCo2O4 with unique nanoflower structure and good conductivity is used as suitable supporting skeleton to stabilize NixCo2x(OH)(6x). NixCo2x(OH)(6x)/NiCo2O4 exhibits high specific capacitance of 827.1 F g(-1) at 1 A g(-1). The long-term cycling stability is obvious improved from 43.3% for NixCo2x(OH)(6x) to 97.8% for NixCo2x(OH)(6x)/NiCo2O4 after 2000 cycles at 20 A g(-1). Low capacitance decay of 42.9% is achieved for NiCo2O4/NixCo2x(OH)(6x) when current density increased from 1 to 50 A g(-1), indicating the improved rate capability. The mechanism of NixCo2x(OH)(6x)/NiCo2O4 with high electrochemical stability is proposed. TiN nanotube array with superior conductivity is adopted as negative electrode to match well with NixCo2x(OH)(6x)/NiCo2O4 positive electrode. All-solid-state asymmetrical supercapacitor based on NixCo2x(OH)(6x)/NiCo2O4 and TiN electrodes achieves high energy density of 35.1 W h kg(-1) at a power density of 900 W kg(-1) and an expanded voltage window of 1.8 V, indicating potential application for energy storage. (C) 2017 Elsevier B.V. All rights reserved.