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

Ni x Co 2x (OH) 6x decorated NiCo 2 O 4 (Ni x Co 2x (OH) 6x /NiCo 2 O 4 ) is synthesized by hydrothermal treatment and electrochemical deposition to improve electrochemical stability of Ni x Co 2x (OH) 6x during charge-discharge process. NiCo 2 O 4 with unique nanoflower structure and good conductivity is used as suitable supporting skeleton to stabilize Ni x Co 2x (OH) 6x . Ni x Co 2x (OH) 6x /NiCo 2 O 4 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 Ni x Co 2x (OH) 6x to 97.8% for Ni x Co 2x (OH) 6x /NiCo 2 O 4 after 2000 cycles at 20 A g −1 . Low capacitance decay of 42.9% is achieved for NiCo 2 O 4 /Ni x Co 2x (OH) 6x when current density increased from 1 to 50 A g −1 , indicating the improved rate capability. The mechanism of Ni x Co 2x (OH) 6x /NiCo 2 O 4 with high electrochemical stability is proposed. TiN nanotube array with superior conductivity is adopted as negative electrode to match well with Ni x Co 2x (OH) 6x /NiCo 2 O 4 positive electrode. All-solid-state asymmetrical supercapacitor based on Ni x Co 2x (OH) 6x /NiCo 2 O 4 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. [ABSTRACT FROM AUTHOR]