The effects of Ni ions' charge disproportionation on the high electrochemical performance of Ni1−xCoxO nanoparticles

Abstract

Ni_1−xCo_xO nanoparticles were synthesized by a solution diffusion synergistic capture doping method and subsequent heat treatment. The charge disproportionation of the Ni ions promoted the REDOX reaction of Ni_1−xCo_xO electrode materials and improved their electrochemical performance. After incorporating Co atoms into the NiO structure, the average valence state of Ni ions increased by 0.1645. The doping of Co atoms also caused the redistribution of interfacial charge, reduced the polarization of the electrode and increased the specific capacitance of the electrode material. The Ni_1−xCo_xO (x = 0.055) electrode material not only manifested a large specific capacitance of 1665.3 F g⁻¹, even at a current density of 1.0 A g⁻¹, but also demonstrated fine rate properties, with 1049.3 F g⁻¹ at a current density of 10 A g⁻¹. The Ni_1−xCo_xO (x = 0.055) electrode material also displayed an excellent rate capacity and high capacitance retention of 90.80% after 50 000 cycles at a current density of 10 A g⁻¹. The outstanding electrochemical properties of Ni_1−xCo_xO electrode materials can be attributed to the Ni ion charge disproportionation, which was caused by Co atom doping. The Ni_1−xCo_xO (x = 0.055) nanoparticles with outstanding electrochemical performance could be a promising candidate as an electrode material for supercapacitor applications.