Hydrothermal synthesis and electrochemical characterization of mesoporous NixCo3-xO4 (0 ≤ x ≤ 1) nanorods as electrode materials for high-performance electrochemical capacitors

High-performance spinel nickel cobaltite (NixCo3-xO4; 0 ≤ x ≤ 1) nanorods with various nickel content were prepared using a facile hydrothermal method and subsequent calcination treatment. The structure and morphology of the obtained nanorods were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption measurement. The nickel cobaltite nanorods consisted of numerous small nanocrystals, forming a porous structure. The diameter of these nanocrystals was decreased with increasing the Ni/Co molar ratio. Among all of the electrodes, the Ni0.75Co2.25O4 electrode exhibited excellent pseudocapacitive performance with the highest specific capacitance of 1078 F g− 1 at 2 A g− 1, excellent cycling stability (94.1% retention rate after 1000 cycles) and a superior rate capability with a capacity of 694 F g− 1 even at a high current density of 20 A g− 1.