One-step preparation of sheet-like α-Ni(OH)2 composite multi-walled carbon nanotubes for high-performance asymmetric supercapacitors

The composite alpha-Ni(OH)2@CNT of multi-walled carbon nanotubes (CNT) and sheet-like alpha-Ni(OH)2 was prepared by a one-step hydrothermal method. The structures and electrochemical properties of alpha-Ni(OH)2@CNT and alpha-Ni(OH)2 have been studied in detail. Since hydroxylated CNT was used in this study, CNT provides the dual role of dispersion and conductivity for alpha-Ni(OH)2@CNT. The structural characterization shows that the thickness of alpha-Ni(OH)2@CNT nanosheets is significantly lower than that of alpha-Ni(OH)2, and the specific surface area and pore volume are significantly higher than that of alpha-Ni(OH)2, which provides more active sites for the composites. The electrochemical test results show that the specific capacitance and rate performance of alpha-Ni(OH)2@CNT are much higher than that of alpha-Ni(OH)2. The asymmetric supercapacitor (ASC) assembled with alpha-Ni(OH)2@CNT and activated carbon (AC) can provide an energy density of 42.8 Wh kg-1 at a power density of 800 W kg-1, and the specific capacity can be maintained by 80% after 20,000 cycles, showing good application value. The theoretical calculation results further confirm that CNT increases the conductivity of alpha-Ni(OH)2@CNT. This work provides a low cost and effective modification method for the practical application of alpha-Ni(OH)2.