Binary metal hydroxide nanorods and multi-walled carbon nanotube composites for electrochemical energy storage applications

Carbon nanotube and metal oxide/hydroxide hybrids have attracted much interest as electrode materials for electrochemical supercapacitors because of their dual storage mechanism. They can complement or replace batteries in electrical energy storage and harvesting applications, where high power delivery or uptake is needed. Multi-walled carbon nanotube (MWCNT) and nickel–cobalt binary metal hydroxide nanorod hybrids have been developed through the chemical synthesis of binary metal hydroxide on a MWCNT surface. These hybrids show enhanced supercapacitive performance and cycling ability. Growth of a thin film consisting of a coating of binary metal hydroxide, as well as further growth of nanorod structures, is demonstrated using FESEM and TEM, showing that this film is a promising structure for supercapacitor applications. These electrodes yield a significantly high capacitance of 502 F g−1 with a high energy density of 69 W h kg−1 at a scan rate of 5 mV s−1. The film is stable up to 5000 cycles with greater than 80% capacitance retention.