Development of Silicon-Embedded Supercapacitors Utilizing Atomic Layer Deposition and Plasma-Enhanced Chemical Vapor Deposition for Functionalization of Carbon Nanotube Electrodes

Supercapacitors utilizing carbon nanotube (CNT) electrodes are next-generation energy storage systems. Various CNT functionalization and graphenation processes can enhance carbon nanotube charge densities, while room-temperature ionic liquids can enhance supercapacitor performance. Functionalization by atomic layer deposition of titania provides pseudocapacitive energy storage mechanisms, while graphenation increases the surface area of the electrodes. Utilizing patented silicon etch methods, a silicon-integrated structure was developed with functionalization and graphenation of the CNTs. The supercapacitors with CNT forests functionalized by titania have a specific energy of 39.4 Wh/kg, those with graphenated CNT forests have a specific energy of 26.0 Wh/kg, and the supercapacitors with both functionalizations have a specific energy of 63.4 Wh/kg. Compared to the supercapacitors using bare CNT forests, which have a specific energy of 2.6 Wh/kg, these results show that the addition of these functionalizations significantly improves the device performance.