As energy demands continue to rise, it becomes imperative to develop efficient energy storage devices with high energy and power density. At the same time, the space inside devices continues to shrink, making energy storage devices which possess not only high energy/power density, but also an adjustable shape to fit into various form factors an ideal solution. Energy storage devices made from flexible electrodes are attractive in a roll-up or surface-conformed format to minimize space usage. A mechanically flexible CNT supercapacitor electrode is demonstrated, as well as a lithium-ion battery electrode using a high-surface area silicon-conformally-coated CNT forest. The CNT supercapacitor electrode is demonstrated using a water solution-assisted film lift-off and densification process. This electrode exhibits the following three features: (1) each CNT has a natural contact to its as-fabricated current-collecting metal layer; (2) the CNTs and the bottom metal layer are intact during the water-assisted lift-off process; and (3) the in-situ liquid evaporation and densification process naturally occurs to dramatically increase volumetric energy density. Because of the ability of the film to be lifted off of its original growth substrate, the application for same-chip CMOS energy storage devices is feasible. In addition, this flexible CNT supercapacitor electrode has the potential to conform to various surfaces, as well as to be implemented in devices which are required to bend with use, such as in roll-up electronics.
Project end date: 02/04/15