Flexible and stretchable electronics have attracted increasing attention over the past decade. Compared with traditional electronics, which based on rigid silicon chips, flexible and stretchable electronics can conform to complex surfaces and sustain large deformations without sacrificing their performance. An important component of flexible or stretchable electronics is energy storage, such as supercapacitors or batteries. Existing stretchable supercapacitors are characterized by complicated fabrication processes, low stretchability and high cost, constraining their potential applications. Due to their electrical characteristics and large surface areas, carbon materials, such as activated carbon, carbon nanotubes, and graphene, have been investigated for supercapacitor applications. In this work, we report two new kinds of flexible and stretchable supercapacitors made from carbon nanotube and hybrid carbon materials using a facile and low-cost method.

Stretchable electrodes were developed using vertically aligned carbon nanotube (CNT) forests grown on a silicon substrate by PECVD. The CNT forests were transferred to a prestretched elastomer substrate using a dry-transfer method. The CNT electrodes can be biaxially stretched up to 300% while maintaining good electrochemical performance. The area specific capacitance is enhanced almost 10x to more than 20mF/cm². CNT forests can form novel micro- and nano- patterns under uniaxial or biaxial prestrains, making it possible to use them as conductive hierarchical scaffolds for functionalization with pseudocapacitive materials, such as MnO₂ for better performance.

Aerosol jet printing and self-organized origami were used to fabricate a stretchable RGO/CNT/PEDOT: PSS supercapacitor. The unique direct-printing method gives the supercapacitor outstanding mechanical properties. No delamination was observed at the interface between the printed film and the substrate during the large deformation process.  The composite electrodes exhibited highly porous structures and high conductivity, which leads to good electrochemical performance: a large specific capacitance (150F/g), high rate capability (>95% at 5A/g compared to 0.1A/g), and high cyclability. Further, there was little performance degradation after hundreds of stretch-release cycles, indicating the excellent reliability of the stretchable devices.

Our designs and methods open a new way for fabricating future energy storage devices with high deformability, high performance and low cost.