Materials and technologies for multifunctional, flexible or integrated supercapacitors and batteries

Electrochemical energy storage has become a key part of portable medical and electronic devices, as well as ground and aerial vehicles. Unfortunately, conventionally produced supercapacitors and batteries often cannot be easily integrated into many emerging technologies such as smart textiles, smart jewelry, paper magazines or books, and packages with data-collection or other unique capabilities, electrical cables, flexible wearable electronics and displays, flexible solar cells, epidermal sensors, and others in order to enhance their design aesthetics, convenience, system simplicity, and reliability. In addition, conventional energy storage devices that cannot conform to various shapes, are typically limited to a single function, and cannot additionally provide, for example, load bearing functionality or impact/ballistic protection to reduce the system weight or volume. Commercial devices cannot be activated by various stimuli, be able to self-destroy or biodegrade over time, trigger drug release, operate as sensors, antennas, or actuators. However, a growing number of future technologies will demand batteries and hybrid devices with the abilities to seamlessly integrate into systems and adapt to various shapes, forms, and design functions. Here we summarize recent progress and challenges made in the development of mostly nanostructured and nanoengineered materials as well as fabrication routes for energy storage devices that offer (i) multifunctionality, (ii) mechanical resiliency and flexibility and (iii) integration for more elegant, lighter, smaller and smarter designs. The geometries of device structures and materials are considered to critically define their roles in mechanics and functionality. With these understandings, we outline a future roadmap for the development, scaleup, and manufacturing of such materials and devices.