Two-Birds-One-Stone: Multifunctional Supercapacitors Beyond Traditional Energy Storage

The last decade has witnessed an extensive uptake of clean and sustainable energy sources to meet the surging energy demand while mitigating the increasing levels of greenhouse gas emission and air pollution. Among various energy systems, electrochemical energy storage devices such as batteries and supercapacitors have attracted worldwide attention for use in electric-powered transport, portable electronics, and biomedical devices. Recently, new multifunctional supercapacitors, which combine energy storage capability with load-carrying and other functions, offer a new "two-birds-one-stone" strategy for next-generation energy storage systems to store energy beyond the traditional systems. Multifunctional supercapacitors show great promise in reducing the size and volume of devices, improving the charge storage capacity, and minimising the cost in materials and fabrication while bringing the benefits of additional functions to the systems. This review describes the recent advances in multifunctional supercapacitors in terms of materials design, device configuration, system integration, and applications. The unique features of multifunctional supercapacitors depend strongly on architectural designs and system integration, which allow elimination of certain components to reduce the size and weight, thus improving the overall system performance. The review focuses specifically on multifunctional supercapacitors with novel mechanical, surface/interfacial, thermal, electronic, photodetection and energy harvesting/conversion functions. In addition, challenges and opportunities for further developments in the emerging field of multifunctional supercapacitors are suggested and discussed.