We have successfully fabricated flexible asymmetric supercapacitors (ASCs) based on acicular Co9S8 nanorod arrays as positive materials and Co3O4@RuO2 nanosheet arrays as negative materials on woven carbon fabrics. Co9S8 nanorod arrays were synthesized by a hydrothermal sulfuration treatment of acicular Co3O4 nanorod arrays, while the RuO2 was directly deposited on the Co3O4 nanorod arrays. Carbon cloth was selected as both the substrate and the current collector for its good conductivity, high flexibility, good physical strength, and lightweight architecture. Both aqueous KOH solutions and polyvinyl alcohol (PVA)/KOH were employed as electrolyte for electrochemical measurements. The as-fabricated ASCs can be cycled reversibly in the range of 0-1.6 V and exhibit superior electrochemical performance with an energy density of 1.21 mWh/cm(3) at a power density of 13.29 W/cm(3) in aqueous electrolyte and an energy density of 1.44 mWh/cm(3) at the power density of 0.89 W/cm(3) in solid-state electrolyte, which are almost 10-fold higher than those reported in early ASC work. Moreover, they present excellent cycling performance at multirate currents and large currents after thousands of cycles. The high-performance nanostructured ASCs have significant potential applications in portable electronics and electrical vehicles.

Integrated nanodevices with the capability of storing energy are widely applicable and have thus been studied extensively. To meet the demand for flexible integrated devices, all-solid-state asymmetric supercapacitors that simultaneously realize energy storage and optoelectronic detection were fabricated by growing Co3 O4 nanowires on nickel fibers, thus giving the positive electrode, and employing graphene as both the negative electrode and light-sensitive material. The as-assembled integrated systems were characterized by an improved energy storage, enhanced power density (at least by 1860 % enhanced) by improving the potential window from 0-0.6 V to 0-1.5 V, excellent photoresponse to white light, and superior flexibility of both the fiber-based asymmetric supercapacitor and the photodetector. Such flexible integrated devices might be used in smart and self-powered sensory, wearable, and portable electronics.

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