Printable Zinc-Ion Hybrid Micro-Capacitors for Flexible Self-Powered Integrated Units

Wearable self-powered systems integrated with energy conversion and storage devices such as solar-charging power units arouse widespread concerns in scientific and industrial realms. However, their applications are hampered by the restrictions of unbefitting size matching between integrated modules, limited tolerance to the variation of input current, reliability, and safety issues. Herein, flexible solar-charging self-powered units based on printed Zn-ion hybrid micro-capacitor as the energy storage module is developed. Unique 3D micro-/nano-architecture of the biomass kelp-carbon combined with multivalent ion (Zn²⁺) storage endows the aqueous Zn-ion hybrid capacitor with high specific capacity (196.7 mAh g^-1 at 0.1 A g^-1). By employing an in-plane asymmetric printing technique, the fabricated quasi-solid-state Zn-ion hybrid micro-capacitors exhibit high rate, long life and energy density up to 8.2 μWh cm^-2. After integrating the micro-capacitor with organic solar cells, the derived self-powered system presents outstanding energy conversion/storage efficiency (η_overall = 17.8%), solar-charging cyclic stability (95% after 100 cycles), wide current tolerance, and good mechanical flexibility. Such portable, wearable, and green integrated units offer new insights into design of advanced self-powered systems toward the goal of developing highly safe, economic, stable, and long-life smart wearable electronics.