Paper-based all-solid-state flexible micro-supercapacitors with ultra-high rate and rapid frequency response capabilities

Paper-based flexible supercapacitors (SCs) have attracted great attention as they enable the realization of next-generation bendable, light-weight, and environmentally-friendly portable electronics. However, conventional paper-based SCs adopt a sandwich-like structure suffering from poor rate performance, slow frequency response and difficulty in direct integration with other micro-devices. We report here for the first time paper-based all-solid-state flexible planar micro-supercapacitors (MSCs) using poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)-CNT/Ag as the electrode material by the inkjet printing technique. The as-fabricated paper-based all-solid-state flexible MSCs deliver the best rate capability among all reported paper-based MSCs/SCs (up to 10 000 mV s^-1), fast frequency response (relaxation time constant τ₀ = 8.5 ms), high volumetric specific capacitance (23.6 F cm^-3) and long cycle stability (92% capacitance retention after 10 000 cycles), which shows a strong dependence on the film thickness and the interdigitated spacing between neighbouring fingers, respectively. Furthermore, the series and parallel connections reveal that the as-prepared paper-based MSCs obey the basic theorem of series and parallel connections of capacitors, respectively. The combination of the simple fabrication technology and excellent performances presented here not only make paper-based all-solid-state flexible MSCs an attractive candidate for powering future flexible portable electronics, but also provide important references for the design and fabrication of other high-performance flexible energy storage devices.