All-inkjet-printed, solid-state flexible supercapacitors on paper

The forthcoming ubiquitous innovations driven by flexible/wearable electronics and Internet of Things (IoT) have inspired the relentless pursuit of advanced power sources with versatile aesthetics. Here, we demonstrate a new class of solid-state flexible power sources that are fabricated directly on conventional A4 paper using a commercial desktop inkjet printer. A salient feature of the inkjet-printed power sources is their monolithic integration with paper, i.e., they look like inkjet-printed letters or figures that are commonly found in office documents. A supercapacitor (SC), which is composed of activated carbon/carbon nanotubes (CNTs) and an ionic liquid/ultraviolet-cured triacrylate polymer-based solid-state electrolyte, is chosen as a model power source to explore the feasibility of the proposed concept. Cellulose nanofibril-mediated nanoporous mats are inkjet-printed on top of paper as a primer layer to enable high-resolution images. In addition, CNT-assisted photonic interwelded Ag nanowires are introduced onto the electrodes to further improve the electrical conductivity of the electrodes. The inkjet-printed SCs can be easily connected in series or parallel, leading to user-customized control of cell voltage and capacitance. Notably, a variety of all-inkjet-printed SCs featuring computer-designed artistic patterns/letters are aesthetically unitized with other inkjet-printed images and smart glass cups, underscoring their potential applicability as unprecedented object-tailored power sources.