Inkjet Printing of MnO 2 Nanoflowers on Surface-Modified A4 Paper for Flexible All-Solid-State Microsupercapacitors.

Printing technologies are gaining growing attention as a sustainable route for the fabrication of high-performance and flexible power sources such as microsupercapacitors (MSCs). Here, the inkjet printing method is utilized for the fabrication of manganese dioxide (MnO)-based, flexible all-solid-state MSCs on surface-modified A4 paper substrate. The appropriate rheology of the formulated ethanol-based ink (Fromm number <10) and the proper dimensions of MnO nanoflowers (average size ∼600 nm) ensure a reliable inkjet printing process. Moreover, the underlying graphene/Ag nanowire pattern serves as a primer and highly conductive ( < 2 Ω sq) layer on top of the paper to facilitate the anchoring of MnO nanoflowers and rapid electron transportation. The resulting all-solid-state MSCs deliver a maximum areal capacitance of 0.68 mF cm at a current density of 25 μA cm, reasonable durability (>80% of capacity remained after 3000 cycles), and remarkable foldability. Additionally, the inkjet-printed MSC devices deliver a superior areal energy density of 0.01 μWh cm and also a power density of 1.19 μW cm. This study demonstrates the power of the inkjet printing method to produce MSCs on flexible substrates, which have great potential for flexible/wearable electronics.