Layer-by-Layer Inkjet-Printed Manganese Oxide Nanosheets on Graphene for High-Performance Flexible Supercapacitors

The widespread adoption of wearable, movable, and implantable smart devices has sparked the evolution of flexible, miniaturized power supplies. High-resolution inkjet printing of flexible microsupercapacitor (μSC) electrodes is a fast, inexpensive, and waste-free alternative manufacturing technology. In this work, a 2D birnessite-type manganese dioxide (δ-MnO₂) water-based ink is used to print 10-25 layers of δ-MnO₂ symmetrically on a preprinted interdigitated cell consisting of 10 layers of electrochemically exfoliated graphene (EEG). The cell with 10 printed layers of δ-MnO₂ achieved the highest specific capacitance, energy density, and power density of 0.44 mF cm^-2, 0.045 μW h cm^-2, and 0.0012 mW cm^-2, respectively. Since inkjet-printing technology supports μSC manufacturing with parallel/series connectivity, four cells were used to study and improve the potential window and capacitance that can be used to construct μSC arrays as power banks. This work provides the first approach for designing an inkjet-printed interdigitated hybrid cell based on δ-MnO₂@EEG that could be a versatile candidate for the large-scale production of flexible and printable electronic devices for energy storage.