Vertical Integration of Multi-Electrodes into a Single Sheet Of Paper and the Control of the Equivalent Circuit for a High-Density Flexible Supercapacitor

Paper is an excellent substrate for flexible devices due to its various advantages such as flexibility, porosity, lightness, thinness, and low cost. Its inherent characteristics can be also exploited to overcome the limitations of conventional substrates, such as weak adhesion and large mass densities. Here, we propose a facile method for fabricating vertically integrated multi-electrodes into only a single sheet of paper. Despite the randomly distributed fibrous networks in a paper, the multi-layered electrodes were uniformly formed and completely separated by applying a removable hydrophobic wax barrier confinement inside a single sheet of paper. The integrated multi-layer electrodes can be used as ultra-thin supercapacitor paper with flexible circuit diversion. Using multi-layered electrodes, we demonstrated the control of the equivalent circuits in the supercapacitor paper by simply changing the contact pad grounding. By changing the circuit structures, the multi-layer electrodes exhibited excellent electrochemical properties without device volume changes and additional components. The single incorporated electrode inside the paper with electrodeposited MnO₂ exhibited a high areal capacitance of 711 mF cm^-2. Moreover, the single sheet of supercapacitor paper with integrated multi-electrodes exhibited greater energy and power densities than a single electrode with the same area by factors of 3.8 and 1.75, respectively, based on the control of the equivalent circuit.<br/><br/>This research was funded and conducted under the Competency Development Program for Industry Specialists of the Korean Ministry of Trade, Industry and Energy(MOTIE), operated by korea Insstitute for Advancement of Technology (KIAT). (No. P0012453, Next-generation Display Expert Training project for Innovation Process and Equipment, Materials Engineers), and supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2022R1A2C1005739)