Vertically Layered Multi‐Pair Interdigital Electrodes within a Single Sheet of Paper for High Energy Density

A paper-based supercapacitor (SC) is a promising flexible energy storage device for wearable electronics. Paper is an alternative flexible substrate to conventional substrates such as metal foil or plastics. Paper's porous structure can be applied as a large surface area of electrode to store more charge. Paper can also be used as a separator between each electrode. We propose a simple method for vertically integrating a multi-pair of interdigital electrodes within only a single sheet of paper. The integrated multi-electrodes were fully separated because of a removable wax barrier. The integrated multi-pair interdigital electrodes in a paper were used as ultra-thin SCs combined in parallel. With an inner space of paper, the device volume can be reduced with high energy density while preserving flexibility. The energy density was 86.58 mu Wh cm(-2), which is three orders of magnitude higher energy density than a single SC at the same size.