P. Das, X.Y. Shi, Q. Fu, Z.-S. Wu*

Advanced Functional Materials, 2019, 30, 1908758.

DOI: 10.1002/adfm.201908758 [PDF]

Micro-supercapacitors (MSCs), albeit powerful are unable to broaden their potential applications primarily because they are not as flexible and shape diverse as electronics. To address this problem, we put forward a universal strategy to fabricate substrate-free, ultrathin, shapeless planar-MSCs with high performance tenability under serious deformation. These represent a new class of “all-inside-one” film supercapacitors, achieved by encapsulating two-dimensional (2D) interdigital microelectrodes within chemically cross-linked polyvinyl alcohol-based hydrogel electrolyte containing graphene oxide (GO). GO nanosheets significantly improve ionic conductivity, enhance the capacitance and greatly boost robustness of hydrogel electrolyte. Consequently, our entire MSC while being only 37 μm thick can be crumpled and self-adjust its shape through fluid channel 10 times smaller than its original size without any damage; demonstrative of shapelessness. Using MXene as active material, high single cell areal capacitance of 40.8 mF cm^-2is achieved from microelectrodes as thin as 5 μm. Furthermore, to demonstrate wide-applicability of our protocol, screen-printing graphene-based highly integrated MSCs connecting 9 cells in series are fabricated to stably output high voltage of 7.2 V while crumpling them from 0.11 to 0.01 cm^-3, manifesting superior performance uniformity. This protocol allows the co-existence of high performance with incredible flexibility that may greatly diversify MSCs’ applications.