Structure engineering of ultrathick-electrode enables high areal capacitance and exceptional flexibility of micro-supercapacitors

Designing thick electrode is of great importance to boost areal capacitance of micro-supercapacitors (MSCs) towards long-time operation of flexible microelectronics. However, conventional thick electrodes can’t fully achieve the trade-off between the high areal capacitance and exceptional flexibility. Herein, we report a general electrode structure engineering strategy, by combining 3D printed graphene-based thick electrodes and grooved array structure achieved by laser etching, simultaneously achieving high areal capacitance and exceptional flexibility of 3D-printed MSCs. Our 3D printed 7-layer MSCs with grooved array electrode (MSCs-7L-GAE), possessing a thickness of 580 μm, show excellent areal capacitance of 185.3 mF cm⁻², energy density of 27.6 μWh cm⁻², exceeding the counterpart with conventional thick electrode (157.7 mF cm⁻², 25.0 μWh cm⁻²). Moreover, our MSCs-7L-GAE display significantly improved mechanical flexibility with almost constant capacitance during 5000 bending cycles. It is demonstrated experimentally and theoretically that the unique grooved array structure can effectively relieve local stress during the deformation process. Also, our devices exhibit excellent cyclability and integration uniformity, thereby holding great potential in wearable microelectronics.