Selective deposition of metal oxide nanoflakes on graphene electrodes to obtain high-performance asymmetric micro-supercapacitors.

To meet the charging market demands of portable microelectronics, there has been a growing interest in high performance and low-cost microscale energy storage devices with excellent flexibility and cycling durability. Herein, interdigitated all-solid-state flexible asymmetric micro-supercapacitors (A-MSCs) were fabricated by a facile pulse current deposition (PCD) approach. Mesoporous Fe2O3 and MnO2 nanoflakes were functionally coated by electrodeposition on inkjet-printed graphene patterns as negative and positive electrodes, respectively. Our PCD approach shows significantly improved adhesion of nanostructured metal oxide with crack-free and homogeneous features, as compared with other reported electrodeposition approaches. The as-fabricated Fe2O3/MnO2 A-MSCs deliver a high volumetric capacitance of 110.6 F cm-3 at 5 μA cm-2 with a broad operation potential range of 1.6 V in neutral LiCl/PVA solid electrolyte. Furthermore, our A-MSC devices show a long cycle life with a high capacitance retention of 95.7% after 10 000 cycles at 100 μA cm-2. Considering its low cost and potential scalability to industrial levels, our PCD technique could be an efficient approach for the fabrication of high-performance MSC devices in the future.