Hand-drawing patterned ultra-thin integrated electrodes for flexible micro supercapacitors

In-plane micro supercapacitors (SCs) are important energy storage devices for portable and wearable electronics due to advantages of miniature size, facile integration with on-chip electronics as well as high power density, fast charging rate, and long cycle life. However, current fabrication methods need expensive raw materials, high-cost equipment, and are complex, inconvenient to fabricate micro SCs of different patterns, and difficult to improve the binding force between current collectors and active materials. In this work, a low-cost, facile, efficient and versatile approach is developed for fabricating flexible micro SCs. In-plane micro SCs with versatile patterns based on ultra-thin, flexible and highly integrated electrodes are readily obtained by directly hand-drawing complementary patterns with an oily mark pen and then successively electro-depositing Ni current collectors and pseudocapacitive MnO2. The obtained patterned micro SCs based on ultra-thin and integrated Ni/MnO2 electrodes show a high energy density, good flexibility and superior stability under multi-directional bending cycles. The hand-drawing assisted method provides a facile way to connect multiple micro SCs in series and parallel without additional circuits, and micro SCs of arbitrary shapes can be easily fabricated by modifying hand-drawing patterns. In addition, the obtained micro SCs present good compatibility with substrates of different materials.