Sand-Milling\nFabrication of Screen-Printable Graphene\nComposite Inks for High-Performance Planar Micro-Supercapacitors

Abstract

Rational\nengineering and simplified production of printable graphene\ninks are essential for building high-energy and flexible graphene\nmicro-supercapacitors (MSCs). However, few graphene-based MSCs show\nimpressive areal capacitance and energy density, especially based\non additive-manufacturing, cost-effective, and printable inks. Herein,\na new-style and solution-processable graphene composite ink is ingeniously\nformulated for scalable screen printing MSCs. More importantly, the\nas-formulated inks consist of interwoven two-dimensional graphene\nand activated carbon nanofillers, which are delaminated by one-step\nsand-milling turbulent flow exfoliation. Notably, embedding the activated\ncarbon nanoplatelets into graphene layers drastically boosts the electrochemical\nperformance of screen-printed micro-supercapacitors (denoted as Gr/AC-MSCs),\nsuch as an outstanding areal capacitance of 12.5 mF cm^–2 (about 20 times than pure graphene). The maximum energy density,\nmaximum power density, and exceptional cyclability are 1.07 μW\nh cm^–2, 0.004 mW cm^–2, and 88.1%\nafter 5000 cycles, respectively. As such, the as-printed MSCs on paper\ndisplay high resolution and pronounced energy-storage performance.\nFurthermore, the packaged and optimized Gr/AC-MSCs showcase remarkable\nmechanical flexibility even under highly folded and excellent water\nresistance, maintaining 91.8% capacitance retention after being washed\nfor 90 min. The versatile methodology highlights the promise of graphene\nand analogous 2D nanosheet functional inks for scalable fabrication\nof flexible energy-storage devices.