Nanoimprint lithography is proposed as a highly versatile method for the production of nanostructured supercapacitors (micro-supercapacitors, MSC). Liquid sucrose- and lignin-precursor printing produces patterns with high quality and a line width down to 500 nm. The liquid-carbon-precursor NIL-printing approach enables nitrogen doping to achieve an increased supercapacitor performance for aqueous electrolytes (Li2SO4). The lines are interconverted into nanoporous carbon materials (d ≈ 1 nm) with high specific surface area (>1000 m2 g-1) to form stable structures reaching specific resistivities as low as ρ = 3.5 × 10-5 Ωm and capacitances up to 7 F cm-3.
A novel three-electrode electrolyte supercapacitor (electric double-layer capacitor [EDLC]) architecture in which a symmetrical interdigital "working" two-electrode micro-supercapacitor array (W-Cap) is paired with a third "gate" electrode that reversibly depletes/injects electrolyte ions into the system controlling the "working" capacity effectively is described. All three electrodes are based on precursor-derived nanoporous carbons with welldefined specific surface area (735 m 2 g −1 ). The interdigitated architecture of the W-Cap is precisely manufactured using 3D printing. The W-Cap operating with a proton conducting PVA/H 2 SO 4 -hydrogel electrolyte and high capacitance (6.9 mF cm −2 ) can be repeatedly switched "on" and "off ". By applying a low DC bias potential (−0.5 V) at the gate electrode, the AC electroadsorption in the coupled interdigital nanoporous carbon electrodes of the W-Cap is effectively suppressed leading to a stark capacity drop by two orders of magnitude from an "on" to an "off " state. The switchable micro-supercapacitor is the first of its kind. This general concept is suitable for implementing a broad range of nanoporous materials and advanced electrolytes expanding its functions and applications in future. The integration of intelligent functions into EDLC devices has extensive implications for diverse areas such as capacitive energy management, microelectronics, iontronics, and neuromodulation.
High-resolution interdigital micro-supercapacitor (MSC) devices are produced by one-step printing of liquid carbon precursors based on renewable resources. A piezo-driven micro-pipetting system allows precise positioning of the ink, offering a high degree of variability in terms of geometric supercapacitor designs. The printed precursor structures were directly converted into nanoporous carbon materials by pyrolysis at 900 °C. A hydrogel electrolyte based on PVA/H 2 SO 4 was used to form quasi-solid-state MSCs. Stable structures with an ohmic serial resistance of around 540 Ω and capacitance up to 151 F cm −3 (3.9 mF cm −2 ) could be produced via additional nitrogen doping of the nanoporous carbon. The capacitance retention of piezoelectric-printed structures after 10,000 cycles remains as high as 96%.
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