Single-operation, multi-phase additive manufacture of electro-chemical double layer capacitor devices

Additive manufacturing (AM) may offer a flexible, cost-effective approach to address conventional manufacturing limitations, such as time-consuming, high work-in-progress, multi-step assembly. In principle AM can also allow more novel geometric or even bespoke designs of structural and functional products. However, in terms of energy storage devices such as batteries and supercapacitors, the benefits of AM have not yet been explored to any significant extent. In this paper, a hybrid-AM system, combining low-cost fused filament fabrication (FFF) and direct ink writing (DIW) techniques, has been designed to fabricate supercapacitors (electro-chemical double layer capacitors, EDLCs) in a single, automated operation. The inherent flexibility of the AM process provided an opportunity to address restrictions in geometric form factor associated with conventional planar supercapacitor manufacturing approaches. Functioning, ring-shaped EDLC devices were manufactured in a single, multi-material operation comprising symmetric activated carbon electrodes in a 1 Μ potassium hydroxide (KOH) electrolyte hydrogel. Gravimetric and areal electrode capacitances were 116.4 ± 0.6 F g−1 and 599.2 ± 3.0 mF cm−2 at 10 mV s−1, with a columbic efficiency of 99.6 ± 0.4% in the as-printed condition. The work aims to accelerate progress towards monolithic integration of energy storage devices in product manufacture, offering an alternative fabrication process for applications with irregular volume/shape and mass-customization requirements.