Water-Based Activated Carbon Ink for Printed Flexible Biodegradable Supercapacitors

Flexible and printed supercapacitors (SCs) have emerged as reliable power sources for wearable and portable electronics. However, developing these SCs as sustainable and eco-benign, with high electrochemical performance, remains a challenge. Herein, scalable fabrication of SCs is demonstrated by formulating an activated carbon (AC) printable ink for the direct ink writing (DIW) of SCs. A water-based ink is prepared using a bio-degradable cellulose-based, sodium carboxymethylcellulose (Na CMC), binder replacing the typically used fluorinated binders, which are not environmentally friendly. Na CMC provides a stable ink dispersion with added mechanical and chemical stability to the printed SCs. The AC-Na CMC electrode produced 127.8 mF cm⁻² of specific capacitance. This AC-Na CMC ink is used to develop fully printed film-SCs and micro-SCs (m-SCs). The m-SC is fabricated with a printing resolution of 150 µm on photo paper. Using DIW enables scalable production, which is demonstrated by printing an array of m-SCs to power a micro-LED. The printed m-SC also demonstrates high mechanical flexibility, retaining 89.6% of its original capacitance at a bending angle of 90⁰. Na CMC as binder and photopaper as the substrate results in the production of biodegradable SCs extending their applicability to the field of transient electronics.