Sustainable conductive ink for printed “greener” supercapacitors

Abstract

The increase in electronic waste highlights the need to develop sustainable, bio-based, and recyclable electronic systems. Printed electronics offer a promising route to reduce material consumption, though the inks used often contain environmentally harmful components. Conductive inks typically comprise functional materials, binders, solvents, and additives, which are not always as sustainable as desired. To address these issues, the development of sustainable ink must focus on using bio-based, biodegradable, and non-toxic materials. While metals such as silver and gold offer high conductivity, they are costly and not sustainable. Alternatives such as carbon materials or conductive polymers are being explored. Biodegradable polymers such as cellulose, chitosan, PLA, and PVA are viable binders, and “greener” solvents such as Cyrene and ethyl lactate could replace harmful solvents. Energy storage applications manufactured by printed electronics could benefit from these sustainable innovations. In particular, the development of greener supercapacitors (SCs, which offer high power density) using green inks in current collectors (CCs) and electrodes is being studied. In this work, the formulation of sustainable conductive inks for CCs in SCs was studied. The proposed inks used natural graphite flakes as functional materials. Two binder matrices were proposed. The first one involved using cellulose nanocrystals dissolved on PEDOT:PSS, and the second one involved using PLA dissolved on Cyrene. The electrical performance and suitability for CCs of printed SCs were evaluated. The PLA binder-matrix was the best option to develop an SC. This ink also provided better electrochemical performance than the commonly used commercial ink. A fully printed SC was manufactured in this work using the developed PLA ink printed onto a PET substrate. The electrodes were printed using YP-80F activated carbon. Cellulose paper was used as the separator. The electrolyte was a biodegradable, reline-based system. The printed SC was compared with the ones manufactured with commercial inks, showing the advantages of using our new formulation.