Sustainable Conductive Ink for Printed Greener Supercapacitors

Abstract

The growth on the electronic demand and the increase of electronic waste highlights the need of developing sustainable, biobased, 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, sustainable ink development has to be focused on using biobased, biodegradable, and non-toxic materials. While metals like 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 like cellulose, chitosan, PLA, and PVA are viable binders, and greener solvents such as Cyrene and ethyl lactate could be proposed as replacements for harmful ones. Energy storage applications manufactured by printed electronics could benefit from these sustainable innovations. Particularly, the development of greener supercapacitors (SCs) (which offer high power density) by using green inks in both current collectors (CCs) and electrodes, is being studied. In this work, the formulation of sustainable conductive inks for SC current collector is studied. The proposed inks use natural graphite flakes as functional materials. Two different binder-matrix were proposed. The first one, using cellulose nanocrystals solved on PEDOT:PSS, and the second one using PLA solved on Cyrene. Electrical performance and suitability for CC of printed SC were evaluated, selecting PLA binder-matrix as the best option to develop SCs. This ink also provided better electrochemical performance than the commonly used commercial ink. A fully printed SC has been manufactured on this work, using the developed PLA ink printed onto a PET substrate. The electrodes were printed using YP-80F activated carbon, a cellulose paper was used as separator and the electrolyte was a biodegradable reline-based system. The printed SC was compared to the ones manufactured with commercial inks, showing the advantages of using the new formulation