Optimization of NMC cathode inks for cost-effective and eco-friendly screen-printed lithium-ion batteries

Li-ion batteries are life-saving energy storage technology. However, the battery manufacturing process still needs complicated and expensive production lines because of the sensitive nature of active materials towards the open atmosphere. Additionally, employing hazardous N-Metil-2-Pirrolidon (NMP) solvents, which are also restricted by the World Health Organization for electrode preparation, contributes to unsafe working conditions. In this study, water-based LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode inks were produced and printed by the screen-printing method, which is widely used in sensors and electronics fabrication due to its potential practical applications and low-cost production possibilities. Despite their suitability for operation at high voltage ranges, NMC811 cathodes typically exhibit rapid capacity drops over time because of side reactions and Cathode-Electrolyte Interphase (CEI) thickening. In this study, to overcome the capacity drop issue and make it possible to produce water-based cathode inks, NMC811 particles were encapsulated with reduced graphene oxide (rGO) via a hydrothermal method. Water-based Carboxymethyl cellulose (CMC) - Polyethylene oxide (PEO) binders are compared with conventional Polyvinylidene fluoride (PVDF)-NMP binders and exhibited promising electrochemical stability of 75 % after 50 cycles within a high voltage range of 2.8-4.6 V. Therefore, the water-based novel cathode ink presented in this study is not only well-suited for advancing the development of printed batteries but also stride towards more eco-friendly processes thanks to replacing the toxic NMP with water. Moreover, battery printing technologies have also a strategic importance by reducing the investment cost of battery-producing.