The Pathway to Environmentally Friendly Battery Production: Comparison of NMP-Based, Water-Based and Semidry Water-Based Production of NMC622 Cathodes for Lithium-Ion Batteries

The transition to renewable energy sources necessitates the development of environmentally friendly and cost-efficient lithium-ion battery production methods. Traditional cathode production is energy-demanding, primarily due to solvent recovery and drying. This study investigates the water-based semidry production processes for NMC622 cathodes, aiming to reduce the energy-intensive drying phase and eliminate toxic solvents like N-methyl-pyrrolidone (NMP). By substituting NMP with water and employing a semidry approach, the solvent content during production can be significantly reduced. This research compares semidry-coated electrodes with NMP-based and water-based wet-coated electrodes, focusing on the electrode properties and the electrochemical characteristics in full cells. Utilizing an extrusion and calendering method, the semidry process demonstrated a five-fold reduction in solvent use compared to the NMP-based method. However, the semidry-produced electrodes exhibited higher resistance, probably due to the fine distribution of binder and carbon black, which lacked long electron transport pathways compared to the wet-coated electrodes. The water-based wet-coated electrode, with lower initial coulombic efficiency, displayed better performance at higher discharge rates and lower capacity loss over cyclization than the NMP-based reference. This study highlights the potential of water-based semidry production in creating more sustainable and efficient lithium-ion batteries.