Recyclable Fluorine‐Free Water‐Borne Binders for High‐Energy Lithium‐Ion Battery Cathodes

The rapidly increasing demand for lithium‐ion batteries and the fight against climate change call for novel materials that enhance performance, enable eco‐friendly processing, and are designed for efficient recycling. In lithium‐ion batteries, the binder polymer, used for cathode production, constitutes an integral but often overlooked component. The currently used polyvinylidene fluoride is processed with toxic organic solvents and has numerous other disadvantages concerning adhesion, conductivity, and recyclability. A change to aqueous processing using new, multi‐functional, purpose‐built materials that are soluble in water and fluorine‐free would thus constitute an important advance in the battery sector. Herein, four water‐soluble surfactant‐like polymers based on 11‐aminoundecanoic acid, that can be obtained in high purity and at a multigram scale are described. Free radical polymerization allows modification of the polymer with a wide variety of comonomers. The materials presented significantly enhance adhesion, are thermally stable at temperatures up to 350 °C, and are compatible with state‐of‐the‐art high‐energy LiNi0.6Mn0.2Co0.2O2 (NMC 622) cathode materials. It is also shown new recycling pathways made possible by the reversible pH‐dependent water‐solubility of the materials. The binders used for lithium‐ion battery cathodes are still based on fluorinated polymers and are processed with toxic organic solvents. Herein, novel binders inspired by polymerizable surfactants are presented as tailorable, water‐processable, fluorine‐free alternatives compatible with state‐of‐the‐art LiNi0.6Mn0.2Co0.2O2 (NMC622) cell chemistry. Additionally, the pH‐dependent solubility gives the developed binders an upside for future recycling challenges.