Striking a Balance: Exploring Optimal Functionalities and Composition of Highly Adhesive and Dispersing Binders for High-Nickel Cathodes in Lithium-Ion Batteries

Nickel-rich layered oxide, LiNi_xCo_yMn_zO₂ (NCM, x > 0.8), has emerged as a promising cathode material for lithium-ion batteries due to its high specific capacity and energy density. However, there remains a challenge regarding NCM degradation during cycling, associated with interfacial side reactions and microcrack formation. Herein, a functional poly(norbornene-co-norbornene dicarboxylic acid-co-heptafluorobutyl norbornene imide) (PNCI)-based binder system is introduced, with controlled functionalities and monomer compositions, to preserve the structural integrity of NCM. The PNCI binder system incorporates three different norbornene-derived monomers with distinct functionalities, allowing for multifunctionality, including electro-chemo-mechanical stability, strong adhesion, and dispersibility. By systematically adjusting the molar composition of the PNCI binders, the overall binder characteristics are fine-tuned, optimizing the adhesion and dispersion of electrode components. The optimized PNCI binder, with desired adhesion strength, surface energy, and polarity, plays a crucial role in facilitating the formation of a uniform electrode structure with a high areal mass loading of NCM, ensuring long-term cycling stability. This study highlights the significance of striking a balance between functionalities and composition in binder systems to achieve high-performance NCM cathodes.