High-solid-content kneading degrades carboxymethyl cellulose as a dispersant and destabilises graphite anode slurries

The stability of particle-polymer dispersions is a critical factor governing the quality of electrode slurries in lithium-ion battery manufacturing. In this study, we reveal that the high-solid-content (HSC) kneading process, commonly applied to improve slurry homogeneity, can instead deteriorate dispersion stability in graphite-based anode slurries containing carboxymethyl cellulose (CMC), a common dispersant for water-based systems. By employing a model slurry without highly cohesive conductive additives, we isolate the intrinsic response of polymer-mediated stabilisation to HSC kneading. Comprehensive characterisation demonstrates that intense kneading reduces the molecular weight of CMC, leading to diminished viscosity and elasticity of the slurries. These changes promote particle sedimentation and coating defects, reflecting the impaired ability of degraded CMC to stabilise dispersed graphite particles. Furthermore, redistribution of the binder during processing increases the electronic resistance of the resulting electrodes, highlighting the practical implications of CMC degradation for electrochemical performance. By systematically varying revolution speed and kneading duration, we establish a quantitative measure of kneading intensity and show that the low-shear viscosity correlates with the accumulated maximum shear strain during kneading, suggesting an accumulation mechanism for CMC degradation. This work provides new insights into the trade-off between dispersion efficiency and polymer stability, and underscores the importance of preserving dispersant integrity in the design of advanced slurry processing strategies.