Mixing-sequence-governed dispersion and processability of electrode slurries with carboxymethyl cellulose and cellulose nanofibrils

초록

We demonstrate that concurrent use of carboxymethyl cellulose (CMC) and cellulose nanofibrils (CNFs) enhances the dispersion and processability of electrode slurries, and elucidate the underlying mechanisms via detailed rheological and microstructural analyses. Sedimentation tests and optical microscopy revealed that slurries containing both dispersants exhibited more uniform dispersion and greater stability than those prepared from CMC or CNFs alone. Dynamic rheological analyses, based on the sequence of physical processes (SPP) framework applied to large-amplitude oscillatory shear (LAOS), demonstrated that combined use of CMC and CNFs effectively suppressed shear-induced aggregation and the resultant stiffening, thereby improving coating processability. Notably, this synergistic effect exhibited a pronounced dependence on the mixing sequence: pre-mixing of CMC with graphite afforded more effective dispersion and stabilization than when CNFs were first mixed with graphite. Based on this sequential dependence and rheological analyses of the dispersant mixture, the improvements in dispersion and stability are attributed to the synergistic effects of steric and electrostatic repulsion from CMC adsorbed onto graphite surfaces, and the stabilization afforded by the CNF-rich matrix. The combined formulation also ensured robust coating and drying performance, minimizing edge defects and enabling homogeneous distribution of the styrene–butadiene rubber (SBR) binder, thereby preventing binder migration.

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