Role of carboxymethyl cellulose binder and its effect on the preparation process of anode slurries for Li-ion batteries

We systematically investigate the role of carboxymethyl cellulose (CMC) and show how it affects the slurry dispersion according to the slurry preparation process. We find that CMC plays various roles as a dispersant, thickener, and gelling agent in the anode slurry depending on its content. CMC acts as a dispersant at lower content than the optimum graft density at which the two particles (carbon black, graphite) are adsorbed and saturated. When the CMC content increases above the optimum graft density, the adsorbed CMC still acts as a dispersant, but the extra free CMC acts as a thickener or a gelling agent depending on the content. In the meanwhile, CMC shows similar adsorption and dispersion mechanism for the two particles. Therefore, at a CMC content lower than the optimum graft density, the adsorption selectivity of CMC for both particles is significantly affected by the mixing sequence of CMC and two particles, resulting in a significant difference in slurry dispersion. On the other hand, at higher CMC content, the slurry dispersion is rarely affected by the CMC mixing sequence as both particles are eventually adsorbed and saturated in the final mixing stage. This study reports for the first time that the adsorption selectivity of the binder for the two particles can be controlled through the slurry preparation process, and that the slurry dispersion can be differently affected by the preparation process depending on the binder content.