Abstract:
Lithium ion batteries have been widely used in many fields such as electronic products, electric vehicles and large-scale energy storage materials due to their excellent performances. Binder directly affects the electrochemical properties of the battery, including the rate capacity, charge and discharge cycle stability and so on. Compared with the PVDF binder, the aqueous binder, sodium carboxymethyl cellulose (CMC), has a better dispersion stabilizing effect on the graphite anode slurry, which could be ascribed to the presence of carboxyl group and hydroxyl group on its molecular chain. The electrostatic repulsion generated by the hydroxyl groups on CMC chains make the graphite disperse homogenously. Accordingly, the substitution degree (DS) which is closely related to the content of carboxyl and hydroxyl groups may have remarkable influences on the dispersion of graphite. The influences of substitution degree of CMC on the rheological properties, dispersion and stability of graphite anode slurry, as well as the pole piece electrical resistivity, were studied in this paper. The mechanism of CMC on graphite slurry was also analyzed by scanning electron microscope (SEM) and Zeta potential. The results showed that the viscosity and stability of graphite slurry were enhanced, while the pole piece electrical resistivity was decreased with the gradual increase in the CMC substitution degree, which could be explained by the stronger electrostatic repulsions as measured by Zeta potential tests. Meanwhile, the content of CMC had significant effects on the rheological properties, stability and the pole piece electrical resistivity of the graphite slurry. The slurry showed the best stability and dispersion, also the pole piece displayed the lowest electrical resistivity in case the dosage of CMC was 1.5%.