How does carboxymethyl cellulose help improve the dispersibility of electrode materials and reduce agglomeration?
Publish Time: 2025-06-16
In the production process of lithium-ion batteries, the uniformity and stability of electrode slurry are one of the key factors that determine battery performance. Among them, the dispersibility of electrode materials directly affects the bonding state between active substances, conductive agents and binders, which in turn affects the energy density, cycle life and charge and discharge efficiency of the battery. As a water-soluble anionic polymer, carboxymethyl cellulose is widely used in aqueous system negative electrode materials due to its excellent dispersibility and good bonding ability, especially in graphite negative electrodes.1. Basic structure and physical properties of carboxymethyl celluloseCarboxymethyl cellulose is a linear polymer compound with an ether bond structure prepared from natural cellulose through multiple chemical reactions such as alkalization and etherification. Its molecular chain contains a large number of negatively charged carboxylic acid groups (—COO⁻), which not only give carboxymethyl cellulose good hydrophilicity and water retention, but also give it certain surface active functions.Since carboxymethyl cellulose is non-toxic, tasteless, odorless, and can be completely dissolved in water to form a transparent solution, it is very suitable as a binder and dispersant in aqueous battery slurry systems. Its molecular weight range is wide, and the appropriate viscosity grade is usually selected according to application requirements.2. How does carboxymethyl cellulose play a dispersing role?In the process of electrode slurry preparation, active materials such as natural graphite or artificial graphite particles often have strong van der Waals forces and electrostatic attraction, which are prone to aggregation, resulting in uneven slurry, coating difficulties and even battery performance degradation. At this time, carboxymethyl cellulose achieves effective dispersion through the following mechanisms:Steric hindrance effect: After dissolving in water, carboxymethyl cellulose molecules will stretch into a mesh structure and adsorb on the surface of the particles to form a protective film. This film can prevent direct contact between particles, thereby effectively preventing the occurrence of agglomeration.Electrostatic repulsion: carboxymethyl cellulose carries a large amount of negative charge. After dissociation in water, it will form a double electric layer structure on the surface of the particles, which will generate electrostatic repulsion between adjacent particles and further inhibit agglomeration.Wetting and wrapping effect: carboxymethyl cellulose can reduce the surface tension of water, improve the wettability of the slurry system to solid particles, make the active material easier to be wrapped by the liquid medium, and promote uniform dispersion.Rheological adjustment function: The appropriate addition of carboxymethyl cellulose can also improve the rheological properties of the slurry, making it have good fluidity and coating properties, which is conducive to the stable operation of subsequent processes.3. The effect of carboxymethyl cellulose on the microstructure of the electrodeThe good dispersion effect is not only reflected in the slurry stage, but also directly affects the microstructure of the final electrode. The presence of carboxymethyl cellulose ensures the close combination of active materials, conductive agents and current collectors, while avoiding local accumulation or voids caused by agglomeration, thereby improving the density and consistency of the electrode.In addition, carboxymethyl cellulose can also enhance the uniformity of the distribution of the internal pore structure of the electrode, which is conducive to the penetration and diffusion of the electrolyte and improves the migration efficiency of lithium ions during the charge and discharge process. This is of great significance for improving the rate performance and cycle stability of the battery.4. Synergistic effect of carboxymethyl cellulose and other adhesivesIn practical applications, carboxymethyl cellulose is usually used together with another commonly used adhesive, carboxymethyl cellulose, to mainly disperse and initially bond, while SBR provides stronger mechanical strength and flexibility.This combination gives full play to their respective advantages: carboxymethyl cellulose ensures the stability of the slurry and the uniformity of the electrode structure, while SBR enhances the flexibility of the electrode and its adhesion to the copper foil current collector. The synergistic effect of the two significantly improves the overall performance of the electrode.5. Dosage control and optimization of carboxymethyl celluloseAlthough carboxymethyl cellulose has good dispersion and bonding effects in electrode materials, its addition amount must be precisely controlled. Too little will lead to poor dispersion effect, and too much may cause the slurry viscosity to be too high, affecting the coating uniformity and even blocking the equipment pipeline.Generally speaking, in graphite negative electrode slurry, the recommended addition ratio of carboxymethyl cellulose is 1%~2% of the solid content. The specific value should be adjusted according to the type of graphite used, particle size distribution, stirring process and other factors. Reasonable formula design and process optimization are the key to give full play to the performance of carboxymethyl cellulose.6. Environmental advantages and sustainable developmentWith the global emphasis on green manufacturing and sustainable development, the environmental advantages of carboxymethyl cellulose as a water-based adhesive are becoming increasingly prominent. It does not contain volatile organic compounds (VOCs) and will not pollute the environment, which is in line with the current development direction of the new energy industry.In addition, carboxymethyl cellulose is derived from natural cellulose, which is a renewable resource and is easy to degrade and separate during battery recycling, which helps to simplify the recycling process and promote the green development of the power battery industry chain.In summary, carboxymethyl cellulose effectively improves the dispersibility of electrode materials and reduces particle agglomeration through its unique molecular structure and multiple dispersion mechanisms, thereby improving the cycle life and overall performance of the battery. It not only performs well in aqueous slurry systems, but also has good environmental protection properties and processability. It is an indispensable and important material in the current lithium-ion battery manufacturing.
