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What are the characteristics of CMC and SBR?

Edit:Guangzhou Songbai Chemical Co., Ltd.UpDate:2019-05-17

The binder initially used to stir the negative electrode is also an oil based binder such as PVDF. However, since the internal polarization of the battery is severe and the water system is more environmentally friendly, its bonding action can be replaced, and thus a water-based binder for the negative electrode has been developed. It has become its mainstream direction.
Waterborne adhesives have the same or better properties as oil based adhesives. Choosing the right amount of lithium-ion battery can improve the performance of the battery, making it a safe, environmentally friendly, low-cost secondary lithium-ion battery. Trends and hot spots in adhesive research.
Sodium hydroxymethylcellulose (CMC) is a sodium salt. Battery grade CMC is an ionic linear polymer material. The pure product is white or light yellow fiber powder. It is non-toxic, odorless, soluble in hot and cold water and polar solvents, and becomes a transparent viscous solution. The addition of CMC to the slurry increases the viscosity of the slurry and prevents the precipitation of the slurry.
CMC adhesive has good adhesion to metal foil and has good electrical conductivity. The viscosity of CMC glue decreases with increasing temperature, is easy to absorb moisture, and has poor elasticity. Styrene-butadiene rubber (SBR) is an aqueous binder that is a polymer material with good water resistance and aging resistance.
SBR has relatively strong cohesiveness, but it is easily broken under long-term agitation, resulting in structural damage and reduced cohesiveness. In general, the SBR latex is selected to be added later in the agitation. At the same time, the dispersion effect of SBR is not as good as that of CMC, and excessive SBR will cause large swelling, so it is impossible to use SBR as a binder.
CMC plays a very good role in the dispersion of negative graphite. CMC can decompose sodium ions and anions in aqueous solutions. As the amount of CMC increases, the decomposition products adhere to the surface of the graphite particles, and due to the action of static electricity, the graphite particles repel each other to achieve a good dispersion effect.
However, CMC also has a fatal flaw. CMC is fragile. If all of CMC is used as the binder, the graphite film will disintegrate during tableting and dicing, resulting in severe powder detachment. At the same time, the electrode material ratio and pH value have a great influence on CMC, and the pole piece may break during charge and discharge, which directly affects the safety of the battery.