Classification and analysis of lithium battery binders

Whenever there is a battery binder that accounts for less than 1 to 2% of the lithium battery, it plays an important core role, and some characteristics of the binder polymer often bring significance to the battery performance. Unexpected impact. Lithium battery.jpg 1. PVDF performance Polyvinylidene fluoride (PVDF) is a polymer material with high dielectric constant. It has good chemical stability and temperature characteristics, and has excellent mechanical properties and productivity. The binding properties have positive uses and are widely used in lithium batteries as a positive and negative electrode binder. The most important factors affecting the adhesion of PVDF are molecular weight, crystallinity, PVDF modification, cathode materials and conductive agent types. The greater the molecular weight of PVDF, the stronger the adhesion and the greater the peel strength of the pole piece. The higher the crystallinity, the closer the molecular chains are stacked, the greater the utility of the molecules, and the better the adhesion. PVDF has good performance as a binder for lithium batteries. What affects its use is the degree of solubility of PVDF powder in NMP solvent and the influence of moisture. 2. CMC and SBRCMC glues have good adhesion to metal foil and have electrical conductivity. The viscosity of CMC glue will decrease with the increase of temperature, it is easy to absorb moisture and has poor elasticity. Styrene butadiene rubber (SBR) is a water-based binder, a polymer material with good water resistance and aging resistance. Relatively speaking, SBR is more cohesive, but it is easy to demulsify under long-term stirring, which will damage the structure and reduce its cohesiveness. In general, SBR is chosen to be added in the late stage of stirring. At the same time, the dispersion effect of SBR is not as good as that of CMC. Too much SBR will cause greater swelling, so SBR cannot be used as a binder. 3. Polyacrylic acid (PAA) and its salt binder Polyacrylic acid is a water-soluble chain polymer that can form polyacrylate with many metal ions. For example, the molecular chain of polyacrylic acid and its salt also contains many Oxygen groups (-COOH) can form hydrogen bonds with the surface of silicon-carbon active materials, give strong binding force between active particles and current collectors, and also have the purpose of alleviating the volume expansion of silicon-based materials, and can also improve batteries The cycle performance of sodium polyacrylate can improve the life of the battery. Sodium polyacrylate is easy to dissolve in water and has the purpose of thickening. It can be used as a thickener for lithium battery slurry. 4. The molecular formula of polytetrafluoroethylene (PTFE) PTFE monomer is (CF2CF2). PTFE has good adhesion and can form an elastic network structure in the electrode matrix. In this structure, the active material Not only are they in good contact with each other, it is beneficial to the conduction of electrons, but also can resist the expansion and contraction caused by the charging and discharging of the electrodes, and can improve the discharge performance and storage life of the lithium battery. 5. Polyvinyl alcohol (PVA) Polyvinyl alcohol (PVA) is a white to slightly yellow solid or powder. It is a common water-soluble polymer compound. Its molecular chain contains a large number of hydroxyl groups, which can be used in carbon anode materials. Hydrogen bonds are formed on the surface, which has good adhesion. In addition to satisfying high adhesion, the binder for lithium batteries must also have good flexibility, insoluble in electrolyte, compactness, chemical and electrochemical stability, and easy electrode coating after bonding. In addition, low cost, environmental protection, etc., it is more difficult to satisfy all the characteristics, and the adhesive still has a long way to go. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to distinguish a good lithium battery for electric vehicles?