How To Choose Suitable PVDF Binder For Lithium Batteries

The following is a summary of PVDF commonly used in industry:

Polyvinylidene fluoride (PVDF), homopolymers of VF2 and copolymers of polyvinylidene fluoride, copolymers of VF2 (vinylidene fluoride)/HFP (hexafluoropropylene) have been widely accepted in lithium-ion battery systems material for adhesive. Their electrochemical performance, thermal stability, chemical stability and the simplicity of their production process are unmatched by other polymer binders. PVDF is a polymer synthesized from VF2 monomer by addition polymerization. Structurally, it is interconnected by CH2 bonds and CF2 bonds. The polymer has the stability typical of fluoropolymers, while the interacting groups on the polymer chain can create a unique polarity that affects the solubility of the polymer and its interaction with lithium ions, active materials and metals The interaction force between the collectors. The most important are electrical stability, purity, molecular mass, melting point, solubility and mechanical properties.

Commonly used PVDF are Solef5130, HSV900, kynar761A

PVDF 5130 is suspended and mixed, the molecular weight is 1.1 million, the particle size of 5130 is slightly larger, 100 microns, and polar functional groups are added, which has better viscosity, less dosage and better purity. HSV900 is emulsion-polymerized, with a molecular weight of 1 million and a smaller particle size of 30 microns. It is pure PVDF, so it has good processing performance, will not drop powder during circulation, and has stronger dissolving ability. Kynar761A, molecular weight is about 50W.

Solef 5130 is easier to process during batching and coating, but during assembly and processing, the phenomenon of powder drop, rebound, etc. is more serious than that of HSV900. 5130 adhesive has better bonding effect and better foil contact. If you want to improve energy density, 5130 adhesive is the first choice. Therefore, 900 are mostly used for lithium cobalt oxide, lithium manganate, and ternary positive electrodes, and 5130 are mostly used for LFP Battery. Copolymerization of PVDF and other groups has higher viscosity, but slightly poor processing performance. In fact, the higher the molecular weight of PVDF, the better the adhesion performance. However, the high content of PVDF in the slurry has a great impact on the internal resistance of the battery. Special small capacity battery. Therefore, it is very important to select the appropriate binder and the appropriate ratio of the binder to the performance of the battery.