What is PVDF? The role of PVDF in lithium batteries
Attention has been paid to the application of PVDF in lithium batteries.
Polyvinylidene fluoride (PVDF) is a semi-crystalline fluoropolymer, which is due to its good mechanical strength, chemical stability, electrochemical stability, thermal stability, and good affinity to electrolytes. PVDF has a steady rise in market demand in the field of petrochemical equipment and industrial coatings, along with the rapid development of technology and the market of lithium-ion batteries, PVDF in the lithium-ion battery industry shows a rapid trend of growth, the annual market demand rose by more than 20%.
PVDF is important as a binder, diaphragm, and diaphragm coating in the lithium-ion battery industry.
Polyvinylidene fluoride (PVDF) is a semi-crystalline polymer with relatively high crystallinity and high crystallization and melting temperature, so at the usual battery temperature, the crystallinity of PVDF makes it difficult to circulate the molecules in the electrolyte body, and the charge/discharge load increases;
When the drying speed is not suitable in the preparation of the battery, the shrinkage rate of PVDF is relatively large compared with the shrinkage rate of the collector, and the coating film containing the active material will be detached from the collector; in the process of use, along with the migration of time, there is a situation where the electrode compound layer is partially or completely peeled off from the collector due to internal stress. The coating film will be detached from the collector;
In the process of use, along with the migration of time, there is this is due to the internal stress of the electrode so that the electrode compound layer is partially or completely peeled off from the collector, resulting in poor load characteristics, resulting in capacity deterioration.
PVDF homopolymer has the above-mentioned problems, using in-depth analysis of the test, released PVDF copolymer, prepared using the introduction of a small number of polar monomers in the polymerization process and VDF copolymerization.
The PVDF copolymer with the introduction of polar groups can greatly enhance the binder bonding performance, avoid electrode shedding, significantly reduce the binder composition, grant the battery higher energy density, smaller internal resistance, provide higher energy density, better power performance, and longer cycle time.
One is used as a positive bonding agent to bond the granular battery positive material so that it can be made into a corresponding shape; the second is applied to diaphragm material and coating.