What are the consequences of the floating of the binder during the preparation of ion batteries?
The coating process is an important link in the lithium battery electrode manufacturing process, and it is the process of completing the transfer of the electrode slurry from the liquid state to the electrode solid active material. After the electrode slurry is prepared, it will be adhered to the current collector after being coated by screw pump, filter, screen and other devices, and coated by extrusion coating head or transfer roll. After the lithium-ion battery is dried in an oven, the liquid slurry is solidified on the surface of the current collector, and the bonding force is stronger.
In the drying process of the oven, there is no obvious abnormality on the surface, but in the rolling process after coating, it is sometimes found that material drop, foil leakage or abnormal blackening of the pressing roll occurs after the pole piece passes the roll. Phenomenon.
This may not be due to a problem with the ratio of the binder during the preparation of the electrode slurry, but may be caused by the binder floating to the surface during the electrode coating and drying process.
After the slurry coating is completed, the product needs to be inspected. The inspection items are generally pole piece surface load, pole piece thickness, peel strength, resistivity, etc., and the electrolyte infiltration effect of the pole piece may also be evaluated. The floating of the binder will reduce the peel strength of the pole piece.
After the slurry preparation is completed, the active substances, conductive agents, binders and other substances in the qualified paste are uniformly dispersed, but if the drying conditions are not set properly, the uniformly dispersed substances will be redistributed, especially when the conductive agent is generated in the The phenomenon of surface enrichment, and the decrease of binder content in contact with the foil, was abnormal in the pole piece peel strength test.
During the rolling process of the pole piece, due to the uneven distribution of the binder, under a large rolling force, the pole piece will adhere to the surface of the pressing roll and peel off from the metal foil, which is very important for the quality of the pole piece. Control is absolutely not allowed.
The floating degree of the binder varies from light to heavy. In severe cases, the peeling strength of the pole piece is low. In the lighter case, there is no obvious problem on the surface of the pole piece, but the life of the lithium ion battery is shortened during the use process. This is because the active material It is easily separated from the foil during the charging and discharging process.
