Binders for Stable Electrodes
Among other polymers, Solef® PVDF is one of the preferred choices as binder material for electrodes thanks to its stable and reliable performance.
In particular Solef® PVDF guarantees:
- Electrochemical stability from 0 to 5 V vs Li+/Li
- Solubility in NMP for easy processing
- Chemical resistance in the electrolyte
- Suitable cohesion between active materials
- Durable adhesion to the current collector
Adhesion is a key property which determines final performance of batteries especially at long term. A good binder guarantees the homogeneous dispersion of active materials and conductive carbon together with stable bonding to the metallic collector.
In order to evaluate the binder effect, some tests have been performed. Cathodes have been prepared from NMP slurry in standard conditions (LiCoO2 as active component, 5 % of carbon black and a fixed amount of Solef® PVDF), then coated onto an aluminum foil and dried in oven at 130 °C. Adhesion has been measured by peeling test following ASTM D903.
It is possible to notice the effect of molecular weight and binder content on mechanical consistency of electrodes. The temperature of drying, the chemistry and quantity of active material as well as post-treatments play also a role in the determination of adhesion performance and may be optimized for improving electrodes quality.
Adhesion to cathode with LiCoO2