The electrodes of commercial lithium batteries are generally composed of current collectors, active substances, conductive agents and binders. The PVDF binder used for preparing lithium ion batteries has the following characteristics:
Polyvinylidene fluoride is a semi-crystalline polymer with high crystallinity and high crystallization melting temperature. Therefore, at the normal use temperature of the battery, the crystallinity of PVDF makes it difficult for molecules with electrolyte to circulate, which increases the charge and discharge load. In addition, PVDF homopolymer also has many problems.
For example, if the drying speed is not suitable when preparing the battery, the shrinkage rate of PVDF is very different from that of the current collector, and the coating containing active substances will be separated from the current collector; During use, due to the internal stress of the electrode, the electrode mixture layer is partially or completely peeled off from the current collector, which leads to the deterioration of load characteristics and capacity.