The role of polymeric binders in Lithium-ion battery performance
Lithium-ion batteries (LiB) show great potential for stationary energy storage and electric mobility. The manufacturing process of the cell is decisive for the battery performance. Optimizing electrode structure and distribution of active components can improve the energy density, specific power, capacity, degradation and cycle stability of the battery.
Electrodes consist of metallic current collectors coated with electrode pastes. In addition to active material, these pastes contain carbon black as a conductivity enhancer and polymers as binder. Despite the vast amount of research activities in the field of LiB, the final contribution of the binder to the cell performance still remains elusive. It provides cohesion in the dry electrode layer as well as adhesion to the current collector. It may also be added as a thickener to control the flow and hence the processing behavior. Finally, polymeric binders act as dispersing agents for active material or carbon black particles, thus strongly determining the component distribution in the dry electrode.
Here we systematically investigate how polymeric binders contribute to the above mentioned paste or electrode features. We vary binder type, concentration and molecular weight, as well as paste preparation conditions. Then rheological properties of the pastes, their microstructure, i.e. the resulting distribution of active material and carbon black as well as the electrochemical performance of corresponding cells including conductivity and cycle stability are thoroughly characterized. Based on these data we will suggest a binder design and paste formulation concept yielding LiB cells with improved electrochemical performance including better long term cycle life of the battery.