Paste manufacture

© Photo Fraunhofer IPA

Most electrodes in energy storage systems are made from active material, conductive carbon black and binders. These are generally in powder form and need to be optimally matched with one another, mixed and homogenized. This is achieved by making an electrode paste.

If the components are distributed well and homogeneously throughout the paste, the quantity of additives required to stabilize them can be reduced. This is advantageous because additives may impair the properties of electrodes. Among the necessary characteristics attained are thinner layer structures, adequate electrical conductivity and, in particular, bonding of the electrode to other add-on layers of the battery.

For process optimization, we use various dispersion processes on a laboratory to pilot scale: dissolver stirrers, planetary mixers, intensive mixers and in-line dispersers. At the same time, we investigate not only the properties of pastes (electrical and electrochemical characteristics, particle size distribution, solids content and rheology) but also relevant parameters (active shear forces and energy input).

When developing new pastes, among other things we investigate rheological properties to determine the homogeneity of the pastes and select the best coating process for the respective material combination. It is important to analyze particles when the paste is in its original state and to analyze the surface after the paste has been applied. These tests are conducted with the aid of particle size measuring instruments, as well as zeta potential and microscopic measurements (laser, SEM).

A further aim is low-cost manufacturing processes, which are energy-efficient and gentle on resources. Electrodes for energy storage systems can only be produced with minimum material and energy requirements without compromising on electrochemical performance if optimized process and formulation strategies are implemented.