Powder compaction and particulate coating

Dry powder compaction electrodes, while one of the oldest techniques, is making a comeback as companies attempt to eliminate the environmental and cost issues associated with solvent based processes. Additionally, companies are attempting to avoid the negative attributes of polymers which coat the surface of active materials, negatively impacting particle to particle conductivity as well as ion diffusion and mobility limitations. As electrode structures become more dependent on nano particulate coatings on the surface of micron size active materials (particulate coating), dry powder processing can be a more effective approach to distributing and maintaining the weak Van der Waal bonds. Of course, certain electrochemical systems require dry powder processing since the choice of compatible binders may be limited to non-soluble polymers such as Teflon (Li-MnO2, Li-SOCl2, Metal-Air, etc.). The main limitation to this type of electrode fabrication is that many of the process controls are coupled with the electrode properties; these include loading, thickness, packing or density. From a process standpoint the size / diameter of the working rolls, their surface roughness, powder flow properties, gap and or force define the electrode characteristic. As a result, it’s difficult, if not impossible, to control electrode thickness while controlling electrode loading and packing. Despite these limitations, with a thorough understanding of these interactions, acceptable electrodes can be produced by this solvent free method of fabrication.