Fluidization and Mixing Behavior of Nano and Micron Sized Particles in a Vibrated Fluidized Bed

All-Solid-State-Batteries (ASSBs) are set to provide high energy densities along with a safer energy storage medium than conventional batteries, which could become crucial in the electrification of transport systems. One of the main challenges of ASSBs is the upscaling of the production process [1]. To that end, the use of a vibrating fluidized bed is proposed for the mixing, coating and aggregation of the battery materials. Thus, the fluidization and mixing behaviour cathode material consisting of lithium iron phosphate (LFP), carbon black (CB) and sodium chloride (SC) is investigated in a vibrated fluidized bed with pulsated gas flow and a high velocity microjet. SC was used as a model material for solid electrolytes, which often react with moisture. Strictly vertical vibration was implemented using a linear shaft. The pulsated gas flow was implemented via solenoid valves. The microjet enhances the fluidization and also plays a major role in the creation of hetero agglomerates or aggregates that consist of multiple species.

A parametric study including vibration parameters, pulsated gas flow parameters and pre-conditioning of the particles via drying or sieving was explored while the fluidization characteristics were investigated via measurement of pressure drop and bed expansion. Lastly, microjet parameters, such as orifice diameter or jet-pressure, were varied. The success of the hetero-agglomerate and aggregate production was determined by SEM and TEM images in conjunction with particle size measurements. Additionally, the electrical powder conductivity of the produced aggregates and agglomerates were measured via a four-point probe method.

It was shown that the vibration-, jet- and the pulsated gas flow parameters influence the fluidization characteristics. Further, the mixing quality improved with extended fluidization time. The successful production of composite material was confirmed via electron microscopic techniques.