(378a) Effect of Shear Rate and Drying Speed in Lithium Ion Battery Slurry Processing

Processing conditions of battery slurries into electrodes are known to affect final battery performance. However, there is a lack of fundamental understanding of how to control processing conditions to achieve better batteries. Previous work has focused on the formulation step of the battery manufacturing process. This study concentrates on two of the slurry processing steps, namely coating and drying, and their effect on film quality and electrode performance. Rheological measurements were used to determine the starting slurry microstructure as well as determining the effect of flow on microstructure evolution. Well-characterized slurries were subjected to a series of shear rates and drying temperatures to examine the effect of flow and drying rate on final electrode performance. The data suggests that there is a complex relationship between surface roughness and shear rate/temperature, but ultimately, performance based on shear rate is dependent on drying time. Wet slurries are well mixed to form homogeneous suspensions. The slurries are spread via an automatic bird applicator coater to the desired thickness. The film is quickly exposed to different baking temperatures to remove solvent. We observe that higher temperatures produce better performing batteries on average. We argue that quicker drying times prevent sedimentation and phase separation of the slurry. The shear rate has a unique influence on the final electrode performance, and the optimum shear rate depends on the temperature if drying. We use discharge capacity data, scanning electron microscopy and energy dispersive spectroscopy studies to characterize the performance and final electrode particle and chemical species dispersion, respectively. While more data is needed to make concrete conclusions, the preliminary data presented here shows for the first-time quantitative relationships between processing conditions and battery performance.