Paper Number
PO6                         My Program 

Session
Poster Session

Title
Critical roles of rheology in the manufacturing of lithium-ion batteries

Presentation Date and Time
October 16, 2024 (Wednesday) 6:30

Track / Room
Poster Session / Waterloo 3 & 4

Authors (Click on name to view author profile)

1. Liu, Qingsong (Northwestern University, Chemical ang biological engineering)
2. Richards, Jeffrey J. (Northwestern University, Chemical and Biological Engineering)

Author and Affiliation Lines (in printed abstract book)
Qingsong Liu and Jeffrey J. Richards
Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208

Speaker / Presenter 
Liu, Qingsong

Keywords
experimental methods; advanced manufacturing; colloids; dense systems; non-Newtonian fluids; polymer solutions; polymers; real-world rheology; sustainability

Text of Abstract
Both shear and extensional rheology are critical to the battery manufacturing process as they dictate the slurry processibility and the structure achieved in the coated thin film. The porous cathodes of LIBs are a composite of micron-sized electrochemically AM (active material) particles, nanometer-scale conductive additive CB (carbon black), and polymer binder PVDF (poly(vinylidene difluoride)).

While it is well understood that the shear rheology of the slurry needs to be leveraged to engineer coating operation and achieve high-quality cathodes, how to engineer the shear rheology remains elusive. CB has an evolving structure under flow, and such behaviors endow the non-equilibrium and shear-thinning properties to LIB slurries. In this poster, we show that while the addition of both PVDF and AM to CB suspensions leads to enhanced breakup of CB agglomerates, the mechanisms remain different. Moreover, contrary to the prevalent assumptions of the PVDF role, we demonstrate that when PVDF is added to AM/CB suspensions, the enhanced CB breakup induced by AM particles is moderated by PVDF. By elucidating the individual roles of the solid components in LIB slurries, we provide a clear pathway for predicting and engineering LIB slurry rheology.

On the industrial scale, slot-die coaters are commonly used to manufacture LIB cathodes. Extensional rheology has been shown to significantly modify the stable coating windows predicted by shear rheology only. Using dripping-onto-substrate, we show that PVDF of different MWs exhibit different extensional rheological behaviors, which we anticipate to heavily influence the coating operations.

Together, this poster will showcase the complex shear and extensional rheology phenomena involved in the manufacturing of LIB cathodes. By providing careful examinations of slurry rheological behaviors, we aim to provide valuable insights that can be leveraged to engineer the manufacturing processes.

Collaborators: Yoshita Gupta, Nadia Nikolova, Welsy Ho, and Vivek Sharma