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This work probes the slurry architecture of a high silicon content electrode slurry with and without low molecular weight polymeric dispersants as a function of shear rate to mimic electrode casting conditions for poly(acrylic acid) (PAA) and lithium neutralized poly(acrylic acid) (LiPAA) based electrodes. Rheology coupled ultra-small angle neutron scattering (rheo-USANS) was used to examine the aggregation and agglomeration behavior of each slurry as well as the overall shape of the aggregates. The addition of dispersant has opposing effects on slurries made with PAA or LiPAA binder. With a dispersant, there are fewer aggregates and agglomerates in the PAA based silicon slurries, while LiPAA based silicon slurries become orders of magnitude more aggregated and agglomerated at all shear rates. The reorganization of the PAA and LiPAA binder in the presence of dispersant leads to a more homogeneous slurry and a more heterogeneous slurry, respectively. This reorganization ripples through to the cast electrode architecture and is reflected in the electrochemical cycling of these electrodes.

This work explores the complex interplay between slurry aggregation, agglomeration, and conformation (i.e., shape) of poly(acrylic acid) (PAA)- and lithiated PAA-based silicon slurries as a functio...

In this work, we explore how the chemical reactivity toward an aprotic battery electrolyte changes as a function of lithium salt and silicon surface termination chemistry. The reactions are highly ...

This study explores low molecular weight polymers with the same chemical repeat structure as high molecular weight poly acrylic acid (PAA) and lithium poly acrylic acid (LiPAA) binders which act as a dispersant to improve the silicon-graphite electrode performance. The electrodes which utilize LiPAA as a dispersant perform, on average, the best with respect to the maximum capacity (compared to theoretical), rate performance, and capacity retention with time. These electrodes also have the poorest dispersion of binder, indicating that the poor binder dispersion is essential to electrode performance. In contrast, this study shows that electrodes formulated using PAA had good dispersion and performs the worst in cycling. Finally, this work demonstrates that the binder is not uniformly distributed in the electrode, but rather resides in local regions. The results indicate these regions accommodate volume expansion during cycling.

Polymeric binder interactions with silicon were investigated as a function of electrode processing and electrochemical behavior. Using ultra-small angle neutron scattering, the evolution of the dynamics between a poly(acrylic acid) and silicon slurry showed that, under shear conditions, the slurry aggregated heavily when compared to the no shear condition. This behavior is undesirable as silicon anode slurries must de-agglomerate under shear conditions for a uniform electrode cast, which facilitates even lithiation across the anode. Electrodes made from these slurries show the connection between the binder/silicon interaction and electrochemical behavior. Additionally, the role of the silicon surface chemistry on the rheology of the electrode slurry was elucidated and connected to electrode processing and electrochemical performance. Based on these results, the binder for the silicon anode materials may need to be re-evaluated in order to improve the viability of silicon anodes. Acknowledgement: This work was supported by the US Department of Energy’s Office of Energy Efficiency and Renewable Energy through the Vehicle Technology Office (Brian Cunningham Program Manager).