With the lithium-ion battery industry moving to high energy density anode materials such as silicon and lithium metal as a substitute for lower specific capacity carbon-based materials like graphite, cathode energy density can become a bottleneck. Typical cathodes have less than 10% practical specific capacity compared to both pure lithium metal and silicon. For these anodes, cathodes with higher active material loadings per unit area would be needed to produce matching electrode pairs. However, cathode thickness cannot indefinitely be increased, as doing so leads to issues with electrolyte transportation, conductivity, and mechanical properties [1,2].

Increasing the loading of the cathode could also be done by reducing the amounts of inactive components, such as the binder and the conductive additive, in the electrode. To achieve this, understanding the role of each component is important. The most important role of the binder is to act as an adhesive among particles and the current collector. But most binders are electronically insulating. The main role of the conductive additive, such as carbon black, is to improve the conductivity of the overall system [1].

As the inactive material percentages are decreased, the distribution of these components in the electrode domain becomes more important to both the electrochemical and mechanical performance of the electrode. The distribution changes with the different process conditions used, such as mixing techniques, order, speeds, times, slurry viscosity, drying conditions, etc. This research consists of a systematic study to understand the effects of the aforementioned process conditions on the particle and polymer distribution as well as its contribution to the mechanical and electrochemical performance. With the use of the current findings, the active material percentage was increased up to 98% in electrodes with 5 mAh/cm² loading, retaining similar performance to electrodes with 92.8% active material, as shown in figure 1. Some contribution of the capacity fade was found to be due to the lithium counter electrode used.

The goal of this ongoing project is to produce a model that could be applied to different materials to identify the best process conditions for thick electrode manufacturing.

References

1. F. Ma, Y. Fu, V. Battaglia, R. Prasher, Microrheological modeling of lithium-ion battery anode slurry, J. Power Sources, 438 (2019), p. 226994
2. Wen Yu, Nanping Deng, Lin Tang, Kewei Cheng, Bowen Cheng, Weimin Kang, Roles of metal element substitutions from the bimetallic solid-state electrolytes in lithium batteries, Particuology, 65 (2022), p. 51-71