Silicon-Graphite Development: Robust, Practical, and Scalable High Performance Electrodes

Lithium-ion batteries in their current state of technology are not able to satisfy the transportation requirements set by the U.S. Department of Energy (DOE) for Hybrid Electric Vehicles, Plug-in Hybrid Electric Vehicles, and Electric Vehicles for gravimetric and volumetric energy capabilities. One approach to meet DOE’s transportation goals is to increase the capacity of the anode using silicon. Silicon has been recognized for several years as the most likely next generation high energy anode material. However, the silicon drop-in replacement of graphite is not as straight forward as it would seem.

Argonne National Laboratory has taken on the task of developing a silicon-graphite blend electrode to advance the lithium-ion battery technology and provide high quality electrodes to the battery community for further electrolyte development. Fabricating a robust, practical, and scalable high performance silicon-graphite electrode, with an emphasis on developing an electrode with >3 mAh/cm², has required efforts to explore various sources of silicon powder, silicon particle sizes, graphite types, binder types, electrode compositions, compatible solvents for slurries, effective slurry mixing, and electrode coating conditions. The approach involved testing silicon-graphite exploratory slurries on the CAMP (Cell Analysis, Modeling, and Prototyping) Facility pilot-scale coating equipment to address processing issues on the coater and verify the scalability of developments.

The result of this work led to a silicon-graphite electrode containing 15 wt.% nano-silicon, 73 wt.% graphite, 2 wt.% carbon black, and 10 wt.% Li-PAA (lithiated poly acrylic acid) binder. The slurry has the capability of coating at least a 3.7 mAh/cm²electrode and shows much improved robustness, practicality, scalability, and reproducibility (Fig.1). Having this standard electrode enables diagnostic work, modeling, and electrolyte composition work. The silicon-graphite electrode is available in the CAMP Facility Electrode Library for the battery research community. The major barriers encountered and breakthroughs in the silicon-graphite electrode fabrication leading to the improved electrode will be discussed in this presentation.

Acknowledgement:

Support from Peter Faguy and David Howell of the U.S. Department of Energy’s Office of Vehicle Technologies Program is gratefully acknowledged.  This work was performed under the auspices of the US Department of Energy, Office of Vehicle Technologies, under Contract no. DE-AC02-06CH11357.