Silicon-Graphite Slurry and High-Loading Electrode Process Development

摘要

Silicon has been in discussion for over a decade as a drop-in replacement for graphite in lithium-ion battery anodes. Incorporating silicon into the anode would allow storing more lithium in less space and thus have a higher energy density. A successful integration of silicon would help meet 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. Early work using silicon showed the promising advantages, but the issues of particle fracturing due to particle expansion and the unknowns of the solid electrolyte interface (SEI) layer has stilled the adoption of silicon for commercial batteries. However, fabricating a uniform and high integrity electrode using silicon and silicon-graphite blends to perform studies to better understand the silicon particle expansion and SEI layer is not a trivial task. In this work, various silicon-graphite-binder blends, mixing methods, and coating settings have been examined with an emphasis in developing a practical silicon-graphite electrode with ＞3 mAh/cm~2 that can aid in the further development of silicon based anode systems and could be embraced by industry. The strategy to achieve a high integrity, high loading silicon-graphite anode involved testing silicon-graphite exploratory slurries using various mixing methods and pilot-scale coating equipment in Argonne's Cell Analysis, Modeling, and Prototyping (CAMP) Facility to identify processing issues. The initial work was also used was to verify the scalability of the processing/coating developments. The culmination of the work resulted in a homogeneous ～4 mAh/cm~2 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 while having high integrity with the ability to survive a 3 mm diameter pin bend test. Silicon-graphite electrodes are available in the CAMP Facility Electrode Library for the battery research community, to help enable further development of an industrial accepted lithium-ion battery containing a silicon based anode. This presentation will discuss the significant challenges faced with the slurry mixing and coating of silicon-graphite electrodes and the encouraging discoveries used to produce a high quality silicon-graphite electrode. Acknowledgements 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.