Silicon

Deep Dive into the Silicon-Graphite Anode for Lithium-Ion Batteries

The dream of a lithium-ion battery with much higher energy density has led to the pursuit of a new graphite composite anode containing silicon.

Argonne National Laboratory is teaming up with Lawrence Berkeley National Laboratory, National Renewable Energy Laboratory, Oak Ridge National Laboratory, Pacific Northwest National Laboratory, and Sandia National Laboratories to surmount the barriers associated with development of an advanced anode based on a mixture of silicon and graphite. This electrode would replace the graphitic carbon electrode now common in the lithium-ion battery.

Silicon is a very attractive complement to graphitic carbon alone due to its much higher theoretical capacity for energy storage, nearly an order of magnitude more per gram. Silicon is also attractive as an anode material because it is the second most abundant element in the Earth’s crust. A small proportion of a silicon-based material is already being included in the anode to boost the energy in the batteries for the Tesla electric vehicle. However, in electrodes with larger amounts of silicon metal (about 15 percent) and thus much higher energy density, several problems seriously limit the cycle life, including large electrode expansion during discharge. The wealth of previous electrochemical studies on anodes with this element is both a testament to its potential and the size of the challenge that must be overcome, requiring innovation on multiple fronts.

This multi-laboratory “deep dive” program now in progress requires silicon materials in quantities sufficient for electrode preparation within the consortium facilities for testing in full cells. Argonne’s Cell Analysis, Modeling, and Prototyping (CAMP) Facility is one such facility. Its main contribution to the project is fabricating needed prototype electrodes and cells for testing, and generating electrochemical data from cell testing.  By having access to these materials and data, Argonne and the other participating laboratories are able to characterize the same materials using different techniques and test these materials in different configurations. As a result, the test data can be reliably compared with that from all six laboratories.

Silicon-based materials are also being fabricated in Argonne’s Materials Engineering Research Facility (MERF), and Argonne’s Post-Test Facility is evaluating the electrodes and cells from the CAMP Facility to elucidate failure mechanisms. These results are fed back to the many researchers in the program to advance their research.