Sustainable, Inexpensive Synthesis of High Purity Graphite from Biomass with Excellent Performance in Li-Ion Battery Anodes

Tuesday, 3 October 2017: 12:20
National Harbor 10 (Gaylord National Resort and Convention Center)
N. A. Banek, D. T. Abele, K. R. McKenzie Jr., and M. J. Wagner (The George Washington University)
Graphite is classified as a strategic and critical mineral by the US and EU. The worldwide market for graphite was ~ $15 billion in 2016. It is used in numerous industries including metallurgy, refractories and dominates the market for active materials in Li-ion battery anodes.

Both natural and synthetic graphites are used for Li-ion anodes. Natural graphite is mined but requires large-scale beneficiation and purification with HF, HCl and H2SO4, with a large environmental impact to water, land and air. In addition, attaining the purity levels required for Li-ion application results in as much as ~70% material loss. The production of synthetic graphite is a very long and extremely energy intensive process (heating at ~ 3000 ˚C for weeks) and results in very large scale environmentally deleterious emissions.

Predicted growth in the graphite market will be driven by sharp increases in the market for Li-ion batteries, with 12 "mega" factory scheduled to begin production by 2020. Tesla's "giga" factory alone is thought to require the output of 4 - 6 new flake graphite mines or the equivalent quantity of synthetic graphite. However, supplies of natural graphite are under pressure with China recently closing ~ 200 flake graphite mines due to their environmental impact. In addition, shortages in the supply of the high quality needle petcoke necessary for synthetic graphite production are predicted. As a result, graphite price have tripled in the past 10 years, as production has been flat.

Here we report the first Li-ion battery grade synthetic graphite made from biomass. The production is carbon negative, rapid, high yield and low cost. We have demonstrated the synthesis from cellulose, lignin and inexpensive whole biomass feedstock including sawdust and corncob. The resulting graphite is extremely high purity and highly crystalline, matching commercial synthetic graphites. Its performance in Li-ion batteries is outstanding, achieving near theoretical capacity with extremely long cycle life (see figure). Details of the synthesis, characterization and performance will be presented.