S.M. Rowland, S.C. Dey, L. Lower, W.J. Sagues, J.A. Gonzalez-Aguirre, B.J. Tremolet de Villers, R.K. Bhardwaj, B. Freel, G. Hopkins, T. Vries, T. Vries, Z.A. Combs, S. Park
National Laboratory of the Rockies,
United States
Keywords: bio-graphite, pyrolysis, bio-oil
Summary:
The global demand for graphite is rapidly increasing due to its use as battery anode material in Li-ion batteries (LIBs). The amount of graphite required for energy storage is projected to grow by approximately 4-fold by 2050, and US graphite production, especially for battery applications, is low compared to US graphite demand. One untapped resource in the US for domestic graphite production is biomass, with approximately 1 billion tons of biomass per year available for energy usage. However, biomass-derived carbons do not easily graphitize due to the high oxygen content, so a catalytic oil upgrading or catalytic graphitization step is required. Further, direct graphitization of biomass yields graphite that contains remnants of the biomass cellular structure which can negatively impact battery performance. The work described here shows the use of biomass-derived pyrolysis oil as a feed for domestic bio-graphite. The process utilizes delayed coking, a common petroleum refinery unit, to convert pyrolysis oils into bio-coke and stabilized fuel intermediates. The bio-coke can then be converted to graphite by traditional graphitization in the case of catalytically upgraded pyrolysis oil or by catalytic graphitization in the case of raw fast pyrolysis oil. Graphite from fast pyrolysis oil shows performance of approximately 370 mA with > 90% 1st cycle coulombic efficiency. The graphitization of fast pyrolysis oil bio-coke was facilitated by the addition of an iron catalyst, which was removed by acid leaching prior to battery performance testing. Material characterization of graphite by XRD, SEM, and Raman were also conducted, indicating > 87% graphitization. Technoeconomic analysis was performed and shows an economically viable pathway to domestic graphite via coking and subsequent graphitization of fast pyrolysis bio-oils.