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Lithium Diffusion Pathways in Graphitic Carbon Anodes
Graphitic carbon is widely used as an anode material in lithium-ion batteries. For high-power applications such as hybrid electric vehicles, however, prolonged cycling at high rates can damage a graphite anode and lead to plating of lithium metal, thereby decreasing the lifetime and capacity of the battery. Elucidating lithium diffusion pathways in graphite provides insight into why these anodes are limited by modest charge/discharge rates. The Persson and Kostecki Groups, in collaboration with other BATT investigators, have quantified lithium-ion diffusivity as a function of transport direction in graphite anodes. Electrochemical experiments combined with first-principles calculations indicate that lithium diffusion in graphite is several orders of magnitude faster in the direction parallel, as opposed to perpendicular, to the graphene plane. These results provide guidelines for designing graphite anodes with preferential orientation for higher rate capability, which translates to faster charging batteries.