Lithium Intercalation Edge Effects and Doping Implications for Graphite Anodes

Abstract

The interface between electrolyte and graphite anodes plays an important role for Li intercalation and has significant impact on the charging/discharging performance of lithium ion batteries (LIBs). However, atomistic understanding of interface effects that would allow to rationally tune the interface is largely missed. In this work, we comprehensively study the energetics of Li near the main non-basal surfaces of graphite, namely the armchair and zigzag edges. Compared with the bulk, both graphite edges provide stronger absorbing Li sites (i.e., sub-surface sites that lithiate at higher voltages). Furthermore, this effect is significantly more pronounced at the zigzag edge compared to the armchair edge due to its unique electronic structure. The “peculiar” topologically stabilized electronic surface state found at zigzag edges strongly interacts with lithium; thereby changing Li diffusion behavior at the surface as well. Finally, boron/nitrogen doping was identified as a promising strategy to tune the Li intercalation behaviors at both edge systems, which might give some guidance for the modification of graphite anodes with a view enhance intercalation kinetics.