Graphite Edge Effects and Doping Implications on Lithium Intercalation for Graphite Anodes

Abstract

The interface between graphite material and electrolyte plays a crucial role for lithium (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 the interface to be rationally tuned is largely missed. Therefore, in this work, we comprehensively study the thermodynamics and kinetics of Li intercalation near the main non-basal surfaces of graphite, namely the armchair and zigzag edges. Both types of edge sites show a stronger adsorption for Li than in the bulk of graphite. Therefore, lithiation of these sites would proceed at higher voltage than in the bulk. 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 Li; thereby changing Li diffusion behavior at the surface as well. Finally, boron (B)/nitrogen (N) 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.