Identifying the Association between Surface Heterogeneity and Electrochemical Properties in Graphite

Abstract

Graphite materials for commercial Li-ion batteries usually undergo special treatment to control specific parameters such as particle size, shape, and surface area to have desirable electrochemical properties. Graphite surfaces can be classified into basal and edge planes in the aspect of the structure of carbons, with the existing defect sites such as functional groups and dislocations. The solid-electrolyte interphase (SEI) mostly forms at the edge plane and defect sites, as Li-ions only intercalate through these non-basal planes, whereas the electrochemical properties of graphite largely depend on its surface heterogeneity due to the difference of reactivity on each plane. In order to quantify the detailed surface structure of graphite materials, local-absorption isotherms were utilized, and the analyzed nanostructural parameters of various commercial graphite samples were correlated with the electrochemical properties of each graphite anode. Thereby, we have confirmed that the fraction of non-basal plane and fast-charging capability has strong linear relations. The pore/non-basal sites are also related to the cycle life by affecting the SEI formation, and the determination of surface heterogeneity and pores of graphite materials can provide powerful parameters that imply the electrochemical performances of commercial graphite.