Determination of the absolute and relative extents of basal plane surface area and "non-basal plane surface" area of graphites and their impact on anode performance in lithium ion batteries

For graphites as anode materials in lithium ion batteries, the chemistry and morphology of the prismatic surfaces of graphite play a major role in chemical and electrochemical reactivity, interaction with the solid electrolyte interphase (SET), kinetics for lithium intercalation and de-intercalation, etc. whereas the basal plane surfaces have only minor or no influence on these reactions. We show how gas adsorption data, such as those, which is used for determination of the Brunett-Emmet-Teller (BET) surface area of solids, can be used to estimate the absolute and relative extents of basal plane surface area and "non-basal plane surface" area of graphites used as anode materials in lithium ion batteries. The "non-basal plane surfaces" can be further sub-divided into prismatic surfaces and "defect surfaces" (the latter contain surface groups and other surface defects). In particular, the relation of the first cycle irreversible capacity to the different types of surfaces will be highlighted. (C) 2001 Elsevier Science B.V. All rights reserved.