Graphites for Lithium‐Ion Cells: The Correlation of the First‐Cycle Charge Loss with the Brunauer‐Emmett‐Teller Surface Area

Abstract

We have investigated the correlation of the irreversible charge loss during the first lithium intercalation into graphite electrodes with the Brunauer‐Emmett‐Teller (BET) specific surface area of Timrex graphites. The irreversible charge loss typically increases with a higher BET specific surface area but also depends strongly on the graphite type. We have found that not only the total external surface area but also the ratio between the prismatic and basal surfaces affects the irreversible charge loss. The latter effect occurs because particular reactions associated with charge losses such as solvated lithium intercalation or "self‐discharge" of intercalated lithium (reaction of with electrolyte components) take place only via/on the prismatic surfaces. The influence of the prismatic and basal surfaces is not taken into account if the irreversible charge losses are correlated only with the entire BET specific surface area of the samples. In order to describe the surface‐dependent irreversible charge loss behavior of graphite we developed simple models that, in addition to the BET specific surface area, also take into account particle size distribution and particle morphology.