Cycling of graphite in lithium-ion batteries is reversible except for the first-cycle, where some charge is “lost” due to irreversible side reactions. The irreversible charge loss of different TIMREX® graphites was found to be a linear function, both of their specific BET surface areas and of the double-layer capacitance of electrodes manufactured from these graphites. Nitrogen-adsorption measurements and differential-porosity calculations indicate that the pore structure of the graphite particles mainly consists of mesopores (2–50nm). The surface area of these mesopores is part of the electroactive surface area determined by impedance spectroscopy, and contributes to the irreversible capacity of the graphite negative electrode in the first-cycle.