Separating Material Reactivity from Residual Oxygen in TGA–TOF MS of Natural and Artificial Graphite Anodes

Graphite anodes are specified by bulk structural and textural parameters, but these converge after graphitization and say little about the surface at which the first cycle is determined. This work aimed to determine whether thermogravimetry coupled with time-of-flight mass spectrometry resolves precursor- and coating-specific surface behavior in graphite anodes and separates that behavior from artifacts of the measurement atmosphere. We examined nine anode materials—natural graphite, coal-tar-, and petroleum-derived artificial graphites, including an uncoated/coated commercial pair from each precursor and a carbonized/graphitized pair—using thermogravimetry coupled to time-of-flight mass spectrometry under helium, Raman spectroscopy, N2 physisorption, and electron microscopy. The CO2 evolved above 600 °C arose from oxidation by residual oxygen: O2 was consumed by 67–80%, while N2, Ar, and He changed by less than 13%, and the CO2 formed matched the available oxygen (r = 0.9988). We therefore did not compare CO2 yields and mass losses between runs, and we corrected oxidation onsets to a common oxygen level. Graphitization raised the onset by 225 °Cat matched oxygen; coal-tar-derived graphites oxidized 6–27 °C later than petroleum-derived ones in all three precursor-matched comparisons; coating lowered the onset by 14–19 °C while moving the BET area in opposite directions, by −18% and +581%. An explicit sensitivity analysis shows that the first two results are independent of the correction, whereas the magnitude of the coating effect depends on it.