In situ X-ray diffraction study of different graphites in a propylene carbonate based electrolyte at very positive potentials

Synchrotron based in situ X-ray powder diffraction was applied for the investigation of the PF6− intercalation behaviour into graphite of different particle size and various crystallinity at very positive potentials above 5 V vs. Li/Li+. In a propylene carbonate based electrolyte, small particles with low crystallinity show almost no anion intercalation and the particle structure remains intact. In graphite particles with increased particle size and/or higher crystallinity PF6− intercalation up to a stage 4 phase occurs but the reversibility is poor and exfoliation of graphene layers takes place as it was proven by post-mortem scanning electron microscopy. Thus, graphites with small particles and less crystallinity are preferred as conductive additive in positive “high voltage” cathodes in terms of structural integrity.