Using 514 nm radiation and a careful experimental protocol allowing us to make quantitative intensity analyses, we have examined the first- and second-order Raman spectra of five varieties of graphite. These include single-crystal graphite and highly oriented pyrolytic graphite as references, then two with a significant content of c-axis translation faults introduced through grinding and exfoliation, and a last sample which is purely turbostratic. We show that full c-axis stacking disorder results in a strong increase of the scattered E2g-mode intensity. We have further shown that even in those strongly disordered stacking sequences, but in which the AB sequence persists over only a few layers, the doublet around 2700 cm−1 is resolved. We argue against assigning the peak around 1355 cm−1 to “disorder,” as is so often done, but to the finite in-plane domain size as proposed a number of years ago; moreover, we suggest that this peak is a more sensitive probe of such small domains than is x-ray diffraction.

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Post mortem scanning electron microscopy, X-ray diffraction analysis, and Raman spectroscopy were applied to study the exfoliation tendency of a high temperature-treated graphite negative electrode material during the first electrochemical lithium insertion in various carbonate electrolyte systems. Exfoliation of the heat-treated graphite electrode material was observed in propylene carbonate ͑PC͒and ethylene carbonate ͑EC͒-containing electrolytes. Using acyclic carbonates and 1-fluoro ethylene carbonate, exfoliation of the graphite structure could be avoided. LiPF 6 used as a conducting salt in the EC-based electrolyte increased the exfoliation tendency of the graphite material. Differential electrochemical mass spectrometry was performed to study the passivation of the untreated and heat-treated graphite surface during the first electrochemical Li ϩ insertion. The heat-treated graphite surface showed a reduced reactivity towards EC, which hindered the graphite surface passivation in EC-based electrolyte systems and led to the exfoliation of the graphite structure so far known only for PC-containing electrolytes.

Previous work demonstrated that TiSnSb is a promising negative electrode material with high electrochemical performance due to the benefit of conversion type reaction vs Li. At low potentials, the volumetric change upon cycling entails electrolyte degradation which remains the main factor limiting the cycling life of TiSnSb based electrodes. To further improve the understanding of the formation of a solid electrolyte interphase (SEI) in the presence of alkyl carbonate based electrolytes and of its evolution upon cycling, powerful surface characterization techniques are combined for studying the electrode/electrolyte interface of TiSnSb composite electrodes. Electrochemical impedance spectroscopy is used for monitoring in situ the resistivity of the SEI, while XPS and solid state NMR spectroscopy can provide useful information on the SEI chemical composition and its evolution during cycling.

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