Spectro-Electrochemical Study of Staging in Graphitic Electrodes for Aluminum Batteries
AdvisorsDa Costa, Pedro M. F. J.
ProgramMaterial Science and Engineering
KAUST DepartmentPhysical Science and Engineering (PSE) Division
Embargo End Date2020-11-14
Permanent link to this recordhttp://hdl.handle.net/10754/660189
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Access RestrictionsAt the time of archiving, the student author of this thesis opted to temporarily restrict access to it. The full text of this thesis will become available to the public after the expiration of the embargo on 2020-11-14.
AbstractAfter three decades of commercialization, graphite remains the preferred active material for intercalation-type Li-ion battery anodes. Still, the characterization of staging continues to be elusive at the sub-micro- and nano-scales, the typical dimensions of graphite crystallites. Here, the intercalation of Al-based anions in graphitic materials was studied using X-ray powder diffraction (XRD) and Raman spectroscopy. While, in the first case, the analysis was done ex-situ and in mm3-samples, a more localized view was provided by the laser probe which could, furthermore, interrogate the electrochemical process in real-time (in-situ). To do this, an electrochemical cell for Raman studies was custom-made for Al batteries working with non-aqueous electrolytes. Two C materials were used: natural graphite (NG) and processed expandable graphite (EG). Owing to the smaller flake size, higher graphitization degree and larger crystallites of the NG, the Al/NG cells exhibited better performance than the Al/EG ones. Interestingly, discrepancies were observed in the stage numbers estimated from XRD and Raman. These were thought to arise from the, respectively, long- and short-range atomic order scales that are analyzed by those two techniques. To confirm this, in-situ Raman multi-point studies were performed. The results show the presence of domains with mixed stage graphite intercalation when the cells were fully charged, explaining the staging discrepancies.