Spectro-Electrochemical Study of Staging in Graphitic Electrodes for Aluminum Batteries
AdvisorsDa Costa, Pedro M. F. J.
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Permanent link to this recordhttp://hdl.handle.net/10754/660189
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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.