Insight into the charging-discharging of magnetite electrodes: XAS and DFT study

• Published in: Physical chemistry chemical physics : PCCP Vol. 23; no. 1; pp. 651 - 661
• Main Authors: Nayak, C, Abharana, N, Modak, B, Halankar, K, Jha, S. N, Bhattacharyya, D
• Format: Journal Article
• Published: 18.03.2021
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d0cp05151a

The structural changes of Fe 3 O 4 nanoparticle electrodes in Li ion batteries during charging-discharging cycles have been investigated using in situ X-ray absorption spectroscopy (XAS). Chemometric methods viz. , Principal Component Analysis (PCA) and Multivariate Curve Resolution-Alternate Least Square (MCR-ALS) have been used for analysis of the in situ XANES data during the charge-discharge cycle, which help to identify the various species formed during the lithiation-delithiation of Fe 3 O 4 . The concentration variation of the different species has also been determined and the detailed intercalation-conversion mechanism of the Fe 3 O 4 electrodes during the first discharge has been established. Subsequently, the first charge and second discharge cycles were also studied to apprehend the difference in redox reaction between the first discharge and subsequent cycles. The above studies clearly identify the four species involved in the whole intercalation-conversion process of Fe 3 O 4 electrode of a Li ion battery and also indicate the irreversibility of the conversion reaction in subsequent cycles which may be one of the reasons for capacity fading of these electrodes. The above results have also been corroborated with density functional theory (DFT)based ab inito calculations. The structural changes of Fe 3 O 4 nanoparticle electrodes during charging-discharging cycles have been investigated using in situ XAS. The mechanism of charge-discharge has been established using chemometric analysis of in situ XAS data.