Nayak C, Abharana N, Modak B, Halankar K, Jha S N, Bhattacharyya D
Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India.
Theoretical Chemistry Section, Bhabha Atomic Research Centre, Trombay, Mumbai, India.
Phys Chem Chem Phys. 2021 Mar 18;23(10):6051-6061. doi: 10.1039/d0cp05151a.
The structural changes of Fe3O4 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 Fe3O4. The concentration variation of the different species has also been determined and the detailed intercalation-conversion mechanism of the Fe3O4 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 Fe3O4 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.
利用原位X射线吸收光谱（XAS）研究了锂离子电池中Fe3O4纳米颗粒电极在充放电循环过程中的结构变化。化学计量学方法，即主成分分析（PCA）和多元曲线分辨交替最小二乘法（MCR-ALS），已被用于分析充放电循环过程中的原位XANES数据，这有助于识别Fe3O4在锂化-脱锂过程中形成的各种物种。还确定了不同物种的浓度变化，并建立了Fe3O4电极在首次放电过程中的详细嵌入-转化机制。随后，还研究了首次充电和第二次放电循环，以了解首次放电与后续循环之间氧化还原反应的差异。上述研究清楚地确定了锂离子电池Fe3O4电极整个嵌入-转化过程中涉及的四种物种，并且还表明了后续循环中转化反应的不可逆性，这可能是这些电极容量衰减的原因之一。上述结果也得到了基于密度泛函理论（DFT）的从头计算的证实。
