Degradation Diagnostics from the Subsurface of Lithium-Ion Battery Electrodes
Degradation Diagnostics from the Subsurface of Lithium-Ion Battery Electrodes
复制标题
锂离子电池电极表面下的退化诊断
DOI：
10.1002/eem2.12221
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发表时间：
2021
影响因子：
15
通讯作者：
Yao X
中科院分区：
文献类型：
--
作者：
Yao X
尽管锂离子电池(LiBS)的摇椅理论由来已久，但发展具有更高时空分辨率的新的表征方法有助于更好地理解固体电解质界面研究以塑造反应机理。在这项工作中，我们发展了一种基于氙离子等离子体聚焦离子束(Xe+PFIB)的表征技术来探测三元阴极和石墨阳极的横截面界面，重点是通过对二次离子的深入分析来揭示电极表面下的化学成分和分布。特别是，在与电解液接触之前，在原始阴极中检测到氟化锂，反映出电极退化的形式是在电极制备过程中损失锂库存。这种降解与阴极材料的水解和PVDF粘结剂的分解有关。通过对过渡金属降解产物的定量分析，发现锰是阴极上新形成的钝化氟沉积的主要元素，而在阳极电极内部没有发现过渡金属的信号。这些通过基于PFIB的表征技术在高分辨率下实现的见解不仅丰富了对LIBS中降解机制的了解，而且还识别并实现了一种高灵敏度的方法来获得亚表面的化学测量，这将有助于消除在大多数LIBS中观察到的容量衰减。
Despite the long‐established rocking‐chair theory of lithium‐ion batteries (LIBs), developing novel characterization methodology with higher spatiotemporal resolution facilitates a better understanding of the solid electrolyte interphase studies to shape the reaction mechanisms. In this work, we develop a Xenon ion plasma focused ion beam (Xe+PFIB)‐based characterization technique to probe the cross‐sectional interface of both ternary cathode and graphite anode electrodes, with the focus on revealing the chemical composition and distribution underneath the electrode surface by in‐depth analysis of secondary ions. Particularly, the lithium fluoride is detected in the pristine cathode prior to contact with the electrolyte, reflecting that the electrode degradation is in the form of the loss of lithium inventory during electrode preparation. This degradation is related to the hydrolysis of the cathode material and the decomposition of the PVDF binder. Through the quantitative analysis of the transition‐metal degradation products, manganese is found to be the dominant element in the newly formed inactive fluoride deposition on the cathode, while no transition metal signal can be found inside the anode electrode. These insights at high resolution implemented via a PFIB‐based characterization technique not only enrich the understanding of the degradation mechanism in the LIBs but also identify and enable a high‐sensitivity methodology to obtain the chemical survey at the subsurface, which will help remove the capacity‐fade observed in most LIBs.