| Abstract |
In situ x-ray absorption spectroscopy study of energy storage materials. X-ray absorption spectroscopy (XAS) is a versatile tool to study the electronic- and local atomic- structure of materials in an elemental selective way. Thanks to its high penetration power, transition metal K-edge XAS has been widely utilized in studying lithium ion battery (LIB) materials under operando conditions, especially during electrochemical charging-discharging. While this standard in situ XAS can provide valuable information about charge compensation mechanism and local structure changes, this technique is limited to the case of slow rates of charge-discharge being used (e.g. slower than 10 hour charge/discharge rate). Several potential applications of LIBs such as hybrid electric vehicle (HEV) and grid scale storage of renewable energy require high power performance, thus emphasizing the need of dynamic study during fast rates of charge/discharge. Therefore, time-resolved spectroscopic techniques, especially under operando conditions, to monitor and study the structural changes during the fast delihiation and lithiation process are greatly needed. In this talk, I will discuss application of newly developed in situ quick XAS (QXAS) technique to the dynamic studies of several cathode materials (e.g., LiFePO4 and Li1.2Ni0.15Co0.10Mn0.55O2) for LIBs during chemical and electrochemical delithiation (i.e., charging). The kinetics and local structural changes upon the fast delithiation will be discussed in comparison with the results obtained from the standard in situ XAS during the slow rate charging (~C/12 rate). This QXAS technique provides a new powerful way to study both electrochemical and chemical reactions in energy storage materials with excellent time-resolving power for dynamic studies. |
