Material Design for High-Performance Energy Storage
High capacity materials store large amount of Li ions/electrons, which always accompanies with huge volume expansion. This normally causes low cycle stability. Properly designed nanostructures effectively accommodate the volume changes during cycling. In addition, nanostructure provides short lithium/electron transport paths, resulting in high rate capability. We have developed a variety of nanomaterials for battery applications.
Operando/In-Situ Analyses Based on Synchrotron X-ray
- Operando X-ray Diffraction and X-ray Microscopy
- X-ray Tomography
There are three types of measurements to analyze the reactions: ex-situ, in-situ and operando measurements (A. Franco, Rechargeable Lithium Batteries: From Fundamentals to Applications, Woodhead. P184). For ex-situ measurement, the cells are stopped at the desired potential, flowed by extraction of the electrode from the electrochemical cell in order to analyze it with the desired technique. For in-situ measurement, the cells are stopped to measure directly the electrode inside the cell at OCV. Operando measurement is performed while the cell is cycling. Most results from in-situ and operando measurements are similar, but the results from ex-situ measurement can be very different, since the state can be changed through relaxation process once cell is stopped. Operando/in-situ (especially, synchrotron based) X-ray techniques are very powerful to obtain important information for revealing reaction mechanisms of electrodes. Our research focuses on mechanistic studies of rechargeable battery electrodes using operando synchrotron X-ray based methods such as X-ray absorption spectroscopy and X-ray diffraction. In particular, we are interested in direct visualizing the evolution of the morphology of materials during the entire battery cycling process.