Investigations of energy storage materials via operando optical spectroscopic ellipsometry

Controlling phase transitions is essential in advancing energy storage technology. In particular, understanding phase transitions in energy storage materials has a significant impact on the performance of batteries and fuel cells. For example, changes in the material’s structure and composition lead to variations in the number of charge carriers and the energy capacity. However, investigating phase transitions in materials has a few challenges such as the complexity of materials and limited characterization tools. Multifaceted dynamics adds additional hurdles as some transformations occur rapidly or over extended periods. Overcoming these challenges requires substantial advancements in both experimental and computational methodologies. To address these issues, this project employs an operando optical spectroscopic ellipsometer, a cutting-edge experimental setup recently supported by e-RPA’s FY23 Equipment Grant, to investigate real-time phase transitions of energy storage materials. We will first investigate complex cobalt oxides, which are model systems for positive electrodes in Li-ion batteries. Our preliminary results on prototype samples are quite promising: We could identify the drastic changes in the real-time optical spectra while the sample undergoes topotactic transitions. We plan to do systematic experiments, spectral analyses, and computational modeling, which will provide not only an understanding of the transitions but also dynamical and electronic structural information. We will form active collaborations between the PI’s group and staff scientists in National Labs. Since our results will provide useful guidance for advancing the next-generation energy storage technology, it will give us a competitive edge to earn a long-term grant from the Basic Energy Sciences program, Department of Energy.