In situ electrochemical synchrotron radiation for Li-ion batteries

Observing the electronic structure, compositional change and morphological evolution of the surface and interface of a battery during operation provides essential information for developing new electrode materials for Li-ion batteries (LIBs); this is because such observations demonstrate the fundamental reactions occurring inside the electrode materials. Moreover, obtaining detailed data on chemical phase changes and distributions by analyzing an operating LIB is the most effective method for exploring the intercalation/de-intercalation process, kinetics and the relationship between phase change or phase distribution and battery performance, as well as for further optimizing the material synthesis routes for advanced battery materials. However, most conventional in situ electrochemical techniques (other than by using synchrotron radiation) cannot clearly or precisely demonstrate structural change, electron valence change and chemical mapping information. In situ electrochemical-synchrotron radiation techniques such as X-ray absorption spectroscopy, X-ray diffraction spectroscopy and transmission X-ray microscopy can deliver accurate information regarding LIBs. This paper reviews studies regarding various applications of in situ electrochemical-synchrotron radiation such as crystallographic transformation, oxidation-state changes, characterization of the solid electrolyte interphase and Li-dendrite growth mechanism during the intercalation/de-intercalation process. The paper also presents the findings of previous review articles and the future direction of these methods.