In situ Raman spectroscopic–electrochemical studies of lithium-ion battery materials: a historical overview

In this review, the recent advances in the development of in situ Raman spectroscopy and electrochemical techniques and their application for the study of lithium-ion batteries are revisited. It is demonstrated that, during a relatively short period of time (1995–2013), the spectroelectrochemical techniques used for the investigation of battery components, benefited directly from the tremendous advances of Raman technology. The most important step was the implementation of confocal Raman microscopy in the battery research, which opened the way to new and more sophisticated applications. This review shows how the discovery of new Raman techniques such as surface-enhanced Raman scattering, tip-enhanced Raman spectroscopy, spatially offset Raman spectroscopy as well as the integration of Raman spectrometers into non-optical microscopes, for example AFM and SEM, allowed to perform two or more analytical techniques on the same sample region, with an exceptionally high resolution. All these progresses led to new insights into battery materials and components such as electrodes and electrolytes, and helped to understand the electrode/electrolyte interface phenomena. This enhanced understanding allowed a deeper insight into important phenomena, as e.g., battery aging and the dynamic nature of the solid electrolyte interfaces in lithium batteries. The high relevance of the information provided by these techniques in the progress of battery modeling is another positive contribution. Another area of high practical significance for the battery field is the screening of electrode materials, which is facilitated by the availability of the data provided by spectroscopic methods.