A novel in situ Raman imaging technique has been developed to visualize the Li-ion battery reaction during the charge/discharge operation. A specially designed cell enables to measure Raman spectra at high speed so that the in situ measurements are carried out during the reaction. The distribution of the state of charge in cross-section of LiCoO 2 cathode has been visualized as a demonstration. Inhomogeneous state of charge distribution is observed and there are some active materials where Li + does not completely return after discharging. This technique enables to evaluate not only the electrode performance but also battery degradation, and thus may promote the realization of the next generation batteries.

The porous network structure of Li-ion battery electrodes has been first studied by combining the X-ray computed tomography (CT) technology and the three-dimensional image processing using medial axis. High resolution X-ray CT images of the electrodes were obtained at the synchrotron facility. Gallium injection technique was utilized to obtain a high contrast CT image for anode, so that the material and void are clearly separated in the further image processing. The tortuosity of voids in x-, y-, and z-directions was calculated after thinning process. The path of Li ion in electrodes is visualized and analyzed by this method. This analysis may accelerate the research and development of Li-ion battery electrode.