In Situ Raman Imaging Applied to the Observation of Li Transport in a LiCoO2 Cathode

Lithium ion batteries are excellent power sources for portable electronic devices, such as cell phones and laptop computers. Lithium ion batteries have also attracted much attention recently as a power source for vehicular applications. However, to achieve higher energy density, power, and reliability for Li ion batteries, it is crucial to understand the degradation mechanism. The growth of cathode impedance with aging or charge/discharge cycling is often responsible for cell degradation. Therefore, the mechanism of cathode degradation and improvement of the cathode material surface have been widely studied [1,2]. In this study, Raman microscopy is used to investigate the detailed characteristics of the local structure of the LiCoO2 cathode material. In situ Raman imaging is a powerful technique that provides unique information regarding the distribution of the local state-of-charge (SOC) in the cathode during charge/discharge cycling, which is responsible for the degradation of electrochemical performance.