Abstract
This study aimed to reveal the electrical characteristics of the composite electrodes of Li-ion batteries. LiCoO2 electrodes were analyzed using atomic force microscopy, and three-dimensional datasets of current–voltage (I–V) curves (IV-datacubes) were obtained. The IV-datacubes were then analyzed using principal component analysis to determine the typical I–V curve corresponding to each LiCoO2 particle on a statistical basis. Detailed analysis based on the thermionic emission model with series resistance showed that some of the particles exhibited poor electrical contact in the electrode. Overall, the obtained results suggested that our IV-datacube analysis can reveal the characteristics of buried electrical contacts within electrodes, which is otherwise difficult to accomplish using alternative methods. We, therefore, believe that the method presented herein is a promising analytical method for composite electrodes.
Highlights
Li-ion batteries (LIBs) are widely used in a variety of products, such as electric vehicles and mobile devices.[1,2,3,4] To improve the performances of LIBs, it is vital to focus on the characteristics of their active materials, and, in particular, their cathode active materials.[5–7] There are other important factors to consider for improving the overall battery performance, such as the electrical contact of the active materials within the composite electrodes, since the disconnection of active materials from the electrical conduction path results in a lower battery capacity, while disconnection during charge/discharge cycling causes degradation.Scanning spreading resistance microscopy (SSRM) is an effective method for investigating the electrical conductivities of composite electrodes
Preliminary current–voltage (I–V) curve analysis of a LIB cathode was performed via the principal component analysis (PCA) of IV-datacubes measured using atomic force microscopy (AFM)
PCA successfully yielded typical I–V curves corresponding to each LiCoO2 particle and the carbon black domain on a statistical basis
Summary
Li-ion batteries (LIBs) are widely used in a variety of products, such as electric vehicles and mobile devices.[1,2,3,4] To improve the performances of LIBs, it is vital to focus on the characteristics of their active materials, and, in particular, their cathode active materials.[5–7] There are other important factors to consider for improving the overall battery performance, such as the electrical contact of the active materials within the composite electrodes, since the disconnection of active materials from the electrical conduction path results in a lower battery capacity, while disconnection during charge/discharge cycling causes degradation.Scanning spreading resistance microscopy (SSRM) is an effective method for investigating the electrical conductivities of composite electrodes. A number of analytical companies (e.g., the Foundation for Promotion of Material Science and Technology of Japan, Toray Research Center, Inc., and Mitsui Chemical Analysis & Consulting Service, Inc.) and manufacturers (e.g., Bruker Corp., Park Systems Corp., and Hitachi High-Tech Corp.) list the analysis of LIBs as an important application of SSRM. This topic is gaining increasing attention, information regarding the SSRM observations of LIBs is limited, with only a few academic papers having been published to date.[8–10]
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