Crystalline Characterization of an Operational Li-Ion Battery by Synchrotron X-Ray Diffraction

Abstract

Lithium-ion LiCoO 2 /graphite batteries have been studied using synchrotron, high-energy X-rays to obtain diffraction patterns on complete multilayer battery packages containing electrodes, separators, current collectors, and electrolyte vacuum sealed in a plastic bag. Reflections associated with both the LiCoO 2 cathode and graphite anode were observed so that both phases could be monitored in detail as a function of the charging and discharging process. The charge-discharge behaviors of cycled batteries were also investigated and compared with fresh ones: for the cycled battery, there is a measurable loss of Li intercalation at the graphite anode on charging and incomplete reintercalation of the LiCoO 2 cathode on discharging. Furthermore, the microstructure of the Li-ion batteries was investigated by cross-sectional electron microscopy. The anode contained spherical particles of mesocarbon microbeads which were composed of a mixture of graphitic plates and many smaller carbon spheres.

Multi-Scale Characterization Studies of Aged Li-Ion Large Format Cells for Improved Performance: An Overview

“…Recently in situ XRD has been demonstrated to analyze the crystalline structure of the cathode material during charging and discharging cycles. 195 Li et al 195 have used Rietveld fitting and quantitative phase analysis to analyze the phase fractions. The two-phase fitting was performed using LiFePO 4 and FePO 4 as end-members and the structural data given by Anderson et al 196 and Channagiri et al 152 The results of quantitative phase analysis demonstrate an increase in FePO 4 phase fraction with aging at a given location on the cathode as seen in Fig.…”