An In-situ Energy Dispersive X-ray Diffraction Measurement of Coin-cell Li-ion Batteries contaning Cr-doped LiFePO4 Cathod Materials

We report the result of an in-situ energy dispersive x-ray diffraction (EDXRD) study for the CR2032 Li-ion coin-cell batteries with Cr-doped LiFePO₄ cathode materials. The EDXRD measurement was performed on the beam line X17B1 of the Brookhaven National Synchrotron Light Source. Our coin-cell batteries have a thickness of about 3.1 mm and contain 7 layers from the top to bottom of the cell: Stainless steel (S.S.) cap, Ni sponge spacer, Li metal disc, very thin separator film, cathode disc of Li_1-3xCr_x FePO₄ (with x = 0 and 0.015), titanium disc, and S.S bottom. In-situ EDXRD patterns were taken at different layers of these materials inside the coin-cell battery at a step of about 63 µm. That is, 50 scans were made between the top and bottom of the coin-cell battery. By comparing the patterns with the XRD patterns of standards, we can produce a clear classification of above-mentioned different materials with precise locations inside the coin-cell Li-ion batteries. This study demonstrates that EDXRD measurement is a very effective technique for in-situ study of internal chemical compositions of batteries.