In Situ Energy Dispersive X-ray Diffraction Study of Prototype LiMnO4- and LiFePO4-Based Coin Cell Batteries

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This in-situ study demonstrates the feasibility of using energy dispersive x-ray diffraction (EDXRD) to characterize the internal structure and chemical composition of coin cell type Li-ion batteries. CR2032 coin cell batteries containing Li1-3xCrxFePO4 (with x = 0.015) or LixMn1.42Ni0.42Co0.16O4 cathode were studied by EDXRD measurement. EDXRD patterns with 50 to 70 scans were made between top and bottom of charged or discharged coin cells of about 3.2 mm thickness. The seven different layers of materials contained in the Li1-3xCrxFePO4 coin cell can be clearly identified from the measured 50 in-situ EXRD patterns. For the LixMn1.42Ni0.42Co0.16O4 cell, the Bragg lines shift to higher energy in the charged cathode consistent with a lattice contraction with decreased Li content. The charged spectrum Bragg lines are broadened due to two phase behavior. The detailed electrochemical phases of the cathode materials and other layers of materials in this prototype LiMn2O4-based coin cell have been profiled, using EDXRD, as a function of state of charge and as a function of z-position in the interior of the cell. Our results demonstrate that in-situ EDXRD characterization of the crystal structures and phase distribution of coin cell batteries in space and time is feasible under different charge/discharge conditions.