Energy Dispersive X-ray Diffraction Profiling of Prototype LiMn2O4-Based Coin Cells

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This 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–xMn1.42Ni0.42Co0.16O4 cathode were studied and profiled by collecting 70 EDXRD patterns collected at equal spatial intervals between top and bottom of charged and discharged coin cells of about 3.2 mm thickness. Diffraction profiling of the discharged cell manifests the spinel structure with essentially constant Li content across the entire cathode. In contrast, the Bragg lines of the charged cathode cell shift to higher energy, consistent with a lattice contraction with decreased Li content. The charged-cell spectrum Bragg lines are also broadened due to two phase behavior and exhibit a distinct Li-content gradient across the cathode. The detailed electrochemical phases of the cathode materials and other layers of materials in these prototype LiMn2O4-based coin cells have been profiled, using EDXRD, as a function of z-position in the interior of the cells. Our results demonstrate that EDXRD characterization of the crystal structures and phase distribution of coin cell batteries in space and under different charge/discharge conditions should be routinely feasible.