American Chemical Society, Chemistry of Materials, 7(27), p. 2525-2531, 2015
DOI: 10.1021/acs.chemmater.5b00119
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The high-voltage LiNi0.5Mn1.5O4 (LNMO) spinel is a promising material for high-energy battery applications, despite problems of capacity fade. This is due in part to transition metal leaching that produces chemical and morphological inhomogeneities. Using fast micro-X-ray fluorescence spectroscopy to scan the sample at medium spatial resolution (500 nm) over millimeter ranges, effects of cycling rate and state-of-charge on the elemental distribution (Ni and Mn) for LiNi0.5Mn1.5O4/carbon composite electrodes in LNMO/Li cells are visualized. Charge distribution is imaged by mapping the Ni oxidation state by acquisition of a stack of elemental maps in the vicinity of the Ni K edge. Our results show significant effects on morphology and elemental distribution, such as formation of elemental hot-spots and material erosion, becoming more pronounced at higher cycling rates. In nickel hot-spots, we observed hampered oxidation of nickel during charging.