1. Volume 2, Issue 3, Pages 464-477 (March 2018)
Charge Heterogeneity and Surface Chemistry in Polycrystalline Cathode Materials 
Chixia Tian, Yahong Xu, Dennis Nordlund, Feng Lin, Jin Liu, Zhihong Sun, Yijin Liu, Marca Doeff 
Joule 
Volume 2, Issue 3, Pages (March 2018)
DOI: /j.joule
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2. Joule 2018 2, DOI: ( /j.joule )
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3. Figure 1 SEM Images of Samples
(A–D) Scanning electron microscopy (EM) images of: (A) pristine NMC-622 powder; (B) 50% chemically delithiated NMC-622 using NO2BF4 as the oxidant in acetonitrile solution; (C) NMC-622 electrode electrochemically charged to 3.88 V (halfway charged); (D) electrochemically discharged (half discharged in the first cycle) NMC-622 electrode. Insets are single secondary particles for each sample.
Scale bar for 1A, 100 μm; 1B–1D, 50 μm; insets, 5 μm.
Joule 2018 2, DOI: ( /j.joule )
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4. Figure 2 Electrochemistry and K-edge XAS Spectra
(A) Charge-discharge curves of NMC-622 half-cells.
(B–D) Normalized Ni (B), Mn (C), and Co (D) K-edge XANES spectra for pristine (black), chemically delithiated (red), electrochemically charged (blue), and electrochemically discharged (green) samples.
Joule 2018 2, DOI: ( /j.joule )
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5. Figure 3 2D Ni Oxidation State Mapping and Statistical Analysis
(A and B) Representative multiple pixels averaged XANES spectra (A) and histogram (B) of Ni K-edge shifts for pristine (black curve), chemically delithiated (red curve), electrochemically charged (blue), and electrochemically discharged (green) samples.
(C–F) 2D mapping of Ni K-edge under different conditions: (C) pristine NMC-622; (D) chemically delithiated NMC-622; (E) electrochemically charged NMC-622 electrode; and (F) electrochemically discharged NMC-622 electrode. The color maps were determined by using the single-pixel Ni K-edge XANES data, where blue represents less oxidized (8,338 eV) and red indicates more oxidized states (8,345 eV).
Scale bar for C–F, 10 μm.
Joule 2018 2, DOI: ( /j.joule )
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6. Figure 4 Color Mapping of Ni Oxidation State Heterogeneity
(A–C) Color mapping of (A) chemically delithiated NMC-622, (B) electrochemically charged NMC-622 electrode, and (C) electrochemically discharged NMC-622 electrode. The color mapping was determined using the statistical peak energy from Figure 3B as the center, and then −1.5 eV (blue) and +1.5 eV (red) as the two ends. Multiple views (single or multiple particles in each view) were collected to avoid sample selection-related error. Arrows in (A) point to regions of microcracks, which are less oxidized than surrounding areas.
Scale bars, 10 μm.
Joule 2018 2, DOI: ( /j.joule )
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7. Figure 5 Results on Samples Delithiated with BR2
(A) Scanning EM image of NMC-622 chemically delithiated with Br2. Inset: scanning EM image at higher magnification.
Scale bar, 10 μm; inset, 1 μm.
(B and C) Representative multiple pixels averaged XANES spectra (B) and histogram (C) of Ni K-edge shifts for NMC-622 chemically delithiated with NO2BF4 (red curve) and Br2 (purple curve) NMC-622 samples.
(D) 2D mapping of Ni K-edge in NMC-622 chemically delithiated with Br2.
Scale bars, 10 μm.
(E) Color mapping of NMC-622 chemically delithiated with Br2, where the color mapping was determined using the statistical peak energy from Figure 5C (purple curve) as the center, and then −1.5 eV (blue) and +1.5 eV (red) as the two end limits.
Scale bar, 10 μm.
Joule 2018 2, DOI: ( /j.joule )
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8. Figure 6 Surface Characteristics of Samples as a Function of History
(A–D) Ni L-edge XAS spectra of (A) pristine NMC-622, (B) NMC-622 chemically delithiated with NO2BF4, (C) electrochemically charged NMC-622 electrode, and (D) electrochemically discharged NMC-622 electrode collected using TEY (solid black curve) and FY (dashed red curve) modes.
Joule 2018 2, DOI: ( /j.joule )
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