Direct differentiation of surface and bulk compositions of powder catalysts: application of electron-yield and fluorescence-yield NEXAFS to LixNi1−xO

Aging of LiNi1/3Mn1/3Co1/3O2 cathode material upon exposure to H2O

“…The presence of lithium carbonate on the surfaces of active cathode materials such as LiNiO 2 and its analogues LiNi 1 − x − y Co x Al y O 2 has long been noted [26][27][28][29][30][31][32][33][34][35]. The surface of the particles in the present work has been characterized after a brief exposure to moisture.…”

Is the Solid Electrolyte Interphase an Extra-Charge Reservoir in Li-Ion Batteries?

“…33−35 A sharp peak observable at 291 eV corresponds to single bond π state absorption of Li 2 CO 3 followed by two peaks at 298.3 and 301.3 eV corresponding to the double C bond σ states of Li 2 CO 3 . 36,37 Carbonates are thus formed up to 0.7 V during the lithiation half cycle. Proceeding with lithiation, i.e., at voltages below 0.7 V, continuous reduction processes involving the electrolyte dramatically modify the C 1s core level absorption spectra.…”

“…In Figure b we report the XAS TEY spectra taken at the C K-edge, after proper background subtraction and normalization to the incident photon flux. Those spectra show two initial major peaks at 285 and 289 eV (see dashed lines), corresponding to single bond π states attributed to CC bonds of an amorphous carbon mixture of the encapsulated nanoparticle and −CH 2 elements of the EC solvent and CMC binder. − A sharp peak observable at 291 eV corresponds to single bond π state absorption of Li 2 CO 3 followed by two peaks at 298.3 and 301.3 eV corresponding to the double C bond σ states of Li 2 CO 3 . , Carbonates are thus formed up to 0.7 V during the lithiation half cycle. Proceeding with lithiation, i.e., at voltages below 0.7 V, continuous reduction processes involving the electrolyte dramatically modify the C 1s core level absorption spectra.…”

Oxidation of polycrystalline Ni studied by spectromicroscopy: Phase separation in the early stages of crystallite growth

“…Changes in the surface morphology during oxygen adsorption were monitored with LEEM and PEEM for constant temperatures between 373 K and 673 K while the sample was exposed to several L at 1 × [19,20,22] with pronounced 3e g and 3a 1g single electron excitations at 531 eV and 539.5 eV, respectively, and a peak due to multi-electron configuration interactions around 536 eV . The interstitial areas between the crystallites, on the other hand, show only weak features caused by drifts of the synchrotron beam but no signal associated with NiO.…”

“…NiO is the most common anti-ferromagnetic component in antiferromagnetic/ferromagnetic compound materials [3,4], where the film homogeneity is of extreme importance. The oxidation of Ni has, therefore, been studied over many years both on single crystal and polycrystalline samples [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. In order to describe the early stages a three-step mechanism has been proposed by Holloway and Hudson [9,10] for Ni{111} and {100}: the first step involves fast dissociative chemisorption of oxygen; secondly, NiO clusters nucleate and grow forming a thin NiO film; the last step involves slow thickening of the NiO film, which is limited by the diffusion of nickel cations through the oxide film [11].…”