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The X-ray photoelectron spectroscopy (XPS) characterization of LiP[F.sub.6], LiB[F.sub.4], LiTFSI and LiBETI salts are presented by recording their core peaks and valence spectra. The results obtained are used to characterize passivation layers formed at the surface of graphite negative electrodes taken from LiCo[O.sub.2]/graphite electrochemical cells by using either LiTFSI or LiBETI salt.

A study is conducted which reports on the X-ray photoelectron spectroscopy (XPS) characterization of synthesized lithium methyl and ethyl carbonates. The findings reveal that Li alkyl carbonates can be identified at the electrode's surface by a combined analysis of XPS core peaks and valence spectra.

The quantum chemical study of the ionic ring opening of diphosphirane was undertaken. All computations were made using the Monstergauss program. Results revealed that pi addition leading to the diphosphirane was the preferred addition mechanism of singlet carbene to diphosphene. No potential energy barrier toward P-P bond rupture exists in the case of cations. The ring opening process in the case of anions goes through a cyclic anionic intermediate prior to an exo-exo open-chain species through a conrotary process.

The role of the transition metal nature and Al2O3 coating on the surface reactivity of LiCoO2 and LiNi(1/3)Mn(1/3)Co(1/3)O2 (NMC) materials were studied by coupling chemisorption of gaseous probes molecules and X-ray photoelectron (XPS) spectroscopy. The XPS analyses have put in evidence the low reactivity of the LiMO2 materials toward basic gaseous probe (NH3). The reactivity toward SO2 gaseous probe is much larger (roughly more than 10 times) and strongly influenced by the nature of metal. Only one adsorption mode (redox process producing adsorbed sulfate species) was observed at the LiCoO2 surface, while NMC materials exhibit sulfate and sulfite species at the surface. On the basis of XPS analysis of bare materials and previous theoretical work, we propose that the acid-base adsorption mode involving the Ni(2+) cation is responsible for the sulfite species on the NMC surface. After Al2O3 coating, the surface reactivity was clearly decreasing for both LiCoO2 and NMC materials. In addition, for LiCoO2, the coating modifies the surface reactivity with the identification of both sulfate and sulfite species. This result is in line with a change in the adsorption mode from redox toward acid-base after Al/Co substitution. In the case of NMC materials, the coating induced a decrease of the sulfite species content at the surface. This phenomenon can be related to the cation mixing effect in the NMC.

Silicon is a very good candidate for the next generation of negative electrodes for Li-ion batteries, due to its high rechargeable capacity. An important issue for the implementation of silicon is the control of the chemical reactivity at the electrode/electrolyte interface upon cycling, especially when using nanometric silicon particles. In this work we observed improved performances of Li//Si cells by using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) with respect to LiPF6. The interfacial chemistry upon long-term cycling was investigated by photoelectron spectroscopy (XPS or PES). A nondestructive depth resolved analysis was carried out by using both soft X-rays (100-800 eV) and hard X-rays (2000-7000 eV) from two different synchrotron facilities and in-house XPS (1486.6 eV). We show that LiFSI allows avoiding the fluorination process of the silicon particles surface upon long-term cycling, which is observed with the common salt LiPF6. As a result the composition in surface silicon phases is modified, and the favorable interactions between the binder and the active material surface are preserved. Moreover a reduction mechanism of the salt LiFSI at the surface of the electrode could be evidenced, and the reactivity of the salt toward reduction was investigated using ab initio calculations. The reduction products deposited at the surface of the electrode act as a passivation layer which prevents further reduction of the salt and preserves the electrochemical performances of the battery.

Li-S rechargeable batteries are attractive for electric transportation because of their low cost, environmentally friendliness, and superior energy density. However, the Li-S system has yet to conquer the marketplace, owing to its drawbacks, namely, soluble polysulfide formation. To tackle this issue, we present here a strategy based on the use of a mesoporous chromium trimesate metal-organic framework (MOF) named MIL-100(Cr) as host material for sulfur impregnation. Electrodes containing sulfur impregnated within the pores of the MOF were found to show a marked increase in the capacity retention of Li-S cathodes. Complementary transmission electron microscopy and X-ray photoelectron spectroscopy measurements demonstrated the reversible capture and release of the polysulfides by the pores of MOF during cycling and evidenced a weak binding between the polysulphides and the oxygenated framework. Such an approach was generalized to other mesoporous oxide structures, such as mesoporous silica, for instance SBA-15, having the same positive effect as the MOF on the capacity retention of Li-S cells. Besides pore sizes, the surface activity of the mesoporous additives, as observed for the MOF, appears to also have a pronounced effect on enhancing the cycle performance. Increased knowledge about the interface between polysulfide species and oxide surfaces could lead to novel approaches in the design and fabrication of long cycle life S electrodes.

A simple way to obtain a conducting nanocomposite is described, and the conducting particles are characterized. Core-shell particles [polystyrene-polyaniline (PANI)] have been obtained by the dispersion process from three types of polystyrene latexes: a no-cross-linked core stabilized by a nonylphenolethoxylate (NP40) and two cross-linked cores stabilized by NP40 and a mixture NP40/Surfamid (a surfactant bearing an amide group). The surface of these particles has been extensively characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and scanning electron microscopy. A maximum coverage of 94% was obtained for the high PANI content as revealed by XPS analysis. A better coverage was obtained for the cross-linked polystyrene latex stabilized by the Surfamid. The amide group of this surfactant allows the H-bonding formation with the PANI backbone and, thus, improves the conductivity. It was shown that a uniform coverage of the core particles was not required to ensure a good conductivity.