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Although Li-rich layered oxides (Li1+xNiyCozMn1−x−y−zO2 > 250 mAh g−1) are attractive electrode materials providing energy densities more than 15% higher than today's commercial Li-ion cells, they suffer from voltage decay on cycling. To elucidate the origin of this phenomenon, we employ chemical substitution in structurally related Li2RuO3 compounds. Li-rich layered Li2Ru1−yTiyO3 phases with capacities of ~240 mAh g−1 exhibit the characteristic voltage decay on cycling. A combination of transmission electron microscopy and X-ray photoelectron spectroscopy studies reveals that the migration of cations between metal layers and Li layers is an intrinsic feature of the charge-discharge process that increases the trapping of metal ions in interstitial tetrahedral sites. A correlation between these trapped ions and the voltage decay is established by expanding the study to both Li2Ru1−ySnyO3 and Li2RuO3; the slowest decay occurs for the cations with the largest ionic radii. This effect is robust, and the finding provides insights into new chemistry to be explored for developing high-capacity layered electrodes that evade voltage decay. [ABSTRACT FROM AUTHOR]

LiFePO4 has monopolized a lot of research efforts over the past decade because it stands as an attractive positive electrode material for the next generation of Li-ion batteries to EVs/HEVs. However, issues concerning aging mechanisms need to be solved before large scale industrial production. In order to get more insight in such mechanisms, the evolution of both electrodes of a LiFePO4 // graphite cell after 200 cycles at RT and 60°C was followed using X-Ray Photoelectron Spectroscopy (XPS). The results have revealed a lack of reversibility of the Fe3+/Fe2+ redox reaction increasing upon cycling and at high temperature. In depth analyses of interfacial layers on both electrodes allowed us to further elucidate the origin of the detrimental loss of active lithium with the formation of small amounts of lithiated species either deposited or partly dissolved in the electrolyte. [ABSTRACT FROM AUTHOR]

The impact of aluminum oxide coatings on LiCoO2 materials for commercial lithium ion batteries has been investigated by X-ray photoelectron spectroscopy (XPS). A low binding energy component in the Al 2p core peak spectra was observed and attributed to the formation of a LiAlxCo(l-x)O2 solid solution interphase for both Al2O3- and AlPO4-coated LiCoO2. The surface chemistry of pristine and Al2O3-coated LiCoO2 cathodes and graphite anodes have been investigated after cycling up to 4.2 V or 4.4 V cutoff voltage and after various levels of capacity fade. The Al2O3 coating enhances the capacity retention at both 4.2 V and 4.4 V cutoff voltages. XPS analyses provided evidence of the inhibition of cobalt dissolution from the LiCoO2 positive electrode by the aluminum coatings. Moreover, the Al2O3 coating lowers the kinetics of degradation of electrolyte species, especially the LiPF6 salt. [ABSTRACT FROM AUTHOR]

Abstract: The electronic structure of Ge x As40− x S60 glasses and amorphous films has been obtained by means of X-ray photoelectron spectroscopy. Core level peaks and valence band spectra in the dependence on the composition as well as on structural changes initiated by illumination and/or annealing have been investigated and discussed. [Copyright &y& Elsevier]

Abstract: Commercial C-LiFe0.33Mn0.67PO4 positive electrode material has been investigated by 57Fe Mössbauer Spectroscopy (MS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The combined use of these experimental techniques provides a better understanding of the electrochemical reaction involved during cycling. 57Fe MS is very efficient to directly follow oxidation state of Fe in the electrode, and gives surprisingly indirect information on the oxidation state of Mn as observed by XAS and XPS. The electrochemical mechanism is proposed based from in situ and operando investigations using both MS and XAS, and is consistent with XPS surface studies. XPS analysis of the electrodes at the end of charge (4.4V) reveals enhanced electrode/electrolyte interface reactivity at this high potential. Aging of C-LiFe0.33Mn0.67PO4/Li cells after 50cycles at 60°C indicates a rather good electrochemical behavior (low capacity fading) of the electrode material. Both 57Fe MS and XPS (Mn 2p and Fe 2p) clearly show no modification on Fe and Mn oxidation state compared to fresh electrode confirming the good electrochemical performances. [Copyright &y& Elsevier]

Abstract: A detailed X-ray photoelectron spectroscopy study has been performed for the CuRh1−x Mg x O2 (x=0, 0.04 and 0.10) series for a better understanding of the role of the Mg2+ substitution on the electrical properties and the value of the Seebeck coefficient. This study is based on an analysis of different compounds such as Rh2O3, Sr2RhO4 and CuCrO2 in order to characterize different oxidation states (Rh3+ and Rh4+ in octahedral oxygen environment and Cu+ in a dumbbell O–Cu–O coordination). The Cu2p signal of copper in the non-doped compounds CuCrO2 and CuRhO2 reveals different electronic structures. An evolution of the Cu2p core signal with the increase of Mg2+ content in the CuRh1−x Mg x O2 is highlighted by XPS. The differences observed, especially for the Cu2p core peaks are discussed for the non-doped compounds CuCrO2 and CuRhO2 as for the CuRh1−x Mg x O2 series upon Mg2+ substitution. [Copyright &y& Elsevier]

Abstract: The present paper deals with a fine physico-chemical analysis of some hybrid materials combining an inorganic layered double hydroxide phase (LDH) with an organic benzene derivative entity R′-C6H4-R with R = –SO3 −, –CO2 − and R′ = –H, –OH. The main topic of this work is, in a nanoscale, to propose a way to approach the understanding of the interactions between inorganic and organic sub-systems. The role of the anionic headgroup R is discussed in term of reactivity with the mineral support. The classical expertise of materials via the PXRD technique puts into light an effective LDH interlayer space enlargement with the organics incorporation and a minimum angle of inclination for every organics within the LDH matrix. The originality of this study is to use the X-Ray Photoelectron spectroscopy (XPS) as a local probe of the chemical environments of the headgroup of the organic entities. In a parallel way, some quantum calculations (by using molecular and periodical codes) are carried out to best appreciate the electronic and structural evolutions before and after the intercalation step. A specific reactivity of the –SO3 − group compared with the –CO2 − one is evidenced. Moreover, a correlation at the first order is then set up between the net charges of atoms and the XPS binding energies of their core levels. [Copyright &y& Elsevier]

Abstract: The response of thin-film copper (II) ion-selective electrodes based on chalcogenide glassy Cu–Sb–Ge–Se is described according to the soaking time in a 10−4 M copper (II) solution. The chalcogenide membrane/solution interface has been investigated by using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) in order to understand the sensing properties. During the first month of the soaking, an alteration of the membrane by a chemical change without alteration of the sensor detection performance has been observed. [Copyright &y& Elsevier]

Abstract: The formation of a passivation film (solid electrolyte interphase, SEI) at the surface of the negative electrode of full LiCoO2/graphite lithium-ion cells using different salts (LiBF4, LiPF6, LiTFSI, LiBETI) in carbonate solvents as electrolyte was investigated by X-ray photoelectron spectroscopy (XPS). The analyzes were carried out at different potential stages of the first cycle, showing the potential-dependent character of the surface film species formation and the specificity of each salt. At 3.8V, for all salts, we have mainly identified carbonated species. Beyond this potential, the specific behavior of LiPF6 was identified with a high LiF deposit, whereas for other salts, the formation process of the SEI appears controlled by the solvent decomposition of the electrolyte. [Copyright &y& Elsevier]

Abstract: Vanadium pentoxide thin films, usable as positive electrode in microbatteries, have been prepared by radio frequency magnetron sputtering in a pure argon or mixed argon/oxygen plasma. Depending on the oxygen pressure in the discharge gas, we have obtained either crystallized or amorphous thin films. These two kinds of thin films having different electrochemical behavior, an extensive X-ray photoelectron spectroscopy (XPS) study (especially suited for thin films analysis) was carried out. The main redox processes occurring during the first discharge–charge cycle were identified. In addition, depending on the crystalline or amorphous character of the samples, we have noticed some differences concerning the kinetic of reduction. Furthermore, the growth of a surface layer between the cathode and the liquid electrolyte was evidenced upon the discharge as well as its partial dissolution upon the charge. [Copyright &y& Elsevier]

The surface of mixed transition metal sulfur TixTa1-xS2 has been studied both by X-ray photoelectron spectroscopy and scanning tunneling microscopy over the entire range of stoichiometry 0⩽x⩽1. For compositions close to the native materials, we highlight according to x an evolution between the existence of a charge density wave (TaS2) and the existence of structural defects (TiS2), interpreted as metal atoms vacancies or migration within the vacant sites of the structure. The results obtained by XPS and scanning probe microscopy for intermediate compositions (0.4⩽x⩽0.6) lead us to propose a model in ordered domains, separated by frontier zones where the metal distribution is random. These various interpretations, supported by our experimental results, find their origin from the different electronic characteristics of native materials and their evolution according to the composition. On the basis of model systems, we have undertaken band structure calculations (FP-LAPW method) in order to highlight specific interactions occurred in TixTa1-xS2 when x varies between 0.4 and 0.6. Those make it possible to rationalize some of our experimental data. [Copyright &y& Elsevier]

The surface of Ni1/4TiS2 was investigated by X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Electronic calculations were performed using the ab initio Hartree–Fock program crystal. The XPS results (chemical shift of core peaks) are satisfactorily accounted for through a Mulliken population analysis. Concerning the STM results, we imaged the top sulfur plane (0 0 1) and interpret the data on the basis of the partial electron density of a slab which consist of seven (0 0 1) Ni1/4TiS2 layers. It was found that the bright spots in experimental STM images correspond to sulfur atoms in a single metallic environment (Ti atoms). Beside higher electronic density, these atoms are highlighted because of their proximity to the tip compared with sulfur atoms in a double environment (Ti and Ni). [Copyright &y& Elsevier]