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The present paper reports the XPS study of different high sulfur content amorphous oxysulfides thin films MOySz (M=W, Ti), prepared by radio frequency magnetron sputtering in a pure argon or mixed oxygen/argon plasma. Two types of thin layers are analyzed in this work, synthesized with an oxygen partial pressure equal to 0 and 2×10-4 Pa. On the basis of both core peaks and valence bands, several types of sulfur ions were observed and revealed the specific character of such amorphous layers. In order to precise the common features and the differences as a function of the nature of the metal atom, a comparison of the XPS data for the two kinds of thin films has been done. The results are also commented with respect to theoretical calculations (FP-LAPW—code WIEN97) undertaken on crystallized reference compounds. [Copyright &y& Elsevier]

Abstract: We have investigated the reaction mechanisms occurring upon the first discharge/charge cycle of a MnSn2//Li electrochemical cell, by using bulk- and surface-sensitive characterization techniques (X-ray Diffraction, 119Sn Mössbauer spectroscopy, magnetic measurements, X-ray photoelectron and Auger spectroscopies). Compared to other tin-transition metal alloys, MnSn2 displays an original behaviour. Lithium insertion into MnSn2 particles results in a nanocomposite consisting of Li7Sn2 phase, and of Mn nanoparticles which are immediately oxidized at their surface. Lithium extraction from this nanocomposite leads to the formation of magnetic MnSn2 particles and to our knowledge it is the first time such a mechanism is observed in tin-based intermetallic electrode materials due to electrochemical reaction with Li. The solid electrolyte interphase (SEI) is formed at the beginning of the first discharge and its thickness slightly increases upon further lithium insertion. A partial re-dissolution process occurs upon lithium extraction from the material, while its chemical composition is very stable over the whole cycle. [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: We have investigated the possible effect of carboxymethylcellulose (CMC) in the SEI film formation at the surface of a graphite composite electrode of LiCoO2/graphite cells. The electrode/electrolyte interface was analyzed by XPS at different potentials of the first electrochemical cycle, and after simple contact of the electrode with the electrolyte. We could evidence a specific reactivity of CMC towards the electrolyte (LiPF6 in a mixture of carbonate solvents), resulting in the formation of new species that contribute to the surface film composition. This result shows that the chemical reactivity of CMC towards the electrolyte takes part in the formation of the surface film, and contributes to the good properties of CMC as binder. [Copyright &y& Elsevier]

Abstract: Sputtered vanadium pentoxide thin films have been used as positive electrode in lithium microbatteries and extensively studied after cycling over the 31st galvanostatic cycles by two complementary techniques, especially well-adapted for thin films analysis: X-ray photoelectron spectroscopy and atomic force microscopy. This study is mainly focussed on the characterization of the surface film (solid electrolyte interface-type) which is formed during subsequent discharges and charges and especially on its composition and its morphology that are changing during cycling. First, the growth of a surface layer between the positive electrode and the liquid electrolyte has been evidenced upon the discharge as well as its partial dissolution upon the charge. Secondly, the chemical and topographic changes of this interfacial layer at various stages of cycling are discussed in correlation with the evolution of the discharge capacity over cycles. [Copyright &y& Elsevier]

Abstract: Research into new negative electrode materials as an alternative to carbonaceous materials brings new questions about electrode/electrolyte interface mechanisms. For graphite, these mechanisms have great importance on the ageing phenomena. What about intermetallic alloys, such as Cu–Sn systems? The nature of the electrode and its potential of lithium ions uptake (different from graphite) may have a great influence on the passivation film formed at the surface of the electrode. In this paper, we report on the XPS study of the electrode/electrolyte interface of a Cu6Sn5-based electrode. The main difference with graphite is not the nature and composition of the passivation layer, but its poor dependence on the electrochemical reaction during cycling. [Copyright &y& Elsevier]

Abstract: In this paper, we report on a study of the electrode/electrolyte interfaces of a LiCoO2/C cell using XPS (X-ray photoelectron spectroscopy). The originality of our work lies in detailed investigations step by step during the first cycle. The results have shown that the formation process of the SEI takes place in different successive stages that are dependent on the potential of the cell. It clearly appears that SEI formation continues in the potential range where lithium ion intercalation proceeds in the carbon electrode. Salt degradation products are formed after solvent decomposition ones. Concerning the LiCoO2/electrolyte interface, the results obtained have shown the formation of a very thin film on the active material but not on the binders. In all cases, the novel XPS approach applied in the lab, combining core peaks and valence band analyses, allows a precise characterization of the main chemical species of the interface layers. On the basis of these results and in conjunction with literature data, the degradation mechanisms have been discussed. [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: This paper reports on investigations of thiogermanate and thiosilicate crystals and glasses by means of XPS valence band spectra and theoretical calculations (FLAPW method). The calculations were achieved on three crystallized phases GeS2, Na2GeS3 and SiS2 and valence band spectra (visualization of the occupied electronic density of states) were precisely interpreted through modulated density of states and charge density maps. This information was used to go further in the structural investigations of some thiogermanate and thiosilicate glasses. In sodium thiogermanates, an increase in Ge–Ge bonds was revealed as the modifier content (Na2S) increases. In thiosilicates, the evolution of the valence spectra according to the nature of the alkaline atoms (Li, Na) has been interpreted as changes in the local connectivity of units (edge or corner sharing tetrahedra). This study exhibits the potentialities of valence band spectra to provide information on glassy systems. [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]

Abstract: The electrochemical properties of several TiO y S z thin films prepared by radio frequency magnetron sputtering in a pure argon or mixed oxygen/argon plasma were investigated. The two thin layers prepared in absence of oxygen presenting the compositions TiO0.6S2.8 and TiO0.9S1.7 exhibit very interesting electrochemical properties. Their behaviour was extensively studied during the first cycle and upon cycling by means of XPS (X-ray photoelectron spectroscopy). Beside titanium ions, this study evidences the contribution of the sulfur anions to the redox processes. This study also displays an analogy between the electrochemical mechanisms occurring into the TiO0.6S2.8 and TiO0.9S1.7 thin films and bulk TiS3. Furthermore, the growth of an interface between the cathode and the liquid electrolyte was evidenced upon the discharge as well as a partial dissolution upon the charge. This paper highlights the correlations that exist between the composition, the structure, the morphology of the thin films and their electrochemical performances. [Copyright &y& Elsevier]

The response of copper (II) ion-selective electrodes based on chalcogenide glassy–crystalline Cu–As–S alloys is described. The potentiometric measurements showed a Nernstian behavior in a large range of copper (II) concentration with short response time and a detection limit close to 1×10−6 M. The selectivity and the effect of the pH on the response have been determined. The chalcogenide membrane/solution interface has been investigated using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) in order to understand the sensing properties. [Copyright &y& Elsevier]