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Lithium 4,4′-tolane-dicarboxylate has been synthesized and examined for use as a negative electrode material in lithium ion batteries. Cycling studies in Swagelok cells, using lithium as a counter electrode, show a reversible capacity of ∼200 mAh g -1 at ∼0.65 V and minimal discharge/charge polarization (∼15 mV). XRD and SEM analyses reveal that the material crystallizes in two different ways depending on the type of solvent used in the synthesis. The changes in structural packing with methanol or ethanol dramatically affect the capacity of the material leading to electrodes that are able to intercalate almost two vs. one Li per unit formula, respectively. © 2011 The Royal Society of Chemistry.

As our society moves toward large volume applications for Li-ion batteries the inorganic materials traditionally associated with this technology will become scarce and expensive, therefore it is important to develop electrodes that can be manufactured from renewable sources. To this end a series of straight chain derivatives of lithium fumarate having conjugation pathways from one to four units and varying isomeric forms (i.e. cis-trans relationships) have been synthesized and studied in batteries utilizing Li as the counter electrode. These experiments have shown that trans versions of molecules with conjugation pathways of 2, 3, and 4 units reversibly intercalate ~ 1 Li per unit formula at a potential of ~ 1.4 V (vs. Li/Li+) while the corresponding cis derivatives show very limited reversible reactivity towards Li. Finally, the trans lithium fumarate shows no reversibility. © 2010 Elsevier B.V.

Compounds like LiF, Li2O, and Li2O2 have considerable importance in batteries; the first two are ubiquitous in the protective SEI at the negative electrode, or the result of conversion reactions with fluorides and oxides. The latter, Li2O2, forms from oxygen reduction in the much vaunted Li/air batteries. Mastering their solubility in Li-based electrolytes is viewed as essential for further progress in battery safety, lifetime, or capacity. Aprotic solvents cannot provide the H-bonds necessary to their dissolution, and simple practical solutions have yet to materialize. Here we disclose a novel and large family of boron esters of general formula Y-C((CH2O)(Z1O)(Z2O))B whose Lewis acidity stems from geometrical constraint and can be tuned via electron affinity either by Y = CH3 → Y = NO2 or Z 1,2 ) CH2 → Z1,2 ) CO so as to partially or fully dissolve the above compounds both in battery solvent EC/DMC and in DMF. The extreme simplicity of synthesis and variability of these boron-based anion carriers, where the exchange rate is fast, are not only a valuable addition to coordination science but also a step forward to improve present battery systems. © 2010 American Chemical Society.

Lithium salts enlisting azide, oxocarbons, dicarboxylates and hydrazides have been identified as a practical mean to compensate the irreversible capacity loss of LIBs negative electrodes. During the first charge, the anion loses electrons and converts to gaseous N 2, CO or CO 2, within an acceptable potential range (3 to 4.5 V). We report an electrochemical study on these easily accessible "sacrificial salts". © 2010 Elsevier B.V.

Metals capable of forming alloys with Li are of great interest as an alternative to present carbon electrodes, hence the importance of knowing their interactions with electrolytes is necessary. Herein we report further on the high-voltage extra irreversibility of Sn electrodeposited thin films vs. Li in EC-DMC 1 M LiPF6 electrolytes. We show that this high-voltage irreversibility is strongly dependent upon the electrolyte composition as demonstrated by its disappearance in EC-free electrolytes. This finding coupled with IR spectroscopy measurements provides direct evidence for the tin-driven catalytic degradation of EC during the discharge of Sn/Li cells. From an electrochemical survey of various metals, capable of alloying with Li, we found that Bi and Pb behaved like Sn while Si and Sb did not act as catalysts towards EC degradation. A rationale for such behaviour is proposed, a procedure to bypass EC degradation with the addition of VC is presented, and an explanation for the non-observance of catalytic-driven EC degradation for Sn/C composites is provided. © 2009 Elsevier B.V. All rights reserved.

Currently, batteries are being both considered and utilized in a variety of large-scale applications. Materials sustainability stands as a key issue for future generations of batteries. One alternative to the use of a finite supply of mined materials is the use of renewable organic materials. However, before addressing issues regarding the sustainability of a given organic electrode, fundamental questions relating to the structure-function relationships between organic components and battery performance must first be explored. Herein we report the synthesis, characterization, and device performance of an organic salt, lithium 2,6-bis(ethoxycarbonyl)-3,7-dioxo-3,7-dihydro-s-indacene-1,5- bis(olate), capable of reversibly intercalating with minimal polarization 1.8 Li per unit formula over two main voltage plateaus located at ∼1.96 and ∼1.67 V (vs. Li/Li+), leading to an overall capacity of 125 mAh/g. Proton NMR and in situ XRD analyses of battery cycling versus Li at room temperature reveal that the insertion-deinsertion process is fully reversible with the dips in the voltage-composition traces, which are associated with changes in the 3D structural packing of the electrochemically active molecules. © 2010 American Chemical Society.

Oxidized stainless steel electrodes containing chromium oxides without any conducting additives or binder have been successfully cycled at high temperatures (up to 100 °C) in organic solvent-based electrolytes with high reversibility. Cycling at high temperature results in an enhancement of the capacity at lower voltages, which is maintained upon cycling. After studying different electrolyte candidates, the best results were obtained using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in ethylene carbonate. © Springer Science+Business Media B.V. 2010.

With EV and HEV developments, battery monitoring systems have to meet the new requirements of car industry. This paper deals with one of them, the battery ability to start a vehicle, also called battery crankability. A fractional order model obtained by system identification is used to estimate the crankability of lead-acid batteries. Fractional order modelling permits an accurate simulation of the battery electrical behaviour with a low number of parameters. It is demonstrated that battery available power is correlated to the battery crankability and its resistance. Moreover, the high-frequency gain of the fractional model can be used to evaluate the battery resistance. Then, a battery crankability estimator using the battery resistance is proposed. Finally, this technique is validated with various battery experimental data measured on test rigs and vehicles. © 2009 Elsevier B.V. All rights reserved.

With hybrid and electric vehicles developments, the energy management in the car has become a major topic of research for the automotive industry. Battery monitoring systems (BMS) have been designed to avoid the battery breakdown, to keep their lifespan, and decrease the fuel consumption. The battery ability to deliver energy was the only aspect of its performances that was really studied by the automotive industry until the 21 st century. The integration of more and more electronics in cars has led to take into account the power not only deliver by the alternator, but also provided by the battery, in order to ensure the availability of a growing number of vehicle functions. Most automotive battery breakdowns are due to a lack of power and rarely a lack of energy. Therefore, the battery available power needs to be monitored and taken in consideration in the BMS design. ©The Electrochemical Society.

The electrical signals generated by a vehicle cranking offer an interesting way to estimate the lead-acid battery resistance. Since resistance and power are correlated, the cranking signals can thus be used to evaluate the battery cranking capability, and possibly to define a new battery SOF (State Of Function). This paper shows how a simple fractional model is suitable for simulating the battery dynamical behavior and especially for measuring its resistance in high-frequencies. The application of the model validation technique to fractional systems is then presented to provide a resistance estimation solution. Finally, a simpler method, meeting the automotive requirements, has been developed and validated with experimental data. © 2009 IFAC.

Today, it is possible to design a mathematical model of lead-acid battery on a laptop from scratch with MATLAB. It still takes time to develop, but nowadays these models alone cannot be considered innovations anymore because anybody is able to do the same with the appropriate tools. More than ever, the actual innovation lies in the answer given to the most important question: a model to do what? Here, the model's main goal is to simulate the flooded battery behavior in all vehicle life cycles. Thus, it seems legitimate to validate them under different operating conditions with experimental data to prove that the simulation results are reliable. It is challenging but feasible, notably by making a correct selection of the parameter value ranges and studying how they influence the output. Another goal is to understand the battery behavior changes due to the physicochemical processes involved at various rates and temperatures to explain Peukert's law and the impact of temperature on vehicle cranking. The final objective of this model is to find parameter changes corresponding to the main aging phenomena to simulate new and also used batteries. © 2009 The Electrochemical Society.

Present Li-ion batteries for portable electronics are based on inorganic electrodes. For upcoming large-scale applications the notion of materials sustainability produced by materials made through eco-efficient processes, such as renewable organic electrodes, is crucial. We here report on two organic salts, Li 2C8H 4O4 (Li terephthalate) and Li 2C6H 4O4(Li trans-trans-muconate), with carboxylate groups conjugated within the molecular core, which are respectively capable of reacting with two and one extra Li per formula unit at potentials of 0.8 and 1.4 V, giving reversible capacities of 300 and 150 mAhg -1. The activity is maintained at 80°C with polyethyleneoxide-based electrolytes. A noteworthy advantage of the Li 2C8H 4O4 and Li 2C6H 4O4 negative electrodes is their enhanced thermal stability over carbon electrodes in 1M LiPF"6 ethylene carbonate-dimethyl carbonate electrolytes, which should result in safer Li-ion cells. Moreover, as bio-inspired materials, both compounds are the metabolites of aromatic hydrocarbon oxidation, and terephthalic acid is available in abundance from the recycling of polyethylene terephthalate. © 2009 Macmillan Publishers Limited. All rights reserved.

Mesoporous single crystal (PSC) oxides have been reported as presenting higher electrochemical performances than bulk materials in lithium ion batteries operating via intercalation processes. Here, we extend this study to the electrochemical behaviour of mesoporous Cr2O3 versus Li+/Li0. We confirm that the Cr2O3 reacts towards Li through a conversion reaction mechanism leading, upon discharge, to the formation of large metallic chromium nanoparticles (10 nm); the latter are embedded into a Li2O matrix together with, in this specific case, a copious amount of polymeric materials coming from electrolyte degradation, surrounding the particles, and filling the pores. During the following charge, re-oxidation of the nanoparticles occurs with the formation of CrO1-x, with the main difference, as opposed to bulk Cr2O3 electrodes, being the preservation of the polymeric layer at the end of the charge. We believe the material mesoporosity, via capillary effects, to be at the origin of such a difference. These electrolyte degradation products are shown to help in maintaining the material mesoporosity for a great number of cycles; and interestingly they are not detrimental to the cell performance in terms of capacity retention while presenting great advantages in terms of charge transfer by reducing diffusion lengths, namely for Li+ ions. The positive attributes of mesoporous material-based electrodes noticed for insertion reactions can then be extended to conversion reaction electrodes as long as we can master their synthesis while controlling their mesoporosity through either soft or hard templating techniques. © 2007 Elsevier B.V. All rights reserved.

Electrolytes are crucial to the safety and long life of Li-ion batteries, however, the understanding of their degradation mechanisms is still sketchy. Here we report on the nature and formation of organic/inorganic degradation products generated at low potential in a lithium-based cell using cyclic and linear carbonate-based electrolyte mixtures. The global formation mechanism of ethylene oxide oligomers produced from EC/DMC (1/1 w/w)-LiPF6 salt (1 M) electrolyte decomposition is proposed then mimicked via chemical tests. Each intermediary product structure/formula/composition is identified by means of combined NMR, FTIR and high resolution mass spectrometry (ESI-HRMS) analysis. The key role played by lithium methoxide as initiator of the electrolyte degradation is evidenced, but more importantly we isolated for the first time lithium methyl carbonate as a side product of the ethylene oxide oligomers chemical formation. The same degradation mechanism was found to hold on for another cyclic and linear carbonate-based electrolyte such as EC/DEC (1/1 w/w)-LiPF6 salt (1 M). Such findings have important implications in the choice of chemical additives for developing highly performing electrolytes. © 2007 Elsevier B.V. All rights reserved.

Battery performance depends on many factors amongst which the selection of the appropriate electrode material and the control of the electrode/electrolyte interface upon cycling. In order to address these issues, electrochemists have to design new electrode materials, and 'enter the private life' of a battery. Transmission Electron Microscopy (TEM) is a powerful tool to help scientists to characterize each part of the device. Recent developments in TEM techniques have been proposed and developed, through the Alistore Electron Microscopy platform (AEMP), to allow the observation of Li-ion air sensitive electrode materials. Our team is now going one step further by using High Resolution Electron Energy Loss Spectroscopy (HREELS) and nanoprobe EDS as well as other TEM techniques exhibiting the advantage of high lateral resolution for chemical analysis and for structural determination (by means of electron diffraction and high-resolution imaging). The AEMP holds at the same time the equipment and the skills to run such experiments copyright The Electrochemical Society.

Analytical high resolution transmission electron microscopy has been used to clearly evidence the electrochemical reactivity of Cr2O3 thin films versus lithium. We showed that during the reduction process, chromium sesquioxide (+III) transforms first into chromium monoxide (+II) and then into metallic chromium nanoparticles embedded into a Li2O matrix at 0 V. On the subsequent recharge up to 3 V, we did not convert back to Cr2O3, but only to a chromium monoxide implying a partial re-oxidation process, thus explaining the irreversibility measured during the first cycle. We extended this study to the comprehension of the electrochemical performances of Cr2O3-based electrodes obtained by thermal treatment, under different atmospheres, of chromium rich stainless steel disks. In addition to the characterization of the particles forming the so-obtained electro-active layers, we showed, using nano-probe EDS, that a mixed "Fe-Cr-O" oxide could react versus lithium, through a conversion reaction mechanism, leading to alloyed metallic nanoparticles upon reduction and nanograins of mixed oxide during the following oxidation. © 2006 Elsevier B.V. All rights reserved.

In the continuing challenge to find new routes to improve the performance of commercial lithium ion batteries cycling in alkyl carbonate-based electrolyte solutions, original designs, and new electrode materials are under active worldwide investigation. Our group has focused on the electrochemical behavior of a new generation of nanocomposite electrodes showing improved capacities (up to 3 times the capacity of conventional electrode materials). However, moving down to "nanometric-scale" active materials leads to a significant increase in electrolyte degradation, compared to that taking place within commercial batteries. Postmortem electrolyte studies on experimental coin cells were conducted to understand the degradation mechanisms. Structural analysis of the organic degradation products were investigated using a combination of complementary high-resolution mass spectrometry techniques: desorption under electron impact, electrospray ionization, and gas chromatography coupled to a mass spectrometer equipped with electron impact and chemical ionization ion sources. Numerous organic degradation products such as ethylene oxide oligomers (with methyl, hydroxyl, phosphate, and methyl carbonate endings) have been characterized. In light of our findings, possible chemical or electrochemical pathways are proposed to account for their formation. A thorough knowledge of these degradation mechanisms will enable us to propose new electrolyte formulations to optimize nanocomposite-based lithium ion battery performance. © 2006 American Chemical Society.

In the hope of meeting the requirements of long term cyclability for polymer electrolyte metallic lithium battery (LMP) (>600 cycles) and widening the scope of their commercial application (low temperature operation), numerous studies have been devoted to the understanding of the intrinsic limitations of these systems. Dendritic lithium growth is known to result in short circuits upon cycling. Before considering ways to master lithium deposits morphologies, we have embarked on a study aimed at characterizing by mean of Scanning Electron Microscopy (SEM): (1) the texture of metallic lithium (2) the influence of cycling parameters, such as current densities and liquid electrolyte formulation, on lithium stripping mechanisms and (3) the lithium deposits morphologies on various lithium surface states (in and ex situ prepared through electrochemical means, physical procedures such as polishing and Pulsed Laser Deposition technique). Different lithium stripping processes have been revealed depending on current densities. They lead to various surface defects from which lithium dendrites will preferentially grow upon following Li plating. Furthermore, cycling experiments have highlighted, for the first time, the internal lithium micro-texture. Pursuing this study, we finally shed light on the crucial role of the electrolytic mix formulation and cell pressure on lithium cycling efficiency. © 2006 Elsevier B.V. All rights reserved.

Aiming toward the identification of carbonate-based electrolyte degradation species formed during high-temperature cycling of Li/M-O cells, we have embarked in the synthesis and characterization of lithium-based alkyl carbonates. Through the reaction of commercial or synthesized lithium alkoxides with carbon dioxide, we succeeded in preparing lithium methyl, ethyl, propyl mono carbonates, and therefore we have extended our work to the synthesis of lithium ethandiol-bis carbonate. Their analytical characterization ( 1H and 13C nuclear magnetic resonance, electrospray ionization-mass spectroscopy, Fourier transform: infrared/attenuated total reflection) is described. Furthermore, to our surprise, we managed to demonstrate that these well-known alkyl carbonates show some electrochemical reactivity toward Li. © 2005 The Electrochemical Society. All rights reserved.

X-ray photoelection spectroscopy (XPS) was used to determine the nature and composition of electrode/electrolyte interfaces forming during the 55°C cycling of Li-based cells in ethylene carbonate:dimethyl carbonate LiPF 6 electrolyte using a heat-treated stainless steel substrate as the positive electrode. From a classical analysis of the XPS C 1s, O 1s, F 1s, P 2p, and Li 1s core peak spectra complemented by an unusual detailed interpretation of XPS valence spectra, we could follow, as a function of the cell cycling history, the evolution and nature of the species constituting the organic/inorganic layer as well as determine its approximate composition. We have shown that this surface layer mainly consists of PEO oligomers (-CH 2-CH2-O-)n, carbonates Li2CO 3 and/or CH3OCO2Li, LiPF6 salt, and of degradation products of the salt such as LiF and phosphates. Moreover, we give evidence that this layer does not only grow but also becomes richer in CH3OCO2Li and LiF species upon cycling. © 2005 The Electrochemical Society. All rights reserved.

Today's rechargeable Li-ion batteries, whose principle goes back to the 1980s, operate by an electrochemical process entailing intercalation reactions that necessitate the use of electrode materials having very specific structures and properties, thus limiting considerably their number. Through the discoveries of new Li electrochemical-driven reactivity mechanisms involving either conversion or displacement reactions, we are showing herein that in the quest for new electrode materials, we no longer need materials with open structures or good electronic ionic conductivity, thus opening a new era for Li-ion research. A review of such new reaction schemes is presented, and their potential impact on applications is discussed. © 2004 Published by Elsevier SAS on behalf of Académie des sciences.

A new effective Gel Polymer Electrolyte membrane based on two polymers, the polyethylene oxide (PEO), a poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) copolymer and a plasticizer, the dibutylphtalate (DBP), was realized. This separator membrane was made by adjunction, through lamination, of an industrially made DBP/PVdF-HFP film and a homemade DBP/PEO thin film. Once the plasticizer was removed and the separator gelled by the electrolyte, the PEO enables the formation of a good interface with the lithium while the PVdF-HFP film brings the mechanical strength to the membrane. The electrochemical behavior of lithium batteries based on this bi-layer separator was investigated versus temperature, cycling potential and cycling rate. Owing to the promising results obtained with laboratory cells, a 1 Ah prototype was successfully assembled, and its cycling and rate performances were reported. © 2005 Elsevier B.V. All rights reserved.

To benefit from the large electrochemical capacity advantages offered by Li-driven conversion reactions and to overcome poor kinetics, a new electrode configuration concept is reported. The originality of this electrode design is nested in metallurgical aspects of stainless steel, namely, the appearance of temperature-driven surface microstructures that enable the growth of a nanostructured, electrochemically active, chromium-rich oxide surface layer in close contact with a current collector. The thickness of the oxide layer can reach hundreds of nanometers and is shown to be rooted in the preferential migration of Cr toward the sample surface. We further show that chemical etching of the stainless steel surface, prior to high-temperature annealing, enables reversible capacities as high as 750 mAh/g of chromium-rich oxide for at least 800 cycles. On the basis of modeling, several scenarios involving stainless steel/chromium-based oxides current collectors of various porosities show how this new electrode configuration could boost the electrode capacity beyond that of today's carbon negative electrodes used in Li-ion cells by a factor of 2 or 3. © 2005 American Chemical Society.

Gel polymer electrolyte (GPE) membranes based on two polymers, the polyethylene oxide (PEO) and a copolymer of polyvinylidene fluoride- hexafluoropropylene (PVdF-HFP), and a plasticizer, the dibutylphthalate (DBP), were elaborated in two ways. First, the polymers and the plasticizer were mixed together to obtain a single membrane. Second, a bilayer separator membrane was made by adjunction, through lamination, of a DBP plasticized PVdF-HFP film and a homemade DBP-PEO thin film. The physicochemical properties of the gels were analyzed. AC impedance spectroscopy was carried out on symmetric Li/GPE/Li cells using either the single layer or bilayer membrane as a function of aging (isothermal at 20 and 70°C), temperature (-40 to 70°C), and finally, galvanostatic cell polarization. Both GPE membranes exhibit high ionic conductivities, but the most spectacular result was the measured decrease in the interface resistance, indicative of a deep modification of the interface Li/GPE when the cells were polarized. Aside from having a good interface with the Li metal electrode, such membranes were also shown to form good interfaces with the cathode because assembled Li/GPE/Li4Ti5O12 flat cells were able to sustain, at room temperature, more than 80% of their initial capacity for more than 300 cycles. © 2004 The Electrochemical Society. All rights reserved.

The nature and composition of gel-like organic films forming during the cycling of Li-based cells functioning through a conversion reaction process were investigated. Besides infrared techniques, both desorption electron impact (DEI) and electrospray ionization (ESI) mass spectrometry were used to study the large amounts of films obtained after extended cycling at 55°C. We give direct evidence for the formation, depending on the type of electrolytes used that differ by the nature of either the Li-based salt (LiPF6, LiCF3SO3) or solvents (dimethyl carbonate, propylene carbonate, ethylene carbonate, and their mixtures), of either phosphate-ending PEG-(polyethylene glycol) type chains, PEG chains (CH2-CH 2-O)n, or polypropylene glycol chains (CH(CH 3)-CH2-O)n with n values ranging from 1 to 9, and also trimethyl phosphate. The reaction schemes involving either electrochemical or chemical processes are proposed to describe the formation of such species. © 2004 The Electrochemical Society. All rights reserved.

The positive attributes of X-ray photoelectron spectroscopy to the field of battery research is illustrated through the study of reaction mechanisms involved during the electrochemical reduction/oxidation of a metal oxide (MO) electrode vs Li. Through the acquisition and interpretation of various (Co 2p, Li 1s, O 1s, and C 1s) XPS spectra during the charge and discharge of a CoO/Li battery, we could confirm the reversibility of the CoO → Co conversion reaction process involving the reversible formation/decomposition of CoO and Li2O together with the reversible growth of an organic layer. More importantly, such measurements suggested that the organic polymer could contain, among others, oligomer chains of poly(ethylene oxide) (CH2CH 2O)n.

In our comprehensive understanding of reactivity of CoO towards Li, we studied the effect of CoO electrode weight and composition (carbon-free or not) on the cycling performances of CoO/Li half-cells. Capacity and lifetime were measured as a function of the cycling rate and temperature. The lightest electrodes (2 mg/cm2) were shown to behave the best, with sustained capacities as high as 600 mAh/g up to about 250 cycles at 20 °C, and with capacities that peaked up to 1700 mAh/g when cycling was performed at 75 °C. Searching for the origin of this huge "extra capacity" over the normal conversion process (Co2+O → Co0, 715 mAh/g), we dissociated phenomena by testing carbon-loaded and carbon-free CoO-based electrodes in CoO/Li half cells. We unravelled a temperature-driven capacity rate increase similar for both cells, although the initial reversible capacity was quite different. The carbon-free CoO/Li half cell showed limited initial reversible capacity due to the poor efficiency of the conversion process for non-conducting electrodes. This increase appears to be nested in the reversible growth of a polymeric gel-like film resulting from kinetically activated electrolyte degradation. Polymeric layers were also shown to form from the Li electrochemical reduction of numerous binary phases, differentiating either by the nature of the 3d-metal (Cu, Ni, Fe instead of Co) or that of the anion (S, F, N instead of O). Finally, purely coincidental or not, from comparative studies of CoO, CoSb3, and CoSb2 Li half-cells, we found that, to a certain extent, the capacity amplitude associated with the growth of the polymer film scales with the surface developed by Co nano-particles. This fact would imply a possible catalytic role of 3d metals in assisting the electrolyte decomposition. © 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

The electrochemical performance of 3d metal oxide (MO) electrode materials for Li-ion batteries was studied in the form of Li/CoO(Co3O4) half-cells. Reversible capacity in the 750-1000 mAh/g range was achieved and sustained over numerous charge-discharge cycles both at room temperature and at 55°C. The studied oxides were then used as negative-electrode active materials to assemble larger plastic MO/LiCoO2 Li-ion cells, which exhibited an average output voltage of 2 V and a stable reversible specific energy of 120 Wh/kg during extended cycling at ambient and elevated temperatures. This value can be compared to 180 Wh/kg obtained for similar C/LiCoO2 Li-ion cells. Based on modeling, several scenarios involving material considerations present the optimum method for boosting the energy density of such MO/LiCoO2 Li-ion systems. © 2002 The Electrochemical Society. All rights reserved.

The unusual low-potential Li reactivity toward simple 3d-metal oxides can be accounted for by classical thermodynamic predictions and simple acido-basic considerations. The Smith's scale, defined in solids for acido-basic reactions involving O2- species exchange, is successfully used to check that, among the numerous simple oxides, the basic ones such as MnO, FeO, CoO, NiO, and CuO should reversibly react with lithium. Besides the basicity criteria, we stressed that the nanometric character of the reduced composite electrode (e.g., metallic nanoparticles immersed in a highly divided Li2O media) is a must to enable the reversible reactivity of metal oxides toward Li. Such a simple approach was finally implemented to other compounds (sulfides, nitrides, vanadates...) and the predictions confronted with experimental data.

In situ deposition of silver particles onto alumina and palladium particles onto mixed Ce-Zr oxides has been achieved upon chemical reduction of the corresponding metal species (AgNO3 and PdCl2) by ethylene glycol in the presence of polyvinylpyrrolidone. The support oxide powders were found to keep their crystalline structure and morphology after treatment with hot ethylene glycol while the BET surface area decreased after metal deposition. Microprobe maps obtained from energy dispersive X-ray analysis revealed a homogeneous distribution of metal nanoparticles on the surfaces of alumina and of the mixed Ce-Zr oxides. Supported silver and palladium were tested as catalytic converters of simulated exhaust automobile gases. The catalytic activity of silver-loaded alumina powder catalyst for CO and hydrocarbon oxidation as well as NO and NOx reduction, was found to be higher than that of a reference silver catalyst. Palladium-loaded mixed Ce-Zr oxides powder catalyst showed a similar performance to that of a reference palladium catalyst as a three-way catalyst converter. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

We report that the room temperature cycling of CoO/Li cells involving two processes, the reduction of CoO → Co0 and the growth of a polymer/gel-like film at high and low potentials, respectively, is extremely sensitive to cycling voltage ranges with the best results obtained when the cells are fully discharged. The low-voltage process is quite reversible over the 0.02 to 1.8 V range with a sustained capacity of about 150 mAh/g over a few hundred cycles. Within such a range of potential the polymer/gel-like is barely evolving while it vanishes as the oxidation potential is increased above 2 V. From the cyclic-voltammogram profiles we conclude that the origin of the low-voltage capacity is nested in the pseudocapacitive character of the in situ made polymeric/gel film. Tentative explanations based on comparisons with existing literature are made to explain such an unusual finding. © 2002 The Electrochemical Society. All rights reserved.

The electrochemical reactivity of tailor-made Cu2O or CuO powders prepared according to the polyol process was tested in rechargeable Li cells. To our surprise, we demonstrated that CuO, a material well known for primary Li cells, and Cu2O could reversibly react with 1.1 Li and 2 Li ions per formula unit, respectively, leading to reversible capacities as high as 400 mAh/g in the 3-0.02 V range. The ability of copper oxide-based Li cells to retain their capacity upon numerous cycles was found to be strongly dependent on the particle size, and the best results (100% of the total capacity up to 70 cycles) were obtained with 1 μm Cu2O and CuO particles. Ex situ transmission electron microscopy data and in situ X-ray experiments show that the reduction mechanism of Cu2O by Li first involved the formation of Cu nanograins dispersed into a lithia (Li2O) matrix, followed by the growth of an organic coating that partially dissolved upon the subsequent charge while Cu converted back to Cu2O nanograins. We believe that the key to the reversible reactivity mechanism of copper oxides or other transition metal oxides toward Li is the electrochemically driven formation of highly reactive metallic nanograins during the first discharge, which enables the formation-decomposition of Li2O upon subsequent cycles. © 2001 The Electrochemical Society. All rights reserved.

The carbon/electrolyte interface was characterized during galvanostatic cycling at different current densities by means of impedance spectroscopy, semi-in situ transmission microscopy and Fourier-transform infrared spectroscopy (FT-IR). These techniques, carried-out in an inert atmosphere, showed that the formation rate strongly influences both the chemical nature and thickness of this interface; its growth will be detailed using a rate corresponding to the intercalation of one lithium in 20 h. © 2001 Elsevier Science B.V.

A brief review of our fundamental studies of the reversible reactivity mechanism of vanadates towards lithium is presented. This mechanism totally differs from the classical one based either on reversible insertion/deinsertion of lithium into host structures or on Li alloying reactions, and has led to the thought of using nanosized transition metal oxides as possible negative electrode materials for rechargeable Li-ion batteries. Electrochemical capacities, as high as 700 mAh/g with a 100% capacity retention up to 100 cycles and high rates, can be achieved with optimized metal oxides (MO, M = Co, Cu, Ni, Fe, etc.) powders. By combining transmission electron microscope (TEM), infrared (IR) and magnetic measurements we directly proved the formation of 10-50 Å metal nanoparticles dispersed into a lithia (Li2O) matrix during the reduction step of MO with Li. Upon oxidation, the metal nanoparticles were shown to convert back to MO while Li2O was decomposed. The new opportunities provided by these metal oxides systems based on the reversible formation/decomposition of Li2O are discussed together with the positive attributes that nanoparticles could have to the field of energy storage. © 2001 Elsevier Science B.V.

Batteries performances depend on many factors amongst which the most critical are the selection/synthesis of the appropriate electrode material and the control of the electrode/electrolyte interface upon cycling. To address these issues, recent efforts have been devoted towards developing new ways to perform in situ measurements. We showed how recent advances in both cell design (e.g. the emergence of plastic cells) and instrumentations have boosted the implementation of in situ SEM and TEM techniques to the field of energy storage. The importance of such techniques to design new electrode materials, to finely tune the electrode texture for maximum electrochemical efficiency, to spot interfacial modifications/growing layers or, in short, to 'enter the private life' of a battery is discussed and commented through descriptive examples selected from various battery technologies. The link between the fundamental findings and their practical relevance to the commercial field is highlighted. Finally, although the use of microscopy techniques within the field of energy storage is rapidly growing, the full use of scanning environmental microscopes in performing in situ studies has yet to come. © 2000 Elsevier Science Ltd.

Electrochemical reactivity and reversibility of cobalt oxides towards lithium. Li-ion batteries, because of their large specific energy and long life cycle have become the technology of choice to meet today's portable electronics devices. Nevertheless, a must to guarantee their long success and to widen their field of applications, is the development of new electrode materials. Here we report on the electrochemical reactivity of cobalt monoxide (CoO), having none of the prerequisites to react with Li on the basis of the known classical Li-insertion/deinsertion or Li-alloying processes. Nevertheless, we found that these materials can reversibly react with two lithiums or more per formula unit leading to reversible capacities as high as 700mA·h·g-1, while maintaining an excellent capacity retention. This finding implies a new Li reactivity mechanism. From transmission electron microscopy, we give direct evidence of the Li-electrochemically driven formation of Co nanoparticles and Li2O during cell discharge that transforms into CoO with the disappearance of Li2O upon the following charge. This highly divided medium is favourable to both the formation/decomposition of Li2O as well as to the growth/disappearance of a protective organic film. Co3O4 was also investigated and shown to electrochemically react with Li by a similar mechanism as CoO, leading to a reversible capacity as high as 900mA·h·g-1. Académie des sciences / Éditions scientifiques et médicales Elsevier SAS © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS.