Philippe Stevens

• BSc, PhD
• Senior Researcher at Électricité de France (EDF)

In this work, the layered double hydroxide (LDH) Mg2Al(OH)6 was intercalated with redox active ferrocene carboxylate anions in order to implement charge storage capability to the interlayer spaces of the LDH structure. Two sets of anions, namely mono‐ and dicarboxylic ferrocene, were intercalated to produce two different active materials: MgAl‐FcMo...

Layered Double Hydroxides (LDHs) are a versatile class of 2D materials, which consist of layered di- and trivalent metal cation hydroxides with intercalated anions (1). They are used in many applications including energy storage electrodes, water purification or drug delivery (2, 3). In this new study, Anthraquinone-2-sulfonate (AQS) intercalated i...

A layered double hydroxide (LDH) compound LDH ([Mg 2 Al(OH) 6 ] ⁺ x 2 H 2 O) intercalated with a redox active organic anion, Anthraquinone-2-sulfonate (AQS), has been envisioned as an electrode material for high power aqueous based battery. The purpose is to use this interlayer redox active molecule for enhancement of the specific capacity at the L...

Nanostructure control is an important issue when using electroactive materials in energy conversion and storage devices. In this study, we report various methods of synthesis of nanostructured copper (II) hydroxide nitrate (Cu2(OH)3NO3) with a layered hydroxide salt (LHS) structure using various synthesis methods and investigate the correlation bet...

By selecting two electroactive species immobilized in a layered double hydroxide backbone (LDH) host, one able to act as a positive electrode material and the other as a negative one, it was possible to match their capacity to design an innovative energy storage device. Each electrode material is based on electroactive species, riboflavin phosphate...

The impressive growth in demand for energy storage systems and the constraints it might bring on the availability of raw materials has promoted research into new battery technologies alongside the dominant lithium ion technology[1,2]. In the last years, organic-based materials have gained attention as promising candidates to replace inorganics: the...

Herein the design, synthesis and electrochemical characterization of a new set of insoluble molecular carbazole derivatives for electrochemical energy storage is proposed. Two strategies, based on the incorporation of an insoluble fragment or dimerization, were carried out to avoid the dissolution of the active material in the organic carbonate‐bas...

Lithium‐ion batteries (LIBs) have triggered the transition from internal combustion engine cars to electric vehicles, and are also making inroads into the grid storage sector, but the future quantity of batteries necessary poses several challenges in terms of raw material availability and sustainability. For this reason, many alternative chemistrie...

Al-doped Li7La3Zr2O12 (LLZO) solid electrolyte is a promising candidate for all-solid-state lithium battery (ASSB) due to its high ionic conductivity and stability against lithium metal. Dense LLZO pellets were prepared by high-temperature sintering and a Li3BO3 melting agent was used to control the microstructure (grain size and grain boundary che...

All solid state battery has gained recently much attention because of their potential to store more energy while being safer to operate compared to liquid electrolyte Li-ion batteries. The development of solid electrolytes with superior electrochemical properties is highly desirable. Representatively, sulfide and oxide-based solid electrolytes have...

Solid state lithium batteries are considered as the next generation of batteries due to its potential higher energy density and better safety compared to Li-ion technology[1]. Oxides, sulfides, polymers and polymer/ceramic hybrid materials can be used as lithium ion conducting solid electrolytes, some of which have very good ionic conductivities (u...

In this study, the effect of flow of the electrolyte on an electrolysis cell and a zinc cell is investigated. The gain of energy brought by the flow is discussed and compared to the viscous losses in the cells. We point out that the balance between the gained electrical power and the viscous loss power is positive only if the hydrodynamic resistanc...

There are many electrochemical systems that are used in the market. All these systems are very different from one another. This is caused by their physical, electrochemical, and mechanical properties. These properties are: (1) energy (specific energy, energy density); (2) power (specific power, power density); (3) efficiency; (4) lifetime (primary...

The demand for high-performance, affordable, and safe energy storage solutions is growing, driven in partby the incorporation of fluctuating electricity sources like wind turbines and solar cells in the electric grid.Batteries offer such a storage solution in both distributed systems such as households and large-scaleindustrial systems. The quest f...

Solid state lithium batteries are considered as the next generation of batteries due to its potential higher energy density and better safety compared to Li-ion technology[1]. Oxides, sulfides, polymers and polymer/ceramic hybrid materials can be used as lithium ion conducting solid electrolytes, some of which have very good ionic conductivities (u...

316 L stainless steel (SS) electrodes were activated for the oxygen evolution reaction (OER) without addition of hetero-elements or incorporation of deposits at their surface. Such activation was either spontaneous (in situ: slow surface modification upon OER operation), or accelerated (ex situ, by alternating potential steps at low/high potential)...

Nanocomposites of Ni(OH)2 or NiO have successfully been used in electrodes in the last five years, but they have been falsely presented as pseudocapacitive electrodes for electrochemical capacitors and hybrid devices. Indeed, these nickel oxide or hydroxide electrodes are pure battery-type electrodes which store charges through faradaic processes a...

Hybrid supercapacitors, which combine a capacitive negative electrode and a faradaic positive electrode operating in an aqueous media, have many potential applications such as frequency regulation on the electrical grid, in particular when used in conjunction with intermittent energy sources. The purpose of this work is to study alternative designs...

Li1.3Al0.3Ti1.7(PO4)3 (LATP) materials are made of a three−dimensional framework of TiO6 octahedra and PO4 tetrahedra, which provides several positions for Li⁺ ions. The resulting high ionic conductivity is promising to yield electrolytes for all-solid-state Li-ion batteries. In order to elaborate dense ceramics, conventional sintering methods ofte...

Aqueous lithiumair batteries have very high theoretical energy densities, which potentially makes this technology very interesting for energy storage in electric mobility application. However, the aqueous electrolyte requires the use of watertight layer to protect the lithium metal typically a thick NASICON glass-ceramic layer, which adds ohmic re...

The electrification of transport is a formidable challenge, however the energy storage possible in Li ion batteries is not sufficient to this purpose. A potential option is Lithium-air battery, first because of their very high energy densities and second because of their low costs. Two different approaches to the development of these batteries are...

Lithium-air batteries have attracted a lot of research interest recently because they can close the gap between the electric vehicle and the internal combustion engine vehicle. Several challenges remain before making this technology fully functional, but using an aqueous electrolyte addresses several of them. However, it requires the use of a prote...

Zinc air batteries use very cheap raw materials (Zinc, Carbon, Potassium Hydroxide) with material costs less than 10€/kWh. The fact that they are water based batteries also makes them much safer and they use environmentally benign and recyclable materials. There is no possibility of thermal runaway or fire either. Zinc-air batteries are therefore a...

Zinc air batteries use very cheap raw materials (Zinc, Carbon, Potassium Hydroxide) with material costs less than 10€/kWh. The fact that they are water based batteries also makes them much safer and they use environmentally benign and recyclable materials. There is no possibility of thermal runaway or fire either. Zinc-air batteries are therefore a...

The aqueous rechargeable lithium battery such as the one developed by EDF and its partners, uses an aqueous electrolyte as opposed to the anhydrous lithium air concept which uses an organic electrolyte. Typical electrolytes used are saturated aqueous solutions of lithium hydroxide or lithium chloride. Since the negative electrode (lithium metal) is...

The impact of alkaline cations (Li+ and K+) on the electrocatalytic properties of high-surface-area carbon (HSAC) and nanometric manganese oxides (MnOx) deposited onto HSAC (MnOx/C) used as oxygen reduction reaction (ORR) electrodes has been studied in concentrated LiOH or KOH media. The electrochemical characterizations firstly reveal that HSAC ha...

The use of commercial 316L stainless steel as a simple, stable and competitive oxygen-evolution electrode in alkaline media for aqueous lithium–air batteries has been studied. In addition to the electrochemical characterization, the electrode was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy di...

The performance of a coaxial vacuum tube solar collector with the air as heat transfer fluid is presented using a numerical model, and experimental measurements are used to validate the simulation results. The vacuum tube is equipped with a coaxial pipe allowing air to flow inside and collect solar energy by forced convection. Experiments were carr...

In order to develop a LISICON separator for an aqueous lithium–air battery, a thin membrane was prepared by a tape-casting of a Li1.3Al0.3Ti1.7 (PO4)3–AlPO4 based slip followed by a sintering step. By optimizing the grain sizes, the slip composition and the sintering treatment, the mechanical properties were improved and the membrane was reduced to...

Unlike traditional batteries, the lithium-air cell is an open system by definition, since it needs to have access to oxygen from the surrounding air to work. This has important implications on the cell design. The traditional lithium-ion or LMP (lithium metal polymer) sealed designs can no longer be applied and completely new architectures need to...

A seasonal chemical heat store based on the hydration/dehydration cycle of a magnesium sulphate (MgSO4) composite material has been developed. During summer, the material stores heat by an endothermic dehydration reaction and heat used for space heating is released in winter by rehydrating the material. For this specific purpose, a new thermal ener...

La présente invention concerne un accumulateur métal-air rechargeable comportant une électrode à air, une électrode de dégagement d'oxygène et un dispositif automatique de protection de l'électrode à air en phase de charge et de décharge de l'accumulateur. L'invention concerne également un procédé de stockage et de restitution d'énergie électrique...

A seasonal chemical heat store based on the hydration/dehydration cycle of a magnesium sulphate (MgSO4) composite material has been developed. During summer, the material stores heat by an endothermic dehydration reaction and heat used for space heating is released in winter by rehydrating the material. For this specific purpose, a new thermal ener...

Rechargeable aqueous lithium-air cells have been developed and manufactured with the objective of analysing the limitations of the technology. The barriers to the technology have been identified and solutions to some of them have been successfully demonstrated in this study.

An electrically rechargeable zinc-air cell was developed and demonstrated using a bi-electrode on the cathode side and a 3D zinc electrode. About 200 cycles corresponding to 5000h of operation was achieved with this configuration. An innovating hybrid bi-electrode was evaluated which significantly increase the energy efficiency of our system to abo...

Electrochemical measurements of fuel cells based on proton conductor electrolyte Ba2(In0.8Ti0.2)2O5.2−n(OH)2n and prepared through a tape casting process and a co-pressing of anode-composite powder and electrolyte tape were performed at 500 °C under wet H2. The varying parameter between the prepared cells was the thickness of the electrolyte that c...

La présente invention concerne un dispositif électrochimique, en particulier une batterie rechargeable, comportant à la fois un électrolyte aqueux saturé et une membrane d'électrolyte solide conducteur de cations alcalins, ces deux électrolytes étant séparés l'un de l'autre par un film de polymère organique.

Zinc air batteries have very high theoretical energy densities, are made of cheap abundant materials, are safe and contain no toxic substances. They are therefore good candidates for electric vehicles. Their major drawback is poor lifetime when cycled due to the bad stability of the air electrode when used to recharge the battery. An alternative ox...

The neodymium-deficient nickelate Nd1.95NiO4+δ, mixed conducting K2NiF4-type oxide, was evaluated as cathode for solid oxide fuel cells. The electrochemical properties were investigated on planar Ni–YSZ anode-supported SOFC based on co-tape casted and co-fired HTceramix® cells. Using a layer of strontium doped lanthanum cobaltite as current collect...

The invention relates to the use of a ceramic of formula (I) Ba2(1-χ)M2χIn2(1-y)M'2yO4+δ(OH)δ, where M represents at least one metal cation of degree of oxidation II or III or a combination of these, M¢ represents at least one metal cation of degree of oxidation III, IV, V or VI, or a combination of these, 0 < x < 1, 0 < y < 1, δ < 2 and 0 < δ' < 2...

A model of a planar anode supported intermediate temperature solid oxide fuel cell stack with direct internal reforming is put forward to provide an understandable prediction of potential, gas concentration, and temperature distribution. This approach uses an efficient method for electrical coupling of unit cells. The model is useful in analyzing t...

This work deals with SOFC single cell tests using neodymium nickelate Nd1.95NiO4+δ as cathode material. This MIEC oxide exhibits high values of both surface exchange coefficient (k) and oxygen diffusion coefficient (D*), as well as high electronic conductivity, which result in an enhanced electrochemical activity with respect to classical materials...

Solid oxide fuel cells (SOFC) are energy conversion devices that produce electricity and heat directly from a fuel such as natural gas. Little attention has been paid to the electrical behaviour of a SOFC stack. This paper presents an electrical interaction model of a planar anode supported intermediate temperature SOFC stack with direct internal r...

BaIn0.3Ti0.7O2.85 (BIT) exhibits high anionic conductivity above 700{degree sign}C. Electrolyte-supported as well as anode-supported single cells based on BIT were fabricated and tested. A Ni/BIT cermet was used as anode and La0.7Sr0.3MnO3-d as cathode. Electrolyte-supported cells were fabricated by coating slurries of anode and cathode materials o...

Dip-coated suspensions were used for preparing YSZ layers on both dense and porous substrates. The microstructure of the as-obtained thick films was studied by varying the characteristics of the organic YSZ suspensions (concentration, viscosity, etc.) used as coating bath. The thickness and the microstructure of the films were found to depend on th...

The aim of this paper is to advance in the field of the development of low-cost synthesis techniques easy to transfer at an industrial scale for electrolyte functional materials in intermediate temperature solid oxide fuel cells (IT-SOFC). We developed an original sol–gel route to synthesize La9.33Si6O26 oxides. This approach is straightforward, in...

Ni-based cermets were prepared and reduced from mixtures of NiO and Ba2In0.6Ti1.4O5.7□0.3. A cermet containing 18.7 vol.% of Ni exhibits promising characteristics: 40% of open porosity and a lower DC resistivity than a Ni/YSZ cermet with a larger Ni content (30 vol.%). Its thermal expansion coefficient is 11.4 × 10− 6 K− 1 whereas that measured for...

The perovskite-type materials, , were prepared by a modified Pechini method and their electrochemical properties investigated using ac impedance and dc polarization methods from 300 to under different oxygen partial pressures. Schouler methodology based on the frequency relaxation has been used to assign different electrochemical processes. A t...

Silicate-based oxides are of interest as electrolytes and electrode materials in intermediate-temperature solid-oxide fuel cells (SOFCs).[1–7] We have developed a sol–gel-based strategy for the production of mesoporous, nanostructured, singlephase La9.33Si6O26 apatite in an aerogel-type framework. Silicon alkoxides react with lanthanum(III) aqueous...

Ln2NiO4+δ based materials (Ln = La, Nd or Pr), show very good electrocatalytic performances as SOFC cathode: the oxygen diffusion coefficient D* and the surface exchange coefficient k measured by isotopic exchange are several orders of magnitude higher than that of the standard LSM cathode material. They are good mixed ionic and electronic conducto...

Solid oxide fuel cells have considerable interest in recent years, because of their high efficiency and environmentally friendly nature. Such systems required oxygen-conducting electrolytes and now the most common electrolyte is yttria stabilized zirconia (YSZ). This compound exhibits high oxide ion conductivity at elevated temperatures (850–1000 °...

L'invention concerne un procédé d'électrolyse de l'eau comportant l'utilisation d'une électrode comprenant au moins un matériau oxyde particulier, particulièrement à haute température. L'invention concerne aussi un dispositif de mise en oeuvre d'un tel procédé pour l'électrolyse de l'eau

Materials formulated Ln2 − x − yyCaxNiO4 + δ (with (i) x = y = 0 for Ln = La, Pr, Nd, (ii) x ≠ 0 when y = 0 or y ≠ 0 when x = 0 for Ln = Nd) have been prepared and characterized using various techniques with respect to their mixed ionic/electronic conducting properties. These oxides exhibit high electronic conductivity (≈ 100 S cm− 1 at T = 700 °C)...

L'invention concerne un nouveau matériau oxyde et aussi une électrode comprenant un tel matériau. L'invention concerne enfin un dispositif de production d'énergie électrique de type pile à combustible comprenant au moins une cellule électrochimique comprenant une cathode qui est une telle électrode.

Solid oxide fuel cells (SOFCs) are electrical energy conversion devices with high efficiency and low pollution. In order to increase performances of SOFCs at intermediate temperature (700–800°C) and to decrease materials cost, an alternative sol–gel synthesis method has been investigated to deposit La1−xSrxMnO3+δ (LSMx) as cathode thin films. Polyc...

Composite cathodes of La1−xSrxMnO3-yttria stabilized zirconia with various molar concentrations were deposited onto dense YSZ electrolytes by dip-coating technique. The dip-coated solution is original and is based on polymeric solution. Different ways were examined to prepare it. Pure composites are only obtained when the final polymeric solution i...

La1–xSrxMnO3+δ oxides with 0⩽x⩽0.6 were synthesized via sol–gel route (Pechini process). The gel decomposition was studied by several thermal analysis methods.After calcination at 1000 °C of the dried gels, the oxides were characterized by X-ray diffraction, thermal analyses, transmission and scanning electron microscopies and chemical analyses. In...

A modified Pechini process is successfully developed for preparation of lanthanum strontium doped manganites thin films. In order to understand the mechanisms of gel formation, correlations are established between viscosity-which is the key parameter-and film thickness. The correlation between the latter and metal salts concentration is also shown....

Les avantages environnementaux des piles à combustible (rendements électrique et énergétique élevés, très faibles émissions de gaz nocifs, faible nuisance sonore, production localisée...) sont des atouts qui deviennent importants pour notre société. Cependant, ils ne sont pas suffisants si les coûts d’investissement sont trop élevés ; c’est sur ce...

Abstract This chapter on fuel cells covers the following topics: (a) fundamental electrochemical aspects and performance analysis; (b) technology research and development and demonstrations of fuel cell power sources for power generation, transportation, portable power, and space applications; (c) the role of fuel cells vs competing technologies, a...

In order to enhance the performance and long-term stability of a water electrolysis pilot plant, IrO2/Ti electrodes were hot-pressed on both sides of a Nafion® membrane and tested. By comparison with Pt electrodes, we obtained much lower anodic overvoltages and a better long-term stability of the cell voltage due to a lower cathode sensitivity to p...

A new method of preparation of Electrode/Membrane/Electrode (EME) assemblies for Proton Exchange Membrane Fuel Cells (PEMFC) has been developed. The electrodes are deposited directly onto a NAFION ® electrolyte membrane from a mixture of platinized carbon. NAFION ® solution, and PTFE by using a spray technique. By this technique, porous electrodes...

Oxygen evolution on PTFE/Nafion-bound porous activated XC-72 carbon and on PTFE- and PTFE/Nafion-bound Ebonex has been studied, using RuO2/IrO2 catalysts. High activity was found for Ebonex, but carbon, even when coated with Nafion, proved qquite unstable.

The use of metal oxides as promoters in the electrooxidation of methanol in acid electrolyte on carbon supported platinum electrodes has been investigated. The addition of zirconium(IV) oxide to carbon supported Pt/Ru electrodes as a third co-promoter and its effect on the electrode activity was studied by varying the Pt:Ru:Zr ratio using a full fa...

A full-factorial statistical method has been used to optimize the amount of binder, the compaction load and the compaction time in order to fabricate Nafion-bound carbon electrodes containing platinum and pyrolysed cobaltmeso-tetramethoxyphenylporphyrin (CoTMPP). These electrodes are designed for oxygen reduction in solid polymer electrolyte fuel c...

The free-living, nitrogen-fixing bacterium Azotobacter chroococcum has recently been shown to contain two nitrogenase systems1. One of these is the well-characterized molybdenum-containing enzyme2,3 and the other, which is encoded by different genes, contains vanadium. Both enzyme systems consist of two proteins: an iron protein and a molybdenum- o...