Eco-Efficient Synthesis of LiFePO4 with Different Morphologies for Li-Ion Batteries

LiFePO4 is presently the most studied electrode material for battery applications. It can be prepared via solution, although it requires well-controlled pH conditions to master the iron valence state in the newly created material. Here we report its synthesis via the use of "latent bases" capable of releasing a nitrogen base upon heating. This way of controlling the reaction pH enables, in the absence of excess Li, the preparation of Fe+3-free LiFePO4 powders having various morphologies and showing good electrochemical performance. This approach is shown to offer great opportunities for the low-temperature synthesis of various electrode materials

Evidence for electronic and ionic limitations at the origin of the second voltage plateau in nickel electrodes, as deduced from impedance spectroscopy measurements

The second plateau occurring during the reduction of the nickel oxyhydroxide electrode (NOE) was studied by impedance spectroscopy on a cell with a pasted electrode prepared from commercial undoped -Ni(OH)2. Measurements were performed at diverse states of reduction and a large variation of impedance upon the transition from the first to the second plateau was observed. This variation mainly takes place at low frequencies and is hence related to ionic diffusion. We observed that the impedance becomes more capacitive on the second plateau meaning that the proton diffusion is limited. These results would be consistent with the gradual formation of an insulating layer of nickel hydroxide at the interface between the NOE and the electrolyte upon reduction. Once this layer becomes compact the ionic diffusion would be hindered and forced to occur through this layer, which could explain the voltage drop observed

Influence of secondary phases during annealing on re-crystallization of CuInSe2 electrodeposited films

Electrodeposited CuInSe2 thin films are of potential importance, as light absorber material, in the next generation of photovoltaic cells as long as we can optimize their annealing process to obtain dense and highly crystalline films. The intent of this study was to gain a basic understanding of the key experimental parameters governing the structural–textural-composition evolution of thin films as function of the annealing temperature via X-ray diffraction, scanning/transmission electron microscopy and thermal analysis measurements. The crystallization of the electrodeposited CuInSe2 films, with the presence of Se and orthorhombic Cu2−xSe (o-Cu2−xSe) phases, occurs over two distinct temperature ranges, between 220 °C and 250 °C and beyond 520 °C. Such domains of temperature are consistent with the melting of elemental Se and the binary CuSe phase, respectively. The CuSe phase forming during annealing results from the reaction between the two secondary species o-Cu2−xSe and Se (o-Cu2−xSe+Se→2 CuSe) but can be decomposed into the cubic β-Cu2−xSe phase by slowing down the heating rate. Formation of liquid CuSe beyond 520°C seems to govern both the grain size of the films and the porosity of the substrate–CuInSe2 film interface. A simple model explaining the competitive interplay between the film crystallinity and the interface porosity is proposed, aiming at an improved protocol based on temperature range, which will enable to enhance the film crystalline nature while limiting the interface porosity

Les batteries sont-elles la bonne option pour un développement durable ?

The challenges related to energy storage have led, over the past decade, to a scientific proliferation giving birth to spectacular innovations in battery research. They have contributed in making todays electric mobility a reality, and have been key enablers in the deployment of renewable energies. However, it is legitimate to wonder what will be the battery of the future and, in particular, if this battery will be the right option for sustainable development. This is what this manuscript addresses by discussing many aspects of battery research enlisting performances improvements in terms of autonomy, durability and safety. Moreover it presents on ongoing strategies aiming towards the development of more eco-compatible and smarter batteries, based either on new chemistries enlisting abundant metals (Na-ion), on innovative recycling processes or on the injections of smart sensing and self-healing functionalities. Such a diversity of fundamental scientific challenges emerging from concrete technological bottlenecks generates a myriad of fascinating opportunities to arouse new generation of talented students to take part in this exciting adventure

Chimie du solide et énergie

Enseignement Cours et séminaires – Électrochimie appliquée : rôle des électrolytes et interfaces pour dispositifs de stockage et conversion Dans le cadre du contexte énergétique, le stockage électrochimique de l’énergie joue un rôle clé, et ce afin de faciliter la mobilité électrique, ainsi que le développement des énergies renouvelables. Ce secteur est en émulation constante avec des avancées notoires répétitives. J’avais précédemment traité certaines de ces avancées au travers des technolog..

Les batteries sont-elles la bonne option pour un développement durable ?

The challenges related to energy storage have led, over the past decade, to a scientific proliferation giving birth to spectacular innovations in battery research. They have contributed in making todays electric mobility a reality, and have been key enablers in the deployment of renewable energies. However, it is legitimate to wonder what will be the battery of the future and, in particular, if this battery will be the right option for sustainable development. This is what this manuscript addresses by discussing many aspects of battery research enlisting performances improvements in terms of autonomy, durability and safety. Moreover it presents on ongoing strategies aiming towards the development of more eco-compatible and smarter batteries, based either on new chemistries enlisting abundant metals (Na-ion), on innovative recycling processes or on the injections of smart sensing and self-healing functionalities. Such a diversity of fundamental scientific challenges emerging from concrete technological bottlenecks generates a myriad of fascinating opportunities to arouse new generation of talented students to take part in this exciting adventure

Nanomaterials for Electrochemical Energy Storage: the Good and the Bad

A critical view on the outcome of research in nanomaterials for electrochemical energy storage devices (batteries and supercapacitors) is provided through selected examples. The nano- approach traces back to the early battery research and its benefits realized even before the nano- term was coined. It has enabled important progresses which have translated, for instance, in the possibility of using LiFePO4 as electrode material. On the other hand, the nano- approach has also been oversold at all levels and hence some examples are also shown on the detrimental side effects of the use of nano-materials which should be taken into account if steady progress is to be made that finally results in practical benefits in energy storage devices

Non-Equilibrium Ionic Liquid-Electrode Interface at Elevated Temperature and Its Influence on Co2+Reduction Process

Electrodeposition in Ionic Liquid (IL) media is still at its infancy stage. Recently much attention is devoted to exploration of the IL-electrode interface for better understanding of the electrochemical processes at the electrified surfaces. Herein, we provide a new perspective of the temperature-driven IL-substrate interface structuring. We observed an increase in Co2+ reduction kinetics induced by applying a high temperature gradient. In contrast, keeping the cell at a high constant temperature (100°C) leads to slower Co2+ reduction kinetics, it results in a shift of the reduction onset and evolution of the cyclic voltammogram shape with time. We could ascribe these phenomena to the disturbance of the electrochemical double layer (induced by heating) and its further slow reorganization at constant temperature. We showed that such non-equilibrium behavior can be beneficial for the synthesis of metallic thin films from ILs. Electrochemical quartz crystal microgravimetry, impedance spectroscopy, cyclic voltammetry and chronoamperometry were employed within this work

Electrochemical Reduction of CO 2 Mediated by Quinone Derivatives: Implication for Li–CO 2 Battery

International audienc

Crystallographic and magnetic structures of the VI3_3 and LiVI3_3 van der Waals compounds

Two-dimensional (2D) layered magnetic materials are generating a great amount of interest for the next generation of electronic devices thanks to their remarkable properties associated to spin dynamics. The recently discovered layered VI$_3$ ferromagnetic phase belongs to this family, although a full understanding of its properties is limited by an ill-defined crystallographic structure. This is not any longer true. Here, we investigate the VI$_3$ crystal structure upon cooling using both synchrotron X-ray and neutron powder diffraction and provide structural models for the two structural transitions occurring at 76 K and 32 K. Moreover, we confirm by magnetic measurements that VI$_3$ becomes ferromagnetic at 50 K and discuss the difficulty of solving its full magnetic structure by neutrons. We equally determined the magnetic properties of our recently reported LiVI$_3$ phase, which is alike the well-known CrI$_3$ ferromagnetic phase in terms of electronic and crystallographic structures and found to our surprise an antiferromagnetic behavior with a N\'eel temperature of 12 K. Such a finding provides extra clues for a better understanding of magnetism in these low dimension compounds. Finally, the easiness of preparing novel Li-based 2D magnetic materials by chemical/electrochemical means opens wide the opportunity to design materials with exotic properties