Matériaux et dispositifs de stockage de l'énergie électrique pour des bâtiments et des transports propres

Li-ion batteries are energy storage devices that have invaded the market for portable electronics and electric cars. They offer a relatively high energy density but have the disadvantage of slow charging due to the negative electrode based on graphite. To achieve shorter charging times, niobium oxides have emerged due to their particular crystallographic structures allowing the insertion of Li+ ions without limiting the diffusion of these ions in the material. With the same aim of increasing the power density of Li-ion batteries, this thesis undertook the synthesis and characterisation of oxides with complex crystallographic structures mainly based on niobium but also composed of Ag, V, Ti, W, and Mo. The formation of vacancies by substitution of silver by lanthanum in the perovskite AgNbO3 allowed obtaining a first model material for fast insertion. Next, the ion exchange properties of a series of materials (KTiNbO5, Cs0.5Nb2.5W2.5O14, Rb2TiNb6O18) were investigated with the aim of replacing K+, Cs+, Rb+ ions with protons or H3O+. Each protonated oxide exhibits much better insertion properties than its alkali ion analogue. A wide range of characterisation methods was used to define the physico-chemical and electrochemical properties of the synthesised materials. On the one hand, structural characterisation using X-ray diffraction (XRD) and transmission electron microscopy (HRTEM) has provided a good understanding of the crystallographic structure of these oxides. On the other hand insertion mechanisms have been solved by using original methods such as in situ XRD, entropy potential measurement or operando calorimetryLes batteries Li-ion sont des dispositifs de stockage de l’énergie ayant envahi le marché de l’électronique portatifve ainsi que celui des voitures électriques. Elles proposent une densité d’énergie relativement haute mais possèdent l’inconvénient d’une recharge lente principalement à cause de l’électrode négative composée de graphite. Pour obtenir des temps de charge plus rapides, les oxydes de niobium ont émergé en raison de leurs structures cristallographiques particulières permettant l’insertion des ions Li+ grâce à de bonnes propriétés de diffusion ionique dans le matériau. Ainsi, dans le but d’augmenter la densité de puissance des batteries Li-ion, cette thèse a entrepris la synthèse et la caractérisation d’oxydes possédant des structures cristallographiques complexes principalement à base de niobium mais également composées d’argent, de vanadium, de titane, de tungstène ou encore de molybdène. La formation de lacunes par substitution de l’argent par du lanthane dans la pérovskite AgNbO3 a permis d’obtenir un premier matériau modèle vis-à-vis de l’insertion rapide. Ensuite, les propriétés d’échange ionique d’une série de matériaux (KTiNbO5, Cs0.5Nb2.5W2.5O14, Rb2TiNb6O18) ont été étudiées dans le but de remplacer les ion K+, Cs+, Rb+ par des protons ou des H3O+. Chaque oxyde protoné présentant des propriétés d’insertion bien supérieures à leurs analogue possédant des ions alcalins. Aussi, durant l’ensemble de ce travail de thèse, un large panel de méthodes de caractérisation a été utilisé dans le but de définir les propriétés physico-chimique et électrochimiques des matériaux synthétisés. D’une part, des caractérisations structurales grâce à l’utilisation de la diffraction des rayons X (DRX) et de la microscopie électronique à transmission ont permis de comprendre la structure cristallographique de ces oxydes. D’autre part, les mécanismes d’insertion ont été résolus grâce à l’utilisation de méthodes originales telles que la DRX in situ, la mesure du potentiel entropique ou encore par l‘utilisation de la calorimétrie operand

Ag2V4O11: from primary to secondary battery

Ag2V4O11 (silver vanadium oxide, SVO) is the positive electrode in primary lithium/SVO batteries that had known an extraordinary success as a power source in implantable cardiac defibrillators (ICD). However, its use in rechargeable batteries is questioned due to the need of the negative lithium metal electrode that acts as the lithium source and that cannot be safely recharged in standard liquid electrolytes. In this study, a proof of concept of rechargeable graphite/SVO battery is demonstrated. The introduction of 3,4-dihydroxybenzonitrile dilithium salt (Li2DHBN) as a sacrificial lithium source in the positive electrode allows in situ lithiation of the graphite electrode. The cell can further be cycled as a secondary battery. Different parameters have been investigated such as the particle size of Ag2V4O11 synthesized by solid state and hydrothermal processes, especially with regard to peak power delivery. In situ XRD was used to investigate the link between irreversible silver reduction, which allows high electronic conductivity, and amorphization of the SVO structure

Revisiting Rb2TiNb6O18 as electrode materials for energy storage devices

International audienceIn the search of new materials for the future generation of Li-ion batteries, a look into the past has brought the multicationic oxide Rb2TiNb6O18 to the foreground. Structural characterization of this material has been carried out thanks to the combination of XRD, SEM and HRTEM highlighting the complex structure of this material. Ion exchange was performed in order to replace the rubidium ions by hydrated protons. Then, a comparative study of Rb2TiNb6O18 and the obtained proton exchanged analogues H2TiNb6O18 when used as negative electrode materials is depicted in terms of both structure and electrochemical behavior. Interestingly, while only a negligible Li+ insertion is evidenced in the rubidium phase, the H2TiNb6O18 exhibits a much higher lithium intercalation between 1 V and 3 V vs Li/Li+. A specific capacity of 118 mAh.g(-1) is reported when cycled at 0.02 A.g(-1). A solid solution type mechanism has been revealed by in situ XRD experiments. Moreover, during the lithiation, the volume of the material increases by only 1% showing the interest of this type of phase to develop "zero-strain" materials

Revisiting Rb2TiNb6O18 as electrode materials for energy storage devices

International audienceIn the search of new materials for the future generation of Li-ion batteries, a look into the past has brought the multicationic oxide Rb2TiNb6O18 to the foreground. Structural characterization of this material has been carried out thanks to the combination of XRD, SEM and HRTEM highlighting the complex structure of this material. Ion exchange was performed in order to replace the rubidium ions by hydrated protons. Then, a comparative study of Rb2TiNb6O18 and the obtained proton exchanged analogues H2TiNb6O18 when used as negative electrode materials is depicted in terms of both structure and electrochemical behavior. Interestingly, while only a negligible Li+ insertion is evidenced in the rubidium phase, the H2TiNb6O18 exhibits a much higher lithium intercalation between 1 V and 3 V vs Li/Li+. A specific capacity of 118 mAh.g(-1) is reported when cycled at 0.02 A.g(-1). A solid solution type mechanism has been revealed by in situ XRD experiments. Moreover, during the lithiation, the volume of the material increases by only 1% showing the interest of this type of phase to develop "zero-strain" materials

Effect of particle microstructure and the role of proton on the lithium insertion properties of HTiNbO5 electrode material

International audienceLayered oxides showing edge-sharing octahedra are promising negative electrode materials for high-power Li-ion batteries. In this sense, we propose the synthesis of the lamellar HTiNbO5 by solid-state (SS), sol-gel (SG) and exfoliation-restacking (NS) syntheses investigating in the same way the charge storage mechanism of this oxide and the influence of the microstructure on material and electrochemical properties. An arsenal of character-ization techniques has been used to investigate these three types of particles using X-Ray Diffraction (XRD), electron microscopy, but also by associating mass spectroscopy to thermogravimetric analyses (TGA). Their ability to intercalate lithium has been compared, showing interesting and very similar specific capacities for solid-state and sol-gel synthesis (> 100 mAh.g -1 at 0.5 A.g -1). In addition, it was shown that the synthesis giving rise to nanosheet (NS) led to lower performance due to the presence of organic molecules in the interlayer spacing of the 2D lamellar structure. Lastly, in situ XRD evidenced a solid-solution reaction for HTiNbO5, with an initial and irreversible phase change leading to the formation of Li0.4HTiNbO5. Moreover, ex situ 1H MAS NMR measurements highlight the essential role of the proton in the charge storage mechanism of HTiNbO5. Thus, this paper demonstrates the interest of HTiNbO5 as a fast negative electrode material for high-power Li-ion batteries as well as the predominant role that the proton can play in the diffusion of lithium ions inside a confined interlayer space

Hexagonal Tungsten Bronze H0.25Cs0.25Nb2.5W2.5O14 as a Negative Electrode Material for Li-Ion Batteries

International audienceOxides derived from the ReO3 structure, such as bronzes or Wadsley-Roth phases, have re-emerged from the past as they offer very attractive properties as negative electrodes for high-power Li-ion batteries. Here, we revisit the hexagonal bronze Cs0.5Nb2.5W2.5O14 and its protonated H0.25Cs0.25Nb2.5W2.5O14 derivative, which was newly obtained after ion exchange. A panel of characterization techniques (HAADF-STEM imaging, EDX mapping, and XRD) revealed a specific cation ordering in the material and a preferential ion exchange in the heptagonal tunnels of this oxide. When used as Li-ion battery electrodes, H0.25Cs0.25Nb2.5W2.5O14 exhibits higher specific capacities as well as better capacity retention at high currents than Cs0.5Nb2.5W2.5O14. The protonated phase provides specific capacities of 132 and 111 mAh center dot g-1 at, respectively, 0.02 and 0.2 A center dot g-1. Kinetic analysis reveals that the good capacity at a high rate is due to favorable diffusion of lithium ions into the tunnels of H0.25Cs0.25Nb2.5W2.5O14. In addition, using in situ XRD, a solid solution mechanism occurring during lithium insertion was proposed, as well as the different lithiation sites of the material

Capacitive tendency concept alongside supervised machine-learning toward classifying electrochemical behavior of battery and pseudocapacitor materials

Abstract In recent decades, more than 100,000 scientific articles have been devoted to the development of electrode materials for supercapacitors and batteries. However, there is still intense debate surrounding the criteria for determining the electrochemical behavior involved in Faradaic reactions, as the issue is often complicated by the electrochemical signals produced by various electrode materials and their different physicochemical properties. The difficulty lies in the inability to determine which electrode type (battery vs. pseudocapacitor) these materials belong to via simple binary classification. To overcome this difficulty, we apply supervised machine learning for image classification to electrochemical shape analysis (over 5500 Cyclic Voltammetry curves and 2900 Galvanostatic Charge-Discharge curves), with the predicted confidence percentage reflecting the shape trend of the curve and thus defined as a manufacturer. It’s called “capacitive tendency”. This predictor not only transcends the limitations of human-based classification but also provides statistical trends regarding electrochemical behavior. Of note, and of particular importance to the electrochemical energy storage community, which publishes over a hundred articles per week, we have created an online tool to easily categorize their data

Investigating the Perovskite Ag1-3xLaxNbO3 as a High-Rate Negative Electrode for Li-Ion Batteries

International audienceThe broader development of the electric car for tomorrow's mobility requires the emergence of new fast-charging negative electrode materials to replace graphite in Li-ion batteries. In this area, the design of new compounds using innovative approaches could be the key to discovering new negative electrode materials that allow for faster charging and discharging processes. Here, we present a partially substituted AgNbO3 perovskite material by introducing lanthanum in the A-site. By creating two vacancies for every lanthanum introduced in the structure, the resulting general formula becomes Ag1-3xLax2xNbO3 (with x <= 0.20 and where is a A-site vacancy), allowing the insertion of lithium ions. The highly substituted Ag0.40La0.200.40NbO3 oxide shows a specific capacity of 40 mAh.g(-1) at a low sweep rate (0.1 mV s(-1)). Interestingly, Ag0.70La0.100.20NbO3 retains 64% of its capacity at a very high sweep rate (50 mV s(-1)) and about 95% after 800 cycles. Ex situ Li-7 MAS NMR experiments confirmed the insertion of lithium ions in these materials. A kinetic analysis of Ag1-3xLax2xNbO3 underlines the ability to store charge without solid-state ion-diffusion limitations. Furthermore, in situ XRD indicates no structural modification of the compound when accommodating lithium ions, which can be considered as zero-strain material. This finding explains the interesting capacity retention observed after 800 cycles. This paper thus demonstrates an alternative approach to traditional insertion materials and identifies a different way to explore not-so common electrode materials for fast energy storage application

Influence of ion implantation on the charge storage mechanism of vanadium nitride pseudocapacitive thin films

International audienceThe influence of microstructural or structural defects is seldom investigated in pseudocapacitive electrodes. Indeed, most of the synthesized materials do present defects at every scales which contribute to the improvement of the charge storage. In this study VN thin films were deposited by reactive magnetron sputtering. The as-deposited VN films were compared with similar films implanted with arsenide cations (As+) with energies ranging from 20 keV up to 150 keV. The influence of the ionic implantation on the structure and microstructure of the pristine films was characterized by several techniques. The initial curing of the internal stress of as-deposited VN films observed for low implantation energies was lost with increasing implantation energy. Concomitantly, the electrochemical behaviors of the VN films were investigated. All the VN films show a pseudocapacitive behavior at 2 mV.s−1. At low scan rates, the as-deposited film exhibits the highest areal capacitance (45 mF.cm−2) which drastically decreases upon increasing the scan rate. Only 30% of the initial capacitance is maintained at 100 mV.s−1. Despite lower capacitances at 2 mV.s−1, As+ implanted VN films exhibit better capacitance retention in the same conditions, i.e. up to 65% of the initial capacitance is maintained at 100 mV.s−1. The contributions coming from surface and subsurface reactions have been determined which enable to propose possible origins for the changes occurring in charge storage mechanisms upon ion implantation

Effect of particle size on thermodynamics and lithium ion transport in electrodes made of Ti2Nb2O9 microparticles or nanoparticles

International audienceThis study compares the charging mechanisms, thermodynamics, lithium ion transport, and operando isothermal calorimetry in lithium-ion battery electrodes made of Ti2Nb2O9 microparticles or nanoparticles synthesized by solid-state or sol-gel methods, respectively. First, electrochemical testing showed that electrodes made of Ti2Nb2O9 nanoparticles exhibited larger specific capacity, smaller polarization, and better capacity retention at large currents than those made of Ti2Nb2O9 microparticles. Furthermore, potentiometric entropy measurements revealed that electrodes made of either Ti2Nb2O9 microparticles or nanoparticles showed similar thermodynamics behavior governed by lithium intercalation in solid solution, as confirmed by in situ XRD measurements. However, electrodes made of Ti2Nb2O9 nanoparticles featured smaller overpotential and faster lithium ion transport than those made of Ti2Nb2O9 microparticles. In fact, operando isothermal calorimetry revealed smaller instantaneous and time-averaged irreversible heat generation rates at electrodes made of Ti2Nb2O9 nanoparticles, highlighting their smaller resistive losses and larger electrical conductivity. Finally, the measured total heat generation over a charging/discharging cycle matched the measured net electrical energy loss. Overall, Ti2Nb2O9 nanoparticles synthesized by the novel sol-gel method displayed excellent cycling performance and reduced heat generation as a fast-charging lithium-ion battery anode material. These features present major advantages for actual battery systems including larger energy and power densities, simpler thermal management, and enhanced safety