Modeling and Characterization of Glass-Based Positive Electrodes for Li-Ion and Na-Ion Batteries
Amorphous cathode materials for Li-ion batteries have regained interest thanks to their practical capacities, which can exceed those of conventional commercial oxide cathode materials. Despite somewhat lower cell voltages, it could lead to significant enhancements in energy density. Nevertheless, the known amorphous cathode materials still face serious challenges prevent them from practical application: i) High irreversible capacity, ii) Low electronic conductivity, iii) Limited cyclability, iv) Lack of understanding of the involved phenomena due to their amorphous state, v) Most of the glassy cathode compositions explored so far are based on toxic vanadium.
In order to gain a deeper understanding of the influence of transition metals, glass formers, and synthesis conditions on the electrochemical performance of the cathode material, a PhD thesis is proposed in collaboration with CEA (Marcoule and Grenoble) and the National University of Singapore. The study will aim to combine various simulation approaches and experimental techniques, such as machine learning to design even more efficient cathode materials, computational modeling coupled with advanced in situ/operando characterization methods, and finally the development and performance evaluation of the synthesized materials.
Comprehensive characterization of bulk and interfaces mechanisms in water-in-salt electrolytes for aqueous batteries
One greener alternative to current Li-ion batteries are aqueous batteries. Unfortunately, water is thermodynamically stable in a very narrow potential window of only 1.23 V, resulting in poor energy efficiency. Using concentrated aqueous electrolytes (Water-In-Salt aqueous Electrolytes (WISEs)), a significant increase in the potential window of aqueous Li batteries up to 3 V can be achieved. Yet, aqueous batteries based on WISE electrolytes suffer from several issues leading to electrochemical failure such as self-discharge, pH evolution, parasitic reactions and instable interfaces layers. There is thus a strong need to understand the reactivity in concentrated electrolytes. In the frame of the ANR project AQUABATT, we will address these issues using a comprehensive approach combining different advanced characterization techniques. The PhD student will address these limitations by providing a comprehensive approach of the reactivity as function of salt concentration. The student will combine electrochemical measurements with infrared and NMR spectroscopies to elucidate the solvation structure of the solutions. The nature of the interface between the electrolyte and the electrode and bulk redox mechanisms in electrodes will be investigated by means of synchrotron operando infrared spectroscopy and operando X-Ray Absorption Spectroscopy (XAS) respectively.
Addressable transition metal complexes as models for quantum bits and logic gates
The project concerns the design, development and study of spin dynamics in binuclear transition metal complexes
as models for quantum logic gates. The first part focuses on Cu(II) complexes. The second part explores Fe(II)-
based complexes that can be optically addressed in the visible range. The complexes will first be characterized by
continuous-mode electron paramagnetic resonance (EPR) spectroscopy to highlight the quantum bit behavior of
the mononuclear complexes used to form the binuclear species. Detailed studies of spin-lattice relaxation time (T1)
and spin-spin relaxation time (coherence time, T2) will then be carried out using pulsed EPR. Studies on
addressable complexes (mononuclear and possibly binuclear) will determine the impact of the presence of one
paramagnetic center on the coherence time of another within the binuclear entity, enabling the robustness of
quantum logic gates manipulatable by visible light to be assessed.
Study of the corrosion behaviour of complex multi-element materials/coatings in H2SO4 and HNO3 environments
This thesis is part of the CROCUS (miCro laboRatory fOr antiCorrosion solUtion design) project. The aim of this project is to develop a micro-laboratory for in situ corrosion analysis that can be brought into line with processes for synthesising anti-corrosion materials or coatings
By testing a wide range of alloy compositions using AESEC (a technique providing access to elementally resolved electrochemistry), the project will provide a real opportunity to build up a corrosion database in different corrosive environments, whether natural or industrial, with varying compositions, concentrations, pH and temperatures.
The aim of the thesis will be to study the corrosion behaviour of promising multi-element complex materials/coatings using electrochemical techniques coupled with AESEC.
The first part of this work concerns the determination of the limits of use of these promising alloys as a function of the proton concentration in H2SO4 and HNO3 media for temperatures ranging from room temperature to 80°C. The passivity of these alloys as a function of acid concentration will be studied using electrochemical techniques (voltammetry, impedance, AESEC).
The presence of certain minor elements in the composition of these alloys, such as molybdenum, may have a beneficial effect on corrosion behaviour. To this end, the passivation mechanisms involved will be studied using model materials (Ni-Cr-Mo), electrochemical techniques (cyclic and/or linear voltammetry, impedance spectroscopy and AESEC) and surface analysis.
The second part deals with the transition between passivity and transpassivity, and in particular the occurrence or non-occurrence of intergranular corrosion (IGC) as a function of oxidising conditions (presence of oxidising ions). The aim will be to determine the different kinetics (comparison between grain and grain boundary corrosion rates), as well as to validate the models set up to study IGC in steels.
Finally, the student will participate in the development of a materials database for corrosion in aggressive environments, whether natural or industrial, with different compositions, concentrations, pH and temperatures, enabling the development of new generations of corrosion-resistant materials or coatings through the use of digital design and artificial intelligence optimisation tools.
Evaluation of nanoscale surface coatings on high energy density positive electrodes for lithium-ion batteries.
Nickel-rich layered oxides LiNi1-x-yMnxCoyO2 (NMC) and LiNi1-x-yCoyAlzO2 (NCA) are exceptional materials for the positive electrode of lithium batteries due to their high reversible storage capacity. However, under real conditions, undesired reactions can lead to the dissolution of transition metals and electrodes cracking, thus affecting their electrochemical properties. This phenomenon is linked to the presence of hydrofluoric acid (HF) in the electrolyte, mainly due to the degradation of the LiPF6 salt. To address this problem, surface treatments are needed to protect the active material and improve performance. The EVEREST project proposes an innovative, flexible, and affordable method for creating inorganic coatings at the nanoscale. This method is based on a recent technique, coaxial electrospinning, which allows the production of nanofibers with a well-defined core-sheath structure. For this project, we propose to evaluate the impact of nanofiber shaping parameters on morphology, electrochemical performance and the underlying mechanism. The electrochemical performances of the coated and the pristine positive electrodes will be compared in a half-cell with Li metal as a counter electrode. Redox processes, charge transfer mechanisms and structural modifications will be studied in the operando mode using the synchrotron radiation beam.
Silver nanowires synthesized from end-of-life solar panels for CO2 reduction and transparent electrodes
Silver nanowires (AgNW) networks are remarkable materials with both the highest electrical and thermal conductivity at ambient temperature, and a good chemical stability. They are used in transparent electrodes, for instance in organic solar cells, heating films or electrochromic devices. Their synthesis has been upscaled at the industrial level with high yield and reproducibility. More recently, they also found promising applications in low-emissivity layers on windows, and in catalysis of CO2 reduction at ambient temperature as a selective electrocatalyst.
In this PhD project, we will turn to recycled sources of silver from dismantled end-of-life silicon solar panels for the synthesis of AgNWs, in a “green chemistry” approach. The quality of the nanomaterial will be checked directly in two relevant devices, namely IR-low-emissivity films for reduction of heat loss, and electroreduction of CO2 for the production of e-fuels. The project will focus on understanding the fundamental basis of the impact of impurities on the synthesis of AgNWs, the physical properties of the AgNW networks, their stability under electrical stress or chemical wear, and their performance as active material in the devices.
The work will take place in Grenoble, the second scientific hub in France. The PhD student will be hired by CEA, a major French research institution with a high focus on alternative energies. He/she will join the fundamental research lab SyMMES, expert in nanomaterial design and energy devices such as solar cells, batteries and electrolyzers. She/he will work in co-supervision in the partner lab LMGP expert in materials science, synthesis and implementation at Grenoble INP. SYMMES and LMGP belong to University Grenoble Alpes and host widely international teams. The project will be actively supported by a local industrial recycling company.
Applicants should hold a Master 2 degree in chemistry, physics or materials science with skills in nanomaterials, electrochemistry or physical chemistry and in basic science for energy. Good English proficiency and a strong interest for innovation and collaborative work are expected.
Monitoring the electrode-electrolyte interface and redox activity in aqueous water-in-salt Na-ion batteries
Using concentrated aqueous electrolytes (Water-In-Salt aqueous Electrolytes), a significant increase in the potential window of aqueous Li batteries can be achieved. This is due to the absence of free water molecules while the interfaces seem to play a crucial role. While WISEs pave the way for sustainable systems, the Li-based solutions use expensive and toxic salts. To look for more sustainable elements, one can envision sodium, which is less expensive and more abundant. While the systems based on Li imide salts have been quite thoroughly investigated, a fundamental understanding of the reactions at stake in sodium batteries based on WISEs, particularly at the interfaces, is needed. The project aims at identifying the reactions occurring at the interphase between the electrodes and the electrolyte in aqueous water-in-salt Na-ion batteries as well as the redox behavior of electrodes in these solutions. To do so, we propose to use cutting-edge in situ/operando techniques, namely infrared spectroscopy (IR) and X-ray absorption spectroscopy (XAS) at SOLEIL. The PhD student will first develop/adapt dedicated cells to perform these measurements. He/she will then conduct in-depth investigation of
the electrodes and interfaces reactivity in aqueous water-in-salt Na-ion batteries. This will provide insights into electrodes behavior in the bulk and also on the chemical composition of the interfaces, on their formation mechanisms and their stability upon cycling.
Relationship between the nature of hard carbons and the properties of electrodes for Na-ion batteries
Hard carbons are the most commonly used negative electrode materials in Na-ion batteries. Their capacity exceeding 300 mAh/g, low operating voltage, long lifespan, and power performance make them the best option for commercializing Na-ion batteries. However, several challenges remain to approach the performance of low-impact Li-ion technologies like LF(M)P/graphite. One major limitation is their low volumetric density. Their disordered nature and resulting microporosity lead to a lower skeletal density compared to graphite. This significantly affects both the volumetric and gravimetric energy densities due to the difficulty of compressing the electrodes.
The main objective of this thesis is to establish a link between the material's skeletal density and the electrode's calendering capability to reduce its porosity. First, we will evaluate the relationship between the structure, morphology, and surface state of hard carbon and the electrode's density. We will attempt to understand the impact of calendering on the material’s properties. Then, we will assess the tortuosity and conductivity of hard carbon electrodes to predict their performance. Finally, we will work on improving and optimizing the electrodes in terms of energy densities, focusing particularly on electrode formulations.
Reactive metals corrosion in innovative binders – Experimental study and hydro-chemo-mechanical modelling
Nuclear waste management requires the packaging of several kinds of metal wastes for long-term storage. These wastes, which can be very reactive metals, are prone to corrosion and commonly immobilised into containers with hydraulic binders as embedding matrices. Innovative binders (low carbon cements, alkali activated materials) are thus developed to increase the packaging performances. The main objective of the European project STREAM (in the frame of the Eurad-2 program) is to evaluate the interactions between these metal wastes and the selected cement matrices. The PhD thesis purpose is to investigate the reactive metal corrosion in the selected binder with electrochemical techniques. A generic experimental protocol will be developed in order to determine the impact of the corrosion products growth at the metal/binder interface on the global mechanical behaviour of the binder-waste composite and possible micro-cracks occurrence. A post-mortem characterisation will be performed on the metal/binder microstructure with mechanical properties measurements of the materials at the interface, especially the corrosion products. Afterwards, these results will feed a simplified Hydro-Chemo-Mechanical (HCM) model aiming the simulation of corrosion consequences on the composite material behaviour. Subsequently, this model will be used for long-term simulation at the waste package scale.
This research project is aimed at a PhD student wishing to improve his/her skills in materials science both in the experimental field and in the modelling/simulation of coupled physicochemical phenomena.
Optimization of the catalytic layer for CO2 electroreduction integrated into a PEM electrolyzer
This thesis focuses on optimizing the catalytic layer for CO2 electroreduction in an acidic medium, integrated into a proton-exchange membrane (PEM) electrolyzer. The aim is to upgrade CO2 by converting it into valuable chemicals, such as carbon monoxide. The acidic environment inherent to PEM electrolyzers helps limit carbonate formation, improving CO2 conversion efficiency. However, CO2 reduction in acidic media competes with the hydrogen evolution reaction, which reduces the selectivity of electroreduction products. This work seeks to develop noble-metal-free catalysts inspired by those used for oxygen reduction in fuel cells, improve the properties of carbon supports, and optimize the design of the catalytic layer, in particular thickness, porosity and hydrophobicity, to maximize CO2 conversion into target molecules. Finally, the active layer will be integrated into a 16 cm² PEM electrolyzer to assess overall performance and gain insights into the mechanisms involved through electrochemical characterization.