JOB ENVIRONMENT:
Institut Mines-Télécom is the leading public group of engineering and management Grandes Écoles in France. Consisting of eight public graduate Grandes Écoles and two subsidiary graduate schools, Institut Mines-Télécom leads and develops a rich ecosystem of partner schools, economic, academic and institutional partners, key players in education, research and economic development.
Mines Saint-Étienne, a graduate school of the Institut Mines-Télécom, is responsible for education, research, innovation, industrial transfer and scientific culture dissemination. With 2,500 students, 500 staff and a budget of €50m, it has 3 campuses dedicated to the industry of the future, health and well-being, and digital sovereignty and microelectronics. It is ranked in the top 15 graduate engineering schools in France and the top 500 universities worldwide.
The 2023-2027 strategy of Mines Saint-Etienne is in line with that of Institut Mines Telecom. It aims to:
JOB DESCRIPTION:
The SPIN Center (« Sciences of Natural and Industrial Processes ») is a teaching and research center recognized for its expertise in Chemical Engineering applied to dispersed media (grains, particles, powders, porous media, soils …). It uses its scientific knowledge and top-notch equipment to bring innovation to industrial companies facing the challenges of energy optimization and high performance materials design.
The PEG (Processes for the Environment and Geo-Resources) research department develops in process engineering and geoprocesses, around a central theme of mineral chemistry (hydrometallurgy, speciation, precipitation, crystallization), implementing multiphase and multiphysics models of changes in spatial scales, from the nanometer to the kilometer. The department brings together a multidisciplinary community of around ten lecturer-researchers with backgrounds in process engineering and crystallization on the one hand, and geosciences on the other. The department is attached to two CNRS units, including the Georges Friedel laboratory (UMR CNRS 5307) for the Process Engineering theme in its industrial dimension.
In this environment, the position to be filled is part of a wider dynamic involving other departments of the SPIN center for the development of inorganic chemistry for Process Engineering. Although the SPIN center, and more specifically the PEG department, currently brings together a number of skills relating to geosciences, crystallization, thermodynamics, hydrometallurgy and multiphase flows, and wishes to strengthen the experimental skills in inorganic chemistry to support the department's existing themes:
Tasks may change depending on the needs of the department and Mines Saint-Etienne.
The position is based on the Saint-Étienne campus.
MISSIONS AND TASKS :
Lithium-ion batteries are being extensively used in the electronics and automobile industry due to their high energy, power density and enhanced cycle life. Commercially available lithium-ion batteries use graphite as the anode, and layered nickel−manganese−cobalt (NMC) based cathode materials.
NMC active particles consist of agglomerates of larger secondary particles span over several micrometers in diameter which contained submicron sized crystalline primary particles. The specific capacity and energy density of cathode active particles depend not only on the chemical composition but also on the size distribution of the secondary particles, internal porosity, and primary particle size. These morphological features are usually determined during the synthesis process. In our process, the NMC hydroxide precursors are prepared from transition metal sulfates through the coprecipitation process. Then the precursors are mixed with lithium hydroxide and calcined at high temperature in oxygen atmosphere to form lithium transition metal oxides Li(NMC)O2.
To maximize the electrochemical properties of lithium-ion battery cathodes, it is important to understand the different steps involved in the preparation of the cathode materials and its impact on the particle morphology. The synthesis of lithium-ion battery cathode materials is based on lab scale experiments which correlate the synthesis conditions (e.g., coprecipitation solution pH, coprecipitation solution ammonia content …) with cell performances. Several operational parameters during the crystallization, such as temperature or impeller speed of the reactor, need to be understood and controlled to achieve consistent narrow particle size distribution around the desired mean, minimal attrition, and homogeneous growth conditions.
The scale-up of the coprecipitate process from the lab scale to the pilot one and then the industrial one represents a complex task as several target quantities must be kept such as yield, purity, and particle morphology and size distribution.
The goal of the thesis is to contribute to the understanding and the scaling up of the hydroxide coprecipitation from a small reactor (5 liters) to a bigger reactor (20-100 liters) based on experimental data already available in the CEA laboratory. Measurement during the hydroxide coprecipitation will be completed with the in-line equipment’s implemented in the Ecole des Mines’s of Saint Etienne small reactor. A predictive model coupling fluid dynamics and crystallization will be proposed and used for the next step, at the various scales up to the pilot line reactor (100 liters).
