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[Master 2] Etude par spectroscopie d’absorption X de la structure locale autour du Cobalt en milieu carbonates fondus

par Anne-Laure Rollet - 23 octobre

Période de stage : Février 2020-juin 2020

Encadrement : Anne-Laure Rollet (équipe ELI) anne-laure.rollet ad


Due to the fast spread of portable electronic devices with limited life time, numerous countries are overwhelmed with cumbersome battery wastes. In parallel, this increasing spread of new technologies combined with the rapid economic development of emerging countries yields to a critical increasing demand in various raw metals. Several metal markets which production is at the country and the company level have shown high turbulences since the beginning of the 21st century. Batteries market is currently dominated by lithium-ion technologies, a trend that will be reinforced in the future owing to the emergence of new fields of applications such as electric vehicles and stationary storage. In consequence, recycling has become compulsory. Our project treats the Lithium Battery recycling using pyrochemistry. The goal is to use molten salts as solvent in order to dissolve batteries, particularly cathodes, and to selectively recover every metallic species. Within all the questions that have to be solved, one concerned the nature and environment of the metallic ion, mainly cobalt, in the molten salt, i.e. its oxidation state and its speciation. In order to solve these questions, X-ray absorption spectroscopy (XAS) is proposed. This synchrotron technique allows us to get information on the oxidation state of a given element and of its local environment.

In the first part of this project,the speciation and complexation of cobalt ions dissolved from Lithium battery cathode in molten carbonates (550°C) should be confirmed. Last year, a whole setup (cell, heating elements, and chamber) has been developed in PHENIX laboratory for these in situ experiments. The preliminary results show surprising result with a reduction of the cobalt from oxidation III up to II even 0 during the experiments. The mechanism has now to be elucidated.

The second part of this project deals with the recovery of cobalt by electrodeposition. The challenge is to develop a setup for operando measurement. The setup is will be based on the setup developed for in situmeasurement that fulfills the requirement of molten salts (high temperature, corrosiveness, etc.) and of X-ray transmission. The present setup iscomposed of several elements :(1)The main carbonate containermade of two graphite plates with a thickness of 300 μm ; (2) compact heating devicespecifically designed for these cells and allowing the passage of the electrode wires.This part is particularly challenging as the space available is highly reduced as compared with standard molten salt electrochemical setup.The Master student will participate to thedevelopment and theoptimization of this whole setup. Four days XAS measurements should be performed on synchrotron SOLEIL beamline ROCK provided the beamtime is granted. Analysis of the data will be performed using Athena software. The results obtained by the Master student during his training will help to understand theprocess ofcobalt dissolution from Lithium-batteryin molten salts and cobalt recovery by electrodeposition.

Specific techniques or methods

X-ray Absorption Spectroscopy (XAS), X-ray diffractommetry (XRD)


P. N. Ruiz Onofre (2019) Évaluation de la voie pyrochimique pour le recyclage des batteries Lithium-ion, Doctoral dissertation, Sorbonne Université.