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[Master 2] Electrochemical study of cathode materials of Li-ion batteries in molten salts

par Anne-Laure Rollet - 23 octobre

Période de stage : janvier 2020 - juin 2020 (6 months)

Encadrement : Ana Gabriela Porras Gutierrez, Denise Krulic,Anne-Laure Rollet (équipe ELI) contact : ana-gabriela.porras-gutierrez ad ; denise.krulic ad ; anne-laure.rollet ad


Batteries market is currently dominated by lithium-ion technologies. The lithium-ion batteries are typically composed of two electrodes and an electrolyte containing a lithium salt dissolved in a non-aqueous solvent. While graphite is the most used anode material, at the cathode side the most common materials are transition-metal based compounds such as LiFePO4 (LFP), LiNi1/3Mn1/3Co1/3O2 (NMC), LiNixCoyAlzO2 (NCA), LiMn2O4 (LMO), and LiCoO2 (LCO).1 The ever-increasing energy demands more complex batteries chemistry, i.e., NCA/NCM and continuous cathode materials growing production. To mitigate supply risk andenvironmental impacts, recycling has become imperative,2 the recycling process allows to reduce production impacts (gas emissions, mining and extraction problems, energy economy). There are three general methods that have been developed for Li-ion batteries recycling, pyrometallurgy, hydrometallurgy and direct recycling.3 Molten salts could offer significant advantages compared to them. In a way, as far as recycling batteries is concerned, they can be considered as halfway between pyrometallurgical and hydrometallurgical processes. Indeed, they combine the advantages of high temperature, which allows dealing with organic matter of the battery (plastic parts and electrolyte), and liquid properties, which allows solubilizing and selectively recovering metallic species via electrodeposition or selective precipitation. Because of a large set family (fluorides, chloride, nitrate, carbonate, hydroxide, sulfite, etc.) associated with general suitable specificities in terms of thermochemical stability (several hundreds of degrees), width of applicable electrochemical window, high thermal conductivity and capacity, moderate viscosity, high electrical conductivity, mutual miscibility, molten salts offers versatile medium/properties that could lead to significant breakthrough in the field of batteries recycling. Previous studies realized at PHENIX laboratory was proven that cathode material LiCoO2 shows a low dissolution in molten chlorides (LiCl-KCl). Nevertheless, a thermal pretreatment of cathode material with MHSO4 (M=Na or K) can enhance its dissolution and recovery of metallic cobalt by electrochemical methods is possible.4 The purpose of this project is to analyze, by electrochemical methods, dissolved species from cathode materials in chloride molten salts, as well as their evolution with time and with the environmental conditions (temperature, operating atmosphere, etc.). The combination of cyclic voltammetry and Square Wave Voltammetry (SWV), as well as chronoamperometry and chronopotentiometry will allow to determine and quantify the species involved in the molten salts following the electrode dissolution.

Specific techniques or methods

Electrochemical methods : cyclic voltammetry, square wave voltammetry, chronoamperometry. X-ray diffractommetry, Thermogravimetric analysis Scanning electron microscopy and energy-dispersive X-ray spectroscopy 3


1.C. Julien, A. Mauger, A. Vijh, K. Zaghib, Lithium Batteries, 2016 Springer.
2. L. Gaines, Sustainable Mater. Technol., 2014, 1–2, 2–7.
3. L. Gaines, K. Richa, J. Spangenberger, MRS Energy Sustain, 5 (2018) 1.
4. P. N. Ruiz Onofre (2019) Évaluation de la voie pyrochimique pour le recyclage des batteries Lithium-ion, Doctoral dissertation, Sorbonne Université