REcycling Li/Li ion batteries: a new concept bAsed on soluBility et (electro)chemical vaLorization of materials in moltEn salts – RELIABLE
Recycling of Li/Li ion batteries: molten salts, a promising route?
The chemistry of molten salts makes it possible to consider recycling processes in a few steps, making battery recycling more profitable with easier deployment. The project aims to evaluate the chemical aspects of the question.
Recycling Li/Li ion batteries
The explosion in the market for devices using Li/Li ion batteries of various technologies makes their recycling imperative both from the point of view of waste management and that of the supply of critical metals (Co, Li). The recycling of used lithium-ion batteries is mainly based on pyrometallurgical processes and to a lesser extent on hydrometallurgical treatments. Pyrometallurgical processes, high temperature treatments, make it possible to recover metals (excluding Li) that can be reused in industry, after additional separation steps. The hydrometallurgical route makes it possible to recover all the elements resulting from leaching, after solvent extraction and selective precipitation stages. In addition to still modest yields, the harmful leaching reagents themselves need to be recycled. Pyrochemistry, a technology based on molten salts, could constitute an interesting route. It can be considered, in this context, halfway between pyrometallurgy and hydrometallurgy. In fact, it combines the advantages of high temperature, to treat the organic materials of the battery (plastics and electrolyte), and those of the liquid, to solubilize and selectively recover the metals by electrodeposition or selective precipitation.
To determine the benefit of pyrochemistry for the recycling of Li/Li ion batteries, it is necessary to select the most appropriate family of salts. Among all the possible families, the RELiABLE project focused on “oxygenated” molten salts and more particularly carbonates, hydrogen sulfates and pyrosulfates, and hydroxides. The project was divided into two main areas of study: I) the transformation of electrode materials in the chosen molten salts and the selective recovery of metals, II) the transformation of organic compounds and the residual products obtained. Experimental studies combine ex situ and post-mortem characterizations with in situ analyses, supported by specific technical developments. The objective is not to develop a process but to decipher the reaction mechanisms associated with the different families of chemical compounds in batteries and the different families of molten salts.
The different molten salt families selected in the RELiABLE project present more varied reaction patterns than expected, both for battery electrode materials and for organic parts (plastic parts and electrolytes). Concerning the electrode materials, a metal reduction phase takes place in a solid phase which can go up to oxidation state 0 and whose reaction mechanism is specific to each molten salt. Similarly, organic compounds are segmented either by oxidation or reduction, sometimes recombining to form new compounds.
The variety of reaction mechanisms observed in this project makes it possible to consider pyrochemistry as a profitable process for the recycling of Li/Li ion batteries. The introduction of waste salt into salt is a key element to control and developments in the field of processes must be carried out.
Upon submission of the report, two PhD thesis have been defended, one paper was published, a second was submitted, and three others were being written. A patent is under study.
RELIABLE 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. Eutectic mixtures of molten carbonates will be used but other oxidizing salts will be also investigated. The project aims to build the basic knowledge for the development of a process and a laboratory pilot. In a first step, the solubility of metals and their speciation in the bath will be studied in function of several parameters such as oxo-acidity, presence of additional species (phosphate…), etc. In a second step, the recovery ways will be explored, in particular electrodeposition. In this aim, Electrochemical studies will be performed. Finally a laboratory pilot will be proposed.
Project coordination
Anne-Laure Rollet (PHysicochimie des Electrolytes et Nanosystèmes InterfaciauX)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partnership
IRCP Institut de Recherche de Chimie Paris
PHENIX PHysicochimie des Electrolytes et Nanosystèmes InterfaciauX
Help of the ANR 465,712 euros
Beginning and duration of the scientific project:
November 2018
- 48 Months
