The bottleneck of recycling chains for spent lithium-ion batteries (LIBs) is the recovery of valuable metals from the black matter that remains after dismantling and deactivation in pre‑treatment processes, which has to be treated in a subsequent step with pyrometallurgical and/or hydrometallurgical methods. In the course of this paper, investigations in a heating microscope were conducted to determine the high-temperature behavior of the cathode materials lithium cobalt oxide (LCO—chem., LiCoO2) and lithium iron phosphate (LFP—chem., LiFePO4) from LIB with carbon addition. For the purpose of continuous process development of a novel pyrometallurgical recycling process and adaptation of this to the requirements of the LIB material, two different reactor designs were examined. When treating LCO in an Al2O3 crucible, lithium could be removed at a rate of 76% via the gas stream, which is directly and purely available for further processing. In contrast, a removal rate of lithium of up to 97% was achieved in an MgO crucible. In addition, the basic capability of the concept for the treatment of LFP was investigated whereby a phosphorus removal rate of 64% with a simultaneous lithium removal rate of 68% was observed.
The complexity of the waste stream of spent lithium-ion batteries poses numerous challenges on the recycling industry. Pyrometallurgical recycling processes have a lot of benefits but are not able to recover lithium from the black matter since lithium is slagged due to its high oxygen affinity. The presented InduRed reactor concept might be a promising novel approach, since it does not have this disadvantage and is very flexible concerning the chemical composition of the input material. To prove its basic suitability for black matter processing, heating microscope experiments, thermogravimetric analysis and differential scanning calorimetry have been conducted to characterize the behavior of nickel rich cathode materials (LiNi0.8Co0.15Al0.05O2 and LiNi0.33Mn0.33Co0.33O2) as well as black matter from a pretreatment process under reducing conditions. Another experimental series in a lab scale InduRed reactor was further used to investigate achievable transfer coefficients for the metals of interest. The promising results show technically feasible reaction temperatures of 800 ∘C to 1000 ∘C and high recovery potentials for nickel, cobalt and manganese. Furthermore, the slagging of lithium was largely prevented and a lithium removal rate of up to 90% of its initial mass was achieved.
Within the e-mobility sector, which represents a major driver of the development of the overall lithium-ion battery market, batteries with nickel-manganese-cobalt (NMC) cathode chemistries are currently gaining ground. This work is specifically dedicated to this NMC battery type and investigates achievable recovery rates of the valuable materials contained when applying an unconventional, pyrometallurgical reactor concept. For this purpose, the currently most prevalent NMC modifications (5-3-2, 6-2-2, and 8-1-1) with carbon addition were analyzed using thermogravimetric analysis and differential scanning calorimetry, and treated in a lab-scale application of the mentioned reactor principle. It was shown that the reactor concept achieves high recovery rates for nickel, cobalt, and manganese of well above 80%. For lithium, which is usually oxidized and slagged, the transfer coefficient into the slag phase was less than 10% in every experimental trial. Instead, it was possible to remove the vast amount of it via a gas phase, which could potentially open up new paths regarding metal recovery from spent lithium-ion batteries.
In terms of an efficient circular economy in the field of the steadily increasing use of lithium-ion batteries, sustainable recycling methods are of fundamental importance. Therefore, the Chair of Thermal Processing Technology at Montanuniversitaet Leoben has developed the so-called InduRed reactor, a carbo-thermal concept to recover valuable metals from this waste stream. For optimization and further development of this technology, it is essential to have a sound knowledge of the cathode materials' behavior in combination with various impurities in the high-temperature range under reducing conditions. Detailed experiments were carried out in a heating microscope at temperatures up to 1620°C and argon purge. Aluminum from the electrode conductor foils and an excessive proportion of graphite from the anode were identified as the impurities with the most significant negative influence on the process. An optimum melting behavior was found during the tests at an admixture of 10 wt. % C and 1.95 wt. % Al to the cathode material NMC622 (LiNi0.6Mn0.2Co0.2O2).
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