Refine
Document Type
Keywords
- NMC (3)
- recycling (3)
- Raman spectroscopy (2)
- degradation (2)
- leaching (2)
- lithium ion battery (2)
- silicon (2)
- AAS (1)
- Batterie (1)
- Eisen (1)
Institute
The present work describes a completely new approach to the solidification refinement of metallurgical-grade silicon. The new process comprises the following steps: (i) The first step involves adding auxiliary metals to the molten silicon in order to segregate the metallic and non-metallic impurities in the secondary phase after cooling. (ii) The melt is rapidly cooled in the cellular solidification regime. This generates a Si microstructure with a defined cell size in which all cell boundaries are surrounded by the secondary phase. Furthermore, the secondary phase should form an interconnected three-dimensional network. (iii) The solids are crushed by shockwaves using electrohydraulic fragmentation techniques. The shockwaves lead to preferential crushing at the interface between the silicon and the secondary phase. (iv) The secondary phases are fast and effectively removed by microwave-assisted high-pressure leaching that was newly developed for this process. The potential of the new refinement procedure is demonstrated with auxiliary metals Ca, Al, and Ti. This new procedure yields a significant decrease in phosphorous and metal impurities.
Recovery of Li(Ni0.33Mn0.33Co0.33)O2 from Lithium-Ion Battery Cathodes: Aspects of Degradation
(2019)
Nickel–manganese–cobalt oxides, with LiNi0.33Mn0.33Co0.33O2 (NMC) as the most prominent compound, are state-of-the-art cathode materials for lithium-ion batteries in electric vehicles. The growing market for electro mobility has led to a growing global demand for Li, Co, Ni, and Mn, making spent lithium-ion batteries a valuable secondary resource. Going forward, energy- and resource-inefficient pyrometallurgical and hydrometallurgical recycling strategies must be avoided. We presented an approach to recover NMC particles from spent lithium-ion battery cathodes while preserving their chemical and morphological properties, with a minimal use of chemicals. The key task was the separation of the cathode coating layer consisting of NMC, an organic binder, and carbon black, from the Al substrate foil. This can be performed in water under strong agitation to support the slow detachment process. However, the contact of the NMC cathode with water leads to a release of Li+ ions and a fast increase in the pH. Unwanted side reactions may occur as the Al substrate foil starts to dissolve and Al(OH)3 precipitates on the NMC. These side reactions are avoided using pH-adjusted solutions with sufficiently high buffer capacities to separate the coating layer from the Al substrate, without precipitations and without degradation of the NMC particles.
Fahrzeugkatalysatoren enthalten wertvolle Edelmetalle wie Platin (Pt), Palladium (Pd) und Rhodium (Rh), wodurch ausgediente und funktionsunfähige Katalysatoren zu einem begehrten Recyclinggut in einem hart umkämpften Marktsegment werden.
Das häufigsten Aufbereitungsverfahren für Altkatalysatoren ist ein Schmelzprozess, in dem vorzerkleinerte Katalysatorfraktionen unter definierter Zugabe von Hilfsstoffen mit Kupfer als Kollektormetall aufgeschmolzen werden. Die Edelmetalle reichern sich im flüssigen Kupfer an, während alle anderen metallischen und nichtmetallischen Bestandteile eine oxidische Schlacke bilden. Ein Recyclingunternehmen im Bundesland Brandenburg hat diesen Prozess innovativ weiterentwickelt, indem es Eisen als Sammlermetall einsetzt. Eisen ist nicht nur preisgünstiger als Kupfer, es kann unter optimalen Schmelzbedingungen bis zu 9% an Edelmetallen aufnehmen, während Kupfer eine maximale Aufnahme von nur 5% besitzt.
Zur Bestimmung der Edelmetallgehalte wird in diese Branche die Kupfer-Dokimasi mit anschließender ICP-OES-Analyse angewandt, was im Falle des Eisensammlers ein Umschmelzen der Proben zur Folge hätte. Eine Methode zur präzisen Quantifizierung der Edelmetallgehalte im Eisensammler existierte bisher nicht.
Im Rahmen eines Forschungsprojektes wurde deshalb ein Bestimmungsverfahren zur zuverlässigen Bestimmung von Pt, Pd und Rh in einem Bereich von 0,1% bis 5% neben einem Eisengehalt von mehr als 80% mittels ICP-OES nach einem MW-Aufschluss entwickelt, dessen Vorteil sich neben einer deutlichen Zeitersparnis auch bezüglich des Einsatzes an Probenmaterial (für den Aufschluss) und Aufschlusschemikalien zeigt. Die analytischen Herausforderungen lagen in der Probenhomogenisierung zur repräsentativen Probenahme, in der Entwicklung eines Mikrowellen-Aufschlussverfahrens und in der Entwicklung einer Methode zur Präzisionsanalytik mittels ICP-OES. Besonderes Augenmerk wurde auf die Identifizierung von spektralen und nichtspektralen Interferenzen gelegt, die durch variierende Gehalte von Nebenkomponenten der Altkatalysatoren und durch das linienreiche Emissionsspektrum der Hauptkomponente Eisen verursacht werden.
Es gelang ein zuverlässiges, präzises und kosteneffizientes Quantifizierungsverfahren für diese Edelmetalle in dieser besonderen Matrix zu entwickeln.
Zur Bestimmung der metallischen Hauptkomponenten in Lithium-Batterie-Kathodenmaterialien ist der nasschemische Aufschluss mit anschließender ICP-OES-Analyse oft das Mittel der Wahl. Da dieses Verfahren jedoch recht zeitaufwendig ist und den Einsatz starker Säuren erfordert, wurde eine Methode zur direkten Feststoffanalyse mittels HRCS-GF-AAS (high resolution continuum source graphit furnace atom absorption spectrometry) nach dem STPF-Konzept (stabilized temperature platform furnace) entwickelt.
Die hohen Analytkonzentrationen erfordern dabei die Messung auf den vergleichsweise wenig intensiven Linien Li = 323,2657 nm, Ni = 294,3912 nm, Mn = 321,6945 nm und Co= 243,5823 nm. Zusätzlich wird das Probenmaterial einer Feststoffverdünnung mit matrixverwandten Komponenten unterzogen. Die Verdünnung senkt zum einen die Konzentration und die Gefahr der Verschleppung der Analyten und begünstigt zum anderen die Freigabe des Analyten aus der Probenmatrix.
Durch Aufnahme von Extinktions-Zeit-Verläufen im Temperaturbereich von 200 - 2600 °C konnten die Freisetzungstemperaturen für jeden Analyten bestimmt werden. Nach anschließenden Optimierungen der Pyrolyse- und Atomisierungstemperaturen wurde mithilfe der Einzeloxide für jeden Analyten die Linearität des Messsignals geprüft und der Arbeitsbereich festgelegt. Durch Vermessung von variierenden Oxidmischungen und Mischoxiden, sowie Zusatz möglicher weiterer Interferenten, wie dem Bindermaterial PVDF wurden Spezifität, Selektivität und Robustheit der Methode überprüft.
Abschließend erfolgte anhand realer Proben (Recyclinggut aus Lithium-Batterie-Kathoden) ein Vergleich zwischen den Ergebnissen der direkten Feststoffanalyse mittels HRCS-GF-AAS und dem bereits etablierten Verfahren der ICP-OES Analyse nach nasschemischem Aufschluss.
Nach umfangreicher Methodenentwicklung kann ein Verfahren der direkten Feststoffanalyse von Recylinggut aus Kathodenmaterialien von Lithium-Ionen-Batterien mittels HRCS-GF-AAS bereitgestellt werden, das eine schnelle und präzise Analyse der Hauptkomponenten Li, Ni, Mn und Co erlaubt.
Automotive technology is increasingly determined by electric vehicles driven by high-performance lithium ion batteries (LIB). Li-ion batteries equipped with layered oxide cathodes, which are constituted by oxides of nickel, manganese and cobalt, are proven as storage devices that combine high electrical power, high cycling stability and compact dimensions. These batteries contain large amount of valuable elements, such as the cathodes consisting of cobalt and nickel, the electrode carrier foils consisting of copper and aluminium. Therefore, spent LIB’s are valuable secondary resources.
Thermal processing as the classical recycling-technology for LIB’s is energy-intensive and allow only a partial recovery of some value elements.
Scientists of the Brandenburg University of Technology (Germany) developed in collaboration with industrial partners (SME) a process, in which the complex system LIB is partly automated dismounted into its basic components. The core of this process is the separation of anodes and cathodes from each other and an almost complete recovery of the cathode material from the foil.
The recovered cathode material has an enormous potential for a re-use in new LIB’s. By a proper combination of separation and post-treatment the material has a quality that is close to virgin cathode material. Preliminary studies made on LIB’s containing a fraction of recycled cathode material up to 50% show an electrical performance comparable to LIB’s made from virgin material.
The compound Li(Ni₀.₃₃Mn₀.₃₃Co₀.₃₃)O₂(NMC) is the state-of-the-art lithium-ion battery cathode material. Due to the increasing demand NMC is of crucial economically importance for the worldwide emerging market of electromobility. Recycling of end-of-life lithium-ion batteries to recover NMC, in particular of batteries from automotive vehicles, is one future strategy to save costs and to become more independent from the supply of the essential elements Co and Mn. Several concepts for NMC recycling from lithium-ion batteries are based on wet-chemical process steps, in particular, to separate the NMC containing cathode layer from the underlying metal foil. However, NMC is very sensitive against the attack by water and reagents that are added to promote the separation process.
The present study deals with the wet-chemical recycling of NMC using aqueous reagent solutions in a under varying process conditions. The recovered NMC samples are characterized in order to study the ongoing degradation at the surface of the NMC particles. In particular, two major degradation pathways are identified: (i) a preferential loss of lithium and nickel and (ii) the formation of passivation layers due to unwanted side reactions. DRIFT measurements are performed to study the NMC surface species after the recovery processes. SEM/EDX mappings are used to detect changes in the chemical composition in the surface region of the chemically treated NMC particles. Finally, a detailed study of the changes in the chemical state at the NMC particle surface is done by Raman microscopy by means of the deconvolution of the recorded spectra into their A1G component (representing the metal-oxide phonons) and into the Eg component (representing the oxide-metal-oxide phonons).
As result of this study, the consequences of different wet-chemical process conditions on the quality of the recovered NMC material are discussed.
The nuclear magnetic resonance (NMR) method was applied for tracking boron impurities in the refining process of metallurgical grade (MG) silicon. From the NMR signal of the 11B isotope at an operating temperature 4.2 K, the boron concentration can be estimated down to the order of 110 wppm B. After melting and resolidification of MG-Si alloyed with Ca and Ti, a major fraction of B impurities remains in the Si solid solution as inferred from the characteristic NMR frequency. The alloying element Ti does not form substantial fractions of TiB2. Acid leaching of crushed powders of MG-Si alloyed with Ca and Ti can diminish the initial impurity content of B suggesting its accumulation in the grain boundary phases.
The compound Li(Ni0.33Mn0.33Co0.33)O2 (NMC) is the state-of-the-art lithium-ion battery cathode material. Due to the increasing demand NMC is of crucial economically importance for the worldwide emerging market of electromobility. Recycling of end-of-life lithium-ion batteries to recover NMC, in particular of batteries from automotive vehicles, is one future strategy to save costs and to become more independent from the supply of the essential elements Co and Mn. Several concepts for NMC recycling from lithium-ion batteries are based on wet-chemical process steps, in particular, to separate the NMC containing cathode layer from the underlying metal foil. However, NMC is very sensitive against the attack by water and reagents that are added to promote the separation process.
The present study deals with the wet-chemical recycling of NMC using aqueous reagent solutions in a under varying process conditions. The recovered NMC samples are characterized in order to study the ongoing degradation at the surface of the NMC particles. In particular, two major degradation pathways are identified: (i) a preferential loss of lithium and nickel and (ii) the formation of passivation layers due to unwanted side reactions. DRIFT measurements are performed to study the NMC surface species after the recovery processes. SEM/EDX mappings are used to detect changes in the chemical composition in the surface region of the chemically treated NMC particles. Finally, a detailed study of the changes in the chemical state at the NMC particle surface is done by Raman microscopy by means of the deconvolution of the recorded spectra into their A1G component (representing the metal-oxide phonons) and into the Eg component (representing the oxide-metal-oxide phonons).
As result of this study, the consequences of different wet-chemical process conditions on the quality of the recovered NMC material are discussed.