TY - GEN A1 - Langner, Thomas A1 - Sieber, Tim A1 - Acker, Jörg T1 - Studies on the deposition of copper in lithium-ion batteries during the deep discharge process T2 - Scientific Reports N2 - End-of-life lithium-ion batteries represent an important secondary raw material source for nickel, cobalt, manganese and lithium compounds in order to obtain starting materials for the production of new cathode material. Each process step in recycling must be performed in such a way contamination products on the cathode material are avoided or reduced. This paper is dedicated to the first step of each recycling process, the deep discharge of lithium-ion batteries, as a prerequisite for the safe opening and disassembling. If pouch cells with different states of charge are connected in series and deep-discharged together, copper deposition occurs preferably in the cell with the lower charge capacity. The current forced through the cell with a low charge capacity leads, after lithium depletion in the anode and the collapse of the solid-electrolyte-interphase (SEI) to a polarity reversal in which the copper collector of the anode is dissolved and copper is deposited on the cathode surface. Based on measurements of the temperature, voltage drop and copper concentration in the electrolyte at the cell with the originally lower charge capacity, the point of dissolution and incipient deposition of copper could be identified and a model of the processes during deep discharge could be developed. KW - lithium ion battery KW - discharge KW - continuum source AAS KW - REM-EXD KW - recycling Y1 - 2021 UR - https://www.nature.com/articles/s41598-021-85575-x U6 - https://doi.org/10.1038/s41598-021-85575-x SN - 2045-2322 IS - 11 ER - TY - GEN A1 - Schönekerl, Stefan A1 - Acker, Jörg T1 - The Role of the Molecular Hydrogen Formation in the Process of Metal Ion Reduction on Multi-crystalline Silicon in a Hydrofluoric Acid Matrix T2 - Nanomaterials N2 - Metal deposition on silicon in hydrofluoric acid (HF) solutions is a well-established process for the surface patterning of silicon. The reactions behind this process, especially the formation or the absence of molecular hydrogen (H2) are controversially discussed in the literature. In this study, several batch experiments with Ag+, Cu2+, AuCl4– and PtCl62– in HF matrix and multi-crystalline silicon were performed. The stoichiometric amounts of the metal depositions, the silicon dissolution and the molecular hydrogen formation were determined analytically. Based on these data and theoretical considerations of the valence transfer, four reasons for the formation of H2 could be identified. Firstly, H2 is generated in a consecutive reaction after a monovalent hole transfer (h+) to a Si–Si bond. Secondly, H2 is produced as a result of a monovalent hole transfer to the Si–H bonds. Thirdly, H2 occurs if Si–Si back bonds of the hydrogen-terminated silicon are attacked by Cu2+ reduction resulting in the intermediate species HSiF3, which is further degraded to H2 and SiF62–. The fourth H2-forming reaction is the reduction of oxonium ions (H3O+) on the silver/, copper/ and gold/silicon contacts via monovalent hole transfer to silicon. In the case of (cumulative) even-numbered valence transfers to silicon, no H2 is produced. The formation of H2 also fails to appear if the equilibrium potential of the 2H3O+/H2 half-cell does not reach the energetic level of the valence bands of the bulk or hydrogen-terminated silicon. Non-hydrogen-forming reactions in silver, copper and gold deposition always occur with at least one H2-forming process. The PtCl62– reduction to Pt proceeds exclusively via even-numbered valence transfers to silicon. This also applies to the reaction of H3O+ at the platinum/silicon contact. Consequently, no H2 is formed during platinum deposition. KW - molecular hydrogen KW - metal deposition KW - silicon KW - etching KW - hydrofluoric acid KW - reaction kinetics KW - dissolution KW - chemical analysis Y1 - 2021 UR - https://www.mdpi.com/2079-4991/11/4/982 U6 - https://doi.org/10.3390/nano11040982 SN - 2079-4991 VL - 11 IS - 4 ER - TY - GEN A1 - Herold, Steven A1 - Acker, Jörg T1 - Strain enhanced chemical oxidation of silicon wafer T2 - Materials Science in Semiconductor Processing N2 - The effect of strain through mechanical processing on the formation of silicon dioxide, one of the most important chemical reactions for the fabrication of semiconductors, biosensors or photovoltaics, has not yet been studied in detail. In this study, we use the surface modification of silicon by alkylsilanes and Raman microscopy techniques to visualise where different oxidants react preferentially on mechanically processed surfaces. We found that HNO3, H2O2 as well as H2SiF6 only oxidise tensile strained silicon areas and do not oxidise unstrained silicon even after long reaction times. Furthermore, a comparison between H2O2 and HNO3 in the presence of HF was also carried out and it was shown that H2O2/HF only etches away tensile strained areas, whereas HNO3/HF initially attacks the tensile strained areas but also forms NOx species. These NOx species then lead to a strain unselective, geometry-based etching mechanism. These results lead to new possibilities in strain lithography,high-precision etching, as well as in the structuring of biosensors and localisation of surface modifications. KW - silicon KW - lattice strain KW - oxidation KW - Raman KW - confocal microscopy Y1 - 2021 U6 - https://doi.org/10.1016/j.mssp.2021.106105 SN - 1369-8001 VL - 135 ER - TY - GEN A1 - Rietig, Anja A1 - Grafe, Hans-Joachim A1 - Acker, Jörg T1 - New insights into boron species in acidic digestion solutions of boron-doped silicon T2 - Journal of Analytical Atomic Spectrometry N2 - The exact and precise determination of the boron concentration in silicon is still a challenge. A systematic investigation dealing with the digestions of 60 silicon samples with HF-HNO3 and subsequent boron determination by ICP-OES revealed that the concentration found could be up to 60% lower than the actual boron concentration depending on the composition of the sample solution. As the original boron–silicon compound that was identified was colloidally precipitated in the presence of an excess of hydrofluoric acid and then partially retained by filtration or by the sample introduction system, systematic lower boron concentrations were determined. In acidic, HF-free digestion solutions, this compound existed in a soluble form parallel to the borate in B(OH)4−. In an excess of hydrofluoric acid, the compound was converted into the colloidal form and, in parallel, B(OH)4− was converted to tetrafluoroborate, BF4−. For the composition of the colloidal compound, a molar ratio of boron to silicon of 1 : 4 could be determined. 11B-ss-NMR analysis revealed a tetrahedral geometry compound with a central boron atom surrounded by four silicon atoms. It is assumed that a soluble form with four –Si(OH)3 groups was present in the hydrofluoric acid-free solutions, while an insoluble form with four –SiF3 groups was present in HF-containing solution. KW - silicon KW - ICP-OES KW - etching KW - hydrofluoric acid KW - nitric acid KW - 11B-NMR KW - high-precision chemical analysis KW - boron KW - digestion Y1 - 2021 UR - https://pubs.rsc.org/en/content/articlelanding/2021/ja/d1ja00190f SN - 1364-5544 VL - 36 IS - 11 SP - 2492 EP - 2500 ER - TY - GEN A1 - Rietig, Anja A1 - Langner, Thomas A1 - Acker, Jörg T1 - Comprehensive stoichiometric studies on the reaction of silicon in HF/HNO3 and HF/HNO3/H2SiF6 mixtures T2 - Physical chemistry, chemical physics KW - silicon KW - etching KW - stoichiometry KW - hydrogen KW - nitrogen oxides KW - mechanism Y1 - 2022 UR - https://pubs.rsc.org/en/content/articlelanding/2022/cp/d1cp05418j U6 - https://doi.org/10.1039/d1cp05418j SN - 1463-9076 VL - 24 IS - 5 SP - 3094 EP - 3108 ER - TY - GEN A1 - Rietig, Anja A1 - Grafe, Hans-Joachim A1 - Acker, Jörg T1 - Understanding the Reasons for Erroneous Determinations of Boron in Silicon following Wet Chemical Digestion in HF/HNO3 T2 - Proceedings of the Silicon for the Chemical & Solar Industry XVI KW - boron KW - silicon KW - species KW - trace element Y1 - 2022 UR - https://ssrn.com/abstract=4123058 SN - 978-82-692919-0-2 U6 - https://doi.org/10.2139/ssrn.4123058 ER - TY - CHAP A1 - Rietig, Anja A1 - Acker, Jörg T1 - Ressourcensicherung durch Recycling von Sekundärrohstoffen T2 - Systemwissen für die vernetzte Energie- und Mobilitätswende KW - Recycling KW - Lithium-Ionen-Batterien KW - Elektroschrott KW - Edelmetalle Y1 - 2022 UR - https://www.ibbf.berlin/assets/images/Dokumente/220627_IBBF_Kompendium_2022_WEB_final%20(1).pdf SN - 978-3-9816861-8-0 SP - 141 EP - 152 PB - Vereinigung für Betriebliche Bildungsforschung e.V. CY - Berlin ET - 2. Auflage ER - TY - GEN A1 - Ernst, Owen C. A1 - Uebel, David A1 - Brendler, Roman A1 - Kraushaar, Konstantin A1 - Steudel, Max A1 - Acker, Jörg A1 - Kroke, Edwin T1 - Silicon-28-Tetrafluoride as an educt of Isotope-Engineered Silicon Compounds and Bulk Materials for Quantum Systems T2 - Molecules N2 - This review provides a summary of the existing literature on a crucial raw material for the production of isotopically pure semiconductors, which are essential for the development of second-generation quantum systems. Silicon-28-tetrafluoride (28SiF4) is used as an educt for several isotope-engineered chemicals, such as silane-28 (28SiH4) and silicon-28-trichloride (28SiHCl3), which are needed in the pursuit of various quantum technologies. We are exploring the entire chain from the synthesis of 28SiF4 to quantum applications. This includes the chemical properties of SiF4, isotopic enrichment, conversion to silanes, conversion to bulk 28Si and thin films, the physical properties of 28Si (spin neutrality, thermal conductivity, optical properties), and the applications in quantum computing, photonics, and quantum sensing techniques. KW - isotopes KW - quantum computing KW - spintronic KW - microelectronics KW - enrichment KW - silane KW - tetrafluorosilane Y1 - 2024 U6 - https://doi.org/10.3390/molecules29174222 SN - 1420-3049 VL - 29 IS - 17 PB - MDPI AG ER - TY - GEN A1 - Dommaschk, Maria A1 - Sieber, Tim A1 - Acker, Jörg T1 - Lithium-ion batteries: direct solid sampling for characterisation of black mass recyclates using graphite furnace atomic absorption spectrometry T2 - Journal of Analytical Atomic Spectrometry N2 - A straightforward, efficient and robust method was developed in this study to analyse the metal content of complex recyclates from cathode coatings (LiNixMnyCo1−x−yO2) recovered from spent lithium-ion batteries. KW - lithium ion battery KW - graphite furnace atomic absorption spectrometry KW - inductively coupled plasma optical emission spectrometry KW - cathode material KW - chemical analysis KW - recycling Y1 - 2024 U6 - https://doi.org/10.1039/D4JA00207E SN - 0267-9477 VL - 39 IS - 10 SP - 2522 EP - 2531 PB - Royal Society of Chemistry (RSC) ER - TY - GEN A1 - Langner, Thomas A1 - Sieber, Tim A1 - Rietig, Anja A1 - Merk, Virginia A1 - Pfeiffer, Lutz A1 - Acker, Jörg T1 - A Phenomenological and Quantitative View on the Degradation of Positive Electrodes from Spent Lithium-ion Batteries in Humid Atmosphere T2 - Scientific Reports N2 - The present study deals with the phenomenological observation of the corrosion of the positive electrode foil of lithium-ion batteries containing LiNi0.6Co0.2Mn0.2O2 (NMC) as cathode material. Due to the presence of moisture, localized water accumulation is formed on the NMC surface. The water absorbed by the electrolyte reacts with the NMC under Li+/H+ exchange and the resulting pH increase leads to dissolution of the carrier foil and characteristic salt-like blooms on the NMC surface. With the increase in the relative area occupied by the holes in the aluminum foil per time, a sufficiently suitable parameter was found with which to quantitatively determine the extent of corrosion. The degree of degradation depends on time and ambient humidity. It was shown that functional recycling with the water jet method is no longer applicable for degraded foils, since the mechanical stability of the foils decreases as corrosion progresses. Lithium, aluminum, sulfur and oxygen were detected in the blooms using SEM–EDX and Laser-Induced-Breakdown-Spectroscopy (LIBS). The underlying NMC layer was found to contain mainly aluminum and significantly lower lithium content than the non-degraded material. SEM and Raman microscopy analyses also showed that the active material is also locally degraded and therefore no longer suitable for functional recycling. KW - Analytical chemistry KW - lithium KW - cathode KW - materials KW - LIBS KW - Raman KW - SEM-EDX KW - degradation Y1 - 2023 U6 - https://doi.org/10.1038/s41598-023-32688-0 SN - 2045-2322 VL - 13 ER - TY - GEN A1 - Rietig, Anja A1 - Langner, Thomas A1 - Acker, Jörg T1 - About determining reliable etching rates and the role of temperature in kinetic experiments on acidic wet chemical etching of silicon T2 - Physical Chemistry Chemical Physics Y1 - 2023 UR - https://pubs.rsc.org/en/content/articlelanding/2023/cp/d2cp05837e U6 - https://doi.org/10.1039/D2CP05837E SN - 1463-9084 VL - 25 IS - 16 SP - 11387 EP - 11397 ER - TY - GEN A1 - Rietig, Anja A1 - Acker, Jörg T1 - Kinetic studies on acidic wet chemical etching of silicon in binary and ternary mixtures of HF, HNO3 and H2SiF6 T2 - Physical Chemistry Chemical Physics Y1 - 2023 U6 - https://doi.org/10.1039/d3cp03188h SN - 1463-9084 SN - 1463-9076 VL - 25 IS - 38 SP - 26245 EP - 26257 ER -