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Braunschweig, Germany

Westphal B.G.,TU Braunschweig | Westphal B.G.,Lion Engineering GmbH | Bockholt H.,TU Braunschweig | Gunther T.,TU Braunschweig | And 4 more authors.
ECS Transactions | Year: 2015

In the present work two of the various drying process parameters, air temperature and nozzle speed, are studied and their influence on the electrode's physical properties is examined by different mechanical and electrical analyzes. It was found that elasticity, electrical volume resistivity and adhesion strength of the coating to the substrate, can be dependent on process parameters used for manufacturing. These properties are also influenced by the electrode's mass loading and its recipe, as the total solvent content and therefore the drying time plays an important role. Assuming binder demixing during drying allows explaining the results, since evaporating solvent induces a temperature dependent compensational flow of solvent and solved binder. If immobilization occurs faster than compensational flow can cause significant demixing, no binder gradient emerges. The driving force counteracts the drying time, but increases demixing, so that optimum drying conditions exist for each mass loading and solid content. © 2015 The Electrochemical Society. Source

Haselrieder W.,TU Braunschweig | Haselrieder W.,Lion Engineering GmbH | Westphal B.,TU Braunschweig | Westphal B.,Lion Engineering GmbH | And 5 more authors.
International Journal of Adhesion and Adhesives | Year: 2015

Abstract The coating adhesion strength of lithium-ion battery electrodes is a very important mechanical property, affecting the electrochemical life time of battery cells and the electrochemical handling during cell manufacturing. Hence the establishment of a standardized pull-off test with high reproducibility was long time overdue. The measurement setup is realized in a material testing machine. Machine and process parameters have been investigated to propose a reliable measurement procedure with a clearly specified parameter setup. Data acquisition rate (f), contact stress (σc), dwell time (td) and pull-off velocity (vpo) were identified to affect the adhesion strength measurement significantly. Finally electrodes with material and process parameter variations were manufactured to assess the applicability of the presented method. The impact of the amount of binder and its molecular weight as well as the influence of the dry mixing and the dispersing process on adhesion strength was verified and the differences can be clearly distinguished by the developed test method. © 2015 Elsevier Ltd. All rights reserved. Source

Hanisch C.,TU Braunschweig | Hanisch C.,Lion Engineering GmbH | Loellhoeffel T.,TU Braunschweig | Diekmann J.,TU Braunschweig | And 7 more authors.
Journal of Cleaner Production | Year: 2015

Lithium-ion batteries will play a crucial role in the development of mobile consumer devices, stationary energy storage systems, and electric mobility. The growth in these fields will bring about a surge in the lithium-ion battery market. This leads experts to agree that more effective recycling processes are needed in conjunction with the recycling of lithium. This calls for an entirely revolutionary recycling process which we here have attempted to develop. Our approach uses thermal decomposition of the polyvinylidene fluoride binder to lessen the cohesion of coated active material particles and weaken the adhesion between coating and foil. Then, an air-jet-separator is able to detach the coating powder from the current collector foils while stressing remaining particulate agglomerates. This separation process named ANVIIL (Adhesion Neutralization via Incineration and Impact Liberation) was tested on a laboratory scale with electrode rejects. We compared this to the widely used mechanical recycling process that utilizes a cutting mill to separate the current collector and coating. Intermediates and products were characterized using thermogravimetric analysis, tape adhesion tests, atomic absorption spectroscopy, particle size analysis, and gravimetric sieve analysis. We found that 97.1% w/w of the electrode coating can be regained with aluminum impurities of only 0.1% w/w, 30 times purer than the comparative process. This demonstrates a more effective recycling process than is currently available that also enables the recapture of lithium from the electrode coating. © 2015 Elsevier Ltd. All rights reserved. Source

Hanisch C.,TU Braunschweig | Hanisch C.,Battery LabFactory Braunschweig | Hanisch C.,Lion Engineering GmbH | Schunemann J.-H.,TU Braunschweig | And 14 more authors.
ECS Transactions | Year: 2015

Having a closer look at the details, recycling of scraps from the production of lithium-ion batteries is different from recycling of spent batteries. On the one hand it is less dangerous on the other hand pristine electrodes retain the original non-aged quality and thus the separation process is more difficult. Two different separation mechanisms, one mechanical and one based on the solvent N-methyl-2-pyrrolidone, are examined in this work. The resulting separated coatings are directly re-applied on new electrodes and electrochemically characterized in full cells. © 2015 The Electrochemical Society. Source

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