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Evaluation of battery recycling processes using exentropy: a novel multi-dimensional circularity indicator of materials concentration and energy preservation

Thesis defender: Minerva Vierunketo
Opponent: Prof. Philippe Nimmegeers, University of Antwerp, Belgium
Custos: Prof. Rodrigo Serna-Guerrero, Aalto University School of Chemical Engineering

Evaluation of battery recycling processes using exentropy: a novel multi-dimensional circularity indicator of materials concentration and energy preservation

During the past century, the growing human population and industrialization has led to the overconsumption of natural resources and thus a decreased availability of raw materials resources. The consumption of resources is dominated by the linear economy model of “produce, use, dispose”, which causes damage to e.g., the environment and critical resources. Therefore, a transition from a linear economy into circular one is crucial. Circular economy (CE) represents a regenerative and restorative system by design, and it aims to minimize the production of waste and thus slow the flow of primary resources by slowing, closing, and narrowing both material and energy loops during the life cycle of a product. The transition from linear economy into circular one requires proper end-of-life strategies, which efficiency can be measured by different quantitative circularity indicators. The problem however is that current indicators focus mainly on one dimension and therefore lack a consensus in the analysis and comparison of different technological solutions.
In this thesis, a newly developed multidimensional indicator, called “exentropy”, is presented. It accounts simultaneously for materials concentrating action and useful energy preservation of transformative stages using statistical entropy analysis (SEA) and exergy analysis (ExA), respectively. The concept of exentropy was tested in the optimization of a hydrometallurgical lithium-ion battery (LIB) recycling process, in the comparison of pyrometallurgical, hydrometallurgical, and direct recycling processes, and in the evaluation of different electrochemical LIB discharging units. The results showed that individual indicators (i.e., SEA and ExA) gave different information on the most optimal process conditions. Exentropy however could identify the processes that offered the most useful compromises for material and useful energy preservation. These results imply that there is indeed a need for more robust analysis using multidimensional indicators, which exentropy could fulfil in the first step towards the multidimensional engineering in CE.

circular economy, circularity indicators, exergy analysis, statistical entropy, relative exergy content, exentropy, hyperspherical engineering, lithium-ion batteries, recycling, saline battery discharge

Thesis available for public display 7 days prior to the defence at .

Contact information: minerva.vierunketo@aalto.fi