Data-assisted vacuum crushing and drying of end-of-life batteries

Data-assisted vacuum crushing and drying of end-of-life batteries

Closing material loops is essential for sustainable electric mobility, for example, to ensure the supply of battery materials. Therefore, efficient recycling systems are needed, which maximize the output quantity and quality while minimizing the associated costs and environmental impacts [1].

A common way for recycling lithium-ion batteries is to crush and dry them. The crushed and dried material can then be separated into the different material fractions by means of several mechanical processes [2]. Anyway, crushing of batteries in particular involves a risk due to possible exothermic reactions, i.e., measures are usually taken to minimize this risk by first deep discharging the batteries before crushing and second purging the crushing chamber with inert gas or by crushing in a wet environment. The subsequent drying process is intended to reduce the potential risk of inflammation of the crushed material by removing components of the electrolyte. This process can be carried out at a (slightly) negative pressure difference at temperatures up to 120°C, but also technologies using much higher temperatures at ambient pressure are known. However, crushing under inert gas consumes an enormous amount of resources, while drying with high temperatures can release hazardous hydrofluorocarbons [3].

In order to understand these complex crushing and drying processes, knowledge about the influence of the process parameters as well as process conditions and about the products is necessary. This can be achieved by analyzing information from various sensors, control loops and analytics integrated into the processes. The information can be used to identify potential cause-effect relationships between process parameters and product quality, which can support increase recycling rates and quality while reducing energy and material consumption [4].

This work presents a novel approach of crushing and drying deeply discharged batteries. The process takes place under vacuum with pressures below 5 mbar. This has the advantage that no inert gas is required for crushing and the low pressure causes a larger quantity of electrolyte components to evaporate already within the shredding process. The subsequent drying process takes place in the same process room, while the maximum temperature of 40°C prevents the formation of hydrofluorocarbons. To further grind the crushed material and maximize the delamination of the electrode foils from the active material, the so-called black mass, additional energy input through the drying process is advantageous by using a high intensity mixer. To gain a better understanding of the process, data from the programmable logic controllers and various sensors, e.g. for pressure or temperature, are recorded and evaluated together with the analytically recorded data. Various conclusions are drawn from the data. As a result, the analyzed data of shredding and drying processes of battery cells are presented. From this, insights are gained to further increase energy efficiency and black mass yield.

REFERENCES

[1] Cerdas, F.“;“ Andrew, S.“;“ Thiede, S.“;“ Herrmann, C. Environmental Aspects of the Recycling of Lithium-Ion Traction Batteries. In: Recycling of Lithium-Ion Batteries. Kwade, A., Diekmann, J., Eds.“;“ Springer International Publishing: Cham, 2018„;“ Vol. 55„;“ pp. 267–288.

[2] Diekmann, J.“;“ Rothermel, S.“;“ Nowak, S.“;“ Kwade, A. The LithoRec Process. In: Recycling of Lithium-Ion Batteries. Kwade, A., Diekmann, J., Eds.“;“ Springer International Publishing: Cham, 2018„;“ Vol. 164„;“ pp. 33–38.

[3] Diekmann, J.“;“ Hanisch, C.“;“ Froböse, L.“;“ Schälicke, G.“;“ Loellhoeffel, T.“;“ Fölster, A.-S.“;“ Kwade, A. Ecological Recycling of Lithium-Ion Batteries from Electric Vehicles with Focus on Mechanical Processes. Journal of The Electrochemical Society, 2016.

[4] Blömeke, S.“;“ Rickert, J.“;“ Mennenga, M.“;“ Thiede, S.“;“ Spengler, T.S.“;“ Herrmann, C. Recycling 4.0 – Mapping smart manufacturing solutions to remanufacturing and recycling operations. Procedia CIRP, 2020, 90, 600–605.