Wolfgang Haselrieder

Recovery of Active Materials from Spent Lithium-Ion Electrodes and Electrode Production Rejects

This article describes two ways to recover valuable and ecologically critical active materials from spent lithium-ion electrodes and electrode production rejects, using the example of a system containing LiNi0.33Co0.33Mn0.33O2 (NMC) active material and a polyvinylidene fluoride (PVdF) binder. First, a physical process using thermal treatment and mechanical stressing to separate the coating from the aluminum foil is discussed. Furthermore, a wet chemical processing using the solvent n-methyl-2-pyrrolidone (NMP) is presented. Recovered coating materials from both processes were characterized by laser diffraction spectroscopy and atomic absorption spectroscopy. Additionally, recycling electrodes were produced and successfully tested in battery test cells.

Discontinuous and Continuous Processing of Low-Solvent Battery Slurries for Lithium Nickel Cobalt Manganese Oxide Electrodes

Different discontinuously and continuously working dispersing devices were investigated to determine their influence on the structural and electrochemical properties of electrodes made from commercial LiNi1/3Co1/3Mn1/3O2 (NCM) cathode active material. A laboratory-scale dispersing device was compared with a discontinuously working laboratory kneader and a continuously working extruder, both using 50% less solvent than the dissolver process. Rheological, mechanical, structural, conductive, imaging, and electrochemical analyses (C-rate test, long-term cycling) were carried out. The dispersing method and time were found to have a considerable impact on the structure and electrochemical performance. The continuous extrusion process resulted in good performance with more than 20% higher specific capacity at elevated C-rates compared with the discontinuous process. This can be attributed to better deagglomeration of the carbon black in the slurries, also resulting in 60% higher electrode conductivity. On top of these positive results, the changes in the drying step due to the reduced solvent use led to a 50% decrease in the time required for the constant-drying-rate period. The continuously working extrusion process was found to be most suitable for large-scale, cost-efficient, environmentally friendly production of slurries for lithium-ion battery electrodes.