Today, manganese from the recycling of spent lithium-ion-batteries is widely unrecognized as a secondary raw material. Although the possibility that manganese, and especially battery-grade-manganese, will be on the European list of critical raw materials in the future is realistic. This thesis aims to investigate and compare three virtually unknown methods for the selective recovery of manganese from NMC-cathode material of spent lithium-ion-batteries. The laboratory experiments include leaching of pyrolyzed active material in an NH3-(NH4)2CO3-Na2SO3-system at temperatures from 60 to 80 °C and solid concentrations between 10 and 50 g·l-1 to selectively precipitate manganese. Next, selective precipitation of Mn from sulphuric solutions with aqueous Mn, Ni, Co, and Li at pH 4–5 and 60 °C by SO2/O2 gas in the following ratios 1/99 and 0,1/99,9 is investigated. The third set of experiments analyzes the enhanced precipitation of manganese from Mn-rich solutions, which are either still or rotated, with UV-light at pH 8,5–9 and room temperature.
The leaching efficiencies in the ammonia-based system are low for Ni, Co, and Li, because high NH3-concentrations lead to high pH-levels. Nevertheless, higher manganese yields in the precipitate are reached at elevated temperature and longer leaching periods.
The SO2-oxidation trials show that with increasing SO2-concentrations in the oxidizing gas mixture, process control becomes significantly more complex. The usage of gas mixtures with lower amounts of SO2 lead to a moderate decline in pH. After approximately 60 minutes, a critical point is reached and further reaction with manganese is inhibited. The formed precipitate shows high Mn- and simultaneously low Ni-, and Co- concentrations.
The UV-enhanced oxidation of aqueous manganese takes place at pH-ranges from 8,5 to 9 and can be further enhanced by rotating the liquid container at 30 rpm.
The findings of this study are relevant for an efficient materials cycle in the field of lithium-ion-batteries in the future. Today, the recycling efforts mainly concentrate on the recovery of cobalt, nickel, and lithium, but the remaining materials should not be forgotten.