[DOI: 10.3390/materproc2021005030]

Recovery of Graphite and Cathode Active Materials from Spent Lithium-Ion Batteries by Applying Two Pretreatment Methods and Flotation Combined with a Rapid Analysis Technique

This work investigates the comprehensive recycling of graphite and cathode active materials (LiNi0.6Mn0.2Co0.2O2, abbreviated as NMC) from spent lithium-ion batteries via pretreatment and flotation. Specific analytical methods (SPME-GC-MS and Py-GC-MS) were utilized to identify and trace the relevant influencing factors. Two different pretreatment methods, which are Fenton oxidation and roasting, were investigated with respect to their influence on the flotation effectiveness. As a result, for NMC cathode active materials, a recovery of 90% and a maximum grade of 83% were obtained by the optimized roasting and flotation. Meanwhile, a graphite grade of 77% in the froth product was achieved, with a graphite recovery of 75%. By using SPME-GC-MS and Py-GC-MS analyses, it could be shown that, in an optimized process, an effective destruction/removal of the electrolyte and binder residues can be reached. The applied analytical tools could be integrated into the workflow, which enabled process control in terms of the pretreatment sufficiency and achievable separation in the subsequent flotation.

Effect of Graphite on the Recovery of Valuable Metals from Spent Li-Ion Batteries in Baths of Hot Metal and Steel

The recycling of valuable metals from spent lithium-ion batteries (LIBs) is highly important to secure the sustainable production of new LIBs and reduce the dependence on virgin resources. The present paper aims to study the smelting behaviour of black mass (BM) from spent LIBs and investigate the effect of graphite on metal recovery in a carbon-saturated hot metal bath and in a low-carbon steel bath. The smelting trials of BM were conducted in a technical scale (150 kg) induction furnace using hot metal and steel scrap at operating temperatures in the range of 1278–1438 °C and 1470–1610 °C, respectively. Two grades of BM were applied in the current study; high-Ni BM and high-Co BM. Parts of both grades of the BM were briquettes to enhance the direct reduction of metal oxides with embedded graphite and to reduce the dust generation during loading into the furnace. The briquette BM was charged to carbon-saturated hot metal bath while the other part of the BM was subjected to de-coking in a muffle furnace in an oxidising atmosphere to remove graphite (37–39%) and to concentrate the valuable metals in the BM. The de-coked BM was loaded directly, without the need for the briquette, to the low-carbon steel bath. The results indicated that smelting of the de-coked BM in a steel bath is more efficient in metal recovery than the smelting of the corresponding briquette BM in a molten hot metal bath. The highest recovery rate of Co, Ni and Cu (98–99%) was obtained by smelting de-coked high-Co BM in a low-carbon molten steel bath, while the lowest recovery rate (38–55%) was obtained by smelting the briquette high-Ni BM in the carbon-saturated hot metal bath.