Microwave thermal treatment of industrial NMC 622 lithium-ion battery shredder and its influence on reaction products compared to conventional pyrolysis
Christin Stallmeister, Niklas Mehl, Bernd Friedrich
Abstract
Thermal pre-treatment has been proven to be a relevant process step in lithium-ion battery recycling. The organic removal and phase transformations are beneficial for subsequent process steps. Recently, the innovative concept of microwave heating has been introduced as an alternative for conventional processes taking the example of black mass and artificial mixtures. This study investigates the transferability of the concept to an industrial NMC 622 (LiNi 0.6 Mn 0.2 Co 0.2 O 2 ) battery shredder, including foils and separator for the first time. The influence of treatment time, power and atmosphere are investigated and finally a scale-up is carried out. For all parameters, the influence on the resulting products off-gas and active mass and the subsequent mechanical treatment and water-based lithium recovery is investigated and compared to a conventional pyrolysis process. The gas analysis showed the enhanced decomposition of organics to shorter molecules compared to conventional heating and a successful organic removal. After a microwave treatment at 6 kW for 14 min, a mass loss of 14.7 % compared to 12 % in conventional pyrolysis at ∼550 °C was achieved and the delamination of the collector foils was improved. Furthermore, the reduction degree of NMC is similar. Accordingly, the lithium recovery shows nearly equal results of 54.2 % (conventional) and 55.5 % (microwave). The microwave process can therefore achieve the same product quality as a conventional treatment and is highly efficient with a timesaving of ∼88 %. Consequently, the study pooves the feasibility of a microwave treatment for complex battery shredder material. • Alike black mass quality after microwave thermal treatment compared to conventional. • Short chain molecules in microwave thermal treatment off-gas. • Water based lithium recovery reaches up to 55.5 % after microwave pyrolysis. • Carbothermic NMC reduction in microwave thermal treatment to metallic Ni.