Comparison of the effects of incineration, vacuum pyrolysis and dynamic pyrolysis on the composition of NMC-lithium battery cathode-material production scraps and separation of the current collector

Artikel i vetenskaplig tidskrift, 2021

The rising demand for lithium batteries is challenging battery producers to increase their production. This is causing an accumulation of production scrap which must be treated to allow re-utilization of cathode material in production. Several industrial lithium battery recycling processes use thermal pre-treatment in an oxidative or inert atmosphere, or in a vacuum, to separate the battery components and remove organic material. However, a comparison of the effects of incineration, dynamic pyrolysis (under a constant flow of inert gas), and pyrolysis under vacuum on the microstructure and composition of scrap cathode material has not been explored. Scrap cathodes, with active material based on Li(NixMnyCoz)Oj, were subjected to incineration, dynamic pyrolysis, and pyrolysis under vacuum at 450˚, 550˚, and 650°C for 30, 60, 90, and 150 min to determine the best approach to cathode material recovery. While the incineration did not cause any chemical transformation of cathode material, under pyrolysis conditions the organic components in the cathodes triggered carbothermic reduction of the active material, yielding Co3O4, NiO, Mn3O4, and Li2CO3 as products. In the gas by-products, formed from the decomposition of the organic material, CO, CO2, and HF were determined. The decomposition especially of the binder in polyvinylidene fluoride (PVDF) facilitated the separation of the active material from the current collector by mechanical treatment. By subsequent ball milling, the best technique to recover cathode material is the incineration at a temperature higher than 550˚ C and below 650˚ C for at least 90 min, with >95% of recovered active material.