Co-upcycling spent lithium-ion batteries and plastics into microwave absorbing materials with Ni-Co catalyst control

Co-upcycling plastics with lithium-ion batteries (LIBs) into carbon nanotubes (CNTs) offers a promising high-value approach; however, it is hindered by the challenge of poisoning metal catalysts by carbon deposition and the uncontrollable particle growth. Here, we propose a co-upcycling strategy to convert spent LiNixCoyMn1-x-yO2 (NCM) and binary plastics—polyethylene terephthalate (PET) and other plastics—into NiCoMnOx/CNTs composites (or materials) for microwave absorption. During the pyrolysis, the generated pyrolysis gas reduces the NCM to NiCoMnOx and Li2CO3, and the NiCoMnOx catalyzes the decomposition of pyrolysis gas to generate CNTs. Importantly, Li2CO3 suppresses the growth of NiCo particles to below 100 nm and PET as both an etching agent and a carbon source, achieving a carbon conversion rate of 33% while preventing NiCoMnOx poisoning. After heat treatment at 800 °C, the resulting material exhibits favorable microwave absorption with an effective absorption bandwidth (EAB, RL