Co-upcycling spent lithium-ion batteries and plastics to microwave absorbing materials: Ni-Co catalyst size confinement and poison mitigation

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 LiNi _x Co _y Mn _1−x−y O ₂ (NCM) and binary plastics—polyethylene terephthalate (PET) and other plastics—into NiCoMnO _x /CNTs composites (or materials) for microwave absorbing. During the pyrolysis, the generated pyrolysis gas reduces the NCM to NiCoMnO _x and Li ₂ CO ₃ , and the NiCoMnO _x catalyzes the decomposition of pyrolysis gas to generate CNTs. Importantly, Li ₂ CO ₃ 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 NiCoMnO _x poisoning. After heat treatment at 800°C, the resulting material exhibits favorable microwave absorption with an effective absorption bandwidth (EAB, RL < − 10 dB) of 7.01 GHz at 2.41 mm. Life cycle analysis (LCA) shows that this strategy has obvious environmental benefits. Overall, PET is a general enabler to prepare (Ni _x Co _y )MnO/CNTs microwave-absorbing materials harnessing carbon from binary plastics and critical metals from battery materials, providing a sustainable solution for upcycling spent LIBs and plastic wastes.