Synergetic pyrolysis of lithium-ion battery cathodes with polyethylene terephthalate for efficient metal recovery and battery regeneration

Abstract

Spent LiNixCoyMnzO2 (x + y + z = 1) and polyethylene terephthalate are major solid wastes due to the growing Li-ion battery market and widespread plastic usage. Here we propose a synergistic pyrolysis strategy to recover valuable metals by thermally treating LiNi1/3Co1/3Mn1/3O2 and polyethylene terephthalate. With polyethylene terephthalate assistance, LiNi1/3Co1/3Mn1/3O2 decomposes at 400 °C, and fully converts to Li2CO3, MnO, and Ni-Co alloy at 550 °C within 30 min, using a 1.0:0.3 mass ratio of LiNi1/3Co1/3Mn1/3O2 to polyethylene terephthalate. Furthermore, density functional theory calculations confirm the preference for O-Li bonding. Surface adsorption and free radical/gaseous reduction reactions explain the role of polyethylene terephthalate in promoting lattice destruction. The complete decomposition facilitates efficient post-treatment, achieving over 99% recovery of Li, Ni, Co, and Mn via water washing. Regenerated LiNi1/3Co1/3Mn1/3O2 was synthesized by using recovered Li- and transition metal-containing products as feedstocks. This study provided a chemical-free, energy-saving, and scalable recovery strategy while addressing polyethylene terephthalate waste minimization.