Study on the pyrolysis mechanism of PE and PP catalyzed by endogenous transition metals in spent lithium-ion batteries

ZX Tian and B Li and MY Zhai and WL Pang and JX Wu and PZ Wang and T Liu and YF Wu, JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING, 13, 119028 (2025).

DOI: 10.1016/j.jece.2025.119028

Investigating the catalytic effect of transition metals on polyethylene (PE) and polypropylene (PP) pyrolysis is crucial for efficient lithium- ion battery (LIB) recycling. Molecular dynamics simulations results were demonstrated that the pyrolysis of PE and PP is effectively catalyzed by transition metals, leading to an increased pyrolysis reaction rate and promoting the production of small molecular compounds. Py-GC/MS results showed that at 460 degrees C, the C1-C10 product content from PE pyrolysis was 1.78 % without a catalyst and increased to 5.82 %, 7.16 %, and 8.09 % with Co, Ni, and Cu catalysts, respectively. For PP, the C1-C10 content was 23.37 % without a catalyst, rising to 36.56 %, 38.33 %, and 41.84 % with Co, Ni, and Cu. These findings indicate that transition metals enhance small molecule production, with PP being more easily pyrolyzed than PE. Quantum calculations revealed electron transfer between metals and H atoms in the polymers, altering electron density and catalyzing pyrolysis by changing bond dissociation energies. Emergy and environmental impact analysis indicates that the pyrolysis of PE and PP under the effect of Ni achieves the best performance in terms of environmental impact control and reduced emergy consumption, compared to Co and Cu, highlighting the excellent catalytic role of Ni in promoting plastic decomposition and improving reaction efficiency.

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