From Plastic Waste to Power Source: Polyethylene-Derived Anodes for Lithium-Ion Batteries

Polyethylene, the largest component of plastic waste, decomposes on heating almost entirely to volatiles rather than to carbon. Here, one post-consumer low-density polyethylene (LDPE) film and one high-density polyethylene (HDPE) bottle were converted into disordered carbons by sulfonation-assisted carbonization. Sulfonation raised the carbon residue at 900 °C from 1.21 to 32.63 wt.% for LDPE and from 0.06 to 8.82 wt.% for HDPE. The two carbons are indistinguishable by X-ray diffraction and high-resolution transmission electron microscopy (interlayer spacing 0.365-0.366 nm, crystallite thickness ≈1.4 nm), have the same Raman disorder ratio (1.01-1.02) and retain little sulfur (≤0.51 at.%), but differ in specific surface area (53.7 and 32.5 m² g^-1). As lithium-ion anodes, the LDPE- and HDPE-derived carbons deliver 338 and 302 mA h g^-1 after 100 cycles at 100 mA g^-1, with capacity still rising, and 155 and 130 mA h g^-1 at 2 A g^-1. The larger first-cycle loss and higher capacity of the LDPE-derived carbon correlate with its larger surface area, consistent with the precursor acting through its response to the sulfonation pretreatment rather than through carbonization. These results are a proof of concept; extension to other and mixed waste streams requires further study.