Synthesizing\nHighly Crystalline Graphite Powder from\nBulk Polyethylene Waste for Lithium-Ion Battery Anodes

Upcycling plastic\nwaste into graphite can potentially\nbe used,\nin conjunction with other methods, to manage existing waste materials\nand diversify graphite supply chains. However, synthesizing large\nquantities of crystalline graphite powder from plastic waste, particularly\npolyethylene (PE), remains a challenge because PE decomposes into\nlight gases during thermal processing and simple methods do not exist\nat any appreciable size scale to address this challenge. In this work,\na method is developed for air processing bulk forms of PE waste to\ncreate stable carbon char that does not readily decompose during\nhigh-temperature processing. This method employs solid additives in\nthe form of salts, which are combined with the PE melt during air\nprocessing to increase the effective surface area of the melt and\nimprove the oxygen-driven chemistry that stabilizes PE for high-temperature\nprocessing. After removal of the solid salt additives from the PE-derived\nchar, it is converted into a highly crystalline bulk graphite powder\nusing an Fe-based catalytic process. The PE-derived graphite anode\nin a lithium-ion coin cell showed a specific capacity of 345 mAh/g\nat 0.05C with an initial Coulombic efficiency of 87% and reversible\ncapacity retention of ∼100% at different current rates. It\nalso showed a specific capacity of up to 313 mAh/g at 0.5 discharge/charge\ncycles per hour (0.5C) and Coulombic efficiency of 99.9% after 250\ncycles, indicating excellent electrochemical performance as an anode\nmaterial for lithium-ion batteries. This method illustrates that there\nare opportunities for upcycling large quantities of PE waste to produce\ngraphite powders suitable for use in LIBs.