Polylactic acid(PLA)is a widely used biomass-derived polymer material.A significant amount of discarded polylactic acid is generated every year in the disposable product sector.Herein,a discarded PLA-based hard carbon was synthesized with discarded PLA as precursor,through cross-link-ing reaction with phosphoric acid and then followed by high-temperature carbonization.The results indi-cate that excessively lower carbonization temperature will result in unstable pore structure with lower sta-bility.Higher carbonization temperature leads to loss innon-carbon elements and decrease in reversible specific capacity.The introduction of phosphorus(P)increases the spacing between the hard carbon la-mellae to 0.37 nm.At carbonization temperature of 700℃,the prepared discarded PLA-based hard car-bon presents a honeycomb-like spherical framework with smaller specific surface area,and richer in high content of heteroatoms P and O,therefore exhibits the best electrochemical performance.By testing the assembled lithium-ion battery with electrode made of the acquired hard carbon,results show that by a current density of 100 mA/g,the specific capacity can reach 552 mAh/g;while for an initial Coulomb effi-ciency of 58.7％(324 mAh/g),the cycle stability is still excellent after 100 cycles.Besides,after multiple cycles at varying current densities,a reversible discharge capacity of 408 mAh/g is still maintained.
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