The liquid-phase carbonization strategy helps to recycle waste polyethylene terephthalate into high-performance hard carbon
image: We ingeniously changed the traditional solid-phase precursor to liquid-phase precursor in the process of carbonizing waste polyethylene terephthalate (PET), which not only formed more intrinsic carbon defects with different topologies, but also regulated the morphology and structure of the hard carbon product. The obtained hard carbon exhibited excellent performance as an anode for SIBs.
Credit: Nano Research, Tsinghua University Press
Although hard carbon is widely recognized as one of the most promising anode materials for commercial sodium-ion batteries, its potential is limited by low performance and high cost. The innovative solution by the team of Prof Jian-Ping Lang and Prof Hongwei Gu from Soochow University, published in Nano Research (Tsinghua University Press), employs a liquid-phase carbonization strategy to recycle waste polyethylene terephthalate into porous micro/nanostructured hard carbon enriched with intrinsic carbon defects having excellent sodium storage performance.
Key Innovation & Synthesis:
The pyrolysis of a mixture solution containing waste polyethylene terephthalate, DMF and Zn(OAc)2 produced a large number of bubbles during the preparation of hard carbon, leading to the formation of LHC-3 with more intrinsic carbon defects in non-zero-curvature carbon structures，which constitute active sites for adsorption of sodium ions. In addition, Zn(OAc)2 can effectively regulate the morphology and structure of the carbonization products of waste polyethylene terephthalate. The porous micro/nanostructure of the resulting LHC-3 not only mitigates mechanical stress caused by volume expansion/contraction during charge/discharge process, but also effectively suppresses the agglomeration of carbon NPs, thereby improving cycling stability. The synergistic interaction between intrinsic carbon defects and nanoscale effects endows this anode with exceptional sodium-ion storage capacity, ultrafast charging characteristics, and ultrastable cycling performance.
Record-Breaking Performance:
The LHC-3 anode exhibits high specific capacity (355 mAh g-1 at 0.1 A g-1), superfast charging capability (132.6 mAh g-1 input within 13 s of charging), and ultralong cycling stability (100,000 stable cycles at 50 A g-1). In addition, the NaV2(PO4)2O2F//LHC-3 full sodium-ion cell displays a high energy density of 251 Wh kg⁻¹.
Mechanism & Confirmation:
The porous micro/nanostructure not only mitigates mechanical stress caused by volume expansion/contraction during charge/discharge process, but also effectively suppresses the agglomeration of carbon NPs, thereby improving cycling stability. In addition, kinetic analyses, ex-situ Raman spectroscopy and XPS studies systematically elucidated the “adsorption-insertion” mechanism of sodium storage in this anode. DFT calculations revealed that intrinsic carbon defects in non-zero-curvature carbon structures can accommodate more sodium ions.
Researcher Insights:
“Our strategy of liquid-phase carbonization solves two challenges at the same time; it not only endows the hard carbon with more carbon defects to be used as active sites for sodium ion storage, but also optimizes the morphology and structure of the hard carbon to greatly extend its lifetime.” explained corresponding author Professor Jian-Ping Lang.
Co-corresponding author Professor Hongwei Gu added “Recycling and carbonizing polyethylene terephthalate to produce high-value hard carbon can reduce environmental pollution while addressing the high costs associated with typical hard carbon precursors.”
Future Directions:
The team plans to extend this powerful strategy to other organic polymer precursors for the preparation of advanced hard carbon. In addition, the team is working to reveal the relationship and mechanism that exists between the microstructure of carbon defects and sodium storage performance.
Collaborators & Funding:
We thank the National Natural Science Foundation of China (U24A20507, 22271203 and 22478152), the State Key Laboratory of Organometallic Chemistry of Shanghai Institute of Organic Chemistry (2024KF005), Open Research Fund of State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, the Collaborative Innovation Center of Suzhou Nano Science and Technology, and the Project of Scientific and Technologic Infrastructure of Suzhou (SZS201905). We would also like to sincerely express our heartfelt gratitude to Professor Pierre Braunstein from the Université de Strasbourg for his guidance in the preparation of the article.
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.