期刊
ADVANCED FUNCTIONAL MATERIALS
卷 32, 期 2, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.202106980
关键词
carbon allotrope; graphite-like crystal; hard carbon; initial coulombic efficiency; Na-ion battery
类别
资金
- National Natural Science Foundation of China [51772337]
- Guangdong Basic and Applied Basic Research Foundation [2021A1515010154]
This study reports a new phenomenon of graphite-like crystals in hard carbon and indicates that these crystals exhibit extremely high initial coulombic efficiency and reversible capacity in sodium-ion batteries. This breakthrough potentially provides a new pathway for obtaining novel crystalline carbon allotropes.
Hard carbon usually refers to non-graphitizable carbon, which does not transform into a crystal structure even at high temperatures. Although hard carbon is considered as the most promising anode material for Na-ion batteries (NIBs), its practical application is still hindered by its low initial coulombic efficiency (ICE). Here, the intergrowth of large area graphite-like crystals in hard carbon is reported using cotton as precursor and graphite as crystal template by calcination under their intimate contact condition. Extensive characterizations provide abundant evidence that graphite-like crystal is a new carbon allotrope belonging to the hexagonal system (a = b = 3.528 angstrom, c = 9.6 angstrom, alpha = beta = 90 degrees, gamma = 120 degrees) with d-spacing of 4.8 angstrom for (002) plane. Its unit cell dimensions and d-spacing of (002) plane are all enlarged by the same factor of 1.428 compared to those of the graphite phase. When applied in NIBs, the hard carbon with graphite-like crystals shows an extremely high ICE of 95.0% with a large reversible capacity of 343 mAh g(-1), which reaches the same level as graphite used in Li-ion batteries. The graphite-like crystal breaks the traditional concept of hard carbon, while the graphite-template induced epitaxial growth mechanism may provide a new way for obtaining novel crystalline carbon allotropes.
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