Microstructure regulation of pitch-based soft carbon anodes by iodine treatment towards high-performance potassium-ion batteries

Abstract

Soft carbon has been regarded as one of the most promising anode materials for potassium-ion batteries. However, the rearrangement of planar aromatics at high carbonization temperature usually yields a highly graphitized structure, which generally leads to inferior rate and cycle performance. In addition, the role of intrinsic carbon defects on potassium storage has not been well reported yet. In this work, crosslinked pitch-based soft carbon nanosheets have been synthesized through the iodination/dehydroiodination process at low temperature and carbonization with NaCl template. The iodine-treatment efficiently crosslinks the planar aromatics to three-dimensional framework by alkyl-bridged linkages, and reduces the strong π-π interaction during carbonization. This unique microstructure yields an ordered-in-disordered carbon microstructure, enlarged interlayer spacing, and abundant intrinsic defect sites. Benefited from these merits, the optimal sample displays 140% increase of reversible capacity to the pristine pitch-based carbon at 5 A g−1. Particularly, it also presents 87.4% capacity retention after 1000 cycles at 1 A g−1. This facile but simple strategy is expected to expand to other high-performance carbon materials and further understand the effect of intrinsic defects for potassium storage and beyond.