Ultra-small B2O3 nanocrystals grown in situ on highly porous carbon microtubes for lithium–iodine and lithium–sulfur batteries

Abstract

B₂O₃-modified carbon microtubes, which possess a highly porous structure and well-dispersed ultra-small B₂O₃ nanocrystals (ca. <5 nm) in the tube wall, are successfully fabricated via a facile thermal-treated process from poplar catkin, and then investigated for the first time as a capture interlayer for lithium–iodine (Li–I₂) and lithium–sulfur (Li–S) batteries. After introduction of the B₂O₃/carbon microtube composite interlayer, the iodine cathode demonstrates a reversible capacity of 176.9 mA h g⁻¹ after 500 cycles at a rate of 20C. When the rate increases to 100C, a high capacity of 140.7 mA h g⁻¹ can still be obtained after 5000 cycles, which makes this the most stable iodine cathode reported for Li–I₂ batteries to date. For Li–S batteries, the sulfur cathodes present excellent cycling performance with a high discharge capacity of 594 mA h g⁻¹ at the rate of 4C. Such excellent cycle stability for the Li–S and Li–I₂ batteries could be mainly attributed to strong interactions between the ultra-small B₂O₃ nanocrystals and polysulfide or iodine ions, which has been proven using first principle calculations.