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Updated: Aug 7, 2026
From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Dynamic Bifunctional Sites on a COF Enable Efficient Immobilization and Conversion of Iodine Species Toward Li-Iodine
Le-Tian Zhang1, Ming Liu2, Yin-Qiang Zhang1
1State Key Laboratory of Elemento-Organic Chemistry, Frontiers Science Center For New Organic Matter, College of Chemistry, Nankai University, Tianjin, China.
Abstract:
The thermodynamic instability of iodine cation (I+) and shuttle effect of polyiodide in the two-electron Li-iodine (Li-I2) batteries remain an unresolved bottleneck. The design and preparation of an advanced cathode capable of effectively anchoring and activating iodine species is a desirable but highly challenging target to overcome these issues. In this study, we strategically synthesized a pyridine-functionalized COF (BPY-COF-HI) cathode that enables highly reversible multivalent transition of iodine (I-/I0/I+) within Li-I2 batteries. The pyridine sites reversibly switch between protonated state (NH+) and neutral state (N), allowing them to anchor I3 - via electrostatic interactions and activate I+ via halogen bonding, respectively. Benefiting from this dynamic bifunctional regulation driven by the single pyridine site, a carbon-nanotube-integrated composite cathode (BPY-COF@CNT-HI) delivers a high-voltage discharge plateau at 3.58 V corresponding to the reversible I+/I0 redox and achieves a gravimetric energy density of 642 Wh kgI -1 at 0.3 A g-1. Remarkably, the cathode maintains ultralong cycling stability over 8000 cycles at 2.0 A g-1 with an exceptionally low capacity fade of 0.0055% per cycle. This result widens perspectives for designing high-performance cathodes for Li-I2 batteries with two-electron redox chemistry.
