Fully extended conjugated azo-bridged covalent triazine framework with maximum dual-redox-active sites for advanced lithium organic batteries

Abstract

Lithium organic batteries based on organic electrode materials (OEMs) have opened up a new way to develop high-performance and environmentally friendly energy storage devices. However, OEMs reported thus far are still severely limited by poor electrical conductivity and unsatisfactory capacity. Herein, we creatively propose to directly conjugate the active motifs with functional linkers in OEMs for simultaneously increasing conductivity and capacity. As the first attempt, an exclusive azo-bridged covalent triazine frameworks (Azo-CTF) where triazine motifs are directly linked with azo groups, is cleverly designed and constructed. By virtue of the thoroughly electron conjugation throughout azo bridges and triazine π units, Azo-CTF with the lowest energy bandgap (2.62 eV) exhibits excellent essential charge conductivity. More excitingly, Azo-CTF achieves maximum redox-active sites integration (with the mass ratio reached to 70 %) to date. Therefore, Azo-CTF anode shows an almost record performance with a high reversible capacity (2332.8 mAh g⁻¹ at 0.1 A g⁻¹) and inspiring rate characteristics (1034.4 mAh g⁻¹ undergoing 500 cycles at 2 A g⁻¹, 690.2 mAh g⁻¹ undergoing 1000 cycles at 5 A g⁻¹). Our work provides a new strategy for synchronously improving the conductivity and capacity of OEMs, which would greatly promote the development of lithium organic batteries.