Cobalt(II)‐Hexaazatriphenylene Hexacarbonitrile Coordination Compounds Based Cathode Materials with High Capacity and Long Cycle Stability

Abstract

Organic cathode materials are plagued by their low cycle stability and poor electronic conductivity, even though they have attracted increasing attention in the context of lithium‐ion batteries (LIBs). Herein, a coordination polymer cobalt‐hexaazatriphenylene hexacarbonitrile (Co(HAT‐CN)) is prepared via a facile solvothermal method, which is composed of the redox‐active HAT‐CN linker and the Co(II) ion center. The fabricated material shows excellent structural stability and high conductivity. Moreover, graphene oxide (GO) is introduced as a substrate, and in‐situ loading of Co(HAT‐CN) on its surface shows enhanced cycling stability. For Co(HAT‐CN)/GO, a high specific capacity of 204 mAh g–1 can be retained even after 200 cycles at a current density of 40 mA g–1 in a voltage window of 1.2–3.9 V. Ex situ and in situ analyses are applied to probe the reversibility of the pyrazine redox‐active center during the cycling process and the lithium storage process. Density functional theory calculations reveal that the high conductivity of Co(HAT‐CN) should be ascribed to the narrow LUMO‐HOMO gap (0.61 eV), and strong binding of lithiated molecules.

Metal organic polymers with dual catalytic sites for oxygen reduction and oxygen evolution reactions

“…The catalysts (M-HAT-CN [M: Co and Ni]) were synthesized from metal salts (cobalt nitrate hexahydrate (Co(NO 3 ) 2 •6H 2 O) or nickel nitrate hexahydrate (Ni(NO 3 ) 2 •6H 2 O)) and hexaazatriphenylene hexacarbonitrile (HAT-CN) in a molar ratio of 4:1 at 120°C for 20 h under a N 2 atmosphere (Figure 1A). 50 The catalytic metal-N 4 sites were constructed by coordinating metal ions with cyan group (C≡N) from redox-active hexaazatriphenylene hexacarbonitrile (HAT-CN) units, and the metal-N 2 sites were formed by coordinating the metal ions with the pyrazine (C═N) bonds in the HAT-CN (Figure 1B The as-synthesized M-HAT-CN was characterized by Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The FTIR spectra for HAT-CN showed that the peaks at 2230 cm -1 were from the C≡N bonds, and the peaks at 1665 cm -1 were due to the C═N bonds (Figure 2A, black curves).…”

Stable Hexaazatrinaphthalene-Based Planar Polymer Cathode Material for Organic Lithium-Ion Batteries

“…In addition, compared with previously reported HATN-based polymers including some composites prepared with CNTs or GO (Figure e), the AZO-HATN-AQ cathode possesses the advantages of high rate capabilities and excellent cycling stability as a cathode material for LIBs (Table S1). − ,, The outstanding comprehensive electrochemical properties of AZO-HATN-AQ are ascribed to the π-conjugated polymer network, abundant redox-active groups, small energy gap, excellent solubility resistance in the electrolyte, and good planarity during cycling.…”

N-Heteroaromatic fused-ring cyanides extended as redox polymers for high rate capability aqueous zinc-ion battery

“…HATN and its derivatives have been investigated as typical pconjugated molecules for reversible electrochemical reactions due to the presence of large numbers of C]N bonds as redoxactive sites. 36,37 Generally, they are synthesized through a Maillard reaction between cores and graed units at appropriate temperatures. Although the core molecule is usually specied to be hexaketocyclohexane (C 6 O 6 ), the diverse graed molecules provide large structural varieties for functional modications (e.g.…”