Covalent organic framework containing dual redox centers as an efficient anode in Li‐ion batteries

Abstract

Covalent organic frameworks (COFs) with periodic channels and tunable chemical structures have been widely considered as promising electrode materials in rechargeable batteries. However, the design and construction of high-performance COFs-based electrodes still face some challenges in the introduction of multiple efficient redox centers as well as the reduction of dead mass. To address these issues, a unique COF containing double active centers (C═N and N═N) is developed as an anode in rechargeable lithium-ion batteries (LIBs). The as-prepared COF displays excellent electrochemical performance due to its remarkable structural stability and the existence of many active groups. Meanwhile, its electrochemical performance is significantly better than that of the small molecule compound or the linear polymer with the same construction units. Even at a high current density of 5 A/g, the LIBs with COF electrodes remain at a high discharge capacity of 227 mAh/g after 2000 cycles. Moreover, the distinction in electrochemical performances of these three materials is further revealed by calculation. This study illustrates the importance of molecular structure design for improving the performance of organic electrodes.

Structure regulation induced high capacity and ultra-stable cycling of conjugated organic cathodes for Li-ion batteries

“…Organic materials, with structural diversity, reasonable sustainability, tunable properties, and possible high capacity/high energy density, have been demonstrated as potential candidates for next generation LIBs. 8,9,16–20 Many types of organic materials containing different redox active centers (carbonyls, nitriles, radicals, imine compounds, etc. ) have been extensively studied.…”

Conjugated Azo Compounds as Active Materials for Rechargeable Sodium‐Metal Batteries with High‐Rate Performance

“…[19] Considering that BADA is extremely soluble in dimethyl sulfoxide (DMSO), its structure was determined by 1 H NMR spectroscopy. Conversely, p-PADA is not soluble in conventional organic solvents, and for this reason, selecting solid-state 13 C magicangle spinning Nuclear Magnetic Resonance Spectroscopy (NMR) has been conducted to ascertain its structure. In the 13 C NMR solid-state spectrum of p-PADA.…”

“…[10] In 2018, Wang groups demonstrated for the inaugural time that N=N groups can be treated as electrochemically-active centers for ion storage, commencing the exploration of azo molecules as electrochemical materials. [11] Shortly thereafter, the first application of highly porous azo-linked polymers (ALPs) as electrode materials for SMBs was carried out by Kaderi et al and a good specific capacity of 170 mAh g À 1 could be obtained at 0.3 C. [12] Based on previous work, [13] we herein selected N=N and C=N as the redox cores and synthesized the conjugated linear polymer terephthalaldehyde-4,4'-diazoaniline (p-PADA) as the electrode material for SMBs via the simple Schiff base reaction of terephthalaldehyde (PA) with 4,4'-diazoaniline (Azo). Its electrochemical properties were compared with those of benzaldehyde-4,4'-diazoanilidine (BADA), a small molecule compound with the same repeating unit synthesized via benzaldehyde (BA) with Azo.…”

Covalent Organic Frameworks: Recent Progress in Biomedical Applications

“…Since the discovery of COFs by Yaghi in 2005, much research on the synthesis, properties, and diverse applications of COF materials has been conducted. COFs are crystalline porous polymers , that mainly comprise light elements, typically C, H, O, N and B, that are connected together through covalent bonds, such as imide, azine, imine, boronate ester, hydrazone, and other linkages. − Over the past two decades, a wide range of 2D and 3D COF structures have been realized and applied in many areas, such as gas storage, − photovoltaics, conductivity, − batteries, ,− catalysis, − optoelectronic devices, electrochemical sensing, and optical sensing because of their excellent features. Moreover, emerging COF materials with large surface areas and ultrathin structures allow for surface modification with versatile components, thus further enabling exquisite tailoring for biomedical applications, biosensors, and multifunctional bioelectronics. − Also, the different pore sizes and surface areas of 2D and 3D COF materials could lead to diverse results in biomedical research.…”