Dual‐Active‐Center of Polyimide and Triazine Modified Atomic‐Layer Covalent Organic Frameworks for High‐Performance Li Storage

Abstract

Covalent organic frameworks (COFs) have received great attention as electrode materials in the lithium-ion batteries due to their exceptional crystallinity, easily chemical modification, and adjustable porous distribution. However, their practical application remains hindered by the insufficient Li + active sites and long ion diffusion in the bulk materials. To tackle those issues, combining the virtues of high stable skeleton structure of large molecular, atomic-layer thickness feature, and multi-active sites, a novel atomic-layer COF cathode (denoted as E-TP-COF) with a dual-active-center of CO and CN group is developed. The atomic-layer thick structure improves the capturing and diffusion of Li-ion. Both active sites of CN and CO groups generate more capacity. The large molecular structure avoids the dissolubility challenge in electrolytes. As a result, the lithium-ion batteries assembled with E-TP-COF delivers a high initial capacity of 110 mAh g −1 with a high capacity retention of 87.3% after 500 cycles. Furthermore, the Li + diffusion mechanism is also confirmed through in(ex) situ technology and density functional theory calculation in detailing. This new strategy may exploit an important application of COFs in electrochemical energy storage and conversion.

A Pyrene-4,5,9,10-Tetraone-Based Covalent Organic Framework Delivers High Specific Capacity as a Li-Ion Positive Electrode

“…The average discharge potential calculated from the PT-COF and the PT-COFX composites is around 2.55 V, which is higher than most other carbonyl functionalized organic electrodes. 16 , 31 − 35 PT-COF delivered a specific capacity of 193 mAh g –1 at 200 mA g –1 , corresponding to 71% of its theoretical capacity of 271 mAh g –1 (see Supporting Information Section 2 for full details). By contrast, the specific capacities of the PT-COFX composites increased up to a maximum of 280 mAh g –1 in PT-COF50 ( Table 1 ).…”

“…10 One advantage of this modularity for battery applications is that redox-active units can be rationally incorporated to prepare COFs with improved electrochemical energy storage capacities. 11 − 16 The well-defined and tunable permanent porosity in COFs can also enhance ion transport to active sites in their structures. COFs can also have better electrolyte stability than discrete organic molecules, which tend to be more soluble, leading to poor cycling stability.…”

Integrated Covalent Organic Framework/Carbon Nanotube Composite as Li‐Ion Positive Electrode with Ultra‐High Rate Performance

“…[20] Recently, several studies have used COFs as the active material in the electrodes of Li-ion batteries. [17,[21][22][23][24] However, since COFs often exhibit poor intrinsic conductivities, conductive coatings or additives are often added to improve their electron transfer and rate performance in batteries. [15,[25][26][27][28] In this regard, a redox-active polyimide COF (D TP -A NDI -COF) was reported as a positive electrode for Li-ion batteries where only 5% of the redox-active sites were utilized at 12 C. [15] By contrast, a composite of the same polyimide COF and CNT (D TP -A NDI -COF@CNTs) exhibited 71% utilization of redox-active sites under the same conditions.…”

Covalent Organic Framework for Rechargeable Batteries: Mechanisms and Properties of Ionic Conduction

“…[ 3,22,23,44–49,120–130 ] Moreover, the emerging ion‐conducting COFs with excellent ionic conductivity and high cation transfer number can reduce the battery polarization and improve the charging/discharging kinetics of electrodes. [ 131–143 ] The distinctive directional selectivity of ionic conduction in COFs is obviously different from the typical inorganic solid conductors and polymer conductors, so that COFs are suitable for diverse battery applications, including lithium‐ion, [ 144–166 ] lithium–sulfur, [ 167–208 ] sodium‐ion, [ 209–214 ] potassium‐ion, [ 215–219 ] lithium–CO 2 , [ 220–223 ] zinc‐ion, [ 224–230 ] zinc–air batteries, [ 231–234 ] etc. In this section, the traditional classification method of battery types is replaced by the classification according to the components among the dif...…”