A Naphthalene Diimide Covalent Organic Framework: Comparison of Cathode Performance in Lithium-Ion Batteries with Amorphous Cross-linked and Linear Analogues, and Its Use in Aqueous Lithium-Ion Batteries

Abstract

We report a two-dimensional (2D) imine-linked covalent organic framework (COF) containing naphthalene diimide (NDI) redox groups, TAPB-NDI COF. Lithium-ion batteries (LIBs) with TAPB-NDI COF-based electrodes exhibited >95% of their theoretical capacity at a C/20 charge/discharge rate, among the highest faradaic efficiency of a NDI-COF electrode. The pores of TAPB-NDI COF are among the largest reported and presumably facilitate efficient Li + ion transport. An amorphous cross-linked network (TAPB-NDI Amp) and a linear polymer (PD-NDI Lp) with similar chemical structures demonstrated lower capacities than the COF at C/20 current rate. However, PD-NDI Lp exhibited an overall higher gravimetric capacity and superior specific capacity retention at higher discharge rates compared to the TAPB-NDI COF. The COF is stable in neutral aqueous solutions, allowing its use as an electrode in neutral aqueous LIBs, which exhibited better rate performances than those in coin-cell set ups. Importantly, the cathodes did not suffer from a competitive hydrogen evolution reaction in aqueous LIBs. This opens up opportunities for using NDI moieties in neutral aqueous batteries and other energy-storage devices. Aqueous devices have been largely limited to "quinone−hydroquinone"-based redox couples, which are, however, operable only in acidic media.

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

“…By contrast, an amorphous polymer analog with a SA BET of 20 m 2 g −1 only delivered 25% of its theoretical capacity under the same conditions. [ 19 ] Moreover, interlayer π‐π stacking interactions between COFs layers have been shown to improve conductivity. [ 20 ] Recently, several studies have used COFs as the active material in the electrodes of Li‐ion batteries.…”

π-Conjugated redox-active two-dimensional polymers as organic cathode materials

“…The imine C]N stretch ($1620 cm À1 ) and the imide C]O stretch ($1607 cm À1 ) are observed to overlap, which prevents denitive observation of the appearance of the expected polymerization chemistry. 15 Collectively, the FT-IR changes observed following polymerization conrm the imine-condensation product of aniline and PDI-DA. Thermolytic alkyl chain removal was veried by the disappearance of the alkyl vibrational modes (2800-3000 cm À1 ) and concomitant increase of the N-H peak (3200 cm À1 ).…”

“…It is noteworthy that the alkyl chain removal protocol should be applicable to many other RA-2DPs with solubilizing side chains to improve their device performance. 15,25 Because the RA-2DPs without the alkyl chains exhibit much higher capacity, we focused on investigating the device performance of TAPPy-PDI and TAPB-PDI.…”

“…Furthermore, these RA-2DPs frequently incorporate contorted phenyl spacers that diminish in-plane conjugation. 15,25 The PDI-DA unit studied here is bay connected through a fused aromatic ring that simultaneously addresses both limitations of previous molecular designs. To demonstrate the generality of these ndings, we study two RA-2DPs prepared from different polyfunctional amine nodes: 1,3,6,8-tetrakis(4-aminophenyl)pyrene (TAPPy) and 1,3,5-tris(4aminophenyl)benzene (TAPB).…”

“…[6][7][8][9][10][11][12] However, RA-2DPs have not reached their potential because the typical structures exhibit poor electrical conductivity 13,14 and their electro-inactive solubilizing moieties reduce the gravimetric energy storage performance. 15 This realization has led researchers to explore incorporating conducting additives [16][17][18] and exfoliating 2DPs into the few-layer limit 19 with the goal of increasing electrochemical accessibility. While these investigations demonstrate that increased electrochemical accessibility can improve faradaic performance in RA-2DPs, these strategies require laborious post-processing, expensive substrates and valuable additives.…”