Isometric Thionated Naphthalene Diimides As Organic Cathodes for High Capacity Lithium Batteries

Abstract

Although naphthalene diimide (NDI) and its derivatives have been widely used for organic Li-ion batteries (OLIBs), they are limited by a low lithium uptake capacity and ambiguous lithiation mechanism. Herein, we report two isometric thionated-NDI cathodes (cis-2S and trans-2S) obtained by replacing O with S in the imide groups which improves the battery performance compared with parent NDI (P-NDI). Remarkably, the position of S atoms plays an important role as the potential plateau of cis-2S was 100 mV higher than trans-2S, 256 mV higher than P-NDI, and the capacity of cis-2S was twice than that of trans-2S, four times as P-NDI after 400 cycles. The in situ Raman, X-ray photoelectron spectroscopy (XPS), and DFT calculations revealed that the lithiation process occurs on the less electronegative S atoms. For cis-2S, the electron density on the lithiation sites is lower than trans-2S because of a stronger electron inductive effect. This in turn enhances the redox potential and cycling stability of cis-2S. This contribution provides an additional molecular engineering strategy to develop novel organic cathode materials for high performance OLIBs.

Ionic Charge Storage in Diketopyrrolopyrrole-Based Redox-Active Conjugated Polymers

“…Figure S1 shows the optimized geometry for this unit. We used molecular electrostatic potential (MESP) mapping, a widely employed tool for identifying ionic binding sites in organic charge storage materials. ,− Figure b shows the MESP map of a single T-DPP-T unit. Two MESP minima were found, one each in the vicinity of the two carbonyl-oxygen atoms on the DPP units, suggesting that these are the most favorable sites for cationic binding .…”

“…Discounting the side chains, which are needed only for enhanced solubility and associated film processability, the theoretical capacity of the polymer backbone alone amounts to ∼90 mAh/g for a single electron transfer reaction. This along with chemical approaches , to stabilize the second redox of the DPP unit could lead to capacities on the order of ∼180 mAh/g which is on par with some of the best intercalation electrode materials . Thus, careful molecular engineering to enhance electrochemical stability coupled with pruning the bulky side chains can lead to redox-active DPP-based polymers that offer necessary cycling stability at high energy densities required for advanced energy storage applications.…”

Strategic Design for Sumanene‐Derived Organic Cathodes with Tailored Redox Activity

“…[6] Zhang et al explored the impact of the partial thionation of carbonyl groups in naphthalene diimide on its electrochemical properties and highlighted the promise of the cis-type thionation outperforming the trans-type thionation. [7] Despite all these significant efforts, the basic principle of "the decrease in the molecular size increasing the redox activity (e.g., benzoquinone vs anthraquinone) and the probability of dissolution into electrolytes" is still applicable to organic cathode systems. Therefore, the problem of dissolution, particularly for small organic molecules, is yet to be fully resolved.…”

“…However, the dissolution of organic compounds is a crucial drawback that retards their practical applications, and hence, considerable studies have been conducted on the topic. [4][5][6][7][8] For instance, Lu et al reported cyclohexanehexone (C 6 O 6 ), which could store six Li atoms and exhibit an ultrahigh charge capacity of 902 mAh g −1 with an average voltage of 1.7 V versus Li/Li + at 20 mA g −1 . [4] They highlighted that the introduction of an ionic liquid with highly polar electrolytes could limit the dissolution of organic compounds, resulting in a high capacity retention of 82% even after 100 cycles.…”

Thienoviologen anolytes for aqueous organic redox flow batteries with simultaneously enhanced capacity utilization and capacity retention

“…11,12 The traditional lithium-ion battery has undergone limited large-scale development due to safety. [13][14][15] Based on the characteristics of high safety and long life, the ow battery stands out among many energy storage technologies, 16,17 which were considered very suitable for solar and wind power storage and transportation. [18][19][20] Among them, aqueous organic redox ow batteries (AORFBs) have become one of the best candidates for large-scale energy storage technology due to their abundant structures, cheap raw materials and high security.…”