Reversible multi-electron redox chemistry of π-conjugated N-containing heteroaromatic molecule-based organic cathodes

Peng, Chengxin; Ning, Guo‐Hong; Su, Jie; Zhong, Guiming; Tang, Wei; Tian, Bingbing; Su, Chenliang; Yu, Dingyi; Zu, Lianhai; Yang, Jinhu; Ng, Man‐Fai; Hu, Yong‐Sheng; Yang, Yong; Armand, Michel; Loh, Kian Ping

doi:10.1038/nenergy.2017.74

Cited by 511 publications

(440 citation statements)

References 56 publications

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“…Except for mixing high amount of conductive additives, the polymerization strategies are usually applied but cause the undesired decrease in the molecular stacking density and electroactive components (Figure 1a). [ 15–17 ] However, the active mass ratio of organic cathodes in the electrode is hard to exceed 60% (Figure 1b), [ 4,18–21 ] much lower than the inorganic materials (more than 90%). This seriously sacrifices the advantages of organic cathodes in energy density, resulting in an energy density much less than those of inorganic batteries.…”

Section: Figurementioning

confidence: 99%

In Situ Coating Graphdiyne for High‐Energy‐Density and Stable Organic Cathodes

Zuo

Wang

et al. 2020

Advanced Materials

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The preparation of organic small‐molecule cathodes is simple and low‐cost; however, their low conductivity and molecular dissolution are two key issues that mean their energy density and power performance are far lower than those of inorganic batteries, thus hindering their practical application. To develop an effective coating technology is the key to obtain high‐performance organic batteries. A general method of in situ weaving all‐carbon graphdiyne nanocoatings is demonstrated. The graphdiyne can be conformally weaved on organic particles under mild conditions so that the conductivity is increased and the dissolution is suppressed. After weaving graphdiyne nanocoat, the active mass of the small‐molecule organic cathodes rise to 93%, thus delivering a higher energy density of 310 W h kg−1 than previously reported, and the power performance and long‐term stability are greatly improved. Additionally, this method shows great potential to become the crucial technology for fabricating organic batteries with energy density close to prevailing lithium‐ion batteries.

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Section: Figurementioning

confidence: 99%

In Situ Coating Graphdiyne for High‐Energy‐Density and Stable Organic Cathodes

Zuo

Wang

et al. 2020

Advanced Materials

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“…27 Furthermore, multiple redox centres are available in the conjugated structure which will aid in further enhancing the capacitance. 28 Therefore, engineering an extensively conjugated macromolecule as a redox-active additive should address the problems brought forward by the small redoxadditive molecules. Irrefutably, engineering a redox-active conjugated macromolecule electrolyte is important towards achieving high energy and power density, however compatible electrode-electrolyte interaction (e.g.…”

Section: Introductionmentioning

confidence: 99%

Indole-based conjugated macromolecules as a redox-mediated electrolyte for an ultrahigh power supercapacitor

Xiong

Lee

Chen

et al. 2017

Energy Environ. Sci.

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aBalancing energy density and power density has been a critical challenge since the inception of supercapacitors. Introducing redox-active additives in the supporting electrolyte has been shown to increase the energy density, however the power density and cycling stability are severely hampered in the process. Herein, an extensively conjugated indole-based macromolecule consisting of 5,6-dihydroxyindole/5,6-quinoneindole motifs, prepared by electrochemical polymerization of dopamine under acidic conditions, was employed as a redox-active additive. By utilizing the conjugation effect, the HOMO-LUMO gap (HLG) of the extensively conjugated indole-based macromolecule was reduced to ca. 2.08 eV, which enhanced the electronic transfer kinetics, in turn improving the power density and reversibility of redox reactions. When coupled with a porous honeycomb-like carbon (PHC) electrode, the assembled supercapacitor delivered an excellent rate performance with a high specific capacitance of 205 F g À1 at 1000 A g À1 . This work reports one of the highest power densities recorded at 153 kW kg À1 for redox-mediated electrolyte systems with a respectable energy density of 8.8 W h kg À1.In addition to an excellent cycling stability of 97.1% capacitance retention after 20 000 charge/discharge cycles, the conjugation degree has to be considered when engineering the redox-active electrolyte so as to improve the power density and stability. Broader contextPortable and reliable energy storage devices (ESDs) have become gradually integrated into technological advancements. Supercapacitors have gained significant recognition as important ESDs due to their high power density arising from fast physical ion adsorption based on the electric double layer (EDL) principle. However, the fast EDL principle is dependent on the electrode surface area which ironically is responsible for poor energy density. Thus, such a limitation has resulted in a research interest shift towards pseudocapacitive capacitors as additional pseudocapacitance can be achieved from the Faradaic reaction. One strategy to incorporate pseudocapacitance is via the addition of small redox species into the supporting electrolyte (resulting in 5-7 times energy density enhancement). However, the use of small redox species typically leads to a poor power density and poor cycling stability which renders such energy density enhancement insignificant. In this work, a supercapacitor based on a novel indole-based conjugated macromolecule redox-mediated electrolyte is reported to achieve one of the highest power densities in redox mediated electrolyte supercapacitor research, while excellent cycling stability was simultaneously attained in this system.

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“…[31,32] Thes ulfur atom, which is found in the same group (group VIA) as the oxygen atom, has al arger atomic radius and higher electron density (atomic radius:1 00 pm, [Ne]3s 2 3p 4 for S) relative to the oxygen atom (atomic radius:6 0pm, [He]2s 2 2p 4 for O). [31,32] Thes ulfur atom, which is found in the same group (group VIA) as the oxygen atom, has al arger atomic radius and higher electron density (atomic radius:1 00 pm, [Ne]3s 2 3p 4 for S) relative to the oxygen atom (atomic radius:6 0pm, [He]2s 2 2p 4 for O).…”

mentioning

confidence: 99%

Organic Thiocarboxylate Electrodes for a Room‐Temperature Sodium‐Ion Battery Delivering an Ultrahigh Capacity

et al. 2017

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Organic room-temperature sodium-ion battery electrodes with carboxylate and carbonyl groups have been widely studied. Herein, for the first time,wereport afamily of sodiumion battery electrodes obtained by replacing stepwise the oxygen atoms with sulfur atoms in the carboxylate groups of sodium terephthalate whichi mproves electron delocalization, electrical conductivity and sodium uptake capacity.T he versatile strategy based on molecular engineering greatly enhances the specific capacity of organic electrodes with the same carbon scaffold. By introducing two sulfur atoms to as ingle carboxylates caffold, the molecular solid reaches ar eversible capacity of 466 mAh g À1 at ac urrent density of 50 mA g À1 .When four sulfur atoms are introduced, the capacity increases to 567 mAh g À1 at ac urrent density of 50 mA g À1 , which is the highest capacity value reported for organic sodium-ion battery anodes until now.Organic battery electrodes are alternatives to traditional metal-oxide electrode materials due to their low costs, absence of heavy metals and easily tunable structures. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Generally,o rganic electrodes accommodate redox centers and alkali-metal ions by functional groups such as carboxylate, [16] carbonyl, [17] organodisulfide, [18] thioether [19] and nitroxyl radicals, [20] while the aromatic cores donate or accept electrons during the redox process. [19] Carboxylate groups are usually applied as lithium/sodium anodes which reversibly store/release Li + /Na + ions through at wo-electron process. [21,22] In the case of alithium-ion anode,far more than two Li + ions can be stored in the carboxylate molecule under deep discharge, [23,24] which leads to the high capacity of organic lithium anodes.H owever,f or sodium-ion battery cells,there is no evidence of super-sodiation. Thesodium ion is larger and less electronegative than the lithium ion.Even though the organic sodium-ion battery has al ower specific capacity than the lithium-ion battery,the sodium-ion battery is attractive because of the less rigid lattice compared with metal-oxide lattices,w hich can accommodate the large sodium ions so that the rate capability and cycle stability are advantageous. [21] As ac lassic organic sodium-ion battery anode,the sodium salt of terephthalate (PTA-Na, compound a in Figure 1) has ac apacity of 295 mAh g À1 at ac urrent density of 0.

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Reversible multi-electron redox chemistry of π-conjugated N-containing heteroaromatic molecule-based organic cathodes

Cited by 511 publications

References 56 publications

In Situ Coating Graphdiyne for High‐Energy‐Density and Stable Organic Cathodes

In Situ Coating Graphdiyne for High‐Energy‐Density and Stable Organic Cathodes

Indole-based conjugated macromolecules as a redox-mediated electrolyte for an ultrahigh power supercapacitor

Organic Thiocarboxylate Electrodes for a Room‐Temperature Sodium‐Ion Battery Delivering an Ultrahigh Capacity

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