Organic carbonyl electrode materials have shown great prospects for rechargeable batteries in view of their high capacity, flexible designability, and sustainable production. However, organic carbonyl electrode materials still suffer from unsatisfactory electrochemical performance, which is highly relevant to their redox processes. Herein, an in-depth understanding on redox processes and the correlated electrochemical performance of organic carbonyl electrode materials is provided. The redox processes discussed mainly involve molecular structure evolution (intermediates), crystal structure evolution (phase transition), and charge storage mechanisms. The properties of intermediates can affect voltage, cycling stability, reversible capacity, and rate performance of batteries. Moreover, the reversible capacity/cycling stability and rate performance would be also influenced by phase transition and charge storage mechanisms (diffusion- or surface-controlled), respectively. To accelerate the practical applications of organic carbonyl electrode materials, future work should focus on developing more in situ or operando characterization techniques and further understanding the intrinsic relationships between redox processes and performance. It is hoped that the work discussed herein will stimulate more attention to the detailed redox processes and their correlations with the performance of organic carbonyl electrode materials in rechargeable batteries.

Insights into Redox Processes and Correlated Performance of Organic Carbonyl Electrode Materials in Rechargeable Batteries.

The quest for advanced energy storage devices with cheaper, safer, more resource‐abundant storage has triggered intense research into zinc ion batteries (ZIBs). Among them, organic materials as cathode materials for ZIBs have attracted great interest due to their flexible structure designability, high theoretical capacity, environmental friendliness, and sustainability. Although numerous organic electrode materials have been studied and different redox mechanisms have been proposed in the past decade, their electrochemical performance still needs further improvement, and the mechanisms require further exploration. This paper provides a systematical overview of three types of organic materials (bipolar‐type conductive polymer, n‐type conjugated carbonyl compounds, and p‐type material) on the energy storage mechanisms and distinct characteristics. We then focus on discussing the design strategies to improve electrochemical performance. Furthermore, the challenges and future research directions are discussed to provide a foundation for further developing organic‐based ZIBs.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/smm2.1110

Organic materials‐based cathode for zinc ion battery

Rechargeable organic multivalent metal‐ion batteries (MMIBs) have attracted a surge of interest as promising alternatives for large‐scale energy storage applications because they can combine the advantages of both organic electrodes and multivalent metal‐ion batteries. However, the development of organic MMIBs is hampered by many factors, which mean they lag far behind organic alkali‐metal‐ (e.g., Li‐, Na‐, and K‐) ion batteries. Herein, the challenges that are specifically faced by organic MMIBs are analyzed and the strategies that can probably solve such challenges are then discussed. As a special challenge that organic MMIBs are facing, the charge‐storage mechanism is particularly underlined to deeply understand the structure–property relationships for guiding the future design of high‐performance organic electrodes for MMIBs. The perspectives are thereby elaborated in this review with the outlook of practical applications of organic MMIBs.

Challenges and Perspectives of Organic Multivalent Metal‐Ion Batteries

A novel catalyst of titanium boride toward V3+/V2+ redox reaction for vanadium redox flow battery

Boosting the cyclability of tetracyanoquinodimethane (TCNQ) as cathode material in aqueous battery with high valent cation

Crossover-free hydroxy-substituted quinone anolyte and potassium ferrocyanide catholyte for aqueous alkaline organic redox flow battery

Aqueous Zn-ion batteries have tremendous potential to penetrate the energy storage market, as an alternative to Li-ion batteries, given the high volumetric capacity of Zn (5853 mAh cm–3), cost-effe...

Electrode and Conductive Additive Compatibility Yielding Excellent Rate Capability and Long Cycle Life for Sustainable Organic Aqueous Zn-Ion Batteries

Prospective high reduction potential cathode materials have been proposed that can be used in non-aqueous redox flow battery applications. A new class of material, 3,6-dibromo-9-(p-tolyl)-9H-carbazole (3) incorporating a carbazole core, showing a very good reversibility is employed as the cathode material and dissolved oxygen in the solvent mixture is used as the anolyte material. Labile positions of the carbazole have been substituted with electron withdrawing groups, which increases the reduction potential of the redox couple. Apart from substituting the labile positions, we have also explored the possible structural modification responsible for stabilizing the cation radical of the carbazole moiety and obtained the reversible behavior thereafter. From this, it is evident that a free radical is stabilized upon delocalization of the charge in the molecule. The mass-transport and redox parameters, diffusion coefficient and heterogeneous electron transfer rate coefficient values are high enough to realize good battery performance. A solvent mixture of acetonitrile and dichloromethane (4 : 1) has been used in this work in order to increase the solubility of electroactive materials in the medium.

Functionalised carbazole as a cathode for high voltage non-aqueous organic redox flow batteries

Donor-π-linker-acceptor (D-π-A) push–pull dye molecules are most common in dye-sensitized solar cells (DSSCs) applications. Selection of dye molecules for DSSCs is based on their ability to absorb light in the visible spectrum. This can be done more efficiently by positioning the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) with respect to the conduction band of the semiconductor and the redox potential of the electrolyte, respectively. The photocurrent is manipulated by the extent of light absorption, planarity of the π-linker for efficient intramolecular charge transfer (ICT), oxidized dye reorganization energy (Λ) and dye regeneration driving force (ΔGreg). In a quest of achieving panchromatic absorption up to near-IR region, mostly electron-rich chromophores and their oligo form were used in the π-segment, but this approach led to poor ICT. In this computational analysis, we have explored the effect of electron-withdrawing (cyano (–CN)) and donating groups (methoxy (-OMe)) in three different π-segment length to understand the carbazole dyes’ suitability for DSSCs using onset wavelength (λonset), Λ, ICT and ΔGreg as the figure-of-merits.

Chinmaya Mirle

Papers

Crossover-free hydroxy-substituted quinone anolyte and potassium ferrocyanide catholyte for aqueous alkaline organic redox flow battery

Electrode and Conductive Additive Compatibility Yielding Excellent Rate Capability and Long Cycle Life for Sustainable Organic Aqueous Zn-Ion Batteries

Functionalised carbazole as a cathode for high voltage non-aqueous organic redox flow batteries

A computational approach on engineering short spacer for carbazole-based dyes for dye-sensitized solar cells

On Capacity Upgradation and In Situ Capacity Rebalancing in Anthrarufin-Based Alkaline Redox Flow Batteries