Aqueous Zn−organic batteries: Electrochemistry and design strategies

Abstract

Organic electroactive materials are increasingly recognized as promising cathode materials for aqueous zinc–ion batteries (AZIBs), owing to their structural diversity and renewable nature. Despite this, the electrochemistry of these organic cathodes in AZIBs is still less than optimal, particularly in aspects such as output voltage, cyclability, and rate performance. In this review, we provide an overview of the evolutionary history of organic cathodes in AZIBs and elucidate their charge‐storage mechanisms. We then delve into the strategies to overcome the prevailing challenges faced by aqueous Zn−organic batteries, including low achievable capacity and output voltage, poor cycling stability, and rate performance. Design strategies to enhance cell performance include tailoring molecular structure, engineering electrode microstructure, and modulation of electrolyte composition. Finally, we highlight that future research directions should cover performance evaluation under practical conditions and the recycling and reuse of organic electrode materials.

Hydrophilic and nanocrystalline carbon quantum dots enable highly reversible zinc-ion batteries

“…36 They have abundant amino and hydroxyl groups, good water solubility and stability, and can be used as additives for aqueous electrolytes of AZIBs. 37 The aqueous solution containing CQDs is a clear and transparent pale-yellow solution under sunlight and fluoresces a striking blue when exposed to ultraviolet light (Fig. 1c).…”

High-energy and durable aqueous Zn batteries enabled by multi-electron transfer reactions

“…The C=O (carbonyl) group is generally preferred over the C=N (imine) group due to its higher reduction potential, better stability, and stronger interaction with zinc ions, enhancing its electrochemical performance. However, some C=N and C≡N compounds have shown excellent electrochemical performance, depending on their specific molecular structures, electrolyte composition, and battery operating conditions [139,141,146,149,[151][152][153] . To tackle the concerns mentioned above, it is imperative to modify the organic cathode structure to enable multi-electron transfer reactions for the enhanced battery performance.…”

“…Addressing the high solubility and weak molecular bonding of organic cathodes requires increased active sites with high stability [21,[152][153][154]162,163] . Peng et al described the benzo[a]benzo [7,8]quinoxalino [2,3i]phenazine-8,17-dione (BBQPH) cathode with reversible multi-electron transferred by the Zn 2+ /H + coinsertion mechanism, exhibiting a superior capacity reservation of 380 mAh g -1 after 1,000 cycles at 5 A g -1 and an excellent energy density of 355 Wh Kg -1[39] .…”

Employing a chelating agent as electrolyte additive with synergistic effects yields highly reversible zinc metal anodes

“…), 8 abundant reserve, 9 easy processing and low cost, 10 aqueous zinc ion batteries (AZIBs) have become one of the most promising candidates for large-scale energy storage. 11,12…”