Wang Wenkang, Balland Véronique, Branca Mathieu, Limoges Benoît
CNRS, Laboratoire d'Electrochimie Moléculaire, Université Paris Cité, F-75013 Paris, France.
J Am Chem Soc. 2024 Jun 5;146(22):15230-15250. doi: 10.1021/jacs.4c02364. Epub 2024 May 20.
Due to their eco-sustainability and versatility, organic electrodes are promising candidates for large-scale energy storage in rechargeable aqueous batteries. This is notably the case of aqueous hybrid batteries that pair the low voltage of a zinc anode with the high voltage of a quinone-based (or analogue of quinone-based) organic cathode. However, the mechanisms governing their charge-discharge cycles remain poorly understood and are even a matter of debate and controversy. No consensus exists on the charge carrier in mild aqueous electrolytes, especially when working in an electrolyte containing a multivalent metal cation such as Zn. In this study, we comprehensively investigate the electrochemical reactivity of two model quinones, chloranil, and duroquinone, either diluted in solution or incorporated into carbon-based composite electrodes. We demonstrate that a common nine-member square scheme proton-coupled electron transfer mechanism allows us to fully describe and rationalize their electrochemical behavior in relation to the pH and chemical composition of the aqueous electrolyte. Additionally, we highlight the crucial role played by the ps associated with the reduced states of quinones in determining the nature of the charge carrier that compensates for the negative charges reversibly injected in the active material. Finally, contrary to the widely reported findings for Zn/organic batteries, we unequivocally establish that the predominant solid-state charge carriers in Zn-based mild aqueous electrolytes are not multivalent Zn cations but rather protons supplied by the weakly acidic hexaaqua metal ions (i.e., [Zn(HO)]]).
由于其生态可持续性和多功能性，有机电极是可充电水系电池大规模储能的有前景的候选材料。水系混合电池尤其如此，它将锌负极的低电压与醌基（或醌基类似物）有机正极的高电压配对。然而，控制其充放电循环的机制仍知之甚少，甚至存在争议。对于温和水系电解质中的电荷载体尚无共识，特别是在含有多价金属阳离子（如锌）的电解质中工作时。在本研究中，我们全面研究了两种模型醌，四氯对苯醌和杜醌，它们要么稀释在溶液中，要么掺入碳基复合电极中。我们证明，一个常见的九元方形质子耦合电子转移机制使我们能够全面描述并合理化它们在与水系电解质的pH值和化学成分相关的电化学行为。此外，我们强调了与醌的还原态相关的皮秒在确定补偿可逆注入活性材料中的负电荷的电荷载体性质方面所起的关键作用。最后，与锌/有机电池广泛报道的结果相反，我们明确确定，锌基温和水系电解质中主要的固态电荷载体不是多价锌阳离子，而是由弱酸性六水合金属离子（即[Zn(HO)]）提供的质子。
