We demonstrate an aqueous organic and organometallic redox flow battery utilizing reactants composed of only earth-abundant elements and operating at neutral pH. The positive electrolyte contains bis((3-trimethylammonio)propyl)ferrocene dichloride, and the negative electrolyte contains bis(3-trimethylammonio)propyl viologen tetrachloride; these are separated by an anion-conducting membrane passing chloride ions. Bis(trimethylammoniopropyl) functionalization leads to ∼2 M solubility for both reactants, suppresses higher-order chemical decomposition pathways, and reduces reactant crossover rates through the membrane. Unprecedented cycling stability was achieved with capacity retention of 99.9943%/cycle and 99.90%/day at a 1.3 M reactant concentration, increasing to 99.9989%/cycle and 99.967%/day at 0.75–1.00 M; these represent the highest capacity retention rates reported to date versus time and versus cycle number. We discuss opportunities for future performance improvement, including chemical modification of a ferrocene center and reducing the membrane resistance without unacceptable increases in reactant crossover. This approach may provide the decadal lifetimes that enable organic–organometallic redox flow batteries to be cost-effective for grid-scale electricity storage, thereby enabling massive penetration of intermittent renewable electricity.

中文翻译：

---

具有超高容量保持能力的中性pH水溶液有机-有机金属氧化还原液流电池

我们展示了一种有机和有机金属氧化还原液流电池，该电池利用仅由富含地球的元素组成的反应物，并在中性pH下运行。正电解质含有二氯化双（（3-三甲基铵）丙基）二茂铁，负电解质含有四氯化双（3-三甲基铵）丙基紫精；这些被通过氯离子的阴离子导电膜隔开。双（三甲基氨丙基）官能团导致两种反应物的溶解度均为〜2 M，抑制了高阶化学分解途径，并降低了反应物穿过膜的穿透率。在1.3 M的反应物浓度下，空前的容量保持率为99.9943％/天和99.90％/天，实现了空前的循环稳定性；在0.75-1.00 M的条件下，容量保持率提高到99.9989％/天和99.967％/天。这些代表了迄今为止报告的最高容量保留率与时间和周期数的关系。我们讨论了未来性能改善的机会，包括对二茂铁中心进行化学修饰和降低膜电阻，而不会增加不可接受的反应物交叉。这种方法可以提供十年的使用寿命，从而使有机-有机金属氧化还原液流电池对于电网规模的储能而言具有成本效益，从而使间歇性可再生电力得以大量渗透。