While aqueous organic redox flow batteries (RFBs) represent potential solutions to large-scale grid storage, their electrolytes suffer from short lifetimes due to rapid degradation. We show how an understanding of these degradation processes can be used to dramatically improve performance, as illustrated here via a detailed study of the redox-active biomolecule, flavin mononucleotide (FMN), a molecule readily derived from vitamin B2. Via in-situ nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) we identify FMN hydrolysis products and show that these give rise to the additional plateau seen during charging of an FMN-cyanoferrate battery. The redox reactions of the hydrolysis product are not reversible, but we demonstrate that capacity is still retained even after substantial hydrolysis, albeit with reduced voltaic efficiency, FMN acting as a redox mediator. Critically, we demonstrate that degradation is mitigated and battery efficiency is substantially improved by lowering the pH to 11. Furthermore, the addition of cheap electrolyte salts to tune the pH results in a dramatic increase in solubility (above 1 M), this systematic improvement of the flavin-based system bringing RFBs one step closer to commercial viability.

虽然水性有机氧化还原液流电池（RFB）代表了大规模电网存储的潜在解决方案，但其电解质由于快速降解而寿命较短。我们展示了如何利用对这些降解过程的理解来显着提高性能，正如本文通过对氧化还原活性生物分子黄素单核苷酸 (FMN)（一种容易衍生自维生素 B2 的分子）的详细研究所说明的那样。通过原位核磁共振 (NMR) 和电子顺磁共振 (EPR)，我们识别了 FMN 水解产物，并表明这些产物会在 FMN-氰基铁酸盐电池充电过程中产生额外的平台。水解产物的氧化还原反应是不可逆的，但我们证明，即使在大量水解后，容量仍然保留，尽管伏打效率降低，FMN 充当氧化还原介体。重要的是，我们证明，通过将 pH 值降低至 11，可以减轻降解并显着提高电池效率。此外，添加廉价的电解质盐来调节 pH 值会导致溶解度显着增加（超过 1 M），这种系统性的改进基于黄素的系统使 RFB 更接近商业可行性。