Aqueous organic redox flow batteries (RFBs) are promising for grid-scale energy storage. However, identifying stable and inexpensive organic redox couples suitable for practical applications has been challenging. Herein, we report a robust anolyte species, dextrosil-viologen (Dex-Vi), that demonstrates record overall RFB performance for anolyte redox species in neutral aqueous media, including ultralow anion-exchange membrane permeability, high volumetric capacity capability, and outstanding chemical stability. Remarkably, at a high concentration of 1.5 M (40.2 Ah·L–1 theoretical anolyte volumetric capacity), Dex-Vi shows extremely stable cycling performance without observable capacity decay over one month of cycling. We present a high-yield hydrothermal synthetic approach for this viologen chloride salt with a low-cost precursor. These results not only establish a new benchmark organic anolyte species that is promising for practical RFB applications but also show that the properties of organic redox species can be enhanced with minute performance trade-offs through rationalized structural and synthetic design.

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Aqueous organic redox flow batteries (RFBs) are promising for grid-scale energy storage, but identifying stable and inexpensive organic redox couples suitable for practical applications has been challenging. Here we report a new, inexpensive, and robust anolyte, Dextrosil-Viologen (Dex-Vi), that demonstrates a record overall RFB performance for anolyte redox species in neutral aqueous media, including ultralow anion-exchange membrane permeability, high volumetric capacity capability, and outstanding chemical stability. Remarkably, at a high concentration of 1.5 M (40.2 Ah·L-1 theoretical anolyte volumetric capacity), Dex-Vi shows extremely stable cycling performance without observable capacity decay over one-month cycling. Furthermore, by rationalizing a high-yield hydrothermal synthetic approach that has never been applied to viologen RFB molecules along with a low-cost precursor, the predicted mass production cost of Dex-Vi is below $10/kAh. These results not only establish a new benchmark organic anolyte promising for practical RFB applications but also shows that the properties of organic redox species can be enhanced with minute performance tradeoffs through rationalized structural and synthetic design.

In metallic systems, increasing the density of interfaces has been shown to be a promising strategy for annealing defects introduced during irradiation. The role of interfaces during irradiation of ceramics is more unclear because of the complex defect energy landscape that exists in these materials. Here, we report the effects of interfaces on radiation-induced phase transformation and chemical composition changes in SiC-Ti3SiC2-TiCx multilayer materials based on combined transmission electron microscopy (TEM) analysis and first-principles calculations. We found that the undesirable phase transformation of Ti3SiC2 is substantially enhanced near the SiC/Ti3SiC2 interface, and it is suppressed near the Ti3SiC2/TiC interface. The results have been explained by ab initio calculations of trends in defect segregation to the above interfaces. Our finding suggests that the phase stability of Ti3SiC2 under irradiation can be improved by adding TiCx, and it demonstrates that, in ceramics, interfaces are not necessarily beneficial to radiation resistance.