Cost, Performance, and Sustainability of Redox Flow Batteries Using 4,5-Dihydroxy-1,3-benzenedisulfonic Acid and Vanadium Enhanced by Cross Compensation of the Activation Process

Vanadium redox flow batteries (VRFBs) receive attentionas a promisingenergy storage device due to high efficiency and excellent long-termdurability although vanadium ore is expensive. To address this priceissue, cheap quinone RFBs (QRFBs) using anthraquinone-2,7-disulfonicacid and 4,5-dihydroxy-1,3-benzenedisulfonic acid (tiron) are introduced.However, QRFBs require additional activation process of tiron. Toalleviate the issues of VRFBs and QRFBs, new RFBs using vanadium andtiron as the anolyte and catholyte are suggested. This redox couplecan exchange their activation process mutually. Thus, additional electrolytesare not needed, saving the considerable amount of active materials.Regarding performance, cell voltage of the new RFBs (1.2 V) is higherthan that of QRFBs (0.76 V), while their capacity retention (decayrate of 0.044% cycle(-1)) is better than that of VRFBs(decay rate of 0.12% cycle(-1)). Bismuth-based catalystsfurther increase the energy density of new RFBs because they promotethe reactivity of V2+/V3+ redox reaction. Evenin economic prospect, cost-normalized discharge energy density ofnew RFBs (0.98 Wh L-1 $(-1)) isbetter than that of VRFBs (0.75 Wh L-1 $(-1)) and QRFBs (0.15 Wh L-1 $(-1)),confirming that RFBs using vanadium and tiron have benefits regardingcost, stability, and performance. Herein,we introduce 4,5-dihydroxy-1,3-benzenedisulfonicacid and vanadium as active materials for aqueous redox flow batteriesadopting a complementary activation process.