Effect of organophosphorus compound additives for thermal stability on the positive electrolyte of a vanadium redox flow battery

A Review of Electrolyte Additives in Vanadium Redox Flow Batteries

“…Part of the highly reductive organic additives can be oxidized by V(V) ions in the positive half-cell electrolyte. This process will generate CO 2 , which gives rise to higher overpotential and lower efficiency of the VRFB, such as that brought about by phosphonoacetic acid and ethylenediaminetetraacetic acid [ 44 ]. Furthermore, introducing additives in inappropriate dosages also affects the electrochemical properties [ 45 ].…”

“…Thus, researchers optimized the testing method of stability by raising another indicator—“remaining vanadium concentration”—to improve the accuracy of stability characterization. For example, Jin and Ding et al [ 44 , 47 ] studied the precipitation time and change of the V(V) concentration in the stability experiment to verify the accuracy of the experimental results. Overall, precipitation time and the remaining vanadium concentration are two major indicators of stability, currently.…”

“…It has been demonstrated, as shown in Table 2 , Table 3 , Table 4 and Table 5 , that organic additives such as pyridinium propyl sulfobetaine (PPS), ammonium acetate, 1-hydroxyethane-1,1-diphosphonic acid (HEDP), acidic amino acids, and organophosphorus compounds, can effectively lengthen the precipitation time and widen the temperature range of the vanadium electrolyte [ 31 , 44 , 53 , 59 , 79 , 89 , 90 ]. For example, PPS was able to delay the induction time for precipitation by an average of 3–6 h at 50 °C [ 59 ].…”

“…The -COOH groups carried by L-aspartic acid are easily coordinated with V(IV) and V(V) ions [ 31 ]. Furthermore, 3-Aminopropylphosphonic acid (3-APPA) was also found to prolong the precipitation induction time of the electrolyte to 6 days at 45 °C, which is because the -OH, =O, and -NH 2 groups are capable of encapsulating vanadate ions to form stable penta-coordinated hydrates [ 44 ].…”

Methyl Viologen Anolyte Introducing Nitrate as Counter-Anion for an Aqueous Redox Flow Battery

“…7,8 Among various RFB systems, vanadium utilizing aqueous RFB (VRFB) is the most popular system and has been investigated on various approaches to performance. [9][10][11][12][13] Also, VRFB has been commercialized by numerous companies. 1,2 However, the corrosive electrolyte solution (e. g., concentrated sulfuric acid) and the high cost of vanadium limit its widespread application.…”