Electrolyte additives for batteries

An iron battery, comprising:

• an aqueous electrolyte that comprises an additive present at 10 parts per million (ppm) to less than 50% weight percent (w/w) of the aqueous electrolyte,
• wherein the additive is according to Formula XI:
• wherein Ar1 and Ar2 are independently selected from phenyl or naphthyl, and independently optionally substituted with at least one substituent selected from a halogen, C1-6alkoxy, C1-6alkyl, NO, NO2, N2+, N(R20)2, OR45, CO2R45, SO2R55, or SO3R30, or combinations thereof;
• wherein R20 is independently H, C1-6alkyl, C(O)R60, wherein R60 is H, C1-6alkyl, or C1-6alkoxy;
• wherein R45 is absent, H, C1-6alkyl, or combinations thereof;
• wherein R55 is H, O−, OH, C1-6alkyl, C1-6alkoxy, C5-8aryl, C5-8heteroaryl, or combinations thereof;
• wherein R30 is absent or H;
• wherein the iron battery is an iron-air, iron-chloride, iron-chromium, iron-zinc, or iron-sodium.