Redox Flow Battery Electrolytes

A combination of:

• (1) a first redox active composition comprising a first redox active compound, the first redox active compound being characterized by any of general formulas (1)-(3), or a mixture thereof;
• and
• (2) a second redox active composition comprising a second redox active compound, the second redox active compound being characterized by any of general formulas (1)-(3), or a mixture thereof:
• wherein
• R1—R18 is each independently selected from hydrogen;
• hydroxyl;
• carboxy;
• linear or branched, optionally substituted C1-6 alkyl optionally comprising at least one heteroatom selected from N, O and S;
• a carboxylic acid;
• an ester;
• halogen;
• optionally substituted C1-6 alkoxy;
• optionally substituted amino;
• amide;
• nitro;
• carbonyl;
• phosphoryl;
• phosphonyl;
• cyanide;
• and sulfonyl (—SO3H), and
• wherein at least one of R1—R4 in General Formula (1), at least one of R5—R10 in General Formula (2) and/or at least one of R11—R18 in General Formula (3) is selected from —SO3H;
• optionally substituted C1-6 alkyl optionally comprising at least one heteroatom selected from N, O and S;
• optionally substituted amino;
• and optionally substituted C1-6 alkoxy.