Redox Flow Battery Electrolytes

Abstract

The present invention relates to novel combinations of redox active compounds for use as redox flow battery electrolytes. The invention further provides kits comprising these combinations, redox flow batteries, and method using the combinations, kits and redox flow batteries of the invention.

1 . 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 mixtures thereof:   
       
         
           
           
               
               
           
         
         
           wherein 
           R 1 -R 18  is each independently selected from hydrogen; hydroxyl; carboxy; linear or branched, optionally substituted C 1-6  alkyl optionally comprising at least one heteroatom selected from N, O and S; a carboxylic acid; an ester; halogen; optionally substituted C 1-6  alkoxy; optionally substituted amino; amide; nitro; carbonyl; phosphoryl; phosphonyl; cyanide; and sulfonyl (—SO 3 H), 
           wherein at least one of R 1 -R 4  in General Formula (1), at least one of R 5 -R 10  in General Formula (2) and/or at least one of R 11 -R 18  in General Formula (3) is selected from —SO 3 H; optionally substituted C 1-6  alkyl optionally comprising at least one heteroatom selected from N, O and S; optionally substituted amino; and optionally substituted C 1-6  alkoxy. 
         
       
     
     
         2 . The combination according to  claim 1 , wherein the first and second redox active compound are characterized by different General Formulas (1)-(3). 
     
     
         3 . The combination according to  claim 1 , wherein the first and second redox active compound are water-soluble. 
     
     
         4 . (canceled) 
     
     
         5 . The combination according to  claim 1 , wherein the first and second redox active composition are provided in separate compartments, and wherein the first and second redox active composition are each provided in a half-cell of a redox flow battery. 
     
     
         6 . (canceled) 
     
     
         7 . The combination according to  claim 1 , wherein the first redox active composition comprises at least one first redox active compound as characterized by any of General Formulas (1), (2) or (3), or a mixture thereof;
 optionally including at least one reduction and/or oxidation product thereof as characterized by General Formula (1)(a) or (b), (2)(a) or (b), or (3)(a) or (b); or a mixture thereof.   
     
     
         8 . The combination according to  claim 1 , wherein the second redox active composition comprises at least one second redox active compound characterized any of General Formulas (1), (2) or (3), or a mixture thereof;
 optionally including at least one reduction and/or oxidation product thereof as characterized by General Formula (1)(a) or (b), (2)(a) or (b), or (3)(a) or (b); or a mixture thereof.   
     
     
         9 . The combination according to  claim 1 , wherein the first redox active composition comprises
 as a first redox active compound at least one benzohydroquinone characterized by General Formula (1), optionally including at least one reduction and/or oxidation product thereof as characterized by General Formula (1)(a) or (b); or a mixture thereof.   
     
     
         10 . The combination according to  claim 1 , wherein the second redox active composition comprises
 as second redox active compound at least one anthraquinone characterized by General formula (3), optionally including at least one reduction and/or oxidation product thereof as characterized by General formula (3) (a) or (b); or   as a second redox active compound at least one benzohydroquinone characterized by General Formula (1), optionally including at least one reduction and/or oxidation product thereof as characterized by General Formula (1)(a) or (b); or a mixture thereof; or   as a second redox active compound at least one naphthoquinone characterized by General formula (2), optionally including at least one reduction and/or oxidation product thereof as characterized by General formula (2)(a) or (b); or   a mixture thereof.   
     
     
         11 . The combination according to  claim 1 , wherein in General Formula (1):
 R 1  is selected from —H, —SO 3 H, optionally substituted C 1-6  alkyl and optionally substituted amine;   R 2  is selected from —H, —OH, —SO 3 H, C 1-6  alkoxy, and optionally substituted amine;   R 3  is selected from —H, —OH and C 1-6  alkoxy; and   R 4  is selected from —H, —SO 3 H, optionally substituted C 1-6  alkyl, optionally substituted amine and halogen.   
     
     
         12 . The combination according to  claim 11 , wherein R 1  and/or R 4  are independently selected from substituted C 1-6  alkyl selected from R 5 —SO 3 H and R 5 —CO 2 H, wherein R 5  is a C 1-6  alkyl optionally comprising at least one heteroatom selected from N, O and S. 
     
     
         13 . The combination according to  claim 11 , wherein R 1 , R 2  and/or R 4  are independently selected from —NH 2 /NH 3   + , —NHR/NH 2 R + , —NR 2 /NHR 2   +  and —NR 3   + , where R is H or optionally substituted C 1-6  alkyl, optionally comprising at least one heteroatom selected from N, O and S. 
     
     
         14 . (canceled) 
     
     
         15 . The combination according to  claim 1 , wherein in General Formula (2):
 R 5  and R 6  are independently selected from —H, —OH and C 1-6  alkoxy; and   R 7 -R 10  are independently selected from —H and —SO 3 H.   
     
     
         16 . The combination according to  claim 1 , wherein in General Formula (3):
 R 11 , R 12  and R 14  are independently selected from —H, —OH and C 1-6  alkoxy; and   R 13  and R 15 -R 18  are independently selected from —H and —SO 3 H.   
     
     
         17 . The combination according to  claim 1 , wherein in General Formula (3):
 R 11  is —SO 3 H;   R 12  is —SO 3 H, R 11 , R 13  and R 14  are —OH;   R 16  is —SO 3 H, R 11  and R 14  or R 11 , R 12  and R 14  are —OH;   R 12  and R 16  are —SO 3 H, R 11  and R 14  or R 11 , R 13  and R 14  are —OH;   R 13  and R 16  are —SO 3 H, R 11 , R 12  and R 14  are —OH;   R 12  and R 17  are —SO 3 H; or   R 11  and R 14  are —SO 3 H;   wherein each of the others of R 11 -R 18  is/are C 1-6  alkoxy or —H.   
     
     
         18 . (canceled) 
     
     
         19 . (canceled) 
     
     
         20 . The combination according to  claim 1 , wherein the first redox active composition and/or the second redox active composition is a liquid. 
     
     
         21 . The combination according to  claim 1 , wherein the first and/or the second redox active composition further comprises a solvent, optionally selected from water, an ionic liquid, methanol, ethanol, propanol, isopropanol, acetonitrile, acetone, dimethylsulfoxide, glycol, a carbonate; a polyether; tetrahydrofuran; dioxolane; sulfolane; dimethylformamide; diethylformamide; CO 2 , supercritical CO 2 ; and a mixture thereof. 
     
     
         22 . (canceled) 
     
     
         23 . (canceled) 
     
     
         24 . The combination according to  claim 1 , wherein the first and/or the second redox active composition has a pH between <0 and about 14, between about 0 and about 14, between about 7 and about 14, or between about 12 and about 14. 
     
     
         25 . The combination according to a  claim 1 , wherein the first and/or the second redox active compound are present in a concentration of between about 0.3 M and about 12 M, between about 0.5 M and about 2 M, between about 2 M and about 4 M, between about 4 M and about 6 M, or between about 6 M and about 10 M. 
     
     
         26 . The combination according to  claim 1 , wherein the first redox active compound has a standard reduction potential that is at least 0.3 volts higher than the standard reduction potential of the second redox active compound. 
     
     
         27 . The combination according to claim  claim 1 , wherein the first redox active compound has a standard reduction potential of at least about 0.0 volts or more against a standard hydrogen electrode; and/or wherein the second redox active compound has a standard electrode potential of about +0.3 V or less, about −0.5 V or less, about −0.6V or less, about −1.0V or less or about −1.2 V or less against a standard hydrogen electrode. 
     
     
         28 . (canceled) 
     
     
         29 . (canceled) 
     
     
         30 . A redox flow battery comprising:
 a positive electrode;   a first redox active composition according to  claim 1  as a positive electrode electrolyte, the positive electrode electrolyte contacting the positive electrode;   a negative electrode;   a second redox active composition according to  claim 1  as a negative electrode electrolyte, the negative electrode electrolyte contacting the negative electrode; and   a separator interposed between the positive electrode and the negative electrode.   
     
     
         31 . The redox flow battery according to  claim 30 , further comprising:
 a positive electrode reservoir comprising the positive electrode immersed within the positive electrode electrolyte, said positive electrode reservoir forming the first redox flow battery half-cell; and   a negative electrode reservoir comprising the negative electrode immersed within the negative electrode electrolyte, said negative electrode reservoir forming the second redox flow battery half-cell.   
     
     
         32 . The redox flow battery according to  claim 31 , wherein said redox flow battery is charged by applying a potential difference across the first and second electrode, such that the first redox active compound is oxidized and the second redox active compound is reduced. 
     
     
         33 . The redox flow battery according to  claim 32 , wherein the redox flow battery is discharged by applying a potential difference across the first and second electrode such that the first redox active compound is reduced, and the second redox active compound comprised by said composition is oxidized. 
     
     
         34 . The redox flow battery according to  claim 30 , wherein the separator comprises or essentially consists of a cation exchange membrane, optionally selected from a polymer membrane. 
     
     
         35 . The redox flow battery according to  claim 30 , wherein the positive and negative electrode comprise or essentially consist of a metal, a carbon material or an electro-conductive polymer. 
     
     
         36 . The redox flow battery according to  claim 30 , further comprising:
 a first circulation loop comprising a storage tank containing the positive electrode electrolyte, piping for transporting the positive electrode electrolyte, a chamber in which the first electrode is in contact with the positive electrode electrolyte, and a pump to circulate the positive electrode electrolyte through the circulation loop;   optionally a second circulation loop comprising a storage tank containing the negative electrode electrolyte, piping for transporting the negative electrode electrolyte, a chamber in which the second electrode is in contact with the negative electrode electrolyte, and a pump to circulate the negative electrode electrolyte through the circulation loop; and   optionally control hardware and software.   
     
     
         37 . A redox flow battery cell stack comprising at least two redox flow batteries according to  claim 30 . 
     
     
         38 . (canceled) 
     
     
         39 . An energy storage system comprising a redox flow battery or redox flow battery cell stack according to  claim 30 ; connected to an electrical grid. 
     
     
         40 . A method of storing electrical energy, comprising applying a potential difference across the first and second electrode of a redox flow battery according to  claim 30 , wherein the first redox active compound is oxidized. 
     
     
         41 . The method according to  claim 40 , wherein the second redox active compound comprised by the second redox active composition is reduced. 
     
     
         42 . A method of providing electrical energy, comprising applying a potential difference across the first and second electrode of a redox flow battery according to  claim 30 , wherein the first redox active compound is reduced. 
     
     
         43 . The method according to  claim 42 , wherein the second redox active compound is oxidized.