Redox Flow Cell for Storing Electrical Energy and Use Thereof

Abstract

Disclosed is a cost-effective and long-living redox flow cell using less corrosive redox-active components.The redox flow cell comprises a reaction cell having two electrode chambers for catholyte and anolyte, which are each connected to at least one store for liquid and are separated by an ion-conducting membrane, and which are equipped with electrodes, wherein the electrode chambers are each filled with electrolyte solutions comprising redox-active components dissolved or dispersed in an electrolyte solvent, as well as optionally conducting salts dissolved therein and optionally further additives. The redox flow cell is characterized by the anolyte comprising a redox-active component having one to six residues of formula I in the molecule or having one to six residues of formula II in the molecule and by the catholyte comprising a redox-active component having one to six residues of formula III in the molecule or having iron salts or by the anolyte and the catholyte having a redox-active component comprising one to six residues of formula I or of formula II in combination with one to six residues of formula III in the moleculewhereinR1 is a covalent C—C-bond or a divalent bridge group,R2 and R3 independently of one another represent alkyl, alkoxy, haloalkyl, cycloalkyl, aryl, aralkyl, heterocyclyl, halogen, hydroxy, amino, nitro or cyano,X is a q-valent inorganic or organic anion,b and c independently of one another are integers from 0 to 4,q is an integer from 1 to 3,a is a number of value 2/q, andR4, R5, R6 and R7 independently of one another represent alkyl, cycloalkyl, aryl or aralkyl.

1 . A redox flow cell for storage of electrical energy comprising a reaction cell having two electrode chambers for catholyte and anolyte, which are each connected to at least one store for liquid and are separated by an ion-conducting membrane, and which are equipped with electrodes, wherein the electrode chambers are each filled with electrolyte solutions comprising redox-active components dissolved or dispersed in an electrolyte solvent, as well as optionally conducting salts dissolved therein and optionally further additives, wherein the catholyte comprises a redox-active component comprising of formula IIIa, formula IIIb, or formula IIIc: 
       
         
           
           
               
               
           
         
         wherein 
         R 4 , R 5 , R 6  and R 7  independently of one another represent alkyl, cycloalkyl, aryl or aralkyl, 
         R 13  is alkoxy, haloalkyl, aryl, aralkyl, heterocyclyl, or nitro, 
         R 16  is an o-times positively charged monovalent organic residue, 
         R 25  is an u-times negatively charged monovalent residue, 
         X is a q-valent inorganic or organic anion or a mixture of such anions, 
         Z is a q-valent inorganic or organic cation or a mixture of such cations, 
         l is a number with the value o/q, 
         o is an integer from 1 to 4, 
         q is an integer from 1 to 3, and 
         u is an integer from 1 to 4. 
       
     
     
         2 . The redox flow cell according to  claim 1 , wherein R 16  is selected from the group consisting of a quaternary ammonium residue, a quaternary phosphonium residue, a ternary sulfonium residue and a heterocyclic residue. 
     
     
         3 . The redox flow cell according to  claim 1 , wherein the anolyte contains a compound of formula Ib or formula IIb 
       
         
           
           
               
               
           
         
         wherein 
         R 2  and R 3  independently of one another represent alkyl, alkoxy, haloalkyl, cycloalkyl, aryl, aralkyl, heterocyclyl, halogen, hydroxy, amino, nitro or cyano; 
         R 8  and R 10  independently of one another represent hydrogen; alkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; cycloalkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; aryl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; aralkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; 
         R 20  and R 21  independently of one another represent hydrogen; alkyl which is optionally substituted with a carboxylic ester group, a carboxylic amide group, a carboxylic acid group, a sulfonic acid group or an amino group; cycloalkyl which is optionally substituted with a carboxylic ester group, a carboxylic amide group, a carboxylic acid group, a sulfonic acid group or an amino group; aryl which is optionally substituted with a carboxylic ester group, a carboxylic amide group, a carboxylic acid group, a sulfonic acid group or an amino group; or aralkyl which is optionally substituted with a carboxylic ester group, a carboxylic amide group, a carboxylic acid group, a sulfonic acid group or an amino group; or two of the residues R 20  and R 21  together form a C 1 -C 3 -alkylene group; 
         a is a number of value 2/q; and 
         b and c independently of one another are integers from 0 to 4. 
       
     
     
         4 . The redox flow cell according to  claim 3 , wherein the anolyte contains a compound of formula 1b. 
     
     
         5 . The redox flow cell according to  claim 4 , wherein the compound of formula IIIb is a salt of 2,2,6,6-tetramethylpiperidin-1-yloxyl-4-(N,N,N-trialkylammonium) and wherein the compound of formula 1b is a salt of N, N′-dialkylviologen. 
     
     
         6 . The redox flow cell according to  claim 1 , wherein X q  is selected from the group consisting of halogenide ions, hydroxide ions, phosphate ions, sulfate ions, perchlorate ions, hexafluorophosphate ions, and tetrafluoroborate ions. 
     
     
         7 . A method of storing electrical energy for stationary and mobile applications comprising utilizing the redox flow cell according to  claim 1 . 
     
     
         8 . A redox flow cell for storage of electrical energy comprising a reaction cell having two electrode chambers for catholyte and anolyte, which are each connected to at least one store for liquid and are separated by an ion-conducting membrane, and which are equipped with electrodes, wherein the electrode chambers are each filled with electrolyte solutions comprising redox-active components dissolved or dispersed in an electrolyte solvent, as well as optionally conducting salts dissolved therein and optionally further additives,
 wherein at least one of the anolyte and the catholyte comprises a redox-active component comprising:   a) one to six residues of formula I in combination with one to six residues of formula III in the molecule or in combination with iron salts; or   b) one to six residues of formula II in combination with one to six residues of formula III in the molecule or in combination with iron salts;   
       
         
           
           
               
               
           
         
         wherein the lines going off the nitrogen atoms in the structures of formulae I and II and the line going off the 4-position in the structure of formula III represent covalent bonds connecting the structures of formulae I, II and III with the remainder of the molecule, 
         R 1  is a covalent C—C-bond or a divalent bridge group, 
         R 2  and R 3  independently of one another represent alkyl, alkoxy, haloalkyl, cycloalkyl, aryl, aralkyl, heterocyclyl, halogen, hydroxy, amino, nitro or cyano, 
         X is a q-valent inorganic or organic anion or a mixture of such anions, 
         b and c independently of one another are integers from 0 to 4, 
         q is an integer from 1 to 3, 
         a is a number of value 2/q, and 
         R 4 , R 5 , R 6  and R 7  independently of one another represent alkyl, cycloalkyl, aryl or aralkyl. 
       
     
     
         9 . The redox flow cell according to  claim 8 , wherein both the anolyte and the catholyte comprise:
 residues of Formula I in combination with residues of Formula III; or   residues of Formula II in combination with residues of Formula III.   
     
     
         10 . The redox flow cell according to  claim 8 , wherein in the anolyte and/or the catholyte a compound of formulae VII, VIIa, VIIb, VIII, VIIIa, VIIIb, IX, IXa, IXb, X, Xa, Xb, XI, Xla, Xlb, XII, Xlla and/or Xllb is used as redox-active component 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         wherein 
         R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , X, b, c, and q have the meaning defined in claim  40 ; 
         R 8  represents hydrogen; alkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; cycloalkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; aryl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; aralkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; 
         R 12  is a covalent bond or a divalent to hexavalent organic bridge group; 
         R 14  is a covalent bond or a divalent organic bridge group; 
         R 15  is a divalent to hexavalent organic bridge group; 
         R 18  is an o-times positively charged divalent to hexavalent organic residue, which is covalently connected via a carbon atom with the nitrogen atom of the bipyridyl residue; 
         R 19  is an o-times positively charged divalent organic residue, which is via a carbon atom covalently connected with the nitrogen atom of the bipyridyl residue; 
         R 23  represents an u-times negatively charged divalent to hexavalent organic residue, which is via a carbon atom covalently connected with the nitrogen atom of the bipyridyl residue; 
         R 24  is an u-times negatively charged divalent organic residue, which is via a carbon atom covalently connected with the nitrogen atom of the bipyridyl residue; 
         g is an integer from 1 to 5; 
         h is an integer from 1 to 5; 
         wherein the sum of g and h is an integer from 2 to 6; 
         i is a number with the value 2h/q; 
         j is an integer from 1 to 5; 
         k is a number with the value (2+2j)/q; 
         o is an integer from 1 to 4; 
         p is a number with the value (o+2h)/q; 
         r is a number with the value (3+3j)/q; 
         u is an integer from 1 to 4; 
         z is a number with the value 2/q; 
         z1 is a number with the value (o+2)/q; 
         Y in case that 2h−u or 2 (2−u)−u are greater than 0, is a v- or x-valent inorganic or organic anion or represents a mixture of such anions; or in case that 2h−u or 2 (2−u)−u are smaller than 0, is a v- or x-valent inorganic or organic cation or represents a mixture of such cations; 
         v is an integer from −1 to −3 or from +1 to +3; 
         x is an integer from −1 to −3 or from +1 to +3; 
         w is 0 or a positive number with value (−u+2h)/v; 
         y is 0 or a positive number with value (2−u) (j+1)/x; 
         Y1 in case 2-2u is smaller than 0, is a x1-valent inorganic or organic cation or a mixture of such cations; 
         x1 is an integer from −1 to −3 or from +1 to +3; and 
         y1 is 0 or a positive number with value (2−2u)/x1. 
       
     
     
         11 . The redox flow cell according to  claim 8 , wherein redox active compounds of formulae VIId, VIIe, VIIId and/or VIIIe are used 
       
         
           
           
               
               
           
         
         wherein 
         R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , X, a, b, c, and q have the meaning defined in claim  40 ; 
         R 8  represents hydrogen; alkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; cycloalkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; aryl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; aralkyl that is optionally substituted with a carboxylic ester group, carboxylic amide group, carboxylic acid group, sulfonic acid group or amino group; 
         R 14  is a covalent bond or a divalent organic bridge group; 
         R 19  is an o-times positively charged divalent organic residue, which is via a carbon atom covalently connected with the nitrogen atom of the bipyridyl residue; and 
         s is a number with value 3/q. 
       
     
     
         12 . The redox flow cell according to  claim 8 ,
 wherein redox active compounds of formula XI or XII are used,   
       
         
           
           
               
               
           
         
         wherein 
         R 14  is a covalent bond or a divalent organic bridge group, and 
         z is a number with the value 2/q. 
       
     
     
         13 . The redox flow cell according to  claim 8 , wherein the catholyte is a redox-active component comprising one to four residues of formula I in combination with iron salts or one to four residues of formula II in combination with iron salts. 
     
     
         14 . The redox flow cell according to  claim 8 , wherein R 4 , R 5 , R 6 , and R 7  are each a C 1 -C 6  alkyl. 
     
     
         15 . A method of storing electrical energy for stationary and mobile applications comprising utilizing the redox flow cell according to  claim 8 .