REDOX FLOW BATTERY FOR STORING ELECTRICAL ENERGY IN UNDERGROUND STORAGE MEANS, AND USE THEREOF

Abstract

A redox flow battery for storing electrical energy is described, comprising a reaction cell with two electrode chambers for catholyte and anolyte, each of which is connected to at least one liquid reservoir, the electrode chambers being separated by a membrane, being equipped with electrodes, and each being filled with electrolyte solutions which contain redox-active components dissolved or dispersed in an aqueous electrolyte solvent, as well as conducting salts dissolved therein and possibly further additives. A second embodiment relates to a redox flow battery for storing electrical energy, comprising a reaction cell with an electrode chamber for an electrolyte solution, which is connected to at least one liquid reservoir, the electrode chamber being equipped with a cathode and an anode, and being filled with electrolyte solution which contains redox-active components dissolved or dispersed in an aqueous electrolyte solvent, as well as conductive salts dissolved therein and possibly further additives. The redox flow cells are characterized in that the at least one liquid reservois is an underground storage means in which temperatures of at least 30° C. prevail, in that the concentration of the salts dissolved in the electrolyte solutions is at least 10% by weight, and in that the catholyte or the electrolyte solution contains selected redox-active and temperature-stable components. In the first embodiment, the anolyte contains a water-soluble redox-active component and in the second embodiment, the anolyte or the electrolyte solution contains a zinc salt.

Claims

1. Redox flow battery for storing electrical energy comprising a reaction cell with two electrode chambers for catholyte and anolyte, which are each connected to at least one liquid reservoir, the electrode chambers being separated by a membrane, being equipped with electrodes, and each being filled with electrolyte solutions which contain redox-active components dissolved or dispersed in an aqueous electrolyte solvent, as well as conductive salts dissolved therein and possibly further additives, characterized in that the at least one liquid reservoir is an underground storage means in which temperatures of at least 30° C. prevail, in that the concentration of the salts dissolved in the electrolyte solutions is at least 10% by weight, in that the anolyte contains a water-soluble or water-dispersible redox-active component, and that the catholyte contains at least one compound or composition selected from one of the groups a), b), c), d) or e) as redox-active component, wherein a) is an organic compound comprising at least one redox-active residue of formula (I)
(X—C.sub.5H.sub.4)Fe(Y—C.sub.5H.sub.3—Z)   (I), b) is an organic compound comprising at least one redox-active residue of formula (Ia) ##STR00020## in combination with hydrochloric acid and/or a salt selected from the group consisting of ammonium salts with inorganic or organic anions, salts with tetrafluoroborate anions or salts of trifluoromethanesulfonic acid, c) is an organic compound comprising at least one redox-active residue of the formula (Ib) ##STR00021## d) is an organic compound comprising at least one redox-active residue of the formula (Ic) ##STR00022## e) is a water-soluble iron salt complexed with nitrogen-containing ligands, wherein X is a residue of the formula —(C.sub.nH.sub.2n)-FG or of the formula —(C.sub.wH.sub.2w)-Sp-(C.sub.nH.sub.2n)-FG or of the formula —(C.sub.nH.sub.2n)-Brgp-, Y is hydrogen or a residue of the formula —(C.sub.nH.sub.2n)-FG or of the formula —(C.sub.wH.sub.2w)-Sp-(C.sub.nH.sub.2n)-FG Z is hydrogen or a covalent bond linking the residue of formula (I) to the remainder of the molecule, FG is a functional group selected from —OH, —H, —NO.sub.3, —NO.sub.2, —CN, —OR.sub.1, —SR.sub.1, —(O—CH.sub.2—CH.sub.2).sub.o—OR.sub.2, —(O—CH.sub.2—CH.sub.2).sub.o—NR.sub.3R.sub.4R.sub.5.sup.+(An.sup.m−).sub.1/m, —COR.sub.2, —COO.sup.−(Kat.sup.u+).sub.1/u, —COOR.sub.2, —SO.sub.3.sup.−(Kat.sup.u+).sub.1/u, —SO.sub.3R.sub.2, —SO.sub.4.sup.−(Kat.sup.u+).sub.1/u, —SO.sub.4R.sub.2, —PO.sub.4.sup.2−(Kat.sup.u+).sub.2/u, —PO.sub.4(R.sub.2).sub.2, —PO.sub.3.sup.2(Kat.sup.u+).sub.2/u, —PO.sub.3(R.sub.2).sub.2, —NR.sub.3R.sub.4R.sub.5.sup.+(An.sup.m−).sub.1/m, —N.sup.+R.sub.3R.sub.4—C.sub.tH.sub.2t—SO.sub.3.sup.− or —NR.sub.2—SO.sub.2—R.sub.3, Brgp is a divalent bridging group linking the residue of formula (I) to the remainder of the molecule, Sp is —O— or —s—, R.sub.1 is C.sub.1-C.sub.4 alkyl, R.sub.2 is hydrogen or C.sub.1-C.sub.4 alkyl, R.sub.3, R.sub.4 and R.sub.5 independently of one another represent hydrogen or alkyl, Kat is an u-valent cation, An is an m-valent anion, m and u independently of one another are integers between 1 and 4, n and w independently of one another are integers between 2 and 4, o is an integer from 1 to 50, t is an integer between 2 and 5, R.sub.7, R.sub.8, R.sub.9 and R.sub.10 represent alkyl or each of R.sub.7 and R.sub.8 and R.sub.9 and R.sub.10 together with the common carbon atom form a cycloaliphatic or heterocyclic residue, Q is —O—, —S—, —NH—, —NR.sub.13a—, —NR.sub.13aR.sub.13b.sup.+—(An.sup.m−).sub.1/m, —PR.sub.13a— or —SiR.sub.13aR.sub.13b—, or —Q— represents a covalent bond, R.sub.11 is —O or —S, R.sub.12 is —CH.sub.2—, —O—, —S—, —SO—, —SO.sub.2——NR.sub.13— or —N.sup.+R.sub.13R.sub.14—(An.sup.m−).sub.1/m, R.sub.13, R.sub.13a, R.sub.13b and R.sub.14 independently of one another are monovalent organic residues, and An and m have the meanings defined above.

2. Redox flow battery for storing electrical energy, comprising a reaction cell with an electrode chamber for an electrolyte solution, which is connected to at least one liquid reservoir, the electrode chamber being equipped with a cathode and an anode, the electrode chamber being filled with electrolyte solution which contains redox-active components dissolved or dispersed in an aqueous electrolyte solvent, as well as conductive salts dissolved therein and optionally further additives, characterized in that the at least one liquid reservoir is an underground storage means in which temperatures of at least 30° C. prevail, in that the concentration of the salts dissolved in the electrolyte solutions is at least 10% by weight, in that the anolyte contains a water-soluble or water-dispersible redox-active component, and that the catholyte contains at least one compound or composition selected from one of the groups a), b), c), d) or e) as redox-active component, wherein a) is an organic compound comprising at least one redox-active residue of formula (I)
(X—C.sub.5H.sub.4)Fe(Y—C.sub.5H.sub.3—Z)   (I), b) is an organic compound comprising at least one redox-active residue of formula (Ia) ##STR00023## in combination with hydrochloric acid and/or a salt selected from the group consisting of ammonium salts with inorganic or organic anions, salts with tetrafluoroborate anions or salts of trifluoromethanesulfonic acid, c) is an organic compound comprising at least one redox-active residue of the formula ##STR00024## d) is an organic compound comprising at least one redox-active residue of the formula (Ic) ##STR00025## e) is a water-soluble iron salt complexed with nitrogen-containing ligands, wherein X is a residue of the formula —(C.sub.nH.sub.2n)-FG or of the formula —(C.sub.wH.sub.2w)-Sp-(C.sub.nH.sub.2n)-FG FG or of the formula —(C.sub.nH.sub.2n)-Brgp-, Y is hydrogen or a residue of the formula —(C.sub.nH.sub.2n)-FG or of the formula —(C.sub.wH.sub.2w)-Sp-(C.sub.nH.sub.2n)-FG Z is hydrogen or a covalent bond linking the residue of formula (I) to the remainder of the molecule, FG is a functional group selected from —OH, —SH, —NO.sub.3, —NO.sub.2, —CN, —OR.sub.1, —SR.sub.1, —(O—CH.sub.2—CH.sub.2).sub.o—OR.sub.2, —(O—CH.sub.2—CH.sub.2).sub.o—NR.sub.3R.sub.4R.sub.5.sup.+(An.sup.m−).sub.1/m, —COR.sub.2, —COO.sup.−(Kat.sup.u+).sub.1/u, —COOR.sub.2, —SO.sub.3.sup.−(Kat.sup.u+).sub.1/u, —SO.sub.3R.sub.2, —SO.sub.4.sup.−(Kat.sup.u+).sub.1/u, —SO.sub.4R.sub.2, —PO.sub.4.sup.2−(Kat.sup.u+).sub.2/u, —PO.sub.4(R.sub.2).sub.2, —PO.sub.3.sup.2(Kat.sup.u+).sub.2/u, —PO.sub.3(R.sub.2).sub.2, —NR.sub.3R.sub.4R.sub.5.sup.+(An.sup.m−).sub.1/m, —N.sup.+R.sub.3R.sub.4—C.sub.tH.sub.2t—SO.sub.3.sup.− or —NR.sub.2—SO.sub.2—R.sub.3, Brgp is a divalent bridging group linking the residue of formula (I) to the remainder of the molecule, Sp is —O— or —S—, R.sub.1 is C.sub.1-C.sub.4 alkyl, R.sub.2 is hydrogen or C.sub.1-C.sub.4 alkyl, R.sub.3, R.sub.4 and R.sub.5 independently of one another represent hydrogen or alkyl, Kat is an u-valent cation, An is an m-valent anion, m and u independently of one another are integers between 1 and 4, n and w independently of one another are integers between 2 and 4, o is an integer from 1 to 50, t is an integer between 2 and 5, R.sub.7, R.sub.8, R.sub.9 and R.sub.10 represent alkyl oder each of R.sub.7 and R.sub.8 and R.sub.9 and R.sub.10 together with the common carbon atom form a cycloaliphatic or heterocyclic residue, Q is —O—, —S—, —NH—, —NR.sub.13a, —, —NR.sub.13aR.sub.13b.sup.+—(An.sup.m−).sub.1/m, —PR.sub.13a— or —SiR.sub.13aR.sub.13b—, or —Q— represents a covalent bond, R.sub.11 is —O or —S, R.sub.12 is —CH.sub.2—, —O—, —S—, —SO—, —SO.sub.2——NR.sub.13— or —N.sup.+R.sub.13R.sub.14—(An.sup.m−).sub.1/m, R.sub.13, R.sub.13a, R.sub.13b and R.sub.14 independently of one another are monovalent organic residues, and An and m have the meanings defined above.

3. Redox-flow-battery according to claim 1, characterized in that the electrode chambers for catholyte and anolyte are separated by a semi-permeable membrane impermeable to the redox couple in the catholyte, and the anolyte contains zinc salt as a redox-active component.

4. Redox-flow-battery according to claim 2, characterized in that the electrode chamber for catholyte and anolyte contains no membrane, and that the anolyte contains zinc salt as a redox-active component.

5. Redox-flow-battery according to claim 3, characterized in that this contains a zinc-solid anode with the redox pair zinc(II)/zinc(0).

6. Redox-flow-battery according to claim 1, characterized in that the temperature in the underground storage means is 30 to 90 ° C., preferably 40 to 70 ° C.

7. Redox-flow-battery according to claim 1, characterized in that the concentration of salts dissolved in the electrolyte solutions is from 14 wt% to the saturation limit.

8. Redox-flow-battery according to claim 1, characterized in that the state of charge of the catholyte or of the catholyte and the anolyte is less than 90%.

9. Redox-flow-battery according to claim 1, characterized in that n is an integer between 2 and 4, preferably 2.

10. Redox-flow-battery according to claim 1, characterized in that Y is hydrogen and that m is 1 or 2.

11. Redox-flow-battery according to claim 1, characterized in that FG is a functional group selected from —(O—CH.sub.2—CH.sub.2).sub.o—OR.sub.2, —(O—CH.sub.2—CH.sub.2).sub.o—SR.sub.2, —COR.sub.2, —COO.sup.−(Kat.sup.u+).sub.1/u, —SO.sub.3.sup.−(Kat.sup.u+).sub.1/u, —SO.sub.4.sup.−(Kat.sup.u+).sub.1/u, —PO.sub.4.sup.2−(Kat.sup.u+).sub.2/u, —PO.sub.3.sup.2−(Kat.sup.u+).sub.2/u or —NR.sub.3R.sub.4R.sub.5.sup.+(An.sup.m−).sub.1/m,

12. Redox-flow-battery according to claim 1, characterized in that Kat is a hydrogen cation, a cation of an alkali metal, of an earth alkaline metal or an ammonium cation, preferably a hydrogen cation, a sodium, potassium, magnesium or calcium cation, or a quaternary ammonium cation.

13. Redox-flow-battery according to claim 1, characterized in that An.sup.m− is selected from the group of halide ions, hydroxide ions, phosphate ions, sulfate ions, perchlorate ions, hexafluorophosphate ions or tetrafluoroborate ions.

14. Redox-flow-battery according to claim 1, characterized in that Z is a covalent bond which connects the residue of the formula (I) to a polymer backbone selected from the group consisting of polymethacrylates, polyacrylates, polystyrenes, polyalkylene glycols, polyalkylene imines or polyvinyl ethers, the polymer backbone preferably having from 5 to 100 groups of the formula (I).

15. Redox-flow-battery according to claim 1, characterized in that this contains oligomers or polymers containing recurring structural units of the formula (II) and optionally further structural units derived from solubility-facilitating comonomers ##STR00026## wherein ME is a recurring structural unit derived from a polymerizable monomer, BG is a covalent bond or a bridging group FC is a residue of the formula (X—C.sub.5H.sub.4)Fe(Y—C.sub.5H.sub.3—Z), X, Y and Z have the meanings defined in claim 1, and r is an integer from 2 to 150.

16. Redox-flow-battery according to claim 1, characterized in that the compound of group a) is a compound of formula (III)
(X—C.sub.5H.sub.4)Fe(Y—C.sub.5H.sub.4)   (III), wherein X and Y have the meaning defined in claim 1.

17. Redox-flow-battery according to claim 1, characterized in that the compound of group a) is a compound of formula (IV)
[(X—C.sub.5H.sub.4)Fe(Y—C.sub.5H.sub.3—)]—R.sub.23—[(—C.sub.5H.sub.3—Y)Fe(C.sub.5H.sub.4—X)].sub.p   (IV), wherein X and Y have the meaning defined in claim 1. R.sub.23 is a di- to tetravalent organic group, and p is an integer from 1 to 4.

18. Redox-flow-battery according to claim 1, characterized in that the electrolyte solution contains a compound having at least one redox-active residue of the formulae (Ia), (Ib) or (Ic), which is covalently bonded to a polymer backbone selected from the group consisting of polymethacrylates, polyacrylates, polystyrenes, polyalkylene glycols, polyalkylene imines or polyvinyl ethers, the polymer backbone preferably having 5 to 100 groups of the formula (Ia), (Ib) or (Ic).

19. Redox-flow-battery according to claim 1, characterized in that the electrolyte solution contains oligomers or polymers containing recurring structural units corresponding to formula (V) and optionally other structural units derived from solubility-facilitating comonomers ##STR00027## wherein ME is a recurring structural unit derived from a polymerizable monomer, BG is a covalent bond or a bridging group Pip is a piperidinyl residue of formula (Ia), (Ib) or (Ic), and r is an integer from 2 to 150

20. Redox-flow-battery according to claim 1, characterized in that the electrolyte solution contains a redox-active compound of formula (VIa) or (VIb) ##STR00028## wherein R.sub.7, R.sub.8, R.sub.9 and R.sub.10 have the meaning defined in claim 1, q is an integer from 1 to 3, R.sub.15 is a monovalent organic residue, which is optionally linked via an oxygen, sulfur oder nitrogen atom with the piperidinyl residue, and R.sub.16 is —O—, —S— or a di- to tetravalent organic residue.

21. Redox-flow-battery according to claim 1, characterized in that the electrolyte solution contains a redox-active compound of formula (VII), (VIII), (IX), (X) or (XI) ##STR00029## wherein R.sub.7, R.sub.8, R.sub.9, R.sub.10, R.sub.11, R.sub.12 and Q have the meaning defined in claim 1, ME, BG and r have the meaning defined in claim 19, q has the meaning defined in claim 20, R.sub.16a is a di- to tetravalent organic residue, and t is 0 or 1.

22. Redox-flow-battery according to claim 20, characterized in that R.sub.15 is —O—(C.sub.sH.sub.2s)—R.sub.23, —S—(C.sub.sH.sub.2s)—R.sub.23 or —NR.sub.2—(C.sub.sH.sub.2s)—R.sub.23, s is an integer from 2 to 4, R.sub.2 has one of the meanings defined in clam 1, R.sub.23 is a functional group selected from aus —OH, —SH, —NO.sub.3, —NO.sub.2, —CN —OR.sub.17, —SR.sub.17, —(O—CH.sub.2—CH.sub.2).sub.v—OR.sub.18, —(O—CH.sub.2—CH.sub.2).sub.v—SR.sub.18, —COR.sub.18, —COO.sup.−(Kat.sup.u+).sub.1/u, —COOR.sub.18, —SO.sub.3.sup.−(Kat.sup.u+).sub.1/u, —SO.sub.3R.sub.18, —SO.sub.4.sup.−(Kat.sup.u+).sub.1/u, —SO.sub.4R.sub.18, —PO.sub.4.sup.2−(Kat.sup.u+).sub.2/u, —PO.sub.4(R.sub.18).sub.2, —PO.sub.3.sup.2−(Kat.sup.u+).sub.2/u, —PO.sub.3(R.sub.18).sub.2 or —NR.sub.19R.sub.20R.sub.21.sup.+(An.sup.m−).sub.1/m, R.sub.17 is C.sub.1-C.sub.4 alkyl, R.sub.18 is hydrogen or C.sub.1-C.sub.4 alkyl, R.sub.19, R.sub.20 and R.sub.21 independently of one another are hydrogen or alkyl, Kat is an u-valent cation, An is an m-valent anion, m and u independently of one another are integers between 1 and 4, and v is an integer from 1 to 50.

Description

[0188] The following examples explain the invention without limiting it thereto.

[0189] FIGS. 1 and 2 explain the redox flow battery according to the invention and its function by way of example.

[0190] FIG. 1 shows schematic designs A, B-1 and B-2 of the electrochemical cell according to the invention without underground storage means.

[0191] FIG. 2 shows schematic designs A, B-1 and B-2 of the RFB according to the invention, i.e. the electrochemical cell with underground storage mean(s).

[0192] FIG. 1 represents in design A an RFB or hybrid RFB with two separate electrolyte circuits, which must therefore be connected to at least two underground storage means.

[0193] Furthermore, FIG. 1 in design B-1 depicts a hybrid RFB with an electrolyte circuit, which must therefore be connected to at least one underground storage means. In design B-1, a membrane (12) is provided which divides the electrochemical cell into a cathode compartment and an anode compartment. Design B-2 of the hybrid RFB according to the invention differs from design B-1 by the absence of a membrane.

[0194] Shown in FIG. 1 in designs A and B-1 are the two polarity-specific chambers separated by a membrane (12) (one each for the catholyte (1) and the anolyte (2)) with the electrodes (4, 5). The two electrodes (4, 5) are used for charging and discharging the battery via the current arrester (13). In the case of design A, the electrolytes are supplied separately via the inflow ports (6, 7) and discharged separately again via the outflow ports (8, 9). In the case of design B, there is only one inflow nozzle (10) and one outflow nozzle (11). In the case of design B-2, only one chamber (3) with the electrodes (4, 5) is provided.

[0195] If the RFB according to the invention is operated as a hybrid RFB, metallic zinc is deposited on the electrode (5), the anode, or the anode consists of zinc and Zn.sup.2+ ions are contained in the anolyte or the electrolyte solution contains Zn.sup.2+ ions.

[0196] FIG. 2 shows a sketch of design A of the RFB according to the invention. The electrochemical cell (14) is shown, which is connected to two caverns (16, 17). These are filled with anolyte (19) and catholyte (20), respectively. Via the piping (23), the anolyte and catholyte (19, 20) are conveyed from the respective caverns (16, 17) into the electrochemical cell (14) by means of pumps (22) and are returned to the caverns (16, 17) via the piping (24). Anolyte (19) and catholyte (20) have a high salt content (brine) in addition to the redox-active compounds. The above-mentioned ferrocene, 2,2,6,6-tetrasubstituted pyridinyl or iron compounds are used as redox-active components in the catholyte (20). For example, the above-mentioned bipyridyl compounds or zinc salts are used as redox-active components in the anolyte (19). Design A can be operated as a conventional RFB or as a hybrid RFB.

[0197] FIG. 2 also shows a sketch of design B of the RFB according to the invention. In this case, the design is considerably simplified. Here, the electrochemical cell (15) is connected to only one cavern (18). This is filled with electrolyte solution (21). The electrolyte solution (21) is conveyed from the cavern (18) into the electrochemical cell (15) via the piping (23) by means of a pump (22) and returned to the cavern (18) via the piping (24). The electrolyte solution (21) has a high salt content (brine) in addition to the redox-active compounds. Electrolyte solution (21) contains both active species in addition to highly concentrated conducting salts (brine), i.e. both a redox-active component for the anode and a redox-active component for the cathode. The above-mentioned ferrocene, 2,2,6,6-tetrasubstituted pyridinyl or iron compounds are used as redox-active components for the cathode. Zinc salts are used as redox-active components for the anode. Design B is operated as a hybrid RFB. The membrane shown schematically for design B in FIG. 2 can also be omitted.

[0198] The caverns (16, 17, 18) are each filled with brine containing redox-active components which are dissolved in the brine or in solid form (i.e. dispersed). If required, further conductive additives and further auxiliary additives can be additionally dissolved.