Redox flow battery with external supply line and/or disposal line

Abstract

A redox flow battery is illustrated and described, having at least one cell frame enclosing a cell interior and having at least one supply line provided outside the cell frame for supplying electrolyte to the cell interior and/or at least one disposal line provided outside the cell frames for removing electrolyte from the cell interior. In order to provide greater degrees of freedom in the design of the cell so as to make available redox flow batteries with improved properties, it is envisaged that the supply line for supplying electrolyte to the cell interior and/or the disposal line for removing electrolyte from the cell interior is in fluid contact with the cell interior via a plurality of separate flow channels in the cell frame.

Claims

1. A redox flow battery comprising: a plurality of cells, wherein each cell comprises two half-cells, wherein each half-cell comprises a cell frame defining a half-cell interior, a supply line positioned outside each of the cell frames of the half-cells to supply electrolyte to the redox flow battery, a disposal line positioned outside each of the cell frames of the half-cells to remove electrolyte from the redox flow battery, wherein each half-cell is provided with a plurality of separate supply channels extending through the cell frame to supply electrolyte to the half-cell interior of the half-cell from the corresponding supply line, wherein each of the supply channels of the half-cells are unconnected to one another inside of the cell frames; each half-cell being further provided with a plurality of separate disposal channels extending through the cell frame to remove electrolyte from the half-cell interior of the half-cell to the corresponding disposal line, wherein each of the disposal channels of the half-cells are unconnected to one another inside of the cell frames.

2. The redox flow battery according to claim 1, wherein the redox flow battery comprises at least 10 supply channels.

3. The redox flow battery according to claim 1, wherein the redox flow battery comprises at least 20 supply channels.

4. The redox flow battery according to claim 1, wherein the redox flow battery comprises at least 30 supply channels.

5. The redox flow battery according to claim 1, wherein at least one of the supply channels has a hydraulic internal diameter of between 0.5 mm and 20 mm.

6. The redox flow battery according to claim 1, wherein at least one of the supply channels has a hydraulic internal diameter of between 1 mm and 10 mm.

7. The redox flow battery according to claim 1, wherein corresponding supply channels and disposal channels are provided on different sides of the half-cell.

8. The redox flow battery according to claim 1, wherein at least a portion of the supply channels are at least substantially non-branched inside of the cell frame.

9. The redox flow battery according to claim 1, wherein the cross-sectional surface area of the supply line is greater at least by a factor of 10 than a cross-sectional surface area of each of the supply channels.

10. The redox flow battery according to claim 1, wherein the cross-sectional surface area of the supply line is greater at least by a factor of 50 than a cross-sectional surface area of each of the supply channels.

11. The redox flow battery according to claim 1, wherein the cross-sectional surface area of the supply line is greater at least by a factor of 100 than a cross-sectional surface area of each of the supply channels.

12. The redox flow battery according to claim 1, wherein the supply channels are surrounded over their entire circumference by the cell frames.

13. The redox flow battery according to claim 1, wherein the plurality of cells are assembled to form a cell stack.

14. A redox flow battery comprising: a plurality of half-cells, each half-cell comprising a cell frame defining a half-cell interior, each half-cell being provided with a plurality of separate supply channels extending through the cell frame to supply electrolyte to the half-cell interior of the half-cell from a supply line provided outside of the cell frame, wherein each of the supply channels of the half-cells are unconnected to one another inside of the cell frames; each half-cell being further provided with a plurality of separate disposal channels extending through the cell frame to remove electrolyte from the half-cell interior of the half-cell to a disposal line provided outside of the cell frame, wherein each of the disposal channels of the half-cells are unconnected to one another inside of the cell frames.

15. A method for operating a redox flow battery comprising a plurality of half-cells, each half-cell comprising a cell frame defining a half-cell interior, the method comprising: supplying electrolyte to an interior of one of the half-cells via a plurality of separate supply channels extending through the cell frame from a supply line provided outside of the cell frame, the supply channels being unconnected to one another inside of the cell frames, and removing electrolyte from the interior of the one of the half-cells via a plurality of separate disposal channels extending through the cell frame to a disposal line provided outside of the cell frame, the disposal channels being unconnected to one another inside of the cell frames.

16. The method according to claim 15, further comprising: supplying electrolyte to an interior of a second one of the half-cells via a second plurality of separate supply channels extending through the cell frame from a second supply line provided outside of the cell frame, the second supply channels being unconnected to one another inside of the cell frames, and removing electrolyte from the interior of the second one of the half-cells via a plurality of second disposal channels extending through the cell frame to a second disposal line provided outside of the cell frame, the second disposal channels being unconnected to one another inside of the cell frames.

17. The method according to claim 15, wherein the plurality of half-cells are assembled to form a cell stack.

18. The redox flow battery of claim 1, wherein the supply channels of each half-cell and/or the disposal channels of each half-cell are parallel to one another and to a plane of the half-cells.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in more detail hereinafter with the aid of drawings simply illustrating exemplary embodiments. In the drawings:

(2) FIGS. 1A and 1B show a longitudinal section of a cell stack of a redox flow battery known from the prior art,

(3) FIG. 2 is a plan view of a cell frame of the cell stack of FIG. 1,

(4) FIG. 3 is a cross-sectional view of a first configuration of a redox flow battery according to the invention,

(5) FIG. 4 is a longitudinal section of the redox flow battery of FIG. 3,

(6) FIG. 5 is a transverse section of a second configuration of a redox flow battery according to the invention, and

(7) FIG. 6 is a section of a cell of the redox flow battery of FIG. 5 perpendicular to the plane of the cell.

DETAILED DESCRIPTION OF THE INVENTION

(8) A cell stack A, i.e. a cell stack of a redox flow battery known from the prior art and described in more detail in the introduction, is illustrated in longitudinal section in FIGS. 1A and 1B. The cell stack A comprises three cells B, which respectively have two half cells C with corresponding electrolytes. Each half cell C has a cell frame D, which encloses a cell interior E through which can be fed an electrolyte stored in a receiver vessel.

(9) The cell interior E is closed adjoining the cell frame D of the second half cell C by a semi-permeable membrane F provided between the cell frame D of the two half cells C. A convective flow of the two different electrolytes of the two half cells C in to the cell interior E of the cell frame D of the other half cell C is thus prevented. However, ions can pass by diffusion from one electrolyte to the other electrolyte through the semi-permeable membrane F, whereby a charge transport takes place. Due to redox reactions of the redox pairs of the electrolytes at the electrodes G of the half cells C of a cell B, electrons are either released or accepted. The released electrons can flow via an electrical connection provided outside the redox flow battery, if necessary comprising an electrical consumer, from one electrode G to the other electrode G of a cell B. At which electrode G reactions take place depends on whether the redox flow battery is being charged of discharged.

(10) The electrodes G also close the cell interiors E adjoining the next cell B. In the illustrated cell stack A the electrode G lies flat on an outside surface H of the cell frame D. The electrode G thus forms in the abutment region with the outside H of the cell frame D a frame surface that acts as a sealing surface I. A sealing material J, in which the membrane F is accommodated in a sealing manner, is disposed between the outside surfaces H facing towards one another of the cell frames D of a cell B. The sealing material J lies over the surface on the outsides K of the adjoining cell frames D and thus forms frame surfaces that act as sealing surfaces L.

(11) In the illustrated redox flow battery four channels extend along the cell stack A. Two of these are supply lines M for supplying the two electrolytes. The other two channels are disposal lines N for removing the electrolytes. FIG. 1A shows respectively a supply line M and a disposal line N. From the disposal line M branch flow channels O in respectively one half cell C of each cell B, through which the electrolyte can be supplied to the corresponding cell interior E of the half cell C. Flow channels P are provided on oppositely facing sections of the corresponding cell frames D, through which the electrolyte can be drained from the cell interiors E into the disposal line N. The supply line M, not illustrated in FIG. 1A, and the disposal line N, likewise not illustrated in FIG. 1A, enable the second electrode to flow via similar flow channels O, P through the respective other cell interiors E of the other half cells C.

(12) A plan view a cell frame D is illustrated in FIG. 2. Four bores Q are provided in the corners of the cell frame D, each bore forming part of a supply line M or a disposal line N. The flow channels O, P are sunk as depressions in the illustrated outside H of the frame jacket R of the cell frame D surrounding the cell interior E. The flow channels O, P have branchings between one another and are respectively connected to a bore Q. The flow channels O, P are therefore all connected to one another in the cell frame D. Consequently separate flow channels are not allocated either to the supply line M or to the disposal line N.

(13) FIG. 3 shows a cross-section through a redox flow battery 1, whose operating principle is substantially the same as the redox flow battery illustrated in FIGS. 1 and 2, in which however the supply line 2 and the disposal line 3 of each cell frame 4 outside the respective cell frame 4 is arranged differently than in the case of the redox flow battery illustrated in FIGS. 1 and 2. The cross-section of the supply line 2 and of the disposal line 3 therefore do not have to be sealed by the frame surfaces of the outsides 6 of the cell frames 4 acting as sealing surfaces 5. The frame surface or sealing surface 5 of the cell frames 4 can accordingly be designed small compared to the cell interior 7 enclosed by the cell frame 4.

(14) The supply of the electrolyte via the cell frames 4 to the cell interior 7 takes place via separate flow channels 8 sunk in the cell frames 4, which run parallel to one another and are distributed uniformly over the width of the cell interior 7. The flow channels 8 have openings 10 on the side of the cell frame 4 facing towards the cell interior 7, through which the electrolyte can be uniformly distributed over the width of the cell interior 7. Also the flow channels 8 on the outer edge of the cell frame 4, i.e. on the outside of the provided frame jacket 11 surrounding the cell interior 7, form openings 12 that are connected separately via thin lines 13 to the common supply line 2. An electrolyte can thus be supplied to the cell interior 7 via the supply line 2, the thin lines 13 and the parallel and separate flow channels 8 in the cell frame 4.

(15) On the oppositely facing frame side of the cell frame 4 and on the oppositely facing side of the frame jacket 11 are provided flow channels 14 that are also parallel and separate, and which are open via corresponding openings 16, 17 to the cell interior 7 and to the edge of the cell frame 4, i.e. to the outside of the frame jacket 11. The separate flow channels 14 are aligned parallel to one another, and are arranged distributed uniformly over the width of the cell interior 7. These flow channels 14 are provided in order to drain the electrolyte from the cell interior 7 via the cell frame 4 to the disposal line 3, for which purpose the separate flow channels are connected via thin lines 18 to a common disposal line 3.

(16) The redox flow battery 1 from FIG. 3 is illustrated in a longitudinal section in FIG. 4. The cells 20 are in this connection composed of similar structural parts, which therefore bear the same reference numerals. The separators are formed as semi-permeable membranes 21 and are provided between the cell frames 4 of the half cells 22 belonging to one another, which are pressed together and thus outwardly seal the membranes 21.

(17) Between the cells 20 there is respectively provided an electrode 23, which outwardly closes off the cell interior 7 from at least one cell frame 4. In the illustrated and to this extent preferred redox flow battery 1 each half cell 22 and each cell frame 4 has a connection to a supply line 2 and a disposal line 3. The supply lines 2 for a same electrolyte can be connected to one another just like the disposal lines 3 for a same electrolyte. The supply line 2 and a disposal line 3 can however also be connected separately to at least one receiver container.

(18) The redox flow battery 1 illustrated in cross-section in FIG. 5 has the same functional structure as the redox flow battery 1 illustrated in FIGS. 3 and 4, though in this case the thin connection lines between the cell frame 4 on the one hand and the supply line 2 and disposal line 3 on the other hand are dispensed with. Instead the supply line 2 and the disposal line 3 on the side facing towards the cell frame 4 have a longitudinal, gap-shaped section 25 of reduced cross-section compared to the adjoining region of the supply line 2 and the disposal line 3. These gap-shaped sections 25 connect a series of separate flow channels 8, 14. The corresponding flow channels 8, 14 are respectively fully sunk in the cell frames 4. A separate sealing of the flow channels 8, 14 over the outsides of the cell frame 4 facing towards the adjoining cells is therefore unnecessary.

(19) The gap-shaped section 25 of the supply line 2 and disposal line 3 are connected via openings 12, 17 in the frame jacket 11 of the cell frame 4 to the flow channels 8, 14 of the electrolyte supply 8, 14. The flow channels 8, 14 are open via further openings 10, 16 to the cell interior 7.

(20) An electrochemical cell 20 formed using cell frames 4, as are illustrated in FIG. 5, is shown in FIG. 6. A plurality of these 20 can be stacked on top of one another to form a cell stack, and specifically according to the basic principle as illustrated in FIG. 4.

(21) The two half cells 22 of the cell 20 comprise respectively a cell frame 4, which surrounds a cell interior 7, through which an electrolyte can be pumped. The cell interiors 7 of the cell frames 4 are separated by separators in the form of a membrane 21, which is permeable to certain ions. The outsides 6 of the cell frames 4 facing away the membrane 21 are closed by means of electrodes 23. In the illustrated and to this extent preferred redox flow battery the electrodes are formed as graphite electrodes. Another electrolyte is supplied to each half cell 22 via the supply lines 2 and the separate flow channels 8 in the cells frame 4 and is removed via separate flow channels 14 and the disposal lines 3.

(22) The electrodes 23, the cell frames 4 and the membrane 21 are pressed together with such a surface pressure that the cell 20 is liquid-tight and the electrolytes cannot undesirably leak.