Device for storing electrical energy, method for assembling and starting up said device, and method for operating said device

Abstract

A device for storing electrical energy is disclosed. The device includes an electrochemical cell having a cathode chamber for holding a liquid cathode material and an anode chamber for holding a liquid anode material. The cathode and anode chambers are separated by a solid electrolyte, wherein the solid electrolyte is surrounded by a planar construction having openings, through which the cathode material can flow. The planar construction is made of an electrically conductive material. The cathode chamber includes at least one segment, wherein each segment has a jacket composed of an electrically conductive material and the jacket is fastened to the planar construction having openings in a fluid-tight and electrically conductive manner and wherein each segment is filled with a porous felt or a porous material different from porous felt. A method for assembling and starting up the device and a method for operating the device is also disclosed.

Claims

1. An apparatus for storing electric energy, which comprises an electrochemical cell having a cathode space for accommodating a liquid cathode material and an anode space for accommodating a liquid anode material, where the cathode space and the anode space are separated by a solid electrolyte, wherein the solid electrolyte is enclosed by a sheet-like structure having openings through which the cathode material can flow, the sheet-like structure is made of an electrically conductive material and the cathode space comprises at least one segment, where each segment has an outer wall composed of an electrically conductive material and the outer wall is fastened in a fluid-tight and electrically conductive manner to the sheet-like structure having openings, wherein each segment is filled with a porous felt or a porous material being different from porous felt and the cathode space is divided by the sheet-like structure having openings into an inner region and an outer region and a porous electrode and a chemical barrier layer composed of a material which does not conduct electrons are accommodated in the inner region between the sheet-like structure having openings and the solid electrolyte and the outer region comprises the at least one segment.

2. The apparatus according to claim 1, wherein the porous material being different from porous felt is a woven fabric, a knitted fabric, a knotted fabric, a network, a non-woven, an open-cell foam, or a three-dimensional netting.

3. The apparatus according to claim 1, wherein the porous felt or the porous material being different from porous felt is made up of oxidized thermally stabilized polymer fibers, fibers composed of oxide ceramic or glass fibers or of oxidized thermally stabilized polymer fibers in mixture with fibers of oxide ceramics or glass fibers.

4. The apparatus according to claim 1, wherein the material which does not conduct electrons is selected from among aluminum oxide, silicon dioxide, mixed oxides of aluminum with silicon, silicates and aluminosilicates.

5. The apparatus according to claim 1, further comprising a container for the anode material, where the container for the anode material is positioned beneath the electrochemical cell and connected via a riser tube to the anode space.

6. The apparatus according to claim 5, wherein a centering rod is arranged beneath the electrochemical cell and the container for the anode material is guided on the centering rod.

7. The apparatus according to claim 1, wherein a displacement body is accommodated in the anode space.

8. The apparatus according to claim 1, wherein the anode material is an alkali metal and the cathode material is sulfur.

9. A method for the assembly and start-up of an apparatus for storing electric energy according to claim 1, which comprises the following steps: (a) mounting of the outer wall of the at least one segment of the cathode space on the sheet-like structure having openings, (b) impregnation of the porous felt or the porous material being different from the porous felt and the porous electrode with alkali metal polysulfide, (c) introduction of porous felt impregnated with alkali metal polysulfide or of porous material being different from porous felt impregnated with alkali metal polysulfide into each segment and insertion of the porous electrode impregnated with alkali metal polysulfide, (d) positioning of the solid electrolyte within the sheet-like structure having openings so that the porous electrode is positioned between the sheet-like structure having openings and the solid electrolyte to form an electrochemical cell, (e) connection of the electrochemical cell with the container for the anode material, (f) heating of the electrochemical cell to an operating temperature, (g) application of an electric voltage in order to charge the apparatus, with the alkali metal polysulfide being dissociated into alkali metal and sulfur, the alkali metal going over into the anode space and being conducted into the container for the anode material and the sulfur remaining in the cathode space.

10. The method according to claim 9, wherein the porous felt or the porous material being different from porous felt and/or the porous electrode are compressed after impregnation or during the impregnation in step (b).

11. The method according to claim 9, wherein the alkali metal is sodium.

12. The method according to claim 9, wherein the alkali metal is conducted via a riser tube into the container for the anode material positioned beneath the electrochemical cell.

13. The method according to claim 9, wherein a pressure in the cathode space is higher than a pressure in the anode space and in the container for the anode material.

14. A method for operation of an apparatus according to claim 1, wherein a pressure in the cathode space is higher than a pressure in the anode space regardless of an operating state.

15. The method according to claim 14, wherein a pressure difference between the anode space and the cathode space is in a range from 0.1 to 5 bar.

Description

(1) Examples of the invention are shown in the figures and are explained in more detail in the following description.

(2) The figures show:

(3) FIG. 1 an exploded view of an apparatus according to the invention for storing electric energy,

(4) FIG. 2 a longitudinal section through an apparatus according to the invention,

(5) FIG. 3 a longitudinal section through a displacement body,

(6) FIGS. 4 to 6 sectional views of a cathode space having one segment,

(7) FIGS. 7 and 8 sectional views of a cathode space having three segments,

(8) FIGS. 9 to 11 sectional views of a cathode space having four segments,

(9) FIG. 12 a sectional view of a cathode space having six segments.

(10) FIG. 1 depicts an exploded view of an apparatus according to the invention for storing electric energy. From this, it is possible to see the components which are required for assembly of an apparatus for storing electric energy.

(11) An apparatus for storing electric energy comprises a solid electrolyte 3 which conducts ions. A ceramic is usually used as material for the solid electrolyte 3. In the case of an alkali metal, in particular sodium, as anode material and sulfur as cathode material, preference is given to using β-aluminum oxide or β″-aluminum oxide which is optionally stabilized with magnesium oxide, lithium oxide or zirconium oxide. The solid electrolyte 3 is configured as a tube closed at the lower end in the embodiment depicted here. After assembly, the anode space of the electrochemical cell is located in the interior of the solid electrolyte 3. In order to seal the anode space of the electrochemical cell, a first sealing ring 5, which is mounted at the top of the solid electrolyte 3, is provided. The solid electrolyte 3 is pushed into a lid 7 for the cell container with a second sealing ring 9. The first sealing ring 5 and the second sealing ring 9 are preferably made of graphite in this case. This is stable toward the materials used in the electrochemical cell and resistant to the temperatures required during operation.

(12) To decrease the volume of the anode space, a displacement body 11 is introduced into the solid electrolyte 3. The outer contour of the displacement body 11 has such a shape that, after installation of the displacement body, merely a gap remains between the interior wall of the solid electrolyte 3 and the outer contour of the displacement body 11. In the embodiment depicted here, the displacement body 11 is made up of two parts and comprises an upper part 13 with the displacement head 17 and a lower part 15. The upper part 13 and the lower part 15 of the displacement body are joined to form a single component, for example by welding.

(13) To install the displacement body 11 in the solid electrolyte 3, a flange 19 is used in the embodiment depicted here. The flange 19 is placed together with a third sealing ring 21, preferably likewise composed of graphite, on the displacement head 17 and attached to the lid 7 of the cell container using fastening means 23, for example nuts. For this purpose, threads 18 are preferably installed on the lid 7 and are conducted through openings in the flange 19 and fastened by means of the nuts used as fastening means 23.

(14) To be able to attach the transport conduit for the anode material to the displacement head 17, a connection element 25 is preferably inserted into the displacement head 17. The connection element 25 is preferably composed of stainless steel in order to ensure good weldability to the transport conduit for the anode material. When a container 27 for anode material is positioned beneath the electrochemical cell and transport of the anode material is effected through a riser tube 29, a connecting tube 31, for example, which is fastened at one end to the connection element 25 and at the other end to the riser tube 29 is utilized.

(15) The container for anode material 27 comprises a container wall 33, a lower lid 35 and an upper lid 37 to close the container and also an insulating bottom plate 39 and an insulating cover plate 41.

(16) To be able to connect the container for anode material flush with the electrochemical cell, the container is preferably, as shown here, ring-shaped with a central hollow space 43 for a centering rod 45. For potential separation, the centering rod 45 is preferably enveloped in insulation 47.

(17) Furthermore, a pressure conduit 49 is provided in order to set the pressure in the anode space and the container 27 for anode material. After assembly, the pressure in the anode space and the container for anode material 27 is preferably set via the pressure conduit 49. The pressure conduit 49 is subsequently closed.

(18) The electrochemical cell further comprises a cell container which is made up of a sheet-like structure 51 having openings. The sheet-like structure 51 having openings is made of an electrically conductive material which is chemically inert toward the materials used in the electrochemical cell, preferably stainless steel. The sheet-like structure 51 having openings is configured so that it completely covers the solid electrolyte 3 on the side of the cathode space. In the case of ring-shaped solid electrolytes 3 as shown in the embodiment depicted here, the sheet-like structure 51 also has a ring shape in the form of a tube. A porous electrode is located in the interior of the tubular sheet-like structure 51 having openings; this porous electrode preferably additionally has a chemical barrier layer on the side which is opposite the sheet-like structure 51 and in the assembled state faces the solid electrolyte 3.

(19) To form the cathode space, outer walls 53 are mounted on the sheet-like structure 51 having openings, for example by welding. In the embodiment depicted here, four outer walls 53, which after assembly form a cathode space having four segments, are provided. Finally, a porous felt 55 which has preferably been impregnated with alkali metal polysulfide for assembly is placed in each of the segments. At the lower end, the segments of the cathode space are closed by a bottom plate 54.

(20) An assembled apparatus for storing electric energy is shown in a sectional view in FIG. 2.

(21) In a preferred embodiment, the container 27 for anode material is located beneath the electrochemical cell 56 of an apparatus 1 for storing electric energy. For precise positioning, the container 27 has an annular shape with a hollow space 43 for accommodating the centering rod 45. In the fully assembled apparatus 1, the container 27 for anode material encloses the centering rod 45 enveloped in insulation 47. The container 27 for anode material is closed by means of a lower lid 35 and an insulating bottom plate 39 and also an upper lid 37 and an insulating cover plate 41.

(22) The container 27 for anode material is connected to the electrochemical cell 56 by the riser tube 29. When the electrochemical cell 56 is discharged, anode material, in particular liquid sodium, flows from the container 27 for anode material through the riser tube 29 into an anode space 57 of the electrochemical cell 56. For this purpose, a connection for the riser conduit 39 which is connected to the connecting tube 31 is provided on the displacement head 17. The connection is effected via the connection element 25. The anode material can then flow through the displacement head 17 into the anode space 57. The anode space 57 is located in the interior of the solid electrolyte 3 and its volume is reduced by the displacement body 11 inserted into the solid electrolyte 3. A gap 59 which is filled with anode material is formed between the displacement body 11 and the solid electrolyte 3.

(23) The solid electrolyte 3 is enclosed by the porous electrode 61 which is optionally provided with a chemical barrier layer. If a chemical barrier layer is present, this is on the side facing the solid electrolyte 3.

(24) The sheet-like structure 51 having openings adjoins the porous electrode 61. The outer walls 53 are installed on the sheet-like structure 51 having openings. The outer walls 53 each enclose individual segments 63, with all the segments 63 together forming the cathode space 65 of the electrochemical cell 56. The outer walls 53 bounding the segments 63 close off the electrochemical cell 56 from the outside and form the cell container. The porous felt 55 is present in the interior of each segment 63.

(25) For production engineering reasons, the displacement body is preferably configured as a hollow body. To prevent the walls from being deformed, for example during charging and discharging operation, it is possible to fill the hollow space with an inert material in order to stabilize this mechanically. For this purpose, the hollow space can be filled with an inert material, for example sand.

(26) FIG. 3 shows a sectional view of a displacement body.

(27) For the anode material to be able to flow from the container for anode material into the anode space, the displacement head is provided with a channel 67 which is connected at one end via the connection element 25 to the connecting tube 31 and at the other end opens into the anode space. For this purpose, a groove 69 can be, as shown here, provided on the displacement head 17, in which groove the cross-sectional area of the anode space is increased compared to the gap between solid electrolyte and displacement body 11. Here too, a hollow space 71 is formed in the interior of the displacement body 11 and is filled with an inert material.

(28) FIGS. 4 to 6 depict embodiments of a cathode space having only one segment.

(29) The cathode space 65 comprises the sheet-like structure 51 having openings and the outer wall 53 which closes off the cathode space 65 on the outside. The cathode material, for example sulfur, is present in the cathode space in the charged state, and the reaction product of cathode material and anode material, for example alkali metal polysulfide, in particular sodium polysulfide, is present in the discharged state. To equalize flow and to prevent cathode material and reaction product from demixing, the cathode space is preferably filled with a porous felt.

(30) In the apparatus of the invention for storing electric energy, the sheet-like structure 51 and the outer wall 53 serve as power outlet leads for the porous electrode 61 which is not shown here. For both sheet-like structure 51 and outer wall 53 to be able to act as power outlet leads, it is necessary for these to be electrically conductively connected to one another. For this purpose, for example in the case of a cathode space 65 having only one segment 63, it is possible to utilize an outer wall element 73 by means of which the outer wall 53 is fastened to the sheet-like structure 51 having openings. Fastening is preferably effected by welding.

(31) The cross-sectional shape of the cell can be chosen freely. Thus, it is possible, for example, to have a triangular cross section, as shown in FIG. 4, by giving the outer wall 53 a triangular shape. Correspondingly, the outer wall 53 can be given a square cross section as in FIG. 5 or a circular cross section as in FIG. 6.

(32) Apart from the shapes depicted here, any other shape is also conceivable for the outer wall. Instead of an outer wall element 73 by means of which the outer wall 53 is connected to the sheet-like structure 51 having openings, it is also possible to configure the outer wall with two side walls which are fastened next to one another to the sheet-like structure 51 having openings. The outer walls 53 of the embodiments shown in FIGS. 7 to 11, for example, are fastened in a corresponding way.

(33) In FIGS. 7 and 8, the cathode space 65 in each case comprises three segments, with each segment having a separate outer wall 53 which is in each case joined on two sides to the sheet-like structure 51 and thus completely closes off the segment 63 from the outside.

(34) As an alternative to the variants depicted here, in which the outer walls 53 of two adjacent segments 63 are in contact with the sheet-like structure 51 in the region of the connection, it is also possible to provide a greater spacing here. In this case, it is necessary for there to be no openings in the sheet-like structure 51 in the region between two segments 63 so that no cathode material can exit between the segments 63.

(35) Furthermore, it is also possible to form a common outer wall instead of a separate outer wall 53 for each segment 63 and to separate the individual segment 63 by outer wall elements 73, as depicted in FIGS. 4 to 6 in the case of one segment 63 and in FIG. 12 for an embodiment having six segments 63.

(36) In a configuration having three segments 63, too, the outer contour of the cathode space 65 can assume any shape. Thus, for example, a triangular cross section, as shown in FIG. 7, or a circular cross section, as shown in FIG. 8, is possible. Any other cross-sectional shape is also conceivable.

(37) Different variants for a configuration having four segments 63 are shown in FIGS. 9 to 11. Here too, it is possible either to provide a spacing between two outer walls 53 enclosing the segments 63 or, as an alternative, to effect separation by means of an outer wall element 73, with the outer wall element 73 separating two segments 63 from one another.

(38) As a particular embodiment, FIG. 9 shows outer walls which are made up of sheet metal strips having unperforated regions for the outer wall 53 and perforated regions for the sheet-like structure 51 having openings. The four segments 63 shown and also the sheet-like structure 51 having openings can thus be made of only four sheet metal strips. These are joined in a fluid-tight manner, for example by welded seams, at the indicated points. Such an embodiment, too, can be utilized for producing any further geometry of the outer wall 53 and of the sheet-like structure 51 having openings.

(39) Furthermore, it is also possible in the case of an embodiment having four segments 63 to configure the cathode space 65 with any cross section. Thus, the cross section can, for example, be circular, as shown in FIG. 9, or essentially square, as shown in FIGS. 10 and 11. In the case of an essentially square cross section, the segments 63 can, for example, in each case extend from the middle of one side via the corner to the middle of the adjacent side, as shown in FIG. 10. As an alternative, it is also possible, as shown in FIG. 11, for the segments 63 to extend along one edge of the square.

(40) An embodiment having six segments 63 is shown in FIG. 12. Here, the segments 63 are in each case separated from one another by an outer wall element 73. The walls on the outside of the individual segments 63 are straight, so that a hexagonal cross section is obtained. However, any other cross section would also be possible here. It is also possible to provide each of the segments 63 with a dedicated outer wall 53 as in the variants shown in FIGS. 7 to 11. To produce a cathode space 65 which has a plurality of segments 63 and in which the segments 63 are in each case separated by an outer wall element 73, it is possible, for example, to use outer wall parts which each comprise the outer wall element 73 and the wall on the outside and subsequently position these next to one another around the sheet-like structure 51 having openings. The individual outer wall parts are then joined to one another in a fluid-tight manner, for example by welding, and thus form the outer wall 53 of the electrochemical cell.

(41) Apart from the embodiments depicted here, any further cross section and any other number of segments 63 are conceivable. However, preference is given here to the cross sections of all segments 63 of an electrochemical cell being identical. Furthermore, instead of the porous felt a porous material being different from porous felt can be introduced into the segments 63. Such a porous material being different from porous felt for example is a woven fabric, a knitted fabric, a knotted fabric, a network, a non-woven, an open-cell foam, or a three-dimensional netting.

LIST OF REFERENCE NUMERALS

(42) 1 Apparatus for storing electric energy

(43) 3 Solid electrolyte

(44) 5 First sealing ring

(45) 7 Lid

(46) 9 Second sealing ring

(47) 11 Displacement body

(48) 13 Upper part of the displacement body 11

(49) 15 Lower part of the displacement body 11

(50) 17 Displacement head

(51) 18 Thread

(52) 19 Flange

(53) 21 Third sealing ring

(54) 23 Fastening means

(55) 25 Connection element

(56) 27 Container for anode material

(57) 29 Riser tube

(58) 31 Connecting tube

(59) 33 Container wall

(60) 35 Lower lid

(61) 37 Upper lid

(62) 39 Insulating bottom plate

(63) 41 Insulating cover plate

(64) 43 Hollow space for accommodating a centering rod

(65) 45 Centering rod

(66) 47 Insulation

(67) 49 Pressure conduit

(68) 51 Sheet-like structure having openings

(69) 53 Outer wall

(70) 54 Bottom plate

(71) 55 Porous felt

(72) 56 Electrochemical cell

(73) 57 Anode space

(74) 59 Gap

(75) 61 Porous electrode

(76) 63 Segment

(77) 65 Cathode space

(78) 67 Channel

(79) 69 Groove

(80) 71 Hollow space

(81) 73 Outer wall element