JPH01194275A - Electrochemical cell - Google Patents

Abstract

PURPOSE: To lower the height of a suction section and improve performance by making the horizontal cross section of the upper portion of a positive electrode chamber larger than that of the lower portion, and filling the lower portion with a positive electrode alkaline metal in the completely discharged state of a battery. CONSTITUTION: A separator tube 24 made of β-alumina is arranged in a case 18, and a positive electrode chamber is formed between the separator tube 24 and the case 18. An electrolyte 14 is filled between a negative electrode 16 made of an electrolyte-permeable matrix and the separator tube 24. The case 18 is constricted at a position 36, the upper portion 40 has a horizontal cross section larger than that of the lower portion 38, and a positive electrode metal made of fused sodium 12 is sealed to fill the lower portion 38 in the completely discharged state. The level of the upper portion of the fused sodium 12 is increased or decreased according to a charge or a discharge, however suction can be set to a relatively low height because the cross sectional area of the upper portion 40 is large.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrochemical cells. More particularly, it relates to rechargeable high temperature electrochemical power storage cells having a molten alkali metal anode separated from a cathode by a separator.

In accordance with the present invention, there is provided a rechargeable high temperature electrochemical power storage battery having a molten alkali metal anode separated from a cathode by a separator, the separator separating an anode compartment containing said alkali metal and a cathode compartment containing a cathode compartment. the separator is for releasing the discharge of the battery in the form of ions from the anode compartment to the cathode compartment;
The cell has an operating position in which it is upright, in which the separator extends at an angle to the horizontal, so that the level of the surface of the anode metal in the anode compartment relative to the separator is The anode compartment has an upper part with a horizontal cross section larger than that of the lower part and the upper part of the anode compartment. and a lower portion that is completely filled with anode metal in a fully discharged state of the cell.

The separator is a solid electrolyte conductor of anode metal ions, the separator is in the form of a cylindrical tube with one end closed and the other end open and having a hollow interior, and the separator tube is inside the battery container. and thus in said operating position of the cell, the closed end of the tube is at the uppermost side and the open end of the tube is at the uppermost side, the interior of the tube forming one electrode compartment, and the tube Set the tube away from the container:
When the compartment is external to the tube it usually has a circular or annular cross section; when the compartment is external to the tube it usually has an annular cross section. Because the horizontal annular cross-section of the lower part of the anode compartment is smaller than that of the upper part, in this type of cell the upper part has a smaller horizontal or radial dimension than the upper part.

Thus, if the anode compartment is annular, the annular band in the upper part will be thicker than that in the lower part.

Separator tubes usually have a constant diameter (as the tubes as mentioned above are typically made), so in a case with a circular cross section, by changing the diameter of the case, different horizontal cross sections can be created on the upper and 1/2 sides. Hold it in a portion. or by positioning the insert in the lower part of the anode compartment (e.g., a tubular inlet if the anode compartment is on the outside of the tube, or a cylindrical or tubular inlet when the anode compartment is inside the tube). 1 note), the insert is concentric to the tube and n radially spaced from it. Alternatively, the insert may be in powder or granular form.

In a special embodiment, the separator tube has a constant diameter, the interior of the tube forms a cathode compartment, the container has a circular cross section in which the tube is arranged concentrically, and the tube and container The space of the gate is circular Il! ! very! Form the Ili chamber.

If the anode compartment is annular in horizontal section, the thickness of the annular band is preferably as small as practicable, for example about 0.1 to 0.2 #l+11 for practical purposes. Similarly, the upper part of the anode compartment should have an upper end as high as practicable, which is at least as high vertically as the center point of the separator. Accordingly, in a particular embodiment of the invention, the thickness of the lower part of the annular band of the anode compartment is preferably at most 0.2 m, such that in said operating position of the cell the lower part of the anode compartment has a thickness of at most 0.2 m. having ends at a level no lower than the midpoint level of the length.

Preferably the volume of the upper part of the anode compartment is selected as follows. That is, when the battery is fully charged, the upper part is substantially filled with the anode metal, and when the battery is fully charged, it is substantially empty, but the lower part remains filled at all times. It is. In other words, the volume of the upper part of the anode compartment is
associated with the battery container such that the upper portion is substantially filled with anode metal when the battery is fully charged;
Thus, when the battery is in its operating position and the battery is fully discharged, the level of anode metal in the anode compartment is illuminated by the anode compartment.

In order to promote wetting of the entire surface of the separator exposed in the anode compartment, said surface can be lined with wicking material in the upper part of the housing. The surface of the separator exposed in the anode compartment is then lined with a wicking material for wicking of the anode metal.

When the cell is in its operating position, the wicking material extends downwardly into contact with the anode metal in all states of charge of the cell. Such wicking materials can be selected from the group consisting of metal gauze, metal powder sieves held to the separator by porous metal screens, sintered porous metal linings, and felt linings. Naturally, it can be suitably converted to other types of wicking materials.

In principle, the height of the suction should be as low as possible, and from this point of view it is desirable for the upper part of the anode compartment to have a cell with a qualitatively constant outer diameter and no spaces between them.

So when the anode compartment is outside the separator tube, it is desirable to have a deep upper section and slightly wider than the lower section.

In practice, the depth and width of the upper section would have to be compromised between these opposing desires in order to give the section the required volume.

Typically, the separator is an alkali metal ion separator, such as Nasicon.
) or beta-alumina, preferably beta-alumina, although the invention is also applicable in principle to other types of separators. Such separators are, for example, molecular sieves of tectosilicate, such as zeolites, which contain the alkali metal of the anode incorporated into its microporous interior, typically less than 50 angstroms F, especially less than 20 angstrom units. It has passageways, windows, and holes of size. In each case, the above-mentioned advantage of reducing the suction to a minimum is achieved in principle.

Sodium/sulfur cells containing thorium sulfide/polysulfide, or the cathode is an electronically conductive electrolyte-permeable matrix impregnated with a liquid electrolyte, the liquid electrolyte being an aluminium-based metal. A molten mine electrolyte of a halide, preferably sodium aluminum chloride, is a 1:1 equimolar mixture of alkali metal halide and aluminum halide. In embodiments of the invention, the matrix is Fe, Ni, co, Cr, M
n.

and at least one member of the group consisting of compounds of said transition metals, together with a script.

and at least one non-metal from the group consisting of silicon, boron, nitrogen and phosphorus.

Typically, the separator is a solid electrolyte conductor of sodium ions, the anode metal is molten sodium, the active cathode material, the electrolyte in the negative compartment, the cathode material in the cathode compartment (kalite), etc. As mentioned above there is a reasonably wide selection.

The invention will be illustrated by way of example with reference to the accompanying schematic drawings, in which: FIG.

In the drawings, reference numeral 10 generally indicates an electrochemical cell 10 according to the invention. Cell 10 comprises a molten sodium active anode material 12, a molten sodium aluminum chloride mine electrolyte, and an electrolyte containing FeCl2 in dispersed form as the electrolytic and charged active cathode material.
Contains a permeable porous iron matrix. Alternatively, for example, the matrix may be porous nickel containing N i G l 2 in dispersed form as the charged active cathode material.

The matrix of cathode 16 is saturated with electrolyte 14;
With a sufficiently finely divided Na1l dispersed therein, the electrolyte 14 is an equimolar mixture of NaCl and AlCl3, i.e. exactly stoichiometrically NaAlc'4, in all loading conditions of the active cathode material. I guarantee that there is.

The battery 10 has an outer container or case 1 of mild steel with a bottom 20.
*Iy, the bottom holds the case in an upright configuration as shown. The case 18 is sealed in an alpha alumina insulating ring 22. A beta alumina separator tube 24 with an open end is located concentrically with the case 18, with the lower end of the tube 24 being open-ended and the upper or open end of the tube 24 being sealed to a ring 22 of alpha alumina. The model is glass-welded. The 1-1 end of the tube 24 is closed with a mild steel closure disc 26, which is surrounded by an alpha alumina ring 22.
is sealed. An anode terminal post 28 is welded to the case 18, while a cathode terminal post 30 extends downwardly into the electrolyte 14 through a sealed central opening in the disk 26. The F portion of the post 30 is embedded in the matrix of the cathode 16 and is in electronic contact therewith. The matrix acts as a cathodic current collector. Above the electrolyte 14 is an inert gas space 32 and also contains sodium 12
Above is an inert gas space 34.

The space between case 18 and tube 24 is occupied by sodium 12 and forms the anode compartment. Also, the tube 24
The interior of the cathode compartment forms the cathode compartment. These compartments are separated from each other by a separator tube 24 and by sealing the tube 24 and by sealing the case 1B and the disk 26 to a ring 22 of alpha alumina.

The overall charge/discharge reaction of the battery is illustrated by the following reaction.

Sodium thus moves from the cathode compartment to the anode compartment through the separation tube 24 during charging, and vice versa during discharge. During the discharge, F e / F e
C; I 2 The volume of active cathode material rises increasing to the level of electrolyte 14 in the cathode compartment, while there is a corresponding fall in the level of active anode material in molten sodium in the anode compartment. During charging, the active molten sodium anode material 12 in the anode compartment rises, while the level of molten electrolyte 14 undergoes a corresponding fall due to a decrease in the volume of the Fe/FeCl2 active pole material. occurs.

1, it can be seen that the container 18 is constricted at 36, so that the anode compartment defined between the tube 24 and the case 18 has a lower portion 38 and an upper portion 40. The upper part has a larger horizontal cross section than the lower part. In other words, the tube 24 and case 1 in the upper part 40 of FIG.
The annular space between 8 and 8 has a substantial width greater than the width indicated at 8 in the lower portion 38.

Referring to FIG. 2, case 18 has a substantially constant diameter. However, a similar effect can be obtained by providing an inert cylindrical insert 42 in the lower part of the case 18, in contact with the case 18 and remote from the tube 24.

Insert 42 may be of solid, hollow or particulate construction. Similarly, the anode compartment has an upper portion 40 and a lower portion 38, with the width A of the upper portion 40 being greater than the width A of the lower portion 38 defined between the tube 24 and the insert 42.

In FIG. 1, the solid line portion of the upper part 40 of the case is the battery compartment. The upper portion 40 therefore has a relatively large depth and a relatively small value. Without considering the density and close packing, the upper part has a smaller depth and a larger value of A, as indicated by the dotted line 40.1 in FIG.

In each upper section 40, the outer surface of the tube 24 is lined with a wick 44. This wick 4
4 is shown in detail in FIGS. 3 and 4, generally designated 44, and it can be seen that it is in contact with a portion of tube 24.

The wick 44 has an inner layer 46 of fine pore porous material, an outer layer 48 of coarse pore porous material, and an outermost gauze layer 5.
It consists of G. The Gurpi layer positions the 8146.1i48 relative to each other and also relative to the tube 24.

Case 18 (Figure 1) and case 18 and insert 4
2 (FIG. 2) are such that the lower part 38 of the anode compartment always remains charged with sodium 12 in all states of charge of the battery, and that each upper part 38 remains charged with sodium 12 when the battery is completely discharged. Portion 40 is selected to be substantially empty of sodium 12.

During charging of the battery, sodium enters the anode compartment, the level of sodium 12 therein increases and the deposits in the gas space 34 decrease. The sodium level also decreases during discharge.

Preferably, however, the entire outer surface of tube 24 is wetted with sodium during all conditions of discharge, so that wick 44 serves to wick molten sodium upwardly over the entire outer surface of tube 24.

However, it is difficult to siphon sodium upward against gravity, and it is not easy to act over a substantial height. That is why the battery 10 includes an upper section 40 and a lower section 38, with the lower section 38 designed to be constantly filled with sodium.

This allows the sodium to be wicked only into the upper section 40, acting over a relatively low height which is less than the overall height of the tube 24. It will be noted in this regard that the spacing is as small as possible, on the order of 0.1 to 0.2 shields, and that one side portion 38 extends at least over half of the tube 24.

Referring to FIGS. 3 and 4, when layer 946 and layer 48 are maintained saturated with sodium at all times and gauze layer 50 is exposed in gas space 34, sodium oxide is added over the layer as shown at 52. It is seen holding pools or droplets of water. From this point of view, it can be seen that the material of the wick is preferably one that can be easily wetted with sodium, and is preferably a transition metal such as iron, nickel, or the like. In the detailed configuration, the gauze layer 5
0 has a plurality of structures 54 that hold the sodium therein as pools or droplets 52. These Wi artificial animals 5
4. basket-shaped, distributed at intervals over the outer portion of said outer layer 48, or with vertically spaced peripherally extending trough-like channels extending around said layer 48; could be. Those in FIG. 3 are partial-circular cross-sections, and those in FIG. 4 show vertically elongated cross-sections. Of course, if necessary, a more rigid gauze or mesh 50 could also be used, including an expanded metal diamond mesh with sodium droplets 52 in contact with the outer layer 48. It fulfills the function of maintaining.

A similar view of another battery of the invention, FIG. 3 a detailed view on an enlarged scale of the wick of the battery, and FIG. 4 a detailed view of a modification of FIG. 3.

10...Battery, 12...Anode material, 1
4... Electrolyte, 16... Cathode material, 1
8... Container (case), 24... Separator tube, 38... Lower part, 40...
・Upper part, 44...Wick (wicking material)
, 52... Sodium pool or droplet, 54
······Structure.

Claims (8)

[Claims] (1) A rechargeable high temperature electrochemical power storage battery having a molten alkali metal anode separated from a cathode by a separator, the separator comprising an anode compartment containing the alkali metal and a cathode compartment containing the cathode. and the separator allows the anode alkali metal to pass therethrough during discharge of the cell from the anode compartment to the cathode compartment, and the alkali metal for reaction with the cathode in the cathode compartment. in the form of ions, and the cell has an operating position in which it is upright, in which the separator extends at an angle to the horizontal, so that the anode separation relative to the separator is It shows the surface level of the anode metal in the chamber, which falls when the battery is discharging and rises when the battery is charged, and the anode compartment is lower than the lower part and the horizontal section of the lower part. a cell having an upper part with a large horizontal cross-section, and a lower part which is completely filled with anode metal in the fully discharged state of the cell. (2) The separator is a solid electrolyte conductor of anode metal ions, and the separator is in the form of a cylindrical tube that is closed at one end and open at the other end and has a hollow interior, and the separator tube is inside the battery container. arranged and thus in said operating position of the cell, the closed end of the tube is at the bottom and the open end of the tube is at the top, the interior of the tube forms one electrode compartment, and the tube 2. The cell of claim 1, wherein the cell is spaced apart from the container, thereby defining a space between the tube and the container, which forms another electrode compartment. (3) the separator tube has a constant diameter, the interior of the tube forms a cathode compartment, the container has a circular cross section and the tube is arranged concentrically therein, and the tube and container are connected; 3. The cell of claim 2, wherein the intervening space forms an annular anode compartment. (4) the radial thickness of the lower part of the annular band of the anode compartment is at most 0.2 mm, and when the cell is in said operating position, the lower part of the anode compartment has a length of the separator; 4. A cell according to claim 3, having an upper end at a level not lower than the level of the midpoint of the cell. (5) The volume of the upper part of the anode compartment is related to the capacity of the battery such that when the battery is fully charged said upper part is substantially filled with anode metal, so that the battery is in its operating position. When the cell is fully discharged, the level of anode metal in the anode compartment is at the top of the lower part of the anode compartment; 5. A battery according to any one of claims 1 to 4, wherein the battery is substantially filled with anode metal. (6) The surface of the separator exposed in the anode compartment is lined with a wicking material to wick the cathode metal, and when the battery is in its operating position, the wicking material is 6. A battery according to any one of claims 1 to 5, wherein the raised material extends downwardly into contact with the anode metal. 7. The battery of claim 6, wherein the wicking material is selected from the group consisting of metal gauze, metal powder held to the separator by a porous metal screen, a sintered porous metal lining, and a felt lining. (8) The battery according to any one of claims 1 to 7, wherein the separator is a solid electrolyte conductor of sodium ions, and the anode metal is molten sodium.