JPS5935373A - Sodium-sulfur battery - Google Patents

Abstract

PURPOSE:To simplify manufacture of a sodium-sulfur battery and enhance its safety by installing inside a solid electrolyte tube a case having an Na path extending up to near the bottom lid, and installing metallic fiber sintered bodies arranged in specified form in the space formed between the case and the electrolyte tube. CONSTITUTION:A case 10 which is made of a melting resistant Na metal and has an Na path penetrating the center of an upper lid 11 and extending up to near the bottom lid, is provided inside the Na-ion conducting bottomed solid electrolyte tube 1 of an Na-S battery the negative chamber of which consists of the internal space of the tube 1. Next, metallic fiber sintered bodies 13 which are continuous in the horizontal direction and spaced at equal intervals in the vertical direction, are installed in the space formed between the case 10 and the tube 1. After that, a gasified matter is packed in the case 10, and a sulfur-holding formed positive conductive member 5 is inserted in a battery case 3. In this battery, even when a crack develops in the sintered body 13 and its upper adjacent sintered body 13 is consumed by directly reacting with sulfur in the worst case thereby securing safety.

Description

[Detailed Description of the Invention] The present invention relates to) IJ Umu sulfur batteries, particularly when solid electrolyte tubes are damaged; +) To improve battery safety by reducing the amount of direct reaction between ram and sulfur The purpose is to simplify battery manufacturing.

A sodium-sulfur battery uses sodium as a cathode active material and sulfur as an anode active material, and these active materials are separated by a sodium ion conductive solid electrolyte tube 2 such as β-alumina, β'-alumina, etc.

It is a high-temperature secondary battery that operates at a high temperature of approximately 600 to 650°C. Figure 1 shows a conventional battery structure.

1 is a sodium ion conductive bottomed solid electrolyte tube made of β'-alumina, 2 is an α-alumina ring formed by glass soldering the solid electrolyte tube 1, and 6 is a heat source connected to the bottom surface of the α-alumina ring 2 through the A1 layer. This is a battery container that also serves as an anode current collector made of pressure-bonded molten sulfur, polysulfide I, and lithium metals. 4 is molten sulfur/sodium polysulfide as an anode active material. 5 is an anode conductive material made of fibers such as graphite or carbon impregnated with the general substance 4.

Reference numeral 6 denotes a cathode lid made of a molten sodium-resistant metal and bonded to the upper surface of the α-alumina ring 2 through a layer A1. 7 is welded to the cathode cover 6) This is the cathode current collector terminal for IJJ umium filling and exhaust. After filling with thorium, the upper end is sealed. 8 is molten sodium as a cathode active material. 9 is a cathode holding side made of melt-resistant gold metal fiber impregnated with cathode active material 8; The cathode chamber of a conventional sodium-sulfur battery having such a configuration will be described in further detail. Inside the solid electrolyte tube 1, there is a metal fiber 9 having a weight that makes the porosity constant, for example, fiber diameter 8 of 5US316L.
With the temporary terminal arranged, insert μ into the open end little by little and push it in so that the top end of the metal fiber is near the top end of the solid electrolyte tube 1 or the top end of the cathode chamber when fully filled, and then insert the temporary terminal. was pulled out, and the cathode current collector terminal 7 to which the cathode cover 6 was welded was inserted. Thereafter, the cathode lid 6 and the α-alumina ring 2 were bonded together by thermopressure via the i-layer.

In the cathode chamber manufactured in this way, firstly, the packing density of the metal fibers 9 in the solid electrolyte tube 1 is uneven at each location and melts.) The battery performance is not constant due to differences in IJJ capacity and wick effect. There was a drawback. A second drawback is that the solid electrolyte tube 1 may be exposed to certain causes 9 such as mechanical shock.

When cracks occur and are destroyed due to thermal shock, etc.

Molten sodium 8 and molten sulfur 4 undergo a direct chemical reaction through the crack location. The degree of this chemical reaction determines the scale of battery damage, and if the damage is small, the battery container 6
The metal fiber 9 does not change or is only slightly deformed.
Although a large amount of IJJum remains inside the battery, if the damage is large enough, a hole will form in the battery container, the active material will leak out and catch fire, and the sodium 8 in the metal fibers 9 will be destroyed by the action of the lamp wick. There were safety and reliability problems, such as continuous supply and ignition at the outermost surface area of the metal fibers 9.

The present invention overcomes the drawbacks of the prior art and simplifies battery manufacturing. FIG. 2 shows an embodiment of the present invention,
The same numbers as in FIG. 1 indicate the same components. 7' is a cathode current collector terminal which also serves as the filling and evacuation of the cathode active material 8, which is welded to the cathode cover A.

It extends slightly below the cathode cover 6.

After filling the cathode active material 8, the upper end is sealed.

10 is a container made of a molten sodium-resistant metal 9, such as stainless steel. Reference numeral 11 is the upper lid of the container 1o, and 12 is a sodium communication passage welded to the center of the upper lid 11 and extending to the vicinity of the bottom lid of the container 1°. 16 is a band-shaped metal fiber sintered body pressure-sintered with metal fibers such as stainless steel or iron nuts;
They are fixed to the outer surface of the container 10 in a ring shape and at regular intervals in the height direction of the battery. Also.

The upper open end of the sodium communication path 12 is connected to the cathode current collector terminal 7.
' is positioned so as to be inserted into or located near the lower open end of the '. More specifically, after the sodium communication passage 12 is welded to the upper lid 11, the upper lid 11 is welded to the container 1o.

Next, on the outer surface of the container 1o, metal fibers with a fiber diameter of about 8 μm to 25 μm are pressure-sintered to have a porosity of 94.5% to 98%. Metal fiber sintered band-shaped (ring-shaped) body 1 having a thickness of
6 are fixed at equal intervals in the height direction of the battery by means such as spot welding. Next, the sintered body 16 and the container 1o are inserted into the solid electrolyte tube 1 which is joined to the a-alumina ring 2 by glass soldering. After insertion, a cathode lid 6 with a cathode current collector terminal 7' welded to the top surface of the α-alumina ring 2 is placed via an aluminum foil ring, and an anode lid is placed on the bottom surface via a similar aluminum ring. . Then place them in a thermopressure bonding jig (not shown) and
A vertical load of approximately 400 kqlcr& is applied to the cathode lid and anode lid located on the upper and lower surfaces of the α-alumina ring while heated to 0° C. or higher, and maintained for a maximum of approximately 15 minutes. Next, the structure shown in FIG. 2 obtained in this way (however, the @ pole side is not arranged in this state) was heated to about 150°C in an argon atmosphere, and kept warm. After evacuating from the cathode current collector terminal 7', it is melted at the same temperature by vacuum impregnation method.) After filling a fixed amount of IJJum, the vacuum is released, and after cooling, the upper opening of the cathode current collector terminal 7' is vacuum sealed. .

Note that a gasified substance is inserted into the container 10. Next, the sulfur-impregnated molded anode conductive material is inserted into the battery container 6, the above-mentioned IJum filling structure is placed in the center, and the anode side is vacuum-sealed.

The battery characteristics of the present invention thus obtained will be explained below. Regarding the first drawback of the conventional method, since the metal fiber is a molded body formed by pressure sintering, the non-uniformity of porosity within the metal fiber can be ignored due to the wicking effect of sodium. (Because the fiber arrangement space is extremely small) IJum supply performance is stable. Figure 6 shows the conventional IJium supply performance as a function of changes in polarization voltage. That is, conventionally (1) is energized (from inside the cathode chamber).
While the polarization voltage value increases with the passage of time (current is applied in the discharge direction where IJum decreases), in the present invention (2), almost no change in the polarization voltage value is observed within the required time. In addition, this polarization voltage value change is caused by the solid electrolyte tube 1)
There is also a relationship with the area in contact with IJium, and if the change is large, there is a possibility that areas not wet with sodium have occurred. This is related to the withstand voltage of the solid electrolyte tube, and also affects the lifespan of the solid electrolyte tube. From this, the present invention was able to improve battery performance and also extend battery life.

Furthermore, regarding the second drawback of the conventional method, if a crank occurs in the solid electrolyte tube 1 and breaks, assuming that the crank occurs at a position that corresponds to the metal fiber sintered body on the cathode chamber side, Sodium was consumed in the direct reaction with sulfur, and in the worst case, sodium was consumed in the space between the metal fiber sintered body and the upper metal edge-fiber sintered body. However, sodium in other areas does not directly contribute to the reaction at all, and the scale of battery damage is extremely small, with only slight discoloration of the battery container 3, and unlike conventional cases, there are holes in the battery container and the active material There was no leakage or ignition. The amount of direct reaction could be reduced in this way by arranging the metal fiber sintered bodies discontinuously and at equal intervals in the height direction of the battery, and by placing the metal fibers in close contact with the inner surface of the solid electrolyte tube and the outer surface of the container. By letting it happen, it suddenly becomes
・The ram holding force is reversed in the space between the metal fiber sintered bodies, and has the function of stopping the IJ umium supply. This space between the metal fibers acts as a restraint zone that minimizes the rapid decrease in sodium content, greatly increasing safety.

Example Outer diameter 29φ made of 5t JS3D 4-phase with approximately 0.2 fighting thickness.

A sodium communication path made of a stainless steel pipe with an outer diameter of 6φ, an inner diameter of 1φ, and a length of 295 mm is welded to the top of the container 10 with a height of 300 mm, and a sodium passageway with a width of 10 mm and a thickness of about 1 am is welded to the outer surface of the container 1o. Iron fiber sintered bodies having a porosity of 94.5% and a fiber diameter of 12 μm were spot-welded concentrically, and similar sintered bodies were placed at intervals of about 10 mm in the height direction.

After this container 10 was inserted into a β'-alumina tube 1 having an inner diameter of 61φ, a cathode lid and an anode lid were joined to the a-alumina ring 2, respectively. Next, in an argon atmosphere, about 17
87 sodium was filled into the cathode chamber by vacuum impregnation,
After cooling, a sulfur-impregnated molded anode conductive material was placed, and the anode and cathode were vacuum-sealed. The battery obtained in this way was
As a result of a charge/discharge test at 0°C, no influence of the cathode side on battery performance was observed. Next, a battery destruction test was conducted by applying voltage. When the charging voltage reached about 25 V or higher, the battery voltage showed fluctuations and the battery temperature rose to a maximum of about 600'C. As a result of the battery disassembly investigation, a crank was observed near the bottom of the solid electrolyte tube.
There was no sodium near the crack, and the purple active material was segregated on the anode side. While doing so.

Sodium remains in areas other than the vicinity of the crack.

In particular, sodium remained in the metal fibers at the height before and after the crack.

As described above, the present invention was able to improve battery performance and reliability, such as improving battery safety.

Note that in the present invention, there are no particular limitations on the battery shape, metal fiber material, shape, spacing between metal fibers, container material and shape, etc.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional IJ Umu sulfur battery.
FIG. 2 is a longitudinal cross-sectional view of an IJ Umu sulfur battery according to the present invention, and FIG. 6 is a diagram showing changes in polarization voltage characteristics. 1...Solid electrolyte tube, 9...Metal fiber. 16... Metal fiber sintered body, 10... Container. Applicant Yuasa Battery Co., Ltd. Figure 1 1 l j Ordinance / Figure 2

Claims (1)

[Scope of Claims] 1) In a sodium-sulfur battery whose cathode chamber is inside a sodium ion-conducting solid electrolyte tube with a bottom, a melt-resistant battery that penetrates the center of the top lid and extends to the vicinity of the bottom lid in the solid electrolyte tube) It is characterized by comprising a container equipped with an IJ aluminum gold metal tube, and metal fiber sintered bodies disposed continuously in the horizontal direction and at regular intervals in the vertical direction in the gap between the solid electrolyte tube and the container. sodium-sulfur battery. 2) The IJ Umu sulfur battery according to claim 1, wherein the metal fiber sintered body is at least partially welded and fixed to the outer surface of the container.