JP3264852B2 - High temperature sodium secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature sodium secondary battery using sodium for a negative electrode and sulfur for a positive electrode, and more particularly to a power storage device, an electric vehicle, an emergency power supply,
UPS, peak shift device for a power system, relates to a suitable high-temperature sodium secondary batteries for use in cell utilization system such as frequency and voltage stabilizer.

[0002]

2. Description of the Related Art A high-temperature sodium secondary battery using sodium as a negative electrode and sulfur as a positive electrode has attracted attention for its efficiency and energy density, and is expected to be used for electric power storage devices and electric vehicles. . As a prior art of this high temperature sodium secondary battery, for example,
Some are disclosed in, for example, JP-A-283101 and JP-A-8-171931.

The conventional high-temperature sodium secondary battery includes a negative electrode container, a positive electrode container containing sulfur, sodium polysulfide and the like, a solid electrolyte bag tube for separating the negative electrode container from the positive electrode container, and A sodium container which is provided between the solid electrolyte bag tube and the negative electrode container, contains sodium therein, and is provided with a small hole for supplying sodium to the solid electrolyte bag tube. is there.

By the way, this high-temperature sodium secondary battery, as its name implies, must be maintained at a considerably high temperature during operation. Therefore, in practice, a plurality of batteries are connected and housed in an insulated container. It is customary to use it in a modular form, and when it is put into an operating state, it is heated as required and kept at a predetermined temperature.

[0005]

The prior art described above does not take into account the volume change of sodium due to the temperature change, and has a problem in maintaining reliability. That is, the high-temperature sodium secondary battery needs to be maintained at a predetermined temperature that is considerably higher than the normal temperature during operation. For this reason, it is usual that the high-temperature sodium secondary battery is modularized in an insulated container as described above. Due to the influence of convection and the like, a temperature distribution occurs in the heat insulating container, and for example, the temperature at the upper part of the battery becomes higher than the temperature at the lower part.

[0006] In an actual use state, an operation stop period is required.
The temperature rises and falls between room temperature and the operating temperature of the battery will be repeated, and as a result, the negative electrode container containing sodium will be damaged, especially at its joints, and will generate heat when air enters inside. In addition, there is a possibility that sodium may leak to the outside, and therefore, when actually used as a module, there is a problem in reliability.

[0007] An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art, and there is no danger of heat generation or sodium leakage even when the temperature is repeatedly increased and decreased when the module is used, so that high reliability is always maintained. It is another object of the present invention to provide a high-temperature sodium secondary battery as described above.

Another object of the present invention is to provide a highly reliable power storage device, an electric vehicle, an emergency power supply, an uninterruptible power supply, and a peak shift of a power system by using the above-mentioned high temperature sodium secondary battery. An object of the present invention is to provide a power supply system such as a device and a frequency / voltage stabilizing device.

[0009]

The object of the present invention is to provide a negative electrode container, a positive electrode container containing a positive electrode active material such as sulfur, selenium, tellurium, sodium polysulfide or a metal halide;
A solid electrolyte bag tube that separates between the negative electrode container and the positive electrode container, and is positioned with a gap inside the solid electrolyte bag tube,
A high-temperature sodium secondary battery comprising: a sodium container having small holes for supplying sodium stored in the space; and a means for absorbing a volume change of sodium in the space. You.

[0010] For this reason, in one aspect of the present invention, a space filled with nitrogen gas or an inert gas is formed outside the sodium container and inside the solid electrolyte bag tube and the negative electrode container. I have. Further, in another embodiment of the present invention, the cross-sectional area of at least a part of the space is increased as going upward, and therefore, at least the upper part of the side wall of the negative electrode container or the sodium container forming the space. part, is inclined so that the cross-sectional area of the space portion is increased toward the top or toward the top is provided with a not large step of the cross-sectional area.

The upper part of the space or the upper part of the side wall means the vicinity of the sodium liquid level at the time of cooling and solidification. Further, in one aspect of the present invention, the volume of the space is at least 1%, preferably at least 1% of the volume of sodium in the void inside the sodium electrolyte bag tube and the inside of the negative electrode container. 2.5% or more.

On the other hand, according to one aspect of the present invention, the means for absorbing a change in volume of sodium in the void is constituted by an elastically deforming portion formed on at least one of the negative electrode container and the sodium container. Things. In addition,
It is desirable that the sodium container and the negative electrode container are integrated by means such as joining or welding.

Further, in one aspect of the present invention, a plurality of the high-temperature sodium secondary batteries according to the present invention are used in combination to thereby provide a power storage device, an electric vehicle, an emergency power source, an uninterruptible power source, and a power system peak. It is characterized in that a power supply system applicable to a shift device, a frequency / voltage stabilizing device, or the like is configured.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A high-temperature sodium secondary battery according to the present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention.
Is a solid electrolyte bag tube of sodium ion conductivity, usually
It is made of β ″ alumina sintered body.
Is a positive electrode container, which constitutes a negative electrode chamber and a positive electrode chamber together with the solid electrolyte bag tube 1, respectively. These containers are generally made of aluminum, iron, SUS (stainless steel), or chromium One provided with a corrosion-resistant layer mainly composed of molybdenum, titanium, or the like is used.

Reference numeral 4 denotes an insulating member, and the negative electrode container 2 and the positive electrode container 3
In a predetermined state. The insulating member 4 is made of α-alumina ceramics, and is joined to the negative electrode container 2 and the positive electrode container 3 by a hot pressing method using aluminum or an aluminum alloy. The opening is generally fixed by glass solder.

Reference numeral 5 denotes a sodium container, which is generally made of a material similar to the negative electrode container 2 and the positive electrode container 3 and has a bag-like shape having a small hole 6 for allowing sodium to pass through at the bottom thereof, and is joined to the negative electrode container 2 at the upper portion. Have been.

Reference numeral 7 denotes a carbon mat, which is made of graphite fibers and carbon particles, is housed in a positive electrode chamber to form a positive electrode mold, and functions to impregnate and hold a positive electrode active material.
As a positive electrode active material impregnated in the carbon mat 7, sulfur or sodium polysulfide is used in a sodium-sulfur battery, but selenium, tellurium, or a halide of a metal element is used in other high-temperature sodium secondary batteries. Sometimes used.

Reference numerals 8 and 9 denote sodium encapsulated as a negative electrode active material, and the sodium remaining in the sodium container 5 is represented by sodium 8, and the outer peripheral surface of the sodium container 5 and the inner peripheral surface of the solid electrolyte bag tube 1 are shown. The portion staying in the void formed between the surfaces is represented by sodium 9;
These are communicated by the small holes 6. Here, the amount (height) of sodium 8 in FIG. 1 indicates the amount when the battery is almost completely charged, that is, the amount at the end of charging. To the state shown in FIG.

Numerals 10 and 11 denote spaces, and the sodium container 5
In the upper part inside and outside of the figure, the parts which are not filled with sodium 8, 9 are shown. These spaces 1
Numerals 0 and 11 are formed when sodium 8 and 9 are sealed, and these portions are filled with an inert gas such as nitrogen, argon or helium. Although not shown, it is also possible to provide a bag-shaped safety tube between the solid electrolyte bag tube 1 and the sodium container 5.

In this embodiment, the space 11 is formed, and the volume of the space 11 is present in the gap formed between the outer peripheral surface of the sodium container 5 and the inner peripheral surface of the solid electrolyte bag tube 1. The volume of sodium 9 to be set to a predetermined value, whereby the present invention provides a configuration defined as a means for absorbing a volume change of sodium existing in the void. However, this is based on the following findings.

First, as described above, in the prior art, the temperature of the battery is raised from room temperature to bring the battery into an operating state.
For example, it was found that when the operating temperature was brought to 300 ° C., the junction between the negative electrode container 2 and the insulating member 4 was peeled off, and the reliability of the battery was impaired.

Then, when we investigated the reason for this,
The following was found. First, sodium has a melting point of about 9
Since it is 7 ° C., it is solid at normal temperature (room temperature), and is liquefied at a high temperature of, for example, 300 ° C. when working as a battery. Then, when sodium changes from a solid to a liquid, the volume increases, and therefore, when the battery is changed from a state in which operation is stopped to an operation state, the volume of sodium increases.

On the other hand, when the temperature is raised from room temperature to bring the battery into an operating state, the upper temperature of the battery becomes higher than that of the lower portion due to the temperature distribution generated in the modularized heat insulating container. Melting starts locally from the upper part of, and the dissolved part moves sequentially to the lower side.

If the space 11 is not provided at this time, if only the upper portion of the sodium 9 is locally melted, the lower side of the sodium 9 remains solidified. The expansion cannot act on the space 10 above the sodium 8 via the small holes 6, but acts only on the upper end of the sodium 9 as it is, and acts to push up the negative electrode container 2. For this reason, in the related art, peeling occurs at the junction between the negative electrode container 2 and the insulating member 4.

Therefore, based on this finding, according to the present invention, as described above, the space 11 is formed and the volume thereof is formed between the outer peripheral surface of the sodium container 5 and the inner peripheral surface of the solid electrolyte bag tube 1. The volume of the sodium 9 existing in the gap is set to a predetermined value, thereby providing a means for absorbing a change in the volume of sodium existing in the gap.

Since the space 11 is filled not with solid or liquid sodium but with a gas such as nitrogen or argon, only the upper portion of the sodium 9 dissolves.
Even if the volume increases, the volume increase only compresses the gas in the space 11, and therefore, if the volume of the space 11 is set to a certain level or more, the space 11 Can be suppressed to a predetermined value or less.

Therefore, according to this embodiment, the occurrence of a situation in which the joint between the negative electrode container 2 and the insulating member 4 is separated can be reliably suppressed, and high reliability can be easily obtained. Specifically, the volume of the space 11 may be set to about 2.5% or more of the volume of the sodium 9. Since the volume expansion when sodium is melted is about 2.5%, the volume of the space 11 is thereby reduced by the space formed between the outer peripheral surface of the sodium container 5 and the inner peripheral surface of the solid electrolyte bag tube 1. The volume of the sodium 9 occupying about 97.5% of the entire volume of the part is expanded at the time of melting, and the volume expansion can be reliably absorbed.

As a result, even if the volume expansion when all the sodium in the space is melted is considered, the space 11
By compressing the gas inside, the volume expansion can be absorbed, the pressure by which sodium 9 pushes up negative electrode container 2 can be reduced, and peeling of the negative electrode container joint at the time of temperature rise can be prevented.

This problem is most severe when the bottom of sodium 9 is solidified and all the sodium on it is melted. However, if all of the sodium 9 is melted, it can flow into the sodium container 5 through the small holes 6 provided at the bottom of the sodium container 5, so that the pressure on the negative electrode container 2 hardly occurs at this time. Even if the entire volume expansion of sodium 9 is not absorbed by the space 11, sufficient reliability can be obtained in practical use.

Therefore, in the above embodiment of the present invention,
The volume of the space 11 is about 1%, which is about half of the above 2.5%.
Only by the above, it is possible to prevent the joint portion of the negative electrode container 2 from being damaged, and to remarkably improve the reliability with respect to the temperature rise and fall in a state where the temperature gradient is provided vertically such as a module.

Further, since the volume ratio of the space portion 11 becomes smallest at the end of charging in which the amount of sodium in the negative electrode shown in FIG. 1 is largest, the temperature rise at the end of charging becomes the most severe.
Therefore, in this case as well, it is desirable that the volume of the space portion 11 satisfies the above value.

Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 2, the parts denoted by the same reference numerals as those in FIG. 1 represent the same parts. Therefore, the difference between the embodiment of FIG. 2 and the embodiment of FIG. The upper portion is formed so as to converge upward in a conical shape. As a result, the cross-sectional area of a void existing between the outside of the sodium container 5 and the inside of the solid electrolyte bag tube 1 and the inside of the negative electrode container 2 is reduced. Inside, is that it gets larger as you go up.

In FIG. 2, a slope is provided at the upper part of the side wall of the sodium container. However, a similar effect can be obtained by providing a step so that the upper cross-sectional area becomes large instead of the slope. According to the embodiment of FIG. 2, since the volume of the space portion 11 can be easily increased without changing the height of the battery, the volume expansion accompanying the melting of sodium can be easily absorbed. In addition, the pushing pressure applied to the negative electrode container 2 can be reduced, and the reliability of the battery can be greatly increased.

At this time, of the space portions to be formed outside the sodium container 5 and inside the solid electrolyte bag tube 1 and the negative electrode container 2, the space portion near the sodium liquid surface at the time of cooling and solidification goes upward. It is desirable that the larger the space cross section is, the larger the space cross section is. In this case, as shown in FIG. 2, if the space cross-sectional area near the sodium liquid surface during cooling and solidification is continuously changed and the cross-sectional area is increased upward, the same applies even if the liquid surface position slightly changes. Product effect is improved, and the product yield is improved.

According to the embodiment shown in FIG. 2, this condition is easily attained by forming the upper portion of the sodium container 5 so as to be conically narrowed upward. As an embodiment of the present invention which satisfies this condition, although not shown, the shape of the sodium container 5 is the same as that of FIG. It may be formed in a shape.

By the way, as an extreme case, assuming that the bottom of sodium 9 is completely solidified and all the sodium thereon is melted, in this case, as described above, the volume of the space 11 is It is necessary that the space volume outside the sodium container 5 is about 2.5% or more of the space volume inside the solid electrolyte bag tube 1 and the negative electrode container 2. However, since the thermal conductivity of sodium is high in practice, Such cases do not usually occur.

That is, actually, when the sodium at the top is melted, the sodium at the bottom is also melted or softened,
As a result, it is normal that the pushing up of the negative electrode container 2 due to the volume expansion of the sodium 9 and the inflow into the sodium container 5 through the small holes 6 occur simultaneously.

In such a case, as in the embodiment of FIG. 2, the cross-sectional area of the upper space inside the solid electrolyte bag tube 1 and the negative electrode container 2 outside the sodium container 5 increases as going upward. In the case of the structure, even if the volume of the space portion 11 is about 2.5% or less of the volume of the space inside the solid electrolyte bag tube 1 and the inside of the negative electrode container 2 outside the sodium container 5, , And a high-temperature sodium secondary battery sufficiently reliable with respect to temperature rise and fall when actually used as a module can be easily obtained.

Next, still another embodiment of the present invention will be described with reference to FIG. Also in the embodiment of FIG. 3, the parts denoted by the same reference numerals as those in FIG. 1 or FIG.
It represents the same part. The embodiment of FIG. 3 is different from the embodiment of FIG. 1 or FIG. 2 in that bellows-like elastic deformation portions 21 and 51 are formed on the cylindrical portion of the negative electrode container 2 and the upper portion of the sodium container 5, respectively. In that it is.

First, the elastic deformation portion 21 is formed in a ring shape swelling in the inner circumferential direction from the cylindrical portion of the negative electrode container 2 and operates as a well-known bellows. Therefore, the deformable portion 21 allows the negative electrode container 2 to easily expand and contract along the axial direction of the cylindrical portion according to the internal pressure.

Next, the elastically deformable portion 51 is formed in a ring shape swelling in the inner circumferential direction from the sodium container 5, and also operates as a bellows. Therefore, the sodium container 5
The deformable portion 51 can easily expand and contract in the axial direction according to the internal pressure.

In the embodiment shown in FIG. 3, the portion corresponding to the space 11 in the embodiment shown in FIGS. 1 and 2 may not be provided. In the illustrated case, the sodium 9 is stored in the negative electrode container 2 and the sodium container. The space between 5 is completely filled without leaving a space at the top.

When the volume of the sodium 9 changes, the respective elastically deforming portions 21 and 51 easily elastically deform accordingly, and the negative electrode container 2 and the sodium container 5 move in the axial direction.
It expands and contracts (in the vertical direction in the figure), and the volume at the top of the gap changes.

Therefore, according to the embodiment shown in FIG. 3, the change in volume of sodium 9 is absorbed by the change in volume at the upper part of the void, and as a result, the pushing pressure applied to the negative electrode container 2 is reduced. As a result, since there is no possibility that excessive stress is generated between the negative electrode container 2 and the insulating member 4, the reliability of the battery can be greatly increased.

In the embodiment shown in FIG. 3, it is desirable to design the elastic deformation portions 21 and 51 so that the amount of deformation does not exceed the elastic limit. If the material constituting these containers exceeds the elastic limit, plastic deformation occurs, and the deformation is accumulated due to repeated temperature rise and fall of the battery, causing permanent deformation, which may make it impossible to follow the volume change of sodium 9. is there.

Here, instead of the ring-shaped elastic deformation portions 21 and 51 in the embodiment of FIG. 3, the upper surface of the negative electrode container 2 is formed thin, and the volume change of the sodium 9 is absorbed by the elastic deformation of this portion. You may be able to. However, even in this case, it is desirable that the amount of deformation does not exceed the elastic limit.

In the embodiments shown in FIGS. 1, 2 and 3, as shown in FIGS.
It is integrated with the negative electrode container 2 by means such as joining or welding. As a result, according to these embodiments, even if the volume of the space portion 11 fluctuates and the liquid level of the sodium 9 decreases, it is possible to eliminate the possibility that the conduction between the sodium 9 and the negative electrode container 2 is interrupted, and therefore, In addition, the reliability of the battery for charging and discharging can be greatly improved.

As described above, according to the embodiment of the present invention, a high-reliability high temperature sodium secondary battery can be easily obtained. This makes it possible to easily realize a power supply system that is useful as a highly reliable power storage device, electric vehicle, emergency power supply, uninterruptible power supply, power system peak shift device, frequency / voltage stabilization device, and the like.

Hereinafter, embodiments of the present invention will be described more specifically. In the specific example, first, a bag tube made of a lithium-doped β ″ alumina sintered body was used as the solid electrolyte tube 1. A high chromium SUS material was used for the negative electrode container 2, the positive electrode container 3, and the sodium container 5. Was.

Then, the inside of the sodium container 5 is filled with sodium and argon gas of about 0.1 atm. At this gas pressure, sodium 8 comes out of the small hole 6 of the sodium container 5 and is filled with the solid electrolyte bag. Into the gap between 1 and
It was retained as sodium 9 so as to cover the inner surface of the solid electrolyte bag tube 1.

The size of the small hole 6 was 0.3 mm in diameter, and the size of the void portion due to the difference between the outer diameter of the sodium container 5 and the inner diameter of the solid electrolyte bag tube was about 1 mm. And
In the embodiment of FIGS. 1 and 2, sodium 9
In a state in which the battery is completely charged (at the end of charging) and argon gas is filled, in the case of FIG. 1, the volume of the space 11 is balanced by about 1% or more of the volume of the sodium 9 in the void. In the case of FIG. 2, the gas pressure in the space 1 was adjusted so that the volume of the space 11 was balanced with about 0.5% or more of the volume of the sodium 9 in the gap.

On the other hand, a positive electrode mold made of sulfur and carbon fiber mat 7 is placed in the inside of the positive electrode container 3, and about 0.1
Atmospheric nitrogen gas was charged.

Further, as the insulating member 4, an α-alumina ring is used, which is glass-bonded to the solid electrolyte bag tube 1 and an aluminum-silicon-magnesium alloy foil is used. The container 3 was joined by a thermal pressure welding method to obtain the sodium-sulfur battery according to the embodiment of FIGS. 1, 2 and 3. And
The capacity of the battery thus obtained was about 360 Wh, the rated output was about 45 W, the electromotive force in the two-phase region was 2.07 V, and the internal resistance of the battery was 3.5 mΩ.

Next, assuming the worst state in an actual module using a plurality of batteries, a temperature difference of about 100 ° C. (high temperature at the top) was given above and below the obtained battery, and the bottom temperature was changed to room temperature. The temperature was repeatedly raised and lowered 100 times within a range of about 300 ° C., and as a result, no damage was found at the joint portion of the negative electrode container 2, which proved to have extremely high reliability.

In the case of the embodiment shown in FIG. 2, the outer diameter of the sodium container 5 at the portion facing the solid electrolyte bag tube 1 is set to 38.
mm, and the outer diameter of the connection portion with the negative electrode container 2 is set to 32 mm.
It had an inclination of 0 °.

This battery is placed in the module in the same vertical temperature distribution as the normal operation state (the upper part of the battery is about 5
(0 ° C high temperature) and the bottom temperature is from room temperature to 350 ° C.
As a result of a temperature rise / fall test performed 100 times in the range of ° C., no damage was found at the joint of the negative electrode container 2.

Here, assuming that the temperature rises and falls twice a year, the above results correspond to the evaluation of the life for 50 years.

Therefore, according to the power supply system in which a plurality of high temperature sodium secondary batteries according to the embodiment of the present invention are modularized, a power storage device, an electric vehicle, and an emergency power supply having high reliability and excellent safety are provided. It is possible to easily realize an uninterruptible power supply, a power system peak shift device, a frequency / voltage stabilizing device, and the like.

[0059]

According to the present invention, even if the temperature rises and falls in a state with a temperature distribution assumed when used as a module, there is no fear that the negative electrode container or its joint is broken, The reliability of the secondary battery can be significantly improved.

Therefore, by using the high-temperature sodium secondary battery according to the present invention, a highly reliable power supply system can be obtained, and a highly reliable and highly safe power storage device, an electric vehicle, an emergency power supply, and an uninterruptible power supply can be obtained. It is possible to easily realize a power supply, a power system peak shift device, a frequency / voltage stabilizing device, and the like.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a high-temperature sodium secondary battery according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the high-temperature sodium secondary battery according to the present invention.

FIG. 3 is a sectional view showing still another embodiment of the high-temperature sodium secondary battery according to the present invention.

[Explanation of symbols]

Reference Signs List 1 solid electrolyte bag tube 2 negative electrode container 3 positive electrode container 4 insulating member 5 sodium container 6 small hole 7 carbon mat (positive electrode mold) 8 sodium (sodium existing in sodium container 5) 9 sodium (solid electrolyte bag tube 1 Sodium container 5
Sodium present in the gap between the two) 10, 11, space 21, 51 elastic deformation

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyoshi Ishihama 3-181-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Ibaraki Hitachi Information Service Co., Ltd. (72) Seiichi Horie Inventor 3-2-1 Sachimachi, Hitachi City, Ibaraki Prefecture No. 1 Hitachi Engineering Co., Ltd. (56) References JP-A-6-163074 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/39

Claims (3)

(57) [Claims] 1. A negative electrode container, a positive electrode container containing a positive electrode active material, a solid electrolyte bag tube for separating the negative electrode container and the positive electrode container, and a space inside the solid electrolyte bag tube, A high-temperature sodium secondary battery including a sodium container having a hole for supplying sodium stored therein into the gap, wherein an outer wall surface of the sodium container, the solid electrolyte bag tube and
And at least one inner wall surface of the negative electrode container.
And the volume is the volume of sodium in the void.
Gas containing at least 1.0% inert gas
A space is formed, and this gas space forms
A high-temperature sodium secondary battery characterized by absorbing a change in volume of lithium. 2. The invention according to claim 1, wherein said space portion is
Less of the negative electrode container and the sodium container to be formed
The upper side wall, the section of the space part
A high-temperature sodium secondary battery characterized by being inclined so as to have a large product or provided with a step . 3. A negative electrode container and a positive electrode containing a positive electrode active material.
Container and a solid-state battery that separates these negative and positive electrode containers.
With a void inside the solid electrolyte bag tube and the solid electrolyte bag tube
To supply the sodium stored inside into the space
Sodium container having a hole for cooling
In the thorium secondary battery, at least one of the negative electrode container and the sodium container
Forming an elastically deformable portion, and the elastically deformable portion forms
High temperature characterized by absorbing the volume change of sodium
Sodium secondary battery.