JP3265941B2 - Sodium sulfur battery and battery system using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reliable and suitable battery system for an electric power storage device, an electric vehicle, an emergency power source, an uninterruptible power source, a power system peak cut device, and a frequency / voltage stabilizing device. TECHNICAL FIELD The present invention relates to a high-performance sodium-sulfur battery and a battery system using the same.

[0002]

2. Description of the Related Art A sodium-sulfur battery using sodium as a negative electrode and sulfur or the like as a positive electrode has attracted attention because of its high efficiency and energy density, and is expected to be used in power storage devices and electric vehicles. However, there is a problem that highly corrosive sulfur and sodium polysulfide corrode the positive electrode container and deteriorate the characteristics of the battery, which is a practical bottleneck. In order to address this problem, many methods have been proposed for providing a corrosion-resistant coating mainly composed of Cr, Mo, Ti, Al, C, etc. on the inner surface of the positive electrode container. Due to defects and the like, the reliability is not sufficient compared to the case where a bulk material is used as the positive electrode container. On the other hand, as an example using a bulk metal material as the positive electrode container,
As disclosed in JP-A-59-165378, JP-A-57-57861 and JP-A-56-130071, Fe alloys containing a large amount of Cr have been proposed. When making a positive electrode container using these materials, it is most preferable in terms of reliability and operation that the positive electrode container is finally sealed by a welding method, but in the conventional method, the corrosion resistance of the welded portion is more than that of the base material. As a result, there is a problem that the corrosion rate due to sulfur or sodium polysulfide becomes larger than the value expected from the corrosion resistance test of the test piece. As a result, there remains a reliability problem that the reliability of the battery becomes insufficient, and the corrosion resistance changes due to the difference in welding conditions, and the life prediction becomes difficult. Examples of using the welding method for the Fe-based positive electrode container include JP-A-2-144858 and JP-A-61-1.
JP-A-0881 and JP-A-48-43129 are known. In JP-A-2-144858, a corrosion-resistant coating material is used as a positive electrode container material. Has a problem that the reliability of the battery is low because the corrosion resistance of the battery is significantly reduced.
On the other hand, in JP-A-61-10881, stainless steel, Fe-Cr-Al alloy, and Al-coated Fe are used as an anode lid.
Stainless steel, Fe-Cr-Al alloy as anode auxiliary lid,
Although the use of an Fe—Cr—Al—Y alloy is described, there is no description about the material of the battery case which is the main body of the cathode container material. Regarding the Fe alloy constituting the auxiliary lid, the amount of Cr,
There is no description of the amount of C. Further, in Japanese Patent Application Laid-Open No. 48-43129, SUS304 (Cr18-20
Wt%, 8-10,5 wt% Ni, Fe remaining). SUS304 is excellent in weldability, but inferior in sulfur resistance, and cannot provide sufficient reliability. In case of Fe alloy, C
O-based alloys and Ni-based alloys have higher residual strain and lower corrosion resistance than Ni-based alloys, and have a higher resistance to corrosion products, iron sulfide, than cobalt sulfide and nickel sulfide. In order to produce a highly positive electrode container by a welding method, it is necessary to limit the composition of the Fe alloy to be used to an appropriate range, but such considerations have not been made conventionally.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable sodium-sulfur battery which is free from the above-mentioned drawbacks of the prior art and is less likely to cause deterioration in characteristics due to corrosion of the positive electrode container. Another object of the present invention is to provide a highly reliable power storage device, an electric vehicle, an emergency power source, an uninterruptible power source, a power system peak cut device, and a frequency / voltage stabilizing device using the sodium-sulfur battery. And other battery systems.

[0004]

In order to achieve the above object, a sodium-sulfur battery of the present invention comprises a negative electrode container containing sodium, a positive electrode container containing a positive electrode mold made of sulfur or sodium polysulfide, and , A sodium ion conductive solid electrolyte separated between positive electrodes, and
Is connected to the solid electrolyte, before SL negative electrode container, Seikyokuyo device to <br/> joined insulated member, the sodium-sulfur cell comprising the positive electrode container, the high corrosion resistance containing Cr Co
Group, or are integrated by welding a plurality of components made of Ni-based alloy material Rutotomoni, the Seikyokumo applied to the weld
A mechanism for reducing the stress from the solder is provided, and the material constituting the positive electrode container has a Co content of 30% by weight or more, a Cr content of 18 to 32% by weight, and a C content of 0.1%.
2 wt% or less Co-based alloy or Ni content 40
The alloy is characterized by being a Ni-based alloy having a Cr content of 18% to 32% by weight and a C content of 0.2% by weight or less.

[0005]

[0006]

[0007] Further, as a material constituting the positive electrode container, instead of a Co-based alloy or a Ni-based alloy, Fe having a Cr content of 22 to 32% by weight and a C content of 0.2% by weight or less is used.
May be used. The alloy preferably further contains 14 to 24% by weight of Ni, and more preferably the content of Cr is 23 to 30% by weight.

As the Fe alloy, a duplex stainless steel comprising austenite and ferrite or a ferritic stainless steel having a high Cr content can be used. Also,
It is particularly desirable that these Fe alloys contain 1 to 10% by weight of Mo.

Furthermore, the battery system of the present invention is a power storage device, an electric vehicle, an emergency power source, an uninterruptible power source, a power system peak cut device or a frequency / voltage stabilizing device using the sodium sulfur battery of the present invention. It is characterized by having.

As a result of various studies by the present inventors, as the corrosion of the weld progresses, even if the weld does not come into direct contact with the positive mold, the metal component of the positive container mixes into the positive mold, and To reduce the efficiency and capacity of the battery and to prevent corrosion of the cathode vessel in sodium-sulfur batteries,
It has been found that it is effective to increase the amount of Cr in the material constituting the positive electrode container to increase the corrosion resistance and to reduce the stress applied to the container. This is because, when the amount of Cr is large, a stable chromium sulfide layer is formed on the surface and the subsequent corrosion is suppressed, and when the stress is small, the formed chromium sulfide layer does not peel off and is stable. It is considered to be held on the surface.

Also, the positive electrode container needs to contain a positive electrode mold inside and seal it. Considering that the vapor pressure of sulfur or sodium polysulfide is high at high temperatures, from the viewpoint of reliability and operability, a plurality of positive electrode containers are required. It is considered that it is most desirable to integrally seal the parts by welding. However, when a metal material having a high Cr content is used as the positive electrode material, C added to the metal material or C unavoidably contained therein reacts with Cr at the time of welding, precipitates as carbide, and remains in the welded portion. Stress, which has been found to adversely affect corrosion resistance. That is, the metal is locally heated during welding and undergoes different heat treatments depending on the distance from the welding interface. As a result, the precipitation state and the metal structure of the chromium carbide change depending on the location, and this is considered to cause residual stress. When the temperature rises and falls using a positive electrode container having such residual stress, stress from the positive electrode mold and residual stress due to temperature change are applied, and the chromium sulfide layer formed on the surface is easily damaged, and the corrosion resistance is reduced. It was found to be lower. In the case of general welding, the residual stress can be reduced by heat treatment before and after welding, but in the case of a sodium-sulfur battery, the heat treatment temperature before and after sealing welding depends on the vapor pressure and corrosiveness of sulfur and sodium polysulfide. Therefore, it is difficult to sufficiently remove the residual stress.

The present invention has been devised based on these findings, and its contents will be described with reference to FIGS.

FIG. 1 is an example of a structural view of a sodium-sulfur battery of the present invention. In the figure, 1 is a solid electrolyte tube of sodium ion conductivity, 2 is a negative electrode container forming a negative electrode chamber 3 together with the solid electrolyte tube 1, 41 and 42 are positive electrode containers 4.
And the positive electrode chamber 5 together with the solid electrolyte tube 1. Reference numeral 61 denotes a welded part between the parts 41 and 42. Reference numeral 7 denotes an insulating member that insulates the negative electrode container 2 and the positive electrode container 4 and is joined thereto, and the insulating member 7 and the opening of the solid electrolyte tube 1 are generally connected by glass solder or the like. It is. Reference numeral 8 denotes a sodium housed in the negative electrode chamber 3, and 9 denotes a positive electrode mold made of sulfur or sodium polysulfide, which is usually impregnated with carbon fiber or the like and housed in the positive electrode chamber 5.

In FIG. 2, parts having the same reference numerals as those in FIG. 1 have the same contents. Reference numeral 43 in this figure denotes a component constituting the positive electrode container 4, which is connected to the component 41 at a welded portion 62. 4
Reference numeral 0 denotes an easily deformable portion provided on the positive electrode container 4, such as a bellows. Reference numeral 10 denotes a sodium container provided in the negative electrode container 3, which is provided with a through hole 11 and supplies sodium 8 to the solid electrolyte tube 1.

In these structures, the components 41, 42, and 43 of the positive electrode container are made of a highly corrosion-resistant metal material containing a high concentration of Cr, and these are integrated by welding. The component 42 is located inside the component 41 and restrains deformation inside the component 41 when the positive electrode mold expands and contracts at the time of temperature rise and fall or changes in volume due to a phase change of sulfur and sodium polysulfide. The stress applied to the portion 61 is reduced. A similar effect is achieved with the component 43, and the stress applied to the weld 62 is reduced by restricting the inward deformation of the component 41. Although not shown, a high-rigidity ring is provided outside the positive electrode container below the welded portion 61 or above the welded portion 62 to restrain deformation of the positive electrode container to the outside, and to the welded portions 61 and 62. Working stress can also be reduced.

Further, the part 42 has an L-shaped cross section,
It easily undergoes angular deformation, absorbs the difference in thermal expansion between the solid electrolyte tube 1 after solidification of the positive electrode mold and the positive electrode container 4, and further reduces stress applied to the welded portion 61 during temperature rise and fall. A similar effect is also observed in the bellows 40 provided in the positive electrode container, and the deformation of the bellows can significantly reduce the stress applied to the welded portion 61. In addition, these bellows 4
It is desirable that the zeros and the parts 42 are provided at positions not in contact with the positive electrode mold 9. When in contact with the positive electrode mold, deformation is suppressed by the solidified positive electrode mold, and the effect of reducing stress due to deformation is reduced.

As described above, according to the present invention, when parts made of a highly corrosion-resistant metal material containing a high concentration of Cr are welded to each other, even if chromium carbide precipitates and residual stress is generated, the welded portion is not heated when the temperature rises or falls. Since the stress applied to the surface is small, the chromium sulfide layer formed on the surface is kept stable. As a result, the corrosion resistance of the positive electrode container can be maintained high, and the reliability of the sodium-sulfur battery can be greatly increased. In addition,
As a material constituting the positive electrode container, it is necessary to have not only excellent corrosion resistance, but also excellent workability and weldability. If these requirements are not satisfied, a battery having excellent reliability cannot be obtained. For example, as a cathode tube material, F with a small amount of Cr is used.
When a material having poor corrosion resistance such as an e-alloy or a coating material is used, the intended effect cannot be obtained due to a lack of corrosion resistance of the material itself or a lack of corrosion resistance of a welded portion. Further, a material in which a residual strain is apt to remain in the welded portion is not preferable because the chromium sulfide layer formed on the surface cannot be stably held.

The material constituting the positive electrode container of the present invention is preferably a Co-based or Ni-based alloy.
These alloys, compared to commonly used Fe alloys,
It has the advantages of low residual stress during welding and high corrosion resistance. Further, since the resistance of the sulfide formed on the surface is smaller than that of the Fe alloy, there is an advantage that the characteristics of the battery are stable and the reliability is further improved. In particular, in the case of a Co-based alloy,
Since the solubility of the formed cobalt sulfide in sodium polysulfide is smaller than that of nickel sulfide, the reliability of the battery can be particularly increased.

The preferred composition ranges of the Co-based and Ni-based alloys are Co content of 30% by weight or more, Cr content of 18 to 32% by weight, C content of 0.2% by weight or less, or Ni content of 40% or less. Weight% or more, Cr content 18 to 32
% By weight, C content is 0.2% by weight or less. If the content of Co or Ni is less than this, a Co-based alloy or N
The effect as an i-base alloy decreases. If the Cr content is less than this range, the corrosion resistance is reduced, and if the Cr content is too large, processing into a positive electrode container becomes difficult. If the C content is larger than this, not only becomes difficult to process into a positive electrode container, but also the amount of chromium carbide deposited during welding increases, the residual strain increases, and the corrosion resistance tends to be impaired. In addition, these alloys may contain 3 to 15% by weight of W or 1 to 10% by weight of Mo, or 0.2 to 4% by weight.
It is particularly desirable that the Al content by weight is further improved because the corrosion resistance is further improved. If the contents of W, Mo and Al are less than the above ranges, the effect of addition is not sufficient, and if the contents are too large, processing into a positive electrode container becomes difficult.

As a material constituting the positive electrode container of the present invention,
An alloy containing Fe as a main component, a Cr content of 22 to 32% by weight, and a C content of 0.2% by weight or less can also be used. Also in this case, if the Cr content is less than this range, the corrosion resistance is reduced, and if it is too large, it becomes difficult to process the cathode container. Also,
If the C content is larger than this, not only becomes difficult to process into a positive electrode container, but also the amount of chromium carbide deposited during welding increases, the residual strain increases, and the corrosion resistance tends to be impaired. When the Fe alloy further contains 14 to 24% by weight of Ni, there is an advantage that the residual stress during welding is reduced and the corrosion resistance is improved. The use of a duplex stainless steel composed of austenite and ferrite as the Fe alloy is also effective in reducing the residual strain in the weld and improving the corrosion resistance. When duplex stainless steel or ferritic stainless steel is used, the coefficient of thermal expansion is smaller than when austenitic stainless steel is used, and there is an advantage that thermal strain is less likely to be applied to the welded portion. Further, the content of Cr is preferably from 23 to 30% by weight, in order to achieve both corrosion resistance and workability, and it is particularly preferable in practical use. Further, when the Fe alloy is 1 to 10
When Mo is contained by weight%, there is an advantage that corrosion resistance to sulfur is improved without impairing workability.

Specifically, SUS310S (24 to 26% by weight of Cr, 19 to 22% by weight of Ni, and Fe remaining) and SUS329J1 (C
r 23 to 28% by weight, Ni 3 to 6% by weight, Mo 3% by weight, Fe remaining) SUS427J1 (Cr 28.5 to 32% by weight,
Mo (2% by weight, Fe remaining) may be used.

Furthermore, by using the sodium-sulfur battery of the present invention, the reliability of the battery system is improved, and a highly reliable power storage device, an electric vehicle, an emergency power source, an uninterruptible power source, and a power system peak cut device are provided. And a frequency / voltage stabilizing device.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

As a specific example, as shown in FIG. 2, a solid electrolyte tube 1 made of a lithium-doped β ″ alumina sintered body was used as a solid electrolyte tube. In addition to joining the solid electrolyte tube with the glass, the insulating member was joined to the negative electrode container 2 and the component 42 of the positive electrode container by a thermal pressure welding method using an aluminum-silicon-magnesium alloy foil. The material of the container 10 is SUS304
The inside of the sodium container is filled with sodium 8 and about 0.1 atm of nitrogen gas and sealed, and the gas pressure causes the sodium to go out of the small hole 11 having a diameter of 0.2 mm at the bottom of the sodium container. It came out and covered the inner surface of the solid electrolyte tube. On the other hand, the components 41, 42, 43 constituting the positive electrode container
The materials shown in Table 1 were used, and these were integrated by TIG welding or electron beam welding. In addition, inside the positive electrode container, a positive electrode mold made of sulfur and carbon fiber mat,
And after filling with about 0.1 atm of nitrogen gas,
43) was sealed by vacuum TIG welding to obtain a sodium-sulfur battery of the second structure. The outer shape of the positive electrode container is about 65m
m, thickness is about 1.5mm, bellows 40 provided on the positive electrode container
Had an axial rigidity of about 10 N / mm.

In a similar manner, a battery having the structure of FIG. 1 and a sodium container similar to that of FIG. 2 provided inside the negative electrode, and
As a comparative example, a battery having the structure shown in FIG. 3 was prepared. In addition,
The axial rigidity of the positive electrode container of FIG. 1 without the bellows is about 25 N / mm, and the axial rigidity of the positive electrode container of FIG.
KN / mm. At 400 ° C., the battery was charged / discharged 500 times at a current density of about 200 mA / cm ² per energized area of the solid electrolyte tube, and the rate of change of the efficiency and capacity of the battery when the temperature was raised and lowered from room temperature to 400 ° C. 20 times on the way. It is shown in Table 1. As can be seen from this table, the sodium-sulfur battery of the present invention was found to have stable characteristics and high reliability.

[0026]

[Table 1]

As described above, since the characteristics of the battery are stable and high in reliability, the reliability of the battery system in which a plurality of the sodium-sulfur batteries of the present invention are combined is high. It has been found that storage devices, electric vehicles, emergency power supplies, uninterruptible power supplies, power system peak cut devices, frequency and voltage stabilization devices, etc. can be realized.

[0028]

According to the present invention, characteristic deterioration due to corrosion of the positive electrode container hardly occurs, and the reliability of the sodium-sulfur battery is greatly improved.

Further, by using the battery of the present invention, the reliability of a battery system using a plurality of batteries can be increased, and a highly reliable power storage device, electric vehicle, emergency power source, uninterruptible power source, A system peak cut device, frequency / voltage stabilization device, etc. are realized.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing an example of a battery structure of the present invention.

FIG. 2 is a structural view showing an example of a battery structure of the present invention.

FIG. 3 is a diagram showing a battery structure of a comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte tube, 2 ... Negative electrode container, 3 ... Negative electrode chamber, 4 ... Positive electrode container, 5 ... Positive electrode chamber, 7 ... Insulating member, 8 ... Sodium,
9: Positive electrode mold, 40: Bellows, 41, 42, 43
... components of the positive electrode container, 61, 62 ... welded parts.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Manabu Gakusho 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Inventor Shigeko Nishimura 7-chome Omika-cho, Hitachi City, Ibaraki Prefecture No. 1-1 Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Katsuhiko Shioda 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Kiyoshi Otaka Benten, Hitachi City, Ibaraki Prefecture 3-10-2, Machi Kachiwa Kogyo Co., Ltd. (56) References JP-A-2-144858 (JP, A) JP-A-4-294070 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01M 10/39

Claims (7)

(57) [Claims] 1. A negative electrode container containing sodium, a positive electrode container containing a positive electrode mold made of sulfur or sodium polysulfide, a sodium ion conductive solid electrolyte separated between the negative electrode and the positive electrode, and the solid electrolyte. Connected
It is, before SL negative electrode container, joined insulated member Seikyokuyo device, in the sodium sulfur cell comprising the positive electrode container,
High corrosion resistance of Co group containing Cr, or are integrated by welding a plurality of components made of Ni-based alloy material Rutotomoni,
Reduces stress from the positive mold applied to the weld
And a material constituting the positive electrode container has a Co content of 30.
Co-based alloy with a Cr content of 18% to 32% by weight, a C content of 0.2% by weight or less, or a Ni content of 4% by weight or more and a C content of 0.2% by weight or less.
A sodium-sulfur battery comprising a Ni-based alloy having a content of 0% by weight or more, a Cr content of 18 to 32% by weight, and a C content of 0.2% by weight or less. 2. The method according to claim 1, wherein said Co-based alloy or Ni-based alloy contains 3 to 15% by weight of W or 1 to 10% by weight.
Or a sodium-sulfur battery containing 0.2 to 4% by weight of Al. 3. A negative electrode container containing sodium, a positive electrode container containing a positive electrode mold made of sulfur or sodium polysulfide, a sodium ion conductive solid electrolyte separated between the negative electrode and the positive electrode, and the solid electrolyte. connected, the negative electrode container, joined insulating member on the positive electrode container, the sodium-sulfur cell comprising the positive electrode container,
The positive electrode mold, wherein a plurality of parts made of an alloy material containing Fe as a main component and having a Cr content of 22 to 32% by weight and a C content of 0.2% by weight or less are welded and integrated, and are added to the welded portion. A sodium-sulfur battery provided with a mechanism for reducing stress from the battery. 4. A negative electrode container containing sodium, a positive electrode container containing a positive electrode mold made of sulfur or sodium polysulfide, a sodium ion conductive solid electrolyte separated between the negative electrode and the positive electrode, and a solid electrolyte. connected, the negative electrode container, joined insulating member on the positive electrode container, the sodium-sulfur cell comprising the positive electrode container,
A plurality of parts made of an alloy material containing Fe as a main component and having a Cr content of 22 to 32% by weight and a C content of 0.2% by weight or less are integrated by welding, and the positive electrode container has an easily deformable portion. A sodium-sulfur battery provided. 5. The method according to claim 4, wherein the alloy material is 14%.
A sodium-sulfur battery characterized by containing Ni in an amount of up to 24% by weight. 6. The method according to claim 4 or 5, Cr content of the alloy material, sodium sulfur battery, which is a 23 to 30% by weight. 7. The sodium-sulfur battery according to claim 4, wherein the alloy material contains 1 to 10% by weight of Mo.