JP4370083B2 - Sodium-sulfur secondary battery module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the reliability and safety improvement in the sodium-sulfur secondary battery Ikemo Joule power storage. More particularly, to sodium sulfur secondary battery module capable of preventing damage due to thermal stress of the sodium conducting electrolyte sintered body.
[0002]
[Prior art]
Sodium-sulfur secondary batteries can use low-cost materials such as sulfur or sodium polysulfide for the positive electrode active material and sodium for the negative electrode active material. Development and commercialization are progressing.
[0003]
As the performance of a single cell or a module comprising a single cell integrated and connected is improved, the single cell becomes larger and the electrolyte sintered body is a sodium ion conductive diaphragm that is indispensable as a component of the cell. However, because of the effects of thermal stress, the problem of damage becomes obvious and the reliability of the performance itself is concerned, and the active material filled inside is a highly dangerous substance such as sodium or sulfur. It is also a safety issue.
[0004]
Here, to describe the structure of sodium-sulfur battery according to the present invention, FIG. 6 is an exploded perspective view of a sodium-sulfur secondary battery using the beta "alumina as a sodium ion-conducting electrolyte membrane.
[0005]
In FIG. 6, reference numeral 107 denotes a negative electrode container having a bottomed cylinder 108 of sodium ion conductive electrolyte, that is, β ″ alumina sintered body in this case as an ion conductive diaphragm, and a small hole 109 at the bottom of the negative electrode container 107. To communicate with the inside of the bottomed cylinder 108 of β ″ alumina. The entire negative electrode container including this β ″ alumina sintered body bottomed cylinder is installed inside the positive electrode container 104. Then, sodium 106 is added to the negative electrode container 107 and the positive electrode container 104 (in detail, the positive electrode container 104). Sulfur or sodium polysulfide 105 is filled between the container 104 and the β ″ alumina sintered body-bottomed cylinder 108. The inside of the β ″ alumina sintered cylinder with a bottom 108 is filled with sodium and the outside is filled with sulfur or sodium polysulfide because of the small hole 109 at the bottom of the negative electrode container 107. The active material of both electrodes is separated and confronted by the diaphragm of the bottomed cylinder 108 of the sintered body.
[0006]
103 fastening bolts for assembly, 101 is connected to the positive electrode container 104 at the positive terminal is connected to the negative electrode chamber 107 at 102 the negative terminal, to the both the machining gap, by connecting an external DC power source or an external load Charge and discharge.
[0007]
A plurality of sodium-sulfur secondary battery single cells configured in this way are integrated and connected to form a module. This situation is shown in FIG. That is, a large number of sodium-sulfur secondary battery cells 201 are integrated, connected in series or in parallel according to the purpose, and integrated with a means including a housing and a frame to be integrated as a module 202 to further control a plurality of modules. The battery unit 203 is installed and connected together with the unit. Although not shown, the apparatus includes a heating unit in addition to the module integration unit or in the battery unit in order to operate at a high temperature, for example, 350 ° C.
[0008]
When the temperature of the sodium-sulfur secondary battery is raised to the operating temperature during the operation start preparation process, the heat supply by the heating means is performed by radiation or heat transfer from the side of the module wall. Since it does not warm, it causes a partial melting phenomenon, which causes various stresses and causes damage to the solid electrolyte.
[0009]
In this way, a molten liquid pool constrained in the solid due to partial melting occurs, and when heating and expansion are continued, if it occurs on the side surface, a large lateral pressure is generated and appears on the bottom surface. In this case, a large pressure is generated in the vertical direction, which propagates and becomes a force for crushing the bottomed cylinder of the β ″ alumina sintered body, which causes damage.
[0010]
When the stress was calculated using an analytical model, the following results were given. FIG. 3 is a calculation model 300 showing a cross section of a single cell. Heat is supplied from the right side of the figure of this cell, and in the solid sodium polysulfide or sulfur 301, partially melted and liquefied sodium polysulfide or sulfur 303 becomes the SUS positive electrode metal container 304 and β "alumina sintered. The body cylinder 302 is heated and expanded to generate pressure P, which causes damage.
[0011]
Further, when the operation is interrupted, the following phenomenon occurs when sulfur or sodium polysulfide on the positive electrode side starts to solidify in the bottom part in the process of the temperature decreasing from the operating temperature to room temperature. This is shown in FIG. 4, where 401 is a state where granular solids are still mixed in the liquid, and 403 is a state where the positive electrode solution is solidified into a solid. Here, austenitic SUS304 is conventionally used for the positive electrode container, and its linear expansion coefficient is 16 × 10 ⁻⁶ , and the β ”alumina sintered body of the diaphragm between the negative electrode and the positive electrode has a linear expansion coefficient of 8 × 10 6. ^Since it is ⁻⁶ , the shrinkage of the outer container is larger than that of the middle β ″ alumina sintered body. Due to the solidification of the bottom portion, all of the longitudinal displacement due to this shrinkage difference is applied to the bottom portion of the β ″ alumina sintered body, and the β ″ alumina sintered body generates cracks 402. And this crack will open at the next temperature rising.
[0012]
When this phenomenon to calculate the stress, that's the case solidification begins from the bottom, the generated stress is reached to 22 kgf / mm ^2, when uniformly solidified was only 5.8kgf / mm ^2. Since the average strength of the β ″ alumina sintered body is about 30 kgf / mm ² , it has been found that the above phenomenon can occur sufficiently in consideration of partial variations and the like.
[0013]
[Problems to be solved by the invention]
Therefore, the present invention has been made in view of such conventional problems, and has a bottomed cylinder made of a sintered body of a sodium conductive electrolyte on the outside, and a negative electrode container communicating with the inside of the bottomed cylinder, In the same module having a positive electrode container in which the negative electrode container is installed, a plurality of sodium sulfur secondary batteries in which sodium is contained in the negative electrode container and sodium polysulfide or sulfur is filled in the positive electrode container. , generated by heating and cooling, to prevent breakage of the sodium conducting electrolyte sintered body, and to provide a high electroforming cell module structure of reliability and safety.
[0014]
[Means for Solving the Problems]
The present invention has a bottomed cylinder made of a sintered body of a sodium conductive electrolyte on the outside, a negative electrode container communicating with the inside of the bottomed cylinder, and a positive electrode container in which the negative electrode container is provided, and a negative electrode container A plurality of sodium-sulfur secondary batteries filled with sodium and a positive electrode container filled with sodium polysulfide or sulfur are integrated and connected, and the plurality of assemblies of sodium-sulfur secondary batteries are connected from the outside of the integrated body. A secondary battery module provided with a heating means for heating is characterized in that the heating means is configured to be capable of being heated independently and separately into a bottom surface portion, a side surface portion, and a top surface portion of the integrated body.
[0015]
As a result, the heat supply can be arbitrarily controlled at the bottom, side, and top surfaces, heating is performed uniformly, and uneven melting is prevented, so that the above-described problem does not occur. Further, even when the temperature is lowered, it is possible to eliminate the cause by lowering the temperature of the whole while supplying heat weakly for a while to only the part that causes solidification due to advance solidification.
[0016]
Furthermore, the sodium-sulfur secondary battery module of the present invention includes a temperature detection unit and a temperature control unit. When the integrated body is heated to the operating temperature, the detection unit detects the temperature in the module and sets the detection temperature. Heating is performed from the bottom surface or side surface until reaching the temperature, and heating is performed only from the top surface above the set temperature so that the control unit can control the temperature so as to reach the operating temperature.
[0017]
That is, until the melting starts, the temperature is raised by bottom or side surface heating with good heat transfer efficiency, and when it reaches just before the melting starts, switching to the top surface heating can avoid uneven melting at the bottom and side surfaces of the battery. .
[0018]
Furthermore, in the sodium-sulfur secondary battery module of the present invention, the sodium-conductive electrolyte of the sodium-sulfur secondary battery constituting the sodium-sulfur secondary battery module is β ″ alumina, the set temperature is approximately 120 ° C., and the operating temperature Is approximately 350 ° C.
[0019]
This is because sodium polysulfide, which is the positive electrode active material of the secondary battery, has a melting point of 260 ° C. and sulfur of 120 ° C., so that sulfur first melts. Further, the maximum temperature reached may be around 350 ° C. of the operating temperature selected from the characteristics of the battery.
[0020]
Furthermore, the present invention has a bottomed cylinder made of a sintered body of sodium conductive electrolyte on the outside, a negative electrode container communicating with the inside of the bottomed cylinder, and a positive electrode container having the negative electrode container provided therein, In a sodium-sulfur secondary battery in which sodium is filled in the negative electrode container and sodium polysulfide or sulfur is filled in the positive electrode container, the linear expansion coefficient of the material of the positive electrode container is the linear expansion coefficient of the sodium conductive electrolyte sintered body. It is preferable to use a metal material in a range not exceeding 150% and not less than 50% .
[0021]
By carrying out like this, the stress which generate | occur | produces by the difference of an above-mentioned linear expansion coefficient can be reduced, and the failure | damage of the sintered compact of a sodium conductive electrolyte can be prevented.
[0022]
Further sodium-sulfur secondary battery of the present invention is sodium conducting electrolyte is beta "alumina, area by the from 4.0 to 12.0 × 10 ^-6 der the linear expansion coefficient of the metal material constituting the positive electrode container .
[0023]
Since the linear expansion coefficient of β ”alumina of the sodium conductive electrolyte is 8.0 × 10 ⁻⁶ , if the linear expansion coefficient of the metal material of the positive electrode container is within 4.0 to 12.0 × 10 ^−6. , that it can be prevented from being damaged, the present inventors have since been found.
[0024]
Furthermore, in the sodium-sulfur secondary battery of the present invention, the positive electrode container is a metal bottomed cylinder, and the bottom plate of the flat plate is bent inwardly with increasing temperature at room temperature, and becomes flat when returning to room temperature. that having a bottom plate to reversibly deformed.
[0025]
As described above, the positive electrode container contracts relatively upward in the vertical direction when the temperature is lowered, and the solid in the bottom portion is displaced upward, and the force that presses the bottom of the sintered body of the sodium conductive electrolyte is increased by increasing the temperature. This is because the bottom that is convex, that is, curved upward, returns and is displaced downward due to a temperature drop, offsets the upward displacement of the solid in the bottom portion, and prevents the generation of stress.
[0026]
Further, in the sodium-sulfur secondary battery preferably applied to the present invention , the bottom plate of the positive electrode container is bonded to a metal material having a different linear expansion coefficient, and the bottom plate escapes to the circumference of the bottom plate using the bottom plate as a positive electrode container. Is restrained .
[0027]
When the bottom plate is made of a laminate structure of two metals and the upper plate is made of a metal having a larger linear expansion coefficient than the lower plate, it is warped upward by heating. The above principle can be achieved by fixing the bottom plate to the circumference of the cylinder so as not to disturb the warpage.
[0028]
Further, in the sodium-sulfur secondary battery preferably applied to the present invention , only the circumference of one metal material of the bottom plate bonded with the metal materials having different linear expansion coefficients is welded to the circumference of the cylinder as the positive electrode container . .
This structure is one of more specific structures that does not hinder the warping of the positive electrode container bottom plate.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Next, exemplary embodiments of the invention will be exemplarily described with reference to the drawings as necessary. However, the dimensions, shapes, materials, relative arrangements, and the like of the products described in the present embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Absent.
[0030]
(Embodiment 1) FIG. 1 is a conceptual diagram of a battery module having a structure in which each surface can be separated and heated. In FIG. 1, reference numeral 802 denotes a single cell, and a plurality of single cells are connected in an integrated manner, and a detection unit 803 capable of detecting the temperature inside the integrated body is disposed. On the upper surface of the single cell integrated body, a resistance heating body is used as the upper surface heating means 804, a resistance heating body is used as the upper surface heating means 805 on the lower surface, and a resistance heating body is used as the side surface heating means 806 on the side surface. , Placed close to the stack.
[0031]
The control unit 807 compares the temperature signal detected by the detection unit 803 with a set temperature, and outputs an operation amount for operating a switch for switching power supplied to each surface and an operation amount for operating a supply voltage based on the result. From the power source 808 connected to the control unit, voltage transformation to the supply destination or switching of the supply destination is operated. The control unit has a terminal for outputting the control voltage of each surface portion thus performed, and is connected to the resistance heating body which is each surface heating means 804, 805, 806 arranged independently of the terminal, Each surface can be separated and temperature controlled independently.
[0032]
(Example 2) A positive electrode vessel was prepared using a conventional austenitic SUS316, the sodium sulfur binary battery was assembled, and the temperature was lowered from the operating temperature to room temperature. ^When a stress of ² was applied and the sample was disassembled and inspected, transverse cracks were observed at the top of the β "alumina tube. On the other hand, as an example of the present invention, a ferrite-based SUS436 having a linear expansion coefficient of 11 × 10 ⁻⁶ is used, the sodium-sulfur binary battery is assembled, and the temperature is lowered from the operating temperature to room temperature. The stress applied to the β ″ alumina tube decreased to 15 kgf / mm ² , and when disassembled and inspected, there was no transverse crack at the top of the β ″ alumina tube.
[0033]
(Embodiment 3) FIG. 5 is a schematic diagram for explaining the situation where the bottom plate of the positive electrode container is curved inwardly.
In the upper part of FIG. 5, a SUS316L disk and a carbon steel disk were laminated to form a bottom plate having a thickness of 1 mm. When the disc flat at room temperature was heated to 350 ° C., the center of the disc was depressed by 1.0 mm and curved as shown in the figure.
[0034]
In the middle of FIG. 5, a bottom plate having a thickness of 1 mm prepared by bonding the SUS316L disk and a carbon steel disk was fixed to a cylinder of SUS316L as shown in the figure. When the temperature of the flat bottom plate was raised to 350 ° C. at room temperature, the center of the disk was depressed by 1.0 mm and curved as shown in the figure.
[0035]
In the lower part of FIG. 5, a bottom plate having a thickness of 1 mm prepared by bonding the SUS316L disk and a carbon steel disk was fixed to the cylinder of SUS316L as shown in the figure. When the temperature of the flat bottom plate at room temperature was raised to 350 ° C., the center of the disk was depressed by 0.2 mm as shown in the figure, and the degree of curvature was low.
[0036]
FIG. 7 is a schematic view of a welding example of a laminated bottom plate of a positive electrode container. In FIG. 7, based on the above phenomenon, a disc having a slight radius difference between SUS304 and SUS436 was cut out and pasted to create a bottom plate of the positive electrode container. Then, as shown in the figure, only one disk of the bottom plate attached to the positive electrode cylinder made of SUS436 was fixed. That is, a SUS436 disk 903 having a low coefficient of linear expansion was welded to a welding plate 904 by making a bead 905, and the welding plate 904 was welded to a cylinder by making a bead 905 to produce a positive electrode container.
[0037]
When the temperature of the bottom plate of the container thus prepared was raised from room temperature to 350 ° C., it was greatly curved inward. When this container was used to assemble a sodium-sulfur secondary battery and used in an actual machine together with the heating means of Example 1, there was no damage to the β ″ alumina tube.
[0038]
【The invention's effect】
As described above, according to the present invention, a negative electrode container having a bottomed cylinder made of a sintered body of sodium conductive electrolyte on the outside and communicating with the inner side of the bottomed cylinder, and a positive electrode container having the negative electrode container provided therein In the negative electrode container, sodium polysulfide filled with sodium sulfide or sulfur in the positive electrode container, or in the same module in which a plurality of the sodium sulfur secondary batteries are integrated and connected. to prevent breakage of the sodium conducting electrolyte sintered body, it made it possible to provide to provide high electroforming cell module structure of reliability and safety.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a battery module configured to be able to control heating by separating each surface.
FIG. 2 is a schematic view of a module in which a plurality of sodium sulfur secondary battery single cells are connected in an integrated manner and a unit in which the modules are installed.
FIG. 3 is a radial cross-sectional view of a sodium-sulfur secondary battery stress analysis model.
FIG. 4 is a longitudinal cross-sectional view illustrating an internal state of the sodium sulfur secondary battery when the temperature is lowered.
FIG. 5 is a schematic diagram illustrating a situation where the bottom plate of the positive electrode container is curved inwardly.
FIG. 6 is an exploded perspective view of a sodium-sulfur secondary battery using β ″ alumina as a diaphragm as a sodium ion conductive electrolyte.
FIG. 7 is a schematic diagram of a welding example of a laminated bottom plate of a positive electrode container.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 Positive electrode terminal 102 Negative electrode terminal 103 Fastening bolt 104 Positive electrode container 105 Sulfur or sodium polysulfide 106 Sodium 107 Negative electrode container 108 β "Alumina sintered body bottomed cylinder 109 Small hole 201 Sodium sulfur secondary battery 202 Cell 203 Battery unit 300 Calculation Model 301 Solid Sodium Polysulfide or Sulfur 302 β ”Alumina Sintered Cylinder 303 Molten Liquid Sodium Polysulfide or Sulfur 304 SUS Cathode Metal Container 401 Liquid Solid Solid Mixed Phase 402 Crack 403 Cathode Liquid Solidified Solid 801 Battery Module 802 Single cell 803 Temperature detection unit 804 Upper surface heating unit 805 Lower surface heating unit 806 Side surface heating unit 807 Control unit 808 Heating power source 901 Positive electrode container cylinder 902 SUS304 disc 903 SUS436 disc 904 Welding Caul plate 905 weld bead

Claims (3)

  It has a bottomed cylinder made of a sintered body of sodium conductive electrolyte on the outside, and has a negative electrode container communicating with the inside of the bottomed cylinder, and a positive electrode container in which the negative electrode container is installed. Sodium is connected to a plurality of sodium-sulfur secondary batteries filled with sodium polysulfide or sulfur in the positive electrode container, and the plurality of sodium-sulfur secondary batteries are heated from outside the integrated body. A sodium-sulfur secondary battery module characterized in that, in the secondary battery module including the means, the heating means is configured to be able to be heated independently and separately into the bottom surface portion, the side surface portion, and the top surface portion of the integrated body.   The sodium-sulfur secondary battery module includes a temperature detection unit and a temperature control unit. When the integrated body is heated to the operating temperature, the detection unit detects the temperature in the module, and the detected temperature reaches the set temperature. 2. The sodium sulfur according to claim 1, which is heated from the bottom surface portion or the side surface portion, and is heated only from the top surface portion at a set temperature or higher so as to reach the operating temperature. Secondary battery module.   The sodium conductive electrolyte of the sodium sulfur secondary battery constituting the sodium sulfur secondary battery module is β ″ alumina, the set temperature is about 120 ° C., and the operation temperature is about 350 ° C. Item 3. A sodium-sulfur secondary battery module according to Item 2.

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