JPH09237637A - Secondary battery structure of solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a cell structure of an Na/X secondary battery, simplify a process of manufacture, improve productivity, so that a cost reducing effect of a cell can be expected, also simplify a module structure, make protection capable even without forming an excessive pressure resisting double structure. SOLUTION: A fused salt is used, a plurality of solid electrolytes making an Na ion pass through are aggregated, a module 12 is constituted. Here, a surface of each solid electrolyte tube 28 of the module 12 is surrounded by a fine hole substance 23 as wetted sufficiently by liquid sodium, a protection tube 24 protecting the solid electrolyte tube 28 is provided in the outside, so as to open a lower part of the protection tube 24 in the liquid sodium 14 also store the module 12 of solid electrolyte in a cylindrical pressure resisting vessel 13 consisting of pressure resisting and heat resisting material storing fused salt or the liquid sodium 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery structure of a solid oxide fuel cell for electric power storage for leveling day and night electric power load of a power plant, for example. It is also intended to be used for load leveling for general industrial factories, power leveling for general households, and storage of solar power.

[0002]

2. Description of the Related Art As a secondary battery for power storage for leveling a power load, for example, a Na / S type or Na / X type secondary battery has been proposed. The outline of this secondary battery is shown in FIG. As shown in FIG. 7, for example, in the case of a Na / X type secondary battery cell (hereinafter referred to as “cell”) 01, the solid electrolyte 03 is housed in each pressure-resistant pressure cylinder 02, and the solid electrolyte of each one is stored. Charging and discharging can be performed with sodium 06 inside and outside and molten salt 05 as an active material, and a plurality of such cells 01 are collected and housed inside a module pressure resistant container.

The Na / X type secondary battery cell 01
8A to 8C are schematic views of a module 07 in which a large number of
It is shown in (C). As shown in FIG. 8, the module 07 is one in which the secondary battery cells 01 are assembled in several rows and columns, and has a structure in which a pressure resistant portion including an inner box 08-1 and an outer box 08-2 is duplicated as a pressure resistant container. The cell itself has a closed pressure-resistant structure, and oil and sand 09 are filled between each single cell 01 and around the inner box 08-2 to ensure heat retention and safety. In the figure, reference numeral 010 is a heat retaining heater, and 011 is a heat insulating member.

[0004]

However, in the case of the module 07, a single cell housed in a pressure-resistant metal container having the function of a secondary battery by itself is first manufactured, and a plurality of these single cells are manufactured. After the individual modules are assembled and assembled as a module, the entire module is housed in a pressure vessel (capsule) to ensure safety and reliability, but there are the following problems. The structure is complicated. The number of manufacturing steps is large and the manufacturing cost is high. The double structure of the pressure container containing the cell and the module-containing pressure container is overused.

[0005]

A structure for a secondary battery for a solid oxide fuel cell according to the present invention, which solves the above problems, is a module in which a plurality of solid electrolyte tubes for passing Na ions using a molten salt are assembled to form a module. Each of the solid electrolyte tubes is surrounded by a porous material that is sufficiently wet with molten salt or liquid sodium, and the outside of the protective tube protects the solid electrolyte. Is opened to the inside of the liquid sodium, and the solid electrolyte module is housed in a pressure-resistant container made of a pressure-resistant heat-resistant material in which molten salt or liquid sodium is stored.

In the solid oxide fuel cell secondary battery structure, the pressure-resistant container is a steel cylindrical vertical container, and an electric heater is provided on the outer periphery of the container to increase the temperature during start-up and charge / discharge. The internal temperature is maintained during standby, and the outer peripheral surface of the container is covered with a heat insulating member.

In the above solid oxide fuel cell secondary cell structure, molten salt or liquid sodium is stored in the lower portion inside the pressure vessel, and molten salt vapor or liquid sodium vapor and dry non-drying are formed in the space above the liquid surface. It is characterized by being filled with active gas.

In the solid oxide fuel cell secondary battery structure, a plurality of solid electrolyte tubes installed inside the secondary battery capsule are connected to a support metal fitting and a support metal fitting supported by an upper mirror portion above the positive electrode. It is characterized in that it is suspended from the upper part by a connecting plate and fixed to each other via a lower spacer piece protruding from the protective tube.

In the above solid oxide fuel cell secondary cell structure, a safety valve or a relief valve is provided on the outer peripheral wall of the gas portion in the secondary cell capsule to release the pressure when the internal pressure of the container rises during an abnormal reaction. At the same time, the released gas is introduced into another gas treatment device.

That is, the secondary battery structure of the present invention has a double structure in which a pressure resistant container and a heat insulating member are provided on the outer periphery of the container, and a plurality of containers containing molten salt or liquid sodium are contained in the pressure resistant container as an interior. A cylindrical solid electrolyte tube module consisting of an assembly of solid electrolyte tubes can be stored as it is, and a bath of liquid sodium or molten salt is provided inside so that the lower tip of the solid electrolyte tube is immersed in this bath. At the same time, the outer peripheral portion of the solid electrolyte tube is provided with a capillary cloth (wick) and its protective tube so that the outer peripheral portion of the solid electrolyte tube is sufficiently wet by the liquid in the hot water bath by utilizing the capillary phenomenon. .

An electrode for impregnating molten salt or liquid sodium is provided inside the cylindrical solid electrolyte tube, and the upper end is sealed with a non-conductive material such as α-alumina. The electrodes protruding to the upper part are commonly connected in parallel for each solid electrolyte tube, and are suspended from above and supported by the electrodes.

The solid electrolyte has a cylindrical shape and is provided with a molten salt (or liquid sodium) and an electrode inside thereof, and has a simple shape in which an upper portion is covered with a non-conductive material, which simplifies the cell structure and facilitates the manufacturing process. The productivity can be improved by simplifying, and the production cost can be reduced.

Liquid sodium or molten salt outside the solid electrolyte tube is stored in the lower part of the pressure vessel so that a plurality of solid electrolyte tubes form a common hot water bath, and the solid electrolyte tip is impregnated therein. By doing so, the pressure-resistant container can be provided with the function of having both the hot-water bath and the container for accommodating the plurality of solid electrolyte tubes, and the module system can be simplified and the production cost can be reduced.

In the present invention, the conventional "single cell" and a "module" in which a plurality of cells are combined and the "pressure resistant container" for storing the module are "integrated and simplified" while maintaining their respective functions. Is intended.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows a first embodiment of the present invention.
2 is a schematic view of a secondary battery structure according to the embodiment of FIG.
In FIG. 1, reference numeral 11 is a secondary battery capsule, 12 is a cylindrical solid electrolyte tube module, 13 is a cylindrical vertical pressure vessel, 1
4 is liquid sodium melt, 15 is an electric heater, 16 is a heat insulating member, 17 is a hanging metal fitting, 18 is an inert gas (N ₂ / A
r gas), 19 is a safety valve, and 20 is a carbon-based main electrode. As shown in FIG. 1, in the present embodiment, a secondary battery capsule (hereinafter referred to as “capsule”) 11 includes a cylindrical vertical pressure vessel 13 including a lid 13a and a body 13b.
And a heat insulating member 16 provided on the outer periphery of the pressure vessel 13.
In the pressure vessel 13, each cylindrical solid electrolyte tube module (hereinafter referred to as “module”) 12 for a secondary battery is a lid body 13 which is a mirror portion of the pressure vessel.
It is hung and supported from a through a metal fitting 17,
A liquid sodium melt 14 is provided below the inside of the cylindrical vertical pressure vessel 13, and the suspended module 12 is provided.
Is soaked in a bath of liquid sodium melt 14. Further, a safety valve or a relief valve 19 is provided in the container 13 and the heat insulating member 16 in the capsule 11, so that the pressure is released when the internal pressure of the storage container increases due to an abnormal reaction, and when gas is released, It is designed to be introduced into another gas processing device.

In the present embodiment, Na / S type or Na /
As a solid electrolyte constituting a module of an X-type secondary battery, for example, a special solid β-alumina (β-Al ₂ O ₃ ) that allows only positive (+) ions to pass is used, and sulfur (S) is used as a molten salt. Alternatively, sulfur tetrachloride (SCl ₄ ) is used. Then, the carbon-based main electrode 2 that is the anode
0 and a metal pressure vessel 13 made of, for example, SUS material, which is a cathode. Here, the operating principle of the sodium / molten salt secondary battery will be described. * During discharge Sodium is divided into sodium ions and electrons. Sodium ions pass through β-alumina and move to the positive electrode. In the molten salt, sulfur tetrachloride releases chlorine ions and receives electrons to become sulfur. On the other hand, chloride ions combine with the transferred sodium ions to become sodium chloride. * During charging Sodium chloride is divided into sodium ions and chlorine ions. On the other hand, sulfur releases electrons and combines with chlorine ions to form sulfur tetrachloride. Sodium ions pass through β-alumina and move to the negative electrode. The sodium ion in the negative electrode receives an electron and becomes sodium.

The solid electrolyte tube made of β-alumina is, for example, 7
The size of the battery is 5 mmφ × 1000 mmL, the battery capacity of a single tube is 4 V × 200 W, and the nominal module capacity is 15 KWh (5 hours discharge) in the 3 KW specification for general household use. This is the capsule 11 accommodating 19 solid electrolyte tubes, and the size will be accommodated in a space of about 650 mmφ × 15000 mmH in consideration of the heat insulating member thickness of 100 mm.

On the other hand, nominally 8000 kW for power storage
In the case of h (8-hour discharge system), when the module system voltage is 400V, the voltage of one capsule is 4V, so 100 capsules are arranged in series. The number of solid electrolyte tubes contained in the capsule 11 is 50 (see FIG. 6),
The installation space is 5m x 5m x 10mH.

<Electric Heater> A cylindrical metal vertical pressure vessel 13 for accommodating the above module has a liquid sodium melt 14 stored in the lower inside thereof, for example, an operating temperature of a Na / X secondary battery of 230 ° C. ± 5.
In order to maintain the temperature at 0 ° C., an electric heater 15 is installed between the capsule 11 and the module 12 on the entire surface of the main body 13b of the pressure resistant container 13 except for the lid side of the capsule. A space between the capsule 11 and the module 12 is covered with a heat insulating member 16 having a sufficient heat insulating effect.

In the Na / X secondary battery, heat is generated as it is charged and discharged, while the internal temperature drop due to heat dissipation is large near the capsule wall and small near the center during switching pauses when charging and discharging are not performed. Capsule 11
There is a risk that temperature imbalance will occur between the cells in the pressure vessel 13 that is the interior of the battery, and the battery performance will be degraded. In order to prevent this, the electric heater 15 disposed inside the heat insulating member 16 that is the capsule exterior is designed so that local heating control is possible, so that the temperature of each cell in the capsule 11 becomes uniform. In addition, it is considered that the internal temperature detection / control system automatically controls the temperature.

Further, while the battery is stopped, the internal temperature decreases due to heat dissipation, and the liquid sodium melt 14 solidifies. For a short-term stop, the liquid storage part is selectively heated by an electric heater to always keep the inside of the capsule at an optimum temperature, and after the long-term stop, when the temperature of the inside of the container 13 that has reached room temperature is raised,
In order to preferentially liquefy the solid sodium layer by heating, the electric heater 15 for heating the lower portion of the container 13 is mounted more densely and has a larger capacity than other portions (see FIG. 1).

<Encapsulation of Inert Gas in Capsule> The active material stored in the cylindrical sealed solid electrolyte module 12 made of β-alumina material of Na / X secondary battery is operated at a temperature of 200 to 230 ° C. saturated vapor pressure reaches ^{4kg / cm 2 g~4kg / cm 2} g. The solid electrolyte has a structure that can withstand this pressure, but in order to minimize the pressure difference between the inside and outside of the solid electrolyte module 12 for the sake of safety, the inert gas 18 such as nitrogen gas or argon gas is pressurized and enclosed in the capsule 11. I am trying.

This inert gas 18 is in direct contact with the liquid sodium melt 14, and if oxygen (O ₂ ) or water droplets / water vapor (H ₂ O) is present, it reacts rapidly with the sodium melt 14, and this is prevented. Therefore, the inert gas 18 uses oxygen-free and moisture-free dry gas to improve safety. The inside of the capsule is 4k due to the inert gas 18.
The pressure is increased to g / cm ² g to ⁴ kg / cm ² g, and under this pressure, the sodium saturated vapor partial pressure at an operating temperature of 200 to 230 ° C. is as low as (1-2) × 10 ⁻³ mmHg, Sodium evaporation is suppressed to the ppm order.

<Peripheral Structure of Solid Electrolyte Tube> FIG. 2 is a schematic sectional view of the assembly of the solid electrolyte tube module. Inside the sealed module 12, a carbon electrode 21 and a molten salt-impregnated carbon foam (hereinafter, referred to as “carbon foam”) 22 impregnated with a molten salt are provided.
And the outer bottom of the module is submerged in the liquid sodium melt 14 provided below the container 13.

At the time of discharging the secondary battery, sodium ions generated from the liquid sodium melt 14 move to the molten salt layer inside by utilizing the entire effective surface of the solid electrolyte module 12, so that the outer surface of the solid electrolyte tube is The cloth-like or sponge-like capillary cloth (hereinafter, referred to as “wick”) 23 sucking up the liquid sodium upward by using the capillary phenomenon so as to sufficiently wet the liquid sodium with the solid electrolyte protective tube 24 and the solid electrolyte 28. It is wrapped in between.

Further, as shown in FIG. 3, the outer protective tube 24 is for protecting the wick 23, for example, a cylinder made of SUS material is wound, and the upper end is exposed to a high temperature for sealing the solid electrolyte. It is affixed to a lid 25 made of alpha-alumina that can withstand. On the other hand, the protective tube 24
The lower end of is opened so that the liquid sodium melt 14 can rise.

<Solid Electrolyte Tube Supporting Structure> As shown in FIG.
Has a parallel connection structure in which the bottom of the module 12 is joined via the liquid sodium melt 14 in the pressure vessel 13 and the top is joined via the carbon electrode 21.

The upper end of the carbon electrode 21, which is the positive electrode, is an electric conductor having a parallel connection function and a function of fixing each cell at the upper end, and is fixed at a fixed position by a connecting plate 26 made of, for example, SUS, which is resistant to corrosion. The carbon-based main electrode 20 drawn out of the capsule 11 is separately connected to the connecting plate 26.

The connecting plate 26 is fixed to the upper part of the capsule 11 by a hanging member 17 from a lid body 13a which is a mirror portion also serving as a lid for opening inspection. Therefore, each cell has a structure that is suspended from the upper portion, and can freely escape downward even if the solid electrolyte or the like expands due to heat.

In addition, the carbon electrode 2 on the connecting plate 26
As for the attachment of No. 1, first, as shown in FIG. 5A, the carbon electrode 21 protruding from each cell is inserted into the round hole 26a of the connecting plate 26 from below. Then, as shown in FIG. 5B, the upper and lower two plates 26-1 and 26-2 that form the connecting plate 26.
By sliding 6-2 in the lateral direction, the elongated hole 26b of the connecting plate 26 is crimped and positioned and fixed in the groove 21a formed in the carbon electrode 21.

In addition, the lower end of each cell has a fixed spacer piece 27 on which the protective tubes 24 are vertically slid and arranged.
Thus, they can be mounted at a predetermined interval so that they do not contact each other (see FIGS. 2 and 6).

The solid spacer piece 27 is installed above the liquid surface of the liquid sodium melt 14 as shown in FIG. 2 so as not to be fixed in the sodium even if the liquid sodium melt 14 solidifies during a long stop. Is desirable.

<Sealing Structure of Solid Electrolyte Tube> In order to satisfy the above-mentioned cell suspension structure, a cylindrical vertical solid electrolyte, a carbon-based electrode rod 21 to be suspended and fixed, and a molten salt to be filled inside the solid electrolyte 28 are sealed. The sealing method is very important.

As shown in FIG. 3, the solid electrolyte tube 28
The carbon electrode 21 and the carbon foam 22 are placed inside, and a lid 25 formed of an α-alumina material is covered, and then the solid electrolyte 28 and the lid 25 are subjected to a primary encapsulation using an encapsulating material 31. As the encapsulating material 31, a glass brazing material or a heat resistant cooperative adhesive is used. Next, the wick 23 is wound around the outer periphery of the solid electrolyte tube 28, and the protective tube 24 is covered. Then, the carbon electrode 21 and the α-alumina lid 25 together with the upper end portion of the protective tube 24 are sealed with the encapsulating material 31 as a secondary material. Enclose. After this sealing, the molten salt injection pipe 3
Molten salt is injected from No. 2, and then the upper end of the tube 32 is hermetically sealed with an injection tube lid 33.

[0036]

As described above, according to the present invention,
The cell structure of the Na / X secondary battery is simplified, the manufacturing process is simplified, the productivity is improved, and the cost reduction effect of the cell can be expected. The module structure becomes simple, and protection is possible even if it is not an excessive pressure resistant double structure. The module system configuration can be arbitrarily determined by the combination for each small unit module, and the system configuration can be easily assembled as compared with the conventional configuration in which the combination of cells in the module must be changed for each specification. Since the outer periphery of each solid electrolyte tube is wrapped with a capillary cloth (wick), electricity can be efficiently stored and discharged. Also, since the outer periphery of the solid electrolyte is covered with a wick and the whole electrolyte can be used by utilizing the capillary phenomenon, clogging is less likely to occur, the battery life can be extended, and even if the amount of sodium decreases, the efficiency is low. Does not fall. Since the structure is such that sodium is collected at one place for a plurality of cells, the structure can be simplified. further,
It is possible to reduce the pressure difference between the inside and outside of the single cell by removing the pressure resistant part of the conventional single cell to form a single module pressure resistant structure and applying an inert gas pressure to the upper part of the liquid sodium. .

[Brief description of drawings]

FIG. 1 is an overall cross-sectional schematic diagram of a secondary battery capsule according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of module assembly according to the embodiment of the present invention.

FIG. 3 is a schematic view of a closed structure of a solid electrolyte tube according to an embodiment of the present invention.

FIG. 4 is a schematic view of an entire capsule according to an embodiment of the present invention.

FIG. 5 is a schematic view of an electrode support structure according to an embodiment of the present invention.

FIG. 6 is a schematic layout diagram of fixed spacers according to an embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view of a conventional single cell.

FIG. 8 is a schematic cross-sectional view of a conventional solid oxide fuel cell module.

[Explanation of symbols]

11 Rechargeable Battery Capsule 12 Cylindrical Solid Electrolyte Tube Module 13 Cylindrical Vertical Pressure Vessel 14 Liquid Sodium Melt 15 Electric Heater 16 Heat Insulating Member 17 Suspension Metal 18 Inert Gas (N ₂ / Ar Gas)

Claims (5)

[Claims] 1. A porous substance in which a plurality of solid electrolyte tubes that pass Na ions using a molten salt are assembled to form a module, and the surface of each solid electrolyte tube is sufficiently wetted with the molten salt or liquid sodium. Is surrounded by a protective tube for protecting the solid electrolyte tube, the lower part of the protective tube is opened in liquid sodium, and the solid electrolyte module stores molten salt or liquid sodium. A solid oxide fuel cell secondary battery structure characterized by being housed in a pressure-resistant container made of the pressure-resistant heat-resistant material. 2. The solid oxide fuel cell secondary battery structure according to claim 1, wherein the pressure-resistant container is a steel cylindrical vertical container, and an electric heater is provided on an outer peripheral portion of the container to raise the temperature at the time of startup. A solid oxide fuel cell secondary battery structure, characterized in that the internal temperature is maintained during standby for temperature and charging / discharging, and the outer peripheral surface of the container is covered with a heat insulating member. 3. The solid oxide fuel cell secondary battery structure according to claim 1, wherein molten salt or liquid sodium is stored in a lower portion inside the pressure vessel, and a space above the liquid surface is molten salt. A solid oxide fuel cell secondary battery structure characterized by being filled with vapor or liquid sodium vapor and dry inert gas. 4. The solid oxide fuel cell secondary battery structure according to claim 1, wherein each of the plurality of solid electrolyte tubes installed inside the secondary battery capsule is an upper mirror portion of the pressure resistant container above a positive electrode. A solid oxide fuel cell, characterized in that the solid electrolyte fuel cell is suspended from an upper portion by a supporting metal fitting supported more and a connecting plate connected to the supporting metal fitting, and is fixed to each other through a lower spacer piece protruding from a protective tube. Secondary battery structure. 5. The solid oxide fuel cell secondary battery structure according to any one of claims 1 to 4, wherein a safety valve or a relief valve is provided on an outer peripheral wall of a gas portion in the secondary battery capsule, and an internal pressure of a container is held when an abnormal reaction occurs. When the pressure rises, the pressure is released, and the released gas is introduced into another gas treatment device. A solid oxide fuel cell secondary battery structure.