KR20150136699A - Sodium-sulfur rechargeable battery - Google Patents

Abstract

The present invention relates to a sodium-sulfur battery, which is to secure excellent adhesion at low costs when a ceramic of a large area is connected with a metallic material. The sodium-sulfur battery comprises: a solid electrolyte of a flat plate shape which selectively moves sodium ions; a positive pole chamber which contains sulfur, and is arranged on one side of the solid electrolyte; a negative pole chamber which contains sodium, and is arranged on the opposite side of the solid electrolyte from the positive pole chamber; an insulator which insulates a space between the positive pole chamber and the negative pole chamber; a positive pole plate connected to the insulator, and sealing the positive pole chamber; and a negative pole plate connected to the insulator, and sealing the negative pole chamber. The insulator is made in a flat plate shape, is arranged on one side of the solid electrolyte, and is connected to the solid electrolyte. An internal space between the solid electrolyte and the insulator has the negative pole chamber. A groove connected to the negative pole chamber is formed in the center of the insulator. The negative pole plate is connected around the groove in an external central portion, and is connected to the negative pole chamber. A side plate, which is extended to cover the side ends of the solid electrolyte and the insulator, is combined with the external tip end of the positive pole plate. An upper plate arranged on the outside of the insulator is combined with the tip end of the side plate. The upper plate has a groove in the center. The upper plate is connected to the insulator by being separated apart from the negative pole plate.

Description

[0001] SODIUM-SULFUR RECHARGEABLE BATTERY [0002]

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a sodium sulfur battery improved in the bonding structure of ceramic and metal.

Generally, a sodium-sulfur battery is developed as a large-capacity power storage battery because of its high energy density, charge / discharge efficiency, self-discharge, and irregular charge / discharge characteristics.

Sodium sulfur battery is a battery that operates at high temperature of about 300 ° C. It uses sodium (Na) as a cathode, sulfur (S) as an anode, and beta-alumina ceramic of a solid electrolyte having sodium ion conductivity as an electrolyte do.

The sodium sulfur battery is an insulator for insulating between the positive electrode and the negative electrode, and alpha-alumina ceramic is used. The ceramic insulator separates the anode and cathode from each other to insulate the cathode and the anode, and is bonded to the electrolyte pipe to block sodium leakage. A ring-shaped metal collar and a metal bracket are bonded to the upper and lower ends of the insulator, respectively. The negative electrode container is coupled to the insulator via the metal collar, and the positive electrode container is coupled to the insulator via the metal bracket.

In order to increase the output characteristics or increase the energy capacity of such a sodium-sulfur battery, enlargement of the area is an important factor. To this end, it is necessary to apply a large-area electrolyte material in addition to increasing the amount of the active material to be supported.

However, when the electrolyte is large-sized, the size of the insulator connected to the electrolyte also increases, so that the area of the junction of the insulator and the metal material bonded to the insulator also increases.

When different materials with different thermal expansion coefficients are bonded to each other, thermal stress is generated due to the difference in thermal expansion coefficient. This value is closely related to the area of the joint. That is, when the junction between the metal and the ceramic is enlarged due to the large-sized electrolyte material, the thermal stress is increased in proportion thereto. If this value exceeds the breaking strength at the corresponding temperature of the insulator material, The sealing is destroyed. There is a problem that when the battery operation is stopped and the battery operation is severe, the battery is ignited.

In order to ensure the bonding strength between the insulator and the metallic material, a metal collar made of a metal and a cathode bracket are bonded to the insulator through a thermal compression bonding (TCB) process. In the case of the heat compression bonding process, high pressure is applied in a high vacuum to bond, so that the bonding strength is excellent, but the manufacturing cost is high and the cost of the product is increased because the process time is long.

A brazing process or an ultrasonic bonding process which does not require a vacuum in addition to the thermal compression bonding process and which can be easily mass-produced can be applied as a process for bonding an insulator and a metallic material. However, in such a process, When the area becomes large, there is a problem that the insulator is broken due to high stress generated at the joint surface.

The present invention provides a sodium sulfur battery capable of preventing breakage of a junction between an insulator and a metal material even if the electrolyte is enlarged due to an increase in cell capacity.

In addition, a sodium sulfur battery capable of securing an excellent bonding force at a lower cost in joining a large-area ceramic and a metal material is provided.

The present invention also provides a sodium sulfur battery capable of manufacturing a large-capacity battery at a lower cost.

The sodium-sulfur battery of this embodiment comprises a solid electrolyte in the form of a flat plate for selectively transferring only sodium ions, an anode chamber accommodating sulfur and disposed on one surface of the solid electrolyte, an anode chamber accommodating sodium and containing sodium on the opposite side of the solid electrolyte And a negative electrode plate connected to the insulator and sealing the negative electrode chamber, wherein the negative electrode plate is disposed between the positive electrode plate and the negative electrode plate,

The insulator is in the form of a flat plate and is disposed on one side of the solid electrolyte and bonded to the solid electrolyte. The inner space between the solid electrolyte and the insulator forms a cathode chamber,

A hole communicating with the cathode chamber is formed at the center of the insulator, the cathode plate is connected to the cathode chamber by being bonded to the outside of the insulator along the periphery of the hole,

The upper plate has a hole formed at the center thereof and spaced apart from the cathode plate, and the upper plate is connected to the lower plate. The upper plate is connected to a side plate extending to surround the solid electrolyte and a side end of the insulator. As shown in Fig.

The junction portion of the upper plate and the insulator may be formed to be shifted toward the center of the insulator front surface facing the upper plate.

The upper plate of the cathode plate may have a structure in which the insulator is bonded to the insulator at an inner front end portion of the hole in the front face.

The outer diameter of the outer end of the joint portion formed between the upper plate and the insulator with respect to the center of the insulator may be 60 mm or less.

The outer diameter formed by the outer ends of the joint portions formed between the upper plate and the insulator with respect to the center of the insulator may be such that the width between the outer end and the inner end of the joint is 5 mm or more.

The insulator may have a structure in which a protrusion is protruded outward at a joint portion between the upper plate or the negative plate and the slope is formed at one side of the protrusion so that the upper plate or the negative plate is bonded to the slope.

The upper plate or the negative plate may have a structure that is brazed to an insulator.

The upper plate or the negative plate may have a structure that is ultrasonically bonded to an insulator.

As described above, according to the present embodiment, it is possible to manufacture a large-capacity battery excellent in durability without damaging through a low-cost bonding process by limiting the area of the junction between the insulator and the metallic material to a range where the insulator is not damaged by the stress applied to the insulator .

Further, since the insulator and the metal material can be bonded at a low cost, the manufacturing cost of the battery can be lowered and the price competitiveness can be ensured.

1 is a cross-sectional view of a sodium sulfur battery according to an embodiment of the present invention.
2 is a schematic view showing the structure of a junction with a sodium sulfur battery according to another embodiment.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Accordingly, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

1 shows a sodium sulfur battery according to this embodiment.

1, a sodium sulfur battery (hereinafter referred to as a battery 10) of the present embodiment includes a solid electrolyte 12 in the form of a flat plate for selectively transferring only sodium ions, a solid electrolyte 12 for containing sulfur, A negative electrode chamber (16) accommodating sodium and disposed on the opposite side of the solid electrolyte (12) to the positive electrode chamber (14), an insulator for insulating between the positive electrode chamber and the negative electrode chamber A positive electrode plate 20 connected to the insulator 18 to seal the positive electrode chamber 14 and an anode plate 30 connected to the insulator 18 to seal the negative electrode chamber 16.

In this embodiment, the battery 10 is a flat plate-like battery. In the following description, upper or upper refers to the upper side in Fig. 1, and lower or lower refers to the lower side opposite.

The solid electrolyte 12 is made of beta-alumina ceramic capable of passing sodium ions. In the present embodiment, the solid electrolyte 12 has a planar plate structure. The solid electrolyte 12 has a disk shape like a disk, and may be formed in a polygonal shape such as a square shape in addition to a disk shape, and the shape is not particularly limited as long as it is a flat plate structure. An anode chamber (14) and a cathode chamber (16) are formed on both surfaces of the solid electrolyte (12).

The anode chamber (14) is located under the solid electrolyte (12). A space between the positive electrode plate 20 and the solid electrolyte 12 forms an anode chamber 14. A felt collector 19 containing sulfur is filled in the anode chamber 14. For example, the felt collectors 19 are filled with carbon felt having pores formed therein, and sulfur is contained in the pores. The shape of the felt current collector may correspond to the shape of the anode chamber 14. An inert gas such as nitrogen gas or argon gas may be filled in the space inside the anode chamber 14 at a predetermined pressure.

The insulator 18 is made of alpha-alumina ceramic to prevent a short between the cathode and the anode. In this embodiment, the insulator 18 is in the form of a flat plate and disposed on the upper surface of the solid electrolyte to form a solid electrolyte 18 . The insulator 18 is bonded to the solid electrolyte 12 at a high temperature using a glass sealant. The insulator 18 is approximately the same size as the solid electrolyte. The lower end of the outer circumferential portion of the insulator 18 is joined to the solid electrolyte so that the inner space between the solid electrolyte 12 and the insulator 18 forms the cathode chamber 16. When the lower end of the insulator is recessed in the form of a groove facing the solid electrolyte and the lower end of the outer periphery of the insulator is joined to the solid electrolyte, the recessed portion in the form of a groove as described above forms a space between the solid electrolyte and the insulator. And the space forms the cathode chamber. A hole (17) communicating with the cathode chamber is formed at the center of the insulator (18).

As described above, the battery 10 of this embodiment is a flat plate type battery in which the insulator 18 is in the form of a flat plate and disposed on the upper surface of the solid electrolyte 12.

In the case of a battery having a flat plate shape, in order to increase the energy capacity, the size of the insulator becomes larger as the electrolytic material becomes larger in size, so that the area of contact between the insulator and the cathode and anode plates becomes larger.

The insulator 18 is disposed on the upper surface of the solid electrolyte 12 and the positive electrode plate 20 and the negative electrode plate 30 made of metal are covered with the insulator 18 made of ceramic material, As shown in Fig. Accordingly, the present battery 10 can minimize the bonding area with the metallic material irrespective of the size of the insulator 18, and minimize the thermal stress applied to the insulator due to the difference in thermal expansion coefficient between the metallic material and the ceramic.

The insulator 18 electrically insulates the positive electrode plate 20 and the negative electrode plate 30 from each other.

In the present embodiment, both the negative electrode plate 30 and the positive electrode plate 20 are bonded to each other on the upper surface of the insulator 18. [

For this, the negative electrode plate 30 has a disk shape having a diameter enough to cover the holes 17, and is bonded to the central portion of the upper surface of the insulator 18. The negative electrode plate 30 is bonded to the insulator 18 along the periphery of the hole 17 to be electrically connected to the negative electrode chamber while sealing the negative electrode chamber 16. The junction between the anode plate 30 and the insulator 18 is referred to as a cathode junction 30 for convenience of explanation. The cathode junction 30 is formed in a circular shape around the hole 17 which is the center of the insulator 18.

In this way, the cathode plate 30 is disposed at the center of the insulator 18, so that the cathode junction 30 with the insulator 18 can be formed close to the center of the insulator 18. Even if the size of the insulator 18 is increased due to the large area of the solid electrolyte 12, the bonding area of the cathode bonding portion 30 between the cathode plate 30 and the insulator 18 is lower than the insulator breakage occurrence level due to thermal stress . The thermal stress is applied to the insulator due to the difference between the thermal expansion coefficient of the metal material and the thermal expansion coefficient of the ceramic material, and the thermal stress is increased in proportion to the bonding area between the metal material and the ceramic material. Thus, if a value equal to or higher than the permissible thermal stress of the insulator is applied to the insulator, the insulator is damaged. If the bonding area is limited to a value lower than a value at which breakage occurs in the insulator by thermal stress, breakage of the insulator can be prevented.

Thus, even if the size of the insulator 18 is increased, the diameter of the cathode joint portion 30 with respect to the center of the insulator 18 can be limited, and the joint area of the cathode joint portion 30 can be continuously restricted below a certain level. Accordingly, the thermal stress applied to the cathode joint portion 30 between the anode plate 30 and the insulator 18 is kept below the allowable level irrespective of the size of the insulator 18, so that even if the battery capacity is increased, 18) can be prevented from being damaged.

In addition, in the present embodiment, the cathode plate 20 is formed in the shape of a disk having a size corresponding to that of the solid electrolyte 12, and is disposed under the solid electrolyte 12. The space between the positive electrode plate 20 and the solid electrolyte 12 constitutes the positive electrode chamber 14. The positive electrode plate 20 includes a side plate 22 coupled to an outer end of the insulator 18 and extending to surround the solid electrolyte 12 and a side end of the insulator 18, And an upper plate 24 disposed thereon. That is, the positive electrode plate 20 is bonded to the insulator 18 via the side plate 22 and the upper plate 24. The upper end of the side plate (22) extends above the insulator (18). The positive electrode plate 20 and the side plate 22 are in the form of a single container to enclose the positive electrode compartment, the solid electrolyte 12 and the electrolyte 12.

And an upper plate 24 disposed on the outer surface of the insulator 18 is coupled to the upper end of the side plate 22. [ The upper plate 24 is formed with a hole 26 at a center thereof so as to be separated from the cathode plate 30. The upper plate 24 is a ring-shaped plate structure having a hole 26 at the center thereof. The upper plate 24 is disposed on the upper surface of the insulator 18 and bonded to the insulator 18. Thus, the positive electrode plate 20 is bonded to the insulator 18 via the side plate 22 and the upper plate 24. The junction between the upper plate 24 and the insulator 18 is referred to as an anode junction 28 for convenience of explanation. The anode connection portion 28 is formed in a circular shape along the hole 26.

The anode connection portion 28 is formed on the center of the insulator 18 on the entire surface of the insulator 18 facing the upper plate 24. The present embodiment has a structure in which the upper plate 24 is bonded to the insulator 18 at the inner front end of the hole 26 side in the front surface facing the insulator 18 as shown in Fig.

As described above, in the present battery, when the upper plate 24 and the insulator 18 are bonded, the positive electrode connection portion 28 may be formed close to the center of the insulator 18. Thus, even if the size of the insulator 18 is increased due to the large-sized solid electrolyte 12, the bonding area of the anodic bonding portion 28 can be limited to a level below the breakage level of the insulator 18 due to thermal stress.

As mentioned above, thermal stress is applied to the insulator due to the difference between the thermal expansion coefficient of the metallic material and the thermal expansion coefficient of the ceramic material. The thermal stress is increased in proportion to the bonding area between the metal material and the ceramic material. Thus, if the junction area increases and a value equal to or higher than the permissible thermal stress of the insulator is applied to the insulator, the insulator is damaged. If the bonding area is limited to a value lower than a value at which breakage occurs in the insulator by thermal stress, breakage of the insulator can be prevented.

In the conventional battery, since the insulator is bonded to the outer surface of the solid electrolyte, the diameter of the insulator becomes larger when the solid electrolyte becomes larger, and the area of contact between the insulator and the metal becomes larger, and the insulator is damaged by the thermal stress applied to the insulator. Therefore, in the case of the conventional battery, the solid electrolyte can not be formed larger than a certain size, and it is difficult to realize a large-capacity battery through the large-sized solid electrolyte.

However, in the case of this embodiment, even if the size of the insulator 18 is increased, the bonding position is located at the center of the insulator, the diameter of the positive electrode connection portion 28 with respect to the center of the insulator 18 is limited, The area can be continuously restricted to a certain level or less. Therefore, regardless of the size of the insulator 18, the thermal stress applied to the positive electrode joint portion 28 is kept below the allowable level, so that breakage of the insulator 18 due to thermal stress can be prevented even if the battery capacity increases.

The joining area of the anode joint portion 28 is determined by the inner diameter which is the inner tip and the outer diameter which is the outer tip. Since the inner diameter of the anodic bonding portion 28 is smaller than the outer diameter and is limited by the holes, the area of the anodic bonding portion 28 greatly varies depending on the size of the outer diameter.

The outer diameter D formed by the outer end of the anode connection portion 28 between the upper plate 24 and the insulator 18 may be 60 mm or less with respect to the center of the insulator 18. [ The outer diameter D formed by the outer tip of the anodic bonding portion may be formed such that the width W between the outer tip and the inner tip of the minimum anodic bonding portion is 5 mm or more.

When the outer diameter D formed by the outer tip of the anode connection part 28 exceeds 60 mm, the junction area of the anode connection part exceeds the allowable thermal stress value of the insulator 18 due to the difference in the thermal expansion coefficient between the ceramics of the metal material, 18 are damaged. When the outer diameter D of the anode connection portion 28 is reduced and the width W of the anode connection portion is 5 mm or less, the bonding force is insufficient and there is a high risk of separation of the top plate 24 from the insulator 18, there is a problem.

The upper plate 24 made of a metal material such as the aluminum alloy and the insulator 18 made of an alpha-alumina ceramic material can be bonded through a thermal compression bonding (TCB) process as in the conventional method.

In this embodiment, the top plate 24 and the insulator 18 can be bonded through brazing or ultrasonic bonding, which is a relatively inexpensive process compared to the thermal compression bonding process. The brazing joint is to metallize the surface of the ceramic material of the insulator and then to bond it by reacting with the metallic material at a high temperature. Ultrasonic bonding is performed by inserting a bonding material between an insulating ceramic material and a metallic material, and then irradiating ultrasonic waves. Since many techniques are disclosed for brazing and ultrasonic bonding, the detailed description is omitted here.

As described above, the upper plate 24 and the insulator 18 can be bonded in an area equal to or smaller than the range in which the insulator 18 is broken due to thermal stress at the bonding portion. Therefore, even if the area of the solid electrolyte 12 is increased to increase the capacity of the battery, the upper plate 24 and the insulator 18 can be joined by brazing or ultrasonic bonding, and the insulator 18 is not damaged. Therefore, the battery of the present embodiment can be manufactured at a low cost without performing a hot compression bonding process, which is a relatively expensive process, and can greatly reduce the manufacturing cost of the battery.

2 and 3 show another embodiment of the present battery.

The battery according to the embodiment of FIGS. 2 and 3 is the same as the structure of the battery described above except for the junction structure of the insulator 18. Therefore, the same reference numerals are used for the same components in the following description, and a detailed description thereof will be omitted.

The protrusions 40 protrude outward from the insulator 18 at portions where the insulators 18 are bonded to the upper plate 24 or the negative electrode plate 30 and the protrusions 40 have sloped surfaces 42 at one side So that the upper plate 24 or the cathode plate 30 is bonded to the inclined surface 42.

The protrusions 40 may be formed in a trapezoidal cross-sectional shape on the insulator 18. The outer side surface of the projection (40) forms an inclined surface (42). The upper plate 24 or the cathode plate 30 is bent along the inclined surface 42 so as to be joined to the inclined surface 42 of the projection 40.

2, the upper plate 24 or the cathode plate 30 may have a structure in which the curved distal end portion is bonded only to the sloped surface 42 in contact with the outer sloped surface 42 of the projection 40 .

3, the upper end of the upper plate 24 or the upper end of the negative electrode 30 is bent so that the tip end of the upper plate 24 contacts the inclined surface 42 of the projection 40 and the inclined surface 42 and the adjacent The protrusion may be joined to the outer surface of the protrusion.

The anode connection portion 28 between the upper plate 24 and the insulator 18 is formed on the surface of the projection including the outer inclined surface 42 and the inclined surface of the projection 40 in the above embodiment. The cathode bonding portion 30 between the cathode plate 30 and the insulator 18 is formed on the surface of the protrusion 40 including the inclined surface 42 and the inclined surface.

The upper plate 24 or the negative plate 30 which is a metal material is bonded to the inclined surface 42 formed on the outer surface of the protrusion while enclosing the protrusion 40 so that the stress generated in the insulator 18, which is a ceramic material, And the possibility of breakage of the insulator is lowered.

As described above, since the anode junction portion 28 or the cathode junction portion 30 is formed in the protrusion 40 protruding from the insulator 18, the thermal stress applied to the insulator 18 can be further reduced. remind

Example

A battery according to this embodiment and a battery according to the prior art were manufactured, and the bonding force between the metal material and the insulator was tested.

The examples in Table 1 below are cells manufactured according to an embodiment of the present invention, and the comparative example is a battery manufactured according to the prior art. In both the examples and the comparative examples, the size of the insulator was the same, and Al3003 aluminum alloy was used as the metal material bonded to the insulator.

The bonding between the metal and the insulator was achieved through hot compression bonding, brazing bonding and ultrasonic bonding. The bonded cell was subjected to leakage evaluation using helium gas. The leakage experiment using the helium gas was performed by injecting the battery manufactured in the chamber and vacuuming the helium gas, injecting helium into the chamber, and forcing it into the cell. Leak evaluation was performed by repeating the temperature rise and the temperature decrease five times between the operating temperature of 300 DEG C and room temperature, and measuring the concentration of helium gas emitted to the outside by using a helium gas concentration meter.

Electrolyte
Diameter (mm) Joining method Leak experiment result After manufacturing After the lift-on test Comparative Example 1 50 Hot compression bonding none none Comparative Example 2 120 Hot compression bonding Leak Insulation ring breakage Comparative Example 3 120 Brazing Insulator breakdown - Comparative Example 4 120 ultrasonic wave Insulator breakdown - Example 1 120 Hot compression bonding none none Example 2 120 Brazing none none Example 3 120 ultrasonic wave none none

Experimental Results As shown in Table 1, in the comparative example, leakage of the battery was confirmed by measuring the helium gas. However, in this embodiment, good battery sealing is maintained without leakage even after the lift-on repetitive test.

While the illustrative embodiments of the present invention have been shown and described, various modifications and alternative embodiments may be made by those skilled in the art. Such variations and other embodiments will be considered and included in the appended claims, all without departing from the true spirit and scope of the invention.

10: Battery 12: Solid electrolyte
14: anode chamber 16: cathode chamber
17: Hole 19: Felt collector
18: insulator 20: positive electrode plate
22: side plate 24: top plate
26: hole 28: anode connection
30: cathode plate 32: cathode joint
40: projection 42:

Claims (8)

An anode chamber that accommodates sulfur and is disposed on one surface of the solid electrolyte; a cathode chamber that contains sodium and is disposed on the opposite surface of the anode chamber with respect to the anode chamber; And a negative electrode plate connected to the insulator to seal the negative electrode chamber, wherein the positive electrode plate is connected to the insulator,
Wherein the insulator is in the form of a flat plate and is disposed on one side of the solid electrolyte and is joined to the solid electrolyte, wherein an inner space between the solid electrolyte and the insulator forms a cathode chamber, a hole communicating with the cathode chamber is formed at the center of the insulator, The cathode plate is connected to the cathode chamber at the outer center portion of the insulator and connected to the cathode chamber. The cathode plate is coupled to a side plate extending to surround the solid electrolyte and the insulator at the outer end, And the upper plate has a hole formed at the center thereof and spaced apart from the negative plate to be bonded to an insulator. The method according to claim 1,
Wherein the insulator has protrusions protruding outwardly from a joint portion between the upper plate or the negative plate and the protrusions are formed at one side with an inclined surface so that the upper plate or the negative plate is bonded to the inclined surface. 3. The method according to claim 1 or 2,
Wherein the junction of the upper plate and the insulator is biased to the center of the insulator facing the upper plate. The method of claim 3,
Wherein the upper plate of the positive electrode plate is joined to the insulator at an inner front end of the hole in the front face facing the insulator. 5. The method of claim 4,
Wherein an outer diameter of the outer end of the joint portion formed between the upper plate and the insulator with respect to the center of the insulator is 60 mm or less. 6. The method of claim 5,
Wherein an outer diameter formed by an outer end of a joint portion formed between the upper plate and the insulator with respect to the center of the insulator is formed to be 5 mm or more in width between an outer end and an inner end of the joint. The method according to claim 6,
Wherein the upper plate or the negative electrode plate is brazed to an insulator. The method according to claim 6,
Wherein the upper plate or the negative plate is ultrasonically bonded to an insulator.

Images