KR101249048B1 - SODIUM SULFUR(NaS) CELL AND MANUFACTURING METHOD THEREOF - Google Patents

Abstract

A sodium sulfur (NsS) battery and a method of manufacturing the same are disclosed. The NaS cell includes an electrolyte, a sodium electrode and a sulfur electrode, and the electrolyte includes a tube and a hemispherical ceramic coated on the tube outer surface. The tube may be made of beta alumina or a two-layer laminated structure of an alpha alumina base material and a beta alumina layer. The hemispherical ceramic may have a diameter of 0.3 to 100 μm, and the ratio of the surface area coated with the hemispherical ceramic to the uncoated surface area may range from 3: 7 to 7: 3. The hemispherical ceramic can be coated with a uniformity of ± 25% in width and height. Such NaS cells prevent sodium sulfide from adhering to the outer surface of the electrolyte tube and allow it to escape easily even if attached. Thus, by keeping the reaction area of sodium and sulfur constant during battery charging and discharging, the input / output quality is improved and long-term output efficiency is stably provided.

Description

Sodium Sulfur (NAS) Battery and Manufacturing Method Thereof {SODIUM SULFUR (NaS) CELL AND MANUFACTURING METHOD THEREOF}

The present invention relates to a sodium sulfur (NaS) battery, and more particularly to a NaS battery with improved solid electrolyte and a method of manufacturing the same.

NaS battery is a large capacity power storage battery, which has high energy density and charging and discharging efficiency, no self-discharge, long life of 15 years or more, and exhibits no deterioration in performance even in irregular charging and discharging. In particular, the raw materials used are inexpensive and easily available, and they are not affected by environmental changes such as ambient temperature changes.

NaS batteries use sodium as the negative electrode active material, sulfur as the positive electrode active material, and solid beta (β) alumina ceramics as the electrolyte. Beta alumina is a ceramic having the property of passing only sodium ions. Through this beta alumina, sodium ions move between the negative electrode and the positive electrode to perform charge and discharge.

The most critical component of NaS cells is beta alumina electrolyte, which depends on the successful development of technologies such as powder synthesis with accurate composition, molding into thin and long tube shapes, and sintering for final dimensional control.

Since the beta alumina electrolyte tube shrinks about 15% from the powder compact to the sintered compact, it is very difficult to control the size of the final product, so it is very important to prepare the starting powder into a spherical powder of uniform size.

Beta alumina has a β phase of Na ₂ O · 11Al ₂ O ₃ composition and Na ₂ O · 5Al ₂ O ₃ The β ^〃 phase of 3Na ₂ O · 16Al ₂ O ₃ composition is collectively referred to.

The specific resistance of the β-phase alumina and the specific resistance of the β ^〃 phase alumina are 16 Ω · cm and 2.5 Ω · cm, respectively. That is, since the β ^〃 phase has a low value of about 1/6, it is excellent, so that the β ^〃 phase content in the final product should be 95% or more.

The theoretical density of the β-phase alumina and the theoretical density of the β- ^VII alumina are 3.25 g / cm 3 and 3.28 g / cm 3, respectively. Considering the specific resistance and density of beta alumina, densification of more than 98% of theoretical density should be achieved.

However, the β ^〃 phase is unstable at a high temperature of more than 1400 ° C., which is a sintering temperature range, and thus decomposes into a β phase or exists as a meta-stable phase. Therefore, many β ^제조 phases should be manufactured to have a stable structure.

To this end, there is a method of lowering the sintering temperature, adding a stabilizer such as MgO or Li ₂ O, or increasing the β ^〃 phase content by heat treatment. However, these methods have a problem that the manufacturing process is complicated, difficult to control and high manufacturing cost.

Meanwhile, sodium located inside the beta alumina tube emits electrons when discharged to become sodium ions. The sodium ions pass through the beta alumina tube to the anode side and then react with sulfur and electrons to produce sodium sulfide.

During charging, sodium sulfide releases electrons to separate sodium ions and sulfur. Sodium ions pass through the beta alumina tube to the cathode and then receive electrons and return to sodium.

However, sodium sulfide produced during discharge is easily attached to the outer surface of the beta alumina tube. Then, since the reaction area is reduced as much as sodium sulfide is attached, the output efficiency of the NaS battery is decreased, and as a result, battery performance is deteriorated with time.

The present invention is to provide a NaS battery comprising a solid electrolyte that prevents the sodium sulfide produced during discharge from adhering to the outer surface of the electrolyte tube, and easily detached even when attached thereto, and a method of manufacturing the same.

The NaS battery according to an embodiment of the present invention includes an electrolyte, a sodium electrode, and a sulfur electrode, and the electrolyte includes a tube and a hemispherical ceramic coated on the tube outer surface.

The tube is made of beta alumina and may be 1 to 2.5 mm thick.

NaS battery according to another embodiment of the present invention comprises an electrolyte, a sodium electrode and a sulfur electrode, the electrolyte, hemispherical coated on the alpha (α) alumina tube, the beta alumina layer coated on the outer surface of the tube, and the beta alumina layer Ceramics of the phase.

The hemispherical ceramic may have a diameter of 0.3 to 100 μm.

Hemispherical ceramics include alumina (Al ₂ O ₃ ), silica (SiO ₂ ), alumina-silica (Al ₂ O ₃ -SiO ₂ ), zirconia (ZrO ₂ ), and mullite (3Al ₂ O ₃ · 2SiO ₂ ) It may be any one of.

The ratio of the surface area coated with the hemispherical ceramic to the uncoated surface area may range from 3: 7 to 7: 3.

The hemispherical ceramic can be coated with a uniformity of ± 25% in width and height.

The alpha alumina tube may be a porous material having a 35 to 70% porosity.

The thickness of the alpha alumina tube is 1 ~ 2.5mm, the thickness of the beta alumina layer may be 5 ~ 500㎛.

NaS manufacturing method according to an embodiment of the present invention, in preparing an electrolyte of a sodium sulfur (NaS) battery including an electrolyte and a sodium electrode and a sulfur electrode, the step of producing a tube, and the hemispherical ceramic on the outer surface of the tube Coating.

Producing the tube may include processes of beta alumina powder synthesis, molding and sintering.

Alternatively, the manufacturing of the tube may include synthesizing beta alumina powder and molding the synthesized powder, and may further include sintering after coating the hemispherical ceramic on the outer surface of the tube. .

The manufacturing of the tube may include synthesizing, molding and sintering an alpha alumina powder, and coating a beta alumina layer on an outer surface of the sintered alpha alumina.

Alternatively, the manufacturing of the tube may include forming a synthesized alpha alumina powder and coating a beta alumina layer on the outer surface of the formed alpha alumina, and after coating the hemispherical ceramic on the outer surface of the tube. It may further comprise the step of sintering.

The hemispherical ceramic may be coated with a diameter of 0.3 to 100 μm using any one of wet spraying followed by drying, thermal spray coating, chemical vapor deposition (CVD), and physical vapor deposition (PVD).

The hemispherical ceramic may be coated such that the ratio of coated and uncoated surface area is in the range of 3: 7 to 7: 3.

The hemispherical ceramic may be coated to have a uniformity of ± 25% in width and height.

The beta alumina layer is formed by using any one of dipping method, drying after wet spraying, sol-gel method, thermal spray coating, chemical vapor deposition (CVD), and physical vapor deposition (PVD). It can be coated to a thickness of 500 μm.

According to the NaS battery according to the present invention, by coating the hemispherical ceramic on the outer surface of the electrolyte tube to prevent the sodium sulfide from adhering to the outer surface of the tube and easily detached even if attached. Therefore, by maintaining a constant reaction area of sodium and sulfur during battery charging and discharging, there is an effect of improving input / output quality and stably providing long-term output efficiency.

When the electrolyte tube has a two-layer laminated structure of an alpha alumina base material and a beta alumina layer, the beta alumina layer is coated with a thin thickness, and thus has low electrical resistance, thereby providing a high performance electrolyte.

In the case of the two-layer laminated structure, the mechanical strength of the entire electrolyte tube is maintained by using the mechanical strength of the alpha-alumina, which is the base material, thereby providing mechanical stability and preventing breakage in advance.

1 is a view showing the internal structure of a NaS unit cell according to an embodiment of the present invention.
2 is a cross-sectional view showing an electrolyte of a NaS battery according to an embodiment of the present invention.
3 is a cross-sectional view showing an electrolyte of a NaS battery according to another embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The following examples are merely provided to make the disclosure of the present invention complete, and to fully convey the scope of the invention to those skilled in the art, and the present invention is defined by the scope of the claims. Is defined. Like reference numerals refer to like elements throughout.

Hereinafter, a NaS battery according to an embodiment of the present invention will be described with reference to the accompanying drawings. For reference, in the following description of the present invention, if it is determined that the detailed description of the related air intelligence function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

1 is a view showing the internal structure of the NaS unit cell 100 according to an embodiment of the present invention.

Referring to FIG. 1, the NaS unit cell 100 has a cylindrical shape and is arranged in the order of the sodium electrode 10, the metal tube 20, the electrolyte 30, the sulfur electrode 40, and the precursor 50 from the center. do.

Such a single cell alone has a low electromotive force of 2 V and a small capacity, thus forming a modular battery in which a plurality of single cells are connected in series and in parallel.

The electrolyte 30 has a tube shape, and the metal tube 20 is housed inside the tube to prevent abnormal current of the unit cell or increase of the internal temperature when the alumina ceramic, which is the electrolyte, is broken.

Referring to an enlarged view of a portion indicated by a dotted circle in FIG. 1, a sodium flow passage 15, which is a passage through which sodium flows, is formed outside the metal tube 20.

2 is a cross-sectional view showing the electrolyte 30.

1 and 2, the electrolyte 30 according to the present invention has a structure including a tube 32 and a hemispherical ceramic 36 coated on an outer surface of the tube 32.

The tube 32 may be made of beta alumina, or may be a two-layer laminated structure.

The tube 32 made of beta alumina may have a thickness of 1 to 2.5 mm.

This is because if the thickness of the beta alumina tube 32 is less than 1 mm, it is too thin to ensure mechanical stability as a solid electrolyte. If the thickness of the tube 32 exceeds 2.5 mm, the beta alumina tube 32 becomes too thick and the electrical resistance becomes high.

3 is a cross-sectional view of the electrolyte 30 showing the case where the tube 32 is a two-layer laminated structure. As shown in FIG. 3, the tube 32 is a two-layer laminated structure in which the beta alumina layer 32b is thinly coated on the alpha alumina base material 32a, and the hemispherical ceramic 36 is formed on the beta alumina layer 32b. Is coated on.

In this case, the alpha alumina base material 32a should be a porous material so that sodium ions can permeate. In this case, the pores are preferably in the form of open pores connected to each other. For example, it is preferable that it is a porous material which has 35 to 70% porosity.

This is because when the porosity is less than 35%, the permeation rate of Na ions decreases, thereby deteriorating the charge / discharge performance of the battery. When the porosity exceeds 70%, the strength is low, and mechanical stability as an electrolyte tube cannot be guaranteed.

The thickness of the alpha alumina base material 32a is determined to an extent that can guarantee mechanical stability as the electrolyte tube, and may be, for example, 1 to 2.5 mm thick.

If the thickness of the alpha alumina base material 32 is less than 1 mm, it is too thin to ensure mechanical stability as the electrolyte tube, and if it exceeds 2.5 mm, it is difficult to manufacture a compact module.

The thinner the beta alumina layer 32b is preferable, the lower the electrical resistance is, but the thickness of the beta alumina layer 32b can be completely covered to cover the outer surface of the alpha alumina base material 32a. For example, the thickness may be 5 to 500 μm.

This is because if the thickness of the beta alumina layer 32b is less than 5 μm, the outer surface of the alpha alumina base material 32 a may not be completely covered.

The thin beta alumina layer 32b as described above has a low specific resistance as well as maintaining the existing β ^값 phase content level, thereby becoming a high performance electrolyte.

The hemispherical ceramic 36 has a diameter of 0.3 to 100 µm and is shaped like water droplets on the surface. The term “semi-spherical” here means that the particles to be coated are coated in island form before forming the film. Therefore, it does not mean a geometric hemisphere exactly half of the sphere, and in some cases, may be a shallow island shape less than the hemisphere, or may be a shape closer to the sphere than the hemisphere.

The hemispherical ceramic 36 may be coated with a uniformity of ± 25% in width and height.

The hemispherical ceramic 36 makes surface unevenness on the outer surface of the tube 32, making it more difficult to attach sodium sulfide than a flat surface having no unevenness. Even if sodium sulfide is difficult to attach, sodium sulfide is easily released by sodium ions moving from the inside of the tube 32 to the outside.

If the diameter of the hemispherical ceramic 36 is outside the range of 0.3 ~ 100㎛ range, the desired effect of preventing the attachment of sodium sulfide.

The material of the hemispherical ceramic 36 does not react with sulfur and does not show a big difference in terms of the distance and structure between the tube 32 and the atom, so that the coating is easily performed and the electrical properties do not vary significantly. It is suitable if the substance does not adversely affect.

For example, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), alumina-silica (Al ₂ O ₃ -SiO ₂ ), zirconia (ZrO ₂ ), and mullite (3Al ₂ O ₃ · 2SiO ₂ ) It may be any one of.

The ratio of the surface area coated with the hemispherical ceramic 36 to the uncoated surface area may range from 3: 7 to 7: 3.

This means that when the ratio of the coated surface area and the uncoated surface area is less than 3: 7, the hemispherical ceramic is coated with too little to reduce the desired sodium sulfide adhesion preventing effect, and when the ratio exceeds 7: 3, the sodium ion is positively coated. This is because battery performance is reduced by preventing movement to the side.

The hemispherical ceramic 36 is preferably distributed as evenly as possible over the entire outer surface of the tube 32.

If the hemispherical ceramic 36 is not evenly distributed over the entire outer surface of the tube 32 and is concentrated in a certain area, other areas remain as uncoated layers. The current flows intensively into the uncoated area, which can overload and destroy the tube 32. For this reason, the hemispherical ceramic 36 is preferably distributed evenly over the entire outer surface of the tube 32.

In the NaS battery according to the embodiment of the present invention, in order to prepare an electrolyte, a tube 32 is first manufactured.

The tube 32 can be manufactured by the conventional ceramic manufacturing process of synthesizing beta alumina powder, shape | molding to a tube shape, and sintering.

Alternatively, the tube 32 may be manufactured in a two-layer laminated structure of the alpha alumina base material 32a and the beta alumina layer 32b. In this case, the alpha alumina base material 32a is produced by the normal ceramic manufacturing process of alpha alumina powder synthesis | combination, shaping | molding to a tube shape, and sintering, and then the beta alumina layer 32b is thinly coated on the outer surface.

In the case of the two-layer laminated structure, the beta alumina layer 32b may be dipped, dried after wet spraying, sol-gel, spray coating, chemical vapor deposition (CVD), or physical vapor deposition ( Coating can be carried out using conventional ceramic coating methods including PVD).

For example, in the immersion method, the alpha alumina base material 32a is immersed in a slurry in which beta alumina powder is dispersed for a predetermined time and then dried to coat the beta alumina layer 32b.

Sintering of the tube 32 may also be carried out after coating the hemispherical ceramic 36.

Next, the hemispherical ceramic 36 is coated on the outer surface of the tube 32.

When coating the hemispherical ceramic 36, conventional ceramic coating methods including wet spraying, drying, sol-gel method, thermal spray coating, chemical vapor deposition (CVD) and physical vapor deposition (PVD) Can be used.

At this time, since the film is formed when the coating time is long, the hemispherical ceramic 36 having a diameter of 0.3 to 100 μm is coated in the same shape as that of water droplets before the coating is finished.

When coating, it is preferable to coat so that the ratio of the surface area coated with the hemispherical ceramic 36 and the uncoated surface area is in the range of 3: 7 to 7: 3, and evenly distributed on the outer surface of the tube 32.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention is not limited to the following examples.

<Examples>

The alpha alumina powder was synthesized, molded into a tube shape, and then sintered to prepare an alpha alumina base material. At this time, the alpha alumina base material was produced with a porosity of 50%, and the thickness was 1.5mm.

A beta alumina layer was coated on the outer surface of the alpha alumina base material to a thickness of 15 μm by the sol-gel method.

The specific resistance of the beta alumina layer was 0.2 Ω · cm at 350 ° C. This was confirmed to be a significantly lower value than the conventional 0.5 Ω · cm.

Next, Al ₂ O ₃ was coated on the beta alumina layer by thermal spraying. At this time, the coated Al ₂ O ₃ had a hemispherical shape with a diameter of 0.8 μm, and the ratio of the hemispherical Al ₂ O ₃ coated surface area and the uncoated surface area was 5: 5, and the hemispherical Al ₂ O ₃ width and height It was uniform in the range of ± 25% in the size of.

Using the electrolyte thus prepared it was confirmed that there is no leakage of sodium and sulfur.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

100: cell 10: sodium electrode
20: metal tube 30: electrolyte
32: tube 36: hemispherical ceramic
32a: alpha alumina base material 32b: beta alumina layer
40: sulfur pole 50: precursor

Claims (19)

In a sodium sulfur (NaS) battery comprising an electrolyte, a sodium electrode and a sulfur electrode,
The electrolyte,
tube; And
Hemispherical ceramic coated on the outer surface of the tube
Sodium sulfur (NaS) battery comprising a. The method of claim 1,
The tube is made of beta alumina, the thickness of 1 ~ 2.5mm sodium sulfur (NaS) battery. In a sodium sulfur (NaS) battery comprising an electrolyte, a sodium electrode and a sulfur electrode,
The electrolyte,
Alpha alumina tubes;
A beta alumina layer coated on the outer surface of the tube; And
Hemispherical ceramic coated on the beta alumina layer
Sodium sulfur (NaS) battery comprising a. The method according to claim 1 or 3,
The hemispherical ceramic is sodium sulfur (NaS) battery having a diameter of 0.3 ~ 100㎛. The method according to claim 1 or 3,
The hemispherical ceramic is alumina (Al ₂ O ₃ ), silica (SiO ₂ ), alumina-silica (Al ₂ O ₃ -SiO ₂ ), zirconia (ZrO ₂ ), and mullite (mullite: 3Al ₂ O ₃ .2SiO ₂₎ Sodium sulfur (NaS) battery of any one of). The method according to claim 1 or 3,
Sodium sulfur (NaS) battery wherein the ratio of the surface area coated with the hemispherical ceramic and the uncoated surface area is in the range of 3: 7 ~ 7: 3. The method according to claim 1 or 3,
The hemispherical ceramic is coated with a sodium sulfur (NaS) battery having a uniformity of ± 25% in width and height. The method of claim 3,
The alpha alumina tube is a sodium sulfur (NaS) battery is a porous material having a 35 to 70% porosity. The method of claim 3,
The thickness of the alpha alumina tube is 1 ~ 2.5mm and the thickness of the beta alumina layer is 5 ~ 500㎛ sodium sulfur (NaS) battery. In the manufacture of a sodium sulfur (NaS) battery comprising an electrolyte, a sodium electrode and a sulfur electrode,
Preparation of the electrolyte,
Manufacturing a tube; And
Coating a hemispherical ceramic on the outer surface of the tube
Sodium sulfur (NaS) battery manufacturing method comprising a. The method of claim 10,
Producing the tube,
Sodium sulfur (NaS) battery manufacturing method comprising the process of beta alumina powder synthesis, molding and sintering. The method of claim 10,
The manufacturing of the tube includes synthesizing beta alumina powder and molding the synthesized powder,
Sodium sulfur (NaS) battery manufacturing method further comprising the step of sintering after coating the hemispherical ceramic on the outer surface of the tube. The method of claim 10,
Producing the tube,
Synthesis, molding and sintering of alpha alumina powder, and coating a beta alumina layer on the outer surface of the sintered alpha alumina. The method of claim 10,
The manufacturing of the tube may include forming a synthesized alpha alumina powder and coating a beta alumina layer on an outer surface of the formed alpha alumina,
Sodium sulfur (NaS) battery manufacturing method further comprising the step of sintering after coating the hemispherical ceramic on the outer surface of the tube. The method according to any one of claims 10 to 14,
The hemispherical ceramic is alumina (Al ₂ O ₃ ), silica (SiO ₂ ), alumina-silica (Al ₂ O ₃ -SiO ₂ ), zirconia (ZrO ₂ ), and mullite (mullite: 3Al ₂ O ₃ .2SiO ₂₎ Sodium sulfur (NaS) battery manufacturing method for coating any one of)) so that the diameter is 0.3 ~ 100㎛. The method according to any one of claims 10 to 14,
The hemispherical ceramic is coated with any one of dry, spray coating, chemical vapor deposition (CVD), and physical vapor deposition (PVD) after wet spraying. The method according to any one of claims 10 to 14,
The hemispherical ceramic is a sodium sulfur (NaS) battery manufacturing method of coating so that the ratio of the surface area and the uncoated surface area coated with the ceramic is in the range of 3: 7 ~ 7: 3. The method according to any one of claims 10 to 14,
The hemispherical ceramic is a sodium sulfur (NaS) battery manufacturing method for coating to have a uniformity of ± 25% in the size of the width and height. The method according to claim 13 or 14,
The beta alumina layer may be dried using any one of dipping, wet spraying, sol-gel, spray coating, chemical vapor deposition (CVD), and physical vapor deposition (PVD). Sodium sulfur (NaS) battery manufacturing method of coating to a thickness of ~ 500㎛.

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