KR102048405B1 - Sodium-base battery operated at intermediate temperature and method for preparing the same - Google Patents

Abstract

The present invention is a negative electrode container for receiving sodium; A cathode container accommodating a cathode active material and a cathode secondary electrolyte; A solid electrolyte positioned between the cathode vessel and the anode vessel to selectively move sodium ions; And a polymer sealing layer formed along an edge of the solid electrolyte and positioned between the solid electrolyte and the negative electrode container and the positive electrode container. In the sodium secondary battery of the present invention, an expensive bonding process and an expensive bonding facility are unnecessary by using the polymer sealing layer, the number of unit cell parts is reduced, and the battery manufacturing process can be simplified.

Description

Mid-low temperature driving sodium secondary battery and a manufacturing method therefor {SODIUM-BASE BATTERY OPERATED AT INTERMEDIATE TEMPERATURE AND METHOD FOR PREPARING THE SAME}

The present invention relates to a low temperature driving sodium battery.

In general, sodium-based batteries (sodium-sulfur batteries, ZEBRA batteries) operating at high temperatures have high energy density, high charge and discharge efficiency, no self-discharge, and low performance for long-term operation. It is developed as a battery.

The high temperature sodium battery is a beta-alumina ceramic solid electrolyte having sodium (Na) as a negative electrode active material and sulfur (S) or metal halide (NiCl ₂ , FeCl ₂ ) as a positive electrode active material, and both having conductivity to sodium ions. The secondary battery is sealed by an Al, Ni, or Fe-based alloy member and driven at a temperature of 280 to 350 ° C. However, in order to impart long-term sealing characteristics at 280 to 350 ° C., heterogeneous bonding between the solid electrolyte ceramic and the external metal member is required, and for this purpose, 550 to 1500 using Al or Mo fillers between the ceramic and the metal member. Thermal compression bonding is used, which is thermally pressed between ℃.

In order to apply such a process, expensive equipment having a complicated structure is required, and due to thermal stress caused by a difference in thermal expansion coefficient, a solid electrolyte is usually manufactured in a small diameter cylinder.

The confidentiality of ¹⁰ mbar · L / sec ^{required-existing} Na / NiCl 10 ^-3 ~ 10 in order to drive the cell at a drive temperature range (~ 300 ℃) of the _second cell in order to suppress the reaction between the active material and the atmosphere, such as oxygen Existing manufacturers use expensive joining methods that require high temperature, high pressure, and high vacuum, such as thermal compression bonding (TCB), glass sealing, electron beam welding, and laser welding. It manufactures a unit cell.

Accordingly, the present invention is operated at a low or medium temperature below 200 ℃, by greatly bonding the metal-metal, ceramic-ceramic, ceramic-metal using a polymer material, the number of parts is greatly reduced, the battery manufacturing process of the sodium battery greatly simplified For design and manufacture purposes.

According to an aspect of the invention, the negative electrode container for receiving sodium; A cathode container accommodating a cathode active material and a cathode secondary electrolyte; A solid electrolyte positioned between the cathode vessel and the anode vessel to selectively move sodium ions; And a polymer sealing layer formed along an edge of the solid electrolyte and positioned between the solid electrolyte and the negative electrode container and the positive electrode container.

The polymer sealing layer is polyethylene, high molecular polyethylene, high molecular polyethylene, polyimide, thermoplastic polyimide, polyvinylidene fluoride, polytetrafluoroethylene ), Perfluoroalkoxy alkane, polyetheretherketone, and one or more selected from fluorinated ethylene propylene.

The solid electrolyte may include at least one selected from beta-alumina and NaSiCon.

The thickness of the solid electrolyte may be 100um to 3mm.

The cathode active material may include at least one selected from Ni, Fe Cu, and Zn, at least one selected from Al, NaI, NaF, S, and FeS, and NaCl.

The cathode secondary electrolyte may include at least one selected from NaAlCl ₄ , NaAlCl ₄ -NaAlBr ₄ , NaAlCl ₄ -LiCl, and NaAlCl ₄ -LiBr.

The driving temperature of the sodium secondary battery may be 95 to 250 ° C.

According to another aspect of the invention, the cathode container containing sodium; A cathode container accommodating a cathode active material and a cathode secondary electrolyte; A solid electrolyte positioned between the cathode vessel and the anode vessel to selectively move sodium ions; And a polymer sealing layer formed along an edge of the solid electrolyte and positioned between the solid electrolyte and the negative electrode container and the positive electrode container. It includes and the polymer sealing layer is to be sealed by a thermocompression process, there is provided a method for producing a sodium secondary battery.

The thermocompression may be performed at 100 to 400 ° C.

In the sodium secondary battery of the present invention, an expensive bonding process and an expensive bonding facility are unnecessary by using the polymer sealing layer, the number of unit cell parts can be reduced, and the battery manufacturing process can be simplified.

 In addition, in the sodium secondary battery of the present invention, as the driving temperature is lowered, the deterioration rate of the cathode material may be greatly reduced.

1 is a schematic diagram schematically showing a concept of a sodium secondary battery of the present invention.
Figure 2 shows the charge and discharge test results of the sodium secondary battery according to Example 1 of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

Hereinafter, the sodium secondary battery of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

As shown in FIG. 1, the sodium secondary battery 7 of the present invention includes a negative electrode container 1, a positive electrode container 2, and a solid electrolyte 3. The negative electrode container 1 and the positive electrode container 2 are disposed outside the sodium battery with the solid electrolyte 3 interposed therebetween to form an appearance, and accommodate the contents therein.

The cathode container 1 accommodates sodium therein and may be made of a metal material such as aluminum or stainless steel. The surface of the cathode container 1 may be coated with a corrosion resistant layer containing chromium, molybdenum and the like as a main component. The negative electrode container 1 also serves as an external terminal of the negative electrode.

The cathode container 2 accommodates a cathode active material and a cathode secondary electrolyte therein and is formed on one side of the solid electrolyte to face the cathode container. Like the cathode container 1, the cathode container 2 may be made of a metal material, such as aluminum or stainless steel, and a corrosion resistant layer mainly composed of chromium, molybdenum, etc. on the surface thereof, similarly to the cathode container 1 This can be coated. In addition, the positive electrode container 2 also serves as an external terminal of the positive electrode.

The cathode active material accommodated in the cathode container may include at least one selected from Ni, Fe Cu, and Zn, at least one selected from Al, NaI, NaF, S, and FeS, and NaCl.

In addition, the cathode secondary electrolyte accommodated with the cathode active material in the cathode container may be NaAlCl ₄ , NaAlCl ₄ -NaAlBr ₄ , NaAlCl ₄ -LiCl and NaAlCl ₄ -LiBr, and preferably NaAlCl ₄ .

The sodium secondary battery according to the present invention uses liquid sodium (Na) as a negative electrode active material and NiCl ₂ as a positive electrode active material as a state of charge. Since the batteries are assembled in a discharged state, nickel (Ni) and salt (NaCl) powders are used as the cathode material, and NaAlCl ₄ (sodium alumino tetra-chloride) is used as the anode secondary electrolyte (or liquid electrolyte). As the sodium ions (Na ⁺ ) contained in NaCl and NaAlCl ₄ move to the cathode part and are reduced, Na (l) is formed, and Cl ^−, which has high activity, reacts with Ni powder to form NiCl ₂ at the anode part. Let's do it.

At this time, the solid electrolyte 3 is in contact with each other between the negative electrode container 1 and the positive electrode container 2 to separate the liquid sodium, the positive electrode active material and the positive electrode secondary electrolyte, the solid electrolyte 3 is the negative electrode active material and the positive electrode Only the active material positive electrode material sodium ions are selectively transmitted, and the positive electrode container 1 and the negative electrode container 2 are insulated from each other.

The solid electrolyte is not necessarily limited thereto, and may be suitably used in the present invention as long as it can be applied in a sodium secondary battery. For example, the solid electrolyte may be beta-alumina (BASE, β / β ”-Al ₂ O ₃ , beta-alumina solid electrolyte), NaSiCon, or the like, and preferably beta-alumina. .

In order to maximize battery performance, it is advantageous to maintain high Na ion conductivity of the solid electrolyte. For this purpose, the thinner the solid electrolyte and the higher the driving temperature of the battery, the lower the area resistance of the solid electrolyte. Therefore, the present invention is not particularly limited, but the thickness of the solid electrolyte may range from about 100 μm to 2 mm.

When liquid sodium contained in the negative electrode container 1 or positive electrode secondary electrolyte contained in the positive electrode container 2 leaks, the safety of the battery is impaired. Thus, the solid electrolyte 3, the negative electrode container 1, and the positive electrode container 2 are sealed by a sealing layer to prevent leakage from each container.

Conventionally, in order to prevent leakage of such metal-ceramic joints, sealing is performed using a thermocompression bonding method using an insert metal material such as aluminum. However, in order to impart long-term sealing characteristics of sodium batteries, heterojunction between the solid electrolyte ceramic and the external metal member is required, and for this purpose, an Al or Mo filler is used between the ceramic and the metal member to 550 to 1500 ° C. There is a problem that a high temperature thermocompression bonding step is required.

Accordingly, the present invention uses a sealing layer 4 made of a polymer material as the sealing layer. In the case of using the polymer sealing layer 4 as proposed in the present invention, it is possible to design a low-cost and simple manufacturing process without an expensive thermocompression process, and to lower the driving temperature to a temperature at which a low-cost bonding process is applicable. Moreover, it can drive even 200 degrees C or less.

The polymer sealing layer may be suitably used as long as the polymer material has excellent heat resistance and can be used at a driving temperature. For example, polyethylene, high molecular polyethylene, polyimide, and thermoplastic poly Thermoplastic polyimide, polyvinylidene fluoride, polytetrafluoroethylene, perfluoroalkoxy alkane, polyetheretherketone and fluorinated ethylene propylene ethylene propylene) and the like, preferably high molecular weight polyethylene.

The temperature at which the polymer for high temperature can be used continuously is usually 220 ° C., but if there is a material that can be used continuously at a higher temperature, the present invention can be applied even at a higher temperature.

The driving temperature of the sodium secondary battery is adjustable according to the material of the sealing layer used, for example, may be 95 to 250 ℃, preferably 160 to 210 ℃.

By lowering the operating temperature of sodium secondary batteries, expensive joints requiring high temperature, high pressure, and high vacuum such as TCB (thermal compression bonding), glass sealing, electron beam welding, and laser welding are required. The method can be replaced by a simple low-cost bonding method such as polymer bonding.

The polymer sealing layer may be formed by a thermocompression process performed in the air.

Although the polymer sealing layer is not particularly limited, sealing the sodium secondary battery by joining adjacent parts by a thermocompression process is preferable because it is inexpensive and easy to process.

The thermal compression may vary depending on the material of the sealing layer used, for example, it may be carried out at 100 to 400 ℃, preferably at 200 to 350 ℃.

When the present invention is applied to a flat design, the cells can be completed through one heating-up and down pressing process after laminating necessary parts one by one. Of course, the same concept can be applied to cell designs having other shapes such as tubular shapes.

[ Example ]

Hereinafter, an Example is given and this invention is demonstrated more concretely. The following examples are intended to illustrate the present invention in more detail, and the present invention is not limited thereto.

Example  One

Nickel powder and salt (NaCl) were mixed in the positive portion at a weight ratio of 1.2: 1 to 2: 1, and additives such as Al, NaI, NaF, S, and FeS _x were added at 0.5 to 3 wt% and mixed. Thus obtained mixture was compressed and pulverized into coarse particles (granule) having an average diameter in the range of 400 μm to 1.5 mm to obtain a positive electrode active material.

Subsequently, the positive electrode active material, 99% or more of high purity NaCl, and AlCl ₃ anhydride are mixed at a 1: 1 ratio, and then a small amount of aluminum is added, and the temperature is raised to 300 in an inert atmosphere to prepare a NaAlCl ₄ cathode electrolyte. Charged.

In the negative electrode portion, sodium was used as the negative electrode active material, and the metal wick was inserted in contact with the solid electrolyte so that the sodium could be well wetted at the beta-alumina solid electrolyte interface. The metal wick of the cathode portion was spot welded so that electrons could flow well through the cathode vessel to the interface of the solid electrolyte.

The positive electrode container and the negative electrode container were formed by processing a Fe-based metal plate, and a beta-alumina solid electrolyte was placed between the positive electrode container and the negative electrode container.

A high molecular PE was used as the polymer sealing layer, and a battery was manufactured by sealing with thermal pressure at 200 ° C.

[ Test Example ]

Test Example  1: long term of sodium secondary battery Cycle  characteristic

Figure 2 shows the charge and discharge test results of the sodium secondary battery according to Example 1 of the present invention (a) is a discharge, (b) is a charging time.

Specifically, the discharge current density was driven at 4.35mA / cm ² and 8.7mA / cm ² , and the cut-off voltage was set at 2.0V. The charge current density was set to 4.35 mA / cm ² and the cut-off voltage was set to 2.77 V.

Claims (9)

A cathode container containing sodium;
A cathode container accommodating a cathode active material and a cathode secondary electrolyte;
A solid electrolyte positioned between the cathode vessel and the anode vessel to selectively move sodium ions; And
A polymer sealing layer formed along an edge of the solid electrolyte and positioned between the solid electrolyte and the negative electrode container and the positive electrode container;
Including,
The polymer sealing layer is formed by thermocompression at 100 to 400 ° C,
The solid electrolyte and the negative electrode container and the positive electrode container are bonded by a polymer sealing layer,
Sodium secondary battery.
The method of claim 1,
The polymer sealing layer is polyethylene, high molecular polyethylene, polyimide, thermoplastic polyimide, polyvinylidene fluoride, polytetrafluoroethylene Sodium secondary battery comprising at least one selected from perfluoroalkoxy alkane, polyetheretherketone and fluorinated ethylene propylene.
The method of claim 1,
Sodium secondary battery, characterized in that the solid electrolyte comprises at least one selected from beta-alumina, NaSiCon.
The method of claim 1,
Sodium secondary battery, characterized in that the thickness of the solid electrolyte is 100um to 3mm.
The method of claim 1,
Sodium secondary battery characterized in that the positive electrode active material comprises at least one selected from Ni, Fe Cu and Zn, at least one selected from Al, NaI, NaF, S and FeS and NaCl.
The method of claim 1,
Sodium secondary battery characterized in that the positive electrode comprises at least one selected from NaAlCl ₄ , NaAlCl ₄ -NaAlBr ₄ , NaAlCl ₄ -LiCl and NaAlCl ₄ -LiBr.
The method of claim 1,
Sodium secondary battery, characterized in that the drive temperature of the sodium secondary battery is 95 to 250 ℃.
A cathode container containing sodium;
A cathode container accommodating a cathode active material and a cathode secondary electrolyte;
A solid electrolyte positioned between the cathode vessel and the anode vessel to selectively move sodium ions; And
A polymer sealing layer formed along an edge of the solid electrolyte and positioned between the solid electrolyte and the negative electrode container and the positive electrode container; Including;
The polymer sealing layer is formed by thermocompression at 100 to 400 ° C,
The solid electrolyte, the negative electrode container and the positive electrode container is bonded by a polymer sealing layer, the method of manufacturing a sodium secondary battery.
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