A pressure-reducing sealing test device for liquid metal batteries

Abstract

This utility model discloses a pressure-reducing sealing test device for liquid metal batteries, relating to the field of liquid metal battery technology. The test device includes a metal battery casing, a metal top cover, a connecting pipe, a sealing piston, and a sealing cap. The metal battery casing is filled with electrodes and electrolyte of the liquid metal battery. The top and side walls of the metal battery casing have a first opening and a second opening, respectively. The metal top cover is sealed to the first opening of the metal battery casing via a sealing material. One end of the connecting pipe is sealed to the second opening of the metal battery casing. The sealing piston is slidably disposed within the connecting pipe to adjust the pressure inside the metal battery casing. The sealing cap is used to perform a secondary seal on the connecting pipe after the sealing piston is in place. This test device can simulate the actual working conditions of the battery, optimize the assembly process, reduce the number of sealing positions and areas, and effectively avoid the impact of sealing failure on test results while reducing experimental costs.

Description

Technical Field

[0001] This utility model relates to the field of liquid metal battery technology, and more specifically, to a depressurization sealing test device for liquid metal batteries. Background Technology

[0002] With the rapid development of renewable energy sources such as wind power and photovoltaics, energy storage technology has become crucial for ensuring the stable operation of the power grid. Liquid metal batteries, due to their advantages such as high energy density, long lifespan, and low cost, are considered one of the ideal choices for large-scale grid energy storage. However, these batteries operate at high temperatures of 200-700℃ and contain active metal vapor and electrolyte salt vapor, making them extremely sensitive to external oxygen and moisture. Therefore, the corrosion resistance of their sealing materials is of paramount importance.

[0003] Currently, verifying sealing performance usually requires manufacturing a complete battery for high-temperature testing, which is not only costly and time-consuming, but also prone to interference with test results due to sealing failure in other parts.

[0004] Therefore, there is an urgent need for a dedicated sealing test device that can simulate actual working conditions, has a simple structure, and is low in cost. Utility Model Content

[0005] In view of this, the purpose of this utility model is to provide a pressure-reducing sealing test device for liquid metal batteries, which can simulate the high temperature, corrosive atmosphere and pressure change environment inside the battery, and is specifically used to verify the corrosion resistance and sealing performance of the sealing material.

[0006] To achieve the above objectives, this utility model provides a pressure-reduced sealing test device for liquid metal batteries, comprising:

[0007] A metal battery casing, which is filled with electrodes and electrolyte of a liquid metal battery, and the top and side walls of the metal battery casing are respectively provided with a first opening and a second opening;

[0008] The metal top cover is sealed to the first opening of the metal battery casing by a sealing material;

[0009] A connecting pipe, one end of which is sealed to the second opening of the metal battery casing;

[0010] A sealing piston is slidably disposed within the communicating pipe for adjusting the pressure inside the metal battery casing.

[0011] A sealing cap is used to provide a secondary seal to the connecting pipe after the sealing piston is in place.

[0012] Preferably, the sealing material is a ceramic ring or a glass-based sealing layer, used to achieve insulation and sealing between the top cover and the metal battery casing.

[0013] Preferably, the ceramic ring is any one of alumina, aluminum nitride, and zirconium oxide ceramic rings, and the upper and lower surfaces of the ceramic ring are respectively connected to the top cover and the metal battery casing.

[0014] Preferably, the glass-based sealing layer is a borosilicate glass layer.

[0015] Preferably, the connecting pipe is a three-way pipe, with its first end connected to the metal battery casing, its second end used to connect to a vacuum device, and its third end used to insert and accommodate the sealing piston.

[0016] Preferably, the outer circumference of the bottom of the sealing piston is provided with a groove, and a rubber sealing ring is provided in the groove. The outer diameter of the rubber sealing ring protrudes from the groove and presses against the inner wall of the third end of the connecting pipe.

[0017] Preferably, the sealing cap is screwed to the third end of the connecting pipe, and as the sealing cap screws forward, it pushes the sealing piston to the bottom of the first end of the connecting pipe.

[0018] Preferably, the metal top cover has a circular sheet structure.

[0019] Preferably, the metal battery casing has a cubic structure with a wall thickness of 2-15 mm, and the diameters of the first opening and the second opening are 1-20 mm.

[0020] Preferably, the electrode is an alkali metal or an alkaline earth metal, and the electrolyte is an inorganic salt.

[0021] Compared with the prior art, this utility model has the following advantages and effects:

[0022] 1. The pressure-reducing sealing test device for liquid metal batteries of this utility model includes a metal battery casing, a metal top cover, sealing material, a connecting pipe, a sealing piston, and a sealing cap. The metal battery casing forms a sealed, high-temperature and high-pressure resistant cavity. A first opening at the top is used to install the sealing material to be tested, and a second opening on the side serves as a channel for working fluid filling and pressure control. The sealing material is placed between the metal top cover and the first opening of the metal battery casing and sealed according to the actual connection process. A fixed amount of electrode material and electrolyte of the liquid metal battery is loaded into the metal battery casing through the second opening on the side wall. One end of the connecting pipe is sealed to the second opening, and the sealing piston is inserted into the connecting pipe. At this time, the sealing piston is not completely sealed, allowing gas to flow through its surrounding gaps. Then, the vacuum pump is connected to the connecting pipe, and the vacuum is started to extract the air from the cavity to achieve the target vacuum level. After the target vacuum level is achieved, the sealing cap is inserted from the open end of the connecting pipe. Pushing the sealing cap causes its bottom to push the sealing piston into the cavity until it is pushed to the bottom of the pipe or a certain mechanical limit. When it is pushed to the bottom, a preliminary mechanical seal is achieved, instantly cutting off the connection between the cavity and the outside world and sealing the high vacuum environment inside the cavity. The sealed device is then heated to the operating temperature of the liquid metal battery. The electrode and electrolyte materials inside the cavity melt and evaporate, generating a large amount of steam. The generation of steam causes the pressure inside the cavity to increase significantly, far exceeding the external atmospheric pressure. This forces the corrosive steam to more violently impact and penetrate the sealing material, thus accelerating aging and strengthening the test.

[0023] 2. This sealing test apparatus can simulate the actual working conditions of a battery. The metal battery casing and metal top cover are insulated and sealed with a sealing material whose corrosion resistance is to be tested. Electrode materials and electrolyte salts are inserted through holes in the side wall of the metal battery casing. A piston device with adjustable internal pressure is used to seal these holes, thus verifying the high-temperature sealing performance of the insulating material. Compared to a complete battery configuration, this test apparatus optimizes the assembly process, reduces sealing positions and areas, lowers experimental costs, and effectively avoids the direct impact of sealing failures in other locations on the test results. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the pressure-reducing sealing test device for liquid metal batteries in this embodiment of the present invention.

[0025] Figure 2 This is a horizontal cross-sectional view of the pressure-reducing sealing test device for liquid metal batteries in an embodiment of this utility model.

[0026] Figure 3 This is a schematic diagram of the structure of the sealing piston in an embodiment of this utility model.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1-Metal battery casing; 11-First opening; 12-Second opening; 2-Metal top cover; 3-Sealing material; 4-Connecting pipe; 41-First end; 42-Second end; 43-Third end; 5-Sealing piston; 51-Groove; 6-Sealing cap; 7-Rubber sealing ring. Detailed Implementation

[0029] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0030] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0031] Currently, large-capacity energy storage technologies are mainly divided into three categories: chemical energy storage (such as lithium-ion batteries, sodium-sulfur batteries, and flow batteries), physical energy storage (such as pumped hydro storage, compressed air storage, and flywheel energy storage), and electromagnetic energy storage (such as superconducting magnetic energy storage and supercapacitors). Among these:

[0032] Chemical energy storage has attracted widespread attention due to its advantages such as pollution-free operation, high conversion efficiency, and low maintenance. However, in large-scale grid energy storage applications, these batteries suffer from problems such as high cost and poor safety. For example, lithium-ion batteries have high production costs and limited lithium resources; vanadium redox flow batteries also face limitations due to the highly toxic and finite nature of vanadium, a raw material for vanadium redox flow batteries. Therefore, the development of batteries with advantages such as low cost, long cycle life, good safety, and abundant raw materials for large-scale grid energy storage technology is urgently needed.

[0033] Liquid metal batteries are a new type of rechargeable battery designed for grid-scale energy storage applications. A single cell mainly consists of a positive electrode, a negative electrode, an electrolyte, and a battery casing. At operating temperatures of 200-700℃, both electrodes are liquid metals, and the electrolyte is a molten inorganic salt. Due to their different densities and immiscibility, the electrodes and electrolyte naturally separate into layers, with the electrolyte naturally separating the two electrodes. This specially designed battery offers advantages such as high coulombic efficiency, long cycle life, good safety performance, and low cost, making it suitable for grid-connected energy storage systems for wind power, solar power, and other energy generation applications.

[0034] However, liquid metal batteries also have their drawbacks during operation. Because the batteries operate at high temperatures, the interior contains active electrode materials (such as reactive metal vapors, for example, vapors of Li, Na, K, Mg, and Ca) and electrolyte salt vapors, while the exterior is exposed to oxygen and moisture that must be kept out. Therefore, the corrosion resistance of this crucial sealing material, which connects the positive and negative electrodes and forms an insulation layer, is of paramount importance.

[0035] Currently, stable sealing technologies primarily utilize alumina ceramics as key sealing and insulation connectors, which are then metallized and brazed to stainless steel structural components. However, the current verification of the sealing performance of insulating and sealing materials mainly involves fabricating complete batteries and conducting high-temperature tests, which is costly. Furthermore, due to the relatively complex battery structure, sealing failures in other locations directly affect the test results.

[0036] Therefore, a sealing test device that can simulate the actual working conditions of a battery needs to be designed to verify the corrosion resistance of the sealing material.

[0037] Based on the aforementioned problems with existing technologies, please refer to Figure 1-3 As shown, this utility model embodiment provides a pressure-reducing sealing test device for liquid metal batteries. The pressure-reducing sealing test device includes a metal battery casing 1, a metal top cover 2, a sealing material 3, a connecting pipe 4, a sealing piston 5, and a sealing cap 6, wherein:

[0038] The metal battery casing 1 is filled with the electrodes and electrolyte of a liquid metal battery. The top and side walls of the metal battery casing 1 are respectively provided with a first opening 11 and a second opening 12. The metal top cover 2 is sealed to the first opening 11 of the metal battery casing 1 by a sealing material 3. One end of the connecting pipe 4 is sealed to the second opening 12 of the metal battery casing 1. The sealing piston 5 is slidably disposed in the connecting pipe 4 to adjust the pressure inside the metal battery casing 1. The sealing cap 6 is used to perform a secondary seal on the connecting pipe 4 after the sealing piston 5 is in place.

[0039] In this embodiment, the core function of the pressure-reducing sealing test device is to simulate and accelerate the extreme operating conditions (high temperature, corrosive atmosphere, pressure change) faced by the sealing material 3 during the actual operation of a liquid metal battery in the laboratory, and to conduct specific and reliable performance verification on it. Therefore, the technical process includes the following key steps:

[0040] Step 1: Build the core test environment (simulating a battery cavity).

[0041] Instead of fabricating a complete and complex liquid metal battery, this device extracts the most critical sealing verification unit (i.e., a sealed cavity composed of a metal top cover 2, sealing material 3, and metal battery casing 1). The metal battery casing 1 forms a sealed cavity that is resistant to high temperature and high pressure. The first opening 11 at the top is used to install the sealing material 3 to be tested, while the second opening 12 on the side serves as a channel for filling the working fluid and regulating the pressure.

[0042] Step 2: Install the seal to be tested (simulating the actual assembly process).

[0043] The sealing material 3 is placed between the metal top cover 2 and the first opening 11 of the metal battery casing 1, and sealed according to its actual connection process (e.g., brazing a ceramic ring or pressurized sintered glass sealant). This step ensures that the test device verifies not only the material itself, but also the performance of the entire sealing system, including its connection process.

[0044] Step 3: Introduce corrosive media and pressure control mechanism.

[0045] Specifically, a fixed amount of liquid metal battery electrode material and electrolyte is loaded into the metal battery casing 1 through the second opening 12 in the side wall. These materials melt and evaporate upon heating, generating highly corrosive metal vapor and electrolyte salt vapor, thereby creating a corrosive atmosphere inside the cavity similar to that inside a real battery.

[0046] One end of the connecting pipe 4 is sealed to the second opening 12 (usually by welding). This pipe becomes the only channel connecting the cavity to the outside world and is crucial for pressure control. The sealing piston 5 is inserted into the connecting pipe 4. At this point, the sealing piston 5 is not completely sealed, allowing gas to flow through its surrounding gaps. A vacuum pump is connected to the connecting pipe 4, and vacuuming is initiated to remove air from the cavity and achieve the target vacuum level. Removing oxygen and water vapor from the cavity prevents them from reacting violently with the high-temperature electrode materials (such as Li and Na), interfering with the observation of the corrosion resistance of the sealing material 3.

[0047] Step 4: Seal and create an internal positive pressure environment.

[0048] Once the target vacuum level is reached, insert the sealing cap 6 into the open end of the connecting pipe 4. Push the sealing cap 6, and its bottom will push the sealing piston 5 into the cavity until it is pushed to the bottom of the pipe or a certain mechanical limit. When it is pushed to the bottom, a preliminary mechanical seal is achieved, instantly cutting off the connection between the cavity and the outside world, and sealing the high vacuum environment inside the cavity.

[0049] To ensure flawless operation during long-term high-temperature testing, the connecting pipe 4 needs to be permanently sealed. This is typically achieved by welding (such as argon arc welding) to completely seal the interface between the sealing cap 6 and the connecting pipe 4, thus creating a secondary seal. At this point, the cavity becomes a completely isolated system.

[0050] The sealed device is heated to the operating temperature of the liquid metal battery (e.g., 400-600℃). The electrode and electrolyte materials inside the chamber melt and evaporate, generating a large amount of vapor. Since the chamber volume is fixed, the vapor generation causes a significant increase in internal pressure, far exceeding the external atmospheric pressure. This positive pressure environment forces the corrosive vapor to more violently impact and penetrate the sealing material 3, thus accelerating aging and enhancing the testing process.

[0051] Step 5: Performance verification and evaluation.

[0052] The device is kept under high temperature and high pressure for hundreds or even thousands of hours. After the process, the device is cooled, and the seal is checked for failure using detection methods (such as helium mass spectrometry leak detection).

[0053] Finally, the device is disassembled, and the sealing material 3 is subjected to microscopic analysis (such as SEM, EDS) to observe its degree of corrosion, element migration, and whether cracks are generated, thereby quantitatively assessing its long-term reliability.

[0054] Therefore, the device structure is highly simplified, eliminating the interference of multi-factor coupling in a complete battery, allowing the test results to directly and accurately reflect the corrosion resistance and sealing performance of the sealing material 3 itself. Compared to fabricating a complete liquid metal battery for testing, this significantly reduces the material and time costs of a single test, enabling numerous repeated experiments and screening of different formulations. By introducing real electrode and electrolyte materials and generating vapor at high temperatures, the chemical environment of the sealing material 3 within a real battery is replicated. The method of vacuuming, sealing, and then heating simulates the real working conditions of the sealing material 3, accelerating aging and shortening the testing cycle. The initial sealing of the sealing piston and the secondary sealing through welding ensure that high-temperature, high-pressure corrosive substances are firmly sealed inside the device, greatly improving the safety of the testing process and avoiding the risk of leakage of toxic and harmful substances.

[0055] It should be noted that this device, as a platform tool, is not only applicable to different sealing materials (such as glass sealants with different formulations and different types of ceramic metallized brazing parts), but also to liquid metal batteries with different chemical systems (such as lithium-based, sodium-based, and antimony-based batteries). Only the electrode and electrolyte materials inside the chamber need to be replaced, making it widely applicable.

[0056] Specifically, in some embodiments, the sealing material 3 is a ceramic ring or a glass-based sealing layer, used to achieve insulation and sealing between the metal top cover 2 and the metal battery casing 1.

[0057] Regardless of the approach taken, an insulating seal was successfully constructed between the metal top cover 2 and the metal battery casing 1. This seal is the core test object of the entire test setup and the only weak point to be verified. All subsequent operations, such as vacuuming, heating, and generating a corrosive atmosphere, are aimed at applying extreme stress to this carefully constructed sealing interface to test its reliability.

[0058] Therefore, ceramics and glass are excellent insulators, fundamentally ensuring electrical isolation between the metal top cover 2 (positive electrode) and the metal battery casing 1 (negative electrode), preventing short circuits. Simultaneously, the sealed interface formed by brazing or sintering has extremely high airtightness, far exceeding that of mechanical seals, effectively sealing the active material.

[0059] In some preferred embodiments, the ceramic ring is any one of alumina, aluminum nitride, and zirconium oxide ceramic rings, and the upper and lower surfaces of the ceramic ring are respectively connected to the metal top cover 2 and the metal battery casing 1.

[0060] Specifically, the ceramic ring can be made of materials such as alumina (Al2O3), aluminum nitride (AlN), and zirconium oxide (ZrO2). Since ceramic is an inert surface, it is difficult to achieve a firm bond with the metal top cover 2 and the metal battery casing 1 directly by brazing. Therefore, in this embodiment, the upper and lower surfaces of the ceramic ring are metallized by processes such as the molybdenum-manganese method (Mo-Mn method) or gold plating, that is, a metal layer (such as Cu or Ni) that is tightly bonded to the ceramic and can be welded is formed on the ceramic surface, creating interface conditions for subsequent metal-ceramic brazing.

[0061] Then, the metallized ceramic ring is placed between the metal top cover 2 and the first opening 11 of the metal battery casing 1. Under the pressure of the fixture, the entire assembly is heated to above the melting point of the brazing filler metal (such as Ag-Cu eutectic brazing filler metal). The molten brazing filler metal wets, spreads, and fills the gaps between the metallized layer and the metal parts. After cooling, it forms a strong metallurgical bond, achieving a permanent connection with high strength, high airtightness, and high insulation from the metal top cover 2 to the ceramic (insulator) and then to the metal battery casing 1.

[0062] In some other preferred embodiments, the glass-based sealing layer is a borosilicate glass layer.

[0063] Specifically, when the sealing material 3 is a glass-based sealing layer (such as borosilicate glass), a glass powder with a specific composition (such as SiO2-B2O3-R2O, where R is an alkali metal) is first mixed with an organic binder and a solvent, and then a pre-formed sheet (i.e., sealing material 3) is made by means of casting, dry pressing or screen printing.

[0064] The glass preform is then placed between the first opening 11 of the metal top cover 2 and the metal battery casing 1. Pressure is applied to ensure tight contact between the components. The glass is heated in a controlled atmosphere furnace to above its softening point but below its melting point. At this point, the glass viscosity decreases, allowing it to flow under pressure, fully wetting the metal surface, expelling air bubbles, and filling all microscopic imperfections. After cooling, the glass and metal surface form a strong seal through chemical bonds. Utilizing the viscous flow characteristics of glass at high temperatures, atomic-level tight contact and chemical bonding with the metal surface are achieved, forming a non-porous, dense, and insulating sealing layer.

[0065] Specifically, please refer to Figure 2 As shown, the connecting pipe 4 is a three-way pipe. The first end 41 of the connecting pipe 4 is connected to the metal battery casing 1, the second end 42 of the connecting pipe 4 is used to connect to the vacuum equipment, and the third end 43 of the connecting pipe 4 is used to insert and accommodate the sealing piston 5.

[0066] Therefore, the three-way pipe integrates three major functions: the material loading channel, the air extraction channel, and the sealing operation channel. Compared with the solution that uses multiple valves and pipes, this design greatly simplifies the device structure and reduces manufacturing costs and potential leakage points.

[0067] Secondly, the entire vacuuming and sealing process is completed in one step, eliminating the need for repeated disassembly and reassembly of components. The operator can complete the dynamic sealing without stopping the pump, minimizing the risk of vacuum drop due to atmospheric backflow during operation and ensuring the purity and consistency of the test conditions.

[0068] Finally, the design achieves a double permanent seal. First, the first end 41 (the connection to the housing) is sealed by welding, followed by the second end 42 and the third end 43. These three welds completely seal the cavity, providing a seal strength and airtightness far exceeding any mechanical seal relying on threads, glands, or single valves. It can withstand the enormous stress generated by internal high temperatures and pressures, ensuring the safety of the testing process and the accuracy of the results.

[0069] For more details, please refer to Figure 2 , 3As shown, a groove 51 is provided on the outer circumference of the bottom of the sealing piston 5, and a rubber sealing ring 7 is provided in the groove 51. The outer diameter of the rubber sealing ring 7 protrudes from the groove 51 and is pressed against the inner wall of the third end 43 of the connecting pipe 4.

[0070] Therefore, the rubber sealing ring 7 protrudes from the groove 51. When the piston is inserted into the pipe, the rubber sealing ring 7 forms an interference fit with the inner wall of the pipe and undergoes elastic deformation due to radial compression. This elastic deformation generates continuous and uniform contact pressure between the sealing ring and the pipe wall, forming the first reliable sealing structure. When the inside is a vacuum and the outside is atmospheric, this pressure difference will further force the sealing ring to deform, pressing it more tightly against the pipe wall, achieving a self-tightening sealing effect and ensuring the absolute reliability of the initial seal.

[0071] For more details, please refer to Figure 2 As shown, the sealing cap 6 is suitable for being spirally connected to the third end 43 of the connecting pipe 4. As the sealing cap 6 spirals forward, it pushes the sealing piston 5 to the bottom of the first end 41 of the connecting pipe 4.

[0072] When the operator rotates the sealing cap 6, utilizing the mechanical advantage of the threads, a small rotational torque can be converted into a large, smooth, and continuous axial thrust. This axial thrust is gradual, rather than an instantaneous impact. This smooth thrust allows the rubber sealing ring 7 to undergo uniform and smooth elastic deformation and slide across the inner wall of the pipe, completely avoiding twisting, extrusion, or damage caused by instantaneous impact, greatly improving the reliability of the initial seal.

[0073] For more details, please refer to Figure 1 As shown, the metal top cover 2 in this embodiment has a circular sheet structure. When internal pressure is generated, the pressure will act evenly on the inner surface of the metal top cover 2, and the stress can be evenly transmitted to the surrounding support points (i.e., the edges of the shell opening surrounded by sealing material).

[0074] Although a circular shape is the preferred and common solution, the scope of protection of this utility model should not be limited to this shape. The shape design of the metal top cover 2 is essentially function-oriented, and its core is to meet the above-mentioned technical effects. Therefore, the shape of the metal top cover 2 can also be elliptical, rounded rectangle, regular hexagon, etc.

[0075] For more details, please refer to Figure 1 As shown, the metal battery casing 1 has a cubic structure. The cube is one of the easiest metal structures to process. It can be formed by directly welding six flat plates together, or better yet, by precision casting or integral milling from a metal block. These processes are very mature, relatively low in cost, and can easily guarantee high dimensional accuracy and surface flatness.

[0076] The wall thickness should be 2-15mm. The wall thickness cannot be too thin; a thin shell (e.g., <2mm) lacks rigidity at high temperatures and will undergo significant elastic or even plastic deformation under internal pressure. This deformation will generate additional stress on the brittle ceramic or glass sealing interface, potentially causing it to crack, thus compromising the seal and causing test failure. Conversely, the wall thickness cannot be too thick either. An excessively thick shell (e.g., >15mm) presents three main problems: firstly, it significantly increases material costs; secondly, it increases processing time and difficulty; and finally, it requires more energy to heat up, resulting in a slower heating rate and extremely slow cooling after the experiment. This greatly reduces testing efficiency and increases energy consumption and time costs.

[0077] The diameters of the first opening 11 and the second opening 12 are 1-20 mm. The openings cannot be too large, as they weaken the shell structure and cause stress concentration at the opening edges. Larger openings result in more severe weakening of the shell's strength, requiring thicker walls to compensate. Secondly, the size of the openings determines the diameter of the connecting pipe 4. An excessively large pipe will lead to an excessively long stroke of the sealing piston 5, making operation inconvenient and increasing the difficulty and cost of final welding the seal.

[0078] As a preferred embodiment, the metal battery casing 1 is made of stainless steel, alloy, etc.

[0079] Preferably, the metal top cover 2 is also made of stainless steel, alloy, etc., with a thickness of 2-15mm and an outer surface roughness Ra of 0.8μm-3.2μm. The top of the metal battery casing 3 is polished and ground, with an outer surface roughness Ra of 0.8μm-3.2μm.

[0080] More specifically, in specific embodiments of this utility model, the electrode is an alkali metal or an alkaline earth metal, and the electrolyte is an inorganic salt.

[0081] Although the present invention has been disclosed above, its protection scope is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A pressure-reducing sealing test device for liquid metal batteries, characterized in that, include: A metal battery casing, which is filled with electrodes and electrolyte of a liquid metal battery, and the top and side walls of the metal battery casing are respectively provided with a first opening and a second opening; The metal top cover is sealed to the first opening of the metal battery casing by a sealing material; A connecting pipe, one end of which is sealed to the second opening of the metal battery casing; A sealing piston is slidably disposed within the communicating pipe for adjusting the pressure inside the metal battery casing. A sealing cap is used to provide a secondary seal to the connecting pipe after the sealing piston is in place.

2. The pressure-reduced sealing test device for liquid metal batteries as described in claim 1, characterized in that: The sealing material is a ceramic ring or a glass-based sealing layer, used to achieve insulation and sealing between the metal top cover and the metal battery casing.

3. The pressure-reduced sealing test device for liquid metal batteries as described in claim 2, characterized in that: The ceramic ring is any one of alumina, aluminum nitride, and zirconium oxide ceramic rings, and the upper and lower surfaces of the ceramic ring are respectively connected to the metal top cover and the metal battery casing.

4. The pressure-reducing sealing test device for liquid metal batteries as described in claim 2, characterized in that: The glass-based sealing layer is a borosilicate glass layer.

5. The pressure-reduced sealing test device for liquid metal batteries as described in claim 1, characterized in that: The connecting pipe is a three-way pipe, with its first end connected to the metal battery casing, its second end used to connect to a vacuum device, and its third end used to insert and accommodate the sealing piston.

6. The pressure-reduced sealing test apparatus for liquid metal batteries as described in claim 5, characterized in that: The outer circumference of the bottom of the sealing piston is provided with a groove, and a rubber sealing ring is provided in the groove. The outer diameter of the rubber sealing ring protrudes from the groove and presses against the inner wall of the third end of the connecting pipe.

7. The pressure-reduced sealing test apparatus for liquid metal batteries as described in claim 1, characterized in that: The sealing cap is adapted to be spirally connected to the third end of the connecting pipe, and as the sealing cap spirals forward, it pushes the sealing piston to the bottom of the first end of the connecting pipe.

8. The pressure-reduced sealing test apparatus for liquid metal batteries as described in claim 1, characterized in that: The metal top cover has a circular sheet structure.

9. The pressure-reduced sealing test apparatus for liquid metal batteries as described in claim 1, characterized in that, The metal battery casing has a cubic structure with a wall thickness of 2-15mm, and the diameters of the first opening and the second opening are 1-20mm.

10. The pressure-reducing sealing test apparatus for liquid metal batteries as described in any one of claims 1-9, characterized in that, The electrode is an alkali metal or an alkaline earth metal, and the electrolyte is an inorganic salt.

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