Lithium-sodium alloy and molten salt electrolysis preparation method thereof

Abstract

The invention belongs to the technical field of non-ferrous metal alloy metallurgy, and particularly discloses a lithium-sodium alloy and a molten salt electrolysis preparation method thereof. According to the method, a molten salt electrolytic bath is used as a cathode, graphite is used as an anode, a mixture of lithium chloride and potassium chloride is used as electrolyte, molten salt electrolysis is carried out, sodium particles are added in the molten salt electrolysis process, and the lithium-sodium alloy is obtained after molten salt electrolysis is completed. According to the preparation method, the alloy with the sodium content smaller than 5% can be prepared, the follow-up burdening remelting procedure can be reduced, the unit energy consumption cost and the production cost can be reduced, product element distribution is more uniform, the production efficiency is improved, and the product quality and the catalytic performance are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nonferrous metal alloy metallurgy, and in particular to a lithium-sodium alloy and a method for preparing the alloy by molten salt electrolysis. Background Art

[0002] Metallic lithium has excellent properties and is widely used in many fields such as atomic energy, aerospace, metallurgy and chemical industry, machinery, glass and ceramics, air conditioning and refrigeration, medicine and health, organic synthesis, new energy, agriculture, etc. It is known as "industrial MSG" and is also a key metal material in the development of high technology in the 21st century. With the rapid development of high-tech industries such as information industry, green energy, nuclear fusion power generation in the 21st century, lithium, as "industrial MSG", "new energy metal" and "important element to promote the world's progress", is constantly developing and expanding its application areas.

[0003] In the fields of new medicines and new materials, metallic lithium is often used as a catalyst, especially lithium-sodium alloys, which have better catalytic effects.

[0004] At present, the preparation method of lithium sodium alloy is batching remelting method, such as the patent application "A method for preparing high sodium metal lithium by recycling lithium sodium alloy and using the method" (patent number: CN201110076049.1) to prepare high sodium metal lithium, which introduces a method for preparing high sodium metal lithium through batching, melting, mixing, impurity removal, casting and other processes, but this method has problems such as long process, high energy consumption, and high unit production cost. There is no report on the preparation of lithium sodium alloy by molten salt electrolysis.

[0005] In terms of preparing alloys by molten salt electrolysis, patent applications such as "Preparing magnesium-lithium alloys by molten salt electrolysis" (patent number: 200610010331.9) and "A method for producing high-lithium content aluminum-lithium alloys by low-temperature molten salt electrolysis" (patent number: 200910072838.0) both introduce a method for preparing alloys by molten salt electrolysis, which uses one metal in the alloy as an electrode, and then molten salt electrolyzes another metal, which is melted and mixed together by the temperature of the electrolytic cell, and then cast into ingots. However, this process has problems such as insufficient and uniform distribution of elements, frequent electrode replacement, and low production efficiency. Summary of the invention

[0006] In view of this, the present invention provides a lithium-sodium alloy and a method for preparing the same by molten salt electrolysis, so as to solve the problems of high energy consumption and high cost in the existing lithium-sodium alloy preparation methods and the lack of reports on the preparation by molten salt electrolysis; it also solves the problems of complicated steps and uneven products in other alloy molten salt electrolysis methods.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for preparing a lithium-sodium alloy by molten salt electrolysis comprises the following steps:

[0009] Using a molten salt electrolytic cell as the cathode, graphite as the anode, and a mixture of lithium chloride and potassium chloride as the electrolyte, molten salt electrolysis is carried out. Sodium particles are added during the molten salt electrolysis, and lithium-sodium alloy is obtained after the molten salt electrolysis is completed.

[0010] Preferably, the temperature of the molten salt electrolysis is 380-420°C, and the voltage of the molten salt electrolysis is 6-8V.

[0011] Preferably, the particle size of the sodium particles is 5 to 8 cm.

[0012] Preferably, the sodium content in the lithium-sodium alloy is ≤5%.

[0013] Preferably, the added mass of the sodium particles is equal to the theoretical mass of sodium in the pre-prepared lithium-sodium alloy.

[0014] Preferably, the mass ratio of lithium chloride to potassium chloride in the electrolyte is 50-55:45-50.

[0015] Another object of the present invention is to provide a lithium-sodium alloy prepared by the preparation method.

[0016] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The preparation method disclosed in the present invention can prepare an alloy with a sodium content of less than or equal to 5%, thereby reducing production processes, reducing labor intensity and production costs, improving the uniformity of product element distribution and production efficiency, and improving product quality and catalytic performance.

[0018] 2. Adding metallic sodium into the metallic lithium molten salt electrolytic cell, directly reaching the electrolyte liquid surface, directly melting into liquid, mixing with the metallic lithium produced by electrolysis, and then casting, cooling and stripping. In this way, lithium-sodium alloy is directly prepared, reducing the subsequent batching and remelting process, which can reduce unit energy consumption cost and production cost, make the product element distribution more uniform, improve production efficiency, and enhance product quality and catalytic performance. DETAILED DESCRIPTION

[0019] The present invention provides a method for preparing a lithium-sodium alloy by molten salt electrolysis, comprising the following steps:

[0020] Using a molten salt electrolytic cell as the cathode, graphite as the anode, and a mixture of lithium chloride and potassium chloride as the electrolyte, molten salt electrolysis is carried out. Sodium particles are added during the molten salt electrolysis, and lithium-sodium alloy is obtained after the molten salt electrolysis is completed.

[0021] In the present invention, the molten salt electrolytic cell is made of ordinary steel.

[0022] In the present invention, the temperature of molten salt electrolysis is 380-420°C, specifically 385°C, 390°C, 395°C, 400°C, 405°C, 410°C, 415°C; the voltage of molten salt electrolysis is 6-8V, specifically 6.2V, 6.5V, 6.8V, 7V, 7.2V, 7.5V, 7.8V.

[0023] In the present invention, the lithium scooping time is fixed, for example, metallic lithium is collected once every three hours, so the total amount of metallic lithium prepared within three hours is certain, and it is only necessary to calculate the required amount of sodium according to the sodium content in the lithium-sodium alloy, and then add it all at once or in batches according to the actual situation; in the present invention, the electrolysis time (lithium scooping interval time) can be adjusted.

[0024] In the present invention, the sodium particles are preferably added after a period of electrolysis, more preferably added at the midpoint of the total electrolysis time, such as adding at 0.5 hours (one time) for electrolysis for 1 hour; adding at 1.5 hours (one time) for electrolysis for 3 hours.

[0025] In the present invention, the particle size of the sodium particles is 5 to 8 cm, specifically 5.5 cm, 6 cm, 6.5 cm, 7 cm, and 7.5 cm. Too large or too small a particle size is not conducive to the solution of the present invention, and will affect the uniformity and catalytic performance of the final product.

[0026] In the present invention, the sodium content in the lithium-sodium alloy is ≤5%, including but not limited to 0.55%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, and 4.5%.

[0027] In the present invention, the added mass of the sodium particles is equal to the theoretical mass of sodium in the pre-prepared lithium-sodium alloy.

[0028] In the present invention, the mass ratio of lithium chloride to potassium chloride in the electrolyte is 50-55:45-50, preferably 52-55:45-48, further preferably 54-55:45-46, and further preferably 55:45.

[0029] The present invention also provides a lithium-sodium alloy prepared by the preparation method.

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] The electrolytic cell is made of steel, with a cell temperature of 400°C, a voltage of 6V, a current of 30KA, a mass ratio of lithium chloride to potassium chloride of 55:45 (this ratio needs to be maintained during the electrolysis process), graphite as the anode, and steel as the cathode. After running for 3 hours, 24KG of lithium-sodium alloy is expected to be produced. According to the sodium mass content of 1.5%, 0.36KG of metallic sodium needs to be added. During the molten electrolysis process, the metallic sodium is cut into cubes with a particle size of 6cm and added to the electrolytic cell twice, 1 hour and 2 hours after electrolysis. After the electrolysis is completed, the alloy is taken out and cast into ingots to obtain a lithium-sodium alloy with a sodium content of 1.5%.

[0033] Example 2

[0034] The electrolytic cell is made of steel, with a cell temperature of 380℃, a voltage of 8V, a current of 30KA, a mass ratio of lithium chloride to potassium chloride of 55:45 (this ratio needs to be maintained during the electrolysis process), graphite as the anode, and steel as the cathode. After running for 2 hours, 16KG of lithium-sodium alloy is expected to be produced. According to the sodium mass content of 1%, 0.16KG of metallic sodium needs to be added. During the molten electrolysis process, the metallic sodium is cut into cubes with a particle size of 8cm, and added to the electrolytic cell after 1 hour of electrolysis. After the electrolysis is completed, the alloy is taken out and cast into ingots to obtain a lithium-sodium alloy with a sodium content of 1%.

[0035] Example 3

[0036] The electrolytic cell is made of steel, with a cell temperature of 420℃, a voltage of 7V, a current of 30KA, a mass ratio of lithium chloride to potassium chloride of 55:45 (this ratio needs to be maintained during the electrolysis process), graphite as the anode, and steel as the cathode. After running for 3 hours, 24KG of lithium-sodium alloy is expected to be produced. According to the sodium mass content of 2%, 0.48KG of metallic sodium needs to be added. During the molten electrolysis process, the metallic sodium is cut into cubes with a particle size of 5cm and added to the electrolytic cell twice, 1 hour and 2 hours after electrolysis. After the electrolysis is completed, the alloy is taken out and cast into ingots to obtain a lithium-sodium alloy with a sodium content of 2%.

[0037] Experimental Example 1

[0038] Repeat Example 2 to prepare 1% lithium-sodium alloy, and the prepared six groups of alloy batches are respectively recorded as 2024051801, 2024051802, 2024051803, 2024053001, 2024053002, and 2024053003. Then, samples are taken at multiple locations (three locations) of the same alloy ingot, and the sampling positions of different alloy ingots are the same. The sodium content in the alloy is detected by the same person according to the method in the national standard "Lithium" GB / T20931.2, and the test results are shown in Table 1.

[0039] Table 1 Sodium content test results

[0040] batch number Test results (%) batch number Test results (%) batch number Test results (%) 2024051801-1 1.052 2024051802-1 1.057 2024051803-1 1.047 2024051801-2 1.060 2024051802-2 1.062 2024051803-2 1.049 2024051801-3 1.055 2024051802-3 1.049 2024051803-2 1.052 batch number Test results (%) batch number Test results (%) batch number Test results (%) 2024053001-1 1.063 2024053002-1 1.058 2024053003-1 1.070 2024053001-2 1.067 2024053002-2 1.058 2024053003-2 1.069 2024053001-3 1.064 2024053002-3 1.059 2024053003-3 1.064

[0041] The -1 in 2024051801-1 represents the first sampling point, and the -2 in 2024051801-2 represents the second sampling point. The other batch numbers are understood in the same way as above.

[0042] It can be seen from Table 1 that the sodium element in the lithium-sodium alloy prepared by the present invention has a high degree of uniform distribution, and the product quality is excellent, which is conducive to optimizing the catalytic performance of the lithium-sodium alloy. In addition, by comparing lithium-sodium alloys of different batches, it can be seen that the preparation method disclosed in the present invention has strong repeatability, small differences between multiple batches, and can ensure stable product quality. The multi-batch preparation process can also reflect that the method disclosed in the present invention is suitable for multiple, large-scale preparation of lithium-sodium alloys, without the need to frequently replace electrodes, and has high production efficiency.

[0043] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0044] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a lithium sodium alloy by molten salt electrolysis, characterized in that: The steps include: Using a molten salt electrolytic cell as the cathode, graphite as the anode, and a mixture of lithium chloride and potassium chloride as the electrolyte, molten salt electrolysis is carried out. Sodium particles are added during the molten salt electrolysis, and lithium-sodium alloy is obtained after the molten salt electrolysis is completed.

2. The method for preparing a lithium sodium alloy by molten salt electrolysis according to claim 1, characterized in that: The temperature of the molten salt electrolysis is 380-420° C., and the voltage of the molten salt electrolysis is 6-8V.

3. The method for preparing a lithium sodium alloy by molten salt electrolysis according to claim 2, characterized in that: The particle size of the sodium particles is 5 to 8 cm.

4. A method for preparing a lithium sodium alloy by molten salt electrolysis according to any one of claims 1 to 3, characterized in that: The sodium content in the lithium sodium alloy is ≤5%.

5. The method for preparing a lithium sodium alloy by molten salt electrolysis according to claim 4, characterized in that: The added mass of the sodium particles is equal to the theoretical mass of sodium in the pre-prepared lithium-sodium alloy.

6. The method for preparing a lithium sodium alloy by molten salt electrolysis according to claim 5, characterized in that: The mass ratio of lithium chloride to potassium chloride in the electrolyte is 50-55:45-50.

7. The lithium-sodium alloy prepared by the preparation method according to any one of claims 1 to 6.