Method for assembling a sodium-ion half-cell in air

Abstract

The present invention provides a method for assembling a sodium-ion half-cell in air, belonging to the technical field of energy storage battery preparation. It is characterized in that liquid paraffin and electrolyte are used to isolate metallic sodium from air, so as to achieve the purpose of assembling a sodium-ion battery in a glove box. The steps are as follows: Heat and perform vacuum pretreatment on the liquid paraffin. Add metallic sodium to the treated liquid paraffin according to 15-20 g∶70-80 ml and heat it to 130-170 °C until all impurities in the metallic sodium are removed, then place it in clean liquid paraffin. Then, prepare a circular thin sodium sheet with a thickness of 0.4-0.6 mm and a diameter of 16 mm in an operating tray containing paraffin oil. Take out the circular thin sodium sheet and place it in the negative electrode case of a button battery containing 0.2-0.4 ml of electrolyte. After removing the paraffin, adding a separator and electrolyte, successively place the positive electrode sheet, gasket, and spring sheet of the battery and encapsulate it into a button battery. The beneficial effect of the present invention is that the sodium-ion battery is assembled in air, replacing the expensive glove box, reducing the research cost of assembling the sodium-ion half-cell, and also lowering the threshold for researching sodium-ion electrode materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemistry, and particularly relates to a method for semi-assembling a sodium-ion battery.

[0002] Background Research

[0003] Energy and environment are important issues faced by all mankind. Among various energy storage systems, the battery system stores electrical energy by converting it into chemical energy, and has advantages such as high charge and discharge efficiency and small volume, becoming an ideal energy storage method.

[0004] Lithium-ion batteries have become ideal energy storage materials in the 21st century due to their high charge and discharge efficiency and good cycle performance. With the progress of technology, the demand for batteries in fields such as electric vehicles and electronic products is increasing. The scarcity of lithium resources has become prominent, and the development of lithium-ion batteries is restricted by cost and lithium resources. From the perspective of the application requirements of large-scale energy storage, an ideal secondary battery must not only have suitable electrochemical properties, but also take into account social and economic benefit indicators such as rich resources and low price.

[0005] Sodium and lithium belong to the same main group and have the same physical and chemical properties. The charge and discharge principles of the battery are basically the same. The sodium element reserves in the earth's crust are 2.64%, which is three orders of magnitude higher than the lithium ion reserves of 0.002%, and it is cheap and widely distributed. Therefore, sodium-ion batteries have become a suitable choice for large-scale energy storage devices. Sodium-ion batteries are heavier in mass and have a larger ionic radius (0.102nm) than lithium (0.069nm), which will cause the deintercalation of Na+ in the electrode to be slow, affecting the cycle and rate performance of the battery. At the same time, the standard electrode potential of the Na+ / Na electrode pair (-1.27V vs SHE) is about 0.3V higher than that of Li+ / Li (-3.04V vs SHE). Therefore, the energy density of sodium-ion batteries is lower than that of lithium-ion batteries. For this reason, researching sodium-ion batteries with good performance and high safety has become the goal pursued by research scholars.

[0006] Generally, a sodium-ion battery consists of a positive electrode material, a negative electrode material, an electrolyte, an adhesive, a separator, etc. In order to study the electrochemical properties of the positive or negative electrode material, researchers assemble the battery into a half-cell (i.e., one end of the electrode is metallic sodium). Since elemental sodium is extremely easy to oxidize in air and reacts violently with water, even explodes, the battery assembly in all reported literatures is carried out in a glove box filled with argon, and it is required that the contents of water and oxygen in the glove box are both less than 0.1 ppm. One of the problems with using a glove box is that the glove box itself is relatively expensive, and the other is that it requires argon protection and continuous inflation, which increases the economic pressure on researchers to a certain extent, and also hinders the research on sodium-ion battery electrode materials in some laboratories without glove boxes. Therefore, the method proposed in the present invention for assembling a sodium-ion battery in air is of great significance for the research on sodium-ion battery electrode materials. Summary of the Invention

[0007] The object of the present invention is to provide a method for assembling a sodium-ion half-cell in air. The metallic sodium is heated and purified in liquid paraffin and then placed in clean liquid paraffin for standby. When assembling the sodium-ion battery, it is taken out and placed in an operation tray with liquid paraffin and formed by a mold. The liquid paraffin on the surface of the metallic sodium sheet is removed by the electrolyte, so that the preparation of the metallic sodium sheet to the whole operation of battery assembly is carried out in an airtight environment, playing the same role as a glove box.

[0008] To achieve the above object, the technical route adopted by the present invention is as follows:

[0009] A method for assembling a sodium-ion battery in air, characterized in that the liquid paraffin and the electrolyte for assembling the battery are effectively utilized to isolate air during the preparation of the metallic sodium sheet and the assembly of the sodium-ion battery, and its oxidation is inhibited. The preparation steps are as follows:

[0010] Step 1: Liquid paraffin treatment. Take 150 ml of liquid paraffin and pour it into a 250 ml beaker, place it in a vacuum drying oven and heat it to 70 °C - 100 °C, evacuate to 0.08 MPa - 0.1 MPa and keep it for 10 minutes, and maintain it for 30 minutes in a vacuum state.

[0011] Step 2: Pretreatment of metallic sodium. Place the cut metallic sodium block in the beaker containing the liquid paraffin in Step 1. The ratio of metallic sodium to liquid paraffin is 15 - 20 g∶70 - 80 ml, and the heating temperature is 130 - 170 °C until the impurities oxidized on the metallic sodium fall off and a liquid sodium fluid with metallic luster is shown. Cool it below 80 °C and repeat this process 2 - 3 times until no impurities are generated.

[0012] Step 3: Cool the product in Step 2 to room temperature, take out the metallic sodium block and place it in the clean liquid paraffin treated in Step 1.

[0013] Step 4: Preparation of metallic sodium sheet in air. Take out the metallic sodium in Step 3, cut the sodium block into 1 cm3 - 3 cm3 and place it in an operation tray containing paraffin oil, roll it into a cake shape, and keep the liquid paraffin level in the tray 6 - 9 mm above the sodium cake. After shaping the metallic sodium with a mold to a thickness of 0.4 - 0.6 mm, use a punch to cut it into a circular thin sodium sheet with a diameter of 16 mm (CR2032 button battery).

[0014] Step 5: Assembly of the sodium-ion battery in air. Take out the circular thin sodium sheet processed in Step 4 and place it in the negative electrode case of a button battery filled with electrolyte. Take 0.2 - 0.4 ml of electrolyte. After the electrolyte fully wets the sodium surface to wash away the paraffin oil on the sodium surface, use a straw to suck up the upper layer of paraffin to achieve the separation state of paraffin and electrolyte. Then add a separator and drop 0.1 - 0.2 ml of electrolyte to wet it. Then place the battery electrode plate, gasket, and spring plate in sequence and seal them.

[0015] Step 6: Testing of battery performance. Conduct electrochemical cycling tests and rate tests on the sodium-ion button battery assembled in Step 5. Description of the Drawings

[0016] Figure 1 It is the electrochemical performance test of the sodium-ion battery assembled in air in Example 1 of the present invention.

[0017] Figure 2 It is the electrochemical performance test of the sodium-ion battery assembled in air in Example 2 of the present invention.

[0018] Figure 3 It is the electrochemical performance test of the sodium-ion battery assembled in a glove box in Example 3 of the present invention.

[0019] The advantages of the present invention are as follows: Assembling the sodium-ion battery in air replaces the use of an expensive glove box, reduces the research cost of assembling the sodium-ion half-cell, and also lowers the threshold for researching sodium-ion electrode materials. **Detailed Description of the Invention**

[0020] Example 1

[0021] Step 1: Pour 150 ml of liquid paraffin into a 250 ml beaker, place it in a vacuum drying oven, heat it to 80°C, evacuate to 0.1 MPa and maintain for 10 minutes, and keep it in a vacuum state for 30 minutes.

[0022] Step 2: Place the cut metal sodium block in the beaker containing the liquid paraffin in Step 1. The ratio of metal sodium to liquid paraffin is 15 g∶70 ml, and the heating temperature is 130°C until the impurities oxidized on the metal sodium fall off to show a liquid sodium fluid with a metallic luster. Cool it below 80°C and repeat this process 3 times until no impurities are generated.

[0023] Step 3: Cool the product in Step 2 to room temperature, take out the metal sodium block, and place it in the clean liquid paraffin processed in Step 1.

[0024] Step 4: Preparation of sodium metal flakes in air. Take out the sodium metal from Step 3, cut the sodium block into pieces of 1 cm3 - 3 cm3 and place them in an operating tray containing paraffin oil. Roll and press them into a cake shape. The height of the paraffin oil liquid level in the tray should be maintained at 6 - 9 mm above the sodium cake. After plasticizing the sodium metal with a mold to a thickness of 0.4 - 0.6 mm, use a punch to cut it into circular thin sodium flakes with a diameter of 16 mm (CR2032 button battery).

[0025] Step 5: Assembly of sodium-ion battery in air. Take out the circular thin sodium flakes processed in Step 4 and place them in the negative electrode shell of a button battery filled with electrolyte. Take 0.2 - 0.4 ml of electrolyte. After the electrolyte fully wets to wash away the paraffin oil on the sodium surface, use a straw to suck up the upper-layer paraffin to achieve the separation state of paraffin and electrolyte. Then add a separator and drop 0.1 - 0.2 ml of electrolyte to wet it. After that, place the battery electrode plate, gasket, and spring plate in sequence and then seal them.

[0026] Step 6: Testing of battery performance. Conduct an electrochemical cycling test on the sodium-ion button battery assembled in Step 5 to obtain Figure 1 .

[0027] Example 2

[0028] Step 1: Pour 150 ml of paraffin oil into a 250 ml beaker, place it in a vacuum drying oven and heat it to 80 °C. Evacuate to 0.1 MPa and maintain for 10 minutes, and keep it in a vacuum state for 30 minutes.

[0029] Step 2: Place the cut sodium metal block in the beaker containing the paraffin oil from Step 1. The ratio of sodium metal to paraffin oil is 20 g∶80 ml. Heat it to 170 °C until the impurities oxidized from the sodium metal fall off, showing a liquid sodium fluid with metallic luster. Cool it below 80 °C and repeat this process 3 times until no impurities are generated.

[0030] Step 3: Cool the product in Step 2 to room temperature, take out the sodium metal block and place it in the clean paraffin oil processed in Step 1.

[0031] Step 4: Preparation of sodium metal flakes in air. Take out the sodium metal from Step 3, cut the sodium block into pieces of 1 cm3 - 3 cm3 and place them in an operating tray containing paraffin oil. Roll and press them into a cake shape. The height of the paraffin oil liquid level in the tray should be maintained at 6 - 9 mm above the sodium cake. After plasticizing the sodium metal with a mold to a thickness of 0.4 - 0.6 mm, use a punch to cut it into circular thin sodium flakes with a diameter of 16 mm (CR2032 button battery).

[0032] Step 5: Assembly of the sodium-ion battery in air. Take out the circular thin sodium sheet processed in Step 4 and place it in the negative electrode case of the button battery filled with electrolyte. Take 0.2 - 0.4 ml of the electrolyte. After the electrolyte fully wets the sodium surface to wash away the paraffin oil on the sodium surface, use a straw to suck the upper-layer paraffin until the paraffin is separated from the electrolyte. Then add the separator and drop 0.1 - 0.2 ml of the electrolyte to wet it. After that, place the battery electrode sheet, gasket, and spring sheet in sequence and then seal them.

[0033] Step 6: Testing of battery performance. Perform electrochemical cycling tests on the sodium-ion button battery assembled in Step 5 to obtain Figure 2 .

[0034] Example 3

[0035] Step 1: Preparation of the sodium metal sheet in the glove box. Control the content of water and oxygen to be less than 0.1 ppm in the glove box. Take out the sodium metal, cut the sodium block into a 1 cm³ cube and roll it into a cake shape. After plasticizing the sodium metal with a mold to a thickness of 0.4 mm, use a punch to cut it into a 16 mm (CR2032) circular thin sodium sheet.

[0036] Step 2: Assembly of the sodium-ion battery in the glove box. Take out the circular thin sodium sheet processed in Step 1 and place it in the negative electrode case of the button battery filled with electrolyte. Take 0.2 ml of the electrolyte, add the battery electrode sheet, gasket, and spring sheet, and then seal them.

[0037] Step 3: Testing of battery performance. Perform electrochemical cycling tests on the sodium-ion button battery assembled in Step 2 to obtain Figure 3 .

Claims

1. A method for assembling a sodium-ion half-cell in air, characterized in that, The steps include: Heat and purify metallic sodium in liquid paraffin, then place it in clean liquid paraffin for standby. When assembling the sodium-ion battery, take it out and place it in an operating tray with liquid paraffin for molding using a mold. Use the electrolyte to remove the liquid paraffin on the surface of the metallic sodium sheet. Take out the processed circular sodium sheet and place it in the negative electrode of a button battery filled with electrolyte. Take the electrolyte to fully wet and wash away the paraffin oil on the sodium surface. After sucking out the upper-layer paraffin with a straw, add a separator and then dropwise add the electrolyte. Then, place the battery electrode plate, gasket, and spring plate in sequence and seal them. Use liquid paraffin and the electrolyte for assembling the battery as a medium to isolate air, so that the preparation of the metallic sodium sheet and the assembly of the sodium-ion battery are both isolated from air to inhibit its oxidation.

2. The method for assembling a sodium-ion half cell in air according to claim 1, wherein: Pour 150 ml of liquid paraffin into a 250 ml beaker, evacuate to 0.08 MPa - 0.1 MPa and maintain for 10 minutes, and keep it in the vacuum state for 30 minutes, then heat in a vacuum drying oven at 70°C - 100°C.

3. The method for assembling a sodium ion half-cell in air according to claim 1, characterized in that: The ratio of metallic sodium to liquid paraffin is 15 - 20 g: 70 - 80 ml, heat at 130°C - 170°C and then cool to 80°C.

4. The method for assembling a sodium-ion half-cell in air according to claim 1, wherein: Sodium block 1 cm 3 -3 cm 3 , the liquid paraffin liquid level is maintained at 6-9 mm above the sodium cake, and the thickness of the shaped sodium metal is 0.4-0.6 mm.

5. The method for assembling a sodium-ion half-cell in air according to claim 1, wherein: One circular sodium sheet with a diameter of 16 mm and a thickness of 0.4 mm - 0.6 mm is added with 0.2 - 0.4 ml of electrolyte.

6. The method for assembling a sodium-ion half cell in air according to claim 1, wherein: Wash away the paraffin oil on the sodium surface with 0.2 - 0.4 ml of electrolyte, suck out the upper-layer paraffin with a straw, add a separator, and then dropwise add 0.1 - 0.2 ml of electrolyte.

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