Preparation method of sodium ion battery cell with ultralow temperature performance

Abstract

The invention relates to a preparation method of a sodium ion battery cell with ultralow temperature performance. The lithium ion battery comprises a positive plate, a negative plate, a diaphragm and electrolyte, the positive plate is prepared by the following steps: uniformly mixing sodium carbonate, ammonium fluoride, ammonium dihydrogen phosphate and ammonium metavanadate, feeding the mixture into a ball milling tank for ball milling, adding sodium acetate for continuous ball milling, and performing vacuum drying to obtain a precursor; fully grinding the precursor, feeding the ground precursor into a tubular furnace, pre-burning under the protection of argon, carrying out high-temperature calcination, and cooling to room temperature to obtain an active material; the preparation method comprises the following steps: uniformly stirring and mixing an active material, a conductive material, polyvinylidene fluoride and N-methyl pyrrolidone, coating the surface of a stainless steel foil with the mixture, and drying to obtain a positive plate; the electrolyte is prepared from sodium hexafluorophosphate, polycarbonate, ethylene carbonate, fluoroethylene carbonate and an ultralow-temperature accelerant; the sodium ion battery cell with ultralow temperature performance prepared by the invention has excellent low-temperature electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion battery cells, and in particular to a method for preparing a sodium ion battery cell with ultra-low temperature performance. Background Art

[0002] Sodium-ion batteries, with their abundant global sodium reserves, low production costs, lack of memory effect, reversible charge and discharge, high safety, and impressive specific capacity and energy, have become a highly competitive alternative energy system in the post-lithium-ion battery era. They are particularly suitable as energy storage equipment for new clean and renewable energy sources. This places high demands on the specific capacity and energy of sodium-ion battery cathode materials, as well as the wide-temperature performance of the entire battery system.

[0003] Chinese patent CN119390038A: A preparation method and vehicle of sodium manganese titanium phosphate positive electrode material for sodium ion battery, belongs to the technical field of synthesis of sodium ion battery positive electrode material, and specifically relates to a preparation method of sodium manganese titanium phosphate positive electrode material for sodium ion battery; the preparation method comprises mixing a sodium source, a phosphorus source, a carbon source, a titanium source, a manganese source and a high entropy metal source, then adding a slurry binder and stirring and dispersing at high speed, sand milling, spray drying and high-temperature calcination to prepare the sodium manganese titanium phosphate positive electrode material for sodium ion battery; the slurry binder comprises at least a polyarylether nitrile derivative, and the polyarylether nitrile derivative has a sulfur element and a cyano group.

[0004] Chinese patent CN119381439A discloses a layered oxide cathode material for sodium-ion batteries based on surface reconstruction and its preparation method, belonging to the field of sodium-ion batteries. The cathode material comprises a layered cathode material and a reconstructed layer with a disordered rock salt structure on the surface of the cathode material, forming a disordered rock salt / layered heterostructure. The reconstructed layer is obtained by quenching the cathode material in a molybdate aqueous solution, and the thickness of the reconstructed layer is 2 to 5 nm.

[0005] Chinese patent CN119361664A: Provides a positive electrode active material and its preparation method, a sodium-ion battery, and an electrical device, belonging to the field of positive electrode active material manufacturing technology. The positive electrode active material comprises a core, a first shell, and a second shell. The first shell is also doped with element B, and the second shell is an inorganic metal oxide layer.

[0006] The sodium ion battery cells prepared by the above patents and prior art are unstable in operation at low temperatures and have poor rate performance and cycle life. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides a method for preparing a sodium ion battery cell with ultra-low temperature performance, the operating steps of which are as follows:

[0008] It includes: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; the preparation method of the positive electrode sheet is:

[0009] S1: 12-18 parts of sodium carbonate, 3-7 parts of ammonium fluoride, 3-7 parts of ammonium dihydrogen phosphate, and 0.1-1 part of ammonium metavanadate are mixed uniformly, transferred to a ball mill, and ball milled for 10-20 minutes. 1-5 parts of sucrose are added and ball milled for 8-12 hours. The mixture is then vacuum dried to obtain a precursor.

[0010] S2: After the precursor is fully ground, it is sent to a tube furnace for pre-sintering under argon protection, calcining at high temperature, and then cooling to room temperature to obtain the active material;

[0011] S3: 50-70 parts of active material, 10-20 parts of conductive material, 5-10 parts of polyvinylidene fluoride, and 1-5 parts of N-methylpyrrolidone are stirred and evenly mixed, and then coated on the surface of stainless steel foil and dried to obtain a positive electrode sheet.

[0012] The drying temperature is 70-90° C. and the drying time is 4-6 hours.

[0013] The pre-firing temperature is 350-450° C., and the pre-firing time is 200-240 minutes.

[0014] The high-temperature calcination temperature is 450-500° C. and the time is 300-360 minutes.

[0015] The conductive material is one of graphene, carbon nanotubes, carbon fibers, superP, acetylene black, carbon nanohorns, Ketjen black, onion-like carbon, vapor-grown carbon fibers, and carbon black.

[0016] The negative electrode plate is sodium titanate.

[0017] The diaphragm is Whitman glass fiber.

[0018] The electrolyte is prepared by dissolving sodium hexafluorophosphate in polycarbonate and ethylene carbonate in a volume ratio of 1:1, adding fluoroethylene carbonate and an ultra-low temperature accelerator, and forming a mixed solution as the electrolyte. The concentration of sodium hexafluorophosphate in the electrolyte is 1 mol / L, the mass concentration of fluoroethylene carbonate is 5%, and the mass concentration of the ultra-low temperature accelerator is 0.5%-3%.

[0019] The preparation method of the ultra-low temperature accelerator is as follows:

[0020] A1: Ring-opening addition reaction of fluoroaniline with ethylene oxide: In a reaction kettle equipped with a stirrer, thermometer, and reflux condenser, add 24-48 parts of fluoro-4-(pentafluorothio)aniline, 17-34 parts of 2-[(thiophen-2-ylmethoxy)methyl]oxirane, and 0.5-2.3 parts of sodium ethoxide, followed by 200-300 parts of DMF. Stir at a rate of 100-120 rpm, slowly raise the temperature to 60-70°C, and react at this temperature for 3-5 hours.

[0021] A2 Post-treatment: After the reaction is completed, DMF is removed by distillation under reduced pressure to obtain an ultra-low temperature accelerator.

[0022] Reaction mechanism

[0023] The amino group (-NH2) of fluoroaniline attacks the CO bond of ethylene oxide to generate a β-hydroxyamine structure; the sulfur atom of the thiophene ring forms an intermolecular interaction with the fluorine atom of fluoroaniline through its lone pair of electrons, reducing the crystallization tendency of the system.

[0024] Technical Effects

[0025] The present invention provides a method for preparing a sodium ion battery cell with ultra-low temperature performance. Compared with the prior art, the present invention has the following significant effects:

[0026] 1. Ultra-low temperature conductivity improvement: Fluoroaniline in the promoter molecules reduces the freezing point of the electrolyte to below -55°C; thiophene derivatives inhibit the orderly arrangement of solvent molecules through π-π stacking, which can effectively improve the electrochemical performance at -40°C.

[0027] 2. Enhanced interface stability: The sulfur atom of the thiophene ring reacts with the sodium electrode to form a sulfur-containing SEI film, which inhibits the growth of sodium dendrites; the amine intermediate forms hydrogen bonds with the hydroxyl groups on the electrode surface through the hydroxyl groups, reducing side reactions.

[0028] 3. Process compatibility: The accelerator is compatible with the existing electrolyte system and there is no need to change the battery production process; the raw material cost is low, the synthesis steps are simple, and it is suitable for large-scale production.

[0029] 4. The sodium ion battery cell with ultra-low temperature performance prepared by the present invention can work stably at low temperatures, has outstanding rate performance and cycle life, and has excellent low-temperature electrochemical performance. DETAILED DESCRIPTION

[0030] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention object, the following is a detailed description in conjunction with examples and comparative examples:

[0031] Electrochemical performance test: Using an electrochemical workstation, the discharge specific capacity was tested at -40°C; the average single-cycle capacity decay was tested after 10,000 cycles at a high rate of 5C.

[0032] Example 1

[0033] A method for preparing a sodium ion battery cell with ultra-low temperature performance, the operating steps are as follows:

[0034] It includes: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; the preparation method of the positive electrode sheet is:

[0035] S1: 12 g of sodium carbonate, 3 g of ammonium fluoride, 3 g of ammonium dihydrogen phosphate, and 0.1 g of ammonium metavanadate were mixed uniformly, transferred to a ball mill, and ball milled for 10 min. 1 g of sucrose was added and ball milled for another 8 h. The mixture was then vacuum dried to obtain a precursor.

[0036] S2: After the precursor is fully ground, it is sent to a tube furnace for pre-sintering under argon protection, calcining at high temperature, and then cooling to room temperature to obtain the active material;

[0037] S3: 50 g of active material, 10 g of conductive material, 5 g of polyvinylidene fluoride, and 1 g of N-methylpyrrolidone were stirred and mixed evenly, and then coated on the surface of stainless steel foil and dried to obtain a positive electrode sheet.

[0038] The drying temperature is 70° C. and the drying time is 4 hours.

[0039] The pre-firing temperature is 350° C. and the pre-firing time is 200 minutes.

[0040] The high-temperature calcination temperature is 450° C. and the time is 300 minutes.

[0041] The conductive material is graphene.

[0042] The negative electrode plate is sodium titanate.

[0043] The diaphragm is Whitman glass fiber.

[0044] The electrolyte is prepared by dissolving sodium hexafluorophosphate in polycarbonate and ethylene carbonate in a volume ratio of 1:1, adding fluoroethylene carbonate and an ultra-low temperature accelerator, and forming a mixed solution as the electrolyte. The concentration of sodium hexafluorophosphate in the electrolyte is 1 mol / L, the mass concentration of fluoroethylene carbonate is 5%, and the mass concentration of the ultra-low temperature accelerator is 0.5%.

[0045] The preparation method of the ultra-low temperature accelerator is as follows:

[0046] A1: Ring-opening addition of fluoroaniline with ethylene oxide: In a reaction kettle equipped with a stirrer, thermometer, and reflux condenser, 24 g of fluoro-4-(pentafluorothio)aniline (CAS: 1240257-25-3), 17 g of 2-[(thiophen-2-ylmethoxy)methyl]oxirane (CAS: 80910-06-1), and 0.5 g of sodium ethoxide were added in sequence. 200 g of DMF was then added. Stirring was started at a rate of 100 rpm, and the temperature was slowly raised to 60°C. The reaction was kept at this temperature for 3 hours.

[0047] A2 Post-treatment: After the reaction is completed, DMF is removed by distillation under reduced pressure to obtain an ultra-low temperature accelerator.

[0048] Example 2

[0049] A method for preparing a sodium ion battery cell with ultra-low temperature performance, the operating steps are as follows:

[0050] It includes: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; the preparation method of the positive electrode sheet is:

[0051] S1: 14 g of sodium carbonate, 4 g of ammonium fluoride, 4 g of ammonium dihydrogen phosphate, and 0.5 g of ammonium metavanadate were mixed uniformly, transferred to a ball mill, and ball milled for 14 min. 2 g of sucrose was added and ball milled for another 9 h. The mixture was then vacuum dried to obtain a precursor.

[0052] S2: After the precursor is fully ground, it is sent to a tube furnace for pre-sintering under argon protection, calcining at high temperature, and then cooling to room temperature to obtain the active material;

[0053] S3: 55 g of active material, 13 g of conductive material, 6 g of polyvinylidene fluoride, and 3 g of N-methylpyrrolidone were stirred and mixed uniformly, and then coated on the surface of stainless steel foil and dried to obtain a positive electrode sheet.

[0054] The drying temperature is 75° C. and the drying time is 5 hours.

[0055] The pre-firing temperature is 380° C. and the pre-firing time is 210 minutes.

[0056] The high-temperature calcination temperature is 460° C. and the time is 320 minutes.

[0057] The conductive material is carbon nanotubes.

[0058] The negative electrode plate is sodium titanate.

[0059] The diaphragm is Whitman glass fiber.

[0060] The electrolyte is prepared by dissolving sodium hexafluorophosphate in polycarbonate and ethylene carbonate in a volume ratio of 1:1, adding fluoroethylene carbonate and an ultra-low temperature accelerator, and forming a mixed solution as the electrolyte. The concentration of sodium hexafluorophosphate in the electrolyte is 1 mol / L, the mass concentration of fluoroethylene carbonate is 5%, and the mass concentration of the ultra-low temperature accelerator is 1%.

[0061] The preparation method of the ultra-low temperature accelerator is as follows:

[0062] A1: Ring-opening addition of fluoroaniline with ethylene oxide: In a reaction kettle equipped with a stirrer, thermometer, and reflux condenser, 32 g of fluoro-4-(pentafluorothio)aniline (CAS: 1240257-25-3), 21 g of 2-[(thiophen-2-ylmethoxy)methyl]oxirane (CAS: 80910-06-1), and 1 g of sodium ethoxide were added in sequence. 240 g of DMF was then added. Stirring was started at a rate of 110 rpm. The temperature was slowly raised to 65°C and the reaction was maintained at this temperature for 4 hours.

[0063] A2 Post-treatment: After the reaction is completed, DMF is removed by distillation under reduced pressure to obtain an ultra-low temperature accelerator.

[0064] Example 3

[0065] A method for preparing a sodium ion battery cell with ultra-low temperature performance, the operating steps are as follows:

[0066] It includes: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; the preparation method of the positive electrode sheet is:

[0067] S1: 16 g of sodium carbonate, 6 g of ammonium fluoride, 6 g of ammonium dihydrogen phosphate, and 0.8 g of ammonium metavanadate were mixed uniformly, transferred to a ball mill, and ball milled for 15 min. 4 g of sucrose was added and ball milled for 11 h. The mixture was then vacuum dried to obtain a precursor.

[0068] S2: After the precursor is fully ground, it is sent to a tube furnace for pre-sintering under argon protection, calcining at high temperature, and then cooling to room temperature to obtain the active material;

[0069] S3: 65 g of active material, 18 g of conductive material, 8 g of polyvinylidene fluoride, and 4 g of N-methylpyrrolidone were stirred and mixed uniformly, and then coated on the surface of stainless steel foil and dried to obtain a positive electrode sheet.

[0070] The drying temperature is 85° C. and the drying time is 5 hours.

[0071] The pre-firing temperature is 430° C. and the pre-firing time is 230 minutes.

[0072] The high-temperature calcination temperature is 480° C. and the time is 350 minutes.

[0073] The conductive material is carbon fiber.

[0074] The negative electrode plate is sodium titanate.

[0075] The diaphragm is Whitman glass fiber.

[0076] The electrolyte is prepared by dissolving sodium hexafluorophosphate in polycarbonate and ethylene carbonate in a volume ratio of 1:1, adding fluoroethylene carbonate and an ultra-low temperature accelerator, and forming a mixed solution as the electrolyte. The concentration of sodium hexafluorophosphate in the electrolyte is 1 mol / L, the mass concentration of fluoroethylene carbonate is 5%, and the mass concentration of the ultra-low temperature accelerator is 2%.

[0077] The preparation method of the ultra-low temperature accelerator is as follows:

[0078] A1: Ring-opening addition of fluoroaniline with ethylene oxide: In a reaction kettle equipped with a stirrer, thermometer, and reflux condenser, 45 g of fluoro-4-(pentafluorothio)aniline (CAS: 1240257-25-3), 31 g of 2-[(thiophen-2-ylmethoxy)methyl]oxirane (CAS: 80910-06-1), and 2 g of sodium ethoxide were added in sequence. 280 g of DMF was then added. Stirring was started at a rate of 110 rpm. The temperature was slowly raised to 65°C and the reaction was maintained at this temperature for 4 hours.

[0079] A2 Post-treatment: After the reaction is completed, DMF is removed by distillation under reduced pressure to obtain an ultra-low temperature accelerator.

[0080] Example 4

[0081] A method for preparing a sodium ion battery cell with ultra-low temperature performance, the operating steps are as follows:

[0082] It includes: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; the preparation method of the positive electrode sheet is:

[0083] S1: 18 g of sodium carbonate, 7 g of ammonium fluoride, 7 g of ammonium dihydrogen phosphate, and 1 g of ammonium metavanadate were mixed evenly, placed in a ball mill, and ball milled for 20 min. 5 g of sucrose was added and ball milled for another 12 h, and then vacuum dried to obtain a precursor.

[0084] S2: After the precursor is fully ground, it is sent to a tube furnace for pre-sintering under argon protection, calcining at high temperature, and then cooling to room temperature to obtain the active material;

[0085] S3: 70 g of active material, 20 g of conductive material, 10 g of polyvinylidene fluoride, and 5 g of N-methylpyrrolidone were stirred and mixed evenly, and then coated on the surface of stainless steel foil and dried to obtain a positive electrode sheet.

[0086] The drying temperature is 90° C. and the drying time is 6 hours.

[0087] The pre-firing temperature is 450° C. and the pre-firing time is 240 minutes.

[0088] The high-temperature calcination temperature is 500° C. and the time is 360 minutes.

[0089] The conductive material is superP.

[0090] The negative electrode plate is sodium titanate.

[0091] The diaphragm is Whitman glass fiber.

[0092] The electrolyte is prepared by dissolving sodium hexafluorophosphate in polycarbonate and ethylene carbonate in a volume ratio of 1:1, adding fluoroethylene carbonate and an ultra-low temperature accelerator, and forming a mixed solution as the electrolyte. The concentration of sodium hexafluorophosphate in the electrolyte is 1 mol / L, the mass concentration of fluoroethylene carbonate is 5%, and the mass concentration of the ultra-low temperature accelerator is 3%.

[0093] The preparation method of the ultra-low temperature accelerator is as follows:

[0094] A1: Ring-opening addition of fluoroaniline with ethylene oxide: In a reaction kettle equipped with a stirrer, thermometer, and reflux condenser, 48 g of fluoro-4-(pentafluorothio)aniline (CAS: 1240257-25-3), 34 g of 2-[(thiophen-2-ylmethoxy)methyl]oxirane (CAS: 80910-06-1), and 2.3 g of sodium ethoxide were added in sequence. 300 g of DMF was then added. Stirring was started at 120 rpm, and the temperature was slowly raised to 70°C. The reaction was kept at this temperature for 5 hours.

[0095] A2 Post-treatment: After the reaction is completed, DMF is removed by distillation under reduced pressure to obtain an ultra-low temperature accelerator.

[0096] Comparative Example 1

[0097] No ultra-low temperature accelerator was added, and the other procedures were the same as in Example 1.

[0098] Comparative Example 2

[0099] The other steps were the same as in Example 1 except that 4-fluoro-(pentafluorothio)aniline was not added.

[0100] Comparative Example 3

[0101] The same procedures as in Example 1 were followed except that 2-[(thiophen-2-ylmethoxy)methyl]oxirane was not added.

[0102] Discharge specific capacity / mA·h / g Single-turn capacity attenuation / mA·h / g Example 1 80.6 0.0030 Example 2 81.4 0.0028 Example 3 82.8 0.0025 Example 4 83.5 0.0023 Comparative Example 1 59.3 0.0055 Comparative Example 2 73.9 0.0040 Comparative Example 3 75.1 0.0036

[0103] Through the data analysis of the above examples and comparative examples, the sodium ion battery cell with ultra-low temperature performance prepared by the present invention has excellent low-temperature electrochemical performance.

[0104] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a sodium ion battery cell with ultra-low temperature performance, the operating steps are as follows: It includes: Positive electrode sheet, negative electrode sheet, diaphragm, electrolyte; The preparation method of the positive electrode sheet is as follows: S1: 12-18 parts of sodium carbonate, 3-7 parts of ammonium fluoride, 3-7 parts of ammonium dihydrogen phosphate, and 0.1-1 part of ammonium metavanadate are mixed uniformly, transferred to a ball mill, and ball milled for 10-20 minutes. 1-5 parts of sucrose are added and ball milled for 8-12 hours. The mixture is then vacuum dried to obtain a precursor. S2: After the precursor is fully ground, it is sent to a tube furnace for pre-sintering under argon protection, calcining at high temperature, and then cooling to room temperature to obtain the active material; S3: 50-70 parts of active material, 10-20 parts of conductive material, 5-10 parts of polyvinylidene fluoride, and 1-5 parts of N-methylpyrrolidone are stirred and evenly mixed, and then coated on the surface of stainless steel foil and dried to obtain a positive electrode sheet.

2. The method for preparing a sodium ion battery cell with ultra-low temperature performance according to claim 1, wherein: The drying temperature is 70-90° C. and the drying time is 4-6 hours.

3. The method for preparing a sodium ion battery cell with ultra-low temperature performance according to claim 1, wherein: The pre-firing temperature is 350-450° C., and the pre-firing time is 200-240 minutes.

4. The method for preparing a sodium ion battery cell with ultra-low temperature performance according to claim 1, wherein: The high-temperature calcination temperature is 450-500° C. and the time is 300-360 minutes.

5. The method for preparing a sodium ion battery cell with ultra-low temperature performance according to claim 1, characterized in that: The conductive material is one of graphene, carbon nanotubes, carbon fibers, superP, acetylene black, carbon nanohorns, Ketjen black, onion-like carbon, vapor-grown carbon fibers, and carbon black.

6. The method for preparing a sodium ion battery cell with ultra-low temperature performance according to claim 1, characterized in that: The negative electrode plate is sodium titanate.

7. The method for preparing a sodium ion battery cell with ultra-low temperature performance according to claim 1, characterized in that: The diaphragm is Whitman glass fiber.

8. The method for preparing a sodium ion battery cell with ultra-low temperature performance according to claim 1, characterized in that: The electrolyte is prepared by dissolving sodium hexafluorophosphate in polycarbonate and ethylene carbonate in a volume ratio of 1:1, adding fluoroethylene carbonate and an ultra-low temperature accelerator, and forming a mixed solution as the electrolyte. The concentration of sodium hexafluorophosphate in the electrolyte is 1 mol / L, the mass concentration of fluoroethylene carbonate is 5%, and the mass concentration of the ultra-low temperature accelerator is 0.5%-3%.

9. The method for preparing a sodium ion battery cell with ultra-low temperature performance according to claim 8, characterized in that: The preparation method of the ultra-low temperature accelerator is as follows: A1: Ring-opening addition reaction of fluoroaniline with ethylene oxide: In a reaction kettle equipped with a stirrer, thermometer, and reflux condenser, add 24-48 parts of fluoro-4-(pentafluorothio)aniline, 17-34 parts of 2-[(thiophen-2-ylmethoxy)methyl]oxirane, and 0.5-2.3 parts of sodium ethoxide, followed by 200-300 parts of DMF. Stir at a rate of 100-120 rpm, slowly raise the temperature to 60-70°C, and react at this temperature for 3-5 hours. A2 Post-treatment: After the reaction is completed, DMF is removed by distillation under reduced pressure to obtain an ultra-low temperature accelerator.