A long cycle life sodium-ion battery electrolyte, a preparation method and application thereof

Abstract

This invention relates to a long-cycle-life sodium-ion battery electrolyte, its preparation method, and its application, belonging to the field of sodium-ion battery technology. Under an inert atmosphere, borane carboxylate and sodium 2-thiopheneformate are dissolved in an organic solvent to obtain a basic electrolyte. A synergistic additive is added to the basic electrolyte, and after mixing and filtration, the long-cycle-life sodium-ion battery electrolyte is obtained. Sodium 2-thiopheneformate is generated by reacting 2-thiopheneformic acid and sodium hydroxide in the same molar ratio at room temperature with stirring. The electrolyte prepared by this invention has high ionic conductivity, excellent ion transport characteristics, and a significantly improved cycle life.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a long-cycle-life sodium-ion battery electrolyte, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries have broad application prospects in large-scale energy storage and electric vehicles due to the abundance of sodium resources, low cost, and excellent safety. The electrolyte, as a core component of sodium-ion batteries, plays a crucial role in ion transport, and its performance directly determines the battery's cycle life, coulombic efficiency, energy density, and other key indicators.

[0003] In the prior art, for example, the invention patent with publication number CN110854436A discloses a secondary lithium metal battery electrolyte, which includes a lithium salt, an organic solvent, and additives; the lithium salt is dissolved in the organic solvent, and the additives are selected from one or more of 5-chlorothiophene-2-carboxylic acid, 2-thiophenecarboxylic acid, and 2,5-thiophenedicarboxylic acid. This invention applies the electrolyte to secondary lithium metal batteries. In the early stages of cycling, the additives in the electrolyte can react with lithium metal to generate LiCl, forming a non-in-situ solid electrolyte interface film with high mechanical strength, uniformity, and stability on the lithium metal anode surface. This film can suppress lithium dendrite growth during charging and discharging, significantly improving the electrochemical performance of the secondary lithium metal battery.

[0004] The invention patent with publication number CN110931872A discloses a lithium-ion battery electrolyte additive and a lithium-ion battery electrolyte. The lithium-ion battery electrolyte includes a non-aqueous organic solvent, lithium salt, and additives. The additives are composed of 2-thiophene carboxynitrile and vinyl sulfonyl fluoride additives. The mass fraction of the additives in the lithium-ion battery electrolyte is 0.5-5%. This invention has the advantages of extending battery life, improving battery safety, and improving battery cycle performance.

[0005] Existing sodium-ion battery electrolytes mostly use sodium salts such as sodium hexafluorophosphate and sodium perchlorate as electrolyte salts, combined with carbonate-based mixed solvents. However, the presence of fluorides easily leads to poor stability of the solid electrolyte interface, which is prone to cracking and dissolving during cycling, causing continuous electrolyte decomposition and sodium dendrite growth, significantly shortening the battery cycle life. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a long-cycle-life sodium-ion battery electrolyte, its preparation method, and its application. The electrolyte prepared by this invention exhibits high ion conductivity, excellent ion transport characteristics, and significantly improved cycle life.

[0007] The specific technical solution of this invention is as follows: This invention provides a method for preparing a long-cycle-life sodium-ion battery electrolyte, comprising the following steps: S1. Under an inert atmosphere, borane carboxylate and sodium 2-thiophenecarboxylate are dissolved in an organic solvent to obtain the basic electrolyte; S2. Add synergistic additives to the base electrolyte, mix and filter to obtain the long cycle life sodium-ion battery electrolyte.

[0008] In some embodiments of the present invention, the components in the preparation step of the basic electrolyte are as follows, by mass parts: 5-10 parts of boron carboxylate; Sodium 2-thiophenecarboxylate accounts for 0.5%-2% of the total mass of the basic electrolyte; 100-145 parts organic solvent.

[0009] In some embodiments of the present invention, the amount of the synergistic additive added is 1-5 parts of the synergistic additive added to 80-100 parts of the base electrolyte.

[0010] In some embodiments of the present invention, the synergistic additive is a mixture of phenyltrimethoxysilane and 1,3,6-hexamethylenetrionitrile; The mass ratio of the phenyltrimethoxysilane to 1,3,6-hexamethylenetrionitrile is 1:0.4-1; The borane carboxylate is sodium boranecarboxylate, CAS number 17363-08-5.

[0011] In some embodiments of the present invention, the sodium 2-thiophenecarboxylate is generated by reacting 2-thiophenecarboxylic acid and sodium hydroxide in the same molar ratio at room temperature under stirring.

[0012] In some embodiments of the present invention, the organic solvent is ethylene glycol dimethyl ether; The inert atmosphere is a high-purity argon atmosphere.

[0013] The reaction mechanism of this invention: Sodium 2-thiophenecarboxylate has a thiophene heterocycle with a conjugated electronic structure, which can form a stable solvation shell with ethylene glycol dimethyl ether. The carboxyl-derived anion can participate in the construction of the SEI film and form a triple synergistic system with sodium borocarboxylate and synergistic additives. The weak interaction between the heterocycle and sodium ions reduces the ion migration barrier, while enhancing the structural stability of the SEI film and inhibiting side reactions related to sodium dendrite growth.

[0014] In some embodiments of the present invention, in step S1, dissolution is carried out by stirring, wherein the stirring temperature is 55-75°C, the stirring time is 2-4 hours, and the stirring rate is 300-500 r / min.

[0015] In some embodiments of the present invention, the filtration employs an inert filter membrane with a pore size of 0.22 μm; The inert filter membrane is a polytetrafluoroethylene filter membrane or a polypropylene filter membrane.

[0016] The present invention also provides a long-cycle-life sodium-ion battery electrolyte prepared by the aforementioned preparation method.

[0017] The present invention also provides the application of the long cycle life sodium-ion battery electrolyte in the preparation of sodium-ion batteries.

[0018] The beneficial effects of this invention are: The present invention provides a method for preparing a long-cycle-life sodium-ion battery electrolyte. Compared with the prior art, the present invention has the following significant advantages: 1. Optimize the electrolyte solvation structure to improve ion conduction efficiency and enhance the continuity and stability of ion transport; 2. Construct an SEI film that combines passivation capability and flexibility to effectively inhibit sodium dendrite growth and electrolyte decomposition; 3. Breaking through the limitations of traditional fluorine-free electrolytes that rely solely on borane salts, it achieves simultaneous optimization of ion conduction and interfacial stability. Detailed Implementation

[0019] Example 1 A method for preparing a long-cycle-life sodium-ion battery electrolyte, comprising the following steps: S1: High-purity argon gas is introduced into the glove box. Inside the glove box, 5g of sodium borocarboxylate (CAS No. 17363-08-5) and 0.5% sodium 2-thiophenecarboxylate (by mass of the basic electrolyte) are added to a dry, sealed reaction vessel. 100g of ethylene glycol dimethyl ether is slowly added dropwise. The mixture is stirred for 2 hours at a stirring temperature of 55℃ and a stirring rate of 300r / min to obtain the basic electrolyte. S2: Add 1g of a mixture of phenyltrimethoxysilane and 1,3,6-hexanetrionitrile (mass ratio 1:0.4) to 80g of basic electrolyte, and continue stirring for 60min to obtain a mixture; S3: Filter the mixture through a 0.22μm polytetrafluoroethylene filter membrane to remove trace impurities and obtain a long-cycle-life sodium-ion battery electrolyte.

[0020] Sodium 2-thiophenecarboxylate is produced by reacting 2-thiophenecarboxylic acid (CAS No.: 527-72-0) with sodium hydroxide in the same molar ratio at room temperature under stirring.

[0021] Example 2 A method for preparing a long-cycle-life sodium-ion battery electrolyte, comprising the following steps: S1: High-purity argon gas is introduced into the glove box. Inside the glove box, 7g of sodium borocarboxylate (CAS No. 17363-08-5) and 1% of sodium 2-thiophenecarboxylate (by mass of the basic electrolyte) are added to a dry, sealed reaction vessel. 120g of ethylene glycol dimethyl ether is slowly added dropwise. The mixture is stirred for 3 hours at a stirring temperature of 65℃ and a stirring rate of 400r / min to obtain the basic electrolyte. S2: Add 2g of a mixture of phenyltrimethoxysilane and 1,3,6-hexanetrionitrile (mass ratio 1:0.6) to 85g of basic electrolyte, and continue stirring for 80min to obtain a mixture; S3: Filter the mixture through a 0.22μm polytetrafluoroethylene filter membrane to remove trace impurities and obtain a long-cycle-life sodium-ion battery electrolyte.

[0022] Sodium 2-thiophenecarboxylate is produced by reacting 2-thiophenecarboxylic acid (CAS No.: 527-72-0) with sodium hydroxide in the same molar ratio at room temperature under stirring.

[0023] Example 3 A method for preparing a long-cycle-life sodium-ion battery electrolyte, comprising the following steps: S1: High-purity argon gas is introduced into the glove box. Inside the glove box, 9g of sodium borocarboxylate (CAS No. 17363-08-5) and 1.5% sodium 2-thiophenecarboxylate (by mass of the basic electrolyte) are added to a dry, sealed reaction vessel. 135g of ethylene glycol dimethyl ether is slowly added dropwise. The mixture is stirred for 3 hours at a stirring temperature of 70℃ and a stirring rate of 400r / min to obtain the basic electrolyte. S2: Add 4g of a mixture of phenyltrimethoxysilane and 1,3,6-hexanetrionitrile (mass ratio 1:0.8) to 95g of basic electrolyte, and continue stirring for 100min to obtain a mixture; S3: Filter the mixture through a 0.22μm polypropylene filter membrane to remove trace impurities and obtain a long-cycle-life sodium-ion battery electrolyte.

[0024] Sodium 2-thiophenecarboxylate is produced by reacting 2-thiophenecarboxylic acid (CAS No.: 527-72-0) with sodium hydroxide in the same molar ratio at room temperature under stirring.

[0025] Example 4 A method for preparing a long-cycle-life sodium-ion battery electrolyte, comprising the following steps: S1: High-purity argon gas is introduced into the glove box. Inside the glove box, 10g of sodium borocarboxylate (CAS No. 17363-08-5) and 2% sodium 2-thiophenecarboxylate (2% of the total mass of the basic electrolyte) are added to a dry, sealed reaction vessel. 145g of ethylene glycol dimethyl ether is slowly added dropwise. The mixture is stirred for 4 hours at a stirring temperature of 75℃ and a stirring rate of 500r / min to obtain the basic electrolyte. S2: Add 5g of a mixture of phenyltrimethoxysilane and 1,3,6-hexanetrionitrile (mass ratio 1:1) to 100g of basic electrolyte, and continue stirring for 120min to obtain a mixture; S3: Filter the mixture through a 0.22μm polypropylene filter membrane to remove trace impurities and obtain a long-cycle-life sodium-ion battery electrolyte.

[0026] Sodium 2-thiophenecarboxylate is produced by reacting 2-thiophenecarboxylic acid (CAS No.: 527-72-0) with sodium hydroxide in the same molar ratio at room temperature under stirring.

[0027] Comparative Example 1 A method for preparing a sodium-ion battery electrolyte, comprising the following steps: S1: High-purity argon gas is introduced into the glove box. Inside the glove box, 5g of sodium borocarboxylate (CAS No. 17363-08-5) is added to a dry, sealed reaction vessel. 100g of ethylene glycol dimethyl ether is slowly added dropwise. The mixture is stirred for 2 hours at a stirring temperature of 25℃ and a stirring rate of 300r / min to obtain the basic electrolyte. S2: Add 1g of a mixture of phenyltrimethoxysilane and 1,3,6-hexanetrionitrile (mass ratio 1:0.4) to 80g of basic electrolyte, and continue stirring for 60min to obtain a mixture; S3: Filter the mixture through a 0.22μm polytetrafluoroethylene filter membrane to remove trace impurities and obtain sodium-ion battery electrolyte.

[0028] Comparative Example 2 A method for preparing a sodium-ion battery electrolyte, comprising the following steps: S1: High-purity argon gas is introduced into the glove box. Inside the glove box, 5g of sodium borocarboxylate (CAS No. 17363-08-5) and 0.5% of the total mass of the basic electrolyte (CAS No. 527-72-0) are added to a dry, sealed reaction vessel. 100g of ethylene glycol dimethyl ether is slowly added dropwise. The mixture is stirred for 2 hours at a stirring temperature of 25℃ and a stirring rate of 300r / min to obtain the basic electrolyte. S2: Add 1g of a mixture of phenyltrimethoxysilane and 1,3,6-hexanetrionitrile (mass ratio 1:0.4) to 80g of basic electrolyte, and continue stirring for 60min to obtain a mixture; S3: Filter the mixture through a 0.22μm polytetrafluoroethylene filter membrane to remove trace impurities and obtain sodium-ion battery electrolyte.

[0029] Comparative Example 3 A method for preparing a sodium-ion battery electrolyte, comprising the following steps: S1: High-purity argon gas is introduced into the glove box. Inside the glove box, 5g of sodium borocarboxylate (CAS No. 17363-08-5) and 0.5% sodium hydroxide (by mass of the basic electrolyte) are added to a dry, sealed reaction vessel. 100g of ethylene glycol dimethyl ether is slowly added dropwise. The mixture is stirred for 2 hours at a stirring temperature of 25℃ and a stirring rate of 300r / min to obtain the basic electrolyte. S2: Add 1g of a mixture of phenyltrimethoxysilane and 1,3,6-hexanetrionitrile (mass ratio 1:0.4) to 80g of basic electrolyte, and continue stirring for 60min to obtain a mixture; S3: Filter the mixture through a 0.22μm polytetrafluoroethylene filter membrane to remove trace impurities and obtain a long-cycle-life sodium-ion battery electrolyte.

[0030] Detection Example 1 Battery assembly: The electrolytes used in the examples and comparative examples were used to assemble CR2032 coin-type sodium-ion batteries: the positive electrode was made of aluminum foil coated with a mixture of Na3V2(PO4)3, acetylene black, and polyvinylidene fluoride, and the negative electrode was made of copper foil coated with a mixture of hard carbon, acetylene black, and sodium carboxymethyl cellulose. The separator was a glass fiber membrane. The entire process was carried out in an argon glove box to assemble the sodium-ion battery.

[0031] 1. Ionic conductivity: The ionic conductivity of the electrolyte in the sodium-ion battery was tested at 25°C using the AC impedance method.

[0032] 2. Capacity retention rate: The capacity retention rate of sodium-ion batteries was calculated by using the Blue Electric CT2001A test system to cycle 100 times in the voltage range of 3.0~3.8V and at a rate of 0.5C.

[0033] Table 1. Results of ion conductivity and capacity retention tests of the electrolytes in the examples and comparative examples. This invention addresses the problem of poor SEI membrane stability in existing fluorinated electrolytes by introducing sodium 2-thiophenecarboxylate, a novel organic carboxylate monomer, at 0.5%-2% of the total mass of the base electrolyte into the electrolyte system. This, combined with sodium borocarboxylate as a synergistic additive, creates a triple synergistic effect. As shown in Table 1 of the test data, the ionic conductivity and cycle capacity retention of the example are significantly higher than those of the comparative example. The novel monomer achieves a substantial performance improvement with a low addition amount. The synergistic effect of its heterocyclic conjugated structure and carboxyl group is the key innovation for improving the overall performance of the electrolyte.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a long-cycle-life sodium-ion battery electrolyte, characterized in that, Includes the following steps: S1. Under an inert atmosphere, borane carboxylate and sodium 2-thiophenecarboxylate are dissolved in an organic solvent to obtain the basic electrolyte; S2. Add synergistic additives to the base electrolyte, mix and filter to obtain the long cycle life sodium-ion battery electrolyte.

2. The preparation method according to claim 1, characterized in that, In step S1, the components are as follows by mass parts: Borane carboxylate, 5-10 parts; Sodium 2-thiophenecarboxylate accounts for 0.5%-2% of the total mass of the basic electrolyte; 100-145 parts organic solvent.

3. The preparation method according to claim 1 or 2, characterized in that, In step S2, the amount of the synergistic additive added is 1-5 parts added to 80-100 parts of the base electrolyte.

4. The preparation method according to claim 1, characterized in that, The synergistic additive is a mixture of phenyltrimethoxysilane and 1,3,6-hexamethylenetrionitrile; The mass ratio of the phenyltrimethoxysilane to 1,3,6-hexamethylenetrionitrile is 1:0.4-1; The borane carboxylate is sodium borane carboxylate.

5. The preparation method according to claim 1, characterized in that, Sodium 2-thiophenecarboxylate is produced by reacting 2-thiophenecarboxylic acid with sodium hydroxide in the same molar ratio.

6. The preparation method according to claim 1, characterized in that, The organic solvent is ethylene glycol dimethyl ether; The inert atmosphere is a high-purity argon atmosphere.

7. The preparation method according to claim 1, characterized in that, In step S1, dissolution is carried out by stirring, with a stirring temperature of 55-75℃, a stirring time of 2-4 hours, and a stirring speed of 300-500 r / min.

8. The preparation method according to claim 1, characterized in that, The filtration process uses an inert filter membrane with a pore size of 0.22 μm; The inert filter membrane is a polytetrafluoroethylene filter membrane or a polypropylene filter membrane.

9. A long-cycle-life sodium-ion battery electrolyte prepared by the preparation method according to any one of claims 1-8.

10. The application of the long cycle life sodium-ion battery electrolyte according to claim 9 in the preparation of sodium-ion batteries.

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