Preparation process of modified diaphragm for lithium-sulfur battery based on amide group modified PIM-1

Abstract

The invention belongs to the field of chemical power sources, and particularly relates to a preparation process of a modified diaphragm for a lithium-sulfur battery based on amide group modified PIM-1. The modified diaphragm aims to solve the problems of poor cycling stability, low sulfur utilization rate and the like caused by a polysulfide shuttle effect in a lithium-sulfur battery. By introducing an amide group, the prepared modified polymer material has a confinement layer with a nanoscale aperture, migration of polysulfide can be effectively inhibited, and coulombic efficiency and cycling stability of the lithium-sulfur battery are remarkably improved. Compared with an existing commercial polyolefin diaphragm, the composite diaphragm has obvious advantages in electrochemical performance. Besides, the method is simple, convenient to operate, low in cost and suitable for large-scale production, has good durability and environmental friendliness, and promotes commercial application of the lithium-sulfur battery in the fields of electric automobiles and renewable energy storage.

Description

Technical Field

[0001] The present invention belongs to the field of chemical power sources, and particularly relates to a preparation process of a modified separator for lithium-sulfur batteries based on amide group-modified PIM-1. Technical Background

[0002] As a cutting-edge energy storage technology solution, lithium-sulfur batteries have attracted wide attention due to their high energy density and relatively low cost, and are regarded as potential alternatives to traditional lithium-ion batteries. However, during the commercialization process, lithium-sulfur batteries still face many technical challenges, mainly including poor cycle stability and low sulfur utilization rate caused by the shuttle effect. The shuttle effect is mainly caused by the dissolution and diffusion of polysulfides during the charge and discharge process, and the resulting loss of active substances will gradually degrade the battery performance. Currently, commercial polyolefin separators in lithium-sulfur batteries perform poorly in preventing the polysulfide shuttle effect, so there is an urgent need to improve the barrier ability of the separator and the overall battery performance through new materials and technologies.

[0003] In view of the deficiencies of the prior art, researchers have explored various modified separator technologies, such as size sieving, chemical adsorption, and electrostatic repulsion, aiming to inhibit the shuttle of polysulfides by controlling the pore size, surface modification, and charge repulsion. However, these traditional methods often fail to comprehensively solve the problem of the shuttle effect, and thus have not significantly improved the cycle stability and sulfur utilization rate of the battery. Based on this, the current technical demand strongly points to the development of new separator materials, such as modified separators based on intrinsically microporous polymer PIM-1, whose unique microporous structure and chemical properties are expected to fundamentally improve the polysulfide shuttle effect, thereby significantly enhancing the commercial application potential of lithium-sulfur batteries.

[0004] To promote the development of lithium-sulfur battery technology, the present invention proposes a new modified separator for lithium-sulfur batteries based on amide group-modified PIM-1. This technology effectively inhibits the transmembrane transport of polysulfides and significantly enhances the cycle performance and energy efficiency of the battery. Compared with the prior art, this invention has obvious advantages in terms of separator performance and battery life, conforms to the technical development trend in the field of lithium-sulfur batteries, and can effectively promote the commercialization process of lithium-sulfur battery energy storage. Summary of the Invention

[0005] In view of this, the present invention uses a polymer material based on amide group-modified PIM-1 for the lithium-sulfur battery separator, and its inherent micropores' physical barrier to polysulfides and the chemical action of the polar groups contained in the polymer itself effectively improve problems such as poor cycle performance and low sulfur utilization rate caused by the shuttle effect.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a modified separator for a lithium-sulfur battery based on amide group-modified PIM-1, comprising the following steps:

[0008] (1) Take 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobiindane (TTSBI), 2,3,5,6-tetrafluoroterephthalonitrile (DCTB) and anhydrous potassium carbonate (K 2 CO 3 ) and add them to a solvent, heat and react to obtain PIM-1;

[0009] The molar ratio of TTSBI, DCTB to K 2 CO 3 is 1 mole part, 0.8 - 1.2 mole parts and 2.04 - 8 mole parts;

[0010] The solvent is one or a mixture of N,N-dimethylformamide, tetrahydrofuran, toluene, N,N-dimethylacetamide;

[0011] (2) Add PIM-1 and a strong base deprotonated solid to a reaction solvent, react at room temperature to obtain a PIM-1 amide modified product;

[0012] The molar ratio of PIM-1 to the strong base deprotonated solid is 1:0.5 - 1:3;

[0013] The strong base deprotonated solid is any one of potassium tert-butoxide, potassium hydroxide, lithium diisopropylamide;

[0014] The reaction solvent is any one of isobutanol, n-butanol, tert-butanol, isopropanol;

[0015] (3) Dissolve the PIM-1 amide modified product in a precursor solvent, with the concentration of the PIM-1 amide modified product being 5 - 50 mg / mL, to prepare a precursor solution;

[0016] The precursor solvent is any one of chloroform, tetrahydrofuran, dimethyl sulfoxide;

[0017] (4) Take the precursor solution, spray it on the surface of the base film to form a composite modified layer, and obtain a modified separator after drying.

[0018] Preferably, the mass concentration of TTSBI in the reaction solution is 15 - 55 mg / mL.

[0019] Further, in step (1), TTSBI, DCTB, K 2 CO 3The reaction temperature in the reaction solution is 50 - 65 °C, and the stirring reaction time is 23 - 70 h; after the heating reaction, the product is dried, the drying temperature is 60 - 120 °C, and the drying time is 12 - 24 h.

[0020] Preferably, in the step (2), the mass concentration of PIM-1 in the reaction solution is 15 - 40 mg / mL.

[0021] Furthermore, PIM-1 is stirred and reacted with the deprotonated solid of strong base, and the reaction time is 12 - 24 h; after the reaction, the product is dried, the drying temperature is 60 - 120 °C, and the drying time is 12 - 24 h.

[0022] Preferably, the base film used in the step (4) includes any one of PP, PE or PP / PE / PP composite diaphragm.

[0023] Furthermore, the spraying thickness on the composite diaphragm is 300 nm - 800 nm.

[0024] Furthermore, the drying temperature of the modified diaphragm is 40 - 120 °C, and the drying time is 12 - 24 h.

[0025] In the second aspect, the present invention provides a modified diaphragm for lithium-sulfur battery modified by amide group-based PIM-1, which is prepared by the method described in the first aspect.

[0026] In the third aspect, the present invention provides an application of the modified diaphragm for lithium-sulfur battery described in the second aspect, which is used as the diaphragm of the lithium-sulfur battery.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] Firstly, the modified polymer material prepared by the present invention has a confinement layer with nano-scale pore size after being used as the diaphragm of the lithium-sulfur battery, which can inhibit the migration of polysulfides through the dual confinement of pore size screening and chemical action, improve the Coulomb efficiency and cycle stability of the lithium-sulfur battery, and show more excellent electrochemical performance. Secondly, the present invention uses a polymer material containing amide groups to hydrophilically modify the commercial polyolefin diaphragm, which is beneficial to reducing the interfacial impedance between the confinement layer and the base film. The modification is persistent, effective, simple in operation, environmentally friendly and harmless. At the same time, the polymer contains rich polar groups, which is beneficial to strengthening the inhibition of the shuttle effect by the modified diaphragm. In addition, the method of the present invention is simple, the operation is simple, the subsequent treatment is simple, the equipment requirements are simple, and the raw material price is low, which is suitable for large-scale production. Description of the Drawings

[0029] Figure 1 SEM photos of the diaphragm surface for the examples and comparative examples;

[0030] (a) Example; (b) Comparative example;

[0031] Figure 2 Long cycle performance of lithium-sulfur batteries prepared in the examples and comparative examples at a current density of 1C. Specific embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0034] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or prepared by existing methods.

[0035] Examples

[0036] (1) Take 4.08 g of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobiindane (TTSBI), 2.4 g of 2,3,5,6-tetrafluoroterephthalonitrile (DCTB), and 3.38 g of anhydrous potassium carbonate (K 2 CO 3 ) and add them to 120 ml of N,N-dimethylformamide (DMF) solution. Heat and stir at 50 °C for 23 h for reaction. After the reaction is completed, take the precipitate for washing and place it in a vacuum drying oven at 60 °C for 12 h to obtain PIM-1 powder;

[0037] (2) Add 0.46 g of PIM-1 powder and 0.34 g of potassium tert-butoxide (KOBu) to 16 ml of tert-butanol (BuOH) solution. Stir at room temperature for 12 h for reaction. After the reaction is completed, take the precipitate for washing and place it in a vacuum drying oven at 60 °C for 12 h to obtain PIM-1 amide-modified powder;

[0038] (3) Dissolve 0.1 g of PIM-1 amide-modified powder in 20 mL of chloroform to prepare a precursor solution;

[0039] (4) Take the precursor solution and spray it on the surface of the PP base film using spraying technology. Place it in a vacuum drying oven at 60 °C for 24 h to form a composite modified layer and obtain a modified separator. The spraying thickness is 400 nm. The SEM image of the surface of the obtained modified separator is shown in the appendix Figure 1。Assemble a lithium-sulfur button battery. At a current density of 1C, the initial discharge capacity is 1301.7 mAh / g, it can stably cycle 200 times, and the average Coulombic efficiency is greater than 99%. See the appendix Figure 2 as shown.

[0040] Comparative example

[0041] Take the PP separator without any treatment and use it for the comparative test. The SEM image of the PP separator surface is shown in the appendix Figure 1 。Assemble a lithium-sulfur button battery. At a current density of 1C, the initial discharge capacity is 1203.9 mAh / g, it can stably cycle 200 times, and the average Coulombic efficiency is greater than 99%. See the appendix Figure 2 as shown.

[0042] The modified separator of the lithium-sulfur battery based on the intrinsically microporous polymer PIM-1 in the example shows significant advantages in effectively addressing the common polysulfide shuttle problem in lithium-sulfur batteries. By combining the physical microporous barrier with the chemical adsorption of polymer polar groups, this new type of separator not only inhibits the migration of polysulfides but also improves the cycle stability and energy efficiency of the battery. This dual confinement mechanism provides new ideas for the development of lithium-sulfur batteries, indicating that integrating physical and chemical properties in battery design may be an effective strategy to overcome current technical bottlenecks. In addition, the advantages of the present invention in terms of operational simplicity and economy mean that it is not only suitable for large-scale production but also may reduce the manufacturing cost of lithium-sulfur batteries, thus accelerating their market promotion. This low-cost and high-performance modified separator is expected to play an important role in the future lithium-sulfur battery industry and promote wider applications, especially in the fields of electric vehicles and renewable energy storage.

Claims

1. A method for preparing a modified diaphragm for a lithium-sulfur battery based on amide group-modified PIM-1, characterized in that: The following steps are involved: (1) 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI), 2,3,5,6-tetrafluoroterephthalonitrile (DCTB) and anhydrous potassium carbonate (K2CO3) are added to a solvent and heated to react to obtain PIM-1; The molar ratios of TTSBI, DCTB and K2CO3 are 1 molar part, 0.8-1.2 molar parts and 2.04-8 molar parts; The solvent is a mixture of one or more of N,N-dimethylformamide, tetrahydrofuran, toluene, and N,N-dimethylacetamide; (2) adding PIM-1 and a strong base deprotonated solid to a reaction solvent and reacting at room temperature to obtain a PIM-1 amide-modified product; The molar ratio of PIM-1 to the strong base deprotonated solid is 1:0.5 to 1:3; The strong base deprotonated solid is any one of potassium tert-butoxide, potassium hydroxide, and lithium diisopropylamide; The reaction solvent is any one of isobutanol, n-butanol, tert-butanol, and isopropanol; (3) dissolving the PIM-1 amide-modified product in a precursor solvent, wherein the concentration of the PIM-1 amide-modified product is 5 to 50 mg / mL, to prepare a precursor solution; The precursor solvent is any one of N-methylpyrrolidone, chloroform, tetrahydrofuran, and dimethyl sulfoxide; (4) Taking the precursor solution, spraying it on the surface of the base film to form a composite modified layer, and obtaining a modified diaphragm after drying.

2. The method for preparing a modified diaphragm for a lithium-sulfur battery based on amide group-modified PIM-1 according to claim 1, characterized in that: The mass concentration of the TTSBI in the reaction solution is 15-55 mg / mL.

3. The method for preparing a modified diaphragm for a lithium-sulfur battery based on amide group-modified PIM-1 according to claim 2, characterized in that: In the step (1), the reaction temperature of TTSBI, DCTB and K2CO3 in the reaction solution is 50-65°C, and the stirring reaction time is 23-70h; the product after the heating reaction is dried at a temperature of 60-120°C and a drying time of 12-24h.

4. The method for preparing a modified diaphragm for a lithium-sulfur battery based on amide group-modified PIM-1 according to claim 1, characterized in that: In the step (2), the mass concentration of PIM-1 in the reaction solution is 15 to 40 mg / mL.

5. The method for preparing a modified diaphragm for a lithium-sulfur battery based on amide group-modified PIM-1 according to claim 5, characterized in that: PIM-1 and the deprotonated solid matter of the strong base are stirred and reacted for 12 to 24 hours. After the reaction, the product is dried at a temperature of 60 to 120° C. for 12 to 24 hours.

6. The method for preparing a modified diaphragm for a lithium-sulfur battery based on amide group-modified PIM-1 according to claim 1, characterized in that: The base film used in the step (4) includes any one of PP, PE or PP / PE / PP composite membrane.

7. The method for preparing a modified diaphragm for a lithium-sulfur battery based on amide group-modified PIM-1 according to claim 7, characterized in that: The spraying thickness on the composite diaphragm is 300nm-800nm; the drying temperature of the modified diaphragm is 40-120°C, and the drying time is 12-24h.

8. A modified separator for lithium-sulfur batteries based on amide group-modified PIM-1, prepared by the method according to any one of claims 1 to 8.

9. Use of the diaphragm according to claim 9 as a diaphragm for lithium-sulfur batteries.

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