A preparation process of a modified separator for lithium-sulfur battery based on amide group modified PIM-1

Abstract

The application belongs to the field of chemical power sources and specifically relates to a preparation process of a modified separator for lithium-sulfur batteries based on amide group modified PIM-1. The modified separator aims to solve the problems of poor cycle stability and low sulfur utilization caused by the polysulfide shuttle effect in lithium-sulfur batteries. By introducing amide groups, the prepared modified polymer material has a nano-scale pore size confining layer, which can effectively inhibit the migration of polysulfides and significantly improve the coulombic efficiency and cycle stability of lithium-sulfur batteries. Compared with existing commercial polyolefin separators, the application has obvious advantages in electrochemical performance. In addition, the method is simple, convenient to operate and low in cost, suitable for large-scale production, has good durability and environmental friendliness, and promotes the commercial application of lithium-sulfur batteries in the fields of electric vehicles and renewable energy storage.

Description

TECHNICAL FIELD

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

[0002] As a cutting-edge energy storage solution, lithium-sulfur batteries have attracted widespread attention due to their high energy density and low cost, and are considered as a potential alternative 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 caused by the shuttle effect. The shuttle effect is mainly caused by the dissolution and diffusion of polysulfides during charging and discharging, and the loss of active materials caused by the shuttle effect will gradually reduce the performance of the battery. The commercial polyolefin separator in the lithium-sulfur battery performs poorly in preventing the shuttle effect of polysulfides, so it is urgent 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 control the pore size, surface modification and charge repulsion to inhibit the shuttle of polysulfides. However, these traditional methods often fail to comprehensively solve the problem of the shuttle effect, thus failing to significantly improve the cycle stability and sulfur utilization of the battery. Based on this, the current technical demand is strongly directed towards the development of new separator materials, such as modified separators based on inherent microporous polymer PIM-1, which are expected to fundamentally improve the shuttle effect of polysulfides and significantly improve the commercial application potential of lithium-sulfur batteries.

[0004] In order to promote the development of lithium-sulfur battery technology, the present application proposes a new type of modified separator for lithium-sulfur batteries based on amide group modified PIM-1. This technology effectively inhibits the transmembrane transport of polysulfides, 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 development trend of lithium-sulfur battery technology, and can effectively promote the commercialization process of lithium-sulfur battery energy storage. SUMMARY

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

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a preparation method of a modified separator for lithium-sulfur batteries 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'-spirobisoindane (TTSBI), 2,3,5,6-tetrafluoroterephthalonitrile (DCTB) and anhydrous potassium carbonate (K2CO3) and add them to a solvent, heat and react to obtain PIM-1;

[0009] The molar ratio of TTSBI, DCTB and K2CO3 is 1 mole, 0.8-1.2 moles and 2.04-8 moles;

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

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

[0012] The molar ratio of PIM-1 and 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 and lithium diisopropylamide;

[0014] The reaction solvent is any one of isobutyl alcohol, n-butyl alcohol, tert-butyl alcohol and isopropyl alcohol;

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

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

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

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

[0019] Further, in step (1), the reaction temperature of TTSBI, DCTB and K2CO3 in the reaction solution is 50-65°C, and the stirring reaction time is 23-70 h; the product is dried after heating reaction, 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] Further, the PIM-1 is stirred with the strong base deprotonated solid for 12-24 h; after the reaction is completed, the product is dried by drying, the drying temperature is 60-120℃, 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] Further, the spraying thickness on the composite diaphragm is 300-800 nm.

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

[0025] In a second aspect, the application provides a modified diaphragm for lithium-sulfur batteries based on amide group modified PIM-1, which is prepared by the method of the first aspect.

[0026] In a third aspect, the application provides an application of the modified diaphragm for lithium-sulfur batteries of the second aspect, which is used as a diaphragm for lithium-sulfur batteries.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] Firstly, the modified polymer material prepared by the application has a nano-scale pore size confining layer for the diaphragm of lithium-sulfur batteries, which can inhibit the migration of polysulfides through pore size screening and chemical action, improve the coulomb efficiency and cycle stability of lithium-sulfur batteries, and exhibit more excellent electrochemical performance. Secondly, the polymer material containing amide groups is used to modify the commercial polyolefin diaphragm, which is beneficial to reduce the interface impedance between the confining layer and the base film, and the modification is durable, effective, simple to operate, environmentally friendly, and the polymer contains rich polar groups, which is beneficial to strengthen the inhibition of the shuttle effect of the modified diaphragm. In addition, the method of the application is simple, simple to operate, simple to handle, simple in equipment requirement, low in raw material price, and suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

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

[0030] (a) examples; (b) comparative examples;

[0031] Figure 2 Long cycle performance of the lithium-sulfur batteries prepared from the examples and comparative examples under 1C current density. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

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

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] Example

[0036] (1) Take 4.08g of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI), 2.4g of 2,3,5,6-tetrafluoroterephthalonitrile (DCTB) and 3.38g of anhydrous potassium carbonate (K2CO3) and add them to 120ml of N,N-dimethylformamide (DMF) solution. Heat and stir at 50℃ for 23h to carry out the reaction. After the reaction is completed, take the precipitate, wash it, and put it in a vacuum drying oven to dry at 60℃ for 12h to obtain PIM-1 powder;

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

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

[0039] (4) The precursor solution was sprayed onto the surface of a PP base film using a spraying technique, and then dried in a vacuum drying oven at 60°C for 24 hours to form a composite modified layer, thus obtaining a modified separator. The spraying thickness was 400 nm. SEM images of the obtained modified separator surface are attached. Figure 1 The assembled lithium-sulfur coin cell exhibits an initial discharge capacity of 1301.7 mAh / g at a 1C current density, can stably cycle 200 times, and has an average coulombic efficiency greater than 99%. (See attached image.) Figure 2 As shown.

[0040] Comparative Example

[0041] The PP separator was not treated and used as a control test. The SEM image of the PP separator surface is shown in Figure 1. Figure 1 The lithium-sulfur button cell was assembled. The initial discharge capacity was 1203.9 mAh / g at a current density of 1C, and it could be stably cycled for 200 cycles with an average coulombic efficiency of more than 99%, as shown in Figure 2. Figure 2

[0042] The PIM-1-based modified separator of the lithium-sulfur battery in the embodiment exhibits significant advantages in effectively addressing the common problem of polysulfide shuttling in lithium-sulfur batteries. By combining the physical barrier of micropores 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 a new approach 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 simplicity and economy of the invention mean that it is not only suitable for large-scale production, but also can reduce the manufacturing cost of lithium-sulfur batteries, thereby accelerating their market promotion. This low-cost, high-efficiency modified separator is expected to play an important role in the future lithium-sulfur battery industry, promoting wider application, especially in the fields of electric vehicles and renewable energy storage.​

Claims

1. A method for preparing a modified separator for lithium-sulfur batteries based on amide-modified PIM-1, characterized in that, Includes the following steps: (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) were added to a solvent and heated to react, to obtain PIM-1; The molar ratios of TTSBI, DCTB, and K2CO3 are 1 mole, 0.8-1.2 moles, and 2.04-8 moles. The solvent is one or a mixture of N,N-dimethylformamide, tetrahydrofuran, toluene, and N,N-dimethylacetamide; (2) PIM-1 and the deprotonated solid of a strong base were added to the reaction solvent and reacted at room temperature to obtain the amide-modified product of PIM-1; The molar ratio of PIM-1 to the deprotonated solid of a strong base is 1:0.5 to 1:3; The strong base deprotonated solid is any one of potassium tert-butoxide, potassium hydroxide, and lithium diisopropylamino. The reaction solvent is any one of isobutanol, n-butanol, tert-butanol, and isopropanol; (3) Dissolve the PIM-1 amide-modified product in a precursor solvent. The concentration of the PIM-1 amide-modified product is 5~50 mg / mL to prepare a precursor solution. The precursor solvent is N-Methylpyrrolidone Any one of chloroform, tetrahydrofuran, and dimethyl sulfoxide; (4) Take the precursor solution, spray it onto the surface of the base film to form a composite modified layer, and obtain the modified diaphragm after drying.

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

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

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

5. The method for preparing a modified separator for lithium-sulfur batteries based on amide-modified PIM-1 according to claim 4, characterized in that, PIM-1 was reacted with a strong base deprotonated solid by stirring for 12-24 hours. After the reaction was completed, the product was dried at 60-120°C for 12-24 hours.

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

7. The method for preparing a modified separator for lithium-sulfur batteries based on amide-modified PIM-1 according to claim 6, characterized in that, The coating thickness on the composite diaphragm is 300nm~800nm; the drying temperature of the modified diaphragm is 40~120℃, and the drying time is 12~24h.

8. A modified separator for lithium-sulfur batteries based on amide-modified PIM-1, prepared by the method described in any one of claims 1 to 7.

9. The application of the separator according to claim 8 as a separator for lithium-sulfur batteries.

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