Methyl beta cyanoethyl siloxane-polyethylene glycol copolymers, methods of making and use

Abstract

This invention discloses a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer, its preparation method, and its applications, relating to the fields of polymer materials and electrochemical technology. The preparation method of this copolymer is as follows: tetramethylethylenediamine is reacted with cuprous oxide under an inert atmosphere to obtain a catalyst; methyldichlorosilane and acrylonitrile are dissolved in solvent A, and the catalyst is added to carry out the reaction; polyethylene glycol is added to the reaction solution, and the reaction continues under concentrated sulfuric acid catalysis to obtain a crude product; solvent B is added to the crude product, followed by washing and vacuum drying to obtain the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer. This invention effectively improves the interfacial stability of the electrolyte and the efficiency of interfacial ion transport, thereby enhancing the cycle and rate performance of lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the fields of polymer materials and electrochemical technology, and in particular to methyl β-cyanoethyl siloxane-polyethylene glycol copolymer, its preparation method and application. Background Technology

[0002] The development of polymer solid electrolytes has long been constrained by the core contradiction of low room-temperature conductivity and the incompatibility between mechanical properties and ionic conductivity in traditional polyethylene oxide (PEO) systems. To overcome this bottleneck, research has shifted towards exploring novel polymer backbones that combine high ionic conductivity with mechanical stability. Among them, intrinsically flexible polysiloxanes and highly polar cyano-containing polymers have shown unique advantages, but when used alone, they still suffer from drawbacks such as weak lithium salt dissociation ability or poor chain segment mobility.

[0003] Therefore, the purpose of this invention is to construct a novel hybrid polymer electrolyte system that achieves comprehensive performance improvement through multifunctional group synergy and microstructure regulation. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, this invention proposes a methyl β-cyanoethyl siloxane-polyethylene glycol copolymer, its preparation method and application, which effectively improves the interfacial stability of the electrolyte and the efficiency of interfacial ion transport, thereby improving the cycle and rate performance of lithium-ion batteries.

[0005] The present invention proposes a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer, the structural formula of which is as follows: Where x ranges from 4 to 91; y ranges from 1 to 8; and n ranges from 20 to 200.

[0006] This invention proposes a method for preparing a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer, wherein the copolymer is as described above, and the method steps are as follows: S1: A catalyst was prepared by reacting tetramethylethylenediamine with cuprous oxide under an inert atmosphere; S2: Methyldichlorosilane and acrylonitrile are dissolved in solvent A, and the catalyst of S1 is added to carry out the reaction; S3: Polyethylene glycol is added to the solution after the S2 reaction, and the reaction continues under the catalysis of concentrated sulfuric acid to obtain the crude product; S4: Solvent B is added to the crude product, followed by washing and vacuum drying to obtain methyl β-cyanoethyl siloxane-polyethylene glycol copolymer.

[0007] Preferably, the molar ratio of tetramethylethylenediamine to cuprous oxide in S1 is 1:0.1-0.8; And / or, the reaction conditions are a temperature of 30-70℃ and a time of 1-6h.

[0008] Preferably, the molar ratio of acrylonitrile to methyldichlorosilane in S2 is 1:1.1-1.3; And / or, the catalyst is the product prepared by S1, and the amount added is 0.1-0.4 times the mass of methyldichlorosilane; And / or, solvent A is one or more of xylene, diethylene glycol dimethyl ether, and toluene; And / or, the reaction conditions are a temperature of 60-80℃ and a time of 2-12h.

[0009] Preferably, the amount of polyethylene glycol added in S3 is 0.02-0.4 times the amount of methyldichlorosilane added in S2; And / or, the number average molecular weight of polyethylene glycol is 400-4000; And / or, the concentration of concentrated sulfuric acid is 60 wt%, and the amount added is 0.05-0.25 times the mass of polyethylene glycol; And / or, the reaction conditions are a temperature of 60-80℃ and a time of 2-12h.

[0010] Preferably, solvent B in S4 is one or more of dichloromethane, tetrahydrofuran, and dimethyl sulfoxide.

[0011] The present invention proposes a solid electrolyte comprising the above-mentioned methyl β-cyanoethyl siloxane-polyethylene glycol copolymer.

[0012] The present invention proposes a method for preparing a solid electrolyte, the solid electrolyte being as described above, and the method steps are as follows: dissolving a methyl β-cyanoethyl siloxane-polyethylene glycol copolymer and a lithium salt in solvent C, and drying to obtain the solid electrolyte.

[0013] Preferably, the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, and lithium trifluoromethanesulfonate.

[0014] The present invention proposes the application of the solid electrolyte as described above in lithium-ion batteries.

[0015] Beneficial technical effects of the present invention: (1) This invention constructs a network structure combining a silicon-oxygen framework and polyethylene glycol segments, enabling the rigid framework and flexible segments to work together, ensuring structural stability while providing necessary space for segment movement. Simultaneously, the introduction of the polar cyano group regulates the internal environment of the system, promoting lithium salt dispersion and improving ion migration efficiency. Experiments show that after introducing the cyano group, the room temperature ionic conductivity increases from 9.04 × 10⁻⁶ to 9.04 × 10⁻⁶. -6 S·cm -1 Increased to 4.94×10 -5 S·cm -1Furthermore, this structure significantly improves the high-voltage stability of the electrolyte, with an electrochemical window of 4.4 V, higher than the 3.9 V of the polyethylene oxide electrolyte.

[0016] (2) This invention achieves automatic separation of cross-linked networks and low-molecular-weight byproducts during the material formation process through a reaction-induced phase separation mechanism, so that the structure construction and purification are completed simultaneously, thereby improving the uniformity and stability of the material, reducing the interference of impurities on ion transport, and improving the overall performance of polymer electrolytes.

[0017] (3) The present invention uses acid-catalyzed rapid cross-linking to effectively fix the transient structure formed during the reaction process, while making the functional groups stably embedded in the network, reducing migration and loss, thereby improving the thermal stability, electrochemical stability and long-term performance of the material. Attached Figure Description

[0018] Figure 1 The infrared spectrum of the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer prepared in Example 1 of this invention is shown below. Figure 2 The NMR spectrum of the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer prepared in Example 1 of this invention is shown below. Figure 3 The thermogravimetric curve of the solid electrolyte prepared in Example 1 of this invention is shown. Figure 4 This is an electrochemical window test diagram of the solid electrolyte prepared in Example 1 of the present invention; Figure 5 The images are of the electrolyte membrane proposed in this invention; (a) is Example 2, (b) is Example 3, and (c) is Example 1. Detailed Implementation

[0019] The present invention will be further explained below with reference to specific embodiments.

[0020] Example 1 A catalyst was prepared by reacting 4g of tetramethylethylenediamine and 1g of cuprous oxide under an inert atmosphere at 55℃ for 1 hour. 6g of acrylonitrile and 15.5g of methyldichlorosilane were dissolved in 40g of toluene, and the mixture was added to the prepared catalyst and reacted at 70℃ for 4 hours. Then, 15g of polyethylene glycol with a number average molecular weight of 2000 and 3.3g of 60wt% concentrated sulfuric acid were added, and the mixture was reacted at 70℃ for 4 hours. The final product was post-treated to obtain a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer.

[0021] Take 2g of the above-mentioned methyl β-cyanoethyl siloxane-polyethylene glycol copolymer and 1g of lithium bis(trifluoromethanesulfonyl)imide and dissolve them in tetrahydrofuran. Then place them in a vacuum drying oven at 90°C to dry and form a film. The resulting product is a solid electrolyte membrane.

[0022] The infrared spectrum of the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer prepared in this embodiment is shown below. Figure 1 The image shows 2950-2850cm. -1 The absorption peak at 2165 cm⁻¹ corresponds to the C–H stretching vibrations of –CH₂– and Si–CH₃ in the polyethylene glycol chain. -1 The absorption peak at 1250 cm⁻¹ is attributed to the presence of the cyano group, indicating that the cyano group of acrylonitrile has been successfully incorporated into the silicon-oxygen chain. This is also observed in the infrared spectrum. -1 The absorption peak for Si–CH3 is located at 1100-1000 cm⁻¹. -1 The strong absorption peak at 1020 cm⁻¹ is attributed to the superposition vibrations of Si–O–Si and C–O–C, indicating that the siloxane and polyether structure form a stable hybrid network. -1 The absorption peak at 900 cm⁻¹ is the C–O–C absorption peak in the polyethylene glycol chain segment. -1 The peak at this point represents the absorption peak of Si–O in the polyethylene glycol chain.

[0023] The 1H NMR spectrum of the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer prepared in this embodiment is shown below. Figure 2 In the figure, the peak of the methylene group in the polyethylene glycol backbone is at 3.64 ppm (corresponding to a), the peak of the methylene group attached to the cyanoethyl side chain is at 2.36 ppm (corresponding to b), the peak of the methylene group directly attached to the silicon atom in the cyanoethyl side chain is at 2.39 ppm (corresponding to c), and the peaks of the methyl groups directly attached to the silicon atom are at 0.07 ppm and 0.23 ppm (corresponding to d). The incorporation of existing reactant groups and the formation of new groups indicate the successful synthesis of the product, methylβ-cyanoethylsiloxane-polyethylene glycol copolymer.

[0024] The thermogravimetric analysis curve of the solid electrolyte membrane prepared in this embodiment is shown in the figure. Figure 3 The initial decomposition temperature of the thin film is 325℃, and the maximum weight loss temperature is 413℃. Its thermal stability is significantly better than that of traditional liquid electrolytes and conventional polymer electrolytes. Therefore, this material can effectively prevent thermal runaway of batteries at high temperatures, thereby enhancing the safety of high-energy-density solid-state batteries.

[0025] The linear sweep voltammetry (LSV) test of the solid electrolyte membrane prepared in this embodiment is shown in [reference needed]. Figure 4 The electrochemical window of the electrolyte membrane is 4.4V, which is higher than that of the polyethylene oxide electrolyte (PEO) at 3.9V, indicating that the structure significantly improves the high-voltage stability of the electrolyte.

[0026] Example 2 A catalyst was prepared by reacting 4g of tetramethylethylenediamine and 1g of cuprous oxide under an inert atmosphere at 55℃ for 1 hour. 6g of acrylonitrile and 15.5g of methyldichlorosilane were dissolved in 40g of toluene. The mixture was added to the prepared catalyst and reacted at 70℃ for 4 hours to obtain an intermediate. 15g of polyethylene glycol with a number average molecular weight of 400 was added to the intermediate, along with 3.3g of 60wt% concentrated sulfuric acid. The mixture was reacted at 70℃ for 4 hours. The final product was then post-treated to obtain a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer.

[0027] Take 2g of the above-mentioned methyl β-cyanoethyl siloxane-polyethylene glycol copolymer and 1g of lithium bis(trifluoromethanesulfonyl)imide and dissolve them in tetrahydrofuran. Then dry them in a vacuum drying oven at 90°C to form a film. The resulting product is the solid electrolyte.

[0028] Example 3 A catalyst was prepared by reacting 4g of tetramethylethylenediamine and 1g of cuprous oxide under an inert atmosphere at 55℃ for 1 hour. 6g of acrylonitrile and 15.5g of methyldichlorosilane were dissolved in 40g of toluene. The mixture was added to the prepared catalyst and reacted at 70℃ for 4 hours to obtain an intermediate. 15g of polyethylene glycol with a molecular weight of 4000 was added to the intermediate, along with 3.3g of 60wt% concentrated sulfuric acid as a catalyst. The mixture was reacted at 70℃ for 4 hours. The final product was post-treated to obtain a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer. 2g of the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer and 1g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in tetrahydrofuran and then dried in a vacuum oven at 90℃ to form a film. The resulting product was the solid electrolyte.

[0029] Example 4 A catalyst was prepared by reacting 4g of tetramethylethylenediamine and 1g of cuprous oxide under an inert atmosphere at 55℃ for 1 hour. 6g of acrylonitrile and 15.5g of methyldichlorosilane were dissolved in 40g of toluene. The mixture was added to the prepared catalyst and reacted at 70℃ for 4 hours to obtain an intermediate. 15g of polyethylene glycol with a number average molecular weight of 2000 was added to the intermediate, along with 3.3g of 60wt% concentrated sulfuric acid as a catalyst. The mixture was reacted at 70℃ for 4 hours. The final product was then post-treated to obtain a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer.

[0030] Take 2g of methyl β-cyanoethylsiloxane-polyethylene glycol copolymer and 0.4g of lithium bis(trifluoromethanesulfonyl)imide and dissolve them in tetrahydrofuran. Then dry them in a vacuum drying oven at 90℃ to form a film. The resulting product is a solid electrolyte membrane.

[0031] Example 5 A catalyst was prepared by reacting 4g of tetramethylethylenediamine and 1g of cuprous oxide under an inert atmosphere at 55℃ for 1 hour. 6g of acrylonitrile and 15.5g of methyldichlorosilane were dissolved in 40g of toluene. The mixture was added to the prepared catalyst and reacted at 70℃ for 4 hours to obtain an intermediate. 15g of polyethylene glycol with a number average molecular weight of 4000 was added to the intermediate, along with 3.3g of 60wt% concentrated sulfuric acid as a catalyst. The mixture was reacted at 70℃ for 4 hours. The final product was then post-treated to obtain a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer.

[0032] Take 2g of methyl β-cyanoethylsiloxane-polyethylene glycol copolymer and 0.6g of lithium bis(trifluoromethanesulfonyl)imide and dissolve them in tetrahydrofuran. Then dry them in a vacuum drying oven at 90℃ to form a film. The resulting product is a solid electrolyte membrane.

[0033] As shown in Examples 1-3, the mechanical properties of polyethylene glycol with a number-average molecular weight of 4000 and 400 are insufficient for film formation, while polyethylene glycol with a number-average molecular weight of 2000 can form a pale yellow, transparent electrolyte film. Figure 5 As shown, (a) and (b) are electrolyte membranes with polyethylene glycol number-average molecular weights of 400 and 4000, respectively; (c) is an electrolyte membrane made with polyethylene glycol number-average molecular weight of 2000. From Examples 1, 4, and 5, it can be seen that when the mass ratio of the product to lithium salt is 1:0.5, the ionic conductivity is 4.26 × 10⁻⁶. -5 S·cm -1 When the mass ratio of the product to the lithium salt is 1:0.2, the resulting ionic conductivity is 6.95 × 10⁻⁶. - 6 S·cm -1 The ionic conductivity of the product prepared when the mass ratio of the product to lithium salt was 1:0.3 was 1.02 × 10⁻⁶. -5 S·cm -1 .

[0034] The method for detecting ionic conductivity is as follows: refer to ASTM D257.

[0035] Linear voltammetric scanning method: Refer to T / SPSTS 020-2021.

[0036] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.

Claims

1. A methyl β-cyanoethyl siloxane-polyethylene glycol copolymer, characterized in that, The structure is as follows: Where x ranges from 4 to 91; y ranges from 1 to 8; and n ranges from 20 to 200.

2. A method for preparing a methyl β-cyanoethylsiloxane-polyethylene glycol copolymer, wherein the copolymer is as described in claim 1, characterized in that, The steps are as follows: S1: A catalyst was prepared by reacting tetramethylethylenediamine with cuprous oxide under an inert atmosphere; S2: Methyldichlorosilane and acrylonitrile are dissolved in solvent A, and the catalyst of S1 is added to carry out the reaction; S3: Polyethylene glycol is added to the solution after the S2 reaction, and the reaction continues under the catalysis of concentrated sulfuric acid to obtain the crude product; S4: Solvent B is added to the crude product, followed by washing and vacuum drying to obtain methyl β-cyanoethyl siloxane-polyethylene glycol copolymer.

3. The method for preparing the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer according to claim 2, characterized in that, The molar ratio of tetramethylethylenediamine to cuprous oxide in S1 is 1:0.1-0.8; And / or, the reaction conditions are a temperature of 30-70℃ and a time of 1-6h.

4. The method for preparing the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer according to claim 2, characterized in that, The molar ratio of acrylonitrile to methyldichlorosilane in S2 is 1:1.1-1.3; And / or, the catalyst is the product prepared by S1, and the amount added is 0.1-0.4 times the mass of methyldichlorosilane; And / or, solvent A is one or more of xylene, diethylene glycol dimethyl ether, and toluene; And / or, the reaction conditions are a temperature of 60-80℃ and a time of 2-12h.

5. The method for preparing the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer according to claim 2, characterized in that, The amount of polyethylene glycol added in S3 is 0.02-0.4 times the amount of methyldichlorosilane added in S2; And / or, the number average molecular weight of polyethylene glycol is 400-4000; And / or, the concentration of concentrated sulfuric acid is 60 wt%, and the amount added is 0.05-0.25 times the mass of polyethylene glycol; And / or, the reaction conditions are a temperature of 60-80℃ and a time of 2-12h.

6. The method for preparing the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer according to claim 2, characterized in that, In S4, solvent B is one or more of dichloromethane, tetrahydrofuran, and dimethyl sulfoxide.

7. A solid electrolyte, characterized in that, It comprises the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer of claim 1.

8. A method for preparing a solid electrolyte, wherein the solid electrolyte is as described in claim 7, characterized in that, The method steps are as follows: Dissolve the methyl β-cyanoethylsiloxane-polyethylene glycol copolymer and lithium salt in solvent C, and then dry to obtain the solid electrolyte.

9. The method for preparing a solid electrolyte according to claim 8, characterized in that, The lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, and lithium trifluoromethanesulfonate.

10. The application of the solid electrolyte as described in claim 7 in lithium-ion batteries.

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