An ionic gel film material based on cellulose and polyaspartamide-derived polymers and a method for preparing the same

Abstract

This invention relates to an ionogel membrane material based on cellulose and polyasparagine-derived polymers, and its preparation method, belonging to the field of ionogel technology. The invention utilizes two environmentally friendly polymer materials as raw materials: cellulose and polyasparagine-derived polymers are combined to prepare a dual-network ionogel membrane electrolyte. After acidification and dissolution with an ionic liquid, cellulose is then fused with the polyasparagine derivative, forming a first-layer network structure through physical cross-linking and entanglement. Simultaneously, glutaraldehyde, a cross-linking agent, is introduced to initiate secondary chemical cross-linking of the hydroxyl groups on the polymer chains, thereby forming a renewable, wide potential window, high ionic conductivity, and highly flexible dual-network ionogel membrane as a solid electrolyte material for application in the design of flexible supercapacitors.

Description

Technical Field

[0001] This invention belongs to the field of ion gel technology, and relates to a method for preparing ion gel membranes based on cellulose and polyasparagine-derived polymers with high ionic conductivity and strong flexibility, as well as their applications. Background Technology

[0002] In recent years, energy shortages and environmental pollution have become focal points of global concern. To address the challenges posed by these issues and meet the urgent needs of modern society, providing eco-friendly, safe, and high-performance energy storage devices has become a key focus for scientists and engineers. With the continuous development and advancement of energy storage devices, flexible and foldable wearable devices (such as smart clothing, watches, and implantable medical devices) have received extensive research attention. Among various energy storage devices (lithium batteries, fuel cells, and supercapacitors), supercapacitors have garnered significant attention due to their unique performance and advantages, including short charging times, long cycle life, high power density, and safety. Flexible supercapacitors, in addition to possessing the advantages of traditional capacitors, also exhibit a series of characteristics such as small size, light weight, wearability, and flexibility. Therefore, converting renewable energy into electrode and electrolyte materials, and developing new, sustainable, environmentally friendly, safe, and high-electrochemical-performance flexible supercapacitors, holds immense application potential.

[0003] The construction of flexible supercapacitors requires not only high-performance electrode materials, but also crucial electrolyte development. An electrolyte is both an electronic insulator and an ionic conductor; an ideal electrolyte should possess characteristics such as environmental friendliness, low cost, wide potential window, high ionic conductivity, strong chemical and electrochemical stability, good compatibility with electrolyte materials, low volatility, and low flammability. Traditional liquid electrolytes are typically formed by dissolving conductive salts in small-molecule liquid solvents and are classified into aqueous electrolytes, organic electrolytes, and ionic liquid electrolytes. However, due to their inability to withstand excessive external forces leading to device deformation and damage, and the risk of leakage of toxic and volatile liquid electrolytes, they struggle to meet the design requirements of high stability and high safety for flexible devices. In this context, solid-state electrolytes have emerged, offering promise for the application of flexible supercapacitors in wearable devices due to their safety and functionality.

[0004] Ionic gels, as a novel type of gel electrolyte, disperse ionic liquids within a three-dimensional polymer or inorganic network. Ionic liquids, acting as ion carriers and solvents, possess advantages such as high ionic conductivity, a wide electrochemical window, and good chemical and thermal stability. Simultaneously, the solid network of the gel acts as a structural matrix, significantly enhancing mechanical strength. Due to the non-volatile nature of ionic liquids, ionic gels exhibit better stability compared to hydrogels and organic gels containing volatile solvents. To fully realize the potential of ionic liquids as electrolytes, large quantities are often dispersed in three-dimensional interconnected solids. However, the presence of a large amount of ionic liquid within the closed gel network can adversely affect its mechanical properties, leading to fragility. Therefore, achieving a balance between the ionic conductivity and mechanical properties of ionic gels is a crucial scientific problem that urgently needs to be solved. Therefore, researchers have explored various approaches to improve the tensile strength, compressive strength, and toughness of hydrogel materials. These include preparing hydrogels with excellent mechanical properties such as slip ring hydrogels, nanocomposite hydrogels, triblock copolymer hydrogels, hydrophobically modified hydrogels, polyethylene glycol hydrogels, polymer microsphere composite hydrogels, and dual-network hydrogels. Dual-network gels are a special type of interpenetrating network gel, comprising a highly cross-linked polyelectrolyte network and a low-crosslinked or non-crosslinked neutral network structure. The former provides a rigid scaffold for the dual-network hydrogel, maintaining its three-dimensional shape; the latter fills within the rigid network, absorbing external stress to improve mechanical properties. In summary, developing a biomass-based dual-network ionogel membrane electrolyte for flexible supercapacitors is of significant scientific and practical value, aiming to improve the potential window, ionic conductivity, and mechanical strength of the gel polymer electrolyte, as well as reduce the environmental pollution of the framework material. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings and deficiencies of traditional water-based and structurally simple hydrogel electrolytes, such as low mechanical strength, narrow potential window, and low ionic conductivity, by providing a method for preparing ionogel membranes based on cellulose and polyasparagine-derived polymers, thereby solving the problems existing in the background art.

[0006] The present invention discloses a method for preparing an ionogel membrane based on cellulose and polyasparagine-derived polymers, the steps of which are as follows:

[0007] (1) Preparation of ionic liquid [DMIM][(MeO)(H)PO2]: Weigh 1-methylimidazolium and dimethyl phosphite, and heat at 100-170 °C o C. Stir magnetically for 10-15 h, wash the synthesized product with ethyl acetate to remove unreacted mixture, and then vacuum dry at room temperature for 4-8 h to obtain ionic liquid [DMIM][(MeO)(H)PO2];

[0008] In step (1), the ratio of 1-methylimidazolium to dimethyl phosphate is 1:1.0~2.0g, and the volume ratio of ethyl acetate to [DMIM][(MeO)(H)PO2] is 5~10:1.

[0009] The reaction temperature in step (1) is 100–170 °C. o C, reaction time 10-15h, vacuum drying time 4-8h.

[0010] (2) Weigh out cellulose and add it to [DMIM][(MeO)(H)PO2], and heat at 70-130 °C. o The cellulose was dissolved under magnetic stirring for 1–5 hours. During the dissolution process, the chemical structure of cellulose reacted with phosphite ions to form phosphorylated cellulose. The hydroxyl group at the C-6 position of cellulose was phosphorylated, and methanol was removed through a condensation reaction.

[0011] In step (2), the ratio of cellulose to [DMIM][(MeO)(H)PO2] is 0.5~1.0g:10ml.

[0012] In step (2), the reaction temperature is 70-130°C and the reaction time is 1-5 hours.

[0013] (3) Preparation of PolyAspAm (EA / API) polymer: Weigh polysuccinimide into a 250ml round-bottom flask, dissolve it in N,N-dimethylformamide, add 1-(3-aminopropyl)imidazolium, heat to 40-70℃, and stir for 30-60h; after the reaction is completed, add ethanolamine, cool to room temperature and stir for 20-40h; the obtained reactants can be put into a dialysis bag, dialyzed with deionized water for 1-3 days, and then freeze-dried under vacuum to obtain the final product PolyAspAm (EA / API);

[0014] In step (3), the ratio of N,N-dimethylformamide solvent to the molar number of succinimide units in polysuccinimide is 1.5–4.5 L: 1 mol.

[0015] In step (3), the number of 1-(3-aminopropyl)imidazolium moles is 0.2 to 2 times the number of succinimide moles, and the number of ethanolamine moles is 0.25 to 2 times the number of succinimide moles.

[0016] (4) Dissolve the PolyAspAm (EA / API) polymer obtained in step (3) in an ionic liquid and add it to the phosphorylated cellulose solution obtained in step (2) to prepare a mixture;

[0017] In step (4), the ratio of PolyAspAm (EA / API) polymer to ionic liquid is 0.5~1.0g: 5ml.

[0018] (5) Glutaraldehyde is added as a crosslinking agent to the mixture obtained in step (3). The mixture is ultrasonicated to become a transparent liquid and then subjected to nitrogen protection for 60–80 minutes. o Stirring at C for 5–8 hours, the resulting viscous liquid is dripped into a polytetrafluoroethylene mold to form a liquid film;

[0019] In step (5), the glutaraldehyde content is 5% to 20% of the total amount of cellulose and PolyAspAm (EA / API) polymer.

[0020] (6) After the liquid film obtained in step (5) is left to stand in air at room temperature for 1-3 days, it is demolded to obtain a double network p-Cel ionogel membrane based on cellulose and polyasparagine-derived polymer.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] A dual-network ionogel membrane electrolyte material was prepared by combining two environmentally friendly polymer materials. The polymer materials used are cellulose and polyasparagine polymers, which have natural advantages in terms of environmental friendliness and biodegradability. By introducing a dual cross-linking mechanism and ionic liquids, the mechanical strength and ionic conductivity of the ionogel electrolyte can be significantly improved, thereby enhancing the electrochemical properties and application prospects of all-solid-state flexible capacitors. Attached Figure Description

[0023] Figure 1 : 1H NMR spectrum of PolyAspAm (API / EA) prepared in Example 2 of this invention.

[0024] Following a series of ammonolysis reactions, the methylene proton peaks G and H in the PolyAspAm (API / EA) spectrum were identified as hydroxyethyl groups on the ethanolamine functional group. Peaks A, B, and C represented the three methylene protons in the API component. Peaks D, E, and F represented the three heteroaromatic proton monomers of the imidazole ring. The composition of different groups in PolyAspAm (API / EA) was determined by the integral ratio between G (δ=3.13-3.31) and A (δ=2.90-3.13). Table 1 shows that 63 mol% of the 1-(3-aminopropyl)imidazolium group was conjugated into the polymer backbone, while 37 mol% of the ethanolamine group was conjugated.

[0025] Table 1. Number of each group in polyasparagine derivative copolymer PolyAspAm (API / EA)

[0026] PolyAspAm <![CDATA[Content(mol%) a ]]> 1-(3-aminopropyl)imidazolium 63 ethanolamine 37

[0027] Figure 2 Infrared spectrum of PolyAspAm (API / EA) prepared in Example 2 of this invention.

[0028] In the spectrum of the polyaspartic imide derivative PolyAspAm (API / EA), 3277.9 cm⁻¹ -1 The broad bands to the left and right represent the -NH groups in the polymer. The characteristic peak of PSI disappears, replaced by a newly appearing amide band (1642.9 cm⁻¹) in the PolyAspAm (API / EA) polymer. -1 and 1509.4cm -1 In addition, 1263 cm -1 The absorption band is the CO group of the hydroxyethyl side chain, 1064 cm⁻¹ -1 The peak is the =CN stretching peak in the imidazole functional group.

[0029] Figure 3 Example 3 of this invention: A diagram showing the toughness of the ion gel prepared in this invention.

[0030] Figure 4 SEM image of the ion gel prepared in Example 3 of this invention. Detailed Implementation

[0031] To better understand the present invention, the following description is based on embodiments, but the implementation of the present invention is not limited thereto.

[0032] Example 1

[0033] The preparation method of the ionic liquid [DMIM][(MeO)(H)PO2] is as follows:

[0034] Weigh 20g of 1-methylimidazole and 25g of dimethyl phosphite, and salicylate at 150°C. o The product was magnetically stirred for 12 hours, washed with ethyl acetate to remove unreacted mixture, and then vacuum dried at room temperature for 6 hours to obtain the ionic liquid [DMIM][(MeO)(H)PO2].

[0035] Example 2

[0036] The preparation method of PolyAspAm (EA / API) polymer is as follows:

[0037] Weigh 5g of polysuccinimide and place it in a 250ml round-bottom flask. Dissolve it in 50ml of N,N-dimethylformamide and add 4.5g of 1-(3-aminopropyl)imidazole. Heat to 40-70℃ and stir for 30-60h. After the reaction is complete, add 3g of ethanolamine and cool to room temperature and stir for 20-40h. The resulting product can be placed in a dialysis bag, dialyzed with deionized water for 1-3 days, and then freeze-dried under vacuum to obtain the final product PolyAspAm (EA / API).

[0038] Example 3

[0039] Add 1g of cellulose to 10ml of [DMIM][(MeO)(H)PO2] and heat at 120°C. o A phosphorylated cellulose solution was obtained by dissolving the polymer under stirring at C for 2 hours. 1 g of PolyAspAm (EA / API) polymer was dissolved in 5 ml of ionic liquid and then added to the phosphorylated cellulose solution to prepare a mixture. 0.2 g of glutaraldehyde was added to the mixture as a crosslinking agent, and the mixture was sonicated to form a transparent liquid. The solution was then purified at 70°C under nitrogen protection. o C. Stir for 6 hours, and the resulting viscous liquid is dropped into a polytetrafluoroethylene mold to form a liquid film. After standing in air at room temperature for two days, a double-network p-Cel ionogel membrane is obtained.

[0040] Figure 3 The morphology of the ionogel membrane from Example 3 is shown. In Example 3, the reaction temperature was 120 °C. o At C, the p-Cel gel appears pale yellow with significant transmittance. Due to the extensive phosphorylation of the hydroxyl groups in cellulose, the gel exhibits strong toughness and can be bent at will.

[0041] SEM morphology analysis of p-Cel ion gel as follows: Figure 4 As shown, p-Cel is transformed into a highly porous structure with micrometer-scale pore sizes after solvent exchange and lyophilization. This porous structure allows the ionogel to transport ion carriers through a continuous conductive path.

[0042] In summary, the p-Cel dual-network ionogel membrane possesses a micron-scale porous structure and good toughness, making it suitable as a continuous ion transport carrier.

Claims

1. A method for preparing a cellulose and polyaspartamide derivative polymer-based ionic gel film material, comprising the following steps: (1) preparing an ionic liquid [DMIM][(MeO)(H)PO2] by weighing 1-methylimidazole and dimethyl phosphite, and dissolving them in 100-170 o C magnetic stirring for 10-15 h, washing the synthesized product with ethyl acetate to remove unreacted mixture, and vacuum drying at room temperature for 4-8 h to obtain the ionic liquid [DMIM][(MeO)(H)PO2]; (2) weighing cellulose and adding it to the [DMIM][(MeO)(H)PO2], and dissolving it under the condition of 70-130 o C magnetic stirring for 1-5 h, in which the chemical structure of the cellulose is phosphorylated by reacting with the phosphite ion; the hydroxyl group at the C-6 position of the cellulose is phosphorylated, and methanol is removed by condensation reaction; (3) preparing a polyaspartamide derivative polymer PolyAspAm by weighing polysuccinimide into a 250 mL round-bottom flask, dissolving it in N,N-dimethylformamide, adding 1-(3-aminopropyl)imidazole, heating to 40-70 °C, and stirring for 30-60 h; after the reaction is completed, adding ethanolamine, reducing the temperature to room temperature, and stirring for 20-40 h; the obtained reaction product is placed in a dialysis bag, dialyzed in deionized water for 1-3 d, and vacuum freeze-dried to obtain the final product PolyAspAm; (4) dissolving the PolyAspAm polymer obtained in step (3) in the ionic liquid, and adding the phosphorylated cellulose solution obtained in step (2) to prepare a mixed solution; (5) adding glutaraldehyde as a crosslinking agent to the mixed solution obtained in step (3), ultrasonically dissolving it into a transparent liquid, and stirring under the protection of nitrogen at 60-80 o C for 5-8 h to obtain a viscous liquid, which is dropped into a polytetrafluoroethylene mold to form a liquid film; (6) after the liquid film obtained in step (5) is left to stand in air at room temperature for 1-3 d, it is demolded to obtain a cellulose-based double-network p-Cel ionic gel film.

2. A process for the preparation of an ionic gel film material based on cellulose and polyaspartamide derived polymers as claimed in claim 1, characterized by: The content ratio of 1-methylimidazole to dimethyl phosphate in step (1) is 1:1.0-2.0 g, and the volume ratio of ethyl acetate to [DMIM][(MeO)(H)PO2] is 5-10:

1.

3. The method for preparing an ionogel membrane material based on cellulose and polyasparagine-derived polymers as described in claim 1, characterized in that: In step (2), the ratio of cellulose to [DMIM][(MeO)(H)PO2] is 0.5-1.0 g:10 mL.

4. The method for preparing an ionogel membrane material based on cellulose and polyasparagine-derived polymers as described in claim 1, characterized in that: In step (3), the ratio of N,N-dimethylformamide solvent to the number of moles of succinimidyl units in polysuccinimide is 1.5-4.5 L:1 mol.

5. The method for preparing an ionogel membrane material based on cellulose and polyasparagine-derived polymers as described in claim 1, characterized in that: In step (3), the number of moles of 1-(3-aminopropyl)imidazole is 0.2-2 times the number of moles of succinimidyl units, and the number of moles of ethanolamine is 0.25-2 times the number of moles of succinimidyl units.

6. The method for preparing an ionogel membrane material based on cellulose and polyasparagine-derived polymers as described in claim 1, characterized in that: In step (4), the ratio of PolyAspAm polymer to ionic liquid is 0.5-1.0 g:5 mL.

7. The method for preparing an ionogel membrane material based on cellulose and polyasparagine-derived polymers as described in claim 1, characterized in that: In step (5), the content of glutaraldehyde is 5%-20% of the total amount of cellulose and PolyAspAm polymer.

8. An ionic gel film material based on cellulose and polyaspartamide derived polymers, characterized by: is prepared by the preparation method of any one of claims 1-7.

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