Modified konjac glucomannan-based diaphragm and preparation method thereof

Abstract

The invention discloses a modified konjac glucomannan-based diaphragm and a preparation method thereof, and belongs to the technical field of supercapacitors. The modified konjac glucomannan-based diaphragm is prepared from the following raw materials in parts by weight: 100 parts of konjac glucomannan, 20 to 30 parts of trehalose, 50 to 70 parts of polyvinyl alcohol, 5 to 10 parts of silicon dioxide and 10 to 20 parts of chitosan. According to the diaphragm, organic-inorganic synergistic modification and precise regulation and control of a porous structure are realized, and the performance limitation of traditional single modification is broken through. According to the invention, PVA and SiO2 form an interpenetrating network, hydroxyl groups of PVA and hydroxyl groups of a KGM chain form hydrogen bonds, SiO2 fills a gap strengthening structure, and meanwhile, water is slowly removed through freeze drying, so that collapse of a pore structure is avoided, and synergistic improvement of mechanical strength and ion transmission performance is realized in mechanism. The diaphragm prepared by the preparation method disclosed by the invention effectively prevents interlayer stripping of the diaphragm in long-term charge-discharge circulation of the super capacitor, and is adaptive to the long-term cycle use scene of the super capacitor.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor technology, specifically relating to a modified konjac glucomannan-based separator and its preparation method. Background Technology

[0002] Supercapacitors, as novel energy storage devices, are widely used in new energy vehicles, portable electronic devices, and other fields due to their advantages of fast charging and discharging rates and long cycle life. The separator, as its core component, must simultaneously meet the core requirements of high ionic conductivity, excellent mechanical strength, and good electrolyte wettability. Its performance directly determines the energy storage efficiency and lifespan of the supercapacitor. Currently, most mainstream supercapacitor separators on the market are polyolefin polymer separators (such as polypropylene and polyethylene). Although they have high mechanical strength, they suffer from poor hydrophilicity, slow electrolyte wetting speed, and are prone to shrinkage at high temperatures, which restricts the safety performance of supercapacitors. Some studies have used bio-based materials (such as agar and cellulose) to prepare separators. While this improves hydrophilicity, single bio-based materials have weak mechanical properties, with tensile strength generally below 2.5 MPa. Furthermore, the rapid evaporation of water in traditional preparation processes easily leads to the collapse of the porous structure, making it difficult to exceed 12 mS / cm in ionic conductivity, thus failing to meet the requirements of high-performance supercapacitors.

[0003] To improve the performance of bio-based membranes, existing technologies often introduce inorganic modifiers (such as silica and alumina). However, inorganic particles are prone to agglomeration, making it difficult to form a uniform composite system with organic substrates, which can actually block ion channels. Alternatively, toxic crosslinking agents (such as formaldehyde and epichlorohydrin) are used to enhance interfacial bonding, which not only pollutes the environment but also poses a risk of residual reagents affecting electrolyte stability. In addition, some processes rely on high-temperature sintering (>150°C) or complex post-treatment (such as multiple soaking modifications), resulting in high energy consumption and increased costs, making it difficult to achieve large-scale mass production. Summary of the Invention

[0004] In order to overcome the problems of low mechanical strength, poor ionic conductivity, insufficient electrolyte wettability, and easy destruction of porous structure in the preparation process of the supercapacitor membranes mentioned above, the present invention aims to provide a modified konjac glucomannan-based membrane and its preparation method.

[0005] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a modified konjac glucomannan-based membrane, comprising the following raw materials in parts by weight: 100 parts konjac glucomannan, 20-30 parts trehalose, 50-70 parts polyvinyl alcohol, 5-10 parts silicon dioxide, and 10-20 parts chitosan.

[0006] A further improvement of the present invention is that the purity of the konjac glucomannan is not less than 98%.

[0007] A further improvement of the present invention is that the silicon dioxide is nanoparticles with a particle size of 40-60 nm.

[0008] A further improvement of the present invention is that the thickness of the diaphragm is 0.1-0.2 mm and the porosity is 60%-80%.

[0009] Secondly, the present invention also provides a method for preparing a modified konjac glucomannan-based membrane, comprising the following steps: Step 1: Vacuum dry konjac glucomannan and trehalose separately; dissolve polyvinyl alcohol in deionized water and add silica for ultrasonic treatment to form a composite modification solution; dissolve chitosan in acetic acid solution to form a crosslinking agent solution. Step 2: Dissolve konjac glucomannan and trehalose in deionized water, then add chitosan solution, polyvinyl alcohol-silica composite modified solution and initiator in sequence, and stir to form a uniform composite sol; Step 3: Inject the composite sol into the mold and let it stand until it is completely gelled to obtain the gel precursor; Step 4: Freeze-dry the gel precursor to obtain a preliminary composite membrane; Step 5: Crosslink the preliminary composite membrane with ultraviolet light radiation, and then perform plasma treatment and hot pressing to obtain the konjac glucomannan-based composite membrane.

[0010] A further improvement of the present invention is that, in step 1, the konjac glucomannan is dried at 65-75°C and a vacuum of -0.07 to -0.09 MPa for 3-5 hours; the polyvinyl alcohol dissolution temperature is 80-90°C; and the silica ultrasonic power is 300-400W for 15-25 minutes.

[0011] A further improvement of the present invention is that, in step 2, the temperature of the deionized water is 70-80℃, the stirring speed is 400-500r / min, and the initiator is ammonium persulfate and N,N'-methylenebisacrylamide, with addition amounts of 0.5%-1% and 0.2%-0.5% of the weight of konjac glucomannan, respectively.

[0012] A further improvement of the present invention is that, in step 4, the vacuum degree of freeze drying is 8-12 Pa, the temperature is -40 to -60°C, and the drying time is 10-12 hours.

[0013] A further improvement of the present invention is that, in step 5, the ultraviolet crosslinking uses ultraviolet light with a wavelength of 250-260nm, a radiation distance of 10-20cm, and a time of 12-18 minutes; the plasma treatment power is 80-100W, and the gas is a mixture of argon and oxygen in a volume ratio of 2:1 to 4:1.

[0014] A further improvement of the present invention is that, in step 5, the hot pressing densification temperature is 80-95℃, the pressure is 0.5-0.7MPa, and the time is 30-50 seconds; after hot pressing, the process also includes rinsing with deionized water and vacuum drying at 60-80℃ for 1-2 hours.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a modified konjac glucomannan-based membrane, which achieves synergistic organic-inorganic modification and precise control of porous structure, overcoming the performance limitations of traditional single-modification methods. In traditional processes, inorganic modifiers are prone to agglomeration, and organic modifiers provide insufficient mechanical enhancement. In this invention, polyvinyl alcohol (PVA) organic phase and silica (SiO2) inorganic phase form an interpenetrating network. The hydroxyl groups of PVA form hydrogen bonds with the hydroxyl groups of konjac glucomannan (KGM) chains, and SiO2 fills the voids to strengthen the structure. Simultaneously, freeze-drying slowly removes moisture, preventing pore structure collapse, thus achieving a synergistic improvement in mechanical strength and ion transport performance from a mechanistic perspective. Specifically, using KGM as the matrix, which possesses good film-forming properties and biodegradability, the introduction of a specific ratio of PVA and SiO2 allows the hydroxyl groups of PVA to form a dense hydrogen bond network with the hydroxyl groups on the KGM molecular chains, significantly enhancing the membrane's toughness and flexibility. Meanwhile, nano-SiO2 particles are uniformly dispersed and fill the voids in the polymer network, effectively improving the membrane's mechanical strength. Trehalose, acting as a plasticizer, further improves the flexibility and processing performance of the polymer chain. The addition of chitosan (CS) utilizes the amino groups on its molecular chain to form secondary cross-linking points with the hydroxyl groups of KGM, enhancing the interfacial bonding and stability of the entire network structure. This precise combination of components fundamentally overcomes the limitations of weak mechanical properties of single organic materials or the tendency of inorganic fillers to agglomerate, endowing the membrane with inherent structural advantages and laying the material foundation for its high ionic conductivity and long cycle life.

[0016] This invention also provides a method for preparing a modified konjac glucomannan-based separator. By preparing the composite modification liquid and crosslinking agent solution in steps, the uniform dispersion of the polyvinyl alcohol-silica (PVA-SiO2) composite and chitosan in the KGM matrix is ​​ensured, laying the foundation for the formation of a uniform structure. Traditional casting methods have a fast drying rate, which can easily lead to uneven pore size in the separator. In contrast, the freeze-drying method of this invention forms a uniform porous structure through ice crystal growth. This structure greatly promotes the rapid wetting of the electrolyte and the efficient transport of ions. Combined with hot-pressing densification to optimize the pore size distribution, it reduces ion transport path loss. Ultraviolet crosslinking further enhances the chemical crosslinking degree between PVA, KGM, and CS molecular chains, making the three-dimensional network more stable and effectively preventing interlayer delamination of the separator during long-term charge-discharge cycles of supercapacitors, making it suitable for long-term cyclic use scenarios of supercapacitors.

[0017] Furthermore, existing technologies often rely on toxic crosslinking agents or high-temperature sintering (>150°C). The KGM, trehalose, and CS selected in this invention are all bio-based materials that are degradable and non-toxic. The PVA-SiO2 composite modifier is low in cost and readily available. Although freeze drying requires low temperatures, it does not require complex post-processing and the raw material reaction efficiency is high, so there is no need to add excessive amounts, thus reducing energy consumption and pollution from the production end. Detailed Implementation

[0018] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0020] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0021] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0022] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0023] This invention provides a modified konjac glucomannan-based membrane, comprising the following raw materials in parts by weight: 100 parts konjac glucomannan, 20-30 parts trehalose, 50-70 parts polyvinyl alcohol, 5-10 parts silicon dioxide, and 10-20 parts chitosan.

[0024] In some embodiments, the purity of the konjac glucomannan is not less than 98%.

[0025] In some embodiments, the silicon dioxide is nanoparticles with a particle size of 40-60 nm.

[0026] In some embodiments, the membrane has a thickness of 0.1-0.2 mm and a porosity of 60%-80%.

[0027] This invention also proposes a method for preparing a modified konjac glucomannan-based membrane, comprising the following steps: Step 1: Konjac glucomannan and trehalose are vacuum dried separately. The konjac glucomannan is dried at 65-75℃ and a vacuum of -0.07 to -0.09 MPa for 3-5 hours, while the trehalose is dried at 55-65℃ for 1.8-2.2 hours. Polyvinyl alcohol is dissolved in deionized water and then mixed with silica and ultrasonically treated to form a composite modification solution. The ultrasonic power is 300-400W and the time is 15-25 minutes. Chitosan is dissolved in acetic acid solution to form a crosslinking agent solution. Step 2: Dissolve konjac glucomannan and trehalose in deionized water at 70-80℃, then sequentially add chitosan solution, polyvinyl alcohol-silica composite modified solution, and initiator, stirring at 400-500 r / min to form a uniform composite sol; the initiator is ammonium persulfate and N,N'-methylenebisacrylamide, added at amounts of 0.5%-1% and 0.2%-0.5% of the weight of konjac glucomannan, respectively. Step 3: Inject the composite sol into a 10×10cm pore. 2 In a polytetrafluoroethylene mold, the mold depth is 0.15±0.1mm. Then, the mold is placed in a constant temperature water bath at 25-35℃ and left to stand for 2-3 hours until it is completely gelled to obtain a gel precursor. Step 4: Freeze-dry the gel precursor. The freeze-drying vacuum degree is 8-12 Pa, the temperature is -40~-60℃, and the drying time is 10-12 hours to obtain a preliminary composite membrane. Step 5: Perform ultraviolet radiation crosslinking on the preliminary composite membrane. The ultraviolet crosslinking uses ultraviolet light with a wavelength of 250-260nm, a radiation distance of 10-20cm, and a time of 12-18 minutes. Then, perform plasma treatment and hot pressing to obtain the konjac glucomannan-based composite membrane.

[0028] In some embodiments, the plasma processing power is 80-100W, and the gas is a mixture of argon and oxygen in a volume ratio of 2:1 to 4:1.

[0029] In some embodiments, the hot pressing densification temperature is 80-95°C, the pressure is 0.5-0.7 MPa, and the time is 30-50 seconds; after hot pressing, the process also includes rinsing with deionized water and vacuum drying at 60-80°C for 1-2 hours.

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0032] Example 1 This embodiment provides a method for preparing a modified konjac glucomannan-based membrane, comprising the following steps: Step 1: Select konjac glucomannan (KGM) powder with a purity of 98%, place it in a vacuum drying oven at 70℃ (vacuum degree -0.08MPa) and dry for 4 hours to remove free water, obtaining dried KGM powder. Weigh 2.0g of dried KGM powder for later use. Weigh 0.5g of trehalose (Tre) and dry it in a vacuum drying oven at 60℃ for 2 hours for later use. Weigh 1.2g of polyvinyl alcohol (PVA) and dissolve it in 60mL of deionized water. Stir magnetically at 85℃ for 30 minutes until completely dissolved. After cooling to 40℃, add 0.15g of silica nanoparticles (SiO2, particle size 50nm) and sonicate at 350W for 20 minutes to prepare a 2wt% PVA-SiO2 composite modified solution for later use. Weigh 0.3g of chitosan (CS) and dissolve it in 10mL of 1wt% acetic acid solution. Stir at 40℃ for 25 minutes until completely dissolved to prepare a 3wt% CS solution for later use.

[0033] Step 2: Dissolve 2.0g KGM powder and 0.5g Tre in 50mL of deionized water at 75℃ and stir at 450r / min for 50min until completely dissolved; then add 3wt% CS solution (6mL in total) in 4 portions, stirring for 10min each time; then add 8mL of PVA-SiO2 composite modification solution and continue stirring for 30min; finally add 0.015g ammonium persulfate and 0.005g N,N'-methylenebisacrylamide and stir for 15min to obtain a uniform composite sol.

[0034] Step 3: Inject the composite sol into a 10×10cm pore. 2The mixture was placed in a polytetrafluoroethylene mold (0.15 mm deep), and then the mold was placed in a constant temperature water bath at 30°C for 2.5 h to allow it to gel completely, thus obtaining the gel precursor.

[0035] Step 4: The gel precursor was transferred to a freeze dryer and pre-frozen at -40℃ for 3 hours, then freeze-dried at -50℃ under 10Pa vacuum for 12 hours. After peeling, a preliminary composite membrane was obtained. The preliminary composite membrane was placed in an ultraviolet crosslinker (254nm, 100W), and the distance between the ultraviolet crosslinker and the preliminary composite membrane was kept at 15cm and irradiated for 15 minutes. Then it was placed in an argon-oxygen mixed gas (3:1) plasma treatment instrument and treated at 90W for 10 minutes. Finally, it was hot-pressed at 90℃ and 0.6MPa for 40 seconds, rinsed with deionized water, and vacuum-dried at 70℃ for 1.5 hours to obtain the KGM-Tre-PVA-SiO2 composite membrane, denoted as E1.

[0036] Step 5: Using E1 as the separator, NCM / graphene as the positive electrode, hard carbon as the negative electrode, and 2 mol / L zinc sulfate and 0.5 mol / L sulfuric acid as the electrolyte, assemble a 30×50 mm assembly. 2 The soft-pack supercapacitor was then tested, and the results are shown in Table 1.

[0037] Example 2 This embodiment provides a method for preparing a modified konjac glucomannan-based membrane, comprising the following steps: Step 1: Select konjac glucomannan (KGM) powder with a purity of 98%, place it in a vacuum drying oven at 70℃ (vacuum degree -0.08MPa) and dry for 4 hours to remove free water, obtaining dried KGM powder. Weigh 2.0g of dried KGM powder for later use. Weigh 0.5g of trehalose (Tre) and dry it in a vacuum drying oven at 60℃ for 2 hours for later use. Weigh 1.2g of polyvinyl alcohol (PVA) and dissolve it in 60mL of deionized water. Stir magnetically at 85℃ for 30 minutes until completely dissolved. After cooling to 40℃, add 0.15g of silica nanoparticles (SiO2, particle size 50nm) and sonicate at 350W for 20 minutes to prepare a 2wt% PVA-SiO2 composite modified solution for later use. Weigh 0.3g of chitosan (CS) and dissolve it in 10mL of 1wt% acetic acid solution. Stir at 40℃ for 25 minutes until completely dissolved to prepare a 3wt% CS solution for later use.

[0038] Step 2: Dissolve 2.0g KGM powder and 0.5g Tre in 50mL of deionized water at 75℃ and stir at 450r / min for 50min until completely dissolved; then add 3wt% CS solution (6mL in total) in 4 portions, stirring for 10min each time; then add 6mL of PVA-SiO2 composite modification solution and continue stirring for 30min; finally add 0.015g ammonium persulfate and 0.005g N,N'-methylenebisacrylamide and stir for 15min to obtain a uniform composite sol.

[0039] Step 3: Inject the composite sol into a 10×10cm pore. 2 The mixture was placed in a polytetrafluoroethylene mold (0.15 mm deep), and then the mold was placed in a constant temperature water bath at 30°C for 2.5 h to allow it to gel completely, thus obtaining the gel precursor.

[0040] Step 4: The gel precursor was transferred to a freeze dryer and pre-frozen at -40℃ for 3 hours, then freeze-dried at -50℃ under 10Pa vacuum for 12 hours. After peeling, a preliminary composite membrane was obtained. The preliminary composite membrane was placed in an ultraviolet crosslinker (254nm, 100W), and the distance between the ultraviolet crosslinker and the preliminary composite membrane was kept at 15cm and irradiated for 15 minutes. Then it was placed in an argon-oxygen mixed gas (3:1) plasma treatment instrument and treated at 90W for 10 minutes. Finally, it was hot-pressed at 90℃ and 0.6MPa for 40 seconds, rinsed with deionized water, and vacuum-dried at 70℃ for 1.5 hours to obtain the KGM-Tre-PVA-SiO2 composite membrane, denoted as E2.

[0041] Step 5: Using E2 as the separator, NCM / graphene as the positive electrode, hard carbon as the negative electrode, and 2 mol / L zinc sulfate and 0.5 mol / L sulfuric acid as the electrolyte, assemble a 30×50 mm assembly. 2 The soft-pack supercapacitor was then tested, and the results are shown in Table 1.

[0042] Example 3 This embodiment provides a method for preparing a modified konjac glucomannan-based membrane, comprising the following steps: Step 1: Select konjac glucomannan (KGM) powder with a purity of 98%, place it in a vacuum drying oven at 70℃ (vacuum degree -0.08MPa) and dry for 4 hours to remove free water, obtaining dried KGM powder. Weigh 2.0g of dried KGM powder for later use. Weigh 0.5g of trehalose (Tre) and dry it in a vacuum drying oven at 60℃ for 2 hours for later use. Weigh 1.2g of polyvinyl alcohol (PVA) and dissolve it in 60mL of deionized water. Stir magnetically at 85℃ for 30 minutes until completely dissolved. After cooling to 40℃, add 0.15g of silica nanoparticles (SiO2, particle size 50nm) and sonicate at 350W for 20 minutes to prepare a 2wt% PVA-SiO2 composite modified solution for later use. Weigh 0.3g of chitosan (CS) and dissolve it in 10mL of 1wt% acetic acid solution. Stir at 40℃ for 25 minutes until completely dissolved to prepare a 3wt% CS solution for later use.

[0043] Step 2: Dissolve 2.0g KGM powder and 0.5g Tre in 50mL of deionized water at 75℃ and stir at 450r / min for 50min until completely dissolved; then add 3wt% CS solution (6mL in total) in 4 portions, stirring for 10min each time; then add 10mL of PVA-SiO2 composite modification solution and continue stirring for 30min; finally add 0.015g ammonium persulfate and 0.005g N,N'-methylenebisacrylamide and stir for 15min to obtain a uniform composite sol.

[0044] Step 3: Inject the composite sol into a 10×10cm pore. 2 The mixture was placed in a polytetrafluoroethylene mold (0.15 mm deep), and then the mold was placed in a constant temperature water bath at 30°C for 2.5 h to allow it to gel completely, thus obtaining the gel precursor.

[0045] Step 4: The gel precursor was transferred to a freeze dryer and pre-frozen at -40℃ for 3 hours, then freeze-dried at -50℃ under 10Pa vacuum for 12 hours. After peeling, a preliminary composite membrane was obtained. The preliminary composite membrane was placed in an ultraviolet crosslinker (254nm, 100W), and the distance between the ultraviolet crosslinker and the preliminary composite membrane was kept at 15cm and irradiated for 15 minutes. Then it was placed in an argon-oxygen mixed gas (3:1) plasma treatment instrument and treated at 90W for 10 minutes. Finally, it was hot-pressed at 90℃ and 0.6MPa for 40 seconds, rinsed with deionized water, and vacuum-dried at 70℃ for 1.5 hours to obtain the KGM-Tre-PVA-SiO2 composite membrane, denoted as E3.

[0046] Step 5: Using E3 as the separator, NCM / graphene as the positive electrode, hard carbon as the negative electrode, and 2 mol / L zinc sulfate and 0.5 mol / L sulfuric acid as the electrolyte, assemble a 30×50 mm assembly. 2The soft-pack supercapacitor was then tested, and the results are shown in Table 1.

[0047] Example 4 This embodiment provides a method for preparing a modified konjac glucomannan-based membrane, comprising the following steps: Step 1: Select konjac glucomannan (KGM) powder with a purity of 98%, place it in a vacuum drying oven at 70℃ (vacuum degree -0.08MPa) and dry for 4 hours to remove free water, obtaining dried KGM powder. Weigh 2.0g of dried KGM powder for later use. Weigh 0.5g of trehalose (Tre) and dry it in a vacuum drying oven at 60℃ for 2 hours for later use. Weigh 1.2g of polyvinyl alcohol (PVA) and dissolve it in 60mL of deionized water. Stir magnetically at 85℃ for 30 minutes until completely dissolved. After cooling to 40℃, add 0.15g of silica nanoparticles (SiO2, particle size 50nm) and sonicate at 350W for 20 minutes to prepare a 2wt% PVA-SiO2 composite modified solution for later use. Weigh 0.3g of chitosan (CS) and dissolve it in 10mL of 1wt% acetic acid solution. Stir at 40℃ for 25 minutes until completely dissolved to prepare a 3wt% CS solution for later use.

[0048] Step 2: Dissolve 2.0g KGM powder and 0.5g Tre in 50mL of deionized water at 75℃ and stir at 450r / min for 50min until completely dissolved; then add 3wt% CS solution (6mL in total) in 4 portions, stirring for 10min each time; then add 8mL of PVA-SiO2 composite modification solution and continue stirring for 30min; finally add 0.015g ammonium persulfate and 0.005g N,N'-methylenebisacrylamide and stir for 15min to obtain a uniform composite sol.

[0049] Step 3: Inject the composite sol into a 10×10cm pore. 2 The mixture was placed in a polytetrafluoroethylene mold (0.15 mm deep), and then the mold was placed in a constant temperature water bath at 30°C for 2.5 h to allow it to gel completely, thus obtaining the gel precursor.

[0050] Step 4: The gel precursor was transferred to a freeze dryer and pre-frozen at -40℃ for 3 hours, then freeze-dried at -50℃ under 10Pa vacuum for 10 hours. After peeling, a preliminary composite membrane was obtained. The preliminary composite membrane was placed in an ultraviolet crosslinker (254nm, 100W), and the distance between the ultraviolet crosslinker and the preliminary composite membrane was kept at 15cm and irradiated for 15 minutes. Then it was placed in an argon-oxygen mixed gas (3:1) plasma treatment instrument and treated at 90W for 10 minutes. Finally, it was hot-pressed at 90℃ and 0.6MPa for 40 seconds, rinsed with deionized water, and vacuum-dried at 70℃ for 1.5 hours to obtain the KGM-Tre-PVA-SiO2 composite membrane, denoted as E4.

[0051] Step 5: Using E4 as the separator, NCM / graphene as the positive electrode, hard carbon as the negative electrode, and 2 mol / L zinc sulfate and 0.5 mol / L sulfuric acid as the electrolyte, assemble a 30×50 mm assembly. 2 The soft-pack supercapacitor was then tested, and the results are shown in Table 1.

[0052] Example 5 This embodiment provides a method for preparing a modified konjac glucomannan-based membrane, comprising the following steps: Step 1: Select konjac glucomannan (KGM) powder with a purity of 98%, place it in a vacuum drying oven at 70℃ (vacuum degree -0.08MPa) and dry for 4 hours to remove free water, obtaining dried KGM powder. Weigh 2.0g of dried KGM powder for later use. Weigh 0.5g of trehalose (Tre) and dry it in a vacuum drying oven at 60℃ for 2 hours for later use. Weigh 1.2g of polyvinyl alcohol (PVA) and dissolve it in 60mL of deionized water. Stir magnetically at 85℃ for 30 minutes until completely dissolved. After cooling to 40℃, add 0.15g of silica nanoparticles (SiO2, particle size 50nm) and sonicate at 350W for 20 minutes to prepare a 2wt% PVA-SiO2 composite modified solution for later use. Weigh 0.3g of chitosan (CS) and dissolve it in 10mL of 1wt% acetic acid solution. Stir at 40℃ for 25 minutes until completely dissolved to prepare a 3wt% CS solution for later use.

[0053] Step 2: Dissolve 2.0g KGM powder and 0.5g Tre in 50mL of deionized water at 75℃ and stir at 450r / min for 50min until completely dissolved; then add 3wt% CS solution (6mL in total) in 4 portions, stirring for 10min each time; then add 8mL of PVA-SiO2 composite modification solution and continue stirring for 30min; finally add 0.015g ammonium persulfate and 0.005g N,N'-methylenebisacrylamide and stir for 15min to obtain a uniform composite sol.

[0054] Step 3: Inject the composite sol into a 10×10cm pore. 2 The mixture was placed in a polytetrafluoroethylene mold (0.15 mm deep), and then the mold was placed in a constant temperature water bath at 30°C for 2.5 h to allow it to gel completely, thus obtaining the gel precursor.

[0055] Step 4: The gel precursor was transferred to a freeze dryer and pre-frozen at -40℃ for 3 hours, then freeze-dried at -50℃ under 10Pa vacuum for 12 hours. After peeling, a preliminary composite membrane was obtained. The preliminary composite membrane was placed in an ultraviolet crosslinker (254nm, 100W), and the distance between the ultraviolet crosslinker and the preliminary composite membrane was kept at 15cm and irradiated for 15 minutes. Then it was placed in an argon-oxygen mixed gas (3:1) plasma treatment instrument and treated at 90W for 10 minutes. Finally, it was hot-pressed at 80℃ and 0.6MPa for 40 seconds, rinsed with deionized water, and vacuum-dried at 70℃ for 1.5 hours to obtain the KGM-Tre-PVA-SiO2 composite membrane, denoted as E5.

[0056] Step 5: Using E5 as the separator, NCM / graphene as the positive electrode, hard carbon as the negative electrode, and 2 mol / L zinc sulfate and 0.5 mol / L sulfuric acid as the electrolyte, assemble a 30×50 mm diaphragm. 2 The soft-pack supercapacitor was then tested, and the results are shown in Table 1.

[0057] Example 6 This embodiment provides a method for preparing a modified konjac glucomannan-based membrane, comprising the following steps: Step 1: Select konjac glucomannan (KGM) powder with a purity of 98%, place it in a vacuum drying oven at 70℃ (vacuum degree -0.08MPa) and dry for 4 hours to remove free water, obtaining dried KGM powder. Weigh 2.0g of dried KGM powder for later use. Weigh 0.5g of trehalose (Tre) and dry it in a vacuum drying oven at 60℃ for 2 hours for later use. Weigh 1.2g of polyvinyl alcohol (PVA) and dissolve it in 60mL of deionized water. Stir magnetically at 85℃ for 30 minutes until completely dissolved. After cooling to 40℃, add 0.15g of silica nanoparticles (SiO2, particle size 50nm) and sonicate at 350W for 20 minutes to prepare a 2wt% PVA-SiO2 composite modified solution for later use. Weigh 0.2g of chitosan (CS) and dissolve it in 10mL of 1wt% acetic acid solution. Stir at 40℃ for 25 minutes until completely dissolved to prepare a 2wt% CS solution for later use.

[0058] Step 2: Dissolve 2.0g KGM powder and 0.5g Tre in 50mL of deionized water at 75℃ and stir at 450r / min for 50min until completely dissolved; then add 3wt% CS solution (6mL in total) in 4 portions, stirring for 10min each time; then add 8mL of PVA-SiO2 composite modification solution and continue stirring for 30min; finally add 0.015g ammonium persulfate and 0.005g N,N'-methylenebisacrylamide and stir for 15min to obtain a uniform composite sol.

[0059] Step 3: Inject the composite sol into a 10×10cm pore. 2 The mixture was placed in a polytetrafluoroethylene mold (0.15 mm deep), and then the mold was placed in a constant temperature water bath at 30°C for 2.5 h to allow it to gel completely, thus obtaining the gel precursor.

[0060] Step 4: The gel precursor was transferred to a freeze dryer and pre-frozen at -40℃ for 3 hours, then freeze-dried at -50℃ under 10Pa vacuum for 12 hours. After peeling, a preliminary composite membrane was obtained. The preliminary composite membrane was placed in an ultraviolet crosslinker (254nm, 100W), and the distance between the ultraviolet crosslinker and the preliminary composite membrane was kept at 15cm and irradiated for 15 minutes. Then it was placed in an argon-oxygen mixed gas (3:1) plasma treatment instrument and treated at 90W for 10 minutes. Finally, it was hot-pressed at 90℃ and 0.6MPa for 40 seconds, rinsed with deionized water, and vacuum-dried at 70℃ for 1.5 hours to obtain the KGM-Tre-PVA-SiO2 composite membrane, denoted as E6.

[0061] Step 5: Using E6 as the separator, NCM / graphene as the positive electrode, hard carbon as the negative electrode, and 2 mol / L zinc sulfate and 0.5 mol / L sulfuric acid as the electrolyte, assemble a 30×50 mm assembly. 2 The soft-pack supercapacitor was then tested, and the results are shown in Table 1.

[0062] Comparative Example 1 This comparative example provides a method for preparing a diaphragm, comprising the following steps: Step 1: Select konjac glucomannan (KGM) powder with a purity of 98%, place it in a vacuum drying oven at 70℃ (vacuum degree -0.08MPa) and dry for 4 hours to remove free moisture, obtaining dried KGM powder. Weigh 2.0g of dried KGM powder for later use; weigh 0.5g of trehalose (Tre) and dry it in a vacuum drying oven at 60℃ for 2 hours for later use; weigh 0.3g of chitosan (CS) and dissolve it in 10mL of 1wt% acetic acid solution, stirring at 40℃ for 25 minutes until completely dissolved to prepare a 3wt% CS solution for later use.

[0063] Step 2: Dissolve 2.0g KGM powder and 0.5g Tre in 50mL of deionized water at 75℃ and stir at 450r / min for 50min until completely dissolved; then add 3wt% CS solution (6mL in total) in 4 portions, stirring for 10min each time; finally add 0.015g ammonium persulfate and 0.005g N,N'-methylenebisacrylamide and stir for 15min to obtain a uniform composite sol.

[0064] Step 3: Inject the composite sol into a 10×10cm pore. 2 The mixture was placed in a polytetrafluoroethylene mold (0.15 mm deep), and then the mold was placed in a constant temperature water bath at 30°C for 2.5 h to allow it to gel completely, thus obtaining the gel precursor.

[0065] Step 4: The gel precursor was transferred to a freeze dryer and pre-frozen at -40℃ for 3 hours, then freeze-dried at -50℃ under 10Pa vacuum for 12 hours. After peeling, a preliminary composite membrane was obtained. The preliminary composite membrane was placed in an ultraviolet crosslinker (254nm, 100W), and the distance between the ultraviolet crosslinker and the preliminary composite membrane was kept at 15cm and irradiated for 15 minutes. Then it was placed in an argon-oxygen mixed gas (3:1) plasma treatment instrument and treated at 90W for 10 minutes. Finally, it was hot-pressed at 90℃ and 0.6MPa for 40 seconds, rinsed with deionized water, and vacuum-dried at 70℃ for 1.5 hours to obtain the KGM-Tre membrane, denoted as C1.

[0066] Step 5: Using C1 as the separator, NCM / graphene as the positive electrode, hard carbon as the negative electrode, and 2 mol / L zinc sulfate and 0.5 mol / L sulfuric acid as the electrolyte, assemble a 30×50 mm assembly. 2 The soft-pack supercapacitor was then tested, and the results are shown in Table 1.

[0067] Comparative Example 2 This comparative example provides a method for preparing a conventional KGM membrane, including the following steps: Step 1: Select konjac glucomannan (KGM) powder with a purity of 98%, place it in a vacuum drying oven at 70℃ (vacuum degree -0.08MPa) and dry for 4 hours to remove free water, obtaining dried KGM powder. Weigh 2.0g of dried KGM powder for later use. Weigh 0.5g of trehalose (Tre) and dry it in a vacuum drying oven at 60℃ for 2 hours for later use. Weigh 1.2g of polyvinyl alcohol (PVA) and dissolve it in 60mL of deionized water. Stir magnetically at 85℃ for 30 minutes until completely dissolved. After cooling to 40℃, add 0.15g of silica nanoparticles (SiO2, particle size 50nm) and sonicate at 350W for 20 minutes to prepare a 2wt% PVA-SiO2 composite modified solution for later use. Weigh 0.3g of chitosan (CS) and dissolve it in 10mL of 1wt% acetic acid solution. Stir at 40℃ for 25 minutes until completely dissolved to prepare a 3wt% CS solution for later use.

[0068] Step 2: Dissolve 2.0g KGM powder and 0.5g Tre in 50mL of deionized water at 75℃ and stir at 450r / min for 50min until completely dissolved; then add 3wt% CS solution (6mL in total) in 4 portions, stirring for 10min each time; then add 8mL of PVA-SiO2 composite modification solution and continue stirring for 30min; finally add 0.015g ammonium persulfate and 0.005g N,N'-methylenebisacrylamide and stir for 15min to obtain a uniform composite sol.

[0069] Step 3: Inject the composite sol into a 10×10cm pore. 2 The material is placed in a polytetrafluoroethylene mold (0.15 mm deep), and then the mold is placed in a 60°C forced-air drying oven for drying to obtain a preliminary composite membrane precursor.

[0070] Step 4: The preliminary composite membrane precursor is transferred to a freeze dryer and pre-frozen at -40℃ for 3 hours, then freeze-dried at -50℃ under 10Pa vacuum for 12 hours. After peeling, the preliminary composite membrane is obtained. Then, the preliminary composite membrane is placed in an argon-oxygen mixed gas (3:1) plasma treatment instrument and treated at 90W for 10 minutes. Finally, it is hot-pressed at 90℃ and 0.6MPa for 40 seconds, rinsed with deionized water, and then vacuum-dried at 70℃ for 1.5 hours to obtain the traditional KGM composite membrane, denoted as C2.

[0071] Step 5: Using C2 as the separator, NCM / graphene as the positive electrode, hard carbon as the negative electrode, and 2 mol / L zinc sulfate and 0.5 mol / L sulfuric acid as the electrolyte, assemble a 30×50 mm assembly. 2 The soft-pack supercapacitor was then tested, and the results are shown in Table 1.

[0072] Table 1. Performance test results of the supercapacitors prepared in the embodiments and comparative examples of the present invention.

[0073] As shown in Table 1, the membrane prepared in Example 1 (E1) exhibits the best performance. The key lies in the optimal amount of PVA-SiO2 composite modified liquid used, which forms an ideal interpenetrating network structure with the KGM matrix. In this system, the hydroxyl groups (-OH) on the PVA molecular chain and the hydroxyl groups on the KGM glucomannan chain are tightly bonded by hydrogen bonds, uniformly filling the network voids with SiO2 nanoparticles. This structure overcomes the weakness of single-phase organic materials in terms of mechanical properties and constructs continuous ion transport channels, thereby increasing the ionic conductivity to 18.5 mS / cm. During the 12-hour freeze-drying process, the slow growth of ice crystals guides the formation of a uniform porous structure, ensuring rapid electrolyte wetting (requiring only 8 seconds). Subsequent hot-pressing densification at 90°C further optimizes the pore size distribution and shortens the ion transport path. Furthermore, the introduction of 3wt% CS enhances interfacial bonding stability by forming secondary crosslinks between the amino groups (-NH2) on its molecular chain and the hydroxyl groups on the KGM chain. Ultimately, this allows the supercapacitor assembled based on this membrane to maintain a capacitance of 93.8% after 5000 cycles, and increases the energy density to 26.5 Wh•kg. -1 .

[0074] In Example 2 (E2), reducing the amount of PVA-SiO2 composite modification solution to 6 mL resulted in a decrease in the coverage of the organic-inorganic network on the KGM matrix. In some areas, the lack of effective support from SiO2 particles led to the breakage of ion channels, causing the ionic conductivity to drop from 18.5 mS / cm to 16.2 mS / cm, and extending the electrolyte wetting time to 11 s. In Example 3 (E3), increasing the modification solution to 10 mL resulted in an excess of SiO2 nanoparticles exceeding the carrying capacity of the KGM-PVA network. Approximately 10% of the SiO2 aggregated, blocking some micron-sized pores. Although the increased inorganic phase improved the tensile strength to 4.5 MPa, the ionic conductivity still decreased to 17.8 mS / cm, reflecting the balance mechanism between dosage, dispersibility, and performance. Example 4 (E4): The freeze-drying time was shortened to 10 hours. Insufficient ice crystal growth led to an increase in the proportion of closed pores in the membrane from 5% in E1 to 15%, hindering effective ion transport. The conductivity decreased to 15.9 mS / cm, and the wetting time was extended to 13 s. Example 5 (E5): The hot-pressing temperature was lowered to 80°C. The KGM-PVA composite was not sufficiently softened, and many structural gaps remained after densification, resulting in a decrease in tensile strength to 3.9 MPa. The electrolyte easily remained in the gaps, affecting ion transport efficiency. Example 6 (E6): The CS concentration was reduced to 2 wt%. The number of amino groups in its molecular chain decreased, and the density of hydrogen bond crosslinking points with KGM decreased. The membrane exhibited a tendency for interlayer delamination during cycling, and the capacitance retention decreased from 93.8% to 88.9%, with the energy density decreasing to 23.7 Wh•kg. -1 .

[0075] Comparative Example 1 (C1) contained no PVA-SiO2 composite modifier. The KGM matrix relied solely on its own hydrogen bonding to form a network structure, resulting in poor mechanical properties of the membrane, with a tensile strength of only 2.1 MPa. Its pore structure was dominated by macropores larger than 200 nm, leading to significant ion transport resistance and an ionic conductivity of only 10.3 mS / cm. The electrolyte wetting time was as long as 25 s. During cyclic testing, the pore structure was prone to collapse, with a capacitance retention rate of only 78.6%. Comparative Example 2 (C2) was prepared using a traditional casting method. Rapid evaporation of moisture at 60℃ caused pore structure collapse, and the lack of UV crosslinking treatment resulted in insufficient crosslinking between PVA and KGM. Its ionic conductivity was 12.5 mS / cm, tensile strength was 2.8 MPa, and capacitance retention rate was 82.3%. This result fully demonstrates that the "sol-gel-freeze-drying + UV crosslinking" process adopted in this invention, combined with the "PVA SiO2-CS" composite system, is irreplaceable in constructing high-performance membranes with stable structure and excellent performance.

[0076] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A modified konjac glucomannan-based membrane, characterized in that, The ingredients include the following parts by weight: 100 parts konjac glucomannan, 20-30 parts trehalose, 50-70 parts polyvinyl alcohol, 5-10 parts silicon dioxide, and 10-20 parts chitosan.

2. The modified konjac glucomannan-based membrane according to claim 1, characterized in that, The purity of the konjac glucomannan is not less than 98%.

3. The modified konjac glucomannan-based membrane according to claim 1, characterized in that, The silica is composed of nanoparticles with a particle size of 40-60 nm.

4. The modified konjac glucomannan-based membrane according to claim 1, characterized in that, The membrane has a thickness of 0.1-0.2 mm and a porosity of 60%-80%.

5. A method for preparing the modified konjac glucomannan-based membrane according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Vacuum dry konjac glucomannan and trehalose separately; dissolve polyvinyl alcohol in deionized water and add silica for ultrasonic treatment to form a composite modification solution; dissolve chitosan in acetic acid solution to form a crosslinking agent solution. Step 2: Dissolve konjac glucomannan and trehalose in deionized water, then add chitosan solution, polyvinyl alcohol-silica composite modified solution and initiator in sequence, and stir to form a uniform composite sol; Step 3: Inject the composite sol into the mold and let it stand until it is completely gelled to obtain the gel precursor; Step 4: Freeze-dry the gel precursor to obtain a preliminary composite membrane; Step 5: Crosslink the preliminary composite membrane with ultraviolet light radiation, and then perform plasma treatment and hot pressing to obtain the konjac glucomannan-based composite membrane.

6. The method for preparing a modified konjac glucomannan-based membrane according to claim 5, characterized in that, In step 1, the konjac glucomannan is dried at 65-75℃ and a vacuum of -0.07 to -0.09 MPa for 3-5 hours; the polyvinyl alcohol is dissolved at 80-90℃; and the silica is ultrasonically heated to 300-400W for 15-25 minutes.

7. The method for preparing a modified konjac glucomannan-based membrane according to claim 5, characterized in that, In step 2, the temperature of the deionized water is 70-80℃, and the stirring speed is 400-500 r / min; the initiator is ammonium persulfate and N,N'-methylenebisacrylamide, and the addition amounts are 0.5%-1% and 0.2%-0.5% of the weight of konjac glucomannan, respectively.

8. The method for preparing a modified konjac glucomannan-based membrane according to claim 5, characterized in that, In step 4, the vacuum degree of freeze drying is 8-12 Pa, the temperature is -40~-60℃, and the drying time is 10-12 hours.

9. The method for preparing a modified konjac glucomannan-based membrane according to claim 5, characterized in that, In step 5, the ultraviolet crosslinking uses ultraviolet light with a wavelength of 250-260nm, a radiation distance of 10-20cm, and a time of 12-18 minutes; the plasma treatment power is 80-100W, and the gas is a mixture of argon and oxygen in a volume ratio of 2:1 to 4:

1.

10. The method for preparing a modified konjac glucomannan-based membrane according to claim 5, characterized in that, In step 5, the hot pressing densification temperature is 80-95℃, the pressure is 0.5-0.7MPa, and the time is 30-50 seconds; after hot pressing, it also includes rinsing with deionized water and vacuum drying at 60-80℃ for 1-2 hours.

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