High-voltage gel polymer electrolyte, preparation method thereof and supercapacitor

Abstract

The invention provides a high-voltage gel polymer electrolyte, a preparation method thereof and a supercapacitor, and belongs to the technical field of supercapacitors. The preparation method comprises the following steps: adding a citric acid aqueous solution into polysaccharide powder, stirring to obtain a polysaccharide solution, adding nanocellulose whiskers into the polysaccharide solution, and performing ultrasonic treatment to form a modified polysaccharide composite solution; the preparation method comprises the following steps: stirring a fluorinated monomer and a cross-linking agent to form a mixed system, adding a photoinitiator into the mixed system, and stirring until the initiator is completely dissolved to obtain a monomer-cross-linking agent mixed solution; mixing and stirring the modified polysaccharide composite solution and the monomer-cross-linking agent mixed solution to form a composite precursor solution; soaking a substrate in a hydroxysilane ethanol solution for surface modification, uniformly coating the surface of the substrate with the composite precursor solution, performing cross-linking polymerization reaction through ultraviolet radiation to obtain a gel film, drying the gel film, soaking the dried gel film in an electrolyte, and extruding to obtain the high-pressure gel polymer electrolyte.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of supercapacitors, and particularly relates to a high-voltage gel polymer electrolyte, a preparation method thereof and a supercapacitor. BACKGROUND

[0002] Traditional liquid electrolytes have safety hazards such as flammability and leakage, while ordinary gel polymer electrolytes (such as PEO, PMMA-based) have insufficient mechanical strength, low ionic conductivity, and lack intrinsic flame retardancy. Based on this, in the prior art, materials are endowed with flame retardant properties by adding flame retardants, which can improve safety, but at the expense of electrochemical performance (such as reducing ion migration number). In addition, conventional gel electrolytes mostly use synthetic polymers (such as PVDF-HFP), which are high in cost and difficult to biodegrade, and such single fluorinated polymers, although having certain high-pressure resistance, lack network support and have insufficient mechanical strength. SUMMARY

[0003] The present disclosure aims to at least solve one of the technical problems existing in the prior art, and provides a high-voltage gel polymer electrolyte, a preparation method thereof and a supercapacitor.

[0004] In one aspect of the present disclosure, a preparation method of a high-voltage gel polymer electrolyte is provided, comprising: adding a citric acid aqueous solution to the polysaccharide powder for constant temperature stirring treatment to obtain a polysaccharide solution, and adding nanocellulose whiskers to the polysaccharide solution for ultrasonic treatment to form a uniformly dispersed modified polysaccharide composite solution; stirring the fluorinated monomer and the crosslinking agent to mix them uniformly to form a mixed system, adding a photoinitiator to the mixed system for continued stirring treatment until the initiator is completely dissolved to obtain a monomer-crosslinking agent mixed solution; mixing the modified polysaccharide composite solution and the monomer-crosslinking agent mixed solution and stirring to form a composite precursor solution; immersing a substrate in a hydroxyl silane ethanol solution for surface modification, uniformly coating the composite precursor solution on the surface of the modified substrate, and performing ultraviolet radiation treatment to cause the precursor to undergo crosslinking polymerization reaction to obtain a gel film, and performing drying treatment on the gel film; immersing the dried gel film in an electrolyte for extrusion treatment to obtain a high-voltage gel polymer electrolyte.

[0005] Optionally, the polysaccharide powder is konjac glucomannan powder; The mass fraction of the citric acid aqueous solution is 3%-10%; The content of the nanocellulose whiskers is 14-16% of the content of the polysaccharide powder.

[0006] Optionally, the temperature for the constant temperature stirring treatment of the polysaccharide powder with the aqueous citric acid solution is 45-55°C, and the time is 1-3h. Optionally, the temperature for the ultrasonic treatment of the polysaccharide solution with the nanocellulose whiskers is 40-50°C, the power is 250-350W, and the time is 25-35min.

[0007] Optionally, the molar ratio of the fluorinated monomer to the crosslinking agent is (3-5):1. Optionally, the amount of the photoinitiator added is 0.5%-1% of the total mass of the mixed system formed by the fluorinated monomer and the crosslinking agent.

[0008] Optionally, the fluorinated monomer is selected from one of the following structural formulas: (Formula I-1); (Formula I-2); (Formula I-3); (Formula I-4); Optionally, the crosslinking agent is selected from one of the following: polyethylene glycol dimethacrylate, polyethylene glycol divinyl ether, bisphenol A difluorodi-acrylate, hexafluorobisphenol A diacrylate, trimethylolpropane triacrylate, and polyethylene glycol diacrylate. Optionally, the photoinitiator is one of the following: 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0009] Optionally, the fluorinated monomer and the crosslinking agent are stirred at 20-30°C for 10-20min. Optionally, the photoinitiator is added to the mixed system and stirred for 5-15min.

[0010] Optionally, the volume ratio of the modified polysaccharide composite solution to the monomer-crosslinking agent mixed solution is 1:(2-4). Optionally, after the mixing of the modified polysaccharide composite solution and the monomer-crosslinking agent mixed solution, the mixture is stirred at 25-35°C for 35-45min.

[0011] Optionally, the hydroxysilane ethanol solution is 3-glycidyl ether oxypropyl trimethoxysilane ethanol solution. Optionally, the thickness of the composite precursor solution uniformly coated on the surface of the pretreated substrate is 20-30μm. Optionally, the wavelength of the ultraviolet radiation treatment is 365nm, and the power is 80-100mW / cm.2 The duration is 45-60 seconds; The gel membrane is dried at a temperature of 60-70°C for 2-3 hours.

[0012] In another aspect of this disclosure, a high-pressure gel polymer electrolyte is provided, which is prepared by the preparation method described above.

[0013] In another aspect of this disclosure, a supercapacitor is provided, the supercapacitor comprising a positive electrode shell, a positive electrode plate, a high-voltage gel polymer electrolyte, a negative electrode plate, a stainless steel sheet, a spring plate, and a negative electrode shell, wherein the high-voltage gel polymer electrolyte is the high-voltage gel polymer electrolyte described above.

[0014] This disclosure discloses a high-voltage gel polymer electrolyte, its preparation method, and a supercapacitor. The preparation method includes: adding citric acid aqueous solution to polysaccharide powder and stirring at a constant temperature to obtain a polysaccharide solution; adding nano-cellulose whiskers to the polysaccharide solution and ultrasonically treating it to form a uniformly dispersed modified polysaccharide composite solution; stirring a fluorinated monomer and a crosslinking agent to mix them evenly to form a mixed system; adding a photoinitiator to the mixed system and continuing stirring until the initiator is completely dissolved to obtain a monomer-crosslinking agent mixture; mixing the modified polysaccharide composite solution with the monomer-crosslinking agent mixture and stirring to form a composite precursor solution; immersing a substrate in a hydroxysilane ethanol solution for surface modification; uniformly coating the modified substrate surface with the composite precursor solution; subjecting the substrate to ultraviolet radiation to induce crosslinking polymerization of the precursor to obtain a gel film; and drying the gel film; immersing the dried gel film in an electrolyte and extruding it to obtain the high-voltage gel polymer electrolyte. This disclosure uses natural polysaccharides and fluorinated monomers as core raw materials, and constructs a gel electrolyte with high ionic conductivity, high voltage and excellent mechanical strength through a pretreatment-composite-photocuring-activation process, which is suitable for supercapacitors with high voltage requirements. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the preparation method of the high-pressure gel polymer electrolyte according to a specific embodiment of this disclosure. Figure 2 The impedance results are shown in the following diagrams: Embodiment 1, Embodiment 3, Embodiment 12, and Comparative Examples 1 and 2. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0017] As shown in Figure 1, one aspect of this disclosure provides a preparation method S100 for a high-pressure gel polymer electrolyte, specifically including the following steps S110~S150: S110. Add citric acid aqueous solution to polysaccharide powder and stir at a constant temperature to obtain polysaccharide solution. Add nanocellulose whiskers to the polysaccharide solution and sonicate to form a uniformly dispersed modified polysaccharide composite solution.

[0018] In step S110, the polysaccharide powder is preferably konjac glucomannan powder, which is a natural polysaccharide with low cost. Compared with other natural polysaccharides (e.g., starch, cellulose), it has high hydroxyl activity, good compatibility with fluorinated monomers, and is less prone to phase separation.

[0019] In step S110, polysaccharide powder is taken and slowly added to a certain mass fraction of citric acid aqueous solution. The mixture is stirred for 1-3 hours in a constant temperature water bath at 45-55℃ until the powder is completely dissolved, resulting in a certain mass fraction of polysaccharide solution. By modifying the polysaccharide powder, the hydrogen bond breaking and molecular diffusion of the polysaccharide are accelerated, promoting the complete dissolution of the polysaccharide and forming a homogeneous solution. In addition, the carboxyl group of citric acid may undergo esterification with the hydroxyl group of the polysaccharide to introduce a carboxylic acid group (-COOH). This modification can improve the compatibility with fluorinated monomers.

[0020] In some preferred embodiments, the citric acid aqueous solution has a mass fraction of 3%-10%, and the mass of the citric acid aqueous solution is preferably 24 times the mass of the polysaccharide powder.

[0021] In step S110, nanocellulose whiskers are further added to the previously obtained konjac glucomannan solution, and then transferred to an ultrasonic instrument for ultrasonic treatment at 40-50°C (e.g., preferably 45°C) and 250-350W (e.g., preferably 300W) for 25-35 minutes (e.g., preferably 30 minutes) to form a uniformly dispersed modified polysaccharide composite solution. The thermal stability of the nanocellulose whiskers can delay the molecular chain slippage of the polysaccharide chains at high temperatures, ensuring the dimensional stability of the electrolyte under high-temperature working conditions. At the same time, the nanofibers of the nanocellulose whiskers and konjac glucomannan are bonded by hydrogen bonds to form a "rigid-flexible" composite network. The rigid framework supports the porous structure, while the flexible chains of the polysaccharide provide ion migration space, synergistically forming a continuous ion transport channel.

[0022] In some preferred embodiments, the content of the nanocellulose whiskers is 14-16% of the content of the polysaccharide powder, for example, preferably 15%.

[0023] S120. Fluorinated monomers and crosslinking agents are added to a three-necked flask at a certain molar ratio and stirred until they are mixed evenly to form a mixed system. Photoinitiator is added to the mixed system and stirring is continued until the initiator is completely dissolved to obtain a monomer-crosslinking agent mixture.

[0024] In step S120, the molar ratio of fluorinated monomer to crosslinking agent is (3-5):1, and the amount of photoinitiator added is 0.5%-1% of the total mass of the mixed system formed by fluorinated monomer and crosslinking agent.

[0025] In step S120, the fluorinated monomer and crosslinking agent are stirred at 20-30°C (e.g., preferably 25°C) for 10-20 min (e.g., preferably 15 min); a photoinitiator is added to the mixture and stirring is continued for 5-15 min (e.g., preferably 10 min). The crosslinking agent reacts with the fluorinated monomer through double bonds or epoxy groups to form a three-dimensional network structure, enhancing mechanical strength and thermal stability. The photoinitiator decomposes into free radicals under ultraviolet radiation, triggering the double bond polymerization of the fluorinated monomer and crosslinking agent to form a crosslinked network.

[0026] In some preferred embodiments, the fluorinated monomer is selected from one of the following structural formulas: (Formula I-1CAS: 121628-53-3); (Formula I-2CAS: 59006-66-5); (Formula I-3 CAS: 29014-57-1); (Formula I-4CAS: 36405-47-7); In some preferred embodiments, the crosslinking agent is selected from one of polyethylene glycol dimethacrylate, polyethylene glycol divinyl ether, bisphenol A difluorodiacrylate, hexafluorobisphenol A diacrylate, trimethylolpropane triacrylate, and polyethylene glycol diacrylate.

[0027] In some preferred embodiments, the photoinitiator is one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0028] S130. The modified polysaccharide composite solution is mixed with the monomer-crosslinking agent mixture and stirred to form a composite precursor solution.

[0029] In step S130, the volume ratio of the modified polysaccharide composite solution to the monomer-crosslinking agent mixture is 1:(2-4).

[0030] In step S130, the modified polysaccharide composite solution is mixed with the monomer-crosslinking agent mixture and then stirred at 25-35℃ for 35-45 min. The homogeneous monomer-crosslinking agent mixture and the modified polysaccharide solution are combined through hydrogen bonds to form a non-layered precursor, providing a uniform reaction basis for UV curing.

[0031] S140. The substrate is immersed in a hydroxysilane ethanol solution for surface modification. The composite precursor solution is uniformly coated on the modified substrate surface. The precursor is subjected to ultraviolet radiation treatment to cause cross-linking polymerization reaction to obtain a gel film. The gel film is then dried.

[0032] In step S140, the substrate can be a polyimide (PI) electrospun film. Compared with the current method where the substrate and film are physically bonded, resulting in high interfacial impedance, difficulty in removing initiator byproducts during curing, activation relying solely on static setting, and slow electrolyte penetration, this embodiment adds a hydroxysilane modification treatment to the substrate, as follows: Take the polyimide (PI) electrospun film and immerse it in a 5% (w / w) hydroxysilane ethanol solution for 5-15 minutes (e.g., preferably 10 minutes). After removal, place it in a 55-65°C (e.g., preferably 60°C) forced-air drying oven and dry for 20 minutes to complete the substrate pretreatment. In this process, the siloxane bond (-Si-O-) of hydroxysilane forms a covalent bond with the PI film surface through a hydrolysis-condensation reaction. At the same time, its epoxy group reacts with the hydroxyl group (-OH) in the gel to construct a seamless chemical bond interface. This chemical bond avoids the interfacial gaps caused by physical adsorption, reduces the charge transport barrier, and the strength of the covalent bond is much higher than that of van der Waals forces or hydrogen bonds, thus suppressing interfacial delamination during charge-discharge cycles.

[0033] In step S140, the hydroxysilane ethanol solution is preferably a 3-glycidyl etheroxypropyltrimethoxysilane ethanol solution.

[0034] In step S140, the composite precursor solution is uniformly coated on the pretreated substrate surface with a thickness of 20-30 μm.

[0035] In step S140, during the ultraviolet radiation treatment, the wavelength of the ultraviolet radiation treatment is 365 nm and the power is 80-100 mW / cm². 2 The drying time is 40-60 seconds. In addition, the gel membrane is transferred to a nitrogen-protected UV curing chamber for drying, maintaining a vacuum of -0.09 MPa, a drying temperature of 60-70℃, and a drying time of 2-3 hours to remove residual citric acid and ethanol solvent from the membrane.

[0036] S150. The dried gel membrane is immersed in the electrolyte and extruded to obtain a high-pressure gel polymer electrolyte.

[0037] In step S150, the electrolyte preparation process is as follows: Lithium hexafluorophosphate (LiPF6) is dissolved in ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) to obtain a LiPF6 / EC / EMC / FEC electrolyte with a concentration of 1 mol / L.

[0038] It should be noted that when immersing the dried gel membrane in the electrolyte for extrusion, it needs to be immersed at 25°C under sealed conditions for a period of time. During this period, the membrane should be gently squeezed every 2 hours to promote full penetration and absorption of the electrolyte. After immersion, the soaked gel membrane should be removed and the residual electrolyte on the surface should be absorbed with lint-free paper to obtain the high-voltage gel polymer electrolyte product.

[0039] In this embodiment, the high hydroxyl density of the polysaccharide powder (e.g., konjac glucomannan) forms a "hydrogen bond-fluorine-induced" dual synergistic network with the fluorinated monomer: the strong hydrogen bonds between the hydroxyl groups in konjac glucomannan and the ester groups in the fluorinated monomer enhance mechanical strength, while the multiple fluorine atoms in the fluorinated monomer weaken the Li through strong electronegativity. + With PF6 - Coordination enhances ion migration efficiency; hydroxysilane-modified substrates construct chemically bonded interfaces, reducing impedance; optimized UV curing reduces byproducts; periodic extrusion activates and breaks local hydrogen bonds, accelerating electrolyte penetration, thereby overcoming the bottleneck of existing technologies where mechanical strength, ion conduction, and interface stability are difficult to coordinate.

[0040] In another aspect of this disclosure, a high-pressure gel polymer electrolyte is proposed, which is prepared by the preparation method described above. For details of the preparation process, please refer to the above description, which will not be repeated here.

[0041] The high-pressure gel polymer electrolyte disclosed herein possesses a hydrogen-bonded-fluorine-induced dual synergistic network, exhibiting excellent network support, strong mechanical properties, and good high-pressure resistance. Furthermore, based on the use of natural polysaccharides and nanocellulose whiskers, it is low-cost and biodegradable.

[0042] In another aspect of this disclosure, a supercapacitor is provided, comprising a positive electrode shell, a positive electrode plate, a high-voltage gel polymer electrolyte, a negative electrode plate, a stainless steel sheet, a spring plate, and a negative electrode shell, wherein the high-voltage gel polymer electrolyte is the high-voltage gel polymer electrolyte described above.

[0043] This disclosure describes a gel electrolyte that combines natural polysaccharide polymers with fluorinated monomers and in-situ ultraviolet light curing technology to construct a gel electrolyte with high ionic conductivity, high voltage, and excellent mechanical strength, suitable for supercapacitors with high voltage requirements.

[0044] The preparation method and application of high-pressure gel polymer electrolytes will be further illustrated below with specific examples: Example 1 Step S110: Weigh 4g of konjac glucomannan powder and slowly add it to 96g of 3% citric acid aqueous solution. Place the mixture in a 50℃ constant temperature water bath, turn on the stirrer, and continue stirring for 60 minutes until the konjac glucomannan powder is completely dissolved to obtain a 4% konjac glucomannan solution. Add 0.6g (15% of the mass of konjac glucomannan) of nanocellulose whiskers to the konjac glucomannan solution, stir for 10 minutes to initially disperse the whiskers, transfer the solution to an ultrasonic instrument, set the ultrasonic temperature to 45℃ and the power to 300W, and ultrasonically treat for 30 minutes to form a uniform and transparent modified polysaccharide composite solution. Let it stand at room temperature for later use.

[0045] Step S120: Weigh 0.3 mol of fluorinated monomer formula I-1 and 0.1 mol of polyethylene glycol diacrylate (PEGDA) (molar ratio 3:1), add them to a 250 mL three-necked flask, and stir at room temperature (25 °C) for 15 minutes to ensure complete mixing; then add 0.2 g (0.5% of the total mass of the fluorinated monomer formula I-1 and PEGDA) of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone to the three-necked flask, and continue stirring for 10 minutes until HMPP is completely dissolved and the solution has no obvious particles, thus obtaining a monomer-crosslinking agent mixture; Step S130: According to the volume ratio of modified polysaccharide composite solution to monomer-crosslinking agent mixture of 1:2, measure 50 mL of the modified polysaccharide composite solution prepared in step S110, and add it dropwise to a three-necked flask at a rate of 2 mL / min through a constant pressure dropping funnel. After the addition is completed, heat to 30℃ and stir for 40 minutes to obtain a non-layered, light yellow, transparent composite precursor solution.

[0046] Step S140: Take a polyimide (PI) electrospun film, immerse it completely in a 5% (w / w) 3-glycidyl ether oxypropyltrimethoxysilane ethanol solution, let it stand at room temperature for 10 minutes, take it out and dry it in a 60℃ forced-air drying oven for 20 minutes to complete the hydroxyl modification of the substrate surface. Using a wire bar coater, the composite precursor solution prepared in step S130 is uniformly coated onto the surface of the pretreated PI film, and immediately transferred to a nitrogen-protected UV curing oven after coating. Turn on the UV lamp and set the wavelength to 365nm and the power to 90mW / cm. 2 Irradiation for 45 seconds causes the precursor to undergo a cross-linking polymerization reaction, forming an elastic gel film. The cured gel film was transferred to a 65°C vacuum drying oven, and the vacuum degree was set to -0.09MPa. It was dried for 2.5 hours to remove residual citric acid and ethanol solvent from the film, resulting in a dry gel film.

[0047] Step S150: Preparation of supercapacitor electrolyte: Under an argon atmosphere, 12.5g of lithium hexafluorophosphate is added to an organic solvent formed by mixing ethyl methyl carbonate, ethylene carbonate and fluoroethylene carbonate, and the mixture is stirred at 10°C to obtain the electrolyte. The dry gel membrane obtained in step S140 was completely immersed in the above electrolyte, sealed and placed in a constant temperature chamber at 25°C for static activation. During this period, the membrane was gently squeezed with tweezers every 2 hours (pressure 0.1MPa) and the immersion was continued for 10 hours. Remove the soaked gel membrane and blot the surface of residual electrolyte with lint-free paper to obtain the high-pressure gel polymer electrolyte product of Example 1.

[0048] Furthermore, a supercapacitor is prepared in the following order: positive electrode shell, positive electrode sheet, gel electrolyte, negative electrode sheet, stainless steel sheet, spring sheet, and negative electrode shell. NCM811 is selected for the positive electrode, and natural graphite is selected for the negative electrode.

[0049] As shown in Table 1, the voltage window of this Example 1 is 5.34V, the ionic conductivity is 1.55S / cm, and the capacity retention rate is 91.4% after 500 cycles.

[0050] Example 2 The only difference between Example 2 and Example 1 is the molar ratio of fluorinated monomer to crosslinking agent in step S120; all other steps and parameters are the same as in Example 1. In step S120, 0.4 mol of the fluorinated monomer compound of formula I-1 and 0.1 mol of polyethylene glycol diacrylate (molar ratio 4:1) are weighed and added to a three-necked flask for subsequent mixing.

[0051] As shown in Table 1, the voltage window of this Example 2 is 5.52V, the ionic conductivity is 1.62S / cm, and the capacity retention rate is 92.1% after 500 cycles.

[0052] Example 3 The only difference between Example 3 and Example 1 is the molar ratio of fluorinated monomer to crosslinking agent in step S120; all other steps and parameters are the same as in Example 1. In step S120, 0.5 mol of the formula I-1 fluorinated monomer compound and 0.1 mol of polyethylene glycol diacrylate (molar ratio 5:1) are weighed and added to a three-necked flask for subsequent mixing.

[0053] As shown in Table 1, the voltage window of this Example 3 is 5.63V, the ionic conductivity is 1.76S / cm, and the capacity retention rate is 92.5% after 500 cycles.

[0054] Example 4 The only difference between Example 4 and Example 1 is that the fluorinated monomer compound of formula I-1 in step S120 is replaced with the fluorinated monomer compound of formula I-2. Otherwise, they are the same as in Example 1.

[0055] As shown in Table 1, the voltage window of this Example 4 is 5.41V, the ionic conductivity is 1.58S / cm, and the capacity retention rate is 90.4% after 500 cycles.

[0056] Example 5 The only difference between Example 5 and Example 1 is that the fluorinated monomer compound of formula I-1 in step S120 is replaced with the fluorinated monomer compound of formula I-4. Otherwise, they are the same as in Example 1.

[0057] As shown in Table 1, the voltage window of this Example 5 is 5.43V, the ionic conductivity is 1.51S / cm, and the capacity retention rate is 90.7% after 500 cycles.

[0058] Example 6 The only difference between Example 6 and Example 1 is that the crosslinking agent polyethylene glycol diacrylate in step S120 is replaced with polyethylene glycol divinyl ether; otherwise, they are the same as in Example 1.

[0059] As shown in Table 1, the voltage window of this Example 6 is 5.43V, the ionic conductivity is 1.57S / cm, and the capacity retention rate is 91.3% after 500 cycles.

[0060] Example 7 The only difference between Example 7 and Example 1 is that the crosslinking agent polyethylene glycol diacrylate in step S120 is replaced with bisphenol A difluorodiacrylate; otherwise, they are the same as in Example 1.

[0061] As shown in Table 1, the voltage window of this Example 7 is 5.47V, the ionic conductivity is 1.46S / cm, and the capacity retention rate is 91.5% after 500 cycles.

[0062] Example 8 The only difference between Example 8 and Example 1 is that the photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone in step S120 is replaced with 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone; otherwise, they are the same as in Example 1.

[0063] As shown in Table 1, the voltage window of this Example 8 is 5.54V, the ionic conductivity is 1.76S / cm, and the capacity retention rate is 89.4% after 500 cycles.

[0064] Example 9 The only difference between Example 9 and Example 1 is that the amount of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone added in step S120 is increased to 1% of the total mass of Formula I-1 and PEGDA. Otherwise, they are the same as in Example 1.

[0065] As shown in Table 1, the voltage window of this Example 9 is 5.70V, the ionic conductivity is 1.87S / cm, and the capacity retention rate is 92.8% after 500 cycles.

[0066] Example 10 The only difference between Example 10 and Example 1 is that the volume ratio of the modified polysaccharide composite solution to the monomer-crosslinking agent mixture in step S120 is 1:3. All other steps and parameters are the same as in Example 1.

[0067] As shown in Table 1, the voltage window of this Example 10 is 5.19V, the ionic conductivity is 1.35S / cm, and the capacity retention rate is 89.5% after 500 cycles.

[0068] Example 11 The only difference between Example 11 and Example 1 is that the ultraviolet light irradiation time in step S140 is 40 seconds, so that the precursor can complete the crosslinking polymerization reaction. The remaining steps and parameters are the same as in Example 1.

[0069] As shown in Table 1, the voltage window of this embodiment 11 is 5.24V, the ionic conductivity is 1.41S / cm, and the capacity retention rate is 87.9% after 500 cycles.

[0070] Example 12 The only difference between Example 12 and Example 1 is that the ultraviolet light irradiation time in step S140 is 60 seconds, so that the precursor can complete the crosslinking polymerization reaction. The remaining steps and parameters are the same as in Example 1.

[0071] As shown in Table 1, the voltage window of this Example 12 is 5.20V, the ionic conductivity is 2.16S / cm, and the capacity retention rate is 93.1% after 500 cycles.

[0072] Comparative Example 1 Comparative Example 1 is used to compare the effect of "natural polysaccharide type". The only difference between it and Example 1 is that "natural polysaccharide is replaced with chitosan" in step S110. All other steps and parameters are the same as in Example 1.

[0073] As shown in Table 1, the voltage window of Comparative Example 1 is 4.60V, the ionic conductivity is 0.9S / cm, and the capacity retention rate is 80.4% after 500 cycles.

[0074] Comparative Example 2 Comparative Example 2 was used to compare the effect of "whether the substrate was modified or not". The only difference from Example 1 was that "the PI film was not modified with hydroxysilane" in step S140. All other steps and parameters were the same as in Example 1. In step S140, the untreated PI electrospun film was directly taken and subjected to composite precursor coating and subsequent curing operations.

[0075] As shown in Table 1, the voltage window of Comparative Example 2 is 4.58V, the ionic conductivity is 1.0S / cm, and the capacity retention rate is 81.5% after 500 cycles.

[0076] Table 1 Results data for each embodiment and comparative example

[0077] In summary, based on Table 1, using Example 1 as the basic scheme, its performance stems from the synergistic effect of the high hydroxyl density of konjac glucomannan and the "hydrogen bond-fluorine-induced" effect of the fluorinated monomer. Examples 2 and 3 increased the molar ratio of fluorinated monomer to crosslinking agent from 3:1 to 4:1 and 5:1, respectively. The increased fluorinated monomer content led to a higher fluorine atom density in the system, and the stronger fluorine electronegativity further weakened the Li in LiPF6. + With PF6 - The coordination effect increases the number of lithium ions that migrate freely, further improving ionic conductivity and voltage window.

[0078] Examples 4, 5, 6, and 7 use different types of fluorinated monomers and crosslinking agents, and the voltage window and ionic conductivity are not significantly different from those in Example 1. Example 9 increases the photoinitiator content to 1%. The increased initiator molecule concentration increases the amount of free radicals generated, resulting in a more uniform crosslinking reaction, reduced network defects, lower charge transport resistance, lower interfacial impedance, and improved capacity retention.

[0079] In Example 10, the volume ratio of the polysaccharide complex solution to the monomer-crosslinking agent mixture was adjusted from 1:2 to 1:3. The reduced proportion of konjac glucomannan led to a decrease in the density of the hydrogen bond network, weakened the mechanical support of the gel membrane, made the network more prone to deformation during electrolyte penetration, and reduced the stability of the ion transport channels. Therefore, the ionic conductivity and capacity retention were slightly reduced.

[0080] In Example 11, the UV irradiation time was shortened to 40 seconds, resulting in insufficient cross-linking reaction, local porosity defects in the gel network, and irregular ion transport paths, leading to a decrease in ionic conductivity, voltage window, and cycling performance. In contrast, in Example 12, the UV irradiation time was extended to 60 seconds, allowing for sufficient cross-linking reaction, resulting in regular ion transport paths and further improvement in ionic electrical properties.

[0081] In Comparative Example 1, chitosan was used instead of konjac glucomannan. The amino (-NH2) and hydroxyl groups of chitosan compete for adsorption, resulting in a low hydroxyl group density. This makes it difficult to form a dense hydrogen bond network with the fluorinated monomer, increasing the porosity of the gel membrane. Ion transport is then easily affected by electrolyte retention in the pores, resulting in an ionic conductivity of only 0.9 × 10⁻⁶. -3 The voltage window narrows to 4.6V due to the high S / cm, and the amino group is easily oxidized under high voltage, resulting in a cycling capacity retention of only 80.4%. In Comparative Example 2, the unmodified PI membrane surface contains only a small number of polar groups, which bind to the gel electrolyte only through physical adsorption. Micro-gap exists at the interface, and a higher potential barrier needs to be overcome during charge transport, resulting in poor ionic conductivity and cycling performance.

[0082] Furthermore, according to Figure 2 As shown, in Example 3 compared to Example 1, the molar ratio of fluorinated monomer to crosslinking agent was increased from 3:1 to 5:1. The increase in the content of fluorinated monomer increased the fluorine atom density of the system, and the stronger fluorine electronegativity further weakened the Li in LiPF6. + With PF6 - The coordination effect increases the number of lithium ions that migrate freely, thus reducing impedance; compared with Example 1, Example 12 has a longer ultraviolet radiation time, which allows for a full cross-linking reaction and reduces impedance.

[0083] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for preparing a high-pressure gel polymer electrolyte, characterized in that, include: A polysaccharide solution is obtained by adding citric acid aqueous solution to polysaccharide powder and stirring at a constant temperature. Nanocellulose whiskers are then added to the polysaccharide solution and subjected to ultrasonic treatment to form a modified polysaccharide composite solution. A fluorinated monomer and a crosslinking agent are stirred to form a mixed system. A photoinitiator is added to the mixed system and the stirring is continued until the initiator is completely dissolved, resulting in a monomer-crosslinking agent mixture. The modified polysaccharide composite solution is mixed with the monomer-crosslinking agent mixture, and then stirred to form a composite precursor solution; The substrate was immersed in a hydroxysilane ethanol solution for surface modification, and the composite precursor solution was uniformly coated on the modified substrate surface. After ultraviolet radiation treatment, the precursor underwent a cross-linking polymerization reaction to obtain a gel film, which was then dried. The dried gel membrane was immersed in an electrolyte and then extruded to obtain a high-pressure gel polymer electrolyte.

2. The preparation method according to claim 1, characterized in that, The polysaccharide powder is konjac glucomannan powder; The citric acid aqueous solution has a mass fraction of 3%-10%; The content of the nanocellulose whiskers is 14-16% of the content of the polysaccharide powder.

3. The preparation method according to claim 1, characterized in that, The temperature for constant temperature stirring of polysaccharide powder with citric acid aqueous solution is 45-55℃, and the time is 1-3h. The polysaccharide solution is subjected to ultrasonic treatment with nano-cellulose whiskers at a temperature of 40-50℃, a power of 250-350W, and a time of 25-35min.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the fluorinated monomer to the crosslinking agent is (3-5):1; The amount of photoinitiator added is 0.5%-1% of the total mass of the mixed system formed by the fluorinated monomer and the crosslinking agent.

5. The preparation method according to claim 1, characterized in that, The fluorinated monomer is selected from one of the following structural formulas: (Formula I-1); (Formula I-2); (Formula I-3); (Formula I-4); The crosslinking agent is selected from one of polyethylene glycol dimethacrylate, polyethylene glycol divinyl ether, bisphenol A difluorodiacrylate, hexafluorobisphenol A diacrylate, trimethylolpropane triacrylate, and polyethylene glycol diacrylate; The photoinitiator is one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

6. The preparation method according to claim 1, characterized in that, The fluorinated monomer and crosslinking agent are stirred at 20-30℃ for 10-20 minutes. Add a photoinitiator to the mixture and continue stirring for 5-15 minutes.

7. The preparation method according to claim 1, characterized in that, The volume ratio of the modified polysaccharide composite solution to the monomer-crosslinking agent mixture is 1:(2-4). The modified polysaccharide composite solution is mixed with the monomer-crosslinking agent mixture and then stirred at 25-35°C for 35-45 minutes.

8. The preparation method according to claim 1, characterized in that, The hydroxysilane ethanol solution is a 3-glycidyl etheroxypropyltrimethoxysilane ethanol solution; The composite precursor solution is uniformly coated on the pretreated substrate surface with a thickness of 20-30 μm; The ultraviolet radiation treatment was performed at a wavelength of 365 nm and a power of 80-100 mW / cm². 2 The duration is 45-60 seconds; The gel membrane is dried at a temperature of 60-70°C for 2-3 hours.

9. A high-pressure gel polymer electrolyte, characterized in that, The high-pressure gel polymer electrolyte is prepared by the preparation method according to any one of claims 1 to 8.

10. A supercapacitor, characterized in that, The supercapacitor includes a positive electrode shell, a positive electrode plate, a high-voltage gel polymer electrolyte, a negative electrode plate, a stainless steel sheet, a spring plate, and a negative electrode shell, wherein the high-voltage gel polymer electrolyte is the high-voltage gel polymer electrolyte as described in claim 9.

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